阅读说明：本技术 基于溶液法加工的选择性太阳能吸收涂层及其制备方法 (Selective solar energy absorbing coating processed based on solution method and preparation method thereof ) 是由 黄宝陵 李洋 于 2020-08-05 设计创作，主要内容包括：本发明提供了一种基于溶液法加工的选择性太阳能吸收涂层及其制备方法。(The invention provides a selective solar energy absorbing coating processed based on a solution method and a preparation method thereof.)

1. A selective solar energy absorbing coating comprising:

an infrared reflective coating;

an absorptive coating comprising ceramic nanoparticles selected from the group consisting of: a transition metal nitride, a transition metal boride, a transition metal carbide, and mixtures thereof disposed on a surface of the infrared-reflective coating; and

SiO₂an anti-reflective coating disposed on a surface of the absorptive coating, wherein the absorptive coating is prepared from ceramic nanoparticles that are solution processable.

2. The selective solar absorbing coating according to claim 1, wherein the ceramic nanoparticles are selected from the group consisting of: TiN (titanium nitride)_x、Al_wTi_zN、ZrN_x、Al_wZr_zN、TiC、ZrC、TiN_xC_y、ZrN_xC_y、TiN_xO_y、ZrN_xO_y、TiN、ZrN、TiB₂And ZrB₂Wherein 0 is<w<1，0.5≤x≤1.5，0≤y≤1，0<z<1。

3. The selective solar energy absorptive coating of claim 1, wherein the ceramic nanoparticles have an average diameter of 10 to 500nm and the absorptive coating has a thickness of 10 to 500 nm.

4. The selective solar energy absorbing coating of claim 1, wherein the infrared reflective coating comprises at least one material selected from the group consisting of metallic materials and ceramic materials; and the infrared reflective coating has a thickness greater than 50 nm.

5. The selective solar absorbing coating according to claim 1, wherein the SiO₂The thickness of the anti-reflection coating is 10-500 nm.

6. The selective solar energy absorbing coating of claim 1, further comprising a substrate, wherein the infrared reflective coating is disposed on a surface of the substrate.

7. The selective solar absorbing coating of claim 1, wherein the selective solar absorbing coating comprises:

an infrared-reflective coating comprising at least one material from the group consisting of a metallic material and a ceramic material, wherein the infrared-reflective coating has a thickness greater than 50 nm;

an absorptive coating disposed on a surface of the infrared-reflective coating, wherein the absorptive coating comprises ceramic nanoparticles selected from the group consisting of: TiN (titanium nitride)_x、Al_wTi_zN、ZrN_x、Al_wZr_zN、TiC、ZrC、TiN_xC_y、ZrN_xC_y、TiN_xO_y、ZrN_xO_y、TiB₂And ZrB₂Wherein 0 is<w<1，0.5≤x≤1.5，0≤y≤1，0<z<1; the average diameter of the ceramic nanoparticles is 10-500 nm; the thickness of the absorption coating is 10-500 nm; and

SiO placed on the surface of the absorption coating₂An anti-reflective coating, wherein said SiO₂The anti-reflective coating has a thickness of 10-500nm, wherein the absorbing coating and the SiO are each independently prepared using a starting material capable of being processed by a solution process₂An anti-reflective coating.

8. A solar thermal conversion system comprising the selective solar energy absorbing coating of claim 1.

9. A method of making the selective solar absorbing coating of claim 1, the method comprising:

providing the infrared reflective coating;

applying a first solvent comprising the ceramic nanoparticles onto an exposed surface of the infrared-reflective coating, thereby forming the absorptive coating disposed on the infrared-reflective coating; and

mixing SiO₂Depositing onto the exposed surface of the absorber coating to form SiO₂An anti-reflection coating is applied on the surface of the substrate,

wherein each of the first solvents is applied using a solution-based method.

10. The method of claim 9, wherein the solution-based process comprises at least one process selected from the group consisting of: spin coating, spray coating, and brush coating.

11. The method of claim 9, wherein the first solvent comprises ceramic nanoparticles selected from the group consisting of: TiN (titanium nitride)_x、Al_wTi_zN、ZrN_x、Al_wZr_zN_y、TiC、ZrC、TiN_xC_y、ZrN_xC_y、TiN_xO_y、ZrN_xO_y、TiB₂And ZrB₂Wherein 0 is<w<1，0.5≤x≤1.5，0≤y≤1，0<z<1。

12. The method of claim 9, wherein the ceramic nanoparticles have an average diameter of 10 to 500nm and the absorptive coating has a thickness of 10 to 500 nm.

13. A method as in claim 9 wherein the infrared-reflective coating comprises at least one material selected from the group consisting of metal and ceramic and the infrared-reflective coating has a thickness greater than 50 nm.

14. The method of claim 9, wherein the SiO₂The thickness of the anti-reflection coating is 10-500 nm.

15. The method of claim 9, wherein the SiO is₂The step of depositing on the surface of the absorbing coating comprises depositing a layer comprising SiO₂A second solvent of the precursor is applied to the exposed surface of the absorber coating to form a SiO layer disposed on the absorber coating₂Coating a precursor; and curing the SiO₂Precursor coating to form SiO disposed on the absorber coating₂An anti-reflective coating.

16. The method of claim 15, wherein the SiO₂The precursor is perhydropolysilazane (PHPS), and the SiO is cured₂The precursor step involves the reaction of PHPS with water and oxygen.

17. The method of claim 9, wherein the method comprises:

providing the infrared reflective coating;

applying the first solvent comprising TiN ceramic nanoparticles onto an exposed surface of the infrared-reflective coating to form an absorptive coating disposed on the infrared-reflective coating, wherein the TiN ceramic nanoparticles have an average diameter of 10-500nm and the infrared-reflective coating has a thickness of 10-500 nm;

applying a second solvent comprising PHPS to the exposed surface of the absorptive coating, thereby forming a PHPS coating disposed on the absorptive coating; and

contacting the PHPS coating with oxygen and water to form SiO having a thickness of 50-500nm disposed on the absorbing coating₂An anti-reflection coating is applied on the surface of the substrate,

wherein each of the first and second solvents is applied independently using a solution-based method.

