Metallic 1t-phase molybdenum disulfide material based on pulse joule heating and preparation and application thereof

Abstract

The present application relates to a kind of metallic 1T phase molybdenum disulfide material based on pulse joule heating and its preparation and application, 2H phase molybdenum disulfide obtained by solvothermal reaction is precursor, transient pulse current is applied under inert atmosphere, and 1T phase is mainly obtained molybdenum disulfide material.Pulse joule heating can realize rapid heating and cooling in very short time, induce 2H phase to 1T phase transition and retain metastable structure.Compared with prior art, the present application has short preparation time, less impurity residue of obtained product, and high phase structure regulation efficiency.Obtained material has large-area metastable metallic phase and good electromagnetic response performance.

Description

Technical Field

[0001] This invention belongs to the field of microwave absorbing materials technology, and relates to a metallic 1T phase molybdenum disulfide material based on pulsed Joule heating, its preparation and application. Background Technology

[0002] The increasingly prominent problems of electromagnetic radiation and electromagnetic interference have placed higher demands on efficient, lightweight, and stable electromagnetic wave absorbing materials. Two-dimensional transition metal sulfides, due to their layered structure, tunable electronic structure, and rich interfacial properties, have shown great potential in the field of electromagnetic wave absorption, with molybdenum disulfide (MoD) being a typical representative of this class of materials. MoD possesses various crystal phase structures; the thermodynamically stable 2H phase typically exhibits semiconductor properties, while the metastable 1T phase possesses a metallic electronic structure and higher carrier transport capability, which can enhance the material's conductivity loss, interfacial polarization, and electromagnetic response behavior, thus holding promise for the construction of high-performance electromagnetic absorbing materials. However, the 1T phase of MoD is thermodynamically metastable and readily transforms into the stable 2H phase, and its controllable preparation, phase structure preservation, and performance stability still face significant challenges.

[0003] Chinese patent CN202211471007.2 discloses a 1T / 2H phase molybdenum disulfide material for electromagnetic wave absorption. This material improves its absorption performance by introducing hexadecyltrimethylammonium bromide into a precursor solution and inducing partial formation of the 1T phase through a high-temperature, high-pressure solvothermal reaction, allowing it to coexist with the 2H phase. However, this preparation method relies on surfactant assistance, easily introducing residual impurities, and the controllability of the 1T phase structure remains insufficient. Summary of the Invention

[0004] The purpose of this invention is to provide a metallic 1T phase molybdenum disulfide material based on pulsed Joule heating, and its preparation and application, thereby solving at least one of the problems in the existing molybdenum disulfide phase transformation method, such as complex process, many impurity residues, and poor electromagnetic response of the obtained material.

[0005] The objective of this invention can be achieved through the following technical solutions: In a first aspect, the present invention provides a method for preparing a metallic 1T phase molybdenum disulfide material based on pulsed Joule heating, comprising the following steps: S1. Add molybdenum source and sulfur source to a mixed solvent of ethanol and deionized water, stir, and carry out a solvothermal reaction. After the reaction is completed, cool, filter, wash, and dry to obtain 2H phase molybdenum disulfide. S2. The 2H phase molybdenum disulfide obtained in S1 is subjected to pulse Joule heating in an inert atmosphere to obtain metallic 1T phase molybdenum disulfide, which is the target product.

[0006] Furthermore, in S1, the molybdenum source is ammonium molybdate tetrahydrate, and the sulfur source is thiourea.

[0007] Furthermore, in S1, the mass ratio of molybdenum source to sulfur source is 1:1.5 to 1:2.5, and can be selected as 1:1.5, 1:2, 1:2.5, etc.

[0008] Furthermore, in S1, the volume ratio of ethanol to deionized water is 1:1 to 1:2, and can be selected as 1:1, 1:1.5, 1:2, etc.

[0009] Furthermore, in S1, the stirring time is 4 to 8 hours.

[0010] Furthermore, in S1, the temperature of the solvothermal reaction is 200~240℃, and the reaction time is 22~26 h.

[0011] Furthermore, in S2, the inert atmosphere is provided by nitrogen or argon, which can effectively prevent the molybdenum disulfide from oxidizing and decomposing at high temperatures, thus ensuring the stability of the material's chemical composition.

[0012] Furthermore, in S2, the pulsed Joule heating temperature is 1000~1600℃, the pulse duration is 1~5 s, the number of pulses is 1~10, and the cooling time after all pulse treatments is 5 s. These conditions enable molybdenum disulfide to complete rapid heating, carrier injection, and rapid cooling in a very short time, inducing the 2H phase to 1T phase transition and stably retaining the metastable structure.

