A preparation method of bismuth telluride-based nanotubes

Abstract

The present invention relates to a method for preparing bismuth telluride-based nanotubes, comprising the following steps: S1, a template is disposed on a substrate, and then a plurality of bismuth wires are deposited on the substrate; S2, the template is removed to obtain bismuth wires supported by the substrate, and the bismuth wires supported by the substrate are immersed in nitric acid to reduce the wire diameter of the bismuth wires and make the wire diameter of the bismuth wires reach the nanoscale; S3, a bismuth telluride cladding is deposited on the bismuth wires supported by the substrate, and then a plurality of hollow bismuth telluride-based nanotubes supported by the substrate are obtained through vacuum annealing treatment. The present invention can prepare regularly arranged bismuth telluride-based nanotubes by using deposition technology in combination with template control and vacuum annealing treatment. Compared with the existing methods for preparing bismuth telluride-based nanotubes, the preparation method is simple, the cost is low, and the obtained bismuth telluride-based nanotubes have good structural uniformity.

Description

Technical Field

[0001] The present invention belongs to the technical field of material synthesis, and particularly relates to a method for preparing bismuth telluride-based nanotubes, and more particularly to a method for preparing bismuth telluride-based nanotubes arranged in a periodic lattice. Background Art

[0002] The thermoelectric (TE) phenomenon is also known as the thermoelectric effect. In 1822, Thomas Seebeck discovered the thermoelectric emf effect (the principle of TE material power generation); in 1834, Jean Peltier discovered the cooling effect at the interface of two different material conductors in a current loop (the principle of TE material refrigeration). In the 1950s, some good semiconductor TE materials were discovered. Materials with a ZT (thermoelectric figure of merit) ≥ 0.5 are usually called TE materials. The larger the ZT, the higher the efficiency of TE devices. To overcome the obstacle of the lack of high-ZT TE materials, people have turned to the structural design of natural TE materials and the research and development of artificially synthesized TE materials - low-dimensional thermoelectric materials. Mesoscopic physical theory research shows that under the same working conditions, low-dimensional thin-film-structured TE materials have a higher ZT value than other bulk materials.

[0003] So far, there are three types of typical low-dimensional thin-film-structured TE materials: (1) Quantum dot structures, which improve the density of states near the Fermi level by means of the quantum confinement effect, thereby increasing the conductivity of the material; (2) Phonon-blocking / electron-transmitting superlattices. In this type of structure, the lattice thermal conductivity (kL) of the material is reduced by introducing a so-called "acoustic mismatch" between the superlattice components. Different from conventional TE alloy materials, usually, the carrier scattering rate of this type of material is significantly reduced, that is, it has a high conductivity; (3) Thin-film-structured materials that use the thermionic effects in semiconductor heterostructures to increase the ZT value of the material. Hicks and Dresslhaus proposed that quantum well superlattices can significantly increase the ZT value of the material, and quantum wire superlattices can even bring a greater increase.

[0004] From a physical point of view, the reason why these systems can improve the ZT value of materials is that the low-dimensional geometric dimensions of quantum wells and nanowires increase the density of electronic states per unit volume. In terms of related principle materials, in February 2006, Kim et al. reported in Phys. Rev. Lett. that the CVD-grown semi-metallic nanocrystal random mosaic superlattice structure material - ErAs (nanoparticles) @ In0.53Ga0.47As (alloy) - was extremely innovative. They claimed that: (1) the large number of point defects in the alloy material effectively suppress short-wave phonons, and the ErAs nanocrystals effectively suppress medium and long-wave phonons, resulting in a significant decrease in the thermal conductivity of the structure; (2) the doping effect of the semi-metallic ErAs nanocrystals slightly increases the electrical conductivity of the structure. The combined effect of the two is that ZT>2 at room temperature. This work has found a way out for the "industrialization" application of thermoelectric nanomaterials. The ideal thermoelectric conversion material is a material with a dimensionless power generation performance index ZT of 2 or higher.

