A microstructure radiator and a manufacturing method thereof

Abstract

The present disclosure relates to the field of radiator technology, and in particular to a microstructure radiator and a manufacturing method. A heat source is converted into electrical energy through a thermophotoelectric conversion system, wherein the thermophotoelectric conversion system includes a heat source unit, a radiator, a filter, a photovoltaic cell, and a thermal control module, the heat source unit is configured to provide a heat source, the radiator is configured to convert the heat source into thermal radiation energy, the filter is configured to filter photons, the photovoltaic cell is configured to achieve photoelectric conversion, and the thermal control module is configured to control the temperature. The combination of nuclear power thermophotoelectric power generation technology and microstructure radiators improves the selective spectral emissivity that matches the photovoltaic cell, thereby improving the power generation efficiency of the device.

Description

Technical Field

[0001] The present disclosure relates to the technical field of radiators, and in particular to a microstructure radiator and a manufacturing method thereof. Background Art

[0002] Nuclear power sources, with their long life and high energy density, have been widely used in space and ocean mission systems. Isotope heat sources heat the radiator and transmit the emission spectrum through filters, which are then converted into electrical energy by photovoltaic cells. The inventors found that the radiator needs to be improved in actual use. Currently, there is a lack of engineering products in nuclear power systems, which cannot meet actual needs while ensuring optical performance. Summary of the invention

[0003] The present disclosure provides a microstructure radiator and a manufacturing method to solve the technical problem recognized by the inventor that the radiator cannot meet actual needs while ensuring optical performance.

[0004] The present disclosure provides a microstructure radiation, comprising:

[0005] A thermal photoelectric conversion system, the thermal photoelectric conversion system comprising a heat source unit, a radiator, a filter, a photovoltaic cell and a thermal control module, the heat source unit being configured to provide a heat source, the radiator being configured to convert the heat source into thermal radiation energy, the filter being configured to filter photons, the photovoltaic cell being configured to achieve photoelectric conversion, and the thermal control module being configured to control temperature.

[0006] In any of the above technical solutions, further, it also includes a test model, and the test model is configured to perform a high temperature stability test on the radiator.

[0007] In any of the above technical solutions, further, the heat source part includes an isotope source and a heat pipe cooled reactor.

[0008] In any of the above technical solutions, further, the radiator is arranged outside the isotope source, and the radiator is arranged outside the heat pipe cooled reactor.

[0009] In any of the above technical solutions, further, a first cover plate is provided at one end of the radiator, and a second cover plate is provided at the other end of the radiator, and the first cover plate and the second cover plate are configured to fix the radiator.

[0010] In any of the above technical solutions, further, the photovoltaic cell is configured as a semiconductor photovoltaic cell.

[0011] In any of the above technical solutions, further, the radiator has a spectral emissivity selection characteristic.

[0012] In any of the above technical solutions, further, when the radiator is a two-dimensional photonic crystal radiator, a two-dimensional array of circular column holes is formed on the substrate.

[0013] The present disclosure also provides a method for manufacturing a microstructure radiator, comprising the following steps:

[0014] (1) After vacuum high temperature annealing, the substrate is polished until the roughness, flatness and parallelism meet the optical requirements;

[0015] (2) depositing a Cr film as a hard mask on the substrate, spin-coating an anti-reflective coating and a photoresist thereon, and using laser interference etching to form circular holes by proximity effect;

[0016] (3) Exposure determines the cavity period, and plasma ashing determines the cavity diameter to form a photolithography pattern;

[0017] (4) Reactive ion etching is used to transfer the pattern to the Cr layer and finally etch to the substrate.

[0018] In any of the above technical solutions, further, a polymer fluid that can be cured by ultraviolet light is coated on the substrate, and a secondary imprinting is performed after the template is obtained by imprinting to form a large-area microstructure.

[0019] The beneficial effects of the present disclosure are mainly:

[0020] The present disclosure provides a microstructure radiator and a manufacturing method, wherein the radiator has precisely customized optical properties and highly selective spectral emissivity, and matches the band gap of a photovoltaic cell. The present disclosure provides a use scheme of using an isotope source and a heat pipe cooled reactor as two different heat sources, and the selective spectral emissivity matching the photovoltaic cell is improved by combining the nuclear power source thermophotovoltaic power generation technology with the microstructure radiator, thereby improving the power generation efficiency of the device; the nuclear power source does not rely on solar energy, can generate energy autonomously, has a high energy density, can meet high-power power generation tasks, and the electric power can reach hundreds of kilowatts. The power generation efficiency can be made above 10% through thermophotovoltaic conversion technology.

