JPS6054888B2 - Far-infrared radiating materials and radiators - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a far-infrared radiator and a far-infrared radiator that emit far-infrared rays at high emissivity.

Infrared rays have a longer wavelength than visible light, but shorter than microwaves, about 0.75 μ to 1 Wg! It is an electromagnetic wave in the wavelength range of l.

In general, near-infrared light is about 2.5μ or less, and 2.
Infrared rays of about 5 to 25μ are called ordinary infrared rays, and those of about 25μ or more are called far infrared rays. Furthermore, far-infrared rays are used as opposed to near-infrared rays, and the total number of infrared rays, including ordinary infrared rays, is about 2.5
Sometimes referred to as wavelengths greater than μ. In the present invention, what is referred to as far infrared rays has the latter meaning. Further, in the radiation with large radiant energy emitted from a heated object, there is particularly little far-infrared rays with long wavelengths, and the wavelength of far-infrared rays that can be discussed as radiant energy is generally 25μ or less. Infrared rays have a strong thermal effect and can travel through space to directly reach and heat low-temperature objects, and have been widely used for drying, heating, treatment, etc. since ancient times.

The infrared rays that have been used up until now have mainly been near-infrared, but research on far-infrared has recently become active due to the fact that far-infrared rays have better thermal efficiency than near-infrared rays. Many heaters and the like that utilize far infrared rays have been proposed. For example, when far infrared rays with a wavelength of 10 μm or more are radiated to the human body, it promotes sweating and blood circulation, which is said to have medical and health benefits. Further, heating or drying using far infrared rays has many features such as high thermal efficiency, no unevenness depending on the color of the heated object, and the ability to heat the inside of the object. When any object becomes hot, at low temperatures the proportion of long-wavelength infrared rays increases, and as the temperature rises, short-wavelength infrared rays become abundant, and eventually visible light is also included.

When using far infrared rays, it is of course necessary that these objects emit radiation rich in far infrared rays. This temperature is generally below 7-800°C. At high temperatures, the amount of far infrared rays increases, but the ratio of near infrared rays and visible rays increases, resulting in poor energy efficiency. Furthermore, if the object that is heated to a high temperature and emits radiation is a perfect black body, the radiant energy for each wavelength at each temperature can be calculated theoretically and shows the maximum value.

However, real objects are completely black bodies.Blackness (emissivity)
, and its radiant energy value is lower than that of a black body. The emissivity of various substances is shown in many documents, but most of these are the emissivity when the emissivity is constant with respect to wavelength (gray body). It is desirable that the far-infrared radiator has high emissivity in the far-infrared region and low emissivity in the low wavelength region.

The present inventors have previously invented a material suitable as a far-infrared radiator, and these materials include Y2O3, L32O3, C
It is ZrO2 in which a rare earth element component such as eO2 is dissolved. The emissivity of far infrared rays of the substance is 40% or less when the wavelength is approximately 6 μm or less, and is 70% or more when the wavelength is 8 μm or more.
An object of the present invention is to provide a material with high far-infrared emissivity and a far-infrared radiator formed from the material.

The far-infrared radiating material according to the present invention includes zirconium oxide, or 10 parts of zirconium oxide, magnesium oxide, magnesium oxide,
It consists of a powder of a zirconium oxide solid solution obtained by adding 4 to 8 parts by weight of calcium oxide or magnesium oxide and calcium oxide to completely or at least two-thirds or more of the solid solution, and the powder has a specific surface area of 10 d/ g
This is a far-infrared radiating material characterized by the following characteristics.
Further, the far-infrared radiator according to the present invention includes sodium silicate, silica sol,
Silica-based binder such as silica gel emulsion is
This far-infrared radiator is characterized in that it is made by adding 2 to 5 parts by weight of the above ingredients, kneading, coating or forming the mixture. In a preferred embodiment of the far-infrared radiating material and radiator according to the present invention, the powder has a specific surface area of 5 to 0.01, more preferably 5 to 0.01.
1 i/g.

