Preparation method of fine-grained industrial diamond

Abstract

The invention discloses a preparation method of fine-grained industrial diamond, which comprises the following steps: step 1, mixing 5-20% by mass of coarse-grained industrial diamond single crystal, 35-50% by mass of powder metal catalyst and 45-60% by mass of scale, and pressing into a primary synthetic rod; step 2, putting the preliminary synthesis rod into a vacuum reduction furnace, removing oxygen element in the catalyst through vacuum high-temperature reduction, and adding liquid nitrogen for cooling after reduction is finished, so as to prepare a finished product synthesis rod; 3, synthesizing the industrial diamond on the finished product synthesis rod under the conditions of high temperature and high pressure; step 4, crushing, electrolyzing and purifying the synthesized synthetic rod to obtain the flocculent continuous crystal diamond; 5, the flocculent continuous crystal diamond is dried and subjected to ball milling, then particle size screening is carried out, and the fine-particle-size industrial diamond is prepared, the fine-particle-size industrial diamond with the particle size ranging from 100 micrometers to 220 micrometers in a concentrated mode can be obtained through the method, the process is simple, and the manufacturing cost is low.

Description

Technical Field

[0001] This invention belongs to the field of diamond synthesis technology, specifically relating to a method for preparing fine-grained industrial diamond. Background Technology

[0002] Industrial diamond, due to its extremely high hardness and wear resistance, is widely used in many industrial fields such as abrasives, grinding tools, and machining. Different diamond particle sizes correspond to different specific applications, making its synthesis and subsequent processing technologies crucial. Currently, my country mainly uses a hinged beam six-sided press to synthesize industrial diamond under high temperature and pressure conditions. A typical process flow includes: mixing Fe70Ni30 alloy powder catalyst with flake graphite in a specific mass ratio and pressing it into a synthetic rod; subjecting the synthetic rod to vacuum reduction to remove oxygen; and then completing the diamond synthesis in the six-sided press. The synthesized product needs to be crushed and electrolyzed to separate and recover the iron-nickel catalyst, and then purified, dried, and sieved to obtain the target product.

[0003] In existing purification processes, diamond and graphite are typically separated by stratification on a shaking table due to differences in density and particle size, with the denser diamond at the bottom and graphite at the top. However, for fine-grained industrial diamonds, their small crystal size leads to a significantly longer suspension time in water, reducing the difference in sedimentation behavior between them and the upper graphite layer. This drastically worsens the stratification effect, making effective separation difficult. Considering both economic efficiency and production efficiency, in practice, most fine-grained industrial diamonds are disposed of as hazardous waste along with graphite, resulting in substantial waste. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing fine-grained industrial diamond, which solves the problem in the prior art that fine-grained diamond and graphite are not easily separated during the purification process.

[0005] The technical solution adopted in this invention is a method for preparing fine-grained industrial diamond, comprising the following steps: Step 1: Mix 5%-20% coarse-grained industrial diamond single crystals, 35%-50% powdered metal catalysts, and 45%-60% flake graphite according to the mass percentage, and press them into preliminary synthetic rods. Step 2: Place the preliminary synthetic rod from Step 1 into a vacuum reduction furnace and remove the oxygen element from the metal catalyst by vacuum high-temperature reduction. After the reduction is completed, add liquid nitrogen for cooling to obtain the finished synthetic rod. Step 3: Place the finished synthetic rod from Step 2 into a six-sided press and synthesize industrial diamond under high temperature and high pressure conditions. Step 4: After crushing, electrolyzing and purifying the synthetic rod synthesized in Step 3, flocculent intercrystalline diamond is obtained; Step 5: Dry the flocculent diamond from Step 4, ball mill it, and then sieve it to obtain fine-grained industrial diamond.

[0006] The invention is further characterized in that, The specific process of step 1 is as follows: Step 1.1: Mix 5%-20% coarse-grained industrial diamond single crystals, 35%-50% powdered metal catalysts, and 45%-60% flake graphite according to the mass percentage to prepare raw materials. Step 1.2: Granulate the raw materials using a roller mill to a particle size of 5mm~10mm, thus preparing raw material granules; Step 1.3: Weigh the raw material particles quantitatively, press them using a four-column press at a hydraulic pressure of 10MPa-30MPa, and prepare preliminary synthetic rods.

[0007] In step 1.1, the powdered metal catalyst is composed of any one or more of Fe, Ni, Co, and Mn. The particle size of the powdered metal catalyst is 38μm-74μm; the particle size of the flake graphite is 38μm-74μm; the particle size of the coarse-grained industrial diamond is 300μm-600μm; the total purity of the metal elements in the powdered metal catalyst is not less than 99 wt%, and the purity of the flake graphite is not less than 99.9 wt%.

[0008] The vacuum degree of the vacuum high-temperature reduction in step 2 is no greater than Pa, the temperature for vacuum high-temperature reduction is 950℃~1150℃, and the reduction time is 5h~15h.

