Artificial diamond single crystal generation process

Abstract

The invention relates to the technical field of artificial diamonds, in particular to an artificial diamond single crystal generation process which comprises the following specific steps: A, mixing and granulating graphite, mother powder and a metal catalyst, and then transferring into a pressing workshop to be pressed into a graphite column; b, pyrophyllite powder and boron nitride powder are mixed and then made into a cylindrical blank, and a cylindrical cavity is machined in the center of the pyrophyllite blank; c, assembling the graphite column, the pyrophyllite cylinder, the plug assembly, the heating assembly and the insulating assembly into a synthetic block; and D, a mechanical arm carries the clamping mechanism to position the synthetic block to the center of a cavity of the cubic press, the surface of the anvil in the equipment is blown and swept, dust particles are removed, then the clamping mechanism is taken back, and the cubic press is started for temperature rising and pressure rising. And more time and energy are consumed.

Description

Technical Field

[0001] The present invention relates to the technical field of artificial diamond, and specifically to a process for generating artificial diamond single crystals. Background Art

[0002] As a carbon-based material with both ultra-high hardness and excellent physical and chemical properties, artificial diamond single crystals have irreplaceable application value in fields such as precision machining and high-end electronic devices. One of the current mainstream generation processes is the high-temperature and high-pressure method. This method constructs a high-pressure and high-temperature environment through equipment such as a six-sided top press, uses catalyst metals such as iron-based and cobalt-based to promote the transformation of graphite into diamond phase, and grows single crystals directionally with a seed crystal as the substrate. Its core advantage is a relatively fast crystal growth rate.

[0003] The six-sided top press applies high pressure to the internal reaction cavity from six directions through the anvils, and together with the heating system, creates a high-pressure and high-temperature environment suitable for diamond growth. If the anvils are not flat, it will cause uneven pressure distribution on the reaction cavity. In such an uneven pressure environment, the conversion process of graphite into diamond will be disturbed, and the directional growth of the seed crystal will also be affected, resulting in defects such as cracks and impurity mixing in the generated artificial diamond single crystals, reducing the quality and performance of the crystals.

[0004] Whether precisely placing the synthesis block into the cavity or completely removing the synthesis block from the cavity, cleaning the surface of the anvils has become an essential step. Currently, when the synthesis block is put into or taken out of the cavity, the surface of the anvils is manually cleaned to prevent the flatness of the anvils from affecting the pressure uniformity and stability of the entire high-pressure cavity. During the manual operation process, one needs to focus on the surface of the anvils and carefully remove the existing debris or residues manually. The entire process requires a lot of time and energy, and the operation is inconvenient. Summary of the Invention

[0005] The purpose of the present invention is to provide a process for generating artificial diamond single crystals to solve the problem that manually removing the debris or residues existing on the anvils requires a lot of time and energy.

[0006] To achieve the above purpose, the present invention provides the following technical solutions: A process for generating artificial diamond single crystals, the specific steps are as follows: A. Mix graphite, mother powder, and metal catalyst, granulate, and then transfer to the pressing workshop to press into graphite columns; B. Mix pyrophyllite powder and boron nitride powder, and then make into a cylindrical blank, and process a cylindrical cavity in the center of the pyrophyllite blank; C. Assemble the graphite column, pyrophyllite cylinder, plug assembly, heating assembly, and insulation assembly into a synthesis block; D. Position the synthesis block in the center of the cavity of the six-sided press through the manipulator carrying the clamping mechanism, purge the surface of the anvil in the equipment to remove dust particles, then retract the clamping mechanism, start the six-sided press to increase the temperature and pressure, and enter the heat preservation and pressure maintenance stage when both the temperature and pressure reach the set values; E. After the heat preservation and pressure maintenance are completed, first stop heating, let the synthesis block cool naturally inside the cavity until the temperature drops below 500 °C, and then start to slowly reduce the pressure until the pressure drops to atmospheric pressure; F. Smoothly take out the synthesis block from the cavity of the six-sided press, disassemble the synthesis block to obtain single-crystal diamond.

