A hexagonal boron nitride nanotube self-supporting film, a preparation method and application thereof

Abstract

The application discloses a hexagonal boron nitride nanotube self-supporting film and a preparation method and application thereof, and belongs to the field of controllable preparation of nanomaterials. The preparation method is as follows: a carbon nanotube film with a self-supporting network structure is used as a template, a hexagonal boron nitride nanotube is hetero-epitaxially grown on the carbon nanotube and a bundle of the carbon nanotubes by adopting a chemical vapor deposition process to form a one-dimensional van der Waals coaxial tubular heterostructure, then etching treatment is adopted to remove the carbon nanotube template, the tube diameter of the hexagonal boron nitride nanotube is controlled by adjusting the diameter of the carbon nanotube and the size of the bundle of the carbon nanotube, the coating efficiency and the number of layers of the hexagonal boron nitride nanotube are controlled by adjusting the chemical vapor deposition condition, and finally a self-supporting film formed by a network of the hexagonal boron nitride nanotube with controllable tube diameter and number of layers is obtained. The preparation method has strong controllability, and can be used to prepare a hexagonal boron nitride nanotube self-supporting film with different number of layers, diameter, high purity, high crystallinity, high flexibility, high light transmittance and excellent stability, and has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of controllable preparation of nanomaterials, specifically relating to a self-supporting thin film of hexagonal boron nitride nanotubes, its preparation method, and its application. Background Technology

[0002] Two-dimensional hexagonal boron nitride nanosheets, due to their atomically flat, dangling-bond-free, inert surface, have become ideal substrates and gate dielectric layers for two-dimensional material devices. Thin films composed of hexagonal boron nitride nanosheets have been a research hotspot in recent years. Researchers have developed "top-down" methods, represented by mechanical exfoliation, and "bottom-up" methods, represented by chemical vapor deposition, to prepare hexagonal boron nitride thin films. However, these methods suffer from poor controllability and the introduction of contamination during the transfer process, severely limiting their widespread application.

[0003] Hexagonal boron nitride nanotubes can be viewed as one-dimensional hollow tubular structures formed by replacing carbon atoms in carbon nanotubes with boron (B) and nitrogen (N) atoms. They possess excellent properties such as high thermal conductivity, wide bandgap, high elastic modulus, and high strength. Thin films constructed from hexagonal boron nitride nanotubes inherit the intrinsic superior properties of carbon nanotubes and have broad application prospects in areas such as high-frequency, high-power electronic heat dissipation, deep ultraviolet sterilization and sensing, and ultra-low-power chips for artificial intelligence. However, due to the low purity, poor crystallinity, and small aspect ratio of hexagonal boron nitride nanotubes prepared by existing technologies, it remains very difficult to prepare self-supporting hexagonal boron nitride nanotube films through post-processing methods. The specific reasons are as follows: First, current methods for preparing hexagonal boron nitride nanotubes generally require catalysts and various boron-containing precursors, resulting in low purity of the prepared products and difficulties in post-processing purification; Second, low-purity hexagonal boron nitride nanotubes need to be dispersed and purified by ultrasonic treatment, which leads to further shortening, resulting in short nanotubes with poor crystallinity; Third, boron nitride nanotubes with poor purity, low crystallinity, and small aspect ratio have poor film-forming properties, making it difficult to obtain highly transparent self-supporting films. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention aims to provide a method for preparing a self-supporting hexagonal boron nitride nanotube thin film. The method involves heteroepitaxially growing hexagonal boron nitride nanotubes with controllable diameter and number of layers on carbon nanotubes and their bundles, and then removing the carbon nanotube template to obtain a self-supporting hexagonal boron nitride nanotube thin film with a thickness ranging from tens of nanometers to several micrometers. The film exhibits high light transmittance, high flexibility, high chemical stability, and insulation and thermal conductivity.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing a self-supporting thin film of hexagonal boron nitride nanotubes. Using a carbon nanotube thin film with a self-supporting network structure as a template, hexagonal boron nitride nanotubes are heteroepitaxially grown on the carbon nanotubes and their bundles using a chemical vapor deposition process to form a one-dimensional van der Waals coaxial tubular heterostructure. Then, the carbon nanotube template is removed by etching. The diameter of the hexagonal boron nitride nanotubes is controlled by adjusting the diameter of the carbon nanotubes and the size of the bundle. The coating efficiency and number of layers of the hexagonal boron nitride nanotubes are controlled by adjusting the chemical vapor deposition conditions, thereby obtaining a self-supporting thin film formed by the overlapping of a network of hexagonal boron nitride nanotubes with controllable diameter and number of layers.

[0007] Furthermore, the thickness of the carbon nanotube film with the self-supporting network structure is 20nm-200nm.

[0008] Furthermore, the diameter of carbon nanotubes and their bundles was controlled to be 2nm-50nm.

[0009] Furthermore, the chemical vapor deposition process can be atmospheric pressure chemical vapor deposition, low pressure chemical vapor deposition, or rapid heating-high temperature chemical vapor deposition.

[0010] Furthermore, the boron-nitrogen precursors used in atmospheric pressure chemical vapor deposition are ammonia borane, cycloborane, or dimethylamine borane.

[0011] Controlled atmospheric pressure chemical vapor deposition conditions: the boron-nitrogen precursor volatilization temperature is 40℃-90℃, the deposition temperature is 500℃-1500℃, the boron nitride growth reaction time is 5min-10h, and the number of boron nitride coating layers is 1-50 layers.

[0012] Furthermore, the boron-nitrogen precursors used in the low-pressure chemical vapor deposition method are ammonia borane and / or borazine;

[0013] Controlling low-pressure chemical vapor deposition conditions: gas pressure < 500 Pa, boron-nitrogen precursor volatilization temperature 40℃-90℃, deposition temperature 500℃-1500℃, boron nitride growth reaction time 5 min-10 h, and boron nitride coating layer number 1-50 layers.

