Study On Fabrication And Properties Of C/C-AlSiB Dissipative Thermal Protective Composites

In this thesis,the preparation of light,high strength,high temperature ablation of the heat-resistant material as the goal,to dissipate heat for the design ideas,using different density C/C composite material as a matrix and C/C-AlSiB dissipation heat-resistant composite materials were prepared on the basis of AlSiB alloy as the impregnating agent.AlSiB alloy was chosen as the impregnant is based on the consideration of the physical properties and thermodynamic properties of the materials.Composites were analyzed by means of advanced analytical method,and the influencing factors were discussed.The anti-ablation properties of the microstructures were characterized by oxygen-acetylene ablation experiments.The mechanism of ablation of the materials was investigated by ablation behavior of the ablation process.C/C-AlSiB composites are more compact and the impregnation agent is uniformly distributed in the matrix.This microstructure plays an important role in improving the mechanical properties of the composites.The phase in the material is mainly C,Al,Si SiB₆ and Al B₁₀.The bending strength of the dissipative heat-resistant composites increased by34.96%and the modulus of elasticity increased by 21.90%compared with the C/C matrix.The thermal expansion coefficient of C/C-AlSiB composites increases than C/C matrix in both XY and Z directions.Oxygen-acetylene ablation test results show that the ablation rate of C/C-AlSiB dissipation heat-resistant composites is lower than that of C/C,especially the1.63CC-AlSiB composites,which indicates that the ablation resistance of the material is improved.The center area of ablation,the surface of the transition zone and the edge area showed different micro-morphology.During the ablation process,the oxide layer was formed on the surface of the material,and the main components were Al₂O₃and SiO₂.The surface penetrant is more likely to react with oxygen under ablation conditions and formed an oxide film covering the surface.Therefore,the C/C matrix is protected.The surface of the liquid oxide layer is sticky,making the mechanical erosion of the material weakened.The thermochemical ablation of the surface of the C/C-AlSiB heat-resistant composite causes the oxygen dissipation,and the endothermic action of the infiltration agent,the thermal barrier of the oxide film,and the heat generated by the gas evolution caused thermal dissipation.The combined effect of these factors improves the ablation resistance of the material.