Oriented si c nanowire array surface secondary growth superfine si c nanowire, preparation method and application

Abstract

This invention relates to a secondary growth method for ultrafine SiC nanowires on the surface of a oriented SiC nanowire array, its preparation, and its applications. First, a oriented SiC nanowire array is prepared on a carbon fiber cloth surface using catalyst-assisted chemical vapor deposition (CVD). Then, using catalyst particles at the tips of the oriented SiC nanowires as catalysts for secondary SiC nanowire growth, ultrafine SiC nanowires are grown in situ at the tips of the oriented SiC nanowires using negative pressure CVD, resulting in hierarchical SiC nanowires with an onion-like flower shape. The prepared hierarchical SiC nanowires have promising development prospects in multiple fields. The random distribution of the ultrafine SiC nanowire growth direction and the bending and entanglement between the nanowires to form a three-dimensional network structure increase the specific surface area of ​​the substrate, showing broad application potential in supercapacitor electrodes. Furthermore, the excellent bonding between the ultrafine SiC nanowires and the oriented SiC nanowire array, along with the structural stability, makes it a promising candidate for strengthening and toughening composite materials.

Description

Technical Field

[0001] This invention belongs to the field of SiC nanowire fabrication technology, and relates to a method for secondary growth of ultrafine SiC nanowires on the surface of a directional SiC nanowire array, its fabrication method, and its applications. Background Technology

[0002] Silicon carbide nanowires (SiCNWs) are an important class of one-dimensional semiconductor materials. Due to their excellent physicochemical properties, such as tunable bandgap, high mechanical strength, high thermal conductivity, large specific surface area, low coefficient of thermal expansion, high breakdown voltage, and chemical inertness, they are widely used in composite material strengthening, electromagnetic shielding / absorption, and optoelectronic devices. SiCNWs are also excellent energy storage materials for supercapacitors, exhibiting excellent cycle stability. However, the poor conductivity and generally low capacitance of SiC electrodes are major problems restricting the widespread application of SiC-based supercapacitors.

[0003] To further improve the electrochemical performance of SiCNWs electrodes, surface modification is commonly performed on SiCNWs, i.e., secondary loading of other nanomaterials onto the SiCNWs surface. For example, Zhao et al. (“J. Power Sources, 2016, 332, 355-365; ACS Sustainable Chem. Eng. 2016, 4, 3598-3608; Adv. Energy Mater. 2018, 8, 1702787”) loaded metal oxides / sulfides / hydroxides onto the SiCNWs electrode surface to improve the electrode's specific capacitance. In addition, loading carbon nanomaterials onto the SiCNWs electrode surface (Patent 1 “CN110690053B”, Patent 2 “CN115020114A”) to improve the electrode's conductivity is also a common method for improving the performance of SiCNWs electrodes. However, while the loading of the aforementioned nanomaterials improves the specific capacitance of SiCNWs to some extent, the structural stability of the introduced nanomaterials is much lower than that of SiC nanomaterials. This reduces the performance stability of SiCNW-based supercapacitors and adversely affects their cycle life. Therefore, further improving the performance of SiCNW-based supercapacitors while maintaining their excellent cycle stability and other characteristics remains a significant challenge.

[0004] This invention first employs catalyst-assisted chemical vapor deposition (CCVD) to prepare a oriented SiC nanowire array on the surface of carbon fiber cloth. Then, using catalyst particles at the tips of the oriented SiC nanowires as catalysts for secondary SiC nanowire growth, ultrafine SiC nanowires are grown in situ at the tips of the oriented SiC nanowires using negative pressure CCVD, resulting in hierarchical SiC nanowires with an onion-flower-like shape. The preparation process of this invention is simple, highly reproducible, produces nanowires with good bonding and structural stability, and the secondary in-situ grown ultrafine SiC nanowires can significantly increase the specific surface area of ​​the substrate, potentially improving the specific capacitance of supercapacitors while maintaining good cycle life. Summary of the Invention

[0005] Technical problems to be solved

[0006] To overcome the shortcomings of existing technologies, this invention proposes a method for secondary growth of ultrafine SiC nanowires on the surface of a oriented SiC nanowire array, along with its application. The provided technical solution features a simple preparation process, high efficiency in secondary growth of ultrafine SiC nanowires without the use of a catalyst, and strong process repeatability. The ultrafine SiC nanowires prepared by this invention are grown in situ on the surface of an oriented SiC nanowire array, with random growth directions and bent, winding nanowires, increasing the specific surface area of ​​the substrate. Furthermore, the ultrafine SiC nanowires exhibit good bonding with the oriented SiC nanowire array, resulting in a stable structure. This invention first prepares an oriented SiC nanowire array on the surface of carbon fiber cloth, and then secondary grows ultrafine SiC nanowires in situ on the oriented SiC nanowires, obtaining onion-flower-like hierarchical SiC nanowires.

