JPS6281799A - Radio wave absorber - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a radio wave absorber, and more specifically, it provides a nonflammable radio wave absorber that covers the ceiling, 1W, and floor of a room in order to construct an anechoic chamber. It is something to do.

Conventional technology Conventional radio wave absorbers used to construct radio anechoic chambers include foam-molded materials made of pre-foamed polystyrene coated with carbon powder, and foamed polyurethane impregnated with carbon powder. Commonly used materials include a material in which a fibrous web is combined with foamed polyurethane mixed with 7J-bon powder, and a hair lock material in which an integrated pine material such as animal hair or chemical fiber is impregnated with conductive rubber containing carbon powder.

C1 Problems to be solved by the invention As mentioned above, the conventional radio wave absorber contains 4T carbon powder.
In order to hold the resistive film in a spatially dispersed manner, plastic foam or a 1 m' dt web is used as a carrier, so it is inferior to the heat resistance required for building materials R1, and is not suitable for disaster prevention such as fire. ,6 was unsatisfactory.

28 Means for Solving the Problems In order to solve the above problems, the present invention first proposed an invention relating to a radio wave absorber using a crow wool mat as a carrier for a resistance coating nA containing carbon powder. 60-29
No. 389, the present invention has succeeded in achieving substantially the same objective by utilizing open-pored mineral foam particles as a carrier.

That is, the present invention accumulates a large number of interconnected porous mineral microporous particles having a carbon powder-containing resistance film adhered to their surfaces and inner communicating pore surfaces, and connects the particles with each other by the film. , a radio wave absorber molded into a predetermined shape.

The open-pored mineral foam particles are usually artificial light matrix aggregates used to lighten concrete, mortar, etc., and are mineral particles that have numerous open pores inside, such as mineral particles. Perlite.

Vermicilite, Brahma phase stone particles 1 foamed glass particles, etc. are suitable, but glass beads and shirasu balloons are not suitable because they do not have continuous pores.

The above-mentioned mineral foam has a chemical composition mainly composed of silicon oxide and aluminum oxide, with small amounts of various metal oxides, and its unit volume g + weight is 0.05 to 0.5 k (1/
Q. It has voids with an oil absorption rate of about 0.5 to 59/g, and its relative magnetic permeability is 105 or less. The average particle size of the particles is 1 to 10 mm, preferably 2 mm.
~5III+1 is used.

The carbon powder-containing resistance coating is made by dispersing 2 to 200 phr of carbon powder in a film-forming synthetic resin, and the amount of carbon powder attached to the mineral foam particles is 0.2 to 100 phr (1/Q). range.

FIG. 1 is a schematic diagram of an enlarged cross section of the radio wave absorber of the present invention, in which a large number of mineral multifoam particles 1 are accumulated, and are bonded to each other by a carbon powder-containing resistance coating 2 on the particle surface. A carbon powder-containing resistive film 2 is also formed on the inner surface of the countless communicating holes 3 that exist inside the particle 1 .

Therefore, each particle 1 has a complex and various electrically conductive three-dimensional network electrical resistance path on its surface and inside, and is a molded body in which a large number of particles are integrated.

E8 Effect: The radio wave absorber of the present invention having the above-mentioned structure is a molded body in which a large number of mineral foam particles having a carbon powder-containing resistance coating adhered to the surface and internal communication holes are integrated and bonded. It allows incoming radio waves to pass through the interior without being reflected on the surface, and inside, the generated current can be effectively converted and absorbed into thermal energy through a complex three-dimensional resistive film.
Moreover, it is mainly made of minerals and is heat resistant and nonflammable.

Example 1 Perlite (manufactured by Fuyolite Co., Ltd., trade name "Venus Light No. 5", particle size 25-3111
m) was used.

As a resistance film forming agent containing carbon powder, a commercially available carbon water dispersion (manufactured by Lion Corporation, trade name CY-311, containing 10% by weight of graphite powder and 10% by weight of vinyl acetate resin) was used, and vinyl acetate resin was added to this. The emulsion adhesive and water were appropriately added and mixed to adjust carbon content and viscosity, and a treatment liquid was prepared.

After stirring and mixing Perlite 05Q and treatment liquid 129 in a container, the mixture was poured into a mold and pressed from the top with a press plate to a thickness of 83 mm.
%, after drying, remove from the mold and 100x
It was made into a flat block of 1oo x 43mm.

