Boron-doped diamond, preparation method and application

Abstract

A boron-doped diamond, a preparation method and an application thereof, belong to the technical field of diamond synthesis. The preparation method of boron-doped diamond comprises a synthesis step: synthesizing boron-doped diamond by subjecting a raw material containing a carbon source, a boron source and a germanium-containing catalyst to a preset temperature and a preset pressure. The preset temperature and the preset pressure are both within the stable range of the diamond phase in the phase diagram, and the preset temperature is not lower than the melting point of the germanium-containing catalyst. Using the germanium-containing catalyst, under temperature and pressure conditions not lower than the melting point of the germanium-containing catalyst and satisfying the stable existence of the diamond phase, the germanium-containing catalyst can be used as a solvent catalyst for diamond, and the germanium-containing catalyst has semi-metallic properties and a diamond-like structure, so that the carbon source and the boron source can form boron-doped diamond with a high boron content.

Description

Technical Field

[0001] The present application relates to the technical field of diamond synthesis, and in particular to a boron-doped diamond, a preparation method and an application thereof. Background Art

[0002] Boron-doped diamond, garnering attention since the 1990s due to its p-type semiconductor properties, received further research after its discovery in 2004 as a superconductor. Due to its numerous outstanding properties, boron-doped diamond has been widely explored for electrochemical applications, and the synthesis of high-quality boron-doped diamond is a key area of ​​materials science research.

[0003] The properties of boron-doped diamond are affected by many factors, including shape and size, surface characteristics, uniformity of boron doping, boron content, sp 2 / sp 3 Currently, of the two main diamond synthesis methods, CVD can produce diamond films with high boron content, but this is limited in volume and difficult to reduce in cost. High-temperature and high-pressure methods, mixing graphite with boron at extremely high pressures and temperatures, can directly produce diamonds with high boron content. However, these high temperature and pressure conditions also increase the cost of synthesis.

[0004] Catalysts can significantly reduce the conditions required for high-temperature and high-pressure diamond synthesis. However, the boron content in boron-doped diamonds synthesized using metal or alloy catalysts based on iron, cobalt or nickel used in most current studies is often low, making it difficult to meet the requirements of electrochemical applications. Summary of the Invention

[0005] In view of the above-mentioned deficiencies, the present application provides a boron-doped diamond and a preparation method thereof, so as to partially or completely improve the problems of high synthesis cost and low boron content of boron-doped diamond in the related art.

[0006] This application is implemented as follows:

[0007] In a first aspect, an example of the present application provides a method for preparing boron-doped diamond, comprising:

[0008] Synthesis steps: synthesizing boron-doped diamond from raw materials containing a carbon source, a boron source and a germanium-containing catalyst at a preset temperature and a preset pressure; wherein the preset temperature and the preset pressure are both within the stable range of the diamond phase in the phase diagram, and the preset temperature is not lower than the melting point of the germanium-containing catalyst.

[0009] In the above implementation process, adding a germanium-containing catalyst to the raw materials can enable the carbon source and the boron source to form boron-doped diamond with a high boron content under relatively low temperature and pressure conditions that meet the diamond phase stability range.

[0010] In combination with the first aspect, in an optional embodiment of the present application, the germanium-containing catalyst is selected from elemental germanium and / or a germanium alloy.

[0011] In the above implementation process, using elemental germanium or germanium alloy as a catalyst can further increase the boron content of the boron-doped diamond and further reduce the synthesis temperature and pressure of the boron-doped diamond.

[0012] In combination with the first aspect, in an optional embodiment of the present application, the preset temperature is not less than 1000°C.

[0013] Optional, preset temperature is 1600-1700℃

[0014] In combination with the first aspect, in an optional embodiment of the present application, the preset pressure is not less than 5 GPa.

[0015] Optionally, the preset pressure is 5-7GPa.

[0016] In the above implementation process, the synthesis of boron-doped diamond is carried out at a temperature of not less than 1000° C. and a pressure of not less than 5 GPa, which can increase the boron content of the boron-doped diamond.

