JPS5934233B2 - far infrared radiation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a far-infrared radiation device that is suitable for baking and drying paint, heating and keeping foods warm, space heating, etc., and also has an excellent design.

In general, a far-infrared radiation device is required to have the following properties.

1) In order to emit strong far-infrared rays, the emissivity of the emissive material must be close to 1 in the wavelength range of 4 to 50μ.

2) The radioactive substance must be thermally stable at high temperatures of 500 to 700°C.

3) It has great adhesion to the heat radiator and does not peel or crack during use in cooling and heating cycles.

4) Strong against mechanical shock.

5) The radioactive material is colorful and has a good design.

On the other hand, conventional far-infrared radiation devices include quartz tube heaters, ceramic tube heaters, thermal spray heaters, and the like. Quartz tube heaters and ceramic heaters have a structure in which a nichrome wire is coiled inside a quartz tube or a ceramic tube, and a thermal spray heater has a structure in which a nichrome wire is coiled inside a quartz tube or a ceramic tube. A heating element having a structure in which a linear heating element 3 having an electrode terminal 2 is pushed through and filled with a heat-resistant insulating filler 4 such as MVO and sealed with an airtight material 5 at both ends, and a heat radiating element 1 on the surface. Fe2O3, Co
It consists of a radiation layer 6 lined with oxides such as O, NiO, Mn0, etc. by plasma spraying. but,
The above quartz tube heater has an emissivity of 0 at wavelengths of 4μ or more.
．． 5 or less, which results in poor performance as a far-infrared radiating device, and in addition to being weak against mechanical shock, the heating wire is exposed to the air, resulting in drawbacks such as wire breakage due to oxidation.

Ceramic tube heaters have a high emissivity between 6μ and 15μ, and while they have excellent characteristics, they are weak against mechanical shock, and because the heating wire is exposed to the air, there is a problem of wire breakage due to progressing oxidation, resulting in a short lifespan. There were flaws. Furthermore, thermal spray heaters have excellent emissivity of 4 to 50μ, are resistant to mechanical shock,
It has the advantage of long life, but the emissive layer is Fe2O3, COO
, NiO3Mn0, etc., only a blackish color tone can be obtained, and blackish colors are preferable in terms of design, such as heating and keeping food warm, space heaters, etc., but are not suitable for applications such as heating and heating. The present invention has been made in consideration of the above-mentioned drawbacks, and is made by thermally spraying a mixed powder of at least 3% by weight or more of a blue radioactive material having a spinel structure of alumina and cobalt oxide and other ceramics. By lining the surface of the radiator, the emissivity is high in the wavelength range of 4 to 50μ, and the
It is possible to provide a far-infrared radiation device that is stable at temperatures of up to 700° C., has good adhesion to the heat radiator, has strong mechanical impact resistance, and is also excellent in color tone.

An embodiment of the present invention will be described below with reference to the drawings.

The compound of alumina and cobalt oxide used as a radioactive substance is made as follows. First, 100 to 300 mesh alumina powder and 250 to 500 mesh cobalt oxide powder are mixed uniformly at a weight ratio of 7:3, and then fired at a temperature of 1000 to 1400°C for 1 to 5 hours to oxidize the alumina and A solid phase reaction of cobalt is carried out. Through a solid-state reaction, cobalt oxide diffuses into alumina, creating a type of solid solution. After firing, excess cobalt oxide that does not participate in the solid phase reaction is dissolved and removed by immersing it in an acidic solvent, such as hydrochloric acid. The solid solution of alumina and cobalt oxide that was dissolved and removed is
Dry after neutral treatment or washing with water. Note that the temperature during firing was limited to 1000 to 1400°C as a temperature suitable for the solid phase reaction between alumina and cobalt oxide to proceed.

Further, the mixed powder after firing does not necessarily need to be treated with an acidic solvent, and the present invention is not limited thereto, but the acidic solvent treatment has the advantage that a clearer blue or cobalt blue color can be obtained. The obtained solid solution contains At, cO,
It was found that each O atom forms a ceramic spinel structure, which is thermally stable and has an emissivity superior to that obtained by simply mechanically mixing alumina and cobalt oxide at a range of 4 to 50μ.

Next, a method of lining the surface of the thermal radiator with a radiation material, which is an aluminum-cobalt oxide, by thermal spraying will be described.

First, as a pretreatment, the surface of the heat radiator is blasted with 30 to 80 mesh of alumina, steel, silicon carbide, or the like. Next, the base layer is lined with 150 to 300 meshes of Ni-Cr alloy to a thickness of 50 to 150 microns by thermal spraying. In the pretreatment mentioned above, the purpose of the blasting treatment is to mechanically roughen the surface of the heat radiator by removing oil and dirt, thereby improving the projection effect of Ni-Cr and, as a result, improving the adhesion of Ni-Cr. do. Also N
The i-Cr surface treatment is necessary for the following reasons. Since the ceramic lining for the radiation layer has a small coefficient of thermal expansion, if it is adhered to the surface of the heat radiator without Ni--Cr intervening, the radiation material may peel off during cold use. However, by providing the Ni--Cr intermediate layer, it serves to absorb thermal stress caused by the thermal expansion coefficients of the heat radiator and the radiation layer. A radiation layer is obtained by lining the Ni--Cr underlayer with, for example, the following ceramic powder by thermal spraying.

The mixture of the above example was applied to the surface of a sheathed heater (length 500" diameter 12fm, 100V, 500W) at 30 to 1
Thermal spray lining was applied to a thickness of 00 μm, and the radiation characteristics were investigated by applying electricity.

As shown in FIG. 2, the radiation characteristics were determined by measuring the specific radiation energy at 25 to 50 .mu. using an infrared spectrophotometer, and the radiation characteristics were superior to the conventional ceramic tube heater mainly composed of COO. Furthermore, the effect of dry baking of the paint was investigated, and the results shown in Table 1 were shown, and it was found that the paint was superior to the conventional example. In addition, taking into consideration the conditions of use in cold and heat, we conducted a cold and heat test between the operating temperature of 600℃ and room temperature, and as a result, no peeling or cracking occurred even after over 1000 cycles, and there was no problem with the product's lifespan. It has been found.

The mechanical impact strength of the radiation layer is very good due to its spinel structure. The reason why ceramics having a spinel structure of Al2O3COO, which is a radiation layer, is made to have a weight ratio of 3 or more is as follows. Ceramics with spinel structure are 3
If it is less than % by weight, the radiation properties are inferior and there is no pigment effect.
It is unsuitable for applications that require color tone. Preferably 1
The content is preferably 0% by weight or more, and ceramics having a 100(f) spinel structure may be used. As mentioned above, it has the characteristics of being able to provide a unique radiating device that has excellent radiation characteristics, cooling and heating properties, lifespan, mechanical strength, etc. that a far-infrared radiating device should have, and also has a cobalt blue color tone in terms of design. .

Claims (1)

[Claims] 1 Mixed powder of alumina and cobalt oxide
At least 3% by weight obtained by calcination at 1400°C. A far-infrared radiation device characterized in that the surface of a thermal radiator is lined with an aluminum-cobalt oxide having the spinel structure described above by a thermal spraying method.