JPS58219359A - Manufacture of solar heat absorption body - Google Patents

Abstract

PURPOSE:To manufacture a solar heat absorption body, in which solar heat absorption rate is high, being not changed with the passage of time, and superior to a heat-resistant and a corrosion-resistant properties, by using an alloy of copper and nickel as a material to manuacture a solar heat selective absorption film. CONSTITUTION:An alloy of copper and nickel are used as a material to manufacture a solar-heat selective absorption film, in a method to obtain a solar heat absorption body coated with a selective absorption film of oxidized copper by an alternating current process. To be concrete, the glanular powder of an alloy of copper and nickel of which average diameter is below 200mu is deposited on the base board whichis separately prepared by the intermediary of an adhesive or the like, and after that, it is treated by chemical conversion treatment: the another method is that the granulated alloy of copper and nickel is deposited on base board by the intermediary of an adhesive or the like after it is processed by alternating current. Besides, the alloy of copper and nickel is used as a base material, and its surface is treated by chemical conversion treatment. A chemical conversion liquid for alternating current process is a mixed solution of an oxidizer and an alkaline additive. As for the oxidizer, NaClO2 or the like is usable, and for the alkaline additive, NaOH or the like is used.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a solar heat absorber used in solar water heaters and the like.

A solar energy absorber is required to have a high absorption rate for electromagnetic waves in the visible light region and near-infrared region, and a low emissivity in the infrared region.

Conventionally, coatings that absorb solar energy well and emit little heat in the infrared region (generally called selective absorption coatings)
A variety of solar heat absorbers have been devised that are formed on the surface of 1-copper oxide (C).
Copper oxide coatings such as uzO) coatings and cupric oxide (CuO) coatings are widely known.

However, conventional solar heat absorbers in which a selective absorption film made of the above-mentioned oxidized steel is formed on the surface of the base material generally have poor heat resistance. As a result, temperatures can sometimes reach temperatures as high as 200°C, causing deterioration. Therefore, in addition to decreasing the absorption rate in the near-infrared region (wavelength 0.7 to 2.5 microns), the underlying copper component is oxidized and the thickness of the selective absorption film gradually increases. This often resulted in problems such as increased radiation.

This invention was made in view of the above circumstances,
The present invention provides a method for producing a solar heat absorber that has a high solar heat absorption rate, does not change over time, and has excellent heat resistance and corrosion resistance. This will be explained below.

The present invention is a method for obtaining a solar heat absorber equipped with a copper oxide selective absorption film by oxidation treatment, and the solar heat absorber is characterized in that a black-nickel alloy is used as a material for manufacturing the selective absorption film. The manufacturing method is summarized in 1-.

The solar heat absorber obtained by the method of the present invention has a three-layer structure in which the surface layer is made of copper oxide with selective absorption characteristics, the middle layer is made of nickel with excellent durability, and the inner layer or lower layer is made of a copper-nickel alloy. It is normal to have one.

In this invention, a copper-nickel alloy is used as a material for manufacturing a selective absorption film, and copper oxide is obtained by subjecting the copper-nickel alloy to oxidation treatment such as chemical conversion treatment. in particular,
Copper-nickel alloy powder is fixed onto a separately prepared base material using an adhesive or the like, and then subjected to chemical conversion treatment, or after oxidation treatment of the copper-nickel alloy powder, It is fixed onto the base material using an adhesive or the like. Furthermore, a copper-nickel alloy plate is used as a base material, and its surface is subjected to chemical conversion treatment.

As the copper-nickel alloy used to manufacture the solar heat absorber according to the present invention, one that is normally commercially available as cupronickel can be used. Cupronickel is nickel (Ni)
The content is 9.0 to 33.04, and also about 1 part iron (Fe), about 1 part zinc (Zn), 0.2 to 1 part
．． Generally, it contains manganese (Mn) of 0'Z, lead (Pb) of 0.005'Z or less, and the rest is copper (Cu), but there are some that contain even higher Ni content. Next, the base material is not particularly limited as long as it is chemically and thermally stable, and for example, glass plates, stainless steel plates, copper plates, etc. are preferably used. In addition, the cupronickel plate described above can also be used. Note that the surface of the base material is preferably cleaned in order to promote the chemical conversion treatment described below.

Prior to the oxidation treatment, the cleaning treatment is performed by degreasing, activating the surface with an acid or the like, and then washing, neutralizing, washing with water, etc.

