A high-density diamond-coated composite material, its preparation method and application

Abstract

This invention discloses a high-density diamond-coated composite material, its preparation method, and its application, comprising the following steps: Step 1: Pre-treating nanodiamond particles by hydrogenation or oxidation modification of the end groups to obtain modified nanodiamonds, wherein the pre-treatment is heat treatment and / or plasma-assisted treatment; Step 2: Dispersing the modified nanodiamonds and surfactants in water to obtain a nano-seed crystal suspension, placing a metal matrix in the nanodiamond seed crystal suspension to plant seed crystals, thereby obtaining a metal matrix with planted seed crystals; Step 3: Performing chemical vapor deposition to grow a diamond coating or a doped diamond coating on the metal matrix with planted seed crystals, thereby obtaining a high-density diamond-coated composite material. The high-density diamond-coated composite material provided by this invention has a dense and uniform diamond coating with excellent performance.

Description

Technical Field

[0001] This invention belongs to the field of diamond composite material preparation technology, specifically relating to a high-density diamond-coated composite material, its preparation method, and its application. Background Technology

[0002] During the chemical vapor deposition (CVD) of diamond films, the significant surface energy difference between diamond and the substrate, coupled with the low adhesion of hydrocarbon groups, typically results in lower nucleation density, longer nucleation incubation period, and slower deposition rate when diamond grows on heterogeneous substrates. Planting nanodiamond seeds on the substrate helps increase nucleation density, shorten the nucleation incubation period, accelerate the nucleation rate, and simultaneously reduce voids generated during the nucleation stage, thereby improving coating quality.

[0003] Nanodiamonds, with particle sizes below 100 nm, like other nanoparticles, possess extremely high specific surface energy, often resulting in aggregates. Physical dispersion methods such as ultrasonication and ball milling are insufficient to achieve satisfactory dispersion, severely hindering their application in many important fields. Therefore, improving their dispersibility and functionalizing their surfaces through surface chemical modification plays a crucial role in their application. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the first objective of this invention is to provide a method for preparing a high-density diamond-coated composite material.

[0005] The second objective of this invention is to provide a high-density diamond-coated composite material prepared by the above-described preparation method.

[0006] The third objective of this invention is to provide an application of a high-density diamond-coated composite material.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] This invention provides a method for preparing a high-density diamond-coated composite material, comprising the following steps:

[0009] Step 1

[0010] Modified nanodiamonds are obtained by hydrogenating or oxidizing the end groups of nanodiamond particles through pretreatment, wherein the pretreatment is heat treatment and / or plasma-assisted treatment.

[0011] Step Two

[0012] Modified nanodiamonds and surfactants were dispersed in water to obtain a nano-seed crystal suspension. A metal substrate was then placed in the nano-seed crystal suspension to plant seed crystals, thus obtaining a metal substrate with planted seed crystals.

[0013] Step 3

[0014] By growing a diamond coating or a doped diamond coating on a metal substrate with a seed crystal through chemical vapor deposition, a high-density diamond coating composite material is obtained.

[0015] The preparation method of this invention first involves surface modification of nanodiamond particles, such as oxidation or hydrogenation, to increase the nucleation density of diamond, thereby creating a strong bond between the nanodiamonds and the diamond coating surface, reducing the amount of nanodiamonds used. Additionally, it improves the dispersibility of microparticles in the composite diamond coating. Furthermore, by adding a surfactant to the nano-seed crystal suspension, the dispersion stability of the nanodiamonds can be further improved. This results in a strong bond between the metal substrate after seed crystal implantation and the diamond coating formed by chemical vapor deposition, leading to a dense, uniform, and high-performance diamond coating.

[0016] In a preferred embodiment, in step one, the particle size of the nanodiamond particles is 10nm-100nm.

