Wide-spectrum emission lanthanum-doped aluminum phosphate radiation refrigeration material and preparation method thereof

Abstract

The invention discloses a wide-spectrum emission lanthanum-doped aluminum phosphate radiation refrigeration material and a preparation method thereof.The lanthanum-doped aluminum phosphate is synthesized by modifying aluminum phosphate with the lanthanum element through a hydrothermal method, the preparation process is simple, the reaction period is short, raw materials are common, the cost is low, controllability is high, a large number of target products can be prepared, and industrial production is easy to achieve; the lanthanum-doped synthesized aluminum phosphate powder has high sunlight reflectivity and high and medium infrared radiance at the same time, and has excellent refrigeration performance; according to the invention, the lanthanum-doped aluminum phosphate powder is dissolved in the tree trunk whitening agent and is applied to the surfaces of trees so as to reduce the temperature of the tree trunks, and the lanthanum-doped aluminum phosphate powder can play a certain role in inhibiting fire disasters when being applied to the trees in forests.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional materials, relates to daytime passive radiative cooling materials, and particularly relates to a lanthanum-doped aluminum phosphate radiative cooling material with broad-spectrum emission and a preparation method thereof. Background Art

[0002] With the continuous growth of the global population, global warming and energy problems have become increasingly serious. To cope with the hot weather environment, active cooling has come onto the historical stage. Usually, a series of devices such as air conditioners and fans are used to meet the indoor cooling requirements. However, these devices not only require electricity to maintain but also have an impact on the environment. Radiative cooling is a new type of highly efficient and energy-saving cooling method, and its greatest advantage compared to active cooling is that it can achieve a similar effect without consuming energy. Therefore, finding new and highly efficient radiative cooling materials has become a new way to solve the problem. To make the radiative cooling material have excellent performance, the material must have an extremely high reflectivity in the solar spectrum band and an extremely high emissivity in the atmospheric window (8 - 13 μm). Thus, the absorbed sunlight and surrounding heat can be converted into internal energy to increase the temperature, and then radiated outward in the form of infrared rays. Since the selectively absorbing gases in the atmosphere have a low absorption rate in the atmospheric window band, the radiative cooling material can transfer heat to outer space through the atmospheric window to achieve the purpose of cooling.

[0003] Currently, there have been corresponding progresses in the research on radiative cooling. In 2014, Professor Shanhui Fan of Stanford University in the United States prepared a photonic crystal radiative cooling material formed by alternately stacking seven different thicknesses of HfO2 and SiO2 coatings, which can achieve a solar reflectivity of 97% and an emissivity in the atmospheric window of 95%, and can lower the ambient temperature by about 5°C. In 2017, Professor Ronggui Yang and Professor Xiaobo Yin of the University of Colorado in the United States developed a radiative cooling thin film material. This material is formed by dispersing resonant polar silica dielectric microspheres in the organic polymer poly(methylpentene) and plating this on a silver layer. The reflectivity of this thin film to solar radiation can reach 0.96, and the infrared emissivity in the atmospheric window band reaches 0.93. Although the above materials all have good performance, due to the overly complex structures and processes of these materials and the high costs, and the need for corresponding sophisticated processing instruments, they have certain limitations. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a lanthanum-doped aluminum phosphate radiative cooling material with broad-spectrum emission and a preparation method thereof. The prepared aluminum phosphate doped with lanthanum has excellent solar reflectivity and excellent mid-infrared emissivity, and shows excellent performance in the field of radiative cooling.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions to implement:

[0006] A preparation method of a wide-spectrum emission lanthanum-doped aluminum phosphate radiation cooling material, comprising the following steps:

[0007] Step 1: Take aluminum salt and lanthanum salt according to the element molar ratio of Al to La being 1: (0.003 - 0.03), and dissolve them separately in deionized water to obtain solution A with an aluminum ion concentration of 0.125 - 1 mol / L and solution B with a lanthanum ion concentration of 0.1 - 0.5 mol / L respectively. Mix the two solutions to obtain solution C;

[0008] Step 2: Take chitosan and glucose according to the molar ratio of chitosan, glucose and aluminum salt being (0.1 - 0.9):(0.1 - 0.9):1, add them to solution C, and stir to mix evenly to obtain solution D;

[0009] Step 3: Take phosphate according to the molar ratio of phosphate group to Al element being 1:1, dissolve it in deionized water to obtain solution E with a concentration of 0.1 - 0.5 mol / L, and mix solution D and solution E and stir well until uniform to obtain solution F;

[0010] Step 4: Transfer solution F to the polytetrafluoroethylene inner lining of a hydrothermal reaction kettle, place it in an oven and react at 120 - 150 °C for 8 - 16 h. After cooling to room temperature, filter, wash and dry, then place it in a box furnace and heat it from room temperature to 800 - 1100 °C at a rate of 5 - 10 °C / min in an air atmosphere, keep it warm for 1 - 4 h, and then naturally cool to room temperature to obtain a wide-spectrum emission lanthanum-doped aluminum phosphate radiation cooling material.

