Synthetic diamond synthesis intelligent control system and method

Abstract

The present application relates to the technical field of synthetic diamond, and particularly relates to a synthetic diamond synthesis intelligent control system and method; the system comprises a phase change analysis module, a pressure compensation control module, a temperature adjustment module and a quality evaluation module. According to the conversion rate, the volume change amount of the synthesis cavity and the volume change amount of the pressure transmission medium, the present application determines the feedforward displacement component, according to the deviation between the measured pressure of the synthesis cavity and the target pressure of the synthesis cavity and the pressure loss amount of the pipeline, the feedback displacement component is determined, and the feedforward displacement component is calculated before the actual pressure deviation occurs, thereby converting the passive compensation mode of the traditional feedback control, i.e. first reducing and then compensating, into the feedforward control mode of active prediction and synchronous compensation, and reducing the pressure fluctuation.

Description

Technical Field

[0001] This invention relates to the field of synthetic diamond technology, specifically to an intelligent control system and method for synthetic diamond synthesis. Background Technology

[0002] In the synthesis of synthetic diamond, graphite is converted into diamond using a catalyst under high temperature and pressure conditions through a six-sided press. During the heat and pressure holding stage, graphite continuously transforms into diamond within the synthesis chamber. This phase transformation process is usually accompanied by volume shrinkage, causing the internal pressure of the synthesis chamber to continuously decrease and fluctuate, directly affecting the growth quality of the crystal.

[0003] To address the aforementioned issues, existing pressure control technologies typically rely on PID feedback regulation based on the deviation between the measured pressure and the target pressure within the synthesis chamber. However, feedback regulation of the synthesis chamber pressure alters the chamber volume, indirectly interfering with the temperature field, and the release of latent heat of phase change also disrupts the temperature gradient. In response, Chinese invention patent CN116555908A discloses a device for adjusting the temperature gradient in the synthesis of lab-grown diamonds using a double-layer heating tube. This device adjusts the internal temperature gradient of the synthesis chamber through a double-layer heating structure consisting of a main graphite heating tube and an auxiliary graphite heating tube.

[0004] However, the existing technologies still have the following problems: 1. The passive compensation mode that relies on pressure deviation has a principle response lag. The process of compensation after the pressure drops makes pressure fluctuations unavoidable, which will still affect the synthesis quality of diamond; 2. Controlling pressure and temperature as independent loops cannot coordinate the response to the pressure's disturbance to the temperature gradient. In addition, the heating power of the synthesis chamber is usually adjusted as a whole, which lacks targeted control of the temperature gradient differences at different axial positions. Summary of the Invention

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is: an intelligent control system for synthetic diamond synthesis, comprising: a phase transition analysis module, used to emit and receive ultrasonic waves into the synthesis cavity, and to obtain the diamond conversion rate and conversion efficiency based on the change of ultrasonic wave velocity.

[0006] The pressure compensation control module is used to determine the feedforward displacement component based on the conversion rate, the change in the volume of the synthesis chamber, and the change in the volume of the pressure transmission medium; to determine the feedback displacement component based on the deviation between the measured pressure and the target pressure of the synthesis chamber and the pressure loss in the pipeline; and to obtain the pressure compensation displacement by combining the feedforward displacement component and the feedback displacement component.

[0007] The temperature adjustment module is used to calculate the real-time temperature gradient based on the temperature at different axial positions and the amount of pressure displacement in the synthesis chamber; based on the real-time temperature gradient and the target temperature gradient, and combined with the latent heat load distribution determined according to the conversion rate and the graphite packing mass, the heating power is adjusted.

[0008] The quality assessment module is used to extract crystal plane geometric parameters based on the three-dimensional contour data of the diamond crystal, thereby determining the geometric deviation between the diamond crystal and the theoretical crystal form, and generating assessment results; and adjusting the target pressure and target temperature gradient of the synthesis cavity based on the assessment results.

[0009] Compared with the prior art, the present invention has the following beneficial effects:

[0010] 1. This invention determines the feedforward displacement component based on the conversion rate, the change in the volume of the synthesis chamber, and the change in the volume of the pressure transmission medium. It also determines the feedback displacement component based on the deviation between the measured pressure and the target pressure in the synthesis chamber, as well as the pressure loss in the pipeline. The feedforward displacement component is calculated before the actual pressure deviation occurs, thereby transforming the passive compensation mode of the traditional feedback control, which involves reducing pressure first and then compensating, into a feedforward control mode that actively predicts and synchronously compensates. This reduces pressure fluctuations and is beneficial to improving the quality of diamond synthesis.

[0011] 2. This invention converts the pressure compensation displacement into a correction amount for the initial temperature gradient, enabling the temperature adjustment module to actively compensate when the pressure compensation action occurs, thus eliminating the interference of pressure compensation on the temperature gradient. By converting the conversion rate and graphite packing mass into latent heat load distribution, the latent heat load distribution further compensates for the temperature gradient, thus offsetting the disturbance of the temperature gradient caused by the release of latent heat of phase change in advance. This achieves coordinated control of pressure and temperature, solving the problem of mutual interference between pressure and temperature.

[0012] 3. Based on the conversion rate and the graphite packing mass of each axial section, this invention calculates the latent heat load of each axial section, and determines the spatial weight of each axial section by combining the maximum gradient zone and the axial temperature gradient value, thereby realizing differentiated control of the heating power of each axial section. This overcomes the shortcomings of existing heating power adjustment, which usually involves the synthesis chamber as a whole and lacks targeted control. Attached Figure Description

[0013] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 This is a schematic diagram of the system module connections of the present invention;

[0015] Figure 2 This is a schematic diagram of the intelligent control method of the present invention;

[0016] Figure 3 This is a schematic diagram illustrating the process of determining the feedforward displacement component in this invention.

[0017] Figure 4 This is a schematic diagram of the process for adjusting the heating power according to the present invention. Detailed Implementation

[0018] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. Furthermore, it should be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale.

[0019] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use. Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and apparatus should be considered part of the specification.

[0020] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0022] The following description, in conjunction with the accompanying drawings, details the specific scheme of the intelligent control system and method for synthesizing artificial diamond provided by this invention.

[0023] Please see Figure 1 The diagram shows a module connection diagram of an intelligent control system for synthetic diamond provided by the present invention, which specifically includes: a phase transition analysis module, a pressure compensation control module, a temperature adjustment module, and a quality evaluation module.

[0024] The phase transition analysis module outputs to the pressure compensation control module and the temperature adjustment module. The pressure compensation control module outputs to the temperature adjustment module. The quality evaluation module outputs the evaluation result based on the diamond crystal after synthesis and inputs the evaluation result into the pressure compensation control module and the temperature adjustment module.

[0025] Please see Figure 3The phase transition analysis module is used to emit and receive ultrasonic waves into the synthesis cavity during the heating and pressurization process, and to obtain the diamond conversion rate and conversion efficiency based on the changes in ultrasonic wave velocity.

[0026] In this embodiment, an ultrasonic transducer coupled to the surface of the top hammer of a six-sided press (hereinafter referred to as the press) emits ultrasonic pulses into the synthesis cavity and receives the ultrasonic time-domain signal after penetrating the synthesis cavity. The transit time and amplitude of the ultrasonic time-domain signal are extracted to obtain the ultrasonic longitudinal wave velocity and ultrasonic attenuation coefficient. The ultrasonic time-domain signal is subjected to Fourier transform to obtain the power spectrum, and the centroid frequency of the spectrum is extracted from the power spectrum. The above processing methods are all existing technologies. The ultrasonic longitudinal wave velocity, ultrasonic attenuation coefficient, and centroid frequency of the spectrum are used together as ultrasonic data. The oil pressure signal is collected by a resistance strain gauge ultra-high pressure sensor installed in the hydraulic pipeline of the press and converted into the measured pressure of the synthesis cavity. The temperature at different positions along the axis of the synthesis cavity is collected by multiple thermocouples arranged along the axis of the synthesis cavity. The arithmetic mean of the temperatures collected by each thermocouple is used as the temperature of the synthesis cavity. In this embodiment, the number of thermocouples is an odd number greater than three.