[0009] Step 3, with its high temperature and high pressure conditions, is specifically divided into two stages, as follows: The first stage: the internal pressure of the synthesis chamber of the six-sided top press is 2GPa~3GPa, the temperature is 1200℃~1350℃, and the duration is 300 seconds~600 seconds; The second stage: The internal pressure of the synthesis chamber of the six-sided top press is 5GPa~5.5GPa, the temperature is 1150℃~1250℃, and the duration is 500 seconds~2000 seconds. During the second stage, when the hydraulic pressure of the six-sided top press is continuously increased, the hydraulic pressure increase process is divided into multiple consecutive control time periods of equal duration. In each control time period, the hydraulic pressure is linearly increased at a constant first speed. The first speeds corresponding to different control time periods are different from each other, and along the time axis, the first speeds of two adjacent control time periods increase segment by segment.

[0010] The specific process of step 4 is as follows: Step 4.1: Crush the synthetic rods synthesized in step 3. The particle size of the crushed synthetic rods shall not exceed 5 mm, and the synthetic rods shall be prepared into synthetic rod powder. Step 4.2: The synthetic rod powder is placed in an electrolytic cell for electrolysis. The electrolyte in the electrolytic cell is an acidic solution of nickel sulfate and sodium chloride with a pH of 2-3. After electrolysis, a mixture of diamond and graphite is obtained and carbon mud is prepared. Step 4.3: Place the carbon mud on a shaker to purify the diamond and obtain flocculent intercrystalline diamond.

[0011] The specific process of step 5 is as follows: Step 5.1: Dry the flocculent diamond from Step 4. The drying process is carried out in an oxygen environment at a temperature of 500℃~700℃. After drying, use a sieve to sieve and obtain flocculent diamond. Step 5.2: Place the flocculent diamond into a ball mill for ball milling at a ball milling speed of 50 r / min-200 r / min for 1 h-10 h to obtain fine-grained diamond single crystals. Step 5.3: Perform particle size sieving on fine-grained industrial diamond single crystals to obtain fine-grained industrial diamond.

[0012] In step 5.3, the fine-grained industrial diamond has a particle size distribution of 100μm~220μm.

[0013] The beneficial effects of this invention are This invention discloses a method for preparing fine-grained industrial diamond. The method first synthesizes flocculent interlocking diamond, which can be separated from graphite during the purification process. Then, the flocculent interlocking diamond is ball-milled and sieved to obtain fine-grained industrial diamond with a particle size distribution of 100μm~220μm. The process is simple and has low manufacturing costs. Simultaneously, the method incorporates coarse-grained industrial diamond single crystals as seed crystals. After a secondary synthesis, the diamond single crystals transform into flocculent interlocking diamond, facilitating the separation of graphite. Attached Figure Description

[0014] Figure 1 This is a process flow diagram of the preparation method of fine-grained industrial diamond of the present invention; Figure 2 This is a size distribution diagram of the flocculent diamond in Embodiment 1 of the present invention; Figure 3 This is a size distribution diagram of the flocculent diamond after ball milling in Embodiment 1 of the present invention. Detailed Implementation

[0015] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0016] The technical solution provided by this invention is a method for preparing fine-grained industrial diamond, such as... Figure 1 As shown, it includes the following steps: Step 1: According to the mass percentage, mix 5%-20% coarse-grained industrial diamond single crystals, 35%-50% powdered metal catalyst, and 45%-60% flake graphite, and press them into a preliminary synthesis rod. The specific process is as follows: Step 1.1: According to the mass percentage, mix 5%-20% coarse-grained industrial diamond single crystals, 35%-50% powdered metal catalyst, and 45%-60% flake graphite to prepare raw materials. The powdered metal catalyst is composed of any one or more of Fe, Ni, Co, and Mn, with a particle size of 38μm-74μm; the flake graphite has a particle size of 38μm-74μm; and the coarse-grained industrial diamond has a particle size of 300μm-600μm. The total purity of the metal elements in the powdered metal catalyst is not less than 99 wt%, and the purity of the flake graphite is not less than 99.9 wt%. Using coarse-grained industrial diamond as a seed crystal, under high temperature and high pressure conditions, the seed crystal region will preferentially synthesize flocculent interlocking diamond, resulting in a high yield. At the same time, coarse-grained industrial diamond single crystals are added as seed crystals, and after secondary synthesis, the diamond single crystals become flocculent interlocking diamond, which facilitates the separation of graphite.

[0017] Step 1.2: Granulate the raw materials using a roller mill to a particle size of 5-10 mm, thus preparing raw material granules; Step 1.3: Weigh the raw material particles quantitatively, press them using a four-column press at a hydraulic pressure of 10MPa-30MPa, and prepare preliminary synthetic rods.

