阅读说明：本技术 一种碳化硅气凝胶的制备方法 (Preparation method of silicon carbide aerogel ) 是由 冯凯萍 赵天晨 周兆忠 石栋 于 2021-09-15 设计创作，主要内容包括：本发明公开了一种碳化硅气凝胶的制备方法,S1、有机质预处理：将有机质切成2cm*2cm的正方形,然后放到冰箱中冻实；S2、将干燥后的有机质放置于低温管式炉中,在800℃的氮气气氛下进行热处理,得到多孔碳材料；S3、称取一定量的硅粉和二氧化硅粉,在研钵中充分混合后得到混合粉末。将混合粉末平铺于刚玉坩埚中,然后把多孔碳小心放置于混合粉末上方,将盛有混合物的坩埚置于高温管式炉中,在氩气气氛中升温至所需温度并保温2h,得到碳化硅气凝胶材料。本发明通过低成本的有机质桔子皮为前驱体,经过冷冻干燥、高温碳化和碳热还原等步骤,成功制备出了密度极低、结构稳定的碳化硅基气凝胶。(The invention discloses a preparation method of silicon carbide aerogel, which comprises the following steps of S1: cutting the organic matter into squares of 2cm by 2cm, and then putting the squares into a refrigerator for freezing; s2, placing the dried organic matter in a low-temperature tube furnace, and carrying out heat treatment at 800 ℃ in a nitrogen atmosphere to obtain a porous carbon material; s3, weighing a certain amount of silicon powder and silicon dioxide powder, and fully mixing in a mortar to obtain mixed powder. And flatly paving the mixed powder in a corundum crucible, carefully placing the porous carbon above the mixed powder, placing the crucible containing the mixture in a high-temperature tube furnace, heating to the required temperature in argon atmosphere, and preserving the heat for 2 hours to obtain the silicon carbide aerogel material. According to the invention, the silicon carbide-based aerogel with extremely low density and stable structure is successfully prepared by taking low-cost organic orange peel as a precursor through the steps of freeze drying, high-temperature carbonization, carbothermic reduction and the like.)

1. A preparation method of silicon carbide aerogel is characterized by comprising the following steps: the method specifically comprises the following steps:

s1, organic matter pretreatment: the organic matter is cut into 2cm by 2cm squares, and then placed in a refrigerator to be frozen and compacted. After the freeze drying treatment, the geometric outline and the internal pore structure of the dried organic matter can be well maintained;

s2, placing the dried organic matter in a low-temperature tube furnace, and carrying out heat treatment at 800 ℃ in a nitrogen atmosphere to obtain a porous carbon material;

s3, mixing the raw materials according to a molar ratio of 1: 1 weighing a certain amount of silicon powder and silicon dioxide powder, and fully mixing in a mortar to obtain mixed powder. The mixed powder is spread in a corundum crucible, then porous carbon is carefully placed above the mixed powder, and the molar ratio of the porous carbon to silicon powder to silicon dioxide powder is controlled to be 1: 2: and 2, ensuring a sufficient silicon source. And (3) placing the crucible containing the mixture in a high-temperature tube furnace, heating to the required temperature in an argon atmosphere, and keeping the temperature for 2 hours to obtain the silicon carbide aerogel material.

2. The method of claim 1, wherein the step of preparing the silicon carbide aerogel comprises: the organic matter in the step S1 is orange peel.

3. The method of claim 1, wherein the step of preparing the silicon carbide aerogel comprises: the heating rate of the heat treatment in the step S2 is 5 ℃/min, the heat preservation time is set to be 2h, after the heat treatment process is finished, the temperature is reduced to 300 ℃ at the rate of 5 ℃/min, and then the furnace is cooled to the room temperature.

4. The method of claim 1, wherein the step of preparing the silicon carbide aerogel comprises: in the step S3, the temperature is raised from room temperature to 800 ℃ at the speed of 10 ℃/min, then raised to 1000 ℃ at the speed of 5 ℃/min, raised to 1300 ℃, 1400 ℃ and 1500 ℃ at the speed of 2.5 ℃/min in the high-temperature stage, and kept for 120min, and is lowered to 1000 ℃ at the speed of 2.5 ℃/min, then lowered to 800 ℃ at the speed of 5 ℃/min, then lowered to 300 ℃ at the speed of 10 ℃/min, and finally cooled to room temperature along with the furnace.

Technical Field

The invention relates to the technical field of aerogel, in particular to a preparation method of silicon carbide aerogel.

