阅读说明：本技术 耐高温SiC气凝胶的制备方法 (Preparation method of high-temperature-resistant SiC aerogel ) 是由 杨春晖 张磊 李季 于 2019-10-31 设计创作，主要内容包括：耐高温SiC气凝胶的制备方法,它涉及一种气凝胶的制备方法。本发明是为了解决现有制备SiC气凝胶的方法产率低、气凝胶的微观结构易破坏的技术问题。本方法如下：一、制备A液、B液并将A液、B液混合得水解液；二、制备湿凝胶；三、制备气凝胶；四、将气凝胶与镁粉反应后,清洗、干燥,即得SiC气凝胶。本发明采用镁热还原,在惰性气体保护下,将气凝胶前驱体还原为SiC气凝胶。成功避免了R<Sub>1</Sub>SiO<Sub>1.5</Sub>还原过程中SiO气体的产生,最大程度上保持产物形貌完整。经超临界干燥制备了孔道结构均一、形状完整的有机硅气凝胶。本发明属于气凝胶的制备领域。(A preparation method of high temperature resistant SiC aerogel relates to a preparation method of aerogel. The invention aims to solve the technical problems that the existing method for preparing the SiC aerogel is low in yield and the microstructure of the aerogel is easy to damage. The method comprises the following steps: firstly, preparing solution A and solution B, and mixing the solution A and the solution B to obtain hydrolysate; secondly, preparing wet gel; thirdly, preparing aerogel; and fourthly, reacting the aerogel with magnesium powder, cleaning and drying to obtain the SiC aerogel. The invention adopts magnesiothermic reduction to reduce the aerogel precursor into SiC aerogel under the protection of inert gas. Successfully avoid R 1 SiO 1.5 SiO gas is generated in the reduction process, and the shape and the integrity of the product are kept to the maximum extent. And preparing the organic silicon aerogel with uniform pore structure and complete shape by supercritical drying. The invention belongs to the field of aerogel preparation.)

1. The preparation method of the high-temperature resistant SiC aerogel is characterized by comprising the following steps:

weighing 9.9g R₁Si(OR₂)₃7.6g of methyl orthosilicate, and magnetically stirring for 5min to obtain a mixed solution A;

weighing 46g of ethanol, 1.8g of deionized water and 0.25g of span-20, and mixing to obtain a mixed solution B;

thirdly, mixing the mixed solution A and the mixed solution B, and dripping 0.5mL of 1mol/L hydrochloric acid into the mixed solution to perform magnetic stirring for 2 hours at normal temperature to obtain hydrolysate;

fourthly, taking 25mL of hydrolysate, dripping 0.5mL of ammonia water with the concentration of 1mol/L into the hydrolysate, transferring the hydrolysate to a closed container, and placing the hydrolysate in a 50 ℃ oven for 0.5 to 10 hours to obtain wet gel;

fifthly, aging the wet gel for 24h at 50 ℃ by 25mL of methanol, exchanging for 2 times by 25mL of ethanol and exchanging for 3 times by 25mL of n-hexane, and drying in a gradient manner under normal pressure to obtain the phenyl hybridized SiO₂An aerogel;

sixthly, 2.0g of phenyl hybridized SiO₂Placing aerogel and 2.5g of magnesium powder with the particle size of 10-100 mu m in a stainless steel reactor, then placing the stainless steel reactor in a tubular furnace, firstly purging the furnace body for 0.5h by adopting argon with the flow rate of 100mL/min, raising the temperature to 650 ℃ at the speed of 5 ℃/min under the protection of argon, keeping the temperature for 5h, and then naturally cooling to room temperature to obtain a crude product;

and seventhly, cleaning the crude product for 3 hours by respectively adopting hydrofluoric acid with the mass concentration of 5%, hydrochloric acid with the concentration of 6mol/L and hydrochloric acid with the concentration of 1mol/L, washing the crude product with deionized water until the washing liquid is neutral, and then drying the washed product in vacuum at 90 ℃ to obtain the SiC aerogel.

2. The method for preparing the high-temperature resistant SiC aerogel according to claim 1, wherein R in the step one is₁Si(OR₂)₃Wherein R is₂＝CH₃Or CH₂CH₃，R₁Aromatic hydrocarbon or alkane with carbon number more than or equal to 6.

