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PLATINUM METALS REVIEW

4 quartwly surve? of rrsenrrh on the platinum metals and of de?:rlopments i n their application in industry

VOL. 26 JULY 1982

Con tents

Dispersion Strengthened Gold-Platinum

The Control of Nitrogen Oxides Emissions

Johnson Matthey Technology Worldwide

The Application of Palladium in Electronic Connectors

A New Platinum-Wired Air Flow Meter

Platinum Electrocatalysts for Phosphoric Acid Fuel Cells

The Palladium-Hydrogen System

The Life and Work of Nikolai Semenovich Kurnakov

Abstracts

New Patents

NO. 3

(.bnmunications should he addresspd to Thr Editor, Platinum Memls Revim

.Inhnson Vatth48v Public Iirnited Company. Ilolton (hrden. I.ondon E C I N 8EK

Dispersion Strengthened Gold-Platinum A NEW MATERIAL FOR GLASS HANDLING EQUIPMENT

By A. E. Heywood and R. A. Benedek Johnson Matthey Metals Limited, Wembley, England

Platinum alloys containing gold e x h i b i t m a r k e d n o n - w e t t i n g characteristics with molten glasses. Simple gold-pal ladium al loys , however, are relatively weak while those that have rhodium added to increase their strength can be difficult to work, and also suffer from embrittlement during service. Now the binary alloys can be dispersion strengthened with zirconia to produce a material with the ductility of the simple binary and the higher hot strengths of rhodium-containing ternary alloys. This dispersion strsng- thened gold-platinum alloy has enhanced resistance to progressive contamination and offers a longer service life. It is being used successfully for specialised applications in the glass industry, for which it has potential, as well as for the apparatus in which samples for X-ray jluorescence analysis are prepared.

The marked effect that gold has upon the contact angle between a platinum surface and molten glass is well documented. In particular, Selman, Spender and Darling carried out considerable work on this subject using soda glass and ‘E’ glass-a glass commonly used for the production of reinforcement fibre (I , 2 ,3 ) . The remarkable increase in contact angle that the addition of gold produces, particularly at levels of 3 per cent and above, is shown in Figure I .

Also of importance is the elimination of the contact angle “trough” that occurs with both platinum and rhodium-platinum alloys between about 900 and I 25ooC, see Figure 2.

Platinum Metals Rev., 1982, 26, (3), 98-104 98

This phenomenon is not restricted to conventional glasses but is also seen with other glassy compounds such as the borate fluxes commonly used in the preparation of samples for X-ray fluorescence analysis (XRF) (4). As a result, gold-platinum and gold-rhodium- platinum apparatus is widely used in analytical and glass research laboratories.

The most common binary composition used is 5 per cent gold-platinum. Higher gold contents produce little further increase in contact angle, as can be seen in Figure 3, but can bring considerable problems with inhomogeneity due to segregation resulting from the considerable difference in solidus and liquidus temperatures in the gold-platinum system, as shown in Figure 4. For many applications the simple binary alloy has insufficient hot strength to give an acceptable service life and a ternary alloy of platinum, gold and rhodium provides increased strength and is commonly used in XRF analysis applications (4,5,6). The exact choice of alloy is, however, something of a compromise. An alloy of 5 gold, I o rhodium and 85 per cent platinum provides good wetting resistance and strength, see Figures 5 and 6, but compared to the binary alloy is difficult to form and has inferior chemical resistance (4). Additionally, the grain boundary gold-rich precipitation noted during Selman’s work is often realised in practice, particularly during the preparation of sample beads for XRF, leading to embrittlement and subsequent cracking. Reducing the gold content to 3 per cent but maintaining the rhodium content significantly reduces the problems of corrosion and embrittlement while retaining a useful strength; a relevant US. Patent 3,672,880 identifies platinum alloys with gold and rhodium contents in the ranges I to 3 per cent and 12 to 25 per cent, respectively.

However, the contact angle of such alloys is reauced as shown in Figure 3, and they are sensitive to any loss of gold from the surface.

All the alloys mentioned so far experience grain growth during use at typical service

temperatures. This is particularly relevant to XRF analysis work in two respects, namely the surface finish of sample beads and also the ability to resist the effects of grain boundary contamination of the type described (7).

Platinum Metals Rev., 1982, 26, (3) 99

Fig. 5a A droplet of ‘E’ glass in equilibrium with the surface of a 10 per cent rhodium- platinum alloy heated in air at I 200OC show-

x 20 ing a relatively l o w contact angle

1‘0 attain a high contact angle, the binary alloy of 5 per cent gold-platinum represents the best option, and also has the benefit of being easily worked. Attempting to provide this alloy with good hot strength leads in turn to other problems outlined earlier, and no previously available option overcame the problem of grain growth. It was clear that a need existed for an alloy with the workability and wetting characteristics of 5 per cent gold-platinum but combined with the hot strength of the rhodium- containing ternary alloys; resistance to grain growth and progressive contamination resistance were also desirable. The solution lay

Fig. 5b The high contact angle assumed by a droplet of ‘E’ glass melted in air at 1200OC on the surface of 5 gold-10 rhodium-8.5 pcr cent platinum alloy (2) x 20

in utilising the techniques developed by Johnson Matthey for the production of dispersion strengthened platinum and rhodium- platinum alloys (8,9). The dispersion of 0.08 to 0.1 per cent zirconia in the binary 5 per cent gold-platinum alloy, coupled with suitable thermomechanical treatment, resulted in the development of an alloy possessing the strength of the ternary alloys and the wettability and the ease of fabrication of the binary alloy. In addition, grain growth at service temperatures was dramatically reduced and the contamination resistance noted by Knapton was clearly demonstrated. This new material has been


designated ZGS 5 per cent gold-platinum, and its ductility and stress rupture characteristics are given in Figures 7, 8 and 9.

The XRF Analysis Application ZGS 5 per cent gold-platinum has been

thoroughly evaluated in the market for which it was primarily developed, that is for making casting dishes used in the preparation of XRF sample beads. A typical moulding dish is illustrated in Figure 10. Service lives in the order of 4 or 5 times that of the conventional alloys have been reported (6). Additionally, and equally important, the surface finish of beads produced in casting discs made from this material is dramatically improved (see Figure 1 1 ) with a consequent improvement in analytical accuracy being reported in many


Fig. 1 0 A typical platinum alloy mould used for the preparation of XRF sample beads of the type shown in Fig. 11; high surface finish and flatness are important requirrmeuts

cases. As a result these dishes are particularly useful for the automated methods of analysis currently gaining wide acceptance for industrial purposes.

The superiority of ZGS 5 per cent gold- platinum over conventional alloys in this application is without doubt, and the response from the market confirms this, even though the

alloy is more expensive to produce than conventional alloys. As a result the demand for ternary alloys has fallen considerably and it is not difficult to envisage a situation where gold- platinum is used for low temperature applications and ZGS gold-platinum at above about XooOC, rendering the troublesome ternary alloys redundant.

Fig. 11 XKF sample heads prepared in moulds that have been in servire fu r some time. The h a d on the left w a s prepared in a ZGS 3 per cent gold-platinum mould and shows a guod surface finish. The poor surfare finish of the head on the right is thc. rvsulf o f rxees~i ir grain growth in a standard gold-platinum mould during servire; the illustrated surface is also notirc-ably conrave


Of the previously available materials, the poor creep strength of the simple binary gold- platinum alloy precludes its use as a bushing baseplate material. Ternary alloys, especially 5 gold-ro rhodium-85 per cent platinum, would be difficult if not impossible to fabricate for this purpose by the existing coining and deep drawing method indicated in Figure 13. Although the wettability of 3 per cent gold- rhodium-platinum is better than that of both 10 per cent rhodium-platinum and 20 per cent rhodium-platinum the alloy has proved to be unstable in service due to the deleterious effect of any loss of gold, however small. This is clearly shown in Figure 3. Unfortunately, adding gold-platinum to a rhodium-platinum jet leads to the diffusion of gold into the baseplate during fabrication and use, so denuding the tip of the jet and reducing the contact angle.

The advent of ZGS gold-platinum has enabled “non wetting” baseplates having the strength of rhodium-platinum alloys to be produced by the existing method ( I I ) and these have performed satisfactorily over a 12 month period. Initial trials were made with conventional designs where flooding of the jets was not necessarily a severe problem; nevertheless, the amount of glass contamination of the baseplate was dramatically reduced. Trials are

Fig. 12 Glass fibre filaments are formed by drawing molten glass thruugh hundreds of small orifices in a bushing baseplate. The stability of the meniscus is critical in the successful operation of the process I’horograph by courtw ot O\ren4 ormng hkrg las Lorparation

Glass Fibre Production The production of continuous glass fibre

utilising platinum bushings as described by Loewenstein is a complex and highly skilled process (10). The stability of the meniscus illustrated in Figure IZ is greatly affected by the wettability of the alloy and the use of gold- containing alloys is an obvious development, either to improve the current designs or to enable jets to be more closely packed and hence increase bushing efficiency.


now proceeding with baseplates of more radical design wliich exploit the improved wetting characterjstics of the alloys.

Conclusions This extension of the ZGS process has

resulted in the development of a new material, ZGS 5 per cent gold-platinum, that reconciles the hitherto conflicting needs of XRF analysis equipment, and which has considerably improved the performance of the apparatus and the product, and thus the accuracy of the results. The availability of this unique material has resulted in considerable interest from other markets, notably the glass fibre industry which foresees its use for the development of new high performance bushings for the production of continuous fibre.

References I G. L. Selman, M. R. Spender and A. S. Darling,

2 G. L. Selman, M. R. Spender and A. S. Darling,

3 G. L. Selman, M. R. Spender and A. S. Darling,

4 H. A. Foner, Lab. Pract., Aug. 1977,625

l’lacinum Mecals Reo., 1965,9, (3), 92

OP. tit., 1965~9, (41, 130

op. cit., 1966,10, (21, 54

A. W’ittmann, J. Chmeleff and H. Herrmann, X-Ray Spectrum., 1974, (41, 137 P. I. Roberts, Proc. Thirty-Third Chemists’ Conf., British Independent Steel Producers Association, Scarborough, England, June 3-5

A. G. Knapton, op. cic., ref. I , 1979, 23, (I), 2, II,12 G. L. Selman, J. G. Day and A. A. Bourne, op. cit., ref. I, 1974, IS, (z), 46 G. L. Selman and A. A. Bourne, op. cit., ref. I , 197610, (3), 86 K.L.Loewenstein,op.ciL,ref.1,1975,19,(3),82 British Patent Appl. 2,085,028 A

1980, P. 74

The Control of Nitrogen Oxides Emissions PROGRESS REVIEWED AT INTERNATIONAL SYMPOSIUM

Nitrogen oxides (NO3 emissions were first identified as major contributors to air pollution after studies made during the 1950s into the formation of photochemical smog in Los Angela. These observations led directly to legislation in the United States of America regulating emission of NO, to the atmosphere from both stationary and mobile sources. Since that time it has been recognised that such emissions constitute a global problem. A recent symposium sponsored by The Netherlands Ministry of Health and Environmental Protec- tion and the U.S. Environmental Protection Agency, held in Maastricht during May, reviewed the state of the art in research and development relating to national and inter- narfonal policies on NO, control. More than 300 delegates attended, demonstrating the clirrent interest in the subject, and over 75

T The control of nitrogen oxides resulting from nitric acid production was the subject of papers presented by W. Toering of UKF, Rotterdam and A. Kayaert of Nederlandse Stikstof Maats- chappij, based on their operational experience. Both pollution control and energy recovery result from the use of suitable platinum metal catalyst systems for the treatment of tail gases.

Emissions from mobile sources were con-

pers were presented.

sidered in papers presented by H. D. Pletka of DEGIJSSA, Hanau and A. E. K. Budd of Johnson Matthey Chemicals Limited. The latter traced the history of ceramic honeycomb supported platinum group metal catalysts from their first recorded industrial application in controlling NO, emissions from the tail gases of nitric acid manufacturing plants, to the development of three-way catalysts for the simultaneous control of NO,, carbon monoxide and hydrocarbon emissions in petrol engined vehicle exhaust gases. In addition, reference was made to the successful application of platinum group metals catalysts in catalytic combustion systems for both gas turbine and catalytic engines. Catalytic combustion, that is flameless combustion promoted by a catalyst, promises a number of advantages, including low NO, emissions without the use of tail gas clean-up devices.

Catalytic clean-up devices are the best developed and most practical method of mobile NOx emission control currently available, and it i s probable that platinum group metal catalyst technology will continue to play an important role in the control of stationary sources of NOx emissions for some time to come.

The full proceeding of the symposium, and the discussion, are to be published in October by Elsevier Scientific Publishing Company.


Johnson Matthey Technology Worldwide PLATINUM METALS FULFIL EVOLVING INDUSTRIAL NEEDS

An exhibition held at the Johnson Matthey Research Centre in May included demonstra- tions of recent research in advanced areas of technology. Some 400 visitors, mainly leading industrialists, academics and government advisors from the U.K. and overseas, attended. Appropriately for the organisation that is the sole marketing agent for the Rustenburg Platinum Mines, many of the activities involved the application of the platinum metals and a selection of these are featured below.

While there is no shortage of platinum metals within the earth’s crust their concentration in ore bodies is generally low, and the Bushveld Igneous Complex is the only major area in the world where platinum is mined as the primary product. With a growing understanding of the mineralogy of these platinum-bearing rocks, and of the refining operations, the efficiencies of the extraction and separation processes are being improved and lead times reduced in collaboration with Rustenburg Platinum Mines. In addition novel methods of secondary refining are being investigated, particularly for emission control catalysts and electronic scrap.

Instantaneous Electricity One of the most spectacular exhibits was a

demonstration of a fuel cell on loan from United Technologies International, the leading organisation in fuel cell development. This unit was the precursor to the power plants used on the recent U.S. Space Shuttle flights, and it produces 12 kW of electricity by combining hydrogen and oxygen at platinum catalysed electrodes. A major advantage of this means of power generation is its high efficiency of conversion of chemical energy to electricity, and its ability to respond very quickly to large changes in load. It is also pollution free and silent in operation. These properties have led to the development in the U.S.A. and Japan of larger fuel cells for grid electricity generation

(megawatt scale), particularly in high popula- tion areas, and combined heat and power systems (kilowatt scale) for on-site applications.

Many platinum metals catalytic systems and their application in energy conservation, pollution control and chemical processing are being examined. Following the successful control of emissions from automobiles fuelled with lead- free gasoline, current work is continuing on the development of both lead tolerant and diesel exhaust control catalysts. A concept that com- bines the economic use of fuel with low emission of exhaust pollutants is a catalytic engine where combustion is achieved on a platinum catalyst sited in the combustion chamber of an internal combustion engine. Another feature of this engine is that it can run on a variety of fuels including methanol, a product of the chemical industry rather than the oilfields.

A continuing requirement for improved structural materials is resulting in further developments of alloys containing, or coated with, platinum metals. Judiciously employed, the platinum metals can enhance the corrosion resistance of base metals thereby extending their application and durability in hostile environments, and a variety of materials and processes are currently under investigation. While the platinum metals increasingly account for only a small part of the total material used in a particular product, there are still situations where a platinum metal alone can serve. A large iridium crucible 20 cm diameter and 20 cm high, to be used during the melting of semiconductor materials for the electronics industry, ably illustrated this point.

The platinum metals are also being actively investigated for a growing number of important medical applications.

Clearly, the Johnson Matthey commitment to progress in platinum technology is thriving, in keeping with the foreseen needs of industry throughout the world. 1.li.C.


The in E

Application of Palladium lectronic Connectors

CONTINUING STUDIES RESULT IN GROWING USE

By Morton Antler Bell Telephone 1,aboratories. Inc.. Columbus, Ohio

I’alladiurri and palladium- hnscd materials arc bring i n ( rcnsingh acccp.ptPd as substitutes for gold in contacts #or scpar(ibl(, idi,ctronic conrw tors. Sinw 107.5 the fm.ournhlc> rapt of pnllarliiirn rdtrtii (1 to

gold has stiinulatcd rcscarrh in niuny arrws of coritnr I tc~chnologi. including manufacturing proccsscjs, contuc’t phcnomcvia, tcistirig and connector dmign. This has resulted in thc dci rdopmcvt of s i w w l n c u materials wstcms involving c1cctrodqx)sitcd coatings. (kt inlays a n d w d d m c ~ n t s ofpal ladium, palladruni -silccr n h s . gold-pollodiurri-cilz cr compositions and composite coatings u ith othvr mctuls thot a r (1

c7quivalmt to all-gold swtcms in many applications. This r(’i ~ P W tracm thP histor, of rcwarch o n palladiiim for usc in connwtors, urid sum- mariscas important results of studivs of the cntwonmwtul , tribological arid contnct propc’rtic’s of pnllnciium motorinls.

Palladium and palladium alloys, such as 60palladium-40 silver and 73 palladium- 27 nickel, have a long history of use in contacts in the electronics industry. Their characteristics of erosion resistance, nobility, ease of fabrication and moderate cost have made palladium materials the premier choice since 1950 for light duty open relay contacts in telecom- munications. The consumption of palladium worldwide for this application was in excess of a million troy ounces in 1974 (I). The need for relays in telephone apparatus is, however, rapidly declining because of the development of solid state switching systems that are smaller, consume less power, operate faster and are less expensive than comparable electromechanical equipment. Nevertheless, palladium will continue to be used in significant amounts to service existing apparatus, at least until the year 2000, as well as in other relay applications.

From about 1955 the use of printed circuit boards and separable electronic connectors has grown rapidly. Their combined annual production in the United States is valued at several

billion dollars. World manufacture is estimated to be about three times greater. This has occurred because printed circuit boards are ideal structures for mounting and interconnect- ing components and integrated circuits, and separable connectors are needed to be able to join printed circuit boards as well as other building blocks of modern electronic systems.

Connector functions can be viewed as occurring at various levels of “pluggability”, from small to large in system complexity. For example, connectors attach components to printed circuit boards, boards to boards on a chassis, one chassis to another in the same cabinet, or one piece of equipment to another, usually via cables ( 2 ) . Figure 1 illustrates several common types of separable electronic connectors.

