JPS58133560A - Selective absorbing material of solar heat - Google Patents

Abstract

PURPOSE:To obtain the titled material having superior and selective absorptivity of solar heat and durability, by a method wherein a glossy nickle-plating layer is provided on the surface of a base body as an intermediate layer on which a black alloy-plating film including tin, molybdenum and a transition metal is provided. CONSTITUTION:A glossy nickle-plating layer or a glossy tin-nickle system alloy- plating layer is provided on the surface of a metallic base body, such as copper or iron as an intermediate layer on which a black alloy-plating film including a transition metal which is selected out of tin, molybdenum, iron, cobalt and nickle is provided. In a selective absorbing material of solar heat in the above constitution, that is, the material shows superior solar heat selective absorbing peculiarity, and shows superior durability through which it is not discolored even under atmospheric exposure for a long period of time.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to solar heat selective absorption materials.

[Technical background of the invention and its problems]

In recent years, technology that utilizes solar energy has been attracting attention as an alternative to oil and nuclear energy.

However, the density of the solar energy that reaches the earth is low, and its characteristics have a peak at a wavelength of 0.5 μm, with nearly 98% of the total energy distributed at a wavelength of 24 m or less.

Therefore, in order to effectively utilize solar energy, a solar heat absorbing material is used that is equipped with a coating that has selective absorption characteristics that maximize energy absorption in the wavelength range and at the same time minimize re-emission of the received energy. This is desirable.

Conventionally, black chromium films and black nickel films are known as films for selectively absorbing solar heat. The black chromium film has an absorption rate (c4 of 0.84 to G, 95) and an emissivity (RI of 0.01).
It has an excellent selective absorption of ~0.10 and high stability, with its properties and appearance not changing even when heated or exposed to the atmosphere.

However, in forming a black chromium film with chromium, it is necessary to use a plating bath containing a high concentration of chromic acid anhydride (200 to 30011/l), expensive wastewater treatment equipment and exhaust treatment equipment, and in addition, plating Conditions: 20A/
dm", and there is also the problem of low energy efficiency. Furthermore, there are various problems such as poor electrodeposition during plating and the inability to form a black chromium film with a uniform thickness. be.

On the other hand, the black nickel film does not have the above-mentioned problems of the black chromium film and has a low absorption rate (→ of 0.84 to 0.95).
Although it has excellent selective absorption with an emissivity (1) of 0.01 to 0.10, it has low weather resistance, and the film changes from black to brown and deteriorates due to short-term exposure to the atmosphere, which is fatal. It has some disadvantages.

In order to eliminate the above-mentioned drawbacks, a solar heat selective absorption material has been developed that has a black alloy plating film containing tin, molybdenum, and a transition metal selected from iron, cobalt, and nickel, which has excellent selective absorption properties. Showa 55-6538
9) However, a solar heat selective absorption material with better durability is desired.

[Purpose of the invention]

The present invention is an improvement on the conventional solar heat selective absorption material described above, and an object of the present invention is to provide a solar heat selective absorption material having excellent solar heat selective absorption properties and durability.

[Summary of the invention]

The present invention has a metallic base, a bright nickel plating layer or a bright tin-nickel alloy plating layer as an intermediate layer on the armpit base surface, and tin, molybdenum, iron,
This is a solar heat selective absorption material characterized by having a black alloy plating film containing a transition metal selected from cobalt and nickel.

Examples of the metal substrate used in the present invention include copper, stainless steel, iron, aluminum, etc., but copper is preferable because of its excellent thermal conductivity.

In the present invention, the bright nickel plating layer has a nickel content of 95 or more, and the bright tin-nickel alloy plating layer has a tin content of 40 to 70, preferably 50 to 6
The nickel content is 30 to 60, preferably 40 to 50. Also, bright nickel plating layer,
Or the thickness of the bright tin-nickel alloy plating layer is 3
It is preferably not less than μm, but preferably within the range of 3 to 10 μm.

Bright nickel plating layer or bright tin layer as intermediate layer
The reason why we chose the nickel-based alloy plating layer is that it has a high reflectance on the long wavelength side, that is, wavelengths of 2μ or more.

In other words, it is required to reduce the heat radiation from the heated object, and for this purpose, a glossy plating layer with a high reflectance is preferable. Furthermore, the reason why we chose the ζ nickel plating layer or the tin-nickel alloy middle layer as the bright plating layer is to improve durability, and this is to prevent the black alloy plating film on the surface from diffusing into the interior during use. (If the black alloy plating film internally diffuses due to exposure to the atmosphere, the absorption rate (C4) decreases and the emissivity (RI) deteriorates significantly.)
This is because it is necessary to have good heat resistance, good electrodepositivity, and good surface reflectance.

In the bath composition and plating conditions when forming a bright nickel plating layer, nickel sulfate is 200 to 3001/l,
Nickel chloride is 30-6011/Is boric acid is 30-50
1/l, bath temperature of 35 to 55°C, pH of 3 to 5, current density of 2 to 6 A/d, and plating time of 4 to 10 minutes. 7 when using sodium naphthalene disulfonate as an agent
~149/l, 0.0 when using butynediol
It is preferably within the respective ranges of 5 to 0.29/l.

