CVD diamond self-supporting film and preparation method and application thereof

Abstract

The invention discloses a preparation method of a CVD diamond self-supporting film. The method comprises the following steps: (1) respectively introducing a first gas phase flow and a second gas phase flow into a CVD diamond deposition furnace, setting deposition parameters of the CVD diamond deposition furnace as first deposition process parameters, and operating for a first deposition duration; (2) introducing a third gas phase flow, adjusting the deposition parameter of the CVD diamond deposition furnace to be a first transition process parameter, and operating for a first transition duration; (3) respectively introducing the first gas phase flow, the second gas phase flow and the third gas phase flow into a CVD diamond deposition furnace, setting the deposition parameter of the CVD diamond deposition furnace as a second deposition parameter, and operating for a second deposition duration; (4) reducing or closing the third gas phase flow, adjusting the deposition parameter of the CVD diamond deposition furnace to be a second transition parameter, and operating for a second transition duration; and (5) circulating the step (1) to the step (4) until the thickness of the CVD diamond self-supporting film meets the requirement. The CVD diamond self-supporting film provided by the invention has good toughness and wear resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of CVD diamond self-supporting films, and particularly relates to a CVD diamond self-supporting film and a preparation method and application thereof. Background Art

[0002] Chemical Vapor Deposition (CVD) diamond has a series of excellent physical and chemical properties close to natural diamond, such as hardness, wear resistance, high thermal conductivity, and low friction coefficient. It is widely used in various fields such as coated tools, thermal conductive materials, semiconductor devices, and optical windows. When used as a superhard material, CVD diamond is a 100% diamond structure and does not contain a metal binder. Compared with the currently commonly used polycrystalline diamond (PCD), it has more excellent high-temperature mechanical properties and can effectively avoid the high-temperature "thermal failure" phenomenon of diamond caused by the presence of metal binders. The thickness of conventional CVD diamond coatings is only a few microns. If the thickness of CVD diamond increases and reaches a millimeter-level self-supporting film, its application scenarios will also increase significantly. In particular, when used as a cutting element for oil drilling, it can effectively avoid the "thermal failure" problem of the current PCD drilling bit under complex geological conditions. It is a fundamental change in the current geological exploration diamond drill bit cutting teeth, and is expected to replace the currently commonly used PCD composite sheets and cutting tool special-shaped teeth, and has a very broad market prospect.

[0003] Hot filament chemical vapor deposition (HFCVD) is a common method for growing tool-grade CVD diamond because of its simple growth method, low equipment cost and high growth efficiency. The thickness of the CVD diamond film can be effectively increased by extending the growth time. However, if the thickness of the CVD diamond film is simply increased by increasing the growth time, its mechanical properties will drop significantly. The main reason is that during the deposition process of diamond, the preferential growth of crystals along a certain direction causes the crystals to gradually present a "V"-shaped columnar crystal that is thin at the bottom and thick at the top as the deposition time increases. The existence of such columnar crystals leads to large internal stress in the diamond film, and the mechanical properties such as impact resistance, toughness, and wear resistance are reduced, which limits the application of diamond self-supporting films.

[0004] Through special deposition processes, especially the deposition of multi-layer diamond films, the internal stress of the diamond film can be effectively reduced, the growth of columnar crystals can be blocked, and the crack propagation can be prevented when the diamond film is subjected to external forces, thereby achieving the effect of improving the mechanical properties of the diamond film.

[0005] Chinese invention patent CN201810127560.1 discloses a low-stress CVD diamond composite coating and its preparation method, which uses a time modal method to control the loading amount of the reaction gas methane, and alternately deposits micron diamond coating and nano diamond coating in sequence to reduce the internal stress of the CVD coating. However, this method is only applicable to the preparation of CVD diamond coatings, and cannot prepare CVD diamond self-supporting films. Summary of the invention

[0006] In view of the problems existing in the prior art, the present invention provides a CVD diamond self-supporting film and its preparation method and application. The CVD self-supporting film of the present invention has a thickness of millimeter level and is a multi-layer composite structure, which is composed of nano-grain size films of smaller particles (hereinafter referred to as NCD) and micro-grain size films of larger particles (hereinafter referred to as MCD) arranged alternately in sequence. The CVD diamond self-supporting film of the present invention has good toughness and wear resistance, and can be used as a cutting element in geological exploration fields such as oil drilling.