[0018] Step 2: Place the preliminary synthetic rod from Step 1 into a vacuum reduction furnace and remove the oxygen element from the metal catalyst by vacuum high-temperature reduction. After the reduction is completed, add liquid nitrogen for cooling to obtain the finished synthetic rod. The vacuum degree of the vacuum high-temperature reduction in step 2 is no greater than Pa, the temperature for vacuum high-temperature reduction is 950℃~1150℃, and the reduction time is 5h~15h.

[0019] Step 3: Place the finished synthetic rod from Step 2 into a six-sided press and synthesize industrial diamond under high temperature and high pressure conditions. The high temperature and high pressure conditions are specifically carried out in two stages, as detailed below: The first stage: the internal pressure of the synthesis chamber of the six-sided top press is 2GPa~3GPa, the temperature is 1200℃~1350℃, and the duration is 300 seconds~600 seconds; The second stage: The internal pressure of the synthesis chamber of the six-sided press is 5GPa~5.5GPa, the temperature is 1150℃~1250℃, and the duration is 500 seconds~2000 seconds. During the second stage, when the hydraulic pressure of the six-sided press is continuously increased, the pressurization process is divided into multiple consecutive control time periods of equal duration. Within each control time period, the hydraulic pressure is linearly increased at a constant first speed to promote diamond growth. The first speeds corresponding to different control time periods are different, and along the time axis, the first speeds of two adjacent control time periods increase segment by segment. The magnitude of the hydraulic pressure increase speed can be selected according to the actual working conditions.

[0020] Step 4: The synthetic rod synthesized in Step 3 is crushed, electrolyzed, and purified to obtain flocculent intercrystalline diamond. The specific process is as follows: Step 4.1: Crush the synthetic rods synthesized in step 3. The particle size of the crushed synthetic rods shall not exceed 5 mm, and the synthetic rods shall be prepared into synthetic rod powder. Step 4.2: The synthetic rod powder is placed in an electrolytic cell for electrolysis. The electrolyte in the electrolytic cell is an acidic solution of nickel sulfate and sodium chloride with a pH of 2-3. After electrolysis, a mixture of diamond and graphite is obtained and carbon mud is prepared. Step 4.3: Place the carbon mud on a shaker to purify the diamond and obtain flocculent diamond. Because the flocculent diamond has a coarser particle size and a heavier weight, it can separate into layers with graphite during the purification process, thus maximizing the collection of diamond during the purification process.

[0021] Step 5: Dry the flocculent diamond from Step 4, ball mill it, and then sieve it to obtain fine-grained industrial diamond. The specific process is as follows: Step 5.1: Dry the flocculent diamond from step 4. The drying process is carried out in an oxygen environment to remove trace amounts of graphite impurities from the diamond surface. The drying temperature is 500℃~700℃. After drying, the diamond is sieved to obtain flocculent diamond. Step 5.2: Place the flocculent diamond into a ball mill for ball milling at a ball milling speed of 50 r / min-200 r / min for 1 h-10 h to obtain fine-grained diamond single crystals. Step 5.3: Fine-grained industrial diamond single crystals are sieved to obtain fine-grained industrial diamond. The particle size distribution of the fine-grained industrial diamond obtained after sieving is 100μm~220μm, and the crystal form is relatively complete. The whole process is simple and easy to industrialize.

[0022] The fine-grained industrial diamond of this invention is specifically embodied in the following embodiments: The method for preparing fine-grained industrial diamond according to the present invention is illustrated in the following specific embodiments: Example 1 This embodiment uses the above-described method for preparing fine-grained industrial diamond, including the following steps: Step 1: According to the mass percentage, mix 5% coarse-grained industrial diamond single crystals, 45% powdered metal catalyst, and 50% flakes, and press them into a preliminary synthesis rod, as detailed below: Step 1.1: According to the mass percentage, mix 5% industrial diamond single crystal with a particle size of 360μm~425μm, 45% Fe70Ni30 alloy powder with a particle size of 50μm~74μm, and 50% flake graphite with a particle size of 50μm~74μm to prepare raw materials. Step 1.2: Granulate the raw material using a roller mill to a particle size of 5mm, thus preparing raw material granules; Step 1.3: Weigh 200g of raw material granules and press them using a four-column press at a hydraulic pressure of 15MPa to prepare cylindrical synthetic rods. Step 2: Place the preliminary synthesis rod from Step 1 into a vacuum reduction furnace, and then... (The sentence is incomplete and requires more context to translate accurately.) Pa was reduced at 1100℃ for 10 hours. After the reduction process, liquid nitrogen was added for cooling, and a synthetic rod was prepared. Step 3: The finished synthetic rod from Step 2 is subjected to high temperature and high pressure conditions to synthesize industrial diamond, as detailed below: The synthetic rod is placed in a six-sided press with a cylinder diameter of Φ650mm for industrial diamond synthesis. In the first stage, the internal pressure of the synthesis chamber of the six-sided press is 2GPa, the heating temperature is 1300℃, and the duration is 400 seconds. In the second stage, the internal pressure of the synthesis chamber of the six-sided press is 5GPa, the heating temperature is 1200℃, and the duration is 1600 seconds. When using a six-sided press with a cylinder diameter of Φ650mm, the oil pressure in the first stage is 50~60MPa, the initial oil pressure in the second stage is 72MPa, and then the oil pressure gradually increases every 100 seconds to 73.1 / 74.4 / 75.9 / 77.6 / 79.5 / 81.6 / 83.9 / 86.4 / 89.1 / 92MPa.

