Non-Van der Waals artificial solid material and preparation method, film, dispersion liquid and application thereof

Abstract

The invention discloses a non-Van der Waals artificial solid material as well as a preparation method, a thin film, a dispersion liquid and application of the non-Van der Waals artificial solid material. According to the preparation method, effective stabilization and structural transformation of a conventional MXene material are realized through a two-step method of first zinc vapor electron injection stabilization and then metal vapor bonding transformation, irreversible transformation of MXene to a rock salt structure at a high temperature can be prevented, the MXene can react with various active metal vapor, and the performance of the MXene material is improved. The invention provides a general way for controllably synthesizing a series of ultrathin non-Van der Waals artificial solid materials, solves the problem that the conventional MXene is unstable at high temperature, can be used for preparing a series of ultrathin layered materials including Al-Ti3C2 and large-area flexible films thereof, and the obtained material has high conductivity, mechanical flexibility and high-temperature oxidation resistance, and has a wide application prospect. The method has a wide application prospect in the fields of flexible electronics, high-temperature electromagnetic shielding and infrared stealth.

Description

Technical Field

[0001] This invention belongs to the field of novel two-dimensional materials and functional ceramics technology, and relates to non-van der Waals artificial solid materials, their preparation methods, thin films, dispersions and applications. In particular, it relates to a method for stabilizing MXene and converting it into high-performance non-van der Waals artificial solid materials and thin films through an electron injection strategy, and its application in the fields of electromagnetic shielding and infrared stealth. Background Technology

[0002] Two-dimensional transition metal carbides, nitrides, or carbonitrides (MXenes) have shown great application potential in energy storage, catalysis, sensing, electromagnetic interference (EMI) shielding, and infrared stealth since their discovery due to their unique layered structure, tunable chemical composition, abundant surface functional groups, high conductivity, and good hydrophilicity. MXenes are typically produced by selectively etching their precursor MAX phase (general formula M...). n+1 AX n Where M is a transition metal element, A is mainly a group IIIA or IVA element, and X is obtained by taking the A atom layer of C or N, its general formula is M n+1 X n T x T x This represents the surface end groups (such as -OH, -F, =O, etc.) introduced during the etching process. This synthesis strategy based on the difference between weak MA bonds and strong MX bonds allows MXene layers to be mainly bonded by van der Waals forces, making them easy to exfoliate into monolayer or few-layer nanosheets.

[0003] In recent years, utilizing the reactivity of MXene surface end groups to transform them into non-van der Waals artificial solids (i.e., layered materials bound by chemical bonds rather than van der Waals forces) through post-synthetic modification (such as intercalation and surface substitution) has become an important research direction for expanding their performance boundaries and exploring new functions. For example, studies have successfully prepared several metal-bonded non-van der Waals MXene derivatives or MAX phase materials by reacting molten metals with halogen-terminated MXenes or by utilizing the interaction between metal atoms and sulfur end groups in molten salts. These materials typically exhibit higher electrical conductivity, thermal stability, and unique mechanical properties than the original MXene.

[0004] However, current techniques for synthesizing non-van der Waals artificial solids mainly rely on MXenes with specific, highly reactive end groups (such as -Cl and -S) as precursors. The preparation conditions for these MXenes are relatively demanding, and they are generally difficult to exfoliate on a large scale into ultrathin two-dimensional nanosheets using simple liquid-phase etching methods, unlike conventional -OH / -F-terminated MXenes. This limits the controllable preparation of ultrathin, large-area non-van der Waals solid materials and their application in flexible devices.

[0005] On the other hand, while readily available and easily fabricated monolayers / few-layers of MXene (primarily -OH, -F-terminated) obtained through conventional hydrofluoric acid or in-situ HF etching are easy to obtain and process into films, their structure is extremely unstable at high temperatures. This is mainly attributed to the presence of unsaturated d orbitals in transition metal centers (such as Ti, Nb, V), which make them prone to irreversible oxidation or structural collapse during heat treatment (typically above 400°C), transforming them into thermodynamically more stable rock-salt carbides (such as TiC), resulting in the loss of their unique layered structure and related properties. This inherent thermal instability severely restricts the application of MXene-based materials in applications requiring high-temperature resistance, such as high-temperature electromagnetic shielding, infrared stealth for engine components, and high-temperature flexible electronics.

[0006] Therefore, developing a general method to effectively stabilize the layered structure of conventional MXene (especially -OH / -F-terminated MXene) and further efficiently and controllably transform it into an ultrathin, large-area, high-performance non-van der Waals artificial solid is of great significance for promoting the application of such materials in practical high-temperature applications, and is also a key technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] To address the aforementioned key technical problems, the first aspect of this invention provides a method for preparing a non-van der Waals artificial solid material, characterized by comprising the following steps: (1) subjecting MXene material to a first heat treatment in an atmosphere containing zinc vapor, and performing electron implantation to obtain electron-implanted MXene material; (2) subjecting the obtained electron-implanted MXene material to a second heat treatment in an atmosphere containing metal Z vapor, so that metal Z forms chemical bonds with the interlayer of the MXene material to obtain the non-van der Waals artificial solid material.

[0008] In some embodiments, prior to step (2) above, the method further includes the step of preparing the electron-injected MXene material into a thin film, a coating, or a bulk material.

[0009] In some embodiments, prior to step (1) above, the step of preparing the MXene material into a thin film, a coating, or a bulk material is further included.

[0010] In some embodiments, the carrier concentration of the electron-injected MXene material obtained in step (1) above is higher than that of the initial MXene material; preferably, the carrier concentration of the electron-injected MXene material reaches 10. 22 cm -3 Magnitude.

[0011] A second aspect of the present invention provides a non-van der Waals artificial solid material obtained by the above preparation method.

[0012] In some embodiments, the general chemical formula of the above-mentioned non-van der Waals artificial solid material is represented as ZM. n+1 X n Z is selected from at least one of Al, Ga, In, Sn, M is at least one of Ti, Nb, V, X is C and / or N, and n = 1 to 4.

[0013] In some embodiments, the above-mentioned non-van der Waals artificial solid material is a Z-M3X2 type compound, preferably Al-Ti3C2, Ga-Ti3C2, In-Ti3C2 or Sn-Ti3C2.

[0014] In some embodiments, the above-mentioned non-van der Waals artificial solid material is a Z-M2X type compound, preferably Al-Ti2C, Al-Nb2C or Al-V2C.

[0015] In some embodiments, the above-mentioned non-van der Waals artificial solid material is an ultrathin sheet with a thickness of less than 10 nm, preferably 1 nm to 5 nm.

[0016] In some embodiments, the above-described non-van der Waals artificial solid material has a layered crystal structure.

[0017] A third aspect of the present invention provides a thin film comprising the above-described non-van der Waals artificial solid material.

[0018] A fourth aspect of the present invention provides a method for preparing a thin film, comprising the steps of:

[0019] (1) The MXene dispersion was coated onto the substrate and molded to obtain an MXene precursor film;

[0020] (2) The MXene precursor film is subjected to a first heat treatment in an atmosphere containing zinc vapor and then electron implanted to obtain an MXene intermediate film containing electron implantation.

[0021] (3) In an atmosphere containing metal Z vapor, the MXene intermediate film obtained in step (2) is subjected to a second heat treatment to form chemical bonds between the metal Z and the MXene material.

[0022] In some embodiments, the MXene dispersion described above has shear-thinning rheological properties and / or viscoelastic gel characteristics.

[0023] In some embodiments, the above coating method includes coating the MXene dispersion onto a substrate by extrusion, blade coating, or spin coating.

[0024] In some embodiments, the above-described coating method further includes: inducing the orientation and alignment of MXene nanosheets in the MXene dispersion by utilizing shearing action.

[0025] In some embodiments, the temperature of the first heat treatment is 400°C to 600°C; and / or, the temperature of the second heat treatment is 600°C to 900°C.

[0026] In some embodiments, the zinc vapor is generated by zinc powder laid at the bottom of the reaction vessel under heating conditions.

[0027] In some embodiments, the aforementioned metal Z vapor is generated by metal Z powder laid at the bottom of the reaction vessel under heating conditions.

[0028] In some embodiments, the metal Z is selected from at least one of Al, Ga, In, and Sn.

[0029] In some embodiments, the MXene described above contains a fluorine functional group.

[0030] In some embodiments, the preparation method of the above-mentioned MXene material includes: etching the MAX phase precursor in a fluorine-containing etching solution, followed by washing, ultrasonic stripping, and centrifugation; preferably, the fluorine-containing etching solution includes a metal fluoride salt and an acid solution, or hydrofluoric acid.