3. The method for preparing the high-temperature resistant SiC aerogel according to claim 1, wherein R in the step one is₁Si(OR₂)₃Is phenyl trimethoxy silane.

4. The preparation method of the high-temperature resistant SiC aerogel is characterized by comprising the following steps:

firstly, weighing 23g to 46g of ethanol, 0.9g to 1.8g of deionized water and 0.125g to 0.25g of span-20, mixing, magnetically stirring for 5min, and then dropwise adding 14.5g to 19.8g R₁Si(OR₂)₃0.5mL of hydrochloric acid with the concentration of 0.1mol/L, and stirring for 2 hours in an oil bath at the temperature of 50-80 ℃ to obtain hydrolysate;

secondly, taking 25mL of hydrolysate, dripping 0.5-1 mL of ammonia water with the concentration of 6-12 mol/L into the hydrolysate, transferring the hydrolysate into a closed container, and placing the container in a 50 ℃ oven for 0.5-10 h to obtain wet gel;

aging the wet gel with 25mL of methanol at 50 ℃ for 24h, exchanging with 25mL of ethanol for 2 times, exchanging with 25mL of n-hexane for 3 times, and then performing supercritical drying at 8MPa and 30 ℃ for 4h to obtain aerogel;

fourthly, placing 1.8g to 2.3g of aerogel and 2.3g to 2.8g of magnesium powder with the grain diameter of 10 to 100 mu m into a stainless steel reactor, then placing the stainless steel reactor into a tubular furnace, firstly purging the furnace body for 0.5h by adopting argon with the flow rate of 100mL/min, heating to 650 ℃ at the speed of 5 ℃/min under the protection of the argon, keeping the temperature for 5h, and then naturally cooling to the room temperature to obtain a crude product;

and fifthly, cleaning the crude product for 3 hours by respectively adopting hydrofluoric acid with the mass concentration of 5%, hydrochloric acid with the concentration of 6mol/L and hydrochloric acid with the concentration of 1mol/L, washing the crude product with deionized water until the washing liquid is neutral, then carrying out vacuum drying at 90 ℃, transferring the washed product into a muffle furnace, and then calcining the dried product for 2 hours at 550 ℃ to obtain the SiC aerogel.

5. The method for preparing the high-temperature SiC aerogel according to claim 4, wherein R is the same as R in the first step₁Si(OR₂)₃Wherein R is₂＝CH₃Or CH₂CH₃，R₁Aromatic hydrocarbon or alkane with carbon number more than or equal to 6.

6. The method for preparing the high-temperature SiC aerogel according to claim 4, wherein R is the same as R in the first step₁Si(OR₂)₃Is phenyl trimethoxy silane or dodecyl trimethoxy silane.

7. The preparation method of the high-temperature resistant SiC aerogel is characterized by comprising the following steps:

firstly, weighing 10.3g of propyl triethoxysilane and 10.4g of ethyl orthosilicate, and magnetically stirring for 5min to obtain a mixed solution A;

weighing 40.8g of ethanol, 4.0g of deionized water and 0.25g of hexadecyl trimethyl ammonium bromide, and mixing to obtain a mixed solution B;

mixing the mixed solution A and the mixed solution B, dripping 1mL of hydrochloric acid with the concentration of 1mol/L, and magnetically stirring for 4 hours at the temperature of 50 ℃ to obtain hydrolysate;

fourthly, taking 25mL of hydrolysate, dripping 0.5mL of ammonia water with the concentration of 1mol/L into the hydrolysate, transferring the hydrolysate to a closed container, and placing the hydrolysate in a 50 ℃ oven for 0.5 to 10 hours to obtain wet gel;

fifthly, aging the wet gel for 24h at 50 ℃ by 25mL of methanol, exchanging for 2 times by 25mL of ethanol and exchanging for 3 times by 25mL of n-hexane, and drying in a gradient manner under normal pressure to obtain the phenyl hybridized SiO₂An aerogel;

