Composite spherical radiation heat preservation structure capable of being used for temperature heat management and preparation method of composite spherical radiation heat preservation structure

Abstract

The invention relates to the technical field of radiation heat dissipation and temperature heat management, in particular to a composite spherical radiation heat preservation structure capable of being used for temperature heat management and a preparation method of the composite spherical radiation heat preservation structure. The microsphere structure comprises a dielectric microsphere layer and a first phase change layer covering the dielectric microsphere layer, and the flat plate layer comprises a metal layer and a second phase change layer which are sequentially stacked from bottom to top. The emissivity modulation (the difference between high-temperature emissivity and low-temperature emissivity) of the composite spherical radiation thermal insulation structure for temperature thermal management in an infrared band can reach 0.70, the high-temperature emissivity reaches up to 0.90, and the composite spherical radiation thermal insulation structure has a good temperature control effect.

Description

Technical Field

[0001] The invention relates to the technical field of radiation heat dissipation and temperature thermal management, and in particular to a composite spherical radiation thermal insulation structure that can be used for temperature thermal management and a preparation method thereof. Background Art

[0002] Precision electronic devices in operation will generate heat to a certain extent, and the environment they are in will also affect their working performance, and stable temperature is a necessary condition for keeping electronic devices working normally. Traditional active thermal management methods usually use mechanical or electronic devices, with complex systems and large power consumption.

[0003] With the vigorous development of the green economy and the vigorous promotion of environmentally friendly clean energy, passive thermal management (PTM) materials have received widespread attention due to their ability to reduce energy consumption and lightweight structure. PTM responds to the thermal state of the protected object through thermal radiation, dynamically adjusts the radiation intensity, and ensures the stability of the internal temperature field of the electronic device. It can effectively improve the heat dissipation capacity of the electronic device and reduce the energy consumption of the cooling system. Phase change materials (PCMs) are also an important type of PTM material. They undergo phase changes within a certain temperature range and maintain a relatively constant temperature by absorbing or releasing heat energy. PCMs have become an attractive choice in fields such as passive temperature control and building thermal management due to their high efficiency and environmental protection.

[0004] Vanadium dioxide (VO2) is a transition metal oxide that undergoes a reversible transition from an insulating state to a metallic state at a phase transition temperature of about 68°C, and its phase transition temperature Tc can be changed by doping elements as donors or acceptors. It is a promising optical phase change material that can achieve a reversible transition from transparent to reflective in a wide wavelength range and within an extremely short time range of picoseconds. Wu et al. proposed a SiO2 / VO2 multilayer metasurface for a radiative cooling device. The cooling power of VO2 before and after the phase transition was 118W / m 2 and 528W / m 2 , the radiative cooling power density of the proposed metasurface can be switched to four times. Dang et al. used a multilayer structure containing a 30nm thick VO2 phase change medium with a modulation depth of 300% on the emissivity at different temperatures. The prepared intelligent temperature management reconfigurable thermal coating based on VO2 phase change material had an emissivity of 0.25 and 0.77 at room temperature and high temperature, respectively. In summary, there have been many excellent studies on the application of switchable radiative films based on VO2 phase change materials, but to date, there have been few reports on the thermochromic properties of composite spherical structure films in the field of thermal management applications. Further investigation is needed to explore whether this structure exhibits superior performance. Summary of the invention

[0005] In view of this, an object of the present invention is to provide a composite spherical radiation insulation structure that can be used for temperature thermal management and a preparation method thereof, so as to further improve the performance of the temperature thermal management system.

[0006] Based on the above purpose, the present invention provides a composite spherical radiation insulation structure that can be used for temperature thermal management, including a flat layer and a microsphere structure arranged on the flat layer, the microsphere structure includes a dielectric microsphere layer and a first phase change layer covering the dielectric microsphere layer, and the flat layer includes a metal layer and a second phase change layer stacked in sequence from bottom to top.

[0007] The metal layer is a silver layer, the first phase change layer and the second phase change layer are both vanadium dioxide thin film layers, and the dielectric microsphere layer is a barium fluoride microsphere array layer.

[0008] The thickness of the dielectric microsphere layer is 1700-1900 nm.

[0009] The thickness of the first phase change layer and the second phase change layer are both 130-170 nm.

[0010] The thickness of the silver layer is 200nm-300nm, not less than 200nm.

[0011] The method for preparing the composite spherical radiation insulation structure that can be used for temperature thermal management comprises the following steps:

[0012] Step 1: depositing a metal layer on a substrate;

[0013] Step 2, depositing a second phase change layer on the metal layer by magnetron sputtering;

[0014] Step 3, preparing a barium fluoride microsphere array layer by an immersion and pulling process;

[0015] Step 4: depositing a first phase change layer on the surface of the barium fluoride microsphere array.

