Porous microstructure foaming white cement radiation refrigeration composite material and preparation method thereof

Abstract

The invention discloses a porous microstructure foaming white cement radiation refrigeration composite material and a preparation method thereof, and belongs to the technical field of building energy-saving materials.According to the material, sulphoaluminate white cement serves as a base material, a foaming agent is added, and evenly-distributed porous microstructures are formed in the preparation process; by utilizing the synergistic effect of the high reflection characteristic of the sulphoaluminate white cement and the enhanced scattering and heat insulation performance of the porous microstructure, the efficient radiation refrigeration function is realized; the problems that a traditional white cement material is low in radiation refrigeration efficiency and insufficient in heat insulation performance are solved, the preparation process is simple, the cost is controllable, the material can be widely applied to building exterior walls, roofs and other building envelopes, and remarkable energy-saving benefits and market application prospects are achieved.

Description

Technical Field

[0001] This invention relates to the field of radiation cooling materials technology, and in particular to a porous microstructured foamed white cement radiation cooling composite material with foamed white cement as the matrix and optimized performance by adding functional materials, and its preparation method. It can be widely used in building energy conservation, cold chain logistics, heat dissipation of electronic equipment and other fields. Background Technology

[0002] With the global energy crisis and environmental problems becoming increasingly prominent, the demand for cooling continues to grow in fields such as buildings, industry, and daily life. Traditional compression refrigeration technology relies on fossil fuel consumption, which not only has low energy efficiency but also emits large amounts of greenhouse gases, exacerbating the environmental burden. Against this backdrop, radiative refrigeration technology, as a passive refrigeration technology, has become a research hotspot in the field of refrigeration due to its advantages of requiring no external energy input and zero pollution emissions.

[0003] The core principle of radiation cooling technology is that the material radiates heat into outer space in the form of electromagnetic waves with a wavelength of 8-13μm (atmospheric window band) through its own infrared radiation characteristics. At the same time, by optimizing the solar reflectivity of the material, the absorption of solar radiation energy is reduced, thereby achieving a cooling effect below the ambient temperature.

[0004] Currently, a few cement-based radiative cooling materials have been proposed, but they differ significantly from this invention. Existing patent CN 120463466 A primarily uses white Portland cement combined with a high proportion of radiative cooling particles such as alumina and barium sulfate to achieve solar reflectivity and atmospheric window emissivity. However, this patent does not consider reducing reliance on expensive functional particles through the microstructure design of the matrix itself. In contrast, this invention abandons the reliance on a high proportion of expensive functional particles and uses a foaming process to construct a porous microstructure within the matrix. The innovative approach of using a controllable foaming process to construct a porous microstructure for radiative cooling proposed in this invention can effectively improve solar reflectivity through the Mie scattering effect generated by bubbles, offering advantages such as lightweight and lower cost. Existing patent CN 115466086 A primarily introduces components such as white cement, quartz powder, and titanium dioxide, and uses a high-temperature autoclaving (>180℃) process to induce the formation of crystals such as tobermorite, thereby optimizing optical properties and pore structure. However, it fails to consider the complexity and energy consumption of the production process. Its high-temperature, high-pressure curing conditions place high demands on equipment and consume a lot of energy, hindering low-cost, large-scale production. In contrast, this invention employs a standard curing process at room temperature and humidity. The innovative approach of constructing porous microstructures using controllable foaming technology proposed in this invention requires only conventional stirring and curing, eliminating the need for complex high-temperature autoclaving. It boasts advantages such as simple process, energy saving, and easier industrialization. Existing patent CN 108975824 A mainly describes a cement-based foamed insulation material that improves the mechanical properties of the pore structure through the use of latex powder and reinforcing materials, aiming to achieve building insulation. However, it does not address the material system and structural design for the high reflectivity and high emissivity required for radiative cooling. In contrast, this invention clearly focuses on radiative cooling as its core function, preferentially using high-whiteness sulfoaluminate cement as the matrix and scientifically incorporating functional fillers. This invention proposes an innovative approach to achieving radiative cooling using porous microstructures, enabling these microstructures not only for lightweight insulation but also, more importantly, for enhancing light scattering to improve reflectivity, offering the advantage of multifunctional integration.