sixthly, 2.0g of phenyl hybridized SiO₂Placing aerogel and 2.5g magnesium powder with particle size of 10-100 μm in stainless steel reactor, and addingPlacing a stainless steel reactor in a tubular furnace, firstly purging the furnace body for 0.5h by adopting argon with the flow rate of 100mL/min, then heating to 650 ℃ at the speed of 5 ℃/min under the protection of argon, keeping the temperature for 5h, and then naturally cooling to room temperature to obtain a crude product;

and seventhly, cleaning the crude product for 3 hours by respectively adopting hydrofluoric acid with the mass concentration of 5%, hydrochloric acid with the concentration of 6mol/L and hydrochloric acid with the concentration of 1mol/L, washing the crude product with deionized water until the washing liquid is neutral, and then drying the washed product in vacuum at 90 ℃ to obtain the SiC aerogel.

8. The method for preparing the high-temperature-resistant SiC aerogel according to claim 7, wherein R in the step one is₁Si(OR₂)₃Wherein R is₂＝CH₃Or CH₂CH₃，R₁Aromatic hydrocarbon or alkane with carbon number more than or equal to 6.

9. The method for preparing the high-temperature-resistant SiC aerogel according to claim 7, wherein R in the step one is₁Si(OR₂)₃Is propyltriethoxysilane.

Technical Field

The invention relates to a preparation method of aerogel.

Background

As a high-porosity three-dimensional porous material, the aerogel has the characteristics of low density, high specific surface area, low thermal conductivity, high acoustic resistance and the like, and is widely applied to the fields of heat insulation, sound insulation, adsorption, catalysis and the like. Currently, the aerogel reported is based on Silicon (SiO)₂Aerogel), carbon-based (carbon aerogel, graphene aerogel, cellulose aerogel) and metal oxide-based (Al)₂O₃Aerogel) is predominant. However, such materials can be more or less problematic:

for SiO₂Although the aerogel has a good thermal insulation coefficient, the high-temperature resistance of the aerogel is poor, and the three-dimensional porous framework is easy to collapse and loses the thermal insulation capability after the temperature is higher than 600 ℃; for carbon aerogel, the oxidation resistance is poor, and the carbon aerogel is easily oxidized and decomposed at a high temperature; for Al₂O₃The aerogel has good high temperature resistance, but the acid and alkali resistance of the aerogel is relatively general, and particularly, the aerogel is easy to generate double decomposition reaction under an acidic condition and loses due performance.

Compared with the materials, the SiC has stable chemical property, excellent wear resistance and high temperature resistance, and is an ideal refractory material. Currently, SiC is mainly prepared by a carbothermic reduction reaction of a silicon source and a carbon source at a high temperature, and for example, chinese patent publication No. CN102897764A discloses a preparation method of SiC aerogel, which uses benzenediol-formaldehyde as a carbon source, 3-aminopropyltriethoxysilane-tetraethoxysilane as a mixed silicon source, and obtains a SiC aerogel material by carbothermic reduction at a high temperature of 1500-. However, the method is very easy to generate SiO gas intermediate phase in the synthesis process, the microstructure of the aerogel is damaged, and the yield of the bulk SiC aerogel is greatly reduced. Compared with a carbothermic reduction method, the reaction temperature of the magnesiothermic reduction method is lower (less than 800 ℃), the generation of SiO intermediate phase can be greatly avoided in the synthesis process of the SiC aerogel, so that the appearance integrity of the precursor can be kept, and the method is suitable for preparing various special-shaped parts. For example, journal of atomic energy science and technology discloses a method for preparing SiC aerogel through magnesiothermic reduction, wherein the SiC aerogel can be prepared at 700 ℃ by using resorcinol-formaldehyde as a carbon source and tetraethoxysilane as a silicon source. However, no matter magnesium thermal reduction or carbon thermal reduction, proper silicon source and carbon source need to be selected, the process is complicated, the product components are complex, and the yield is relatively low.

Disclosure of Invention

The invention aims to solve the technical problems that the existing method for preparing SiC aerogel is low in yield and the microstructure of the aerogel is easy to damage, and provides a method for preparing high-temperature resistant SiC aerogel.