[0023] Step 4: The synthetic rod synthesized in Step 3 is crushed, electrolyzed, and purified to obtain flocculent intercrystalline diamond. The specific process is as follows: Step 4.1: Crush the synthesized synthetic rods. The particle size of the crushed synthetic rods should not be greater than 5 mm to prepare synthetic rod powder. Step 4.2: The synthetic rod powder is placed in an electrolytic cell for electrolysis. The electrolyte is an acidic solution of nickel sulfate and sodium chloride with a pH of 2. After electrolysis, a mixture of diamond and graphite is obtained and carbon mud is prepared. Step 4.3: Place the carbon mud on a shaking table to purify the diamond, obtaining flocculent intercrystalline diamond, such as... Figure 2 As shown, the size distribution of flocculent diamond is between 400 and 700 μm. Because the flocculent diamond has a coarser particle size and a heavier weight, it can separate from graphite in the purification process, thus maximizing the collection of diamond in the purification process.

[0024] Step 5: Dry the flocculent diamond from Step 4, ball mill it, and then perform particle size sieving to obtain fine-grained industrial diamond. The specific process is as follows: Step 5.1: After drying the industrial diamond, use a 50-mesh sieve for preliminary particle size separation. The material on the sieve mainly consists of diamond single crystals and impurities, while the material under the sieve mainly consists of flocculent diamond. Step 5.2: Place the flocculent diamond crystals into a ball mill for ball milling at a speed of 50 r / min for 5 hours to obtain fine-grained diamond single crystals, such as... Figure 3 As shown, after spheroidizing flocculent diamond, fine-grained diamond single crystals are obtained, with their size distribution between 74 and 250 μm. Step 5.3: Perform particle size sieving on the fine-grained industrial diamond single crystals to obtain fine-grained industrial diamonds. The particle size distribution of fine-grained industrial diamonds is 100μm~140μm.

[0025] Example 2 This embodiment uses the above-described method for preparing fine-grained industrial diamond, including the following steps: Step 1: According to the mass percentage, mix 10% coarse-grained industrial diamond single crystals, 35% powdered metal catalyst, and 45% flakes, and press them into a preliminary synthesis rod. The specific process is as follows: Step 1.1: Calculate by mass ratio, mix 10% of industrial diamond single crystals with a particle size of 0.2μm~360μm, 40% of Fe70Ni30 alloy powder with a particle size of 50μm~74μm, and 50% of flake graphite with a particle size of 50μm~74μm to prepare raw materials; Step 1.2: Granulate the raw material using a roller mill to a particle size of 5mm, thus preparing raw material granules; Step 1.3: Weigh 300g of raw material particles and press them using a four-column press at a hydraulic pressure of 10MPa to prepare cylindrical synthetic rods. Step 2: Place the preliminary synthesis rod from Step 1 into a vacuum reduction furnace, and then... (The sentence is incomplete and requires more context to translate accurately.) The reduction was carried out at 950℃ for 5 hours. After the reduction was completed, liquid nitrogen was added for cooling to prepare a synthetic rod. Step 3: The finished synthetic rod from Step 2 is subjected to high temperature and high pressure conditions to synthesize industrial diamond, as detailed below: The synthetic rod is placed in a six-sided press with a cylinder diameter of Φ650mm for industrial diamond synthesis. The first stage involves a synthesis chamber pressure of 2.5GPa and a heating temperature of 1200℃ for 300 seconds. The second stage involves a synthesis chamber pressure of 5.2GPa and a heating temperature of 1150℃ for 500 seconds. When using a six-sided press with a cylinder diameter of Φ650mm, the oil pressure in the first stage is 50~60MPa, and the initial oil pressure in the second stage is 68MPa, subsequently increasing every 100 seconds to 69 / 70.2 / 71.6 / 73.2 / 75 / 77 / 79.2 / 81.6 / 84.2 / 87MPa.

