A silicon carbide / boron-doped diamond semiconductor composite coating material, its preparation method and application
By setting gradient boron-doped SiC and diamond semiconductor layers on a silicon carbide substrate, the conductivity and bonding problems of silicon carbide/BDD composite coating materials during the electrochemical oxidation process were solved, achieving efficient current conduction and stable film-substrate bonding.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HU-NAN NEW FRONTIER SCI & TECH LTD
- Filing Date
- 2023-12-28
- Publication Date
- 2026-05-26
AI Technical Summary
Existing silicon carbide/BDD composite coating materials exhibit poor substrate conductivity during electrochemical oxidation, resulting in significant energy loss. Furthermore, their insufficient film-substrate bonding performance negatively impacts service stability.
A gradient boron-doped SiC semiconductor transition layer and a gradient boron-doped diamond semiconductor layer are formed on the surface of a silicon carbide substrate. By controlling the boron content gradient and forming grooves through surface etching, the conductivity of the substrate and the adhesion between the film and the substrate are improved.
It improves the current efficiency in the electrochemical oxidation process, reduces energy loss, and enhances the service stability and film-substrate bonding performance of the composite coating material.
Abstract
Description
Technical Field
[0001] This invention relates to a silicon carbide / 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] Silicon carbide (SiC) is a typical material in third-generation semiconductors. Due to its good thermal stability, large bandgap, and high thermal conductivity, it is widely used in optoelectronic devices, high-frequency high-power, and high-temperature electronic devices. Furthermore, SiC's coefficient of thermal expansion is similar to that of diamond, it is chemically stable, inexpensive, and its ceramic substrate can be molded according to specific applications, making it highly promising for the preparation of BDD coating materials. In practical applications, the main failure mode of composite coating materials is coating peeling. Improving the service life of composite coating materials hinges on enhancing the film-substrate adhesion. However, SiC ceramics have poor electrical conductivity, preventing rapid electron transport through the substrate in BDD composite coating materials. Electron conduction relies solely on the thin coating layer, leading to significant energy loss during electrochemical oxidation and hindering engineering applications. Summary of the Invention
[0004] To address the shortcomings of existing technologies, the first objective of this invention is to provide a silicon carbide / boron-doped diamond semiconductor composite coating material that combines high bonding strength and high stability.
[0005] The second objective of this invention is to provide a method for preparing a silicon carbide / boron-doped diamond semiconductor composite coating material.
[0006] The third objective of this invention is to provide an application of a silicon carbide / boron-doped diamond semiconductor composite coating material.
[0007] To achieve the above objectives, the present invention adopts the following technical solution:
[0008] This invention discloses a silicon carbide / boron-doped diamond semiconductor composite coating material, comprising a silicon carbide substrate, a gradient boron-doped SiC semiconductor transition layer disposed on the surface of the silicon carbide substrate, and a gradient boron-doped diamond semiconductor layer disposed on the surface of the gradient boron-doped SiC semiconductor transition layer. In the gradient boron-doped SiC semiconductor transition layer, the boron content decreases from top to bottom; in the gradient boron-doped diamond semiconductor layer, the boron content decreases from bottom to top.
[0009] In this invention, boron doping of SiC semiconductors yields p-type semiconductors, which helps improve the substrate conductivity, thereby increasing the current efficiency during electrochemical oxidation. Simultaneously, it further enhances the chemical bonding between the SiC substrate and the BDD coating, improving the service stability of the BDD composite coating material. The lower boron content in the bottom transition layer helps maintain the good chemical stability and thermal conductivity of the silicon carbide substrate; the higher boron content in the top layer enhances the chemical bonding between the transition layer and the BDD coating, improving the substrate conductivity; the gradual decrease in boron content in the middle layer helps alleviate the hardness gradient between the substrate and the transition layer, ensuring good bonding between the transition layer and the substrate.
[0010] This invention discloses a silicon carbide / boron-doped diamond semiconductor composite coating material, wherein the surface of the gradient boron-doped SiC semiconductor transition layer contains several grooves, the depth of which is 0.5–3 μm. The grooves are obtained by plasma etching of the gradient boron-doped SiC semiconductor transition layer.
[0011] In this invention, etching the substrate surface containing the gradient boron-doped SiC semiconductor transition layer helps to increase the specific surface area and further improve the current density at the film-substrate bonding interface; at the same time, increasing the surface roughness of the substrate helps to increase the diamond nucleation rate, further improve the film-substrate bonding force, and enhance the material's service performance.