[0027] The sampling period for the aforementioned ultrasonic transducer, resistance strain gauge ultra-high pressure sensor, and thermocouple is 100ms, with the end time of each sampling period being the sampling time. Furthermore, the ultrasonic data, measured pressure in the synthesis chamber, and synthesis chamber temperature are time-aligned; the specific processing procedure is existing technology and will not be elaborated here.

[0028] The absolute value of the difference between the ultrasonic longitudinal wave velocities at two adjacent sampling times is taken as the change in ultrasonic longitudinal wave velocity. Similarly, the changes in ultrasonic attenuation coefficient, spectral centroid frequency, measured pressure in the synthesis cavity, and temperature in the synthesis cavity are obtained.

[0029] Based on the convergence law of standard deviation in statistics, after the ultrasonic transducer starts collecting data, the time span from the first sampling time to the thirtieth sampling time is used as the initial statistical window.

[0030] The standard deviations of the changes in ultrasonic longitudinal wave velocity, ultrasonic attenuation coefficient, and spectral centroid frequency within the initial statistical window are calculated and used as the wave velocity fluctuation benchmark, ultrasonic attenuation fluctuation benchmark, and frequency fluctuation benchmark, respectively. Similarly, the measured pressure fluctuation benchmark and the temperature fluctuation benchmark of the synthesis cavity are obtained. Based on the Laida criterion: if the change in data exceeds three times its historical fluctuation standard deviation, it indicates that the change is not caused by random fluctuations, but by changes in the system state. Therefore, the above fluctuation benchmarks are multiplied by three to obtain the corresponding judgment threshold.

[0031] Starting from the initial statistical window, when the changes in ultrasonic longitudinal wave velocity, ultrasonic attenuation coefficient, spectral centroid frequency, measured pressure in the synthesis cavity, and temperature in the synthesis cavity at three consecutive sampling times are all less than their respective judgment thresholds, a thermally stable state is confirmed, and the first sampling time among the three consecutive sampling times is recorded as the thermal stability start time in the synthesis cavity; otherwise, a thermally stable state is determined not to have been reached, and the above five changes are calculated again at each sampling time, and three consecutive sampling times that meet the conditions are searched for until a thermally stable state is confirmed.

[0032] Since the graphite in the synthesis cavity has not yet begun to transform into diamond at the initial moment of thermal stabilization, the entire synthesis cavity is composed of the graphite phase. Therefore, the ultrasonic longitudinal wave velocity, ultrasonic attenuation coefficient, and spectral centroid frequency corresponding to the initial moment of thermal stabilization are used as the reference values ​​for graphite phase wave velocity, graphite phase attenuation coefficient, and graphite phase frequency, respectively, forming a set of graphite phase reference values.

[0033] Subsequently, the graphite phase wave velocity reference value, graphite phase attenuation coefficient reference value, and graphite phase frequency reference value are multiplied by the ultrasonic longitudinal wave velocity ratio, ultrasonic attenuation coefficient ratio, and spectral centroid frequency ratio, respectively, to obtain the diamond phase reference value set, which includes the diamond phase wave velocity reference value, diamond phase attenuation coefficient reference value, and diamond phase frequency reference value.

[0034] Among them, the ratio of ultrasonic longitudinal wave velocity, the ratio of ultrasonic attenuation coefficient, and the ratio of spectral centroid frequency were all obtained by ultrasonic transmission measurement of graphite and diamond samples under reference conditions of room temperature and normal pressure. The ultrasonic detection process is existing technology and will not be described in detail here.

[0035] Then, the difference between the synthesis cavity temperature at the current sampling time and the synthesis cavity temperature at the start of thermal stabilization is multiplied by the wave velocity temperature coefficient, attenuation temperature coefficient and frequency temperature coefficient of graphite, respectively, to obtain the wave velocity temperature correction, attenuation temperature correction and frequency temperature correction.

[0036] The difference between the measured pressure of the synthesis cavity at the current sampling moment and the measured pressure of the synthesis cavity at the start of thermal stabilization is multiplied by the wave velocity pressure coefficient, attenuation pressure coefficient and frequency pressure coefficient of graphite, respectively, to obtain the wave velocity pressure correction, attenuation pressure correction and frequency pressure correction.

[0037] Then, the graphite phase wave velocity reference value, wave velocity temperature correction, and wave velocity pressure correction are added together to obtain the graphite ultrasonic longitudinal wave velocity at the current sampling time; similarly, the graphite ultrasonic attenuation coefficient and graphite spectral centroid frequency at the current sampling time are obtained. The graphite ultrasonic longitudinal wave velocity, graphite ultrasonic attenuation coefficient, and graphite spectral centroid frequency at the current time are used as graphite ultrasonic parameters.

[0038] Similarly, based on the diamond's wave velocity temperature coefficient, wave velocity pressure coefficient, attenuation temperature coefficient, attenuation pressure coefficient, frequency temperature coefficient, and frequency pressure coefficient, the diamond ultrasonic parameters at the current sampling time can be obtained, namely the diamond ultrasonic longitudinal wave velocity, the diamond ultrasonic attenuation coefficient, and the diamond spectral centroid frequency.

[0039] It should be noted that the wave velocity temperature coefficient and wave velocity pressure coefficient of graphite and diamond are obtained through the following process: the density of graphite and the density of diamond are obtained directly from chemical and chemical engineering property data handbooks, and the elastic modulus at different temperatures and pressures is obtained directly from high-pressure physics academic literature. Substitute: Where ρ is the density of graphite or diamond (kg / m³). Then, the longitudinal wave velocity was calculated using linear fitting. The slope of the wave velocity changes with temperature and pressure; the slope is the corresponding wave velocity temperature coefficient and wave velocity pressure coefficient.

[0040] The attenuation temperature coefficient and attenuation pressure coefficient of graphite and diamond were determined by ultrasonic transmission experiments on graphite and diamond samples. The frequency temperature coefficient and frequency pressure coefficient of graphite and diamond were obtained by performing ultrasonic transmission experiments on graphite and diamond samples, and extracting the spectral centroid frequency and the rate of temperature and pressure change, respectively. All the above experiments and extraction processes used existing techniques and will not be described in detail here.

[0041] Based on the thermodynamic phase equilibrium theory, when the measured pressure in the synthesis chamber is higher than the phase equilibrium pressure calculated by the Bellman-Simon formula, and the temperature in the synthesis chamber is higher than the melting point of the catalyst used at the corresponding pressure, it is determined that the synthesis chamber has entered the stable graphite-diamond transformation region, and the graphite phase in the synthesis chamber is transformed into a mixed phase.

[0042] Calculate the difference between the ultrasonic longitudinal wave velocity at the current sampling time and the ultrasonic longitudinal wave velocity of graphite at the current sampling time, and use it as the numerator difference of the wave velocity; calculate the difference between the ultrasonic longitudinal wave velocity of diamond at the current sampling time and the ultrasonic longitudinal wave velocity of graphite at the current sampling time, and use it as the denominator difference of the wave velocity; divide the wave velocity numerator difference by the wave velocity denominator difference to obtain the single-parameter conversion rate based on the ultrasonic longitudinal wave velocity, i.e., the wave velocity conversion rate.

[0043] Similarly, we obtain the single-parameter conversion rate based on the ultrasonic attenuation coefficient and the single-parameter conversion rate based on the spectral centroid frequency, namely the attenuation conversion rate and the frequency conversion rate.

