A hyperstructured photonic crystal core-shell filler, a preparation method and application thereof, and a radiation cooling film, a preparation method and application thereof

Abstract

The application discloses a super-structured photonic crystal core-shell filler and a preparation method and application thereof, and a radiation refrigeration film and a preparation method and application thereof, and relates to the technical field of radiation refrigeration. The super-structured photonic crystal core-shell filler comprises an infrared emissive material and reflective nanomaterials coated on the surface of the infrared emissive material through mechanical resonance, the infrared emissive material is micron silicon dioxide, and the reflective nanomaterials are nanobarium sulfate, nanozinc oxide or nanofluoride oxide. The super-structured photonic crystal core-shell filler is designed through a core-shell structure, the synergistic optimization of a high infrared emissive material and a wide-spectrum high reflective material is realized, and the problems of uneven material coating and easy agglomeration are solved. The carbon ceramic sol further enhances the dispersion stability and compatibility of the filler in a polymer matrix. The radiation refrigeration film material has high cooling performance in the field of building energy saving.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of radiation refrigeration, in particular to a super-structured photonic crystal core-shell filler, a preparation method and application thereof, and a radiation refrigeration film, a preparation method and application thereof. BACKGROUND

[0002] Passive radiation refrigeration technology realizes cooling without energy input through the high reflectivity of materials to solar radiation (0.3-2.5 μm) and the high emissivity of materials to atmospheric window infrared radiation (8-13 μm), and has great application value in the fields of building energy saving and electronic device heat dissipation. However, the existing radiation refrigeration materials still face key technical bottlenecks: single inorganic fillers (such as TiO2 and Al2O3) or traditional composite coatings are difficult to synergistically optimize the solar reflectivity and infrared emissivity, and the environmental durability is insufficient. For example, although the TiO2-based coating has high reflectivity, the infrared emissivity is limited by the crystal form, and the performance may be attenuated due to humidity and ultraviolet light during long-term use.

[0003] Under this background, composite structure materials with high infrared emission and high solar reflectivity have become the focus of research. Such materials usually use inorganic materials with strong infrared emission characteristics (such as SiO2, which has excellent chemical stability and outstanding emission performance in the atmospheric window band (8-13 μm)) as the infrared radiation substrate, and use nanomaterials with wide-spectrum high reflectivity (such as BaSO4, which has high reflectivity and wide-spectrum low absorption characteristics in the solar radiation band) as the reflection layer. Theoretically, the synergistic combination of the two can break through the performance limitations of single materials. However, there are significant obstacles in the existing technology to effectively combine such high infrared emission materials and high reflectivity materials: in the composite structure prepared by traditional liquid deposition and chemical precipitation methods, the interface between the reflection layer material and the infrared emission substrate is only physically adsorbed, with weak bonding force and poor uniformity of coating, which leads to aggregation of the reflection layer material and poor dispersion in the coating, and the optical performance cannot be fully utilized. Even if the existing technology tries to improve through sol-gel method, conventional sol systems (such as silica sol and alkoxide sol) are difficult to precisely control the nucleation sites of the reflection layer material, which easily leads to homogeneous nucleation and further aggravates the problem of uneven coating. Therefore, how to combine such high infrared emission materials and high reflectivity materials in a stable and uniform composite structure to achieve synergistic optimization of "high infrared emission-high solar reflectivity" is still a technical problem that has not been solved by the existing technology.

[0004] In view of this, the present application is proposed. SUMMARY

[0005] The application aims to provide an ultracstructure photonic crystal core-shell filler, a preparation method and application thereof, and a radiation cooling film, a preparation method and application thereof, to solve the problems of the prior art, realize high-efficiency reflection of the material in the 0.3-2.5 mu m solar band by precisely controlling the core-shell interface combination and micro-nano structure, the reflectivity can reach 90 %, and strong infrared emission in the 8-13 mu m atmospheric window, and meanwhile, the environmental durability and coating dispersibility of the core-shell structure are improved, and the passive cooling demand in the fields of buildings, electronic equipment and the like is met.

[0006] To achieve the above-mentioned purpose, the application provides the following solutions.

[0007] One of the technical solutions of the application: an ultracstructure photonic crystal core-shell filler is provided, which comprises an infrared emission material and reflective nanomaterial coated on the surface of the infrared emission material; the reflective nanomaterial is coated on the surface of the infrared emission material through mechanical resonance, and the infrared emission material is micron silicon dioxide with phonon polariton resonance in the atmospheric window; the reflective nanomaterial is wide-spectrum high-reflectivity nanomaterial, such as nano-barium sulfate, nano-zinc oxide or nano-hafnium oxide.

