Composite material with sandwich structure, composite-based doped diamond material and preparation method and application of composite material and composite-based doped diamond material

Abstract

The invention discloses a composite material with a sandwich structure, a composite-based doped diamond material and a preparation method and application of the composite-based doped diamond material. The composite material is composed of a non-metal inorganic material / metal composite layer located in the middle and doped non-metal inorganic material layers located on the two sides. The non-metal inorganic material / metal composite layer is obtained by compounding a non-metal inorganic material and metal; the composite base doped diamond material is composed of the composite material and a doped diamond coating arranged on the surface of the composite material, the sandwich structure design is adopted, and the conductivity and corrosion resistance of the composite material are remarkably improved through the synergistic effect of the outer layer doped nonmetal inorganic material and the middle composite layer; and the bonding performance of the composite material and a diamond film layer is improved. When the composite base doped diamond material provided by the invention is used as an electrode, not only is the efficiency excellent, but also the service life is greatly prolonged.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite material preparation technology, and in particular relates to a composite material with a sandwich structure, a composite-based doped diamond material, and a preparation method and application thereof. Background Art

[0002] Doped diamond coating materials are known for their extremely high oxygen evolution potential, excellent electrochemical stability and extremely high corrosion resistance. This material performs well in electrocatalytic degradation of wastewater. As an electrochemical advanced oxidation method, it is particularly suitable for treating pre-treatment of difficult-to-biodegrade organic wastewater, high-salt organic wastewater, highly toxic organic wastewater, high-concentration wastewater, high-ammonia nitrogen wastewater and strong acid and alkali organic wastewater. This technology has great potential and is considered to be an effective means of treating these complex wastewaters. However, at present, the main substrate materials used in the industrial large-scale preparation of doped diamond electrodes are single crystal, polycrystalline silicon or metal-based materials. Single crystal and polycrystalline materials have problems such as high resistivity, high degradation energy consumption and insufficient corrosion resistance, while metal-based materials have poor matching of thermal expansion coefficients with diamonds and poor membrane-based bonding. Therefore, designing a doped diamond electrode with high conductivity, high adhesion and strong corrosion resistance has become a technical problem that needs to be solved urgently. Summary of the invention

[0003] In view of the shortcomings of the prior art, the first object of the present invention is to provide a sandwich structure composite material which has excellent electrical conductivity, strong corrosion resistance and excellent adhesion to the diamond coating.

[0004] The second object of the present invention is to provide a method for preparing a composite material with a sandwich structure.

[0005] The third object of the present invention is to provide a sandwich structured composite-doped diamond material. The composite-doped diamond material provided by the present invention not only has excellent efficiency when used as an electrode, but also greatly improves the service life.

[0006] A fourth object of the present invention is to provide a method for preparing a composite material with a sandwich structure.

[0007] A fifth object of the present invention is to provide an application of a composite-based doped diamond material with a sandwich structure.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

[0009] The present invention discloses a composite material with a sandwich structure, which is composed of a non-metallic inorganic material / metal composite layer in the middle and doped non-metallic inorganic material layers on both sides, wherein the non-metallic inorganic material / metal composite layer is obtained by composite non-metallic inorganic material and metal.

[0010] The sandwich structure composite material provided by the present invention is composed of a non-metallic inorganic material / metal composite layer in the middle and doped non-metallic inorganic material layers on both sides, wherein the non-metallic inorganic material / metal composite layer has a low thermal expansion coefficient and excellent electrical conductivity, and the doped inorganic non-metallic material layers on both sides have a lower thermal expansion coefficient than the non-metallic inorganic material / metal composite layer, and have a certain electrical conductivity, which matches the thermal expansion coefficient of diamond; at the same time, it has excellent corrosion resistance, and the two work together to improve the conductivity of the substrate as a whole and reduce the thermal expansion coefficient. When it is used as a substrate material to grow a diamond coating, it can avoid the diamond coating from peeling off from the substrate due to the large difference in thermal expansion coefficient when the diamond coating is grown at high temperature; and the inorganic non-metallic material can form a covalent bond with the diamond, such as a covalent bond (Si-C bond) can be formed between silicon and carbon atoms, which has a strong bonding force and makes the composite material and the diamond coating have high adhesion, and at the same time has excellent electrical conductivity and strong corrosion resistance.

