CN105222381A - A kind of double absorption layer coating for selective absorption of sunlight spectrum and preparation method thereof - Google Patents

Abstract

The invention relates to the field of solar light selective absorption coatings, in particular to a double absorption layer solar spectrum selective absorption coating and a preparation method thereof. The preparation method comprises the following steps: cleaning the base layer; preparing an infrared reflection layer on the base layer by a coating method; preparing a double-structure absorbing layer on the infrared reflection layer by a coating method; An anti-reflection layer is prepared on the absorbing layer; the absorbing layer includes a high-refractive-index absorbing sublayer and a low-refractive-index absorbing sub-layer from bottom to top, and both the high-refractive-index absorbing sub-layer and the low-refractive-index absorbing sub-layer are made of Coating methods are prepared sequentially. The absorbing coating is prepared by the above-mentioned preparation method. The coating preparation method has simple process and low requirements for coating equipment, and is suitable for large-scale and low-cost production.

Description

A double-absorbing layer solar spectrum selective absorption coating and its preparation method

technical field

The invention relates to the field of spectrally selective absorption coatings, in particular to a double-absorbing layer solar spectrum selective absorption coating and a preparation method thereof.

Background technique

The solar spectrum selective absorption coating is the core material to realize the conversion of solar energy to heat. On the one hand, it has a high absorption rate in the solar light band (0.3μm-2.5μm), absorbing sunlight energy and converting it into heat energy, and the other On the one hand, it has a low emissivity in the infrared thermal radiation band (2.5μm-50μm), which can effectively suppress radiation heat dissipation. One of the important indicators to measure the selective absorption performance of the coating is the ratio of the solar spectral absorptivity α to the infrared radiation rate ε(T), α/ε, the larger the value of α/ε, the more suitable for medium and high temperature applications above 200°C.

At present, the spectrally selective coating film structure used in solar collectors can generally be summarized as base layer/infrared reflection layer/solar spectrum absorption layer/surface anti-reflection layer. The infrared reflective layer is a metal with high conductivity, which has a high reflectivity to the infrared spectrum, which is the main reason for the low-radiation performance of the coating; the surface anti-reflection layer reduces the reflection of sunlight at the interface between the coating and the air, making more The energy of sunlight enters the absorbing layer, which increases the absorption rate of the solar spectrum, thereby improving the heat collection efficiency.

Absorbing layer materials in selective absorbing coatings currently on the market mainly include Cr ₂ O ₃ -Cr, AlN-Al(NiO _x , TiN), Al(Mo, W, Ni, Co)-Al ₂ O ₃ , Al ₂ O ₃ -Mo-Al ₂ O ₃ , NiCrN _x O _y , TiN _x O _y , etc. Among them, NiCrN _x O _y and TiN _x O _y are mostly used. In Chinese Patent Publication No. CN1584445A, the composition gradient NiCrN _x O _y is adopted, the highest solar spectral absorption rate is 92%, the lowest radiation rate is 10%, and the maximum α/ε is 9.2; Ratio, a selective coating based on multilayer gradient TiN _x O _y absorption with an absorption rate of 96% and an emissivity of 4% is obtained, and the maximum α/ε (80°C) is 24, which is mainly suitable for low temperature applications below 200°C. Al(Mo, W, Ni, Co, NiO _x , TiN)-Al ₂ O ₃ , Al ₂ O ₃ -Mo-Al ₂ O ₃ and other cermets and thin metal interference film systems have a common feature of high coating The absorption rate and low radiation rate are obtained by strictly controlling the composition of the composite material, the size and shape of the metal or metal nitride particles, or the continuous or discontinuous island or other morphological structures during the growth of the metal film, and the manufacturing process is complicated. , and the process stability has a great influence on the performance of the coating, it is not easy to obtain a coating with excellent performance, resulting in a high solar spectral absorptivity α (generally higher than 90%), and a high infrared radiation rate ε(T) ( Generally higher than 5%, 80°C), and the transition zone from sunlight absorption to infrared reflection is wide, and the infrared radiation rate ε(T) rises rapidly with temperature (the medium and high temperature area is greater than 10%), and α/ε is generally less than 20. Therefore, when the coating is applied to a collector with a relatively low focus, there is generally a problem of low photothermal conversion efficiency of the collector when the working temperature is above 200 °C.

Contents of the invention

The invention provides a double-absorbing layer solar spectrum selective absorption coating. The coating has low emissivity, high ratio of solar spectrum absorptivity α to infrared radiance ε(T), and is suitable for medium and high temperature applications above 200°C.

The purpose of the present invention and the solution to its technical problems are achieved by adopting the following technical solutions.