[0005] So far, the main materials are bismuth intermetallic compounds such as bismuth telluride (Bi2Te3), lead telluride (PtTe), zinc antimonide (ZnSb), germanium, iron silicide (FeSi2), etc. Among them, Bi2Te3-based compounds have a large ZT value at relatively low temperatures, which continues to rise from room temperature to about 450K, and are currently the most widely used thermoelectric conversion materials.

[0006] Recently, the research group of Researcher Taikeping Liao and Researcher Chang Liu from the Institute of Metal Research, Chinese Academy of Sciences, together with their collaborators, developed a high-performance bismuth telluride / single-walled carbon nanotube (Bi2Te3 / SWCNT) flexible thermoelectric material. The researchers used a self-designed and improved magnetron sputtering deposition system, with a self-supporting three-dimensional network of carbon nanotubes with excellent mechanical and electrical properties as the framework. By utilizing the sub-nanoscale carbon nanotube bundle grooves to restrict diffusion and induce ordered nucleation, as well as the temperature-selective crystal plane growth mechanism of thin film materials, they successfully prepared for the first time a Bi2Te3 / SWCNT composite self-supporting thermoelectric thin film material with highly ordered microscopic features. This composite material has a nanoporous structure, and the deposited Bi2Te3 nanocrystals are tightly attached to the surface of the carbon nanotube bundles, and have a highly (000l) plane texture. The Bi2Te3 <-12-10> crystal orientation is parallel to the axis of the carbon nanotube bundles, and the adjacent Bi2Te3 nanocrystals are separated by small-angle orientation tilt grain boundaries. The Bi2Te3 (000l) plane texture is beneficial to improving the in-plane conduction of carriers, and the small-angle grain boundaries can further reduce the scattering effect on the conduction carriers. Defects such as the nanoporous structure and the Bi2Te3 / SWCNT interface play a role in scattering phonons and reducing the thermal conductivity. The research shows that in this (000l) plane texture, the -Te1-Te1- atomic plane connected by weak van der Waals forces is parallel to the free surface of the composite film. The relative movement between the van der Waals layers is an important mechanism for the composite film to exhibit good flexibility during out-of-plane bending deformation. The adjacent Bi2Te3 <-12-10> crystal orientations are highly aligned, and it is an easy slip direction on the (000l) van der Waals force crystal plane, which is conducive to the transfer of van der Waals layer displacement between adjacent grains. In addition, the nanoporous structure is also beneficial to accommodating the relative displacement during the flexible deformation of the material, further improving the flexible deformation ability. The unique microscopic structure endows this composite material with a thermoelectric figure of merit (ZT) as high as ~0.9 along the in-plane (000l) direction in the temperature range from room temperature to 100 °C, which is comparable to the ZT performance of commercial bulk brittle thermoelectric materials, and at the same time has very excellent bending flexible mechanical properties. Further research shows that due to the good bending flexibility and self-supporting structure of this composite material, it can be cut into any geometric shape and transferred to various types of substrates using micro-nano processing methods such as ion beams and femtosecond lasers, which is beneficial for the flexible and convenient preparation of thermoelectric devices with various structures. It can even be manipulated by non-contact methods such as electrostatic force. At the same time, the research shows that the preparation principle and technology of this composite material can also be applied to other layered semiconductor material systems with weak van der Waals force connections, and has broad application prospects in the field of flexible semiconductor materials and devices. The research on new low-dimensional TE structure materials has great theoretical and application value. Discovering materials with high ZT values (ZT>4) will trigger technological revolutions in the refrigeration industry, energy industry, and semiconductor microelectronics industry.Although thermoelectric materials with a dimensionless figure of merit factor of more than 2 can be obtained from quantum dots or superlattice materials, the high preparation cost of such structural materials, the complex process of device fabrication, poor reliability, high cost, and difficulty in mass production limit their applications. Therefore, the preparation of hybrid composite materials is one of the important methods to improve the thermoelectric performance of bulk thermoelectric materials. The nanomaterials are located at grain boundaries or uniformly dispersed in the matrix. The matrix material forms a continuous conductive network to maintain the same conductivity within the matrix. In addition, the second phase dispersed in the matrix can scatter phonons. Adding 2D materials introduces heterojunction interfaces, which can disperse carriers and reduce their mobility, thereby further improving the thermoelectric performance. By adding nano-fillers to the matrix, the relationship between conductivity, Seebeck coefficient, and thermal conductivity can be decoupled by modulating the transport properties of electrons and phonons.

