High temperature and high pressure method for industrial diamond seed synthesis

Abstract

The application discloses a high-temperature and high-pressure industrial diamond seed pretreatment synthesis method, which comprises the following steps: S1, removing oil stains and impurities on the surface of the diamond seed, and washing the diamond seed with deionized water until no residual alkaline solution is left; S2, sequentially performing sensitization treatment and activation treatment on the treated diamond seed, and then placing the diamond seed in a chemical nickel plating solution to perform chemical nickel plating; S3, placing the diamond seed after the formation of a nickel layer in an electroplating solution, and performing electroplating by adopting a barrel plating mode to form a catalyst alloy coating; and S4, uniformly mixing the diamond seed after the formation of the catalyst alloy coating with a catalyst, graphite and an additive, placing the mixture in a high-temperature and high-pressure synthesis device, and synthesizing the mixture under preset temperature and pressure conditions to obtain diamond. The high-temperature and high-pressure industrial diamond seed synthesis method provided by the application solves the technical problem of poor consistency and distribution uniformity of the seed in the synthesis in the prior art.

Description

Technical Field

[0001] This invention belongs to the technical field of methods for synthesizing industrial diamond, specifically relating to a high-temperature, high-pressure method for synthesizing industrial diamond seed crystals. Background Technology

[0002] In modern industrial development, the high-temperature, high-pressure synthesis technology for industrial diamonds is a crucial supporting technology in materials science. Diamond, with its superior properties such as high hardness, excellent wear resistance, excellent thermal conductivity, and strong chemical stability, is widely used in numerous industrial fields, including stone processing, concrete cutting, and glass processing. This significantly improves the processing efficiency and precision of hard and brittle materials, effectively reducing production costs. As various industries continue to demand higher diamond quality, research into optimizing the high-temperature, high-pressure diamond synthesis process continues to advance, aiming to further improve diamond product quality and meet market demands.

[0003] Currently, while significant progress has been made in the technology and equipment for high-temperature, high-pressure synthesis of industrial diamonds, the lack of mature and effective pretreatment methods in the seed crystal processing stage remains a key bottleneck restricting further improvement in diamond synthesis quality. In existing high-temperature, high-pressure diamond synthesis processes, the seed crystal state directly affects the diamond growth quality. Due to the lack of standardized pretreatment of the seed crystals, the consistency and uniformity of seed crystal distribution in the synthesis system are poor, easily leading to localized over-density or over-sparseness of seed crystals. Uneven seed crystal distribution can disrupt the diamond growth process, easily forming intergrowth crystals and reducing the yield of high-grade diamonds; it also easily produces irregularly shaped materials with large dimensional deviations, reducing product qualification rates and increasing production costs. Furthermore, the existing physicochemical properties of the seed crystal surface have poor compatibility with the synthesis system, requiring a long period of melt co-infiltration under high temperature and high pressure conditions to form a metal catalyst coating. This not only affects diamond growth efficiency but also, due to the unstable quality of the catalyst coating, affects the deposition and crystallization of carbon atoms, ultimately reducing the quality of the diamond crystals.

[0004] The aforementioned problems severely restrict the development and application of high-temperature, high-pressure diamond synthesis technology. Therefore, developing a pretreatment method that can improve the surface condition of seed crystals, enhance the uniformity and consistency of seed distribution, and improve the compatibility between seed crystals and the synthesis system is of great significance for improving the quality of diamond synthesis and reducing the generation of intercalated crystals and irregularly shaped materials. Summary of the Invention

[0005] The purpose of this invention is to provide a high-temperature and high-pressure method for synthesizing industrial diamond seed crystals, which solves the technical problem of poor seed consistency and uniform distribution in the synthesis process in the prior art.

[0006] The technical solution adopted in this invention is a high-temperature and high-pressure method for synthesizing industrial diamond seed crystals, comprising the following steps:

[0007] S1, remove oil and impurities from the surface of the diamond seed crystal, and rinse with deionized water until no alkaline solution remains. S2, the diamond seed crystals treated by S1 are sensitized and activated in sequence, and then placed in a chemical nickel plating solution for chemical nickel plating to form a nickel layer. S3, the diamond seed crystal after the nickel layer formed in S2 is placed in the electroplating solution and electroplated by barrel plating to form a catalyst alloy coating on the surface of the nickel layer. S4 involves uniformly mixing diamond seed crystals coated with a catalyst alloy by electroplating in S3 with catalyst, graphite, and additives. After uniform mixing, the mixture is placed in a high-temperature and high-pressure synthesis device and synthesized under preset temperature and pressure conditions to obtain diamond.

[0008] The technical solution of this invention is also characterized by, S1 specifically involves immersing the diamond seed crystal in an alkaline solution for cleaning to remove surface oil and impurities, and then rinsing the diamond seed crystal with deionized water to ensure that no alkaline solution remains on the surface. The alkaline solution is a sodium hydroxide solution with a mass concentration of 5% to 15%, and the cleaning time is 20 to 40 minutes.

[0009] The sensitization process in S2 is as follows: after immersing the diamond seed crystal in the sensitization solution for 15-20 minutes, rinse it with cold pure water at least twice. The activation process is as follows: Immerse the sensitized diamond seed crystal in the activation solution for 10-15 minutes, and then rinse with cold purified water at least twice. The sensitization solution is composed of 20-30 g / L stannous chloride and 30-40 ml / L hydrochloric acid; the activation solution is composed of 1.0-1.5 g / L palladium chloride and 30-40 ml / L hydrochloric acid.

