CN117362039A

CN117362039A - Material, structure and device for daytime radiation refrigeration and preparation method thereof

Info

Publication number: CN117362039A
Application number: CN202310068250.8A
Authority: CN
Inventors: 黄宝陵; 李洋
Original assignee: Hong Kong University of Science and Technology HKUST
Current assignee: Hong Kong University of Science and Technology HKUST
Priority date: 2022-07-06
Filing date: 2023-01-13
Publication date: 2024-01-09

Abstract

The invention discloses a ceramic composite material for radiation refrigeration, a radiation refrigeration structure and a preparation method thereof, a radiation refrigeration device and a preparation method thereof, and application thereof in the energy-saving field, in particular to the daytime radiation refrigeration field. The radiation refrigeration structure and the radiation refrigeration device have the advantages of very high solar reflectivity, infrared selectivity, infrared emissivity and excellent mechanical strength, and the preparation method is simple and easy to implement, low in cost and suitable for large-scale manufacturing.

Description

Material, structure and device for daytime radiation refrigeration and preparation method thereof

Technical Field

The invention relates to a ceramic composite material for radiation refrigeration, a radiation refrigeration structure and a preparation method thereof, a radiation refrigeration device comprising the structure and a preparation method thereof, and belongs to the field of radiation refrigeration, in particular to passive radiation refrigeration.

Background

The high temperature in summer makes people have to stay in the air-conditioning room, but the long-term air-conditioning is not beneficial to the health of people on one hand, and a large amount of electric energy is consumed on the other hand, and the used refrigerant has strong greenhouse effect. In 2019, space refrigeration using air conditioning and electric fans accounts for about 20% of the total electricity consumption of the global building, which produces carbon emissions of about 1 Gt. In tropical and subtropical areas, the power consumption and the carbon emission are larger due to long summer time, strong solar radiation, high ambient temperature and high humidity.

The passive radiation refrigeration structure can reflect sunlight with the wavelength range of about 0.3-2.5 mu m back, and simultaneously dissipate heat energy of the passive radiation refrigeration structure to the outer space with the extremely low temperature (-270 ℃) through an atmospheric transparent window with the wavelength of 8-13 mu m in the form of Infrared (IR) light. Therefore, the self-cooling of the building surface can be realized without electric energy loss, and the air compression-based refrigerating system is hopeful to be replaced. Unlike the active radiation refrigeration technology, the passive radiation refrigeration technology is a green technology, and can realize the refrigeration with zero energy consumption and lower than the ambient temperature.

Research into the technology of night radiation refrigeration has long been carried out. Recently, intensive research into passive radiation refrigeration (daytime passive radiative cooling, DPRC) has been conducted in the daytime to push the technology from night to daytime. Passive radiation cooling during the daytime is more challenging than passive radiation cooling during the night. Because there is no solar radiation at night, the ground or building is not heated, and during the daytime there is solar radiation, the ground or building absorbs thermal energy from the sun faster than it is emitted. Thus, in order to achieve passive radiative cooling during the day, in addition to high infrared emissivity, it is desirable that the cooling device or cooling material have an ultra high solar reflectance (> 95%) to minimize the large heat gain from the sun.

During the last few years, a great deal of research has been conducted on daytime radiation refrigeration, employing a number of effective strategies to construct daytime radiation refrigeration devices, including multilayer photonic structures, porous polymer films, inorganic particle-polymer composites, and inorganic particle coatings. Document 1 (Passive radiative cooling below ambient air temperature under direct sunlight, a.p. raman et al, nature 515,540-544 (2014)) by realityIt is proved that by seven layers of HfO ₂ And SiO ₂ The one-dimensional photonic crystal composed achieves refrigeration of 5 ℃ below ambient temperature in winter noon of Stanford, california, U.S. Document 2 (Scale-manufactured randomized glass-polymer hybrid metamaterial for daytime radiative cooling, Y. Zhai et al, science 355 (2017)) developed a SiO ₂ Composite films of particles and TPX polymer have a solar irradiance of greater than 900Wm in autumn noon (hole stream, arizona, USA) ^-2 Is about 93Wm ^-2 Is used for the cooling of the air conditioner. Document 3 (Hierarchically porous polymer coatings for highly efficient passive daytime radiative cooling, j.Mandal et al, science 362,315-318 (2018)) reports a porous poly (vinylidene fluoride-co-hexafluoropropylene) PVdF-HFP coating with a solar reflectance of 0.96, an infrared emissivity of 0.97, and a solar irradiance of 890Wm at 3 months (in phoenix, arizona, usa) ^-2 Refrigeration of 6 c below ambient temperature is achieved. Document 4 (A radiative cooling structural material, t.li et al, science 364,760-763 (2019)) developed a refrigerator based on white wood with a solar reflectance of 0.96 and an infrared window infrared emissivity of 0.90, producing refrigeration 4 ℃ below ambient temperature in 10 months (hole stream, arizona) noon. Recently, document 5 (Scalable and hierarchically designed polymer film as a selective thermal emitter for high-performance all-day radiative cooling.Nat.Nanotechnol, D.Li et al,16,153-158 (2021)) shows by electrospinning a selective thermal infrared emitter based on polyethylene oxide (PEO) nanofibers having a solar reflectance of 0.96 and an infrared emissivity of 0.78 in the wavelength range of 8-13 μm, with a solar irradiance of 900Wm at 12 months (south tokyo in china) ^-2 Shows refrigeration 5 ℃ below ambient temperature.

Despite these fizeau achievements, most previously reported radiant refrigeration devices and materials/coatings achieve sub-ambient refrigeration in the non-summer months of mid-latitude areas. It is well known that in summer in tropical/subtropical coastal areas, the demand for refrigeration is particularly great due to high solar intensity (e.g. up to 1.0 kw per square meter in hong kong), high humidity (e.g. up to 95% in hong kong) and high ambient temperature (e.g. up to 40 ℃ in hong kong), which are all negative factors, the radiation refrigeration is severely challenged. Thus, the radiant cooling devices or materials/coatings reported in the above documents are likely to fail to meet the summer cooling requirements of tropical/subtropical coastal areas (e.g., hong kong), and only those near perfect radiant cooling devices with infrared selectivity will achieve sub-ambient temperature cooling in these areas.

In addition, most of the current radiation refrigeration devices are too complex in structure to meet the requirements of large-scale application. To date, only a few polymer film-based refrigeration devices without infrared selectivity have been realized for large-scale manufacturing. An ideal radiant refrigeration device should have a solar reflectance approaching 1, a high infrared emissivity at the atmospheric window, and a high spectral selectivity to ensure low infrared emissivity outside the window. Furthermore, from a practical point of view, an ideal radiant refrigeration device should have scalability, low cost and environmental stability.

