Binder-free nano polycrystalline diamond and preparation method thereof
By developing a binder-free method for preparing polycrystalline diamond nanoparticles, the complexity and instability issues caused by binders in the synthesis of polycrystalline diamond were resolved. This method produces polycrystalline diamond nanoparticles with a hardness of 42–141 GPa and simplifies the sintering process.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- YANSHAN UNIV
- Filing Date
- 2026-02-10
- Publication Date
- 2026-05-01
AI Technical Summary
In existing technologies, the synthesis of polycrystalline diamond requires the use of a binder, which increases the complexity and instability of the synthesis.
A method for preparing binder-free polycrystalline diamond nanoparticles was adopted. After pre-pressing in a cemented carbide mold, the nanocrystalline diamond was sintered under high temperature and high pressure. The sintering pressure was 7-25 GPa, the temperature was 1600-2250℃, and the holding time was 5-60 min.
The prepared binder-free nano-polycrystalline diamond has a Vickers hardness of 42–141 GPa, which reduces the complexity of sintering conditions, avoids the use of binders, and improves the hardness of the material.
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Abstract
Description
A binder-free nanocrystalline diamond and its preparation method Technical Field
[0001] This invention belongs to the field of polycrystalline diamond technology, specifically, it relates to a binder-free nano-polycrystalline diamond and its preparation method. Background Technology
[0002] Polycrystalline diamond (PCD) has high hardness and wear resistance. It overcomes the shortcomings of anisotropy and {111} crystal plane dissociation damage of single crystal diamond and is widely used in many fields such as aerospace, electronics, construction, gem processing, oil drilling and geological exploration.
[0003] The existing methods for synthesizing PCD include: (1) using Si-Ti-B powder as a binder, and preparing silicon-titanium based PCD with diamond micro powder under high temperature and high pressure conditions. It was found that the binder and diamond react to form a bonding phase mainly composed of compounds such as SiC, TiC, and TiB2, which firmly bond the diamond particles together to form a dense structure, thus improving the overall performance of PCD. (2) preparing alumina binder type PCD by detonation sintering. It was found that alumina binder type PCD has good thermal stability in air and no diamond oxidation phenomenon; and the powder has good dispersibility, with a particle size between 0.5 and 0.7 µm. PCD is composed of large particles with a particle size of 100 to 200 nm, which are aggregates formed by the tight bonding of 2 to 10 nm nanodiamond particles with alumina. (3) Boron-containing PCD was synthesized using a six-sided press under high temperature and high pressure conditions via a Co melting-deep catalytic method. Samples synthesized with different volume fractions of boron-containing diamond were tested, and the microstructure of the PCD was observed by scanning electron microscopy and analyzed by XRD. The results showed that the compressive impact toughness and heat resistance of the samples were significantly improved. (4) PCD was synthesized by sintering OLC with micron-sized diamond (MD) under high temperature and high pressure conditions (4–5 GPa / 1000–1400 ℃ / holding for 5–30 min). Its hardness and density reached 55.9 GPa and 3.02 g / cm³, respectively. 3 It was proposed that micron-sized diamonds can not only serve as seed crystals to promote diamond growth, but also balance internal pressure loss to reduce sintering pressure. However, due to the excessively low sintering pressure and temperature, OLC cannot be completely converted, resulting in poor performance of the synthesized PCD.
[0004] The synthesis of polycrystalline diamond (PCD) requires high temperature and high pressure conditions, and also requires the assistance of a corresponding binder, which increases the complexity and instability of the synthesis. Summary of the Invention
[0005] In view of this, the technical problem to be solved by the present invention is to provide a binder-free nano-polycrystalline diamond and its preparation method, which solves the problem that the synthesis of polycrystalline diamond in the prior art requires the use of a binder, which increases the complexity and instability of the synthesis.
