A high-quality millimeter-sized coarse-grained diamond cubic synthesis process

Abstract

The present application belongs to the technical field of synthetic diamond, and proposes a high-grade millimeter-level coarse-grained diamond cubic crystal synthesis process, wherein a powder catalyst and a spherical graphite with a mesh size of -300 are prepared; the prepared raw materials are premixed and regranulated; the granulated mixture is loaded into a mold, and a core column is pressed by using a four-column press; the core column is placed in a vacuum furnace for vacuum heat reduction treatment; after cooling, the core column is taken out of the furnace and vacuum packaged; the core column is subjected to high-temperature and high-pressure compression synthesis by using a six-sides press; the synthesized graphite rod is soaked in mixed acid, and then placed in aqua regia for heating; the cooked water is fried and dried; and after the particle size is screened, coarse-grained pure cubic crystal can be obtained from the diamond with the main and secondary peak particle sizes; the proportion of the cubic crystal with the main particle size can reach more than 80%; compared with ordinary hexagonal-octahedral polyhedral synthetic diamond, the cubic crystal has more and sharper cutting edges, high sharpness and wear resistance, greatly improves the grinding performance of diamond cutters, and is suitable for large-scale promotion.

Description

Technical Field

[0001] This invention belongs to the field of synthetic diamond technology, and particularly relates to a process for synthesizing high-grade millimeter-sized coarse-grained diamond cubic crystals. Background Technology

[0002] High-quality, synthetically produced diamond single crystals possess excellent physical, chemical, electrical, and optical properties, as well as extremely high hardness and good wear resistance, making them a versatile and extreme functional material. They are widely used in industries such as industry, science and technology, defense, and medical devices. Because synthetic diamond exhibits superior performance in superhard tools and ultra-precise machining, and given the increasingly stringent requirements for tool material properties, the performance requirements for synthetic diamond are constantly rising.

[0003] In recent years, those skilled in the art have obtained specific crystal forms by changing the formulation and process of synthetic diamond, as well as special assembly structures, to meet the needs of certain special fields in the market. There are many kinds of diamond synthesis processes. The synthesis processes of diamonds with different crystal forms or different properties are different. The material formulation used in synthetic diamonds and the parameters in the synthesis process can all change the crystal form and properties of diamonds.

[0004] Currently, most domestic diamond manufacturers use powder synthesis to synthesize high-grade diamonds, mainly in the form of round crystal 1 and round crystal 2. While their grade and performance indicators are excellent, in actual downstream applications of diamond tools, there are still problems such as diamond passivation caused by high speed and high temperature when cutting granite, reduced diamond holding power, easy diamond falling off, poor self-sharpening properties, and rounded but not sharp crystals. These issues hinder and limit their application. Summary of the Invention

[0005] This invention addresses the technical problems existing in the above-mentioned synthetic diamond by proposing a high-grade millimeter-scale coarse-grained diamond cubic crystal synthesis process. The diamond products synthesized using this process have high sharpness and wear resistance, which greatly improves the grinding performance of diamond tools.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The present invention provides a process for synthesizing high-grade millimeter-scale coarse-grained diamond cubic crystals, comprising the following steps:

[0007] S1. Prepare a powder catalyst with a fineness of -300 mesh. The raw materials of the powder catalyst, by weight percentage, include: Ni 27%, Co 2%, Si 0.2%, Ta 0.2%, Mo 0.5%, FeF 30.05%, Ce 0.05%, Re 0.015%, with the balance being Fe.

[0008] S2. Select spherical graphite with a fineness of -300 mesh or less, and ensure that the graphite purity has an impurity content of less than 30 PPM.

[0009] S3. Add FeF3 and Ce to the powdered catalyst and premix for 3 hours. Then mix the premixed catalyst with graphite in a three-dimensional mixer at a mass ratio of 10:3 to 10:6 for 3-5 hours. Then put it into a granulator for two granulations for later use.

[0010] S4. Load the granulated mixture into a mold and press it into a core column using a four-column press.

[0011] S5. Place the core column pressed in step S4 into a vacuum furnace. The temperature inside the vacuum furnace is 1080±5 degrees. Vacuum treatment is carried out for 8 to 10 hours. Impurities are removed by hydrogen reduction. Then, the core column is naturally cooled to room temperature under nitrogen protection. After being taken out of the furnace, it is vacuum packaged.