[0026] Step 4: The synthetic rod synthesized in Step 3 is crushed, electrolyzed, and purified to obtain flocculent intercrystalline diamond. The specific process is as follows: Step 4.1: Crush the synthesized synthetic rods. The particle size of the crushed synthetic rods should not be greater than 5 mm to prepare synthetic rod powder. Step 4.2: The synthetic rod powder is placed in an electrolytic cell for electrolysis. The electrolyte is an acidic solution of nickel sulfate and sodium chloride with a pH of 2.5. After electrolysis, a mixture of diamond and graphite is obtained, which is then prepared as carbon mud. Step 4.3: Place the carbon mud on a shaker to purify the diamond and obtain flocculent intercrystalline diamond; Step 5: Dry the flocculent diamond from Step 4, ball mill it, and then perform particle size sieving to obtain fine-grained industrial diamond. The specific process is as follows: Step 5.1: After drying the industrial diamond, it is sieved using a 50-mesh sieve. The main components of the material on the sieve are diamond single crystals and impurities, while the main components of the material under the sieve are flocculent diamond. Step 5.2: Place the flocculent diamond into a ball mill for ball milling at a ball milling speed of 150 r / min for 1 hour to obtain fine-grained diamond single crystals. Step 5.3: Perform particle size sieving on the fine-grained industrial diamond single crystals to obtain fine-grained industrial diamonds with a particle size distribution of 140μm~180μm.

[0027] Example 3 This embodiment uses the above-described method for preparing fine-grained industrial diamond, including the following steps: This embodiment provides a method for preparing the fine-grained industrial diamond in Example 2 above, including the following steps: Step 1: According to the mass percentage, mix 20% coarse-grained industrial diamond single crystals, 50% powdered metal catalyst, and 60% flakes, and press them into a preliminary synthesis rod. The specific process is as follows: Step 1.1: Calculate by mass ratio, mix 10% of industrial diamond single crystal with a particle size of 300μm~360μm, 40% of Fe70Ni30 alloy powder with a particle size of 50μm~74μm, and 50% of flake graphite with a particle size of 50μm~74μm to prepare raw materials; Step 1.2: Granulate the raw materials using a roller mill to a particle size of 10mm, thus preparing raw material granules; Step 1.3: Weigh 150g of raw material particles and press them using a four-column press at a hydraulic pressure of 30MPa to prepare cylindrical synthetic rods. Step 2: Place the preliminary synthesis rod from Step 1 into a vacuum reduction furnace, and then... (The sentence is incomplete and requires more context to translate accurately.) The reduction was carried out at 1150℃ for 15 hours. After the reduction was completed, liquid nitrogen was added for cooling to prepare a synthetic rod. Step 3: The finished synthetic rod from Step 2 is subjected to high temperature and high pressure conditions to synthesize industrial diamond, as detailed below: The synthetic rod is placed in a six-sided press with a cylinder diameter of Φ650mm for industrial diamond synthesis. The first stage involves a synthesis chamber pressure of 3GPa and a heating temperature of 1250℃ for 600 seconds. The second stage involves a synthesis chamber pressure of 5.4GPa and a heating temperature of 1250℃ for 2000 seconds. With a cylinder diameter of Φ650mm, the oil pressure in the first stage is 50~60MPa, and the initial oil pressure in the second stage is 67MPa, subsequently increasing every 100 seconds to 68.1 / 84 / 69.3 / 70.4 / 72.3 / 74.1 / 76.1 / 78.3 / 80.7 / 83.3MPa.

[0028] Step 4: The synthetic rod synthesized in Step 3 is crushed, electrolyzed, and purified to obtain flocculent intercrystalline diamond. The specific process is as follows: Step 4.1: Crush the synthesized synthetic rods. The particle size of the crushed synthetic rods should not be greater than 5 mm to prepare synthetic rod powder. Step 4.2: The synthetic rod powder is placed in an electrolytic cell for electrolysis. The electrolyte is an acidic solution of nickel sulfate and sodium chloride with a pH of 3. After electrolysis, a mixture of diamond and graphite is obtained and carbon mud is prepared. Step 4.3: Place the carbon mud on a shaker to purify the diamond and obtain flocculent intercrystalline diamond; Step 5: Dry the flocculent diamond from Step 4, ball mill it, and then perform particle size sieving to obtain fine-grained industrial diamond. The specific process is as follows: Step 5.1: After drying the industrial diamond, it is sieved using a 50-mesh sieve. The main components of the material on the sieve are diamond single crystals and impurities, while the main components of the material under the sieve are flocculent diamond. Step 5.2: Place the flocculent diamond into a ball mill for ball milling at a ball milling speed of 200 r / min for 10 h to obtain fine-grained diamond single crystals. Step 5.3: Perform particle size sieving on the fine-grained industrial diamond single crystals to obtain fine-grained industrial diamonds with a particle size distribution of 140μm~180μm.

