A method for preparing near-room temperature vanadium-based nano phase change material

Abstract

The present application relates to the technical field of nanomaterials, and specifically discloses a method for preparing a near-room-temperature vanadium-based nano phase change material. The method includes the steps of pretreatment, grinding, coating treatment and post-treatment, using vanadium pentoxide as a vanadium source, adding tungsten dopants and tin dopants, and coordinating silane coupling agents as dispersants, and adopting wet grinding to obtain a ground wet powder; then the surface of the ground wet powder is coated with a silica gel shell material, and then annealing treatment is performed at 300-720°C to obtain a near-room-temperature vanadium-based nano phase change material. The method of the present application is simple, suitable for large-scale production, and does not require high temperature and high pressure control. The phase change temperature of the obtained near-room-temperature vanadium-based nano phase change material is 25±3°C, and it has excellent stability, high visible light transmittance, and excellent sunlight regulation ability.

Description

Technical Field

[0001] The present application relates to the technical field of nanomaterials, and more specifically, to a method for preparing a near-room temperature vanadium-based nano phase-change material. Background Art

[0002] Thermochromic energy-saving glass is a smart material that can automatically adjust light transmittance according to the temperature difference between indoor and outdoor. Thermochromic materials include vanadium dioxide (M phase), perovskite, etc. Among them, VO2 has a phase transition temperature close to room temperature and is currently a research hotspot in the industry.

[0003] VO2 undergoes a reversible phase transition at the phase transition temperature, changing from a monoclinic structure to a tetragonal rutile structure; below the phase transition temperature, VO2 is in a semiconductor state, infrared rays can pass through; above the phase transition temperature, VO2 is in a metallic state, infrared rays are reflected. However, VO2 is difficult to be used in thermochromic energy-saving glass for the following reasons: the VO2 phase transition temperature is close to 68°C, while the optimal phase transition temperature of thermochromic energy-saving glass should be 25±3°C, which is too high.

[0004] In the related art, the preparation methods of VO2 include magnetron sputtering, pulsed laser deposition, hydrothermal method, sol-gel method, chemical vapor deposition method and ball milling method. In the hydrothermal method, vanadium pentoxide and ammonium vanadate are used as sources of vanadium, oxalic acid and hydrazine hydrate are used as reducing agents, stannic acid and stannates, tungstic acid and tungstates are used as dopants, and water is used as the reaction raw material and solvent. Under high pressure conditions, the reaction raw materials are dissolved in water to promote the reaction in the gas phase or liquid phase. Although the nanomaterials synthesized by the hydrothermal method have high purity and well-developed grains, the actual production process requires a high temperature and high pressure environment, and the reaction time is long, and industrial production is difficult.

[0005] The ball milling method uses the rotation or vibration of the ball mill to make the hard balls strongly impact, grind and stir the raw materials, and crush the metal powder into particles. In the related technology, CN112456555A uses vanadium pentoxide as the vanadium source, lactose and glucose as reducing agents, and tungstic acid and its salts as dopants to obtain tungsten-doped vanadium dioxide powder by ball milling. However, the strong impact of the grinding ball causes the VO2 powder to easily agglomerate, and the phase transition temperature of the nanopowder in actual use is 35±3℃, which is difficult to meet the use requirements close to room temperature.

[0006] Based on the above situation, the industry needs to develop a preparation method so that the phase change temperature of the prepared vanadium-based nano phase change material can reach the range of 25±3°C and the production method is simple. Summary of the invention

[0007] In response to the above-mentioned related issues, the present application provides a method for preparing a near-room temperature vanadium-based nano phase change material. The method is simple, and the phase change temperature of the prepared material is close to room temperature, with excellent stability, visible light transmittance and sunlight modulation capability.