[0008] The second technical solution of the application: a preparation method of the above-mentioned ultracstructure photonic crystal core-shell filler is provided, which comprises the following steps.

[0009] The infrared emission material and the reflective nanomaterial are mixed and subjected to mechanical resonance to obtain the ultracstructure photonic crystal core-shell filler.

[0010] The parameters of the mechanical resonance are as follows: frequency 20 Hz-100 Hz, amplitude 4 mm-15 mm, time 10-120 min, and acceleration 10-200 g, wherein, 1 g=9.8 m / s².

[0011] As a further preferred embodiment of the application, the mass ratio of the infrared emission material to the reflective nanomaterial is (1-9):(9-1).

[0012] As a further preferred embodiment of the application, the mass ratio of the infrared emission material to the reflective nanomaterial is 1:9, 3:7, 5:5, 7:3 or 9:1.

[0013] The third technical solution of the application: the above-mentioned ultracstructure photonic crystal core-shell filler is provided for use in preparing a radiation cooling material.

[0014] The fourth technical solution of the application: a preparation method of a radiation cooling film is provided, which comprises the following steps.

[0015] (1) Preparation of the super-structured photonic crystal core-shell filler: mixing an infrared emissivity material and a reflective nanomaterial, and performing mechanical resonance to obtain the super-structured photonic crystal core-shell filler; the infrared emissivity material is micron-sized silicon dioxide; the reflective nanomaterial is nano-sized barium sulfate, nano-sized zinc oxide or nano-sized hafnium oxide;

[0016] (2) Preparation of the carbon ceramic sol: dispersing the super-structured photonic crystal core-shell filler into an organic sol, adding a surfactant and a silane coupling agent, and adding 5-15% of an organic carbon source (phenolic resin powder or polyvinyl alcohol) based on the mass of the core-shell filler to obtain a mixed system; after mechanical resonance dispersion of the mixed system, pre-crosslinking at 50-80°C for 30-60 min to preliminarily form a linear chain structure of the organic carbon source, and obtaining the carbon ceramic sol; the organic carbon source will be further crosslinked to form a three-dimensional network in a subsequent film forming process;

[0017] (3) Preparation of the radiation cooling film: adding the carbon ceramic sol into a polymer matrix, mechanically blending and dispersing, and then flow casting to form a film and curing at 60-120°C for 3-12 h; during the curing process, the organic carbon source undergoes polycondensation reaction to form a three-dimensional network structure in cooperation with the polymer matrix, the network wraps the super-structured photonic crystal core-shell filler, inhibits agglomeration and enhances the mechanical properties of the film, and finally the radiation cooling film is obtained.

[0018] As a further preferred embodiment of the present application, the parameters of the mechanical resonance in step (1) are as follows: frequency 20-100 Hz; amplitude 4-15 mm; time 10-120 min; acceleration 10-200 g, wherein 1 g = 9.8 m / s²; and the parameters of the mechanical resonance dispersion in steps (2) and (3) are as follows: frequency 20-100 Hz; amplitude 4-15 mm; time 10-120 min; acceleration 10-200 g, wherein 1 g = 9.8 m / s².

[0019] As a further preferred embodiment of the present application, the diameter of the cylindrical mechanical resonance intensifier cavity is less than 100 cm, and the length-diameter ratio is 0.2-2.

[0020] As a further preferred embodiment of the present application, the mass ratio of the infrared emissivity material to the reflective nanomaterial is (1-9):(9-1).

[0021] As a further preferred embodiment of the present application, in step (2), the mass fraction of the super-structured photonic crystal core-shell filler in the organic sol is 20-70%; and in step (3), the mass fraction of the super-structured photonic crystal core-shell filler in the polymer matrix in the carbon ceramic sol is 20-80%.

[0022] As a further preferred embodiment of the present application, the organic sol is a silicone sol or a polyurethane sol; the polymer matrix comprises polyvinylidene fluoride or polymethyl methacrylate; the organic carbon source comprises phenolic resin or polyvinyl alcohol; and the organic carbon source forms a three-dimensional network structure through cross-linking reaction during preparation of the radiative cooling film, which is used to enhance the dispersion stability of the core-shell filler and the mechanical strength of the film material.

[0023] The fifth technical solution of the present application provides a radiative cooling film prepared by the method.