[0010] The steps for electroless nickel plating in S2 are as follows: First, pour the electroless nickel plating solution into a container and adjust the pH value of the solution to 9-10. Then, heat the solution and maintain it at a reaction temperature of 80-90°C. After the pH value and temperature of the solution stabilize, immerse the activated and rinsed diamond seed crystal in the solution. The entire immersion reaction process lasts for 10-20 minutes, forming a nickel layer with a thickness of 100-200 nm on the surface of the diamond seed crystal.

[0011] The electroless nickel plating solution is composed of 20-30 g / L nickel sulfate, 30-40 g / L sodium hypophosphite, and 10-15 g / L sodium citrate.

[0012] S3 specifically involves: pouring the electroplating solution into the reaction tank of the barrel plating equipment, adjusting the pH value of the electroplating solution to 2-3, and after the pH value stabilizes, placing the diamond seed crystals treated with electroless nickel plating into the reaction tank, starting the barrel plating equipment and adjusting the rotation speed to 5-10 r / min to begin the electroplating reaction, and directly forming an alloy coating on the surface of the diamond seed crystals through electroplating.

[0013] The electroplating solution is composed of a mixture of 70-80 g / L nickel sulfate hexahydrate, 120-140 g / L ferrous sulfate heptahydrate, 40-50 g / L sodium chloride and 20-30 g / L boric acid. The mass ratio of Fe to Ni in the alloy coating is controlled at 3:(1~1.5), and the coating thickness is 3~5μm.

[0014] S4 specifically involves: mixing diamond seed crystals coated with a catalyst alloy by electroplating (S3), along with catalyst, graphite, and additives, in a mass ratio of 1:(290~310):(690~710):2 in a mixer until homogeneous; placing the homogeneous mixture into the reaction chamber of a high-temperature, high-pressure synthesis device for synthesis reaction at a temperature of 1200~1400℃, a pressure of 5~7GPa, and a time of 30~60 minutes, to obtain diamond after the reaction is complete.

[0015] The mass ratio of diamond seed crystal to catalyst is 1:(290~310), the mass ratio of diamond seed crystal to graphite is 1:(690~710), and the mass ratio of diamond seed crystal to additive is 1:2; the additive is any one of stearic acid, paraffin or PEG.

[0016] The beneficial effects of this invention are: (1) The high temperature and high pressure method for synthesizing industrial diamond seeds provided by the present invention optimizes the physical and chemical properties of the seed surface by coating modification treatment, so that it has better compatibility with the graphite system, can be uniformly dispersed in the synthesis system, improves the consistency and uniformity of seed distribution, effectively reduces seed agglomeration, and enables carbon atoms to be deposited and grown more uniformly on the seed surface, laying a stable foundation for the synthesis of high-quality diamond.

[0017] (2) The high-temperature and high-pressure industrial diamond seed synthesis method provided by the present invention can effectively reduce crystal growth defects and decrease the crystal bonding rate and the production of irregularly shaped materials through coating treatment. The improvement of seed uniformity and consistency makes the diamond growth process more orderly and avoids crystal growth abnormalities caused by uneven seed distribution; at the same time, the coating layer can promote the rapid diffusion and stable deposition of carbon atoms, which is conducive to the formation of diamond crystals with fewer defects and complete structure, improving the purity, hardness and stability of diamond, and improving the overall quality of the product. Attached Figure Description

[0018] Figure 1 is a schematic diagram comparing the state of untreated diamond seeds and diamond seeds pretreated using the method of the present invention to synthesize diamonds. Figure 2 is a schematic diagram of the pretreated diamond seed crystals of the present invention under a scanning electron microscope. Detailed Implementation

[0019] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] This invention provides a method for synthesizing industrial diamond seeds using a high-temperature, high-pressure method, comprising the following steps: S1, remove oil and impurities from the surface of the diamond seed crystal, and rinse with deionized water until no alkaline solution remains. S1 specifically involves immersing the diamond seed crystal in an alkaline solution for cleaning to remove surface oil and impurities, and then rinsing the diamond seed crystal with deionized water to ensure that no alkaline solution remains on the surface. The alkaline solution is a sodium hydroxide solution with a mass concentration of 5% to 15%, and the cleaning time is 20 to 40 minutes.

[0021] S2, the diamond seed crystals treated by S1 are sensitized and activated in sequence, and then placed in a chemical nickel plating solution for chemical nickel plating to form a nickel layer. The sensitization process in S2 is as follows: immerse the diamond seed crystal in the sensitization solution for 15-20 minutes, and then rinse it with cold purified water at least twice; the activation process is as follows: immerse the sensitized diamond seed crystal in the activation solution for 10-15 minutes, and then rinse it with cold purified water at least twice. The steps for electroless nickel plating are as follows: First, pour the electroless nickel plating solution into a container and adjust the pH value of the solution to 9-10. Then, heat the solution and maintain it at a reaction temperature of 80-90℃. After the pH value and temperature of the solution stabilize, immerse the activated and rinsed diamond seed crystal in the solution. The entire immersion reaction process lasts for 10-20 minutes, forming a nickel layer with a thickness of 100-200nm on the surface of the diamond seed crystal.

[0022] The sensitizing solution is composed of a mixture of 20-30 g / L stannous chloride and 30-40 ml / L hydrochloric acid; the activating solution is composed of a mixture of 1.0-1.5 g / L palladium chloride and 30-40 ml / L hydrochloric acid; and the electroless nickel plating solution is composed of a mixture of 20-30 g / L nickel sulfate, 30-40 g / L sodium hypophosphite, and 10-15 g / L sodium citrate.

