One-dimensional coaxial niobium selenide / carbon nanotube heterojunction and preparation method thereof

Abstract

This invention discloses a one-dimensional coaxial niobium selenide / carbon nanotube heterojunction and its preparation method. The preparation method includes: using a confined-filling method, open carbon nanotubes, elemental selenium, and elemental niobium undergo solid-phase synthesis and chemical vapor transport reactions in a closed reaction chamber to obtain the one-dimensional coaxial niobium selenide / carbon nanotube heterojunction. The method provided by this invention can significantly improve the stability of the material, avoid the stress generated by traditional heterojunctions, and better demonstrate the excellent superconducting properties of the one-dimensional coaxial van der Waals heterojunction. Furthermore, this one-step preparation method combining confined-filling and improved selenization treatment greatly simplifies the manufacturing process. The one-dimensional heterojunction superconductor prepared by this invention has a simpler structure than other two-dimensional superconducting heterojunctions, therefore, it is theoretically simpler to study its electro-acoustic interactions, electron / hole transport, and phase transitions, allowing for a better understanding of the underlying principles through theoretical research, thus enabling better control and optimization of material properties.

Description

Technical Field

[0001] This invention relates to a method for preparing a coaxial heterojunction of carbon nanotubes, specifically to a one-dimensional coaxial niobium selenide / carbon nanotube superconducting van der Waals heterojunction and its preparation method, belonging to the field of superconducting materials technology. Background Technology

[0002] Niobium selenide (NbSe2), as a conventional type-II superconductor, possesses a wide range of interesting physical properties. It maintains superconductivity in strong magnetic fields, and its unique electronic structure and physical characteristics make it a valuable superconducting material with broad applications in scientific research, medicine, and transportation. Currently, researchers have reached a consensus on the superconducting mechanism of conventional superconductors, but unconventional superconductivity still lacks a unified theoretical explanation. At the macroscopic level, when the dimension decreases from three dimensions to lower dimensions (usually one or two dimensions smaller than the coherence length), charge carriers are confined to a lower-dimensional space, leading to many novel physical phenomena, such as quantum Griffith singularity, Ising superconductivity, anomalous metallic states, and phase slip. These properties are beneficial for understanding superconductivity. Furthermore, in low-dimensional confined systems, particle systems may exhibit states vastly different from those under isolated conditions. Therefore, exploring the superconducting properties of materials in low-dimensional confined systems is of great value to research in the field of superconductivity.

[0003] In confined systems, the study of phase transitions in the confined space of nanotubes is a hot topic in condensed matter physics. Carbon nanotubes, due to their numerous excellent physicochemical properties, have always been a focus of research in various fields. The weak van der Waals interactions between molecules and carbon nanotubes within the confined space easily form one-dimensional van der Waals heterostructures, providing a near-perfect research model for studying one-dimensional confined nanostructures. Exploring the laws governing the changes in matter within one-dimensional nanoconfined systems has always been a new research area. The interaction between carbon nanotubes and the filler makes the high-pressure behavior of the host and guest components significantly different from that of individual components. High-pressure studies of carbon nanotube-confined systems can not only reveal novel physical phase transition mechanisms under the nanoconfinement effect and deepen our understanding of their new properties, but also provide ideas for constructing new functional materials.

[0004] Current research on the superconducting properties of niobium selenide mainly focuses on the few-layer structure of superconducting materials. However, the instability of few-layer niobium selenide crystal sheets in air and the severe degradation of device performance have limited in-depth research. The one-dimensional axial channel space of carbon nanotubes not only restricts the growth direction and arrangement of the filler but also provides excellent protection for the internal structure, ensuring its stability. Simultaneously, the interaction between the filler and the carbon nanotube, as well as the reverse charge transfer energy, greatly improves the physical and chemical properties of the nanotubes. By fabricating one-dimensional coaxial carbon nanotube-niobium selenide heterojunctions, it is possible to generate superconducting physical properties distinctly different from those of superconducting films. Studying the electrical properties of carbon nanotubes, niobium selenide superconductors within confined spaces, and heterojunctions coupling the two in horizontal planes is expected to reveal the physical mechanism of low-dimensional weak connections in superconductors and interface problems within confined spaces. This will provide theoretical guidance for improving the critical parameters of micro / nano-scale superconducting quantum devices, lay the foundation for exploring new principle devices, and may also open up new practical applications in the field of topological quantum computing.

