The Use of Organometallic Precursors to Silicon Nitride as Binders

ABSTRACTCurrent techniques of advanced ceramic component fabrication are based on pressureless green body consolidation technology in which voids often remain in the final microstructure. Much of this residual porosity is created when the organic binder used to consolidate the ceramic powder burns off on sintering. A new concept in the field of ceramic processing is the use of an organometallic binder material which will pyrolyze on sintering and convert into a predetermined ceramic. Silicon nitride (Si3N4) is a ceramic material in great demand for elevated temperature applications because of its excellent high temperature properties. At the present time, silicon nitride cannot be successfully processed without the use of costly pressure sintering (e.g., hot pressing), or the addition of a glassy phase, which degrades the high temperature properties.Various preceramic polymers to be used as binders for cold pressing operations have been synthesized and studied. It has been demonstrated that these polymers may be dissolved in an appropriate organic solvent and mixed with a powder. Removal of the solvent yields homogeneous mixtures which may be consolidated into highly dense (> 66% of theoretical) green bodies. The ceramic yields of these polymers have also been determined.