Disclosure of Invention

The present invention aims at solving one or more problems of the prior art, and provides a ceramic composite material for radiation refrigeration, a radiation refrigeration structure and a preparation method thereof, a radiation refrigeration device and a preparation method thereof, and applications thereof in the energy saving field, particularly in the daytime radiation refrigeration field. The ceramic composite material, the radiation refrigeration structure and the radiation refrigeration device have very high solar reflectivity, infrared selectivity, infrared emissivity and excellent mechanical strength, and the preparation method is simple and easy to implement, green and environment-friendly, low in cost and suitable for large-scale manufacturing.

According to a first aspect of the present invention there is provided a ceramic composite for radiation refrigeration comprising a silicon oxycarbide matrix, for example SiCxOy, wherein x is from 0 to 2 and y is from 0 to 2, and infrared emission enhancing particles.

In some embodiments, the infrared emission enhancement particles have a mass fraction of 0-99%, such as 10% -80%, based on the total mass of the ceramic composite.

In some embodiments, the infrared emission enhancement particles are dispersed in and/or embedded in the silicon oxycarbide layer.

In some embodiments, the infrared emission enhancement particles are micro-or nano-sized particles, such as at least one, two or more of silica particles, alumina particles, calcium carbonate particles, barium sulfate particles, and zirconium dioxide particles.

In some embodiments, the infrared emission-enhancing particles have a particle size of 10nm to 100 μm, preferably 100nm to 10 μm, more preferably 200nm to 5 μm.

In some embodiments, the ceramic composite has an infrared emissivity above 0.85, such as greater than or equal to 0.88, in the wavelength range of 8-13 μm.

In some embodiments, the ceramic composite has an infrared selectivity greater than 1.35, such as greater than or equal to 1.4.

In some embodiments, the ceramic composite is prepared by the following method: mixing the infrared emission-enhancing particles with a silicon oxycarbide precursor solution to obtain a mixture, and allowing the silicon oxycarbide precursor in the mixture (e.g., with water and oxygen) to react and solidify to form a silicon oxycarbide matrix, thereby forming the ceramic composite material.

In some embodiments, the silicon oxycarbide precursor comprises a hydroxyl-terminated polydimethylsiloxane.

According to a second aspect of the present invention, there is provided a radiation refrigeration structure comprising:

a solar reflecting layer;

and the infrared emission layer is positioned on the solar reflection layer and comprises silicon oxycarbide.

In some embodiments, the silicon oxycarbide is SiCxOy, wherein x is 0-2 and y is 0-2.

In some embodiments, the infrared emitting layer comprises or is a ceramic composite according to the first aspect of the invention or is made of a ceramic composite according to the first aspect of the invention.

In some embodiments, the infrared emitting layer has a thickness of 1 to 100 μm, preferably 2 to 50 μm, more preferably 3 to 10 μm.

In some embodiments, the solar reflecting layer has a reflectance of greater than 0.95, such as greater than or equal to 0.98, in the solar wavelength range of 0.3-2.5 μm.

In some embodiments, the solar reflecting layer comprises or is made of a metal or ceramic material having a solar reflectance of greater than 0.9, such as greater than or equal to 0.95, the metal comprising at least one of silver, copper, aluminum, or gold, for example, preferably silver.

In some embodiments, the solar reflecting layer has a thickness of 30-1000nm, such as 100-500nm.

In some embodiments, the radiant refrigeration structure further comprises an oxidation resistant layer positioned between the solar reflective layer and the infrared emissive layer.

In some embodiments, the thickness of the oxidation resistant layer is 1-100nm, such as 3-10nm.

In some embodiments, the oxidation resistant layer comprises or is made of an oxidation resistant material comprising a metal oxide, such as alumina.

In some embodiments, the oxide layer is transparent.

In some embodiments, the radiant refrigeration structure has a solar reflectance of greater than 0.95, such as greater than or equal to 0.98.

In some embodiments, the infrared emissivity of the radiant refrigeration structure is greater than 0.85, such as greater than or equal to 0.88, over the wavelength range of 8-13 μm.

In some embodiments, the infrared selectivity of the radiant refrigeration structure is greater than 1.35, such as greater than or equal to 1.4.

According to a third aspect of the present invention there is provided a method for preparing a radiant refrigeration structure according to the second aspect of the present invention, comprising:

providing a solar reflecting layer;

optionally, providing an anti-oxidant layer on the solar reflecting layer;

an infrared emitting layer is provided on the solar reflecting layer or the anti-oxidation layer.

According to a fourth aspect of the present invention there is provided a radiant refrigeration unit comprising:

a base layer;

a radiant refrigeration structure according to any of the embodiments of the second aspect of the present invention located on top of the base layer.

In some embodiments, the radiant refrigeration device further includes a superhydrophobic layer positioned over the radiant refrigeration structure.

According to a fifth aspect of the present invention there is provided a method for preparing a radiant refrigeration unit according to the fourth aspect of the present invention, comprising:

providing a base layer;

providing a radiant refrigeration structure on the base layer;

optionally, a superhydrophobic layer is provided on the radiation refrigeration structure.

According to a sixth aspect of the present invention there is provided the use of a ceramic composite material according to the first aspect of the present invention, a radiation refrigeration structure according to the second aspect of the present invention, a radiation refrigeration structure prepared according to the method according to the third aspect of the present invention, a radiation refrigeration device according to the fourth aspect of the present invention, or a radiation refrigeration device prepared according to the method according to the fifth aspect of the present invention in the field of energy conservation, in particular in the field of daytime radiation refrigeration.

According to a seventh aspect of the present invention there is provided a method of cooling/removing heat comprising contacting a ceramic composite according to the first aspect of the present invention, a radiant refrigeration structure according to the second aspect of the present invention, a radiant refrigeration structure prepared according to the method of the third aspect of the present invention, a radiant refrigeration device according to the fourth aspect of the present invention, or a radiant refrigeration device prepared according to the method of the fifth aspect of the present invention, with an object to be cooled/removed, or placed in an environment to be cooled/removed, or with an environment to be cooled/removed.

Drawings

In the drawings, wherein like reference numerals refer to identical or functionally similar elements, the drawings comprise a drawing of certain embodiments to further illustrate and explain the above and other aspects, advantages and features of the disclosure. It should be understood that the drawings depict exemplary embodiments and are not therefore intended to limit the scope of the disclosure. The disclosure will be described and explained with additional specificity and detail through the use of the accompanying drawings.

Fig. 1 is a schematic diagram illustrating a radiant refrigeration device according to some embodiments of the present invention.

Fig. 2 is a schematic diagram illustrating a radiant refrigeration device according to some embodiments of the present invention.

Fig. 3 is a schematic diagram illustrating a radiant refrigeration device according to some embodiments of the present invention.

Fig. 4 illustrates a process for manufacturing a radiant refrigeration device according to some embodiments of the invention.

Fig. 5 shows an SEM image of the ceramic composite material prepared in example 1, where a is an SEM image obtained by scanning the surface thereof, and b is an SEM image obtained by scanning the cross section thereof.

Fig. 6 shows absorption and infrared emission spectra of the ceramic composite material prepared in example 1, and AM 1.5G solar spectrum and atmospheric transmission spectrum of the radiant refrigeration device prepared in example 1.