[0017] In the preferred embodiment, in step one, the heat treatment process is as follows: the nanodiamond particles are placed in a hydrogen atmosphere or an oxygen atmosphere for heat treatment. The heat treatment temperature is 300-900℃, the heat treatment time is 10-30 min, and the gas pressure is 10000-30000 Pa, preferably 20000 Pa.

[0018] In this invention, the nanodiamond pretreatment technology modulates the surface end groups of nanodiamonds through high-temperature heat treatment or plasma-assisted treatment, thereby controlling the electronegativity of nanodiamonds. The heat treatment can be carried out in either a hydrogen atmosphere or an oxygen atmosphere. By heat treatment in a hydrogen atmosphere, hydrogen-terminated surface-modified nanodiamonds (H-NDs) are obtained, and by heat treatment in an oxygen atmosphere, oxygen-terminated surface-modified nanodiamonds (O-NDs) are obtained.

[0019] In a further preferred embodiment, when the nanodiamond particles are subjected to heat treatment in a hydrogen atmosphere, the heat treatment temperature is 600-700°C.

[0020] The inventors accidentally discovered that the suspension of H-NDs prepared by heat treatment at 600℃-700℃ had the highest Zeta potential, the best dispersibility, and the finest and most uniform solute particle size. The corresponding pretreated samples had the densest and most uniform nucleation and the best nucleation effect. The samples of H-NDs seed crystals planted after heat treatment at 600℃-700℃ had fine and uniformly distributed diamond grains and a smooth coating after CVD nucleation growth for 6 hours.

[0021] In a further preferred embodiment, when the nanodiamond particles are subjected to heat treatment in an oxygen atmosphere, the temperature of the heat treatment is 300-500°C.

[0022] The inventors also discovered that after using modified O-NDs at 300-500℃ for ultrasonic seed planting, the diamond particles were fine and the coating had good uniformity, density and smoothness after CVD nucleation growth for 6 hours.

[0023] In the preferred embodiment, in step one, the plasma-assisted treatment process involves placing the nanodiamond particles in a microwave plasma chemical vapor deposition device, introducing a hydrogen atmosphere, controlling the microwave power to be 500-900W, and the treatment time to be 10-30 minutes.

[0024] Hydrogen-terminated surface-modified nanodiamonds (H-NDs) were obtained through plasma-assisted treatment.

[0025] In a preferred embodiment, in step one, the nanodiamond particles are pretreated to undergo end-group hydrogenation modification to obtain modified nanodiamonds. The pretreatment involves heat treatment followed by plasma-assisted treatment.

[0026] The inventors discovered that by first performing heat treatment in a hydrogen atmosphere and then performing plasma-assisted treatment, the number of hydrogen-terminated groups can be further increased, thereby improving the performance of the resulting diamond coating.

[0027] In a preferred embodiment, in step two, the mass fraction of modified nanodiamond in the nano-seed crystal suspension is 0.01%-0.05%.

[0028] In a preferred embodiment, in step two, the surfactant in the nanodiamond seed crystal suspension is selected from at least one of OP-10, polyisobutylene bis(succinimide) (T154), sodium hexametaphosphate, sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, potassium chloride, sodium phosphate, polyethylene glycol, Tween, lysine, and glutamic acid. The inventors have discovered that by appropriately adding a surfactant to the nanodiamond seed crystal suspension, the dispersion stability of nanodiamonds can be improved.

[0029] In a preferred embodiment, in step two, the material of the metal matrix is ​​selected from one of nickel, niobium, tantalum, copper, titanium, cobalt, tungsten, molybdenum, chromium, and iron, or an alloy thereof; or a composite material composed of one or more of the above metals and one or more of the ceramics Al2O3, ZrO2, SiC, Si3N4, BN, B4C, AlN, TiB2, TiN, WC, Cr7C3, Ti2GeC, Ti2AlC and Ti2AlN, Ti3SiC2, Ti3GeC2, Ti3AlC2, Ti4AlC3, and BaPO3.

