Studies On Fiber Reinforced Silica Aerogel Super Thermal Insulation Materials Prepared By Ambient Drying Process

Aerogels are light nanometer solid materials which consist of ultra-fine particles conglomerating nano-porous three-dimensional network structure and have continuous random network structure filling with gaseous dispersive medium. Super thermal insulation materials refer to the materials which thermal conductivity is lower than the thermal conductivity of "no-air convection" under the scheduled using conditions.Silica aerogels are in full compliance with the basic characteristics of super-insulation materials on the structure.Silica aerogels can essentially cut off the heat conduction of gas molecules because its porous size is smaller than the average free path of air molecules,and its enough small pouous can control the convection heat conduction of gas molecules.When the solid volume of silica aerogel is smaller than 5%,it can reduce the solid-state thermal conductivity. Aerogel adulterated infrared screenings can effectively reduce the infrared radiation heat conduction.Therefore, silica aerogel nano-insulating materials have excellent insulation properties in the range of using temperature.In this thesis,silica aerogels were prepared by sol-gel method with ambient drying technique.The aerogel were made from industrial water glass and fiber brucite.The basic parpameters of this material: density of 0.23 g/cm³, shrinkage rate of 4.3%, porosity of 88%,grain diameter of 50 to80 nm, most of aperture lower than100 nm, SiO₂ content of 90.06%, the effective thermal conductivity of 0.015to 0.025W / m·K, compressive strength of 5.4 MPa, bending strength of 0.5 MPa.This thesis study the effects of the sol-gel progress on the aerogel's gel time, density,volume shrinkage rate,porosity,strength,thermal conductivity,and so on.The results show that the best technology ratio is water glass/ water/ ethanol/ FB/FSN up to 1/0.4/0.04/0.04/0.07,the best preparation for the temperature is from 20 to 25℃.This thesis study the effects of the heat treatment on the aerogel's density and strength.The results show that, heat treatment process is almost helpless to improve the performance of silica aerogel.