JPS5995342A - Solar heat selective absorption material - Google Patents

Abstract

PURPOSE:To prevent the deterioration of selective absorption characteristics and improve the durability of the material by a method wherein the film of Al2O3 of 0.1-0.3mum is coated on a black alloy plating of Sn-M-Mo series having the specified values of absorption rate and radiation rate as a solar heat selective absorption member. CONSTITUTION:The film of Sn-M-Mo series black alloy plating (M is Co, Ni or Fe) having the absorption rate (alpha) of 0.85 or more and the radiation rate (epsilon) of 0.1 or less is formed on the base surface of a metal while the film of Al2O3 of 0.1-0.3mum is coated on the surface. In the material plated by Sn-Ni-Mo series black alloy, in which the film of Al2O3 does not exist on the surface, alpha is decreased, epsilon is increased and the selective absorption characteristics are deteriorated when the temperature thereof arrives at 250 deg.C. On the other hand, when the film of Al2O3 is coated on the surface, the values of alpha, epsilon will never be changed at the temperature of 250 deg.C. The excellent selective absorption characteristics may be kept when alpha is 0.90 or more and epsilon is 0.1 or less. The durability of the Sn-Ni-Mo series black alloy plating film may be improved by the film of Al2O3 or 0.1mum.

Description

[Detailed Description of the Invention] [Technical field to which the invention pertains] Recently, technology that uses solar energy as an alternative to oil and nuclear energy has been attracting attention.

The solar energy that reaches the earth has a low energy density, with its characteristic peaking at a wavelength of 0.5 μm, and nearly 98% of the total energy is distributed at a wavelength of 2 μm or less. Therefore, in order to utilize solar energy effectively, it is necessary to use a solar heat absorbing material that has a coating that has selective absorption characteristics that maximizes the absorption of energy in the above wavelength range and at the same time minimizes the re-emission of the received energy. is desirable.

[Prior art and its problems] Black chromium films and black nickel films have been known as films for selectively absorbing solar heat. The former black chrome film has an absorption rate @) of 0.85 to 0.95 and an emissivity (ε) of 0.0.
It has good selective absorption of 1 to 0.1 and high stability, with its properties and appearance not changing even when heated or exposed to the atmosphere. However, in order to form this black chromium film, 200
- Since a plating bath containing chromic anhydride at a high concentration of 300 g/l is used, expensive wastewater treatment equipment and exhaust treatment equipment are required, and the plating conditions are 2OA/drn2 (
! In addition, there are problems with low first flow efficiency as it requires a high rl flow density, and there are also various problems such as poor electrodeposition during plating and the inability to form a black chromium film with a uniform thickness. There is an inconvenience.

The latter black nickel film does not have the disadvantages of the black chromium film mentioned above, and has an absorption rate (α) of 0985 to 0.9.
5. The emissivity (ε) is 0.01 to 0.1. Although it has excellent selective absorption, it has poor weather resistance and can be used in the atmosphere for a short time.
Exposure causes the coating to change from black to brown and deteriorate.

In order to solve the above-mentioned deficiencies, S
There is n-M-MO black alloy plating (M represents co, Ni, or Fe).

[Object of the Invention] The present invention relates to a method for further improving the durability of a Sn-M-MO system as a solar heat selective absorption member having an absorption rate @) of 0.85 or more and an emissivity (ε) of 0.1 or less. It is characterized by coating A12o3 pattern with a thickness of 0.1 to 0.3 μm on black alloy plating.

[Summary of the invention and effect 1] The present invention provides that the surface rco is coated with an A12O3 pattern of The purpose is to improve durability.If the Al2O3 film as a surface coating film is less than 0.1/Am, sn - Ni -
It has no effect on improving the durability of the Mo-based black alloy plating film, and when the thickness exceeds 0.3 μm, the durability improves, but as α becomes smaller and ε becomes larger, selective absorption deteriorates. -Nr-MO based black alloy plating film is made of metal using a plating bath mainly composed of, for example, pyrophosphate, amino acid salt or ammonium salt, Daiichi Tin Tantan, metal salt of cobalt, nickel or iron, and molybdate. Manufactured by electroplating using a substrate.