As a fixing agent for fixing the copper-nickel alloy powder to the base material, for example, a resin material such as a plastic molding material such as polyethylene, or a heat-resistant adhesive such as silicone-based, fluorine-based, or #iBT resin is used. or an inorganic adhesive such as a water glass adhesive, but is not particularly limited to these.

The fixing method is to mix and knead copper-nickel alloy powder into the resin material and attach it to the base material using a spray method, or to apply adhesive onto the base material with a brush or the like.
Alternatively, a method may be used in which the adhesive is adhered to the surface of the substrate by immersing the substrate in an adhesive liquid, and then the copper-nickel alloy powder is spread and adhered to the surface of the substrate. The mixing and kneading method is less likely to be oxidized in the subsequent chemical conversion treatment process and tends to cause variations in oxidation, so the spraying method is preferable. Note that, after the copper-nickel alloy powder is attached to the base material via an adhesive or the like, it is hardened to be completely fixed.

The size of the particles when pulverizing a copper-nickel alloy plate or the like is not particularly limited, but it is preferable to set it to 200 μm or less because good results can be obtained. This means that the particles are 200μ
This is considered to be due to the fact that when the particles are smaller than the following, a multiple reflection effect is added due to the physical structure unique to the metal particles, in addition to the selective performance of cupric oxide (Cub) in the surface layer and porous nickel in the middle layer.

When using a cupronickel plate, the surface of the cupronickel plate may be cleaned and then oxidized.

Copper-nickel alloys are extremely susceptible to oxidation and have excellent corrosion resistance. Therefore, the chemical conversion treatment performed as oxidation treatment must be performed under conditions that are much more severe than those for copper.

The chemical conversion treatment liquid for oxidation treatment is a mixed bath liquid containing an oxidizing agent and an alkaline additive, and the oxidizing agent includes sodium chlorite (NaC10z), sodium hypochlorite (NaC
10), Potassium persulfate (KzSzOa) * Sodium persulfate (NaC10z), Ammonium persulfate ((N
H4') 25208) are used, as are chlorites, hypochlorites or persulfates such as alkali IJ? For machining, sodium hydroxide (NaOH), potassium hydroxide (KOH), etc. are used. NaC as oxidizing agent
It is practically best to use lO2 and NaOH as an alkaline additive.

Copper ions may be added to these chemical conversion treatment solutions in order to promote the oxidation action. For example, copper sulfate (CuSO4)
, copper nitrate (Cu(NOa)2), copper chloride (CuC1
A method may be employed in which a trace amount of an aqueous solution of a copper salt such as z') is added, or a method may be employed in which metallic copper is immersed in a chemical conversion treatment solution and treated with this solution to increase copper ions. It is effective to set the concentration of copper ions in the chemical conversion treatment solution to 10 to 200 ppm.

In the chemical conversion treatment, a similar effect can be obtained using an AgNO3 aqueous solution.

If oxidation treatment is performed using such a chemical conversion treatment solution, copper-
The surface of the nickel alloy is oxidized to form cupric oxide (Cu), which has a fibrous or leaf-like shape on the surface.
O) A selective absorption film made of crystals, below that (middle layer) is a nickel layer in which copper is diluted by changing Cu to CuO through chemical conversion treatment (a trace amount of Cu exists), and further below that (lower layer or inner layer). ) has a copper-nickel 6-gold layer that has not undergone oxidation. However, this structure may exhibit such a compositional distribution in a state where the components of each layer are mixed to some extent.

When the composition was analyzed by Auger electron spectroscopy from the surface copper oxide film to the middle, lower, or inner layers while performing reverse sputtering, it was confirmed that the middle and lower layers exhibited compositional changes as shown in Figure 1. In other words, the middle layer, which ranges from 50 to 1000 A in depth from the surface, is formed mostly of nickel, and from the middle layer to the lower or inner layer, the nickel content gradually decreases and the copper content increases, and when the lower or inner layer is reached, the original copper is lost. - It is back to the composition range of nickel alloys. In addition, in the case of O-1 Dier electron spectroscopy, the analysis error is considered to be about 104, so a very small amount of Cu remains in the nickel layer.
However, such a small amount of Cu is not recognized to have an adverse effect on heat resistance, even from the results of Examples described later. Fig. 2 schematically shows each structure when the material is a cupronickel plate, and Fig. 3 when the material is cupronickel particles. In the figure, l is a CuO layer, 2 is a Ni-rich layer, and 3 is a Cu-
Spray the Ni alloy layer.

