Study On Preparation And Properties Of Low Thermal Conductivity Insulation Composite

Silicate Aluminum fiber has the advantages of high strength and high modulus, furthermore it can resist high temperature and heat insulation, which is widely used in the field of heat-insulating in heat equipment and high-speed aircraft. Owing to great improvement in spaceflight and aviation technology, the traditional thermal insulation material can not meet the current demand. Aerogel with advantages of low density, porous and specific surface area have great value of research, but the disadvantage of low intensity is the major limitation to application. To meet the strict heat insulation requirement, In this paper, the preparing technique, heat insulation performance and practical application of Aluminum-silicon fiber reinforced aerogel composite was preliminarily studied through two different method. Major reseach content of this project include two parts:The first part:the aluminum silicon fiber reinforced aerogel composites were manufactured by mechanical mixing, the aluminum fiber was used as reinforcement, aluminasol was used as adhesive, aerogel was used as filler. The main findings were as follows:(1) The mixing of SiO2aerogel could decrease the thermal conductivity of composites, the thermal conductivity decrease with the increase of proportion and the optimum ratio is 75%. (2) The heat resistance of composites were connected to the optimum ratio of aerogel and aluminum silicon fiber, the optimum ratio was firber(25%), aerogel(65%), aluminasol(10%), In the meanwhile, the thermal conductivity of composite was 0.044 W/(m·K) at 500℃, the bending strength was 0.69MP and the tensile strength was 0.34MPa.The other part:the heat-insulating composites with low thermal-conductive prepared via Sol-Gel process, the silica solution was composited on the surface of fiber by using a series of reduction, silicon dioxide aerogel was formed after drying treatment. The main findings were as follows:(1) Under the optimum synthesis condition with temperature was 95℃, silica solution gelation rapidly under the hydrolyzing of urea, then became aerogel, which has a average diameter of 20-30nm, and was evenly distributed. (2) The silica solution content determine the thermal conductivity and mechanical property, the coposites had good performance when the volume ratio of the silica solution and anhydrous alcohol wasl:1, the thermal conductivity of composite was 0.072W/(m·K) at 500℃, the bending strength was 2.16MPa and the tensile strength was 2.13MPa.On the basis of research, we carried out the Research on preparation of thermally isolating layer in a steel cylinder using the first method. The cylindric isolating layer had high strengths and was very close with the steel cylinder, and the thickness of layer was controllable. The heat insulation effect of the layer raised 20～30% as using asbestos sheet with identical thickness.