In-situ generated silicon carbide whisker reinforced graphite material and method for preparing the same

Abstract

This invention relates to the field of graphite composite material technology, specifically to an in-situ generated silicon carbide whisker-reinforced graphite material and its preparation method. The in-situ generated silicon carbide whisker-reinforced graphite material comprises the following raw materials by weight: 100 parts diamond micro powder, 6-60 parts active silicon powder, 3-60 parts active carbon black, 5-10 parts binder, and 0.5-3 parts surfactant. The preparation method is as follows: (1) Slurry preparation: Weigh the raw materials according to the above weight parts, mix them evenly, and prepare a slurry; (2) Dry, grind, crush, and finally sieve and granulate the slurry; (3) Mold and form a solid block; (4) Generate silicon carbide whiskers in situ under high temperature conditions; (5) Place the block material processed in step (4) into a mold, and then load it into a sintering furnace for sintering under high temperature conditions to obtain the in-situ generated silicon carbide whisker-reinforced graphite material. This invention introduces activated carbon black as a second carbon source and uses micron-sized diamond powder instead of the commonly used nano-sized diamond, which greatly reduces the material production cost without reducing the material performance, and is conducive to promoting the industrial application of high-performance graphite materials.

Description

Technical Field

[0001] This invention relates to the field of graphite composite materials technology, specifically to an in-situ generated silicon carbide whisker-reinforced graphite material and its preparation method. Background Technology

[0002] Graphite is an important industrial material with advantages such as high temperature resistance, corrosion resistance, good electrical conductivity, and high thermal and electrical conductivity. It is widely used in many fields such as electronics, aerospace, energy, chemical industry, metallurgy, machinery, and petrochemicals. With the continuous advancement of science and technology, increasingly higher requirements are being placed on the strength, hardness, and toughness of graphite. Therefore, the preparation of high-strength graphite materials has received attention from both academia and industry.

[0003] Chinese patent (a glassy carbon material and its preparation method, CN112830784A) discloses a method for preparing glassy carbon materials using nanodiamonds as a precursor via spark plasma sintering. Chinese patent (a glassy carbon material and its preparation method, CN 110357074A) discloses a method for preparing nano-onion carbon porous materials by in-situ transformation of nanodiamonds under high temperature and pressureless conditions, followed by high temperature and low pressure sintering.

[0004] Although high-performance graphite prepared based on diamond conversion has significant advantages over traditional graphite materials, the graphitization of diamond at high temperatures results in a lack of a hard, high-strength phase within the material, limiting further improvements in strength, hardness, and toughness. Silicon carbide whiskers possess high strength, hardness, and toughness, and can withstand high temperatures; therefore, adding silicon carbide whiskers to high-strength graphite is beneficial for obtaining graphite materials with even higher strength, toughness, and hardness. However, current methods for preparing high-strength graphite materials generally employ micro / nano materials, making it difficult to uniformly disperse silicon carbide whiskers. Summary of the Invention

[0005] The purpose of this invention is to provide an in-situ generated silicon carbide whisker-reinforced graphite material and its preparation method, thereby achieving the goal of preparing high-performance graphite materials in a more economical and simple way.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] An in-situ generated silicon carbide whisker-reinforced graphite material comprises the following raw materials in parts by weight: 100 parts diamond micro powder, 6-60 parts active silicon powder, 3-60 parts active carbon black, 5-10 parts binder, and 0.5-3 parts surfactant.

[0008] Preferably, it also includes anhydrous ethanol, wherein the amount of anhydrous ethanol is 1.0-2.5 times the total mass of diamond micron powder, carbon black and silicon powder.

[0009] Preferably, the diamond micro powder has a D 50 The active silicon powder has a D value of less than 50 μm. 50 The original particle size D of the activated carbon black micro powder is less than 5 μm. 50 Less than 50 nm.