[0024] The sixth technical solution of the present application provides an application of the radiative cooling film in the field of radiative cooling.

[0025] The surfactant is one or two of cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), sodium dodecyl benzene sulfonate (SDBS), sodium lignosulfonate, cetyltrimethylammonium chloride (CTAC), and polydimethyl diallyl ammonium chloride (PDDA); and the silane coupling agent is one or more of 3-aminopropyl triethoxysilane (APTES), N-(2-aminoethyl)-3-aminopropyl trimethoxysilane (DAMO), 3-mercaptopropyl trimethoxysilane (MPTMS), vinyl triethoxysilane (VTES), N-phenyl-γ-aminopropyl trimethoxysilane (KH-550P), and bis-(γ-triethoxysilylpropyl) amine (KH-792).

[0026] The present application mainly utilizes frictional collision between materials and acoustic mixing to achieve physical combination of the materials. The acoustic mixing technology is different from traditional mechanical impeller or paddle stirring, and mainly realizes combination between materials through reciprocating motion, thereby reducing device wear caused by mechanical impeller stirring. The present application does not need to use organic solvents in the key step of mechanical resonance coating of core-shell fillers, is green and environmentally friendly, and is suitable for large-scale industrial production. The infrared emissivity material and the reflective nanomaterial do not need to be subjected to complex surface modification, and only need to be subjected to network confinement effect of the carbon-ceramic sol system and interface collision strengthened by mechanical resonance to realize efficient heterogeneous combination of the materials. By accurately adjusting precursor concentration and reaction kinetics parameters, barium sulfate nanocrystals are deposited on the surface of silica microspheres in a directional manner to form a "core-shell" super-photonic crystal structure. This special structure endows the material with excellent spectral selectivity: the reflectivity in the solar radiation band is as high as 90%, and the reflectivity and emissivity are synergistically optimized. In addition, the three-dimensional network structure of the carbon-ceramic sol system can also act as a nanoreactor to effectively inhibit agglomeration and sedimentation of barium sulfate particles, and significantly improve the dispersion stability of the core-shell structure in the coating, thereby achieving the purpose of preparing an efficient radiative cooling super-photonic crystal material and a carbon-ceramic-based composite coating thereof.

[0027] The super-photonic crystal structure of the application can synergistically enhance the reflection ability of the material to short-wave solar radiation, while promoting the efficient emission of long-wave infrared radiation, and at the same time, combining with the mechanical resonance dispersion to form a carbon ceramic sol with excellent stability, solving the compatibility problem of inorganic fillers and organic matrix, inhibiting the settling of fillers, and enhancing the radiation cooling performance.

[0028] The application selects silicon dioxide with a high emission coefficient as a filler, coats a material with a wide spectrum and high reflectivity on the surface of the silicon dioxide to form a special coating layer with a "core-shell" structure, uses the high refractive index and wide spectrum low absorption characteristics of the shell material, combines the Bragg scattering effect of the core-shell structure, breaks through the limitation of low emissivity of single barium sulfate material, and realizes the decoupling optimization of "reflection-radiation" dual functions.

[0029] The application uses silicon dioxide with high emissivity and nanomaterials with wide spectrum and high reflectivity as raw materials, uses the network confinement effect of the carbon ceramic sol system and the interface bonding effect between materials, and finally forms a core-shell super-photonic crystal structure. This special structure is like a "spectrum control armor" for the silicon dioxide microspheres, which retains the high emissivity of the inner core in the 8-13 mu atmospheric window, and through the synergistic effect of the high reflectivity of the outer shell in the solar wave band, builds a dual-function unit with "reflecting solar radiation-high efficient thermal radiation". Then the super-photonic crystal core-shell filler is uniformly dispersed in a polymer matrix film such as polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), and polydimethylsiloxane (PDMS), and the prepared radiation cooling composite film has good passive cooling effect, and is suitable for building exterior wall cooling, electronic chip cooling, solar cell panel cooling, satellite thermal control system and other fields.

[0030] The application optimizes the process (such as the mechanical resonance coating link of the core-shell filler does not need organic solvent), compared with the process of preparing composite structure materials such as traditional liquid deposition method and chemical precipitation method, the volatile organic compound (VOC) emission is low, and the overall process steps are simple and repeatable, which is suitable for large-scale industrial production.

