us 2005o112o18a1 (19) united states (12) patent application … · 2017-09-30 · (5 g c o c 92 ....

(19) United States US 2005O112O18A1

(12) Patent Application Publication (10) Pub. No.: US 2005/0112018A1 Schulz et al. (43) Pub. Date: May 26, 2005

(54) CA-MG-NI CONTAINING ALLOYS, METHOD FOR PREPARING THE SAME AND USE THEREOF FOR GAS PHASE HYDROGEN STORAGE

(75) Inventors: Robert Schulz, Ste Julie (CA); Guoxian Liang, Longueuil (CA)

Correspondence Address: HAYNES AND BOONE, LLP 901 MAIN STREET, SUITE 3100 DALLAS, TX 75202 (US)

(73) Assignee: HERA, Hydrogen Storage Systems, Inc., Longueuil (CA)

(21) Appl. No.: 10/926,578

(22) Filed: Aug. 26, 2004

Related U.S. Application Data

(63) Continuation-in-part of application No. PCT/CAO3/ O0058, filed on Jan. 17, 2003.

(60) Provisional application No. 60/497.554, filed on Aug. 26, 2003.

(30) Foreign Application Priority Data

Feb. 27, 2002 (CA)................................... CA 2,373,553

Publication Classification

(51) Int. CI.7. (52) U.S. Cl. ............................................

- - - - - - - - C22C 19/03

420/.455; 420/900

(57) ABSTRACT

Disclosed are new Ca, Mg and Ni-containing alloys of the general formula:

(Ca,Mg,Me) (NiZT,)a where:

M is at least one metal Selected from the group consisting of Y, Ce, La, Pr, Nd, Th, Nd, Ti, V, Zr, Ta, Hf, Sr., Ba and Misch metals;

T is at least one element Selected from the group consist ing of Al, Zn, Cu, Fe, Co, Mn, Cr, Mo, W, Si, Ga, Ge, In, Sn, Ag, C and B;

a is an integer equal to 2 or 5, Z is a number ranging from 0 to 0.5, and when a is equal to 2, then 0.9sbs 1.1; and when a is equal to 5, then either 1.75s bs 2.25 or

O.75sbs. 131.

These alloys which are of the AB, ABs or ABs types, may be single phase or multiphase and are useful for reversibly absorbing hydrogen from a gas phase. Also disclosed is a method for preparing the above alloys.

Mg125Cao.62s Mmo.12sNi487sSiolis, after the first hydrogen desorptio

SliggSO&4&nningSOOSEU)Si282002 Goul? after 400 cycles

SAFO 44th:500SEU)Si2002 . 300

Patent Application Publication May 26, 2005 Sheet 1 of 65 US 2005/0112018A1

Fig. I-1

Cao.4Mgo.6Ni, -Ni

0 CaNi, type

20 30 40 50 60 70 80

Two theta ()


Fig.I-2

20 30 40 50 60 70 80

Two theta ()


Fig.1-3

Cao.3Mgo.7Ni2

20 30 40 50 60 70 8O

Two theta ()

Patent Application Publication May 26, 2005 Sheet 4 of 65 US 2005/0112018 A1

Fig.I-4

After 1 h annealing at 1000C

20 30 40 50 6O 70 8O

Two theta ()


Fig.I-5

100

10

0,1 0,0 0,3 0,6 0,9 12 15

Hydrogen content, wt.%


Fig.I-6

Zn substitution on the B site

Cao.4Mgo.6Ni197no1

Cao.4Mgo.6Ni2

Cao.4MgosMmo.Niz

Mm Substitution on the A

20 30 40 50 60 70 8O

Two theta ()


Fig.I-7

Cao.3Mgo.NisC lo.2

O (Ni,Fe)

Cao.3Mgo.7NisFe0.2 O

Cao.2Mgo.7Mmo. Ni

Cao.3Mgo.Ni,

20 30 40 50 60 70 80

Two theta ()


Fig.I-8

100

(Cao.4-Mgo.6-yMmy)Ni2

10 S

. (5

g C O

c 92 . n- 1 -KX- Mg,CaMmoNi

-V-Mg,CaMmosNi -A- Mgo Cao Ni -O-MgCaoni -O-MgCaMm,Ni

0,1 O,O 0,2 0,4 0,6 O,8 1.0 . 12 14 1,6



Fig.I-9

100

1 O Mg,CaMmoNi, MgoCaMnoni,

Absorption Mg,CaMmoNi,

Desorption Mgo Cao MmooNi,

O O Mg-Ca-Ni O Mg-Ca-Mm-Ni

1

O, 1

O,O1 6,88 6,90 6,92 6,94. 6,96 6,98 7,00

Lattice parameter, X10 nm


Fig. 2-1

(Cao.4Mgo.6)2Nis Mg/Ca ratio= 1.5

20 30 40 50 60

Two theta ()


Fig. 2-2

(Cao.4Mgo.6)b Nis

AB3 A/B = b/5 = 0.35

5 E AB2+A2B5 A/B = b/5 = 0.45

A/B = b/5 = 0.5

20 30 40 50 60 70 80

TWOtheta ()


Fig. 2-3

Mg/Ca ratio=1.67

20 3O 40 50 60 70 80

Two theta ().


Fig. 2-4

100

(Cao.37sMgo.625)Nis

10 (VS O

g -o-as-milled

CD - -d- 600°C ?h- 1 o

-A- 800C

----. 900C

-X-1000°C

-Sk- 1045°C

O,O O,3 0,6 O,9 12 15



Fig. 2-5

100

(Cao.37sMgo.625)2Nis Milled for 20h and annealed at 1000C

10

0,1 O,O 0.2 0,4 O,6 O,8 10 12 14 1,6

- Hydrogen content, wt.%


Fig. 2-6

(Cao.35Mgo.625)2Nis

Mg/Ca = 1.67 (Cao.37sMgo.625)2Nis

(Cao.4Mgo.6);Nis

Mg/Ca = 1.2 g (Cao.46Mgoss)2Nis

20 30 40 50 60 70 80

Two theta ()


Fig. 2-7

100

Mg/Ca = 1.5

Mg/Ca = 1.67

Mg/Ca = 1.79 0,1 --

O,O 0.2 0,4 O,6 O,8 1,0 12 14 1,6 1,8 Hydrogen Content, wt.%


Fig. 2-8 - Substitution on the A site

(Cao.375-Mgo. 62.5M.m)2.N.is (Cao.37sMgosMmolas);Nis

(CaosMgo.37sMmolis).Nis S. 2 (Cao.25Mgo.625Mmo.125);Nis 2 9. C

(Cao.3125Mgo.625Mmo.0625);Nis

(Cao.37sMgo.62s);Nis

20 30 40 50 60 70 80

Two theta ()


Fig. 2-9

100

(Cao.375-Mgo. 625-Mn)2Nis

0,1 0,0 0,3 0,6 0.9 12 1,5 18

Hydrogen Content, wt.%


Fig. 2-10

(CaosMgo.37sMmo.125)2Nish

(CaosMgo.37sMmo.12s)2Nis

20 40 60 80

Two theta ()


Fig. 2-11 - Substitution on the B site

(Cao.37sMgo.62s);Nis x MgNigCo.75 + 2 wt.% carbon

(Cao.37sMgo.62s);Nis

(C a037.svgo.62s)2(Nio.95Alo,05)s O

0.

20 30 40 50 60 70 80

Two theta ()


Fig. 2-12

100

10

0,1 0.0 0,3 0.6 0.9 12

Hydrogen Content, wt.%

(4) is (cous" a

(b) S (Coe 31s Mesa: (Noas (voes)s S. Z

C-Y Q ? P C S (Ca, Mg), N + 2.12 can

0/09 .OG

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5 0.4944 d O) S S c Crs s O,396 Ol 9

g 0.4936 3 - -

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Fig. 3-3

0,0 0.2 0,4 0,6 0.8 1.0 12 14 1,6



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After milling

s

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2O 30 40 50 60 70 80

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Fig. 3-4b

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c N/

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Fig. 3-5a

2O 3O 40 50 60 70 80

Two theta ()

20 3O 40 50 6O 7O 8O

Two theta ()


Fig. 3-6

(Mimo.333Cao.417Mgo.2s)12Nis

(Mino.333CaosMgol67)1.2Nis

(Mmo.4CaosNis

20 30 40 50 60 70 80

Two theta ()


Fig. 3-7

(Mino.44Caoss)osNis

(Mino Cao)Nis

2O 30 40 50 60 70 80

Two theta ()


Fig. 3-8

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A. -o- (Mmo,Ca)Nis 1 -v- (MmossCaoes), Nis

-a- (MimossCaosMgos), Nis -O-(Mimocao,Mgoas), Nis -+- (MnoCa osse)osNis

O,O O,2 0,4 O,6 0.8 1.0 1,2 14 1,6 Hydrogen content, wt.%


Fig. 3-9a

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9. 2S (Mm 0.38s Cao.assMgo.3)1.3Nis c und e

(Mm 0.357 Cao.4.29M go.214) 14N is

(Mm 0.38sCao.61s).3 Nis

2O 3O 40 5O 60 70 8O

Two theta ()

Fig. 3-9b

O,O O,2 O,4 O,6 o,8 1,O 12 14 16 Hydrogen content, wt.%


Fig. 3-10a

(Mino.167Cao.583Mgo.2s)Nis

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a. (Mino.174Cao.696Mgo.13)Nis

(Mimo.2 Cao.8)Nis

2O 3O 40 50 60 70 80

Fig. 3-10b Two theta (o)

1 OO

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g s

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0,0 O,2 O,4 O,6 0,8 1,0 12 14 1,6 Hydrogen content, wt.%


Fig. 3

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E V V MmCa,Mg,Nis 10

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US 2005/011 2018 A1

CA-MG-N CONTAINING ALLOYS, METHOD FOR PREPARING THE SAME AND USE THEREOF FOR

GAS PHASE HYDROGEN STORAGE

FIELD OF THE INVENTION

0001. The present invention is directed to Ca, Mg and Ni-containing alloys. It is also directed to a method for preparing these alloys and to their use for reversibly absorb ing hydrogen from a gas phase.

