Synthetic diamond and method of making the same

Abstract

The present application belongs to the technical field of diamond synthesis, and particularly relates to a kind of artificial diamond and a preparation method thereof.The preparation method comprises the following steps: (1) graphite powder, seed crystal and catalyst are mixed by ball milling, and then a synthesis column is made by moulding; the synthesis column is subjected to high temperature and high pressure synthesis to obtain artificial diamond mixture; (2) the artificial diamond mixture is subjected to acid treatment, filtration, washing, drying and sieving to obtain artificial diamond; wherein the seed crystal is modified graphdiyne-coated diamond; the catalyst is MoS2-modified high-entropy alloy powder, and the high-entropy alloy powder is composed of the following components with atomic percentage: 20-30 at% Fe, 20-30 at% Co, 10-25 at% Ni, 15-25 at% Ti and 10-15 at% Sm.The artificial diamond of the present application has fast growth rate, high growth quality and excellent toughness.

Description

Technical Field

[0001] This invention belongs to the field of diamond synthesis technology, specifically relating to a synthetic diamond and its preparation method. Background Technology

[0002] Each carbon atom in a diamond crystal passes through sp 3 The hybrid orbitals form covalent bonds 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 also possesses extremely high thermal conductivity (2000-2200 W / m·K) and an extremely low coefficient of thermal expansion (0.8 × 10⁻⁶ W / m·K). -6 Its unique properties, such as its high density (5.47 eV) and wide bandgap, make it irreplaceable in fields such as precision machining tools, optical windows, semiconductor heat dissipation, and quantum devices. However, natural diamond reserves are limited, and diamond mining has a significant negative impact on the environment. Therefore, synthetic diamonds have always been a research hotspot in academia and industry.

[0003] Currently, the mainstream synthesis technologies for synthetic diamonds include chemical vapor deposition (CVD) and high-temperature, high-pressure (HPHT). HPHT, by simulating the environment deep within the Earth's crust (5-6 GPa, 1300-1600 ℃), achieves the phase transformation from graphite to diamond under catalytic catalysis, enabling mass production of millimeter-sized single crystals and accounting for 80% of global industrial diamond production capacity. The core challenges of this method are: 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 lead to a three-order-of-magnitude increase in dislocation density; second, residual catalyst metal affects purity, requiring mixed acid treatment to reduce impurities to the ppm level; and third, the slow growth rate of large-size single crystals (approximately 1 mm / day), with the risk of cracking increasing exponentially with size. In recent years, by improving catalyst alloys (such as Fe-Co-Cr systems) and employing stepped pressure ramping technology, it has become possible to prepare diamonds larger than 10 carats. However, the contradictions between crystal size and growth cycle, and between preparation methods and energy consumption, remain technical challenges that need to be overcome. Summary of the Invention

[0004] The primary objective of this invention is to provide a method for preparing synthetic diamond.

[0005] The second objective of this invention is to provide a synthetic diamond crystal with a fast growth rate, high growth quality, and excellent toughness.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing synthetic diamond includes the following steps:

[0008] (1) Graphite powder, seed crystals and catalyst ball milling are mixed and then molded into a synthetic column; the synthetic column is subjected to high temperature and high pressure synthesis to obtain artificial diamond mixture;

[0009] (2) The artificial diamond mixture is subjected to acid treatment, filtration, washing, drying and sieving to obtain the artificial diamond;

[0010] The seed crystal in step (1) is modified graphyne-coated diamond; the catalyst is MoS2-modified high-entropy alloy powder, which is composed of the following atomic percentage components: 20-30 at% Fe, 20-30 at% Co, 10-25 at% Ni, 15-25 at% Ti, and 10-15 at% Sm.

[0011] Further, the seed crystals described in step (1) are prepared by the following process:

[0012] After cleaning the diamond particles, the edges are etched using a laser to obtain edge-etched diamond; the edge-etched diamond is then immersed in a hexaethynylbenzene solution, soaked, filtered, and heat-treated to obtain graphyne-coated diamond; the graphyne-coated diamond is then microwave-treated in an inert gas atmosphere to obtain the seed crystal.