[0007] The first aspect of the present invention provides a method for preparing a CVD diamond self-supporting film, wherein the thickness of the CVD diamond self-supporting film is not less than 1.0 mm, preferably 1.2 to 2.0 mm, and the method comprises:

[0008] (1) depositing an MCD layer on a substrate by a first deposition process, wherein the first deposition process comprises respectively passing a first gas phase flow and a second gas phase flow into a CVD diamond deposition furnace, setting a deposition parameter of the CVD diamond deposition furnace to a first deposition process parameter, and running a first deposition time;

[0009] (2) using a first transition process to perform transition processing on the deposition process in step (1), wherein the first transition process is to introduce a third gas phase flow, adjust the deposition parameters of the CVD diamond deposition furnace to the first transition process parameters, and run the first transition time;

[0010] (3) continuing deposition by using a second deposition process, wherein the second deposition process is to respectively pass the first gas phase flow, the second gas phase flow and the third gas phase flow into the CVD diamond deposition furnace, set the deposition parameters of the CVD diamond deposition furnace to the second deposition parameters, and run the second deposition time;

[0011] (4) using a second transition process to perform transition processing on the deposition process in step (3), wherein the second transition process is to reduce or shut down the third gas phase flow, adjust the deposition parameters of the CVD diamond deposition furnace to the second transition parameters, and run the second transition time;

[0012] (5) Repeat steps (1) to (4) until the thickness of the CVD diamond self-supporting film meets the requirements.

[0013] In the above-mentioned CVD diamond self-supporting film preparation method, the first gas phase flow in step (1) can be one or more of gaseous organic matter containing carbon elements and / or liquid organic matter containing carbon elements that are easily gasified, and the second gas phase flow in step (1) is hydrogen. Specifically, the gaseous organic matter containing carbon elements can be one or more of methane, ethane, acetylene, propane, propylene, propyne, etc.; the liquid organic matter containing carbon elements that are easily gasified can be one or more of methanol, ethanol, acetone, and petroleum ether.

[0014] In the above-mentioned CVD diamond self-supporting film preparation method, the first deposition process parameters in step (1) are: the deposition furnace pressure is 2000-5000Pa, the single filament power is 0.8-1.2kW, the filament temperature is 2200-2700°C, the substrate temperature is 750-1050°C, and the distance between the filament and the substrate is 4-8mm; preferably, the deposition furnace pressure is 3000-4000Pa, the single filament power is 0.85-0.95kW, the single filament temperature is 2200-2600°C, and the substrate temperature is 800-950°C.

[0015] In the above CVD diamond self-supporting film preparation method, in step (1), the volume flow ratio of the first gas phase flow to the second gas phase flow is controlled to be 1:50 to 1:20, preferably 3:100 to 1:25.

[0016] In the above CVD diamond self-supporting film preparation method, the first deposition time in step (1) is 120 to 600 minutes, preferably 240 to 360 minutes.

[0017] In the above-mentioned CVD diamond self-supporting film preparation method, the third gas phase flow in step (2) is argon gas.

[0018] In the above-mentioned CVD diamond self-supporting film preparation method, in step (2), the first transition process parameters are that within the first transition time, the deposition furnace pressure, single filament power, and gas phase flow volume flow rate linearly change to the parameters required for the second deposition process, and the first transition time is 10 to 60 minutes, preferably 20 to 40 minutes.

[0019] In the above-mentioned CVD diamond self-supporting film preparation method, the second deposition process in step (3) is: the deposition furnace pressure is 6000~15000Pa, the single filament power is 0.3~0.7kW, the filament temperature is 2200~2700℃, the substrate temperature is 700~1050℃, and the distance between the filament and the substrate is 4~8mm; preferably, the deposition furnace pressure is 8000~13000Pa, the single filament power is 0.45~0.6kW, the single filament temperature is 2300~2600℃, and the substrate temperature is 750~850℃.

[0020] In the above-mentioned CVD diamond self-supporting film preparation method, in step (3), the volume flow ratio of the first gas phase flow, the second gas phase flow and the third gas phase flow is controlled as follows: first gas phase flow: (first gas phase flow and second gas phase flow) is 0.01 to 0.3, preferably 0.04 to 0.2; third gas phase flow: (second gas phase flow and third gas phase flow) is 0.5 to 0.95, preferably 0.9 to 0.95.

