CN102504760B - Preparation method of silicon carbide and carbon nano tube composite wave-absorbing material - Google Patents

Abstract

A method for preparing a silicon carbide and carbon nanotube composite wave-absorbing material is to disperse silicon carbide in a nitrate solution and impregnate to form a metal-silicon carbide composite with a metal component of 5-15% by weight; after the impregnation is completed, Evaporate the slurry to dryness, dry at 60-120°C for 6-24h; calcinate at 300-600°C for 4-6h, put the ground material into a quartz tube after cooling, one end of the quartz tube is fed with methane, and the other end is connected to the atmosphere In the same way, set the heating rate to 5-15°C/min, the reaction space velocity to 300-3000/h, raise the temperature to 500-900°C, keep the temperature down to room temperature after 1-5h, and take out the obtained material, which is silicon carbide and carbon Nanotube composite absorbing material. The invention has the advantages of high temperature resistance, enhanced wave-absorbing performance and stability of the material.

Description

A preparation method of silicon carbide and carbon nanotube composite wave-absorbing material

technical field

The invention belongs to a method for preparing a wave-absorbing material, in particular to a method for preparing a composite wave-absorbing material of silicon carbide and carbon nanotubes.

Background technique

With the development of modern science and technology, absorbing materials are widely used in aerospace, military and environmental fields. In particular, high-temperature-resistant microwave-absorbing materials, as key materials in the fields of national defense, military and aerospace, have received great attention from all countries in the world. Therefore, the development and research of high-performance absorbing materials has become a hot topic in the material field. At present, there are many kinds of absorbing materials, with different use environments and performances. The most commonly used absorbing material is represented by ferrite, which is a typical magnetic loss absorbing material with high density and easy to corrode, and is affected by Curie temperature and skin depth, so it is difficult to play its role at high frequency and high temperature. Absorption; polymer absorbing materials developed in recent years, including chiral absorbing materials, are difficult to use in high-temperature atmospheric environments; resistive absorbing materials, such as carbon fiber and silicon carbide, can be used in high-temperature environments environment, but its absorbing efficiency and absorbing range face serious challenges. Therefore, we need to further improve the absorbing performance of absorbing materials and obtain new high-efficiency absorbing materials with high temperature resistance and corrosion resistance.

The absorbing performance of materials is related to the shape and structure of materials, especially the compounding of various absorbing materials can significantly improve the absorbing performance of materials. Silicon carbide and carbon nanotubes, as wave-absorbing materials with stable physical and chemical properties, high temperature resistance, corrosion resistance, oxidation resistance and high mechanical strength, have attracted the attention of relevant researchers. For example: Chinese patent (publication number: CN 1544723) discloses a composite fiber absorbing material containing silicon carbide, which is made by blending nano-silicon carbide, polyacrylonitrile-based carbon and additives, spinning, and then surface treatment , to produce silicon carbide polyacrylonitrile carbon fiber composite absorbing material, which can be woven into clothes and other radiation-proof fabrics. Chinese patent (publication number: 101045533) discloses a preparation method of a carbon nanotube composite material with magnetic alloy particles loaded on the surface. It attenuates electromagnetic waves through the contribution of carbon nanotubes in terms of dielectric loss and the contribution of magnetic alloy particles in terms of electromagnetic loss. Chinese patent (publication number: 101289569) discloses a method for preparing a multi-walled carbon nanotube/epoxy resin wave-absorbing stealth composite material. The method utilizes the dielectric loss of carbon nanotubes and epoxy resin to attenuate electromagnetic waves, and improves the dielectric loss of materials through defects caused by NaOH on the surface of carbon nanotubes. However, the research on the formation of composite absorbing materials of carbon nanotubes and silicon carbide by using silicon carbide as the matrix and growing in situ has not been reported yet.

Contents of the invention

The invention proposes a method for preparing a high temperature-resistant composite wave-absorbing material of silicon carbide and carbon nanotubes.

The invention uses silicon carbide as the substrate, supports transition metal particles on the surface, and then uses methane as the reducing and reactive gas to catalytically crack methane in situ at a certain temperature and space velocity to form carbon nanotubes and silicon carbide. Composite absorbing material.

The present invention is achieved by the following methods:

(1) Using an impregnation method, dispersing silicon carbide in a nitrate solution, impregnating to form a metal-silicon carbide composite with a metal component of 5-15% by weight;

(2) After the impregnation is completed, the slurry is evaporated to dryness and dried at 60-120° C. for 6-24 hours;

(3) Calcining the dried material at 300-600°C for 4-6h, and grinding after cooling;

(4) Put the ground material into a quartz tube, one end of the quartz tube is fed with methane, the other end is connected to the atmosphere, the heating rate is set to 5-15°C/min, the reaction space velocity is 300-3000/h, and the temperature is raised to 500-900°C, keep the temperature constant for 1-5 hours, then cool down to room temperature, and take out the obtained material, which is the composite wave-absorbing material of silicon carbide and carbon nanotubes.

The nitrates mentioned above are iron nitrate, nickel nitrate or cobalt nitrate.

The specific surface area of silicon carbide as mentioned above is 30-150m ² /g.

The present invention is characterized in that silicon carbide is used as the substrate, metal particles are loaded, methane is used as the reducing gas and the required carbon source, and carbon nanotubes are formed on the silicon carbide in situ to form carbon nanotube-coated silicon carbide. Absorbing material with special structure. The formed absorbing material has a very low metal content and is wrapped in silicon carbide and carbon nanotubes, which can effectively prevent its corrosion and oxidation. At the same time, silicon carbide and carbon nanotubes are evenly combined with each other, which is conducive to enhancing the wave-absorbing performance and stability of the material. The obtained carbon nanotubes have an outer diameter of 10-100nm, an inner diameter of 5-30nm, and a length of 0.5-20um.