[0013] 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 edge etching diamond to hexaethynylbenzene solution is (20-70) mg:1 mL; and the concentration of hexaethynylbenzene solution is 2-5 mg / mL.

[0014] Furthermore, the soaking temperature is 50-80 ℃ and the time is 20-30 h; the heat treatment temperature is 300-400 ℃ and the time is 1-2 h; the microwave treatment power is 100-500 W and the time is 30-120 s.

[0015] Furthermore, the catalyst described in step (1) is prepared by the following process:

[0016] (a) Mix the components of the high-entropy alloy powder and melt it 3-5 times in an inert gas atmosphere to obtain a high-entropy alloy ingot;

[0017] (b) The high-entropy alloy ingot is melted, poured into the intermediate package of the atomization equipment, and inert gas is introduced for gas atomization. The powder is then collected and sieved to obtain high-entropy alloy powder.

[0018] (c) The high-entropy alloy powder is added to an aqueous solution of ammonium tetrathiomolybdate and ultrasonically stirred. Then, the solvent is removed by heating, heat treatment, cooling, cleaning and drying are performed to obtain the catalyst.

[0019] Further, in step (b), the temperature of the atomizing gas during gas atomization is 10-30 ℃ 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 for heating to remove the solvent is 50-80 ℃; and the heat treatment temperature is 500-700 ℃ for 1-2 h.

[0020] Further, in step (1), the mass ratio of graphite powder, seed crystal and catalyst 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.

[0021] Furthermore, the high-temperature and high-pressure synthesis in step (1) is carried out at a pressure of 5.0-6.0 GPa, a temperature of 1300-1500℃, and a time of 20-40 min.

[0022] Further, the acid treatment step in step (2) is as follows: 98% concentrated sulfuric acid and 65% concentrated nitric acid are mixed at a volume ratio of (2.5-3.5):1, heated to 50-80 ℃, and then placed in the artificial diamond mixture for treatment for 10-60 min.

[0023] A synthetic diamond is prepared by the above-described method for preparing synthetic diamond.

[0024] The beneficial technical effects of this invention are as follows:

[0025] 1. This invention utilizes modified graphyne-coated diamond particles as seed crystals, which are prepared by sequentially etching the edges of the diamond, depositing graphyne on the surface, and performing microwave modification. First, by adding diamond as a seed crystal to synthetic diamond, this invention guides the diamond to grow along a specific crystal phase, reducing lattice defects caused by random nucleation, lowering the nucleation barrier, shortening the synthesis time, and reducing energy consumption. Next, laser etching of the edges of the diamond seed crystals creates nanoscale grooves or pores, exposing more dangling carbon atoms, enhancing the adsorption capacity of the carbon source, promoting graphyne deposition, and dispersing the thermal stress during growth, preventing cracks or peeling due to differences in lattice expansion coefficients. Furthermore, this invention deposits a graphyne layer on the seed crystal surface; graphyne has sp-sp... 2The complex hybrid bonds and hexagonal symmetry structure exhibit high chemical reactivity and good matching with diamond crystal faces, which can reduce the nucleation barrier of diamond and induce epitaxial growth. As a seed surface in carbon source deposition, it can improve growth efficiency. At the same time, the flexible two-dimensional structure and high interfacial thermal conductivity can alleviate thermal stress during diamond growth and improve thermal stability. Finally, the microwave-modified graphyne surface is rich in defects and functional groups, with more active sites, which can further improve the nucleation density and growth rate of diamond. Moreover, microwave treatment can optimize the crystal orientation of graphyne, resulting in a higher matching degree with the diamond lattice, effectively reducing lattice defects and improving the quality of diamond epitaxial growth.

