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An influence of p-eucryptite glassceramics on the sintering ability, sintering mechanisms, and structure of alumina ceramics has been researched by methods of DTA, TG, DTG, XRD, dilatometry, optical and electronic microscopy. The thermal incompatibility between A l l 0 3 and p-eucryptite glassceramics that results fiom the difference between their thermal coefficients of expansion (TEC) has been overcome by use of superfine powders and thorough blending of the base mixture. A phase composition, microstructure, TEC, mechanical and electrical properties, and thermal-shock resistance of alumina ceramics containing p-eucryptite glassceramics have been determined.A possibility of replacing P-eucryptite glassceramics by the equivalent amount of Li~0.2Si02 containing glass or a mixture of Li2CO3 u SiOl powders has been demonstrated.

This work is part of a program on composites used in thermoelectric devices. Tribological properties of dynamic vulcanizate blends of polypropylene and ethylene-propylene-diene rubber filled with 5 wt% of microscale powder have been studied. The microscale thermal-shock-resistant ceramic filler contains α-Al 2 O 3 , mullite (3Al 2 O 3 · 2SiO 2 or 2Al 2 O 3 SiO 2 ), β-spodumene glass-ceramic and aluminium titanate. We found that our ceramic particles are abrasive; they cause strong abrasion of softer steel ball surfaces during dry sliding friction. To overcome the difficulty of particle dispersion and adhesion, the filler was modified through grafting using three types of organic molecules. Dry sliding friction was measured using four types of counter-surfaces: tungsten carbide, Si 3 N 2 , 302 steel and 440 steel. Thermoplastic vulcanizate filled with neat ceramic powder shows the lowest friction compared to composites containing the same but surface-treated powder. We introduce a 'bump' model to explain the tribological responses of our composites. 'Naked' or untreated ceramic particles protrude from the polymer surface and cause a decrease of the contact area compared to neat polymer. The ball partner surface has only a small contact area with the bumps. As contact surface area decreases, so does friction and the amount of heat generated during sliding friction testing. Chemical coupling of the ceramic to the matrix smoothens the bumps and increases the contact surface, giving a parallel increase in friction.

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