[0031] The application discloses the following technical effects:

[0032] The present application realizes the synergistic optimization of high infrared emissivity material and wide-spectrum high reflectivity material through the design of core-shell structure super-structured photonic crystal, which can significantly improve the reflectivity of solar radiation (0.3-2.5 μm) and enhance the infrared emissivity of atmospheric window (8-13 μm), effectively breaking through the performance bottleneck of single material; at the same time, the mechanical resonance preparation technology makes the core-shell structure more uniform and the interface bonding force stronger, solving the problems of uneven coating and easy agglomeration in traditional methods; the carbon ceramic sol system further enhances the dispersion stability and compatibility of fillers in the polymer matrix; in addition, the material not only has excellent environmental durability, but also has more environmentally friendly preparation process and is suitable for industrial production, finally making the radiation cooling film material show high cooling performance in the field of building energy saving. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments will be briefly introduced below. Obviously, the drawings in the following description only constitute some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0034] Figure 1 The preparation process diagram of the super-structured photonic crystal core-shell filler (Example 1) of the present application.

[0035] Figure 2 The scanning electron microscope photo of the super-structured photonic crystal core-shell filler (BaSO4@SiO2) prepared in Example 1.

[0036] Figure 3 The preparation process diagram of the radiation cooling film of Example 1 of the present application.

[0037] Figure 4 The reflectivity diagram of the radiation cooling film prepared in Example 1 step (3) with different amounts of super-structured photonic crystal core-shell fillers.

[0038] Figure 5 The emissivity diagram of the radiation cooling film prepared in Example 1 step (3) with different amounts of super-structured photonic crystal core-shell fillers.

[0039] Figure 6 The reflectivity diagram of the radiation cooling film prepared in Comparative Example 1 with different amounts of random mixed fillers. DETAILED DESCRIPTION

[0040] The various exemplary embodiments of the present application will now be described in detail, which should not be considered as limiting the present application, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present application.

[0041] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. Additionally, for a range of values of, an intermediate value of is specifically contemplated if this intermediate value is within the range. Every intermediate value of, as well as every

[0042] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned herein are incorporated by reference to disclose and describe in detail the methods and / or materials which are related to the present application. In the case of conflict between the present specification and any document incorporated herein by reference, the present specification will control.

[0043] Many modifications and variations of the present application described in the detailed description of the application can be made by those skilled in the art without departing from the scope or spirit of the application. Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application. The specification and examples are illustrative only.

[0044] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having", "contains", "containing", or variations thereof, are intended to be open-ended terms that mean including, but not limited to.

[0045] The present application is further described in detail by the following examples. It should be noted that the present application is not limited by the details of the examples which are not described in detail.

[0046] The resonance instrument used in the embodiments of the present application is a HAM100 desktop acoustic resonance instrument (Hummingbird acoustic resonance, China).

[0047] The emissivity of the radiation cooling film material prepared in the following examples was tested by a Fourier transform infrared spectrometer (FTIR, model InvenioS, Bruker Corporation), which was equipped with a gold integrating sphere (model A562). The infrared spectrum of the material was characterized to determine its emissivity.

[0048] The morphology of the super-structured photonic crystal core-shell filler prepared in the following examples was observed by a scanning electron microscope (SEM, model FEI Nova NanoSEM 450, FEI Corporation, USA).

[0049] The mesoporous silica adopted in the application has a diameter of 10 microns and a plurality of pores on the surface.

[0050] Figure 1 A preparation process schematic diagram of the super-structured photonic crystal core-shell filler.

[0051] Figure 3 A preparation process schematic diagram of the radiation refrigeration film of Example 1.

[0052] Example 1

[0053] A preparation method of a radiation refrigeration film:

[0054] (1) Preparation of super-structured photonic crystal core-shell filler (BaSO4@SiO2)

[0055] a. Raw material mixing: dry nano-BaSO4 and micron-sized mesoporous SiO2 are mixed uniformly at a mass ratio of 9:1 to obtain a mixed raw material;

[0056] b. Resonance coating: the mixed raw material is placed into a cylindrical resonator reinforcement cavity (diameter 90 cm, length-diameter ratio 1) and fixed in a resonance instrument; mechanical resonance parameters are set as follows: frequency 100 Hz, amplitude 10 mm, time 60 min, and acceleration 100 g (1 g = 9.8 m / s²); the BaSO4 is uniformly coated on the surface of the SiO2 through resonance, and after screening and separation, the super-structured photonic crystal core-shell filler (BaSO4@SiO2) is obtained.

