JPH10154894A - Single layer magnetic wave absorbing material and use thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a single layer magnetic wave absorbing material which can be dismantled easily at the time of discard while preventing pollution by subjecting a titanate and an iron oxide or an oxide containing titanium and iron to reduction firing at a temperature higher than the melting point thereof, crushing a substance produced through quenching and subjecting the crushed substance again to reduction firing at a temperature lower than the melting point thereof. SOLUTION: A titanate and an iron oxide or an oxide containing titanium and iron containing 5-95wt.% of TiO2 for total 100% of TiO2 and Fe2 O3 expressed in term of oxide by weight ratio is subjected to reduction firing at a temperature higher than the melting point thereof. It is poured into a graphite container and cooled down with water to produce a mass of substance which is then crushed. It is subjected again to reduction firing at a temperature lower than the melting point thereof to produce a composition which is fixed and shaped with an insulating resin having dielectric constant of 4 or less. According to the method, a material which can be dismantled easily at the time of discard while preventing pollution can be produced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an electromagnetic wave absorber.

[0002]

2. Description of the Related Art A conventionally used electromagnetic wave absorbing material employs a method of attenuating electromagnetic waves by attaching a conductor plate to the back side. (Guidebook for measures against radio interference caused by radio wave absorbers 1981 Japan Broadcasting Corporation) The reason for this is to maximize the magnetic loss of ferrite by attaching a conductor plate to the back side to maximize the magnetic loss of ferrite. Because it must be. (A radio wave absorber Yoshiyuki Naito New OHM Bunko Ohmsha)

[0003]

In the method using a dielectric as an electromagnetic wave absorber, the thickness of the dielectric is large and is not practical in many cases. Theoretically, it has been found that the complete absorption of electromagnetic waves is limited to the case where the spatial impedance and the impedance of the electromagnetic wave absorber are equal, but such a material has not been obtained in practice. On the other hand, an increase in manufacturing cost, an increase in weight, and an increase in construction cost due to a multilayer structure or a structure backed by a metal plate for impedance matching are inevitable. Naturally, there is a demand for a material that is easily dismantled even at the time of disposal and does not cause pollution.

[0004]

Means for Solving the Problems The inventors of the present invention obtain a titanium oxide and an iron oxide, or an oxide containing titanium and iron, by reducing and firing the material at a temperature equal to or higher than the melting temperature of the material and rapidly cooling the material. A composition obtained by pulverizing the refractory substance and reducing and firing it again at a melting temperature or lower (Japanese Patent Publication No. 5-156).
No. 64) and other fillers can cause magnetic loss and dielectric loss at the same time. Therefore, it is necessary to attach a metal plate which has been used to eliminate unnecessary electromagnetic waves to be absorbed mainly by magnetic loss. I found it unnecessary.
In addition, when this combination is used as an electromagnetic wave absorber, a single-layer structure that does not require a conductor plate on the back side may be used, so that it is easy to manufacture, light in weight, simple in construction, and can reduce overall cost. I also found that. Furthermore, since non-polluting iron and titanium are used as main materials, there is no problem in environmental measures in all processes from production to disposal.

Hereinafter, the present invention will be described specifically. As an example of a method for producing a composition according to Japanese Patent Publication No. 5-15664, iron oxide, Fe ₂ O ₃
And titanium oxide, TiO
_{Use 2} . The two materials are mixed well and melted in an induction furnace, and the melt is immediately cooled with water, crushed, crushed and sieved. After further hydrogen reduction, pulverization and sieving are performed again to obtain fine powder. Various additives and binders are added to the fine powder to form and process. In general, it is known that an electromagnetic wave absorbing material completely absorbs an electromagnetic wave that reaches vertically to the surface of the electromagnetic wave absorbing material when the following formula is satisfied. (Yoshiyuki Fujitsu, Radio Wave Absorber New OHM Bunko Ohmsha) (√ (μ / ε)) ・ tanh (j ・ ω ・ (√ (ε ・ μ)) ・
d) = 377 [Ω] μ: complex permeability of electromagnetic wave absorbing material ε: complex permittivity of electromagnetic wave absorbing material j: imaginary unit vector ω: angular frequency of electromagnetic wave d: thickness of electromagnetic wave absorber When this formula is satisfied Can absorb all electromagnetic waves using only electromagnetic wave absorbing materials.