[0010] Preferably, the adhesive is an organic adhesive that does not contain metal ions to avoid introducing impurities, such as phenolic resin or polyvinyl alcohol;

[0011] Preferably, the activated carbon black powder is pyrolytic carbon black, and the surfactant is a silane coupling agent or polyethyleneimine.

[0012] The above-mentioned method for preparing in-situ silicon carbide whisker-reinforced graphite materials includes the following steps:

[0013] (1) Slurry preparation:

[0014] Weigh out the diamond micro powder, active silicon powder, active carbon black, binder, and surfactant according to the above-mentioned weight proportions, add anhydrous ethanol, mix evenly, and prepare a slurry.

[0015] (2) Slurry drying and granulation

[0016] The slurry obtained in step (1) is dried at 40-80℃, then ground, crushed, and finally sieved for granulation.

[0017] (3) Molding

[0018] The granules obtained in step (2) are placed into a mold for molding to obtain solid blocks;

[0019] (4) In-situ generation of silicon carbide whiskers

[0020] The solid block material obtained in step (3) is placed in a heating furnace and kept at 1450-1550℃ for 1-8 hours under inert gas conditions to generate silicon carbide whiskers in situ; then the temperature is raised to 1600-1800℃ and kept for 4-24 hours to fully crystallize the silicon carbide whiskers.

[0021] (5) High-temperature sintering

[0022] The block material processed in step (4) is placed into the mold and then loaded into the sintering furnace for high-temperature sintering to obtain in-situ generated silicon carbide whisker-reinforced graphite material.

[0023] Preferably, the mixing in step (1) is carried out by ultrasonic dispersion for 1-10 hours.

[0024] Preferably, the drying in step (2) is to dry the solid phase to a content of 0.8-1.0% of ethanol.

[0025] Preferably, the high-temperature sintering in step (5) is as follows: Under vacuum conditions, the mold is placed into the SPS furnace, and under vacuum conditions, a pressure of 40-70 MPa is applied, and the temperature is raised to 1600-2000℃ at a rate of 50-300℃ / minute, and held for 5-60 minutes to obtain in-situ generated silicon carbide whisker-reinforced graphite material.

[0026] Preferably, the high-temperature sintering in step (5) is as follows: the block material processed in step (4) is loaded into the high-pressure assembly block mold, and then loaded into the six-sided top pressure cavity. The pressure is first raised to 1-6 GPa, and then the temperature is raised to 1200-2000℃ and held for 5-60 minutes to obtain in-situ generated silicon carbide whisker reinforced graphite material.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. Compared with the high-strength carbon preparation process using pure diamond micron powder as a precursor, the in-situ generation of silicon carbide whisker-reinforced graphite material provided by this invention introduces active carbon black as a second carbon source and uses micron-sized diamond micron powder to replace the currently commonly used nano-sized diamond. This greatly reduces the material production cost without reducing the material performance, which is conducive to promoting the industrial application of high-performance graphite materials.

[0029] 2. The preparation method of the present invention improves the uniformity of diamond and activated carbon black distribution by uniformly mixing diamond micro powder, activated carbon black and phenolic resin in anhydrous ethanol and then crushing and granulating them, which can avoid the reduction of material properties caused by uneven distribution of the first carbon source (diamond) and the second carbon source (activated carbon black).

[0030] 3. The present invention utilizes a two-step heating process, namely, pre-pressing in step (3) and heating in steps (4) and (5), to facilitate the full formation of silicon carbide whiskers. The in-situ generation of silicon carbide whiskers is formed by the reaction of silicon melting and volatilization with carbon. Pre-pressing reduces silicon volatilization and maximizes the production of silicon carbide whiskers. Simultaneously, holding the temperature at a lower temperature allows silicon to evaporate slowly, retaining more silicon vapor to react with carbon and form silicon carbide whiskers. After sufficient in-situ whisker generation, holding the temperature at a higher temperature further crystallizes the generated silicon carbide whiskers, improving their mechanical properties. In-situ whisker generation ensures uniform and random distribution of whiskers within the product. Compared with the commonly used ball milling mixing process, this method not only improves dispersion uniformity but also avoids damage to the properties of silicon carbide whiskers caused during ball milling.