BACKGROUND OF THE INVENTION

0002 The use of hydrogen gas as a fuel for PEM fuel cells has received considerable attention in recent years because PEM fuel cells using pure hydrogen can provide high efficiency and ultra clean power. Unfortunately, wide Spread use of hydrogen energy is not currently feasible because of economic and technological barriers. One of the important barriers is the lack of cost effective, Safe hydrogen Storage method. 0.003 Hydrogen gas is very light. It can be compressed under high pressure and Stored in pressurized vessels. It can also be liquefied and Stored in liquid form. Hydrogen also reacts with metal or non-metals to form hydrides. Some metal hydrides called “low temperature metal hydrides” are reversible at ambient temperature and pressure. The Volu metric density of hydrogen Storage in metal hydrides is usually high. 0004. The most serious shortcomings of the reversible metal hydrides and more particularly the low temperature metal hydrides are their low gravimetric Storage density and the high cost. For Stationary and Some mobile applications, the weight of the hydrogen Storage tank is not a problem. However, the high cost of conventional low temperature metal hydrides results in too expensive Storage devices. 0005 Amongst the known hydrogen storage materials, conventional lanthanum or mischmetal-based alloys of the AB, type like LaNis alloys are inherently expensive because they make use of a rare earth metal. CaNis is isomorphic to LaNis and has higher Storage capacity than that of LaNis based hydrides. In the Ca-Ni system, there are four stable compounds, CaNi, CaNis, Ca-Ni, and CaNis, but only the CaNis has been considered to be of practical interest Since the plateau pressures of CaNis are adequate for applications. The other three compounds do form very stable hydrides. However, hydrogen can not be extracted at temperatures below 100° C. under normal pressure. 0006 In a paper published in 1980 (and identified Ain the attached list of references), Osterreicher et al disclosed a Ca,MgosNia alloy prepared by liquid phase sintering in a Ta tube. They also disclosed that Such a Caos MgosNialloy can absorb hydrogen to form Caos MgosNiHe at 300 K (corresponding to 1.7 wt.%). However, this hydride can only desorbs partially (half of the amount absorbed) at 400 K and 1 bar. The desorption isotherm is strongly sloped. According to these authors, the low reversibility of this alloy limits practical applications. However, this publication teaches that substitution of Ca by Mg in CaNi is possible. The alloys of the type CaMg-Ni, are predominantly of CaNi, structure (C15 type) when x is larger or equal to 0.5. 0007. In a recent paper (B) Terashita et al. disclosed a CaMg,Ni System. Moreover, they presented results of tests made on a Caos-Mgo.g., Ni, alloy prepared by high frequency induction melting. Once again, the plateau pres Sure of this alloy CaMg,Ni is still too low for most

May 26, 2005

hydrogen Storage applications and it is impossible to raise the plateau pressure by Substituting more Mg for Causing the induction melt casting method because the MgNi phase precipitates. That phase is known for not absorbing hydro gen and consequently the properties deteriorate. 0008 Since Ca and Mg have very high evaporation rate,

it is very hard to produce a stoichiometric Ca-Mg-Ni alloy in large quantity. For example, if use is made of a melt casting method, the Mg and Ca alloy in liquid form has to be protected by argon or SF because of the rapid oxidization and possible explosion. The composition has to be adjusted by trial and error due to evaporation loss of Mg and Ca. The So-cast alloys usually have very high macro-Segregation and micro-Segregation. Homogenization by long annealing treat ments is required but adds costs to the alloys. In paper A, the Ca-Mg-Ni alloys were synthesized by liquid phase sin tering in closed Ta tubes Starting from elemental Mg, Ca and Ni at a temperature below 1250 C. Such a method also needs high temperature and long Sintering time to reach complete reaction. 0009 Mg-Ca-Nialloys of the AB type have also been Synthesized by a powder Sintering method. In a recent publication (C), Kadir et al disclosed a CaMg2Nio ternary alloy prepared by Sintering fine powder mixtures of MgNi and CaNis. This paper States that the Sintering process involved raising the temperature stepwise to 600 C., 850 C. and 990° C. (in 0.6 MPa Argas), with set temperature holds for 2-3 h. Several attempts were necessary until an optimum composition was found. A slight excess of CaNis over the stoichiometric composition was necessary in order to compensate for the evaporative loSS of Ca. 0010 Mg and Ca are known to react with all type of ceramic crucible at elevated temperatures and Ni is known to react with refractive metals at high temperatures. There fore, all the Sintering of alloys containing Mg, Ca and Ni were performed so far in Mo or Ta crucible, especially when long Sintering times were needed. In practice, this means that the use of this technology would be expensive.

SUMMARY OF THE INVENTION

0011. The present invention as claimed hereinafter relates to new Ca, Mg, and Ni-containing alloys of the general formula:

0012) 0013 M is at least one metal selected from the group consisting of Y, Ce, La, Pr, Nd, Th, Nd, Ti, V, Zr, Ta, Hf, Sr., Ba and mischmetals;

where:

0014 T is at least one element selected from the group consisting of Al, Zn, Cu, Fe, Co, Mn, Cr, Mo, W, Si, Ga., Ge, In, Sn, Ag, C and B;

0015 0016

a is an integer equal to 2 or 5 Z is a number ranging from 0 to 0.5, and

0017 when a is equal to 2, then b, c, d, e are numbers Selected So that:

0018 0.9sbs 1.1 0019 c=0.4-x, 0020) d=0.6-y, and 0021 e=x+y, with

US 2005/011 2018 A1

0022 -0.4<ys 0.5 0023 -0.5s x<0.4, and 0024 x+y>0; 0025 when a is equal to 5, then b, c, d, e, are numbers Selected So that either

0026) 1.75s bs 2.25 0027 c=0.4-X, 0028) d=0.6-y, and 0029 e=x+y, with 0030) -0.4s xs 0.2, 0031) -0.2sys 0.4, and 0032) x+y20 0033) or 0.75sbs 1.31, 0034) c=0.6-y, 0035) d=x+y, and 0036) e=0.4-X, with 0037 -0.6-x-0.4, 0038 -0.4<y<0.6, and 0039) 0<x+ys 0.5

0040. When a is equal to 2, the alloys according to the invention can be said to be of the AB type. 0041 When a is equal to 5 and b is ranging between 1.75 and 2.25, the alloys according to the invention can be said to be of the ABs type. In one embodiment, Such ABs alloy is one where M is a mischmetal and where T is at least one element Selected from the group consisting of Si, Ga, and Ge.

0042. When a is equal to 5 and b is ranging between 0.75 and 1.31, the alloys according to the invention can be said to be of the ABs type. In one embodiment, such ABs alloy is one where M is a mischmetal and where T is at least one element Selected from the group consisting of Si, Ga, and Ge.

0043. In all cases, the alloys may be single phase or multiphase.

0044) The invention also relates to a method for prepar ing the above mentioned alloys, comprising the Steps of: milling a mixture of elemental powders and/or pre-alloyed combination of elemental powders of Ca, Mg, M, Ni and T annealing and/or Sintering the milled mixture at a tempera ture higher than 600 C. In another embodiment, the tem perature is higher than 800 C. 004.5 The invention further relates to the use of the above-mentioned alloys for reversibly absorbing hydrogen from a gas phase. In this respect, the above-mentioned alloys are capable of being hydrogenated and dehydrogenated. Hydrogenation is the proceSS whereby hydrogen is absorbed by the hydrogen Storage composition. Hydrogenation is not intended to indicate that complete hydrogenation of the hydrogen Storage composition has necessarily occurred, and contemplates both a complete hydrogenation and a partial hydrogenation resulting from the absorption of hydrogen by the hydrogen Storage composition. Similarly, dehydrogena

May 26, 2005

tion is not intended to indicate that complete dehydrogena tion has necessarily occurred, and contemplates both a complete dehydrogenation and a partial dehydrogenation resulting from the desorption of at least a part of the hydrogen content of the hydrogen Storage composition. Absorption of hydrogen by the metallic Substance refers to the association of hydrogen with a metallic Substance. Also mechanisms for association include dissolution, covalent bonding, or ionic bonding. Dissolution describes a proceSS where hydrogen atoms is incorporated in the Voids of a lattice Structure of a metal or intermetallic alloy. 0046) To this end, the present invention provides a pro ceSS of hydrogenating and dehydrogenating the above-men tioned alloys comprising the Steps of effecting absorption of hydrogen by the Subject alloy and effecting desorption of the Subject alloy, wherein the absorption and desorption Steps are carried out in any order. 0047 The invention and its advantages will be better understood upon reading the following non-restrictive description and examples made with reference to the accom panying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

0048. With Respect to the Alloys of the AB. Type: 0049 FIG. 1-1 shows the XRD (x-ray diffraction) spec tra of a Sample of composition CaMg,Ni made by milling a powder mixture of Ca, Mg and Ni powders as a function of milling time; 0050 FIG. 1-2 shows the XRD spectra of a series of CaMg,Ni, samples for x=0, 0.2, 0.4, 0.5, 0.7 and 1 obtained after 20 h of milling; 0051 FIG. 1-3 shows the XRD spectra of a mechanically alloyed CaMg,Ni Sample annealed for 1 hour at differ ent temperature 600° C., 800° C. and 1000° C.; 0.052 FIG. 1-4 shows the XRD spectra of mechanically alloyed CaMg,Ni for x=0,0.2,0.3, 0.4 and 0.8 after 1 h annealing at 1000 C.; 0.053 FIG. 1-5 shows PCT (pressure-concentration iso therm) of CaMg,Ni alloys measured at 30° C.; 0054 FIG. 1-6 shows the XRD spectra of Zn (on the B Site) and Mm (on the A site) Substituted CaMg,Ni alloy after annealing at 1000 C. for 1 h; 0.055 FIG. 1-7 shows the XRD spectra of Cu and Fe (on the B site) and Mm (on the A site) Substituted CaMg,Ni alloy after annealing at 1000 C. for 1 h;

(0056 FIG. 1-8 shows the PCT of various (Ca,Mgo. yMm)Ni Substituted alloys; and 0057 FIG. 1-9 shows the position of the plateau pres Sures versus the lattice parameters for various CaMg,Ni alloys and (Ca,Mg,Mn)Ni. The substitution of Ca by Mm does not change much the lattice parameter but increases significantly the plateau preSSures. 0.058 With Respect to the Alloys of the AB. Type: 0059 FIG. 2-1 shows the XRD spectra of (Ca,Mgo)-Nis after ball milling for various durations (i.e. starting with a mixture of intermetallics and elemental powders).

