A wavelength-selective emitter for a thermal photovoltaic system and a method of making the same

Abstract

The application belongs to the technical field of wavelength selective radiators, and particularly relates to a wavelength selective radiator for a thermophotovoltaic system and a preparation method thereof. 12 The wavelength selective radiator for the thermophotovoltaic system is prepared by weighing Er2O3 and excess Al2O3 powders respectively, mixing, powdering, blank making, glue discharging, sintering, annealing and grinding. The wavelength selective radiator for the thermophotovoltaic system has high directional transparency, and the whole body can output effective photons that can be utilized, so that the whole material thermal excitation emission of millimeter level thickness is realized. The space volume utilization rate and radiation efficiency of the radiator are high, and the blocky ceramic device has a dense and fine microstructure, good integrity and thermal stability, and meets the long-term high-temperature use requirement.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of wavelength selective radiators, and particularly relates to a wavelength selective radiator for a thermophotovoltaic system and a preparation method thereof. BACKGROUND

[0002] A thermophotovoltaic (TPV) system can convert heat source energy into photons to drive a semiconductor photovoltaic cell to realize electric energy output. The TPV system has the advantages of high energy output density, various heat sources, no moving parts, quietness, portability, and no influence of external environmental conditions, and has a wide application prospect in many fields such as military, transportation, aerospace and industrial production. The biggest challenge of the TPV technology at present is the low system thermoelectric conversion efficiency, and the spectral efficiency of the radiator is one of the most fundamental influencing factors. The selection of the radiator material needs to comprehensively consider the functional characteristics and structural stability, including good thermal stability in the application environment, good thermal shock resistance, and an emission spectrum matched with the energy band of the photovoltaic cell.

[0003] Compared with a black body / gray body and other wide-band radiators, a wavelength selective radiator has a higher in-band emissivity and a lower out-of-band emissivity, and is one of the core components of a high-efficiency TPV system, mainly including material type and micro / nano structure type. Among them, the material type selective radiator is mainly based on rare earth element compounds, which uses the 4f layer valence electrons of the rare earth ions to produce characteristic narrow-band emission, and matches the corresponding photovoltaic cell band gap width. For example, Er 3+ ions have a strong emission band at 1.5 μm, which coincides with the sensitive region of a GaSb photovoltaic cell, so the corresponding compound is considered as an important radiator material in the TPV system.

[0004] In the prior art, the material type selective radiator is mainly used in the form of a coating, and an Er 3+ ion compound (such as erbium oxide) is attached to the surface of a carrier (substrate, fiber, etc.) by dipping, spraying, deposition and other methods, which generally has the following problems:

[0005] 1. Limited by the coating thickness and the material transparency, only the radiators in the surface 100 μm deep region can output the effective photons that can be utilized, and the overall space volume utilization rate is low.

[0006] 2. The coating and the substrate do not match in thermal expansion coefficient, the bonding force is weak, and the coating is easy to peel off. SUMMARY

[0007] In order to solve the problems of the prior art, the present application provides a wavelength selective radiator for a thermophotovoltaic system, which is prepared from Er2O3 and excess Al2O3 powders in a stoichiometric ratio of Er3Al5O 12The blocky ceramic structure is prepared after mixing, powdering, blank making, glue discharging, sintering, annealing and grinding. Compared with the selective radiator in the form of coating in the prior art, the wavelength selective radiator for the thermal photovoltaic system of the application has high directional transparency, and the whole material can output effective photons that can be utilized, so that the whole material thermal excitation emission of millimeter level thickness is realized, and the space volume utilization rate and radiation efficiency of the radiator are high.

[0008] The technical effects achieved by the application are as follows:

[0009] The wavelength selective radiator for the thermal photovoltaic system of the application is a blocky ceramic structure that is mirror polished on the side close to the photovoltaic cell and is frosted on the side close to the heat source. 12 The blocky ceramic structure is prepared after mixing, powdering, blank making, glue discharging, sintering, annealing and grinding.

[0010] Further, the selective radiator outputs characteristic emission light with a wavelength of 1450nm-1600nm after heating, and the maximum transmittance is greater than 80%.

[0011] Further, the roughness of the side of the selective radiator close to the cell is less than or equal to 0.5μm.