[0021] In the above CVD diamond self-supporting film preparation method, the second deposition time in step (3) is 120 to 1440 minutes, preferably 240 to 360 minutes.

[0022] In the above-mentioned CVD diamond self-supporting film preparation method, the second transition process in step (4) is that within the second transition time, the deposition furnace pressure, single filament power, and gas phase flow volume flow rate linearly change to the parameters required by the first deposition process; the second transition time is 10 to 60 minutes, preferably 20 to 40 minutes.

[0023] In the above CVD diamond self-supporting film preparation method, the substrate can be selected as needed, and can be at least one of metal molybdenum, silicon, tungsten, titanium, graphite, etc. The shape of the substrate can be any shape, and the size of the substrate is not limited.

[0024] In the above CVD diamond self-supporting film preparation method, the filament can be at least one of tantalum filament, tungsten filament, etc. The length and diameter of the filament are not limited and can be adapted to the size of the CVD deposition furnace and substrate used.

[0025] The second aspect of the present invention provides a CVD diamond self-supporting film prepared by the above method.

[0026] Furthermore, the CVD diamond self-supporting film comprises NCD layers and MCD layers which are alternately arranged in sequence, the diamond grain size of the NCD layer is less than 1 μm, and the diamond grain size of the MCD layer is between 10 and 100 μm.

[0027] Further, the MCD layer includes a diamond phase and a graphite phase, and the diamond phase is a diamond polycrystalline structure. The crystals of the polycrystalline structure are one or more of a cubic morphology, an octahedral morphology, a truncated octahedral morphology, and a more complex faceted morphology, or a chaotic non-preferred orientation crystal composed of the above structures, preferably an octahedral morphology.

[0028] Furthermore, in the diamond polycrystalline structure of the MCD layer, crystals are tightly connected via DD bonds, and there are no obvious grain boundaries between the crystals.

[0029] Furthermore, the carbon in the diamond of the MCD layer is SP3 Hybrid diamond phase is dominant. Characterized by Raman spectroscopy, SP 2 Characteristic peak intensity of hybrid graphite phase I G and SP 3 Characteristic peak intensity of hybrid diamond phase I D The ratio is I G / I D <0.3, preferably 1 G / I D <0.25.

[0030] Further, the NCD layer includes a diamond phase and a graphite phase, and the diamond phase is a diamond polycrystalline structure. The crystal of the polycrystalline structure is one or more of a cubic morphology, an octahedron morphology, a truncated octahedron morphology and a more complex faceted morphology, or a chaotic non-preferentially oriented crystal composed of the above structures, preferably a chaotic non-preferentially oriented crystal composed of the above structures.

[0031] Furthermore, there are obvious grain boundaries between the diamond polycrystalline crystals in the NCD layer, and the grain boundaries are formed by SP 2 Hybridized graphite phase filled with carbon atoms.

[0032] Furthermore, the carbon in the diamond of the NCD layer is SP 3 Hybrid diamond phase and SP 2 The hybrid graphite phases are uniformly mixed.

[0033] Furthermore, according to Raman spectroscopy, in the NCD layer, SP 3 The characteristic peaks of the hybrid diamond phase are sharp, and SP 2 Characteristic peak intensity of hybrid graphite phase I G and SP 3 Characteristic peak intensity of hybrid diamond phase I D The ratio is I G / I D It is 0.4 to 1.0, preferably 0.5 to 0.8.

[0034] Furthermore, the thickness of the MCD layer is 10-100 μm, and the thickness of the NCD layer is 1-20 μm.

[0035] The third aspect of the present invention provides the application of the above CVD diamond self-supporting film in the field of geological drilling.

[0036] Furthermore, the CVD diamond self-supporting film can be used in the field of geological drilling for oil drilling, deep drilling and other conditions.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] (1) The CVD diamond self-supporting film provided by the present invention has a two-layer structure arranged in a specific order, that is, the MCD layer and the NCD layer are arranged alternately. In this way, when the diamond self-supporting film is subjected to external force, the crack extension is prevented and the crack deflection is induced. The interlayer slippage offsets part of the external force, thereby significantly improving the mechanical properties of the CVD diamond self-supporting film. The wear of the CVD diamond self-supporting film provided by the present invention is more than doubled compared with conventional CVD diamond self-supporting films.

