Preparation And Properties Analysis Of Silicon Aerogel From Diatomite

SiO₂ aerogel is a kind of nano-structured material with high specific surface area,high porosity,low density,low dielectric constant and excellent thermal insulation properties,which is widely used in various fields such as catalysis,adsorption,insulation and drug delivery.However,the traditional preparation method of aerogel has high preparation requirements,complex process,high preparation cost and long time consumption,and it is difficult to realize the real industrialization of the preparation of aerogel.In this paper,the cheap diatomite is mainly used as the raw material to prepare sodium silicate,and the sodium silicate is continued to be used as the silicon source to prepare Si O₂ aerogel by drying under atmospheric pressure.Rapid and low-cost preparation of aerogel under atmospheric pressure has been achieved,providing a new idea of simple,rapid,low consumption and green environmental protection for the industrial production of Si O₂ aerogel.The experimental research results are as follows:（1）In the alkali melting experiment using diatomite as raw material,the key factors that have a great influence on the experimental results are analyzed through the results of single factor experiment data:the addition amount of alkali Na OH,reaction temperature,liquid-solid ratio.Then,the response optimization method was used to comprehensively analyze the combined effects of all factors,and the variance fitting analysis of the experimental data was carried out by the Design Expert V8.0.6 software to obtain the optimal preparation process:The water bath was heated at 90℃,40g diatomite was added,Na OH12.5g of alkali was added,the liquid-solid ratio was 2.5,and the sodium silicate with modulus M=3.35 and dissolution rate R=83.38%was obtained after 4h reaction.Compared with the single factor experiment,the response optimization method can make a comprehensive analysis of multiple influencing factors,and the performance of the final prepared sample is better than that of the single factor analysis,with the modulus increased from 3.05 to 3.35.（2）The final modulus and silicon content were used to determine the performance of sodium silicate prepared by alkali melting process.The subsequent preparation of aerogel was performed with different modules and different silicon content as variables,and it was concluded that the aerogel prepared with the best modulus M=3.05 and silicon content 6%had the best performance.In addition,one-step method was adopted in the preparation process to replace and modify the solvent at the same time,reducing the use of solvent and saving the preparation time.The whole process of preparation was carried out under atmospheric pressure,and the operation was more simple,creating conditions for the subsequent promotion of low-cost large-scale rapid preparation of high-performance aerogel.Since the hydrophobic modifier HMDZ needs to be catalyzed under acidic conditions to play a modified role,the effects of different p H values of gel,different acidic catalysts and the amount of modifier on the performance of aerogel were analyzed and studied.The optimal acid catalyst was HNO₃.Based on the analysis of the aerogel properties of alkaline gel,the gel was performed at p H=5,which not only increased the specific surface area of aerogel from 579m²/g to 704m²/g,but also enhanced the effect of hydrophobic modification while reducing the amount of hydrophobic modifier,increasing the hydrophobic Angle from 151°to 158°,and reducing the amount of modifier from 12ml to 10ml.It can not only improve the preparation performance of aerogel,but also reduce the amount of expensive hydrophobic modifier and reduce the preparation cost.