[0023] S3, the diamond seed crystal after the nickel layer formed in S2 is placed in the electroplating solution and electroplated by barrel plating to form a catalyst alloy coating on the surface of the nickel layer. S3 specifically involves: pouring the electroplating solution into the reaction tank of the barrel plating equipment, adjusting the pH value of the electroplating solution to 2-3, and after the pH value stabilizes, placing the diamond seed crystals treated with electroless nickel plating into the reaction tank, starting the barrel plating equipment and adjusting the rotation speed to 5-10 r / min to begin the electroplating reaction, and directly forming an alloy coating on the surface of the diamond seed crystals through electroplating.

[0024] The electroplating solution is composed of 70-80 g / L nickel sulfate hexahydrate, 120-140 g / L ferrous sulfate heptahydrate, 40-50 g / L sodium chloride and 20-30 g / L boric acid; the mass ratio of Fe to Ni in the alloy coating is controlled at 3:(1~1.5), and the coating thickness is 3~5 μm.

[0025] S4 involves uniformly mixing diamond seed crystals coated with a catalyst alloy by electroplating in S3 with catalyst, graphite, and additives. After uniform mixing, the mixture is placed in a high-temperature and high-pressure synthesis device and synthesized under preset temperature and pressure conditions to obtain diamond.

[0026] S4 specifically involves: mixing diamond seed crystals coated with a catalyst alloy by electroplating (S3), along with catalyst, graphite, and additives, in a mass ratio of 1:(290~310):(690~710):2 in a mixer until homogeneous; placing the homogeneous mixture into the reaction chamber of a high-temperature and high-pressure synthesis device for synthesis reaction, with a synthesis temperature of 1200~1400℃, a synthesis pressure of 5~7GPa, and a synthesis time of 30~60 minutes, to obtain diamond after the reaction is completed.

[0027] The catalyst is an iron-nickel-cobalt based alloy or a nickel-cobalt based alloy. The mass ratio of diamond seed crystal to catalyst is 1:(290~310), the mass ratio of diamond seed crystal to graphite is 1:(690~710), and the mass ratio of diamond seed crystal to additive is 1:2. The additive is any one of stearic acid, paraffin wax, or PEG (polyethylene glycol).

[0028] Example 1 This embodiment provides a method for synthesizing industrial diamond seed crystals using a high-temperature, high-pressure method, including the following steps: S1, remove oil and impurities from the surface of the diamond seed crystal, and rinse with deionized water until no alkaline solution remains. S1 specifically involves immersing industrial-grade diamond micronized seed crystals in a 5% sodium hydroxide solution and cleaning for 20 minutes to remove surface oil and impurities. Subsequently, the seed crystals are rinsed with deionized water until no alkaline solution residue remains on the surface, and then drained for later use.

[0029] S2, the diamond seed crystals treated by S1 are sensitized and activated in sequence, and then placed in a chemical nickel plating solution for chemical nickel plating to form a nickel layer. S2 specifically involves: sensitizing and activating the diamond seed crystals treated in S1, followed by electroless nickel plating in a solution to form a nickel layer. The sensitization process involves immersing the cleaned seed crystals in a solution composed of 20 g / L stannous chloride and 30 ml / L hydrochloric acid for 15 minutes, then rinsing them at least twice with cold purified water. The activation process involves immersing the sensitized seed crystals in an activation solution composed of 1.0 g / L palladium chloride and 30 ml / L hydrochloric acid for 10 minutes, then rinsing them twice with cold purified water. The electroless nickel plating process involves pouring a solution composed of 20 g / L nickel sulfate, 30 g / L sodium hypophosphite, and 10 g / L sodium citrate into a container, adjusting the pH to 9, heating and maintaining the temperature at 80°C, and then immersing the activated and rinsed seed crystals in the solution for 10 minutes to form a 100 nm thick nickel layer on the seed crystal surface. The solution is then dried for later use.

[0030] S3, the diamond seed crystal after the nickel layer formed in S2 is placed in the electroplating solution and electroplated by barrel plating to form a catalyst alloy coating on the surface of the nickel layer. S3 specifically involves placing the diamond seed crystal after the nickel layer is formed in S2 into an electroplating solution and performing electroplating using a barrel plating method to form a catalyst alloy coating on the surface of the nickel layer. The electroplating solution is composed of a mixture of 70 g / L nickel sulfate hexahydrate, 120 g / L ferrous sulfate heptahydrate, 40 g / L sodium chloride, and 20 g / L boric acid. This electroplating solution is poured into the reaction tank of the barrel plating equipment, the pH is adjusted to 2, and after the pH stabilizes, the seed crystal after electroless nickel plating is placed in, the barrel plating is started, and the rotation speed is adjusted to 5 r / min to carry out the electroplating reaction, forming a catalyst alloy coating with a Fe to Ni mass ratio of 3:1 and a thickness of 3 μm on the surface of the nickel layer. The coated crystal is then removed, dried, and set aside for later use.

[0031] S4 involves uniformly mixing diamond seed crystals coated with a catalyst alloy by electroplating in S3 with catalyst, graphite, and additives. After uniform mixing, the mixture is placed in a high-temperature and high-pressure synthesis device and synthesized under preset temperature and pressure conditions to obtain diamond.