[0012] Further, the roughness of the side of the selective radiator close to the heat source is greater than 25μm.

[0013] Further, the Al2O3 is in excess of 5%-10%.

[0014] Further, the purity of the Er2O3 is greater than or equal to 99.99%, and the particle size is less than 1μm; and the purity of the Al2O3 is greater than or equal to 99.99%, and the particle size is less than 0.5μm.

[0015] Further, the average grain size of the selective radiator is less than 5μm.

[0016] The preparation method of the wavelength selective radiator for the thermal photovoltaic system of the application comprises the following steps:

[0017] S01, mixing Er3Al5O 12Respectively, Er2O3 and excess 5%-10% Al2O3 powder is weighed, placed in a stirring tank, stirred for 4h-8h in anhydrous ethanol medium, mixed uniformly, then placed in a heating box, dried at 80℃-90℃, and sieved to obtain the powder raw material;

[0018] S02, the powder raw material is added into a muffle furnace, calcined in air at normal pressure, the calcination temperature is 1200℃-1400℃, and the temperature is kept for 2h-6h to obtain Er3Al5O 12 -Al2O3 powder;

[0019] S03, the expected mass of Er3Al5O 12 -Al2O3 powder is weighed, 0.5% of tetraethyl orthosilicate (TEOS) and anhydrous ethanol of the same mass are added, the alumina grinding ball is used with a ball-to-material ratio of (3-5):1, and the planetary ball milling is performed for 12h-24h, then the grinding ball is filtered out, added into a heating box, dried at 80℃-90℃, and sieved to obtain the ceramic powder;

[0020] S04, the expected mass of the ceramic powder is weighed, dry-pressed in a steel mold, and the green body is subjected to cold

[0021] isopressing after demolding, the green body is degassed in an air atmosphere at a temperature of 800℃-900℃ for 3h-6h to obtain the preform body;

[0022] S05, the preform body is sintered in an environment with a vacuum degree of ≤10 -3 Pa to obtain the sintered body product;

[0023] S06, the sintered body product is annealed in an air atmosphere at a temperature of 1100℃-1500℃ for 5h-10h to obtain the annealed sample;

[0024] S07, mirror polishing and roughening treatment are respectively performed on two surfaces of the annealed sample to obtain the wavelength-selective radiator.

[0025] Further, in the S01 step, the filter diameter of the sieving is ≤100 mesh; and in the S03 step, the filter diameter of the sieving is ≤200 mesh.

[0026] Further, in the S05 step, the temperature is first increased to 1750℃-1850℃ at a rate of <10℃ / min, then rapidly decreased to 1500℃-1600℃ at a rate of >100℃ / min, kept for 5h-15h, and then decreased with the furnace to obtain the sintered body product.

[0027]

[0028] In summary, the present application has at least the following advantages:

[0029] ​1. The wavelength selective radiator for the thermal photovoltaic system of the present application is a bulk ceramic structure made of Er2O3 and excess Al2O3 powders in stoichiometric ratio Er3Al5O12. 12 After mixing, powdering, blank making, glue discharging, sintering, annealing and grinding, the bulk ceramic structure is prepared.

[0030] Compared with the selective radiator in the form of coating in the prior art, the wavelength selective radiator for the thermal photovoltaic system of the present application is mirror polished on the side close to the photovoltaic cell and frosted on the side close to the heat source, has higher directional transparency, and the whole body can output effective photons that can be utilized to realize thermal excitation emission of the whole material with millimeter level thickness, and has high space volume utilization rate and radiation efficiency.

[0031]

[0032] 2. The wavelength selective radiator for the thermal photovoltaic system of the present application is a bulk ceramic structure that does not have the problems of mismatching of the thermal expansion coefficients and easy peeling off of the base, has a dense and fine microstructure, good integrity and thermal stability, meets the long-term high-temperature use requirement, and can further effectively ensure the system use efficiency.

