Study On Preparation Of SiO₂ Aerogels Composite Thermal Insulation Material Supported On Expanded

SiO₂ aerogel is a lightweight superabsorbent material with a three-dimensional mesh nanopore structure.Its Density is 0.003⁰.03 g / cm3,thermal conductivity as low as 0.01W/m·K,porosity up to 90%,surface area is 700¹200 m2/g,pore size is range in 5¹00nm.As the preparation of SiO2 aerogel drying method is generally a high cost of supercritical drying method,and atmospheric drying prepared by the preparation of the SiO₂ airgel is difficult to maintain the integrity of the block,plus SiO2 aerogel is not hydrophobic,these factors restrict the application and development of SiO2 aerogels.Expanded perlite is a traditional lightweight low thermal conductivity particles,the thermal conductivity is usually 0.054 W/m·K,it has a strong water absorption and internal macro-disorder channel.In this paper,hydrophobic?TEOS?,methyl triethoxysilane?MTES?and MTES/TEOS were used as the silicon source and anhydrous ethanol?EtOH?as solvent to prepare SiO2 aerogel.The selection of raw material ratio,condensation pH control,gel time,aging,modifier selection and dosage,atmospheric drying method were explored.The volume density,thermal conductivity,hydrophobicity,surface area and pore size distribution of the prepared silica aerogels were tested,and the microscopic morphology of the samples was analyzed.The results show that the viscosity of the silica gel was 0.108 g/cm3,the thermal conductivity was 0.032 W/m·K and the contact angle was 140.0° when the TEOS?EtOH?H₂O = 1?5?14.And the surface area was 727.48 cm2/g and the pore size was 5.0⁹.0 nm.When MTES?EtOH?H₂O = 1?15?10,the volume shrinkage rate was2.1%,the density was 0.088 g/cm3,the thermal conductivity was 0.04 W/m·K,contact angle of 145.5°;MTES ? TEOS ? EtOH ? H2 O = 0.2 ? 0.8 ? 7 ? 15,pH value of polycondensation reaction was adjusted to 7.5,V?Block??V?TMCS??V?N-hexane??V?EtOH?= 2?1?2?0.4,the lowest thermal conductivity was 0.031 W/m·K,the contact angle was 153.5°,the lowest thermal conductivity was 0.08 g/cm3,the lowest thermal conductivity was 0.031 W/m·K,the surface area is 877.21 cm2/g,the pore volume is 3.68cc/g,the pore size is 5¹2 nm;On the basis of controlling the gel time,it was vacuum-adsorbed into the internal pore structure of the expanded perlite in the sol-gel phase and the gel was aged,hydrophobically modified and dried at atmospheric to prepare the expanded perlite/SiO2 aerogels Composite materials,the purpose was to SiO2 aerogels super insulation material to enhance the thermal insulation properties of expanded perlite.The microstructures of the composites were characterized and their properties such as apparent density,thermal conductivity,specific surface area and pore size distribution were tested.The vacuum adsorption vacuum degree was 0.06 MPa,the change of adsorption was 27%,the bulk density of the expanded perlite/SiO2 aerogel?TEOS as the silicon source?composites was 99.54 g/cm3,the surface area was 83.13 m2/g,and the thermal conductivity was0.038 W/m·K and reduced by 24%.The density of the expanded perlite/SiO2 aerogels?mixed silicon source?composites was 96.22 g/cm3,the surface area was 112.57 m2/g,and the thermal conductivity was 0.036 W/m·K and reduced by 28%.