A method for preparing a solar spectrum selective absorption coating with a double-absorbing layer comprises the following steps: cleaning the base layer; preparing an infrared reflection layer on the base layer by a coating method; preparing an infrared reflection layer on the infrared reflection layer by a coating method Double structure absorbent layer;

An anti-reflection layer is prepared on the double-structured absorbing layer by a coating method; the absorbing layer includes a high-refractive-index absorbing sublayer and a low-refractive-index absorbing sublayer sequentially from bottom to top, and the high-refractive index absorbing sublayer and the high-refractive index absorbing sublayer are The low-refractive-index absorbing sublayers are sequentially prepared by coating method.

In the aforementioned double-absorbing layer solar spectrum selective absorbing coating, the material of the base layer is glass, aluminum, copper or stainless steel;

In the aforementioned double-absorbing layer solar spectrum selective absorbing coating, the cleaning process of the base layer includes: firstly, using a neutral washing liquid to initially clean the base layer; then, after bombarding the base layer with a radio frequency ion source, The surface is cleaned twice, and the working gas is an inert gas.

In the aforementioned double-absorbing layer solar spectrum selective absorbing coating, the coating method is magnetron sputtering.

In the aforementioned double-absorbing layer solar spectrum selective absorbing coating, when preparing the double-structured absorbing layer, the target material selected is a chromium target.

In the aforementioned double-absorbing layer solar spectrum selective absorbing coating, when preparing the infrared reflective layer, the selected target is an aluminum target, a copper target, a gold target, a silver target, a nickel target or a chromium target, and the working gas is an inert gas;

In the aforementioned double-absorbing layer solar spectrum selective absorbing coating, when preparing the anti-reflection layer, the selected targets are silicon targets, aluminum targets, thorium targets, dysprosium targets, europium targets, gadolinium targets, yttrium targets, lanthanum targets, magnesium targets Target or samarium target, the working gas is inert gas and oxygen.

In the aforementioned double-absorbing layer solar spectrum selective absorbing coating, when preparing the high-refractive index absorbing sub-layer, the sputtering power of the pulsed DC power supply is 1400-1600w, the working pressure is 2-4mTorr, and the working gas flow rate is 40-60sccm. The sheet transmission rate is 0.6-1m/min, and the substrate moves back and forth under the target for 2-4 times;

In the aforementioned double-absorbing layer solar spectrum selective absorbing coating, when preparing the low-refractive index absorbing sub-layer, the sputtering power of the pulsed DC power supply is 1400-1600w, the working pressure is 2-4mTorr, and the flow rate of the working gas inert gas is 40-60sccm , the working gas N ₂ flow rate is 40-60 sccm, the working gas O ₂ flow rate is 8-12 sccm, the substrate transmission rate is 0.2-0.6m/min, and the substrate moves back and forth under the target 4-7 times.

In the aforementioned double-absorbing layer solar spectrum selective absorbing coating, when preparing the infrared reflective layer, the sputtering power of the pulsed DC power supply is 1180-1240w, the working pressure is 4.8-5.2mTorr, the working gas flow rate is 49-51sccm, and the substrate transmission The speed is 0.2-1.6m/min, and the substrate moves back and forth under the target 2-4 times.

In the aforementioned double-absorbing layer solar spectrum selective absorbing coating, when preparing the anti-reflection layer, the sputtering power of the pulsed DC power supply is 1900-2050w, the working pressure is 4.8-5.2mTorr, and the flow rate of the working gas inert gas is 29-31sccm, The flow rate of the working gas O ₂ is 13-15.5 sccm, the transfer rate of the substrate is 0.8-1.2 m/min, and the substrate moves 8-14 times under the target.

The purpose of the present invention can also be achieved through the following technical solutions.

Through a double-absorbing layer solar spectrum selective absorption coating, the double-absorbing layer solar spectrum selective absorption coating is prepared by the above preparation method, including: a base layer; the base layer is arranged sequentially from bottom to top There are an infrared reflection layer, a double-structure absorption layer and an anti-reflection layer; the double-structure absorption layer sequentially includes a high-refractive-index absorption sublayer and a low-refraction-index absorption sublayer from bottom to top; wherein: the material of the infrared reflection layer for conductive metals.

In the above-mentioned double-absorbing layer solar spectrum selective absorption coating, the material of the base layer is glass, aluminum, copper or stainless steel; the material of the infrared reflection layer is aluminum, copper, gold, silver, nickel or chromium The material of the high refractive index absorption sublayer is CrN _x ; the material of the low refractive index absorption sublayer is CrN _x O _y ; the material of the antireflection layer is SiO ₂ , Al ₂ O ₃ , ThO ₂ , Dy ₂ O ₃ , Eu ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , La ₂ O ₃ , MgO or Sm ₂ O ₃ ;

In the above-mentioned double-absorbing layer solar spectrum selective absorbing coating, the thickness of the base layer is 0.2-10mm; the thickness of the infrared reflection layer is 50-200nm; the total thickness of the double-structure absorbing layer is 45nm-125nm, wherein : the thickness of the high refractive index absorption sublayer is 25nm-55nm, the thickness of the low refractive index absorption sublayer is 20nm-70nm; the thickness of the anti-reflection layer is 50-150nm.

