Carrier-assisted preparation method of boron nitride nanotubes and boron nitride nanotubes

Abstract

This application discloses a carrier-assisted preparation method for boron nitride nanotubes and the boron nitride nanotubes. The carrier-assisted preparation method comprises mixing a boron source and a carrier catalyst component and placing the mixture into a reactor; heating the interior of the reactor to a reaction temperature under an inert atmosphere to generate a precursor; and placing the interior of the reactor under an ammonia atmosphere, maintaining the reaction temperature, and continuously reacting and growing the boron nitride nanotubes. This application utilizes a carrier-assisted growth method for boron nitride nanotubes. The carrier effectively increases the contact area between the boron source and the metal element, improving the efficiency of precursor generation, and correspondingly increases the contact area between the precursor and ammonia, significantly improving the growth efficiency of the boron nitride nanotubes and achieving the goal of efficiently growing boron nitride nanotubes.

Description

Technical Field

[0001] The present application belongs to the technical field of nanotube materials, and specifically relates to a carrier-assisted preparation method of boron nitride nanotubes and boron nitride nanotubes. Background Art

[0002] Boron nitride nanotubes (BNNTs) are hexagonal nanotubes composed of boron and nitrogen atoms. Their structure is similar to that of carbon nanotubes (CNTs), and they possess similar high thermal conductivity and mechanical strength. Unlike CNTs, BNNTs are insulators with a band gap of 5.5 to 6.0 eV and exhibit high oxidation resistance up to 800°C in air and up to 2800°C in inert atmospheres. Therefore, BNNTs hold great promise for applications in microelectromechanical systems (MEMs), biomedicine (e.g., targeted drug delivery and neutron capture therapy), cathodoluminescence, and solid-state neutron detectors. Furthermore, BNNTs can serve as highly useful nanofillers, improving the thermal conductivity of fibers and polymer films. Furthermore, BNNTs have potential applications in spintronics devices and various nano- and microscale electronics.

[0003] Currently, the main methods for synthesizing boron nitride nanotubes include arc discharge, laser heating, induction thermal plasma, and chemical vapor deposition (CVD). The first three methods all require high-temperature and high-pressure growth conditions (5000°C / 1.4MPa), which significantly increases production costs and causes boron and nitrogen to combine in unpredictable ways, resulting in poor product purity. In contrast, the CVD method offers good process control, low cost, and provides high-quality boron nitride nanotubes, making it more suitable for industrial manufacturing. However, the current growth efficiency of boron nitride nanotubes produced by the CVD method is relatively low, which is largely related to both the precursor material and the growth method. Therefore, how to efficiently produce boron nitride nanotubes is a key research topic. Summary of the Invention

[0004] The purpose of the present application is to provide a carrier-assisted preparation method of boron nitride nanotubes and boron nitride nanotubes, so as to solve the technical problem of low growth efficiency of boron nitride nanotubes prepared by CVD method in the prior art.

[0005] To achieve the above purpose, a technical solution adopted in this application is:

[0006] Provided is a carrier-assisted preparation method for boron nitride nanotubes, comprising:

[0007] Mixing the boron source and the supported catalyst component and placing them in a reactor;

[0008] heating the interior of the reactor to a reaction temperature under an inert atmosphere to generate a precursor;

[0009] The interior of the reactor is placed under an ammonia atmosphere, the reaction temperature is maintained, and the reaction is continued to grow boron nitride nanotubes.

[0010] In one or more embodiments, the supported catalyst includes one or a combination of vermiculite and hydrotalcite.

[0011] In one or more embodiments, the mass ratio of the boron source to the supported catalyst is 1:(1-3).

[0012] In one or more embodiments, the supported catalyst includes a support component and a metal catalyst component, and the metal catalyst component includes one or more combinations of magnesium oxide, ferric chloride, and magnesium boride.

[0013] In one or more embodiments, the carrier component includes glucose and a foaming agent.

[0014] In one or more embodiments, the mass ratio of the boron source, the glucose, the foaming agent and the metal catalyst component is 1:(1-5):0.4:(1-3).

[0015] In one or more embodiments, the support component includes boron nitride nanofibers.

