Montmorillonite-based sodium aluminum silicate radiation refrigeration powder material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of radiation refrigeration materials, in particular to a montmorillonite-based sodium aluminum silicate radiation refrigeration powder material and a preparation method and application thereof.The preparation method comprises the following steps that S1, montmorillonite, sodium carbonate and aluminum hydroxide are mixed according to a certain weight ratio and then ground in a ball mill, and evenly-mixed precursor powder is obtained; s2, putting the precursor powder obtained in the step S1 into a crucible, transferring the crucible into a muffle furnace, and carrying out solid-phase reaction sintering under certain temperature and time conditions to obtain a sodium aluminum silicate reaction product; s3, grinding and powdering the reaction product obtained in the step S2, sieving and drying to obtain the sodium aluminum silicate radiation refrigeration powder material with a certain particle size; the problems that an existing injection refrigeration material is complex in process, high in cost and not prone to mass production are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of radiation refrigeration materials, and in particular to a montmorillonite-based sodium aluminum silicate radiation refrigeration powder material, a preparation method thereof, and applications thereof. Background Art

[0002] Global warming is a major environmental challenge facing the world, increasing the demand for cooling. To address this issue, various active cooling methods are widely used. However, traditional active cooling methods, such as air conditioning, consume large amounts of electricity and emit greenhouse gases, further exacerbating global warming and driving the demand for cooling capacity even higher in the future. Therefore, new, energy-efficient, and environmentally friendly cooling methods are crucial for mitigating the greenhouse effect and achieving energy conservation and emission reduction.

[0003] Benefiting from the principle of zero energy consumption and passive cooling, radiative cooling is a technology that is expected to be applied on a large scale to reduce energy consumption. Radiative cooling works by emitting the energy of an object into outer space in the form of electromagnetic waves, and is completely spontaneous, without the need for external energy input. To achieve the cooling effect, the radiator needs to be highly reflective in the solar spectrum band to reduce energy absorption, and highly emissive in the 8-13μm atmospheric window infrared band to enhance energy dissipation. Currently, most of the publicly available radiative cooling materials have complex preparation processes and high costs, and their UV resistance and water resistance need to be further enhanced, which brings certain difficulties to the practical application of this technology. Therefore, the development of new low-cost technologies to prepare high-performance radiative cooling materials with UV resistance and water resistance has great practical value. In addition, in order to promote the promotion and application of radiative cooling technology, radiative cooling materials should be cheap.

[0004] Montmorillonite is an inexpensive and widely distributed mineral composed of aluminum-magnesium silicate, exhibiting the characteristics of a layered clay material. Montmorillonite mined from mines can be used as a high-purity chemical raw material after simple processing. The primary Si-O and Al-O bonds in montmorillonite possess radiative cooling properties, but its layered structure results in low UV resistance and poor environmental stability due to its tendency to absorb water vapor in air. Therefore, the development of novel preparation technologies is necessary to convert inexpensive montmorillonite into a high-value radiative cooling material. Furthermore, benefiting from the low cost of montmorillonite, the resulting radiative cooling material will be low-cost. Developing novel preparation technologies to transform montmorillonite into a radiative cooling material with high solar spectral reflectance and high atmospheric window emissivity will greatly promote the practical application of radiative cooling technology. Summary of the Invention

[0005] The present invention aims to provide a montmorillonite-based sodium aluminum silicate radiative cooling powder material, its preparation method, and its application. This overcomes the complex processing, high cost, and difficulty in mass production of existing radiative cooling materials. Furthermore, the polymer / sodium aluminum silicate flexible film and all-inorganic radiative cooling coating described in this invention are simple to prepare and have low production costs, demonstrating promising application prospects in the construction industry.