US 2005/011 2018 A1

0060 FIG. 2-2 shows the XRD spectra of (Ca,Mgo), Nis for various A/B=b/5 ratios after annealing at 1000° C.; 0061 FIG. 2-3 shows the XRD Spectra of p

( a,Mgo.62s).Nis made by by milling elemental powder of Ca, Mg, and Ni and annealed 1 h at various temperature; 0062 FIG. 2-4 shows the PCT curves measured at 30° C. of (Caozs Mgos) Nils annealed at various temperatures, 0063 FIG. 2-5 shows the PCT curves of (Ca,Mgo.62s).Nis annealed at 1000 C. and measured at various temperatures,

0064 FIG. 2-6 shows the XRD spectra of various (CaMg.).Nis with various Mg/Ca ratios; 0065 FIG. 2-7 shows the PCT curves measured at 30° C. of the various samples shown in FIG. 2-5; 0.066 FIG. 2-8 shows the XRD spectra of various Mm Substituted (Caos:7s-Mgo.62s-Mm).Nis alloys with vari ous Mm Substitutions on the A site;

0067 FIG. 2-9 shows the PCT curves of the various substituted alloys shown in FIG. 2-8; 0068 FIG. 2-10 shows the XRD (Ca,Mgo.37s Mmolas).Nis and its hydride; 0069 FIG. 2-11 shows the XRD spectra of various ABs type alloys with Substitution on the B site; 0070 FIG. 2-12 shows the PCT curves of various sub stituted alloys shown in FIG. 2-11; 0071 FIG. 2-13 illustrates the XRD spectra of various Mm-substituted alloys; 0072 FIG. 2-14 illustrates the PCT curve of Example 2-14 Mm-Substitutions;

0073 FIG. 2-15 illustrates the PCT curves of one of the Mm-substituted alloys of example 2-14, after cycles of hydrogen absorption/desorption;

0.074 FIG. 2-16 illustrates a comparison between the cycling stability of a non-substituted alloy and Mm-substi tuted alloy of example 2-14 and; 0075 FIG. 2-17 illustrates the XRD spectra of an Mm Substituted alloy of example 2-14, before and after cycling, 0076 FIG. 2-18 illustrates a typical PCT curve for pur poses of demonstrating calculation of maximum hydrogen Storage capacity, reversible hydrogen Storage capacity and hysteresis,

0077 FIG. 2-19 illustrates the XRD spectra of an alloy of example 2-15, Substituted on the B-site by Si; 0078 FIG. 2-20 illustrates PCT curves of the alloy of example 2-15 (see FIG. 2-19); 007.9 FIG. 2-21 illustrates an XRD spectra of an alloy of example 2-16, Substituted on the B-site by Ga; 0080 FIG. 2-22 illustrates a PCT curves of the alloy of example 2-16 (see FIG. 2-21); 0081 FIG.2-23 to FIG.2-25 illustrates the XRD spectra of the various alloys of example 2-17, Substituted on the B-site by Si;

Spectra of

May 26, 2005

0082 FIG. 2-26 to FIG.2-28 illustrates the correspond ing PCT curves of various alloys of example 2-17 (see FIGS. 2-23 to FIG. 2-25); 0.083 FIG. 2-29 illustrates the maximum and reversible Storage capacities for Mg1.2s Cao.625 Mmo.12s NiszsSio.12s and Mg12sCao. 62.5Mmo.12sNis. 0084 FIG. 2-30 illustrates an SEM photograph of par ticles of an alloy composition of example 2-17, before and after 400 hydrogen absorption/desorption cycles,

0085 FIG. 2-31 illustrates the XRD curve for Mg, Cao.625 Mmo.12sNi487s Geo.12s after various cycles; 0.086 FIG. 2-32 illustrates the PCT curves for Mg, Cao.625 Mmo.12sNi487s Geo.12s after various cycles; 0087 FIG. 2-33 illustrates the PCT curves for each of Mg, Cao.62s Mino.12sNis7sGeo.12s and Mg1.25 Cao.265Mmo.12sNia.75Geo.2s; 0088 FIG. 2-34 illustrates the maximum hydrogen stor age capacity as a function of degree of Si and Ge Substitu tion; 0089 FIG. 2-35 illustrates the hydrogen desorption curve of the alloy of FIG. 2-15; 0090 FIG. 2-36 illustrates the normalized maximum and reversible Storage capacity as a function of Si content, for example 2-17, 0091 FIG. 2-37 illustrates first hydrogen absorption kinetics for Mgos Caos Mimoos Ni-Si, for example 2-17, 0092 FIG. 2-38 illustrates the PCT curves of Mg, Cao.62s Mmolas Nis-Si alloys with different Si con tent; and

0093 FIG. 2-39 illustrates the XRD spectra of the Mg, Cao as Mmolas Nis-Si alloys shown in FIG. 2-38. 0094. With Respect to the Alloys of the AB. Type: 0.095 FIG. 3-1 shows the XRD spectra of CaMm-Nis alloys made by mechanical alloying followed by annealing. 0096 FIG. 3-2 shows the lattice parameters of the CaMm, Nis alloys shown in FIG. 3-1; 0097 FIG.3-3 shows representative PCT curves of some of the ternary CaMm-Ni alloys shown in FIG. 3-1; 0.098 FIG. 3-4akb show XRD spectra of ball milled Ca-Mg-Ni ternary alloys before and after annealing treatment and demonstrate that the solubility of Mg in CaNis is very low; 0099 FIG. 3-5a&b show XRD spectra of ball milled Mm-Mg-Ni ternary alloys before and after annealing treatment and demonstrate that the solubility of Mg in MmNi, is also very low; 0100 FIG. 3-6 shows XRD spectra of various mechani cally alloyed Mm-Ca-Mg-Ni quaternary alloys before annealing treatment;

0101 FIG. 3-7 shows XRD spectra of various mechani cally alloyed Mm-Ca-Mg-Ni quaternary alloys after annealing treatment; 0102 FIG. 3-8 shows the PCT curves of the quaternary alloys shown in FIG. 3-7;

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0103 FIG. 3-9a&b shows the XRD spectra of various Mm-rich quaternary Mm-Ca-Mg-Ni alloys (a) and the corresponding PCT curves (b); 0104 FIG. 3-10a&b show the XRD spectra of various Mm-poor quaternary Mm-Ca-Mg-Nialloys (a) and the corresponding PCT curves (b); 0105 FIG. 3-11 shows the relationship between the plateau pressure and the c/a parameter of various (Mm Ca-Mg), Nis alloys; 0106 FIG. 3-12 is a curve giving the hydrogen storage capacity of an alloy of formula (Caos Mimos). Nis as a function of the pressure after 3 cycles and 250 cycles; 0107 FIG. 3-13 is a curve similar to the one of FIG. 3-12, but with alloy of formula (Cao.6Mmoso). Nio Sio.1; 0108 FIG. 3-14 is a curve similar to the one of FIG. 3-12, but with alloy of formula (Cao.6Mmolas). Nias Sio2; 0109 FIG. 3-15 is a X-ray analysis of the alloy of formula (Cao Mimos). Nissio mentioned hereinabove (see FIG. 3-14); 0110 FIG. 3-16 is an X-ray analysis of the alloy of formula (Cao Mimos). Nis mentioned hereinabove (see FIG. 3-12); and 0111 FIG. 3-17 is a curve similar to the one of FIG. 3-12, but with alloy of formula (Cao.6Mmoso). NissGeo.1s.

DETAILED DESCRIPTION OF THE INVENTION

0112) 1. Alloys of the AB. Type 0113. In one aspect, the present invention provides an AB, type alloy according to the formula:

(Cao.4-xMgo.6-yMxy)b(Ni-T)2 0114 where

0115 M is at least one metal selected from the group consisting of Y, Ce, La, Pr, Nd, Th, Nd, Ti, V, Zr, Ta, Hf, Sr., Ba and mischmetals;

0116 T is at least one element selected from the group consisting of Al, Zn, Cu, Fe, Co, Mn, Cr, Mo, W, Si, Ga., Ge, In, Sn, Ag, C and B;

0117 0.9sbs 1.1, 0118 -0.5s xs0.4, 0119) -0.4<ys 0.5, 0120 x+y>0; and 0121 0szsO.5.

0122) Preferably: 0123 -0.1s Xs O.25; and 0124 -0.1 sys 0.15.

0.125. A suitable mischmetal is one of the composition 51 wt % Ce, 26.4 wt % La, 16.4 wt % Nd and 5.3 wt % Pr. A further suitable mischmetal is one of the composition 62 wit % La, 21 wt % Ce, 3 wt % Pr, and 14 wt % Nd. Many further

May 26, 2005

compositions are Suitable, and differ in the properties of the constituent elements La, Ce, Pr, and Nd. 0.126 These alloys are single or multiphase hydrogen Storage compounds of the AB type, which are capable of absorbing and desorbing hydrogen from a gas phase at ambient temperature with a flat plateau pressure and a Storage capacity larger than 1.2 wt %. 0127. These alloys may be prepared by a method com prising the following two steps. The first one consists of preparing a powder by milling a mixture of elemental powders and/or pre-alloyed combination of the elemental powders (ex.: Ca, Mg, Ni, Mm, CaNi, MgNi, MmNis, when M=Mm) in respective amounts selected to obtain the requested alloy. The milling can be a conventional ball milling or a more intensive mechanical alloying (by a high energy ball mill) that can be carried out at room temperature or at high temperatures with or without anti-Sticking agents and in various kinds of atmosphere. 0128. The second step consists of annealing and/or sin tering the milled powder at elevated temperatures in a crucible made of, for example, StainleSS Steel, for a short period of time in an inert or reactive atmosphere. This is an essential Step to achieve a high reversible absorption capac ity and a flat plateau. The annealing temperature should be higher than 800° C. but not higher than 1050° C. 0129. The invention is based on the discovery that the mechanical alloying of elemental powders (Such as powders of Ca, Mg, Ni) and/or of mixtures of intermetallic com pounds (Such as powders of CaNis, Mg,Ni) corresponding to the composition of the formula:

CaMg,Ni2.

0.130 leads to a nanocrystalline ternary intermetallic compound with the CaNi structure (C15-type) for x 20.3. This so-milled nanocrystalline alloy can reversibly absorb and desorb hydrogen at room temperature. However, the reversible absorption capacity is Small and the slope of the PCT curves is very big like in the case of conventional large-grain polycrystalline CaMg-Ni, alloys already reported in the art (see reference B). 0131 The invention is also based on the discovery that, when a thermal treatment of the present invention is applied to this mechanically alloyed powder, a Substantial improve ment in properties is achieved. Indeed, the hydrogen Storage properties of the mechanically alloyed Mg-Ca-Ni are Substantially improved by annealing the powder at tempera tures higher than 800° C. for short period of time, typically at 1000 C. or slightly higher, for 0.5 h to 1 h. Annealing at temperatures lower than 800° C. does not improve the hydrogen Storage properties very much.

0132) The ball milling time can vary from a few minutes to several hours. When the milling time is of about 10 hours, then a true alloy is formed between the components (see FIG. 1-1), i.e. a nanocrystalline ternary intermetallic com pound with the CaNi structure (C15-type). Thus, in that case, the ball milling Step is a mechanical alloying. Under these conditions, the post-thermal Step becomes an anneal ing treatment which could be as short as 0.5 to 1 hour as indicated above.

0133) On the other hand, when the ball milling step is only carried out for a few minutes, the powder particles are

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then only agglomerates of the various constituents. In that case, the post-thermal Step is a Sintering treatment which could take a few hours to produce the final alloy product. 0134) Further improvements to these alloys may be achieved by adding other elements to Ca,Mg, and Nior their combinations. Such an addition may raise the plateau pres Sure and improve hydrogen Storage properties Such as pla teau slope and the long-term Stability while keeping the AB (C15-type) structure as the main phase.

