A silicon carbide / hafnium carbide nanowire modified silicon carbide coating reinforced graphene honeycomb-based nanoaerogel thermal insulation and microwave absorption composite material

Abstract

This invention discloses a silicon carbide / hafnium carbide nanowire modified silicon carbide coating reinforced graphene honeycomb-based nano-aerogel thermal insulation and microwave absorption composite material. It consists of silicon carbide-coated reinforced graphene honeycomb, silicon carbide / hafnium carbide nanowires, and nano-aerogel. First, a silicon carbide coating is formed on the surface of the graphene honeycomb using chemical vapor deposition (CVD). Then, silicon carbide / hafnium carbide nanowires are formed in the internal pores of the silicon carbide-reinforced graphene honeycomb using liquid vapor deposition (LCVD). Finally, nano-aerogel is formed on the surface of the silicon carbide / hafnium carbide nanowires using sol-gel technology, supercritical drying, and a carbonization reaction. The resulting three-dimensional network structure effectively blocks heat transfer and promotes the absorption and dissipation of electromagnetic waves, synergistically providing the composite material with thermal insulation and microwave absorption properties.

Description

Technical Field

[0001] This invention patent relates to a heat-insulating and microwave-absorbing composite material, and more particularly to a silicon carbide / hafnium carbide nanowire modified silicon carbide coating reinforced graphene honeycomb-based nano-aerogel heat-insulating and microwave-absorbing composite material, which can be used for long-term service in high-temperature and complex environments. Technical Background

[0002] Electromagnetic waves are the carriers upon which modern information transmission and reception rely. In the civilian sector, with the development of electronic information technology, wireless electronic communication technologies and related products based on the transmission, transmission, and processing of electromagnetic waves have rapidly developed and been widely applied. However, the resulting electromagnetic radiation and interference have become increasingly serious, becoming a new source of pollution affecting health and quality of life. In the military sector, the development of wireless detection technology and ultra-high-speed precision-guided weapons urgently requires weapons and equipment to have excellent electromagnetic stealth characteristics. Furthermore, in the fields of aerospace and next-generation weaponry, absorbing materials are required to possess multiple functions such as lightweight, high-temperature resistance, multi-band operation, and adjustability. Therefore, researching the electromagnetic properties of materials and developing high-performance electromagnetic absorbing materials that meet the requirements of "strong, wide, lightweight, and thin" has urgent needs and broad application value in both civilian and military fields.

[0003] On January 7, 2021, Northwestern Polytechnical University published an article entitled "Preparation and Performance Study of SiC Nanowire-Reinforced C / (PyC-SiC)n Composite Material". The article describes the matrix modification of carbon / carbon composite material and the growth of silicon carbide nanowires inside and on the surface of the material. The advantages of this material are: (1) SiC nanowires enhance the bonding force of the matrix and inhibit crack propagation through pull-out, bridging and debonding mechanisms. The multilayer matrix structure consumes crack energy and alleviates stress concentration through the deflection and branching of cracks at the interface; (2) The introduction of the SiC phase increases the activation energy of the oxidation reaction of the material and weakens the oxidation reaction rate; (3) On the basis of improving the oxidation resistance of carbon-carbon composite material by matrix modification, the mechanical properties are further improved by SiC nanowires and (PyC-SiC)n multilayer structure.

[0004] Chinese invention patent application number 201510735616.8 discloses a method for preparing a graphene-modified ceramic-based stealth transparent composite material. The method involves liquid-phase impregnation of a quartz fiber-based fabric with a composite silica sol, followed by high-temperature sintering to prepare a quartz composite ceramic material. This material is then liquid-phase impregnated with a graphene solution to prepare the graphene-modified ceramic-based stealth transparent composite material. This method enables missile weapon seekers to exhibit good wave transmission performance within their operating frequency band and good electromagnetic shielding performance in non-operating frequency bands. This allows for frequency-selective wave transmission of the composite material, achieving a stealth effect for the wave-transmitting windows and radomes in the missile weapon system against radar detection, thereby improving the penetration capability of the missile weapon system. The advantages of this invention are: (1) The preparation method uses quartz fiber-shaped fabric liquid phase impregnation composite silica sol, and at the same time adopts vacuum impregnation and concentration integrated composite, which quickly realizes the densification of quartz composite ceramic material, shortens the number of impregnation composites, and reduces the production cycle of the material; (2) The preparation method uses liquid phase impregnation composite graphene solution, which quickly realizes the uniform deposition of graphene in the internal pores and surface of the material, and connects graphene with the quartz composite ceramic matrix by Si-O-Si bonds; (3) The graphene modified ceramic matrix stealth wave-transparent composite material prepared by this invention has good mechanical properties and high temperature resistance, and at the same time effectively utilizes the good electromagnetic wave shielding performance of graphene in the high frequency band, realizing the frequency band selective wave transmission of the composite material.