Fig. 7 shows the ambient temperature during hong Kong summer day and the temperature of the radiant refrigeration unit made in example 1 during the measurement period.

Fig. 8 shows solar radiation intensity and relative humidity during hong Kong summer daytime during the measurement period.

Fig. 9 shows the ambient temperature during the daytime in hong Kong autumn and the temperature of the radiant refrigeration unit prepared in example 1 during the measurement period.

Fig. 10 shows the intensity of solar radiation and relative humidity during the daytime in hong Kong autumn during the measurement period.

Fig. 11 shows the ambient temperature during the daytime in hong Kong spring and the temperature of the radiant refrigeration unit made in example 1 during the measurement period.

Fig. 12 shows the solar radiation intensity and relative humidity during the daytime in hong Kong spring during the measurement period.

Reference numerals illustrate: 10-a substrate layer; 20-a solar reflecting layer; 30-an oxidation resistant layer; a 40-silicon oxycarbide matrix; 41-infrared emission enhancement particles; 50-superhydrophobic particles.

Detailed Description

The present invention will now be described in more detail with reference to the drawings and examples, it being understood that the preferred examples described herein are for the purpose of illustration and explanation only and are not to be construed as limiting the invention.

Definition of the definition

References in the specification to "one embodiment," "a preferred embodiment," "an example embodiment," etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

Any numerical value recited in this disclosure includes all values incremented by one unit from the lowest value to the highest value if there is only a two unit interval between any lowest value and any highest value. For example, if the amount of one component, or the value of a process variable such as temperature, pressure, time, etc., is stated to be 50-90, it is meant in this specification that values such as 51-89, 52-88 … …, and 69-71, and 70-71 are specifically recited. For non-integer values, 0.1, 0.01, 0.001 or 0.0001 units may be considered as appropriate. This is only a few examples of the specific designations. In a similar manner, all possible combinations of numerical values between the lowest value and the highest value enumerated are to be considered to be disclosed in this application.

As used herein, the term "about" or "approximately" is used to refer to ± 10% of each particular value, e.g., ±9%, ±8%, ±7%, ±6%, ±5%, ±4%, ±3%, ±2%, ±1%, ±0.5%, etc., prior to all values associated with the amount, weight percentage, etc. of the particular value. For example, the expression "about 10%" should be interpreted to include a value of 9% to 11%. Thus, amounts within 10% of the claimed values are included within the scope of the present invention.

As used herein, the term "a" is used to include one or more unless otherwise indicated, and the term "or" is used to mean a non-exclusive "or". In addition, when the terms used herein are not otherwise defined, they are to be understood as being used for descriptive purposes only and not for limiting purposes. In addition, all publications, patents, and patent documents mentioned in the specification are incorporated by reference in their entirety as if individually incorporated by reference. If usage between this document and those documents incorporated by reference is inconsistent, the usage in the cited references should be considered as supplementary to this document. The use herein controls for non-reconcilable inconsistencies.

In the manufacturing method described in the specification, the steps may be performed in any order other than the explicitly described time or order of operation without departing from the principles of the present invention. The claims point out that one step is performed first, followed by several other steps. It should be considered that the first step is performed before any other step, and that other steps may be performed in any other step, unless the order is further listed in that step in the other step. For example, the claims reciting "step a, step B, step C, step D, and step E" should be interpreted to mean that step a is performed first, step E is performed last, and steps B, C and D are performed in steps a and E. They may be performed in any order and still fall within the literal scope of the claimed process. Likewise, a given step or sub-step may be repeated.

As used herein, the term "optionally" means that the described feature/component/element/step may or may not be present unless otherwise indicated. For example, "optionally providing an anti-oxidant layer on the solar reflective layer" means that an anti-oxidant layer may or may not be provided on the solar reflective layer.

Ceramic composite material

According to some embodiments of the present invention, there is provided a ceramic composite for radiation refrigeration comprising a silicon oxycarbide matrix and infrared emission enhancement particles.

In some embodiments, the silicon oxycarbide is SiCxOy, where x is about 0-2, e.g., about 0.1, 0.3, 0.5, 0.7, 1.0, 1.3, 1.5, 1.8, and any value and any range therebetween, e.g., about 0.5-1.0; y is about 0-2, e.g., about 0.1, 0.3, 0.5, 0.7, 1.0, 1.3, 1.5, 1.8, and any value and any range therebetween, e.g., about 0.5-1.33.

In some embodiments, 0.ltoreq.x < 2 and 0.ltoreq.y.ltoreq.2.

In some embodiments, the mass fraction of the infrared emission-enhancing particles is about 0-99%, such as about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, and any value or any range therebetween, such as about 10-80%, 20-70%, 30-50%, based on the total mass of the ceramic composite.

In some embodiments, the infrared emission-enhancing particles are dispersed in the silicon oxycarbide matrix. In some embodiments, the infrared emission enhancement particles are embedded in the silicon oxycarbide matrix.

In some embodiments, the infrared emission enhancement particles are micro-or nano-sized particles, such as white micro-nano particles. In some specific embodiments, the infrared emission enhancement particles include or are at least one, two or more, or any combination thereof, of silica particles, alumina particles, calcium carbonate particles, barium sulfate particles, and zirconium dioxide particles.

In some embodiments, the infrared emission enhancement particles are white particles of micro-or nano-scale, such as at least one, two or more, or any combination thereof, of silica particles, alumina particles, calcium carbonate particles, barium sulfate particles, and zirconium dioxide particles.

In some embodiments, the infrared emission-enhancing particles have a particle size of about 10nm to 100 μm, for example about 10nm, 50nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm, 5 μm, 10 μm, 50 μm, 100 μm and any value or any range therebetween, preferably about 100nm to 10 μm, more preferably about 200nm to 5 μm.

In some embodiments, the ceramic composite includes a silicon oxycarbide matrix as described above and infrared emission enhancement particles as described above dispersed/embedded therein.

In some embodiments, the ceramic composite consists of a silicon oxycarbide matrix and infrared emission enhancement particles as described above.

In some embodiments, the ceramic composite is comprised of a silicon oxycarbide matrix and infrared emission enhancement particles as described above, wherein the infrared emission enhancement particles are dispersed in and/or embedded in the silicon oxycarbide matrix.

In some embodiments, the ceramic composite is prepared by the following method: providing a silicon oxycarbide precursor solution optionally comprising infrared emission enhancing particles, and allowing the silicon oxycarbide precursor therein (e.g., with water and oxygen) to react and solidify to form a silicon oxycarbide matrix, thereby forming the ceramic composite.

In some embodiments, the silicon oxycarbide precursor solution comprises a silicon oxycarbide precursor and a solvent, wherein the mass fraction of the silicon oxycarbide precursor is about 20-80%, e.g., about 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, and any value or any range therebetween.

