| With the development of aeronautic industry and the gradual increasing attention to energy conservation,the high temperature thermal insulation materials attracted broad attention of the researchers.The temperature resistance,compressive resistance,elasticity and the performance of thermal insulation materialg are associated with the safety coefficient and economic benefits of the aircraft.The mul ite fiber has good heat resistance,and fiber fabric also have good elasticity characteristics.In the first stage of this experiment,the mul ite fiber is designed to be the matrix,using silica sol as binder,perpare the mul ite-based elastic insulating material whose subject is formed with mul ite fiber and SiO2 by immersion,filtration,drying and heat treatment.The influence of acidic or alkaline,concentration of silica sol and heat treatment temperature on the microstructure,mechanical properties and thermal properties of the material were studied.In the second stage of this experiment,ceramic coating were coated on the surface of the above material.The best ratio of coating were explored by analyzing the effect of binder,boron oxide and boric acid on the fracture resistance and impact performance of the coating.Conclusions were the folowings:1.The sample prepared with alkaline silica sol has higher heat resistance,the compressive strength reached the maximum 0.948 MPa after heating at 1300 ?.And the heat resistance of acidic silica sol is worse,the compressive strength of the sample reached the maximum 0.835 MPa after heat treatment at 1200?.With the increase of heat treatment temperature,we could find that the structure of material was destroyed.2.The density of material was influenced by the acidic or alkaline and the concentration of silica sol.The density of material prepare with acidic silica sol was lower than that with alkaline silica sol.And the densities of all the material increased with the increasing of the concentration of silica sol.3.With the increasing of sintering temperature from 1100 to 1400 ?,the coefficient of thermal conductivity of alkaline sample raised from 0.065 W/(m·K)to 0.104W/(m·K).The rebound rate at 4% compression of alkaline silica sol decreased from 90.4 to 77.6%.The rebound rate at 4% compression of acidic one decreased from 82.5 to 55.8%.4.With the concentration of silica sol increaseing from 10 to 30%,the compressive strength of acidic and alkaline samples both increased,the thermal conductivity and the rebound rate were also improved and reached and reach the maximum at the point of maximum concentration.5.The precipitation and stratification of the coating slurry could be prevented by adding PVP or PVA.The coating without binder would produce crack in the process of drying and sintering.When the 7wt% PVP solution was used as a dispersion medium,the coating exhibited good performance.6.With the increasing of the content of boric acid and boron oxide,the flexural strength of the sample increased.When the content of the boric acid is 16.8wt%,the flexural strength of the sample reached the maximum 3.174 MPa which was lower than the flexural strenth of the sample with the corresponding percentage content of boron oxide whose flexural strength was 3.595 MPa.With the increasing of the content of boric acid and boron oxide,the impact resistance capacity of the sample increased first and then decrease.When the content of the boric acid was 11.2wt%,that of the sample reached the maximum 1.309 J/cm2 which was higher than the impact toughness of the sample with the corresponding percentage content of boron oxide whose impact toughness was 1.083 J/cm2. |
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