A niobium-based boron-doped diamond semiconductor composite coating material, a preparation method and application thereof

Abstract

This invention discloses a niobium-based boron-doped diamond semiconductor composite coating material, its preparation method, and its application. The niobium-based boron-doped diamond semiconductor composite coating material consists of a niobium substrate, an Nb-B compound gradient transition layer disposed on the surface of the niobium substrate, and a gradient boron-doped diamond semiconductor layer disposed on the surface of the Nb-B compound gradient transition layer. The Nb-B compound gradient transition layer has a boron content that increases from bottom to top; the gradient boron-doped diamond semiconductor layer has a boron content that decreases from bottom to top. The Nb-B compound gradient transition layer contains Nb₂C phase and / or NbC phase. By setting an Nb-B compound gradient transition layer on the surface of the niobium substrate and then setting a gradient boron-doped diamond semiconductor layer on the surface of the transition layer, the composite coating material obtained by this invention has good film-substrate bonding performance, excellent conductivity, high stability, and good electrochemical performance.

Description

Technical Field

[0001] This invention relates to a niobium-based boron-doped diamond semiconductor composite coating material, its preparation method, and its application, belonging to the field of materials preparation. Background Technology

[0002] Diamond possesses excellent physicochemical properties. Its hardness, molar density, thermal conductivity, sound velocity, and elastic modulus are the highest among known materials. It also exhibits good corrosion resistance, light transmittance, heat resistance, and radiation resistance. Pure diamond has a very high resistivity, making it an excellent electrical insulator. Doping diamond with boron atoms transforms it from an insulator with a bandgap of 5.47 eV into a semiconductor or even a conductor, greatly expanding its application range. At low doping levels, diamond exhibits semiconductor properties, with high electron / hole mobility, making it an ideal material for fabricating high-temperature semiconductors and radiation-resistant semiconductors. At high doping levels, diamond exhibits semi-metallic conductivity, making it an ideal anolyte material for electrochemical synthesis, electrochemical oxidation, and electrochemical analysis. Using chemical vapor deposition (CVD) technology, boron-doped diamond (BDD) coatings can be deposited on various substrates within a reasonable timescale and controllable doping range.

[0003] As a functional material of significant strategic importance, nitrogen (Nb) possesses advantages such as high melting point, low vapor pressure, good cold working performance, high chemical stability, strong resistance to liquid metal and acid / alkali corrosion, and high dielectric constant of surface oxide film, making it an ideal metal matrix for preparing BDD composite coating materials.

[0004] However, on the one hand, the coefficients of thermal expansion between the diamond coating and the metal substrate differ significantly. CVD growth typically occurs in the range of 600-1000℃. During the cooling process to room temperature after deposition, the shrinkage of the substrate material is significantly greater than that of the diamond film, generating substantial thermal stress within the film and affecting the bonding strength between the film and the substrate. On the other hand, Nb, as a strong carbide-forming element, strongly absorbs C atoms during BDD, forming a carbide interlayer. During electrochemical oxidation, when the electrolyte penetrates the interface between the coating and the substrate through pores, the coating detachment rate is determined by the electrolyte's propagation rate at the coating / substrate interface. The corrosion resistance of the compounds at the interface between the coating and the substrate is a crucial factor affecting the coating detachment rate. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the first objective of this invention is to provide a niobium-based boron-doped diamond semiconductor composite coating material that possesses both high adhesion and high stability in a composite coating.

[0006] The second objective of this invention is to provide a method for preparing a niobium-based boron-doped diamond semiconductor composite coating material.

[0007] The third objective of this invention is to provide an application of a niobium-based boron-doped diamond semiconductor composite coating material.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] This invention discloses a niobium-based boron-doped diamond semiconductor composite coating material, comprising a niobium substrate, an Nb-B compound gradient transition layer disposed on the surface of the niobium substrate, and a gradient boron-doped diamond semiconductor layer disposed on the surface of the Nb-B compound gradient transition layer. The Nb-B compound gradient transition layer has a boron content gradient increasing from bottom to top; the gradient boron-doped diamond semiconductor layer has a boron content gradient decreasing from bottom to top; and the Nb-B compound gradient transition layer contains an Nb₂C phase and / or an NbC phase.

[0010] In this invention, an Nb-B compound gradient transition layer is formed on the surface of the niobium substrate. All Nb-B compounds are highly conductive phases with thermal expansion coefficients between those of diamond and pure niobium, allowing for a smooth transition between Nb and BDD (Biodesyl Dioxide). During electrochemical oxidation, the corrosion resistance of Nb-B compounds is significantly higher than that of Nb-C compounds, effectively reducing coating peeling rates and improving material service stability. The bottom layer of the transition layer has a low boron content, which helps retain the mechanical properties and excellent conductivity of the metal substrate. The top layer has a higher boron content to enhance the chemical bonding between the transition layer and the BDD coating, further improving film-substrate adhesion. The intermediate layer uses a gradient increase in boron content, which helps alleviate the hardness gradient between the substrate and the transition layer, resulting in a natural transition between coatings, reducing the likelihood of separation and breakage, and improving adhesion.