[0006] In order to achieve the above technical objectives and the above technical effects, the present invention is implemented through the following technical solutions:

[0007] A method for preparing a montmorillonite-based sodium aluminum silicate radiation refrigeration powder material comprises the following steps:

[0008] S1: Mixing montmorillonite, sodium carbonate, and aluminum hydroxide in a certain weight ratio, and grinding them in a ball mill to obtain a uniformly mixed precursor powder;

[0009] S2: placing the precursor powder obtained in step S1 into a crucible, transferring it to a muffle furnace, and sintering it under certain temperature and time conditions to obtain a sodium aluminum silicate reaction product by solid phase reaction;

[0010] S3: grinding and powdering the reaction product obtained in step S2, sieving, and drying to obtain a sodium aluminum silicate radiation refrigeration powder material with a certain particle size;

[0011] In another aspect, the present invention provides a method for preparing a flexible polymer / sodium aluminum silicate film, comprising: uniformly mixing polymethylpentene (TPX) and cyclohexane in a specific mass ratio, and then heating to completely dissolve the TPX. After the TPX is completely dissolved, a specific proportion of a sodium aluminum silicate radiative cooling powder is added, and after uniform mixing, the TPX / cyclohexane / sodium aluminum silicate mixture is coated on a glass sheet using a casting method, thereby producing a flexible polymer / sodium aluminum silicate radiative cooling functional film with high water resistance and high UV stability.

[0012] On the other hand, the present invention provides a method for preparing an all-inorganic radiant cooling coating, comprising: adding commercial potassium silicate water glass with a modulus of 3.1-3.4 and sodium aluminum silicate powder in a certain mass ratio to a ball mill jar, ball milling and mixing at a certain speed and time to obtain an inorganic coating, spraying the mixture on a clean wood or metal plate substrate surface with a spray gun to obtain a wet coating, drying the wet coating in air for a certain time to remove solvent water, and then placing the wet coating in an oven at 120°C to dry the remaining water in the coating and promote the complexation of silicon-oxygen bonds between potassium silicates, thereby obtaining an all-inorganic radiant cooling coating.

[0013] Furthermore, the weight ratio of montmorillonite: sodium carbonate: aluminum hydroxide is (10:4:5) to (5:6:4).

[0014] Furthermore, the temperature range of solid phase reaction sintering montmorillonite is 800-1200° C., and the sintering time is 2-5 hours.

[0015] Furthermore, the particle size of the powder after sieving is 1200 to 2800 mesh.

[0016] Furthermore, the ratio of polymethylpentene (TPX): cyclohexane: sodium aluminum silicate is (1:19:1) to (1:19:5).

[0017] Furthermore, the prepared polymer / sodium aluminum silicate flexible film has a thickness of 100 μm to 1 mm.

[0018] Furthermore, the mass ratio of the potassium silicate water glass to the sodium aluminum silicate powder is (1:1) to (4:1).

[0019] Furthermore, the ball milling speed is 400-800 r / min, and the ball milling time is 0.5-3 h.

[0020] Furthermore, the clean wood and metal plate substrates were polished with sandpaper for 5 minutes, and then ultrasonically treated in deionized water, acetone, and anhydrous ethanol for 10 minutes to remove dirt.

[0021] Furthermore, the wet coating is dried in air for 5 to 24 hours.

[0022] Furthermore, the thickness of the sodium aluminum silicate all-inorganic radiation cooling coating is 50 to 500 μm.

[0023] Furthermore, the prepared polymer / sodium aluminum silicate flexible film exhibited a solar spectral reflectivity of 85.6% to 92% and an atmospheric window infrared emissivity of 90% to 95%. After being maintained in an environment with 80% humidity for 24 hours, the solar spectral reflectivity was 85.6% to 90%, and the atmospheric window infrared emissivity was 90% to 95%. After 60 hours of standard solar ultraviolet radiation, the solar spectral reflectivity was 85.6% to 92%, and the atmospheric window infrared emissivity was 90% to 95%.

[0024] Furthermore, the prepared sodium aluminum silicate all-inorganic radiation cooling coating has a solar spectrum reflectivity of 89% to 92% and an atmospheric window infrared emissivity of 93% to 96%.

[0025] Beneficial effects of the present invention:

[0026] The present invention uses natural montmorillonite as the core raw material and efficiently synthesizes sodium aluminum silicate powder through a solid-phase sintering method combined with a precise ratio of sodium carbonate and aluminum hydroxide. The layered silicate structure of montmorillonite undergoes dissociation and recombination during the high-temperature sintering process, rearranging the Al-O and Si-O bond networks to form stable three-dimensional spinel-type sodium aluminum silicate crystals. This process avoids the solvent consumption and complex purification steps required by traditional wet chemical methods. The efficient conversion of mineral raw materials can be achieved through ball milling and a single high-temperature sintering step, significantly reducing energy consumption and equipment costs. The micron-level particle size and high specific surface area characteristics of the sintered product enable it to be directly dispersed in organic or inorganic matrices without the need for secondary processing, further reducing material loss. The natural source of the raw materials and the simplified process design make the overall material cost only 20% to 30% of that of traditional radiant refrigeration materials, showing the potential for large-scale industrial production.

