Silicon carbide whisker, and preparation method therefor and use thereof

Abstract

A silicon carbide whisker, and a preparation method therefor and the use thereof. The silicon carbide whisker comprises a single-crystal fibrous main body and a silicon dioxide layer that covers the surface of the single-crystal fibrous main body, wherein one end of the single-crystal fibrous main body is provided with a block; and the block contains SiO2 and SiC. In the provided silicon carbide whisker, by means of the arrangement of the silicon dioxide layer, the interfacial affinity between the silicon carbide whisker and the oxide is improved, the stress transfer is promoted, and a toughening mechanism is activated, such that the fracture toughness of a composite material is improved; moreover, the silicon dioxide layer further protects the whisker from oxidation or chemical attack, and maintains the reinforcing effect thereof. By means of the arrangement of the block at one end of the single-crystal fibrous main body, the block enhances the interfacial bonding force by means of a mechanical interlocking effect, and significantly improves the whisker pull-out work, thereby optimizing crack propagation resistance and improving the toughness of the composite material.

Description

A silicon carbide whisker, its preparation method and application Technical Field

[0001] This invention belongs to the field of inorganic materials technology, and relates to a silicon carbide material, and more particularly to a silicon carbide whisker and its preparation method and application. Background Technology

[0002] The production of silicon carbide whiskers faces problems such as inconsistent quality and purity as well as low yield. Generally speaking, the physical properties of silicon carbide whiskers depend on the reaction parameters of the growth process. The reaction parameters that affect the growth process include the physicochemical properties of the raw materials, catalysts, sintering atmosphere and reaction temperature. In addition, some studies have pointed out that in the VS (Vapor-Solid) growth mechanism of whiskers, the supersaturation of the reaction gas in the growth device has a great influence on the growth of whiskers.

[0003] Existing technologies focus on the large-scale preparation of silicon carbide whiskers in open or semi-open environments. However, in such reaction systems, the flow of inert gas throughout the reaction device will cause the loss of SiO and CO, resulting in a reaction gas concentration gradient within the reaction device and having a continuous impact on the supersaturation of the reaction gas in the environment.

[0004] Therefore, how to break the concentration gradient and control the supersaturation of the reaction gas to obtain silicon carbide whiskers with controllable morphology is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a silicon carbide whisker, its preparation method and application, wherein the silicon carbide whisker has a specific morphological structure, which can enhance the interfacial affinity between the whisker and the oxide, and can provide a mechanical interlocking function to enhance the toughness of toughened ceramics.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a silicon carbide whisker, the silicon carbide whisker comprising a single-crystal fibrous body and a silicon dioxide oxide layer covering the surface of the single-crystal fibrous body;

[0008] One end of the single-crystal fibrous host has a bulk; the bulk contains SiO2 and SiC.

[0009] The silicon carbide whiskers provided by this invention improve the interfacial affinity between silicon carbide whiskers and oxides through the addition of a silicon dioxide oxide layer, promoting stress transfer and activating the toughening mechanism, thereby enhancing the fracture toughness of the composite material. Simultaneously, the silicon dioxide oxide layer protects the whiskers from oxidation or chemical corrosion, maintaining their reinforcing effect. By setting a bulk material at one end of the single-crystal fibrous matrix, this bulk material enhances the interfacial bonding force through a mechanical interlocking effect, significantly increasing the whisker pull-out work, thereby optimizing crack propagation resistance and improving the toughness of the composite material.

[0010] Preferably, the average diameter of the silicon carbide whiskers is 0.1 μm to 5 μm.

[0011] Preferably, the aspect ratio of the silicon carbide whiskers is 10 to 200.

[0012] Preferably, the average thickness of the silicon dioxide oxide layer is 1 nm to 10 nm.

[0013] Preferably, the equivalent diameter of the block is 0.3 μm to 5 μm.

[0014] Preferably, the method for preparing the silicon carbide whiskers includes:

[0015] Silicon carbide hollow sphere precursors are prepared; then sintered in a protective atmosphere to remove carbon, yielding silicon carbide clusters; the silicon carbide clusters are dispersed to obtain silicon carbide whiskers;

[0016] The silicon carbide hollow sphere precursor is a hollow sphere with at least two shell layers;

[0017] The innermost layer of the at least two-shell structure is a silicon dioxide layer;

[0018] The outermost layer of the at least two-layer shell structure is an organic carbon layer, and the residual carbon rate of the organic carbon layer is more than 40%.

[0019] Preferably, the method for preparing the silicon carbide hollow sphere precursor includes a spray drying method, which includes the following steps:

[0020] By mixing organic carbon sources and silicon sources, a mixed slurry is obtained;

[0021] The mixed slurry is spray-dried to obtain the silicon carbide hollow sphere precursor.

[0022] Preferably, the organic carbon source includes any one or a combination of at least two of phenolic resin, polyimide, or modified carboxymethyl cellulose;

[0023] Preferably, the silicon source includes any one or a combination of at least two of silicon dioxide, diatomaceous earth, rice husk ash, or silicon monoxide;

[0024] Preferably, the mass ratio of the organic carbon source to the silicon source is 1:1 to 5:1;

[0025] Preferably, the solid content of the mixed slurry is 15wt%-50wt%;

[0026] Preferably, the inlet air temperature of the spray dryer is 120℃-180℃, and the outlet air temperature is 80℃-110℃.

[0027] Preferably, the sintering temperature is 1400℃-1600℃.

[0028] Preferably, the decarbonization is carried out in an oxygen-containing atmosphere at a temperature of 500℃-900℃.

[0029] In a second aspect, the present invention provides a composite material comprising the silicon carbide whiskers described in the first aspect.

[0030] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The silicon carbide whiskers provided by this invention improve the interfacial affinity between silicon carbide whiskers and oxides by setting a silicon dioxide oxide layer, promote stress transfer, and activate the toughening mechanism, thereby improving the fracture toughness of the composite material; at the same time, the silicon dioxide oxide layer also protects the whiskers from oxidation or chemical erosion and maintains their reinforcing effect.