In some embodiments, the solvent is selected from organic solvents common in the art, such as alcohols, alkanes or aromatic hydrocarbons, e.g., monohydric or polyhydric alcohols of C1-C6, linear or linear alkanes of C1-C6, or aromatic hydrocarbons of C6-C10, e.g., ethanol, hexane, benzene, toluene, and the like.

In some embodiments, the silicon oxycarbide precursor solution is a solution of hydroxyl-terminated polydimethylsiloxane in ethanol, wherein the weight fraction of hydroxyl-terminated polydimethylsiloxane is from about 30 to about 70%, such as from about 40 to about 50%.

In some embodiments, the mass ratio of the infrared emission enhancing particles to the silicon oxycarbide precursor solution is about 1:20, e.g., about 2:20, 5:20, 10:20, 15:20, 2:5, 2:10, 2:15, 2:20, 5:10, and any value or any range therebetween, e.g., about 2:10.

In some embodiments, the mixture of infrared emission-enhancing particles and silicon oxycarbide precursor solution is subjected to a treatment, such as an ultrasonic and agitation treatment, to uniformly disperse the particles.

In some embodiments, the power of the sonication is from 0 to 2000W for a period of about 1 to 3 hours, such as about 2 hours.

In some embodiments, the stirring process is at a rate of 0 to 1000rpm for a period of about 0.5 to 2.5 hours, such as about 1 to 2 hours.

In some embodiments, the silicon oxycarbide precursor is reacted with water and oxygen to produce silicon oxycarbide. In some embodiments, a mixture of infrared emission-enhancing particles and a solution of a silicon oxycarbide precursor, i.e., a silicon oxycarbide precursor that reacts with water and oxygen in the air, is exposed to air.

Without intending to be limited by theory, the ceramic composite material of the present invention utilizes the silicon oxycarbide matrix to achieve high infrared emissivity and selectivity, while properly combining the infrared emission enhancement particles, and utilizes the same to form a gradient refractive index sub-wavelength structure to inhibit surface reflection, further increasing the infrared emissivity in the range of 8-13 μm, thereby obtaining the ceramic composite material with high infrared emissivity and selectivity. The ceramic composite material of the present invention exhibits high infrared emissivity in the range of the atmospheric window, but has lower infrared emissivity in other bands outside the atmospheric window, so that it is possible to avoid obtaining heat from the surrounding environment.

In some embodiments, the ceramic composite has an infrared selectivity greater than 1.30, such as greater than or equal to 1.4.

In the present invention, infrared selectivity refers to the ratio of infrared emissivity in the wavelength range of 8-13 μm to infrared emissivity in the wavelength range of 0-20 μm.

According to some embodiments, the ceramic composite consists of SiCxOy and infrared emission enhancement particles, wherein 0.ltoreq.x < 2, 0.ltoreq.y.ltoreq.2; and/or the ceramic composite has a thickness of about 1-100 μm; and/or the infrared emission-enhancing particles have an average particle size of about 10nm to 100 μm; and/or the infrared emission enhancement particles are white micro-nano particles, such as at least one, two or more of silica particles, alumina particles, barium sulfate particles, calcium carbonate particles, and zirconium dioxide particles; and/or, the infrared emission enhancement particles are present in a mass fraction of about 0-99% based on the total mass of the ceramic composite.

Radiation refrigeration structure

According to some embodiments of the invention there is provided a radiant refrigeration structure comprising:

A solar reflecting layer;

In some embodiments, 0.ltoreq.x < 2 and 0.ltoreq.y.ltoreq.2.

In some embodiments, the infrared emitting layer is a silicon oxycarbide layer.

In some embodiments, the infrared emission layer further comprises infrared emission enhancing particles. In some specific embodiments, the infrared emission enhancement particles are dispersed/embedded in the silicon oxycarbide layer.

According to some embodiments of the invention, the silicon oxycarbide layer is equivalent to a silicon oxycarbide matrix.

In some embodiments, the infrared emitting layer comprises or is a ceramic composite material or is made from the ceramic composite material of any of the embodiments described above.

In some embodiments, the infrared emissive layer comprises a silicon oxycarbide matrix as described above and infrared emission enhancing particles as described above dispersed/embedded therein.

In some embodiments, the infrared emissive layer consists of a silicon oxycarbide matrix as described above and infrared emission enhancing particles as described above dispersed/embedded therein.

In some embodiments, the infrared emissive layer has a thickness of about 1-100 μm, e.g., about 2 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, and any value or any range therebetween, e.g., about 2-50 μm, e.g., about 3-10 μm.

In some embodiments, the infrared emissive layer is a silicon oxycarbide layer having embedded therein infrared emissive enhancement particles, wherein the mass fraction of the infrared emissive enhancement particles is about 0-99%, such as about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, and any value or any range therebetween, such as about 10-80%, 20-70%, 30-50%, based on the total mass of the infrared emissive layer, and the thickness of the infrared emissive layer is about 1-100 μm, such as about 2 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, and any value or any range therebetween, such as about 2-50 μm, such as about 3-10 μm.

In some embodiments, the infrared emitting layer is a silicon oxycarbide layer having silica particles embedded therein, wherein the silica particles have a mass fraction of about 20-50%, a particle size of 200nm-5 μm, and a thickness of about 3-10 μm based on the total mass of the infrared emitting layer.

In some embodiments, the infrared emission layer is a silicon oxycarbide layer having aluminum oxide particles embedded therein, wherein the aluminum oxide particles have a mass fraction of 20-50%, a particle diameter of 200nm-5 μm, and a thickness of 3-10 μm based on the total mass of the infrared emission layer.

In some embodiments, the infrared emitting layer is a silicon oxycarbide layer having calcium carbonate particles embedded therein, wherein the calcium carbonate particles have a mass fraction of 20-50%, a particle size of 200nm-5 μm, and a thickness of 3-10 μm based on the total mass of the infrared emitting layer.

In some embodiments, the infrared emission layer is a silicon oxycarbide layer having barium sulfate particles embedded therein, wherein the barium sulfate particles have a mass fraction of 20-50%, a particle size of 200nm-5 μm, and a thickness of 3-10 μm based on the total mass of the infrared emission layer.

In some embodiments, the infrared emission layer is a silicon oxycarbide layer having zirconium dioxide particles embedded therein, wherein the zirconium dioxide particles have a mass fraction of 20-50%, a particle size of 200nm-5 μm, and a thickness of 3-10 μm based on the total mass of the infrared emission layer.

In some embodiments, the infrared emissive layer is prepared by the following method:

mixing the infrared emission enhancement particles with a silicon oxycarbide precursor solution to obtain a mixture;

optionally, subjecting the mixture to ultrasonic and stirring treatments to obtain a dispersion;

reacting the silicon oxycarbide precursor in the mixture/dispersion with water and oxygen to form silicon oxycarbide, thereby forming the infrared emissive layer.

applying the mixture/dispersion to the solar reflective layer surface;

reacting the silicon oxycarbide precursor in the mixture/dispersion with water and oxygen to form silicon oxycarbide, thereby forming an infrared emission layer having infrared emission enhancing particles embedded in the silicon oxycarbide layer.

