Artificial diamond and preparation method thereof

Abstract

The invention belongs to the technical field of diamond synthesis, and particularly relates to an artificial diamond and a preparation method thereof. The preparation method comprises the following steps: (1) carrying out ball-milling mixing on graphite powder, a seed crystal and a catalyst, and then carrying out compression molding to prepare a synthetic column; performing high-temperature and high-pressure synthesis on the synthetic column to obtain an artificial diamond mixture; (2) carrying out acid treatment on the artificial diamond mixture, filtering, washing, drying and screening to obtain the artificial diamond; wherein the seed crystal is diamond coated with modified graphdiyne; the catalyst is MoS2 modified high-entropy alloy powder, and the high-entropy alloy powder is prepared from the following components in atomic percent: 20 to 30 at% of Fe, 20 to 30 at% of Co, 10 to 25 at% of Ni, 15 to 25 at% of Ti and 10 to 15 at% of Sm. The artificial diamond disclosed by the invention is high in growth rate, high in growth quality and excellent in toughness.

Description

Technical Field

[0001] The present invention belongs to the technical field of diamond synthesis, and in particular relates to an artificial diamond and a preparation method thereof. Background Art

[0002] Each carbon atom in a diamond crystal is connected by sp 3 The hybrid orbital forms a covalent bond with four adjacent carbon atoms, with a bond length of 154.45 pm and a bond angle of 109°28', forming a perfect isotropic tetrahedral unit. This structure makes diamond the hardest material in nature, with a Mohs hardness of 10, and it has ultra-high thermal conductivity (2000-2200 W / m·K), extremely low thermal expansion coefficient (0.8×10 -6 Its unique properties, such as a high-energy density (1000 nm / K) and a wide bandgap (5.47 eV), make it irreplaceable in applications such as precision machining tools, optical windows, semiconductor heat dissipation, and quantum devices. However, natural diamond reserves are limited, and diamond mining has significant adverse environmental impacts. Therefore, the synthesis of artificial diamonds has been a research hotspot in academia and industry.

[0003] Currently, the mainstream synthetic diamond synthesis technologies include chemical vapor deposition (CVD) and high-pressure, high-temperature (HPHT). The HPHT method simulates the conditions deep within the Earth's crust (5-6 GPa, 1300-1600°C) to achieve a catalytic phase transition from graphite to diamond. This method can mass-produce millimeter-sized single crystals and accounts for 80% of global industrial diamond production capacity. Key challenges of this method include: first, the need for precise control of the pressure and temperature gradient to avoid crystal defects. Studies have shown that pressure fluctuations exceeding 0.1 GPa can increase dislocation density by three orders of magnitude; second, residual catalyst metals affect purity, requiring mixed acid treatment to reduce impurities to the ppm level; and third, the slow growth rate of large single crystals (approximately 1 mm / day), with the risk of cracking increasing exponentially with size. In recent years, improvements in catalyst alloys (such as Fe-Co-Cr) and the use of a stepped pressure-increasing technique have enabled the production of diamonds weighing over 10 carats. However, the trade-offs between crystal size and growth cycle, and between the preparation method and energy consumption, remain technical challenges that need to be overcome. Summary of the Invention

[0004] The first object of the present invention is to provide a method for preparing artificial diamond.

[0005] The second object of the present invention is to provide an artificial diamond having a fast crystal growth rate, high growth quality and excellent toughness.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is: A method for preparing artificial diamond comprises the following steps: (1) Graphite powder, seed crystals and catalyst are ball-milled and then molded into synthetic columns; the synthetic columns are subjected to high temperature and high pressure synthesis to obtain artificial diamond mixture; (2) subjecting the artificial diamond mixture to acid treatment, filtering, washing, drying, and screening to obtain the artificial diamond; The seed crystal in step (1) is a modified graphyne-coated diamond; the catalyst is a MoS2-modified high-entropy alloy powder, and the high-entropy alloy powder is composed of the following components in atomic percentage: 20-30 at% Fe, 20-30 at% Co, 10-25 at% Ni, 15-25 at% Ti, and 10-15 at% Sm.

[0007] Furthermore, the seed crystals in step (1) are prepared by the following preparation process: After cleaning the diamond particles, the edges are etched by laser to obtain edge-etched diamonds; the edge-etched diamonds are immersed in a hexaethynylbenzene solution, and the solution is soaked, filtered, and heat-treated to obtain graphyne-coated diamonds; and the graphyne-coated diamonds are subjected to microwave treatment in an inert gas atmosphere to obtain the crystal seeds.

