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CN-122011816-A - High-temperature solar photo-thermal conversion coating with high heat conduction and preparation method and application thereof

CN122011816ACN 122011816 ACN122011816 ACN 122011816ACN-122011816-A

Abstract

The invention relates to a high-temperature solar photo-thermal conversion coating with high heat conduction, and a preparation method and application thereof, and belongs to the technical field of new energy materials. The method uses Sr or Ca doped LaCoO 3 oxide material with high heat conduction as a main component of the coating, and adopts double-layer spraying preparation of a 'bulk layer and a surface layer'. Compared with the traditional spinel oxide-based coating, the coating prepared by the invention has significantly higher thermal conductivity, high absorbance (higher than 95%) and low emissivity (lower than 0.65), and significantly reduces surface heat radiation and heat convection loss under the high-temperature working condition, thereby improving the photo-thermal conversion efficiency. The photo-thermal conversion efficiency of the coating is obviously higher than that of a commercial product Pyromark2500, and the preparation method is simple, low in cost and large in scale.

Inventors

  • LI CAN
  • YE QI
  • LI JUN
  • WANG SHENGYANG

Assignees

  • 中国科学院大连化学物理研究所

Dates

Publication Date
20260512
Application Date
20260312

Claims (10)

  1. 1. A high-temperature solar photo-thermal conversion coating with high heat conduction is characterized by comprising an alloy substrate, a coating body layer and a surface layer which are arranged from bottom to top, wherein the coating body layer and the surface layer both comprise oxides La 1-x Sr x CoO 3 , x=0.1-0.3 or La 1-x Ca x CoO 3 , and x=0.1-0.5.
  2. 2. The coating of claim 1, wherein the alloy substrate is stainless steel or a nickel-based alloy, and the bulk and surface layers of the coating further comprise silicon oxide formed by thermal decomposition of silicone grease.
  3. 3. The coating of claim 1, wherein the oxide material used in the bulk layer of the coating has a large particle size and the oxide material used in the surface layer has a small particle size.
  4. 4. The coating according to claim 1, wherein the solar spectrum absorptivity of the high-temperature solar photo-thermal conversion coating is more than 95%, the emissivity is less than 0.650, and the thermal conductivity of the high-temperature solar photo-thermal conversion coating is higher than that of the high-temperature solar photo-thermal conversion coating at the working temperature The photo-thermal efficiency is higher than that of a Pyromark2500 coating sprayed on the same substrate.
  5. 5. The method for preparing the high-temperature solar photo-thermal conversion coating with high heat conductivity according to any one of claims 1 to 4, which is characterized in that a coating body layer and a surface layer are sprayed on an alloy substrate by using a spraying method, and the preparation steps comprise oxide powder preparation, slurry preparation, spraying and post-treatment.
  6. 6. The method according to claim 5, wherein the method for producing oxide powders for the bulk layer and the surface layer of the coating corresponds to the following method 1 and method 2, respectively: According to the stoichiometric ratio of metal cations, grinding and mixing La 2 O 3 、Co 3 O 4 and SrCO 3 powder or La 2 O 3 、Co 3 O 4 and CaCO 3 powder uniformly, tabletting, placing into a muffle furnace, calcining at 1100-1200 ℃ for 2-10 hours, naturally cooling, grinding and crushing a tabletting material to obtain black light-absorbing oxide powder; The method 2 comprises the following steps: (1) According to the stoichiometric ratio of the metal cations, preparing an aqueous solution A, wherein the aqueous solution A comprises La (NO 3 ) 3 、 Co(NO 3 ) 2 and Sr (NO 3 ) 2 , or La (NO 3 ) 3 、 Co(NO 3 ) 2 and Ca (NO 3 ) 2 , wherein the concentration of Co ions is 20-100 mM; (2) Preparing oxalic acid aqueous solution B with the same volume as that of the aqueous solution A, wherein the concentration of oxalic acid is 3 times that of Co ions in the step (1), and adding sodium hydroxide solution to adjust the pH to 4.0-4.5; (3) Slowly adding the solution obtained in the step (2) into the stirred aqueous solution A to form oxalate precipitate, continuously stirring until the precipitate is completely precipitated, centrifugally separating the precipitate, and washing for multiple times to remove residual sodium ions; (4) Drying, grinding and uniformly mixing oxalate precipitate, putting the mixture into a muffle furnace, calcining the mixture at a high temperature of 850-900 ℃ for 2-10 hours to completely thermally decompose the oxalate precipitate, and naturally cooling the mixture to obtain black oxide powder capable of absorbing light; In the two modes, when SrCO 3 or Sr (NO 3 ) 2 ) is used, the addition amount is in terms of a molar ratio La: sr: co=1-x: x:1, wherein x=0.1-0.3, and when CaCO 3 or Ca (NO 3 ) 2 ) is used, the addition amount is in terms of a molar ratio La: ca: co=1-x: x:1, wherein x=0.1-0.5.
  7. 7. The method according to claim 5, wherein the slurry comprises two kinds of slurry, and the preparation methods are as follows: adding 1-3% by mass of polyvinyl butyral and 2-10% by mass of oxide powder for preparing a coating body layer into an isobutanol solvent, ball milling for more than 3 hours, and uniformly mixing; and adding 2-5% of silicone grease and 2-10% of oxide powder for preparing a surface layer into a dimethylbenzene solvent, ball-milling for more than 3 hours, and uniformly mixing.
  8. 8. The method of claim 5, wherein the spraying process is performed by using a spray gun with air pressure of 40-50 psi, the metal substrate is first fixed on a hot table with the temperature of 100-150 ℃, the slurry 1 is sprayed, the slurry 2 is sprayed on the sprayed surface immediately, and the volume ratio of the two slurries is 2-3:1.
  9. 9. The preparation method of the paint, which is characterized in that the post-treatment process comprises the steps of drying and ageing for more than 24 hours in the air at room temperature after the spraying is finished, sequentially heating to 120 ℃ at a rate of 5-10 ℃ per minute in a muffle furnace for 2 hours, heating to 250 ℃ for 2 hours, heating to 540 ℃ for 1 hour, heating to the target working temperature of 550-850 ℃ for 2-10 hours, and naturally cooling.
  10. 10. The application of the coating obtained by the preparation method of any one of claims 1-4 or 5-9 for high-temperature solar photo-thermal conversion, wherein the coating absorbs sunlight at the working temperature and converts the sunlight into heat energy, and the heat is transferred to the metal substrate surface for output.