[0008] In a first aspect, the present application provides a method for preparing a near-room temperature vanadium-based nano phase change material, using the following technical solution:

[0009] A method for preparing a near-room temperature vanadium-based nano phase-change material comprises the following steps:

[0010] Pretreatment: mixing a water-soluble reducing agent with water to obtain a reducing solution;

[0011] Grinding: vanadium pentoxide, tin dopant, tungsten dopant, silane coupling agent and reducing solution are mixed, and ball milled for 1 to 12 hours at a rotation speed of 1500 to 1800 r / min and a ball-to-material ratio of 1:(1.5 to 3) to obtain a ground wet powder, wherein the molar ratio of vanadium, tin and tungsten is (96 to 98):(0.5 to 2):(1.5 to 2), and the molar ratio of vanadium pentoxide, water-soluble reducing agent and silane coupling agent is 1:(0.1 to 0.3):(0.002 to 0.005);

[0012] Coating treatment: grind the wet powder and disperse it in an ethanol solution, adjust the pH value of the system to 9-10, drop a silicon source, and the molar ratio of the silicon source to the silane coupling agent is (2-4):1, heat to 50-70°C, stir and disperse, and after the reaction is completed, centrifuge and wash to obtain a core-shell structured phase change precursor;

[0013] Post-treatment: The core-shell structured phase change precursor is annealed at 300-720°C to obtain a near-room temperature vanadium-based nano phase change material.

[0014] Furthermore, the water-soluble reducing agent is one or more of glucose, lactose and oxalic acid.

[0015] Furthermore, the tin dopant is stannous sulfate and / or tin oxide.

[0016] Furthermore, the tungsten dopant is one or more of tungsten oxide, tungstic acid, sodium tungstate and ammonium tungstate.

[0017] Furthermore, the silane coupling agent is an aminosilane coupling agent.

[0018] Furthermore, in the grinding step, the ball milling parameters are: rotation speed 1600r / min, ball-to-material ratio 1:2.5, and ball milling for 3h.

[0019] Furthermore, in the grinding step, the molar ratio of vanadium, tin and tungsten is 98:0.5:1.5, and the molar ratio of vanadium pentoxide, water-soluble reducing agent and silane coupling agent is 1:0.2:0.0025.

[0020] Furthermore, in the coating treatment step, the silicon source is ethyl orthosilicate, methyl orthosilicate and propyl orthosilicate.

[0021] Furthermore, in the coating treatment step, the molar ratio of the silicon source to the silane coupling agent is 3:1, the temperature is raised to 60° C., and the mixture is stirred and dispersed at a speed of 200 r / min. After the reaction is kept warm for 1±0.5 h, centrifugal separation is performed.

[0022] Furthermore, in the post-treatment step, annealing is performed at 600° C. for 1 hour.

[0023] This application has at least the following advantages:

[0024] First, the present invention uses vanadium pentoxide as a vanadium source, adds tungsten dopants and tin dopants, and adopts wet grinding. A silane coupling agent is used as a dispersant to promote the dispersion of vanadium pentoxide, tungsten dopants and tin dopants during the grinding process, and the grinding parameters are matched to control the average particle size of the ground wet powder within the range of 20 to 50 nm; a water-soluble reducing agent is pre-dissolved in water to form a uniform solution. During the wet grinding process, the reducing agent can fully contact vanadium pentoxide, tungsten dopants and tin dopants, so that tin and tungsten are co-doped in the M phase VO2; tungsten is W 6+ Tin exists in the form of Sn 4+ The two elements co-doping enables the vanadium-based phase change nanomaterials to significantly reduce the phase change temperature at a lower atomic percentage, and the phase change temperature is controlled at around 25°C.

[0025] Second, the silane coupling agent acts as a dispersant in the coating process and can also act as a partial silicon source, fully covering the surface of the ground wet powder and forming a silica gel shell in combination with the silicon source. There are a small number of holes on the surface of the silica gel shell material, which can facilitate the escape of thermal decomposition gases during annealing and partially block oxygen, reducing the possibility of oxidation failure of the M-phase VO2, making the core-shell structure phase change precursor have better stability.