[0008] Furthermore, the laser power is 1-5 W, the scanning speed is 200-500 mm / s, and the spot diameter is 5-15 μm; the ratio of the edge-etching diamond to the hexaethynylbenzene solution is (20-70) mg:1 mL; and the concentration of the hexaethynylbenzene solution is 2-5 mg / mL.

[0009] Furthermore, the soaking temperature is 50-80°C and the time is 20-30 h; the heat treatment temperature is 300-400°C and the time is 1-2 h; the microwave treatment power is 100-500 W and the time is 30-120 s.

[0010] Furthermore, the catalyst in step (1) is prepared by the following preparation process: (a) mixing the components of the high entropy alloy powder and smelting them 3-5 times under an inert gas atmosphere to obtain a high entropy alloy ingot; (b) melting the high entropy alloy ingot, pouring it into a tundish of an atomizing device, introducing an inert gas for atomization, and collecting and sieving to obtain high entropy alloy powder; (c) adding the high entropy alloy powder to an aqueous solution of ammonium tetrathiomolybdate and stirring the mixture with ultrasonic waves, and then heating the mixture to remove the solvent, heat-treating the mixture, cooling the mixture, washing the mixture, and drying the mixture to obtain the catalyst.

[0011] Furthermore, during the gas atomization in step (b), the temperature of the atomizing gas is 10-30°C and the pressure is 2-5 MPa; in step (c), the mass ratio of the high entropy alloy powder to ammonium tetrathiomolybdate is (5-10):1; the ultrasonic stirring time is 1-2 h; the temperature of the heating to remove the solvent is 50-80°C; the temperature of the heat treatment is 500-700°C and the time is 1-2 h.

[0012] Furthermore, the mass ratio of the graphite powder, seed crystals and catalyst in step (1) is 1: (0.05-0.1): (0.3-0.6); the particle size of the graphite powder is 5-10 μm, the particle size of the seed crystal is 10-20 μm, and the particle size of the catalyst is 0.5-5 μm.

[0013] Furthermore, the high temperature and high pressure synthesis in step (1) is performed at a pressure of 5.0-6.0 GPa, a temperature of 1300-1500° C., and a time of 20-40 min.

[0014] Furthermore, the acid treatment step in step (2) is as follows: 98% concentrated sulfuric acid and 65% concentrated nitric acid are mixed in a volume ratio of (2.5-3.5):1, heated to 50-80°C, and then placed in the artificial diamond mixture for treatment for 10-60 minutes.

[0015] An artificial diamond is prepared by the above-mentioned method for preparing artificial diamond.

[0016] The beneficial technical effects of the present invention are: 1. The present invention utilizes modified graphyne-coated diamond particles as seed crystals, and prepares the diamond by sequentially etching its edges, depositing graphyne on its surface, and subjecting it to microwave modification treatment. First, the present invention adds diamond as a seed crystal to artificial diamond, which can guide the diamond to grow along a specific crystal phase, reduce lattice defects caused by random nucleation, and simultaneously reduce the nucleation energy barrier, shortening the synthesis time and reducing energy consumption. Next, laser etching is performed on the edge of the diamond seed crystal, which forms nanoscale grooves or holes on the edge of the seed crystal, exposing more dangling carbon atoms, enhancing the adsorption capacity of the carbon source, and promoting the deposition of graphyne. The etched edge structure can disperse the thermal stress during the growth process, avoiding cracks or peeling caused by differences in the lattice expansion coefficient. In addition, the present invention also deposits a graphyne layer on the surface of the seed crystal, and graphyne has sp-sp 2The complex hybrid bonds and hexagonal symmetrical structure have high chemical activity and good matching with the diamond crystal plane, which can reduce the nucleation barrier of diamond and induce epitaxial growth. As the seed surface in carbon source deposition, it can improve the growth efficiency. At the same time, the flexible two-dimensional structure and high interface thermal conductivity can relieve the thermal stress during the diamond growth process and improve thermal stability. Finally, the surface of the microwave-modified graphyne is rich in defects and functional groups, and has more active sites, which can further improve the nucleation density and growth rate of diamond. Microwave treatment can optimize the crystallization orientation of graphyne, and has a higher matching degree with the diamond lattice, which can effectively reduce lattice defects and improve the quality of diamond epitaxial growth.

