Mechanical and thermal properties of Si–C–N material from polyvinylsilazane

Abstract

Commercial polyvinylsilazane was crosslinked and then crushed to powder. The powder was compacted by cold isostatic pressing at 630 MPa and pyrolysed at 1050 °C in flowing argon. Crack-free Si–C–N material was obtained. Bulk density of the material was 1.95 Mg m−3. Open porosity was 9.6%. The material was amorphous as a result of X-ray diffraction analysis. Elastic modulus measured by pulse–echo method was 105 GPa. Vicker's hardness calculated from indentation at 98 MPa was 6.1 GPa. Fracture toughness measured by indentation fracture method was 2.1 MPa m1/2. Average bending strength was 118 MPa. The material shrank 1.9% in length during heating up to 1400 °C in nitrogen. The thermal expansion coefficient of the material heat treated up to 1400 °C increase from 3.08 × 10−6 °C−1 at 100 °C to 3.96 × 10−6 °C−1 at 1200 °C.