[0005] Currently reported superconducting heterojunctions mainly consist of superconducting materials combined with graphene, utilizing traditional mechanical stacking methods. However, the mechanical vertical stacking process easily introduces impurities, causing stress-induced material performance degradation. Furthermore, mechanical stacking results in low yields and high technological barriers, hindering further development. The niobium selenide-graphene heterojunction preparation method used in patent CN110429174A is complex, employing vapor deposition technology. While this solves the problems of weak van der Waals forces between layers in vertically stacked graphene / niobium selenide / graphene heterojunctions, easy introduction of impurities, difficulty in controlling product size, and low yield, the process remains overly cumbersome. The prepared materials also suffer from instability in air and severe device performance degradation. Patent CN107634089A, for example, explores other semiconductors with special properties besides graphene as options for superconducting heterojunctions. However, these patents are largely top-level designs and concepts without concrete implementation, lacking practical application and thus failing to provide significant traction in real-world scenarios.

[0006] In summary, traditional superconducting thin-film heterojunction materials have drawbacks such as weak van der Waals bonding between layers, instability in air, and device performance degradation. Summary of the Invention

[0007] The main objective of this invention is to provide a one-dimensional coaxial niobium selenide / carbon nanotube heterostructure and its preparation method, so as to overcome the shortcomings of traditional superconducting thin film heterostructure materials, such as weak van der Waals bonding between layers, instability in air, and device performance degradation.

[0008] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0009] This invention provides a method for preparing a one-dimensional coaxial niobium selenide / carbon nanotube heterostructure, comprising:

[0010] Carbon nanotubes that provide openings;

[0011] A one-dimensional coaxial niobium selenide / carbon nanotube heterostructure was prepared by using a confined filling method to conduct solid-phase synthesis and chemical vapor transport reactions of the open carbon nanotubes, selenium, and niobium in a closed reaction chamber.

[0012] In some embodiments, the preparation method specifically includes:

[0013] Selenium, niobium, and open carbon nanotubes were placed together at the bottom of the reaction chamber, which was then sealed to form a closed reaction chamber. The air in the reaction chamber was then removed to ensure a vacuum level of no more than 3 × 10⁻⁶. -3 Pa;

[0014] The sealed reaction chamber is heated to raise the temperature inside the chamber, resulting in solid-phase synthesis and chemical vapor transport reactions, thus producing a one-dimensional coaxial niobium selenide / carbon nanotube heterostructure.

[0015] This invention also provides a one-dimensional coaxial niobium selenide / carbon nanotube heterostructure prepared by the aforementioned method, comprising carbon nanotubes and niobium selenide grown confined within the carbon nanotubes.

[0016] Compared with the prior art, the beneficial effects of the present invention are at least as follows:

[0017] 1) This invention provides a method for preparing one-dimensional coaxial niobium selenide / carbon nanotube heterostructures using a confined filling method. This method significantly improves the stability of the material, avoids the stress generated by traditional heterostructures, and better demonstrates the excellent superconducting properties of one-dimensional coaxial van der Waals heterostructures. Furthermore, this one-step preparation method combining confined filling and improved selenization treatment greatly simplifies the manufacturing process compared to commonly used mechanical stacking and chemical vapor deposition methods, offering significant advantages in cost control. Using this invention, the superconducting heterostructure bonding process can be significantly simplified, reducing stress generated during layer-to-layer stacking and minimizing impurities, pores, and cracks caused by excessive distortion energy, thus fully demonstrating the excellent superconducting properties of one-dimensional coaxial heterostructures.

[0018] 2) The one-dimensional heterojunction superconductor prepared by the present invention has a simpler structure than other two-dimensional superconducting heterojunctions. Therefore, it is theoretically simpler to study its electro-acoustic interaction, electron / hole transport, phase transition, etc., and it is more possible to grasp the laws through theoretical research so as to better control and optimize the material properties. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the synthesis of a one-dimensional coaxial niobium selenide / carbon nanotube heterostructure (i.e., NbSe2@carbon nanotube heterostructure) in a typical embodiment of the present invention.

