A heat-generating and heat-storing tungsten bronze composite powder and a preparation method thereof

Abstract

This application relates to a heat-generating and heat-storing tungsten bronze composite powder. The composite powder has a three-layer wrapping structure, with a core layer of nano tungsten bronze (M x WO 3 ), a middle layer of mesoporous oxide, and a surface layer of organic heat storage material; the organic heat storage material is grafted onto the middle layer. The composite powder of the present invention has high heat-generating and heat-storing efficiency, fast heat transfer, good ultraviolet light stability, solves the problem of loss during solid-liquid phase change, and through the optimization of the preparation process, the prepared composite powder has excellent heat-generating and heat-storing stability.

Description

Technical Field

[0001] The present invention relates to the field of C30B28 / 00, and particularly relates to a heat-generating and heat-storing tungsten bronze composite powder and a preparation method thereof. Background Art

[0002] With the sharp increase in people's demand for energy, how to make full use of clean and infinite solar radiation energy has become the mainstream research direction. Existing organic phase change heat storage materials have a large heat storage density and high thermal efficiency, but their poor stability and easy liquid-phase loss limit their use. Among inorganic heat-generating materials, tungsten bronze nanometer powder has a low resistivity, superconducting properties, and near-infrared shielding properties, has good absorption in the near-infrared region (wavelength 800 - 1200 nm), and also shows good transmittance in the visible light region (wavelength 380 - 780 nm), and has wide applications in fields such as transparent heat-insulating coatings, automotive films, heat-insulating window films, laser welding, photothermal diagnosis and treatment, infrared filters, and warm fibers. However, it also has certain problems, such as low heat-generating and heat-storing effects, poor resistance to ultraviolet irradiation, unstable heat-generating and heat-storing effects, and low production repeatability, etc. Therefore, preparing a material with good heat-generating and heat-storing effects and stable performance to make full use of solar energy is the problem to be solved in this research.

[0003] Chinese Patent CN111547771A, Chinese Patent CN111498906A, and Chinese Patent CN110342578B publicly proposed a preparation method and uses of alkali metal tungsten bronze powder. This method has a clear reaction mechanism, a simplified process, no by-products generated, and is convenient for controlling the reaction. However, its powder properties are single, and its dispersibility is average, and further improvement is needed. And Chinese Patent CN110407255A discloses a carbon-coated cesium tungsten bronze composite powder and a preparation method thereof. Through carbon layer coating, the nano powder maintains good dispersibility. Moreover, through carbon coating, the photothermal conversion performance can be further improved. However, its heat storage capacity is not strong, and due to the carbon layer coating, the color of the powder becomes darker and blacker, resulting in limited downstream applications.

[0004] Chinese Patent CN110067038A discloses a preparation method of a nano intelligent fiber for heat storage, which uses polyvinyl butyral doped with cesium tungsten bronze as a shell layer to wrap n-octadecane, and prepares nano intelligent fibers by electrospinning. Although the phase change latent heat of this material is high, cesium tungsten bronze is directly exposed on the outer surface of the material, and after long-term ultraviolet irradiation, the heat-generating and heat-storing effects of this material will be significantly reduced. Chinese Patent CN109778424B discloses a phase change thermal insulation floc and a preparation method thereof. In its technical solution, phase change microcapsules with paraffin wrapped by silica are used. There is still a risk of phase change material loss during the solid-liquid transition of this kind of microcapsule, resulting in a reduction or even loss of heat storage capacity. Summary of the Invention

[0005] To solve the above technical problems, the present invention first provides a heat-generating and heat-storing tungsten bronze composite powder; the composite powder has a three-layer wrapped structure, with the core layer being nano tungsten bronze (M x WO 3 ), the middle layer being a mesoporous oxide, and the surface layer being an organic heat storage body; the organic heat storage body is grafted onto the middle layer.

[0006] Nano tungsten bronze has good heat-generating and heat-storing effects, but its anti-ultraviolet irradiation performance is poor, resulting in unstable heat storage performance. A mesoporous oxide layer is wrapped on the surface of nano tungsten bronze to reduce the influence of ultraviolet irradiation, and combined with an organic phase change heat storage material to improve the heat storage efficiency.

[0007] Further, M in the M x WO 3 is any one of alkali metal, alkaline earth metal element, and rare earth metal element.

[0008] Further, M in the M x WO 3 is selected from any one of lithium, sodium, potassium, rubidium, cesium, neodymium, and lanthanum.

