Flexible thermal shielding material, method of making and use thereof

Abstract

The application provides a flexible heat shielding material and a preparation method and application thereof. A fiber base material is first treated to make it rich in active groups; a mixed solution of sodium tungstate, ammonium sulfate and lithium sulfate is prepared, the pH is adjusted, and then n-butanol is added to obtain a precursor solution; the fiber base material is placed in the precursor solution for high-temperature reaction, and finally calcination is performed under nitrogen to obtain the flexible heat shielding material. The application improves the activity of the surface groups of the base material by adjusting the pH, and through the regulation of ammonium sulfate and n-butanol, combined with the process and parameters, the tungsten trioxide in an interlaced structure with the fiber base material is obtained; the doping of lithium improves the free carrier concentration in the triangular tunnel and W-O hexagonal tunnel of WO3, so that the surface plasmon resonance benefit of the flexible heat shielding material is enhanced when applied, and the near-infrared shielding performance is improved. The flexible heat shielding material can realize adjustable near-infrared absorption performance according to voltage changes, has an intelligent heat shielding function, and is suitable for the field of intelligent wearable devices.

Description

Technical Field

[0001] This invention relates to the field of shielding device technology, and in particular to a flexible thermal shielding material, its preparation method, and its application. Background Technology

[0002] Currently, heat shielding materials are mainly used for the functionalization of windows or exterior surfaces of moving objects such as buildings and automobiles. This is because heat shielding devices have high visible light transmittance and low far-infrared emissivity, achieving both heat insulation and high blocking of the infrared portion of sunlight. This makes a significant contribution to energy consumption, comfort, and energy conservation and emission reduction in buildings and automobiles. For example, patent publication number JP4470736B2 discloses an infrared shielding glass. The preparation method of this infrared shielding glass involves coating at least one surface of a glass substrate with a coating liquid containing conductive oxide particles and a matrix component, followed by calcination at 350–750°C for 1–60 minutes to form an infrared shielding film. The conductive oxide particles are selected from one or more of ATO particles and fluorine-containing ITO particles, and the matrix component is selected from one or more of silicon oxide precursors and zirconium compounds. This infrared shielding glass exhibits excellent heat resistance, high visible light transmittance, low infrared transmittance, and high electromagnetic wave transmittance, making it suitable for use in vehicle or architectural glass.

[0003] With the development of technology, wearable smart clothing has become increasingly popular. Based on existing rigid substrate infrared shielding glass, flexible infrared shielding materials have become a research hotspot in the field. Wearable smart shielding devices will become an important component of future smart wearable electronic products. Flexible shielding devices are expected to be applied in fields such as display, decoration, safety warnings, and sensors, including portable miniaturized and smart electronic products, artificial skin, wearable optics or information communication, and sensing modules in the Internet of Things, as well as real-time information interaction in outdoor environments.

[0004] Patent publication number JP 5360656B2 discloses a heat-insulating and light-transmitting film material and its manufacturing method, comprising a fiber base fabric and a flexible resin coating on at least one surface thereon. The flexible resin coating has an island structure composed of an immiscible mixture of synthetic resins. In the island structure, the sea component or island component contains a thermally controlled colorant, which includes metal oxides, microparticles, metal composite oxide microparticles, and one or more near-infrared absorbing substances selected from phthalocyanine compounds, naphthol quinone compounds, yttrium compounds, anthraquinone compounds, amino compounds, and nickel-thiol complex compounds. This heat-insulating and light-transmitting film material has excellent heat insulation performance and is suitable for awnings, decorative tents, truck hoods, blinds, partitions, and thin panels for agricultural and horticultural use.

[0005] However, although the aforementioned heat-insulating and light-transmitting film material uses a flexible fiber base fabric as a substrate, the thermal control colorant is mixed with the resin and then coated onto the surface of the fiber base fabric, which reduces the comfort of the fiber base fabric. This limits its use to areas where material comfort requirements are not high, and it cannot be applied to the field of smart wearables. In addition, the coating method applied to the fiber base fabric results in poor load-bearing strength, making it prone to detachment during application and causing performance degradation.

[0006] In view of this, it is necessary to design an improved flexible thermal shielding material, its preparation method, and its application to solve the above problems. Summary of the Invention

[0007] The purpose of this invention is to provide a flexible heat shielding material, its preparation method, and its application. Sodium tungstate and lithium sulfate are mixed, and the activity of surface groups on a fiber substrate is increased by limiting the pH. Ammonium sulfate and n-butanol are added, and the reaction process and parameters are adjusted accordingly to obtain tungsten trioxide with a special structure, which forms an interleaved structure with the fiber substrate, thereby improving the bonding ability between tungsten trioxide and the fiber substrate. This flexible heat shielding material can achieve adjustable near-infrared light absorption performance according to voltage changes, possessing intelligent heat shielding function, and is suitable for the field of smart wearables.

[0008] To achieve the above-mentioned objectives, this invention provides a method for preparing a flexible heat-shielding material, comprising the following steps:

[0009] S1. The fiber substrate is subjected to a decontamination treatment and a hydrophilic treatment in sequence to give the surface of the fiber substrate active groups; the fiber substrate is a high-temperature resistant conductive fabric.