The purpose of the present invention can also be achieved through the following technical solutions.

A heat collector includes a shell, a cover plate on the shell, and a heat absorbing layer and an insulating layer are arranged under the cover plate, and the heat absorbing layer is the above-mentioned double absorbing layer solar spectrum selective Absorbs coating.

By virtue of the above technical solution, a double-absorbing layer solar spectrum selective absorbing coating and its preparation method proposed by the present invention have at least the following advantages:

1) The double-absorbing layer solar spectrum selective absorbing coating disclosed by the present invention has excellent spectral selectivity. The absorption-reflection transition zone is steep, the medium-high temperature (200°C-400°C) emissivity ε of the selective absorbing coating is lower than 3%, the absorption rate α is higher (about 90%), and α/ε is higher than that of existing commercial products , suitable for medium and high temperature solar collectors with low magnification focusing.

2) The absorbing layer is a dual-structure absorbing layer composed of an inner high-refractive-index absorbing sublayer and an outer low-refractive-index absorbing sublayer, and the material has good thermal stability. Since CrN _x and CrN _x O _y have good thermal stability at medium and high temperatures, the solar spectrum selective absorption coating in the present invention has good thermal stability at medium and high temperatures.

3) The coating preparation process is simple, and the requirements for coating equipment are low, which is suitable for large-scale and low-cost production.

4) When the material of the infrared metal reflective layer is selected as aluminum, it has a high refractive index and extinction in the entire light wave band (solar light band and thermal radiation infrared band) compared with gold, silver, copper and other metals with similar infrared radiation properties. coefficient, to realize that the selective absorption coating has a low infrared radiation rate, and the solar spectrum absorption rate of the coating is further improved through the participation of aluminum in the solar spectrum absorption.

5) When the wavelength is greater than 2000nm, the extinction coefficient of CrN _x and CrN _x O _y is much smaller than that of the infrared reflection layer Al (greater than 21), so the influence on the infrared reflection spectrum of Al is small, so the emissivity of the coating is low .

The above description is only an overview of the technical solutions of the present invention. In order to understand the technical means of the present invention more clearly and implement them according to the contents of the description, the preferred embodiments of the present invention and accompanying drawings are described in detail below.

Description of drawings

Fig. 1 is the structural representation of the solar spectrum selective absorption coating that the present invention proposes;

Fig. 2 is an absorption spectrum diagram in the ultraviolet-infrared band of the embodiment of the present invention.

detailed description

In order to further explain the technical means and effects of the present invention to achieve the intended purpose of the invention, a detailed description of a dual-absorbing layer solar spectrum selective absorbing coating proposed according to the present invention will be described below in conjunction with the accompanying drawings and preferred embodiments. As later.

A method for preparing a solar spectrum selective absorption coating with a double-absorbing layer, comprising the following steps: cleaning a base layer; preparing an infrared reflection layer on the base layer by a coating method; preparing a double-layer coating on the infrared reflection layer by a coating method. Structural absorption layer; an anti-reflection layer is prepared on the double-structure absorption layer by coating method; the absorption layer includes a high refractive index absorption sublayer and a low refractive index absorption sublayer from bottom to top, and the high refractive index Both the absorbing sublayer and the low refractive index absorbing sublayer are sequentially prepared by coating method.

Another embodiment of the present invention proposes a double-absorbing layer solar spectrum selective absorption coating. Compared with the above-mentioned embodiment, the material of the base layer is glass, aluminum, copper or stainless steel; the cleaning process of the base layer includes : Firstly, the base layer is initially cleaned by using a neutral washing solution; then, the surface of the base layer is subjected to secondary cleaning after being bombarded by a radio frequency ion source, and the working gas is an inert gas.

During specific implementation, the base layer may be a glass plate with a thickness ranging from 0.5-10 mm; it may also be a metal material with a thickness ranging from 0.2-2 mm, such as copper, aluminum or stainless steel. In order to increase the surface activity of the base layer, it is necessary to carry out radio frequency ion cleaning after mechanical cleaning, so as to remove the pollution layer and oxide layer on the surface of the base layer.

In order to achieve the purpose of the above invention, the present invention also adopts the following technical solutions to prepare the double-absorbing layer solar spectrum selective absorbing coating. The above base layer, infrared reflective layer, double structure absorbing layer and anti-reflection layer are prepared into coating films sequentially by plating. beam or thermal evaporation, ion plating, chemical vapor deposition and spraying.

The spraying method has the advantages of low cost and simple process, but generally has the disadvantages of poor coating adhesion, easy peeling, high emissivity, and pollution problems like the electrochemical method. The magnetron sputtering method is used to prepare spectrally selective absorption. Thin films can overcome these shortcomings, improve the efficiency of light-to-heat conversion and the service life of the coating. At the same time, the magnetron sputtering process has the characteristics of fast film deposition, uniform and dense film layer, easy large-area film formation and environmental protection. When coating the plate core of flat-plate solar collectors, it is beneficial to build a large-scale horizontal continuous automatic production line, improve production efficiency, and further reduce costs.