[0029] Example 4 This embodiment uses the above-described method for preparing fine-grained industrial diamond, including the following steps: Step 1: According to the mass percentage, mix 20% coarse-grained industrial diamond single crystals, 35% powdered metal catalyst, and 45% flakes, and press them into a preliminary synthesis rod. The specific process is as follows: Step 1.1: Calculate by mass ratio, mix 20% industrial diamond single crystal with a particle size of 300μm~360μm, 35% Fe70Ni30 alloy powder with a particle size of 50μm~74μm, and 45% flake graphite with a particle size of 50μm~74μm to prepare raw materials; Step 1.2: Granulate the raw materials using a roller mill to a particle size of 10mm, thus preparing raw material granules; Step 1.3: Weigh 150g of raw material particles and press them using a four-column press at a hydraulic pressure of 17MPa to prepare cylindrical synthetic rods. Step 2: Place the preliminary synthesis rod from Step 1 into a vacuum reduction furnace, and then... (The sentence is incomplete and requires more context to translate accurately.) The reduction was carried out at 1150℃ for 10 hours. After the reduction was completed, liquid nitrogen was added for cooling to prepare a synthetic rod. Step 3: The finished synthetic rod from Step 2 is subjected to high temperature and high pressure conditions to synthesize industrial diamond, as detailed below: The synthetic rod is placed in a six-sided press with a cylinder diameter of Φ650mm for industrial diamond synthesis. The first stage involves a synthesis chamber pressure of 3GPa and a heating temperature of 1250℃ for 600 seconds. The second stage involves a synthesis chamber pressure of 5.5GPa and a heating temperature of 1250℃ for 1450 seconds. When using a Φ650mm cylinder diameter press, the oil pressure in the first stage is 50-60MPa, and the initial oil pressure in the second stage is 75MPa, subsequently increasing every 145 seconds to 76 / 77.2 / 78.6 / 80.2 / 82 / 84 / 86.2 / 88.6 / 91.2 / 94MPa.

[0030] Step 4: The synthetic rod synthesized in Step 3 is crushed, electrolyzed, and purified to obtain flocculent intercrystalline diamond. The specific process is as follows: Step 4.1: Crush the synthesized synthetic rods. The particle size of the crushed synthetic rods should not be greater than 5 mm to prepare synthetic rod powder. Step 4.2: The synthetic rod powder is placed in an electrolytic cell for electrolysis. The electrolyte is an acidic solution of nickel sulfate and sodium chloride with a pH of 2.5. After electrolysis, a mixture of diamond and graphite is obtained, which is then prepared as carbon mud. Step 4.3: Place the carbon mud on a shaker to purify the diamond and obtain flocculent intercrystalline diamond; Step 5: Dry the flocculent diamond from Step 4, ball mill it, and then perform particle size sieving to obtain fine-grained industrial diamond. The specific process is as follows: Step 5.1: After drying the industrial diamond, it is sieved using a 50-mesh sieve. The main components of the material on the sieve are diamond single crystals and impurities, while the main components of the material under the sieve are flocculent diamond. Step 5.2: Place the flocculent diamond into a ball mill for ball milling at a ball milling speed of 150 r / min for 15 h to obtain fine-grained diamond single crystals. Step 5.3: Perform particle size sieving on the fine-grained industrial diamond single crystals to obtain fine-grained industrial diamonds with a particle size distribution of 160μm~200μm.

[0031] Example 5 This embodiment uses the above-described method for preparing fine-grained industrial diamond, including the following steps: Step 1: According to the mass percentage, mix 5% coarse-grained industrial diamond single crystals, 45% powdered metal catalyst, and 50% flakes, and press them into a preliminary synthesis rod. The specific process is as follows: Step 1.1: Calculate by mass ratio, mix 5% industrial diamond single crystal with a particle size of 600μm~700μm, 35% Fe70Ni30 alloy powder with a particle size of 50μm~74μm, and 45% flake graphite with a particle size of 50μm~74μm to prepare raw materials; Step 1.2: Granulate the raw materials using a roller mill to a particle size of 10mm, thus preparing raw material granules; Step 1.3: Weigh 150g of raw material particles and press them using a four-column press at a hydraulic pressure of 17MPa to prepare cylindrical synthetic rods. Step 2: Place the preliminary synthesis rod from Step 1 into a vacuum reduction furnace, and then... (The sentence is incomplete and requires more context to translate accurately.) The reduction was carried out at 1150℃ for 10 hours. After the reduction was completed, liquid nitrogen was added for cooling to prepare a synthetic rod. Step 3: The finished synthetic rod from Step 2 is subjected to high temperature and high pressure conditions to synthesize industrial diamond, as detailed below: The synthetic rod is placed in a six-sided press with a cylinder diameter of Φ650mm for industrial diamond synthesis. The first stage involves a synthesis chamber pressure of 3GPa and a heating temperature of 1250℃ for 600 seconds. The second stage involves a synthesis chamber pressure of 5.5GPa and a heating temperature of 1250℃ for 1450 seconds. When using a Φ650mm cylinder diameter press, the oil pressure in the first stage is 50-60MPa, and the initial oil pressure in the second stage is 80MPa, subsequently increasing every 200 seconds to 81.1 / 82.4 / 83.9 / 85.6 / 87.5 / 89.6 / 91.9 / 94.4 / 97.1 / 100MPa.