[0031] In some embodiments, the chemical formula of the above-mentioned MXene material is M n+1 X n T x Where M is at least one of Ti, Nb, V, Mo, Cr, Ta, Hf, and Zr, X is C and / or N, n = 1 to 4, and T x The surface end group is indicated; preferably, M is at least one of Ti, Nb, and V; more preferably, the MXene material is selected from Ti3C2T. x Ti2CT x Nb2CT x V2CT x At least one of them.

[0032] A fifth aspect of the present invention provides a thin film obtained by the above-described preparation method.

[0033] In some embodiments, the thin film has an oriented layered structure.

[0034] In some embodiments, the above-described orientation structure is formed by stacking layers of the non-van der Waals artificial solid material.

[0035] In some embodiments, the Hermann orientation factor f of the above-described thin film is greater than 0.7, preferably greater than 0.8.

[0036] In some embodiments, the thickness of the film is less than 10 μm, preferably 1 μm to 5 μm.

[0037] In some embodiments, the sheet resistance of the above-mentioned thin film is less than 2Ω□-1, preferably less than 1Ω□-1, and more preferably about 0.5Ω□-1.

[0038] In some embodiments, the above-described film exhibits stability, and after heat treatment at 800°C for 2 hours in an air atmosphere, the weight loss does not exceed 1 wt.%, preferably not more than 0.5 wt.%, and more preferably not more than 0.1 wt.%.

[0039] A sixth aspect of the present invention provides a dispersion comprising a solvent and the aforementioned non-van der Waals artificial solid material dispersed in the solvent.

[0040] In some embodiments, the concentration of the dispersion is greater than 10 mg / mL, preferably from 20 mg / mL to 50 mg / mL.

[0041] The seventh aspect of the present invention provides the use of the above-mentioned non-van der Waals artificial solid material or the above-mentioned thin film in electromagnetic shielding, infrared stealth, low infrared emissivity coatings, and flexible electronic devices.

[0042] The eighth aspect of the present invention provides an electromagnetic shielding device comprising the above-mentioned non-van der Waals artificial solid material or the above-mentioned thin film.

[0043] In some embodiments, the total shielding effectiveness of the electromagnetic shielding device in the frequency range of 8.2-12.4 GHz is greater than 30 dB, preferably greater than 40 dB, and more preferably greater than 45 dB.

[0044] In some embodiments, after the electromagnetic shielding device is heat-treated at 500°C for 12 hours, the attenuation rate of its electromagnetic interference shielding effectiveness is less than 10%, preferably less than 5%.

[0045] The ninth aspect of the present invention provides an infrared stealth device or a coating containing the above-mentioned non-van der Waals artificial solid material or the above-mentioned thin film.

[0046] In some embodiments, the average infrared emissivity of the infrared stealth device or the coating described above in the 7-14 μm band is less than 0.4, preferably less than 0.3.

[0047] In some embodiments, the surface radiation temperature of the infrared stealth device or the coating is significantly lower than that of the bulk MAX phase material under the same conditions at a high temperature of 500°C; preferably, the surface radiation temperature is lower than 200°C within the object temperature range of 100-550°C.

[0048] In some embodiments, the infrared stealth device or the coating with low infrared emissivity described above can still maintain its infrared stealth function after being exposed to air at 500°C for 48 hours.

[0049] The tenth aspect of the present invention provides a flexible electronic device, characterized in that it contains the above-mentioned non-van der Waals artificial solid material or the above-mentioned thin film.

[0050] Compared with the prior art, the present invention has the following beneficial technical effects:

[0051] (1) The preparation method provided by this invention achieves effective stabilization and structural transformation of conventional MXene materials through a two-step process of “first stabilization by zinc vapor electron injection, and then conversion by metal vapor bonding”. This method has strong universality, can prevent the irreversible transformation of MXene to rock salt structure at high temperature, and enables it to react with a variety of active metal vapors, providing a general approach for the controllable synthesis of a series of ultrathin non-van der Waals artificial solid materials.

[0052] (2) The non-van der Waals artificial solid material prepared by this method has high conductivity and high temperature oxidation resistance, which breaks through the bottleneck of poor thermal stability and limited application of traditional MXene, and further constitutes a class of high-performance, high-temperature resistant, flexible ceramic thin film materials.

[0053] (3) Based on the unique comprehensive properties of the above-mentioned materials, this invention has expanded their application in harsh environments such as high temperature and flexibility. The material exhibits high shielding effectiveness and long-term stability in the field of high-temperature electromagnetic shielding, while also showing low emissivity and long-term durability in high-temperature infrared stealth applications, solving the key technical problem that existing materials cannot simultaneously achieve high efficiency and long-term service at high temperatures. Attached Figure Description

[0054] Figure 1 In Example 1 of this invention, MXene was synthesized from metal Z (Z = Al, Ga, In, Sn) vapor via a topological reaction to form a non-van der Waals artificial solid (ZM). n+1 X n A schematic diagram of layered materials.

[0055] Figure 2 The Ti3C2T in Embodiment 1 of the present invention x Morphological characterization. Where a) and b) are the morphological characteristics of Ti3C2T after exfoliation. x Scanning electron microscope (SEM) images show a large number of ultrathin nanosheets with good flexibility.

[0056] Figure 3 The initial Ti3C2T in Embodiment 1 of the present invention x and electron-injected Ti3C2T x Structural characterization of layered materials. Where a) and c) represent the initial Ti3C2T on the copper mesh. x (a) and electron-injected Ti3C2T x(c) High-angle annular dark-field scanning transmission electron microscopy (HADDF-STEM) images of layered materials, with interlayer spacing of approximately and b) and d) are the initial Ti3C2T x (b) and electron-injected Ti3C2T x (d) Energy dispersive spectroscopy (EDS) of layered materials, electron-injected Ti3C2T x The presence of signal peaks for Zn species indicates the intercalation of Zn atoms.

[0057] Figure 4 a) is the comparative sample Ti3C2T aluminum vapor treatment in Example 1 of this invention. x The XRD patterns show that from the initial Ti3C2T x a) Structural transformation to rock salt phases TiC and Al2O3; b) Aluminum vapor treatment of Ti3C2T x The corresponding HADDF-STEM image shows a rock salt-type atomic structure.

[0058] Figure 5 a) shows the vapor pressure diagrams of different metals (including Au, Cu, Al, Sn, Ga, In, and Zn) at 500 °C, revealing that Zn metal has a significantly high vapor pressure (178 Pa). b) shows the initial Ti3C2T... x Electron-injected Ti3C2T x XRD patterns of non-van der Waals Al-Ti3C2 layered materials show that the (002) crystal plane position varies from 7.5°, 6.1° to 9.5°. c) is ultraviolet photoelectron spectroscopy (UPS), showing electron-injected Ti3C2T x The electron density at the Fermi level is enhanced. d) shows a comparison of carrier concentrations, indicating electron injection into Ti3C2T. x Increased carrier concentration in (~10) 22 cm -3 ).

[0059] Figure 6 a) is a SEM image of the non-van der Waals Al-Ti3C2 layered material in Example 1 of the present invention, showing a large number of flexible nanosheets; b to d) are EDS mappings of the corresponding elements, showing the uniform distribution of Ti, Al and C elements.

[0060] Figure 7a) is a transmission electron microscope (TEM) image of the non-van der Waals Al-Ti3C2 layered material in Example 1 of the present invention, showing an ultrathin layered structure; b) is a high-resolution transmission electron microscope (HRTEM) image and the corresponding selected area electron diffraction (FFT) pattern (inset), with an interlayer spacing of 0.25 nm, corresponding to the (110) crystal plane; ce) is the corresponding EDS mappings, showing the uniform distribution of Ti, Al and C elements.

[0061] Figure 8 The image (a) and corresponding height analysis (b) of the non-van der Waals Al-Ti3C2 sheet in Example 1 of this invention show an ultrathin structure with a thickness of approximately 4.6 nm.

[0062] Figure 9 The images show SEM images of the non-van der Waals Ga-Ti3C2(a) and In-Ti3C2(b) layered materials in Example 2 of this invention, revealing a large number of flexible nanosheet morphologies.

[0063] Figure 10 (c) are SEM images of the non-van der Waals Al-Ti2C(a), Al-Nb2C(b), and Al-V2C(c) layered materials in Example 3 of this invention, showing a large number of flexible nanosheets; (df) are the corresponding EDS mappings, showing the uniform distribution of Ti / Nb / V and Al elements.

[0064] Figure 11 This section describes the morphological characterization of different bulk MAX phases and their corresponding MXenes in Embodiment 3 of the present invention. SEM images of the Ti2AlC(a), Nb2AlC(b), and V2AlC(c) MAX phases show blocky morphologies with layered structures; df) Ti2CT x (d) Nb2CT x (e) and V2CT x (f) shows the SEM image of the flexible nanosheet morphology.

