Silicon carbide powder and method for producing the same

Abstract

The application belongs to the field of silicon carbide materials, and discloses a silicon carbide powder and a preparation method thereof. The preparation method comprises the following steps: adding silicon carbide particles into an alkaline activation solution for activation treatment to obtain activated silicon carbide, then adding the activated silicon carbide into an alcohol aqueous solution containing a silane coupling agent, and heating and stirring to obtain modified silicon carbide powder, wherein the silane coupling agent contains amino groups; placing the modified silicon carbide powder into an epoxy resin bonding solution for primary coating treatment to obtain epoxy-coated particles; adding the epoxy-coated particles into a polyurethane bonding solution for secondary coating to obtain coated wet powder particles; and granulating and drying the coated wet powder particles to obtain silicon carbide granulated powder, wherein the polyurethane contains amino groups or hydroxyl groups. The silicon carbide granulated powder prepared by the above method can effectively improve the granulation quality of the silicon carbide itself, and further improve the density of a silicon carbide blank.

Description

Technical Field

[0001] This application relates to the field of silicon carbide materials, specifically to a silicon carbide powder and its preparation method. Background Technology

[0002] Silicon carbide powder is an important raw material for preparing recrystallized silicon carbide ceramics. It has the characteristics of high high-temperature strength, good oxidation resistance, strong corrosion resistance, and excellent thermal shock resistance. During the sintering process, recrystallized silicon carbide mainly relies on its own evaporation-condensation mechanism to achieve interparticle bonding. Its typical structure consists of a skeleton formed by large particles and small particles migrating at high temperatures and forming sintering necks at the contact points with large particles. Therefore, the density and uniformity of the green body before sintering directly affect the density and internal defects of the ceramic after sintering. Especially in the cold isostatic pressing process, the physical properties of the powder, such as flowability and bulk density, directly affect the density and uniformity of the formed green body. Spray granulation can uniformly combine silicon carbide powder with binders to form granulated powder with a certain particle size and flowability, thereby improving the packing state of the powder and increasing the loose density, tap density, and density of the green body obtained in subsequent molding.

[0003] However, the raw material powder used for recrystallizing silicon carbide is usually a large-particle powder, with a particle size exceeding 50 μm, or even 250 μm or more. During the spray granulation process, the rapid settling velocity of the particles causes a decrease in the stability of the slurry, and the high solid content slurry does not easily enter the atomization device. Large particles also cause nozzle blockage during the conveying and atomization process, resulting in uneven atomization. At the same time, the large particles are affected by the coating of atomized droplets and the uneven bonding between particles, resulting in granulated particles with wide particle size distribution, irregular morphology, large differences in internal pores, and insufficient bonding strength. This leads to a decrease in the accumulation and compaction performance of the granulated powder, affecting the density of the subsequent green body. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a silicon carbide powder and its preparation method, which aims to solve the problem of decreased stacking and compaction performance of large silicon carbide powder during spray granulation, resulting in a decrease in the density of silicon carbide preform.

[0005] To address the aforementioned technical problems, a method for preparing silicon carbide granulated powder is proposed, comprising the following preparation steps: S1. Silicon carbide particles are added to an alkaline activation solution for activation treatment to obtain activated silicon carbide. Then, the activated silicon carbide is added to an alcohol-water solution containing a silane coupling agent, heated and stirred to obtain modified silicon carbide powder, wherein the silane coupling agent contains amino groups. S2. The modified silicon carbide powder is placed in an epoxy resin binder solution for a one-time coating treatment to obtain epoxy-coated particles. S3. Epoxy-coated particles are added to a polyurethane binder solution for secondary coating to obtain coated wet powder particles. The coated wet powder particles are granulated and dried to obtain silicon carbide granulated powder, wherein the polyurethane contains amino or hydroxyl groups.

[0006] In addition, a silicon carbide granulated powder is also provided, which is prepared by the method described above for preparing silicon carbide granulated powder.

[0007] As can be seen from the above technical solutions, the exemplary embodiments disclosed herein possess at least the following advantages and positive effects: On the one hand, by using alkaline treatment solution to activate silicon carbide particles and further using amino-containing silane coupling agents to modify the surface of activated silicon carbide, alkaline activation can improve the surface activity of silicon carbide particles, providing favorable conditions for the bonding of silane coupling agents on the particle surface. This allows a modified layer with good interfacial activity to be formed on the surface of large silicon carbide particles, thereby solving the problem of insufficient surface activity of large silicon carbide powder and the difficulty in stable adhesion of subsequent organic bonding systems, and improving the surface activity and interfacial bonding basis of silicon carbide particles.

[0008] On the other hand, by first coating modified silicon carbide with epoxy resin and then coating it with polyurethane containing hydroxyl or amino groups, the epoxy resin forms a stable inner layer bonding structure with the surface of silicon carbide particles modified by silane coupling agent, and provides an adhesion base for the outer layer of polyurethane. The polyurethane then uses its flexibility to form an outer layer bonding structure with a certain deformation capability, so that adjacent large particles can be stably connected and buffer the local stress between particles. This solves the problems of insufficient bonding between particles and difficulty in taking into account the bonding stability and flexibility of a single bonding layer when granulating large silicon carbide particles in the prior art. This achieves the effect of improving the integrity and stacking stability of granulated particles, improving the loose density and tap density of granulated powder, and increasing the density of silicon carbide preform.

[0009] In summary, alkaline activation and silane coupling agent modification enhance the surface activity of silicon carbide, while epoxy resin and polyurethane secondary coating improve interparticle bonding and flexibility, thereby increasing the bulk density of the granulated powder and consequently the density of the silicon carbide preform. Attached Figure Description

[0010] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure. It is obvious that the drawings described below are merely some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. In the drawings: Figure 1This is a schematic diagram of a method for preparing silicon carbide granulated powder in one embodiment; Figure 2 This is a schematic diagram of step S1 in a method for preparing silicon carbide granulated powder in one embodiment; Figure 3 This is a schematic diagram of step S2 in a method for preparing silicon carbide granulated powder in one embodiment; Figure 4 This is a schematic diagram of step S3 in the method for preparing silicon carbide granulated powder in one embodiment. Detailed Implementation

[0011] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be more thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art.

[0012] Furthermore, the described features or characteristics may be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this disclosure. However, those skilled in the art will recognize that the technical solutions of this disclosure may be practiced without one or more of the specific details, or other methods, steps, etc. may be employed. In other instances, well-known methods, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this disclosure.

