A diamond synthetic core column surface coating and a method of making the same

Abstract

The present application belongs to the technical field of superhard material synthesis structure, and particularly relates to a diamond synthesis core column surface coating and a preparation method thereof. The diamond synthesis core column surface coating is made of the following raw materials in percentage by weight: mullite powder 66-78%, sodium carboxymethyl cellulose 1-1.5%, calcium-based bentonite 1-1.5%, and water 20-32%. The diamond synthesis core column surface coating is applied to the preparation of diamond products by using a synthesis core column, can replace the original bowl structure, and by spraying a coating with insulation and heat preservation performance on the surface of the synthesis core column of the metal shell, the volume of the synthesis cavity occupied by the original heat preservation material is reduced, the volume of the synthesis cavity can be effectively increased, the volume of the synthesis core column in the synthesis cavity is increased, the single piece output is increased, the single piece output rate is increased by 30% or more, the original heat preservation material is cancelled, the use of materials is saved, the production cost is reduced, and the yield of synthetic diamond is increased.

Description

Technical Field

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

[0002] Diamond, with its unique physical and chemical properties, is widely used in various fields related to national economy and people's livelihood, such as national defense, aerospace, machinery, electronics, automobiles, machine tools, precision manufacturing, medical, and clean energy. It is an indispensable new functional material in fields such as information technology, energy technology, modern ultra-precision machining technology, aerospace technology, and military technology. It has a large market demand and broad application prospects.

[0003] Currently, in the diamond production field, how to continuously improve the output and efficiency of a single diamond block is a common goal pursued by the industry. However, due to the limitations of equipment and the assembly structure of diamond synthesis chambers, the volume of the chambers has been difficult to expand effectively.

[0004] In the process of preparing diamond using graphite, the graphite core is the core component. Dolomite is fabricated into cups and inserted into a pyrophyllite cavity, forming a composite pressure-transmitting medium around the graphite core. This medium supports the diamond block under high temperature and pressure conditions. During the fabrication process, the dolomite cups primarily serve as insulation and heat preservation. Although this structure is a mature technology, the numerous and thick-walled attachments outside the graphite core during assembly significantly limit the increase in core volume and result in high unit cost. Therefore, it is difficult to effectively improve the yield per unit.

[0005] To address this, some solutions have been disclosed in the prior art. For example, Chinese Patent Publication No. CN208320741U discloses a coating structure for diamond-synthetic graphite pillars. By replacing the original metal cup and insulating cup with an insulating coating, the volume occupied in the synthesis cavity can be reduced, and the volume of the synthetic graphite pillars within the synthesis cavity can be increased. However, the structure in this patent still cannot effectively improve the performance of the synthetic diamond block.

[0006] Addressing the problems in existing technologies, this invention, based on the existing synthetic block assembly structure, designs the coating composition and content on the surface of the synthetic core column to replace the dolomite cup, aiming to increase the production of synthetic diamond while improving its performance. Furthermore, since the density of the graphite core column is much greater than that of the dolomite cup, it may also reduce the synthesis pressure to some extent. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a surface coating for synthetic diamond cores, replacing the original cup-shaped structure. This solves the problems of difficult transportation and high losses associated with cup-shaped structures, while also increasing the volume of the synthetic diamond core, thereby increasing the production of synthetic diamonds. Furthermore, it isolates harmful substances from entering the synthetic core, improving product quality.

[0008] The present invention also provides a method for preparing the surface coating of the diamond synthetic core.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A surface coating for a diamond synthetic core pillar, made from the following raw materials by weight percentage:

[0011]

[0012] More preferably, the surface coating of the diamond synthetic core post is made from the following raw materials by weight percentage:

[0013]

[0014] Specifically, the mullite powder, wherein the Al2O3 content (by weight) is 40% or more, includes two different particle sizes: mullite powder I with an average particle size of 200 mesh and mullite powder II with an average particle size of 800 mesh; wherein the mass ratio of mullite powder I to mullite powder II is (4.5-5):1.

