A system and method for preparing isostatically pressed graphite materials for sapphire.

Abstract

This invention provides a system and method for preparing isostatically pressed graphite materials for sapphire, relating to the field of isostatically pressed graphite materials. The system includes: a raw material processing unit for mixing aggregates and binders; an isostatic pressing unit; a calcination unit; an impregnation and strengthening unit; and a graphitization and purification unit. The raw material processing unit has at least a primary crushing module, a mixing module, and a secondary crushing module. The primary crushing module processes the aggregates to prepare primary powder. The mixing module mixes the primary powder and binder to prepare a paste. The secondary crushing module processes the paste to prepare pressed powder. The isostatic pressing unit has at least a cold isostatic pressing pre-forming module and a hot isostatic pressing densification module. The calcination unit has at least a calcination furnace, which is a directional gradient calcination furnace capable of staged temperature control. This invention can rapidly produce graphite materials with high comprehensive performance.

Description

Technical Field

[0001] This invention relates to the field of isostatic graphite materials, specifically to a system and method for preparing isostatic graphite materials for sapphire. Background Technology

[0002] Isostatically pressed graphite refers to graphite materials produced using the isostatic pressing method. It is a novel graphite material developed in the 1960s. Because isostatically pressed graphite is produced under uniform and constant liquid pressure during the molding process, it exhibits excellent properties, including large forming sizes, uniform microstructure, high density, high strength, and high isotropy (its properties are independent of size, shape, and sampling direction). Therefore, isostatically pressed graphite is also known as "isotropic" graphite. Isostatically pressed graphite materials are widely used in the semiconductor industry, such as in thermal components in silicon wafer pulling, epitaxy, and SOI processes, as well as in the production of third-generation semiconductor materials such as silicon carbide single crystals and GaN substrate epitaxy. Isostatically pressed graphite also plays a crucial role in processes such as optical fiber preforms, optical fiber drawing, ion implantation, and MOCVD, providing key material support for the technological development of related industries.

[0003] Temperature control is a crucial factor in ensuring crystal quality during sapphire crystal growth. High-quality sapphire crystals can be grown by precisely controlling the temperature at different stages. This precise temperature control typically relies on advanced thermal field equipment, such as heaters and crucibles made of isostatically pressed graphite. This equipment provides a stable thermal environment, ensuring the smooth progress of the crystal growth process. In sapphire thermal field equipment, isostatically pressed graphite can press irregularly shaped products. By changing the mold shape, complex shapes of sapphire furnace materials can be directly pressed to meet the needs of different applications. Furthermore, isostatically pressed graphite can produce large-scale thermal field equipment with fine structures, suitable for the growth of sapphire crystals of various sizes and shapes.

[0004] The production process of isostatic graphite includes fine grinding, sieving, batching, mixing, molding, calcination, impregnation, graphitization, and purification. Isostatic graphite requires structurally isotropic raw materials, necessitating the grinding of these materials into finer powders. Cold isostatic pressing technology is required, resulting in a very long calcination cycle. To achieve the target density, multiple impregnation-calcination cycles are necessary, and the graphitization cycle is also longer than that of ordinary graphite. However, isostatic graphite materials used in large-format sapphire hot zone components have a high consumption rate, and existing isostatic graphite materials suffer from long production cycles and low production efficiency, failing to meet the application requirements. Summary of the Invention

[0005] This invention addresses the problems of long production cycles, low production efficiency, and high consumption rates of isostatic graphite materials in existing technologies, which lead to insufficient production capacity and impact sapphire production. It provides a system and method for preparing isostatic graphite materials for sapphire that can improve production efficiency, optimize performance, and extend service life, thereby reducing the consumption rate of graphite materials in the sapphire production process.

[0006] The technical solution adopted in this invention is: A system for preparing isostatically pressed graphite materials for sapphire, comprising: The raw material processing unit is used to mix aggregates and binders to prepare pressed powder; An isostatic pressing unit is used to press the powder to prepare isostatic pressed products; A calcining unit is used to calcine the isostatically pressed product to prepare calcined raw products; Impregnation strengthening unit, used for impregnation treatment of the isostatic pressing product to prepare impregnated articles; The graphitization and purification unit is used to graphitize and remove impurities from the isostatic pressing product to prepare isostatic graphite material products. The raw material processing unit includes at least a primary crushing module, a mixing module, and a secondary crushing module. The primary crushing module processes the aggregate to prepare primary powder. The mixing module mixes the primary powder with a binder to prepare a paste. The secondary crushing module processes the paste to prepare pressed powder. The isostatic pressing unit includes at least a cold isostatic pressing pre-forming module and a hot isostatic pressing densification module. The calcining unit includes at least a calcining furnace, which is a directional gradient calcining furnace capable of staged temperature control.

[0007] Furthermore, the primary crushing module includes a dual-chamber hydraulic jaw crusher, a roller crusher, and a cyclone mill; the dual-chamber hydraulic jaw crusher and roller crusher are used for multi-stage crushing of the aggregate; the cyclone mill is used for grinding; and the secondary crushing module includes a centrifugal spray tower; the centrifugal spray tower is used for drying and grinding to prepare the pressed powder.

[0008] Furthermore, the bottom layer of the roasting furnace in the roasting unit is provided with 0.5-1mm artificial graphite particles; the side of the roasting furnace is provided with a nano-alumina coating; and the top of the roasting furnace is provided with 2-3mm coke particles.

[0009] Furthermore, the graphitization purification unit has at least an Atchison furnace and a cooling module; the Atchison furnace is capable of heating the impregnated product and introducing chlorine gas to remove impurities; the cooling module includes an air-cooled fan and a water mist fan.

[0010] Furthermore, the graphitization purification unit has at least a graphitization furnace substrate; a microwave generating module is provided on the outside of the furnace cavity of the graphitization furnace substrate, and the microwave generating module has at least a ring array microwave generator; electromagnetic field generating modules are provided at both the upper and lower ends of the furnace body of the graphitization furnace substrate; and a detection feedback module is provided on the furnace body of the graphitization furnace substrate, and a central control module is provided on the outside of the graphitization furnace substrate, and the central control module is signal connected to the microwave generating module, the electromagnetic field generating module and the detection feedback module.

[0011] Furthermore, the cold isostatic pressing preforming module has at least a double-layered cylinder, with a flexible mold disposed inside the double-layered cylinder, a multi-directional pressurization mechanism disposed outside the double-layered cylinder, a vibration mechanism disposed at the bottom of the double-layered cylinder, and a vacuum tube and a medium input tube disposed on the double-layered cylinder, both of which are connected to the inside and outside of the double-layered cylinder; the hot isostatic pressing densification module has at least a high-temperature isostatic pressing furnace body, which is connected to a compressor unit.