[0065] Figure 12The images above illustrate the structural characterization of the non-van der Waals artificial solid layered materials in Examples 2 and 3 of this invention. a) shows XRD patterns, including Ga-Ti3C2, In-Ti3C2, Al-Ti2C, Al-Nb2C, and Al-V2C. b) shows HADDF-STEM images and corresponding atomic models of non-van der Waals Al-Ti3C2 and Ga-Ti3C2, demonstrating the characteristic layered crystal structure of three Ti atomic layers and one Al / Ga atomic layer periodically stacked. f, g) show HADDF-STEM images and corresponding atomic models of non-van der Waals Al-V2C, demonstrating the characteristic layered crystal structure of two V atomic layers and one Al atomic layer periodically stacked. Red, orange, green, and blue spheres represent Ti, V, Al, and Ga atoms, respectively.

[0066] Figure 13 a) is the high-concentration Ti3C2T in Example 4 of this invention. x Optical images of the dispersion show viscoelastic characteristics. (b) is a high concentration of Ti3C2T. x The polarizing microscope (POM) image of the dispersion shows birefringence, indicating its liquid crystal properties.

[0067] Figure 14 The high-concentration Ti3C2T in Example 4 of this invention x Rheological properties of the dispersion. a) Viscosity-shear rate curve, showing the high concentration of Ti3C2T. x The dispersion exhibits good shear-thinning behavior; b) shows storage modulus and loss modulus, indicating viscoelastic gel properties.

[0068] Figure 15 a) is a schematic diagram of the topological reaction between an over-oriented MXene film and metal vapor to produce an oriented non-van der Waals solid film in Example 4 of the present invention. b) is a diagram of Ti3C2T. x The photo shows the Al-Ti3C2 thin film, which changes color from purple to gray and exhibits good flexibility.

[0069] Figure 16 The XRD pattern of the non-van der Waals Al-Ti3C2 thin film in Example 4 of the present invention shows a series of diffraction peaks at 9.8°, 19.6° and 38.4°, corresponding to the (002), (004) and (008) crystal planes of the non-van der Waals Ti3AlC2 (PDF#52-0875).

[0070] Figure 17 The images show SEM images and corresponding EDS mappings of the non-van der Waals Al-Ti3C2 thin film surface in Example 4 of this invention, demonstrating the uniform distribution of Ti, Al, and C elements.

[0071] Figure 18The images show cross-sectional SEM (a) and corresponding TEM (b) images of the non-van der Waals Al-Ti3C2 thin film in Example 4 of this invention, revealing a dense stacked structure.

[0072] Figure 19 Images a and b) show cross-sectional HRTEM images and corresponding line profiles of the Al-Ti3C2 thin film in Example 4 of this invention, revealing a characteristic layered crystal structure with a periodic stacking of three Ti atomic layers and one Al atomic layer, and a lattice fringe spacing of approximately 0.98 nm. Image c) shows the (002) pole figure of the Al-Ti3C2 thin film, displaying a preferred crystal texture. Image d) shows the azimuth diagram and 2D wide-angle X-ray scattering (WAXS) image of the Al-Ti3C2 thin film, revealing a high degree of orientation (f = 0.82).

[0073] Figure 20 The non-van der Waals Al-Ti3C2 thin film in Example 4 of this invention exhibits excellent mechanical flexibility in its self-supported state (a), 360° bending (b), and winding around cylinders with radii of 5 mm, 7 mm, and 10 mm (c).

[0074] Figure 21 This is the current-voltage curve of the Al-Ti3C2 thin film in Example 4 of the present invention, and its sheet resistance (R) s The value is 0.5Ω□-1, which is lower than that of Ti3C2T. x Thin film (0.7 Ω□-1) and bulk Ti3AlC2 (13.9 Ω□-1) demonstrate that non-van der Waals Al-Ti3C2 thin film has excellent conductivity.

[0075] Figure 22 a) shows the normalized Ti K-edge X-ray absorption near-edge structure spectrum (XANES) of the non-van der Waals Al-Ti3C2 thin film in Example 4 of this invention, compared with that of Ti3C2T x The shift towards lower energies reveals a decrease in the valence state of Ti. (b, c) represent the k values ​​from the corresponding extended X-ray absorption fine structure spectra (EXAFS). 2 Weighted Fourier transform and wavelet transform plots show approximately [data missing] in non-van der Waals Al-Ti3C2 thin films. Ti-T at the location x Coordination strength decreases, and in approximately A new Ti-Al coordination peak appears at this location. d) shows the flexural deformation cycle performance of the Al-Ti3C2 film, which can withstand 20,000 flexural deformation cycles at a bending distance of 2 mm, similar to Ti3C2T. x (25,000 times) Equivalent. e) Thermogravimetric analysis of Al-Ti3C2 thin films showed that they were weight stable in air at 800°C with only slight changes (~0.1 wt.%), which is superior to Ti3C2T.x Thin film and bulk Ti3AlC2.

[0076] Figure 23 This is a comparison of the total EMI shielding effectiveness of the Al-Ti3C2 thin film before and after heat treatment at 500℃ for 12 hours in Example 6 of the present invention. ET The value is 45.7 dB, and the attenuation rate is only ~4.5%; significantly better than Ti3C2T. x Thin film (S) ET The value is 19.2 dB, and the attenuation rate is ~60.7%.

[0077] Figure 24 The non-van der Waals Al-Ti3C2(a) and Ti3C2T in Embodiment 6 of the present invention x (b) SEM image of the film after heat treatment at 500℃ for 12 h. The non-van der Waals Al-Ti3C2 film maintains a stable layered structure, while the Ti3C2T... x The film contains a large number of particles.

[0078] Figure 25 The infrared emission spectrum of the non-van der Waals Al-Ti3C2 thin film in Example 7 of this invention is shown. The average infrared emissivity is about 0.26, which is significantly lower than that of bulk Ti3AlC2 (about 0.76).

[0079] Figure 26 The infrared camouflage performance of non-van der Waals Al-Ti3C2 films at different temperatures in Example 7 of the present invention is shown.

[0080] Figure 27 This refers to Ti3C2T at different temperatures in control experiment 1 of Example 7 of the present invention. x Infrared camouflage properties of thin films.

[0081] Figure 28 This is to show the infrared camouflage performance of bulk Ti3AlC2 in Comparative Experiment 2 at different temperatures in Example 7 of the present invention.

[0082] Figure 29 The non-van der Waals Al-Ti3C2 thin films and Ti3C2T films at different temperatures in Example 7 of this invention are examples of such films. x The radiation temperature-object temperature curves of thin film and bulk Ti3AlC2 show a linear relationship between radiation temperature and object temperature.

[0083] Figure 30 (a) shows the high-temperature infrared stealth performance of the Al-Ti3C2 thin film in Example 7 of this invention. After heat treatment at 500°C in air for 48 hours, the radiation temperature is as low as 153.8°C, which is significantly better than that of Ti3C. x T xa) The thin film reached 369.3°C after only 4 hours. b) Demonstrated infrared stealth performance in multiple scenarios, exhibiting excellent infrared stealth capabilities in various settings including aircraft models, water bottles, and the BUAA logo. c) Comparison of Al-Ti3C2 thin film with previously reported materials (such as rGO-SSA, ANF / MXene, and Ti3C2T). x The comparison of temperature drop and heating time of the thin film demonstrates the superior high-temperature infrared stealth performance of Al-Ti3C2 thin film with high radiation temperature drop and long high-temperature service life.

[0084] Figure 31 The non-van der Waals Al-Ti3C2 thin film (a) and Ti3C2T in Example 7 of this invention. x Infrared thermographs of the thin film (b) and titanium foil (c) after heat treatment at 800℃ for 2 hours in air. Inset (ac) is the optical image of the corresponding sample after heat treatment at 800℃ for 2 hours in air; d) is the corresponding cooling histogram of the Al-Ti3C2 thin film after heat treatment at 800℃ for 2 hours in air, showing a cooling range of 307.1℃, which is significantly higher than that of Ti3C2T under the same conditions. x Thin film (41.1℃) and titanium foil (145.8℃). Detailed Implementation

[0085] The technical solution of the present invention is illustrated below through specific embodiments. It should be understood that the one or more steps mentioned in the present invention do not preclude the existence of other methods and steps before or after the combined steps, or that other methods and steps may be inserted between these explicitly mentioned steps. It should also be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Unless otherwise stated, the numbering of each method step is only for the purpose of identifying each method step, and not for limiting the order of each method or limiting the scope of the present invention. Changes or adjustments to their relative relationships, without substantial changes to the technical content, can also be considered as within the scope of the present invention.