[0011] Furthermore, in the Nb-B compound gradient transition layer, this invention also introduces Nb2C and / or NbC phases through carbon doping. The inventors have found that the introduction of Nb2C and / or NbC phases can further mitigate the hardness gradient between the phases in the transition layer, improve the density and quality of the transition layer, and enhance the adhesion between the transition layer and the substrate. Moreover, the lattice distortion caused by the entry of B and C atoms will increase the roughness of the transition layer, which is beneficial for providing more nucleation sites for the subsequent deposition of boron-doped diamond semiconductor layers, further improving the adhesion between the BDD coating and the substrate, and enhancing the film-substrate bonding performance and service stability.

[0012] This invention discloses a niobium-based boron-doped diamond semiconductor composite coating material, wherein the top of the Nb-B compound gradient transition layer is a single phase of Nb3B2, NbB, Nb5B6, Nb3B4, or NbB2, or a composite phase composed of two or more of them.

[0013] The Nb-B compound gradient transition layer provided by this invention has a B content that increases from bottom to top. The bottom layer has a lower B content and preferentially forms the Nb3B2 phase. Nb3B2 further combines with B to form the NbB phase, NbB further combines with B to form the Nb5B6 phase, Nb5B6 further combines with B to form the Nb3B4 phase, and Nb3B4 further combines with B to form the NbB2 phase. These phases are distributed in a gradient in the form of single phases or one or more composite phases.

[0014] In a further preferred embodiment, the top of the Nb-B compound gradient transition layer is a single-phase NbB2, with an atomic ratio of B of 63% to 75%. When the top of the Nb-B compound gradient transition layer is a single-phase NbB2, the boronization reaction of niobium is most complete, resulting in the optimal bonding performance of the obtained niobium-based boron-doped diamond semiconductor composite coating material.

[0015] In a preferred embodiment, the Nb2C phase and / or NbC phase are dispersedly distributed in the Nb-B compound gradient transition layer, wherein the atomic ratio of C in the Nb-B compound gradient transition layer is 1% to 5%.

[0016] In this invention, the C / B atomic ratio in the transition layer is controlled within this range, resulting in optimal bonding performance of the niobium-based boron-doped diamond semiconductor composite coating material. Above this range, the corrosion resistance of the transition layer decreases due to the lower corrosion resistance of the Nb-C compound compared to the Nb-B compound, thus failing to effectively improve the service life of the composite coating material; below this range, the Nb-C compound content is too low, failing to achieve the optimal coupling effect.

[0017] This invention discloses a niobium-based boron-doped diamond semiconductor composite coating material, wherein the thickness of the Nb-B compound gradient transition layer is 5-100 μm. The inventors discovered that the optimal performance is achieved when the thickness of the transition layer is controlled within this range. If the transition layer is too thin, the boron content in the transition layer is low, which fails to effectively improve the chemical bonding with the gradient boron-doped diamond coating; if the transition layer is too thick, the bonding between the transition layer and the substrate is weak, resulting in high brittleness and easy peeling.

[0018] This invention discloses a niobium-based boron-doped diamond semiconductor composite coating material. The gradient boron-doped diamond semiconductor layer comprises, from bottom to top, a boron-doped diamond bottom layer, a boron-doped diamond intermediate layer, and a boron-doped diamond top layer. The boron-doped diamond bottom layer has a uniform boron content, with a B / C ratio of 46,666-60,000 ppm on an atomic ratio basis. The boron content in the boron-doped diamond intermediate layer decreases linearly from bottom to top, with the boron content in the boron-doped diamond bottom layer being the maximum value and decreasing linearly to the boron content in the boron-doped diamond top layer.

[0019] In this invention, the boron-doped diamond bottom layer uses a uniform boron content to maximize the conductivity of the substrate, enhance the chemical bonding between the BDD coating and the Nb-B compound gradient transition layer, and further improve the film-substrate bonding performance. The boron-doped diamond top layer also uses a uniform boron content to maximize the corrosion resistance of the top layer, while enabling the composite coating material to obtain a wider potential window during electrochemical processes. The boron-doped diamond intermediate layer adopts a linearly decreasing boron gradient, which allows for a natural transition between coatings, making it less prone to separation and breakage, and improving the bonding strength.

[0020] The present invention discloses a niobium-based boron-doped diamond semiconductor composite material, wherein the gradient boron-doped diamond semiconductor layer is uniformly deposited on the surface of the Nb-B compound gradient transition layer by chemical vapor deposition, and the thickness of the gradient boron-doped diamond semiconductor layer is 1μm-2mm.

[0021] The process involves first depositing a boron-doped diamond bottom layer, a boron-doped diamond intermediate layer, and finally depositing a boron-doped diamond top layer on the substrate surface.

[0022] In this invention, the boron-doped diamond bottom layer, the boron-doped diamond middle layer, and the boron-doped diamond top layer all have the same thickness range.

[0023] This invention relates to a niobium-based boron-doped diamond semiconductor composite coating material, wherein the niobium in the niobium matrix is ​​selected from pure Nb or Nb alloy.