[0012] A method for preparing isostatically pressed graphite material for sapphire, using the isostatically pressed graphite material preparation system for sapphire as described above; the method for preparing isostatically pressed graphite material for sapphire includes the following steps: S10. Add the aggregate to the primary crushing module, crush and grind it to obtain primary powder; S20. Add the adhesive and the primary powder to the mixing module and knead to obtain a paste; S30. The paste is added to the secondary crushing module to obtain pressed powder; S40. The pressed powder is subjected to cold isostatic pressing preforming and hot isostatic pressing densification treatment in sequence to obtain a hot isostatic pressing product; S50. The hot isostatic pressing product is added to the roasting unit for roasting to obtain a roasted raw product; S60. The roasted raw product is added to the impregnation strengthening unit for impregnation treatment to obtain an impregnated product; S70. The impregnated product is subjected to graphitization and purification treatment, and then cooled to obtain an isostatic graphite material product.

[0013] Further, in step S20, a composite modifier is added to the mixture, the composite modifier including sodium dodecylbenzenesulfonate, alkylphenol polyoxyethylene ether, and nano-cerium oxide; and step S20 includes a dry mixing stage, a wet mixing stage, and a maturation stage; in the dry mixing stage, the primary powder, binder, and composite modifier are added; in the wet mixing stage, an ethanol solution is added and ultrasonically dispersed; in the maturation stage, the mixture is kept at a constant temperature and allowed to stand to form a stable coating layer.

[0014] Furthermore, in step S50, the working process of the roasting furnace of the roasting unit includes: heating at 1℃ / h before 300℃; heating at 3℃ / h from 300℃ to 600℃; and heating at 10℃ / h above 600℃.

[0015] Further, in step S70, the graphitization process includes: in the 0-2000℃ stage, the heating rate is controlled at 50℃ / h; in the 2000-3000℃ stage, the heating rate is controlled at 15℃ / h; and in the 3000-3200℃ stage, the temperature is maintained and chlorine gas is introduced for purification.

[0016] The beneficial effects of this invention are: 1. The sapphire isostatic graphite material preparation system of the present invention significantly reduces the production cycle of isostatic graphite materials through staged temperature control in the calcination furnace 310 of the calcination unit; it improves the isotropic properties of isostatic graphite materials through two isostatic pressing processes using a cold isostatic pressing preforming module and a hot isostatic pressing densification module; it further improves the strength of isostatic graphite materials by using a multi-stage crushing module before and after kneading in conjunction with the two isostatic pressing processes; it improves the thermal conductivity of isostatic graphite materials by using the hot isostatic pressing densification treatment of the hot isostatic pressing densification module; and it improves the density of isostatic graphite materials and reduces the coefficient of thermal expansion by using an impregnation strengthening unit. This system achieves the production of graphite materials with high purity, high strength, high thermal conductivity, low coefficient of thermal expansion, and good isotropic properties within a short cycle, solving the problems of long production cycles, low production efficiency, and high consumption rate when used as hot zone components in sapphire, which lead to failure to meet usage requirements and affect sapphire production capacity in the prior art. 2. The sapphire isostatic graphite material preparation system of the present invention, by setting up a microwave generating module 530 and an electromagnetic field generating module 540 that cooperate with each other, relies on microwaves to provide rapid heating energy and magnetic fields to regulate the atomic arrangement direction. The two work together to significantly shorten the graphitization time and significantly reduce the carbon element loss rate. This achieves precise temperature control, shortens the graphitization cycle, and improves material performance. It solves the problems of large temperature gradient, high energy consumption, and long cycle of traditional graphitization furnaces in the above embodiments. 3. The pressure forming apparatus of the present invention, by employing a cold isostatic pressing preforming module and a hot isostatic pressing densification module, performs two isostatic pressing processes under different temperature and pressure conditions, which enables the obtained isostatic graphite material to have higher isotropic properties than ordinary isostatic graphite materials.

[0017] 4. The method for preparing isostatically pressed graphite material for sapphire of the present invention significantly reduces the production cycle of isostatically pressed graphite material by using staged temperature control in the calcination furnace 310 of the calcination unit; it improves the isotropic properties of isostatically pressed graphite material by using a two-stage isostatic pressing process of cold isostatic pressing preforming module and hot isostatic pressing densification module; it further improves the strength of isostatically pressed graphite material by using a multi-stage crushing module before and after kneading in conjunction with the two-stage isostatic pressing process; it improves the thermal conductivity of isostatically pressed graphite material by using the hot isostatic pressing densification treatment of the hot isostatic pressing densification module; and it improves the density of isostatically pressed graphite material and reduces the coefficient of thermal expansion by using an impregnation strengthening unit. This method achieves the production of graphite material with high purity, high strength, high thermal conductivity, low coefficient of thermal expansion and good isotropic properties in a short cycle, solving the problems of long production cycle, low production efficiency and high consumption rate when used as a hot zone component of sapphire in the prior art, which leads to failure to meet the needs of use and affects the production capacity of sapphire. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the preparation system of Embodiment 1 of the present invention; Figure 2 This is a flowchart of the preparation system of Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the molding apparatus according to Embodiment 2 of the present invention; Figure 4 This is a schematic diagram of the preparation system of Embodiment 3 of the present invention; Figure 5 This is a flowchart of the preparation system of Embodiment 3 of the present invention; Figure 6 This is a schematic diagram of the preparation system of Embodiment 4 of the present invention; Figure 7 This is a schematic diagram of the graphitization purification unit in Embodiment 4 of the present invention; Figure 8 This is a flowchart of the preparation method of Embodiment 5 of the present invention.

[0020] Reference numerals: 100-Raw material processing unit, 110-Primary crushing module, 111-Dual-chamber hydraulic jaw crusher, 112-Roller crusher, 113-Cyclone mill, 120-Melting module, 122-Heating furnace, 130-Mixing module, 132-Heated kneader, 140-Secondary crushing module, 142-Centrifugal spray tower; 200 - Isostatic pressing forming unit, 210 - Cold isostatic pressing preforming module, 212 - Double-layer cylinder, 213 - Vacuum tube, 214 - Multi-directional pressurization mechanism, 215 - Medium input pipe, 216 - Vibration mechanism, 220 - Hot isostatic pressing densification module, 222 - High temperature isostatic pressing furnace body, 224 - Compressor unit; 300 - Calcination unit; 310 - Calcination furnace; 400 - Impregnation strengthening unit; 410 - High-pressure impregnation tank; 500 - Graphitization purification unit, 510 - Atchison furnace, 522 - Air-cooled fan, 524 - Water mist fan, 530 - Microwave generator module, 540 - Electromagnetic field generator module, 550 - Detection and feedback module, 560 - Central control module, 570 - Graphitization furnace substrate; 600 - Surface treatment unit, 610 - Chemical vapor deposition furnace. Detailed Implementation

[0021] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0022] The following disclosure provides many different embodiments or examples for implementing different structures of the present invention. To simplify the disclosure of the present invention, the components and arrangements of specific examples are described below. Of course, these are merely examples and are not intended to limit the present invention.

[0023] The embodiments of the invention will now be described in detail with reference to the accompanying drawings.

[0024] Example 1

[0025] The isostatic graphite material used in sapphire hot zone components has a high consumption rate, while the existing isostatic graphite material has low production efficiency and cannot meet the needs of use, thus affecting the production capacity of sapphire.