[0015] Specifically, sodium carboxymethyl cellulose (CMC-Na) has a medium viscosity. When using it, it should first be dissolved in 10-20 times its weight of water to form a solution before mixing with other components. The pH should be 6.5–8.5. CMC-Na is used in this coating primarily because it acts as an anti-settling agent, emulsifier, dispersant, leveling agent, and binder. It ensures that the solid raw materials in the coating are evenly distributed in the solvent, preventing the coating from separating over a long period. It also absorbs water and swells, forming a transparent, viscous liquid when dissolved in water. Its pH is close to neutral.

[0016] Specifically, calcium-based bentonite has a particle size of 200-325 mesh. Its important properties are as a binder in this coating and as a thermal insulation material. It is neutral in acidity and alkalinity.

[0017] Furthermore, based on a general inventive concept, the present invention also provides a method for preparing a surface coating of a diamond synthetic core, comprising the following steps:

[0018] (1) Weigh out mullite powder, sodium carboxymethyl cellulose, calcium bentonite and water according to the proportions and set aside; add sodium carboxymethyl cellulose to water and stir evenly, let stand to form a uniform slurry solution I;

[0019] (2) Mix mullite powder and calcium-based bentonite, add them to solution I, stir, and mix thoroughly to make a coating solution;

[0020] (3) The coating solution prepared in step (2) is sprayed onto the surface of the diamond synthetic core using an automatic spraying machine to form a coating layer, ensuring that the coating is uniform around the core and on the top and bottom surfaces.

[0021] (4) Dry the diamond synthetic core column containing the spray coating in step (3), and finally air dry it to room temperature to obtain the surface coating of the diamond synthetic core column.

[0022] Preferably, the settling time in step (1) is 24-48 hours.

[0023] Preferably, the stirring speed in step (2) is 10000-20000 r / min.

[0024] Preferably, in step (3), the spraying process parameters are: spraying pressure 0.1-0.2MPa, spraying output speed 30-50cm / s, nozzle size 2-3mm, and spraying time 15-20s.

[0025] Preferably, in step (3), the thickness of the sprayed coating is 0.3-0.5 mm; more preferably, in actual production, the thickness of the coating on the surface of the diamond synthetic core is, for example, 0.35 mm, 0.4 mm, or 0.45 mm.

[0026] Preferably, in step (4), during drying, a micro-controlled oven is used for segmented drying. The specific process parameters are: first, bake at 20-30℃ for 1-2 hours, then heat up to 50-60℃ for 1-2 hours, and then heat up to 110-120℃ for 1-2 hours.

[0027] Furthermore, based on a general inventive concept, the present invention also provides the application of the surface coating of the diamond synthetic core in the preparation of diamond products.

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

[0029] 1. This invention uses mullite powder as refractory powder, water as carrier liquid, selects a compatible binder, and effectively combines them through a suitable preparation method, so that they can synergistically exert the effects of suspension, thixotropy, and bonding. The resulting product has excellent film-forming properties, high temperature resistance, insulation, and dense coating, which is very suitable for the high temperature resistance required in the synthesis of diamond synthetic cores.

[0030] 2. This invention uses a novel material as a protective coating. The novel material uses fire-retardant material as the main coating. The main material is inorganic and will not affect the core. At the same time, due to its high temperature resistance and insulation, it further improves the temperature and pressure transmission effect in the cavity, making the temperature and pressure field of diamond synthesis more uniform, thereby improving the quality of diamond products.

[0031] 3. The inorganic thickener and binder used in the formulation of this invention play a role in thickening and binding in the coating. After mixing and spraying, they help the coating to sinter and act as a sintering promoter.

[0032] 4. This invention employs a novel surface coating solution applied to the preparation of diamond products using synthetic cores. The synthetic cavity of this invention reduces the volume occupied by the original insulation material by spraying an insulating and heat-preserving coating onto the surface of the synthetic core with a metal shell. This effectively increases the volume of the synthetic cavity, improves the volume of the synthetic core within the cavity, and increases the yield per piece by 30% or more. Eliminating the original insulation material also saves on material usage and reduces production costs. Furthermore, it facilitates the effective transfer of temperature and pressure within the synthetic cavity, which is more conducive to the synthesis of high-quality diamonds. Detailed Implementation

[0033] To make the technical objectives, technical solutions, and beneficial effects of the present invention clearer, the technical solutions of the present invention will be further described below in conjunction with specific embodiments. However, the embodiments are intended to explain the present invention and should not be construed as limiting the present invention. Where no specific technology or conditions are specified in the embodiments, the technology or conditions described in the literature in the field or the product manual shall apply.

