Preparation And Properties Of Anti-insulation Aluminum-chromium Phosphate Matrix Composites

Phosphate composites are considered to be one of the most effective anti-insulation materials for future aerospace applications due to their simple preparation process,low thermal conductivity and excellent high temperature performance.In this study,different aluminum-chromium phosphate based anti-insulation composites were designed and prepared,and the effects of process parameters on the microscopic morphology,phase composition,mechanical properties and thermal properties of the materials were systematically investigated,and the low temperature curing mechanism,thermal insulation and ablation resistance of the aluminum-chromium phosphate based anti-insulation materials were investigated,and the thermal insulation and ablation mechanisms were elucidated.The main results of the study are as follows.:（1）When the metal oxygen La₂O₃ is added at 30%and 40%,the La-Al-based phosphate materials produced have the properties of low-temperature curing,light weight and dense microstructure.The modified La-Al phosphate materials with different microstructures can be obtained by adding ZrB₂ and Al N particle modifications.The unsaturated and undirected cross-linked condensation of La³⁺,[（H₂PO₄）₂Al（HPO₄）]-plasma in La-Al phosphate during the low-temperature curing reaction promotes the formation of network macromolecules for curing.（2）La-Al-based phosphate and 3ZrB₂-Al N/La-Al-based phosphate materials are bonded to the carbon base in two main ways,including embedded and chemical bonding,and the phosphate materials and carbon base materials are closely connected together through chemical bonds such as C-O-H,C-O-C and C-P,which have good compatibility.（3）The compressive strength of La-Al phosphate can be increased from 16.15 MPa before the non-addition of ZrB₂ and Al N particles to 39.77MPa for 3ZrB₂-Al N/La-Al phosphate by introducing appropriate amounts of ZrB₂-Al N particulate matter into the La-Al phosphate material.（4）Both La-Al phosphates and ZrB₂-Al N/La-Al phosphates have low thermal conductivity（<1.2 W/m K）,where the La-Al phosphate materials have better thermal insulation properties during the flame ablation process of up to 120 s.The backside temperature is always maintained below150°C.In addition La-Al-based phosphate and its composites,after heat treatment,the thermal weight loss of the materials decreased from 18%before heat treatment to 2%-5%after heat treatment.（5）Oxyacetylene ablation was used to study the temperature resistance and oxidation resistance of La-Al phosphate and ZrB₂-Al N/La-Al phosphate.Among them,the La-Al phosphate with 40%La has a more compact and flat surface after ablation,and a compact granular layer is formed in the center of ablation,with La PO₄ as the main phase and mixed with a small amount of Al PO₄ phase.The surface of ZrB₂-Al N/La-Al phosphate forms a smooth ablated morphology due to the presence of additional particulate matter,showing a certain"metallic"ductility effect and some ablation pits at the ablation site.