A method for transfer growth of high-density vertical carbon nanotube-diamond composite materials

Abstract

This invention provides a method for the transfer growth of high-density vertical carbon nanotube-diamond composite materials, belonging to the field of functional materials and device manufacturing technology. The method includes: growing high-density VCNTs on a Si substrate; repeatedly coating the VCNT-Si composite substrate surface with a nucleation liquid; gradually growing a continuous diamond film on the VCNT-Si surface using CVD technology; separating the Si and VCNT-diamond composite materials by utilizing the superior adhesion of VCNTs on the diamond substrate compared to the Si substrate; and removing excess metal catalyst from the surface of the VCNT-diamond composite material to obtain an all-carbon VCNT-diamond composite material. This invention uses carbon nanotubes embedded within diamond to reinforce the connection between high-density VCNTs and diamond, preparing all-carbon allotropic composites based on one-dimensional and three-dimensional carbon. This method is suitable for the preparation of large-size, high-density, highly uniform, strongly interface-bonded, and highly heat-transferring ultra-black VCNT-diamond composite materials, and can be used in extreme environments such as high radiation and strong magnetic fields.

Description

Technical Field

[0001] This invention belongs to the field of functional materials and device manufacturing, and relates to a method for transfer growth of high-density vertical carbon nanotube-diamond composite materials. Background Technology

[0002] Infrared remote sensing technology has wide applications in weather forecasting, climate monitoring, and disaster prevention and mitigation. Infrared radiometric calibration is the core of these devices, and rapid calibration requires the inclusion of ultra-black material components. Ultra-black materials possess extremely strong stray light elimination capabilities and are visually aesthetically pleasing. Furthermore, as functional devices continue to develop towards higher precision and higher efficiency, there are two main requirements: firstly, ultra-black coating materials must extend their spectral response band to a wider range, achieving ideal absorption across the entire spectrum from ultraviolet and visible to far-infrared; secondly, higher demands are placed on strong interface bonding and heat transfer efficiency.

[0003] Vertical carbon nanotubes (VCNTs) possess a unique one-dimensional structure and a huge aspect ratio; they exhibit high thermal conductivity (3000-3500 W / m·K) and ultra-high light absorption (over 99% absorption across a wide wavelength range of 0.25-16 μm), making them one of the "blackest" light-absorbing materials. Generally, high-density VCNTs are easily fabricated on Si substrates; however, the weak adhesion between VCNTs and Si substrates leads to easy detachment, resulting in enhanced thermal accumulation at the carbon interface and causing the ultra-black coating of VCNTs to fail. Diamond, on the other hand, possesses high chemical stability and high thermal conductivity, and is an allotrope of carbon like VCNTs. A strong chemical bond can be formed between the VCNT array and the diamond substrate at the interface, significantly improving the adhesion between VCNTs and the diamond substrate.

[0004] Chinese patent CN 112981364 B describes the growth of VCNTs on diamond substrates for application in the optical field. However, due to the interaction between the diamond substrate and the catalyst, the quality of VCNTs grown directly on the diamond surface differs significantly from that grown on a silicon substrate. The high density of VCNTs on diamond substrates, the strong bonding between VCNTs and diamond, and the excellent thermal transfer potential of the interface are not fully realized.

[0005] Therefore, exploring a method for preparing all-carbon VCNTs that can achieve high-density VCNTs while also ensuring strong interfacial bonding with diamond substrates is of significant application value. Summary of the Invention

[0006] The technical problem to be solved by this invention is to strengthen the interface between vertical carbon nanotubes (VCNT) and diamond, thereby achieving the preparation of VCNT-diamond composite samples with strong bonding, high density, and large size. This helps to improve the thermal transmission and light absorption properties of VCNT-diamond and reduce the risk of composite material failure.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0008] A method for transfer-growing high-density vertical carbon nanotube-diamond composite materials is disclosed, which achieves the composite of diamond films and high-density, large-area VCNTs. The method includes: first, growing high-density VCNTs on a Si substrate; then, repeatedly coating the VCNT-Si composite substrate surface with a nucleation liquid; using CVD technology, gradually growing a continuous diamond film on the VCNT-Si surface; utilizing the superior adhesion of VCNTs on the diamond substrate compared to the Si substrate, separating the Si and VCNT-diamond composite materials; finally, removing excess metal catalyst from the surface of the VCNT-diamond composite material to obtain an all-carbon VCNT-diamond composite material.

