A preparation device and densification method of a cylindrical carbon-carbon preform by vapor deposition
Patent Information
- Application Number
- CN202611490181.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-09-23
- Publication Date
- 2026-11-03
AI Technical Summary
In existing technologies, the vapor deposition on the inner and outer surfaces of cylindrical carbon preforms is uneven, resulting in low densification efficiency, long manufacturing cycles, and high production costs.
A preparation device for vapor deposition of a cylindrical carbon preform is used, including a gas distribution plate, a lifting ring, a flow guide plate, a positioning gas guide pipe and a gas limiting cylinder. The gas distribution plate performs primary flow splitting, the flow guide plate performs secondary flow splitting, and the positioning gas guide pipe and gas limiting cylinder guide the inner and outer surfaces of the cylindrical carbon preform to ensure uniform distribution of the deposited gas.
This achieves uniform gas phase densification on both the inner and outer surfaces of the carbon preform, shortening the manufacturing cycle and reducing production costs.
Smart Images
Figure CN123027554A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of carbon-carbon composite material preparation technology, and in particular to a preparation apparatus and densification method for cylindrical carbon-carbon preform vapor deposition. Background Technology
[0002] Carbon-carbon composite materials are characterized by low density, high temperature resistance, and excellent high-temperature mechanical properties, and are widely used in the thermal field of silicon crystal pulling in photovoltaics. As the main load-bearing component in the thermal field, carbon-carbon support rods need to have a high and uniform bulk density to ensure their high-temperature service performance.
[0003] Carbon-carbon support rods and similar products are typically cylindrical, thick-walled structures. Existing processes often employ a combination of chemical vapor deposition (CVD) and liquid phase impregnation for densification. This involves first performing CVD, followed by multiple liquid phase impregnations for further densification. However, because the deposited gas is difficult to distribute evenly to each product and its inner and outer surfaces within the furnace chamber, it can easily lead to localized preferential deposition and premature closure of surface pores. This hinders the penetration of the deposited gas into the preform, making it difficult to achieve uniform densification of thick-walled products using CVD alone.
[0004] To increase the density of the product, existing processes usually require two to three liquid phase impregnations and corresponding post-treatments, making the entire manufacturing cycle 60 to 90 days. This results in many processes, long cycles, high energy consumption, and high production costs.
[0005] Therefore, how to achieve uniform and rapid gas phase densification on the inner and outer surfaces of cylindrical carbon preforms, and shorten the manufacturing cycle and reduce production costs, is a technical problem that needs to be solved by those skilled in the art. Summary of the Invention
[0006] In view of this, the purpose of the present invention is to provide a preparation apparatus for vapor deposition of cylindrical carbon preforms, so as to solve the technical problems of uneven vapor deposition on the inner and outer surfaces of existing straight cylindrical thick-walled carbon products, low densification efficiency and high production cost.
[0007] Another object of the present invention is to provide a method for densifying a cylindrical carbon preform by vapor deposition using a preparation apparatus for cylindrical carbon preform vapor deposition.
[0008] To achieve the above objectives, the present invention provides the following technical solution: An apparatus for preparing a cylindrical carbon-carbon preform by vapor deposition includes: The gas distribution plate is located inside the deposition furnace and is connected to the gas inlet at the bottom of the furnace. The gas distribution plate has multiple gas distribution holes. A lifting ring is provided on the bottom of the furnace and surrounds the outside of the gas distribution plate; Multiple guide plates are arranged at vertical intervals. The guide plate at the bottom is set on the lifting ring and forms a pressure equalization cavity with the lifting ring and the furnace bottom. Each guide plate has multiple guide holes. Multiple hollow positioning air guide tubes are provided, with their lower ends connected to the corresponding flow guide holes and their upper ends used to extend into the inner hole of the cylindrical carbon preform to position the cylindrical carbon preform and guide air into the inner hole; the flow guide holes not connected to the positioning air guide tubes are used to guide air to the outside of the cylindrical carbon preform. At least one gas limiting cylinder is disposed between two adjacent flow guide plates and surrounds the outside of the plurality of cylindrical carbon preforms, so that the flow guide plates and the gas limiting cylinder form a deposition space vertically.
[0009] Preferably, the bottom of the air distribution plate is provided with an air intake channel communicating with the air inlet, and a plurality of air distribution holes are spaced apart along the outer peripheral surface of the air distribution plate and communicate with the air intake channel.