[0011] The present invention also has the following technical features:

[0012] Preferably, during the dissolution process of the aluminum salt in Step 1, add a 5 - 20 wt% hydrochloric acid solution with the same volume as the deionized water, and stir at room temperature for 2 - 5 h to fully dissolve it.

[0013] Preferably, the aluminum salt includes one of aluminum isopropoxide and aluminum lactate.

[0014] Preferably, the lanthanum salt includes one of lanthanum nitrate hexahydrate and lanthanum chloride heptahydrate.

[0015] Preferably, the stirring in Step 2 is carried out at room temperature for 1 - 2 h.

[0016] Preferably, the phosphate includes one of sodium hexametaphosphate and sodium pyrophosphate.

[0017] Preferably, the stirring in Step 3 is carried out at room temperature for 0.5 - 2 h.

[0018] Preferably, the washing and drying in step four is to cross-wash three times with deionized water and ethanol and then place it in a drying oven to dry at 50-80 °C for 2-5 h.

[0019] The present invention also protects a broadband emission lanthanum-doped aluminum phosphate radiation cooling material prepared by the method as described above.

[0020] Compared with the prior art, the present invention has the following technical effects:

[0021] The present invention uses a hydrothermal method to synthesize a lanthanum-doped aluminum phosphate material, which has both a high solar light reflectivity and a high mid-infrared emissivity, has excellent refrigeration performance, and has a simple preparation process, a short reaction period, common raw materials, low cost, strong controllability, can be prepared in large quantities of the target product, and is easy to realize industrial production. Description of the Drawings

[0022] Figure 1 XPS diagram of La-doped AlPO4 prepared in Example 1;

[0023] Figure 2 Emissivity diagram of La-doped AlPO4 prepared in Example 1 in the mid-infrared band;

[0024] Figure 3 Reflectivity diagram of La-doped AlPO4 prepared in Example 1 in the solar band;

[0025] Figure 4 Cooling effect diagram of La-doped AlPO4 prepared in Example 1;

[0026] Figure 5 Cooling effect diagram of La-doped AlPO4 prepared in Example 1 in the tree trunk whitening agent;

[0027] Figure 6 XRD diagram of La-doped AlPO4 prepared in Examples 1 to 3; Detailed Embodiments

[0028] The following further explains the specific content of the present invention in detail with reference to the embodiments.

[0029] Example 1:

[0030] This example provides a preparation method of a broadband emission lanthanum-doped aluminum phosphate radiation cooling material, including the following steps:

[0031] Step 1: Weigh 0.005 mol of aluminum isopropoxide, 10 ml of deionized water, and 10 ml of 7.5 wt% hydrochloric acid solution according to the element molar ratio of Al to La being 1:0.003, and stir at room temperature for 2 h to fully dissolve it to form solution A;

[0032] Weigh La(NO3)3·6H2O and dissolve it in deionized water to prepare solution B with a concentration of 0.1 mol / L.

[0033] Mix solution A and solution B to obtain solution C.

[0034] Step 2: According to the molar ratio of chitosan, glucose and aluminum salt of 0.1:0.1:1, take chitosan and glucose and add them into solution C, stir for 1 h to make them evenly mixed, and obtain solution D.

[0035] Step 3: According to the molar ratio of phosphate group to Al element of 1:1, take phosphate and dissolve it in deionized water, stir well at 60 °C for 0.5 h to obtain solution E with a concentration of 0.1 mol / L, and mix solution D and solution E and stir well until evenly mixed to obtain solution F.

[0036] Step 4: Transfer solution F to the polytetrafluoroethylene liner of the hydrothermal reactor, put it into the oven and react at 120 °C for 16 h. After cooling to room temperature, filter it, then wash it three times alternately with deionized water and ethanol, put it into the drying oven and dry it at 50 °C for 5 h, then place it in a box furnace and heat it from room temperature to 1100 °C at a rate of 5 °C / min in an air atmosphere, keep it warm for 1 h, and then naturally cool it to room temperature to obtain a broadband emission lanthanum-doped aluminum phosphate radiative cooling material.