[0032] Specifically, S4 involves uniformly mixing diamond seed crystals coated with a catalyst alloy by electroplating (S3), along with an iron-nickel-cobalt based alloy, graphite, and additives. The mixture is then placed in a high-temperature, high-pressure synthesis apparatus and synthesized under preset temperature and pressure conditions to obtain diamond. The mass ratio of diamond seed crystals to the iron-nickel-cobalt based alloy is 1:290, the mass ratio of diamond seed crystals to graphite is 1:690, and the mass ratio of diamond seed crystals to additives is 1:2. The additive is stearic acid. The preset synthesis temperature is 1200℃, the synthesis pressure is 5 GPa, and the synthesis time is 30 minutes. After the reaction is complete, the material is cooled and discharged to obtain diamond.

[0033] Example 2 This embodiment provides a method for synthesizing industrial diamond seed crystals using a high-temperature, high-pressure method, including the following steps: S1, remove oil and impurities from the surface of the diamond seed crystal, and rinse with deionized water until no alkaline solution remains. S1 specifically involves immersing industrial-grade diamond micronized seed crystals in a 10% sodium hydroxide solution for 30 minutes to remove surface oil and impurities; then rinsing the seed crystals with deionized water until no alkaline solution residue remains on the surface, and draining them for later use.

[0034] S2, the diamond seed crystals treated by S1 are sensitized and activated in sequence, and then placed in a chemical nickel plating solution for chemical nickel plating to form a nickel layer. S2 specifically involves: sensitizing and activating the diamond seed crystals treated in S1, followed by electroless nickel plating in a solution to form a nickel layer. The sensitization process involves immersing the cleaned seed crystals in a solution composed of 25 g / L stannous chloride and 35 ml / L hydrochloric acid for 18 minutes, then rinsing them at least twice with cold purified water. The activation process involves immersing the sensitized seed crystals in an activation solution composed of 1.25 g / L palladium chloride and 35 ml / L hydrochloric acid for 12.5 minutes, then rinsing them at least twice with cold purified water. The electroless nickel plating process involves pouring a solution composed of 25 g / L nickel sulfate, 35 g / L sodium hypophosphite, and 12.5 g / L sodium citrate into a container, adjusting the pH to 9.5, heating and maintaining the temperature at 85°C, and immersing the activated and rinsed seed crystals in the solution for 15 minutes to form a 150 nm thick nickel layer on the seed crystal surface. The solution is then dried for later use.

[0035] S3, the diamond seed crystal after the nickel layer formed in S2 is placed in the electroplating solution and electroplated by barrel plating to form a catalyst alloy coating on the surface of the nickel layer. S3 specifically involves placing the diamond seed crystal, after the nickel layer is formed in S2, into an electroplating solution and performing electroplating using a barrel plating method to form a catalyst alloy coating on the surface of the nickel layer. The electroplating solution is composed of a mixture of 75 g / L nickel sulfate hexahydrate, 130 g / L ferrous sulfate heptahydrate, 45 g / L sodium chloride, and 25 g / L boric acid. This electroplating solution is poured into the reaction tank of the barrel plating equipment, and the pH is adjusted to 2.5. After the pH stabilizes, the seed crystal after electroless nickel plating is placed in, the barrel plating is started, and the rotation speed is adjusted to 7.5 r / min to carry out the electroplating reaction. A catalyst alloy coating with a Fe to Ni mass ratio of 3:1.25 and a thickness of 4 μm is formed on the surface of the nickel layer. The coated crystal is then removed, dried, and set aside for later use.

[0036] S4 involves uniformly mixing diamond seed crystals coated with a catalyst alloy by electroplating in S3 with an iron-nickel-cobalt based alloy, graphite, and additives. After uniform mixing, the mixture is placed in a high-temperature and high-pressure synthesis device and synthesized under preset temperature and pressure conditions to obtain diamond.

[0037] Specifically, S4 involves uniformly mixing diamond seed crystals coated with a catalyst alloy by electroplating (S3), along with an iron-nickel-cobalt based alloy, graphite, and additives. The mixture is then placed in a high-temperature, high-pressure synthesis apparatus and synthesized under preset temperature and pressure conditions to obtain diamond. The mass ratio of diamond seed crystals to the iron-nickel-cobalt based alloy is 1:300, the mass ratio of diamond seed crystals to graphite is 1:700, and the mass ratio of diamond seed crystals to additives is 1:2. The additive is PEG. The preset synthesis temperature is 1300℃, the synthesis pressure is 6 GPa, and the synthesis time is 45 minutes. After the reaction is complete, the material is cooled and discharged to obtain diamond.

[0038] Example 3 This embodiment provides a method for synthesizing industrial diamond seed crystals using a high-temperature, high-pressure method, including the following steps: S1, remove oil and impurities from the surface of the diamond seed crystal, and rinse with deionized water until no alkaline solution remains. S1 specifically involves immersing industrial-grade diamond micronized seed crystals in a 15% sodium hydroxide solution for 40 minutes to remove surface oil and impurities; then rinsing the seed crystals with deionized water until no alkaline solution residue remains on the surface, and draining them for later use.

[0039] S2, the diamond seed crystals treated by S1 are sensitized and activated in sequence, and then placed in a chemical nickel plating solution for chemical nickel plating to form a nickel layer. S2 specifically involves: sensitizing and activating the diamond seed crystals treated in S1, followed by electroless nickel plating in a solution to form a nickel layer. The sensitization process involves immersing the cleaned seed crystals in a solution composed of 30 g / L stannous chloride and 40 ml / L hydrochloric acid for 20 minutes, then rinsing them at least twice with cold purified water. The activation process involves immersing the sensitized seed crystals in an activation solution composed of 1.5 g / L palladium chloride and 40 ml / L hydrochloric acid for 15 minutes, then rinsing them at least twice with cold purified water. The electroless nickel plating process involves pouring a solution composed of 30 g / L nickel sulfate, 40 g / L sodium hypophosphite, and 15 g / L sodium citrate into a container, adjusting the pH to 10, heating and maintaining the temperature at 90°C, and then immersing the activated and rinsed seed crystals in the solution for 20 minutes to form a 200 nm thick nickel layer on the seed crystal surface. The solution is then dried for later use.