[0014] Furthermore, the rapid heating-high temperature chemical vapor deposition method uses ammonia borane, cycloborane, or dimethylamine borane as the boron-nitrogen precursor. The boron-nitrogen precursor is supplied after being heated to 60℃-120℃, and the supply method includes any of the following:

[0015] (1) Intracavitary synchronous pyrolysis power supply: The solid boron-nitrogen precursor is placed in a vacuum chamber and decomposed during rapid heating-high temperature process;

[0016] (2) External vaporization and transport source supply: The boron-nitrogen precursor is sublimated by an external heating device and the source is transported into the cavity by a carrier gas;

[0017] The heating rate for rapid heating-high temperature chemical vapor deposition was set to 10. 2 ℃ / s-10 4 ℃ / s, heating temperature is 1000℃-3000℃, boron nitride growth reaction time is 5s-60s, and the number of boron nitride coating layers is 1-100 layers.

[0018] Furthermore, the etching process can be carried out using oxidation etching or plasma etching.

[0019] Oxidation etching involves heat treatment at 350℃-850℃ for 10h-30h in flowing air or oxygen.

[0020] Plasma etching is the etching process using hydrogen, argon, or oxygen plasma at a power of 10W-50W for 10 minutes to 15 hours.

[0021] Secondly, the present invention provides a hexagonal boron nitride nanotube self-supporting film, which is prepared by the above-mentioned method for preparing hexagonal boron nitride nanotube self-supporting film. The diameter of the hexagonal boron nitride nanotube is 2nm-100nm, and the thickness of the hexagonal boron nitride nanotube self-supporting film is 20nm-300nm.

[0022] Thirdly, this invention provides an application of a hexagonal boron nitride nanotube self-supporting thin film for fields such as extreme ultraviolet lithography protection, high-frequency and high-power electronic heat dissipation, deep ultraviolet sterilization and sensing, and ultra-low power chips.

[0023] Advantages and effects of the present invention:

[0024] 1. The preparation method of the present invention has strong controllability and can achieve controllable preparation of hexagonal boron nitride nanotubes with different numbers of layers and diameters;

[0025] 2. The preparation method of the present invention can grow hexagonal boron nitride nanotubes on carbon nanotubes and their bundle templates through efficient heteroepitaxial growth. Since there are no chemical bonds between the carbon nanotubes and the hexagonal boron nitride, the carbon nanotube template can be removed efficiently and controllably by taking advantage of their difference in chemical stability, so as to obtain high-purity and highly crystalline hexagonal boron nitride nanotubes.

[0026] 3. The hexagonal boron nitride nanotube self-supporting film obtained by this invention has high purity, high crystallinity, and also has high flexibility, high light transmittance and excellent stability, and has broad application prospects. Attached Figure Description

[0027] Figure 1 An optical photograph of the single-walled carbon nanotube@hexagonal boron nitride nanotube composite film of Example 1;

[0028] Figure 2The image shows the Raman spectrum of the single-walled carbon nanotube@hexagonal boron nitride nanotube composite film of Example 1.

[0029] Figure 3 The UV-Vis absorption spectrum of the single-walled carbon nanotube@hexagonal boron nitride nanotube composite film in Example 1 is shown.

[0030] Figure 4 This is a transmission electron microscope (TEM) image of the single-walled carbon nanotube@hexagonal boron nitride nanotube composite film of Example 1;

[0031] Figure 5 The image shows the Raman spectrum of the self-supporting hexagonal boron nitride nanotube film of Example 1.

[0032] Figure 6 This is a transmission electron microscope (TEM) image of the self-supporting hexagonal boron nitride nanotube thin film of Example 1;

[0033] Figure 7 The temperature rise and fall curves for rapid heating-high temperature chemical vapor deposition in Example 2 are shown.

[0034] Figure 8 An optical photograph of the single-walled carbon nanotube@hexagonal boron nitride nanotube composite film of Example 2;

[0035] Figure 9 The UV-Vis absorption spectrum of the single-walled carbon nanotube@hexagonal boron nitride nanotube composite film in Example 3 is shown.

[0036] Figure 10 This is a transmission electron microscope (TEM) image of the single-walled carbon nanotube@hexagonal boron nitride nanotube composite film of Example 3. Detailed Implementation

[0037] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0038] A method for preparing a self-supporting thin film of hexagonal boron nitride nanotubes involves using a carbon nanotube film with a self-supporting network structure and a thickness of 20 nm-200 nm as a template. Hexagonal boron nitride nanotubes are heteroepitaxially grown on the carbon nanotubes and their bundles using atmospheric pressure chemical vapor deposition (CVD), low pressure CVD, or rapid temperature-high temperature CVD to form a one-dimensional van der Waals coaxial tubular heterostructure. Then, the carbon nanotube template is removed by oxidation etching or plasma etching. The diameter of the carbon nanotubes and their bundles is controlled to be 2 nm-50 nm, and the diameter of the hexagonal boron nitride nanotubes is controlled to be 2 nm-100 nm. By adjusting the CVD conditions, the coating efficiency and number of layers of the hexagonal boron nitride nanotubes are controlled, resulting in a self-supporting thin film with a thickness of 20 nm-300 nm formed by the overlapping of a network of hexagonal boron nitride nanotubes with controllable diameter and number of layers.

[0039] The specific method for chemical vapor deposition is as follows:

[0040] (1) The boron-nitrogen precursors used in atmospheric pressure chemical vapor deposition are ammonia borane, cycloborane or dimethylamine borane;

[0041] Controlled atmospheric pressure chemical vapor deposition conditions: the boron-nitrogen precursor volatilization temperature is 40℃-90℃, the deposition temperature is 500℃-1500℃, the boron nitride growth reaction time is 5min-10h, and the number of boron nitride coating layers is 1-50 layers.

[0042] (2) The boron-nitrogen precursors used in the low-pressure chemical vapor deposition method are ammonia borane and / or borazine;

[0043] Controlling low-pressure chemical vapor deposition conditions: gas pressure < 500 Pa, boron-nitrogen precursor volatilization temperature 40℃-90℃, deposition temperature 500℃-1500℃, boron nitride growth reaction time 5 min-10 h, and boron nitride coating layer number 1-50 layers.