[0009] Furthermore, the method includes the following steps:

[0010] Preparation of S1 and VCNT-Si

[0011] To grow VCNTs on a Si substrate, a discontinuous catalyst layer is first deposited on the cleaned Si substrate using radio frequency magnetron sputtering. Then, the Si substrate is annealed in a CVD apparatus to transform the discontinuous catalyst layer into nano-catalyst particles. Finally, VCNTs are grown on the surface of the Si substrate containing catalyst particles using a CVD apparatus again.

[0012] Preferably, the catalyst is Fe, Ni, or Fe2+. x Ni y One of them has a catalyst layer thickness of 3~15 nm.

[0013] Preferably, the radio frequency magnetron sputtering parameters are: vacuum 2.0 × 10⁻⁶. -4 ~5.0×10 -4 Pa, the ambient temperature of the Si substrate is room temperature, the Ar flow rate is 40~70 sccm, and the sputtering power is 50~100 W.

[0014] Preferably, the CVD equipment is selected from one of microwave plasma chemical vapor deposition (MPCVD), plasma enhanced chemical vapor deposition (PECVD), and thermal CVD (TCVD).

[0015] Preferably, the annealing parameters are: H2 flow rate of 200-300 sccm, holding at a temperature of 500-700℃ for 1-3 min, followed by annealing for 5-20 min, so that the discontinuous catalyst layer on the Si surface becomes nano-catalyst particles.

[0016] Preferably, the parameters for growing VCNTs on the Si substrate using CVD equipment are: CH4 flow rate of 20-100 sccm, H2 flow rate of 50-300 sccm, deposition temperature of 450-700℃, and deposition time of 20-120 min, to obtain VCNT-Si composite material.

[0017] Preferably, the VCNT has a length of 50–300 μm.

[0018] S2 and VCNT-Si surfaces coated with diamond nucleating liquid

[0019] First, to avoid the influence of metal catalyst on diamond film growth, the surface of the VCNT-Si composite material obtained in step S1 is acid-washed to remove excess metal catalyst. After acid washing, it is rinsed and dried with deionized water. To prevent hydrogen plasma from etching VCNT during diamond film growth, a hydroxyl-containing nanodiamond-carbon nanotube nucleation solution is prepared. The hydroxyl-containing nanodiamond-carbon nanotube nucleation solution is then spin-coated onto the VCNT-Si surface and vacuum dried.

[0020] Preferably, the hydroxyl-containing nanodiamond-carbon nanotube nucleation solution is prepared by the following method: Nanodiamond powder is continuously boiled in a mixed acid for 1 hour. The mixed acid is obtained by mixing concentrated nitric acid (volume V1) and concentrated sulfuric acid (volume V2), with a mass concentration of 68% for the concentrated nitric acid and 98% for the concentrated sulfuric acid, and a V1:V2 ratio of 1:3. Excess acid is then removed by ultrasonic cleaning in flowing deionized water, and finally, the nanodiamond containing hydroxyl groups is dried to obtain the nanodiamond containing hydroxyl groups. To prevent uneven nucleation, 1 mg of commercially available hydroxylated multi-walled carbon nanotubes (MWCNT / OH, purity 99%) and 9 mg of hydroxyl-containing nanodiamond are placed in 500 mL of ethanol solution, ultrasonicated, and stirred for 1 hour to obtain a composite nucleation solution in which hydroxyl-containing carbon nanotubes adsorb nanodiamond.

[0021] Preferably, the amount of nucleation solution used for surface spin coating is 3-5 mL; the spin coating speed is 300-500 rpm; and the spin coating time is 10-30 s. This operation is repeated 3-5 times to form a dense nanodiamond and CNT protective layer on the VCNT surface.

[0022] S3, diamond nucleus

[0023] The VCNT-Si coated with nucleation solution obtained in S2 was placed in a CVD device to perform diamond nucleation on its surface.