[0011] In a preferred embodiment, in the composite material, the thickness of the non-metallic inorganic material / metal composite layer is 0.5-5 mm, and the thickness of the doped non-metallic inorganic material layer is 0.1-1 mm. The performance is optimal when the thickness of each layer in the composite material is controlled within the above range. If the composite material is too thin, it cannot provide sufficient support for the subsequent growth of diamonds and is prone to deformation or fracture during the deposition process. The heat capacity of the thin substrate is small, and it is difficult to effectively dissipate the heat generated during the deposition of diamonds. In addition, the thermal stress and residual stress generated during the deposition of the diamond coating can easily cause the thin substrate to bend and deform; and it is too thin and fragile during use; if the composite material is too thick, it will affect the heat transfer, resulting in uneven temperature distribution of the coating growth, and will also increase costs. In addition, the thick substrate requires longer heating and cooling time, reducing production efficiency; and if the doped non-metallic inorganic material layer is too thin, it cannot effectively alleviate the thermal stress and lattice mismatch between the substrate and the diamond coating; it is difficult to form sufficient nucleation sites, affecting the nucleation density of diamonds; and if the doped non-metallic inorganic material layer is too thick, it will lead to excessive internal stress accumulation, which is prone to cracking or delamination, and affect the electrical conductivity of the overall material, and will also increase production costs and preparation time.

[0012] In a preferred embodiment, in the non-metallic inorganic material / metal composite layer, the volume fraction of the non-metallic inorganic material is 70-98%, preferably 80-90%, and the volume fraction of the metal is 2%-30%, preferably 10-20%. In the non-metallic inorganic material / metal composite layer, the volume fraction of the non-metallic inorganic material and the metal is controlled within the above range, and the performance is optimal. If the volume fraction of the metal is too large, the overall thermal expansion coefficient of the composite material will increase, which is not conducive to the combination of the substrate and the diamond coating. If the volume fraction of the metal is too small, the overall electrical conductivity of the composite material will decrease, resulting in an increase in the resistivity of the overall material and a large energy consumption.

[0013] In a preferred embodiment, in the non-metallic inorganic material / metal composite layer, the non-metallic inorganic material is selected from at least one of polysilicon, silicon carbide, silicon nitride, zirconium oxide, aluminum oxide, and mullite, and the metal is selected from at least one of titanium, tantalum, niobium, chromium, zirconium, molybdenum, and tungsten.

[0014] In a preferred embodiment, the non-metallic inorganic material in the doped non-metallic inorganic material layer is selected from at least one of polysilicon, silicon carbide, silicon nitride, zirconium oxide, aluminum oxide and mullite.

[0015] In a preferred embodiment, the doping element in the doped non-metallic inorganic material layer is selected from one of boron, nitrogen, phosphorus and sulfur, and the concentration of the doping element in the doped non-metallic inorganic material layer is 1×10 17 -1×10 20 atoms / cm³.

[0016] In the present invention, the concentration of the doping element in the doped non-metallic inorganic material layer is controlled within the above range, and the performance of the final obtained material is optimal. Too high or too low a doping concentration will lead to a decrease in the conductivity of the doped non-metallic inorganic material.

[0017] Further preferably, when the doping element is boron, its concentration in the doped non-metallic inorganic material layer is 1×10 18 -1×10 20 atoms / cm³.

[0018] Further preferably, when the doping element is nitrogen, its concentration in the doped non-metallic inorganic material layer is 1×10 17 -1×10 19 atoms / cm³.

[0019] Further preferably, when the doping element is phosphorus, its concentration in the doped non-metallic inorganic material layer is 1×10 18 -1×10 20 atoms / cm³.

[0020] Further preferably, when the doping element is sulfur, its concentration in the doped non-metallic inorganic material layer is 1×10 17 -1×10 19 atoms / cm³.

[0021] The present invention also provides a method for preparing a composite material with a sandwich structure, wherein non-metallic inorganic material powder and metal powder are mixed to obtain composite powder, three layers of powder, namely, doped non-metallic inorganic material powder, composite powder, and doped non-metallic inorganic material powder, are laid in sequence in a mold, and then sintered to obtain the composite material.

[0022] In a preferred embodiment, in the composite powder, the volume fraction of the non-metallic inorganic material powder is 70-98%, preferably 80-90%, and the volume fraction of the metal powder is 2%-30%, preferably 10-20%.