[0007] Technical solution

[0008] A method for secondary growth of ultrafine SiC nanowires on the surface of a directional SiC nanowire array, characterized by the following steps:

[0009] Step 1: Preparation of oriented SiC nanowire array on carbon fiber cloth surface: Acid-treated carbon fibers are immersed in an ethanol solution of metal salt catalyst and then dried to obtain carbon fiber cloth loaded with catalyst.

[0010] SiO2, Si, and C mixed powders were placed at the bottom of a graphite reaction mold, and carbon fibers carrying catalysts were arranged above the powders. The reaction mold was placed in a horizontal tube furnace, and under the protection of an argon atmosphere with a flow rate of 20-150 mL / min, the temperature was raised to 1200-1700℃ at a heating rate of 5-10℃ / min. The reaction was carried out for 1-8 hours, and then cooled to room temperature with the furnace to obtain a SiC nanowire array oriented on the surface of carbon fiber cloth.

[0011] Step 2: Secondary growth of ultrafine SiC nanowires on the surface of the oriented SiC nanowire array: Carbon fibers with grown SiC nanowire arrays are arranged in the center of the temperature zone of a vertical chemical vapor deposition furnace. Vacuum is drawn, and the vacuum degree of the deposition furnace is controlled at 0.1-0.4 Pa. The deposition furnace is heated to 1000-1300℃ at a heating rate of 5-10℃ / min. After the furnace temperature reaches the reaction temperature, hydrogen and argon are introduced, and trichloromethylsilane (MTS) is introduced into the reaction zone by bubbling. The flow rates of argon, hydrogen, and MTS are controlled at 100-1000 mL / min, 100-1000 mL / min, and 100-1000 mL / min, respectively. The furnace pressure is 3-10 kPa. After reacting for 5-30 min, the gas supply is stopped, the power is turned off, and the furnace is cooled to room temperature to obtain ultrafine SiC nanowires secondary-grown on the surface of the oriented SiC nanowire array.

[0012] The acid-treated carbon fiber is prepared by first treating the carbon fiber cloth with concentrated nitric acid in a 60°C water bath, then washing it with deionized water and anhydrous ethanol until the surface of the carbon fiber cloth is neutral, and then drying it in an oven at 60-100°C for 8-24 hours.

[0013] The carbon fibers were immersed in an ethanol solution of a metal salt catalyst for 2–24 hours.

[0014] The concentration of the metal salt in the ethanol solution of the metal salt catalyst is 0.1–2 mol / L.

[0015] The mass percentage of the SiO2, Si, and C powders is 1:0.1-0.6:0.2-0.7.

[0016] The SiO2, Si, and C powders are ball-milled at 100–200 rpm for 12–24 hours and then dried.

[0017] The metal salts mentioned are one or more of the following, including but not limited to: cobalt nitrate, ferric nitrate, nickel nitrate, ferrous sulfate, cobalt sulfate, nickel sulfate, ferric chloride, cobalt chloride, or nickel chloride.

[0018] An ultrafine SiC nanowire prepared by the method described above is characterized in that: the ultrafine SiC nanowires are grown in situ on the surface of a directional SiC nanowire array, the growth positions are at the endpoints of the SiC nanowires and the directions are randomly distributed, the nanowires are bent and twisted, forming an onion-flower-like multi-level structure of SiC nanowires; the diameter of the secondary-grown SiC nanowires is 110-150 nm and the length is 4-10 μm.

[0019] The SiC nanowire array has SiC nanowires with a diameter of 0.5–1 μm and a length of 30–50 μm.

[0020] An application of a composite material containing ultrafine SiC nanowires prepared by the method described above is characterized in that: the ultrafine SiC nanowires are randomly distributed in growth direction, and the nanowires are bent and entangled to form a three-dimensional network structure, which increases the specific surface area of ​​the substrate and is used as a supercapacitor electrode.

