Polycrystalline diamond anvil cell as well as preparation method and application thereof

Abstract

The invention provides a polycrystalline diamond anvil cell as well as a preparation method and application thereof, and belongs to the field of large-cavity ultrahigh-pressure devices. According to the polycrystalline diamond anvil cell, the diamond with different particle sizes is matched, so that the density of the anvil cell is enhanced, the porosity is reduced, and the compression resistance of the anvil cell is greatly improved; silicon in the anvil is combined with diamond to form silicon carbide, the thermal expansion coefficient of the silicon carbide is closer to that of the diamond, the heat-resistant temperature of the anvil can be increased, and a sample is kept stable; silicon in the anvil is a fragile material and has no magnetism, but the compressive strength is low, and the impact toughness and compressive property of the anvil can be improved by adding titanium or transition metal carbide, so that the service life is prolonged; the Vickers hardness of the polycrystalline diamond anvil cell reaches more than 4000 Hv, the compressive strength reaches more than 3 GPa, and the pressure of an on-machine test oil gauge is reduced to less than 4 MN, so that the secondary anvil cell standard is reached; the working face of the polycrystalline diamond anvil cell is larger than or equal to 14 mm, and the polycrystalline diamond anvil cell can be used in an in-situ detection device under synchrotron radiation and high pressure.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of large cavity ultra-high pressure devices, and particularly relates to a polycrystalline diamond anvil and a preparation method and application thereof. BACKGROUND

[0002] At present, in industrial production and basic research, a large cavity static high pressure device plays a main role. As a core pressure transmission component of a Kawai type multi-anvil device (KMA), the mechanical properties of the anvil directly determine the limit working parameters of the high pressure cavity. At present, the domestic KMA device generally uses hard alloy (such as tungsten carbide) as the secondary anvil material. Limited by the material hardness and deformation resistance, the cavity pressure is difficult to break through 40 GPa. This pressure is only equivalent to the environment at a depth of about 1000 kilometers in the earth (the top of the lower mantle), and there is a huge gap from the simulation demand of the earth core (about 360 GPa). When the pressure is increased to ultra-high pressure, the hard alloy anvil cannot meet the demand.

[0003] Sintered diamond is a polycrystalline diamond sintered body, which has the advantages of high hardness and high strength, and can obtain greater cavity pressure than WC anvil, and is an ideal material for realizing ultra-high pressure environment. The existing polycrystalline diamond anvil without binder and single crystal diamond can produce a cavity pressure greater than 120 GPa, but the working surface of the anvil is less than 300 μm, and the size is small. Limited by the size, only micron-sized samples can be synthesized, and the sample is too small to be used for research. The size of the cavity is limited by the small size of the diamond anvil. There are two kinds of cobalt-based and silicon-based PCD anvil at home and abroad. The cobalt-based diamond anvil is suitable for impact extreme high pressure (such as ultra-high pressure geophysical simulation or synthesis of superhard material), because cobalt metal has good ductility, high compressive strength and high pressure resistance. However, the cobalt-based diamond anvil is not suitable for high pressure in-situ X-ray diffraction. The silicon-based diamond anvil is a brittle material with low compressive strength and no magnetism, and is suitable for conventional high pressure experiments, and can also be used for high pressure in-situ X-ray diffraction and Raman spectrum detection. At the same time, with the deepening of research, researchers need to carry out in-situ detection under high pressure, so a large size diamond anvil is needed to meet the in-situ XRD detection. SUMMARY

[0004] Therefore, it is necessary to provide a polycrystalline diamond anvil suitable for an ultrahigh pressure device and a preparation method and application thereof, the polycrystalline diamond anvil has a Vickers hardness of 4000 Hv or more, a compressive strength of 3 GPa or more, an oil gauge pressure of 4 MN or less in a machine test (20 GPa), a working surface of 14 mm or more, and a surface roughness Ra of 50 nm or less, reaches the standard of a large-size secondary anvil, and can improve the internal pressure of a synthesis cavity, thereby facilitating high-pressure synthesis under a larger cavity and a larger pressure and the emergence of superhard new materials, and promoting the paradigm innovation of extreme condition material science research; meanwhile, the polycrystalline diamond secondary anvil can be used for in-situ detection under synchrotron radiation and high pressure.