[0026] 2. This invention uses molybdenum disulfide-modified high-entropy alloy powder as a catalyst. High-entropy alloys exhibit hysteresis diffusion and lattice distortion effects, maintaining structural stability under high temperature and pressure, withstanding mechanical stress during synthesis, and reducing uneven pressure distribution caused by catalyst deformation. Compared to traditional alloy catalysts, the multi-component composition provides more active sites, and the synergistic effect between components optimizes carbon atom diffusion paths, lowers the diamond nucleation energy barrier, and increases crystal growth rate. Furthermore, molybdenum disulfide modification of the high-entropy alloy powder passivates the high-entropy alloy grain boundaries and diamond growth interface, reducing catalyst embrittlement caused by oxygen segregation under high temperature and pressure, as well as dislocations and inclusion defects in the diamond crystal. The layered structure of molybdenum disulfide itself provides low-barrier carbon atom transport channels. Simultaneously, the multi-component composition of the high-entropy alloy and the sulfur vacancies of molybdenum disulfide synergistically regulate the electronic structure, both accelerating the phase transition kinetics from graphite to diamond. Attached Figure Description

[0027] Figure 1 Scanning electron microscope image of the catalyst prepared in Example 5. Detailed Implementation

[0028] The following is a further detailed description of the present invention in conjunction with specific preferred embodiments, and it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention. Specific conditions not specified in the embodiments are performed according to conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, all reagents or instruments used are conventional products obtained through commercial channels.

[0029] (a) Preparation example

[0030] Preparation Example 1

[0031] Preparation Example 1 provides a seed crystal, which is prepared by the following process:

[0032] Diamond particles were cleaned and their edges were etched using a 3 W laser with a spot diameter of 10 μm at a scanning rate of 350 mm / s to obtain edge-etched diamond. The edge-etched diamond was added to a 3 mg / mL solution of hexaethynylbenzene pyridine at a ratio of 50 mg: 1 mL. The solution was then heated to 70 °C and soaked for 24 h. After filtration, the collected solid was heat-treated at 350 °C for 1 h to obtain graphyne-coated diamond. The graphyne-coated diamond was then microwaved at 300 W for 80 s in an argon atmosphere to obtain seed crystals with a particle size of 15 μm.

[0033] Preparation Example 2

[0034] Preparation Example 2 provides a seed crystal, which is prepared by the following process:

[0035] Diamond particles were cleaned and their edges were etched using a 1 W laser with a spot diameter of 5 μm at a scanning rate of 200 mm / s to obtain edge-etched diamond. The edge-etched diamond was added to a 2 mg / mL solution of hexaethynylbenzene in pyridine at a ratio of 20 mg: 1 mL. The solution was then heated to 50 °C and soaked for 20 h. After filtration, the collected solid was heat-treated at 300 °C for 1 h to obtain graphyne-coated diamond. The graphyne-coated diamond was then microwaved at 100 W for 30 s in an argon atmosphere to obtain seed crystals with a particle size of 10 μm.

[0036] Preparation Example 3

[0037] Preparation Example 3 provides a seed crystal, which is prepared by the following process:

[0038] Diamond particles were cleaned and their edges were etched using a 5 W laser with a spot diameter of 15 μm at a scanning rate of 500 mm / s to obtain edge-etched diamond. The edge-etched diamond was added to a 5 mg / mL solution of hexaethynylbenzene pyridine at a ratio of 70 mg: 1 mL. The solution was then heated to 80 °C and soaked for 30 h. After filtration, the collected solid was heat-treated at 400 °C for 2 h to obtain graphyne-coated diamond. The graphyne-coated diamond was then microwaved at 500 W for 120 s in an argon atmosphere to obtain seed crystals with a particle size of 20 μm.

[0039] Preparation Example 4

[0040] Preparation Example 4 is basically the same as Preparation Example 1, except that the microwave treatment operation is omitted and the diamond coated with graphyne is used as the seed crystal.

[0041] Preparation Example 5

[0042] Preparation Example 5 provides a catalyst prepared by the following process:

[0043] (a) Weigh and mix the metal raw materials according to the atomic percentages of 25 at% Fe, 25 at% Co, 20 at% Ni, 20 at% Ti, and 10 at% Sm. Melt the mixture in a medium-frequency melting furnace. During the melting process, argon gas is continuously introduced into the furnace mouth. After melting to the molten state, the mixture is cooled. Repeat this operation 4 times to obtain a high-entropy alloy ingot with uniform composition.