[0012] S6. The core column after being taken out of the furnace is put into the synthesis block, baked and heated, and then subjected to high temperature and high pressure synthesis using a six-sided top press. The synthesis temperature during the synthesis process is 1280 degrees-1320 degrees, the heating time is 9000 seconds, and the internal pressure of the synthesis chamber is 4.9-5.0 Gpa.

[0013] S7. After the synthesized graphite rod is crushed, it is soaked in mixed acid for 1-2 hours to remove the graphite, and then placed in a beaker with aqua regia and heated for 20 minutes to remove the catalyst.

[0014] S8. Boil the product treated in S7 in water, dry it, and then sieve it to obtain coarse-grained pure cubic crystals from diamonds with the main and secondary peak values.

[0015] In step S6, the pressure of the six-sided press is adjusted in real time.

[0016] a1. After the pressure of the six-sided top press is uniformly increased to 42 MPa at a speed of 0.7 MPa / s by the hydraulic system, heating begins.

[0017] a2. Increase the pressure to 48 MPa at an overpressure rate of 0.35 MPa / s and hold the pressure for 580s to 620s;

[0018] a3. Increase the pressure to 62 MPa within 15 seconds and hold the pressure for 180 seconds;

[0019] a4. Increase the pressure to 73 MPa at a constant rate within 7980s to 8080s, and hold the pressure for 90s to end the heating process.

[0020] a5. After stopping the heat and holding the pressure for 120-150 seconds, release the pressure.

[0021] a6. Depressurization complete.

[0022] In step S6, the power of the six-sided top press is adjusted in real time.

[0023] b1. The starting power of the six-sided top press is 7.8kw~8.3kw, and the starting power is maintained for 620s~660s;

[0024] b2. The first power reduction will lower the power to 7.0kw~7.5kw within 20 seconds;

[0025] b3. Hold for 180s to 210s, then gradually reduce the power to 6.8kw to 7.3kw.

[0026] b4. Keep heating for 200s to 230s and then stop heating.

[0027] Preferably, in step S4, the core column size is ￠57mm x 49mm, and the core column density is 3.2~3.4g / cm3.

[0028] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0029] 1. This invention provides a high-grade millimeter-scale coarse-grained diamond cubic crystal synthesis process. The proportion of cubic crystals in the main particle size of diamond synthesized using this process can reach more than 80%, which is no less than the 60% proportion of synthesized cubic crystals abroad. Compared with ordinary hexahedral aggregate diamonds, cubic crystals have more and sharper cutting edges, which is beneficial to improving the cutting rate of diamond saw blades, especially tile cutting blades. They have high sharpness and wear resistance, which greatly improves the grinding performance of diamond tools and is conducive to improving the efficiency of using diamond tools to perform related tasks. This is suitable for large-scale promotion. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 A process curve diagram of a high-grade millimeter-scale coarse-grained diamond squaring crystal synthesis process provided for an embodiment;

[0032] Figure 2 (a) is a schematic diagram of the microstructure during cutting with a conventional diamond tool;

[0033] Figure 2 (b) is a schematic diagram of the microstructure during cutting with a cubic diamond tool;

[0034] Figure 3 Electron micrograph of high-quality squared diamond with a principal grain size of 18 / 20;

[0035] Figure 4 Electron micrograph of a high-quality coarse-grained diamond prismatic crystal mixture. Detailed Implementation

[0036] Numerous specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways than those described herein, and therefore the invention is not limited to the specific embodiments disclosed in the following specification.

[0037] Examples, such as Figures 1-4 As shown, the present invention provides a process for synthesizing high-grade millimeter-scale coarse-grained diamond cubic crystals, comprising the following steps:

[0038] S1. Prepare a powder catalyst with a fineness of -300 mesh. The raw materials of the powder catalyst, by weight percentage, include: Ni 27%, Co 2%, Si 0.2%, Ta 0.2%, Mo 0.5%, FeF 30.05%, Ce 0.05%, Re 0.015%, with the balance being Fe.

[0039] S2. Select spherical graphite with a fineness of -300 mesh or less, and ensure that the graphite purity has an impurity content of less than 30 PPM.

