Carbon ceramic porous structure adjustable resistance heating body

Abstract

The application relates to the technical field of carbon ceramic material preparation, in particular to a carbon ceramic porous structure adjustable resistance heating body, which comprises a needle-punched preform, the heating body is made through the needle-punched preform, the heating body is in a circular ring shape, the needle-punched preform comprises plain cloth and a net tire, an interlaced fiber network structure is formed between the plain cloth and the net tire, a plurality of regularly arranged holes are arranged on the heating body, the number of the holes is adjusted according to the size of the resistance of the heating body, and a silicon carbide coating is formed on the heating body body through reaction infiltration treatment; the application has the effects of improving the corrosion resistance of the heating body and effectively resisting the erosion of silicon vapor.

Description

Technical Field

[0001] This application relates to the field of carbon ceramic material preparation technology, and in particular to a carbon ceramic porous structure adjustable resistive heating element. Background Technology

[0002] Photovoltaic power generation, as an important component of green energy, has experienced rapid development globally in recent years. Monocrystalline silicon, as the core component of solar cells, relies heavily on the Czochralski (CZ) silicon furnace—a key piece of equipment in its production process—for improving its quality. During the monocrystalline silicon melting process, the heating element is the core component of the thermal field system, directly affecting melting efficiency and monocrystalline quality. Currently, heating elements on the market are mainly divided into isostatically pressed graphite heating elements and carbon / carbon composite material heating elements. Each has its own characteristics in performance and application, providing crucial support for monocrystalline silicon production.

[0003] For the preparation and application of heating elements in the melting process of monocrystalline silicon, existing technologies typically use isostatically pressed graphite or carbon / carbon composite materials as the main materials. Isostatically pressed graphite heating elements are prepared by mixing materials such as artificial graphite, pitch coke, and binders, followed by processes including kneading, crushing, molding, impregnation carbonization, and high-temperature graphitization. Carbon / carbon composite heating elements are prepared by needle-punching carbon cloth and a mesh into a preform in a specific ratio, followed by hardening, deposition, impregnation carbonization, and high-temperature treatment. While these methods can meet basic heating requirements, they still present many challenges in practical applications.

[0004] Regarding the aforementioned technologies, existing carbon / carbon composite heating elements are susceptible to corrosion from silicon vapor in high-temperature environments, leading to problems such as wall thinning and heating element breakage, thus significantly reducing the service life of the heating element. In addition, to improve corrosion resistance, the industry commonly uses chemical vapor deposition technology to deposit a silicon carbide coating on the surface of carbon / carbon composite materials. However, due to the mismatch in the coefficient of thermal expansion between the silicon carbide coating and the substrate material, cracking and peeling are prone to occur under continuous thermal shock conditions, further aggravating the aging problem of the heating element. Therefore, how to effectively solve the corrosion resistance and service life problems of carbon / carbon composite heating elements in high-temperature environments has become a technical bottleneck that urgently needs to be overcome. Utility Model Content

[0005] To overcome the above problems, this application provides a carbon ceramic porous structure adjustable resistive heating element.

[0006] The carbon-ceramic porous adjustable resistive heating element provided in this application adopts the following technical solution:

[0007] A carbon-ceramic porous adjustable resistive heating element includes a needle-punched preform, the heating element being formed by the needle-punched preform and being annular in shape. The needle-punched preform includes a plain weave fabric and a mesh, with the plain weave fabric and the mesh forming an interlaced fiber network structure. The heating element has multiple holes arranged in a regular pattern, the number of which is adjusted according to the resistance of the heating element. The heating element body undergoes a reactive melting infiltration treatment to form a silicon carbide coating.

[0008] By adopting the above technical solution, the heating element is made of a needle-punched preform. The plain weave fabric and the mesh in the needle-punched preform form an interwoven fiber network structure, which improves the mechanical strength and thermal conductivity of the heating element. Multiple regularly arranged holes are set on the heating element; the number of holes is adjusted according to the resistance, which not only allows for flexible control of the resistance value but also optimizes heat distribution and avoids localized overheating. The silicon carbide coating formed by reactive melting treatment significantly improves the corrosion resistance of the heating element, effectively resisting the erosion of silicon vapor, thereby greatly extending the service life of the heating element.

[0009] In one specific feasible implementation, the hole is a round hole or a rectangular hole.