[0034] The amounts of raw materials used in the following examples are shown in Table 1 below. The main material, mullite powder, was purchased from Fengju Mineral Products Processing Plant in Lingshou County, Hebei Province; calcium-based bentonite was purchased from Henan Borun New Materials Co., Ltd.; and sodium carboxymethyl cellulose was purchased from Zhongchen Technology Co., Ltd.

[0035] Table 1. Raw material formulation composition (raw material components and content) for Examples 1-5

[0036]

[0037] The above raw materials must meet the following requirements:

[0038] Mullite powder: containing Al2O3 by weight of 40% or more, specifically using mullite powder with two different particle sizes: 200 mesh and 800 mesh;

[0039] Sodium carboxymethyl cellulose: medium viscosity. When using, first prepare a solution of sodium carboxymethyl cellulose and water at a weight of 10-20 times before mixing with other ingredients. The pH should be 6.5-8.5.

[0040] Calcium-based bentonite: average particle size is 200-325 mesh, and its acidity / alkalinity is neutral;

[0041] Water: Pure water.

[0042] The preparation method of the present invention is described below using Example 1 as an example. The equipment used in the following examples, such as high-speed mixers, micro-controlled ovens, and automatic spraying machines, are all commonly used tools in the art.

[0043] Example 1

[0044] A method for preparing a surface coating on a synthetic diamond core, comprising the following steps:

[0045] (1) Weigh out mullite powder, sodium carboxymethyl cellulose, calcium bentonite and water according to the proportions in Table 1 above, and set aside; add sodium carboxymethyl cellulose to water and stir until there are no particles, let stand for 48 hours to form a uniform slurry solution I.

[0046] (2) Mix 200-mesh mullite powder, 800-mesh mullite powder and calcium-based bentonite, add them to solution I, and stir in a mixer at a speed of 15000 r / min. After thorough mixing, a coating solution is prepared.

[0047] (3) The coating solution prepared in step (2) is sprayed onto the surface of the diamond synthetic core using an automatic spraying machine to form a coating layer. The coating is uniform around the core and on the top and bottom surfaces, with a thickness of 0.3-0.5 mm. In actual production, the coating thickness on the surface of the diamond synthetic core is, for example, 0.35 mm, 0.4 mm, or 0.45 mm. The spraying process parameters are: spraying pressure 0.2 MPa, spraying output speed 40 cm / s, nozzle size 2-3 mm, and spraying time 20 s.

[0048] (4) Place the diamond synthetic core column containing the spray coating in step (3) in a micro-controlled oven, bake at 30°C for 1 hour, then heat to 60°C for 1 hour, then heat to 120°C for 1 hour, and finally air dry to room temperature to obtain the surface coating of the diamond synthetic core column.

[0049] Examples 2-5 were prepared using the same method as in Example 1 to create the surface coating of the diamond synthetic core.

[0050] Performance Test 1

[0051] The coatings prepared on the surface of diamond synthetic cores in Examples 1-5 were subjected to performance tests, and the test results are shown in Table 2.

[0052] Table 2

[0053] <![CDATA[Density (g / cm 3 )]]> 2.0-2.2 Single-layer coating thickness (mm) 0.3-0.5 solution state homogeneous, particle-free solution pH value 5-6.8 High-temperature crack resistance (1400℃, 50s) No cracks

[0054] As can be seen from Table 2, the coatings prepared in Examples 1-5 of the present invention can all meet the standards, indicating that the solutions of the diamond synthetic core column surface coatings prepared in Examples 1-5 can all be smoothly sprayed in an automatic spraying machine and can automatically form a film after spraying.

[0055] Performance Test 2

[0056] When using the surface coating of the diamond synthetic core, the coating solution prepared according to the method in Example 1 is sprayed onto the surface of four identical diamond synthetic cores using the spraying method in Example 1. After drying, they are assembled according to the diamond synthesis process and synthesized using high temperature and high pressure technology. During assembly, the cup structure is reduced. The final synthesis effect is compared as shown in the table below:

[0057] Table 3

[0058]

[0059] As can be seen from the table above, after the coating described in this invention is sprayed onto the surface of the diamond synthetic core, the synthesized diamond single product can meet the production requirements and can be well used for diamond synthesis, replacing the original cup-shaped structure and effectively solving the technical problems existing in the prior art.

