A green radiation refrigeration film based on near-infrared light conversion material and a preparation method and application thereof

Abstract

The present application belongs to the technical field of radiation refrigeration, and particularly relates to a green radiation refrigeration film based on near-infrared light conversion material and a preparation method and application thereof. The present application prepares a green radiation refrigeration film based on near-infrared light conversion material by compounding a polymer, a green pigment and inorganic microspheres; the film selectively absorbs visible light and efficiently emits near-infrared light, and has excellent reflectivity in the near-infrared wave band, and the two synergistically achieve excellent radiation refrigeration effect; wherein the porous structure of the polymer enhances the diffuse reflection of light; the green pigment gives the film a green appearance, selectively absorbs visible light and efficiently emits near-infrared light, and has excellent reflectivity in the near-infrared wave band; the phonon polarization-phonon resonance characteristics of the inorganic microspheres help to radiate heat and reduce the absorption of sunlight; the preparation method of the present application is simple, low in cost, safe and environmentally friendly, and the prepared film can be widely used in the preparation of cooling materials.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of radiative cooling. More particularly, it relates to a green radiative cooling film based on near-infrared light conversion material and its preparation method and application. BACKGROUND

[0002] With the global climate warming, the sharp increase in demand for refrigeration has become a significant problem, and the electricity consumption for refrigeration has accounted for about 10% of the total electricity consumption in the world. Traditional refrigeration technologies (such as liquid vaporization method, gas expansion method, thermoelectric method, etc.) not only consume a large amount of energy, but also exacerbate the greenhouse effect, causing serious impact on the ecological environment. Under this background, passive cooling strategy, with its environmental friendliness and significant carbon reduction effect, is gradually becoming one of the key technologies to promote energy reform and industrial upgrading.

[0003] Radiative cooling, as a new star in the field of passive cooling, is mainly realized in the form of coating or film (coating film), which utilizes the atmospheric window (8-14 μm) to radiate heat to the cold outer space in the form of black body radiation. However, the existing radiative cooling film is mostly white or silver, which is designed to maximize the reflection of sunlight and reduce heat absorption. Although this design effectively reduces the heat effect, its monotonous color limits the aesthetic application. For example, Chinese patent application CN116515219A discloses a porous radiative cooling film, which has no metal reflection layer and the film radiative cooling can reach 6.7℃, bringing significant refrigeration effect to the surface of objects or buildings. However, the reflectivity of the film in the near-infrared waveband (800nm-1600nm) is only about 56%, which greatly limits the improvement of its cooling effect. In practical application, the aesthetic value of color is as important as the thermal effect of material. However, traditional colored coating film usually absorbs energy in the visible light waveband (380-760nm) and converts it into heat, thereby weakening the performance of radiative cooling. This problem sets an irreconcilable contradiction between the performance requirement and color requirement of colored radiative cooling coating.

[0004] Therefore, it is urgent to develop a colored radiative cooling film that integrates color richness, high reflectivity in the near-infrared waveband and excellent cooling effect by using photoluminescence material. SUMMARY

[0005] The technical problem to be solved by the present application is to overcome the conflict between color and thermal effect of radiative cooling film, and the defects and deficiencies of near-infrared waveband reflectivity and cooling effect, and to provide a green radiative cooling film based on near-infrared light conversion material.

[0006] Another object of the present application is to provide a preparation method of the above-mentioned green radiative cooling film based on near-infrared light conversion material.

[0007] Another object of the present application is to provide the application of the green radiative cooling film based on near-infrared light conversion material in the preparation of cooling materials.

[0008] The above-mentioned objects of the present application are achieved by the following technical solutions.

[0009] The present application protects a green radiative cooling film based on near-infrared light conversion material, the composition of the green radiative cooling film includes a high polymer, a green pigment and inorganic microspheres.

[0010] The green pigment includes one or more of chromium-nickel co-doped magnesium oxide, chromium-nickel co-doped lithium gallate and chromium-nickel co-doped magnesium gallate.

[0011] In the chromium-nickel co-doped magnesium oxide, the doping amount of chromium is 10% to 20% and the doping amount of nickel is 0.1% to 1%, based on the total mole percentage of magnesium, chromium and nickel elements.

[0012] In the chromium-nickel co-doped lithium gallate or chromium-nickel co-doped magnesium gallate, the doping amount of chromium is 10% to 20% and the doping amount of nickel is 0.1% to 1%, based on the total mole percentage of gallium, chromium and nickel elements.

[0013] The present application uses a high polymer, a green pigment and inorganic microspheres to prepare a green radiative cooling film based on near-infrared light conversion material. The porous structure constructed by the high polymer can increase the diffuse reflection; the green pigment includes one or more of chromium-nickel co-doped magnesium oxide, chromium-nickel co-doped lithium gallate and chromium-nickel co-doped magnesium gallate, wherein the Cr 3+ d-d transition leads to specific absorption and emission characteristics, i.e. absorbing red light and reflecting green light, the doping of Ni 2+ also causes optical absorption and color change of the material, resulting in the chromium-nickel co-doped magnesium oxide, chromium-nickel co-doped lithium gallate and chromium-nickel co-doped magnesium gallate appearing green, and the green pigment can convert strong visible light absorption into near-infrared light energy, and at the same time emit the absorbed energy in the form of fluorescence; the inorganic microspheres have significant phonon-polariton resonance characteristics near 9.6 μm, which can significantly improve the reflectivity in the solar radiation region, i.e. helping to radiate heat and reduce the absorption of sunlight, and the inorganic microspheres have low thermal conductivity and are not easy to exchange heat with objects. Therefore, the obtained green radiative cooling film exhibits good absorption performance in the visible light band (380-760 nm), can realize coloration while emitting the absorbed visible light band energy in the near-infrared band, and has excellent reflectivity in the near-infrared band (800-1600 nm), thereby realizing excellent radiative cooling effect.

[0014] Further, the high polymer includes one or more of polylactic acid fiber, polydimethylsiloxane, polystyrene, polyvinyl chloride, polyethylene, polyvinylidene fluoride.