[0010] S2. Prepare a sodium tungstate solution by adding ammonium sulfate and lithium sulfate to the sodium tungstate solution to obtain a mixed solution; add sulfuric acid to the mixed solution to adjust the pH to 1.4-2.2, then add n-butanol and stir to obtain a precursor solution;

[0011] S3. The fiber substrate treated in step S1 is placed in the precursor solution of step S2 for high-temperature reaction at a temperature of 80-220°C for 8-12 hours. After removal, it is washed and dried multiple times.

[0012] S4. The fiber substrate treated in step S3 is calcined in a nitrogen atmosphere and then naturally cooled to obtain the flexible heat shielding material.

[0013] As a further improvement of the present invention, in step S2, the amount of n-butanol added is 8% to 15% of the volume of the mixed solution.

[0014] As a further improvement of the present invention, in step S2, the concentration of the sodium tungstate solution is 0.02-0.04 mol / L; and in the mixed solution, the molar ratio of sodium tungstate, ammonium sulfate and lithium sulfate is 1:(0.05-0.1):(0.25-0.5).

[0015] As a further improvement of the present invention, in step S2, the concentration of sulfuric acid is 2-5 mol / L, and the sulfuric acid is added to the mixed solution by stirring and dropping, adjusting the pH to 1.6-2.0, and stirring for 20-40 min.

[0016] As a further improvement of the present invention, in step S1, the hydrophilic treatment involves placing the decontaminated fiber substrate as the positive electrode and the platinum electrode as the negative electrode in an anhydrous sodium sulfate solution and treating it with a constant voltage of 10V for 3 to 5 minutes to obtain a fiber substrate with active groups; the concentration of the anhydrous sodium sulfate solution is 1.5 to 2 mol / L.

[0017] As a further improvement of the present invention, the high-temperature resistant conductive fabric is carbon cloth, and the calcination temperature is 500-900℃ for 1-2 hours.

[0018] As a further improvement of the present invention, in step S1, the decontamination treatment involves ultrasonically cleaning the fiber substrate with deionized water for 15-30 minutes, then ultrasonically cleaning it with ethanol for 15-30 minutes, repeating the cleaning process 2-3 times, and then drying it at 50-65°C.

[0019] The present invention also provides a flexible heat shielding material prepared by the preparation method of the flexible heat shielding material described in any one of the above-mentioned methods, wherein the flexible heat shielding material comprises a fiber substrate and a nanomaterial functional layer loaded on the surface of the fiber substrate, wherein the nanomaterial functional layer is a lithium-doped WO3 nanomaterial with a nanorod structure.

[0020] As a further improvement of the present invention, the WO3 nanomaterial has a nanorod diameter of 100-600 nm and an aspect ratio of (30-60):1; the flexible thermal shielding material has an infrared thermal absorption efficiency of 80%-85%.

[0021] The present invention also provides an application of the flexible heat shielding material described in any one of the above-mentioned methods, wherein a gel electrolyte is used to coat one end of two flexible heat shielding materials respectively, the coated ends of the two flexible heat shielding materials are overlapped together, and the flexible heat shielding device is obtained after drying at room temperature; the infrared absorption performance of the flexible heat shielding device is adjustable and it is suitable for the field of smart wearable devices.

[0022] As a further improvement of the present invention, the gel electrolyte is prepared by mixing a propylene carbonate solution containing 10wt% to 15wt% lithium perchlorate with polymethyl methacrylate having a mass percentage concentration of 25wt% to 30wt%, and then stirring and heating it in a water bath at 80 to 90°C for 8 to 10 hours.

[0023] The beneficial effects of this invention are:

[0024] 1. This invention provides a flexible heat shielding material and its preparation method. First, a fiber substrate is subjected to a decontamination treatment and a hydrophilic treatment. A sodium tungstate solution is prepared, and ammonium sulfate and lithium sulfate are added to the sodium tungstate solution to obtain a mixed solution. Sulfuric acid is added to the mixed solution to adjust the pH to 1.4–2.2, and then n-butanol is added and stirred to obtain a precursor solution. The fiber substrate is then placed in the precursor solution for a high-temperature reaction. Finally, the fiber substrate is calcined under a nitrogen atmosphere and naturally cooled to obtain the flexible heat shielding material. This invention mixes sodium tungstate and lithium sulfate, and by limiting the pH, increases the activity of surface groups on the fiber substrate. By adding ammonium sulfate and n-butanol, and by adjusting the reaction process and parameters, tungsten trioxide with a special structure is obtained, forming an interleaved structure with the fiber substrate, thus improving the bonding ability between tungsten trioxide and the fiber substrate. This flexible heat shielding material can achieve adjustable near-infrared light absorption performance according to voltage changes, possessing intelligent heat shielding function, and is suitable for the field of smart wearables.