[0021] Figure 2 This is a transmission electron microscope image and structural schematic diagram of a one-dimensional coaxial niobium selenide / carbon nanotube superconducting van der Waals heterostructure in a typical embodiment of the present invention. Detailed Implementation

[0022] In view of the shortcomings of traditional superconducting thin-film heterojunction materials, such as weak van der Waals bonding between layers, instability in air, and device performance degradation, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. Its main function is to provide a method for preparing one-dimensional niobium selenide chains that is simple to process, significantly reduces impurities, and optimizes superconducting performance. The following will further explain and illustrate this technical solution, its implementation process, and its principles.

[0023] One aspect of this invention provides a method for preparing a one-dimensional coaxial niobium selenide / carbon nanotube heterostructure, comprising:

[0024] Carbon nanotubes that provide openings;

[0025] A one-dimensional coaxial niobium selenide / carbon nanotube heterostructure was prepared by using a confined filling method to conduct solid-phase synthesis and chemical vapor transport reactions of the open carbon nanotubes, selenium, and niobium in a closed reaction chamber.

[0026] In some implementations, the preparation method may specifically include:

[0027] Selenium, niobium, and open carbon nanotubes were placed together at the bottom of the reaction chamber, which was then sealed to form a closed reaction chamber. The air in the reaction chamber was then removed to ensure a vacuum level of no more than 3 × 10⁻⁶. -3 Pa;

[0028] The sealed reaction chamber is heated to raise the temperature inside the chamber, resulting in solid-phase synthesis and chemical vapor transport reactions, thus producing a one-dimensional coaxial niobium selenide / carbon nanotube heterostructure.

[0029] In some embodiments, the preparation method includes: calcining and annealing carbon nanotubes to obtain open carbon nanotubes.

[0030] Furthermore, the calcination annealing temperature is 350–650°C, and the holding time is 30–120 min.

[0031] Furthermore, the carbon nanotubes are single-walled or multi-walled carbon nanotubes with a purity of 75% to 98%, and the specific opening treatment is to open the carbon nanotubes by calcining and annealing in a tube furnace.

[0032] In some embodiments, the preparation method further includes: cleaning the calcined and annealed carbon nanotubes, followed by centrifugal drying, wherein the cleaning conditions are: the cleaning agent used is hydrochloric acid with a concentration of 6-12 mol / L, and the cleaning (soaking) time is 8-24 h.

[0033] Please see Figure 1 As shown, in some more specific embodiments, the method for preparing one-dimensional coaxial NbSe2 / carbon nanotube superconducting van der Waals heterostructures by confined filling includes the following steps:

[0034] (1) Opening treatment of single-walled carbon nanotubes to obtain open single-walled carbon nanotubes;

[0035] (2) The open single-walled carbon nanotubes, amorphous elemental selenium, and elemental niobium were placed together in a quartz tube and vacuum sealed.

[0036] (3) The sealed quartz tube is placed in a heating furnace and heated to cause selenization and gas phase transport, resulting in a one-dimensional coaxial NbSe2 / carbon nanotube van der Waals heterostructure.

[0037] In some embodiments, the diameter of the open carbon nanotube is 1 to 10 nm, and it is open at both ends.

[0038] In some implementations, in step (2), the mass ratio of elemental selenium, elemental niobium, and open carbon nanotubes is 50–90:20–40:10–30. For example, specifically, the mass of elemental selenium can be 50–90 mg, the mass of elemental niobium can be 20–40 mg, the mass of open single-walled carbon nanotubes can be 10–30 mg, and the diameter of the quartz tube is 10–20 mm.

[0039] In some implementation schemes, in step (2), the elemental selenium, elemental niobium, and open single-walled carbon nanotubes are weighed using a semi-automatic electro-optical balance. The quartz tube vacuum sealing step is as follows: one end is evacuated using a combination of a molecular pump and a mechanical pump, the other end is heated with a high-temperature flame, and then sealed. The vacuum degree inside the quartz tube is no greater than 3 × 10⁻⁶. -3 Pa.

[0040] In some implementations, step (3) specifically includes: heating the sealed reaction chamber to raise the temperature inside the sealed reaction chamber from room temperature to 500°C to 900°C at a rate of 5 to 20°C / min, keeping it at that temperature for 1 to 15 days, and then slowly lowering it to room temperature.

[0041] In other implementations, in addition to solid-phase synthesis and chemical vapor transport reaction methods, selenium and niobium particles can also be filled into carbon nanotubes via solution methods.