[0015] Further, the lithium gallate is LiGa50s, which is prepared by sintering Li source and Ga source at 1300-1800 °C to obtain LiGa50s crystal.

[0016] Further, the lithium gallate is LiGa50s, which is prepared by sintering Li source and Ga source at 1300-1800 °C to obtain LiGa50s crystal.

[0017] Further, the magnesium gallate is MgGa20, which is prepared by sintering Mg source and Ga source at 1300-1800 °C to obtain MgGa20 crystal.

[0018] Further, the magnesium gallate is MgGa20, which is prepared by sintering Mg source and Ga source at 1300-1800 °C to obtain MgGa20 crystal.

[0019] Preferably, the green pigment includes Mg (1-x-y) Cr x Ni y O, Li(Ga (1-x-y) Cr x Ni y )50s, Mg(Ga (1-x-y) Cr x Ni y )20, wherein 0.1≤x≤0.2, 0.001≤y≤0.01.

[0020] More preferably, the green pigment includes Mg 0.79 Cr 0.2 Ni 0.01 O, Mg 0.84 Cr 0.15 Ni 0.01 O, Mg 0.89 Cr 0.1 Ni 0.01 O, LiGa 3.95 CrNi 0.05 O8, LiGa 4.495 Cr 0.5 Ni 0.005 O8, LiGa 3.995 CrNi 0.005 O8, MgGa 1.598 Cr 0.4 Ni 0.002 O4, MgGa 1.798 Cr0.2 Ni 0.002 One or more of O4.

[0021] Furthermore, the Cr source in the green pigment includes one or more of chromium oxide, chromium carbonate, and chromium sulfate, preferably chromium oxide.

[0022] Furthermore, the Ni source in the green pigment includes one or more of nickel oxide, nickel carbonate, and nickel sulfate, preferably nickel oxide.

[0023] Furthermore, the Mg source in the green pigment includes one or more of magnesium oxide, magnesium carbonate, and magnesium sulfate, preferably magnesium oxide.

[0024] Furthermore, the Ga source in the green pigment includes one or more of gallium oxide, gallium carbonate, and gallium sulfate, preferably gallium oxide.

[0025] Furthermore, the Li source in the green pigment includes one or more of lithium carbonate, lithium oxide, and lithium sulfate, preferably lithium carbonate.

[0026] Furthermore, the method for preparing the green pigment includes the following steps:

[0027] According to the stoichiometric ratio of each component element, the raw materials are accurately weighed, and the solvent is added at a material-to-liquid ratio of 1:(1~5)g / mL. After thorough grinding, the mixture is fully calcined at 1300~1800℃, cooled, and then ground again to obtain the green pigment.

[0028] Furthermore, the solvent includes one or more of ethanol, methanol, and water.

[0029] Furthermore, the time for complete burning is 1 to 6 hours.

[0030] Furthermore, the thorough grinding time is 1 to 3 hours.

[0031] Furthermore, the grinding time after cooling is 10 to 60 minutes.

[0032] Preferably, the inorganic microspheres include one or more of titanium dioxide, magnesium oxide, silicon dioxide, aluminum oxide, zirconium dioxide, and barium sulfate.

[0033] Preferably, the particle size of the inorganic microspheres is 100 nm to 10 μm.

[0034] Preferably, the mass ratio of the polymer, green pigment, and inorganic microspheres is 1:(0.02-0.5):(0.02-0.5).

[0035] This invention protects a method for preparing the above-mentioned green radiation-cooling thin film based on near-infrared light conversion materials, comprising the following steps:

[0036] S1. Mix the polymer, green pigment and inorganic microspheres in an organic solvent to obtain a suspension;

[0037] S2. Coat the suspension obtained in step S1 onto the substrate, dry it to form a thin film on the substrate, and peel it off to obtain a green radiation cooling film based on near-infrared light conversion material.

[0038] The green radiative cooling film prepared by this invention has a simple preparation process and a fast film formation rate. The film prepared by this method can achieve functions such as reducing indoor temperature, refrigeration, freezing, and thermoelectric power generation, thereby achieving the goal of energy conservation and emission reduction.

[0039] Preferably, in step S1, the organic solvent includes one or more of formic acid, tetrahydrofuran, carbon disulfide, dichloromethane, trichloromethane, and toluene.

[0040] Preferably, in step S1, the mass-to-volume ratio of the polymer to the organic solvent is 1 g:

[0041] (0.01~0.05)L.

[0042] Furthermore, in step S1, the mixing is performed by ultrasonic stirring followed by mixing.

[0043] Preferably, in step S2, the drying conditions are drying in a constant temperature and humidity chamber at 10–40°C and a relative humidity (RH) of 40%–95% for 0.1–10 hours.

[0044] More preferably, the drying conditions are drying in a constant temperature and humidity chamber at 20-40°C and RH of 40%-90% for 0.5-5 hours.

[0045] Furthermore, the solvent used to maintain humidity in the constant temperature and humidity chamber includes one or more of deionized water, ethanol, and methanol.

[0046] Preferably, in step S2, the thickness of the green radiation cooling film is 50 to 1000 μm. Films within this thickness range have better solar transmittance, enabling them to fully utilize their cooling performance with the help of the green pigment in the film.

[0047] This invention protects the application of the above-mentioned green radiation-cooling thin film based on near-infrared light conversion material in the preparation of cooling materials.

[0048] Compared with existing technologies, this invention has the following advantages: This invention prepares a green radiative cooling film based on near-infrared light conversion materials by combining polymer, green pigment, and inorganic microspheres. This film selectively absorbs visible light and then efficiently emits near-infrared light, exhibiting excellent reflectivity in the near-infrared band. The two components work synergistically to achieve a superior radiative cooling effect. Specifically, the porous structure of the polymer enhances diffuse reflection of light; the green pigment gives the film a green appearance, selectively absorbs visible light, and then efficiently emits near-infrared light, exhibiting excellent near-infrared reflectivity; the phonon polarization-phonon resonance characteristics of the inorganic microspheres help dissipate heat radiatively and reduce the absorption of sunlight; the preparation method of this invention is simple, low-cost, safe, and environmentally friendly, and the resulting film can be widely used in the preparation of cooling materials. Attached Figure Description

[0049] Figure 1 This is a photograph of the green film in Example 1.