According to some embodiments of the invention, the solar reflecting layer is configured to reflect sunlight, thereby minimizing the energy of the sunlight. Furthermore, in most cases, the solar reflective layer may also reflect mid-infrared light, creating multiple absorption in the radiant refrigeration structure, which is advantageous for achieving high infrared absorption/emission.

In some embodiments, the solar reflecting layer comprises or is made of a (specular) metal or ceramic material with a solar reflectance higher than 0.9, such as higher than 0.95, such as equal to or higher than 0.98.

In some embodiments, metals suitable for use in the solar reflective layer of the invention include at least one of silver, copper, aluminum, or gold.

In some embodiments, ceramic materials suitable for use in the solar reflective layer of the invention include at least one of titanium nitride, indium tin oxide.

In the case of radiation refrigeration devices for daytime radiation refrigeration, the solar reflecting layer is made of a metal or ceramic material, preferably a silver material, with a solar reflectance of greater than 0.95, for example greater than or equal to 0.98, for example a mirror silver film or a mirror silver plate.

In some embodiments, the solar reflecting layer is flexible or inflexible.

In some embodiments, the solar reflective layer has a thickness of about 30-1000nm, such as about 30nm, 50nm, 120nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, 850nm, 900nm, 950nm, and any value or any range therebetween, such as about 120-500nm.

In some embodiments, the solar reflecting layer is a specular silver film having a thickness of about 100-300nm, such as about 150nm.

In some embodiments, the solar reflective layer has a solar reflectance of greater than 0.95, such as greater than or equal to 0.98, over a solar wavelength range of 0.3-2.5 μm.

In some embodiments, the anti-oxidant layer is located between the solar reflecting layer and the infrared emitting layer and is located above the solar reflecting layer.

In some embodiments, the anti-oxidant layer is used to protect the solar reflective layer, for example, to prevent oxidation of its metal or to avoid reflection attenuation. For example, when the solar reflecting layer is a specular silver film, the anti-oxidant layer may prevent the film from being oxidized and reflection attenuated.

In some embodiments, the oxidation resistant layer is transparent.

In some embodiments, the oxidation resistant layer comprises or is made of a transparent oxide.

In some embodiments, the thickness of the oxidation resistant layer is about 1-100nm, such as about 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 15nm, 20nm, 30nm, 40nm, 50nm, and any value or range therebetween, such as about 3-50nm.

The material and thickness of the antioxidation layer can be selected according to the requirements of the solar reflecting layer, and the like. In some embodiments, the solar layer is an aluminum oxide film having a thickness of 5nm.

In embodiments in which the oxidation resistant layer is a metal oxide, the oxidation resistant layer is prepared by oxidizing a metal plated on the solar reflecting layer.

For example, in one embodiment, aluminum is deposited on the solar reflecting layer and exposed to air oxidation to create an aluminum oxide protective layer.

In some embodiments, there is provided a radiation refrigeration structure comprising:

a solar reflecting layer;

and the infrared emission layer is positioned on the solar reflection layer and is a silicon oxycarbide layer.

the solar energy reflecting layer is a silver film;

a solar reflecting layer;

and the infrared emission layer is positioned on the solar reflection layer and comprises a silicon oxycarbide matrix and infrared emission enhancement particles.

the solar energy reflecting layer is a silver film;

an infrared emitting layer over the solar reflecting layer, the infrared emitting layer comprising or being a silicon oxycarbide layer having silicon dioxide particles embedded therein.

The solar reflecting layer is a silver film and has the thickness of 100-200nm;

an infrared emission layer on the solar reflection layer, wherein the infrared emission layer is a silicon oxycarbide layer embedded with silicon dioxide particles and has a thickness of 2-20 μm,

wherein the mass fraction of the silicon dioxide particles in the infrared emission layer is 20-40%, and the particle size is 200nm-5 μm.

a solar reflecting layer;

an anti-oxidation layer over the solar reflective layer;

and an infrared emission layer positioned on the oxidation resistant layer, wherein the infrared emission layer comprises silicon oxycarbide.

the solar energy reflecting layer is a silver film;

the anti-oxidation layer is positioned on the solar reflecting layer, and the solar reflecting layer is an alumina film;

and the infrared emission layer is positioned on the antioxidant layer, and the infrared emission layer is a silicon oxycarbide layer.

a solar reflecting layer;

An anti-oxidation layer over the solar reflective layer;

an infrared emitting layer over the oxidation resistant layer, the infrared emitting layer comprising or being a silicon oxycarbide layer having infrared emission enhancing particles embedded therein.

the solar reflecting layer is a silver film and has the thickness of 100-200nm;

the antioxidation layer is positioned on the reflection layer, is an alumina film and has the thickness of 3-15nm;

an infrared emission layer on the protective layer, wherein the infrared emission layer is a silicon oxycarbide layer embedded with silicon dioxide particles and has a thickness of 2-20 μm,

In some embodiments, the thickness of the radiant refrigeration structure is 1-100 μm, e.g., 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, and any value or any range therebetween, e.g., 5-50 μm, e.g., 10-20 μm.

Without intending to be bound by theory, the radiant refrigeration structure of the present invention utilizes the reflective layer to reflect sunlight, thereby minimally obtaining the energy of the sunlight; high infrared emissivity and selectivity are achieved in the atmospheric window range by the infrared emission layer, and thus solar reflectance of more than 0.95, for example, 0.98 or more, infrared emissivity in the wavelength range of 8-13 μm of more than 0.85, for example, 0.88 or more, infrared selectivity of more than 1.30, for example, 1.4 or more can be obtained.

Preparation of radiation refrigeration structure

According to some embodiments of the present invention, there is provided a method for preparing the above-described radiation refrigeration structure, comprising:

providing a solar reflecting layer;

optionally, providing an anti-oxidant layer on the solar reflecting layer;

In the present invention, the method for providing the solar reflecting layer is not particularly limited, and may be selected by one skilled in the art according to prior knowledge. For example, in some embodiments, the solar reflecting layer may be obtained by depositing a metal on a substrate. The method for depositing the metal is not particularly limited and may be selected by one skilled in the art. For example, in some embodiments, this may be achieved by electron beam evaporation or the like.

In some embodiments, providing an oxidation resistant layer comprises: plating a metal on the reflective layer, and oxidizing the metal plated on the solar reflective layer to prepare the anti-oxidation layer.

In the present invention, the manner of plating is not particularly limited, and may be selected by one skilled in the art. For example, in some embodiments, this may be achieved by magnetron sputtering, electroplating, electron beam evaporation, or the like.

In the present invention, the method of oxidizing the metal applied to the solar reflecting layer is not particularly limited, and may be selected by one skilled in the art.

In some embodiments, providing an infrared emissive layer comprises: and mixing the infrared emission enhancement particles with a silicon oxycarbide precursor solution to obtain a mixture, and reacting and curing the silicon oxycarbide precursor in the mixture to generate a silicon oxycarbide matrix so as to form an infrared emission layer with the infrared emission enhancement particles embedded in the silicon oxycarbide matrix.

