MXene visible light uniform scattering-infrared high reflection film and preparation method thereof

Abstract

The present application belongs to the technical field of MXene material and multispectral compatibility performance, and particularly relates to a kind of MXene visible light uniform scattering-infrared high reflection film and preparation method thereof.By establishing the substrate type→film microstructure→visible light scattering-infrared reflection performance regulation path, the present application realizes the directional promotion of visible light scattering intensity while taking into account the infrared high reflection performance;By using high-temperature ultrasonic + vacuum freeze-drying combined process, the transverse size of MXene nanosheet prepared is more uniform, and the dispersion stability is better, which solves the problem of large fluctuation of film performance in large-scale production, and realizes long-term stable storage and precise quantitative preparation of MXene material.The present application has simple and controllable process, wide substrate adaptability, low cost and good repeatability, and can realize large-scale and continuous preparation on large-size rigid / flexible substrate.

Description

Technical Field

[0001] This invention belongs to the field of MXene materials and multispectral compatibility performance technology, specifically relating to an MXene visible light uniform scattering-infrared high reflectivity thin film and its preparation method. Based on substrate roughness control, it is suitable for application scenarios that require synergistic control of visible light scattering and infrared high reflectivity, such as multispectral compatibility, glare suppression, optical display, and building energy conservation. Background Technology

[0002] MXene, as a novel two-dimensional transition metal carbide / nitride, possesses metal-like conductivity, tunable surface chemical properties, and good physicochemical stability. It has great potential for application in the field of multispectral optical performance control. Its thin films have unique optical responses in the visible light and mid-to-far infrared bands, which can meet the needs of scenarios such as diffuse scattering control, glare suppression, photothermal, heat preservation and energy saving, and thermal radiation management.

[0003] However, the preparation and application of existing MXene thin films face many bottlenecks:

[0004] Poor performance synergy: MXene continuous films prepared by traditional methods mostly use smooth PET substrates, which mainly reflect visible light specularly and have weak scattering ability. Furthermore, there is an inherent contradiction between enhanced visible light scattering and high infrared reflectivity. Modification to improve scattering performance can easily damage infrared reflectivity.

[0005] Precursor preparation and slurry process defects: Ice bath low temperature ultrasonic exfoliation of MXene has problems such as low efficiency, insufficient single layer yield and uneven nanosheet size. The high-speed centrifugation method of traditional slurry preparation results in poor batch stability of concentration and inability to accurately quantify. The material is difficult to store for a long time, which in turn causes fluctuations in film performance and makes it difficult to adapt to large-scale production.

[0006] Fabrication process limitations: Existing visible light scattering control relies on precision micro-nano processes such as photolithography and nanoimprinting, which are costly and difficult to scale up on different materials and large-size substrates, resulting in low engineering practicality.

[0007] Existing technologies cannot simultaneously solve the core problems of dual-band performance compatibility, process simplification, and large-scale production. Therefore, developing a method for preparing MXene thin films that is simple in process, low in cost, has wide substrate adaptability, and can achieve synergistic optimization of visible light scattering and infrared high reflectivity has become an urgent technical problem to be solved in this field. Summary of the Invention

[0008] To address the problems of weak visible light scattering control capability, difficulty in achieving compatibility between visible and infrared dual-band performance, and complex and costly fabrication processes in existing MXene-based thin films, this invention provides an MXene visible light uniform scattering and infrared high reflectivity thin film and its fabrication method. Based on substrate roughness control, a precise control path is established from substrate type to thin film surface microstructure to visible light scattering and infrared reflectivity performance. Combined with a high-temperature ultrasonic high-efficiency exfoliation process, the visible light scattering intensity is directionally enhanced while simultaneously maintaining high reflectivity thermal radiation control performance in the infrared band, meeting the application requirements of different engineering scenarios.

[0009] An MXene visible light uniform scattering-infrared high reflectivity thin film is composed of a functional substrate and an MXene functional layer formed by surface coating. By coating the MXene functional layer on the surface of the substrate according to the substrate type, the surface microstructure of the MXene thin film can be precisely controlled to form thin film morphologies with different diffuse scattering characteristics, thereby achieving synergistic and customized control of visible light band scattering enhancement and infrared band high reflectivity.

[0010] The functional substrate is selected from any one of rigid cardboard, sandpaper, sandblasted metal substrate, and PET substrate; among which rigid cardboard, sandpaper, and sandblasted metal substrate are rough substrates, and PET substrate is a smooth reference substrate, with a substrate thickness of 50~1000μm.