[0026] To address the aforementioned problems in the prior art, this embodiment provides a system for preparing isostatically pressed graphite materials for sapphire. This system is used to produce isostatically pressed graphite materials for sapphire thermal field components. In production practice, we have found that sapphire thermal field components require graphite materials with improved comprehensive properties, including high purity, high strength, high thermal conductivity, low coefficient of thermal expansion, and good isotropy, in order to reduce consumption rates. Therefore, the isostatically pressed graphite material preparation system for sapphire of this embodiment can improve the production efficiency of isostatically pressed graphite materials while optimizing their performance and extending their service life, thereby reducing the consumption rate of graphite materials in the sapphire production process. Please refer to [link to previous document]. Figures 1-2 The sapphire isostatic graphite material preparation system mainly includes: a raw material processing unit 100, an isostatic pressing unit 200, a calcination unit 300, an impregnation and strengthening unit 400, and a graphitization and purification unit 500.

[0027] The raw material processing unit 100 is used for the preliminary processing of raw materials for isostatic pressing graphite material production. In this embodiment, the raw materials used by the raw material processing unit 100 mainly include mesophase pitch coke and high-purity calcined petroleum coke as aggregates, and coal tar pitch as a binder. Figure 1 , Figure 2 As shown, the raw material processing unit 100 mainly includes a primary crushing module 110, a melting module 120, a mixing module 130, and a secondary crushing module 140. The raw material processing unit 100 can perform multi-stage processing on aggregates and binders, producing pressed powder for use as molding raw materials after mixing. The primary crushing module 110 mainly includes crushing equipment and grinding equipment. It processes mesophase pitch coke and high-purity calcined petroleum coke, producing primary powder through crushing and grinding. The melting module 120 mainly includes a heating furnace 122 for processing coal tar pitch, producing softened coal tar pitch binder after heating. Simultaneously, the mixing module 130 mainly includes a heated kneader 132, where primary powder and softened coal tar pitch binder are added and kneaded to uniformly coat the surface of the primary powder with a layer of binder, resulting in a paste. After kneading, the paste is removed and cooled. The cooled paste is added to the secondary crushing module 140, which mainly includes grinding equipment, etc., and can process the paste into powder to produce pressing powder for molding.

[0028] The isostatic pressing unit 200 is used to press the powder produced by the raw material processing unit 100 into shape and improve the isotropy of the final graphite material. The isostatic pressing unit 200 mainly includes a cold isostatic pressing pre-forming module 210 and a hot isostatic pressing densification module 220. The cold isostatic pressing pre-forming module 210 uses cold isostatic pressing technology. Unlike extrusion molding and compression molding, the isostatic pressing machine of the cold isostatic pressing pre-forming module 210 fills the raw material powder into a rubber mold. Through high-frequency electromagnetic vibration, the powder is compacted, sealed, and then vacuumed to remove air between the powder particles. Then, a liquid medium such as water or oil is injected to increase the pressure to 120–200 MPa, and the pressure is maintained to form a cold-pressed product of the required shape. In one or more other embodiments, after vacuuming, the powder can be transferred to another high-pressure container, and then a liquid medium such as water or oil can be injected to increase the pressure. The hot isostatic pressing (HIP) densification module 220 primarily utilizes a high-temperature isostatic pressing furnace. This furnace heats the cold-pressed product to 1600–1800°C and pressurizes it to over 180 MPa. Particle rearrangement eliminates residual porosity from the cold isostatic pressing process; diffusion creep promotes grain boundary slip, increasing density; and plastic flow completely eliminates closed pores, ultimately yielding a high-strength, high-thermal-conductivity HIP product. In this embodiment, pressure is applied to the rubber mold via a liquid medium such as water. According to Pascal's principle, the pressure is equal in all directions. Therefore, through the isostatic pressing unit 200, the pressed powder particles are not oriented according to the filling direction in the mold, but are compressed in an irregular arrangement. Thus, although graphite is anisotropic in crystallographic properties, the final isostatic graphite product is isotropic overall. The two isostatic pressing processes in this embodiment result in a higher isotropic isostatic ratio of the obtained isostatic graphite material compared to typical isostatic graphite materials.

[0029] The calcination unit 300 is used to calcine hot isostatic pressed products, causing complex chemical reactions between the aggregate and binder to obtain calcined raw products. The calcination unit 300 mainly includes a calcination furnace 310, which employs a two-stage operating mode: a low-temperature preheating stage and a heating stage. In the low-temperature preheating stage, the hot isostatic pressed products expand due to heat; in the subsequent heating stage, the hot isostatic pressed products shrink in volume due to a condensation reaction. Because of the fine structure of isostatic graphite, the calcination process in typical production systems needs to be carried out very slowly, and the temperature inside the furnace needs to be very uniform, especially at the temperature stage where asphalt volatiles are rapidly released. The heating process must be carried out cautiously and slowly, with a heating rate not exceeding 1℃ / h, and the temperature difference inside the furnace required to be less than 20℃. This process requires approximately 1 to 2 months. The calcining furnace 310 in this embodiment adopts a directional gradient calcining furnace, which uses staged temperature control to adapt to the physical and chemical changes required at each stage in the furnace. Before 300℃, a slow temperature increase of 1℃ / h is used; from 300℃ to 600℃, a medium-speed temperature increase of 3℃ / h is used; and above 600℃, a rapid temperature increase of 10℃ / h is used. This can significantly reduce the calcination time and ensure the performance of the material.

[0030] The impregnation strengthening unit 400 is used to treat the tiny pores left in the roasted green product during gas discharge and volume shrinkage, impregnating the interior of the roasted green product with coal tar pitch through the predominantly open pores. In this embodiment, the impregnation strengthening unit 400 mainly includes a high-pressure impregnation tank 410. The high-pressure impregnation tank 410 is first evacuated, and then the preheated roasted green product is added and impregnated under pressure. Impregnation strengthening treatment can improve the bulk density, mechanical strength, electrical conductivity, thermal conductivity, and chemical resistance of the roasted green product, and reduce its coefficient of thermal expansion.

[0031] The graphitization purification unit 500 is used to heat the impregnated product to a high temperature for graphitization and impurity removal, obtaining isostatically pressed graphite material products. The graphitization purification unit 500 mainly includes an Atchison furnace 510 and a cooling module. In this embodiment, the Atchison furnace 510 has a loading capacity of 80 tons and is equipped with 48 sets of bidirectional silicon controlled rectifier electrodes. The Atchison furnace 510 heats the impregnated product to approximately 3000°C, causing the carbon atoms to arrange in an orderly lattice, completing the transformation from carbon to graphite, i.e., graphitization. Chlorine gas can be introduced at high temperatures to remove impurities, ensuring that the ash content of the product is ≤50ppm, meeting the requirements for sapphire production. The cooling module is used for gradient cooling of the high-temperature graphitized product. The cooling module mainly includes an air-cooled fan 522 and a water mist fan 524. The high-temperature graphitized product undergoes natural cooling, forced air cooling by the air-cooled fan 522, and water mist cooling by the water mist fan 524. Through gradient cooling from fast to slow, the high-temperature graphitized product effectively prevents cracking during the cooling process.