Next, each plating component in the above-mentioned manufacturing method will be described.

1) Pyrophosphate Pyrophosphate contributes to the stability of the plating bath, uniform electrodeposition, high current efficiency, etc., and the amount occupied in the plating bath is 150 to 25%.
0g71 is desirable. Examples of pyrophosphate include potassium pyrophosphate and sodium pyrophosphate.

2) Amino acid or ammonium salt The amino acid salt or ammonium salt contributes to the glossiness of the alloy plating film, and its amount is preferably 5 to 30 fl. Amino acid salts include glycine and alanine, and ammonium salts include citric acid, ammonium, ammonium acetate, and ammonium tartrate.

3) Stannous salt The stannous salt contributes to improving the durability of the ternary alloy plating film formed by electrodeposition alloying with two other metal ions. The amount is preferably 10-40 g/l. If it is less than 10g/l, weather resistance will be poor and
/it or more, the strong IJj of the formed plating film may become low. In addition, as the stannous salt, pyrophosphoric acid stannous
Examples include soot and soot dichloride.

4) A metal salt of cobalt, nickel, or iron.This metal salt contributes to improving the strength of the ternary alloy plating film formed by electrodeposition and alloying with two other metal ions.The song is 5. ~30 Ill is desirable. If it is less than 5 fl/II, it is difficult to contribute to the strength of the film. If it is more than 30 g/1, the balance between analysis and alloying with other metal ions is only one cone, and it is not possible to form an alloy that meets the purpose. It disappears. Cobalt salts include cobalt chloride and cobalt sulfate, nickel salts include nickel chloride and nickel sulfate, and iron salts include ferric chloride.

5) Molybdate Molybdate contributes to the blackening of the ternary alloy plating film formed by electrodeposition and alloying with two other metal ions, and its amount is 30 to 120 g/11. This is because if it exceeds the amount, the balance of electrodeposition and alloying with other metal ions will be impaired. Examples of molybdates include sodium molybdate and ammonium molybdate.

Peptone and gelatin can be added in an amount of 1 to 10 gA to the plating bath having the above-mentioned composition, if necessary.

This improves the uniformity of the film. The electroplating conditions in the above method are preferably such that the pH of the plating bath is 8.5 to 10 and the bath temperature is 40 to 70 DEG. The plating bath is preferably mechanically stirred, a cathode rocker, or a combination thereof is used. According to Auger analysis, the composition of the sn-Ni-MO black alloy plating film obtained under these conditions was 5nlO-&5,M
(co, Ni or Fe) 15-50, MO
3-15°020-35 (both atomic percent), α is 0.85 or more, and ε is 0.1.
The following excellent selective absorption coatings are available. The film thickness is preferably 0.1 to 0.5 μm.

The selective absorption characteristics are determined by measuring the reflectance of the film using a spectrophotometer, and the absorption rate (@) is determined by measuring the measured value and solar energy (0.36~
relative energy, emissivity (ε
) is the blackbody radiant energy at 90°C (2.5-30μm
(within the range of ) and the relative energy.

[Embodiments of the invention] This will be explained below using examples.

Example 3n-Ni-MO black alloy plating was carried out under the composition and conditions of 1° or less.