[0005] Specifically, the present application provides the following technical solutions: In a first aspect, the present application provides a preparation method of a polycrystalline diamond anvil, comprising: Mixing: first, uniformly mix 80-99 wt% of diamond mixed particles and 0.1-20 wt% of a binder with a particle size of 0.1-10 μm to obtain a mixture; then, perform pre-pressing forming treatment on the mixture to obtain a blank; wherein the diamond mixed particles are composed of 5-45 wt% of diamond particles with a particle size of 0.1-5 μm, 0-50 wt% of diamond particles with a particle size of 5-10 μm, and 0-80 wt% of diamond particles with a particle size of 10-30 μm; the binder is composed of a silicon source and a toughening agent with a mass ratio of 1:1-1:3; and the toughening agent is titanium or a transition metal carbide; High-temperature and high-pressure sintering: perform high-temperature and high-pressure sintering treatment on the blank to obtain a polycrystalline diamond composite sintered body.

[0006] To improve the hardness and heat resistance of the anvil, preferably, the silicon source is at least one of silicon blocks, silicon powder, and silicon carbide. To improve the toughness of the sintered anvil, the transition metal carbide is at least one of titanium carbide, niobium carbide, and tungsten carbide.

[0007] To further improve the hardness and compressive strength of the polycrystalline diamond composite sintered body, so as to ensure that a lower oil pressure can be used in a machine test to obtain a higher cavity pressure, the diamond mixed particles are composed of three sizes of diamond particles. Preferably, the diamond mixed particles are composed of 5-20 wt% of diamond particles with a particle size of 0.1-5 μm, 0-30 wt% of diamond particles with a particle size of 5-10 μm, 40-60 wt% of diamond particles with a particle size of 10-20 μm, and 0-40 wt% of diamond particles with a particle size of 20-30 μm.

[0008] In one specific embodiment, the high-temperature and high-pressure sintering step includes: subjecting the billet to high-temperature and high-pressure sintering treatment at 1200–1600°C and 4.5–7 GPa to obtain the polycrystalline diamond composite sintered body.

[0009] To further improve the hardness and compressive strength of the polycrystalline diamond composite sintered body, and to ensure that higher cavity pressure can be obtained with lower oil pressure during machine testing, the high-temperature and high-pressure sintering step includes: using a six-sided top press to perform segmented heating and segmented overpressure sintering treatment on the billet, wherein the process parameters for each segment are as follows: First stage: pressure 4.5~5.5 GPa, sintering temperature about 1200~1450℃, heating rate 3~7℃ / s, holding time 3~5 min; Second stage: pressure 5-7 GPa, sintering temperature about 1400-1600℃, heating rate 1-5℃ / s, holding time 3-8 min, to obtain the polycrystalline diamond composite sintered body with dense and uniform structure.

[0010] Furthermore, the preparation method also includes precision machining of the polycrystalline diamond composite sintered body to obtain an anvil working surface with optical-grade surface finish, wherein the anvil working surface is ≥14mm. The precision machining includes grinding, lapping, and polishing. The shape of the anvil working surface can be machined according to actual requirements.

[0011] Secondly, the present invention provides a large-size polycrystalline diamond secondary anvil prepared by the above preparation method, wherein the working surface of the polycrystalline diamond anvil is ≥14mm, and the polycrystalline diamond anvil includes a polycrystalline diamond phase and a silicon-bonded phase uniformly dispersed in the polycrystalline diamond phase; the silicon-bonded phase is formed by a molten silicon source penetrating into the pores of the billet under high temperature and high pressure (HPHT) conditions and reacting with the diamond surface in contact with it to generate silicon carbide (SiC).

[0012] Thirdly, the present invention provides an application of the aforementioned polycrystalline diamond anvil cell in a large-cavity static high-pressure device. The large-cavity static high-pressure device includes, but is not limited to, a high-pressure in-situ X-ray diffraction detection device, a synchronous Raman spectroscopy detection device, etc. The surface finish Ra of the polycrystalline diamond anvil cell is <50 nm.