[0025] 2. This invention first hydrophilically treats the fiber substrate, increasing the number of active groups on the substrate surface. Then, by adjusting the pH, the activity of the groups during the reaction is further improved, resulting in better bonding between tungsten trioxide and the fiber substrate during the formation process, while ensuring the uniformity of tungsten trioxide loading. The addition of n-butanol can immobilize the WO3 crystal nuclei, increasing the interaction force between them and the groups on the fiber substrate surface. This is beneficial for the contact between the WO3 crystal nuclei and the fabric interface, especially for bonding with the weaving nodes of the fiber substrate. It also influences the growth direction of the crystal nuclei, causing them to grow along a one-dimensional direction, forming nanosheet or nanorod-like structures. During calcination, the surface morphology of WO3 nanorods / sheets gradually transforms into nanorods. The nanorods become larger during calcination, their hexagonal crystal morphology becomes clearer, and they eventually form hexagonal crystals. Lithium doping in WO3 also facilitates the formation of high aspect ratio hexagonal nanorods. These high aspect ratio nanorods intertwine with the fiber substrate to form an interwoven structure, anchoring between fibers and significantly improving the bonding ability between WO3 and the fabric substrate, further enhancing the stability of the loaded nanomaterial functional layer. Furthermore, the morphology-capping effect of ammonium sulfate maintains the aspect ratio of the nanorods grown during calcination within a certain range, promoting the formation of a more stable hexagonal lattice structure and endowing them with excellent near-infrared shielding performance.

[0026] 3. The WO3 nanomaterials obtained by adding lithium sulfate in this invention have a large aspect ratio, which increases the structural uniformity of the nanomaterials. In addition, the addition of lithium sulfate improves the filling rate of triangular tunnels and WO hexagonal tunnels, that is, it increases the free carrier concentration, which enhances the surface plasmon resonance effect of the prepared flexible thermal shielding material during application and greatly improves the near-infrared shielding performance of WO3 nanomaterials.

[0027] 4. The color of the tungsten trioxide nanomaterials on the surface of the fiber substrate of this invention can also change with voltage, exhibiting significant and stable color-changing performance. This color change can also adjust its absorption in the near-infrared region, thereby improving the flexible control of the shielding performance of the flexible heat shielding material. When used as a heat insulation device, it can significantly reduce the temperature rise of the shielded object. It can provide non-contact heat insulation like glass, or contact heat insulation like clothing, with a wide range of applications. The method for preparing the flexible heat shielding material of this invention is simple, cost-effective, and pollution-free, making it suitable for industrial production. Attached Figure Description

[0028] Figure 1 This is a scanning electron microscope image of the flexible heat shielding material prepared using carbon cloth as the fiber substrate in Example 1.

[0029] Figure 2 The image shows a scanning electron microscope image of the flexible heat shielding material prepared using carbon cloth as the fiber substrate in Example 2.

[0030] Figure 3 The image shows a scanning electron microscope image of the flexible heat shielding material prepared using carbon cloth as the fiber substrate, which is Comparative Example 1.

[0031] Figure 4 The time-temperature curves of the flexible heat shielding material (colored state), pure carbon cloth and cotton cloth prepared in Examples 1, 3 to 6 under simulated light irradiation are shown.

[0032] Figure 5 The time-temperature variation curves of the flexible heat shielding materials (colored state) and cotton fabric prepared in Examples 1, 7-11 under simulated light irradiation.

[0033] Figure 6 The image shows the infrared shielding experimental model (left) and the result (right) of the flexible thermal shielding material prepared in Example 1. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] It should also be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0036] Additionally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0037] A method for preparing a flexible heat shielding material includes the following steps:

[0038] S1. The fiber substrate is subjected to decontamination and hydrophilic treatment in sequence to give the surface of the fiber substrate active groups; the fiber substrate is a high temperature resistant conductive fabric.

[0039] The hydrophilic treatment involves placing a cleaned fiber substrate as the positive electrode and a platinum electrode as the negative electrode in an anhydrous sodium sulfate solution and treating it at a constant voltage of 10V for 3–5 minutes to obtain a fiber substrate with active groups. The concentration of the anhydrous sodium sulfate solution is 1.5–2 mol / L. This hydrophilic treatment increases the number of active groups on the fiber surface, which is beneficial for improving the degree of subsequent reactions and thus increasing the adhesion of nanomaterials.

[0040] S2. Prepare sodium tungstate solution: Add ammonium sulfate and lithium sulfate to the sodium tungstate solution and stir for 3-5 minutes until the solution is uniform and clear to obtain a mixed solution; add sulfuric acid to the mixed solution to adjust the pH to 1.4-2.2, then add n-butanol and stir to obtain the precursor solution;

[0041] S3. The fiber substrate treated in step S1 is placed in the precursor solution of step S2 for high-temperature reaction at a temperature of 80-220°C for 8-12 hours. After removal, it is washed and dried multiple times. Specifically, it is washed with deionized water and ethanol alternately, and then dried in an oven at 60°C for 12 hours.

[0042] S4. The fiber substrate treated in step S3 is calcined in a nitrogen atmosphere and then naturally cooled to obtain a flexible heat shielding material.