[0021] Beneficial effects

[0022] This invention proposes a method for secondary growth of ultrafine SiC nanowires on the surface of a oriented SiC nanowire array, along with its application. This method enables the rapid growth of fine-diameter SiC nanowires onto the surface of coarse-diameter SiC nanowires. First, a oriented SiC nanowire array is prepared on the surface of a carbon fiber cloth using catalyst-assisted chemical vapor deposition (CVD). Then, using catalyst particles at the tips of the oriented SiC nanowires as catalysts for secondary SiC nanowire growth, ultrafine SiC nanowires are grown in situ at the tips of the oriented SiC nanowires using negative pressure CVD, resulting in multi-level SiC nanowires with an onion-flower-like shape.

[0023] The technical solution provided by this invention features a simple preparation process, rapid secondary growth of ultrafine SiC nanowires, and the absence of an external catalyst. This simplifies the process and avoids catalyst etching of the SiC nanowires, while also ensuring high process repeatability. The ultrafine SiC nanowires prepared by this invention are grown in situ on the surface of a oriented SiC nanowire array via a gas-solid growth mechanism. The prepared hierarchical SiC nanowires have promising development prospects in multiple fields. The random distribution of the growth direction of the ultrafine SiC nanowires, with their bending and entanglement forming a three-dimensional network structure, increases the specific surface area of ​​the substrate, offering broad application potential in supercapacitor electrodes. Furthermore, the excellent bonding between the ultrafine SiC nanowires and the oriented SiC nanowire array, along with structural stability, makes them promising candidates for strengthening and toughening composite materials. Attached Figure Description

[0024] Figure 1 SEM characterization image of the oriented SiC nanowire array on the carbon fiber cloth surface prepared in this invention;

[0025] Figure 2 Low-magnification SEM characterization image of the directional SiC nanowire array surface secondary-grown ultrafine SiC nanowires prepared in this invention;

[0026] Figure 3 High-magnification SEM characterization image of the directional SiC nanowire array with secondary growth on the surface prepared by this invention;

[0027] The accompanying drawings and dimensions illustrate the beneficial effects of the invention:

[0028] Figure 1This is a SEM image of the oriented SiC nanowire array on the carbon fiber cloth surface prepared in this invention. The prepared SiC nanowire array is grown in situ, oriented, and uniformly on the surface of the carbon fiber cloth, with a uniform morphology, smooth nanowire surface, diameter of 0.5–1 μm, and length of 30–50 μm. Furthermore, a spherical catalyst can be observed at the top of the SiC nanowire array, indicating that the growth mechanism of this SiC nanowire array is a catalyst-assisted gas-liquid-solid mechanism.

[0029] Figure 2 This is a SEM image of the directional SiC nanowire array with secondary growth of ultrafine SiC nanowires on the surface prepared by this invention. It clearly shows that a large number of ultrafine SiC nanowires were grown in situ at the catalyst top of the SiCNWs array, with an overall shape resembling an onion flower. Since no catalyst was involved, the growth mechanism of these ultrafine SiC nanowires is likely a gas-solid mechanism.

[0030] Figure 3 As shown, the secondary-grown SiC nanowires have a diameter of 110–150 nm and a length of 4–10 μm. The growth directions are randomly distributed and intersect to form a three-dimensional network structure, increasing the specific surface area of ​​the substrate. Detailed Implementation

[0031] The present invention will now be further described in conjunction with the embodiments and accompanying drawings:

[0032] A method for secondary growth of ultrafine SiC nanowires on the surface of a directional SiC nanowire array, the specific steps of which are as follows:

[0033] Step 1: Preparation of oriented SiC nanowire arrays on carbon fiber cloth surface: First, treat the carbon fiber cloth with concentrated nitric acid in a 60℃ water bath, then wash it with deionized water and anhydrous ethanol until the surface of the carbon fiber cloth is neutral, and dry it in an oven at 60-100℃ for 8-24 hours. Prepare an ethanol solution of metal salt catalyst with a concentration of 0.1-2 mol / L, and immerse the acidified carbon fiber array in the catalyst solution for 2-24 hours, then remove and dry it for later use. Weigh SiO2, Si, and C powders in a mass percentage ratio of 1:0.1-0.6:0.2-0.7, ball mill them at 100-200 rpm for 12-24 hours, and then dry them. Weigh 1-8g of the mixed powder and place it at the bottom of the graphite reaction mold. Arrange the carbon fiber carrying the catalyst above the powder. Place the reaction mold in a horizontal tube furnace and, under the protection of an argon atmosphere with a flow rate of 20-150mL / min, raise the temperature to 1200-1700℃ at a heating rate of 5-10℃ / min. React for 1-8h and then cool the furnace to room temperature to obtain a SiC nanowire array oriented on the surface of the carbon fiber cloth.