[0044] (3) The boron-nitrogen precursor used in the rapid heating-high temperature chemical vapor deposition method is ammonia borane, cycloborane, or dimethylamine borane. The boron-nitrogen precursor is supplied after being heated to 60℃-120℃, and the supply method includes any of the following:

[0045] 1) Intracavitary synchronous pyrolysis power supply: The solid boron-nitrogen precursor is placed in a vacuum chamber and decomposed during rapid heating-high temperature process;

[0046] 2) External vaporization and transport source supply: The boron-nitrogen precursor is sublimated using an external heating device and the source is transported into the cavity by a carrier gas;

[0047] The heating rate for rapid heating-high temperature chemical vapor deposition was set to 10. 2 ℃ / s-10 4 ℃ / s, heating temperature is 1000℃-3000℃, boron nitride growth reaction time is 5s-60s, and the number of boron nitride coating layers is 1-100 layers.

[0048] The specific etching process is as follows:

[0049] Oxidation etching involves heat treatment at 350℃-850℃ for 10h-30h in flowing air or oxygen.

[0050] Plasma etching is the etching process using hydrogen, argon, or oxygen plasma at a power of 10W-50W for 10 minutes to 15 hours.

[0051] A self-supporting thin film of hexagonal boron nitride nanotubes is prepared by the above-mentioned preparation method of self-supporting thin film of hexagonal boron nitride nanotubes. The diameter of the hexagonal boron nitride nanotubes is 2nm-100nm, and the thickness of the self-supporting thin film of hexagonal boron nitride nanotubes is 20nm-300nm.

[0052] An application of a hexagonal boron nitride nanotube self-supporting thin film is proposed for extreme ultraviolet lithography protection, high-frequency and high-power electronic heat dissipation, deep ultraviolet sterilization and sensing, and ultra-low power chips.

[0053] Example 1

[0054] A method for preparing a self-supporting thin film of hexagonal boron nitride nanotubes, employing low-pressure chemical vapor deposition and high-temperature oxidation etching, is detailed below:

[0055] (1) The single-walled carbon nanotube film collected on the cellulose filter membrane is imprinted and transferred onto the graphite ring to form a self-supporting single-walled carbon nanotube film with a thickness of about 50 nm, wherein the single-walled carbon nanotube bundle size is about 2 nm-30 nm.

[0056] (2) The self-supporting single-walled carbon nanotube film was placed in a low-pressure chemical vapor deposition system. Ammonia borane was used as the boron-nitrogen precursor. The chamber pressure was pumped to <20 Pa using a mechanical pump. A 300 sccm argon + hydrogen mixed gas (hydrogen content 3%) was introduced as the carrier gas. The pressure was adjusted to 100 Pa. The temperature of the reaction zone of the low-pressure chemical vapor deposition furnace was raised to 1200 °C at a heating rate of 20 °C / min. Then the temperature of the boron-nitrogen precursor evaporation zone was raised to 70 °C. The volatilized ammonia borane vapor was transported to the downstream reaction zone using the carrier gas. Hexagonal boron nitride was grown on the surface of the single-walled carbon nanotube. The growth reaction time was 3 h. The film was naturally cooled to room temperature to obtain the single-walled carbon nanotube@hexagonal boron nitride nanotube composite film.

[0057] (3) The single-walled carbon nanotube@hexagonal boron nitride nanotube composite film was placed in a muffle furnace and heated to 550°C at a heating rate of 10°C / min under air atmosphere, held for 20h, and then naturally cooled to room temperature to obtain the self-supporting hexagonal boron nitride nanotube film.

[0058] The hexagonal boron nitride nanotube self-supporting film prepared by the method of Example 1 has a diameter of 5nm-20nm and a thickness of approximately 50nm.

[0059] Structural characterization:

[0060] (1) Structural characterization of single-walled carbon nanotube@hexagonal boron nitride nanotube composite films

[0061] like Figure 1The optical photographs shown demonstrate that the single-walled carbon nanotube@hexagonal boron nitride nanotube composite film prepared by low-pressure chemical vapor deposition still maintains high light transmittance and a self-supporting structure.

[0062] Raman spectroscopy characterization, such as Figure 2 As shown, the crystallinity of the single-walled carbon nanotube@hexagonal boron nitride nanotube composite film did not change significantly compared with the single-walled carbon nanotube film before the growth of hexagonal boron nitride.

[0063] Perform ultraviolet-visible absorption spectroscopy characterization, such as Figure 3 As shown, the characteristic peak at 200 nm in the spectrum corresponds to the optical band gap (~6.2 eV) of the hexagonal boron nitride nanotubes, confirming the successful preparation of hexagonal boron nitride. At the same time, the absorbance of the film at 550 nm before and after the growth of hexagonal boron nitride remains basically unchanged, indicating that the high-temperature growth process did not damage the carbon nanotube template and effectively inherited the excellent light transmittance of the substrate material.

[0064] Single-walled carbon nanotube@hexagonal boron nitride nanotube composite films were directly transferred onto a copper mesh microgrid and characterized by transmission electron microscopy. Figure 4 As shown, the carbon nanotube bundles are uniformly coated with a layered boron nitride structure, with approximately 1 to 10 layers and an interlayer spacing of 0.335 nm, proving that the coating layer is highly crystalline hexagonal boron nitride.

[0065] (2) Structural characterization of self-supporting hexagonal boron nitride nanotube thin films

[0066] Raman spectroscopy characterization, such as Figure 5 As shown, on the one hand, no characteristic G peak of carbon nanotubes was detected in the film after high-temperature oxidation etching, indicating that the 20-hour annealing process completely removed the single-walled carbon nanotubes in the film; on the other hand, the Raman signal of boron nitride nanotubes appeared in the Raman spectrum, and the peak corresponds to the in-plane phonon vibration mode of the hexagonal boron nitride (BN) bond, reflecting the ordered arrangement of the BN covalent bonds, indicating that the boron nitride nanotubes in the film have good crystallinity.

[0067] Self-supporting hexagonal boron nitride nanotube films were directly transferred onto a copper mesh microgrid and characterized by transmission electron microscopy. Figure 6 As shown, after high-temperature oxidation etching, the single-walled carbon nanotubes have been removed, and the self-supporting film consists of 1 to 10 layers of boron nitride nanotubes with a diameter of 5 nm to 20 nm.