[0030] The base metal substrate in this invention includes rod-shaped, tubular, two-dimensional continuous mesh structure and two-dimensional closed plate structure.

[0031] In the preferred embodiment, in step two, the seed crystal planting method is selected from one of ultrasonic adsorption, electrostatic self-assembly, and electrophoretic deposition, with electrophoretic deposition being the preferred method.

[0032] Further optimization involves using ultrasonic adsorption to implant seed crystals. The seed crystal implantation process is as follows: place the metal substrate in a nano-seed crystal suspension, ultrasonically vibrate for 5-30 minutes, and then rinse and dry with ultrapure water.

[0033] In a further preferred embodiment, when the seed crystal is planted by electrophoretic deposition, the seed crystal planting process is as follows: the metal substrate and the metal electrode are placed together in the nano-seed crystal suspension, a DC electric field is applied, and the nano-diamond particles are electrophoretically deposited on the metal substrate. After rinsing and drying with ultrapure water, the seed crystal is obtained. The distance between the metal substrate and the metal electrode is 5-15 mm, the voltage of the applied DC electric field is 15-30 V, and the electrophoretic deposition time is 1-3 min.

[0034] The metal electrodes are selected from gold, silver, platinum, stainless steel, etc.

[0035] The inventors discovered that electrophoresis technology has advantages such as simple equipment, controllable movement speed, and uniform deposition on irregular surfaces. When using electrophoresis for nano-seed crystal planting, the nucleation density on the matrix surface increases with the increase of the absolute value of the surface potential of the diamond particles in the suspension, which can greatly improve the uniformity of nucleation. Of course, the suspension stability of nanoparticles is crucial in the process of manipulating nanomaterials using electrophoresis. Because nanodiamonds are prone to agglomeration and aggregation, their suspension stability is poor, usually requiring surface modification. However, in this invention, by appropriately adding surfactants to the nano-seed crystal suspension, the dispersion stability of nanodiamonds can be effectively improved.

[0036] In a preferred embodiment, in step three, the doped diamond coating is a boron-doped diamond coating.

[0037] In the preferred embodiment, the temperature of the metal substrate during chemical vapor deposition is 600-1000℃, and the growth time is 5-10h.

[0038] In a preferred embodiment, when growing a diamond coating by chemical vapor deposition, the mass flow rate ratio of the introduced gas is methane:hydrogen = 2-5:90-96; when growing a doped diamond coating by chemical vapor deposition, the mass flow rate ratio of the introduced gas is methane:borane:hydrogen = 2-5:2-5:90-96.

[0039] In a preferred embodiment, the chemical vapor deposition is selected from at least one of hot filament chemical vapor deposition, microwave plasma chemical vapor deposition, direct current plasma chemical vapor deposition, radio frequency ion chemical vapor deposition, flame combustion chemical vapor deposition, and direct current jet plasma chemical vapor deposition, preferably hot filament chemical vapor deposition.

[0040] In a further preferred embodiment, during the hot filament chemical vapor deposition, the temperature of the hot filament is controlled to be 1800-2500℃.

[0041] The present invention also provides a high-density diamond-coated composite material prepared by the above preparation method.

[0042] The present invention also provides an application of a high-density diamond-coated composite material prepared by the above preparation method, wherein the high-density diamond-coated composite material is applied to one of electrochemical biosensors, electrochemical synthesis, and electrochemical detection.

[0043] The present invention also provides an application of a dense diamond-coated composite material prepared by the above preparation method, wherein the dense diamond-coated composite material is applied to the degradation of organic wastewater.

[0044] Beneficial effects:

[0045] The preparation method of this invention first involves surface modification of nanodiamond particles through oxidation or hydrogenation to increase the nucleation density of diamond, thereby creating a strong bond between the nanodiamonds and the diamond coating surface, reducing the amount of nanodiamonds used. Additionally, it improves the dispersibility of microparticles in the composite diamond coating. Furthermore, by adding a surfactant to the nano-seed crystal suspension, the dispersion stability of the nanodiamonds can be further improved. This results in a strong bond between the metal substrate after seed crystal implantation and the diamond coating formed by chemical vapor deposition, leading to a dense, uniform, and high-performance diamond coating.