[0007] Preferably, in step A, the graphite column is subjected to high-temperature reduction to remove moisture to obtain a pure graphite column.

[0008] Preferably, in step C, the synthesis block is baked at 120-125 °C for 10 hours.

[0009] Preferably, in step C, during the assembly of the synthesis block, pyrophyllite fine powder is coated in the gap between the heating component and the graphite column.

[0010] Preferably, in step E, while the synthesis block is naturally cooling, argon is introduced to displace the air in the cavity.

[0011] Preferably, in step F, the synthesis block is soaked in dilute hydrochloric acid, washed, crushed, electrolyzed, ball-milled and sieved, separated by a shaking table, dried, purified and washed with pure water to obtain single-crystal diamond.

[0012] Preferably, in step D, the clamping mechanism is provided with a jet port connected to a jet pump. During the process of the clamping mechanism loading the synthesis block into the six-sided press, the jet pump is started to purge the surface of the anvil through the jet port.

[0013] Preferably, the clamping mechanism includes a clamping seat and clamping claws. A horizontally movable cutting shovel plate is installed at the top of the clamping seat. In step F, when the synthesis block is taken out of the cavity, the cutting shovel plate is horizontally moved to shovel off the residual pyrophyllite on the surface of the anvil.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1. The conical tip of the slitting shovel plate can directly shovel off the residual pieces of pyrophyllite adhered to the surface of the anvil under high temperature and high pressure. At the same time, the air nozzle synchronously sprays out air flow to blow away the fine particles remaining after mechanical shoveling, avoiding abrasive wear, surface scratches and pits on the anvil caused by dust particles or pyrophyllite residues, maintaining the flatness accuracy of the anvil working surface. The improvement of the anvil cleanliness can ensure uniform pressure distribution in the synthesis cavity, reduce the crystal form distortion rate of products such as diamond caused by uneven pressure, improve the stability of the finished product quality. The cleaning and peeling functions can be integrated into the automated process of the six-sided press to achieve integrated operation, reduce manual intervention, shorten the downtime for cleaning, and improve production efficiency; 2. By coating fine pyrophyllite powder between the graphite column and the heating tube, the residual bubbles are reduced and the pressure transmission uniformity is improved; 3. After the six-sided press finishes heat preservation and pressure holding, argon is introduced to displace the air in the cavity until the temperature drops below 500 °C to prevent high-temperature oxidation. Description of the Drawings

[0015] Figure 1 It is the state effect diagram of the clamping mechanism of the present invention clamping the synthesis block; Figure 2 It is the structural schematic diagram of the clamping mechanism of the present invention; Figure 3 It is the structural schematic diagram of the slitting shovel plate of the present invention; Figure 4 It is the state effect diagram of the reverse movement of the slitting shovel plate of the present invention.

[0016] In the figure: 1, clamping seat; 2, clamping claw; 3, rotating seat; 4, guiding chute; 5, limiting slider; 6, slitting shovel plate; 7, air spray pipe; 8, rotating shaft; 9, support frame; 10, connecting arm. Detailed Embodiment

[0017] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

[0018] Please refer to Figures 1 to 3 , the present invention provides a technical solution: An artificial diamond single crystal generation process, characterized in that the specific steps are as follows: Graphite is selected as the carbon source material. The mother powder includes diamond powder. Graphite is mixed with a certain proportion of metal catalyst and mother powder according to the product model required for production, and then mixed and granulated. The granulation size is about 3mm. After granulation, 0.1-0.2% dimethyl silicone oil is sprayed on the surface of the particles to improve the fluidity and mold release during pressing. After the above process is completed, it is transferred to the pressing workshop to press out the required graphite column size.

[0019] The graphite column is reduced at high temperature. The graphite column may be damp and contaminated due to other reasons during mixing and pressing. The purpose of high temperature reduction is to burn the moisture and contamination at high temperature, remove the moisture and contamination, and obtain a pure graphite column.