[0057] Figure 2 The scanning electron microscope photo of the super-structured photonic crystal core-shell filler (BaSO4@SiO2) prepared in Example 1 is shown. It can be seen that there is interaction between the nano-BaSO4 and the micron-sized mesoporous SiO2, and there is obvious force of action between them.

[0058] (2) Preparation of carbon ceramic sol

[0059] c. Raw material mixing: the BaSO4@SiO2 core-shell filler prepared above is dispersed into an organic sol (polyurethane sol), and the addition amount of the super-structured photonic crystal core-shell filler is 20-70% by mass ratio; then, 2% of the mass of the super-structured photonic crystal core-shell filler of a surfactant (hexadecyl trimethyl ammonium bromide, CTAB) and 5% of the mass of the super-structured photonic crystal core-shell filler of a silane coupling agent (3-aminopropyl triethoxysilane, APTES), and 8% of the mass of the super-structured photonic crystal core-shell filler of an organic carbon source (phenolic resin powder) are added, and the mixture is stirred uniformly to obtain a mixed system;

[0060] d. Resonance dispersion: the mixed system is loaded into a resonance cavity and placed in a resonance instrument for processing, with a frequency of 100 Hz; amplitude of 10 mm; resonance time of 60 min; acceleration of 100 g (1 g = 9.8 m / s²), and the components are uniformly dispersed by mechanical resonance; then pre-crosslinking at 60°C for 40 min with stirring to form a carbon-tao sol with excellent stability.

[0061] (3) Preparation of the radiative cooling film

[0062] e. Composite dispersion: the carbon-tao sol is added to a pre-degassed polymer matrix solution system (polyvinylidene fluoride dissolved in DMF at 45°C for 4 h, mass fraction of 15%) in which the hyperstructured photonic crystal core-shell filler in the carbon-tao sol accounts for 20-80% of the mass of the polymer matrix (polyvinylidene fluoride, PVDF);

[0063] f. Film forming treatment: the mixed system is mixed again by the resonance instrument (parameters are the same as step d), and then cast into a film and vacuum cured at 120°C for 3 h; during the curing process, the phenolic resin undergoes polycondensation reaction to form a three-dimensional network structure, which wraps the BaSO4@SiO2core-shell filler, and a radiative cooling film with a thickness of about 150 μm is obtained.

[0064] Figure 4 is the reflectivity test result of the radiative cooling film prepared in Example 1 (core-shell filler mass ratio of 20%, 30%, 40%, 50%, 70%, and 80%) in the 0.3-2.5 μm wide waveband, which is tested by a UV-visible-near infrared spectrometer (model Lambda 950, PerkinElmer, USA) with a 150 mm diameter integrating sphere in a diffuse reflection mode;

[0065] From the reflectivity spectrum of the radiative cooling film prepared in Example 1 with different mass ratios (20-80%) of the hyperstructured photonic crystal core-shell filler in the polymer matrix solution, Figure 4 it can be seen that in step (3), as the mass ratio of the core-shell filler in the polymer matrix solution increases, the reflectivity of the radiative cooling film in the solar radiation waveband (0.3-2.5 μm) gradually increases, and the reflectivity can reach more than 90%. This change trend shows that the addition amount of the hyperstructured photonic crystal core-shell filler has a significant effect on the reflectivity of the film, which is due to the light scattering synergistic effect of the core-shell interface and the waveband matching design of the photonic crystal structure to the solar spectrum, and the appropriate addition ratio is beneficial to improving the refrigeration effect of the material.

[0066] Figure 5 is the emissivity spectrum (test waveband 4-20 μm) of the radiation cooling film prepared in Example 1 with different mass ratios of super-structured photonic crystal core-shell fillers (20-80%). It can be seen that as the mass ratio of core-shell fillers in the polymer matrix increases, the emissivity of the film in the atmospheric window waveband (8-13 μm, the radiation cooling core heat dissipation interval) gradually increases.

[0067] This law shows that the amount of super-structured photonic crystal core-shell fillers has a precise control effect on the infrared radiation cooling capacity (key waveband emissivity) of the radiation cooling film: the ordered dispersion and interface effect of the core-shell fillers enable the material to achieve efficient infrared radiation in the atmospheric window, combined with the law that the reflectivity increases with the filler ratio (Figure 4), a filler ratio of 50-80% can synergistically enhance the spectral characteristics of "high solar radiation reflection + high infrared heat dissipation emission", directly supporting the optimization of radiation cooling performance.