[0016] In one or more embodiments, the mass ratio of the boron source, the boron nitride nanofibers, and the metal catalyst component is 2:1:(0.5-2).

[0017] In one or more embodiments, in the step of heating the interior of the reactor to the reaction temperature under an inert atmosphere, the inert atmosphere is specifically argon with a flow rate of 20 to 100 standard milliliters per minute, the heating is specifically uniformly heated at a rate of 10 to 30° C. / min, and the reaction temperature is 1200 to 1400° C.;

[0018] In the step of placing the interior of the reactor under an ammonia atmosphere, maintaining the reaction temperature, and continuously reacting to generate boron nitride nanotubes, the ammonia atmosphere is specifically ammonia gas with a flow rate of 20 to 100 standard milliliters per minute, and the reaction time of the continuous reaction is 60 to 180 minutes.

[0019] To achieve the above purpose, another technical solution adopted by this application is:

[0020] Provided is a boron nitride nanotube prepared by the carrier-assisted preparation method described in any one of the above embodiments.

[0021] Different from the prior art, the present invention has the following advantages:

[0022] This application will use a carrier to assist in the growth of boron nitride nanotubes. The carrier can effectively increase the contact area between the boron source and the metal element, improve the generation efficiency of the precursor, and correspondingly increase the contact area between the precursor and ammonia gas, significantly improving the growth efficiency of the boron nitride nanotubes, thereby achieving the purpose of efficiently growing boron nitride nanotubes.

[0023] The carrier of the present application can be a combination of glucose and a foaming agent. When glucose is heated, it forms a porous structure under the action of the foaming agent to increase the reaction contact area. Boron nitride nanofibers can also be used to effectively increase the reaction contact area. Vermiculite and hydrotalcite rich in metal elements can also be used. When heated, they will form a porous structure to increase the reaction contact area, and the rich metal elements can act as a catalyst to form a precursor with the boron source to improve the reaction efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic flow chart of an embodiment of the carrier-assisted preparation method of boron nitride nanotubes of the present application;

[0025] Figure 2 This is the XRD diffraction pattern of Example 1 of the present application;

[0026] Figure 3 This is the Raman spectrum of Example 1 of the present application;

[0027] Figure 4 is a scanning electron microscope image of the boron nitride nanotubes prepared in Example 1 of the present application;

[0028] Figure 5 is a scanning electron microscope image of the boron nitride nanotubes prepared in Example 4 of the present application;

[0029] Figure 6 is a scanning electron microscope image of the boron nitride nanotubes prepared in Example 7 of the present application;

[0030] Figure 7 is a scanning electron microscope image of the boron nitride nanotubes prepared in Example 8 of the present application;

[0031] Figure 8 is a scanning electron microscope image of the boron nitride nanotubes prepared in Example 9 of the present application;

[0032] Figure 9 This is a scanning electron microscope image of the boron nitride nanotubes prepared in Example 10 of the present application. DETAILED DESCRIPTION

[0033] The present application will be described in detail below with reference to the various embodiments shown in the accompanying drawings. However, these embodiments do not limit the present application, and any structural, methodological, or functional modifications made by a person skilled in the art based on these embodiments are included within the scope of protection of the present application.

[0034] Boron nitride nanotubes (BNNTs) are hexagonal nanotubes composed of boron and nitrogen atoms with a structure similar to carbon nanotubes. BNNTs have high thermal conductivity and mechanical strength similar to carbon nanotubes, with a Young's modulus of ~1.2 TPa. Unlike carbon nanotubes, BNNTs are insulators with a band gap of 5.5 to 6.0 eV. More importantly, BNNTs are highly resistant to oxidation in air up to 800°C and in an inert atmosphere up to 2800°C.

[0035] Therefore, BNNTs have very broad application prospects in microelectromechanical systems (MEMs), biomedicine (such as targeted drug delivery and neutron capture therapy), cathodoluminescence, and solid-state neutron detectors. In addition, BNNTs can also serve as very useful nanofillers, which can improve the thermal conductivity of fibers and polymer films. In addition, they also have potential applications in spintronics devices and various nano- and microscale electronics.

[0036] However, the current market price of BNNTs is very expensive, which seriously hinders their basic research in many fields. This is mainly due to the low growth efficiency and high preparation cost of boron nitride nanotubes.

