WO2023159413A1 - 辐射散热装置及其制备方法和应用 - Google Patents

辐射散热装置及其制备方法和应用 Download PDF

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WO2023159413A1
WO2023159413A1 PCT/CN2022/077583 CN2022077583W WO2023159413A1 WO 2023159413 A1 WO2023159413 A1 WO 2023159413A1 CN 2022077583 W CN2022077583 W CN 2022077583W WO 2023159413 A1 WO2023159413 A1 WO 2023159413A1
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radiation
cooling device
thermal
heat dissipation
unit
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PCT/CN2022/077583
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English (en)
French (fr)
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万德辉
蔡孟廷
陈彦任
张思伟
陈学礼
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万德辉
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Priority to PCT/CN2022/077583 priority Critical patent/WO2023159413A1/zh
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/02—Layered products comprising a layer of synthetic resin in the form of fibres or filaments
    • G—PHYSICS
    • G12—INSTRUMENT DETAILS
    • G12B—CONSTRUCTIONAL DETAILS OF INSTRUMENTS, OR COMPARABLE DETAILS OF OTHER APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G12B15/00—Cooling
    • G12B15/06—Cooling by contact with heat-absorbing or radiating masses, e.g. heat-sink

Definitions

  • the present application relates to the field of materials and heat dissipation, in particular to a radiation heat dissipation device and its preparation method and application.
  • Radiation is one of the most important energy transmission methods that affect the surface temperature, and radiation cooling is also a passive cooling method. Radiant cooling releases heat into space for cooling without input power. Radiation cooling includes night radiation cooling and day radiation cooling. During the day, the surface absorbs more energy from the sun than the surface emits, so the temperature rises. In the evening, because there is no sunlight and the ground continuously emits heat energy, the temperature of the ground drops.
  • the technical problem to be solved in this application is to provide a radiation cooling device, which uses high-durability materials and a simple manufacturing process that can be mass-produced, reduces the absorption of solar radiation energy by objects and increases the thermal radiation energy of objects, so that the radiation cooling device It can also help the target object effectively dissipate excess heat under strong solar radiation during the day.
  • This application proposes a fiber stack structure with micro-nano dimensions.
  • the solar radiation irradiates the surface of the fiber, it will produce multiple scattering, which will lead to extremely high diffuse reflection;
  • the heat energy is released in the form of thermal radiation.
  • This technology can make the covering under direct sunlight exposure, reduce heat energy absorption, increase heat energy dissipation, and finally achieve the purpose of cooling. It can be applied to passive cooling of buildings, refrigerated storage, large computer rooms, outdoor appliances, low-temperature logistics, electronic components, etc. used by.
  • the present application provides a radiation heat dissipation device, including a radiation heat dissipation layer, the radiation heat dissipation layer is composed of a plurality of polarized materials with high energy gap, the polarized material has at least one light scattering unit and a The heat radiation unit, wherein the light scattering unit can interact with a solar radiation to generate scattering, and the heat radiation unit can interact with a heat radiation and increase the energy intensity of the heat radiation.
  • the polarizing material is a sub-wavelength structure.
  • the sub-wavelength structures are interleaved and stacked to form a self-supporting structure.
  • the sub-wavelength structures are stacked alternately to form a pore structure
  • the pore structure includes a plurality of pores
  • the solar radiation interacts with the surface of the polarized material through the pores.
  • the sub-wavelength structure is a fibrous structure with a diameter of nanometer.
  • a plurality of nanometer-sized particles are attached to the fibrous structure.
  • the polarized material further includes a thermal energy transfer unit, and the polarized materials transfer energy to each other through the thermal energy transfer unit.
  • the thermal energy transfer unit can couple energy to the thermal radiation unit, and the thermal radiation unit increases the energy intensity of the thermal radiation.
  • the method of the radiation cooling device includes the following steps: providing a fiber membrane material precursor solution and a spinning-assisting polymer, uniformly mixing to form an electrospinning sol, and then injecting a fiber structure through an electrospinning machine platform, controlling The process parameters control the fiber diameter and the thickness of the fiber film, and finally the nano-micron fiber film is formed through heat treatment.
  • the radiation cooling device provided by this application can be used on electronic components in a closed system.
  • the radiation cooling device is used to cover the surface of the object, and even under the sun exposure, it can achieve passive and effective cooling without the need for additional power.
  • This technology can break through the bottleneck of zero-energy passive cooling technology, and can be applied to buildings, refrigerated storage, large computer rooms, outdoor appliances, low-temperature logistics, or heat dissipation of electronic components.
  • FIG. 1 is a schematic diagram of a radiation cooling device according to an embodiment of the present application.
  • FIG. 2 is a schematic diagram of a polarized material according to an embodiment of the present application.
  • FIG. 3 is a schematic cross-sectional view of a radiation cooling device according to an embodiment of the present application.
  • FIG. 4 is an SEM image of a polarized material according to an embodiment of the present application.
  • FIG. 5 is a schematic cross-sectional view of a radiation cooling device disposed on a curved substrate according to an embodiment of the present application
  • FIG. 6 is a reflection and emission spectrum of a radiation cooling device according to an embodiment of the present application in the solar radiation spectrum band and the black body radiation spectrum band;
  • FIG. 7 is a schematic cross-sectional view of a radiation cooling device according to another embodiment of the present application.
  • This application relates to electromagnetic radiation of different wavelengths, wherein the "solar radiation” refers to any electromagnetic radiation whose wavelength is in the “solar radiation spectral band”, and “solar radiation spectral band” mainly refers to wavelengths from about 0.3 ⁇ m to 4 ⁇ m ; “thermal radiation” refers to any electromagnetic radiation whose wavelength is in the “black body radiation spectral band”, “black body radiation spectral band” mainly refers to wavelengths from about 4 ⁇ m to 25 ⁇ m; “atmospheric transparent window band” mainly refers to wavelengths from about 8 ⁇ m to 13 ⁇ m wavelength.
  • the representations of the above wavelengths are only exemplary rather than limiting. Distinguishing different radiation wavelengths is currently used to explain the principles and effects of the technical features of the application, and its purpose is not to limit the application to Specific wavelengths described.
  • Diffuse reflectance as used herein in reference to a material or structure is the fraction of any incident electromagnetic radiation that is diffusely reflected from a surface.
  • a perfect reflector is defined as having 100% diffuse reflectance.
  • the high diffuse reflectance in this application means that the material or structure has a diffuse reflectance greater than about 60% within the specified range; the better diffuse reflectance can reach more than 80%; the best diffuse reflectance can reach 95% above.
  • Emissivity refers to the effectiveness with which electromagnetic radiation energy is emitted.
  • a perfect black body emitter is defined as having 100% emissivity.
  • the high emissivity in this application means that the material or structure has an emissivity greater than about 70% within a specified range; a better emissivity can reach more than 80%; the best emissivity can reach more than 95%.
  • the "transmittance" used in this application with respect to materials or structures refers to the ratio of electromagnetic waves passing through materials or structures within a specified wave band.