[0034] Step 2: Secondary growth of ultrafine SiC nanowires on the surface of the oriented SiC nanowire array: The carbon fibers with SiC nanowire arrays obtained in Step 1 are arranged in the center of the temperature zone of a vertical chemical vapor deposition furnace. A vacuum is drawn, and the vacuum level of the deposition furnace is controlled at 0.1–0.4 Pa. The furnace is heated to 1000–1300 °C at a heating rate of 5–10 °C / min. After the furnace temperature reaches the reaction temperature, hydrogen and argon are introduced, and then trichloromethylsilane (MTS) is introduced into the reaction zone by bubbling. The flow rates of argon, hydrogen, and MTS are controlled at 100–1000 mL / min, 100–1000 mL / min, and 100–1000 mL / min, respectively, and the furnace pressure is 3–10 kPa. After reacting for 5–30 min, the gas supply is stopped, the power is turned off, and the furnace is cooled to room temperature to obtain ultrafine SiC nanowires secondary-grown on the surface of the oriented SiC nanowire array.

[0035] Preferably, the metal salt mentioned in step one is a mixture of one or more of these, but not limited to: cobalt nitrate, ferric nitrate, nickel nitrate, ferrous sulfate, cobalt sulfate, nickel sulfate, ferric chloride, cobalt chloride, and nickel chloride. Specific implementation examples:

[0037] Example 1:

[0038] Step 1: Preparation of oriented SiC nanowire arrays on carbon fiber cloth surface: First, the carbon fiber cloth was treated with concentrated nitric acid in a 60℃ water bath, then washed with deionized water and anhydrous ethanol until the surface of the carbon fiber cloth was neutral, and dried in a 60℃ oven for 24 hours. A 0.2mol / L cobalt nitrate ethanol solution was prepared, and the acidified carbon fibers were immersed in the catalyst solution for 12 hours, then removed and dried for later use. SiO2, Si, and C powders were weighed in a mass ratio of 1:0.45:0.55, ball-milled at 100 rpm for 24 hours, and then dried. 2g of the mixed powder was placed at the bottom of a graphite reaction mold, and the carbon fibers carrying the catalyst were arranged on top of the powder. The reaction mold was placed in a horizontal tube furnace, and under an argon atmosphere with a flow rate of 50mL / min, the temperature was raised to 1550℃ at a heating rate of 5℃ / min and reacted for 2 hours. Then, the furnace was cooled to room temperature to obtain an oriented SiC nanowire array on the surface of the carbon fiber cloth.

[0039] Step 2: Secondary growth of ultrafine SiC nanowires on the surface of the oriented SiC nanowire array: The carbon fibers with SiC nanowire arrays obtained in Step 1 are arranged in the center of the temperature zone of a vertical chemical vapor deposition furnace. A vacuum is drawn, and the vacuum level of the deposition furnace is controlled at 0.2 Pa. The furnace is heated to 1150 °C at a heating rate of 5 °C / min. After the furnace reaches the reaction temperature, hydrogen and argon are introduced, and MTS is introduced into the reaction zone by bubbling. The flow rates of argon, hydrogen, and MTS are controlled at 500 mL / min, 150 mL / min, and 150 mL / min, respectively, and the furnace pressure is 4 kPa. After reacting for 5 min, the gas supply is stopped, the power is turned off, and the furnace is cooled to room temperature to obtain ultrafine SiC nanowires secondary-grown on the surface of the oriented SiC nanowire array.