[0046] Compared with the prior art, the advantages of the present invention are as follows:

[0047] 1. Electrophoresis technology has the advantages of simple equipment, controllable movement speed, and uniform deposition on irregular surfaces. When using electrophoresis technology to plant nanodiamond seed crystals, the nucleation density on the substrate surface increases with the increase of the absolute value of the surface potential of diamond particles in the suspension, which can greatly improve the uniformity of nucleation.

[0048] 2. In the process of manipulating nanomaterials using electrophoresis, the suspension stability of nanoparticles is crucial. Because nanodiamonds are prone to agglomeration and stacking, their suspension stability is poor. Surface modification of nanodiamonds can effectively address this issue.

[0049] 3. Surface modification of nanodiamonds, such as oxidation and hydrogenation, can further increase the nucleation density of diamonds, giving nanodiamonds a strong bond with the coating surface, reducing the amount of nanodiamonds used, and improving the dispersion of particles in the composite coating, resulting in significant performance improvement and a more obvious strengthening effect of the film. Attached Figure Description

[0050] Figure 1 The images show the nucleation process of H-NDs with H terminals obtained after pretreatment in Examples 1 and 2, followed by ultrasonic treatment and electrophoretic deposition of seed crystals. Figure 1 (a) to (d) show the morphology of the seed crystals during seed crystal planting in Example 1 as time progresses. Figure 1 (e) to (h) show the morphology of the seed crystals during seed crystal planting in Example 2 as time progresses.

[0051] Figure 2 This refers to the nucleation process of O-NDs with O terminals obtained after pretreatment in Examples 4 and 5, followed by ultrasonic treatment and electrophoretic deposition of seed crystals. Figure 2 (a) to (d) show the morphology of the seed crystals during seed crystal planting in Example 4 as time progresses. Figure 2 (e) to (h) show the morphology of the seed crystals during seed crystal planting in Example 5 as time progresses.

[0052] Figure 3 The growth morphology of the diamond coatings obtained by chemical vapor deposition in Examples 1 and 2 is shown. Figure 3 (a) to (d) show the growth morphology of the diamond coating deposited by chemical vapor deposition over time in Example 1. Figure 3 (e) to (h) show the growth morphology of the diamond coating deposited by chemical vapor deposition over time in Example 2.

[0053] Figure 4 The growth morphology of the diamond coatings obtained by chemical vapor deposition in Examples 4 and 5 is shown. Figure 4 (a) to (d) show the growth morphology of the diamond coating deposited by chemical vapor deposition over time in Example 4. Figure 4 (e) to (h) show the growth morphology of the diamond coating deposited by chemical vapor deposition over time in Example 5.

[0054] As can be seen from the above figure, after the diamond material is modified by H-terminal or O-terminal, nanodiamond seed crystals are planted on the material through electrophoresis and ultrasonic technology. The nucleation density on the matrix surface is increased, and the formed film is dense and uniform, thereby improving the wastewater degradation performance of the diamond composite material. Detailed Implementation