[0043] Specifically, in this preparation method, the fiber substrate is first hydrophilically treated to increase the number of active groups on the substrate surface. Then, the activity of the groups during the reaction is further improved by adjusting the pH, resulting in better bonding between tungsten trioxide and the fiber substrate during the formation process, while ensuring the uniformity of tungsten trioxide loading. The addition of n-butanol can immobilize the WO3 crystal nuclei, increase the interaction force between them and the groups on the fiber substrate surface, which is beneficial to the contact between the WO3 crystal nuclei and the fabric interface, especially the bonding at the weaving nodes of the fiber substrate. At the same time, it affects the growth direction of the crystal nuclei, causing them to grow along a one-dimensional direction to form nanosheet or nanorod-like structures. During calcination, the surface morphology of WO3 nanorods / sheets gradually transforms into nanorods. The nanorods become larger during calcination, their hexagonal crystal morphology becomes clearer, and they eventually form hexagonal crystals. Lithium doping in WO3 also facilitates the formation of high aspect ratio hexagonal nanorods. These high aspect ratio nanorods intertwine with the fiber substrate to form an interwoven structure, anchoring between fibers and significantly improving the bonding ability between WO3 and the fabric substrate, further enhancing the stability of the loaded nanomaterial functional layer. Furthermore, the morphology-capping effect of ammonium sulfate maintains the aspect ratio of the nanorods grown during calcination within a certain range, promoting the formation of a more stable hexagonal lattice structure and endowing them with excellent near-infrared shielding performance.

[0044] Specifically, in step S2, the amount of n-butanol added is 8% to 15% of the volume of the mixed solution. The addition of n-butanol shares the characteristics of both small-molecule and large-molecule alcohols: it can dissolve some polar compounds but is insoluble in water. Therefore, using n-butanol can form an oil film on the solution surface, improving the sealed environment of the reaction system, preventing side reactions of other impurities and gases, and facilitating the smooth progress of the reaction. On the other hand, it reduces solvent loss and can extract polar impurities from the precursor solution, ensuring that the obtained product is more stable and free of byproducts.

[0045] The concentration of the sodium tungstate solution was 0.02–0.04 mol / L; in the mixed solution, the molar ratio of sodium tungstate, ammonium sulfate, and lithium sulfate was 1:(0.05–0.1):(0.25–0.5). The WO3 nanomaterials obtained after lithium sulfate doping exhibited a large aspect ratio, increasing the structural uniformity of the nanomaterials. Furthermore, the addition of lithium sulfate improved the filling rate of triangular and hexagonal WO3 tunnels, i.e., increased the free carrier concentration, thus enhancing the surface plasmon resonance effect of the prepared flexible thermal shielding material during application and significantly improving the near-infrared shielding performance of the WO3 nanomaterials. It is important to note that the amount of lithium sulfate doping should not be excessive, as excessive doping will lead to an excessively large aspect ratio of the WO3 nanomaterials, which is detrimental to their near-infrared shielding performance.

[0046] As a further improvement of the present invention, in step S2, the concentration of sulfuric acid is 2-5 mol / L, and the sulfuric acid is added to the mixed solution by stirring and dropping, adjusting the pH to 1.6-2.0, and stirring for 20-40 minutes. Under this pH environment, the obtained flexible heat shielding material exhibits the best near-infrared shielding performance and color-changing performance, as well as good mechanical properties, and the structure of the nanomaterial functional layer on the surface of the fiber substrate is more uniform and stable.

[0047] Preferably, in step S3, the high-temperature reaction temperature is 160–200°C. At lower reaction temperatures, it is difficult to generate uniform hexagonal WO3 nanorods on the fiber substrate surface. At excessively high reaction temperatures, the crystal size becomes too large, resulting in coarse rod-shaped WO3 with unequal aspect ratios, affecting its infrared absorption performance. Under conditions of 160–200°C and pH 1.6–2.0, WO3 tends to synthesize rod-shaped and more slender and uniform nanorod morphology. This nanomaterial exhibits strong light absorption in the near-infrared region and has better near-infrared light absorption performance.

[0048] Specifically, the high-temperature resistant conductive fabric is carbon cloth, and the calcination temperature is 500–900℃ for 1–2 hours. In practical applications, high-temperature resistant conductive fabrics also include other conductive fabrics, such as silver-plated nylon cloth and other fiber cloths with conductive treatment. It should be noted that when using other conductive fabrics, their high-temperature resistance must be considered, and the calcination temperature and time should be adjusted to avoid damage to the substrate during the calcination process.

[0049] In some specific embodiments, in step S1, the decontamination treatment involves ultrasonically cleaning the fiber substrate with deionized water for 15-30 minutes, then ultrasonically cleaning it with ethanol for 15-30 minutes, repeating the cleaning process 2-3 times, and finally drying it at 50-65°C.

[0050] In some specific embodiments, calcination is carried out in a tubular furnace, and the nitrogen flow rate introduced into the tubular furnace is 400-500 mL / min.