[0068] Example 2

[0069] A method for preparing a self-supporting thin film of hexagonal boron nitride nanotubes, employing rapid heating-high temperature chemical vapor deposition and high temperature oxidation etching, is detailed below:

[0070] (1) The single-walled carbon nanotube film collected on the cellulose filter membrane is imprinted onto the graphite ring to form a self-supporting single-walled carbon nanotube film with a thickness of about 20 nm, wherein the single-walled carbon nanotube bundle size is about 2 nm-30 nm.

[0071] (2) In the vacuum heating chamber, a graphite plate with a thickness of 1 mm was used as the heating stage. A self-supporting single-walled carbon nanotube film template was placed on the graphite plate. The chamber pressure was pumped down to <100 Pa using a mechanical pump. High-purity argon gas (volume purity 99.999%) was introduced to atmospheric pressure. 50 mg of ammonia borane was heated at 60 °C using an external heating device and kept at that temperature for 15 min to allow the ammonia borane to fully sublimate and be transported into the chamber with the carrier gas to supply the boron-nitrogen source. Subsequently, a DC power supply was started to perform Joule heating on the graphite plate. The heating current was set to 270 A, and the total heating time was 40 s. The heating rate during this process was approximately 320 °C / s, and the highest temperature of the sample reached approximately 1700 °C (e.g., ...). Figure 7 (The temperature rise and fall curves shown) indicate that after growth, the material was naturally cooled to room temperature to obtain a single-walled carbon nanotube@hexagonal boron nitride nanotube composite film.

[0072] (3) The single-walled carbon nanotube@hexagonal boron nitride nanotube composite film was placed in a tube furnace and 300 sccm of high-purity oxygen was introduced as the carrier gas (volume purity 99.999%). The temperature was increased to 400℃ at a heating rate of 20℃ / min, held for 30h, and then naturally cooled to room temperature to obtain the self-supporting hexagonal boron nitride nanotube film.

[0073] The hexagonal boron nitride nanotube self-supporting film prepared by the preparation method of the hexagonal boron nitride nanotube self-supporting film in Example 2 has a diameter of 10nm-20nm and a thickness of about 20nm.

[0074] Structural characterization:

[0075] (1) Structural characterization of single-walled carbon nanotube@hexagonal boron nitride nanotube composite films

[0076] like Figure 8 The optical photographs shown demonstrate that the single-walled carbon nanotube@hexagonal boron nitride nanotube composite film prepared by rapid heating-high temperature chemical vapor deposition still maintains high light transmittance and a self-supporting structure.

[0077] Perform ultraviolet-visible absorption spectroscopy characterization, such as Figure 9 As shown, the significant characteristic peak at 200 nm in the spectrum confirms the successful growth of hexagonal boron nitride on the surface of carbon nanotubes. Meanwhile, the absorbance of the film at 550 nm remains basically unchanged before and after the growth of hexagonal boron nitride, indicating that the high-temperature rapid growth process did not damage the carbon nanotube template and effectively preserved the excellent optical transmittance of the substrate material.

[0078] Single-walled carbon nanotube@hexagonal boron nitride nanotube composite films were directly transferred onto a copper mesh microgrid and characterized by transmission electron microscopy. Figure 10 As shown, carbon nanotubes are uniformly coated with boron nitride nanotubes with a clear layered structure, with approximately 1 to 5 coating layers. The continuous coating morphology demonstrates that the method has high coating efficiency, and the prepared boron nitride nanotubes have high crystallinity.

[0079] (2) Structural characterization of self-supporting hexagonal boron nitride nanotube thin films

[0080] Raman spectroscopy characterization revealed that no characteristic G peak of carbon nanotubes was detected in the film after high-temperature oxidation etching. However, a Raman signal of boron nitride nanotubes appeared in the Raman spectrum. This peak corresponds to the in-plane phonon vibration mode of the hexagonal boron nitride (BN) bond, reflecting the ordered arrangement of the BN covalent bonds and indicating that the boron nitride nanotubes in the film have good crystallinity.

[0081] Self-supporting hexagonal boron nitride nanotube films were directly transferred onto a copper mesh microgrid and characterized by transmission electron microscopy. After high-temperature oxidation etching, the single-walled carbon nanotubes were removed, and the self-supporting films consisted of 1 to 5 layers of boron nitride nanotubes with diameters of 10 nm to 20 nm.

[0082] Example 3

[0083] A method for preparing a self-supporting thin film of hexagonal boron nitride nanotubes, employing low-pressure chemical vapor deposition and plasma etching, is detailed below:

[0084] (1) The single-walled carbon nanotube film collected on the cellulose filter membrane is imprinted onto the graphite ring to form a self-supporting single-walled carbon nanotube film with a thickness of about 100 nm, wherein the single-walled carbon nanotube bundle size is about 2 nm-50 nm.

[0085] (2) The self-supporting single-walled carbon nanotube film was placed in a low-pressure chemical vapor deposition system. Ammonia borane was used as the boron-nitrogen precursor. The chamber pressure was pumped to <20 Pa using a mechanical pump. A 400 sccm argon + hydrogen mixed gas (5% hydrogen) was introduced as the carrier gas. The pressure was adjusted to 200 Pa. The temperature of the reaction zone of the low-pressure chemical vapor deposition furnace was raised to 1300 °C at a heating rate of 20 °C / min. Then the temperature of the boron-nitrogen precursor evaporation zone was raised to 40 °C. The volatilized ammonia borane vapor was transported to the downstream reaction zone using the carrier gas. Hexagonal boron nitride was grown on the surface of the single-walled carbon nanotube. The growth reaction time was 2 h. The film was naturally cooled to room temperature to obtain the single-walled carbon nanotube@hexagonal boron nitride nanotube composite film.

[0086] (3) The single-walled carbon nanotube@hexagonal boron nitride nanotube composite film was placed in the plasma cleaner chamber, and the vacuum in the chamber was first evacuated to <10.-3 The plasma was charged at 30 sccm and hydrogen gas was introduced. After the gas flow stabilized, the plasma power was set to 50 W. After processing for 10 minutes, the plasma was charged to atmospheric pressure and then removed to obtain a self-supported hexagonal boron nitride nanotube film.

[0087] The hexagonal boron nitride nanotube self-supporting film prepared by the method of Example 3 has a diameter of 2nm-50nm and a thickness of approximately 100nm.

