A synthetic method for inhibiting the occurrence of a crack in a synthetic gemstone grade diamond

Abstract

The application provides a synthesis method for inhibiting the occurrence of a crack phenomenon of artificial gem-grade diamond, and relates to the technical field of artificial gem-grade diamond synthesis. The synthesis method for inhibiting the occurrence of the crack phenomenon of the artificial gem-grade diamond comprises the following steps: a pressure transmission heat preservation material ball milling step; a raw material and auxiliary component preparation step, which comprises a raw material and auxiliary component preparation substep and a raw material preparation substep; an assembly component baking process treatment step; an assembly synthesis block and heat treatment step; a high-temperature and high-pressure crystal growth step; and an acid washing post-processing step, so as to obtain a gem-grade diamond single crystal. The synthesis method for inhibiting the occurrence of the crack phenomenon of the artificial gem-grade diamond provided by the application can effectively inhibit the occurrence of the crack phenomenon by adopting a catalyst component optimization method, significantly improves the yield of the diamond single crystal, and further greatly reduces the synthesis cost of the diamond single crystal.

Description

Technical Field

[0001] The present invention relates to the technical field of synthetic gem-grade diamonds, and in particular to a synthetic method for suppressing crystal cracking of synthetic gem-grade diamonds. Background Art

[0002] Artificial diamond, also known as "cultivated diamond", is a representative of superhard materials. It is a functional material that combines many excellent extreme properties such as maximum hardness, widest light transmittance band, maximum thermal conductivity, radiation resistance, and corrosion resistance. It is widely used in many fields such as industry, science and technology, national defense, military, aerospace, and the diamond industry.

[0003] The synthesis methods of artificial gem-grade diamond mainly adopt the high-temperature and high-pressure method and the low-pressure vapor deposition method. To date, the high-temperature and high-pressure method is still the mainstream synthesis method for synthesizing artificial gem-grade diamond single crystals. For the high-temperature and high-pressure method to grow artificial gem-grade diamond single crystals, since the diamond single crystal is epitaxially grown in a liquid catalytic solvent, metal impurities, lattice defects, surface pits, polycrystals and crystal cracks often appear in the synthesized crystals. Compared with other crystal defects, diamond single crystal crack defects are the most destructive to crystal quality. Since the causes of diamond single crystal crack defects are very complex, how to avoid the occurrence of crystal cracks in the growth of artificial gem-grade diamond single crystals has always been a technical problem that has plagued scientific researchers and related practitioners.

[0004] Currently, in the synthesis of synthetic gem-grade diamond single crystals, a slow cooling and decompression process is typically performed on the diamond single crystals at the end of growth to reduce the probability of crack defects. For large diamond single crystals that still exhibit small cracks (non-through cracks) after the slow cooling and decompression process, laser cutting is typically used to remove the cracks and then grind them into smaller crystals for reuse to reduce economic losses. However, diamond single crystals with through cracks within them have virtually no utility value. In the current international high-pressure field, ultrahigh-pressure diamond anvil cells can generate pressures exceeding 300 GPa. Therefore, the occurrence of crystal cracks under high-temperature, high-pressure diamond single crystal synthesis conditions, which generally do not exceed 10 GPa, is inevitably due to the poor quality and low compressive strength of the corresponding crystal. However, the process of simply subjecting the diamond single crystal to a slow cooling and decompression process to partially eliminate the internal stresses of the crystal growth and reduce the external stresses generated by the catalyst solidification cannot fundamentally solve the problem of crack defects in the synthesis of synthetic gem-grade diamond single crystals.

[0005] In summary, the existing slow cooling and pressure reduction process can only reduce the probability of crack defects to a certain extent, but cannot solve the problem of crystal cracking from the source; the slow cooling and pressure reduction process takes several or even more than ten hours, which greatly increases the synthesis cost of diamond single crystals. Summary of the Invention

[0006] The objectives of the present invention include, for example, providing a synthesis method for suppressing the occurrence of crystal cracking in artificial gem-grade diamonds. The method adopts a method of optimizing catalyst components, which can effectively suppress the occurrence of crystal cracking without undergoing a time-consuming slow cooling and pressure reduction process, significantly improve the yield of diamond single crystals, and thus significantly reduce the synthesis cost of diamond single crystals.