[0040] Example 2:

[0041] Step 1: Preparation of oriented SiC nanowire arrays on carbon fiber cloth surface: First, the carbon fiber cloth was treated with concentrated nitric acid in a 60℃ water bath, then washed with deionized water and anhydrous ethanol until the surface of the carbon fiber cloth was neutral, and dried in an 80℃ oven for 12 hours. A 0.5mol / L ferric nitrate ethanol solution was prepared, and the acidified carbon fibers were immersed in the catalyst solution for 2 hours, then removed and dried for later use. SiO2, Si, and C powders were weighed in a mass ratio of 1:0.4:0.6, ball-milled at 200 rpm for 12 hours, and then dried. 4g of the mixed powder was placed at the bottom of a graphite reaction mold, and the carbon fibers carrying the catalyst were arranged on top of the powder. The reaction mold was placed in a horizontal tube furnace, and under an argon atmosphere with a flow rate of 100mL / min, the temperature was raised to 1450℃ at a rate of 8℃ / min and reacted for 4 hours. Then, the furnace was cooled to room temperature to obtain an oriented SiC nanowire array on the surface of the carbon fiber cloth.

[0042] Step 2: Secondary growth of ultrafine SiC nanowires on the surface of the oriented SiC nanowire array: The carbon fibers with SiC nanowire arrays obtained in Step 1 are arranged in the center of the temperature zone of a vertical chemical vapor deposition furnace. A vacuum is drawn, and the vacuum level of the deposition furnace is controlled at 0.3 Pa. The furnace is heated to 1200℃ at a heating rate of 7℃ / min. After the furnace temperature reaches the reaction temperature, hydrogen and argon are introduced, and MTS is introduced into the reaction zone by bubbling. The flow rates of argon, hydrogen, and MTS are controlled at 400 mL / min, 200 mL / min, and 150 mL / min, respectively, and the furnace pressure is 5 kPa. After reacting for 15 min, the gas supply is stopped, the power is turned off, and the furnace is cooled to room temperature to obtain ultrafine SiC nanowires secondary-grown on the surface of the oriented SiC nanowire array.

[0043] Example 3:

[0044] Step 1: Preparation of oriented SiC nanowire arrays on carbon fiber cloth surface: First, the carbon fiber cloth was treated with concentrated nitric acid in a 60℃ water bath, then washed with deionized water and anhydrous ethanol until the surface of the carbon fiber cloth was neutral, and dried in a 60℃ oven for 24 hours. A 0.1mol / L nickel nitrate ethanol solution was prepared, and the acidified carbon fibers were immersed in the catalyst solution for 24 hours, then removed and dried for later use. SiO2, Si, and C powders were weighed in a mass ratio of 1:0.6:0.5, ball-milled at 150 rpm for 12 hours, and then dried. 5g of the mixed powder was placed at the bottom of a graphite reaction mold, and the carbon fibers carrying the catalyst were arranged on top of the powder. The reaction mold was placed in a horizontal tube furnace, and under an argon atmosphere with a flow rate of 20mL / min, the temperature was raised to 1600℃ at a rate of 10℃ / min and reacted for 5 hours. Then, the furnace was cooled to room temperature to obtain an oriented SiC nanowire array on the surface of the carbon fiber cloth.

[0045] Step 2: Secondary growth of ultrafine SiC nanowires on the surface of the oriented SiC nanowire array: The carbon fibers with SiC nanowire arrays obtained in Step 1 are arranged in the center of the temperature zone of a vertical chemical vapor deposition furnace. A vacuum is drawn, and the vacuum level of the deposition furnace is controlled at 0.1 Pa. The furnace is heated to 1100℃ at a heating rate of 10℃ / min. After the furnace temperature reaches the reaction temperature, hydrogen and argon are introduced, and MTS is introduced into the reaction zone by bubbling. The flow rates of argon, hydrogen, and MTS are controlled at 800 mL / min, 100 mL / min, and 150 mL / min, respectively, and the furnace pressure is 8 kPa. After reacting for 30 min, the gas supply is stopped, the power is turned off, and the furnace is cooled to room temperature to obtain ultrafine SiC nanowires secondary-grown on the surface of the oriented SiC nanowire array.

[0046] This invention provides a method for secondary growth of ultrafine SiC nanowires on the surface of a oriented SiC nanowire array. The technical solution provided by this invention involves preparing an oriented SiC nanowire array on the surface of a carbon fiber cloth using catalyst-assisted chemical vapor deposition (CVD). Subsequently, using catalyst particles at the tips of the oriented SiC nanowires as catalysts for secondary SiC nanowire growth, ultrafine SiC nanowires are grown in situ at the tips of the oriented SiC nanowires using negative pressure CVD, resulting in a multi-level structured SiC nanowire resembling an onion flower. The technical solution provided by this invention features a simple preparation process, high reproducibility, good nanowire bonding, and structural stability. It can significantly increase the specific surface area of ​​the substrate and has strong application potential in fields such as composite material strengthening and toughening, and supercapacitor electrodes.