[0031] 4. Compared with existing methods for preparing high-performance graphite materials based on diamond conversion, the preparation method of the present invention significantly reduces production costs, has a relatively simple process, high production efficiency, and does not cause a reduction in material performance. It has obvious comprehensive advantages in cost and performance, and is particularly suitable for industrial-scale preparation of high-performance graphite materials and products. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention are described in detail below. However, the following embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0033] This invention discloses an in-situ generated silicon carbide whisker-reinforced graphite material, comprising the following raw materials by weight: 100 parts diamond micropowder, 6-60 parts activated silicon powder, 3-60 parts activated carbon black, 5-10 parts binder, 0.5-3 parts surfactant, and anhydrous ethanol, wherein the amount of anhydrous ethanol is 1.0-2.5 times the total mass of the diamond micropowder, carbon black, and silicon powder. The diamond micropowder has a D... 50 The active silicon powder has a D value of less than 50 μm. 50 The original particle size D of the activated carbon black micro powder is less than 5 μm. 50 The nanometer size is less than 50 nm. The binder is an organic binder that does not contain metal ions to avoid introducing impurities, such as phenolic resin or polyvinyl alcohol; the activated carbon black powder is pyrolytic carbon black; and the surfactant is a silane coupling agent or polyethyleneimine.

[0034] The method for preparing in-situ silicon carbide whisker-reinforced graphite material according to the present invention includes the following steps:

[0035] (1) Slurry preparation:

[0036] Weigh out the diamond micro powder, active silicon powder, active carbon black, binder, and surfactant according to the above-mentioned weight proportions, add anhydrous ethanol, mix evenly, and prepare a slurry.

[0037] (2) Slurry drying and granulation

[0038] The slurry obtained in step (1) is dried at 40-80℃, then ground, crushed, and finally sieved for granulation.

[0039] (3) Molding

[0040] The granules obtained in step (2) are placed into a mold for molding to obtain solid blocks;

[0041] (4) In-situ generation of silicon carbide whiskers

[0042] The solid block material obtained in step (3) is placed in a heating furnace and kept at 1450-1550℃ for 1-8 hours under inert gas conditions to generate silicon carbide whiskers in situ; then the temperature is raised to 1600-1800℃ and kept for 4-24 hours to fully crystallize the silicon carbide whiskers.

[0043] (5) High-temperature sintering

[0044] The block material processed in step (4) is placed into the mold and then loaded into the sintering furnace for high-temperature sintering to obtain in-situ generated silicon carbide whisker-reinforced graphite material.

[0045] In step (1), the mixing is carried out by ultrasonic dispersion for 1-10 hours; in step (2), the drying is carried out until the ethanol content in the resulting solid phase is 0.8-1.0%.

[0046] The high-temperature sintering in step (5) is as follows: Under vacuum conditions, the mold is placed into the SPS furnace, and under vacuum conditions, a pressure of 40-70MPa is applied, and the temperature is raised to 1600-2000℃ at a rate of 50-300℃ / minute, and held for 5-60 minutes to obtain in-situ generated silicon carbide whisker-reinforced graphite material.

[0047] Alternatively, the high-temperature sintering described in step (5) is as follows: the block material processed in step (4) is loaded into a high-pressure assembly block mold, and then loaded into a six-sided top pressure cavity. The pressure is first raised to 1-6 GPa, and then the temperature is raised to 1200-2000℃ and held for 5-60 minutes to obtain in-situ generated silicon carbide whisker-reinforced graphite material. Example

[0048] An in-situ generated silicon carbide whisker-reinforced graphite material comprises the following raw materials by weight fraction:

[0049] 100 parts of 3μm diamond micro powder, 20 parts of 2.0μm activated silica powder, 20 parts of virgin 30nm activated carbon black, 8 parts of phenolic resin and 0.8 parts of silane coupling agent, and 160 parts of anhydrous ethanol.