[0013] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0014] Please refer to Figure 1 This invention proposes a method for preparing silicon carbide granulated powder, the method comprising the following steps: S1. Silicon carbide particles are added to an alkaline activation solution for activation treatment to obtain activated silicon carbide. Then, the activated silicon carbide is added to an alcohol-water solution containing a silane coupling agent, heated and stirred to obtain modified silicon carbide powder, wherein the silane coupling agent contains an amino group.

[0015] The silicon carbide particles have a particle size ≥ 50 μm, and the silane coupling agent includes at least one of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-β-aminoethyl-γ-aminopropyltrimethoxysilane, N-β-aminoethyl-γ-aminopropyltriethoxysilane, and γ-aminopropylmethyldiethoxysilane.

[0016] By performing alkaline activation treatment and using amino-containing silane coupling agents to modify the surface of large silicon carbide particles, the surface activity and interfacial bonding ability of silicon carbide particles are improved, resulting in a more uniform surface state for large silicon carbide particles with a particle size ≥50μm. This improves the contact state and natural packing state between silicon carbide powder particles, reduces local packing unevenness caused by differences in particle surface properties, and provides a basis for improving the loose packing density and tapped density of the powder.

[0017] Reference Figure 2 Step S1 includes: S1.1 Add silicon carbide particles to an alkaline activation solution and stir for 30-90 minutes at 50-80℃ and 400-600 rpm. Filter and wash with deionized water to obtain activated silicon carbide. The mass ratio of silicon carbide particles to alkaline activation solution is 1:(8-12). The alkaline activation solution is an aqueous solution containing 10-20 wt% alkaline substances, including at least one of sodium hydroxide, potassium hydroxide, and sodium carbonate.

[0018] Silicon carbide particles are placed in an alkaline activation solution containing 10-20 wt% alkaline substances and stirred at 50-80°C and 400-600 rpm. The alkaline environment is used to fully treat the surface of the silicon carbide particles, activating some inert areas on the particle surface and forming more reactive surface sites. At the same time, an appropriate solid-liquid ratio is used to ensure full contact between the alkaline activation solution and the silicon carbide particles, thereby improving the uniformity of the activation treatment.

[0019] S1.2 Add activated silicon carbide to an alcohol-water solution containing silane coupling agent, stir at 50~70℃ and 400~800rpm for 30~90min, filter to obtain pre-modified silicon carbide powder, wherein the mass ratio of activated silicon carbide, silane coupling agent and alcohol-water solution is 100:(6~10):(30~60), and the alcohol-water solution is composed of ethanol and deionized water in a mass ratio of (60~90):(10~40).

[0020] Adding activated silicon carbide to an alcohol-water solution containing a silane coupling agent and stirring at 50-70°C and 400-800 rpm promotes sufficient contact and stable bonding between the silane coupling agent and the active sites on the activated silicon carbide surface, resulting in a more uniform distribution of the silane coupling agent on the surface of the silicon carbide particles. Simultaneously, using a mass ratio of 100:(6-10):(30-60) for activated silicon carbide, silane coupling agent, and alcohol-water solution balances the coverage and dispersion of the silane coupling agent. An appropriate ratio of ethanol to deionized water also facilitates the uniform dispersion of the silane coupling agent in the treatment system.

[0021] S1.3 Wash the pre-modified silicon carbide powder 2-3 times with an alcohol-water solution of ethanol and deionized water in a mass ratio of (60-90):(10-40), and dry it at 60-90℃ for 2-6 hours to obtain modified silicon carbide powder.

[0022] The pre-modified silicon carbide powder is washed 2-3 times with an alcohol-water solution composed of ethanol and deionized water to remove unbound silane coupling agent and residual treatment liquid from the particle surface, reduce the residue of free silane on the particle surface, and avoid damage to the bound silane layer caused by excessive washing. Then, it is dried at 60-90℃ for 2-6 hours to fully remove ethanol and water from the particle surface, stabilize the silane-modified layer, and reduce the influence of residual solvent on the powder state.

[0023] S2. The modified silicon carbide powder is placed in an epoxy resin binder solution for a single coating treatment to obtain epoxy-coated particles.

[0024] The epoxy resin includes at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, and phenolic epoxy resin.

[0025] By forming an epoxy resin coating layer on the surface of modified silicon carbide particles, the bonding stability between the adhesive layer and the silicon carbide particles is improved. This allows the epoxy resin to adhere to the surface of the silicon carbide particles and form a continuous inner layer adhesive structure, thereby improving the structural integrity and anti-breakage ability of individual coated particles. This avoids particle structure damage due to insufficient bonding of the adhesive layer during subsequent granulation, and provides a stable bonding basis for forming complete granulated particles.

[0026] Reference Figure 3 Step S2 includes: S2.1. Epoxy resin, wetting agent, dispersant, and organic solvent are mixed in a mass ratio of 100:(1~2):(1~3):(100~300) and stirred at 30~50℃ and 300~600rpm for 20~40min to obtain an epoxy resin-containing binder solution. The wetting agent includes at least one of polyethylene glycol, propylene glycol, glycerin, polyoxyethylene ether, and polyether-modified siloxane. The dispersant includes at least one of polyvinylpyrrolidone, sodium polyacrylate, sodium hexametaphosphate, sodium citrate, and sodium dodecyl sulfate. The organic solvent includes at least one of xylene, methyl ethyl ketone, and acetone.

[0027] Epoxy resin, wetting agent, dispersant and organic solvent are mixed in a specific ratio and stirred at 30~50℃ and 300~600rpm for 20~40min to promote the full dissolution and uniform dispersion of epoxy resin in organic solvent. At the same time, the wetting agent can improve the wetting state between the components of the system, and the dispersant can inhibit the formation of epoxy resin molecules or local aggregates, so that the bonding system maintains good uniformity and stability.

[0028] S2.2 Add the modified silicon carbide powder to the epoxy resin binder solution, stir for 30-90 min at 30-50℃ and 300-600 rpm, filter to obtain epoxy-coated particles, wherein the mass ratio of the modified silicon carbide powder to the epoxy resin binder solution is 1:(1-3).

