Preparation method and application of flame-retardant radiation refrigeration cellulose foam

Abstract

The invention discloses a preparation method and application of flame-retardant radiation refrigeration cellulose foam, and belongs to the technical field of material science. The method comprises the following steps: firstly, adding cellulose fibers, inorganic nanoparticles and a surfactant into a cellulose derivative solution, and preparing uniform cellulose fiber wet foam in a high-speed stirring manner; and then, drying the wet foam to finally obtain the cellulose fiber foam material with excellent flame retardance and radiation refrigeration performance. The prepared cellulose fiber foam has a graded porous structure, can effectively reflect sunlight and emit infrared light, and has excellent radiation refrigeration performance. In addition, inorganic nanoparticles are introduced into the foam material, so that the radiation refrigeration capacity of the material is further improved, and meanwhile, the foam is endowed with a good flame-retardant characteristic.

Description

Technical Field

[0001] The invention belongs to the technical field of material science, and in particular relates to a method for preparing a flame-retardant and radiation-refrigerating cellulose foam and an application thereof. Background Art

[0002] As the global climate change problem intensifies, governments and the public are paying more and more attention to reducing greenhouse gas emissions to achieve the goal of carbon neutrality. In this context, the problem of building energy consumption is particularly prominent. Building energy consumption usually accounts for 30%-40% of the total social energy consumption. Therefore, how to effectively reduce building energy consumption has become one of the important ways to achieve carbon neutrality. Current building energy-saving technologies mainly focus on several aspects: improving the thermal insulation performance of buildings, optimizing the operating efficiency of air-conditioning systems, and utilizing renewable energy such as solar energy.

[0003] Although these technical means can reduce building energy consumption to a certain extent, they generally have some limitations. Improving the thermal insulation performance of buildings usually requires increasing the thickness of the walls or using high-efficiency thermal insulation materials, which may increase construction costs and complexity; although optimizing the air-conditioning system can improve energy efficiency, it still relies on electricity consumption and it is difficult to completely get rid of dependence on traditional energy; the use of renewable energy such as solar energy and wind energy has potential, but requires high initial investment and is limited by climate and geographical conditions in some areas. In addition, these methods also have some technical bottlenecks in terms of energy conversion efficiency and emission reduction effects.

[0004] Radiative cooling technology is a passive cooling method that does not require additional energy input. It achieves a cooling effect by radiating heat into outer space in the form of infrared radiation through materials. The "infrared window" (8-13μm wavelength range) of the earth's atmosphere makes this cooling method possible because the atmosphere has extremely low absorption of infrared radiation within this wavelength range. Incorporating radiative cooling properties into thermal insulation materials can effectively reduce the temperature inside buildings in high temperature environments during the day and further reduce the energy consumption of air-conditioning systems. Therefore, the development of thermal insulation materials with radiative cooling functions can significantly improve the energy-saving effect of buildings and is one of the future development directions of building energy-saving technologies. Summary of the invention

[0005] In view of the above technical problems, the present invention proposes a method for preparing and applying a flame-retardant and radiation-cooling cellulose foam. By introducing inorganic nanoparticles, surfactants, cellulose derivatives and other functional additives into the cellulose fiber matrix, a foam material with both radiation-cooling and flame-retardant properties is prepared. While meeting the cooling needs of buildings, this material can also reduce dependence on petrochemical resources, reduce environmental pollution, and meet the requirements of modern green buildings and sustainable development. The invention aims to provide an efficient, environmentally friendly and safe solution for building energy conservation, and help achieve the global carbon neutrality goal.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] Technical purpose 1: A method for preparing a flame retardant and radiation cooling cellulose foam, comprising the following steps:

[0008] dissolving a cellulose derivative in water to prepare a cellulose derivative solution;

[0009] adding inorganic nanoparticles and cellulose fibers to the cellulose derivative solution to obtain a mixed solution;

[0010] A surfactant is added into the mixed solution, stirred and dried to obtain a flame retardant and radiation cooling cellulose foam.

[0011] Furthermore, the mass concentration of the cellulose derivative in the cellulose derivative solution is 0.1-1%; the cellulose derivative is one of carboxymethyl cellulose, hydroxypropyl cellulose and hydroxypropyl carboxymethyl cellulose.