[0040] S3, the diamond seed crystal after the nickel layer formed in S2 is placed in the electroplating solution and electroplated by barrel plating to form a catalyst alloy coating on the surface of the nickel layer. S3 specifically involves placing the diamond seed crystal, after the nickel layer is formed in S2, into an electroplating solution and performing electroplating using a barrel plating method to form a catalyst alloy coating on the surface of the nickel layer. The electroplating solution is composed of a mixture of 80 g / L nickel sulfate hexahydrate, 140 g / L ferrous sulfate heptahydrate, 50 g / L sodium chloride, and 30 g / L boric acid. This electroplating solution is poured into the reaction tank of the barrel plating equipment, the pH is adjusted to 3, and after the pH stabilizes, the seed crystal after electroless nickel plating is placed in, the barrel plating is started, and the rotation speed is adjusted to 10 r / min to carry out the electroplating reaction, forming a catalyst alloy coating with a Fe to Ni mass ratio of 3:1.5 and a thickness of 5 μm on the surface of the nickel layer. The coated crystal is then removed, dried, and set aside for later use.

[0041] S4 involves uniformly mixing diamond seed crystals coated with a catalyst alloy by electroplating in S3 with an iron-nickel-cobalt based alloy, graphite, and additives. After uniform mixing, the mixture is placed in a high-temperature and high-pressure synthesis device and synthesized under preset temperature and pressure conditions to obtain diamond.

[0042] Specifically, S4 involves uniformly mixing diamond seed crystals coated with a catalyst alloy by electroplating (S3), along with an iron-nickel-cobalt based alloy, graphite, and additives. The mixture is then placed in a high-temperature, high-pressure synthesis apparatus and synthesized under preset temperature and pressure conditions to obtain diamond. The mass ratio of diamond seed crystals to the iron-nickel-cobalt based alloy is 1:310, the mass ratio of diamond seed crystals to graphite is 1:710, and the mass ratio of diamond seed crystals to additives is 1:2. The additive is paraffin wax. The preset synthesis temperature is 1400℃, the synthesis pressure is 7 GPa, and the synthesis time is 60 minutes. After the reaction is complete, the material is cooled and discharged to obtain diamond.

[0043] Example 4 This embodiment provides a method for synthesizing industrial diamond seed crystals using a high-temperature, high-pressure method, including the following steps: S1, remove oil and impurities from the surface of the diamond seed crystal, and rinse with deionized water until no alkaline solution remains. S1 specifically involves immersing industrial-grade diamond micronized seed crystals in a 6% sodium hydroxide solution and cleaning for 25 minutes to remove surface oil and impurities. Subsequently, the seed crystals are rinsed with deionized water until no alkaline solution residue remains on the surface, and then drained for later use.

[0044] S2, the diamond seed crystals treated by S1 are sensitized and activated in sequence, and then placed in a chemical nickel plating solution for chemical nickel plating to form a nickel layer. S2 specifically involves: sensitizing and activating the diamond seed crystals treated in S1, followed by electroless nickel plating in a solution to form a nickel layer. The sensitization process involves immersing the cleaned seed crystals in a solution composed of 22 g / L stannous chloride and 32 ml / L hydrochloric acid for 16 minutes, then rinsing them at least twice with cold purified water. The activation process involves immersing the sensitized seed crystals in an activation solution composed of 1.1 g / L palladium chloride and 32 ml / L hydrochloric acid for 11 minutes, then rinsing them at least twice with cold purified water. The electroless nickel plating process involves pouring a solution composed of 22 g / L nickel sulfate, 32 g / L sodium hypophosphite, and 11 g / L sodium citrate into a container, adjusting the pH to 9.2, heating and maintaining the temperature at 82°C, and immersing the activated and rinsed seed crystals in the solution for 12 minutes to form a 120 nm thick nickel layer on the seed crystal surface. The solution is then dried for later use.

[0045] S3, the diamond seed crystal after the nickel layer formed in S2 is placed in the electroplating solution and electroplated by barrel plating to form a catalyst alloy coating on the surface of the nickel layer. S3 specifically involves placing the diamond seed crystal, after the nickel layer is formed in S2, into an electroplating solution and performing electroplating using a barrel plating method to form a catalyst alloy coating on the surface of the nickel layer. The electroplating solution is composed of a mixture of 72 g / L nickel sulfate hexahydrate, 125 g / L ferrous sulfate heptahydrate, 42 g / L sodium chloride, and 22 g / L boric acid. This electroplating solution is poured into the reaction tank of the barrel plating equipment, and the pH is adjusted to 2.2. After the pH stabilizes, the seed crystal after electroless nickel plating is placed in, the barrel plating is started, and the rotation speed is adjusted to 6 r / min to carry out the electroplating reaction. A catalyst alloy coating with a Fe to Ni mass ratio of 3:1.1 and a thickness of 3.5 μm is formed on the surface of the nickel layer. The coated crystal is then removed, dried, and set aside for later use.