Description of drawings

Fig. 1 is the wave-absorbing reflectivity collection of examples 1 composite material different thicknesses

Fig. 2 is the absorbing reflectivity spectrogram of embodiment 2 composite material different thicknesses

Fig. 3 is the spectrum of absorbing reflectivity of the composite material of Example 3 with different thicknesses.

Detailed ways

Example 1

1. Weigh 0.25g Ni(NO ₃ ) ₂ ·6H ₂ O and dissolve it in 30ml distilled water. After stirring evenly, 1 g of silicon carbide powder was added and impregnated to form a metal-silicon carbide composite with a metal component of 5% by weight.

2. Evaporate the appealing slurry to dryness, put it in an oven, and dry it at 60°C for 24 hours.

3. Calcinate the dried material in a muffle furnace at 300°C for 6h.

4. Grind the calcined material into powder, weigh 0.5g and put it into a quartz tube with a diameter of 12mm.

5. Load the quartz tube on the tube furnace on the fixed bed. One end of the quartz tube is fed with methane, and the other end is connected to the atmosphere. Set the heating rate to 5°C/min, and the reaction space velocity to 300/h. 5h.

6. After the running time of the fixed bed is over, the temperature is lowered to room temperature, and the obtained material is taken out, which is the silicon carbide/carbon nanotube composite material. The specific surface area of the silicon carbide is 30m ² /g, and the obtained carbon nanotubes have an outer diameter of 10-50nm, an inner diameter of 5-20nm, and a length of 0.5-15um..

7. Figure 1 is the absorbing reflectance spectrum of the composite material with different thicknesses. It can be seen that the absorption bandwidth below -10dB (more than 90% absorption, -20dB is 99% absorption) can reach 3.5GHZ, and the absorption intensity can reach Up to 39.5dB.

Example 2

1. Weigh 0.74g Ni(NO ₃ ) ₂ ·6H2O and dissolve it in 30ml distilled water. After stirring evenly, 1 g of silicon carbide powder was added and impregnated to form a metal-silicon carbide composite with a metal component of 15% by weight.

2. Evaporate the appealing slurry to dryness, put it in an oven, and dry it at 100°C for 12 hours.

3. Calcinate the dried material in a muffle furnace at 500°C for 5h.

4. Grind the calcined material into powder, weigh 0.5g and put it into a quartz tube with a diameter of 12mm.

5. Load the quartz tube on the tube furnace on the fixed bed. One end of the quartz tube is fed with methane, and the other end is connected to the atmosphere. Set the heating rate to 10°C/min, and the reaction space velocity to 1200/h. 3h.

6. After the running time of the fixed bed is over, the temperature is lowered to room temperature, and the obtained material is taken out, which is the silicon carbide/carbon nanotube composite material. The specific surface area of the silicon carbide is 60m ² /g, the outer diameter of the obtained carbon nanotube is between 30-100nm, the inner diameter is 10-30nm, and the length is 1-20um.

7. Figure 2 is the absorbing reflectance spectrum of the composite material with different thicknesses. It can be seen that the absorption bandwidth below -10dB (90% absorption, -20dB is 99% absorption) can reach 5.1GHZ, and the absorption intensity Up to 37.6dB.

Example 3

1. Weigh 0.5g Co(NO ₃ ) ₂ .6H ₂ O and dissolve it in 30ml distilled water. After stirring evenly, 1 g of silicon carbide powder was added and impregnated to form a metal-silicon carbide composite with a metal component of 10% by weight.

2. Evaporate the appealing slurry to dryness, put it in an oven, and dry it at 120°C for 6 hours.

3. Calcinate the dried material in a muffle furnace at 600°C for 4h.

4. Grind the calcined material into powder, weigh 0.5g and put it into a quartz tube with a diameter of 12mm.

5. Load the quartz tube on the tube furnace on the fixed bed. One end of the quartz tube is fed with methane, and the other end is connected to the atmosphere. Set the heating rate to 15°C/min, and the reaction space velocity to 3000/h. 1h.

6. After the running time of the fixed bed is over, the temperature is lowered to room temperature, and the obtained material is taken out, which is the silicon carbide/carbon nanotube composite material. The specific surface area of the silicon carbide is 150m ² /g, the outer diameter of the obtained carbon nanotube is between 20-80nm, the inner diameter is 8-25nm, and the length is 1-15um.

7. Figure 3 is the absorption reflectance spectrum of the composite material with different thicknesses. It can be seen that the absorption bandwidth below -10dB (more than 90% absorption, -20dB is 99% absorption) can reach 3.6GHZ, and the absorption intensity can reach 50.5dB.

Claims (1)

1. a preparation method of silicon carbide and carbon nanotube composite absorbing material, is characterized in that comprising the steps: (1) Using an impregnation method, dispersing silicon carbide in a nitrate solution, impregnating to form a metal-silicon carbide composite with a metal component of 5-15% by weight; (2) After the impregnation is completed, the slurry is evaporated to dryness and dried at 60-120 °C for 6-24 h; (3) Calcinate the dried material at 300-600°C for 4-6 hours, and grind it after cooling; (4) Put the ground material into a quartz tube. One end of the quartz tube is fed with methane, and the other end is connected to the atmosphere. 500-900 ℃, constant temperature for 1-5 hours, then lower to room temperature, take out the obtained material, which is the composite wave-absorbing material of silicon carbide and carbon nanotubes; The specific surface area of the silicon carbide is 30-150 m ² /g; Described nitrate is ferric nitrate, nickel nitrate or cobalt nitrate.

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