[0026] Third, the parameters of the coating step are controlled, and the thickness of the silica gel shell material is moderate. Under the premise of ensuring good coating of the ground wet powder, the thickness of the silica gel shell material does not affect the phase change temperature of the vanadium-based phase change nanomaterial. At the same time, after the vanadium-based phase change nanomaterial is coated, due to the barrier effect of the silica gel shell material, the M-phase VO2 is not easy to agglomerate during the annealing process, and the size of the vanadium-based phase change nanomaterial is maintained at a size level of about 50nm, which has little effect on the optical properties of the vanadium-based phase change nanomaterial itself, and the visible light transmittance is maintained at a high level.

[0027] Fourth, annealing treatment can effectively increase the ball milling doping rate, which helps to further reduce the phase change temperature of vanadium-based phase change nanomaterials, thereby controlling the doping rates of tungsten and tin within a moderate range, and ensuring that the phase change temperature of vanadium-based phase change nanomaterials is within the room temperature range. Under the premise, the crystallinity and lattice distortion have little effect on the optical properties of vanadium-based phase change nanomaterials, and the visible light transmittance is improved.

[0028] Fifth, optimize various parameters during grinding, coating and annealing treatments so that the core size range of the final near-room temperature vanadium-based nanophase change material is maintained within a certain range, and the thickness of the silica gel shell material is small, balancing the lowering of the phase change temperature and the improvement of the stability of the vanadium-based phase change nanomaterial. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the technical solutions of the present application are further described below in conjunction with embodiments and comparative examples.

[0030] Unless otherwise specified, the raw materials in the following examples and comparative examples are all analytically pure.

[0031] Example 1

[0032] A near-room-temperature vanadium-based nano phase-change material is prepared according to the following steps:

[0033] Preprocessing:

[0034] Weigh 0.3 mol of glucose and add it to 180 mL of deionized water to prepare a reducing glucose solution for later use;

[0035] Grinding: weigh 1 mol of vanadium pentoxide, 0.0417 mol of tin oxide, 0.0417 mol of tungsten oxide, 0.005 mol of silane coupling agent propyltriethoxysilane (LA-331) and reducing glucose solution, and add the reducing glucose solution, silane coupling agent, vanadium pentoxide, stannous sulfate and tungstic acid into a planetary grinder in sequence;

[0036] The rotation speed of the grinder was adjusted to 1500 r / min, the ball-to-material ratio was 1:3, and the ball milling time was 1 h to obtain a ground wet powder;

[0037] Coating treatment: grind the wet powder and add it to an ethanol-water solution with a concentration of 10wt%, add ammonia water to adjust the pH value of the system to the range of 9 to 10, add 0.01mol of ethyl orthosilicate, and stir and disperse at a speed of 200r / min while adding. After the addition, the system is heated to 50°C and kept warm for 1h. After the reaction, centrifuge and wash three times with anhydrous ethanol and deionized water in turn, and filter to obtain a core-shell structure phase change precursor;

[0038] Post-treatment: The core-shell structured phase change precursor is sent to a calcining furnace for annealing. The annealing temperature is controlled at 300°C and the annealing time is 1 hour to obtain a near-room temperature vanadium-based nano phase change material.

[0039] Example 2

[0040] A near-room-temperature vanadium-based nano phase-change material is prepared according to the following steps:

[0041] Preprocessing:

[0042] Weigh 0.1 mol of glucose and add it to 120 mL of deionized water to prepare a reducing glucose solution for later use;

[0043] Grinding: weigh 1 mol of vanadium pentoxide, 0.0206 mol of stannous sulfate, 0.0412 mol of tungstic acid, 0.002 mol of silane coupling agent propyltriethoxysilane (LA-331) and reducing glucose solution, and add the reducing glucose solution, silane coupling agent, vanadium pentoxide, stannous sulfate and tungstic acid into a planetary grinder in sequence;

[0044] The rotation speed of the grinder was adjusted to 1500 r / min, the ball-to-material ratio was 1:3, and the ball milling time was 1 h to obtain a ground wet powder;