[0060] Meanwhile, tests showed that the surface coatings of the diamond synthetic core obtained in Examples 2-5 all achieved the same synthesis effect as in Example 1.

[0061] In summary, the surface coating of the diamond synthetic core prepared by this invention, when applied to the preparation of diamond products using synthetic cores, can replace the original cup-shaped structure. By spraying an insulating and heat-preserving coating onto the surface of the synthetic core with a metal shell, the volume occupied by the original insulation material in the synthesis cavity is reduced, effectively increasing the volume of the synthesis cavity, increasing the volume of the synthetic core within the synthesis cavity, and improving the yield per piece. The yield per piece increases by 30% or more. Eliminating the original insulation material also saves material usage and reduces production costs, thereby achieving increased production of synthetic diamonds.

[0062] Finally, it should be noted that the above embodiments are only for illustration and not for limiting the technical solutions of the present invention. Any equivalent substitutions, modifications or partial substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A surface coating for a diamond synthetic core, characterized in that, It is made from the following raw materials in weight percentage: 66-78% mullite powder, 1-1.5% sodium carboxymethyl cellulose, 1-1.5% calcium bentonite, and 20-32% water; The mullite powder contains 40% or more Al2O3 by weight; the mullite powder includes mullite powder I with an average particle size of 200 mesh and mullite powder II with an average particle size of 800 mesh; wherein the mass ratio of mullite powder I to mullite powder II is (4.5-5):1; The sodium carboxymethyl cellulose has a medium viscosity. When using it, it should first be prepared into a solution with 10-20 times its weight of water before being mixed with other components. The pH should be 6.5-8.

5. The particle size of the calcium-based bentonite is 200-325 mesh; The surface coating of the diamond synthetic core post is prepared by the following steps: (1) Weigh out mullite powder, sodium carboxymethyl cellulose, calcium bentonite and water according to the proportions and set aside; add sodium carboxymethyl cellulose to water and stir evenly, let stand to form a uniform slurry solution I; (2) Mix mullite powder and calcium-based bentonite, add them to solution I, stir, and mix thoroughly to make a coating solution; (3) The coating solution prepared in step (2) is sprayed onto the surface of the diamond synthetic core using an automatic spraying machine to form a coating layer, ensuring that the core is uniformly coated around the periphery and on the top and bottom surfaces. (4) Dry the diamond synthetic core containing the spray coating in step (3), and finally air dry it to room temperature to obtain the surface coating of the diamond synthetic core.

2. The surface coating of the diamond synthetic core pillar according to claim 1, characterized in that, It is made from the following raw materials in weight percentage: 68-74% mullite powder, 1-1.5% sodium carboxymethyl cellulose, 1-1.5% calcium-based bentonite, and 24-30% water.

3. The surface coating of the diamond synthetic core pillar according to claim 1, characterized in that, The settling time in step (1) is 24-48 hours.

4. The surface coating of the diamond synthetic core pillar according to claim 1, characterized in that, The stirring speed in step (2) is 10000-20000 r / min.

5. The surface coating of the diamond synthetic core pillar according to claim 1, characterized in that, In step (3), the spraying process parameters are: spraying pressure 0.1-0.2MPa, spraying output speed 30-50cm / s, nozzle size 2-3mm, and spraying time 15-20s.

6. The surface coating of the diamond synthetic core pillar according to claim 1, characterized in that, In step (3), the thickness of the sprayed coating is 0.3-0.5 mm.

7. The surface coating of the diamond synthetic core pillar according to claim 1, characterized in that, In step (4), during drying, a micro-controlled oven is used for segmented drying. The specific process parameters are: first, bake at 20-30℃ for 1-2 hours, then heat up to 50-60℃ for 1-2 hours, and then heat up to 110-120℃ for 1-2 hours.

8. The application of the surface coating of the diamond synthetic core as described in any one of claims 1-7 in the preparation of diamond products.

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