Oversized SiC whisker as well as preparation method and application thereof

Abstract

The invention provides an oversized SiC whisker as well as a preparation method and application thereof, and belongs to the technical field of inorganic non-metallic materials. The silicon-coated carbon powder with the carbon source uniformly coated with the silicon source is prepared by taking the carbon source and the silicon source as raw materials and adopting a sol-gel method, a pre-forming process is not needed, the silicon-coated carbon powder is directly poured into a crucible to be heated, and the silicon-coated carbon powder is prepared by controlling the rate of microwave input power. According to the method, the microwave coupling heat effect generated in the microwave heating process is intensified to induce the growth of the synthesized SiC whiskers, the high-purity SiC powder with the oversized SiC whisker morphology can be synthesized in a short time, and a new development approach and solution thought are provided for microelectronic devices and the like used in a specific environment.

Description

Technical Field

[0001] The invention relates to the technical field of inorganic non-metallic materials, and in particular to an oversized SiC whisker and a preparation method and application thereof. Background Art

[0002] SiC has a wide range of applications and has always attracted much attention from the public. SiC whiskers have high tensile strength and elastic modulus, good high temperature resistance, wear resistance, corrosion resistance and thermal stability, and excellent semiconductor properties. They can be used as microelectronic devices and are widely used in aerospace, automotive industry, energy industry, electronics industry, biomedical engineering and other fields.

[0003] There are various methods for preparing SiC whiskers, such as chemical vapor deposition, polymer precursor conversion, activated carbon fiber conversion, etc. The stable preparation of large-sized SiC whiskers is an important requirement for promoting the rapid development of the industrial industry. However, the above preparation processes have problems such as high energy consumption, high pollution, and high cost. It is also difficult to efficiently prepare high-purity and large-sized SiC whiskers.

[0004] With further research on SiC whiskers, researchers have discovered the advantages of synthesizing SiC whiskers by microwave heating. Microwave heating is a green, environmentally friendly, energy-efficient preparation technology. Microwave synthesis of SiC relies on the microwave heating effect and non-thermal effect during the reaction process. Wang et al. (Wang J, Zhang Y, Li J, Zhang H, Song S, Zhang S. Catalytic effect of cobalt on microwave synthesis of β-SiC powder. Powder Technology. 2017 Jul 15; 317: 209-15.) used silicon powder and phenolic resin as raw materials to synthesize SiC whiskers with a diameter of 30 to 100 nm by microwave under an argon protective atmosphere; Yuan et al. (Yuan K, Han D, Liang J, Zhao W, Li M, Zhao B, Liu W, Lu H, Wang H, Xu H, Shao G. Microwave induced in-situ formation of SiC nanowires on SiCNO ceramic aerogels with excellent electromagnetic wave absorption performance. Journal of Advanced Ceramics. 2021 Oct; 10: 1140-51.) combined with SiC aerogel substrate to synthesize SiC whiskers and nanowires by microwave under a nitrogen atmosphere; Hao et al. (Hao W, Zhang X, Li G, Zhang J, Guan L, Li M, Zhao B, Gao Q, Fan B, Zhang R. Typical growth of SiC fibers prepared by microwave heating with NiCl2 catalyst. Journal of Alloys and Compounds. 2023Jun 15; 946: 169437.) The reaction process of microwave catalytic synthesis of SiC fibers with nickel chloride as catalyst in an oxygen-containing atmosphere was investigated. By controlling the microwave reaction conditions, reaction raw materials, catalyst and its concentration, the synthesis of SiC with different micromorphologies can be achieved.

[0005] However, although there are various preparation methods for microwave synthesized SiC whiskers, the preparation of large-sized SiC whiskers has not yet been achieved. Summary of the invention

[0006] The purpose of the present invention is to provide an ultra-large-sized SiC whisker and a preparation method and application thereof, which can synthesize high-purity SiC powder with ultra-large-sized SiC whisker morphology, and solve the problem that it is difficult to prepare ultra-large-sized microscopic whisker morphology in the existing SiC whisker preparation process.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The present invention provides a method for preparing an oversized SiC whisker, comprising the following steps:

[0009] Mixing a carbon source, an organic acid, water and a dispersant to obtain a carbon source dispersion;

[0010] After mixing the carbon source dispersion with the silicon source, adding an alkali solution to the obtained mixture to perform a sol-gel reaction to obtain a gel precursor;

[0011] The gel precursor is sequentially dried and ground to obtain silicon-coated carbon powder;

[0012] The silicon-coated carbon powder is subjected to microwave sintering to obtain super-large SiC whiskers;

[0013] The diameter of the super-large SiC whisker is 2-10 μm and the length is 20-400 μm.