[0037] Figure 1 XPS diagram of La-doped AlPO4 prepared in Example 1; It can be seen from Figure 1 that the peak of La3d has appeared in the sample, indicating that lanthanum element has been successfully doped into aluminum phosphate.

[0038] Figure 2 Emissivity diagram of La-doped AlPO4 prepared in Example 1 in the mid-infrared band; It can be seen from Figure 2 that La-doped AlPO4 has excellent emissivity in the atmospheric window, reaching more than 90%.

[0039] Figure 3 Reflectivity diagram of La-doped AlPO4 prepared in Example 1 in the solar band; It can be seen from Figure 3 that La-doped AlPO4 has excellent solar reflectivity, reaching 95%.

[0040] Figure 4 Cooling effect diagram of La-doped AlPO4 prepared in Example 1; It can be seen from Figure 4 that the temperature of La-doped AlPO4 is about 8 °C lower than the surrounding environment temperature and 2 °C lower than undoped aluminum phosphate.

[0041] Take the tree trunk whitewash and the lanthanum-doped aluminum phosphate radiative cooling material prepared in Example 1, and prepare a 10 wt% solution. Stir for 4 h at room temperature and apply it to the simulated tree trunk to reduce the tree trunk temperature. Using it on trees in the forest can play a certain role in suppressing the occurrence of fires. Figure 5 The cooling effect diagram of La-doped AlPO4 prepared in Example 1 in the tree trunk whitewash; from Figure 5 it can be seen that the functional whitewash containing La-doped AlPO4 can be about 5 °C lower than the surrounding environmental temperature and about 3 °C lower than the whitewash.

[0042] Example 2:

[0043] This example provides a preparation method of a wide-spectrum emission lanthanum-doped aluminum phosphate radiative cooling material, including the following steps:

[0044] Step 1: According to the elemental molar ratio of Al to La being 1:0.005, weigh 0.01 mol of aluminum isopropoxide, 15 ml of deionized water, and 15 ml of 10 wt% hydrochloric acid solution, and stir at room temperature for 2 h to fully dissolve it to form solution A;

[0045] Weigh La(NO3)3·6H2O and dissolve it in deionized water to prepare a 0.2 mol / L solution B;

[0046] Mix solutions A and B to obtain solution C;

[0047] Step 2: According to the molar ratio of chitosan, glucose, and aluminum salt being 0.9:0.9:1, take chitosan and glucose and add them to solution C, and stir for 1 h to mix them evenly to obtain solution D;

[0048] Step 3: According to the molar ratio of phosphate group to Al element being 1:1, take phosphate and dissolve it in deionized water, and stir at 50 °C for 1 h to obtain a 0.5 mol / L solution E, and mix solutions D and E and stir well until uniform to obtain solution F;

[0049] Step 4: Transfer solution F to the polytetrafluoroethylene inner lining of a hydrothermal reaction kettle, place it in an oven and react at 130 °C for 12 h. After cooling to room temperature, filter, then cross-wash three times with deionized water and ethanol, place it in a drying oven and dry at 60 °C for 4 h, then place it in a box furnace and heat it from room temperature to 1000 °C at a rate of 7 °C / min in an air atmosphere, hold for 2 h, and then naturally cool to room temperature to obtain a wide-spectrum emission lanthanum-doped aluminum phosphate radiative cooling material.

[0050] Take the tree trunk whitewash and the lanthanum-doped aluminum phosphate radiative cooling material prepared in Example 2, and prepare a 15 wt% solution. Stir for 5 h at room temperature and apply it to the simulated tree trunk for practical application.