[0007] In summary, the preparation of bulk thermoelectric materials with nano-unit composites has become the mainstream trend of next-generation high-performance thermoelectric materials. Thus, it is increasingly important to prepare nano monomer materials for composite bulk thermoelectric materials at low cost. However, the preparation of existing nano monomer materials such as bismuth telluride-based nanotubes, prepared by the self-designed and improved magnetron sputtering deposition system as described above, or the traditional chemical method (such as in Chinese Patent CN113582143A, prepared by solvothermal synthesis), has poor compositional controllability, slow growth rate, poor structural uniformity, and difficulty in industrial production. Summary of the Invention

[0008] To solve the problems of poor compositional controllability, slow growth rate, and poor structural uniformity of existing bismuth telluride nanostructured semiconductor thermoelectric materials, the present invention provides a method for preparing bismuth telluride-based nanotubes that is easy to produce industrially.

[0009] To achieve the above object, the technical solution adopted by the present invention is:

[0010] A method for preparing bismuth telluride-based nanotubes, comprising the following steps:

[0011] S1. Set a template on a substrate, and then deposit a plurality of bismuth wires on the substrate;

[0012] S2. Remove the template to obtain bismuth wires supported by the substrate, and immerse the bismuth wires supported by the substrate in nitric acid to reduce the wire diameter of the bismuth wires and make the wire diameter of the bismuth wires reach the nanoscale;

[0013] S3. Deposit a bismuth telluride cladding on the bismuth wires supported by the substrate, and then obtain a plurality of hollow bismuth telluride-based nanotubes supported by the substrate through vacuum annealing treatment.

[0014] In the present invention, the nanoscale refers to any value between 1 nm and 100 nm.

[0015] According to a further implementation aspect of the present invention, the template has regularly arranged mold holes, such that the multiple bismuth telluride-based nanotubes are regularly arranged on the substrate. Preferably, the mold holes on the template are arranged in a periodic hexagonal array, such that the multiple bismuth telluride-based nanotubes are arranged in a periodic hexagonal array. The bismuth telluride-based nanotubes arranged in a periodic hexagonal array correspond to the layered hexagonal structure of bismuth telluride and have a certain synergistic effect, achieving a better thermoelectric effect.

[0016] Specifically, each hexagon in each period contains six bismuth telluride-based nanotubes and forms the six vertices of the hexagon.

[0017] Furthermore, the distance between two adjacent bismuth telluride-based nanotubes within each hexagon of each period is 100 - 400 μm. The two adjacent bismuth telluride-based nanotubes refer to two adjacent bismuth telluride-based nanotubes on each side of the six sides of the hexagon.

[0018] The distance between two adjacent templates within each hexagon of each period on the template is 100 - 400 μm. The preferred distance is 300 μm.

[0019] In the present invention, the distance between two adjacent bismuth telluride-based nanotubes is the same as the distance between two adjacent mold holes. The distance refers to the distance between the centers of two adjacent mold holes.

[0020] The mold holes are formed by laser ablation.

