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

Abstract

The application discloses a preparation method and application of a zirconium-based boron-doped diamond semiconductor composite coating material, and the zirconium-based boron-doped diamond semiconductor composite coating material is composed of a zirconium base, a Zr-B compound gradient transition layer arranged on the surface of the zirconium base and a gradient boron-doped diamond semiconductor layer arranged on the surface of the Zr-B compound gradient transition layer; the Zr-B compound gradient transition layer has a gradient increase of boron content from bottom to top; and the gradient boron-doped diamond semiconductor layer has a gradient decrease of boron content from bottom to top. The composite coating material prepared by arranging the Zr-B compound gradient transition layer on the surface of the zirconium base and then arranging the gradient boron-doped diamond semiconductor layer on the surface of the transition layer has good film base combination performance and high stability.

Description

Technical Field

[0001] This invention relates to a zirconium-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] Zirconium and its alloys possess excellent corrosion and radiation resistance and a low neutron absorption cross section, making them suitable for use as core materials in nuclear reactors, such as fuel cladding and guide tubes. However, at high temperatures, zirconium reacts with water coolant and corrodes, releasing hydrogen gas. Under certain circumstances, the released hydrogen gas can be sufficient to trigger an explosion, potentially causing catastrophic consequences. Diamond, on the other hand, has the highest thermal conductivity in nature and a low atomic number, thus it does not absorb neutrons and affect nuclear reactions. Depositing diamond on the surface of Zr helps to efficiently transfer heat from the fuel rods to the cooling water, preventing direct contact between Zr and water at high temperatures.

[0004] However, the formation of carbides from Zr and C requires temperatures as high as 2000℃, making it difficult to form stable carbides at CVD deposition temperatures to improve the adhesion between the diamond coating and the substrate. Furthermore, the ZrO2 passivation layer formed by the reaction of Zr with oxygen at room temperature is difficult to reduce with hydrogen, and the ZrO2 residue at the coating interface also negatively impacts the film-substrate adhesion. In addition, Zr's coefficient of thermal expansion is approximately 5.7 times that of diamond. During the cooling process after high-temperature deposition to room temperature, the shrinkage of the substrate material is significantly greater than that of the diamond film, generating substantial thermal stress within the film and leading to coating detachment. Summary of the Invention

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

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

[0007] The third objective of this invention is to provide an application of a zirconium-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 zirconium-based boron-doped diamond semiconductor composite coating material, comprising a zirconium substrate, a Zr-B compound gradient transition layer disposed on the surface of the zirconium substrate, and a gradient boron-doped diamond semiconductor layer disposed on the surface of the Zr-B compound gradient transition layer. The boron content in the Zr-B compound gradient transition layer increases from bottom to top, while the boron content in the gradient boron-doped diamond semiconductor layer decreases from bottom to top.

[0010] This invention discloses a zirconium-based boron-doped diamond semiconductor composite coating material, wherein the Zr-B compound gradient transition layer is a composite phase of Zr and ZrB2, with the highest ZrB2 content at the top of the transition layer and the ZrB2 mass fraction ≥99.5%, and the boron content gradually decreases from the top to the bottom layer.

[0011] In this invention, during the preparation of the Zr-B compound gradient transition layer, ZrO2 on the substrate surface is reduced to ZrB2, which improves the adverse effects of ZrO2 on the film-substrate adhesion. ZrB2 has good high-temperature resistance, corrosion resistance, and radiation resistance, and its coefficient of thermal expansion is between that of diamond and zirconium, which can form a good transition between the zirconium substrate and the BDD coating. The lower boron content at the bottom of the transition layer helps to retain the good core application performance of the zirconium substrate; the higher boron content at the top enhances the chemical bonding force between the transition layer and the BDD coating, optimizes the interfacial bonding performance, and improves the overall thermal conductivity of the composite material; the intermediate layer adopts a gradient reduction in boron content, which helps to alleviate the gradient between the substrate and the transition layer, making the transition between coatings natural, less prone to separation and breakage, and improving the film-substrate adhesion.

[0012] This invention discloses a zirconium-based boron-doped diamond semiconductor composite coating material, wherein the thickness of the Zr-B compound gradient transition layer is 5-100 μm.