Many ceramic materials have high emissivity in the long wavelength region, but wavelength characteristics vary depending on the material. Zirconia series,
Zircon and the like are said to be suitable as far-infrared emitting materials, but materials that have a sufficiently high emissivity in the far-infrared region of approximately 10 μm or more and a sufficiently low emissivity in the wavelength region of 5 μm or less. was not seen. As mentioned above, the inventors of the present invention have repeatedly researched zirconia-based ceramics and have discovered an excellent far-infrared radiator.

As a result of further research by the present inventors, we found that zirconium oxide (ZrO2) generally has a high emissivity in the far infrared region of 10 μm or more, and is small below that, but this emissivity is significantly affected by the particle size of ZrO2. The present invention was completed based on this discovery. That is, the required particle size range of ZrO2 powder is 10 to 0.01 d/g1, preferably 5 to 0.01 d/g in specific surface area.
It is 0.1 i/g. Until now, the relationship between the particle size of a radiator and its radiation characteristics has hardly been studied, and it was through research by the present inventors that for the first time a ZrO2 powder having a particle size range that exhibits excellent radiation characteristics was discovered. It is desirable that the purity of the ZrO2 powder is high, but it does not need to be almost 100%, and Fe2O3, TiO2 of about 1% or less that is unavoidably mixed or difficult to remove.
There is no problem with the mixture of the following. In addition, ZrO2 is 1000 to 1
Transformation occurs at 100°C and expansion and contraction occurs at this temperature, so when using it above that temperature, it is necessary to add other metal oxides to ZrO2 in advance to stabilize it as a solid solution with it. ing. In the case of a far-infrared radiator for the purpose of the present invention, magnesium oxide (MgO) is added to ZrO2.
Alternatively, the same emissivity can be obtained by adding 4 to 8% of calcium oxide (CaO) and converting two-thirds or more into a solid solution. ZrO2 is CaO, . MgO,. When Y2O2 or the like is dissolved as a solid solution, the monoclinic system changes to the cubic system, and the coefficient of thermal expansion increases from ~7x10-6/°C to 11x10-6/°C. Therefore, it is desirable that the coefficient of thermal expansion is small, and 10
If it is not heated to 00°C or higher, it is better not to form a solid solution. When used in applications where a large coefficient of thermal expansion is better or even acceptable, for example when dispersing on a metal substrate, it is best to make it into a solid solution to increase the coefficient of thermal expansion and stabilize it. The difference in thermal expansion with the substrate is reduced, making it resistant to heat cycles. However, ZrO2 is replaced by CaO or/
It is not easy to form a complete solid solution with ZrO and MgO, and if it is electrically melted, it will completely become a solid solution and become a single phase of cubic ZrO2, but if the firing temperature is low, for example 1600 ° C or less, It does not completely become a solid solution, but becomes a semi-stable state in which it forms three phases consisting of cubic ZrO2, monoclinic ZrO2, and CaO or/and MgO.

Further, when the amount of CaO and/or ρ is 3% or less, which is about half of the amount required for complete solid solution, a partially stabilized state is created in which monoclinic and cubic ZrO2 coexist. This state is intentionally maintained from the beginning, such as when creating a ZrO2 sintered body that is resistant to thermal shock. When such multiple phases exist, the far-infrared radiation characteristics deteriorate, so CaO. M
When forming a far-infrared ray emitting material in a solid solution with gO, it is desirable to form a complete solid solution, and at least 213 must be in a solid solution.

The state of solid solution formation can be determined based on the analysis value of CaO and/or MgO by X-rays and the quantitative ratio of cubic ZrO2 and monoclinic ZrO2. The emissivity of the far-infrared radiation material of the present invention produced as described above is 40% or less in the wavelength region of 5 μm or less, and Cri9O% or more in the wavelength region of 10 pm or more.

Next, examples of far-infrared radiating materials according to the present invention will be shown. ZrO2 or ZrO with the components, specific surface area and solid solution rate in Table 1
FIGS. 1 and 2 show the results of measuring the emissivity spectrum of the two solid solution powders.