[0010] Preferably, the positioning air guide tube is a hollow tube with openings at both ends, one end of which is provided with an insertion end, the outer diameter of which is smaller than the outer diameter of the positioning air guide tube.
[0011] Preferably, a plurality of the flow guide holes are spaced apart on the flow guide plate, and each of the positioning air guide pipes is connected to one of the flow guide holes, so that a plurality of cylindrical carbon preforms are spaced apart on the flow guide plate.
[0012] Preferably, the gas limiting cylinder is a cylinder with openings at both ends, and its two ends are respectively connected to two adjacent guide plates to form a flow limiting space to accommodate multiple cylindrical carbon preforms.
[0013] Preferably, the outer periphery of the guide plate is provided with a support ring, the top end of the lifting ring and both ends of the air limiting cylinder are provided with flanges, and each flange is provided with an annular groove on the side facing the guide plate that engages with the outer edge of the guide plate, and the flange abuts against the support ring; the thickness of the support ring and the depth of the annular groove are both less than the thickness of the guide plate.
[0014] A method for vapor deposition densification of a cylindrical carbon preform, using the aforementioned apparatus for preparing a cylindrical carbon preform by vapor deposition, includes the following steps: S1. The multiple cylindrical carbon preforms are respectively fitted onto the positioning gas guide pipes on each of the guide plates and placed inside the gas limiting cylinder; depositing gas containing natural gas is introduced into the air inlet, so that the depositing gas enters the pressure equalization chamber after being first-stage diverted through the gas distribution hole of the gas distribution plate, and then diverted second-stage through the guide hole of the guide plate. The depositing gas enters the inner hole of the cylindrical carbon preform through the positioning gas guide pipe, and enters the outer side of the cylindrical carbon preform through the guide hole that is not connected to the positioning gas guide pipe, so that the depositing gas flows along the inner and outer surfaces of the cylindrical carbon preform and performs gas phase deposition and densification to obtain carbon preform; S2. High-temperature heat treatment of carbon-carbon billets; S3. Perform surface machining on the carbon-carbon billet after high-temperature heat treatment to obtain cylindrical carbon-carbon products.
[0015] Preferably, the deposition gas is natural gas; or the deposition gas is a mixture of natural gas and at least one of propylene, propane, hydrogen and nitrogen, wherein the volume fraction of natural gas in the deposition gas is 50% to 100%.
[0016] Preferably, in step S1, the deposition temperature is 800℃~1200℃, the gas pressure in the deposition furnace is 1kPa~15kPa, and the deposition time is 20h~360h.
[0017] Preferably, in step S2, the high-temperature heat treatment temperature is 1800℃~2500℃, and the holding time is 1h~3h; in step S3, the surface machining amount is 0.5mm~5mm.
[0018] Compared with the above-mentioned background technology, the apparatus for preparing cylindrical carbon preforms by vapor deposition provided by the present invention has the following beneficial effects: The deposition gas entering through the inlet is first-stage diverted by a gas distribution plate, and a pressure equalization chamber is formed by the lifting ring, guide plate, and furnace bottom, ensuring a more uniform distribution of the deposition gas before it enters the guide plate. The guide holes on the guide plate further distribute the deposition gas. Those connected to the positioning guide pipe guide the deposition gas into the inner hole of the cylindrical carbon-carbon preform, while those not connected to the positioning guide pipe direct the deposition gas to the outside of the preform. Simultaneously, a gas limiting cylinder constrains the flow range of the outer airflow. This allows the deposition gas to flow more evenly across the inner and outer surfaces of the cylindrical carbon-carbon preform, improving gas distribution and deposition uniformity during the vapor deposition process, increasing densification efficiency, and helping to shorten the product manufacturing cycle and reduce production costs. Attached Figure Description
[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.
[0020] Figure 1 This is a cross-sectional schematic diagram of the overall structure of the preparation device of the present invention; Figure 2 This is a schematic diagram of the structure of the air distribution plate of the present invention; Figure 3 This is a schematic diagram of the lifting ring structure of the present invention; Figure 4 This is a schematic diagram of the structure of the flow guide plate of the present invention; Figure 5 This is a schematic diagram of the positioning air guide tube of the present invention; Figure 6 This is a schematic diagram of the structure of the gas limiting cylinder of the present invention.
[0021] Figure Labels
[0022] 1-Gas distribution plate; 2-Furnace bottom; 3-Gas inlet; 4-Gas distribution hole; 5-Lifting ring; 6-Guide plate; 7-Equalizing chamber; 8-Guide hole; 9-Positioning gas guide pipe; 10-Cylindrical carbon preform; 11-Inner hole; 12-Gas limiting cylinder; 13-Insertion end; 14-Support ring. Detailed Implementation
[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0024] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.