[0017] 2. The present invention uses high-entropy alloy powder modified with molybdenum disulfide as a catalyst. High-entropy alloys exhibit delayed diffusion and lattice distortion effects, maintaining structural stability under high temperature and high pressure, withstanding mechanical stress during the synthesis process and reducing uneven pressure distribution caused by catalyst deformation. Compared to traditional alloy catalysts, the multicomponents provide more active sites. The synergistic effect between the components optimizes carbon atom diffusion pathways, lowers the diamond nucleation energy barrier, and increases crystal growth rate. Furthermore, modification of the high-entropy alloy powder with molybdenum disulfide can passivate the high-entropy alloy grain boundaries and diamond growth interfaces, reducing catalyst embrittlement caused by oxygen segregation under high temperature and high pressure environments, as well as dislocations and inclusion defects in diamond crystals. The layered structure of molybdenum disulfide itself provides low-barrier carbon atom transport channels. Furthermore, the multicomponents of the high-entropy alloy and the sulfur vacancies in molybdenum disulfide synergistically regulate the electronic structure, accelerating the phase transition kinetics from graphite to diamond. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a scanning electron microscope image of the catalyst prepared in Preparation Example 5. DETAILED DESCRIPTION

[0019] The following is a further detailed description of the present invention in conjunction with specific preferred embodiments, and it is not intended that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art of the present invention, without departing from the inventive concept, several simple deductions or replacements can also be made, all of which should be considered to belong to the scope of protection of the present invention. The specific conditions not indicated in the examples are carried out according to conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used, unless otherwise specified, are conventional products obtained through commercial channels.

[0020] (1) Preparation example Preparation Example 1 Preparation Example 1 provides a seed crystal, which is prepared by the following preparation process: The diamond particles were cleaned and the edges of the diamonds were etched at a scanning rate of 350 mm / s using a 3 W laser with a spot diameter of 10 μm and a power of 3 W to obtain edge-etched diamonds. The edge-etched diamonds were added to a 3 mg / mL hexaethynylbenzene pyridine solution at a dosage ratio of 50 mg:1 mL. The solution was then heated to 70°C and soaked for 24 h. The collected solid was filtered and heat-treated at 350°C for 1 h to obtain gydne-coated diamonds. The gydne-coated diamonds were then treated with a 300 W microwave in an argon atmosphere for 80 s to obtain seed crystals with a particle size of 15 μm.

[0021] Preparation Example 2 Preparation Example 2 provides a seed crystal, which is prepared by the following preparation process: The diamond particles were cleaned and the edges of the diamonds were etched at a scanning rate of 200 mm / s using a 1 W laser with a spot diameter of 5 μm to obtain edge-etched diamonds. The edge-etched diamonds were added to a 2 mg / mL hexaethynylbenzene pyridine solution at a dosage ratio of 20 mg:1 mL. The solution was then heated to 50°C and soaked for 20 h. The collected solid was filtered and heat-treated at 300°C for 1 h to obtain gydne-coated diamonds. The gydne-coated diamonds were then treated with a 100 W microwave in an argon atmosphere for 30 s to obtain seed crystals with a particle size of 10 μm.

[0022] Preparation Example 3 Preparation Example 3 provides a seed crystal, which is prepared by the following preparation process: The diamond particles were cleaned and the edges of the diamonds were etched at a scanning rate of 500 mm / s using a 5 W laser with a spot diameter of 15 μm. The edge-etched diamonds were then added to a 5 mg / mL hexaethynylbenzene pyridine solution at a ratio of 70 mg:1 mL. The solution was then heated to 80°C and soaked for 30 h. The collected solid was then filtered and heat-treated at 400°C for 2 h to obtain gydne-coated diamonds. The gydne-coated diamonds were then treated with a 500 W microwave in an argon atmosphere for 120 s to obtain seed crystals with a particle size of 20 μm.

[0023] Preparation Example 4 The content of Preparation Example 4 is basically the same as that of Preparation Example 1, except that the microwave treatment operation is omitted, that is, the diamond coated with graphyne is used as the seed crystal.