[0020] The pressure transmission medium is pyrophyllite powder, which is sieved through 100-200 meshes to remove impurity particles, and then an appropriate amount of deionized water is added, and it is dried at 100-150°C for 24 hours to make its moisture content less than 1%. After cooling, 0.5-1% mass fraction of boron nitride powder is added, and the mixture is evenly dispersed by a three-dimensional mixer for 1-2 hours to improve the thermal conductivity of the pressure transmission medium. Then, a cylindrical blank is made. On a clean operating table, a cylindrical cavity is hollowed out from the center of the dried pyrophyllite cylindrical blank. After processing, the inner surface of the blank is ultrasonically cleaned with deionized water to remove graphite dust and debris. The graphite column, pyrophyllite cylinder, plug assembly, heating assembly, and insulation assembly are assembled in order according to size. The heating component adopts a graphite resistance heating tube, the heating tube is sleeved on the outer surface of the graphite column, the pyrophyllite cylinder is sleeved on the outer surface of the heating tube, and the plug assembly is plugged at the upper and lower ends of the pyrophyllite cylinder. The thickness of the outer layer of pyrophyllite is uniform, ensuring that a stable pressure transmission environment can be provided under high temperature and high pressure. A layer of pyrophyllite fine powder is evenly coated on the gap between the outer surface of the graphite column and the inner surface of the heating component to improve the uniformity of interface pressure transmission and reduce bubble residue. Insulating components, such as mica sheets, are wrapped between the outer surface of the heating tube and the pyrophyllite cylinder to isolate the heating element from the pressure transmission medium and prevent current leakage or short circuit. The upper and lower plug assemblies are also made of pyrophyllite, with built-in ceramic heating plates to compensate for axial temperature gradients.

[0021] The synthetic blocks are baked at high temperature. When assembling and transporting the synthetic blocks, the assembled synthetic blocks may be damp due to weather and human factors. In order to ensure product quality and equipment stability, they need to be baked at 120-125℃ for 10 hours.

[0022] By controlling the opening and closing of the clamping mechanism, slowly open the clamping jaws 2, align them with the synthesis block, and then slowly close the clamping jaws 2, apply an appropriate clamping force, and ensure that the synthesis block is firmly clamped. The robotic arm transports the clamped synthesis block smoothly above the feed inlet of the six-sided top press according to the preset movement path, adjusts the position and posture of the robotic arm to make the axis of the synthesis block coincide with the central axis of the six-sided top press, slowly move the robotic arm, and place the synthesis block at the central position of the cavity of the six-sided top press, ensuring uniform contact between the synthesis block and the six punches without tilt or deviation, and calibrate with a micrometer or a laser rangefinder.

[0023] Start the hydraulic system of the six-sided top press, control the pressure increase rate at 10 - 50 MPa / min until the pressure reaches 5.5 - 6 GPa. During the pressure increase process, monitor the pressure values of each pressure cylinder in real time to ensure uniform pressure increase, and the pressure difference between each pressure cylinder does not exceed ±0.1 GPa.

[0024] When the pressure reaches the preset value, start the heating system and heat the synthesis block at a heating rate of 50 - 200 °C / min until the temperature rises to 1300 - 1600 °C. This temperature range can melt the carbon source and form a solution environment for diamond growth. During the heating process, monitor the temperature in real time through the temperature sensor installed inside the cavity to ensure uniform temperature distribution, and the temperature error does not exceed ±5 °C.

[0025] When both the temperature and pressure reach the set values, enter the heat preservation and pressure maintenance stage. The heat preservation and pressure maintenance time is determined according to the size of the diamond single crystal to be synthesized, generally 2 - 24 hours. During the heat preservation and pressure maintenance process, continuously monitor the pressure and temperature to ensure that they are stable within the set range, the pressure fluctuation does not exceed ±0.05 GPa, and the temperature fluctuation does not exceed ±2 °C, providing a stable high-temperature and high-pressure environment for the growth of diamond single crystals.