[0025] This embodiment provides a preparation apparatus for vapor deposition of cylindrical carbon-carbon preforms, which can be used for vapor-phase densification of straight-cylinder, thick-walled products such as the lower shaft of carbon-carbon support rods in the silicon crystal pulling thermal field of photovoltaic crystals. See also Figure 1 The preparation device includes a gas distribution plate 1, a lifting ring 5, multiple guide plates 6, multiple hollow positioning gas guide pipes 9, and at least one gas limiting cylinder 12, which are sequentially assembled in the deposition furnace to form a deposition tooling that integrates gas guiding and product positioning.
[0026] The gas distribution plate 1 is located inside the deposition furnace and is positioned near the furnace bottom 2. It is connected to the gas inlet 3 on the furnace bottom 2 and is used to receive the deposition gas entering the furnace cavity through the gas inlet 3. The gas distribution plate 1 has multiple gas distribution holes 4, through which the deposition gas undergoes primary diversion and then diffuses to the surrounding areas.
[0027] The lifting ring 5 is located on the furnace bottom 2 and surrounds the outside of the gas distribution plate 1. The lifting ring 5 facilitates the overall lifting and transportation of the upper tooling and products during the loading and unloading process, and also forms the flow space required for gas diffusion between itself and the gas distribution plate 1.
[0028] Multiple guide plates 6 are arranged vertically at intervals. The guide plate 6 at the bottom rests on the top of the lifting ring 5, and together with the lifting ring 5 and the furnace bottom 2, they form a pressure equalization chamber 7. The pressure equalization chamber 7 is used to receive the deposition gas flowing out of the gas distribution hole 4, so that the gas tends to be evenly distributed before entering the upper deposition area, thereby forming a relatively uniform gas intake state. Each guide plate 6 has multiple guide holes 8 for secondary diversion of the incoming deposition gas.
[0029] Multiple hollow positioning gas guide tubes 9 are vertically arranged on the guide plate 6, with their lower ends connected to corresponding guide holes 8 and their upper ends extending upwards into the inner hole 11 of the cylindrical carbon-carbon preform 10. The positioning gas guide tubes 9 serve two purposes: firstly, they support and position the cylindrical carbon-carbon preform 10, ensuring each preform maintains a relatively fixed position on the guide plate 6; secondly, they guide the deposition gas into the inner hole 11, allowing the gas to flow along the inner surface of the preform. The guide holes 8, not connected to the positioning gas guide tubes 9, direct the deposition gas to the outside of the cylindrical carbon-carbon preform 10, allowing the gas to flow along the outer surface of the preform, thereby achieving simultaneous deposition on the inner and outer surfaces of the product.
[0030] At least one gas-limiting cylinder 12 is disposed between two adjacent guide plates 6 and surrounds the outside of multiple cylindrical carbon preforms 10, forming a relatively enclosed deposition space together with the upper and lower guide plates 6 in the vertical direction. The gas-limiting cylinder 12 is used to restrict the flow range of the deposition gas, allowing more gas to pass through the surface of the product, reducing ineffective diffusion, and helping to improve deposition efficiency and density uniformity.
[0031] The assembly relationship is as follows: the gas distribution plate 1 is placed above the gas inlet 3 of the furnace bottom 2, the lifting ring 5 is sleeved on the outer periphery of the gas distribution plate 1 and supports the bottom guide plate 6; the lower end of the positioning gas guide pipe 9 is inserted into the guide hole 8 of the bottom guide plate 6, the cylindrical carbon preform 10 is sleeved on the outside of the positioning gas guide pipe 9 and stands on the bottom guide plate 6; the gas limiting cylinder 12 is sleeved on the outside of the preform, and its upper end is supported by the next layer of guide plate 6. In this way, they are stacked layer by layer to form a multi-layer deposition unit.
[0032] In this embodiment, the cylindrical carbon preform 10 takes the carbon fiber support rod lower shaft preform as an example. Its outer diameter is about Φ126mm, the inner hole diameter is about Φ65mm, the length is about 1270mm, and the initial bulk density is about 0.45g / cm³.