In some embodiments, the silicon oxycarbide precursor solution is a solution of hydroxyl-terminated polydimethylsiloxane in ethanol, wherein the hydroxyl-terminated polydimethylsiloxane is present in a mass fraction of about 30-70%, such as about 40-50%.

In some embodiments, the mixture of infrared emission-enhancing particles and the silicon oxycarbide precursor solution is subjected to a treatment, such as an ultrasonic and agitation treatment, to uniformly disperse the particles.

In some embodiments, the stirring process is at a rate of about 0 to 1000rpm for a period of about 0.5 to 2.5 hours, such as about 1 to 2 hours.

In some embodiments, the silicon oxycarbide precursor is reacted with water and oxygen to produce silicon oxycarbide.

applying the dispersion/mixture to the solar reflective layer surface;

reacting the silicon oxycarbide precursor in the mixture with water and oxygen to form a silicon oxycarbide matrix, thereby forming an infrared emission layer with infrared emission enhancing particles embedded in the silicon oxycarbide matrix.

Radiation refrigerating device

According to some embodiments of the invention there is provided a radiant refrigeration device comprising:

a base layer;

the radiant refrigeration structure of the present invention as described in any of the embodiments above located above the substrate layer.

In some embodiments, the base layer is for supporting a radiant refrigeration structure.

According to some embodiments, the substrate layer may be of any material, such as a pure material or an alloy material, as long as the purpose of supporting the radiant refrigeration structure is achieved.

In some embodiments, the base layer is stainless steel (304, 310, 316, 321), glass, copper, or aluminum material.

The shape of the base layer is not particularly limited, and may be selected by those skilled in the art according to the actual circumstances. For example, in some embodiments, the substrate layer is tubular, flat, or planar.

In some embodiments, the radiation refrigeration structure is a radiation refrigeration structure as defined in any of the above embodiments.

In some embodiments, the solar reflecting layer of the radiant refrigeration structure interfaces with the base layer.

In some embodiments, the superhydrophobic layer is positioned above the radiant refrigeration structure and interfaces with an infrared emission layer of the radiant refrigeration structure.

In some embodiments, the superhydrophobic layer includes superhydrophobic particles having a particle size of about 1-1000nm, such as about 5nm, 50nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm, and any value or any range therebetween.

In some embodiments, the superhydrophobic particles comprise/are at least one of hydrophobic nanoparticles of silica, alumina, polytetrafluoroethylene, and the like.

In some embodiments, there is provided a radiation refrigeration device comprising:

A base layer;

a solar reflecting layer over the base layer;

and the infrared emission layer is positioned on the reflection layer and is a silicon oxycarbide layer.

the substrate layer is a silicon wafer substrate;

the solar reflecting layer is positioned on the basal layer and is a silver film;

a base layer;

a solar reflecting layer over the base layer;

and an infrared emission layer positioned on the solar reflecting layer, wherein the infrared emission layer comprises silicon oxycarbide and infrared emission enhancement particles embedded therein.

a base layer;

and the infrared emission layer is positioned above the reflection layer, and the infrared emission layer is a silicon oxycarbide layer with silicon dioxide particles embedded therein.

the substrate layer is a silicon wafer substrate;

the solar reflecting layer is positioned on the basal layer, is a silver film and has the thickness of 100-200nm;

a base layer;

a solar reflecting layer over the base layer;

an anti-oxidation layer over the solar reflective layer;

the substrate layer is a silicon wafer substrate;

a base layer;

a solar reflecting layer over the base layer;

an anti-oxidation layer over the solar reflective layer;

and an infrared emission layer positioned on the oxidation resistant layer, wherein the infrared emission layer comprises silicon oxycarbide and infrared emission enhancement particles embedded therein.

the substrate layer is a silicon wafer substrate;

the antioxidation layer is positioned on the solar reflecting layer, is an alumina film and has the thickness of 3-15nm;

a base layer;

a solar reflecting layer over the base layer;

an anti-oxidation layer over the solar reflective layer;

an infrared emission layer located over the protective layer, the infrared emission layer comprising silicon oxycarbide;

and a superhydrophobic layer positioned over the infrared emission layer.

the substrate layer is a silicon wafer substrate;

the anti-oxidation layer is positioned on the solar reflecting layer and is an alumina film;

the infrared emission layer is positioned above the antioxidant layer and is a silicon oxycarbide layer;

the super-hydrophobic layer is positioned on the infrared emission layer and comprises at least one of hydrophobic nano particles such as silicon dioxide, aluminum oxide, polytetrafluoroethylene and the like.

a base layer;

a solar reflecting layer over the base layer;

An anti-oxidation layer over the solar reflective layer;

an infrared emission layer positioned over the oxidation resistant layer, the infrared emission layer comprising silicon oxycarbide and infrared emission enhancement particles embedded therein;

and a superhydrophobic layer positioned over the infrared emission layer.

the substrate layer is a silicon wafer substrate;

the infrared emission layer is positioned above the oxidation resistant layer, the infrared emission layer is a silicon oxycarbide layer in which silicon dioxide particles are embedded, the thickness of the infrared emission layer is 2-20 mu m, wherein the mass fraction of the silicon dioxide particles in the infrared emission layer is 20-40%, and the particle size of the silicon dioxide particles is 200nm-5 mu m;

the super-hydrophobic layer is positioned above the infrared emission layer and comprises hydrophobic nano particles such as silicon dioxide, aluminum oxide, polytetrafluoroethylene and the like.

Preparation radiation refrigerating device

According to some embodiments of the present invention, there is provided a method for manufacturing a radiant refrigeration device according to any of the preceding embodiments, comprising:

Providing a base layer;

providing a radiant refrigeration structure on the base layer;

In the present invention, the method for providing the base layer is not particularly limited, and may be selected by one skilled in the art according to prior knowledge.

In some embodiments, the method of providing a radiation refrigeration structure is as described in any of the above embodiments for preparing a radiation refrigeration structure, and is not described herein.

In some embodiments, the superhydrophobic layer is provided comprising at least one of hydrophobic nanoparticles of silica, alumina, polytetrafluoroethylene, and the like.

In some embodiments, there is provided a method of making a radiant refrigeration device as described in any of the preceding embodiments, comprising:

providing a base layer;

providing a solar reflecting layer over the base layer;

optionally, providing an anti-oxidant layer over the solar reflecting layer;

applying the mixture/dispersion to the solar reflective layer surface;

Reacting the silicon oxycarbide precursor in the mixture with water and oxygen to form a silicon oxycarbide matrix, thereby forming an infrared emission layer with infrared emission enhancing particles embedded in the silicon oxycarbide matrix;

optionally, a superhydrophobic layer is provided over the infrared emission layer.

Application of

According to some embodiments of the present invention there is provided the use of a radiant refrigeration structure or radiant refrigeration device according to any of the embodiments of the present invention in the field of energy conservation, in particular in the field of daytime radiant refrigeration.