  • a perfectly transmissive material or structure is defined as 100% transmissive.
  • the high transmittance in this application means that the material or structure has a transmittance greater than about 60% within a specified range; the preferred transmittance in this application can reach more than 80%; the best transmittance can reach more than 95%.
  • a "subwavelength structure” means a material or structure that includes at least one directional dimension that is smaller than the wavelength of electromagnetic radiation being compared.
  • the scale of at least one direction is close to or smaller than the wavelength of the maximum black-body radiation intensity of the material, or the structure composed of arbitrary-shaped fibers whose diameter is smaller than the wavelength of the maximum black-body radiation intensity of the material.
  • the wavelength at which the maximum radiation intensity of a material black body is located can be calculated from the temperature of the material through Wien's displacement law.
  • the "radiation heat dissipation layer” in this application is a material with a high energy gap, which absorbs very little in the solar radiation spectral band, such as but not limited to various oxides (Al 2 O 3 , ZnO, MgO, TiO 2 , SiO 2 , HfO 2 , ZrO 2 , etc.), nitrides (AlN, hBN, cBN, Si 3 N 4 , GaN, etc.), SiC, metal fluorides (CaF 2 , MgF 2 , BaF 2 ), carbonates (CaCO 3 , CaMg ( CO 3 ) 2 and other compounds containing CO 3 2- ), sulfates (BaSO 4 , CaSO 4 and other compounds containing SO 4 2- ), phosphates (compounds containing PO 4 3- ), etc. kind.
  • various oxides Al 2 O 3 , ZnO, MgO, TiO 2 , SiO 2 , HfO 2 , Zr
  • optical phonon in this application refers to the collective oscillation of atoms in crystals, the quantization of excitation modes. If there are two or more atoms with different charge distributions in the lattice, the dipoles generated between these different atoms interact with the incident electromagnetic waves, changing the relative position of each atom in the lattice. , the phonon mode at this time is called an optical phonon.
  • the optical phonons that occur in the spectral band of the material's blackbody radiation significantly increase the emissivity of the material's electromagnetic radiation energy.
  • the acoustic phonon refers to the overall translational vibration of the crystal lattice in the crystal, and the relative positional relationship of the internal atoms remains unchanged.
  • FIG. 1 is a schematic diagram of a radiation cooling device 1 according to an embodiment of the present application.
  • FIG. 2 is a schematic diagram of a polarized material 111 according to an embodiment of the present application.
  • the radiation heat dissipation device 1 includes a radiation heat dissipation layer 11 , and the radiation heat dissipation layer 11 is composed of a plurality of polarized materials 111 .
  • the radiation heat dissipation layer 11 can respectively interact with a solar radiation ⁇ solar and a thermal radiation ⁇ IR .
  • the radiation heat dissipation layer 11 has different interactions with electromagnetic radiation in different wavebands, and has different optical properties in different electromagnetic radiation wavebands.
  • the radiation heat dissipation layer 11 has high diffuse reflectance in the solar radiation spectral band, and high emissivity in the black body radiation spectral band.
  • the surface of the polarizing material 111 has at least one light scattering unit 112 , and the polarizing material 111 has a heat emitting unit 113 .
  • the light scattering unit 112 refers to the point where the surface of the polarized material 111 interacts with the solar radiation ⁇ solar to generate diffuse reflection
  • the thermal radiation unit 113 refers to the interaction between the polarized material 111 and the thermal radiation ⁇ IR and gains the energy of the thermal radiation ⁇ IR Intensity, the thermal radiation unit 113 emits the thermal radiation ⁇ IR from the polarizing material 111 .
  • the radiation heat dissipation layer 11 is a pore structure and a self-supporting structure composed of a plurality of polarized materials 111 staggered stacks, and the pores or holes formed in the pore structure can allow solar radiation ⁇ solar to pass through it.
  • the solar radiation ⁇ solar interacts with the light scattering unit 112 to produce scattering.
  • the solar radiation ⁇ solar enters from one side of the radiation cooling device 1, touches the light scattering unit 112, and will be scattered in the light scattering unit 112.
  • the pore structure of the radiation heat dissipation layer 11 of the present application and the high surface area ratio of the polarizing material 111 can achieve the effect of generating high diffuse reflectance for the incident solar radiation ⁇ solar . It can be understood that the pore structure is composed of a plurality of polarized materials 111 staggered stacks, wherein the staggered stacks of polarized materials 111 can be arranged regularly or irregularly, as long as a pore structure with pores or holes can be formed and a high
  • the diffuse reflectance is the scope covered by the spirit of the present application.
  • the air in the pores can also regulate the equivalent optical constant of the radiation heat dissipation layer 11 as a whole, and the porosity of the pore structure
  • a slight increase in ⁇ helps to dilute the overall equivalent optical constant of the radiation heat dissipation layer 11, and increase the emissivity of thermal radiation ⁇ IR by reducing the fiber density adjustment and porosity of the interlaced stack.
  • the pores of the pore structure can also be filled with substances whose refractive index is lower than that of the polarizing material 111, so as to achieve the control of the overall equivalent optical constant of the radiation heat dissipation layer 11.
  • the void ratio of this application is between 30%-90%.
  • a plurality of polarized materials 111 of the radiation heat dissipation layer 11 of the present application are stacked staggeredly to form a self-supporting structure, no need to use polymers as substrates, and the disadvantages of using polymers can be avoided, because polymers are usually in ultraviolet light (290-350nm) ) or near-infrared light (1500-2500nm) band will have absorption, in addition to not being able to effectively reduce the absorption of sunlight, the weather resistance of polymers is not good, and outdoor use for a long time may cause yellowing due to ultraviolet light exposure to absorb more sunlight or It is the crack aging that makes the mechanical properties worse, and the polymer is not resistant to high temperature and lacks flameproof properties, which is not conducive to construction use.
  • the size of the polarizing material 111 of the present application is a sub-wavelength structure
  • the sub-wavelength structure is a fiber structure of any shape with a diameter close to or smaller than the wavelength of the compared electromagnetic radiation.
  • the wavelength of the electromagnetic radiation to be compared is the wavelength of the maximum radiation intensity of the material blackbody
  • the sub-wavelength structure can be, for example but not limited to, nanometer-sized particles with a diameter distribution between 50nm and 8000nm, preferably between 100nm and 2000nm.
  • the polarizing material 111 is a random-shaped fiber whose scale in at least one direction is close to or smaller than the wavelength of the compared electromagnetic radiation, or a plurality of nanometer-sized particles attached to a fibrous structure superior.
  • the present application does not require that all the polarizing materials 111 have the same size, as long as the radiation heat dissipation layer 11 includes a certain number of polarizing materials 111 with sub-wavelength structure characteristics, that is the scope covered by the spirit of the present application.
  • FIG. 4 it is a SEM image of the polarized material 111 of the present application.
  • the polarizing material 111 of the present application is formed by stacking many fibers intersecting each other, the diameter of the fibers is between tens of nanometers and tens of microns, and the thickness of the stack can fall between tens of nanometers and several centimeters.