[0033] During furnace loading, multiple cylindrical carbon preforms 10 are vertically erected on the guide plate 6 and arranged at intervals along the circumference of the guide plate 6. The guide plate 6, positioning gas guide pipe 9, cylindrical carbon preforms 10, and gas limiting cylinder 12 are stacked vertically layer by layer to form a column, and multiple columns are arranged side by side in the furnace. Taking the carbon fiber support rod lower shaft preform as an example, about 37 preforms can be arranged at intervals on a single guide plate 6, each column can be set with about 4 layers along the vertical direction, about 18 columns can be arranged per furnace, and the single furnace loading capacity can reach about 2664 columns. This allows for the simultaneous densification of a large batch of products within one deposition cycle, which is beneficial for improving production efficiency and reducing the manufacturing cost per unit.
[0034] See Figure 1 and Figure 2 Based on the above embodiments, the gas distribution plate 1 is generally disc-shaped, and its bottom is provided with an air intake channel connected to the air inlet 3. The air intake channel extends along the interior of the gas distribution plate 1 and is used to guide the deposited gas entering from the air inlet 3 to various positions of the gas distribution plate 1.
[0035] Multiple air distribution holes 4 are spaced apart along the outer circumferential surface of the air distribution plate 1 and are connected to the air inlet channel. After the deposited gas enters the air inlet channel through the air inlet 3, it overflows to the outer circumference of the air distribution plate 1 through the multiple air distribution holes 4 distributed circumferentially, realizing primary flow division. Since the air distribution holes 4 are spaced apart along the outer circumferential surface, the gas can flow out simultaneously in multiple directions, which helps to make the airflow entering the equalizing chamber 7 more balanced in the circumferential direction and reduces the phenomenon of local airflow imbalance caused by the concentrated gas entering from a single direction.
[0036] The connection between the air inlet channel and the air inlet 3 can be sealed to reduce gas leakage at the connection point. The diameter and number of the gas distribution holes 4 can be set according to the furnace cavity size and the number of furnaces loaded, so as to meet the gas supply requirements while keeping the gas flow rate within a suitable range, laying the foundation for the pressure equalization effect in the subsequent pressure equalization chamber 7. The gas distribution plate 1 can be made of graphite or carbon-carbon material to adapt to the high-temperature deposition environment in the furnace. The gas distribution plate 1, the lifting ring 5, and the guide plate 6 are arranged vertically in sequence to allow the deposition gas to flow in an orderly manner from bottom to top.
[0037] See Figure 1 and Figure 5 Based on the above embodiments, the positioning gas guide tube 9 is a hollow tube with openings at both ends, and its cavity is axially continuous to allow the deposited gas to pass through from bottom to top. One end of the positioning gas guide tube 9 is provided with an insertion end 13, the outer diameter of which is smaller than the outer diameter of the rest of the positioning gas guide tube 9, thereby forming a stepped transition between the insertion end 13 and the tube body.
[0038] During assembly, the insertion end 13 is inserted downwards into the guide hole 8 of the guide plate 6 and mates with the guide hole 8 to achieve connection and positioning between the positioning air guide tube 9 and the guide plate 6. The stepped transition can be placed on the edge of the guide hole 8 to limit and support the positioning air guide tube 9, keeping it vertical on the guide plate 6. The upper end of the positioning air guide tube 9 extends upwards into the inner hole 11 of the cylindrical carbon preform 10 to position the preform and introduce deposition gas into the inner hole 11. The number of each positioning air guide tube 9 corresponds to the number of cylindrical carbon preforms 10 arranged on a single guide plate 6, so that each preform's inner hole 11 has a corresponding positioning air guide tube 9 for gas guidance and positioning.
[0039] Since the outer diameter of the insertion end 13 is smaller than the outer diameter of the tube body, and the fit between the insertion end 13 and the guide hole 8 helps to reduce the side leakage of gas at the connection point, the deposited gas enters the inner hole 11 along the lumen of the positioning guide tube 9, thereby improving the gas supply efficiency of the inner surface.
[0040] See Figure 1 and Figure 4 Based on the above embodiments, multiple guide holes 8 are distributed at intervals along the guide plate 6, and can be arranged regularly in the circumferential and radial directions. Each positioning air guide tube 9 is connected to one of the guide holes 8, so that multiple cylindrical carbon preforms 10 sleeved on the positioning air guide tube 9 are arranged at intervals along the guide plate 6.
[0041] Because the guide holes 8 are spaced apart, an appropriate gap is maintained between adjacent cylindrical carbon preforms 10, providing a channel for gas to flow along the outer surface of the product and reducing the situation where the outer walls of adjacent products stick to each other and affect the deposition on the outer surface.