[0024] Preparation Example 5 Preparation Example 5 provides a catalyst, which is prepared by the following preparation process: (a) Metal raw materials were weighed and mixed according to the atomic percentage of 25 at% Fe, 25 at% Co, 20 at% Ni, 20 at% Ti, and 10 at% Sm. The raw materials were then melted in a medium frequency melting furnace. Argon was continuously introduced into the furnace mouth during the melting process. The raw materials were melted to a molten state and then cooled. This process was repeated four times to obtain a high-entropy alloy ingot with uniform composition. (b) A high-entropy alloy ingot is melted to obtain a high-entropy alloy liquid, which is then transferred to the tundish of an atomizing furnace while flowing. High-purity argon gas is introduced simultaneously, and the high-entropy alloy liquid is then allowed to flow into the atomizing chamber from the bottom guide tube. The liquid is then atomized using nitrogen at a temperature of 20°C and a pressure of 3 MPa to produce a powder. The powder is then collected and sieved to obtain the high-entropy alloy powder. (c) The high entropy alloy powder was added to a 0.08 mol / L aqueous solution of ammonium tetrathiomolybdate at a mass ratio of 8:1, and ultrasonic stirring was performed for 1 h. The solvent was then removed by heating at 70 °C. The remaining solid material was then heat-treated at 600 °C for 1 h. After cooling, washing, and drying, D 50 The catalyst is 2 μm.

[0025] The scanning electron microscope image of the catalyst prepared in this preparation example is as follows Figure 1 As shown, from Figure 1 It can be seen that the alloy particles prepared by gas atomization have good sphericity, with a small amount of satellite balls adhering to each other. After modification with molybdenum disulfide, a uniform nano-level layered coverage is formed on the powder surface, and the powder surface smoothness decreases.

[0026] Preparation Example 6 Preparation Example 6 provides a catalyst prepared by the following preparation process: (a) Metal raw materials were weighed and mixed according to the atomic percentages of 20 at% Fe, 30 at% Co, 25 at% Ni, 15 at% Ti, and 10 at% Sm. The raw materials were then melted in a medium frequency melting furnace. Argon was continuously introduced into the furnace mouth during the melting process. The raw materials were melted to a molten state and then cooled. This process was repeated three times to obtain a high-entropy alloy ingot with uniform composition. (b) A high-entropy alloy ingot is melted to obtain a high-entropy alloy liquid, which is then transferred to the tundish of an atomizing furnace while flowing. High-purity argon gas is introduced simultaneously, and the high-entropy alloy liquid is then allowed to flow into the atomizing chamber from the bottom guide tube. The liquid is then atomized using nitrogen at a temperature of 10°C and a pressure of 2 MPa to produce a powder. The high-entropy alloy powder is then collected and sieved to obtain the powder. (c) According to the mass ratio of high entropy alloy powder to ammonium tetrathiomolybdate of 5:1, the high entropy alloy powder was added to a 0.05 mol / L ammonium tetrathiomolybdate aqueous solution, and ultrasonically stirred for 1 h. The solvent was then removed by heating at 50 °C. The remaining solid material was then heat-treated at 500 °C for 1 h. After cooling, washing, and drying, D 50 The catalyst is 0.5 μm.

[0027] Preparation Example 7 Preparation Example 7 provides a catalyst prepared by the following preparation process: (a) Metal raw materials were weighed and mixed according to the atomic percentages of 30 at% Fe, 20 at% Co, 10 at% Ni, 25 at% Ti, and 15 at% Sm. The raw materials were then melted in a medium frequency melting furnace. Argon was continuously introduced into the furnace mouth during the melting process. The mixture was melted to a molten state and then cooled. This process was repeated five times to obtain a high-entropy alloy ingot with uniform composition. (b) A high-entropy alloy ingot is melted to obtain a high-entropy alloy liquid, which is then transferred to the tundish of an atomizing furnace while flowing. High-purity argon gas is introduced simultaneously, and the high-entropy alloy liquid is then allowed to flow from the bottom guide tube into the atomizing chamber. The liquid is then atomized using nitrogen at a temperature of 30°C and a pressure of 5 MPa to produce a powder. The high-entropy alloy powder is then collected and sieved to obtain the powder. (c) The high entropy alloy powder was added to a 0.1 mol / L ammonium tetrathiomolybdate aqueous solution at a mass ratio of 10:1, and ultrasonic stirring was performed for 2 h. The solvent was then removed by heating at 80 °C. The remaining solid material was then heat-treated at 700 °C for 2 h. After cooling, washing, and drying, D was obtained. 50 The catalyst is 5 μm.