[0010] By adopting the above technical solution, the resistance value of the heating element can be effectively adjusted, the heat distribution can be optimized, and local overheating can be avoided. In addition, the hole design helps to improve the electrical performance of the heating element, while ensuring that the structural strength meets the requirements of practical applications.

[0011] In one specific feasible implementation, the hole can be a rhomboid hole or a hexagonal hole.

[0012] By adopting the above technical solutions, not only is the surface area of ​​the heating element increased, but heat transfer efficiency is also improved. For example, diamond-shaped holes can guide airflow in a specific direction, reducing heat loss; hexagonal holes can better disperse stress concentration points, improving the overall strength of the heating element. In addition, the arrangement of irregularly shaped holes can be flexibly adjusted according to actual needs, such as using staggered or spiral arrangements, to further optimize the performance of the heating element, effectively alleviate thermal stress accumulation, reduce the risk of heating element breakage, and thus extend its service life.

[0013] In a specific feasible implementation, the number of holes is evenly distributed in ≥1 row and ≥1 column according to the height of the heating element.

[0014] By adopting the above technical solution, the holes are evenly distributed on the heating element, ensuring the uniformity of the surface temperature distribution of the heating element. On the one hand, by adjusting the number of rows and columns of holes, the layout of the holes can be flexibly adjusted according to the height of the heating element to optimize the heat distribution and avoid local overheating. On the other hand, the number of holes is adjusted according to the resistance of the heating element, which ensures both electrical performance and structural strength.

[0015] In one specific feasible implementation, the heating element is processed by vapor deposition, and the density of the deposited sample is 1.1-1.3 g / cm³. 3 between.

[0016] By employing the above technical solution, vapor deposition treatment generates a dense carbon layer inside the carbon / carbon composite material, improving the material's oxidation resistance and ensuring the uniformity and density of the heating element. The density of the deposited sample is 1.1-1.3 g / cm³. 3 between.

[0017] In one specific feasible implementation, a silicon carbide fiber reinforcement layer is added to the outer layer of the heating element.

[0018] By adopting the above technical solution, the mechanical strength and high-temperature resistance of the heating element are significantly improved. Specific effects include: the reinforcing layer increases the bending strength of the heating element by 30%-50%, while also improving its stability in high-temperature environments, effectively resisting the effects of harsh working conditions such as high temperature and corrosion, thereby extending the service life of the heating element and ensuring its reliable operation during the monocrystalline silicon melting process.

[0019] In one specific implementation scheme, a support assembly is also included, which includes two support rods and two connectors. The two support rods are evenly distributed around the circumference of the heating element, and the direction of the support rods is consistent with the axial direction of the heating element. The connectors correspond one-to-one with the support rods and are connected to the end of the support rods near the heating element. The support rods are detachably connected to the heating element through the connectors.

[0020] By adopting the above technical solution, the support assembly effectively enhances the overall structural stability of the heating element. Two support rods are evenly distributed along the circumference of the heating element, and their orientation is consistent with the axis of the heating element. This layout evenly distributes the force and avoids localized stress concentration. The connectors detachably connect the support rods to the heating element, facilitating installation and maintenance and improving the system's flexibility.

[0021] In one specific implementation scheme, the support rod has a placement groove for placing the heating element at one end near the heating element, and the wall of the placement groove is in contact with the outer wall of the heating element.

[0022] By adopting the above technical solution, the design of the placement groove makes the contact between the support rod and the heating element more stable, effectively preventing the heating element from shifting or shaking during use. The groove wall fits snugly against the outer wall of the heating element, further improving the fit accuracy between the two and ensuring the reliability of the support structure, thereby enhancing the overall mechanical stability of the heating element.

[0023] In summary, this application includes at least one of the following beneficial technical effects:

[0024] 1. The designed carbon-ceramic porous adjustable resistive heating element features multiple regularly arranged holes. The number of holes can be adjusted according to the resistance, achieving flexible control of the resistance value and optimizing heat distribution to avoid localized overheating. The silicon carbide coating formed through reactive melting treatment significantly improves the corrosion resistance of the heating element, effectively resisting the erosion of silicon vapor and thus greatly extending the service life of the heating element.

[0025] 2. The designed carbon ceramic porous adjustable resistive heating element can effectively adjust the resistance value of the heating element, optimize heat distribution, and avoid local overheating.

[0026] 3. The designed carbon ceramic porous adjustable resistive heating element features a slot design that makes the contact between the support rod and the heating element more stable, effectively preventing the heating element from shifting or shaking during use. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the overall structure in Example 1.

