fabrication of al2o3–zrb2 in situ composite by shs dynamic compaction: a novel approach

COMPOSITES

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Composites Science and Technology 67 (2007) 2447–2453

SCIENCE ANDTECHNOLOGY

Fabrication of Al2O3–ZrB2 in situ composite by SHSdynamic compaction: A novel approach

S.K. Mishra a,*, S.K. Das a, V. Sherbacov b

a National Metallurgical Laboratory, Jamshedpur 831007, Indiab Institute of Structural Mackrokinetics and Materials Science (ISMAN), Moscow Region, Russia

Received 4 February 2006; received in revised form 20 December 2006; accepted 22 December 2006Available online 12 January 2007

Abstract

Al2O3–ZrB2 in situ composites of 97% of theoretical density were successfully fabricated by a novel self-propagating high temperaturesynthesis (SHS) dynamic compaction, using less expensive raw materials zirconium oxide, boron oxide, and aluminium. The process isfast, energy efficient, where no furnace sintering is required. The process inhibits and controls the grain growth and microstructure. Thedensification behaviour and correlation with microstructure of the SHS dynamic compacts were compared with the furnace sintered com-posite samples where the composite powder was prepared by SHS process. The furnace sintered samples showed coarser grain growthand maximum density of 94.5% of theoretical density was achieved. The SHS dynamic compacted in situ composite had much finergrains in the range of 0.5–3 lm with density 95.5% of the theoretical value. The average grain size was found to decrease from 10 lmto 1.4 lm for alumina and from 5.4 lm to 1.0 lm for zirconium diboride from furnace sintering to SHS dynamic compaction, respec-tively. Addition of Al2O3 as a diluent during SHS reaction enhanced the density to 97%. During SHS dynamic compaction, the amountof liquid and the time interval at which the sample stays at high temperature are the controlling factor of the final microstructure and thedensification of the composite.� 2007 Elsevier Ltd. All rights reserved.

Keywords: In situ composite; SHS; Borides; Boride alumina composite; Sintering

1. Introduction

Incorporation of high temperature borides particulate toimprove the properties of ceramic matrix composite is oneof the interests in recent material research. Among the var-ious borides, zirconium diboride (ZrB2) is an importantmaterial due to its high melting point, hardness, elasticmodulus, electrical conductivity, and excellent chemicalresistance to HCl, HF, and other non-ferrous metals, cryo-lite and non-basic slags [1]. Alumina is one of the veryimportant ceramics used for various applications such ascutting tools, crucibles, high temperature furnace tubesand liners. For many of the applications the strength,

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doi:10.1016/j.compscitech.2006.12.017

* Corresponding author. Tel.: +91 657 2271709; fax: +91 657 2270527.E-mail address: [email protected] (S.K. Mishra).

impact resistance, toughness and hardness of alumina isnot sufficient. Hence enormous efforts have been made toenhance these properties and composites with dispersionof hard particulates such as boride and carbides. Additionof zirconium diboride to alumina matrix is expected todemonstrate high mechanical strength similar to titaniumdiboride–alumina composite. Titanium diboride dispersionin alumina has shown excellent mechanical properties ofstrength, hardness, fracture toughness and impact resis-tance [2]. The TiB2–Al2O3 composite has been preparedby mixing alumina and titanium diboride particulate fol-lowed by sintering. Aluminothermic reduction of oxidesin furnace [3] has also been used to fabricate the composite.The alumina matrix dispersed with Ti/Zr diboride becomeselectrically conducting even if only 20 wt% of borides arepresent in the matrix, which makes the composite machin-able by electro discharge machining (EDM). Hence the

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2448 S.K. Mishra et al. / Composites Science and Technology 67 (2007) 2447–2453

components can be machined easily and precisely. Zirco-nium diboride addition has also advantage over titaniumdiboride, because it does not have many stable intermedi-ate phases, which makes the ZrB2 reinforced compositepreferable despite having higher density than the titaniumdiboride. So far very few reports are available in literatureon the fabrication of zirconium diboride–alumina compos-ites [4,5].