[0005] Therefore, there is an urgent need to develop a low-cost, simple-process, and multifunctional integrated cement-based radiative cooling material that can ensure excellent optical performance, namely high reflectivity and high emissivity, while also being lightweight, heat-insulating, and having good mechanical properties, so as to promote the large-scale application of radiative cooling technology in fields such as construction, cold chain, and electronic heat dissipation.

[0006] This invention is proposed against this backdrop. By using sulfoaluminate white cement as a matrix and combining it with a controllable foaming process to construct a porous microstructure, and guiding the orderly generation of ettringite crystals within the pores, the invention synergistically optimizes the pore structure, enhances Mie scattering, and improves the material's mechanical properties and durability. Simultaneously, low-cost functional fillers are introduced for synergistic reinforcement. This achieves synergistic optimization of radiative cooling, thermal insulation, lightweighting, and structural reinforcement without requiring high-temperature, high-pressure, or complex equipment, providing a new and more promising path for the industrialization of cement-based radiative cooling materials. Summary of the Invention

[0007] The purpose of this invention is to overcome the problems of high cost, limited performance, and poor adaptability of existing radiation cooling materials, and to provide a porous microstructured foamed white cement radiation cooling composite material and its preparation method. By optimizing the formula and process, the material achieves synergistic improvement in radiation cooling performance, mechanical properties, and interfacial bonding, thus meeting the application needs of multiple fields.

[0008] To achieve the above-mentioned technical objectives, the technical solution adopted by this invention is as follows: A porous microstructured foamed white cement radiation cooling composite material, the raw materials of which include the following components in parts by weight: 100 parts of sulfoaluminate white cement; 0.2-0.5 parts of foaming agent; 0-5 parts of functional filler; 40-50 parts water; The atmospheric window emissivity of the composite material is greater than 90%, and the overall solar reflectivity is greater than 90%.

[0009] As one possible implementation, the foaming agent described in this solution further includes sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium alpha-olefin sulfonate, hydrogen peroxide, and / or aluminum powder; preferably, the foaming agent is sodium dodecyl sulfate.

[0010] As a preferred implementation method, the foaming agent described in this scheme is pre-diluted with water at a mass ratio of foaming agent:water = 1:25 when added.

[0011] As one possible implementation, the functional filler described in this solution further includes one or more of cellulose nanofibers, nano-silica particles, polyester microfibers, cellulose nanowhiskers, attapulgite, water glass, and waterborne epoxy resin. The functional filler is mainly used to improve mechanical and optical properties.

[0012] As one possible implementation, the composite material described in this solution has a processing length and width dimension of 12cm × 12cm and a processing thickness of 1cm to 2cm.

[0013] Based on the above, this solution also proposes a method for preparing a porous microstructured foamed white cement radiation cooling composite material, which includes the following steps: 1) Weigh sodium dodecyl sulfate and water according to the raw material composition of the composite material described above, dilute them at a mass ratio of 1:25, and stir at 400-500 r / min for 3-5 min to produce stable foam. 2) Weigh out the sulfoaluminate white cement powder and water, stir at 200-300 r / min for 2-3 min to disperse it evenly, and obtain a white cement paste; 3) Take the functional filler cellulose nanofiber dispersion and add it to the cement slurry. Stir at 200-300 r / min for 2-3 min to ensure the slurry is fully mixed. 4) Add the foam obtained in step 1) to the white cement paste prepared in step 2) in two batches. After each addition, stir at 200-300 r / min for 2-3 minutes to ensure that the air bubbles and white cement paste are fully mixed. 5) Pour the cement slurry obtained in step 4) into the mold and cure it to obtain a porous microstructured foamed white cement radiation cooling composite material.

[0014] As a preferred implementation method, the curing conditions used in step 5) of this scheme are preferably: temperature 25±5℃, humidity 90%±10%, and curing time 7 days.