[0046] S4 involves uniformly mixing diamond seed crystals coated with a catalyst alloy by electroplating in S3 with an iron-nickel-based alloy, graphite, and additives. After uniform mixing, the mixture is placed in a high-temperature and high-pressure synthesis device and synthesized under preset temperature and pressure conditions to obtain diamond.

[0047] Specifically, S4 involves uniformly mixing diamond seed crystals coated with a catalyst alloy by electroplating (S3), along with an iron-nickel-based alloy, graphite, and additives. The mixture is then placed in a high-temperature, high-pressure synthesis apparatus and synthesized under preset temperature and pressure conditions to obtain diamond. The mass ratio of diamond seed crystals to the iron-nickel-based alloy is 1:295, the mass ratio of diamond seed crystals to graphite is 1:695, and the mass ratio of diamond seed crystals to additives is 1:2. The additive is paraffin wax. The preset synthesis temperature is 1250℃, the synthesis pressure is 5.5 GPa, and the synthesis time is 35 minutes. After the reaction is complete, the material is cooled and discharged to obtain diamond.

[0048] Example 5 This embodiment provides a method for synthesizing industrial diamond seed crystals using a high-temperature, high-pressure method, including the following steps: S1, remove oil and impurities from the surface of the diamond seed crystal, and rinse with deionized water until no alkaline solution remains. S1 specifically involves immersing industrial-grade diamond micronized seed crystals in a 12% sodium hydroxide solution for 35 minutes to remove surface oil and impurities; then rinsing the seed crystals with deionized water until no alkaline solution residue remains on the surface, and draining them for later use.

[0049] S2, the diamond seed crystals treated by S1 are sensitized and activated in sequence, and then placed in a chemical nickel plating solution for chemical nickel plating to form a nickel layer. S2 specifically involves: sensitizing and activating the diamond seed crystals treated in S1, followed by electroless nickel plating in a solution to form a nickel layer. The sensitization process involves immersing the cleaned seed crystals in a solution composed of 28 g / L stannous chloride and 38 ml / L hydrochloric acid for 19 minutes, then rinsing them at least twice with cold purified water. The activation process involves immersing the sensitized seed crystals in an activation solution composed of 1.4 g / L palladium chloride and 38 ml / L hydrochloric acid for 14 minutes, then rinsing them at least twice with cold purified water. The electroless nickel plating process involves pouring a solution composed of 28 g / L nickel sulfate, 38 g / L sodium hypophosphite, and 14 g / L sodium citrate into a container, adjusting the pH to 9.8, heating and maintaining the temperature at 88°C, and then immersing the activated and rinsed seed crystals in the solution for 18 minutes to form a 180 nm thick nickel layer on the seed crystal surface. The solution is then dried for later use.

[0050] S3, the diamond seed crystal after the nickel layer formed in S2 is placed in the electroplating solution and electroplated by barrel plating to form a catalyst alloy coating on the surface of the nickel layer. S3 specifically involves placing the diamond seed crystal, after the nickel layer is formed in S2, into an electroplating solution and performing electroplating using a barrel plating method to form a catalyst alloy coating on the surface of the nickel layer. The electroplating solution is composed of a mixture of 78 g / L nickel sulfate hexahydrate, 135 g / L ferrous sulfate heptahydrate, 48 g / L sodium chloride, and 28 g / L boric acid. This electroplating solution is poured into the reaction tank of the barrel plating equipment, and the pH is adjusted to 2.8. After the pH stabilizes, the seed crystal after electroless nickel plating is placed in, the barrel plating is started, and the rotation speed is adjusted to 9 r / min to carry out the electroplating reaction. A catalyst alloy coating with a Fe to Ni mass ratio of 3:1.4 and a thickness of 4.5 μm is formed on the surface of the nickel layer. The coated crystal is then removed, dried, and set aside for later use.

[0051] S4 involves uniformly mixing diamond seed crystals coated with a catalyst alloy by electroplating in S3 with catalyst, graphite, and additives. After uniform mixing, the mixture is placed in a high-temperature and high-pressure synthesis device and synthesized under preset temperature and pressure conditions to obtain diamond.

[0052] Specifically, S4 involves uniformly mixing diamond seed crystals coated with a catalyst alloy by electroplating (S3) with a catalyst, graphite, and additives. The mixture is then placed in a high-temperature, high-pressure synthesis apparatus and synthesized under preset temperature and pressure conditions to obtain diamond. The mass ratio of diamond seed crystals to catalyst is 1:305, the mass ratio of diamond seed crystals to graphite is 1:705, and the mass ratio of diamond seed crystals to additives is 1:2. The additive is stearic acid. The preset synthesis temperature is 1350℃, the synthesis pressure is 6.5 GPa, and the synthesis time is 50 minutes. After the reaction is complete, the material is cooled and discharged to obtain diamond.

[0053] Example 6 This embodiment provides a method for synthesizing industrial diamond seed crystals using a high-temperature, high-pressure method, including the following steps: S1, remove oil and impurities from the surface of the diamond seed crystal, and rinse with deionized water until no alkaline solution remains. S1 specifically involves immersing industrial-grade diamond micronized seed crystals in a 14% sodium hydroxide solution for 38 minutes to remove surface oil and impurities; then rinsing the seed crystals with deionized water until no alkaline solution residue remains on the surface, and draining them for later use.