[0042] In the above technical solutions, this invention relates to a method for preparing one-dimensional coaxial NbSe / carbon nanotube superconducting heterostructures using a confined filling method. This method primarily involves first annealing single-walled carbon nanotube raw materials in air to create openings. Then, using solid-phase synthesis and chemical vapor deposition (CVD), niobium selenide is confined and filled into the carbon nanotubes under capillary action, directly forming a one-dimensional NbSe / carbon nanotube coaxial van der Waals heterostructure. This invention significantly improves the material's stability, avoids the stress, defects, and complex processes associated with traditional heterostructures, and further demonstrates the superior superconducting properties of the one-dimensional coaxial van der Waals heterostructure. Furthermore, this one-step preparation method combining confined filling and improved selenization treatment greatly simplifies the manufacturing process compared to commonly used mechanical stacking and CVD methods, offering significant advantages in cost control.

[0043] The above-mentioned technical solution of this invention uses a one-pot method for synthesizing heterojunctions, directly synthesizing them and avoiding the drawbacks of traditional heterojunction mechanical stacking or complex and cumbersome chemical vapor deposition processes. Compared with the traditional heterojunction preparation process, the stress generated by the confined filling reaction during chemical vapor deposition is much smaller than the corresponding stress in the formation of heterojunctions by stacking two-dimensional materials. This has a significant effect on simplifying the reaction process and optimizing the quality of heterojunctions, especially the superconducting properties of NbSe2. Therefore, this invention can significantly simplify the superconducting heterojunction synthesis process, reduce the stress generated by the stacking process between layers, and reduce impurities, pores, and cracks caused by excessive distortion energy, fully demonstrating the excellent superconducting properties of one-dimensional coaxial heterostructures.

[0044] Another aspect of the present invention provides a one-dimensional coaxial niobium selenide / carbon nanotube heterostructure prepared by the aforementioned preparation method, comprising carbon nanotubes and niobium selenide grown confined within the carbon nanotubes.

[0045] The content of niobium selenide in the one-dimensional coaxial niobium selenide / carbon nanotube heterostructure is 10-50 wt%.

[0046] Furthermore, the superconducting transition temperature of the one-dimensional coaxial niobium selenide / carbon nanotube heterostructure is 4–8 K.

[0047] This invention employs a novel confined-filling method to prepare one-dimensional coaxial NbSe2 / carbon nanotube heterostructures, providing an alternative to traditional heterostructure preparation methods and avoiding the drawbacks of high difficulty and low success rate associated with transfer pressing processes. Furthermore, the one-dimensional heterostructure superconductor prepared by this invention has a simpler structure than other two-dimensional superconducting heterostructures, making it theoretically simpler to study its electro-acoustic interactions, electron / hole transport, and phase transitions. This allows for a better understanding of the underlying principles through theoretical research, leading to more effective control and optimization of material properties.

[0048] Another aspect of the present invention provides the application of the aforementioned two-dimensional magnetic material—carbon nanotube coaxial heterojunction material—in the field of electronic devices.

[0049] In summary, this invention, by leveraging the stable structure of the outer carbon nanotubes and through the coupling of the two materials, overcomes the shortcomings of weak van der Waals forces between layers in superconducting thin-film heterojunction materials, which lead to instability in air and degradation of device performance. It provides a method for preparing one-dimensional niobium selenide chains that can significantly reduce impurities and optimize superconducting stability.

[0050] The invention will be more fully understood through the following detailed description, which should be read in conjunction with the accompanying drawings. Detailed embodiments of the invention are disclosed herein; however, it should be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, the specific functional details disclosed herein should not be construed as limiting, but rather as the basis for the claims and as intended to teach those skilled in the art to employ the representative basis of the invention in different ways in any suitable detailed embodiment.

[0051] Example 1

[0052] The fabrication process of the one-dimensional coaxial NbSe2 / carbon nanotube superconducting van der Waals heterojunction in this embodiment includes the following steps:

[0053] 1. First, the single-walled carbon nanotubes were annealed at 350℃ for 120 min, then cleaned with 6 mol / L hydrochloric acid for 24 h, and dried to obtain well-opened single-walled carbon nanotubes.

[0054] 2. Using a semi-automatic electro-optical balance, 81 mg of amorphous elemental selenium and 40 mg of elemental niobium were weighed and placed together with 20 mg of open carbon nanotubes in a 10 mm diameter quartz tube. The tube was then vacuum-sealed, with one end evacuated using a combination of a molecular pump and a mechanical pump, and the other end heated by an oxyhydrogen flame. The tube was then sealed, achieving a vacuum level of 3 × 10⁻⁶. -3 Pa.

