Control methods and systems for high-temperature coating furnaces for pyrolytic graphite

Abstract

This invention discloses a control method and system for a high-temperature coating furnace for pyrolytic graphite, belonging to the field of material preparation and high-temperature heat treatment technology. It solves the problems of poor deposition uniformity, contradiction between deposition efficiency and quality, and poor process repeatability that exist in coating furnace control methods when preparing workpieces. The technical solution includes the following steps: The substrate to be deposited is placed in the furnace chamber of the high-temperature coating furnace for pyrolytic graphite and pretreated; the pretreated substrate is subjected to multi-stage variable temperature and flow rate deposition control to complete the deposition operation. The multi-stage variable temperature and flow rate deposition control includes four sub-stages performed sequentially: preheating and degassing, interface nucleation, stable growth, and final densification; after the deposition operation is completed, the substrate is cooled, and the substrate coated with pyrolytic graphite is removed. This invention is applied to coating furnaces.

Description

Technical Field

[0001] This invention relates to the field of material preparation and high-temperature heat treatment technology, specifically to a control method and system for a high-temperature coating furnace for pyrolytic graphite. Background Technology

[0002] Existing pyrolytic graphite coating equipment typically employs high-temperature graphite tube furnaces. The basic process involves placing the substrate (such as graphite parts, carbon-carbon composite parts, etc.) inside the furnace chamber, evacuating it, and then introducing hydrocarbon gases (such as methane, propane, etc.). The furnace is then heated to a high temperature (usually >1800℃), causing the gas to pyrolyze on the substrate surface and deposit to form a PG coating. However, existing process control methods have the following significant problems: 1. Poor coating uniformity: Traditional control methods are mostly simple temperature-time program control, which is insufficient for controlling the uniformity of temperature field and airflow field in the furnace. This results in large differences in coating thickness and density on substrate surfaces of different locations and shapes. Especially for workpieces with complex shapes, defects such as excessively thick or loose coatings are prone to occur at edges and corners.

[0003] 2. Contradiction between deposition efficiency and quality: Increasing gas concentration or temperature to improve deposition rate can easily lead to homogeneous nucleation in the gas phase, generating carbon black particles. These particles adhere to the coating surface and form defects, severely reducing the density and performance of the coating.

[0004] 3. Poor process repeatability: Due to the lack of real-time monitoring and feedback of the deposition process, the process parameters are fixed and cannot adapt to the slow changes in the furnace conditions (such as aging of graphite heating elements and degradation of insulation layer performance), resulting in quality fluctuations in different batches of products.

[0005] 4. High energy consumption and high cost: The entire process is usually maintained at a single high temperature, lacking refined energy management for different deposition stages, resulting in energy waste.

[0006] Therefore, there is an urgent need for a method to control a high-temperature coating furnace for pyrolytic graphite that can achieve uniform, dense, high-performance coatings with good process repeatability. Summary of the Invention

[0007] In order to solve the technical problems of poor deposition uniformity, contradiction between deposition efficiency and quality, and poor process repeatability in the preparation of workpieces by existing coating furnace control methods, this invention proposes a control method and system for a high-temperature coating furnace for pyrolytic graphite.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a control method for a high-temperature coating furnace for pyrolytic graphite, comprising the following steps: Step S1: The substrate to be deposited is placed in the furnace chamber of a pyrolytic graphite high-temperature coating furnace for pretreatment. Step S2: Perform multi-stage variable temperature and flow rate deposition control on the pretreated substrate to complete the deposition operation. The multi-stage variable temperature and flow rate deposition control includes four sub-stages: preheating and degassing, interface nucleation, stable growth, and final densification. During the preheating and degassing stage, interface nucleation stage, and stable growth stage, the temperature inside the furnace is gradually increased. After transitioning from the stable growth stage to the final densification stage, the temperature inside the furnace is reduced to a preset value and maintained at the preset temperature for a period of time. During the deposition of the substrate, the state inside the furnace is monitored and evaluated in real time, and based on the results of the real-time monitoring and evaluation, closed-loop feedback control is used to control each execution unit that performs the deposition operation. Step S3: After the deposition process is completed, cool the substrate and remove the substrate coated with pyrolytic graphite.

[0009] Furthermore, the pretreatment includes at least: heating the substrate to a pretreatment temperature in a vacuum environment and maintaining it at a first preset temperature for a time in an inert protective gas atmosphere; After pretreatment, the pressure inside the furnace is in a slightly negative pressure state, with a pressure range of -0.02 to -0.01 MPa.

