Study On Preparation And Properties Of Alumina Hollow Sphere Thermal Insulation Ceramics Prepared By In-situ Curing With Silicone Rubber

Hypersonic vehicles have special advantages over traditional military weapons and are an important guarantee for national defense security.The high flying speed of a hypersonic vehicle can cause serious aerodynamic heating,and the high temperature is a great challenge to the internal components of a hypersonic vehicle.The development of heat-insulating materials with high temperature resistance,thermal matching,low density and low thermal conductivity is of great strategic importance.Traditional materials can no longer meet the requirements of thermal protection materials for aircraft surface geometry and dimensional changes.It is urgent to develop a ceramic insulation material that can withstand higher temperatures,complex shapes,and full temperature service.In this study,the precursor conversion ceramics process was applied to the preparation of alumina hollow sphere ceramics,using cheap silicon rubber as a binder precursor and glass beads,silicon powder,aluminum powder,boron carbide,and lowmelting glass as additives.After being mixed with alumina hollow spheres,injection molding and sintering in an oxidizing atmosphere,alumina hollow sphere ceramics with amorphous silica as a binder are prepared.The method can prepare a ceramic body with complicated shapes at a lower cost,and the prepared body has very good elasticity and workability,and can be used for preparing a heat insulation member with complicated shape and size requirements.The research content of this paper is mainly divided into the following aspects:(1)Study on the process and performance of heat sealing ceramic materials prepared by conversion of silica rubber precursor bonding alumina hollow spheres.In this study,alumina hollow spheres were used as matrix,condensed dimethyl silicone rubber was used as binder,and dimethyl silicone oil with different viscosity was used as diluent to prepare a heat seal with high elasticity by casting method.It mainly studies the influence of the ratio of raw materials of silica gel,silicon oil and alumina hollow spheres on the forming performance,the machinability of the green body,the decomposition and conversion mechanism of the silicone rubber,and the normal and high temperature mechanical properties of the sample.(2)Enhancement of mid-temperature section heat-sealing ceramic material made of silicone rubber bonded alumina hollow spheres.In this study,in order to solve the problem of material failure during the decomposition of silica gel(about 350 °C)to the sintering of the body(above 1300 °C),low-melting glass,boron carbide,aluminum powder,and silicon powder were selected as the reinforcing fillers.Then the heat seal material with certain mechanical properties in the whole temperature section was prepared.The effects of various additives on the morphology and mechanical properties of the samples,and the mechanism of the reinforcement of the samples are studied.