[0039] (2) The CVD diamond self-supporting film with alternating arrangement of MCD and NCD provided by the present invention can effectively block the formation of a columnar crystal structure with thin bottom and thick top due to the preferential rapid and long-term deposition of crystals in a certain direction in the traditional CVD diamond self-supporting film deposition process, thereby avoiding the situation where the columnar crystal structure seriously affects the mechanical properties of CVD diamond.

[0040] (3) In the method for preparing a CVD diamond self-supporting film provided by the present invention, the MCD layer prepared in step (1) ensures the hardness and wear resistance of the CVD diamond, and the NCD layer prepared in step (3) improves the toughness of the CVD diamond. Through the interaction between the MCD layer and the NCD layer, the technical problem in the prior art that diamond as a superhard material cannot take both toughness and hardness into account is overcome, and the wear ratio of the CVD diamond self-supporting film is significantly improved.

[0041] (4) In the CVD diamond self-supporting film preparation method provided by the present invention, the transition section between step (2) and step (4) ensures a smooth transition of the condition parameters in the CVD diamond deposition furnace, so that the diamond layers are stably combined, thereby ensuring the quality and deposition time of the CVD diamond self-supporting film, and achieving a self-supporting film thickness of the millimeter level.

[0042] (5) The CVD diamond film provided by the present invention is composed entirely of C elements and does not contain any binder or catalyst, which can effectively avoid the problem of thermal damage. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a cross-sectional scanning electron microscope image of the CVD diamond self-supporting film of Example 1 of the present invention;

[0044] Figure 2 This is a scanning electron microscope image of the CVD diamond self-supporting film MCD layer of Example 1 of the present invention;

[0045] Figure 3 This is a Raman spectrum of the CVD diamond self-supporting film MCD layer in Example 1 of the present invention;

[0046] Figure 4 This is a scanning electron microscope image of the CVD diamond self-supporting film NCD layer in Example 1 of the present invention;

[0047] Figure 5 This is a Raman spectrum of the CVD diamond self-supporting film NCD layer in Example 1 of the present invention;

[0048] Figure 6 This is a cross-sectional scanning electron microscope image of the CVD diamond self-supporting film of Comparative Example 1. DETAILED DESCRIPTION

[0049] The method of the present invention is further described in detail below by way of examples. The examples are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following examples.

[0050] The scanning electron microscope image of the present invention adopts Zeiss EVO MA15;

[0051] The Raman spectra of the present invention adopt LabRAM HR Evolution;

[0052] SP of the present invention 2 , SP 3 Hybridization was determined using Raman spectroscopy;

[0053] The present invention adopts the mechanical property of the CVD diamond self-supporting film which is reacted by the wear ratio, and the test method is in accordance with "JB / T-3235-1999".

[0054] Example 1

[0055] (1) The first deposition process is set as follows: methane gas at a flow rate of 30 sccm and hydrogen gas at a flow rate of 1000 sccm are respectively introduced into the CVD diamond deposition furnace, and the parameters of the CVD diamond deposition furnace are set as follows: the deposition furnace pressure is 3500 Pa, the single filament power is 0.9 kW, the filament temperature is 2350°C, the substrate temperature is 850°C, the distance between the filament and the substrate is 6 mm, and the first growth operation time is 300 min.

[0056] (2) The first transition time is set to 30 minutes, and the parameters of the CVD diamond deposition furnace are controlled to change linearly from the first deposition process to the second deposition process within the first transition time.

[0057] (3) The second deposition process is set as follows: methane gas at 10 sccm, hydrogen at 100 sccm, and argon at 900 sccm are introduced into the CVD diamond deposition furnace respectively; the CVD diamond deposition furnace parameters are set as follows: the deposition furnace pressure is 9000 Pa, the single filament power is 0.5 kW, the filament temperature is 2350°C, the substrate temperature is 800°C, the distance between the filament and the substrate is 7 mm, and the second growth operation time is 240 min.

[0058] (4) The second transition time is set to 30 minutes, and the parameters of the CVD diamond deposition furnace are controlled to change linearly from the second deposition process to the first deposition process within the second transition time.

[0059] (5) Repeat steps (1) to (4) for 80 cycles to obtain the CVD diamond self-supporting film.