Corrosion resistance, high conductivity and mechanical durability are essential requirements of a contact material. Ease of fabrication and availability are also necessary. Gold is the dominant metal for high reliability in long life separable electronic contacts, and recently


Fig. 1 Various types of electronic connectors:

Top. ( a ) Dual-in-line semiconductor integrated circuit receptacle \riddle ( b ) Connectors for printed circuit boards with edge contacts

Bottom ( c ) Rectangular connector for chassis mounting

(a) Lourtvc) of the Rurnd) Cnrporatian (h)and(r)(vurtrk.efAMPIncnrporalpd


annual world consumption of gold for this purpose has been in excess of a million troy ounces. Its expense is a significant part of the costs of connectors and printed circuit boards, and from their earliest use there has been interest in lower cost alternative contact materials (3). It is obvious, therefore, that palladium would be a focus of attention as a replacement for gold in these products. However, the economic incentive to exploit palladium was not compelling until the decade of the 1970s when gold costs began to escalate, price trends are illustrated in Figure 2 .

Early Use of Palladium in Connector Contacts

The use of palladium was small in the 1960s, the main application being in a British Post Office prototype system when 3,000 to 4,000

troy ounces a year were used for contacts electroplated directly on the edges of printed circuit boards (4). Although it was recognised that palladium might have some technical disadvantages in being less noble than gold, a compensating factor was the better com- patibility of palladium plating solutions with board materials by comparison with common gold plating solutions of the time. Also, its resistance to sliding wear from contact engage- ment and separation was better than that of a gold electrodeposit against which it was compared (4). Experience with the system of gold alloy contact connectors mated to palladium edge plated boards was satisfactory (5).

During the 1960s studies of palladium electroplating processes and contact properties continued, and in 1972 a major connection system was committed to palladium (6). This consisted of wire contacts soldered in holes in printed circuit boards forming a pin field to which separable connectors with 75 gold- 25silver alloy contacts were joined. In this product palladium is electrodeposited on nickel wire pins, with the initial annual consumption of 10,000 to 20,000 troy ounces a year (7). As the price differential between palladium and gold continued to widen during the late 1970s to the present, interest in palladium heightened

and commercial connectors with palladium and palladium alloy contacts have begun to appear in the United States, Japan and West Germany, as well as in other countries. There is interest also in palladium as a gold replacement in switches for low energy applications, an example being a small multi-pole device that can be mounted on printed circuit boards (8). This device has 6opalladium-40 silver contacts that mate to gold plated members.

Fabrication of Palladium Connector Contacts

Palladium is used on connector contacts as weldments, electrodeposits or claddings. Weld- ments are made by fusing palladium wire to a copper alloy contact spring, clipping the wire, and then coining to the desired shape, usually a dome. Metal thickness usually ranges from 25 to 75,um. Most palladium is currently used as the electrodeposit at thicknesses from 0.5 to 2.5 pm on nickel underplate. Processes that plate the metal selectively on the functional


surfaces are widely used to reduce costs. Clay inlay palladium and palladium alloys

are becoming increasingly important because their placement on a contact structure is inherently selective and because novel alloys, unobtainable by electrodeposition and having especially desirable contact properties, can be obtained. Typical inlay thicknesses range from I to 5 ,urn. Little palladium is presently used for the edge contacts of printed circuit boards. The following discussion considers electroplated and clad coatings in detail.

Electrodeposited Palladium There are several considerations in palladium

deposition in common with all plating processes; the solutions should: [i] be easy to control, [ii] be usable at a wide range of operating conditions (including temperature, agitation and cathode current densities), and have good throwing power, [iii] not be easily poisoned by impurities, and be able to plate on common substrates without attacking them or depositing spontaneously prior to the application of current, [iv] be capable of operating at both the high speeds of modern plating equipment used for gold at current densities of T O to 5 0 A/dm2, as well as the modest plating rates of conventional barrel and rack equipment, and [v] give smooth crack-free adherent coatings.

Many palladium plating processes evolve hydrogen at the workpiece which is readily absorbed by the deposit. The absorption limit is 67 atom per cent at one atmosphere and 20°C, while the solubility limit of a-palladium is 3 atom per cent hydrogen. At higher concentrations, P-PdH forms, this having the same face centred cubic structure as a-I’d, but with a 4 per cent larger lattice constant. Furthermore, P-PdH spontaneously loses hydrogen at room temperature, causing severe internal stress in the deposit which is relieved by crack formation (9). Figure 3 shows a slightly cracked deposit obtained from a commercial palladium plating process. Such deposits may be porous to the substrate and can, of course, have inferior mechanical characteristics.

Important palladium electroplating processes


Fie. 3 Palladium electrodeposit (2.5 ,unr thick). (:racks wrre caused by the spontaneous convwsion of D-l’dH LO ru-Pd with 1osq of hydrogen and shrinking of the drposil

include: [a] ammoniacal systems in which the palladium is complexed in diammino or tetra- ammino forms (91, such as Pd(NH,),(NO,), (p-salt), and Pd(NH,),CI,, [b] slightly acid systems containing chelated palladium (TO),

and [c] strongly acidic electrolytes like one containing palladium nitrate, palladium sulphite, and sulphuric acid (9). The latter system co- deposits from o . ~ to 10 per cent sulphur depending upon operating conditions, and the plating is said to contain very little hydrogen. Palladium electrodeposition processes with improved operating characteristics are, however, rapidly being developed. Recent studies have described the pulse plating of palladium (I I, IZ), while deposit structures, mechanical characteristics and contact behaviours of palladium electrodeposits are also being studied, although little critical information has thus far appeared in the technical literature. Until now no process for electroplating palladium has emerged which is clearly superior for electric contacts, most of the cited systems being deficient in some respect when considered from the process requirements for electroplating listed earlier. In t h s respect, the development of palladium plating for contact applications is in about the same status as gold twenty years ago.

Special mention should be made of palladium alloy electrodeposits. Palladium-nickel platings, xPd( ~oo-x)Ni, where x typically ranges from 50

to 80 per cent, are available ( I 3). While cheaper than pure palladium, such deposits can be expected to be less noble, although undoubtedly suitable for some applications. Processes that yield gold-palladium ( I 4) and palladium-silver (I 5 ) have been described, the latter electrodeposit being of great interest because of the good contact properties of palladium-silver alloys, described later; however, the bath that was developed is extremely corrosive and requires gold undercoats to protect the base metal substrates from the plating solution.

Clad Palladium Initial development of clad inlay processes

for electronic connector contacts occurred in the early 1960s. Their acceptance in the United States was slow at first because inlays require that connectors be designed specifically for them, involving stamping from sheet metal followed by forming to the finished shape with the inlay located in the contact position. Manufacturing processes involving screw machining of wire to form pins and sockets were entrenched, gold electroplating technology was well developed, the economic incentive to conserve noble metal was less than it is now, and finally there was general reluctance to locate noble metals selectively on contact

assemblies because of concern that base metal corrosion might occur in use which could result in contamination of the contact surface. The development of large scale applications for clad inlay contacts came first in Europe.

The clad inlay process is illustrated in Figure 4. Precious metal strip, usually a bimetallic layer of thin noble metal on thick nickel, called an interliner, is placed in a groove produced by skiving the substrate. The composite is then compressed at high pressure between rolls; a metallurgical bond forms due to extension of the rolled material which creates fresh surface at the layer interface. Several heat treatment and rolling stages may be necessary to obtain the desired reduction and substrate temper. Surface contamination, including transfer of base metal from the substrate to the rolls from which it can back transfer to the noble metal in subsequent production, is minimised by lubrication of the workpiece and dressing of the rolls.

Electroplated metals cannot generally with- stand forming because they are relatively brittle and tend to crack. B’rought ductile metals, however, lend themselves to this purpose. Pure gold and gold-silver alloys, for example 70 gold- 30 silver, have been extensively used in inlays, and this practice has been extended to palladium and palladium-silver, from 60 palladium-40 silver to 30 palladium-70 silver (16). Figure 5 shows stamped formed contacts made from clad inlay palladium. As discussed later, 6opalladium-40 silver is a unique contact material, more noble that pure palladium, as well as being considerably cheaper, see Table. The non-availability of a practical electroplating process for making palladium-silver alloys is an added incentive to use clad materials. Gold- palladium-silver alloys, such as 39Au3oPd(3 I-

x)Ag(xSn,In) ( I 7) that combine high nobility with good formability, have rccently been developed.

A disadvantage of claddings is that it is difficult to make them as thin as electrodeposits without their becoming highly porous. This is because slight roughening at the two interfaces, substrate to interliner and interliner to noble metal, occurs during rolling and can lead to


Fig. 5 Stamped formrd contarts made from clad inlay palladium arr now w i d d y used for elrctronic connectors

Gold

70Gold-30Silver

Palladium

60 Palladium-40Silver

penetration of the noble layer. Nevertheless, there seems to be no practical lower limit to the average thickness of noble metal, and palladium-containing inlays thinner than I pm can be produced for contact applications.

Contact Resistance The contact resistance of electrodeposited

palladium, 80 palladium-20 nickel, and clad palladium and palladium-silver alloys has been found to be from I to 3 ml2. These values were obtained with a solid gold probe at loads of from 25 to 200 grams on coatings having thicknesses in the range of practical interest (0.5 to 2.5 ,urn) on nickel and copper or copper alloy substrates (10, 16, 18). The contact resistance of 50 palladium-so nickel is greater than that of So palladium-20 nickel. These contact resistance levels are similar to or slightly higher than those of clad gold alloys or cobalt hardened electrodeposited golds.

There was little change in contact resistance on ageing palladium coatings in air at iz5OC for 30 days, except for palladium-nickel eiectrodeposits which showed a significant increase at 10 grams contact force (13). The rise may be due to thermal diffusion of nickel from the alloy to the surface where it oxidised to a non-conductive layer. Flash gold coatings on

100

64

19

12

pqlladium and palladium-nickel electrodeposits were found to mitigate such increases as well as to lower contact resistance slightly ( I 3). Palladium and its alloys may be degraded, however, by exposure to chemically aggressive environments which are considered next.

Environmental Effects A major concern in using palladium and high

palladium content alloys for electric contacts is their lesser nobility compared to gold. Contact resistance increases when the forces available for joining contact members are insufficient to penetrate tarnish films, or if the low open circuit voltages of electronic circuits are unable electrically to puncture them. Another potential problem with palladium stems from its ability

Relative Metal Costs by Volume


Where:gold::$500,palladium-$150 and silver..$25 per troy

ounce

to catalyse the formation of tough insulating organic surface layers which originate from traces of organic air pollutants. Considerable research has been conducted recently on both the corrosion and polymerisation problems.

Corrosion and Tarnishing Field exposures of clad inlay palladium,

6opalladium-40 silver, and 40 palladium- 60 silver on copper-nickel-tin alloy substrates were conducted in air-conditioned telephone central offices in the United States and in a non-air-conditioned room of one of the central office buildings located in an urban industrial area ( I 8). Coupons of the materials were returned to the laboratory after exposures of up to 40 months for contact resistance probing, Auger electron spectroscopic examination com- plemented by argon ion bombardment, and X-ray photoelectron spectroscopic analysis (ESCA) (19, 20). It was found that palladium and the palladium-silver alloys were virtually unaffected in the central offices. On the other hand, these materials acquired visible tarnish in the non-airxonditioned location. The films were hydrated palladium chloride in the case of

palladium, and palladium chloride-silver chloride for 60 palladium-40 silver, and 4opalladium-60 silver. Figure 6 gives the chloride film thickness versus exposure time, and their rates of growth fit a parabolic model (19). The total film thickness on 4opalladium- 60 silver was actually greater than shown in the Figure, for it contained both chlorine and sulphur compounds. Since the air pollutants and their levels were similar in the central office and the non-air-conditioned room, it was pre- sumed that the tarnishing was strongly dependent on relative humidity which exceeded 55 per cent for 5 per cent of the time in the non-air-conditioned room and not more than 0.2 per cent of the time in the other sites. The contact resistances of the central office-exposed samples were little different from their initial values, but those of the tarnished samples, especially 40 palladium-60 silver, were significantly higher than in the air-conditioned site.

Other recent field studies are of interest. The alloys, 70 silver-30 palladium, 5 0 silver- sopalladium and 85palladium-15 copper, were exposed for a year in a non-air-conditioned industrial site at Mannheim, West Germany (21). Contact resistance was found to have increased many times for all of these materials, and surface films were rich in chlorine and sulphur. Palladium was exposed in telephone equipment cabinets in a variety of sheltered outdoor sites and in factories where chemical processing took place (22). In several cases, after only one year or less, contact resistance at I 00 grams rose to I ooo f2 or more, this being attributed to the presence of chloride films.

Exposures of palladium and palladium alloys in laboratory chambers have been conducted with a variety of single and mixed gases in concentrations rangmg from less than I ppm up to roo ppm (21, 23-28) with the objective of duplicating field grown films. Procedures involving low levels of chlorine or chlorine and hydrogen sulphide at elevated relative humidity appear to be among the more relevant, and meaningful accelerated tests can be conducted that enable qualification studies to be made of palladium and palladium-silver alloy contacts


(28). An evaluation of clad 39Au3oPd(31- x)Ag(xSn,In) in a mixed gas test showed it to be comparable to the widely used high gold alloy, 7ogold-josilver (17). An interesting study of creep of tarnish films from a copper alloy over the surfaces of gold and palladium with which it was in contact has recently been made (29). This configuration can occur with selectively coated materials such as inlays. In a hydrogen sulphide atmosphere at 50 per cent relative humidity, sulphide creep was significantly greater over gold than over palladium.

To summarise, palladium appears to be stable in many environments provided relative humidity does not exceed 55 per cent. The 6opalladium-40 silver alloy is more noble than palladium, and alloys having 60 per cent or greater silver contents are less noble than palladium. Gold-palladium-silver alloys constitute another class of wrought metals having low reactivity. Sulphur compounds, such as hydrogen sulphide, and parts per billion levels of certain gaseous chlorine compounds, may react with palladium and many of its alloys. Although pure gold is little affected by these environments, creep of tarnish films from adjacent base metals onto palladium may be less extensive than onto gold. Porous palladium would appear similarly to have an advantage over porous gold.

Reactivity of Pal lad ium with Organic Air Pol lutants

Palladium, platinum and rhodium when exposed to room air have been found to acquire fragile films which were determined to be hydrocarbons by pyrolysis gas chromatographic analysis (30). After about one year films on the palladium were 10 nm thick, and using a gold probe a force of 270 grams was required to penetrate the film on polished palladium and to establish substantial metallic contact, defined as a contact resistance below 10 m.0. These observations are in agreement with earlier work in which palladium was exposed at room temperature to organic vapours (3 I) . In comparable conditions gold does not produce such films. It is believed that the platinum group

metals catalyse polymerisation of adsorbed organic air pollutants to produce these insulating layers. The term “static polymer” refers to such films, which differentiates them from “frictional polymers” that are discussed later.

There is some conjecture concerning the practical significance of static polymers on connector contacts. According to one investigator (32), it is possible that plastic materials commonly used in the construction of connector housings and other electronic components may produce volatiles above IOOT which can significantly increase the contact resistance of electrodeposited palladium in their vicinity due to polymer formation. A flash of gold plate on palladium was found to reduce this tendency.

Tribological Properties It is essential that contacts be wear resistant,

since separable electronic connectors may be mated and disengaged many times. Badly disrupted coatings in which base metal substrates and underplates are exposed generally result in high contact resistance, particularly in aggressive environments. It is desirable also that sliding friction be low so as to allow large numbers of contacts to be designed into a connector. Tribology refers to the friction and wear of mated contacts during sliding, and included in this field of study is wear due to fretting which originates in differential expansions of the contact members due to fluctuating ambient temperature, external vibrations, and other causes. Motions of the order of tens of pm may occur which can lead to the formation of insulating frictional polymers on palladium and other catalytically active metals, and to the accumulation of oxidised wear debris in the contact zone once the noble metal coating has worn through.

Sl iding W e a r The basic mechanisms of the wear and

lubrication of metallic contacts have been extensively reviewed by the author (33-37). It is appropriate, however, to identify those aspects of wear that are especially relevani to palladium. Pure wrought palladium-like gold,


Fig. 7 Prow formation on the brush rontart ( 0 . 5 mm diameter) from a slip ring assembly, which ha6 resulted from the accumulation of coarse wear dehris. The ar row indicates Ihe dirertion of rotation of thr ring

silver, platinum and several other contact metals-being relatively soft, is a poor wearing metal. It is prone to cold welding, severe metallic transfer, roughening of the contact surfaces and the formation of coarse wear debris. This mechanism of wear is called “prow formation” from the shape of the transfer material that accumulates on the surface having the smaller area involved in sliding, for example the socket in a pin-socket connector or the brush in an instrument slip ring assembly, see Figure 7. Wrought alloys having a hardness of at least 200 kdmm2 are significantly less prone to wear in this way, and have rates of metal loss which are only a thousandth to a tenth of that of pure palladium at forces used in separable electronic connectors, which typically are from 50 to 250 grams. Thus, 6opalladium-4o silver is a more durable material than palladium (37). Palladium and 60 palladium-40 silver hardened by ion implantation, with several per cent of boron, wore less than the non-implanted metals

Electrodeposited palladium is of interest as a possible replacement for electroplated gold. The comparative wear rates of electroplated palladium and of gold are less well described. Gold deposits containing from 0.1 to 0.3 weight per cent of cobalt, obtained from mildly acid cyanide baths, are the standard against which all other contact metals must be compared

(37).

because of their good wear resistance. Some workers claim that electroplated palladium is superior to electroplated gold (38); other research suggests the opposite ( I 3). A third view is that the durability of palladium electrodeposits depends on the processes from which they are obtained (40), some deposits being comparable to cobalt-gold with other palladium platings being inferior to it. The latter opinion is probably correct and parallels that of early wear studies (41) which were conducted at lightly loaded (3 to 20 grams) conditions using palladium obtained from a variety of electrolytes as well as other metals. What is needed is a comparative evaluation of the behaviour of palladium deposits from modern electroplating systems. The metallurgical and mechanical properties of deposits are process- related, and wear of palladium certainly will be found to depend on characteristics such as hardness, ductility, crystallite size, microcrack density, surface nodularity, and the presence of other metals (such as nickel), as well as on deposit thickness and substrate mechanical properties. The coefficient of friction of palladium electrodeposits depends on the same structural and mechanical factors as does wear behaviour.