[0013] The inventors discovered that the optimal performance is achieved when the thickness of the transition layer is controlled within the aforementioned range. If the transition layer is too thin, the boron content in the transition layer will be low, which will not effectively improve the interfacial bonding performance with the gradient boron-doped diamond coating. If the transition layer is too thick, the transition layer will not bond firmly with the substrate, will be brittle, and will easily peel off.

[0014] This invention discloses a zirconium-based boron-doped diamond semiconductor composite coating material, wherein the boron content in the gradient boron-doped diamond semiconductor layer decreases from bottom to top; the initial transient B / C ratio is 20,000-40,000 ppm, and the cutoff transient B / C ratio is 1,000-15,000 ppm. The boron content at the bottom of the gradient boron-doped diamond layer is linearly reduced from the initial transient maximum to the cutoff transient minimum at the top of the gradient boron-doped diamond layer.

[0015] The present invention discloses a zirconium-based boron-doped diamond semiconductor composite coating material, wherein the thickness of the gradient boron-doped diamond semiconductor layer is 1μm-2mm.

[0016] In this invention, the boron content in boron-doped diamond decreases gradually from bottom to top, with the highest boron content at the bottom. This increases the diamond nucleation density, enhances the chemical bonding between the BDD coating and the Zr-B compound gradient transition layer, optimizes interfacial bonding performance, and improves the overall thermal conductivity of the composite material. The boron content is lowest at the top of the boron-doped diamond to improve the crystal quality of the diamond and maximize the thermal conductivity of the top layer. The gradient decrease also ensures a natural transition between coatings, reducing the likelihood of separation and breakage, and improving the film-substrate adhesion.

[0017] This invention relates to a zirconium-based boron-doped diamond semiconductor composite coating material, wherein the zirconium substrate is pure zirconium or a zirconium alloy.

[0018] This invention relates to a zirconium-based boron-doped diamond semiconductor composite coating material, wherein the zirconium substrate has a structure of zero-dimensional, one-dimensional, two-dimensional, or three-dimensional.

[0019] This invention discloses a zirconium-based boron-doped diamond semiconductor composite coating material, wherein the zirconium substrate surface has a micro-nano structure.

[0020] 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.

[0021] The present invention discloses a zirconium-based boron-doped diamond semiconductor composite coating material, wherein diamond particles are embedded in the zirconium matrix, and the particle size of the diamond particles is 250-500 μm.

[0022] In this invention, embedding diamond particles as a matrix can promote the homogeneous epitaxial growth of the BDD coating, improve the adhesion between the BDD coating and the metal substrate, optimize the interfacial bonding performance, and improve the overall thermal conductivity of the composite material. Furthermore, compared to BDD semiconductor coating materials on a flat metal substrate, embedding diamond particles in the matrix can expand the contact area between the matrix and the diamond, further improving the overall thermal conductivity of the composite material. More importantly, the inventors discovered that when an appropriate amount of diamond particles is introduced, the gradient boron-doped diamond semiconductor layer grown on the metal substrate exhibits the most obvious diamond phase and a preferred growth trend of the (111) crystal plane, which further improves the performance of the semiconductor composite coating material.

[0023] In this invention, the particle size of the embedded diamond needs to be effectively controlled. If it is not within the scope of this invention, it will not only fail to be effectively embedded in the metal substrate, but the final composite material will also have poor performance.

[0024] In a further preferred embodiment, the diamond particles are distributed at a density of 5% to 60% on the zirconium matrix.

[0025] If the diamond particle density is too low, it cannot provide enough nucleation sites for the homogeneous growth of BDD, and cannot effectively improve the diamond growth quality and film-matrix bonding performance; if the particle density is too high, the particles will squeeze each other, affecting the bonding force between the particles and the matrix, thereby further affecting the film-matrix bonding performance.

[0026] In a further preferred embodiment, the diamond particles are embedded to a depth of 100–350 μm in the zirconium matrix.

[0027] The optimal performance is achieved by controlling the embedding depth of diamond particles in the zirconium matrix within the aforementioned range. If the embedding depth is too shallow, the diamond particles will not be effectively embedded in the zirconium matrix, which may cause a large number of particles to fall off. The low strength between the diamond particles and the matrix can also easily cause the BDD film to collapse. If the embedding depth is too deep, the area of ​​diamond particles exposed on the matrix will be small, which will not provide enough nucleation sites for the homogeneous growth of BDD.