[0044] (b) The high-entropy alloy ingot is melted to obtain a high-entropy alloy liquid, which is transferred to the intermediate jar of the atomizing furnace in a flowing state. At the same time, high-purity argon gas is introduced, and the high-entropy alloy liquid is allowed to flow into the atomizing chamber from the bottom guide tube. Then, nitrogen gas at a temperature of 20 ℃ and a pressure of 3 MPa is used for atomization to produce powder. After collection and sieving, high-entropy alloy powder is obtained.

[0045] (c) According to the mass ratio of high-entropy alloy powder to ammonium tetrathiomolybdate (8:1), the high-entropy alloy powder was added to an aqueous solution of 0.08 mol / L ammonium tetrathiomolybdate, and ultrasonically stirred for 1 h. Then, the solvent was removed by heating at 70 °C, and the remaining solid was heat-treated at 600 °C for 1 h. After cooling, cleaning, and drying, D was obtained. 50 It is a catalyst with a thickness of 2 μm.

[0046] The scanning electron microscope image of the catalyst prepared in this example is shown below. Figure 1 As shown, from Figure 1 As can be seen, the alloy particles prepared by gas atomization have good sphericity, with a small number of satellite spheres adhering together. After modification with molybdenum disulfide, a uniform nanoscale layered coating is formed on the powder surface, and the smoothness of the powder surface decreases.

[0047] Preparation Example 6

[0048] Preparation Example 6 provides a catalyst prepared by the following process:

[0049] (a) Weigh and mix the metal raw materials according to the atomic percentages of 20 at% Fe, 30 at% Co, 25 at% Ni, 15 at% Ti, and 10 at% Sm. Melt the mixture in a medium-frequency melting furnace. During the melting process, argon gas is continuously introduced into the furnace mouth. Melt the mixture to the molten state and then cool it. Repeat this operation 3 times to obtain a high-entropy alloy ingot with uniform composition.

[0050] (b) The high-entropy alloy ingot is melted to obtain a high-entropy alloy liquid, which is transferred to the intermediate jar of the atomizing furnace in a flowing state. At the same time, high-purity argon gas is introduced, and the high-entropy alloy liquid is then allowed to flow into the atomizing chamber from the bottom guide tube. Then, nitrogen gas at a temperature of 10 ℃ and a pressure of 2 MPa is used for atomization to produce powder. After collection and sieving, high-entropy alloy powder is obtained.

[0051] (c) According to the mass ratio of high-entropy alloy powder to ammonium tetrathiomolybdate (5:1), the high-entropy alloy powder was added to an aqueous solution of 0.05 mol / L ammonium tetrathiomolybdate, and ultrasonically stirred for 1 h. Then, the solvent was removed by heating at 50 °C, and the remaining solid was heat-treated at 500 °C for 1 h. After cooling, cleaning, and drying, D was obtained. 50 The catalyst is 0.5 μm.

[0052] Preparation Example 7

[0053] Preparation Example 7 provides a catalyst prepared by the following process:

[0054] (a) Weigh and mix the metal raw materials according to the atomic percentages of 30 at% Fe, 20 at% Co, 10 at% Ni, 25 at% Ti, and 15 at% Sm. Melt them in a medium-frequency melting furnace. During the melting process, argon gas is continuously introduced into the furnace mouth. Melt to the molten state and then cool. Repeat this operation 5 times to obtain a high-entropy alloy ingot with uniform composition.

[0055] (b) The high-entropy alloy ingot is melted to obtain a high-entropy alloy liquid, which is transferred to the intermediate jar of the atomizing furnace in a flowing state. At the same time, high-purity argon gas is introduced, and the high-entropy alloy liquid is then allowed to flow into the atomizing chamber from the bottom guide tube. Then, nitrogen gas at a temperature of 30 ℃ and a pressure of 5 MPa is used for atomization to produce powder. After collection and sieving, high-entropy alloy powder is obtained.