[0021] In some preferred and specific implementation manners, in step S1, the wire diameter of the bismuth wire is less than or equal to 130 μm; in step S2, the bismuth wire is immersed in nitric acid such that the wire diameter of the bismuth wire is less than or equal to 50 nm; in step S3, the thickness of the bismuth telluride cladding is 20 - 40 nm, and the inner hollow diameter of the bismuth telluride-based nanotube is 10 - 50 nm.

[0022] Preferably, in step S1, the wire diameter of the bismuth wire is 130 μm and the wire length is 150 μm; in step S2, the bismuth wire is immersed in nitric acid such that the wire diameter of the bismuth wire is 50 nm; in step S3, the thickness of the bismuth telluride cladding is 20 nm, and the inner hollow diameter of the bismuth telluride-based nanotube is 10 - 50 nm.

[0023] Furthermore, the template is a stainless steel template with a thickness of 0.15 - 0.25 mm, and the aperture diameter of the mold holes on the template is 100 - 150 μm. Preferably, the template thickness is 0.2 mm, and the aperture diameter of the mold holes is 130 μm.

[0024] According to a further implementation aspect of the present invention, the substrate is a flexible substrate, such that the bismuth telluride-based nanotubes with substrate support according to the present invention can be applied to flexible devices.

[0025] Further, the substrate is a PI substrate. Preferably, the thickness of the PI substrate is 40 - 60 μm. More preferably, the thickness of the substrate is 50 μm.

[0026] In some specific embodiments, the size of the substrate is the same as the size of the template. For example, if the template is square, the side length of the template can be 1.5 - 2.5 cm, such as 2 cm, or it can be other size ranges.

[0027] According to some implementation aspects of the present invention, in step S1, the deposition is carried out by electron beam evaporation, and the process parameters used include: the vacuum degree is better than 4E - 4 Pa, the evaporation electron beam current is 0.04 A - 0.08 A, the evaporation voltage is 5 - 15 KV, and the temperature is 25 - 250 °C.

[0028] According to some implementation aspects of the present invention, in step S2, the concentration of the nitric acid is above 63%. Preferably, the concentration of the nitric acid is 63%, the molar concentration is about 14.5 mol / L, and the density is about 1.45 g / cm 3 。

[0029] In some preferred specific implementation manners, in step S2, the soaking is single soaking or multiple soakings. After each soaking, the wire diameter of the bismuth wire is detected. If it is detected that the wire diameter of the bismuth wire is greater than 50 nm, the soaking step is repeated; if it is detected that the wire diameter of the bismuth wire is less than or equal to 50 nm, the soaking step is ended and the next step is carried out.

[0030] The wire diameter of the bismuth wire is detected by SEM method or laser particle size analyzer.

[0031] Preferably, the single soaking time does not exceed 10 s - 30 s. After the soaking, it is rinsed with hydrophobic water, and the water flow rate is not greater than 0.2 m / s. More preferably, the water flow rate is 0.1 - 0.2 m / s, and the rinsing time is more than 20 s. Further, the rinsing time is 20 s.

[0032] In some embodiments, after the rinsing is completed, it is dried with nitrogen.

[0033] According to some implementation aspects of the present invention, in step S3, the deposition is carried out by electron beam evaporation, and the process parameters used include: the vacuum degree is better than 4E-4 Pa, the evaporation electron beam current is 0.02 A to 0.06 A, the evaporation voltage is 5 to 15 KV, the temperature is 25 to 250 °C, and the evaporation source used is a bismuth telluride compound deviating from the stoichiometric ratio to obtain a bismuth telluride cladding layer containing one or more of P-type bismuth telluride, N-type bismuth telluride, and intrinsic bismuth telluride.

[0034] According to some implementation aspects of the present invention, in step S3, the process parameters of the vacuum annealing treatment include: the annealing temperature is 280 to 290 °C; the annealing time is 10 to 15 h; the vacuum degree is better than 10 -4 Pa.