[0033]

[0034] 3. The present application is suitable for the preparation method of the wavelength selective radiator for the thermal photovoltaic system, the raw materials are simple and easy to obtain, the process steps are simple, and the large-scale production and application of the radiator are easy. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is a physical photo of the wavelength selective radiator in Example 1 of the present application;

[0036] Figure 2 is an XRD pattern of the wavelength selective radiator in the example of the present application;

[0037] Figure 3 is an SEM image of the polished surface of the wavelength selective radiator in Example 1 of the present application;

[0038] Figure 4 is a thermal radiation spectrum diagram of the wavelength selective radiator in Example 1 of the present application under laser heating. DETAILED DESCRIPTION

[0039] In the first aspect, the present application provides a wavelength selective radiator for a thermal photovoltaic system, which is a bulk ceramic structure mirror polished on the side close to a photovoltaic cell and frosted on the side close to a heat source; and the selective radiator is made of Er2O3 and excess Al2O3 powders in stoichiometric ratio Er3Al5O12. 12 After the Er2O3 and excess Al2O3 powders are weighed respectively, the bulk ceramic structure is prepared after mixing, powdering, blank making, glue discharging, sintering, annealing and grinding. ​​

[0040] Further, the selective radiator outputs characteristic emission light with a wavelength of 1450nm-1600nm after heating, which is well matched with the band gap of the GaSb battery and has a maximum transmittance of >80%; the average grain size of the selective radiator is <5μm. Preferably, the roughness of the side of the selective radiator close to the battery is ≤0.5μm, the roughness of the side close to the heat source is >25μm; the Al2O3 is in excess by 5%-10%, which can limit the grain growth of the selective radiator and does not affect the transmittance of the selective radiator, and the purity of the Al2O3 is ≥99.99% and the particle size is <0.5μm; the purity of the Er2O3 is ≥99.99% and the particle size is <1μm. 12 Further, the selective radiator outputs characteristic emission light with a wavelength of 1450nm-1600nm after heating, which is well matched with the band gap of the GaSb battery and has a maximum transmittance of >80%; the average grain size of the selective radiator is <5μm. Preferably, the roughness of the side of the selective radiator close to the battery is ≤0.5μm, the roughness of the side close to the heat source is >25μm; the Al2O3 is in excess by 5%-10%, which can limit the grain growth of the selective radiator and does not affect the transmittance of the selective radiator, and the purity of the Al2O3 is ≥99.99% and the particle size is <0.5μm; the purity of the Er2O3 is ≥99.99% and the particle size is <1μm.

[0041] In a second aspect, the present application further provides a preparation method of the wavelength selective radiator for the thermo-photovoltaic system, which comprises the following steps:

[0042] S01, Er3Al5O 12 Al2O3 powder in a stoichiometric ratio is weighed and placed in a stirring tank, and then stirred for 4h-8h to mix uniformly, and then dried in a heating box at 80℃-90℃, and then sieved to obtain the powder raw material;

[0043] S02, the powder raw material is added into a muffle furnace and calcined in air at normal pressure, the calcination temperature is 1200℃-1400℃, and after holding for 2h-6h, Er3Al5O 12 -Al2O3 powder is obtained;

[0044] S03, the expected mass of Er3Al5O 12 -Al2O3 powder is weighed, and then 0.5% of tetraethyl orthosilicate (TEOS) and an equal mass of anhydrous ethanol are added, and then the ceramic powder is obtained after planetary ball milling for 12h-24h with an alumina ball to ball ratio of (3-5):1, and then the ball is filtered out, and then dried in a heating box at 80℃-90℃, and then sieved;

[0045] S04, the expected mass of the ceramic powder is dry-pressed in a steel mold, and then the green body is cold isostatic pressed after demolding, and then the green body is degassed in an air atmosphere at a temperature of 800℃-900℃ and holding for 3h-6h, to obtain a preform;

[0046] S05, the preform is sintered in an environment with a vacuum degree of ≤10 -3 Pa, to obtain a sintered body product;

[0047] S06, the sintered body product is annealed in an air atmosphere at a temperature of 1100℃-1500℃ for 5h-10h, to obtain an annealed sample;

[0048] S07. The two surfaces of the annealed sample are mirror polished and roughened respectively to obtain a wavelength-selective radiator.

[0049] Furthermore, in step S01, the sieve diameter is ≤100 mesh; in step S03, the sieve diameter is ≤200 mesh. In step S05, the temperature is first raised to 1750℃-1850℃ at a rate of <10℃ / min, then rapidly cooled to 1500℃-1600℃ at a rate of >100℃ / min without holding, and held for 5h-15h. Then, the temperature is lowered in the furnace to obtain the sintered product.