Background

Most of the silicon carbide-based wave-absorbing materials on the market at present are solid powder samples. In practical application, the silicon carbide-based powder wave-absorbing material is generally required to be combined with matrix materials such as resin or ceramic and the like to be prepared into a coating or a structural device for use. This introduces complex manufacturing processes and results in higher material densities. In addition, if the absorbing powder is agglomerated in the matrix, the wave absorbing performance of the material is further reduced. Some silicon carbide is made into aerogel, but the adopted precursor has high cost and complex preparation process, which is not beneficial to mass production.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a preparation method of silicon carbide aerogel, and solves the problems of simplification of a preparation process of the silicon carbide aerogel and reduction of preparation cost.

In order to achieve the purpose, the invention is realized by the following technical scheme: a preparation method of silicon carbide aerogel specifically comprises the following steps:

s1, organic matter pretreatment: the organic matter is cut into 2cm by 2cm squares, and then placed in a refrigerator to be frozen and compacted. After the freeze drying treatment, the geometric outline and the internal pore structure of the dried organic matter can be well maintained;

s2, placing the dried organic matter in a low-temperature tube furnace, and carrying out heat treatment at 800 ℃ in a nitrogen atmosphere to obtain a porous carbon material;

s3, mixing the raw materials according to a molar ratio of 1: 1 weighing a certain amount of silicon powder and silicon dioxide powder, and fully mixing in a mortar to obtain mixed powder. The mixed powder is spread in a corundum crucible, then porous carbon is carefully placed above the mixed powder, and the molar ratio of the porous carbon to silicon powder to silicon dioxide powder is controlled to be 1: 2: and 2, ensuring a sufficient silicon source. And (3) placing the crucible containing the mixture in a high-temperature tube furnace, heating to the required temperature in an argon atmosphere, and keeping the temperature for 2 hours to obtain the silicon carbide aerogel material.

Preferably, the organic matter in step S1 is orange peel.

Preferably, the temperature rise rate of the heat treatment in the step S2 is 5 ℃/min, the heat preservation time is set to 2 hours, and after the heat treatment process is finished, the temperature is reduced to 300 ℃ at the rate of 5 ℃/min, and then the temperature is cooled to room temperature along with the furnace.

Preferably, in the step S3, the temperature is raised from room temperature to 800 ℃ at a rate of 10 ℃/min, then raised to 1000 ℃ at a rate of 5 ℃/min, and raised to 1300 ℃ to 1500 ℃ at a rate of 2.5 ℃/min in the high-temperature stage, and the temperature is maintained for 120min, and in the temperature-lowering stage, the temperature is lowered to 1000 ℃ at a rate of 2.5 ℃/min, then lowered to 800 ℃ at a rate of 5 ℃/min, then lowered to 300 ℃ at a rate of 10 ℃/min, and finally cooled to room temperature with the furnace.

Advantageous effects

The invention provides a preparation method of silicon carbide aerogel. Compared with the prior art, the method has the following beneficial effects: according to the invention, green, cheap and easily available organic orange peel is used as a raw material, complicated steps such as porous forming and the like are not needed, and the silicon carbide-based aerogel is prepared through simple steps of freeze drying, high-temperature carbonization and carbothermic reduction. The density of the prepared silicon carbide-based aerogel is 0.050-0.076g/cm³And the special appearance of a porous silicon carbide structure is realized.

Drawings

FIG. 1 is an SEM image of a silicon carbide aerogel according to the present invention;

FIG. 2 is a graph of the density of silicon carbide aerogels prepared according to the present invention at various temperatures.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1-2, the embodiment of the present invention provides three technical solutions: a preparation method of silicon carbide aerogel specifically comprises the following embodiments:

example 1

S1, organic matter pretreatment: the orange peel was cut into 2cm by 2cm squares and then placed in a refrigerator to be frozen. After the freeze drying treatment, the geometric outline and the internal pore structure of the dried organic matter can be well maintained;

s2, placing the dried organic matter in a low-temperature tube furnace, and carrying out heat treatment at 800 ℃ in a nitrogen atmosphere, wherein the heating rate of the heat treatment is 5 ℃/min, the heat preservation time is set to 2h, after the heat treatment process is finished, the temperature is reduced to 300 ℃ at the rate of 5 ℃/min, and then the organic matter is cooled to room temperature along with the furnace to obtain the porous carbon material;