Three aspects of the wear and friction of palladium are of special significance to electrical connectors:

I. It is normal to use contact lubricants, and those which are effective on gold, such as polyphenyl ether, appear to be suitable for palladium (6). 2. Palladium mated to palladium is generally unsatisfactory because of frictional polymer formation discussed later. It is more relevant to consider the wear of palladium (wrought, clad, and electrodeposited) when mated to g o l d , e s p e c i a l l y c o b a l t - h a r d e n e d electrodeposits. Early wear results from the British Post Office experiments of the 196os, see earlier, with this combination were encouraging. 3. The effect on wear of using thin (0.05 to 0.25 pm) coatings of gold on thicker palladium underplating is of considerable


interest. Such coatings reduce the rate of wear of palladium and have a salutory effect on its tarnishing (39,42).

Fretting and Friction Yolymerisatian The catalytic properties of freely exposed

palladium can lead to the formation of electrically insulating static polymers. When palladium is mated to palladium and fretting occurs, the rate of frictional polymer formation is much greater than in the static case and high contact resistance often develops (43). It has been postulated that wiping creates fresh surfaces that enhance polymer development and, because fretting displacements are small, there is little chance that contact surfaces will be scrubbed clean.

Practical experience with all-palladium contacts has generally shown them to be poor, but palladium mated to gold appears to solve the frictional polymer problem (8, 44). This is attributable to a tendency for gold to transfer to palladium, which makes the contact system effectively all-gold. This finding also reflects early experience with palladium in relay contacts (43) where the practice of using clad palladium against 22 carat gold-silver, on a palladium substrate, was found necessary to circumvent contact resistance difficulties due to frictional polymer. Alloying palladium with large amounts of non-polymer-forming metals can reduce the polymer problems to manage- able proportions; this is technologically important with many palladium-silver, gold-palladium, and gold-palladium-silver systems (45).

It is important also that contact metals be durable. Thus, the thin palladium and gold- palladium composite coatings of current interest must have low fretting wear rates so as to avoid exposure of base substrate metal. If wear*ut occurs, oxide accumulation due to fretting corrosion also can cause unacceptably high contact resistance (46). The number of fretting cycles required to achieve a given rise in contact resistance due to frictional polymers increases with increasing force, and is inversely related to wipe distance (47).

Recent work has shown that contact

lubricants promote frictional polymerisation (47). Surprisingly, however, contact resistance is much less likely to rise because adhesion of polymers to the contact surface, a necessary requirement for polymer to accumulate, is retarded when lubricants are present. It is possible also that frictional polymers from some organic lubricants are structurally different from those that originate from adsorbed air pollutants on unlubricated surfaces.

Salient facts concerning contact resistance degradation due to the frictional polymerisation of palladium are summarised in Figure 8. Experiments were conducted using an apparatus whose movements could be precisely controlled and contact resistance was determined in small steps across the fretting track. Maximum values of contact resistance in the track are plotted against cycles of fretting for various metal combinations. It is clear that with clean palladium significant increases of contact resistance occurred in air after only 1,000


cycles of fretting on a 20 ,um track. Palladium versus gold is comparable to an all-gold system. Coating with a thin film of a fluid contact lubricant significantly lowered the tendency for contact resistance to rise.

Solderability In many cases it is necessary to join contact

members using tin-lead solders, and solid palladium and palladium electroplates on copper and copper alloys can be easily soldered (48). However, storage of palladium in damp environments prior to soldering may cause poor wetting when non-activated rosin fluxes are used; midly activated fluxes enhance wetting in such cases. Dissolution of palladium in solder is slower than in gold, but with I weight per cent and greater levels of palladium in 60 tin-40 lead solder, brittle joints are obtained. Another

study ( I 3) showed the quality of solder joints to rank in the order: gold (best), palladium and palladium-nickel alloy.

Conclusions T h e contact industry has long been

interested in palladium as a substitute for gold on separable electronic connectors, but only recently has the ratio of the costs of palladium to gold been sufficiently attractive to stimulate serious work on palladium-based materials. New manufacturing processes, novel palladium alloys and composite contact finishes have been developed which are in many applications equivalent i n performance to all-gold systems, while being considerably less expensive. Acceptance of palladium-based contacts is growing, and is a trend that is likely to continue in the foreseeable future.

References

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2 M. Antler, “Kirk-Othmer Encyclopedia of Chemical Technology”, Vol. 8, 3rd Edn., Wiley- Interscience, New York, p. 641

3 M. Antler, IEEE Trans. PHP, 1975, 11, 216 4 F. H. Reid, Plating, 1965, 51, 531 5 P. Preston, British Post Office, private

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Ind. Symp., Am. Electroplaters’ SOC., New York, ‘975, P. 28

7 J. G. Donaldson, Plating, 1974,61, 222

8 W. R. Hain, J. A. Clisura and L. W. Rudloff, Proc. Holm Conf. on Electrical Contacts, Chicago, 1981, p. 241

9 C. J. Raub, Proc. Symp. on Economic IJse of and Substitution for Precious Metals in the Electronics Ind., Am. Electroplaters’ SOC., Danvers, Mass., 1980

10 R. J. Morrissey, Plating S u f . Finish., 1980, 67,

11 J.-M. Locarnini and N. Ibl, Proc. Second Int. Pulse Plating. Symp., Am. Electroplaters’ SOC., Roscmont, Ill., Oct. 1981

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Symp. on Economic Use of and Substitution for Precious Metals in the Electronics Ind., Am. Electroplaters’ Soc., Danvers, Mass., 1980

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Electrochem. SOC. Meeting, Denver, Oct. I 98 I

16 R. J. Russell and R. 0. Capp., Insul.lCircuiis, Mar. 1981, p. 34

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18 M. Antler, M. H. Drozdowicz and C. A. Haque, IEEE Truns. Components, Hybrids Munuf. Technol., 1981, CHMT-4, (4), 482

19 C. A. Haque and M. Antler, Proc. Holm Conf. on Electrical Contacts, Chicago, 1981, p. I 83

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and K. L. Schiff, Proc. Ninth Int. Conf. on Electric Contact Phenom., Chicago, 1978, p. 273

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23 S. Shimosato, Electron. Commun. Jpn., 1972,

24 W. H. Abbott, Proc. Holm Seminar on Electrical Contacts, Chicago, 1973, p. 94

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26 M. Antler and J. J. Dunbar, op. cit., ref. 18, 1978, CHMT-I, 17

27 L. Borchert and M. Murr, Proc. Tenth Int. Conf. on Electric Contact Phenom., Vol. 11, Budapest,

28 S. P. Sharma and E. S. Sproles, Proc. Holm Conf. on Electrical Contacts, 1981, p. 203

29 I<. R. Conrad, Proc. Annu. Connectors and Interconnections Symp., Philadelphia, Nov.

1981, P. 89

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30 A. Fairweather, F. Lazenby and D. Marr, Trans.

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Contact Phenom., Chicago, 1978, p. 619 33 M. Antler, Platinum Metals Rev., 1966, 10, (I), 2

34 M. Antler, IEEE Trans. PHP, 1973, 9 ,4 35 M. Antler, up. cif., ref. 18, 1981, CHMT-4, (I),

1s 36 M. Antler, “Fretting of Electrical Contacts”,

Symp. on Mater. Eval. Under Fretting Condi- tions, Natl. Bur. Stand., Gaithersburg, Md., 3 June I 98 r , (ASI’M Spec. Tech. Publ. No. 780)

37 M. Antler, C. M. Preece and E. N. Kaufmann, op. cif., ref. 18, 1982, CHMT-5, (I), 8 1

38 H. Grossman, Trans. Imf. Met. Finish., 1978, 56, 54

39 T. Sato, Y. Matsui, M. Okada, K. Murakawa, and 2. Henmi, op. cit., ref. 18, 1981, CHMT-4, (I), 10

Inst. Met. Finish, 1976,54, 145 40

47 42

43

44

45

46

47

48

J. N. Crosby, Proc. Symp. on Economic IJse of and Substitution for Precious Metals in the Electronics Ind., Am. Electroplaters’ SOC., Danvers, Mass., r.980 H. C. Angus, Instrum. Prac., 1966, 20, 241 H. Grossmann and M. Huck, Proc. Tenth Int. Conf. on Electric Contact Phenom., Vol. 1, Budapest, I 980, p. 401 H. W, Hermance and 1‘. F. Egan, Bell Syst. Tech.

E. S. Sproles, Proc. Annu. Connectors and Interconnections Symp., Philadelphia, Nov., 1 9 8 1 , ~ . 267 W’. A. Crossland and l’. M. K . Murphy, IEEE Trans. PHI‘, 1974, 10, (I), 64 M. Antler, Proc. Electronic Components Conf., San Diego, Cal., May 1982 M. Antler and E. S. Sproles, op. cit., ref. 18, 1982,CHMT-5,(1), 158 R. G. Rader, op. cit., rrf. 40

39 ‘ 9 5 8 , 3 7 , 739

A New Platinum-Wired Air Flow Meter FUEL ECONOMY OF PETROL INJECTION ENGINES IMPROVED

‘The possibility of determining the velocity of air by measuring the electric current required to keep a resistance wire at a given temperature was suggested early this century by A. E. Kennelly and his colleagues, and was soon developed independently by a number of investigators. In I 9 14 work by Professor I,. \:. King of McGill University on the convection of heat from small cylinders in a stream of fluid was reported to the Koyal Society (Philos. Trans. R . Sac., London, Series A, 1914, 2x4, 373). His experiments had been undertaken to study the laws of convection of heat from thin platinum wires heated by an electric current, in order that the results could be used in the design of an anemometer capable of accurately measuring wind velocity. However his linear anemometer was considered to be useful for a number of applications including studies of tur- bulent flow and of air velocities in the neighbourhood of aeroplane surfaces and revolving blades, and for the measurement of temperatures and velocities of heated gases, or of flames.

Since that time the principle involved has been applied to an increasing number of‘ uses. Now a hot wire air mass meter is being developed by Robert Bosch GmbH of Stuttgart, \ h c t Germany to measure the mass of air drawn into automobile petrol injection engines and thus, with appropriate systems, to optimise the air to fuel ratio and hence fuel economy

-*,,

while limiting exhaust emissions (K. Sauer, S.A.E. Technical Paper 800468).

In the new meter a 70 micron diameter platinum wire forms part of a Wheatstone bridge circuit where the output voltage is held steady by regulating the heating current. Any increase in air flow cools the wire and causes a resistance drop. ’l’his is corrected within milliseconds as a controlled increase in the heating current signals the mass flow rate of the air and brings the platinum wire back to its former temperature. ‘1.0 allow for changes in the temperature of the intake air a temperature compensating resistor is located in the air stream. This has to be stable, corrosion-proof and fast responding, therefore a platinum film resistor is employed.

A disadvantage of the hot wire anemometer has always been the effects of dirt building up on the wire. Now the quality of the platinum employed enables this problem to be overcome by a process,that burns off the organic matter, and removes any inorganic particles embedded in it. This involves heating the platinum anemometer wire to a temperature of 800 to IOOOT for one or two seconds immediately after the engine has been stopped. A most important contribution to the overall performance is the quality control of the platinum wire by automatic and continuous monitoring of mechanical integrity, electrical resistance and its temperature coefficient. T h e process is now being optimised by vehicle testing.


Platinum Electrocatalysts for Phosphoric Acid Fuel Cells A t the Spring Meeting of the Electrochemical Society, held in Montreal, Canada during May, twenty-three papers were presented on a variety of topics concerned with fuel cell development. The trend in electrocatalysts for this application is clearly towards platinum alloys rather than to alternative metals.

JMOSt of the emphasis at this symposium was on the more efficient use of platinum electrocatalysts particularly when used in oxygen electrodes for aqueous electrolyte fuel cells either of the acid or alkaline type. The alternative catalyst systems discussed were either considerably inferior in performance to those based on platinum or at a very early stage of development.

P. N. Ross Jr. of the Lawrence Berkeley Laboratory, IJniversity of California summarised the improvements made in platinum catalysed fuel cell electrodes over the last fifteen years. Most notable of these were: [i] A 40-fold reduction in the overall platinum loading in a phosphoric acid fuel cell had been achieved initially by moving from platinum black to catalysts dispersed on conductive carbon supports, and subsequently by improving the supported catalyst technology. [ii] An extension of electrode and consequently cell stack life by more than an order of magnitude. [iii] A four- fold reduction in voltage losses due to cell resistance and diffusion polarisation.

Typical platinum loadings for electrodes based on platinum on carbon black type supports arc now o.z5mgicm2 on the anode and o.5mg/cm2 on the cathode. Cell performance with these electrodes at 177°C is about 0.65V at zzom&'cm2 at 80 per cent hydrogen utilisation and 2.5 times stoichiometric air at the beginning of life. Decay rates are typically 10mV per 10) hours under constant load. Studies indicate that voltage losses in the air cathode are due to gas phase and ionic diffusion and not the liquid phase diffusion of dissolved oxygen. There is a negative platinum crystallite size effect for

oxygen reduction with carbon supported platinum in phosphoric acid at elevated temperatures indicating that there is little benefit to dispersion of platinum below about z d crystallites. The degree of wetting of the catalyst in electrodes which have small liquid diffusion losses is typically around 80 per cent.

Platinum Alloy Catalysts Ross concluded that there was at most 20 to

30mV to be gained by refinement in air electrode structures using the platinum supported catalyst. However alloy supported catalysts, particularly platinum-vanadium and platinum-tantalum are more active by a factor of four to five than those with platinum alone. Initial results show a 20 to 30mV improvement in air cathode potential at 2oomA/cm2. The gain in catalytic activity may eventually lead to a factor of two reduction in catalyst loading at the cathode.

Further information on these new platinum alloy catalysts, which seem likely to form the next generation of fuel cell electrocatalysts, was provided by V. Jalan (Giner, Inc.) although only in abstract form as the paper was not presented. These alloy systems are prepared by soaking a carbon supported platinum catalyst in either a colloidal dispersion of the base metal oxide or in a base metal salt solution, which subsequently reacts to deposit highly dispersed metal oxide/hydroxide onto the support. In either case the mixture of supported platinum and metal oxide is heated to about 900°C in an inert atmosphere.

Alloy catalysts comprising platinum with each of aluminium, cerium, silicon, strontium, titanium, tungsten and vanadium were reported.

Hutinurn MetuZsRev., 1982, 26, (3), 118-120 118

All have greater activity for oxygen reduction in phosphoric acid than the platinum only system, with platinum-vanadium being the most active. Furthermore this superior activity was maintained over 10,ooo hours testing. This improved stability appears to be related to a lower rate of loss of metal area for platinum alloy catalysts.

A subsequent paper by P. J. Hyde, C. J. Maggiore and S. Srinivasan at the Los Alamos National Laboratory, however, described the use of Ion Beam Analysis to study both new and aged electrode systems, and showed that the vast majority of the vanadium migrated from the cathode to the anode over 3000 hours. Thus platinum-vanadium is unlikely to be the optimum alloy system.

Another unpresented paper by V. Jalan discussed the deposition of a thin carbon layer on and around carbon supported platinum particles which is achieved by heating a platinum on carbon catalyst at 360°C under a carbon monoxide atmosphere. This inhibits migration of platinum particles and improves electrode stability. It should be noted that all of Jalan’s work quoted for the symposium is the subject of patents held by I!nited Technologies Corporation. M. F. Weber, M. J. Dignam and R. D. Venter, of the University of Toronto, presented a paper on preliminary work aimed at catalyst preparation using sputtering techniques. Much development would be required to turn this into a practical production method.

Fuel Cell Electrolytes A number of papers dealt with the interac-

tion of oxygen with platinum at the cathode and the mechanisms involved for both acid and alkaline electrolytes. Despite some good physical and chemical properties, concentrated phosphoric acid is an indifferent fuel cell electrolyte due to the marked irreversibility of the dioxygen reduction reaction in this medium even at 200OC. E. Yeager, J. C. Huang and S. J. Clouser of the Case Western Reserve IJniversity examined the dioxygen reduction mechanism in purified phosphoric acid at various temperatures from 25 to 250°C. Direct reduc-

tion to water is the predominant path with only 5 per cent proceeding via hydrogen peroxide production at room temperature with virtually no peroxide detected at the high temperatures. Absorbed impurities tend to increase the hydrogen peroxide yield while slowing down the overall reduction. Studies at high polarisation suggest that a first electron transfer step is rate controlling.

Yeager and E. J. M. O’Sullivan (Case Western Keserve IJniversity) reported results of preliminary studies on alternative electrolytes, namely fluoronated acids. Most of the results reported were for monofluorophosphoric acid which is the most stable of the fluorophosphoric acids, although not sufficiently stable to hydrolysis for high temperature application. It is a stronger acid than phosphoric acid and less likely to be strongly adsorbed. The fluoro system gave high dioxygen diffusion limiting currents, more than an order of magnitude greater than for phosphoric acid. The authors concluded that the apparently high overall catalytic activity in monofluorophosphoric acid was caused by a higher dioxygen solubility. These results give impetus to the search for a stable pure fluoro acid electrolyte.

Papers by S. Sarangapani and I,. (3. Edwards of the IJnion Carbide Corporation and J. Molla and E. Yeager (Case Western Reserve University) considered the reduction of dioxygen on various carbon surfaces in alkaline electrolytes. In the absence of a catalytic metal the reaction proceeds largely through a peroxide intermediate. The first mentioned authors described a model for estimating the surface concentration of peroxides when using different carbons at the cathode. The second paper compared results for a carbon (Ket- jenblack) with and without platinum, and showed that the platinum was catalysing the direct reduction to water as well as caialys- ing the reduction and decomposition of peroxide. The nature of the carbon affected the ability of peroxide to escape from the pore structure prior to electrochemical or heterogeneous catalytic decomposition.