[0026] After the heat preservation and pressure maintenance are completed, first stop the heating system, let the synthesis block cool naturally inside the cavity, control the cooling rate at 50 - 100 °C / min, and at the same time introduce argon to displace the air in the cavity until the temperature drops below 500 °C to prevent high-temperature oxidation, and then start to slowly reduce the pressure, control the pressure reduction rate at 10 - 50 MPa / min until the pressure drops to atmospheric pressure, ensuring that the synthesis block will not crack or be damaged due to sudden changes in temperature and pressure during the removal process.

[0027] Start the robotic arm and move it above the discharge outlet of the six-sided top press according to the preset movement path. Adjust the posture of the robotic arm to make the clamping jaws 2 of the clamping mechanism apply an appropriate clamping force, smoothly remove the synthesis block from the cavity of the six-sided top press, and the robotic arm carries the synthesis block and moves to the synthesis block unloading position according to the predetermined path, release the clamping jaws 2, and place the synthesis block on the unloading platform.

[0028] The obtained synthetic block is immersed in a dilute hydrochloric acid solution with a concentration of 10 - 20% for 1 - 2 hours, causing the pyrophyllite pressure - transmitting medium to react with hydrochloric acid and gradually dissolve. Then, the synthetic block is washed multiple times with deionized water to remove the residual hydrochloric acid and dissolved pyrophyllite impurities until the pH value of the washing water is neutral, obtaining an unpurified synthetic rod. The inside of the synthetic rod contains diamond, metal, and untransformed graphite, etc.

[0029] The original synthetic rod is crushed into pieces with a size of 5 - 10 mm and packed into a pre - prepared woven bag. This is the preparatory work before electrolysis. The semi - finished synthetic rod produced is larger in size, which is for the convenience of electrolysis.

[0030] The pre - proportioned electrolyte is put into the electrolytic cell, and then the synthetic rod packed in the woven bag undergoes an electrolysis reaction for 4 - 5 days. The time can be adjusted according to the electrolysis effect.

[0031] After electrolysis, the synthetic rod packed in the woven bag changes from solid to fluid, with diamond and graphite mixed inside. First, it is poured into a ball mill for ball - milling, and then screened. The screened material is put into the shaker cylinder and water is added to separate diamond from other materials.

[0032] The diamond separated from the shaker is dried for subsequent convenient processing. Nitrogen is introduced during the drying process to prevent diamond from reacting with oxygen at high temperatures, ensuring that the moisture content after drying is <0.1%.

[0033] The dried diamond is purified. Because the electrolysis process is not complete, all other materials on the diamond surface need to be removed, and a certain amount of purification time is required to remove other impurities. The purification time depends on the actual situation.

[0034] After the purification process, due to chemical reactions, certain chemical components will adhere to the diamond surface, affecting the product color. Therefore, during the final washing process, it must be washed with pure water to obtain a diamond with a clean surface.

[0035] The diamond washed with pure water is dried.

[0036] It includes a clamping mechanism. The clamping mechanism includes a clamping seat 1 and clamping claws 2. The clamping claws 2 are driven by a motor to clamp the synthetic block. At the top of the clamping seat 1, there is a horizontally movable cutting shovel plate 6. One end of the cutting shovel plate 6 is provided with a jet orifice, and its interior is integrated with a jet channel communicating with the jet orifice. The jet channel is connected to a jet pump through a jet pipe 7. When the jet pump is started, the jet orifice can jet outwards. This function can purge the surface of the anvil in the equipment during the process of loading the synthetic block into the six-sided top press, removing dust particles, and preventing the anvil from being scratched and pitted due to abrasive wear under the high-pressure working condition of pressurization, resulting in a decrease in the flatness accuracy of the anvil working surface, further affecting the pressure uniformity of the synthesis cavity, and ultimately leading to an increase in the crystal form distortion rate of products such as diamond.