[0055] 3. The sealed quartz tube is placed in a heating furnace and heated to induce a solid-phase reaction and a chemical vapor transport reaction, yielding a one-dimensional coaxial NbSe2 / carbon nanotube superconducting van der Waals heterostructure (i.e., a one-dimensional coaxial NbSe2@carbon nanotube heterostructure). The temperature rise program is as follows: the temperature is increased from room temperature to 750°C at a rate of 5°C / min, held at that temperature for 3 days, and then cooled to room temperature. The niobium selenide content in the product obtained in this embodiment is 20–50 wt%.

[0056] The inventors of this case characterized the morphology of the one-dimensional coaxial NbSe2 / carbon nanotube superconducting van der Waals heterostructure obtained in this embodiment, and its transmission electron microscopy image and structural schematic diagram are shown below. Figure 2 As shown.

[0057] Example 2

[0058] The fabrication process of the one-dimensional coaxial NbSe2 / carbon nanotube superconducting van der Waals heterojunction in this embodiment includes the following steps:

[0059] 1. First, the single-walled carbon nanotubes were annealed at 450℃ for 100 min, then cleaned with 8 mol / L hydrochloric acid for 20 h, and dried to obtain well-opened single-walled carbon nanotubes.

[0060] 2. Using a semi-automatic electro-optical balance, 90 mg of amorphous elemental selenium and 40 mg of elemental niobium were weighed and placed together with 30 mg of open carbon nanotubes in a 10 mm diameter quartz tube. The tube was then vacuum-sealed, with one end evacuated using a combination of a molecular pump and a mechanical pump, and the other end heated by an oxyhydrogen flame. The tube was then sealed, achieving a vacuum level of 3 × 10⁻⁶. -3 Pa.

[0061] 3. The sealed quartz tube is placed in a heating furnace and heated to induce a solid-phase reaction and a chemical vapor transport reaction, resulting in a one-dimensional coaxial NbSe2 / carbon nanotube superconducting van der Waals heterostructure (i.e., a one-dimensional coaxial NbSe2@carbon nanotube heterostructure). The temperature rise program is as follows: the temperature is raised from room temperature to 750°C at a rate of 5°C / min, held at that temperature for 3 days, and then cooled to room temperature.

[0062] Example 3

[0063] The fabrication process of the one-dimensional coaxial NbSe2 / carbon nanotube superconducting van der Waals heterojunction in this embodiment includes the following steps:

[0064] 1. First, the single-walled carbon nanotubes were annealed at 550℃ for 80 min, then cleaned with 10 mol / L hydrochloric acid for 15 h, and dried to obtain well-opened single-walled carbon nanotubes.

[0065] 2. Using a semi-automatic electro-optical balance, 81 mg of amorphous elemental selenium and 40 mg of elemental niobium were weighed and placed together with 20 mg of open carbon nanotubes in a 20 mm diameter quartz tube. The tube was then vacuum-sealed, with one end evacuated using a combination of a molecular pump and a mechanical pump, and the other end heated by an oxyhydrogen flame. The tube was then sealed, achieving a vacuum level of 3 × 10⁻⁶. -3 Pa.

[0066] 3. The sealed quartz tube is placed in a heating furnace and heated to induce a solid-phase reaction and a chemical vapor transport reaction, resulting in a one-dimensional coaxial NbSe2 / carbon nanotube superconducting van der Waals heterostructure (i.e., a one-dimensional coaxial NbSe2@carbon nanotube heterostructure). The temperature rise program is as follows: the temperature is raised from room temperature to 750°C at a rate of 5°C / min, held at that temperature for 3 days, and then cooled to room temperature.

[0067] Example 4

[0068] The fabrication process of the one-dimensional coaxial NbSe2 / carbon nanotube superconducting van der Waals heterojunction in this embodiment includes the following steps:

[0069] 1. First, the single-walled carbon nanotubes were annealed at 650℃ for 30 min, then cleaned with 12 mol / L hydrochloric acid for 8 h, and dried to obtain well-opened single-walled carbon nanotubes.