During specific implementation, the coating method is a magnetron sputtering method, and when preparing a double-structure absorbing layer, the selected target material is a chromium target. When preparing the infrared reflective layer, the selected targets are aluminum targets, copper targets, gold targets, silver targets, nickel targets or chromium targets, and the working gas is an inert gas; when preparing the anti-reflection layer, the selected targets are silicon targets, aluminum targets target, thorium target, dysprosium target, europium target, gadolinium target, yttrium target, lanthanum target, magnesium target or samarium target, and the working gas is inert gas and oxygen.

When the infrared reflective layer, the double-structure absorbing layer and the anti-reflective layer are sequentially prepared on the base layer by magnetron sputtering, the specific parameter ranges are as follows:

When preparing the infrared reflective layer, the sputtering power of the pulsed DC power supply is 1180-1240w, the working pressure is 4.8-5.2mTorr, the working gas flow rate is 49-51sccm, the substrate transmission rate is 0.2-1.6m/min, and the substrate is under the target Back and forth movement 2-4 times.

When preparing the high refractive index absorbing sub-layer, the sputtering power of the pulsed DC power supply is 1400-1600w, the working pressure is 2-4mTorr, the working gas flow rate is 40-60sccm, the substrate transmission rate is 0.6-1m/min, and the substrate is on the target Go back and forth 2 to 4 times.

When preparing the low refractive index absorbing sublayer, the sputtering power of the pulsed DC power supply is 1400-1600w, the working pressure is 2-4mTorr, the flow rate of the working gas inert gas is 40-60 sccm, the flow rate of the working gas _N2 is 40-60 sccm, the working gas O ₂ The flow rate is 8-12 sccm, the substrate transmission rate is 0.2-0.6m/min, and the substrate moves back and forth under the target 4-7 times.

When preparing the anti-reflection layer, the sputtering power of the pulsed DC power supply is 1900-2050w, the working pressure is 4.8-5.2mTorr, the flow rate of the working gas inert gas is 29-31sccm, the flow rate of the working gas _O2 is 13-15.5sccm, and the substrate transmission The speeds are 0.8-1.2m/min respectively, and the substrate moves 8-14 times under the target.

The specific structure of the double-absorbing layer solar spectrum selective absorption coating prepared by the above parameters is as shown in Figure 1. The double-absorbing layer solar spectrum selective absorption coating comprises: a base layer; An infrared reflection layer 2, a double-structure absorption layer 3 and an anti-reflection layer 4 are arranged; the double-structure absorption layer 3 sequentially includes a high-refractive index absorption sub-layer 31 and a low-refractive index absorption sub-layer 32 from bottom to top; wherein: The material of the infrared reflection layer 2 is conductive metal.

Through the joint action of the infrared reflective layer 2, the double-structure absorbing layer 3 and the anti-reflection layer 4, sunlight can be reflected and absorbed multiple times between the double-structure absorbing layer 3 and the infrared reflective layer 2, and the infrared reflective layer 2 also participates in Part of the solar spectrum is absorbed, so that the double-absorbing layer solar spectrum selective absorbing coating has excellent spectral selectivity. The absorption-reflection transition zone of the double-absorbing layer solar spectrum selective absorption coating is steep, has a higher absorptivity α in the solar spectrum range (0.3-2.5 microns), and has a Extremely low emissivity ε, the high temperature (200°C-400°C) emissivity ε in the solar spectrum selective absorption coating of the double-absorbing layer is lower than 3%, and the absorptivity α is relatively high (about 90%), α/ε It is higher than existing commercial products, and is suitable for low-power focusing medium-high temperature solar collectors; and the preparation process is simple, and the requirements for coating equipment are low, and it is suitable for large-scale and low-cost production.

Another embodiment of the present invention proposes a double-absorbing layer solar spectrum selective absorbing coating. Compared with the above-mentioned embodiment, the material of the high refractive index absorbing sub-layer 31 is CrN _x , and the CrN _x is at 350nm The refractive index in the wavelength range of ~2500nm is 2.4-4.4, the extinction coefficient in the wavelength range of 350-1250nm is 1.76-1.24, and the extinction coefficient of the wavelength greater than 2000nm is less than 0.9. CrNx has good thermal stability.

Another embodiment of the present invention proposes a double-absorbing layer solar spectrum selective absorbing coating. Compared with the above embodiment, the material of the low-refractive index absorbing sub-layer 32 is CrN _x O _y , and the CrN _x The refractive index of O _y is 2.2-2.4 in the wavelength range of 350nm-2500nm, the extinction coefficient is 0.52-0.11 in the wavelength range of 350-1250nm, and the extinction coefficient of the wavelength greater than 2000nm is less than 0.07. The thermal stability of CrN _x O _y is good.