[0060] Example 2

[0061] (1) The first deposition process is set as follows: methane gas at a flow rate of 40 sccm and hydrogen gas at a flow rate of 1000 sccm are respectively introduced into the CVD diamond deposition furnace, and the parameters of the CVD diamond deposition furnace are set as follows: the deposition furnace pressure is 4000 Pa, the single filament power is 0.85 kW, the filament temperature is 2200°C, the substrate temperature is 800°C, the distance between the filament and the substrate is 8 mm, and the first growth operation time is 240 min.

[0062] (2) The first transition time is set to 20 minutes, and the parameters of the CVD diamond deposition furnace are controlled to change linearly from the first deposition process to the second deposition process within the first transition time.

[0063] (3) Setting the second deposition process as follows: introducing methane gas at 2 sccm, hydrogen at 47 sccm, and argon at 900 sccm into the CVD diamond deposition furnace respectively; setting the CVD diamond deposition furnace parameters as follows: deposition furnace pressure of 8000 Pa, single filament power of 0.45 kW, filament temperature of 2300°C, substrate temperature of 750°C, distance between filament and substrate of 8 mm; and running the second growth process for 300 min.

[0064] (4) The second transition time is set to 20 minutes, and the parameters of the CVD diamond deposition furnace are controlled to change linearly from the second deposition process to the first deposition process within the second transition time.

[0065] (5) Repeat steps (1) to (4) for 100 times to obtain the CVD diamond self-supporting film.

[0066] Example 3

[0067] (1) The first deposition process is set as follows: methane gas at a flow rate of 30 sccm and hydrogen gas at a flow rate of 1500 sccm are respectively introduced into the CVD diamond deposition furnace, and the parameters of the CVD diamond deposition furnace are set as follows: the deposition furnace pressure is 5000 Pa, the single filament power is 1.0 kW, the filament temperature is 2650°C, the substrate temperature is 1050°C, the distance between the filament and the substrate is 4 mm, and the first growth operation time is 600 min.

[0068] (2) The first transition time is set to 30 minutes, and the parameters of the CVD diamond deposition furnace are controlled to change linearly from the first deposition process to the second deposition process within the first transition time.

[0069] (3) The second deposition process is set as follows: methane gas at 10 sccm, hydrogen at 100 sccm, and argon at 900 sccm are introduced into the CVD diamond deposition furnace respectively; the CVD diamond deposition furnace parameters are set as follows: the deposition furnace pressure is 9000 Pa, the single filament power is 0.5 kW, the filament temperature is 2350°C, the substrate temperature is 800°C, the distance between the filament and the substrate is 7 mm, and the second growth operation time is 240 min.

[0070] (4) The second transition time is set to 30 minutes, and the parameters of the CVD diamond deposition furnace are controlled to change linearly from the second deposition process to the first deposition process within the second transition time.

[0071] (5) Repeat steps (1) to (4) 40 times to obtain the CVD diamond self-supporting film.

[0072] Example 4

[0073] (1) The first deposition process is set as follows: methane gas at a flow rate of 30 sccm and hydrogen gas at a flow rate of 1000 sccm are respectively introduced into the CVD diamond deposition furnace, and the parameters of the CVD diamond deposition furnace are set as follows: the deposition furnace pressure is 3500 Pa, the single filament power is 0.9 kW, the filament temperature is 2350°C, the substrate temperature is 850°C, the distance between the filament and the substrate is 6 mm, and the first growth operation time is 300 min.

[0074] (2) The first transition time is set to 30 minutes, and the parameters of the CVD diamond deposition furnace are controlled to change linearly from the first deposition process to the second deposition process within the first transition time.

[0075] (3) Setting the second deposition process as follows: introducing methane gas at 5 sccm, hydrogen at 500 sccm, and argon at 500 sccm into the CVD diamond deposition furnace respectively; setting the CVD diamond deposition furnace parameters as follows: deposition furnace pressure of 15000 Pa, single filament power of 0.3 kW, filament temperature of 2200°C, substrate temperature of 700°C, distance between filament and substrate of 4 mm; and running the second growth process for 120 min.

[0076] (4) The second transition time is set to 30 minutes, and the parameters of the CVD diamond deposition furnace are controlled to change linearly from the second deposition process to the first deposition process within the second transition time.

[0077] (5) Repeat steps (1) to (4) for 80 cycles to obtain the CVD diamond self-supporting film.