[0007] The embodiments of the present invention can be implemented as follows:

[0008] The embodiment of the present invention provides a synthesis method for suppressing crystal cracking of artificial gem-grade diamond, comprising:

[0009] The ball milling step of the pressure-transmitting and heat-insulating material is as follows: the pressure-transmitting and heat-insulating material composed of industrial-grade MgO powder and ZrO2 calcined at 1600°C is mixed and ball milled to form MgO+ZrO2 pressure-transmitting and heat-insulating material powder;

[0010] The steps of preparing raw materials and auxiliary components include:

[0011] The raw and auxiliary component preparation sub-steps are as follows: the MgO+ZrO2 pressure-transmitting and heat-insulating material powder after ball milling is placed in a mold and pressed into a block crystal bed, a plug and an annular container by a tablet press; at the same time, a copper plate is placed in the mold and punched into a sheet-shaped conductive copper sheet by a tablet press; and,

[0012] Raw material preparation sub-step: placing high-purity graphite powder into a mold and pressing it into a block using a tablet press; placing a catalyst alloy plate into a mold and punching it into a sheet-shaped catalyst alloy plate using a tablet press, wherein the catalyst alloy plate is Ni x Mn y Co z Alloy, where x, y, and z represent the weight ratio of the three metals and x+y+z=100;

[0013] The baking process steps of the assembled components are as follows: the MgO+ZrO2 block of the pressure-transmitting and heat-insulating component is placed in a medium-temperature furnace for baking; the pressed graphite carbon source block and the graphite heating tube are placed in a drying oven for drying; the catalyst alloy sheet and the diamond seed crystal are placed in anhydrous alcohol and cleaned using ultrasonic waves. After cleaning, they are placed in a drying oven for drying;

[0014] Assembling the synthesis block and heat treatment steps: assembling the crystal bed, plug, annular container, graphite carbon source block, catalyst metal sheet, diamond seed crystal, graphite heating tube, conductive graphite sheet, conductive copper sheet, conductive steel cap and pyrophyllite composite block into a diamond synthesis block; placing the diamond synthesis block in a drying oven for drying;

[0015] High temperature and high pressure crystal growth steps: placing the heat-treated diamond synthesis block into the pressure chamber of the hinged beam type six-sided top press to synthesize diamond; when the crystal growth is completed, removing the carbon source catalyst rod from the diamond synthesis block;

[0016] Post-pickling treatment steps: Place the catalyst rod with the diamond crystal embedded in it into a boiling dilute nitric acid solution for preliminary pickling treatment to separate the diamond single crystal sample and the catalyst alloy; then place the diamond single crystal obtained from the initial pickling into a boiling mixture of concentrated HNO3 and concentrated H2SO4 for fine washing to obtain gem-grade diamond single crystals.

[0017] Furthermore, in an optional embodiment, in the ball milling step of the pressure-transmitting heat-insulating material, the weight ratio of industrial-grade MgO powder to ZrO2 calcined at 1600°C is 1:4, the ball milling speed is 300 rpm, and the ball milling time is 240 minutes.

[0018] Furthermore, in an optional embodiment, in the raw material preparation sub-step, the catalyst alloy plate is Ni x Mn y Co z alloy, and 40<x<60, 5<z<15.

[0019] Furthermore, in an optional embodiment, in the raw material preparation sub-step, high-grade abrasive-grade hexahedral diamond with a diameter of 0.8-1.0 mm is selected as a seed crystal for standby use.

[0020] Furthermore, in an optional embodiment, in the baking process treatment steps of the assembly components, the heating rate of the pressure transmission and heat insulation component MgO+ZrO2 block is 400°C / hour, the baking temperature is 900-1100°C, the baking time is 8 hours, and the cooling rate is 100°C / h; the drying time of the graphite carbon source block and the graphite heating tube is 5-8 hours, and the drying temperature is 230-250°C; the drying time of the catalyst metal sheet and the diamond seed crystal is 6-8 hours, and the drying temperature is 100-120°C.