[0024] This invention relates to a niobium-based boron-doped diamond semiconductor composite coating material, wherein the niobium substrate has a structure of zero-dimensional, one-dimensional, two-dimensional, or three-dimensional.

[0025] This invention discloses a niobium-based boron-doped diamond semiconductor composite coating material, wherein the niobium substrate surface has a micro-nano structure.

[0026] In this invention, the fabrication method of the micro-nano structure is not limited, such as at least one of high-temperature atmosphere etching, high-temperature metal etching, and plasma etching.

[0027] This invention discloses a method for preparing a niobium-based boron-doped diamond semiconductor composite coating material. The method involves simultaneously performing boron and carbon doping on the surface of a niobium substrate to obtain a gradient transition layer of Nb-B compounds containing Nb₂C and / or NbC phases. Then, a gradient boron-doped diamond semiconductor layer is grown on the niobium substrate containing the Nb-B compound gradient transition layer via chemical vapor deposition to obtain the niobium-based boron-doped diamond semiconductor composite coating material.

[0028] In practical operation, pure Nb or Nb alloys of different sizes and alloy element contents are used as substrate materials. After cleaning and degreasing, a porous structure can be formed on the surface by acid etching, which further improves the adhesion between the substrate and the film in subsequent film formation. For example, the Nb substrate is placed in a mixed solution of 10% HF + 10% HNO3 + 80% H2O and ultrasonically etched for 60 seconds.

[0029] In this invention, the preparation method of the Nb-B compound gradient transition layer is not limited, as long as the thickness and composition requirements of the transition layer can be met. For example, one of the existing technologies such as electroplating, vapor deposition, magnetron sputtering, chemical vapor deposition, and physical vapor deposition can be used.

[0030] In a preferred embodiment, a gradient transition layer of Nb-B compound containing Nb2C phase and / or NbC phase is prepared on the surface of a niobium substrate by magnetron sputtering or high-temperature heat treatment.

[0031] The inventors discovered that when using a high-temperature heat treatment method, since the penetration of boron is from the surface to the interior, a gradient transition layer of boron-doped Nb-B compounds can be formed, in which the boron content increases from bottom to top. When using a magnetron sputtering method, the boron content in the Nb-B compound gradient transition layer can be adjusted by the sputtering power and the proportion of boron-containing atmosphere.

[0032] In a preferred embodiment, the process of obtaining a gradient transition layer of Nb-B compound containing Nb2C phase and / or NbC phase on the surface of a niobium substrate by magnetron sputtering is as follows: the niobium substrate is placed in a sputtering atmosphere for magnetron sputtering; in the magnetron sputtering, a dual-target magnetron sputtering is performed using one of an Nb target or an NbB target and an NbC target, the distance between the niobium substrate and the target is 5-12 cm, the working gas pressure is 0.2-3 Pa, the co-sputtering time is 5-100 min, the sputtering power of the NbC target is 50-100 W, the sputtering power of the NbB target is 120-200 W, and the sputtering power of the Nb target is 120-200 W; the sputtering atmosphere consists of a boron-containing gas and a protective gas.

[0033] In a further preferred embodiment, the boron-containing gas is borane.

[0034] In this invention, the purity of all targets used is ≥99.99%, and the doping amount is controlled by controlling the sputtering power of different targets.

[0035] In a further preferred embodiment, after the magnetron sputtering process is completed, the niobium substrate containing the Nb-B compound gradient transition layer is subjected to low-temperature heat treatment. The temperature of the low-temperature heat treatment is 500-1100℃, the time is 1-6h, the pressure is 8-25kPa, and the atmosphere of the low-temperature heat treatment is an inactive atmosphere.

[0036] More preferably, the inactive atmosphere is selected from at least one of hydrogen, argon, and helium.

[0037] The inventors discovered that after magnetron sputtering, the niobium substrate containing the Nb-B compound gradient transition layer is subjected to low-temperature heat treatment, and the resulting gradient boron-doped diamond semiconductor layer deposited and grown has higher uniformity and better bonding performance.

[0038] The preferred embodiment of obtaining a gradient transition layer of Nb-B compound containing Nb2C phase and / or NbC phase on the surface of a niobium substrate by high-temperature heat treatment is as follows: the niobium substrate is placed in a B source and a C source and subjected to high-temperature heat treatment at a temperature of 800-1200℃ for 1-20 hours at a pressure of 2-10 kPa; the atmosphere for the high-temperature heat treatment is an inactive atmosphere, such as at least one of hydrogen, argon, and helium, preferably argon.

[0039] In a further preferred embodiment, the temperature of the high-temperature heat treatment is 1000-1200℃.

[0040] In this invention, the introduction of B and C atoms causes lattice distortion. Within this temperature range, the number of microcracks and pores near the transition layer is relatively small, resulting in a continuous and dense transition layer structure with good quality. Below this temperature, microcracks and pores easily appear near the Nb-B compound, increasing the brittleness of the transition layer and leading to spalling. Above this temperature, C elements preferentially react with B elements to form compounds instead of diffusing into the matrix, making it impossible to prepare a transition layer structure.