[0086] In the examples, the MAX phase powders (such as Ti3AlC2, Ti2AlC, Nb2AlC, V2AlC) were purchased from Jinan Sanchuan New Materials Technology Co., Ltd. Other raw materials and instruments used were not subject to specific restrictions on their source; they could be purchased from the market or prepared using conventional methods well-known to those skilled in the art.

[0087] Conventional MXenes (such as those with -OH / -F caps) are prone to structural collapse at high temperatures due to the presence of unsaturated d orbitals in their transition metal centers, transforming into thermodynamically stable rock salt phases. This severely limits their use as precursors for preparing high-performance heat-resistant materials. The core technical concept of this invention lies in introducing a "pre-stabilized" intermediate state. This is achieved through intercalation and electron injection of a high vapor pressure metal (such as Zn), preferentially saturating or partially saturating the active orbitals of the transition metal, thereby "passivating" the MXene at the molecular level and enabling it to withstand subsequent higher-temperature processing without disintegration. Based on this, this stabilized intermediate is then used to conduct a high-temperature topological chemical reaction with target metal vapors (such as Al, Ga, In, Sn), forming strong chemical bonds in situ between layers, ultimately constructing a well-defined, high-performance non-van der Waals artificial solid. The technical features of this invention are further clarified below through specific embodiments:

[0088] Example 1

[0089] This embodiment provides a non-van der Waals artificial solid and its preparation method, such as Figure 1 As shown, the steps include: performing a first heat treatment on the MXene material in an atmosphere containing zinc vapor, followed by electron implantation to obtain electron-implanted MXene material (intermediate product); and performing a second heat treatment on the electron-implanted MXene material in an atmosphere containing metal Z vapor, so that metal Z forms chemical bonds with the interlayer of the MXene material to obtain the non-van der Waals artificial solid material. Specifically, the technical features of this invention are illustrated using the preparation of Al-Ti3C2 layered material as an example, and its steps include:

[0090] (1) Provide MXene materials

[0091] The MAX phase material is etched using a fluorinated etching solution (such as hydrofluoric acid or a fluoride salt + hydrochloric acid), followed by washing, ultrasonic stripping, and centrifugation. In this embodiment, MAX phase Ti3AlC2 powder is added to an etching solution of lithium fluoride (LiF) and hydrochloric acid (HCl) to obtain MXene Ti3C2T. x A more specific implementation method includes: weighing 2.0 g of Ti3AlC2 powder and adding it to a solution containing 2.4 g of LiF and 30 mL of 9M hydrochloric acid, stirring at 35°C for 24 h. After the reaction, repeatedly centrifuge and wash with deionized water until neutral. Disperse the precipitate and sonicate at 10°C for 1 h, centrifuge at 3000 rpm for 5 min, and collect the supernatant. Freeze-dry to obtain Ti3C2T. x Powder, obtained Ti2C3T x For ultrathin nanosheets with good flexibility ( Figure 2 ).

[0092] (2) Zinc vapor electron injection treatment (first heat treatment)

[0093] Ti3C3T x The powder and zinc powder (Zn) are heated to a certain temperature (e.g., 400–600°C) in a sealed environment and held at that temperature for a predetermined time (e.g., 0.5–5 h) before cooling to obtain the product; a more specific embodiment includes: Ti3C3T x The powder was placed in an alumina boat (with porous carbon paper supporting the sample) lined with approximately 2 mm of zinc powder and sealed. Under an argon atmosphere, the temperature was increased to 500 °C at 5 °C / min and held for 2 h, followed by furnace cooling. The intermediate product, electron-implanted Ti3C2T, was obtained. x (denoted as Zn@Ti3C2).

[0094] This stage of heat treatment removes most of the surface end groups (-OH, -F, etc.) of MXene, while Zn vapor spontaneously intercalates into Ti3C2T. x The interlayer structure of the layered material. HAADF-STEM test results reveal the electron-injected Ti3C2T x The interlayer spacing of layered materials from Expand to ( Figure 3 (a, c). The corresponding EDS tests confirmed the incorporation of Zn species. Figure 3 (d). Hall effect measurements show that the carrier concentration of the material increased to approximately 10 after this treatment. 22 cm -3 The magnitude is significantly higher than that of the initial Ti3C2T. x (approximately 10) 21 cm -3 ,like Figure 5 (d).

[0095] (3) Aluminum vapor bonding conversion (second heat treatment)

[0096] The Zn@Ti3C2 and aluminum (Al) powder were heated to a certain temperature (600–900°C) in a sealed environment and held at that temperature for a predetermined time (0.5–48 h), followed by cooling. A more specific embodiment includes: dispersing Zn@Ti3C2 on carbon paper, transferring it to an alumina boat with approximately 2 mm of aluminum powder, placing the carbon paper loaded with the sample on top of the aluminum powder, and sealing the container. Under an argon atmosphere, the temperature was increased to 800°C at 5°C / min and held for 24 h, followed by furnace cooling. The final product, a non-van der Waals Al-Ti3C2 layered material, was obtained.

[0097] This step involves placing the electron-injected intermediate Zn@Ti3C2 from step (2) into a second, higher-temperature heat treatment environment with another metal (such as Al) vapor. Under these conditions, the material maintains good structural stability and successfully forms Ti-Al bonds between adjacent layers, thus transforming into a non-van der Waals Al-Ti3C2 layered material. In contrast, the initial Ti3C2T without zinc vapor pretreatment... x Under the same aluminum vapor treatment conditions, it irreversibly transforms into rock salt phase titanium carbide (TiC). Figure 1 and Figure 4 This comparison confirms that the pre-treatment with electron injection effectively reduces the reactivity of titanium atoms, which is key to obtaining the target layered structure.

[0098] The first heat treatment in this invention uses metallic zinc (Zn) because zinc has a significantly higher vapor pressure than target metals such as aluminum (Al) and gallium (Ga) at relatively low temperatures (e.g., at 500°C, the vapor pressure of Zn is approximately 178 Pa, much higher than that of Al, see...). Figure 5 (a) This allows Zn atoms to be efficiently transported in the gas phase at a sufficient concentration and intercalated into the interlayer of MXene. The intercalated Zn atoms act as effective electron donors, injecting electrons into the unsaturated d orbitals of transition metals (such as Ti) in MXene, effectively reducing the reactivity of the transition metals (or "passivating"), thereby stabilizing the layered framework of MXene at the molecular level. This electron injection allows MXene to withstand subsequent high-temperature bonding reactions with more reactive metal vapors (such as Al and Ga) without structural collapse. Without this step, MXene would irreversibly transform into a more thermodynamically stable rock salt phase (such as TiC) when directly exposed to high temperatures and reactive metals, rather than the target layered compound.

[0099] The structural and morphological characterization of the obtained non-van der Waals Al-Ti3C2 layered material shows that ( Figure 6-8 SEM images show that it is a structure of numerous flexible, ultrathin sheets. Figure 6 (a); EDS surface scan analysis confirmed that titanium, aluminum, and carbon elements were uniformly distributed on the sheets. Figure 6 (bc); TEM and HRTEM images show that it has single-crystal characteristics, and the lattice fringe spacing of the (110) crystal plane is approximately 0.25 nm. Figure 7 (a, b); AFM measurements showed that the thickness of the single-layer sheet was approximately 4.6 nm, confirming its ultrathin characteristics. Figure 8 (a, b)

[0100] Example 2

[0101] The preparation method of this invention is applicable not only to aluminum (Al) vapor, but also to other metal vapors, such as gallium (Ga) vapor and indium (In) vapor. In this embodiment, by changing the type of metal Z in the second heat treatment, a series of non-van der Waals artificial solids (Z-Ti3C2, Z = Ga, In, Sn) with different chemical compositions but all having ultrathin layered structures are directionally synthesized.

[0102] The specific implementation method is similar to that of Example 1, and the zinc vapor prepared in step (2) of Example 1 is electron-implanted into Ti3C2T. x (Zn@Ti3C2) was used as the reaction precursor. The difference was that the aluminum powder in Example 1 was replaced with gallium (Ga) powder and indium (In) powder, respectively, and the heating temperature was adjusted. The specific reaction conditions are shown in items 2 and 3 of Table 1. SEM images of the resulting non-van der Waals Ga-Ti3C2 and InTi3C2 Ga-Ti3C2 layered materials are shown below. Figure 9 As shown, it exhibits a large number of flexible nanosheet morphologies, similar to the Al-Ti3C2 morphology of Example 1.