[0054] S2, the diamond seed crystals treated by S1 are sensitized and activated in sequence, and then placed in a chemical nickel plating solution for chemical nickel plating to form a nickel layer. S2 specifically involves: sensitizing and activating the diamond seed crystals treated in S1, followed by electroless nickel plating in a solution to form a nickel layer. The sensitization process involves immersing the cleaned seed crystals in a solution composed of 29 g / L stannous chloride and 39 ml / L hydrochloric acid for 19.5 minutes, then rinsing them at least twice with cold purified water. The activation process involves immersing the sensitized seed crystals in an activation solution composed of 1.45 g / L palladium chloride and 39 ml / L hydrochloric acid for 14.5 minutes, then rinsing them at least twice with cold purified water. The electroless nickel plating process involves pouring a solution composed of 29 g / L nickel sulfate, 39 g / L sodium hypophosphite, and 14.5 g / L sodium citrate into a container, adjusting the pH to 9.9, heating and maintaining the temperature at 89°C, and then immersing the activated and rinsed seed crystals in the solution for 19 minutes to form a 190 nm thick nickel layer on the seed crystal surface. The solution is then dried for later use.

[0055] S3, the diamond seed crystal after the nickel layer formed in S2 is placed in the electroplating solution and electroplated by barrel plating to form a catalyst alloy coating on the surface of the nickel layer. S3 specifically involves placing the diamond seed crystal, after the nickel layer is formed in S2, into an electroplating solution and performing electroplating using a barrel plating method to form a catalyst alloy coating on the surface of the nickel layer. The electroplating solution is composed of a mixture of 79 g / L nickel sulfate hexahydrate, 138 g / L ferrous sulfate heptahydrate, 49 g / L sodium chloride, and 29 g / L boric acid. This electroplating solution is poured into the reaction tank of the barrel plating equipment, and the pH is adjusted to 2.9. After the pH stabilizes, the seed crystal after electroless nickel plating is placed in, the barrel plating is started, and the rotation speed is adjusted to 9.5 r / min to carry out the electroplating reaction, forming a catalyst alloy coating with a Fe to Ni mass ratio of 3:1.45 and a thickness of 4.8 μm on the surface of the nickel layer. The coated crystal is then removed, dried, and set aside for later use.

[0056] S4 involves uniformly mixing diamond seed crystals coated with a catalyst alloy by electroplating in S3 with catalyst, graphite, and additives. After uniform mixing, the mixture is placed in a high-temperature and high-pressure synthesis device and synthesized under preset temperature and pressure conditions to obtain diamond.

[0057] Specifically, S4 involves uniformly mixing diamond seed crystals coated with a catalyst alloy by electroplating (S3), along with a catalyst, graphite, and additives. The mixture is then placed in a high-temperature, high-pressure synthesis apparatus and synthesized under preset temperature and pressure conditions to obtain diamond. The mass ratio of diamond seed crystals to catalyst is 1:308, the mass ratio of diamond seed crystals to graphite is 1:708, and the mass ratio of diamond seed crystals to additives is 1:2. The additive is PEG. The preset synthesis temperature is 1380℃, the synthesis pressure is 6.8 GPa, and the synthesis time is 58 minutes. After the reaction is complete, the material is cooled and discharged to obtain diamond.

[0058] Comparative Example 1 This comparative example uses the same raw materials, equipment, and synthesis process as Example 2 of the present invention, except that the sensitization, activation, electroless nickel plating, and catalyst alloy coating pretreatment steps of diamond seed crystals are omitted. A comparative experiment is conducted between this comparative example (untreated seed crystals) and Example 2 of the present invention (pretreated seed crystals), using the same raw material ratio, pressing process, synthesis equipment, and synthesis process. After synthesis, both samples undergo purification, sieving, and selection operations. The quantity and purity of the continuous crystals and high-grade materials are statistically analyzed. The specific results are shown in Table 1.

[0059] like Figure 1 As shown, the left side shows the fracture surface of the untreated seed crystal, which exhibits obvious light-colored enriched bands, uneven distribution of surface crystalline phase bright spots, and localized impurity segregation. The overall structure of the sample is loose, making it difficult to guarantee the stability of the product's structure and properties. The right side shows the synthesized state of the seed crystal after pretreatment according to this invention. The fracture surface is clean with no obvious impurity enriched bands, the surface crystalline phase bright spots are evenly and densely distributed, and the overall structure of the sample is more dense and uniform, with no obvious local defects or segregation.

[0060] The purity of diamonds synthesized by the two methods was analyzed using X-ray diffraction (XRD), with a scanning range of 20°–80° and a scanning speed of 0.02° / s. The results showed that the diamond synthesized in the comparative example (untreated seed crystals) had a purity of approximately 95%; the diamond synthesized in Example 2 of this invention (pretreated seed crystals) achieved a purity of over 98%. Figure 2 The image shows the scanning electron microscope (SEM) morphology of the seed crystals after pretreatment. The seed crystals exhibit an irregular polyhedral morphology with clear edges and complete crystal faces, and the crystalline structure remains intact. The particle size distribution is concentrated in the 5–15 μm range, with good uniformity and no obvious agglomeration, adhesion, or pulverization. The particle surface is clean, free of impurities or amorphous coatings, and exhibits excellent dispersibility. These characteristics ensure high uniformity in nucleation activity and growth induction ability of individual seed crystals, laying a quality foundation for consistent seed distribution. Furthermore, they allow for full spreading and prevent local enrichment in the synthesis system, effectively guaranteeing uniform distribution and providing a crucial prerequisite for the structural uniformity of the subsequent synthesized product. The method of this invention effectively reduces the introduction of impurities and improves the purity of diamond. This is attributed to the optimization of the seed crystal surface by the coating treatment, which reduces defects and impurity adsorption during crystal growth. By comparing and analyzing diamonds synthesized using traditional methods, the novel high-temperature and high-pressure diamond seed treatment method of this invention has significant advantages in improving diamond hardness and purity, reducing crystal fusion rate and irregular shapes, effectively improving the quality of diamond synthesis, and verifying the effectiveness and superiority of the method of this invention.