[0017] In combination with the first aspect, in an optional embodiment of the present application, the boron source is selected from boron element and / or boron compounds; and in the raw material, the mass content of boron in the boron source does not exceed 5%.

[0018] In the above implementation process, when synthesizing boron-doped diamond, the mass of boron in the boron source such as boron element or boron compound in the raw material does not exceed 5% of the total mass, and the boron content of the boron-doped diamond can be increased under the condition of obtaining boron-doped diamond.

[0019] In combination with the first aspect, in an optional embodiment of the present application, the carbon source is selected from graphite and / or carbon compounds.

[0020] Optionally, in the raw materials, the mass ratio of the carbon source to the germanium in the germanium-containing catalyst is 1:1-10.

[0021] Optionally, the mass ratio of the carbon source to the germanium in the germanium-containing catalyst is 1:1.

[0022] In the above implementation process, when preparing boron-doped diamond, graphite or carbon compounds are used as the carbon source, and the mass of germanium in the germanium-containing catalyst is not lower than the mass of the carbon source, which can increase the boron content of the boron-doped diamond.

[0023] In combination with the first aspect, in an optional embodiment of the present application, diamond seeds are added to the raw material.

[0024] In the above implementation process, diamond seeds are added to the raw materials to improve the synthesis efficiency of boron-doped diamonds synthesized from carbon sources and boron sources.

[0025] In combination with the first aspect, in an optional embodiment of the present application, the preparation method further includes an impurity removal step: the boron-doped diamond obtained in the synthesis step is acid-washed to reduce the metal impurity content of the boron-doped diamond.

[0026] In the above implementation process, the boron-doped diamond obtained in the synthesis step is acid-washed to remove metal impurities such as germanium in the boron-doped diamond, thereby improving the purity of the boron-doped diamond.

[0027] In a second aspect, the present application provides a boron-doped diamond obtained by the boron-doped diamond preparation method provided in the first aspect, wherein the boron content of the doped diamond is not less than (3±1)×10 20 cm -3 .

[0028] In a third aspect, an example of the present application provides a use of the boron-doped diamond provided in the second aspect in preparing an electrochemical device.

[0029] In the above implementation process, the doped diamond prepared according to the preparation method provided in the first aspect has a density of not less than (3±1)×10 20 cm -3 The boron content can be used in electrochemical devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art.

[0031] Figure 1 A schematic diagram of the preparation process of boron-doped diamond provided in an embodiment of the present application;

[0032] Figure 2 Schematic diagram of the diamond phase diagram;

[0033] Figure 3 This is an SEM image of the boron-doped diamond provided in Example 1 of the present application;

[0034] Figure 4 This is the Raman spectrum of boron-doped diamond provided in Example 1 of the present application. DETAILED DESCRIPTION

[0035] The embodiments of the present application will be described in detail below with reference to the examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, the conditions are carried out according to conventional conditions or manufacturer recommendations. The reagents or instruments used are not specified by the manufacturer and are conventional products that can be purchased commercially.

[0036] Boron-doped diamond has been widely used in electrochemistry. The properties of doped diamond are affected by many factors. Applications in electrochemistry and other fields have put forward a series of requirements for the quality of boron-doped diamond, including shape and size, surface characteristics, uniformity of boron doping, boron content, sp 2 / sp 3 Ratios, etc.

[0037] The boron content is a key factor influencing the electrochemical performance of boron-doped diamond. To produce high-boron-doped diamond, graphite is typically mixed with boron and synthesized at extremely high pressures and temperatures to obtain diamond with a high boron content. For example, boron-doped diamond can be synthesized directly at temperatures above 3000°C and pressures above 10 GPa. However, these higher temperatures and pressures also increase the cost of synthesizing boron-doped diamond.

[0038] In order to reduce the temperature and pressure conditions for the synthesis of boron-doped diamond, currently, most methods use iron, cobalt, nickel or manganese metals or alloys as catalysts to synthesize boron-doped diamond.

[0039] However, boron content in boron-doped diamonds prepared using iron, cobalt, nickel or manganese metals or alloys as catalysts is relatively low.