[0042] Meanwhile, the guide hole 8 connected to the positioning air guide pipe 9 is used to supply air to the inner hole 11, and the guide hole 8 not connected to the positioning air guide pipe 9 is used to supply air to the outside of the product. The two types of guide holes 8 are staggered on the guide plate 6, which helps to make the air supply to the inner and outer surfaces more balanced.
[0043] The diameter, spacing and number of the guide holes 8 can be designed in conjunction with the size of the cylindrical carbon preform 10 and the number of furnace loads, so that each product can obtain a more uniform gas distribution on the guide plate 6, thereby achieving a more uniform deposition process from the inside to the outside.
[0044] See Figure 6 Based on the above embodiments, the gas limiting cylinder 12 is a cylinder with openings at both ends, and its inner cavity is used to accommodate multiple cylindrical carbon preforms 10. The two ends of the gas limiting cylinder 12 are respectively connected to two adjacent guide plates 6, and together with the upper and lower guide plates 6, they form a flow limiting space for accommodating multiple cylindrical carbon preforms 10.
[0045] In the assembled state, the lower guide plate 6 supports the cylindrical carbon preform 10 and the gas-limiting cylinder 12. The gas-limiting cylinder 12 is fitted onto the outside of the preform, and its top end is connected to the upper guide plate 6. This process is repeated vertically layer by layer to form a multi-layer deposition structure. The gas-limiting cylinder 12 confines the flow range of the deposition gas within the limited space. After entering from the lower guide plate 6, the gas flows upward along the inner and outer surfaces of the product, reducing ineffective diffusion of gas to the outside of the cylinder. In the multi-layer stacked structure, the deposition gas flows upward from the bottom guide plate 6 through the products within each layer of the gas-limiting cylinder 12, ensuring that each layer of the product receives deposition gas flowing along its inner and outer surfaces.
[0046] The inner diameter of the gas limiting cylinder 12 is larger than the outer perimeter occupied by the multiple cylindrical carbon preforms 10, thus maintaining an appropriate flow gap between the outer surface of the product and the inner wall of the gas limiting cylinder 12. This allows for both gas supply to the outer surface and corresponding constraint on the airflow, which helps to improve deposition efficiency and density uniformity. Adjacent gas limiting cylinders 12 are separated by guide plates 6, and each layer of deposition space is relatively independent, which facilitates layered and relatively uniform densification of the entire batch of products.
[0047] See Figure 1 , Figure 3 and Figure 4 Based on the above embodiments, a support ring 14 is provided on the outer periphery of the guide plate 6. The support ring 14 is located at the center of the outer periphery of the guide plate 6 and extends in the circumferential direction. Its thickness is less than the thickness of the guide plate 6.
[0048] Specifically, flanges are provided at the top of the lifting ring 5 and at both ends of the air limiting cylinder 12. Each flange has an annular groove on the side facing the guide plate 6. The annular groove engages with the outer edge of the guide plate 6, thereby achieving the positioning connection between the guide plate 6 and the lifting ring 5 and the air limiting cylinder 12. At the same time, the flange abuts against the support ring 14.
[0049] During assembly, the outer edge of the bottom guide plate 6 is engaged in the annular groove of the top flange of the lifting ring 5, and the end face of the flange abuts against the end face of the support ring 14, so that the bottom guide plate 6 is positioned and supported on the lifting ring 5; the annular grooves of the flanges at both ends of the air limiting cylinder 12 are also engaged with the outer edge of the adjacent guide plate 6 and abut against the support ring 14, thereby connecting the air limiting cylinder 12 and the upper and lower guide plates 6 into one unit, and assembling them layer by layer in the vertical direction.
[0050] The thickness of the support ring 14 and the depth of the annular groove are both less than the thickness of the guide plate 6. This allows the flange end face to abut against the support ring 14 end face when engaged, while maintaining adequate clearance between the outer edge of the guide plate 6 and the bottom of the annular groove. This reduces the possibility of interference between the bottom of the groove and the outer edge of the guide plate 6, resulting in a more stable connection between the various structural layers and facilitating assembly and disassembly during furnace loading and unloading. This combination of engagement and abutment ensures a good seal at all connection points when gas flows vertically, helping to reduce gas leakage through connection gaps.
[0051] The present invention also provides a vapor-phase deposition densification method for cylindrical carbon preforms, which uses the above-mentioned preparation apparatus and mainly includes the following steps.