EXAMPLE 1-1

Compound According to the Prior Art Made by the Method According to the Invention

0135 CaMg,Ni (b=1, x=0.1, y=-0.1, z=0) was syn thesized in a SPEXOR high energy ball mill under the protection of argon. A Mg powder (>99%, +100 mesh), Ca granules (>99.5, -2 mm in size) and a Ni powder (<99.9%, -325 mesh) were used as starting materials. 0.136 Isothermal annealing was performed in a tubular furnace under the protection of argon. The mechanically alloyed powder was Sealed in a stainleSS Steel crucible before annealing. The powder was heated to 1000 C. at a heating rate of 30 C/min, and held at 1000 C. for 1 hour, then cooled down to room temperature in the furnace. 0.137 Hydrogen absorption/desorption properties were measured by using an automated Sievert's type apparatus. The annealed powder normally needs mild activation treat ment, such as heated to 200 C. under vacuum and then cooled down. EDX analysis shows that the Fe content in the end product less than 0.2 at. 76. The composition of the end product was close to the nominal composition. The activated alloy exhibited a relatively flat plateau and a high capacity.

EXAMPLE 1-2

Compound According to the Invention Made by the Method According to the Invention

0138 Caos Mg,MnosNi (x=0.25, y=-0.1, M=Mm, x+y=0.15, b=1, Z=0) was synthesized by mechanical alloy ing of elemental powder blends. The alloy was annealed in the same manner as in Example 1-1. This alloy had a hydrogen Storage capacity of 1.25 wt. 76. The plateau preSSure was drastically raised, and the plateau slope was much less than that of Cao. Mg,Ni of the Example 1-1

EXAMPLES 1-3 AND SUBSEQUENT

0.139. Other examples similar to Example 1-2 were car ried out. The results of these other examples are reported in the accompanying drawings (see FIGS. 1-1 to 1-9). 0140 2. Alloys of the AB. Type 0.141. In another aspect, the present invention provides an ABs type alloy according to the formula:

0142 where

0.143 M is at least one metal selected from the group consisting of Y, Ce, La, Pr, Nd, Th, Nd, Ti, V, Zr, Ta, Hf, Sr., Ba and mischmetals;

May 26, 2005

014.4 T is at least one element selected from the group consisting of Al, Zn, Cu, Fe, Co, Mn, Cr, Mo, W, Si, Ga., Ge, In, Sn, Ag, C and B;

0145) 1.75s bs 2.25, 0146 -0.4s Xs O.2, 0147 -0.2sys 0.4, 0148 x+y 20, and 0149 0szs0.5.

0150 Preferably:

0151 -0.1 sxs 0.1, and 0152 -0.1 sys 0.2.

0153. Preferably also, Mg and Ca are present in a Mg/Ca ratio ranging from 0.5 to 2 and more preferably from 1.5 to 1.75.

0154 (a) Ca-Mg-Ni Alloys of the AB. Type O155 As mentioned before, in a Ca-Nisystem, there are four stable compounds CaNi, CaNi, Ca-Ni, and CaNis. The CaNi-type system (also called AB) has been the subject of PART I hereinabove. This system has a cubic C15 structure and Mg can substitute Ca up to X=0.3 in the CaMg-Ni, alloys while maintaining a cubic structure. The unit cell Volume decreases and the plateau pressure increases with increasing the Mg content. 0156. In accordance with the invention, it has been found that the replacement of Ca and/or Mg by Mm in a quaternary AB type Ca-Mg-Mn-Ni system improves the hydro gen Storage properties significantly. 0157 Canis type alloys have been investigated in great details. The intermetallic compound CaNi can absorb hydrogen readily to form CaNiH, but cannot release hydrogen under ambient conditions (see reference A). Oes terreicher et al. have investigated the pseudo-binary CaMg. xNi and found that Mg can substitute Ca up to X=0.7(see again reference A). Recently, Kadir et al. reported a Series of AB alloys of the type ABC identified as RMg-Ni, where (R=La, Ce, Pr, Nd, Sm and Gd) (reference D) and a CaMg,Nio alloy (reference C) synthesized by sintering a mixture of elemental powders or intermetallic compounds. They found that these ABC type compounds have the PuNi, structure (reference D). The unit cell volume and hydrogen Storage properties can be altered by different Substitutions for the A, B and C elements.

0158. In between CaNi and CaNi, a metastable CaNis compound with an hexagonal P63/m Structure (space group 176) has previously been reported (see reference E). This material was prepared from the melt by a peritectic reaction at 1035 C. The present inventors have not been able to Synthesize this compound by using the method of prepara tion described in this document but have discovered that when one substitutes some Caby Mg in the virtual CaNis compound, a new phase having a structure different from those of AB (MgCu-cubic), AB (Puni-hexagonal) and CaNis (BaC6-hexagonal) is formed when the com pound is prepared by the method of the present invention. This new phase has a large hydrogen Storage capacity and an adequate plateau pressure for reversibly Storing hydrogen gas at room temperature.

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0159. Therefore, the second range of composition encompassed by the present invention is the range where the A/B ratio is between 0.45 and 0.35. As mentioned previ ously, A means (Cao Mgo-M) and B means (Ni-T). This range corresponds to alloys of the ABs type. 0160. As discussed hereinabove, an AB phase with a cubic C15 structure is formed when the A/B ratio is bigger than 0.45. When the A/B ratio is less than 0.35, an AB phase with the PuNi structure is formed. However, when the A/B ratio is in the range of 0.35-0.45, a new ABS-type phase with a crystallographic structure which has not yet been identified, is obtained. This new alloy is made by the same method as the one discussed previously, which comprises first preparing a powder by milling a mixture of elemental powders and/or pre-alloyed combinations of elemental pow ders (ex.: Ca, Mg, Ni, CaNis, MgNi . . . ) in amounts Sufficient to achieve the requested composition, and then annealing and/or sintering the So milled mixture at an elevated temperature of about 1000 C. to form the requested hydrogen Storage alloy.

0.161 Thus, the invention is based on the discovery of new hydrogen storage alloys of the A-B type which con tains Ca, Mg, Ni and other optional elements. These new alloys are capable of absorbing and desorbing hydrogen from the gas phase at ambient temperature with a flat plateau preSSure and a storage capacity larger than 1.5 wt %. 0162 These alloys may be prepared by a method com prising two StepS. 0163 The first step consists of preparing a powder by milling a mixture of elemental powders and/or pre-alloyed combinations of the elemental powders (ex.: Ca, Mg, Ni, Mm, CaNis, MgNi, MmNis, when M=Mm) in respective amounts Selected to obtain the desired alloy. The milling can be a conventional ball milling or a more intensive mechani cal alloying by a high energy ball mill. It can be carried out at room temperature or at high temperatures with or without anti-Sticking agents and in various kinds of atmosphere. 0164. The second step consists of annealing and/or sin tering the milled powder at elevated temperatures in a crucible made of, for example, Stainless Steel, for a short period of time in an inert or reactive atmosphere. This is an essential Step to achieve high reversible capacity and a flat plateau. The annealing temperature should be higher than 900° C. but not higher than 1080° C. 0.165. Once again, the invention is based on the discovery that mechanical alloying of elemental powders (such as Ca, Mg,Ni) and/or mixtures of intermetallic compounds (Such as CaNis, MgNi) corresponding to the requested composi tion (Ca,Mg)Nis leads to a highly disordered structure when the Mg/Ca ratio is between 0.33 and 1.67. The So-milled alloy can reversibly absorb and desorb hydrogen at room temperature. However, the reversible capacity is small and the slope of the PCT curves is very big. 0166 The invention is also based on the discovery that a new A-B type phase is formed when the mechanically alloyed (Ca,Mg)Nis is annealed at temperature above 600 C. The formation range of this new phase depends on the Mg/Ca ratio and the (Ca+Mg)/Ni ratio. For a stoichio metric ABs composition, the new phase no longer forms when the Mg/Ca ratio is lower than 0.3. If the Mg/Ca ratio is higher than 1.75, a large amount of MgNiphase is formed

May 26, 2005

and, as a result, the Storage capacity is reduced. When the Mg/Ca ratio is set at 1.5, the new phase is formed when the (Mg+Ca)/Ni ratio is between 0.35 and 0.45. 0.167 The invention is further based on the discovery that when a thermal treatment is applied to this mechanically alloyed powder, Substantial improvement in properties is achieved. Indeed, the hydrogen Storage properties of the ball milled Ca-Mg-Ni are significantly improved by anneal ing the powder at temperatures higher than 900 C. prefer ably around 1000 C. or slightly higher for a short period of time, preferably 0.5 to 1 hour. Annealing at temperatures lower than 900 C. does not improve the hydrogen storage properties very much.

EXAMPLE 2-1

0168 (Caois Mgos) Nis (x=0.025, y=-0.025, b=2, Z=0) was synthesized in a SPEX high energy ball mill under an argon protective atmosphere. A Mg powder (>99%, +100 mesh), Cagranules (>99.5%, 2 mm in size) and a Nipowder (>99.9%, -325 mesh) were used as starting materials. 0169 Isothermal annealing was performed in a tubular furnace under argon. The mechanically alloyed powder was Sealed in a stainless Steel crucible before annealing. The powder was heated to 1000 C. at a heating rate of 30 C./min, held at 1000 C. for 1 hour and then cooled down to room temperature in the furnace. 0170 Hydrogen absorption/desorption properties were measured by using an automatic Sievert's type apparatus. The annealed powder was Subjected to a mild activation treatment, Such as a heating treatment to 200 C. under vacuum followed by a cooling. EDX analysis showed that the Fe content in the end product is less than 0.2 at. %. The composition of the end product was close to the nominal composition. The activated alloy exhibited a relatively flat plateau and a high capacity.

EXAMPLE 2-2. TO 2-13

0171 Other examples similar to examples 2-1 were car ried out. The results of these other examples are reported in the accompanying drawings (see FIGS. 2-1 to 2-7). 0172 It has also been discovered that further improve ments are achieved by adding other elements to the basic elements used for preparing the alloys. Such an addition raises the plateau pressure and improves other hydrogen Storage properties Such as plateau slope, long term Stability, and resistance to decrepitation (see FIG. 2-8 to FIG. 2-12). 0173 (b) Mm Substitutions for Mg/Ca on the “A” Site of the AB. Type Alloy. 0.174 Mg and/or Ca can be substituted for by mischmetal ("Mm”) in any of the above-described Ca-Mg-Ni alloys of the ABs type. In this respect, with reference to the above-described formula, (Cao MgoM),(Ni-T)s, the present invention also provides Such an ABs type alloy where M is Mm.

0.175. A suitable mischmetal is one of the composition 51 wt % Ce, 26.4 wt % La, 16.4 wt % Nd and 5.3 wt % Pr. A further suitable mischmetal is one of the composition 62 wit % La, 21 wt % Ce, 3 wt % Pr, and 14 wt % Nd. Many further compositions are Suitable, and differ in the properties of the constituent elements La, Ce, Pr, and Nd.

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0176) The embodiment of ABs type alloys with Mm substitutions for Mg/Ca on the “A” site will be described in further detail with reference to the following non-limitative examples.