[0040] Currently, it is difficult to synthesize boron-doped diamond with high boron content under low temperature and pressure conditions.

[0041] Based on this, the present application provides an example method for preparing boron-doped diamond to reduce the synthesis conditions of boron-doped diamond and increase the boron content.

[0042] The following is a further detailed description of the method for preparing boron-doped diamond provided by the examples of this application in conjunction with the accompanying drawings.

[0043] See also Figure 1 , the preparation method of boron-doped diamond includes:

[0044] S1. Synthesis steps:

[0045] Boron-doped diamond is synthesized from raw materials containing a carbon source, a boron source and a germanium-containing catalyst at a preset temperature and a preset pressure; wherein the preset temperature and the preset pressure are both within the stable range of the diamond phase in the phase diagram, and the preset temperature is not lower than the melting point of the germanium-containing catalyst.

[0046] A germanium-containing catalyst is added to the raw materials. Under the temperature and pressure conditions in the diamond phase stability range and the synthesis temperature is higher than the melting point of the germanium-containing catalyst, the germanium-containing catalyst can serve as a solvent catalyst for diamond. The germanium-containing catalyst has semi-metallic properties and a diamond-like structure, so that the carbon source and the boron source can form boron-doped diamond with a high boron content under the above temperature and pressure conditions.

[0047] The stable range of the diamond phase in the phase diagram described in this application refers to the pressure and temperature range within which diamond can exist stably in the phase diagram with temperature as the horizontal axis and pressure as the vertical axis.

[0048] For example, the stable range of the diamond phase in the phase diagram can be found in Figure 2 .

[0049] The present application does not limit the specific type of carbon source, and relevant personnel can select the carbon source for synthesizing diamond as needed.

[0050] In some possible embodiments, the carbon source is selected from at least one of graphite and carbon compounds.

[0051] Exemplarily, the carbon source may be selected from graphite.

[0052] Exemplarily, the carbon source may be selected from nanographite.

[0053] Exemplarily, the carbon source can be selected from C 16 H 30 B2.

[0054] Furthermore, the present application does not limit the specific type of boron source, and relevant personnel can select the boron source as needed.

[0055] In some possible embodiments, the boron source may be selected from at least one of elemental boron and boron compounds.

[0056] Illustratively, the boron source may be selected from elemental boron.

[0057] Exemplarily, the boron source may be selected from B2H6.

[0058] Exemplarily, the boron source may be selected from BN.

[0059] Exemplarily, the boron source may be selected from AlB2.

[0060] Furthermore, the present application does not limit the specific type of germanium-containing catalyst, and relevant personnel can make corresponding selections as needed.

[0061] In one possible embodiment, the germanium-containing catalyst is selected from elemental germanium.

[0062] Exemplarily, the germanium-containing catalyst is selected from α-Ge.

[0063] In one possible embodiment, the germanium-containing catalyst may be selected from germanium alloys.

[0064] For example, the germanium-containing catalyst may be selected from an alloy of one or more of iron, cobalt or nickel and germanium, for example, an iron-germanium alloy, a nickel-germanium alloy, a cobalt-germanium alloy, an iron-nickel-germanium alloy, an iron-cobalt-germanium alloy, a nickel-cobalt-germanium alloy or an iron-cobalt-nickel-germanium alloy.

[0065] Furthermore, the present application does not limit the specific contents of the carbon source, boron source and germanium-containing catalyst in the raw materials.

[0066] In some possible embodiments, in the raw material, the mass ratio of the carbon source to the germanium in the germanium-containing catalyst is 1:1-10.

[0067] When preparing boron-doped diamond, the mass of germanium in the germanium-containing catalyst is not less than the mass of the carbon source, which can increase the boron content of the boron-doped diamond.

[0068] Illustratively, the mass ratio of the carbon source to the germanium in the germanium-containing catalyst is in a range of one or between any two of 1:1, 1:2, 1:3, 1:5 or 1:10.

[0069] Exemplarily, the mass ratio of the carbon source to the germanium in the germanium-containing catalyst is 1:1.