The preparation method of the high-temperature resistant SiC aerogel comprises the following steps:

weighing 9.9g R₁Si(OR₂)₃7.6g of methyl orthosilicate, and magnetically stirring for 5min to obtain a mixed solution A;

weighing 46g of ethanol, 1.8g of deionized water and 0.25g of span-20, and mixing to obtain a mixed solution B;

thirdly, mixing the mixed solution A and the mixed solution B, and dripping 0.5mL of 1mol/L hydrochloric acid into the mixed solution to perform magnetic stirring for 2 hours at normal temperature to obtain hydrolysate;

fourthly, taking 25mL of hydrolysate, dripping 0.5mL of ammonia water with the concentration of 1mol/L into the hydrolysate, transferring the hydrolysate to a closed container, and placing the hydrolysate in a 50 ℃ oven for 0.5 to 10 hours to obtain wet gel;

fifthly, aging the wet gel for 24h at 50 ℃ by 25mL of methanol, exchanging for 2 times by 25mL of ethanol and exchanging for 3 times by 25mL of n-hexane, and drying in a gradient manner under normal pressure to obtain the phenyl hybridized SiO₂An aerogel;

sixthly, 2.0g of phenyl hybridized SiO₂Placing aerogel and 2.5g of magnesium powder with the particle size of 10-100 mu m in a stainless steel reactor, then placing the stainless steel reactor in a tubular furnace, firstly purging the furnace body for 0.5h by adopting argon with the flow rate of 100mL/min, raising the temperature to 650 ℃ at the speed of 5 ℃/min under the protection of argon, keeping the temperature for 5h, and then naturally cooling to room temperature to obtain a crude product;

and seventhly, cleaning the crude product for 3 hours by respectively adopting hydrofluoric acid with the mass concentration of 5%, hydrochloric acid with the concentration of 6mol/L and hydrochloric acid with the concentration of 1mol/L, washing the crude product with deionized water until the washing liquid is neutral, and then drying the washed product in vacuum at 90 ℃ to obtain the SiC aerogel.

In step one, R is₁Si(OR₂)₃Wherein R is₂＝CH₃Or CH₂CH₃，R₁Aromatic hydrocarbon or alkane with carbon number more than or equal to 6.

The preparation method of the high-temperature resistant SiC aerogel comprises the following steps:

firstly, weighing 23g to 46g of ethanol, 0.9g to 1.8g of deionized water and 0.125g to 0.25g of span-20, mixing, magnetically stirring for 5min, and then dropwise adding 14.5g to 19.8g R₁Si(OR₂)₃0.5mL of hydrochloric acid with the concentration of 0.1mol/L, and then performing oil bath at the temperature of between 50 and 80 DEG CStirring for 2h to obtain hydrolysate;

secondly, taking 25mL of hydrolysate, dripping 0.5-1 mL of ammonia water with the concentration of 6-12 mol/L into the hydrolysate, transferring the hydrolysate into a closed container, and placing the container in a 50 ℃ oven for 0.5-10 h to obtain wet gel;

aging the wet gel with 25mL of methanol at 50 ℃ for 24h, exchanging with 25mL of ethanol for 2 times, exchanging with 25mL of n-hexane for 3 times, and then performing supercritical drying at 8MPa and 30 ℃ for 4h to obtain aerogel;

fourthly, placing 1.8g to 2.3g of aerogel and 2.3g to 2.8g of magnesium powder with the grain diameter of 10 to 100 mu m into a stainless steel reactor, then placing the stainless steel reactor into a tubular furnace, firstly purging the furnace body for 0.5h by adopting argon with the flow rate of 100mL/min, heating to 650 ℃ at the speed of 5 ℃/min under the protection of the argon, keeping the temperature for 5h, and then naturally cooling to the room temperature to obtain a crude product;

and fifthly, cleaning the crude product for 3 hours by respectively adopting hydrofluoric acid with the mass concentration of 5%, hydrochloric acid with the concentration of 6mol/L and hydrochloric acid with the concentration of 1mol/L, washing the crude product with deionized water until the washing liquid is neutral, then carrying out vacuum drying at 90 ℃, transferring the washed product into a muffle furnace, and then calcining the dried product for 2 hours at 550 ℃ to obtain the SiC aerogel.

In step one, R is₁Si(OR₂)₃Wherein R is₂＝CH₃Or CH₂CH₃，R₁Aromatic hydrocarbon or alkane with carbon number more than or equal to 6.