[0068] Example 2

[0069] A method for preparing a radiation cooling film:

[0070] (1) Preparation of super-structured photonic crystal core-shell fillers (ZnO@SiO2)

[0071] a. Mixing of raw materials: dry nano-ZnO and micron-sized mesoporous SiO2 are mixed in a mass ratio of 9:1 to obtain a mixed raw material;

[0072] b. Resonance coating: the mixed raw material is placed in a cylindrical resonator strengthening cavity (diameter 90 cm, length-diameter ratio 1) and fixed in the resonator; the mechanical resonance parameters are set as follows: frequency 50 Hz, amplitude 10 mm, time 100 min, acceleration 150 g (1 g = 9.8 m / s²), the ZnO is uniformly coated on the surface of SiO2 by resonance, and after screening and separation, the super-structured photonic crystal core-shell fillers (ZnO@SiO2) are obtained.

[0073] (2) Preparation of carbon ceramic sol

[0074] c. Mixing of raw materials: the ZnO@SiO2 core-shell fillers prepared above are dispersed into an organic sol (polyurethane sol), and the filling ratio of the core-shell fillers is 20-70% by mass fraction, then 3% of the mass of the super-structured photonic crystal core-shell fillers of a surfactant (hexadecyl trimethyl ammonium bromide) and 5% of the mass of the super-structured photonic crystal core-shell fillers of a silane coupling agent (3-aminopropyl triethoxysilane), and 8% of the mass of the super-structured photonic crystal core-shell fillers of an organic carbon source (phenolic resin powder) are added, and the mixture is stirred uniformly to obtain a mixed system;

[0075] d. Resonance dispersion: The mixed system is loaded into a resonance cavity and processed in a resonance instrument, with a frequency of 50 Hz; an amplitude of 10 mm; a resonance time of 100 min; and an acceleration of 150 g (1 g = 9.8 m / s²). The components are uniformly dispersed by mechanical resonance. Then, the pre-crosslinking is performed at 60°C for 40 min with stirring, to form a carbon ceramic sol with excellent stability.

[0076] (3) Preparation of the radiation refrigeration film

[0077] e. Composite dispersion: The carbon ceramic sol is added to a pre-deaerated polymer matrix solution system (polyvinylidene fluoride is dissolved in DMF at 45°C for 4 h, with a mass fraction of 15%). The super-structured photonic crystal core-shell filler in the carbon ceramic sol accounts for 20-80% of the mass of the polyvinylidene fluoride (polymer matrix).

[0078] f. Film forming treatment: The mixed system is mixed again in a resonance instrument (parameters are the same as in step d), and then cast into a film and vacuum cured at 120°C for 3 h. During the curing process, the phenolic resin undergoes a condensation reaction to form a three-dimensional network structure, which encapsulates the ZnO@SiO2 core-shell filler, to obtain a radiation refrigeration film with a thickness of about 150 μm.

[0079] The same test method and conditions as in Example 1 are used for testing, and the results show that the reflectivity of the sample also increases with the increase of the mass fraction of the super-structured photonic crystal filler. The above results further confirm that the light scattering synergistic effect of the core-shell interface and the band matching characteristics of the photonic crystal structure to the solar spectrum have a positive effect on improving the radiation refrigeration performance.

[0080] Example 3

[0081] A method for preparing a radiation refrigeration film:

[0082] (1) Preparation of super-structured photonic crystal core-shell filler (HfO2@SiO2)

[0083] a. Raw material mixing: Dry nano-HfO2 and micron-sized mesoporous SiO2 are mixed uniformly at a mass ratio of 9:1 to obtain a mixed raw material.

[0084] b. Resonance coating: The mixed raw material is placed in a cylindrical resonator intensifier cavity (diameter 90 cm, length-diameter ratio 0.5) and fixed in a resonance instrument. The mechanical resonance parameters are set as follows: frequency 80 Hz, amplitude 8 mm, time 60 min, and acceleration 100 g (1 g = 9.8 m / s²). HfO2 is uniformly coated on the surface of SiO2 by resonance action. After screening and separation, the super-structured photonic crystal core-shell filler (HfO2@SiO2) is obtained.