[0103] Table 1. Synthesis conditions of different non-van der Waals artificial solids of the present invention

[0104] Serial Number MXene material First heat treatment reaction conditions Second heat treatment reaction conditions product 1 <![CDATA[Ti3C2T x ]]> Zinc, 500℃, 2 hours Aluminum, 800℃, 24 hours <![CDATA[Al-Ti3C2]]> 2 <![CDATA[Ti3C2T x ]]> Zinc, 500℃, 2 hours Gallium, 700℃, 24 hours <![CDATA[Ga-Ti3C2]]> 3 <![CDATA[Ti3C2T x ]]> Zinc, 500℃, 2 hours Indium, 800℃, 24 hours <![CDATA[In-Ti3C2]]> 4 <![CDATA[Ti2CT x ]]> Zinc, 500℃, 2 hours Aluminum, 800℃, 24 hours <![CDATA[Al-Ti2C]]> 5 <![CDATA[Nb2CT x ]]> Zinc, 500℃, 2 hours Aluminum, 800℃, 24 hours <![CDATA[Al-Nb2C]]> 6 <![CDATA[V2CT x ]]> Zinc, 500℃, 2 hours Aluminum, 800℃, 24 hours <![CDATA[Al-V2C]]> 7 <![CDATA[Ti3C2T x ]]> Zinc, 500℃, 2 hours Tin, 800℃, 24 hours <![CDATA[Sn-Ti3C2]]>

[0105] Example 3

[0106] The preparation method of this invention is applicable to various types of MXene precursors, such as Ti2CT. x Nb2CT x V2CT x The process transforms these materials into corresponding non-van der Waals Al-M2C (M = Ti, Nb, V) layered materials, demonstrating universal applicability. This embodiment successfully prepared non-van der Waals Al-Ti2C, Al-Nb2C, and Al-V2C layered materials by changing different MAX phase raw materials and following similar preparation methods. Specific reaction conditions are shown in items 4 to 6 of Table 1. SEM images of the non-van der Waals products are shown below. Figure 10 As shown, it exhibits a large number of flexible nanosheet morphologies, similar to the Al-Ti3C2 morphology of Example 1.

[0107] In this embodiment, different MXene precursors were prepared using Ti2AlC, Nb2AlC, and V2AlC MAX phase powders as raw materials, and the corresponding monolayer / few-layer MXenes were prepared by in-situ liquid-phase etching as described in step (1) of Example 1. The prepared Ti2CT x Nb2CT x and V2CT x Morphological characterization of MXene, such as Figure 11As shown, they all exhibit typical flexible nanosheet morphologies.

[0108] XRD patterns of various non-van der Waals artificial solids, represented by Ga-Ti3C2, In-Ti3C2, Al-Ti2C, Al-Nb2C, and Al-V2C. Figure 12 The diffraction peaks (a) are significantly different from those of the initial MXene precursor, demonstrating that by changing the MAX phase precursor or the type of metal vapor, a series of non-van der Waals materials with different chemical compositions and specific crystal structures can be successfully synthesized, confirming the universality of the synthesis strategy and the structural tunability of the products. HAADF-STEM images of Al-Ti3C2 and Ga-Ti3C2 ( Figure 12 The alternating light and dark periodic stripes shown in images b and d visually reveal its layered atomic arrangement. Image analysis clearly identifies that in Al-Ti3C2 ( Figure 12 In Ga-Ti3C2, three Ti atomic layers and one Al atomic layer are stacked alternately; while in Ga-Ti3C2 (b,c), Figure 12 In the diagram (d, e), three Ti atomic layers are alternately stacked with one Ga atomic layer. This structure matches the theoretical model, where the red, orange, and green spheres represent Ti, Al, and Ga atoms, respectively. These results confirm that the method of this invention can introduce target metal atoms between adjacent MXene sheets and form chemical bonds, constructing an atomically ordered non-van der Waals crystal structure.

[0109] The specific conditions provided in Examples 1, 2, and 3 (such as Zn treatment at 500℃ for 2 hours and Al treatment at 800℃ for 24 hours) are preferred embodiments of the present invention. Those skilled in the art can adjust and optimize key parameters based on the principles disclosed in this invention and the need for product optimization. For example, in some other embodiments, the temperature of the first heat treatment can be selected and optimized within the range of 450℃ to 550℃, and the treatment time can be adjusted within the range of 1 hour to 5 hours; the temperature of the second heat treatment can be implemented within the range of 750℃ to 850℃, and the treatment time can be adjusted within the range of 10 to 48 hours according to the crystallinity and specific morphology requirements of the target product.

[0110] Example 4

[0111] This embodiment provides a thin film and its preparation method. The thin film contains the non-van der Waals artificial solid layered material (ZM) of this invention. n+1 X n It possesses excellent mechanical flexibility, high electrical conductivity, and thermal stability. For example... Figure 15As shown in the schematic diagram in Figure a, the thin film of the present invention is prepared by using an oriented MXene thin film as a precursor, followed by first and second heat treatments to achieve electron injection and metal Z vapor bonding of the MXene material, thereby obtaining a novel thin film material containing non-van der Waals artificial solids and maintaining an oriented structure.

[0112] This embodiment uses Ti3C2T x Taking MXene as an example, the implementation steps for thin film preparation are explained, including:

[0113] (1) High concentration of Ti3C2T x Preparation of dispersion

[0114] MXene Ti3C2T was prepared by etching according to the method described in Example 1. x The difference lies in the following: the supernatant obtained by centrifugation is further centrifuged at 11,000 rpm for 10 minutes, and the precipitate is collected. This precipitate is then redispersed in 5 mL of deionized water by mechanical stirring to obtain a high concentration of Ti3C2T. x The dispersion has a concentration of approximately 40 mg / mL. For example... Figure 13 As shown in Figure a, this dispersion exhibits viscous properties. Polarizing microscopy (POM) observation ( Figure 13 (b) shows obvious birefringence, confirming its liquid crystal properties. Rheological property testing ( Figure 14 This indicates that the dispersion exhibits shear-thinning behavior and viscoelastic gel characteristics.

[0115] (2) Orientation Ti3C2T x Preparation of precursor thin films

[0116] The above high-concentration Ti3C2T was produced by direct extrusion. x The dispersion was injected into a 3 mL syringe equipped with a self-made flat needle. Using a benchtop robot (Fisnar F4200n), the syringe was controlled to extrude the dispersion at a constant rate and coat it onto a polypropylene (PP) substrate. Shear flow was used to induce liquid crystal phase alignment, and the coated wet film was subsequently vacuum-dried at 80 °C to obtain highly oriented Ti3C2T. x Precursor film.

[0117] (3)Ti3C2T x Topological transformation of precursor thin films (electron injection and aluminum vapor bonding)

[0118] The orientation Ti3C2T obtained in step (2) x The thin film is used as a precursor and undergoes a two-step gas-phase treatment:

[0119] Step 1 (Electron Injection): Place the film in an alumina boat coated with zinc powder (approximately 2 mm thick) and seal it. Heat-treat at 500°C for 2 hours under an argon atmosphere, then cool with the furnace.

[0120] Step 2 (Aluminum Vapor Bonding): The zinc-treated film is transferred to a new alumina boat coated with aluminum powder (approximately 2 mm thick) and sealed again. It is then heat-treated at 800°C for 2 hours under an argon atmosphere and cooled in the furnace.

[0121] Ultimately, a large-area, continuous non-van der Waals Al-Ti3C2 film was obtained, whose color changed from the purple of the precursor to the final gray. Figure 15 (b) The XRD pattern of the obtained thin film ( Figure 16 The initial (002) peak of MXene disappeared, and new diffraction peaks appeared at 9.8°, 19.6°, and 38.4°, corresponding to the (002), (004), and (008) crystal planes of non-van der Waals Ti3AlC2, respectively, confirming successful transformation. SEM images of the film surface showed a smooth and uniform surface, and EDS surface scanning analysis confirmed the uniform distribution of Ti, Al, and C elements in the film. Figure 17 Cross-sectional SEM image of the thin film ( Figure 18 Image a) shows a dense, ordered layered stacked structure. Cross-sectional HRTEM image ( Figure 18 China b and Figure 19 Figures a and b) further reveal a clear atomic layer stacking sequence, showing a characteristic periodic structure with three Ti atomic layers and one Al atomic layer alternating, and the measured lattice fringe spacing is approximately 0.98 nm.

[0122] The orientation of the thin film was characterized using wide-angle X-ray scattering (WAXS). Based on azimuth scan data (method described in the invention description), the Hermann orientation factor f of the Al-Ti3C2 thin film reached 0.82. Figure 19 (d) with Ti3C2T x The film (f = 0.81) is comparable to, and significantly higher than, the unoriented bulk Ti3AlC2, indicating that the film perfectly inherits the high orientation of the precursor.