[0021] It should be understood that both the foregoing general description and the following specific embodiments are for the purpose of example and illustration and do not necessarily limit the present disclosure. The accompanying drawings, which are incorporated into and constitute a part of the specification, illustrate the subject matter of the present disclosure. At the same time, the specification and the drawings are used to explain the principles of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the specific embodiments of the present disclosure or the technical solutions in the prior art, the drawings required for use in the specific embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 A schematic diagram of a thermal photoelectric conversion system according to an embodiment of the present disclosure;

[0024] Figure 2 A schematic diagram of a three-dimensional structure of a heat source and a radiator combined in an embodiment of the present disclosure;

[0025] Figure 3 It is a schematic diagram of the surface structure of a radiator according to an embodiment of the present disclosure;

[0026] Figure 4 A schematic diagram showing a comparison of cylindrical microcavities with different diameters in an embodiment of the present disclosure;

[0027] Figure 5 A schematic diagram showing a comparison of cylindrical microcavities of different depths in an embodiment of the present disclosure;

[0028] Figure 6 Schematic diagram of comparison of cylindrical microcavities with different periods in the embodiments of the present disclosure;

[0029] Figure 7 It is a schematic diagram comparing the microstructure and the emissivity of different metal Ta in the embodiment of the present disclosure;

[0030] Figure 8 is a schematic diagram of the emission spectrum of the radiator in the embodiment of the present disclosure;

[0031] Fig. 9 is a schematic diagram of a photoelectric wafer quantum efficiency curve in an embodiment of the present disclosure;

[0032] Fig.10 A schematic diagram of power generation efficiency of a thermophotovoltaic system in an embodiment of the present disclosure;

[0033] Fig.11 Schematic diagram of the laser interference principle in the embodiment of the present disclosure.

[0034] icon:

[0035] 100 - thermal photoelectric conversion system; 101 - heat source; 102 - radiator; 103 - filter; 104 - first cover plate; 105 - second cover plate. DETAILED DESCRIPTION

[0036] The technical solution of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present disclosure, rather than all of the embodiments.

[0037] Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in the field without making any creative work shall fall within the scope of protection of the present disclosure.

[0038] In the description of the present disclosure, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present disclosure and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present disclosure. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0039] In the description of the present disclosure, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present disclosure can be understood according to specific circumstances.

[0040] See also Figure 1 In one or more embodiments, a microstructure radiator is provided, which includes a thermal photoelectric conversion system 100. The thermal photoelectric conversion system 100 includes a heat source part 101, a radiator 102, a filter 103, a photovoltaic cell and a thermal control module. The heat source part 101 is configured to provide a heat source, the radiator 102 is configured to convert the heat source into thermal radiation energy, the filter 103 is configured to filter photons, the photovoltaic cell is configured to achieve photoelectric conversion, the thermal control module is configured to control temperature, and the photovoltaic cell is set as a semiconductor photovoltaic cell.

[0041] See also Fig.11 , also includes a test model, which is configured to perform a high temperature stability test on the radiator 102.

[0042] It should be noted that the stability test and specific method of the microstructure radiator are as follows:

[0043] The working temperature of the isotope source is about 1200-1500K, and the working temperature of the reactor source is about 1000-1300K. The two-dimensional radiator with a composite structure of tungsten and carbon nanotubes is heated at 1000℃ (1273K) for 168 hours; the upper layer is plated with 20-40nm HfO 2 The tungsten-tantalum alloy two-dimensional photonic crystal was annealed at 1000℃ (1273K) for 300 hours and at 1200℃ (1473K) for 1 hour. The above tests showed that the optical performance of the radiator was almost unchanged.

[0044] The main reactions that lead to degradation of the surface stability of microstructured radiators are oxidation, recrystallization, grain growth, surface diffusion, evaporation and recondensation. Except for the oxidation test, all other tests were carried out under vacuum. The samples were placed at the operating temperature for 100 hours. The thermal degradation was monitored regularly by cross-sectional scanning electron micrographs and emissivity measurements.

[0045] The stability test uses the high temperature accelerated life test model - Arrhenius model to characterize the influence of temperature stress accelerated life. The relationship between the characteristic life L and the operating temperature T is as follows:

[0046]

[0047] Among them, M p is the failure value of the measured characteristic value, M 1 is the initial value of the measured eigenvalue, A 0 is a constant, E a is the activation energy, which is a constant related to the material and has nothing to do with temperature.