[0015] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art: 1) Excellent radiative cooling performance: This solution utilizes the Mie scattering effect of porous microstructures. The atmospheric window emissivity of the porous microstructure foamed white cement radiative cooling composite material is greater than 90%, and the overall solar reflectivity is greater than 90%. Under outdoor sunlight, it can achieve a cooling effect of ≥5℃. 2) Excellent thermal insulation performance: The air stored in the porous microstructure of the material matrix can act as a thermal insulation material, which significantly reduces the overall thermal conductivity of the material, effectively blocks the transfer of heat from the interior of the building to the cooling surface, and improves the actual cooling effect. 3) Low cost and environmentally friendly: This solution uses white cement as the base material, which has a wide range of raw material sources and low cost; there is no emission of toxic and harmful substances during the production process, and the materials can be recycled after disposal, which meets the requirements of green environmental protection. 4) Simple and controllable preparation process: The entire preparation process of this solution does not require special equipment. The steps of stirring, foaming and curing are easy to scale up and can meet the batch application needs of different fields. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 A digital photograph of the porous microstructured foamed white cement radiation cooling composite material prepared in Example 1 of this scheme; Figure 2 This is a microscopic photograph of the cross-section of the porous microstructured foamed white cement radiation cooling composite material prepared in Example 1 of this scheme, as observed by a scanning electron microscope. Figure 3 This is a magnified microscopic photograph of the cross-section of the porous microstructured foamed white cement radiation cooling composite material prepared in Example 1 of this scheme, observed under a scanning electron microscope. Figure 4 A magnified microscopic photograph of the porous microstructured foamed white cement radiation cooling composite material prepared in Example 1 of this scheme, observed under a scanning electron microscope, showing a local magnified view of the pores. Figure 5 Microscopic images of the porous microstructured foamed white cement radiation cooling composite material prepared in Example 1 of this scheme, observed under a scanning electron microscope; Figure 6 Microscopic images of the porous microstructured foamed white cement radiation cooling composite material prepared for Example 1 of this scheme, observed under a scanning electron microscope, showing the inside of the pores and the cross-section. Figure 7 This is a schematic diagram of the reflectance curve of the porous microstructured foamed white cement radiation cooling composite material prepared in Example 1 of this scheme in the wavelength range of 200-2500nm. The overall solar reflectance of the porous microstructured foamed white cement radiation cooling composite material is 92.81%. Figure 8 This is a schematic diagram of the emissivity curve of the porous microstructured foamed white cement radiation cooling composite material prepared in Example 1 of this scheme in the wavelength range of 2.5-25 μm. The atmospheric window emissivity of the porous microstructured foamed white cement radiation cooling composite material is 98.49%. Figure 9 This is a schematic diagram of the reflectance curve of the ordinary gray silicate cement-based material prepared in Comparative Example 2 of this scheme in the wavelength range of 200-2500nm. The overall solar reflectance of the ordinary gray silicate cement-based material is 42.07%. Figure 10A schematic diagram showing the temperature changes over one hour between the porous microstructured foamed white cement radiation cooling composite material prepared in Example 1 of this scheme and the ordinary gray silicate cement-based material prepared in Comparative Example 2 of this invention. Figure 11 This is a schematic diagram of the working process of the porous microstructured foamed white cement radiation cooling composite material prepared in Example 1 of this scheme; Figure 12 This is a schematic diagram of the compressive strength curve of the porous microstructured foamed white cement radiation cooling composite material prepared in Example 1 of this scheme. The compressive strength of the porous microstructured foamed white cement radiation cooling composite material is 2.63 MPa. Figure 13 This is a schematic diagram of the compressive strength curve of the porous microstructured foamed white cement radiation cooling composite material prepared in Example 5 of this scheme. The compressive strength of the porous microstructured foamed white cement radiation cooling composite material is 5.28 MPa, which is an improvement over the compressive strength of the porous microstructured foamed white cement radiation cooling composite material prepared in Example 1 of this scheme. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be particularly noted that the following embodiments are for illustrative purposes only and do not limit the scope of the invention. Similarly, the following embodiments are only some, not all, embodiments of the present invention, and all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Example 1 This embodiment discloses a method for preparing a porous microstructured foamed white cement radiation cooling composite material, which includes the following steps: 1) Weigh out sodium dodecyl sulfate and water (0.25 parts sodium dodecyl sulfate, 6.25 parts water) according to the formula, dilute at a mass ratio of 1:25, and stir at 400-500 r / min for 3-5 min to produce stable foam; 2) Weigh out the sulfoaluminate white cement powder and water (100 parts cement powder, 40 parts water) according to the formula, stir at 200-300 r / min for 2-3 min to disperse it evenly, and obtain white cement paste; 3) Add the foam obtained in step 1) to the cement paste in two batches. After each addition, stir at 200-300 r / min for 2-3 minutes to ensure that the air bubbles and cement paste are fully mixed. 4) Pour the cement slurry obtained in step 3) into a mold with dimensions of 12cm×12cm×1.5cm (length, width and height) and cure it for 7 days (temperature 25±5℃, humidity 90%±10%) to obtain a porous microstructured foamed white cement radiation cooling composite material.

