Preparation Of TiO₂Doped Silicon Aerogels And Study On The High Temperature Thermal Insulation Properties

The thermal conductivity of super insulating material silica aerogels is only0.02W/（m·K）, which is lower than still air’s thermal conductivity at room temperature. But whenthe temperature rises over500℃and infrared radiation goes higher, The radiation thermalconductivity will increase dramaticly as the infrared can go through the pure silica aerogels,which Limits its application in high temperature environment. In order to reduce its thermalconductivity at high temperature, This paper doped the pure silica aerogels with opacifierwhich has a reflection and infrared absorption effect, and we studied the doped technics.This paper select TiO₂powder （titanium dioxide） as opacifier which has a high reflectionand infrared absorption effect. In the course of1%-15%（by mass）TiO₂-doped silica aerogels,water glass as silica source, diluted with cation exchange resin exchange processing,formamide as a chemical desiccant, adjust pH value by1mol/L of ammonia, aging after thegel finishes by TEOS ethanol mixture, and classification drying after solvent exchange withN-hexane. The thesis studied the doped technics of TiO₂opacifier，and analysed the typeand the content of opacifier, alkaline catalyst, high temperature environment which influenceon the microstructure and high temperature insulation properties of TiO₂-doped silica aerogels.The organization performance, surface morphology, pore structure and high-temperaturethermal conductivity of TiO₂-doped silica aerogels were analysed and evaluated with SEM,XRD, N2adsorption-desorption method，as well as fourier transform infrared spectroscopyand thermal conductivity instrument.The results showed that TiO₂-doped silica aerogels belong to nano-porousthree-dimensional network materials, and the best effect to put the titanium dioxide in thesystem is about30min（gel2h） after the exchange processing,700r/min stirring ultrasound30min,and that TiO₂particles are embedded in the silica aerogels system, uniform size andwell dispersed. The pore distribution was gradually widening with the doping increasing, thesample’s specific surface area was more than650cm²/g, and the average pore diameter wasabout40nm. The sample’s infrared transmittance decreased with the doping increasing. The 10%doped of TiO₂effectively reduce the material’s2⁸μm infrared transmittance by50%.The doped of TiO₂distinctly improve the role of the infrared extinction of the materials.Doped silica aerogels showed amorphous state after the300-1000℃temperature heattreatment, the opacifier and SiO₂colloidal particles was not chemical bonding, and theorganization performance was stable, The infrared transmittance of doped silica aerogels has alittle down and the wave move to the left after the heat treatment. The thermal conductivitymeasurements show that the10%TiO₂-doped silica aerogels thermal conductivity is only0.0372W/（m K） and0.0495W/（m K） at500°C and800°C, Equivalent thermalradiation calculations showed that the doped of TiO₂greatly increased the high temperaturethermal insulation properties of silica aerogels.