[0013] In a second aspect, the present invention provides a metallic 1T phase molybdenum disulfide based on pulsed Joule heating, which is prepared by the preparation method described in the first aspect above.

[0014] Furthermore, the metallic 1T phase molybdenum disulfide based on pulsed Joule heating has a lamellar structure and contains a large area (more than 80%) of metallic 1T phase.

[0015] In a third aspect, the present invention provides an application of metallic 1T phase molybdenum disulfide based on pulsed Joule heating as an electromagnetic functional material in the field of electromagnetic wave absorption.

[0016] Compared with the prior art, the present invention has the following advantages: (1) The 2H phase molybdenum disulfide prepared by solvothermal method is used as a precursor. The precursor has a lamellar structure and good compositional uniformity, which can provide a stable structural basis for subsequent electrothermal induced phase transition.

[0017] (2) Pulsed Joule heating is used to achieve transient electrothermal drive, so that molybdenum disulfide can complete rapid heating, carrier injection and rapid cooling in a short time, induce the transformation of the 2H phase to the 1T phase, and retain the metastable structure.

[0018] (3) By adjusting the pulse temperature, pulse time and pulse number, the phase composition and 1T phase ratio of molybdenum disulfide can be adjusted, thereby achieving coordinated control of the electronic structure and electromagnetic response performance of the material.

[0019] (4) The metastable 1T phase molybdenum disulfide obtained has stronger metallic phase characteristics and carrier transport capability, which is beneficial to enhance conductivity loss, interface polarization and electromagnetic energy dissipation, and improve the electromagnetic wave absorption performance of the material.

[0020] (5) This invention does not require the use of alkali metal intercalation agents or surfactants to assist phase transformation. It has a short reaction time, few impurities, and a simple process flow. It avoids the problems of ion residue and complicated post-processing in traditional chemical intercalation methods, and has good operability and application prospects. Attached Figure Description

[0021] Figure 1 This is a scanning electron microscope (SEM) image of the 1T phase molybdenum disulfide prepared in Example 2.

[0022] Figure 2 The image shows a high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) image and corresponding elemental distribution map of the 1T phase molybdenum disulfide prepared in Example 2.

[0023] Figure 3 This is an atomic resolution high-angle annular dark-field scanning transmission electron microscope image of the 1T phase molybdenum disulfide prepared in Example 2.

[0024] Figure 4 The image shows an atomic resolution high-angle annular dark-field scanning transmission electron microscope and corresponding elemental distribution map of the 1T phase molybdenum disulfide prepared in Example 2.

[0025] Figure 5 The X-ray diffraction (XRD) spectra of the 1T phase molybdenum disulfide prepared in Examples 1, 2 and 3 are shown.

[0026] Figure 6 The X-ray photoelectron spectroscopy (XPS) of Mo3d in Example 2.

[0027] Figure 7 The relative complex permittivity is given by the 1T phase molybdenum disulfide prepared in Examples 1, 2 and 3, wherein (a) is the real part of the relative complex permittivity and (b) is the imaginary part of the relative complex permittivity.

[0028] Figure 8 The relative complex permeability of 1T phase molybdenum disulfide prepared in Examples 1, 2 and 3, wherein (a) is the real part of the relative complex permeability; and (b) is the imaginary part of the relative complex permeability.

[0029] Figure 9 The reflection loss of 1T phase molybdenum disulfide prepared in Examples 1, 2 and 3 in the frequency range of 2-18 GHz, wherein (a) 1T-MoS2-1000, (b) 1T-MoS2-1300, and (c) 1T-MoS2-1600.

[0030] Figure 10 This is an atomic resolution high-angle annular dark-field scanning transmission electron microscope image of the 2H phase molybdenum disulfide prepared in Comparative Example 1.

[0031] Figure 11 The reflection loss of the 2H phase molybdenum disulfide prepared in Comparative Example 1 in the frequency range of 2-18 GHz is shown.

[0032] Figure 12 The reflection loss of the 2H phase molybdenum disulfide prepared in Comparative Example 2 is shown in the frequency range of 2-18 GHz.

[0033] Figure 13 The reflection loss of the 2H phase molybdenum disulfide prepared in Comparative Example 1 in the frequency range of 2-18 GHz is shown. Detailed Implementation

[0034] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0036] As used herein, the terms "and / or," "or / and," and "and / or" encompass any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected using at least two conjunctions selected from "and / or," "or / and," and "and / or," it should be understood that, in this application, the technical solution undoubtedly includes solutions connected by "logical AND," and also undoubtedly includes solutions connected by "logical OR."