[0050] The above-mentioned method for preparing in-situ silicon carbide whisker-reinforced graphite materials includes the following steps:

[0051] (1) Raw material dispersion and slurry preparation

[0052] Weigh the raw materials according to the above weight proportions, and add diamond micro powder, activated silica powder, activated carbon black, phenolic resin and silane coupling agent to anhydrous ethanol. Disperse the mixture ultrasonically for 3.5 hours to uniformly disperse and mix the components to form a slurry.

[0053] (2) Slurry drying and granulation

[0054] The slurry obtained in step (1) is placed in a vacuum drying oven and dried at 50°C for 8 hours to obtain a solid material with an ethanol content of about 0.8%. Then it is ground and crushed in a corundum mortar and granulated through a 60-mesh standard sieve.

[0055] (3) Pre-compression molding

[0056] The granules obtained in step (2) are loaded into an alloy mold with a diameter of 40 mm and pre-pressed at 30 MPa to obtain solid blocks.

[0057] (4) In-situ generation of silicon carbide whiskers

[0058] The solid block obtained in step (3) is placed in a graphite heating furnace and heated to 1450℃ under an argon atmosphere for 8 hours to generate silicon carbide whiskers in situ; then the temperature is raised to 1600℃ and held for 20 hours to fully crystallize the silicon carbide whiskers.

[0059] (5) High-temperature sintering

[0060] The bulk material processed in step (4) is placed into a graphite mold and then loaded into an SPS furnace. Under vacuum, a pressure of 40 MPa is applied, and the temperature is raised to 1600°C at a rate of 100°C / minute. The temperature is held for 60 minutes to obtain in-situ generated silicon carbide whisker high-strength graphite material.

[0061] The bulk density of the in-situ generated silicon carbide whisker high-strength graphite material obtained in this embodiment was measured to be 1.82 g / cm³. 3 Its Vickers microhardness is 3.56 GPa, and its three-point bending strength is 180.36 MPa. Example

[0062] An in-situ generated silicon carbide whisker-reinforced graphite material comprises the following raw materials by weight fraction:

[0063] 100 parts of 3μm diamond micro powder, 40 parts of 2.0μm active silica powder, 40 parts of active carbon black with a native particle size of 30nm, 10 parts of phenolic resin and 1.0 part of silane coupling agent, and 220 parts of anhydrous ethanol.

[0064] The above-mentioned method for preparing in-situ silicon carbide whisker-reinforced graphite materials includes the following steps:

[0065] (1) Raw material dispersion and slurry preparation

[0066] Weigh the raw materials according to the above weight proportions, and add diamond micro powder, active silicon powder, active carbon black, phenolic resin and silane coupling agent into anhydrous ethanol. Disperse the mixture ultrasonically for 4 hours to uniformly disperse and mix the components to form a slurry.

[0067] (2) Slurry drying and granulation

[0068] The slurry obtained in step (1) is placed in a vacuum drying oven and dried at 50°C for 8 hours to obtain a solid material with an ethanol content of about 0.9%. Then it is ground and crushed in a corundum mortar and granulated through a 60-mesh standard sieve.

[0069] (3) Pre-compression molding

[0070] The granules obtained in step (2) are loaded into an alloy mold with a diameter of 40 mm and pre-pressed at 30 MPa to obtain solid blocks.

[0071] (4) In-situ generation of silicon carbide whiskers

[0072] The solid block obtained in step (3) is placed in a graphite heating furnace and heated to 1550°C for 6 hours under an argon atmosphere to generate silicon carbide whiskers in situ; then the temperature is raised to 1800°C and held for 10 hours to fully crystallize the silicon carbide whiskers.