Claims

1. A method for synthesizing industrial diamond seed crystals using a high-temperature, high-pressure process, characterized in that, Includes the following steps: S1, remove oil and impurities from the surface of the diamond seed crystal, and rinse with deionized water until no alkaline solution remains. S2, the diamond seed crystals treated by S1 are sensitized and activated in sequence, and then placed in a chemical nickel plating solution for chemical nickel plating to form a nickel layer. S3, the diamond seed crystal after the nickel layer formed in S2 is placed in the electroplating solution and electroplated by barrel plating to form a catalyst alloy coating on the surface of the nickel layer. S4 involves uniformly mixing diamond seed crystals coated with a catalyst alloy by electroplating in S3 with catalyst, graphite, and additives. After uniform mixing, the mixture is placed in a high-temperature and high-pressure synthesis device and synthesized under preset temperature and pressure conditions to obtain diamond.

2. The method for synthesizing industrial diamond seeds using the high-temperature and high-pressure method according to claim 1, characterized in that, S1 specifically involves: cleaning the diamond seed crystal in an alkaline solution to remove surface oil and impurities, and then rinsing the diamond seed crystal with deionized water to ensure that there is no residual alkaline solution on the surface. The alkaline solution is a sodium hydroxide solution with a mass concentration of 5% to 15%, and the cleaning time is 20 to 40 minutes.

3. The method for synthesizing industrial diamond seeds using the high-temperature and high-pressure method according to claim 1, characterized in that, The sensitization treatment step described in S2 is as follows: after immersing the diamond seed crystal in the sensitization solution for 15-20 minutes, rinse it with cold pure water at least twice. The activation treatment step is as follows: immerse the sensitized diamond seed crystal in the activation solution, soak for 10-15 minutes, and then rinse with cold purified water at least twice.

4. The method for synthesizing industrial diamond seeds using the high-temperature and high-pressure method according to claim 3, characterized in that, The sensitization solution is composed of 20-30 g / L stannous chloride and 30-40 ml / L hydrochloric acid; the activation solution is composed of 1.0-1.5 g / L palladium chloride and 30-40 ml / L hydrochloric acid.

5. The method for synthesizing industrial diamond seeds using the high-temperature and high-pressure method according to claim 1, characterized in that, The electroless nickel plating steps described in S2 are as follows: First, pour the electroless nickel plating solution into a container, adjust the pH value of the electroless nickel plating solution to 9~10, then heat the nickel plating solution and maintain it at a reaction temperature of 80~90℃. After the pH value and temperature of the nickel plating solution stabilize, immerse the activated and rinsed diamond seed crystal in the nickel plating solution. The entire immersion reaction process lasts for 10~20 minutes, forming a nickel layer with a thickness of 100~200nm on the surface of the diamond seed crystal.

6. The method for synthesizing industrial diamond seeds using the high-temperature and high-pressure method according to claim 5, characterized in that, The electroless nickel plating solution is composed of a mixture of 20-30 g / L nickel sulfate, 30-40 g / L sodium hypophosphite, and 10-15 g / L sodium citrate.

7. The method for synthesizing industrial diamond seeds using the high-temperature and high-pressure method according to claim 1, characterized in that, S3 specifically involves: pouring the electroplating solution into the reaction tank of the barrel plating equipment, adjusting the pH value of the electroplating solution to 2-3, and after the pH value stabilizes, placing the diamond seed crystals treated with electroless nickel plating into the reaction tank, starting the barrel plating equipment and adjusting the rotation speed to 5-10 r / min to begin the electroplating reaction, and directly forming an alloy coating on the surface of the diamond seed crystals through electroplating.

8. The method for synthesizing industrial diamond seeds using the high-temperature and high-pressure method according to claim 7, characterized in that, The electroplating solution is composed of a mixture of 70-80 g / L nickel sulfate hexahydrate, 120-140 g / L ferrous sulfate heptahydrate, 40-50 g / L sodium chloride and 20-30 g / L boric acid. The mass ratio of Fe to Ni in the alloy coating is controlled at 3:(1~1.5), and the coating thickness is 3~5μm.

9. The method for synthesizing industrial diamond seeds using the high-temperature and high-pressure method according to claim 1, characterized in that, Specifically, S4 involves: mixing diamond seed crystals coated with a catalyst alloy by electroplating in S3 with catalyst, graphite, and additives in a mass ratio of 1:(290~310):(690~710):2 in a mixer until homogeneous; placing the homogeneous mixture into the reaction chamber of a high-temperature and high-pressure synthesis device for synthesis reaction at a synthesis temperature of 1200~1400℃, a synthesis pressure of 5~7GPa, and a synthesis time of 30~60 minutes, and obtaining diamond after the reaction is completed.

10. The method for synthesizing industrial diamond seeds using the high-temperature and high-pressure method according to claim 9, characterized in that, The mass ratio of the diamond seed crystal to the catalyst is 1:(290~310), the mass ratio of the diamond seed crystal to graphite is 1:(690~710), and the mass ratio of the diamond seed crystal to the additive is 1:2; the additive is any one of stearic acid, paraffin, or PEG.

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