[0052] S1, Furnace loading and vapor deposition.
[0053] First, place the gas distribution plate 1 at the bottom of the deposition furnace near the gas inlet 3. Then, place the lifting ring 5 on the outside of the gas distribution plate 1. Next, place the bottom guide plate 6 on the lifting ring 5 so that the bottom guide plate 6, the lifting ring 5, and the furnace bottom 2 form a pressure equalization chamber 7.
[0054] Then, the insertion ends 13 of multiple hollow positioning air guide tubes 9 are inserted into the guide holes 8 of the bottom guide plate 6, and multiple cylindrical carbon carbon preforms 10 are respectively sleeved on each positioning air guide tube 9, so that the inner hole 11 of the preform corresponds to the cavity of the positioning air guide tube 9. Then, the air-limiting cylinder 12 is fitted onto the outside of the precast body, and the lower end of the air-limiting cylinder 12 is connected to the bottom guide plate 6, while the upper end receives the upper guide plate 6.
[0055] Stack the guide plate 6, positioning gas guide pipe 9, cylindrical carbon preform 10 and gas limiting cylinder 12 vertically layer by layer in the manner described above until the entire furnace is charged.
[0056] After the furnace is loaded, a deposition gas containing natural gas is introduced into the gas inlet 3. The deposition gas is first-diverted through the gas distribution holes 4 of the gas distribution plate 1 and then enters the pressure equalization chamber 7, where it tends to be evenly distributed. It is then diverted again through the guide holes 8 of the guide plate 6. Part of the deposition gas enters the inner hole 11 of the cylindrical carbon-carbon preform 10 through the positioning gas guide pipe 9 and flows upward along the inner surface of the preform. The other part of the deposition gas enters the outer side of the cylindrical carbon-carbon preform 10 through the guide holes 8 that are not connected to the positioning gas guide pipe 9 and flows upward along the outer surface of the preform. The gas is simultaneously cracked and pyrolytic carbon is deposited on the inner and outer surfaces of the product, achieving gas phase deposition and densification from the inside out, resulting in a carbon-carbon billet.
[0057] S2, High-temperature heat treatment.
[0058] The carbon-carbon billet obtained by deposition is taken out of the deposition furnace and loaded into a graphitization furnace for high-temperature heat treatment to further adjust the microstructure of the billet and improve its high-temperature performance.
[0059] S3, surface machining.
[0060] After high-temperature heat treatment, the carbon-carbon billet is surface-machined to remove excess deposits and bring the product to the designed dimensions, resulting in a cylindrical carbon-carbon product, such as the lower shaft of a carbon-carbon support rod.
[0061] The densification method in this embodiment achieves densification by simultaneously and rapidly depositing on multiple surfaces, both inside and outside the billet. While ensuring the uniformity of carbon-carbon density, it helps to shorten the manufacturing cycle of carbon-carbon cylindrical thick-walled parts and reduce manufacturing costs. Compared to the traditional process that combines vapor deposition with multiple liquid phase impregnation, this method can shorten the overall manufacturing cycle from approximately 60-90 days to approximately 45-60 days, reducing the liquid phase impregnation process and corresponding energy consumption.
[0062] Based on the above embodiments, the composition of the deposited gas in step S1 will be further explained.
[0063] The deposition gas can be natural gas, or a mixture of natural gas and at least one of propylene, propane, hydrogen, and nitrogen. When a mixture is used, the volume fraction of natural gas in the deposition gas shall not be less than 50%, and the remaining components can be selected and proportioned according to the deposition rate and the requirements of the pyrolytic carbon structure.
[0064] Propylene and propane can be used as supplementary carbon sources to help regulate the carbon source concentration and deposition rate in the furnace; hydrogen helps regulate the deposition morphology of pyrolytic carbon; nitrogen can be used as a dilution and pressure regulating gas to adjust the atmosphere and gas flow rate in the furnace. Taking the densification of the carbon fiber support rod lower shaft preform as an example, the flow rate of natural gas can be controlled at approximately 3500 L / min and the flow rate of nitrogen can be controlled at approximately 300 L / min during the deposition process, so that the carbon source supply and gas flow in the furnace are in a more suitable state, which is conducive to obtaining a more uniform deposition effect on the inner and outer surfaces of the product. When using a mixture of natural gas and nitrogen, the relative concentration of carbon source in the furnace can be controlled by adjusting the flow ratio of the two, taking into account both the deposition rate and the densification degree of pyrolytic carbon.
