A biomimetic diamond and its preparation method and application

Abstract

This invention relates to a method for preparing biomimetic diamonds with shell-like structures, aiming to effectively enhance the toughness of superhard materials. Using highly oriented pyrolytic graphite as raw material, a high-temperature, high-pressure method was employed to manipulate the sample's microstructure and graphite content, resulting in the successful preparation of biomimetic diamonds with a shell-like nacreous structure. This method bends the highly oriented graphite under high pressure to replicate the cross-interlocking structure found in shells, while simultaneously utilizing the martensitic phase transformation properties of graphite to control the diamond grain orientation. Experimental results indicate that the biomimetic diamonds produced exhibit extremely high hardness (HV > 120 GPa) and excellent toughness (K IC =15.9 MPa·m 0.5 ), with toughness approximately four times that of single-crystal diamond. Compared to traditional nano-polycrystalline diamond (NPD), its toughness is nearly doubled while maintaining similar hardness. This invention resolves the contradiction between hardness and toughness in superhard materials, providing a new technical path for the application of extremely hard and high-toughness NPD, and has important industrial application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation of high-toughness and extremely hard materials, and in particular to a bionic diamond and a preparation method and application thereof. Background Art

[0002] In the field of nano-polycrystalline diamond (NPD) and its toughening technology, existing technologies generally face the dilemma of balancing hardness and toughness. Although diamond has extremely high hardness, its inherent brittleness limits its service life and performance in high-impact environments. Several existing technologies have attempted to improve the toughening of diamond materials, but they all have different defects, because hardness and toughness are often contradictory in materials. Generally, the higher the hardness, the lower the toughness. A typical example is diamond, which has a Vickers hardness of up to 80 to 120 GPa. It is the hardest material in nature and has important uses in mineral mining, industrial manufacturing, and military fields. It is an important national strategic material. However, due to the strong covalent bond structure of diamond, its fracture toughness is only 4 to 6 MPa∙m 0.5 , poor impact resistance, seriously reducing its cutting efficiency and service life.

[0003] To address this issue, existing technologies typically use the method of introducing adhesives. For example, in the preparation of polycrystalline diamond (PCD), metal adhesives such as Ni, Co, Fe, etc. are often added and sintered under high pressure and high temperature conditions. Although this type of technology enhances the toughness of the material to a certain extent, it significantly reduces its hardness (usually to about 40 GPa). In addition, the thermal expansion coefficient of the metal adhesive is significantly different from that of diamond, causing the material to easily fall off in high-temperature environments, significantly affecting the thermal stability and durability of PCD. In addition, although some studies have attempted to replace metal adhesives with hard ceramics such as B4C or c-BN, their hardness still cannot reach the level of single-crystal diamond (usually below 80 GPa).

[0004] In addition, the development of nano-polycrystalline diamond (NPD) provides a new direction for improving the toughness of diamond. By introducing high-density grain boundaries, NPD changes the fracture mode of the material from transgranular fracture to intergranular fracture. This change effectively improves the fracture toughness of the material, making the toughness of NPD approximately twice that of single-crystal diamond (K IC ≈ 8 MPa·m 0.5 ), while also achieving hardness values ​​exceeding 120 GPa. However, despite the improvements in hardness and toughness achieved by NPD, diamond's inherent brittleness remains, resulting in unsatisfactory fracture toughness and impact resistance under extreme conditions. This demonstrates that simply adjusting grain boundary density cannot fully address the hardness-toughness balance issue, and more effective microstructural design is urgently needed.