[0051] Example 3:

[0052] This example provides a method for preparing a wide-spectrum emission lanthanum-doped aluminum phosphate radiation cooling material, including the following steps:

[0053] Step 1: According to the element molar ratio of Al to La being 1:0.01, weigh 0.015 mol of aluminum isopropoxide, 20 ml of deionized water, and 20 ml of 15 wt% hydrochloric acid solution, stir at room temperature for 4 h to fully dissolve them, and form solution A;

[0054] Weigh La(NO3)3·6H2O and dissolve it in deionized water to prepare solution B with a concentration of 0.4 mol / L;

[0055] Mix solutions A and B to obtain solution C;

[0056] Step 2: According to the molar ratio of chitosan, glucose, and aluminum salt being 0.1:0.9:1, take chitosan and glucose and add them to solution C, stir for 2 h to mix them evenly, and obtain solution D;

[0057] Step 3: According to the molar ratio of phosphate group to Al element being 1:1, take phosphate and dissolve it in deionized water, stir fully at 40 °C for 1.5 h to obtain solution E with a concentration of 0.2 mol / L, and mix solutions D and E and stir until evenly mixed to obtain solution F;

[0058] Step 4: Transfer solution F to the polytetrafluoroethylene inner lining of a hydrothermal reaction kettle, place it in an oven and react at 140 °C for 10 h, cool to room temperature, filter, then wash it three times alternately with deionized water and ethanol, place it in a drying oven and dry at 70 °C for 3 h, then place it in a box furnace and heat it from room temperature to 900 °C at a rate of 8 °C / min in an air atmosphere, hold for 3 h, and then naturally cool to room temperature to obtain a wide-spectrum emission lanthanum-doped aluminum phosphate radiation cooling material.

[0059] Take the tree trunk whitening agent and the lanthanum-doped aluminum phosphate radiation cooling material prepared in Example 3, prepare a 20 wt% solution, stir at room temperature for 6 h, and apply it to the simulated tree trunk for practical application.

[0060] Figure 6 XRD patterns of La-doped AlPO4 prepared in Examples 1 to 3; From Figure 6 It can be seen that a small amount of La doping has no significant effect on the AlPO4 phase, but it will induce the growth of crystal systems.

[0061] Example 4:

[0062] This example provides a method for preparing a wide-spectrum emission lanthanum-doped aluminum phosphate radiation cooling material, including the following steps:

[0063] Step 1: Weigh 0.02 mol of aluminum isopropoxide, 10 ml of deionized water and 10 ml of 20 wt% hydrochloric acid solution according to the element molar ratio of Al to La being 1:0.03, and stir at room temperature for 5 h to fully dissolve them to form solution A;

[0064] Weigh La(NO3)3·6H2O and dissolve it in deionized water to prepare a 0.5 mol / L solution B;

[0065] Mix solutions A and B to obtain solution C;

[0066] Step 2: According to the molar ratio of chitosan, glucose and aluminum salt being 0.9:0.1:1, take chitosan and glucose and add them to solution C, and stir for 1.5 h to mix them evenly to obtain solution D;

[0067] Step 3: According to the molar ratio of phosphate group to Al element being 1:1, take phosphate and dissolve it in deionized water, and stir thoroughly at 30 °C for 2 h to obtain a 0.3 mol / L solution E, and mix solutions D and E and stir thoroughly until uniform to obtain solution F;

[0068] Step 4: Transfer solution F to the polytetrafluoroethylene liner of a hydrothermal reaction kettle, place it in an oven and react at 150 °C for 8 h. After cooling to room temperature, filter, then wash it three times alternately with deionized water and ethanol, place it in a drying oven and dry at 80 °C for 2 h, then place it in a box furnace and heat it from room temperature to 800 °C at a rate of 10 °C / min in an air atmosphere, keep it warm for 4 h, and then naturally cool to room temperature to obtain a wide-spectrum emission lanthanum-doped aluminum phosphate radiative cooling material.

[0069] Example 5

[0070] This example provides a preparation method of a wide-spectrum emission lanthanum-doped aluminum phosphate radiative cooling material, including the following steps:

[0071] Step 1: Weigh 0.005 mol of aluminum isopropoxide, 20 ml of deionized water and 20 ml of 5 wt% hydrochloric acid solution according to the element molar ratio of Al to La being 1:0.03, and stir at room temperature for 2 h to fully dissolve them to form solution A;

[0072] Weigh La(NO3)3·6H2O and dissolve it in deionized water to prepare a 0.1 mol / L solution B;

[0073] Mix solutions A and B to obtain solution C;

[0074] Step 2: According to the molar ratio of chitosan, glucose and aluminum salt being 0.5:0.5:1, take chitosan and glucose and add them to solution C, and stir for 1 h to mix them evenly to obtain solution D;

[0075] Step 3: Take phosphate and dissolve it in deionized water according to the molar ratio of phosphate radical to Al element being 1:1, and stir it fully for 0.5 h at 60 °C to obtain solution E with a concentration of 0.4 mol / L. Then mix solution D and solution E and stir them fully until uniform to obtain solution F;

[0076] Step 4: Transfer solution F to the polytetrafluoroethylene inner liner of a hydrothermal reactor, place it in an oven and react at 120 °C for 16 h. After cooling to room temperature, filter it, then wash it three times alternately with deionized water and ethanol, place it in a drying oven and dry it at 50 °C for 5 h, then place it in a box furnace and heat it from room temperature to 1100 °C at a rate of 5 °C / min in an air atmosphere, hold for 1 h, and then naturally cool to room temperature to obtain a broadband emission lanthanum-doped aluminum phosphate radiative cooling material.