s3, mixing the raw materials according to a molar ratio of 1: 1 weighing a certain amount of silicon powder and silicon dioxide powder, and fully mixing in a mortar to obtain mixed powder. The mixed powder is spread in a corundum crucible, then porous carbon is carefully placed above the mixed powder, and the molar ratio of the porous carbon to silicon powder to silicon dioxide powder is controlled to be 1: 2: and 2, ensuring a sufficient silicon source. And (2) placing the crucible containing the mixture in a high-temperature tube furnace, heating to a required temperature in an argon atmosphere, preserving heat for 2h, heating from room temperature to 800 ℃ at a speed of 10 ℃/min, then heating to 1000 ℃ at a speed of 5 ℃/min, respectively heating to 1300 ℃ at a high-temperature stage at a speed of 2.5 ℃/min, preserving heat for 120min, cooling to 1000 ℃ at a speed of 2.5 ℃/min, then cooling to 800 ℃ at a speed of 5 ℃/min, then cooling to 300 ℃ at a speed of 10 ℃/min, and finally cooling to room temperature along with the furnace to obtain the silicon carbide aerogel material.

Example 2

S1, organic matter pretreatment: the orange peel was cut into 2cm by 2cm squares and then placed in a refrigerator to be frozen. After the freeze drying treatment, the geometric outline and the internal pore structure of the dried organic matter can be well maintained;

s2, placing the dried organic matter in a low-temperature tube furnace, and carrying out heat treatment at 800 ℃ in a nitrogen atmosphere, wherein the heating rate of the heat treatment is 5 ℃/min, the heat preservation time is set to 2h, after the heat treatment process is finished, the temperature is reduced to 300 ℃ at the rate of 5 ℃/min, and then the organic matter is cooled to room temperature along with the furnace to obtain the porous carbon material;

s3, mixing the raw materials according to a molar ratio of 1: 1 weighing a certain amount of silicon powder and silicon dioxide powder, and fully mixing in a mortar to obtain mixed powder. The mixed powder is spread in a corundum crucible, then porous carbon is carefully placed above the mixed powder, and the molar ratio of the porous carbon to silicon powder to silicon dioxide powder is controlled to be 1: 2: and 2, ensuring a sufficient silicon source. And (2) placing the crucible containing the mixture in a high-temperature tube furnace, heating to a required temperature in an argon atmosphere, preserving heat for 2h, heating from room temperature to 800 ℃ at a speed of 10 ℃/min, then heating to 1000 ℃ at a speed of 5 ℃/min, respectively heating to 1400 ℃ at a high-temperature stage at a speed of 2.5 ℃/min, preserving heat for 120min, cooling to 1000 ℃ at a speed of 2.5 ℃/min, then cooling to 800 ℃ at a speed of 5 ℃/min, then cooling to 300 ℃ at a speed of 10 ℃/min, and finally cooling to room temperature along with the furnace to obtain the silicon carbide aerogel material.

Example 3

S1, organic matter pretreatment: the orange peel was cut into 2cm by 2cm squares and then placed in a refrigerator to be frozen. After the freeze drying treatment, the geometric outline and the internal pore structure of the dried organic matter can be well maintained;

s2, placing the dried organic matter in a low-temperature tube furnace, and carrying out heat treatment at 800 ℃ in a nitrogen atmosphere, wherein the heating rate of the heat treatment is 5 ℃/min, the heat preservation time is set to 2h, after the heat treatment process is finished, the temperature is reduced to 300 ℃ at the rate of 5 ℃/min, and then the organic matter is cooled to room temperature along with the furnace to obtain the porous carbon material;

s3, mixing the raw materials according to a molar ratio of 1: 1 weighing a certain amount of silicon powder and silicon dioxide powder, and fully mixing in a mortar to obtain mixed powder. The mixed powder is spread in a corundum crucible, then porous carbon is carefully placed above the mixed powder, and the molar ratio of the porous carbon to silicon powder to silicon dioxide powder is controlled to be 1: 2: and 2, ensuring a sufficient silicon source. And (2) placing the crucible containing the mixture in a high-temperature tube furnace, heating to a required temperature in an argon atmosphere, keeping the temperature for 2h, heating from room temperature to 800 ℃ at a speed of 10 ℃/min, then heating to 1000 ℃ at a speed of 5 ℃/min, respectively heating to 1500 ℃ at a high-temperature stage at a speed of 2.5 ℃/min, keeping the temperature for 120min, cooling to 1000 ℃ at a speed of 2.5 ℃/min, then cooling to 800 ℃ at a speed of 5 ℃/min, then cooling to 300 ℃ at a speed of 10 ℃/min, and finally cooling to room temperature along with the furnace to obtain the silicon carbide aerogel material.

It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.