[0033] By setting a block at one end of the single-crystal fibrous matrix, the block enhances the interfacial bonding force through the mechanical interlocking effect, significantly improves the whisker pull-out work, thereby optimizing crack propagation resistance and improving the toughness of the composite material. Attached Figure Description

[0034] Figure 1 is a schematic diagram of the structure of the silicon carbide hollow sphere precursor obtained by the preparation method of the present invention;

[0035] Figure 2 is a schematic diagram of the structure of the material obtained after sintering in the preparation method of the present invention;

[0036] Figures 3 and 4 are SEM images of the silicon carbide hollow sphere precursor obtained by spray drying in Example 1 of the present invention.

[0037] Figure 5 is a SEM image of the silicon carbide hollow sphere precursor after sintering in Example 1 of the present invention.

[0038] Figure 6 is a SEM image of the silicon carbide clusters obtained after carbon removal in Example 1 of the present invention.

[0039] Figure 7 is a SEM image of the silicon carbide whiskers obtained in Example 1 of the present invention;

[0040] Figures 8 and 9 are TEM images of the silicon carbide whiskers obtained in Example 1 of the present invention;

[0041] Figure 10 is the XRD pattern of the silicon carbide whiskers obtained in Example 1 of the present invention;

[0042] Figures 11-14 are TEM analysis images of the silicon carbide whiskers obtained in Example 1 of the present invention;

[0043] Figures 15 and 16 are TEM images of the bulk structure of silicon carbide whiskers obtained in Embodiment 1 of the present invention;

[0044] Figure 17 is an EDS mapping diagram of the silicon carbide whisker bulk structure obtained in Embodiment 1 of the present invention;

[0045] Figure 18 is a SEM image of the silicon carbide hollow sphere precursor obtained by spray drying in Example 2 of the present invention;

[0046] Figure 19 is a SEM image of the silicon carbide hollow sphere precursor after sintering in Example 2 of the present invention.

[0047] Figure 20 is a SEM image of the silicon carbide clusters obtained after carbon removal in Example 2 of the present invention;

[0048] Figure 21 is a SEM image of the silicon carbide hollow sphere precursor obtained by spray drying in Example 3 of the present invention;

[0049] Figure 22 is a SEM image of the silicon carbide hollow sphere precursor after sintering in Example 3 of the present invention;

[0050] Figure 23 is a SEM image of the silicon carbide clusters obtained after carbon removal in Example 3 of the present invention.

[0051] Wherein: 1, silicon dioxide layer; 2, organic carbon layer. Detailed Implementation

[0052] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0053] An embodiment of the present invention provides a silicon carbide whisker, the silicon carbide whisker comprising a single-crystal fibrous body and a silicon dioxide oxide layer covering the surface of the single-crystal fibrous body;

[0054] One end of the single-crystal fibrous host has a bulk; the bulk contains SiO2 and SiC.

[0055] The silicon carbide whiskers provided by this invention improve the interfacial affinity between silicon carbide whiskers and oxides through the addition of a silicon dioxide oxide layer, promoting stress transfer and activating the toughening mechanism, thereby enhancing the fracture toughness of the composite material. Simultaneously, the silicon dioxide oxide layer protects the whiskers from oxidation or chemical corrosion, maintaining their reinforcing effect. By setting a bulk material at one end of the single-crystal fibrous matrix, this bulk material enhances the interfacial bonding force through a mechanical interlocking effect, significantly increasing the whisker pull-out work, thereby optimizing crack propagation resistance and improving the toughness of the composite material.

[0056] In some embodiments, the average diameter of the silicon carbide whiskers is 0.1 μm to 5 μm, for example, it can be 0.1 μm, 0.2 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 4 μm or 5 μm, etc.

[0057] In some embodiments, the aspect ratio of the silicon carbide whiskers is 10 to 200, for example, it can be 10, 30, 50, 80, 100, 120, 150, 160, 180 or 200.

[0058] In some embodiments, the average thickness of the silicon dioxide oxide layer is 1 nm to 10 nm, for example, it can be 1 nm, 3 nm, 5 nm, 6 nm, 8 nm or 10 nm.

[0059] In some embodiments, the equivalent diameter of the block is 0.3μm to 5μm, for example, it can be 0.3μm, 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 4μm or 5μm, etc.

[0060] In some embodiments, the method for preparing the silicon carbide whiskers includes:

[0061] Silicon carbide hollow sphere precursors were prepared; then sintered in a protective atmosphere (the structural schematic diagram of the material obtained after sintering is shown in Figure 2) to remove carbon and obtain silicon carbide clusters; the silicon carbide clusters were dispersed to obtain silicon carbide whiskers.

[0062] Figure 1 shows a schematic diagram of the structure of the silicon carbide hollow sphere precursor obtained by the preparation method of the present invention. The innermost layer is a silicon dioxide layer 1, and the outermost layer is an organic carbon layer 2.

[0063] In some embodiments, the method for preparing the silicon carbide hollow sphere precursor includes spray drying or template method.

[0064] For example, the spray drying method includes the following steps: mixing an organic carbon source and a silicon source to obtain a mixed slurry; spray drying the mixed slurry to obtain the silicon carbide hollow sphere precursor.

[0065] This invention uses an organic carbon source to obtain a mixed slurry for spray drying, and then spray drying can be used to prepare silicon carbide hollow sphere precursors.

[0066] In some embodiments, the silicon source includes any one or a combination of at least two of silicon dioxide, diatomaceous earth, rice husk ash, or silicon monoxide. Typical but non-limiting combinations include combinations of silicon dioxide and diatomaceous earth, combinations of diatomaceous earth and rice husk ash, combinations of rice husk ash and silicon monoxide, combinations of silicon dioxide, diatomaceous earth, and rice husk ash, combinations of diatomaceous earth, rice husk ash, and silicon monoxide, or combinations of silicon dioxide, diatomaceous earth, rice husk ash, and silicon monoxide.