[0009] Preferably, M in the M x WO 3 is cesium; the radius of the cesium ion is slightly larger than the radius of the hexagonal channel in the tungsten oxygen octahedron. When lattice distortion occurs, the doping efficiency of the cesium ion in the tungsten oxygen octahedron is higher and more stable, and due to the increase in surface defects, the infrared absorption ability can be greatly improved.

[0010] Further, x is 0.01 - 0.5; preferably, x is 0.1 - 0.33.

[0011] Further, the present invention does not strictly require the structure of M x WO 3 , including but not limited to spherical, rod-shaped, sheet-shaped, and flower-shaped.

[0012] In a preferred embodiment, the M x WO 3 has a nano-sheet structure; preferably, the width of the sheet structure is 3 - 35 nm, the length is 15 - 200 nm, and the thickness is 2 - 25 nm.

[0013] Further, the mesoporous oxide in the middle layer is selected from at least one of mesoporous titanium oxide, mesoporous aluminum oxide, mesoporous silicon oxide, mesoporous tungsten oxide, mesoporous chromium oxide, mesoporous magnesium oxide, mesoporous iron oxide, mesoporous indium oxide, mesoporous cerium oxide, mesoporous cobalt oxide, and combinations thereof.

[0014] Further, the mesoporous oxide is selected from at least one of mesoporous alumina, mesoporous silica, and mesoporous tungsten oxide.

[0015] In a preferred embodiment, the mesoporous oxide is mesoporous alumina.

[0016] Further, the thickness of the intermediate layer ≤ 30 nm.

[0017] Further, the thickness of the intermediate layer is 5 - 20 nm.

[0018] Preferably, the thickness of the intermediate layer is 5 - 10 nm.

[0019] Further, the organic heat storage body on the surface layer is grafted onto the intermediate layer; in the prior art, the organic phase change material is usually intercalated into the inorganic phase through hydrogen bonds, but this force is too small, and there is a risk of loss of the phase change material; in this application, the organic heat storage body is grafted onto the surface of alumina through chemical action, avoiding its loss during endothermic phase change and increasing the heat generation and heat storage stability of the composite powder.

[0020] Further, the organic heat storage body is selected from any one of paraffin, fatty acid, carboxylate, polyol, and polyethylene.

[0021] Preferably, the organic heat storage body is fatty acid.

[0022] Further, the organic heat storage body is a straight-chain fatty acid with 8 - 18 carbon atoms.

[0023] Further, the grafting thickness of the surface layer is 10 - 40 nm; preferably 10 - 20 nm.

[0024] Secondly, the present invention also provides a preparation method of the heat-generating and heat-storing tungsten bronze composite powder.

[0025] Further, the preparation method of the composite powder includes:

[0026] (1) Preparation of tungsten bronze powder: Tungsten bronze powder is prepared by using a metal source, a tungsten source, and tungsten trioxide. x WO 3 Preparation of tungsten bronze powder: Tungsten bronze powder is prepared by using a metal source, a tungsten source, and tungsten trioxide.

[0027] (2) Preparation of mesoporous oxide-coated tungsten bronze powder: A metal salt and a surfactant are dispersed in deionized water to make the metal ion concentration 0.05 - 0.15 mol / L, and then the pH of the solution is adjusted to 8 - 9.5 with ammonia water. This solution is slowly added to the tungsten bronze powder and stirred for a period of time. After suction filtration, washing, drying, and pulverization, a precursor A is obtained. The precursor A is calcined at 300 - 400 °C for 1 - 2 h to obtain the mesoporous oxide-coated tungsten bronze powder.

[0028] (3) Grafting of the surface organic heat storage body: Add the organic heat storage body and the tungsten bronze powder wrapped with mesoporous oxide to freshly distilled tetrahydrofuran and stir for 30 minutes. Under nitrogen protection, add N,N'-dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP), then stir under reflux condensation at 75 °C. After completion, filter and dry.

[0029] The preparation of the tungsten bronze powder in step (1) includes two preparation methods. Method 1: First, mix the required alkali metal source, tungsten source, and tungsten trioxide, and then calcine them under vacuum at a temperature of 400 - 800 °C for 1.5 - 9 h to obtain the required alkali metal tungsten bronze powder.

