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

Commercial polyvinylsilazane was crosslinked and then crushed to powder. Th e powder was compacted by cold isostatic pressing at 630 MPa and pyrolysed at 1050 degrees 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. Elast ic modulus measured by pulse-echo method was 105 GPa. Vicker's hardness cal culated from indentation at 98 MPa was 6.1 GPa. Fracture toughness measured by indentation fracture method was 2.1 MPa m(1/2). Average bending strengt h was 118 MPa. The material shrank 1.9 % in length during heating up to 140 0 degrees C in nitrogen. The thermal expansion coefficient of the material heat treated up to 1400 degrees C increase from 3.08 x 10(-6) degrees C-1 a t 100 degrees C to 3.96 x 10(-6) degrees C-1 at 1200 degrees C. (C) 1998 Kl uwer Academic Publishers.