[0005] Chinese invention patent application No. 201810591706.8 discloses a CVI-SiC nanowire-reinforced composite carbon foam material. This material is composed of a three-dimensional network of carbon foam and silicon carbide nanowires grown on the carbon foam. The cross-section of the carbon foam wall is circular, elliptical, or triangular, with a size of 1-10 μm. The porosity of the carbon foam is 95-99.5%, the pore size is 10-50 μm, the aspect ratio is 5-20, and the compressive strength is 20-50 kPa. The silicon carbide nanowires are β-SiC nanowires with metal spheres at the tips, with a purity ≥99%, a diameter of 10-80 nm, and a length of 0.5-50 μm. The invention also discloses a method for preparing the CVI-SiC nanowire-reinforced composite carbon foam material. The advantages of this invention are: (1) The reinforced composite carbon foam has a low density of 5-20 mg / cm³. 3 (1) The compressive strength is significantly improved; (2) This material can be used in supercapacitors. Its porous composite skeleton structure with interlaced nanowires can store energy particles, greatly improving energy storage efficiency; (3) Due to the skeleton structure of nanowires and carbon composite, this material has an ultra-high specific surface area and can also be used in the catalysis industry. However, the invention directly prepares silicon carbide nanowires on the surface of carbon foam, and the performance improvement is not obvious. In addition, the preparation process and structural design of silicon carbide nanowires are not detailed, and their heat insulation and wave absorption performance are not mentioned.

[0006] Chinese invention patent application number 201710115405.3 discloses a lightweight, high-strength foamed carbon-based thermal insulation composite material. The foamed carbon-based composite material comprises a foamed carbon substrate, a silicon carbide coating, and a network of silicon carbide nanowires. The silicon carbide coating coats the surface of the foamed carbon skeleton, and the network of silicon carbide nanowires fills the three-dimensional pores. The porosity is 90–95%, the average pore size is 50–500 nm, and the apparent density is 0.05–0.2 g / cm³. 3 The compressive strength is 5-15 MPa. The foamed carbon is a flexible foamed carbon, obtained by high-temperature pyrolysis of melamine foam, with a porosity of over 99%, an average pore size of 20-50 μm, a silicon carbide coating thickness of 0.5-1 μm, and silicon carbide nanowires with a diameter of 50-300 nm and an average length of 30-50 μm, all prepared by chemical vapor deposition. The advantages of this invention are: (1) silicon carbide coating on the surface of the foamed carbon skeleton improves the oxidation resistance of the composite material; (2) silicon carbide coating on the surface of the foamed carbon skeleton improves the mechanical properties of the composite material; (3) silicon carbide nanowires divide the internal pores of the foam, reducing the internal pore size and reducing the thermal conductivity of the material. However, in this patent, silicon carbide coating on the surface of the foamed carbon skeleton and mesh silicon carbide nanowires filling the three-dimensional pores can improve the overall mechanical properties and thermal insulation properties of the material to a certain extent, but the continuous silicon carbide coating and the penetrating silicon carbide nanowires will promote solid conduction and significantly increase the apparent density of the material.