[0011] The MXene functional layer is made of Ti3C2T. x Ti2CT x Nb2CT x or V2CT x system.

[0012] Furthermore, the functional substrate is a smooth PET substrate with an average reflectivity of ≥80% in the infrared band and specular reflection in the visible light band, resulting in low scattering intensity, making it suitable for low-scattering scenarios requiring high infrared thermal radiation control.

[0013] Furthermore, the functional substrate is a rough substrate with an average reflectivity of ≥65% in the infrared band, and the visible light scattering intensity is significantly improved compared to a smooth PET substrate, increasing scattering uniformity and achieving dual-band performance compatibility.

[0014] The above-mentioned method for preparing MXene visible light uniform scattering and infrared high reflectivity thin films achieves directional control of dual-band optical performance by adjusting the microstructure of the thin film surface through substrate type and combining it with a blade coating process. The specific steps are as follows:

[0015] Step 1: Preparation of MXene precursor;

[0016] MXene dispersions were prepared using a LiF-HCl selective etching method: A Ti3AlC2 MAX phase was used as a precursor and etched with a LiF-HCl solution at 35–45 °C for 20–28 h to remove the Al atomic layer. The solution was repeatedly washed with deionized water and centrifuged until the pH of the supernatant reached 5–7. After further treatment with high-temperature water bath sonication and centrifugation, a monolayer Ti3C2 MAX dispersion with a concentration of 5–10 mg / mL was obtained. x MXene dispersion.

[0017] Furthermore, the temperature of the high-temperature water bath ultrasound is 70°C, the ultrasound power is 100~300W, and the ultrasound time is 10~30min.

[0018] Step 2: Preparation of MXene coating slurry;

[0019] The MXene dispersion prepared in step 1 was freeze-dried under vacuum to obtain MXene freeze-dried solid powder, enabling large-scale, long-term stable storage of the material. The powder was quantitatively dissolved in deionized water and stirred until uniformly dispersed, yielding a solid content of 50–150 mg / mL. -1 MXene slurry; let stand for 1~2 hours to degas, and obtain a slurry suitable for the scraping process.

[0020] Step 3: Apply coating and allow it to dry and cure;

[0021] The pre-treated functional substrate is coated with a blade at a spacing of 20-200 μm and a speed of 5-20 mm / s. -1 The MXene slurry is uniformly coated onto the substrate surface using a doctor blade; then dried at room temperature for 12-24 hours until fully cured, so that the MXene functional layer is tightly bonded to the substrate, thus obtaining the target thin film.

[0022] Dual-band performance regulation mechanism

[0023] Visible light band: The dominant principle is the synergistic control of geometric optical diffuse reflection and Mie scattering. The microstructure on the substrate surface is transferred to the MXene film surface through the template effect. The rough substrate causes the film to form microstructures that match the wavelength of visible light, breaking specular reflection and causing incident light to undergo multi-directional diffuse reflection, which significantly improves the scattering intensity and uniformity. By changing different substrates, the scattering characteristics can be precisely controlled, effectively suppressing specular glare.

[0024] Infrared band: The dominant principles are Fresnel reflection and Kirchhoff's laws of thermal radiation. MXene's intrinsic high metallic conductivity gives it natural high infrared reflectivity, and the substrate-induced microstructure size is much smaller than the infrared atmospheric window wavelength, thus not destroying the infrared specular reflection characteristics. Therefore, films on different substrates can maintain an average infrared reflectivity of over 65%. High monolayer ratio and high dispersion MXene nanosheets prepared by high-temperature ultrasonication can form films with higher density and better conductivity, further improving infrared reflectivity and reducing emissivity.

[0025] Cross-band synergistic mechanism: Based on the wavelength difference of three orders of magnitude between the visible and infrared bands, the optical response of the two bands is partially decoupled. The substrate-induced micro-nano structure only precisely controls the visible light scattering characteristics and has no significant negative impact on the infrared high reflectivity characteristics. By changing the substrate, the performance of the two bands can be simultaneously optimized, thus resolving the inherent contradiction between them.