[0041] In a further preferred embodiment, the ratio of the B source to the C source, in terms of atomic ratio, is C:B = 2-4:6-8.

[0042] In this invention, the C / B atomic ratio in the B and C sources is controlled within this range. A small amount of active C atoms accumulating on the niobium substrate surface can effectively promote the borylation reaction, resulting in the optimal performance of the resulting transition layer. If the C / B atomic ratio is higher than this range, since C atoms have a smaller atomic radius than B atoms, they will preferentially react with niobium. Excessive active C atoms may form a deposition layer on the substrate surface, inhibiting the niobium borylation reaction. If the ratio is lower than this range, under the condition that the heating temperature and holding time remain unchanged, after the borylation reaction reaches its maximum saturation value, excessive active B atoms will lead to more pores in the transition layer, which is not conducive to improving the overall performance.

[0043] In a further preferred embodiment, the B source is selected from a gaseous boron source and a solid boron source. The gaseous boron source is selected from one of borane, boron chloride, and boron bromide, preferably diborane. The solid boron source is selected from one of B powder and B salt, preferably B powder.

[0044] In this invention, compared to other preparation methods, the reaction of elemental B directly with the matrix requires a lower temperature and results in a more complete reaction.

[0045] More preferably, the particle size of the solid B powder is ≤20μm.

[0046] The inventors discovered that by using a niobium matrix coated with high-purity ultrafine boron powder with a particle size ≤20μm and controlling the heat treatment temperature within the above-mentioned preferred range, the final transition layer has the best quality, and the resulting niobium-based boron-doped diamond semiconductor composite coating material also has the best performance.

[0047] In a further preferred embodiment, the C source is selected from a gaseous carbon source and a solid carbon source, wherein the gaseous carbon source is selected from methane or acetylene, preferably methane, and the solid carbon source is selected from carbon powder or carbon-containing salts, preferably carbon powder.

[0048] A preferred embodiment of the process for growing a gradient boron-doped diamond semiconductor layer from a niobium substrate containing an Nb-B compound gradient transition layer via chemical vapor deposition is as follows: First, the niobium substrate containing the Nb-B compound gradient transition layer is placed in a suspension containing a mixture of nanocrystalline and / or microcrystalline diamond particles; ultrasonic treatment is performed, followed by drying; a niobium substrate with surface-adsorbed nanocrystalline and / or microcrystalline diamond is obtained. Then, the niobium substrate with surface-adsorbed nanocrystalline and / or microcrystalline diamond is placed in a chemical vapor deposition furnace, and hydrogen, boron-containing gas, and carbon-containing gas are introduced to perform chemical vapor deposition to grow a gradient boron-doped diamond semiconductor layer. The temperature of the chemical vapor deposition is 600-1000℃, and the gas pressure is 10. 3 -10 4 Pa, time is 3-20h.

[0049] In a further preferred embodiment, the suspension containing nanocrystalline and / or microcrystalline diamond mixed particles has a diamond mixed particle mass fraction of 0.01%-0.05%; the diamond mixed particles have a particle size of 5-30 nm and a purity of ≥97%; and the ultrasonic treatment time is 5-30 min.

[0050] In a further preferred embodiment, during the chemical vapor deposition, the percentage of carbon-containing gas in the total gas mass flow rate in the furnace is 0.5-10.0%, preferably 2-5%.

[0051] In a further preferred embodiment, during the chemical vapor deposition, the percentage of boron-containing gas in the total mass flow rate of the furnace is first controlled to be 0.069%-0.0884% to obtain a boron-doped diamond underlayer. Then, the boron doping concentration is reduced linearly until the percentage of boron-containing gas in the total mass flow rate of the furnace is 0.03968%-0.0593% to obtain a boron-doped diamond transition layer. Then, the percentage of boron-containing gas in the total mass flow rate of the furnace is controlled to be 0.03968%-0.0593% again to obtain a boron-doped diamond outer layer; thus, a gradient boron-doped diamond semiconductor layer is obtained.

[0052] The present invention also provides an application of niobium-based boron-doped diamond semiconductor composite material, wherein the semiconductor composite coating material is applied to at least one of semiconductor devices, electrochemical oxidation, electrochemical synthesis, and electrochemical analysis.

[0053] Beneficial effects

[0054] This invention addresses the significant difference in thermal expansion coefficients between Nb and BDD, as well as the poor corrosion resistance of the compound at the interface between the coating and the substrate. It proposes a method where an Nb-B compound gradient transition layer is formed on the surface of a niobium substrate, followed by a gradient boron-doped diamond semiconductor layer. This creates an Nb-Nb-B compound gradient transition layer-gradient boron-doped diamond semiconductor composite coating material configuration. This significantly improves the film-substrate bonding performance and service stability of the Nb-based BDD semiconductor composite coating material, reducing the risk of material peeling during the chemical vapor deposition cooling stage and subsequent service stages. Attached Figure Description

[0055] Figure 1 The graph shows the change in borane concentration when preparing the Nb-B compound gradient transition layer by magnetron sputtering in Example 3. Detailed Implementation

[0056] Example 1

[0057] Pure Nb matrix was encapsulated in solid boron powder and solid carbon powder. The solid boron powder had a particle size of 5 μm and the C / B ratio of the solid boron powder and solid carbon powder was 3:7. Argon gas was introduced into a tube furnace as a protective gas for heat treatment. The gas pressure was set to 3 kPa and the heating temperature was 1100℃. After holding at this temperature for 4 hours, the furnace was cooled.