[0005] Shells in nature provide inspiration for bionic design. The "brick + mud" structure of shells is composed of alternating layers of hard calcium carbonate and soft protein layers, forming a multi-level interlocking structure. This structure gives shells excellent hardness, toughness and impact resistance, and their toughness even far exceeds that of a single component material. Based on this bionic design concept, some studies in recent years have begun to apply shell structures to ceramics and composite materials, significantly improving the toughness of the materials. However, there are relatively few attempts to introduce this structure into diamond materials in existing technologies. In particular, how to further improve toughness under the premise of extremely high hardness is still an unresolved technical bottleneck. Summary of the Invention

[0006] One of the technical problems to be solved by the present invention is how to improve the fracture toughness of nano-polycrystalline diamond (NPD) while maintaining high hardness, overcome the problems of short service life and poor impact resistance caused by the brittleness of traditional diamond materials, and provide a method for preparing bionic diamond with a shell-like structure.

[0007] The present invention provides a method for preparing a biomimetic diamond, comprising the following steps:

[0008] S1: Preparation of highly oriented pyrolytic graphite as raw material for biomimetic diamond;

[0009] S2: subjecting the highly oriented pyrolytic graphite to a high temperature and high pressure treatment at a preparation pressure of 13-22 GPa and a preparation temperature of 1400-2000° C.;

[0010] S3: Cooling the highly oriented pyrolytic graphite treated in step S2 to room temperature, and releasing the pressure to obtain bionic diamond.

[0011] Compared with existing technologies, this invention offers the following advantages: By processing highly oriented pyrolytic graphite under high temperature and high pressure conditions, a biomimetic diamond with an interlocking layered structure is achieved. This structure, similar to the alternating arrangement of calcium carbonate and protein in seashells, exhibits extremely high hardness and excellent toughness. Compared with existing nano-polycrystalline diamond (NPD), this invention significantly improves the material's fracture toughness by precisely controlling pressure and temperature while maintaining excellent hardness, overcoming the poor impact resistance and short service life associated with the brittleness of traditional diamond materials. Through this technical solution, the biomimetic diamond preparation method of the present invention successfully addresses the brittleness of traditional diamond materials while achieving a balance between high hardness and high toughness, resulting in excellent performance in industrial applications.

[0012] In a possible embodiment, in step S2, the conditions of the high temperature and high pressure treatment are: pressure P = 15-22 GPa, temperature T = 1400-2000°C, and insulation time 30 min.

[0013] By controlling the conditions of high temperature and high pressure treatment through the above possible implementation methods, the graphite material can be fully converted into diamond and form a stable layered structure, thereby effectively improving the hardness and toughness of the material.

[0014] In a possible embodiment, in step S2, the conditions of the high temperature and high pressure treatment are: pressure P=13~15 GPa, T=1600~2000°C, and insulation time of 30 min.

[0015] Through the above possible implementation methods, the conditions of high temperature and high pressure treatment are controlled. The pressure and temperature within this range are more suitable for forming the cross-interlocking structure of bionic diamond, further improving the impact resistance of the material while maintaining a high hardness.

[0016] In a possible embodiment, in step S2, the high temperature and high pressure treatment is performed by wrapping the highly oriented pyrolytic graphite with hexagonal boron nitride, heating it with a rhenium tube, and simultaneously measuring the temperature with a tungsten-rhenium thermocouple.

[0017] Through the above possible implementation methods, the above specific heating method can achieve uniform temperature increase, ensure that the material is heated evenly, reduce the generation of local thermal stress, and ensure the structural integrity and performance stability of the bionic diamond.

[0018] In a possible embodiment, in step S2, the high temperature and high pressure treatment is performed by applying pressure using a large cavity press.

[0019] Through the above possible implementation methods, the large-cavity press can provide a more stable pressure environment, reduce the impact of pressure fluctuations on the material structure during the pressing process, and ensure that the diamond material can evenly form an ideal layered interlocking structure.

[0020] In a possible implementation, in step S3, the cooling rate of the highly oriented pyrolytic graphite is 90-110° C. / min.

[0021] Through the above possible implementation methods, a cooling rate of 90-110°C / min can effectively control the stress release inside the material, prevent material structure damage caused by too fast or too slow cooling, and further improve the toughness and impact resistance of the material.

[0022] The second technical problem to be solved by the present invention is to provide a bionic diamond to solve the problems of short service life and poor impact resistance of conventional diamond materials due to brittleness.