[0029] Modified silicon carbide powder is added to an epoxy resin binder solution and stirred for 30-90 minutes at 30-50℃ and 300-600 rpm. This allows the epoxy resin binder solution to fully contact and wet the surface of the modified silicon carbide particles, enabling the epoxy resin to be uniformly deposited and adhered to the particle surface, forming a continuous epoxy coating layer.

[0030] S3. Epoxy-coated particles are added to a polyurethane binder solution for secondary coating to obtain coated wet powder particles. The coated wet powder particles are granulated and dried to obtain silicon carbide granulated powder, wherein the polyurethane contains amino or hydroxyl groups.

[0031] Among them, polyurethane is amino-terminated polyurethane or hydroxyl-terminated polyurethane.

[0032] By further forming a polyurethane coating layer on the outside of the epoxy-coated particles, the good flexibility and deformation capacity of polyurethane are utilized to enable the granulated particles to undergo a certain degree of elastic or plastic deformation when subjected to external forces. This buffers the local stress inside the particles and between the coating layers, reducing the possibility of the granulated particles breaking due to stress, while maintaining the integrity of the granulated particle structure. This results in silicon carbide granulated powder with good particle integrity and anti-breakage performance, which is beneficial for maintaining a stable particle morphology during subsequent stacking and compaction.

[0033] The preparation method of amino-terminated polyurethane or hydroxyl-terminated polyurethane is as follows: Diol and diisocyanate are mixed at a molar ratio of hydroxyl to isocyanate groups of 1:(1.8~2.2) and reacted at 65~85℃ for 2~4h in an inert atmosphere to obtain isocyanate-terminated polyurethane prepolymer; then a hydroxyl-termining agent or an amino-termining agent is added to make the molar ratio of hydroxyl / amino to isocyanate groups (1.02~1.30):1, and reacted at 60~80℃ for 1~3h to obtain hydroxyl-terminated polyurethane or amino-terminated polyurethane.

[0034] The diols include at least one of polytetramethylene ether glycol, polypropylene glycol, polycaprolactone glycol, and polybutylene adipate glycol; the diisocyanates include at least one of isophorone diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, hydrogenated 4,4'-diphenylmethane diisocyanate, toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, and phenylenediamine diisocyanate; the hydroxyl end-capping agent includes at least one of polyethylene glycol, 1,4-butanediol, and propylene glycol; and the amino end-capping agent includes at least one of ethylenediamine, hexamethylenediamine, and isophorone diamine.

[0035] First, diol and diisocyanate are reacted at a molar ratio of hydroxyl to isocyanate groups of 1:(1.8~2.2), with diisocyanate in excess relative to diol. This results in isocyanate groups remaining at both ends of the polyurethane molecular chain, yielding an isocyanate-terminated polyurethane prepolymer. Subsequently, a hydroxyl-termining agent or an amino-termining agent is added according to the target end group. The hydroxyl groups in the hydroxyl-termining agent can react with the isocyanate groups at both ends of the prepolymer, allowing some hydroxyl groups to remain at the ends of the polyurethane molecular chain after the reaction, thus obtaining a hydroxyl-terminated polyurethane. The amino groups in the amino-termining agent have high reactivity with the isocyanate groups. By controlling the molar ratio of amino to isocyanate groups to be slightly excess, the isocyanate end groups are fully consumed, and amino groups are retained at the ends of the molecular chain, thus obtaining an amino-terminated polyurethane.

[0036] Reference Figure 4 Step S3 includes: S3.1. Mix polyurethane, wetting agent, dispersant and organic solvent in a mass ratio of 100:(1~2):(1~2):(100~300) and stir for 20~40 min at 30~50℃ and 300~600 rpm to obtain a polyurethane-containing binder solution. The wetting agent includes at least one of polyethylene glycol, propylene glycol, glycerin, polyoxyethylene ether and polyether-modified siloxane. The dispersant includes at least one of polyvinylpyrrolidone, sodium polyacrylate, sodium hexametaphosphate, sodium citrate and sodium dodecyl sulfate. The organic solvent includes at least one of xylene, methyl ethyl ketone and acetone.

[0037] Mixing polyurethane, wetting agent, dispersant and organic solvent in a specific ratio and stirring at 30~50℃ and 300~600rpm for 20~40min can promote the full dissolution or uniform dispersion of polyurethane in organic solvent. At the same time, the wetting agent improves the wetting state between polyurethane and solvent, and the dispersant inhibits the agglomeration between polyurethane segments or polyurethane particles, so that the resulting adhesive system maintains good uniformity and stability.

[0038] S3.2 Add epoxy-coated particles to a polyurethane binder solution, stir for 30-120 minutes at 40-80℃ and 300-600 rpm, filter to obtain coated wet powder particles, wherein the mass ratio of epoxy-coated particles to polyurethane binder solution is 1:(1-3).

[0039] Epoxy-coated particles are added to a polyurethane binder solution and stirred for 30-120 minutes at 40-80°C and 300-600 rpm. The polyurethane binder solution fully wets the surface of the epoxy-coated particles, so that the polyurethane is uniformly attached to the outer surface of the epoxy-coated particles, forming a continuous polyurethane coating layer.

[0040] S3.3 Add the coated wet powder particles into a high-speed mixer and granulator. First, premix at 300~600 rpm for 5~10 min, then granulate at 800~1500 rpm for 10~25 min. The resulting wet particles are first dried at 40~50℃ for 1~3 h, then heated to 80~110℃ and dried for 2~5 h to obtain silicon carbide granulated powder.

[0041] The coated wet powder particles are first premixed at 300-600 rpm to fully disperse them in the granulator and initially form a uniform particle system. Then, they are subjected to high-speed shearing at 800-1500 rpm, which causes the particles to gradually aggregate into granules under shearing, collision, and bonding effects, thereby promoting the formation of silicon carbide particles with relatively uniform particle size and complete structure. After granulation, the particles are first slowly dried at 40-50℃ to allow the solvent inside and on the surface of the particles to gradually escape, reducing the risk of particle cracking or structural collapse caused by rapid evaporation. Then, the temperature is raised to 80-110℃ for further drying, which can fully remove residual solvent and gradually solidify and stabilize the bonding layer, thereby obtaining silicon carbide granulated powder with good particle integrity, structural stability, and drying uniformity.

[0042] In addition, a silicon carbide granulated powder is also provided, which is prepared by the method described above for preparing silicon carbide granulated powder.

[0043] It should be noted that this application is not only used for the granulation of large-particle silicon carbide powder, but also for large-particle powders such as boron carbide, boron nitride, and silicon nitride.