Comparative examples of those with a specific surface area of 10 d/g or more and those with a solid solution rate of two-thirds or less shown in Table 2 are also shown in Figures 1 and 2.
As shown in the figure. The emissivity spectrum was obtained using a Hitachi infrared spectrometer 260.
-30, the radiant energy of the perfect black body and the sample was measured for each wavelength, and the emissivity was calculated and displayed.

The measurement temperature was 500°C. Normally 350~650℃
However, in this temperature range, the change in the radiant energy spectrum due to material temperature is small. The far-infrared radiator according to the present invention is obtained by kneading the above-mentioned infrared ray radiating material with a silica-based binder, and forming the coating 2.

Good results cannot be obtained if a phosphate-based binder is used. As a binder, water glass (sodium silicate)
A silica-based binder such as silica sol, silica gel emulsion, or ethyl silicate is used as SiO2 in an amount of 2 to 5% for the infrared radiation material. In one example, 100g of ZrO2 powder (99% product)
Water glass (No. 4) 15C. C (10~
201). Possible within the range of C.

) Water 40C. Mix 1 g of C carboxymethyl cellulose in a pot mill for 2 hours, dry it, and apply 0.1Tn onto ceramics and metal substrates by brushing, dipping, spraying, etc.
After coating and drying the film to a thickness of 100° C., heat treatment was performed at 400° C. for 2 hours. When the rapid heating and air cooling test at 800° C. was repeated 10 times, the coating applied to ceramics did not cause any peeling or cracking, but the coating applied to the metal substrate showed some cracking.

The far-infrared radiator according to the present invention can be formed by coating it on a substrate, or by constructing a required mold, pouring a mixture of far-infrared radiating material and a binder into the mold, molding, drying, and baking. You can. When the emissivity spectrum of the far-infrared radiator according to the present invention was measured, a spectrum substantially similar to that of the far-infrared radiator was obtained.

As described above, the far-infrared radiating material and radiator according to the present invention have a large emissivity in the long wavelength region of far infrared rays of 10 pm or more, and a small emissivity in the short wavelength region of 5 μm or less. Radiant energy can be radiated with excellent efficiency, and the radiant energy can be enriched in long-wavelength far-infrared rays.

Therefore, the radiant energy can be efficiently used for drying, heating, treatment, etc.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are emissivity spectra of far-infrared radiating materials of Examples and Comparative Examples of the present invention, respectively.

Claims (1)

[Scope of Claims] 1. Zirconium oxide, or 4 to 8 parts by weight of magnesium oxide, calcium oxide, or magnesium oxide and calcium oxide are added to 100 parts by weight of zirconium oxide, and completely or at least two-thirds or more of it is made into a solid solution. 1. A far-infrared radiating material comprising a powder of a zirconium oxide solid solution obtained by the above-mentioned method, wherein the powder has a specific surface area of 10 m^2/g or less. 2. The far-infrared radiating material according to claim 1, wherein the powder has a specific surface area of 10 to 0.01 m^2/g. 3. The far-infrared radiating material according to claim 1, wherein the powder has a specific surface area of 5 to 0.1 m^2/g. 4. Zirconium oxide, or zirconium oxide obtained by adding 4 to 8 parts by weight of magnesium oxide, calcium oxide, or magnesium oxide and calcium oxide to 100 parts by weight of zirconium oxide, and completely or at least two-thirds or more of it as a solid solution. A silica-based binder such as sodium silicate, silica sol, or silica gel emulsion is added to 100 parts by weight of a far-infrared radiation material that is a solid solution powder and has a specific surface area of 10 to 0.01 m^2/g.
A far-infrared radiator characterized in that it is formed by adding 2 to 5 parts by weight of 2 to 5 parts by weight, kneading, coating or forming. 5. The far-infrared radiator according to claim 3, wherein the powder has a specific surface area of 5 to 0.1 m^2/g.