[0014] Preferably, the carbon source includes activated carbon, coal powder or graphite; the particle size of the carbon source is 150 to 300 meshes;

[0015] The organic acid includes citric acid or oxalic acid; the molar ratio of the carbon source to the organic acid is 100:(8-15).

[0016] Preferably, the silicon source includes tetraethyl orthosilicate or silica sol; and the molar ratio of the carbon element in the carbon source to the silicon element in the silicon source is 3:(0.8-1.5).

[0017] Preferably, the dispersant comprises anhydrous ethanol or water; the volume ratio of the silicon source, the dispersant and water is (1-3): (5-10): (5-10).

[0018] Preferably, the alkali solution includes ammonia water or sodium hydroxide solution; the endpoint pH value of the sol-gel reaction is 8-10; and the temperature of the sol-gel reaction is 40-60°C.

[0019] Preferably, the drying temperature is 80-110° C., and the drying time is 8-12 hours; and the particle size of the silicon-coated carbon powder is 100-200 meshes.

[0020] Preferably, during microwave sintering, the thickness of the silicon-coated carbon powder in the crucible is 15 to 60 mm.

[0021] Preferably, the microwave sintering conditions include: temperature of 1100-1300° C., microwave frequency of 2450 MHz, wavelength of 1 mm-1 m, input power rate of 0.1-0.7 kW / min, and holding time of 10-60 min.

[0022] The present invention provides an ultra-large-sized SiC whisker prepared by the preparation method described in the above technical solution.

[0023] The present invention provides the use of the super-large-size SiC whiskers described in the above technical solution in reinforced and toughened composite materials, electronic packaging materials, fuel cell electrode materials or high-temperature structural materials.

[0024] The invention provides a method for preparing an ultra-large-sized SiC whisker. The method uses a carbon source and a silicon source as raw materials, adopts a sol-gel method to prepare a silicon-coated carbon powder in which a silicon source uniformly coats a carbon source, directly performs microwave heating treatment on the silicon-coated carbon powder without a preforming step (i.e., without a pressing block, without burying a wave-transmitting powder for atmosphere protection), controls the rate of microwave input power, strengthens the growth-inducing effect of the microwave coupling thermal effect generated during the microwave heating process on the synthesized SiC whisker, has accurate temperature measurement, fast temperature rise, and is conducive to gas phase generation in the reaction. Therefore, the method can synthesize a high-purity SiC powder with an ultra-large-sized SiC whisker morphology in a short time, and provides a new development path and solution idea for microelectronic devices for specific environments.

[0025] The present invention adopts a sol-gel method to prepare raw material powder with silicon dioxide uniformly coating the surface of carbon particles. The sol-gel method can increase the contact area between the carbon source and the silicon source, promote the rapid reaction of the raw materials, and accelerate the melting of silicon dioxide during the reaction.

[0026] The present invention uses a non-preformed processing process to process silicon-coated carbon powder, which strengthens the influence of microwave coupling thermal effect on the synthesis of SiC during the microwave heating reaction process of preparing SiC. By adjusting the input power rate of microwave heating to prepare SiC powder, SiC whiskers with super large size can be prepared in a short time.

[0027] The invention further strengthens the gain effect of the strong microwave coupling thermal effect brought by the preform-free raw material processing process by adjusting the input power rate in the SiC preparation reaction process by microwave heating, induces the rearrangement of SiC grains generated in the reaction process, and completes the perfect crystal growth of SiC in a short time, thereby growing SiC whiskers with ultra-large size.

