阅读说明：本技术 一种实现辐射制冷的二氧化硅热超材料及其应用 (Silicon dioxide thermal metamaterial for realizing radiation refrigeration and application thereof ) 是由 范春珍 殷怀远 于 2021-01-19 设计创作，主要内容包括：本发明属于热超材料及辐射制冷技术领域,公开一种实现辐射制冷的二氧化硅热超材料及其应用。所述二氧化硅热超材料由反射层及位于其上的吸收层组成,所述吸收层由基底层和图案层组成；所述反射层由从上到下交替排列的二氧化钛层和氟化镁层组成；所述基底层由从上到下依次排列的二氧化硅层、氮化硅层和二氧化钛层组成,所述图案层由在二氧化硅层上表面上呈周期性排布的二氧化硅结构单元组成,所述二氧化硅结构单元包括两个大小相等的二氧化硅等腰直角三棱柱,这两个二氧化硅等腰直角三棱柱关于二氧化硅结构单元的几何中心对称。本发明热超材料,结构简单,易于制作,并且在大气窗口有近完美吸收并在太阳光波段有较高的反射。(The invention belongs to the technical field of thermal metamaterials and radiation refrigeration, and discloses a silicon dioxide thermal metamaterial for realizing radiation refrigeration and application thereof. The silicon dioxide thermal metamaterial is composed of a reflecting layer and an absorbing layer positioned on the reflecting layer, and the absorbing layer is composed of a substrate layer and a pattern layer; the reflecting layer consists of titanium dioxide layers and magnesium fluoride layers which are alternately arranged from top to bottom; the pattern layer is composed of silicon dioxide structural units which are periodically arranged on the upper surface of the silicon dioxide layer, the silicon dioxide structural units comprise two silicon dioxide isosceles right triangular prisms with the same size, and the two silicon dioxide isosceles right triangular prisms are symmetrical about the geometric center of the silicon dioxide structural units. The thermal metamaterial has the advantages of simple structure, easy manufacture, near perfect absorption at an atmospheric window and higher reflection at a sunlight wave band.)

1. A silicon dioxide thermal metamaterial for realizing radiation refrigeration is characterized in that: the silicon dioxide thermal metamaterial is composed of a reflecting layer and an absorbing layer positioned on the reflecting layer, and the absorbing layer is composed of a substrate layer and a pattern layer; the reflecting layer consists of titanium dioxide layers and magnesium fluoride layers which are alternately arranged from top to bottom; the pattern layer is composed of silicon dioxide structure units which are periodically arranged on the upper surface of the silicon dioxide layer, the upper surface of the silicon dioxide layer is marked as an x-y plane, the arrangement periods of the silicon dioxide structure units on the upper surface of the silicon dioxide layer along the x axis and the y axis are respectively marked as Px and Py, and Px = Py =8 +/-0.1 mu m;

the silicon dioxide structure unit comprises two silicon dioxide isosceles right triangular prisms with the same size, the two silicon dioxide isosceles right triangular prisms are symmetrical about the geometric center of the silicon dioxide structure unit, and the vertexes of the right angles of the upper/lower bottom surfaces of the two silicon dioxide isosceles right triangular prisms and the orthographic projection points of the geometric center of the silicon dioxide structure unit on the upper surface of the silicon dioxide layer are on the same straight line; the height d1=3 ± 0.1 μm of the isosceles right triangle of the upper/lower bottom surfaces of the silica isosceles right triangular prisms, the distance d2=1 ± 0.1 μm between two silica isosceles right triangular prisms, and the height t1=3 ± 0.1 μm of the silica isosceles right triangular prisms.

2. The silica thermal metamaterial for achieving radiation refrigeration as claimed in claim 1, wherein: the base layer has a silicon dioxide layer thickness t2=7 ± 0.1 μm, a silicon nitride layer thickness t3=6 ± 0.1 μm, and a titanium dioxide layer thickness t4=6 ± 0.1 μm.