[0010] Furthermore, in step S2, the multi-stage variable temperature and variable flow rate deposition control includes the following processes: Step S201: After pretreatment of the substrate, the preheating and degassing stage is entered. In the preheating and degassing stage, an inert protective gas is introduced, and the temperature inside the furnace is heated to a preset first temperature. After holding the temperature for a first preset time, the interface nucleation stage is entered. Step S202: In the interface nucleation stage, switch to the introduction of a mixed gas containing reactant gas and carrier gas, and at the same time heat the temperature in the furnace from the first temperature to the preset second temperature, hold it at the temperature for a second preset time, and then enter the stable growth stage. Step S203: In the stable growth stage, increase the concentration of the reactant gas and the total gas flow rate in the mixed gas, and at the same time heat the temperature in the furnace from the second temperature to the preset third temperature, hold it at the temperature for a third preset time, and then enter the final densification stage. Step S204: In the final densification stage, reduce the concentration of the reactant gas in the mixed gas, and lower the temperature inside the furnace to a preset fourth temperature and hold it at that temperature for a fourth preset time.

[0011] Furthermore, in step S2, the real-time monitoring and evaluation of the state inside the furnace includes the following processes: Step S211: Real-time acquisition of data to be evaluated: Real-time temperature field data inside the furnace is collected using temperature sensors. The concentration distribution of reaction precursors and byproducts at different locations within the furnace is monitored in real time using a gas composition analyzer. The optical monitoring device acquires real-time data on the particle size of the deposited particles, optical signals reflecting the coating growth rate, and optical signals reflecting the coating thickness. Step S212: Based on the data to be evaluated collected by real-time monitoring, dynamically evaluate the uniformity index, homogeneous nucleation risk index, and completion rate of the current substrate coating.

[0012] Furthermore, in step S212, the uniformity index is evaluated using a fusion analysis based on multi-source data. Temperature field uniformity: Based on real-time collected three-dimensional spatial temperature field data inside the furnace, the deviation between the temperature of each monitoring point inside the furnace and the preset temperature of the current deposition control stage is obtained. The smaller the temperature deviation, the higher the uniformity contribution value. Gas concentration distribution: Based on the real-time collection of the concentrations of reaction precursors and by-products at different locations in the furnace, the deviation of the concentrations of reaction precursors and by-products at each monitoring point in the furnace from the preset concentrations at the current deposition control stage is obtained. The uniformity of gas concentration distribution is evaluated based on the dispersion of the concentration deviation. The uniformity index is negatively correlated with the dispersion of the concentrations of reaction precursors and by-products at each location in the furnace from the preset concentrations. Growth rate consistency: Based on the optical signals reflecting the coating growth rate at each monitoring point in the furnace collected in real time, the current growth rate of the pyrolytic graphite coating on the substrate is inferred, the deviation between the current coating growth rate on the substrate and the preset growth rate is obtained, and a growth rate consistency coefficient is generated. The evaluation results of three dimensions—temperature field uniformity, gas concentration distribution, and growth rate consistency—are weighted and integrated to obtain a uniformity index in the range of 0-1. The closer the index is to 1, the more uniform the pyrolytic graphite coating on the current substrate is.

[0013] Furthermore, in step S212, a homogeneous nucleation risk index is generated by comparing the real-time collected sediment particle size data with a preset particle diameter threshold.

[0014] Furthermore, in step S212, the completion rate of the deposition stage is evaluated based on the cumulative changes of multiple parameters: Time progress benchmark: Based on the preset insulation time of the current stage, obtain the ratio of the completed time to the preset insulation time of the current stage as the basic completion rate; Thickness feedback correction: The thickness of the pyrolytic graphite coating on the substrate is obtained in real time through optical signals that reflect the coating thickness. When the thickness value of the pyrolytic graphite coating on the substrate reaches the preset thickness threshold, the completion is corrected to 100%. Byproduct concentration: The concentration trend of reaction byproducts is collected and monitored in real time. When the concentration of reaction byproducts tends to stabilize, it indicates that the reaction is nearing completion. Temperature-pressure stability: When the temperature and pressure inside the furnace remain stable for a relatively long period of time and the fluctuation range is within the corresponding preset fluctuation range, it indicates that the deposition process has entered the final stage of steady state. The evaluation results of four dimensions—time progress, thickness feedback, by-product concentration, and temperature-pressure stability—are comprehensively judged according to preset evaluation criteria, and a completion index of 0-100% is output.

[0015] Furthermore, in step S2, the closed-loop feedback control includes: Temperature control: The real-time monitored temperature data is compared with the preset temperature value of the current deposition control stage. The output power of the heating device of the pyrolytic graphite high-temperature coating furnace is dynamically adjusted through the PID algorithm so that the actual temperature fluctuation range of the substrate surface is controlled within the predetermined temperature fluctuation threshold. Gas control: The flow rate and pressure inside the furnace are monitored in real time by the flow meter and pressure sensor configured in the pyrolytic graphite high-temperature coating furnace. The gas concentration and pressure at each deposition control stage are kept stable at the corresponding preset values ​​by adjusting the opening of the inlet valve and the exhaust valve. Uniformity control: When the coating growth rate in a certain area is detected to deviate from the preset growth rate, the output power of the heating device in the corresponding zone is dynamically adjusted to fine-tune the temperature in that area and coordinate the flow rate and direction of multiple devices for conveying reaction gases to optimize the local reaction gas supply. Controlling the conflict between deposition efficiency and quality: When the real-time monitored homogeneous nucleation risk index exceeds the safety threshold, the concentration of reactant gas is reduced and the temperature is fine-tuned first; after the risk is reduced, the temperature is gradually restored to the preset value. Process repeatability compensation: Based on the historical operating data of the heating device, a performance degradation model reflecting the relationship between heating power and temperature response is established. According to the performance degradation model, the preset temperature value of each deposition control stage is dynamically compensated.