[0012] However, the inventors discovered that plasma etching is required, and the depth of the grooves must be controlled so that the grooves only achieve optimal performance on the surface of the gradient boron-doped SiC semiconductor transition layer.
[0013] This invention discloses a silicon carbide / boron-doped diamond semiconductor composite coating material, wherein the total amount of boron atoms in the top of the gradient boron-doped SiC semiconductor transition layer is 10. 16 ~10 19 cm -3 The proportion of boron atoms directly doped between SiC lattices is 20%–30%, while the proportion of boron atoms in B4C is 70%–80%.
[0014] The inventors discovered that by controlling the total amount of boron atoms within the range of this invention, the final semiconductor composite coating material exhibits optimal performance. If the boron doping level is high, a higher thermal diffusion temperature is required, which can lead to the oxidation of SiC to form SiO2 residues, and the poor conductivity of SiO2 ultimately affects the electrical properties of the substrate. If the boron doping level is too low, it cannot effectively improve the conductivity of the substrate and the film-substrate bonding performance. Furthermore, by controlling the proportion of boron atoms directly doped into SiC within the range of this invention, the overall performance of the resulting silicon carbide / boron-doped diamond semiconductor composite coating material is also better.
[0015] This invention discloses a novel silicon carbide / boron-doped diamond semiconductor composite coating material, wherein the thickness of the gradient boron-doped SiC semiconductor transition layer is 0.5–5 μm.
[0016] This invention discloses a silicon carbide / boron-doped diamond composite coating material. The gradient boron-doped diamond layer, from bottom to top, comprises 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. 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. 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 and decreasing linearly to the boron content in the boron-doped diamond top layer.
[0017] In this invention, the boron-doped diamond bottom layer adopts a uniform boron content to maximize the conductivity of the coating, enhance the chemical bonding force between the BDD coating and the gradient boron-doped SiC transition layer, and further improve the film-substrate bonding performance. The boron-doped diamond top layer also adopts a uniform boron content to maximize the corrosion resistance of the top layer, effectively reduce the coating peeling rate, and improve the service life of the composite coating material. 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 force.
[0018] This invention discloses a silicon carbide / boron-doped diamond semiconductor composite coating material, wherein the gradient boron-doped diamond semiconductor layer is uniformly deposited on the surface of the gradient boron-doped SiC semiconductor transition layer by chemical vapor deposition, and the thickness of the gradient boron-doped diamond semiconductor layer is 1μm-2mm.
[0019] Specifically, a boron-doped diamond underlayer, a boron-doped diamond intermediate layer, and a boron-doped diamond top layer are deposited first on the surface of the gradient boron-doped SiC semiconductor transition layer, and finally a boron-doped diamond top layer is deposited. In this invention, the boron-doped diamond underlayer, boron-doped diamond intermediate layer, and boron-doped diamond top layer all have the same thickness range.
[0020] The present invention discloses a silicon carbide / boron-doped diamond semiconductor composite coating material, wherein the silicon carbide substrate is at least one of amorphous, monocrystalline, and polycrystalline, wherein the crystal form of monocrystalline or polycrystalline is selected from at least one of 3C, 4H, 6H, and 15R.
[0021] In this invention, both silicon carbide and diamond can be single crystals, polycrystalline, or a combination of single crystals and polycrystalline.
[0022] The present invention discloses a silicon carbide / boron-doped diamond semiconductor composite coating material, wherein the morphology of the silicon carbide substrate is selected from at least one of zero-dimensional, one-dimensional, two-dimensional to three-dimensional.
[0023] This invention discloses a method for preparing a silicon carbide / boron-doped diamond semiconductor composite coating material. A gradient boron-doped SiC semiconductor transition layer is obtained on the surface of a silicon carbide substrate through thermal diffusion treatment. Then, a gradient boron-doped diamond semiconductor layer is grown on the silicon carbide substrate containing the gradient boron-doped SiC semiconductor transition layer through chemical vapor deposition to obtain a silicon carbide / boron-doped diamond semiconductor composite coating material.
[0024] In a preferred embodiment, the thermal diffusion treatment process is as follows: immersing a silicon carbide substrate in a solution containing boron oxide powder, drying it to obtain a silicon carbide substrate coated with boron oxide powder, then heating the silicon carbide substrate to 200–650°C and holding it at that temperature for 20–50 min, then heating it to 1250–1400°C and holding it at that temperature for 45–90 min, and finally heating it to 1450–1650°C and holding it at that temperature for 30–60 min; the thermal diffusion treatment atmosphere is at least one of air, oxygen, and nitrogen.