[0073] (5) High-temperature sintering

[0074] The bulk material processed in step (4) is placed into a graphite mold and then loaded into an SPS furnace. Under vacuum, a pressure of 50 MPa is applied, and the temperature is raised to 1600°C at a rate of 100°C / minute. The temperature is held for 60 minutes to obtain in-situ generated silicon carbide whisker high-strength graphite material.

[0075] The bulk density of the in-situ generated silicon carbide whisker high-strength graphite material obtained in this embodiment was measured to be 2.16 g / cm³. 3 Its Vickers microhardness is 4.35 GPa, and its three-point bending strength is 230.45 MPa. Example

[0076] An in-situ generated silicon carbide whisker-reinforced graphite material comprises the following raw materials by weight fraction: 100 parts of 20 μm diamond micro powder, 40 parts of 2.0 μm active silicon powder, 40 parts of active carbon black with a native particle size of 30 nm, 10 parts of phenolic resin and 1.0 part of silane coupling agent, and 220 parts of anhydrous ethanol.

[0077] The above-mentioned method for preparing in-situ silicon carbide whisker-reinforced graphite materials includes the following steps:

[0078] (1) Raw material dispersion and slurry preparation

[0079] Weigh the raw materials according to the above weight proportions, and add diamond micro powder, active silicon powder, active carbon black, phenolic resin and silane coupling agent into anhydrous ethanol. Disperse the mixture ultrasonically for 4 hours to uniformly disperse and mix the components to form a slurry.

[0080] (2) Slurry drying and granulation

[0081] The slurry obtained in step (1) is placed in a vacuum drying oven and dried at 50°C for 8 hours to obtain a solid material with an ethanol content of about 1.0%. Then it is ground and crushed in a corundum mortar and granulated through a 60-mesh standard sieve.

[0082] (3) Pre-compression molding

[0083] The particles obtained in step (2) are loaded into an alloy mold with a diameter of 40 mm and pre-pressed at 30 MPa to obtain solid blocks; (4) Silicon carbide whiskers are generated in situ.

[0084] (4) In-situ generation of silicon carbide whiskers

[0085] The solid block obtained in step (3) is placed in a graphite heating furnace and heated to 1550°C for 6 hours under an argon atmosphere to generate silicon carbide whiskers in situ; then the temperature is raised to 1800°C and held for 10 hours to fully crystallize the silicon carbide whiskers.

[0086] (5) High-temperature sintering

[0087] The bulk material processed in step (4) is placed into a graphite mold and then loaded into an SPS furnace. Under vacuum, a pressure of 50 MPa is applied, and the temperature is raised to 1600°C at a rate of 100°C / minute. The temperature is held for 60 minutes to obtain in-situ generated silicon carbide whisker high-strength graphite material.

[0088] The bulk density of the in-situ generated silicon carbide whisker high-strength graphite material obtained in this embodiment was measured to be 2.07 g / cm³. 3 Its Vickers microhardness is 4.06 GPa, and its three-point bending strength is 219.78 MPa. Example

[0089] An in-situ generated silicon carbide whisker-reinforced graphite material comprises the following raw materials by weight fraction: 100 parts of 20 μm diamond micro powder, 40 parts of 2.0 μm silicon powder, 40 parts of virgin activated carbon black with a particle size of 30 nm, 10 parts of phenolic resin and 1.0 part of silane coupling agent, and 220 parts of anhydrous ethanol.

[0090] The above-mentioned method for preparing in-situ silicon carbide whisker-reinforced graphite materials includes the following steps:

[0091] (1) Raw material dispersion and slurry preparation

[0092] Weigh the raw materials according to the above weight proportions, and add diamond micro powder, active silicon powder, active carbon black, phenolic resin and silane coupling agent into anhydrous ethanol. Disperse the mixture ultrasonically for 4 hours to uniformly disperse and mix the components to form a slurry.

[0093] (2) Slurry drying and granulation

[0094] The slurry obtained in step (1) is placed in a vacuum drying oven and dried at 50°C for 8 hours to obtain a solid material with an ethanol content of about 1.0%. Then it is ground and crushed in a corundum mortar and granulated through a 60-mesh standard sieve.