[0045] Coating treatment: grind the wet powder and add it to an ethanol-water solution with a concentration of 10wt%, add ammonia water to adjust the pH value of the system to the range of 9 to 10, add 0.004mol of ethyl orthosilicate, and stir and disperse at a speed of 200r / min while adding. After the addition is completed, the system is heated to 50°C and kept warm for 1h. After the reaction is completed, centrifuge and wash three times with anhydrous ethanol and deionized water in turn, and filter to obtain a core-shell structure phase change precursor;

[0046] Post-treatment: The core-shell structured phase change precursor is sent to a calcining furnace for annealing. The annealing temperature is controlled at 300°C and the annealing time is 1 hour to obtain a near-room temperature vanadium-based nano phase change material.

[0047] Example 3

[0048] A near-room-temperature vanadium-based nano phase-change material is prepared according to the following steps:

[0049] Preprocessing:

[0050] Weigh 0.2 mol of glucose and add it to 60 mL of deionized water to prepare a reducing glucose solution for later use;

[0051] Grinding: weigh 1 mol of vanadium pentoxide, 0.0102 mol of tin oxide, 0.0306 mol of ammonium tungstate, 0.0025 mol of silane coupling agent propyltriethoxysilane (LA-331) and reducing glucose solution, and add the reducing glucose solution, silane coupling agent, vanadium pentoxide, stannous sulfate and tungstic acid into a planetary grinder in sequence;

[0052] The rotation speed of the grinder was adjusted to 1500 r / min, the ball-to-material ratio was 1:3, and the ball milling time was 1 h to obtain a ground wet powder;

[0053] Coating treatment: grind the wet powder and add it to an ethanol-water solution with a concentration of 10wt%, add ammonia water to adjust the pH value of the system to the range of 9-10, add 0.005mol of ethyl orthosilicate, and stir and disperse at a speed of 200r / min while adding. After the addition, the system is heated to 50°C and kept warm for 1h. After the reaction, centrifuge and wash three times with anhydrous ethanol and deionized water in turn, and filter to obtain a core-shell structure phase change precursor;

[0054] Post-treatment: The core-shell structured phase change precursor is sent to a calcining furnace for annealing. The annealing temperature is controlled at 300°C and the annealing time is 1 hour to obtain a near-room temperature vanadium-based nano phase change material.

[0055] Embodiment 4-5

[0056] A near-room temperature vanadium-based nano phase change material, which differs from Example 3 in that: in the grinding process step, the grinding parameters of the planetary grinder are different, specifically:

[0057] In Example 4, the rotation speed of the grinder was adjusted to 1800 r / min, the ball-to-material ratio was 1:1.5, and the ball milling time was 12 h to obtain a ground wet powder;

[0058] In Example 5, the rotation speed of the grinder was adjusted to 1600 r / min, the ball-to-material ratio was 1:2.5, and the ball milling time was 3 h to obtain a ground wet powder.

[0059] Example 6

[0060] A near-room temperature vanadium-based nano phase-change material, which differs from Example 5 in that an equimolar amount of aminosilane coupling agent KH-550 is used instead of LA-331.

[0061] Embodiment 7-8

[0062] A near-room temperature vanadium-based nano phase change material, which differs from Example 5 in that the parameters of the coating treatment step are different, as follows:

[0063] In Example 7, 0.01 mol of ethyl orthosilicate was added dropwise, and the mixture was stirred and dispersed at a speed of 200 r / min. After the addition was completed, the system was heated to 70° C. and kept warm for 1.5 hours. After the reaction was completed, the mixture was centrifuged, washed three times with anhydrous ethanol and deionized water in sequence, and filtered to obtain a phase change precursor with a core-shell structure;

[0064] In Example 8, 0.0075 mol of ethyl orthosilicate was added dropwise, and the mixture was stirred and dispersed at a speed of 200 r / min. After the addition was completed, the system was heated to 60°C and kept warm for 0.5 h. After the reaction was completed, centrifugation was performed, and the mixture was washed three times with anhydrous ethanol and deionized water in sequence, and filtered to obtain a core-shell structured phase change precursor.