[0013] Compared with the prior art, the technical solution provided by the present invention has the following characteristics: the combination of diamonds of different particle sizes enhances the density of the polycrystalline diamond composite sintered body and reduces the porosity, thereby greatly improving the compressive strength of the polycrystalline diamond anvil; the silicon in the polycrystalline diamond anvil combines with diamond to form silicon carbide, whose coefficient of thermal expansion is closer to that of diamond, which can increase the heat resistance temperature of the polycrystalline diamond anvil and maintain sample stability; the silicon in the polycrystalline diamond anvil is a brittle material, which, although non-magnetic, has low compressive strength. The addition of titanium or transition metal carbides can improve the impact toughness of the polycrystalline diamond anvil, improve its compressive strength, and thus extend its service life; the Vickers hardness of the polycrystalline diamond anvil reaches 4000-4500 Hv, the compressive strength reaches 3-4 GPa, and the oil gauge pressure during machine testing (20 GPa) reaches 2.5-4 MN; thus, the working surface of the polycrystalline diamond secondary anvil provided by the present invention is ≥14mm, which can be used in in-situ detection devices under synchrotron radiation and high pressure. Attached Figure Description

[0014] Figure 1 This is a SEM image of the microstructure of the polycrystalline diamond composite sintered body synthesized in Example 1 of the present invention; Figure 2 This is a schematic diagram of the polycrystalline diamond anvil cell structure used in Embodiment 1 of the present invention. Detailed Implementation

[0015] All terms used in this invention are common terms in the relevant field. Unless otherwise specified, the raw materials, equipment, preparation processes, testing methods, etc., used are all existing technologies in the relevant field.

[0016] To provide a large-size polycrystalline diamond anvil (anvil working surface ≥14mm) suitable for synchrotron radiation and in-situ detection, this invention mainly optimizes the diamond micropowder and silicon composite binder system, employs a six-sided press for high-temperature and high-pressure (HPHT) sintering, and uses a segmented heating and overpressure method to ultimately obtain a sintered diamond anvil with a uniform microstructure. This provides a polycrystalline diamond anvil, its preparation method, and its application. The specific embodiments of this invention mainly adopt the following technical solutions: A method for preparing a polycrystalline diamond anvil cell includes: Mixing: First, 80-99 wt% of diamond mixed particles and 0.1-20 wt% of binder with a particle size of 0.1-10 μm are uniformly mixed to obtain a mixture; then, the mixture is pre-pressed and shaped under a pressure of 50-300 MPa for 1-4 min using existing cold pressing or isostatic pressing methods to obtain a blank; wherein, the diamond mixed particles are composed of 5-45 wt% of diamond particles with a particle size of 0.1-5 μm, 0-50 wt% of diamond particles with a particle size of 5-10 μm, and 0-80 wt% of diamond particles with a particle size of 10-30 μm, and the binder is composed of a silicon source and a toughening agent in a mass ratio of 1:1 to 1:3, and the toughening agent is titanium or a transition metal carbide; High-temperature and high-pressure sintering: The billet is placed in a shielded cup and then in an assembly block. During sintering, heating elements are provided around the billet and at both ends to keep the billet material in a stable temperature field. A six-sided top press is used to perform segmented heating and segmented high-pressure sintering on the billet, with the process parameters for each segment as follows: First stage: pressure 4.5~5.5 GPa, sintering temperature about 1200~1450℃, heating rate 3~7℃ / s, holding time 3~5 min. The first stage mainly achieves all-round melting and infiltration of silicon. The second stage involves a pressure of 5–7 GPa, a sintering temperature of approximately 1400–1600℃, a heating rate of 1–5℃ / s, and a holding time of 3–8 min. This stage primarily aims to trigger the diamond-silicon reaction, thereby forming a SiC interface reaction. It also allows silicon elements that have penetrated into the pores of the billet to react with the diamond surface to generate silicon carbide (SiC), while simultaneously achieving near-full densification of the material. After the holding time is completed, the material is cooled to a safe temperature and then depressurized to obtain a dense and uniform polycrystalline diamond composite sintered body, providing a foundation for obtaining a large-size anvil working surface.