Relatively few alternatives to platinum


electrocatalysis were discussed. R. R. Durand Jr. and F. C. Anson of the California Institute of Technology, Pasadena, presented studies on co-facial dimeric cobalt porphyrins. These have the advantage of catalysing the four-electron reduction of dioxygen to water without peroxide formation while the reaction proceeds at unusually positive potentials in acidic electrolytes. However, dimers in the correct orientation are difficult to make and the chemical stability needs to be greatly improved before use at I 8o°C could be contemplated.

In situ Mossbauer spectroscopy studes of iron phthalocyanine (FePc) absorbed on high surface area carbon electrodes were presented by D. A. Scherson, S. B. Yao, E. Yeager, J. Eldridge, M. E. Kordesch and R. W. Hoffman (Case Western Reserve University). The aim of the work was to gain insight into the stability problems of metal macrocyclics. The preliminary conclusion is that electrodes with polycrystalline FePc show superior activity to adsorbed species in monolayer form.

B. C. H. Steele, W. J. Albery and E. J. Calvo of the Imperial College of Science and Technology, London presented studies on lanthanum-nickel perovskites as potential oxygen electrocatalysts. Steady state oxygen reduction curves for LaNiO,, La,NiO, and La,NiO, enriched phases show comparable activity to platinum but with low limiting currents. Rotating ring disc electrode studies confirm that this is due to the oxygen adsorption step being rate limiting. This appears to be a general feature for perovskite oxides which are therefore unlikely to be viable alternatives to platinum for this application.

Novel Solar and Fuel Cell System A different application area for fuel cells and

platinum catalysts was described in a paper by G. G. Barna, S. N. Frank and T. H. ‘I’eherani of Texas Instruments Inc. This involves domestic heat’ and power generation using a novel solar pulsar system. Generator panels comprise silica semiconductor spheres which electrolyse IIBr using solar energy to produce hydrogen and bromine which are stored and fed to a H,/Br,

fuel cell when electricity is required. The oxidation of hydrogen on platinum, in 48 per cent HBr is kinetically controlled and carbon supported platinum catalysts are required for optimum platinum usage. Optimisation of the fabrication process has led to small scale platinudcarbon anodes with limiting currents approaching the calculated kinetic limits. However a major problem is the lack of scaling of these limiting currents as the hydrogen partial pressure is increased to IOO per cent. Current studies are aimed at altering the nature of agglomerated catalyst by varying the colloid chemistry of the catalyst suspension and the type of carbon support. ’The development of this novel combination of solar energy and fuel cells will be followed with great interest.

Platinum Availability M. J. Cleare of Johnson Matthey reassured

the meeting as to the availability of platinum for use in electrocatalytic systems in general and fuel cells in particular. Reserves in active mines comprise 13,000 tonnes while a further 20 to 30,000 tonnes are estimated to be in presently unexplored deposits. The installation of 30,000 MW of phosphoric acid fuel cell capacity in the U.S.A. during the decade 1990 to 2000 would represent a requirement of around I 5 tonnes of platinum per annum. This represents I 5 per cent of world production and 28 per cent of predicted U.S. platinum usage in 1988. This should be compared with current platinum usage in automobile catalysts which is in excess of 50 per cent of U.S. consumption. Lead times of 18 to 24 months are required to establish new supply capacity and should present no problems in fulfilling requirements in advanced technology areas, which can be monitored during the many years they take to develop.

The symposium was well attended consider- ing it was one of fifteen symposia taking place in parallel. There continues to be great interest in the theory and practice of phosphoric acid fuel cells. The trend in electrocatalysts for these is undoubtedly towards platinum alloys rather than alternative metals. M.J.C.


The Palladium-Hydrogen System P A R T 111: ALLOY SYSTEMS A N D HYDROGEN PERMEATION

By F. A. Lewis 'Ilie Queen's I 'nibersity of Belfast

Hydrogen absorption b y series of palladium alloys with s e v c d other metals has nou: b p e r i quite c.xtcnsiwIy invesligated with rcjference to systematic alterations o,f pressurr- co m p os i t io n o t h e r rrlated thermodynamic factors and 2: a r io us p a r a rn P t e r s . Ilydrogen permeation has b r w i an important area o,f both academic rind technological intercJst with relation, f o r examplP, to ( f f w t i n g reductions of dqformations asaoriaird with phasp transitions, whilr rptairiing thr high calues of hydrogen solubilities nnd hydrogcm ditfusion coefficients in palladium at convc:nicmt tcmp(Jraiuros.

r e la t io ns h ips,

p h y s ic a 1

Characteristic examples of three types of change of form of p n relationships at 25T, as the contents of elements alloying with pa l lad ium a r e gradual ly increased (4,37,70,74-83,95-98,~04,108,153,154), are illustrated in Figure 9. As for the palladium- hydrogen system itself (4), such relationships have been determined from direct equilibrations with hydrogen gas, as well as being derived from measurements of electrode potential. Similarly as for palladium-hydrogen, temperature dependences of the p n relationships have been used to supplement calorimetric data ( I 10) in deriving heats and cntropies of hydrogen absorption, both at initially low values (79-82,95,100,108) of hydrogen content (n- to) and over (Y = p transition regions

The sequence of relationships in Figure 9(c) (4,37,70,74-83,'04,I54,I78).

shows gradual increases with increasing rhodium content in the range o f n over which (Y

and /J' phases coexist. This sequence now seems unique to the palladium-rhodium-hydrogen system (45,75, I 53,154), since some suggestions of similarities of the palladium-manganese- hydrogen system (179) seem doubtful in view of possible incomplete equilibrations.

'The remaining families of p n isotherms for palladium alloy-hydrogen systems would thus seem to be divisible into two groups represented by those in Figures 9(a) and 9 (b). In both cases the ranges of n over t i + p phase regions are successively shortened with increasing content of the alloying element, even in the cases of alloys with readily hydride-forming transition or inner transition elements such as vanadium ( 8 2 ) or cerium (76), but the corresponding values of equilibrium pressure are being successively increased (74,794 1,82), as in Figure 9(a), or decreased (37,70,75,80), Figure 9(b).

Decreases, in the range of n over (r +/I regions, with increasing amounts of alloying elements, have continued to be deduced from X-ray determinations of and /3 phase lattice constants for additional palladium alloy- hydrogen systems (4,79-82,157, I 80-1 82).

Apart from the probable case of the palladium-nickel-hydrogen system (so), these general trends of decreasing extents of ( Y , p coexistence with increasing contents of alloying element are similar to the effects of increasing temperature in the palladium-hydrogen system, being accompanied by decreases in the extents of hystereses of absorption and desorption relationships between hydrogen contents and other experimental parameters (4,69,96-98). This has been taken as complementary to decreases in the value of critical temperatures for two phase coexistence and, as discussed


later, has importance in choices of alloy compositions as hydrogen permeation membranes.

In addition to the arguments concerning the solubility of hydrogen in the palladium-silver alloys, the extents of decreases of hydrogen solubilities with increasing contents of other alloying metals have been used (95,104,108) in support of an essentially protonic nature of the hydrogen entities. However, in order to allow for proposed levels of electron donation it has seemed necessary to postulate adoptions of oxidation states by the alloying elements which can be difficult to reconcile with their relative positions in sequence of electronegaiivities.

Moreover as for the palladium-hydrogen system, latterly there has been increasing emphasis on the account to be taken of lattice expansions accompanying hydrogen absorption (26,37,166) in palladium alloys. There has also been attention to the localised as well as to the continuing effects of the alloying metals as exemplified by appearance, potential measure-

ments ( 1 83) and by Mossbauer Spectroscopy examinations ( I 33,180,184,185). For example, evidence of preferential location of hydrogen around rhodium atoms (186) might be correlated with wider ranges of (Y and /3 phase coexistence with rhodium content in the palladium-rhodium-hydrogen system in Figure 9(c). A particular example of the significance of differences in the distribution of alloying atoms has been provided by measurements, made under high pressures of hydrogen, of changes of electrical resistivity of a palladium-iron alloy of approximate composition Pd,Fe ( I 87). Figure I o illustrates the substantial differences between the ranges of pressures (hydrogen chemical potentials) over which evidence was found of significant hydrogen absorption in ordered and disordered structures of the alloy.

The two main families of p n isotherms illustrated in Figures 9(a) and 9(b) also differ from one another in regard to the direction of changes of the heats of hydrogen absorption with alteration of' alloying metal content (4,37,70,74-76,79-82,100,178), relative to heats of hydrogen absorption in pure palladium. Thus those alloys with the pattern of Figure 9(b) in general exhibit more exothermic heats of hydrogen absorption than palladium, both at infinite dilution (n + 0) and over regions of (r and B coexistence, while the converse ;less exothermic heats of absorption than palladium) appears generally true for alloy series associated with families of p n isotherms as in Figure 9(a).

Attempts to provide underlving reasons have so far stressed two alternative ways by which the different series of alloys may themselves be divided. In one line of argument (100,178), emphasising differences in electronic structure, it has been pointed out that patterns similar to Figure 9(a) are followed by alloys formed by palladium with other transition elements, and those of Figure 9(b), accompanied by more exothermic heats of hydrogen absorption, tend to occur with alloys of non transition elements.

An alternative division (76, 82, 100) has been based on findings that the patterns of p-n relationships in Figure 9(b) are followed by alloys of palladium with elements which


reported has been - I 7 K with a Pd,,Cu,, composition (46). With increasing content of alloying element in several alloy series the transition temperature passes through a maximum value and, as for PdH,(D,), plots of transition temperature against hydrogen content also exhibit maxima (46). Recent studies with palladium-silicon alloys ( T 91) have shown that superconducting transitions also can be found with amorphous materials.

For many of the investigated palladium alloy-hydrogen systems, the alloy element can only be considered 10 be in solid solution up to relatively low limits of concentration (37,75, 80,82,85,108,133,180, I 81,189,190,192,193), and only a few studies have so far been reported produce overall average increases of f.c.c. lattice

constants (“expanded alloys”) and vice versa. Since additions of platinum to palladium produce very small increases of lattice constant ( I 88), the palladium-platinum-hydrogen system constitutes a marginal exception to this latter division. However, it may be possible that differences of elastic constants provide a decid- ing feature in this case. In explanations based on size factors, it might be argued that atoms of alloying elements causing increases of lattice parameters in an elastic medium could produce overall expansions in the volumes of interstices which could result in lower energies being required to introduce hydrogen, as reflected by the high exothermic heats of hydrogen absorption. It is in any event interesting, as illustrated in Figure I I , that relative extents of increases of initial lattice parameter with contents of alloying element, quite closely parallel extents of decreases of isobaric ( J atm) hydrogen solubilities in such chemically diverse sub- stitutionally alloying metals as cerium (76), silver (70-72,86,95-98,r04,160), lead (80) and with interstitially incorporated boron (37, T 89).

Occurrences of superconducting transitions at very high contents of hydrogen have been studied with several series of palladium alloys. In some series higher transition temperatures have been recorded than with pure palladium (46,r 43,r 90), and again slightly higher values have been found for corresponding deuterides (46). The highest transition temperature so far


with higher alloy percentage intermetallic

However, palladium can form binary alloys with certain neighbouring elements also crystallising in the f.c.c. structure, which approximate to solid solutions over the entire composition range.

In principle these systems have offered possibilities of studying gradual changes in alloying behaviour from pure palladium to that of the pure alloying element. In practice this has required extension of studies into the range of high hydrogen pressures, which at upper limits correspond to particularly high fugacities (45,196). Here, difficulties of making direct measurements of hydrogen contents have so far required that these are inferred from changes in

phases (1 94, I 95). physical properties such as thermoelectric power (50,197) and electrical resistivity.

Examples of relationships derived between electrical resistivity and high hydrogen pressures obtained with three such series of alloys (45,50,68,69,154,196), combined with data previously derived over lower ranges of pressure (4,70,75), are illustrated in Figure 12.

The somewhat complex case of the palladium-silver-hydrogen system (70,r 96) in Figure I 2(a) at 25°C illustrates, in keeping with the family of p n isotherms in Figure 9(bj, that initial increases of silver content are associated with pronounced changes of resistivity, complementary to regions of i i + /3 transitions or quasi transition, at increasingly lower pressures than for the ( Y -/I transition for pure palladium.


This trend may be seen to continue for compositions of up to approximately Pd,$g,,, but for still higher silver contents significant changes of resistivity only become perceptible at increasingly higher pressures, as shown by the examples of Pd,,Ag,, and Pdlag81. These provide an indication that substantial absorg tion of hydrogen by pure silver should only occur at 25°C a t hydrogen pressures in excess of 30 kilobars.

Trends in the form of relationships for the palladium-rhodium-hydrogen and palladium- platinum-hydrogen systems (50,68,69,154) in Figures I 2(b) and (c) are somewhat more simply continuous in appearance.

In the case of the palladium-rhodium- hydrogen system ( I 54), measurements of approximate hydrogen contents attained under high Eydrogen pressures have endorsed indications from the persistence of the hysteresis effects illustrated in Figure rz(b) that (1 e p phase hydride transitions continued to occur for alloying contents up to 80 per cent rhodium. These findings suggested the possibility of the formation of a P-phase hydride by pure rhodium at still higher pressures, and subsequent analogous studies of resistivity changes at 250°C have since indicated the formation of such a rhodium hydride at pressures in the region of 40 kilobars (I 55).

Figure I 2(c) illustrates, for the palladium- platinum series of alloys, that continuously increasing hydrogen pressures again are needed to effect significant hydrogen absorption as platinum contents are increased (68,69). This is consistent with trends in p-n relationships (474) similar to those in Figure 9(a) which also would be consistent with universal decreases of hydrogen solubility with increasing hydrogen content at any given reference of hydrogen pressure at 25°C.

In contrast to the pattern in Figure 12(b) for the palladium-rhodium-hydrogen system, Figure I 2(c) also illustrates a gradual reduction of hysteretic differences between “absorption” and “desorption” relationships with increasing platinum content. Again this is consistent with indications from p n relationships and X-ray

studies (4,50,69,74) of complementary decreases of the critical temperature of rn and P phase coexistence to around zs”C, for platinum contents of about 25 per cent. However the resistivity changes with hydrogen pressure in Figure 12(c) also provide evidence of a con- tinuation of substantial hydrogen absorption by alloys with platinum contents much higher than 20 per cent, over what have been termed regions of quasi two phase coexistence (68). Even for an alloy containing 70 per cent platinum, the onset of what would seem likely to be a further such region of absorption has been detected at hydrogen pressures of around 30 kilobar (50,69). Extrapolations of available data have suggested that analogous absorptions of hydrogen by pure platinum could be expected to occur at hydrogen pressures of near IOO kilobar, at 25°C.

For the palladium-platinum alloys with 2 20

per cent platinum, the absence of hysteretic effects and accompanying lower levels of macroscopic deformation in cycles of absorption and desorption of hydrogen have been found to be of some practical advantage. Because of this, measurements of changes of the electrical resistivity of certain palladium- platinum and other suitable alloy compositions have been usefully employed for repetitive analytical determinations of the solubility of hydrogen in solutions (4,198), and for estimating high values of hydrogen chemical potentials in electrochemical studies (39,50,62).

Hydrogen Diffusion Coefficients and Hydrogen Permeation Studies

Determination of diffusion coefficients of hydrogen in palladium have now been extended over a wide range of temperatures by a variety of techniques. These include, in addition to derivatives from steady rates of hydrogen permeation across a known concentration gradient and from breakthrough times related to detec- tion of hydrogen at the side of membranes remote from hydrogen introduct ion (4,7 I-73,86,89,104, t 69), phase boundary independent methods such as nuclear magnetic resonance (4, I 04,200), Mossbauer studies ( I 84),


q u a s i e l a s t i c n e u t r o n s c a t t e r i n g (29, I 18, I 36,163-1 65,201) and anelastic Gorsky Effect measurements (51,169-173). At very low ix phase hydrogen contents, a large measure of agreement now exists between values derived by the various methods (104,202). At 25°C these are of the order of I o -‘/cm2/s representing an average value over the narrow a phase range of contents within which the only reported trend has been that of a slight decrease with increasing hydrogen content (86). Only a few studies have been reported of hydrogen diffusion coefficients in platinum but these (57,58,203,204) have suggested values of approximately two orders of magnitude lower (say ~ o ~ ’ / c m ~ / s ) than in palladium, near 25OC.

Values of about ro-h/cmz/s have been derived for the Fick hydrogen diffusion coefficient in p

phase palladium hydride for hydrogen contents of 11-0.7 (4,71,72,86). Such values are thus about an order of magnitude higher than the a phase values. However studies of breakthrough times (86) and of relaxation times associated with changes of electrical resistivity at high pressures (45,205) have indicated that at still higher hydrogen contents there are marked decreases of diffusion coefficient. These have been attributed to “blocking” of the diffusion process due to reductions in the numbers of vacant octahedral interstitial positions (206).

Academic interest has been sustained in correlations between Fick and Einstein diffusions coefficients (7 1,72,86,104,17 I), differences between values for the three hydrogen isotopes (including the finding over a wide temperature range of higher values for deuterium than protium (hydrogen)) ( 5 1,104,


I 7 I ,204), and problems of interpretation at low temperatures ( I 8,51,169-171,201,207,208), and near ohase transitions and critical points

Much interest also has continued in the method of hydrogen purification by its permeation through palladium alloys. As quite recently reviewed by Knapton (209), a wide variety of alloys already have been proposed for this purpose, and others continue to be examined (2 10). Factors which influence practical utilisation include those of resistance to poisoning of surface catalytic activity, suitable mechanical properties over desirable ranges of temperature, and also convenience of manufacture- including quality control.

Other basic considerations are that concentrations of the alloying element should be sufficient for critical temperatures, corresponding to (I and phase coexistence, to be decreased to ambient or below in order to reduce deformation in cycles of use (4,62,96-98, 104,158,176,181), and that diffusion coefficients and solubilities of hydrogen at convenient input pressures should both continue to have high values.

In regard to values of diffusion coefficients, characteristic examples in Figure I 3 show that initial, small percentage, additions of most binary alloying elements (77,78,85,86,97,98, 104,170,173,~81,206) produce only relatively small decreases from values (at 25OC) for pure palladium-when compared at low values of hydrogen content, that is as n + 0.