[0032] One specific working method of this embodiment is as follows: First, mesophase pitch coke and high-purity calcined petroleum coke, used as aggregates, are added to the primary crushing module 110 for crushing and grinding to obtain primary powder. Then, the softened coal tar pitch binder processed by the melting module 120 and the primary powder are added to the mixing module 130 for kneading to obtain a paste. Next, the paste is added to the secondary crushing module 140 for pulverization to obtain pressed powder. Then, the pressed powder is sequentially processed through the cold isostatic pressing preforming module 210 and the hot isostatic pressing densification module 220 to obtain a hot isostatic pressing product. After that, the hot isostatic pressing product is calcined in the calcining furnace 310 to obtain a calcined green product. The calcined green product is then impregnated in the high-pressure impregnation tank 410 to obtain an impregnated product. Then, the impregnated product is heated and graphitized and purified in the Atchison furnace 510, and then cooled in stages by the cooling module to obtain an isostatic pressed graphite material product.

[0033] In this embodiment, the sapphire isostatic graphite material preparation system significantly reduces the production cycle of isostatic graphite materials through staged temperature control in the calcination furnace 310 of the calcination unit 300; it enhances the isotropic properties of isostatic graphite materials through two isostatic pressing processes using a cold isostatic pressing preforming module 210 and a hot isostatic pressing densification module 220; it further enhances the strength of isostatic graphite materials by using a multi-stage crushing module before and after kneading in conjunction with the two isostatic pressing processes; it improves the thermal conductivity of isostatic graphite materials through the hot isostatic pressing densification treatment of the hot isostatic pressing densification module 220; and it increases the density of isostatic graphite materials and reduces the coefficient of thermal expansion by using an impregnation strengthening unit 400. This system achieves the production of graphite materials with high purity, high strength, high thermal conductivity, low coefficient of thermal expansion, and good isotropic properties within a short cycle, solving the problems of long production cycles, low production efficiency, and high consumption rate when used as hot zone components in sapphire, which lead to insufficient performance and affect sapphire production capacity. The isostatic graphite material preparation system for sapphire in this embodiment has achieved a performance breakthrough of isostatic graphite in sapphire hot field applications through technological innovation. Its technical parameters have comprehensively exceeded the original standard requirements, realizing the efficient and stable production of isostatic graphite for sapphire hot field applications. Under the extreme operating conditions of the crystal growth furnace (long-term use at 1600-2100℃), it exhibits excellent durability and thermal stability, providing a reliable material guarantee for sapphire crystal growth.

[0034] Furthermore, the primary crushing module 110 of the raw material processing unit 100 in this embodiment includes a dual-chamber hydraulic jaw crusher 111, a roller crusher 112, and a cyclone mill 113. The dual-chamber hydraulic jaw crusher 111 discharges a particle size <10mm; the output of the dual-chamber hydraulic jaw crusher 111 enters the roller crusher 112, whose roller spacing is 0.5mm, producing intermediate material with a particle size of 1-3mm; the intermediate material then enters the cyclone mill 113, which is an integrated staged airflow mill with a working air pressure of 0.8MPa, capable of cyclone ultrafine grinding to achieve an ultrafine particle size ≤5μm, thereby allowing for better mixing of aggregates and binders. Simultaneously, the heating kneader 132 used in the mixing module 130 of the raw material processing unit 100 is a double-cone mixer. Furthermore, the secondary crushing module 140 includes a centrifugal spray tower 142, which employs a gradient temperature field design. The tower body is divided into three temperature zones: the upper zone is around 200℃; the middle zone is around 160℃; and the lower zone is around 120℃. The centrifugal spray tower 142 can produce dense granules with a sphericity >0.92. Moreover, the spray granulation particle size of the centrifugal spray tower 142 can reach 50–100 μm, and the moisture content can be controlled to ≤0.3%. Preferably, the raw material processing unit 100 can also be equipped with a quality control module, which is configured with various online monitoring devices, including a laser particle size analyzer (Malvern Mastersizer 3000), a specific surface area analyzer (BET method), and an XRF online elemental analyzer. The laser particle size analyzer is installed at the discharge end of the primary crushing module 110 and the secondary crushing module 140, and automatically samples every 30 minutes to monitor the particle size of the powder after the two crushing processes in real time. The specific surface area analyzer is installed at the discharge end of the primary crushing module 110 and the secondary crushing module 140 to control the specific surface area of ​​the powder in real time at 6-8 m² / g. The XRF online elemental analyzer is installed at the discharge end of the secondary crushing module 140 to ensure that metal impurities such as Fe and Ni are <50ppm, thereby reducing impurities in the isostatic graphitized products and avoiding contamination of sapphire with high purity requirements.

[0035] Furthermore, in this embodiment, argon gas is introduced into the hot isostatic pressing densification module 220 of the isostatic pressing molding unit 200 for protection to prevent material oxidation.

[0036] Furthermore, the roasting furnace 310 of the roasting unit 300 in this embodiment is internally filled with a composite filler to prevent deformation of the hot isostatic pressed product during roasting. The bottom layer of the roasting furnace 310 contains 0.5–1 mm artificial graphite particles with a thermal conductivity of 35 W / m·K, enhancing heat conduction. The sides of the roasting furnace 310 are coated with a nano-alumina coating to prevent adhesion. The top of the roasting furnace 310 contains 2–3 mm coke particles, forming an insulation layer to reduce heat loss. The roasting furnace 310 is also equipped with an atmosphere control assembly, which mainly includes a nitrogen flow meter, a zirconia sensor, and a pressure sensor. The nitrogen flow meter controls the nitrogen flow rate to approximately 50 L / min; the zirconia sensor controls the residual oxygen in the furnace to be <50 ppm; and the pressure sensor maintains a slight positive pressure of approximately +50 Pa inside the furnace to prevent contamination from external gases.

[0037] Typically, isostatically pressed graphite requires multiple impregnation-calcination cycles. However, in this embodiment, the high-pressure impregnation tank 410 further employs pulse impregnation technology, using electric field pulses to assist the impregnation process. The pressure fluctuation range of the high-pressure impregnation tank 410 can reach ±0.2MPa; the frequency can reach 0.5Hz, thereby increasing the impregnation depth by 2mm in one pass, eliminating the need for multiple impregnation cycles and significantly reducing impregnation time.

[0038] Example 2 Based on the above embodiments, a pressure forming apparatus is further proposed for performing an isostatic pressing process on graphite materials. This pressure forming apparatus can improve the isotropic properties of the obtained isostatic graphite materials. The pressure forming apparatus mainly includes the isostatic pressing unit described in the above embodiments.

[0039] Please see Figure 3 In the second embodiment, the isostatic pressing unit of the pressure forming apparatus mainly includes a cold isostatic pressing preforming module 210 and a hot isostatic pressing densification module 220.

