The influence of preceramic binders on the microstructural development of silicon nitride

A number of polymeric precursors to silicon nitride were prepared and evaluated as binders in cold pressing/pressureless sintering operations. These polymers exhibited ceramic yields in excess of 75 percent by weight, and powder compacts made using them as binders displayed improved green handling properties. Compacts pyrolyzed at 800 deg C exhibited unusual microstructures, including the development of whiskers in situ. Based on microstructural observation, compacts sintered under pressureless conditions appeared to show enhanced densification relative to those processed without preceramic binders. Preceramic binders appeared to enhance the formation of Beta-Si3N4 and may enhance densification of compacts sintered under pressureless conditions. (Author)