Sustained or increased hydrogen solubilities at convenient input pressures and temperatures are features generally associated with palladium alloy-hydrogen systems exhibiting similar sequences of changes of form of p n isotherms to those in Figure 9(b) and also for a specific case in Figure I 3. As examples of this group of systems, compositions from the palladium- boron series (37,211,212) and from series of alloys of palladium with transition metals of Subgroup 111 and the closely allied lanthanide series have been suggested for practical utilisation, the palladium-yttrium system being a promising example (I 8 I ,z I 0). The palladium-

(36,86,104,17 1).

gold (207) and, as illustrated in Figure 9(b), the palladium-silver series (4,95,96) alloys also belong to this general class of systems. Com- positions from the latter series such as Pd,,Ag,3 and Pd,,Ag,, have continued to be widely employed as commercially suitable materials, although certain measures of deformation still have been observed after many cycles of use (98,160,21 I). Several studies of both hydrogen and deuterium diffusion coefficients in these c o m p o s i t i o n s h a v e b e e n r e p o r t e d

For the palladium-silver series of alloys measurements have been reported of gradual changes of diffusion coefficient with changes of hydrogen content, principally by the electrochemical breakthrough technique (86,104,2 14). For alloys with relatively high contents of silver, such as Pd,&g,, and Pd,,Ag,,, results (86,104) show a continuous increase of diffusion coefficient with increasing hydrogen content from initially lower values than those of pure palladium at n + 0; this is consistent with trends suggested by studies of the shifts with temperature of internal friction peaks associated with Zener relaxation effects (97, I 27,2 I 6). However, for compositions near to I'd,,AgZ3 two alternative trends of change of diffusion coefficient have been suggested from results so far available (97) as diagrammatically represented in Figure I 3.

(71,72,85,86,170,214,215).

Some Concluding Comments The last two decades have seen substantial

expansions of experimental information concerning the palladium-hydrogen system over wider ranges of temperature and pressure, with generally increased precision of the measurement and control of hydrogen content. Several further physical parameters have been studied.

These advances have taken place against a background of much increased levels of activity in the research field of metallic hydrides formed by other transition elements and alloys, with which a need for correlation of ideas concerning chemical binding, including the gradual modification of bond type from those of the alkali, alkaline earth, lanthanon and actinon


hydrides, has now been increasingly appreciated. stress and spatial influences on neighbouring In regard to structural considerations, there palladium atoms, with reference to such issues

has been increasing attention to evaluation of as mechanisms of diffusion, isotope effects,

the effects of introduction of individual phase transitions and associated hysteresis and hydrogen entities, in regard to their localised gross deformational phenomena.

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(2)>44

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( 2 l ‘49 ‘Frankfurt am Main]

The Life and Work of Nikolai Semenovich Kurnakov A FOUNDER OF THE RUSSIAN PLATINUM INDUSTRY

By Professor George B. Kauffman California State University, Fresno, U.S.A

For more than six decades, Nikolai Semenovich Kurnakov, one of Russia’s most distinguished and versatile chemists, was an active force in the development of science and technology both in his homeland and abroad. He is regarded as the founder of a new chemical discipline, physicochemical analysis, probably the largest contemporary school of Soviet chemistry with applications in numerous branches of technology (1-23).

A beloved teacher as well as a creative theorist and experimentalist of the first rank,

Kurnakov organised and served as director of a number of laboratories, research institutes, and national and international commissions. He was largely responsible for the construction of several new chemical, mining, and metallurgical plants and was a pioneer in the systematic exploitation of Russian mineral resources, especially platinum, potassium, and magnesium. His more than 200 published articles and texts testify to his immense productivity in the widely-scattered fields of mineralogy, metallurgy, metallography, and

Nikolai Semenovich Kurnakov 1860-1 94 1

This internationally recognised scientist, regarded as the originator of physicochemical analysis, was one of the principal founders of the platinum industry in the U.S.S.R. His discovery of the reaction still used to differentiate cis from trans isomers of divalent platinum is his best- known contribution to co-ordination chemistry t’hutograph b\ I V U T ~ P U 01 the late Ararlem~nan I I Lhrrnram


salt technology, and inorganic, analytical, organic and physical chemistry. Through his active participation in scientific, public and governmental affairs, he became a public figure and a recipient of numerous honours.

Nikolai Semenovich Kurnakov was born in Nolinsk, Vyatka province, on December 6, 1860. From 1871 to 1877 he received the equivalent of a high school education at Gorki, and following this he entered the Saint Petersburg Mining Institute where independent research under chemists Sushin and Lisenko and mineralogist Yeremyev resulted in his first publication, a crystallographic study of alum and Schlippe’s salt (Na,SbS4.9H,0). After graduation in 1882, with the degree of Mining Engineer, he was retained by the chemical laboratory of the institute.

Kurnakov’s interest in chemical industry would not permit him to remain exclusively a laboratory worker, and he now began the first of his many trips to plants, factories, smelting operations and laboratories. A detailed study of salt manufacturing in Prussia, Lorraine, Wurttemberg, Baden, Bavaria and the Austrian Tyrol, made in the summer of 1884, resulted the following year in his dissertation for the position of Assistant in metallurgy, halurgy (salt technology), and assaying, a post which he held for eight years. This work, “Evaporative Systems of Salt Boilers”, containing the germs of Kurnakov’s subsequent studies of salt equilibria, appeared long before van’t Hoff s research on the Stassfurt salt beds.

Kurnakov’s Reaction

In 1893 Kurnakov was appointed Professor of Inorganic Chemistry following the successful presentation of his dissertation “On Complex Metallic Bases”, in which he described the reaction of Pt(I1) and Pd(I1) isomers with thiourea, now known as Kurnakov’s reaction (24). In I 899 he was appointed Professor of Analytical Chemistry at the Mining Institute and organised the teaching of physical chemistry at the Saint Petersburg Electrotechnical Institute, where he taught until 1908. In 1902 he was appointed Professor of General Chemistry at

the Saint Petersburg Polytechnic Institute, which he had organised together with Mendeleev and Menschutkin, and he held this post until 1930.

During the first decade of the 20th century, Kurnakov was concerned with the solution of industrial problems such as platinum refining, metallic alloys, metallography, and salt manufacturing, and he played a vital role in the planning and construction of new laboratories at the three institutes.

In 1909 Kurnakov was awarded the degree of Doctor of Chemical Sciences honoris causa by Moscow University, became a contributing editor of the Zeitschrqt fur anorganische Chemie, and was appointed a member of the Mining and Scientific Committee. In 1910 he directed studies of the Russian Council on Platinum Refining, and the following year he went abroad to study methods of transporting warm sulphur waters.

Official recognition abroad followed recognition at home. In 1912 Kurnakov was elected a council member in the SocikttC Chimique and became a member of the Russian Department of the International Commission on the Nomenclature of Inorganic Compounds. As a delegate of the Russian Physical-Chemical Society, he participated in the meetings of the International Association of Chemical Societies held at Berlin (1912) and Brussels (1913) . In 1913 he was elected vice-president of the Russian Metallurgical Society and became Ordinary Academician in chemistry at the Akademiia Nuuk (Academy of Sciences). The laboratory of the academy had been inactive for a number of years, but it experienced a rebirth as a result of Kurnakov’s extraordinary organisational talent.

The difficult years of World War I and the period following it brought many new tasks for Kurnakov. He was instrumental in the creation of a number of new institutes and commissions. In I 9 I 5 , together with fellow academicians V. I. Vernadski? and A. E. Fersman, he organised and became assistant chairman of the Commis- sion for the Study of Russian Natural Produc- tive Sources (K.E.P.S.) at the Academy. Here he


established a Salt Commission, and the study of salt solutions and related problems occupied much of his time for the next few years.

In I 9 I 9 he organised and became director of the State Institute of Applied Chemistry, a position held until 1927, with facilities located at Vasil’yevskiI Island on the Neva at Petrograd, which had grown out of the first‘ Russian laboratory founded by Mikhail Vasil’yevich Lomonosov (171 1-1765). Here scientific workers from the provinces gathered, especially during the summers, to work under Kurnakov’s guidance. They then returned home with ideas and projects for the next few years, and in this manner Kurnakov disseminated his ideas and expanded his rapidly growing school.

Institute for Study of Platinum In 1918 at K.E.P.S., Kurnakov founded and

became director of the initially-small Institute of l’hysicochemical Analysis, and the following year he became editor of its journal Izvestzya Instituta Fiziko-Khimicheskogo Analiza (now Izvestiya Sektora Fiziko-Khimicheskogo Analiza); he held both positions until his death. The year 1922 saw Kurnakov become director of the General Chemistry Laboratory of the Academy and, upon the death of Lev Aleksandrovich Chugaev, director of the Institute for Study of l’latinum and Other Noble Metals, and a member of the Gottingen Akademie (25).

In 1934 the Institute of Physicochemical Analysis, the Platinum Institute, and the General Chemistry Laboratory of the Academy merged into the Institute of General and Inorganic Chemistry with headquarters in Moscow and with Kurnakov as its director. This rapidly became one of the leading scientific research institutes in the U.S.S.R. and a centre for physicochemical investigations of metallurgy, halurgy, noble metals, organic sub- stances, and other economically-significant problems (26). Following Kurnakov’s death in 1941, it was renamed the N. S. Kurnakov Institute, and it has continued in the tradition of its founder.

From 1920 to the end of his life there were few chemical or metallurgical conferences in


which Kurnakov failed to participate as chairman, lecturer, or delegate. He was chairman of the Chemical Association of the Academy of Sciences of the U.S.S.R. (1930 to 1938), vice- president of the D. I. Mendeleev All-Union Society, and in 1939 to 1940 chairman of the society’s All-Union Competition Jury for the selection of the best scientific research works. In addition to his industrial consulting, in which he gave technical advice to plants and factories throughout the U.S.S.R., Kurnakov was extremely active in public affairs.

\nr e r e acknowledged on numerous occasions by high awards from the Soviet government, including one to recognise the fourth edition of his book “Vvedenie v Fiziko-Khimicheskii Analiz” (Introduction to Physicochemical Analysis) (27), which was dedicated to the memory of his closest friend, his wife Anna Mikhailovna, who for more than half a century had accompanied him everywhere and supported him in all his endeavours. In 195 I Kurnakov’s portrait appeared on a postage stamp, part of a com- memorative issue honouring Mendeleev, Butlerov, hbachevskii, Kalinnikov, and other outstanding figures of Russian art and science.

His wife’s death in 1940 had serious effects on Kurnakov’s health. Ignoring the cancer which was soon to claim his life, he,continued his full work schedule almost to the very end, and when his colleagues enquired as to the state of his health, which was visibly deteriorating, he quickly shifted the conversation to scientific topics. At the beginning of March, 1941 he entered the sanatorium at Barvikha where he died on March 19th. Although a scientist of international reputation, he remained a modest and considerate person, approachable to colleagues and students alike.

’The Kurnakovs had two children-a son Dr. Nikolai Nikolaevich Kurnakov (born in 1889), a chemist who worked at the Baikov Metallurgical Institute of the Academy of Sciences of the U.S.S.R., and a daughter Vera Nikolaevna Kurnakov (born in 1898), who died at the age of 23 while still a student. Kurnakov’s work is continued by an extensive

K u r n a k o v’ s c o n t r i b u t i o n s

school of scientists armed with new research methods, new apparatus, new theories, and new applications which he himself had created.

Kurnakov’s Work on Co-ordination Compounds

Kurnakov’s studies of complex compounds ( I , 16, 17, 19), carried out largely during the years 1891 to 1902 and following closely upon his early works on halurgy, constitute his first mature research. Two factors attracted Kurnakov to the field of platinum complexes- his interest in Russian natural resources and the then current controversy between the widely- accepted Blomstrand-JBrgensen chain theory and the revolutionary Werner co-ordination theory (28). While not completely accepting or rejecting either theory, Kurnakov regarded complexes as intermediate between chemical compounds of fixed composition and phases of varying composition (29), a harbinger of his later ( I y I 4) “berthollide-daltonide” dichotomy.

Kurnakov did not limit himself to the synthesis of new complexes, but he investigated and sought relationships between a number of their physical and chemical properties, a search which eventually led him to the development of physicochemical analysis. His analogy between complex ions and simple metallic ions was subsequently developed by Chugaev and his school, while Kurnakov’s investigation of the relationship between acid-base properties of complexes and their solubilities (30), opened an area later explored more fully by A. A. Grinberg and co-workers. Kurnakov’s study of refractive indexes is still of importance in connection with dipoles. His use of colour as a means of investigating complex species in solution (31) was later continued by Niels Bjerrum in his elucidation of the composition of chromium complexes.

In 1893, the year of the publication of Werner’s co-ordination theory, Kurnakov observed an important regularity in the substitution reactions of co-ordination compounds. Chemical reactions permitting a distinction between inorganic geometric isomers are unfortunately all too rare, and Kurnakov’s

discovery of a reaction still used to differentiate cis from rrans isomers of divalent platinum or palladium undoubtedly represents his most widely-known contribution to co-ordination chemistry (24). While investigating the substitution of ligands by thiourea and thioacetamide, Kurnakov found that replacement occurred with all the ligands of the cis compound, but only with acid radicals of the trans compound:

+2tu


where A NH, or an amine; X = halogen or acid radical; tu = thiourea). Kurnakov’s classic reaction later played a crucial role in Werner’s proof of the square planar configuration of Pt(I1) and in the formulation of Il’ya Il’ich Chernyaev’s trans effect (32).

Kurnakov is regarded as one of the principal founders of the platinum industry of the U.S.S.R. Although platinum had been and continues to be one of that vast countryf most valuable natural resources, prior to the work of Kurnakov and his colleagues Russia was forced to export raw platinum abroad and to import the refined metal because refining methods were kept secret by foreign refining companies. With the nationalisation of the Russian platinum industry following the Bolshevik Revolution of 1917, it became necessary to organise the refining of all the metals of the platinum group within the U.S.S.R. Industrial organisations in the Urals turned to Kurnakov, who, as Chair- man of the Refining Council of the Platinum Institute of the Academy of Sciences, accomplished the task in co-operation with factory workers. By 1930 all six platinum metals were being successfully produced in

great purity within the U.S.S.R. (17, 21).

While directing the Institute of General and Inorganic Chemistry, Kurnakov did much to facilitate the development of co-ordination theory and the application of complexes to the refining of the platinum metals. In Kurnakov’s laboratory at the Leningrad Mining Institute, his co-workers N. I. Podkopaev and N. N. Baraboshkin developed methods for refining raw platinum which were later realised on a larger scale at the Sverdlovsk Refinery, thus making the U.S.S.R. independent of other nations for its refining of platinum (16,33) .

The two-volume “Collection of the Selected Works of N. S. Kurnakov” (34), issued in 1938-39, contains a complete list of his

research published up to that time. Although one must allow for the inevitable overvaluation found in the Russian articles which were an important source of information for this paper, the majority of Kurnakov’s works, even those pub:ished as much as a half century ago, are still of great theoretical and practical interest.

Acknowledgements

The author wishes to acknowledge the assistance of the late Academician Il’ya I. Chernyaev, who graciously provided information, reprints, and the photograph which appears in this article. The present study resulted from interest in Kurnakov aroused by a research project on the separation of inorganic geometric isomers sponsored by the Research Corporation and the National Science Foundation (NSF G-I 1241).

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17 0. E. Zvyagintsev, Izvest. Sektora Platiny i DrugikR 3lagorodnykh Meral., Inst. Obshchei i Neorn. Khim., Akad. Nauk S.S.S.R., 1954,z8, 133

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(lo), 2281 22 S.Z.Makarov, Izvest. Akad. Nauk. S.S.S.R., Otdel.

Khim. Nauk, 1960, (12), 2073; A. S. Berezhnoi, Ukrain. Khim. Zh. 1960, 26, (6), 684; 0. E. Zvyaginrsev, Zh. Priklad. Khim. (Leningrad), 1960, 33, (IO), 2385; M. A. Klochko, Zh. Obshchei Khim., 1960, 30, ( I I), 3509; “Nikolai Semenovich Kurnakov v vospominaniyakh savremennikov i uchenikov”, Akad. Nauk S.S.S.R., Moskva, 1961; Yu. I. Solov’ev and 0. E. Zvyagintsev, “Nikolai Sernenovich Kurnakov”, Izdatel’stvo Akad. Nauk S.S.S.R., Moskva, 1960

23 G. B. Kauffman and A. Beck, 3. Chem. Educ., 1962, 399 (I), 44

24 N. S. Kurnakov, 3. Russ. Phys. Chem. SOC., 1893, 25, 565,693;J. Prakt. Chem., 1894, so, (11-12),

25 G. B. Kauffman, Platinum Metals Hey., 1973, 17,

26 N.S.Kurnakov, Uspekhi Khim., 1936,5,(7-8),957 27 N. S. Kurnakov, “Vvedenie v Fiziko-

Khimicheskii Analiz”, 4% lzd., Akad. Nauk S.S.S.R., Moskva, 1940

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481

(4), 144; ibid., 1974~18, (41, 142

24,629

(41, 126

113

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ABS TRA C T S of current literature on the platinum metals and their alloys

PROPERTIES XPS and UPS Study of thrx Reaction of Carbon Monoxide with Oxygen and Nitrogen Monoxide on Platinum- Rhenium Alloy .u. AIJN(YI‘, A. CASSIXO, K. IXCKOS, I. J. EHKHAKDT and 13. VJEIWK, Surf. Sci., 1982, 114, (2/3), L&L56 Room temperature interactions between CO with 0, and NO were studied on a 4oYGl’t-6o%Re alloy by XPS and UPS. There was a total removal of adsorbed CO by gaseous O L (which is not possible on Pt and difficult on Re); partial removal of adsorbed 0, by CO from the gas phase (impossible on Re); and total removal of adprbed CO gas, NO and total reversibility of this reaction (impossible on both Pt and Re).

The Interaction of CO and 0, with Thin Islands of Pd H. POPPA and I;. SORIA, Suq. Sci., 1982, 115, (2), 1 ~ 1 0 ~ - 1 ~ 1 1 0

‘l’he adsorption and co-adsorption of CO and. 0, on Pd islands -7 monolayers thick was investigated by TIT) and AIIS. CO decomposcd much less on Pd islands grown on K’(I iokc( r4 x 7)-0 than on small Pd particles on bulk oxide substrates (mica, sapphire). 0, interacted unusually strongly with the island surfaces at 6ooK. These results are attributed to a strong metal-support interaction.