[0006] To address the aforementioned technical problems, this invention discloses a method for preparing binder-free nano-polycrystalline diamond, comprising the following steps: pre-pressing nano-diamond (ND) powder into a cemented carbide mold at a pressure of 400–600 MPa for a holding time of 30–60 s; then, placing the pre-pressed sample into the mold for high-temperature and high-pressure sintering. The sintering pressure is 7–25 GPa, the sintering temperature is 1600–2250 °C, and the holding time is 5–60 min; subsequently, the sample is cooled and depressurized to obtain a blank.
[0007] Furthermore, the Vickers hardness of the binder-free nano-polycrystalline diamond obtained by ND sintering is 42-141 GPa.
[0008] Furthermore, the pre-pressed sample is placed in a BN crucible, ensuring good contact between the crucible and the rhenium sheet, and then placed in a LaCrO3 insulator. Subsequently, the entire sample is placed into an MgO octahedron, an Al2O3 plug is added, and a four-hole tube with electrodes is placed on the plug. The assembly is then completed by sealing with Al2O3 glue.
[0009] Further, the sample is slowly subjected to a pressure of 7–25 GPa over 10–24 h; then, the temperature is increased from room temperature to 1600–2250 °C at a heating rate of 10–30 °C / min, and held at that temperature for 5–60 min. The sample is then cooled in the furnace to obtain a blank. The prepared blank is then subjected to surface grinding and deburring to obtain a binder-free polycrystalline diamond nanoparticle.
[0010] A binder-free polycrystalline nanodiamond, the nanodiamond (ND) is prepared by detonation method, with an average grain size of about 5 nm.
[0011] Compared with the prior art, this application can achieve the following technical effects: the binder-free nanoscale polycrystalline diamond prepared by this invention has a Vickers hardness of 42 to 141 GPa. By utilizing the characteristics of ND having a large number of surface dangling bonds and satisfying the basic principle of solid-state reaction, the sintering conditions of OLC are reduced, and no binder is required during the sintering process. This solves the problem of high sintering conditions or the need for binders in PCD, and provides a binder-free nanoscale polycrystalline diamond and its preparation method.
[0012] Of course, any product implementing this application does not necessarily need to achieve all of the technical effects described above at the same time. Detailed Implementation
[0013] The following will describe the implementation of this application in detail with reference to the embodiments, so that the implementation process of how this application uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.
[0014] A method for preparing binder-free polycrystalline nanodiamond includes the following steps: nanodiamond (ND) powder is pre-pressed into a cemented carbide mold; the pre-pressed sample is placed in a BN crucible, ensuring good contact between the crucible and rhenium sheets; then, it is placed in a LaCrO3 insulator, and subsequently, the entire sample is placed into an MgO octahedron. An Al2O3 plug is added, and a four-hole tube with electrodes is placed on the plug. The assembly is completed using Al2O3 adhesive, with a pressure of 400–600 MPa and a holding time of 30–60 s. Then, the pre-pressed sample is placed into a mold for high-temperature, high-pressure sintering. The sintering pressure is 7–25 GPa, the sintering temperature is 1600–2250 °C, and the holding time is 5–60 min. The sample is then cooled and depressurized to obtain a blank. The prepared blank is then surface-ground and deburred to obtain a binder-free polycrystalline nanodiamond. Example 1
[0015] A binder-free polycrystalline diamond nanoparticle and its preparation method include the following steps: ND powder is loaded into a cemented carbide mold and pre-pressed at a pressure of 400 MPa for 30 seconds. Then, the pre-pressed sample is placed into the mold for high-temperature and high-pressure sintering. First, the sample is slowly pressurized to 7 GPa over 10 hours; then, the temperature is increased from room temperature to 1600℃ at a rate of 10℃ / min and held for 5 minutes. The sample is then cooled in the furnace to obtain a blank. The prepared blank is then subjected to surface grinding and deburring to obtain the binder-free polycrystalline diamond nanoparticle.