  • the fiber stack structure has a large number of light scattering units 112
  • sunlight will form diffuse reflection (Diffuse reflection) and leave the surface layer of the fiber, so that neither the fiber itself nor the underlying covering will heat up due to the absorption of solar radiation ⁇ solar .
  • the fiber size is close to or smaller than the thermal radiation ⁇ IR band, heat energy will be radiated in the form of infrared light (heat emission).
  • the thickness of the stack is larger, it is equivalent to more heat contained in the polarized material 111.
  • the radiation unit 113 finally leads to the purpose of reducing the overall temperature of the radiation cooling device 1 .
  • FIG. 2 is a schematic diagram of the interaction between the polarized material 111 of the fiber structure of the present application and the solar radiation ⁇ solar and thermal radiation ⁇ IR .
  • the surface of the polarizing material 111 has multiple light scattering units 112.
  • the polarizing material 111 of the present application is a high-energy-gap material, which absorbs little solar radiation in the spectral band of solar radiation and produces high diffuse reflectance.
  • the fibrous structure also releases heat energy in the form of heat radiation through its high specific surface area.
  • the polarized material 111 has a heat radiation unit 113, and the heat radiation unit 113 is an optical phonon, and the optical phonon refers to that when the atoms constituting the crystal lattice of the material vibrate, the relative positions between each other change, and the energy generated between different atoms.
  • the phenomenon of coupling and resonance between the dipole and the electromagnetic wave of a specific frequency helps to extract the photons containing this energy range from the resonant band interval.
  • the phonon mode at this time is called optical phonon, and the optical Phonons can enhance the emission rate of electromagnetic waves.
  • the thermal radiation unit 113 when the thermal radiation unit 113 interacts with the thermal radiation ⁇ IR of a specific frequency to generate resonance, the thermal radiation unit 113 can increase the emission energy intensity of the thermal radiation ⁇ IR of the specific frequency.
  • the polarized material 111 of the present application contains more energy state density of the thermal radiation unit 113 in the polarized material 111 of the present application, and the emission energy intensity of thermal radiation ⁇ IR at a specific frequency will be greater than that of the polymer polymer. The emitted energy intensity of the object.
  • the polarized material 111 of the present application also has a thermal energy transfer unit 114, which is an acoustic phonon.
  • the acoustic phonon refers to the overall translational vibration of the crystal lattice formed by the material, and the relative positional relationship of each internal atom remains unchanged.
  • the thermal energy transfer unit 114 can interact with thermal energy, and the polarized materials 111 can transfer energy to each other through the thermal energy transfer unit 114, that is, the transfer of thermal energy can also be carried out efficiently between different polarized materials 111, and the thermal energy transfer unit 114 will gain The heat transfer efficiency reduces the overall thermal resistance of the radiation heat dissipation layer 111 .
  • the thermal energy transfer unit 114 can couple the energy to the thermal radiation unit 113, that is, the heat can be emitted by the thermal radiation unit 113 to extract the thermal radiation ⁇ IR in the resonant band interval, gaining the emission of the thermal radiation ⁇ IR of a specific frequency energy intensity.
  • the radiation cooling device 1 is assembled on a heat source body 12 , and the heat energy of the heat source body 14 can be transferred to the radiation cooling layer 11 .
  • part of the polarized material 111 of the radiation heat dissipation layer 11 is in direct contact with the heat source body 12, and heat energy is directly transferred to the polarized material 111.
  • the contact area between the polarized material 111 and the heat source body 12 of the fiber structure of the present application is large, Make heat transfer more efficient.
  • the thermal energy received by the polarized material 111 can be transferred to other polarized materials 111 by the thermal energy transfer unit 114 .
  • the thermal energy transfer unit 114 Due to the heat transfer of the thermal energy transfer unit 114 , the overall thermal resistance of the radiation heat dissipation layer 11 is minimized, and the temperature difference between the two sides of the radiation heat dissipation layer 11 is reduced.
  • the polarized material 111 is then extracted and emitted by the thermal radiation unit 113 in the form of thermal radiation ⁇ IR to gain the energy intensity of the thermal radiation ⁇ IR at a specific frequency.
  • the radiation heat dissipation layer 11 of the present application reduces the overall thermal resistance value through the heat transfer of the heat energy transfer unit 114, and increases the emission intensity of the thermal radiation ⁇ IR through the heat radiation unit 113, so that the radiation cooling power of the radiation heat dissipation layer 11 is improved, helping the main body of the heat source 12 heat dissipation. Therefore, the overall radiation cooling device 1 of the present application can achieve effective heat transfer and radiation cooling effects.
  • FIG. 5 is a schematic cross-sectional view of a radiation cooling device 2 located on a curved substrate according to another embodiment of the present application.
  • the radiation heat dissipation layer 21 is a porous structure and a self-supporting structure composed of a plurality of polarized materials 211 stacked alternately.
  • the size of the polarizing material 211 is a sub-wavelength fiber structure of any shape.
  • the fibers with a high aspect ratio are also flexible, and the radiation heat dissipation layer 21 stacked by the fibers is also flexible, and the flexible structure can adapt to more uneven surfaces in use. surface.
  • the radiation heat dissipation layer 21 is located on a heat source body 22 , and when the shape of the heat source body 22 is curved, the radiation heat dissipation layer 21 can also be attached thereon.
  • the heat energy of the heat source body 22 can be transferred to the radiation heat dissipation layer 21 .
  • the micro-nano fiber material of the device of the present application can be an inorganic material (oxide, nitride, semiconductor, glass, etc.) or a composite material. At the same time, it can have the characteristics of light weight, bendability, large area, and high ignition point (flame resistance).
  • the fiber structure of the present application makes the contact area between the polarizing material 212 and the heat source body 14 larger, so that the heat energy transfer is more efficient.
  • the thermal energy received by the polarized material 21 can be transferred to other polarized materials 211 by the thermal energy transfer unit 214 . Due to the heat transfer of the thermal energy transfer unit 214 , the overall thermal resistance of the radiation heat dissipation layer 21 is minimized, and the temperature difference between the two sides of the radiation heat dissipation layer 11 is reduced.
  • the polarized material 211 is extracted and emitted by the thermal radiation unit 213 in the form of thermal radiation ⁇ IR to gain energy intensity of the thermal radiation ⁇ IR at a specific frequency.
  • FIG. 6 shows the reflection and emission spectra of the radiation cooling device of the present application in the solar radiation spectral band and the black body radiation spectral band.
  • the radiation cooling device can reflect more than 95% in the solar radiation spectral band.
  • the emission in the spectral band of black body radiation can reach 85-90%.
  • the former means that most of the solar heat can be blocked, and the latter means that the cooling can be achieved through passive heat radiation.
  • FIG. 7 is a schematic cross-sectional view of a composite heat sink 3 according to yet another embodiment of the present application.
  • a heat conducting material 13 is located above the heat source body 12 .