[0007] Chinese invention patent application number 201911121756.0 discloses a method for preparing silicon carbide-porous carbon one-dimensional nano-absorbing material and its application. The absorbing material is composed of silicon carbide nanowires and porous carbon, and is generally in the form of a gray-black powder. The porous carbon forms a core-shell structure with the silicon carbide nanowires on the surface. This invention uses silicon carbide as the main material, resulting in stable material properties and easy mass production. The pore microstructure of the porous carbon can be easily controlled by heat treatment time, which can effectively adjust the dielectric properties of silicon carbide, thereby improving its absorption performance. When it is uniformly mixed with paraffin, accounting for 10% of the total mass, and with a matching thickness of 2.69 mm, the frequency bandwidth with a reflection loss of less than -10 dB in the 2-18 GHz frequency range can reach 7.16 GHz. When the matching thickness is 2.38 mm, the lowest reflection loss occurs at 15.24 GHz, at which point the reflection loss is -56.34 dB. However, this invention is a one-dimensional nano-absorbing material and does not possess the structural advantages of a three-dimensional spatial network.

[0008] As shown in the above patent, in order to prepare high-temperature resistant, heat-insulating, and wave-absorbing materials, silicon carbide is generally used as the main material in the design. However, it is difficult to effectively balance heat insulation and wave absorption performance during the preparation process. At the same time, the design of the spatial structure is relatively simple and cannot achieve the expected goal. Summary of the Invention

[0009] The purpose of this invention patent is to overcome the shortcomings of the prior art and provide a ceramic matrix composite material that integrates lightweight, high strength, load-bearing capacity, heat insulation, and wave absorption.

[0010] The technical solution adopted to achieve the purpose of this invention patent is: a silicon carbide / hafnium carbide nanowire modified silicon carbide coated and reinforced graphene honeycomb-based nano-aerogel thermal insulation and microwave absorption composite material, which is composed of silicon carbide coated and reinforced graphene honeycomb, silicon carbide / hafnium carbide nanowires and nano-aerogel, characterized in that the graphene honeycomb in the silicon carbide coated and reinforced graphene honeycomb is composed of closely arranged regular hexagonal or equilateral triangular units, the unit side length is 0.1-1.0 cm, and the graphene honeycomb density is 0.3-0.5 g / cm³. 3 The silicon carbide coating was prepared on the surface of the graphene honeycomb using chemical vapor deposition (CVD), exhibiting a discontinuous and intermittent distribution, with a thickness of 1.0-1.5 μm. Silicon carbide / hafnium carbide nanowires were prepared by chemical liquid vapor deposition (CLVD) to reinforce the internal pores of the graphene honeycomb with the silicon carbide coating. The silicon carbide / hafnium carbide nanowires were perpendicular to the surface of the graphene honeycomb reinforced by the silicon carbide coating, without overlapping or entanglement, and had a diameter of 50.0-80.0 nm and a length of 2.0-5.0 μm. The nano-aerogel, composed of graphene-crosslinked carbon hollow sphere aerogel, was prepared on the surface of the silicon carbide / hafnium carbide nanowires using sol-gel technology, supercritical drying, and a carbonization reaction, with a density of 40.0-50.0 mg / cm³. 3 Its specific surface area is 650.0-800.0 m². 2 / g.

[0011] Furthermore, the preparation method of the silicon carbide / hafnium carbide nanowire modified silicon carbide coating reinforced graphene honeycomb-based nano-aerogel thermal insulation and microwave absorption composite material is characterized by including the following steps:

[0012] (1) The untreated graphene honeycomb was placed in the center of a glass container in a liquid phase furnace and fixed. Liquid xylene was added to the container. The liquid phase furnace was heated to 800-900℃ for densification and kept at the temperature for 6.0-7.0h. After cooling with the furnace, it was taken out and cleaned. It was dried at 80-90℃ to obtain the modified graphene honeycomb.

[0013] (2) The modified graphene honeycomb was loaded into a vapor deposition furnace, vacuumed and the airtightness was checked. Then argon was introduced, followed by hydrogen and trichloromethylsilane was introduced into the reaction zone. The vapor deposition furnace was heated to the deposition temperature. The deposition process conditions were: the molar ratio of hydrogen to trichloromethylsilane was 8.0-10.0:1, the deposition temperature was 1200-1300℃, and the deposition time was 1.0-6.0h. After cooling with the furnace, silicon carbide-coated reinforced graphene honeycomb was obtained.

