A CVD diamond film and its preparation method and application

Abstract

The present invention discloses a CVD diamond film, its preparation method, and application. The CVD diamond film comprises a rigid growth layer and a flexible toughening layer arranged alternately in sequence; the rigid growth layer comprises an SP3 hybrid diamond phase; the flexible toughening layer comprises a mixed phase of an SP3 hybrid diamond phase and an SP2 hybrid graphite phase; the rigid growth layer ensures the hardness of the CVD diamond film, while the flexible toughening layer ensures the flexibility of the CVD diamond film. The CVD diamond film provided by the present invention can effectively improve its toughness without sacrificing diamond hardness, achieving a balanced balance between hardness and toughness of the CVD diamond film, expanding the product's application areas and conditions, and increasing its service life.

Description

Technical Field

[0001] The present invention belongs to the technical field of material processing, and in particular relates to a CVD diamond film and a preparation method and application thereof. Background Art

[0002] Diamond is a superhard material with unique mechanical, optical, acoustic, and electrical properties. Since the 1950s and 1960s, American and Soviet scientists, while researching methods for the artificial synthesis of single-crystal diamond, have successfully achieved chemical vapor deposition (CVD) of polycrystalline diamond films at low pressures, marking a remarkable achievement in CVD diamond synthesis. Subsequently, extensive research has been conducted on various applications of CVD diamond film materials and related tool products, gradually advancing from the laboratory stage to industrial and market-oriented practical applications. Currently, they are widely used in various technical fields such as craft cutting, machining, and geological drilling.

[0003] However, its application conditions are still limited. For example, although single-crystal CVD diamond films have high hardness and wear resistance, they have cleavage planes in a specific direction, which makes them very prone to cracking along the crystal direction under external forces, making them unable to withstand the impact during use as a superhard material. Polycrystalline CVD diamond films avoid fracture along the cleavage plane direction, but they still have poor deformability, low toughness, high brittleness, and are very prone to brittle fracture. Because CVD diamond films cannot simultaneously achieve both hardness and toughness, they cannot be used under high-impact and high-stress conditions, which greatly limits their application scenarios.

[0004] CN202010202431.1 discloses an impact-resistant CVD diamond self-supporting material and manufacturing method. This method blocks the extension of cleavage cracks by presenting a multilayer structure with multiple fine grains and coarse grains interlaced on the diamond cross section, thereby improving the impact resistance and fracture toughness of the CVD diamond. However, when constructing the interlaced multilayer structure, the carbon source concentration is increased multiple times, which will lead to an increase in the content of graphite structure carbon and amorphous structure carbon in the CVD diamond, reducing the proportion of diamond structure, and thus sacrificing the hardness and wear resistance of the CVD diamond.

[0005] CN201820307329.6 discloses a composite structure that enhances the toughness of single-crystal diamond. This composite structure includes pure single-crystal diamond layers and nitrogen-doped single-crystal diamond layers; the pure single-crystal diamond layers and nitrogen-doped single-crystal diamond layers are interlaced, with the pure single-crystal diamond layers located at the outermost edges of the composite layer structure. By constructing a composite structure with interlaced pure single-crystal diamond layers and nitrogen-doped single-crystal diamond layers, this composite structure improves the toughness and hardness of single-crystal diamond. However, this does not prevent directional fracture of the single-crystal diamond along the cleavage plane. Summary of the Invention

[0006] In response to the problems existing in the prior art, the present invention provides a CVD diamond film, a preparation method and application thereof. The CVD diamond film of the present invention can effectively improve the toughness of the diamond without losing its hardness, and can take into account both the hardness and toughness of the CVD diamond film, thereby expanding the application field and application conditions of the product and improving its service life.

[0007] A first aspect of the present invention provides a CVD diamond film, which includes a rigid growth layer and a flexible toughening layer arranged alternately in sequence; the rigid growth layer is an SP3 hybrid diamond phase; and the flexible toughening layer is a mixed phase of the SP3 hybrid diamond phase and the SP2 hybrid graphite phase.

[0008] Furthermore, the rigid growth layer is used to ensure the hardness of the CVD diamond film. The flexible toughening layer is used to ensure the flexibility of the CVD diamond film.

[0009] Furthermore, there is an obvious phase interface between the rigid growth layer and the flexible toughening layer.

[0010] Furthermore, in the rigid growth layer, the SP3 hybrid diamond phase is a polycrystalline structure. The crystals contained in the polycrystalline structure exhibit distinct chaotic microscopic faceting characteristics without preferred orientation. The content of crystals displaying (111) facets in the SP3 hybrid diamond phase is 10% to 30%, and the content of crystals displaying (110) facets is 70% to 90%. The crystals are tightly connected to each other by DD bonds to form twins, and there are no obvious grain boundaries between the crystals.