[0021] Furthermore, in an optional embodiment, in the steps of assembling the synthetic block and heat treating, the diamond synthetic block is dried for 2-3 hours at a drying temperature of 110-130°C.

[0022] Further, in the optional embodiment, in the high-temperature high-pressure crystal growth step, the synthesis pressure used in the crystal growth is 5.6 GPa, the synthesis temperature is 1250-1450℃, the pressure increasing speed time is 10-15 minutes, the temperature increasing rate is 40℃ / minute, and the crystal growth time is 8 hours or more.

[0023] Further, in the optional embodiment, in the acid pickling post-processing step, the volume ratio of concentrated HNO3 and concentrated H2SO4 is 2:1, and the fine cleaning time is 2-3 hours. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0025] Figure 1 A schematic diagram of the synthesis method for inhibiting the occurrence of the crack phenomenon of artificial gem-grade diamond described in the specific embodiments of the present application;

[0026] Figure 2 Fe 70 Ni 30 Optical photograph of the poor-quality diamond single crystal synthesized by catalyst;

[0027] Figure 3 Fe 60 Ni 30 Co 10 Optical photograph of the poor-quality diamond single crystal synthesized by catalyst.

[0028] Figure 4 Ni 55 Mn 35 Co 10 Optical photograph of the high-quality diamond single crystal synthesized by catalyst; DETAILED DESCRIPTION

[0029] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the following will make a detailed description of the specific embodiments of the present application in combination with the drawings.

[0030] In order to make the purposes, technical solutions and advantages of the embodiments of the present application more clear, the following will make a clear and complete description of the technical solutions in the embodiments of the present application in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, not all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0031] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0032] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0033] See also Figure 1 This embodiment provides a synthesis method for suppressing the occurrence of crystal cracking in artificial gem-grade diamonds. The method adopts a catalyst component optimization method, which can effectively suppress the occurrence of crystal cracking, significantly improve the yield of diamond single crystals, and thus significantly reduce the synthesis cost of diamond single crystals.

[0034] like Figure 1 As shown, an embodiment of the present invention provides a synthesis method for suppressing the occurrence of artificial gem-grade diamond cracking, which includes a pressure-transmitting and heat-insulating material ball milling step, an original and auxiliary component and raw material preparation step, a baking process treatment step for assembled components, an assembly synthesis block and heat treatment step, a high-temperature and high-pressure crystal growth step, and an acid-washing post-treatment step. Each step is described in detail below.

[0035] Ball milling steps for pressure-transmitting and heat-insulating materials: mixing and ball milling the pressure-transmitting and heat-insulating materials composed of industrial-grade MgO powder and ZrO2 calcined at 1600°C to form MgO+ZrO2 pressure-transmitting and heat-insulating material powder.

[0036] Optionally, in the step of ball milling the pressure-transmitting and heat-insulating material, the weight ratio of industrial-grade MgO powder to ZrO2 calcined at 1600°C is 1:4, the ball milling speed is 300 rpm, and the ball milling time is 240 minutes. The ball milling can be performed using a ball mill, wherein the industrial-grade MgO powder and the ZrO2 calcined at 1600°C are placed in a stainless steel ball milling jar, which is fixed to a ball mill (e.g., a planetary ball mill) and ball milled at a predetermined speed for a predetermined period of time.

[0037] The steps of preparing raw and auxiliary components and raw materials include the steps of preparing raw and auxiliary components and the steps of preparing raw materials. The steps of preparing raw and auxiliary components are as follows: the MgO+ZrO2 pressure-transmitting and heat-insulating material powder after ball milling is placed in a mold and pressed into a block crystal bed, a plug and an annular container by a tablet press; at the same time, a copper plate is placed in a mold and punched into a sheet of conductive copper plate by a tablet press; the steps of preparing raw materials are as follows: high-purity graphite powder is placed in a mold and pressed into a block by a tablet press; a catalyst alloy plate is placed in a mold and punched into a sheet of catalyst alloy plate by a tablet press, wherein the catalyst alloy plate is Ni x Mn y Coz alloy, wherein x, y, z represent the weight ratio of three metals, and x+y+z=100; meanwhile, under microscope, high-grade abrasive grade hexahedral diamond with diameter of 0.8-1.0 mm is used as seed for standby.