[0058] The resulting Nb-B compound has a dense gradient transition layer structure, while the Nb-C compound is distributed in a diffuse manner, with a C / B atomic ratio of 2.03% in the transition layer.

[0059] Then, an Nb substrate with an Nb-B compound gradient transition layer on its surface is placed in a suspension containing a mixture of nanocrystalline and / or microcrystalline diamond particles; ultrasonic treatment is performed, followed by drying; a substrate material with nanocrystalline and / or microcrystalline diamond adsorbed on its surface is obtained; the mass fraction of the diamond mixture particles in the suspension containing nanocrystalline and / or microcrystalline diamond particles is 0.03%; the particle size of the diamond mixture particles is 5-10 nm, and the purity is ≥97%; the ultrasonic treatment time is 30 min.

[0060] A substrate material with surface-adsorbed nanocrystalline and / or microcrystalline diamond is placed in a chemical vapor deposition furnace, and hydrogen, boron-containing gas, and carbon-containing gas are introduced. First, the percentage of boron-containing gas in the total gas flow rate in the furnace is controlled to be 0.0884% to obtain a boron-doped diamond bottom layer. Then, the boron doping concentration is reduced in a linear decreasing manner until the percentage of boron-containing gas in the total gas flow rate in the furnace is 0.0593% to obtain a boron-doped diamond intermediate layer. Then, the percentage of boron-containing gas in the total gas flow rate in the furnace is controlled to be 0.03968% to obtain a boron-doped diamond top layer. Thus, a gradient boron-doped diamond semiconductor layer is obtained.

[0061] The carbon-containing gas accounts for 2.5% of the total gas mass flow rate in the furnace, the boron-doped diamond deposition temperature is 800℃, and the gas pressure is 10. 3 Pa, deposition time was 15h.

[0062] Using the coating material as the anode and a Ti plate of the same specifications as the cathode, the current density was controlled at 60 mA / cm². 2 A degradation experiment was conducted using simulated dye wastewater (500 mL of 0.1 g / L RB-19 solution, 0.5 M sodium sulfate) as the research object. After 4 hours of degradation, the wastewater changed from deep blue to colorless and clear, with a color removal rate of 99% and an energy consumption of 1.5 kWh / m³ for color removal. 3 ·A -1 .

[0063] Using the coated electrode as the anode and a Ti plate of the same specifications as the cathode, the current density was controlled at 1 A / cm². 2 An accelerated service life test was conducted in a 1 mol / L H₂SO₄ solution. After 800 hours of electrolysis, the cell voltage rapidly increased, and the electrode completely failed. The accelerated service life of this electrode, converted to an actual service life of 320,000 hours, demonstrates long stability and lifespan, making it suitable for industrial applications.

[0064] Example 2

[0065] Other conditions were the same as in Example 1, except that pure Nb matrix was encapsulated in solid boron powder and solid carbon powder. The solid boron powder had a particle size of 5 μm and the C / B ratio in the solid boron powder and solid carbon powder was 3:7. Argon gas was introduced into a tube furnace as a protective gas for heat treatment. The gas pressure was set to 3 kPa and the heating temperature was 800°C. After holding at this temperature for 4 hours, the furnace was cooled.

[0066] The surface roughness of the gradient transition layer of the obtained Nb-B compound is high, and there are obvious pores near the transition layer. The Nb-C compound is distributed in a diffuse form, and the C / B atomic ratio in the transition layer is 1.17%.

[0067] Using the coating material as the anode and a Ti plate of the same specifications as the cathode, the current density was controlled at 60 mA / cm². 2 A degradation experiment was conducted using simulated dye wastewater (500 mL of 0.1 g / L RB-19 solution, 0.5 M sodium sulfate) as the research object. After 4 hours of degradation, the wastewater changed from deep blue to colorless and clear, with a color removal rate of 99% and an energy consumption of 1.5 kWh / m³ for color removal. 3 ·A -1 .

[0068] Using the coated electrode as the anode and a Ti plate of the same specifications as the cathode, the current density was controlled at 1 A / cm². 2 An accelerated service life test was conducted in a 1 mol / L H₂SO₄ solution. After 700 hours of electrolysis, the cell voltage rapidly increased, and the electrode completely failed. The accelerated service life of this electrode, converted to an actual service life of 280,000 hours, demonstrates long stability and lifespan, making it suitable for industrial applications.

[0069] Example 3

[0070] In the magnetron sputtering, dual-target magnetron sputtering was performed using both an Nb target and an NbC target. The distance between the niobium substrate and the target was 5 cm, the working pressure was 0.5 Pa, the sputtering power of the NbC target was controlled at 50 W, the sputtering power of the Nb target was 150 W, and the sputtering time was 60 min. The sputtering atmosphere was a mixture of diborane and argon, with an initial borane concentration of 5%, which was increased by 10% every 10 min until the borane concentration reached 30% (see [link to relevant documentation]). Figure 1 ).