[0012] Furthermore, the inorganic nanoparticles are one of metakaolin, calcined kaolin, silicon dioxide, titanium oxide and zinc oxide; the particle size of the inorganic nanoparticles is 0.5-5 μm, and the whiteness is >90%.

[0013] Furthermore, the cellulose fibers have an average length of 0.1-1 mm and an average diameter of 1-10 μm.

[0014] Furthermore, in the mixed solution, the mass concentration of the cellulose fibers is 1-5%, and the mass concentration of the inorganic nanoparticles relative to the cellulose fibers is 50-150%.

[0015] Furthermore, the surfactant is one of sodium alkyl sulfonate, sodium alkyl aryl sulfonate, sodium alkyl sulfate, sodium dodecylbenzene sulfonate and sodium secondary alkyl sulfate; in the mixed solution, the mass concentration of the surfactant is 0.1-1%.

[0016] Furthermore, the stirring speed is 500-5000 rpm; the drying temperature is 30-80° C., and the drying time is 5-50 h.

[0017] Technical purpose 2: A flame-retardant and radiation-cooling cellulose foam prepared by the preparation method.

[0018] Technical purpose three: Application of the flame-retardant and radiation cooling cellulose foam in building radiation cooling materials.

[0019] Technical purpose four: An application of the flame-retardant and radiation-cooling cellulose foam in building flame-retardant materials.

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

[0021] (1) The present invention uses a surfactant for foaming treatment, a cellulose derivative as a binder, cellulose fibers as a skeleton of the foam structure, and inorganic nanoparticles as a filler and a flame retardant to prepare a foam with excellent radiant cooling and flame retardant capabilities.

[0022] (2) The present invention utilizes cellulose, which is abundant in resources and has the advantages of being renewable and degradable, as a raw material to prepare high-performance cellulose materials, which is of great significance for promoting the high-value application of cellulose. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0024] Figure 1 This is a surface SEM image of the flame retardant and radiation cooling cellulose foam prepared in Example 1;

[0025] Figure 2 This is a cross-sectional SEM image of the flame-retardant and radiation-cooling cellulose foam prepared in Example 1;

[0026] Figure 3 The reflectivity and emissivity of the flame-retardant and radiation-cooling cellulose foam prepared in Example 1. DETAILED DESCRIPTION

[0027] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0028] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0029] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0030] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0031] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0032] A method for preparing a flame-retardant and radiation-cooling cellulose foam comprises the following steps:

[0033] (1) dissolving a cellulose derivative in water to prepare a cellulose derivative solution;

[0034] (2) adding inorganic nanoparticles and cellulose fibers to the cellulose derivative solution to obtain a mixed solution;

[0035] (3) adding a surfactant to the mixed solution, stirring, and drying to obtain a flame retardant and radiation cooling cellulose foam.

[0036] In step (1) of some preferred embodiments of the present invention, the mass concentration of the cellulose derivative in the cellulose derivative solution is 0.1-1%, preferably 0.5-1%; and the cellulose derivative is one of carboxymethyl cellulose, hydroxypropyl cellulose and hydroxypropyl carboxymethyl cellulose.

[0037] In step (2) of some preferred embodiments of the present invention, the inorganic nanoparticles are one of metakaolin, calcined kaolin, silicon dioxide, titanium oxide and zinc oxide, preferably calcined kaolin or metakaolin; the particle size of the inorganic nanoparticles is 0.5-5 μm, and the whiteness is >90%. The average length of the cellulose fibers is 0.1-1 mm, preferably 0.4-1 mm, and the average diameter is 1-10 μm, preferably 5-10 μm. In the mixed solution, the mass concentration of the cellulose fibers is 1-5%, and the mass concentration of the inorganic nanoparticles relative to the cellulose fibers is 50-150%.

[0038] In some preferred embodiments of the present invention, in step (3), the surfactant is one of sodium alkyl sulfonate, sodium alkyl aryl sulfonate, sodium alkyl sulfate, sodium dodecylbenzene sulfonate and sodium secondary alkyl sulfate; in the mixed solution, the mass concentration of the surfactant is 0.1-1%, preferably 0.5-1%. The stirring speed is 500-5000rpm, preferably 1000-5000rpm, and the stirring time is 20-50min; the drying temperature is 30-80°C, and the drying time is 5-50h, preferably 6-50h.