[0028] In a further preferred embodiment, the diamond particles are embedded in a zirconium matrix.

[0029] The inventors discovered that by embedding diamond particles onto a zirconium matrix, most of the diamond particles are embedded on the surface of the zirconium matrix; a small portion of the diamond particles detach from the surface of the metal matrix, leaving pits on the metal matrix. Both the protruding diamond particles and the pits can increase the specific surface area of ​​the metal substrate and effectively increase the nucleation sites during subsequent chemical vapor deposition of diamond, which is conducive to the formation of a dense and uniform diamond film with a large specific surface area, thereby enhancing the overall performance of the composite material.

[0030] In a further preferred embodiment, the diamond particles are selected from pure diamond particles or boron-doped diamond particles, preferably boron-doped diamond particles.

[0031] This invention discloses a method for preparing a zirconium-based boron-doped diamond semiconductor composite coating material. A Zr-B compound gradient transition layer is prepared on the surface of a zirconium substrate. Then, a gradient boron-doped diamond semiconductor layer is grown on the zirconium substrate containing the Zr-B compound gradient transition layer by chemical vapor deposition to obtain a zirconium-based boron-doped diamond semiconductor composite coating material.

[0032] In a preferred embodiment, diamond particles are first embedded in a zirconium matrix to obtain a zirconium matrix inlaid with diamond particles, and then a Zr-B compound gradient transition layer is prepared on the surface of the zirconium matrix inlaid with diamond particles.

[0033] In actual operation, diamond particles are laid flat on the surface of zirconium matrix according to the designed distribution density of embedded diamond particles, and then the diamond particles are embedded in zirconium matrix by mechanical pressing using a powder pressing machine.

[0034] In a further preferred embodiment, the pressing pressure is 60-100 kN. By controlling the pressure within the above range, the final pressing depth can be effectively controlled to be 100-350 μm.

[0035] In this invention, the preparation method of the Zr-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.

[0036] In a preferred embodiment, a Zr-B compound gradient transition layer is prepared on the surface of a zirconium substrate by magnetron sputtering or high-temperature heat treatment.

[0037] 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 Zr-B compound can be formed, in which the boron content increases from bottom to top. When using a magnetron sputtering method, the boron content in the Zr-B compound gradient transition layer can be adjusted by the sputtering power and the proportion of boron-containing atmosphere.

[0038] In a further preferred embodiment, when preparing the Zr-B compound gradient transition layer using magnetron sputtering, a Zr target with a purity ≥99.99% is used, the distance between the zirconium substrate and the target is 5-12 cm, the working pressure is 0.2-3 Pa, the sputtering power is 40-200 W, and the sputtering time is 5-100 min; the sputtering atmosphere is a B-containing atmosphere, preferably borane.

[0039] In a further preferred embodiment, after the magnetron sputtering process is completed, the zirconium substrate containing the Zr-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.

[0040] More preferably, the inactive atmosphere is selected from at least one of hydrogen, argon, and helium.

[0041] The inventors discovered that after magnetron sputtering, the zirconium substrate containing a Zr-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.

[0042] In a further preferred embodiment, when preparing the Zr-B compound gradient transition layer by high-temperature heat treatment, the zirconium substrate is wrapped with boron-containing powder and then subjected to high-temperature heat treatment under vacuum or a protective atmosphere. The temperature of the high-temperature heat treatment is 1200-2000℃, the time of the high-temperature heat treatment is 1-20h, and the working pressure is 2-10kPa.

[0043] More preferably, the boron-containing powder is selected from a boron source or a mixture of a boron source and a C powder, wherein the boron source is selected from at least one of B powder, B4C powder, boric acid, sodium borohydride, and boron oxide, and when the boron-containing powder is selected from a mixture of a boron source and a C powder, the molar ratio of B to C is 1:3-5.

[0044] A further preferred method involves encapsulating the zirconium substrate with solid boron powder and subjecting it to high-temperature heat treatment under an argon atmosphere at a temperature of 1400–1600°C. When using solid boron powder for boron doping via heat treatment, controlling the heat treatment temperature within the aforementioned range results in optimal film-substrate bonding and degradation performance of BDD. This is because, compared to other preparation methods, the temperature required for direct reduction of ZrO2 using elemental boron is lower, leading to a more complete reaction. However, the high-temperature heat treatment temperature needs to be effectively controlled. If the temperature is below this range, the chemical potential of boron atoms is low, resulting in a low boron content at the top of the transition layer, which fails to effectively reduce and suppress ZrO2 on the substrate surface. If the temperature is above this range, sintering is likely to occur on the substrate surface, and the significant thermal stress between the substrate and the coating will also adversely affect the film-substrate bonding performance.

