JPS6043896B2 - Direct solar heat absorbing material and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a direct solar heat absorbing material that has excellent absorption properties for solar radiant heat energy.

Techniques for utilizing solar energy are being developed as an alternative energy to oil.

These technologies can be roughly divided into methods that directly use solar energy in the form of heat, such as air conditioning, and indirect methods that convert solar energy into another form of energy, such as solar cells, wind power, and tidal power generation. There is a method. The present invention is primarily aimed at the former, direct use of solar heat.
This device uses materials that efficiently absorb the sun's radiant heat energy. The sun's radiant thermal energy is concentrated between wavelengths of 0.2 to 4.0 μm, but the wavelength at which the energy density peaks is 0.425 μm, with energy at wavelengths of 1.5 μm or less accounting for most of the energy. Therefore, in order to efficiently absorb solar energy, it is necessary to have a high absorption rate in the visible light wavelength region of 1.5 μm or less. The conventional method for improving the absorption characteristics of solar energy is mainly surface treatment of metals. For example, there is a method of depositing or coating a semiconductor such as germanium, silicon, or lead sulfide on the surface of an aluminum plate and utilizing the selective absorption characteristics of the semiconductor. There are also methods of chemical conversion treatment on the surface of stainless steel and copper plates to form oxide films such as Fe2O3 and CuO, methods of blackening the surfaces of aluminum and copper plates by plating them with nickel or chromium,
There is a method of applying black paint to an aluminum plate.
These methods are not necessarily sufficient in terms of economy, material durability, or performance itself. Another way to improve the solar energy absorption characteristics is to roughen the surface of the metal plate and increase its surface area, but it is generally difficult to control the roughness, and it is difficult to control the roughness and the degree of roughness that is appropriate for the solar energy absorption characteristics. Its control method has not been established. The present invention provides a material that efficiently absorbs solar radiant heat energy, which is completely different from conventional metal materials and surface-treated materials, and a device using the same.

It is known that light absorption in metals is caused by conduction electrons in the far-infrared region, and the absorption rate increases as the electrical resistance increases, but in the visible light region, the mechanism of light absorption is complex. It behaves differently depending on the type of metal, and its quantitative rules have not been elucidated. Copper plates, which are often used as solar heat absorbing substrates, have a temporary increase in absorption on the short wavelength side in the visible light range, but the absorption rate at a wavelength of 0.45 μm is about 60%, making it insufficient as an absorption material. . Furthermore, aluminum also has an absorption rate of only about 10% in a wavelength range of 0.2 μm or more. Various substances produced by treating metal surfaces can have various properties; for example, CU2
Although O has an absorption edge at 0.63 μm, it is difficult to use it industrially effectively using conventional techniques, as it can be obtained in the form of extremely thin plate-like crystals. The present inventors have discovered that an amorphous metal consisting of a combination of metallic elements and metalloid elements exhibits solar energy absorption characteristics that are different from those of conventional metals. We have devised a device with excellent solar heat absorption efficiency by using it as a solar heat absorbing material.

Amorphous metal refers to a substance in which a diffraction pattern characteristic of crystals cannot be obtained by ordinary X-ray or electron beam diffraction, but a wide halo pattern is obtained. Although the atomic arrangement of amorphous metal metal is currently unknown, for example, the specific electrical resistance of amorphous Fe8Opl3c7 component rapidly cooled from a molten state is 135 μΩ・o at room temperature, which is about twice that of pure iron.
Although it is called a metal, the bonding state of the atoms is expected to be quite different from the metallic bonding in the crystalline state. The present inventors noted that since the optical properties of metals are controlled by the electronic states of metal atoms, amorphous metals can have properties that are different from those of conventional metal materials in their solar energy absorption properties. , developed an efficient solar heat absorbing material by using amorphous metals. Next, the present invention will be explained in detail.