EXAMPLE 2-14

0177 Commercial grade calcium particles (1-2 mm in diameter, >99% pure) from Timminco Inc., nickel, alumi num, Silicon, germanium and other powders (>99.5% pure) purchased from Alfa were used as raw materials. Mg pow ders were +100 mesh, >99% pure. Mm powders were made inside a glove-box by pulverizing the ingots (from Aldrich) under the protection of argon. The mischmetal Mm contains 51% Ce, 26.4% La, 16.4% Nd and 5.3% Pr (in weight percent). 0.178 Mechanical alloying was performed in a Spex 8000 ball mill at room temperature (25 C.). The powders were mixed in the desired composition and mechanically milled in a steel milling vial filled with argon. Three steel balls of a diameter of 11 mm were used. The ball to powder mass ratio was 10:1. All the handling was performed in a glove box.

0179 The as-milled powder was sealed in a stainless Steel tube inside the glove-box and then placed in a tubular furnace for isothermal annealing treatment under the pro tection of argon. In this respect, the powder was heated to 1000° C. at a heating rate of 30° C./min., held at 1000° C. for 1 hour, and then cooled to room temperature in the furnace. The composition was then activated by heating 200 C. under vacuum, and then cooled to room tempera ture.

0180. The hydrogen storage properties were evaluated by using an automated Sievert's apparatus. The X-ray powder diffraction was performed on a Siemens D500 apparatus with CuKO. radiation.

0181. The hydrogen absorption/desorption cycling experiment was performed at 30° C. under an absorption pressure of 3.5 MPa and a desorption pressure of 0.01 MPa. The absorption and desorption time was 12 minutes respec tively. Under these conditions, the alloys could be cycled between fully hydrided and dehydrided conditions. The hydrogen purity was 99.999%. 0182. The XRD spectra of various Mm-substituted alloys being compared to a non-Substituted ABs type alloy are illustrated in FIG. 2-13. In all cases, an ABs main phase is obtained for (Mg+Ca)/Ni=0.4, no matter which element (Mg or Ca) is substituted by Mm. The substitution leads to an obvious change of diffraction peak position, indicating a Significant change of lattice parameters and unit cell Volume. 0183 Mm Substitution for Mg leads to a larger unit cell volume and a lower plateau pressure as shown in FIG. 2-14. Mm Substitution for Ca does not lead to a significant change of the unit cell Volume, however, the plateau pressure is Substantially increased. In the case of Ca,Mg, as Mmolas Nis alloy, full Storage capacity has not been reached as the PCT apparatus has reached its pressure limit.

0184 FIG. 2-15 illustrates the PCT curves of the Mg, Cao.62 MmasNis alloy after various cycles of hydro gen absorption/desorption. A clear decrease in both maxi mum and reversible hydrogen Storage capacity is observed

May 26, 2005

with cycling. Further, the plateau slope is observed to increase with cycling. The hydrogen desorption curves are illustrated in FIG. 2-35. The hydrogen desorption capacity drops 43% after 400 cycles. The reason is probably that Mm does not form an alloy with Ca, and the quaternary Ca-Mm-Mg-Ni alloy may have a strong tendency to decompose upon hydrogenation.

0185 FIG. 2-16 illustrates a comparison between the cycling Stability of the maximum and reversible hydrogen Storage capacities of the Mg25Caos Mimos Nis and the Mg,CaozsNis alloy. There is no significant difference in the long term stability of both alloys with or without Mm substitution. The reason is probably that Mm does not form an alloy with Ca. Without wishing to be bound by theory, it is believed that the quaternary Ca-Mm-Mg-Ni alloy has a strong tendency to decompose upon hydrogenation. Also there is a significant decrease in hydrogen capacity upon cycling for both alloyS. 0186 FIG. 2-17 illustrates the XRD spectra of the Mg, Cao.62s Mmolas Nis alloy before and after cycling. The diffraction peaks become broader and shift to lower angles with increasing cycling number. Annealing treatment of the hydrogen cycled sample at 600 C. for 1 h restores the Structure and recovers the hydrogen Storage properties simi lar to those for Ca-Mg-Ni alloy without Mm. As shown on the XRD spectra, the diffraction peaks shift back to their original positions and the peak width decrease after anneal ing treatment. 0187 (c) Si/Ge/Ga Substitutions for Ni on the “B” Site 0188 Nican be substituted for by at least one of Si, Ge, and Gain any of the above-described Ca-Mg-Nialloys of the ABs type. In this respect, with reference to the above described formula, (Cao-Mgos) (Ni-T)s, the present invention also provides Such an ABs type alloy where T is at least one of Si, Ge and Ga (including any combination of these elements). 0189 Substitution on the “B” site of the A-B type alloy by at least one of Si, Ga and Ge improves cycling Stability and hysteresis characteristics of the A-B type alloy. 0.190 Changes to each of the “maximum storage capac ity' and “reversible Storage capacity' during cycling are measures of cycling Stability of a hydrogen Storage compo Sition, Such as the ABs type alloys described above. Maxi mum hydrogen Storage capacity, under the highest preSSure experimentally applied at a given temperature, can be experimentally determined using an automated Sievert's apparatus. With reference to a typical PCT curve illustrated in FIG.2-18, maximum storage capacity is identified on the x-axis by the indication “Capacity (H/M)max”. Reversible Storage capacity can also be determined from the typical PCT curve illustrated in FIG. 2-18. In this respect, revers ible storage capacity is the maximum storage capacity (i.e. Capacity (H/M)max) less the hydrogen content which can not be desorbed from the hydrogen Storage composition (indicated by “Capacity (H/M)min)”. 0191 In a preferred embodiment, after 400 cycles, the percentage change in maximum Storage capacity of the Si/Ge/Ga Substituted ABs alloy is no more than 5%. In another preferred embodiment, after 400 cycles, the percent age change in reversible Storage capacity of the Si/Ge/Ga substituted ABs alloy is no more than 10%.

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0.192 Hysteresis is evaluated based on relative behaviour of absorption and desorption isotherms of a PCT curve, and particularly the corresponding equilibrium plateau pressure for each of the absorption and desorption isotherms. Equi librium plateau pressure “P” for each of the absorption and desorption isotherms (hereinafter, “P” and “P”) is esti mated at the midpoint of the corresponding absorption and desorption plateaus. In this respect, hysteresis is calculated by the following formula:

Hysteresis=ln(PVP)

0193 Values for each of P and P are taken from PCT curves as illustrated in the typical PCT curve in FIG. 2-18. 0194 In a preferred embodiment, after 400 cycles, the hysteresis of the Si/Ge/Ga Substituted ABs alloy is less than O.1.

0195 Substitution on the “B” site of the A-B type alloy by at least one of Si, Ga, and Ge also mitigates decrepitation of the Subject ABs type alloy. In this respect, Such Substi tuted ABs type alloys do not Suffer from appreciable par ticle size decrease upon repeated cycling. Preferably, after 400 cycles, the percentage change in the average particle Size in Such Substituted ABs type alloys is less than 10%. Average particle size can be determined from SEM photo graphs of the particles (see, for example FIG. 2-30). In this respect, an average is taken of the maximum diameter of a random Selection of 40 particles appearing in the photograph before and after repeated cycling (400 absorption/desorption cycles). 0196. The embodiment of A-B type alloys with Si/Ge/ Ga Substitutions for Ni on the “B” site will be described in further detail with reference to the following non-limitative examples.

EXAMPLE 2-15

0197) ABs alloys having Si Substituted on the “B” site were prepared in a similar manner as the alloy in Example 2-14.

0198 The hydrogen storage properties were evaluated by using an automated Sievert's apparatus. The X-ray powder diffraction was performed on a Siemens D500 apparatus with CuKO. radiation.

0199 The hydrogen absorption/desorption cycling experiment was performed at 30° C. under an absorption pressure of 3.5 MPa and a desorption pressure of 0.01 MPa. The absorption and desorption time was 12 minutes respec tively. Under these conditions, the alloys could be cycled between fully hydrided and dehydrided conditions. The hydrogen purity was 99.999%. 0200. The XRD of MgCaozsNias, Sios is illus trated in FIG. 2-19. The PCT curves of this alloy during cycling is illustrated in FIG. 2-20. Clearly, the Si Substitu tion has a beneficial effect on cycling Stability. The maxi mum Storage capacity does not noticeably change with cycling. The reversible Storage capacity, however, decreases with increased cycling, but leSS Significantly in comparison with unsubstituted ABs type alloys.

EXAMPLE 2-16

0201 ABs alloys having Ga Substituted on the “B” site were prepared in a similar manner as the alloy in Example 2-14.

May 26, 2005

0202) The hydrogen storage properties were evaluated by using an automated Sievert's apparatus. The X-ray powder diffraction was performed on a Siemens D500 apparatus with CuKO. radiation.

0203 The hydrogen absorption/desorption cycling experiment was performed at 30° C. under an absorption pressure of 3.5 MPa and a desorption pressure of 0.01 MPa. The absorption and desorption time was 12 minutes respec tively. Under these conditions, the alloys could be cycled between fully hydrided and dehydrided conditions. The hydrogen purity was 99.999%. 0204 The XRD of MgCaors Nis, Gaos is illus trated in 2-21. The PCT curves of this alloy during cycling is illustrated in FIG. 2-22. Clearly, the Ga Substitution has a beneficial effect on cycling Stability. The maximum Storage capacity does not noticeably change with cycling. The reversible Storage capacity, however, decreases with increased cycling, but leSS Significantly in comparison with unsubstituted ABs type alloyS. 0205 (d) Concomitant Substitution of Mm on “A” Site and Si/Ge/Ga on “B” Site of the AB. Type Alloy 0206. Substitution of at least one of Si, Ge and Ga for Ni on the “B” site of the ABs type alloy improves cycling stability. However, such substitution also lowers the plateau preSSure. In order to raise the plateau preSSure of the Si/Ge/Ga-Substituted alloys, Mm is substituted on the “A” Site.

0207 Mg or Ca can be substituted on the “A” site for by Mm, and Nican be substituted on the “B” site by at least one of Si, Ge and Ga (including any combination of these elements), in any of the above-described Ca/Mg/Nialloys of the ABs type. In this respect, with reference to the above described formula, (Ca,Mg,M)(Ni-T), or (Cao xMgos-M),(Ni-T)s, the present invention also pro vides such an A-B type alloy where M is Mm and T is at least one of Si, Ge and Ga. 0208. In the preferred embodiment, Z is greater than 0.025. For a Z less than 0.025, reversible storage capacity of the Subject ABs composition is less stable during repeated cycling.

0209. The embodiment of the A-B type alloys with Mm substitutions for Mg/Ca on the “A” site and with Si and/or Ge and/or Ga Substitutions for Ni on the “B” site will be described in further detail with reference to the following non-limitative examples.

EXAMPLE 2-17

0210 ABs alloys were prepared having Mm substituted on the “A” site and having Si Substituted on the “B” site, with varying degrees of Si Substitution. These were prepared in a similar manner as the alloy in Example 2-14. 0211 The hydrogen storage properties were evaluated by using an automated Sievert's apparatus. The X-ray powder diffraction was performed on a Siemens D500 apparatus with CuKO. radiation.