Pyroline and potassium 200g/l stannous pyrophosphate 151 nickel sulfate
25g/l Sodium Molybdate 10
0g/l glycine 2oFL/l
Peptone 5g/l bath temperature
Blade “C current density
150mA7dm2 plating time 2 minutes, 0.2μm s
An n-Ni-MO black alloy plating was obtained. The film had an absorption rate of 0.92 and an emissivity of 0.08. Al2 was deposited on this film by vacuum evaporation using an electron beam as a heat source.
An O3 film of 0.1 μm was formed. Selective absorption of coating is 0
．． A 1 μm Al2O3 film caused no change. A
Regarding the Bn-Hl-M0 black alloy plating film coated with 0.1 μm of l2O3 film, 150, 200, 2
Durability was examined by heating at 50°C for 100 hours. For comparison, Sn of the same thickness without Al2O3 coating was used.
-Nt-MO based black alloy plated items were subjected to a heating test under the same conditions. In both cases, absorption rate (α) and emissivity (ε) were measured. The results are summarized in Table 1. Note that the metal substrate used was a copper plate.

As shown in Table 1, the material plated with 3n-Ni-MO black alloy without All 203 film on the surface is 250
At °C, α becomes smaller, ε becomes larger, and the selective absorption characteristics deteriorate. - When an Al2O3 film is applied to the blade surface, neither α nor C changes at 250°C. α is 0.90 or more
H.6 maintains excellent selective absorption characteristics below 0.10. p 5n-N;- by 0.1 μm Al2O3 film
The durability of the MO-based black alloy plating film is improved.

Example 8n-Ni-MO black alloy plating with a thickness of 0.2 μm was obtained in 3 minutes using a bath composition of 2° or less and plating conditions.

Potassium pyrophosphate 200g/l stannous pyrophosphate 35g/l nickel chloride
1511 ammonium molyftate 40g/
/Il ammonium citrate 10νl gelatin 5 g/l bath temperature
50 '01 Flow density 100
mA7/dm2Sn-Nt-MO-based black alloy Metsukino absorption rate (α) hao was 92, and emissivity (ε) was 0.10. On this film, an Al2O3 film having a thickness of 03 μm was formed by vapor deposition in vacuum using a single beam as a heat source. The selective absorption property did not change due to the formation of the Al2O3 film. A 5n-Ni-MO black alloy plating film coated with an Al2O3 film of 0.3 μm was subjected to an exposure test in the air for 6 months. For comparison, sn-N with the same thickness without A12o3 coating was used.
Materials plated with i-MO black alloy were also subjected to exposure tests under similar conditions. α and ε were measured for these materials. The results are shown in Table 2. Note that the metal substrate used was a copper plate.

Al2O3 on the surface of 3n-Nj-MO black alloy plating
(!: Even after 6 months of exposure, there was no change in both α and ε compared to the values before exposure. - A12o3 on the blade surface.
When the uncoated 3n-Ni-MO black alloy plating material is exposed to the air, ε increases and the selective absorption characteristics deteriorate.

In both Examples 1 and 2, Sn-Ni-Mo based black alloy plating films were described, but in both cases of Sn-Co-MO and 3n-Fe-MO based, the plating film was 0.1 to 0.
When a 3 μm Al2O3 film was applied to the surface and subjected to heating and atmospheric exposure tests, there was no change in α or ε, similar to the sn-Ni-Mo black alloy plating film, and it was effective in improving durability. When a copper plate (solar heat selective absorption material) on which a black alloy plating film was formed was exposed to the atmosphere, no discoloration of the film or decrease in selective absorption was observed even after one year, indicating that it has excellent durability. understood.

As described above, the present invention has excellent selective absorption of solar heat,
The absorption coefficient (α) is 0.85 or more, and the emissivity (α) is 0.85 or more.
The object of the present invention is to provide a highly durable solar heat selective absorption material that has a \j break of 1 or less and does not discolor even after long-term exposure to the atmosphere.

In the embodiment, steel is used as the metal base, but other materials such as stainless steel, iron, aluminum, etc. may also be used.

Claims (1)

[Claims] A Sn-M-MO black alloy plating (M is co, Ni, or Fe) coating with an absorption rate of 0.85 or more and an emissivity of 0.1 or less is formed on the surface of the metal substrate, and the surface to 0
．． A solar heat selective absorption material characterized by being coated with an Al2O3 film of 1 to 0.3 μm.