[0038] It should be noted that the embodiment of the present application optimizes and improves the components of the catalyst alloy plate. In the embodiment of the present application, the catalyst alloy plate is Ni x Mn y Co z alloy, Fe m Ni n alloy, Fe s Ni k Co t alloy as a control group (wherein m, n represent the weight ratio of two metals, m+n=100; s, k, t represent the weight ratio of three metals, s+k+t=100). Alternatively, Fe m Ni n alloy, 20 s Ni k Co t alloy, 20

[0039] The baking process treatment step of the assembled components: the pressure transmission and heat preservation component MgO+ZrO2 block is placed into a medium temperature furnace for baking treatment; the pressed graphite carbon source block and graphite heating tube are placed into a drying box for drying treatment; the catalyst alloy sheet and diamond seed are respectively placed into anhydrous alcohol and cleaned by ultrasonic wave, and then placed into a drying box for drying treatment.

[0040] Alternatively, in the embodiment of the present application, the heating speed of the pressure transmission and heat preservation component MgO+ZrO2 block is 400℃ / h, the baking temperature is 900-1100℃, the baking time is 8 hours, and the cooling speed is 100℃ / h; the drying time of the graphite carbon source block and graphite heating tube is 5-8 hours, and the drying temperature is 230-250℃; the drying time of the catalyst metal sheet and diamond seed is 6-8 hours, and the drying temperature is 100-120℃.

[0041] The assembling and heat treatment step of the synthesis block: the crystal bed, plug, ring container, graphite carbon source block, catalyst metal sheet, diamond seed, graphite heating tube, conductive graphite sheet, conductive copper sheet, conductive steel cap and lepidolite composite block are assembled into a diamond synthesis block; the diamond synthesis block is placed into a drying box for drying treatment.

[0042] Alternatively, in the embodiment of the present application, in the assembling and heat treatment step of the synthesis block, the drying time of the diamond synthesis block is 2-3 hours, and the drying temperature is 110-130℃.

[0043] High temperature and high pressure crystal growth step: the heat-treated diamond synthesis block is put into the pressure chamber of a hinge-beam type cubic anvil press, and synthesis diamond is synthesized; when the crystal growth is completed, the carbon source catalyst rod material is taken out from the diamond synthesis block.

[0044] Optionally, in the embodiment of the present application, in the high temperature and high pressure crystal growth step, the synthesis pressure used in the crystal growth is 5.6 GPa, the synthesis temperature is 1250-1450℃, the pressure increasing speed time is 10-15 minutes, the temperature increasing rate is 40℃ / minute, and the crystal growth time is 8 hours or more.

[0045] It should be noted that in the prior art of the gem diamond single crystal synthesis process, there are a temperature increasing curve, a temperature holding curve and a slow temperature and pressure decreasing curve. The reason for adopting the slow temperature and pressure decreasing process is that when the crystal cracking problem is not very serious, the slow temperature and pressure decreasing process can effectively inhibit the occurrence of diamond single crystal cracking defects to a certain extent. In the embodiment of the present application, in order to avoid the interference of the slow temperature and pressure decreasing process on the research conclusion, the slow temperature and pressure decreasing process is not adopted at the end of the diamond growth experiment, and the temperature condition is removed by using the heating stop mode. After 10 minutes of heating stop, the pressure is unloaded to the normal pressure within 15 minutes.

[0046] Acid pickling post-processing step: the catalyst rod material with the embedded diamond crystal is put into a boiling dilute nitric acid solution for preliminary acid pickling treatment, so as to separate the diamond single crystal sample and the catalyst alloy; the diamond single crystal obtained by the preliminary acid pickling is put into a boiling mixed solution of concentrated HNO3 and concentrated H2SO4 for fine pickling, so as to obtain the gem diamond single crystal.