[0011] Furthermore, in the rigid growth layer, the crystals of the SP3 hybrid diamond phase are micrometer-scale and / or nanometer-scale.

[0012] Furthermore, in the rigid growth layer, the crystals of the SP3 hybrid diamond phase are at least one of chaotic non-preferentially oriented crystals composed of cubic morphology, octahedral morphology, truncated octahedral morphology and more complex facet morphology.

[0013] Furthermore, in the flexible toughening layer, the crystals of the mixed phase of the SP3 hybrid diamond phase and the SP2 hybrid graphite phase appear as cauliflower-type crystals.

[0014] Furthermore, in the Raman spectrum characterization of the flexible toughening layer, the characteristic peak intensity I of the SP3 hybrid diamond phase crystal is D and SP2 hybrid graphite phase characteristic peak intensity I G The ratio is I D / I G =1.1~2.0, preferably 1.3~1.6.

[0015] Furthermore, in the flexible toughening layer, the SP3 hybrid diamond phase crystals and the SP2 hybrid graphite phase crystals are micron-scale and / or nano-scale.

[0016] Furthermore, in the flexible toughening layer, the SP3 hybrid diamond phase crystals and SP2 hybrid graphite phase crystals are cauliflower-shaped crystals. The cauliflower-shaped crystals include cauliflower-shaped cluster units and carbon nanotube-like structures within the units. The carbon nanotube-like structures can tightly connect the rigid growth layer and the flexible toughening layer. The carbon nanotube-like structures are tubular structures with a diameter of 1 to 5 nm and a length of 10 to 200 nm.

[0017] Furthermore, the thickness of the CVD diamond film is greater than or equal to 1 mm, preferably 1.2 to 2.0 mm.

[0018] Furthermore, the thickness of the rigid growth layer is 10 to 100 microns; the thickness of the flexible toughening layer is 1 to 20 microns.

[0019] A second aspect of the present invention provides a method for preparing the above-mentioned CVD diamond film, the method comprising: alternately growing a rigid growth layer and a flexible toughening layer on a substrate.

[0020] The above-mentioned CVD diamond film preparation method specifically includes:

[0021] (1) growing a first phase on a substrate using a first growth process, wherein the first growth process comprises respectively introducing a first gas phase flow and a second gas phase flow into a CVD diamond growth furnace, setting parameters of the CVD diamond growth furnace to first growth process parameters, and running the furnace for a first growth time;

[0022] (2) using a second treatment process to treat the material obtained in step (1), wherein the second treatment process is based on the flow rate of the first gas phase flow in the first growth process, reducing the flow rate of the first gas phase flow in the first growth process, adjusting the CVD diamond growth furnace parameters to the second treatment process parameters, and running the second treatment time;

[0023] (3) cyclically operating steps (1) and (2) for n number of cycles to obtain a rigid growth layer;

[0024] (4) using a third growth process to grow a flexible toughening layer on the rigid growth layer; the third growth process is based on the flow rate of the first gas phase flow in the first growth process, increasing the flow rate of the first gas phase flow in the first growth process, adjusting the CVD diamond growth furnace parameters to the third growth process parameters, and running the third growth time;

[0025] (5) Repeat steps (1) to (4) for m cycles to obtain the CVD diamond film.

[0026] In the above-mentioned CVD diamond film preparation method, the first gas phase flow in step (1) can be one or more of a carbon-containing gaseous organic matter and / or a readily gasifiable carbon-containing liquid organic matter, and the second gas phase flow in step (1) can be one or more of a reducing gas. Specifically, the carbon-containing gaseous organic matter can be one or more of methane, ethane, acetylene, propane, propylene, propyne, etc.; the readily gasifiable carbon-containing liquid organic matter can be one or more of methanol, ethanol, acetone, and petroleum ether. The reducing gas can be one or more of hydrogen, carbon monoxide, decomposed ammonia gas, incomplete combustion of ammonia gas, gas generated by the reaction of hydrocarbons with water vapor, exothermic gas generated by incomplete combustion of hydrocarbons, endothermic gas released by incomplete combustion of hydrocarbons, etc.

[0027] In the above-mentioned CVD diamond film preparation method, the volume flow ratio of the first gas phase flow and the second gas phase flow in step (1) is controlled to be 1:50 to 1:20, preferably 3:100 to 1:25.

[0028] In the above-mentioned CVD diamond film preparation method, the first growth process parameters in step (1) are: the growth furnace pressure is 2000~5000Pa, the filament current intensity is 630~690A, the filament temperature is 2200~2700℃, the substrate temperature is 750~1050℃, and the distance between the filament and the substrate is 4~8mm; preferably, the growth furnace pressure is 3000~4000Pa, the filament current intensity is 650~670A, the filament temperature is 2200~2600℃, and the substrate temperature is 800~950℃.