[0024] Preferably, the diamond nucleation parameters are: nucleation temperature of 750–850 °C, H2 flow rate of 200–300 sccm, CH4 flow rate of 30–50 sccm, and nucleation time of 5–20 min.

[0025] S4, grown diamond self-supporting film

[0026] Diamond growth continues on one side of the VCNT-Si coated nucleation liquid until a diamond self-supporting film of a certain thickness is formed at the top of the carbon nanotube.

[0027] Preferably, the CVD is MPCVD or HFCVD.

[0028] Preferably, the diamond growth parameters are: deposition temperature of 700–800 ℃, H2 flow rate of 200–300 sccm, CH4 flow rate of 5–10 sccm, and growth time of 100–200 h.

[0029] Preferably, the thickness of the self-supporting membrane is 100–500 μm.

[0030] S5. Obtaining VCNT-diamond composite material

[0031] Using a mechanical separation method, the Si substrate in the VCNT-Si with diamond self-supporting film obtained in S4 was peeled off from the VCNT-diamond composite material. The metal catalyst on the surface of the VCNT-diamond composite material was washed away with dilute acid, and then rinsed with flowing deionized water and vacuum dried to obtain an all-carbon VCNT-diamond composite material.

[0032] Preferably, the dilute acid is either dilute hydrochloric acid or dilute sulfuric acid, with a mass concentration of 5-10%.

[0033] Preferably, the vacuum drying temperature is 90–120 °C, and the duration is 20–40 min.

[0034] The present invention also provides a high-density vertical carbon nanotube-diamond composite material prepared by the method, and the application of the material in the field of light absorption.

[0035] The present invention has the following beneficial effects:

[0036] High-density CNT arrays cannot be directly fabricated on diamond substrates using existing technologies. Since silicon substrates readily support CNT growth, this invention first prepares a VCNT-Si composite material, then connects the tips of carbon nanotubes to the diamond substrate using a nucleation solution. Because carbon nanotubes are hydrophobic / alcohol-phobic, the hydrophilicity of the carbon nanotubes and the mixed nucleation solution during spin-coating determines the uniformity of seeding on the carbon nanotube surface (the silicon substrate). Adding carbon nanotubes to the composite nucleation solution to adsorb modified nanodiamond particles increases seeding uniformity. The cyclical seeding and nucleation process prevents hydrogen ion etching of the carbon nanotubes on the Si substrate surface and provides growth conditions for the growth of self-supporting diamond films.

[0037] Subsequently, taking advantage of the fact that the adhesion between CNTs and silicon is less than that between CNTs and diamond, the silicon substrate and the VCNT-diamond composite material were directly separated to obtain an interface-reinforced high-density carbon nanotube-diamond composite material. This material possesses characteristics such as high heat dissipation, excellent light absorption, and high density. Furthermore, the VCNT-diamond interface is an embedded, all-carbon interface with strong adhesion, providing a novel alternative material for thermal and optical applications. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a flowchart illustrating the preparation process of the VCNT-diamond composite material of the present invention.

[0040] Figure 2 The image shown is a SEM image of the diamond-VCNT-Si composite material obtained in step 5 of Example 1.

[0041] Figure 3 Images of the composite materials after 5 hours of ultrasonic vibration are shown below. (a) is an image of the VCNT-diamond composite material before ultrasonic vibration, (b) is an image of the VCNT-diamond composite material after ultrasonic vibration, (c) is an image of the VCNT-Si composite material before ultrasonic vibration, and (d) is an image of the VCNT-Si composite material after ultrasonic vibration.

[0042] Figure 4 The light absorption properties of the VCNT-composite material obtained in Example 1 are shown, where (a) is the light absorption property in the ultraviolet band and (b) is the light absorption property in the infrared band.

[0043] Figure 5The light absorption properties of the VCNT-composite material obtained in Comparative Example 1 are shown, where (a) represents the light absorption properties in the ultraviolet band and (b) represents the light absorption properties in the infrared band. Detailed Implementation

[0044] In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0045] Example 1

[0046] 1) Place the cleaned Si substrate into the RF magnetron sputtering equipment, and evacuate the cavity to 3.0 × 10⁻⁶. -4 Pa, the matrix is ​​at 250℃, then Ar is introduced at 70 sccm until the chamber pressure reaches 3.6 × 10⁻⁶. -1 Pa, sputtering power of 80 W, self bias of 270 V, voltage of 1000 V, current of 210 mA, applied bias of 100 V, duty cycle of 50%, frequency of 42 Hz, Fe was deposited on the Si surface for 1 min to the required film thickness of 6 nm (the film is discontinuous and has gaps).