  • the thermally conductive material 13 can fill the gap between the radiation heat dissipation layer 11 and the heat source body 12 and between the partially polarized material 111 to improve heat transfer efficiency and reduce interface thermal resistance.
  • the heat conduction material 13 has a high heat transfer coefficient, and its viscosity, fluidity, coating ductility and other properties can be adjusted according to the application situation.
  • thermally conductive materials 13 include but are not limited to potting glue, silicone paste, silicone grease, thermally conductive mud, silicone sheet, thermally conductive silicon cloth, thermal oil, thermally conductive paint, plastic, thermally conductive film, insulating material, interface material, double-sided tape , heat conduction and heat dissipation substrates, phase change materials, heat dissipation films, mica sheets, gaskets, tapes, liquid metal heat conduction sheets, etc.
  • the thickness of the heat conducting material 13 is smaller than that of the radiation heat dissipation layer 11, so that the outer surface of the radiation heat dissipation layer 11 has sufficient heat radiation emission area. It can be understood that in other implementation manners, the material with high heat transfer coefficient can also be used to fill the gaps, so as to improve the heat transfer efficiency and reduce the interface thermal resistance.
  • the heat source bodies 12 and 22 described in this application can be understood as various components that need to dissipate heat, such as but not limited to the central processing unit (CPU) of a computer, chips in a smart phone, or light emitting diodes (LEDs). Modules, solar module chips, thermoelectric chips, automotive chips, chips used in outdoor electronic components and buildings, etc.
  • CPU central processing unit
  • LEDs light emitting diodes
  • the closed space blocks the traditional heat dissipation channels of convection and conduction, which easily causes the overall space temperature to rise rapidly, which in turn leads to a decrease in the operating efficiency of each component. Correctness drops.
  • the technology of the present application can automatically reduce the temperature in a way of nearly zero energy consumption under the scorching sun in this closed environment.
  • the closed system mentioned in this application refers to the application in the fields with poor heat convection or heat conduction or no heat convection or heat conduction.
  • the poor heat conduction here means that the cooling efficiency of the system or device to be cooled through heat conduction is not good. Because no medium is needed for radiation transmission, the application uses passive thermal radiation to cool down, which can effectively improve the effect that cannot be achieved by the prior art.
  • the light scattering units 112 and 212 and the thermal radiation units 113 and 213 of the present application have different optical characteristics for different spectral applications.
  • This application can be applied not only in the field with direct sunlight but also in the field without direct sunlight. However, it can be understood that the application of the present application can achieve more excellent effects in fields with direct sunlight. This is also the effect that general electronic component heat dissipation solutions cannot achieve.
  • This application uses acoustic phonon thermal energy transfer units to transfer heat, which is different from the heat transfer method using metals, because this application simultaneously considers the different optical characteristics of the solar radiation spectral band and the black body radiation spectral band.
  • the advantage of the present application is that the material of the radiation heat dissipation layer with a specific resonance band can be selected, which is helpful for the regulation of the spectrum, and it is still possible to make a wide-band high-radiation radiation cooling body by combining a plurality of radiation heat dissipation layer materials with different resonance bands.
  • various bonding vibration modes are produced by functional groups composed of carbon, hydrogen, oxygen and other elements.
  • the characteristic peak wavelengths of these functional groups are often very close to each other so that they overlap with the infrared light band to form half-height wavelengths.
  • the larger absorption peak forms a wide-band emitter that is difficult to modulate the high-emissivity band, and the radiation intensity of the infrared light band of the polymer is weak, so a larger thickness is required in the application, and the increased thickness will also cause heat resistance increases.
  • the polarized material of this application has a thermal radiation unit and a thermal energy transfer unit.
  • the advantage of this application in the application of radiation heat dissipation is to control the band of emissivity to achieve selective narrow-band or wide-band radiators through the structure and selection of single or composite materials where the thermal radiation unit falls in the blackbody radiation band, so as to Cooling requirements for different scenarios.
  • the radiation heat dissipation layer can provide high mechanical properties, UV stability, and heat resistance, so it can overcome the bottleneck of polymer radiation cooling materials in application.
  • the difference between the radiation heat dissipation layer of the present application and the polymer material of the prior art is that the polymer usually absorbs in the ultraviolet (290-350nm) or near-infrared (1500-2500nm) band, except that it cannot effectively reduce the absorption of sunlight, and the polymerization
  • the weather resistance of the material is not good, and the outdoor use for a long time may cause yellowing due to ultraviolet exposure, absorb more sunlight or crack and age, making the mechanical properties worse, and the polymer is not resistant to high temperature ( ⁇ 300 degrees) and lacks waterproofing. Flame characteristics, not conducive to building use.
  • the radiation heat dissipation layer of the present application has the technical advantages of large-area mass production, mature technology, easy shaping, light weight and low price.
  • the radiation heat dissipation layer is a self-supporting structure composed of a plurality of polarized materials interlaced and stacked.
  • the radiation heat dissipation layer prepared in this application does not need a supporting substrate, and can be used directly with the object to be cooled. Direct contact can achieve high cooling efficiency in use.
  • the radiation heat dissipation layer of the present application may be a silica nanofibrous film, wherein the diameter of the polarizing material is a nanometer-sized fibrous structure, or a plurality of nanometer-sized particles are attached to a fibrous structure.
  • the preparation method of the fibrous structure can be produced by electrospinning (Electrospinning), including but not limited to the following steps: configuring a silica precursor solution, adding tetraethoxysilane (Tetraethyl orthosilicate), phosphoric acid (H 3 PO 4 ), after the secondary deionized water is mixed, stir at room temperature; configure polyvinyl alcohol aqueous solution as the spinning polymer solution, the method is to add polyvinyl alcohol into the secondary deionized water, and heat and stir to make it dissolve uniformly; Then the silicon dioxide precursor solution is mixed with the spinning-assisting polymer solution to form a uniform electrospinning sol; the prepared electrospinning sol is filled into a syringe and fixed on a microinjection pump.
  • electrospinning Electrospinning
  • the repulsive force between the charges will offset the surface tension of the liquid, making the droplet elongate, forming a conical droplet Qin Le cone; when the voltage rises above a certain threshold, the charge repulsion is greater than the surface tension of the liquid, and the A jet of liquid is generated towards the collector, while the solvent is evaporated in the process, and finally the nanofiber film is deposited on the collector.
  • the diameter of the prepared fibers can be controlled by adjusting the composition, concentration and flow rate of the solution and the applied voltage.
  • the thickness of the prepared fibrous layer can be controlled by the injection rate and time.
  • the silica nano-micron fiber can be obtained after cooling down to room temperature. It can be understood that the above steps are only for illustration, and are not intended to strictly limit the scope of rights of the present application.
  • the radiation cooling device disclosed in this application can realize mass production and take into account the efficiency of radiation heat dissipation. Covering the surface of the object achieves passive and effective cooling without the need for additional power.

