A method for synthesizing and preparing a doped sioc microsphere reinforced aerogel composite

Abstract

The application relates to a synthesis and preparation method of a doped SiOC microsphere reinforced aerogel composite material, which comprises the following steps: SiOC microsphere preparation and SiOC microsphere and aerogel compounding. Tetraethyl orthosilicate, phenyltrimethoxysilane and dimethyldimethoxysilane are used as precursors, hydrochloric acid and ammonia are used as catalysts for polymerization, and high-temperature calcination is carried out in a muffle furnace to obtain SiOC microspheres; methyltrimethoxysilane, dimethyldimethoxysilane, hydrochloric acid, CTAB and urea are added to the SiOC microsphere system under ultrasonic dispersion, and stirring is carried out to obtain a wet gel; a normal-pressure drying process is used for drying, and finally, the SiOC microsphere doped aerogel composite material is obtained. The raw materials such as tetraethyl orthosilicate and phenyltrimethoxysilane used in the application have simple sources, low prices and are green and environment-friendly; the SiOC microspheres have good compatibility with the aerogel matrix, can effectively avoid defects generated in the aerogel due to the compounding of the SiOC microspheres and the aerogel, and can effectively enhance the mechanical properties. The normal-pressure drying operation is simple and safe, and the obtained aerogel composite material has low density, good hydrophobicity and low thermal conductivity.

Description

[0001] The present application relates to the field of aerogel composite thermal insulation, especially using SiOC microspheres to dope aerogel matrix to improve the performance of aerogel materials. BACKGROUND

[0002] Aerogel is an excellent thermal insulation material, which has the advantages of low density, high porosity and low thermal conductivity. It is currently used in pipeline insulation, petrochemical industry, aerospace and other fields. According to the type of different precursors, aerogel is divided into silica aerogel, carbon aerogel and so on. However, pure aerogel material is easy to break and has poor mechanical properties, and is generally in powder form. Moreover, the current supercritical drying technology for drying wet gel has high risk and high cost of purchasing equipment, which seriously limits the widespread use of aerogel. When used at high temperature, aerogel will shrink in volume, collapse in pore, and ablate, etc. Without solving the above problems, aerogel is difficult to use at high temperature, which limits the temperature range of aerogel.

[0003] In view of the above problems, it is very important to develop an aerogel material with excellent mechanical properties, low preparation process cost and complete structure at high temperature. At present, most researchers choose to prepare aerogel composite material by compounding aerogel with other substances, but the compatibility of the doped substance with aerogel is poor, which leads to a large number of defects in the material, and the existence of defects seriously affects the performance of aerogel composite material. Therefore, there is an increasing demand for aerogel composite material with good compatibility between doped substance and aerogel matrix, high hydrophobicity and excellent thermal insulation performance. SUMMARY

[0004] In view of the problems of existing aerogel material such as easy to break, poor mechanical properties and poor ablation resistance, the purpose of the present application is to provide a synthetic preparation method of SiOC microsphere reinforced aerogel composite material, which is simple, green, low in cost, easy to operate and high in safety.

[0005] The synthetic preparation method of SiOC microsphere reinforced aerogel composite material provided by the present application is as follows: first, prepare SiOC microspheres, select tetraethyl orthosilicate, phenyltrimethoxysilane and dimethyldimethoxysilane as precursors, and perform polymerization under the catalysis of acid and ammonia water, centrifuge the solution after polymerization to obtain white substance, and then calcine the white substance in a muffle furnace at high temperature to obtain SiOC microspheres. The SiOC microspheres are uniformly dispersed in deionized water, and methyltrimethoxysilane, dimethyldimethoxysilane, CTAB, urea and hydrochloric acid are added for hydrolysis, and then placed in a specific temperature environment for aging, and then solvent replacement is performed using ethanol and n-hexane, and finally dried by using atmospheric drying technology to obtain SiOC microsphere reinforced aerogel composite material.

[0006] The main preparation steps are as follows:

[0007] Step (1) Stir tetraethyl orthosilicate, phenyltrimethoxysilane, dimethyldimethoxysilane and deionized water system evenly, add hydrochloric acid dropwise to system, stir for several hours, add the solution after stirring to a specific concentration of ammonia solution and stir for several days.

[0008] After stirring in step (2), the solution is centrifuged, and the white substance obtained by centrifugation is dried at a specific temperature. Then, the dried white substance is calcined in a muffle furnace at a temperature of 800-1200℃. After the calcination process is completed, SiOC microspheres are obtained.

[0009] Step (3) The calcined SiOC microspheres were mixed with deionized water at different mass ratios, and methyltrimethoxysilane, dimethyldimethoxysilane, CTAB, urea, and hydrochloric acid were added. The mixture was stirred and hydrolyzed for several hours. After hydrolysis, the solution was transferred to a specific temperature environment for gel aging. The gel was then subjected to solvent replacement with ethanol and n-hexane at a frequency of 8 hours per replacement for several days.

[0010] Step (4) involves drying the replaced wet gel under normal pressure at a temperature of 60℃-80℃ for 4-7 days.