[0017] In the mixing step, the use of diamonds of different particle sizes can significantly improve the tap density of the mixture, reduce voids, and optimize the spatial distribution and skeletal structure of the diamond particles. This is beneficial for enhancing the density of the polycrystalline diamond composite sintered body, reducing porosity, and thus greatly improving the compressive strength of the diamond anvil. Therefore, the diamond mixed particles are composed of at least two-size diamonds. The two-size particles can be 0.1–2 μm and 10–30 μm, 0.1–1 μm and 5–8 μm, 0.1–1 μm and 10–20 μm, etc.; the three-size particles can be 0.1–1 μm, 5–8 μm and 13–18 μm, 0.1–1 μm, 5–8 μm and 10–18 μm, 0.1–2 μm, 5–10 μm and 15–20 μm, 0.1–5 μm, 10–15 μm and 20–30 μm, etc. Preferably, the diamond mixed particles are composed of diamond particles of three sizes; specifically, the diamond mixed particles can be composed of 5-20 wt% diamond particles with a particle size of 0.1-5 μm, 0-30 wt% diamond particles with a particle size of 5-10 μm, 40-60 wt% diamond particles with a particle size of 10-20 μm, and 0-40 wt% diamond particles with a particle size of 20-30 μm. In this way, the Vickers hardness of the polycrystalline diamond composite sintered body can reach 4300-4500 Hv, the compressive strength can reach 3.5-4 GPa, and the oil gauge pressure in the machine test (20 GPa) can reach 2.5-3 MN.

[0018] The main reason why the binder in the mixing step is composed of a silicon source and a toughening agent is as follows: the silicon source melts under high temperature and high pressure (HPHT) conditions and penetrates into the pores of the billet, reacting with the diamond surface to form silicon carbide (SiC), which is used to achieve strong bonding and pore filling between the components; since the coefficient of thermal expansion of silicon carbide is closer to that of diamond, it can increase the heat resistance temperature of the polycrystalline diamond anvil and maintain sample stability; silicon in the polycrystalline diamond anvil is a brittle material with low compressive strength and no magnetism. The addition of titanium or transition metal carbide binder can improve the impact toughness and compressive strength of the polycrystalline diamond anvil, thereby increasing its service life. The silicon source is at least one of silicon ingot, silicon powder, or silicon carbide. The transition metal carbide powder is at least one of titanium carbide, niobium carbide, or tungsten carbide.

[0019] If the amount of silicon source is too large, it will lead to a decrease in the toughness of the anvil, resulting in the risk of explosion during overpressure; if the amount of toughening agent is too large, the hardness of the anvil will not be high, and it will be difficult to withstand more pressure during use; therefore, the mass ratio of silicon source to toughening agent is 1:1 to 1:3, such as 1:1, 1:2, 1:3, etc.

[0020] To ensure that the polycrystalline diamond composite sintered body has high hardness and compressive strength and can be used as a secondary anvil for large-size polycrystalline diamond, the amount of binder in the mixture is limited to 0.1-20 wt%, preferably 4-15 wt%, such as 4 wt%, 5 wt%, 7 wt%, 8 wt%, 10 wt%, 12 wt%, 15 wt%, etc.

[0021] Furthermore, the preparation method of the polycrystalline diamond anvil also includes the step of: precision machining the polycrystalline diamond composite sintered body to obtain the desired anvil working surface shape and surface finish. Existing precision machining methods include grinding, lapping, and polishing. For example, a planetary wheel grinder can be used to grind the polycrystalline diamond composite sintered body (generally a cylinder) to a predetermined height; then, laser grinding can be used to process the blank shape of the anvil; the anvil can be polished to a predetermined size using a grinding wheel, while the chamfer is machined using a special tooling; finally, the desired shape of the anvil working surface is obtained, and the anvil working surface achieves an optical-grade surface finish Ra < 50 nm and a size ≥ 14 mm. Preferably, the surface finish Ra of the anvil working surface is 30–48 nm, and the working surface is 14–25 mm. The working surface of the anvil can be a plane, sphere, concave surface, or cone, etc.

[0022] The present invention also provides a polycrystalline diamond anvil prepared by the above preparation method, wherein the surface finish of the working surface of the anvil is Ra<50nm and the size is ≥14mm; the anvil includes a polycrystalline diamond phase and a silicon-bonded phase uniformly dispersed in the polycrystalline diamond phase; the silicon-bonded phase is formed by a molten silicon source penetrating into the pores of the blank under high temperature and high pressure (HPHT) conditions and reacting with the diamond surface in contact with it to generate silicon carbide (SiC).