[0067] In some embodiments, the mass ratio of the organic carbon source to the silicon source is 1:1 to 5:1, for example, it can be 1:1, 2:1, 3:1, 4:1 or 5:1.

[0068] The solid content of the mixed slurry is related to the wall thickness of the silicon carbide hollow sphere precursor obtained by spray drying. If the solid content is too high, the wall thickness will be too large, making the internal space of the hollow sphere too small, which is not conducive to the growth of silicon carbide whiskers. If the solid content is too low, the particle size of the hollow sphere will be too small and the wall too thin, which is also not conducive to the growth of silicon carbide whiskers.

[0069] In some embodiments, the solid content of the mixed slurry is 15wt%-50wt%, for example, it can be 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, or 50wt%.

[0070] The solvent of the mixed slurry of the present invention is capable of dissolving organic carbon sources. For example, the solvent of the mixed slurry includes water and / or organic solvents.

[0071] In some embodiments, the inlet air temperature of the spray dryer is 120°C-180°C, and the outlet air temperature is 80°C-110°C.

[0072] When using spray drying to prepare silicon carbide hollow sphere precursors, the inlet air temperature for spray drying is 120℃-180℃, for example, it can be 120℃, 130℃, 140℃, 150℃, 160℃, 170℃ or 180℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0073] The outlet air temperature of spray drying is 80℃-110℃, for example, it can be 80℃, 90℃, 100℃ or 110℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0074] For example, the template method includes: first preparing carbon spheres, then preparing a silicon dioxide layer on the outside of the carbon spheres, and then removing the internal carbon spheres in an oxygen-containing atmosphere to obtain hollow silicon dioxide spheres. An organic carbon layer is grown on the outer surface of the hollow silicon dioxide spheres to obtain the silicon carbide hollow sphere precursor.

[0075] The preparation method provided by this invention is simple to operate and can obtain a silicon carbide hollow sphere precursor with an innermost silicon dioxide layer and an outermost organic carbon layer with a residual carbon rate of more than 40%. The morphology and structure of the silicon carbide hollow sphere precursor can control the gas supersaturation during silicon carbide crystal preparation, avoid the escape of internal gas, and obtain silicon carbide whiskers with specific morphology.

[0076] In some embodiments, the template method for preparing hollow silica spheres includes:

[0077] (1) Mix carbon source and deionized water at a mass ratio of 1:1 to 1:20, and then perform hydrothermal treatment at 150℃ to 200℃ to obtain carbon balls;

[0078] (2) Mix hexadecyltrimethylammonium bromide with the carbon spheres obtained in step (1) at a mass ratio of 0.5:1 to 0.8:1 to obtain a carbon sphere mixture; add the carbon sphere mixture to an ethanol mixture to obtain a suspension; then pour the TEOS-ethanol solution into the suspension and react for 1 to 10 hours, filter and dry to obtain a precipitate;

[0079] (3) The precipitate obtained in step (2) is decarbonized in an oxygen-containing atmosphere to obtain hollow silica spheres.

[0080] In step (1), the mass ratio of carbon source to deionized water is 1:1 to 1:20, for example, it can be 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19 or 1:20, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0081] If the hydrothermal treatment temperature is too low, the sphere formation rate will be too slow and the sphere size will be too small, resulting in incomplete reaction; if the hydrothermal treatment temperature is too high, the reaction rate will be too fast and the sphere appearance will be poor. Therefore, the hydrothermal treatment temperature in step (1) of this invention is controlled to be 150℃~200℃, for example, it can be 150℃, 160℃, 170℃, 180℃, 190℃ or 200℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0082] The mass ratio of hexadecyltrimethylammonium bromide to carbon spheres in step (2) is 0.5:1 to 0.8:1, for example, it can be 0.5:1, 0.6:1, 0.7:1 or 0.8:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0083] In some embodiments, the carbon source in step (1) includes sucrose.

[0084] The gases used in the oxygen-containing atmosphere described in this invention include oxygen and / or air.

[0085] In some embodiments, the carbon removal temperature in step (3) is 500℃ to 900℃, for example, it can be 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃, 850℃ or 900℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0086] In some embodiments, the ethanol mixture in step (2) comprises ammonia, water, and ethanol.

[0087] The volume ratio of the ammonia to the water is 1:5 to 1:50, for example, it can be 1:5, 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45 or 1:50, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0088] The volume ratio of the ammonia to the ethanol is 1:10 to 1:100, for example, it can be 1:10, 1:20, 1:30, 1:40, 1:50, 1:60, 1:70, 1:80, 1:90 or 1:100, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0089] Optionally, the concentration of the ammonia water is 25wt% to 28wt%, for example, it can be 25wt%, 26wt%, 27wt% or 28wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0090] In some embodiments, the mass ratio of tetraethyl orthosilicate to ethanol in the TEOS-ethanol solution in step (2) is 1:1250 to 1:2000, for example, it can be 1:1250, 1:1300, 1:1400, 1:1500, 1:1600, 1:1700, 1:1800, 1:1900 or 1:2000, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0091] The amount of TEOS-ethanol solution used in step (2) determines the concentration of silicon source in the reaction system, which in turn affects the yield and particle size of hollow silica spheres. When the amount of TEOS-ethanol solution is too large, although it can increase the yield of hollow silica spheres, there is a risk of causing the local reaction to be too fast, resulting in the particle size of hollow silica spheres being too large or the formation of unwanted agglomerates.

[0092] In some embodiments, the mass ratio of the ethanol mixture to the TEOS-ethanol solution in step (2) is 0.5:1 to 0.75:1, for example, it can be 0.5:1, 0.55:1, 0.6:1, 0.65:1, 0.7:1 or 0.75:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0093] In some embodiments, the method for growing the organic carbon layer includes chemical vapor deposition, impregnation, or in-situ polymerization.