[0016] The metal layer is directly prepared on the substrate by physical vapor deposition.

[0017] The physical vapor deposition method includes electron beam evaporation and magnetron sputtering methods.

[0018] Preferably, the phase change layer is directly deposited on the metal by magnetron sputtering. The base pressure of the vacuum chamber is 4×10 -4 Pa, argon (purity 99.9%) was introduced into the vacuum chamber at a flow rate of 48 sccm. The working pressure during deposition was 2 Pa, and the sputtering power was 120 W. The amount of vanadium used was controlled by the sputtering time.

[0019] The barium fluoride microsphere array layer is prepared by an immersion and pulling process, which is convenient for better batch preparation.

[0020] The immersion and pulling process comprises the following steps: mixing the barium fluoride solution and n-butanol evenly to form a suspension with a concentration of 0.01 to 0.03 mol / L, and then dropping the mixed solution on the surface of deionized water; immersing the prepared second phase change layer and metal layer in deionized water at a speed of 0.2 μm / min, and pulling at a speed of 0.02 μm / min to prepare a regularly arranged microsphere array.

[0021] The method of depositing the first phase change layer on the surface of the barium fluoride microsphere array is: sputtering a top layer of vanadium metal film on the surface of the BaF2 microsphere array. Finally, all samples were rapidly heat treated in oxygen at 450℃ for 30s to oxidize the vanadium into VO2.

[0022] Beneficial effects of the present invention:

[0023] 1. The thermal insulation film proposed in the present invention for protecting the normal operation of precision electronic devices can improve its own emissivity in a high-temperature environment to radiate unnecessary heat, and reduce its own emissivity in a low-temperature environment to reduce heat loss, thereby greatly reducing the operating temperature variation range of precision devices and reducing the energy loss of the thermal management system. The composite spherical radiation insulation structure proposed in the present invention for temperature thermal management can achieve an emissivity modulation of 0.70 in the infrared band (the difference between the high-temperature emissivity and the low-temperature emissivity), and a high-temperature emissivity of up to 0.90, with good temperature control effects.

[0024] 2. The present invention prepares the dielectric material into a spherical structure, so that the microsphere structure and the air between adjacent microsphere structures form a mixed medium. At low temperatures, the absorption rate of the entire structure is low, and at high temperatures, a Fabry-Perot-like cavity structure is formed. This Fabry-Perot-like resonance causes light to be reflected and strongly absorbed in the microsphere, thereby enhancing the thermal insulation performance.

[0025] 3. The composite microsphere thermal insulation film for protecting precision electronic devices provided by the present invention has a simple structure and is easy to prepare on a large scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only for the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 It is a schematic diagram of the overall structure of the composite spherical radiation insulation structure that can be used for temperature thermal management of the present invention;

[0028] Figure 2It is a cross-sectional schematic diagram of a composite spherical radiation thermal insulation structure that can be used for temperature thermal management of the present invention;

[0029] Figure 3 It is a spectrum diagram of high-temperature emissivity and low-temperature emissivity in the infrared band of the composite spherical radiation thermal insulation structure that can be used for temperature thermal management of the present invention;

[0030] The markings in the figure are:

[0031] 1. First phase change layer; 2. Dielectric microsphere layer; 3. Metal layer; 4. Second phase change layer. DETAILED DESCRIPTION

[0032] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0033] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0034] The present invention relates to a composite spherical radiation heat-insulating structure that can be used for temperature thermal management, comprising a flat plate layer and a microsphere structure arranged on the flat plate layer, the microsphere structure comprising a dielectric microsphere layer 2 and a first phase change layer 1 covering the dielectric microsphere layer 2, and the flat plate layer comprising a metal layer 3 and a second phase change layer 4 stacked in sequence from bottom to top.

[0035] As a preferred embodiment, the metal layer 3 is a silver layer, the first phase change layer 1 and the second phase change layer 4 are both vanadium dioxide thin film layers, and the dielectric microsphere layer 2 is a barium fluoride microsphere array layer.

[0036] As an optional embodiment, the thickness of the dielectric microsphere layer 2 is 1700-1900 nm, the thickness of the phase change layer is 130-170 nm, and the thickness of the metal silver layer is 200 nm-300 nm, not less than 200 nm.