[0037] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0038] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0039] This document only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0040] Unless otherwise specified, the temperature parameters in this application may be either constant temperature processing or processing within a certain temperature range. The constant temperature processing allows temperature fluctuations within the precision range controlled by the instrument, such as ±5℃, ±4℃, ±3℃, ±2℃, or ±1℃.

[0041] In this document, the term "suitable" as used in phrases such as "suitable combination," "suitable method," and "any suitable method" refers to the ability to implement the technical solution of this application, solve the technical problem of this application, and achieve the expected technical effect of this application.

[0042] In this application, terms such as "further," "even further," and "particularly" are used to describe purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0043] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0044] In the description of the application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0045] Unless otherwise specified, all preparations and tests described herein took place at 25°C.

[0046] The terms “comprising,” “including,” “containing,” “having,” “comprising,” or other variations thereof are intended to cover non-closed inclusion, and no distinction is made between these terms. The term “comprising” means that other steps and ingredients may be added without affecting the final result. The compositions and methods / processes of the present invention comprise, consist of, and substantially consist of the essential elements and limitations described herein, as well as any additional or optional ingredients, components, steps, or limitations described herein. No distinction is made between the terms “efficacy,” “performance,” “effect,” and “potency” herein.

[0047] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions. Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical solutions.

[0048] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, but sequentially is preferred.

[0049] Example 1: Preparation of 1T-MoS2-1000 molybdenum disulfide (1T-MoS2-1000): (1) Dissolve 0.981 g ammonium molybdate tetrahydrate and 1.596 g thiourea in a mixed solvent of 30 mL ethanol and 30 mL deionized water and stir at room temperature for 6 h until fully dispersed; transfer the mixed solution to a 100 mL stainless steel reactor lined with polytetrafluoroethylene and react at 220 °C for 24 h. After naturally cooling to room temperature, filter the supernatant, wash with ethanol and centrifuge to collect the precipitate, and vacuum dry at 60 °C for 6 h to obtain 2H phase molybdenum disulfide; (2) The obtained 2H phase molybdenum disulfide was heated by pulse Joule heating under a nitrogen atmosphere at a temperature of 1000℃, a pulse time of 1 s, a cooling time of 5 s, and 5 pulses to obtain 1T phase molybdenum disulfide, which is denoted as 1T-MoS2-1000.

[0050] Example 2: Preparation of 1T-MoS2-1300 molybdenum disulfide (1T-MoS2-1300): Compared with Example 1, most of the results are the same, except that the temperature of the pulse Joule heating is adjusted to 1300°C, and the resulting product is denoted as 1T-MoS2-1300.

[0051] Example 3: Preparation of 1T-MoS2-1600 molybdenum disulfide (1T-MoS2-1600): Compared with Example 1, the process steps remained the same, except that the temperature of the pulse Joule heating was adjusted to 1600°C, and the resulting product was denoted as 1T-MoS2-1600.

[0052] Figure 1 The image shows a scanning electron microscope (SEM) image of the 1T-MoS2-1300 sample prepared in Example 2. As can be seen from the image, the obtained molybdenum disulfide exhibits a flower-like lamellar structure formed by a large number of thin sheets stacked in an interlaced manner. The layers overlap each other and form open multi-level spaces, which is beneficial for increasing the interfacial contact area and promoting multiple scattering and dissipation of electromagnetic waves within the material.

[0053] Figure 2 The image shows a high-angle annular dark-field scanning transmission electron microscope (STEM) image and corresponding elemental distribution map (scale bar: 100 nm) of the 1T-MoS2-1300 sample prepared in Example 2. As can be seen from the image, the obtained sample is assembled from wrinkled, lamellar molybdenum disulfide, with clear and overlapping lamellar edges. Mo and S elements are relatively uniformly distributed within the sample area, indicating that no significant elemental segregation occurred after pulsed Joule heating treatment, and the material maintains good chemical compositional homogeneity.

[0054] Figure 3 The image shows an atomic resolution high-angle annular dark-field scanning transmission electron microscope (scale bar 2 nm) image of the 1T-MoS2-1300 sample prepared in Example 2. As can be seen from the image, the sample exhibits a regular and ordered lattice arrangement at the atomic scale, with clearly distributed Mo atomic pillars, displaying typical 1T phase atomic structure characteristics. Simultaneously, slight lattice distortion caused by atomic displacement can be observed in local areas, indicating the possible presence of 1T′ twisted octahedral structural features in the sample, further demonstrating that pulsed Joule heating can induce a phase transformation in molybdenum disulfide.