[0028] The preparation steps of the invention are simple and easy to implement, the preparation time is short, there is no pollution, and the raw material price is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a heating curve diagram of the process of preparing SiC powder by microwave heating in Example 1 of the present invention;

[0030] Figure 2 This is the XRD pattern of the SiC powder sample prepared by microwave heating in Example 1 of the present invention;

[0031] Figure 3 This is the XRD pattern of the SiC powder sample prepared by microwave heating in Example 2 of the present invention;

[0032] Figure 4 This is a SEM image (10 μm) of a SiC powder sample prepared by microwave heating in Example 1 of the present invention;

[0033] Figure 5 This is a SEM image (1 μm) of a SiC powder sample prepared by microwave heating in Example 1 of the present invention;

[0034] Figure 6 This is a SEM image (10 μm) of a SiC powder sample prepared by microwave heating in Example 2 of the present invention;

[0035] Figure 7 This is a SEM image (10 μm) of a SiC powder sample prepared by microwave heating in Example 3 of the present invention;

[0036] Figure 8 This is a SEM image (10 μm) of a SiC powder sample prepared by microwave heating in Example 4 of the present invention;

[0037] Fig. 9 This is a SEM image (10 μm) of a SiC powder sample prepared by microwave heating in Example 5 of the present invention;

[0038] Fig.10 This is the SEM image (5 μm) of the SiC powder sample prepared by microwave heating in Example 6 of the present invention. DETAILED DESCRIPTION

[0039] In the present invention, unless otherwise specified, the required raw materials or reagents are commercially available products well known to those skilled in the art.

[0040] The present invention provides a method for preparing an oversized SiC whisker, comprising the following steps:

[0041] Mixing a carbon source, an organic acid, water and a dispersant to obtain a carbon source dispersion;

[0042] After mixing the carbon source dispersion with the silicon source, adding an alkali solution to the obtained mixture to perform a sol-gel reaction to obtain a gel precursor;

[0043] The gel precursor is sequentially dried and ground to obtain silicon-coated carbon powder;

[0044] The silicon-coated carbon powder is subjected to microwave sintering to obtain super-large SiC whiskers;

[0045] The diameter of the super-large SiC whisker is 2-10 μm and the length is 20-400 μm.

[0046] The present invention mixes a carbon source, an organic acid, water and a dispersant to obtain a carbon source dispersion.

[0047] In the present invention, water and an organic acid are preferably mixed to obtain an acidic solution with a pH of 2 to 3, a carbon source is added to the acidic solution and stirred for 30 minutes, and a dispersant is added to obtain a carbon source dispersion.

[0048] In the present invention, the carbon source preferably includes activated carbon, coal powder or graphite; the activated carbon preferably includes fruit shell activated carbon, wood activated carbon or coal activated carbon; the particle size of the carbon source is preferably 150 to 300 meshes, more preferably 200 meshes. The present invention has no particular limitation on the source of the carbon source, which can be obtained in a manner known in the art or a commercially available product.

[0049] In the present invention, the organic acid preferably includes citric acid or oxalic acid; the molar ratio of the carbon source to the organic acid is preferably 100:(8-15), more preferably 100:(9-11).

[0050] After obtaining the carbon source dispersion, the present invention mixes the carbon source dispersion with a silicon source, and then adds an alkali solution to the obtained mixture to perform a sol-gel reaction to obtain a gel precursor.

[0051] The present invention preferably adds the silicon source after stirring the carbon source dispersion in a constant temperature water bath at 40-60°C for 30-60 minutes, and continues stirring for 120 minutes or until there is no particle suspension on the surface of the liquid mixture and no particle aggregation inside, and then titrates with an alkaline solution to the endpoint pH to obtain a precursor in a gel state; the stirring speed is preferably 270-380 r / min, more preferably 300-320 r / min.

[0052] In the present invention, the silicon source preferably includes tetraethyl orthosilicate or silica sol; the molar ratio of carbon element in the carbon source to silicon element in the silicon source is preferably 3:(0.8-1.5), more preferably 3:1-1.5. In the present invention, the carbon source plays a role in absorbing microwaves and rapidly coupling to generate heat, and the silicon source can be uniformly coated on the surface of carbon particles through the sol-gel method, increasing the contact area with carbon, and achieving a rapid, uniform and sufficient reaction.

[0053] In the present invention, the dispersant preferably includes anhydrous ethanol or water; the present invention utilizes the dispersant to assist in the uniform dispersion of the carbon source; the volume ratio of the silicon source, the dispersant and the water is preferably (1-3):(5-10):(5-10), more preferably 1:5:5 or 1:10:10.

[0054] In the present invention, the alkali solution preferably includes aqueous ammonia (mass concentration 23%) or sodium hydroxide solution; the endpoint pH value of the sol-gel reaction is preferably 8-10, more preferably 9; the temperature of the sol-gel reaction is preferably 40-60°C, more preferably 40-50°C.