[0023] In a preferred solution, the mixing method is ball milling, the speed of the ball milling is 700-1200 rpm, and the time is 10-36 hours. In the present invention, a faster ball milling speed is used, on the one hand, the composite powder is fully refined and evenly dispersed, and on the other hand, the effect of mechanical alloying is enhanced and the difficulty of subsequent sintering is reduced.

[0024] According to a preferred embodiment, the preparation process of the doped non-metallic inorganic material powder is as follows: the doping source powder and the non-metallic inorganic material powder are ball-milled at a rotation speed of 700-1200 rpm for 10-36 hours to obtain a mixed powder, and the mixed powder is sintered under a protective atmosphere, the heating rate during sintering is controlled to be 5-10°C / min, the sintering temperature is 800-2000°C, and the sintering time is 5-24 hours.

[0025] Further preferably, when the doping element is boron, the doping source powder is selected from one of boric acid (H3BO3), boron oxide (B2O3), boron carbide (B4C), boron (B), and boron nitride (BN) powders;

[0026] When the doping element is phosphorus, the doping source powder is selected from one of ammonium phosphate ((NH4)3PO4), red phosphorus, P2O5, diammonium phosphate (NH4H2PO4), and calcium phosphate (Ca3(PO4)2) powders;

[0027] When the doping element is nitrogen, the doping source powder is selected from one of boron nitride (BN), melamine (C3H6N6), urea (CH4N2O), aluminum nitride (AlN), and Si3N4 powder;

[0028] When the doping element is phosphorus, the doping source powder is selected from one of ammonium phosphate ((NH4)3PO4), red phosphorus, P2O5, diammonium phosphate (NH4H2PO4), and calcium phosphate (Ca3(PO4)2) powders;

[0029] When the doping element is sulfur, the doping source powder is selected from one of sulfur (S), thiourea (CH4N2S), ammonium sulfate ((NH4)2SO4), and zinc sulfide (ZnS) powder.

[0030] In a preferred embodiment, the sintering is hot pressing sintering or SPS sintering, preferably SPS sintering. SPS spark plasma sintering can achieve rapid densification technology, effectively control grain growth, and improve the mechanical properties of the material.

[0031] Further preferably, the hot pressing sintering temperature is 1000-1800° C., the holding time is 0.5-5 h, the heating rate is 5-25° C. / min, and the pressure is 10-60 MPa.

[0032] Further preferably, the SPS sintering temperature is 1000-1900° C., the holding time is 10-300 min, the heating rate is 80-200° C. / min, the pressure is 10-60 MPa, and the pulse duty cycle is 50%-90%.

[0033] The present invention also provides a composite-based doped diamond material with a sandwich structure, which is composed of a composite material with a sandwich structure and a doped diamond coating arranged on the surface of the composite material.

[0034] The present invention also provides a method for preparing a composite-based doped diamond material with a sandwich structure, wherein the composite material is subjected to surface pretreatment and then a doped diamond coating is grown on the surface of the composite material by chemical vapor deposition.

[0035] In a preferred solution, the process of surface pretreatment of the composite material is: firstly grinding the surface of the composite material, then sandblasting it, and finally placing the sandblasted composite material in a diamond nanocrystal suspension for seed crystal planting.

[0036] In the present invention, the composite material is firstly ground to remove the oxide layer, reduce the roughness and make the surface flat, and then the surface micro-roughness is increased by sandblasting to provide more nucleation sites; the surface area is increased to improve the adhesion ability of the seed crystal; surface micro-pits are generated, which are beneficial to the mechanical bite of the seed crystal. In the present invention, grinding provides a good surface foundation for sandblasting, and sandblasting creates an ideal microstructure for seed crystal planting, and then cooperates with the seed crystal planting, and finally grows a high-quality doped diamond coating through the cooperation of the above-mentioned surface pretreatment means.

[0037] If only grinding is performed without sandblasting, the surface will be too smooth and lack micro-roughness; the seed crystals will be difficult to adhere to and fix on the substrate surface; there will be insufficient nucleation sites, affecting the subsequent growth quality of the diamond film. If only sandblasting is performed without grinding, the original impurities and oxide layer on the surface cannot be completely removed; the sandblasting effect is uneven, resulting in inconsistent surface treatment; there may be large protrusions and defects on the substrate surface, affecting the uniformity of subsequent film growth.

[0038] Further preferably, during the grinding, the grinding speed is controlled to be 15-30 rpm and the time is 5-20 min.

[0039] Further preferably, during the sandblasting treatment, the pressure is controlled to be 0.1-0.3 MPa, the time is 5-60 s, and the distance is 10-30 cm.