[0047] 2) The Fe film on the Si surface was nano-sized using MPCVD. First, 200 sccm of H2 was introduced, the chamber pressure was 3 kPa, the temperature was raised to 650℃, held for 1 min, and then annealed for 8 min to obtain Fe catalyst particles. To grow VCNTs, the temperature was raised to 600℃, 180 sccm of H2 and 20 sccm of CH4 were introduced, the chamber pressure was 3 kPa, and the process was continued for 60 min to grow VCNTs on the Si surface, resulting in a VCNT-Si composite material with a VCNT length of 220 μm.

[0048] 3) To prevent the metal catalyst from affecting the quality of diamond, the VCNT-Si was reversed so that only the top surface of the VCNTs came into contact with dilute hydrochloric acid to remove Fe catalyst particles from the surface of the VCNTs. The reversed VCNT-Si was then contacted with flowing deionized water to remove excess Fe ions and dilute hydrochloric acid from the surface of the VCNTs, and then dried in a vacuum drying oven at 100°C for 30 min.

[0049] 4) The nanodiamond powder was placed in a mixture of concentrated nitric acid (volume V1) and concentrated sulfuric acid (volume V2) (volume concentration of concentrated nitric acid was 68%, and that of concentrated sulfuric acid was 98%, V1:V2 = 1:3) and boiled for 1 hour. Afterward, it was ultrasonically washed in flowing deionized water to remove excess acid, and finally dried to obtain hydroxyl-containing nanodiamonds. To prevent uneven nucleation, 1 mg of commercially available hydroxylated multi-walled carbon nanotubes (MWCNT / OH, purity 99%) and 9 mg of hydroxyl-containing nanodiamonds were placed in 500 mL of ethanol solution, ultrasonicated and stirred for 1 hour to obtain a composite nucleation solution of hydroxyl-containing carbon nanotubes adsorbing nanodiamonds. Then, 3 mL of the composite nucleation solution was dropwise added to the VCNT-Si surface and spin-coated, first at 300 rpm for 5 seconds, then at 500 rpm for 60 seconds. Next, after heating at 110°C for 25 minutes in a vacuum drying oven, the VCNT-Si was placed in the MPCVD chamber, and 250 sccm of H2 and 50 sccm of CH4 were introduced into the chamber at 800°C for 10 minutes to perform diamond nucleation. The spin-coating composite nucleation solution-CVD nucleation process was repeated 8 times, and then dried at 110°C for 35 minutes in a vacuum drying oven.

[0050] 5) After the 8th diamond nucleation, the CH4 flow rate was reduced from 50 sccm to 5 sccm, the temperature was 750℃, the growth time was 120 h, and the diamond film thickness was 150 μm.

[0051] 6) Finally, the Si substrate and the diamond substrate were fixed and separated by tweezers. The metal catalyst on the surface of the VCNT-diamond was washed away with 15% dilute hydrochloric acid. The Fe ions and excess dilute hydrochloric acid remaining on the surface of the VCNT-diamond were rinsed with flowing deionized water. Then, the VCNT-diamond was vacuum dried at 110°C for 20 min to finally obtain the all-carbon VCNT-diamond composite material.

[0052] Figure 1 This is a flowchart illustrating the preparation process of the VCNT-diamond composite material of the present invention. The invention first deposits a catalyst on the surface of a Si substrate, then grows VCNTs on the catalyst-coated side, and subsequently removes the catalyst by acid washing. A hydroxyl-containing nanodiamond-carbon nanotube nucleation solution is coated onto the side of the VCNTs furthest from the silicon substrate, followed by diamond nucleation on the surface to grow a diamond self-supporting film. Using a mechanical separation method, the Si substrate and the VCNT-diamond composite material are exfoliated to obtain the VCNT-diamond composite material.

