Abstract
The purpose of the present study was to synthesize SiC-AlN ceramic alloy powders (solid-solutions and their composites) by the reaction sintering of the mixed powders of Si, C and Al in a N2 atmosphere. This present process, which employs the direct reactions between the constituent elements in the SiC-AlN system, was revealed to be effective for the powder preparation in the SiC-AlN system. The reaction was found to occur significantly above 1073 K with preferential formation of AlN and followed by SiC at higher temperature. Although Si3N4 was also formed due to the reaction between Si and N2 during the reaction sintering, its formation can be avoided by conducting the 2-step reaction sintering; first in N2 gas containing 10%H2 at 1073 K and subsequently in Ar gas at 1773 K. Such a process resulted in a porous product compact of SiC-AlN alloys without other phases, which can be simply pulverized to powder. X-ray diffraction showed that solid solutions were formed in the powder state although the extent of solid solution formation was not clarified. The synthesized powder was further densified by hot-isostatic pressing (HIP) at 2123 K and 200 MPa for 2 h, and the mechanical properties, such as microreaders, strength and fracture toughness, were investigated.