[0030] Method 2: Add hydrogen peroxide solution to a certain mass of tungsten powder (tungsten source) and tungsten trioxide to dissolve and obtain a sol; then add the salt of M and stir. After drying, obtain the precursor B; grind the precursor B and calcine it at 400 - 800 °C for 1.5 - 9 h to obtain the tungsten bronze powder.

[0031] Further, in step (1), the molar ratio of M to tungsten (W) is 1:2 - 1:100, and the amount of tungsten is the total amount of tungsten in the tungsten source and tungsten trioxide.

[0032] Preferably, in step (1), the molar ratio of M to tungsten (W) is 1:3 - 1:10. This application's research found that: when the amount of cesium increases, the infrared heat storage effect of tungsten bronze also increases. This may be because the doping of cesium ions causes more defects inside and on the surface of the crystal, increasing the carrier content and improving the infrared shielding performance; while when the amount of cesium ions rises to a certain extent, the heat storage effect significantly decreases because when there are too many cesium ions, some cesium ions do not incorporate into the tungsten-oxygen lattice but exist in the form of cesium trioxide, resulting in a decrease in the photoinduced heating performance. Therefore, the doping amount needs to be controlled to improve the heat storage effect.

[0033] Further, in step (2), the mass ratio of the metal salt to the surfactant is 5:1 - 14:1.

[0034] Further, in step (2), the mass ratio of the metal salt to the surfactant is 8:1 - 12:1.

[0035] Further, in step (2), the surfactant is a cationic surfactant or an amphoteric surfactant; preferably an amphoteric surfactant.

[0036] Preferably, in step (2), the surfactant is polyethylene glycol.

[0037] In a preferred embodiment, when PEG400 is selected, the heat generation performance of the material is optimal and the batch stability of the material is also higher. The speculated reason is that PEG400 can bind to the surface of the colloidal particles of aluminum hydroxide, and the extension of the other end in the solution avoids the agglomeration of adjacent colloidal particles. The size and surface distribution of the oxide wrapped in the middle layer are more uniform, improving the uniformity of the prepared composite powder and making its performance more stable.

[0038] Further, in the step (2), the mass ratio of the metal salt to the tungsten bronze powder is (0.5 - 3):1.

[0039] Further, in the step (2), the mass ratio of the metal salt to the tungsten bronze powder is (0.5 - 1.5):1.

[0040] Further, in the step (2), the stirring reaction time is 3 - 8h to control the thickness of the alumina layer. The coating of the alumina layer can promote the diffuse reflection and absorption of infrared light on the material surface. However, when the soaking time of the sol is too long, it is speculated that the coating layer is too thick, shielding the heat generation effect of the core. When the coating layer is too thin, the thermal conductivity of the material is low.

[0041] Further, in the step (3), the mass of the organic heat storage body is 50% - 80% of the tungsten bronze nanoparticles wrapped by the mesoporous oxide.

[0042] Further, in the step (3), the mass of DCC is 1.1 - 1.5 times that of the organic heat storage body.

[0043] Further, in the step (3), the mass of DMAP is 0.1% - 2% of the organic heat storage body.

[0044] Further, in the step (3), the reaction time is 48 - 72h to control the grafting density and thickness of the organic heat storage body, so that the synergistic effect of the three-layer structure is optimal.

[0045] Beneficial effects

[0046] 1. In the present invention, mesoporous alumina is coated on the surface of tungsten bronze powder, which can quickly transfer the heat generated after the tungsten bronze nanoparticles heat up to the surface layer, accelerate the heat generation and heat storage efficiency of the composite powder, and improve the ultraviolet light stability of the tungsten bronze powder; an organic heat storage body is grafted on the surface to further improve the heat generation and heat storage efficiency and solve the loss problem during solid-liquid phase change.

[0047] 2. By controlling the doping amount of metal M in the nano tungsten bronze, the thickness of the middle layer mesoporous oxide, the thickness and grafting amount of the organic heat storage material, the present invention makes the composite powder have excellent heat generation and heat storage effects by utilizing the synergistic performance of the three.

[0048] 3. Through the optimization of the preparation method, the present invention makes the crystal growth of the core layer, the coating of the surface layer and the particle distribution more uniform, enabling the composite powder prepared each time to have a stable heat generation effect. The preparation method has high controllability and repeatability and can achieve industrial production. Detailed Embodiments

[0049] Examples

[0050] Example 1

[0051] This example provides a heat - generating and heat - storing tungsten bronze composite powder. The composite powder has a three - layer coating structure. The core layer is nano - cesium tungsten bronze (Cs 0.2 WO 3 ), the middle layer is mesoporous alumina, and the surface layer is an organic heat - storage body; the Cs 0.2 WO 3 has a nano - sheet structure.