[0088] Structural characterization:

[0089] (1) Structural characterization of single-walled carbon nanotube@hexagonal boron nitride nanotube composite films

[0090] As can be seen from the optical photographs, the single-walled carbon nanotube@hexagonal boron nitride nanotube composite film prepared by low-pressure chemical vapor deposition still maintains high light transmittance and a self-supporting structure.

[0091] Raman spectroscopy characterization showed that the crystallinity of the single-walled carbon nanotube@hexagonal boron nitride nanotube composite film did not degrade compared with the single-walled carbon nanotube film before the growth of hexagonal boron nitride.

[0092] The UV-Vis absorption spectroscopy characterization showed a significant characteristic peak at 200 nm, confirming the successful growth of hexagonal boron nitride on the surface of carbon nanotubes.

[0093] The single-walled carbon nanotube@hexagonal boron nitride nanotube composite film was directly transferred onto a copper mesh microgrid and characterized by transmission electron microscopy. The carbon nanotube bundles were uniformly coated with a layered boron nitride structure, with approximately 1 to 10 layers, confirming that the surface of the single-walled carbon nanotubes was successfully coated with a hexagonal boron nitride layer.

[0094] (2) Structural characterization of self-supporting hexagonal boron nitride nanotube thin films

[0095] Raman spectroscopy characterization revealed that no characteristic G peak of carbon nanotubes was detected in the film after high-temperature oxidation etching. However, a Raman signal of boron nitride nanotubes appeared in the Raman spectrum. This peak corresponds to the in-plane phonon vibration mode of the hexagonal boron nitride (BN) bond, reflecting the ordered arrangement of the BN covalent bonds and indicating that the boron nitride nanotubes in the film have good crystallinity.

[0096] Self-supporting hexagonal boron nitride nanotube films were directly transferred onto a copper mesh microgrid and characterized by transmission electron microscopy. After high-temperature oxidation etching, the single-walled carbon nanotubes were removed, and the self-supporting films consisted of 1 to 10 layers of boron nitride nanotubes with diameters of 2 nm to 50 nm.

[0097] Example 4

[0098] A method for preparing a self-supporting thin film of hexagonal boron nitride nanotubes, employing atmospheric pressure chemical vapor deposition and plasma etching, is detailed below:

[0099] (1) The single-walled carbon nanotube film collected on the cellulose filter membrane is imprinted onto the alumina frame to form a self-supporting single-walled carbon nanotube film with a thickness of about 50 nm, wherein the single-walled carbon nanotube bundle size is about 2 nm-30 nm.

[0100] (2) The self-supporting single-walled carbon nanotube film was surface functionalized by air plasma at 10W for 60s. Then it was placed in the reaction chamber of the atmospheric pressure chemical vapor deposition system. Cycloborane was used as the boron-nitrogen precursor. The chamber pressure was pumped to <20Pa by a mechanical pump. A mixture of argon and hydrogen (3% hydrogen) at 400sccm was introduced as the carrier gas to maintain the system pressure at atmospheric pressure. The temperature of the reaction zone of the low-pressure chemical vapor deposition furnace was raised to 950℃ at a heating rate of 20℃ / min. Then the temperature of the boron-nitrogen precursor evaporation zone was raised to 60℃. The volatilized cycloborane vapor was transported to the downstream reaction zone by the carrier gas. Hexagonal boron nitride was grown on the surface of the single-walled carbon nanotube. The growth reaction time was 3h. Then it was naturally cooled to room temperature with the furnace under the protection of high-purity nitrogen to obtain the single-walled carbon nanotube@hexagonal boron nitride nanotube composite film.

[0101] (3) The single-walled carbon nanotube@hexagonal boron nitride nanotube composite film was placed in the plasma cleaner chamber, and the vacuum in the chamber was first evacuated to <10. -3 The plasma was charged at 30 sccm and hydrogen gas was introduced. After the gas flow stabilized, the plasma power was set to 30 W. After treatment for 6 hours, the plasma was charged to atmospheric pressure and then removed to obtain a self-supported hexagonal boron nitride nanotube film.

[0102] The hexagonal boron nitride nanotube self-supporting film prepared by the method of Example 4 has a diameter of 5nm-20nm and a thickness of approximately 50nm.

[0103] Structural characterization:

[0104] (1) Structural characterization of single-walled carbon nanotube@hexagonal boron nitride nanotube composite films

[0105] As can be seen from the optical photographs, the single-walled carbon nanotube@hexagonal boron nitride nanotube composite film prepared by atmospheric pressure chemical vapor deposition still maintains high light transmittance and a self-supporting structure.

[0106] Raman spectroscopy characterization showed that the crystallinity of the single-walled carbon nanotube@hexagonal boron nitride nanotube composite film did not degrade compared with the single-walled carbon nanotube film before the growth of hexagonal boron nitride.

[0107] Ultraviolet-visible absorption spectroscopy characterization revealed a significant characteristic peak at 200 nm, confirming the successful growth of hexagonal boron nitride on the carbon nanotube surface. Furthermore, the absorbance at 550 nm remained essentially unchanged before and after boron nitride growth, indicating that the high-temperature rapid growth process did not damage the carbon nanotube template and effectively preserved the excellent optical transmittance of the substrate material.

[0108] The single-walled carbon nanotube@hexagonal boron nitride nanotube composite film was directly transferred onto a copper mesh microgrid and characterized by transmission electron microscopy. The carbon nanotube bundles were uniformly coated with a layered boron nitride structure, with the number of layers ranging from 1 to 10, which confirmed that the surface of the single-walled carbon nanotubes was successfully coated with a hexagonal boron nitride layer.

[0109] (2) Structural characterization of self-supporting hexagonal boron nitride nanotube thin films

[0110] Raman spectroscopy characterization revealed that no characteristic G peak of carbon nanotubes was detected in the film after high-temperature oxidation etching. However, a Raman signal of boron nitride nanotubes appeared in the Raman spectrum. This peak corresponds to the in-plane phonon vibration mode of the hexagonal boron nitride (BN) bond, reflecting the ordered arrangement of the BN covalent bonds and indicating that the boron nitride nanotubes in the film have good crystallinity.