[0028] Figure 2 This is a schematic diagram of the structure of the needle-punched preform in Example 1.

[0029] Figure 3 This is a schematic diagram of the structure of the heating element with diamond-shaped holes in Example 2.

[0030] Figure 4 This is a schematic diagram of the structure of the heating element with hexagonal holes in Example 2.

[0031] Figure 5 This is a schematic diagram of the structure in Example 3.

[0032] Explanation of reference numerals in the attached drawings: 1. Needle-punched preform; 11. Plain weave fabric; 12. Mesh; 13. Silicon carbide fiber reinforcement layer; 2. Support assembly; 21. Support rod; 211. Placement groove; 22. Connector; 221. Connecting screw. Detailed Implementation

[0033] The following is in conjunction with the appendix Figure 1-5 This application will be described in further detail.

[0034] This application discloses a carbon ceramic porous structure adjustable resistive heating element.

[0035] Reference Figure 1 A carbon ceramic porous adjustable resistive heating element includes a needle-punched preform 1 and a support component 2. The heating element body is made by the needle-punched preform 1, and the support component 2 is connected to the needle-punched preform 1.

[0036] The preparation process of carbon ceramic porous heating element is as follows: needle-punched preform → vapor deposition → high temperature → machining → reactive infiltration

[0037] Reference Figure 1 The needle-punched preform 1 includes a plain weave fabric 11 and a mesh 12. The plain weave fabric 11 can be made of aramid fiber or carbon fiber, and its areal density ranges from 200-400 g / m². 2 The mesh 12 can be made of polyester mesh 12 or glass fiber mesh 12, with an areal density ranging from 50-200 g / m². 2 Plain weave fabric 11 and mesh 12 are connected by mechanical interlocking to form an interlaced fiber network structure, which improves the mechanical strength and thermal conductivity of the heating element. For example, when aramid fiber plain weave fabric 11 is used, its surface is specially treated to form a tight bonding interface with carbon fiber mesh 12, thereby improving the stability of the overall structure. Plain weave fabric 11 is laid on a cylindrical foam mold, and then 1-2 layers of mesh 12 are laid on the plain weave fabric 11. The cylindrical mold is rotated to start needle punching. After two rounds of needle punching, the next layer of plain weave fabric 11 and mesh 12 is laid down and needle punching begins. This process is repeated until the required thickness is achieved. The heating element is in the shape of a ring. Then the foam mold and the preform are placed in an oven at 280℃-300℃ for baking and demolding.

[0038] Reference Figure 1 In the vapor deposition process, the pre-formed heating element is placed in the deposition furnace, the furnace lid is closed, a vacuum is first created, and then nitrogen is introduced for protective atmosphere heating. After half an hour, the temperature begins to rise, increasing from room temperature to 900-1100℃ over 40-60 hours, with nitrogen continuously introduced during the heating phase. When the temperature reaches 1100℃-1200℃, the nitrogen valve is closed, and propylene is introduced into the deposition furnace at a flow rate of 0.2L / min. The temperature is maintained for 400-450 hours, and then cooling begins. When the temperature drops below 850℃, propylene is stopped from being introduced into the deposition furnace, and nitrogen is introduced until the temperature drops to between 180-200℃. The furnace lid is then opened, and the sample is removed after cooling to room temperature. The density of the deposited sample is 1.1-1.3 g / cm³. 3 If the deposition continues, a dense carbon layer is formed inside the carbon / carbon composite material, improving its oxidation resistance. The density of the deposited sample is between 1.1 and 1.3 g / cm³. 3 This ensures the uniformity and density of the heating element itself.

[0039] Reference Figure 1In the high-temperature treatment stage, the carbonized preform is placed in a high-temperature furnace, and after vacuuming, it is heated from room temperature to 2200-2300℃ over 35-40 hours. After holding at this temperature for 10-15 hours, it is naturally cooled to room temperature. When the temperature drops to 200℃, nitrogen gas is introduced into the high-temperature furnace to atmospheric pressure, the furnace lid is opened, and the preform is removed after the temperature drops to room temperature, thus obtaining a carbon / carbon heating element preform. This process further improves the graphitization degree of the carbon / carbon composite material, reduces the resistivity, and enhances the high-temperature resistance of the material. For example, the grain size of the carbon / carbon composite material after high-temperature treatment is significantly increased, and the electrical conductivity is significantly improved.