Glass-Forming Ability and Crystallization Kinetics of Amorphous Palladium-Boron Alloys A. I.UC(:I and I.. RAI’II~%%AII, Thermochz’m. Acta, 1982, 54, (31, 343-348 I’d-B alloys were prepared to check their ability to produce metallic glasses when spun from the melt. ‘Ihe alloys were ablc to produce amorphous ribbons by melt spinning. The crystallisation kinetics of Pd,, (B3,. , metallic glass were found to follow the Avrami rate equation over a wide range of transfor- med fractions (5-95‘2 j; and the Avrami coefficient indicated that the crystals grow in a spherulite form.

Low Temperature Alloying in lhe PdIAu System H. I). SHIH, li. RAUEK and H. POPPA, Thin Solid Films, 1982, 88, (2), L21-1-24

AES studies of low temperature alloying in the Pd- Au system were made on one to two monolayers of I’d deposited onto Au(II1) at room temperature. The results showed that the surface alloying between I’d and Au occurs at room temperature, while massive alloying takes place by 530K.

Are VPd:, and NbPd, Itinerant Ferro- magnets u’. I.. XI’RMESI ER and I). J. SI.:LI.MYEK, 3. Appl. Phys., 1982,53, ( 3 1 9 2024-2026 Low-field magnetic susceptibility and high field magnetisation results are reported for plycrystalline samples of NbPd,, VPd, and Fc doped VPd,. Recent self-consistent, spin-polarised band calculations have predicted that the purc compounds are itinerant ferromagnets. The Fe-doped alloys exhibit a low temperature transition to a magnetic cluster-glass state.

Temper at ure U e pe n d e n ce of the Sensitivities of Metal-TiO, Junctions to Various Heducing Gases N. YAMAhtO 10; S. ‘1‘0N0211:R.A and 11. ~ 1 s ~ ; X O M I ; K A . 3. f9ecrrochetti. Snc., I 982, 129, (2) , 444-446 The current through a P d T i 0 , diode is sensitive to H2 at room temperature and becomes sensitive to other redycing gases and vapours such as CO, C,H,OH and propylene at high temperatures. Experiments were performed with T i 0 2 and I’t, Au, Al, Ni, Cu, Mg and Zn. I’t-’l’iO, and Au-‘I‘iO, diodes are also scnsitive to H,, the sensitivity being in ,the order Pd>Pt>Au. The diode sensitivity depends on the catalytic properties of the metal to the reduction between 0, adsorbed on the metal surface and reducing gases, resulting in a lowered potential barrier height at the interface.

Crystal Structure, Superconducting and Magnetic Properties of New Ternary Silicides LaRhSi, LalrSi and NdlrSi

IOI:KNFAL:, Solid Srarc Cowiniiiti., 1982, 41, ( I I), 80 1-804 New ternary silicides LaRhSi, LaIrSi and NdIrSi were synthesised by arc melting, and their powder patterns were indexed. 1,aKhSi and LaIrSi have a superconducting transition at 4.35K and 2.3K, respectively. NdIrSi has spontaneous magnetisation below ‘Ic= IOK.

8. C I W \ ~ A I . I I ~ K , 1’. l.I.,JAY, A. COLE, M. VlASSli and I. 1.

Low Temperature Specific Heats of H ( NbIrO) and R( NbPtO) B. COK1, A. I.. GIOHGI and G. K. STEWAH 1,3. Low Temp. Phys., 1 9 x 4 4 , (1/2), 179-185 l’he specific heats of hexagonal structures H(NbIr0) and R(NbPt0) were measured from 1.2 to ISK. The R-phase compound was superconducting with TL= 3.8K. The reduction in TC from 10.1 to 3.8K between the two phases is accounted for by corresponding reductions in the density of states and Debye temperature using the BCS theory.


Chemical Vapour Transport of Transition Metal Oxides ( I ) Crystal Growth of RuO,, IrO, and Ru,-,O, c. A. GI~ORG, r. 'I'RIGGS and F. I . ~ V Y , Mazer. Res. Bull., 1982, 17, (I), 105-1 10

Single crystals of KuO,, IrO, and the mixtures RuO,:IrO, have been prepared from the vapour phase. This is the first time it has been possible to grow single crystals of different concentrations of RuO,:IrO,.

The Interation of Coadsorbed Hydrogen and Carbon Monoxide on Ru(001) 1). E. PEEHI.ES, J. A. SCHKBIFELS and J. M. WHITE, Sug.

The cc-adsorption of H, and D, with CO on RU(OOI) at rooK was studied by various techniques. Pre- adsorbed CO strongly blocks H, adsorption. Pre- adsorbed H, blocks CO adsorption, but less strongly. The desorption of pre-dosed H, from a co-adsorbed layer shows strong long-range CO-H repulsive interactions. The CO sticking coefficient decreases in proportion to the amount of uncovered Ru sites.

Phase Transformations in Hapidly Quenched Aluminium-Ruthenium Alloys

SIJRYASARAYASA, L Metallkd., I 982, 73, (4), 201-206 Rapid quenching of two AI-Ru-melts containing I o and I gwt."i. Ru formed supersaturated solid solutions. Subsequent annealing abovc room tcmperature indicated a metastable A1,Ru phase with a cubic CaF,-type structure, and an equilibrium A1,Ru phase.

SCi., 1982, 116, (I), 117-134

1. A. CHAIJIIHURY, G. V. 5. SAS'TRY and C.

CHEMICAL COMPOUNDS

Cobalt, Rhodium and Iridium: Annual Survey Covering the Year 1979; Cobalt, Khodium and Iridium: Annual Survey Covering the Year 1980 K. L). \V. KEMMI'II and 1). R. RL3SI:I.I.; '1'. J. MACXIE, 3. Organornet. Chem., 1982,230, 1-98; 99-260 Two annual surveys covering metal C 0-bonded compounds, carbene, isocyanide and carbonyl complexes; homonuclear carbonyl compounds, heteronuclear metal-metal bonded carbonyl compounds metal (I), (11) and (111) compounds, nitrosyl, aryldiazo compounds, metal alkene, alkyne, allyl, cyclo- and other compounds are presented. (421 Refs.; 5 5 I Refs.)

Structure and Chemistry of Some Car- bony1 Cluster Compounds of Osmium and Ruthenium J. I.E\Y'IS and B. I:. ri. JOHNSON, Pure Appl. Chem., 1982, 545 ( I ) , 97-1 12 A review of the cluster compounds of Ku and 0 s with particular reference to the alternative ways of the bond breaking process. A survey of carbido derivatives and Au-Os complexes is presented. (3 I Refs.)

ELECTROCHEMISTRY Structural Effects in Electrocatalysis R. R. A I I i I C , 4. \ I . TRIPKOVIC and w. E. O'GRADY, Nature (London), 1982, 296, (5853), 137-138 The oxidation kinetics of HCOOH, CH,OH and CH,O on single crystal Pt electrodes with (100), ( I 10) and ( I I I ) orientiations are reported. Pronounced dependence of the kinetics of these reactions on the crystallographic orientation of the surface was observed. The intermediate completely blocks the Pt( loo) surface; the smallest adsorption was at the (I 11) plane. On activation, the (100)

surface had the highest activity. The results suggest that electrocatalytic reactions exhibit structural sensitivity.

Electroreduction of Oxygen on Reduced Platinum in 85% Phosphoric Acid a'. 1:. O'GRADY, E. J . TAYLOR and S . SRINIVASAN, 7. Eltctroavul. Cizem. interfacial i:'lecirochem., 1982, 1327 '37-1 50 Oxygen reduction in highly purified 85% H,PO, was studied on reduced Pt by rotating ring-disc techniques. The data suggest that the 0, reduction proceeds by the parallel mechanisms of direct four- electron transfer to H,O and through the multistep mechanism involving peroxide intermediate. A value of 7 . 6 x io-7cm2/s was determined for the diffusion coefficient in 85% H,PO, at 25°C.

The Study of Electrode Processes of Sulphur Dioxide on Platinized Electrode by the Radiochemical Method M. S%KI.ARC%YK, A. CZERWINSKI and T. SOBKOWSKI, J . 1:'lectroanul. Chem. Interfacial Blectrochem., I 982, 132,263-27 I

The adsorption of SO, and the electrode reactions of adsorbed molecules at a platinised Pt electrode were studied by potentiodynamic and radiometric tecbni- ques. The surface concentration of adsorbed species as well as the charges of their reduction and oxidation were determined. Sulphur adatoms and Pt sul- phides as products of SO, adsorption in "double- layer" and H, regions of potentials are proposed.

The Development of an Energy-Efficient Insoluble Anode for Nickel Electrowin- ning. I . Single Layer Precious Metal Coatings. 11. Multilayer Precious Metal Coatings A. J . SCARPElllSO and G. I.. FISHER, 3. Eleczrochem. Soc., 1982, 129, (3), 515-521, 522-525

Precious metal-coated Ti insoluble anodes with increased energy efficiency over conventional Pb electrowinning anodes were developed. Precious metal microlayers extended the life of the Ru-4% Ir coating and made it economical to use at electrowinning temperatures up to 70°C. Several of the mul- tilayererd precious metal Ti coatings could operate efficiently as anodes for Ni electrowinning for at least 20,000 h at operating current densities.


Electrocatalytic Activation of Ruthenium Electrode for the C1, and 0, Evolution Reactions by AnodicICathodic Cycling M. VUKOVIC, H. ANGERSTEIN-KOZI.O~~~~SKA and B. E. CONWAY, 3. Appl. Electrochem., 1982, 12, (2),

193-204 The kinetics of CI, and 0, evolution on two types of oxidised Ru electrode surfaces subjected to an anodicicathodic cycling regime from 0.06 to 1.4VE,, were studied by a steady-state polarisation technique. Current densities for C1, evolution at the cycled Ru surface oxide are -30 times greater than those at the original Ru surface. 0, evolution current densities are increased by -8 times.

Kinetics of Secondary Processes on Ruthenium-Titanium Anodes in Chloride Solutions M. M. PECHBRSKII, v. v. GORODETSKII, N. 1A. BUNE and V. V. I.OsEv,Elecrrokhim2_t'u, 1982, 18, (3), 41 5-422 The effect of current density and acidity of the solution on corrosion and electrochemical behaviour was studied on treated Ku-Ti anodes prepared by electrodeposition of Ru on Ti in gM NaCl at 80°C. After thermal and anodic treatment, the secondary processes of Ru dissolving and evolution of 0, were observed in the surface layer of the electrode without any changes in C1, evolution.

Reactivities of Ruthenium Cluster Anions: Implications for Catalysis of the Water-Gas Shift Reaction J. c. RRICKER, c . c. NAGEL and s. ti. SHORE, 3. Am. Chem. Soc., 1982,104, (5), 1444-1445 [HRu,(CO),J- was used in catalysis in the water-gas shift reaction and its functions were observed. The anion functioned as an apparent hydride donor in the presence of CO at atmospheric pressure and room temperature. Three reactions were observed with CO, [Ph,C][BFJ and CO, and with H,O and CO. All suggest hydridic behaviour for the anion. A new mechanism for the water-gas shift reaction is proposed, whereby [HRu,(CO), ,I--Ru,(CO),, plays the major role for the reaction in basic media, irrespective of whether the reaction is initiated by ;etranuclear or trinuclear Ru carbonylates.

PHOTOCONVERSION Photochemical Diode Model of Pt/TiO, Particle and Its Photocatalytic Activity T. SAKATA. '1'. KAWAI and K. HASHIMOTO, Chem. Phys. Leu. , 1982, 88, (I) , 5-54 The photocatalytic properties of a powdered semiconductor loaded with Pt catalyst are discussed using a photochemical diode model. The rate of H, evolution depends on particle size and correlates with the irreversibility of the oxidation of the reactants. Only a small amount of Pt, smaller than I ~ I O O monolayer on TiO, is required to produce a remarkable effect on photocatalytic activity.

Photoelectrochemical Behaviour of Ruthenium Disulphide Electrodes in Contact with Aqueous Electrolytes R. HEINDI., R. PARSONS, A. M. KEDON, H. TKIBCI'SCH and J. VIGNERON, Sur/. Sci., 1982,115, (I) , 91-103 ?'he photoreaction of a RuS, electrode with water for catalytic 0, evolution was studied as a function of photon energy, electrolyte pH and electrochemical history of the electrode.

Mechanism of the Uncatalyzed Formation of Dihydrogen in the Radiolytically Induced Reduction of Tris( 2,2'- bipyridine)rhodium( 111) Ion in Aqueous Solution Q. G. MIJLAZZANI, M. VENI'URI and M. Z. HOFFMAN', J. Ph.ys. Chem., 1982,86, (z), 242-247 The reaction of Rh(byp):' with radiation generated e;q and (CH,),COH in deareated aqueous solutions containing o.rM 2-propanol generates H, in the absence of any catalyst. The H, yield above the background from the radiolytic act is greatest at pH 4.2, but diminishes to zero at pH 2 and 7. A mechanism for uncatalysed H , production is postulated with RhH(bpy); as the direct precursor. This arises from reduction of RhH(bpy)f' by Rh(bpy):'. The maximum turnover number for H, generation is -12.

in Vitro Analogues of Photosystem. 11. Comhined Flash Photolytic and Con- ductometric Study of Light-induced Oxygen Evolution from Water Mediated by Colloidal Ru0,/Ti02 K. HUMPHRY-RAKEK, J. LILIR and M. CKAIZEI., J . Am. Chem. Soc., 1982, 104, (2), 422-425 Colloidal TiO, particles when charged with ultrafine RuO, deposits are extremely active catalysts for water oxidation. A photochemical model system of aqueous Ru(bpy):' and S,08- solutions was used to examine the details of the 0, evolution reaction qKu(bpy):+ + zH,O + 4H+ + 0, + ?Ru(bpy)T. Flash photolysis and conductance techniques show that hole transfer from Ru(bpy):+ to the catalyst and proton release from water decomposition occur simultaneously within milliseconds at 3mg RuO,/I.

Visible Light Induced Generation of Hydrogen from H,S in CdS-Dispersions, Hole Transfer Catalysis by RuO,

and I:. PELIZZET~. Helv. Chim. Acru, 1982, 65, ( I ) , 243-248 Studies of illumination of CdS dispersions by visible light in solutions containing H,S or sulphide ions leading to efficient generation of H, and S showed that very small quantities of RuO, deposited on the CdS particles greatly improve the quantum yield of H, formation, for which the optimum value obtained so far is 4 = 0.35 & 0.1. The effect of RuO, is attributed to catalysis of hole transfer from the valence band of CdS to H,S or sulphide in solution.

R. HORGARELI.0, K. KAI.YANASUNI)AKAM, M. GRATLEI.


ELECTRODEPOSITION AND SURFACE COATINGS Electrodeposition of Precious Metals 1966-January, 1982 (Citations from the Metals Abstracts Data Base) National Technical Information Service, Springfield, VA. Jan. 1982, PB82-860289, Materials Science, NTIS,March 30, 1982,p. 131 A bibliography on electrodeposition of precious metals is discussed including both pure metals and alloys. Plating conditions and substrate materials for Pt, Pd, Rh, Ir, Ru are discussed. Emphasis is placed on fused salt electrolytes. The properties of the plated surface are discussed. (I 76 Refs.)

FUEL CELLS Design of a Cell for Electrode Kinetic Investigations of Fuel Cell Reactions H. OIXNDER, J. McRREEN, W'. E. O'GRADY, S . SRINIVASAN and K. V. KORDESCH,J. Electrochem. SOL, 1982, 129, ( I ) , 735-137 Two designs of cell for investigating the electrode kinetics of fuel cell reactions in acid media are described. The cells, simulating a phosphoric acid fuel cell at elevated temperature and pressure are used to evaluate Pt/C electrodes.

HETEROGENEOUS CATALYSIS Bifunctional Oxidation of Ammonia with Metal Oxide-Pt/Al,O, Mechanical Mixtures Y. KOSAKI, A. MIYAMOIO and Y. MURAKAMI, Bull. Chem. SOC. Jpfz., 1982, 55, (I), 63-68 Selectivity to N, in the reaction of NII, with metal oxides was greatly increased by the addition of Pt/A1,03 to the metal oxides. In the oxidation of NH, with metal oxide-Pt/Al,O, mixtures, NH, was at first oxidised by metal oxides to form NO, and N, and then the NO, components were transferred through the gas phase from the metal oxides to Pt particles on Al,O,. Finally, the NO, components reacted with NH, on Pt particles to form N, selectively.

Effect of Sulfur Poisoning on the Hydrogenolysis Activity of Pt in Pt-Al,O, Catalysts

Eng. Chem., Prod. Hes. Dev., 1982,21, (I), 52-56 The S poisoning of Pt/Al,O, catalysts was studied during the hydrogenolysis of n-pentane by the gas chromatographic pulse titration technique at 30"38o0C. The hydrogenolysis activity was reduced to zero only when the atomic ratio of S per exposed Pt atom, S/Pt,- I . The suppression of hydrogenolysis and increase in isomerisation and aromatisation can be achieved only by reversibly adsorbed S on the l't above that held irreversibly.

P. C. MENON, G. B. MARIN and G. F. FKOMENT, Ind.

Self-Sustained Oscillations during CO Oxidation on a Pt/y-Al,O, Catalyst P. c. LIAO and E. E. WOI.F, Chem. Eng. Commun., 1982, 13, (4-(4,315-326 A study of the reaction environment and catalyst surface effects on self-sustained oscillations during CO oxidation on Pt/y-Al,O, catalysts is presented. The oscillations occurred in a narrow temperature range and low 0,:CO ratios. Oscillation pattern depended upon catalyst pretreatment; amplitude and frequency varied with surface pretreatment, and decreased as temperature and 0,:CO ratio increased. There was an overshoot of CO, outlet concentration in excess to the 100% conversion, which indicated the participation of surface stored CO.