[0048] The degradation parameter of the same characteristic value in the high temperature accelerated life test is expressed by the acceleration factor α, that is, the normal temperature L 0 With high temperature T 1 Product life under L 1 Ratio:

[0049]

[0050] See also Figure 2 In some embodiments, the heat source unit 101 includes an isotope source and a heat pipe cooling reactor. The isotope source utilizes its radioactive isotope decay energy to generate 90 Sr. 238 Pu, 210Po, etc., the radiator 102 is installed on the outer surface, the heat pipe cools the reactor through reactor fission, the heat is taken out by the heat pipe, the heat pipe is used as the heat source part, and the radiator 102 is wrapped on the outer layer of the heat pipe for use. For the isotope source, taking a standard general heat source (GPHS) as an example, the power generation surface is close to the radiator 102, and the position is fixed by the first cover plate 104 and the second cover plate 105, and the first cover plate 104 and the second cover plate 105 use the non-power generation surface; for the heat pipe cooling reactor, the heat pipe is arranged in an equilateral triangle, and the surrounding is filled with high thermal conductivity graphite to a hexagonal prism, and the six sides are close to the radiator 102 and fixed by the first cover plate 104 and the second cover plate 105.

[0051] It should be noted that the physical quantity that describes the radiation capacity of an object to the outside world at a certain temperature is called radiation force, that is, the energy within the full wavelength range radiated by a unit surface area in all directions of its hemisphere space per unit time. The relationship between the radiation force and temperature of an object is stipulated by the Stefan-Boltzmann law:

[0052]

[0053] Among them, E r is the radiation force, in W / m 2 ; δ is the Stefan-Boltzmann constant, δ = 5.67 × 10 8 W / m 2 ·K 4 ; ε is the emissivity of the object; T is the temperature of the object, in K; T 0 is the external environment temperature, in K.

[0054] The emission rate of photons of a specific wavelength of the radiator indicates the probability of emission of photons of that specific wavelength per unit time; the emission rate of the radiator reflects the radiation power of the entire radiator, that is, the strength of the energy radiated by the radiator at a certain moment, which is expressed by the ratio of the radiation power of the radiator to the radiation power of a black body under the same conditions. The radiation power of the radiator is the total energy of photons of different wavelengths radiated by the radiator to the outside world. Therefore, its radiation power is the sum of the product of the energy of photons of different wavelengths and their number per unit time, expressed as:

[0055]

[0056] In the formula, E r is the total energy of photons radiated by the radiator; E(λ) is the photon energy of the corresponding wavelength; ε(λ) is the emissivity of photons of the corresponding wavelength. The absorptivity of the black body is 1. According to Kirchhoff's law, it can be regarded as the emissivity of the black body under the same conditions as the radiator. Then the black body radiation force is expressed as:

[0057]

[0058] Then the emissivity ε of the radiator is r That is:

[0059]

[0060] Where h is Planck's constant, h = 4.136 × 10 -15 eV·s; c is the speed of light, c=3.0×10 8 m / s.

[0061] The optical performance of a radiator is its ability to preferentially transmit in-band photons and suppress out-band photons, which is intuitively described by the emissivity. The energy of in-band photons is higher than the band gap of the photovoltaic cell, while the energy of out-band photons is lower than the band gap of the photovoltaic cell. Preferential in-band emission can be achieved through spectral control.

[0062] See also Figure 3 , the radiator 102 is a specialized radiator structure having precisely tailored optical properties and highly selective spectral emissivity, and matching the band gap of a suitable small band gap photovoltaic cell.

[0063] It should be noted that at the microscopic scale, the characteristic size of the surface of an object will be of the same order of magnitude as the wavelength of thermal radiation, or even smaller than the wavelength of thermal radiation. The spectrum of thermal radiation can be selectively regulated through special microstructure surfaces, such as gratings, photonic crystal structures, metamaterial structures, etc., combined with the unique radiation characteristics of the microstructure surface and its ability to regulate radiation.

[0064] The nuclear power photovoltaic cell part in this disclosure has a band gap energy that matches the infrared, and can choose to use indium gallium arsenide (InGaAs) or gallium antimonide (GaSb) photoelectric wafer arrays. The band gap width is represented by Eg:

[0065] E g =(GaSb)=0.7eV

[0066] E g =(InGaAs)=0.55eV

[0067] Since the quantum efficiency of the selected wafer material has a higher peak value at 0.8-2.5μm, a radiator with matching optical properties needs to be selected.