There are various methods for manufacturing amorphous metals, such as rapid cooling from a liquid state, vapor deposition, and plating, but since the amorphous state is thermally unstable, the material is manufactured during the material manufacturing process to prevent crystallization. It is necessary to lower the temperature of

For this reason, the material is usually in the form of a thin piece. The thickness varies depending on the composition of the material, and with the composition of Pd8OSi2O, it is possible to make it into an amorphous state with a thickness of about 1TnIn by rapid cooling from a liquid, but when the main elements are iron, nickel, etc. In component systems, the thickness is usually several + Pm. Depending on the manufacturing conditions of amorphous metals, particularly the cooling rate, there are cases where the entire material is crystallized, and cases where regions in a partially crystalline state are mixed, and various physical properties change accordingly. Although the transition between the amorphous state and the crystalline state is not always clearly distinguished, the inclusion of the crystalline state usually causes spots or stripes peculiar to crystals to coexist in the halo pattern of the X-ray diffraction image. The present invention is characterized by utilizing the fact that the electronic state of an amorphous material is different from that of a crystal, and there is no need to use a material that is 100% amorphous. The optimal component system and amorphous state can be selected by considering solar heat absorption efficiency, corrosion resistance, and economic efficiency.In order to take advantage of the characteristics of amorphous metals, it is possible to It is sufficient if the area occupied is 30% or more. Therefore, in the present invention, the degree of amorphousness required for the solar heat absorbing material is set to 30% or more in terms of the number of atoms. There have been many reports on the component systems of amorphous metals. It is important for the amorphous metal of the present invention to withstand temperature rises due to absorption of solar heat, and the composition is not particularly limited, but it is economically and industrially easy to obtain in large quantities from a molten state. The following components are preferable. That is, B, C, Si,,
Combinations of transition metals such as Fe, CO, Ni, and Cr containing 5 to 30 atomic percent of elements such as Al, P, S, and Se can be cooled from the molten state to a non-thermal state at a cooling rate of 1 (1 f' to 1 Cf' C/sec). It is a component system that easily crystallizes.Among these, C
r, Ni has the effect of particularly improving corrosion resistance and is suitable for long-term use as a solar heat absorbing material. Corrosion resistance is further improved by swelling by atomic percent. If it is less than 2%, the effect is small, and if it is more than 40%, ductility is lost and handling becomes difficult.

Furthermore, with Fe as the basic component, Cr, MO, W, etc.
% or more of the component will easily become amorphous. Amorphous metals convert to a crystalline state as the temperature increases. Although the temperature varies depending on the composition of the material, when the sample temperature is increased in the measurement of specific heat, an exothermic peak occurs, and this temperature is taken as the crystallization temperature. For solar heat absorbing materials, the temperature of the material increases, so materials with a low crystallization temperature or materials whose properties change drastically as the temperature rises as they absorb solar heat are unsuitable. The reference temperature is the boiling temperature of the medium for recovering heat from the material, usually water. Therefore, the present invention targets amorphous metals with a crystallization temperature of 100°C, but one aspect of the present invention is to heat amorphous metals and partially transform them into a crystalline state or a state close to it. It's about adding. The amorphous metal in the present invention is B, C
, Si, Al, S, Se, P, and other so-called metalloid elements. Therefore, in the process of converting from an amorphous state to a crystalline state, an electronic state different from that of normal metallic bonds is created between metal elements and metalloid elements or between metalloid atoms, resulting in the absorption of solar energy. Characteristics that differ from those of ordinary metals arise. In the present invention, heat treatment is applied to the amorphous metal. In this case, the heating temperature was set to 130°C or higher because if heating at a temperature lower than that causes a noticeable change in state, the temperature rises due to absorption of solar heat and changes over time during use. This is because it is inappropriate.

Also, if the heating temperature is too high, crystallization will progress. However, the amorphous characteristics are lost. Therefore, in the present invention, it has been found that it is practical to set the upper limit of the heating temperature to the crystallization temperature plus 500°C. The appropriate holding time at the heating temperature varies depending on the temperature and material composition. As mentioned earlier, the change from the amorphous state to the crystalline state involves local nucleation and growth processes, so the size of the region in the crystalline or semi-crystalline state depends on the processing temperature and time. This is because it can be controlled by This condition varies depending on the type of material, and the relationship between temperature and time is complex, so general quantitative expression is difficult, but this is not the essential point of the present invention. Note that since an amorphous metal material has a higher electrical resistance than a crystalline metal, it is generally expected that its emissivity in the infrared region is higher than that of a crystalline metal.