[0029] In the above-mentioned CVD diamond film preparation method, the first growth time in step (1) is 30 to 240 minutes, preferably 60 to 90 minutes.

[0030] In the above-mentioned CVD diamond film preparation method, in step (2), the flow rate of the first gas phase flow is 0%-31% of the flow rate of the first gas phase flow in step (1), preferably 0%-20%; the flow rate of the second gas phase flow is 80%-200% of the flow rate of the second gas phase flow in step (1), preferably 90%-150%.

[0031] In the above-mentioned CVD diamond film preparation method, the second processing parameters are: the growth furnace pressure is 2000~5000Pa, the filament current intensity is 630~690A, the filament temperature is 2200~2700℃, the substrate temperature is 750~1050℃, and the distance between the filament and the substrate is 4~8mm; preferably, the growth furnace pressure is 3000~4000Pa, the filament current intensity is 650~670A, the filament temperature is 2200~2600℃, and the substrate temperature is 800~950℃.

[0032] In the above-mentioned CVD diamond film preparation method, in step (2), the ratio of the second treatment time to the first growth time is 1:2 to 1:20, preferably 1:3 to 1:10.

[0033] In the above-mentioned CVD diamond film preparation method, the number of cycles n in step (3) is 1 to 50, preferably 5 to 10.

[0034] In the above CVD diamond film preparation method, the flow rate of the first gas phase flow in step (4) is 150%-350% of the flow rate of the first gas phase flow in step (1), preferably 150%-200%. The flow rate of the second gas phase flow in step (4) is 95%-105% of the flow rate of the second gas phase flow in step (1).

[0035] In the above-mentioned CVD diamond film preparation method, the third growth process parameters are: the growth furnace pressure is 1000~3000Pa, the filament current intensity is 580~650A, the filament temperature is 2000~2400℃, the substrate temperature is 700~1050℃, and the distance between the filament and the substrate is 4~8mm; preferably, the growth furnace pressure is 1500~2500Pa, the filament current intensity is 600~620A, the filament temperature is 2000~2150℃, and the substrate temperature is 800~900℃.

[0036] In the above-mentioned CVD diamond film preparation method, the third growth time in step (4) is 20 to 240 minutes, preferably 20 to 120 minutes.

[0037] In the above-mentioned CVD diamond film preparation method, the number of cycles m in step (5) is 1 to 100, preferably 10 to 60.

[0038] In the above-mentioned CVD diamond film preparation method, the thickness of the CVD diamond film reaches or exceeds 1 mm, preferably 1.2 to 2.0 mm.

[0039] In the above CVD diamond film preparation method, the substrate can be selected as needed and can be at least one of metals such as molybdenum, silicon, tungsten, titanium, and graphite. The shape of the substrate can be any shape, and the size of the substrate is not limited.

[0040] A third aspect of the present invention provides the application of the above-mentioned CVD diamond film in the field of geological drilling.

[0041] Furthermore, CVD diamond films can be used in the fields of geological drilling, such as oil drilling and deep drilling.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] (1) The CVD diamond film provided by the present invention has a specific two-layer structure arranged alternately in sequence, that is, a layered structure in which a rigid growth layer and a flexible toughening layer are arranged alternately. This ensures the hardness and toughness of the CVD diamond film. At the same time, this layered structure can also effectively block the formation of a columnar crystal structure with a thin bottom and a thick top due to the preferential rapid and long-term growth of crystals in a certain orientation in the traditional CVD diamond growth process, thereby avoiding the situation in which the thin bottom and the thick top columnar crystals seriously affect the mechanical properties of the CVD diamond.

[0044] (2) In the preparation method of the CVD diamond film provided by the present invention, the rigid growth layer prepared by step (1) ensures the hardness of the CVD diamond film, and step (2) modifies and improves the prepared rigid growth layer, so that the hardness and wear resistance of the rigid growth layer are further improved. The prepared diamond film presents a layered structure in which the rigid layer and the flexible layer are arranged alternately in sequence. Through the alternating arrangement and interaction of the rigid growth layer and the flexible toughening layer, the technical problem in the prior art that diamond as a superhard material cannot take into account both its toughness and hardness is overcome, and the overall toughness and bending strength of the diamond film are significantly improved. The fracture toughness of the CVD diamond film provided by the present invention is improved by more than 80% compared with the conventional CVD diamond film.

