Ceramics composites Si 3N 4–SiC (w) containing rare earth concentrate (CRE) as sintering aids

Abstract

Due to densification difficulties related to ceramics composites fabrication, a considerable research effort is being made to optimize processing methods of these materials, such as selection of adequate sintering aids and advanced powder synthesis technology. The use of rare earth concentrate (CRE) as sintering aid in Si 3N 4–SiC (w) ceramics composites is a new approach, to obtain silicon nitride based ceramics with good mechanical properties. Using CRE as obtained, makes unnecessary to perform the step of individual rare earth separation, with resultant time and cost reduction. In this work, different compositions of silicon nitride based matrix reinforced with silicon carbide whiskers were hot uniaxially pressed, followed by physical (specific mass, X-ray diffraction and scanning electron microscopy analysis) and mechanical (microhardness and fracture toughness) properties evaluation. For comparison, density and mechanical properties of the unreinforced silicon nitride matrix samples were also evaluated. Good density and mechanical properties results confirmed the viability and efficiency of the CRE as sintering aid, to obtain dense and tough Si 3N 4–SiC (w) ceramics composites.