[0055] Example 1

[0056] 10nm-100nm nanodiamond particles were placed in a heat treatment furnace and subjected to a hydrogen atmosphere to obtain modified nanodiamond H-NDs. The heat treatment temperature was 600℃, the heat treatment time was 30min, and the gas pressure was 20000Pa. The modified nanodiamond and OP-10 surfactant were added to water to obtain a nanodiamond seed crystal suspension, wherein the mass fraction of modified nanodiamond particles was 0.02%, and the mass fraction of surfactant in the nanodiamond seed crystal suspension was... The content was 3wt%. Then, the tantalum metal substrate was placed in a suspension of nanodiamond seed crystals, ultrasonically vibrated for 10 min, and then rinsed and dried with ultrapure water to obtain the metal substrate with the seed crystals. The metal substrate with the seed crystals was coated with diamond by hot-wire chemical vapor deposition. During the chemical vapor deposition, the temperature of the metal substrate was 900℃, the temperature of the hot wire was 1800℃, the growth time was 5 h, and the mass flow ratio of the introduced gas was methane:borane:hydrogen = 2:2:96, thus obtaining a high-density diamond-coated composite material. The prepared high-density diamond-coated composite material was filled between electrodes with a pure titanium plate as the cathode plate and a boron-doped diamond plate as the anode plate to form an electrochemical degradation module. A degradation experiment was carried out with a water-to-oil ratio of 1:3. A glucose solution with an initial TOC of 3000 mg was used as simulated wastewater, and sodium sulfate with 2% electrolyte was added. The voltage was adjusted to 5.03V, and degradation began. After approximately 5 hours, a TOC analyzer showed a total carbon removal rate of 90% in the simulated wastewater, with an energy consumption of 19.01 kWh / m³. 3 .

[0057] Example 2

[0058] Other conditions were the same as in Example 1, except that the seed crystal planting method was electrophoresis. The seed crystal planting process was as follows: a tantalum metal substrate was placed in a suspension of nanodiamond seed crystals, a DC electric field was applied, and nanodiamond particles were electrophoretically deposited on the metal substrate. The substrate was then rinsed and dried with ultrapure water. The distance between the metal substrate and the metal electrode was 10 mm, the applied DC electric field voltage was 20 V, and the electrophoretic deposition time was 2 min. The prepared high-density diamond coating composite material was filled between electrodes using a pure titanium plate as the cathode and boron-doped diamond as the anode to create an electrochemical degradation module. A water-to-volume ratio of 1:3 was used for the degradation experiment. A glucose solution with an initial TOC of 3000 mg was used as simulated wastewater, and 2% sodium sulfate was added as the electrolyte. The voltage was adjusted to 5.03 V, and degradation began. After approximately 5 hours, a TOC analyzer detected a total carbon removal rate of 92% in the simulated wastewater, and the energy consumption per ton of water was calculated to be 20.50 kWh / m³. 3 .

[0059] Example 3

[0060] Nanodiamond particles of 10nm-100nm were placed in a heat treatment furnace and subjected to heat treatment in a hydrogen atmosphere at a temperature of 700℃ for 30 minutes at a pressure of 20000Pa. The heat-treated nanodiamond particles were then placed in a microwave plasma chemical vapor deposition apparatus under a hydrogen atmosphere, with a microwave power of 800W, for 10 minutes to obtain modified nanodiamonds (H-NDs). The modified nanodiamonds and OP-10 surfactant were then added to water to obtain a nanodiamond seed suspension containing the modified nanodiamond particles. The mass fraction of the surfactant in the nanodiamond seed crystal suspension was 0.02%, and the mass fraction of the surfactant in the nanodiamond seed crystal suspension was 5 wt%. Then, a metal substrate was placed in the nanodiamond seed crystal suspension and ultrasonically vibrated for 10 min. After rinsing and drying with ultrapure water, a metal substrate with the seed crystal was obtained. The metal substrate with the seed crystal was then coated with a diamond layer using hot-wire chemical vapor deposition. During chemical vapor deposition, the temperature of the metal substrate was 900°C, the temperature of the hot wire was 1800°C, the growth time was 5 h, and the mass flow ratio of the introduced gas was methane:borane:hydrogen = 2:2:96, resulting in a high-density diamond-coated composite material. The prepared high-density diamond-coated composite material was filled between electrodes using a pure titanium plate as the cathode and boron-doped diamond as the anode to create an electrochemical degradation module. A degradation experiment was conducted using a water-to-gas ratio of 1:3, with a glucose solution with an initial TOC of 3000 mg as simulated wastewater, and 2% sodium sulfate added as the electrolyte. The voltage was adjusted to 5.03V, and degradation began. After approximately 5 hours, a TOC analyzer showed a total carbon removal rate of 92.6% in the simulated wastewater, with an energy consumption of 17.13 kWh / m³. 3 .