[0016] After high-pressure sintering, the binder-free nanocrystalline diamond sample was polished and its microstructure and properties were tested. The Vickers hardness value of the obtained sintered block was 42 GPa. Example 2
[0017] A binder-free polycrystalline diamond nanoparticle and its preparation method include the following steps: ND powder is loaded into a cemented carbide mold and pre-pressed at a pressure of 500 MPa for 40 seconds. Then, the pre-pressed sample is placed into the mold for high-temperature and high-pressure sintering. First, the sample is slowly pressurized to 8 GPa over 11 hours; then, the temperature is increased from room temperature to 1700℃ at a rate of 10℃ / min and held for 10 minutes. The sample is then cooled in the furnace to obtain a blank. The prepared blank is then subjected to surface grinding and deburring to obtain the binder-free polycrystalline diamond nanoparticle.
[0018] After high-pressure sintering, the binder-free nanocrystalline diamond sample was polished and its microstructure and properties were tested. The Vickers hardness value of the resulting sintered block was 48 GPa. Example 3
[0019] A binder-free polycrystalline diamond nanoparticle and its preparation method include the following steps: ND powder is loaded into a cemented carbide mold and pre-pressed at a pressure of 600 MPa for 50 seconds. Then, the pre-pressed sample is placed into the mold for high-temperature and high-pressure sintering. First, the sample is slowly pressurized to 9 GPa over 12 hours; then, the temperature is increased from room temperature to 1600℃ at a rate of 10℃ / min and held for 5 minutes. The sample is then cooled in the furnace to obtain a blank. The prepared blank is then subjected to surface grinding and deburring to obtain the binder-free polycrystalline diamond nanoparticle.
[0020] After high-pressure sintering, the binder-free nanocrystalline diamond sample was polished and its microstructure and properties were tested. The Vickers hardness value of the obtained sintered block was 53 GPa. Example 4
[0021] A binder-free polycrystalline diamond nanoparticle and its preparation method include the following steps: ND powder is loaded into a cemented carbide mold and pre-pressed at a pressure of 400 MPa for 60 seconds. Then, the pre-pressed sample is placed into the mold for high-temperature and high-pressure sintering. First, the sample is slowly pressurized to 10 GPa over 13 hours; then, the temperature is increased from room temperature to 2150℃ at a rate of 30℃ / min and held for 30 minutes. The sample is then cooled in the furnace to obtain a blank. The prepared blank is then subjected to surface grinding and deburring to obtain the binder-free polycrystalline diamond nanoparticle.
[0022] After high-pressure sintering, the binder-free nanocrystalline diamond sample was polished and its microstructure and properties were tested. The Vickers hardness value of the obtained sintered block was 56 GPa. Example 5
[0023] A binder-free polycrystalline diamond nanoparticle and its preparation method include the following steps: ND powder is loaded into a cemented carbide mold and pre-pressed at a pressure of 500 MPa for 30 seconds. Then, the pre-pressed sample is placed into the mold for high-temperature and high-pressure sintering. First, the sample is slowly pressurized to 12 GPa over 15 hours; then, the temperature is increased from room temperature to 1600℃ at a rate of 10℃ / min and held for 60 minutes. The sample is then cooled in the furnace to obtain a blank. The prepared blank is then subjected to surface grinding and deburring to obtain the binder-free polycrystalline diamond nanoparticle.
[0024] After high-pressure sintering, the binder-free nanocrystalline diamond sample was polished and its microstructure and properties were tested. The Vickers hardness value of the obtained sintered block was 85 GPa. Example 6
[0025] A binder-free polycrystalline diamond nanoparticle and its preparation method include the following steps: ND powder is loaded into a cemented carbide mold and pre-pressed at a pressure of 600 MPa for 40 seconds. Then, the pre-pressed sample is placed into the mold for high-temperature and high-pressure sintering. First, the sample is slowly pressurized to 14 GPa over 17 hours; then, the temperature is increased from room temperature to 1800℃ at a rate of 10℃ / min and held for 5 minutes. The sample is then cooled in the furnace to obtain a blank. The prepared blank is then subjected to surface grinding and deburring to obtain the binder-free polycrystalline diamond nanoparticle.