[0037] The synthesis methods of BNNTs mainly include arc discharge, laser heating, induction thermal plasma, chemical vapor deposition (CVD), ball milling and annealing. The growth conditions of the first three methods require high temperature and high pressure (up to 5000℃ / 1.4MPa), which greatly increases the production cost and causes boron and nitrogen to combine in an unpredictable manner, resulting in poor product purity. In contrast, the CVD method has good process control, low cost, and provides high-quality BNNTs, making it more suitable for industrial manufacturing. In addition, ball milling combined with CVD annealing can improve the growth efficiency of BNNTs. Therefore, the preparation of boron nitride nanotubes by CVD method is the key to achieving mass production.

[0038] However, the current growth efficiency of boron nitride nanotubes is low, which is closely related to the precursor material and growth method. Therefore, how to efficiently prepare boron nitride nanotubes is the key to current research.

[0039] In order to improve the synthesis efficiency of boron nitride nanotubes, the applicant provides a carrier-assisted preparation method, which improves the preparation efficiency of boron nitride nanotubes through the auxiliary effect of the carrier, thereby achieving efficient preparation of boron nitride nanotubes.

[0040] Specifically, see Figure 1 , Figure 1 It is a schematic flow chart of one embodiment of the carrier-assisted preparation method of boron nitride nanotubes of the present application.

[0041] The carrier-assisted preparation method comprises:

[0042] S100, mixing the boron source and the supported catalyst component and placing them into a reactor.

[0043] S200 , heating the reactor to a reaction temperature under an inert atmosphere to generate a precursor.

[0044] S300, placing the reactor under an ammonia atmosphere, maintaining the reaction temperature, and continuing the reaction to grow boron nitride nanotubes.

[0045] In one embodiment, the boron source may be boron powder. In other embodiments, the boron source may be other materials containing boron elements such as boron oxide, sodium tetraborate, or a combination of multiple materials containing boron elements, all of which can achieve the effects of this embodiment.

[0046] The carrier catalyst component is used to provide a carrier and catalyst for the reaction. The catalyst can be evenly dispersed in the carrier, thereby increasing the contact area between the catalyst and the boron source and efficiently generating the precursor. It can also increase the contact area between the precursor and ammonia, making the reaction more thorough and efficient, and improving the growth efficiency of boron nitride nanotubes.

[0047] In one embodiment, the supported catalyst may be a material integrating a support and a catalyst. Specifically, the supported catalyst may be vermiculite, hydrotalcite, or a combination of vermiculite and hydrotalcite.

[0048] The mass ratio of the boron source to the supported catalyst may be 1:(1-3).

[0049] The chemical formula of vermiculite is (Mg, Ca) 0.7 (Mg, Fe, Al) 6.0 (Al, Si) 8.0 (OH 4.8 H2O), which is rich in metal elements; at the same time, when vermiculite is calcined at 800-1000℃, its volume will expand rapidly, increasing by 6-15 times, and up to 30 times, and a rich pore structure will be formed inside.

[0050] When heated to the reaction temperature, the boron source reacts with the metal elements in the vermiculite within the pores to form a precursor, significantly increasing the efficiency of the reaction between the boron source and the metal elements. Consequently, the precursor can fully contact the ammonia gas within the pore structure, significantly improving the growth efficiency of boron nitride nanotubes and achieving the goal of efficient growth.

[0051] The chemical formula of hydrotalcite is [Mg6Al2(OH) 16CO3]·4H2O, which is similar to vermiculite and rich in metallic elements. Furthermore, when hydrotalcite is heated to 450-500°C, it undergoes thermal decomposition, with the carbonate radical completely converted into nitrogen dioxide and the formation of bimetallic composite oxides. Simultaneously, during the heating process, the ordered layered structure of the hydrotalcite is destroyed, increasing its surface area and pore volume.

[0052] When heated to the reaction temperature, the boron source reacts with the metal element within the pores formed by the thermal decomposition of the hydrotalcite to form a precursor, significantly improving the efficiency of the reaction between the boron source and the metal element. Consequently, the precursor can fully contact the ammonia gas within the pore structure, significantly improving the growth efficiency of boron nitride nanotubes and achieving the goal of efficient growth of boron nitride nanotubes.