According to some embodiments of the present invention, there is provided a method of cooling/removing heat, comprising contacting a radiation refrigeration structure or radiation refrigeration device according to any of the above embodiments of the present invention with an object to be cooled/removed, transferring heat from the object to the radiation refrigeration structure or radiation refrigeration device, or placing the object in an environment to be cooled/removed, or contacting the environment to be cooled/removed, and radiating heat out through the radiation refrigeration structure or radiation refrigeration device, thereby cooling/removing heat for the object.

Examples

The invention is further illustrated by the following specific examples.

Referring to fig. 1, there is shown a radiant refrigeration device according to some embodiments of the present invention, comprising a substrate layer 10, a solar reflecting layer 20, and an infrared emitting layer comprising a silicon oxycarbide matrix 40 and infrared emission enhancement particles 41 embedded therein.

Referring to fig. 2, there is shown a radiant refrigeration device according to further embodiments of the present invention, the radiant refrigeration device comprising a substrate layer 10, a solar reflective layer 20, an oxidation resistant layer 30, and an infrared emissive layer comprising a silicon oxycarbide matrix 40 and infrared emission enhancement particles 41 embedded therein.

Referring to fig. 3, there is shown a radiant refrigeration device according to still other embodiments of the present invention, the radiant refrigeration device comprising a substrate layer 10, a solar reflecting layer 20, an oxidation resistant layer 30, an infrared emitting layer comprising a silicon oxycarbide matrix 40 and infrared emission enhancement particles 41 embedded therein, and superhydrophobic particles 50.

Example 1

In the embodiment, a radiation refrigeration device for daytime passive radiation refrigeration is provided, which consists of a silicon wafer substrate and a radiation refrigeration junctionThe radiation refrigeration structure consists of a silver film, an alumina film and a ceramic composite material, wherein the ceramic composite material consists of a silicon oxycarbide matrix and SiO embedded therein ₂ Particle composition. The radiation refrigerating device is prepared by the following method:

first, a 150nm thick silver film was deposited by electron beam evaporation on a 4 inch silicon wafer substrate. Then, aluminum having a thickness of 3nm was deposited on the silver thin film, which was oxidized to aluminum oxide after being exposed to air, thereby forming an aluminum oxide thin film on the silver thin film.

Dissolving the hydroxyl-terminated polydimethylsiloxane in ethanol (99% purity) to obtain a precursor solution, wherein the weight fraction of the hydroxyl-terminated polydimethylsiloxane is 50%; siO with particle diameter of 300-500nm ₂ Particles are added to the precursor solution, wherein SiO ₂ The weight ratio of the particles to the precursor solution is 2:10, namely SiO ₂ The weight ratio of hydroxyl-terminated polydimethylsiloxane to ethanol was 2:5:5. The mixture was subjected to ultrasonic treatment (ultrasonic power 1000W) for 2 hours and magnetic stirring (500 rpm) for 1 hour to disperse the mixture.

Then spin-coating the dispersed mixture on the formed alumina film at 1000rpm, standing in open air at room temperature for 3 days, reacting the hydroxyl-terminated polydimethylsiloxane with water vapor and oxygen to form silicon oxycarbide, and determining its chemical formula as SiCO by X-ray photoelectron spectroscopy (XPS) _1.33 Thereby forming a ceramic composite material having a thickness of 10 μm.

The ceramic composite material obtained was characterized by a Scanning Electron Microscope (SEM), and the SEM image obtained was shown in fig. 5, where a is an SEM image obtained by scanning the surface thereof, and b is an SEM image obtained by scanning the cross section thereof.

The absorption and infrared emission spectra of the obtained radiation refrigeration device were measured using an ultraviolet-visible-near infrared spectrometer and a fourier infrared spectrometer, and the results are shown in fig. 6. The standard AM 1.5G solar spectrum and US1976 atmospheric transmission spectrum are shown in fig. 6.

The solar reflectance R is calculated according to the following formula _solar ：

Wherein E is _solar (lambda), R (lambda) and I _solar Respectively representing the power of the AM 1.5G solar spectrum at a single wavelength lambda, the single wavelength reflectivity and the total solar power, wherein dlambda is the wavelength;

thermal infrared emissivity epsilon _8-13μm And infrared selectivity eta _ε ：

Wherein I is _BB And ε (λ) respectively represent the single wavelength radiant power and the single wavelength emissivity of the blackbody radiation, T _amb ＝300K。

The radiation refrigeration device manufactured in this example has an average solar reflectance of 0.98, a thermal infrared emissivity of 0.88 in an atmospheric window of 8-13 μm, and an infrared selectivity of 1.42.

The refrigeration performance of the radiant refrigeration unit was tested in hong Kong (summer in tropical regions) at day 7 and 9 of 2021 and the results are shown in FIGS. 7 and 8. The test of the refrigerating performance is carried out on the roof of a building of the university of hong Kong science and technology. First, a T-shaped thermocouple was attached to the back of the radiation refrigerator, and the thermocouple was connected to a temperature recorder. Next, the radiant refrigeration unit was mounted on a high density polystyrene foam table (30 x 30cm ³ ) So that the upper surface of the radiant refrigeration unit is flush with the upper surface of the polystyrene foam. Weather data including air temperature, relative humidity, wind speed and solar intensity are recorded in real time by a portable weather meter. The height of the portable weather instrument is adjusted to ensure that the air temperature testing module and the radiation refrigerating device are positioned on the same horizontal plane and are higher than the roof plane by more than 1 meter. During the daytime period of testing (11:00-15:00), solar radiationPeak intensity of 1000Wm ^-2 The ambient temperature is 32-38 ℃, and the relative humidity is 50-65%. In such a severe environment, the radiation refrigerating apparatus of the present embodiment achieves a temperature drop of 0-4 ℃ and an average temperature drop of 1.8 ℃ as compared with the environment.

Further, according to the above method, the refrigerating performance of the radiation refrigerating apparatus was tested in hong Kong (autumn in tropical region) on day 10, 11 of 2021, and the results are shown in fig. 9 and 10; the refrigeration performance of the radiant refrigeration unit was tested in hong Kong (spring in tropical regions) at days 4, 5-6 of 2022 and the results are shown in FIGS. 11 and 12.

Example 2

In the present embodiment, there is provided a radiation refrigeration device for daytime passive radiation refrigeration, which is composed of a silicon wafer substrate, a radiation refrigeration structure and a superhydrophobic layer, the radiation refrigeration structure is composed of a silver thin film, an aluminum oxide thin film and a ceramic composite material, wherein the ceramic composite material is composed of a silicon oxycarbide substrate and SiO embedded therein ₂ Particle composition. The radiation refrigerating device is prepared by the following method:

Dissolving the hydroxyl-terminated polydimethylsiloxane in ethanol (purity 99%) to obtain a precursor solution, wherein the weight fraction of the hydroxyl-terminated polydimethylsiloxane is 50%; siO with particle diameter of 50-250nm ₂ Particles are added to the precursor solution, wherein SiO ₂ The weight ratio of particles to precursor solution was 1.5:10, i.e. SiO ₂ The weight ratio of hydroxyl-terminated polydimethylsiloxane to ethanol was 1.5:5:5. The mixture was subjected to ultrasonic treatment (ultrasonic power 1000W) for 2 hours and magnetic stirring (500 rpm) for 1 hour to disperse the mixture.

