Preparation And Ablation Properties Of AlSiB-ZrC-C/C Dissipative Thermal Protective Composites

Trough the combination of precursor infiltration pyrolysis and pressure infiltration,the thermal protection composite materials with different densities and types of carbon fiber preforms were fabricated using the design ideas of dissipation and thermal protection in this paper.According to the advances in carbon-carbon composite materials,ZrC and its oxides have significant anti-ablation performance during the ablation process.AlSiB ternary alloy was selected as a synergistic dissipative agent to study the comprehensive performance of dissipative thermal protection composites.The effects of the dissipative agent on the mechanical properties of the composite material were studied for the changes of the flexural strength,compressive strength and flexural modulus before and after impregnation with the dissipative agent.The phase structure and micromorphology of the composites before and after ablation were analyzed with XRD,SEM and other analytical methods,based on the characteristics of ablation products and ablation mechanism of composites were studied.The influences of the different variables on the ablation performance were compared and analyzed by factors such as the ablation resistance of the substrate,the type of dissipative agent,the type of carbon fiber preform and the ablation direction.The Zr element is introduced with the precursor infiltration and pyrolysis method,and the Al,Si,and B alloys are impregnated by the pressure infiltration way.The two methods impregnate and infiltrate the carbon-carbon composite material.The liquid precursor and the dissipating agent are dispersed between the carbon fiber bundle and the substrate.The materials' phase composition is C,Al,Si,and the Zr element exists in the form of monoclinic and tetragonal zirconia and ZrC.The bending strength of the composites impregnated with AlSiB dispersant is increased by 16.85%-38.81%.The bending strength of ASB-ZrC-C/C is increased by 31.08%-82.47%,reaching a maximum of 267.46 MPa,and the compressive strength and bending modulus are also significantly improved.The mechanical properties of the composites after impregnation are more excellent.Thermodynamic analysis shows that the element of precursor and dissipating agent is more easily oxidized under high temperature conditions.The results of the oxygenacetylene ablation experiment indicate that the ablation resistance of the carbon-carbon matrix and the amount of infiltration are the factors that affect the ablation resistance of composites.At the same dissipating agent type,the carbon-carbon composite with a density of 1.64 has both the matrix strength and the weight gain rate of the impregnating agent,and the linear ablation rate is generally low.Fine weave pierced has better penetration resistance due to better penetration strength of Z-directional fiber bundles than needle-punched fiber bundles,best thread ablation rate,weaker bonding force between 3D braided layers,poor in-plane mechanical properties,and ablation rate highest.The oxidation ceramic coating is formed on the surface of the composites during the ablation process of the dissipative agent.Its main components are Al2O3,Si O2,Zr O2,etc.,which plays a protective role on the surface of the C/C matrix.The XY ablation is significantly better than the Z ablation.The line ablation rate as little as 10.37um/s,ZrC and Zr O2 greatly reduce the heat conduction,and protect the substrate from high temperature within a certain period of time.Through the establishment of the moving boundary layer ablation model in Comsol,the C diffusion convection process and temperature field distribution of the carbon-carbon composite material were simulated,and the boundary ablation rate was calculated to obtain the ideal linear ablation rate.