[0085] (2) Preparation of carbon ceramic sol

[0086] c. Raw material mixing: The HfO2@SiO2core-shell filler prepared above is dispersed into an organic sol (methyltrimethoxysilane sol), and the core-shell filler accounts for 20-70% by mass fraction. Then, 2% of the mass of the super-photonic crystal core-shell filler of a surfactant (cetyltrimethylammonium bromide) and 5% of the mass of the super-photonic crystal core-shell filler of a silane coupling agent (3-aminopropyl triethoxysilane), and 8% of the mass of the super-photonic crystal core-shell filler of an organic carbon source (phenolic resin powder) are added, and the mixture is stirred uniformly to obtain a mixed system;

[0087] d. Resonance dispersion: The mixed system is loaded into a resonance cavity and placed in a resonance instrument for processing. The frequency is set to 80 Hz, the amplitude is 8 mm, the resonance time is 60 min, and the acceleration is 100 g (1 g = 9.8 m / s²). The components are uniformly dispersed by mechanical resonance. Then, pre-crosslinking is performed at 60°C for 40 min, and a carbon ceramic sol with excellent stability is formed.

[0088] (3) Preparation of a radiation cooling film

[0089] e. Composite dispersion: The carbon ceramic sol is added to a pre-degassed polymer matrix solution system (polymethyl methacrylate dissolved in DMAC, 60°C for 4 h, mass fraction 15%). In the carbon ceramic sol, the super-photonic crystal core-shell filler accounts for 20-80% of the mass of the polymethyl methacrylate (polymer matrix).

[0090] f. Film forming treatment: The mixed system is mixed again by the resonance instrument (parameters are the same as step d), and then it is cast into a film and vacuum cured at 120°C for 3 h. During the curing process, the phenolic resin undergoes a condensation reaction to form a three-dimensional network structure, which encapsulates the HfO2@SiO2core-shell filler, and a radiation cooling film with a thickness of about 150 μm is obtained.

[0091] The test is carried out according to the same test method and conditions as in Example 1, and the test results show that the reflectivity of the sample also shows a trend of increasing with the increase of the mass fraction of the super-photonic crystal filler. This result further proves that the light scattering synergistic effect of the core-shell interface and the band matching characteristics of the photonic crystal structure to the solar spectrum have a positive impact on the improvement of the radiation cooling performance.

[0092] Comparative Example 1

[0093] The difference between Example 1 and Comparative Example 1 is that the BaSO4@SiO2core-shell filler is replaced by an equal amount of a random mixture of BaSO4and SiO2filler (the mass ratio of BaSO4and SiO2is the same as in Example 1).

[0094] Under the same test conditions (solar radiation band reflectivity test: using a UV-visible-near infrared spectrophotometer (model Lambda 950, PerkinElmer, USA), integral sphere diffuse reflection mode); Figure 6 The reflectivity of the radiation cooling film prepared for different amounts of randomly mixed fillers shows that the average reflectivity of the film prepared in Comparative Example 1 is 75% in the solar radiation band, while the average reflectivity under the same conditions in Example 1 reaches 90%. The difference is due to the band matching design of the core-shell super-structured photonic crystal structure to the solar spectrum and the synergistic effect of light scattering at the core-shell interface, realizing wide-spectrum high reflectivity.

[0095] The above results show that randomly mixed BaSO4 and SiO2 cannot realize the optimized matching of reflection and emission performance due to the lack of synergistic effect of the core-shell structure, further confirming the key role of the core-shell super-structured photonic crystal structure in improving the comprehensive performance of the radiation cooling material.

[0096] Comparative Example 2

[0097] The difference between Example 2 and Comparative Example 2 is that the ZnO@SiO2 core-shell filler is replaced with an equal amount of randomly mixed ZnO and SiO2 fillers (the mass ratio of ZnO to SiO2 is the same as in Example 2).

[0098] The same test method and conditions are used for testing, and the results show that the average reflectivity of the randomly mixed ZnO and SiO2 filler sample is 71%, which is also lower than the average reflectivity of 89% of the super-structured photonic crystal filler sample. The above results further confirm that randomly mixed ZnO and SiO2 cannot realize the optimized matching of reflection and emission performance due to the lack of synergistic effect of the core-shell structure, while the light scattering synergistic effect at the core-shell interface of the super-structured photonic crystal filler and the band matching characteristics of the photonic crystal structure to the solar spectrum have a positive effect on improving the radiation cooling performance.

[0099] Comparative Example 3

[0100] The difference between Example 3 and Comparative Example 3 is that the HfO2@SiO2 core-shell filler is replaced with an equal amount of randomly mixed HfO2 and SiO2 fillers (the mass ratio of HfO2 to SiO2 is the same as in Example 3).

