Study On Hydrophobic Modification Of SiO₂ Thermal Insulation Material Based On Carbon Layer Surface Deposition

As a high-performance thermal insulation material,SiO₂ aerogel can be applied in many fields such as construction,furnaces,pipes,aerospace and many other fields.The existing hydrophobic SiO₂ aerogel mainly replaces the surface functional group with a hydrophobic functional group by a chemical modification method to achieve a hydrophobic effect,but the surface-linked hydrophobic functional group will be broken under the action of external high temperature,and the SiO₂ aerogel loses hydrophobic properties and is severe.Affect the thermal insulation effect.Therefore,it is important to study the hydrophobic modification method of SiO₂ aerogel heat resistance.In this paper,the heat resistance of SiO₂ aerogel particles modified by traditional hydrophobic method was studied.Then,the hydrophobic carbon layer was deposited on the surface of SiO₂ aerogel particles by chemical vapor deposition.Different preparation conditions were studied for SiO₂ aerogel.The influence of the hydrophobic modification effect of the particles;finally,the boric acid impregnation method improves the thermal inertia of the hydrophobic carbon layer.The traditional method modified SiO₂ aerogel was prepared by sol-gel method and trimethylchlorosilane modifier.The traditional method modified SiO₂ aerogel was studied by Fourier transform infrared spectroscopy and hydrophobic angle measuring instrument.The number of hydrophobic functional groups on the surface and the variation of hydrophobic properties with temperature and heating time.The relationship between the hydrophobic angle and the number of hydrophobic functional groups is clarified.It is found that when the temperature is higher than 200°C,the hydrophobic functional group and the hydrophobic angle of the surface of the modified SiO₂ aerogel begin to decrease.When the temperature reaches 600°C,the hydrophobic functional group disappears completely,and the hydrophobic SiO₂ aerogel completely loses hydrophobicity.The carbon layer was successfully loaded on the surface of the SiO₂ aerogel by a self-built chemical vapor deposition reactor.Using the control variable method,the effects of reaction temperature change on the surface-loaded carbon layer of SiO₂ aerogel on the surface of SiO₂ aerogel were analyzed by the reaction temperature,catalyst concentration,growth time,injection rate and injection volume.Optimal conditions.The study found that the carbon layer supported on the surface of SiO₂ aerogel is relatively good at a reaction temperature of750°C,a catalyst concentration of 20 mg·ml^-1,a growth time of 60 min,and an injection rate of 10 ml·h^-1.The heat resistance of the surface-loaded carbon layer is improved by a boric acid impregnation method.The effects of evaporation state,amount of boric acid,reaction temperature,annealing time and surface carbon layer on the heat resistance of surface carbon layer were analyzed by controlled variable method.The heat resistance of surface layer of SiO₂ aerogel was improved by impregnation method.The best conditions.The heat resistance of the carbon layer on the surface of the modified SiO₂ aerogel was analyzed by thermogravimetric analyzer.The results show that the surface carbon layer has good heat resistance in the natural evaporation state,the ratio of boric acid to sample is 1:1,the reaction temperature is 700°C,and the annealing time is 3 h,and the carbon layer before modification is improved 50°.