18. The method of claim 17, wherein the first solvent and the second solvent are each independently an organic solvent.

19. The method of claim 17, further comprising the steps of: removing the first solvent comprising TiN ceramic nanoparticles at a temperature of 20-200 ℃ after applying the first solvent to the exposed surface of the infrared-reflective coating; after the step of applying the second solvent comprising PHPS onto the exposed surface of the absorbent coating, removing the second solvent at a temperature of 20-400 ℃.

20. A selective solar energy absorbing coating prepared according to the method of claim 9.

21. A selective solar energy absorbing coating prepared according to the method of claim 17.

Technical Field

The present disclosure relates generally to selective solar energy absorbing materials, and more particularly to selective solar energy absorbing coatings that can be used in solution process based processes in solar thermal conversion systems such as concentrated solar power, solar thermal photovoltaic power, heating, and solar steam generation, and methods of making such solar energy absorbing coatings.

Background

The spectrum selective solar energy absorption coating is a key component in solar heat conversion systems such as concentrated solar power generation, solar thermal photovoltaic power generation, solar steam generation and the like, so that high energy conversion efficiency is realized. The ideal selective solar energy absorbing coating can completely absorb sunlight in the visible and near infrared range, and simultaneously completely reflect light with longer wavelength, thereby avoiding heat loss caused by heat re-radiation. The cut-off wavelength strongly depends on the operating temperature of the absorbing coating and the solar concentration coefficient. Both lower operating temperatures and higher concentration coefficients result in larger cutoff wavelengths. The solar thermal conversion efficiency η of the selective solar energy absorbing coating can be calculated as follows:

in the formula (I), the compound is shown in the specification,andrespectively, the spectral average solar absorptance and the spectral average thermal emittance of the selective solar absorptive coating. C and T represent the concentration coefficient and the operating temperature, respectively, of the selective solar energy absorbing coating. I is_{Solar energy}Is the total radiation of solar energy, which is 1000W/m under the AM 1.5G standard². Therefore, in order to obtain the maximum solar heat conversion efficiency η under given conditions, the selective solar energy absorbing coating should have both high solar absorptance and low thermal emittance.

According to the carnot efficiency theory, it is desirable that solar thermal systems operate at high temperatures, such as above 673K, to achieve higher power generation efficiency. However, the high temperature causes the emission spectrum of the blackbody to approach that of solar radiation (0.3-2.5 μm), so that considerable overlap occurs. As the temperature increases, the total emitted power of the black body also becomes larger. In addition, higher operating temperatures require excellent thermal stability of the selective solar energy absorbing coating. Finally, scalable selective solar energy absorbing coatings made by simple-process and less costly methods are preferred because of their greater potential for large-scale applications. In summary, solar absorptive coatings with spectral selectivity, thermal stability and low cost are the best choice for all solar thermal conversion systems.

Over the past decades, scholars have explored a variety of selective solar energy absorbing coatings, including: intrinsic absorbing coatings, semiconductor metal tandem coatings, ceramic metal composites (cermets), multilayer metal/ceramic nanomembranes, photonic crystals, and plasma metamaterials. However, almost all of the most advanced selective solar energy absorbing coatings are prepared by costly high vacuum techniques such as physical vapor deposition, chemical vapor deposition and various photolithography-based methods. Although selective solar energy absorbing coatings produced by conventional preparation methods (US7585568B 2; US7909029B 2; US8893711B 2; US9476115B 2; US9726402B 2; WO2013088451A 1; US20160003498A 1; CN 101598468B; CN 101818328B; CN102602071B) have high solar heat conversion efficiency and good thermal stability, their high-vacuum preparation process is complicated and the large-scale production cost is high.

Solution-based techniques, such as spin coating, spray coating, and brush coating, are simpler and less costly to prepare than high vacuum deposition techniques. In recent years, selective solar absorptive coatings based on solution process processing have attracted considerable attention. Although solution processed selective solar energy absorbing coatings comprising transition metal carbides have been developed to date, the resin binders used in the preparation are less thermally stable at high temperatures (US 4937137A). Is reported to be in<Temperature of 373K, CuCoMoO_xAnd Ni-Al₂O₃Exhibits a solution processed selective solar energy absorbing coating>90% solar absorptance and<a thermal emissivity of 10%; however, its thermal stability: (<673K) Are far from satisfactory for high temperature applications.^2,3,4

A commercial high temperature coating Pyromark 2500 for solar thermal systems has 97% high solar absorptance and high operating temperatures up to 900K, but also has a high absorptance in the mid-infrared range (80% to 100%), resulting in an undesirably high thermal emissivity, 80% and 90% at room temperature and 1,173K, respectively. More recently, ceramics made of metals processed by solution processesPorcelain Co₃O₄-SiO₂Black solar absorbing coating of composition exhibiting high solar absorptance: (>90%) and good thermal stability (1023K). Likewise, the solar absorbing coating does not exhibit selectivity for solar absorption.

Accordingly, there remains a need to develop improved selective solar energy absorbing coatings and solution-based methods for making the same.

Disclosure of Invention

It is an object of the present disclosure to address the drawbacks of conventional solution processed selective solar energy absorbing coatings, such as poor spectral selectivity and thermal stability. Accordingly, the present disclosure provides a selective solar absorptive coating based on solution process processing and a method of preparing the same, the selective solar absorptive coating comprising: an infrared reflecting layer; an absorptive coating comprising ceramic nanoparticles selected from the group consisting of: transition metal nitrides, transition metal borides, transition metal carbides, and mixtures thereof; an anti-reflective coating having excellent spectral selectivity and excellent long-term thermal stability up to 1000K.

