A method for increasing the hardness of diamond particles by mosaic splicing

Abstract

This invention provides a method for increasing the hardness of diamond particles through mosaic splicing, belonging to the field of superhard materials. The method comprises the following steps: 1) selecting single-crystal diamond particles to be processed and machining micropores on the surface of a copper substrate; 2) splicing the single-crystal diamond particles into the micropores, placing the copper substrate in a CVD apparatus, and pulse-depositing a layer of doped diamond on the exposed surface of the diamond particles; 3) removing the film formed by the pulsed deposition of the doped diamond layer from the particles and placing it inverted onto alloy powder to form an alloy substrate encapsulating the doped diamond surface; 4) placing the substrate in a CVD apparatus and pulse-depositing the doped diamond on the surface of the diamond particles until the thickness reaches the initial pulsed deposition thickness; and 5) crushing the deposited diamond particles. Diamond particles produced using this method have a hardness increase of 2 to 4.5 times. This method can also improve the quality of diamond powder. Its simple and low-cost preparation process makes it suitable for various industrial applications requiring high hardness.

Description

Technical Field

[0001] The invention belongs to the technical field of superhard material preparation, and particularly relates to a method for improving the hardness of diamond particles through mosaic splicing. Background Art

[0002] Diamond particles are widely used in industry due to their ultra-high hardness and excellent wear resistance, particularly in high-precision cutting tools such as diamond wire saws and rope saws. Their high hardness and wear resistance significantly improve cutting efficiency and machining accuracy. However, existing diamond particles produced by existing technologies have limitations in terms of hardness and uniformity. Traditional preparation methods primarily include high-temperature and high-pressure synthesis and chemical vapor deposition (CVD). While these methods can produce diamond particles with high hardness, the difficulty in precisely controlling particle size and morphology results in unstable mechanical properties in practical applications, impacting the service life of cutting tools and machining results.

[0003] Existing techniques make it difficult to form multilayer structures using a single deposition method. Diamond particles often develop significant internal stress and defects during deposition, which degrade their overall performance. Researchers have proposed improved methods that enhance mechanical properties by introducing doping elements (such as nitrogen, boron, and argon) into the diamond structure through doping techniques. However, these methods still face challenges in practical application, such as poor doping uniformity, complex processes, and high costs.

[0004] Furthermore, while existing high-temperature, high-pressure annealing processes can improve the toughness of single-crystal diamond, they are limited by equipment and process conditions, making large-scale industrial application difficult. Existing CVD methods also have similar limitations, making it difficult to achieve ideal doping effects and multilayer structures within diamond particles, further limiting the performance of diamond wire saws and rope saws. Summary of the Invention

[0005] To address the above issues, the present invention proposes a method for increasing the hardness of diamond particles through mosaic splicing. This method involves machining micropores into a substrate, splicing undoped single-crystal diamond particles onto a copper substrate, and partially embedding the diamond particles within the copper substrate. A doped diamond layer is then deposited on the surface of the diamond particles using CVD technology in a pulsed manner. Diamond is then combined with alloy powder to form a secondary deposition substrate. The exposed diamond particles on the secondary deposition substrate are then etched and then pulsed with doped diamond. Finally, the resulting diamond film is fragmented, yielding ultrahard diamond particles with a multilayer structure.

[0006] The diamond particles produced by this method possess higher hardness and toughness, significantly improving the cutting efficiency and service life of diamond wire saws and rope saws, making them suitable for a variety of high-precision cutting and processing applications. This method simplifies the process flow, reduces production costs, and has broad industrial application prospects. Through multi-layer structural design and optimized deposition processes, this method effectively solves multiple problems in the existing technology and provides a new solution for the production of high-hardness diamond particles.

[0007] To achieve the above objectives, the present invention provides the following technical solutions:

[0008] The present invention provides a method for increasing the hardness of diamond particles by mosaic splicing, the method comprising the following steps:

[0009] 1) Substrate preparation: Select the single-crystal diamond particles to be processed, measure the diamond particle size, and then use an indenter of the same size as the diamond particles to machine fixedly arranged micropores on the surface of the copper substrate;

[0010] 2) First pulse deposition after diamond particle splicing: Single crystal diamond is spliced ​​into micropores machined into a copper substrate. The copper substrate with the diamond particles is placed in a vapor deposition (CVD) device. Different doping gases are introduced in a pulsed manner to deposit a layer of doped diamond on the surface of the exposed diamond particles. The deposited layer connects the diamond particles to form a film.