Self-propagating high temperature synthesis (SHS) hasrecently been used extensively for preparing refractorymaterials such as carbides, silicides, nitrides, and variouscomposite materials [6–8]. The advantages, fundamentaland technological aspects of SHS process have beenreviewed in literature [9–11]. SHS of the composite makesan in situ composite powder and is energy efficient com-pared to the conventional processes [12] such as solid-state reaction, carbothermal reactions etc. Normally theseconventional processes require very high temperature pro-cessing and multi-steps such as calcinations, grinding inbetween, pelletisation. Sintering along with hiping is nor-mally required for better dense materials. Defects inducedduring SHS process due to the high rate of heating andcooling should reduce the sintering temperature signifi-cantly. Often in composite fabrication, the powders havebeen made by SHS process and then sintered at highertemperatures. Multiple processing steps make the processtime consuming. Though higher densities have beenachieved during furnace sintering, the large grain growthdegrades the mechanical properties of the composite.Another way is to use an economical process, which notonly synthesize but also densifies the composite in situ.The SHS dynamic compaction is one such process, whichcan be used for in situ fabrication of the composite. SHSdynamic compaction is energy efficient, fast process andcan be used for simultaneous densification during theSHS reaction to form the in situ composite. SHS dynamiccompaction means that loads are applied during the SHSreaction to densify the SHS reaction product. Oftendynamic compactions are done with metallic powder[13,14]. A few reports show oxide use during SHS propa-gation and simultaneous densification of the product[15,16]. Feng and Moore [16] have made alumina–tita-nium carbide composite where the compact of TiO2, Al,C was combustion reacted by heating the whole pelletto the ignition temperature and then loads were appliedfor compaction simultaneously. The present process,described by authors, is basically a similar approach butthe ignition was not carried out in thermal explosion

mode, rather it was in propagating mode. In thermal

explosion mode the sample is heated from all sideswhereas in propagating mode ignition is done at a pointof the pellet and combustion wave propagates throughoutthe sample. The reactions were carried out in a steel dienot in a graphite die. The material was not in direct con-tact of the die so no reactions were observed with diematerial, whereas in the Feng et al. process the reactionwith graphite was observed. SHS dynamic compaction is

an attractive process, where proper control of the SHSprocessing parameters such as time of pressing, intervalof loading and load applied during the process are verycritical to yield a fully dense product. Improper synthesistime, loading time and load lead to cracked and porousmaterials. Metallic binders and diluents are often usedto control the SHS process [17,18]. Metallic binder, whichhas the lower melting temperatures, melts during the reac-tion and also rate of reaction changes due to its presencethat leads to better densification. Beside the metallic dilu-ents, similar powders are also used as diluents to controlthe SHS reaction. These diluents not only give higher den-sification but also inhibit grain growth dependent on theamount of diluent and thereby affect on the SHS reaction,which are beneficial for many applications. Al2O3–ZrB2

composites have applications as high strength armour,cutting tools, impact resistant parts, rocket nozzles etc.

In the present investigation, alumina–zirconium dibo-ride dense composite has been synthesized by SHS dynamicprocess. Results are compared with the sintered productmade from the composite powder prepared by SHSprocess.