[0045] (3) The diamond film provided by the present invention has a rigid growth layer composed entirely of SP3 hybrid diamond phase crystals, preferably exhibiting distinct chaotic, non-preferred orientation microscopic facets. Combined with the content of each facet, this ensures the hardness of the CVD diamond. The flexible toughening layer is a hybrid structure composed of an SP3 hybrid diamond phase and an SP2 hybrid graphite phase, ensuring the flexibility of the CVD diamond. This effect is enhanced by preferably exhibiting cauliflower-shaped crystals with excellent toughness. Furthermore, the different layers are tightly connected using a carbon nanotube-like structure, preventing delamination between the layers during use, which could cause the diamond film to fail.

[0046] (4) The CVD diamond film provided by the present invention is entirely composed of carbon elements and does not contain any binder or catalyst, which can effectively avoid the problem of thermal damage. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 Flowchart of the CVD diamond film preparation method of the present invention;

[0048] Figure 2 Schematic diagram of an optical microscope showing the alternating arrangement of rigid growth layers and flexible toughening layers of a CVD diamond film according to Example 1 of the present invention;

[0049] Figure 3 This is a Raman spectrum of the rigid growth layer of the CVD diamond film according to Example 1 of the present invention;

[0050] Figure 4 This is a Raman spectrum of the flexible toughening layer of the CVD diamond film according to Example 1 of the present invention;

[0051] Figure 5 This is a scanning electron microscope image of the rigid growth layer of the CVD diamond film according to Example 1 of the present invention;

[0052] Figure 6 This is an XRD spectrum of the rigid growth layer of the CVD diamond film according to Example 1 of the present invention;

[0053] Figure 7 This is a scanning electron microscope image of the flexible toughening layer of the CVD diamond film of Example 1 of the present invention;

[0054] Figure 8 This is a scanning electron microscope image of the flexible toughening layer of the CVD diamond film in Example 1 of the present invention. DETAILED DESCRIPTION

[0055] The method of the present invention is further described in detail below through examples. The examples are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operating processes, but the scope of protection of the present invention is not limited to the following examples.

[0056] The scanning electron microscope images of the present invention were obtained using a Zeiss EVO MA 15;

[0057] The optical microscope images of the present invention were taken using a Leica DM 6M;

[0058] The XRD spectrum of the present invention adopts PNAlytical X'-Pert PRO;

[0059] The Raman spectrum of the present invention adopts LabRAM HR Evolution.

[0060] The bending strength performance test of the CVD diamond film of the present invention is performed using an Instron universal material testing machine. The hardness test is performed using an Anton-Paar TriTec NHT 2 Nanoindenter.

[0061] The SP2 and SP3 hybridizations of the present invention are determined by Raman spectroscopy.

[0062] The CVD diamond film preparation process of the present invention is described as follows:

[0063] (1) growing a first phase on a substrate using a first growth process, wherein the first growth process comprises introducing a first gas phase flow and a second gas phase flow into a CVD diamond growth furnace at certain flow rates, setting parameters of the CVD diamond growth furnace to first growth process parameters, and running the furnace for a first growth time;

[0064] (2) using a second treatment process to treat the material obtained in step (1), wherein the second treatment process is to adjust the parameters of the CVD diamond growth furnace to the second treatment process parameters and run the process for a second treatment time;

[0065] (3) cyclically operating steps (1) and (2) for n number of cycles to obtain a rigid growth layer;

[0066] (4) growing a flexible toughening layer on the material obtained in step (3) using a third growth process; the third growth process comprises adjusting the CVD diamond growth furnace parameters to the third growth process parameters and running the process for a third growth time;

[0067] (5) Repeat steps (1) to (4) for m cycles to obtain the CVD diamond film.

[0068] The CVD growth furnace used in the following examples is a HF-800CVD growth furnace.

[0069] Example 1

[0070] (1) The first phase was grown using the first growth process: methane gas was introduced into the CVD diamond growth furnace at a flow rate of 30 sccm and hydrogen gas was introduced into the CVD diamond growth furnace at a flow rate of 1000 sccm, respectively. The parameters of the CVD diamond growth furnace were set as follows: the growth furnace pressure was 4000 Pa, the filament current intensity was 665 A, the filament temperature was 2300° C., the substrate temperature was 910° C., and the distance between the filament and the substrate was 5 mm. The first growth operation lasted for 90 min.

[0071] (2) The first phase was then treated using a second treatment process: the methane gas flow rate was adjusted to 0 sccm, and the hydrogen gas flow rate was adjusted to 1000 sccm. The CVD diamond growth furnace parameters were adjusted to: the growth furnace pressure was 4000 Pa, the filament current was 665 A, the filament temperature was 2300° C., the substrate temperature was 910° C., and the distance between the filament and the substrate was 5 mm. The second treatment was run for 30 minutes.

[0072] (3) Repeat steps (1) and (2) for 8 cycles.