[0014] (3) The silicon carbide-coated graphene honeycomb was placed in a nickel nitrate aqueous solution with a mass fraction of 10.0-40.0% and soaked for 2.0-4.0 h. After soaking, it was taken out and dried in an oven at 80-90℃. Then, the sample was placed in a glass container of a liquid phase furnace and a mixed solution of xylene, polycarbosilane and organohafnium polymer was poured in. The mass ratio of organohafnium polymer to polycarbosilane was 1:3.0-4.0. The liquid phase furnace was heated to 800-900℃, the heating rate was adjusted to 8.0-12.0℃ / min, and the holding time was 5.0-7.0 h. The deposition was repeated 2-4 times. After cooling with the furnace, it was washed with water and dried at 80-90℃ to obtain silicon carbide / hafnium carbide nanowire modified silicon carbide-coated graphene honeycomb.

[0015] (4) First, the polyaniline-polypyrrole copolymer precursor is dissolved in a graphene oxide suspension and ultrasonically treated for 0.5-1.0 h. Then, ascorbic acid is added, with a mass ratio of ascorbic acid to graphene oxide of 3.0-4.0:1. The mixture is then allowed to stand at 50-60℃ for 8.0-10.0 h. Subsequently, silicon carbide / hafnium carbide nanowire-modified silicon carbide coating-reinforced graphene honeycomb is added to the solution, and solvent is replaced with ethanol. Then, supercritical drying technology is used for drying. Finally, the mixture is placed in a tube furnace, and argon gas is introduced, with the argon gas flow rate adjusted to 100-150 cm³. 3 The heating rate was set to 6.0-9.0℃ / min, the reaction temperature to 950-1050℃, and the reaction time to 12.0-14.0h. The final sample was obtained by cooling with the furnace.

[0016] The beneficial effects of this invention are: (1) Using silicon carbide-reinforced graphene honeycomb as the matrix of the composite material, the lightweight and high-strength characteristics of silicon carbide-reinforced graphene honeycomb effectively reduce the overall density of the composite material while ensuring the overall strength. In addition, graphene honeycomb is also a high-performance electromagnetic wave absorbing and shielding material, which can effectively improve the overall absorption performance of the material; (2) Using chemical vapor deposition to deposit a silicon carbide coating on the surface of the graphene honeycomb, and the silicon carbide coating is discontinuously distributed, which can block the continuous solid-phase heat transfer, but at the same time can effectively improve the mechanical properties of the graphene honeycomb, improve its impedance matching characteristics, and achieve maximum electromagnetic wave incidence; (3) Using chemical liquid gas Phase deposition process grows silicon carbide / hafnium carbide nanowires in the pores inside the graphene honeycomb reinforced by silicon carbide coating. The silicon carbide / hafnium carbide nanowires are intertwined with the graphene honeycomb skeleton and silicon carbide coating to form a three-dimensional network structure, which can effectively block gas phase heat and absorb and dissipate electromagnetic waves, and synergistically improve the heat insulation and wave absorption performance of the composite material; (4) Graphene crosslinked carbon hollow sphere aerogel is prepared on the surface of silicon carbide / hafnium carbide nanowires using sol-gel process, supercritical drying technology and carbonization reaction. A large number of micropores are created on the submicron hollow sphere shell, which effectively ensures the specific surface area of ​​the composite material, restricts the free movement of air and reduces the efficiency of heat transfer, so that the material has good heat insulation performance. Detailed Implementation

[0017] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. After reading the present invention, any modifications of the present invention in various equivalent forms by those skilled in the art will fall within the scope defined by the appended claims.