[0028] Preparation Example 8 Preparation Example 8 is basically the same as Preparation Example 5, except that the high entropy alloy in step (a) is replaced by Fe with a composition of 60 at% Fe and 40 at% Ni. 60 Ni 40 Alloy, that is, alloy powder modified by MoS2 is used as catalyst.

[0029] Preparation Example 9 Preparation Example 9 is basically the same as Preparation Example 5, except that step (c) is omitted, that is, high entropy alloy powder is used as a catalyst.

[0030] (2) Implementation Example 1 Example 1 provides a method for preparing an artificial diamond, comprising the following steps: (1) Graphite powder with a particle size of 8 μm, the seed crystal with a particle size of 15 μm in Preparation Example 1, and D in Preparation Example 5 were mixed.50 The catalysts with a particle size of 2 μm were ball-milled in a mass ratio of 1:0.08:0.45. After being uniformly mixed, synthetic columns were prepared by compression molding. The synthetic columns were placed in a six-sided press at 5.0 GPa and 1400°C for 30 minutes to synthesize diamonds, thereby obtaining an artificial diamond mixture. (2) Mix 98% concentrated sulfuric acid and 65% concentrated nitric acid in a volume ratio of 3:1, add the above-mentioned artificial diamond mixture, treat at 60°C for 40 minutes, filter, wash, dry and sieve to obtain artificial diamonds with a particle size of mainly 35-40 mesh.

[0031] This embodiment also provides an artificial diamond prepared by the above preparation method.

[0032] Example 2 Example 2 provides a method for preparing an artificial diamond, comprising the following steps: (1) Graphite powder with a particle size of 5 μm, the seed crystal with a particle size of 10 μm in Preparation Example 2, and D in Preparation Example 6 were mixed. 50 The catalysts with a particle size of 0.5 μm were ball-milled and mixed in a mass ratio of 1:0.05:0.3. After being uniformly mixed, synthetic columns were prepared by compression molding. The synthetic columns were placed in a six-sided press at 5.0 GPa and 1300°C for 20 minutes to synthesize diamonds, thereby obtaining an artificial diamond mixture. (2) Mix 98% concentrated sulfuric acid and 65% concentrated nitric acid in a volume ratio of 2.5:1, add the above-mentioned artificial diamond mixture, treat at 50°C for 10 minutes, filter, wash, dry and sieve to obtain artificial diamonds with a particle size of mainly 35-40 mesh.

[0033] This embodiment also provides an artificial diamond prepared by the above preparation method.

[0034] Example 3 Example 3 provides a method for preparing an artificial diamond, comprising the following steps: (1) Graphite powder with a particle size of 10 μm, the seed crystal with a particle size of 20 μm in Preparation Example 3, and D in Preparation Example 7 were mixed. 50 The catalysts with a particle size of 5 μm were ball-milled in a mass ratio of 1:0.1:0.6. After being uniformly mixed, synthetic columns were prepared by compression molding. The synthetic columns were placed in a six-sided press at 6.0 GPa and 1500°C for 40 minutes to synthesize diamonds, thereby obtaining an artificial diamond mixture. (2) Mix 98% concentrated sulfuric acid and 65% concentrated nitric acid in a volume ratio of 3.5:1, add the above-mentioned artificial diamond mixture, treat at 80°C for 60 minutes, filter, wash, dry and sieve to obtain artificial diamonds with a particle size of mainly 35-40 mesh.

[0035] This embodiment also provides an artificial diamond prepared by the above preparation method.

[0036] (3) Comparative Example Comparative Example 1 Comparative Example 1 is substantially the same as Example 1, except that the seed crystals in step (1) of Example 1 are replaced with an equal amount of diamond particles.

[0037] Comparative Example 2 Comparative Example 2 is substantially the same as Example 1, except that the seed crystals in step (1) of Example 1 are replaced by the seed crystals of Preparation Example 4.

[0038] Comparative Example 3 Comparative Example 3 is substantially the same as Example 1, except that the catalyst in step (1) of Example 1 is replaced by the catalyst of Preparation Example 8.

[0039] Comparative Example 4 The contents of Comparative Example 4 are basically the same as those of Example 1, except that the catalyst in step (1) of Example 1 is replaced by the catalyst of Preparation Example 9.