[0040] Further preferably, the diamond nanocrystal suspension is obtained by dispersing nanodiamonds in pure water, and the particle size of the nanodiamonds is 1-25 nm.

[0041] Further preferably, the seed crystal planting is carried out under ultrasound, and the ultrasound time is 30-60 minutes.

[0042] In a preferred embodiment, the process of chemical vapor deposition growth of doped diamond coating is as follows: placing the surface pretreated composite material in a chemical deposition furnace, introducing gas at a mass flow ratio of hydrogen:methane:doping gas source = (100-120): (2-10): (0.05-3), a growth pressure of 1-4 KPa, a growth temperature of 650-1000°C, and a growth frequency of 2-4 times. Each time the composite material is grown, the composite material is replaced with a positive and a negative electrode, and then the growth is continued. The single growth time is 10-40 hours, and the doping gas source is selected from at least one of ammonia, phosphine, borane, and carbon disulfide.

[0043] The present invention also provides an application of a composite-based doped diamond material with a sandwich structure, and the composite-based doped diamond material is used as an electrode in the field of environmental protection or the field of disinfection.

[0044] Beneficial Effects

[0045] The present invention adopts a sandwich structure design, and through the synergistic effect of the outer layer doped with non-metallic inorganic materials and the middle composite layer, the conductivity and corrosion resistance of the composite material, as well as the bonding performance of the composite material with the diamond film layer are significantly improved. In the present invention, in the preparation process of the composite material, the SPS rapid densification technology is preferably used to effectively control the grain growth and improve the mechanical properties of the material.

[0046] When the composite material is used as a substrate for composite-based doped diamond material, the composite material is pretreated before the diamond coating is deposited. Grinding provides a good surface basis for sandblasting, and sandblasting creates an ideal microstructure for seed crystal planting. In conjunction with the seed crystal planting, a substrate basis is provided for growing a high-quality doped diamond coating. During the growth process of the doped diamond coating, high-quality growth of the diamond film is achieved by optimizing the doping process parameters, thereby improving the electrochemical performance of the electrode.

[0047] The composite-based doped diamond material provided by the present invention exhibits excellent degradation efficiency and service life in wastewater treatment and has good application prospects. DETAILED DESCRIPTION

[0048] The preparation process of the boron-doped silicon carbide powder in the following examples is as follows: the boron doping amount is 1×10 20 atoms / cm³, high-purity SiC powder (purity ≥99.9%), B4C powder (purity ≥99.9%), and sintering aids Al2O3 and Y2O3 are mixed by ball milling at a speed of 800rpm for 24 hours to obtain a mixed powder, wherein the mass fraction of the sintering aid Al2O3 in the mixed powder is 0.5%, and the mass fraction of Y2O3 in the mixed powder is 0.5%. Then, under the protection of argon, the temperature is first increased to 1000℃ at a heating rate of 15℃ / min and kept for 1 hour, and then increased to 1800℃ and kept for 2h to obtain.

[0049] Example 1

[0050] Preparation of composite materials

[0051] 1. Silicon carbide powder (80 vol%) and titanium powder (20 vol%) were mixed and ball milled in a ball mill at 1200 rpm for 36 h to obtain a mixed powder;

[0052] 2. Lay the boron-doped silicon carbide powder, mixed powder and boron-doped silicon carbide powder in the mold in sequence, with the thickness of each doped layer being 0.5 mm and the thickness of the middle composite layer being 3 mm;

[0053] 3. SPS sintering was adopted with a temperature of 1550°C, a holding time of 120 min, a heating rate of 150°C / min, a pressure of 40 MPa, and a pulse duty cycle of 80%.

[0054] A composite material with a resistivity of 0.2 mΩ·cm was prepared. The resistivity of existing single crystal silicon is 2 mΩ·cm, which is 10 times lower than that of existing single crystal silicon substrate.

[0055] Preparation of composite matrix doped diamond materials

[0056] 4. The sintered sandwich structure composite substrate was surface treated by grinding at 20 rpm for 15 min, sandblasting (pressure 0.2 MPa, time 30 s, distance 20 cm), and then seeding in 10 nm diamond suspension (4 g / L) by ultrasonication for 45 min;

[0057] 5. Hot filament chemical vapor deposition (HFCVD) was used to grow doped diamond, with a gas flow ratio of (H2:CH4:B2H6) = 110:5:2, a pressure of 2 KPa, a temperature of 800 °C, and three growths, each for 30 hours. After each growth, the positive and negative electrodes were replaced.