2. Experimental

The raw materials, zirconium oxide (99% pure, <100lm, Sdfine India), fine aluminium (99% pure, less than5 lm in size, Aldrich USA) powder and boron oxide(99% <200 lm, Sdfine, India) powders, were mixed in aball mill for one hour. Batches with stoichiometric compo-sition and with 5 wt% extra alumina addition as SHS dilu-ent to the stoichiometric mixture were used for the SHSdynamic compaction process. The mixture was pelletisedin the cylindrical form of 60 mm diameter and 15 mmlength. The pelletisation was carried out at 10 ton load.The green density of the pellets was approximately 55%of the theoretical density. The SHS reaction and dynamiccompaction processing’s were carried out in an air atmo-sphere, in a die made of die steel. Fine sand was filled allaround the samples to decrease heat loss during the reac-tion. The facility for SHS dynamic compaction used wasdeveloped at Institute of Structural Mackrokinetics andMaterials Science (ISMAN), Moscow region, Russia. Thereaction of the pellets was ignited with an electricallyheated tungsten coil placed at the side surface of the greenpellets. When the reaction started, the ignition source wasswitched off. The reactions were carried out for synthesistimes, (ts), 6 s, with loading times, called as delay time(td) 3 s. When ts was reached a pressure of 12 MPa wasapplied for the set delay time (3 s). The details of the pro-cess is described in patent [19] and schematically shown inFig. 1.

For furnace sintering the composite powder was pre-pared from the same raw materials by SHS reaction inthe powder form. The reaction was

3ZrO2 þ 3B2O3 þ 10Al! 3ZrB2 þ 5Al2O3 ð1Þ

Fig. 1. Schematic diagram of SHS dynamic compaction.

S.K. Mishra et al. / Composites Science and Technology 67 (2007) 2447–2453 2449

The reacted powder was further milled for 5 min in a vibra-tory cup mill using WC grinding material. The powder waspelletised into disc of 15 mm diameter and thickness 5 mmof approximately 50–55% of theoretical density. These pel-lets were sintered in a graphite furnace at the optimiseddensification temperature 1800 �C for 30 min in argonatmosphere. The detailed results on pressureless sinteringat different temperatures have been published elsewhere[20].

The particle size analysis of the as synthesised SHS pow-der was carried out by laser scattering process by using par-ticle size analyser (Master sizer ‘S’ Malvern, UK). Thepowders were dispersed ultrasonically in deionised waterand then were measured under particle size analyser. Thephase analyses of the synthesised composite were carriedout from the X-ray diffraction (XRD) patterns of thecrushed powder using Co Ka radiation. XRD, densityand microstructure analyses were carried out from the rect-angular samples cut from the SHS densified as well as sin-tered composite. A diamond blade at low speed was used tocut the sample cross-sectionally. The micro structural char-acterisation and elemental composition analysis of Zr andAl were studied by scanning electron microscope (SEM),model JEOL 840A attached with KEVEX Energy disper-sive X-ray spectroscopy (EDS) analyser. The density ofthe samples was measured by liquid immersion techniquein water using Archimedes principle. The grain size analy-ses of the densified composite were calculated from SEMmicrostructures by intercept method. The average grainsize for alumina and zirconium diboride was quoted.

3. Results and discussion

In the SHS process, the self-sustainability of the exo-thermic reaction and the propagation of combustion wavedepend largely on the enthalpy change associated with thereaction and the rate of energy dissipation from the system.

The exothermic reaction, which results in the formation ofAl2O3–ZrB2 composite is given below

3ZrO2 þ 3B2O3 þ 10Al! 3ZrB2 þ 5Al2O3 ð1ÞThe theoretical combustion temperature (adiabatic temper-ature, Tad), defined as the temperature rise during reactionunder adiabatic condition, was calculated using thermody-namic calculation software ‘‘THERMO’’ developed at IS-MAN. These calculations were based on the total changein enthalpy during chemical reaction that will raise the tem-perature of the product under adiabatic condition. The adi-abatic temperature and product enthalpy were estimated as2327 K and �7121.4 kJ for reaction (1). The percentages ofproduct phases at adiabatic temperature was theoreticallyestimated as 40 wt% ZrB2 solid phase, 52 wt% Al2O3

(liquid phase) and 8 wt% Al2O3 (solid phase) when the stoi-chiometric composition of 43.6 wt% ZrO2, 31.8 wt% Aland 24.6 wt% B2O3 was considered as staring material forreaction. A detailed investigation on the SHS parameterssuch combustion velocity, combustion temperature andmicrostructure evolution was carried out. The measuredcombustion temperature and velocities were found as2223 K and 5 mm/s, respectively when the initial raw mix-ture was in the stoichiometric ratio of reaction (1).The de-tailed process, results and discussion have been publishedelsewhere [21,22].