In a first aspect, the present invention provides a selective solar energy absorptive coating comprising an infrared reflective coating, an absorptive coating disposed on a surface of the infrared reflective coating, and SiO disposed on a surface of the absorptive coating₂An anti-reflective coating, the absorbing coating comprising ceramic nanoparticles selected from the group consisting of: transition metal nitrides, transition metal borides, transition metal carbides and mixtures thereof, wherein the absorptive coating is prepared from solution processable ceramic nanoparticles.

In a first implementation of the first aspect, the invention provides the selective solar energy absorbing coating of the first aspect, wherein the ceramic nanoparticles are selected from the group consisting of: TiN (titanium nitride)_x、Al_wTi_zN、ZrN_x、Al_wZr_zN、TiC、ZrC、TiN_xC_y、ZrN_xC_y、TiN_xO_y、ZrN_xO_y、TiN、ZrN、TiB₂And ZrB₂Wherein: 0<w<1，0.5≤x≤1.5，0≤y≤1，0<z<1。

In a second embodiment of the first aspect, the present disclosure provides the selective solar energy absorbing coating of the first aspect, wherein the average diameter of the ceramic nanoparticles is 10 to 500nm, and the thickness of the absorbing coating is 10 to 500 nm.

In a third embodiment of the first aspect, the present disclosure provides the selective solar energy absorbing coating of the first aspect, wherein the infrared reflective coating comprises at least one material selected from the group consisting of a metallic material and a ceramic material, and the infrared reflective coating has a thickness greater than 50 nm.

In a fourth embodiment of the first aspect, the present disclosure provides the selective solar energy absorbing coating of the first aspect, wherein the SiO is₂The thickness of the anti-reflection coating is 10-500 nm.

In a fifth embodiment of the first aspect, the present disclosure provides the selective solar energy absorbing coating of the first aspect, further comprising a substrate, wherein: the infrared reflective coating is disposed on the surface of the substrate.

In a sixth embodiment of the first aspect, the present disclosure provides the selective solar energy absorbing coating of the first aspect, wherein the selective solar energy absorbing coating comprises: an infrared reflective coating comprising at least one material selected from the group consisting of metallic materials and ceramic materials, wherein the infrared reflective coating thickness is greater than 50 nm; an absorptive coating disposed on a surface of the infrared-reflective coating, wherein the absorptive coating comprises ceramic nanoparticles selected from the group consisting of: TiN (titanium nitride)_x、Al_wTi_zN、ZrN_x、Al_wZr_zN、TiC、ZrC、TiN_xC_y、ZrN_xC_y、TiN_xO_y、ZrN_xO_y、TiN，、ZrN，TiB₂And ZrB₂Wherein 0 is<w<X is more than or equal to 1, 0.5 and less than or equal to 1.5, y is more than or equal to 0 and less than or equal to 1 and 0<z<1, the ceramic is nanoThe average diameter of the particles is 10-500 nm; the thickness of the absorbing coating is about 10-500 nm; and SiO disposed on the surface of the absorption coating₂An anti-reflection layer, wherein the SiO₂The thickness of the anti-reflection layer is 10-500 nm; wherein the absorbing coating and the SiO₂The anti-reflective coatings are each independently prepared using a material capable of solution processing.

In a second aspect, the invention provides a solar thermal conversion system comprising a selective solar energy absorbing coating according to the first aspect.

A third aspect of the invention provides a method for processing the selective solar energy absorbing coating of the first aspect, comprising: providing an infrared reflective coating; applying a first solvent comprising ceramic nanoparticles to an exposed surface of an infrared-reflective coating to form an absorptive coating disposed over the infrared-reflective coating; mixing SiO₂Depositing on the exposed surface of the absorbing coating, thereby forming SiO₂Anti-reflective coating, wherein each first solution is coated using a solution-based process.

In a first embodiment of the third aspect, there is provided the method of the third aspect, wherein the solution-based method comprises at least one method selected from the group consisting of: spin coating, spray coating and brush coating.

In a second embodiment of the third aspect, there is provided the method of the third aspect, wherein the first solvent comprises a colloidal dispersion of ceramic nanoparticles selected from the group consisting of: TiN (titanium nitride)_x、Al_wTi_zN、ZrN_x、Al_wZr_zN_y、TiC、ZrC、TiN_xC_y、ZrN_xC_y、TiN_xO_y、ZrN_xO_y、TiN、ZrN、TiB₂And ZrB₂Wherein 0 is<w<1，0.5≤x≤1.5，0≤y≤1，0<z<1。

In a third embodiment of the third aspect, there is provided the method of the third aspect, wherein the average diameter of the ceramic nanoparticles is 10 to 500nm, and the thickness of the absorbing coating is 10 to 500 nm.

In a fourth embodiment of the third aspect, there is provided the method of the third aspect, wherein the infrared-reflective coating comprises at least one material selected from the group consisting of metal and ceramic, the infrared-reflective coating having a thickness of greater than 50 nm.

In a fifth embodiment of the third aspect, there is provided the method of the third aspect, wherein the SiO is₂The thickness of the anti-reflection coating is 10-500 nm.

In a sixth embodiment of the third aspect, there is provided the method of the third aspect, wherein the SiO is₂The step of depositing on the surface of the absorptive coating comprises: will contain SiO₂A second solvent for the precursor is applied to the exposed surface of the absorber coating, thereby forming SiO disposed on the absorber coating₂Precursor coating, and curing the SiO₂Precursor coating to form SiO disposed on the absorber coating₂An anti-reflective coating.

In a seventh embodiment of the third aspect, there is provided the method of the sixth embodiment of the third aspect, wherein the SiO is₂The precursor is perhydropolysilazane (PHPS), and SiO is solidified₂The precursor step involves the reaction of PHPS with water and oxygen.

