JPH05301788A - Infrared ray emitter - Google Patents

Abstract

PURPOSE:To provide an infrared ray emitter capable of stably obtaining a high emissivity even in a short wavelength region of <=7mum and withstand the use at temperature as high as about 300 deg.C. CONSTITUTION:The objective infrared ray emitter is obtained by forming an anodized film 4 having >=10mum thickness on the surface of a complex sintered compact in which 2-50vol.% ceramic fine powder particles 3 are dispersed in an aluminum base material 2 as a substrate 1. One or two or more selected from respective oxides of Al, Si, Mg, Ni, Cr, Zr, Cu, Fe, Mn and Ti, double oxides thereof and SiC are used as the ceramic and particles having 325 mesh particle size are used as the fine powder particles.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared radiator which emits infrared rays for heating, cooking, heating and drying, heat treatment of materials, and various other types of radiant heating, and particularly to a far infrared region having a short wavelength. The present invention relates to an infrared radiator having excellent infrared (far infrared) radiation characteristics.

[0002]

2. Description of the Related Art Generally, in heaters utilizing infrared rays, the infrared emissivity of the radiator is high and the temperature is 100 ° C.
The above-mentioned relatively low surface temperature emits a small amount of radiation in the visible region, while it requires a large amount of radiation in the far infrared region. As a radiator satisfying such requirements, conventionally, alumina,
Those made of various ceramic materials such as graphite and zirconia have been put into practical use. Among these materials, it is known that alumina has excellent performance in comparison with other ceramic materials in terms of far infrared radiation characteristics and heat resistance.

However, the infrared radiator made of a conventional ceramic material has a large weight and is easily broken,
Furthermore, it is difficult to make a thin one, and the thermal conductivity is inferior, so the heating efficiency of the radiator is poor.

Therefore, a radiator in which ceramics are sprayed on the surface of a metal substrate has been put into practical use, but in this case, the manufacturing cost is high and it is difficult to obtain a thin plate or a radiator having a complicated shape. There is a problem such as.

On the other hand, recently, there is also known an infrared radiator in which an anodized film is formed on the surface of an aluminum alloy wrought material to form an anodized film (alumite film) having a thickness of about 20 μm or more. In this case, the anodized film on the surface is
For infrared rays with a wavelength of about 7 μm or more, the emissivity is 0.
It is known to exhibit excellent radiation characteristics of 8 or more. In addition, since the base material of such an infrared radiator is an aluminum alloy wrought material, it is lighter in weight and less prone to cracking than when it is entirely made of a ceramic material, and various molding processes are easy, and further, heat conduction It has various advantages such as good property.

[0006]

As described above, an infrared radiator formed by forming an anodized film on the surface of an aluminum alloy wrought material exhibits excellent radiation characteristics at a wavelength of 7 μm or more, but has a wavelength of 7 μm or less. In the region, the emissivity was extremely low. The anodized film of aluminum alloy wrought material has low heat resistance, and is formed by long-term use at a surface temperature of about 150 ° C or higher, or by heat cycle between normal temperature and high temperature of about 200 ° C or higher. There is a problem that cracks tend to occur. If cracks occur in the anodized film in this manner, the emissivity becomes unstable and the corrosion resistance deteriorates. In addition, when the thickness of the aluminum alloy wrought material that produced the anodized film is thin,
There is also a problem that thermal deformation occurs due to long-term use at about 150 ° C. or higher or heat cycle use, which causes warping or abnormal deformation of the infrared radiator.

The present invention has been made in view of the above circumstances. As described above, the characteristics of the aluminum anodic oxide film exhibiting excellent radiation characteristics in the wavelength range of 7 μm or more are effectively utilized, and at the same time, the aluminum alloy is expanded. Eliminates the drawbacks of conventional infrared radiators that have an anodized film formed on the material,
It is intended to provide a novel infrared radiator. Specifically, not only the wavelength range of 7 μm or more but also 7 μm
It has excellent radiation characteristics even in a short wavelength range of m or less, and has excellent heat resistance. It shows stable radiation performance up to about 300 ° C without causing cracks even at high temperatures exceeding 150 to 200 ° C, and also causes thermal deformation. It is intended to provide a difficult infrared radiator.