[0056] (c) According to the mass ratio of high-entropy alloy powder to ammonium tetrathiomolybdate of 10:1, the high-entropy alloy powder was added to an aqueous solution of ammonium tetrathiomolybdate with a concentration of 0.1 mol / L, and ultrasonically stirred for 2 h. Then, the solvent was removed by heating at 80 ℃, and the remaining solid material was heat-treated at 700 ℃ for 2 h. After cooling, cleaning and drying, D was obtained. 50 The catalyst is 5 μm in size.

[0057] Preparation Example 8

[0058] Preparation Example 8 is basically the same as Preparation Example 5, except that the high-entropy alloy in step (a) is replaced with Fe alloy with a composition of 60 at% Fe and 40 at% Ni. 60 Ni 40 The alloy, namely the MoS2 modified alloy powder, is used as a catalyst.

[0059] Preparation Example 9

[0060] Preparation Example 9 is basically the same as Preparation Example 5, except that step (c) is omitted, i.e., high-entropy alloy powder is used as a catalyst.

[0061] (II) Implementation Examples

[0062] Example 1

[0063] Example 1 provides a method for preparing synthetic diamond, comprising the following steps:

[0064] (1) Graphite powder with a particle size of 8 μm, seed crystals with a particle size of 15 μm from Preparation Example 1, and D from Preparation Example 5 were used. 50 A 2 μm catalyst was ball-milled and mixed at a mass ratio of 1:0.08:0.45. After uniform mixing, a synthetic column was prepared by compression molding. The synthetic column was then placed in a six-sided press at 5.0 GPa and 1400 ℃ to synthesize diamond for 30 min, resulting in a synthetic diamond mixture.

[0065] (2) Mix 98% concentrated sulfuric acid and 65% concentrated nitric acid at a volume ratio of 3:1, add the above-mentioned artificial diamond mixture, treat at 60 °C for 40 min, filter, wash, dry and sieve to obtain artificial diamond with a particle size of 35-40 mesh.

[0066] This embodiment also provides a synthetic diamond, prepared by the above-described preparation method.

[0067] Example 2

[0068] Example 2 provides a method for preparing synthetic diamond, comprising the following steps:

[0069] (1) Graphite powder with a particle size of 5 μm, seed crystals with a particle size of 10 μm as in Preparation Example 2, and D as in Preparation Example 6 50 A catalyst with a particle size of 0.5 μm was ball-milled and mixed at a mass ratio of 1:0.05:0.3. After uniform mixing, a synthetic column was prepared by compression molding. The synthetic column was then placed in a six-sided press at 5.0 GPa and 1300 ℃ to synthesize diamond for 20 min, resulting in a synthetic diamond mixture.

[0070] (2) Mix 98% concentrated sulfuric acid and 65% concentrated nitric acid at a volume ratio of 2.5:1, add the above-mentioned artificial diamond mixture, treat at 50 °C for 10 min, filter, wash, dry and sieve to obtain artificial diamond with a particle size of 35-40 mesh.

[0071] This embodiment also provides a synthetic diamond, prepared by the above-described preparation method.

[0072] Example 3

[0073] Example 3 provides a method for preparing synthetic diamond, comprising the following steps:

[0074] (1) Graphite powder with a particle size of 10 μm, seed crystals with a particle size of 20 μm as in Preparation Example 3, and D as in Preparation Example 7 50 A 5 μm catalyst was ball-milled and mixed at a mass ratio of 1:0.1:0.6. After uniform mixing, a synthetic column was prepared by compression molding. The synthetic column was then placed in a six-sided press at 6.0 GPa and 1500 ℃ to synthesize diamond for 40 min, resulting in a synthetic diamond mixture.

[0075] (2) Mix 98% concentrated sulfuric acid and 65% concentrated nitric acid at a volume ratio of 3.5:1, add the above-mentioned artificial diamond mixture, treat at 80 ℃ for 60 min, filter, wash, dry and sieve to obtain artificial diamond with a particle size of 35-40 mesh.

[0076] This embodiment also provides a synthetic diamond, prepared by the above-described preparation method.

[0077] (III) Comparative Example

[0078] Comparative Example 1

[0079] Comparative Example 1 is basically the same as Example 1, except that the seed crystal in step (1) of Example 1 is replaced with an equal amount of diamond particles.