[0065] By adjusting the composition of the deposition gas and the flow rate of each component, the deposition rate and density uniformity of pyrolytic carbon can be well balanced under different product specifications and furnace loading conditions.
[0066] Based on the above embodiments, the vapor deposition process parameters in step S1 are further explained. During the vapor deposition process, the deposition temperature can be controlled between 800℃ and 1200℃, the gas pressure in the deposition furnace can be controlled between 1kPa and 15kPa, and the deposition time can be between 20h and 360h, which can be selected in combination with the size, initial density, and target density of the cylindrical carbon preform.
[0067] Taking the densification of the carbon fiber support rod lower shaft preform as an example, the furnace temperature can be stably controlled at approximately 1150℃ and the furnace pressure at approximately 4500Pa during the deposition process, with a deposition time of approximately 300 hours. Under these process conditions, the deposition gas continuously decomposes and deposits pyrolytic carbon along the inner and outer surfaces of the product, and the product gradually densifies from the inside out. After the above deposition, the average bulk density of the carbon-carbon preform can be increased from the initial approximately 0.45 g / cm³ to approximately 1.45 g / cm³, achieving a relatively high and uniform bulk density level.
[0068] Because the deposited gas is distributed relatively evenly to the inner and outer surfaces of each product after primary and secondary diversion, the volume density of each layer and column product after deposition is relatively close, and the density uniformity is good.
[0069] In actual production, the deposition rate and density uniformity can be matched by adjusting parameters such as deposition temperature, furnace pressure and deposition time, thereby shortening the deposition cycle as much as possible while taking into account product quality.
[0070] Based on the above embodiments, the high-temperature heat treatment in step S2 and the surface machining in step S3 are further explained.
[0071] In step S2, the carbon-carbon billet is placed in a graphitization furnace for high-temperature heat treatment. The temperature of the high-temperature heat treatment can be 1800℃~2500℃, and the holding time can be 1h~3h. High-temperature heat treatment helps to adjust the microstructure of pyrolytic carbon and improve the high-temperature mechanical properties and structural stability of the product.
[0072] Taking the carbon fiber support rod lower shaft blank as an example, the high-temperature heat treatment temperature can be controlled at approximately 1850℃, and the entire high-temperature heat treatment process lasts for about 28 hours, with the holding time at the target temperature falling within the aforementioned range. After high-temperature heat treatment, the microstructure of the blank tends to be stable, which is beneficial for maintaining good performance in the high-temperature service environment of the photovoltaic crystal pulling thermal field.
[0073] In step S3, the carbon-carbon billet after high-temperature heat treatment undergoes surface turning, with a machining allowance ranging from 0.5 mm to 5 mm. This surface turning removes excess deposits from the billet surface and brings the product to the designed dimensions and surface quality requirements, resulting in the final cylindrical carbon-carbon product, such as the lower shaft of a carbon-carbon support rod. The machining allowance can be selected based on the actual dimensional deviations and surface condition of the billet, minimizing material waste while maintaining dimensional accuracy. The resulting cylindrical carbon-carbon product can be used as the lower shaft of a carbon-carbon support rod in the photovoltaic crystal pulling thermal field. Its high and relatively uniform bulk density helps maintain good load-bearing performance in high-temperature service environments.
[0074] In summary, the present invention, through the cooperation of the gas distribution plate 1, the flow guide plate 6, the positioning gas guide pipe 9 and the gas limiting cylinder 12, performs primary and secondary diversion of the deposited gas and guides the gas to the inner and outer surfaces of the cylindrical carbon preform 10 respectively, so that the product is denser more uniformly and quickly from the inside to the outside, which is beneficial to shorten the manufacturing cycle and reduce the production cost.
[0075] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.
Claims
1. A preparation apparatus for cylindrical carbon preform vapor deposition, characterized in that, include: The gas distribution plate (1) is located inside the deposition furnace and is connected to the gas inlet (3) of the furnace bottom (2). Multiple gas distribution holes (4) are provided on the gas distribution plate (1). The lifting ring (5) is set on the furnace bottom (2) and surrounds the outside of the gas distribution plate (1); Multiple guide plates (6) are arranged at vertical intervals. The guide plate (6) located at the bottom is set on the lifting ring (5) and forms a pressure equalization cavity (7) with the lifting ring (5) and the furnace bottom (2). Each guide plate (6) has multiple guide holes (8). Multiple hollow positioning air guide tubes (9) have their lower ends connected to the corresponding flow guide holes (8) and their upper ends used to extend into the inner hole (11) of the cylindrical carbon preform (10) to position the cylindrical carbon preform (10) and guide air into the inner hole (11); the flow guide holes (8) not connected to the positioning air guide tubes (9) are used to guide air to the outside of the cylindrical carbon preform (10). At least one gas limiting cylinder (12) is disposed between two adjacent flow guides (6) and surrounds the outside of the plurality of cylindrical carbon preforms (10) so that the flow guides (6) and the gas limiting cylinder (12) form a deposition space in the vertical direction.
