Synthesis And Thermal Insulation Property Study Of Silica Aerogel And Its Inorganic Binding Material Composites

As a kind of nano porous material,silica aerogel has great application prospect in thermal insulation field,but its low strength disadvantage hinders its further application and popularization in thermal insulation field.The development of composite materials based on silica aerogel and inorganic cementing materials can take into account the advantages of both and overcome the defects of both.In this study,pure water was used as the only solvent to prepare MTES based aerogel under ambient pressure drying conditions,and silica aerogel/foamed concrete composite materials were prepared by foaming method and impregnation method respectively.The influence of silica aerogel particle size and content on physicochemical properties and heat insulation performance of composite materials was systematically discussed.This work provides a new idea for the wide application of aerogel in thermal insulation field.The main research contents are as follows:(1)Under ambient pressure drying,MTES based aerogel was synthesized with pure water as the only solvent.It found that the precursor concentration had no effect on chemical composition.At a lower precursor concentration,the silica skeleton of aerogel will be denser and finer,vice versa.The lowest density(0.057g/cm~3),the highest porosity(97.5%)and the lowest thermal conductivity(29.4 m W/m/K)were obtained when the precursor concentration is 14.4 vol%.In addition,aerogel with dense and slender silica skeleton has relatively greater compressive strength and Young’s modulus.(2)Aerogel/concrete composites were prepared by foaming method,and the effects of particle size and content of aerogel on physicochemical properties of composites were studied.The density(0.24-0.42 g/cm~3),compressive strength(0.3-1.2 MPa)and thermal conductivity(58-82m W/m/K)of the composites increased with the decrease of aerogels particle size,and decreased first and then increased with the increase of aerogels content.The hydrophobicity of materials is mainly determined by the distribution of aerogel particles.The applicability of a Maxwell modified model was verified based on the content of each component of the composite.(3)MTES based aerogel/foamed concrete composites were prepared by impregnation method,and the effects of different water-cement ratios on physicochemical properties and heat insulation performance were studied emphatically.It is found that porosity is positively correlated with water-cement ratio,density is negatively correlated with water-cement ratio,and compressive strength is positively correlated with density.The composite with low thermal conductivity(38.9 m W/m/K),hydrophobic and certain strength(0.23 MPa)was prepared.In addition,when the porous structure of foamed concrete matrix evolves into a relatively regular shape,the thermal conductivity of the material is in good agreement with the predicted value of Levy model.