[0027] The spinel crystal structure of sodium aluminum silicate powder imparts unique optical properties: within the solar spectrum, the micron-sized powder forms a continuous reflective interface through multiple scattering, significantly enhancing the material's reflectivity to sunlight. In the atmospheric window band, the vibrational frequencies of the Al-O and Si-O bonds in its crystal lattice closely match those of infrared radiation, enhancing thermal radiation efficiency through phonon-photon coupling. When the powder is composited with a TPX matrix, the transparency of TPX allows the powder to fully utilize its scattering function, while the inorganic potassium silicate matrix chemically bonds with aluminum ions on the powder surface through a silicon-oxygen network, further enhancing the coating's density and radiation stability.

[0028] The material of the present invention achieves strong tolerance to moisture, heat, ultraviolet light and temperature changes through matrix modification and interface design. The high crystallinity and non-polar molecular chain structure of the TPX matrix effectively block the penetration of water molecules and inhibit powder agglomeration, ensuring the stability of optical properties in high humidity environments; its saturated CC bond chemical structure is intrinsically inert to ultraviolet light, avoiding material degradation caused by photooxidation. For all-inorganic coatings, potassium silicate and sodium aluminum silicate powders form a chemical cross-linking network through Al-O-Si bonds, which enhances the adhesion of the coating to substrates such as wood and metal. At the same time, the thermal expansion coefficient of the silicon-oxygen network matches that of the powder to avoid cracking problems caused by temperature cycles. In addition, the material can be flexibly formed by cast or spraying processes, adapting to the needs of multiple scenarios such as building exterior walls, car surfaces, and outdoor equipment, and has both long-term durability and engineering adaptability.

[0029] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 XRD patterns of products sintered at different temperatures.

[0032] Figure 2 This is the SEM image of the sodium aluminum silicate powder sample.

[0033] Figure 3 This is a picture of the polymer / sodium aluminum silicate flexible film sample described in Example 1.

[0034] Figure 4 This is the solar spectrum reflection diagram of the polymer / sodium aluminum silicate flexible film described in Example 1.

[0035] Figure 5 This is the infrared spectral emissivity diagram of the polymer / sodium aluminum silicate flexible film described in Example 1.

[0036] Figure 6 This is a solar spectrum reflection graph of the polymer / sodium aluminum silicate flexible film described in Example 1 after being kept in an environment with a humidity of 80% RH for 24 hours.

[0037] Figure 7 This is a solar spectrum reflection graph of the polymer / sodium aluminum silicate flexible film described in Example 1 after being irradiated with standard solar ultraviolet radiation for 60 hours.

[0038] Figure 8 This is a photo of the all-inorganic radiative cooling coating sample described in Example 2.

[0039] Figure 9 This is the infrared spectral emissivity diagram of the all-inorganic radiative cooling coating sample described in Example 2.

[0040] Figure 10 This is the infrared spectral emissivity diagram of the all-inorganic radiative cooling coating sample described in Example 2. DETAILED DESCRIPTION

[0041] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0042] Example 1

[0043] In this embodiment, montmorillonite is used as a raw material, sodium carbonate and aluminum hydroxide are used as modifying additives, and a method for preparing a sodium aluminum silicate radiation cooling powder material and a film by heat treatment is carried out in the following steps:

[0044] S1: Weigh a certain weight ratio of montmorillonite, sodium carbonate, and aluminum hydroxide and mix them using a ball mill. Use a balance to weigh montmorillonite, sodium carbonate, and aluminum hydroxide in a molar ratio of 2:1:1 and add them to a ball mill. Mix them using a ball mill and grind at 800 rpm for 30 minutes. Sieve and obtain a homogenized precursor.

[0045] S2: Sinter the precursor powder to prepare the sodium aluminum silicate product. Add the precursor to a crucible and transfer it to a muffle furnace. Set the heating rate to 5°C / min, heat it to 1100°C, and keep it warm for 5 hours to finally convert the precursor into the initial sodium aluminum silicate product. Grind the initial product into powder, sieve it with an 800-mesh screen, and dry it to obtain a sodium aluminum silicate radiation refrigeration powder material with a certain particle size. Place the powder in a dryer in a drying oven for later use.