[0016] Furthermore, in step S3, after the deposition operation is completed, the reaction gas is stopped, an inert protective gas is introduced, and the cooling system is started to control the cooling rate. After the temperature inside the furnace drops below the sixth temperature value, the furnace is opened and the substrate coated with pyrolytic graphite is taken out.

[0017] A control system for a pyrolytic graphite high-temperature coating furnace used to implement the control method described above includes: The central control unit incorporates a multi-physics coupling model and intelligent control algorithms. A multi-zone independent precision temperature control module, which communicates with the central control unit, is used for independent heating and temperature regulation of different areas inside the furnace; An adjustable intelligent gas distribution module, which communicates with the central control unit, is used to control the flow rate and concentration of the reaction gas and carrier gas introduced into the furnace. The multi-sensor fusion monitoring module communicates with the central control unit and is used to collect status parameters inside the furnace in real time. The human-computer interaction and data management module communicates with the central control unit and is used to display and store the status parameters and deposition control process inside the furnace. The central control unit is configured as follows: The system controls a multi-zone independent precision temperature control module and an adjustable intelligent gas distribution module to perform multi-stage variable temperature and variable flow deposition control on the pretreated substrate. The deposition control includes four sub-stages: preheating and degassing, interface nucleation, stable growth, and final densification. During the preheating and degassing stage, the interface nucleation stage, and the stable growth stage, the temperature inside the furnace is gradually increased. After transitioning from the stable growth stage to the final densification stage, the temperature inside the furnace is controlled to decrease to a preset value and remain constant. During the deposition process, the state parameters collected in real time by the multi-sensor fusion monitoring module are dynamically evaluated to assess the state inside the furnace. Based on the evaluation results, closed-loop feedback control is performed on the multi-zone independent precision temperature control module and the adjustable intelligent gas distribution module. After deposition, the cooling system is controlled to cool the substrate.

[0018] The advantages of this invention over the prior art are as follows: 1. The method and system of this invention sequentially perform four sub-stages on the pretreated substrate: preheating and degassing, interface nucleation, stable growth, and final densification. During the preheating and degassing, interface nucleation, and stable growth stages, the temperature inside the furnace is gradually increased. After transitioning from the stable growth stage to the final densification stage, the temperature inside the furnace is controlled to decrease to a preset value. During the deposition process on the substrate, the state inside the furnace is monitored and evaluated in real time. Based on the results of real-time monitoring and evaluation, closed-loop feedback control is used to control each execution unit performing the deposition operation. This allows for safe operation in the high deposition rate range or proactive intervention when risks occur, fundamentally reducing the generation of defects such as carbon black. As a result, high-quality coatings are obtained with high efficiency, effectively solving the problem of the contradiction between deposition rate and quality.

[0019] 2. The method and system of the present invention evaluate the uniformity of the coating on the substrate to be deposited by weighted integration of the evaluation results of three dimensions: temperature field uniformity, gas concentration distribution, and growth rate consistency. This can actively compensate for the effects of furnace inhomogeneity and workpiece geometry, so that the coating thickness and density on each surface of complex workpieces are uniform and consistent.

[0020] 3. This invention integrates a multi-zone independent precision temperature control module, an adjustable intelligent gas distribution module, and a multi-sensor fusion monitoring module through a central control unit. This enables synchronous regulation of temperature, reactant gas concentration, and gas flow rate, achieving fully automated control of the entire process from pretreatment, four-stage deposition, real-time monitoring, feedback control to cooling and unloading. Furthermore, the phased process design precisely matches energy input with process requirements, avoiding unnecessary energy waste and significantly reducing production costs. Simultaneously, the human-machine interaction and data management modules reduce reliance on operator experience, facilitating process replication and promotion. It can be widely applied in semiconductor, photovoltaic, aerospace, and other fields, possessing significant industrialization value. Attached Figure Description

[0021] The present invention will be further described below with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the method flow of the present invention; Figure 2 This is a schematic diagram of the system structure of the present invention. Detailed Implementation

[0022] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate relative orientations or positional relationships and are used only for the convenience of describing the 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, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0023] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0024] like Figures 1 to 2 As shown, the present invention provides a control method for a high-temperature coating furnace for pyrolytic graphite, comprising the following steps: Step S1: After placing the substrate to be deposited into the furnace chamber of the pyrolytic graphite high-temperature coating furnace, pretreatment is performed. The pretreatment includes: evacuating the furnace chamber and measuring the pressure rise rate until it reaches the preset pressure rise rate value (e.g., pressure rise rate < 5 Pa / h). Then, the furnace chamber is heated to the pretreatment temperature and maintained for a first preset holding time under an inert protective gas atmosphere to ensure that the pressure inside the furnace chamber is in a slightly negative pressure state. The pressure range of the slightly negative pressure is -0.02 to -0.01 MPa.