[0035] In the present invention, the two growth routes of nanocrystal formation can be modulated by the coordinated control of the parameters in step S1, step S2, and step S3: one is through monomer growth, and this growth mode is controlled by diffusion and surface reaction; the other is through the direct fusion between particles to achieve growth.

[0036] In the present invention, for the composition and structure of the nanotubes, the adjustment of the temperature range corresponding to the highest thermoelectric figure of merit coefficient can be achieved through the optimized combination of various process parameters.

[0037] The preparation method of the present invention can also be applied to the preparation of nanotubes such as bismuth / antimony, silicon, carbon, etc.

[0038] Due to the application of the above technical solutions, the present invention has the following advantages compared with the prior art:

[0039] The present invention can prepare regularly arranged bismuth telluride-based nanotubes by using deposition technology in combination with template control and vacuum annealing treatment. Compared with the existing preparation methods of bismuth telluride-based nanotubes, the preparation method is simple, the cost is low, and the obtained bismuth telluride-based nanotubes have good structural uniformity.

[0040] The thermoelectric figure of merit coefficient of the bismuth telluride-based nanotubes prepared by the preparation method of the present invention has a wide adjustment range, the growth process is visible, it is easy to control, the energy efficiency is high, and there is no pollution.

[0041] The preparation method of the present invention has a simple preparation process, low cost, is easy to industrialize production, achieve mass production, and the prepared bismuth telluride-based nanotubes can not only be used as nano-filling materials for composite bulk thermoelectric materials, but also can be used on flexible devices, with a wide application range and great application value.

[0042] The preparation method of the present invention can also be applied to the preparation of nanotubes such as bismuth / antimony, silicon, carbon, etc., and has strong applicability. Description of the Drawings

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the accompanying drawings required for the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0044] Figure 1 Schematic diagram of the template structure adopted in the representative embodiment of the present invention;

[0045] Figure 2 Schematic diagram of the enlarged structure of bismuth wire with substrate support prepared in the representative embodiment of the present invention;

[0046] Figure 3 Schematic diagram of the enlarged structure of bismuth wire with substrate support prepared in the representative embodiment of the present invention after being treated with nitric acid;

[0047] Figure 4 Schematic diagram of the enlarged structure of bismuth / tellurium bismuth core-shell nanowire with substrate support prepared in the representative embodiment of the present invention;

[0048] Figure 5 Schematic diagram of the enlarged structure of tellurium bismuth-based nanotube prepared in the representative embodiment of the present invention;

[0049] In the figure: 1. Template; 2. Die hole; 3. Substrate; 4. Bismuth wire; 5. Bismuth / tellurium bismuth nanowire; 6. Tellurium bismuth-based nanotube. Detailed implementation manners

[0050] To enable those skilled in the art to better understand the solution of the present invention, and to more clearly understand the purpose, technical solution and its advantages of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be noted that the implementation manners not depicted or described in the drawings are forms known to those of ordinary skill in the art. Additionally, although this document may provide examples containing parameters with specific values, it should be understood that the parameters do not necessarily have to be exactly equal to the corresponding values, but may approximate the corresponding values within an acceptable tolerance or design constraint. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention. In addition, the terms "including" and "having" and any variations thereof in the specification and claims of the present invention are intended to cover non-exclusive inclusion. For example, a process, method, device, product or equipment that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or equipment.

[0051] In one embodiment of the present invention, a method for preparing bismuth telluride-based nanotubes is provided, including the following steps:

[0052] (1) Set a template on a substrate, and then deposit a plurality of bismuth wires on the substrate;

[0053] (2) Remove the template to obtain bismuth wires supported by the substrate, and soak the bismuth wires supported by the substrate in nitric acid to reduce the wire diameter of the bismuth wires and make the wire diameter of the bismuth wires reach the nanoscale;

[0054] (3) Deposit a bismuth telluride cladding on the bismuth wires supported by the substrate, and then obtain a plurality of hollow bismuth telluride-based nanotubes supported by the substrate through vacuum annealing treatment.