[0037] One end of the cutting shovel plate 6 is a conical tip, and the jet orifice is opened at the conical tip. When there is residual pyrophyllite on the surface of the anvil, the pyrophyllite softens and melts due to high temperature and high pressure, and adheres to the anvil interface with strong adsorption force. The cutting shovel plate 6 can be horizontally moved. Through the physical contact of the conical tip, the residual pyrophyllite is shoveled off and pushed to the outside of the anvil. At the same time, a manipulator can be additionally equipped to carry a receiving cover and move synchronously below the anvil to receive the falling pyrophyllite residue particles in real time. During this process, the jet orifice jets air synchronously, forming a synergistic effect with the conical tip to purge the fine particles that may remain after mechanical shoveling, further improving the cleaning effect.

[0038] The top of the clamping seat 1 is rotatably connected with a rotating seat 3, and the cutting shovel plate 6 is slidably connected to the top of the rotating seat 3. In the production of synthetic diamond, due to physical and chemical reactions under high temperature and high pressure, such as the infiltration of molten catalyst into the microscopic scratches of the anvil and solidification, mechanical wear, or process parameter deviation, the synthetic block is prone to adhesion to the anvil. When there is unilateral adhesion of the synthetic block to the anvil in the cavity of the six-sided top press, at this time, to avoid damage to the robotic arm caused by forcibly pulling with the robotic arm, it is convenient to handle according to the structure of this application. Refer to Figure 4 , rotate the rotating seat 3 to arrange the conical tip of the cutting shovel plate 6 in the opposite direction to the clamping claws 2 to avoid mechanical interference. Drive the cutting shovel plate 6 to horizontally extend along the rotating seat 3, align the conical tip with the adhesion interface between the synthetic block and the anvil. Through the physical wedging action of the conical tip and the air impact force generated by the synchronous jetting of the jet orifice, the adhesion interface is gradually peeled off layer by layer. Using the spatial dislocation design, the clamping mechanism will not interfere with the cutting shovel plate 6 moving into the space between the synthetic block and the anvil, realizing the non-interference insertion of the cutting shovel plate 6.

[0039] The bottom end of the slitting shovel plate 6 is fixedly connected with a limit slider 5. The top end of the rotating seat 3 is provided with a guiding chute 4 for the horizontal sliding of the limit slider 5. The guiding chute 4 provides horizontal sliding guidance for the limit slider 5. Its horizontal movement mechanism adopts a screw drive scheme. The motor drives the screw to rotate. The screw penetrates through the limit slider 5 and is threadedly connected thereto. When the motor drives the screw to rotate, the limit slider 5 horizontally moves along the axis of the screw through thread transmission, and then drives the slitting shovel plate 6 to move synchronously.

[0040] The side surface of the clamping seat 1 is rotatably connected with a rotating shaft 8. The surface of the rotating shaft 8 is fixedly connected with a support frame 9. The support frame 9 is rigidly connected with the robotic arm through a connecting arm 10. When the rotating seat 3 drives the slitting shovel plate 6 to turn to the opposite direction of the clamping jaw 2, please refer to Figure 4 ., the motor synchronously drives the rotating shaft 8 to rotate, drives the support frame 9 and the connecting arm 10 to rotate around the axis of the rotating shaft 8, so that the posture of the robotic arm is the same as that of the clamping jaw 2. This design adjusts the angle of the rotating shaft 8, and when the slitting shovel plate 6 intervenes in the gap between the anvil and the synthesis block, the robotic arm synchronously completes the azimuth adjustment to avoid the spatial interference with the slitting shovel plate 6.

[0041] The specific scheme of this is as follows: Raw material preparation: Select high-purity graphite powder as the carbon element source. The layered structure of graphite can be transformed into the cubic structure of diamond under specific conditions. Add metal powders such as iron, cobalt, and nickel as catalysts. Similar to the role of a catalyst, its role is to promote the rearrangement of carbon atoms in graphite into the diamond structure under high temperature and high pressure, reducing the energy threshold required for the transformation. Prepare tiny natural or artificial diamond single crystals as seeds, and later diamond crystals will grow around the seed crystals.