[0044] For example, the present invention provides the following specific embodiments to illustrate the specific preparation method: Unless otherwise specified, the preparation methods of amino-terminated polyurethane used in the following examples and comparative examples are as follows: Polypropylene glycol and isophorone diisocyanate were mixed at a molar ratio of hydroxyl to isocyanate groups of 1:2 and reacted at 75°C for 3 hours in an inert atmosphere to obtain an isocyanate-terminated polyurethane prepolymer. Subsequently, hexamethylenediamine was added to make the molar ratio of amino to isocyanate groups in hexamethylenediamine 1.1:1, and the mixture was reacted at 70°C for 2 hours to obtain an amino-terminated polyurethane.

[0045] The method used to prepare the hydroxyl-terminated polyurethane is as follows: Polypropylene glycol and isophorone diisocyanate were mixed at a molar ratio of hydroxyl to isocyanate groups of 1:2 and reacted at 75°C for 3 hours in an inert atmosphere to obtain an isocyanate-terminated polyurethane prepolymer. Subsequently, 1,4-butanediol was added to make the molar ratio of hydroxyl to isocyanate groups in 1,4-butanediol 1.1:1, and the mixture was reacted at 70°C for 2 hours to obtain a hydroxyl-terminated polyurethane.

[0046] Example 1: S1.1 Add silicon carbide particles with a particle size of 60±5μm to an alkaline activation solution, stir at 65℃ and 500rpm for 60min, filter and wash with deionized water to obtain activated silicon carbide. The mass ratio of silicon carbide particles to alkaline activation solution is 1:10, and the alkaline activation solution is an aqueous solution containing 15wt% sodium hydroxide. S1.2 Add activated silicon carbide to an alcohol-water solution containing γ-aminopropyltriethoxysilane, stir at 60°C and 600 rpm for 60 min, filter to obtain pre-modified silicon carbide powder, wherein the mass ratio of activated silicon carbide, γ-aminopropyltriethoxysilane and alcohol-water solution is 100:8:45, and the alcohol-water solution is composed of ethanol and deionized water in a mass ratio of 80:20; S1.3 The pre-modified silicon carbide powder was washed three times with an alcohol-water solution of ethanol and deionized water in a mass ratio of 80:20, and dried at 75°C for 4 hours to obtain modified silicon carbide powder. S2.1. Bisphenol A type epoxy resin, polyethylene glycol, polyvinylpyrrolidone and acetone are mixed in a mass ratio of 100:1.5:2:200 and stirred at 40℃ and 450rpm for 30min to obtain an epoxy resin-containing adhesive solution. S2.2 Add modified silicon carbide powder to an epoxy resin binder solution, stir for 60 min at 40℃ and 450 rpm, filter to obtain epoxy-coated particles, wherein the mass ratio of modified silicon carbide powder to epoxy resin binder solution is 1:2. S3.1 Mix amino-terminated polyurethane, polyethylene glycol, polyvinylpyrrolidone and acetone in a mass ratio of 100:1.5:1.5:200 and stir at 40°C and 450 rpm for 30 min to obtain a polyurethane-containing adhesive solution. S3.2 Add epoxy-coated particles to a polyurethane binder solution, stir for 60 min at 60℃ and 450 rpm, filter to obtain coated wet powder particles, wherein the mass ratio of epoxy-coated particles to polyurethane binder solution is 1:2. S3.3 Add the coated wet powder particles to a high-speed mixer and granulator, premix at 450 rpm for 8 min, and then granulate at 1200 rpm for 18 min. The resulting wet particles are dried at 45℃ for 2 h, and then heated to 90℃ for 3 h to obtain silicon carbide granulated powder.

[0047] Example 2: S1.1 Add silicon carbide particles with a particle size of 60±5μm to an alkaline activation solution, stir at 65℃ and 500rpm for 60min, filter and wash with deionized water to obtain activated silicon carbide. The mass ratio of silicon carbide particles to alkaline activation solution is 1:10, and the alkaline activation solution is an aqueous solution containing 15wt% sodium hydroxide. S1.2 Add activated silicon carbide to an alcohol-water solution containing γ-aminopropyltriethoxysilane, stir at 60°C and 600 rpm for 60 min, filter to obtain pre-modified silicon carbide powder, wherein the mass ratio of activated silicon carbide, γ-aminopropyltriethoxysilane and alcohol-water solution is 100:8:45, and the alcohol-water solution is composed of ethanol and deionized water in a mass ratio of 80:20; S1.3 The pre-modified silicon carbide powder was washed three times with an alcohol-water solution of ethanol and deionized water in a mass ratio of 80:20, and dried at 75°C for 4 hours to obtain modified silicon carbide powder. S2.1. Bisphenol A type epoxy resin, polyethylene glycol, polyvinylpyrrolidone and acetone are mixed in a mass ratio of 100:1.5:2:200 and stirred at 40℃ and 450rpm for 30min to obtain an epoxy resin-containing adhesive solution. S2.2 Add the modified silicon carbide powder to the epoxy resin binder solution, stir for 60 min at 40℃ and 450 rpm, filter to obtain epoxy coated particles, wherein the mass ratio of modified silicon carbide powder to epoxy resin binder solution is 1:1. S3.1 Mix amino-terminated polyurethane, polyethylene glycol, polyvinylpyrrolidone and acetone in a mass ratio of 100:1.5:1.5:200 and stir at 40°C and 450 rpm for 30 min to obtain a polyurethane-containing adhesive solution. S3.2 Add epoxy-coated particles to a polyurethane binder solution, stir for 60 min at 60℃ and 450 rpm, filter to obtain coated wet powder particles, wherein the mass ratio of epoxy-coated particles to polyurethane binder solution is 1:1. S3.3 Add the coated wet powder particles to a high-speed mixer and granulator, premix at 450 rpm for 8 min, and then granulate at 1200 rpm for 18 min. The resulting wet particles are dried at 45℃ for 2 h, and then heated to 90℃ for 3 h to obtain silicon carbide granulated powder.