Selective Steam Reforming of Aromatic Hydrocarbons.II1. Interaction of CO and Toluene in Steam and Hydrodealkylation over RhPt Bimetallic Catalysts D. DUPREZ, R. MAUREI., A. MILOUDI and P. PEREIRA, N0uv.J. Chim., 1982,6, (3), 163-169 Well dispersed KhPt/Al,O, catalysts were prepared and characterised, and their activities in benzene hydrogenation, steam dealkylation (SDA) and hydrodealkylation (HDA) were studied. The surface compositions were richer in Rh at each composition. During steam dealkylation an inhibiting effect of CO on Rh is ascribed. Hydrodealkylation, a side-reaction in SDA, is more sensitive to CO than the main reaction. This is related to the metallic specificity of the HDA. A reaction scheme is proposed. (33 Refs.)

Methanation Studies over Well- Characterized Silica-Supported Pt-Ru Bimetallic Clusters H. MIURA and R. I). GONZALEZJ. Catal., 1982, 74, (2), 2 I 6-224 A methanation study over a well-characterised series of SiO, supported Pt-Ru bimetallic clusters was performed. Turnover numbers and activation energies for CH, formation were determined for Pt- Ru bimetallic cluster catalysts with the following Pt surface composition: 17.9, 50, 73 and 99%. The results suggest that Ru ensembles are necessary to catalyse the methanation reaction as Pt-Ru dual sites show a catalytic behaviour characteristic of Pt. A temperature programmed pulse technique was used to study C formation by pulsing CO over each catalyst as the temperature was increased, in He.

Carbon Monoxide Oxidation on Copper Chromite and Platinum-Copper Chromite Catalysts G. K . CHIINIS, 1 % ~ . Thesis, University of Notre Dame, 1982, Diss. Absrr. Int. B, 1982,42, (7), 2918 CO oxidation was investigated on a Pt-CuO.Cr,O, bimodal catalyst. The most active catalysts resulted after a reduction which led to the formation of Cn crystallites (zoo-350A) supported on amorphous Cr,Oy The catalyst activity was found to be a combination of Pt and CuO.Cr,O, functionality.


Hydrogenated Amination of Aldehydes by Nitrobenzene in the Presence of Com- plexes of Platinum Group Metals with Chloroanylic Acid M. V. KLYIIEV, s. I. KONI)RAT’EV and M. I.. KHIDEKEL, Kinet. Kutul., 1982, 23, (I), 71-76 Complexes of platinum group metals with chloroanylic acid fixed on supports catalyse hydrogenated amination of nitrobenzene. The catalytic activity of the complexes increased in the order: Pt)I’d>Rh>Ir.

Colloidal Platinum and Palladium Catalysts in the Hydrogenation of Alkyne under Hydrogen Pressure I). v. SOKOI.’SKII and A. VAI.IKHANOVA, .Zh. Obshch. Khim., 1982,52, ( I ) , 186-190 Studies of the catalytic properties of colloidal Pt and Pd made during hydrogenation of isomeric hexyne under H, pressure, showed that specific activity and general selectivity on Pd particles was higher than that on Pt. The C = C bond migrates on Pd into Cz-C3 and C3-C4 positions. Both on Pt and Pd cis-trans isomerisation occurs. Catalysts were stable during saturation of the triple bond of the hexyne. The gradual decrease in activity was observed during hydrogenation of the olefin reaction.

Preparation of Permanent Pd-Catalysts for Petrochemistry S. YAMAGIJCHI, Muter. Chein., 1982, 7, (I), 137-142 An aqueous suspension containing a- and y-Al,03 served as an abrasive for rubbing I’d plate and Si ingots. The rubbing sludge obtained with Pd and Si particles in even dispersion was an active and durable contact catalyst for the low temperature oxidation of hydrocarbons. Aluminosilicate formed and solidified.

Effect of Titania on Activity of Alumina Supported Palladium Catalyst during Hydrogenation of Benzene I,. S. KRAVCHUK, E. A. MAKAROVA, I. A. YURSHA, T. I. I.ARIONOVA, N. I. IVASHCHENKO and S. V. MARKEVICH, NeJekhinzi.~u, 1982, 22, (I), 42-45 The effect of TiO, addition on the activity of a o.3u~l’d/yAl2O, catalyst was studied during benzene hydrogenation. Samples reduced in H, at atmospheric pressure retained their activity after calcination at 600-800°C. The increase of H, pressure to I .5MPa decreases activity of the catalyst.

Spectrophotometric Study of Alumina Supported Palladium Catalysts 1.. S. KKAVCHL:K and 5. v. vAL.IEVA, vex Akad. Nauk BSSK, Ser. Khim. Nauk, 1982, (2), 50-54 The solubility of oxidised Pd catalysts supported on yAl,O, containing o.i-r.owt.% Pd was studied in dilute HCl by U.V. spectroscopy. A decrease in Pd solubility was observed in samples containing 2o.5wt.8 Pd. This was due to the substantial aggregation ._ . occurring during PdO phase formation.

Methane and Methanol Synthesis over Supported Palladium Catalysts F. FAJULA, R. G. ANTHONY and J. H. I.lJNSFORI),J. Catal., 1982,73, (21,237-256 Hydrogenation of CO over Pd supported on three different S O , and on HY and NaY zeolites was studied at 260-340OC and 5 and 50 atrn pressure. The selectivity and activity of the catalysts are strongly dependent on the nature of the support and on the state of the metal on its surface. Methanol is produced on the catalysts with small size crystallites on which CO is weakly adsorbed, whereas the formation of methane is directly related to the density of acidic sites at the surface of the support. Pd undergoes structural and electronic modifications due to transformation into hydride phases.

Selective Hydrogenation of Carbon Monoxide on Supported Rh Catalysts Prereduced in Situ with H,O and CO or H2 Y. IWASAWA, l’, HAYASAKA and S. OGASAWAKA, Chem. h t l . , 1982, ( I ) , 131-134 CO was selectively converted to ethylene and propylene (>80% of C,C, hydrocarbons produced) at 433-447K over Rh/SiO, catalysts prereduced in situ with a CO-H,O mixture; while other Rh catalysts, obtained by pretreatment in situ with a H,-H,O mixture yielded ethanol and acetaldehyde at a higher selectivity, by a factor of about roo at 453K3, than a usual Rh(o) catalyst reduced by H,.

Magnetic Resonance Studies on Catalytic Adsorption on Rhodium on Titanium Dioxide ‘I. M. APPLE, lJh.ll. Thesis, IJniversity of Delaware, 1981,Uiss. Abstr. Int. R, 1982,42, (7), 2846 The adsorption of H, and CO on Rh/TiO, was studied by NMR. The spectra of the surface species formed upon H adsorption revealed the presence of four types of H, three of which are irreversibly bound, and one is reversibly bound and formed by spillover from the Rh metal. Upon cc-adsorption of CO this spillover H is not formed. There is an interaction between adsorbed CO and adsorbed H at room temperature.

Support Effects on the Catalytic Activity and Selectivity of Ruthenium on CO and N, Activation A. BOSSI, F. GAKHASSI and G. I’ETRINI, J. Chem. suc., Furada.y Truns. I, 1982, 78, (4), 1029-1038 CO and N, isotopic equilibration reactions were studied on Ru catalysts supported on A1203, SiO, and MgO. The reactivity in CO equilibration was found to follow the order: Al,O, > MgO > SiO, Ru/MgO catalysts heated in vacuum at 673K and then reduced showed the highest activity. The Fischer- ’l’ropsch reaction carried out on samples supported on A1,0, or MgO at -50 atrn and 530K produced a great amount of oxygenated components.


Structure Physic o - C h e m i c a I Properties of Skeletal Ruthenium Catalysts Q. A. KII.'DIBEKOVA, A. B. FASMAN, A. 1. IJASHENKO and v. N. EKMOLAEV, Zh. Prikl. Khim. (Leningradj, 1982, 553 (I1,72-76 Studies of the structure and physico-chemical properties of Ru catalysts made from Ru-Fe, Ru-Co and Ru-Ni alloys containing 1wt.X Ru showed that the products of their electrochemical disintegration were finely dispersed amorphic powders. Ru-Ni slurry contained metallic Ru and Ni oxides, Ru-Co- Ru, Co,RuO, and a-Co. Selectivity of the catalysts during hydrogenation of industrial acetylene was first order.

H y d r o g e n at i o n t o Cyclohexene on a Ruthenium Catalyst. Physical and Chemical Characterisation of the Catalyst and Its Precursors C. U. I. OBENRRAND and s. I.. T. ANUERSSON, 3. Chem. Technol. Bzorechnol., 1982,32, (2), 365-375 The chemical and physical characteristics of a Ru catalyst, consisting of metallic Ru obtained by H, reduction of the precursor suspended in the alkaline aqueous phase, were studied during the hydrogenation of benzene. The precursor consists of hydrous oxides of Ru with a surface area of 27m2/g. After reduction the surface area increases to I I 2m2/g and the average pore diameter decreases from 28 to 13 nm and the number of pores (8nm increases sub- stantially. The macroscopic particle size (25-40 pm) decreases along with decreasing Ru concentration.

Homologation of Methanol by Cnbalt- Ruthenium Mixed Catalysts K. KUDO and N. SlIGIlA, Nippon Kagaku Kaishi, 1982, (31,462-47 1

The homologation of methanol to ethanol was performed by a Ru-Co catalyst containing iodide promoters using (H2€O) gas under pressure. Reac- tion variables were examined; yield and selectivity of ethanol depend significantly on the Ru:Co ratio and the H,:CO ratio. Yield increased with the charge ratio RuCl ,.nH,O:CoiCO),, reached a maximum, then decreased at larger ratios. The optimum Ru:Co ratio was 0.2-0.4.

and

o f B e n z e n e

An Infrared Study of Supported Ruthenium Catalysts Prepared from Rud CO) 12 'I. KIMURA, T. OKIIHARA, ,\I. MISONO and Y. YONEDA, Nippon Kagaku Kaishi, 1 ~ 8 2 , (a), 162-169 The structure and decomposition of Ru,(CO),, dispersed on SiO, ZnO, y-A120, and MgO was examined by i.r. spectroscopy. With pAl,O, Ru3(CO),, strongly interacted, forming a very stable species. Thermal decomposition of Ru3(CO),4p Al,O, followed by H, reduction at 450°C formed Ru catalysts with high dispersion. CO was adsorbed in linear- and twin-types on Ru/A1,0,.

Effect of Preparation Procedure o n the Properties of Ruthenium Black

and KH. G. OMASHEV, Kiner. Karal., 1982, 13, (z), 474-480 Studies of the effect of preparation procedure for Ru black on the adsorption of H,O in liquid and gaseous phases showed that dispersion of the catalyst depends on the nature of complex salts used during its preparation, on H, pressure, temperature and time of reduction. Temperature of H,O adsorption on Ku-black was measured.

G. 2. ZAKI:,WMBAEVA, B, K. KARAKEEV, I.. R. SHAP0VAIX)VA

HOMOGENEOUS CATALYSIS Rh( I ) Complexes Containing Fully Alkylated Mono- and Diphosphine Ligands as Highly Active Hydrogenation Catalysts for Carbonyl Compounds K. 'I'ANI, K. XJWA, ti. ' I ANIGAWA, '1'. YOSHIUA, T. OKANO and s. O'I'SUKA, Chcm. Ixr/., 1982, (31, 261-264 Cationic Rh(1) complexes with fully alkylated diphosphine ligands [Rh{(i-Pr),P(CHJnP(i-Pr),] (NBD)]CIO, (n=3, 4) have been produced. These have been found to be versatile and efficient catalysts for the hydrogenation of a variety of carbonyl compounds, including aldehydes.

C a t a l y t i c H y d r o g e n a t i o n o f 3,4-Epoxybut- 1 -ene with Cationic Rhodium Complexes FI. FLJI'ISI!, I<, MA'ISL~MUKA, S. SFIIRAHAMA, K. 'IAKESHrlA and I. MOCHII>A, y. Chem. soc., I'erkin Tram. I , I 982, (31, 855-859 Catalytic hydrogenation of 3,4-epoxybut-r-ene with cationic Rh complexes was studied under ~ a t m of H, at 3oOC. The catalytic activity of the epoxide depended on the nature of the P ligands of the catalyst. The order of activity of the ligands for the formation of alcohols was different from that observed for hydrogenation of I,z-epoxy-1- phenylethane. It is noted that the diphos- and PPh3- catalysts which showed quite limited activity for both the carbonyl compound and I ,2-epoxy-1- phenylethane, exhibited considerable activity for the title compound.

Oxidation uf Unsaturated and Hydroxy Fatty Acids by Ruthenium Tetroxide and Ruthenium Oxyanions Y. NAKANO and 'I. A. POGLIA, J . Am. Oil Chem. k., 1982,59, (413 163-166 The reactions of RuO, RuO; and R u q - with hydroxy substituted and unsaturated fatty acids were studied. At a I : I molar ratio, RuO, and both oxyanions oxidised I 2-hydroxystearic acid to 12- kerostearic acid. With 9-1 o-dihydroxystearic acid the type of oxidation products depended on the amount of Ku used. Oxidation of oleic acid with excess RuO, or RuO, gave pelargonic and azelaic acid. R u q - did not react with oleic acid.


ELECTRICAL AND ELECTRONIC ENGINEERING A Comparison of the Performance of Gold and Platinum Killed Power Diodes s. I). BROTHERTON and r. BRAIXEY, Solid-State Elecrron., 1982, 25, ( 2 ) , I 19-125 Measurement of leakage current, switching time and forward voltage drop are presented for Pt and Au killed diodes. Under specified conditions improved switching is obtained from Pt killed devices due to the life time profile produced at elevated temperatures by the shallow recombination centre.

Auger Electron Spectroscopy Analysis of the Contact Reaction of Pt-Si Codeposited Films and Silicon M. EIZENBERG and R. RRENER, Thin Solid f:ilms, 1982, 88, (I),4’-48 Codeposited alloy films of Pt-Si on Si, used for the formation of shallow Schottky contacts, were studied by AES. The coat depth after annealing was larger than expected. An accumulation of Si and depletion of Pt in the outer 200-300A of the film was also observed. Studies of the line shape for Auger transitions showed that the outer Si-rich region consists of a mixture of PtSi and elemental Si.

N E W P A T E N T S

ELECTROCHEMISTRY Recombination Device for Storage Batteries ATOMIC ENERGY OF CANADA LTD.

British Appl. 2,084,388 A The amount of H,O lost in a recombination process is reduced by using a water-resistant PTFE supported platinised C catalyst which is not degraded when recombined H,O is drained over the catalyst particles.

Platinum Metal Coated Electrodes DIAMOND SHAMROCK CORP. European Appls. 46,44719 A Ti or other valve metal substrate is coated with a platinum group metal or platinum group metal oxide coating by application of a dilute solution containing an Ir, Rh, Ru or other platinum group metal salt and HC1 or another agent which will attack the Ti base.

New Ion Exchange Resins HOECHST A.G. European Appls. 47,94 515 0

New ion exchange resins are made from perfluorocar- bony1 sulphonic acid fluorides which are obtained by the electrolysis of monohydroperfluoroalkane sulphonic halides against a Pt wire electrode. 0 s and Ir electrodes are also claimed.

MEDICAL USES High-Performance Liquid Chromatogra- phy Studies on Platinum Thymine Blue

21, (3), 1280-1282 Platinum thymine blue, PTB which has antitumour properties was examined by high-performance liquid chromatography. This revealed that typical prepara- tions of PTB contain several colourless Pt compounds (“whites”) as well as a number of blue species. This is the first time that the various blue components in P T R have been separated.

Osmium-Carbohydrate Polymers as Anti- Arthritic Drugs C. c. HINCKLEY, J. s. REMILLER, L. E. STKACK and I,. D. RUSSELI, Rook of Abstracts, I X3rd Am. Chem. SOC. Natl. Meeting, Las Vegas, Na., 1982, Inorganic Paper 68 Osmiumi-arbohydrate polymers (osmarins) have been prepared and characterised, and are now being investigated as potential anti-inflammaiory agents for some forms of arthritis. When dilute osmarin solutions are injected into the synovial space of a joint they bind irreversibly to articular cartilage and to the joint capsule.

J. D. VC’OOLI.INS and R. ROSENRERG, InOrg. Chem., 1982,

Activated Cathode for Aqueous Solution Electrolysis

An electrode which controls the amount of hypochlorous ion formed in electrolysis reactions and which has excellent corrosion resistance is made from a valve metal or alloy substrate, and an oxide coating containing a Ru, Rh, I’d, Os, Tr andor Pt oxide.

Photochemical Electrode for Water Decomposition

HODOGAYA CHEMICAL CO. LID. U.S. Patent 4,300,992

NAT’IONAI. RESEARCH DEVELOPMENT CORP. U.S. Patent 4,305,794

A photochemical electrode which can decompose H,O when irradiated with visible light is obtained by treating a Pt mesh with red mercuric sulphide blackened by iodide treatment.

Catalysed Chloralkali Cathode

A cathode for use in brine or H,O electrolysis Celts is made from an electrically conductive matrix carrying a surface deposit of a platinum group metal, Au or Ag catalyst, preferably Pt and/or Ru. The matrix may be made of Ni, Cu, austenitic steel or another base metal on to which the catalyst is deposited by chemical displacement.

JOHNSON MATI’HEY & CO. LIT). French Appl. 2,480,795


ELECTRODEPOSITION AND SURFACE COATINGS

Electrodeposition of Ruthenium-Iridium Alloy INCO EUROPE L'I'I). European Appl. 47,566 It has been found that valve metals such as T i may be successfully plated with a Ru-Ir alloy from a bath which contains a soliible Ru compound, a soluble Ir compound, a soluble Huoroboratc and acid.

Palladium Plating Bath AMI~.RICAh' CIIIIMI(:AI . &! Rl!FIh'IN(; (XI. IN(:.

U.S. Patent 4,297,179 A cyanide-free bath for producing bright, adherent Pd coatings at a wide range of current densities contains a 3-butyne-2-01 brightener.

LABORATORY APPARATUS AND TECHNIQUE

Analyser for Determining the Organic Carbon Content of Solids I'lKKIN-ELMER CORP. European Appl. 46,178 One portion of the sample is introduced into a Pt vial together with an acidic fluid, such as phosphoric acid, and the results obtained from analysing the content of the vial in a single channel 'elemental analyser are compared with a second portion of the test material introduced directly into the analyser.