[0068] The two-dimensional photonic crystal radiator is made with a two-dimensional array of cylindrical holes on the substrate, the microcavity diameter is r, the depth is d, and the period is a.

[0069] For photonic crystals with cavities, each individual cavity acts as a waveguide to enhance emission at wavelengths below the cutoff wavelength.

[0070]

[0071] See also Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 , Fig. 9 and Fig.10 , making radiators based on tantalum:

[0072] (1) With a fixed depth of d = 8 μm and a period of a = 1.3 μm, different diameters have different effects on the emissivity of the microstructure radiator. The cutoff wavelength increases with the increase of the diameter, and there are multiple emission peaks in the wavelength band less than the cutoff wavelength, with an average emissivity of 0.8-0.9. When the depth remains unchanged, the cutoff wavelength increases with the increase of the diameter, and the light waves less than the cutoff wavelength can couple with other high-order resonant modes of the resonant cavity and be absorbed by the radiator, and then there are multiple emission peaks in the wavelength band less than the cutoff wavelength.

[0073] (2) Fixed period and diameter, changing depth. The radiator still has selective emission. The influence of the cylindrical hole depth is mainly reflected in the band less than the cut-off wavelength. As the hole depth increases, the average emissivity increases. When the diameter and period are fixed, At this time, the change in depth has almost no effect on the cutoff wavelength. In addition, as the depth increases, the light wave can interact with the resonant cavity for a longer time, making the light wave more effectively absorbed, resulting in an increase in the average emissivity of the band less than the cutoff wavelength.

[0074] (3) Fix the diameter at 1.1 μm and the depth at 8 μm and change the period. As the period increases, the cutoff wavelength changes very little. At positions greater than the cutoff wavelength and corresponding to the period size, the emissivity decreases as the period increases. At positions greater than the cutoff wavelength, the light wave will not react with the cavity, which mainly reflects the high reflectivity of the material itself. Therefore, the larger the period, the closer the spectral emissivity of the microstructure radiator is to the spectral emissivity of planar tantalum. On the other hand, the spectral emissivity of the microstructure radiator is also affected by surface plasmon polarization and diffracted plane waves. The effect of surface plasmon polarization is very small under the above-mentioned geometric dimensions and can be ignored. In the band less than the cutoff wavelength, especially at the position corresponding to the period size, the existence of the diffraction mode will affect the coupling of the light wave with the resonant cavity, enhance the reflection of light, and significantly reduce the emissivity in this band.

[0075] In the present disclosure, within the effective band of 0.8 to 2.5 μm, the average emissivity of ordinary metal tantalum is significantly lower than that of microstructure tantalum. The use of microstructure has a significant effect on improving the proportion of useful bands. Through simulation design, the microstructure optimization parameters matching gallium antimonide and indium gallium arsenide battery wafers are obtained, as shown below:

[0076]

[0077] In the nuclear power system, in order to focus on the influence of the radiator on the power generation system, the filter influence is ignored in this analysis. The net radiation heat flux q(λ)dy converted by the radiator at the wavelength interval λ~dλ is:

[0078]

[0079] Where ε is the emissivity of the radiator at wavelength λ; T is the surface temperature of the radiator; k is the Boltzmann constant, k = 1.380649 × 10 -23 J / K.

[0080] The energy converted by the radiator exists in the form of photons. The spectrum reaches the surface of the wafer and generates a photoelectric effect. The photon energy hv = hc / λ, and the amount of light measured within the wavelength interval λ ~ dλ is obtained;

[0081]

[0082] The working temperature of the isotope source is about 1200~1500K, and the working temperature of the reactor source is about 1000~1300K. Here, a heat source of 1200K is selected to heat the radiator.

[0083] The electric flux generated by the photoelectric effect is as follows:

[0084]

[0085] Where α is the effective distribution rate; Q(λ) is the external quantum efficiency of the wafer.

[0086] See also Fig.10 Taking InGaAs wafer as an example, under filter-free debugging, the final system efficiency of microstructure Ta is compared with that of ordinary metal Ta. The microstructure radiator significantly improves the efficiency of nuclear power system.