[0061] Example 4

[0062] 10nm-100nm nanodiamond particles were placed in a heat treatment furnace and subjected to an oxygen atmosphere to obtain modified nanodiamond O-NDs. The heat treatment temperature was 400℃, the heat treatment time was 30min, and the pressure was 20000Pa. The modified nanodiamonds and O-P10 surfactant were added to water to obtain a nanodiamond seed crystal suspension, wherein the mass fraction of modified nanodiamond particles was 0.02%, and the mass fraction of surfactant in the nanodiamond seed crystal suspension was 5wt%. Then, a tantalum metal substrate is placed in a suspension of nanodiamond seed crystals, ultrasonically vibrated for 10 minutes, and then rinsed and dried with ultrapure water to obtain a metal substrate with seed crystals. The metal substrate with seed crystals is then coated with a diamond coating by hot-wire chemical vapor deposition. During the chemical vapor deposition, the temperature of the metal substrate is 900℃, the temperature of the hot wire is 1800℃, the growth time is 5 hours, and the mass flow ratio of the introduced gas is methane:borane:hydrogen = 2:2:96%2-5:2-5:90-96, thus obtaining a high-density diamond coating composite material.

[0063] The prepared high-density diamond-coated composite material was filled between electrodes consisting of a pure titanium plate as the cathode and a boron-doped diamond plate as the anode to create an electrochemical degradation module. A degradation experiment was conducted using a water-to-oil ratio of 1:3. A glucose solution with an initial TOC of 3000 mg was used as simulated wastewater, with 2% sodium sulfate added as the electrolyte. The voltage was adjusted to 5.03 V, and degradation began. After approximately 5 hours, a TOC analyzer detected a total carbon removal rate of 96.7% in the simulated wastewater, and the energy consumption per ton of water was calculated to be 10.45 kWh / m³. 3

[0064] Example 5

[0065] Other conditions were the same as in Example 3, except that the seed crystal planting method was electrophoresis. The seed crystal planting process was as follows: a heat-treated tantalum metal substrate was placed in a suspension of nanodiamond seed crystals, a DC electric field was applied, and nanodiamond particles were electrophoretically deposited on the metal substrate. The substrate was then rinsed and dried with ultrapure water. The distance between the metal substrate and the metal electrode was 10 mm, the applied DC electric field voltage was 20 V, and the electrophoretic deposition time was 2 min. The prepared high-density diamond coating composite material was filled between electrodes using a pure titanium plate as the cathode and boron-doped diamond as the anode to create an electrochemical degradation module. A water-to-volume ratio of 1:3 was used for the degradation experiment. A glucose solution with an initial TOC of 3000 mg was used as simulated wastewater, and 2% sodium sulfate was added as the electrolyte. The voltage was adjusted to 5.03 V, and degradation began. After approximately 5 hours, a TOC analyzer detected a total carbon removal rate of 97.0% in the simulated wastewater, and the energy consumption per ton of water was calculated to be 9.15 kWh / m³.

[0066] Comparative Example 1

[0067] Other conditions were the same as in Example 1, except that OP-10 was not added when planting the seed crystals. The prepared high-density diamond-coated particle composite material was filled between electrodes using a pure titanium plate as the cathode and boron-doped diamond as the anode to create an electrochemical degradation module. A water-to-volume ratio of 1:3 was used for the degradation experiment. A glucose solution with an initial TOC of 3000 mg was used as the simulated wastewater, and 2% sodium sulfate was added as the electrolyte. The voltage was adjusted to 5.03 V, and degradation began. After approximately 5 hours, a TOC analyzer showed that the total carbon removal rate in the simulated wastewater was 82%, and the energy consumption per ton of water was calculated to be 31.75 kWh / m³. 3 .