[0058] Use a high current density of 1000mA / cm 2 A life comparison test was conducted on single crystal silicon doped diamond and the composite-based doped diamond prepared in Example 1. The operating life of the composite-based doped diamond was twice that of the single crystal silicon doped diamond, and the energy consumption was reduced by 60%.

[0059] Example 2

[0060] Preparation of composite materials

[0061] 1. Silicon carbide powder (85 vol%) and titanium powder (15 vol%) were mixed and ball milled in a ball mill at 900 rpm for 24 h to obtain a mixed powder;

[0062] 2. Lay the boron-doped silicon carbide powder, mixed powder and boron-doped silicon carbide powder in the mold in sequence, with the thickness of each doped layer being 0.5 mm and the thickness of the middle composite layer being 2 mm;

[0063] 3. SPS sintering was adopted with a temperature of 1500°C, a holding time of 120 min, a heating rate of 150°C / min, a pressure of 40 MPa, and a pulse duty cycle of 80%.

[0064] A composite material with a resistivity of 0.5 mΩ·cm was prepared. The resistivity of existing single crystal silicon is 2 mΩ·cm, which is 4 times lower than that of existing single crystal silicon substrate.

[0065] Preparation of composite matrix doped diamond materials

[0066] 4. The sintered sandwich structure composite substrate was surface treated by grinding at 20 rpm for 15 min, sandblasting (pressure 0.2 MPa, time 30 s, distance 20 cm), and then seeding in 10 nm diamond suspension (4 g / L) by ultrasonication for 45 min;

[0067] 5. Hot filament chemical vapor deposition (HFCVD) was used to grow doped diamond, with a gas flow ratio of (H2:CH4:B2H6) = 110:5:2, a pressure of 2 KPa, a temperature of 800 °C, and three growths, each for 30 hours. After each growth, the positive and negative electrodes were replaced.

[0068] Use a high current density of 1000mA / cm 2 A life comparison test was conducted on single crystal silicon doped diamond and composite base doped diamond. The operating life of composite base doped diamond is 2.5 times that of single crystal silicon doped diamond, and the energy consumption is reduced by 40%.

[0069] The preparation process of the boron-doped silicon nitride powder in the following examples is as follows: the boron doping amount is 1×10 20 atoms / cm³, high-purity Si3N4 powder (purity ≥99.9%), BN powder (purity ≥99.9%), and sintering aids Al2O3 and Y2O3 are mixed by ball milling at a speed of 700rpm for 24 hours to obtain a mixed powder, wherein the mass fraction of the sintering aid Al2O3 in the mixed powder is 0.5%, and the mass fraction of Y2O3 in the mixed powder is 0.5%. Then, under the protection of high-purity nitrogen, the temperature is raised to 1600℃ at a heating rate of 15℃ / min and kept for 5 hours to obtain the obtained powder.

[0070] Example 3

[0071] Preparation of composite materials

[0072] 1. Silicon nitride powder (80 vol%) and titanium powder (20 vol%) were mixed and ball milled in a ball mill at 900 rpm for 24 h to obtain a mixed powder;

[0073] 2. Lay the boron-doped silicon nitride powder, mixed powder and boron-doped silicon nitride powder in the mold in sequence, with the thickness of each doped layer being 0.5 mm and the thickness of the middle composite layer being 2 mm;

[0074] 3. SPS sintering was adopted with a temperature of 1400°C, a holding time of 120 min, a heating rate of 150°C / min, a pressure of 40 MPa, and a pulse duty cycle of 80%.

[0075] A composite material with a resistivity of 0.25 mΩ·cm was prepared. The resistivity of existing single crystal silicon is 2 mΩ·cm, which is 8 times lower than that of existing single crystal silicon substrate.

[0076] Preparation of composite matrix doped diamond materials

[0077] 4. The sintered sandwich structure composite substrate was surface treated by grinding at 20 rpm for 15 min, sandblasting (pressure 0.2 MPa, time 30 s, distance 20 cm), and then seeding in 10 nm diamond suspension (4 g / L) by ultrasonication for 45 min;

[0078] 5. Hot filament chemical vapor deposition (HFCVD) was used to grow doped diamond, with a gas flow ratio of (H2:CH4:B2H6) = 110:5:2, a pressure of 2 KPa, a temperature of 800 °C, and three growths, each for 30 hours. After each growth, the positive and negative electrodes were replaced.