[0044] The conversion rates at the current moment are obtained by multiplying the wave velocity conversion rate, attenuation conversion rate, and frequency conversion rate by their respective conversion weights and then summing them. The conversion weights for wave velocity conversion rate, attenuation conversion rate, and frequency conversion rate are all non-negative, and their sum equals one. Since the relative rate of change of ultrasonic longitudinal wave velocity during the graphite-diamond phase transition is the largest, followed by the relative rate of change of the ultrasonic attenuation coefficient, and the relative rate of change of the spectral centroid frequency is the smallest, the conversion weight for wave velocity conversion rate is the largest, and the conversion weight for frequency conversion rate is the smallest. Specifically, the conversion weight for wave velocity conversion rate is set to 0.5, the conversion weight for attenuation conversion rate is set to 0.3, and the conversion weight for frequency conversion rate is set to 0.2.

[0045] Furthermore, the difference between the conversion rate at the current sampling time and the conversion rate at the previous sampling time is calculated, and the difference is divided by the sampling period to obtain the conversion rate.

[0046] The pressure compensation control module is used to determine the feedforward displacement component based on the conversion rate, the change in the volume of the synthesis chamber, and the change in the volume of the pressure transmission medium; to determine the feedback displacement component based on the deviation between the measured pressure in the synthesis chamber and the target pressure in the synthesis chamber, as well as the pressure loss in the pipeline; and to obtain the pressure compensation displacement by combining the feedforward displacement component and the feedback displacement component.

[0047] During the heating and pressurization process, graphite is transformed into diamond, and the total volume inside the synthesis cavity continues to shrink, causing the pressure to drop and fluctuate. In order to reduce pressure fluctuations, this invention improves the pressure compensation mechanism.

[0048] Please see Figure 3 Specifically, before loading graphite powder into the synthesis chamber, the total mass of the graphite powder is weighed using a precision balance and taken as the total mass of the reactants in the synthesis chamber. The reciprocal of the graphite density is subtracted from the reciprocal of the diamond density to obtain the volume shrinkage per unit mass of graphite. The volume shrinkage per unit mass of graphite is multiplied by the total mass of the reactants in the synthesis chamber and the conversion rate at the current moment to obtain the volume shrinkage of the synthesis chamber at the current moment.

[0049] Next, the volumetric thermal expansion coefficient of the synthesis cavity material is obtained from the materials physics handbook. The difference between the synthesis cavity temperature at the current sampling time and the synthesis cavity temperature at the start of thermal stability is multiplied by the total volume of the reactants in the synthesis cavity and the volumetric thermal expansion coefficient to obtain the thermal expansion and contraction of the synthesis cavity. The volume shrinkage of the synthesis cavity is added to the thermal expansion and contraction of the synthesis cavity to obtain the volume change of the synthesis cavity.

[0050] The pressure-transmitting medium refers to the solid assembly inside the synthesis chamber, encasing the graphite pillars, catalyst sheets, and conductive steel ring. Based on the dimensional parameters indicated in the design drawings, the geometric volume of the synthesis chamber, the volume of the graphite pillars within the chamber, the total volume of the catalyst sheets, and the total volume of the conductive steel ring are calculated. Subtracting the volumes of these components from the geometric volume of the synthesis chamber yields the initial volume of the pressure-transmitting medium.

[0051] Then, the difference between the measured pressure in the synthesis chamber at the current sampling time and the measured pressure in the synthesis chamber at the start of thermal stabilization is multiplied by the initial volume of the pressure-transmitting medium and the volume compressibility coefficient of the pressure-transmitting medium to obtain the volume change of the pressure-transmitting medium at the current time. The material of the pressure-transmitting medium is pyrophyllite, and the reciprocal of the bulk modulus of pyrophyllite is used as the volume compressibility coefficient. The bulk modulus of pyrophyllite is 37 GPa, which is obtained directly from academic literature in the field of mineralogy.

[0052] Next, obtain the cylinder inner diameter from the press main unit drawings, and then calculate the cross-sectional area of ​​the press cylinder: ;in, The cross-sectional area of ​​the press cylinder ( ), where π is the mathematical constant pi (taken as 3.14), and D is the cylinder bore diameter (m).

[0053] The total volume change is obtained by superimposing the volume change of the synthesis chamber with the volume change of the pressure transmission medium. The total volume change is then divided by the cross-sectional area of ​​the press cylinder to obtain the feedforward displacement component. The feedforward displacement component represents the pressure compensation displacement component that needs to be applied in advance to compensate for the volume change in the synthesis chamber caused by physical effects such as phase change volume shrinkage, thermal expansion and contraction, and compression of the pressure transmission medium.

[0054] Furthermore, to improve the accuracy of pressure compensation, this invention introduces a feedback displacement component. The specific calculation process is as follows: At the initial moment of thermal stabilization, the pressure compensation control module sends a displacement increment to the press cylinder. The difference between the measured pressure in the synthesis chamber after the displacement increment is applied and the measured pressure in the synthesis chamber before the displacement increment is applied is calculated as the pressure difference. The ratio of the pressure difference to the displacement increment is used as the pressure-displacement conversion coefficient. The displacement increment is taken as five times the minimum actual executable displacement of the press cylinder, thus ensuring that the displacement increment produces a clearly distinguishable pressure change. In this embodiment, the minimum displacement is specifically taken as three times the resolution of the displacement sensor shown on the press cylinder nameplate.

[0055] The pressure deviation compensation displacement is obtained by multiplying the difference between the measured pressure in the synthesis chamber and the target pressure in the synthesis chamber by the pressure displacement conversion coefficient. For the first synthesis, the target pressure in the synthesis chamber is directly obtained from the synthesis process specification. For subsequent synthesis, the target pressure in the synthesis chamber is automatically updated by the system based on the evaluation results of the previous synthesis.

[0056] Next, the volume shrinkage rate of the synthesis chamber is obtained by multiplying the volume shrinkage of graphite per unit mass, the total mass of reactants in the synthesis chamber, and the conversion rate. This volume shrinkage rate is then used as the instantaneous oil flow rate in the hydraulic pipeline during pressurization. Pipeline geometric parameters, including hydraulic pipeline length, inner diameter, and wall roughness, are obtained from the system design drawings. Hydraulic oil viscosity parameters (kinematic viscosity) and hydraulic oil density are obtained from the manufacturer's oil product manual.

[0057] Divide the product of the instantaneous oil flow rate and the inner diameter of the pipeline by the hydraulic oil viscosity parameter to obtain the Reynolds number Re (dimensionless) at the corresponding instantaneous oil flow rate. Determine the internal flow state of the hydraulic pipeline based on the Reynolds number and calculate the friction coefficient λ (dimensionless).

[0058] The judgment process is as follows: Based on engineering fluid mechanics, when the Reynolds number is greater than 2320, it indicates that the hydraulic pipeline is in a turbulent state. The calculation formula used is: When the Reynolds number is less than or equal to 2320, it indicates that the hydraulic pipeline is in a laminar flow state. The calculation formula used is: .

[0059] After determining the friction coefficient, calculate the pressure loss along the hydraulic line using the following formula:

[0060] ;

[0061] in, Where: pressure loss along the pipeline (Pa); L is the length of the hydraulic pipeline (m); d is the inner diameter of the hydraulic pipeline (m). Hydraulic oil density (kg / ); v is the instantaneous oil flow rate (m / s).

[0062] Meanwhile, the quantity of components, including elbows and valves, in the hydraulic pipeline is obtained from the hydraulic pipeline installation drawings, and the local resistance coefficient of each component is obtained from the product manuals provided by the component manufacturers.

[0063] When the local resistance coefficient cannot be obtained directly, the local resistance coefficient ξ of each component is calculated based on the flow coefficient Cv obtained from the product manual. The conversion formula is as follows: Multiply the local resistance coefficient of each component by half the product of the hydraulic oil density and the square of the instantaneous oil flow velocity to obtain the local pressure loss of each component; add up the local pressure losses of all components to obtain the total local pressure loss of the pipeline.

[0064] The pressure loss along the pipeline is added to the total local pressure loss of the pipeline to obtain the pipeline pressure loss. The pipeline pressure loss is divided by the cross-sectional area of ​​the compressor cylinder to obtain the pipeline loss compensation displacement. The pressure deviation compensation displacement is added to the pipeline loss compensation displacement to obtain the feedback displacement component.