[0025] The inventors discovered that by using boron oxide powder as the boron source and employing the aforementioned process parameters, the content and distribution of boron at the top of the gradient boron-doped SiC semiconductor transition layer can be controlled within the range of this invention, ultimately achieving optimal performance. Since the penetration of boron during thermal diffusion proceeds from the surface inwards, a gradient boron-doped SiC semiconductor transition layer can be formed, with the boron content increasing gradually from bottom to top within the transition layer.
[0026] However, the inventors discovered that the temperature of thermal diffusion needs to be controlled. If the thermal diffusion temperature is too high or too low, the proportion of B atoms directly doped between SiC lattices will decrease, and the decrease in the proportion of B atoms directly doped between SiC lattices will lead to a decrease in the overall performance of the semiconductor coating material.
[0027] Further preferably, the purity of the boron oxide powder is 99.99%.
[0028] In a preferred embodiment, after thermal diffusion treatment, the thermally diffused silicon carbide substrate is sequentially subjected to chemical cleaning and mechanical polishing treatment.
[0029] In a further preferred embodiment, the chemical cleaning process involves cleaning the surface of the thermally diffused silicon carbide substrate using a BOE solution or an HF solution.
[0030] In a further preferred embodiment, the mechanical polishing process involves heating the chemically cleaned silicon carbide substrate to 50–80°C, then coating it with paraffin wax. The paraffin-coated silicon carbide substrate is then symmetrically placed onto the surface of the sample block to ensure uniformity of the polishing thickness in different areas of the surface, followed by mechanical polishing. The substrate is then removed, cooled, and the paraffin wax is removed for cleaning. The polishing fluid has a composition of water:alumina = (8–10):1; the polishing fluid rotation speed is 80–100 r / min; and the mechanical polishing time is 60–120 min.
[0031] Secondary cleaning processes, including chemical cleaning and mechanical polishing, can remove residual vitrified boron oxide from the transition layer surface, facilitating subsequent deposition of the BDD semiconductor coating.
[0032] In this invention, the method for preparing the gradient boron-doped SiC semiconductor transition layer is not limited to the thermal diffusion method. As long as the thickness and composition requirements of the transition layer can be met, one of the existing technologies, such as PECVD or ion implantation, can be used.
[0033] In a preferred embodiment, the silicon carbide substrate containing a gradient boron-doped SiC semiconductor transition layer is first subjected to plasma etching, and then a gradient boron-doped diamond semiconductor layer is grown by chemical vapor deposition.
[0034] In a further preferred embodiment, the plasma etching atmosphere includes an etching gas, an auxiliary gas, and a diluting gas. The etching gas is selected from one of SF6, CF4, CHF3, NF3, and Cl2, preferably SF6. The auxiliary gas is selected from one of HBr, O2, and Ar, preferably O2. The diluting gas is selected from one of He, Ne, and N2. The auxiliary gas accounts for 1-20% of the total gas flow rate, preferably 1-8.3%, and the diluting gas accounts for 15%-30% of the total gas flow rate, preferably 20%-30%. During the etching process, the cavity pressure is 4-10 Pa, the RF power adjustment range is 200-400 W, and the process time is 50-600 s.
[0035] In this invention, the etching quality and etching rate of the SiC substrate gradually increase with the extension of etching time. However, if the etching time is higher than this range, the etching depth will be too deep, exposing the SiC substrate at the bottom of the transition layer, which will not effectively improve the chemical bonding force and conductivity of the film-substrate interface. If the etching time is too short, the etching depth will be insufficient, the surface roughness of the substrate will be low, and the etching effect will be insignificant.
[0036] In this invention, the plasma etching rate of SiC first increases and then decreases with increasing auxiliary gas concentration. When the auxiliary gas concentration is 1-20%, it can effectively promote the chemical reaction between the etching gas and the SiC substrate, thereby increasing the etching reaction rate. Excessive auxiliary gas concentration will result in an insufficient plasma concentration in the etching atmosphere, affecting the etching effect.
[0037] In this invention, the etching gas is used to etch the SiC substrate, and the diluent gas is used to dilute the concentration of the plasma excited by the etching gas. A higher proportion of the diluent gas in the etching atmosphere results in a greater difference in etching rate between the edge and center of the etched structure. This leads to a pit structure with depth gradually decreasing from the bottom center to the edge, further improving substrate roughness and providing more nucleation sites for the deposition of gradient boron-doped diamond semiconductor layers, thereby further improving the film-substrate bonding performance and service stability. However, excessively high diluent gas concentration will result in an excessively low plasma concentration in the etching atmosphere, severely affecting the etching effect.