[0079] Use a high current density of 1000mA / cm 2 A life comparison test was conducted on single crystal silicon doped diamond and composite base doped diamond. The operating life of composite base doped diamond is 2.2 times that of single crystal silicon doped diamond, and the energy consumption is reduced by 55%.

[0080] Example 4

[0081] Preparation of composite materials

[0082] 1. Silicon nitride powder (90 vol%) and titanium powder (10 vol%) were mixed and ball milled in a ball mill at 900 rpm for 24 h to obtain a mixed powder;

[0083] 2. Lay the boron-doped silicon nitride powder, mixed powder and boron-doped silicon nitride powder in the mold in sequence, with the thickness of each doped layer being 0.5 mm and the thickness of the middle composite layer being 2 mm;

[0084] 3. SPS sintering was adopted with a temperature of 1400°C, a holding time of 120 min, a heating rate of 150°C / min, a pressure of 40 MPa, and a pulse duty cycle of 80%.

[0085] A composite material with a resistivity of 0.25 mΩ·cm was prepared. The resistivity of existing single crystal silicon is 2 mΩ·cm, which is 8 times lower than that of existing single crystal silicon substrate.

[0086] Preparation of composite matrix doped diamond materials

[0087] 4. The sintered sandwich structure composite substrate was surface treated by grinding at 20 rpm for 15 min, sandblasting (pressure 0.2 MPa, time 30 s, distance 20 cm), and then seeding in 10 nm diamond suspension (4 g / L) by ultrasonication for 45 min;

[0088] 5. Hot filament chemical vapor deposition (HFCVD) was used to grow doped diamond, with a gas flow ratio of (H2:CH4:B2H6) = 110:5:2, a pressure of 2 KPa, a temperature of 800 °C, and three growths, each for 30 hours. After each growth, the positive and negative electrodes were replaced.

[0089] A composite material with a resistivity of 1 mΩ·cm was prepared. The resistivity of existing single crystal silicon is 2 mΩ·cm, which is 2 times lower than that of existing single crystal silicon substrate.

[0090] Use a high current density of 1000mA / cm 2 A life comparison test was conducted on single crystal silicon doped diamond and composite base doped diamond. The operating life of composite base doped diamond is 3 times that of single crystal silicon doped diamond, and the energy consumption is reduced by 30%.

[0091] Comparative Example 1

[0092] Other conditions were the same as those in Example 1, except that the mixing ratio of silicon carbide to titanium was changed to silicon carbide powder (60 vol%) and titanium powder (40 vol%). However, a diamond coating on the substrate could not be obtained, and the diamond coating grown on the substrate surface was easy to fall off.

[0093] Comparative Example 2

[0094] Other conditions are the same as those in Example 1, except that the silicon carbide powder layer is not doped with boron. The bonding strength between the substrate and the diamond coating is poor, and peeling is likely to occur during repeated use.

[0095] Comparative Example 3

[0096] The other conditions were the same as those in Example 3, except that the mixture of silicon carbide and titanium was changed to pure silicon carbide powder. The resistivity of the obtained substrate was 100 mΩ·cm, which was relatively high.

[0097] Comparative Example 4

[0098] Other conditions were the same as those in Example 3, except that the SPS sintering temperature was lowered to 900° C. The resulting composite material had insufficient density and a resistivity of 3.5 mΩ·cm, which was higher than that of the existing polycrystalline silicon substrate.

[0099] Comparative Example 5

[0100] The other conditions were the same as those in Example 3, except that the sandblasting step was eliminated, which resulted in uneven attachment of the diamond seed crystals and poor quality of the diamond coating that was eventually grown, with local shedding.

Claims

1. A composite material with a sandwich structure, characterized in that: The composite material consists of a non-metallic inorganic material / metal composite layer located in the middle and doped non-metallic inorganic material layers located on both sides. The non-metallic inorganic material / metal composite layer is obtained by composite non-metallic inorganic material and metal.

2. The composite material of sandwich structure according to claim 1, characterized in that: In the composite material, the thickness of the non-metallic inorganic material / metal composite layer is 0.5-5 mm, and the thickness of the doped non-metallic inorganic material layer is 0.1-1 mm.

