Structure Design And Process Research Of Aerogel For Infrared Thermal Radiation Control

All objects with temperatures above absolute zero will generate infrared thermal radiation,which does not require a medium for propagation and is spontaneous and universal.The characteristics of thermal radiation have led to the development of detection and imaging technology based on it,corresponding to stealth technology.For detectors in the infrared band,the main purpose of stealth technology is to reduce the infrared radiation characteristics of the target.There are generally two methods,one of which is to reduce the surface temperature of the target.Aerogel is an excellent heat insulation material.As one of the most widely studied aerogel,silica aerogel is the solid material with the lowest thermal conductivity in the world.The aerogel in film form has similar performance characteristics to the aerogel in block form.It can be integrated with the traditional silicon based process,and has great application potential in integration,miniaturization and other fields.However,at present,the conventional preparation method of silica aerogel is sol gel method,which is complex and slow,and aerogel itself is vulnerable to moisture,which limits the wide application of silica aerogel.In this paper,the problems encountered in the simulation and preparation of silica aerogel films were studied in depth.The main work are summarized as follows:1.The heat transfer process of silica aerogel was analyzed,and the mathematical relationship between various material parameters of silica aerogel and its thermal conductivity was studied.Based on the unit structure model of equivalent thermal conductivity,the effects of the macro density,porosity,specific surface area,temperature,solid particle diameter and other factors of silica aerogel on the gas phase thermal conductivity,solid phase thermal conductivity,gas-solid coupling thermal conductivity,radiation thermal conductivity and equivalent thermal conductivity of aerogel were studied.The optimum density range of aerogel with good thermal insulation performance is 21～253 kg/m~3,and the optimum porosity range is 0.96～0.97.2.The effects of various preparation parameters on the characteristics of silica aerogel were studied through a series of experiments.The effect of precursor solution hydrolysis time on its coagulation time was studied,and a good hydrolysis time of 4 hours was obtained based on production practice and preparation results;The effects of different modifiers on the morphology,structure and thermal insulation of silica aerogel were studied.The effect of the viscosity of precursor solution on the thickness,morphology and thermal insulation ability of silica aerogel was studied;The influence of the thickness of silica aerogel film on its thermal insulation performance was studied;The effect of multiple spin coating on the structure and thermal insulation of aerogel films was studied.Matlab algorithm is compiled to study the thermal insulation performance of silica aerogel multilayer films with different film thicknesses under ideal growth conditions.3.In order to enhance the ability of silica aerogel to regulate infrared radiation,titanium dioxide was introduced to prepare silica aerogel,explore the preparation method of composite aerogel,study the role of titanium dioxide in infrared thermal radiation isolation,and finally successfully prepared silica titanium dioxide composite aerogel with good infrared thermal radiation regulation performance.