[0050] Figure 2 These are microscope images of the green films in Examples 1 and 3.

[0051] Figure 3 This is the X-ray diffraction pattern of the green thin film in Example 4.

[0052] Figure 4 The image shows the Raman spectrum of the green thin film obtained by changing the chromium doping ratio in Example 4.

[0053] Figure 5 The image shows the absorption spectrum of the green film in the ultraviolet-visible-near-infrared band in Example 1.

[0054] Figure 6 The images show the excitation spectrum of the green thin film in Examples 1 and 3 under 420 nm excitation and the emission spectrum at 1240 nm.

[0055] Figure 7 The images show the excitation spectrum of the green thin film in Example 4 at 460 nm and the emission spectrum at 1335 nm.

[0056] Figure 8 The temperature curves are shown in Example 1 and Comparative Example 1, comparing the green film with ambient air.

[0057] Figure 9 The temperature curves are shown in Example 1 and Comparative Example 2, comparing the green film with ambient air.

[0058] Figure 10 The temperature curves are shown in Example 1 and Comparative Example 3, comparing the green film with ambient air.

[0059] Figure 11The temperature curves are shown in Example 1 and Comparative Example 4, comparing the green film with ambient air. Detailed Implementation

[0060] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0061] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0062] Example 1: Preparation of a green radiation-cooling thin film based on near-infrared light conversion materials

[0063] 1. Green pigment Mg 0.79 Cr 0.2 Ni 0.01 Preparation of O

[0064] Preparation of Mg 0.79 Cr 0.2 Ni 0.01 O, with MgO as the matrix, and the percentage of Cr dopant ions in the total molar amount of Mg, Cr, and Ni. 3+ and Ni 2+ The doping amounts were 20% and 1%, respectively. According to the stoichiometric ratio of each component, 1g of the mixed raw material was accurately weighed, with a molar ratio of MgO:Cr2O3:NiO = 0.79:0.1:0.01. The 1g mixed raw material was placed in an agate mortar, followed by the addition of 3mL of ethanol and grinding for 1 hour to ensure thorough mixing. The mixture was then transferred to a corundum crucible, covered, and placed in a high-temperature furnace at 1600℃ for 2 hours. After natural cooling to room temperature, the sample was removed and ground for 15 minutes to obtain the green pigment Mg. 0.79 Cr 0.2 Ni 0.01 O.

[0065] 2. Preparation of Green Radiation-Cooling Thin Films Based on Near-Infrared Light Conversion Materials

[0066] First, add 0.45g of polyvinyl chloride powder to 5mL of carbon disulfide and stir magnetically at room temperature to form a solution with a concentration of 90mg / mL. Then, add 0.05g of Mg to the solution. 0.79 Cr 0.2 Ni 0.01O and 0.05 g of SiO2 nanoparticles (100 nm in diameter) were stirred and ultrasonically dispersed at room temperature using a magnetic stirrer to form a uniformly dispersed suspension. The suspension was poured into a square glass mold (500 μm deep), and the mold was transferred to a constant temperature and humidity chamber at 20 °C and 90% RH for drying for 0.5 h. Finally, a porous green radiation-cooling film was obtained after peeling it off from the mold.

[0067] Example 2: Preparation of a green radiation-cooling thin film based on near-infrared light conversion materials

[0068] 1. Green pigment Mg 0.84 Cr 0.15 Ni 0.01 Preparation of O

[0069] Preparation of Mg 0.84 Cr 0.15 Ni 0.01 O, the matrix is ​​MgO, and the percentage of Cr dopant ions is based on the total molar amount of Mg, Cr, and Ni. 3+ and Ni 2+ The doping amounts were 15% and 1%, respectively. According to the stoichiometric ratio of each component, 1g of the mixed raw material was accurately weighed, with a molar ratio of MgO:Cr2O3:NiO = 0.84:0.075:0.01. The 1g mixed raw material was placed in an agate mortar, followed by the addition of 3mL of ethanol, and ground for 1 hour to ensure thorough mixing. The mixture was then transferred to a corundum crucible, covered, and placed in a high-temperature furnace at 1600℃ for 2 hours. After natural cooling to room temperature, the sample was removed and ground for 15 minutes to obtain the green pigment Mg. 0.84 Cr 0.15 Ni 0.01 O.

[0070] 2. Preparation of Green Radiation-Cooling Thin Films Based on Near-Infrared Light Conversion Materials

[0071] First, add 0.3g of polyethylene powder to 5mL of tetrahydrofuran and stir magnetically at room temperature to form a solution with a concentration of 60mg / mL. Then, add 0.02g of Mg to the solution. 0.84 Cr 0.15 Ni 0.01 O and 0.02 g TiO2 nanoparticles (particle size 300 nm) were stirred and ultrasonically dispersed at room temperature using a magnetic stirrer to form a uniformly dispersed suspension. The suspension was poured into a square glass mold (depth 200 μm), and the mold was transferred to a constant temperature and humidity chamber at 30 °C and 60% RH for drying for 1 h. Finally, a porous green radiation-cooling film was obtained after peeling it off from the mold.

[0072] Example 3: A Green Radiation-Cooling Thin Film Based on Near-Infrared Light Conversion Materials

[0073] 1. Green pigment Mg 0.89 Cr 0.1 Ni 0.01 Preparation of O

[0074] Preparation of Mg 0.89 Cr 0.1 Ni 0.01 O, the matrix is ​​MgO, and the percentage of Cr dopant ions is based on the total molar amount of Mg, Cr, and Ni. 3+ and Ni 2+ The doping amounts were 10% and 1%, respectively. According to the stoichiometric ratio of each component, 1g of the mixed raw material was accurately weighed, with a molar ratio of MgO:Cr2O3:NiO = 0.89:0.05:0.01. The 1g mixed raw material was placed in an agate mortar, followed by the addition of 3mL of ethanol and grinding for 1 hour to ensure thorough mixing. The mixture was then transferred to a corundum crucible, covered, and placed in a high-temperature furnace at 1600℃ for 2 hours. After natural cooling to room temperature, the sample was removed and ground for 15 minutes to obtain the green pigment Mg. 0.89 Cr 0.1 Ni 0.01 O.