[0040] The cold isostatic pressing preforming module 210 is formed using cold isostatic pressing technology. The cold isostatic pressing preforming module 210 mainly includes a double-layer cylinder 212, a flexible mold, a multi-directional pressing mechanism 214, and a vibration mechanism 216. The inner layer of the double-layer cylinder 212 is a high-strength stainless steel layer, and the outer layer is a prestressed steel wire winding layer. A vacuum tube 213 and a media input tube 215 connecting the interior and exterior are installed on the double-layer cylinder 212. The flexible mold is located inside the double-layer cylinder 212. The multi-directional pressing mechanism 214 is located outside the double-layer cylinder 212 and employs radial + axial synchronous pressing technology. The radial pressure source uses four sets of high-pressure pump stations; the axial compensation pressure uses two sets of auxiliary hydraulic cylinders. Simultaneously, the vibration mechanism 216 is located at the bottom of the double-layer cylinder 212 and is used to provide high-frequency electromagnetic vibration, making the pressed powder more compact.

[0041] The hot isostatic pressing densification module 220 mainly includes a high-temperature isostatic pressing furnace body 222 and a compressor unit 224. The high-temperature isostatic pressing furnace body 222 uses graphite heating elements. The interior of the furnace body 222 is divided into upper, middle, and lower zones with independent temperature control. A circulating cooling water jacket is installed between the inner and outer walls of the furnace body 222 for cooling. Furthermore, the compressor unit 224 includes four isothermal compressor units. The compressor unit 224 is connected to the interior of the high-temperature isostatic pressing furnace body 222 and uses high-purity argon gas as the pressure medium to regulate the pressure inside the furnace body 222.

[0042] One specific working method of this embodiment is as follows: The cold isostatic pressing preforming module 210 fills the raw material powder into a flexible mold. The high-frequency electromagnetic vibration of the vibration mechanism 216 makes the powder compacted. After sealing, the vacuum tube 213 connects to an external vacuum pump to evacuate the air between the powder particles. Then, water or oil or other liquid media are injected through the medium input pipe 215 to increase the pressure to 120-200 MPa. The pressure is held to form a cold isostatic pressing product of the required shape. Then, the cold isostatic pressing product is placed in the high-temperature isostatic pressing furnace 222. The high-temperature isostatic pressing furnace 222 heats the cold isostatic pressing product to 1600-1800℃ and pressurizes it to more than 180 MPa through the compressor unit 224. The particle rearrangement eliminates the residual porosity of the cold isostatic pressing. The density is increased by diffusion creep, which causes grain boundary slip. Then, the plastic flow completely eliminates closed pores, and finally, a high-strength, high-thermal-conductivity hot isostatic pressing product is obtained.

[0043] In this embodiment, the pressure forming device employs a cold isostatic pressing preforming module 210 and a hot isostatic pressing densification module 220 to perform two isostatic pressing processes under different temperature and pressure conditions, which enables the isostatic graphite material obtained in this embodiment to have higher isotropic properties than ordinary isostatic graphite materials.

[0044] Example 3 In the above embodiments, the problem of adapting isostatic graphite materials for sapphire production was solved. In order to further improve the performance of isostatic graphite materials for sapphire production based on the above embodiments, the isostatic graphite material preparation system for sapphire in the above embodiments is further improved. The third embodiment is provided below.

[0045] Please see Figures 4-5 The sapphire isostatic graphite material preparation system in the third embodiment is largely the same as that in the first embodiment in terms of the raw material processing unit 100, isostatic pressing unit 200, calcination unit 300, impregnation strengthening unit 400 and graphitization purification unit 500. The main difference is that the sapphire isostatic graphite material preparation system in the third embodiment is also provided with a surface treatment unit 600.

[0046] The surface treatment unit 600 in this embodiment mainly includes a chemical vapor deposition furnace 610, used for further CVD coating treatment of the isostatic graphite material product obtained from the graphitization purification unit 500. The chemical vapor deposition furnace 610 includes an upper furnace body and a lower furnace body, and is equipped with a lifting mechanism, a rotating mechanism, a heating chamber, a weighing instrument, electric valves, and a water ring pump, enabling precise control of the deposition process. The chemical vapor deposition furnace 610 uses a CH3SiCl3 / H2 mixed gas as the deposition gas. The oxidation resistance temperature of the treated isostatic graphite material product can reach approximately 2200°C from around 1900°C, which is more compatible with the maximum temperature range of 2050°C to 2150°C in sapphire production. Furthermore, the thermal expansion difference between the treated isostatic graphite material product and sapphire is less than 5%, thereby reducing the damage rate and further extending its service life.

[0047] Example 4 In the above embodiments, the problem of adapting the production of isostatic graphite materials for sapphire production was solved. In order to further improve the performance of the isostatic graphite material preparation system for sapphire production based on the above embodiments, the isostatic graphite material preparation system for sapphire in the above embodiments is further improved. The fourth embodiment is provided below.

[0048] Please see Figures 6-7 The sapphire isostatic graphite material preparation system in the fourth embodiment is largely the same as that in the first embodiment in terms of the arrangement of the raw material processing unit 100, the isostatic pressing unit 200, the calcination unit 300 and the impregnation strengthening unit 400. The main difference lies in the change of the graphitization purification unit 500 in the fourth embodiment.

[0049] Traditional Atchison graphitization furnaces suffer from problems such as large temperature gradients, high energy consumption, and long cycles; in particular, their reliance on resistance heating leads to uneven temperature distribution, resulting in uneven internal stress in the material and a tendency to crack. Figure 7 As shown, the graphitization purification unit 500 in this embodiment employs a mechanism combining microwave-assisted heating and intelligent electromagnetic field control, enabling rapid and uniform graphitization of large-size isostatically pressed graphite blanks. This overcomes the technical bottlenecks of traditional processes, such as large temperature gradients, high energy consumption, and significant product performance fluctuations. The graphitization purification unit 500 in this embodiment mainly includes a microwave generation module 530, an electromagnetic field generation module 540, a detection and feedback module 550, a central control module 560, and a graphitization furnace substrate 570. The graphitization furnace substrate 570 adopts the furnace body structure of an Atchison graphitization furnace.

[0050] The microwave generation module 530 employs a ring array microwave generator with a frequency of 2.45 GHz ± 50 MHz, coupled with a tapered waveguide. Multiple magnetrons work together to radiate microwave energy, forming a three-dimensional uniform standing wave field. Microwaves can directly penetrate the graphite blank, interacting with π electrons in carbon atoms to generate eddy currents and dielectric losses, rapidly heating from the inside (200-300°C / min). The microwave energy is then converted into heat energy through the dielectric losses of the graphite material (mainly conductivity and polarization losses), achieving rapid overall heating of the blank. Simultaneously, a phase adjuster dynamically adjusts the output phase of each magnetron in the standing wave field, eliminating blind spots caused by field strength superposition and preventing localized overheating or unheated areas. For example, when a decrease in the dielectric constant of the central region is detected, indicating weakened energy absorption, the system automatically increases the phase delay Δφ of the magnetron in that direction to compensate for energy loss. Therefore, the tapered waveguide design optimizes the microwave transmission path, reduces reflection losses, and ensures the uniformity of the microwave field distribution within the blank. Specifically, the microwave generating module 530 mainly includes 12 sets of magnetrons, each with a power of 30kW, and the total power of the 12 sets of magnetrons is 360kW. The 12 sets of magnetrons are distributed in a ring on the outside of the furnace cavity of the graphitization furnace substrate 570. The waveguide adopts a TE10 mode rectangular waveguide connected to a tapered transition section to ensure that the standing wave ratio of the microwave field in the Φ1200mm×2000mm cavity is <1.5.