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Abstract

本申请提供一种辐射散热装置，包括一辐射散热层，该辐射散热层是由具有高能隙的多个极化材料所组成，该极化材料具有至少一光散射单元以及一热放射单元，其中该光散射单元可以与一太阳辐射相互作用产生散射，该热放射单元可以与一热辐射交互作用并增益该热辐射能量强度。

Description

辐射散热装置及其制备方法和应用 技术领域
本申请涉及材料和散热领域，尤其是涉及一种辐射散热装置及其制备方法和应用。
背景技术
全球气温纷创新高，特别是亚热带地区如中国台湾，在夏季时有大量的冷气空调使用需求，但空调冷却的方法昂贵且需消耗大量电力与能量，使得电力供给频频面临满载。全球皆面临能源短缺的问题，需要更节省的能源消耗方案。
太阳光被地球表面所吸收，地表将所吸收的太阳能向天空发射出长波辐射，传入的能量和逸出的热量相当以达到热平衡。辐射是影响地表温度重要的能量传播方式之一，辐射冷却也是一种被动的冷却方法。辐射散热将热量释放到太空中，无需输入电力即可进行冷却。辐射冷却包括夜间辐射冷却和日间辐射散热，日间因地表吸收由太阳射来的能量比地表放出的为多，所以温度上升。在晚间由于没有太阳照射，而地面又不断散发热能，因此地面温度下降。
在白天，建筑物暴露于直射阳光下，物体温度高，对降温的需求大，因此，白天的辐射冷却应用比夜间的冷却更有实用的意义。然而，白天阳光照射的能量会使物体加热到实质上高于环境空气温度，以致于辐射散热的效应在白天并不明显。现有的被动日间辐射冷却系统主要通过复杂且昂贵的光谱选择性纳米光子结构，以达到冷却效果。这些光子结构辐射器通常需要严格的纳米精密制造包括电子束光刻，真空沉积等等。这种复杂且昂贵的制造技术极大地限制了散热器的批量生产，使它们难以满足大范围应用的需求。
另外，也有使用聚合物的复合材料，但聚合物除了无法有效降低太阳光吸收，聚合物耐候性也不佳，户外长时间使用可能会因为紫外光曝晒导致泛黄吸收更多太阳光或是龟裂老化使机械性质变差。
现有的辐射降温材料，难以实现大规模量产以及兼顾辐射散热的效率。
发明内容
本申请所要解决的技术问题在于提供一种辐射散热装置，使用耐久性高的 材料且可大量生产的简单制程，降低物体对太阳辐射能量的吸收及增益物体的热放射能量，使该辐射散热装置能够在日间强烈太阳辐射下也能帮助目标物体有效散逸多余热量。
本申请提出一种具有微纳米尺寸的纤维堆栈结构，当太阳辐射照射在此纤维表面时将会产生多次散射，进而导致极高的漫反射；同时此纤维结构会通过其高比表面积大幅地将热能以热辐射形式放出。此技术可使覆盖物在日光直接曝晒下，减少热能吸收，增加热能逸散，最终达到降温的目的，可应用于建筑物、冷冻仓储、大型机房、户外用具、低温物流、电子组件等被动式降温所使用。
为了实现上述目的，本申请提供一种辐射散热装置，包括一辐射散热层，该辐射散热层是由具有高能隙的多个极化材料所组成，该极化材料具有至少一光散射单元以及一热放射单元，其中该光散射单元可以与一太阳辐射相互作用产生散射，该热放射单元可以与一热辐射交互作用并增益该热辐射能量强度。
较佳地，所述的辐射散热装置，其中该极化材料为次波长结构。
较佳地，所述的辐射散热装置，其中该些次波长结构交错堆栈组成一自支撑结构。
较佳地，所述的辐射散热装置，其中该些次波长结构交错堆栈组成一孔隙结构，该孔隙结构包含多个孔隙，该太阳辐射穿过该些孔隙和该极化材料表面交互作用。
较佳地，所述的辐射散热装置，其中该次波长结构为直径为奈微米尺寸的纤维状结构。
较佳地，所述的辐射散热装置，其中该纤维状结构上还附着多个奈微米尺寸的颗粒物。
较佳地，所述的辐射散热装置，其中该极化材料还包含一热能传递单元，该些极化材料间通过该热能传递单元相互传递能量。
较佳地，所述的辐射散热装置，该热能传递单元可以将能量耦合至该热放射单元，该热放射单元增益该热辐射能量强度。
较佳地，所述的辐射散热装置的方法，包括下列步骤：提供纤维膜材料前驱溶液以及助纺聚合物，均匀混合后形成静电纺丝溶胶，再通过电纺机台注射 出纤维结构，控制制程参数调控纤维直径尺寸与纤维膜厚度，最终经过热处理形成奈微米纤维膜。
本申请提供的辐射散热装置，可以使用在一封闭系统中的电子组件上。
本申请利用辐射冷却降温装置覆盖于物体表面，即使在日光曝晒下，可在不需额外电力的情况下，达到被动式有效降温。本技术可突破零耗能被动降温技术的瓶颈，可应用建筑物、冷冻仓储、大型机房、户外用具、低温物流或是电子组件散热等方面。
有关本申请的其它功效及实施例的详细内容，配合图式说明如下。
附图说明
为了更清楚地说明本申请实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请中记载的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其它的附图。
图1为本申请一实施方式辐射散热装置的示意图；
图2为本申请一实施方式极化材料的示意图；
图3为本申请一实施方式的辐射散热装置的剖面示意图；
图4为本申请一实施方式的极化材料SEM图；
图5为本申请一实施方式的辐射散热装置设置于一弯曲基板上的剖面示意图；
图6为本申请一实施方式的辐射散热装置在太阳辐射光谱波段和黑体辐射光谱波段的反射及发射光谱；
图7为本申请又一实施方式的辐射散热装置的剖面示意图。
附图标记：
1、2、3辐射散热装置，        11、21辐射散热层，
111、211极化材料，           112、212光散射单元，
113、213热放射单元，         114、214热能传递单元，
12、22热源主体，             13热传导材料，
λ solar太阳辐射，         λ IR热辐射。
具体实施方式
为了更清楚地说明本申请的技术方案，以下将通过各个实施例以及附图作详细描述。然而，应当理解，其目的不是将本申请限制于所描述的特定实施例。相反，对于各个实施例的修改，等同或替代形式的替换，只要是符合本申请精神，都属本申请权利要求所涵盖的范围。另外，在本申请中使用的术语仅是示例性的，而不是限制性的。本申请所述的“第一”、“第二”是用于区别不同对象，并非用以限制特定顺序。