[0018] Example 1

[0019] A silicon carbide / hafnium carbide nanowire modified silicon carbide coated and reinforced graphene honeycomb-based nano-aerogel thermal insulation and microwave absorption composite material is disclosed. The composite material comprises silicon carbide coated and reinforced graphene honeycomb, silicon carbide / hafnium carbide nanowires, and nano-aerogel. Its key feature is that the graphene honeycomb in the silicon carbide coated and reinforced graphene honeycomb is composed of closely packed regular hexagonal units, with each unit having a side length of 1.0 cm and a graphene honeycomb density of 0.4 g / cm³. 3The silicon carbide coating was prepared on the graphene honeycomb surface using chemical vapor deposition (CVD) and exhibited a discontinuous distribution with a thickness of 1.2 μm. Silicon carbide / hafnium carbide nanowires were prepared by chemical liquid vapor deposition (CLV) to reinforce the internal pores of the graphene honeycomb with the silicon carbide coating. The silicon carbide / hafnium carbide nanowires were perpendicular to the surface of the graphene honeycomb reinforced with the silicon carbide coating, without overlapping or entanglement. The diameter of the silicon carbide / hafnium carbide nanowires was 60.0 nm, and the length was 3.0 μm. The nano-aerogel consisted of graphene-crosslinked carbon hollow sphere aerogel, prepared on the surface of the silicon carbide / hafnium carbide nanowires using sol-gel technology, supercritical drying, and a carbonization reaction, with a density of 45.0 mg / cm³. 3 The specific surface area is 700.0 m². 2 / g.

[0020] Furthermore, the preparation method of the silicon carbide / hafnium carbide nanowire modified silicon carbide coating reinforced graphene honeycomb-based nano-aerogel thermal insulation and microwave absorption composite material is characterized by including the following steps:

[0021] (1) The untreated graphene honeycomb was placed in the center of a glass container in a liquid phase furnace and fixed. Liquid xylene was added to the container. The liquid phase furnace was heated to 850°C for densification and kept at the temperature for 6.5 hours. After cooling with the furnace, it was taken out and cleaned. It was then dried at 85°C to obtain the modified graphene honeycomb.

[0022] (2) The modified graphene honeycomb was loaded into the vapor deposition furnace, the vacuum was drawn and the airtightness was checked, then argon was introduced, then hydrogen was introduced and trichloromethylsilane was introduced into the reaction zone, the vapor deposition furnace was heated to the deposition temperature, and the deposition process conditions were: the molar ratio of hydrogen to trichloromethylsilane was 9.0:1, the deposition temperature was 1250℃, the deposition time was 4.0h, and after cooling with the furnace, silicon carbide coated graphene honeycomb was obtained.

[0023] (3) The silicon carbide-coated graphene honeycomb was placed in a 30.0% nickel nitrate aqueous solution and soaked for 3.0 h. After that, it was taken out and dried in an oven at 85°C. Then, the sample was placed in a glass container of a liquid phase furnace and a mixed solution of xylene, polycarbosilane and organic hafnium polymer was poured in. The mass ratio of organic hafnium polymer to polycarbosilane was 1:3.5. The liquid phase furnace was heated to 850°C and the heating rate was adjusted to 10.0°C / min. The holding time was 6.0 h. The deposition was repeated 4 times. After cooling with the furnace, the sample was washed with water and dried at 85°C to obtain silicon carbide / hafnium carbide nanowire modified silicon carbide-coated graphene honeycomb.

[0024] (4) First, the polyaniline-polypyrrole copolymer precursor was dissolved in a graphene oxide suspension and ultrasonically treated for 0.8 h. Then, ascorbic acid was added, with a mass ratio of ascorbic acid to graphene oxide of 3.5:1. The mixture was allowed to stand at 55 °C for 9.0 h. Subsequently, silicon carbide / hafnium carbide nanowire-modified silicon carbide-reinforced graphene honeycomb was added to the solution, and solvent was replaced with ethanol. Then, supercritical drying technology was used for drying. Finally, the mixture was placed in a tube furnace, and argon gas was introduced, with the argon gas flow rate adjusted to 120 cm³. 3 The heating rate was set to 7.0℃ / min, the reaction temperature to 950℃, and the reaction time to 12.0h. The final sample was obtained by cooling with the furnace.