[0078] Example 5

[0079] (1) The first deposition process is set as follows: methane gas at a flow rate of 40 sccm and hydrogen gas at a flow rate of 1000 sccm are respectively introduced into the CVD diamond deposition furnace, and the parameters of the CVD diamond deposition furnace are set as follows: the deposition furnace pressure is 4000 Pa, the single filament power is 0.85 kW, the filament temperature is 2200°C, the substrate temperature is 800°C, the distance between the filament and the substrate is 8 mm, and the first growth operation time is 240 min.

[0080] (2) The first transition time is set to 60 minutes, and the parameters of the CVD diamond deposition furnace are controlled to change linearly from the first deposition process to the second deposition process within the first transition time.

[0081] (3) Setting the second deposition process as follows: introducing methane gas at 2 sccm, hydrogen at 47 sccm, and argon at 900 sccm into the CVD diamond deposition furnace respectively; setting the CVD diamond deposition furnace parameters as follows: deposition furnace pressure of 8000 Pa, single filament power of 0.45 kW, filament temperature of 2300°C, substrate temperature of 750°C, distance between filament and substrate of 8 mm; and running the second growth process for 300 min.

[0082] (4) The second transition time is set to 60 minutes, and the parameters of the CVD diamond deposition furnace are controlled to change linearly from the second deposition process to the first deposition process within the second transition time.

[0083] (5) Repeat steps (1) to (4) for 100 times to obtain the CVD diamond self-supporting film.

[0084] Comparative Example 1

[0085] Methane gas at a flow rate of 40 sccm and hydrogen gas at a flow rate of 1000 sccm were respectively introduced into the CVD diamond deposition furnace, and the parameters of the CVD diamond deposition furnace were set as follows: the deposition furnace pressure was 4000 Pa, the single filament power was 0.85 kW, the filament temperature was 2200°C, the substrate temperature was 800°C, the distance between the filament and the substrate was 8 mm, and the operating time was 24000 min, so as to obtain a CVD diamond self-supporting film.

[0086] Comparative Example 2

[0087] (1) The first deposition process is set as follows: methane gas at a flow rate of 30 sccm and hydrogen gas at a flow rate of 1000 sccm are respectively introduced into the CVD diamond deposition furnace, and the parameters of the CVD diamond deposition furnace are set as follows: the deposition furnace pressure is 3500 Pa, the single filament power is 0.9 kW, the filament temperature is 2350°C, the substrate temperature is 850°C, the distance between the filament and the substrate is 6 mm, and the first growth operation time is 300 min.

[0088] (2) The second deposition process is set as follows: methane gas at 10 sccm, hydrogen at 100 sccm, and argon at 900 sccm are introduced into the CVD diamond deposition furnace respectively; the CVD diamond deposition furnace parameters are set as follows: the deposition furnace pressure is 9000 Pa, the single filament power is 0.5 kW, the filament temperature is 2350°C, the substrate temperature is 800°C, the distance between the filament and the substrate is 7 mm, and the second growth operation time is 240 min.

[0089] (3) The second transition time is set to 30 minutes, and the parameters of the CVD diamond deposition furnace are controlled to change linearly from the second deposition process to the first deposition process within the second transition time.

[0090] (4) The steps (1) to (4) are repeated 80 times to obtain a CVD diamond self-supporting film.

[0091] Comparative Example 3

[0092] (1) The first deposition process is set as follows: methane gas at a flow rate of 40 sccm and hydrogen gas at a flow rate of 1000 sccm are respectively introduced into the CVD diamond deposition furnace, and the parameters of the CVD diamond deposition furnace are set as follows: the deposition furnace pressure is 4000 Pa, the single filament power is 0.85 kW, the filament temperature is 2200°C, the substrate temperature is 800°C, the distance between the filament and the substrate is 8 mm, and the first growth operation time is 240 min.

[0093] (2) The first transition time is set to 20 minutes, and the parameters of the CVD diamond deposition furnace are controlled to change linearly from the first deposition process to the second deposition process within the first transition time.

[0094] (3) Setting the second deposition process as follows: introducing methane gas at 2 sccm, hydrogen at 47 sccm, and argon at 900 sccm into the CVD diamond deposition furnace respectively; setting the CVD diamond deposition furnace parameters as follows: deposition furnace pressure of 8000 Pa, single filament power of 0.45 kW, filament temperature of 2300°C, substrate temperature of 750°C, distance between filament and substrate of 8 mm; and running the second growth process for 300 min.