[0053] In another embodiment, the supported catalyst may also be composed of an independent support component and a metal catalyst component, wherein the metal catalyst component may include one or more combinations of magnesium oxide, ferric chloride, and magnesium boride.

[0054] Specifically, the carrier components can include glucose and a foaming agent. When heated to the reaction temperature, the glucose foams under the action of the foaming agent, forming a porous structure. The boron source can adhere to the porous structure formed by the glucose foaming and react with the metal element to form a precursor. The precursor then reacts with ammonia within the porous structure formed by the glucose foaming to grow boron nitride nanotubes, significantly improving the efficiency of precursor generation and boron nitride nanotube growth.

[0055] In the above embodiment, the foaming agent may be azodicarbonamide or a type of foaming agent, as long as it can achieve the foaming reaction of glucose during the heating process, and both can achieve the effect of this embodiment.

[0056] In the above embodiment, the mass ratio of the boron source, glucose, foaming agent and metal catalyst component can be 1:(1-5):0.4:(1-3).

[0057] In another example, the carrier component may also include boron nitride nanofibers, which have a rich pore structure and a large specific surface area, which facilitates the contact between the boron source and the metal catalyst component, as well as the contact between the precursor and ammonia, significantly improving the precursor generation efficiency and the growth efficiency of boron nitride nanotubes.

[0058] In the above embodiment, the mass ratio of the boron source, the boron nitride nanofibers and the metal catalyst component is 2:1:(0.5-2).

[0059] In one embodiment, the inert atmosphere may be argon gas with a flow rate of 20 to 100 standard milliliters per minute; preferably, the inert atmosphere may be argon gas with a flow rate of 50 standard milliliters per minute.

[0060] In one embodiment, the temperature rising process may be specifically a uniform temperature rising process at a rate of 10 to 30° C. / min; preferably, the temperature may be uniformly raised to the reaction temperature at a rate of 20° C. / min.

[0061] In one embodiment, the reaction temperature may be specifically 1200-1400°C; preferably, the reaction temperature may be 1300°C.

[0062] In one embodiment, the ammonia atmosphere may be ammonia gas with a flow rate of 20 to 100 standard milliliters per minute; preferably, the ammonia atmosphere may be ammonia gas with a flow rate of 50 standard milliliters per minute.

[0063] In one embodiment, the reaction time of the continuous reaction may be 60 to 180 minutes; preferably, the continuous reaction time may be 120 minutes.

[0064] The beneficial effects of the technical solution of the present application are further explained in detail below with reference to specific embodiments.

[0065] Example 1:

[0066] A boron nitride nanotube is prepared by the following method:

[0067] Boron powder and vermiculite were mixed in a mass ratio of 1:1, placed in a tube furnace, introduced with 50 sccm of argon, and heated to 1300°C;

[0068] Then, the argon gas was turned off, and 50 sccm of ammonia gas was introduced, and the temperature was kept for 120 minutes to grow boron nitride nanotubes.

[0069] Example 2:

[0070] A boron nitride nanotube is prepared by the following method:

[0071] Boron powder and vermiculite were mixed in a mass ratio of 1:1, placed in a tube furnace, introduced with 100 sccm of argon, and heated to 1200°C;

[0072] Then, the argon gas was turned off, and 100 sccm of ammonia gas was introduced, and the temperature was kept for 60 minutes to grow boron nitride nanotubes.

[0073] Example 3:

[0074] A boron nitride nanotube is prepared by the following method:

[0075] Boron powder and vermiculite were mixed in a mass ratio of 1:3, placed in a tube furnace, introduced with 20 sccm of argon, and heated to 1400°C;

[0076] Then, the argon gas was turned off, and 20 sccm of ammonia gas was introduced, and the temperature was kept for 180 minutes to grow boron nitride nanotubes.

[0077] Example 4:

[0078] A boron nitride nanotube is prepared by the following method:

[0079] Boron powder and hydrotalcite were mixed in a mass ratio of 1:1, placed in a tube furnace, introduced with 50 sccm of argon, and heated to 1300°C;

[0080] Then, the argon gas was turned off, and 50 sccm of ammonia gas was introduced, and the temperature was kept for 120 minutes to grow boron nitride nanotubes.