[0071] The resulting Nb-B compound gradient transition layer has a dense structure, while the NbC compound is distributed in a diffuse form, with a C / B atomic ratio of 1.72% in the transition layer.

[0072] After the magnetron sputtering process is completed, the niobium substrate containing the Nb-B compound gradient transition layer is subjected to low-temperature heat treatment. The temperature of the low-temperature heat treatment is 600℃, the time of the low-temperature heat treatment is 2h, the gas pressure is 10kPa, and the atmosphere of the low-temperature heat treatment is argon.

[0073] Then, an Nb substrate with an Nb-B compound gradient transition layer on its surface is placed in a suspension containing a mixture of nanocrystalline and / or microcrystalline diamond particles; ultrasonic treatment is performed, followed by drying; a substrate material with nanocrystalline and / or microcrystalline diamond adsorbed on its surface is obtained; the mass fraction of the diamond mixture particles in the suspension containing nanocrystalline and / or microcrystalline diamond particles is 0.03%; the particle size of the diamond mixture particles is 5-10 nm, and the purity is ≥97%; the ultrasonic treatment time is 30 min.

[0074] A substrate material with surface-adsorbed nanocrystalline and / or microcrystalline diamond is placed in a chemical vapor deposition furnace, and hydrogen, boron-containing gas, and carbon-containing gas are introduced. First, the percentage of boron-containing gas in the total gas flow rate in the furnace is controlled to be 0.0884% to obtain a boron-doped diamond bottom layer. Then, the boron doping concentration is reduced in a linear decreasing manner until the percentage of boron-containing gas in the total gas flow rate in the furnace is 0.0593% to obtain a boron-doped diamond intermediate layer. Then, the percentage of boron-containing gas in the total gas flow rate in the furnace is controlled to be 0.03968% to obtain a boron-doped diamond top layer; thus, a gradient boron-doped diamond semiconductor layer is obtained.

[0075] The carbon-containing gas accounts for 2.5% of the total gas mass flow rate in the furnace, the boron-doped diamond deposition temperature is 800℃, and the gas pressure is 10. 3 Pa, deposition time was 15h.

[0076] Using the coating material as the anode and a Ti plate of the same specifications as the cathode, the current density was controlled at 60 mA / cm². 2 A degradation experiment was conducted using simulated dye wastewater (500 mL of 0.1 g / L RB-19 solution, 0.5 M sodium sulfate) as the research object. After 4 hours of degradation, the wastewater changed from deep blue to colorless and clear, with a color removal rate of 99% and an energy consumption of 1.6 kWh / m³ for color removal. 3 ·A -1 .

[0077] Using the coated electrode as the anode and a Ti plate of the same specifications as the cathode, the current density was controlled at 1 A / cm². 2 An accelerated service life test was conducted in a 1 mol / L H₂SO₄ solution. After 850 hours of electrolysis, the cell voltage rapidly increased, and the electrode completely failed. The accelerated service life of this electrode, converted to an actual service life of 340,000 hours, demonstrates long stability and lifespan, making it suitable for industrial applications.

[0078] Comparative Example 1

[0079] All other conditions were the same as in Example 1, except that no Nb-B compound gradient transition layer was prepared on the substrate. During the chemical vapor deposition process, an NbC intermediate layer was formed between the coating and the substrate.

[0080] Using the coating material as the anode and a Ti plate of the same specifications as the cathode, the current density was controlled at 60 mA / cm². 2 A degradation experiment was conducted using simulated dye wastewater (500 mL of 0.1 g / L RB-19 solution, 0.5 M sodium sulfate) as the research object. After 4 hours of degradation, the wastewater changed from deep blue to colorless and clear, with a color removal rate of 99% and an energy consumption of 2.1 kWh / m³ for color removal. 3 ·A -1 .

[0081] Using the coated electrode as the anode and a Ti plate of the same specifications as the cathode, the current density was controlled at 1 A / cm². 2 An accelerated service life test was conducted in a 1 mol / L H₂SO₄ solution. After 500 hours of electrolysis, the cell voltage rapidly increased, and the electrode completely failed. The accelerated service life of this electrode, converted to an actual service life of 200,000 hours, is far less than that of Example 1.

[0082] Comparative Example 2

[0083] All other conditions were the same as in Example 1, except that the Nb-B compound gradient transition layer was not doped with Nb-C compound. The resulting Nb-B compound gradient transition layer had a dense structure and a relatively smooth surface.

[0084] Using the coating material as the anode and a Ti plate of the same specifications as the cathode, the current density was controlled at 60 mA / cm². 2 A degradation experiment was conducted using simulated dye wastewater (500 mL of 0.1 g / L RB-19 solution, 0.5 M sodium sulfate) as the research object. After 4 hours of degradation, the wastewater changed from deep blue to colorless and clear, with a color removal rate of 99% and an energy consumption of 1.9 kWh / m³ for color removal. 3 ·A -1 .