In an eighth embodiment of the third aspect, there is provided the method of the third aspect, wherein the method comprises: providing the infrared reflective coating; applying a first solvent containing TiN ceramic nanoparticles onto the exposed surface of the infrared reflective coating, thereby forming an absorptive coating disposed on the infrared reflective coating, wherein the TiN ceramic nanoparticles have an average diameter of 10-500nm, and the infrared reflective coating has a thickness of 10-500 nm; applying a second solvent comprising PHPS to the exposed surface of the adsorbent coating, thereby forming a PHPS coating disposed on the adsorbent coating; and contacting the PHPS coating with oxygen and water, thereby forming SiO having a thickness of 50 to 500nm disposed on the absorbing coating₂An anti-reflective coating, wherein each of the first and second solvents is applied independently using a solution-based process.

In a ninth embodiment of the third aspect, there is provided the method of the eighth embodiment of the third aspect, wherein the first solvent and the second solvent are each independently an organic solvent.

In a tenth embodiment of the third aspect, there is provided the method of the eighth embodiment of the third aspect, further comprising the steps of: removing the first solvent at a temperature of 20-200 ℃ after the step of applying the first solvent comprising TiN ceramic nanoparticles on the exposed surface of the infrared reflective coating, and removing the second solvent at a temperature of 20-400 ℃ after the step of applying the second solvent comprising PHPS on the exposed surface of the absorptive coating.

In a fourth aspect, there is provided a selective solar energy absorbing coating processed according to the method of the third aspect.

In a fourth aspect, there is provided a selective solar energy absorbing coating prepared according to the method of the eighth embodiment of the third aspect.

The selective solar energy absorbing coating may include the use of titanium nitride, such as titanium nitride (TiN) infrared reflective coatings, which may provide 95% solar absorptance with 3% and 22% thermal emittance at 300K and 1000K, respectively. Moreover, after long-term (150 hours) thermal testing, the selective solar energy absorbing coating is thermally stable up to 1000K in vacuum. The preparation method is based on a solution method, has simple manufacturing process and low cost, and provides great possibility for large-scale preparation of the selective solar energy absorption coating.

The selective solar energy absorbing coating of the present invention comprises an adsorption coating based on solution process made of colloidal ceramic nanoparticles selected from the group consisting of: transition metal nitrides, transition metal borides, transition metal carbides and mixtures thereof, which are capable of strongly absorbing solar radiation and converting it into thermal energy, while strongly reflecting infrared light, thereby avoiding heat loss due to re-heat radiation. Colloidal ceramic nanoparticles are applied to the infrared reflective coating to form a uniform absorptive coating for solar absorption. The high dispersibility of the colloidal nanoparticles ensures the uniformity of the absorbing coating. The absorption bandwidth or cut-off wavelength of sunlight can be adjusted by controlling the thickness of the absorbing coating. In particular, the thickness of the absorbing coating is adjusted by the concentration of the colloidal ceramic nanoparticles or parameters of the coating process.

The invention also provides SiO₂Anti-reflective coatings and surface protective coatings. Preparation of SiO₂The method of anti-reflective coating is not limited to the specific method described above, and is known in the art for depositing SiO₂All methods of coating are contemplated by the present disclosure. In certain embodiments, the SiO₂The coating is from solution processable SiO₂Precursors such as perhydropolysilazane (PHPS) react by reaction with water (e.g., water vapor) and oxygen in the environment. The preparation may be carried out at room temperature or at higher temperatures. SiO2₂Anti-reflective coatings increase absorption in a broad band by reducing surface reflection. Furthermore, the SiO is added₂The anti-reflective coating also serves to immobilize the ceramic nanoparticles in the absorptive coating, improving the stability of the absorptive coating at high temperatures, and also increasing the hydrophobicity of the coated surface. With SiO prepared by chemical vapour deposition₂Thin film comparison, using solution processable SiO such as PHPS₂Precursors have many advantages, including lower processing temperatures, higher thermal stability, greater surface hydrophobicity, and lower processing costs.

Drawings

The referenced drawings illustrate exemplary embodiments. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than restrictive.

FIG. 1 shows a schematic cross-sectional view of a selective solar absorptive coating based on solution process processing according to certain embodiments of the present invention.

Fig. 2 is a diagram illustrating a process for manufacturing a selective solar absorptive coating based on solution process processing according to some embodiments of the present invention.

Fig. 3 is a graph showing the absorption spectra of a selective solar absorptive coating based on solution process processing before and after vacuum thermal annealing at a temperature of 1000K for 150 hours according to certain embodiments of the present invention.

Fig. 4 is a graph showing the absorption spectrum of a selective solar absorptive coating based on solution process processing on a stainless steel substrate.

FIG. 5 is a cross-sectional view showing a selective solar absorptive coating based on solution process processing further comprising a tie layer according to certain embodiments of the present invention;

fig. 6 is a cross-sectional view showing a solution process based processed selective solar absorptive coating further comprising a protective layer according to certain embodiments of the present invention.

Detailed Description

The invention provides a selective solar energy absorbing coating, comprising: infrared reflective coating, absorptive coating disposed on surface of infrared reflective coating, and SiO disposed on surface of absorptive coating₂An anti-reflective coating, wherein the absorbing coating comprises ceramic nanoparticles selected from the group consisting of: transition metal nitrides, transition metal borides, transition metal carbides, and mixtures thereof. Advantageously, the absorbing coating and the SiO₂The antireflective coatings can each be prepared from starting materials capable of solution processing, which provides an economical means for preparing the selective solar absorptive coatings described herein, as compared to conventional deposition methods for preparing existing selective solar absorptive coatings.

As used herein, "solution processable," "solution process-based," "solution processed," and similar terms refer to materials or compositions that can be used in a variety of solution phase processes including spin coating, printing (e.g., ink jet printing, gravure printing, offset printing, etc.), spray coating, electrospraying, drop casting, dip coating, blade coating, and the like.

FIG. 1 shows an exemplary cross-sectional view of a selective solar energy absorptive coating as described herein, the selective solar energy absorptive coating 1 may include, from bottom to top, an optional substrate 10, an infrared reflective coating 20, an absorptive coating 30 comprising ceramic nanoparticles 31, and SiO₂An anti-reflective coating 40.