[0052] The preparation method of the transparent heat - generating ceramic powder is as follows:

[0053] (1) Preparation of cesium tungsten bronze powder: First, mix the required alkali metal source (cesium carbonate), tungsten source (tungstic acid), and tungsten trioxide, and then calcine them under vacuum at 600 °C for 5 h. The molar ratio of cesium to tungsten is 1:5.

[0054] (2) Preparation of mesoporous alumina - coated cesium tungsten bronze powder: Disperse aluminum nitrate and PEG400 in deionized water at a mass ratio of 10:1 to make the aluminum ion concentration 0.1 mol / L. Then adjust the pH of the solution to 8.5 with 15 wt.% ammonia water. Slowly drop this solution into the tungsten bronze powder at a mass ratio of aluminum nitrate:tungsten bronze powder of 1:1 and stir for 5 h. After suction filtration, washing, drying, and pulverization, obtain precursor A. Heat precursor A to 350 °C at a heating rate of 5 °C / min and calcine for 1 h to obtain mesoporous oxide - coated tungsten bronze powder.

[0055] (3) Grafting of the surface organic heat - storage body: Add myristic acid and mesoporous oxide - coated tungsten bronze powder to redistilled tetrahydrofuran and stir for 30 minutes. Under nitrogen protection, add N,N'-dicyclohexylcarbodiimide (DCC) (the mass of DCC is 1.3 times the mass of myristic acid) and 4 - dimethylaminopyridine (DMAP) (the mass of DMAP is 1% of the mass of myristic acid), and stir under reflux condensation at 75 °C for 60 h. After completion, filter and dry; the mass of myristic acid is 65% of the mass of mesoporous alumina - coated cesium tungsten bronze powder.

[0056] Example 2

[0057] This example provides a heat - generating and heat - storing tungsten bronze composite powder. The composite powder has a three - layer coating structure. The core layer is nano - cesium tungsten bronze (Cs0.33 WO 3 )), the middle layer is mesoporous alumina, and the surface layer is an organic heat storage material; the Cs 0.33 WO 3 is in a nano-sheet structure;

[0058] The preparation method of the transparent heat-generating ceramic powder is as follows:

[0059] (1) Preparation of cesium tungsten bronze powder: First, mix the required alkali metal source (cesium carbonate), tungsten source (tungstic acid), and tungsten trioxide, and then calcine them in a vacuum at 800 °C for 1.5 h. The molar ratio of cesium to tungsten is 1:3.

[0060] (2) Preparation of mesoporous alumina-coated cesium tungsten bronze powder: Disperse aluminum nitrate and PEG400 in deionized water at a mass ratio of 12:1 to make the aluminum ion concentration 0.05 mol / L. Then adjust the pH of the solution to 9.5 with 15 wt.% ammonia water. Slowly drop this solution into the tungsten bronze powder at a mass ratio of aluminum nitrate:tungsten bronze powder of 0.5:1 and stir for 8 h. After suction filtration, washing, drying, and pulverization, the precursor A is obtained. Heat the precursor A to 300 °C at a heating rate of 5 °C / min and calcine for 2 h to obtain the mesoporous oxide-coated tungsten bronze powder.

[0061] (3) Grafting of the surface organic heat storage material: Add myristic acid and mesoporous oxide-coated tungsten bronze powder to redistilled tetrahydrofuran and stir for 30 minutes. Under nitrogen protection, add N,N'-dicyclohexylcarbodiimide (DCC) (the mass of DCC is 1.1 times the mass of myristic acid) and 4-dimethylaminopyridine (DMAP) (the mass of DMAP is 2% of the mass of myristic acid), and stir under reflux at 75 °C for 72 h. After completion, filter and dry; the mass of myristic acid is 80% of the mass of mesoporous alumina-coated cesium tungsten bronze powder.

[0062] Example 3

[0063] This example provides a heat-generating and heat-storing tungsten bronze composite powder. The composite powder has a three-layer coating structure. The core layer is nano-cesium tungsten bronze (Cs 0.1 WO 3 ), the middle layer is mesoporous alumina, and the surface layer is an organic heat storage material; the Cs 0.1 WO 3 is in a nano-sheet structure;

[0064] The preparation method of the transparent heat-generating ceramic powder is as follows:

[0065] (1) Preparation of cesium tungsten bronze powder: First, mix the required alkali metal source (cesium carbonate), tungsten source (tungstic acid), and tungsten trioxide, and then calcine them in a vacuum at 400 °C for 9 h. The molar ratio of cesium to tungsten is 1:10.