[0023] This invention also provides an application of the aforementioned polycrystalline diamond anvil cell in a large-cavity static high-pressure device. The large-cavity static high-pressure device includes, but is not limited to, a high-pressure in-situ X-ray diffraction detection device, a synchronous Raman spectroscopy detection device, etc.

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0025] Example 1 This embodiment provides a polycrystalline diamond anvil and its preparation method, including: selecting diamond particles with a particle size of 0.1-1μm (10wt%), diamond particles with a particle size of 5-8μm (25wt%), and diamond particles with a particle size of 13-18μm (60wt%). The binder component consists of silicon powder with an average particle size of 1μm and titanium powder with an average particle size of 2μm, with a total mass fraction of 5%, wherein the mass ratio of silicon powder to titanium powder is 1:2. The diamond particles of different particle sizes and the binder component are mixed evenly to obtain a mixture; the mixture is pre-formed by unidirectional cold pressing at 200MPa, and the blank is placed into a niobium cup. After assembly, high-temperature and high-pressure sintering is performed: the first stage pressure is 5 GPa, the temperature is 1300°C, the heating rate is 5°C / s, and the holding time is 4 min; then the pressure is increased to 6.0 GPa, the temperature is increased to 1500°C, the heating rate is 2°C / s, and the holding time is 5 min, resulting in a dense and uniform polycrystalline diamond composite sintered body, such as... Figure 1 As shown. From Figure 1 As can be seen, the silicon-bound phase is uniformly dispersed in the polycrystalline diamond phase (black), without obvious binder agglomeration.

[0026] The polycrystalline diamond composite sintered body is subjected to precision machining processes in sequence. Specifically, firstly, the polycrystalline diamond composite sintered body is ground to a predetermined height using a planetary wheel grinder; then, the blank shape of the anvil is processed by laser grinding; the anvil is polished to a predetermined size using a grinding wheel, while the chamfer is machined using a special tooling; finally, the desired shape is obtained. Figure 2 The anvil shown has a flat working surface with a surface finish of approximately 45 nm (Ra) and a size of 24.5 mm.

[0027] Example 2 This embodiment provides a polycrystalline diamond anvil and its preparation method, including: selecting diamond particles with a particle size of 0.1-2 μm accounting for 20 wt% and diamond particles with a particle size of 10-30 μm accounting for 70 wt%. The binder component consists of silicon powder with an average particle size of 1 μm and titanium carbide powder with an average particle size of 2 μm, with a total mass fraction of 10%, wherein the mass ratio of silicon powder to titanium carbide powder is 1:2. After uniformly mixing the diamond particles of different particle sizes and the binder component, a mixture is obtained; the mixture is pre-formed by unidirectional cold pressing at 200 MPa, and the blank is placed into a metal niobium cup. After assembly, high-temperature and high-pressure sintering is performed: the first stage pressure is 4.5 GPa, the temperature is 1200 degrees Celsius, the heating rate is 5℃ / s, and the holding time is 4 min; then the pressure is increased to 7.0 GPa, the temperature is increased to 1600 degrees Celsius, the heating rate is 2℃ / s, and the holding time is 5 min, to obtain a dense and uniform polycrystalline diamond composite sintered body.

[0028] Using the same method as in Example 1, the polycrystalline diamond composite sintered body was precision machined to obtain an anvil, and the surface finish Ra of the anvil working surface was about 35 nm and the size was 24.5 mm.

[0029] Example 3 This embodiment provides a polycrystalline diamond anvil and its preparation method, including: selecting diamond particles with a particle size of 0.1-1 μm accounting for 45 wt% and diamond particles with a particle size of 5-8 μm accounting for 50 wt%. The binder component consists of silicon powder with an average particle size of 1 μm and titanium powder with an average particle size of 2 μm, with a total mass fraction of 5%, wherein the mass ratio of silicon powder to titanium powder is 1:1.5. After uniformly mixing the diamond particles of different particle sizes and the binder component, a mixture is obtained; the mixture is pre-formed by unidirectional cold pressing at 200 MPa, and the blank is placed into a metal niobium cup. After assembly, high-temperature and high-pressure sintering is performed: the first stage pressure is 5 GPa, the temperature is 1300 degrees Celsius, the heating rate is 5℃ / s, and the holding time is 4 min; then the pressure is increased to 6.0 GPa, the temperature is increased to 1500 degrees Celsius, the heating rate is 2℃ / s, and the holding time is 5 min, to obtain a dense and uniform polycrystalline diamond composite sintered body.