[0040] S3. Add FeF3 and Ce to the powdered catalyst and premix for 3 hours. Then mix the premixed catalyst with graphite in a three-dimensional mixer at a mass ratio of 10:3 to 10:6 for 3-5 hours. Then put it into a granulator for two granulations for later use.

[0041] S4. Load the granulated mixture into a mold and press it into a core column using a four-column press.

[0042] S5. Place the core column pressed in step S4 into a vacuum furnace. The temperature inside the vacuum furnace is 1080±5 degrees Celsius. Vacuum treatment is carried out for 8 to 10 hours. Impurities are removed by reduction with hydrogen. Then, the core column is naturally cooled to room temperature under nitrogen protection. After being removed from the furnace, it is vacuum packaged.

[0043] S6. The core column after being taken out of the furnace is put into the synthesis block, baked and heated, and then subjected to high temperature and high pressure synthesis using a six-sided top press. The synthesis temperature during the synthesis process is 1280 degrees-1320 degrees, the heating time is 9000 seconds, and the internal pressure of the synthesis chamber is 4.9-5.0 Gpa.

[0044] S7. After the synthesized graphite rod is crushed, it is soaked in mixed acid for 1-2 hours to remove the graphite, and then placed in a beaker with aqua regia and heated for 20 minutes to remove the catalyst.

[0045] S8. Boil the product treated in S7 in water, dry it, and then sieve it to obtain coarse-grained pure cubic crystals from diamonds with the main and secondary peak values.

[0046] To improve the production quality and efficiency of synthetic diamond, this invention dynamically adjusts the pressure and power of the six-sided press in real time in step S6. For example, the adjustment steps for the pressure of the six-sided press during operation include:

[0047] a1. After the pressure of the six-sided top press is uniformly increased to 42 MPa at a speed of 0.7 MPa / s by the hydraulic system, heating begins.

[0048] a2. Increase the pressure to 48 MPa at an overpressure rate of 0.35 MPa / s and hold the pressure for 580s to 620s;

[0049] a3. Increase the pressure to 62 MPa within 15 seconds and hold the pressure for 180 seconds;

[0050] a4. Increase the pressure to 73 MPa at a constant rate within 7980s to 8080s, and hold the pressure for 90s to end the heating process.

[0051] a5. After stopping the heat and holding the pressure for 120-150 seconds, release the pressure.

[0052] a6. Depressurization complete.

[0053] In conjunction with the pressure adjustment step of the six-sided top press, the real-time power adjustment step of the six-sided top press in step S6 is as follows:

[0054] b1. The starting power of the six-sided top press is 7.8kw~8.3kw, and the starting power is maintained for 620s~660s;

[0055] b2. The first power reduction will lower the power to 7.0kw~7.5kw within 20 seconds;

[0056] b3. Hold for 180s to 210s, then gradually reduce the power to 6.8kw to 7.3kw.

[0057] b4. Keep heating for 200s to 230s and then stop heating.

[0058] By controlling the composition and ratio of catalyst additives and matching specific processes, including premixing, secondary mixing, mixing time, vacuum treatment at the vacuum furnace station, and high-temperature and high-pressure processes at the six-sided top press station, especially by adjusting the pressure and power of this process, after drying and particle size screening, coarse-grained pure cubic crystals can be obtained from the diamond particles with the main and secondary peak values. The proportion of main-grained cubic crystals can reach more than 80%, which is no less than the 60% proportion of synthetic cubic crystals abroad. Compared with ordinary hexahedral aggregate diamond, cubic crystals have more and sharper cutting edges, which is beneficial to improving the cutting speed of diamond saw blades, especially ceramic tile cutting blades. Specially made diamond cubic crystals have longer unidirectional cutting edges, and because the hardness of the (100) facet of synthetic diamond is lower than that of the (111) facet, while the fracture surface energy and fracture toughness are significantly higher than those of the (111) facet, the diamond cubic crystals can better maintain their original crystal shape (cutting edge) during high-speed cutting, which helps to improve the cutting speed of the cutting blade when cutting hard materials, such as ceramic tiles. Using only cubic crystals, compared to conventional hexahedral polycrystalline diamond, the cutting speed of ordinary porcelain ceramic tiles can be increased by more than 40%, and that of ultra-hard ceramic tiles by 27%. By matching the cutting speed of the tile with a "weakened" metal matrix containing different lubricant contents, the cutting speed can be further enhanced. When the lubricant content is 6wt%, the test saw blade showed a cutting speed increase of over 60% compared to conventional cutting saw blades; even when cutting ultra-hard porcelain ceramic tiles, the speed can be increased by more than 30%.