[0037] Embodiment 1

[0038] like Figure 1 and Figure 2 As shown, the present invention provides a composite spherical radiation insulation structure that can be used for temperature thermal management, including a first phase change layer 1, a dielectric microsphere layer 2, and a metal layer 3. Among them, the first phase change layer 1 and the second phase change layer 4 are both vanadium dioxide films, the dielectric microsphere layer 2 is barium fluoride microspheres, and the metal layer 3 is a silver film. With the characteristics of vanadium dioxide, it is possible to increase its own emissivity in a high-temperature environment to radiate unnecessary heat, and reduce its own emissivity in a low-temperature environment to reduce heat loss, thereby greatly reducing the operating temperature variation range of precision devices and reducing the energy loss of the thermal management system.

[0039] A method for preparing a composite spherical radiation insulation structure that can be used for temperature thermal management comprises the following steps:

[0040] Step 1: depositing a 200 nm thick metal layer on the substrate;

[0041] Step 2: depositing a second phase change layer on the metal layer by magnetron sputtering with a thickness of 150 nm;

[0042] Step 3: Prepare a barium fluoride microsphere array layer by an immersion and pulling process, wherein the microsphere radius is 900 nm;

[0043] Step 4: depositing a first phase change layer on the surface of the barium fluoride microsphere array, wherein the thickness of the first phase change layer is 150 nm.

[0044] The relationship between the optical response of the phase change material VO2 and the principal axis direction at low temperature, and the components on the main diagonal of its relative dielectric constant matrix can be described by the Lorentz equation:

[0045]

[0046] Where S n is the phonon intensity, ω n is the phonon frequency, γ n is the damping factor, N L is the number of phonon modes; i is the imaginary unit and n is the lower bound of the summation.

[0047] Above the phase transition temperature, the dielectric function of vanadium dioxide is calculated by the following formula:

[0048]

[0049] where ε ∞ =9,γ=1.88×10 15 rad / s; p represents plasma, plasma frequency ω p =1.51×10 15 rad / s; i is the imaginary unit.

[0050] Figure 3The optical properties of the composite spherical radiation insulation structure of the present invention in the 2-25μm band are discussed. It can be found that below the phase transition temperature, VO2 is in a semiconductor state, with peaks near 15.1μm and 19.2μm, and BaF2 and VO2 have high transparency to the mid-infrared band. At this time, the composite spherical radiation insulation structure of the present invention is similar to a mirror reflector, and most of the light is reflected by the Ag substrate, so that the entire structure has a lower spectral emissivity. After the temperature rises, VO2 is in a metallic state, with peaks at about 15.1μm and 19.2μm wavelengths, and the spectral absorptivity in the 8-18μm band is higher than 0.9, with strong emission in most of the studied bands.

[0051] Those skilled in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the present invention is limited to these examples; under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes in different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity. Any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A composite spherical radiation insulation structure that can be used for temperature thermal management, characterized in that: It comprises a flat layer and a microsphere structure arranged on the flat layer. The microsphere structure comprises a dielectric microsphere layer and a first phase change layer covering the dielectric microsphere layer. The flat layer comprises a metal layer and a second phase change layer stacked in sequence from bottom to top.

2. The composite spherical radiation insulation structure for temperature thermal management according to claim 1, characterized in that: The metal layer is a silver layer, the first phase change layer and the second phase change layer are both vanadium dioxide thin film layers, and the dielectric microsphere layer is a barium fluoride microsphere array layer.

3. The composite spherical radiation insulation structure for temperature thermal management according to claim 1 or 2, characterized in that: The thickness of the dielectric microsphere layer is 1700-1900 nm.

4. The composite spherical radiation insulation structure for temperature thermal management according to claim 1 or 2, characterized in that: The thickness of the first phase change layer and the second phase change layer are both 130-170 nm.

5. The composite spherical radiation insulation structure for temperature thermal management according to claim 2, characterized in that: The thickness of the silver layer is 200nm-300nm.

6. The method for preparing the composite spherical radiation insulation structure for temperature thermal management according to any one of claims 1 to 5, characterized in that: The steps include: Step 1: depositing a metal layer on a substrate; Step 2, depositing a second phase change layer on the metal layer by magnetron sputtering; Step 3, preparing a barium fluoride microsphere array layer by an immersion and pulling process; Step 4: depositing a first phase change layer on the surface of the barium fluoride microsphere array.

7. The method for preparing the composite spherical radiation insulation structure for temperature thermal management according to claim 6, characterized in that: The immersion and pulling process comprises the following steps: mixing the barium fluoride solution and n-butanol evenly to form a suspension with a concentration of 0.01 to 0.03 mol / L, and then dropping the mixed solution on the surface of deionized water; immersing the prepared second phase change layer and metal layer in deionized water at a speed of 0.2 μm / min, and pulling at a speed of 0.02 μm / min to prepare a regularly arranged microsphere array.

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