[0026] After high-pressure sintering, the binder-free nanocrystalline diamond sample was polished and its microstructure and properties were tested. The Vickers hardness value of the resulting sintered block was 90 GPa. Example 7
[0027] A binder-free polycrystalline diamond nanoparticle and its preparation method include the following steps: ND powder is loaded into a cemented carbide mold and pre-pressed at a pressure of 400 MPa for 50 seconds. Then, the pre-pressed sample is placed into the mold for high-temperature and high-pressure sintering. First, the sample is slowly pressurized to 16 GPa; then, the temperature is increased from room temperature to 1900℃ at a rate of 20℃ / min and held for 30 minutes. The sample is then cooled in the furnace to obtain a blank. The prepared blank is then subjected to surface grinding and deburring to obtain the binder-free polycrystalline diamond nanoparticle.
[0028] After high-pressure sintering, the binder-free nanocrystalline diamond sample was polished and its microstructure and properties were tested. The Vickers hardness value of the obtained sintered block was 103 GPa. Example 8
[0029] A binder-free polycrystalline diamond nanoparticle and its preparation method include the following steps: ND powder is loaded into a cemented carbide mold and pre-pressed at a pressure of 500 MPa for 60 seconds. Then, the pre-pressed sample is placed into the mold for high-temperature and high-pressure sintering. First, the sample is slowly pressurized to 16 GPa; then, the temperature is increased from room temperature to 2000℃ at a rate of 20℃ / min and held for 30 minutes. The sample is then cooled in the furnace to obtain a blank. The prepared blank is then subjected to surface grinding and deburring to obtain the binder-free polycrystalline diamond nanoparticle.
[0030] After high-pressure sintering, the binder-free nanocrystalline diamond sample was polished and its microstructure and properties were tested. The Vickers hardness value of the obtained sintered block was 112 GPa. Example 9
[0031] A binder-free polycrystalline diamond nanoparticle and its preparation method include the following steps: ND powder is loaded into a cemented carbide mold and pre-pressed at a pressure of 600 MPa for 30 seconds. Then, the pre-pressed sample is placed into the mold for high-temperature and high-pressure sintering. First, the sample is slowly pressurized to 19 GPa over 22 hours; then, the temperature is increased from room temperature to 2250℃ at a rate of 30℃ / min and held for 60 minutes. The sample is then cooled in the furnace to obtain a blank. The prepared blank is then subjected to surface grinding and deburring to obtain the binder-free polycrystalline diamond nanoparticle.
[0032] After high-pressure sintering, the binder-free nanocrystalline diamond sample was polished and its microstructure and properties were tested. The Vickers hardness value of the obtained sintered block was 141 GPa. Example 10
[0033] A binder-free polycrystalline diamond nanoparticle and its preparation method include the following steps: ND powder is loaded into a cemented carbide mold and pre-pressed at a pressure of 400 MPa for 40 seconds. Then, the pre-pressed sample is placed into the mold for high-temperature and high-pressure sintering. First, the sample is slowly pressurized to 20 GPa; then, the temperature is increased from room temperature to 1900℃ at a rate of 20℃ / min and held for 15 minutes. The sample is then cooled in the furnace to obtain a blank. The prepared blank is then subjected to surface grinding and deburring to obtain the binder-free polycrystalline diamond nanoparticle.
[0034] After high-pressure sintering, the binder-free nanocrystalline diamond sample was polished and its microstructure and properties were tested. The Vickers hardness value of the obtained sintered block was 99 GPa. Example 11
[0035] A binder-free polycrystalline diamond nanoparticle and its preparation method include the following steps: ND powder is loaded into a cemented carbide mold and pre-pressed at a pressure of 500 MPa for 50 seconds. Then, the pre-pressed sample is placed into the mold for high-temperature and high-pressure sintering. First, the sample is slowly pressurized to 23 GPa; then, the temperature is increased from room temperature to 1800℃ at a rate of 10℃ / min and held for 5 minutes. The sample is then cooled in the furnace to obtain a blank. The prepared blank is then subjected to surface grinding and deburring to obtain the binder-free polycrystalline diamond nanoparticle.