[0040] (IV) Test Examples The diamonds synthesized in Examples 1-3 and Comparative Examples 1-4 were subjected to the following tests: (1) Static pressure strength test: A single diamond with a particle size of 35 / 40 is selected and crushed under the action of static pressure. The automatic static pressure instrument measures the compressive strength of the single particle. Each grain is subjected to pressure from the anvil. As the pressure gradually increases, until the grain is broken, the resistance pressure per unit area during the crushing is the compressive strength.

[0041] (2) Impact toughness test: TI and TTI performance tests were carried out in accordance with GB / T 33144-2016 “Determination of impact toughness of superhard abrasives”. The results are shown in Table 1.

[0042] Table 1 Diamond performance test As can be seen from Table 1, the artificial diamonds prepared in Examples 1-3 of the present invention have high growth rates and excellent epitaxial growth quality.

[0043] Compared with Example 1, Comparative Example 1 replaces the seed in step (1) of Example 1 with an equal amount of diamond particles; Comparative Example 2 omits microwave treatment when preparing the seed, that is, diamond coated with graphyne is used as the seed, and the artificial diamond prepared has a low mixing amount and poor diamond toughness. Specific analysis shows that: using modified graphyne coated diamond particles as seeds, adding diamond as a seed in artificial diamond can guide the diamond to grow along a specific crystal phase, reduce the lattice defects caused by random nucleation, and at the same time reduce the nucleation energy barrier, shorten the synthesis time and reduce energy consumption; laser etching the edge of the diamond seed will form nano-scale grooves or holes on the edge of the seed, exposing more dangling carbon atoms, enhancing the adsorption capacity of the carbon source, and promoting the deposition of graphyne, and the edge structure after etching can disperse the thermal stress during the growth process, avoiding cracks or peeling caused by differences in the lattice expansion coefficient; a graphyne layer is deposited on the surface of the seed, and graphyne has sp-sp 2 The composite hybrid bond and hexagonal symmetrical structure have high chemical activity and good matching with the diamond crystal plane, which can reduce the nucleation barrier of diamond and induce epitaxial growth. As the seed surface in carbon source deposition, it can improve the growth efficiency. At the same time, the flexible two-dimensional structure and high interface thermal conductivity can relieve the thermal stress during the diamond growth process and improve thermal stability. The surface of graphyne modified by microwave is rich in defects and functional groups, and has more active sites, which can further improve the nucleation density and growth rate of diamond. In addition, microwave treatment can optimize the crystallization orientation of graphyne, and has a higher matching degree with the diamond lattice, which can effectively reduce lattice defects and improve the quality of diamond epitaxial growth.

[0044] Compared with Example 1, in Comparative Example 3, when preparing the catalyst, the high entropy alloy powder was replaced with Fe2O3 powder with a composition of 60 at% Fe and 40 at% Ni. 60 Ni 40Alloy powder, that is, alloy powder modified with MoS2 is used as a catalyst; in comparative example 4, step (c) is omitted when preparing the catalyst, that is, high entropy alloy powder is used as a catalyst, the mixed unit yield is slightly lower, and the toughness is slightly worse. Specific analysis shows that: molybdenum disulfide modified high entropy alloy powder is used as a catalyst, and the high entropy alloy powder has a hysteresis diffusion effect and a lattice distortion effect, and can still maintain structural stability under high temperature and high pressure, withstand mechanical stress during the synthesis process, and reduce the uneven pressure distribution caused by catalyst deformation. Compared with traditional alloy catalysts, the multi-component components will provide more active sites, and the synergistic effect between the components can optimize the diffusion path of carbon atoms, reduce the diamond nucleation energy barrier, and increase the crystal growth rate. Modification of high-entropy alloy powder with molybdenum disulfide can passivate the high-entropy alloy grain boundaries and diamond growth interfaces, reduce catalyst embrittlement caused by oxygen segregation under high temperature and high pressure environments, as well as dislocations and inclusion defects in diamond crystals. The layered structure of molybdenum disulfide itself can provide a low-energy barrier carbon atom transmission channel. At the same time, the multi-components of high-entropy alloy powder and the sulfur vacancies of molybdenum disulfide synergistically regulate the electronic structure, both of which can accelerate the phase transition kinetics of graphite to diamond.