[0065] Finally, the feedforward displacement component and the feedback displacement component are added together to obtain the pressure compensation displacement. If the absolute value of the pressure compensation displacement is less than the displacement execution threshold, the pressure compensation action is not performed, and the current measured pressure in the synthesis chamber remains unchanged; if the pressure compensation displacement is greater than the maximum allowable stroke of the top hammer, the maximum allowable stroke of the top hammer is used as the pressure compensation displacement, and the top hammer is driven to complete the pressure compensation action.

[0066] If the absolute value of the pressure compensation displacement is greater than or equal to the displacement execution threshold, and the absolute value of the pressure compensation displacement is less than or equal to the maximum allowable stroke of the top hammer, then the pressure compensation displacement is sent to the press cylinder to drive the top hammer to complete the pressure compensation action.

[0067] The maximum allowable stroke of the top hammer is obtained from the press's product manual; the displacement execution threshold is the minimum displacement that the press cylinder can actually perform, and the displacement execution threshold is less than the maximum allowable stroke of the top hammer.

[0068] The temperature adjustment module is used to calculate the real-time temperature gradient based on the temperature at different axial positions and the amount of pressure compensation displacement within the synthesis chamber; and to adjust the heating power based on the real-time temperature gradient and the target temperature gradient, combined with the latent heat load distribution determined according to the conversion rate and the graphite packing mass.

[0069] During diamond synthesis, the pressure and temperature inside the synthesis chamber influence each other. Therefore, while compensating for the pressure, it is also necessary to adjust the heating power to regulate the temperature.

[0070] Please see Figure 4 In specific implementation, firstly, the temperature collected by the thermocouples arranged axially in the synthesis cavity at the moment of thermal stabilization is obtained as the instantaneous temperature at different positions in the axial direction of the synthesis cavity; the central axis of the synthesis cavity is used as the coordinate axis, the intersection of the bottom surface of the synthesis cavity and the central axis is used as the origin of the coordinate axis, and the upward direction along the central axis is used as the positive direction of the coordinate axis.

[0071] The distance from the center of the sensing element of each thermocouple to the bottom surface of the synthesis cavity is directly read from the design drawings and used as the axial distance between the center of the sensing element of the thermocouple and the origin of the coordinate system. With the axial distance as the abscissa and the instantaneous temperature at the axial position of the synthesis cavity as the ordinate, a linear fit is performed on the five sets of coordinate points to obtain the distribution function of temperature variation with the axial position of the synthesis cavity under thermally stable conditions. Taking the first derivative of the distribution function, the slope obtained is the initial temperature gradient of the synthesis cavity, and the intercept obtained is the fitted temperature at the origin. α is the instantaneous temperature at the axial position of the synthesis cavity (°C); α is the initial temperature gradient (°C / m); z is the axial distance (m); b is the fitted temperature at the origin (°C).

[0072] Then, based on the response relationship between the synthesis chamber temperature and the displacement increment, the displacement-temperature coupling coefficient is determined: at the initial moment of thermal stabilization, the pressure compensation control module sends a displacement increment to the press cylinder. The difference between the temperature gradient after the displacement increment and the initial temperature gradient before the displacement increment is calculated as difference 1. The ratio of difference 1 to the displacement increment is used as the displacement-temperature coupling coefficient. The displacement-temperature coupling coefficient characterizes the disturbance of the axial temperature gradient of the synthesis chamber by the pressure compensation action. The displacement increment is determined using the aforementioned method, and the determination method for the temperature gradient after displacement is the same as that for the initial temperature gradient.

[0073] The product of the pressure compensation displacement and the displacement-temperature coupling coefficient is added to the initial temperature gradient to obtain the corrected temperature gradient, thereby dynamically linking the pressure compensation action with the temperature response and achieving coordinated control of pressure and temperature.

[0074] Simultaneously, based on the response relationship between the synthesis chamber temperature and heating power, the latent heat temperature coupling coefficient is determined: at the initial moment of thermal stabilization, the temperature adjustment module sends a heating power increment to the heating element. The difference between the post-heating temperature gradient after the heating power increment is applied and the initial temperature gradient before the heating power increment is applied is calculated as difference two. The ratio of difference two to the heating power increment is used as the latent heat temperature coupling coefficient. The latent heat temperature coupling coefficient characterizes the disturbance of the axial temperature gradient of the synthesis chamber caused by the change in heating power. The method for determining the post-heating temperature gradient is the same as that for determining the initial temperature gradient; the heating power increment is taken as 10 times the adjustment output resolution shown in the product specification of the heating power supply to ensure that a clearly distinguishable temperature gradient change is generated.

[0075] Subsequently, the product of the conversion rate, graphite packing density, and latent heat temperature coupling coefficient is superimposed with the corrected temperature gradient to obtain the real-time temperature gradient; the difference between the real-time temperature gradient and the target temperature gradient is taken as the gradient deviation. The graphite packing density is obtained by dividing the total mass of reactants in the synthesis chamber by the geometric volume of the synthesis chamber.

[0076] For the first synthesis, the target temperature gradient is determined before synthesis begins by: obtaining the type of catalyst used in this batch of synthesis and the axial length of the synthesis chamber from the synthesis process specification; obtaining the catalyst melting point and upper limit of the synthesis temperature under the target pressure in the synthesis chamber from published superhard materials technical literature based on the catalyst type; obtaining the rated heating power and minimum heating power from the heating element's product specifications; determining the maximum temperature difference inside the synthesis chamber (existing technology) through calibration experiments at the rated and minimum heating power; subtracting the maximum temperature difference from the difference between the upper limit of the synthesis temperature and the catalyst melting point, and dividing the result by the axial length of the synthesis chamber to obtain the target temperature gradient. For subsequent synthesis, the target temperature gradient is automatically updated based on the evaluation results of the previous synthesis.

[0077] Furthermore, to more precisely control the temperature of the synthesis chamber, the synthesis chamber is uniformly divided into several axial segments along the axial direction. Each axial segment corresponds to a thermocouple, and each thermocouple is located at the axial center of its respective segment. Moreover, each axial segment has the same volume and is obtained by equally dividing the geometric volume of the synthesis chamber.

[0078] Next, the graphite packing mass of each axial section was obtained by weighing layer by layer using a precision balance; the latent heat of phase transition per unit mass of graphite to diamond was directly obtained from the chemical and chemical engineering property data handbook. The latent heat load of each axial section was obtained by multiplying the conversion rate, the graphite packing mass of each axial section, and the latent heat of phase transition per unit mass of graphite to diamond.

[0079] Simultaneously, the instantaneous temperatures collected by each thermocouple along the axial direction of the synthesis cavity at the initial moment of thermal stabilization are acquired, and each axial segment is sequentially numbered along the axial direction. The instantaneous temperature of each thermocouple is used as the representative temperature value of the corresponding axial segment. The first and last axial segments are located at the two ends of the synthesis cavity, while the remaining axial segments are located in the middle of the synthesis cavity.

[0080] Then, the absolute value of the difference between the representative temperature values ​​of adjacent axial segments is calculated in turn as the axial temperature gradient. The maximum value is selected from all axial temperature gradients, and the axial interval between the two thermocouples corresponding to the maximum value is taken as the maximum gradient region.

[0081] Next, the spatial weights of each axial segment are determined: for the two axial segments corresponding to the maximum gradient region, the maximum value of the axial temperature gradient is taken as the initial spatial weight; for the other axial segments, when an axial segment has two adjacent axial segments, the reciprocal of the larger of the two corresponding axial temperature gradients is taken as the initial spatial weight; when an axial segment has only one adjacent axial segment, the reciprocal of the corresponding axial temperature gradient is taken as the initial spatial weight.

[0082] Then, the initial spatial weight of each axial segment is divided by the sum of the initial spatial weights of all axial segments to obtain the spatial weight of each axial segment; the latent heat load of each axial segment is multiplied by the corresponding spatial weight to obtain the weighted latent heat load of each axial segment.