[0073] (4) After step (3), a third growth process was used to grow a flexible toughening layer: the methane gas flow rate was adjusted to 50 sccm, and the hydrogen gas flow rate was adjusted to 1000 sccm. The CVD diamond growth furnace parameters were adjusted to: the growth furnace pressure was 2000 Pa, the filament current was 615 A, the filament temperature was 2150° C., the substrate temperature was 800° C., and the distance between the filament and the substrate was 5 mm. The third growth process was run for 60 minutes.

[0074] (5) Repeat steps (1) to (4) 30 times to complete the preparation and obtain the CVD diamond film A. The rigid growth layer of the CVD diamond film A is tested as follows: Figure 3 As shown, it only contains the SP3 hybrid diamond phase but not the SP2 hybrid graphite phase.

[0075] Example 2

[0076] (1) The first phase was grown using the first growth process: methane gas was introduced into the CVD diamond growth furnace at a flow rate of 50 sccm and hydrogen gas was introduced into the CVD diamond growth furnace at a flow rate of 1500 sccm, respectively. The parameters of the CVD diamond growth furnace were set as follows: the growth furnace pressure was 3000 Pa, the filament current intensity was 655 A, the filament temperature was 2250°C, the substrate temperature was 870°C, and the distance between the filament and the substrate was 4 mm. The first growth operation lasted for 60 min.

[0077] (2) The first phase was then treated using a second treatment process: the methane gas flow rate was adjusted to 5 sccm, and the hydrogen gas flow rate was adjusted to 1700 sccm. The CVD diamond growth furnace parameters were adjusted to: the growth furnace pressure was 3000 Pa, the filament current was 655 A, the filament temperature was 2250° C., the substrate temperature was 870° C., and the distance between the filament and the substrate was 4 mm. The second treatment was run for 6 minutes.

[0078] (3) Repeat steps (1) and (2) 10 times.

[0079] (4) After step (3), a third growth process was used to grow a flexible toughening layer, with the methane gas flow rate adjusted to 100 sccm and the hydrogen gas flow rate adjusted to 1500 sccm. The CVD diamond growth furnace parameters were adjusted as follows: the growth furnace pressure was 2500 Pa, the filament current was 600 A, the filament temperature was 2000° C., the substrate temperature was 850° C., and the distance between the filament and the substrate was 4 mm. The third growth process was run for 20 minutes.

[0080] (5) The operation steps (1) to (4) were repeated 50 times to complete the preparation and obtain the CVD diamond film B. The rigid growth layer of the CVD diamond film B was tested to contain only the SP3 hybridized diamond phase, but no SP2 hybridized graphite phase.

[0081] Example 3

[0082] (1) The first phase was grown using the first growth process: methanol gas was introduced into the CVD diamond growth furnace at a flow rate of 60 sccm and hydrogen gas was introduced into the CVD diamond growth furnace at a flow rate of 1300 sccm, respectively. The parameters of the CVD diamond growth furnace were set as follows: the growth furnace pressure was 2500 Pa, the filament current intensity was 690 A, the filament temperature was 2650°C, the substrate temperature was 965°C, and the distance between the filament and the substrate was 8 mm. The first growth operation lasted for 100 min.

[0083] (2) The first phase was then treated using a second treatment process: the methanol gas flow rate was adjusted to 18 sccm, and the hydrogen gas flow rate was adjusted to 2000 sccm. The CVD diamond growth furnace parameters were adjusted to: the growth furnace pressure was 2500 Pa, the filament current was 690 A, the filament temperature was 2650° C., the substrate temperature was 965° C., and the distance between the filament and the substrate was 8 mm. The second treatment was run for 10 minutes.

[0084] (3) Repeat steps (1) and (2) 20 times.

[0085] (4) After step (3), a third growth process was used to grow a flexible toughening layer: the methanol gas flow rate was adjusted to 100 sccm, and the hydrogen gas flow rate was adjusted to 1300 sccm. The CVD diamond growth furnace parameters were adjusted to: the growth furnace pressure was 1000 Pa, the filament current was 630 A, the filament temperature was 2300° C., the substrate temperature was 860° C., and the distance between the filament and the substrate was 6 mm. The third growth process was run for 20 minutes.

[0086] (5) The operation steps (1) to (4) were repeated 20 times to complete the preparation and obtain the CVD diamond film C. The rigid growth layer of the CVD diamond film C was tested to contain only the SP3 hybridized diamond phase, but no SP2 hybridized graphite phase.

[0087] Example 4

[0088] (1) The first phase was grown using the first growth process: methane gas at a flow rate of 40 sccm and hydrogen gas at a flow rate of 1600 sccm were introduced into the CVD diamond growth furnace, and the CVD diamond growth furnace parameters were set as follows: the growth furnace pressure was 4500 Pa, the filament current intensity was 640 A, the filament temperature was 2200°C, the substrate temperature was 790°C, and the distance between the filament and the substrate was 4 mm; the first growth operation lasted 40 min.