[0020] Example 2 This embodiment discloses a method for preparing a porous microstructured foamed white cement radiation cooling composite material, which includes the following steps: 1) Weigh out sodium dodecyl sulfate and water (0.25 parts sodium dodecyl sulfate, 6.25 parts water) according to the formula, dilute at a mass ratio of 1:25, and stir at 400-500 r / min for 3-5 min to produce stable foam; 2) Weigh out the sulfoaluminate white cement powder and mixing water (100 parts cement powder, 40 parts water) according to the formula, stir at 200-300 r / min for 2-3 min to disperse it evenly, and obtain white cement paste; 3) Weigh out 3 parts of the functional filler cellulose nanofiber dispersion according to the formula, add it to the cement paste, and stir at 200-300 r / min for 2-3 min to ensure the paste is fully mixed; 4) Add the foam obtained in step 1) to the cement paste in two batches. After each addition, stir at 200-300 r / min for 2-3 minutes to ensure that the air bubbles and cement paste are fully mixed. 5) Pour the cement slurry obtained in step 4) into a mold with dimensions of 12cm×12cm×1.5cm (length, width and height) and cure it for 7 days (temperature 25±5℃, humidity 90%±10%) to obtain a porous microstructured foamed white cement radiation cooling composite material.

[0021] After performance testing, the atmospheric window emissivity of the composite material prepared by the scheme in this embodiment is greater than 90%, and the overall solar reflectivity is greater than 90%.

[0022] Example 3 This embodiment describes a method for preparing a porous microstructured foamed white cement radiation cooling composite material, which is largely the same as that in Embodiment 2.

[0023] The difference between this embodiment and embodiment 2 is in step 3). In this embodiment, step 3) involves weighing 3 parts of the functional filler attapulgite according to the formula, adding it to the cement slurry, and stirring at 200-300 r / min for 2-3 minutes to ensure the slurry is fully mixed.

[0024] The rest are the same as in Example 2, and will not be repeated here.

[0025] Example 4 This embodiment describes a method for preparing a porous microstructured foamed white cement radiation cooling composite material, which is largely the same as that in Embodiment 2.

[0026] The difference between this embodiment and embodiment 2 lies in step 3). In this embodiment, step 3) involves weighing 1.5 parts of functional filler cellulose nanofiber dispersion and 1.5 parts of attapulgite clay according to the formula, adding them to the cement slurry, and stirring at 200-300 r / min for 2-3 minutes to ensure the slurry is fully mixed.

[0027] The rest are the same as in Example 2, and will not be repeated here.

[0028] Example 5 This embodiment describes a method for preparing a porous microstructured foamed white cement radiation cooling composite material, which is largely the same as that in Embodiment 2.

[0029] The difference between this embodiment and embodiment 2 is in step 3). In this embodiment, step 3) involves weighing out 3 parts of the functional filler nano-silica according to the formula, adding it to the cement paste, and stirring at 200-300 r / min for 2-3 minutes to ensure the paste is fully mixed.

