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

s1, fully mixing a silicon source, ethanol and water according to a certain proportion, and fully stirring in a hydrochloric acid solution with a certain concentration for 18-24 hours; taking a certain amount of carbon source, putting the carbon source into a mixed solution of deionized water and DMF, carrying out ultrasonic treatment for 2-4 hours, and then stirring for 3 hours;

s2, slowly dripping ammonia water into the hydrolysis solution of the silicon source while stirring, and adding the dispersion liquid of the carbon source into the solution before forming gel; slowly stirring, and adding a small amount of ammonia water; stopping stirring after 1 minute, standing the carbonaceous silicone gel for 15 minutes, and then placing the carbonaceous silicone gel in a water bath kettle at the temperature of 45-50 ℃ for more than 24 hours until the gel is stably formed;

s3, freezing the mixed gel in a refrigerator at the temperature of-40 ℃ for 24 hours, and transferring the frozen gel to a freeze dryer to obtain dry gel; putting the xerogel into an alumina crucible, putting the whole crucible into a vacuum tube type high-temperature furnace for reaction, introducing protective gas, preserving at a certain temperature for 4 hours, naturally cooling to room temperature, and taking out solids;

and S4, finally, standing the solid in a mixed solution of hydrofluoric acid and ionized water thereof for 2 hours, and freeze-drying the solid with the solution removed to obtain the final silicon carbide composite material.

2. The method for preparing a silicon carbide composite material according to claim 1, wherein: the silicon source in the step S1 is tetraethoxysilane, and the carbon source is graphene oxide.

3. The method for preparing a silicon carbide composite material according to claim 1, wherein: in the step S1, the ratio of the silicon source to the ethanol to the water is 1:6:4, and the concentration of the hydrochloric acid solution is 0.02mol L^-1。

4. The method for preparing a silicon carbide composite material according to claim 1, wherein: in the step S3, the protective gas is nitrogen, and the certain temperature is 1400 ℃.

Background

The electromagnetic wave can bear and transfer the life of people to bring convenience. However, as the application range of electromagnetic waves is expanded and the number of applications is increased, it also brings about some unnecessary troubles and negative effects. The silicon carbide composite material has high-efficiency wave-absorbing performance. Many efforts have been made to develop the preparation of silicon carbide composites. However, the preparation process of the silicon carbide composite material at present usually involves a relatively complex process and is relatively high in cost. Therefore, a novel preparation method of the silicon carbide composite material, which has simple operation and process, low cost and simple equipment, is needed.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a preparation method of a silicon carbide composite material, and solves the problems of complex preparation process and high cost of the silicon carbide composite material.

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

2. a preparation method of a silicon carbide composite material is characterized by comprising the following steps: the method specifically comprises the following steps:

s1, fully mixing a silicon source, ethanol and water according to a certain proportion, and fully stirring in a hydrochloric acid solution with a certain concentration for 18-24 hours; taking a certain amount of carbon source, putting the carbon source into a mixed solution of deionized water and DMF, carrying out ultrasonic treatment for 2-4 hours, and then stirring for 3 hours;

s2, slowly dripping ammonia water into the hydrolysis solution of the silicon source while stirring, and adding the dispersion liquid of the carbon source into the solution before forming gel; slowly stirring, and adding a small amount of ammonia water; stopping stirring after 1 minute, standing the carbonaceous silicone gel for 15 minutes, and then placing the carbonaceous silicone gel in a water bath kettle at the temperature of 45-50 ℃ for more than 24 hours until the gel is stably formed;

s3, freezing the mixed gel in a refrigerator at the temperature of-40 ℃ for 24 hours, and transferring the frozen gel to a freeze dryer to obtain dry gel; putting the xerogel into an alumina crucible, putting the whole crucible into a vacuum tube type high-temperature furnace for reaction, introducing protective gas, preserving at a certain temperature for 4 hours, naturally cooling to room temperature, and taking out solids;

and S4, finally, standing the solid in a mixed solution of hydrofluoric acid and ionized water thereof for 2 hours, and freeze-drying the solid with the solution removed to obtain the final silicon carbide composite material.

Preferably, the silicon source in step S1 is tetraethoxysilane, and the carbon source is graphene oxide.

Preferably, in the step S1, the ratio of the silicon source to the ethanol to the water is 1:6:4, and the concentration of the hydrochloric acid solution is 0.02mol L^-1。

Preferably, the protective gas in step S3 is nitrogen, and the certain temperature is 1400 ℃.

Advantageous effects

The invention provides a preparation method of a silicon carbide composite material. Compared with the prior art, the method has the following beneficial effects: the invention ensures that the dielectric constant of the prepared composite material is maximum at 1400 ℃ and the wave absorbing effect is best under the conditions of simple operation and process, low cost and simple equipment. The impedance matching and attenuation characteristics are best, and the maximum development potential is achieved.

Drawings

FIG. 1 is an SEM image of a composite material obtained at 1400 ℃ according to the present invention;

FIG. 2 is a graph of reflection loss versus frequency for a composite material obtained at 1400 ℃ in accordance with the present invention.

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, an embodiment of the present invention provides a technical solution: a preparation method of a silicon carbide composite material specifically comprises the following embodiments:

example 1

S1, mixing ethyl orthosilicate, ethanol and water in a ratio of 1:6:4 sufficiently, and adding 0.02mol L of the mixture^-1Fully stirring the mixture in a hydrochloric acid solution for 18 to 24 hours; taking a certain amount of graphene oxide, putting the graphene oxide in a mixed solution of deionized water and DMF (dimethyl formamide), carrying out ultrasonic treatment for 2-4 hours, and then stirring for 3 hours;

s2, slowly dropping ammonia water into the hydrolysis solution of ethyl orthosilicate while stirring, and adding the dispersion liquid of graphene oxide into the solution before forming gel; slowly stirring, and adding a small amount of ammonia water; stopping stirring after 1 minute, standing the carbonaceous silicone gel for 15 minutes, and then placing the carbonaceous silicone gel in a water bath kettle at the temperature of 45-50 ℃ for more than 24 hours until the gel is stably formed;

s3, freezing the mixed gel in a refrigerator at the temperature of-40 ℃ for 24 hours, and transferring the frozen gel to a freeze dryer to obtain dry gel; putting the xerogel into an alumina crucible, putting the whole crucible into a vacuum tube type high-temperature furnace for reaction, introducing nitrogen, preserving at 1400 ℃ for 4 hours, naturally cooling to room temperature, and taking out solids;

and S4, finally, standing the solid in a mixed solution of hydrofluoric acid and ionized water thereof for 2 hours, and freeze-drying the solid with the solution removed to obtain the final silicon carbide composite material.

In order to further verify that the composite material prepared by the invention has good wave absorbing performance and good attenuation loss capability as the composite material prepared by other methods, please refer to fig. 2, fig. 2 is a graph of the reflection loss value and the frequency of the composite material obtained at 1400 ℃, and it can be seen from the graph that when the thickness of the composite material is 3.2mm, the effective absorption bandwidth is greater than 9GHz from the frequency of 9.5GHz to the maximum frequency of 18GHz, and when the incident wave frequency of the composite material is 15.4GHz, the absorption effect is best, and the reflection loss value reaches-45.6 GHz. This shows that the participation of graphene can effectively improve the attenuation loss capability of silicon carbide electromagnetic waves.

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.