[0038] A preferred embodiment of the process for growing a graded boron-doped diamond semiconductor layer on a silicon carbide substrate containing a graded boron-doped SiC semiconductor transition layer via chemical vapor deposition is as follows: First, the silicon carbide substrate containing the graded boron-doped SiC semiconductor 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 silicon carbide substrate with surface-adsorbed nanocrystalline and / or microcrystalline diamond is obtained. Then, the silicon carbide 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 graded 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.
[0039] 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.
[0040] 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%.
[0041] 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.
[0042] This invention also provides an application of a silicon carbide / boron-doped diamond semiconductor composite coating material, which is used in at least one of novel semiconductor devices, electrochemical oxidation, electrochemical synthesis, and electrochemical analysis.
[0043] Beneficial effects
[0044] This invention addresses the problem of poor substrate conductivity in silicon carbide / BDD semiconductor composite coatings during electrochemical oxidation. It proposes a method where a gradient boron-doped SiC semiconductor transition layer is formed on the surface of the silicon carbide substrate, followed by a gradient boron-doped diamond semiconductor layer. This creates a SiC-gradient boron-doped SiC semiconductor transition layer-gradient boron-doped diamond semiconductor composite coating material configuration. This improves substrate conductivity while further enhancing the film-substrate bonding performance and service stability of the silicon carbide / BDD semiconductor composite coating material, reducing the risk of material peeling during the chemical vapor deposition cooling stage and subsequent service stages. Detailed Implementation
[0045] Example 1
[0046] 99.99% pure boron oxide powder was dissolved in anhydrous ethanol, placed in a silicon carbide matrix, and heated and dried until the solvent was dry. The sample was then placed in a tube annealing furnace for step heat treatment. The heat treatment atmosphere was nitrogen. The temperature was first raised to 200°C and held for 30 min, then raised to 1250°C and held for 60 min, and finally raised to 1450°C and held for 30 min.
[0047] After thermal diffusion, the transition layer surface undergoes a secondary cleaning process, which includes chemical cleaning and mechanical polishing. The chemical cleaning process involves using BOE solution to clean the sample surface. The mechanical polishing process involves placing the sample block on a heated platform and heating it to 60°C, uniformly coating it with paraffin wax, and then symmetrically placing the sample block on the surface to ensure uniformity of the polishing thickness in different areas. Mechanical polishing is then performed. The sample block is then removed, cooled, and the paraffin wax is removed for cleaning. The polishing solution has a water:alumina ratio of 10:1, a polishing speed of 100 r / min, and a mechanical polishing time of 60 min.
[0048] The thickness of the gradient boron-doped SiC semiconductor transition layer is 2.98 μm, and the total amount of B atoms at the top of the transition layer is 2 × 10⁻⁶. 18 cm -3 The proportion of B atoms directly doped in SiC is 23.1%, while the proportion of B atoms in B4C is 76.9%.
[0049] Then, a silicon carbide substrate with a gradient boron-doped SiC semiconductor 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 0.02%; the particle size of the diamond mixture particles is 5-10 nm, and the purity is ≥97%; the ultrasonic treatment time is 30 min.
[0050] A silicon carbide substrate with surface-adsorbed nanocrystalline and / or microcrystalline diamond is placed in a chemical vapor deposition furnace. Hydrogen, boron-containing gas, and carbon-containing gas are introduced. First, the percentage of boron-containing gas in the furnace mass flow rate is controlled to be 0.0884% to obtain a boron-doped diamond bottom layer. Then, the boron doping concentration is reduced linearly until the percentage of boron-containing gas in the furnace mass flow rate is 0.0593% to obtain a boron-doped diamond intermediate layer. Then, the percentage of boron-containing gas in the furnace mass flow rate is controlled to be 0.03968% to deposit a boron-doped diamond top layer. This yields a gradient boron-doped diamond semiconductor layer.
[0051] The carbon-containing gas accounts for 3.0% 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 The deposition time was 10 h. The thickness of the gradient boron-doped diamond semiconductor layer was 10.24 μm.
[0052] 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. 2A 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 color removal rate of the solution reached 99%, the TOC removal rate was 49.8%, the energy consumption was 37.382 KJ, and the energy consumption per unit of TOC removal was 10.754 KJ / Kg. TOC .