[0030] The rest are the same as in Example 2, and will not be repeated here.

[0031] Example 6 This embodiment describes a method for preparing a porous microstructured foamed white cement radiation cooling composite material, which is largely the same as that in Embodiment 2.

[0032] The difference between this embodiment and embodiment 2 is in step 3). In this embodiment, step 3) involves weighing out 3 parts of functional filler water glass according to the formula, adding it to the cement paste, and stirring at 200-300 r / min for 2-3 minutes to ensure the paste is fully mixed.

[0033] The rest are the same as in Example 2, and will not be repeated here.

[0034] Comparative Example 1 The difference between this comparative example and the embodiment is that this comparative example does not contain functional fillers or foaming agents. It includes: 1) Weigh out the sulfoaluminate white cement powder and mixing water (100 parts cement powder, 40 parts water) according to the formula, stir at 200-300 r / min for 2-3 min to disperse it evenly, and obtain white cement paste; 2) Pour the cement slurry obtained in step 1) into a mold with dimensions of 12cm×12cm×1.5cm (length, width and height) and cure it for 7 days (temperature 25±5℃, humidity 90%±10%) to obtain white Portland cement base.

[0035] Comparative Example 2 This comparative example illustrates the preparation of ordinary gray silicate cement, which includes: 1) Weigh 100 parts of ordinary gray silicate cement and 40 parts of water by mass fraction, stir at 200-300 r / min for 2-3 min to disperse evenly, and obtain ordinary gray silicate cement paste; 2) Pour the cement slurry obtained in step 1) into a mold with dimensions of 12cm×12cm×1.5cm (length, width and height) and cure it for 7 days (temperature 25±5℃, humidity 90%±10%) to obtain ordinary gray silicate cement-based material.

[0036] Comparative Test The composite materials prepared in the examples and comparative examples were subjected to image acquisition, microscopic characterization, and / or performance characterization, and the results are as follows: Figure 1 A digital photograph of the porous microstructured foamed white cement radiation cooling composite material prepared in Example 1 of this scheme; Figure 2 This is a microscopic photograph of the cross-section of the porous microstructured foamed white cement radiation cooling composite material prepared in Example 1 of this scheme, as observed by a scanning electron microscope. Figure 3 This is a magnified microscopic photograph of the cross-section of the porous microstructured foamed white cement radiation cooling composite material prepared in Example 1 of this scheme, observed under a scanning electron microscope. Figure 4 A magnified microscopic photograph of the porous microstructured foamed white cement radiation cooling composite material prepared in Example 1 of this scheme, observed under a scanning electron microscope, showing a local magnified view of the pores. Figure 5 Microscopic images of the porous microstructured foamed white cement radiation cooling composite material prepared in Example 1 of this scheme, observed under a scanning electron microscope; Figure 6 Microscopic images of the porous microstructured foamed white cement radiation cooling composite material prepared for Example 1 of this scheme, observed under a scanning electron microscope, showing the inside of the pores and the cross-section. Figure 7 This is a schematic diagram of the reflectance curve of the porous microstructured foamed white cement radiation cooling composite material prepared in Example 1 of this scheme in the wavelength range of 200-2500nm. The overall solar reflectance of the porous microstructured foamed white cement radiation cooling composite material is 92.81%. Figure 8 This is a schematic diagram of the emissivity curve of the porous microstructured foamed white cement radiation cooling composite material prepared in Example 1 of this scheme in the wavelength range of 2.5-25 μm. The atmospheric window emissivity of the porous microstructured foamed white cement radiation cooling composite material is 98.49%. Figure 9This is a schematic diagram of the reflectance curve of the ordinary gray silicate cement-based material prepared in Comparative Example 2 of this scheme in the wavelength range of 200-2500nm. The overall solar reflectance of the ordinary gray silicate cement-based material is 42.07%. Figure 10 A schematic diagram showing the temperature changes over one hour between the porous microstructured foamed white cement radiation cooling composite material prepared in Example 1 of this invention and the ordinary gray silicate cement-based material prepared in Comparative Example 2 of this invention.