0212. The hydrogen absorption/desorption cycling experiment was performed at 30° C. under an absorption pressure of 3.5 MPa and a desorption pressure of 0.01 MPa. The absorption and desorption time was 12 minutes respec

US 2005/011 2018 A1

tively. Under these conditions, the alloys could be cycled between fully hydrided and dehydrided conditions. The hydrogen purity was 99.999%. 0213) The XRDS for Mg1.2s Cao.62s Mmo.12sNi4.875 Sio.12s. and Mg1.25Cao.625 Mmo.125N14.7s.Sio.2s, and Mg, Cao.62s Mmolas Niosis Siologos are illustrated in FIGS. 2-23, 2-24, and 2-25, respectively. The corresponding PCT curves of these alloys during cycling is illustrated in FIGS. 2-26, 2-27, and 2-28, respectively. The maximum and reversible capacities for each of Mg, Cao.625Mmo.125Ni4.875 Sio.12s and Mg, Cao as Mmolas Nis is illustrated in FIG. 2-29. FIG. 2-36 illustrates the normalized maximum and reversible Storage capacity as a function of Si content. 0214) For Mg1.2s Cao.625 Mmo.12s NiszsSio.12s, maxi mum hydrogen Storage capacity does not change with cycling, as reported for the Mg1.25 Cao.7sNiasz's Sio.12s alloy. The reversible Storage capacity decreases slightly in the first 30 cycles and then remains almost unchanged up to 400 cycles.

0215 Clearly, increasing the Si Substitution has a ben eficial effect on cycling stability (see FIG. 2-27). Further, hysteresis is relatively not significant, maximum hydrogen capacity increases slightly, and reversible Storage capacity and plateau slope remain unchanged. (see FIG. 2-27). Additionally, Si Substitution improves resistance to decrepi tation (decrepitation can result in Volume expansion and increased stress on the container), see FIG. 2-30. SEM analyses show that the particle size of Mg, Cao.62s Mmolas Niasis Sious does not significantly change after 400 cycles of hydrogen absorption/desorption. The powders show irregular shape. The average particle size is about 30 lum. 0216). A SEM photograph of the Mg, Cao.62s Mmolas Ni467s Sious alloy after 400 cycles of hydrogen absorption/desorption is illustrated in FIG. 2-30, to illustrate the alloy in particulate form. 0217. The negative effect of Substituting Si for Ni is the reduction of initial storage capacity. As shown in FIG. 2-37, the maximum hydrogen Storage capacity decreases with increasing Si content. Also, the alloys become more and more difficult to activate. FIG. 2-38 shows the first hydrogen absorption curves of the Mg2sCaos Mimos Nis-Si alloys with different Si content. Before doing the first hydrogen absorption, all the alloys have been treated at 300 C. under vacuum for 10 minutes.

0218. The XRD spectra of the Mg, Cao as Mmolas Nis. xSi alloys are shown in FIG. 2-39. There is no clear difference in the structure of various alloys with different Si contents. The lattice parameters do not change much with increasing Si content.

0219 Reduced Si content still provides a beneficial effect on cycling stability (see FIG.2-28). The maximum storage capacity even appears to increase upon cycling. However, Stabilization of the reversible Storage capacity is not observed.

0220 Referring to FIG.2-29 and 2-36, Sisubstitution for Ni results in a significant decrease in hydrogen Storage capacity.

May 26, 2005

EXAMPLE 2-18

0221) An ABs alloy was prepared by having Mm Sub stituted on the “A” site and having Ge substituted on the “B” Site, of the formula, Mg25Cao.625 Mmolas Nis7s Geo.12s. This alloy was prepared in a similar manner as the alloy in example 2-14. 0222. The hydrogen storage properties were evaluated by using an automated Sievert's apparatus. The X-ray powder diffraction was performed on a Siemens D500 apparatus with CuKO. radiation.

0223) The hydrogen absorption/desorption cycling experiment was performed at 30° C. under an absorption pressure of 3.5 MPa and a desorption pressure of 0.01 MPa. The absorption and desorption time was 12 minutes respec tively. Under these conditions, the alloys could be cycled between fully hydrided and dehydrided conditions. The hydrogen purity was 99.999%. 0224. The XRD for the alloy, before and after cycling, is shown in FIG. 2-31. The corresponding PCT curve of this alloy after cycling is illustrated in FIG.2-32. Ge Substitution for Ni appears to cause a reduction in the maximum hydro gen Storage capacity. The maximum storage capacity increases slightly with cycling. This is similar to what was observed in the Si-substituted alloys. FIG. 2-33 illustrates PCT curves for each of Mg25Caos Mimos NizsGeos and Mg125Cao. 62.5Mmo.12sNias 7s Geo.12s., for purposes of comparison. Hydrogen Storage capacity decreases with increasing Ge content. 0225 FIG.2-34 illustrates the comparison of the effect of Si and Ge Substitution on the maximum hydrogen Storage capacity of the alloy. It appears that Ge Substitution is Superior to Si Substitution in retaining higher hydrogen Storage capacity. Both types of Substitutions improve cycling Stability. 0226) 3. Alloys of the AB. Type 0227. In another aspect, the present invention provides an ABs type alloy according to the formula:

(CaosyMgxy Mo4-x)e(Ni-T)s

0228 when M is at least one metal selected from the group consisting of Y, Ce, La, Pr, Nd, Th, Nd, Ti, V, Zr, Ta, Hf, Sr., Ba and Misch metals;

0229) T is at least one element selected from the group consisting of Al, Zn, Cu, Fe, Co, Mn, Cr, Mo, W, Si, Ga., Ge, In, Sn, Ag, C and B;

0230) 0.75sbs 1.31,

0231 -0.64x<0.4, 0232 -0.4ky<0.6,

0233 0<x+ys 0.5, and

0234) 0szss 0.5. 0235 Preferably:

0236 -0.2s Xs O.2, 0237 -0.2sys 0.2, and

0238 0.1s x+ys 0.4

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0239). In one embodiment, M is a mischmetal, and T is at least one of Si, Ga and Ge (including any combination of these elements). 0240 A suitable mischmetal is one of the composition 51 wt % Ce, 26.4 wt % La, 16.4 wt % Nd and 5.3 wt % Pr. A further suitable mischmetal is one of the composition 62 wit % La, 21 wt % Ce, 3 wt % Pr, and 14 wt % Nd. Many further compositions are Suitable, and differ in the properties of the constituent elements La, Ce, Pr, and Nd.

0241 Alloys of the AB type have already been studied in great detail (see references C, D, F, G, H). Some of them have even been recently patented for battery applications (see references I and J). For example, the patent identified as reference I discloses alloys of the formula (Mg, tR1M1)Ni where 3s Zs3.8. Such corresponds to alloys AB where the ratio A/B is ranging between 0.263 and 0.33. 0242. The alloys according to the invention as defined hereinabove are of the AB type. LaNis- and MmNis-based ABs type alloys have been widely investigated as hydrogen Storage materials (see reference 1 and 2). The La, Mm and Niatoms can be substituted by many other elements to tailor the hydrogen Storage properties for different applications (see reference 3). However, substitution of La by Mg in LaNi has not been Successful. A second phase with an approximate composition of LaMg,Nio was found with a nickel-rich LaNis main phase in a melt casting Mg, Lao Nis sample (see reference 4). The hydrogen stor age capacity was reduced due to the formation of this Second phase.

0243 Canis intermetallic compound represents a cat egory of low cost hydrogen Storage materials with a Storage capacity up to 1.9 wt.% (see references 5 to 7). However, little attention has been paid So far to Such a System, probably due to its well-known bad cycling stability (see reference 8). Improvement of the hydrogen Storage proper ties of CaNis by Substitution of Ca or Ni with other elements has been tried (see references 5 to 8; A and K). Ternary CaMm-Nis alloys were produced by melt casting and were also investigated (see reference 5). Mm substitution for Ca can raise the plateau pressure of CaNis. However, the plateau slope is big for the as-cast ternary alloys due to Segregation.

0244 Annealing at elevated temperatures (>1000 C.) can reduce the slope to Some extent. Previous works made by the present inventors have shown that CaNis and Mm or Zn-substituted CaNis type alloys with relatively flat plateau can be produced by mechanical alloying followed by an annealing treatment at low temperatures (640 C) (see refer ence L). 0245 Substitution of Mg for Ca in a CaNis structure has also been investigated. The reported results show that the Ca,Mg,Nis does not extend homogeneously beyond X=0.06 (see reference A). 0246 The invention is based on the discovery that slight substitution of Mg in the CaNis destroys the ABs structure, and a mixture of AB and free nickel is formed. The hydrogen Storage capacity is also reduced. However, when the alloy of the ABs type containing Mg comprises more than 3 elements, the solubility limit can be extended and the plateau can be tailored by the Mg content. The plateau slope

May 26, 2005

is also Small and the reversible hydrogen Storage capacity is bigger in comparison to ternary Ca-Mim-Ni ABs type alloys. 0247 Thus, the present invention provides new hydrogen Storage alloys of the ABs type, which contains Ca, Mg, Ni and M. These alloys are capable of absorbing and desorbing hydrogen from a gas phase at ambient temperature with a flat plateau pressure and a storage capacity larger than 1.3 wt.%. 0248. These new alloys may be prepared by a method Similar to those already disclosed, which comprises two StepS.

0249. The first step consists of preparing a powder by milling a mixture of elemental powders and/or pre-alloyed combination of the elemental powders (ex.: Ca, Mg, Ni, Mm, CaNi, MgNi, MmNis, when M=Mm) in respective amounts Selected to obtain the requested composition. The milling can be a conventional ball milling or a more inten Sive or mechanical alloying by a high energy ball mill which can be carried out at room temperature or at high tempera tures with or without anti-Sticking agents and in various kinds of atmosphere. 0250) The second step consists of annealing and/or sin tering the mechanically alloyed powder at elevated tempera tures in a crucible made of, for example, Stainless Steel for a short period of time in an inert or reactive atmosphere. This is an essential Step to achieve high reversible capacity and a flat plateau. The annealing temperature should be higher than 800° C. but not higher than 1100° C. 0251 Once again, the invention is based on the discovery that mechanical alloying of elemental powders (Such as Ca, Mm, Ni) and/or mixtures of intermetallic compounds (such as CaNis, MmNis) corresponding to the requested compo Sition CaMm-Nis leads to a nanocrystalline ABs type structure. The so-milled alloy can reversibly absorb and deSorb hydrogen at room temperature. However, the revers ible capacity is small and the slope of the PCT curves is very big.

0252) The invention is also based on the discovery that when a thermal treatment is applied to this mechanically alloyed powder, Substantial improvement in properties is achieved. Indeed, the hydrogen Storage properties of the mechanically alloyed Mg-Ca-Ni are substantially improved when the powder is annealed at temperatures higher than 800° C. typically at 1000 C. or slightly higher, for short period of time, preferably 0.5 h-1 h. Annealing at temperatures lower than 800° C. does not improve the hydrogen Storage properties very much. 0253) It has also been discovered that further improve ments are achieved by adding other elements (M) to the basic elements used for preparing the alloys. Such an addition raises the plateau preSSure and improves other hydrogen Storage properties Such as plateau slope and the long-term Stability while keeping predominantly the ABS type Structure.