[0089] (2) The first phase was then treated using a second treatment process: the methane gas flow rate was adjusted to 10 sccm, and the hydrogen gas flow rate was adjusted to 1280 sccm. The CVD diamond growth furnace parameters were adjusted to: the growth furnace pressure was 4500 Pa, the filament current was 640 A, the filament temperature was 2200° C., the substrate temperature was 790° C., and the distance between the filament and the substrate was 4 mm. The second treatment was run for 2 minutes.

[0090] (3) Repeat steps (1) and (2) for 4 cycles.

[0091] (4) After step (3), a third growth process was used to grow a flexible toughening layer: the methane gas flow rate was adjusted to 90 sccm, and the hydrogen gas flow rate was adjusted to 1600 sccm. The CVD diamond growth furnace parameters were adjusted to: the growth furnace pressure was 2600 Pa, the filament current was 595 A, the filament temperature was 2000° C., the substrate temperature was 710° C., and the distance between the filament and the substrate was 8 mm. The third growth process was run for 25 minutes.

[0092] (5) The operation steps (1) to (4) were repeated 60 times to complete the preparation and obtain the CVD diamond film D. The rigid growth layer of the CVD diamond film D was tested to contain only the SP3 hybridized diamond phase, but no SP2 hybridized graphite phase.

[0093] Comparative Example 1

[0094] The following process was used to grow a diamond film: methane gas at a flow rate of 30 sccm and hydrogen gas at a flow rate of 1000 sccm were introduced into a CVD diamond growth furnace. The CVD diamond growth furnace parameters were set as follows: furnace pressure of 4000 Pa, filament current of 665 A, filament temperature of 2300°C, substrate temperature of 910°C, and a distance of 5 mm between the filament and the substrate. The run time was 27,000 min. The CVD diamond film E was prepared. The characteristic peak intensity I of the SP3 hybrid diamond phase crystal in CVD diamond film E was tested. D and SP2 hybrid graphite phase characteristic peak intensity I G The ratio is I D / I G =5.3:1, indicating that it contains both SP3 hybridized diamond phase and SP2 hybridized graphite phase.

[0095] Comparative Example 2

[0096] The following process was used to grow a diamond film: methane gas at a flow rate of 50 sccm and hydrogen gas at a flow rate of 1500 sccm were introduced into a CVD diamond growth furnace. The CVD diamond growth furnace parameters were set as follows: furnace pressure of 3000 Pa, filament current of 655 A, filament temperature of 2250°C, substrate temperature of 870°C, and a distance of 4 mm between the filament and the substrate. The run time was 27,000 min. The CVD diamond film F was prepared. The characteristic peak intensity I of the SP3 hybrid diamond phase crystal in the CVD diamond film F was detected. D and SP2 hybrid graphite phase characteristic peak intensity I G The ratio is I D / I G =5.6:1, indicating that it contains both SP3 hybridized diamond phase and SP2 hybridized graphite phase.

[0097] Comparative Example 3

[0098] (1) The first phase was grown using the first growth process: methane gas was introduced into the CVD diamond growth furnace at a flow rate of 30 sccm and hydrogen gas was introduced into the CVD diamond growth furnace at a flow rate of 1000 sccm, respectively. The parameters of the CVD diamond growth furnace were set as follows: the growth furnace pressure was 4000 Pa, the filament current intensity was 665 A, the filament temperature was 2300° C., the substrate temperature was 910° C., and the distance between the filament and the substrate was 5 mm. The first growth operation lasted for 90 min.

[0099] (2) The first phase was then treated using a second treatment process: the methane gas flow rate was adjusted to 0 sccm, and the hydrogen gas flow rate was adjusted to 1000 sccm. The CVD diamond growth furnace parameters were adjusted to: the growth furnace pressure was 4000 Pa, the filament current was 665 A, the filament temperature was 2300° C., the substrate temperature was 910° C., and the distance between the filament and the substrate was 5 mm. The second treatment was run for 30 minutes.

[0100] (3) Repeat steps (1) and (2) for 300 cycles. CVD diamond film G is obtained. Detection shows that CVD diamond film G contains only SP3 hybridized diamond phase, but no SP2 hybridized graphite phase.

[0101] Comparative Example 4

[0102] (1) The first phase was grown using the first growth process: methane gas was introduced into the CVD diamond growth furnace at a flow rate of 50 sccm and hydrogen gas was introduced into the CVD diamond growth furnace at a flow rate of 1500 sccm, respectively. The parameters of the CVD diamond growth furnace were set as follows: the growth furnace pressure was 3000 Pa, the filament current intensity was 655 A, the filament temperature was 2250°C, the substrate temperature was 870°C, and the distance between the filament and the substrate was 4 mm. The first growth operation lasted for 60 min.