[0094] In some embodiments, the impregnation method includes:

[0095] Hollow silica spheres are immersed in an aqueous solution of phenolic resin with a solid content of 30wt% to 60wt%, mixed evenly, and then dried after solid-liquid separation to complete the growth of the organic carbon layer.

[0096] The solid content of the phenolic resin aqueous solution affects the application of the resulting silicon carbide hollow sphere precursor. For example, too low a solid content will result in an incomplete organic carbon layer and the leakage of SiO and CO gases; while too high a solid content will result in a violent carbonization process of the phenolic resin during application, which will damage the morphology of the hollow sphere.

[0097] The solid content of the phenolic resin aqueous solution is 30wt%-60wt%, for example, it can be 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt% or 60wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0098] In some embodiments, the phenolic resin is a water-soluble phenolic resin.

[0099] In some embodiments, the drying temperature is 60°C-100°C, for example, it can be 60°C, 70°C, 80°C, 90°C or 100°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0100] The silicon carbide hollow sphere precursor of the present invention is a hollow sphere having at least two shell layers;

[0101] The innermost layer of the at least two-shell structure is a silicon dioxide layer;

[0102] The outermost layer of the at least two-layer shell structure is an organic carbon layer, and the residual carbon rate of the organic carbon layer is more than 40%.

[0103] In some embodiments, the organic carbon source includes any one or a combination of at least two of phenolic resin, polyimide, or modified carboxymethyl cellulose. Typical but non-limiting combinations include combinations of phenolic resin and polyimide, combinations of polyimide and modified carboxymethyl cellulose, combinations of phenolic resin and modified carboxymethyl cellulose, or combinations of phenolic resin, polyimide, and modified carboxymethyl cellulose.

[0104] The organic carbon source selected in this invention can form a large amount of carbonaceous structure during sintering, with a residual carbon rate of over 40%. As the outermost layer of the silicon carbide hollow sphere precursor, the organic carbon source forms a pyrolytic carbon layer with a sealed structure during sintering, controlling the escape of SiO and CO, thereby controlling the supersaturation of reactive gases, and thus obtaining silicon carbide whiskers with a specific morphology.

[0105] The residual carbon rate mentioned in this invention refers to the percentage of the residual sample mass to the initial sample mass when measured at 1000℃ using a differential calorimeter DSC200 manufactured by Hitachi Scientific Instruments Co., Ltd., under the measurement conditions of heating from room temperature to 1000℃ at a rate of 10℃ / min in an argon atmosphere.

[0106] The residual carbon rate of the organic carbon layer described in this invention is 40% or more, which means that the residual carbon rate of the organic carbon layer material, measured according to the residual carbon rate test method, can reach 40% or more.

[0107] As a preferred technical solution, the organic carbon source is a water-soluble phenolic resin.

[0108] Phenolic resin can form a large amount of carbonaceous structure during sintering, with a residual carbon rate of over 40%. As the outermost layer of the silicon carbide hollow sphere precursor, phenolic resin can form a closed pyrolytic carbon layer during sintering, controlling the escape of SiO and CO, thereby controlling the supersaturation of reactive gases, and thus obtaining silicon carbide whiskers and silicon carbide clusters with the desired specific morphology.

[0109] For example, the modified carboxymethyl cellulose is obtained by modifying carboxymethyl cellulose with N,N-dimethylacrylamide (DMA). The modification with DMA can make the residual carbon content of the modified carboxymethyl cellulose more than 40% at 1000°C.

[0110] In some embodiments, the sintering temperature is 1400℃-1600℃, for example, it can be 1400℃, 1450℃, 1500℃, 1550℃ or 1600℃, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0111] In some embodiments, the decarbonization is carried out in an oxygen-containing atmosphere at a temperature of 500°C-900°C, such as 500°C, 600°C, 700°C, 800°C or 900°C, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0112] The gases used in the oxygen-containing atmosphere described in this invention include oxygen and / or air.

[0113] The method for dispersing silicon carbide clusters to obtain silicon carbide whiskers according to the present invention can employ conventional dispersion methods in the art. In some embodiments, the dispersion method can be ball milling and / or ultrasonic dispersion.

[0114] The ball milling dispersion method specifically involves pouring silicon carbide whisker agglomerates into a polyurethane container, mixing the silicon carbide whisker clusters with alcohol at a solid-liquid ratio of 1:2 to 1:5, using zirconium oxide or silicon nitride balls as the grinding media with a ball-to-material ratio of 4:1 to 10:1, controlling the ball milling speed at 50 r / min to 150 r / min, and milling for 48 h to 120 h. After ball milling, the mixture is dried and sieved to obtain uniformly dispersed silicon carbide whiskers.

[0115] The ultrasonic dispersion method specifically involves pouring silicon carbide whisker agglomerates into a glass beaker, mixing the silicon carbide whisker clusters with alcohol at a solid-liquid ratio of 1:2 to 1:5, adding 0.2wt% to 1wt% of dispersant PVA or PVP, first ultrasonically treating with a low-frequency power of 20kHz to 50kHz for 30 to 60 minutes, and then ultrasonically treating with a high-frequency power of 50kHz to 200kHz for 60 to 120 minutes. After ultrasonic treatment, the mixture is dried and sieved to obtain uniformly dispersed silicon carbide whiskers.

[0116] One embodiment of the present invention provides a composite material comprising silicon carbide whiskers as described in any embodiment.

[0117] The silicon carbide whiskers of the present invention are used as reinforcing components in plastic matrices, metal matrices or ceramic matrices to enhance and toughen them, thereby obtaining plastic matrix composites, metal matrix composites or ceramic matrix composites.

[0118] For example, the composite material of the present invention can be ceramics, cemented carbide, etc., such as alumina ceramics, seron ceramics, TiCN-based ceramics, WC-based cemented carbide, etc.