[0065] Examples 9-10

[0066] A near-room temperature vanadium-based nano phase change material, which differs from Example 8 in that: in the post-treatment step, the annealing parameters are different, specifically:

[0067] In Example 9, the annealing temperature is controlled at 720° C. and the annealing time is 1 h, thereby obtaining a near-room temperature vanadium-based nano phase change material;

[0068] In Example 10, the annealing temperature is controlled at 600° C. and the annealing time is 1 h, thereby obtaining a near-room temperature vanadium-based nano phase change material.

[0069] Comparative Example 1

[0070] A vanadium-based nano phase-change material, which differs from Example 1 in that an equal molar amount of tungstic acid is used instead of stannous sulfate.

[0071] Comparative Example 2

[0072] A vanadium-based nano phase-change material, which differs from Example 1 in that an equal molar amount of stannous sulfate is used instead of tungstic acid.

[0073] Comparative Example 3

[0074] A vanadium-based nano phase-change material, which differs from Example 1 in that: there is no coating treatment step, and after grinding, it is directly sent to a calcining furnace for annealing treatment.

[0075] Comparative Example 4

[0076] A vanadium-based nano phase-change material is different from Example 1 in that: there is no annealing step, and after the coating step, the core-shell structured phase-change precursor is sent to a drying box for drying to obtain the vanadium-based nano phase-change material.

[0077] Comparative Examples 5-6

[0078] A vanadium-based nano phase change material, which differs from Example 1 in that: in the post-processing step, the annealing parameters are different, specifically:

[0079] In Comparative Example 5, the annealing temperature was controlled at 200° C. and the annealing time was 1 h to obtain a vanadium-based nano phase change material;

[0080] In Comparative Example 6, the annealing temperature was controlled at 900° C. and the annealing time was 1 h to obtain a vanadium-based nano phase change material.

[0081] Comparative Examples 7-8

[0082] A vanadium-based nano phase change material, which is different from Example 1 in that: in the grinding process step, the grinding parameters of the planetary grinder are different, specifically:

[0083] In Comparative Example 7, the rotation speed of the grinder was adjusted to 1000 r / min, the ball-to-material ratio was 1:4, and the ball milling time was 1.5 h to obtain a ground wet powder;

[0084] In Comparative Example 8, the rotation speed of the grinder was adjusted to 2000 r / min, the ball-to-material ratio was 1:1, and the ball milling time was 1.5 h to obtain a ground wet powder.

[0085] Comparative Example 9

[0086] A vanadium-based nano phase-change material, which differs from Example 1 in that no water is added, and a reducing agent is added together with vanadium pentoxide.

[0087] Comparative Example 10

[0088] A vanadium-based nano phase change material, which is different from Example 1 in that an equimolar amount of activated carbon is used to replace glucose.

[0089] Comparative Example 11

[0090] A vanadium-based nano phase change material, which differs from Example 1 in that an equimolar amount of liquid glucose is used instead of a reducing glucose solution.

[0091] Comparative Example 12

[0092] A vanadium-based nano phase-change material, which is different from Example 1 in that no silane coupling agent is used.

[0093] Performance Testing

[0094] The phase change materials prepared in Examples 1-10 and Comparative Examples 1-12 were made into a phase change film with a thickness of 1 μm by a coating film forming process. The amount of the phase change material added in the phase change film was 10 wt %. The film was used as a test sample and the following tests were performed:

[0095] Phase change temperature detection: According to ISO11357-1, the scanning curve is drawn by differential scanning calorimetry, and the phase change temperature T1 is recorded in °C;

[0096] Stability test: Place the test sample in a salt spray test chamber, and perform high and low temperature cycles at a rate of 1°C / min in an environment of -10°C to 60°C and a relative humidity of 80%. The cycle time is 240 hours. Take out the sample after 240 hours and record the phase change temperature T2, unit: °C; phase change temperature change rate = (T2-T1) / T1×100%;