[0070] For example, the carbon source is selected from graphite, and the germanium-containing catalyst is selected from elemental germanium. In the raw materials, the mass content of graphite and elemental germanium is the same.

[0071] In some possible embodiments, the ratio of boron in the boron source to the total mass of the raw material does not exceed 5%.

[0072] Exemplarily, the boron source is selected from elemental boron. In the raw material, the content of elemental boron is 5%.

[0073] Furthermore, diamond seeds may be added to the raw material.

[0074] Adding diamond seeds to the raw materials can improve the synthesis efficiency of boron-doped diamonds synthesized from carbon sources and boron sources.

[0075] Furthermore, the present application does not limit the particle size range of the diamond seed crystals, and relevant personnel can make corresponding selections as needed.

[0076] In some possible implementations, the particle size of the diamond seed crystals may be 1-500 μm.

[0077] For example, the particle size of the diamond seed crystal may be one of 1 μm, 10 μm, 50 μm, 100 μm, or 500 μm, or a range between any two of them.

[0078] Furthermore, the present application does not limit the presence forms of the boron source, carbon source, germanium-containing catalyst and seed crystal in the raw materials, and relevant personnel can make corresponding selections as needed.

[0079] In one possible embodiment, the boron source, the carbon source, the germanium-containing catalyst and the seed crystal are uniformly mixed.

[0080] Furthermore, the weighed boron source, carbon source, germanium-containing catalyst and seed crystals can be placed in a ball mill to mix the raw materials by ball milling.

[0081] Exemplarily, weighed boron source, carbon source, germanium-containing catalyst and seed crystals are placed in a planetary ball mill, and then stainless steel balls or agate balls are added, and the mixture is ball-milled at a speed of 200-1000 r / min for 1-5 hours according to a ball-to-material ratio of 1-10:1 to obtain a mixed powder.

[0082] Furthermore, the mixed raw materials may be pre-pressed to form a green body, which is then placed under high temperature and high pressure conditions to synthesize boron-doped diamond.

[0083] Alternatively, in another possible embodiment, the boron source, the carbon source, the germanium-containing catalyst, and the seed crystal may be stacked and nested.

[0084] For example, a seed crystal can be placed in a germanium-containing catalyst and a boron source and compacted to form a column. A carbon source and a boron source in a certain ratio are then mixed and molded into a cylindrical shell. The cylindrical shell is nested within the outer surface of the column. After these raw materials are assembled by stacking and nesting, boron-doped diamond is synthesized under high temperature and high pressure.

[0085] Furthermore, the present application does not limit specific synthesis temperature and synthesis pressure. In some possible embodiments, the synthesis temperature is not less than 1000°C.

[0086] At a synthesis temperature that satisfies the stable existence temperature of the diamond phase in the phase diagram and is higher than the melting point of metallic germanium, metallic germanium can serve as a solvent for diamond.

[0087] For example, the synthesis temperature may be 1600-1700°C.

[0088] For example, the synthesis temperature may be 1700°C.

[0089] In some possible implementations, the synthesis pressure is not less than 5 GPa.

[0090] Exemplarily, the synthesis pressure may be 5-7 GPa.

[0091] For example, a raw material containing graphite, elemental boron, elemental germanium and diamond seed crystals may be sintered at a synthesis temperature of 1700° C. and a synthesis pressure of 7 GPa to obtain boron-doped diamond.

[0092] Furthermore, the present application does not limit the specific heating rate, and relevant personnel can make corresponding selections based on the performance of the synthesis equipment.

[0093] For example, the temperature may be increased to 1000° C. at a heating rate of 20° C. / min, and then increased to 1700° C. at a heating rate of 5° C. / min.

[0094] Furthermore, the present application does not limit the synthesis time. In some possible implementations, the synthesis time is not less than 0.5 min.

[0095] For example, the synthesis time may be 1 min, 10 min, 100 min or 1000 min.

[0096] Furthermore, the raw materials are sintered at high temperature and high pressure in a vacuum environment to synthesize boron-doped diamond.