[0040] Reference Figure 1 and Figure 2 In the machining process, a certain number of holes are machined on the heating element to adjust the resistance. Simultaneously, to ensure uniform heating, holes are uniformly drilled on the carbon heating element. These holes can be round or rectangular, with diameters ranging from 5mm to 50mm. The number of rows of holes is ≥1, and the number of columns is ≥1, with the holes arranged according to a specific rule. The number of holes is adjusted based on the resistance of the heating element. For example, when the hole diameter is φ20mm, three rows of holes can be evenly distributed on the heating element, with each row containing 10 holes. The hole spacing is maintained at approximately 15mm to ensure uniform temperature distribution on the heating element surface. Furthermore, the number of holes can be flexibly adjusted according to the resistance of the heating element, ensuring both the electrical performance of the heating element and structural strength.

[0041] Reference Figure 1In the reactive infiltration process, the processed heating element is placed in a special graphite fixture, and high-purity silicon powder (99.3%-99.999% purity) is added. A suitable infiltration fixture is selected based on the sample size. Silicon powder is added to the outer or inner ring of the heating element until it reaches the same height as the fixture. The silicon powder is then leveled with a scraper. The heating element and graphite fixture are then placed together in a silicon infiltration furnace. The furnace lid is closed, and a vacuum is drawn to 900-1000 Pa. The temperature is increased to 1500-1700℃ at a rate of 5-10℃ / min, and held for 120-150 minutes. The furnace is then cooled to room temperature. The vacuum level is adjusted, the furnace lid is opened, and the sample is removed. During this process, silicon reacts chemically with the carbon / carbon composite material to form a continuous silicon carbide coating, significantly improving the corrosion resistance of the heating element. For example, silicon carbide coatings can achieve thicknesses of 10-100 μm and exhibit strong adhesion to the substrate material, enabling long-term stable operation at high temperatures. Improving the reactive infiltration process parameters further enhances the quality of the silicon carbide coating. Specifically, controlling the vacuum level in the infiltration furnace at 800-900 Pa, the heating rate at 8-12 °C / min, and the holding time at 150-180 minutes, while appropriately increasing the amount of silicon powder added, ensures a more uniform coating thickness. For instance, increasing the silicon powder addition by 20% achieves a coating thickness of 80-120 μm, significantly improving the coating's protective effect and further enhancing its quality and performance. The improved process not only increases the coating's density but also strengthens its adhesion to the substrate material, thereby significantly extending the lifespan of the heating element. For example, at high temperatures, the improved silicon carbide coating exhibits excellent corrosion resistance, effectively resisting silicon vapor erosion and providing a more reliable guarantee for the single-crystal silicon melting process.

[0042] Reference Figure 1 The support assembly 2 includes two support rods 21 and two connectors 22. The two support rods 21 are evenly distributed around the circumference of the heating element, and the direction of the support rods 21 is consistent with the axial direction of the heating element. A placement groove 211 for placing the heating element is opened at the end of the support rod 21 near the heating element. The groove wall of the placement groove 211 fits against the outer wall of the heating element. The connectors 22 correspond one-to-one with the support rods 21. The connectors 22 include multiple connecting screws 221. In this embodiment, there are four connecting screws 221. The four connecting screws 221 located on the same support rod 21 are arranged in a matrix. The connecting screws 221 are sequentially inserted through the support rod 21 and the heating element, and are sequentially threaded to the support rod 21 and the heating element. The support rod 21 and the heating element are detachably connected by the connecting screws 221. The matrix arrangement of the four connecting screws 221 further enhances the connection stability between the support rod 21 and the heating element, ensuring the reliable operation of the heating element in a high-temperature environment.

[0043] The implementation principle of Example 1 is as follows: a carbon-ceramic heating element with a porous structure is prepared through processes such as needle-punching preform 1, vapor deposition, high-temperature treatment, machining, and reactive infiltration. The porous structure not only adjusts the resistance value of the heating element but also optimizes the heat distribution, avoiding local overheating. The presence of the silicon carbide coating effectively blocks the erosion of the carbon / carbon composite material by silicon vapor, while solving the problem of easy cracking and peeling of traditional coatings. The overall solution significantly improves the corrosion resistance and service life of the heating element, providing reliable technical support for the single-crystal silicon melting process.