[0051] This invention mixes sodium tungstate and lithium sulfate, and enhances the activity of surface groups on a fiber substrate by controlling the pH. By adding ammonium sulfate and n-butanol, and adjusting the reaction process and parameters, a tungsten trioxide with a unique structure is obtained, exhibiting an interleaved structure with the fiber substrate, thus improving the bonding ability between the tungsten trioxide and the fiber substrate. This flexible heat shielding material can achieve adjustable near-infrared light absorption performance according to voltage changes, possessing intelligent heat shielding functionality, and is suitable for the field of smart wearables. The method for preparing the flexible heat shielding material is simple, cost-effective, and pollutant-free, making it suitable for industrial production.

[0052] A flexible thermal shielding material prepared by the above preparation method includes a fiber substrate and a nanomaterial functional layer loaded on the surface of the fiber substrate. The nanomaterial functional layer is a lithium-doped WO3 nanomaterial with a nanorod structure. The WO3 nanomaterial has a nanorod diameter of 100-600 nm and an aspect ratio of (30-60):1. The infrared thermal absorption efficiency of the flexible thermal shielding material is 80%-85%.

[0053] An application of a flexible heat shielding material involves coating one end of two flexible heat shielding materials with a gel electrolyte, overlapping the coated ends of the two materials, and drying them at room temperature to obtain a flexible heat shielding device. This flexible heat shielding device exhibits excellent flexibility, achieving improvements in softness, the ability to be twisted and folded without performance degradation. The infrared absorption performance of this flexible heat shielding device is adjustable, allowing it to adapt to non-planar surfaces, giving it significant potential advantages in smart wearables and driving the development of next-generation adaptive camouflage, biomimetic technologies, flexible wearable displays, and smart clothing—all man-made controllable smart fabrics.

[0054] In some specific embodiments, the gel electrolyte is prepared by mixing a propylene carbonate solution containing 10wt% to 15wt% lithium perchlorate with polymethyl methacrylate having a mass percentage concentration of 25wt% to 30wt%, and then stirring and heating it in a water bath at 80 to 90°C for 8 to 10 hours.

[0055] In practical applications, the color of the nanomaterial functional layer of flexible heat shielding material can also change with voltage, exhibiting obvious and stable color-changing performance. The color change can also adjust its absorption in the near-infrared region, thereby improving the flexible control of the shielding performance of the flexible heat shielding material. When used as a heat insulation device, it can significantly reduce the temperature rise of the shielded object. It can be used for non-contact heat insulation like glass, or for contact heat insulation like clothing, with a wide range of applications.

[0056] Example 1

[0057] This embodiment provides a flexible heat shielding material, its preparation method, and its application, including the following steps:

[0058] S1. Place two 1×3cm carbon cloths in deionized water for ultrasonic cleaning for 20 minutes, then ultrasonic cleaning with ethanol for 20 minutes. Repeat the alternating cleaning process twice, then dry them in an oven at 60℃ and store them for later use. Prepare an anhydrous sodium sulfate solution with a concentration of 2 mol / L. Use the treated carbon cloth as the positive electrode and the platinum electrode as the negative electrode in the anhydrous sodium sulfate solution. Treat it with a constant voltage of 10V for 3-5 minutes to obtain carbon cloth with active groups.

[0059] S2. Prepare a sodium tungstate solution with a concentration of 0.02 mol / L using deionized water. After stirring for 5 min, add ammonium sulfate and lithium sulfate to the sodium tungstate solution and continue stirring for 3 min until the solution is homogeneous and clear, obtaining a mixed solution. The molar ratio of sodium tungstate, ammonium sulfate, and lithium sulfate is 1:0.05:0.25. Add sulfuric acid with a concentration of 3 mol / L to the mixed solution to adjust the pH to 1.6, and then add n-butanol and stir. The amount of n-butanol added is 10% of the volume of the mixed solution, obtaining the precursor solution.

[0060] S3. Arrange the carbon treated in step S1 in the precursor solution of step S2 and carry out a high-temperature reaction at 200℃ for 12 hours. After taking it out, wash it alternately with deionized water and ethanol, and then dry it in an oven at 60℃ for 12 hours.

[0061] S4. The carbon cloth treated in step S3 is calcined in a tube furnace with nitrogen gas (flow rate of 400 mL / min) at 600°C for 1 hour. After natural cooling to room temperature, a flexible heat shielding material is obtained.

[0062] S5. Lithium perchlorate was dried at 120℃ for 24 hours, and polymethyl methacrylate particles were dried at 80℃ for 24 hours. A certain amount of lithium perchlorate was dissolved in a propylene carbonate solution and stirred thoroughly to prepare a 10wt% LiClO4:PC solution to form a liquid electrolyte. Polymethyl methacrylate particles were added to the above electrolyte solution, and the mixture was stirred continuously at 80℃ for 10 hours to form a homogeneous viscous colloid, thus obtaining a gel electrolyte.

[0063] S6. Take two pieces of flexible heat shielding material prepared in step S4, and uniformly coat one end of the two pieces of flexible heat shielding material (with carbon cloth as the fiber substrate) with the gel electrolyte obtained in step S5, leaving a blank length of 5-10 mm at the other end. Overlap the parts of the two flexible heat shielding materials covered with gel electrolyte, and dry them at room temperature to obtain a flexible heat shielding device.