[0097] Average transmittance in the visible light band T lum and solar transmittance T sol :Use the international standard ISO9050:2003(E) to digitize the optical transmittance spectrum and record the average transmittance T in the visible light band at 20℃ and 50℃ lum and solar transmittance T sol ; Follow the following formula:

[0098] Formula 1:

[0099] ;

[0100] Formula 2:

[0101] ;

[0102] The meanings of the parameters in formula 1 are as follows: τ represents the wavelength range. The wavelength range corresponding to τ in this formula is 380-780nm, which is the visible light band; therefore, T lum (τ) represents the average transmittance in the visible light band; λ represents the wavelength, ψ represents the standard luminous efficiency function of human vision; T(λ) represents the optical transmittance at wavelength λ;

[0103] The meanings of the parameters in Formula 2 are as follows: τ represents the wavelength range. The wavelength range corresponding to τ in this formula is 250-2500nm, which is the sunlight wavelength range; T sol (τ) represents the solar energy transmittance over the entire area; λ represents the wavelength, ψ sol It represents the radiation spectrum of sunlight corresponding to the atmospheric mass of 1.5; T(λ,τ) refers to the optical transmittance at the wavelength of solar energy λ.

[0104] Solar light modulation capability ΔT so =Tsol-20 -T sol-50 , unit: %,ΔT so The larger the difference, the stronger the sunlight modulation ability.

[0105] Test results

[0106] Table 1. Test results of Examples 1-10

[0107]

[0108] Table 2. Test results of comparative examples 1-12

[0109]

[0110] Combining Example 1 and Comparative Examples 1-2 and Table 1-2, it can be seen that the same molar amount of W is added in Comparative Example 1. According to the phase change data, it can be seen that the phase change temperature can be reduced by single doping with W, but the reduction in the phase change temperature is smaller than that in Example 1, and the phase change temperature still exceeds the range of 25±3°C. It can be seen that the single doping with tungsten needs to increase the doping ratio to further reduce the temperature; and at this doping ratio, although the solar light modulation ability of the phase change material obtained in Comparative Example 1 is slightly high, the visible light transmittance is too low and the optical performance is poor. In Comparative Example 2, the same molar amount of Sn is added. According to the phase change data, it can be seen that the single doping with Sn has little effect on the reduction of the phase change temperature, and the phase change temperature is much higher than room temperature. Therefore, within the range of 20-50°C, the solar light modulation ability is 0. By adopting wet grinding, W and Sn are co-doped, and the phase change temperature of the obtained phase change material is significantly reduced to the room temperature range; at the same time, the average transmittance in the visible light band reaches more than 55%, and the solar light modulation ability is increased to 3.62%.

[0111] Combining Example 1 and Comparative Example 3 and Table 1-2, it can be seen that in Comparative Example 3, no silicon dioxide shell coating is used, and the phase change temperature of the obtained phase change material is not much different from that of the phase change material in Example 1, but after aging test, the phase change temperature is significantly increased. The reason is that: without the external shell protection, VO2 is oxidized and the phase change temperature is significantly increased; at the same time, due to the lack of shell protection, the phase change material partially agglomerates during the annealing process, resulting in the final phase change material being larger in size and the visible light transmittance being significantly reduced.

[0112] Combining Example 1 and Comparative Examples 4-6 with Tables 1-2, it can be seen that in Comparative Example 4, no annealing treatment is used, the ball milling doping rate is extremely low, and there is almost no effect on the reduction of the phase change temperature of the phase change material. Although annealing treatment is used in Comparative Example 5, the annealing temperature is low, the ball milling doping rate is still low, and the phase change temperature of the phase change material is high. In Comparative Example 6, the annealing temperature is high. Although the W and Sn doping rates are increased and the phase change temperature of the phase change material is reduced, the visible light transmittance of the phase change material is significantly reduced, and the optical performance deteriorates.