[0055] Among them, in step (1), the template is a template with regularly arranged die holes. Preferably, the die holes are arranged in a periodic hexagonal array. More preferably, each hexagonal shape in each period contains 6 die holes, which are respectively used as the vertices of the hexagon. The thickness of the template is 0.15 - 0.25 mm, and the aperture of the die hole is 100 - 150 μm. Preferably, the template thickness is 0.2 mm, and the aperture of the die hole is 130 μm. The substrate is a flexible substrate, preferably a PI substrate, with a thickness of 40 - 60 μm, preferably 50 μm. The deposition is carried out by electron beam evaporation. The process parameters used include: the vacuum degree is better than 4E-4 Pa, the evaporation electron beam current is 0.04 A - 0.08 A, the evaporation voltage is 5 - 15 KV, and the temperature is 25 - 250 °C. Preferably, the evaporation voltage is 10 KV, and the temperature is 25 °C, 50 °C, 100 °C, 200 °C or 250 °C. The wire diameter of the deposited bismuth wire is less than or equal to 130 μm, and the wire length is greater than or equal to 130 μm. Preferably, the deposited bismuth wire is 100 - 130 μm.

[0056] In step (2), the nitric acid is nitric acid with a mass concentration of more than 63%, preferably 63%. Its molar mass concentration is about 14.5 mol / L, and the density is 1.45 g / cm 3 ; The soaking can be single soaking or multiple soakings. Preferably, it is multiple soakings. After each soaking, the wire diameter of the bismuth wire is detected by the SEM method. If the detected wire diameter of the bismuth wire is greater than 50 nm, the soaking step is repeated; if the detected wire diameter of the bismuth wire is less than or equal to 50 nm, the soaking step ends and the next step is carried out; The single soaking time does not exceed 10 s - 30 s, preferably 20 s. After soaking, it is rinsed with hydrophobic water, the water flow rate is not greater than 0.2 m / s, preferably 0.2 m / s, and the rinsing time is more than 20 s, preferably 20 s.

[0057] In step (3), the deposition is carried out by electron beam evaporation. The process parameters used include: the vacuum degree is better than 4E-4 Pa, the evaporation electron beam current is 0.02 A - 0.06 A, the evaporation voltage is 5 - 15 KV, and the temperature is 25 - 250 °C. Preferably, the evaporation voltage is 10 KV, and the temperature is 25 °C, 50 °C, 100 °C, 200 °C or 250 °C. The process parameters of the vacuum annealing treatment include: the annealing temperature is 280 - 290 °C, preferably 285 °C; the annealing time is 10 - 15 h, preferably 12 h; the vacuum degree is better than 10-4 Pa; the thickness of the deposited bismuth telluride cladding is 20 - 40 nm, preferably 20 nm. The hollow aperture of the obtained bismuth telluride-based nanotube is 10 - 50 nm, preferably 10 - 30 nm. The bismuth telluride-based nanotubes are orderly arranged on the substrate, showing a periodic lattice arrangement. Specifically, it forms a periodic hexagonal array arrangement. Each hexagon in each period contains 6 bismuth telluride-based nanotubes, and they are the six vertices of the hexagon.

[0058] In one embodiment of the present invention, the two growth routes of nanocrystal formation can be modulated by the synergistic control of the parameters in step (1), step (2), and step (3): one is monomer growth, which is controlled by diffusion and surface reaction; the other is growth achieved by direct fusion between particles. For the composition and structure of nanotubes, the adjustment of the temperature range corresponding to the highest thermoelectric figure of merit can be realized through the optimized combination of various process parameters. It should be noted that the preparation method of the present invention is also applicable to the preparation of nanotubes such as bismuth / antimony, silicon, carbon, etc. Bismuth telluride in this embodiment can be replaced by bismuth / antimony, silicon, carbon, etc., and these equivalent replacement materials are also within the protection scope of the present invention.

