Laser Chemical Vapor Precipitation of Ceramic Powders

摘要

The properties of ceramics are usually superior to those of metals at high-temperatures and under corrosive conditions. Silicon nitride, Si3N4, is one of the most promising structural ceramics, because of its high-temperature strength, thermal shock resistance and good chemical stability. Si3N4 ceramics are, therefore, prime candidates, for high-temperature applications such as lightweight heat engine components. In this work the formation of Si3N4 powders is studied by using as synthesis technique Laser Chemical Vapor Precipitation. The combination of gas phase reaction and laser heating technique results in an optimal control of the particle sizes and, because it is a cold wall, in a strong reduction of impurities. The use of chlorinated silanes and ammonia, NH3, as reactants can result in cost-effective production of Si3N4. Also these chlorinated silanes as well as other halogenated silanes reduce silicon contamination in the product compared to the generally used silane, SiH4. A reactor and electrostatic precipitator were developed in order to produce and collect high quality Si3N4 powders from halogenated silanes and NH3.