Description

High-temperature solar photo-thermal conversion coating with high heat conduction and preparation method and application thereof Technical Field The invention relates to a high-temperature solar photo-thermal conversion coating with high heat conduction, and a preparation method and application thereof, and belongs to the technical field of new energy materials. Background Concentrated Solar (CSP) photothermal is a highly efficient renewable energy technology that converts focused sunlight into thermal energy by absorbing the thermal energy with a photothermal conversion material, further used for power generation, thermal catalysis, metal smelting, etc., or stores thermal energy in a thermal storage medium. Thanks to the high efficiency and low cost of heat energy storage, the photo-thermal power generation technology can be complementary with photovoltaic power generation, wind power generation and the like, so that the intermittence and fluctuation of power generation are effectively relieved, and the power output stability is improved. The tower-type condensing system has the highest condensing ratio (more than 1000 times) and working temperature (more than 700 ℃), and can reach the highest theoretical photo-thermal power generation efficiency (more than 35%). The power generation efficiency of the tower type photo-thermal power station includes collector efficiency (photo-to-heat) and heat engine efficiency (thermo-to-electricity), wherein the heat engine efficiency is positively correlated with the hot end temperature, but the high temperature causes heat convection of the collector surface, heat radiation loss increases, thereby limiting the photo-to-heat efficiency. The existing common oxide-based high-temperature collector photo-thermal coating materials are represented by a commercial material Pyromark2500, and based on spinel light absorbing materials (Cu-Fe-Mn-O, cu-Cr-Mn-O and the like) and silicone grease, the coatings have excellent light absorption and high-temperature stability, but are limited by the lower thermal conductivity of the spinel materials, the overall thermal conductivity of the coatings is lower, so that heat energy generated by surface light absorption cannot be rapidly led out, and the surface temperature is too high, so that obvious heat radiation and heat convection loss are caused. In order to improve the heat conductivity of the coating, one common strategy is to add a high heat conduction filler, but the method has the following defects that 1, a common metal high heat conduction additive such as Al or Cu is extremely easy to oxidize and lose effectiveness under the tower type photo-thermal working condition, a ceramic high heat conduction material such as SiC or BN is used as the additive, the particle size is small, the ceramic high heat conduction material is easy to oxidize completely in a high-temperature air environment, 2, the additive generally does not have light absorptivity and can reduce the light absorption performance of the coating, 3, the additive causes more heterogeneous interfaces, has larger interface thermal resistance than a homogeneous interface, interface mismatch can reduce high-temperature stability and thermal shock resistance, and 4, the process difficulty for preparing the coating is increased by using the additive, and the dispersibility is difficult to control accurately. Based on the above drawbacks, a more suitable approach is to use a coating material that is integral with the light absorbing and heat conducting material. Disclosure of Invention The invention aims to solve the problems of surface heat radiation and heat convection loss of a coating under a high-temperature working condition and reduce photo-thermal efficiency by using a high-heat-conductivity material, and provides a high-temperature solar photo-thermal coating with high photo-thermal conversion efficiency and a preparation method thereof. The invention uses Sr or Ca doped LaCoO 3 oxide material with high heat conduction as the main component of the coating, the oxide material has obviously higher heat conductivity compared with spinel material, and the material has better full spectrum solar energy absorption performance. The coating light absorption structure adopts a double-layer design, the lower layer body layer adopts a large-particle oxide material, the heat conductivity is higher, the basic light absorption is provided, the spray coating slurry of the upper layer surface layer is added with silicone grease, and the silicone grease is thermally decomposed to form a small-particle silicon oxide network, so that the effect of surface antireflection is achieved, meanwhile, organic matters in the heat treatment process are decomposed to generate gas, a pore structure is naturally formed in the coating, and the light absorption of the coating is further improved. The technical scheme of the invention is as follows: The high-temperature solar photo-thermal conversion c