[0070] 2. Using a semi-automatic electro-optical balance, 50 mg of amorphous elemental selenium and 20 mg of elemental niobium were weighed and placed together with 10 mg of open carbon nanotubes in a 10 mm diameter quartz tube. The tube was then vacuum-sealed, with one end evacuated using a combination of a molecular pump and a mechanical pump, and the other end heated by an oxyhydrogen flame. The tube was then sealed, achieving a vacuum level of 3 × 10⁻⁶. -3 Pa.

[0071] 3. The sealed quartz tube is placed in a heating furnace and heated to induce a solid-phase reaction and a chemical vapor transport reaction, resulting in a one-dimensional coaxial NbSe2 / carbon nanotube superconducting van der Waals heterostructure (i.e., a one-dimensional coaxial NbSe2@carbon nanotube heterostructure). The temperature rise program is as follows: the temperature is raised from room temperature to 850°C at a rate of 5°C / min, held at that temperature for 3 days, and then cooled to room temperature.

[0072] Example 5

[0073] The fabrication process of the one-dimensional coaxial NbSe2 / carbon nanotube superconducting van der Waals heterojunction in this embodiment includes the following steps:

[0074] 1. First, the single-walled carbon nanotubes were annealed at 500℃ for 50 min, then cleaned with 9 mol / L hydrochloric acid for 10 h, and dried to obtain well-opened single-walled carbon nanotubes.

[0075] 2. Using a semi-automatic electro-optical balance, 90 mg of amorphous elemental selenium and 40 mg of elemental niobium were weighed and placed together with 30 mg of open carbon nanotubes in a 10 mm diameter quartz tube. The tube was then vacuum-sealed, with one end evacuated using a combination of a molecular pump and a mechanical pump, and the other end heated by an oxyhydrogen flame. The tube was then sealed, achieving a vacuum level of 3 × 10⁻⁶. -3 Pa.

[0076] 3. The sealed quartz tube is placed in a heating furnace and heated to induce a solid-phase reaction and a chemical vapor transport reaction, resulting in a one-dimensional coaxial NbSe2 / carbon nanotube superconducting van der Waals heterostructure (i.e., a one-dimensional coaxial NbSe2@carbon nanotube heterostructure). The temperature rise program is as follows: the temperature is raised from room temperature to 500℃ at a rate of 10℃ / min, held at that temperature for 15 days, and then cooled to room temperature.

[0077] Example 6

[0078] The fabrication process of the one-dimensional coaxial NbSe2 / carbon nanotube superconducting van der Waals heterojunction in this embodiment includes the following steps:

[0079] 1. First, the single-walled carbon nanotubes were annealed at 450℃ for 100 min, then cleaned with 8 mol / L hydrochloric acid for 18 h, and dried to obtain well-opened single-walled carbon nanotubes.

[0080] 2. 80 mg of amorphous elemental selenium and 20 mg of elemental niobium were weighed using a semi-automatic electro-optical balance. These were then placed together with 20 mg of open-ended carbon nanotubes in a 40 mm diameter tube furnace. A mechanical pump was used to evacuate the furnace at one end, maintaining a vacuum of 1 × 10⁻⁶. -3 Pa, argon flow rate 10 sccm.

[0081] 3. The tube furnace is heated to induce a solid-phase reaction and a chemical vapor transport reaction to obtain a one-dimensional coaxial NbSe2 / carbon nanotube superconducting van der Waals heterostructure (i.e., a one-dimensional coaxial NbSe2@carbon nanotube heterostructure); the temperature rise program is as follows: the temperature is raised from room temperature to 900℃ at a rate of 20℃ / min, held at that temperature for 1 day, and then cooled to room temperature.

[0082] In summary, the method provided by this invention can significantly improve the stability of materials, avoid the stress generated by traditional heterojunctions, better demonstrate the excellent superconducting performance of one-dimensional coaxial van der Waals heterojunctions, and this one-step preparation method combining confined filling and improved selenization treatment greatly simplifies the manufacturing process.

[0083] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0084] Compare with Example 1

[0085] The solution-based preparation process for one-dimensional coaxial NbSe2 / carbon nanotube superconducting van der Waals heterostructures includes the following steps:

[0086] 1. First, the single-walled carbon nanotubes are annealed by heating, cleaned, and dried to obtain single-walled carbon nanotubes with good openings.