[0023] In order to solve the above technical problems, the present invention provides a bionic diamond, which is prepared by the above preparation method.

[0024] In a possible embodiment, the bionic diamond has a layered structure or a cross-interlocking layered structure.

[0025] This type of structure enables the bionic diamond to effectively disperse stress when subjected to high-intensity loads, thereby greatly improving its impact resistance and service life.

[0026] The third technical problem to be solved by the present invention is the application of the above-mentioned bionic diamond, which includes the application of the bionic diamond in industrial fine cutting and finishing.

[0027] Through the improved bionic diamond structure, it greatly improves the impact resistance while maintaining high hardness, making it particularly suitable for use in high-precision, high-strength industrial cutting and finishing fields, significantly improving processing quality and efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is the X-ray diffraction pattern of the biomimetic diamond prepared in Example 1;

[0029] Figure 2 is a SEM image of the biomimetic diamond prepared in Example 1;

[0030] Figure 3 is the X-ray diffraction pattern of the biomimetic diamond prepared in Example 2;

[0031] Figure 4 is the indentation image of the biomimetic diamond prepared in Example 2;

[0032] Figure 5 is a SEM image of the biomimetic diamond prepared in Example 2;

[0033] Figure 6 is the X-ray diffraction pattern of the biomimetic diamond prepared in Example 3;

[0034] Figure 7 is the indentation image of the biomimetic diamond prepared in Example 3;

[0035] Figure 8 is a SEM image of the biomimetic diamond prepared in Example 3;

[0036] Figure 9 is a TEM image of the biomimetic diamond prepared in Example 3;

[0037] Figure 10 is the X-ray diffraction pattern of the biomimetic diamond prepared in Example 4;

[0038] Figure 11 is the indentation image of the biomimetic diamond prepared in Example 4;

[0039] Figure 12 is a SEM image of the biomimetic diamond prepared in Example 4;

[0040] Figure 13 is the X-ray diffraction pattern of the biomimetic diamond prepared in Example 5;

[0041] Figure 14 is the indentation image of the biomimetic diamond prepared in Example 5;

[0042] Figure 15 is a SEM image of the biomimetic diamond prepared in Example 5;

[0043] Figure 16 is the X-ray diffraction pattern of the biomimetic diamond prepared in Example 6;

[0044] Figure 17 is the indentation image of the biomimetic diamond prepared in Example 6;

[0045] Figure 18 is a SEM image of the biomimetic diamond prepared in Example 6;

[0046] Figure 19 is the X-ray diffraction pattern of the biomimetic diamond prepared in Example 7;

[0047] Figure 20 is the indentation image of the biomimetic diamond prepared in Example 7;

[0048] Figure 21 is a SEM image of the biomimetic diamond prepared in Example 7;

[0049] Figure 22 is the X-ray diffraction pattern of the biomimetic diamond prepared in Example 8;

[0050] Figure 23 is the indentation image of the biomimetic diamond prepared in Example 8;

[0051] Figure 24 This is the SEM image of the bionic diamond prepared in Example 8. DETAILED DESCRIPTION

[0052] First, those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the embodiments of the present application and are not intended to limit the scope of protection of the embodiments of the present application. Those skilled in the art may adjust them as needed to suit specific application scenarios.

[0053] The present invention provides a method for preparing a biomimetic diamond, comprising the following steps:

[0054] S1: Preparation of highly oriented pyrolytic graphite as raw material for biomimetic diamond;

[0055] S2: subjecting the highly oriented pyrolytic graphite to a high temperature and high pressure treatment at a preparation pressure of 13-22 GPa and a preparation temperature of 1400-2000° C.;

[0056] S3: Cooling the highly oriented pyrolytic graphite treated in step S2 to room temperature, and releasing the pressure to obtain bionic diamond.