In the case of ordinary copper oxide-based selective absorption films, the underlying copper is copper, so if it is exposed to heat of 150°C or higher, the underlying copper will oxidize.
The thickness of the copper oxide layer increases.

As a result, the absorption rate in the visible light range (0.3-0.7μ) does not change, but the absorption rate in the near-infrared range (0.7-2.5μ) decreases and the emissivity increases.

On the other hand, the solar heat absorber made by the method according to the present invention has a wavelength range of sunlight (0.3 to 2.5μ).
Among them, those in the visible range (0.3 to 0.7μ) are absorbed by the cupric oxide (Cub) film, and those in the near-infrared region (0.7 to 2.5μ) are absorbed by the cupric oxide (Cub) film.
) is absorbed by multiple reflections of the cupric oxide (Cub') microstructure and the nickel microstructure, and as a result, the absorption rate ω of sunlight usually shows a high value of 0.93 or more. On the other hand, the emissivity (ε) is small because the fine structure of nickel is extremely small and presents a situation where it can be seen as a flat surface to infrared light. Moreover, the second oxidation
There is a nickel layer under the copper (CuO), so it has excellent heat resistance.
Never deteriorates. Therefore - no oral changes in absorption rate ω and emissivity (ε) occur. Moreover, since the bottom layer or inner layer is made of a copper-nickel alloy, it has even better corrosion resistance. Particularly, in a solar heat absorber obtained by fixing copper-nickel alloy powder to a base material, the above effect is remarkable because each particle on the base material acts as a selective absorption surface.

Also, compared to the conventional method of obtaining a solar heat absorber through a complicated manufacturing process of nickel plating on a base material, copper plating on the base material with a nickel surface, and further oxidation treatment, According to the present invention, when producing a selective absorption film, the plating process and the like are significantly shortened and simplified by simply oxidizing a copper-nickel alloy as a raw material.

Examples will be described below along with comparative examples.

[Examples 1 to 6], [Comparative Examples 1 to 2] The following two types of cupronickel plates manufactured by Kobe Steel, Ltd. were used as nickel-copper alloy materials.

Cupronickel plate C7060 (class 1 cupronickel): Nickel content 9.0
～11,0 yen Cupronickel plate C7150 (2 types of cupronickel): Contains nickel 29,
The cupronickel plate having a ratio of 0 to 33.0 was mechanically coarsened in advance, and then ground in a stainless steel bot mill to obtain three types of powders having different particle sizes.

Table 1 <Example 1> A paste-like material obtained by diluting straight silicone varnish KR-177N (N-Etsu Chemical Co., Ltd.) with xylene and having a solid content concentration of 10% by weight was applied to a glass whose surface had been cleaned in advance. C70f was applied to the surface of the board using a brush.
After sprinkling iO type A powder, the resin was cured by heating at 100° C. for 15 minutes.

After curing NaCl0z 90g/l, NaOH90
Chemical conversion treatment was performed at 100° C. for 3 minutes using a treatment solution of 11/l.

<Example 2> Silicone varnish TBS-400 (Nippon Colcoat Co., Ltd.) was diluted with isobrobyl alcohol to obtain a solid content concentration of 20.
C7150 type A powder in an amount twice the weight of the solid content was mixed into a weight varnish to obtain a paste, which was spray applied onto the surface of a glass plate whose surface had been previously cleaned. This was heated at 100°C for 10 minutes to harden the resin, and then heated at 100°C for 10 minutes using the same chemical conversion treatment solution as in Example 1.
Chemical conversion treatment was performed for 5 minutes.

<Example 3> 20 parts of BT2170 (Mitsubishi Gas Chemical Co., Ltd.), 80 parts of carboxylic acid-containing acrylic resin, ethyl acetoacetate □5
Using a brush, 0.00 parts of the paint-containing paste was applied onto the surface of stainless steel (304) with a thickness of 0.5 mm, which had been previously degreased. After scattering C7150 type B powder on the surface, baking was performed at 140° C. for 20 minutes. Then K2S2O8101/l.

NaOH50,! i+// treatment solution at 100℃, 3
A minute chemical conversion treatment was performed.