[0050] To better illustrate the objectives, technical solutions, and advantages of this invention, the invention will be further described below with reference to specific embodiments. Those skilled in the art should understand that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0051] Unless otherwise specified, the experimental methods used in the embodiments are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0052] Example 1:

[0053] This embodiment provides a method for preparing a wavelength-selective radiator for a thermophotovoltaic system, including the following steps:

[0054] S01. Weigh 3 mol of Er2O3 powder (purity ≥99.99%, particle size <1μm) and 5.25 mol of Al2O3 powder (purity ≥99.99%, particle size <0.5μm) respectively, place them in a 4L mixing jar, add 2L of anhydrous ethanol, stir at 100rpm for 6h to mix evenly, place in a heating oven, dry at 80℃ for 12h, and then sieve through a 100-mesh sieve to obtain the powder raw material;

[0055] S02. The powder raw material is added to a muffle furnace and calcined in air at atmospheric pressure at a temperature of 1200℃ for 4 hours to obtain Er3Al5O. 12 -5% Al2O3 powder, that is, powder with 5% excess Al2O3 powder;

[0056] S03, Weigh 300g of Er3Al5O 12 -5% Al2O3 powder, 1.5g tetraethyl silicate (TEOS), 300g anhydrous ethanol and 1500g alumina grinding balls were ball-milled in a planetary ball mill at 300rpm for 12h to refine the powder. After filtering out the grinding balls, the powder was added to a heating box and dried at 80℃ for 12h. Finally, it was sieved through a 200-mesh sieve to obtain ceramic powder.

[0057] S04. Weigh 250g of ceramic powder and dry press it in a 120mm diameter steel mold at a pressure of 30MPa. After demolding, the green body is subjected to cold isostatic pressing at a pressure of 300MPa. The green body is then placed in a muffle furnace and debinded in air at a temperature of 800℃ for 6 hours to obtain the precast green body.

[0058] S05. The preform is placed in a vacuum tungsten wire furnace with a vacuum degree ≤10. -3 Sintering is carried out in an environment of Pa; specifically, the temperature is first raised to 1800℃ at a rate of 10℃ / min, then rapidly cooled to 1600℃ without holding at a rate of 100℃ / min, held for 10 hours, and then cooled with the furnace to obtain the sintered product.

[0059] S06. The sintered product is placed in a muffle furnace and annealed in an air atmosphere at a temperature of 1200℃ for 6 hours to obtain the annealed sample.

[0060] S07. One side of the annealed sample was mirror polished for 20 hours using 1μm diamond polishing powder, and the other opposite side of the annealed sample was roughened and ground for 5 hours using 100-mesh diamond abrasive to obtain wavelength selective radiator 1.

[0061] Example 2:

[0062] This embodiment provides a method for preparing a wavelength-selective radiator for a thermophotovoltaic system, including the following steps:

[0063] S01. Weigh 3 mol of Er2O3 powder (purity ≥99.99%, particle size <1μm) and 5.3 mol of Al2O3 powder (purity ≥99.99%, particle size <0.5μm) respectively, place them in a 4L mixing jar, add 2L of anhydrous ethanol, stir at 100rpm for 4h to mix evenly, place in a heating oven, dry at 80℃ for 12h, and then sieve through a 100-mesh sieve to obtain the powder raw material;

[0064] S02. The powdered raw material is added to a muffle furnace and calcined in air at atmospheric pressure at a temperature of 1200℃ for 2 hours to obtain Er3Al5O. 12 -6% Al2O3 powder, that is, powder with 6% excess Al2O3 powder;

[0065] S03, Weigh 300g of Er3Al5O 12 -6% Al2O3 powder, 1.5g tetraethyl silicate (TEOS), 300g anhydrous ethanol and 900g alumina grinding balls were ball-milled in a planetary ball mill at 300rpm for 12h to refine the powder. After filtering out the grinding balls, the powder was added to a heating box and dried at 80℃ for 12h. Finally, it was sieved through a 200-mesh sieve to obtain ceramic powder.