[0083] The weighted latent heat load of each axial segment is normalized. Specifically, the weighted latent heat loads of each axial segment are added together to obtain the total weighted latent heat load; the weighted latent heat load of each axial segment is divided by the total weighted latent heat load to obtain the normalized latent heat load value of each axial segment; the set of normalized latent heat load values ​​of each axial segment is the latent heat load distribution along the axis of the synthesis cavity.

[0084] Next, based on the different heat transfer media, each axial segment is divided into a solid heat-conducting section and a cooling water convection section. For the solid heat-conducting section, the equivalent heat transfer length from the solid heat-conducting section to the cooling boundary is first taken as the heat transfer path. According to the physical assembly structure of the synthesis cavity, the heat transfer path is decomposed radially along the synthesis cavity into a pressure-transmitting medium layer, a conductive steel ring layer, and a top hammer body layer.

[0085] Among them, the equivalent heat transfer length of the pressure transmission medium layer and the top hammer body layer is the difference between their corresponding outer diameter and inner diameter; the equivalent heat transfer length of the conductive steel ring layer is its own thickness; the cooling boundary refers to the interface between the cooling water channel inside the top hammer and the top hammer wall, and the interface is determined from the top hammer water channel design drawings.

[0086] Subsequently, based on the geometric parameters of the pressure transmission medium layer, the conductive steel ring layer, and the top hammer body layer obtained from the press design drawings, the lengths of each axial section, and the thermal conductivity of the materials obtained from the material physics handbook, the thermal resistance of the pressure transmission medium layer, the conductive steel ring layer, and the top hammer body layer were calculated respectively.

[0087] Specifically, for the pressure-transmitting medium layer and the top hammer body layer, the calculation formula is as follows:

[0088] ;

[0089] For the conductive steel ring layer, the calculation formula is:

[0090] ;

[0091] Where R is the thermal resistance (K / W); The outer diameter of the pressure-transmitting medium or the outer diameter of the top hammer (m); is the inner diameter of the pressure-transmitting medium or the inner diameter of the top hammer (m); k is the thermal conductivity of each layer (W / m / K). The length of each axial segment (m); The thickness (m) of the conductive steel ring; π represents the area (m²) of the annular end face of the conductive steel ring; π is the mathematical constant pi, with a value of 3.14.

[0092] For the cooling water convection section, the dynamic viscosity, specific heat capacity, thermal conductivity, and density of the cooling water are obtained from the water property table. Taking a circular cross-section cooling water channel as an example, the equivalent diameter and equivalent length of the cooling water channel are obtained from the press design drawings. The cooling water flow rate is collected in real time by a flow sensor installed in the cooling water pipeline. The cross-sectional area of ​​the cooling water channel is obtained by multiplying the square of the equivalent diameter of the cooling water channel by pi and then dividing by four. The average flow velocity of the cooling water is obtained by dividing the cooling water flow rate by the cross-sectional area of ​​the cooling water channel.

[0093] Prandtl number is obtained by multiplying the dynamic viscosity of cooling water by its specific heat capacity and then dividing by its thermal conductivity. The Reynolds number is obtained by multiplying the density of cooling water, its average flow rate, and the equivalent diameter of the cooling water channel, and then dividing the product by the dynamic viscosity of the cooling water.

[0094] Substituting Prandtl number and Reynolds number into the cooling water heat transfer correlation: Where Nu is the Nusselt number, Re is the Reynolds number, and Pr is the Prandtl number, all of which are dimensionless. The convective heat transfer coefficient of the cooling water is obtained by multiplying the Nusselt number by the thermal conductivity of the cooling water and then dividing by the equivalent diameter of the cooling water channel.

[0095] Next, the equivalent diameter of the cooling channel, the equivalent length of the cooling channel, and the product of pi are calculated to obtain the heat transfer area of ​​the cooling channel; the reciprocal of the product of the convective heat transfer coefficient and the heat transfer area of ​​the cooling channel is calculated to obtain the convective thermal resistance of the cooling water troposphere.

[0096] The total equivalent thermal resistance of the axial section is obtained by adding the convective thermal resistance to the thermal resistance of the pressure transmission medium layer, the conductive steel ring layer, and the top hammer body layer.

[0097] Furthermore, the graphite packing mass of each axial segment is multiplied by the specific heat capacity of the synthesis cavity to obtain the heat capacity of each axial segment; the heat capacity and total equivalent thermal resistance of each axial segment are multiplied by the feedback calibration coefficient to obtain the feedback correction coefficient; the product of the gradient deviation and the feedback correction coefficient is used as the feedback power adjustment amount of each axial segment.

[0098] Meanwhile, the feedforward correction coefficient is determined by multiplying the latent heat of phase change per unit mass of graphite into diamond, the thermal conductivity of the synthesis cavity material, and the feedforward calibration coefficient; the product of the latent heat load distribution and the feedforward correction coefficient is used as the feedforward power adjustment amount for each axial segment.

[0099] The thermal conductivity of the synthesis cavity material was obtained from the materials physics handbook. The feedback calibration coefficient characterizes the quantitative relationship between thermal inertia and the feedback correction coefficient, while the feedforward calibration coefficient characterizes the quantitative relationship between the latent heat load change and the feedforward correction coefficient. Both the feedback calibration coefficient and the feedforward calibration coefficient were determined through independent step response experiments at the initial moment of thermal stability.

[0100] Specifically, at the initial moment of thermal stability, the temperature adjustment module applies an incremental heating power to the heating element of any axial segment corresponding to the maximum gradient region. The difference in temperature gradient before and after the application of the incremental heating power is taken as the temperature gradient change. At the same time, the thermal time constant representing the axial segment is determined using the existing step response method. The ratio of the incremental heating power to the temperature gradient change is divided by the thermal time constant to obtain the feedback calibration coefficient. The ratio of the temperature gradient change to the incremental heating power is taken as the feedforward calibration coefficient.

[0101] The heating power increment is taken as five percent of the product of real-time voltage and real-time current to avoid triggering the risk of overheating; the real-time voltage and real-time current are directly read from the output monitoring terminal of the heating power supply; the process of measuring the thermal time constant is existing technology and will not be described in detail here.

[0102] Then, the feedback power adjustment is multiplied by the spatial weight of the corresponding axial segment to obtain the weighted feedback power adjustment. The weighted feedback power adjustment is then superimposed with the feedforward power adjustment to obtain the total power adjustment for each axial segment. The total power adjustment represents the total change in heating power that the corresponding axial segment needs to perform at the current sampling time to eliminate gradient bias and compensate for the impending latent heat disturbance.

[0103] Next, the absolute value of the difference between the total power adjustment in the current sampling period and the actual power adjustment executed in the previous sampling period is calculated as the power change. If the power change is less than or equal to the maximum allowable power change, the total power adjustment for the current sampling period is executed directly.

[0104] If the power change is greater than the maximum allowable power change, and the total power adjustment is greater than the power adjustment actually performed in the previous sampling period, then the power adjustment actually performed in the previous sampling period plus the maximum allowable power change is taken as the power adjustment actually performed in the current sampling period.

[0105] If the power change is greater than the maximum allowable power change, and the total power adjustment is less than or equal to the power adjustment actually performed in the previous sampling period, then the power adjustment actually performed in the previous sampling period minus the maximum allowable power change is taken as the power adjustment actually performed in the current sampling period.

[0106] The maximum allowable power change is taken as the upper limit of the power change corresponding to the rated output response rate of the heating power supply, and the upper limit of the power change is obtained directly from the product specification of the heating power supply.

[0107] Finally, the temperature adjustment module sends the actual power adjustment amount performed in the current sampling period to the heating element corresponding to each axial segment, driving each heating element to perform the corresponding power adjustment.

