CONTROLLING INTERFACE CHEMISTRY AND STRUCTURE TO PROCESS AND TOUGHEN SILICON-CARBIDE

Silicon carbide is difficult to process and the product is a brittle c eramic; however, the control of chemistry and structure at grain bound ary interfaces offer the opportunity to enhance processing as well as to enhance the toughness (K-c > 9 MPa m(1/2)) and strength of this cer amic. An active chemistry and structure can alter the kinetics of inte rfacial motion during the processing of a structurally dense and unifo rm microstructure. The residual chemistry and structure at grain bound aries can control the mechanical properties both at ambient and high t emperatures. The Al, B and C additives in ABC-SIC are discussed in thi s work, with regards to the effects of structure and chemistry on proc essing and properties.