[0097] Furthermore, boron-doped diamond can be prepared by a large-cavity press.

[0098] Exemplarily, a six-sided top press is used for high temperature and high pressure synthesis.

[0099] When boron-doped diamond is synthesized using single germanium or germanium alloy as a germanium-containing catalyst to catalyze carbon and boron sources, there are often metal impurities at least from the germanium-containing catalyst, such as metallic germanium impurities.

[0100] Further, in order to improve the purity of the prepared boron-doped diamond, please continue to refer to Figure 1 , the preparation method provided in the example of this application also includes:

[0101] S2, impurity removal step: acid-washing the boron-doped diamond obtained in the synthesis step S1 to reduce the metal impurity content of the boron-doped diamond.

[0102] Furthermore, this application does not limit the specific conditions for pickling, and relevant personnel can make corresponding choices as needed.

[0103] For example, the boron-doped diamond obtained in step S1 is pickled using an acidic solution such as nitric acid, hydrochloric acid, sulfuric acid or potassium dichromate to reduce or even remove metal impurities in the boron-doped diamond.

[0104] Furthermore, after pickling, the pickled sample can be cleaned by ultrasound or other methods.

[0105] According to the above preparation method, a boron content of not less than (3±1)×10 20 cm -3 Boron-doped diamond.

[0106] For example, the boron content of boron-doped diamond may be 2×10 20 cm -3 , 3×10 20 cm -3 or 4×10 20 cm -3 One of them or the range between any two of them.

[0107] Furthermore, the boron-doped diamond can be applied to electrochemical devices.

[0108] This application does not limit the specific type of electrochemical device, and relevant personnel can make corresponding adjustments as needed.

[0109] In one possible implementation, the boron-doped diamond can be used to prepare an electrode, which is placed in wastewater to be treated and connected to an external power source for wastewater treatment.

[0110] The boron-doped diamond of the present application is further described in detail below with reference to the examples.

[0111] Example 1

[0112] Example 1 provides a boron-doped diamond, which is prepared by the following method:

[0113] (1) Synthesis steps

[0114] Graphite, metallic germanium, elemental boron, and 1μm diamond seeds were weighed as the reaction materials. The diamond seeds accounted for 0.5wt% of the total raw material mass, while elemental boron accounted for 5wt%. Graphite and metallic germanium were weighed in a 1:1 mass ratio. These materials were ball-milled and compacted, and the compacted body was placed in a high-pressure synthesis machine. Synthesis was carried out at 7GPa and 1800°C for 5 hours.

[0115] (2) Impurity removal step

[0116] The synthetic product obtained in step (1) is pickled with nitric acid to separate impurities, and then ultrasonically cleaned to obtain boron-doped diamond.

[0117] The microstructure of the boron-doped diamond obtained in Example 1 was analyzed. Figure 3 shown.

[0118] according to Figure 3 It can be seen that the grain size of the boron-doped diamond provided in Example 1 is 10-100 μm.

[0119] Example 2

[0120] Example 2 provides a boron-doped diamond, which differs from Example 1 in that:

[0121] In step (1), a seed crystal of 500 μm size is used.

[0122] Example 3

[0123] Example 3 provides a boron-doped diamond, which differs from Example 1 in that:

[0124] In step (1), a weighed diamond seed crystal is placed in a mixture of germanium powder and boron powder and compacted to form a cylinder. Graphite powder and boron powder are mixed and formed into a cylindrical shell using a mold. The cylindrical shell is nested outside the cylinder. The nested sample is subjected to high temperature and high pressure to synthesize boron-doped diamond.

[0125] Comparative Example 1

[0126] Comparative Example 1 provides a boron-doped diamond, which differs from Example 1 in that:

[0127] In step (1), graphite, iron-nickel alloy, elemental boron, and 1 μm-sized diamond seed crystals are weighed as reaction raw materials. The diamond seed crystals account for 0.5 wt.% of the total mass of the raw materials, the elemental boron accounts for 5 wt.% of the total mass of the raw materials, and the graphite and iron-nickel alloy are weighed in a mass ratio of 1:1.