[0103] (2) A third growth process was used to grow a flexible toughening layer: the methane gas flow rate was adjusted to 100 sccm, and the hydrogen gas flow rate was adjusted to 1500 sccm. The CVD diamond growth furnace parameters were adjusted to: the growth furnace pressure was adjusted to 2500 Pa, the filament current was adjusted to 600 A, the filament temperature was adjusted to 2000° C., the substrate temperature was adjusted to 850° C., and the distance between the filament and the substrate was adjusted to 4 mm. The third growth process was run for 20 minutes.

[0104] (3) Repeat steps (1) and (2) 450 times to complete the preparation of CVD diamond film H. The characteristic peak intensity I of the SP3 hybrid diamond phase crystal in the CVD diamond film H was detected. D and SP2 hybrid graphite phase characteristic peak intensity I G The ratio is I D / I G =5.4:1, indicating that it contains both SP3 hybridized diamond phase and SP2 hybridized graphite phase.

[0105] Application Example 1

[0106] The above-mentioned CVD diamond films A, B, C, D, E, F, G, and H were characterized and performance tested respectively.

[0107] The thickness of the rigid growth layer and the flexible toughening layer was characterized by a Leica DM 6M optical microscope. The XRD spectra of the PNAlytical X'-Pert PRO were used to characterize the crystal facets. The Raman spectra of the LabRAM HR Evolution were used to characterize the characteristic peak intensities I of the SP3 hybrid diamond phase crystals in the rigid growth layer and the flexible toughening layer. D and SP2 hybrid graphite phase characteristic peak intensity I G The characterization data of each are shown in Table 1.

[0108] The test conditions were as follows: Samples were uniformly ground to 1.0 mm before testing, then double-sided ground and polished. When testing hardness using a nanoindenter, the maximum load was set to 10 mN, with a single indentation loading and unloading time of 30 seconds and a dwell time of 10 seconds. The flexural strength test span was 8 mm. The respective performance values ​​are shown in Table 2.

[0109] Table 1 Evaluation results of CVD diamond films of various embodiments and comparative examples

[0110]

[0111] Table 2 Test results of CVD diamond films of various embodiments and comparative examples

[0112] product Hardness / GPa Bending strength / MPa CVD diamond film A 97.4 1691 CVD diamond film B 94.3 1588 CVD diamond film C 90.6 1231 CVD diamond film D 88.5 1373 CVD diamond film E 79.4 940 CVD diamond film F 73.6 710 CVD diamond film G 91.1 780 CVD diamond film H 77.4 1170

[0113] The above describes in detail the specific embodiments of the present invention, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as the contents disclosed by the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for preparing a CVD diamond film, the CVD diamond film comprising a rigid growth layer and a flexible toughening layer arranged alternately in sequence; the rigid growth layer is an SP3 hybrid diamond phase; the flexible toughening layer is a mixed phase of the SP3 hybrid diamond phase and the SP2 hybrid graphite phase; the preparation method comprising: (1) growing a first phase on a substrate using a first growth process, wherein the first growth process comprises respectively introducing a first gas phase flow and a second gas phase flow into a CVD diamond growth furnace, setting parameters of the CVD diamond growth furnace to first growth process parameters, and running the furnace for a first growth time; (2) using a second treatment process to treat the material obtained in step (1), wherein the second treatment process is based on the flow rate of the first gas phase flow in the first growth process, reducing the flow rate of the first gas phase flow in the first growth process, adjusting the CVD diamond growth furnace parameters to the second treatment process parameters, and running the second treatment time; (3) Repeat steps (1) and (2) for n cycles to obtain a rigid growth layer; (4) using a third growth process to grow a flexible toughening layer on the rigid growth layer; the third growth process is based on the flow rate of the first gas phase flow in the first growth process, increasing the flow rate of the first gas phase flow in the first growth process, adjusting the CVD diamond growth furnace parameters to the third growth process parameters, and running the third growth time; (5) Repeating steps (1) to (4) for m cycles to obtain the CVD diamond film; The first growth process parameters in step (1) are: growth furnace pressure of 2000-5000 Pa, filament current intensity of 630-690 A, filament temperature of 2200-2700° C., substrate temperature of 750-1050° C., and a distance between the filament and the substrate of 4-8 mm; The second processing parameters in step (2) are: growth furnace pressure of 2000~5000Pa, filament current intensity of 630~690A, filament temperature of 2200~2700℃, substrate temperature of 750~1050℃, and distance between filament and substrate of 4~8mm; The third growth process parameters in step (4) are: growth furnace pressure of 1000~3000Pa, filament current intensity of 580~650A, filament temperature of 2000~2400℃, substrate temperature of 700~1050℃, and distance between filament and substrate of 4~8mm.