[0026] In summary, the MXene visible light uniform scattering-infrared high reflectivity thin film and its preparation method provided by this invention solve the technical bottlenecks of insufficient visible light scattering intensity, incompatibility of visible light and infrared dual-band performance, and complex and costly preparation process of existing MXene thin films by establishing a precise control path of "substrate type → thin film surface microstructure → visible light scattering-infrared reflectivity". This provides new functional materials and industrial preparation technology support for fields such as industrial thermal management, anti-glare in consumer electronics, building energy conservation, and optical display, and has important practical application value. Attached Figure Description

[0027] Figure 1. Surface microstructure of MXene films on different substrates in the embodiments;

[0028] Figure 2. Infrared reflectance spectra of MXene films on different substrates in the embodiments;

[0029] Figure 3. Comparison curves of visible light scattering intensity of MXene films on different substrates in the embodiments. Detailed Implementation

[0030] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0031] A method for preparing an MXene visible light uniform scattering-infrared high reflectivity thin film, comprising the following specific steps:

[0032] Step 1: Preparation of MXene precursor;

[0033] Mix 1.6g LiF with 20mL 9M HCl solution and stir magnetically for 5min until completely dissolved. Slowly add 1g of 400-mesh Ti3AlC2MAX phase powder and etch in a 40℃ water bath with continuous stirring for 24h. After etching, wash the reaction product repeatedly with deionized water and centrifuge at 4000rpm until the pH of the supernatant is 6. Then, sonicate in a 60℃ water bath at 200W for 15min, followed by centrifugation at 3500rpm for 15min. Collect the supernatant to obtain a monolayer Ti3C2T with a concentration of 8mg / mL. x The MXene dispersion exhibited a significant Tyndall effect after dilution, confirming that the nanosheets were uniformly dispersed.

[0034] Step 2: Preparation of MXene coating slurry;

[0035] The MXene dispersion prepared in step 1 above was placed in a vacuum freeze dryer and freeze-dried at -50°C and a vacuum of 15 Pa for 36 h to obtain Ti3C2T. x MXene lyophilized solid powder; according to the requirements of the coating process, a quantitative amount of MXene lyophilized solid powder was weighed and dissolved in deionized water, and magnetically stirred at room temperature for 2 hours until completely dispersed and uniform, yielding a solid content of 100 mg / mL. -1 The MXene slurry was allowed to stand for 1.5 hours to degas, resulting in an MXene slurry suitable for the scraping process.

[0036] Step 3: Apply coating and allow it to dry and cure;

[0037] Substrate pretreatment: Hard cardboard, 800-grit sandpaper, sandblasted aluminum sheet, and smooth PET film were selected as functional substrates, with a thickness of 100μm for each substrate. The substrates except for the cardboard and sandpaper were ultrasonically cleaned with anhydrous ethanol and deionized water for 8 minutes in sequence, dried with nitrogen, and then subjected to plasma treatment for 3 minutes to complete the substrate pretreatment.

[0038] The four pretreated substrates were fixed onto the platform of an automatic coating machine, with a coating gap of 50 μm and a coating speed of 10 mm / s. -1 MXene slurry was uniformly coated onto the surface of different substrates using a doctor blade and dried at room temperature (25°C) for 20 hours to ensure complete bonding between the MXene functional layer and the substrate, resulting in four sets of MXene visible light uniform scattering-infrared high reflectivity films.

[0039] Performance test results

[0040] Structure and morphology: As shown in Figure 1, the MXene film on the rigid cardboard, sandpaper, and sandblasted aluminum sheet exhibits a microstructure that is highly matched with the substrate, completely replicating the surface morphology of the substrate. The layered stacked structure of MXene nanosheets is clear, without defects such as pinholes and cracks, and is tightly bonded to the substrate.

[0041] Visible light scattering performance: As shown in Figure 3, the MXene film on the smooth PET substrate mainly exhibits specular reflection in the visible light band, with extremely low scattering intensity. However, the scattering intensity of the MXene film on the three rough substrates is significantly improved. Among them, the scattering intensity of the MXene film on the sandpaper substrate is significantly improved compared to the smooth PET substrate, and the scattering uniformity is significantly improved. This effectively suppresses specular glare and achieves excellent uniform diffuse scattering effect of visible light.

[0042] Infrared thermal radiation modulation performance: tested using a Fourier transform infrared spectrometer (FTIR) with an integrating sphere, such as... Figure 2 As shown, the infrared reflectance of PET film remains above 80%, while sandpaper, although reducing the infrared reflectance, maintains the excellent low infrared emissivity and infrared thermal radiation modulation characteristics of MXene material.