[0119] Example 1

[0120] This embodiment provides a silicon carbide whisker, the preparation method of which includes the following steps:

[0121] (1) Phenolic resin (YHY-5211, Meisheng Engineering Plastics, the residual carbon rate of this type of phenolic resin was 40% according to the residual carbon rate test method described in this invention) and silica were mixed in a mass ratio of 3:1, and then mixed with water to prepare a slurry with a solid content of 30wt%. The mixture was ball-milled at 300r / min for 5h to ensure uniform mixing.

[0122] (2) Spray drying is performed at a feed rate of 10 r / min to obtain silicon carbide hollow sphere precursor (see Figures 3 and 4 for SEM images; as shown in Figures 3 and 4, the surface of the silicon carbide hollow sphere precursor obtained in this embodiment is smooth); wherein the inlet air temperature of the spray drying is 120°C and the outlet air temperature is 83°C.

[0123] (3) The silicon carbide hollow sphere precursor was sintered at 1450℃ for 3h in an argon atmosphere (the SEM image of the sintered material is shown in Figure 5. As can be seen from Figure 5, the particle morphology after sintering is good); then, under an oxygen atmosphere, carbon was removed at 800℃ for 3h to obtain silicon carbide clusters (the SEM image is shown in Figure 6).

[0124] (4) Disperse the silicon carbide clusters obtained in step (3) to obtain silicon carbide whiskers.

[0125] The silicon carbide whiskers obtained in this embodiment include a first silicon carbide whisker and a second silicon carbide whisker. The first silicon carbide whisker includes a single-crystal fibrous body and a silicon dioxide oxide layer covering the surface of the single-crystal fibrous body. The second silicon carbide whisker also has a bulk structure at one end of the single-crystal fibrous body. The second silicon carbide whisker is the main whisker structure, and this is used as the silicon carbide whisker obtained in this embodiment.

[0126] The SEM image of the silicon carbide whiskers obtained in this embodiment is shown in Figure 7, the TEM images are shown in Figures 8 and 9, the XRD image is shown in Figure 10, the TEM analysis images are shown in Figures 11-14, the TEM images of the bulk structure of the obtained silicon carbide whiskers are shown in Figures 15 and 16, and the EDS mapping image of the bulk structure of the obtained silicon carbide whiskers is shown in Figure 17. As shown in Figure 10, the single-crystal fibrous body of the silicon carbide whiskers obtained in this embodiment has a crystal form of 3C-SiC and contains stacking faults. As shown in Figures 11-14, the surface of the silicon carbide whiskers obtained in this embodiment is coated with a silicon dioxide oxide layer. As shown in Figure 17, the bulk structure contains SiO2 and SiC.

[0127] Example 2

[0128] This embodiment provides a silicon carbide whisker, the preparation method of which includes the following steps:

[0129] (1) Phenolic resin (YHY-5211, Meisheng Engineering Plastics, the residual carbon rate of this type of phenolic resin was 40% according to the residual carbon rate test method described in this invention) and silica were mixed in a mass ratio of 3:1, and then mixed with water to prepare a slurry with a solid content of 30wt%. The mixture was ball-milled at 300r / min for 5h to ensure uniform mixing.

[0130] (2) Spray drying was carried out at a feed rate of 10 r / min to obtain silicon carbide hollow sphere precursor (SEM image see Figure 18); the inlet air temperature of the spray drying was 120℃ and the outlet air temperature was 92℃.

[0131] (3) The silicon carbide hollow sphere precursor was sintered at 1450℃ for 3h in an argon atmosphere (the SEM image of the sintered material is shown in Figure 19); then carbon was removed at 800℃ for 3h in an oxygen atmosphere to obtain silicon carbide clusters (the SEM image is shown in Figure 20).

[0132] (4) Disperse the silicon carbide clusters obtained in step (3) to obtain silicon carbide whiskers.

[0133] The silicon carbide whiskers obtained in this embodiment include a first silicon carbide whisker and a second silicon carbide whisker. The first silicon carbide whisker includes a single-crystal fibrous body and a silicon dioxide oxide layer covering the surface of the single-crystal fibrous body. The second silicon carbide whisker also has a bulk structure at one end of the single-crystal fibrous body. The second silicon carbide whisker is the main whisker structure, and this is used as the silicon carbide whisker obtained in this embodiment.

[0134] Example 3

[0135] This embodiment provides a silicon carbide whisker, the preparation method of which includes the following steps:

[0136] (1) Phenolic resin (YHY-5213, Meisheng Engineering Plastics, the residual carbon rate of this type of phenolic resin was 47% according to the residual carbon rate test method described in this invention) and silicon dioxide were mixed at a mass ratio of 3:1, and then mixed with water to prepare a slurry with a solid content of 30wt%. The mixture was ball-milled at 300r / min for 5h to ensure uniform mixing.

[0137] (2) Spray drying was carried out at a feed rate of 10 r / min to obtain silicon carbide hollow sphere precursor (SEM image see Figure 21); the inlet air temperature of the spray drying was 120℃ and the outlet air temperature was 85℃.

[0138] (3) The silicon carbide hollow sphere precursor was sintered at 1450°C for 3 hours in an argon atmosphere (the SEM image of the sintered material is shown in Figure 22); then carbon was removed at 800°C for 3 hours in an oxygen atmosphere to obtain silicon carbide clusters (the SEM image is shown in Figure 23).

[0139] The silicon carbide whiskers obtained in this embodiment include a first silicon carbide whisker and a second silicon carbide whisker. The first silicon carbide whisker includes a single-crystal fibrous body and a silicon dioxide oxide layer covering the surface of the single-crystal fibrous body. The second silicon carbide whisker also has a bulk structure at one end of the single-crystal fibrous body. The second silicon carbide whisker is the main whisker structure, and this is used as the silicon carbide whisker obtained in this embodiment.

[0140] Example 4

[0141] This embodiment provides a silicon carbide whisker, the preparation method of which includes the following steps:

[0142] (1) Phenolic resin (YHY-5213, Meisheng Engineering Plastics, the residual carbon rate of this type of phenolic resin was 47% according to the residual carbon rate test method described in this invention) and silica were mixed at a mass ratio of 4:1, and then mixed with water to prepare a slurry with a solid content of 15wt%. The mixture was ball-milled at 300r / min for 5h to ensure uniform mixing.