[0064] Please see Figure 1 The image shown is a scanning electron microscope image of the flexible heat shielding material prepared using carbon cloth as the fiber substrate in Example 1. As can be seen from the image, the morphology of WO3 is that of uniformly structured nanorods approximately 10 μm long and 200 nm in diameter; a tightly packed morphology of tungsten trioxide nanorods can be observed on the surface of the carbon cloth.

[0065] Please see Figure 6The figure shows the infrared shielding experimental model (left) and results (right) of the flexible thermal shielding material prepared in Example 1. As can be seen from the figure, under simulated sunlight irradiation, the flexible thermal shielding material exhibits significant differences in temperature shielding performance inside the container in its bleached (left 2) and colored (left 3) states. The upper right of the figure shows the temperature inside the shielded container after the same irradiation time, and the lower right shows the surface temperature of the shielding fabric after the same irradiation time. The figure shows that the temperature difference in the colored state is 15.1℃, and the temperature difference in the bleached state is 10.8℃, both significantly better than the shielding effect of ordinary cotton cloth (left 1). Furthermore, the colored state exhibits stronger absorption of near-infrared radiation, resulting in a more pronounced thermal shielding effect.

[0066] Example 2

[0067] This embodiment provides a flexible thermal shielding material, its preparation method, and its application. Compared with Embodiment 1, the difference is that in step S2, the pH of the mixed solution is 2.0, and in step S3, the temperature of the high-temperature reaction is 140°C. The rest is roughly the same as in Embodiment 1, and will not be repeated here.

[0068] Please see Figure 2 The image shown is a scanning electron microscope image of the flexible heat shielding material prepared using carbon cloth as the fiber substrate in Example 2. As can be seen from the image, the morphology of WO3 at this stage is mainly a nanorod structure with a side length of 3–5 μm and a width of approximately 200 nm. Because the high-temperature reaction temperature is 140 °C, the final carbon cloth surface still has some nanosheet-like structures; and it can be observed that the carbon cloth surface is tightly coated with tungsten trioxide nanomaterials.

[0069] Comparative Example 1

[0070] Comparative Example 1 provides a flexible thermal shielding material, its preparation method, and its application. Compared with Example 1, the difference is that step S4 was not performed. The rest is roughly the same as Example 1, and will not be repeated here.

[0071] Please see Figure 3 The image shows a scanning electron microscope image of the flexible heat shielding material prepared using carbon cloth as the fiber substrate in Comparative Example 1. As can be seen from the image, the WO3 nanomaterials on the surface of the uncalcined flexible heat shielding material are mainly in a blocky structure. Because it has not undergone calcination treatment and has not had its morphology regulated by lithium and ammonium sulfate during the calcination process, the WO3 nanomaterials cannot continue to grow and transform into more clearly defined hexagonal crystals. Furthermore, the bonding force between these structures and the carbon cloth is weak, resulting in poor near-infrared shielding performance and electrochromic properties.

[0072] Examples 3-11

[0073] Examples 3 to 11 respectively provide a flexible thermal shielding material and its preparation method and application. Compared with Example 1, the difference is that the pH of the mixed solution in step S2 and the temperature of the high-temperature reaction in step S3 are shown in the table below. The rest are roughly the same as Example 1, and will not be repeated here.

[0074] Comparative Examples 2-4

[0075] Comparative Examples 2-4 provide a flexible thermal shielding material, its preparation method, and its application. Compared with Example 1, the differences are as follows: the pH of the mixed solution in step S2 and the temperature of the high-temperature reaction in step S3 are shown in the table below. The rest are roughly the same as Example 1 and will not be repeated here.

[0076] In Comparative Example 2, the excessively acidic mixed solution affected the hydroxyl activity of the carbon cloth surface after hydrophilic treatment, resulting in fewer WO3 particles adhering to the carbon cloth fibers and failing to successfully and uniformly load the carbon cloth with WO3 nanomaterials. In Comparative Example 3, the weak acidity of the mixed solution and the low acidification degree of sodium tungstate resulted in a small amount of WO3 obtained after the reaction. Furthermore, the rapid growth of WO3 in the weakly acidic environment led to larger crystal sizes, affecting the bonding between the WO3 nanomaterials and the fabric. Although Comparative Example 3 produced a carbon cloth with a relatively thick functional layer of WO3 nanomaterials on its surface, the bonding strength between this nanomaterial functional layer and the fabric was poor, making it prone to detachment and unsuitable for practical applications. In Comparative Example 4, the low reaction temperature resulted in a small amount of WO3 on the surface of the carbon cloth after the reaction, which was mostly granular and blocky. This resulted in poor bonding strength between the nanomaterial functional layer and the fabric, and also poor thermal shielding and electrochromic properties.

[0077] Table 1 shows the parameter settings for Examples 3-11 and Comparative Examples 2-4.

[0078]

[0079]

[0080] The flexible heat shielding materials prepared in Examples 1-11 were coated with gel electrolyte to form a flexible heat shielding device with a "sandwich structure". Different voltages were applied to achieve color switching between bleaching (colorless / fabric base color) and coloring (dark blue), and the device was subjected to heat shielding test under simulated light.