[0025] Specifically, preprocessing includes: After the substrate to be deposited is cleaned and dried, it is placed in the homogenization zone inside the furnace of the pyrolytic graphite high-temperature coating furnace. Subsequently, the pyrolytic graphite high-temperature coating furnace was shut down, and the vacuum system was started to evacuate the furnace chamber, so that the vacuum degree inside the furnace chamber was less than or equal to 5.0×10⁻²Pa. During the vacuuming process, the pressure rise rate is measured. When the real-time measured pressure rise rate is less than 5 Pa / h, the temperature of multiple areas in the furnace is independently controlled to rise to the pretreatment temperature (e.g., 500-800℃), and the heating rate is controlled at 5-15℃ / min. At the same time, inert protective gas is introduced to purge the furnace for 20-60 minutes to ensure that the oxygen content in the furnace is less than 50 ppm.

[0026] Step S2: The pretreated substrate is subjected to multi-stage variable temperature and flow rate deposition control to complete the deposition operation. This multi-stage variable temperature and flow rate deposition control includes four sub-stages performed sequentially: preheating and degassing, interface nucleation, stable growth, and final densification. During the preheating and degassing, interface nucleation, and stable growth stages, the temperature inside the furnace is gradually increased. After transitioning from the stable growth stage to the final densification stage, the temperature inside the furnace is reduced to a preset value and maintained at this constant temperature for a period of time. During the deposition process, the state inside the furnace is monitored and evaluated in real time, and based on the results of the real-time monitoring and evaluation, closed-loop feedback control is used to execute each unit performing the deposition operation.

[0027] Specifically, multi-stage variable temperature and variable flow rate deposition control includes the following processes: Step S201: After pretreatment of the substrate, the preheating and degassing stage is entered. In the preheating and degassing stage, an inert protective gas (such as argon) is introduced, and the temperature inside the furnace is heated to a preset first temperature (1200-1400℃) at a first heating rate (in this embodiment, the first heating rate is 10-20℃ / min). After holding at this temperature for a first preset time (10-30min), the interface nucleation stage is entered. In this stage, the pressure inside the furnace is maintained within 10-100Pa to fully remove the adsorbed water and gas remaining in the substrate and furnace.

[0028] Step S202: In the interface nucleation stage, the inert protective gas is stopped, and a mixed gas containing hydrocarbon reactive gases (such as methane) and a carrier gas (such as argon) is introduced. Simultaneously, the temperature inside the furnace is heated from the first temperature to a preset second temperature (1600-1800℃) at a second heating rate (5-15℃ / min). After holding at this temperature for a second preset time (10-40min), the furnace enters the stable growth stage. The purpose of holding the temperature is to form a uniform and dense nucleus layer on the substrate surface. In this stage, the total gas flow rate is F2, the volume fraction of the reactive gas is controlled at 5%-15%, and the pressure inside the furnace is controlled at 100-500Pa.

[0029] Step S203: In the stable growth stage, increase the concentration of reactant gases and the total gas flow rate in the mixed gas, while simultaneously heating the furnace temperature from the second temperature to a preset third temperature T3 (1900-2200℃). Maintain this temperature for a preset time (1-5 hours to achieve rapid and stable coating growth) before entering the final densification stage. Specifically, in this stage, the total gas flow rate is increased to F3 (F3 > F2), the volume fraction of the reactant gases is controlled to increase to 15%-30%, and the pressure inside the furnace is controlled to increase to 1-5 kPa.

[0030] Step S204: In the final densification stage, the concentration of the reactant gas in the mixed gas is reduced, and the temperature inside the furnace is lowered to a preset fourth temperature T4 (T4 = T3 - 50~100℃) and held at that temperature for a preset fourth time (20-60 min), while maintaining the pressure inside the furnace at 0.5-2 kPa. Specifically, the volume fraction of the reactant gas is reduced to 5%-10%. This stage, by reducing deposition activity, promotes the full migration and arrangement of carbon atoms on the surface of the formed coating, fills microscopic defects, and improves the final density and gloss of the coating.

[0031] In step S2, the real-time monitoring and evaluation of the state inside the furnace includes the following processes: Step S211: Real-time acquisition of data to be evaluated: Real-time temperature field data of the three-dimensional space inside the furnace is collected by temperature sensors; the temperature sensors are distributed thermocouples or infrared thermal imagers. The concentration distribution of reaction precursors and byproducts at different locations within the furnace is monitored in real time using a gas composition analyzer; the gas composition analyzer is either a gas mass spectrometer or a laser spectrometer. The optical monitoring device acquires in real time the particle size data of the deposited particles, the optical signal reflecting the coating growth rate, and the optical signal reflecting the coating thickness. The optical signal reflecting the coating growth rate is an indirect signal obtained by monitoring the plasma state through a laser interferometer or optical emission spectrum. When the interference fringes move, the coating thickness growth can be inferred, thereby indirectly assessing the completion of the deposition stage. The optical signal reflecting the coating thickness is a reflected interference signal.