[0032] Step 4: The synthetic rod synthesized in Step 3 is crushed, electrolyzed, and purified to obtain flocculent intercrystalline diamond. The specific process is as follows: Step 4.1: Crush the synthesized synthetic rods. The particle size of the crushed synthetic rods should not be greater than 5 mm to prepare synthetic rod powder. Step 4.2: The synthetic rod powder is placed in an electrolytic cell for electrolysis. The electrolyte is an acidic solution of nickel sulfate and sodium chloride with a pH of 2.5. After electrolysis, a mixture of diamond and graphite is obtained, which is then prepared as carbon mud. Step 4.3: Place the carbon mud on a shaker to purify the diamond and obtain flocculent intercrystalline diamond; Step 5: Dry the flocculent diamond from Step 4, ball mill it, and then perform particle size sieving to obtain fine-grained industrial diamond. The specific process is as follows: Step 5.1: After drying the industrial diamond, it is sieved using a 50-mesh sieve. The main components of the material on the sieve are diamond single crystals and impurities, while the main components of the material under the sieve are flocculent diamond. Step 5.2: Place the flocculent diamond into a ball mill for ball milling at a ball milling speed of 150 r / min for 4 hours to obtain fine-grained diamond single crystals. Step 5.3: Perform particle size sieving on the fine-grained industrial diamond single crystals to obtain fine-grained industrial diamonds with a particle size distribution of 100μm~140μm.

[0033] Example 6 This embodiment uses the above-described method for preparing fine-grained industrial diamond, including the following steps: Step 1: According to the mass percentage, mix 20% coarse-grained industrial diamond single crystals, 35% powdered metal catalyst, and 45% flakes, and press them into a preliminary synthesis rod. The specific process is as follows: Step 1.1: Calculate by mass ratio, mix 20% industrial diamond single crystal with a particle size of 300μm~360μm, 35% Fe70Ni30 alloy powder with a particle size of 50μm~74μm, and 45% flake graphite with a particle size of 50μm~74μm to prepare raw materials; Step 1.2: Granulate the raw materials using a roller mill to a particle size of 10mm, thus preparing raw material granules; Step 1.3: Weigh 150g of raw material particles and press them using a four-column press at a hydraulic pressure of 17MPa to prepare cylindrical synthetic rods. Step 2: Place the preliminary synthesis rod from Step 1 into a vacuum reduction furnace, and then... (The sentence is incomplete and requires more context to translate accurately.) The reduction was carried out at 1150℃ for 10 hours. After the reduction was completed, liquid nitrogen was added for cooling to prepare a synthetic rod. Step 3: The finished synthetic rod from Step 2 is subjected to high temperature and high pressure conditions to synthesize industrial diamond, as detailed below: The synthetic rod is placed in a six-sided press with a cylinder diameter of Φ650mm for industrial diamond synthesis. The first stage involves a synthesis chamber pressure of 3GPa and a heating temperature of 1250℃ for 400 seconds. The second stage involves a synthesis chamber pressure of 5.5GPa and a heating temperature of 1250℃ for 1000 seconds. With a cylinder diameter of Φ650mm, the oil pressure in the first stage is 50~60MPa, and the initial oil pressure in the second stage is 82MPa, subsequently increasing every 100 seconds to 82.9 / 84 / 85.3 / 86.8 / 88.5 / 90.4 / 92.5 / 94.8 / 97.3 / 99.8MPa.

[0034] Step 4: The synthetic rod synthesized in Step 3 is crushed, electrolyzed, and purified to obtain flocculent intercrystalline diamond. The specific process is as follows: Step 4.1: Crush the synthesized synthetic rods. The particle size of the crushed synthetic rods should not be greater than 5 mm to prepare synthetic rod powder. Step 4.2: The synthetic rod powder is placed in an electrolytic cell for electrolysis. The electrolyte is an acidic solution of nickel sulfate and sodium chloride with a pH of 2.5. After electrolysis, a mixture of diamond and graphite is obtained, which is then prepared as carbon mud. Step 4.3: Place the carbon mud on a shaker to purify the diamond and obtain flocculent intercrystalline diamond; Step 5: Dry the flocculent diamond from Step 4, ball mill it, and then perform particle size sieving to obtain fine-grained industrial diamond. The specific process is as follows: Step 5.1: After drying the industrial diamond, it is sieved using a 50-mesh sieve. The main components of the material on the sieve are diamond single crystals and impurities, while the main components of the material under the sieve are flocculent diamond. Step 5.2: Place the flocculent diamond into a ball mill for ball milling at a ball milling speed of 130 r / min for 10 h to obtain fine-grained diamond single crystals. Step 5.3: Perform particle size sieving on the fine-grained industrial diamond single crystals to obtain fine-grained industrial diamonds with a particle size distribution of 160μm~220μm.