[0051] The electromagnetic field generating module 540 mainly includes a superconducting coil array, which is made of Nb3Sn material and cooled by liquid helium. The electromagnetic field generating module 540 is arranged at the upper and lower ends of the graphitization furnace substrate 570 to generate an axial pulsed magnetic field. The frequency of the pulsed magnetic field is in the range of 1–10 Hz; the maximum field strength is about 2 T, and the field strength can be adjusted within the range of 0.5–2 T; the pulse width of the magnetic field can be adjusted within the range of 1–100 ms. The electromagnetic field generating module 540 can induce carbon atoms to preferentially align along the (002) crystal plane by superimposing a pulsed magnetic field on top of microwave heating, resulting in an isotropic deviation of less than 3% in the material. Compared with the isotropic deviation of more than 15% in traditional processes, the isotropic properties are significantly improved. The magnetic field-induced orientation process takes place in a high-temperature range of 2200–2800℃. The pulsed magnetic field orients the magnetic moments of carbon atoms, promoting the ordering of the hexagonal lattice. The RD display of the sapphire isostatic pressing graphite material preparation system shows that the full width at half maximum (FWHM) of the (002) peak decreases from 1.2° to 0.7°. Furthermore, the electromagnetic field generation module 540 in this embodiment uses a 10Hz alternating magnetic field to disrupt dendrite growth paths and reduce grain boundary stress cracks. Since the magnetic field strength is inversely proportional to the graphitization activation energy, the activation energy is detected to decrease significantly from 450 kJ / mol to 320 kJ / mol, thereby accelerating the graphitization reaction rate.

[0052] The detection feedback module 550 mainly includes an infrared thermal imager, a vector network analyzer (VNA), and a Hall sensor array mounted on the graphitization furnace substrate 570. The infrared thermal imager is used to monitor the surface temperature distribution of the billet in real time; the vector network analyzer (VNA) is used to acquire reflected power signals and calculate the change in dielectric constant; and the Hall sensor array is used to measure the magnetic field strength and spatial gradient.

[0053] The central control module 560 is located outside the graphitization furnace substrate 570. It is signal-connected to the microwave generating module 530, the electromagnetic field generating module 540, and the detection feedback module 550. The central control module 560 incorporates a multiphysics coupling control algorithm using the MPC-ANN model, enabling dynamic adjustment of microwave power distribution, magnetic field pulse width, and frequency. Furthermore, it features a dynamic impedance matching algorithm. This algorithm uses a vector network analyzer (VNA) to monitor the reflected power signal in real time and dynamically adjusts the microwave phase and power distribution through dielectric constant feedback (ε', ε''). A particle swarm optimization (PSO) algorithm is employed to minimize power fluctuations and temperature deviations, with the objective function being power uniformity and temperature field consistency. The dynamic impedance matching algorithm works as follows: the dielectric parameter is detected online and the reflection coefficient Γ is updated every 5 seconds; the complex dielectric constant is calculated using the formula: ε' = (1 + |Γ|² - 2|Γ|cosθ) / (1 + |Γ|² + 2|Γ|cosθ)) The absorption state of the billet is determined, followed by dynamic adjustment of phase and power. When a decrease in ε'' is detected in a local area, the phase shifter adjusts the phase of the corresponding magnetron in 0.1° steps to ensure that the electric field vector is superimposed and enhanced at the center of the billet. Simultaneously, the PSO algorithm optimizes the power distribution of each magnetron, keeping the temperature field uniformity error within ±1.5%. In this embodiment, the microwave phase is adjusted based on real-time dielectric constant feedback to match load changes, and the microwave energy absorption efficiency is improved from 40% to 85%.

[0054] The graphitization purification unit 500 in this embodiment adopts a multi-stage temperature control mode. The preheating stage is from room temperature to 800℃, during which microwaves penetrate the interior of the blank, eliminating residual stress through Joule heating. The lattice reconstruction stage is from 800℃ to 2200℃, during which a magnetic field drives carbon atoms to slide along the (002) plane, forming an ordered layered structure. The magnetic field-induced orientation stage is from 2200℃ to 2800℃. The annealing stage is from 2800℃ to 2000℃, during which an alternating magnetic field eliminates residual stress and stabilizes the lattice orientation. After the annealing stage, chlorine gas is introduced for purification and impurity removal. After purification and impurity removal, the temperature is lowered by a cooling module.

[0055] In this embodiment, the sapphire isostatic graphite material preparation system uses a microwave generating module 530 and an electromagnetic field generating module 540 that work together to provide rapid heating energy via microwaves and regulate the atomic alignment via magnetic fields. The two work together to shorten the graphitization time from over 150 hours to about 20 hours and reduce the carbon loss rate from 10.5% to 2.1%. This achieves precise temperature control, shortens the graphitization cycle, and improves material performance. It solves the problems of large temperature gradient, high energy consumption, and long cycle in traditional graphitization furnaces in the above embodiments.

[0056] Meanwhile, the sapphire isostatic graphite material preparation system of this embodiment uses a microwave generating module 530 and an electromagnetic field generating module 540 that work together to promote carbon atom diffusion and repair interlayer pores by utilizing the microwave thermal effect; the magnetic field-induced lattice orientation reduces the number of grain boundaries, thereby increasing the bending strength of the produced isostatic graphite material from an average of 60 MPa to 95 MPa, an improvement of 58.3%.

[0057] Example 5 Based on the above embodiments, a method for preparing sapphire isostatic graphite material using the sapphire isostatic graphite material preparation system in the above embodiments is further proposed. The fifth embodiment is provided below.

[0058] Please see Figure 8The fifth embodiment of the method for preparing isostatically pressed graphite material for sapphire uses the isostatically pressed graphite material preparation system described in the above embodiments to produce isostatically pressed graphite material. This method can improve the production efficiency of isostatically pressed graphite material, optimize its performance, and extend its service life, thereby reducing the consumption rate of graphite material in the sapphire production process. The method mainly includes the following steps: S10. Add the aggregate to the primary crushing module 110, crush and grind to obtain primary powder; the aggregate used in this embodiment includes mesophase pitch coke and high-purity calcined petroleum coke, etc.

[0059] S20. The softened adhesive obtained from the melting module 120 and the primary powder obtained in step S10 are added together to the mixing module 130 and kneaded to obtain a paste; the adhesive used in this embodiment mainly includes coal tar pitch, etc. S30. Add the paste obtained in step S20 to the secondary crushing module 140 to grind powder and obtain pressed powder; S40. The pressed powder obtained in step S30 is processed sequentially through the cold isostatic pressing preforming module 210 and the hot isostatic pressing densification module 220 to obtain a hot isostatic pressing product. S50. Add the hot isostatic pressing product obtained in step S40 to the calcination unit 300 for calcination to obtain the calcined raw product; S60. Add the roasted raw product obtained in step S50 to the impregnation strengthening unit 400 for impregnation treatment to obtain the impregnated product; S70. The impregnated product obtained in step S60 is added to the graphitization and purification unit 500 for graphitization and purification treatment, and then cooled in stages by the cooling module of the graphitization and purification unit 500 to obtain an isostatic graphite material product.