3. The silica thermal metamaterial for achieving radiation refrigeration as claimed in claim 1, wherein: the reflecting layer comprises a titanium dioxide layer with the thickness of 70 +/-0.1 nm, a magnesium fluoride layer with the thickness of 100 +/-0.1 nm, a titanium dioxide layer with the thickness of 120 +/-0.1 nm, a magnesium fluoride layer with the thickness of 110 +/-0.1 nm, a titanium dioxide layer with the thickness of 100 +/-0.1 nm, a magnesium fluoride layer with the thickness of 72 +/-0.1 nm, a titanium dioxide layer with the thickness of 53 +/-0.1 nm, a magnesium fluoride layer with the thickness of 100 +/-0.1 nm and a titanium dioxide layer with the thickness of 75 +/-0.1 nm from top to bottom.

4. Use of the silica thermal metamaterial for realizing radiation refrigeration as claimed in any one of claims 1 to 3 in building materials and passive refrigeration devices.

Technical Field

The invention belongs to the technical field of thermal metamaterials and radiation refrigeration, and particularly relates to a silicon dioxide thermal metamaterial for realizing radiation refrigeration and application thereof.

Background

With the increasing demand of energy consumption, the emission of greenhouse gases has threatened the life of people. Especially, the conventional refrigeration method consumes a large amount of electric energy and generates heat, which further increases the emission of carbon dioxide, resulting in global warming. Therefore, it is highly desirable to find an effective cooling method for reducing the size of buildings, vehicles and the likeThe temperature of the laundry and the reduction of energy consumption. Radiation refrigeration is a technique for reducing temperature by selective emission within atmospheric windows without consuming energy. As early as 1975, Catalanotti et al proposed the concept of radiative cooling and the thermodynamic correlation of temperature to heat. In 2014, Raman et al first demonstrated a multilayer structure of silicon dioxide and hafnium dioxide alternately arranged on a metal substrate, and the cooling power at room temperature can reach 40.1W/m²。

The thermal metamaterial is an artificial material with unique performance. The transmission characteristics of heat flow in the medium are changed through the structural units which are arranged periodically, and the characteristics which do not exist in some natural materials are realized. This structure can be used for selective radiative cooling, with significant advances.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention aims to provide a silicon dioxide thermal metamaterial for realizing radiation refrigeration and application thereof.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

the silicon dioxide thermal metamaterial for realizing radiation refrigeration is composed of a reflecting layer and an absorbing layer positioned on the reflecting layer, wherein the absorbing layer is composed of a substrate layer and a pattern layer; the reflecting layer consists of titanium dioxide layers and magnesium fluoride layers which are alternately arranged from top to bottom; the pattern layer is composed of silicon dioxide structure units which are periodically arranged on the upper surface of the silicon dioxide layer, the upper surface of the silicon dioxide layer is marked as an x-y plane, the arrangement periods of the silicon dioxide structure units on the upper surface of the silicon dioxide layer along the x axis and the y axis are respectively marked as Px and Py, and Px = Py =8 +/-0.1 mu m;

the silicon dioxide structure unit comprises two silicon dioxide isosceles right triangular prisms with the same size, the two silicon dioxide isosceles right triangular prisms are symmetrical about the geometric center of the silicon dioxide structure unit, and the vertexes of the right angles of the upper/lower bottom surfaces of the two silicon dioxide isosceles right triangular prisms and the orthographic projection points of the geometric center of the silicon dioxide structure unit on the upper surface of the silicon dioxide layer are on the same straight line; the height d1=3 ± 0.1 μm of the isosceles right triangle of the upper/lower bottom surfaces of the silica isosceles right triangular prisms, the distance d2=1 ± 0.1 μm between two silica isosceles right triangular prisms, and the height t1=3 ± 0.1 μm of the silica isosceles right triangular prisms.

Preferably, the base layer has a silicon dioxide layer thickness t2=7 ± 0.1 μm, a silicon nitride layer thickness t3=6 ± 0.1 μm, and a titanium dioxide layer thickness t4=6 ± 0.1 μm.

Preferably, the reflecting layer consists of 70 +/-0.1 nm of titanium dioxide layer, 100 +/-0.1 nm of magnesium fluoride layer, 120 +/-0.1 nm of titanium dioxide layer, 110 +/-0.1 nm of magnesium fluoride layer, 100 +/-0.1 nm of titanium dioxide layer, 72 +/-0.1 nm of magnesium fluoride layer, 53 +/-0.1 nm of titanium dioxide layer, 100 +/-0.1 nm of magnesium fluoride layer and 75 +/-0.1 nm of titanium dioxide layer from top to bottom in terms of the thickness of each layer.