[0045] Finally, it should be noted that the above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit the same. The basic principles and main features of the present invention have been described above using specific implementation schemes. Modifications or substitutions may be made based on the present invention, but such modifications or substitutions do not detract from the essence of the corresponding technical solutions from the scope of protection claimed by the present invention.

Claims

1. A method for preparing artificial diamond, characterized in that: The following steps are involved: (1) Graphite powder, seed crystals and catalyst are ball-milled and then molded into synthetic columns; the synthetic columns are synthesized under pressure and heating conditions to obtain artificial diamond mixtures; (2) subjecting the artificial diamond mixture to acid treatment, filtering, washing, drying, and screening to obtain the artificial diamond; The seed crystal in step (1) is a diamond coated with modified graphyne; The catalyst is a MoS2-modified high-entropy alloy powder, which consists of the following components in atomic percentage: 20-30 at% Fe, 20-30 at% Co, 10-25 at% Ni, 15-25 at% Ti, and 10-15 at% Sm.

2. The method for preparing artificial diamond according to claim 1, characterized in that: The seed crystals in step (1) are prepared by the following preparation process: After cleaning the diamond particles, the edges are etched by laser to obtain edge-etched diamonds; the edge-etched diamonds are immersed in a hexaethynylbenzene solution, and the solution is soaked, filtered, and heat-treated to obtain graphyne-coated diamonds; and the graphyne-coated diamonds are subjected to microwave treatment in an inert gas atmosphere to obtain the crystal seeds.

3. The method for preparing artificial diamond according to claim 2, characterized in that: The laser power is 1-5 W, the scanning speed is 200-500 mm / s, and the spot diameter is 5-15 μm; the ratio of the edge-etched diamond to the hexaethynylbenzene solution is (20-70) mg:1 mL; and the concentration of the hexaethynylbenzene solution is 2-5 mg / mL.

4. The method for preparing artificial diamond according to claim 2, characterized in that: The soaking temperature is 50-80°C and the time is 20-30 h; the heat treatment temperature is 300-400°C and the time is 1-2 h; the microwave treatment power is 100-500 W and the time is 30-120 s.

5. The method for preparing artificial diamond according to claim 1, characterized in that: The catalyst in step (1) is prepared by the following preparation process: (a) mixing the components of the high entropy alloy powder and smelting them 3-5 times under an inert gas atmosphere to obtain a high entropy alloy ingot; (b) melting the high entropy alloy ingot, pouring it into a tundish of an atomizing device, introducing an inert gas for atomization, and collecting and sieving to obtain high entropy alloy powder; (c) adding the high entropy alloy powder to an aqueous solution of ammonium tetrathiomolybdate and stirring the mixture with ultrasonic waves, and then heating the mixture to remove the solvent, heat-treating the mixture, cooling the mixture, washing the mixture, and drying the mixture to obtain the catalyst.

6. The method for preparing artificial diamond according to claim 5, characterized in that: During the atomization process in step (b), the temperature of the atomizing gas is 10-30°C and the pressure is 2-5 MPa; in step (c), the mass ratio of the high entropy alloy powder to ammonium tetrathiomolybdate is (5-10):1; the ultrasonic stirring time is 1-2 h; the temperature of the heating to remove the solvent is 50-80°C; the temperature of the heat treatment is 500-700°C and the time is 1-2 h.

7. The method for preparing artificial diamond according to claim 1, characterized in that: The mass ratio of the graphite powder, seed crystals and catalyst in step (1) is 1: (0.05-0.1): (0.3-0.6); the particle size of the graphite powder is 5-10 μm, the particle size of the seed crystal is 10-20 μm, and the particle size of the catalyst is 0.5-5 μm.

8. The method for preparing artificial diamond according to claim 1, characterized in that: The pressurizing pressure in step (1) is 5.0-6.0 GPa, the heating temperature is 1300-1500°C, and the heating time is 20-40 min.

9. The method for preparing artificial diamond according to claim 1, characterized in that: The acid treatment step in step (2) is as follows: 98% concentrated sulfuric acid and 65% concentrated nitric acid are mixed in a volume ratio of (2.5-3.5):1, heated to 50-80°C, and then placed in the artificial diamond mixture for treatment for 10-60 minutes.

10. An artificial diamond, characterized in that: The artificial diamond is prepared by the preparation method of any one of claims 1 to 9.

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