[0066] (2) Preparation of mesoporous alumina-coated cesium tungsten bronze powder: Aluminum nitrate and PEG400 were dispersed in deionized water at a mass ratio of 8:1 to make the aluminum ion concentration 0.15 mol / L. Then, the pH of the solution was adjusted to 8 with 15 wt.% ammonia water. This solution was slowly dropped into the tungsten bronze powder at a mass ratio of aluminum nitrate:tungsten bronze powder of 1.5:1 and stirred for 3 h. After suction filtration, washing, drying, and pulverization, precursor A was obtained. Precursor A was heated to 400 °C at a heating rate of 10 °C / min and calcined for 1 h to obtain the mesoporous oxide-coated tungsten bronze powder.

[0067] (3) Grafting of the surface organic heat storage body: Myristic acid and the mesoporous oxide-coated tungsten bronze powder were added to redistilled tetrahydrofuran and stirred for 30 minutes. Under nitrogen protection, N,N'-dicyclohexylcarbodiimide (DCC) (the mass of DCC was 1.5 times the mass of myristic acid) and 4-dimethylaminopyridine (DMAP) (the mass of DMAP was 0.1% of the mass of myristic acid) were added, and the mixture was stirred under reflux at 75 °C for 48 h. After completion, it was filtered and dried; the mass of myristic acid was 50% of the mass of the mesoporous alumina-coated cesium tungsten bronze powder.

[0068] Example 4

[0069] Basically the same as Example 1, the difference is that in step (1), the molar ratio of M to tungsten is 1:1.

[0070] Example 5

[0071] Basically the same as Example 1, the difference is that in step (1), the M element is silver.

[0072] Example 6

[0073] Basically the same as Example 1, the difference is that the mass ratio of aluminum nitrate to PEG400 is 5:1.

[0074] Example 7

[0075] Basically the same as Example 1, the difference is that the mass ratio of aluminum nitrate to PEG400 is 14:1.

[0076] Example 8

[0077] Basically the same as Example 1, the difference is that in step (2), the stirring reaction time is 10 h.

[0078] Example 9

[0079] Basically the same as Example 1, the difference is that in step (2), the calcination temperature is 500 °C.

[0080] Example 10

[0081] It is basically the same as Example 1, except that: in the step (3), the mass of myristic acid is 25% of the mesoporous alumina-coated cesium tungsten bronze powder.

[0082] Example 11

[0083] It is basically the same as Example 1, except that: in the step (3), the mass of myristic acid is 100% of the mesoporous alumina-coated cesium tungsten bronze powder.

[0084] Example 12

[0085] It is basically the same as Example 1, except that: in the step (2), the amphoteric surfactant is sodium dodecyl sulfonate.

[0086] Example 13

[0087] It is basically the same as Example 1, except that: in the step (2), the mass ratio of aluminum nitrate to tungsten bronze powder is 3:1.

[0088] Example 14

[0089] It is basically the same as Example 1, except that: in the step (2), the metal salt is chromium nitrate.

[0090] Comparative Example 1

[0091] It is basically the same as Example 1, except that: in the step (2), no surfactant is added.

[0092] Comparative Example 2

[0093] It is basically the same as Example 1, except that: the step (3) is: mixing myristic acid and mesoporous oxide-coated tungsten bronze powder and stirring evenly, then drying; wherein the mass of myristic acid is 65% of the mesoporous alumina-coated cesium tungsten bronze powder.

[0094] Comparative Example 3

[0095] It is basically the same as Example 1, except that: step (3) is not carried out, and the prepared product is mesoporous oxide-coated tungsten bronze powder.

[0096] Comparative Example 4

[0097] This comparative example is basically the same as Example 1, except that: in the step (2), the aluminum ion concentration is 0.01 mol / L.

[0098] Comparative Example 5

[0099] This comparative example is basically the same as Example 1, except that: in the step (2), the aluminum ion concentration is 0.3 mol / L.

