Study On Preparation Process Of Silica Aerogels Doped TiO₂and Aluminum Silicate Fiber Felt

With the development of industrial technology, and in some special field of thetraditional thermal insulation materials have been unable to meet the high requirements ofhigh temperature thermal insulation performance and new energy conservation and emissionsreduction requirements. SiO₂aerogel is a kind of efficient thermal insulation material withnano porous network structure, density of0.003⁰.5g/cm3, coefficient of thermalconductivity is less than0.02W/（m K）, porosity as high as80%⁹9%, is a very goodthermal insulation performance at room temperature. But the pure silica aerogel for2⁸microns of infrared radiation has a penetrability, and its mechanical properties is poor, socannot be used alone as the high temperature heat insulation material. By doping TiO₂andaluminum silicate fiber, effectively reduces the infrared transmittance, and improve themechanical strength, high temperature is expected to become a highly efficient light insulationmaterials.This paper uses the cheap sodium silicate as silicon source, combination of SiO₂aerogelpreparation of sol gel process, by doping TiO₂effectively reduces the infrared transmittance.Concrete study of TiO₂content and add process, pH value for the whole preparation process,the influence of silane coupling agent on the improvement of TiO₂disperse process, theresults showed that TiO₂after ultrasonic dispersion is evenly dispersed to sol solution,dispersing time and the power of control on the pore structure of SiO₂aerogel and the TiO₂dispersion degree is very important to determine the200KHz separate1min is the bestprocess; TiO₂doped on the density of SiO₂aerogel, dosage is too small and not block infraredradiation effects, according to the infrared transmittance curve found that content was5%and5%is very close, but the density is much smaller, so the final content5%; pH can control thesol of hydrolysis and polycondensation rate, for the formation of the pore structure isextremely important, experimental research on the effect of TiO₂is introduced to the pH value,found TiO₂sol to pH had little impact; Silane coupling agent as both contain hydrophobicgroups, and containing a hydrophilic group, it can have the effect of organic material and inorganic material connection, by a silane coupling agent surface modification of TiO₂by line,can improve the dispersion of TiO₂, and reduce the reunion, and silane coupling agent andinduction of SiO₂nanoparticles directional long effect, achieve control of the role of the porestructure, through the experiment discovered when the silane coupling agent content is70w%when the specific surface area is497.23m2/g, cumulative pore volume of1.8993ml/g, theaverage pore diameter of37.51nm, cumulative pore area of399.62m2/g, the pore structure ofmesoporous.Because of aluminum silicate fiber slightly alkaline, introducing will rise after sol sol ofpH value, so before the introduction of the sol solution pH values should keep a low value,before the introduction of aluminum silicate fiber sol according to the experiment of the pHvalue should be around4.5advisable; Found in the experiment, the fiber mat thickness on theinfluence of the preparation process is larger, and the thickness of the fiber mat affect aging,exchange, modify etc, to control the thickness of the blanket can achieve the purpose ofcontrol the follow-up process, through the fiber mat thickness experiment it can be seen thatwith the increase of thickness of the tendency of increase with the density occurs, and isaccompanied by the emergence of the yellow block, when thickness more than1cm densitybegan to rise sharply, the final choice1cm for the aluminum silicate fiber mat thickness isone of the biggest online; Through adjustment of aging process, to master the effect of agingtime and aging time is insufficient will cause the collapse of hole structure, is not conduciveto form low density aerogel, extend the experiment cycle longer aging time and waste ofresources, should use ethyl orthosilicate aging2d, in anhydrous ethanol,2d can meet therequirements of the aging, aging is density smaller aluminum silicate fiber composite aerogelblanket; After modification process still remain in the pore structure of aerogels have somewater and HCl, and through further exchange can ensure that residual water and HCl wasremoved, is advantageous to the drying process, the experiment showed that n-hexane andanhydrous ethanol by9:1cooperate to exchange the best effect, the density of aluminum silicate fiber composite aerogel blanket is0.1627g/cm3, coefficient of thermal conductivity is0.02818w/（m K）.