[0066] S04, 250g of ceramic powder is weighed and dry-pressed in a 120mm diameter steel mold at a pressure of 30MPa; after demolding, the green body is cold isostatic pressed at a pressure of 300MPa; the green body is loaded into a muffle furnace for debinding in an air atmosphere at a temperature of 800℃ for 3h to obtain a preform;

[0067] S05, the preform is placed in a vacuum tungsten wire furnace for sintering in an environment with a vacuum degree of ≤10 -3 Pa; specifically, first heated to 1750℃ at a heating rate of 10℃ / min, rapidly cooled to 1550℃ at a cooling rate of 100℃ / min without holding, and then held for 5h, and then cooled with the furnace to obtain a sintered body product;

[0068] S06, the sintered body product is loaded into a muffle furnace for annealing in an air atmosphere at a temperature of 1100℃ for 5h to obtain an annealed sample;

[0069] S07, one side of the annealed sample is mirror polished for 20h using 1μm diamond polishing powder, and the other side of the annealed sample is roughened and ground for 5h using 100 mesh corundum abrasive to obtain a wavelength selective radiator 2.

[0070] Example 3:

[0071] The embodiment provides a preparation method of a wavelength selective radiator for a thermal photovoltaic system, comprising the following steps:

[0072] S01, 3mol of Er2O3 powder (purity ≥99.99%, particle size <1μm) and 5.35mol of Al2O3 powder (purity ≥99.99%, particle size <0.5μm) are weighed respectively and placed in a 4L stirring tank, 2L of anhydrous ethanol is added, and after stirring at a speed of 100rpm for 6h, the mixture is placed in a heating box, dried at 80℃ for 12h, and then sieved through a 100 mesh sieve to obtain a powder raw material;

[0073] S02, the powder raw material is added to a muffle furnace for calcination in air at normal pressure, and after holding at a calcination temperature of 1200℃ for 4h, an Er3Al5O 12 -7% Al2O3 powder, i.e., the Al2O3 powder is 7% excessive;

[0074] S03, 300g of Er3Al5O 12 -7% Al2O3 powder, 1.5g of tetraethyl orthosilicate (TEOS), 300g of anhydrous ethanol, and 1200g of alumina grinding balls are ball milled in a planetary ball mill at a speed of 300rpm for 18h, the grinding balls are filtered out, added to a heating box, dried at 80℃ for 12h, and then sieved through a 200 mesh sieve to obtain a ceramic powder.

[0075] S04, 250 g of ceramic powder is weighed and dry-pressed in a 120 mm diameter steel mold at a pressure of 30 MPa; after demolding, the green body is cold isostatic pressed at a pressure of 300 MPa; the green body is loaded into a muffle furnace, and the binder is removed in an air atmosphere at a temperature of 800 ℃ for 5 h to obtain a preform;

[0076] S05, the preform is placed in a vacuum tungsten wire furnace and sintered in an environment with a vacuum degree ≤10 -3 Pa; specifically, first heated to 1800 ℃ at a heating rate of 10 ℃ / min, rapidly cooled to 1600 ℃ at a cooling rate of 100 ℃ / min without holding, and then cooled with the furnace to obtain a sintered body product;

[0077] S06, the sintered body product is loaded into a muffle furnace and annealed in an air atmosphere at a temperature of 1200 ℃ for 10 h to obtain an annealed sample;

[0078] S07, one side of the annealed sample is mirror polished for 20 hours using 1 μm diamond polishing powder, and the other opposite side of the annealed sample is roughened and ground for 5 hours using 100 mesh gold sand abrasive to obtain a wavelength selective radiator 3.

[0079] Example 4:

[0080] The embodiment provides a preparation method of a wavelength selective radiator for a thermal photovoltaic system, comprising the following steps:

[0081] S01, 3 mol of Er2O3 powder (purity ≥ 99.99%, particle size < 1 μm) and 5.4 mol of Al2O3 powder (purity ≥ 99.99%, particle size < 0.5 μm) are weighed respectively, placed in a 4 L stirring tank, 2 L of anhydrous ethanol is added, stirred at a speed of 100 rpm for 6 h, mixed uniformly, then placed in a heating box, dried at 80 ℃ for 12 h, and then sieved through a 100 mesh sieve to obtain a powder raw material;

[0082] S02, the powder raw material is added to a muffle furnace and calcined in air at normal pressure, calcined at a temperature of 1200 ℃ for 4 h to obtain an Er3Al5O 12 -8% Al2O3 powder, i.e. powder with an excess of 8% Al2O3 powder;