[0055] The present invention has no particular limitation on the concentration of the alkali solution, and the concentration can be adjusted to a desired pH value according to actual needs.

[0056] After obtaining the gel precursor, the present invention sequentially dries and grinds the gel precursor to obtain silicon-coated carbon powder.

[0057] In the present invention, the gel precursor is preferably dried in a blast drying oven to a water-free agglomerate state, and then ground in a mortar to obtain silicon-coated carbon powder.

[0058] In the present invention, the drying temperature is preferably 80 to 110° C., more preferably 90 to 100° C., and the drying time is preferably 8 to 12 hours, more preferably 8 to 10 hours.

[0059] In the present invention, the particle size of the silicon-coated carbon powder is preferably 100-200 meshes.

[0060] After obtaining the silicon-coated carbon powder, the present invention performs microwave sintering on the silicon-coated carbon powder to obtain super-large SiC whiskers; the super-large SiC whiskers have a diameter of 2 to 10 μm and a length of 20 to 400 μm.

[0061] In the present invention, when microwave sintering is performed, the thickness of the silicon-coated carbon powder in the crucible is preferably 15 to 60 mm, more preferably 30 to 50 mm.

[0062] In the present invention, the conditions for the microwave sintering preferably include: a temperature of 1100-1300°C, a microwave frequency of 2450MHz, a wavelength of 1mm-1m, an input power rate of 0.1-0.7kW / min, and a holding time of 10-60min; the temperature of the microwave sintering is more preferably 1200-1300°C, the holding time is more preferably 10min, and the input power rate is more preferably 0.14-0.7kW / min.

[0063] The present invention provides an ultra-large-sized SiC whisker prepared by the preparation method described in the above technical solution.

[0064] The present invention provides the use of the super-sized SiC whiskers described in the above technical solution in reinforced and toughened composite materials, electronic packaging materials, fuel cell electrode materials or high-temperature structural materials. The present invention has no special limitation on the method of the application, and the application method of SiC whiskers well known in the art can be used in the corresponding field.

[0065] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention. The experimental methods described in the embodiments of the present invention are conventional methods unless otherwise specified.

[0066] The following experimental methods and detection methods, unless otherwise specified, are conventional methods; the following reagents and raw materials, unless otherwise specified, are commercially available.

[0067] Example 1

[0068] This embodiment provides a method for preparing ultra-large SiC whiskers by microwave, comprising the following steps:

[0069] (1) Preparation of silicon-coated carbon powder by sol-gel method:

[0070] S1. Mix 375 mL of deionized water and 5 g of citric acid to obtain an acidic solution with a pH of 3, add 1 mol of activated carbon powder with a particle size of 200 mesh into the solution and stir for 30 min, then add anhydrous ethanol, stir the obtained carbon source dispersion in a constant temperature water bath at 40°C for 30 min, add tetraethyl orthosilicate, continue stirring in a constant temperature water bath at 40°C at 300 r / min for 120 min, and then titrate with ammonia water (mass concentration of 23%) to a pH of 9 to obtain a precursor in a gel state; wherein the molar ratio of the activated carbon powder to the citric acid is 100:11; the molar ratio of the carbon element in the activated carbon to the silicon element in the tetraethyl orthosilicate is 3:1; the volume ratio of the tetraethyl orthosilicate, anhydrous ethanol, and deionized water is 1:5:5;

[0071] S2, placing the precursor in the gel state in step S1 in a blast drying oven, drying at 100° C. for 8 h, and grinding to obtain silicon-coated carbon powder with a particle size of 100 to 200 meshes;

[0072] (2) Preparation of SiC powder by microwave heating:

[0073] A 30 mm thick silicon-coated carbon powder was placed in a cylindrical crucible, and the silicon-coated carbon powder was heated by microwave. The microwave input power rate was adjusted to 0.14 kW / min, the microwave wavelength was set to 1 m, the frequency was set to 2450 MHz, the sintering temperature was set to 1200° C., and the temperature was kept for 10 minutes to obtain SiC powder.