[0123] The thin film of this invention possesses mechanical flexibility and electrical conductivity. The 5 μm thick Al-Ti3C2 film exhibits excellent flexibility: it is self-supporting (…). Figure 20 (a) can withstand 360° bending. Figure 21 (b) and can be tightly wound around cylinders with a radius as small as 5 mm without breaking. Figure 20 (c) The sheet resistance (R0) of the Al-Ti3C2 thin film was measured using the four-probe method. s Its conductivity is as low as 0.5 Ω□-1, which is better than that of the original Ti3C2T. xThin film (0.7Ω□-1) and bulk Ti3AlC2 (13.9Ω□-1).

[0124] To further elucidate the changes in the chemical valence state of titanium in non-van der Waals Al-Ti3C2 thin films revealed by XANES spectral analysis, such as... Figure 22 As shown in Figure a, the Ti K-edge XANES spectrum of the Al-Ti3C2 thin film compared to the initial Ti3C2T x The film shifts towards lower energies, indicating a decrease in the valence state of titanium. This is attributed to the removal of surface end groups and the redistribution of electron density due to bonding with aluminum atoms. EXAFS analysis corroborates this, with its k... 2 The weighted Fourier transform spectra show that in non-van der Waals Al-Ti3C2 films, approximately The intensity of the coordination peak corresponding to Ti-O / F (surface end group) at this location is significantly reduced; meanwhile, at approximately A new coordination peak appeared at this point, which is attributed to the formation of the Ti-Al bond. Figure 22 (b, c). This result is consistent with the analysis results from FTIR spectroscopy (showing end-group removal) and HRTEM images (showing atomic layer stacking).

[0125] The mechanical flexibility of the film was evaluated through bending deformation testing. For example... Figure 22 Middle d and Figure 20 As shown, the 5 μm thick Al-Ti3C2 film exhibits excellent flexibility, capable of withstanding 360° bending and tightly wound around cylinders with a radius as small as 5 mm. In quantitative cyclic bending tests (bending distance 2 mm), the film can withstand more than 20,000 bending cycles while maintaining structural integrity, demonstrating fatigue resistance comparable to Ti3C2T. x The thin film is comparable to, and far superior to, the brittle bulk Ti3AlC2 material.

[0126] Thermogravimetric analysis (TGA) was used to evaluate the stability of the film under high-temperature oxidizing conditions. Figure 22 As shown in Figure e, the non-van der Waals Al-Ti3C2 film exhibits only a slight weight change (approximately 0.1 wt.%) during heating in air from room temperature to 800°C, demonstrating excellent high-temperature oxidation resistance. Under the same conditions, Ti3C2T... x Thin films and bulk Ti3AlC2 exhibit significant weight increases or losses, attributed to their oxidation or decomposition.

[0127] The mechanical flexibility, conductivity, and thermal stability of the thin film of this invention make it a promising candidate for application in the field of flexible electronic devices.

[0128] Example 5

[0129] This invention provides a process for preparing non-van der Waals solid films from MXene dispersions. This process is scalable and applicable to other types of MXene materials. By changing the type of MXene precursor (e.g., Ti2CT), the process can be adapted to other materials. x Nb2CT x By varying the type of metal vapor used in the second heat treatment step (e.g., Ga vapor), non-van der Waals artificial solid films with different chemical compositions (such as Al-Ti2C, Al-Nb2C, and Ga-Ti3C2) can be successfully prepared. The resulting non-van der Waals solid films exhibit characteristics of large area, continuity, high orientation, dense structure, and uniform elemental distribution, while also possessing excellent mechanical flexibility and high electrical conductivity. Examples are provided below:

[0130] (1) Preparation of Al-Ti2C thin films

[0131] Using Ti2AlC MAX phase as raw material, high-concentration Ti2CT was prepared according to the methods described in Examples 1 and 4. x MXene dispersion. This dispersion was molded onto a substrate using direct extrusion and then dried to obtain oriented Ti2CT. x Precursor film. Subsequently, the precursor film was treated with zinc vapor (500°C, 2h) and aluminum vapor (800°C, 48h) according to the two-step heat treatment process of Example 4. A large-area, continuous non-van der Waals Al-Ti2C film was obtained.

[0132] (2) Preparation of Al-Nb2C thin films

[0133] Using Nb2AlC MAX phase as raw material, the above process was repeated. That is: first, a high concentration of Nb2CT was prepared. x Dispersion and Orientation Nb2CT x The precursor film is then subjected to zinc vapor and aluminum vapor treatments (under the same conditions as before) to finally obtain a non-van der Waals Al-Nb2C film.

[0134] (3) Preparation of Ga-Ti3C2 thin films

[0135] Oriented Ti3C2T was prepared according to Example 4. x Precursor thin film. The first step of the vapor phase treatment (zinc vapor treatment, 500℃, 2h) remains unchanged. In the second heat treatment, aluminum powder is replaced with an equal amount of gallium (Ga) powder, and heat treatment is carried out under an argon atmosphere (700℃, 48h) to finally obtain a non-van der Waals Ga-Ti3C2 thin film.

[0136] Example 6

[0137] This embodiment provides an application of the non-van der Waals artificial solid material or film of the present invention in the field of electromagnetic shielding (EMI). The non-van der Waals artificial solid film is used as an electromagnetic shielding film, and its electromagnetic shielding effect is tested and evaluated. Specifically, the electromagnetic shielding performance of the 5 μm thick non-van der Waals Al-Ti3C2 film prepared in Example 4 is tested and explained.

[0138] Waveguide testing revealed that the thin film exhibits excellent shielding performance across the entire X-band. Figure 23 As shown in Figure a, its average total shielding effectiveness (SE) T The impedance reaches approximately 47.9 dB, meaning it can block over 99.998% of incident electromagnetic waves. This performance is comparable to that of initial Ti3C2T of the same thickness. x Thin film equivalent.

[0139] To evaluate the performance durability of the film under high-temperature conditions, identical Al-Ti3C2 film samples were heat-treated in air at 500°C for 12 hours. After heat treatment, their EMI shielding effectiveness was measured again. Figure 23 As shown, after high-temperature heat treatment, the SE of the Al-Ti3C2 film... T The value remains at a high level of approximately 45.7 dB. Compared to the performance before heat treatment (47.9 dB), the degradation rate is only about 4.5%, demonstrating excellent high-temperature stability. For comparison, initial Ti3C2T with the same thickness (~5 μm) was compared... x The thin film was heat-treated and tested under the same conditions (air, 500℃, 12h). The results showed that after heat treatment, Ti3C3T x SE of thin films T The value dropped significantly to approximately 19.2 dB, representing a degradation rate of approximately 60.7% compared to its initial value. This performance difference is directly related to the material's high-temperature stability. The SEM image of the Al-Ti3C2 film after heat treatment at 500℃ for 12 hours (…) Figure 24 a) shows that the layered morphology remains intact. Meanwhile, Ti3C2T... x After the same treatment, the SEM images of the thin film ( Figure 24 b) shows a large number of particles and obvious structural damage, which is the fundamental reason for the sharp decline in its shielding effectiveness.

[0140] Example 7

[0141] This embodiment provides an application of the non-van der Waals artificial solid material or film of the present invention in the field of infrared stealth. The non-van der Waals artificial solid film is used as an infrared stealth functional layer or coating, and its infrared camouflage effect is tested and evaluated. Specifically, the 5 μm thick non-van der Waals Al-Ti3C2 film prepared in Example 4 is tested and described.

[0142] (1) Infrared emissivity test

[0143] like Figure 25 As shown, the average infrared emissivity of the non-van der Waals Al-Ti3C2 thin film in the 7-14 μm band is approximately 0.26. This value is significantly lower than that of bulk Ti3AlC2 (approximately 0.76), indicating that it has inherently lower infrared radiation characteristics, which is beneficial for achieving infrared stealth.

[0144] (2) Radiative temperature drop performance at different temperatures

[0145] Al-Ti3C2 thin films were placed on heating stages with different set temperatures (100℃, 200℃, 300℃, 400℃, 500℃, 560℃), and their surface radiation temperature was measured. Figure 26 As shown, the radiation temperatures of the thin film measured at the above temperature points were 42.9℃, 64.5℃, 93.9℃, 126.0℃, 159.5℃ and 179.8℃, respectively, showing a significant radiation temperature reduction effect.

[0146] Control Experiment 1: Under the same conditions, Ti3C2T x The radiation temperatures of the thin films were 42.4℃, 68.6℃, 95.0℃, 125.9℃, 153.8℃, and 173.0℃, respectively. Figure 27 Its properties are similar to those of Al-Ti3C2 thin films.