本申请涉及不同波长的电磁辐射，其中所述的“太阳辐射”是指其波长位于“太阳辐射光谱波段”中的任意电磁辐射，“太阳辐射光谱波段”主要是指从约0.3μm至4μm波长；“热辐射”是指其波长位于“黑体辐射光谱波段”中的任意电磁辐射，“黑体辐射光谱波段”主要是指从约4μm至25μm波长；“大气透明窗波段”主要是指从约8μm至13μm波长。然而，应当理解，以上各波长的表示仅是示例性的，而不是限制性的，区分不同的辐射波长，目前是用来解释本申请技术特征的原理及功效，其目的不是将本申请限制于所描述的特定波长。
本申请中关于材料或结构所使用的“漫反射率”是从表面漫反射出的任何入射电磁辐射的分率。将完美反射体定义为具有100％的漫反射率。本申请的高漫反射率，是指该材料或结构在规定范围内具有大于约60％的漫反射率；较佳的漫反射率可以达到80％以上；最佳的漫反射率可以达到95％以上。
本申请中关于材料或结构所使用的“发射率”是指发射电磁辐射能量的有效性。将完美黑体发射体定义为具有100％的发射率。本申请的高发射率，是指该材料或结构在规定范围内具有大于约70％的发射率；较佳的发射率可以达到80％以上；最佳的发射率可以达到95％以上。
本申请中关于材料或结构所使用的“透射率”是指在规定波段内，穿过材料或结构的电磁波的比率。将完美透射材料或结构定义为100％的透射率。本申请的高透射率，是指该材料或结构在规定范围内具有大于约60％的透射率；本申请较佳的透射率可以达到80％以上；最佳的透射率可以达到95％以上。
本申请中关于材料或结构所使用的“次波长结构”是指材料或结构包含至少一个方向的尺度小于相比较的电磁辐射的波长。如至少一个方向的尺度接近或小于材料黑体辐射强度最大值所在波长的任意形状颗粒，或直径小于材料黑体辐射强度最大值所在波长的任意形状纤维组成的结构。材料黑体辐射强度最大值所在波长可通过维恩位移定律以材料温度计算得出。
本申请中关于“辐射散热层”是具有高能隙的材料，于太阳辐射光谱波段吸收甚小，例如但不限于各类氧化物(Al 2O 3、ZnO、MgO、TiO 2、SiO 2、HfO 2、ZrO 2等)、氮化物(AlN、hBN、cBN、Si 3N 4、GaN等)、SiC、金属氟化物(CaF 2、MgF 2、BaF 2)、碳酸盐类(CaCO 3、CaMg(CO 3) 2等含CO 3 2-的化合物)、硫酸盐类(BaSO 4、CaSO 4等含SO 4 2-的化合物)、磷酸盐类(含PO 4 3-的化合物)等中的任何一种。
本申请中关于“光学声子”是指晶体中原子的集体振荡、激发模式的量子化。若晶格中存在两种或两种以上的原子带有不同的电荷分布，这些不同原子之间产生的偶极(dipole)与入射电磁波产生交互作用，使晶格内部各原子的相对位置发生改变，此时的声子模态称为光学声子。而发生于材料黑体辐射光谱波段的光学声子则显著的提升了材料电磁辐射能量的发射率的目的。另外，声学声子是指晶体中晶格整体平移振动，内部各原子的相对位置关系不变。
请参考图1和图2，图1为本申请一实施方式辐射散热装置1的示意图。图2为本申请一实施方式极化材料111的示意图。所述辐射散热装置1包括一辐射散热层11，辐射散热层11是由多个极化材料111所组成。所述辐射散热层11可以分别与一太阳辐射λ solar和一热辐射λ IR交互作用。辐射散热层11与不同波段的电磁辐射有不同的交互作用，在不同的电磁辐射波段具有不同的光学特性。所述辐射散热层11在太阳辐射光谱波段具有高漫反射率，在黑体辐射光谱波段具有高发射率。如图2所示，所述极化材料111的表面具有至少一光散射单元112，以及极化材料111具有一热放射单元113。光散射单元112是指极化材料111的表面与太阳辐射λ solar相互作用产生漫反射的点，热放射单元113是指极化材料111和热辐射λ IR交互作用并增益该热辐射λ IR能量强度，热放射单元113将热辐射λ IR从极化材料111中发射出来。
如图3所示，为本申请一实施方式的辐射散热装置1的剖面示意图。本实施方式中，辐射散热层11是由多个极化材料111交错堆栈组成的一孔隙结构及一自支撑结构，所述孔隙结构中所形成的孔隙或孔洞可以让太阳辐射λ solar穿过其中，太阳辐射λ solar和光散射单元112交互作用产生散射。太阳辐射λ solar从辐射散热装置1的一面进入，接触到光散射单元112，会在光散射单元112产生散射，由于散射会产在不同的方向，被散射的太阳辐射λ solar可以再和多个光散射单元112产生多次散射。本申请辐射散热层11的孔隙结构以及极化材料111的高表面积比，可以达到对入射的太阳辐射λ solar产生高漫反射率的功效。可以理解的，由多个极化材料111交错堆栈所组成的孔隙结构，其中极化材料111的交错堆栈可以是规则或是不规则的排列，只要能形成具孔隙或孔洞的孔隙结构并产生高漫反射率，即是本申请精神所涵盖的范围。
本实施方式中，孔隙结构中的孔隙除能对入射的太阳辐射λ solar产生高漫反射率外，在孔隙中的空气亦可调控辐射散热层11整体的等效光学常数，孔隙结构的孔隙率的些微增加有助于稀释辐射散热层11整体的等效光学常数，通过降低交错堆栈的纤维密度调整与孔隙率，提升热辐射λ IR的放射率。可以理解，在其它实施方式中，若要达成上述目的，孔隙结构的孔隙中也可以填充折射率低于极化材料111折射率的物质，以达到调控辐射散热层11整体的等效光学常数的目的。本申请孔隙比介于30％-90％。本申请辐射散热层11的多个极化材料111交错堆栈形成一自支撑结构，无需再使用聚合物当作衬底，可以避免使用聚合物的缺点，因聚合物通常在紫外光(290-350nm)或近红外光(1500-2500nm)波段会有吸收，除了无法有效降低太阳光吸收，聚合物耐候性也不佳，户外长时间使用可能会因为紫外光曝晒导致泛黄吸收更多太阳光或是龟裂老化使机械性质变差，且聚合物不耐高温及缺乏防焰特性，不利于建筑使用。
本申请极化材料111的尺寸为次波长结构，所述次波长结构为直径接近或小于相比较的电磁辐射的波长的任意形状纤维结构。若相比较的电磁辐射的波长为材料黑体辐射强度最大值所在波长，次波长结构可以例如但不限于为奈微米尺寸的颗粒物，直径分布在50nm到8000nm之间，更佳地在100nm到2000nm。可以理解的，在其它实施方式中，极化材料111是至少一个方向的尺度接近或小于相比较的电磁辐射的波长的任意形状纤维，或是多个奈微米尺寸的颗粒物 附着于一纤维状结构上。本申请也不要求所有的极化材料111的尺寸大小完全相同，只要辐射散热层11包括有一定数量具有次波长结构特征的极化材料111，即为本申请精神所欲涵盖的范围。