[0030] Using the same method as in Example 1, the polycrystalline diamond composite sintered body was precision machined to obtain an anvil, and the surface finish Ra of the anvil working surface was about 42 nm and the size was 24.5 mm.

[0031] Example 4 This embodiment provides a polycrystalline diamond anvil and its preparation method, including: selecting diamond particles with a particle size of 0.1-2 μm accounting for 20 wt% and diamond particles with a particle size of 10-30 μm accounting for 70 wt%. The binder component consists of silicon powder with an average particle size of 1 μm and tungsten carbide powder with an average particle size of 2 μm, with a total mass fraction of 10%, wherein the mass ratio of silicon powder to tungsten carbide powder is 1:2. After uniformly mixing the diamond particles of different particle sizes and the binder component, a mixture is obtained; the mixture is pre-formed by unidirectional cold pressing at 200 MPa, and the blank is placed into a metal niobium cup. After assembly, high-temperature and high-pressure sintering is performed: the first stage pressure is 4.5 GPa, the temperature is 1200 degrees Celsius, the heating rate is 5℃ / s, and the holding time is 4 min; then the pressure is increased to 7.0 GPa, the temperature is increased to 1600 degrees Celsius, the heating rate is 2℃ / s, and the holding time is 5 min, to obtain a dense and uniform polycrystalline diamond composite sintered body.

[0032] Using the same method as in Example 1, the polycrystalline diamond composite sintered body was precision machined to obtain an anvil, and the surface finish of the anvil working surface was about 37 nm and the size was 24.5 mm.

[0033] Example 5 This embodiment provides a polycrystalline diamond anvil and its preparation method, comprising: selecting diamond particles with a particle size of 0.1-1 μm accounting for 10 wt%, diamond particles with a particle size of 5-8 μm accounting for 25 wt%, and diamond particles with a particle size of 13-18 μm accounting for 60 wt%. The binder component consists of silicon powder with an average particle size of 1 μm and titanium powder with an average particle size of 2 μm, with a total mass fraction of 5%, wherein the mass ratio of silicon powder to titanium powder is 1:2. The diamond particles of different particle sizes and the binder component are mixed evenly to obtain a mixture; the mixture is pre-formed by unidirectional cold pressing at 200 MPa, and the blank is placed into a niobium cup. After assembly, high temperature and high pressure sintering is performed at a pressure of 6.0 GPa, a temperature of 1500℃ at a heating rate of 5℃ / s, and a holding time of 5 minutes to obtain a polycrystalline diamond composite sintered body.

[0034] Using the same method as in Example 1, the polycrystalline diamond composite sintered body was precision machined to obtain an anvil, and the surface finish of the anvil working surface was approximately 48 nm with a size of 24.5 mm.

[0035] Example 6 This embodiment provides a polycrystalline diamond anvil and its preparation method, which is basically the same as the preparation method of the polycrystalline diamond anvil provided in Example 1, the main difference being the raw materials: in this embodiment, diamond particles with a particle size of 0.1-5 μm account for 10 wt%, diamond particles with a particle size of 10-15 μm account for 40 wt%, and diamond particles with a particle size of 20-28 μm account for 40 wt%. The binder component consists of silicon powder with an average particle size of 1 μm and titanium powder with an average particle size of 2 μm, with a total mass fraction of 10%, wherein the mass ratio of silicon powder to titanium powder is 1:4. The final anvil obtained has a surface finish of approximately 42 nm and a size of 24.5 mm.

