CN1168788C - Solar Spectrum Selective Absorbing Coatings - Google Patents

Abstract

The invention belongs to the technical field of solar heat collectors, which includes using glass and polished metal as the substrate, feeding pure argon gas, depositing an aluminum film on it to form the bottom layer of the selective absorption coating, and then introducing an appropriate amount of air to deposit and form the absorption layer. layer and anti-reflection layer of pure dielectric. The invention has the advantages of simple and easy to control process, low price, high film stability, good anti-reflection effect, no pollution and danger, and the like.

Description

Solar Spectrum Selective Absorbing Coatings

technical field

The invention belongs to the technical field of solar heat collectors, in particular to a solar spectrum selective absorption coating prepared by magnetron sputtering vacuum coating technology.

Background technique

The selective absorption coating is composed of three parts: the bottom infrared high reflection (that is, infrared low emission) layer material, such as gold, silver, copper, aluminum, etc.; the middle part is the absorption layer, which has a strong absorption effect on solar radiation; The topmost layer is an anti-reflection layer, which is used to reduce the reflection of the surface on the incident sunlight and improve the absorption performance of the surface. Solar selective absorbing coatings are used in solar thermal elements such as flat plate collectors and evacuated tube collectors. When used for the former, the coating works in an atmospheric state, and when used for the latter, it works in a vacuum state. The solar radiation energy absorbed by the selective absorbing coating is taken away by the heat transfer medium.

The selective absorption coating involved in U.S. Patent No. 339.484 is to first sputter deposit a layer of infrared highly reflective copper film on the glass, and then deposit stainless steel-carbide as the absorption layer, and the solar absorption ratio of the coating (AM2)α ≈0.92, emissivity ε≈0.05 (100°C). This type of selective absorbing coating has the following disadvantages: one, two kinds of material cathodes (copper and stainless steel) must be arranged during preparation, and a baffle must be added between the two cathodes to prevent them from contaminating each other in use. The existence of the equipment greatly reduces the utilization rate. Second, use inert gas (argon), methane or acetylene during preparation, and the latter two are combustible gases.

The Chinese invention patent CN 1056159A relates to an AlN _x O _y selective absorption coating. During the preparation, a single aluminum material is used as the cathode, and three gases of argon, nitrogen, and oxygen are used. The solar absorption ratio of the coating is α≈0.90 ~0.94, infrared emissivity ε=0.07~0.12.

The Chinese invention patent CN 1077018A relates to an aluminum-carbon absorption layer, and the aluminum-nitrogen is a selective absorption coating for an anti-reflection film. Also be single aluminum cathode during preparation, the gas that feeds is three kinds of argon, nitrogen, methane (or acetylene), wherein methane (or acetylene) is combustible gas, solar absorption ratio α=0.92～0.95, emissivity ε= 0.05～0.07 (80°C). The disadvantages of the above two patents are: first, two active gases must be used, and one of them is combustible, or combustion-supporting, which increases unsafe factors; second, there must be three independently controllable gas circuit systems to The amount of gas in the coating chamber is controlled, so there are many variable parameters, the difficulty of the process is increased, and the cost of the coating is also increased.

Chinese invention patent CN8510014 relates to an aluminum-nitrogen (or aluminum-carbon-oxygen) selective absorption coating, with a single aluminum cathode, the active gas is high-purity nitrogen (carbon monoxide), the solar absorption ratio α≈0.93, and the emissivity ε≈0.06 (100°C). The disadvantages of this patent are: firstly, limited by the refractive index of the pure medium (aluminum-nitrogen), the anti-reflection effect of the surface layer is not obvious enough; secondly, high-purity nitrogen and carbon monoxide are relatively expensive.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the above-mentioned patents, and provide a high-stability solar spectrum selective absorption coating with aluminum-air as the absorption layer and anti-reflection layer. Using sputtering deposition technology, alloy aluminum is used as the cathode, and air is used as the active gas. It has the advantages of simple process and easy control, low price, high film stability, good anti-reflection effect, and no pollution and danger.