[0147] Control Experiment 2: Under the same conditions, the radiation temperature of bulk Ti3AlC2 increased significantly, reaching 77.6℃, 145.6℃, 217.0℃, 283.0℃, 366.9℃, and 406.8℃ respectively. Figure 28 It has very poor infrared camouflage capabilities.

[0148] Figure 29 A direct comparison was made between non-van der Waals Al-Ti3C2 thin films and Ti3C2T films at different temperatures. x The radiation temperature-body temperature curves of thin film and bulk Ti3AlC2 show that Al-Ti3C2 thin film can achieve the same temperature as Ti3C2T. x Similar infrared camouflage capabilities to thin films.

[0149] (3) High-temperature durability test

[0150] To assess the reliability of long-term use in high-temperature environments, we conducted more stringent tests: after continuously placing the Al-Ti3C2 film in air at 500°C for 48 hours, we tested its radiation temperature on a 500°C heating stage again, and the result was still as low as 153.8°C. Figure 30 (a) indicates that its infrared stealth performance remains good.

[0151] Control Experiment 3: Under the same conditions, Ti3C2T x After the film was exposed to air at 500°C for only 4 hours, its radiant temperature rose sharply to 369.3°C. Figure 30 In section a), the infrared stealth capability has essentially failed. This significant difference is attributed to the Ti3C2T... x Oxidation and structural damage of thin films at high temperatures Figure 24 ).

[0152] Al-Ti3C2 thin films were actually attached to the surfaces of various objects, including airplane models, water bottles, and the "BUAA" logo. Infrared thermal images show ( Figure 30 In b), the radiation temperature of the coated area blends very well with the background environment, clearly demonstrating its excellent infrared camouflage capability in complex scenarios.

[0153] (4) Performance testing after extreme high temperature treatment

[0154] Al-Ti3C2 thin film, Ti3C2T x Thin films and commercial titanium foils were heat-treated at 800°C for 2 hours in air, followed by testing their radiative temperature drop capability. Figure 31 As shown in the infrared thermograms and statistics, the Al-Ti3C2 thin film exhibits a temperature drop of up to 307.1℃, which is significantly better than that of Ti3C2T. x Thin film (41.1℃) and titanium foil (145.8℃) demonstrate their performance advantages in extreme environments.

[0155] This embodiment fully demonstrates that the non-van der Waals Al-Ti3C2 thin film prepared by this invention possesses excellent infrared stealth performance: it has a low infrared emissivity (~0.26); it can achieve a significant radiative temperature drop over a wide temperature range (100-800℃); most importantly, thanks to its excellent high-temperature oxidation resistance, the infrared stealth function of this film maintains long-term stability for up to 48 hours in air at 500℃, far superior to traditional MXene films. Therefore, Al-Ti3C2 thin film is a high-performance, high-temperature resistant infrared stealth material with great application potential.

[0156] Example 8

[0157] This embodiment provides a dispersion containing the non-van der Waals artificial solid material of the present invention and a thin film prepared using the dispersion. More specifically, taking Al-Ti3C2 layered material as an example, a dispersion is first prepared, and then a functional thin film is prepared on a substrate using common wet processes such as blade coating or spin coating. Specific implementation steps include:

[0158] (1) Preparation of non-van der Waals artificial solid (Al-Ti3C2) dispersion

[0159] Take the non-van der Waals Al-Ti3C2 layered material powder prepared in Example 1. Since this material no longer possesses the hydrophilic surface end groups of the initial MXene, its dispersion requires the selection of a suitable solvent or the addition of a dispersant. Add a certain mass of Al-Ti3C2 powder to an organic solvent (e.g., N-methylpyrrolidone (NMP), dimethylformamide (DMF), or isopropanol (IPA)) or an aqueous solution containing a suitable amount of surfactant (e.g., polyvinylpyrrolidone (PVP)). In some embodiments, a suitable amount of binder may be added to improve the adhesion between the film and the substrate.

[0160] The mixture is dispersed by ultrasonic treatment. The ultrasonically treated suspension is then centrifuged at low speed (1000-3000 rpm, 10 minutes) to remove unpeeled thick flakes or agglomerates. The supernatant is collected to obtain the Al-Ti3C2 dispersion. The concentration of the dispersion can be controlled by adjusting the amount of powder added and the centrifugation parameters, for example, to obtain a stable dispersion in the range of 5-20 mg / mL.

[0161] (2) Thin film preparation by blade coating method

[0162] Select a substrate with a smooth surface (such as glass, polyimide (PI) film, or silicon wafer). Drop the Al-Ti3C2 dispersion onto one end of the substrate and use a doctor blade or automatic coater to coat the dispersion into a uniform wet film at a constant speed and gap (e.g., gap set to 100-500 μm). Dry the wet film at a suitable temperature (e.g., 60-100°C) to evaporate the solvent and form a continuous Al-Ti3C2 film. If necessary, the dried film can be subjected to a mild hot-pressing treatment (e.g., treatment at 100-200°C under certain pressure) to enhance the contact between layers and the film's density.

[0163] (3) Thin film preparation by spin coating

[0164] The substrate (such as metal foil, silicon wafer, glass slide, polymer, etc.) is fixed on a spin coater. An Al-Ti3C2 dispersion is dropped into the center of the substrate. First, the coating is rotated at a low speed (e.g., 500 rpm) for several seconds to spread the dispersion. Then, the speed is immediately increased to a high speed (e.g., 1000-3000 rpm) for 30-60 seconds, using centrifugal force to remove excess dispersion and form a uniform thin layer on the substrate surface. After spin coating, the film is dried on a hot plate or in an oven (e.g., 80-120℃) to remove residual solvent, yielding an Al-Ti3C2 film. The final film thickness can be controlled by adjusting the dispersion concentration and spin coating speed.

[0165] While the orientation degree of films formed directly by this dispersion method may not be as high as that of the shear-induced extrusion method described in Example 4, its advantages lie in its simple process, good compatibility with existing semiconductor or printed electronics processes, and suitability for rapid coating on substrates of various shapes and materials. It is particularly suitable for preparing functional coatings on large-area, irregular surfaces. The resulting films retain the intrinsic properties of Al-Ti3C2 materials, such as excellent conductivity and low infrared emissivity, and can be used to prepare infrared stealth coatings, electromagnetic shielding films, and electronic devices (especially flexible electronic devices, such as wearable electronic devices).

[0166] Example 9

[0167] This embodiment provides a flexible conductive and electromagnetic shielding component for wearable electronic devices using the non-van der Waals artificial solid material and film of the present invention. The Al-Ti3C2 film (thickness ~5μm) prepared in Example 6 is cut into a specific pattern and laminated onto an elastic fabric or flexible polymer substrate using a flexible adhesive to prepare a wearable conductive strip or shielding patch. Utilizing the excellent flexibility and low sheet resistance of the film, it maintains stable conductive connections even under deformation conditions such as human joint movement. Simultaneously, its high electromagnetic interference shielding effectiveness effectively protects wearable devices or the human body from environmental electromagnetic radiation interference. Replacing traditional bulky and brittle metal foils or conductive coatings, this provides a lightweight, flexible, durable, and efficient electromagnetic compatibility solution for wearable devices, solving the problem of incompatibility between rigid shielding materials and flexible wearable carriers.

[0168] Example 10

[0169] This embodiment provides an application scenario for the thin film of the present invention as an infrared stealth and thermal protection coating on the surface of high-temperature equipment, providing a lightweight surface treatment solution that combines infrared stealth and certain physical protection functions for equipment operating in high-temperature and oxidizing environments. It overcomes the contradictions of poor temperature resistance of traditional infrared stealth coatings (such as polymer-based coatings) and the generally high infrared emissivity of high-temperature ceramic coatings.

[0170] The thin film containing a non-van der Waals artificial solid material (such as Al-Ti3C2 film) of this invention is bonded to the metal surface of simulated high-temperature equipment components (such as engine housings and high-temperature pipes) using a high-temperature resistant adhesive or physical method. Utilizing the film's low infrared emissivity (~0.26) and high thermal stability, the film significantly reduces the infrared radiation temperature of its surface during component operation (significant temperature drop at 500°C), achieving infrared stealth. Simultaneously, it exhibits almost no oxidation or weight loss in air at 800°C, acting as a physical barrier to delay the erosion of the substrate material by high temperatures and oxidation.

[0171] The test or calculation involved in this embodiment are explained as follows:

[0172] Hermann orientation factor calculation: used to quantify the degree of orientation of a thin film. Based on azimuth intensity data obtained from WAXS or pole figure measurements. Through formula Perform calculations, where The closer the f-value is to 1, the higher the degree of orientation.