[0108] The quality assessment module is used to extract crystal plane geometric parameters based on the three-dimensional contour data of diamond crystals, determine the geometric deviation between the diamond crystal and the ideal crystal form, and generate assessment results; and adjust the target pressure and target temperature gradient of the synthesis cavity according to the assessment results.

[0109] Specifically, after synthesis, the diamond crystal is extracted, and industrial CT equipment is used to generate three-dimensional contour data of the diamond crystal, i.e., three-dimensional CT voxel data. Random noise and artifacts in the three-dimensional CT voxel data are removed by filtering to improve image quality; then, the moving cube algorithm is used to extract a continuous closed surface model composed of triangular facets from the discrete three-dimensional CT voxel data, which serves as the three-dimensional contour surface of the diamond crystal.

[0110] Based on the three-dimensional profile surface, the length along the longest direction of the diamond crystal is taken as the crystal's major axis dimension; the shortest length of the diamond crystal in the direction perpendicular to the crystal's major axis is taken as the crystal's minor axis dimension.

[0111] Simultaneously, the quality assessment module counts the total number of internal voxels surrounded by the 3D contour surface, multiplies it by the volume per unit voxel, and obtains the volume of the 3D contour surface. This volume is then used as the volume of the sphere. (m³), and substitute into the formula for the volume of a sphere: The diameter of the sphere obtained by solving the problem The equivalent volumetric particle size (m) of the crystal is used. The unit voxel volume is obtained directly from the product technical documents of the industrial CT equipment. The crystal's major axis dimension, minor axis dimension, and equivalent volumetric particle size obtained above are used together as the crystal plane geometry parameters.

[0112] Next, based on the statistical characteristics of the grayscale histogram of the 3D CT voxel data, by traversing the grayscale levels, the grayscale value with the largest inter-class variance between the segmented background (air or other low-density support medium) region and the diamond crystal region is taken as the first grayscale threshold. Voxel regions in the 3D CT voxel data with grayscale values ​​higher than the first grayscale threshold are extracted as diamond crystal regions.

[0113] Within the diamond crystal region, the K-means clustering algorithm is used to divide all voxels into Class I and Class II voxels based on their gray values. The algorithm is iteratively calculated until the cluster centers of Class I and Class II voxels converge. The converged center values ​​of Class I and Class II voxels are then used as the average gray values ​​of Class I and Class II voxels, respectively. The specific iterative process is existing technology and will not be elaborated here.

[0114] Based on statistical principles, when the absolute value of the difference between the average gray values ​​of the first type of voxels and the second type of voxels is greater than three times the standard deviation of the gray values ​​of the background area, it indicates that the gray distribution of the first type of voxels and the second type of voxels is significantly different. At the same time, since the density of diamond is less than that of inclusions, and gray value is directly proportional to density, the type with the smaller average gray value is identified as the diamond matrix, and the type with the larger average gray value is identified as the internal inclusions.

[0115] When the absolute value of the difference between the average gray values ​​of the first type voxels and the second type voxels is less than or equal to three times the standard deviation of the gray values ​​of the background area, it indicates that the gray distribution is highly consistent and there are no inclusions. In this case, both the first type voxels and the second type voxels are identified as diamond matrix types.

[0116] The space occupied by the voxels contained in the diamond matrix is ​​defined as the diamond matrix region, and the space occupied by the voxels contained in the internal inclusions is defined as the internal inclusion region.

[0117] Next, the total volume of inclusions is calculated by multiplying the total number of voxels in the internal inclusion region by the volume per voxel; the total volume of diamond crystal is calculated by multiplying the sum of the total number of voxels in the diamond matrix region and the total number of voxels in the internal inclusion region by the volume per voxel; and the inclusion content is obtained by dividing the total volume of inclusions by the total volume of diamond crystal.

[0118] In this embodiment, the theoretical crystal form is specifically a hexahedral aggregate, which is composed of hexahedral and octahedral faces. The lattice constant of diamond is obtained from a crystallographic database. Based on the crystal structure and geometric crystallography principles of diamond, the interplanar spacing of the hexahedral faces is numerically equal to the lattice constant, and the interplanar spacing of the octahedral faces is numerically equal to the lattice constant divided by 1 / 2. Divide the lattice constant by This yields half the length of the face diagonal of the hexahedron, denoted as . .

[0119] Based on the spatial geometric relationship between hexahedral and octahedral faces, calculate the distance from the intersection of the octahedral and hexahedral faces to the diagonal of the hexahedral face. : ;Will and The ratio of τ to τ is used as the theoretical value.

[0120] Next, spatial registration is performed between the 3D contour surface and the hexoctahedral aggregate. When the sum of the squares of the Euclidean distances between each point on the 3D contour surface and the corresponding point on the hexoctahedral aggregate surface is minimized, the 3D contour surface and the hexoctahedral aggregate are determined to be aligned in spatial position; otherwise, the registration is determined to have failed, and no subsequent calculation of geometric deviation is performed.

[0121] After aligning the 3D contour surface with the hexahedral aggregate in space, the hexahedral faces of the 3D contour surface are determined using a plane fitting algorithm based on the normal vector direction (i.e., crystal axis direction) of the hexahedral faces of the hexahedral aggregate. Convex hull calculation is then performed on the point cloud data of the hexahedral faces of the 3D contour surface. The line connecting the two vertices with the largest Euclidean distance among the vertices of the obtained convex hull is taken as the diagonal. The arithmetic mean of the diagonal lengths of the six hexahedral faces is calculated, and half of the arithmetic mean of the diagonal lengths is taken as... .

[0122] The 12 common edges formed by the intersections of octahedral and hexahedral faces in the hexoctahedral aggregate are taken as theoretical intersection lines. Using spatial analytic geometry, the spatial intersection points of each theoretical intersection line and the corresponding diagonals of the hexahedral faces on the 3D contour surface are obtained by simultaneously solving the equations of the straight lines. The distance from the spatial intersection point to the inner endpoint of the diagonal is taken as the distance value corresponding to the theoretical intersection line; the inner endpoint is the endpoint of the diagonal located inside the hexahedral face. The arithmetic mean of the distance values ​​of the 12 theoretical intersection lines is taken as... ,Will and The ratio is used as the τ value of the diamond crystal. The process of calculating the convex hull and obtaining the spatial intersection points is existing technology and will not be elaborated here.

[0123] The difference between the τ value of the diamond crystal and the theoretical τ value is taken as the τ value deviation, and the absolute value of the τ value deviation is taken as the geometric deviation; the smaller the geometric deviation, the closer the diamond crystal is to a hexoctahedral aggregate.

[0124] Furthermore, an evaluation result is generated based on the crystal plane geometry parameters, inclusion content, and geometric deviation. Specifically, the equivalent volumetric particle size is compared with the nominal size range of the corresponding particle size mark in the superhard abrasive particle size inspection. If the equivalent volumetric particle size falls within the nominal size range corresponding to a certain particle size mark (such as the 40 / 45 particle size mark), the particle size of the diamond crystal is determined to be that particle size mark; if the equivalent volumetric particle size does not fall within the nominal size range of any known particle size mark, the particle size of the diamond crystal is determined to be unidentifiable, an abnormal alarm is generated, and it is recorded in the evaluation result.

[0125] Simultaneously, the ratio of the major axis dimension to the minor axis dimension of the crystal is calculated to obtain the aspect ratio. Based on the grading requirements for crystal form in the technical specifications for superhard abrasive synthetic diamond, the crystal size grade is determined: when the aspect ratio is less than or equal to 1.2, it is excellent; when the aspect ratio is greater than 1.2 and less than or equal to 1.5, it is first-class; when the aspect ratio is greater than 1.5 and less than or equal to 2, it is qualified; when the aspect ratio is greater than 2, it is unqualified.

[0126] Furthermore, based on the method for testing the impurity content of superhard abrasive synthetic diamond, the inclusion content grade is determined as follows: when the inclusion content is less than or equal to 0.05%, it is excellent; when the inclusion content is greater than 0.05% and less than or equal to 0.1%, it is first-class; when the inclusion content is greater than 0.1% and less than or equal to 0.5%, it is qualified; and when the inclusion content is greater than 0.5%, it is unqualified.