[0039] Cellulose is one of the most abundant natural polymer materials on earth, with good mechanical properties, renewability and environmental friendliness. Cellulose materials have high specific surface area and unique microscopic pore structure, showing excellent thermal conductivity and thermal insulation properties. The present invention can prepare a foam material with both excellent thermal insulation performance and mechanical strength by combining cellulose with inorganic nanoparticles and appropriate surfactants. In addition, the addition of inorganic nanoparticles can not only improve the whiteness and structural stability of the material, but also give the foam material certain flame retardant properties and improve the safety of the material. The added cellulose derivative can strengthen the binding ability between cellulose fibers and inorganic nanoparticles, and achieve good mechanical properties of the foam. The foam material uses low-cost, renewable natural cellulose and inorganic nanoparticles as the main raw materials, which not only maintains excellent thermal insulation performance, but also has good environmental protection and sustainability. The cellulose flame-retardant and radiant cooling foam of the present invention shows broad prospects in the application of the construction field, and is a new material that meets the needs of modern green buildings. By adjusting the proportion of inorganic nanoparticles and the concentration of the cellulose derivative solution, the radiant cooling effect of the foam can be flexibly adjusted to make it suitable for different building environments and climatic conditions.

[0040] The preparation method can be used to prepare flame-retardant and radiation-cooling cellulose foam.

[0041] The flame retardant and radiation cooling cellulose foam can be applied to building radiation cooling materials and can also be used in building flame retardant materials.

[0042] The raw materials used in the present invention are all purchased from the market. Among them, cellulose fiber is provided by Fujian Qingshan Paper Co., Ltd.; calcined kaolin is purchased from Henan Hengyuan New Materials Co., Ltd.; foaming agents such as sodium alkyl sulfonate, sodium alkyl aryl sulfonate, sodium alkyl sulfate, sodium dodecylbenzene sulfonate, and sodium secondary alkyl sulfate, binders such as carboxymethyl cellulose and carboxymethyl cellulose, hydroxypropyl cellulose and hydroxypropyl carboxymethyl cellulose, and inorganic particles such as silicon dioxide and zinc oxide are purchased from Shanghai MacLean Biochemical Technology Co., Ltd.

[0043] The technical solution of the present invention is further illustrated by the following embodiments.

[0044] Example 1

[0045] 1) dissolving carboxymethyl cellulose in water to obtain a carboxymethyl cellulose solution with a mass concentration of 1%;

[0046] 2) adding cellulose fibers (average length of 0.8 mm, average diameter of 7 μm) and metakaolin (particle size of 0.5 μm, whiteness of 92%) to a carboxymethyl cellulose solution to prepare a mixed solution; wherein the mass concentration of the cellulose fibers in the mixed solution is 5%, and the amount of the metakaolin added relative to the mass concentration of the cellulose fibers is 100% (i.e., the mass concentration of the metakaolin in the mixed solution is 5%, the same below);

[0047] 3) adding sodium alkyl sulfonate to the mixed solution to make its mass concentration 1%, stirring at a speed of 1000 rpm for 40 minutes, and drying at 60° C. for 10 hours to prepare a flame retardant and radiation cooling cellulose foam.

[0048] The foam was placed in a UV-Vis spectrophotometer for testing to measure the reflectivity of the foam. The reflectivity was >92% and the emissivity was >95% in the atmospheric window band. The average temperature drop throughout the day was 6.8°C, and it extinguished quickly after ignition.

[0049] Figure 1 This is a surface SEM image of the flame retardant and radiation cooling cellulose foam prepared in Example 1; Figure 2 This is a cross-sectional SEM image of the flame retardant and radiation cooling cellulose foam prepared in Example 1. Figure 1 and 2 It can be seen that the foam prepared in this embodiment exhibits a highly cross-linked mesh porous structure in terms of microstructure, which helps to increase its specific surface area, thereby improving the light reflection efficiency and reducing light absorption.