[0111] Self-supporting hexagonal boron nitride nanotube films were directly transferred onto a copper mesh microgrid and characterized by transmission electron microscopy. After high-temperature oxidation etching, the single-walled carbon nanotubes were removed, and the self-supporting films consisted of 1 to 10 layers of boron nitride nanotubes with diameters of 5 nm to 20 nm.

[0112] Example 5

[0113] A method for preparing a self-supporting thin film of hexagonal boron nitride nanotubes, employing atmospheric pressure chemical vapor deposition and high-temperature oxidation etching, is detailed below:

[0114] (1) The single-walled carbon nanotube film collected on the cellulose filter membrane is imprinted onto the alumina frame to form a self-supporting single-walled carbon nanotube film with a thickness of about 200 nm, wherein the single-walled carbon nanotube bundle size is about 2 nm-50 nm.

[0115] (2) The self-supporting single-walled carbon nanotube film was surface functionalized by air plasma at 10W for 60s. Then it was placed in the reaction chamber of the atmospheric pressure chemical vapor deposition system. Ammonia borane was used as the boron-nitrogen precursor. The chamber pressure was pumped to <20Pa by a mechanical pump. A mixture of argon and hydrogen (3% hydrogen) at 400sccm was introduced as the carrier gas to maintain the system pressure at atmospheric pressure. The temperature of the reaction zone of the low-pressure chemical vapor deposition furnace was raised to 500℃ at a heating rate of 20℃ / min. Then the temperature of the boron-nitrogen precursor evaporation zone was raised to 40℃. The volatilized ammonia borane vapor was transported to the downstream reaction zone by the carrier gas. Hexagonal boron nitride was grown on the surface of the single-walled carbon nanotube. The growth reaction time was 5min. Then it was naturally cooled to room temperature with the furnace under the protection of high-purity nitrogen to obtain the single-walled carbon nanotube@hexagonal boron nitride nanotube composite film.

[0116] (3) The single-walled carbon nanotube@hexagonal boron nitride nanotube composite film was placed in a muffle furnace and heated to 850°C at a heating rate of 10°C / min under air atmosphere, held for 10h, and then naturally cooled to room temperature to obtain the self-supported hexagonal boron nitride nanotube film.

[0117] The hexagonal boron nitride nanotube self-supporting film prepared by the preparation method of the hexagonal boron nitride nanotube self-supporting film in Example 5 of this paper consists of 1 to 2 layers of boron nitride nanotubes with a diameter of 2nm to 50nm, and the thickness of the hexagonal boron nitride nanotube self-supporting film is about 200nm.

[0118] Example 6

[0119] A method for preparing a self-supporting thin film of hexagonal boron nitride nanotubes, employing atmospheric pressure chemical vapor deposition and high-temperature oxidation etching, is detailed below:

[0120] (1) The single-walled carbon nanotube film collected on the cellulose filter membrane is imprinted onto the alumina frame to form a self-supporting single-walled carbon nanotube film with a thickness of about 200 nm, wherein the single-walled carbon nanotube bundle size is about 2 nm-50 nm.

[0121] (2) The self-supporting single-walled carbon nanotube film was surface functionalized by air plasma at 10W for 60s. Then it was placed in the reaction chamber of the atmospheric pressure chemical vapor deposition system. Dimethylamine borane was used as the boron-nitrogen precursor. The chamber pressure was pumped to <20Pa by a mechanical pump. A mixture of argon and hydrogen (3% hydrogen) at 400sccm was introduced as the carrier gas to maintain the system pressure at atmospheric pressure. The temperature of the reaction zone of the low-pressure chemical vapor deposition furnace was raised to 1500℃ at a heating rate of 20℃ / min. Then the temperature of the boron-nitrogen precursor evaporation zone was raised to 90℃. The volatilized dimethylamine borane vapor was transported to the downstream reaction zone by the carrier gas. Hexagonal boron nitride was grown on the surface of the single-walled carbon nanotube. The growth reaction time was 10h. Then it was naturally cooled to room temperature with the furnace under the protection of high-purity nitrogen to obtain the single-walled carbon nanotube@hexagonal boron nitride nanotube composite film.

[0122] (3) The single-walled carbon nanotube@hexagonal boron nitride nanotube composite film was placed in a muffle furnace and heated to 350°C at a heating rate of 10°C / min under air atmosphere. It was kept at the temperature for 30 hours and then naturally cooled to room temperature to obtain the self-supporting hexagonal boron nitride nanotube film.

[0123] The hexagonal boron nitride nanotube self-supporting film prepared by the preparation method of the hexagonal boron nitride nanotube self-supporting film in Example 6 of this paper consists of 10 to 50 layers of boron nitride nanotubes with a diameter of 20 nm to 100 nm, and the thickness of the hexagonal boron nitride nanotube self-supporting film is about 300 nm.

[0124] Example 7

[0125] A method for preparing a self-supporting thin film of hexagonal boron nitride nanotubes, employing low-pressure chemical vapor deposition and plasma etching, is detailed below:

[0126] (1) The single-walled carbon nanotube film collected on the cellulose filter membrane is imprinted onto the graphite ring to form a self-supporting single-walled carbon nanotube film with a thickness of about 50 nm, wherein the single-walled carbon nanotube bundle size is about 2 nm-50 nm.

[0127] (2) The self-supporting single-walled carbon nanotube film was placed in a low-pressure chemical vapor deposition system. Borazine was used as the boron-nitrogen precursor. The chamber pressure was pumped to <20 Pa using a mechanical pump. A 300 sccm mixture of argon and hydrogen (3% hydrogen) was introduced as the carrier gas. The pressure was adjusted to 200 Pa. The temperature of the reaction zone of the low-pressure chemical vapor deposition furnace was raised to 500 °C at a heating rate of 20 °C / min. Then the temperature of the boron-nitrogen precursor evaporation zone was raised to 90 °C. The volatilized borazine vapor was transported to the downstream reaction zone using the carrier gas. Hexagonal boron nitride was grown on the surface of the single-walled carbon nanotube. The growth reaction time was 5 min. The film was naturally cooled to room temperature to obtain a single-walled carbon nanotube@hexagonal boron nitride nanotube composite film.