[0043] As can be seen from the above embodiments, the present invention achieves precise customization of the visible light scattering characteristics and infrared thermal radiation modulation performance of MXene thin films by changing different functional substrates. Multiple sets of parallel embodiments verify the applicability of the method of the present invention on different substrates. Test results show that a rough substrate can significantly improve the visible light scattering intensity of MXene films while maintaining an average infrared reflectance of over 65%, providing a clear process basis for dual-band performance regulation. The substrate regulates the surface microstructure of the film through the template effect, and combined with the visible light diffuse scattering mechanism and infrared high reflectance characteristics, achieves synergistic optimization of dual-band performance with a clear structure-property relationship. Performance can be customized by changing the substrate. This invention significantly improves the exfoliation efficiency and monolayer yield of MXene nanosheets through a combination of "high-temperature ultrasound + vacuum freeze-drying" process, achieving stable material storage and precise slurry preparation, solving the problems of low exfoliation efficiency, large slurry concentration fluctuations, and high storage difficulty in traditional processes. The preparation method uses a blade coating method, which does not require precision micro-nano processing equipment. The process is simple, low-cost, widely adaptable to substrates, and has good repeatability. It can achieve continuous large-scale preparation on large-size substrates. The resulting material has excellent performance and strong environmental stability, and has potential for engineering applications.

Claims

1. An MXene visible light uniform scattering-infrared high reflectivity thin film, characterized in that: It consists of a functional substrate and an MXene functional layer; the MXene functional layer is formed by coating the substrate surface according to the substrate type, and the surface microstructure of the MXene film is controlled to form film morphologies with different diffuse scattering characteristics, so as to achieve synergistic and customized control of visible light band scattering enhancement and infrared band high reflectance. The functional substrate is selected from any one of rigid cardboard, sandpaper, sandblasted metal substrate, and PET substrate; among which rigid cardboard, sandpaper, and sandblasted metal substrate are rough substrates, and PET substrate is a smooth reference substrate, with a substrate thickness of 50~1000μm; The MXene functional layer is made of Ti3C2T. x Ti2CT x Nb2CT x or V2CT x system.

2. The MXene visible light uniform scattering-infrared high reflectivity thin film as described in claim 1, characterized in that: The functional substrate is a PET substrate film with an average infrared reflectance of ≥80%, used in low-scattering scenarios with high infrared thermal radiation modulation.

3. The MXene visible light uniform scattering-infrared high reflectivity thin film as described in claim 1, characterized in that: The functional substrate is a rough substrate with an average reflectivity of ≥65% in the infrared band, achieving dual-band performance compatibility.

4. The method for preparing the MXene visible light uniform scattering-infrared high reflectivity thin film as described in any one of claims 1-3, characterized in that, The specific steps are as follows: Step 1: Preparation of MXene precursor; MXene dispersions were prepared using a LiF-HCl selective etching method: A Ti3AlC2 MAX phase was used as a precursor and etched with a LiF-HCl solution at 35–45 °C for 20–28 h to remove the Al atomic layer. The solution was repeatedly washed with deionized water and centrifuged until the pH of the supernatant reached 5–7. After further treatment with high-temperature water bath sonication and centrifugation, a monolayer Ti3C2 MAX dispersion with a concentration of 5–10 mg / mL was obtained. x MXene dispersion; Step 2: Preparation of MXene coating slurry; The MXene dispersion prepared in step 1 was freeze-dried under vacuum to obtain MXene lyophilized solid powder; the powder was quantitatively dissolved in deionized water, stirred and dispersed evenly to obtain a solid content of 50-150 mg / mL. -1 MXene slurry; let stand for 1~2 hours to degas, and obtain a slurry suitable for the scraping process; Step 3: Apply coating and allow it to dry and cure; The pre-treated functional substrate is coated with a blade at a spacing of 20-200 μm and a speed of 5-20 mm / s. -1 The MXene slurry is uniformly coated onto the substrate surface using a doctor blade; then dried at room temperature for 12-24 hours until fully cured, so that the MXene functional layer is tightly bonded to the substrate, thus obtaining the target thin film.

5. The method for preparing the MXene visible light uniform scattering-infrared high reflectivity thin film as described in claim 4, characterized in that: In step 1, the temperature of the high-temperature water bath ultrasound is 70℃, the ultrasound power is 100~300W, and the ultrasound time is 10~30min.

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