[0045] However, when the transition layer is set within the temperature range of 1200–2000°C controlled by this invention, the performance of the resulting composite coating material is superior to that without the transition layer.

[0046] More preferably, the particle size of the solid B powder is ≤20μm.

[0047] The inventors discovered that by using a zirconium substrate 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 quality of the resulting transition layer is optimal, and the performance of the resulting zirconium-based boron-doped diamond semiconductor composite coating material is also optimal.

[0048] In this invention, the preparation method of the Zr-B compound gradient transition layer is not limited to the above two methods. As long as the thickness and composition requirements of the transition layer can be met, one of the existing technologies such as electroplating, vapor deposition, magnetron sputtering, chemical vapor deposition, and physical vapor deposition can be used.

[0049] A preferred embodiment of the process for growing a gradient boron-doped diamond semiconductor layer on a zirconium substrate containing a Zr-B compound gradient transition layer via chemical vapor deposition is as follows: First, the zirconium substrate containing the Zr-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 zirconium substrate with surface-adsorbed nanocrystalline and / or microcrystalline diamond is obtained. Then, the zirconium 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

[0050] 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.

[0051] 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%.

[0052] In a further preferred embodiment, during the chemical vapor deposition, the initial transient B / C ratio of the introduced gas is controlled to be 20,000-40,000 ppm, and the cutoff transient B / C ratio is 1,000-15,000 ppm. During the deposition process, the boron content decreases linearly from the initial transient value to the cutoff transient value.

[0053] The present invention also provides an application of zirconium-based boron-doped diamond semiconductor composite material, wherein the semiconductor composite coating material is applied to at least one of semiconductor devices, electrochemistry, chemical industry, medical, electronics, aerospace, and nuclear industry.

[0054] Beneficial effects

[0055] This invention addresses the problem of poor film-substrate adhesion caused by the mismatch in thermal expansion coefficients between zirconium metal and BDD (bipolar distillation). It proposes a Zr-B compound gradient transition layer on the zirconium substrate surface, followed by a gradient boron-doped diamond semiconductor layer on the transition layer surface. This forms a Zr-Zr-B compound gradient transition layer-gradient boron-doped diamond semiconductor composite coating material configuration, significantly improving the film-substrate adhesion and thermal conductivity of the zirconium-based BDD composite coating material, and reducing the risk of material peeling during the chemical vapor deposition cooling stage and subsequent service life. Attached Figure Description

[0056] Figure 1 Example 1: Relationship between borane concentration and time. Detailed Implementation

[0057] Example 1

[0058] The pure Zr matrix was encapsulated with solid boron powder and placed in a tube furnace under argon gas as a protective gas for heat treatment. The gas pressure was set to 3000 Pa, the heating temperature was 1500℃, and the temperature was held for 4 hours before cooling with the furnace. After preparation, the mass fraction of ZrB2 at the top of the resulting transition layer was approximately 99.95%.

[0059] A Zr substrate with a Zr-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 surface-adsorbed nanocrystalline and / or microcrystalline diamond 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 15 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. The initial transient B / C ratio is controlled to be 10000 ppm, and the cutoff transient B / C ratio is 2000 ppm. The boron content is linearly decreased from the initial transient boron content to the cutoff transient boron content as the maximum value, thus obtaining a gradient boron-doped diamond semiconductor layer.

[0061] The carbon-containing gas accounts for 3% 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 8h.

[0062] After preparation, the thickness of the resulting gradient boron-doped diamond semiconductor transition layer was 7.9 μm.

[0063] The resulting zirconium-based boron-doped diamond composite coating material exhibits good adhesion, with no peeling after being removed from the furnace and no peeling after being scratched.

[0064] The thermal conductivity of the composite coating material obtained by laser flare method was 601 W / mK.