如图4所示，为本申请极化材料111的SEM图。本申请极化材料111是由许多纤维互相交叉堆栈而成，纤维直径介于几十纳米到几十微米之间，其堆栈厚度可以落在几十纳米到几厘米之间。首先，由于其尺寸与太阳辐射λ solar波长范围有高度重叠，因此当太阳辐射λ solar与纤维表面交互作用时，会导致非常强的散射，而同时此纤维堆栈结构具有大量的光散射单元112，最终将使太阳光形成漫反射(Diffuse reflection)而离开纤维表层，也因此使得纤维本身及底下的覆盖物皆不会因为吸收太阳辐射λ solar而升温。除此之外，由于纤维尺寸接近或小于热辐射λ IR波段，将会使得热能得以红外光形式辐射(heat emission)出去，当堆栈厚度越大，相当于极化材料111内含越多的热放射单元113，最终导致辐射散热装置1整体温度下降的目的。
请再参考图2，图2所示为本申请纤维结构的极化材料111和太阳辐射λ solar以及热辐射λ IR交互作用的示意图。因为纤维结构具有高比表面积，极化材料111的表面具有多个光散射单元112，当太阳辐射λ solar照射在此纤维结构表面时会向各个方向产生散射，进而导致极高的漫反射。本申请极化材料111为高能隙材料，对于太阳辐射光谱波段的太阳辐射吸收甚小，且会产生高漫反射率。同时此纤维结构也会通过其高比表面积大幅地将热能以热辐射形式放出。极化材料111具有一热放射单元113，所述热放射单元113为一光学声子，光学声子是指材料构成晶格的原子振动时，彼此间相对位置发生改变，不同原子之间产生的偶极(dipole)与特定频率的电磁波产生耦合及共振的现象，有助于自共振波段区间萃取(extract)出蕴含该能量区间的光子，此时的声子模态称为光学声子，光学声子可以增强电磁波的放射率。本实施方式中，当热放射单元113和特定频率的热辐射λ IR交互作用产生共振，热放射单元113可以增益该特定频率热辐射λ IR的发射能量强度。本申请极化材料111相较于高分子聚合物，本申请极化材料111中蕴含较多的热放射单元113的能态密度，对特定频率热辐射λ IR的发射能量强度会大于高分子聚合物的发射能量强度。
本申请的极化材料111还具有一热能传递单元114，热能传递单元114为一声学声子，所述声学声子是指材料构成晶格整体平移振动，内部各原子的相对位置关系不变。热能传递单元114可以和热能交互作用，极化材料111间通过热能传递单元114相互传递能量，也就是热能的传递也可以在不同的极化材料111间有效率的进行，热能传递单元114会增益热量的传递效率，使辐射散热层111的整体热阻值降低。热能传递单元114可以将能量耦合至热放射单元113，也就是热量可以再通过热放射单元113把共振波段区间的热辐射λ IR萃取(extraction)发射出来，增益特定频率的热辐射λ IR的发射能量强度。
请再参考图1，辐射散热装置1装配在一热源主体12上，热源主体14的热能可以传递至辐射散热层11。具体而言，辐射散热层11的部分极化材料111和热源主体12直接接触，热能直接传递至该极化材料111中，本申请纤维结构的极化材料111和热源主体12的接触面积大，使得热能传递更有效率。另外，极化材料111所接收的热能可以由热能传递单元114再传递至其它的极化材料111。因热能传递单元114的热传递，辐射散热层11的整体热阻值会最小，辐射散热层11的两侧表面温差减小。极化材料111再通过热放射单元113以热辐射λ IR的方式对外萃取发射出来，增益特定频率的热辐射λ IR能量强度。本申请辐射散热层11通过热能传递单元114的热传递降低整体的热阻值，并通过热放射单元113增加热辐射λ IR的发射强度，使辐射散热层11的辐射冷却功率提升，帮助热源主体12的散热。故本申请辐射散热装置1的整体可以达到有效的热传递及辐射散热功效。
图5所示，为本申请另一实施方式辐射散热装置2位于一弯曲基板的剖面示意图。辐射散热层21是由多个极化材料211交错堆栈组成的一孔隙结构及一自支撑结构，辐射散热层21包含光散射单元212、热放射单元213和热能传递单元214。极化材料211的尺寸为次波长结构的任意形状纤维结构。纤维结构除了具有高比表面积，高长宽比的纤维也具有可挠性，由纤维所堆栈而成的辐射散热层21也具有可挠性，可挠性的结构在使用上可以适应更多不平坦的表面。辐射散热层21位于一热源主体22上，当热源主体22的形状为曲形时，辐射散热层21也可以贴附在其上。热源主体22的热能可以传递至辐射散热层21。本申请装置 的微纳米纤维材料可为无机材料(氧化物、氮化物、半导体、玻璃等)或复合材料。同时可以兼具轻量、可弯曲、大面积、高燃点(防焰)等特性。
本申请纤维结构使极化材料212和热源主体14的接触面积大，使得热能传递更有效率，在热源主体22弯曲时使表面展延，极化材料21和热源主体22的接触面积变的更大。极化材料21所接收的热能可以由热能传递单元214再传递至其它的极化材料211。因热能传递单元214的热传递，辐射散热层21的整体热阻值会最小，辐射散热层11的两侧表面温差减小。极化材料211通过热放射单元213以热辐射λ IR的方式对外萃取发射出来，增益特定频率的热辐射λ IR能量强度。
图6所示为本申请辐射散热装置在太阳辐射光谱波段和黑体辐射光谱波段的的反射及发射光谱。辐射散热装置在太阳辐射光谱波段反射可达95％以上。在黑体辐射光谱波段的发射可达85-90％。前者代表可以阻隔绝大部分的太阳热，后者更说明了可以通过被动热辐射来达到降温的目的。
图7所示为本申请又一实施方式的复合式散热装置3的剖面示意图，和图3的差别在于包括一热传导材料13位于热源主体12上方。热传导材料13可以填补辐射散热层11和热源主体12间以及部分极化材料111间的空隙，增进热传递效率以降低界面热阻。热传导材料13具有高热传系数，且可以视使用情形调整其黏度、流动性及涂布延展性等其他性能。热传导材料13的种类包括但不限于灌封胶、硅胶膏、胶硅脂、导热泥、硅胶片、导热硅布、散热油、导热涂料、塑料、导热膜、绝缘材料、界面材料、双面胶、导热散热基板、相变材料、散热膜、云母片、垫片、胶带、液态金属导热片等。热传导材料13的厚度小于辐射散热层11的厚度，使辐射散热层11的外面表具有足够的热辐射发射面积。可以理解的，在其它实施方式中，也可以用此一高热传系数的材料填补空隙，增进热传递效率以降低界面热阻。