The substrate 10 may be used to support the selective solar energy absorbing coating 1. The substrate 10 may comprise any conventional substrate material, such as stainless steel (e.g., 304, 310, 316, 321), glass, copper, aluminum, silicon, and mixtures thereof. The substrate 10 may be tubular, planar, curved, or any other shape. It should be noted here that the nature of the substrate 10 is not critical in the overall structure, and any conventional substrate that can be used in the field of solar thermal conversion systems can be used to support the selective solar energy absorption coating 1.

The infrared-reflective coating 20 can be used to reflect infrared light into free space to minimize heat loss from re-emission of the infrared light. Meanwhile, the infrared reflective coating 20 can also absorb some of the solar photons in the visible-Near Infrared (NIR) range due to its inherent absorption and reflect other photons in the visible-NIR range to the top coating to increase the optical path length of the photons. The infrared-reflective coating 20 may comprise a reflective material having a relatively strong reflective power in the infrared region, the reflective material being selected from the group consisting of: metallic materials, ceramic materials, and combinations thereof. In some embodiments, the infrared-reflective coating comprises a metallic material selected from the group consisting of: silver (Ag), gold (Au), aluminum (Al), chromium (Cr), molybdenum (Mo), copper (Cu), nickel (Ni), titanium (Ti), niobium (Nb), tantalum (Ta), tungsten (W), palladium (Pd), a mixture of two or more of them, and an alloy thereof. For example, Au, Ag, Cu, Al, stainless steel, and combinations thereof are suitable for low temperature applications. For high temperature applications, the infrared-reflective coating 20 may include refractory metals such as W, Mo, Ta, Zr, Ni, Ti, or refractory ceramics such as nitrides, carbides, and borides of transition metals (Ti, Zr, Ta, Nb, W, and Hf), and combinations thereof. Further, the infrared reflective coating 20 can be flexible or inflexible, typically greater than 50nm in thickness. In some embodiments, the infrared-reflective coating 20 has a thickness of 50 to 300nm or 100 to 200 nm.

In some embodiments, the infrared-reflective coating has a high reflectivity for infrared light having a wavelength greater than 2.5 μm. In some embodiments, the infrared reflective coating reflects 85% to 100% of light having a wavelength of 2.5 to 20 μm.

The infrared-reflective coating 20 can also be used as a substrate, as the mechanical/physical properties of the coating allow. In such embodiments, the substrate 10 is optional.

The present disclosure also provides that the solution process based adsorption coating 30 comprising ceramic nanoparticles 31 is capable of strongly absorbing solar radiation and converting it into thermal energy, showing no infrared light absorption, avoiding heat loss from re-radiation. The ceramic nanoparticles may include a transition metal from group IVB, VB or VIB. In some embodiments, the ceramic nanoparticles are selected from the group consisting of: TiN (titanium nitride)_x、ZrN_x、HfN_x、VN_x、NbN_x、TaN_x、CrN_x、MoN_x、WN_x、TiN_xO_y、ZrN_xO_y、HfN_xO_y、VN_xO_y、NbN_xO_y、TaN_xO_y、CrN_xO_y、MoN_xO_y、WN_xO_y、TiC_x、ZrC_x、HfC_x、VC_x、NbC_x、TaC_x、CrC_x、MoC_x、WC_x、TiN_xC_y、ZrN_xC_y、HfN_xC_y、VN_xC_y、NbN_xC_y、TaN_xC_y、CrN_xC_y、MoN_xC_y、WN_xC_y、Al_wZr_zN、Al_wTi_zN、TiN、ZrN、TiB₂、ZrB₂、HfB₂、VB₂、NbB₂、TaB₂、CrB₂、MoB₂、WB₂And mixtures thereof, wherein 0<w<1，0.5≤x≤1.5，0≤y≤1，0<z<1. In certain embodiments, the adsorbent coating or the ceramic nanoparticles are free of aluminum. In certain embodiments, the absorptive coating or the ceramic nanoparticles do not comprise ZrNAl, ZrAlNO, TiNAl, or TiAlNO. The size range of the ceramic nanoparticles 31 is 10 to 500 nm. In certain embodiments, the ceramic nanoparticles range in size from about 10 to 100 nm. The shape of the ceramic nanoparticles 31 may be any shape such as spherical, rod-like, star-like, irregular and the likeAnd (4) combining.

The ceramic nanoparticles 31 can be deposited on the infrared reflective coating 20 to form a uniform absorptive coating 30 for solar absorption. Deposition may be by solution-based methods such as spin coating, spray coating, brush coating. In certain embodiments, the ceramic nanoparticles are colloidal ceramic nanoparticles. The high dispersibility of the colloidal ceramic nanoparticles 31 ensures the uniformity of the absorptive coating 30. The thickness of the absorptive coating 30 can be controlled to adjust the absorption bandwidth or cut-off wavelength. In order to achieve good spectral selectivity, the thickness of the absorption coating 30 is generally in the range of 10 to 500 nm. The optimum thickness depends on the operating conditions and is usually 50 to 200 nm.

In certain embodiments, the selective solar energy absorptive coating 1 comprises more than one absorptive coating 30. The selective solar energy absorptive coating may then comprise 2, 3, 4, 5, 6, 7, 8, 9, 10 or more absorptive coatings 30 applied on each successive surface of the absorptive coating.

The present disclosure also provides SiO disposed on the surface of the adsorption coating₂An anti-reflective coating 40, which acts as a surface protective coating. In certain embodiments, the SiO₂The anti-reflective coating 40 may be from a raw material that can be processed based on a solution process. SiO2₂The thickness of the anti-reflective coating 40 is usually 10-500nm, and SiO is used for different conditions₂The optimal thickness of the anti-reflective coating 40 may be 30 to 150 nm.