[0008]

In order to solve the above-mentioned problems, the infrared radiator according to the invention of claim 1 is basically 2 to 50 vol% in the base material made of aluminum or aluminum alloy. As a base material, a composite sintered body in which the ceramic fine powder particles of
The structure is such that an anodized film having a thickness of 0 μm or more is formed.

An infrared radiator according to a second aspect of the present invention is the infrared radiator according to the first aspect, wherein the ceramic fine powder particles are Al, Si, Mg, Ni, Cr, Zr, C.
One kind or two or more kinds selected from each oxide of u, Fe, Mn, and Ti, a composite oxide thereof, or SiC is used.

Furthermore, the infrared radiator according to the invention of claim 3 is
In the infrared radiator according to claim 1, the fine ceramic powder particles have a particle size of -325 mesh.

[0011]

The concept of the infrared radiator of the present invention is shown in FIG.
Shown in. In FIG. 1, a base material 1 is composed of a composite sintered body in which ceramic fine powder particles 3 are uniformly dispersed in a base material 2 made of aluminum or an aluminum alloy. The fine ceramic powder particles 3 are evenly dispersed in the oxide film 4. Here, the anodic oxide coating of an aluminum material itself has good infrared radiation characteristics, particularly excellent radiation characteristics at 7 μm or more, and the ceramic fine particles dispersed therein have excellent infrared radiation characteristics. It has excellent radiation characteristics, especially in a wavelength range of 7 μm or more as well as in a short wavelength range of 7 μm or less, and the dispersion of the ceramic fine powder particles causes the coating to have a muddy color tone and a reduced brightness. As a result of these synergistic effects, the anodized film in which the fine ceramic powder particles are uniformly dispersed exhibits excellent infrared radiation characteristics, and particularly excellent radiation is obtained not only in the wavelength range of 7 μm or more but also in the short wavelength range of 7 μm or less. It will show characteristics.

Further, since the ceramic fine powder particles uniformly dispersed in the anodized film serve as stress relaxation points, there is little possibility that cracks will occur in the film due to thermal strain due to heat cycle and the like, and further cracks will occur. However, since the propagation of cracks is blocked by the fine ceramic powder particles, the growth of cracks is prevented. That is, since the cracks due to thermal strain in the film are less likely to grow or grow, the heat resistance of the film is excellent, long-term continuous use at high temperature, or heat cycle like between room temperature and high temperature. Without cracking even when used,
It exhibits stable infrared radiation characteristics up to about 300 ° C.

Further, the base material itself is made of a composite sintered body in which fine ceramic powder particles are dispersed in aluminum or an aluminum alloy, and such a composite sintered body is compared with a wrought material made of aluminum or an aluminum alloy. It has remarkably high strength, especially high temperature strength, and therefore there is little risk that the substrate itself is deformed due to thermal strain at high temperature, and it can be sufficiently used up to about 300 ° C. Also, since the base material is a sintered body, an infrared radiator with a complicated shape, which is difficult to form by cutting or the like,
It can be obtained accurately, easily and inexpensively.

Further, the anodized film is formed by subjecting the surface of the base material to anodizing treatment, and it is integrated with the base material portion so that they are completely adhered to each other. Since the ceramic fine powder particles are embedded in the anodized film in a dispersed state, there is little risk that the ceramic fine powder particles will fall off.

The blending ratio of the fine ceramic powder particles in the base material must be in the range of 2 to 50 vol% in total. If the ratio of the ceramic fine powder is less than 2 vol%, the effect of obtaining excellent radiation characteristics cannot be sufficiently obtained even in a short wavelength region of 7 μm or less as described above. On the other hand, if the ratio of the ceramic fine powder exceeds 50 vol%, it becomes difficult to produce a sound sintered body with few defects, and the anodizing treatment property deteriorates to form a uniform anodized film. It will be difficult. Even within the range of 2 to 50 vol%, especially 5 to 2
It is preferably within the range of 5 vol%, and especially between 10 and 2
The optimum range is 0 vol%.