[0143] (2) Spray drying is performed at a feed rate of 10 r / min to obtain silicon carbide hollow sphere precursor; wherein the inlet air temperature of spray drying is 130℃ and the outlet air temperature is 85℃.

[0144] (3) The silicon carbide hollow sphere precursor was sintered at 1400℃ for 3 hours in an argon atmosphere; then carbon was removed at 500℃ for 3 hours in an oxygen atmosphere to obtain silicon carbide clusters.

[0145] (4) Disperse the silicon carbide clusters obtained in step (3) to obtain silicon carbide whiskers.

[0146] The silicon carbide whiskers obtained in this embodiment include a first silicon carbide whisker and a second silicon carbide whisker. The first silicon carbide whisker includes a single-crystal fibrous body and a silicon dioxide oxide layer covering the surface of the single-crystal fibrous body. The second silicon carbide whisker also has a bulk structure at one end of the single-crystal fibrous body. The second silicon carbide whisker is the main whisker structure, and this is used as the silicon carbide whisker obtained in this embodiment.

[0147] Example 5

[0148] This embodiment provides a silicon carbide whisker, the preparation method of which includes the following steps:

[0149] (1) Phenolic resin (YHY-5212, Meisheng Engineering Plastics, the residual carbon rate of this type of phenolic resin was 46% according to the residual carbon rate test method described in this invention) and silica were mixed at a mass ratio of 2:1, and then mixed with water to prepare a slurry with a solid content of 50wt%. The mixture was ball-milled at 300r / min for 5h to ensure uniform mixing.

[0150] (2) Spray drying is performed at a feed rate of 10 r / min to obtain silicon carbide hollow sphere precursor; wherein the inlet air temperature of spray drying is 180℃ and the outlet air temperature is 110℃.

[0151] (3) The silicon carbide hollow sphere precursor was sintered at 1600℃ for 3 hours in an argon atmosphere; then carbon was removed at 900℃ for 3 hours in an oxygen atmosphere to obtain silicon carbide clusters.

[0152] (4) Disperse the silicon carbide clusters obtained in step (3) to obtain silicon carbide whiskers.

[0153] The silicon carbide whiskers obtained in this embodiment include a first silicon carbide whisker and a second silicon carbide whisker. The first silicon carbide whisker includes a single-crystal fibrous body and a silicon dioxide oxide layer covering the surface of the single-crystal fibrous body. The second silicon carbide whisker also has a bulk structure at one end of the single-crystal fibrous body. The second silicon carbide whisker is the main whisker structure, and this is used as the silicon carbide whisker obtained in this embodiment.

[0154] Example 6

[0155] This embodiment provides a silicon carbide whisker, which is the same as in Example 1 except that the phenolic resin is replaced by modified carboxymethyl cellulose (C804618, Maclean, the residual carbon rate of this type of carboxymethyl cellulose reaches 40% according to the residual carbon rate test method described in this invention).

[0156] The silicon carbide whiskers obtained in this embodiment include a first silicon carbide whisker and a second silicon carbide whisker. The first silicon carbide whisker includes a single-crystal fibrous body and a silicon dioxide oxide layer covering the surface of the single-crystal fibrous body. The second silicon carbide whisker includes a single-crystal fibrous body and a silicon dioxide oxide layer covering the surface of the single-crystal fibrous body. One end of the single-crystal fibrous body also has a bulk structure. The second silicon carbide whisker is the main whisker structure, and thus it is used as the silicon carbide whisker obtained in this embodiment.

[0157] Example 7

[0158] This embodiment provides a silicon carbide whisker, the preparation method of which includes the following steps:

[0159] (1) Mix sucrose (CAS-57-50-1) and deionized water at a mass ratio of 1:10, and then perform hydrothermal treatment at 180℃ to obtain carbon spheres;

[0160] (2) Mix hexadecyltrimethylammonium bromide (CTAB) with the carbon spheres obtained in step (1) at a mass ratio of 0.75:1 to obtain a carbon sphere mixture; prepare an ethanol mixture solution with a volume ratio of ammonia (25wt%) / deionized water / ethanol of 9:50:100, add the carbon sphere mixture to the above carbon sphere mixture to obtain a suspension; then prepare a TEOS-ethanol solution according to a mass ratio of tetraethyl orthosilicate / ethanol of 3:4000, pour the TEOS-ethanol solution into the above suspension at one time under vigorous stirring and react for 4 hours, then filter and dry to obtain a precipitate, the mass ratio of TEOS-ethanol solution to ethanol mixture solution is 1209:1672;

[0161] (3) The above precipitate was decarbonized at 500°C for 2 hours in an oxygen atmosphere to obtain hollow silica spheres;

[0162] (4) The hollow silica spheres obtained in step (3) are immersed in an aqueous solution of phenolic resin (YHY-5212, Meisheng Engineering Plastics, the residual carbon rate of this type of phenolic resin was measured to be 46% according to the residual carbon rate test method described in this invention) with a solid content of 50%, and mixed evenly.

[0163] (5) Dry the sample obtained in step (4) at 80°C to obtain the silicon carbide hollow sphere precursor;

[0164] (6) The silicon carbide hollow sphere precursor was sintered at 1450°C for 3 hours in an argon atmosphere; then carbon was removed at 800°C for 3 hours in an oxygen atmosphere to obtain silicon carbide clusters; the silicon carbide clusters were dispersed to obtain silicon carbide whiskers.

[0165] Figure 1 shows a schematic diagram of the silicon carbide hollow sphere precursor. The silicon carbide hollow sphere precursor is a hollow sphere with a two-layer core-shell structure, with the innermost layer being a silicon dioxide layer 1 and the outermost layer being an organic carbon layer 2.