[0060] In this embodiment, the method for preparing isostatically pressed graphite material for sapphire significantly reduces the production cycle of isostatically pressed graphite material by using staged temperature control in the calcination furnace 310 of the calcination unit 300; the isostatic pressing process of the cold isostatic pressing preforming module 210 and the hot isostatic pressing densification module 220 is used to improve the isotropic properties of the isostatically pressed graphite material; the multi-stage crushing module before and after kneading is used in conjunction with the two isostatic pressing processes to improve the strength of the isostatically pressed graphite material; the hot isostatic pressing densification treatment of the hot isostatic pressing densification module 220 is used to improve the thermal conductivity of the isostatically pressed graphite material; and the impregnation strengthening unit 400 is used to improve the density of the isostatically pressed graphite material and reduce the coefficient of thermal expansion. This method achieves the production of graphite material with high purity, high strength, high thermal conductivity, low coefficient of thermal expansion, and good isotropic properties within a short cycle. This solves the problems of long production cycle, low production efficiency, and high consumption rate when used as a hot zone component in sapphire, which leads to failure to meet usage requirements and affects sapphire production capacity. The isostatic graphite material preparation system for sapphire in this embodiment has achieved a performance breakthrough of isostatic graphite in sapphire hot field applications through technological innovation. Its technical parameters have comprehensively exceeded the original standard requirements, realizing the efficient and stable production of isostatic graphite for sapphire hot field applications. Under the extreme operating conditions of the crystal growth furnace (long-term use at 1600-2100℃), it exhibits excellent durability and thermal stability, providing a reliable material guarantee for sapphire crystal growth.

[0061] Furthermore, in step S10 of the method for preparing isostatically pressed graphite material for sapphire in this embodiment, the mesophase pitch coke is selected from high-quality raw materials with a quinoline insoluble content of <0.3%, and its isotropy reaches 1.03. XRD analysis shows that the interlayer spacing d002 of the (002) crystal plane is 0.337 nm, indicating excellent graphitization potential. The petroleum coke is selected from needle coke with a sulfur content of <0.3%, a true density ≥2.10 g / cm³, and an ash content ≤300 ppm after calcination at 1500℃.

[0062] Compared to ordinary graphite materials used in the production of graphite electrodes, the production of isostatically pressed graphite typically requires a higher binder dosage, higher temperature, and longer mixing time to ensure the effectiveness of isostatic pressing. To reduce the required binder dosage, temperature, and mixing time, in step S20 of the sapphire isostatically pressed graphite material preparation method of this embodiment, a composite modifier is further added to the mixture during the kneading process. The composite modifier mainly includes sodium dodecylbenzenesulfonate, alkylphenol polyoxyethylene ether, and nano-cerium oxide. Specifically, sodium dodecylbenzenesulfonate is added at 1.1–1.3 wt% to reduce the surface tension of the slurry; alkylphenol polyoxyethylene ether is added at 0.35–0.45 wt% to improve powder dispersion stability; and nano-cerium oxide is added at 0.04–0.06 wt% to inhibit high-temperature grain boundary migration. Furthermore, the modification process of the composite modifier employs a three-stage mixing process, including a dry mixing stage, a wet mixing stage, and a curing stage. The process involves premixing the dry mixture in a double cone mixer for 30 minutes at 15 rpm; adding 40% ethanol solution and ultrasonically dispersing (20 kHz) for 2 hours during the wet mixture stage; and maintaining a constant temperature of 50°C for 12 hours during the maturation stage to form a stable coating layer.

[0063] Furthermore, in step S30 of the method for preparing isostatically pressed graphite material for sapphire in this embodiment, powder is prepared by spray drying granulation. The inlet air temperature of the centrifugal spray tower 142 is controlled at 185±5℃, the atomizing disc speed is 18000rpm, the granulation particle size distribution is controlled at D50=75μm, the span (D90~D10) / D50=0.8, and the moisture content is controlled at ≤0.3% to ensure its isostatic pressing performance.

[0064] Furthermore, in step S40 of the method for preparing sapphire isostatic graphite material in this embodiment, the pressurization process of the cold isostatic pressing preforming module 210 includes an initial pressurization stage, a main pressurization stage, and a final pressurization stage. Specifically, the initial pressurization stage has a pressure of 20 MPa and is held for 5 minutes for venting; the main pressurization stage has a pressure of 120 MPa, using a linear pressurization rate of 5 MPa / min; and the final pressurization stage has a pressure of 150 MPa and is held for 20 minutes. Simultaneously, the high-temperature isostatic pressing furnace of the hot isostatic pressing densification module 220 uses argon gas as the medium, with a holding temperature above 1800°C and a working pressure above 180 MPa. The heating program of the high-temperature isostatic pressing furnace is also a multi-stage, graded heating process: below 800°C, the heating rate is 10°C / min; between 800°C and 1800°C, the heating rate is 5°C / min; and above 1800°C, the temperature is held for 2 hours.

[0065] Furthermore, in step S50 of the method for preparing isostatic graphite material for sapphire in this embodiment, nitrogen gas is introduced into the calcination furnace 310 of the calcination unit 300 as a protective gas. The nitrogen flow rate is 50 L / min, and the residual oxygen content in the furnace is controlled to be <50 ppm, and a slight positive pressure of approximately +50 Pa is maintained in the furnace. During the operation of the calcination furnace 310, a slow temperature increase of 1 °C / h is used before reaching 300 °C, a medium-speed temperature increase of 3 °C / h is used from 300 °C to 600 °C, and a rapid temperature increase of 10 °C / h is used above 600 °C, thereby significantly reducing the calcination time.

[0066] Furthermore, in step S60 of the method for preparing isostatically pressed graphite material for sapphire in this embodiment, the impregnating agent used includes: zero-quinoline modified pitch and nano-additives. The modified pitch has a softening point of 95°C (ring and ball method), a coking value of 68%, and a quinoline insoluble content of 0%. The nano-additive uses silicon carbide whiskers with a diameter of approximately 200 nm and an aspect ratio > 50. The amount of silicon carbide whiskers added is 1.4–1.6 wt%. The introduction of silicon carbide whiskers enhances the thermal shock resistance of the material and can increase the flexural strength of the isostatically pressed graphite material by more than 40%. In addition, the high-pressure impregnation tank 410 used in step S60 has a vacuum degree of 0–0.098 MPa, a working pressure of 3.5 MPa, and a temperature controlled within the range of 185 ± 2°C. Preferably, step S60 of this embodiment can also incorporate pulse impregnation technology for auxiliary processing. Pulse impregnation technology uses a pulse frequency of 0.5Hz, which can control the pressure fluctuation range within the high-pressure impregnation tank 410 to ±0.2MPa and increase the impregnation depth by more than 2mm. Compared with traditional processes, the number of impregnations can be reduced from more than three times to one, the density increase from 0.12g / cm³ / time to 0.25g / cm³ / time, and the production cycle is significantly shortened. Furthermore, micropores can be pre-reserved for silica sol injection, generating a SiC protective layer at high temperature. The SiC protective layer contains a SiC precursor, which can automatically release for repair upon reaching the trigger temperature (>1600℃). The repair layer thickness can reach 10-20μm / time, thus enabling the isostatic graphite material product to have a self-healing defect function.