2. The 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 1:50-1:

20.

3. The method according to claim 2, 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 3:100~1:

25.

4. The method according to claim 1, wherein The first growth process parameters in step (1) are: the growth furnace pressure is 3000~4000Pa, the filament current intensity is 650~670A, the filament temperature is 2200~2600℃, the substrate temperature is 800~950℃, and the first growth time is 30~240min.

5. The method according to claim 4, characterized in that In the first growth process in step (1), the first growth time is 60 to 90 minutes.

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

7. The method according to claim 1, characterized in that The flow rate of the first gas phase flow in step (2) is 0%-31% of the flow rate of the first gas phase flow in step (1); the flow rate of the second gas phase flow in step (2) is 80%-200% of the flow rate of the second gas phase flow in step (1).

8. The method according to claim 7, characterized in that The flow rate of the first gas phase flow in step (2) is 0%-20% of the flow rate of the first gas phase flow in step (1); the flow rate of the second gas phase flow in step (2) is 90%-150% of the flow rate of the second gas phase flow in step (1).

9. The method according to claim 1, characterized in that The second processing parameters are: the growth furnace pressure is 3000-4000 Pa, the filament current intensity is 650-670 A, the filament temperature is 2200-2600° C., and the substrate temperature is 800-950° C.

10. The method according to claim 1, characterized in that In step (2), the ratio of the second treatment time to the first growth time is 1:2 to 1:

20.

11. The method according to claim 1, wherein In step (2), the ratio of the second treatment time to the first growth time is 1:3 to 1:

10.

12. The method according to claim 1, characterized in that The number of cycles n in step (3) is 1 to 50.

13. The method according to claim 12, characterized in that The number of cycles n in step (3) is 5 to 10.

14. The method according to claim 1, wherein The flow rate of the first gas phase flow in step (4) is 150% to 350% of the flow rate of the first gas phase flow in step (1); the flow rate of the second gas phase flow in step (4) is 95% to 105% of the flow rate of the second gas phase flow in step (1).

15. The method according to claim 14, characterized in that The flow rate of the first gas phase flow in step (4) is 150% to 200% of the flow rate of the first gas phase flow in step (1).

16. The method according to claim 1, wherein The third growth process parameters are: growth furnace pressure of 1500~2500Pa, filament current intensity of 600~620A, filament temperature of 2000~2150℃, substrate temperature of 800~900℃, and third growth time of 20~240min.

17. The method according to claim 16, characterized in that In the third growth process, the third growth time is 20 to 120 minutes.

18. The method according to claim 1, wherein The number of cycles m in step (5) is 1 to 100.

19. The method according to claim 18, characterized in that The number of cycles m in step (5) is 10 to 60.

20. A CVD diamond film prepared by the method according to any one of claims 1 to 19.

21. The CVD diamond film according to claim 20, wherein In the rigid growth layer, the SP3 hybrid diamond phase is a polycrystalline structure.

22. The CVD diamond film according to claim 21, wherein In the rigid growth layer, the content of crystals showing (111) facets in the SP3 hybrid diamond phase is 10% to 30%, and the content of crystals showing (110) facets is 70% to 90%.

23. The CVD diamond film according to claim 20, wherein In the flexible toughening layer, the crystals of the mixed phase of the SP3 hybrid diamond phase and the SP2 hybrid graphite phase appear as cauliflower-shaped crystals.

24. The CVD diamond film according to claim 20, wherein In the Raman spectrum characterization of the flexible toughening layer, the characteristic peak intensity I of the SP3 hybrid diamond phase crystal is D and SP2 hybrid graphite phase characteristic peak intensity I G The ratio is I D / I G =1.1~2.

0.

25. The CVD diamond film according to claim 24, wherein In the Raman spectrum characterization of the flexible toughening layer, the characteristic peak intensity I of the SP3 hybrid diamond phase crystal is D and SP2 hybrid graphite phase characteristic peak intensity I G The ratio is I D / I G = 1.3~1.

6.

26. The CVD diamond film according to claim 20, wherein The thickness of the rigid growth layer is 10-100 microns; the thickness of the flexible toughening layer is 1-20 microns.

27. The CVD diamond film according to claim 20, wherein The thickness of the CVD diamond film is greater than or equal to 1 mm.

28. The CVD diamond film according to claim 27, wherein The thickness of CVD diamond film is 1.2~2.0mm.

29. Use of the CVD diamond film according to any one of claims 20 to 28 in the field of geological drilling.

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