[0025] The above is merely one specific embodiment of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial modifications made to the present invention using this concept shall be considered as infringing upon the scope of protection of the present invention. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A silicon carbide / hafnium carbide nanowire modified silicon carbide coated and reinforced graphene honeycomb-based nano-aerogel thermal insulation and microwave absorption composite material, comprising silicon carbide coated and reinforced graphene honeycomb, silicon carbide / hafnium carbide nanowires and nano-aerogel, characterized in that silicon carbide... The graphene honeycomb in the coated reinforced graphene honeycomb consists of closely packed regular hexagonal or equilateral triangular units, with a unit side length of 0.1-1.0 cm and a graphene honeycomb density of 0.3-0.5 g / cm³. 3 The silicon carbide coating was prepared on the surface of the graphene honeycomb using chemical vapor deposition (CVD), exhibiting a discontinuous and intermittent distribution, with a thickness of 1.0-1.5 μm. Silicon carbide / hafnium carbide nanowires were prepared by chemical liquid vapor deposition (CLVD) to reinforce the internal pores of the graphene honeycomb with the silicon carbide coating. The silicon carbide / hafnium carbide nanowires were perpendicular to the surface of the graphene honeycomb reinforced by the silicon carbide coating, without overlapping or entanglement, and had a diameter of 50.0-80.0 nm and a length of 2.0-5.0 μm. The nano-aerogel, composed of graphene-crosslinked carbon hollow sphere aerogel, was prepared on the surface of the silicon carbide / hafnium carbide nanowires using sol-gel technology, supercritical drying, and a carbonization reaction, with a density of 40.0-50.0 mg / cm³. 3 Its specific surface area is 650.0-800.0 m². 2 / g.

2. A method for preparing the silicon carbide / hafnium carbide nanowire modified silicon carbide coating reinforced graphene honeycomb-based nano-aerogel thermal insulation and microwave absorption composite material according to claim 1, characterized in that... Includes the following steps: (1) The untreated graphene honeycomb was placed in the center of a glass container in a liquid phase furnace and fixed. Liquid xylene was added to the container. The liquid phase furnace was heated to 800-900℃ for densification and kept at the temperature for 6.0-7.0h. After cooling with the furnace, it was taken out and cleaned. It was dried at 80-90℃ to obtain the modified graphene honeycomb. (2) The modified graphene honeycomb was loaded into a vapor deposition furnace, vacuumed and the airtightness was checked. Then argon was introduced, followed by hydrogen and trichloromethylsilane was introduced into the reaction zone. The vapor deposition furnace was heated to the deposition temperature. The deposition process conditions were: the molar ratio of hydrogen to trichloromethylsilane was 8.0-10.0:1, the deposition temperature was 1200-1300℃, and the deposition time was 1.0-6.0h. After cooling with the furnace, silicon carbide-coated reinforced graphene honeycomb was obtained. (3) The silicon carbide-coated graphene honeycomb was placed in a nickel nitrate aqueous solution with a mass fraction of 10.0-40.0% and soaked for 2.0-4.0 h. After soaking, it was taken out and dried in an oven at 80-90℃. Then, the sample was placed in a glass container of a liquid phase furnace and a mixed solution of xylene, polycarbosilane and organohafnium polymer was poured in. The mass ratio of organohafnium polymer to polycarbosilane was 1:3.0-4.

0. The liquid phase furnace was heated to 800-900℃, the heating rate was adjusted to 8.0-12.0℃ / min, and the holding time was 5.0-7.0 h. The deposition was repeated 2-4 times. After cooling with the furnace, it was washed with water and dried at 80-90℃ to obtain silicon carbide / hafnium carbide nanowire modified silicon carbide-coated graphene honeycomb. (4) First, the polyaniline-polypyrrole copolymer precursor is dissolved in a graphene oxide suspension and ultrasonically treated for 0.5-1.0 h. Then, ascorbic acid is added, with a mass ratio of ascorbic acid to graphene oxide of 3.0-4.0:

1. The mixture is then allowed to stand at 50-60℃ for 8.0-10.0 h. Subsequently, silicon carbide / hafnium carbide nanowire-modified silicon carbide coating-reinforced graphene honeycomb is added to the solution, and solvent is replaced with ethanol. Then, supercritical drying technology is used for drying. Finally, the mixture is placed in a tube furnace, and argon gas is introduced, with the argon gas flow rate adjusted to 100-150 cm³. 3 The heating rate was set to 6.0-9.0℃ / min, the reaction temperature to 950-1050℃, and the reaction time to 12.0-14.0h. The final sample was obtained by cooling with the furnace.