[0032] Step S212: Based on the data to be evaluated collected by real-time monitoring, dynamically evaluate the uniformity index, homogeneous nucleation risk index, and completion rate of the current substrate coating.

[0033] Specifically, the uniformity index is evaluated using a fusion analysis based on multi-source data: Temperature field uniformity: Based on real-time collected three-dimensional spatial temperature field data inside the furnace, the deviation between the temperature of each monitoring point inside the furnace and the preset temperature of the current deposition control stage is obtained. The smaller the temperature deviation, the higher the uniformity contribution value. Gas concentration distribution: Based on the real-time collection of the concentrations of reaction precursors and by-products at different locations in the furnace, the deviation of the concentrations of reaction precursors and by-products at each monitoring point in the furnace from the preset concentrations at the current deposition control stage is obtained. The uniformity of gas concentration distribution is evaluated based on the dispersion of the concentration deviation. The uniformity index is negatively correlated with the dispersion of the concentrations of reaction precursors and by-products at each location in the furnace from the preset concentrations. Growth rate consistency: Based on the optical signals reflecting the coating growth rate at each monitoring point in the furnace collected in real time, the current growth rate of the pyrolytic graphite coating on the substrate is inferred, the deviation between the current coating growth rate on the substrate and the preset growth rate is obtained, and a growth rate consistency coefficient is generated. The evaluation results of three dimensions—temperature field uniformity, gas concentration distribution, and growth rate consistency—are weighted and integrated to obtain a uniformity index in the range of 0-1. The closer the index is to 1, the more uniform the pyrolytic graphite coating on the current substrate is.

[0034] Specifically, a homogeneous nucleation risk index is generated by comparing real-time collected sediment particle size data with a preset particle diameter threshold.

[0035] Specifically, the completion of the deposition stage is assessed based on the cumulative changes of multiple parameters: Time progress benchmark: Based on the preset insulation time of the current stage, obtain the ratio of the completed time to the preset insulation time of the current stage as the basic completion rate; Thickness feedback correction: The thickness of the pyrolytic graphite coating on the substrate is obtained in real time through optical signals that reflect the coating thickness. When the thickness value of the pyrolytic graphite coating on the substrate reaches the preset thickness threshold, the completion is corrected to 100%. Byproduct concentration: The concentration trend of reaction byproducts is collected and monitored in real time. When the concentration of reaction byproducts tends to stabilize, it indicates that the reaction is nearing completion. Temperature-pressure stability: When the temperature and pressure inside the furnace remain stable for a relatively long period of time and the fluctuation range is within the corresponding preset fluctuation range, it indicates that the deposition process has entered the final stage of steady state. The evaluation results of four dimensions—time progress, thickness feedback, by-product concentration, and temperature-pressure stability—are comprehensively judged according to preset evaluation criteria, and a completion index of 0-100% is output.

[0036] Specifically, in step S2, the closed-loop feedback control includes: Temperature control: The real-time monitored temperature data is compared with the preset temperature value of the current deposition control stage. The output power of the heating device of the pyrolytic graphite high-temperature coating furnace is dynamically adjusted through the PID algorithm so that the actual temperature fluctuation range of the substrate surface is controlled within the predetermined temperature fluctuation threshold (±3℃ of the set value). Gas control: The flow rate and pressure inside the furnace are monitored in real time by the flow meter and pressure sensor configured in the pyrolytic graphite high-temperature coating furnace. The gas concentration and pressure at each deposition control stage are kept stable at the corresponding preset values ​​by adjusting the opening of the inlet valve and the exhaust valve. Uniformity control: When the coating growth rate in a certain area is detected to deviate from the preset growth rate, the output power of the heating device in the corresponding zone is dynamically adjusted to fine-tune the temperature in that area and coordinate the flow rate and direction of multiple reaction gas delivery devices to optimize the local reaction gas supply. Controlling the conflict between deposition efficiency and quality: When the real-time monitored homogeneous nucleation risk index exceeds the safety threshold, the concentration of reactant gas is reduced and the temperature is fine-tuned first; after the risk is reduced, the temperature is gradually restored to the preset value. Process repeatability compensation: Based on the historical operating data of the heating device, a performance degradation model reflecting the relationship between heating power and temperature response is established. According to the performance degradation model, the preset temperature value of each deposition control stage is dynamically compensated.

[0037] Step S3: After the deposition process is completed, cool the substrate and remove the substrate coated with pyrolytic graphite.

[0038] Specifically, in step S3, after the deposition operation is completed, the flow of reaction gas is stopped, an inert protective gas is introduced, and the cooling system is started to control the cooling rate. After the temperature inside the furnace drops below the sixth temperature value (below 80°C), the furnace is opened and the substrate coated with pyrolytic graphite is removed. The cooling rate is controlled at 5-15°C / min.