The SiO₂The anti-reflective coating 40 may further enhance the absorption of broadband light by reducing surface reflections. In addition, SiO is added₂The anti-reflective coating 40 can improve the stability of the absorbing coating, especially at high temperatures and its hydrophobicity. And SiO prepared by chemical vapor deposition₂PHPS-derived said SiO₂The anti-reflective coating 40 has many advantages such as low processing temperature, higher thermal stability, greater hydrophobicity, and lower cost.

The uppermost coating of the antireflective material may be textured to increase light energy absorption and minimize surface reflection, wherein the texturing comprises any suitable method, such as bombarding the surface or etching.

In certain embodiments, the selectively absorbing coating further comprises a tie layer 50 disposed between the infrared-reflective coating 20 and the absorptive coating 30, wherein the tie layer has transparency in the near infrared and infrared bands that improves adhesion of the absorptive coating to the infrared-reflective coating (fig. 5). Suitable materials for making the bonding layer 50 include, but are not limited to, PHPS. The thickness of the bonding layer may be 5-50 nm.

In certain embodiments, the selective solar energy absorptive coating further comprises a protective layer 60 disposed between the infrared reflective coating 20 and the absorptive coating 30, wherein the protective layer exhibits transparency in the near infrared and infrared bands that improves the resistance of the infrared reflective coating 20 to corrosion, oxidation, and mechanical damage (fig. 6). The protective layer may include Al₂O₃Or SiO₂The thickness is varied within a range of 5 to 50 nm.

The selective solar energy absorbing coating has excellent photo-thermal and physical properties.

In certain embodiments, the selective absorbing coating 30 described herein has an absorption rate of up to 95%. In certain embodiments, the selective solar absorbing coating described herein has an absorptivity in the range of 85-95%, 87-95%, 89-95%, 90-95%, 91-95%, 92-95%, 93-95%, or 94-95%.

The selective solar energy absorbing coating layer disclosed by the invention shows a thermal emissivity of 2-20% at 300K. In certain embodiments, the selective solar energy absorbing coatings described herein can exhibit a thermal emissivity of 15-40% at 1000K.

The present invention also provides a solar thermal conversion system, such as concentrated solar power, solar thermal photovoltaic power, heating, and solar steam generation, comprising the selective solar absorbing coating described herein.

The invention also provides a method for producing a selective solar energy absorption coating 1. A schematic diagram showing the steps of an exemplary method for producing a selective solar energy absorbing coating 1 is shown in fig. 2.However, the method of producing a selective solar absorptive coating according to the invention may comprise one or more cost-effective solution-based deposition steps for depositing one or more of the absorptive coatings 30 and optionally SiO₂An anti-reflective coating 40. In certain embodiments, the method comprises: providing an infrared reflective coating; applying a first solvent comprising ceramic nanoparticles to an exposed surface of the infrared-reflective coating, thereby forming an absorptive coating disposed on the infrared-emissive coating; will contain SiO₂A second solvent of the precursor is applied to the exposed surface of the absorber coating, thereby forming SiO disposed on the absorber coating₂Coating a precursor; curing SiO₂Precursor generation of SiO₂Thereby forming SiO disposed on the absorbing coating₂An anti-reflective coating, wherein a first solvent and a second solvent are applied independently using a solution-based process.

The method of preparing the infrared reflective coating is not limited to any particular method. Accordingly, the present disclosure contemplates all known methods for making infrared-reflective coatings. In certain embodiments, the infrared-reflective coating is prepared by physical vapor deposition techniques in a vacuum in the vapor phase (PVD, physical vapor deposition), such as thermal evaporation, electron gun, ion implantation, sputtering, etc., chemical vapor deposition techniques (CVD, chemical vapor deposition), or electrolytic baths.

A first solvent comprising the ceramic nanoparticles 31 may be applied to the exposed surface of the infrared-reflective coating. The first solvent is not limited to any particular solvent, and may generally include an organic solvent, water, or a mixture thereof. In the case where the first solvent includes an organic solvent, the first solvent may be selected from alkane solvents such as pentane, hexane, cyclohexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, and the like; aryl groups such as toluene, xylene, mesitylene, trimethylbenzene, chlorobenzene, dichlorobenzene, trichlorobenzene, nitrobenzene, cyanobenzene, and the like; alcohols such as methanol, ethanol, propanol, butanol, etc.; ethers such as tetrahydrofuran, tetrahydropyran, dibutyl ether, tert-butyl methyl ether, tetrahydrofuran, and the like; n, N-Dimethylformamide (DMF); acetonitrile and combinations thereof. In certain embodiments, the first solvent comprises water, ethanol, polyethylene, polyvinyl methyl ether, polypropylene methyl ether, propylene glycol alkyl ether esters (such as Propylene Glycol Methyl Ether Acetate (PGMEA)), and mixtures thereof. In some embodiments, the first solvent has a boiling point of 60 to 200 ℃, 60 to 160 ℃, 100 to 160 ℃, 80 to 200 ℃, 100 to 200 ℃, 120 to 180 ℃, or 140 to 160 ℃.

The concentration of the ceramic nanoparticles 31 in the first solvent is 1-70% w/w. In certain embodiments, the concentration of the ceramic nanoparticles 31 in the first solvent is 1-70%, 1-60%, 1-50%, 1-40%, 10-30%, 10-25%, or 15-25% w/w.

The first solvent may include a colloidal solution of the ceramic nanoparticles 31. The colloidal solution of ceramic nanoparticles 31 may be prepared using any conventional method for preparing colloidal solutions of metal nanoparticles currently known in the art. In certain embodiments, the colloidal solution may be prepared by pre-dispersing the ceramic nanoparticles ultrasonically and optionally using a method to reduce the particle size of the ceramic nanoparticles 31.