2. The apparatus for preparing cylindrical carbon preforms by vapor deposition according to claim 1, characterized in that, The bottom of the air distribution plate (1) is provided with an air intake channel that communicates with the air inlet (3), and a plurality of air distribution holes (4) are arranged at intervals along the outer peripheral surface of the air distribution plate (1) and communicate with the air intake channel.
3. The apparatus for preparing cylindrical carbon preforms by vapor deposition according to claim 1, characterized in that, The positioning air guide tube (9) is a hollow tube with openings at both ends, and one end is provided with an insertion end (13). The outer diameter of the insertion end (13) is smaller than the outer diameter of the positioning air guide tube (9).
4. The apparatus for preparing cylindrical carbon preforms by vapor deposition according to claim 1, characterized in that, Multiple flow guide holes (8) are spaced apart on the flow guide plate (6), and each of the positioning air guide pipes (9) is connected to one of the flow guide holes (8) so that multiple cylindrical carbon preforms (10) are spaced apart on the flow guide plate (6).
5. The apparatus for preparing cylindrical carbon preforms by vapor deposition according to claim 1, characterized in that, The gas limiting cylinder (12) is a cylinder with openings at both ends. Its two ends are respectively connected to two adjacent guide plates (6) to form a flow limiting space to accommodate multiple cylindrical carbon preforms (10).
6. The apparatus for preparing cylindrical carbon preforms by vapor deposition according to claim 1, characterized in that, The outer periphery of the guide plate (6) is provided with a support ring (14). The top of the lifting ring (5) and both ends of the air limiting cylinder (12) are provided with flanges. Each flange has an annular groove on the side facing the guide plate (6) that engages with the outer edge of the guide plate (6), and the flange abuts against the support ring (14). The thickness of the support ring (14) and the depth of the annular groove are both less than the thickness of the guide plate (6).
7. A method for vapor-phase deposition densification of a cylindrical carbon preform, characterized in that, The preparation apparatus for cylindrical carbon preform vapor deposition according to any one of claims 1 to 6 includes the following steps: S1. Multiple cylindrical carbon preforms (10) are respectively fitted onto the positioning gas guide pipes (9) on each of the guide plates (6) and placed inside the gas limiting cylinder (12); deposit gas containing natural gas is introduced into the air inlet (3), so that the deposit gas enters the pressure equalization chamber (7) after being first-stage diverted through the gas distribution hole (4) of the gas distribution plate (1), and then diverted second-stage through the guide hole (8) of the guide plate (6). The deposit gas enters the inner hole (11) of the cylindrical carbon preform (10) through the positioning gas guide pipe (9), and enters the outer side of the cylindrical carbon preform (10) through the guide hole (8) which is not connected to the positioning gas guide pipe (9), so that the deposit gas flows along the inner and outer surfaces of the cylindrical carbon preform (10) and performs gas phase deposition and densification to obtain carbon preforms; S2. High-temperature heat treatment of carbon-carbon billets; S3. Perform surface machining on the carbon-carbon billet after high-temperature heat treatment to obtain cylindrical carbon-carbon products.
8. The vapor deposition densification method for cylindrical carbon preforms according to claim 7, characterized in that, The depositing gas is natural gas; or the depositing gas is a mixture of natural gas and at least one of propylene, propane, hydrogen and nitrogen, wherein the volume fraction of natural gas in the depositing gas is 50% to 100%.
9. The vapor deposition densification method for cylindrical carbon preforms according to claim 7, characterized in that, In step S1, the deposition temperature is 800℃~1200℃, the gas pressure in the deposition furnace is 1kPa~15kPa, and the deposition time is 20h~360h.
10. The vapor deposition densification method for cylindrical carbon preforms according to claim 7, characterized in that, In step S2, the high-temperature heat treatment temperature is 1800℃~2500℃, and the holding time is 1h~3h; in step S3, the surface machining amount is 0.5mm~5mm.