[0074] Figure 1 1 is a heating curve diagram of the process of preparing SiC powder by microwave heating in Example 1 of the present invention; Figure 1 As shown, by using microwave heating and adjusting the rate of microwave input power, the sample reached 600°C in 35 minutes and 1200°C in 53 minutes, followed by 10 minutes of insulation. The whole process was completed within 62 minutes.

[0075] Example 2

[0076] The difference from Example 1 is that the rate of regulating the microwave input power is 0.7 kW / min.

[0077] Example 3

[0078] The difference from Example 1 is that the molar ratio of activated carbon to citric acid is 100:9;

[0079] The molar ratio of carbon in activated carbon to silicon in ethyl orthosilicate is 3:1.5.

[0080] Example 4

[0081] The difference from Example 1 is that the microwave heating temperature is 1300°C.

[0082] Example 5

[0083] The difference from Example 1 is that: the silicon source is silica sol;

[0084] The volume ratio of silica sol, anhydrous ethanol and deionized water is 1:10:10.

[0085] Example 6

[0086] The only difference from Example 1 is that the carbon source is graphite powder with a particle size of 200 meshes;

[0087] The stirring speed of the sol-gel reaction was 320 r / min in a constant temperature water bath at 40°C.

[0088] Test Case

[0089] (a) X-ray diffraction test:

[0090] The SiC powders prepared in Examples 1 and 2 were tested by XRD using a SmartLab X-ray diffraction analyzer (XRD) from Rigaku Corporation. The results are as follows: Figure 2 and Figure 3 As shown;

[0091] Depend on Figure 2 It can be seen that the precursor prepared by the sol-gel method does not need to be preformed. Under the action of the microwave input power rate of 0.14kW / min, microwave heating at 1200℃ and heat preservation for 10 minutes can obtain high-purity SiC powder. This shows that the sol-gel method greatly increases the contact area between the carbon source and the silicon source, ensuring the stable reaction.

[0092] Depend on Figure 3 It can be seen that by changing the microwave input power rate, the main diffraction peak of SiC is also detected in the sample synthesized by the reaction, which shows that by using the method of the present invention, large-sized SiC whiskers can be synthesized even if the input power rate and temperature conditions are changed.

[0093] (ii) Scanning electron microscope test:

[0094] The microscopic morphology of the SiC powder samples of Examples 1 to 6 was tested using a JSM-7001F scanning electron microscope (SEM) produced by JEOL Ltd. The results are as follows: Figures 4 to 10 As shown;

[0095] Figure 4 This is the microscopic morphology of the SiC sample prepared in Example 1. It can be seen that the microscopic morphology of the SiC powder prepared by microwave heating of silicon-coated carbon powder is oversized SiC whiskers with a diameter of 4 to 10 μm and a length of 20 to 300 μm.

[0096] Figure 5 This is a further enlarged microscopic morphology of the SiC sample prepared in Example 1. It can be seen that the surface of the whiskers is very clean, which is due to the removal effect of the microwave plasma effect during the microwave preparation process.

[0097] Figure 6 In the microscopic morphology of the SiC sample prepared in Example 2, the morphology of ultra-large-sized whiskers can also be observed. The diameter of the whiskers is 4-10 μm and the length is 20-80 μm. It is confirmed that under the same experimental conditions such as sintering temperature and holding time, carbon-silicon ratio of raw materials, the size of the ultra-large SiC whiskers can be controlled by changing the rate of microwave input power, that is, by increasing the input power rate, reducing the coupled thermal effect generated by the reaction raw materials under the action of microwaves and the newly generated SiC in the reaction process, the length of the synthesized SiC whiskers is controlled to be shorter under the same sintering temperature and holding time.

[0098] Figure 7 From the microscopic morphology of the SiC sample prepared in Example 3, the oversized whisker morphology can also be observed. The diameter of the whiskers is 2-10 μm and the length is 20-70 μm. This proves that under the same experimental conditions such as sintering temperature, holding time, input power rate, etc., the size of the oversized SiC whiskers can be controlled by changing the carbon-silicon ratio of the raw material, that is, the raw material increases the silicon source ratio, and the temperature is increased by absorbing microwaves to generate coupled heat in the initial stage of the reaction. The increase in the silicon source ratio will lead to a decrease in the reaction rate, thereby affecting the growth of the whiskers.