[0037] This solution utilizes the Mie scattering effect of porous microstructures. The porous microstructured foamed white cement radiative cooling composite material has an atmospheric window emissivity greater than 90% and an overall solar reflectivity greater than 90%, achieving a cooling effect of ≥5℃ under outdoor sunlight. Additionally, referencing... Figure 11 As shown, the air stored in the porous microstructure of the material matrix in this solution can act as a heat insulation material, significantly reducing the overall thermal conductivity of the material, effectively blocking the transfer of heat from the building interior to the cooling surface, and improving the actual cooling effect.

[0038] Figure 12 This is a schematic diagram of the compressive strength curve of the porous microstructured foamed white cement radiation cooling composite material prepared in Example 1 of this scheme. The compressive strength of the porous microstructured foamed white cement radiation cooling composite material is 2.63 MPa.

[0039] Figure 13 This is a schematic diagram of the compressive strength curve of the porous microstructured foamed white cement radiation cooling composite material prepared in Example 5 of this scheme. The compressive strength of the porous microstructured foamed white cement radiation cooling composite material is 5.28 MPa, which is an improvement over the compressive strength of the porous microstructured foamed white cement radiation cooling composite material prepared in Example 1 of this scheme.

[0040] The above description is only a part of the embodiments of the present invention and does not limit the scope of protection of the present invention. Any equivalent device or equivalent process transformation made based on the content of the present invention specification and drawings, or direct or indirect application in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A porous microstructured foamed white cement radiation cooling composite material, characterized in that, Its raw materials include the following components in parts by weight: 100 parts of sulfoaluminate white cement; 0.2-0.5 parts of foaming agent; 0-5 parts of functional filler; 40-50 parts water; The atmospheric window emissivity of the composite material is greater than 90%, and the overall solar reflectivity is greater than 90%.

2. The porous microstructured foamed white cement radiation cooling composite material as described in claim 1, characterized in that, The foaming agent includes sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium alpha-olefin sulfonate, hydrogen peroxide, and / or aluminum powder.

3. The porous microstructured foamed white cement radiation cooling composite material as described in claim 2, characterized in that, The foaming agent is sodium dodecyl sulfate.

4. The porous microstructured foamed white cement radiation cooling composite material as described in claim 2 or 3, characterized in that, When adding the foaming agent, it is pre-diluted with water at a mass ratio of foaming agent:water = 1:

25.

5. The porous microstructured foamed white cement radiation cooling composite material as described in claim 1, characterized in that, The functional fillers include one or more of the following: cellulose nanofibers, nano-silica particles, polyester microfibers, cellulose nanowhiskers, attapulgite, bamboo fiber, water glass, and waterborne epoxy resin.

6. A method for preparing porous microstructured foamed white cement radiation cooling composite material, characterized in that: It includes the following steps: 1) According to the raw material composition of the composite material according to any one of claims 1 to 5, weigh sodium dodecyl sulfate and water, dilute them at a mass ratio of 1:25, and stir at 400-500 r / min for 3-5 min to generate stable foam. 2) Weigh out the sulfoaluminate white cement powder and water, stir at 200-300 r / min for 2-3 min to disperse it evenly, and obtain a white cement paste; 3) Take the functional filler cellulose nanofiber dispersion and add it to the cement slurry. Stir at 200-300 r / min for 2-3 min to ensure the slurry is fully mixed. 4) Add the foam obtained in step 1) to the white cement paste prepared in step 2) in two batches. After each addition, stir at 200-300 r / min for 2-3 minutes to ensure that the air bubbles and white cement paste are fully mixed. 5) Pour the cement slurry obtained in step 4) into the mold and cure it to obtain a porous microstructured foamed white cement radiation cooling composite material.

7. The method for preparing the porous microstructured foamed white cement radiation cooling composite material according to claim 6, characterized in that: The curing conditions used in step 5) are: temperature 25±5℃, humidity 90%±10%, and curing time 7 days.

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