[0047] Optionally, in the embodiment of the present application, in the acid pickling post-processing step, the volume ratio of the concentrated HNO3 to the concentrated H2SO4 is 2:1, and the fine pickling time is 2-3 hours.

[0048] Example 1

[0049] In this example, Fe 70 Ni 30 The synthesis of the gem diamond single crystal by the catalyst is taken as an example. The synthesized poor-quality diamond single crystal sample with cracks is shown in Fig. Figure 2 Figure 2 (a) The crystal is cracked at nearly 1 / 2 of the crystal volume from the upper left to the lower right of the crystal; Figure 2 (b) The crystal is cracked at about 1 / 3 of the crystal volume from top to bottom in the picture.

[0050] Example 2

[0051] In this example, Fe 60 Ni 30 ​Co 10 Take the catalytic synthesis of gem-grade diamond single crystals as an example. The synthesized low-quality diamond single crystal samples with cracks are as follows Figure 3 shown. Figure 3 (a) The crystal shown is split from the main crystal at a position about 1 / 3 of the crystal volume on the left side of the crystal; Figure 3 (b) There is a crystal crack about 4 / 5 of the crystal diameter at the position indicated by the dotted line in the image.

[0052] Example 3

[0053] To choose Ni 55 Mn 35 Co 10 Take the catalytic synthesis of gem-grade diamond single crystals as an example. The synthesized high-quality crack-free diamond single crystal samples are as follows: Figure 4 shown.

[0054] In summary of the above three embodiments, the embodiment of the present invention controls the composition of Ni, Fe, and Co metal elements in the catalyst alloy, and utilizes the Ni x Mn y Co z (x+y+z=100, weight ratio, where: 40<x<60, 5<z<15) catalyst alloy was used to grow gem-grade diamond single crystals, which greatly reduced the probability of crack defects. The synthesized high-quality diamond single crystals such as Figure 4 As shown. During the peak period of crystal cracking in autumn and winter, among the three groups of 60 diamond samples that were not treated by the slow cooling and pressure reduction process, in the first group of Fe m Ni n (m+n=100, weight ratio, where: 20<n<40) The probability of diamond crack defects appearing in 20 crystals synthesized by catalyst is 75%; in the second group of Fe s Ni k Co t (s+k+t=100, weight ratio, where: 20<k<35, 5<t<15) The probability of diamond crack defects appearing in 20 crystals synthesized by catalyst is 60%; while in the third group Ni x Mn y Co z Among the 20 crystals synthesized by catalytic synthesis of diamond single crystals, the probability of diamond crack defects is reduced to 20% and the rate of excellent crystals is increased to 80%. Figure 4 As shown. It can be seen that the embodiment of the present invention effectively suppresses the occurrence of crystal cracking by adopting the method of optimizing catalyst components without performing a time-consuming slow cooling and pressure reduction process, significantly improves the yield of diamond single crystals, and thus significantly reduces the synthesis cost of diamond single crystals.

[0055] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the scope defined by the claims.