Claims

1. A method for preparing fine-grained industrial diamond, characterized in that, Includes the following steps: Step 1: Mix 5%-20% coarse-grained industrial diamond single crystals, 35%-50% powdered metal catalysts, and 45%-60% flake graphite according to the mass percentage, and press them into preliminary synthetic rods. Step 2: Place the preliminary synthetic rod into a vacuum reduction furnace, reduce it under vacuum at high temperature, and then add liquid nitrogen for cooling to obtain the finished synthetic rod. Step 3: Place the finished synthetic rod into a six-sided press and synthesize industrial diamond under high temperature and high pressure conditions; Step 4: After crushing, electrolyzing and purifying the synthetic rod synthesized in Step 3, flocculent intercrystalline diamond is obtained; Step 5: Dry the flocculent diamond, ball mill it, and then sieve it to obtain fine-grained industrial diamond.

2. The method for preparing fine-grained industrial diamond according to claim 1, characterized in that, The specific process of step 1 is as follows: Step 1.1: Mix 5%-20% coarse-grained industrial diamond single crystals, 35%-50% powdered metal catalysts, and 45%-60% flake graphite according to the mass percentage to prepare raw materials. Step 1.2: Granulate the raw materials using a roller mill to a particle size of 5mm~10mm, thus preparing raw material granules; Step 1.3: Weigh the raw material particles quantitatively, press them using a four-column press at a hydraulic pressure of 10MPa-30MPa, and prepare preliminary synthetic rods.

3. The method for preparing fine-grained industrial diamond according to claim 2, characterized in that, The powdered metal catalyst mentioned in step 1.1 is specifically composed of any one or more of Fe, Ni, Co, and Mn, with a particle size of 38μm-74μm; the particle size of the flake graphite is 38μm-74μm; the particle size of the coarse-grained industrial diamond is 300μm-600μm; the total purity of the metal elements in the powdered metal catalyst is not less than 99 wt%, and the purity of the flake graphite is not less than 99.9 wt%.

4. The method for preparing fine-grained industrial diamond according to claim 1, characterized in that, The vacuum degree of the vacuum high-temperature reduction in step 2 is no greater than Pa, the temperature of the vacuum high-temperature reduction is 950℃~1150℃, and the reduction time of the vacuum high-temperature reduction is 5h~15h.

5. The method for preparing fine-grained industrial diamond according to claim 1, characterized in that, The high temperature and high pressure conditions described in step 3 are specifically carried out in two stages, as follows: The first stage: the internal pressure of the synthesis chamber of the six-sided top press is 2GPa~3GPa, the temperature is 1200℃~1350℃, and the duration is 300 seconds~600 seconds; The second stage: The internal pressure of the synthesis chamber of the six-sided top press is 5GPa~5.5GPa, the temperature is 1150℃~1250℃, and the duration is 500 seconds~2000 seconds. During the second stage, when the hydraulic pressure of the six-sided top press is continuously increased, the hydraulic pressure increase process is divided into multiple consecutive control time periods of equal duration. Within each control time period, the hydraulic pressure is linearly increased at a constant first speed. The first speeds corresponding to different control time periods are different from each other, and along the time axis, the first speeds of two adjacent control time periods increase segment by segment.

6. The method for preparing fine-grained industrial diamond according to claim 1, characterized in that, The specific process of step 4 is as follows: Step 4.1: Crush the synthetic rods synthesized in step 3. The particle size of the crushed synthetic rods shall not be greater than 5 mm, and the synthetic rods shall be prepared into synthetic rod powder. Step 4.2: The synthetic rod powder is placed in an electrolytic cell for electrolysis. The electrolyte in the electrolytic cell is an acidic solution of nickel sulfate and sodium chloride, and the pH value of the acidic solution is 2-3. After electrolysis, a mixture of diamond and graphite is obtained and carbon mud is prepared. Step 4.3: Place the carbon mud on a shaker to purify the diamond and obtain flocculent intercrystalline diamond.

7. The method for preparing fine-grained industrial diamond according to claim 1, characterized in that, The specific process of step 5 is as follows: Step 5.1: Dry the flocculent diamond from Step 4. The drying process is carried out in an oxygen environment at a temperature of 500℃~700℃. After drying, use a sieve to sieve and obtain flocculent diamond. Step 5.2: Place the flocculent diamond into a ball mill for ball milling at a ball milling speed of 50 r / min-200 r / min for 1 h-10 h to obtain fine-grained diamond single crystals. Step 5.3: Perform particle size sieving on fine-grained industrial diamond single crystals to obtain fine-grained industrial diamond.

8. The method for preparing fine-grained industrial diamond according to claim 7, characterized in that, The fine-grained industrial diamonds mentioned in step 5.3 have a particle size distribution of 100μm to 220μm.

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