The preparation method of the high-temperature resistant SiC aerogel comprises the following steps:

firstly, weighing 10.3g of propyl triethoxysilane and 10.4g of ethyl orthosilicate, and magnetically stirring for 5min to obtain a mixed solution A;

weighing 40.8g of ethanol, 4.0g of deionized water and 0.25g of hexadecyl trimethyl ammonium bromide, and mixing to obtain a mixed solution B;

mixing the mixed solution A and the mixed solution B, dripping 1mL of hydrochloric acid with the concentration of 1mol/L, and magnetically stirring for 4 hours at the temperature of 50 ℃ to obtain hydrolysate;

fourthly, taking 25mL of hydrolysate, dripping 0.5mL of ammonia water with the concentration of 1mol/L into the hydrolysate, transferring the hydrolysate to a closed container, and placing the hydrolysate in a 50 ℃ oven for 0.5 to 10 hours to obtain wet gel;

fifthly, aging the wet gel for 24h at 50 ℃ by 25mL of methanol, exchanging for 2 times by 25mL of ethanol and exchanging for 3 times by 25mL of n-hexane, and drying in a gradient manner under normal pressure to obtain the phenyl hybridized SiO₂An aerogel;

sixthly, 2.0g of phenyl hybridized SiO₂Placing aerogel and 2.5g of magnesium powder with the particle size of 10-100 mu m in a stainless steel reactor, then placing the stainless steel reactor in a tubular furnace, firstly purging the furnace body for 0.5h by adopting argon with the flow rate of 100mL/min, then raising the temperature to 650 ℃ at the speed of 5 ℃/min under the protection of argon, keeping the temperature for 5h, and then naturally cooling to room temperature to obtain a crude product;

and seventhly, cleaning the crude product for 3 hours by respectively adopting hydrofluoric acid with the mass concentration of 5%, hydrochloric acid with the concentration of 6mol/L and hydrochloric acid with the concentration of 1mol/L, washing the crude product with deionized water until the washing liquid is neutral, and then drying the washed product in vacuum at 90 ℃ to obtain the SiC aerogel.

In step one, R is₁Si(OR₂)₃Wherein R is₂＝CH₃Or CH₂CH₃，R₁Aromatic hydrocarbon or alkane with carbon number more than or equal to 6.

The invention has the following advantages:

1. starting from the source, raw material components are simplified, and organic silicon only containing C, Si and O elements is used as a single precursor. The general structural formula can be written as R₁Si(OR₂)₃Wherein R is₂＝CH₃Or CH₂CH₃，R₁The aromatic hydrocarbon or alkane with the carbon number being more than or equal to 6 comprises but not limited to one or more of phenyl, hexyl, heptyl and octyl.

2. Adopts a sol-gel method and is subjected to supercritical drying to prepare the organic silicon aerogel with uniform pore channel structure and complete shape, and the structural general formula can be written as R₁SiO_1.5Wherein R is₁The aromatic hydrocarbon or alkane with the carbon number being more than or equal to 6 comprises but not limited to one or more of phenyl, hexyl, heptyl and octyl.

3. And reducing the aerogel precursor into SiC aerogel by adopting magnesiothermic reduction under the protection of inert gas. The method successfully avoids R₁SiO_1.5SiO gas is generated in the reduction process, and the product is kept to the maximum extentThe appearance is complete.

Drawings

FIG. 1 is a schematic view of a magnesiothermic stainless steel reactor;

FIG. 2 is a schematic diagram of hydrolytic polymerization in experiment one;

FIG. 3 is a schematic diagram of hydrolytic polymerization in experiment two;

FIG. 4 is an XRD pattern of the SiC aerogel obtained in experiment one;

fig. 5 is an SEM image of the SiC aerogel obtained in experiment one;

fig. 6 is a BET image of the SiC aerogel obtained in experiment one;

fig. 7 is a pore size distribution diagram of the SiC aerogel obtained in experiment one;

fig. 8 is a thermogravimetric plot of the SiC aerogel obtained in experiment one.

Detailed Description

The technical solution of the present invention is not limited to the following specific embodiments, but includes any combination of the specific embodiments.