By the above manufacturing method, the adhesive resin content is 509/cross, the carbon content is +, 2.3.6.10.20
．． Nine flat block samples of 30, 60.100 (1/l) were manufactured and their dielectric constants were measured.

The dielectric constant is measured using the Q meter method for 10 to 50 MHz.
For frequencies from 100 MHz to 6 GHz, measurement was performed using the standing wave method (short-circuit method) in a waveguide. The obtained dielectric constant ε,.

The attenuation constant α and phase constant β were calculated from the dielectric loss tangent tan δ using the following equations.

Here, λ is the free space wavelength.

Furthermore, we can convert the above value into the vacuum phase constant β, =2π7′λ
Divide by the normalized attenuation constant α/β0. Normalized phase constant β/
β was calculated.

Figure 2 shows the carbon content σ characteristics of α7′β0 when the radio frequency f is O, Ot, 0.05, 0.2, 1,6G l−(
Figure 3 shows the frequency f characteristics of α/β when the carbon content is 1.10, 30, 60, 100g/
Q (7) Figure 4 is a graph showing the relationship between α/β and β/β using the regression line for the measured data of the sample. Normalized propagation window 'e! I7. ．． was calculated using the following formula.

f≦0.4G)-1z-o, oooke'? 3G'-"f-'°722) f≧
lG1-1z Figure 5 shows the empirical formula for the normalized propagation constant using the above formula,
Based on this, this is a graph showing the carbon content G characteristics of α/β for each frequency f, and for comparison, graphite 1
～Coated polystyrene foam density 22g/Q
, 1 to 10 inside the foamed polystyrene with a foam diameter of 4 mm.
As a comparative example, a characteristic graph of a conventional radio wave absorber (containing carbon of 0 (]/Q) based on an experimental formula for a normalized propagation constant based on measurements similar to those described above is also shown by a dotted line.

From the figure, the radio wave absorber of the present invention has a carbon content of approximately 1
0 to 30 (in the range of J/l, the normalized attenuation constant value is approximately the same as that of the conventional graphite-coated polystyrene foam type <comparative example>), and as the carbon content decreases, it is greater than the comparative example. When it collapses and increases, it becomes clear that it is inferior.

The carbon content in the pyramid part of the pyramid-shaped radio wave absorber, which is currently generally accepted to have the best reflective properties, is around 10 g/cm when using a conventional sample, and around 30 g/cm in the base part. .

Therefore, it can be seen that by using the radio wave absorbing material according to the present invention, fewer carbon skewers are required to achieve the same normalized attenuation constant. For example, conventional materials have a carbon content of 10
g/Father's f=IG+-12 α/β is 0
2, but with the material according to the invention the same G02 is achieved with about 3 g/,Q.

Therefore, it is economical.

As described in detail in Section 1 of the invention, the radio wave absorber of the present invention is molded using mineral foam particles having a large number of communicating holes as a carrier for the carbon powder-containing resistive film. It is nonflammable, and its radio wave absorption characteristics are approximately the same as conventional ones.

In addition, since the manufacturing process involves simply treating the particles with a carbon-containing binder liquid and then forming and drying them, the particles can be formed into any shape such as flat, horizontal, or pyramidal.

It is easy to shape the dimensions, and it is also possible to adjust the treatment liquid impregnation conditions so as to change the carbon content in the thickness direction, so that desired radio wave absorption characteristics can be easily obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an enlarged cross section of the radio wave absorber of the present invention,
Figure 2 shows graph 2 showing the carbon content Her characteristics of the normalized attenuation constant α/β in the example for each frequency f, and Figure 3 shows the frequency If characteristics of the normalized attenuation constant α7/β at the carbon content θ. The graph shown separately, Figure 4, is a graph showing the relationship between the normalized attenuation constant α/β and the normalized phase religion β/β0,
FIG. 5 is a graph showing the carbon content ζ characteristics of the normalized attenuation constant α/β0 obtained from the experimental formula of the normalized propagation constant, for each frequency f. 1... Mineral multifoam particles

Claims (1)

[Claims] Open-pore mineral foam particles (1) coated with a carbon powder-containing resistance coating (2) on the surface and inner open-hole surface.
) are accumulated in large numbers, and the particles (1) are covered with the film (
2) A radio wave absorber characterized by being bonded by.