[0006] The electromagnetic wave absorber of the present invention is characterized in that
By combining the composition according to JP-A-156664 with a binder having material properties satisfying the above formula, it was realized that there was no need to attach a conductor plate to the back side of the electromagnetic wave absorber. As the material of the binder, an insulating material having a relative dielectric constant of 4 or less, for example, various resins, glass, ceramics, concrete, paper, and the like can be used.

Conventionally, the presence of a steel frame, a reinforcing bar, or the like may make the conductor plate unnecessary, but in such a case, pay close attention to the construction taking into account the structure of the steel frame and the pitch of the reinforcing bar. I had to. However, the electromagnetic wave absorber of the present invention, for example, a solid content adjusted paint to be formed as a dry coating film building, container,
If a coating film is formed by coating the inner and outer walls of a case or the like, materials and construction for attaching a molded article of the electromagnetic wave absorber as in the related art are not required. As a result, efficient use of space, weight reduction, simplification of the construction method, and the like can be achieved, and a significant cost reduction can be achieved overall. Furthermore, since the use period of the electromagnetic wave absorbing material applied to a structure generally extends for a long time, the conventional product has the problem that the electromagnetic wave absorbing effect due to the corrosion of the conductor plate adhered to the back side is lost during that time, and the work is performed again. However, such a problem is solved in the product of the present invention.

[0008]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0009]

Example 1 800 g of iron oxide and Fe ₂ O ₃ powder and 200 g of titanium oxide and TiO ₂ powder were weighed, mixed well with a mixer, placed in a graphite crucible, and placed in an induction furnace for 180 minutes.
It was melted at 0 ° C., immediately poured into another graphite container and cooled with water. Next, this lump was crushed, ground in an alumina mortar, wet-pulverized with a zirconia ball mill for 12 hours, and dried at 105 ° C. for 24 hours to obtain a powder of 150 mesh pass. This powder was spread on a stainless steel foil to a thickness of about 5 mm, and hydrogen reduced at 1150 ° C. for 5 hours. Then, crush it again in an alumina mortar,
A powder of 150 mesh pass was obtained.

[0010]

Example 2 The hydrogen-reduced powder obtained in Example 1,
8 g of polyamide resin (Tomide 225-X manufactured by Fuji Kasei Kogyo Co., Ltd.) was added to 200 g, and 13.3 g of epoxy resin (Epicoat 828 manufactured by Shell Chemical Co., Ltd.), 50 g of xylene solvent, and 150 g of high alumina beads were made of stainless steel. The mixture was placed in a container and shaken for 2 hours to form a paint.
(P / B = 9.38)

This paint is 10 mm thick and 20.7 m in outer diameter.
Samples A and B were obtained by coating a hollow hollow disc made of concrete having a diameter of 9.0 mm and an inner diameter of 9.0 mm so that the coating film thickness when dried was 2 mm and 3 mm. A network analyzer (37629A manufactured by Wiltron) was used for measuring the radio wave absorption capacity. Table 1 shows the measurement results.

[0012]

[Table 1]

From the results shown in Table 1, it is clear that the electromagnetic wave absorber of the present invention has a small thickness and a wide specific bandwidth showing performance, and is compared with an electromagnetic wave absorber using a conventional backing plate. There is no inferiority.

Claims (2)

[Claims] 1. An oxide-based TiO ₂ and Fe _{2 by} weight ratio.
_A titanium oxide and an iron oxide having a TiO ₂ content of 5 to 95% by weight, when the total with ₂ O ₃ is 100%,
Or, an oxide containing titanium and iron is reduced and calcined at a temperature equal to or higher than the melting temperature of the substance, and then rapidly cooled and pulverized,
A single-layered electromagnetic wave absorber characterized by fixing and molding a composition obtained by reducing and firing again at a melting temperature or lower with an insulating resin having a relative dielectric constant of 4 or less. 2. A method of using the electromagnetic wave absorber of claim 1 as a coated film.