The adiabatic temperature for addition of 1 mol ofexcess Al2O3 as diluent, as per reaction

3ZrO2 þ 3B2O3 þ 10AlþAl2O3 ! 3ZrB2 þ 6Al2O3 ð2Þwas estimated as 2326 K and the calculated product enth-alpy was �8778.4 kJ. The calculated amount of the differ-ent phases changed compared to reaction (1). It was foundas 35.6 wt% ZrB2 in solid phase, 24% Al2O3 in liquid phaseand 40.4 wt% alumina in solid phase. The adiabatic tem-perature though remained similar but the effective solidand liquid phase of alumina is changed, due to more massin the sample by the addition of 1 mol% of Al2O3. In theprevious case when additional alumina was not added theAl2O3 phase is the by-product of the reaction and hencethe volume fraction of solid and liquid phase is different.In later case the added alumina is not taking part in reac-tion but it will help in removal of heat faster and hence so-lid phase percentage will increase in the product.

The X-ray diffraction analysis of as-prepared powderrevealed the presence of Al2O3 and ZrB2 phases only.The absence of any other peak in the pattern suggests thecompletion of SHS reaction. This work has been describedand discussed in our previous work [21]. The particle sizeanalysis gave a mean diameter of 3.2 lm [D (V, 0.5)], whereD (V, 0.5) means that 50% particles are less than 3.2 lm.The combustion temperature of the reaction (1) was mea-sured as 2173 K [21]. The combustion temperature mea-sured was lower than the thermodynamically calculatedvalue under adiabatic condition because in the thermody-namic calculation losses are not considered where as inactual experiment there are heat losses due to thermal

Table 1Variation of composition at surface and bulk for furnace sinteredAl2O�3 ZrB2 composite at 1800 �C and 1850 �C

Element Sintered at 1800 �C Sintered at 1850 �C

Surface Bulk (centre) Surface Bulk (centre)

Al (wt%) 50.27 52.35 33.77 50.28Zr (wt%) 49.73 47.65 66.23 49.72


conductivity of the reactant and products, radiation andthe density of the pellets. From the rule of mixture, the the-oretical density was calculated as 4.53 g cm�3. The as-pre-pared powders showed good compressibility and the pelletscould be compacted to a green density of 2.27 g cm�3,which is about 50% of the theoretical density.

The samples sintered at 1800 �C for 30 min showed amicrostructure of a good sintered product with 94.6%density of the theoretical value. The back-scatteredelectron (BSE) micrograph of the sample is shown inFig. 2, where the bright phase is ZrB2 and the darkphase is Al2O3. The ZrB2 distribution was observed ashomogeneously distributed in the sample, a large areaBSE microstructure is shown in Fig. 2a. The aluminagrains were found to be quite coarse in the range of10–15 lm, whereas boride grains were in the range of0.5–7 lm (Fig. 2b). The average grain sizes for aluminaand zirconium boride was found as 9.36 and 5.37 lm.Higher sintering temperatures leads to pore formation inthe sample, this was attributed to alumina evaporationduring sintering. The EDX analysis of the sample

Fig. 2. BSE microstructure of furnace sintered Al2O3–ZrB2 composite: (a)large area, (b) at higher magnification; bright phase is ZrB2 and darkphase is Al2O3.

sintered at 1800 �C and 1850 �C are given in Table 1.A detailed study on pressureless sintering of these pow-ders has been published elsewhere [20].

The SHS dynamic compacted samples were found tohave 95% of the theoretical density. The XRD of the sam-ple showed the presence of alumina and zirconium diboridephase formation only (Fig. 3) suggesting the SHS reactionwas complete. The electrical resistivity, at room tempera-ture, of the composite prepared by both process was foundto be in the range of 200–400 l X cm, as measured by fourprobe method with silver paint as contact.