The absorbing layer is disposed on the infrared reflective layer 2, and has a double-structured absorbing layer 3 composed of an inner high-refractive-index absorbing sub-layer 31 and an outer low-refractive-index absorbing sub-layer 32, with a thickness of preferably 75nm-115nm. The main optical characteristics of this layer are that the CrN _x extinction coefficient is 1.76-1.24 in the wavelength range of 350-1250nm, which accounts for more than 80% of the solar spectral energy distribution; the extinction coefficient of CrN _x O _y is 0.52-0.11; The extinction coefficient reaches a peak near 480nm. After 2000nm, the CrN _x extinction coefficient is less than 0.9, and the CrN _x O _y extinction coefficient is less than 0.07.

The solar spectrum selective absorption coating selects the extinction coefficient in the range of 350-1250nm, which accounts for more than 80% of the solar spectrum energy distribution, to reach a peak value, and CrN _x and CrN _x O _y with a refractive index from high to low form a double-structured absorption layer, The refractive index of the absorbing layer 3, the anti-reflection layer 4, and the air gradually decreases, which effectively reduces the reflection of sunlight on the surface of CrN _x with a higher refractive index, forming a layer-by-layer absorption of sunlight, and realizing the Effective absorption of the solar spectrum in the wavelength range of 350-1250nm, the absorption rate is over 90%.

When the wavelength range is greater than 2000nm, the extinction coefficient of CrN _x and CrN _x O _y is much smaller than that of the infrared reflection layer 2 (greater than 21), so the influence on the infrared reflection spectrum is small, so the emissivity of the coating is low. Moreover, since CrN _x and CrN _x O _y have good thermal stability at medium and high temperatures, the solar spectrum selective absorption coating in the present invention has good thermal stability at medium and high temperatures.

Another embodiment of the present invention proposes a double absorbing layer solar spectrum selective absorbing coating. Compared with the above embodiment, the total thickness of the double structure absorbing layer 3 is 45nm-125nm, wherein: the high The thickness of the refractive index absorption sublayer 31 is 25nm˜55nm, and the thickness of the low refractive index absorption sublayer 32 is 20nm˜70nm.

Another embodiment of the present invention proposes a double-absorbing layer solar spectrum selective absorption coating. Compared with the above embodiment, the thickness of the infrared reflection layer 2 is 50-200 nm.

Another embodiment of the present invention proposes a double-absorbing layer solar spectrum selective absorption coating, compared with the above-mentioned embodiment, the material of the infrared reflection layer 2 is aluminum, copper, gold, silver, nickel or chromium . Infrared metal reflective layer, the preferred Al has a high refractive index and extinction coefficient in the entire light wave band (solar light band and thermal radiation infrared band) compared with gold, silver, copper and other metals with similar infrared radiation properties, and achieves selectivity While the absorbing coating has low infrared radiation rate, the solar spectrum absorption rate of the coating is further improved by Al participating in the solar spectrum absorption.

The infrared reflective layer 2 is arranged on the base layer 1, and the function of the infrared reflective layer 2 is to reflect the incident spectrum of the whole band, especially the infrared spectrum, especially the infrared light with a wavelength of 2.5 microns or more. . The material of the infrared reflection layer 2 is aluminum, and the thickness is preferably 50nm-130nm.

Another embodiment of the present invention proposes a double-absorbing layer solar spectrum selective absorption coating. Compared with the above embodiment, the thickness of the anti-reflection layer 4 is 50-150 nm. The anti-reflection layer 4 is a SiO ₂ dielectric layer with an ideal stoichiometric ratio. In the wavelength range of 350nm-2500nm, the refractive index is between 1.47-1.43 and the extinction coefficient is less than 0.03; the thickness is preferably 80nm-120nm.

Another embodiment of the present invention proposes a double-absorbing layer solar spectrum selective absorption coating. Compared with the above embodiment, the material of the anti-reflection layer 4 is SiO ₂ , Al ₂ O ₃ , ThO ₂ , Dy ₂ O ₃ , Eu ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , La ₂ O ₃ , MgO, or Sm ₂ O ₃ .

In the following, the magnetron sputtering coating method is taken as an example for further description. Al, CrN _x , CrN _x O _y and SiO ₂ thin films are sequentially deposited on the base layer 1 of glass, aluminum, copper, stainless steel, etc.

For the preparation of the base layer 1, a polished metal plate or glass plate is selected, and after mechanical cleaning, radio-frequency argon ion cleaning is performed to remove the surface contamination layer and oxide layer, so as to improve the surface activity of the base layer 1 .

For the preparation of the infrared reflection layer 2, a layer of metal infrared reflection layer 2 is prepared on the surface of the base layer by (pulse) DC magnetron sputtering method, and the selected target material can be metal aluminum (purity above 99.7%).

The preparation of the absorbing layer 3 is to prepare the absorbing layer 3 on the above-mentioned infrared reflective layer 2 by (pulse) DC magnetron sputtering method, and the selected target material is metal Cr (above 99.7% purity).