[0065] To simulate abnormal operating conditions in a nuclear reactor, the obtained composite coating material was oxidized in 1100℃ hot steam for 30 minutes. After the hot steam oxidation test, the composite material gained 1.37 g / dm³. 2 After the thermal steam test, the composite coating was peeled off. At 60 nm below the sample surface, the O:Zr ratio was the same as that of the original Zr material. The composition of the Zr matrix covered by the composite coating was very similar to that of the original Zr material.

[0066] Example 2

[0067] Other conditions were the same as in Example 1, except that the pure Zr matrix was encapsulated with solid boron powder and placed in a tube furnace under argon gas as a protective gas for heat treatment. The gas pressure was set to 3000 Pa, the heating temperature was 1200 °C, and the temperature was maintained for 4 hours before cooling with the furnace. After preparation, the mass fraction of ZrB2 at the top of the resulting transition layer was approximately 99.63%.

[0068] The resulting zirconium-based boron-doped diamond composite coating material exhibits good adhesion, with no peeling after being removed from the furnace and no peeling after being scratched.

[0069] The thermal conductivity of the composite coating material obtained by laser flare method was 574 W / mK.

[0070] To simulate abnormal operating conditions in a nuclear reactor, the obtained composite coating material was oxidized in 1100℃ hot steam for 30 minutes. After the hot steam oxidation test, the composite material gained 1.48 g / dm³. 2 After the thermal steam test, the composite coating was peeled off. At 70 nm below the sample surface, the O:Zr ratio was the same as that of the original Zr material. The composition of the Zr matrix covered by the composite coating was very similar to that of the original Zr material.

[0071] Example 3

[0072] Then, 300μm boron-doped diamond particles were taken and mechanically embedded into the etched zirconium substrate using a powder press. The embedding pressure was controlled at 60kN to obtain a zirconium substrate with embedded diamond particles. The embedding depth of the diamond particles was 100μm and the distribution density of the diamond particles was 20%.

[0073] Then, when preparing the Zr-B compound gradient transition layer using magnetron sputtering, a Zr target with a purity ≥99.99% was used, the distance between the zirconium substrate and the target was 8 cm, the working pressure was 0.5 Pa, and the sputtering power was 150 W; the sputtering atmosphere was a mixture of borane and argon; the sputtering time was 60 min, the initial borane concentration was 5%, and the concentration was increased by 10% every 10 min until the borane concentration reached 30% (see...). Figure 1 After preparation, the mass fraction of ZrB2 at the top of the resulting transition layer was approximately 99.95%.

[0074] After the magnetron sputtering process is completed, the zirconium substrate containing the Zr-B compound gradient transition layer is subjected to low-temperature heat treatment. The temperature of the low-temperature heat treatment is 800℃, the time is 1h, the gas pressure is 10kPa, and the atmosphere of the low-temperature heat treatment is argon.

[0075] Then, a Zr substrate with a Zr-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 surface-adsorbed nanocrystalline and / or microcrystalline diamond 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 15 min.

[0076] 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. The initial transient B / C ratio is controlled at 20000 ppm, and the cutoff transient B / C ratio is controlled at 2000 ppm. The boron content is linearly decreased from the initial transient boron content to the cutoff transient boron content as the maximum value, thus obtaining a gradient boron-doped diamond semiconductor layer.

[0077] The carbon-containing gas accounts for 2% 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 10h.

[0078] After preparation, the thickness of the resulting gradient boron-doped diamond semiconductor transition layer was 9.2 μm.

[0079] The resulting zirconium-based boron-doped diamond composite coating material exhibits good adhesion, with no peeling upon exiting the furnace or being scraped off. The Zr-B compound gradient transition layer is covered by a gradient boron-doped diamond film grown in a directional (111) pattern.

[0080] The thermal conductivity of the composite coating material obtained by laser flare method was 692 W / mK.

[0081] To simulate abnormal operating conditions in a nuclear reactor, the obtained composite coating material was oxidized in 1100℃ hot steam for 30 minutes. After the hot steam oxidation test, the composite material gained 1.17 g / dm³. 2 After the thermal steam test, the composite coating was peeled off. At 50 nm below the sample surface, the O:Zr ratio was the same as that of the original Zr material. The composition of the Zr matrix covered by the composite coating was very similar to that of the original Zr material.