Spin-coating the dispersed mixture on an alumina film at 1000rpm, and then spin-coating SiO having a particle diameter of 20nm ₂ Particles (superhydrophobic particles) are coated on the silicon oxycarbide layer and exposed to the open air at room temperatureStanding for 3 days, reacting hydroxyl-terminated polydimethylsiloxane with water vapor and oxygen to form silicon oxycarbide, and determining its chemical formula as SiCO by X-ray photoelectron spectroscopy (XPS) _1.33 Thereby forming a ceramic composite material having a thickness of 10 μm.

The absorption and infrared emission spectra of the radiation refrigeration device are measured by an ultraviolet-visible-near infrared spectrometer and a Fourier infrared spectrometer. The radiation refrigeration device of this example obtained by the method of example 1 had an average solar reflectance of 0.96, a thermal infrared emissivity of 0.89 in the atmospheric window of 8-13 μm and an infrared selectivity of 1.36.

It should be noted that the above-described embodiments are only for explaining the present invention and do not constitute any limitation of the present invention. The invention has been described with reference to exemplary embodiments, but it is understood that the words which have been used are words of description and illustration, rather than words of limitation. Modifications may be made to the invention as defined in the appended claims, and the invention may be modified without departing from the scope and spirit of the invention. Although the invention is described herein with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed herein, as the invention extends to all other means and applications which perform the same function.

Claims

1. A ceramic composite for radiation refrigeration comprising a silicon oxycarbide matrix, such as SiCxOy, wherein x is 0-2 and y is 0-2, and infrared emission enhancement particles.

2. Ceramic composite according to claim 1, wherein the mass fraction of the infrared emission-enhancing particles is 0-99%, such as 10% -80%, based on the total mass of the ceramic composite; and/or, the infrared emission enhancement particles are dispersed in and/or embedded in the silicon oxycarbide matrix.

3. The ceramic composite of claim 1 or 2, wherein the infrared emission enhancement particles are micro-or nano-sized particles, such as at least one of silica particles, alumina particles, zirconia particles, barium sulfate particles, and calcium carbonate particles; and/or the infrared emission-enhancing particles have a particle diameter of 10nm to 100 μm, preferably 100nm to 10 μm, more preferably 200nm to 5 μm.

4. A ceramic composite according to any of claims 1-3, wherein the ceramic composite has an infrared emissivity above 0.85, such as above 0.88, in the wavelength range of 8-13 μm; and/or the ceramic composite has an infrared selectivity of greater than 1.30, such as greater than or equal to 1.4.

5. The ceramic composite of any one of claims 1-4, wherein the ceramic composite is prepared by a method comprising: mixing the infrared emission enhancement particles with a silicon oxycarbide precursor solution to obtain a mixture, and allowing the silicon oxycarbide precursor in the mixture (e.g., with water and oxygen) to react and solidify to form a silicon oxycarbide matrix, thereby forming the ceramic composite material; and/or, the silicon oxycarbide precursor comprises a hydroxyl-terminated polydimethylsiloxane.

6. A radiant refrigeration structure comprising:

a solar reflecting layer;

and an infrared emission layer positioned on the solar reflection layer, wherein the infrared emission layer comprises silicon oxycarbide, such as SiCxOy, wherein x is 0-2, and y is 0-2.

7. The radiant refrigeration structure of claim 6, wherein the infrared emitting layer comprises or is a ceramic composite of any of claims 1-5 or is made of a ceramic composite of any of claims 1-5.

8. A radiant refrigeration structure as claimed in claim 6 or claim 7 wherein the infrared emissive layer has a thickness of 1 to 100 μm, preferably 2 to 50 μm, more preferably 3 to 10 μm.

9. A radiant refrigeration structure according to any of claims 6 to 8 wherein the solar reflective layer comprises or is made of a metal or ceramic material having a solar reflectance of greater than 0.9, such as greater than or equal to 0.95, the metal comprising for example silver; and/or the solar reflecting layer has a thickness of 30-1000nm, for example 100-500nm.

10. A radiant refrigeration structure according to any of claims 6 to 9 wherein the solar reflective layer has a reflectance of greater than 0.95, such as greater than or equal to 0.98, in the solar wavelength range of 0.3 to 2.5 μm.

11. The radiant refrigeration structure as set forth in any one of claims 6 to 10 further including an oxidation resistant layer between the solar reflective layer and the infrared emissive layer.

12. A radiation refrigeration structure according to any one of claims 6-11, wherein the thickness of the oxidation resistant layer is 1-100nm, such as 3-10nm.

13. A radiant refrigeration structure as claimed in any one of claims 6 to 12 wherein the oxidation resistant layer comprises or is made of an oxidation resistant material comprising a metal oxide such as alumina; and/or the oxidation-resistant layer is transparent.

14. The radiant refrigeration structure of any one of claims 6 to 13, wherein the radiant refrigeration structure has a solar reflectance of greater than 0.95, such as greater than or equal to 0.98; and/or the infrared emissivity of the radiant refrigeration structure is above 0.85, such as greater than or equal to 0.88, in the wavelength range of 8-13 μm; and/or the infrared selectivity of the radiant refrigeration structure is greater than 1.35, such as greater than or equal to 1.4.

15. A method for preparing the radiant refrigeration structure of any of claims 6-14, comprising:

Providing a solar reflecting layer;

optionally, providing an anti-oxidant layer on the solar reflecting layer;

16. A radiant refrigeration device comprising:

a base layer;

the radiant refrigeration structure of any of claims 6-14 located above the base layer.

17. The radiant refrigeration unit as set forth in claim 16 further comprising a superhydrophobic layer positioned over said radiant refrigeration structure.

18. A method for making the radiant refrigeration unit of claim 16 or 17, comprising:

providing a base layer;

providing a radiant refrigeration structure on the base layer;

19. Use of the ceramic composite of any one of claims 1-5, the radiation refrigeration structure of any one of claims 6-14, the radiation refrigeration structure prepared according to the method of claim 15, the radiation refrigeration device of claim 16 or 17, or the radiation refrigeration device prepared according to the method of claim 18 in energy saving applications, in particular in the daytime radiation refrigeration applications.

20. A method of cooling/removing heat comprising contacting the ceramic composite of any one of claims 1-5, the radiant refrigeration structure of any one of claims 6-14, the radiant refrigeration structure prepared according to the method of claim 15, the radiant refrigeration device of claim 16 or 17, or the radiant refrigeration device prepared according to the method of claim 18 with an object to be cooled/removed, or placed in an environment to be cooled/removed, or with an environment to be cooled/removed.