[0059] In a specific embodiment of the present invention, bismuth telluride-based nanotubes are specifically prepared by the following steps:

[0060] S1. Select a stainless steel plate with a periodically arranged hexagonal array of holes as template 1. As Figure 1 shown, the inner diameter of the mold holes 2 in the hole array is 130 μm, the thickness of template 1 is 0.2 mm, the side length of template 1 is 2 cm, and in the hexagonal array of holes in each period, the distance between two adjacent mold holes 2 is 300 μm.

[0061] S2. Select a square PI film with a thickness of 50 μm and a side length of 2 cm as substrate 3. Superimpose and fix template 1 and substrate 3, and then use the substrate 3 covered by template 1 as the electron beam evaporation substrate. Use the electron beam evaporation method to prepare bismuth wires with a regular arrangement, a wire diameter of 130 μm, and a wire length of 150 μm. As Figure 2 shown, among them, the process parameters of electron beam evaporation are: the vacuum degree is better than 4E-4 Pa, the evaporation electron beam current is 0.06 A, the evaporation voltage is 10 KV, and the temperature is 100 °C.

[0062] S3. Remove template 1, and then immerse the bismuth wire 4 supported by substrate 3 in concentrated nitric acid with a concentration of 63% for 20 s, take it out and immediately rinse it hydrophobically for 20 s, the water flow rate is 0.2 m / s, then dry it with high-purity nitrogen, and then use SEM to measure the wire diameter of bismuth wire 4. If the wire diameter is greater than 50 nm, repeat the immersion, rinsing, and drying steps until the wire diameter of bismuth wire 4 is less than or equal to 50 nm. As Figure 3 shown.

[0063] S4. Place the bismuth wire 4 supported by substrate 3 prepared in step S3 in an electron beam evaporation system, and use the electron beam evaporation method to prepare a bismuth telluride cladding for the bismuth wire to obtain a bismuth / bismuth telluride nanowire 5, and control the thickness of the bismuth telluride cladding to be 20 nm. As Figure 4As shown, the evaporation source used is a bismuth telluride compound with a deviation from stoichiometry. The process parameters of electron beam evaporation are a vacuum better than 4E-4 Pa, an evaporation electron beam current of 0.04 A, an evaporation voltage of 10 KV, and a temperature of 100 °C.

[0064] S5. Place the bismuth / bismuth telluride nanowires 5 supported by the substrate 3 prepared in step S4 in a high-vacuum system for annealing treatment, so that the inner-core bismuth wire melts and oozes out, or interdiffuses with the outer-shell bismuth telluride to obtain a hollow bismuth telluride-based nanotube 6 supported by the substrate 3, as Figure 5 shown, where the annealing temperature is 285 °C, the annealing time is 12 h, and the vacuum is better than 10-4 Pa.

[0065] In this example, Figure 3 and Figure 4 seem to have the same structural schematic because Figure 3 the bismuth wire 4 in Figure 4 is nanoscale, and the bismuth / bismuth telluride nanowires in

[0066] are also nanoscale. Therefore, it is not easy to distinguish them in the macroscopic schematic. The hollow bismuth telluride-based nanotubes 6 supported by the substrate 3 prepared in this embodiment are arranged orderly in a periodic lattice arrangement, specifically forming a periodic hexagonal array arrangement. Each hexagon in each period contains 6 bismuth telluride-based nanotubes, and they are the six vertices of the hexagon. The distance H between two adjacent bismuth telluride-based nanotubes in the array arranged in a hexagon for each period is 300 μm. The inner hollow diameter of each bismuth telluride-based nanotube is detected to be between 10 and 30 nm, and SEM detection or laser particle size analyzer detection is used.

