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Aqueous tape casting of PMN-PT powder, prepared by the partial oxalate route, using PVA and glycerol as a binder and a plasticizer has been studied. The amount of PVA and glycerol required for forming green tape with good strength and flexibility has been optimized. The tape cast PMN-PT sintered to near theoretical density (>99% TD) at lower temperature (1200 °C) are compared to the samples prepared by uni-axial pressing (1270 °C). Flat PMN-PT tapes with good surface finish could be prepared by binder removal and sintering of the green tapes. The piezoelectric properties of the sintered tapes are comparable to that of PMN-PT ceramics reported in literature.

Pyrochlore phase free PMN-PT powder of morphotrophic phase boundary (MPB) composition has been prepared using the partial oxalate method. The synthesis process has been optimized by thorough characterization of the intermediate compounds such as columbite and (Mg 1/3 Nb 2/3 ) 0.675 Ti 0.325 )O 2 by XRD analysis, particle size analysis, surface area measurement and morphological studies. Lead oxalate produced by in situ precipitation in a suspension of (Mg 1/3 Nb 2/3 ) 0.675 Ti 0.325 )O 2 powder expected to coat on the particle surface, which improved the homogeneity of the precursors and resulted in the formation of pure PMN-PT phase during calcination at 750 °C. The PMN-PT powder contains more than 95% submicron particle with D 50 0.4 μm. The process eliminates the formation of detrimental pyrochlore phase from the PMN-PT powder.

MoSi2 and its composite with TiB2 (10 and 20 wt.%) particulates were synthesized by the hot pressing technique. Dry sliding wear experiments were done on these samples by pin-on-disc method on an EN-24 steel disc. It was observed that the densification and the reinforcement of the matrix are beneficial in reducing the friction and wear Of MoSi2. The tribofilm that was formed during sliding contained both the disc and the pin material. (C) 2002 Elsevier Science B.V. All rights reserved.

Wear tests were done in a pin-on-disc machine by sliding MoSi2 pins against hard-steel discs in a normal load range of 5-140 N and a speed of 0.5 m/s under nominally dry conditions in the ambient. The specific wear rate of the pin undergoes two transitions: severe to mild at low load and mild to severe at high load. The mild-wear domain is distinguished by the formation of a protective mechanically mixed layer of steel and its oxides, transferred from the counterface in particulate form. Increasing the hardness by densification and TiB2 reinforcement lowers the specific wear rate and expands the mild-wear load domain. However, even when the volume wear rate is normalised with respect to the real contact area (load/hardness) the non-dimensional wear factor is still seen to decrease with densification and reinforcement. This indicates that fracture toughness may also play an important role in determining the wear-resistance of these materials. The surface coverage on the pin by the mechanically mixed layer increases with densification and reinforcement.

Nanocrystalline zirconia powders stabilized with varying concentration of yttria (YSZ) were synthesized following urea solution combustion route. Thermogravimetric analysis combined with differential scanning calorimetry was carried out for the intermediate gel for analyzing reaction kinetics. The final products were characterized by X-ray diffractometry, transmission electron microscopy and specific surface area measurements. Sintering behavior of theses powders were studied. The powder quality is poor in respect of surface area and sintered density.

Wear experiments performed on steel disc with increasing load for monolithic MoSi2 of different densities and its composite with TiB2 showed three distinct wear regimes. The specimens exhibited severe wear rate below the lower and above the upper critical loads and mild wear in between the two critical loads. The increase in density of the monolith and the reinforcement of TiB2 were effective in reducing the coefficient of friction and the specific wear rate. The wear experiments have been performed in these three regimes (15, 50 and 75 N). The tribofilm formed on the pin surface was found to contain both pin and disc materials. The temperature of the pins during the sliding against EN-24 disc was calculated using one dimensional heat transfer equation at different loads for each composition. The composite experiences lower temperatures compared to the monoliths. (C) 2002 Elsevier Science B.V. All rights reserved.