Claims

1. A method for synthesizing artificial gem-grade diamonds to inhibit crystal cracking, characterized in that: include: The ball milling step of the pressure-transmitting and heat-insulating material is as follows: the pressure-transmitting and heat-insulating material composed of industrial-grade MgO powder and ZrO2 calcined at 1600°C is mixed and ball milled to form MgO+ZrO2 pressure-transmitting and heat-insulating material powder; The steps of preparing raw materials and auxiliary components include: The raw and auxiliary component preparation sub-steps are as follows: the MgO+ZrO2 pressure-transmitting and heat-insulating material powder after ball milling is placed in a mold and pressed into a block crystal bed, a plug and an annular container by a tablet press; at the same time, a copper plate is placed in the mold and punched into a sheet-shaped conductive copper sheet by a tablet press; and, Raw material preparation sub-step: placing high-purity graphite powder into a mold and pressing it into a block using a tablet press; placing a catalyst alloy plate into a mold and punching it into a sheet-shaped catalyst alloy plate using a tablet press, wherein the catalyst alloy plate is Ni x Mn y Co z Alloy, where x, y, and z represent the weight ratio of the three metals, and x+y+z=100; The baking process steps of the assembled components are as follows: the MgO+ZrO2 block of the pressure-transmitting and heat-insulating component is placed in a medium-temperature furnace for baking; the pressed graphite carbon source block and the graphite heating tube are placed in a drying oven for drying; the catalyst alloy sheet and the diamond seed crystal are placed in anhydrous alcohol and cleaned using ultrasonic waves. After cleaning, they are placed in a drying oven for drying; Assembling the synthesis block and heat treatment steps: assembling the crystal bed, plug, annular container, graphite carbon source block, catalyst metal sheet, diamond seed crystal, graphite heating tube, conductive graphite sheet, conductive copper sheet, conductive steel cap and pyrophyllite composite block into a diamond synthesis block; placing the diamond synthesis block in a drying oven for drying; High temperature and high pressure crystal growth steps: placing the heat-treated diamond synthesis block into the pressure chamber of the hinged beam type six-sided top press to synthesize diamond; when the crystal growth is completed, removing the carbon source catalyst rod from the diamond synthesis block; Acid wash post-treatment steps: placing the catalyst rod with the embedded diamond crystal in a boiling dilute nitric acid solution for preliminary acid wash treatment to separate the diamond single crystal sample and the catalyst alloy; placing the diamond single crystal obtained from the initial acid wash in a boiling mixture of concentrated HNO3 and concentrated H2SO4 for fine washing to obtain gem-grade diamond single crystals; In the raw material preparation sub-step, the catalyst alloy plate is Ni x Mn y Co z alloy, and 40<x<60, 5<z<15.

2. The method for synthesizing artificial gem-grade diamonds to suppress crystal cracking according to claim 1, wherein: In the ball milling step of the pressure-transmitting heat-insulating material, the weight ratio of industrial-grade MgO powder to ZrO2 calcined at 1600°C is 1:4, the ball milling speed is 300 rpm, and the ball milling time is 240 minutes.

3. The method for synthesizing artificial gem-grade diamonds to suppress crystal cracking according to claim 1, wherein: In the raw material preparation sub-step, high-grade abrasive grade hexahedral diamond with a diameter of 0.8-1.0 mm is selected as a seed crystal for standby use.

4. The method for synthesizing artificial gem-grade diamonds to suppress crystal cracking according to claim 1, wherein: In the baking process steps of the assembly components, the heating rate of the pressure-transmitting and heat-insulating component MgO+ZrO2 block is 400°C / hour, the baking temperature is 900-1100°C, the baking time is 8 hours, and the cooling rate is 100°C / h; the drying time of the graphite carbon source block and the graphite heating tube is 5-8 hours, and the drying temperature is 230-250°C; the drying time of the catalyst metal sheet and the diamond seed crystal is 6-8 hours, and the drying temperature is 100-120°C.

5. The method for synthesizing artificial gem-grade diamonds to suppress crystal cracking according to claim 1, wherein: In the steps of assembling the synthetic block and heat treating, the diamond synthetic block is dried for 2-3 hours at a temperature of 110-130°C.

6. The method for synthesizing artificial gem-grade diamonds to suppress crystal cracking according to claim 1, characterized in that: In the high temperature and high pressure crystal growth step, the synthesis pressure used in the crystal growth is 5.6GPa, the synthesis temperature is 1250-1450℃, the pressure increase time is 10-15 minutes, the heating rate is 40℃ / minute, and the crystal growth time is more than 8 hours.

7. The method for synthesizing artificial gem-grade diamonds to suppress crystal cracking according to claim 1, characterized in that: In the pickling post-treatment step, the volume ratio of concentrated HNO3 to concentrated H2SO4 is 2:1, and the fine washing time is 2-3 hours.

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