[0173] Electromagnetic interference shielding effectiveness calculation: Based on scattering parameters (S) measured by a vector network analyzer 11 ,S 21 (etc.), according to the formula:

[0174]

[0175] SE T =SE A +SE R

[0176] Calculate the reflection loss, absorption loss, and total shielding effectiveness separately. This is the standard calculation method in the field of microwave engineering.

[0177] Infrared emissivity measurement: Using a Fourier transform infrared spectrometer, the radiation spectrum of the sample is measured in a specific band (e.g., 7-14 μm) using either the reflection method or the direct emission method, and the result is calculated by comparing it with a standard blackbody.

[0178] Radiation temperature drop assessment: By comparing the set temperature of the heating stage (heat source) with the radiation temperature measured by the infrared thermal imager on the surface of the sample, the difference directly reflects the infrared camouflage (cooling) effect of the material.

[0179] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for preparing a non-van der Waals artificial solid material, characterized in that, Includes the following steps: (1) The MXene material is subjected to a first heat treatment in an atmosphere containing zinc vapor to obtain electron-injected MXene material; (2) In an atmosphere containing metal Z vapor, the obtained electron-injected MXene material is subjected to a second heat treatment to form chemical bonds between the metal Z and the MXene material, thereby obtaining the non-van der Waals artificial solid material.

2. The preparation method according to claim 1, characterized in that, The metal Z is selected from at least one of Al, Ga, In, and Sn; and / or, The MXene contains a fluorine functional group; And / or, The preparation method of the MXene material includes: etching the MAX phase precursor in a fluorinated etching solution, followed by washing, ultrasonic stripping, and centrifugation; preferably, the fluorinated etching solution includes a metal fluoride salt and an acid solution, or hydrofluoric acid; and / or, The chemical formula of the MXene material is M. n+1 X n T x Where M is at least one of Ti, Nb, V, Mo, Cr, Ta, Hf, and Zr, X is C and / or N, n = 1 to 4, and T x The surface end group is indicated; preferably, M is at least one of Ti, Nb, and V; more preferably, the MXene material is selected from Ti3C2T. x Ti2CT x Nb2CT x V2CT x At least one of them.

3. The preparation method according to claim 1, characterized in that, The temperature of the first heat treatment is 400°C to 600°C; and / or, The temperature of the second heat treatment is 600°C to 900°C.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The zinc vapor is generated by zinc powder spread at the bottom of the reaction vessel under heating conditions; and / or, The metal Z vapor is generated by metal M powder deposited at the bottom of the reaction vessel under heating conditions; and / or, Prior to step (2), the method further includes the step of preparing the electron-implanted MXene material into a thin film, coating, or bulk material; and / or, Prior to step (1), the method further includes the step of preparing the MXene material into a thin film, coating, or bulk material; and / or, The carrier concentration of the electron-injected MXene material obtained in step (1) is higher than that of the initial MXene material; preferably, the carrier concentration of the electron-injected MXene material reaches 10. 22 cm -3 Magnitude.

5. A non-van der Waals artificial solid material obtained by the preparation method according to any one of claims 1 to 4; preferably, its general chemical formula is ZM n+1 X n Z is selected from at least one of Al, Ga, In, and Sn; M is at least one of Ti, Nb, and V; X is C and / or N; and n = 1 to 4. More preferably, the non-van der Waals artificial solid material is an M'-M3X2 type compound, preferably Al-Ti3C2, Ga-Ti3C2, In-Ti3C2, or Sn-Ti3C2; or, the non-van der Waals artificial solid material is an M'-M2X type compound, preferably Al-Ti2C, Al-Nb2C, or Al-V2C.

6. The non-van der Waals artificial solid material as described in claim 5, characterized in that, The non-van der Waals artificial solid material is an ultrathin sheet with a thickness of less than 10 nm, preferably 1 nm to 5 nm; and / or, The non-van der Waals artificial solid material has a layered crystal structure.

7. A thin film, characterized in that, Contains a non-van der Waals artificial solid material as described in any one of claims 5 or 6.

8. A method for preparing a thin film, characterized in that the step... include: (1) The MXene dispersion was coated onto the substrate and molded to obtain an MXene precursor film; (2) The MXene precursor film is subjected to a first heat treatment in an atmosphere containing zinc vapor and then electron implanted to obtain an MXene intermediate film containing electron implantation. (3) In an atmosphere containing metal Z vapor, the MXene intermediate film obtained in step (2) is subjected to a second heat treatment to form chemical bonds between the metal Z and the MXene material.

9. The preparation method according to claim 8, characterized in that, The MXene dispersion exhibits shear-thinning rheological properties and / or viscoelastic gel characteristics; And / or, The coating method includes: coating the MXene dispersion onto a substrate by extrusion, blade coating, or spin coating; and / or... The coating method further includes: inducing the orientation and alignment of MXene nanosheets in the MXene dispersion using shearing action; and / or The zinc vapor is generated by zinc powder spread at the bottom of the reaction vessel under heating conditions; and / or, The metal Z vapor is generated by metal Z powder laid at the bottom of the reaction vessel under heating conditions.

10. The thin film as claimed in claim 8 or 9, characterized in that, The metal Z is selected from at least one of Al, Ga, In, and Sn; and / or, The preparation method of the MXene material includes: etching the MAX phase precursor in a fluorinated etching solution, followed by washing, ultrasonic stripping, and centrifugation; preferably, the fluorinated etching solution includes a metal fluoride salt and an acid solution, or hydrofluoric acid; and / or, The chemical formula of the MXene material is M. n+1 X n T x Where M is at least one of Ti, Nb, V, Mo, Cr, Ta, Hf, and Zr, X is C and / or N, n = 1 to 4, and T x The surface end group is indicated; preferably, M is at least one of Ti, Nb, and V; more preferably, the MXene material is selected from Ti3C2T. x Ti2CT x Nb2CT x V2CT x At least one of them; and / or, The temperature of the first heat treatment is 400°C to 600°C; and / or, The temperature of the second heat treatment is 600°C to 900°C.

11. A thin film obtained by the preparation method according to any one of claims 8 to 10.

12. The thin film as claimed in claim 7 or 11, characterized in that, The film has an oriented layered structure; preferably, the oriented structure is formed by stacking layers of the non-van der Waals artificial solid material; more preferably, the Hermann orientation factor f of the film is greater than 0.7, preferably greater than 0.8; and / or, The thickness of the film is less than 10 μm, preferably 1 μm to 5 μm; and / or, The sheet resistance of the thin film is 2Ω□- 1 The following is preferred: 1Ω□- 1 The following is more preferably 0.5Ω□- 1 Left and right; and / or, The film is stable, and after heat treatment at 800°C in air for 2 hours, the weight loss does not exceed 1 wt.%, preferably not more than 0.5 wt.%, and more preferably not more than 0.1 wt.%.

13. A dispersion, characterized in that, It comprises a solvent and a non-van der Waals artificial solid material as described in claim 5 or 6 dispersed in the solvent; preferably, the concentration of the dispersion is greater than 10 mg / mL, more preferably from 20 mg / mL to 50 mg / mL.

14. Use of a non-van der Waals artificial solid material as described in claim 5 or 6, or a thin film as described in claim 7, 11, or 12, in electromagnetic shielding, infrared stealth, low infrared emissivity coatings, or flexible electronic devices.

15. An electromagnetic shielding device, characterized in that, Contains a non-van der Waals artificial solid material as described in claim 5 or 6, or a thin film as described in claim 7, 11, or 12; Preferably, the total shielding effectiveness of the electromagnetic shielding device in the 8.2-12.4 GHz frequency range is greater than 30 dB, more preferably greater than 40 dB, and even more preferably greater than 45 dB; or, After the electromagnetic shielding device is heat-treated at 500°C for 12 hours, the attenuation rate of its electromagnetic interference shielding effectiveness is less than 10%, preferably less than 5%.

16. An infrared stealth device or coating, characterized in that, Contains a non-van der Waals artificial solid material as described in claim 5 or 6, or a thin film as described in claim 7, 11, or 12; Preferably, the infrared stealth device or coating has an average infrared emissivity of less than 0.4 in the 7-14μm band, more preferably less than 0.3; or, The infrared stealth device or coating exhibits a significantly lower surface radiation temperature than the bulk MAX phase material under the same conditions at a high temperature of 500°C; preferably, within an object temperature range of 100-550°C, its surface radiation temperature is below 200°C, or... The infrared stealth device or coating can still maintain its infrared stealth function after being exposed to air at 500°C for 48 hours.

17. A flexible electronic device, characterized in that, Contains a non-van der Waals artificial solid material as described in claim 5 or 6, or a thin film as described in claim 7, 11, or 12.

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