Influence of Additives and Hot-Press Sintering on Lipophilic Properties of Silicon Nitride Ceramics

Fe 3 O 4 and Mo and were added to hot-press sintered Si 3 N 4 ceramics to improve their lipophilic and mechanical properties. The bending strength, relative density, hardness and fracture toughness of Si 3 N 4 ceramics with addition of Fe 3 O 4 and Mo were improved by hot-press sintering compared with samples prepared with the pressureless process. In particular, the bending strength and relative density were improved to about 200% and 104%, respectively. Both the macro- and micro-lipophilicity of Fe 3 O 4 - and Mo-added ceramics were improved when prepared with the hot-press process, compared with those prepared with the pressureless process. This can be attributed to the addition of Fe 3 O 4 , and the formation of MoO 3 and Si 2 N 2 O during hot-press sintering. The lower friction coefficient and high wear resistance of Fe 3 O 4 - and Mo-added ceramics have been achieved by applying the hot press process. The high wear resistance is considered to be due to the improvement of hardness and fracture toughness, which decreased the loss of particles during the wear test.