<Example 4> Solid content concentration 1 obtained by diluting fluorine-based coating material Florard FC-721 (Sumitomo 3M) with xylene
A mixed paste was obtained by mixing C7060 type B powder with a weight of 3 times the weight of the solid content into a varnish weighing 5 weight, and this was mixed onto a 0.5 mm thick stainless steel plate (the surface of which had been degreased in advance). 304) Sprayed on the surface. This was heated at 100° C. for 15 minutes to harden the resin, and then chemical conversion treatment was performed at 100° C. for 15 minutes using the same chemical conversion treatment solution as in Example 3.

<Example 5> A liquid obtained by diluting No. 3 water glass with purified water to a solid content of 10 g/w was mixed with JI whose surface had been previously degreased.
A SH3100 copper plate (thickness 0.3 mm) was immersed.

After scattering C7150 type B powder on the surface, 5
It was pre-dried at 0°C for 10 minutes, and then heated at 250°C for 30 minutes to harden the resin. This was subjected to chemical conversion treatment under the same conditions as in Example 1.

<Example 6> In Example 3, copper-nickel alloy material and C71
The procedure of Example 3 was followed except that 50 Type C powder was used.

<Comparative Example 1> In Example 1, JI was used as the powder to be sprinkled on the surface of the base material.
The procedure of Example 1 was followed, including the particle size, except that SH3100 copper powder was used.

<Comparative Example 2> In Example 5, JI was used as the powder to be sprinkled on the surface of the base material.
The procedure of Example 5 was followed, including the particle size, except that SH3100 copper powder was used.

Examples 1-6. The performance of the selective absorption membranes obtained in Comparative Examples 1 and 2 is shown in Table 2.

[Examples 7 to 12], [Comparative Examples 3 to 4] Two types of cupronickel plates (C7060) as copper-nickel alloy materials.

C7150), and each was added to a 4 oy/l solution of 48Y degreaser (Dipsol Co., Ltd.) at 50°C to 60°C for 1 to 10 minutes.
It was soaked for 5 minutes and completely degreased. After degreasing - thoroughly wash,
The surface was activated by immersing it in 2%-F (C1) for 2 minutes. After that, it was thoroughly washed, neutralized with 2%-NaOH, and further washed with water. The performance of the selective absorption membrane obtained is shown in Table 4.

(Margin below) (15) Table 3 In addition, the test methods in the above Examples and Comparative Examples are as follows.

(Test method) Copper plating thickness: An electrolytic film thickness measuring device manufactured by Chuo Seisakusho was used.

CuO, Cu2O film thickness: Measured using a combination of constant current reduction method and X-ray diffraction method.

Here α: Absorption rate (relative to total solar energy) αλ: Absorption rate at wavelength λ IA: Radiation intensity at wavelength λ of sunlight Here ε: Emissivity (relative to total blackbody radiation energy) (18) SAT= 16゜: Radiation intensity ε of wavelength λ from a black body at 150°C; wavelength wavelength number emissivity (relative to a black body) In addition, the reflectance P in the infrared region was measured with an infrared spectrophotometer,
It was set as t=IPa.

λ As is clear from the comparison of Examples 1 to 12 and Comparative Examples 1 to 40 above, the solar heat absorber made by the method of the present invention has a high solar heat absorption rate ω and radiation even after testing at 200°C for 1000 hours. The ratio (ε) was good with no change over time, and the heat resistance was excellent.

[Brief explanation of the drawing]

Figure 1 is a graph showing the composition change in the portion below a depth of 50λ of a solar heat absorber obtained by the method according to the present invention, Figure 2 is a graph showing the composition change when the material is a copper-nickel alloy plate, and Figure 3 is when the material is copper-nickel alloy particles,
FIG. 2 is an explanatory diagram schematically showing the surface and internal structures of plates and particles. 1...CuO layer 2...Ni-rich skin 3...C
u-Ni alloy layer patent applicant Matsushita Electric Works Co., Ltd. agent Patent attorney Takehiko Matsumoto (21) Figure 1 Figure 2 Figure 3

Claims (4)

[Claims] (1) A method for producing a solar heat absorber equipped with an oxidized steel selective absorption film by oxidation treatment, characterized in that a copper-nickel alloy is used as the material for producing the selective absorption film. . (2) A method for manufacturing a solar heat absorber according to claim 1, which is an alloy plate of copper alloy and nickel. (3) The method for manufacturing a solar heat absorber according to claim 1, wherein the material is copper-nickel alloy particles fixed on a base material. (4) The method for manufacturing a solar heat absorber according to claim 3, wherein the average particle size of the copper-nickel alloy particles is 200 μm or less.