3. A sandwich structure composite material according to claim 1 or 2, characterized in that: In the non-metallic inorganic material / metal composite layer, the volume fraction of the non-metallic inorganic material is 70-98%, and the volume fraction of the metal is 2%-30%; In the non-metallic inorganic material / metal composite layer, the non-metallic inorganic material is selected from at least one of polysilicon, silicon carbide, silicon nitride, zirconium oxide, aluminum oxide, and mullite, and the metal is selected from at least one of titanium, tantalum, niobium, chromium, zirconium, molybdenum, and tungsten; The non-metallic inorganic material in the doped non-metallic inorganic material layer is selected from at least one of polycrystalline silicon, silicon carbide, silicon nitride, zirconium oxide, aluminum oxide, and mullite; In the doped non-metallic inorganic material layer, the doping element is selected from one of boron, nitrogen, phosphorus and sulfur, and the concentration of the doping element in the doped non-metallic inorganic material layer is 1×10 17 -1×10 20 atoms / cm³.

4. The method for preparing a composite material with a sandwich structure according to any one of claims 1 to 3, characterized in that: The non-metallic inorganic material powder is mixed with the metal powder to obtain the composite powder. In a mold, three layers of powder, including the doped non-metallic inorganic material powder, the composite powder and the doped non-metallic inorganic material powder, are laid in sequence, and then sintered to obtain the composite material.

5. The method for preparing a sandwich structure composite material according to claim 4, characterized in that: In the composite powder, the volume fraction of the non-metallic inorganic material powder is 70-98%, and the volume fraction of the metal powder is 2%-30%; The mixing method is ball milling, the rotation speed of the ball mill is 700-1200 rpm, and the time is 10-36 hours.

6. The method for preparing a sandwich structure composite material according to claim 4, characterized in that: The preparation process of the doped non-metallic inorganic material powder is as follows: ball milling the doping source powder and the non-metallic inorganic material powder at a rotation speed of 700-1200rpm for 10-36h to obtain a mixed powder, and sintering the mixed powder under a protective atmosphere, controlling the heating rate during sintering to be 5-10℃ / min, the sintering temperature to be 800-2000℃, and the sintering time to be 5-24h.

7. The method for preparing a sandwich structure composite material according to claim 4, characterized in that: The sintering is hot pressing sintering or SPS sintering, The hot pressing sintering temperature is 1000-1800°C, the holding time is 0.5-5h, the heating rate is 5-25°C / min, and the pressure is 10-60Mpa; The SPS sintering temperature is 1000-1900° C., the holding time is 10-300 min, the heating rate is 80-200° C. / min, the pressure is 10-60 MPa, and the pulse duty cycle is 50%-90%.

8. A sandwich structured composite matrix doped diamond material, characterized in that: The composite material is composed of the composite material according to any one of claims 1 to 3 and a doped diamond coating arranged on the surface of the composite material.

9. The method for preparing a sandwich structure composite matrix doped diamond material according to claim 8, characterized in that: After the surface of the composite material is pretreated, a doped diamond coating is grown on the surface of the composite material by chemical vapor deposition; The process of surface pretreatment of the composite material is: firstly grinding the surface of the composite material, then sandblasting, and finally placing the sandblasted composite material in a diamond nanocrystal suspension for seed crystal planting; During the grinding, the grinding speed is controlled to be 15-30 rpm and the grinding time is 5-20 min; During the sandblasting treatment, the pressure is controlled to be 0.1-0.3 MPa, the time is 5-60 s, and the distance is 10-30 cm; The diamond nanocrystal suspension is obtained by dispersing nanodiamonds in pure water, and the particle size of the nanodiamonds is 1-25 nm; The seed crystal planting is carried out under ultrasound, and the ultrasound time is 30-60 minutes; The process of chemical vapor deposition growth of doped diamond coating is as follows: placing the composite material with surface pretreatment in a chemical deposition furnace, introducing gas with a mass flow ratio of hydrogen: methane: doping gas source = 100-120: 2-10: 0.05-3, a growth pressure of 1-4 Kpa, a growth temperature of 650-1000°C, and a growth number of 2-4 times. Each time the composite material is grown, the composite material is replaced with a positive and a negative, and then the growth is continued. The single growth time is 10-40 hours, and the doping gas source is selected from at least one of ammonia, phosphine, borane, and carbon disulfide.

10. The use of a sandwich structure composite matrix doped diamond material as claimed in claim 8, characterized in that: The composite-based doped diamond material is used as an electrode in the field of environmental protection or disinfection.