[0036] Comparative Example 1 This comparative example provides a polycrystalline diamond composite sintered body suitable for polycrystalline diamond anvils, comprising: 20 wt% diamond particles with a particle size of 0.1–2 μm and 70 wt% diamond particles with a particle size of 10–30 μm. The binder component is silicon powder with an average particle size of 1 μm, with a total mass fraction of 10%. The diamond particles of different particle sizes and the binder component are mixed uniformly to obtain a mixture; the mixture is pre-formed by unidirectional cold pressing at 200 MPa, and the blank is placed into a metal cup. After assembly, high-temperature and high-pressure sintering is performed: the first stage pressure is 4.5 GPa, the temperature is 1200°C, the heating rate is 5°C / s, and the holding time is 4 min; subsequently, the pressure is increased to 7.0 GPa, the temperature is increased to 1600°C, the heating rate is 2°C / s, and the holding time is 5 min, to obtain the polycrystalline diamond composite sintered body.

[0037] Comparative Example 2 This comparative example provides a polycrystalline diamond composite sintered body suitable for polycrystalline diamond anvils, comprising: 20 wt% diamond particles with a particle size of 0.1–2 μm and 70 wt% diamond particles with a particle size of 10–30 μm. The binder component consists of silicon powder with an average particle size of 1 μm and titanium carbide powder with an average particle size of 2 μm, with a total mass fraction of 10%, wherein the mass ratio of silicon powder to titanium carbide powder is 1:4. The diamond particles of different particle sizes and the binder component are mixed evenly to obtain a mixture; the mixture is pre-formed by unidirectional cold pressing at 200 MPa, and the blank is placed into a metal cup. After assembly, high-temperature and high-pressure sintering is performed: the first stage pressure is 4.5 GPa, the temperature is 1200 degrees Celsius, the heating rate is 5℃ / s, and the holding time is 4 min; subsequently, the pressure is increased to 7.0 GPa, the temperature is increased to 1600 degrees Celsius, the heating rate is 2℃ / s, and the holding time is 5 min, to obtain the polycrystalline diamond composite sintered body.

[0038] Comparative Example 3 This comparative example provides a polycrystalline diamond composite sintered body suitable for polycrystalline diamond anvil cells, which is basically the same as the polycrystalline diamond composite sintered body synthesized in Example 1, the main difference being the raw materials: in this comparative example, diamond particles with a particle size of 0.1-1 μm account for 10 wt%, diamond particles with a particle size of 5-8 μm account for 30 wt%, and diamond particles with a particle size of 13-18 μm account for 38 wt%. The binder component consists of silicon powder with an average particle size of 1 μm and titanium powder with an average particle size of 2 μm, with a total mass fraction of 22%, wherein the mass ratio of silicon powder to titanium powder is 1:2 as the raw material.

[0039] The polycrystalline diamond composite sintered bodies synthesized in Examples 1-6 and Comparative Examples 1-3 were prepared into samples with dimensions of 24.5 mm × 24.5 mm × 24.5 mm. Hardness (Vickers hardness tester), compressive strength (universal testing machine), and mechanical testing (DIA press) were performed. The results are shown in Table 1. Zinc sulfide was used as the standard pressure material during the mechanical testing.

[0040] Table 1. Test Results of Polycrystalline Diamond Composite Sintered Body As can be seen from Table 1, the Vickers hardness of the sintered bodies suitable for polycrystalline diamond anvils provided in Examples 1 to 6 of the present invention reaches 4000-4500 Hv, the compressive strength reaches 3-4 GPa, and the oil gauge pressure in the machine test (20 GPa) can reach 2.5-4 MN. The high hardness of the polycrystalline diamond composite sintered body does not mean that it can withstand higher pressure. It also needs to have a compressive strength of more than 3 GPa to be suitable for use as a large-size polycrystalline diamond secondary anvil.

[0041] Comparing Example 1 and Example 5, Example 1 employs segmented sintering. In the first stage, silicon is fully infiltrated, and in the second stage, a diamond-silicon reaction is triggered, forming a SiC interface reaction. This allows the silicon elements infiltrated into the pores of the blank to react with the diamond surface to generate silicon carbide (SiC), while simultaneously achieving near-full densification of the material. Consequently, the hardness and compressive strength tested in machine tests are significantly better than those in Example 5.

[0042] Comparing the results of Examples 1, 6 and 3, the three-particle size ratio is better than the single-particle size or two-particle size ratio. The three-particle size ratio can more effectively achieve densification and achieve the densest packing.

