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Preparation method for silicon carbide aerogel

An aerogel and silicon carbide technology is applied in the field of preparation of silicon carbide aerogel, which can solve the problems of poor mechanical properties and high temperature resistance of silicon carbide aerogel, and achieve a simple preparation method, high mechanical properties and high temperature resistance. The effect of high temperature performance and easy source of raw materials

Active Publication Date: 2016-05-25
NINGBO INST OF MATERIALS TECH & ENG CHINESE ACADEMY OF SCI
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0006] However, in the above technology, due to the high oxygen content, amorphous SiC will be formed during the preparation of SiC airgel. x o y Intergranular phase, SiC x o y The intergranular phase decomposes at high temperature and produces CO and SiO gases. The escape of small gas molecules will produce a large number of cavities and cracks in the airgel skeleton. Therefore, the mechanical properties of silicon carbide aerogels prepared by the above technology Poor performance and high temperature resistance; in addition, in order to remove excess silicon dioxide in silicon carbide airgel, it needs to go through complicated processes such as hydrofluoric acid soaking, washing, and drying

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0033] 1) Polycarbosilane (2g, Si-H molar content is 34mmol), trivinylmethylsilane (0.43g, vinyl molar content is 10.3mmol) and trace karstedt catalyst are dissolved in toluene (30mL), in nitrogen React under protection at 80°C for 6 hours to obtain a jelly-like polycarbosilane gel;

[0034] 2) The obtained polycarbosilane gel is treated with supercritical CO 2 Dry to obtain polycarbosilane airgel;

[0035] 3) Place the obtained polycarbosilane airgel in a tube furnace, raise the temperature to 1600°C at a rate of 2°C / min under the protection of nitrogen and keep it warm for 5 hours, then transfer it to a muffle furnace after cooling, Under the atmosphere, the temperature was raised to 600°C at a rate of 10°C / min and kept for 3 hours.

[0036] The obtained silicon carbide airgel has a density of 0.233g / cm 3 , with an average pore diameter of 15nm and a specific surface area of ​​676m 2 / g, the compressive strength is 2.9MPa.

Embodiment 2

[0038] 1) Dissolve polycarbosilane (2 g, Si-H molar content of 34 mmol), divinyldimethylsilane (0.77 g, vinyl molar content of 13.8 mmol) and a small amount of karstedt catalyst in cyclohexane (46 mL) , and reacted at 80°C for 6 hours under the protection of nitrogen to obtain a jelly-like polycarbosilane gel;

[0039] 2) The obtained polycarbosilane gel is treated with supercritical CO 2 Dry to obtain polycarbosilane airgel;

[0040] 3) Place the obtained polycarbosilane airgel in a tube furnace, raise the temperature to 1600°C at a rate of 1°C / min under the protection of nitrogen and keep it warm for 5 hours, transfer it to a muffle furnace after cooling, and place it in the air Under the atmosphere, the temperature was raised to 600°C at a rate of 10°C / min and kept for 3 hours.

[0041] The obtained silicon carbide airgel has a density of 0.175g / cm 3 , with an average pore diameter of 38nm and a specific surface area of ​​831m 2 / g, the compressive strength is 1.4MPa. ...

Embodiment 3

[0043] 1) Polycarbosilane (2g, Si-H molar content is 34mmol), trivinylmethylsilane (0.64g, vinyl molar content is 15.5mmol) and trace karstedt catalyst are dissolved in toluene (33mL), in nitrogen React under protection at 80°C for 6 hours to obtain a jelly-like polycarbosilane gel;

[0044] 2) The obtained polycarbosilane gel is treated with supercritical CO 2 Dry to obtain polycarbosilane airgel;

[0045] 3) Place the obtained polycarbosilane airgel in a tube furnace, raise the temperature to 1800°C at a rate of 2°C / min under the protection of nitrogen and keep it warm for 3 hours, then transfer it to a muffle furnace after cooling, Under the atmosphere, the temperature was raised to 600°C at a rate of 10°C / min and kept for 3 hours.

[0046] The obtained silicon carbide airgel has a density of 0.381g / cm 3 , with an average pore diameter of 8nm and a specific surface area of ​​527m 2 / g, the compressive strength is 5.1MPa.

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Abstract

The invention relates to a preparation method for silicon carbide aerogel. The preparation method comprises the following steps: dissolving polycarbosilane and a vinyl compound in an organic solvent, and performing a catalytic reaction at 70-90 DEG C for 4-8 hours in the presence of a karstedt catalyst to obtain polycarbosilane gel, wherein the vinyl compound contains two or more vinyls; drying the polycarbosilane gel to obtain polycarbosilane aerogel; performing heat treatment on the polycarbosilane aerogel to obtain silicon carbide / carbon compound aerogel; and calcining the silicon carbide / carbon compound aerogel at 500-700 DEG C for 1-5 hours under the aerobic condition to obtain the silicon carbide aerogel. According to the preparation method, a raw material source is simple and convenient, the preparation method is simple, and the use of toxic hydrofluoric acid as a SiO2 remover is avoided; and the polycarbosilane aerogel in the preparation process does not contain oxygen, so that the silicon carbide aerogel has higher mechanical property and better high temperature resistance.

Description

technical field [0001] The invention relates to a silicon carbide material, in particular to a preparation method of a silicon carbide airgel. Background technique [0002] Silicon carbide has the characteristics of superhardness, wear resistance, high strength, corrosion resistance, low thermal expansion coefficient, and good thermal stability. Industry and other fields have important use value. Studies have shown that the preparation of silicon carbide into porous materials has the characteristics of porous materials while maintaining its above-mentioned excellent properties, thereby expanding its application fields, such as for filtration, adsorption, catalysis, wave absorption, heat insulation, etc. . [0003] Airgel is a nano-porous material with many special properties, such as high specific surface area (100-1600m 2 / g), low density (0.003~0.5g / cm 3 ), high porosity (70-99.8%), and low thermal conductivity, it is the lightest solid material with the best heat insu...

Claims

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Application Information

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IPC IPC(8): C01B31/36
CPCC01P2006/10C01P2006/12C01P2006/16
Inventor 裴学良何流钟希强苗玉龙杨建行黄庆
Owner NINGBO INST OF MATERIALS TECH & ENG CHINESE ACADEMY OF SCI
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