[0011] 3) Preparation of a secondary deposition substrate: The film formed by the particles of the pulsed deposited doped diamond layer is removed and inverted onto the alloy powder, allowing the diamond film to combine with the alloy powder to form an alloy substrate that wraps the diamond-doped surface. This step ensures that the pulsed deposited doped diamond layer is in full contact with the substrate, preparing for the subsequent deposition process.

[0012] 4) Second pulse deposition: The substrate is placed in a CVD device and hydrogen is introduced to etch the diamond particles to prevent graphitization damage during bonding with the alloy powder. Doped diamond is then pulse-deposited on the surface of the diamond particles until the thickness reaches the same as the initial pulse deposition. This step involves continuing the pulse deposition of doped diamond on the lower surface of the diamond particles (i.e., the surface not previously deposited). The deposition conditions for this step are the same as those in step 2) to ensure uniformity and consistency of the deposited layers on both sides.

[0013] 5) Fragmentation: The deposited diamond particles, which have formed a diamond film, are acid-etched to remove any metal residue from the surface. The film is then fragmented to produce diamond particles with a deposited layer. This multi-layered structure significantly improves the hardness and toughness of the diamond particles.

[0014] Preferably, in step 1), single-crystal diamond particles are spliced ​​into the machined micropores of the copper substrate to increase the contact area between the diamond particles and the substrate. The spacing around the micropores should be less than twice the thickness of the pulsed-deposited doping layer. If the spacing is too large, the doped diamond in step 2) will not completely fill the gaps between the diamond particles, preventing the diamond particles from being connected to form a film.

[0015] Preferably, in step 1), the particle size of the undoped diamond particles is micrometer-sized, preferably 4-8 μm, the maximum width of the micropores processed on the substrate is 4-8 μm, the hole depth is 2-4 μm, and the micropore spacing is preferably <3 μm.

[0016] Preferably, in step 3), the alloy powder for preparing the secondary deposition substrate is selected from one of titanium-based alloys, nickel-based alloys, and copper-based alloys, and the melting point of the above alloy powder is lower than 1100°C. The process for preparing the secondary deposition substrate is vacuum heat melting. The above alloy powder has a lower melting point than the diamond particles, and the diamond-doped surface can be wrapped by vacuum heat melting. The reason why a copper substrate is used in step 1) is that the diamond particles need to be spliced ​​and arranged, and the surface of the diamond particles is relatively regular, and a pressing head can be used to process the corresponding shape on the copper substrate. The alloy powder is selected as the substrate in step 3) because a layer of doped diamond has been deposited on one side of the diamond particles, and the surface is irregular, and a pressing head cannot be used to process a shape that matches the diamond surface.

[0017] Preferably, in step 4), the temperature for etching the exposed diamond by introducing hydrogen is 700-1000° C., and the etching time is 5-60 minutes.

[0018] Preferably, in steps 2) and 4), the thickness of the pulsed deposited doped diamond layer is 2000-3000 nm, and the doping elements are boron-nitrogen co-doping or boron-argon co-doping. These doping elements are commonly used in the field of diamond doping and can increase the hardness of diamond.

[0019] Preferably, in steps 2) and 4), the pulsed deposition conditions for doped diamond are: a hydrogen flow rate of 300 sccm, a methane flow rate of 10-40 sccm, an argon flow rate of 6-40 sccm, a trimethylboron (B(CH3)3) flow rate of 0-3 sccm, and a nitrogen flow rate of 1-20 sccm. The gas flow rates can be adjusted using flow valves to control the amount of dopant gas added, i.e., different dopant gases are introduced in a pulsed manner. The diamond growth temperature is 800-1000°C, the power range is 4000-7000 W, the chamber pressure is 10-25 kPa, and the pulsed deposition single layer thickness is 50-300 nm.

[0020] The present invention also provides diamond particles with a deposition layer prepared by the method.

[0021] Preferably, in step 5), the diamond particles in the deposited layer have a particle size of less than 15 μm. The diamond particles prepared by the above method have a multilayer structure, i.e., pulsed deposition of doped diamond envelops undoped diamond particles to form a multilayer structure of doped diamond. This structure increases the hardness of the diamond particles by 2 to 4.5 times.