[0081] Please see Figure 4 The figure shows the time-temperature variation curves of the flexible heat shielding material (colored state), pure carbon cloth, and cotton cloth prepared in Examples 1, 3-6, under simulated light irradiation. Figure 4It can be seen that pure cotton cloth and carbon cloth have poor heat shielding effects; as pH increases, the heat shielding effect of different materials first increases and then decreases, and the prepared flexible heat shielding material has the best heat shielding effect when pH=1.6.

[0082] Please see Figure 5 The figure shows the time-temperature variation curves of the flexible heat shielding material (colored state) and cotton cloth prepared according to Examples 1 and 7-11 under simulated light illumination. Both the flexible heat shielding material and the cotton cloth are used as non-contact shielding devices, i.e., as windows of a sealed box, to detect the temperature change inside the sealed box over time. The figure shows that the best heat shielding effect is achieved at 200℃. This is attributed to the fine nanorod-like structures formed under these conditions, which tightly coat the carbon cloth, exhibiting good color-changing stability and excellent near-infrared light absorption.

[0083] Please refer to Table 2, which shows the thermal shielding data of the flexible thermal shielding devices prepared in Examples 1 and 7-11 under simulated sunlight. The temperature difference is characterized by the temperature change of the flexible thermal shielding device itself. The table shows that when the illumination time is less than 5 minutes, the synthesized flexible thermal shielding materials exhibit varying degrees of thermal absorption, reaching the highest value at a reaction temperature of 160℃. This is attributed to the good infrared absorption generated by the dense micron-shaped rod structure. However, after 10 minutes of illumination, the surface temperature difference between the WO3 electrochromic carbon cloth and the shielded cotton cloth increases with increasing reaction temperature. This indicates that the higher the reaction temperature, the better the near-infrared absorption capability of the electrochromic layer, reaching its optimum at 200℃. This is directly related to the reduced size of the nanorods and their larger aspect ratio, which improves their absorption efficiency in the near-infrared region. This material can be used as a novel intelligent wearable thermal shielding fabric.

[0084] Table 2 Material thermal shielding data for Examples 1 and 7-11

[0085] cotton 0 15.8 21.8 Carbon cloth / cotton 0 18.3 24.0 Example 1 0 25.9 35.0 Example 7 0 23.2 25.7 Example 8 0 20.5 27.4 Example 9 0 23.9 30.2 Example 10 0 26.8 32.5 Example 11 0 25.3 33.0

[0086] Comparative Example 5

[0087] Comparative Example 5 provides a flexible thermal shielding material, its preparation method and application. Compared with Example 1, the difference is that lithium sulfate was not added in step S2. The rest is roughly the same as Example 1, and will not be repeated here.

[0088] Comparative Example 6

[0089] Comparative Example 6 provides a flexible thermal shielding material, its preparation method and application. Compared with Example 1, the difference is that n-butanol was not added in step S2. The rest is roughly the same as Example 1, and will not be repeated here.

[0090] Comparative Example 7

[0091] Comparative Example 7 provides a flexible thermal shielding material and its preparation method and application. The difference from Example 1 is that ammonium sulfate was not added in step S2. The rest is roughly the same as Example 1, and will not be repeated here.

[0092] Comparative Example 8

[0093] Comparative Example 8 provides a flexible thermal shielding material, its preparation method, and its application. Compared with Example 1, the difference is that in step S2, ethanol is used instead of n-butanol. The rest is roughly the same as Example 1, and will not be repeated here.

[0094] Comparative Example 9

[0095] Comparative Example 9 provides a flexible thermal shielding material, its preparation method, and its application. Compared with Example 1, the difference is that in step S2, isoamyl alcohol is used instead of n-butanol. The rest is roughly the same as in Example 1, and will not be repeated here.

[0096] The flexible heat shielding materials prepared in Examples 1, 1, and 5-9 were tested for heat shielding performance and color change performance under simulated light. The results are shown in the table below.

[0097] Table 3 Performance characterization of flexible thermal shielding materials in Examples 1, 1 Comparative Examples, and 5-9

[0098]

[0099] Table 3 shows that the heat shielding effect of the heat shielding fabric that has not undergone calcination treatment is significantly reduced (ΔT = 4.1℃), and its electrochromic properties are also somewhat reduced (ΔCE = 4.7cm). 2 / C); The color-changing efficiency of the undoped tungsten trioxide layer is significantly reduced (ΔCE=5.5cm). 2 / C), the heat shielding efficiency in the colored state is also affected; among them, the effect of doping with ammonium sulfate and lithium sulfate individually is not as good as the effect of synergistic doping of the two in a certain proportion to improve the electrochromic performance and near-infrared heat shielding performance. The absence of n-butanol or the use of other alcohols to replace n-butanol reduces the coloring efficiency of the fabric and increases the bleaching time; the comparison shows that calcination and doping elements are important factors affecting the near-infrared heat shielding absorption capacity of the fabric, and n-butanol also has a certain impact on the coloring and bleaching of the fabric.