[0127] According to the well-known crystal form grading criteria in the diamond industry, the crystal form grade is determined as follows: when the geometric deviation is less than or equal to 0.25, it is excellent; when the geometric deviation is greater than 0.25 and less than or equal to 0.35, it is first-class; when the geometric deviation is greater than 0.35 and less than or equal to 0.50, it is qualified; when the geometric deviation is greater than 0.50, it is unqualified.

[0128] Subsequently, the lowest grade among the crystal size grade, inclusion content grade, and crystal form grade of the synthesized diamond crystal is taken as the comprehensive quality grade. For example, if the crystal size grade is first-class, the inclusion content grade is qualified, and the crystal form grade is excellent, then the comprehensive quality grade is the lowest grade among the above three indicators, that is, qualified.

[0129] The final evaluation results include: crystal major axis size, crystal minor axis size, equivalent volume particle size, particle size grade, inclusion content grade, crystal size grade, crystal form grade, and overall quality grade.

[0130] Next, the adjustment amount of the target pressure in the synthesis chamber is calculated from the arithmetic mean of the inclusion content and the conversion rate during the heat preservation and pressure holding stages in this synthesis, as well as the synthesis chamber temperature during the heat preservation and pressure holding stages (which needs to be converted to thermodynamic temperature).

[0131] Specifically, first calculate the average shrinkage rate of the synthesis chamber volume during the heat preservation and pressure holding stage:

[0132] ;

[0133] in, The average shrinkage rate of the synthesis cavity volume (m³ / s); This represents the total mass (kg) of the reactants in the synthesis chamber during this synthesis. This is the arithmetic mean of the conversion rates during the heat preservation and pressure holding stages of this synthesis. ); is the density of graphite (kg / m³). The density of diamond is (kg / m³).

[0134] The average volume shrinkage rate is then divided by the geometric volume of the synthesis chamber to obtain the crystal growth rate. The adjustment amount of the target pressure in the synthesis chamber is then calculated using the following formula:

[0135] ;

[0136] in, The adjustment amount (Pa) for the target pressure of the synthesis chamber; This is the gas constant, i.e., 8.314 J / (mol·K); This is the temperature (K) of the synthesis chamber during the heat preservation and pressure holding stage of this synthesis process. The activated volume for carbon diffusion (m³ / mol) was obtained directly from high-pressure physics academic literature. The content of this synthetic inclusion is dimensionless. Crystal growth rate ( ); Reference growth rate ( ).

[0137] The process for determining the reference growth rate is as follows: when the number of batches with an overall quality grade of qualified or above is less than 3, the arithmetic mean of the conversion rate is recorded during the heat preservation and pressure holding stage of the first synthesis, and the corresponding crystal growth rate is calculated as the reference growth rate; when the number of batches with an overall quality grade of qualified or above is greater than or equal to 3, the arithmetic mean of the crystal growth rate during the heat preservation and pressure holding stage of the synthesis with an overall quality grade of qualified or above is used as the reference growth rate.

[0138] Next, the target pressure of the synthesis chamber in this synthesis is superimposed with the adjustment amount of the target pressure of the synthesis chamber to obtain the target pressure of the synthesis chamber for the next synthesis.

[0139] Furthermore, the adjustment amount of the target temperature gradient is calculated from the deviation of the τ value in this synthesis, as well as the arithmetic mean of the real-time temperature gradient and the arithmetic mean of the conversion rate during the heat preservation and pressure holding stages.

[0140] Specifically, from the previous synthesis that was of acceptable or above quality, the next synthesis adjacent to this synthesis is selected, and the arithmetic mean of the real-time temperature gradient during the heat preservation and pressure holding stage of the selected synthesis is extracted as the reference temperature gradient.

[0141] When historical data is insufficient, the arithmetic mean of the real-time temperature gradients during the initial synthesis in the heat preservation and pressure holding stage is directly used as the reference temperature gradient. The adjustment amount of the target temperature gradient is calculated using the following formula:

[0142] ;

[0143] in, The adjustment amount for the target temperature gradient (°C / mm); Reference temperature gradient (°C / mm); This represents the arithmetic mean (°C / mm) of the real-time temperature gradient during the heat preservation and pressure holding stage of this synthesis. The deviation of τ in this synthesis is dimensionless.

[0144] Finally, the target temperature gradient synthesized in this study is superimposed with the adjustment amount of the target temperature gradient to obtain the target temperature gradient for the next synthesis.

[0145] Please see Figure 2 The present invention also provides a method for intelligent control of synthetic diamond synthesis, comprising the following steps: S1, transmitting and receiving ultrasonic waves into the synthesis cavity, and obtaining the diamond conversion rate and conversion speed based on the change of ultrasonic wave velocity.

[0146] S2. Determine the feedforward displacement component based on the conversion rate, the change in volume of the synthesis chamber, and the change in volume of the pressure transmission medium; determine the feedback displacement component based on the deviation between the measured pressure in the synthesis chamber and the target pressure in the synthesis chamber, as well as the pressure loss in the pipeline; combine the feedforward displacement component and the feedback displacement component to obtain the pressure compensation displacement.

[0147] S3. Calculate the real-time temperature gradient based on the temperature at different axial positions and the amount of pressure displacement within the synthesis chamber; adjust the heating power based on the real-time temperature gradient and the target temperature gradient, combined with the latent heat load distribution determined according to the conversion rate and graphite packing mass.

[0148] S4. Extract crystal plane geometric parameters based on the three-dimensional contour data of the diamond crystal to determine the geometric deviation between the diamond crystal and the theoretical crystal form, and generate evaluation results; adjust the target pressure and target temperature gradient of the synthesis cavity according to the evaluation results.

[0149] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, in the form of a computer program product.

[0150] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0151] In addition, the functional modules in the various embodiments of the present invention can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0152] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

[0153] Finally, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A smart control system for the synthesis of synthetic diamond, characterized in that, include: The phase transition analysis module is used to transmit and receive ultrasonic waves into the synthesis cavity, and to analyze the conversion rate and conversion efficiency of diamond based on the changes in ultrasonic wave velocity. The pressure compensation control module is used to determine the feedforward displacement component based on the conversion rate, the change in the volume of the synthesis chamber, and the change in the volume of the pressure transmission medium; and to determine the feedback displacement component based on the deviation between the measured pressure in the synthesis chamber and the target pressure in the synthesis chamber, as well as the pressure loss in the pipeline. By combining the feedforward displacement component and the feedback displacement component, the pressure compensation displacement is obtained; The temperature adjustment module is used to calculate the real-time temperature gradient based on the temperature at different axial positions and the amount of pressure compensation displacement within the synthesis chamber; and to adjust the heating power based on the real-time temperature gradient and the target temperature gradient, combined with the latent heat load distribution determined according to the conversion rate and graphite packing mass. The quality assessment module is used to extract crystal plane geometric parameters based on the three-dimensional contour data of the diamond crystal, thereby determining the geometric deviation between the diamond crystal and the theoretical crystal form, and generating assessment results; and adjusting the target pressure and target temperature gradient of the synthesis cavity based on the assessment results.