[0075] 2. Preparation of Green Radiation-Cooling Thin Films Based on Near-Infrared Light Conversion Materials

[0076] First, add 0.45g of polystyrene powder to 5mL of formic acid and stir magnetically at room temperature to form a solution with a concentration of 90mg / mL. Then, add 0.03g of Mg to the solution. 0.89 Cr 0.1 Ni 0.01 O and 0.03 g TiO2 nanoparticles (500 nm in diameter) were stirred and ultrasonically dispersed at room temperature using a magnetic stirrer to form a uniformly dispersed suspension. The suspension was poured into a square glass mold (300 μm deep), and the mold was transferred to a constant temperature and humidity chamber at 40 °C and 80% RH for drying for 2 h. Finally, the porous green radiation-cooling film was obtained after peeling it off from the mold.

[0077] Example 4: Preparation of a green radiation-cooling thin film based on near-infrared light conversion materials

[0078] 1. Green pigment LiGa 3.95 CrNi 0.05 Preparation of O8

[0079] Preparation of LiGa 3.95 CrNi 0.05 O8, with LiGa5O8 as the matrix, and the percentage of Cr dopant ions in the total molar amount of Ga, Cr, and Ni. 3+and Ni 2+ The doping amounts were 20% and 1%, respectively. According to the stoichiometric ratio of each component, 1g of the mixed raw material was accurately weighed. The molar ratio of each component in the mixed raw material was Li₂CO₃:Ga₂O₃:Cr₂O₃:NiO = 0.55:1.975:0.5:0.05. The 1g mixed raw material was placed in an agate mortar, and then 3mL of ethanol was added. After grinding for 1 hour to ensure thorough mixing, the mixture was transferred to a corundum crucible, covered, and placed in a high-temperature furnace at 1600℃ for 2 hours. After natural cooling to room temperature, the sample was removed and ground for 15 minutes to obtain the green pigment LiGa. 3.95 CrNi 0.05 O8.

[0080] 2. Preparation of Green Radiation-Cooling Thin Films Based on Near-Infrared Light Conversion Materials

[0081] First, add 0.15g of polydimethylsiloxane powder to 5mL of dichloromethane and stir magnetically at room temperature to form a solution with a concentration of 30mg / mL. Then, add 0.01g of LiGa to the solution. 3.95 CrNi 0.05 O8 and 0.01g ZnS nanoparticles (particle size 200nm) were stirred and ultrasonically dispersed at room temperature using a magnetic stirrer to form a uniformly dispersed suspension. The suspension was poured into a square glass mold (depth 400μm), and the mold was transferred to a constant temperature and humidity chamber at 30℃ and 70% RH for drying for 5h. Finally, a porous green radiation-cooling film was obtained after peeling it off from the mold.

[0082] Example 5: Preparation of a green radiation-cooling thin film based on near-infrared light conversion materials

[0083] 1. Green pigment LiGa 4.495 Cr 0.5 Ni 0.005 Preparation of O8

[0084] Preparation of LiGa 4.495 Cr 0.5 Ni 0.005 O8, with LiGa5O8 as the matrix, and the percentage of Cr dopant ions in the total molar amount of Ga, Cr, and Ni. 3+ and Ni 2+The doping amounts were 10% and 0.1%, respectively. According to the stoichiometric ratio of each component, 1g of the mixed raw material was accurately weighed. The molar ratio of each component in the mixed raw material was Li₂CO₃:Ga₂O₃:Cr₂O₃:NiO = 0.55:2.2475:0.25:0.005. The 1g mixed raw material was placed in an agate mortar, and 3mL of ethanol was added. After grinding for 1 hour to ensure thorough mixing, the mixture was transferred to a corundum crucible, covered, and placed in a high-temperature furnace at 1600℃ for 2 hours. After natural cooling to room temperature, the sample was removed and ground for 15 minutes to obtain the green pigment LiGa. 4.495 Cr 0.5 Ni 0.005 O8.

[0085] 2. Preparation of Green Radiation-Cooling Thin Films Based on Near-Infrared Light Conversion Materials

[0086] First, add 0.45g of polystyrene powder to 5mL of toluene and stir magnetically at room temperature to form a solution with a concentration of 90mg / mL. Then, add 0.03g of LiGa to the solution. 4.495 Cr 0.5 Ni 0.005 O8 and 0.03g Al2O3 nanoparticles (particle size 10μm) were stirred and ultrasonically dispersed at room temperature using a magnetic stirrer to form a uniformly dispersed suspension. The suspension was poured into a square glass mold (depth 300μm), and the mold was transferred to a constant temperature and humidity chamber at 20℃ and 50% RH for drying for 4h. Finally, a porous green radiation cooling film was obtained after peeling it off from the mold.

[0087] Example 6: Preparation of a green radiation-cooling thin film based on near-infrared light conversion materials

[0088] 1. Green pigment LiGa 3.995 CrNi 0.005 Preparation of O8

[0089] Preparation of LiGa 3.995 CrNi 0.005 O8, with LiGa5O8 as the matrix, and the percentage of Cr dopant ions in the total molar amount of Ga, Cr, and Ni. 3+ and Ni 2+The doping amounts were 20% and 0.1%, respectively. According to the stoichiometric ratio of each component, 1g of the mixed raw material was accurately weighed. The molar ratio of each component in the mixed raw material was Li₂CO₃:Ga₂O₃:Cr₂O₃:NiO = 0.55:1.9975:0.5:0.005. The 1g mixed raw material was placed in an agate mortar, and then 3mL of ethanol was added. After grinding for 1 hour to ensure thorough mixing, the mixture was transferred to a corundum crucible, covered, and placed in a high-temperature furnace at 1600℃ for 2 hours. After natural cooling to room temperature, the sample was removed and ground for 15 minutes to obtain the green pigment LiGa. 3.995 CrNi 0.005 O8.