[0059] To improve the compatibility between the core and the six-sided press, the present invention uses a six-sided press with a cylinder diameter of 850 mm, a hammer face of 70 x 70 mm, a hammer face angle of 42 degrees, and HT-V electronic control. Moreover, the core produced in step S4 has a size of 57 mm x 49 mm and a core density of 3.2–3.4 g / cm³, which is beneficial for the six-sided press to apply external force to the synthesis block and the core and to provide a high-temperature and high-pressure environment, thus helping to control the synthesis efficiency of synthetic diamond.

[0060] To ensure the performance of the strong acid in step S7, the mixed acid used in this invention is sulfuric acid: nitric acid = 3:1, and aqua regia is hydrochloric acid: nitric acid = 3:1.

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A high quality millimetre sized coarse particle diamond cubic synthesis process characterised in that, The method comprises the following steps: S1, preparing a -300 mesh fine powder catalyst, the raw materials of the powder catalyst include, by weight percentage, Ni 27%, Co 2%, Si 0.2%, Ta 0.2%, Mo 0.5%, FeF3 0.05%, Ce 0.05%, Re 0.015%, and the balance is Fe; S2, selecting -300 mesh fine spherical graphite, the purity of the graphite reaches 30 PPM or less of impurity content; S3, adding FeF3 and Ce into the powder catalyst for premixing for 3 hours, then mixing the premixed catalyst with the graphite in a three-dimensional mixer at a mass ratio of 10:3-10:6 for 3-5 hours, and then putting into a granulator for twice granulation for standby; S4, loading the granulated mixture into a mold, and pressing into a core column by using a four-column press; S5, placing the core column pressed in step S4 into a vacuum furnace, setting the temperature in the vacuum furnace to 1080±5 degrees, vacuum treating for 8-10 hours, removing impurities by hydrogen reduction, and then naturally cooling to room temperature under nitrogen protection, and vacuum packaging after being taken out of the furnace; S6, loading the core column taken out of the furnace into a synthetic block, baking and heating the synthetic block, and high-temperature and high-pressure pressing the synthetic block by using a six-surface press, the synthesis temperature in the synthesis process is 1280-1320 degrees, the heating time is 9000 seconds, and the internal pressure of the synthesis cavity is 4.9-5.0 GPa; S7, crushing the synthesized graphite rod, soaking in mixed acid for 1-2 hours to remove the graphite, and then putting into a beaker and heating for 20 minutes to remove the catalyst; S8, boiling water and drying the product treated in S7, and then performing particle size screening to obtain coarse-grained pure cubic crystals in the diamond with the main and secondary peak particle sizes.

2. The process as claimed in claim 1, wherein the process is characterized by, In step S6, the pressure of the six-surface press is adjusted in real time as follows: a1, uniformly increasing the pressure of the six-surface press to 42 MPa at a speed of 0.7 MPa / s by using a hydraulic system, and then starting heating; a2, increasing the pressure to 48 MPa at a speed of 0.35 MPa / s, and keeping the pressure for 580-620 seconds; a3, increasing the pressure to 62 MPa, and keeping the pressure for 180 seconds; a4, uniformly increasing the pressure to 73 MPa in 7980-8080 seconds, and keeping the pressure for 90 seconds to end heating; a5, stopping heating and keeping the pressure for 120-150 seconds, and then releasing the pressure; a6, completing pressure release.

3. The process as claimed in claim 2, wherein the process is characterized by, In step S6, the power of the six-surface press is adjusted in real time as follows: b1, the initial power of the six-surface press is 7.8-8.3 kW, and the initial power is kept for 620-660 seconds; b2, first reducing the power to 7.0-7.5 kW within 20 seconds; b3, keeping the power for 180-210 seconds, and then uniformly reducing the power to 6.8-7.3 kW; b4, keeping the power for 200-230 seconds to stop heating.

4. The process as claimed in claim 3, wherein the process is characterized by, The core size in the step S4 is 57mm X 49mm, and the core density is 3.2-3.4g / cm 3 .

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