[0039] The heating device, the vacuum pumping device for controlling the vacuum level and pressure inside the furnace, the device for conveying inert protective gas, the device for conveying carrier gas, and the device for conveying reaction gas are collectively referred to as the execution unit.

[0040] The following example, using the deposition of a 200 μm thick pyrolytic graphite coating on a planar graphite substrate, further illustrates the method of the present invention, specifically including the following steps: Step S1: After ultrasonically cleaning and drying the graphite substrate with anhydrous ethanol, place it into the furnace chamber of a pyrolytic graphite high-temperature coating furnace for pretreatment. Inert protective gas is then introduced to purge the furnace chamber for 20-60 minutes, maintaining the vacuum level within the furnace chamber at 5.0 × 10⁻⁶. -2 Pa ensures that the oxygen content in the furnace is below 50 ppm.

[0041] Step S2: After pretreatment of the matrix, the preheating and degassing stage is entered. In the preheating and degassing stage, the temperature is increased to 1300℃ at a heating rate of 15℃ / min. Argon gas is introduced and the pressure inside the furnace is maintained at 50Pa. After holding for 20min, the interface nucleation stage is entered. During the interface nucleation stage, the inert protective gas was stopped, and a methane / argon mixture (methane volume fraction 10%) was introduced at a total flow rate of 500 sccm. The pressure inside the furnace was controlled at 300 Pa, and the temperature inside the furnace was increased to 1750℃ at a heating rate of 10℃ / min. After holding at this temperature for 30 min, the furnace entered the stable growth stage. During the stable growth stage, the temperature inside the furnace is raised to 2100℃, the volume fraction of methane is increased to 25%, the total flow rate is increased to 1500 sccm, the pressure is controlled at 3 kPa, and after 3 hours of heat preservation and deposition, the final densification stage is entered. In the final densification stage, the methane volume fraction was reduced to 8%, the furnace temperature was reduced to 2050℃, the pressure was controlled at 1.5kPa, and the temperature was held for 40min.

[0042] Throughout the deposition control phase, an infrared thermometer was used to monitor the substrate surface temperature in real time, and PID control was employed to ensure that temperature fluctuations remained stable within ±3℃ of the set value. Simultaneously, a closed-loop control system using flow meters and pressure sensors within the pyrolytic graphite high-temperature coating furnace was used to manage gas and ambient pressure.

[0043] Step S3: After the deposition operation is completed, stop the introduction of methane into the furnace and introduce a large flow of argon gas. Cool the furnace to 60°C at a rate of 10°C / min before removing the sample.

[0044] Results: The obtained pyrolytic graphite coating was found to be 205±8μm thick, with a smooth and dense surface, free of visible cracks and carbon black particles. The pyrolytic graphite coating showed strong adhesion to the substrate, with a density of 2.18g / cm³, which is far superior to coatings prepared by traditional single processes (density approximately 2.10g / cm³, thickness deviation ±25μm).

[0045] This invention provides a control system for a high-temperature coating furnace for pyrolytic graphite to implement the control method described above, comprising: The central control unit incorporates a multi-physics coupling model and intelligent control algorithms. A multi-zone independent precision temperature control module, which communicates with the central control unit, is used for independent heating and temperature regulation of different areas inside the furnace; An adjustable intelligent gas distribution module, which communicates with the central control unit, is used to control the flow rate and concentration of the reaction gas and carrier gas introduced into the furnace. The multi-sensor fusion monitoring module communicates with the central control unit and is used to collect status parameters inside the furnace in real time. The human-computer interaction and data management module communicates with the central control unit and is used to display and store the status parameters and deposition control process inside the furnace. The central control unit is configured as follows: The system controls a multi-zone independent precision temperature control module and an adjustable intelligent gas distribution module to perform multi-stage variable temperature and flow rate deposition control on the pretreated substrate. The deposition control includes four sub-stages: preheating and degassing, interface nucleation, stable growth, and final densification. During the preheating and degassing stage, the interface nucleation stage, and the stable growth stage, the temperature inside the furnace is gradually increased. After transitioning from the stable growth stage to the final densification stage, the temperature inside the furnace is reduced to a preset value and kept constant. During the deposition process, the state parameters collected in real time by the multi-sensor fusion monitoring module are dynamically evaluated to assess the state inside the furnace. Based on the evaluation results, closed-loop feedback control is performed on the multi-zone independent precision temperature control module and the adjustable intelligent gas distribution module. After deposition, the cooling system is controlled to cool the substrate.