[0085] Using the coated electrode as the anode and a Ti plate of the same specifications as the cathode, the current density was controlled at 1 A / cm². 2 An accelerated service life test was conducted in a 1 mol / L H₂SO₄ solution. After 600 hours of electrolysis, the cell voltage rapidly increased, and the electrode completely failed. The accelerated service life of this electrode, converted to an actual service life of 240,000 hours, is far less than that of Example 1.

[0086] Comparative Example 3

[0087] All other conditions were the same as in Example 1, except that pure Nb matrix was encapsulated in solid boron powder and solid carbon powder. The solid boron powder had a particle size of 5 μm and the C / B ratio of the solid boron powder and solid carbon powder was 7:3. Argon gas was introduced into a tube furnace as a protective gas for heat treatment. The gas pressure was set to 3 kPa and the heating temperature was 800°C. After holding at this temperature for 4 hours, the furnace was cooled.

[0088] The resulting Nb-B compound gradient transition layer was significantly thinner, making it impossible to form a continuous Nb-B compound. The C / B atom ratio in the transition layer was 6.99%. This is because the excess active C atoms inhibited the borylation reaction.

[0089] Using the coating material as the anode and a Ti plate of the same specifications as the cathode, the current density was controlled at 60 mA / cm². 2 A degradation experiment was conducted using simulated dye wastewater (500 mL of 0.1 g / L RB-19 solution, 0.5 M sodium sulfate) as the research object. After 4 hours of degradation, the wastewater changed from deep blue to colorless and clear, with a color removal rate of 99% and an energy consumption of 2.0 kWh / m³ for color removal. 3 ·A -1 .

[0090] Using the coated electrode as the anode and a Ti plate of the same specifications as the cathode, the current density was controlled at 1 A / cm². 2 An accelerated service life test was conducted in a 1 mol / L H₂SO₄ solution. After 550 hours of electrolysis, the cell voltage rapidly increased, and the electrode completely failed. The accelerated service life of this electrode, converted to an actual service life of 220,000 hours, is far less than that of Example 1.

[0091] Comparative Example 4

[0092] All other conditions were the same as in Example 1, except that pure Nb matrix was encapsulated in solid boron powder and solid carbon powder. The solid boron powder had a particle size of 5 μm and the C / B ratio of the solid boron powder and solid carbon powder was 3:7. Argon gas was introduced into a tube furnace as a protective gas for heat treatment. The gas pressure was set to 3 kPa and the heating temperature was 1600°C. After holding at this temperature for 4 hours, the furnace was cooled.

[0093] The resulting Nb-B compound gradient transition layer contains almost no continuous Nb-B compounds. At high temperatures, elemental boron and elemental carbon preferentially react, and a loose B4C structure is attached to the surface of the transition layer. Gradient boron-doped diamond semiconductor layers are deposited directly on this structure, and the coating is directly detached.

Claims

1. A niobium-based boron-doped diamond semiconductor composite coating material, characterized in that: The niobium-based boron-doped diamond semiconductor composite coating material comprises a niobium substrate, an Nb-B compound gradient transition layer disposed on the surface of the niobium substrate, and a gradient boron-doped diamond semiconductor layer disposed on the surface of the Nb-B compound gradient transition layer. The Nb-B compound gradient transition layer has a boron content gradient increasing from bottom to top; the gradient boron-doped diamond semiconductor layer has a boron content gradient decreasing from bottom to top. The Nb-B compound gradient transition layer contains Nb₂C phase and / or NbC phase; the Nb₂C phase and / or NbC phase are dispersedly distributed in the Nb-B compound gradient transition layer; and the atomic ratio of C in the Nb-B compound gradient transition layer is 1% to 5%.

2. The niobium-based boron-doped diamond semiconductor composite coating material according to claim 1, characterized in that: The top of the gradient transition layer of the Nb-B compound is a single phase of Nb3B2, NbB, Nb5B6, Nb3B4, or NbB2, or a composite phase consisting of two or more of them.

3. The niobium-based boron-doped diamond semiconductor composite coating material according to claim 1, characterized in that: The thickness of the Nb-B compound gradient transition layer is 5-100 μm.

4. A niobium-based boron-doped diamond semiconductor composite coating material according to any one of claims 1-3, characterized in that: The gradient boron-doped diamond semiconductor layer, from bottom to top, includes a boron-doped diamond bottom layer, a boron-doped diamond intermediate layer, and a boron-doped diamond top layer. The boron-doped diamond bottom layer has a uniform boron content, with a B / C ratio of 46,666-60,000 ppm on an atomic ratio basis. The boron-doped diamond top layer has a uniform boron content, with a B / C ratio of 26,666-40,000 ppm on an atomic ratio basis. The boron content in the boron-doped diamond intermediate layer decreases linearly from bottom to top, with the boron content in the boron-doped diamond bottom layer being the maximum value and decreasing linearly to the boron content in the boron-doped diamond top layer. The gradient boron-doped diamond semiconductor layer is uniformly deposited on the surface of the Nb-B compound gradient transition layer by chemical vapor deposition, and the thickness of the gradient boron-doped diamond semiconductor layer is 1μm-2mm.