On the other hand, when forming a bright tin-nickel alloy plating layer, tin pyrophosphate is 20-4011/l, nickel chloride is 20-409/l, potassium pyrophosphate is 150-25011/l, citric acid is Ammonium Ha5~
15g/11 Bath temperature: 50-70℃, pH: 8-10.
It is preferable that the current density is within the range of 1 to 5 A/di, the plating time is within the range of 4 to 10 min, and the R noton or gelatin is preferably within the range of 2 to 511/l.

Next, as an example of the black alloy plating film, a pyrophosphate, an amino acid or an ammonium salt, a stannous salt, and cobalt, nickel, or iron are used as means for forming a tin-molybdenum-nickel black alloy plating film. Examples include a method of electroplating a metal substrate with a plating bath containing a metal salt and a molybdate as main components.

Each key component in the method for forming the plating film I described above will be described below.

1) Pyrophosphate Pyrophosphate contributes to the stability, uniform electrodeposition, high current efficiency, etc. of the plating bath, and the amount in the plating bath is 150-2501
/l is desirable. Examples of the pyrophosphate include potassium pyrophosphate, sodium pyrophosphate, and stannous pyrophosphate.

2) Amino acid or ammonium salt Amino acid or ammonium salt contributes to the glossiness of the alloy plating film, and the amount thereof is preferably 5 to 309/l. Examples of adenanoic acids include glycine and alanine, and examples of ammonium salts include ammonium citrate, ammonium acetate, ammonium tartrate, and the like.

3) The stannous ion of the stannous salt contributes to improving the weather resistance of the ternary alloy plating film formed by electrodeposition and alloying with the metal ions of the other two metal salts, and the amount thereof is 10 It is desirable that the amount is as high as ~4011/l. If it is less than 1011/l, the weather resistance will be poor, and if it is more than 409/1, the strength of the formed plating film will be reduced. Examples of stannous salts include tin pyrophosphate,
Examples include tin-tin chloride.

4) Metal salts of cobalt, nickel, or iron The metal ions of these metal salts contribute to improving the strength of the ternary alloy plating film formed by electrodeposition and alloying with the metal ions of the other two metal salts. However, the amount is preferably 5 to 301/l. 51/! Below 301171, the contribution to the strength of the plating film becomes difficult, and above 301171, the balance between electrodeposition and alloying with metal ions of other metal salts becomes difficult, and it is impossible to form an alloy that meets the purpose. . Examples of cobalt salts include cobalt chloride and cobalt sulfate, examples of nickel salts include nickel chloride and nickel sulfate, and examples of iron salts include ferric chloride.

5) Molybdate Molybdate ions contribute to the blackening of the ternary alloy plating film formed by electrodeposition and alloying together with the metal ions of the other 02 metal salts, and the amount thereof is 30 to 12011/I. This is desirable. If it is less than 309/l, the blackening will be insufficient, and if it is more than 1201/1, the balance of electrodeposition and alloying with other o*lI salts and metal ions will be impaired. Examples of molybdates include sodium molyzodate, ammonium molybdate, and the like.

In the plating bath having the above-mentioned nine compositions, if necessary, gelatin or gelatin may be added in the range of 1 to 10 g/l. This improves the uniformity of the shimetsu skin II (layer). In the electroplating conditions in the above method, the pH of the plating bath is 8.5-10.The bath temperature is 40-70°C, the current density is 10-300 WA/d7FL11, and the plating time is 1-10.
Preferably each range is 10 minutes. For stirring the plating bath, it is preferable to use mechanical stirring, a cathode rocker, or a combination thereof.

Further, the thickness of the black alloy plating film is 0.1 to 0.5μ.
It is preferable that it is m.

According to Auger analysis, the composition of the black alloy plating film obtained under these conditions is 10 to 35 inches of tin, 3 to 15 inches of molybdenum, 15 to 50 inches of transition metal, and 20 to 35 inches of oxygen.
(each atom) is within the range of -sen θ, which results in an absorption rate of 0.85 or more and an emissivity (g) of 0.1.
An excellent selective absorption film with the following characteristics was obtained.The selective absorption characteristics were determined by measuring the reflectance of the film using a spectrophotometer. , 36 to 2.5), and the emissivity (ε) is the black body radiant energy at 90°C (2,5
~30μ within the range of the door), respectively.

Hereinafter, the present invention will be explained in detail based on examples.

[Embodiments of the invention]

Example 1 A bright nickel plating layer was formed using a copper plate as a metal substrate under the bath composition and plating conditions shown below.

Nickel sulfate zsop/1 Nickel chloride 451/1 Boric acid 401/1 gloss
Sodium naphthalene disulfonate 1011/I or butynediol 0.1171 Bath temperature 45°C PH4.0 Current density 4 μ/dy/Plating time 5 minutes A bright nickel plating layer with a thickness of 4 μm was formed using MIIK. Ta.