[0095] (3) Pre-compression molding

[0096] The granules obtained in step (2) are loaded into an alloy mold with a diameter of 40 mm and pre-pressed at 30 MPa to obtain solid blocks.

[0097] (4) In-situ generation of silicon carbide whiskers

[0098] The solid block obtained in step (3) is placed in a graphite heating furnace and heated to 1550°C for 6 hours under an argon atmosphere to generate silicon carbide whiskers in situ; then the temperature is raised to 1800°C and held for 10 hours to fully crystallize the silicon carbide whiskers.

[0099] (5) High-temperature sintering

[0100] The bulk material processed in step (4) is placed into a graphite mold and then loaded into an SPS furnace. Under vacuum, a pressure of 70 MPa is applied, and the temperature is raised to 1800°C at a rate of 100°C / min. The temperature is held for 60 minutes to obtain in-situ generated silicon carbide whisker high-strength graphite material.

[0101] The bulk density of the in-situ generated silicon carbide whisker high-strength graphite material obtained in this embodiment was measured to be 2.23 g / cm³. 3 Its Vickers microhardness is 4.78 GPa, and its three-point bending strength is 250.62 MPa. Example

[0102] An in-situ generated silicon carbide whisker-reinforced graphite material comprises the following raw materials by weight fraction: 100 parts of 20 μm diamond micro powder, 40 parts of 2.0 μm silicon powder, 40 parts of virgin activated carbon black with a particle size of 30 nm, 10 parts of phenolic resin and 1.0 part of silane coupling agent, and 220 parts of anhydrous ethanol.

[0103] The above-mentioned method for preparing in-situ silicon carbide whisker-reinforced graphite materials includes the following steps:

[0104] (1) Raw material dispersion and slurry preparation

[0105] Weigh the raw materials according to the above weight proportions, and add diamond micro powder, active silicon powder, active carbon black, phenolic resin and silane coupling agent into anhydrous ethanol. Disperse the mixture ultrasonically for 4 hours to uniformly disperse and mix the components to form a slurry.

[0106] (2) Slurry drying and granulation

[0107] The slurry obtained in step (1) is placed in a vacuum drying oven and dried at 50°C for 8 hours to obtain a solid material with an ethanol content of about 1.0%. Then it is ground and crushed in a corundum mortar and granulated through a 60-mesh standard sieve.

[0108] (3) Pre-compression molding

[0109] The granules obtained in step (2) are loaded into an alloy mold with a diameter of 40 mm and pre-pressed at 30 MPa to obtain solid blocks.

[0110] (4) In-situ generation of silicon carbide whiskers

[0111] The solid block obtained in step (3) is placed in a graphite heating furnace and heated to 1550℃ under an argon atmosphere for 6 hours to generate silicon carbide whiskers in situ; then the temperature is raised to 1600℃ and held for 10 hours to fully crystallize the silicon carbide whiskers.

[0112] (5) High-temperature sintering

[0113] The block material processed in step (4) is loaded into the high-pressure assembly block and then into the six-sided top pressure cavity. The pressure is first increased to 5GPa, and then the temperature is increased to 1800℃ and kept at that temperature for 10 minutes to obtain in-situ generated silicon carbide whisker-reinforced high-strength graphite material.

[0114] The bulk density of the in-situ generated silicon carbide whisker high-strength graphite material obtained in this embodiment was measured to be 2.56 g / cm³. 3 Its Vickers microhardness is 8.31 GPa, and its three-point bending strength is 344.61 MPa.

[0115] No silicon powder was added to the raw materials; otherwise, it was the same as in Example 2.

[0116] The obtained graphite block had a bulk density of 1.52 g / cm³. 3 Its Vickers microhardness is 1.77 GPa, and its three-point bending strength is 85.20 MPa.