[0100] Performance testing method:

[0101] 1. Infrared absorption rate: Measure the near-infrared absorption rate of the material using a U-4100 ultraviolet-visible spectrophotometer produced by Hitachi, Japan;

[0102] 2. Material repeatability: Take 3 samples of the material in each example to measure the infrared absorption rate, and use the relative standard deviation RSD of 3 measurements to measure the material repeatability;

[0103] 3. Heat storage capacity: Use a Mettler Toledo DSC3+ differential scanning calorimeter to test the phase change enthalpy value of the material during the heating process from 25°C to 200°C;

[0104] 4. Material stability: Heat cycle the material in the examples 1000 times at 200°C, and use an inspection scanner to observe its heat storage density retention rate;

[0105] 5. Material dispersibility: Mix the material in the examples with PET chips at a mass ratio of 1:19 and melt-extrude them at 280°C to obtain a heat-generating and heat-storing PET masterbatch. Use a FCC-3 type filtration performance tester from Linzi Fangchen Masterbatch Factory in Zibo City, and use a 1400-mesh filter screen to test the pressure filtration value (MPa) of the masterbatch;

[0106] 6. Heat-generating and heat-storing effect of the material: Use a YZYP-20T type film press produced by Yizong Machinery Equipment Co., Ltd. to make the above PET masterbatch into a 0.2-mm film. Use a 150-W infrared lamp to irradiate the film, and use an infrared thermometer gun to record the surface temperature of the film after 2 minutes of irradiation and the surface temperature of the film 1 minute after removing the light source, and record them in Table 2.

[0107] Performance test results:

[0108] Table 1

[0109]

[0110] Table 2

[0111]

[0112]

[0113] Analysis of the above data shows that:

[0114] The heat-generating and heat-storing tungsten bronze composite powders prepared in Examples 1-3 have high infrared absorption ability, good stability, good dispersibility, and good heat-generating and heat-storing effects. Among them, in Example 3, due to the relatively low grafting amount of the surface organic heat storage body, the phase change enthalpy value of the composite powder prepared in Example 3 is relatively low.

[0115] By comparing Example 1 with Example 4, it can be seen that the amount of cesium added will affect the infrared absorption of the composite powder by affecting the crystal structure and surface roughness of the tungsten bronze powder. When the cesium content is too high, part of the cesium exists in the form of cesium oxide, resulting in a decrease in infrared absorption capacity.

[0116] Comparing Example 1 with Example 5, it can be seen that the radius of the cesium ion is slightly larger than the radius of the hexagonal channel in the tungsten oxide octahedron. When lattice distortion occurs, the doping efficiency of the cesium ion in the tungsten oxide octahedron is higher and more stable, which increases the stability of the material, and due to the increase in surface defects, the infrared absorption capacity can be greatly improved. In Example 5, silver is selected as the doping element of tungsten bronze because the radius of the silver ion is small, resulting in fewer surface defects of the doped tungsten bronze, which in turn leads to a decrease in infrared absorption rate.

[0117] By comparing Example 1 with Examples 6-7, it can be seen that the surfactant will seriously affect the distribution and crystal growth of the middle layer of aluminum oxide. When the amount of surfactant is too much and the particle size of the colloidal particles in the water is too small, it may cause incomplete or insufficient coating of some tungsten bronze, affecting its surface grafting effect and material stability, and further affecting the heat storage effect of the material; when the surfactant content is insufficient, the internal aluminum hydroxide may agglomerate, and the crystal particle size and distribution after calcination are uneven, which not only affects the heating effect of the tungsten bronze powder, but also may affect the grafting and stability of the surface organic heat storage body.

[0118] By comparing Example 1 with Example 8, it can be seen that when the stirring reaction time of aluminum hydroxide and tungsten bronze powder is too long, the thickness of the middle layer of aluminum oxide is too high, resulting in a reduction in the heating effect.

[0119] By comparing Example 1 with Example 9, it can be seen that when the calcination temperature of aluminum hydroxide is too high, the mesoporous structure formed therein may collapse or deform, thereby affecting the infrared absorption rate of the composite powder, and reducing the surface hydroxyl content, affecting the grafting rate of the organic heat storage body, resulting in a decrease in the heat generation and heat storage capacity.

[0120] Comparing Example 1 with Examples 10-11, it can be seen that when the organic heat storage body is not enough, the heat storage effect is not improved much, and the compatibility with the polymer resin is poor, resulting in poor dispersibility. When it is too thick, it affects the infrared absorption capacity of the core layer, and the hydroxyl groups on the surface of aluminum oxide are limited, so part of the organic heat storage body cannot be grafted on the surface of the intermediate layer, resulting in loss after thermal cycling and reduced thermal stability.