[0166] The silicon carbide whiskers obtained in this embodiment include a first silicon carbide whisker and a second silicon carbide whisker. The first silicon carbide whisker includes a single-crystal fibrous body and a silicon dioxide oxide layer covering the surface of the single-crystal fibrous body. The second silicon carbide whisker also has a bulk structure at one end of the single-crystal fibrous body. The second silicon carbide whisker is the main whisker structure, and this is used as the silicon carbide whisker obtained in this embodiment.

[0167] Example 8

[0168] This embodiment provides a silicon carbide whisker, the preparation method of which includes the following steps:

[0169] (1) Mix sucrose (CAS-57-50-1) and deionized water at a mass ratio of 1:1, and then perform hydrothermal treatment at 150℃ to obtain carbon spheres;

[0170] (2) Mix hexadecyltrimethylammonium bromide (CTAB) with the carbon spheres obtained in step (1) at a mass ratio of 0.5:1 to obtain a carbon sphere mixture; prepare an ethanol mixture solution with a volume ratio of ammonia (25wt%) / deionized water / ethanol of 1:5:10, add the carbon sphere mixture to the above ethanol mixture solution to obtain a suspension; then prepare a TEOS-ethanol solution at a mass ratio of tetraethyl orthosilicate / ethanol of 1:1250, pour the TEOS-ethanol solution into the above suspension at one time under vigorous stirring and react for 10h, then filter and dry to obtain a precipitate, the mass ratio of TEOS-ethanol solution to ethanol mixture solution is 0.5:1;

[0171] (3) The above precipitate was decarbonized at 700°C for 2 hours in an oxygen atmosphere to obtain hollow silica spheres;

[0172] (4) The hollow silica spheres obtained in step (3) are immersed in an aqueous solution of phenolic resin (YHY-5212, Meisheng Engineering Plastics, the residual carbon rate of this type of phenolic resin was measured to be 46% according to the residual carbon rate test method described in this invention) with a solid content of 30%, and mixed evenly.

[0173] (5) Dry the sample obtained in step (4) at 60°C to obtain the silicon carbide hollow sphere precursor;

[0174] (6) The silicon carbide hollow sphere precursor was sintered at 1400°C for 3 hours in an argon atmosphere; then carbon was removed at 500°C for 3 hours in an oxygen atmosphere to obtain silicon carbide clusters; the silicon carbide clusters were dispersed to obtain silicon carbide whiskers.

[0175] The silicon carbide whiskers obtained in this embodiment include a first silicon carbide whisker and a second silicon carbide whisker. The first silicon carbide whisker includes a single-crystal fibrous body and a silicon dioxide oxide layer covering the surface of the single-crystal fibrous body. The second silicon carbide whisker also has a bulk structure at one end of the single-crystal fibrous body. The second silicon carbide whisker is the main whisker structure, and this is used as the silicon carbide whisker obtained in this embodiment.

[0176] Example 9

[0177] This embodiment provides a silicon carbide whisker, the preparation method of which includes the following steps:

[0178] (1) Mix sucrose (CAS-57-50-1) and deionized water at a mass ratio of 1:20, and then perform hydrothermal treatment at 200℃ to obtain carbon spheres;

[0179] (2) Mix hexadecyltrimethylammonium bromide (CTAB) with the carbon spheres obtained in step (1) at a mass ratio of 0.8:1 to obtain a carbon sphere mixture; prepare an ethanol mixture solution with a volume ratio of ammonia (25wt%) / deionized water / ethanol of 1:50:100, add the carbon sphere mixture to the above ethanol mixture solution to obtain a suspension; then prepare a TEOS-ethanol solution at a mass ratio of tetraethyl orthosilicate / ethanol of 1:2000, pour the TEOS-ethanol solution into the above suspension at one time under vigorous stirring and react for 1 hour, then filter and dry to obtain a precipitate. The mass ratio of TEOS-ethanol solution to ammonia / deionized water / ethanol mixture solution is 0.75:1.

[0180] (3) The above precipitate was decarbonized at 900°C for 2 hours in an oxygen atmosphere to obtain hollow silica spheres;

[0181] (4) The hollow silica spheres obtained in step (3) are immersed in an aqueous solution of phenolic resin (YHY-5212, Meisheng Engineering Plastics, the residual carbon rate of this type of phenolic resin was measured to be 46% according to the residual carbon rate test method described in this invention) with a solid content of 60%, and mixed evenly.

[0182] (5) Dry the sample obtained in step (4) at 100°C to obtain the silicon carbide hollow sphere precursor;

[0183] (6) The silicon carbide hollow sphere precursor was sintered at 1600°C for 3 hours in an argon atmosphere; then carbon was removed at 900°C for 3 hours in an oxygen atmosphere to obtain silicon carbide clusters; the silicon carbide clusters were dispersed to obtain silicon carbide whiskers.

[0184] The silicon carbide whiskers obtained in this embodiment include a first silicon carbide whisker and a second silicon carbide whisker. The first silicon carbide whisker includes a single-crystal fibrous body and a silicon dioxide oxide layer covering the surface of the single-crystal fibrous body. The second silicon carbide whisker also has a bulk structure at one end of the single-crystal fibrous body. The second silicon carbide whisker is the main whisker structure, and this is used as the silicon carbide whisker obtained in this embodiment.

[0185] Example 10

[0186] This embodiment provides a silicon carbide whisker, except that the phenolic resin is replaced by polyimide (AZ1036, Kaixuan Plastics Technology, the residual carbon rate of this type of polyimide is 40% as measured by the residual carbon rate test method described in this invention), and everything else is the same as in Example 1.

[0187] Example 11

[0188] This embodiment provides a silicon carbide whisker, which is the same as in Example 7 except that the phenolic resin is replaced by modified carboxymethyl cellulose (C804618, Maclean, the residual carbon rate of this type of carboxymethyl cellulose is 40% as measured by the residual carbon rate test method described in this invention).