[0113] Combining Example 1 and Comparative Examples 7-8 and Tables 1-2, it can be seen that the particle size of the phase change precursor obtained by grinding in Comparative Example 7 is too large, resulting in insufficient reduction during the subsequent annealing process, low doping rates of W and Sn, and high phase change temperature of the phase change material. Although the particle size of the phase change precursor obtained by grinding in Comparative Example 8 is small, which helps the phase change precursor to contact the reducing agent during the annealing process, the phase change temperature decreases less, indicating that the phase change precursor and the reducing agent have reacted more fully at 500°C.

[0114] Combining Example 1 and Comparative Examples 9-11 and Table 1-2, it can be seen that in Comparative Example 9, dry grinding is used, and the phase change temperature of the obtained phase change material is high. The reason is that dry grinding is not conducive to the dispersion of the reducing agent, which leads to insufficient contact between the reducing agent and the phase change precursor during the annealing process, and the doping rates of W and Sn are low. In Comparative Example 10, activated carbon is used as the reducing agent. The activated carbon is difficult to be fully dispersed with water, and the contact with the phase change precursor is insufficient, and the doping rates of W and Sn are low. In Comparative Example 11, liquid glucose is used as the reducing agent. The viscosity of liquid glucose is high, which easily leads to insufficient grinding of the phase change precursor during the grinding process, and there is a situation where the local particle size is too large, which leads to low W and Sn doping rates of the overall phase change material and high phase change temperature of the phase change material.

[0115] Combining Example 1 and Comparative Example 12 and Tables 1-2, it can be seen that in Comparative Example 12, no dispersant is added, and the powder size distribution range is wide during high-speed grinding, resulting in insufficient contact between the final phase change precursor and the reducing agent, and the phase change temperature is high. Therefore, the phase change temperature, stability, visible light transmittance and sunlight modulation ability of the phase change material are balanced and improved.

[0116] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0117] Moreover, the above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims.

Claims

1. A method for preparing a near-room temperature vanadium-based nano phase change material, characterized in that: The steps include: Pretreatment: mixing a water-soluble reducing agent with water to obtain a reducing solution; Grinding: vanadium pentoxide, tin dopant, tungsten dopant, silane coupling agent and reducing solution are mixed, and ball milled for 3 hours at a rotation speed of 1600 r / min and a ball-to-material ratio of 1:2.5 to obtain a ground wet powder; wherein the molar ratio of vanadium, tin and tungsten is 98:0.5:1.5, and the molar ratio of vanadium pentoxide, water-soluble reducing agent and silane coupling agent is 1:0.2:0.0025; Coating treatment: Grind the wet powder and disperse it in an ethanol solution, adjust the pH value of the system to 9-10, drop a silicon source, and the molar ratio of the silicon source to the silane coupling agent is 3:

1. Heat to 60°C, stir and disperse at a speed of 200r / min, keep the reaction warm for 1±0.5h, centrifuge and wash to obtain a core-shell structured phase change precursor; Post-treatment: The core-shell structured phase change precursor is annealed at 300-720°C for 1h to obtain a near-room temperature vanadium-based nano phase change material.

2. The method for preparing a near-room temperature vanadium-based nano phase change material according to claim 1, characterized in that: The water-soluble reducing agent is one or more of glucose, lactose and oxalic acid.

3. The method for preparing a near-room temperature vanadium-based nano phase change material according to claim 2, characterized in that: The tin dopant is tin oxide and / or stannous sulfate.

4. The method for preparing a near-room temperature vanadium-based nano phase change material according to claim 3, characterized in that: The tungsten dopant is one or more of tungsten oxide, tungstic acid, sodium tungstate and ammonium tungstate.

5. The method for preparing a near-room temperature vanadium-based nano phase change material according to claim 4, characterized in that: The silane coupling agent is an aminosilane coupling agent.

6. The method for preparing a near-room temperature vanadium-based nano phase change material according to claim 1, characterized in that: In the coating treatment step, the silicon source is ethyl orthosilicate, methyl orthosilicate and propyl orthosilicate.

7. The method for preparing a near-room temperature vanadium-based nano phase change material according to claim 1, characterized in that: In the post-treatment step, annealing is performed at 600° C. for 1 hour.

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