[0095] (4) Adjusting various parameters from the second deposition process to the first deposition process.

[0096] (5) Repeat steps (1) to (4) for 100 times to obtain a CVD diamond self-supporting film.

[0097] Application Example 1

[0098] The CVD diamond self-supporting films obtained in Examples 1-5 and Comparative Examples 1-3 were subjected to abrasion ratio tests. The abrasion ratio test conditions were as follows: the samples were uniformly laser cut to Double-sided grinding and polishing were performed. The core-forming surface was used as the working surface, the grinding wheel hardness was 3.7, the initial test speed was 25 m / s, and the rest of the test conditions and steps were carried out in accordance with JB / T-3235-1999.

[0099] Table 1 Test results of CVD diamond films of various embodiments and comparative examples

[0100] product Film thickness / mm Wear ratio / 10,000 Remark Example 1 1.52 110 - Example 2 1.68 124 - Example 3 1.36 97 - Example 4 1.41 84 - Example 5 1.66 77 - Comparative Example 1 1.39 44 - Comparative Example 2 1.11 60 The specified number of cycles was not completed and the filament was broken. Comparative Example 3 1.08 58 The specified number of cycles was not completed and the filament was broken.

[0101] pass Figure 1 and Figure 6 In contrast, the cross section of the CVD diamond self-supporting film prepared by this method has an obvious layered structure, with MCD layers and NCD layers arranged alternately. The NCD layer effectively blocks the thin-at-bottom and coarse-at-top layered structure formed by the MCD layer due to long-term deposition. Moreover, the layered structure can prevent crack extension and induce crack deflection when the CVD diamond self-supporting film is subjected to external force, and the interlayer slippage offsets part of the external force, thereby significantly improving the mechanical properties of the CVD diamond self-supporting film.

[0102] The above describes the specific implementation of the present invention in detail, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the various technical features being combined in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing a CVD diamond self-supporting film, wherein the thickness of the CVD diamond self-supporting film is not less than 1.0 mm, preferably 1.2 to 2.0 mm, the method comprising: (1) depositing an MCD layer on a substrate by a first deposition process, wherein the first deposition process comprises respectively passing a first gas phase flow and a second gas phase flow into a CVD diamond deposition furnace, setting a deposition parameter of the CVD diamond deposition furnace to a first deposition process parameter, and running a first deposition time; (2) using a first transition process to perform transition processing on the deposition process in step (1), wherein the first transition process is to introduce a third gas phase flow, adjust the deposition parameters of the CVD diamond deposition furnace to the first transition process parameters, and run the first transition time; (3) continuing deposition by using a second deposition process, wherein the second deposition process is to respectively pass the first gas phase flow, the second gas phase flow and the third gas phase flow into the CVD diamond deposition furnace, set the deposition parameters of the CVD diamond deposition furnace to the second deposition parameters, and run the second deposition time; (4) using a second transition process to perform transition processing on the deposition process in step (3), wherein the second transition process is to reduce or shut down the third gas phase flow, adjust the deposition parameters of the CVD diamond deposition furnace to the second transition parameters, and run the second transition time; (5) Repeat steps (1) to (4) until the thickness of the CVD diamond self-supporting film meets the requirements.

2. The preparation method according to claim 1, characterized in that: In step (1), the first gas phase flow is one or more of gaseous organic matter containing carbon elements and / or liquid organic matter containing carbon elements that is easily gasified, and the second gas phase flow in step (1) is hydrogen.

3. The preparation method according to claim 1, characterized in that: The first deposition process parameters in step (1) are: deposition furnace pressure of 2000-5000 Pa, single filament power of 0.8-1.2 kW, filament temperature of 2200-2700°C, substrate temperature of 750-1050°C, and distance between filament and substrate of 4-8 mm; preferably, the deposition furnace pressure is 3000-4000 Pa, single filament power of 0.85-0.95 kW, single filament temperature of 2200-2600°C, and substrate temperature of 800-950°C.

4. The preparation method according to claim 1, characterized in that: In step (1), the volume flow ratio of the first gas phase flow to the second gas phase flow is controlled to be 1:50 to 1:20, preferably 3:100 to 1:

25.