[0083] S03, 300 g of Er3Al5O 12-8% Al2O3 powder, 1.5 g of tetraethyl orthosilicate (TEOS), 300 g of anhydrous ethanol, and 1500 g of alumina grinding balls, after being refined in a planetary ball mill at a rotation speed of 300 rpm for 20 h, the grinding balls were filtered out, added to a heating box, dried at 80℃ for 12 h, and then sieved through a 200 mesh screen to obtain the ceramic powder;

[0084] S04, 250 g of ceramic powder was weighed and dry-pressed in a steel mold with a diameter of 120 mm at a pressure of 30 MPa; after demolding, the green body was cold isostatic pressed at a pressure of 300 MPa; the green body was loaded into a muffle furnace, and the binder was removed in an air atmosphere at a temperature of 800℃ for 5 h to obtain a preform;

[0085] S05, the preform was placed in a vacuum tungsten wire furnace and sintered in an environment with a vacuum degree ≤10 -3 Pa; specifically, first heated to 1800℃ at a heating rate of 10℃ / min, rapidly cooled to 1600℃ at a cooling rate of 100℃ / min without holding, and then held for 8 h, and then cooled with the furnace to obtain a sintered body product;

[0086] S06, the sintered body product was loaded into a muffle furnace and annealed in an air atmosphere at a temperature of 1200℃ for 8 h to obtain an annealed sample;

[0087] S07, one side of the annealed sample was mirror polished for 20 hours using 1 μm diamond polishing powder, and the other opposite side of the annealed sample was roughened and ground for 5 hours using 100 mesh gold sand abrasive to obtain a wavelength selective radiator 4.

[0088] Example 5:

[0089] The embodiment provides a preparation method of a wavelength selective radiator for a thermophotovoltaic system, comprising the following steps:

[0090] S01, 3 mol of Er2O3 powder (purity ≥ 99.99%, particle size < 1 μm) and 5.45 mol of Al2O3 powder (purity ≥ 99.99%, particle size < 0.5 μm) were weighed respectively and placed in a 4 L stirring tank, 2 L of anhydrous ethanol was added, and after being stirred at a rotation speed of 100 rpm for 8 h, the mixture was uniformly mixed, then placed in a heating box, dried at 90℃ for 12 h, and then sieved through a 100 mesh screen to obtain the powder raw material;

[0091] S02, the powder raw material was added to a muffle furnace and calcined at normal pressure in air, the calcination temperature was 1400℃, and after holding for 6 h, an Er3Al5O 12 -9% Al2O3 powder, i.e. powder with an excess of 9% Al2O3 powder;

[0092] S03, 300 g of Er3Al5O12 -9% Al203 powder, 1.5 g of tetraethyl orthosilicate (TEOS), 300 g of anhydrous ethanol, and 1500 g of alumina grinding balls, after being refined in a planetary ball mill at a rotation speed of 300 rpm for 24 h, the grinding balls were filtered out, added into a heating box, dried at 90℃ for 12 h, and then sieved through a 200 mesh screen to obtain the ceramic powder;

[0093] S04, 250 g of the ceramic powder was weighed and dry-pressed in a steel mold with a diameter of 120 mm at a pressure of 30 MPa; after demolding, the green body was cold isostatic pressed at a pressure of 300 MPa; the green compact was loaded into a muffle furnace, and the binder was removed in an air atmosphere at a temperature of 900℃ for 6 h to obtain a preform;

[0094] S05, the preform was placed in a vacuum tungsten wire furnace and sintered in an environment with a vacuum degree ≤10 -3 Pa; specifically, first heated to 1850℃ at a heating rate of 10℃ / min, rapidly cooled to 1600℃ at a cooling rate of 100℃ / min without holding, and then held for 15 h, and then cooled with the furnace to obtain a sintered body product;

[0095] S06, the sintered body product was loaded into a muffle furnace and annealed in an air atmosphere at a temperature of 1500℃ for 5 h to obtain an annealed sample;

[0096] S07, one side of the annealed sample was mirror polished for 20 hours using 1 μm diamond polishing powder, and the other opposite side of the annealed sample was roughened and ground for 5 hours using 100 mesh gold sand abrasive to obtain a wavelength selective radiator 5.