The fine ceramic powder particles are A
l, Si, Mg, Ni, Cr, Zr, Cu, Fe, M
It is suitable to use one or two or more kinds of mixed powder selected from oxides of n and Ti, composite oxides thereof, and SiC. Specifically, for example, Al ₂
O ₃ , SiO ₂ , MgO, SiC, NiO, Cr
₂ O ₃ , ZrO ₂ , CuO, Fe ₂ O ₃ and MnO ₂ are typical, and one or more of these may be used. According to the experiments conducted by the present inventors, all of these ceramic fine powders are uniformly dispersed in the anodic oxide coating to provide the anodic oxide coating with excellent infrared radiation characteristics even in a short wavelength region of 7 μm or less. It has been found that it contributes to the heat resistance of the film. Further, in producing the infrared radiator of the present invention, it is essential to carry out anodizing treatment with an aqueous solution of acid or alkali, and therefore the ceramic powder particles are dissolved by these treating liquids during anodizing treatment,
Although it is necessary to avoid causing structural changes, the ceramic materials listed above are not particularly problematic in this respect as well.

Of the ten types of ceramic materials described above, only one type can be used, but since the radiation characteristics differ at least slightly depending on the ceramic material, a plurality of types of ceramic materials are used in combination. It is desirable to average the different radiative properties of the ceramic material so that they exhibit excellent radiative properties on average. When only one type of ceramic material is used, it is desirable that the mixing ratio of the ceramic fine powder is 5 vol% or more in order to stably obtain excellent radiation characteristics even in a short wavelength region of 7 μm or less.

Further, as the fine ceramic powder particles, it is desirable to use those having a particle size of -325 mesh (325 mesh under, that is, about 44 μm or less). If the particle size is larger than this, it becomes difficult to obtain the above-mentioned effects sufficiently.

Any aluminum or aluminum alloy can be used as the base material of the composite sintered body of the base material, but it is usually preferable to use pure aluminum having a purity of 99% or more. The particle size of the base material (aluminum or aluminum alloy) powder before sintering is not particularly limited, but it is usually -3 as with the ceramic fine powder particles.
It is preferably about 25 mesh.

The film thickness of the anodized film must be 10 μm or more. If the film thickness is less than 10 μm, the infrared radiation performance deteriorates, and it becomes difficult to obtain a stable high emissivity over a wide wavelength range.

A specific method for producing the composite sintered body of the base material is not particularly limited, but powder of aluminum or aluminum alloy and one kind or two or more kinds of ceramic fine powder are mixed at a predetermined mixing ratio, After stirring, the mixed powder may be molded and sintered by the same method as applied to ordinary aluminum-based sintered materials, such as press molding, extrusion molding, rubber pressing, and explosion. Any method such as a powder molding method using force, a high temperature pressing method (hot pressing), a method of continuously obtaining a strip, or a slip casting method can be applied.

Further, the method of anodizing the surface of the base material is not particularly limited. For example, in the case of acidic electrolyte, inorganic acid such as sulfuric acid and oxalic acid, or organic acid,
Furthermore, an anodizing treatment may be performed using an electrolytic bath of these mixed acids or the like and using an arbitrary waveform such as direct current, alternating current, alternating / direct combination, or alternating / superimposed waveform as the electrolytic waveform.
However, from the viewpoint of economy and work efficiency, it is desirable to use a direct current in the sulfuric acid bath. By anodizing the base material in this way, the anodized film grows with the ceramic fine powder particles in the base material taken in as it is, and the fine ceramic powder is uniformly dispersed in the anodized film. Is formed.

[0023]

Example No. 1 in Table 1 1-No. 19 and 1 or 2 or more types of ceramic fine powder (grain size -325 mesh) and pure aluminum powder (grain size -32).
5 mesh) was mixed, mixed and stirred, and then a rubber compact was used to prepare a cylindrical powder compact having a diameter of 50 mm and a length of 100 mm, which was sintered to obtain a sintered body. A 5 mm x 30 mm x 30 mm square flat plate-shaped sample was cut out from each cylindrical sintered body, and anodized by direct current using a sulfuric acid electrolytic bath, and then 5 μm, 10 μm, 20 μm, 30 μm, 40 μm.
Anodized films with various thicknesses of m were formed.