The microstructure of the SHS dynamic compactedsamples show distinct difference from the furnace sinteredsamples. The grains were very fine in the case of SHSdynamic compaction, having a higher density than the fur-nace sintered samples. The grain sizes of alumina and zir-conium diboride were in the range of 0.5–5 lm. Theaverage grain size for alumina and zirconium diboridecomposite was found as 1.9 and 1.45 lm, respectively.The SEM microstructure and the corresponding BSEmicrostructure is shown the Fig. 4a and b. The sampleswere homogeneous throughout. The bulk EDX analysis,a similar size 90 lm · 50 lm frame was chosen in eachanalysis, across the cross-section of the pellets showedmore or less similar compositions with average wt% ratioof Zr:Al as 49:51. The oxygen and boron could not bedetected due to limitations of the EDX detector, whichcannot detect less than atomic no.11.

The addition of SHS diluents is an effective method tocontrol the reaction. As described earlier, 5 wt% aluminaof the total weight of the stoichiometric mixture was added

Fig. 3. XRD pattern of Al2O3–ZrB2 in situ composite prepared by SHSdynamic compaction.

Fig. 4. SEM microstructure of in situ SHS dynamic compacted Al2O3–ZrB2 composite (a) SE micrograph, and (b) corresponding BSEmicrograph.

Fig. 5. SEM microstructure of in situ SHS dynamic compacted Al2O3–ZrB2 composite with 5 wt% Al2O3 as diluents (a) SE micrograph, and (b)BSE micrograph.


as diluent during mixing. The thermodynamic calculationof the adiabatic temperature with 5 wt% alumina as dilu-ents does not change, but the diluent was very effective infurther inhibiting the grain growth. It also led to higherdensification. The density of the 5 wt% alumina addedsample was measured to be 97% of the theoretical density.The secondary and backscattered electron micrographs areshown in Fig. 5a and b. From microstructure, it wasobserved that the grain growth inhibition was significantcompared to the pressureless sintered and SHS dynamiccompacted sample without any diluents. The grains werefound to be in the range of 0.5–2 lm range for both alu-mina as well as borides. Here the average grain size for alu-mina as well as zirconium diboride was found as 1.4 and1.0 lm, respectively. The grain growth was significant whenthe samples were sintered at 1800 �C in furnace due to longcycle duration at higher temperature. When compactionwas allowed dynamically during SHS reactions, the samplesdid not remain at high temperature for longer time. There-fore, the grain growth was reduced compared to that offurnace sintered samples. The further grain growth inhibi-

tion observed in sample with 5 wt% Al2O3 diluents is due tothe additional alumina not taking part in the reaction, butas second phase it inhibits the grain growth and also theheat transfer changes due to the presence of diluents phasein the sample.

The increase in density during in situ SHS dynamic com-paction compared to furnace sintering is due to many rea-sons such as in SHS dynamic compaction, the load isapplied during the reaction itself hence it is similar to hotpressing of the samples, and finer grain distribution tendsto give a better sintering conditions or arrangements ofgrains, whereas in the sintered samples the grains growby different mechanism which can lead to increased poreformation. The densification is caused by the flux of matterfrom the grain boundaries (the source) to the pores (thesink). For sintering by diffusion mechanism, the densifica-tion rate increases with the reduction of grain size. Thedensification rate is expressed as [23]

1=qdq=dt ¼ K=Gm ð3Þwhere k is constant, G is grain size and m is equal to threeor four for lattice diffusion on grain boundary diffusion,respectively. For rapid densification, the distance between


source and sink must be kept small i.e the G must remainsmall. Hence during SHS dynamic compaction the higherdensity is also achieved due to finer grainsize. If the grainsize is larger, longer firing times are required. Also poresget trapped between large grains, as happens in furnace sin-tering, and is difficult to annihilate and hence lesser densi-fication is achieved as observed in the case of furnacesintered sample in the present case. Also in the case ofSHS dynamic compaction the simultaneous applicationof load during synthesis, when the pellet is at higher tem-perature, helps in achieving higher density. When pressureis applied during sintering the densification rate can be pre-sented as