[0077] Those of ordinary skill in the art will realize that the embodiments described herein are for helping readers understand the principles of the present invention, and it should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those of ordinary skill in the art can make various other specific deformations and combinations without departing from the essence of the present invention according to the technical revelations disclosed in the present invention, and these deformations and combinations are still within the protection scope of the present invention.

Claims

1. A preparation method of a lanthanum-doped aluminum phosphate radiation cooling material with broadband emission, characterized in that, It includes the following steps: Step 1: Take aluminum salt and lanthanum salt according to the molar ratio of Al to La of 1:(0.003 - 0.03), dissolve them separately in deionized water to obtain solution A with an aluminum ion concentration of 0.125 - 1 mol / L and solution B with a lanthanum ion concentration of 0.1 - 0.5 mol / L respectively, and mix the two solutions to obtain solution C; Step 2: Take chitosan and glucose according to the molar ratio of chitosan, glucose and aluminum salt of (0.1 - 0.9):(0.1 - 0.9):1, add them to solution C, and stir to make them evenly mixed to obtain solution D; Step 3: Take phosphate salt according to the molar ratio of phosphate radical to Al element of 1:1, dissolve it in deionized water to obtain solution E with a concentration of 0.1 - 0.5 mol / L, and mix solution D and solution E and stir well until evenly mixed to obtain solution F; Step 4: Transfer solution F to the polytetrafluoroethylene inner liner of a hydrothermal reaction kettle, put it into an oven and react at 120 - 150 °C for 8 - 16 h. After cooling to room temperature, filter, wash and dry, then place it in a box furnace and heat it from room temperature to 800 - 1100 °C at a rate of 5 - 10 °C / min in an air atmosphere, keep it warm for 1 - 4 h, and then naturally cool to room temperature to obtain a broad-spectrum emission lanthanum-doped aluminum phosphate radiation cooling material.

2. The preparation method of the lanthanum-doped aluminum phosphate radiation cooling material with broad-spectrum emission according to claim 1, wherein During the dissolution process of the aluminum salt described in Step 1, add a 5 - 20 wt% hydrochloric acid solution with the same volume as deionized water, and stir at room temperature for 2 - 5 h to make it fully dissolve.

3. The preparation method of the broad-spectrum emission lanthanum-doped aluminum phosphate radiation cooling material according to claim 1 or 2, characterized in that, The aluminum salt includes one of aluminum isopropoxide and aluminum lactate.

4. The preparation method of the broad-spectrum emission lanthanum-doped aluminum phosphate radiation cooling material according to claim 1, characterized in that, The lanthanum salt includes one of lanthanum nitrate hexahydrate and lanthanum chloride heptahydrate.

5. The preparation method of the lanthanum-doped aluminum phosphate radiation cooling material with broadband emission according to claim 1, characterized in that, The stirring described in Step 2 is stirring at room temperature for 1 - 2 h.

6. The preparation method of the wide-spectrum emission lanthanum-doped aluminum phosphate radiation cooling material according to claim 1, characterized in that, The phosphate salt includes one of sodium hexametaphosphate and sodium pyrophosphate.

7. The preparation method of the broad-spectrum emission lanthanum-doped aluminum phosphate radiation cooling material according to claim 1, characterized in that, The stirring described in Step 3 is stirring at room temperature for 0.5 - 2 h.

8. The preparation method of the lanthanum-doped aluminum phosphate radiation cooling material with broad-spectrum emission according to claim 1, characterized in that, The washing and drying described in Step 4 is to cross-clean three times with deionized water and ethanol, and then put it into a drying oven and dry at 50 - 80 °C for 2 - 5 h.

9. A broad-spectrum emission lanthanum-doped aluminum phosphate radiation cooling material prepared by the method according to any one of claims 1 to 8.

Images