[0090] 2. Preparation of Green Radiation-Cooling Thin Films Based on Near-Infrared Light Conversion Materials

[0091] First, add 0.3g of polylactic acid fiber powder to 5mL of chloroform and stir magnetically at room temperature to form a solution with a concentration of 60mg / mL. Then, add 0.05g of LiGa to the solution. 3.995 CrNi 0.005 O8 and 0.05 g ZrO2 nanoparticles (particle size 200 nm) were stirred and ultrasonically dispersed at room temperature using a magnetic stirrer to form a uniformly dispersed suspension. The suspension was poured into a square glass mold (depth 100 μm), and the mold was transferred to a constant temperature and humidity chamber at 20 °C and 40% RH for drying for 4.5 h. Finally, a porous green radiation-cooling film was obtained after peeling it off from the mold.

[0092] Example 7: Preparation of a green radiation-cooling thin film based on near-infrared light conversion materials

[0093] 1. Green pigment MgGa 1.598 Cr 0.4 Ni 0.002 Preparation of O4

[0094] Preparation of MgGa 1.598 Cr 0.4 Ni 0.002 O4, with MgGa2O4 as the matrix, and the percentage of Cr dopant ions in the total molar amount of Ga, Cr, and Ni. 3+ and Ni 2+The doping amounts were 20% and 0.1%, respectively. According to the stoichiometric ratio of each component, a total mass of 1g of mixed raw material was accurately weighed. The molar ratio of each component in the mixed raw material was MgO:Ga₂O₃:Cr₂O₃:NiO = 1:0.799:0.2:0.002. The 1g mixed raw material was placed in an agate mortar, followed by the addition of 3mL of ethanol and grinding for 1 hour to ensure thorough mixing. The mixture was then transferred to a corundum crucible, covered, and placed in a high-temperature furnace at 1600℃ for 2 hours. After natural cooling to room temperature, the sample was removed and ground for 15 minutes to obtain the green pigment MgGa₂O₃. 1.598 Cr 0.4 Ni 0.002 O4.

[0095] 2. Preparation of Green Radiation-Cooling Thin Films Based on Near-Infrared Light Conversion Materials

[0096] First, add 0.15g of polyethylene powder to 5mL of chlorobenzene and stir magnetically at room temperature to form a solution with a concentration of 30mg / mL; then add 0.03g of MgGa to the above solution. 1.598 Cr 0.4 Ni 0.002 O4 and 0.03g ZrO2 nanoparticles (5μm in diameter) were stirred and ultrasonically dispersed at room temperature using a magnetic stirrer to form a uniformly dispersed suspension. The suspension was poured into a square glass mold (500μm deep), and the mold was transferred to a constant temperature and humidity chamber at 30℃ and 80% RH for drying for 2 hours. Finally, the porous green radiation cooling film was obtained after peeling it off from the mold.

[0097] Example 8: Preparation of a green radiation-cooling thin film based on near-infrared light conversion materials

[0098] 1. Green pigment MgGa 1.798 Cr 0.2 Ni 0.002 Preparation of O4

[0099] Preparation of MgGa 1.798 Cr 0.2 Ni 0.002 O4, with MgGa2O4 as the matrix, and the percentage of Cr dopant ions in the total molar amount of Ga, Cr, and Ni. 3+ and Ni 2+The doping amounts were 10% and 0.1%, respectively. According to the stoichiometric ratio of each component, 1g of the mixed raw material was accurately weighed. The molar ratio of each component in the mixed raw material was MgO:Ga₂O₃:Cr₂O₃:NiO = 1:0.899:0.1:0.002. The 1g mixed raw material was placed in an agate mortar, and then 3mL of ethanol was added. After grinding for 1 hour to ensure thorough mixing, the mixture was transferred to a corundum crucible, covered, and placed in a high-temperature furnace at 1600℃ for 2 hours. After natural cooling to room temperature, the sample was removed and ground for 15 minutes to obtain the green pigment MgGa₂O₃. 1.798 Cr 0.2 Ni 0.002 O4.

[0100] 2. Preparation of Green Radiation-Cooling Thin Films Based on Near-Infrared Light Conversion Materials

[0101] First, add 0.45g of polyvinylidene fluoride powder to 5mL of xylene and stir magnetically at room temperature to form a solution with a concentration of 90mg / mL; then add 0.01g of MgGa to the above solution. 1.798 Cr 0.2 Ni 0.002 O4 and 0.01g ZrO2 nanoparticles (500nm in diameter) were stirred and ultrasonically dispersed at room temperature using a magnetic stirrer to form a uniformly dispersed suspension. The suspension was poured into a square glass mold (300μm deep), and the mold was transferred to a constant temperature and humidity chamber at 40℃ and 90% RH for drying for 3.5h. Finally, a porous green radiation-cooling film was obtained after peeling it off from the mold.

[0102] Comparative Example 1: Preparation of a white radiation-cooling thin film with porous microspheres

[0103] This comparative example is based on Example 1, but differs from Example 1 in that no green pigment Mg was added. 0.79 Cr 0.2 Ni 0.01 O.

[0104] 0.45g of polyvinyl chloride powder was added to 5mL of carbon disulfide and magnetically stirred at room temperature to form a solution of 90mg / mL. 0.05g of SiO2 nanoparticles (100nm in diameter) were added to the solution and ultrasonically dispersed at room temperature using a magnetic stirrer to form a uniformly dispersed suspension. The suspension was poured into a square glass mold (500μm deep) and the mold was transferred to a constant temperature and humidity chamber at 20℃ and 90% RH for drying for 0.5h. Finally, a porous white radiation-cooling film was obtained after peeling it off from the mold.