[0022] The technical principles of the present invention are as follows:

[0023] The present invention improves the hardness of diamond particles through mosaic splicing. The method is to process micropores on the surface of the substrate, which ensure that about half of the diamond particles are exposed. Undoped single crystal diamond is spliced ​​into the micropores of the copper substrate to form an alloy substrate embedded with diamond particles. Doped diamond is pulsed and deposited on the surface of the undoped diamond particles. After the deposition is completed, the diamond particles that have formed a film are removed and placed upside down on the alloy powder. The diamond and alloy powder are combined to prepare a substrate with a diamond-doped surface. The substrate is placed in a CVD device. Hydrogen is first introduced to etch the exposed diamond particles. After that, doped diamond of the same thickness is pulsed and deposited again. The diamond film is then acid-etched. After removing the metal residue on the surface of the diamond film, the diamond film is crushed to form diamond particles with a multilayer structure. This method not only significantly improves the hardness and uniformity of the diamond particles, but also simplifies the process flow, reduces production costs, and has broad industrial application prospects. It is particularly suitable for the manufacture of high-precision cutting, grinding and polishing tools.

[0024] The advantages of the present invention are as follows:

[0025] (1) The present invention adopts mosaic splicing technology, which has a simple process flow, is easy to operate, is suitable for large-scale production, and reduces manufacturing complexity and time cost.

[0026] (2) Through process design, a substrate that partially encapsulates the diamond particles is prepared, increasing the contact area between the diamond and the substrate. During the deposition process, this effectively prevents graphitization damage to the undoped diamond particles caused by high power and high temperature, increases the power and deposition rate of the CVD equipment, improves heat dissipation efficiency, and ensures the integrity and performance of the diamond particles.

[0027] (3) The present invention introduces doping gas in a pulsed manner, sequentially depositing doped diamond on the surface of diamond particles in a pulsed manner, thereby preparing diamond with a multilayer doped structure and obtaining diamond particles with ultra-high hardness. The multilayer doped structure contains a high density of twins and stacking faults, thereby enhancing the hardness of the diamond.

[0028] (4) By combining diamond with alloy powder to prepare a secondary deposition substrate, the substrate tightly wraps the diamond to increase the contact area, improve the heat dissipation efficiency, and solve the heat dissipation problem of secondary pulse deposition pulse-doped diamond. If an ordinary substrate is used, there will be a gap between the diamond and the substrate, and untimely heat dissipation will lead to graphitization damage of the diamond film.

[0029] (5) The bare diamond particles are etched by hydrogen etching technology to prevent graphitization damage of the diamond particles during the vacuum hot melting process and ensure the performance of the final sample.

[0030] (6) The final diamond particle size can be controlled within a relatively small range through crushing, meeting high-precision requirements. The present invention can improve the grade of diamond powder through this method. The prepared high-hardness diamond particles significantly improve the cutting efficiency and service life of diamond wire saws and rope saws, and are suitable for high-precision cutting and processing applications, meeting the industry's demand for high-performance cutting tools. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0032] Figure 1 A process flow chart of the method for increasing the hardness of diamond particles by mosaic splicing provided by the present invention;

[0033] Figure 2 This is a schematic diagram of the structure of a diamond with a deposited layer obtained by the present invention;

[0034] Among them, 1-CVD pulsed deposition of doped diamond layer, 2-undoped diamond particles;

[0035] Figure 3 The figure shows the hardness improvement multiples of different samples using the method of the present invention.

[0036] Figure 4 This is the Raman surface scanning data of multi-layer diamond particles prepared by the method of the present invention. DETAILED DESCRIPTION

[0037] In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0038] Figure 1The present invention provides a process flow chart for the method of increasing the hardness of diamond particles by mosaic splicing. The method comprises machining micropores into a copper substrate, splicing undoped single-crystal diamond particles onto the copper substrate, and partially embedding the diamond particles into the copper substrate. A doped diamond layer is pulse-deposited on the surface of the diamond particles using CVD technology. Diamond is combined with alloy powder, and a secondary deposition substrate is prepared using vacuum hot-melt technology. The exposed diamond particles on the secondary deposition substrate are etched, and then doped diamond is pulse-deposited again. Finally, the connected diamond film is acid-etched, and the metal residue on the surface of the diamond film is removed, followed by fragmentation to ultimately obtain ultra-hard diamond particles with a multilayer structure.