[0128] (3) The single-walled carbon nanotube@hexagonal boron nitride nanotube composite film was placed in the plasma cleaner chamber, and the vacuum in the chamber was first evacuated to <10. -3 At 30 sccm, argon gas was introduced. After the gas flow stabilized, the plasma power was set to 50 W. After 15 hours of treatment, the gas was introduced to atmospheric pressure and the film was removed, thus obtaining a self-supported hexagonal boron nitride nanotube film.

[0129] The hexagonal boron nitride nanotube self-supporting film prepared by the preparation method of the hexagonal boron nitride nanotube self-supporting film in Example 7 consists of 1 to 5 layers of boron nitride nanotubes with a diameter of 2 nm to 50 nm, and the thickness of the hexagonal boron nitride nanotube self-supporting film is about 50 nm.

[0130] Example 8

[0131] A method for preparing a self-supporting thin film of hexagonal boron nitride nanotubes, employing low-pressure chemical vapor deposition and plasma etching, is detailed below:

[0132] (1) The single-walled carbon nanotube film collected on the cellulose filter membrane is imprinted onto the graphite ring to form a self-supporting single-walled carbon nanotube film with a thickness of about 50 nm, wherein the single-walled carbon nanotube bundle size is about 2 nm-50 nm.

[0133] (2) The self-supporting single-walled carbon nanotube film was placed in a low-pressure chemical vapor deposition system. Ammonia borane was used as the boron-nitrogen precursor. The chamber pressure was pumped to <20 Pa using a mechanical pump. A 300 sccm argon + hydrogen mixed gas (hydrogen content 3%) was introduced as the carrier gas. The pressure was adjusted to 200 Pa. The temperature of the reaction zone of the low-pressure chemical vapor deposition furnace was raised to 1500 °C at a heating rate of 20 °C / min. Then the temperature of the boron-nitrogen precursor evaporation zone was raised to 90 °C. The volatilized ammonia borane vapor was transported to the downstream reaction zone using the carrier gas. Hexagonal boron nitride was grown on the surface of the single-walled carbon nanotube. The growth reaction time was 10 h. After natural cooling to room temperature, the single-walled carbon nanotube@hexagonal boron nitride nanotube composite film was obtained.

[0134] (3) The single-walled carbon nanotube@hexagonal boron nitride nanotube composite film was placed in the plasma cleaner chamber, and the vacuum in the chamber was first evacuated to <10. -3 At 30 sccm, oxygen was introduced. After the gas flow stabilized, the plasma power was set to 10 W. After processing for 15 minutes, the pressure was increased to atmospheric pressure and the material was removed, thus obtaining a self-supported hexagonal boron nitride nanotube film.

[0135] The hexagonal boron nitride nanotube self-supporting film prepared by the preparation method of the hexagonal boron nitride nanotube self-supporting film in Example 8 of this paper consists of 10 to 50 layers of boron nitride nanotubes with a diameter of 2 nm to 50 nm, and the thickness of the hexagonal boron nitride nanotube self-supporting film is about 100 nm.

[0136] Example 9

[0137] A method for preparing a self-supporting thin film of hexagonal boron nitride nanotubes, employing rapid heating-high temperature chemical vapor deposition and high temperature oxidation etching, is detailed below:

[0138] (1) The single-walled carbon nanotube film collected on the cellulose filter membrane is imprinted onto the graphite ring to form a self-supporting single-walled carbon nanotube film with a thickness of about 50 nm, wherein the single-walled carbon nanotube bundle size is about 2 nm-50 nm.

[0139] (2) In the vacuum heating chamber, a graphite plate with a thickness of 1 mm is used as a heating stage. The self-supporting single-walled carbon nanotube film template is placed on the graphite plate. The chamber pressure is pumped to <100 Pa using a mechanical pump. High-purity argon gas (volume purity 99.999%) is introduced to atmospheric pressure. 50 mg of cycloborane is heated at 120 °C in the evaporation zone and kept at that temperature for 15 min to allow the cycloborane to fully sublimate. Then, the DC power supply is started to perform Joule heating on the graphite plate. The heating current is set to 500 A and the total heating time is 5 s. The heating rate during this process is about 10000 °C / s. The highest temperature of the sample reaches about 3000 °C. After the growth is completed, the sample is naturally cooled to room temperature to obtain a single-walled carbon nanotube@hexagonal boron nitride nanotube composite film.

[0140] (3) The single-walled carbon nanotube@hexagonal boron nitride nanotube composite film was placed in a muffle furnace and heated to 550°C at a heating rate of 10°C / min under air atmosphere, held for 20h, and then naturally cooled to room temperature to obtain the self-supporting hexagonal boron nitride nanotube film.

[0141] The hexagonal boron nitride nanotube self-supporting film prepared by the preparation method of the hexagonal boron nitride nanotube self-supporting film in Example 2 of this paper consists of 1 to 10 layers of boron nitride nanotubes with a diameter of 2 nm to 50 nm, and the thickness of the hexagonal boron nitride nanotube self-supporting film is about 50 nm.

[0142] Example 10

[0143] A method for preparing a self-supporting thin film of hexagonal boron nitride nanotubes, employing rapid heating-high temperature chemical vapor deposition and high temperature oxidation etching, is detailed below:

[0144] (1) The single-walled carbon nanotube film collected on the cellulose filter membrane is imprinted onto the graphite ring to form a self-supporting single-walled carbon nanotube film with a thickness of about 50 nm, wherein the single-walled carbon nanotube bundle size is about 2 nm-50 nm.

[0145] (2) In the vacuum heating chamber, a graphite plate with a thickness of 1 mm is used as a heating stage. The self-supporting single-walled carbon nanotube film template is placed on the graphite plate. The chamber pressure is pumped to <100 Pa using a mechanical pump. High-purity argon gas (volume purity 99.999%) is introduced to atmospheric pressure. 50 mg of dimethylamine borane is heated at 90 °C using an external heating device and kept at that temperature for 15 min to allow the dimethylamine borane to fully sublimate and be transported into the chamber with the carrier gas to supply the boron-nitrogen source. Subsequently, the DC power supply is started to perform Joule heating on the graphite plate. The heating current is set to 40 A and the total heating time is 60 s. The heating rate during this process is about 100 °C / s. The highest temperature of the sample reaches about 1000 °C. After the growth is completed, the sample is naturally cooled to room temperature to obtain a single-walled carbon nanotube@hexagonal boron nitride nanotube composite film.