[0057] As a preferred embodiment, in step S2, the high-temperature and high-pressure treatment conditions are: pressure P = 15-22 GPa, temperature T = 1400-2000°C, and holding time of 30 minutes. The temperature and pressure range in this step not only facilitates the efficient conversion of graphite into diamond, but also promotes the formation of a layered interlocking structure, resulting in the material exhibiting superior mechanical properties at the microscopic level.

[0058] As a preferred solution, in step S2, the high-temperature and high-pressure treatment conditions are: pressure P = 13-15 GPa, T = 1600-2000°C, and a holding time of 30 minutes. By regulating the temperature and pressure within this range, not only can the cross-interlocking structure of the biomimetic diamond be achieved, but its performance under high impact loads can also be enhanced.

[0059] As a preferred embodiment, in step S2, the high-temperature and high-pressure treatment employs a heating method comprising wrapping the highly oriented pyrolytic graphite in hexagonal boron nitride, heating it with a rhenium tube, and simultaneously measuring the temperature with a tungsten-rhenium thermocouple. This heating method ensures uniform heating of the sample, thereby reducing microstructural defects caused by uneven temperature and further improving the uniformity and strength of the produced diamond.

[0060] As a preferred solution, in step S2, the high temperature and high pressure treatment is performed using a large-cavity press. Using a large-cavity press can provide a more stable pressure environment, thereby reducing stress concentration in the material during processing and ensuring that the layered interlocking structure of the diamond is effectively maintained and strengthened.

[0061] As a preferred solution, in step S3, the cooling rate of the highly oriented pyrolytic graphite is 90-110°C / min. By controlling the cooling rate, the material's internal stress is properly released, preventing structural damage due to improper cooling, while further improving the material's toughness and impact resistance.

[0062] The present invention also provides a bionic diamond, which is prepared by any one of the preparation methods of claims 1-6.

[0063] As a preferred solution, the biomimetic diamond has a layered structure or a cross-interlocking layered structure. This structure, inspired by the structure of shells in nature, effectively disperses energy through slippage and interaction between different layers when subjected to external impact, avoiding brittle fracture caused by stress concentration. This structure effectively disperses externally applied stress, significantly improving the material's impact resistance and service life.

[0064] The present invention also provides an application of the bionic diamond, which includes application of the bionic diamond in industrial fine cutting and finishing.

[0065] The present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0066] Example 1

[0067] S1: Using highly oriented pyrolytic graphite (20*20*1mm) as raw material, laser cutting into cylindrical shape (2mm diameter, 1mm height);

[0068] S2: The highly oriented pyrolytic graphite is wrapped with hexagonal boron nitride, heated by a rhenium tube, and simultaneously measured in temperature by a tungsten-rhenium thermocouple. A Kawai-type large-volume multi-stage anvil cell experimental apparatus is used to prepare biomimetic diamond at a pressure of P = 13 GPa and a temperature of T = 1400 °C. The holding time range is 30 min.

[0069] S3: Slowly cool to room temperature at a rate of 100°C / min, then release the pressure. The sample is mainly composed of graphite, hexagonal diamond, and cubic diamond, with a layered morphology.

[0070] The X-ray diffraction results of the samples are shown in Figure 1 ; SEM images are shown in Figure 2 .

[0071] Example 2

[0072] Example 2 is similar to Example 1, using the same experimental assembly, method, and pressure conditions as Example 1 (pressure P = 13 GPa). The graphite content in the biomimetic diamond was regulated by controlling the temperature, and the biomimetic diamond was prepared at a temperature of T = 1600 ° C. As the synthesis temperature increases, the graphite content in the sample decreases. Its main components are graphite, hexagonal diamond, and cubic diamond, and its morphology is a layered structure. Its hardness HV = 130.0~139.4 GPa, (F = 9.8 N), fracture toughness K IC =8.3~12.6MPa.m 0.5 . XRD see Figure 3 , indentation diagram see Figure 4 , SEM images are shown in Figure 5 .