[0036] After high-pressure sintering, the binder-free nanocrystalline diamond sample was polished and its microstructure and properties were tested. The Vickers hardness value of the obtained sintered block was 87 GPa. Example 12
[0037] A binder-free polycrystalline diamond nanoparticle and its preparation method include the following steps: ND powder is loaded into a cemented carbide mold and pre-pressed at a pressure of 600 MPa for 60 seconds. Then, the pre-pressed sample is placed into the mold for high-temperature and high-pressure sintering. First, the sample is slowly pressurized to 25 GPa; then, the temperature is increased from room temperature to 1800℃ at a rate of 10℃ / min and held for 10 minutes. The sample is then cooled in the furnace to obtain a blank. The prepared blank is then subjected to surface grinding and deburring to obtain the binder-free polycrystalline diamond nanoparticle.
[0038] After high-pressure sintering, the binder-free nano-polycrystalline diamond sample was polished and its microstructure and properties were tested. The Vickers hardness value of the sintered block was 90 GPa.
[0039]
[0040] As shown in Examples 1-12 above, sintering temperature, sintering pressure, and holding time have a significant impact on the properties of the composite material. A horizontal comparison of Examples 1-4, 5-9, and 10-12 reveals that the composite material exhibits the best performance at a sintering pressure of 10-20 GPa. A longitudinal comparison of Examples 1-4 shows that when the sintering pressure is less than 10 GPa, the hardness of the sample increases with increasing sintering pressure. A longitudinal comparison of Examples 5-9 shows that when the sintering pressure is greater than 10 GPa, the hardness of the sample increases with increasing sintering temperature. Comparisons of Examples 11 and 12 demonstrate that the hardness of the sample increases with prolonged holding time.
[0041] The foregoing description illustrates and describes several preferred embodiments of the present invention. However, as previously stated, it should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the inventive concept described herein through the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.
Claims
1. A method for preparing binder-free polycrystalline diamond nanoparticles, comprising the following steps: Nanodiamond (ND) powder is pre-pressed into a cemented carbide mold at a pressure of 400–600 MPa for 30–60 s. The pre-pressed sample is then placed back into the mold for high-temperature, high-pressure sintering at a pressure of 7–25 GPa, a temperature of 1600–2250 °C, and a holding time of 5–60 min. The sample is then cooled and depressurized to obtain a blank.
2. The method for preparing binder-free polycrystalline diamond nanoparticles as described in claim 1, characterized in that, The binder-free nano-polycrystalline diamond obtained by sintering the ND has a Vickers hardness of 42-141 GPa.
3. The method for preparing binder-free polycrystalline diamond as described in claim 2, characterized in that, The pre-pressed sample is placed in a BN crucible, ensuring good contact between the crucible and the rhenium sheet. It is then placed in a LaCrO3 insulator and subsequently placed into an MgO octahedron. An Al2O3 plug is added, and a four-hole tube with electrodes inserted into it is placed on the plug. The assembly is then completed by sealing with Al2O3 adhesive.
4. The method for preparing binder-free polycrystalline diamond as described in claim 3, characterized in that, First, the sample is slowly subjected to a pressure of 7–25 GPa over 10–24 h; then, the temperature is increased from room temperature to 1600–2250 °C at a heating rate of 10–30 °C / min and held for 5–60 min. The sample is then cooled in the furnace to obtain a blank. The prepared blank is then subjected to surface grinding and deburring to obtain a binder-free polycrystalline diamond nanoparticle.
5. The nanocrystalline diamond prepared by the method described in claim 4, characterized in that, The nanodiamond (ND) is prepared by detonation and has an average grain size of about 5 nm.