Sinterability of SiC powder coated uniformly with Al ions

Abstract

SiC particles coated uniformly with Al ions (0.25 mass% Al2O3) in an aluminum nitrate solution were consolidated by filtration through a gypsum mold. Hot-pressing in vacuum gave dense SiC (above 99% relative density) in the temperature range of 1900–1950 °C under a pressure of 39 MPa. The microstructures of dense SiC consisted of 2–5 μm grains of low aspect ratios (below 2). The fracture toughness and flexural strength of SiC increased gradually as the hot-pressing temperature became higher and were 4.3 Mpa m0.5 and 350 MPa, respectively, with hot-pressing at 1950 °C. Crack propagation in SiC shifted from intergrain to intragrain with increasing hot-pressing temperature.