[0117] Remove the pre-compression molding in step (3), otherwise it is the same as in Example 2.

[0118] The obtained graphite block had a bulk density of 2.12 g / cm³. 3 Its Vickers microhardness is 4.01 GPa, and its three-point bending strength is 195.32 MPa.

[0119] Step (4), in-situ generation of SiC whiskers, is changed to "Place the bulk material obtained in step (3) into a graphite heating furnace, and heat it to 1550℃ under an argon atmosphere for 6 hours to generate silicon carbide whiskers in situ".

[0120] Everything else is the same as in Example 2.

[0121] The obtained graphite block had a bulk density of 2.15 g / cm³. 3 Its Vickers microhardness is 4.28 GPa, and its three-point bending strength is 170.32 MPa.

[0122] Step (4), in-situ generation of SiC whiskers, is changed to "Place the block obtained in step (3) into a graphite heating furnace, and under an argon atmosphere, place the block obtained in step 3 into a graphite heating furnace, heat it to 1800℃ and hold it for 10 hours to generate silicon carbide whiskers and fully crystallize them."

[0123] Everything else is the same as in Example 2.

[0124] The obtained graphite block had a bulk density of 1.92 g / cm³. 3 Its Vickers microhardness is 3.36 GPa, and its three-point bending strength is 159.82 MPa.

[0125] 1. As can be seen from Example 2 and Comparative Example 1, under the same conditions, adding silicon powder to generate silicon carbide whiskers in situ increases the bulk density, microhardness, and flexural strength of the graphite material by approximately 42%, 146%, and 170%, respectively. This indicates that the present invention, by introducing silicon powder to generate silicon carbide whiskers in situ as a hard reinforcing phase, achieves the purpose of significantly increasing hardness and improving strength.

[0126] 2. As can be seen from Example 2 and Comparative Example 2, under the same conditions, pre-compression molding can better seal silicon powder inside the block, reduce silicon volatilization, and increase the content of in-situ generated silicon carbide whiskers. Therefore, the bulk density, microhardness, and flexural strength of the resulting graphite material increased by approximately 7%, 14%, and 24%, respectively. This indicates that the present invention can effectively reduce silicon volatilization and increase the content of in-situ generated silicon carbide whiskers through pre-compression molding, thereby producing graphite materials with better performance.

[0127] 3. As can be seen from Example 2 and Comparative Example 3, under the same conditions, high-temperature heat preservation can better promote the crystallization of in-situ silicon carbide whiskers and improve the mechanical properties of silicon carbide whiskers. Although the bulk density of the obtained graphite materials is similar, the microhardness and flexural strength increase by about 16% and 35%, respectively. This shows that the present invention can promote the crystallization of in-situ silicon carbide whiskers and improve their mechanical properties through two-step heating and high-temperature heat preservation, thereby obtaining graphite materials with better performance.

[0128] 4. As can be seen from Example 2 and Comparative Example 4, under the same conditions, low-temperature holding can reduce the vapor pressure of silicon, decrease silicon volatilization loss, better promote the in-situ formation of silicon carbide whiskers, and increase the amount of whiskers formed. Therefore, the bulk density, microhardness, and flexural strength of the resulting graphite material increased by approximately 10%, 22%, and 42%, respectively. This indicates that the present invention, through two-step heating and low-temperature holding, can better promote the in-situ formation of silicon carbide whiskers and increase the content of in-situ silicon carbide whiskers, thereby obtaining graphite materials with better performance. Whisker content,

[0129] 5. By comparing Example 2 with Example 1, it can be seen that, under the same conditions, increasing the silicon powder content can increase the content of in-situ generated silicon carbide whiskers, thus increasing the bulk density, microhardness, and flexural strength of the graphite material by about 19%, 22%, and 28%, respectively.

[0130] 6. A comparison between Example 3 and Example 2 shows that, under the same conditions, increasing the diamond particle size leads to a decrease in overall reactivity, resulting in a reduction of approximately 4%, 7%, and 5% in the bulk density, microhardness, and flexural strength of the prepared graphite material.