[0044] Example 2

[0045] Reference Figure 3 and Figure 4 The difference between this embodiment and Embodiment 1 is that the hole design is further optimized by introducing irregular hole structures, such as diamond-shaped holes or hexagonal holes on the heating element. The hole diameter range is still 5mm to 50mm. These irregular holes not only increase the surface area of ​​the heating element, but also improve the heat transfer efficiency. For example, the design of diamond-shaped holes can guide the airflow to flow in a specific direction and reduce heat loss; hexagonal holes can better disperse stress concentration points and improve the overall strength of the heating element. In addition, the arrangement of irregular holes can be flexibly adjusted according to actual needs, such as by using staggered or spiral arrangements, to further optimize the performance of the heating element.

[0046] The implementation principle of Example 2 is as follows: by introducing an irregularly shaped hole structure, the heat dissipation performance and mechanical strength of the heating element are further improved. The design of the irregularly shaped hole not only enriches the functional characteristics of the heating element, but also provides more possibilities for its application under complex working conditions. For example, in the process of melting single-crystal silicon, the irregularly shaped hole can effectively alleviate the accumulation of thermal stress, reduce the risk of heating element fracture, and thus extend its service life.

[0047] Example 3

[0048] Reference Figure 5 The difference between this embodiment and Embodiment 1 lies in the introduction of a multi-layer composite structure design, which further enhances the overall performance of the heating element. Specifically, a silicon carbide fiber reinforcement layer 13 is added to the outer layer of the carbon / carbon composite heating element, with a thickness of 0.5-1.5 mm. The silicon carbide fiber reinforcement layer 13 is prepared by a slurry impregnation method, wherein the slurry consists of silicon carbide powder, binder, and solvent. The introduction of the reinforcement layer not only improves the corrosion resistance of the heating element but also enhances its mechanical strength. For example, after adding the silicon carbide fiber reinforcement layer 13, the flexural strength of the heating element can be increased by 30%-50%, while its high-temperature resistance is also significantly improved.

[0049] The implementation principle of Example 3 is as follows: By introducing a multi-layer composite structure design, the performance of the heating element is comprehensively improved. The presence of the silicon carbide fiber reinforcement layer 13 not only provides an additional protective barrier for the heating element, but also significantly enhances its mechanical properties, enabling it to maintain stable operation under harsh conditions. For example, in the process of melting monocrystalline silicon, the multi-layer composite structure can effectively resist multiple challenges such as high temperature and corrosion, providing a solid technical guarantee for the high-quality production of monocrystalline silicon.

[0050] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A carbon-ceramic porous adjustable resistive heating element, characterized in that: The device includes a needle-punched preform (1), and the heating element is made by the needle-punched preform (1). The heating element is annular. The needle-punched preform (1) includes a plain weave fabric (11) and a mesh (12). The plain weave fabric (11) and the mesh (12) form an interlaced fiber network structure. The heating element has multiple holes arranged in a regular pattern. The number of holes is adjusted according to the resistance of the heating element. The heating element body is coated with silicon carbide by reaction melting and infiltration treatment.

2. The adjustable resistive heating element with a porous carbon ceramic structure according to claim 1, characterized in that: The hole can be round or rectangular.

3. The adjustable resistive heating element with a porous carbon ceramic structure according to claim 1, characterized in that: The hole is either rhomboid or hexagonal.

4. A carbon ceramic porous adjustable resistive heating element according to any one of claims 2-3, characterized in that: The number of holes is ≥1 row and ≥1 column, with the height of the heating element being evenly distributed.

5. The adjustable resistive heating element with a porous carbon ceramic structure according to claim 1, characterized in that: The heating element was processed by vapor deposition, and the density of the deposited sample was 1.1-1.3 g / cm³. 3 between.

6. The adjustable resistive heating element with a porous carbon ceramic structure according to claim 2, characterized in that: A silicon carbide fiber reinforcement layer is added to the outer layer of the heating element (13).

7. The adjustable resistive heating element with a porous carbon ceramic structure according to claim 6, characterized in that: It also includes a support assembly (2), which includes two support rods (21) and two connectors (22). The two support rods (21) are evenly distributed around the heating element. The direction of the support rods (21) is consistent with the axial direction of the heating element. The connectors (22) correspond one-to-one with the support rods (21). The connectors (22) are connected to the end of the support rod (21) near the heating element. The support rods (21) are detachably connected to the heating element through the connectors (22).

8. The adjustable resistive heating element with a porous carbon ceramic structure according to claim 7, characterized in that: The support rod (21) has a placement groove (211) for placing the heating element at one end near the heating element, and the groove wall of the placement groove (211) is in contact with the outer wall of the heating element.

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