[0050] Figure 3 The reflectivity and emissivity of the flame-retardant and radiation cooling cellulose foam prepared in Example 1 are as follows: Figure 3It can be seen that the flame retardant and radiation cooling cellulose foam has an average reflectivity of >94% and an emissivity of >96% in the atmospheric window band.

[0051] Example 2

[0052] 1) dissolving carboxymethyl cellulose in water to obtain a carboxymethyl cellulose solution with a mass concentration of 0.5%;

[0053] 2) adding cellulose fibers (average length of 0.5 mm, average diameter of 5 μm) and metakaolin (particle size of 1 μm, whiteness of 91%) to a carboxymethyl cellulose solution to prepare a mixed solution; wherein the mass concentration of the cellulose fibers in the mixed solution is 3%, and the amount of the metakaolin added relative to the mass concentration of the cellulose fibers is 100%;

[0054] 3) adding sodium alkyl aryl sulfonate with a mass concentration of 0.5% to the mixed solution, stirring at a speed of 5000 rpm for 20 minutes, and drying at 80° C. for 6 hours to prepare a flame retardant and radiation cooling cellulose foam.

[0055] The foam was placed in a UV-Vis spectrophotometer for testing to measure the reflectivity of the foam. The reflectivity was >94% and the emissivity was >96% in the atmospheric window band. The average temperature drop throughout the day was 9°C and it extinguished quickly after ignition.

[0056] Example 3

[0057] 1) dissolving hydroxypropyl cellulose in water to obtain a carboxypropyl cellulose solution with a mass concentration of 0.8%;

[0058] 2) adding cellulose fibers (average length of 0.5 mm, average diameter of 5 μm) and calcined kaolin (particle size of 5 μm, whiteness of 90%) into a carboxypropyl cellulose solution to prepare a mixed solution; wherein the mass concentration of the cellulose fibers in the mixed solution is 4%, and the amount of the calcined kaolin added relative to the mass concentration of the cellulose fibers is 100%;

[0059] 3) adding 1% sodium alkyl sulfate to the mixed solution, stirring at 3000 rpm for 30 min, and drying at 50° C. for 10 h to prepare a flame retardant and radiation cooling cellulose foam.

[0060] The foam was placed in a UV-Vis spectrophotometer for testing to measure the reflectivity of the foam. The reflectivity was >96% and the emissivity was >93% in the atmospheric window band. The average temperature drop throughout the day was 7.5°C and it extinguished quickly after ignition.

[0061] Example 4

[0062] 1) dissolving carboxymethyl cellulose in water to obtain a carboxymethyl cellulose solution with a mass concentration of 1%;

[0063] 2) adding cellulose fibers (average length of 1 mm, average diameter of 10 μm) and calcined kaolin (particle size of 2.5 μm, whiteness of 94%) into a carboxymethyl cellulose solution to prepare a mixed solution; wherein the mass concentration of the cellulose fibers in the mixed solution is 1%, and the amount of the calcined kaolin added relative to the mass concentration of the cellulose fibers is 100%;

[0064] 3) adding 1% sodium alkyl sulfate to the mixed solution, stirring at a speed of 2000 rpm for 40 minutes, and drying at 30° C. for 48 hours to prepare a flame retardant and radiation cooling cellulose foam.

[0065] The foam was placed in a UV-Vis spectrophotometer for testing to measure the reflectivity of the foam. The reflectivity was >95% and the emissivity was >95% in the atmospheric window band. The average temperature drop throughout the day was 8°C and it extinguished quickly after ignition.

[0066] Example 5

[0067] 1) dissolving hydroxypropyl carboxymethyl cellulose in water to obtain a hydroxypropyl carboxymethyl cellulose solution with a mass concentration of 0.7%;

[0068] 2) adding cellulose fibers (average length of 0.8 mm, average diameter of 8 μm) and calcined kaolin (particle size of 4 μm, whiteness of 95%) to a hydroxypropyl carboxymethyl cellulose solution to prepare a mixed solution; wherein the mass concentration of the cellulose fibers in the mixed solution is 2%, and the amount of the calcined kaolin added relative to the mass concentration of the cellulose fibers is 50%;

[0069] 3) adding sodium dodecylbenzene sulfonate with a mass concentration of 0.5% to the mixed solution, stirring at a speed of 1000 rpm for 50 minutes, and drying at 40° C. for 36 hours to prepare a flame retardant and radiation cooling cellulose foam.