The preparation of the anti-reflection layer 4 is to prepare the anti-reflection layer 4 on the above-mentioned absorbing layer by (pulse) direct current reactive magnetron sputtering, and the target material selected is a silicon-aluminum target (aluminum content 30%wt, purity more than 99.7%) ).

Further description is given below with specific thickness examples of the infrared reflective layer 2, the double-structure absorbing layer 3 and the anti-reflection layer 4:

Table 1 shows the process-controlled thickness of each single-layer film in an embodiment of a double-absorbing layer spectrally selective absorbing coating prepared by magnetron sputtering.

The process control thickness of each monolayer film in the embodiment of table 1

sample Al layer/nm CrN _x layer/nm CrN _x O _y layer/nm SiO ₂ /nm example 120 45 50 110

Carry out the preparation of embodiment according to above-mentioned preparation method, concrete operation steps are as follows:

1) Cleaning of the glass substrate: Firstly, the glass substrate is initially cleaned with a neutral detergent; then, the surface of the glass substrate is bombarded by a radio frequency ion source in the film feeding chamber of the coating equipment for secondary cleaning, and the process parameters are set as follows: radio frequency The sputtering power of the power supply is 200w, the flow rate of the working gas Ar (99.99% purity) is 45sccm, the working pressure is 9.8×10 ^-2 mTorr, and the sputtering time is 360s.

2) The glass substrate is transported into the sputtering chamber through the film feeding chamber of the coating equipment, wherein the background vacuum of the sputtering chamber is better than 6×10 ^-6 Torr.

3) Preparation of the infrared reflective layer Al on the glass substrate: The metal Al film was deposited on the glass substrate by bombarding the metal aluminum target (purity 99.7%) by magnetron sputtering with pulsed DC power supply. Its process parameters are set as follows: the sputtering power of the pulsed DC power supply is 1200w, the working pressure is 5mTorr, the working gas Ar (purity 99.99%) flow rate is 50sccm, the substrate transmission rate is 0.4m/min, the glass substrate is placed between the metal aluminum target The bottom moves back and forth 3 times, and the substrate temperature is room temperature.

4) Preparation of absorbing layer CrN _x on (Al/glass): a CrN _x film was deposited on (Al/glass) by bombarding a Cr target (purity 99.7%) by magnetron sputtering with a pulsed DC power supply. Its process parameters are set as follows: the sputtering power of the pulsed DC power supply is 1500w, the working pressure is 3mTorr, the working gas Ar (purity 99.99%) flow rate is 50 sccm, the N2 (purity 99.99%) flow rate is 50 sccm, and the substrate is transported at a speed of 0.8m/ Min moves back and forth twice under the metal Cr target, moves once under the metal Cr target at a transmission speed of 1m/min, and the substrate temperature is room temperature.

5) Preparation of absorbing sublayer CrN _x O _y on (CrN _x /Al/glass): Deposited on (CrN _x /Al/glass) by using pulsed DC power supply oxidation reaction magnetron sputtering Cr target (purity 99.7%) _{CrNxOy film} . The process parameters are set as follows: the sputtering power of the pulsed DC power supply is 1500w, the working pressure is 3mTorr, the working gas Ar (purity 99.99%) flow rate is 50 sccm, the N ₂ (purity 99.99%) flow rate is 50 sccm, O ₂ (purity 99.99%) The flow rate is 10 sccm, the substrate transport rate is 0.4m/min, the base layer 1 glass moves back and forth 5 times under the Cr target, and the substrate temperature is room temperature.

6) Preparation of anti-reflection layer SiO ₂ on (CrN _x O _y /CrN _x /Al/glass): using pulsed direct current power supply oxidation reaction magnetron sputtering silicon aluminum target (aluminum content 30%wt, purity 99.7%) method in (CrN _x O _y /CrN _x /Al/glass) deposited SiO ₂ film. Its coating process parameters are set as follows: the sputtering power of the pulsed DC power supply is 2000w, the working pressure is 5mTorr, the working gas Ar (purity 99.99%) flow rate is 30 sccm, O ₂ (purity 99.99%) flow rate is 14 sccm, and the substrate transfer rate is 1m /min, the base layer 1 glass moves back and forth 11 times under the silicon-aluminum target, and the substrate temperature is room temperature.

7) After the above preparation steps are completed, the sample is cooled for 20 minutes, the tablet is released, and the machine is stopped.

Figure 2 shows the absorption spectrum of the embodiment of the present invention and the traditional TiN _x O _y selective absorption coating material in the 0.3-48 μm band, as well as the solar spectral energy distribution and 100 ° C, 200 ° C, 300 ° C, 400 ° C blackbody radiation energy distributed. Among them, the absorption spectrum in the 0.3-2.5 μm band is obtained by Hitachi U-4100 spectrophotometer, and the absorption spectrum in the 2.5-48 μm band is obtained by Bruker’s Tensor27 Fourier transform infrared spectrometer.