[0053] Figure 2This is a SEM image of the diamond-VCNT-Si composite material obtained in step 5) of Example 1. This image ensures the authenticity of the example. It can be seen that one side of the VCNT is a diamond self-supporting film, and the other side is a silicon substrate. The diamond self-supporting film formed by CVD can serve as a high thermal conductivity diamond substrate, converting the radiation absorption of vertical carbon nanotubes into heat and quickly conducting it away, thus solving the problem of temperature calibration failure caused by interfacial heat accumulation effect.

[0054] Figure 3 Images of the composite material after 5 hours of ultrasonic vibration are shown. The upper half of each small image is a macroscopic image taken with a digital camera, and the lower half is a SEM image, used to detect the adhesion of VCNTs to the substrate surface. (a) shows the VCNT-diamond composite material before ultrasonic vibration, where VCNTs are neatly distributed on the diamond surface; (b) shows the VCNT-diamond composite material after ultrasonic vibration, where some VCNTs are tilted but still present on the diamond surface; (c) shows the VCNT-Si composite material before ultrasonic vibration, where the distribution of VCNTs on the silicon substrate surface is the same as in (a); and (d) shows the VCNT-Si composite material after ultrasonic vibration, where almost no carbon nanotubes are distributed on the silicon substrate surface. Comparing images (a) to (d), it can be seen that the adhesion of carbon nanotubes on the diamond substrate is much greater than that on the silicon substrate. Ultrasonic vibration can remove most of the carbon nanotubes on the silicon substrate surface, but cannot remove the carbon nanotubes on the diamond surface. Tweezers are used to directly separate silicon and the carbon nanotube-diamond composite material in the examples to provide supplementary evidence.

[0055] Figure 4 The light absorption properties of the VCNT-composite material obtained in Example 1 are shown, where (a) represents the light absorption properties in the ultraviolet band and (b) represents the light absorption properties in the infrared band. This demonstrates that the material exhibits an absorption value of 99% in both the 0.25-2.5 μm ultraviolet band and the 2.5-16 μm infrared band. It can be applied to infrared optical thermal imagers and can also serve as a planar standard heat sink for calibrating thermal imagers. Due to the influence of infrared stray radiation, the image contrast and temperature indication accuracy of thermal imagers often decrease, and because the sources of stray radiation vary under different conditions, it is difficult to correct for this through pre-calibration. Therefore, the ultra-black VCNT-diamond composite material will provide accurate thermal imaging, including FTIR microscopy, heat screening, environmental remote sensing, and infrared telescopes, to detect highly redshifted early universe stars or exoplanet atmospheres. Furthermore, maximizing the infrared emissivity of the thin film will increase the light power emitted by the light source at a given temperature. The ultra-black VCNT-diamond composite material has potential for aerospace applications, effectively transferring heat through radiation, and the high infrared emissivity coating ensures the accuracy of temperature calibration.

[0056] Example 2

[0057] 1) Place the cleaned Si substrate into the RF magnetron sputtering equipment, and evacuate the cavity to 3.0 × 10⁻⁶. -4 Pa, the matrix is ​​220℃, then Ar is introduced at 40 sccm until the chamber pressure is 1.6 × 10⁻⁶. -1 Pa, sputtering power of 65 W, self bias of 250 V, voltage of 950 V, current of 200 mA, applied bias of 100 V, duty cycle of 50%, frequency of 42 Hz, Ni is deposited on Si surface for 1.5 min to the required film thickness of 10 nm (the film is discontinuous and has gaps).

[0058] 2) The Ni film on the Si surface was nano-sized using TCVD. First, 300 sccm of H2 was introduced, the chamber pressure was 600 Pa, the temperature was raised to 700℃, held for 1 min, and then annealed for 10 min to obtain Ni catalyst particles. To grow VCNTs, the temperature was raised to 680℃, 200 sccm of H2 and 100 sccm of CH4 were introduced, the chamber pressure was 600 Pa, and the process was continued for 100 min. VCNTs with a length of 200 μm were grown on the Si surface, resulting in a VCNT-Si composite material.