1=qdq=dt ¼ HDunP n=GmkT ð4ÞHere H, is a constant, D is diffusion co-efficient, u is stressintensification factor, G grain size, P applied pressure, T isabsolute temperature, m and n exponent factor dependenton mechanism involved. It is clear from the equation thatwith the applied pressure the densification rate increases.The pressure enhances the driving forces for densification.The dependence of densification rate on driving force isdependent on sintering stress and applied pressure. Forachieving high density with lower grain growth the dq/dt:dG/dt should be large, dG/dt is the grain growth rate[23]. In the case of hot pressing such conditions areachieved, because of higher driving force the densificationrate is larger and grains do not get sufficient time to grow.Hence in case of SHS dynamic compaction both load andthe grain size leads to higher and faster densification com-pared to the furnace sintered one.

The presence of liquid phase will also enhance the den-sification. This depends on the shape and angle of the sidesof the grains. The evaporation loss of alumina during fur-nace sintering had strong effect on densification of the sam-ple. This loss was reduced during in situ formation of thecomposite by SHS dynamic compaction, since samplesdid not remain at high temperatures for long. This alsoleads to less porosity and improved densification. The fur-ther increase in density in the case of diluent addition dur-ing SHS dynamic compaction is due to further inhibition ofgrain growth. Also it was observed in thermodynamic cal-culation that liquid alumina content is decreased with1 mol addition of Al2O3 compared to the reaction whenno such diluent was used. The amount of liquid in the sam-ple during cooling is important for grain growth as well asdensification. For the sample when no diluent Al2O3 wasthere, the liquid content was more. It is possible that duringdynamic compaction liquid squeezed out and also for moreamount of liquid how the pores have been filled will deter-mine the densification. It was confirmed that at the sides ofthe sintered discs alumina content was more, whereas when1 mol% alumina was added the liquid content hasdecreased and liquid squeezing effect was much less whichhelped in getting higher density. For smaller fraction ofliquid, it uniformly distributes at the particle necks. How-ever, to understand this more detailed experiments with

different percentage of diluent additions are required andshall be communicated as separate publication.

Thus in situ fabrication of the densified alumina matrixcomposite with zirconium diboride dispersion by SHSdynamic compaction presents a novel approach. The pro-cess is not only fast, in situ and yields a higher densificationbut also inhibits the grain growth, which is desirable forhigher strength of the material. The process can be usedin tailoring the microstructure of the composite by suitableadditions of diluent, loading time and load.

4. Conclusions

SHS dynamic compaction was found to be very usefulin fabricating an in situ Al2O3–ZrB2 composite. The pro-cess was novel, economic, energy efficient. The process isfast, energy efficient, where no furnace sintering wasrequired. The results were compared with the samples,where the composite powder was prepared by SHS pro-cess and then furnace sintered at 1800 �C temperature.The furnace sintered samples have coarser grains andthe maximum density achieved was 94.5% of the theoret-ical density. The SHS dynamic compacted in situ compos-ite had much finer grains with density 95.5% of theoreticalvalue. Further densification to 97% of theoretical wasachieved by adding 5 wt% alumina as diluent duringSHS dynamic compaction. The process has been usedvery successfully to inhibit and control the grain growth.The average grain size was found to decrease from 10 lmto 1.4 lm for alumina and from 5.4 lm to 1.0 lm for zir-conium diboride from furnace sintering to SHS dynamiccompaction, respectively.

Acknowledgements

The authors acknowledge the support of Department ofScience and technology ILTP programme and Russianacademy of science under which the research work wascarried out. The authors are particularly thankful toAcad. A.G. Merzhanov, Director ISMAN for valuablediscussions.