[0039] Figure 2 The structure diagram of the diamond with deposited layers obtained by the present invention is as follows: The hardness of the diamond particles can be significantly improved by coating the surface of the undoped diamond particles 2 with multiple layers of CVD pulsed deposited doped diamond layers 1.

[0040] Figure 3 The hardness of the samples obtained after different diamond particles were prepared using the method of Example 1, as well as the hardness increase factor. The figure shows that after the four samples with different initial hardnesses were hardened using the method of the present invention, the hardness of the samples increased to over 170 GPa. This shows that this method can effectively increase the hardness of diamond particles. Diamond particles of different initial hardnesses can all be increased to over 170 GPa, with the hardness increase being approximately 2 to 4.5 times depending on the initial hardness.

[0041] Figure 4 This is the Raman surface scanning data of the sample prepared in Example 1. Through Raman surface scanning, it can be seen that the undoped diamond particles are wrapped by the pulsed doping layer. The pulsed doping layer has a multi-layer structure and can significantly improve the hardness of the diamond particles.

[0042] Example 1

[0043] This example describes a method for increasing the hardness of diamond particles using mosaic splicing technology. First, undoped single-crystal diamond particles of approximately 5 μm in diameter are selected. A comparably sized indenter is then used to create regularly arranged micropores on a copper substrate. The single-crystal diamond particles are then spliced ​​onto the copper substrate. The substrate, with the single-crystal diamond particles spliced ​​onto the copper substrate, is then placed into an MPCVD apparatus. 300 sccm of ultrapure hydrogen and 15 sccm of methane are introduced. Argon and nitrogen are then pulsed at a deposition temperature of 850°C, a microwave power of 6000 W, and a chamber pressure of 12 kPa. The argon flow rate is 10–20 sccm, and the nitrogen flow rate is 5–15 sccm. Gas flow rates are adjusted by controlling flow valves to achieve varying doping effects. A doped diamond layer is pulsed onto the surface of the diamond particles, with a single layer thickness of 100 nm, and the deposition time is 6 hours. The particles with the deposited diamond-doped layer were removed from the substrate and placed, doped side down, on copper-nickel alloy powder. The particles were heated at 1000°C for 5 minutes in a vacuum heat-melting apparatus to prepare an alloy substrate coated with the diamond-doped surface. After cooling, the particles were placed back into the MPCVD apparatus, where they were etched for 30 minutes at 900°C with 300 sccm of ultrapure hydrogen. The same deposition conditions were then repeated, with a pulsed deposition of the doped diamond layer on the other side of the diamond particles. Finally, the deposited diamond film was acid-etched to remove any metal residue from the surface, and then the film was broken apart to produce multilayered ultrahard diamond particles with a hardness increase of 2-4.5 times. The diamond particles prepared by this method exhibit significant advantages in hardness and uniformity, making them suitable for the manufacture of high-precision cutting, grinding, and polishing tools.

[0044] Example 2

[0045] This example describes a method for increasing the hardness of diamond particles using mosaic splicing technology. First, undoped single-crystal diamond particles of approximately 5 μm in diameter are selected. A comparably sized indenter is then used to create regularly arranged micropores on a copper substrate. The single-crystal diamond particles are then spliced ​​onto the copper substrate. The substrate, with the spliced ​​single-crystal diamond particles, is then placed in an MPCVD apparatus. 300 sccm of ultrapure hydrogen is introduced at 900°C for 30 minutes. Then, 20 sccm of methane is introduced. Trimethylboron (B(CH₃)₃) at 0–0.2 sccm and argon at 5–10 sccm are pulsed at a deposition temperature of 900°C, a microwave power of 6000 W, and a chamber pressure of 15 kPa. Gas flow rates are adjusted by controlling flow valves to achieve varying doping effects. A doped diamond layer is pulsed onto the surface of the diamond particles, with a single layer thickness of 200 nm and a deposition time of 3 hours. The particles with the deposited diamond-doped layer were removed from the substrate and placed, doped side down, on copper-nickel alloy powder. The particles were heated at 1000°C for 5 minutes in a vacuum heat-melting apparatus to prepare an alloy substrate coated with the diamond-doped surface. After cooling, the particles were placed back into the MPCVD apparatus, where they were etched at 900°C for 30 minutes using 300 sccm of ultrapure hydrogen. The same deposition conditions were then repeated, with a pulsed deposition of the doped diamond layer on the other side of the diamond particles. Finally, the deposited diamond film was acid-etched to remove any metal residue from the surface, and then the film was crushed to produce multilayered, ultrahard diamond particles with a hardness increase of 2-4.5 times. The diamond particles prepared by this method exhibit significant advantages in hardness and uniformity, making them suitable for the manufacture of high-precision cutting, grinding, and polishing tools.