[0048] Example 3: S1.1 Add silicon carbide particles with a particle size of 60±5μm to an alkaline activation solution, stir at 65℃ and 500rpm for 60min, filter and wash with deionized water to obtain activated silicon carbide. The mass ratio of silicon carbide particles to alkaline activation solution is 1:10, and the alkaline activation solution is an aqueous solution containing 15wt% sodium hydroxide. S1.2 Add activated silicon carbide to an alcohol-water solution containing γ-aminopropyltriethoxysilane, stir at 60°C and 600 rpm for 60 min, filter to obtain pre-modified silicon carbide powder, wherein the mass ratio of activated silicon carbide, γ-aminopropyltriethoxysilane and alcohol-water solution is 100:8:45, and the alcohol-water solution is composed of ethanol and deionized water in a mass ratio of 80:20; S1.3 The pre-modified silicon carbide powder was washed three times with an alcohol-water solution of ethanol and deionized water in a mass ratio of 80:20, and dried at 75°C for 4 hours to obtain modified silicon carbide powder. S2.1. Bisphenol A type epoxy resin, polyethylene glycol, polyvinylpyrrolidone and acetone are mixed in a mass ratio of 100:1.5:2:200 and stirred at 40℃ and 450rpm for 30min to obtain an epoxy resin-containing adhesive solution. S2.2 Add modified silicon carbide powder to an epoxy resin binder solution, stir for 60 min at 40℃ and 450 rpm, filter to obtain epoxy-coated particles, wherein the mass ratio of modified silicon carbide powder to epoxy resin binder solution is 1:3. S3.1 Mix amino-terminated polyurethane, polyethylene glycol, polyvinylpyrrolidone and acetone in a mass ratio of 100:1.5:1.5:200 and stir at 40°C and 450 rpm for 30 min to obtain a polyurethane-containing adhesive solution. S3.2 Add epoxy-coated particles to a polyurethane binder solution, stir for 60 min at 60℃ and 450 rpm, filter to obtain coated wet powder particles, wherein the mass ratio of epoxy-coated particles to polyurethane binder solution is 1:3. S3.3 Add the coated wet powder particles to a high-speed mixer and granulator, premix at 450 rpm for 8 min, and then granulate at 1200 rpm for 18 min. The resulting wet particles are dried at 45℃ for 2 h, and then heated to 90℃ for 3 h to obtain silicon carbide granulated powder.

[0049] Example 4: S1.1 Add silicon carbide particles with a particle size of 60±5μm to an alkaline activation solution, stir at 65℃ and 500rpm for 60min, filter and wash with deionized water to obtain activated silicon carbide. The mass ratio of silicon carbide particles to alkaline activation solution is 1:10, and the alkaline activation solution is an aqueous solution containing 15wt% sodium hydroxide. S1.2 Add activated silicon carbide to an alcohol-water solution containing γ-aminopropyltriethoxysilane, stir at 60°C and 600 rpm for 60 min, filter to obtain pre-modified silicon carbide powder, wherein the mass ratio of activated silicon carbide, γ-aminopropyltriethoxysilane and alcohol-water solution is 100:8:45, and the alcohol-water solution is composed of ethanol and deionized water in a mass ratio of 80:20; S1.3 The pre-modified silicon carbide powder was washed three times with an alcohol-water solution of ethanol and deionized water in a mass ratio of 80:20, and dried at 75°C for 4 hours to obtain modified silicon carbide powder. S2.1. Bisphenol A type epoxy resin, polyethylene glycol, polyvinylpyrrolidone and acetone are mixed in a mass ratio of 100:1.5:2:200 and stirred at 40℃ and 450rpm for 30min to obtain an epoxy resin-containing adhesive solution. S2.2 Add modified silicon carbide powder to an epoxy resin binder solution, stir for 60 min at 40℃ and 450 rpm, filter to obtain epoxy-coated particles, wherein the mass ratio of modified silicon carbide powder to epoxy resin binder solution is 1:2. S3.1. Hydroxyl-terminated polyurethane, polyethylene glycol, polyvinylpyrrolidone and acetone are mixed in a mass ratio of 100:1.5:1.5:200 and stirred at 40°C and 450 rpm for 30 min to obtain a polyurethane-containing adhesive solution. S3.2 Add epoxy-coated particles to a polyurethane binder solution, stir for 120 min at 70℃ and 450 rpm, filter, and obtain coated wet powder particles, wherein the mass ratio of epoxy-coated particles to polyurethane binder solution is 1:2. S3.3 Add the coated wet powder particles to a high-speed mixer and granulator, premix at 450 rpm for 8 min, and then granulate at 1200 rpm for 18 min. The resulting wet particles are dried at 45℃ for 2 h, and then heated to 90℃ for 3 h to obtain silicon carbide granulated powder.

[0050] It is basically the same as Example 1, except that the polyurethane used in step S3.1 is hydroxyl-terminated polyurethane.

[0051] Comparative Example 1: S1.1 Add silicon carbide particles with a particle size of 60±5μm to an alkaline activation solution, stir at 65℃ and 500rpm for 60min, filter and wash with deionized water to obtain activated silicon carbide. The mass ratio of silicon carbide particles to alkaline activation solution is 1:10, and the alkaline activation solution is an aqueous solution containing 15wt% sodium hydroxide. S1.2 Add activated silicon carbide to an alcohol-water solution containing γ-glycidoxypropyltrimethoxysilane, stir at 60°C and 600 rpm for 60 min, filter to obtain pre-modified silicon carbide powder, wherein the mass ratio of activated silicon carbide, γ-glycidoxypropyltrimethoxysilane and alcohol-water solution is 100:8:45, and the alcohol-water solution is composed of ethanol and deionized water in a mass ratio of 80:20; S1.3 The pre-modified silicon carbide powder was washed three times with an alcohol-water solution of ethanol and deionized water in a mass ratio of 80:20, and dried at 75°C for 4 hours to obtain modified silicon carbide powder. S2.1. Bisphenol A type epoxy resin, polyethylene glycol, polyvinylpyrrolidone and acetone are mixed in a mass ratio of 100:1.5:2:200 and stirred at 40℃ and 450rpm for 30min to obtain an epoxy resin-containing adhesive solution. S2.2 Add modified silicon carbide powder to an epoxy resin binder solution, stir for 60 min at 40℃ and 450 rpm, filter to obtain epoxy-coated particles, wherein the mass ratio of modified silicon carbide powder to epoxy resin binder solution is 1:2. S3.1 Mix amino-terminated polyurethane, polyethylene glycol, polyvinylpyrrolidone and acetone in a mass ratio of 100:1.5:1.5:200 and stir at 40°C and 450 rpm for 30 min to obtain a polyurethane-containing adhesive solution. S3.2 Add epoxy-coated particles to a polyurethane binder solution, stir for 60 min at 60℃ and 450 rpm, filter to obtain coated wet powder particles, wherein the mass ratio of epoxy-coated particles to polyurethane binder solution is 1:2. S3.3 Add the coated wet powder particles to a high-speed mixer and granulator, premix at 450 rpm for 8 min, and then granulate at 1200 rpm for 18 min. The resulting wet particles are dried at 45℃ for 2 h, and then heated to 90℃ for 3 h to obtain silicon carbide granulated powder.

[0052] It is basically the same as Example 1, except that the silane coupling agent used in step S1 does not contain amino groups.

[0053] Comparative Example 2: S1.1 Add silicon carbide particles with a particle size of 60±5μm to an alkaline activation solution, stir at 65℃ and 500rpm for 60min, filter and wash with deionized water to obtain activated silicon carbide. The mass ratio of silicon carbide particles to alkaline activation solution is 1:10, and the alkaline activation solution is an aqueous solution containing 15wt% sodium hydroxide. S1.2 Add activated silicon carbide to an alcohol-water solution containing γ-aminopropyltriethoxysilane, stir at 60°C and 600 rpm for 60 min, filter to obtain pre-modified silicon carbide powder, wherein the mass ratio of activated silicon carbide, γ-aminopropyltriethoxysilane and alcohol-water solution is 100:8:45, and the alcohol-water solution is composed of ethanol and deionized water in a mass ratio of 80:20; S1.3 The pre-modified silicon carbide powder was washed three times with an alcohol-water solution of ethanol and deionized water in a mass ratio of 80:20, and dried at 75°C for 4 hours to obtain modified silicon carbide powder. S2.1 Mix amino-terminated polyurethane, polyethylene glycol, polyvinylpyrrolidone and acetone in a mass ratio of 100:1.5:1.5:200 and stir at 40°C and 450 rpm for 30 min to obtain a polyurethane-containing adhesive solution. S2.2 Add the modified silicon carbide powder to the polyurethane binder solution, stir for 60 min at 60℃ and 450 rpm, filter to obtain coated wet powder particles, wherein the mass ratio of modified silicon carbide powder to polyurethane binder solution is 1:2. S2.3 Add the coated wet powder particles to a high-speed mixer and granulator, premix at 450 rpm for 8 min, and then granulate at 1200 rpm for 18 min. The resulting wet particles are dried at 45℃ for 2 h, and then heated to 90℃ for 3 h to obtain silicon carbide granulated powder.

[0054] It is basically the same as Example 1, except that the silicon carbide particles are not coated with epoxy resin.

[0055] Comparative Example 3: S1.1 Add silicon carbide particles with a particle size of 60±5μm to an alkaline activation solution, stir at 65℃ and 500rpm for 60min, filter and wash with deionized water to obtain activated silicon carbide. The mass ratio of silicon carbide particles to alkaline activation solution is 1:10, and the alkaline activation solution is an aqueous solution containing 15wt% sodium hydroxide. S1.2 Add activated silicon carbide to an alcohol-water solution containing γ-aminopropyltriethoxysilane, stir at 60°C and 600 rpm for 60 min, filter to obtain pre-modified silicon carbide powder, wherein the mass ratio of activated silicon carbide, γ-aminopropyltriethoxysilane and alcohol-water solution is 100:8:45, and the alcohol-water solution is composed of ethanol and deionized water in a mass ratio of 80:20; S1.3 The pre-modified silicon carbide powder was washed three times with an alcohol-water solution of ethanol and deionized water in a mass ratio of 80:20, and dried at 75°C for 4 hours to obtain modified silicon carbide powder. S2.1. Bisphenol A type epoxy resin, polyethylene glycol, polyvinylpyrrolidone and acetone are mixed in a mass ratio of 100:1.5:2:200 and stirred at 40℃ and 450rpm for 30min to obtain an epoxy resin-containing adhesive solution. S2.2 Add the modified silicon carbide powder to the epoxy resin binder solution, stir for 60 min at 40℃ and 450 rpm, filter to obtain coated wet powder particles, wherein the mass ratio of modified silicon carbide powder to epoxy resin binder solution is 1:2. S3. Add the coated wet powder particles to a high-speed mixer and granulator. First, premix at 450 rpm for 8 min, then granulate by high-speed shearing at 1200 rpm for 18 min. The resulting wet particles are first dried at 45℃ for 2 h, then heated to 90℃ and dried for 3 h to obtain silicon carbide granulated powder.

[0056] It is basically the same as Example 1, except that the silicon carbide particles are not coated with polyurethane.

[0057] Comparative Example 4: S1.1 Add silicon carbide particles with a particle size of 60±5μm to an alkaline activation solution, stir at 65℃ and 500rpm for 60min, filter and wash with deionized water to obtain activated silicon carbide. The mass ratio of silicon carbide particles to alkaline activation solution is 1:10, and the alkaline activation solution is an aqueous solution containing 15wt% sodium hydroxide. S1.2 Add activated silicon carbide to an alcohol-water solution containing γ-aminopropyltriethoxysilane, stir at 60°C and 600 rpm for 60 min, filter to obtain pre-modified silicon carbide powder, wherein the mass ratio of activated silicon carbide, γ-aminopropyltriethoxysilane and alcohol-water solution is 100:8:45, and the alcohol-water solution is composed of ethanol and deionized water in a mass ratio of 80:20; S1.3 The pre-modified silicon carbide powder was washed three times with an alcohol-water solution of ethanol and deionized water in a mass ratio of 80:20, and dried at 75°C for 4 hours to obtain modified silicon carbide powder. S2.1. Bisphenol A type epoxy resin, polyethylene glycol, polyvinylpyrrolidone and acetone are mixed in a mass ratio of 100:1.5:2:200 and stirred at 40℃ and 450rpm for 30min to obtain an epoxy resin-containing adhesive solution. S2.2 Add the modified silicon carbide powder to a high-speed mixer and granulator, and stir at 1000 rpm for 30 min. At the same time, spray the epoxy resin binder solution in the form of atomization during the stirring process. Then, dry at 45℃ for 2 h, and then heat to 90℃ for 3 h to obtain silicon carbide granulated powder. The mass ratio of modified silicon carbide powder to epoxy resin binder solution is 1:2.

[0058] The process is basically the same as in Example 1, except that only an epoxy resin binder solution is added in atomized form during the stirring and granulation process to coat the silicon carbide powder.

[0059] Comparative Example 5: S1.1 Add silicon carbide particles with a particle size of 60±5μm to an alkaline activation solution, stir at 65℃ and 500rpm for 60min, filter and wash with deionized water to obtain activated silicon carbide. The mass ratio of silicon carbide particles to alkaline activation solution is 1:10, and the alkaline activation solution is an aqueous solution containing 15wt% sodium hydroxide. S1.2 Add activated silicon carbide to an alcohol-water solution containing γ-aminopropyltriethoxysilane, stir at 60°C and 600 rpm for 60 min, filter to obtain pre-modified silicon carbide powder, wherein the mass ratio of activated silicon carbide, γ-aminopropyltriethoxysilane and alcohol-water solution is 100:8:45, and the alcohol-water solution is composed of ethanol and deionized water in a mass ratio of 80:20; S1.3 The pre-modified silicon carbide powder was washed three times with an alcohol-water solution of ethanol and deionized water in a mass ratio of 80:20, and dried at 75°C for 4 hours to obtain modified silicon carbide powder. S2.1 Mix amino-terminated polyurethane, polyethylene glycol, polyvinylpyrrolidone and acetone in a mass ratio of 100:1.5:1.5:200 and stir at 40°C and 450 rpm for 30 min to obtain a polyurethane-containing adhesive solution. S2.2 Add the modified silicon carbide powder to a high-speed mixer and granulator, and stir at 1000 rpm for 30 min. At the same time, spray the polyurethane binder solution in the form of atomization during the stirring process. Then, dry at 45℃ for 2 h, and then heat to 90℃ for 3 h to obtain silicon carbide granulated powder. The mass ratio of modified silicon carbide powder to polyurethane binder solution is 1:2.

[0060] The process is basically the same as in Example 1, except that a polyurethane binder solution is added in an atomized form during the stirring and granulation process to coat the silicon carbide powder.

[0061] Comparative Example 6: S1.1 Add silicon carbide particles with a particle size of 60±5μm to an alkaline activation solution, stir at 65℃ and 500rpm for 60min, filter and wash with deionized water to obtain activated silicon carbide. The mass ratio of silicon carbide particles to alkaline activation solution is 1:10, and the alkaline activation solution is an aqueous solution containing 15wt% sodium hydroxide. S1.2 Add activated silicon carbide to an alcohol-water solution containing γ-aminopropyltriethoxysilane, stir at 60°C and 600 rpm for 60 min, filter to obtain pre-modified silicon carbide powder, wherein the mass ratio of activated silicon carbide, γ-aminopropyltriethoxysilane and alcohol-water solution is 100:8:45, and the alcohol-water solution is composed of ethanol and deionized water in a mass ratio of 80:20; S1.3 The pre-modified silicon carbide powder was washed three times with an alcohol-water solution of ethanol and deionized water in a mass ratio of 80:20, and dried at 75°C for 4 hours to obtain modified silicon carbide powder. S2.1. Bisphenol A type epoxy resin, polyethylene glycol, polyvinylpyrrolidone and acetone are mixed in a mass ratio of 100:1.5:2:200 and stirred at 40℃ and 450rpm for 30min to obtain an epoxy resin-containing adhesive solution. S2.2 Add the modified silicon carbide powder to a high-speed mixer and granulator, and stir at 1000 rpm for 15 min. During the stirring process, spray the epoxy resin binder solution in an atomized form. Then continue stirring at 1000 rpm for 15 min, and spray the polyurethane binder solution in an atomized form during the stirring process. Finally, dry at 45℃ for 2 h, and then heat to 90℃ and dry for 3 h to obtain silicon carbide granulated powder. The mass ratio of modified silicon carbide powder to epoxy resin binder solution and polyurethane binder solution is 1:2:2.

[0062] The process is basically the same as in Example 1, except that the epoxy resin adhesive solution and the polyurethane adhesive solution are added sequentially in the form of spray during the stirring and granulation process to coat the silicon carbide powder.

[0063] Performance testing: Loose packing density: Take dried silicon carbide granulated powder, mix it gently, and test it using a graduated cylinder of specified volume. Slowly add the powder along the container wall until it exceeds the graduation mark, without vibration or compaction. Then, gently level the powder surface with a ruler along the container opening, making the powder surface flush with the opening. Weigh the total mass of the container and powder, subtract the mass of the empty container to obtain the powder mass, and calculate the loose packing density based on the container's caliber. Perform the test in triplicate and take the average value. The unit is g / cm³. 3 ; Tapped density: Take dried silicon carbide granulated powder and place it into a graduated cylinder of a specified volume. Record the initial powder volume. Fix the container on a tapped density meter and vibrate it 1000 times at a vibration frequency of 250 times / min to fully rearrange and compact the powder particles. After vibration, read the final powder volume and weigh the powder. Calculate the tapped density based on the powder mass and the final volume after tapping. Perform the test in triplicate and take the average value. The unit is g / cm³. 3 .

[0064] The test results are shown in Table 1.

[0065] Table 1. Density test of silicon carbide granulated powder: As shown in Table 1, Example 1, which uses aminosilane modification, epoxy resin one-time coating and amino-terminated polyurethane two-time coating, has the highest loose density and tap density. After changing the amount of epoxy coating in Examples 2 and 3, the densities of both are lower than those of Example 1. In Example 4, after changing the amino-terminated polyurethane to hydroxyl-terminated polyurethane, the density is also reduced.

[0066] Compared to Example 1, Comparative Example 1 used an amino-free silane coupling agent, Comparative Example 2 eliminated epoxy resin coating, and Comparative Example 3 eliminated polyurethane coating, resulting in further reductions in both loose packing density and tapped density. Comparative Examples 4 and 5 used a single binder solution for direct spray granulation, resulting in the lowest density. Although Comparative Example 6 used both epoxy resin and polyurethane, it changed to adding the two binder solutions sequentially by spray, and its density was still lower than that of Example 1.

[0067] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the following claims.

Claims

1. A method for preparing silicon carbide granulated powder, characterized in that, The preparation method includes the following preparation steps: S1. Silicon carbide particles are added to an alkaline activation solution for activation treatment to obtain activated silicon carbide. Then, the activated silicon carbide is added to an alcohol-water solution containing a silane coupling agent, heated and stirred to obtain modified silicon carbide powder, wherein the silane coupling agent contains amino groups. S2. The modified silicon carbide powder is placed in an epoxy resin binder solution for a one-time coating treatment to obtain epoxy-coated particles. S3. Epoxy-coated particles are added to a polyurethane binder solution for secondary coating to obtain coated wet powder particles. The coated wet powder particles are granulated and dried to obtain silicon carbide granulated powder, wherein the polyurethane contains amino or hydroxyl groups.

2. The method for preparing silicon carbide granulated powder according to claim 1, characterized in that, In step S1, the particle size of the silicon carbide particles is ≥50μm, and the silane coupling agent includes at least one of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-β-aminoethyl-γ-aminopropyltrimethoxysilane, N-β-aminoethyl-γ-aminopropyltriethoxysilane, and γ-aminopropylmethyldiethoxysilane.

3. The method for preparing silicon carbide granulated powder according to claim 2, characterized in that, Step S1 includes: S1.1 Add silicon carbide particles to an alkaline activation solution, stir at 50-80℃ and 400-600rpm for 30-90min, filter, and wash with deionized water to obtain activated silicon carbide. The mass ratio of silicon carbide particles to alkaline activation solution is 1:(8-12). The alkaline activation solution is an aqueous solution containing 10-20wt% alkaline substances, including at least one of sodium hydroxide, potassium hydroxide, and sodium carbonate. S1.2 Add activated silicon carbide to an alcohol-water solution containing silane coupling agent, stir at 50-70℃ and 400-800rpm for 30-90min, filter to obtain pre-modified silicon carbide powder, wherein the mass ratio of activated silicon carbide, silane coupling agent and alcohol-water solution is 100:(6-10):(30-60), and the alcohol-water solution is composed of ethanol and deionized water in a mass ratio of (60-90):(10-40); S1.3 Wash the pre-modified silicon carbide powder 2-3 times with an alcohol-water solution of ethanol and deionized water in a mass ratio of (60-90):(10-40), and dry it at 60-90℃ for 2-6 hours to obtain modified silicon carbide powder.

4. The method for preparing silicon carbide granulated powder according to claim 1, characterized in that, The epoxy resin in step S2 includes at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, and phenolic epoxy resin.

5. The method for preparing silicon carbide granulated powder according to claim 4, characterized in that, Step S2 includes: S2.

1. Epoxy resin, wetting agent, dispersant, and organic solvent are mixed in a mass ratio of 100:(1~2):(1~3):(100~300) and stirred at 30~50℃ and 300~600rpm for 20~40min to obtain an epoxy resin-containing binder solution. The wetting agent includes at least one of polyethylene glycol, propylene glycol, glycerin, polyoxyethylene ether, and polyether-modified siloxane; the dispersant includes at least one of polyvinylpyrrolidone, sodium polyacrylate, sodium hexametaphosphate, sodium citrate, and sodium dodecyl sulfate; and the organic solvent includes at least one of xylene, methyl ethyl ketone, and acetone. S2.2 Add the modified silicon carbide powder to the epoxy resin binder solution, stir for 30-90 min at 30-50℃ and 300-600 rpm, filter to obtain epoxy-coated particles, wherein the mass ratio of the modified silicon carbide powder to the epoxy resin binder solution is 1:(1-3).

6. The method for preparing silicon carbide granulated powder according to claim 1, characterized in that, In step S3, the polyurethane is an amino-terminated polyurethane or a hydroxyl-terminated polyurethane.

7. The method for preparing silicon carbide granulated powder according to claim 6, characterized in that, The preparation method of amino-terminated polyurethane or hydroxyl-terminated polyurethane is as follows: Diol and diisocyanate are mixed at a molar ratio of hydroxyl to isocyanate groups of 1:(1.8~2.2) and reacted at 65~85℃ for 2~4h in an inert atmosphere to obtain isocyanate-terminated polyurethane prepolymer; then a hydroxyl-termining agent or an amino-termining agent is added so that the molar ratio of hydroxyl to amino to isocyanate groups in the hydroxyl-termining agent is (1.02~1.30):1, and the mixture is reacted at 60~80℃ for 1~3h to obtain hydroxyl-terminated polyurethane or amino-termined polyurethane.

8. The method for preparing silicon carbide granulated powder according to claim 7, characterized in that, The diols include at least one of polytetramethylene ether glycol, polypropylene glycol, polycaprolactone glycol, and polybutylene adipate glycol; the diisocyanates include at least one of isophorone diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, hydrogenated 4,4'-diphenylmethane diisocyanate, toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, and phenylenediamine diisocyanate; the hydroxyl end-capping agent includes at least one of polyethylene glycol, 1,4-butanediol, and propylene glycol; and the amino end-capping agent includes at least one of ethylenediamine, hexamethylenediamine, and isophorone diamine.

9. A method for preparing silicon carbide granulated powder according to any one of claims 6-8, characterized in that, Step S3 includes: S3.

1. Polyurethane, wetting agent, dispersant and organic solvent are mixed in a mass ratio of 100:(1~2):(1~2):(100~300) and stirred at 30~50℃ and 300~600rpm for 20~40min to obtain a polyurethane-containing binder solution. The wetting agent includes at least one of polyethylene glycol, propylene glycol, glycerin, polyoxyethylene ether and polyether-modified siloxane. The dispersant includes at least one of polyvinylpyrrolidone, sodium polyacrylate, sodium hexametaphosphate, sodium citrate and sodium dodecyl sulfate. The organic solvent includes at least one of xylene, methyl ethyl ketone and acetone. S3.2 Add epoxy-coated particles to a polyurethane binder solution, stir for 30-120 minutes at 40-80℃ and 300-600 rpm, filter to obtain coated wet powder particles, wherein the mass ratio of epoxy-coated particles to polyurethane binder solution is 1:(1-3). S3.3 Add the coated wet powder particles into a high-speed mixer and granulator. First, premix at 300~600 rpm for 5~10 min, then granulate at 800~1500 rpm for 10~25 min. The resulting wet particles are first dried at 40~50℃ for 1~3 h, then heated to 80~110℃ and dried for 2~5 h to obtain silicon carbide granulated powder.

10. A silicon carbide granulated powder, characterized in that, The silicon carbide granulated powder is prepared by any one of the silicon carbide granulated powder preparation methods according to claims 1-9.

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