[0128] Comparative Example 2

[0129] Comparative Example 2 provides a boron-doped diamond, which differs from Example 1 in that:

[0130] In step (1), graphite, nickel-manganese alloy, elemental boron, and 1 μm-sized diamond seed crystals are weighed as reaction raw materials. The diamond seed crystals account for 0.5 wt.% of the total mass of the raw materials, the elemental boron accounts for 5 wt.% of the total mass of the raw materials, and the graphite and iron-nickel alloy are weighed in a mass ratio of 1:1.

[0131] Test Example 1

[0132] The boron content of the boron-doped diamonds provided in Example 1, Example 2, Example 3, Comparative Example 1 and Comparative Example 2 was tested, and the test results are shown in Table 1.

[0133] Table 1

[0134]

[0135] Result analysis: Combining Examples 1-3 and Comparative Examples 1-2, it can be seen that the boron-doped diamond prepared by the preparation method provided in this application has a higher boron content.

[0136] Test Example 2

[0137] The boron-doped diamonds provided in Example 1, Example 2 and Comparative Example 1 were subjected to Raman spectroscopy testing. The test results of the boron-doped diamonds provided in Example 1, Example 2 and Comparative Example 1 are as follows: Figure 4 shown.

[0138] Result analysis: From Figure 4 It can be seen that at 550cm 1 About 1200cm 1 The small peaks appearing at the left and right sides meet the Raman spectrum curve signature of highly boron-doped diamonds, confirming the presence of high concentrations of boron in the diamond lattice. 1 The peak at 1200 cm is believed to be attributed to the local vibration mode of the boron pairs in the lattice. 1 The band corresponds to the maximum of the phonon density of states caused by the disorder introduced by boron doping. The diamond Raman line is relatively close to the intrinsic diamond (1332.5 cm 1 ) have a large lateral shift, appearing at 1311cm 1 and 1306cm 1 , indicating a high level of boron doping. A slight asymmetry of this peak is also observed due to the Fano resonance. The Fano effect arises from quantum mechanical interference between discrete Raman phonon transitions and inter-band transitions of energy-continuous subbands, which is a result of the Fermi level shifting to the conduction band due to high levels of boron doping. The diamond Raman line in Comparative Example 1 has a small lateral shift relative to intrinsic diamond, appearing at 1330 cm 1 , indicating a very low level of boron doping.

[0139] The test sample in Example 1 is a sample obtained without the impurity removal step. It can be seen from the curve of Example 1 that about 300 cm 1 The characteristic peaks of metallic germanium are shown.

[0140] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A method for preparing boron-doped diamond, characterized in that: include: Synthesis steps: synthesizing boron-doped diamond from a raw material containing a carbon source, a boron source and a germanium-containing catalyst at a preset temperature and a preset pressure; wherein the preset temperature and the preset pressure are both within the stable range of the diamond phase in the phase diagram, and the preset temperature is not lower than the melting point of the germanium-containing catalyst; the germanium-containing catalyst is selected from elemental germanium and / or a germanium alloy; the boron source is selected from elemental boron and / or a boron compound; the carbon source is selected from graphite and / or a carbon compound; the preset temperature is not lower than 1000°C; the preset pressure is not lower than 5 GPa; in the raw material, the mass content of boron in the boron source does not exceed 5%, and the mass ratio of the carbon source to the germanium in the germanium-containing catalyst is 1:1-10; and diamond seeds are added to the raw material.

2. The method for preparing boron-doped diamond according to claim 1, wherein: The preset temperature is 1600-1700°C.

3. The method for preparing boron-doped diamond according to claim 1, wherein: The preset pressure is 5-7 GPa.

4. The method for preparing boron-doped diamond according to claim 1, wherein: The mass ratio of the carbon source to the germanium in the germanium-containing catalyst is 1:

1.

5. The method for preparing boron-doped diamond according to claim 1, wherein: The preparation method further comprises an impurity removal step: acid washing the boron-doped diamond obtained in the synthesis step to reduce the metal impurity content of the boron-doped diamond.

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