[0121] Comparing Comparative Example 1 with Example 12, it can be seen that when sodium dodecyl sulfate is selected as the surfactant, the infrared absorption ability, stability, dispersibility, and heat generation and heat storage effects of the material all decrease to varying degrees. The reason is speculated as follows: Compared with PEG400, the binding force between sodium dodecyl sulfate and the surface of the colloidal particles of aluminum hydroxide is weak, resulting in the aggregation of colloidal particles in the solution, leading to poor size and surface distribution uniformity of the oxides wrapped in the intermediate layer, and then affecting the uniformity of the composite powder prepared, and ultimately resulting in a decline in performance.

[0122] Comparing Example 1 with Example 13, it can be seen that too high a content of aluminum nitrate easily leads to too thick a mesoporous alumina layer in the material, affecting the infrared absorption effect and then the heat generation and heat storage effects.

[0123] Comparing Example 1 with Example 14, it can be seen that the mesoporous alumina layer has excellent thermal conductivity, so it can accelerate the heat generation efficiency of the material.

[0124] Comparing Example 1 with Comparative Example 1, it can be seen that no surfactant is added in step (2), resulting in serious aggregation of colloidal particles in the solution, leading to a significant decrease in the infrared absorption ability and stability of the material, and a decrease in the grafting rate of the organic heat storage body, and then affecting the heat generation and heat storage effects and dispersibility of the material.

[0125] Comparing Example 1 with Comparative Example 2, it can be seen that grafting the organic heat storage body onto the surface of alumina through chemical action can avoid its loss during the endothermic phase change, increasing the heat generation and heat storage stability and dispersibility of the composite powder.

[0126] Comparing Example 1 with Comparative Example 3, it can be seen that grafting the organic heat storage body onto the surface of the heat-generating powder coated with mesoporous tungsten oxide can enhance the heat storage performance and dispersibility of the composite powder.

[0127] Comparing Example 1 with Comparative Examples 4-5, it can be seen that an appropriate aluminum ion concentration is beneficial to the crystal growth of the core layer, so that the coating of the surface layer and the particle distribution are more uniform, enabling the composite powder prepared each time to have a stable heat generation effect, and the preparation method has high controllability and repeatability.

Claims

1. Preparation method of heat-generating and heat-storing tungsten bronze composite powder Characterized in that The composite powder has a three-layer coating structure, with the core layer being nano tungsten bronze M x WO 3 , the middle layer being a mesoporous oxide, and the surface layer being an organic heat storage material. The preparation method includes: Step (1) M x WO 3 Preparation of tungsten bronze powder: Tungsten bronze powder is prepared using a metal source, a tungsten source, and tungsten trioxide; Step (2) Preparation of mesoporous oxide-coated tungsten bronze powder: Disperse metal salt and surfactant in deionized water to make the metal ion concentration 0.05 - 0.15 mol / L, then adjust the pH of the solution to 8 - 9.5 with ammonia water. Slowly add this solution to tungsten bronze powder and stir for a period of time. After suction filtration, washing, drying and pulverization, obtain precursor A. Calcinate precursor A at 300 - 400 °C for 1 - 2 h to obtain mesoporous oxide-coated tungsten bronze powder; Step (3) Grafting of surface organic heat storage body: Add organic heat storage body and mesoporous oxide-coated tungsten bronze powder to redistilled tetrahydrofuran and stir for 30 minutes. Under nitrogen protection, add N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine, and stir under reflux condensation at 75 °C. After completion, filter and dry.

2. The preparation method of tungsten bronze composite powder according to claim 1 Characterized in that In the said step (1), the molar ratio of M to tungsten is 1:2 - 1:100, and the amount of substance of tungsten is the total amount of tungsten in tungsten source and tungsten trioxide.

3. The preparation method of tungsten bronze composite powder according to claim 1 Characterized in that The surfactant in the said step (2) is polyethylene glycol.

4. The preparation method of tungsten bronze composite powder according to claim 3 Characterized in that In the said step (2), the mass ratio of metal salt to tungsten bronze powder is (0.5 - 3):1, and the stirring reaction time is 3 - 8 h.

5. The preparation method of tungsten bronze composite powder according to claim 4 Characterized in that In the said step (3), the mass of the organic heat storage body is 50 - 80% of the mesoporous oxide-coated tungsten bronze nano powder.

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