Table 2 shows the absorptivity α, emissivity ε(T) at different temperatures, and α/ε(T) of the embodiment of the present invention and the traditional TiN _x O _y selective absorbing coating material.

Examples The emissivity at different temperatures (100°C, 200°C, 300°C, 400°C) is calculated according to the following formula.

$\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; um</span>}}{\overset{\mathrm{<span\; class="notranslate">\; 48</span>}\mathrm{<span\; class="notranslate">\; um</span>}}{<span\; class="notranslate">\; \&Integral;</span>}}{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>\mathrm{<span\; class="notranslate">\; d\&lambda;</span>}<span\; class="notranslate">\; /</span>\underset{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; um</span>}}{\overset{\mathrm{<span\; class="notranslate">\; 48</span>}\mathrm{<span\; class="notranslate">\; um</span>}}{<span\; class="notranslate">\; \&Integral;</span>}}{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; d\&lambda;</span>}$

Where E _T (λ) is the distribution of blackbody radiation with wavelength (2μm-48μm) at working temperature T (100°C, 200°C, 300°C, 400°C)

The solar spectral absorptivity is calculated according to the following formula:

$\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; 300</span>}\mathrm{<span\; class="notranslate">\; um</span>}}{\overset{\mathrm{<span\; class="notranslate">\; 2500</span>}\mathrm{<span\; class="notranslate">\; um</span>}}{<span\; class="notranslate">\; \&Integral;</span>}}\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>\mathrm{<span\; class="notranslate">\; d\&lambda;</span>}<span\; class="notranslate">\; /</span>\underset{\mathrm{<span\; class="notranslate">\; 300</span>}\mathrm{<span\; class="notranslate">\; um</span>}}{\overset{\mathrm{<span\; class="notranslate">\; 2500</span>}\mathrm{<span\; class="notranslate">\; um</span>}}{<span\; class="notranslate">\; \&Integral;</span>}}\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; d\&lambda;</span>}$

Wherein A(λ) is the solar radiation spectral irradiance (W/m2 μm) when the air quality AM=1.5, and R(λ) is the reflectance spectrum (300-2500nm) of the solar spectrum selective absorption coating obtained by the spectrophotometer test.

Comparing the performance of the embodiment of the invention and the traditional TiN _x O _y coating in Fig. 2 and Table 2, it can be seen that the embodiment of the invention is closer to the solar spectrum region than the absorption-reflection transition region of the traditional selective absorbing coating, and in the solar spectrum The absorption rate near 480nm with the highest energy distribution is larger, and the absorption rate (ie radiation rate) in the infrared band is lower than that of traditional selective absorption coating materials. The embodiment has a higher absorption rate α in the solar spectrum range (0.3-2.5 microns), and a low emissivity ε in the thermal radiation infrared region (2-50 microns), and α/ε is higher than traditional TiN _x O _y , etc. Coated product, suitable for medium and high temperature applications above 100°C with low power focus.

Table 3 shows the test results of sample absorptivity, emissivity and thermal stability evaluation value PC (performancecriterion, PC=△α) of the coated samples of the embodiment before and after annealing for more than 120 hours under 400°C vacuum condition and 250°C atmospheric condition -0.5△ε). It can be seen that the change of the PC value of the sample in the embodiment of the present invention before and after heat treatment is less than 1.5%, indicating that the coating has good stability in a medium-temperature atmospheric environment and a high-temperature vacuum environment.

Table 2. TiN _x O _y coating solar spectrum absorptivity and infrared radiance in the embodiment and prior art

Table 3. Absorptivity and emissivity of examples after annealing under different conditions

Not annealed 400℃ vacuum 250℃atmosphere alpha 90.9 89.1 89.5 ε(250℃) 3.2 2.5 ε(400℃) 4.1 3.2 △α-0.5△ε 1.35 1.05

collector embodiment

A heat collector, comprising a shell, a cover plate on the shell, and a heat absorbing layer and a thermal insulation layer are arranged under the cover plate, and the heat absorbing layer is the continuously adjustable absorbing edge in the above embodiment Selective absorption coatings for the solar spectrum.

By selecting different solar spectrum selective absorption coatings with continuously adjustable absorption edges, low-temperature heat collectors, medium-temperature heat collectors and high-temperature heat collectors can be prepared.

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention in any form. Any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention still belong to the present invention. within the scope of the technical solution of the invention.

Claims (10)

1. a preparation method for double absorption layer coating for selective absorption of sunlight spectrum, is characterized in that, comprises the following steps:

Basalis cleans;

Film plating process is adopted to prepare infrared reflecting layer on described basalis;

Film plating process is adopted to prepare double structure absorbed layer on described infrared reflecting layer;

Film plating process is adopted to prepare anti-reflection layer on described double structure absorbed layer;

Described absorbed layer comprises high index of refraction absorption subgrade from bottom to top successively and low-refraction absorbs subgrade, and described high index of refraction absorption subgrade and low-refraction absorb subgrade and all adopt film plating process to prepare successively.