[0046] S3: Preparation of polymer / sodium aluminum silicate flexible film. After polymethylpentene (TPX) and cyclohexane are mixed evenly according to a TPX solid content of 5%, the mixture is placed in a water pot and heated to 70°C to dissolve the TPX. After the TPX is completely dissolved, a sodium aluminum silicate radiative cooling powder material with a solid content of 5% is added. After stirring evenly, the TPX / cyclohexane / sodium aluminum silicate mixture is coated on the surface of a glass sheet using a casting method to obtain a polymer / sodium aluminum silicate flexible radiative cooling functional film with a thickness of 240μm, high water resistance, and high UV radiation stability.

[0047] S4: Water resistance test of polymer / sodium aluminum silicate flexible film. The polymer / sodium aluminum silicate flexible film was placed in a constant temperature and humidity chamber at 95% relative humidity and 25°C for 240 hours to test its water absorption. After the water absorption test, the film's reflectivity and emissivity were measured.

[0048] S5: Testing the UV resistance of polymer / sodium aluminum silicate flexible films. The film was exposed to UV light at nine times the intensity of sunlight and subjected to an accelerated UV aging test at a distance of 5 cm from a 150W mercury lamp for 60 hours. Following the UV irradiation test, the film's reflectivity and emissivity were measured.

[0049] In this embodiment, the relevant data of the test are as follows:

[0050] XRD patterns of montmorillonite-based precursor samples sintered at different temperatures ( Figure 1 );

[0051] The SEM of sodium aluminum silicate powder obtained by sintering at 1100℃ and ball milling and sieving was ( Figure 2 );

[0052] Actual picture of polymer / sodium aluminum silicate film ( Figure 3 );

[0053] The solar spectrum reflection curve of polymer / sodium aluminum silicate film has an average reflectivity of 91.8% ( Figure 4 );

[0054] Infrared emissivity curve of polymer / sodium aluminum silicate film, the average emissivity is 95% ( Figure 5 );

[0055] The solar spectrum reflection curve after the water resistance test of polymer / sodium aluminum silicate film has an average reflectivity of 89.6% ( Figure 6 );

[0056] The solar spectrum reflection curve of the polymer / sodium aluminum silicate film after UV irradiation test shows an average reflectivity of 88.4% ( Figure 7 );

[0057] Example 2

[0058] This example uses the preparation of sodium aluminum silicate all-inorganic radiation cooling coating

[0059] S1: Weigh a certain weight ratio of montmorillonite, sodium carbonate, and aluminum hydroxide and mix them using a ball mill. Use a balance to weigh montmorillonite, sodium carbonate, and aluminum hydroxide in a molar ratio of 2:1.05:1.05 and add them to a ball mill. Mix them using a ball mill and grind at 1000 rpm for 60 minutes. Sieve and obtain a homogenized precursor.

[0060] S2: Sinter the precursor powder to prepare the sodium aluminum silicate product. Add the precursor to a crucible and transfer it to a muffle furnace. Set the heating rate to 2°C / min, heat it to 1100°C, and keep it warm for 10 hours to finally convert the precursor into the initial sodium aluminum silicate product. Grind the initial product into powder, sieve it with a 1000 mesh screen, and dry it to obtain a sodium aluminum silicate radiation refrigeration powder material with a certain particle size. Place the powder in a dryer in a drying oven for later use.

[0061] S3: Weigh a certain weight ratio of potassium silicate water glass and sodium aluminum silicate powder and mix them evenly. Use a balance to weigh potassium silicate (modulus 3.1-3.4) and the prepared aluminum silicate powder in a weight ratio of 5:3, add them to a ball mill, and grind at 800 rpm for 30 minutes to obtain a mixed inorganic coating.

[0062] S4: Preparation of a fully inorganic sodium aluminum silicate radiative cooling coating. First, the wood and metal plates were sanded for 5 minutes, then ultrasonically immersed in deionized water, acetone, and anhydrous ethanol for 10 minutes to remove contaminants. The plates were then dried using a hot air blower. A uniformly mixed solution of potassium silicate and aluminum silicate was added to the spray gun's reservoir and sprayed onto the dried wood and metal substrates to produce a wet coating. The wet coating was air-dried for 24 hours to remove the solvent water, then dried in a 120°C oven for 24 hours to remove the remaining water in the coating and promote the complexation of silicon-oxygen bonds between the potassium silicates, resulting in a fully inorganic radiative cooling coating.