[0046] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for increasing the hardness of diamond particles by mosaic splicing, characterized in that: The method comprises the following steps: 1) Substrate preparation: Select the single-crystal diamond particles to be processed, measure the diamond particle size, and then use an indenter of the same size as the diamond particles to machine fixedly arranged micropores on the surface of the copper substrate; 2) First pulse deposition after diamond particles are spliced: Single crystal diamonds are spliced ​​into micropores machined into a copper substrate, with half of the diamond particles exposed. The copper substrate with the spliced ​​diamond particles is placed in a CVD device, and different doping gases are introduced in a pulsed manner. A layer of doped diamond is pulsed and deposited on the surface of the exposed diamond particles. The deposited layer then connects the diamond particles to form a film. 3) Preparation of secondary deposition substrate: The film formed by the particles of the pulsed deposition doped diamond layer is removed and placed upside down on the alloy powder to combine the diamond sheet with the alloy powder to form an alloy substrate covering the diamond doped surface; 4) Second pulse deposition: Place the substrate in a CVD device, introduce hydrogen to etch the diamond particles, and then pulse-deposit doped diamond on the surface of the diamond particles until the thickness reaches the same as the first pulse deposition. 5) Crushing treatment: The diamond particles that have been connected to form a diamond film after deposition are subjected to acid etching to remove metal residues on the surface of the diamond film and then the diamond film is crushed to obtain diamond particles with a deposited layer; In step 1), the size of the undoped diamond particles is micrometer-sized; In step 3), the alloy powder for preparing the secondary deposition substrate is selected from one of titanium-based alloy, nickel-based alloy, and copper-based alloy, and the process for preparing the secondary deposition substrate is vacuum hot melting; In steps 2) and 4), the thickness of the pulsed deposited doped diamond layer is 2000-3000 nm, and the doping elements are boron-nitrogen co-doping or boron-argon co-doping.

2. The method for increasing the hardness of diamond particles by mosaic splicing according to claim 1, characterized in that: In step 1), single crystal diamond particles are spliced ​​into the processed micropores of the copper substrate, and the micropore circumference spacing is less than twice the thickness of the pulsed deposited doping layer.

3. The method for increasing the hardness of diamond particles by mosaic splicing according to claim 1, characterized in that: In step 1), the particle size of the undoped diamond particles is 4-8 μm, the maximum width of the microholes processed on the substrate is 4-8 μm, the hole depth is 2-4 μm, and the microhole spacing is less than 3 μm.

4. The method for increasing the hardness of diamond particles by mosaic splicing according to claim 1, characterized in that: In step 4), the temperature for etching the exposed diamond with hydrogen is 700-1000°C and the etching time is 5-60 minutes.

5. The method for increasing the hardness of diamond particles by mosaic splicing according to claim 1, characterized in that: In steps 2) and 4), the conditions for pulsed deposition of doped diamond are: hydrogen flow rate of 300 sccm, methane flow rate of 10-40 sccm, argon flow rate of 6-40 sccm, trimethylboron flow rate of 0-3 sccm, and nitrogen flow rate of 1-20 sccm. Different doping gases are introduced in a pulsed manner.

6. The method for increasing the hardness of diamond particles by mosaic splicing according to claim 5, characterized in that: In steps 2) and 4), the diamond growth temperature is 800~1000℃, the power range is 4000~7000W, the chamber pressure is 10~25 kPa, and the pulsed deposition single layer deposition thickness is 50~300 nm.

7. Diamond particles having a pulsed deposition layer prepared by the method according to any one of claims 1 to 6.

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