[0067] The above embodiments are only for illustrating the technical concept and characteristics of the present invention, and their purpose is to enable those familiar with this technology to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

[0068] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and a single point value, and between single point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

Claims

1. A preparation method of bismuth telluride-based nanotubes, characterized in that, It includes the following steps: S1. Set a template on a substrate, and then deposit a plurality of bismuth wires on the substrate; S2. Remove the template to obtain bismuth wires supported by the substrate, and soak the bismuth wires supported by the substrate in nitric acid to reduce the wire diameter of the bismuth wires and make the wire diameter of the bismuth wires reach the nanometer level; S3. Deposit a bismuth telluride cladding on the bismuth wires supported by the substrate, and then obtain a plurality of hollow bismuth telluride-based nanotubes supported by the substrate through vacuum annealing treatment.

2. The preparation method of the bismuth telluride-based nanotubes according to claim 1, wherein: The template has regularly arranged die holes, so that the plurality of bismuth telluride-based nanotubes are regularly arranged on the substrate.

3. The preparation method of the bismuth telluride-based nanotubes according to claim 2, wherein: The die holes on the template are arranged in a periodic hexagonal array, so that the plurality of bismuth telluride-based nanotubes are arranged in a periodic hexagonal array.

4. The preparation method of the bismuth telluride-based nanotube according to claim 1, characterized in that: In step S1, the wire diameter of the bismuth wire is less than or equal to 130 μm; and / or, in step S2, the bismuth wire is soaked in nitric acid so that the wire diameter of the bismuth wire is less than or equal to 50 nm; and / or, in step S3, the thickness of the bismuth telluride cladding is 20-40 nm, and the inner diameter of the hollow of the bismuth telluride-based nanotube is 10-50 nm.

5. The preparation method of the bismuth telluride-based nanotube according to claim 1 or 4, characterized in that: In step S2, the concentration of the nitric acid is more than 63%; and / or, the soaking is single soaking or multiple soakings. After each soaking, the wire diameter of the bismuth wire is detected. If it is detected that the wire diameter of the bismuth wire is greater than 50 nm, the soaking step is repeated; if it is detected that the wire diameter of the bismuth wire is less than or equal to 50 nm, the soaking step ends and the next step is carried out.

6. The preparation method of the bismuth telluride-based nanotubes according to claim 5, wherein: The single soaking time does not exceed 10 s - 30 s, and after the soaking, hydrophobic rinsing is carried out, and the water flow rate is not greater than 0.2 m / s.

7. The preparation method of the bismuth telluride-based nanotubes according to claim 1, characterized in that: In step S1, the deposition adopts the electron beam evaporation method, and the process parameters adopted include a vacuum better than 4E-4 Pa, an evaporation electron beam current of 0.04 A - 0.08 A, an evaporation voltage of 5 - 15 KV; the temperature is 25 - 250 °C; and / or, in step S3, the deposition adopts the electron beam evaporation method, and the process parameters adopted include a vacuum better than 4E-4 Pa, an evaporation electron beam current of 0.02 A - 0.06 A, an evaporation voltage of 5 - 15 KV; the temperature is 25 - 250 °C, and the evaporation source adopted is a bismuth telluride compound deviating from the stoichiometric ratio to obtain a bismuth telluride cladding containing one or more of p-type bismuth telluride, n-type bismuth telluride, and intrinsic bismuth telluride.

8. The preparation method of the bismuth telluride-based nanotube according to claim 1, characterized in that: In step S3, the process parameters of the vacuum annealing treatment include: an annealing temperature of 280 - 290 °C; an annealing time of 10 - 15 h; a vacuum better than 10-4 Pa.

9. The preparation method of the bismuth telluride-based nanotube according to any one of claims 1 to 3, characterized in that: The substrate is a flexible substrate; and / or, the template is a stainless steel template.

10. The preparation method of the bismuth telluride-based nanotubes according to claim 9, characterized in that: The substrate is a PI substrate; and / or, the thickness of the template is 0.15 - 0.25 mm, and the aperture of the die hole of the template is 100 - 150 μm.

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