For each sample, the spectral emissivity curve from wavelength 3 μm to 30 μm was examined at a temperature of 300 ° C., and the total emissivity in that case was calculated. The results are shown in Table 2 for each thickness of the anodized film for each sample. Further, among the samples, the sample number No. The spectral emissivity curve at 300 ° C. when the anodic oxide film having a film thickness of 30 μm was formed on the sample No. 5 (using a composite sintered body containing 10 kinds of fine ceramic powders) is shown by the curve No. 2 in FIG. 5 and the sample number No. Sample No. 1 (using an aluminum single sintered body not containing fine ceramic powder) Film thickness 30
The spectral emissivity curve at 300 ° C. when the anodic oxide film having a thickness of μm is formed is shown in FIG. It shows with 1. Furthermore, the sample number No. Spectral emissivity curves under the same conditions as above for Nos. 4, 6, 7, 8, 9, and 10 are the curve No. of FIG. 4,
It is shown by 6, 7, 8, 9, and 10. For comparison, a conventional ordinary pure aluminum wrought material that is not a sintered body has a thickness of 30 μm.
FIG. 3 shows a spectral emissivity curve at 300 ° C. when the anodic oxide film of 1 is formed.

[0025]

[Table 1]

[0026]

[Table 2]

As is apparent from Table 2, No. 1 using a composite sintered body in which 10 kinds of ceramic fine powders were mixed in 1.5 vol% at a total of 15 vol% was used. In the sample of No. 5, the total emissivity at 300 ° C. is 0.
No. 98 using a sintered body in which a fine ceramic powder was not compounded, which was a remarkably high value of 98. The same film thickness of one sample,
It can be seen that it is significantly higher than the total emissivity of 0.68 at the same temperature. And this No. In the case of the sample of No. 5, the curve No. of FIG. As shown in 5, it was confirmed that a high emissivity can be stably obtained even in a short wavelength region of 7 μm or less.

No. 2 to No. Each of the samples of No. 4 uses a sintered body in which two kinds of ceramic fine powders are blended in a total amount of 10 vol%. Although lower than the sample of No. 5, No. 5 using a sintered body containing no ceramic fine powder was used. The value of total emissivity (0.
85) was obtained with a film thickness of 30 μm. These sample No.
2 to No. No. 4 of No. 4 FIG. 2 shows the spectral emissivity curve for No. 4, which shows that a relatively stable and high emissivity is obtained in a short wavelength range of 7 μm or less.

Further, No. 6-No. All 10 samples used one kind of alumina as a ceramic fine powder,
Although the compounding amount is changed in the range of 1 to 15 vol%, as shown in Table 2, if the compounding amount is 2 vol% or more, the film thickness is 10 μm or more and the total emissivity is 0.7 or more. It can be seen that a high emissivity is obtained and that a relatively high emissivity is obtained even in a short wavelength region as shown in FIG.

And again, No. 11-No. Each of the samples of No. 19 used a sintered body in which 5 vol% of one kind of ceramic fine powder was mixed, and in this case also, as shown in Table 2, No. Higher total emissivity values were obtained for the 1 sample.

[0031]

EFFECTS OF THE INVENTION According to the infrared radiator of the present invention, a high infrared emissivity can be stably obtained even in a short wavelength range of 7 μm or less as in the wavelength range of 7 μm or more, and the heat resistance of the anodized film is high. It has high properties, and even when it is used at a high temperature of about 300 ° C., a high emissivity can be stably obtained without cracks in the anodized film on the surface.
Also, the heat resistance and high temperature strength of the base material itself are excellent, so 3
There is little risk of warping or deformation of the base material due to thermal strain even at a high temperature of about 00 ° C, and eventually continuous use at that high temperature up to about 300 ° C or heat cycle use between normal temperature and high temperature. It can be used stably regardless of the above.

[Brief description of drawings]

FIG. 1 is a schematic view conceptually showing the cross-sectional structure of an example of the infrared radiator of the present invention.

FIG. 2 is a characteristic diagram showing a spectral emissivity curve in an infrared radiator of an example.

FIG. 3 is a characteristic diagram showing a spectral emissivity curve of an infrared radiator using a conventional ordinary aluminum wrought material.

Claims (3)

[Claims] 1. An anode having a thickness of 10 μm or more as a base material, which is a composite sintered body in which 2 to 50 vol% of fine ceramic powder particles are dispersed in a base material made of aluminum or an aluminum alloy. An infrared radiator having an oxide film formed thereon. 2. The fine ceramic powder particles are Al, S
i, Mg, Ni, Cr, Zr, Cu, Fe, Mn, Ti
2. The infrared radiator according to claim 1, which is one kind or two or more kinds selected from the respective oxides, complex oxides thereof, or SiC. 3. The infrared radiator according to claim 1, wherein the fine ceramic powder particles have a particle size of −325 mesh.