[0055] Figure 4 The image shows an atomic resolution high-angle annular dark-field scanning transmission electron microscope image and corresponding elemental distribution map of the 1T-MoS2-1300 sample prepared in Example 2. As can be seen from the figure, Mo and S elements are uniformly distributed at the atomic scale, indicating that the obtained molybdenum disulfide has good elemental uniformity and structural integrity.

[0056] Figure 5 X-ray diffraction patterns of the 1T-MoS2-1000, 1T-MoS2-1300, and 1T-MoS2-1600 samples prepared in Examples 1, 2, and 3 are shown. The results indicate that the samples exhibit characteristic diffraction peaks related to the 1T phase after pulsed Joule heating treatment, demonstrating that this method can induce the transformation of the 2H phase molybdenum disulfide to the metastable 1T phase. As the treatment temperature increases, the intensity of the diffraction peaks corresponding to the 1T phase increases, indicating that the proportion and content of the 1T phase can be adjusted by controlling the pulsed Joule heating temperature.

[0057] Figure 6The X-ray photoelectron spectroscopy (XPS) of Mo3d in Example 2, further quantitative compositional analysis showed that after the above-mentioned pulsed Joule heating treatment, the proportion of metallic 1T phase in the obtained molybdenum disulfide material could reach over 80%. The continuous distribution of a large amount of 1T phase not only constructs an efficient three-dimensional conductive network, enhancing carrier transport and conductivity loss, but also, the large number of 1T / 2H phase interfaces generated during this process greatly promotes interfacial polarization, laying the structural foundation for excellent electromagnetic response performance.

[0058] Figure 7 The real and imaginary parts of the complex permittivity of the 1T-MoS2-1000, 1T-MoS2-1300, and 1T-MoS2-1600 samples prepared in Examples 1, 2, and 3 are shown in the frequency range of 2-18 GHz, where a is the real part ε' of the complex permittivity and b is the imaginary part ε''. As the pulsed Joule heating temperature increases, ε' and ε'' of the samples generally show an increasing trend, indicating that electrothermal treatment can enhance the dielectric response of molybdenum disulfide. This phenomenon is mainly related to the transformation from the 2H phase to the metallic 1T phase. Increasing the proportion of the 1T phase can enhance carrier transport capacity and conductivity loss. Simultaneously, defects, boundaries, and phase interfaces in the lamellar structure also facilitate the induction of interfacial polarization and dipole polarization, thereby improving the material's ability to dissipate electromagnetic waves.

[0059] Figure 8 The real and imaginary parts of the complex permeability of the 1T-MoS2-1000, 1T-MoS2-1300, and 1T-MoS2-1600 samples prepared in Examples 1, 2, and 3 are shown in the frequency range of 2-18 GHz, where a is the real part of the complex permeability μ' and b is the imaginary part of the complex permeability μ''. These values ​​of μ' and μ'' are near 1 and 0, respectively, indicating that the enhanced electromagnetic wave absorption mainly originates from the dielectric loss, conductivity loss, and polarization relaxation induced by the metallic 1T phase, rather than from magnetic loss contributions.

[0060] Figure 9 The figure shows the reflection loss of the 1T-MoS2-1000, 1T-MoS2-1300, and 1T-MoS2-1600 samples prepared in Examples 1, 2, and 3 in the frequency range of 2-18 GHz. As can be seen from the figure, 1T-MoS2-1300, at a thickness of 2.0 mm, has an effective electromagnetic wave absorption bandwidth covering 5.44 GHz (10.56 GHz-16.00 GHz). At a thickness of 4.5 mm, the minimum reflection loss reaches -42.7 dB. The different colored lines in the figure represent the electromagnetic wave absorption performance of the material at different thicknesses, with the thickness unit being mm.

[0061] Comparative Example 1: Compared with Example 1, most of them are the same, except that step (2) is omitted to obtain 2H phase molybdenum disulfide as comparative sample 1.

[0062] The resulting product is 2H phase molybdenum disulfide, such as Figure 10 As shown, the sample exhibits a regular and ordered atomic arrangement of the 2H phase, with no obvious 1T phase or 1T′ structural distortion observed, indicating that molybdenum disulfide without pulsed Joule heating is more likely to form a thermodynamically stable 2H phase structure. Figure 11 As shown, in the 2-18 GHz range, the effective absorption bandwidth of this sample is limited and the impedance matching is poor, indicating that its microwave absorption performance is far inferior to that of the embodiments of the present invention.

