Research On Properties Of SiO₂ Nano-micoporous Complex Thermal Insulating Material

Fumed silica powder has many merits,like light weight,large specific surface area and great thermal stability.Using it as matrix,SiO₂ nano-microporous thermal insulating material is processed by adding fibers,opacifiers and inhibition of sintering to have excellent thermal insulation so that it has become a research hotspot presently in the field of high-performance thermal insulating material.The research about adding the BaCO₃ powder,the Fe₃O₄ powder and the fumed Al₂O₃ powder respectively,testing their thermal conductivity,volume shrinkage rates and microstructures during the different temperatures,pointed that the fumed Al₂O₃ powder is the best inhibition of sintering.Then making comparison analysis about the thermal conductivity,volume shrinkage rates and microstructure of the sample of fumed silica which was proportionally replaced by zirconium powder,silica fume,coal ash,and micro-alumina,it was proved that the coal ash and the micro-alumina are better ones.And the best mass percent is 30%.Last,the function of coal ash and the micro-alumina influenced by fumed Al₂O₃ has been researched.Through researching,the obtained results as follows:?1?SiO₂ nanoporous therrmal insulating material added inhibition of sintering was compared with A₀ was not added it generally increased at every temperature spot.When adding the fumed Al₂O₃ as inhibition of sintering,the volume shrinkage rate decreased obviously.which was far lower than the volume shrinkage rates of blank sample A and the samples added other inhibitions of sintering.?2?Making comparison analysis of the thermal conductivity,volume shrinkage rate and microstructure of four kinds of larger particles about zirconium powder,silica fume,coal ash,and micro-alumina which replaced the certain proportion of fumed silica powder was aim to find the best one and the best mass percent of substitute.The addition of zirconium powder promoted the viscous sintering of fumed silica.By measuring the volume shrinkage rate of samples at the different temperature spots,which far lower than the blank sample A when the mass percent of coal ash and micro-alumina was 30%.It was concluded that the best substitute of fumed silica powder is coal ash and micro-alumina,and the best mass percents both are 30%.?3?Researching the function of two kinds of large particles influenced by fumed Al₂O₃,the results indicated that the thermal conductivity of the sample added fumed Al₂O₃ at different temperatures were higher than blank sample A.Due to the light change which remained the low level,it impacted little on the heat insulation performance of materials,it was found that the fumed Al₂O₃ didn't inhibit the sample with 30%mass percent of coal ash from sintering.The general performance was that the volume shrinkage rate was not decrease while fumed Al₂O₃ inhibited the sample with 30%mass percent of micro-alumina from sintering.All the volume shrinkage rates decreased as the amount of fumed Al₂O₃ increased.But the particles of the one with 30%mass percent of micro-alumina added fumed Al₂O₃ were useful and sintered lightly while a bit of amorphous fumed silica particles still existed internally.