Improvement offered by coprecipitation of sintering additives on ultra-fine SiC materials

The effectiveness of a chemical procedure for introducing sintering aids (yttria and alumina) into a commercial silicon carbide powder mixture, consisting of the coprecipitation from nitrates, is compared to a conventional ultrasonic mixing technique for powder additives. the surface properties of the two powder mixtures are investigated using the electroacoustic technique. they are densified by hot pressing and the densification behaviour, microstructure and mechanical properties of the resulting materials are compared and discussed. the results obtained indicate that, compared to the ultrasonic technique, the coprecipitation process allows to obtain a refinement of the microstructure of about 33% and a reduction from 6 to 3 wt % of the amount of intergranular phase in dense samples.