[0087] The present disclosure also provides a method for manufacturing a microstructure radiator, comprising the following steps:

[0088] (1) After vacuum high temperature annealing, the substrate is polished until the roughness, flatness and parallelism meet the optical requirements;

[0089] (2) depositing a Cr film as a hard mask on the substrate, spin-coating an anti-reflective coating and a photoresist thereon, and using laser interference etching to form circular holes by proximity effect;

[0090] (3) Exposure determines the cavity period, and plasma ashing determines the cavity diameter to form a photolithography pattern;

[0091] (4) Reactive ion etching is used to transfer the pattern to the Cr layer and finally etch to the substrate.

[0092] In any of the above technical solutions, further, a polymer fluid that can be cured by ultraviolet light is coated on the substrate, and a secondary imprinting is performed after the template is obtained by imprinting to form a large-area microstructure.

[0093] Specifically, the working principle of a microstructure radiator provided by the present disclosure is: the microstructure selective radiator is applied to the nuclear power system, coupled with the heat source, filter 103, photovoltaic cell and thermal control module in the thermophotoelectric conversion system 100, and the thermal energy is converted into thermal radiation energy, which is converted into electrical energy through the photoelectric effect of the photovoltaic cell. The present disclosure provides two different heat source use schemes, namely, isotope source and thermo-optical cooling reactor, and the nuclear power thermophotoelectric generator room is combined with the microstructure radiator to improve the selective spectral emissivity matched with the photovoltaic cell, thereby improving the power generation efficiency of the device. At the same time, the microstructure radiator is tested for high temperature stability using a high temperature accelerated life test model to quantitatively monitor thermal degradation.

[0094] It should be noted that the specific models and specifications of the radiator 102 and the filter 103 need to be selected and determined according to the actual specifications of the device disclosed in the present invention, and the specific selection calculation method adopts the existing technology in this field, so it will not be described in detail.

[0095] The power supply and principle of the radiator 102 and the filter 103 are clear to those skilled in the art and will not be described in detail here.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present disclosure, rather than to limit them. Although the present disclosure has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present disclosure.

Claims

1. A microstructure radiator, characterized in that: include: A thermal photoelectric conversion system, the thermal photoelectric conversion system comprising a heat source, a radiator, a filter, a photovoltaic cell and a thermal control module, the heat source being configured to provide a heat source, the radiator being configured to convert the heat source into thermal radiation energy, the filter being configured to filter photons, the photovoltaic cell being configured to achieve photoelectric conversion, and the thermal control module being configured to control temperature; When the radiator is a two-dimensional photonic crystal radiator, a two-dimensional array of circular column holes is formed on the substrate, and the structure of the two-dimensional array of circular column holes is determined based on the following expression: Among them, k represents the Boltzmann constant, r represents the diameter of the microcavity formed by the hole, and d represents the depth of the hole.

2. The microstructure radiator according to claim 1, characterized in that: Also included is a test model configured to perform a high temperature stability test on the radiator.

3. The microstructure radiator according to claim 1, characterized in that: The heat source section includes an isotope source and a heat pipe cooling reactor.

4. The microstructure radiator according to claim 3, characterized in that: The radiator is arranged outside the isotope source, and the radiator is arranged outside the heat pipe cooling reactor.

5. The microstructure radiator according to claim 1, characterized in that: A first cover plate is disposed at one end of the radiator, and a second cover plate is disposed at the other end of the radiator, and the first cover plate and the second cover plate are configured to fix the radiator.

6. The microstructure radiator according to claim 1, characterized in that: The photovoltaic cell is configured as a semiconductor photovoltaic cell.

7. The microstructure radiator according to claim 1, characterized in that: The radiator has a spectral emissivity selective characteristic.

8. A method for manufacturing a microstructure radiator, applicable to the microstructure radiator according to any one of claims 1 to 7, characterized in that: The steps include: (1) After vacuum high temperature annealing, the substrate is polished until the roughness, flatness and parallelism meet the optical requirements; (2) depositing a Cr film as a hard mask on the substrate, spin-coating an anti-reflective coating and a photoresist thereon, and using laser interference etching to form circular holes by proximity effect; (3) Exposure determines the cavity period, and plasma ashing determines the cavity diameter to form a photolithography pattern; (4) Reactive ion etching is used to transfer the pattern to the Cr layer and finally etch to the substrate.

9. The method for manufacturing a microstructure radiator according to claim 8, characterized in that: A polymer fluid that is cured by ultraviolet light is coated on the substrate, and a template is obtained by imprinting, and then a secondary imprinting is performed to form a large-area microstructure.

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