[0105] Comparative Example 2: Preparation of a Green Radiation-Cooling Thin Film Based on Near-Infrared Light Conversion Material

[0106] This comparative example is based on Example 1, but differs from Example 1 in that SiO2 inorganic microspheres were not added.

[0107] 1. Green pigment Mg 0.79 Cr 0.2 Ni 0.01 Preparation of O

[0108] Preparation of Mg 0.79 Cr 0.2 Ni 0.01 O, the matrix is ​​MgO, and the percentage of Cr dopant ions is based on the total molar amount of Mg, Cr, and Ni. 3+ and Ni 2+ The doping amounts were 20% and 1%, respectively. According to the stoichiometric ratio of each component, 1g of the mixed raw material was accurately weighed, with a molar ratio of MgO:Cr2O3:NiO = 0.79:0.1:0.01. The 1g mixed raw material was placed in an agate mortar, followed by the addition of 3mL of ethanol and grinding for 1 hour to ensure thorough mixing. The mixture was then transferred to a corundum crucible, covered, and placed in a high-temperature furnace at 1600℃ for 2 hours. After natural cooling to room temperature, the sample was removed and ground for 15 minutes to obtain the green pigment Mg. 0.79 Cr 0.2 Ni 0.01 O.

[0109] 2. Preparation of Green Radiation-Cooling Thin Films Based on Near-Infrared Light Conversion Materials

[0110] First, add 0.45g of polyvinyl chloride powder to 5mL of carbon disulfide and stir magnetically at room temperature to form a solution with a concentration of 90mg / mL. Then, add 0.05g of Mg to the solution. 0.79 Cr 0.2 Ni 0.01 O, use a magnetic stirrer to stir and ultrasonically disperse at room temperature to form a uniformly dispersed suspension. Pour the suspension into a square glass mold (100 μm deep). Transfer the mold to a constant temperature and humidity chamber at 20 °C and 40% RH and dry for 4.5 h. Finally, peel it off from the mold to obtain a porous green radiation cooling film.

[0111] Comparative Example 3: Preparation of a Green Radiation-Cooling Thin Film Based on Near-Infrared Light Conversion Material

[0112] This comparative example is based on Example 1, but differs from Example 1 in that Cr is used... 3+ The molar doping amount was changed from 20% to 30%.

[0113] 1. Green pigment Mg 0.69 Cr 0.3 Ni0.01 Preparation of O

[0114] Preparation of Mg 0.69 Cr 0.3 Ni 0.01 O, the matrix is ​​MgO, and the percentage of Cr dopant ions is based on the total molar amount of Mg, Cr, and Ni. 3+ and Ni 2+ The doping amounts were 30% and 1%, respectively. According to the stoichiometric ratio of each component, 1g of the mixed raw material was accurately weighed, with a molar ratio of MgO:Cr2O3:NiO = 0.69:0.15:0.01. The 1g mixed raw material was placed in an agate mortar, followed by the addition of 3mL of ethanol and grinding for 1 hour to ensure thorough mixing. The mixture was then transferred to a corundum crucible, covered, and placed in a high-temperature furnace at 1600℃ for 2 hours. After natural cooling to room temperature, the sample was removed and ground for 15 minutes to obtain the green pigment Mg. 0.69 Cr 0.3 Ni 0.01 O.

[0115] 2. Preparation of Green Radiation-Cooling Thin Films Based on Near-Infrared Light Conversion Materials

[0116] First, add 0.45g of polyvinyl chloride powder to 5mL of carbon disulfide and stir magnetically at room temperature to form a solution with a concentration of 90mg / mL. Then, add 0.05g of Mg to the solution. 0.69 Cr 0.3 Ni 0.01 O and 0.05 g of SiO2 nanoparticles (100 nm in diameter) were stirred and ultrasonically dispersed at room temperature using a magnetic stirrer to form a uniformly dispersed suspension. The suspension was poured into a square glass mold (500 μm deep), and the mold was transferred to a constant temperature and humidity chamber at 20 °C and 90% RH for drying for 0.5 h. Finally, a porous green radiation-cooling film was obtained after peeling it off from the mold.

[0117] Comparative Example 4: Preparation of a Green Radiation-Cooling Thin Film Based on Near-Infrared Light Conversion Material

[0118] This comparative example is based on Example 1, but differs from Example 1 in that Ni is used. 2+ The molar doping level was changed from 1% to 2%.

[0119] 1. Green pigment Mg 0.78 Cr 0.2 Ni 0.02 Preparation of O

[0120] Preparation of Mg 0.78 Cr 0.2 Ni 0.02O, the matrix is ​​MgO, and the percentage of Cr dopant ions is based on the total molar amount of Mg, Cr, and Ni. 3+ and Ni 2+ The doping amounts were 20% and 2%, respectively. According to the stoichiometric ratio of each component, 1g of the mixed raw material was accurately weighed, with a molar ratio of MgO:Cr2O3:NiO = 0.78:0.1:0.02. The 1g mixed raw material was placed in an agate mortar, followed by the addition of 3mL of ethanol, and ground for 1 hour to ensure thorough mixing. The mixture was then transferred to a corundum crucible, covered, and placed in a high-temperature furnace at 1600℃ for 2 hours. After natural cooling to room temperature, the sample was removed and ground for 15 minutes to obtain the green pigment Mg. 0.78 Cr 0.2 Ni 0.02 O.

[0121] 2. Preparation of Green Radiation-Cooling Thin Films Based on Near-Infrared Light Conversion Materials

[0122] First, add 0.45g of polyvinyl chloride powder to 5mL of carbon disulfide and stir magnetically at room temperature to form a solution with a concentration of 90mg / mL. Then, add 0.05g of Mg to the solution. 0.78 Cr 0.2 Ni 0.02 O and 0.05 g of SiO2 nanoparticles (100 nm in diameter) were stirred and ultrasonically dispersed at room temperature using a magnetic stirrer to form a uniformly dispersed suspension. The suspension was poured into a square glass mold (500 μm deep), and the mold was transferred to a constant temperature and humidity chamber at 20 °C and 90% RH for drying for 0.5 h. Finally, a porous green radiation-cooling film was obtained after peeling it off from the mold.