[0053] Example 2
[0054] All other conditions were the same as in Example 1, except that the gradient boron-doped SiC semiconductor transition layer was subjected to plasma etching. The etching gas was SF6, the auxiliary gas was O2, and the diluent gas was N2. The auxiliary gas accounted for 5% of the total gas flow rate, and the diluent gas accounted for 15% of the total gas flow rate. During the etching process, the cavity pressure was 5 Pa, the radio frequency power was 300 W, and the process time was 300 s. A groove structure with a depth gradually decreasing from the bottom center to the edge was prepared, and the etching depth was 2 μm.
[0055] 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 color removal rate of the solution reached 99%, the TOC removal rate was 58.7%, the energy consumption was 30.297 KJ, and the energy consumption per unit of TOC removal was 8.716 KJ / Kg. TOC .
[0056] Example 3
[0057] All other conditions were the same as in Example 2, except that when performing plasma etching on the gradient boron-doped SiC semiconductor transition layer, the dilution gas accounted for 25% of the gas flow rate; a groove structure with a depth gradually decreasing from the bottom center to the edge was prepared, with an etching depth of 1.5 μm.
[0058] The coating material is used as the anode, and a Ti plate of the same specifications is used as the cathode, with a controlled current density of 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 color removal rate of the solution reached 99%, the TOC removal rate was 64.2%, the energy consumption was 25.462 KJ, and the energy consumption per unit of TOC removal was 7.325 KJ / Kg. TOC .
[0059] Comparative Example 1
[0060] All other conditions were the same as in Example 1, except that the heat treatment process during the preparation of graded boron-doped SiC was as follows: 99.99% pure boron oxide powder was dissolved in anhydrous ethanol, placed in a silicon carbide matrix, and heated and dried until the solvent was dry; the sample was placed in a tube annealing furnace for step heat treatment; the heat treatment atmosphere was nitrogen; then the temperature was first raised to 200°C and held for 30 min, then raised to 1600°C and held for 60 min, and finally raised to 1650°C and held for 30 min.
[0061] The surface of the gradient boron-doped SiC semiconductor transition layer sample exhibited obvious local oxidation.
[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 color removal rate of the solution reached 99%, while the TOC removal rate was only 37.2%, with an energy consumption as high as 50.291 KJ and a unit TOC removal energy consumption as high as 14.468 KJ / Kg. TOC .
[0063] Comparative Example 2
[0064] All other conditions were the same as in Example 2, except that the plasma etching time for the gradient boron-doped SiC semiconductor transition layer was 1000 s, resulting in an etching depth of 5 μm. The resulting composite coating material had a high surface roughness, and obvious pores appeared in the diamond coating.
[0065] 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 color removal rate of the solution reached 99%, while the TOC removal rate was only 49.2%, with an energy consumption of 44.866 KJ and a unit TOC removal energy consumption of 12.907 KJ / Kg. TOC .
[0066] Comparative Example 3
[0067] All other conditions were the same as in Example 2, except that no dilution gas was introduced during plasma etching of the gradient boron-doped SiC semiconductor transition layer. The sidewalls of the resulting groove structure were almost perpendicular to the bottom, and the etching depth was 3.5 μm.
[0068] 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. 2A 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 color removal rate of the solution reached 99%, while the TOC removal rate was only 52.3%, with an energy consumption of 41.769 KJ and a unit TOC removal energy consumption of 12.016 KJ / Kg. TOC .
Claims
1. A silicon carbide / boron-doped diamond semiconductor composite coating material, characterized in that: The silicon carbide / boron-doped diamond semiconductor composite coating material consists of a silicon carbide substrate, a gradient boron-doped SiC semiconductor transition layer disposed on the surface of the silicon carbide substrate, and a gradient boron-doped diamond semiconductor layer disposed on the surface of the gradient boron-doped SiC semiconductor transition layer. In the gradient boron-doped SiC semiconductor transition layer, the boron content decreases from top to bottom; in the gradient boron-doped diamond semiconductor layer, the boron content decreases from bottom to top. The thickness of the gradient boron-doped SiC semiconductor transition layer is 0.5~5μm, excluding 2.98μm.
2. The silicon carbide / boron-doped diamond semiconductor composite coating material according to claim 1, characterized in that: The surface of the gradient boron-doped SiC semiconductor transition layer contains several grooves, the depth of which is 0.5~3μm; At the top of the gradient boron-doped SiC semiconductor transition layer, the total amount of B atoms is 10. 16 ~10 19 cm -3 The proportion of B atoms directly doped between SiC lattices is 20-30%, while the proportion of B atoms in B4C is 70-80%.