[0101] The same test conditions are used for testing, and the results show that the randomly mixed HfO2 and SiO2 cannot realize the optimized matching of reflection and emission performance due to the lack of synergistic effect of the core-shell structure, with an average reflectivity of 73%, which is also lower than the average reflectivity of 90% of the radiation cooling film prepared from the super-structured photonic crystal filler. The above results further confirm that the light scattering synergistic effect at the core-shell interface and the band matching characteristics of the photonic crystal structure to the solar spectrum can positively contribute to the improvement of the radiation cooling performance.

[0102] The radiation cooling coating prepared by the application can achieve passive cooling effect under direct sunlight in the daytime without additional energy consumption, and is suitable for building energy saving (such as roof coating), electronic device thermal management (such as 5G base station heat dissipation), cold chain transportation and other fields, and has broad application prospect.

[0103] The above-described embodiments are only used to describe the preferred modes of the application, and do not limit the scope of the application. Without departing from the design spirit of the application, various modifications and improvements of the technical solutions of the application made by those skilled in the art shall fall within the protection scope determined by the claims of the application.

Claims

1. A hyper-photonic crystal core-shell filler, characterized in that, The infrared emissivity material and the reflective nanomaterial coated on the surface thereof; the reflective nanomaterial is coated on the surface of the infrared emissivity material through mechanical resonance; The infrared emissivity material is micron silicon dioxide; the reflective nanomaterial is nano barium sulfate, nano zinc oxide or nano hafnium oxide.

2. The method for preparing the metaphotonic crystal core-shell filler as described in claim 1, characterized in that, The method comprises the following steps: The infrared emissivity material and the reflective nanomaterial are mixed and subjected to mechanical resonance to obtain the super-structured photonic crystal core-shell filler; the parameters of the mechanical resonance are as follows: frequency 20-100 Hz, amplitude 4-15 mm, time 10-120 min, and acceleration 10-200 g; wherein, 1 g=9.8 m / s². The mass ratio of the infrared emissivity material to the reflective nanomaterial is (1-9):(9-1).

3. The application of the super-structured photonic crystal core-shell filler in claim 1 in the preparation of a radiation cooling material.

4. A method of making a radiative cooling film, the method comprising: The method comprises the following steps: (1) Preparation of the super-structured photonic crystal core-shell filler: the infrared emissivity material and the reflective nanomaterial are mixed and subjected to mechanical resonance to obtain the super-structured photonic crystal core-shell filler; the infrared emissivity material is micron silicon dioxide; the reflective nanomaterial is nano barium sulfate, nano zinc oxide or nano hafnium oxide; (2) Preparation of a carbon ceramic sol: the super-structured photonic crystal core-shell filler is dispersed into an organic sol, a surfactant and a silane coupling agent are added, and an organic carbon source is added; the obtained mixed system is subjected to mechanical resonance dispersion, and is subjected to pre-crosslinking at 50-80°C to obtain the carbon ceramic sol; (3) Preparation of a radiation cooling film: the carbon ceramic sol is added into a polymer matrix, is subjected to mechanical resonance dispersion, and is subjected to film forming treatment to obtain the radiation cooling film.

5. The preparation method according to claim 4, characterized in that, The parameters of the mechanical resonance in step (1) are as follows: frequency 20-100 Hz, amplitude 4-15 mm, time 10-120 min, and acceleration 10-200 g; wherein, 1 g=9.8 m / s²; the parameters of the mechanical resonance dispersion in steps (2) and (3) are as follows: frequency 20-100 Hz, amplitude 4-15 mm, time 10-120 min, and acceleration 10-200 g; wherein, 1 g=9.8 m / s².

6. The preparation method according to claim 4, characterized in that, The mass ratio of the infrared emissivity material to the reflective nanomaterial is (1-9):(9-1).

7. The preparation method according to claim 4, characterized in that, In step (2), the mass proportion of the super-structured photonic crystal core-shell filler in the organic sol is 20-70%; in step (3), the mass proportion of the super-structured photonic crystal core-shell filler in the polymer matrix in the carbon ceramic sol is 20-80%.

8. The preparation method according to claim 4, characterized in that, The organic sol comprises an organic silicon sol or a polyurethane sol; the polymer matrix comprises polyvinylidene fluoride or polymethyl methacrylate; and the organic carbon source comprises phenolic resin or polyvinyl alcohol.

9. The radiation cooling film prepared by the preparation method in any one of claims 4-8.

10. The application of the radiation cooling film in claim 9 in the field of radiation cooling.

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