[0046] Regarding the specific structure of this invention, it should be noted that the connection relationships between the various component modules used in this invention are definite and achievable. Except as specifically described in the embodiments, their specific connection relationships can bring about corresponding technical effects and solve the technical problems proposed by this invention without relying on the execution of corresponding software programs. The models of the components, modules, and specific components appearing in this invention, the connection methods between them, and the conventional usage methods and expected technical effects brought about by the above technical features, unless specifically described, are all publicly disclosed content in patents, journal articles, technical manuals, technical dictionaries, and textbooks that can be obtained by those skilled in the art before the application date, or belong to conventional technology, common knowledge, and other existing technologies in this field. There is no need to elaborate, which makes the technical solution provided in this case clear, complete, and achievable, and can reproduce or obtain corresponding physical products based on this technical means.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A control method for a high-temperature coating furnace for pyrolytic graphite, characterized in that, Includes the following steps: Step S1: The substrate to be deposited is placed in the furnace chamber of a pyrolytic graphite high-temperature coating furnace for pretreatment. Step S2: Perform multi-stage variable temperature and flow rate deposition control on the pretreated substrate to complete the deposition operation. The multi-stage variable temperature and flow rate deposition control includes four sub-stages: preheating and degassing, interface nucleation, stable growth, and final densification. During the preheating and degassing stage, interface nucleation stage, and stable growth stage, the temperature inside the furnace is gradually increased. After transitioning from the stable growth stage to the final densification stage, the temperature inside the furnace is reduced to a preset value and maintained at the preset temperature for a period of time. During the deposition of the substrate, the state inside the furnace is monitored and evaluated in real time, and based on the results of the real-time monitoring and evaluation, closed-loop feedback control is used to control each execution unit that performs the deposition operation. Step S3: After the deposition process is completed, cool the substrate and remove the substrate coated with pyrolytic graphite.

2. The control method for the high-temperature coating furnace of pyrolytic graphite according to claim 1, characterized in that, The pretreatment includes at least: heating the substrate to a pretreatment temperature in a vacuum environment and maintaining it at a first preset temperature for a time in an inert protective gas atmosphere; After pretreatment, the pressure inside the furnace is in a slightly negative pressure state, with a pressure range of -0.02 to -0.01 MPa.

3. The control method for the high-temperature coating furnace of pyrolytic graphite according to claim 1, characterized in that, In step S2, the multi-stage variable temperature and variable flow deposition control includes the following process: Step S201: After pretreatment of the substrate, the preheating and degassing stage is entered. In the preheating and degassing stage, an inert protective gas is introduced, and the temperature inside the furnace is heated to a preset first temperature. After holding the temperature for a first preset time, the interface nucleation stage is entered. Step S202: In the interface nucleation stage, switch to the introduction of a mixed gas containing reactant gas and carrier gas, and at the same time heat the temperature in the furnace from the first temperature to the preset second temperature, hold it at the temperature for a second preset time, and then enter the stable growth stage. Step S203: In the stable growth stage, increase the concentration of the reactant gas and the total gas flow rate in the mixed gas, and at the same time heat the temperature in the furnace from the second temperature to the preset third temperature, hold it at the temperature for a third preset time, and then enter the final densification stage. Step S204: In the final densification stage, reduce the concentration of the reactant gas in the mixed gas, and lower the temperature inside the furnace to a preset fourth temperature and hold it at that temperature for a fourth preset time.

4. The control method for the high-temperature coating furnace of pyrolytic graphite according to claim 1, characterized in that, In step S2, real-time monitoring and evaluation of the state inside the furnace includes the following processes: Step S211: Real-time acquisition of data to be evaluated: Real-time temperature field data inside the furnace is collected using temperature sensors. The concentration distribution of reaction precursors and byproducts at different locations within the furnace is monitored in real time using a gas composition analyzer. The optical monitoring device acquires real-time data on the particle size of the deposited particles, optical signals reflecting the coating growth rate, and optical signals reflecting the coating thickness. Step S212: Based on the data to be evaluated collected by real-time monitoring, dynamically evaluate the uniformity index, homogeneous nucleation risk index, and completion rate of the current substrate coating.

5. The control method for the high-temperature coating furnace of pyrolytic graphite according to claim 4, characterized in that, In step S212, the uniformity index is evaluated using a fusion analysis based on multi-source data. Temperature field uniformity: Based on real-time collected three-dimensional spatial temperature field data inside the furnace, the deviation between the temperature of each monitoring point inside the furnace and the preset temperature of the current deposition control stage is obtained. The smaller the temperature deviation, the higher the uniformity contribution value. Gas concentration distribution: Based on the real-time collection of the concentrations of reaction precursors and by-products at different locations in the furnace, the deviation of the concentrations of reaction precursors and by-products at each monitoring point in the furnace from the preset concentrations at the current deposition control stage is obtained. The uniformity of gas concentration distribution is evaluated based on the dispersion of the concentration deviation. The uniformity index is negatively correlated with the dispersion of the concentrations of reaction precursors and by-products at each location in the furnace from the preset concentrations. Growth rate consistency: Based on the optical signals reflecting the coating growth rate at each monitoring point in the furnace collected in real time, the current growth rate of the pyrolytic graphite coating on the substrate is inferred, the deviation between the current coating growth rate on the substrate and the preset growth rate is obtained, and a growth rate consistency coefficient is generated. The evaluation results of three dimensions—temperature field uniformity, gas concentration distribution, and growth rate consistency—are weighted and integrated to obtain a uniformity index in the range of 0-1. The closer the index is to 1, the more uniform the pyrolytic graphite coating on the current substrate is.