[0043] Comparing the results of Examples 2, 4, and Comparative Examples 1-3, titanium carbide, tungsten carbide, and silicon can all be used as binders. However, excessive binder dosage makes it difficult to maintain a balance between hardness and compressive strength, potentially leading to no test results during testing due to the failure to detect phase transition points or damage to the anvil (Comparative Example 3). Therefore, the binder dosage is limited to 0.1-20 wt%. Simultaneously, the silicon source and toughening agent must be used together. Excessive dosage of toughening agents such as Ti and carbides will result in lower hardness (Comparative Example 2); if the binder contains only silicon, it will lead to insufficient compressive strength (Comparative Example 1). Therefore, the preferred mass ratio of silicon source to toughening agent is 1:1 to 1:3. Furthermore, regarding toughening agents, TiC can provide lighter weight, while silicon carbide is inherently a high-temperature resistant material. Although WC has higher hardness, its toughness is slightly inferior to titanium carbide. Therefore, Ti is the preferred metallic binder, and the binder is preferably a combination of Si and Ti.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A method for preparing a polycrystalline diamond anvil cell, comprising: Mixing: First, 80-99 wt% of diamond mixed particles and 0.1-20 wt% of binder with a particle size of 0.1-10 μm are uniformly mixed to obtain a mixture; then, the mixture is pre-pressed to obtain a blank; wherein, the diamond mixed particles are composed of 5-45 wt% of diamond particles with a particle size of 0.1-5 μm, 0-50 wt% of diamond particles with a particle size of 5-10 μm, and 0-80 wt% of diamond particles with a particle size of 10-30 μm, and the binder is composed of a silicon source and a toughening agent in a mass ratio of 1:1 to 1:3, and the toughening agent is titanium or a transition metal carbide; High-temperature and high-pressure sintering: The billet is subjected to high-temperature and high-pressure sintering treatment to obtain a polycrystalline diamond composite sintered body.

2. The preparation method according to claim 1, characterized in that, The silicon source is at least one of silicon ingot, silicon powder, and silicon carbide; the transition metal carbide is at least one of titanium carbide, niobium carbide, and tungsten carbide.

3. The preparation method according to claim 2, characterized in that, The diamond mixed particles consist of 5-20 wt% diamond particles with a particle size of 0.1-5 μm, 0-30 wt% diamond particles with a particle size of 5-10 μm, 40-60 wt% diamond particles with a particle size of 10-20 μm, and 0-40 wt% diamond particles with a particle size of 20-30 μm.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The billet is subjected to high-temperature and high-pressure sintering at 1200–1600℃ and 4.5–7 GPa to obtain the polycrystalline diamond composite sintered body.

5. The preparation method according to claim 4, characterized in that, The high-temperature and high-pressure sintering step includes: using a six-sided top press to perform segmented heating and segmented high-pressure sintering treatment on the billet, wherein the process parameters for each segment are as follows: First stage: pressure 4.5~5.5 GPa, sintering temperature about 1200~1450℃, heating rate 3~7℃ / s, holding time 3~5 min; Second stage: pressure 5-7 GPa, sintering temperature about 1400-1600℃, heating rate 1-5℃ / s, holding time 3-8min, to obtain the polycrystalline diamond composite sintered body with dense and uniform structure.

6. The preparation method according to claim 1, 2, 3, or 5, characterized in that, It also includes precision machining of the polycrystalline diamond composite sintered body to obtain an anvil working surface with a surface finish Ra < 50 nm, and the anvil working surface is ≥14 mm.

7. A polycrystalline diamond anvil prepared by the preparation method according to any one of claims 1 to 6, wherein the working surface of the polycrystalline diamond anvil is ≥14mm and the surface finish Ra is <50 nm.

8. The polycrystalline diamond anvil cell according to claim 7, characterized in that, It includes a polycrystalline diamond phase and a silicon-bonded phase uniformly dispersed in the polycrystalline diamond phase; the silicon-bonded phase is formed by molten silicon source penetrating into the pores of the billet under high temperature and high pressure conditions, and reacting with the diamond surface in contact with it to generate silicon carbide.

9. The application of the polycrystalline diamond anvil cell as described in claim 7 or 8 in a large-cavity static high-pressure device.

10. The application according to claim 9, characterized in that, The large-cavity static high-pressure device is a high-pressure in-situ X-ray diffraction detection device or a synchronous Raman spectroscopy detection device.

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