[0073] Example 3

[0074] Example 3 is similar to Example 1, and adopts the same experimental assembly, method and pressure conditions as Example 1 (pressure P=13 GPa). Bionic diamond was prepared at a temperature of T=1800 ℃. As the synthesis temperature continues to increase, the graphite content in the sample further decreases. XRD test shows that its main components are hexagonal diamond and cubic diamond. TEM test shows that trace graphite (thickness less than 10nm) is discontinuously distributed in the sample. SEM test morphology is a cross-interlocking layered structure similar to a shell. Its hardness HV=126.6~144.0GPa, (F=9.8 N), fracture toughness increases, K IC =14.8~20.2MPa.m 0.5 Its toughness is about 3 to 4 times that of single crystal diamond, and its shell-like microstructure effectively balances the contradiction between hardness and toughness in NPD.

[0075] XRD see Figure 6 , indentation diagram see Figure 7 , SEM images are shown in Figure 8 , TEM image see Figure 9 , indicating that trace amounts of graphite (less than 10 nm in thickness) are discontinuously distributed in the sample.

[0076] Example 4

[0077] Example 4 is similar to Example 1, using the same experimental assembly, method, and pressure conditions (pressure P = 13 GPa) as Example 1. A biomimetic diamond was prepared at a temperature of T = 2000 °C. As the synthesis temperature increased, the sample did not contain graphite. Its main components were hexagonal diamond and cubic diamond, and the SEM test morphology still showed a cross-interlocking layered structure. Its hardness HV = 126.6 ~ 139.7 GPa, (F = 9.8 N) was close to that of Example 3, and the fracture toughness K decreased. IC =10.1~12.0 MPa.m 0.5 .

[0078] XRD see Figure 10 , indentation diagram see Figure 11 , SEM images are shown in Figure 12 .

[0079] Example 5

[0080] Example 5 is similar to Example 1, using the same experimental assembly and method as Example 1, and the same temperature as Example 4 (T=2000 ℃). At a temperature of T=2000 ℃, the layered structure in the biomimetic diamond is regulated by regulating the synthesis pressure. Bionic diamond is prepared at a pressure of P=15GPa. As the synthesis pressure increases, the sample is still a composite phase of hexagonal diamond and cubic diamond. SEM testing shows that the sample is a layered interlocking structure. Compared with Example 4, its hardness increases HV=130.4~144.4GPa, (F=9.8 N), and the fracture toughness decreases K IC =8.2~11.3 MPa.m 0.5 .

[0081] XRD see Figure 13 , indentation diagram see Figure 14 , SEM images are shown in Figure 15 .

[0082] Example 6

[0083] Example 6 is similar to Example 1, using the same experimental assembly and method as Example 1 and the same temperature as Example 4 (T = 2000 °C). The synthesis pressure was increased to P = 18 GPa to prepare biomimetic diamond. As the synthesis pressure increased, the sample remained a composite phase of hexagonal diamond and cubic diamond. SEM testing showed that the layered structure of the sample was destroyed. Compared with Example 5, its hardness increased by HV = 137.5~152.8 GPa, (F = 9.8 N), and the fracture toughness decreased by K IC =7.5~10.3 MPa.m 0.5 .

[0084] XRD see Figure 16 , indentation diagram see Figure 17 , SEM images are shown in Figure 18 .

[0085] Example 7

[0086] Example 7 is similar to Example 1, using the same experimental assembly and method as Example 1 and the same temperature as Example 4 (T=2000 ℃). The synthesis pressure was increased to P=20 GPa to prepare biomimetic diamond. As the synthesis pressure continued to increase, the sample was still a composite phase of hexagonal diamond and cubic diamond. SEM testing showed that the layered structure of the sample was further destroyed and granular. Compared with Example 6, its hardness continued to increase HV=142.1~159.1 GPa, (F=9.8 N), and the fracture toughness further decreased, K IC =7.2~9.1 MPa.m 0.5 .

[0087] XRD see Figure 19 , indentation diagram see Figure 20 , SEM images are shown in Figure 21 .