There are various known methods of reducing the particle size of the material and avoiding agglomeration of the nanoparticles, including comminution or deagglomeration by grinding and/or sieving. Exemplary methods of reducing particles include, but are not limited to, jet milling, hammer milling, compression milling, drum milling (e.g., ball milling). The particle size control parameters for such processes are understood by those skilled in the art. For example, the particle size reduction achieved in jet milling is controlled by adjusting a number of parameters, the main ones being mill pressure and feed rate. During the hammer milling process, the particle size reduction is controlled by the feed rate, the hammer speed and the size of the openings in the grate/screen at the outlet. In compression grinding, the particle size reduction is controlled by the feed rate and the amount of compression applied to the material (e.g., the amount of force applied to the press rolls).

In certain embodiments, the ceramic nanoparticles 31 are subjected to high energy ball milling. In this case, the ceramic may be treated by ultrasonicationThe nanoparticles are pre-dispersed in any suitable organic solvent. The pre-dispersed solution is thereafter subjected to high energy ball milling for e.g. 10 hours to obtain a better dispersion. In certain embodiments, ZrO is sized from 0.05 to 5mm₂The balls act as grinding media. The weight ratio of the balls to the material is 100: 1-10: 1. The polishing speed can be controlled between 200 rpm and 2000 rpm. The solution may be diluted to a desired concentration by adding an additional volume of the first solvent or a volume of another solvent to form a first solvent comprising ceramic nanoparticles. Next, a first solvent comprising ceramic nanoparticles 31 is deposited by one or more solution-based methods on top of the infrared-reflective coating 20, and the first solvent is optionally removed, thereby forming an absorptive coating disposed on the infrared-reflective coating.

Exemplary solution-based methods include, but are not limited to, spin coating, spray coating, and brush coating. The thickness of the absorptive coating 30 may be adjusted by the concentration of the ceramic nanoparticles 31 in the first solvent, changing the coating conditions (e.g., coating speed), and/or applying multiple absorptive coatings 30.

The first solvent may be removed by any method known to those skilled in the art. In certain embodiments, the first solvent may be removed by one or more of applying heat or reducing pressure. In some embodiments, the first solvent is removed by heating at 60-200 ℃, 60-160 ℃, 100-160 ℃, 80-200 ℃, 100-200 ℃, 120-180 ℃ or 140-160 ℃.

In the case where the selective solar energy absorptive coating 1 described herein comprises more than one absorptive coating 30, the step of applying the absorptive coating may be repeated. In this case, the adsorption coating 2, 3, 4, 5, 6, 7, 8, 9, 10 or more times may be applied, with each subsequent one of the adsorption coatings being applied on the surface of the previously applied adsorption coating.

The SiO₂The preparation method of the anti-reflective coating 40 is not limited to any particular method for SiO₂Methods of deposition, any such method known to those skilled in the art, are used in conjunction with the methods described herein. In certain embodiments, use is made ofCVD technique, sol-gel method, SiO₂Deposition of precursors and SiO₂Chemical conversion of the precursor to SiO (e.g. by curing)₂Isodepositing the SiO₂An anti-reflective coating 40.

In certain embodiments, the SiO₂The precursor is a silicon-containing polymer such as polysilazane, polysiloxane, polysiloxazane and polysilane. In certain embodiments, the polysilazane is PHPS. Additional SiO₂The precursor may include tetraalkyloxysilanes such as tetramethoxysilane and tetraethoxysilane, orthosilicic acid, and the like.

Deposition of SiO₂The method of the anti-reflective coating 40 can include applying a second solvent comprising a SiO2 precursor onto the absorptive coating 30, thereby forming a SiO disposed on the absorptive coating 30₂Coating a precursor; curing SiO₂Precursor to produce SiO₂Thereby forming SiO₂An anti-reflective coating 40.

SiO in the second solvent₂The concentration of the precursor may be 1-80% w/w. In certain embodiments, the second solvent is SiO₂The concentration of the precursor is 1-80% w/w, 1-70% w/w, 1-60% w/w, 1-50% w/w, 1-40% w/w, 1-30% w/w, 1-20% w/w, 1-10% w/w, 2-8% w/w or 4-6% w/w.

The second solvent may be an organic solvent such as an alkane, an aryl, an alcohol, an ether, a halogenated solvent, a dialkyl ketone, an ester, a formamide, and mixtures thereof. Exemplary second solvents may include alkane solvents such as pentane, hexane, cyclohexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane; aryl groups such as toluene, xylene, mesitylene, trimethylbenzene, chlorobenzene, dichlorobenzene, trichlorobenzene, nitrobenzene, cyanobenzene, and the like; alcohols such as methanol, ethanol, propanol, butanol, etc.; ethers such as tetrahydrofuran, tetrahydropyran, dibutyl ether, t-butyl methyl ether, Propylene Glycol Methoxy Ether (PGME), Propylene Glycol Monomethyl Ether Acetate (PGMEA), tetrahydrofuran, and the like; n, N-Dimethylformamide (DMF); acetonitrile; and combinations thereof.

Once the SiO is mixed₂Deposition of precursor solution toBy processing the surface of the absorptive coating 30 based on solution methods, such as spin coating, spray coating, and brush coating, it can be cured to form SiO₂Thereby forming SiO₂An anti-reflective coating 40. Curing SiO₂The step of precursor may comprise heating the SiO₂Precursor, SiO₂Reacting the precursor with water and SiO₂At least one step in the reaction of the precursor with oxygen. In certain embodiments, the SiO is cured₂The step of precursor includes heating the SiO in air (e.g., in the presence of oxygen and water vapor)₂And (3) precursor.

In certain embodiments, the PHP SSiO₂The precursor solution is coated on the surface of the absorption coating 30 and heated in the air (e.g., in the presence of water vapor and oxygen) at a temperature of 60 to 400 ℃, 60 to 350 ℃, 60 to 300 ℃, 60 to 250 ℃, 60 to 200 ℃, 60 to 180 ℃, 80 to 180 ℃, 100 to 180 ℃, 120 to 160 ℃, or 140 to 160 ℃ to form SiO₂An anti-reflective coating 40.