Next, a tin-molybdenum-nickel black alloy plating film was formed using the bath composition and plating conditions shown below.

Potassium pyrophosphate 2001/lj Tin-pyrophosphate ISI/l Nickel sulfate
251/1 Sodium Molybdenum 1001
/J Glycine 201/1 - Septon
5I/! Bath temperature 5G'C PH8.5 Current density 150 mA/d/plating time
By performing the above treatment for 2 minutes, a tin-molybdenum-nickel black alloy plating film having a thickness of 0.211 na was formed.

The solar heat selective absorption material thus obtained was heated in air at temperatures of 150, 200 and 250° C. for 100 hours to examine its durability. As a comparison, a copper plate was directly plated with a tin-molybdenum-nickel black alloy of the same thickness without being plated with bright nickel. Moreover, absorption rate (■) and emissivity (-) were used as measurement items. The results are shown in Table 1.

Table 1: For comparison and comparison, a material in which a steel plate was directly plated with a tin-buten-nickel black alloy without bright nickel plating was heated at 250°C for 100 hours, and the absorption rate ( It is clear that when B) is small, the emissivity (g) increases and the selective absorption characteristics deteriorate.In contrast, the solar heat selective absorption material of the present invention is coated with a bright nickel plating layer as an intermediate layer. is 100 at 250℃
It was found that the absorbance (b) and emissivity (6) hardly changed even after heating for a period of time, indicating excellent durability. or,
Its absorption rate (b) is 0.90 or more, and its emissivity is 0.90 or more.
10 or less, indicating that it has excellent selective absorption characteristics.

Example 2 A bright tin-nickel alloy plating layer was formed using a copper plate as a metal substrate under the bath composition and plating conditions shown below.

Tin birophosphate 301/it Nickel chloride 301/1 Potassium birophosphate
2001/1 Ammonium citrate 1011/1
−Sea' ton
31/11 Bath temperature 60°C pH 8.5 Current density 2A/dtrt Plating time 5 minutes By the above treatment, a bright tin-nickel alloy plating layer with a thickness of 4 μm was formed. Gelatin may also be used in the same meal.

Next, a tin-molybdenum-nickel black alloy plating film was formed using the bath composition and plating conditions shown below.

Potassium peaphosphate 2001/1 Tin bitetraphosphate 351/1 Nickel chloride 151/1 Ammonium molybdate 40171 Ammonium citrate 1011/1 Gelatin 51/1
1 Bath temperature: 50° C. pH: 8.5 Current density: 100 mA/d Plating time: 3 minutes By the above treatment, a colorless tin-molybdenum-nickel alloy plating film having a thickness of 0.2 Jm was formed.

The thus obtained solar heat selective absorption material was subjected to an exposure test in the air for 6 months.As a comparison, a bright tin-nickel system was used.

Tin of the same thickness is applied directly to the copper plate without alloy plating.
Absorption rate (b) and emissivity (g) were used as measurement items for the test piece using molybdenum-nickel black alloy plating. The results are shown in Table 2.

Table 2 The materials used for comparison and comparison, in which the tin-molybdenum-nickel black alloy plating was directly applied to the copper plate without applying the bright tin-nickel alloy plating, had an emissivity ( It is clear that I) increases and the selective absorption characteristics deteriorate.

In contrast, the solar heat selective absorption material of the present invention, which has a bright tin-nickel plating layer as an intermediate layer, shows little change in absorption rate (B), emissivity (I), and 4 even after exposure for 6 months. It was found that the absorbance (3) was 0.90 or more, and the emissivity (C) was 0.1 or more, indicating that it had excellent durability and selective absorption.

In Examples 1 and 2, the tin-molybdenum-nickel based black alloy plating film is described, but in both cases of the tin-molybdenum pult-based and the tin-molybdenum-iron based black alloy plating film, the thickness is 3 μm. By applying the above bright nickel plating layer or bright tin-nickel alloy plating layer as an intermediate layer, in the heating and atmospheric exposure tests, the absorption rate was increased in the same manner as in the case where the tin-molypide/-nickel black alloy plating film was used. (b) and emissivity (e
) was not observed, and the effect of improving durability was observed.

When copper plates (solar heat selective absorption materials) coated with these black alloy plating films were exposed to the atmosphere for one year, no discoloration of the film or deterioration of selective absorption properties was observed, indicating that they had excellent durability. did.

〔Effect of the invention〕

According to the present invention, it has solar heat selective absorption characteristics with an absorption rate of 0.8.5 or more and an emissivity of 0.1 or less, and has excellent durability that does not discolor even after long-term exposure to the atmosphere. □
It is possible to provide a solar heat selective absorption material having:

Claims (1)

[Claims] A metallic substrate, having a bright nickel plating layer or a bright-nickel alloy plating layer as an intermediate layer on the surface of the substrate, and a transition metal selected from tin, molybdenum, iron, cobalt and nickel on the intermediate layer. A solar heat selective absorption material characterized by having a black alloy plating film comprising: