High-density silicon carbide ceramic semiconductor material and method for manufacturing the same

Abstract

The application relates to the technical field of silicon carbide ceramics, and discloses a high-density silicon carbide ceramic semiconductor material and a preparation method thereof. The material comprises: 100 parts of silicon carbide raw powder; and a composite homogeneous precursor solution. The raw powder is added into the solution, pre-mixed and cyclically grinded to prepare a composite slurry; the slurry is sent into a closed nitrogen gas spray drying tower for atomization and granulation, organic esterification and cross-linking polycondensation are triggered, and granulated powder coated with a surface cross-linking network is collected; the powder is loaded into a mold, leveled and placed in a vacuum hot pressing furnace, degassing and surface conversion heat treatment are carried out under a pressureless state, high-purity argon gas is filled in, the temperature is continuously raised, and a unidirectional axial pressure is synchronously applied, and a hot-pressed blank is prepared through high-temperature pressure preservation. In-situ cross-linking anchoring and pressureless degassing are cooperated, high-temperature auxiliary segregation and closed pores are avoided, high-density forming of the semiconductor material is realized, and the heat transfer performance of the silicon carbide ceramic is effectively improved.

Description

Technical Field

[0001] This invention relates to the field of silicon carbide ceramic technology, specifically to a high-density silicon carbide ceramic semiconductor material and its preparation method. Background Technology

[0002] Silicon carbide is an inorganic material covalently bonded to silicon and carbon, possessing semiconductor properties such as a wide bandgap and high thermal conductivity. When it is fabricated into silicon carbide ceramic semiconductor materials, the grain bonding state directly determines the macroscopic properties of the material. High density means that the material has extremely low internal porosity and tight grain boundary bonding, which is the physical basis for ensuring the effective transport of charge carriers and phonons in the matrix and providing mechanical support.

[0003] Due to the difficulty in sintering caused by the strong covalent bonds of silicon carbide, the existing inorganic ceramic material preparation process usually involves mixing the raw powder with a solid carbon source and boron-containing compounds as auxiliary sintering phases. Then, in the molding equipment, high temperature and continuous axial pressure are used to force the powder particles to undergo mass transfer and become dense and solidified.

[0004] This preparation method has limitations in terms of microscopic mass transfer and densification control. Conventional powder mixing makes it difficult to uniformly disperse trace amounts of dopant around the particles, and conventional boron carbide auxiliary materials are prone to melting and liquid-phase migration upon heating, leading to localized sintering delays and abnormal fluctuations in electrical conductivity caused by component segregation within the matrix. Simultaneously, the oxide thin layer on the silicon carbide surface undergoes a reduction reaction at high temperatures, continuously releasing associated gases. Traditional methods maintain external high pressure throughout the heating process, directly blocking the gas escape channels and forcing the unreleased gases to be trapped in the gaps, forming closed pores. These residual pores, along with the uneven distribution of components at grain boundaries, collectively block the phonon thermal conduction path, severely limiting the final density improvement of the product.

[0005] Therefore, this invention proposes a high-density silicon carbide ceramic semiconductor material and its preparation method to overcome the shortcomings of the prior art. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a high-density silicon carbide ceramic semiconductor material and its preparation method, which solves the problems of easy liquid phase segregation of the auxiliary phase when heated and the formation of closed pores due to the retention of gases associated with the reduction reaction in the matrix under traditional powder preparation and pressure sintering processes.

[0007] To address the above problems, the present invention provides the following technical solution: In a first aspect, the present invention provides a high-density silicon carbide ceramic semiconductor material, employing the following technical solution: A high-density silicon carbide ceramic semiconductor material is prepared from raw materials comprising the following parts by weight: Silicon carbide raw powder: 100 parts; composite homogeneous precursor solution, wherein the composite homogeneous precursor solution is prepared from raw materials containing the following parts by weight and dilute ammonia water: deionized water: 30-50 parts; anhydrous ethanol: 30-50 parts; polyethylene glycol 4000: 0.5-2.5 parts; sucrose: 2.0-5.0 parts; anhydrous citric acid: 1.0-3.0 parts; tributyl borate: 0.5-1.5 parts; silane coupling agent: 0.5-2.0 parts; wherein, the silane coupling agent in the composite homogeneous precursor solution is hydrolyzed and grafted, and the organic phase as carbon source and the boron-containing component are esterified, complexed and crosslinked to form a polymer coating layer with a three-dimensional network structure in situ outside the silicon carbide raw powder.

[0008] By employing the above technical solution, due to the use of a multi-component composite homogeneous precursor solution, the organic components and boron-containing components undergo complexation and hydrolysis-condensation reactions in solution. In this mixed system, tributyl borate undergoes hydrolysis in a solvent composed of deionized water and anhydrous ethanol to generate microphase boric acid.

[0009] The generated boric acid readily undergoes esterification complexation with the carboxyl and hydroxyl groups in anhydrous citric acid molecules. This reaction achieves a stable combination of the boron source molecule and the organic phase, which serves as the carbon source, at the liquid phase level.

[0010] Simultaneously, the silane coupling agent dispersed within the system undergoes hydrolysis, transforming into highly active silanol groups. These groups undergo dehydration condensation with the free hydroxyl groups on the surface of the silicon carbide powder, completing the chemical grafting of coupling molecules onto the particle surface. Using these grafted silane ends as binding sites, polyethylene glycol, sucrose, and the aforementioned boron-containing complex rapidly crosslink. This hydrolytic grafting and associated crosslinking behavior form the aforementioned three-dimensional network polymer coating layer in situ outside the silicon carbide powder.

[0011] Therefore, this mesh-like coating structure can be used to limit the liquid phase segregation and thermal volatilization of carbon and boron sources in the early stage of heating. When entering the high-temperature sintering zone, the uniformly distributed coating layer is transformed into a sintering auxiliary phase in situ, which promotes the diffusion of grain boundary materials and fills micropores, thereby reducing the number of closed pores inside the matrix. It also clears the phonon conduction path by eliminating pore defects, thus improving the overall thermal conductivity of the material.

[0012] Preferably, the high-density silicon carbide ceramic semiconductor material is prepared from raw materials comprising the following parts by weight: Silicon carbide raw powder: 100 parts; The composite homogeneous precursor solution is prepared from the following raw materials and dilute ammonia water in parts by weight: deionized water: 40 parts; anhydrous ethanol: 40 parts; polyethylene glycol 4000: 1.5 parts; sucrose: 3.5 parts; anhydrous citric acid: 2.0 parts; tributyl borate: 1.0 part; silane coupling agent: 1.2 parts.

[0013] By employing the above technical solution, equal amounts of deionized water and anhydrous ethanol are mixed primarily to adjust solvent polarity and control the hydrolysis rate of tributyl borate, thus preventing the reaction from being too rapid and generating large precipitate particles. The ratio of sucrose to anhydrous citric acid must consider both the amount of residual carbon required for later densification and the provision of sufficient functional groups to meet the complexation requirements of boric acid.

[0014] Controlling the amounts of polyethylene glycol and coupling agent aims to control the physical thickness of the surface coating layer. Thicker amorphous precursors leave behind excessive free carbon phase after pyrolysis. Considering that the presence of impurity carbon often increases the scattering of phonons by the lattice, appropriately controlling the coating layer thickness helps to balance the relationship between the densification driving force and the thermal conductivity of the material.

[0015] Preferably, the silane coupling agent is one of 3-aminopropyltriethoxysilane or γ-glycidoxypropyltrimethoxysilane; The purity of the silicon carbide raw powder is greater than or equal to 99.0%, and the particle size ranges from 0.3 micrometers to 0.8 micrometers.

[0016] By adopting the above technical solutions, these two coupling agents have amino or epoxy end groups, which can easily undergo ring-opening or condensation reactions with carboxyl or hydroxyl groups in the organic phase when in the liquid phase, thereby increasing the crosslinking density of the polymer network.

[0017] On the other hand, when the particle size of silicon carbide powder is in the range of 0.3 to 0.8 micrometers, its specific surface area is matched with the amount of coupling agent in the solution, which can better adsorb silane molecules released in the liquid phase, reduce the possibility of local agglomeration of free additives in the mixture, and reduce the risk of sintering delay caused by powder agglomeration.

[0018] Preferably, the preparation steps of the composite homogeneous precursor solution include: The deionized water and the anhydrous ethanol were mixed and kept at 45-55°C. The polyethylene glycol 4000, the sucrose and the anhydrous citric acid were added in sequence and stirred to dissolve to obtain a basic organic phase solution. The tributyl borate was added dropwise at a uniform rate to the basic organic phase solution, and the mixture was stirred to allow the boric acid generated by the hydrolysis of tributyl borate to undergo a complexation reaction with the anhydrous citric acid, thereby obtaining a boron-containing pre-complexed solution. The silane coupling agent is added to the boron-containing pre-complexed solution, and the mixture is stirred to hydrolyze the siloxane bonds to generate silanol groups, thus obtaining the crude precursor solution. The pH value was adjusted to 3.5-4.0 by adding 5%-10% dilute ammonia solution to the crude precursor solution and stirring. The composite homogeneous precursor solution was then obtained.

[0019] By employing the above technical solution, setting the reaction temperature to 45-55℃ accelerates the dissolution of polymeric raw materials, improves the dispersion uniformity of polyethylene glycol 4000, sucrose, and anhydrous citric acid in a water / ethanol mixed solvent, and, combined with the uniform dropwise addition of tributyl borate, reduces the rapid hydrolysis, phase separation, or aggregation and precipitation of tributyl borate due to localized contact with the aqueous phase. Subsequent addition of dilute ammonia fine-tunes the system to a weakly acidic range, effectively suppressing early self-condensation between silanol groups. This pH intervention prolongs the homogeneous stability period of the precursor solution, allowing sufficient operating time for subsequent slurry mixing processes.

[0020] Secondly, the present invention provides a method for preparing a high-density silicon carbide ceramic semiconductor material, employing the following technical solution: A method for preparing a high-density silicon carbide ceramic semiconductor material includes the following steps: S1: Add silicon carbide raw powder to a composite homogeneous precursor solution and premix to obtain a mixed slurry; perform cyclic grinding on the mixed slurry to obtain a silicon carbide composite slurry; S2: The silicon carbide composite slurry is fed into a closed-loop circulating nitrogen spray drying tower for atomization granulation. During the granulation process, the solvent evaporates and the organic components undergo esterification and cross-linking polycondensation reactions. Silicon carbide granulated powder with a cross-linked network on the surface is collected. S3: The silicon carbide granulated powder is loaded into a mold and leveled to obtain a sintering component containing the powder. S4: The component to be sintered is placed in a vacuum hot press sintering furnace and a vacuum is drawn. The temperature is raised and held without applying axial pressure to perform pressureless degassing and surface conversion heat treatment to obtain a degassed blank. S5: Stop vacuuming and fill the vacuum hot pressing sintering furnace with high-purity argon to restore the pressure. Continue to heat up under the protection of argon and apply unidirectional axial pressure while heating up. Maintain the temperature and pressure under high temperature and high pressure to obtain a hot pressing sintered blank. S6: After the heat preservation and pressure holding are completed, the unidirectional axial pressure is gradually unloaded, allowing the hot-pressed sintered blank to cool naturally with the furnace. After demolding, the high-density silicon carbide ceramic semiconductor material is obtained.

[0021] By adopting the above technical solution, the spray drying process removes the solvent while simultaneously triggering the chemical reconstruction of the organic system on the slurry surface using the heat within the drying tower. During heated granulation, polyethylene glycol, sucrose, and boron-containing complexes undergo dehydration and esterification, and free silanol groups condense, generating a polymer network primarily composed of silicon-oxygen bonds and ester bonds in situ on the surface of silicon carbide particles. This network acts as a physical barrier, limiting the liquid-phase segregation of carbon and boron source molecules driven by capillary forces in the subsequent pyrolysis temperature range, thus maintaining the consistency of the additive distribution.

[0022] During the heat treatment process after molding, the pressureless degassing section plays a role in eliminating microstructural obstacles. Maintaining a pressureless state in the early stage of heating provides an escape channel for the carbon dioxide and carbon monoxide produced by the reduction reaction between the surface silicon oxide thin layer and the carbon source, avoiding the premature application of axial high pressure to trap these gases in the gaps between the powder particles.

[0023] After the residual gas is vented, the stress concentration sources caused by gas trapping are eliminated, and the high-pressure densification stage begins. The active phase, uniformly distributed around the grain boundaries, directly drives mass transport, causing the grains to undergo plastic deformation and bonding at high temperatures. This combination of processes reduces closed pores and homogenizes the grain boundary composition, which macroscopically manifests as an increase in material density and a reduction in volume resistivity fluctuations.

[0024] Preferably, in step S1, the premixing time is 1.0 to 2.0 hours; the circulating grinding is performed using a continuous sand mill, with the silicon carbide grinding media having a diameter of 0.3 to 0.5 mm, a rotation speed of 1500 to 2500 r / min, and a circulating grinding time of 2 to 4 hours. In step S2, high-purity nitrogen gas with a purity greater than or equal to 99.9% is used as the drying medium in the closed-loop circulating nitrogen spray drying tower, the inlet air temperature of the closed-loop circulating nitrogen spray drying tower is set to 200 to 240°C, and the outlet air temperature of the closed-loop circulating nitrogen spray drying tower is controlled to 135 to 145°C.

[0025] By adopting the above technical solution, the high-frequency shearing force provided by the continuous sand mill can break the hard agglomeration of silicon carbide raw powder, thereby exposing the uncontaminated particle surface and providing active sites for the adhesion of polymer networks.

[0026] The outlet air temperature of the spray drying tower is controlled between 135 and 145°C. This temperature range meets the reaction energy requirements for the dehydration and esterification of polyhydroxy components and the silane polycondensation. If the temperature is too low, organic molecules are prone to remain in a free state and be lost in the early stages of pyrolysis; if the temperature is too high, the outer polymer layer may become brittle and break prematurely. High-purity nitrogen is used as the medium to prevent uncontrollable oxidation reactions of the organic precursor within the set thermodynamic window.

[0027] Preferably, in step S4, the furnace cavity of the vacuum hot-pressing sintering furnace is evacuated to a vacuum state with an absolute pressure of 5-10 Pa; then, the furnace temperature of the vacuum hot-pressing sintering furnace is raised from 25°C to 1500-1600°C at a heating rate of 5-10°C / min, and held at the temperature of 1500-1600°C for 60-120 minutes. In step S5, high-purity argon gas with a purity of ≥99.99% is introduced into the vacuum hot-pressing sintering furnace to restore the pressure inside the furnace and maintain it at 0.05-0.1 MPa; the temperature is further raised to 1900-1950°C at a heating rate of 10-15°C / min, and a unidirectional axial pressure of 30-40 MPa is applied linearly and uniformly, and held at 1900-1950°C and 30-40 MPa for 60-120 minutes. In step S6, the unidirectional axial pressure is reduced at a rate of 3 to 5 MPa / min until it is completely unloaded.

[0028] By adopting the above technical solution, the vacuum level of the furnace chamber to 5 to 10 Pa can reduce the partial pressure of the reducing gas, thereby accelerating the discharge of associated gases from the pores. The holding time is set in the range of 1500 to 1600℃, considering that this temperature is the main reaction temperature range for the reduction and stripping of the surface silica layer by carbon; holding the temperature is beneficial for the complete purification reaction at the particle interface.

[0029] The high-pressure argon gas introduced during the densification stage is mainly used to suppress the sublimation and decomposition of silicon carbide at extremely high temperatures. The temperature field of 1900 to 1950 °C, combined with a mechanical force of 30 to 40 MPa, provides the driving force required for grain boundary slip and atomic diffusion. The final linear slow decompression process slows down the release rate of internal strain, reduces the probability of microcracks caused by sudden mechanical stress changes, and ensures the integrity of the ceramic blank structure.

[0030] This invention provides a high-density silicon carbide ceramic semiconductor material and its preparation method. It has the following beneficial effects: 1. This invention introduces a multi-component precursor solution into the preparation method, causing the boric acid hydrolysis product to undergo liquid-phase complexation with citric acid and grafting with a coupling agent. Subsequent granulation triggers dehydration and polycondensation, forming a polymer cross-linked network in situ on the powder surface. This network structure restricts the thermal migration of liquid additives during the heating stage, preventing the segregation of carbon and boron components, thereby providing a uniform microcrystalline boundary reaction environment for the sintering process of silicon carbide ceramic semiconductor materials.

[0031] 2. This invention provides an effective escape channel for the associated gases generated by the surface carbothermic reduction reaction by setting up a pressureless degassing section in the early stage of heat treatment, combined with a deep vacuum environment. This operation avoids the formation of closed pores due to gas trapping caused by premature application of axial high pressure. With the removal of internal porosity defects, subsequent high-temperature and high-pressure sintering can more effectively drive grain boundary material transport and grain bonding, ensuring the integrity of the internal structure of the silicon carbide ceramic semiconductor material and achieving high-density forming of the material.

[0032] 3. This invention, through the synergy of in-situ cross-linking coating and pressureless venting, eliminates the obstruction of heat transfer paths by micropores and homogenizes the spatial distribution of carbon-boron doped phases at grain boundaries. This preparation method eliminates the volume resistivity fluctuation problem caused by local enrichment of free carbon, resulting in a material exhibiting consistent electrical conductivity characteristics. Simultaneously, the reduction of microscopic grain boundary defects lowers the internal phonon scattering probability, optimizing the macroscopic thermal conductivity and mechanical bending resistance of the high-density molded body. Attached Figure Description

[0033] Figure 1 This is a comparison of the Fourier transform infrared spectra of each test object in Test Example 1 of the present invention; Figure 2 This is a comparison chart of the thermogravimetric analysis mass changes of each test object in Test Example 2 of the present invention; Figure 3 The graphs show the volume density and apparent porosity test results of each test object in Test Example 3 of the present invention; where (a) is the volume density test result and (b) is the apparent porosity test result. Detailed Implementation

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0036] Silicon carbide raw powder, which is silicon carbide with a purity of ≥99.0% and a particle size range of 0.3 micrometers to 0.8 micrometers, CAS number 409-21-2.

[0037] Polyethylene glycol 4000, with a purity of ≥99.0% and a number average molecular weight of 3600 to 4400.

[0038] Tributyl borate, purity greater than or equal to 99.0%, CAS number 688-74-4.

[0039] 3-Aminopropyltriethoxysilane, purity greater than or equal to 98.0%, CAS number 919-30-2.

[0040] γ-glycidoxypropyltrimethoxysilane, with a purity of ≥98.0%, CAS number 2530-83-8.

[0041] The other conventional raw materials required for the preparation, such as anhydrous ethanol, sucrose, anhydrous citric acid, dilute ammonia (mass fraction of 5% to 10%), deionized water, high-purity nitrogen (purity greater than or equal to 99.9%), and high-purity argon (purity greater than or equal to 99.99%), are all commercially available products of conventional specifications in this field.

[0042] Preparation Example 1: This preparation example provides a method for preparing a composite homogeneous precursor solution, including the following steps: Step 1: Add 40 parts by weight of deionized water and 40 parts by weight of anhydrous ethanol to a reaction vessel equipped with a stirring function and a temperature control jacket. Start the stirring and set the speed to 300 r / min. Heat the mixture to 50°C using the jacket heating to obtain a mixed solvent.

[0043] Step 2: While maintaining a stirring temperature of 50℃ and a stirring speed of 300r / min, add 1.5 parts by weight of polyethylene glycol 4000, 3.5 parts by weight of sucrose and 2.0 parts by weight of anhydrous citric acid to the above mixed solvent in sequence, and continue stirring for 45 minutes to dissolve them, so as to obtain the basic organic phase solution.

[0044] Step 3: Add 1.0 part by weight of tributyl borate dropwise to the above basic organic phase solution at a uniform rate over 10 minutes. After the addition is complete, stir continuously for 30 minutes at 50°C and 300 r / min to allow the boric acid generated by the hydrolysis of tributyl borate to undergo a complexation reaction with the citric acid in the reaction solution, thereby obtaining a boron-containing pre-complexed solution.

[0045] Step 4: Add 1.2 parts by weight of 3-aminopropyltriethoxysilane to the above boron-containing pre-complexed solution, and continue stirring at 50°C and 300 r / min for 30 minutes to hydrolyze the siloxane bonds to generate silanol groups, thus obtaining the crude precursor solution.

[0046] Step 5: Add dilute ammonia to the crude precursor solution to adjust the pH of the reaction solution to 3.8. After adjustment, continue stirring at 300 r / min for 15 minutes to obtain a composite homogeneous precursor solution.

[0047] Preparation Example 2: This preparation example provides a method for preparing a composite homogeneous precursor solution, including the following steps: Step 1: Add 30 parts by weight of deionized water and 30 parts by weight of anhydrous ethanol to a reaction vessel equipped with a stirring function and a temperature control jacket. Start stirring and set the speed to 200 r / min. Heat the mixture to 45°C and maintain the temperature through the jacket heating to obtain a mixed solvent.

[0048] Step 2: While maintaining a stirring temperature of 45℃ and a stirring speed of 200r / min, add 0.5 parts by weight of polyethylene glycol 4000, 2.0 parts by weight of sucrose and 1.0 parts by weight of anhydrous citric acid to the above mixed solvent in sequence, and continue stirring for 60 minutes to dissolve them, so as to obtain the basic organic phase solution.

[0049] Step 3: Add 0.5 parts by weight of tributyl borate dropwise to the above basic organic phase solution at a uniform rate over 15 minutes. After the addition is complete, stir continuously for 40 minutes at 45°C and 200 r / min to allow the boric acid generated by the hydrolysis of tributyl borate to undergo a complexation reaction with the citric acid in the reaction solution, thereby obtaining a boron-containing pre-complexed solution.

[0050] Step 4: Add 0.5 parts by weight of γ-glycidoxypropyltrimethoxysilane to the above boron-containing pre-complexed solution, and continue stirring at 45°C and 200 r / min for 40 minutes to hydrolyze the siloxane bonds to generate silanol groups, thus obtaining the crude precursor solution.

[0051] Step 5: Add dilute ammonia dropwise to the crude precursor solution to adjust the pH of the reaction solution to 3.5. After adjustment, continue stirring at 200 r / min for 20 minutes to obtain a composite homogeneous precursor solution.

[0052] Preparation Example 3: This preparation example provides a method for preparing a composite homogeneous precursor solution, including the following steps: Step 1: Add 50 parts by weight of deionized water and 50 parts by weight of anhydrous ethanol to a reaction vessel equipped with a stirring function and a temperature control jacket. Start the stirring and set the speed to 400 r / min. Heat the mixture to 55°C using the jacket heating to obtain a mixed solvent.

[0053] Step 2: While maintaining a stirring temperature of 55℃ and a stirring speed of 400r / min, add 2.5 parts by weight of polyethylene glycol 4000, 5.0 parts by weight of sucrose and 3.0 parts by weight of anhydrous citric acid to the above mixed solvent in sequence, and continue stirring for 30 minutes to dissolve them, so as to obtain the basic organic phase solution.

[0054] Step 3: Add 1.5 parts by weight of tributyl borate dropwise to the above basic organic phase solution at a uniform rate over 5 minutes. After the addition is complete, stir continuously for 20 minutes at 55°C and 400 r / min to allow the boric acid generated by the hydrolysis of tributyl borate to undergo a complexation reaction with the citric acid in the reaction solution, thereby obtaining a boron-containing pre-complexed solution.

[0055] Step 4: Add 2.0 parts by weight of 3-aminopropyltriethoxysilane to the above boron-containing pre-complexed solution, and continue stirring at 55°C and 400 r / min for 20 minutes to hydrolyze the siloxane bonds to generate silanol groups, thus obtaining the crude precursor solution.

[0056] Step 5: Add dilute ammonia dropwise to the crude precursor solution to adjust the pH of the reaction solution to 4.0. After adjustment, continue stirring at 400 r / min for 10 minutes to obtain a composite homogeneous precursor solution.

[0057] Example 1: This embodiment provides a method for preparing a high-density silicon carbide ceramic semiconductor material, including the following steps: S1: 100 parts by weight of silicon carbide raw powder were continuously stirred in a mixing tank at a speed of 500 r / min and added uniformly to the composite homogeneous precursor solution prepared in Preparation Example 1 within 30 minutes. The mixture was premixed for 1.5 hours to obtain a mixed slurry. The mixed slurry was pumped into a continuous sand mill and circulated and ground for 3 hours at a speed of 2000 r / min using silicon carbide grinding media with a diameter of 0.4 mm to obtain silicon carbide composite slurry.

[0058] S2: The above-mentioned silicon carbide composite slurry is pumped into a closed-loop circulating nitrogen spray drying tower. High-purity nitrogen with a purity of ≥99.9% is used as the drying medium. The inlet air temperature is set to 220℃ and the outlet air temperature is controlled to 140℃ for atomization granulation. During the granulation process, the solvent evaporates and the organic components undergo esterification and cross-linking polycondensation reactions. Silicon carbide granulated powder with a cross-linked network on the surface is collected.

[0059] S3: The above-mentioned silicon carbide granulated powder is loaded into a high-strength graphite mold with graphite paper on the inner wall, and then gently pressed and leveled to obtain a component to be sintered containing the powder.

[0060] S4: Place the above-mentioned component containing powder into a vacuum hot press sintering furnace, evacuate the furnace cavity to a vacuum state with an absolute pressure of 8 Pa, and keep the upper and lower pressure heads of the mold from applying axial pressure; then raise the furnace temperature from 25°C to 1550°C at a heating rate of 8°C / min, and hold at this temperature for 90 minutes to perform pressureless degassing and surface conversion heat treatment to obtain a degassed blank.

[0061] S5: After the heat preservation is completed, stop the vacuuming and fill the vacuum hot pressing sintering furnace with high-purity argon gas with a purity of ≥99.99% to make the pressure inside the furnace rise and maintain at 0.08MPa; under the protection of argon gas, continue to heat up to 1920℃ at a heating rate of 12℃ / min. At the same time as heating, start the pressurization device and apply a unidirectional axial pressure of 35MPa at a linear and uniform rate. Hold at 1920℃ and 35MPa pressure for 90 minutes to obtain the hot-pressed sintered blank.

[0062] S6: After the heat preservation and pressure holding are completed, the axial pressure of the pressurizing device is reduced at a rate of 4MPa / min until it is completely unloaded; the heating power is cut off, and the hot-pressed sintered blank is allowed to cool naturally to 25°C under argon protection. After the furnace is opened and the mold is removed, high-density silicon carbide ceramic semiconductor material is obtained.

[0063] Example 2: This embodiment provides a method for preparing a high-density silicon carbide ceramic semiconductor material, including the following steps: S1: 100 parts by weight of silicon carbide raw powder were continuously stirred in a mixing tank at a speed of 400 r / min and added uniformly to the composite homogeneous precursor solution prepared in Preparation Example 2 within 20 minutes. The mixture was premixed for 1.0 hour to obtain a mixed slurry. The mixed slurry was pumped into a continuous sand mill and circulated and ground for 2 hours at a speed of 1500 r / min using silicon carbide grinding media with a diameter of 0.3 mm to obtain silicon carbide composite slurry.

[0064] S2: The above-mentioned silicon carbide composite slurry is pumped into a closed-loop circulating nitrogen spray drying tower. High-purity nitrogen with a purity of ≥99.9% is used as the drying medium. The inlet air temperature is set to 200℃ and the outlet air temperature is controlled to 135℃ for atomization granulation. During the granulation process, the solvent evaporates and the organic components undergo esterification and cross-linking polycondensation reactions. Silicon carbide granulated powder with a cross-linked network on the surface is collected.

[0065] S3: The above-mentioned silicon carbide granulated powder is loaded into a high-strength graphite mold with graphite paper on the inner wall, and then gently pressed and leveled to obtain a component to be sintered containing the powder.

[0066] S4: Place the above-mentioned component containing powder into a vacuum hot press sintering furnace, evacuate the furnace cavity to a vacuum state with an absolute pressure of 10 Pa, and keep the upper and lower pressure heads of the mold from applying axial pressure; then raise the furnace temperature from 25°C to 1500°C at a heating rate of 5°C / min, and hold at this temperature for 60 minutes to perform pressureless degassing and surface conversion heat treatment to obtain a degassed blank.

[0067] S5: After the heat preservation is completed, stop the vacuuming and fill the vacuum hot pressing sintering furnace with high-purity argon gas with a purity of ≥99.99% to make the pressure inside the furnace rise and maintain at 0.05MPa; under the protection of argon gas, continue to heat up to 1900℃ at a heating rate of 10℃ / min. At the same time as heating, start the pressurizing device and apply a unidirectional axial pressure of 30MPa at a linear and uniform rate. Hold at 1900℃ and 30MPa pressure for 60 minutes to obtain the hot-pressed sintered blank.

[0068] S6: After the heat preservation and pressure holding are completed, the axial pressure of the pressurizing device is reduced at a rate of 3MPa / min until it is completely unloaded; the heating power is cut off, and the hot-pressed sintered blank is allowed to cool naturally to 25°C under argon protection. After the furnace is opened and the mold is removed, high-density silicon carbide ceramic semiconductor material is obtained.

[0069] Example 3: This embodiment provides a method for preparing a high-density silicon carbide ceramic semiconductor material, including the following steps: S1: 100 parts by weight of silicon carbide raw powder were continuously stirred in a mixing tank at a speed of 600 r / min and added uniformly to the composite homogeneous precursor solution prepared in Preparation Example 3 within 40 minutes. The mixture was premixed for 2.0 hours to obtain a mixed slurry. The mixed slurry was pumped into a continuous sand mill and circulated and ground for 4 hours at a speed of 2500 r / min using silicon carbide grinding media with a diameter of 0.5 mm to obtain silicon carbide composite slurry.

[0070] S2: The above-mentioned silicon carbide composite slurry is pumped into a closed-loop circulating nitrogen spray drying tower. High-purity nitrogen with a purity of ≥99.9% is used as the drying medium. The inlet air temperature is set to 240℃ and the outlet air temperature is controlled to 145℃ for atomization granulation. During the granulation process, the solvent evaporates and the organic components undergo esterification and cross-linking polycondensation reactions. Silicon carbide granulated powder with a cross-linked network on the surface is collected.

[0071] S3: The above-mentioned silicon carbide granulated powder is loaded into a high-strength graphite mold with graphite paper on the inner wall, and then gently pressed and leveled to obtain a component to be sintered containing the powder.

[0072] S4: Place the above-mentioned component containing powder into a vacuum hot press sintering furnace, evacuate the furnace cavity to a vacuum state with an absolute pressure of 5 Pa, and keep the upper and lower pressure heads of the mold from applying axial pressure; then raise the furnace temperature from 25°C to 1600°C at a heating rate of 10°C / min, and hold at this temperature for 120 minutes to perform pressureless degassing and surface conversion heat treatment to obtain a degassed blank.

[0073] S5: After the heat preservation is completed, stop the vacuuming and fill the vacuum hot pressing sintering furnace with high-purity argon gas with a purity of ≥99.99% to make the pressure inside the furnace rise and maintain at 0.1MPa; under the protection of argon gas, continue to heat up to 1950℃ at a heating rate of 15℃ / min. At the same time as heating, start the pressurizing device and apply a unidirectional axial pressure of 40MPa at a linear and uniform rate. Hold at 1950℃ and 40MPa pressure for 120 minutes to obtain the hot-pressed sintered blank.

[0074] S6: After the heat preservation and pressure holding are completed, the axial pressure of the pressurizing device is reduced at a rate of 5MPa / min until it is completely unloaded; the heating power is cut off, and the hot-pressed sintered blank is allowed to cool naturally to 25°C under argon protection. After the furnace is opened and the mold is removed, high-density silicon carbide ceramic semiconductor material is obtained.

[0075] It should be noted that the silicon carbide abrasive media in Examples 1 to 3 above can be silicon carbide abrasive microspheres, and the pressurizing device can be a servo hydraulic cylinder.

[0076] Comparative Example 1: The difference from Example 1 is that anhydrous citric acid was not added in the step of preparing the composite homogeneous precursor solution, while the rest were the same.

[0077] Comparative Example 2: The difference from Example 1 is that 3-aminopropyltriethoxysilane was not added in the step of preparing the composite homogeneous precursor solution, while the rest were the same.

[0078] Comparative Example 3: Compared with Example 1, the difference is that in step S2, the outlet air temperature of the closed-loop nitrogen spray drying tower is controlled at 90°C, while the rest are the same.

[0079] Comparative Example 4: Compared with Example 1, the difference lies in that steps S4 and S5 are replaced with the traditional one-step pressurized hot-pressing sintering method. Specifically, the component to be sintered, containing powder, is placed in a vacuum hot-pressing sintering furnace. After the furnace cavity is evacuated to a vacuum state with an absolute pressure of 8 Pa, high-purity argon gas with a purity greater than or equal to 99.99% is immediately introduced to raise the furnace pressure and maintain it at 0.08 MPa. Under argon protection, the pressurizing device is activated to directly apply a unidirectional axial pressure of 35 MPa, while simultaneously raising the furnace temperature continuously from 25°C to 1920°C at a heating rate of 10°C / min. During this heating process, the axial pressure of 35 MPa is maintained throughout, and the furnace is held at 1920°C and 35 MPa for 90 minutes to obtain the hot-pressed sintered blank. The remaining steps are the same as in Example 1.

[0080] Comparative Example 5: Compared with Example 1, the difference lies in that step S2 is replaced by static drying and pulverization. Specifically, the silicon carbide composite slurry obtained in step S1 is poured into a stainless steel drying tray and placed in an electric heating forced-air drying oven. The drying temperature is set to 100°C and dried continuously for 12 hours to completely evaporate the free deionized water and anhydrous ethanol, resulting in a hard, agglomerated solid dry material. Subsequently, the agglomerated solid dry material is fed into a high-speed pulverizer and pulverized for 5 minutes at a speed of 10,000 r / min. Finally, the pulverized material is sieved through a 100-mesh stainless steel standard sieve with a pore size of 150 micrometers, and the undersized powder is collected to replace the original silicon carbide granulation powder and loaded into the mold. The remaining steps are the same as in Example 1.

[0081] Test Example 1: This test case mainly verifies whether the organosilicon precursor and the organic carbon and boron sources on the surface of silicon carbide under the set spray drying temperature conditions undergo dehydration esterification and cross-linking polycondensation reactions.

[0082] The test group consisted of silicon carbide granulated powder prepared and collected in step S2 of Example 1; the control group consisted of silicon carbide composite slurry prepared in step S1 of Example 1. This slurry was not spray-dried but was directly placed in a 25°C vacuum drying oven and dried to constant weight, and uncrosslinked powder was collected.

[0083] Experimental steps: Weigh approximately 2.0 mg of silicon carbide granulated powder from the test group and uncrosslinked powder from the control group, and place them separately in an agate mortar.

[0084] Add approximately 200 mg of thoroughly dried chromatographic grade potassium bromide powder to each mortar and grind them thoroughly until they are evenly mixed.

[0085] The mixed powder is transferred to a tableting mold, and a pressure of 10 MPa is applied and held for 2 minutes to press it into a semi-transparent infrared test sheet with uniform thickness.

[0086] The prepared pellet was placed in the sample chamber of the Fourier transform infrared spectrometer. The instrument's scanning wavenumber range was set to 4000 cm⁻¹. -1 Up to 400cm -1 The spectral resolution was set to 4cm. -1 The number of scans for both the background and the sample was set to 32.

[0087] The corresponding infrared absorption spectrum signals were collected, and after baseline calibration, the relative peak intensity data of the wavenumber positions of specific functional groups were extracted and compared and analyzed.

[0088] Experimental results (see Table 1): Table 1: Relative Peak Intensity Test Data of Key Absorption Peaks in Fourier Transform Infrared Spectroscopy (FTIR)

[0089] Test conclusion: According to Table 1 and Figure 1 As shown, the silicon carbide granulated powder in the test group was at a density of 3350 to 3450 cm⁻¹. -1 The intensity of the characteristic absorption peak of hydroxyl groups in the range was significantly reduced compared to the control group of uncrosslinked powder, with the absorbance decreasing from 0.864 to 0.281. This significant consumption of hydroxyl groups indicates that under an outlet air temperature of 140°C, polyethylene glycol 4000, sucrose, and silanol groups generated by hydrolysis in the precursor may have undergone a dehydration reaction.

[0090] Observed from 1725 to 1745 cm -1 In the wavenumber range, positions that initially showed only weak signals in the control group became absorption peaks with absorbance reaching 0.547 for ester groups (C=O) in the test group granulated powder. This indicates that the polyhydroxy carbon source and the boron-containing citric acid complex may have undergone further polycondensation through esterification.

[0091] Between 1000 and 1100 cm -1 In the wavelength range, the test group exhibited a silicon-oxygen covalent bond (Si-O-Si) peak intensity of 0.819, showing characteristics of increased peak width and enhanced intensity. During this stage, silane hydrolysis products not only undergo condensation polymerization within the organic phase but also dehydrate and condense with residual hydroxyl groups on the surface of silicon carbide particles, binding the resulting cross-linked network to the surface of the inorganic powder. This coating layer helps restrict the migration of carbon and boron source additives during subsequent high-temperature processing.

[0092] Test Example 2: This test case primarily verifies whether the cross-linked network formed on the silicon carbide surface effectively locks in the carbon and boron sources, and evaluates its role in inhibiting the melting and loss of organic matter and improving the residual carbon rate.

[0093] The test group consisted of silicon carbide granulated powder prepared in step S2 of Example 1; the control group consisted of silicon carbide granulated powder prepared in step S2 of Comparative Example 3. The spray drying outlet temperature of the control group was only controlled at 90°C, and its degree of crosslinking and polycondensation was lower than that of the test group.

[0094] Experimental steps: Weigh approximately 10.2 mg of the test group silicon carbide granulation powder and approximately 10.5 mg of the control group silicon carbide granulation powder, and place them separately into clean alumina crucibles.

[0095] The alumina crucible containing the sample is placed inside the heating chamber of the thermogravimetric analyzer.

[0096] Turn on the high-purity argon gas line, adjust the gas flow rate to 50 mL / min, and purge the furnace cavity for 20 minutes to remove the air.

[0097] The heating program was started, and the furnace temperature was continuously heated from 25℃ to 1000℃ at a heating rate of 10℃ / min. Real-time data on the change of sample mass with temperature during the heating process were collected.

[0098] The initial mass at 25°C before heating began, and the real-time masses of the sample at 50°C, 250°C, 600°C, and 1000°C were extracted. The first weight loss difference was obtained by subtracting the real-time mass at 250°C from the real-time mass at 50°C. This first weight loss difference was then divided by the initial mass to calculate the weight loss rate from 50°C to 250°C. The second weight loss difference was obtained by subtracting the real-time mass at 600°C from the real-time mass at 250°C. This second weight loss difference was then divided by the initial mass to calculate the weight loss rate from 250°C to 600°C. The third weight loss difference was obtained by subtracting the real-time mass at 1000°C from the real-time mass at 600°C. This third weight loss difference was then divided by the initial mass to calculate the weight loss rate from 600°C to 1000°C. Finally, the final residual mass percentage at 1000°C was obtained by dividing the real-time mass at 1000°C by the initial mass.

[0099] Experimental results (see Table 2): Table 2: Weight loss rate and final residual mass test data for each temperature range in thermogravimetric analysis

[0100] Test conclusion: According to Table 2 and Figure 2 As shown, the control group of silicon carbide granulated powder exhibited a significant weight loss of 2.15% in the low-temperature range of 50 to 250°C. This phenomenon stems from the fact that the outlet air temperature of 90°C failed to provide sufficient temperature to trigger the cross-linking and polycondensation of the organic components, resulting in a large amount of unreacted polyethylene glycol and citric acid molecules being in a free state, which rapidly volatilized and were lost in the initial stage of heating.

[0101] Entering the main pyrolysis range of 250 to 600℃, the weight loss rate of the control group increased to 4.39%. Liquid carbon sources not bound by cross-linked networks are prone to melting and liquefaction in this temperature range. Driven by capillary forces between inorganic powders, the molten components undergo significant migration, aggregation, and decomposition, resulting in the loss of a large amount of carbon elements due to heat. The final residual mass at 1000℃ is only 92.72%.

[0102] Observing the data of silicon carbide granulated powder in the test group, its weight loss rate was significantly reduced to 0.82% in the range of 50 to 250°C. This improvement in low-temperature thermal stability indicates that the precursor liquid is more conducive to dehydration esterification and polycondensation reactions at a drying temperature of 140°C. This structure is conducive to the restricted distribution of carbon and boron sources on the surface of silicon carbide particles and reduces the volatilization of free molecules.

[0103] As the temperature increased to the range of 250 to 600℃, the weight loss rate of the test group was stably controlled at 3.47%. During this stage, the cross-linked polymer network gradually sheds non-carbon heteroatoms, transforming in situ into a highly chemically active amorphous carbon layer, resulting in an increase and stabilization of the final residual mass at 1000℃ to 95.10%. The delayed pyrolysis behavior and the increase in residual mass indicate that this hybrid coating layer helps reduce the risk of segregation caused by thermal migration of organic matter, providing a highly uniform grain boundary microenvironment for subsequent high-temperature densification sintering.

[0104] Test Example 3: This test case mainly verifies the elimination of internal pores and the overall densification degree of silicon carbide ceramic semiconductor materials, thereby evaluating the impact of degassing heat treatment and uniform component distribution on the final sintering performance.

[0105] The test subjects were the high-density silicon carbide ceramic semiconductor materials prepared in Examples 1 to 3, and the silicon carbide ceramic semiconductor materials prepared in Comparative Examples 1 to 5.

[0106] Experimental steps: Each test object was cut into block samples with dimensions of approximately 10mm × 10mm × 5mm using a diamond cutter. After ultrasonic cleaning to remove surface powder and impurities, the samples were dried in a drying oven at 110℃ until constant weight. After cooling to room temperature in a desiccator, the dried mass of the samples was weighed and recorded as m1.

[0107] Place the weighed and dried sample into a vacuum desiccator, evacuate to an absolute pressure below 2000 Pa and maintain for 30 minutes to remove air from the sample opening pores.

[0108] While maintaining a vacuum, slowly inject enough deionized water into the container to completely submerge the sample, and continue to maintain the vacuum for 20 minutes. Then, release the vacuum and soak the sample in deionized water at normal pressure for 2 hours to ensure that the open pores are fully filled with water.

[0109] The sample submerged in water is suspended in a basket equipped with a hydrostatic balance. The mass of the sample in the water in a suspended state is weighed and recorded as the suspended mass m2.

[0110] Remove the sample from the water, quickly wipe off the excess water on the sample surface with a damp, lint-free cloth, weigh it on a balance and record the mass of the sample after it has absorbed water, which is recorded as the saturated mass m3.

[0111] The data of dried mass m1, suspended mass in water m2, and saturated mass m3 were extracted and calculated. The volume of the sample was obtained by subtracting the suspended mass in water m2 from the saturated mass m3; the dried mass m1 was then divided by this volume, and multiplied by the density of deionized water at the test temperature (1.0 g / cm³).3 The bulk density is calculated by subtracting the dry mass m1 from the saturated mass m3 to obtain the mass of water in the open pores. This mass is then divided by the difference between the saturated mass m3 and the suspended mass m2 in the water, and multiplied by 100% to calculate the apparent porosity.

[0112] Experimental results (see Table 3): Table 3: Test data of bulk density and apparent porosity

[0113] Test conclusion: According to Table 3 and Figure 3 As shown, the bulk density of Examples 1 to 3 all reached 3.159 g / cm³. 3 The apparent porosity is no higher than 0.18%, indicating that the material has achieved high densification. In comparison, Comparative Example 4, by eliminating the pressureless degassing heat treatment step and applying an axial pressure of 35 MPa throughout the heating process, showed an increase in apparent porosity to 3.18% and a decrease in bulk density to 2.814 g / cm³. 3 .

[0114] This is because the reduction reaction between the oxide layer on the silicon carbide surface and the carbon source releases gas. The unreleased gas is trapped in the powder gaps under external high pressure, forming closed pores that hinder further densification of the material. The embodiment solution, by setting a pressureless degassing section in the 1500℃ to 1600℃ range, helps to reduce the interference of gas trapping on sintering.

[0115] On the other hand, Comparative Example 1 (without anhydrous citric acid), Comparative Example 2 (without silane coupling agent), and Comparative Example 5 (which underwent static drying and pulverization) showed significantly higher apparent porosities, reaching 1.42%, 1.60%, and 1.85%, respectively. This decrease in density was mainly attributed to the uneven distribution of the additives.

[0116] When the mixture lacks complexation centers or chemical bonding points, boron-carbon additives are prone to segregation during heating, resulting in additive-depleted microregions in the matrix. This leads to localized impaired mass transfer in the liquid phase, thereby creating micropores.

[0117] This invention combines liquid-phase pre-complexation with spray-drying crosslinking anchoring, which helps to limit the migration of boron-carbon additives during high-temperature processes, avoids high-temperature melting migration, and ensures that the surface of silicon carbide particles has a uniform sintering driving force, thereby reducing the densification differences in the microstructure.

[0118] Test Example 4: This test case mainly verifies the consistency of the internal conductive network of silicon carbide ceramics. By analyzing the differences in the macroscopic spatial distribution of resistivity, it evaluates the actual effect of the cross-linking anchoring mechanism on suppressing the segregation and migration of boron-carbon doped components during sintering.

[0119] The test subjects were the high-density silicon carbide ceramic semiconductor materials prepared in Examples 1 and 2, and the silicon carbide ceramic semiconductor materials prepared in Comparative Examples 1 and 5.

[0120] Experimental steps: The silicon carbide ceramic semiconductor materials of the above test objects were selected and processed into circular samples with a diameter of about 30 mm and a thickness of about 2 mm using diamond cutting equipment.

[0121] The surface of the cut circular sample was ground and polished using diamond polishing paste of different mesh sizes until the surface roughness Ra of the sample was less than 0.1 μm, so as to ensure that the test probe could form a stable contact with the material surface.

[0122] The polished sample was sequentially immersed in beakers containing acetone, anhydrous ethanol, and deionized water, and ultrasonically cleaned for 15 minutes in each case to remove free abrasive and organic contaminants adhering to the surface. The sample was then placed in an 80°C drying oven for 2 hours for later use.

[0123] On the test surface of each circular sample, eight different spatial test sites are uniformly marked radially and circumferentially with the center of the circle as the geometric reference.

[0124] Under ambient temperature (25℃) and in the dark, a four-probe resistivity meter was used to sequentially test at eight designated sites. A constant DC current of 10mA was applied during the measurement process, and the volume resistivity values ​​at each test site were recorded after the voltage readings stabilized.

[0125] The volume resistivity values ​​of the eight test sites of the sample are extracted and summed. The sum is then divided by the total number of sites, which is eight, to calculate the average volume resistivity. The standard deviation of these eight volume resistivity values ​​is then calculated. The standard deviation is divided by the average volume resistivity and multiplied by 100% to calculate the coefficient of variation of the test object.

[0126] Experimental results (see Table 4): Table 4: Test data of average volume resistivity and coefficient of variation for each test object

[0127] Test conclusion: According to the data in Table 4, the coefficients of variation of volume resistivity for Examples 1 and 2 were only 2.15% and 2.08%, respectively, indicating that the values ​​measured at different spatial sites were highly consistent. This electrical response characteristic suggests that the carbon and boron elements, which play a role in conductivity regulation, have good uniformity of distribution within the silicon carbide ceramic matrix.

[0128] Comparative Example 1, lacking anhydrous citric acid in its formulation, failed to establish a stable molecular complex structure, resulting in significant fluctuations in resistivity at various test points on its surface, with the coefficient of variation rising to 108.4%. Comparative Example 5, which underwent static drying and pulverization treatment, also exhibited obvious uneven distribution, with a coefficient of variation reaching 105.6%, indicating significant differences in the electrical properties of different regions of the material.

[0129] The fundamental reason for this difference in electrical performance lies in the fact that the liquid-phase organic carbon source and boron source are prone to melting and softening during the heating stage. Driven by surface tension and capillary forces, these free liquid components locally enrich into the pores of the powder, ultimately leaving behind enriched and depleted regions with severe carbon-boron segregation inside the sintered body. The carbon-rich region exhibits a significant decrease in resistivity due to the formation of a continuous conductive network caused by the aggregation of free carbon, while the carbon-depleted region exhibits high impedance due to the lack of acceptor carriers.

[0130] The preparation process of this invention constructs a cross-linked network in situ on the surface of silicon carbide powder through a dehydration esterification reaction during spray drying. This cross-linked layer stably binds precursor molecules to the surface of inorganic particles through chemical bonding, which to some extent restricts component migration during heating. This spatial confinement effect is beneficial for the final sintered material to exhibit more uniform electrical conductivity.

[0131] Test Example 5: This test case primarily verifies the direct improvement of macroscopic mechanical and thermal properties caused by eliminating internal pores and improving the grain boundary environment in silicon carbide ceramic materials.

[0132] The test subjects were the high-density silicon carbide ceramic semiconductor materials prepared in Examples 1 to 3, and the silicon carbide ceramic semiconductor materials prepared in Comparative Examples 1 to 5.

[0133] Experimental steps: Each test object was machined into a standard cuboid specimen with dimensions of 3mm × 4mm × 36mm using a diamond cutter. The specimen surface was ground and polished, and the edges were chamfered. The treated specimens were placed in a universal testing machine, and the three-point bending method was used for testing, with a span of 30mm and a loading rate of 0.5mm / min. The maximum breaking load at which the specimen fractured was recorded. This load value was extracted, multiplied by 1.5 times the span, and then divided by the product of the specimen width and the square of the specimen thickness to calculate the bending strength of each test object.

[0134] Each test object was processed into a block specimen with dimensions of 10mm × 10mm × 5mm, and the 10mm × 10mm surface on one side of each specimen was ground and polished to a scratch-free mirror finish. A Vickers hardness indentation test was performed on the polished surface using a Vickers hardness tester, applying a test load of 49N and holding it for 15 seconds. After the test, the lengths of the two diagonals of the indentation on the specimen surface were read using the micrometer eyepiece of the Vickers hardness tester, and the average value was calculated. Ten different locations were randomly selected for testing on each specimen, and the arithmetic mean of the diagonal lengths at each point was taken as the final diagonal length. This diagonal length value and the applied load value were extracted, and the load value was multiplied by a constant of 1.854 according to the Vickers hardness standard conversion relationship, and then divided by the square of the diagonal length value to calculate the Vickers hardness of each test object.

[0135] Each test object was processed into a circular sample with a diameter of 12.7 mm and a thickness of 2 mm, and an extremely thin layer of graphite was sprayed on both sides to enhance the absorption of laser energy. The samples were tested using a laser flare thermal conductivity meter at room temperature of 25°C. The room temperature thermal diffusivity was obtained by recording the temperature change curve of the rear surface after laser pulse irradiation of the sample over time. The measured thermal diffusivity was extracted, converted to the correct units, and multiplied by the bulk density of the corresponding sample obtained in Test Example 3, as well as the constant specific heat capacity of silicon carbide at that temperature (valued at 0.68 J / (g·K)). The room temperature thermal conductivity of each test object was then calculated.

[0136] Experimental results (see Table 5): Table 5: Test data of mechanical and thermal conductivity properties

[0137] Test conclusion: According to the data in Table 5, the flexural strength of Examples 1 to 3 was maintained above 448.7 MPa, the Vickers hardness was not less than 26.1 GPa, and the room temperature thermal conductivity was stable at a relatively high level of 148.9 W / (m·K).

[0138] In contrast, Comparative Example 4, which omitted the pressureless degassing heat treatment section, saw its flexural strength decrease to 214.6 MPa and its thermal conductivity drop to 68.7 W / (m·K). This is because Comparative Example 4 failed to effectively remove the reducing reaction gas within the powder interstices. The closed pores remaining inside the material transformed into stress concentration sources under load, making crack initiation easier. Simultaneously, the low thermal conductivity gas remaining in the pores blocked the heat transfer network of the solid medium, exacerbating phonon scattering. The embodiment utilizes a high-temperature degassing stage to mitigate the adverse effects of microscopic pore defects on performance, which is beneficial for maintaining the continuity of stress and phonon transmission channels.

[0139] In addition, the experimental data of Comparative Example 1 (without anhydrous citric acid), Comparative Example 2 (without silane coupling agent), and Comparative Example 5 (which underwent static drying and pulverization) also showed significant decreases to varying degrees compared to the examples.

[0140] The lack of effective molecular-level complexation control or cross-linking network coating in these three comparative examples led to the molten agglomeration of free boron-carbon additives during the high-temperature sintering stage, forming regions with uneven compositional distribution at the silicon carbide grain boundaries. This deterioration of the grain boundary environment not only weakened the interfacial bonding force between grains and induced local residual stress, but also additionally increased the phonon scattering probability at the lattice boundaries, ultimately reducing the mechanical and thermal transfer efficiency of the material.

[0141] This invention relies on the synergistic effect of liquid-phase pre-complexation and cross-linked network coating to improve the uniformity of additive distribution in the grain boundary region, thereby enhancing the macroscopic mechanical and thermal conductivity properties of semiconductor ceramic materials.

[0142] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-density silicon carbide ceramic semiconductor material, characterized in that, It is prepared from raw materials comprising the following parts by weight: Silicon carbide raw powder: 100 parts; A composite homogeneous precursor solution, wherein the composite homogeneous precursor solution is prepared by mixing raw materials and dilute ammonia water in parts by weight: Deionized water: 30-50 parts; Anhydrous ethanol: 30-50 parts; Polyethylene glycol 4000: 0.5–2.5 parts; Sucrose: 2.0–5.0 parts; Anhydrous citric acid: 1.0–3.0 parts; Tributyl borate: 0.5–1.5 parts; Silane coupling agent: 0.5–2.0 parts; In this process, the silane coupling agent in the composite homogeneous precursor solution is hydrolyzed and grafted, and the organic phase, which serves as the carbon source, is esterified, complexed, and crosslinked with the boron-containing component to form a polymer coating layer with a three-dimensional network structure in situ outside the silicon carbide raw powder.

2. The high-density silicon carbide ceramic semiconductor material according to claim 1, characterized in that, It is prepared from raw materials comprising the following parts by weight: Silicon carbide raw powder: 100 parts; The composite homogeneous precursor solution is prepared from the following raw materials and dilute ammonia water in parts by weight: deionized water: 40 parts; anhydrous ethanol: 40 parts; polyethylene glycol 4000: 1.5 parts; sucrose: 3.5 parts; anhydrous citric acid: 2.0 parts; tributyl borate: 1.0 part; Silane coupling agent: 1.2 parts.

3. The high-density silicon carbide ceramic semiconductor material according to claim 1, characterized in that, The silane coupling agent is one of 3-aminopropyltriethoxysilane or γ-glycidoxypropyltrimethoxysilane; The silicon carbide raw powder has a purity of ≥99.0% and a particle size range of 0.3 micrometers to 0.8 micrometers.

4. The high-density silicon carbide ceramic semiconductor material according to claim 1, characterized in that, The preparation steps of the composite homogeneous precursor solution include: The deionized water and the anhydrous ethanol were mixed and kept at 45-55°C. The polyethylene glycol 4000, the sucrose and the anhydrous citric acid were added in sequence and stirred to dissolve to obtain a basic organic phase solution. The tributyl borate was added dropwise to the basic organic phase solution at a uniform rate, and the mixture was stirred to allow the boric acid generated by the hydrolysis of tributyl borate to undergo a complexation reaction with the anhydrous citric acid, thereby obtaining a boron-containing pre-complexed solution. The silane coupling agent is added to the boron-containing pre-complexed solution, and the mixture is stirred to hydrolyze the siloxane bonds to generate silanol groups, thus obtaining the crude precursor solution. The pH value was adjusted to 3.5-4.0 by adding 5%-10% dilute ammonia solution to the crude precursor solution and stirring. The composite homogeneous precursor solution was then obtained.

5. A method for preparing a high-density silicon carbide ceramic semiconductor material according to any one of claims 1-4, characterized in that, Includes the following steps: S1: Add silicon carbide raw powder to a composite homogeneous precursor solution and premix to obtain a mixed slurry; perform cyclic grinding on the mixed slurry to obtain a silicon carbide composite slurry; S2: The silicon carbide composite slurry is fed into a closed-loop circulating nitrogen spray drying tower for atomization granulation. During the granulation process, the solvent evaporates and the organic components undergo esterification and cross-linking polycondensation reactions. Silicon carbide granulated powder with a cross-linked network on the surface is collected. S3: The silicon carbide granulated powder is loaded into a mold and leveled to obtain a sintering component containing the powder. S4: The component to be sintered is placed in a vacuum hot press sintering furnace and a vacuum is drawn. The temperature is raised and held without applying axial pressure to perform pressureless degassing and surface conversion heat treatment to obtain a degassed blank. S5: Stop vacuuming and fill the vacuum hot pressing sintering furnace with high-purity argon to restore the pressure. Continue to heat up under the protection of argon and apply unidirectional axial pressure while heating up. Maintain the temperature and pressure under high temperature and high pressure to obtain a hot pressing sintered blank. S6: After the heat preservation and pressure holding are completed, the unidirectional axial pressure is gradually unloaded, allowing the hot-pressed sintered blank to cool naturally with the furnace. After demolding, the high-density silicon carbide ceramic semiconductor material is obtained.

6. The method for preparing high-density silicon carbide ceramic semiconductor material according to claim 5, characterized in that, In step S1, the premixing time is 1.0 to 2.0 hours; the circulating grinding is carried out using a continuous sand mill, the diameter of the silicon carbide grinding media is 0.3 to 0.5 mm, the rotation speed is 1500 to 2500 r / min, and the circulating grinding time is 2 to 4 hours.

7. The method for preparing high-density silicon carbide ceramic semiconductor material according to claim 5, characterized in that, In step S2, high-purity nitrogen with a purity of ≥99.9% is used as the drying medium of the closed-loop nitrogen spray drying tower. The inlet temperature of the closed-loop nitrogen spray drying tower is set to 200-240℃, and the outlet temperature of the closed-loop nitrogen spray drying tower is controlled to 135-145℃.

8. The method for preparing high-density silicon carbide ceramic semiconductor material according to claim 5, characterized in that, In step S4, the furnace cavity of the vacuum hot pressing sintering furnace is evacuated to a vacuum state with an absolute pressure of 5-10 Pa; then the furnace temperature of the vacuum hot pressing sintering furnace is raised from 25°C to 1500-1600°C at a heating rate of 5-10°C / min, and held at the temperature of 1500-1600°C for 60-120 minutes.

9. The method for preparing high-density silicon carbide ceramic semiconductor material according to claim 5, characterized in that, In step S5, high-purity argon gas with a purity of ≥99.99% is introduced into the vacuum hot-pressing sintering furnace to raise the pressure inside the furnace and maintain it at 0.05-0.1 MPa; the temperature is then raised to 1900-1950°C at a heating rate of 10-15°C / min, and a unidirectional axial pressure of 30-40 MPa is applied linearly and uniformly, and the temperature and pressure are maintained at 1900-1950°C and 30-40 MPa for 60-120 minutes.

10. The method for preparing high-density silicon carbide ceramic semiconductor material according to claim 5, characterized in that, In step S6, the unidirectional axial pressure is reduced at a rate of 3 to 5 MPa / min until it is completely unloaded.

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