[0082] Comparative Example 1

[0083] The conditions were the same as in Example 1, except that the Zr-B compound transition layer was not prepared on the substrate. Due to the mismatch in thermal expansion coefficients and the influence of zirconium oxide, the coating of the resulting composite coating material was severely peeled off after it was taken out of the furnace.

[0084] Comparative Example 2

[0085] The conditions were the same as in Example 1, except that the gradient boron-doped diamond semiconductor bottom and top layers used uniform boron doping. The B / C ratio of the gradient boron-doped diamond bottom layer was 10000 ppm, and the B / C ratio of the gradient boron-doped diamond top layer was 2000 ppm. The intermediate layer's B / C ratio decreased linearly from the maximum value of the gradient boron-doped diamond bottom layer to the B / C ratio of the gradient boron-doped diamond top layer. The thickness of the gradient boron-doped diamond bottom, intermediate, and top layers was all 5 μm.

[0086] The thermal conductivity of the composite coating material obtained by laser flare method was 445 W / mK, which is significantly lower than that of Example 1.

[0087] To simulate abnormal operating conditions in a nuclear reactor, the obtained composite coating material was oxidized in 1100℃ hot steam for 30 minutes. After the hot steam oxidation test, the composite material gained 1.84 g / dm³. 2 After the thermal steam test, the composite coating was peeled off. At 90 nm below the sample surface, the O:Zr ratio was the same as that of the original Zr material. The composition of the Zr matrix covered by the composite coating was significantly different from that of the original Zr material.

[0088] Comparative Example 3

[0089] All other conditions were the same as in Example 1, except that the initial transient B / C ratio of the graded boron-doped diamond was 50,000 ppm, the cutoff transient B / C ratio was 500 ppm, and the boron content was linearly decreased from the initial transient to the cutoff transient, with the initial transient boron content as the maximum value.

[0090] The thermal conductivity of the composite coating material obtained by laser flare method was 512 W / mK, which is significantly lower than that of Example 1.

[0091] To simulate abnormal operating conditions in a nuclear reactor, the obtained composite coating material was oxidized in 1100℃ hot steam for 30 minutes. After the hot steam oxidation test, the composite material gained 1.72 g / dm³. 2 After the thermal steam test, the composite coating was peeled off. At 80 nm below the sample surface, the O:Zr ratio was the same as that of the original Zr material. The composition of the Zr matrix covered by the composite coating was significantly different from that of the original Zr material.

[0092] Comparative Example 4

[0093] All other conditions were the same as in Example 1, except that the heat treatment temperature for preparing the Zr-B compound gradient transition layer was 2000°C. Due to the excessively high temperature, the transition layer detached directly from the substrate.

[0094] Comparative Example 5

[0095] All other conditions were the same as in Example 1, except that the heat treatment temperature for preparing the Zr-B compound gradient transition layer was 600°C. After preparation, the mass fraction of ZrB2 at the top of the resulting transition layer was approximately 59.46%. Due to the influence of zirconium oxide, many pore defects appeared on the surface of the resulting BDD coating.

[0096] The thermal conductivity of the composite coating material obtained by laser flare method was 451 W / mK, which is significantly lower than that of Example 1.

[0097] To simulate abnormal operating conditions in a nuclear reactor, the obtained composite coating material was oxidized in 1100℃ hot steam for 30 minutes. The weight gain of the composite material after the hot steam oxidation test was 2.37 g / dm³. 2 The reaction between the matrix and water molecules leads to an increase in oxygen content. After the thermal steam test, the composite coating was peeled off, and the O:Zr ratio at 120 nm below the sample surface was the same as that of the original Zr material. The composition of the Zr matrix covered by the composite coating is significantly different from that of the original Zr material.

Claims

1. A zirconium-based boron-doped diamond semiconductor composite coating material, characterized in that: The zirconium-based boron-doped diamond semiconductor composite coating material consists of a zirconium substrate, a Zr-B compound gradient transition layer disposed on the surface of the zirconium substrate, and a gradient boron-doped diamond semiconductor layer disposed on the surface of the Zr-B compound gradient transition layer. The boron content in the Zr-B compound gradient transition layer increases from bottom to top, while the boron content in the gradient boron-doped diamond semiconductor layer decreases from bottom to top. The gradient boron-doped diamond semiconductor layer has a boron content that decreases from bottom to top; the initial transient B / C ratio is 20,000-40,000 ppm, and the cutoff transient B / C ratio is 1,000-15,000 ppm. The boron content at the bottom of the gradient boron-doped diamond layer is the maximum value at the initial transient state, and decreases linearly to the minimum value at the top of the gradient boron-doped diamond layer.