[0088] Example 8

[0089] Example 8 is similar to Example 1, using the same experimental assembly and method as Example 1 and the same temperature as Example 4 (T = 2000 °C). The synthesis pressure was further increased to P = 22 GPa to prepare biomimetic diamond. As the synthesis pressure increased, the sample remained a composite phase of hexagonal diamond and cubic diamond. SEM testing showed that the sample was nano-granular. Compared with Example 7, its hardness continued to increase HV = 151.8~181.7 GPa, (F = 9.8 N), and the fracture toughness further decreased K IC =6.8~9.2MPa.m 0.5 .

[0090] XRD see Figure 22 , indentation diagram see Figure 23 , SEM images are shown in Figure 24 .

[0091] From the above examples, it can be found that the present invention uses highly oriented pyrolytic graphite as raw material, utilizes its high-pressure bending and martensitic phase transformation, and can form a cross-interlocking layered structure by reasonably controlling the temperature and pressure of high-temperature and high-pressure treatment. By regulating its microstructure and graphite content through a unique high-temperature and high-pressure method, a shell-like structure biomimetic diamond is prepared. Its hardness is higher than that of single-crystal diamond (111) crystal plane, and its toughness is about 3 to 4 times that of single crystal, effectively balancing the contradiction between hardness and toughness in diamond.

[0092] It can be seen from the above examples that the bionic diamonds prepared by the preparation methods of Examples 3, 4, and 5 of the present invention all have layered interlocking structures and cross-interlocking layered structures, and the bionic diamonds prepared by controlling the pressure to P=13~15 GPa, T=1600~2000 ℃, and keeping warm for 30 minutes under high temperature and high pressure conditions all have this structure. Furthermore, through the slip and interaction between different layers, effective energy dispersion is achieved, and brittle fracture caused by stress concentration is avoided. This structure can effectively disperse the externally applied stress, thereby significantly improving the impact resistance and service life of the material, and solving the problems existing in the background technology. Although the bionic diamonds prepared in other examples do not have the above structure, their strength and toughness have reached values ​​above a level, further proving that the present invention solves the technical problems existing in the background technology through an improved preparation method.

[0093] The above are only preferred embodiments of the present invention. The embodiments within the range are not listed one by one. Without departing from the principle of this patent (using highly oriented pyrolytic graphite as raw material, regulating its layered structure by pressure, regulating the graphite content by temperature, and preparing bionic diamonds with shell-like structures), improvements and embellishments should be included in the scope of protection of the present invention.

[0094] In the description of the present application, the description with reference to the terms "one embodiment", "some embodiments", "in the present embodiment", "specific example", or "some examples" means that the specific features, mechanisms, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, mechanisms, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples, unless they are contradictory.

[0095] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A method for preparing biomimetic diamond, characterized in that: The method comprises the following steps: S1: preparing highly oriented pyrolytic graphite as a raw material for biomimetic diamond; S2: subjecting the highly oriented pyrolytic graphite to a high temperature and high pressure treatment at a preparation pressure of 13 GPa and a preparation temperature of 1800° C. for 30 minutes; S3: Cooling the highly oriented pyrolytic graphite after the treatment in step S2 to room temperature, and releasing the pressure to obtain a biomimetic diamond, wherein the biomimetic diamond has a cross-interlocking layered structure and discontinuously distributed trace graphite, and the thickness of the trace graphite is less than 10 nm; In step S2, the high temperature and high pressure treatment is performed by wrapping the highly oriented pyrolytic graphite with hexagonal boron nitride, heating it with a rhenium tube, and simultaneously measuring the temperature with a tungsten-rhenium thermocouple; In step S2, the high temperature and high pressure treatment is performed by applying pressure using a large cavity press; In step S3, the cooling rate of the highly oriented pyrolytic graphite is 90-110° C. / min.

2. A bionic diamond, characterized in that: The bionic diamond is prepared by the preparation method according to claim 1.

3. An application of the biomimetic diamond according to claim 2, characterized in that: The application includes application of the bionic diamond in industrial fine cutting and finishing.

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