MECHANICAL AND TRIBOLOGICAL PROPERTIES OF POLYMER-DERIVED Si/C/N SUBMILLIMETER THICK MINIATURIZED COMPONENTS FABRICATED BY DIRECT CASTING

摘要

The utilization of silicon-based polymers as a source of amorphous non- oxide ceramics obtained upon pyrolytic treatment of them is increasingly gaining attention in research and is currently expanding into the field of commercial products. This work is focused on the near-net shaped fabrication, mechanical and tribological properties of a polymer-derived Si/C/N system. Small sub-millimetre thick ceramic test discs and bars were fabricated by casting of polysilazane and/or polycarbosilane precursor mixtures into elastomeric polydimethylsiloxane forms, thermal cross-linking and subsequent pyrolysis. Additional carbon was introduced on the molecular level using triphenylvinylsilane as the precursor, its cross-linking with the polymers via hydrosilylation prohibits phase separation of graphite. The characteristic strength of nearly 700 MPa along with stable low friction coefficients in sliding against similar polymer-derived ceramics testifies to their potential in micro electro mechanical system applications.