3. The silicon carbide / boron-doped diamond semiconductor composite coating material according to claim 1, characterized in that: The gradient boron-doped diamond 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 gradient boron-doped SiC semiconductor transition layer by chemical vapor deposition, and the thickness of the gradient boron-doped diamond semiconductor layer is 1μm-2mm.
4. The silicon carbide / boron-doped diamond semiconductor composite coating material according to claim 1, characterized in that: The silicon carbide substrate is at least one of amorphous, monocrystalline, and polycrystalline, wherein the crystal form of monocrystalline or polycrystalline is selected from at least one of 3C, 4H, 6H, and 15R; The morphology of the silicon carbide substrate is selected from at least one of zero-dimensional, one-dimensional, two-dimensional to three-dimensional.
5. A method for preparing a silicon carbide / boron-doped diamond semiconductor composite coating material according to any one of claims 1-4, characterized in that: A gradient boron-doped SiC semiconductor transition layer is obtained on the surface of a silicon carbide substrate by thermal diffusion treatment. Then, a gradient boron-doped diamond semiconductor layer is grown on the silicon carbide substrate containing the gradient boron-doped SiC semiconductor transition layer by chemical vapor deposition to obtain a silicon carbide / boron-doped diamond semiconductor composite coating material.
6. The method for preparing a silicon carbide / boron-doped diamond semiconductor composite coating material according to claim 5, characterized in that: The thermal diffusion treatment process is as follows: the silicon carbide substrate is immersed in a solution containing boron oxide powder, dried, and a silicon carbide substrate coated with boron oxide powder is obtained. Then, the silicon carbide substrate is first heated to 200~650℃ and held for 20~50 min, then heated to 1250~1400℃ and held for 45~90 min, and finally heated to 1450~1650℃ and held for 30~60 min. The thermal diffusion treatment atmosphere is at least one of air, oxygen or nitrogen.
7. The method for preparing a silicon carbide / boron-doped diamond semiconductor composite coating material according to claim 5 or 6, characterized in that: After thermal diffusion treatment, the thermally diffused silicon carbide substrate is subjected to chemical cleaning and mechanical polishing treatment in sequence. The chemical cleaning process involves cleaning the surface of the thermally diffused silicon carbide substrate with BOE solution or HF solution. The mechanical polishing process involves heating a chemically cleaned silicon carbide substrate to 50-80°C, then coating it with paraffin wax. The paraffin-coated silicon carbide substrate is then symmetrically placed onto the surface of a sample block to ensure uniformity of the polishing thickness in different areas of the surface, followed by mechanical polishing. The sample block is then removed, cooled, and the paraffin wax is removed for cleaning. The polishing solution has a water:alumina ratio of 8-10:1, a polishing speed of 80-100 r / min, and a mechanical polishing time of 60-120 min.
8. The method for preparing a silicon carbide / boron-doped diamond semiconductor composite coating material according to claim 5 or 6, characterized in that: The silicon carbide substrate containing a gradient boron-doped SiC semiconductor transition layer is first etched by plasma etching, and then a gradient boron-doped diamond semiconductor layer is grown by chemical vapor deposition. The plasma etching atmosphere includes an etching gas, an auxiliary gas, and a dilution gas. The etching gas is selected from one of SF6, CF4, CHF3, NF3, and Cl2. The auxiliary gas is selected from one of HBr, O2, and Ar. The dilution gas is selected from one of He, Ne, and N2. The auxiliary gas accounts for 1-20% of the total gas flow rate, and the dilution gas accounts for 15%-30% of the total gas flow rate. During the etching process, the cavity pressure is 4-10 Pa, the RF power adjustment range is 200-400 W, and the process time is 50-600 s.
9. A method for preparing a silicon carbide / boron-doped diamond semiconductor composite coating material according to claim 5 or 6, characterized in that: The process of growing a graded boron-doped diamond semiconductor layer on a silicon carbide substrate containing a graded boron-doped SiC semiconductor transition layer via chemical vapor deposition is as follows: First, the silicon carbide substrate containing the graded boron-doped SiC semiconductor 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 silicon carbide substrate with surface-adsorbed nanocrystalline and / or microcrystalline diamond is obtained. Then, the silicon carbide 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 graded 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 silicon carbide / boron-doped diamond semiconductor composite coating material according to any one of claims 1-4, characterized in that: Semiconductor composite coating materials are used in at least one of novel semiconductor devices, electrochemical oxidation, electrochemical synthesis, and electrochemical analysis.