[0059] 3) To prevent the metal catalyst from affecting the quality of diamond, the VCNT-Si was reversed so that only the top surface of the VCNTs came into contact with dilute sulfuric acid to remove Ni catalyst particles from the surface of the VCNTs. The reversed VCNT-Si was then contacted with flowing deionized water to remove excess Ni ions and dilute sulfuric acid from the surface of the VCNTs, and then dried in a vacuum drying oven at 110°C for 20 min.

[0060] 4) The nanodiamond powder was placed in a mixture of concentrated nitric acid (volume V1) and concentrated sulfuric acid (volume V2) (volume concentration of concentrated nitric acid was 68%, and that of concentrated sulfuric acid was 98%, V1:V2 = 1:3) and boiled for 1 hour. Afterward, it was ultrasonically washed in flowing deionized water to remove excess acid, and finally dried to obtain hydroxyl-containing nanodiamonds. To prevent uneven nucleation, 1 mg of commercially available hydroxylated multi-walled carbon nanotubes (MWCNT / OH, purity 99%) and 9 mg of hydroxyl-containing nanodiamonds were placed in 500 mL of ethanol solution, ultrasonicated and stirred for 1 hour to obtain a composite nucleation solution of hydroxyl-containing carbon nanotubes adsorbing nanodiamonds. Subsequently, 5 mL of the composite nucleation solution was dropped onto the top surface of the VCNTs for spin coating, first at 350 rpm for 5 seconds, then at 400 rpm for 60 seconds. After heating at 100℃ for 30 min in a vacuum drying oven, VCNT-Si was placed in the HFCVD chamber, and 250 sccm of H2 and 50 sccm of CH4 were introduced into the chamber at 820℃ for 15 min to perform diamond nucleation. The spin-coating composite nucleation solution-diamond nucleation process was repeated 10 times.

[0061] 5) After the 10th diamond nucleation, the CH4 flow rate was reduced from 50 sccm to 10 sccm, the temperature was 800℃, the growth time was 110 h, and the diamond film thickness was 170 μm.

[0062] Finally, the Si substrate and diamond substrate were fixed and separated using tweezers. The metal catalyst on the surface of the VCNT-diamond was washed away with 10% dilute sulfuric acid. The Ni ions and excess dilute sulfuric acid remaining on the surface of the VCNT-diamond were rinsed with flowing deionized water. Subsequently, the VCNT-diamond was vacuum dried at 105℃ for 25 min to obtain an all-carbon VCNT-diamond composite material. Its light absorption performance was tested in the infrared and ultraviolet bands, and the absorbance values ​​were both above 99%.

[0063] Comparative Example 1

[0064] 1) Place the cleaned Si substrate into the RF magnetron sputtering equipment, and evacuate the cavity to 3.0 × 10⁻⁶. -4 Pa, the matrix is ​​220℃, then Ar is introduced at 40 sccm until the chamber pressure is 1.6 × 10⁻⁶. -1 The sputtering power was 65 W, the self-bias voltage was 250 V, the voltage was 950 V, the current was 200 mA, the applied bias voltage was 100 V, the duty cycle was 50%, and the frequency was 42 Hz. Fe was deposited on the Si surface. x Ni y Continue for 2 minutes until the desired film thickness of 11 nm is achieved (the film is discontinuous and contains voids).

[0065] 2) Using TCVD to study Fe on Si surfaces x Ni y The membrane was nano-sized by first introducing 300 sccm of H2, setting the chamber pressure to 600 Pa, raising the temperature to 700℃, holding at that temperature for 1 min, and then annealing for 10 min to obtain Fe. x Ni y Catalyst particles. To grow VCNTs, the temperature was raised to 680℃ and 200 sccm of H2 and 100 sccm of CH4 were added at a chamber pressure of 600 Pa for 100 min. VCNTs with a length of 200 μm were grown on the Si surface, resulting in a VCNT-Si composite material.

[0066] 3) To prevent the metal catalyst from affecting the quality of diamond, the VCNT-Si was reversed, allowing only the top surface of the VCNTs to contact dilute sulfuric acid to remove Ni catalyst particles from the VCNTs surface. Subsequently, the reversed VCNT-Si was contacted with flowing deionized water to remove excess Fe from the VCNTs surface. Ni The ions and dilute sulfuric acid were dried in a vacuum drying oven at 100°C for 25 minutes.