6. The control method for the high-temperature coating furnace of pyrolytic graphite according to claim 4, characterized in that, In step S212, a homogeneous nucleation risk index is generated by comparing the real-time collected sediment particle size data with a preset particle diameter threshold.

7. The control method for the high-temperature coating furnace of pyrolytic graphite according to claim 4, characterized in that, In step S212, the completion of the deposition stage is evaluated based on the cumulative changes of multiple parameters: Time progress benchmark: Based on the preset insulation time of the current stage, obtain the ratio of the completed time to the preset insulation time of the current stage as the basic completion rate; Thickness feedback correction: The thickness of the pyrolytic graphite coating on the substrate is obtained in real time through optical signals that reflect the coating thickness. When the thickness value of the pyrolytic graphite coating on the substrate reaches the preset thickness threshold, the completion is corrected to 100%. Byproduct concentration: The concentration trend of reaction byproducts is collected and monitored in real time. When the concentration of reaction byproducts tends to stabilize, it indicates that the reaction is nearing completion. Temperature-pressure stability: When the temperature and pressure inside the furnace remain stable for a relatively long period of time and the fluctuation range is within the corresponding preset fluctuation range, it indicates that the deposition process has entered the final stage of steady state. The evaluation results of four dimensions—time progress, thickness feedback, by-product concentration, and temperature-pressure stability—are comprehensively judged according to preset evaluation criteria, and a completion index of 0-100% is output.

8. The control method for the high-temperature coating furnace of pyrolytic graphite according to claim 1, characterized in that, In step S2, the closed-loop feedback control includes: Temperature control: The real-time monitored temperature data is compared with the preset temperature value of the current deposition control stage. The output power of the heating device of the pyrolytic graphite high-temperature coating furnace is dynamically adjusted through the PID algorithm so that the actual temperature fluctuation range of the substrate surface is controlled within the predetermined temperature fluctuation threshold. Gas control: The flow rate and pressure inside the furnace are monitored in real time by the flow meter and pressure sensor configured in the pyrolytic graphite high-temperature coating furnace. The gas concentration and pressure at each deposition control stage are kept stable at the corresponding preset values ​​by adjusting the opening of the inlet valve and the exhaust valve. Uniformity control: When the coating growth rate in a certain area is detected to deviate from the preset growth rate, the output power of the heating device in the corresponding zone is dynamically adjusted to fine-tune the temperature in that area and coordinate the flow rate and direction of multiple devices for conveying reaction gases to optimize the local reaction gas supply. Controlling the conflict between deposition efficiency and quality: When the real-time monitored homogeneous nucleation risk index exceeds the safety threshold, the concentration of reactant gas is reduced and the temperature is fine-tuned first; after the risk is reduced, the temperature is gradually restored to the preset value. Process repeatability compensation: Based on the historical operating data of the heating device, a performance degradation model reflecting the relationship between heating power and temperature response is established. According to the performance degradation model, the preset temperature value of each deposition control stage is dynamically compensated.

9. The control method for the high-temperature coating furnace of pyrolytic graphite according to claim 1, characterized in that, In step S3, after the deposition operation is completed, the reaction gas is stopped, an inert protective gas is introduced, and the cooling system is started to control the cooling rate. After the temperature inside the furnace drops below the sixth temperature value, the furnace is opened and the substrate coated with pyrolytic graphite is taken out.

10. A control system for a high-temperature coating furnace for pyrolytic graphite used to implement the control method according to any one of claims 1-9, characterized in that, include: The central control unit incorporates a multi-physics coupling model and intelligent control algorithms. A multi-zone independent precision temperature control module, which communicates with the central control unit, is used for independent heating and temperature regulation of different areas inside the furnace; An adjustable intelligent gas distribution module, which communicates with the central control unit, is used to control the flow rate and concentration of the reaction gas and carrier gas introduced into the furnace. The multi-sensor fusion monitoring module communicates with the central control unit and is used to collect status parameters inside the furnace in real time. The human-computer interaction and data management module communicates with the central control unit and is used to display and store the status parameters and deposition control process inside the furnace. The central control unit is configured as follows: The system controls a multi-zone independent precision temperature control module and an adjustable intelligent gas distribution module to perform multi-stage variable temperature and flow rate deposition control on the pretreated substrate. The deposition control includes four sub-stages: preheating and degassing, interface nucleation, stable growth, and final densification. During the preheating and degassing stage, the interface nucleation stage, and the stable growth stage, the temperature inside the furnace is gradually increased. After transitioning from the stable growth stage to the final densification stage, the temperature inside the furnace is controlled to decrease to a preset value and remain constant. During the deposition process, the state parameters collected in real time by the multi-sensor fusion monitoring module are dynamically evaluated to assess the state inside the furnace. Based on the evaluation results, closed-loop feedback control is performed on the multi-zone independent precision temperature control module and the adjustable intelligent gas distribution module. After deposition, the cooling system is controlled to cool the substrate.

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