[0123] Performance determination of radiation-cooled thin films in experimental cases

[0124] The cooling performance of the radiative cooling films provided in each embodiment and comparative example was measured.

[0125] 1. Morphological diagram

[0126] The green radiation-cooling thin film obtained in Example 1 was photographed with a camera, and the results are as follows: Figure 1 As shown, the green near-infrared light conversion material Mg 0.79 Cr 0.2 Ni 0.01 O is uniformly distributed in polyvinyl chloride powder to obtain a homogeneous green radiation-cooling film.

[0127] Microscopic images were taken of the green radiation-cooling films obtained in Example 1 (left image) and Example 3 (right image), and the results are as follows: Figure 2As shown, interconnected pores can be observed inside the film. The porous structure of varying sizes can trap some air, and by utilizing the difference in refractive index between air and powder, it can enhance the reflection and scattering of sunlight.

[0128] The morphology of the green films obtained in the other embodiments is basically the same as that in Example 1, and will not be described again here.

[0129] 2. X-ray diffraction pattern and Raman spectrum

[0130] The green radiation-cooled thin film obtained in Example 4 was measured using a Bruker D8 ADVANCE X-ray powder diffractometer (Germany). The results are as follows: Figure 3 As shown, the measured spectrum is consistent with the LiGa5O8 standard card (JCPDS 38-1371), proving that no other phases or impurities were introduced onto the surface of the thin film sample prepared in this application, verifying the successful preparation of a green radiation-cooling thin film based on near-infrared light conversion materials; to further verify Cr 3+ / Ni 2+ Successful doping was achieved using an Agilent Cary 5000 UV-Vis-NIR spectrophotometer, as demonstrated in Example 4 by altering the Cr content. 3+ The Raman spectra of the green radiation-cooling thin films prepared with the specified doping ratios are shown in the following figures. Figure 4 As shown, with Cr 3+ As the amount of Ga increases, the amount of Ga that it substitutes in the matrix LiGa5O8 increases, resulting in a gradual decrease in the relative strength of Ga. Figure 3 The dashed box section confirms that Cr 3+ / Ni 2+ Successful doping of the matrix LiGa5O8.

[0131] 3. Absorption / Emission Spectra

[0132] The absorbance / emissivity in the ultraviolet-visible-near-infrared bands of Example 1 was measured using an Agilent Cary 5000 UV-Vis-NIR spectrophotometer. The results are as follows: Figure 5 As shown, in the visible light region (380–800 nm), the absorption rate of the green radiation-cooling film can reach 40%–50%, which means that the film can effectively absorb this part of the visible light energy; in the near-infrared region (800–1600 nm), the reflectivity is as high as 95%–99%, which can reflect most of the solar radiation energy away, reduce heat absorption, and thus significantly reduce the temperature of the film.

[0133] Figure 6 Cr prepared in Examples 1 and 3 3+ / Ni 2+ Doped green pigment Mg 0.79 Cr0.2 Ni 0.01 O and Mg 0.89 Cr 0.1 Ni 0.01 The fluorescence spectral characteristics of O, as shown in the figure, indicate that under 420 nm excitation, Cr... 3+ / Ni 2+ The doped sample emits near-infrared light centered at 1240 nm, meaning it emits absorbed energy at 1240 nm; similarly, Figure 7 The Cr prepared in Example 4 3+ / Ni 2+ Doped green pigment LiGa 4.79 Cr 0.2 Ni 0.01 The fluorescence emission spectrum of O8, under 460 nm excitation, shows that Cr... 3+ / Ni 2+ The fact that the doped sample can emit the absorbed energy at 1335 nm indicates that the film can absorb energy in the visible light region and emit the absorbed energy efficiently in the near-infrared region.

[0134] 4. Daytime temperature tracking curve

[0135] The radiative cooling performance of the thin film was tested under clear outdoor natural light conditions using a self-made apparatus. This apparatus consisted of a polystyrene foam box covered with aluminum foil and a K-type thermocouple (a type of temperature sensor). The thin film was placed on top of the foam box to receive ample natural light, and the K-type thermocouple was firmly attached to the bottom of the film sample using polyimide adhesive. The polystyrene foam box covered with aluminum foil was used to reduce the influence of ambient heat. During the test, the specific time periods were recorded, and the temperature changes of the thin film were continuously monitored. After the test, the collected temperature data were processed and analyzed to evaluate the radiative cooling performance of the thin film. Figure 8 The figures show the daytime temperature tracking curves of the green radiation-cooling films prepared in Example 1 and Comparative Example 1 from 10:00 to 13:00. As can be seen from the figure, the maximum temperature difference between Comparative Example 1 and the environment is 6.3℃, and the average temperature difference is 2.6℃. The maximum temperature difference between Example 1 and the environment is 10.8℃, and the average temperature difference is 5.8℃. With the addition of green pigment, the maximum temperature difference between Example 1 and Comparative Example 1 can reach 6.6℃, and the average temperature difference is 4℃. This indicates that after adding green pigment, the film can reflect the energy absorbed in the visible light region in the near-infrared region, achieving a passive cooling effect and further significantly reducing the temperature of the film. Figure 9The daytime temperature tracking curves of the films prepared in Example 1 and Comparative Example 2 from 9:30 to 15:00 show that the maximum temperature difference between Comparative Example 2 and the environment was 3.4℃, and the average temperature difference was 2.0℃. The maximum temperature difference between Example 1 and the environment was 8.1℃, and the average temperature difference was 5.1℃. With the addition of nanoparticles, the maximum temperature difference between Example 1 and Comparative Example 2 was 5.1℃, and the average temperature difference was 3.3℃. This indicates that only green radiative cooling films based on near-infrared light conversion materials prepared by simultaneously combining polymer, green pigment, and inorganic microspheres possess excellent cooling effects. Compared to films prepared without inorganic microspheres or green pigments, their cooling effect is inferior to films with the synergistic effect of these three components.

