EFFECT OF SINTERING METHOD ON DENSIFICATI ON AND MECHANICAL-PROPERTIES OF SI3N4 SIC COMPOSITES WITH NITRATES AS SINTERING ADDITIVES/

The effects of various sintering methods, such as pressureless-sinteri ng, hot-pressing and spark-plasma-sintering, on the densification and mechanical properties of Si3N4/ (0-30 mass%) SiC composites were exami ned. Two sets of starting powders mixed with nitrates and oxides as si ntering additives, respectively, were used. By pressureless-sintering, density of the Si3N4/SiC composites generally decreased with increase in SIC content, and the composites with nitrate additives were denser than those of oxide additives at the same amount of SiC. The Si3N4/Si C composites sintered by hot-pressing and spark-plasma-sintering were fully densified regardless of the type of sintering additives and amou nt of SiC, The mechanical properties strongly depended on the amount o f SiC and sintering additives, i.e., on the sintered density and morph ology of Si3N4 grains. The mechanical properties of the monolithic Si3 N4 and the Si3N4/10 mass % SiC composite fabricated by pressureless-si ntering were nearly the same as those of hot-pressed specimens.