本申请所述的热源主体12、22可以理解为各种需要散热的组件，例如但不限于计算机的中央处理器(CPU)、智能型手机内的芯片、或是发光二极管(LED)内的发光模块、太阳能模块芯片，热电芯片、车用芯片、户外电子组件使用的芯片以及建筑物等。在实际应用中，一些封闭系统使用的电子组件，当长时间受到日光的照射，其封闭空间阻绝了传统上对流及传导的散热途径，易使得整 体空间温度快速上升，进而导致各个组件运作效率或正确性下降。本申请技术可以实现在烈日照射于此封闭环境下，以近零耗能的方式使温度自动下降。本申请所述封闭系统是指应用在热对流或是热传导不佳或是无热对流或是热传导的场域，这里的热传导不佳是指欲降温的系统或装置通过热传导降温效率不佳。因辐射传播无需介质，故本申请通过被动热辐射来降温，可以有效改善现有技术无法达到的功效。
本申请光散射单元112、212以及热放射单元113、213针对不同光谱应用有不同的光学特性。本申请不仅可以能应用在有太阳光直射的场域也可以应用在非阳光直射的场域。但可以理解的是，本申请应用在有太阳光直射的场域可以达到更优异的效果。这也是一般电子组件散热方案所无法达到的功效。
本申请通过利用声学声子的热能传递单元做热量的传递，有别于使用金属的热传递方式，因为本申请同时考虑太阳辐射光谱波段和黑体辐射光谱波段的不同光学特性。本申请的优势在于可以选择具有特定共振波段的辐射散热层材料，对于光谱的调控性有所帮助，并且依然能通过组合复数具不同共振波段的辐射散热层材料制作宽波段高放射辐射冷却体。而现有高分子聚合物以碳、氢、氧等元素组成的官能基产生的各项键结振动模态，这些官能基的特征峰波长多十分接近以致其于红外光波段重叠形成半高波宽较大的吸收峰，形成难以调制高放射率波段的宽波段放射体，且高分子聚合物的红外光波段放射强度较弱，在应用上需要更大的厚度，而增加的厚度也会导致热阻增加。
本申请极化材料具有热放射单元和热能传递单元。本申请在辐射散热应用上的优势为通过结构与选择热放射单元落在黑体辐射波段的单一或是复合材料，以控制其发射率的波段以达到选择性窄频或是宽波段辐射体，以适用于不同情境的冷却需求。此外，辐射散热层可以提供较高的机械性质、紫外光稳定性、耐热性，因此可以克服聚合物辐射冷却材料在应用上的瓶颈。本申请辐射散热层和现有技术聚合物材料的区别在于，聚合物通常在紫外光(290-350nm)或近红外光(1500-2500nm)波段会有吸收，除了无法有效降低太阳光吸收，聚合物耐候性也不佳，户外长时间使用可能会因为紫外光曝晒导致泛黄吸收更多太阳光或是龟裂老化使机械性质变差，且聚合物不耐高温(＜300度)及缺乏防焰 特性，不利于建筑使用。而本申请辐射散热层具有可大面积量产且技术成熟、塑形容易、轻量、价格低廉的技术优势。
本实施方式中，辐射散热层是由多个极化材料交错堆栈组成的一自支撑结构，本申请所制备的辐射散热层不需要再有一支撑底材，在应用上可以直接和欲降温的物体直接接触，在使用上更能达到高的冷却效率。本申请辐射散热层可以为二氧化硅奈微米纤维膜，其中极化材料的直径为奈微米尺寸的纤维状结构，或是多个奈微米尺寸的颗粒物附着于一纤维状结构上。纤维状结构的制备方法可以通过静电纺丝(Electrospinning)的方式制作，包括但不限于下述步骤：配置二氧化硅前驱物溶液，将四乙氧基硅烷(Tetraethyl orthosilicate)、磷酸(H 3PO 4)、二次去离子水混合后，在室温下搅拌；配置聚乙烯醇水溶液用作助纺聚合物溶液，方法为将聚乙烯醇加入二次去离子水中，并加热搅拌使其均匀溶解；再将二氧化硅前驱物溶液与助纺聚合物溶液混合，以形成均匀的静电纺丝溶胶；将已配好的静电纺丝溶胶填入注射器内并固定在微量注射帮浦上。在外加电场下，电荷之间的排斥力将抵消液体的表面张力，使得液滴拉长，形成圆锥形液滴秦勒锥；当电压上升超过某阈值，此时电荷斥力大于液体表面张力，将产生朝收集器喷射的液流，而溶剂将在过程中蒸发，最终奈微米纤维膜沉积于收集器上。可通过调整溶液的组成、浓度及流速和施加的电压，来控制所制备纤维的直径。可通过注射的速率及时间，来控制所制备纤维层的厚度。最后，经过高温处理移除助纺聚合物以及形成辐射散热层奈微米纤维，在降至室温后即可获得二氧化硅奈微米纤维。可以理解的，以上步骤仅为例示说明，并非要严格限制本申请的权利范围。
本申请所揭露的辐射冷却装置可以实现大规模量产以及兼顾辐射散热的效率。覆盖于物体表面在不需额外电力的情况下，达到被动式有效降温。
以上所述的实施例及/或实施方式，仅是用以说明实现本申请技术的较佳实施例及/或实施方式，并非对本申请技术的实施方式作任何形式上的限制，任何本领域技术人员，在不脱离本申请内容所公开的技术手段的范围，当可作些许的更动或修饰为其它等效的实施例，但仍应视为与本申请实质相同的技术或实施例。

Claims (10)

  1. 一种辐射散热装置，其特征在于，包括辐射散热层，所述辐射散热层是由具有高能隙的多个极化材料所组成，所述极化材料具有至少一光散射单元以及一热放射单元，其中所述光散射单元可以与太阳辐射相互作用产生散射，所述热放射单元可以与热辐射交互作用并增益所述热辐射能量强度。
  2. 根据权利要求1所述的辐射散热装置，其特征在于，所述极化材料为次波长结构。
  3. 根据权利要求2所述的辐射散热装置，其特征在于，所述次波长结构交错堆栈组成自支撑结构。
  4. 根据权利要求2所述的辐射散热装置，其特征在于，所述次波长结构交错堆栈组成孔隙结构，所述孔隙结构包含多个孔隙，所述太阳辐射穿过所述孔隙和所述极化材料表面交互作用。
  5. 根据权利要求2所述的辐射散热装置，其特征在于，所述次波长结构为直径为奈微米尺寸的纤维状结构。
  6. 根据权利要求5所述的辐射散热装置，其特征在于，所述纤维状结构上还附着多个奈微米尺寸的颗粒物。
  7. 根据权利要求1至6中任一项所述的辐射散热装置，其特征在于，所述极化材料还包含热能传递单元，所述极化材料间通过所述热能传递单元相互传递能量。
  8. 根据权利要求7所述的辐射散热装置，其特征在于，所述热能传递单元可以将能量耦合至所述热放射单元，所述热放射单元增益所述热辐射能量强度。
  9. 一种制备如权利要求1至6中任一项所述的辐射散热装置的方法，其特征在于，包括下列步骤：
    提供纤维膜材料前驱溶液以及助纺聚合物，均匀混合后形成静电纺丝溶胶，再通过电纺机台注射出纤维结构，控制制程参数调控纤维直径尺寸与纤维膜厚度，最终经过热处理形成奈微米纤维膜。
  10. 一种使用权利要求1至6中任一项所述的辐射散热装置的电子装置，其特征在于，在封闭系统中，电子组件上被使用了所述辐射散热装置。
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