Sintering of a - sic at high pressures and temperatures (original) (raw)

Abstract

The high temperature properties of sintered silicon carbide are critically dependent on additives which are used for consolidation by conventional hot pressing into pore-free bodies. The sintering aids provide increase in shrink-age rate and high densities at low sintering temperatures. However, the presence of sintering aids results in a second phase at the grain boundaries which13; has adverse effects on the high temperature properties. An effort has been made to produce fully dense self bonded Sic without using sintering aids by high pressure-high temperature sintering. The Sic powder has been sintered13; at pressures (1.7-3.0 GPa) at 18OO0C for 5-30 minutes. The densities 'of the sintered compacts are gt; 99% theoretical density. The compacts show room temperature hardness values in the range 26.7-33.5 GPa. The indentation frac-13; ture toughness values range between 3.5 and 3.9 MPaJ;;E. The microstructural studies have shown that pressure plays an important role in the dens...

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