The silicon dioxide thermal metamaterial for realizing radiation refrigeration is applied to building materials and passive refrigeration devices.

The actual fabrication of the thermal metamaterials of the present invention can be achieved by using well-established physical vapor deposition (Thielsch R, Gatto A and Heber J. 2020 Thin Solid Films 410(1-2) 86-93) to fabricate multi-layer film structures, including reflective and absorptive layers, and the upper triangular prism structures can be fabricated by nanoimprint lithography (Kim SH, Lee KD and Kim JY 2007 Nanotechnology 18(5) 55306-.

The invention has the beneficial effects that:

1) the thermal metamaterial is characterized in that two equal-size silicon dioxide isosceles right triangular prisms are in a two-dimensional mode and are periodically arranged on a silicon dioxide layer, the structure is simple and easy to manufacture, and the structure has near perfect absorption in an atmospheric window and higher reflection in a sunlight wave band; the absorption in the first and second atmospheric windows can be effectively adjusted by regulating and controlling the geometric parameters;

2) the thermal metamaterial has wide application prospect in the aspects of building materials, passive refrigeration devices and the like.

Drawings

FIG. 1 is a schematic diagram of the overall structure of a silica thermal metamaterial (a), a top view (b) and an absorption layer side view (c);

FIG. 2 shows a reflection spectrum (a) of a reflective layer and an absorption spectrum (b) of an absorption layer of the silica thermal metamaterial according to the present invention;

FIG. 3 is an electric field distribution diagram of the silicon dioxide thermal metamaterial of the invention at the integral absorption spectrum and the peak value of a first atmospheric window and a second atmospheric window, (a) -the integral absorption spectrum, and (b) - (g) are electric field distribution diagrams corresponding to the peak values of I-VI in (a), respectively;

FIG. 4 is a schematic diagram showing the variation of the average emissivity of the silica thermal metamaterial according to the present invention with the incident angle in the range of the first and second atmospheric windows, wherein TE and TM respectively represent the electric field polarization direction of the incident light along the x-axis and y-axis directions, and 1 and 2 respectively represent the first and second atmospheric windows;

FIG. 5 is a graph showing the modulation effect of structural parameters of a silicon dioxide thermal metamaterial on average emissivity, wherein first and second represent integration intervals as first and second atmospheric windows, respectively;

FIG. 6 shows the effect of the thermal metamaterial of the present invention on the cooling power under different temperature and convection parameters, Prad is the total radiation power, P_dayAnd P_nightFor a net daytime and nighttime radiation power, h_cAre convection parameters.

Detailed Description

The technical solutions of the present invention are further described below with reference to the following examples, but the present invention is not limited thereto, and any modifications or equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Example 1

As shown in fig. 1, a silica thermal metamaterial for realizing radiation refrigeration, the silica thermal metamaterial is composed of a reflecting layer 1 and an absorbing layer 2 positioned on the reflecting layer 1, and the absorbing layer 2 is composed of a base layer 21 and a pattern layer 22; the reflecting layer 1 is composed of titanium dioxide layers and magnesium fluoride layers which are alternately arranged from top to bottom, and the total number of the reflecting layer 1 is nine, specifically, the thickness of each layer is as follows: the thickness of the titanium dioxide layer is 70 nm, the thickness of the magnesium fluoride layer is 100 nm, the thickness of the titanium dioxide layer is 120 nm, the thickness of the magnesium fluoride layer is 110 nm, the thickness of the titanium dioxide layer is 100 nm, the thickness of the magnesium fluoride layer is 72 nm, the thickness of the titanium dioxide layer is 53 nm, the thickness of the magnesium fluoride layer is 100 nm, and the thickness of the titanium dioxide layer is 75 nm; the base layer 21 is composed of a silicon dioxide layer, a silicon nitride layer and a titanium dioxide layer which are sequentially arranged from top to bottom, wherein the thickness of the silicon dioxide layer is t2=7 μm, the thickness of the silicon nitride layer is t3=6 μm, and the thickness of the titanium dioxide layer is t4=6 μm; the pattern layer 22 is composed of silicon dioxide structural units which are periodically arranged on the upper surface of the silicon dioxide layer, the upper surface of the silicon dioxide layer is marked as an x-y plane, the arrangement periods of the silicon dioxide structural units on the upper surface of the silicon dioxide layer along an x axis and a y axis are respectively marked as Px and Py, and Px = Py =8 μm; the silicon dioxide structure unit comprises two silicon dioxide isosceles right triangular prisms with the same size, the two silicon dioxide isosceles right triangular prisms are symmetrical about the geometric center of the silicon dioxide structure unit, and the vertexes of the right angles of the upper bottom surfaces of the two silicon dioxide isosceles right triangular prisms and the orthographic projection points of the geometric center of the silicon dioxide structure unit on the upper surface of the silicon dioxide layer are on the same straight line; the height d1=3 μm of the isosceles right triangle of the upper bottom surface of the silica isosceles right triangular prism, the distance d2=1 μm between two silica isosceles right triangular prisms, and the height t1=3 μm of the silica isosceles right triangular prism.