2. The zirconium-based boron-doped diamond semiconductor composite coating material according to claim 1, characterized in that: The Zr-B compound gradient transition layer is a composite phase of Zr and ZrB2, with the highest ZrB2 content at the top of the transition layer and the mass fraction of ZrB2 being ≥99.5%. The boron content decreases from the top to the bottom layer. The thickness of the Zr-B compound gradient transition layer is 5-100 μm.

3. The zirconium-based boron-doped diamond semiconductor composite coating material according to claim 1 or 2, characterized in that: The zirconium matrix is ​​pure zirconium or a zirconium alloy; The zirconium matrix has a structure that is one-dimensional, two-dimensional, or three-dimensional. The zirconium substrate surface has a micro / nano structure.

4. The zirconium-based boron-doped diamond semiconductor composite coating material according to claim 1 or 2, characterized in that: The zirconium matrix is ​​embedded with diamond particles, the diamond particles having a diameter of 250~500μm; The diamond particles are distributed at a density of 5% to 60% on the zirconium matrix. The diamond particles are embedded in the zirconium matrix at a depth of 100~350μm; The diamond particles are embedded in a zirconium matrix; The diamond particles are selected from pure diamond particles or boron-doped diamond particles.

5. A method for preparing a zirconium-based boron-doped diamond semiconductor composite coating material according to any one of claims 1-4, characterized in that: A Zr-B compound gradient transition layer is prepared on the surface of a zirconium substrate. Then, a gradient boron-doped diamond semiconductor layer is grown on the zirconium substrate containing the Zr-B compound gradient transition layer by chemical vapor deposition to obtain a zirconium-based boron-doped diamond semiconductor composite coating material.

6. The method for preparing a zirconium-based boron-doped diamond semiconductor composite coating material according to claim 5, characterized in that: Diamond particles are first embedded in a zirconium matrix to obtain a zirconium matrix with embedded diamond particles, and then a Zr-B compound gradient transition layer is prepared on the surface of the zirconium matrix with embedded diamond particles. The pressing pressure is 60-100kN.

7. The method for preparing a zirconium-based boron-doped diamond semiconductor composite coating material according to claim 5 or 6, characterized in that: A Zr-B compound gradient transition layer was prepared on the surface of a zirconium substrate by magnetron sputtering or high-temperature heat treatment. When preparing Zr-B compound gradient transition layers using magnetron sputtering, a Zr target with a purity ≥99.99% is used, the distance between the zirconium substrate and the target is 5-12 cm, the working pressure is 0.2-3 Pa, the sputtering power is 40-200 W, and the sputtering time is 5-100 min; the sputtering atmosphere is a boron-containing atmosphere. When preparing the Zr-B compound gradient transition layer by high-temperature heat treatment, the zirconium substrate is wrapped with boron-containing powder and then subjected to high-temperature heat treatment under vacuum or protective atmosphere. The temperature of the high-temperature heat treatment is 1200-2000℃, the time of the high-temperature heat treatment is 1-20h, and the working pressure is 2-10kPa.

8. A method for preparing a zirconium-based boron-doped diamond semiconductor composite coating material according to claim 5 or 6, characterized in that: The process of growing a gradient boron-doped diamond semiconductor layer on a zirconium substrate containing a Zr-B compound gradient transition layer via chemical vapor deposition is as follows: First, the zirconium substrate containing the Zr-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 zirconium substrate with surface-adsorbed nanocrystalline and / or microcrystalline diamond is obtained. Then, the zirconium 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, the initial transient B / C ratio of the introduced gas is controlled to be 20,000-40,000 ppm, and the cutoff transient B / C ratio is 1,000-15,000 ppm. During the deposition process, the boron content decreases linearly from the initial transient value to the cutoff transient value.

9. The application of the zirconium-based boron-doped diamond semiconductor composite coating material according to any one of claims 1-4, characterized in that: The semiconductor composite coating material is applied to at least one of the following industries: chemical industry, medical industry, electronics industry, aerospace industry, and nuclear industry.

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