However, the present inventor obtained a value of 0.20 as the emissivity at a wavelength of 5 μm when an amorphous metal such as Nl75B8Sil7 is heated to 150° C. This value is sufficiently acceptable for a solar heat absorbing material, and the emissivity can be further reduced by coating the surface of the material with an antireflection material such as SiO. Next, examples of the present invention are shown in Table-1.

Although the specific structure of the device using an amorphous metal as a solar heat absorbing material in the present invention is not particularly limited, it is preferable to use the device in such a way that the temperature of the material does not exceed 300°C.

For example, as shown in FIG. 1, there is a structure in which water 3 is passed through a stainless steel box 2 containing an amorphous ribbon 1 (4 in the figure is a cover glass), or a structure in which water 3 is allowed to flow as shown in FIG.
A device having a structure in which an amorphous metal thin piece 6 is adhered to the surface of a vibrator 5 made of aluminum or stainless steel is effective. To give an example of the characteristics of the material of the present invention used in such a device, an amorphous metal such as Ni75Sil7B8 (quenched from a molten state) has an absorption rate of 0.80 in the visible wavelength region of 0.45 μm, which is normal. This is an excellent value of less than one-third that of stainless steel. In addition, the emissivity of this material in the infrared region of 8 μm is 0.19 at 150°C, which is comparable to stainless steel, and the ratio of visible light absorption rate to infrared emissivity, which is characterized as a solar heat absorbing material. It has far superior properties compared to stainless steel. In addition, the material obtained by aging this material at 400°C for 1000 particles and cooling it has a visible light absorption rate of 0.
70 to 0.82, and the emissivity in the infrared region is 0.15 to 0.82.
It is extremely excellent at 0.10. Furthermore, Fe72cr
The material (quenched from the molten state) having the composition of 8pl3c7 had an absorption rate of 0.76 to 0.85 in the visible light region and an emissivity of 0.20 to 0.15 in the infrared region.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the device of the present invention using an amorphous metal ribbon solar heat absorbing material and running water as a heat recovery medium. Fig. 2 shows an amorphous metal bonded to the outer surface of an aluminum vibrator and heat recovery on the inner surface of the vibrator. FIG. 1 is a schematic diagram of an apparatus of the present invention in which water as a medium is allowed to pass through. 1...Amorphous ribbon, 2...Stainless steel box, 3...Water, 4...Glass cover, 5...Aluminum Vibrator, 6...
・Amorphous metal flakes.

Claims (1)

[Claims] 1 or 2 of B, C, P, Ci, Al, S, Se
5 to 30% of the species or more in atomic percent, and the balance Fe, Co
, Ni, Cr, and unavoidable impurities, and is a metal in which at least 30% of atoms are in an amorphous state. 2 One or two of B, C, P, Ci, Al, S, Se
5 to 30% in atomic percent of species or more, Cr, Cu, T
Consisting of 2 to 40% of one or more of i, Mo, and W, and the balance of one or more of Fe, Co, and Ni and unavoidable impurities, and at least 30% of the atoms are in an amorphous state. A direct absorber of solar combustion, which is a metal. 3 One or two of B, C, P, Ci, Al, S, Se
5 to 30% in atomic percent of species or more, balance Fe, Co
, Ni, Cr, or a metal consisting of one or more of Cr and unavoidable impurities, or B, C, P, Ci, Al, S, S
5 to 30% by atomic percent of one or more types of e
, 2 to 40% of one or more of Cr, Cu, Ti, Mo, and W and the balance of one or more of Fe, Co, and Ni and unavoidable impurities at 130°C or higher, and the amorphous 1. A method for producing a direct solar heat absorbing material, which comprises heating the material to a temperature of 500° C. or less above the crystallization temperature of a quality metal and cooling it immediately or after holding.