[0136] Figure 10 The daytime temperature tracking curves of the films prepared in Example 1 and Comparative Example 3 from 11:30 to 13:00 show that the maximum temperature difference between Comparative Example 3 and the environment was 4.0℃, and the average temperature difference was 2.1℃. The maximum temperature difference between Example 1 and the environment was 7.9℃, and the average temperature difference was 4.9℃. With the increase of Cr... 3+ With the increase in Cr content, the maximum temperature difference in Example 1 compared to Comparative Example 3 was 3.9°C, and the average temperature difference was 2.2°C, indicating that the film doped with 20% Cr... 3+ Its cooling effect is better than that of 30% Cr 3+ ; Figure 11 The daytime temperature tracking curves of the films prepared in Example 1 and Comparative Example 4 from 10:00 to 15:30 show that the maximum temperature difference between Comparative Example 4 and the environment was 3.3°C, and the average temperature difference was 1.9°C. The maximum temperature difference between Example 1 and the environment was 7.7°C, and the average temperature difference was 5.0°C. With the increase of Ni... 2+ With the increase of Ni, the maximum temperature difference in Example 1 compared to Comparative Example 2 was 4.1°C, and the average temperature difference was 2.8°C, indicating that the film doped with 1% Ni... 2+ The cooling effect is better than that of 2% Ni. 2+ Comparative Examples 3 and 4 demonstrate that only when the chromium-nickel doping amount of the green pigment in the green radiative cooling film simultaneously satisfies a chromium molar doping ratio of 10%–20% and a nickel molar doping ratio of 0.1%–1% can a superior cooling effect be achieved. In Example 1, the film was compared with the films prepared in Comparative Examples 1, 2, 3, and 4 using daytime temperature tracking curves. It is worth noting that since these comparative examples were conducted on different days, and the intensity of sunlight naturally varies daily, therefore… Figures 8 to 11 The daytime temperature tracking curves of the thin film in Example 1 shown in the figure exhibit some differences. These differences are a natural result of the experimental conditions (i.e., different solar radiation intensities on different days), and are reasonable phenomena in the experimental process, which do not affect the validity of the experimental conclusions.

[0137] In summary, Examples 1-8, by simultaneously combining polymer, green pigment, and inorganic microspheres, and with the green pigment containing Cr... 3+ The molar doping ratio is 10%–20% and Ni 2+ A green radiative cooling thin film based on a near-infrared light conversion material was successfully prepared with a molar doping ratio ranging from 0.1% to 1%. This film exhibits excellent absorption performance in the visible light band and efficient emission in the near-infrared band, while also possessing excellent reflectivity in the near-infrared band. This characteristic significantly reduces the temperature of the object's surface or surrounding environment, thus achieving a highly efficient radiative cooling effect.

[0138] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A green radiation-cooling thin film based on near-infrared light conversion materials, characterized in that, The green radiation cooling film is mainly prepared from high molecular polymers, green pigments and inorganic microspheres; The green pigment includes one or more of chromium-nickel co-doped magnesium oxide, chromium-nickel co-doped lithium gallate, and chromium-nickel co-doped magnesium gallate. In the chromium-nickel co-doped magnesium oxide, the chromium doping amount is 10%~20% and the nickel doping amount is 0.1%~1% based on the percentage of the total molar amount of magnesium, chromium and nickel elements. In the chromium-nickel co-doped lithium gallate or chromium-nickel co-doped magnesium gallate, the chromium doping amount is 10%~20% and the nickel doping amount is 0.1%~1% based on the percentage of the total molar amount of gallium, chromium and nickel. The inorganic microspheres include one or more of titanium dioxide, magnesium oxide, silicon dioxide, aluminum oxide, zirconium dioxide, and barium sulfate; The inorganic microspheres have a particle size of 100 nm to 10 μm; The polymer includes one or more of polylactic acid fiber, polydimethylsiloxane, polystyrene, polyvinyl chloride, polyethylene, and polyvinylidene fluoride; The mass ratio of the polymer, green pigment and inorganic microspheres is 1:(0.02~0.5):(0.02~0.5).

2. The green radiation-cooling thin film based on near-infrared light conversion material according to claim 1, characterized in that, The green pigment includes Mg （1-x-y） Cr x Ni y O, Li (Ga （1-x-y） Cr x Ni y )5O8, Mg(Ga （1-x-y） Cr x Ni y One or more of 2O4; wherein, 0.1≤x≤0.2, 0.001≤y≤0.

01.

3. The green radiation-cooling thin film based on near-infrared light conversion material according to claim 2, characterized in that, The green pigment includes Mg 0.79 Cr 0.2 Ni 0.01 O, Mg 0.84 Cr 0.15 Ni 0.01 O, Mg 0.89 Cr 0.1 Ni 0.01 O, LiGa 3.95 CrNi 0.05 O8, LiGa 4.495 Cr 0.5 Ni 0.005 O8, LiGa 3.995 CrNi 0.005 O8, MgGa 1.598 Cr 0.4 Ni 0.002 O4, MgGa 1.798 Cr 0.2 Ni 0.002 One or more of O4.

4. The method for preparing the green radiation-cooling thin film based on near-infrared light conversion material according to any one of claims 1 to 3, characterized in that, Includes the following steps: S1. Mix the polymer, green pigment, and inorganic microspheres in an organic solvent to obtain a suspension; S2. Coat the suspension obtained in step S1 onto the substrate, dry it to form a thin film on the substrate, and peel it off to obtain a green radiation cooling film based on near-infrared light conversion material.

5. The preparation method according to claim 4, characterized in that, In step S1, the organic solvent includes one or more of formic acid, tetrahydrofuran, carbon disulfide, dichloromethane, trichloromethane, and toluene.

6. The preparation method according to claim 4, characterized in that, In step S1, the mass-to-volume ratio of the polymer and the organic solvent is 1 g: (0.01~0.05) L.

7. The application of the green radiation-cooling thin film based on near-infrared light conversion material as described in any one of claims 1 to 3 in the preparation of cooling materials.

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