[0080] Comparative Example 2

[0081] Comparative Example 2 is basically the same as Example 1, except that the seed crystal in step (1) of Example 1 is replaced with the seed crystal of Preparation Example 4.

[0082] Comparative Example 3

[0083] Comparative Example 3 is basically the same as Example 1, except that the catalyst in step (1) of Example 1 is replaced with the catalyst of Preparation Example 8.

[0084] Comparative Example 4

[0085] Comparative Example 4 is basically the same as Example 1, except that the catalyst in step (1) of Example 1 is replaced with the catalyst of Preparation Example 9.

[0086] (iv) Test Cases

[0087] The diamonds synthesized in Examples 1-3 and Comparative Examples 1-4 were subjected to the following tests:

[0088] (1) Static compressive strength test: Select the load value of a single diamond with a particle size of 35 / 40 under static pressure. The automatic static compressive strength of a single particle is measured. Each grain is subjected to pressure from the anvil. As the pressure gradually increases, it continues until the grain is broken. The resistance pressure per unit area during the breakage is the compressive strength.

[0089] (2) Impact toughness test: The TI and TTI performance were tested according to GB / T 33144-2016 "Method for determining the impact toughness of superhard abrasives". The results are shown in Table 1.

[0090] Table 1 Diamond performance testing

[0091]

[0092] As shown in Table 1, the synthetic diamonds obtained in Examples 1-3 of this invention have high growth rates and excellent epitaxial growth quality.

[0093] Compared to Example 1, Comparative Example 1 replaced the seed crystal in step (1) of Example 1 with an equal amount of diamond particles; Comparative Example 2 omitted microwave treatment when preparing the seed crystal, that is, used graphyne-coated diamond as the seed crystal, resulting in a low mixing content and poor diamond toughness in the artificial diamond. Specific analysis shows that: using modified graphyne-coated diamond particles as seed crystals, adding diamond as a seed crystal to artificial diamond can guide the diamond to grow along a specific crystal phase, reduce lattice defects caused by random nucleation, lower the nucleation energy barrier, shorten the synthesis time, and reduce energy consumption; laser etching of the edges of the diamond seed crystal will form nanoscale grooves or holes at the edges of the seed crystal, exposing more dangling carbon atoms, enhancing the adsorption capacity of the carbon source, promoting the deposition of graphyne, and the etched edge structure can disperse the thermal stress during the growth process, avoiding cracks or peeling caused by differences in lattice expansion coefficients; depositing a graphyne layer on the surface of the seed crystal, graphyne has sp-sp... 2 The complex hybrid bonds and hexagonal symmetry structure exhibit high chemical activity and good matching with diamond crystal faces, which can reduce the nucleation barrier of diamond and induce epitaxial growth. As a seed surface in carbon source deposition, it can improve growth efficiency. At the same time, the flexible two-dimensional structure and high interfacial thermal conductivity can alleviate thermal stress during diamond growth and improve thermal stability. The microwave-modified graphyne surface is rich in defects and functional groups, with more active sites, which can further improve the nucleation density and growth rate of diamond. Moreover, microwave treatment can optimize the crystal orientation of graphyne, resulting in a higher matching degree with the diamond lattice, effectively reducing lattice defects and improving the quality of diamond epitaxial growth.