Fig. 2 shows a reflection spectrum (a) of a reflection layer and an absorption spectrum (b) of an absorption layer of the silicon dioxide thermal metamaterial having the structure of example 1 of the present invention. As shown, the results show: the solar energy absorption spectrum has nearly perfect absorption in high reflection of solar spectrum wave band and wide wave band of atmospheric window, the reflection of solar wave band is up to 93%, and the absorption of atmospheric window can reach up to 98%.

Simulation experiment

The structure of example 1 was simulated using three-dimensional finite element multi-physics simulation software COMSOL Multiphysics. During simulation, only one silicon dioxide structure unit is needed to be calculated, and an infinite large array structure is simulated by arranging a periodic boundary in the plane direction. The plane electromagnetic wave is incident perpendicular to the substrate, the incident polarization direction of an electric field is along the y axis by default, periodic boundary conditions are adopted in the x axis direction and the y axis direction, and a perfect matching layer is used in the z axis direction to eliminate non-physical reflection at the boundary. And the corresponding transmission spectrogram is subjected to meshing setting to be specially refined, then frequency domain scanning is respectively carried out, and the transmission result is calculated, so that the corresponding transmission spectrum is obtained.

The electric field distribution diagrams of the structural silicon dioxide thermal metamaterial in the embodiment 1 of the invention at the integral absorption spectrum and the peak value of the first and second atmospheric windows are shown in fig. 3, wherein (a) -integral absorption spectrum, and (b) - (g) are electric field distribution diagrams corresponding to the peak value of I-VI in (a), respectively, and it can be seen that: the thermal metamaterial structure affects absorption at different locations.

Further, in order to study the influence of the incident angle (the incident angle refers to the included angle between the incident light and the normal line, namely the z-axis), the structural parameters, the temperature and the convection parameters of the silica thermal metamaterial on the performance of the thermal metamaterial, in the simulation test, the incident angle, the structural parameters, the temperature and the convection parameters of the silica thermal metamaterial are sequentially changed except for the variable parameters on the premise of ensuring that other parameters are the same as those in the embodiment 1. The simulation test results are as follows:

1. variation of average emissivity with incident angle in first and second atmospheric windows

FIG. 4 is a graph showing the average emissivity of a silica thermal metamaterial according to the present invention as a function of incident angle over a first and second atmospheric window. As can be seen from fig. 4: the structure shows near perfect absorption at incidence angles less than 30 deg., with increasing angle the average emissivity gradually decreases and remains constant at 70% after 50 deg.. The results show high absorption with multi-angle adaptation.

Influence of structural parameters on average emissivity

FIG. 5 shows the effect of the structural parameters of the silica thermal metamaterial on the modulation of the average emissivity. As can be seen from fig. 5: under the premise that other parameters are kept unchanged, the average emissivity of the structure shows obvious change with the increase of t1, and the average emissivity also changes with the increase of d1 and d 2. This shows the height-adjustable nature of the structure.

Temperature and convection parameters on refrigeration power

FIG. 6 shows the thermal metamaterials of silicon dioxide of the present invention at different temperatures (a)) And the effect on the refrigeration power under convection parameter (b). As can be seen from fig. 6 (a): the total radiation power of the device is 324.94W/m at the temperature of 300K²The daytime net radiation power is 188.96W/m²Better radiation refrigeration effect is achieved; also as can be seen in fig. 6 (a) and (b): as the temperature increases, the radiation power increases gradually, and the convection coefficient has a significant effect on the cooling power of the structure.