[0070] The foam was placed in a UV-Vis spectrophotometer for testing to measure the reflectivity of the foam. The reflectivity was >95% and the emissivity was >93% in the atmospheric window band. The average temperature drop throughout the day was 7.5°C and it extinguished quickly after ignition.

[0071] Example 6

[0072] 1) dissolving carboxymethyl cellulose in water to obtain a carboxymethyl cellulose solution with a mass concentration of 0.7%;

[0073] 2) adding cellulose fibers (average length of 0.6 mm, average diameter of 6 μm) and calcined kaolin (particle size of 0.5 μm, whiteness of 91%) to a carboxymethyl cellulose solution to prepare a mixed solution; wherein the mass concentration of the cellulose fibers in the mixed solution is 3%, and the amount of the calcined kaolin added relative to the mass concentration of the cellulose fibers is 100%;

[0074] 3) adding sodium alkyl sulfonate with a mass concentration of 0.5% to the mixed solution, stirring at a speed of 5000 rpm for 10 minutes, and drying at 50° C. for 24 hours to prepare a flame retardant and radiation cooling cellulose foam.

[0075] The foam was placed in a UV-Vis spectrophotometer for testing to measure the reflectivity of the foam. The reflectivity was >93% and the emissivity was >92% in the atmospheric window band. The average temperature drop throughout the day was 7°C and it extinguished quickly after ignition.

[0076] Example 7

[0077] 1) dissolving carboxymethyl cellulose in water to obtain a carboxymethyl cellulose solution with a mass concentration of 0.5%;

[0078] 2) adding cellulose fibers (average length of 0.4 mm, average diameter of 6 μm) and calcined kaolin (particle size of 2.5 μm, whiteness of 95%) to a carboxymethyl cellulose solution to prepare a mixed solution; wherein the mass concentration of the cellulose fibers in the mixed solution is 3%, and the amount of the calcined kaolin added relative to the mass concentration of the cellulose fibers is 150%;

[0079] 3) adding 1% by mass concentration of secondary alkyl sodium sulfate to the mixed solution, stirring at a speed of 3000 rpm for 30 min, and drying at 30° C. for 50 h to prepare a flame retardant and radiation cooling cellulose foam.

[0080] The foam was placed in a UV-Vis spectrophotometer for testing to measure the reflectivity of the foam. The reflectivity was >92% and the emissivity was >94% in the atmospheric window band. The average temperature drop throughout the day was 6°C and it extinguished quickly after ignition.

[0081] Comparative Example 1

[0082] 1) dissolving carboxymethyl cellulose in water to obtain a carboxymethyl cellulose solution with a mass concentration of 0.5%;

[0083] 2) adding calcined kaolin to the carboxymethyl cellulose solution to prepare a mixed solution; wherein the amount of calcined kaolin (particle size of 0.5 μm, whiteness of 90%) added relative to the mass concentration of the carboxymethyl cellulose is 3%;

[0084] 3) Sodium dodecyl sulfate with a mass concentration of 1% was added to the mixed solution, and the mixture was stirred at a speed of 3000 rpm for 30 minutes, and dried at 30° C. for 50 hours. It was found that the foam structure could not be formed by the method of this comparative example.

[0085] Comparative Example 2

[0086] 1) dissolving carboxymethyl cellulose in water to obtain a carboxymethyl cellulose solution with a mass concentration of 0.5%;

[0087] 2) adding cellulose fibers (average length of 0.6 mm and average diameter of 6 μm) into the carboxymethyl cellulose solution to prepare a mixed solution; wherein the mass concentration of the cellulose fibers in the mixed solution is 3%;

[0088] 3) adding sodium dodecyl sulfate with a mass concentration of 1% into the mixed solution, stirring at a speed of 3000 rpm for 30 minutes, and drying at 30° C. for 50 hours to prepare a flame retardant and radiation cooling cellulose foam.