[0081] Example 5:

[0082] A boron nitride nanotube is prepared by the following method:

[0083] Boron powder and hydrotalcite were mixed in a mass ratio of 1:1, placed in a tube furnace, introduced with 100 sccm of argon, and heated to 1200°C;

[0084] Then, the argon gas was turned off, and 100 sccm of ammonia gas was introduced, and the temperature was kept for 60 minutes to grow boron nitride nanotubes.

[0085] Example 6:

[0086] A boron nitride nanotube is prepared by the following method:

[0087] Boron powder and hydrotalcite were mixed in a mass ratio of 1:3, placed in a tube furnace, introduced with 20 sccm of argon, and heated to 1400°C;

[0088] Then, the argon gas was turned off, and 20 sccm of ammonia gas was introduced, and the temperature was kept for 180 minutes to grow boron nitride nanotubes.

[0089] Example 7:

[0090] A boron nitride nanotube is prepared by the following method:

[0091] Boron powder, glucose, azodicarbonamide, and magnesium oxide were mixed in a mass ratio of 1:3:0.4:2, placed in a tube furnace, introduced with 50 sccm of argon, and heated to 1300°C;

[0092] Then, the argon gas was turned off, and 50 sccm of ammonia gas was introduced, and the temperature was kept for 120 minutes to grow boron nitride nanotubes.

[0093] Example 8:

[0094] A boron nitride nanotube is prepared by the following method:

[0095] Boron powder, glucose, azodicarbonamide, and ferric chloride were mixed in a mass ratio of 1:5:0.4:3, placed in a tube furnace, introduced with 100 sccm of argon, and heated to 1200°C;

[0096] Then, the argon gas was turned off, and 100 sccm of ammonia gas was introduced, and the temperature was kept for 60 minutes to grow boron nitride nanotubes.

[0097] Example 9:

[0098] A boron nitride nanotube is prepared by the following method:

[0099] Boron oxide, glucose, azodicarbonamide, and magnesium boride were mixed in a mass ratio of 1:1:0.4:1, placed in a tube furnace, introduced with 20 sccm of argon, and heated to 1400°C;

[0100] Then, the argon gas was turned off, and 20 sccm of ammonia gas was introduced, and the temperature was kept for 180 minutes to grow boron nitride nanotubes.

[0101] Example 10:

[0102] A boron nitride nanotube is prepared by the following method:

[0103] Boron powder, boron oxide, boron nitride nanofibers, and ferric chloride were mixed in a mass ratio of 1:1:1:1, placed in a tube furnace, introduced with 50 sccm of argon, and heated to 1300°C;

[0104] Then, the argon gas was turned off, and 50 sccm of ammonia gas was introduced, and the temperature was kept for 120 minutes to grow boron nitride nanotubes.

[0105] Example 11:

[0106] A boron nitride nanotube is prepared by the following method:

[0107] Boron powder, boron nitride nanofibers, and magnesium oxide were mixed in a mass ratio of 2:1:0.5, placed in a tube furnace, introduced with 100 sccm of argon gas, and heated to 1200°C;

[0108] Then, the argon gas was turned off, and 100 sccm of ammonia gas was introduced, and the temperature was kept for 60 minutes to grow boron nitride nanotubes.

[0109] Example 12:

[0110] A boron nitride nanotube is prepared by the following method:

[0111] Boron powder, boron nitride nanofibers, and magnesium boride were mixed in a mass ratio of 2:1:2, placed in a tube furnace, introduced with 20 sccm of argon, and heated to 1400°C;

[0112] Then, the argon gas was turned off, and 20 sccm of ammonia gas was introduced, and the temperature was kept for 180 minutes to grow boron nitride nanotubes.

[0113] Effect example 1:

[0114] XRD diffraction analysis was performed on the boron nitride nanotubes prepared in Examples 1, 4, 7, and 10, and the results were as follows: Figure 2 .