A kind of solar spectrum selective absorption coating proposed by the present invention is characterized in that, with glass and polished metal as the substrate, pure argon gas is passed through, and an aluminum film is first deposited on it to form the bottom layer of the selective absorption coating, and then passed through A proper amount of air is deposited to form an aluminum-air absorption layer and a pure dielectric anti-reflection layer. The thickness of said absorbing layer is 0.15×10 ^-6 m to 0.5×10 ^-6 m. The thickness of said antireflection layer is 0.04×10 ^-6 m to 0.2×10 ^-6 m.

The present invention can use domestic LY11-13 aluminum alloy as cathode.

When bright copper and aluminum are used as the polishing metal, argon and air can be introduced to deposit the anti-reflection layer that constitutes the absorbing layer and the pure medium.

When the glass is used as the substrate, the aluminum film is deposited under pure argon as an infrared high-reflection layer, and its thickness can be greater than 0.09×10 ^-6 m, and then air is deposited to form an absorption layer and a pure dielectric anti-reflection layer.

The advantages of the present invention are: (1) the anti-reflection effect of the pure dielectric anti-reflection film obtained by the reaction of aluminum and air is greater than that of pure aluminum-nitrogen film; (2) the absorption layer and the anti-reflection layer adopt the same material and gas; (3) the used The reaction gas is air, which does not cost money and does not cause any pollution or danger; (4) the film layer has high stability; (5) the process is simple and easy to control, and the price is low.

Description of drawings

Fig. 1 is a schematic structural diagram of an embodiment of a solar spectrum selective absorption coating of the present invention.

Detailed ways

The structure and preparation process of the solar spectrum selective absorption coating of the present invention are explained in conjunction with FIG. 1 . Using glass and polished metal as the substrate 1, alloy aluminum (domestic LY11-13) as the cathode, and sputtering and depositing an aluminum film with a thickness greater than 0.09×10 ^-6 m of infrared high-reflective material in a pure argon atmosphere as the bottom layer material 2; Strictly control the amount of air introduced to prepare the absorbing layer 3 by reactive sputtering. With the increase of the amount of air, the aluminum content in the absorbing layer material gradually decreases, that is, the refractive index and extinction coefficient of the film layer gradually decrease. When the aluminum content in the film is zero , it is the anti-reflection layer 4 of the film system. The thickness of the absorbing layer 3 is 0.15×10 ^-6 m to 0.5×10 ^-6 m; the thickness of the antireflection layer is 0.04×10 ^-6 m to 0.2×10 ^-6 m.

The solar spectrum selective absorption coating of the present embodiment is through 550 ℃, after 40 hours of baking, its solar absorption ratio α can reach 0.968 at the highest, emissivity ε=0.06～0.08 (80 ℃), the stability of coating good.

Claims (4)

1, a kind of solar spectrum selective absorption coating, it is characterized in that, take glass, polished metal as substrate, pass into pure argon gas, deposit aluminum film on it first and form the bottom layer of selective absorption coating, pass into appropriate amount again The air deposition constitutes the aluminum-air absorption layer and the anti-reflection layer of pure dielectric; the thickness of the absorption layer is 0.15×10 ^-6 m to 0.5×10 ^-6 m; the thickness of the anti-reflection layer is 0.04×10 ^-6 m to 0.2×10 ^-6 m. 2. The solar spectrum selective absorption coating according to claim 1, characterized in that the domestic LY11-13 aluminum alloy is used as the cathode. 3. solar spectrum selective absorption coating according to claim 1, is characterized in that, when said polishing metal adopts bright copper and aluminum, feeds argon gas and air deposition and forms the anti-reflection layer of absorption layer and pure medium . 4. The solar spectrum selective absorption coating according to claim 1, characterized in that, when said glass is used as a substrate, the aluminum film deposited in pure argon is an infrared high reflection layer, and its thickness is greater than 0.09×10 ^-6 m, and then pass through the air to deposit the anti-reflection layer that constitutes the absorbing layer and the pure medium.