[0089] The foam was placed in a UV-Vis spectrophotometer for testing to measure the reflectivity of the foam. The reflectivity was <80% and the emissivity was <90% in the atmospheric window band. There was no cooling effect throughout the day and it continued to burn after ignition.

[0090] Comparative Example 3

[0091] 1) adding cellulose fibers (average length of 0.6 mm, average diameter of 6 μm) and calcined kaolin into water to prepare a mixed solution; wherein the mass concentration of the cellulose fibers in the mixed solution is 3%, and the amount of the calcined kaolin (particle size of 5 μm, whiteness of 93%) added is 150% relative to the mass concentration of the cellulose fibers;

[0092] 2) Sodium dodecyl sulfate with a mass concentration of 1% was added to the mixed solution, and the mixture was stirred at a speed of 3000 rpm for 30 minutes, and dried at 30° C. for 50 hours. It was found that a stable foam structure could not be formed using the comparative example method.

[0093] Comparative Example 4

[0094] Same as Example 1, except that the mass of carboxymethyl cellulose is replaced by ethyl cellulose.

[0095] The structure of the material prepared by the method of this comparative example is unstable.

[0096] Comparative Example 5

[0097] Same as Example 1, except that the cellulose fibers are replaced by chitosan.

[0098] The material prepared by the comparative example method has a dense structure, a reflectivity of <75%, an emissivity of <80%, and has no cooling effect throughout the day.

[0099] Comparative Example 6

[0100] Same as Example 1, except that the mass of metakaolin is replaced by iron oxide nanoparticles.

[0101] The material prepared by the comparative example method has a reflectivity of <50%, an emissivity of <90%, and no cooling effect throughout the day.

[0102] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for preparing flame retardant and radiation cooling cellulose foam, characterized in that: The following steps are involved: dissolving a cellulose derivative in water to prepare a cellulose derivative solution; adding inorganic nanoparticles and cellulose fibers to the cellulose derivative solution to obtain a mixed solution; A surfactant is added into the mixed solution, stirred and dried to obtain a flame retardant and radiation cooling cellulose foam.

2. The method for preparing flame-retardant and radiation-cooling cellulose foam according to claim 1, characterized in that: The mass concentration of the cellulose derivative in the cellulose derivative solution is 0.1-1%; the cellulose derivative is one of carboxymethyl cellulose, hydroxypropyl cellulose and hydroxypropyl carboxymethyl cellulose.

3. The method for preparing flame-retardant and radiation-cooling cellulose foam according to claim 1, characterized in that: The inorganic nanoparticles are one of metakaolin, calcined kaolin, silicon dioxide, titanium oxide and zinc oxide; the particle size of the inorganic nanoparticles is 0.5-5 μm, and the whiteness is greater than 90%.

4. The method for preparing flame-retardant and radiation-cooling cellulose foam according to claim 1, characterized in that: The cellulose fibers have an average length of 0.1-1 mm and an average diameter of 1-10 μm.

5. The method for preparing flame retardant and radiation cooling cellulose foam according to claim 1, characterized in that: In the mixed solution, the mass concentration of the cellulose fibers is 1-5%, and the mass concentration of the inorganic nanoparticles relative to the cellulose fibers is 50-150%.

6. The method for preparing flame retardant and radiation cooling cellulose foam according to claim 1, characterized in that: The surfactant is one of sodium alkyl sulfonate, sodium alkyl aryl sulfonate, sodium alkyl sulfate, sodium dodecylbenzene sulfonate and sodium secondary alkyl sulfate; in the mixed solution, the mass concentration of the surfactant is 0.1-1%.

7. The method for preparing flame retardant and radiation cooling cellulose foam according to claim 1, characterized in that: The stirring speed is 500-5000 rpm, and the stirring time is 20-50 min; the drying temperature is 30-80° C., and the drying time is 5-50 h.

8. A flame retardant and radiation cooling cellulose foam prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the flame-retardant and radiation cooling cellulose foam as claimed in claim 8 in building radiation cooling materials.

10. Use of the flame retardant and radiation cooling cellulose foam as claimed in claim 8 in flame retardant building materials.

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