[0115] See also Figure 2 , Figure 2 This is the XRD diffraction pattern of Example 1 of the present application. As shown in the figure, the XRD diffraction patterns of the boron nitride nanotubes prepared in Examples 1, 4, 7, and 10 all show five peaks at the (002), (100), (101), (102), and (110) planes, which are characteristic signals of h-BN. These peaks correspond to the characteristic signals of h-BN in the JCPDS card (No. 73-2095), proving that the grown samples have a pure h-BN structure.

[0116] The boron nitride nanotubes prepared in Examples 1, 4, and 7 were analyzed by Raman spectroscopy to obtain Figure 3 .

[0117] See also Figure 3 , Figure 3 This is the Raman spectrum of Example 1 of the present application. As shown in the figure, the Raman spectra of the boron nitride nanotubes prepared in Examples 1, 4, and 7 all show a peak at 1368 cm -1 There is a strong absorption band at , which is related to the E2g in-plane vibration mode of h-BN.

[0118] From the above experiments, it can be seen that Examples 1, 4, 7, and 10 all grow high-purity boron nitride nanotubes.

[0119] Effect Example 2:

[0120] The boron nitride nanotubes prepared in Examples 1, 4, 7, 8, 9, and 10 were characterized and analyzed to obtain Figure 4 、 5 , 6, 7, 8, 9.

[0121] See also Figures 4 to 9 , Figure 4 This is a scanning electron microscope image of the boron nitride nanotubes prepared in Example 1 of the present application. Figure 5 This is a scanning electron microscope image of the boron nitride nanotubes prepared in Example 4 of the present application. Figure 6 This is a scanning electron microscope image of the boron nitride nanotubes prepared in Example 7 of the present application. Figure 7 This is a scanning electron microscope image of the boron nitride nanotubes prepared in Example 8 of the present application. Figure 8 is a scanning electron microscope image of the boron nitride nanotubes prepared in Example 9 of the present application, Figure 9This is a scanning electron microscope image of the boron nitride nanotubes prepared in Example 10 of the present application.

[0122] As shown in the figure, a large number of high-quality boron nitride nanotubes grew in the porous structure prepared in Example 7; and a large number of high-quality boron nitride nanotubes were prepared in Examples 1, 4, 8, 9, and 10.

[0123] From the above experiments, it can be seen that Examples 1, 4, 7, 8, 9, and 10 all grow high-quality boron nitride nanotubes.

[0124] The foregoing description of the present disclosure is provided to enable any person skilled in the art to implement or use the present disclosure. Various modifications to the present disclosure will be readily apparent to those skilled in the art, and the general principles herein may be applied to other variations without departing from the scope of the present disclosure. Therefore, the present disclosure is not limited to the examples and designs described herein, but is intended to be consistent with the widest range of principles and novel features disclosed herein.

Claims

1. A carrier-assisted preparation method for boron nitride nanotubes, characterized in that: include: Mixing the boron source and the supported catalyst component and placing them in a reactor; heating the interior of the reactor to a reaction temperature under an inert atmosphere to generate a precursor; placing the interior of the reactor under an ammonia atmosphere, maintaining the reaction temperature, and continuously reacting and growing boron nitride nanotubes; The supported catalyst comprises a support component and a metal catalyst component, the metal catalyst component comprises one or more combinations of magnesium oxide, ferric chloride and magnesium boride, and the support component comprises glucose and a foaming agent.

2. The carrier-assisted preparation method according to claim 1, characterized in that: The mass ratio of the boron source, the glucose, the foaming agent and the metal catalyst component is 1:(1-5):0.4:(1-3).

3. The carrier-assisted preparation method according to claim 1, characterized in that: In the step of heating the interior of the reactor to the reaction temperature under an inert atmosphere, the inert atmosphere is specifically argon with a flow rate of 20 to 100 standard milliliters per minute, the heating is specifically uniformly heated at a rate of 10 to 30°C / min, and the reaction temperature is 1200 to 1400°C; In the step of placing the interior of the reactor under an ammonia atmosphere, maintaining the reaction temperature, and continuously reacting to generate boron nitride nanotubes, the ammonia atmosphere is specifically ammonia gas with a flow rate of 20 to 100 standard milliliters per minute, and the reaction time of the continuous reaction is 60 to 180 minutes.

4. Boron nitride nanotubes prepared by the carrier-assisted preparation method according to any one of claims 1 to 3.

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