[0087] 2. Using a semi-automatic electro-optical balance, 229.5 mg of amorphous elemental selenium chloride and 135 mg of niobium pentachloride were weighed and placed together with 20 mg of opened carbon nanotubes in 50 ml of carbon tetrachloride solution. The mixture was stirred for 3 days, centrifuged, and the centrifuged product was washed three times with alcohol. The product was then placed in a tube furnace. A mechanical pump was used to evacuate one end of the tube furnace, maintaining a vacuum of 1 × 10⁻³ Pa and an argon flow rate of 10 sccm.

[0088] 3. The tube furnace is heated to induce a solid-phase reaction and a chemical vapor transport reaction to obtain a one-dimensional coaxial NbSe2 / carbon nanotube superconducting van der Waals heterostructure (i.e., a one-dimensional coaxial NbSe2@carbon nanotube heterostructure); the temperature rise program is as follows: the temperature is raised from room temperature to 750℃ at a rate of 5℃ / min, held at that temperature for 3 days, and then cooled to room temperature.

[0089] Solution methods require stepwise synthesis and cannot achieve one-step synthesis of the target product. After filling carbon nanotubes using solution methods, further annealing is required to achieve crystal sintering within the carbon nanotubes, and many toxic and harmful reagents are used, which is not conducive to large-scale production. The preparation method of this invention can synthesize the target product in one step. Furthermore, solution-synthesized samples cannot achieve complete filling, with a filling amount of less than 10 wt%, which is not conducive to the display of material properties in practical use.

[0090] Although the invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions, and / or additions can be made without departing from the spirit and scope of the invention, and that elements of the embodiments can be substituted with substantially equivalents. Furthermore, many modifications can be made without departing from the scope of the invention to adapt particular situations or materials to the teachings of the invention. Therefore, this invention is not intended to be limited to the specific embodiments disclosed for carrying out the invention, but rather is intended to encompass all embodiments falling within the scope of the appended claims. Moreover, unless specifically stated otherwise, any use of the terms first, second, etc., does not indicate any order or importance, but is used to distinguish one element from another.

Claims

1. A method for preparing a one-dimensional coaxial NbSe2 / carbon nanotube heterostructure, characterized in that, include: Carbon nanotubes that provide openings; Using a confined filling method, the open carbon nanotubes, elemental selenium, and elemental niobium are placed together at the bottom of the reaction chamber, sealed to form a closed reaction chamber, and then the air in the reaction chamber is removed to ensure that the vacuum degree of the reaction chamber does not exceed 3 × 10⁻⁶. -3 Pa; The mass ratio of the selenium, niobium and open carbon nanotubes is 50-90:20-40:10-30; The sealed reaction chamber is heated to raise the temperature inside the sealed reaction chamber. The temperature inside the sealed reaction chamber is raised from room temperature to 500℃~900℃ at a rate of 5~20℃ / min to carry out solid-phase synthesis and chemical vapor transport reaction. After holding at this temperature for 1~15 days, it is slowly lowered to room temperature to obtain a one-dimensional coaxial NbSe2 / carbon nanotube heterostructure. The superconducting transition temperature of the one-dimensional coaxial NbSe2 / carbon nanotube heterojunction is 4–8 K.

2. The preparation method according to claim 1, characterized in that, include: Carbon nanotubes are calcined and annealed to obtain open carbon nanotubes. The calcination and annealing temperature is 350-650℃ and the time is 30-120 min.

3. The preparation method according to claim 2, characterized in that: The carbon nanotube package consists of single-walled carbon nanotubes and / or multi-walled carbon nanotubes with a purity of 75% to 98%.

4. The preparation method according to claim 2, characterized in that, Also includes: The calcined and annealed carbon nanotubes are cleaned and then dried. The cleaning agent used is hydrochloric acid with a concentration of 6-12 mol / L, and the cleaning time is 8-24 hours.

5. The preparation method according to claim 1 or 2, characterized in that: The diameter of the open carbon nanotube is 1–10 nm, and it is open at both ends.

6. A one-dimensional coaxial NbSe2 / carbon nanotube heterojunction prepared by any one of claims 1-5, comprising carbon nanotubes and NbSe2 confined and filled within the carbon nanotubes, wherein the superconducting transition temperature of the one-dimensional coaxial NbSe2 / carbon nanotube heterojunction is 4-8 K.

7. The one-dimensional coaxial NbSe2 / carbon nanotube heterostructure according to claim 6, characterized in that: The NbSe2 content in the one-dimensional coaxial NbSe2 / carbon nanotube heterostructure is 10~50wt%.

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