[0100] In summary, this invention provides a flexible thermal shielding material, its preparation method, and its application. First, a fiber substrate is sequentially treated with decontamination and hydrophilicity. A mixed solution of sodium tungstate, ammonium sulfate, and lithium sulfate is prepared. Sulfuric acid is added to the mixed solution to adjust the pH, followed by the addition of n-butanol and stirring to obtain a precursor solution. The fiber substrate is then placed in the precursor solution for a high-temperature reaction. Finally, the fiber substrate is calcined under a nitrogen atmosphere and naturally cooled to obtain the flexible thermal shielding material. This invention enhances the activity of surface groups on the fiber substrate by limiting the pH. By adding ammonium sulfate and n-butanol, and by adjusting the reaction process and parameters, tungsten trioxide with a special structure is obtained, forming an interleaved structure with the fiber substrate, thus improving the bonding ability between tungsten trioxide and the fiber substrate. Doping with lithium and ammonium sulfate gives the obtained WO3 nanomaterials a suitable aspect ratio, increasing the structural uniformity of the nanomaterials. Furthermore, the addition of lithium sulfate increases the filling rate of triangular tunnels and WO6 hexagonal tunnels, i.e., increases the free carrier concentration, enhancing the surface plasmon resonance effect of the prepared flexible thermal shielding material during application and significantly improving the near-infrared shielding performance of the WO3 nanomaterials. This flexible heat shielding material can adjust its near-infrared light absorption performance according to voltage changes, and has the function of intelligent heat shielding, making it suitable for the field of smart wearables.

[0101] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a flexible thermal shielding material, characterized in that, Includes the following steps: S1. The fiber substrate is subjected to a decontamination treatment and a hydrophilic treatment in sequence to give the surface of the fiber substrate active groups; the fiber substrate is a high-temperature resistant conductive fabric. S2. Prepare a sodium tungstate solution by adding ammonium sulfate and lithium sulfate to the sodium tungstate solution to obtain a mixed solution; Sulfuric acid was added to the mixed solution to adjust the pH to 1.4–2.2, and then n-butanol was added and stirred to obtain the precursor solution. S3. The fiber substrate treated in step S1 is placed in the precursor solution of step S2 for high-temperature reaction at a temperature of 80-220°C for 8-12 hours. After removal, it is washed and dried multiple times. S4. The fiber substrate treated in step S3 is calcined in a nitrogen atmosphere and then naturally cooled to obtain the flexible heat shielding material.

2. The method for preparing the flexible heat shielding material according to claim 1, characterized in that, In step S2, the amount of n-butanol added is 8% to 15% of the volume of the mixed solution.

3. The method for preparing the flexible thermal shielding material according to claim 1, characterized in that, In step S2, the concentration of the sodium tungstate solution is 0.02–0.04 mol / L; in the mixed solution, the molar ratio of sodium tungstate, ammonium sulfate, and lithium sulfate is 1:(0.05–0.1):(0.25–0.5).

4. The method for preparing the flexible thermal shielding material according to claim 1, characterized in that, In step S2, the concentration of sulfuric acid is 2-5 mol / L. The sulfuric acid is added to the mixed solution by stirring and dropping, the pH is adjusted to 1.6-2.0, and the stirring time is 20-40 min.

5. The method for preparing the flexible thermal shielding material according to claim 1, characterized in that, In step S1, the hydrophilic treatment involves placing the decontaminated fiber substrate as the positive electrode and the platinum electrode as the negative electrode in an anhydrous sodium sulfate solution and treating it with a constant voltage of 10V for 3-5 minutes to obtain a fiber substrate with active groups; the concentration of the anhydrous sodium sulfate solution is 1.5-2 mol / L.

6. The method for preparing the flexible heat shielding material according to claim 1, characterized in that, The high-temperature resistant conductive fabric is carbon cloth, and the calcination temperature is 500-900℃ for 1-2 hours.

7. The method for preparing the flexible thermal shielding material according to claim 1, characterized in that, In step S1, the decontamination treatment involves ultrasonically cleaning the fiber substrate with deionized water for 15-30 minutes, then ultrasonically cleaning it with ethanol for 15-30 minutes, repeating the cleaning process 2-3 times, and finally drying it at 50-65°C.

8. A flexible heat shielding material prepared by the method for preparing flexible heat shielding material according to any one of claims 1 to 7, characterized in that, The flexible thermal shielding material includes a fiber substrate and a nanomaterial functional layer loaded on the surface of the fiber substrate. The nanomaterial functional layer is a lithium-doped WO3 nanomaterial with a nanorod-like structure.

9. The flexible heat shielding material according to claim 8, characterized in that, The WO3 nanomaterial has a nanorod diameter of 100–600 nm and an aspect ratio of (30–60):1; the flexible thermal shielding material has an infrared thermal absorption efficiency of 80%–85%.

10. The application of a flexible heat shielding material prepared by the preparation method according to any one of claims 1 to 7 or the flexible heat shielding material according to any one of claims 8 to 9, characterized in that, A flexible heat shielding device is obtained by coating one end of two flexible heat shielding materials with a gel electrolyte, overlapping the coated ends of the two flexible heat shielding materials together, and drying them at room temperature. The infrared absorption performance of the flexible heat shielding device is adjustable and it is suitable for the field of smart wearable devices.

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