[0063] Physical picture of potassium silicate / sodium aluminum silicate all-inorganic radiative cooling coating ( Figure 8 );

[0064] The thickness of the potassium silicate / sodium aluminum silicate all-inorganic radiative cooling coating is 152μm;

[0065] The reflectivity curve of potassium silicate / sodium aluminum silicate all-inorganic radiative cooling coating has an average reflectivity of 93% ( Figure 9 );

[0066] The emission curve of potassium silicate / sodium aluminum silicate all-inorganic radiative cooling coating has an average emissivity of 95% ( Figure 10 ).

[0067] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to the specific embodiments described. Obviously, many modifications and variations are possible based on the content of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a sodium aluminum silicate radiation refrigeration powder material based on montmorillonite, characterized in that: The following steps are involved: S1: Mixing montmorillonite, sodium carbonate, and aluminum hydroxide in a weight ratio of (10:4:5) to (5:6:4) and ball milling to obtain a precursor powder; S2: sintering the precursor powder at 800-1200° C. for 2-5 hours to generate a sodium aluminum silicate reaction product; S3: Grinding and sieving the reaction product to a particle size of 1200-2800 mesh, and drying to obtain a sodium aluminum silicate radiation refrigeration powder material.

2. The preparation method according to claim 1, wherein The ball milling process in step S1 is performed at a rotation speed of 400 to 800 r / min, and the ball milling time is 0.5 to 3 hours.

3. The sodium aluminum silicate radiation refrigeration powder material prepared by the method according to claim 1 or 2, characterized in that: The powder material has a spinel crystal structure, and its reflectivity in the solar spectrum band of 0.25 to 2.5 μm is 85.6% to 92%, and its infrared emissivity in the atmospheric window band of 8 to 13 μm is 90% to 95%.

4. A method for preparing a polymer / sodium aluminum silicate flexible radiative cooling film based on the powder material of claim 3, characterized in that: The following steps are involved: Polymethylpentene, cyclohexane and sodium aluminum silicate radiation refrigeration powder material are mixed in a mass ratio of 1:19:(1-5), heated and dissolved, and then cast into a film to prepare a flexible film with a thickness of 100 μm to 1 mm.

5. The preparation method according to claim 4, wherein After the film casting, the further step includes: treating the flexible film in an environment with a humidity of 80% RH for 24 hours, wherein the solar spectrum reflectivity thereof is maintained at 85.6% to 90% and the infrared emissivity thereof is maintained at 90% to 95%; Or after 60 hours of standard solar ultraviolet irradiation, its solar spectrum reflectivity remains at 85.6% to 92%, and its infrared emissivity remains at 90% to 95%.

6. A method for preparing an all-inorganic radiative cooling coating based on the powder material according to claim 3, characterized in that: The following steps are involved: Potassium silicate water glass with a modulus of 3.1 to 3.4 and sodium aluminum silicate radiation refrigeration powder material are ball-milled in a mass ratio of (1 to 4):1 to prepare an inorganic coating; the inorganic coating is sprayed on the surface of a substrate, dried in air for 5 to 24 hours, and then cured at 120°C to form a coating with a thickness of 50 to 500 μm.

7. The preparation method according to claim 6, wherein The substrate is wood or metal plate, which is polished with sandpaper and ultrasonically cleaned with deionized water, acetone, and anhydrous ethanol before spraying.

8. An all-inorganic radiative cooling coating prepared according to any one of claims 6-7, characterized in that: The reflectivity of the coating in the solar spectrum band is 89% to 92%, and the infrared emissivity in the 8-13 μm atmospheric window band is 93% to 96%.

9. A radiation cooling product, characterized in that: It comprises any one or more of the sodium aluminum silicate radiative cooling powder material according to claim 3, the flexible film according to claim 4 or 5, or the all-inorganic radiative cooling coating according to claim 8.

10. Use of the radiant cooling product according to claim 9 in thermal management of building exterior walls, automobile surfaces or outdoor equipment.

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