[0067] 4) Nanodiamond powder was boiled in a mixture of concentrated nitric acid (V1:V2) and concentrated sulfuric acid (V2:V1 = 1:3) for 1 hour. Excess acid was then removed by ultrasonic cleaning in flowing deionized water, and finally dried to obtain hydroxyl-containing nanodiamonds. 9 mg of the hydroxyl-containing nanodiamonds was then added to 500 mL of ethanol solution and ultrasonicated and stirred for 1 hour to obtain a composite nucleation solution for hydroxyl-containing carbon nanotubes adsorbing nanodiamonds. 5 mL of the hydroxyl-containing nanodiamond nucleation solution was added to the top surface of VCNTs for spin coating, first at 350 rpm for 5 seconds, then at 400 rpm for 60 seconds. After heating at 100°C for 30 minutes in a vacuum drying oven, the VCNT-Si was placed in the HFCVD chamber. The chamber was purged with 250 sccm H2 and 50 sccm CH4 at 820°C for 15 minutes to induce diamond nucleation. This spin coating nucleation solution-diamond nucleation process was repeated 10 times.

[0068] 5) After the 10th diamond nucleation, the CH4 flow rate was reduced from 50 sccm to 10 sccm, the temperature was 800℃, the growth time was 110 h, and the diamond film thickness was 170 μm.

[0069] Finally, the Si substrate and the diamond substrate were fixed and separated by tweezers. The metal catalyst on the surface of the VCNT-diamond was washed away with dilute sulfuric acid. The Ni ions and excess dilute sulfuric acid remaining on the surface of the VCNT-diamond were rinsed with flowing deionized water. The VCNT-diamond was then dried in a vacuum at 105°C for 25 min to obtain a carbon-based VCNT-diamond composite material.

[0070] Figure 5 (a) and Figure 5 (b) The UV and IR absorption spectra of the comparative VCNT-diamond composite material are shown. The maximum UV absorption is only 5%, and the maximum IR absorption is 80%, which is unstable. This is because no commercially available hydroxyl carbon nanotube solution was added during the nucleation process, resulting in uneven distribution of the nanodiamonds during spin-coating. During the nucleation and diamond growth processes, the carbon nanotubes on the CNT-Si composite substrate surface are etched by hydrogen plasma, leading to a highly uneven distribution of carbon nanotubes on the diamond surface and a sharp decrease in UV-IR absorption performance.

[0071] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for transfer growth of high-density vertical carbon nanotube-diamond composite materials, characterized in that, The method includes: High-density VCNTs are grown on the surface of a Si substrate; Nucleation liquid was coated multiple times on the surface of the VCNT-Si composite substrate. The nucleation liquid was a hydroxyl-containing nanodiamond-carbon nanotube nucleation liquid. Using CVD technology, a continuous diamond film was gradually grown on the VCNT-Si surface; Taking advantage of the superior adhesion of VCNT to diamond substrates compared to Si substrates, Si and VCNT-diamond composite materials were separated. Excess metal catalyst was removed from the surface of the VCNT-diamond composite material to obtain an all-carbon VCNT-diamond composite material.

2. A method for transfer growth of high-density vertical carbon nanotube-diamond composite materials, characterized in that, The method includes the following steps: Preparation of S1 and VCNT-Si First, a discontinuous catalyst layer is deposited on a cleaned Si substrate using radio frequency magnetron sputtering; then, the Si substrate is annealed in a CVD apparatus to transform the discontinuous catalyst layer into nano-catalyst particles; finally, VCNTs are grown on the surface of the Si substrate containing catalyst particles using a CVD apparatus again. S2 and VCNT-Si surfaces coated with diamond nucleating liquid The surface of the VCNT-Si composite material obtained in step S1 was acid-washed, and then spin-coated on the VCNT-Si surface using a hydroxyl-containing nanodiamond-carbon nanotube core liquid and vacuum dried. S3, diamond nucleus The VCNT-Si coated with nucleation solution obtained in S2 was placed into a CVD device to perform diamond nucleation on its surface; S4, grown diamond self-supporting film Diamond growth continued on one side of the VCNT-Si coated nucleation liquid until a diamond self-supporting film was formed at the top of the carbon nanotube. S5. Obtaining VCNT-diamond composite material Using a mechanical separation method, the Si substrate in the VCNT-Si with diamond self-supporting film obtained in S4 was peeled off from the VCNT-diamond composite material. The metal catalyst on the surface of the VCNT-diamond composite material was washed away with dilute acid, and then rinsed with flowing deionized water and vacuum dried to obtain an all-carbon VCNT-diamond composite material.