2. The intelligent control system for synthetic diamond synthesis as described in claim 1, characterized in that, The process of obtaining conversion rate and conversion speed is as follows: When the changes in ultrasonic longitudinal wave velocity, ultrasonic attenuation coefficient, spectral centroid frequency, measured pressure in the synthesis cavity, and temperature in the synthesis cavity are all less than the corresponding judgment thresholds for a series of consecutive sampling times, the first sampling time in the series of consecutive sampling times is determined as the thermal stability start time. The ultrasonic longitudinal wave velocity, ultrasonic attenuation coefficient, and spectral centroid frequency at the initial moment of thermal stability were used as the reference values ​​for the graphite phase. Based on the ratio of ultrasonic longitudinal wave velocity, ultrasonic attenuation coefficient, and spectral centroid frequency between diamond and graphite, and combined with the graphite phase reference value set, the diamond phase reference value set is obtained. After determining the thermal stability initiation time, the graphite phase reference value group and the diamond phase reference value group are corrected according to the synthesis chamber temperature and the measured pressure of the synthesis chamber at the current sampling time, so as to obtain the graphite ultrasonic parameters and the diamond ultrasonic parameters. The ultrasonic longitudinal wave velocity, ultrasonic attenuation coefficient, and spectral centroid frequency are linearly interpolated with the graphite ultrasonic parameters and diamond ultrasonic parameters, respectively, to calculate the corresponding single-parameter conversion rate. The single-parameter conversion rates are then weighted and fused to obtain the conversion rate. The conversion rate is obtained by differentiating the conversion rate over time.

3. The intelligent control system for synthetic diamond synthesis as described in claim 1, characterized in that, The process of determining the feedforward displacement components is as follows: The volume shrinkage of the synthesis chamber is calculated based on the conversion rate, the total mass of reactants in the synthesis chamber, the density of graphite, and the density of diamond. The thermal expansion and contraction of the synthesis cavity is calculated based on the volumetric thermal expansion coefficient of the synthesis cavity and the deviation between the temperature of the synthesis cavity at the current sampling time and the temperature of the synthesis cavity at the start of thermal stability. The change in the volume of the synthesis cavity is obtained by adding the shrinkage of the synthesis cavity volume to the thermal expansion and contraction of the synthesis cavity. Based on the deviation between the measured pressure in the synthesis chamber at the current sampling time and the measured pressure in the synthesis chamber at the start of thermal stability, and combined with the volume compressibility coefficient of the pressure transmission medium, the volume change of the pressure transmission medium is calculated. The total volume change is obtained by superimposing the change in the volume of the synthesis chamber with the change in the volume of the pressure transmission medium; the total volume change is then converted into a feedforward displacement component based on the cross-sectional area of ​​the press cylinder.

4. The intelligent control system for synthetic diamond synthesis as described in claim 3, characterized in that, The process of determining the feedback displacement components is as follows: Based on the deviation between the measured pressure in the synthesis chamber and the target pressure in the synthesis chamber, the pressure deviation compensation displacement is determined. Calculate the instantaneous oil flow rate in the hydraulic line during pressure replenishment based on the conversion rate, graphite density, and diamond density. Calculate the pipeline pressure loss based on the instantaneous oil flow rate, pipeline geometric parameters, and hydraulic oil viscosity parameters; The ratio of pipeline pressure loss to the cross-sectional area of ​​the press cylinder is used as the pipeline loss compensation displacement. The pressure deviation compensation displacement is superimposed with the pipeline loss compensation displacement to obtain the feedback displacement component.

5. The intelligent control system for synthetic diamond synthesis as described in claim 2, characterized in that, The process of calculating the real-time temperature gradient is as follows: By fitting and analyzing the temperature at different axial positions within the synthesis cavity, the temperature distribution function along the axial direction of the synthesis cavity is obtained, and the initial temperature gradient is obtained by differentiating the distribution function. The displacement-temperature coupling coefficient is determined based on the temperature and displacement increment of the synthesis cavity. The corrected temperature gradient is obtained by superimposing the product of the pressure compensation displacement and the displacement-temperature coupling coefficient with the initial temperature gradient. The latent heat temperature coupling coefficient is determined based on the temperature of the synthesis chamber and the increase in heating power. The real-time temperature gradient is obtained by superimposing the product of the conversion rate, graphite packing density and latent heat temperature coupling coefficient with the corrected temperature gradient.

6. The intelligent control system for synthetic diamond synthesis as described in claim 5, characterized in that: The synthesis cavity is evenly divided into multiple axial segments along the axial direction; At the moment of thermal stabilization, the absolute value of the first-order temperature difference between adjacent axial segments of the synthesis cavity is calculated as the axial temperature gradient.

7. The intelligent control system for synthetic diamond synthesis as described in claim 6, characterized in that, The process of determining the latent heat load distribution is as follows: Calculate the latent heat load of each axial section based on the conversion rate and the graphite packing mass of each axial section. The spatial weight of each axial segment is determined based on the axial temperature gradient corresponding to each axial segment. The latent heat load of each axial segment is multiplied by the corresponding spatial weight to obtain the weighted latent heat load of each axial segment. The weighted latent heat load of each axial segment is normalized to obtain the latent heat load distribution along the axial direction of the synthesis cavity.

8. A synthetic diamond synthesis intelligent control system as described in claim 7, characterized in that, The process of adjusting the heating power is as follows: The difference between the real-time temperature gradient and the target temperature gradient is used as the gradient bias; The feedback correction coefficient for each axial segment is determined based on the heat capacity and total equivalent thermal resistance of each axial segment. The product of the gradient deviation and the feedback correction coefficient is used as the feedback power adjustment amount for each axial segment. The feedforward correction coefficients for each axial segment are determined based on the latent heat of phase transition per unit mass of graphite to diamond and the thermal conductivity of the synthesis cavity. The product of the latent heat load distribution and the feedforward correction coefficient is used as the feedforward power adjustment amount for each axial segment. Multiply the feedback power adjustment amount by the spatial weight of the corresponding axial segment to obtain the weighted feedback power adjustment amount; The weighted feedback power adjustment is superimposed with the feedforward power adjustment to obtain the total power adjustment for each axial segment. The heating power of each axial section is adjusted based on the weighted power adjustment.

9. The intelligent control system for synthetic diamond synthesis as claimed in claim 1, characterized in that, The process of generating the evaluation results is as follows: Based on the three-dimensional contour data of diamond crystal, the three-dimensional contour surface of diamond crystal is obtained through surface reconstruction. Crystalline geometric parameters are obtained from three-dimensional profile surface analysis. These parameters include the major axis dimension, minor axis dimension, and equivalent volumetric grain size of the diamond crystal. Based on the difference in grayscale values ​​between the diamond and the inclusions, the diamond matrix and the internal inclusions are identified. Then, the total volume of the inclusions and the total volume of the diamond crystal are calculated by combining the volume per unit voxel. The inclusion content is obtained by dividing the total volume of the inclusions by the total volume of the diamond crystal. The three-dimensional profile surface is registered with the theoretical crystal form; based on the length of the cube face diagonal in the registered three-dimensional profile surface, and the distance from the intersection of the octahedral face and the cube face to the cube face diagonal, the geometric deviation between the diamond crystal and the theoretical crystal form is determined. Based on the crystal geometry parameters, inclusion content, and geometric deviation, an evaluation result is generated, and the target pressure and target temperature gradient of the synthesis chamber are adjusted according to the evaluation result.

10. A method for intelligent control of synthetic diamond synthesis, characterized in that, Includes the following steps: Ultrasonic waves are emitted and received into the synthesis cavity, and the conversion rate and conversion efficiency of diamond are obtained by analyzing the changes in ultrasonic wave velocity. The feedforward displacement component is determined based on the conversion rate, the change in the volume of the synthesis chamber, and the change in the volume of the pressure-transmitting medium; the feedback displacement component is determined based on the deviation between the measured pressure in the synthesis chamber and the target pressure in the synthesis chamber, as well as the pressure loss in the pipeline. By combining the feedforward displacement component and the feedback displacement component, the pressure compensation displacement is obtained; The real-time temperature gradient is calculated based on the temperature at different axial positions within the synthesis chamber and the amount of pressure compensation displacement; the heating power is adjusted based on the real-time temperature gradient and the target temperature gradient, combined with the latent heat load distribution determined according to the conversion rate and graphite loading mass. Crystalline parameters are extracted from the three-dimensional contour data of the diamond crystal to determine the geometric deviation between the diamond crystal and the theoretical crystal form, and an evaluation result is generated. The target pressure and target temperature gradient of the synthesis cavity are adjusted according to the evaluation result.

Images