Claims

1. A method for preparing a high-density diamond-coated composite material, characterized in that: Includes the following steps: Step 1 Modified nanodiamonds are obtained by hydrogenating the end groups of nanodiamond particles through pretreatment, wherein the pretreatment is first heat treatment followed by plasma-assisted treatment. The heat treatment process is as follows: the nanodiamond particles are placed in a hydrogen atmosphere and heat-treated at a temperature of 600-700℃ for 10-30 minutes and at a pressure of 10000-30000Pa. The plasma-assisted treatment process involves placing nanodiamond particles in a microwave plasma chemical vapor deposition device, introducing a hydrogen atmosphere, controlling the microwave power to be 500-900W, and the treatment time to be 10-30 minutes. Step Two Modified nanodiamonds and surfactants were dispersed in water to obtain a nano-seed crystal suspension. A metal substrate was then placed in the nano-seed crystal suspension to plant seed crystals, thus obtaining a metal substrate with planted seed crystals. In the nano-seed crystal suspension, the surfactant is selected from at least one of OP-10, polyisobutylene bis(succinimide), sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, polyethylene glycol, and Tween. Step 3 By growing a diamond coating or a doped diamond coating on a metal substrate with a seed crystal through chemical vapor deposition, a high-density diamond coating composite material is obtained.

2. The method for preparing a high-density diamond-coated composite material according to claim 1, characterized in that: In step one, the particle size of the nanodiamond particles is 10nm-100nm.

3. The method for preparing a high-density diamond-coated composite material according to claim 1, characterized in that: In step two, the mass fraction of modified nanodiamond in the nano-seed crystal suspension is 0.01%-0.05%.

4. The method for preparing a high-density diamond-coated composite material according to claim 1, characterized in that: In step two, the seed crystal planting method is selected from one of ultrasonic adsorption, electrostatic self-assembly, and electrophoretic deposition; When the seed crystal is planted by ultrasonic adsorption, the seed crystal planting process is as follows: place the metal substrate in the nano-seed crystal suspension, ultrasonically vibrate for 5-30 minutes, and then rinse and dry with ultrapure water to obtain the seed crystal. When the seed crystal is planted by electrophoretic deposition, the seed crystal planting process is as follows: the metal substrate and the metal electrode are placed together in the nano-seed crystal suspension, a DC electric field is applied, and the nano-diamond particles are electrophoretically deposited on the metal substrate. After rinsing and drying with ultrapure water, the seed crystal is obtained. The distance between the metal substrate and the metal electrode is 5-15 mm, the voltage of the applied DC electric field is 15-30 V, and the electrophoretic deposition time is 1-3 min.

5. The method for preparing a high-density diamond-coated composite material according to claim 1, characterized in that: During the chemical vapor deposition, the temperature of the metal substrate is 600-1000℃, and the growth time is 5-10 hours. When growing diamond coatings by chemical vapor deposition, the mass flow rate ratio of the introduced gases is methane:hydrogen = 2-5:90-96. When growing a diamond-doped coating by chemical vapor deposition, the mass flow rate ratio of the introduced gas is methane:borane:hydrogen = 2-5:2-5:90-96. The chemical vapor deposition is selected from one of the following: hot filament chemical vapor deposition, microwave plasma chemical vapor deposition, direct current plasma chemical vapor deposition, radio frequency ion chemical vapor deposition, flame combustion chemical vapor deposition, and direct current jet plasma chemical vapor deposition.

6. A high-density diamond-coated composite material prepared by the preparation method according to any one of claims 1-5.

7. The application of a high-density diamond-coated composite material prepared by the preparation method according to any one of claims 1-5, characterized in that: The dense diamond-coated composite material is applied to one of the following: electrochemical biosensors, electrochemical synthesis, and electrochemical detection.

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