[0067] Furthermore, in step S70 of the method for preparing isostatically pressed graphite material for sapphire in this embodiment, the temperature of the graphitization process is controlled in multiple stages. Specifically, during the initial heating stage from 0 to 2000°C, the heating rate is controlled at approximately 50°C / h; during the high-temperature purification stage from 2000 to 3000°C, the heating rate is controlled at approximately 15°C / h; and during the extremely high-temperature stage from 3000 to 3200°C, the temperature is maintained while chlorine gas is introduced for purification. In the chlorine purification process of step S70, the chlorine flow rate is controlled at 5 m³ / h; the main reactions include: 4Al + 6Cl2 → 4AlCl3↑ (boiling point 183℃) It can achieve an ash removal rate of over 90%. Simultaneously, different cooling methods are combined during the cooling stage: natural cooling is used in the 3200℃~2000℃ range, with a cooling rate of approximately 50℃ / h; forced air cooling is used in the 2000℃~800℃ range, with a cooling rate of approximately 100℃ / h; and water mist cooling is used below 800℃, with a cooling rate of approximately 200℃ / h.

[0068] Furthermore, the method for preparing sapphire isostatic graphite material using the third embodiment employs the preparation system, with the addition of a surface treatment unit 600. Therefore, the preparation method of this embodiment may further include: S80. The isostatic graphite material product obtained in step S70 is subjected to chemical vapor deposition (CVD) coating treatment; by depositing a pyrolytic carbon layer of more than 200 μm, the oxidation resistance of the isostatic graphite material product is improved, and the oxidation resistance temperature can be increased to more than 2000℃.

[0069] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing isostatically pressed graphite material for sapphire, characterized in that, A sapphire isostatic graphite material preparation system is used; the sapphire isostatic graphite material preparation system includes: a raw material processing unit (100), an isostatic pressing unit (200), a calcination unit (300), an impregnation strengthening unit (400), and a graphitization purification unit (500); wherein, the raw material processing unit (100) has at least a primary crushing module (110), a mixing module (130), and a secondary crushing module (140); the isostatic pressing unit (200) has at least a cold isostatic pressing preforming module (210) and a hot isostatic pressing densification module (220); the calcination unit (300) has at least a calcination furnace (310), the calcination furnace (310) is a directional gradient calcination furnace, which is capable of staged temperature control; The method for preparing isostatically pressed graphite material for sapphire includes the following steps: S10. Add the aggregate to the primary crushing module (110), crush and grind to obtain primary powder; S20. Add the adhesive and the primary powder to the mixing module (130) and knead to obtain a paste; S30. The paste is added to the secondary crushing module (140) to obtain pressed powder; S40. The pressed powder is subjected to cold isostatic pressing preforming and hot isostatic pressing densification treatment in sequence to obtain a hot isostatic pressing product; S50. The hot isostatic pressing product is added to the calcination unit (300) for calcination to obtain the calcined raw product; the calcination process includes: heating at 1℃ / h before 300℃; heating at 3℃ / h from 300℃ to 600℃; and heating at 10℃ / h above 600℃. S60. The roasted raw product is added to the impregnation strengthening unit (400) for impregnation treatment to obtain an impregnated product; S70. The impregnated product is subjected to graphitization and purification treatment, and cooled to obtain an isostatic graphite material product; the graphitization process includes: in the 0~2000℃ stage, the heating rate is controlled at 50℃ / h; in the 2000~3000℃ stage, the heating rate is controlled at 15℃ / h; in the 3000~3200℃ stage, the temperature is maintained and chlorine gas is introduced for purification.

2. The method for preparing isostatically pressed graphite material for sapphire as described in claim 1, characterized in that, In step S20, a composite modifier is added to the mixture, which includes sodium dodecylbenzenesulfonate, alkylphenol polyoxyethylene ether, and nano-cerium oxide; and step S20 includes a dry mixing stage, a wet mixing stage, and a maturation stage; in the dry mixing stage, the primary powder, binder, and composite modifier are added; in the wet mixing stage, an ethanol solution is added and ultrasonic dispersion is performed; in the maturation stage, the mixture is kept at a constant temperature and allowed to stand to form a stable coating layer.

3. The method for preparing isostatically pressed graphite material for sapphire as described in claim 1, characterized in that, The primary crushing module (110) includes a dual-chamber hydraulic jaw crusher (111), a roller crusher (112), and a cyclone mill (113); the dual-chamber hydraulic jaw crusher (111) and the roller crusher (112) are used for multi-stage crushing of the aggregate; the cyclone mill (113) is used for grinding; and the secondary crushing module (140) includes a centrifugal spray tower (142); the centrifugal spray tower (142) is used for drying and grinding to prepare the pressed powder.

4. The method for preparing isostatically pressed graphite material for sapphire as described in claim 1, characterized in that, The bottom layer of the roasting furnace (310) of the roasting unit (300) is provided with 0.5-1mm artificial graphite particles; the side of the roasting furnace (310) is provided with a nano-alumina coating; and the top of the roasting furnace (310) is provided with 2-3mm coke particles.

5. The method for preparing isostatically pressed graphite material for sapphire as described in claim 1, characterized in that, The graphitization purification unit (500) has at least an Atchison furnace (510) and a cooling module; the Atchison furnace (510) is capable of heating the impregnated product and introducing chlorine gas to remove impurities; the cooling module includes an air-cooled fan (522) and a water mist fan (524).

6. The method for preparing isostatically pressed graphite material for sapphire as described in claim 1, characterized in that, The graphitization purification unit (500) has at least a graphitization furnace base (570); a microwave generating module (530) is provided on the outside of the furnace cavity of the graphitization furnace base (570), and the microwave generating module (530) has at least a ring array microwave generator; an electromagnetic field generating module (540) is provided at both the upper and lower ends of the furnace body of the graphitization furnace base (570); and a detection feedback module (550) is provided on the furnace body of the graphitization furnace base (570), and a central control module (560) is provided on the outside of the graphitization furnace base (570), and the central control module (560) is connected to the microwave generating module (530), the electromagnetic field generating module (540) and the detection feedback module (550) by signal connection.

7. The method for preparing isostatically pressed graphite material according to any one of claims 1-6, characterized in that, The cold isostatic pressing preforming module (210) has at least a double-layered cylinder (212), a flexible mold is provided inside the double-layered cylinder (212), a multi-directional pressurization mechanism (214) is provided outside the double-layered cylinder (212), a vibration mechanism (216) is provided at the bottom of the double-layered cylinder (212), and a vacuum tube (213) and a medium input tube (215) are provided on the double-layered cylinder (212), and the vacuum tube (213) and the medium input tube (215) are both connected to the inside and outside of the double-layered cylinder (212); the hot isostatic pressing densification module (220) has at least a high-temperature isostatic pressing furnace body (222), and the high-temperature isostatic pressing furnace body (222) is connected to a compressor unit (224).

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