[0094] Compared to Example 1, in Comparative Example 3, the high-entropy alloy powder was replaced with Fe powder with a composition of 60 at% Fe and 40 at% Ni during catalyst preparation. 60Ni 40 In the first example, MoS2-modified alloy powder was used as a catalyst. In the second example, step (c) was omitted during catalyst preparation, and high-entropy alloy powder was used as the catalyst. The mixed yield was slightly lower and the toughness was slightly worse. Specific analysis shows that using molybdenum disulfide-modified high-entropy alloy powder as a catalyst, the high-entropy alloy powder has a hysteresis diffusion effect and lattice distortion effect. It can still maintain structural stability under high temperature and high pressure, withstand the mechanical stress during the synthesis process, reduce the uneven pressure distribution caused by catalyst deformation, and compared with traditional alloy catalysts, the multi-component components provide more active sites. The synergistic effect between components can optimize the carbon atom diffusion path, reduce the diamond nucleation energy barrier, and improve the crystal growth rate. Molybdenum disulfide (MoD) modification of high-entropy alloy powder can passivate the grain boundaries of high-entropy alloys and the diamond growth interface, reduce catalyst embrittlement caused by oxygen segregation under high temperature and high pressure, and reduce dislocations and inclusion defects in diamond crystals. The layered structure of MoD itself can provide low-barrier carbon atom transport channels. At the same time, the multi-component composition of high-entropy alloy powder and the sulfur vacancies of MoD synergistically regulate the electronic structure, which can accelerate the phase transition kinetics of graphite to diamond.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. The basic principles and main features of the present invention have been described above with specific implementation schemes. Based on the present invention, some modifications or substitutions can be made, but these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of protection claimed by the present invention.

Claims

1. A method for preparing synthetic diamond, characterized in that, Includes the following steps: (1) Graphite powder, seed crystals and catalyst ball milling are mixed and then molded into a synthetic column; the synthetic column is subjected to high temperature and high pressure synthesis to obtain artificial diamond mixture; (2) The artificial diamond mixture is subjected to acid treatment, filtration, washing, drying and sieving to obtain the artificial diamond; The seed crystal mentioned in step (1) is modified graphyne-coated diamond; The catalyst is a MoS2-modified high-entropy alloy powder, which is composed of the following atomic percentage components: 20-30 at% Fe, 20-30 at% Co, 10-25 at% Ni, 15-25 at% Ti, and 10-15 at% Sm. The seed crystals mentioned in step (1) are obtained by the following preparation process: After cleaning the diamond particles, the edges are etched using a laser to obtain edge-etched diamond; the edge-etched diamond is then immersed in a hexaethynylbenzene solution, soaked, filtered, and heat-treated to obtain graphyne-coated diamond; the graphyne-coated diamond is then microwave-treated in an inert gas atmosphere to obtain the seed crystal.

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

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

4. The method for preparing synthetic diamond according to claim 1, characterized in that, The catalyst mentioned in step (1) is prepared by the following process: (a) Mix the components of the high-entropy alloy powder and melt it 3-5 times in an inert gas atmosphere to obtain a high-entropy alloy ingot; (b) The high-entropy alloy ingot is melted, poured into the intermediate package of the atomization equipment, and inert gas is introduced for gas atomization. The powder is then collected and sieved to obtain high-entropy alloy powder. (c) The high-entropy alloy powder is added to an aqueous solution of ammonium tetrathiomolybdate and ultrasonically stirred. Then, the solvent is removed by heating, heat treatment, cooling, cleaning and drying are performed to obtain the catalyst.

5. The method for preparing synthetic diamond according to claim 4, characterized in that, In step (b), the temperature of the atomizing gas during the gas atomization process is 10-30 ℃ 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 for heating to remove the solvent is 50-80 ℃; and the heat treatment temperature is 500-700 ℃ for 1-2 h.

6. The method for preparing synthetic diamond according to claim 1, characterized in that, In step (1), the mass ratio of graphite powder, seed crystals and catalyst 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 crystals is 10-20 μm, and the particle size of the catalyst is 0.5-5 μm.

7. The method for preparing synthetic diamond according to claim 1, characterized in that, The high-temperature and high-pressure synthesis in step (1) is carried out at a pressure of 5.0-6.0 GPa, a temperature of 1300-1500 ℃, and a time of 20-40 min.

8. The method for preparing synthetic diamond according to claim 1, characterized in that, The acid treatment step in step (2) is as follows: mix 98% concentrated sulfuric acid and 65% concentrated nitric acid at a volume ratio of (2.5-3.5):1, heat to 50-80 ℃, and then put artificial diamond mixture into the mixture for 10-60 min.

9. A synthetic diamond, characterized in that, It is prepared by the method for preparing synthetic diamond according to any one of claims 1-8.

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