Preceramic Polysilazanes for Structural Applications

Chemical methods of producing structural ceramics are currently of considerable interest because traditional, power-based processing techniques appear incapable of yielding components that can satisfy advanced performance requirements in a cost efficient manner. Because of its strength-to weight ratio, oxidation resistance, and other properties, silicon nitride (Si{sub 3}N{sub 4}) is a particularly attractive material for high temperature applications, such as in the hot zone of jet or internal combustion engines. Despite its high potential to improve the performance of power systems, the combination of brittle fracture behavior and manufacturing difficulties have hindered the utilization of Si{sub 3}N{sub 4}, components by design engineers. One approach to alleviating brittle fracture behavior is through the incorporation of high strength fibers nor the production of complex shapes. The authors have developed a series of low viscosity, thermosetting polysilazanes which are suitable for the production of Si{sub 3}N{sub 4} composites through infiltration/pyrolysis techniques. The fabrication technique and composite properties will be discussed along with the analysis of the polymer-to-ceramic conversion process and the nature of the polysilazane-derived ceramic.