Microminiative Palladium Oxide Gas Detector A-T-0 INC. US. Patent 4,296,399 A zero-stable combustible gas detector is made by winding a thin (O.OOOI-O.OO~ cm) I'd or Pt wire about a Mo mandrel, coating the wound wire with a binder, of, for example, reduced chromic and phosphoric acids, and after curing the binder, coating it with a I'd oxide catalyst.

Hydrogen Gas Detector RABCOCK & WIIGOX CO. U S . Patent 4,298,574 A differential thermocouple H, gas detector is provided by coating one thermocouple junction with a Pd-Ag alloy catalyst and the other junction with a non-catalyst. Heated H, reacts with the catalyst to heat the junction and hence to cause an e.m.f. proportional to the amount of H L in the gas.

Catalytic Gas Sensor DIFFKAC 10 1;I'D. U.S. Patent 4,303,612 Pellistor type detectors for measuring the amount of CH, present in air are prepared by applying AI,O, (particle size below T O O A) on to a Pt filament and then impregnating a I't or Pd catalyst on to the dried Al2O3 coating. The Pt wire is stabilised before being coated with the A1,@, via an Al layer obtained by the electrical decomposition of an Al salt.

Soot Detector for Monitoring Diesel Exhausts ROBERT BOSCH G.m.b.H. U S . Patent 4,307,061 A sensor for detecting soot and free C consists of two Pt-SVLAI oxide electrodes separated by a narrow (0.1 mm) high resistance support of, for example, A1,0,. Deposition of soot upon the electrodes causes the resistance between the electrodes to drop and a catalyst layer, such as small amounts of Pt in a base metal oxidc matrix of' Al,@,, is used to oxidise the deposited soot after measurement has taken place.

HETEROGENEOUS CATALYSIS Isothermal Methanation - I1 JOHNSON M A i - i - m Y & CO. III'II.

British Patenr 2,008,147 B Improved conversion rates may be obtained from a highly exothermic methanation process in which synthesis gas is converted in the presence of a supported catalyst of I't, Pd, Rh, Ir, Ru, Fe, Co, Ni, Cu, W, and their alloys if gases leaving the converter are brought into contact with high surface area bodies having cooling liquid sprayed over their contact surfaces. The preferred catalyst is Ru and/or Ni in a support, such as pellets or a honeycomb monolith.

Liquid Hydrocarbon Synthesis from Coal SHEI.1. INI'EK?;A'I'IONAI, RESEARCH Mi]. B.V.

British Patent 2,009,778 B Ru Fischer-'Iropsch catalysts may be used in a three stage process for preparing high octane petroleum products from coal. Coal is gasified to a mixture of C.0 and H, and this mixture is converted to hydrocarbons over a crystalline Fe silicate catalyst. An isobutane fraction is alkylated to obtain a gasoline fraction Nshich is mixed with a second gasoline fraction obtained from the hydrocarbon mixture.

Platinum or Palladium Catalyst for a Laser SECKETARY OF STA1.F: FOR L>EFBNCE

British Appl. z,oX3,944 A The lasing medium of a C@d-NIHe) laser is brought into contact with an Al-containing ferritic steel supporting a Pt or Pd catalyst in order to convert any CO present to CO, and to alleviate degradation of the laser caused by CO, breakdown by the electrical discharge.

Platinum Metal-Phosphinopolymer Catalysts DEGCSSA A.G. British Appl. 2,084,166 A Polymeric complex compounds of Rh, Ir or Ru have a SiO,-like structure where the platinum group metal is bonded via phosphine groups to an insoluble, silicone, cross-linked polgcondensate. A typical metallopolymer is obtained from RhCI, and a phosphinosiloxiane, PhP[(CH,),Si(OEt),],. The products may be used as heterogeneous catalysts for a variety of reactions.

Platinum Metals Rev., 1982, 26, ( 3 ) 141

Unsaturated Carboxylic Acid Production \'ACKER-(:I l l~ . \ l fE ti.m.b.11. European Appl. 48,946 Unsaturated acids are obtained in improved yields when olefins are reacted with 0, and a carboxylic acid in the presence of a Group VIII catalyst, an acetate and 1-8oooppm of an organic chlorocompound. In one example the catalyst consists of bentonite carrying 2.2'%. Pd, 1.9% K, I .7-1.9% Cd and 0.077, Mn.

Zirconia-Alumina Supported Iridium Reforming Catalyst S'I ANDAKD 011. CO. ;INI)IANA: U.S. Patent 4,297,205 A catalyst especially suitable for reforming naphthas consists of Ir (o.o5-1.5%) supported on an A1,0, carrier containing either 3-155 ZrO, or more than 6 0 X ZrO,.

Platinum-Rhenium Hydrocarbon Con- version Catalyst S'l ANIIARD 011. CO. ,:lNI>IAS.A; U.S. Patent 4,298,46 1

A platinurn group metal catalyst, such as platinum deposited on a composite consisting of A1,0, and Re deposited on Si0 , may be used without the conventional pre-sulphiding treatment and does not suffer any loss of reforming performance.

Acidic Multimetallic Reforming Catalyst U.C).I'. INC. US. Parent 4,298,462 A catalyst especially suitable for dehydrocyclising 6-JOC paraffins contains O.OI-Z%, of a platinum group metal, O.OS-~';{~ Ni, 0.01-596 Zn and 0.1-3.5 of a halogen component.

Catalytic Combustion in Boilers JOHNSON M A I I HEY & co. LTII. US. Patenz 4,299,192 Combustion within a boiler takes place in at least two stages with heat extraction between the stages in order to reduce the temperature of the reactor to one which conventional catalysts and supports will with- stand. 'The 0, content of the final stage is preferably reduced to zero and catalysts used in the reactor are PeAlCrY alloy-supported platinum group metals with an intermediate layer of AI,O,.

Palladium-Copper Catalyst for Ether Preparation I'HII.I.IPS PETROI.EUM co. U.S. Patent 4,299,998 Ethers may be prepared from olefins and alcohols under relatively mild conditions when a catalyst containing l'd, Cu, a Group IA or IIA metal halide and optionally a surfactant component is used.

Catalytic Cracking SI'AN1)AKI) 011. C0. :IKlXANA: U.S. Pafent4,300, 997 Small amounts of Pd and Ru, in a I'd : Ru ratio of 0.1 : I to 1 0 : I , enhance the combustion of CO within the regeneration zone of a catalytic cracking unit without causing excess formation of NO, The Pd-Ru promoter also enhances the capture of SO, by suitable absorbents within the regeneration zone.

Methanation Process

A catalyst for producing fuel gas from synthetic or natural hydrocarbon feedstocks consists of an inters- persed mixture of Group IVB, VB or VIB metals in combination with Group VIII metals supported on an inorganic oxide carrier having specified pore and volume characteristics. A preferred catalyst contains Pt, Ni and Cr.

Photocatalytic Decarboxylation of Saturated Carboxylic Acids IrwIiKsrrY OF m x A s US. Patent 4,303,486 The heterogeneous photocatalytic decarboxylation of saturated carboxylic acids on to various n-type semiconductor powders may be carried out using platinised anatase catalysts.

Diesel Exhaust Purification Catalyst W. K. GKiKE & CO. U.S. Patent 4,303,552 A catalyst is formed from a mixture of A1,0,- or Zr0,-supported Pt or I'd and/or Cr oxide together with a bulk material of Ag a n d o r Hf which effectively catalyses the combustion of C particles.

Platinum Catalysts for Boiler Gas Exhaust Treatment

(XION 011. CO. OF CALIFORNIA U.S. Patenr 4,302,2 19

U S . Parent 4,303,625 Steam boiler exhausts are used to maintain the gas volume in an oil reservoir but there is a need to remove corrosive materials present in the exhausts. This is now accomplished by means of a Group VIII metal, especially a I't catalyst, supported on a low acidity Ai,O, base.

Conversion of Butane to Petrol I'.O.l'. Is(;. U S . Parent 4,304,948 A multi-step hydrocarbon conversion process for producing petroleum fractions from butane includes dehydrogenation of the butane over Pt and/or Pd.

Nonacidic Multimetallic Dehydrogenation Catalyst

U S . Patent 4,304,950 Cl.O.1'. ISC. An active, selective, stable catalyst for hydrocarbon dehydrogenation contains 0.0 1-27; of a platinum group metal-Pt, Ir, Kh or l'd; 0.05-5% Co; 0.01-5\F . la and o.r-g% of a Group IA or IIA metal.

Stabilised Platinum-Rhenium Reforming Catalyst A I'I.ANTIC RICHI:II:I.D co. U.S. Parents 4,305~8 IO/I

The thermal stability of halided Pt-Re catalysts is improved by using an A1,0, support which has been prepared from at least 7 5 % boehmite having an average crystallite diameter no more than 60A. The thermal stability may be further improved by adding a low-Na colloidal Si0, dispersion to a mull of AI,O, prior to its extrusion and calcination,


EXXON RESEARCH & ENGINEERING CO.

Preparation of Acetaldehyde INI~ITSTRIES U.S. Patent 4,306,091

The addition of small amounts of Ru to a catalyst system having a low Co content considerably improves the selectivity and production rates for the preparation of acetaldehyde by the carbonylation of methanol.

Turbocharged I.C. Engines IOHSSOK MAITHEY& CO. 1,TD. French App,pl. 2,479,323 The exhaust from turbocharged engines contains particles of hydrocarbons, C and other solids. These are now eliminated by catalytic oxidation in a special chamber. In one example a 94.3Pt-5.796Kh catalyst layer is deposited on washcoated stainless steel wire.

Platinum Metal Hydrocarhon Conversion Catalysts S l'lr. FK.4SCAISE DI!S I'KOIX'I'I'S I'OIJR Cr27'AI.YSIi

French App2. 4 4 8 I , I 44 Catalysts which may be used In severe conditions contain 0.05-0.6'C of a platinum group metal (Pt or Ir); 0.05-57 Bi; o.oog-5r'r of Zn and/or Pb; and 0.1-1 5 7 , of a halogen component.

Propylene Hydroformylation H A S P .4G. German Offen. 3, I o2,28 I

In a combined process of improved efficiency, effluent gases from the high-pressure hydroformylation of propylene in the presence of a Co catalyst are reacted further at a lower pressure in the presence of a Kh catalyst.

Platinum Group Metal and Base Metal Catalysts-Lead Tolerant JOHNSOX .WA'I-l'HEY & CO. 1.7'1).

German Offen. 3,108,922 An oxidation catalyst for exhaust gas treatment consists of one or more platinum group metals and a base metal component deposited on a surface coated with a refractory oxide, for examplc an Al,O,-coated ceramic or metallic monolith. Suitable base metal components are SnO,, WO,, Ti02 a n d o r NiMoO,. The catalyst has improved poison resistance.

HOMOGENEOUS CATALYSIS Ethylene Glycol Continuous Production I'NIOK C A R B I D E COKI'. European Appl. 48,980 Glycol and ethanol are produced from H, and CO in a continuous process using a solubilised Ku carbonyl catalyst, such as Ru acetylacetonate reacted with CO.

Selective Ethanol and Methanol Production from Synthesis Gas I'NION CARBIDE C O K P . US. Patent 4,30 I ,253 A homogeneous Ru catalyst used in conjunction with a halogen promoter and an organic phosphine oxide compound is used for the synthesis of ethanol and methanol from svnthesis gas under mild conditions.

Platinum-Catalysed Organosilicon Conductive Polymers r o s F i m A SII,K:OX~! co. 1;m. US. Purenr 4,303,572 Poor curing rates obtained from silicone elastomer compositions containing W or Ag conductive particles are ovcrcomc by using a I't catalyst such as Pt[P(OPhj,], Pt[P(OBu),], and Pt(PPh,l,.

Ruthenium Carhonyl 0x0 Catalyst IXIYIKSI'IT OF TEXAS U S . Patenr 4,306,084 A method for producing specific isomers of the next higher normal alcohol from the reaction of an olefin in an 0x0 process uses a Ku carbonyl catalyst, especially KL(CO'i,, .

ARS Polymer Hydrogenation JOHNSON .Mt\I"IHEY & CO. 1.1'1).

German Offen. 3,107,084 The hydrogenation of an unsaturated organic material by contact with gaseous or dissolved H, is enhanced by using the material in the form of an emulsion. Suitable catalysts are Rh-phosphine arsine or stibine complexes, for example (Ph,P),RhCI. Using this method the susceptibility of certain polymers to oxidative degradation is contained.

FUEL CELLS Fuel Cell Electrocatalyst III'I'ACHI 1.7 13. European Appl. 4 7,3 2 2

A 'Kaney type' method is used to produce fine metal particles having a large surface area, especially Pt black particles, suhable for use in fuel cell electrodes, for example. A solution containing Pt (or the other metal required) and at least one other metal ion, with redox potential different to Pt, is reduced and the second metal is removed from the particles by elution. The second metal may be I'd.

Gas Diffusion Electrode AbAtiI GLASS CO. LTD. US. Parent 4,299,682 A gas diffusion-electrode, for use in brine electrolysis and in the oxidiser side of a fuel cell having high performance, has a porous layer prepared by sinter- ing a mixture ofcatalysts, especially 1'1, I'd and Kaney Ag, hydrophobic material, filler and, as a pore forming agent, a Ni, Co or Fe carboxylate salt.


CATHODIC PROTECTION Two Piece Electrical Connector for Cathodic Protection Systems IMI MARS'I'ON I. 1'11. Brirish Patenr 2,001,807 B Connector systems which may be connected and disconnected under salt water are made of Nb or another valve metal and have their contact surfaces coated with a platinum group metal or platinum group metal oxide. 'l'he two parts may be joined by screw threading or by bolting together spade por- tions. 'l'hc connectors arc used for oil rigs.

GLASS TECHNOLOGY Glass Fibre Bushing OWENS-CORNING FIBEKGLAS CORP.

U S . Patent 4,303,429 The base plate of the bushing is made from a porous material, such as sintered Pt-Rh powder, diffusion bonded Pt-Rh wire cloth or foamed Pt-Rh alloy. It has elongated rods, also of Pt-Rh alloy, projecting downwards from the base plate, to prevent flooding beneath the base plate.

ELECTRICAL AND ELECTRONIC ENGINEERING Resistive Material and Electrocatalyst EXXON RESEARCH & ENGINEERING CO.

European Appls. 46,05314 New pyrochlore materials for use in electrical and electronic circuits have the composition A J B 2 - ~ J 0 7 - v , where A is Pb and/or Bi, B is Ru and/or Ir, and.x and y are up to 1.0. Ru and Pb are a preferred combination. In European Appl. 46,054 A may be T1 for electrocatalysts in organic oxidation.

Metal Silicide Film on Silicon I.H.M. ~ECISCHLANU tim.b.H. European Appl. 4899 I A mask for an electron or X-ray beam has an opening of pyramidal shape made in a flat Si body and a coating of metal silicide. The metal may be Ir, Pt or Pd, for example.

Bismuth Strontium Rhodate Resistance Material us. PH~LIPS cow. US. Patent 4,301,042 Bi,Sr,-,Rh r.50S-F.5 resistance materials, where x is 0-0.5, may be used together with a glass frit binder and a temporary binder to produce positive TCR resistances having short firing times.

Fabrication of Emitter Regions Integrated Circuits INTERNATIONAL BUSINESS MACHINES CORP.

US. Patent 4,301

of

,588 Ion implantation via a sputtered amorphous Si buffer layer allows precise shallow emitter regions to be obtained. The depth of the n-type region is thinned to a single crystal surface by consuming the polysilicon partly through oxidation and partly by conversion to Pt silicide contacts.

Stable, Pyrochlore Resistor Materials E. 1. DI: PONT IIE NEMOIJKS & CO.

U S . Patent 4,302,362 Stable thick film resistor compositions contain 20-75 parts of a pyrochlore having the formula (M$i2-J (M'$I''Z_J07-z, where M is Y, Th, In, Cd, Pb, Cu andor a'lanthanide metal, M' is Pt, Rh, Ti, Cr and/or Sb, and M" is Ru and/or Ir. Preferred compositions are Bi$u20, and Pb,Ru,O,.

Platinum Metals Rev., 1982,26, ( 3 )

Ruthenium-Tipped Reed Contacts BELL TELEPHONE LABORATORIES INC.

U.S. Patent 4,307,360 Ru coatings (0.5- 1.5pm thickj on Cu reed contacts have reduced erosion and sticking failure.

TEMPERATURE MEASUREMENT Thermocouple Cold Junction 9. GREGSON British Appl. 2,082,774 A A network having a number of temperature sensitive elements, such as Pt resistors, is used to simulate the cold junction output of a thermocouple, which may be Pt : Pt-Rh or a base metal couple.

Resistance Thermometer L1NI)E A.G. German Offen. 3,022,942 A thermometer of improved design for measuring temperatures up to 400K includes elements of C and spectrally pure Pt.

MEDICAL USES

Tobacco Composition Including Palladium LIGGE'IT G R O W INC. British Appl. 2,082,438 A An aqueous solution of a Pd compound is mixed with a reducing agent to deposit highly active Pd on tobacco products. Sugars are the preferred reducing agents. The Pd reduces the biological activity of the tobacco smoke.

Vinyl Silicone Mass for Tooth Moulding HAYER A.G. European Appl. 46,907 Pd or a Pd alloy is deposited on a zeolite and added to a catalysed and filled vinyl silicone paste for moulding teeth in order to absorb any H, generated. The curing catalyst itself may contain a Pt complex.

Metal Chelate Anticancer and Dye Compounds AMERICAN CYANAMID co. U.S. Patent 4,296,030 Pt and other transition metal chelates of symmetrical bis(substituted amino)dihydroxy-anthraquinones possess anti-tumour activity.

Perfusate Redox Potential Controller S?'. LOUIS UNIVERSITY U.S. Patent 4,299,919 Pt electrodes and Ag/AgCl reference electrodes are used in a redox controller fitted in an apparatus which preserves human organs for transplantation.

Platinum Complex for Cancer Treatment SANOFI French Appl. 2,481,289 A complex of improved water-solubility, for the treatment of tumours, is cis-isocitrato( I ,z-diamino- cyc1ohexanc)platinum.

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