3. The method for transfer growth of high-density vertical carbon nanotube-diamond composite material according to claim 2, characterized in that, In step S1, the catalyst is Fe, Ni, or Fe2+. x Ni y One of them has a catalyst layer thickness of 3~15 nm.

4. The method for transfer growth of high-density vertical carbon nanotube-diamond composite material according to claim 2, characterized in that, In step S1, the RF magnetron sputtering parameters are: vacuum 2.0 × 10⁻⁶. -4 ~5.0×10 -4 Pa, the ambient temperature of the Si substrate is room temperature, the Ar flow rate is 40~70 sccm, and the sputtering power is 50~100 W; And / or, the annealing parameters are: H2 flow rate of 200-300 sccm, holding at a temperature of 500-700℃ for 1-3 min, followed by annealing for 5-20 min, so that the discontinuous catalyst layer on the Si surface becomes nano-catalyst particles; And / or, VCNTs are grown on the surface of a Si substrate using a CVD device with the following parameters: CH4 flow rate of 20–100 sccm, H2 flow rate of 50–300 sccm, deposition temperature of 450–700℃, and deposition time of 20–120 min, to obtain VCNT-Si composite materials. And / or, the VCNT length is 50–300 μm.

5. The method for transfer growth of high-density vertical carbon nanotube-diamond composite material according to claim 2, characterized in that, In step S2, the hydroxyl-containing nanodiamond-carbon nanotube core liquid is prepared by the following method: Nanodiamond powder was placed in a mixed acid and boiled for 1 hour. The mixed acid was obtained by mixing concentrated nitric acid (volume V1) and concentrated sulfuric acid (volume V2). The mass concentration of the concentrated nitric acid was 68%, the mass concentration of the concentrated sulfuric acid was 98%, and the ratio of V1 to V2 was 1:

3. Then, the powder was ultrasonically cleaned in flowing deionized water to remove excess acid and dried to obtain hydroxyl-containing nanodiamond powder. Take 1 mg of commercially available hydroxylated multi-walled carbon nanotubes and 9 mg of hydroxyl-containing nanodiamonds and place them in 500 mL of ethanol solution. Sonicate and stir for 1 h to obtain a composite nucleation solution in which hydroxyl-containing carbon nanotubes adsorb nanodiamonds.

6. The method for transfer growth of high-density vertical carbon nanotube-diamond composite material according to claim 2, characterized in that, In step S2, the amount of nucleation solution used for surface spin coating is 3-5 mL; the spin coating speed is 300-500 rpm; the spin coating time is 10-30 s; the above operation is repeated 3-5 times to form a dense nanodiamond and CNT protective layer on the VCNT surface.

7. The method for transfer growth of high-density vertical carbon nanotube-diamond composite material according to claim 2, characterized in that, In step S3, the diamond nucleation parameters are: nucleation temperature of 750–850 °C, H2 flow rate of 200–300 sccm, CH4 flow rate of 30–50 sccm, and nucleation time of 5–20 min.

8. The method for transfer growth of high-density vertical carbon nanotube-diamond composite material according to claim 2, characterized in that, In step S4, the diamond growth parameters are: deposition temperature of 700-800 ℃, H2 flow rate of 200-300 sccm, CH4 flow rate of 5-10 sccm, and growth time of 100-200 h; And / or, the thickness of the self-supporting membrane is 100–500 μm.

9. The high-density vertical carbon nanotube-diamond composite material prepared by the method according to any one of claims 1 to 8.

10. The application of the high-density vertical carbon nanotube-diamond composite material according to claim 9 in the field of light absorption.

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