[0011] The present invention has the following advantages:

[0012] (1) The raw materials are low in cost, widely available, and easy to operate, making them green and environmentally friendly;

[0013] (2) The diameter of the prepared SiOC microspheres can be selected according to specific needs. The SiOC microspheres have low aggregation degree, stable microstructure, and large yield. The SiOC microspheres can be well dispersed in the aerogel precursor sol.

[0014] (3) The prepared aerogel composite material has low density, high porosity, and low thermal conductivity. Furthermore, there is no obvious interface between the SiOC microspheres and the aerogel matrix, indicating that the two are compatible and can effectively reduce defects in the internal structure of the material and improve the mechanical properties of the aerogel composite material.

[0015] (4) The aerogel composite material with SiOC microspheres prepared has a small volume shrinkage rate under high temperature environment, and the high temperature ablation resistance of the aerogel composite material is improved. Attached Figure Description

[0016] Figure 1 SEM images of SiOC microspheres

[0017] Figure 2 FTIR curve image of SiOC microspheres

[0018] Figure 3 Picture of SiOC microsphere composite aerogel DETAILED DESCRIPTION

[0019] The application will be further described in the following specific examples, but not limited to the application.

[0020] Example 1:

[0021] (1) In the process of preparing SiOC microspheres, the molar ratio of added phenyltrimethoxysilane, tetraethyl orthosilicate, and dimethyldimethoxysilane can be 5:1:0.1, the volume of added deionized water can be 20 ml, the volume of added hydrochloric acid can be 20 μL, and the stirring time of the system can be 24 hours. The obtained solution is referred to as A; the concentration of the ammonia solution can be 8 wt%, A is added to the 8 wt% ammonia solution and stirred for 5 days, after stirring, centrifugation is performed, the white material obtained by centrifugation is dried at 60°C, and the white material is calcined in a muffle furnace, and the temperature can be 800°C.

[0022] (2) The added SiOC microspheres can be 1% of the mass of added methyltrimethoxysilane and dimethyldimethoxysilane, the SiOC microspheres are uniformly stirred in 50 ml of aqueous solution, methyltrimethoxysilane and dimethyldimethoxysilane are added, the molar ratio between the two can be 3:1, 0.1 g of CTAB and 5 g of urea are added, 30 μL of hydrochloric acid is added and stirred for 24 h, then the solution is placed in an environment of 40°C for gel aging, the aging time is 5 days, and during the aging period, solvent replacement with ethanol and n-hexane is performed at a frequency of every 8 hours / time. The wet gel is taken out and placed in an environment of 60°C for drying for 4 days, and finally a SiOC microsphere doped aerogel composite material is obtained.

[0023] The above has specifically described some embodiments of the application, but the application is not limited to the described embodiments, and those skilled in the art can make equivalent modifications or replacements without departing from the spirit of the application, and these equivalent modifications or replacements are all included in the scope defined by the claims of the present application.

Claims

1. A method for synthesizing and preparing a doped SiOC microsphere reinforced aerogel composite, the main preparation steps being as follows: Step (1) uniformly stirring tetraethyl orthosilicate, phenyltrimethoxysilane, and dimethyldimethoxysilane with a deionized water system, adding hydrochloric acid dropwise to the system, stirring for several hours, and then adding the completed solution to a 4-10 wt% ammonia solution and stirring for several days; Step (2) after the stirring is completed, centrifuging the solution, drying the white material obtained by centrifugation at 50-100℃, and then calcining the dried white material in a muffle furnace at a calcination temperature of 800-1200℃, and obtaining SiOC microspheres after the calcination process is completed; Step (3) mixing the calcined SiOC microspheres with deionized water according to different mass ratios, uniformly ultrasonically dispersing, adding methyltrimethoxysilane, dimethyldimethoxysilane, CTAB, urea, and hydrochloric acid for stirring, hydrolyzing for several hours, and then transferring the solution to a 40-80℃ environment for gel aging, solvent exchanging the gel with ethanol and n-hexane at a replacement frequency of 8 hours / time and for several days; Step (4) performing normal pressure drying on the exchanged wet gel, and the normal pressure drying process time is 4-7 days and the drying temperature is 60-80℃.

2. The method according to claim 1, characterized in that In step (1), the molar ratio of phenyltrimethoxysilane, tetraethyl orthosilicate, and dimethyldimethoxysilane is 5:1:0.1-5:1:2, the added hydrochloric acid is 10-30 μL, the added deionized water volume is 20-40 ml, and the stirring time is 24-48 hours.

3. The method of claim 1, wherein, In step (3), the SiOC microsphere mass is 1%-10% of the mass of methyltrimethoxysilane and dimethyldimethoxysilane, the molar ratio of methyltrimethoxysilane to dimethyldimethoxysilane is 3:1-8:1, the CTAB is 0.1-1 g, the urea is 5-10 g, the hydrochloric acid is 20-50 μL, the stirring time is 24-48 hours, and the aging time is 5-8 days.

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