[0097] Example 6:

[0098] The embodiment provides a preparation method of a wavelength selective radiator for a thermal photovoltaic system, comprising the following steps:

[0099] S01, 3 mol of Er203 powder (purity ≥ 99.99%, particle size < 1 μm) and 5.5 mol of Al203 powder (purity ≥ 99.99%, particle size < 0.5 μm) were weighed respectively and placed in a 4 L stirring tank, 2 L of anhydrous ethanol was added, and after being stirred at a rotation speed of 100 rpm for 8 h, the mixture was uniformly mixed, then placed in a heating box, dried at 90℃ for 12 h, and then sieved through a 100 mesh screen to obtain the powder raw material;

[0100] S02, the powder raw material was added into a muffle furnace and calcined in air at normal pressure, and after being calcined at a temperature of 1400℃ for 6 h, Er3Al5O 12 -10% Al203 powder, that is, the powder with an excess of 10% Al203 powder;

[0101] S03, take 300 g of Er3Al5O 12 -10% Al2O3 powder, 1.5 g of tetraethyl orthosilicate (TEOS), 300 g of anhydrous ethanol and 1500 g of alumina grinding balls, after refining in a planetary ball mill at a speed of 300 rpm for 24 h, the grinding balls are filtered out, added to a heating box, dried at 90℃ for 12 h, and then sieved with a 200 mesh sieve to obtain ceramic powder;

[0102] S04, take 250 g of ceramic powder, dry pressing in a 120 mm diameter steel mold, pressure 30 MPa; after demolding, the green body is cold isostatic pressed, pressure 300 MPa; the green body is loaded into a muffle furnace, degassing in an air atmosphere, temperature 900℃, holding for 6 h, to obtain a preform;

[0103] S05, the preform is placed in a vacuum tungsten wire furnace and sintered in an environment with a vacuum degree ≤10 -3 Pa; specifically, first heated to 1850℃ at a rate of 10℃ / min, rapidly cooled to 1600℃ at a rate of 100℃ / min without holding, then held for 10 h, and then cooled with the furnace to obtain a sintered body product;

[0104] S06, the sintered body product is loaded into a muffle furnace and annealed in an air atmosphere, temperature 1500℃, holding time 5 h, to obtain an annealed sample;

[0105] S07, one side of the annealed sample is mirror polished for 20 hours using 1 μm diamond polishing powder, and the other opposite side is roughened and ground for 5 hours using 100 mesh corundum abrasive, to obtain a wavelength selective radiator 6.

[0106] The actual wavelength selective radiator 1 obtained in Example 1 is shown in the accompanying Figure 1 , which has a complete shape, high transparency, and when placed on grid paper, the pattern of the grid paper can be clearly seen.

[0107] The XRD pattern of the wavelength selective radiators obtained in Examples 1-3, 6 of the accompanying Figure 2 , it can be seen that the wavelength selective radiator of the application has a typical garnet structure and a small amount of alumina phase, the diffraction peak is complete, the intensity is high, there is no impurity phase, the purity is high, and the crystallinity is good.

[0108] The polished surface SEM image of the wavelength selective radiator 1 obtained in Example 1 of the accompanying Figure 3 , it can be seen that the microstructure of the wavelength selective radiator of the application is dense and fine, there is no pore impurity, and the average size of the crystal grains is less than 5 μm.

[0109] The polished surface SEM image of the wavelength selective radiator 1 obtained in Example 1 of the accompanying Figure 4The thermal radiation spectrum of the wavelength selective radiator obtained from the middle embodiment 1 under laser heating shows that the main output wavelength of the wavelength selective radiator is 1450nm-1600nm, which is well matched with the band gap of the GaSb battery.

[0110] As can be seen from the technical solutions of the above embodiments, the present application provides a wavelength selective radiator for a thermophotovoltaic system, which is mirror polished on the side close to the photovoltaic cell and is frosted on the side close to the heat source, has high directional transparency, and the whole body can output effective photons that can be utilized, realizes the thermal excitation emission of the whole material with a millimeter level thickness, and has high space volume utilization rate and radiation efficiency of the radiator. In addition, the blocky ceramic structure does not have the problems of mismatching with the thermal expansion coefficient of the base and easy peeling, has a dense and fine microstructure, good integrity and thermal stability, meets the long-term high-temperature use requirement, and can further effectively ensure the use efficiency of the system. The present application also provides a preparation method of the wavelength selective radiator for the thermophotovoltaic system, which has simple and easily available raw materials and simple process steps, and is easy for large-scale production and application of the radiator.