2. the preparation method of double absorption layer coating for selective absorption of sunlight spectrum according to claim 1, is characterized in that,

The material of described basalis is glass, aluminium, copper or stainless steel;

Basalis cleaning process comprises: first, adopts neutral detergent solution tentatively to clean described basalis; Then, bombarded by radio-frequency ion source, carrying out secondary cleaning to described substrate surface, working gas is inert gas.

3. the preparation method of double absorption layer coating for selective absorption of sunlight spectrum according to claim 1, is characterized in that,

Described film plating process is magnetron sputtering method.

4. the preparation method of double absorption layer coating for selective absorption of sunlight spectrum according to claim 3, is characterized in that,

During preparation double structure absorbed layer, the target selected is chromium target.

5. the preparation method of double absorption layer coating for selective absorption of sunlight spectrum according to claim 3, is characterized in that,

When preparing infrared reflecting layer, the target selected is aluminium target, copper target, gold target, silver-colored target, nickel target or chromium target, and working gas is inert gas;

When preparing anti-reflection layer, the target selected is silicon target, aluminium target, thorium target, dysprosium target, europium target, gadolinium target, yttrium target, lanthanum target, magnesium target or samarium target, and working gas is inert gas and oxygen.

6. the preparation method of double absorption layer coating for selective absorption of sunlight spectrum according to claim 3, is characterized in that,

When preparation high index of refraction absorbs subgrade, pulse dc power sputtering power is 1400 ~ 1600w, and operating air pressure is 2 ~ 4mTorr, and working gas flow is 40 ~ 60sccm, and substrate transfer speed is 0.6 ~ 1m/min, substrate back and forth movement 2 ~ 4 times under target;

When preparing low-refraction absorption subgrade, pulse dc power sputtering power is 1400 ~ 1600w, and operating air pressure is 2 ~ 4mTorr, and working gas inert gas flow is 40 ~ 60sccm, working gas N ₂flow is 40 ~ 60sccm, working gas O ₂flow is 8 ~ 12sccm, and substrate transfer speed is 0.2 ~ 0.6m/min, substrate back and forth movement 4 ~ 7 times under target.

7. the preparation method of double absorption layer coating for selective absorption of sunlight spectrum according to claim 3, is characterized in that,

When preparing infrared reflecting layer, pulse dc power sputtering power is 1180-1240w, and operating air pressure is 4.8-5.2mTorr, and working gas flow is 49-51sccm, and substrate transfer speed is 0.2 ~ 1.6m/min, substrate back and forth movement 2-4 time under target.

When preparing anti-reflection layer, pulse dc power sputtering power is 1900-2050w, and operating air pressure is 4.8-5.2mTorr, and the flow of working gas inert gas is 29-31sccm, working gas O ₂flow is 13-15.5sccm, and substrate transfer speed is 0.8 ~ 1.2m/min, and substrate moves 8-14 time under target.

8. a double absorption layer coating for selective absorption of sunlight spectrum, is characterized in that, described double absorption layer coating for selective absorption of sunlight spectrum is prepared by the preparation method according to any one of claim 1 to 7, comprising:

Basalis; Infrared reflecting layer, double structure absorbed layer and anti-reflection layer is placed with from bottom to top successively at basalis; Described double structure absorbed layer comprises high index of refraction absorption subgrade from bottom to top successively and low-refraction absorbs subgrade; Wherein: the material of described infrared reflecting layer is conducting metal.

9. double absorption layer coating for selective absorption of sunlight spectrum according to claim 8, is characterized in that,

The material of described basalis is glass, aluminium, copper or stainless steel; The material of described infrared reflecting layer is aluminium, copper, gold, silver, nickel or chromium; The material that described high index of refraction absorbs subgrade is CrN _x; The material that described low-refraction absorbs subgrade is CrN _xo _y; The material of described anti-reflection layer is SiO ₂, Al ₂o ₃, ThO ₂, Dy ₂o ₃, Eu ₂o ₃, Gd ₂o ₃, Y ₂o ₃, La ₂o ₃, MgO or Sm ₂o ₃;

The thickness of described basalis is 0.2 ~ 10mm; The thickness of described infrared reflecting layer is 50 ~ 200nm; The gross thickness of double structure absorbed layer is 45nm ~ 125nm, and wherein: the thickness that described high index of refraction absorbs subgrade is 25nm ~ 55nm, the thickness that low-refraction absorbs subgrade is 20nm ~ 70nm; The thickness of described anti-reflection layer is 50 ~ 150nm.

10. a heat collector, comprises housing, on the housing cover plate, is provided with heat-sink shell and heat-insulation layer below described cover plate, the double absorption layer coating for selective absorption of sunlight spectrum of described heat-sink shell according to any one of claim 8 to 10.