EXAMPLE 3-1

Compound According to the Prior Art Made by the Method According to the Invention

0254 Mmo Cao Nis (x=0, y=0, b=1, Z=0) was synthe sized in a SPEX high energy ball mill under an argon

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protective atmosphere. A Mm powder (>99%, +100 mesh), Ca granules (>99.5, -2 mm in size) and a Ni powder (<99.9%, -325 mesh) were used as starting materials. 0255 Isothermal annealing was performed in a tubular furnace under argon. The mechanically alloyed powder was Sealed in a stainless Steel crucible before annealing. The powder was heated to 1000 C. at a heating rate of 30 C./min, held at 1000 C. for 1 hour and then cooled down to room temperature in the furnace. 0256 Hydrogen absorption/desorption properties were measured by using an automatic Sievert's type apparatus. The annealed powder normally needs mild activation treat ment, Such as a heating treatment to 200 C. under vacuum followed by a cooling. EDX analysis shows that the Fe content in the end product is less than 0.3 at. 9%. The composition of the end product was close to the nominal composition. The activated Mmo Cao Nis alloy exhibited a relatively flat plateau and a high capacity.

EXAMPLE 3-2


0257 (MmoCaMg.). Nis (M=Mm, x=0.067, y=0.1, x+y=0.167, b=1.2 and b/5=0.24, Z=0) was synthe sized by mechanical alloying of elemental powder blends. The alloy was annealed in the same manner as in Example 3-1. This alloy had a hydrogen storage capacity of 1.45 wt. %. The plateau pressure and reversible hydrogen Storage capacity were significantly improved in comparison to those of the prior art alloy Cao Mimo Nis.

EXAMPLE 3-3


0258 (Mimo Cao.,Mgos). Nis (M=Mm, x=0.067, y=0.183, x+y=0.25, b=1.2 and b/5=0.24, Z=0) was synthe sized by mechanical alloying of elemental powder blends. The alloy was annealed in the same manner as in Example 3-1. This alloy had a hydrogen Storage capacity of 1.4 wt.%. The plateau pressure was flat and even higher than the one of Example 3-2.

EXAMPLE 3-4 TO 3-15

0259) Other examples similar to those of Examples 3-2 and 3-3 were carried out. The results of these other examples are reported in the accompanying drawings (see FIGS. 3-1 to 3-11). 0260. Other Substituted AB. Type Alloys 0261. It has also been found that substitution of Si, Ge and Some other metalloid elements (also called “semi metals”) for Ni in a ternary Ca-Mm-Ni alloy of the ABs type can Substantially improve the long term Stability of Such an alloy without causing much reduction of the Storage capacity. ESSentially, no capacity loSS has been observed after 500 hydrogen absorption and desorption cycles. 0262. Such Ca-Mm-Ni based alloys of the ABs type, which are capable of absorbing and desorbing hydrogen from a gas phase at ambient temperature with a relative flat

May 26, 2005

plateau pressure and a storage capacity larger than 1.2 wt.%. These new alloys are of the formula (I):

(CaM1-x),(Ni-T)s (I) 0263 where M can be any mischmetal or any rare earth metal. M can also be an homogeneous or an inhomogeneous combination of any of: (i) at least two mischmetals, (ii) at least two rare earth metals, or (iii) at least one mischmetal and at least one rare earth metal;

0264 T can be a metalloid. T can also be an homoge neous or an inhomogeneous combination of at least two metalloids,

0265 0<xs 1 (xz0), preferably 0.4sxs 1; 0266) 0<ys 0.5 (yz0), preferably 0<ys 0.3; and 0267 0.8sts 1.2.

0268 A process for the preparation of the above men tioned alloys of formula (I), comprises the following Steps:

0269 a) preparing a powder by milling a mixture of elemental powders and/or pre-alloyed Substances of the elemental ingredients of the alloy to be prepared (Such as, for example, Ca, Ni, Mm, CaNi, CaNis, MmNis and So on) in adequate proportions to obtain the required alloy; and

0270 b) annealing and/or sintering the so prepared powder at elevated temperatures in a crucible for a short period of time in an inert or reactive atmosphere.

0271 In use, step a) may consist of a ball milling or of a mechanical alloying and can be carried out at room tem perature or at high temperatures with or without anti Sticking agents.

0272 Step b) is essential to the above process. This step must actually be carried out to achieve high reversible capacity and a flat plateau. In use, the annealing can be carried in a crucible made of Stainless Steel at a temperature higher than 600° C. but not higher than 1100° C. 0273 Alternatively, these compounds can be produced by conventional melt casting methods or powder Sintering methods.

0274 These compounds can be useful for hydrogen stor age.

0275 A suitable mischmetal is one of the composition 51 wt % Ce, 26.4 wt/o La, 16.4 wt % Nd and 5.3 wt % Pr. A further suitable mischmetal is one of the composition 62 wit % La, 21 wt % Ce, 3 wt % Pr, and 14 wt % Nd. Many further compositions are Suitable, and differ in the properties of the constituent elements La, Ce, Pr, and Nd. 0276 Examples of rare earth metals are Y, La, Ce, Pr, Nd, Sm, Dy, Gd, Ho, Th, U, Pm, Tb, Er, and Lu. Preferably, the rare earth metal is any of La, Ce, Pr, Nd, Dy, Th, and Y. Suitable metalloids include Si, Ge, and Ga. 0277. In one embodiment, M is a mischmetal, and T is any of Si, Ge and Ga. 0278 Significant improvements have been achieved by substituting Si, Ge and/or other metalloids for Ni in the above mentioned Ca-Mm-Ni alloy of the ABs type (see the definition of T in the formula given hereinabove). This

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Substitution has significant effect of improving the long-term Stability while keeping predominantly the ABs structure and hydrogen Storage capacity that are particularly useful. 0279. The substutited Ca-Mm-Ni alloys of the ABs type with improved properties can be made by mechanical alloying of elemental powders (such as Ca, Mm, Nis) and/or mixtures of intermetallic compounds (Such as CaNis, MmNis) corresponding to the required composition, fol lowed by an thermal annealing treatment at temperatures higher than 600 C. for short period of time, typically at 1000 C. or slightly higher for 0.5 h-1 h in a steel crucible. Annealing at temperatures lower than 600 C does not improve the hydrogen Storage properties very much. 0280 The following non-limitative examples are illus trative of the Substituted ternary Ca-Mm-Ni alloys of the ABs type.

EXAMPLE 3-16

0281 (CaMmos). Nis was Synthesized by mechani cal alloys in a SPEX high energy ball mill under argon. A MmNi, powder (>99%, +100 mesh), Cagranules (>99.5, -2 mm in size) and Ni powders (<99.9%, -325 mesh) were used as Starting materials. 0282. After alloying, an isothermal annealing was per formed in a tubular furnace under argon. The mechanically alloyed powder was Sealed in a stainleSS Steel crucible before annealing. The powder was heated to 1050 C. at a heating rate of 30° C./min, and held at 1050 C. for 1 hour, then cooled down to room temperature in the furnace. 0283 The hydrogen absorption/desorption properties were measured by using an automatic Sievert's type appa ratus. The annealed powder normally needs mild activation treatment, such as heated to 200 C. under vacuum and then cooled down. The activated (CaMmos). Nis alloy exhibits a relative flat plateau and a maximum Storage capacity of 1.44 wt.% under 4.0 MPa of charging pressure. 0284. A hydrogen absorption/desorption cycling experi ment was performed at 30° C. under an absorption pressure of 3.5 MPa and a desorption pressure of 0.01 MPa. The absorption and desorption time was 12 minutes respectively. Under these conditions, the alloys could be fully hydrided and dehydrided. The hydrogen purity was 99.999%. As shown in FIG. 3-12, the maximum Storage capacity was reduced to 1.23 wt.% after 250 cycles (20% loss). The reduction of the effective reversible Storage capacity is even bigger.

EXAMPLE 3-17

0285 (Cao Mimos). NicSio was Synthesized by mechanical alloying of elemental Ca, Si and MmNis powder blends. The alloy was annealed in the same manner as in Example 3-16. This alloy had a maximum hydrogen Storage capacity of 1.4 wt.%. The maximum hydrogen Storage capacity are slightly reduced by 8% after 250 cycles as shown in FIG. 3-13 in contrast to the 20% loss in the (Cao.6Mmoss). Nis.

EXAMPLE 3-18

0286 (Cao Mimos). Nissio was Synthesized by mechanical alloying of elemental Ca, Si and MmNis powder blends. The alloy was annealed in the same manner as in Example 3-16. This alloy had a hydrogen Storage capacity of 1.3 wt.%. The maximum and reversible hydrogen storage

May 26, 2005

capacities are slightly improved upon hydrogen absorption and desorption cycling as shown in FIG. 3-14. 0287 X-ray analyses show that Si-substituted alloys have very high resistance to peak broadening upon cycling as shown in FIG. 3-15. While the (CaMmo), Nis alloy without Si Substitution shows obvious peak broadening after cycling as shown in FIG. 3-16. It was believed that hydro gen absorption/desorption cycling introduces defects, Such as microStrain, chemical disorders and grain boundaries (reduced grain size), therefore leads to reduced Storage capacity. The peak broadening reflects the defects intro duced during cycling experiments.

EXAMPLE 3-19

0288 Cao, Mmo NissGeos was Synthesized by mechanical alloying of elemental powder blends. The alloy was annealed in the same manner as in Example 3-16. This alloy had a maximum hydrogen Storage capacity of 1.3 wt. % in the as-Synthesized State. Substantial improvement in the maximum and reversibly Storage capacity is observed after 500 cycles as shown in FIG. 3-17. 0289 Although the disclosure describes and illustrates preferred embodiments of the invention, it is to be under stood that the invention is not limited to these particular embodiments. Many variations and modifications may occur to those skilled in the art within the scope of the invention. For definition of the invention, reference is to be made to the appended claims.