[0042] Synthesis block assembly: Make a graphite column from graphite powder, catalyst metal powder and seed crystals according to a specific structure, and assemble the synthesis block.

[0043] High temperature and high pressure synthesis: Put the assembled synthesis block into a high temperature and high pressure device, such as a six-sided press. The device applies a huge pressure through the hydraulic system, and at the same time heats up by the resistance heating method to form an extreme environment inside the cavity. In this environment, the carbon atoms in graphite obtain enough energy to break away from the layered structure. Under the action of the catalyst metal, with the seed crystal as the core, they gradually arrange into the crystal structure of diamond and slowly grow into larger single crystals.

[0044] Cooling and disassembly: After the synthesis is completed, the device slowly cools down and reduces the pressure to make the diamond crystal stably formed, and take out the synthesis block.

[0045] Although embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A process for generating synthetic diamond single crystals, characterized in that, The specific steps are as follows: A. Mix graphite, master powder, and metal catalyst, granulate them, and then transfer them to the pressing workshop to press them into graphite columns. B. Mix pyrophyllite powder and boron nitride powder, and then make them into cylindrical blanks. Process a cylindrical cavity in the center of the pyrophyllite blank. C. Assemble the graphite column, pyrophyllite cylinder, plug assembly, heating assembly, and insulation assembly into a synthesis block. D. Use a robotic arm to carry a clamping mechanism to position the synthesis block in the center of the cavity of a six-sided top press. Purge the surface of the anvil in the equipment to remove dust particles. Then retract the clamping mechanism and start heating and pressurizing the six-sided top press. When both the temperature and pressure reach the set values, enter the heat preservation and pressure holding stage. E. After the heat preservation and pressure holding are completed, first stop heating and let the synthesis block cool naturally inside the cavity until the temperature drops below 500 °C. Then start to slowly reduce the pressure until the pressure drops to atmospheric pressure. F. Steadily take out the synthesis block from the cavity of the six-sided top press, disassemble the synthesis block, and obtain single crystal diamonds.

2. The synthetic diamond single crystal generation process according to claim 1, characterized in that, In step A, the graphite column is subjected to high-temperature reduction to remove moisture to obtain a pure graphite column.

3. A synthetic diamond single crystal generation process according to claim 1, characterized in that, In step C, the synthesis block is baked at 120 - 125 °C for 10 hours.

4. A process for generating single-crystal synthetic diamond according to claim 1, characterized in that, In step C, during the assembly of the synthesis block, fine pyrophyllite powder is coated in the gap between the heating assembly and the graphite column.

5. A synthetic diamond single crystal generation process according to claim 1, characterized in that, In step E, while the synthesis block is cooling naturally, argon is introduced to displace the air in the cavity.

6. The synthetic diamond single crystal generation process according to claim 1, characterized in that, In step F, the synthesis block is soaked in dilute hydrochloric acid, washed, crushed, electrolyzed, screened by ball milling, separated by a shaking table, dried, purified, and washed with pure water to obtain single crystal diamonds.

7. A synthetic diamond single crystal generation process according to claim 1, characterized in that, In step D, the clamping mechanism is provided with a jet orifice, and the jet orifice is connected to a jet pump. During the process of the clamping mechanism loading the synthesis block into the six-sided top press, the jet pump is started to purge the surface of the anvil through the jet orifice.

8. A process for generating synthetic diamond single crystals according to claim 1, characterized in that, The clamping mechanism includes a clamping seat (1) and clamping claws (2). A horizontally movable cutting shovel plate (6) is installed at the top of the clamping seat (1). In step F, after the synthesis block is taken out of the cavity, when the cutting shovel plate (6) is horizontally moved to shovel off the residual pyrophyllite on the surface of the anvil.

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