The Preparation And Properties Of Inorganic Fiber Reinforced Heat Insulating Silica Aerogels Composites

In the field of heat insulating materials,SiO₂ aerogels have attracted much attention because of its high porosity,low density and excellent thermal insulation properties for its nano-porous microstructure.Its density is as low as to 0.003g/cm³and thermal conductivity is as low as 0.013W/m·K at room temperature and atmosphere pressure,amost half of the air.It is a new kind of thermal insulation material with nano-level hole,and there is great potential for application in aerospace and in many civil areas.However,the poor mechanical properties of SiO₂aerogels restrict its application in many industrial fields.Therefore,it is the direction of many scholars to improve their mechanical properties so as to meet the practical application.In this paper,TEOS is used as silicon source precursor and aluminosilicate fiber as reinforcement to strength the skeleton of SiO₂ aerogels,preparing a kind of aluminosilicate fiber/SiO₂ aerogels composites by sol-gel method and atmospheric pressure drying.In order to prepare SiO₂ composites with good mechanical properties and retain the thermal insulation properties of aerogels,this paper starts from two aspects.One is by discussing the process parameters to control the microstructure of the SiO₂ aerogel,mainly the component proportion,solution pH,reaction temperature and time,aging time and dry conditions;Second is to explore the fiber content on the mechanical strength,thermal conductivity of composites and the influence for the important properties such as density,porosity,finding out the optimal fiber content makes SiO₂ aerogel insulation composites mechanical performance was improved and continue to maintain its insulation properties.In the process of preparation of composites,with 7vol%of TMCS as hydrophobic modification,and silane coupling agent KH-550 as the fiber surface pretreatment to improve the wettability between fibers and aerogels.The properties of the composites are characterized by electronic universal testing machine,SEM,automatic contact angel measure device,thermal conductivity meter and BET and so on.The results indicate that the adding of aluminosilicate fiber provide a a variety of new energy consumption mechanisms for the composites under applied force,and mechanical property of the composites are increased efficiently.The surface area and average pore diameters of the composites are 383.5m2/g and 8.4nm respectively,belonging to typical mesopore material.At the same time,the thermal conductivity of composites is as low as 0.02⁰.04W/?m·K?,showing good thermal-insulating performance,which can meet the aerogel mechanics and application requirements of high temperature heat insulation performance.