The SiO₂The thickness of the anti-reflective coating layer 40 can be controlled by properly adjusting the SiO in the second solvent₂Precursor concentration, by changing the coating conditions (e.g., the speed of the coating process), and/or by applying more than one coating in succession of the antireflective coating 40.

Examples

Example 1:

in this example, a selective solar energy absorbing coating was prepared according to the procedure described above. The selective solar energy absorbing coating based on solution process processing comprises a silicon wafer substrate 10, a TiN infrared reflecting coating 20, an absorbing coating 30 containing colloidal TiN ceramic nanoparticles 31 and SiO₂An anti-reflective coating 40. Firstly, a high-reflection TiN film with the thickness of 200nm is deposited on a 4-inch silicon chip by DC reactive sputtering, and the deposition base vacuum degree is 6 multiplied by 10^-6Torr, direct current power is 10kW, substrate temperature is 220 deg.C, target is high purity (99.9%) Ti target, deposition atmosphere is 150sccm Ar and 100sccm N₂. Mixing commercially available TiN ceramic nanoparticles having a size of 20-30 nm with Propylene Glycol Methyl Ether Acetate (PGMEA) to form a mixture, wherein the TiN ceramicThe weight ratio of the nano particles is about 20%. Pre-dispersing the mixture for 1 hour through ultrasonic treatment, and further processing the pre-dispersed mixture for more than 10 hours through high-energy ball milling, thereby obtaining a homogeneous colloid TiN solution with good dispersion. The ball milling medium is spherical ZrO with the diameter of 5mm₂The weight ratio of the balls to the material was 20:1, and the ball milling speed was controlled at 700 rpm. Then, 9ml of ethanol was added to dilute 1ml of the resulting colloidal solution. A drop of diluted colloidal TiN solution was spin coated onto the TiN infrared reflective coating at 6000rpm for 60 seconds to form an adsorbed coating. The above coating step is repeated again. Thereafter, the prepared TiN absorption coating layer was baked on a heating stage at 150 ℃ for 5 minutes to evaporate the excess solvent. A drop of PHPS (5% by weight) solution in dibutyl ether was spin coated at 2000rpm for 60 seconds to deposit on the adsorbent coating surface. The coating process is repeated again. The prepared PHPS coating was baked on a heating stage at 150 ℃ for 5 minutes to evaporate the solvent, and then baked at a higher temperature of 180 ℃ for 2 hours to form SiO₂An anti-reflective coating. Finally, a selective solar absorbing coating based on solution process processing is obtained.

The absorption spectrum of the selective solar energy absorbing coating is shown in fig. 3. The selective solar energy absorbing coating can obtain broad spectrum sunlight with high solar absorptivity of 95%, and simultaneously strongly reflects infrared light, the heat emissivity is only 3% at 300K, and is only 22% at 1000K. Finally, at 400 solar illuminances and a temperature of 1000K, a high solar thermal conversion of 92% is obtained, which is the highest value of the selective solar absorptive coatings based on solution process reported so far. Thermal stability test results show that the selective absorber coating has good thermal stability after annealing for 150 hours at temperatures up to 1000K in vacuum, as shown in figure 3. The water contact angle measurement result shows that the SiO exists₂The coating has a selective solar energy absorbing coating contact angle of 90 °. The overall performance of the selective solar absorptive coating is comparable to the best performing absorptive coating made by high vacuum technology. The absorption layer based on solution processing is simpler and less costly to manufacture compared to high vacuum nanotechnology in clean rooms, which will greatly reduce large scale manufacturingThe cost of manufacture.

Example 2:

in this example, a selective solar energy absorbing coating was prepared according to the above procedure. The selective solar energy absorptive coating based on solution process processing includes a polished stainless steel infrared reflective material 20 also as a substrate, an absorptive coating 30 comprising colloidal TiN ceramic nanoparticles 31, and SiO₂An anti-reflective coating 40.

Commercially available TiN ceramic nanoparticles with the size of 20-30 nm are mixed with Propylene Glycol Methyl Ether Acetate (PGMEA) to form a mixture, wherein the weight ratio of the TiN ceramic nanoparticles is 20%. The mixture was pre-dispersed by sonication. And then further carrying out high-energy ball milling on the pre-dispersed mixture for more than 10 hours to obtain a homogeneous and well-dispersed colloidal TiN solution. The grinding medium is ZrO with a diameter of 5mm₂A ball. The weight ratio of balls to material was 20: 1. The milling speed was controlled at 700 rpm. 1mL of the obtained colloidal solution was diluted by adding 9mL of ethanol. A drop of diluted colloidal TiN solution was spin coated onto the TiN infrared reflective coating at 6000rpm for 60 seconds. The coating process is repeated once more to form an absorptive coating. The prepared TiN absorption coating was then baked at a heating stage of 150 ℃ for 5 minutes to evaporate the solvent. A drop of PHPS solution in dibutyl ether (5% by weight) was deposited on top of the absorber coating by spin coating at 2000rpm for 60 seconds. Baking the prepared PHPS coating on a heating table at a high temperature of 200 ℃ for 2 hours to form SiO₂An anti-reflective coating.

The absorption spectra of the samples before and after application of the selective solar energy absorbing coating are shown in fig. 4. The selective solar energy absorbing coating can obtain 95% of wide-spectrum sunlight with high solar absorptivity, simultaneously strongly reflects infrared light, and has the thermal radiance of only 10% at 300K.

Reference to the literature

1.C.E.Kennedy,“Review of mid-to-high-temperature solar selective absorber materials”published in 2002by the National Renewable Energy Laboratory,and also in the review article by L.A.Weinstein et al.,“Concentrating solar power”published on the journal Chemical Reviews in2015。

L. Kaluza et al, Solar energy materials & Solar cells,2001,70, 187-.

J.Vince et al, Solar energy materials & Solar cells,2003,79, 313-330; t. bostrom et al, Solar energy,2003,74, 497-503.

T.Bostrom et al, Solar energy materials & Solar cells,2007,97, 38-43; wang et al, Applied physics letters,2012,101,203109.