5. The preparation method according to claim 1, characterized in that: In step (1), the first deposition time is 120 to 600 min, preferably 240 to 360 min.

6. The preparation method according to claim 1, characterized in that: The third gas phase flow in step (2) is argon.

7. The preparation method according to claim 1, characterized in that: In step (2), the first transition process parameters are that within the first transition time, the deposition furnace pressure, single filament power, and gas phase flow volume flow rate linearly change to the parameters required for the second deposition process. The first transition time is 10 to 60 minutes, preferably 20 to 40 minutes.

8. The preparation method according to claim 1, characterized in that: The second deposition process in step (3) is: the deposition furnace pressure is 6000-15000Pa, the single filament power is 0.3-0.7kW, the filament temperature is 2200-2700°C, the substrate temperature is 700-1050°C, and the distance between the filament and the substrate is 4-8mm; preferably, the deposition furnace pressure is 8000-13000Pa, the single filament power is 0.45-0.6kW, the single filament temperature is 2300-2600°C, and the substrate temperature is 750-850°C.

9. The preparation method according to claim 1, characterized in that: In step (3), the volume flow ratio of the first gas phase flow, the second gas phase flow and the third gas phase flow is controlled as follows: the first gas phase flow: (the first gas phase flow and the second gas phase flow) is 0.01 to 0.3, preferably 0.04 to 0.2; the third gas phase flow: (the second gas phase flow and the third gas phase flow) is 0.5 to 0.95, preferably 0.9 to 0.

95.

10. The preparation method according to claim 1, characterized in that: In step (3), the second deposition time is 120 to 1440 minutes, preferably 240 to 360 minutes.

11. The preparation method according to claim 1, characterized in that: In step (4), the second transition process is that within the second transition time, the deposition furnace pressure, single filament power, and gas phase flow volume flow rate linearly change to the parameters required by the first deposition process; the second transition time is 10 to 60 minutes, preferably 20 to 40 minutes.

12. Prepare a CVD diamond self-supporting film by using the preparation method according to any one of claims 1 to 11.

13. The CVD diamond self-supporting film according to claim 13, characterized in that: The CVD diamond self-supporting film comprises an NCD layer and an MCD layer which are alternately arranged in sequence, the diamond grain size of the NCD layer is less than 1 μm, and the diamond grain size of the MCD layer is between 10 and 100 μm.

14. The CVD diamond self-supporting film according to claim 13, characterized in that: The MCD layer includes a diamond phase and a graphite phase, and the diamond phase is a diamond polycrystalline structure.

15. The CVD diamond self-supporting film according to claim 13, characterized in that: The carbon in the diamond of the MCD layer is characterized by Raman spectroscopy, SP 2 Characteristic peak intensity of hybrid graphite phase I G and SP 3 Characteristic peak intensity of hybrid diamond phase I D The ratio is I G / I D <0.3, preferably 1 G / I D <0.

25.

16. The CVD diamond self-supporting film according to claim 13, characterized in that: The NCD layer includes a diamond phase and a graphite phase, and the diamond phase is a diamond polycrystalline structure.

17. The CVD diamond self-supporting film according to claim 13, characterized in that: There are obvious grain boundaries between the diamond polycrystalline crystals in the NCD layer. 2 Hybridized graphite phase filled with carbon atoms.

18. The CVD diamond self-supporting film according to claim 13, characterized in that: The carbon in the diamond of the NCD layer is SP 3 Hybrid diamond phase and SP 2 The hybrid graphite phases are uniformly mixed.

19. The CVD diamond self-supporting film according to claim 13, characterized in that: According to Raman spectroscopy, in the NCD layer, SP 3 The characteristic peaks of the hybrid diamond phase are sharp, and SP 2 Characteristic peak intensity of hybrid graphite phase I G and SP 3 Characteristic peak intensity of hybrid diamond phase I D The ratio is I G / I D It is 0.4 to 1.0, preferably 0.5 to 0.

8.

20. The CVD diamond self-supporting film according to claim 13, characterized in that: The thickness of the MCD layer is 10-100 μm, and the thickness of the NCD layer is 1-20 μm.

21. Application of the CVD diamond self-supporting film prepared by the preparation method according to any one of claims 1 to 20 in the field of geological drilling.

Images