References

[1] Upadhaya K, Yang JM, Hoffman WP. Material for ultrahightemperature structural applications. Am Ceram Soc Bull1997;76:51–6.

[2] Liu J, Ownby PD. Enhanced mechanical properties of alumina bydispersed titanium diboride particulate inclusions. J Am Ceram Soc1991;74:241–3.

[3] Sundaram V, Logan KV, F Speyer R. Aluminothermic reaction pathin the synthesis of TiB2–Al2O3 composite. J Mater Res1997;12:1681–4.

[4] Ray SP. Boride–Alumina composite-synthesis and fabrication. MetallTrans A 1992;23A:2381–5.

[5] Postrach S, Potschke J. Pressureless sintering of Al2O3 containing upto 20 vol% zirconium diboride. J Ceram Soc 2000;20:1459–68.

[6] Merzhanov AG, Borovinskaya IP. A new class of combustionprocess. Combust Sci Technol 1975;10:195–200.


[7] Sheppard LM. Powder that explode into materials. Adv Mater Proc1986;2(2):25–32.

[8] Merzhanov AG. Combustion process that synthesis materials. JMater Process Technol 1996;56:222–41.

[9] Merzhanov AG. In: Munir ZA, Holt JB, editors. Combustion andplasma synthesis of high temperature materials. NY: VCH Publishers;1990. p. 1.

[10] Munir ZA. Reaction synthesis processes mechanism and character-istics. Metall Trans A 1992;23A:7–13.

[11] Bermann OR, Barrington J. Effect of explosion shock waves onceramic powders. J Am Ceram Soc 1966;49:502–7.

[12] Golubjatnikov KA, Stangle GC, Spriggs RM. The economics ofadvanced self-propagating high temperature synthesis material fab-rication. Am Ceram Soc Bull 1993;72(12):96–102.

[13] Gutmanas EY, Gotman I. Dense high-temperature ceramics bythermal explosion under pressure. J Eur Ceram Soc 1999;19:2381–93.

[14] Wang L, Wixom MR, Thompson LT. Structural and mechanicalproperties of TiB2 and TiC prepared by self-propagating hightemperature synthesis/dynamic compaction. J Mater Sci1994;29:534–43.

[15] Meyers MA, Olevsky EA, Ma J, Jamet M. Combustion synthesis/densification of an Al2O3–TiB2 composite. Mater Sci Eng A2001;311:83–99.

[16] Feng HJ, Moore JJ. In situ combustion synthesis of dense ceramicsmetal interpenetrating phase composite. Metall Mater Trans B1995;26:265–73.

[17] Hoke Darren A, Meyers Marc A. Consolidation of combustionsynthesised titanium diboride based materials. J Am Ceram Soc1995;78(2):275–81.

[18] Monteverde F, Bellosi A, Guicciardi S. Processing and properties ofzirconium diboride based composites. J Eur Ceram Soc2002;22:279–88.

[19] Mishra SK, Shcherbakov V. An improved process for dense ceramicalumina –boride composite – patent alumina-ZrB2. US patent filed0238NF2003/US, Indian 1654/del/2004.

[20] Mishra SK, Das SK, Pathak LC. Sintering behaviour of self-propagating high temperature synthesised ZrB2–Al2O3 compositepowder. Mater Sci Eng A 2006;426:229–34.

[21] Mishra SK, Das SK, Ramachandra rao P, Belov D, Mamyan S.Synthesis of zirconium diboride–alumina composite by SHS process.Metall Trans A 2003;34(9):979–1983.

[22] Mishra SK, Das SK, Ramachandrarao P, Belov D, Mamyan SS. SHSsynthesis of zirconium diboride–alumina composite – a dynamic X-ray study and phase evolution. Phil Mag Lett 2004;84(1):41–6.

[23] Rahaman MN, [chapter 9], ‘‘Ceramic processing and sintering’’published by Marcel Dekker, Inc. 1995.

fabrication of al2o3–zrb2 in situ composite by shs dynamic compaction: a novel approach

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