[0131] 7. A comparison between Example 4 and Example 3 shows that, under the same conditions, increasing the sintering temperature and pressure increases the bulk density, microhardness, and flexural strength of the graphite material by approximately 8%, 18%, and 14%, respectively. This indicates that when the diamond particle size is large, it is necessary to appropriately increase the sintering temperature and pressure.

[0132] 8. By comparing Example 5 with Example 4, it can be seen that, under the same conditions, the high-pressure sintering method increases the bulk density, microhardness, and flexural strength of the graphite material by about 15%, 74%, and 38%, respectively. This shows that compared with the spark plasma sintering process, high temperature and high pressure are more conducive to the preparation of graphite materials with better performance.

[0133] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An in-situ generated silicon carbide whisker-reinforced graphite material, characterized in that, The raw materials include the following by weight: 100 parts diamond micro powder, 6-60 parts activated silica powder, 3-60 parts activated carbon black, 5-10 parts binder, and 0.5-3 parts surfactant. It also includes anhydrous ethanol, wherein the amount of anhydrous ethanol is 1.0-2.5 times the total mass of diamond micro powder, activated carbon black and activated silicon powder; The diamond micro powder D 50 The active silicon powder has a D value of less than 50 μm. 50 The primary particle size D of the activated carbon black is less than 5 μm. 50 Less than 50nm; The activated carbon black is pyrolytic carbon black, the binder is an organic binder, and the surfactant is a silane coupling agent or polyethyleneimine; The preparation method of the graphite material includes the following steps: (1) Slurry preparation Weigh out diamond micro powder, active silicon powder, active carbon black, binder, and surfactant according to the above-mentioned weight proportions, add anhydrous ethanol, mix evenly, and prepare a slurry; (2) Slurry drying and granulation The slurry obtained in step (1) is dried at 40-80℃, then ground, crushed, and finally sieved for granulation. (3) Molding The granules obtained in step (2) are placed into a mold for molding to obtain solid blocks; (4) In-situ generation of silicon carbide whiskers The solid block material obtained in step (3) is placed in a heating furnace and kept at 1450-1550℃ for 1-8 hours under inert gas conditions to generate silicon carbide whiskers in situ; then the temperature is raised to 1600-1800℃ and kept for 4-24 hours to fully crystallize the silicon carbide whiskers. (5) High-temperature sintering The block material processed in step (4) is placed into the mold and then loaded into the sintering furnace for high-temperature sintering to obtain in-situ generated silicon carbide whisker-reinforced graphite material.

2. The in-situ generated silicon carbide whisker-reinforced graphite material according to claim 1, characterized in that, The mixing in step (1) is carried out by ultrasonic dispersion for 1-10 hours.

3. The in-situ generated silicon carbide whisker-reinforced graphite material according to claim 1, characterized in that, The drying in step (2) refers to drying until the ethanol content in the obtained solid phase is 0.8-1.0%.

4. The in-situ generated silicon carbide whisker-reinforced graphite material according to claim 1, characterized in that, The high-temperature sintering in step (5) is as follows: Under vacuum conditions, the mold is placed into the SPS furnace, and under vacuum conditions, a pressure of 40-70MPa is applied, and the temperature is raised to 1600-2000℃ at a rate of 50-300℃ / minute, and held for 5-60 minutes to obtain in-situ generated silicon carbide whisker-reinforced graphite material.

5. The in-situ generated silicon carbide whisker-reinforced graphite material according to claim 1, characterized in that, The high-temperature sintering in step (5) is as follows: the block material processed in step (4) is loaded into the high-pressure assembly block mold, and then loaded into the six-sided top pressure cavity. The pressure is first raised to 1-6 GPa, and then the temperature is raised to 1200-2000℃ and held for 5-60 minutes to obtain in-situ generated silicon carbide whisker reinforced graphite material.