REFERENCES

0290 (A) “Hydriding Behavior of Ca-Mg-Ni-B” by H. Oesterreicher, K. Ensslen, A. Kerlin and E. Bucher, Mat. Res. Bull., 15 (1980) 275

0291 (B) “Structural and Hydriding Properties of (Ca,Mg)Nia Laves phases alloys" by N. Terashita, K. Kobayashi, T. Sasai, E. Akiba, J. of Alloys and Com pounds 327 (2001) 275

0292 (C) "Structural investigation and hydrogen capacity of CaMg2Nic: a new phase in the AB2C9 system isostructural with LaMg2Ni9” by K. Kadir, N. Kuriyama, T. Sakai, I. Uehara, L. ErickSSon, J. of Alloys and Compounds 284 (1999) 145

0293 (D) “Synthesis and structure determination of a Series of hydrogen storage alloys, RMg2Nio (R=La, Ce, Pr, Nd, Sm, and Gd) built from MgNi Laves-type layers alternating with ABs layers', by K. Kadir, T. Sakai, I. Uehara, J. of Alloys and Compounds 257 (1997) 115

0294 (E) International Centre for Diffraction Data, JCPDS File # 19-0243 on CaNis

0295 (F) “Structural investigation and hydrogen stor age capacity of LaMg,Nio and (LaCaos)(Mg132Cao.6s)Nio of the AB2Co type structure” by K. Kadir, T. Sakai and I. Uehara, J. of Alloys and Compounds 302 (2000) 112

0296 (G) “Hydriding properties of LaNi and CaNis and their substitutes with PuNi-type structure” by J. Chen, H. T. Takeshita, H. Tanaka, N. Kuriyama, T. Sakai, I. Uehara, M. Haruta, J. of Alloys and Com pounds 302 (2000) 304

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0297 (H) “Hydrogen storage properties of new ternary System alloys: LaMg,Nio, Las Mg-Ni, LaMg,Ni” by T. Kohno, H. Yoshida, F. Kawashima, T. Sakai, M. Yamamoto and M. Kanda, J. of Alloys and Compounds 311 (2000)L5

0298) (I) “Hydrogen-Absorbing Alloy” U.S. Pat. No. 6,130,006 (2000)

0299 (J) Japanese Patent JP 11-217643 (1999) 0300 (K) J. O. Jensen, N.J. Bjerrum, J. of Alloys and Compounds, 293 (1999) 185

0301 (L) G. Liang, J. Huot and R. Schulz, J. of Alloys and Compounds 321 (2001) 146

0302) (1) K. H. Buschow, in Handbook on the Physics and Chemistry of Rare Earths, vol. 6, edited by K. A. Gschneider, Jr. and L. Eyring, Elsevier Science Pub lishers, B.V. (1984) chap 47

0303 (2) T. Sakai, in Handbook on the Physics and Chemistry of Rare Earths, vol. 21, edited by K. A. Gschneider, Jr. and L. Eyring, Elsevier Science Pub lishers, B.V. (1995) chap 142

0304 (3) G. D. Sandrock and G. Thomas, IEA tech nical report, compilation of IEA/DOE/SNL hydride database, (1997)

0305 (4) P. D. Goodell, G. D. Sandrock and E. L. Huston, Pept. SAND 79-7095, Sandia N. L. Albuquer que, N.Mex. 87185 (1980) pp 1-176

0306 (5) G. D. Sandrock, proc. 12" intersociety energy conversion engineering conference, Am. Nuclear Soc., 1 (1977) 951

0307 (6) G. D. Sandrock, in A. F. Andersen, A. J. Mealand (eds.) Proc. Int. Symp. on Hydrides for Energy Storage 9, Pergamon, Oxford (1979), 1625

0308) (7) G. D. Sandrock, J. J. Murray, M. L. Post and J. B. Taylor, Mat. Res. Bull., 17(1982)887

0309 (8) P. D. Goodell, J. Less-Common Met., 99 (1984) 1

1. An alloy of the formula: (Ca,Mg,Me),(Ni-T),

where:

M is at least one metal Selected from the group consisting of Y, Ce, La, Pr, Nd, Th, Nd, Ti, V, Zr, Ta, Hf, Sr., Ba and mischmetals,


a is an integer equal to 2 or 5, Z is a number ranging from 0 to 0.5, and when a is equal to 2, then b, c, d, e are numbers Selected

So that:

0.9sbs 1.1

c=0.4-X, d=0.6-y, and

May 26, 2005

e=X+y, with -0.5s XCO.4

-0.4<ys 0.5 and x+y>0;

when a is equal to 5, then b, c, d, e are numbers Selected So that either

1.75s bs 2.25

c=0.4-X, d=0.6-y, and e=X+y, with -0.4sXs 0.2, -0.2sys 0.4, and x+ye0 or 0.75sbs 1.31, c=0.6-y, d=X+y, and e=0.4-X, with -0.6-X-0.4, -0.4<y<0.6, and

2. An alloy as claimed in claim 1, wherein Said alloy is of the formula:

where M and T are defined as in claim 1 and

0.9sbs 1.1, -0.5sX-0.4,

Os Zs().5. 3. An alloy as claimed in claim 2, wherein: -0.1sXs 0.25 and

-0.1 sys 0.15. 4. An alloy as claimed in claim 1, wherein Said alloy is of

the formula:

where M and T are defined as claimed in claim 1 and

1.75s bs 2.25,

-0.4sXs 0.2, -0.2sys 0.4, X+ye0, and Os Zs().5. 5. An alloy as claimed in claim 4, wherein: -0.1sXs 0.1, and -0.1 sys 0.2. 6. An alloy as claimed in claim 4, wherein Mg and Ca are

present in a Mg/Ca ratio ranging between 0.5 and 2.

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7. An alloy as claimed in claim 6, wherein the Mg/Ca ratio is ranging between 1.5 and 1.75.

8. An alloy as claimed in claim 1, wherein Said alloy is of the formula:

(Cao.syMgxy Mo4-x),(Ni-T)s where M and T are defined as in claim 1 and

0.75sbs 1.31,

-0.64X-0.4,

0<x+ys 0.5, and Os Zs().5. 9. An alloy as claimed in claim 8, wherein: -0.2sXs 0.2, -0.2sys 0.2, and 0.1s x+ys 0.4. 10. An alloy as claimed in any one of claims 1 to 9,

wherein Said alloy is a Single phase alloy. 11. An alloy as claimed in any one of claims 1 to 9,

wherein Said alloy is a multiphase alloy. 12. A method for preparing an alloy as claimed in any one

of claims 1 to 9, comprising the Step of: milling a mixture of elemental powders and/or pre-al

loyed combination of elemental powders of Ca,Mg,M, Ni and T, and

annealing and/or Sintering the milled mixture at a tem perature higher than 600 C.

13. Use of an alloy as claimed in any one of claims 1 to 9 for reversibly absorbing hydrogen from a gas phase.

14. A composition of the formula:

where

M is a mischmetal;

T is at least one element Selected from the group consist ing of Si, Ga, and Ge;

1.75s bs 2.25,

-0.4sXs 0.2, -0.2sys 0.4, X+ye0, and O<Zs 0.5. 15. An alloy as claimed in claim 14, wherein: -0.1sXs 0.1, and -0.1 sys 0.2. 16. An alloy as claimed in claim 14 or 15, wherein Mg and

Ca are present in a Mg/Ca ratio ranging between 0.5 and 2. 17. An alloy as claimed in claim 16, wherein the Mg/Ca

ratio is ranging between 1.5 and 1.75. 18. The composition as claimed in claim 14, wherein Z is

greater than 0.0625. 19. The composition as claimed in claims 14 or 18,

wherein (x+y) is greater than 0. 20. The composition as claimed in claim 18, wherein T is

Si.

May 26, 2005

21. The composition as claimed in claim 18, wherein T is Ge.

22. The composition as claimed in claim 14, wherein the change in the maximum Storage capacity after 400 hydrogen absorption/desorption cycles is less than 5%.

23. The composition as claimed in claim 14, wherein the change in the reversible Storage capacity after 400 hydrogen absorption/desorption cycles is less than 10%.

24. The composition as claimed in claim 14, wherein the change in average particle Size after 400 hydrogen absorp tion/desorption cycles is less than 10%.

25. A hydride of an alloy of the formula: (Cao.4x Mgo.6-yMxy)b(Ni-T)s

where

M is a mischmetal; T is at least one element Selected from the group consist

ing of Si, Ga, and Ge; 1.75s bs 2.25, -0.4sXs 0.2, -0.2sys 0.4, X+ye0, and O<ZSO.5. 26. An alloy as claimed in claim 25, wherein: -0.1sXs 0.1, and

-0.1 sys 0.2. 27. An alloy as claimed in claim 25 or 26, wherein Mg and


ratio is ranging between 1.5 and 1.75. 29. The hydride as claimed in claim 25, wherein Z is

greater than 0.0625. 30. The hydride as claimed in claims 25 or 29, wherein

(x+y) is greater than 0. 31. The hydride as claimed in claim 29, wherein T is Si. 32. The hydride as claimed in claim 29, wherein T is Ge. 33. A process of hydrogenating and dehydrogenating a

composition of the formula:

where

M is a mischmetal;

T is at least one element Selected from the group consist ing of Si, Ga, and Ge;

1.75s bs 2.25, -0.4sXs 0.2, -0.2sys 0.4, X+ye0, and

comprising the Steps of: effecting absorption of hydrogen by the composition; and effecting desorption of hydrogen by the composition; wherein the absorption and desorption StepS are carried

out in any order.

US 2005/011 2018 A1

34. An alloy as claimed in claim 33, wherein: -0.1sXs 0.1, and -0.1 sys 0.2. 35. An alloy as claimed in claim 33 or 34, wherein Mg and


ratio is ranging between 1.5 and 1.75. 37. The process as claimed in claim 33, wherein Z of the

composition is greater than 0.0625. 38. The process as claimed in claims 33 or 37, wherein

(x+y) of the composition is greater than 0. 39. The process as claimed in claim 37, wherein T of the

composition is Si. 40. The process as claimed in claim 37, wherein T of the

composition is Ge. 41. The process as claimed in claim 33, wherein the

change in the maximum Storage capacity of the composition after 400 hydrogen absorption/desorption cycles is less than 5%.

42. The process as claimed in claim 33, wherein the change in the reversible Storage capacity of the composition after 400 hydrogen absorption/desorption cycles is less than 10%.

43. The process as claimed in claim 33, wherein the change in average particle size of the composition after 400 hydrogen absorption/desorption cycles is less than 10%.

44. An alloy of the formula (Cao.6 yMgxyMo.4-x) (Nil-2T2)s

where

M is a mischmetal; T is at least one element Selected from the group consist

ing of Si, Ge and Ga; 0.75sbs 1.31, -0.64X-0.4, 0.4<y<0.6, 0<x+ys 0.5, and Os Zs().5.

May 26, 2005

45. An alloy of the formula:

M is at least one metal Selected from the group consisting of Y, Ce, La, Pr, Nd, Th, Nd, Ti, V, Zr, Ta, Hf, Sr., Ba and mischmetals,


1.75s bs 2.25,

-0.4sXs 0.2, -0.2sys 0.4, X+ye0, and O<ZSO.5. 46. The alloy as claimed in claim 45, wherein: -0.1sXs 0.1, and

-0.1 sys 0.2. 47. The alloy as claimed in claim 45, wherein:

48. The alloy as claimed in claim 45, wherein M is at least one mischmetal and Z=0.

49. The alloy as claimed in claim 48, wherein: 0.0625s x+ys 0.625. 50. The alloy as claimed in claim 45, wherein X-y=0 and

T is at least one of Cu and Al.

51. The alloy as claimed in claim 49 or 50, wherein Mg and Ca are present in a Mg/Ca ratio ranging between 0.5 and 2

52. The alloy as claimed in claim 51, wherein the Mg/Ca ratio is ranging between 1.5 and 1.75.

k k k k k

us 2005o112o18a1 (19) united states (12) patent application … · 2017-09-30 · (5 g c o c 92 ....

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