[0047] The technical solution of this invention is not limited to the specific embodiments listed above, and various changes can be made. That is, all other embodiments obtained based on the claims and description of this invention are within the protection scope of this invention.

Claims

1. A method for secondary growth of ultrafine SiC nanowires on the surface of a directional SiC nanowire array, characterized in that... The steps are as follows: Step 1: Preparation of oriented SiC nanowire array on carbon fiber cloth surface: Acid-treated carbon fibers are immersed in an ethanol solution of metal salt catalyst and then dried to obtain carbon fiber cloth loaded with catalyst. SiO2, Si, and C mixed powders were placed at the bottom of a graphite reaction mold, and carbon fibers carrying catalysts were arranged above the powders. The reaction mold was placed in a horizontal tube furnace, and under the protection of an argon atmosphere with a flow rate of 20-150 mL / min, the temperature was raised to 1200-1700℃ at a heating rate of 5-10℃ / min. The reaction was carried out for 1-8 h, and then cooled to room temperature with the furnace to obtain a SiC nanowire array oriented on the surface of carbon fiber cloth. Step 2: Secondary growth of ultrafine SiC nanowires on the surface of the oriented SiC nanowire array: Carbon fibers with grown SiC nanowire arrays are arranged in the center of the temperature zone of a vertical chemical vapor deposition furnace. Vacuum is drawn and the vacuum degree of the deposition furnace is controlled at 0.1~0.4 Pa. The deposition furnace is heated to 1000~1300℃ at a heating rate of 5~10℃ / min. After the furnace temperature reaches the reaction temperature, hydrogen and argon are introduced. Trichloromethylsilane (MTS) is then introduced into the reaction zone by bubbling. The flow rates of argon, hydrogen, and MTS are controlled at 100~1000 mL / min, 100~1000 mL / min, and 100~1000 mL / min, respectively. The pressure inside the furnace is 3~10 kPa. After reacting for 5~30 min, the gas supply is stopped, the power is turned off, and the furnace is cooled to room temperature to obtain ultrafine SiC nanowires secondary-grown on the surface of the oriented SiC nanowire array. The acid-treated carbon fiber is prepared by first treating the carbon fiber cloth with concentrated nitric acid in a 60°C water bath, then washing it with deionized water and anhydrous ethanol until the surface of the carbon fiber cloth is neutral, and then drying it in an oven at 60~100°C for 8~24 h. The concentration of the metal salt in the ethanol solution of the metal salt catalyst is 0.1~2 mol / L; The mass percentage of the SiO2, Si, and C powders is 1:0.1~0.6:0.2~0.7; The metal salt is one or more of cobalt nitrate, ferric nitrate, nickel nitrate, ferrous sulfate, cobalt sulfate, nickel sulfate, ferric chloride, cobalt chloride, and nickel chloride.

2. The method for secondary growth of ultrafine SiC nanowires on the surface of a directional SiC nanowire array according to claim 1, characterized in that: The carbon fibers were immersed in an ethanol solution of a metal salt catalyst for 2–24 h.

3. The method for secondary growth of ultrafine SiC nanowires on the surface of a directional SiC nanowire array according to claim 1, characterized in that: The SiO2, Si, and C powders are ball-milled at 100-200 rpm for 12-24 hours and then dried.

4. An ultrafine SiC nanowire prepared by the method according to any one of claims 1 to 3, characterized in that: Ultrafine SiC nanowires are grown in situ on the surface of a directional SiC nanowire array. The growth location is at the endpoint of the SiC nanowire and the direction is randomly distributed. The nanowires are bent and twisted, forming a multi-level structure of SiC nanowires in the shape of onion flowers. The diameter of the secondary-grown SiC nanowires is 110~150 nm and the length is 4~10 μm.

5. The ultrafine SiC nanowires according to claim 4, characterized in that: The SiC nanowire array has SiC nanowires with diameters of 0.5~1 μm and lengths of 30~50 μm.

6. The application of the ultrafine SiC nanowires as described in claim 4 or 5 in composite materials, characterized in that: The growth direction of ultrafine SiC nanowires is randomly distributed, and the nanowires are bent and twisted to form a three-dimensional network structure, which increases the specific surface area of ​​the substrate and is used as a supercapacitor electrode.

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