[0146] (3) The single-walled carbon nanotube@hexagonal boron nitride nanotube composite film was placed in a muffle furnace and heated to 550°C at a heating rate of 10°C / min under air atmosphere, held for 20h, and then naturally cooled to room temperature to obtain the self-supporting hexagonal boron nitride nanotube film.

[0147] The hexagonal boron nitride nanotube self-supporting film prepared by the preparation method of the hexagonal boron nitride nanotube self-supporting film in Example 2 of this paper consists of 5 to 100 layers of boron nitride nanotubes with a diameter of 2 nm to 50 nm, and the thickness of the hexagonal boron nitride nanotube self-supporting film is about 100 nm.

[0148] As can be seen from the above embodiments, the hexagonal boron nitride nanotube film prepared by the method of the present invention has an adjustable diameter and number of tubes. It can achieve self-support at the nanometer-level thickness. In particular, the film is insulating and thermally conductive and can withstand plasma etching. Its application scenarios can be broadened to extreme service environments such as high concentration of atomic oxygen / hydrogen, high concentration of plasma, strong light irradiation, high temperature oxygen content, and strong airflow impact.

[0149] The design concept and implementation scheme of this invention have been described in detail above. However, some modifications and improvements can still be made based on this invention. All such modifications or improvements made without departing from the spirit of this invention fall within the scope of protection claimed by this invention.

Claims

1. A method for preparing a self-supporting thin film of hexagonal boron nitride nanotubes, characterized in that, Using a carbon nanotube film with a self-supporting network structure as a template, hexagonal boron nitride nanotubes are heteroepitaxially grown on the carbon nanotubes and their bundles using chemical vapor deposition (CVD) to form a one-dimensional van der Waals coaxial tubular heterostructure. The carbon nanotube template is then removed by etching. The diameter of the hexagonal boron nitride nanotubes is controlled by adjusting the diameter of the carbon nanotubes and the size of the bundles. The coating efficiency and number of layers of the hexagonal boron nitride nanotubes are controlled by adjusting the CVD conditions, thus obtaining a self-supporting film formed by the overlapping of a hexagonal boron nitride nanotube network with controllable diameter and number of layers.

2. The method for preparing a self-supporting thin film of hexagonal boron nitride nanotubes as described in claim 1, characterized in that, The thickness of the carbon nanotube film with a self-supporting network structure is 20nm-200nm.

3. The method for preparing a hexagonal boron nitride nanotube self-supporting thin film as described in claim 1, characterized in that, The diameter of carbon nanotubes and their bundles can be controlled from 2 nm to 50 nm.

4. The method for preparing a self-supporting thin film of hexagonal boron nitride nanotubes as described in claim 1, characterized in that, The chemical vapor deposition process includes atmospheric pressure chemical vapor deposition, low pressure chemical vapor deposition, or rapid heating-high temperature chemical vapor deposition.

5. The method for preparing a self-supporting thin film of hexagonal boron nitride nanotubes as described in claim 4, characterized in that, The boron-nitrogen precursors used in atmospheric pressure chemical vapor deposition are ammonia borane, cycloborane, or dimethylamine borane; Controlled atmospheric pressure chemical vapor deposition conditions: the boron-nitrogen precursor volatilization temperature is 40℃-90℃, the deposition temperature is 500℃-1500℃, the boron nitride growth reaction time is 5min-10h, and the number of boron nitride coating layers is 1-50 layers.

6. The method for preparing a self-supporting thin film of hexagonal boron nitride nanotubes as described in claim 4, characterized in that, The boron-nitrogen precursors used in low-pressure chemical vapor deposition are ammonia borane and / or borazine; Controlling low-pressure chemical vapor deposition conditions: gas pressure < 500 Pa, boron-nitrogen precursor volatilization temperature 40℃-90℃, deposition temperature 500℃-1500℃, boron nitride growth reaction time 5 min-10 h, and boron nitride coating layer number 1-50 layers.

7. The method for preparing a self-supporting thin film of hexagonal boron nitride nanotubes as described in claim 4, characterized in that, The rapid heating-high temperature chemical vapor deposition method uses ammonia borane, cycloborane, or dimethylamine borane as the boron-nitrogen precursor. The boron-nitrogen precursor is heated to 60℃-120℃ and then supplied. The supply method includes any of the following: (1) Intracavitary synchronous pyrolysis power supply: The solid boron-nitrogen precursor is placed in a vacuum chamber and decomposed during rapid heating-high temperature process; (2) External vaporization and transport source supply: The boron-nitrogen precursor is sublimated by an external heating device and the source is transported into the cavity by a carrier gas; The heating rate for rapid heating-high temperature chemical vapor deposition was set to 10. 2 ℃ / s-10 4 ℃ / s, heating temperature is 1000℃-3000℃, boron nitride growth reaction time is 5s-60s, and the number of boron nitride coating layers is 1-100 layers.

8. The method for preparing a self-supporting thin film of hexagonal boron nitride nanotubes as described in claim 1, characterized in that, The etching process can be carried out by oxidation etching or plasma etching. Oxidation etching involves heat treatment at 350℃-850℃ for 10h-30h in flowing air or oxygen. Plasma etching is the etching process using hydrogen, argon, or oxygen plasma at a power of 10W-50W for 10 minutes to 15 hours.

9. A hexagonal boron nitride nanotube self-supporting thin film, prepared using the hexagonal boron nitride nanotube self-supporting thin film according to claim 1, characterized in that, The diameter of hexagonal boron nitride nanotubes ranges from 2nm to 100nm, and the thickness of the self-supporting thin film of hexagonal boron nitride nanotubes ranges from 20nm to 300nm.

10. An application of the hexagonal boron nitride nanotube self-supporting thin film according to claim 9, characterized in that, It is used in extreme ultraviolet lithography protection, high-frequency and high-power electronic heat dissipation, deep ultraviolet sterilization and sensing, and ultra-low power chip fields.

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