[0111] Although the description of the present application is made in combination with the above specific embodiments, it is obvious that many substitutions, modifications and changes can be made according to the above content by those skilled in the art. Therefore, all such substitutions, modifications and changes are included in the spirit and scope of the appended claims.

Claims

1. A wavelength-selective radiator for a thermophotovoltaic system, characterized in that, The selective radiator is a blocky ceramic structure with a mirror-polished side near the photovoltaic cell and a frosted side near the heat source; and the selective radiator is based on the stoichiometric ratio of Er3Al5O 12 The product was prepared by weighing Er2O3 and excess Al2O3 powder separately, followed by mixing, powdering, blanking, debinding, sintering, annealing, and grinding. The selective radiator, when heated, outputs characteristic emitted light with a wavelength of 1450nm-1600nm, and has a maximum transmittance >80%. The method for preparing the wavelength-selective radiator for the thermophotovoltaic system includes the following steps: S01, according to stoichiometric ratio Er3Al5O 12 Weigh Er2O3 and 5%-10% excess Al2O3 powder separately, place them in a mixing tank, use anhydrous ethanol as a medium, stir for 4-8 hours to mix evenly, then place in a heating box and dry at 80℃-90℃, and then sieve to obtain powder raw material. S02. The powdered raw material is added to a muffle furnace and calcined in air at atmospheric pressure at a temperature of 1200℃-1400℃ for 2-6 hours to obtain Er3Al5O. 12 -Al2O3 powder; S03, Weigh the expected mass of Er3Al5O 12 -Al2O3 powder, after adding 0.5% tetraethyl silicate (TEOS) and an equal mass of anhydrous ethanol, is refined by planetary ball milling with alumina grinding balls at a ball-to-powder ratio of (3-5):1 for 12-24 hours. After filtering out the grinding balls, the powder is placed in a heating box and dried at 80℃-90℃, and then sieved to obtain ceramic powder. S04. Weigh the expected mass of ceramic powder, dry press it in a steel mold, and after demolding, perform cold isostatic pressing on the green body. Remove the glue from the green body in an air atmosphere at a temperature of 800℃-900℃ and keep it at that temperature for 3-6 hours to obtain the preformed green body. S05. Precast blanks are in a vacuum degree ≤10 -3 Sintering is carried out in a Pa environment to obtain sintered products; S06. The sintered product is annealed in air at a temperature of 1100℃-1500℃ for 5h-10h to obtain the annealed sample. S07. The two surfaces of the annealed sample are mirror polished and roughened respectively to obtain a wavelength-selective radiator.

2. The wavelength-selective radiator for a thermophotovoltaic system according to claim 1, characterized in that, The roughness of the selective radiator on the side adjacent to the battery is ≤0.5μm.

3. The wavelength-selective radiator for a thermophotovoltaic system according to claim 1, characterized in that, The roughness of the selective radiator on the side near the heat source is >25μm.

4. The wavelength-selective radiator for a thermophotovoltaic system according to claim 1, characterized in that, The Er2O3 has a purity ≥ 99.99% and a particle size < 1 μm; the Al2O3 has a purity ≥ 99.99% and a particle size < 0.5 μm.

5. The wavelength-selective radiator for a thermophotovoltaic system according to claim 1, characterized in that, The average grain size of the selective radiator is <5 μm.

6. The wavelength-selective radiator for a thermophotovoltaic system according to claim 1, characterized in that, In step S01, the sieve diameter is ≤100 mesh; in step S03, the sieve diameter is ≤200 mesh.

7. The wavelength-selective radiator for a thermophotovoltaic system according to claim 1, characterized in that, In step S05, the temperature is first raised to 1750℃-1850℃ at a rate of <10℃ / min, then rapidly cooled to 1500℃-1600℃ at a rate of >100℃ / min without holding, and held for 5-15 hours. Then the temperature is lowered in the furnace to obtain the sintered product.

Images