Preparation Of C/C-SiC-ZrC Composites By Reaction Melt Infiltration And Study On Performance Of The Materials

Abstract:C/C composites are widely used in aviation, aerospace and other areas as a thermal structure material, so that it is necessary to develop new thermal protection materials. On the base of ultra-high temperature materials research abroad and at home, this dissertation investigated C/C-SiC-ZrC composites. The effects of preparation parameters on C/C-SiC-ZrC composites’density were studied; the mechanical properties, the oxidation performance and the ablation performance of the C/C-SiC-ZrC composite were studied. The main conclusions are as follows:(1) The experiments show that the density of the material rises as the infiltrating temperature rises. The high fiber content of the preform can cause the reduction of the ceramic phase, so the density of the material doesn’t rise easily. By RMI process, the density of the preform can be densificated from1.4g/cm3to2.16g/cm.(2) The3D composite fibres are badly connected with the pyrolytic carbon,so they can not absorb so much energy when broke up. The less ceramic phases in the internal leading to the lower density. Besides, part of the internal fiber take part in the infiltration reaction and change into high brittleness ceramic phase. These reasons all lead to poor mechanical properties of3D composites. The bending strength and compression strength of2.5D composites are147.38Mpa and252.4MPa, while that of3D composites are50.4MPa and132.3Mpa. Flexural strength of two materials are increased by17.6%and23.4%after modification.(3) As the self-healing of SiO2is not so good at low temperature, the oxidation behavior of materials is decreased. The oxidation behavior of3D composites with less ceramic phases is not good. Weight loss rate of2.5D composites oxidated at1200℃for30min is1.473%, showing better oxidation properties/while is14.097%.(4) Materials with a smooth surface show good ablation performance due to small mechanical erosion; the mat layer at the axial direction having high content of ceramic phases show good ablation performance;3D composites having less ceramic phase content show bad ablation performance. Using oxyacetylene ablation for20s upon2.5D composite material from axial direction, the mass ablative rate is1.768mg/s, the linear ablation rate was9.6μm/s while that of3D composite materials is2.445mg/s and19μm/s.