[0189] Comparative Example 1

[0190] This comparative example provides a silicon carbide whisker, except that the phenolic resin in step (1) is replaced by acetylene black (the residual carbon rate of acetylene black is 0.3% as measured by the residual carbon rate test method described in this invention), and all other aspects are the same as in Example 1.

[0191] In this comparative example, after replacing phenolic resin with acetylene black, it was impossible to prepare silicon carbide hollow sphere precursor by spray drying, and the residual carbon rate of acetylene black was less than 40%. This method could not obtain silicon carbide whiskers with the specific morphology of the present invention because the lack of a closed carbon layer would cause SiO and CO to escape, resulting in the growth of silicon carbide nanowires outside the sphere.

[0192] Comparative Example 2

[0193] This comparative example provides a silicon carbide whisker, except that the phenolic resin in step (1) is replaced by water-soluble starch (CAS: 9005-84-9, the residual carbon rate of the water-soluble starch is 0.5% as measured by the residual carbon rate test method described in this invention), and everything else is the same as in Example 1.

[0194] In this comparative example, after replacing the phenolic resin with water-soluble starch, it was impossible to prepare the silicon carbide hollow sphere precursor by spray drying, and the residual carbon rate of the water-soluble starch was less than 40%. This method could not obtain the silicon carbide whiskers with the specific morphology of the present invention because the lack of a closed carbon layer would cause SiO and CO to escape, resulting in the growth of silicon carbide nanowires outside the sphere.

[0195] Comparative Example 3

[0196] This comparative example provides a silicon carbide whisker, except that the phenolic resin in step (1) is replaced by polyvinylpyrrolidone (CAS: 9003-39-8, the residual carbon rate of polyvinylpyrrolidone was 18.3% as measured by the residual carbon rate test method described in this invention), and all other aspects are the same as in Example 1.

[0197] In this comparative example, after replacing the phenolic resin with polyvinylpyrrolidone, it was impossible to prepare the silicon carbide hollow sphere precursor by spray drying, and the residual carbon rate of polyvinylpyrrolidone was less than 40%. This method could not obtain the silicon carbide whiskers with the specific morphology of the present invention because the lack of a closed carbon layer would cause SiO and CO to escape, resulting in the growth of silicon carbide nanowires outside the sphere.

[0198] Performance Characterization

[0199] The average diameter, aspect ratio, average thickness of the silicon dioxide oxide layer, and equivalent bulk diameter of the silicon carbide whiskers obtained in the above embodiments were measured, and the results are shown in Table 1.

[0200] Table 1

[0201] In summary, the silicon carbide whiskers provided by this invention, through the application of a silicon dioxide oxide layer, improve the interfacial affinity between the silicon carbide whiskers and oxides, promote stress transfer, and activate the toughening mechanism, thereby enhancing the fracture toughness of the composite material. Simultaneously, the silicon dioxide oxide layer also protects the whiskers from oxidation or chemical corrosion, maintaining their reinforcing effect. By setting a bulk material at one end of the single-crystal fibrous matrix, this bulk material enhances the interfacial bonding force through a mechanical interlocking effect, significantly increasing the whisker pull-out work, thereby optimizing crack propagation resistance and improving the toughness of the composite material.

[0202] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A silicon carbide whisker, characterized by, The silicon carbide whisker comprises a single-crystal fibrous body and a silicon dioxide oxide layer covering the surface of the single-crystal fibrous body; one end of the single-crystal fibrous body has a bulk; the bulk contains SiO2 and SiC.

2. The silicon carbide whisker of claim 1, wherein The average diameter of the silicon carbide whiskers is 0.1 μm to 5 μm.

3. The silicon carbide whiskers of claim 2, wherein The aspect ratio of the silicon carbide whiskers is 10 to 200.

4. The silicon carbide whisker of claim 1 wherein, The average thickness of the silicon dioxide oxide layer is 1 nm to 10 nm.

5. The silicon carbide whisker of claim 1 wherein, The equivalent diameter of the block is 0.3 μm to 5 μm.

6. A method of producing silicon carbide whiskers, characterized by, The silicon carbide whiskers are selected from the silicon carbide whiskers of claim 1, and the preparation method includes: Silicon carbide hollow sphere precursors are prepared; then sintered in a protective atmosphere to remove carbon, yielding silicon carbide clusters; the silicon carbide clusters are dispersed to obtain silicon carbide whiskers; The silicon carbide hollow sphere precursor is a hollow sphere with at least two shell layers; The innermost layer of the at least two-shell structure is a silicon dioxide layer; The outermost layer of the at least two-layer shell structure is an organic carbon layer, and the residual carbon rate of the organic carbon layer is more than 40%.

7. The production method according to claim 6, wherein The method for preparing the silicon carbide hollow sphere precursor includes a spray drying method, which comprises the following steps: By mixing organic carbon sources and silicon sources, a mixed slurry is obtained; The mixed slurry is spray-dried to obtain the silicon carbide hollow sphere precursor.

8. The preparation method according to claim 7, characterized in that, The organic carbon source includes any one or a combination of at least two of phenolic resin, polyimide, or modified carboxymethyl cellulose.

9. The preparation method according to claim 7, characterized in that, The silicon source includes any one or a combination of at least two of the following: silicon dioxide, diatomaceous earth, rice husk ash, or silicon monoxide.

10. The preparation method according to claim 7, characterized in that, The mass ratio of the organic carbon source to the silicon source is 1:1 to 5:

1.

11. The preparation method according to claim 7, characterized in that, The solid content of the mixed slurry is 15wt%-50wt%.

12. The method of claim 7, wherein, The inlet air temperature of the spray dryer is 120℃-180℃, and the outlet air temperature is 80℃-110℃.

13. The preparation method according to claim 6, characterized in that, The sintering temperature is 1400℃-1600℃.

14. The method of claim 6, wherein, The decarbonization is carried out in an oxygen-containing atmosphere at a temperature of 500℃-900℃.

15. A composite material, characterized in that, The composite material includes silicon carbide whiskers as described in any one of claims 1 to 6.

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