5. A niobium-based boron-doped diamond semiconductor composite coating material according to any one of claims 1-3, characterized in that: The niobium in the niobium matrix is ​​selected from pure Nb or Nb alloy; The niobium matrix has a structure that is one-dimensional, two-dimensional, or three-dimensional. The niobium substrate surface has a micro / nano structure.

6. A method for preparing a niobium-based boron-doped diamond semiconductor composite coating material according to any one of claims 1-5, characterized in that: A gradient transition layer of Nb-B compound containing Nb2C phase and / or NbC phase is obtained by simultaneously performing boron doping and carbon doping on the surface of a niobium substrate. Then, a gradient boron-doped diamond semiconductor layer is grown on the niobium substrate containing the Nb-B compound gradient transition layer by chemical vapor deposition to obtain a niobium-based boron-doped diamond semiconductor composite coating material.

7. The method for preparing a niobium-based boron-doped diamond semiconductor composite coating material according to claim 6, characterized in that: The process of obtaining a gradient transition layer of Nb-B compound containing Nb2C phase and / or NbC phase on the surface of a niobium substrate by magnetron sputtering is as follows: the niobium substrate is placed in a sputtering atmosphere for magnetron sputtering; in the magnetron sputtering, a dual-target magnetron sputtering is performed using one of an Nb target or an NbB target and an NbC target, the distance between the niobium substrate and the target is 5-12 cm, the working gas pressure is 0.2-3 Pa, the co-sputtering time is 5-100 min, the sputtering power of the NbC target is 50-100 W, the sputtering power of the NbB target is 120-200 W, and the sputtering power of the Nb target is 120-200 W; the sputtering atmosphere consists of a boron-containing gas and a protective gas. After the magnetron sputtering process is completed, the niobium substrate containing the Nb-B compound gradient transition layer is subjected to low-temperature heat treatment. The temperature of the low-temperature heat treatment is 500-1100℃, the time is 1-6h, the pressure is 8-25kPa, and the atmosphere of the low-temperature heat treatment is an inactive atmosphere.

8. The method for preparing a niobium-based boron-doped diamond semiconductor composite coating material according to claim 6, characterized in that: The process of obtaining a gradient transition layer of Nb-B compound containing Nb2C phase and / or NbC phase on the surface of a niobium substrate by high-temperature heat treatment is as follows: the niobium substrate is placed in a B source and a C source and subjected to high-temperature heat treatment at a temperature of 800-1200℃ for 1-20 hours at a pressure of 2-10 kPa; the high-temperature heat treatment atmosphere is an inactive atmosphere. In the B source and the C source, the atomic ratio is C:B = 2-4:6-8.

9. The method for preparing a niobium-based boron-doped diamond semiconductor composite coating material according to claim 6, characterized in that: The process of growing a gradient boron-doped diamond semiconductor layer on a niobium substrate containing an Nb-B compound gradient transition layer via chemical vapor deposition is as follows: First, the niobium substrate containing the Nb-B compound gradient transition layer is placed in a suspension containing a mixture of nanocrystalline and / or microcrystalline diamond particles; ultrasonic treatment is performed, followed by drying; a niobium substrate with surface-adsorbed nanocrystalline and / or microcrystalline diamond is obtained. Then, the niobium substrate with surface-adsorbed nanocrystalline and / or microcrystalline diamond is placed in a chemical vapor deposition furnace, and hydrogen, boron-containing gas, and carbon-containing gas are introduced to perform chemical vapor deposition to grow a gradient boron-doped diamond semiconductor layer. The temperature of the chemical vapor deposition is 600-1000℃, and the gas pressure is 10. 3 -10 4 Pa, time is 3-20h; In the suspension containing nanocrystalline and / or microcrystalline diamond mixed particles, the mass fraction of diamond mixed particles is 0.01%-0.05%; the particle size of the diamond mixed particles is 5-30 nm, and the purity is ≥97%; the ultrasonic treatment time is 5-30 min. During the chemical vapor deposition process, the percentage of carbon-containing gas in the total gas mass flow rate within the furnace is 0.5-10.0%. During the chemical vapor deposition process, the percentage of boron-containing gas in the total mass flow rate of the furnace is first controlled to be 0.069%-0.0884% to obtain a boron-doped diamond underlayer. Then, the boron doping concentration is reduced linearly until the percentage of boron-containing gas in the total mass flow rate of the furnace is 0.03968%-0.0593% to obtain a boron-doped diamond transition layer. Then, the percentage of boron-containing gas in the total mass flow rate of the furnace is controlled to be 0.03968%-0.0593% again to obtain a boron-doped diamond outer layer; thus, a gradient boron-doped diamond semiconductor layer is obtained.

10. The application of the niobium-based boron-doped diamond semiconductor composite coating material according to any one of claims 1-5, characterized in that: The semiconductor composite coating material is applied to at least one of semiconductor devices, electrochemical oxidation, electrochemical synthesis, and electrochemical analysis.

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