[0099] Figure 8 From the microscopic morphology of the SiC sample prepared in Example 4, it can be seen that the oversized whisker morphology is observed, with a diameter of 2 to 10 μm and a length of 20 to 250 μm. This proves that under the same experimental conditions of holding time, input power rate, carbon-silicon ratio of raw materials, the size of the oversized SiC whiskers can be controlled by changing the sintering temperature, that is, by increasing the reaction temperature, the SiC synthesized by the reaction will diffuse and rearrange its surface atoms during the high temperature and holding stage, which helps the growth of SiC whiskers.

[0100] Fig. 9 In the microscopic morphology of the SiC sample prepared in Example 5, the morphology of ultra-large-sized whiskers can also be observed. The diameter of the whiskers is 2-10 μm and the length is 20-80 μm. This proves that under the same experimental conditions such as sintering temperature and holding time, input power rate, and raw material carbon-silicon ratio, the size of the ultra-large SiC whiskers can be controlled by changing the silicon source raw material, that is, the encapsulation of the carbon source after hydrolysis of silica sol is not as good as the encapsulation of the hydrolyzate of ethyl orthosilicate, so the size of the SiC whiskers can be controlled by changing the silicon source to silica sol.

[0101] Fig.10 From the microscopic morphology of the SiC sample prepared in Example 6, the oversized whisker morphology can also be observed. The diameter of the whisker is 2-5 μm and the length is 20-50 μm. It is confirmed that under the same experimental conditions such as sintering temperature and holding time, input power rate, and raw material carbon-silicon ratio, the size of the oversized SiC whiskers can be controlled by changing the carbon source, that is, the graphite particles are composed of layered atomic crystals, which are more regular than the structure of activated carbon. There are a large number of micropores and mesopores inside the activated carbon particles and they have a large specific surface area. Activated carbon is more likely to generate coupled heat during the reaction process. After adjusting the carbon source to graphite, the reaction rate will be reduced, which can reduce the size of the whiskers.

[0102] Figures 4 to 10 The results show that Examples 1 to 6 of the present invention all produce SiC powders having an ultra-large SiC whisker morphology.

[0103] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing an oversized SiC whisker, characterized in that: The following steps are involved: Mixing a carbon source, an organic acid, water and a dispersant to obtain a carbon source dispersion; After mixing the carbon source dispersion with the silicon source, adding an alkali solution to the obtained mixture to perform a sol-gel reaction to obtain a gel precursor; The gel precursor is sequentially dried and ground to obtain silicon-coated carbon powder; The silicon-coated carbon powder is subjected to microwave sintering to obtain super-large SiC whiskers; The diameter of the super-large SiC whisker is 2-10 μm and the length is 20-400 μm.

2. The preparation method according to claim 1, characterized in that: The carbon source includes activated carbon, coal powder or graphite; the particle size of the carbon source is 150-300 mesh; The organic acid includes citric acid or oxalic acid; the molar ratio of the carbon source to the organic acid is 100:(8-15).

3. The preparation method according to claim 1 or 2, characterized in that: The silicon source includes tetraethyl orthosilicate or silica sol; the molar ratio of the carbon element in the carbon source to the silicon element in the silicon source is 3:(0.8-1.5).

4. The preparation method according to claim 3, characterized in that: The dispersant comprises anhydrous ethanol or water; the volume ratio of the silicon source, the dispersant and the water is (1-3):(5-10):(5-10).

5. The preparation method according to claim 1, characterized in that: The alkaline solution includes ammonia water or sodium hydroxide solution; the endpoint pH value of the sol-gel reaction is 8-10; and the temperature of the sol-gel reaction is 40-60°C.

6. The preparation method according to claim 1 or 5, characterized in that: The drying temperature is 80-110° C. and the drying time is 8-12 hours; the particle size of the silicon-coated carbon powder is 100-200 meshes.

7. The preparation method according to claim 1, characterized in that: During microwave sintering, the thickness of the silicon-coated carbon powder in the crucible is 15 to 60 mm.

8. The preparation method according to claim 1 or 7, characterized in that: The microwave sintering conditions include: temperature of 1100-1300° C., microwave frequency of 2450 MHz, wavelength of 1 mm-1 m, input power rate of 0.1-0.7 kW / min, and heat preservation time of 10-60 min.

9. The super-large SiC whisker prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the super-sized SiC whiskers according to claim 9 in reinforced and toughened composite materials, electronic packaging materials, fuel cell electrode materials or high-temperature structural materials.

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