[0063] Comparative Example 2: Compared with Example 1, most of them are the same, except that the 2H phase molybdenum disulfide obtained in step (1) is calcined in a tube furnace under a nitrogen atmosphere, heated to 800°C at 1°C / min, held for 2 h, and cooled to room temperature to obtain Comparative Sample 2.

[0064] The resulting product tends to maintain a thermodynamically stable 2H phase structure. Its electromagnetic wave absorption properties are as follows: Figure 12 As shown, the overall absorption intensity is weak in the 2-18 GHz range, indicating that conventional long-term calcination is unlikely to effectively improve its electromagnetic response.

[0065] Comparative Example 3: Compared with Example 1, most of them are the same, except that the mixed solvent in step (1) is replaced with an equal volume of deionized water as a single solvent (i.e., no ethanol is added), resulting in Comparative Sample 3.

[0066] The resulting product was not pure 2H-phase molybdenum disulfide, but contained intermediate impurity phases. Treating this impurity product under the same pulsed Joule heating conditions not only failed to induce a metallic 1T-phase molybdenum disulfide structure, but also resulted in a large number of oxide impurities within the material severely hindering the formation of the conductive network, such as... Figure 13 As shown, its microwave absorption performance is far inferior to that of Embodiment 1 of the present invention.

[0067] This invention utilizes the rapid thermal response and non-equilibrium carrier modulation during transient pulsed Joule heating to achieve a rapid transformation of molybdenum disulfide from the stable 2H phase to the metallic 1T phase, effectively preserving the metastable phase structure. By adjusting the pulsed Joule heating temperature, the degree of 1T phase formation and phase composition can be controlled, thereby enhancing the material's carrier transport capacity, conductivity loss, and polarization response behavior. The resulting molybdenum disulfide material exhibits excellent electromagnetic parameters and electromagnetic wave absorption properties, showing potential application value in electromagnetic protection, conductive functional devices, and low-dimensional electromagnetic functional materials.

[0068] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing metallic 1T phase molybdenum disulfide material based on pulsed Joule heating, characterized in that, Includes the following steps: S1. Add molybdenum source and sulfur source to a mixed solvent of ethanol and deionized water, stir, and carry out a solvothermal reaction. After the reaction is completed, cool, filter, wash, and dry to obtain 2H phase molybdenum disulfide. S2. The 2H phase molybdenum disulfide obtained in S1 is subjected to pulse Joule heating in an inert atmosphere to obtain metallic 1T phase molybdenum disulfide, which is the target product.

2. The method for preparing metallic 1T phase molybdenum disulfide material based on pulsed Joule heating according to claim 1, characterized in that, In S1, the molybdenum source is ammonium molybdate tetrahydrate, and the sulfur source is thiourea; the mass ratio of the molybdenum source to the sulfur source is 1:1.5 to 1:2.

5.

3. The method for preparing metallic 1T phase molybdenum disulfide material based on pulsed Joule heating according to claim 1, characterized in that, In S1, the volume ratio of ethanol to deionized water is 1:1 to 1:

2.

4. The method for preparing a metallic 1T phase molybdenum disulfide material based on pulsed Joule heating according to claim 1, characterized in that, In S1, the stirring time is 4~8 hours.

5. The method for preparing a metallic 1T phase molybdenum disulfide material based on pulsed Joule heating according to claim 1, characterized in that, In S1, the temperature of the solvothermal reaction is 200~240℃ and the time is 22~26 h.

6. The method for preparing a metallic 1T phase molybdenum disulfide material based on pulsed Joule heating according to claim 1, characterized in that, In S2, the inert atmosphere is provided by nitrogen or argon.

7. The method for preparing a metallic 1T phase molybdenum disulfide material based on pulsed Joule heating according to claim 1, characterized in that, In S2, the pulse Joule heating temperature is 1000~1600℃, the pulse time is 1~5 s, and the number of pulses is 1~10.

8. The method for preparing a metallic 1T phase molybdenum disulfide material based on pulsed Joule heating according to claim 7, characterized in that, The cooling time after each pulse processing is 5 seconds.

9. A metallic 1T phase molybdenum disulfide material based on pulsed Joule heating, characterized in that, It is prepared by any one of the preparation methods described in claims 1-8, and has a lamellar structure and contains more than 80% metallic 1T phase.

10. The application of the metallic 1T phase molybdenum disulfide material based on pulse Joule heating as described in claim 9 as an electromagnetic functional material in the field of electromagnetic wave absorption.

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