Study On Preparation And Properties Of Porous YSZ Materials For Thermal Insulation

In this thesis, lightweight zirconia porous insulation materials were innovatively prepared by using silica aerogel as pore forming agent. Systematic investigations were made on the influence of silica aerogel addition amount, glycerin consumption, p H value of the slurry and heat treatment temperature on the thermal conductivity, compressive strength and density of insulation materials by means of XRD, FTIR, FE-SEM, TEM, universal testing machine and thermal conductivity instrument. In order to further improve the comprehensive performance of insulation material, hollow Zr O2 spheres were successful fabricated by carbon template method. Study was made on the effect of carbon template modification time on the preparation of hollow zirconia spheres. It is found that:(1) When adding 30wt% Si O2 aerogels, slurry viscosity is appropriate, the pore size of sample is small and uniform, the thermal conductivity reaches the minimum value, the thermal insulation properties is the best; however excess or less Si O2 aerogel content may lead to an increase or decrease viscosity of the slurry and uneven distribution of pore.(2) An appropriate amount of glycerol can effectively prevent agglomeration of nano powder in slurry during the drying process and form uniform pores, which can improve the thermal insulation performance of samples. Too little or too much glycerol is not conducive to homogeneous pores distributed that will reduce the thermal insulation properties of the samples.(3) With p H changes from 4 to12, the thermal conductivity of insulation material shows "W" type change. The absolute value of the slurry zeta potentials reaches the maximum when p H is 10. It is benefit for the dispersion of YSZ powder and Si O2 aerogels. And it is also conducive to the homogeneous pore distribution, which can decrease the thermal conductivity.(4) When the heat treatment temperature is too low(less than or equal to 400 ?C), the residual C will greatly affect the insulating performace of the material. While heat treatment temperature is more than 600 ?C, the formation of submicron or even micron pores replace the uniform nano pores, resulting in the increase of thermal conductivity.(5) YSZ insulation materials were prepared by the application of optimization of process parameters(Si O2 aerogel content is 30 wt%, glycerol content is 50 wt%, the p H value of slurry is 10, and the heat treatment temperature is 600 ?C). The comprehensive performance of material is better than the the results of relevant literature. The indicators are: the thermal conductivity of the sample is 0.043 W/(m?k), compressive strength is 35.6 MPa, density is 1.51 g/cm3, and porosity is 60.9%.(6) When zirconia hollow sphere is prepared via carbon template method, the submicron hollow spheres are composed of tetragonal Zr O2 phase. Base-treatment can effectively increase the number of functional groups on the surface of carbon templates and modify the charge state and hydrophilicity of the carbon templates, so that the shell thickness of the core-shell structure can be controlled; and with increasing modification time of carbon templates from 0 h to 6 h, the wall thickness of the hollow spheres gradually increases, while the specific surface area decreases from 104.7 m2?g-1 to 47.9 m2?g-1.