RU2494507C1 - Material for absorbing electromagnetic waves - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: material for absorbing waves is a porous vitreous material containing more than 85 wt % glass phase. The porous amorphous material contains a crystalline phase in form of quartz in amount of 5-14.5 wt % and size smaller than 0.5 mcm, and the gas-forming agent used is soot in amount of 0.5 wt %. The absorbent is characterised, in the frequency range from 0.03 to 100 GHz, by an absorption factor ranging from 11 to 27 dB/cm, reflection coefficient of -10 to -27 dB, is broadband, non-flammable and ecologically clean.

EFFECT: high absorption factor and mechanical strength, while maintaining low reflection coefficient of the material.

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Description

The invention relates to radio engineering, in particular to absorbers of electromagnetic waves (EMW), including in the microwave range, and can be used to equip multifunctional shielded rooms, as well as to reduce the radar visibility of various objects. The technical result of the invention is to increase the radar absorbing properties of the material, increase its mechanical strength while maintaining a relatively low density.

Foam glass used to protect against electromagnetic radiation fields is one of the promising materials, as it has the ability to protect in a wide frequency range of electromagnetic waves, moisture resistance, incombustibility, adaptability, is an environmentally friendly absorber.

Known ultrawide absorber EMW [RU 2110122 H01Q 17/00, 27.04. 1998], which is a structure consisting of a dielectric material made on the basis of radar absorbing foam glass and magnetic material of radar absorbing nickel-zinc ferrite, which are mounted on a metal substrate. The claimed foam glass has the following characteristics: specific attenuation of 0.2-0.4 dB / cm at a frequency of 4 GHz with a bulk density of not more than 190 kg / m ³ and a thickness of 200-350 mm. The disadvantage of this absorber is the design complexity of the absorber made of at least three materials. Moreover, the claimed foam glass should have a thickness of 200-350 mm, which is technologically unfeasible. The maximum thickness of block foam glass is 180 mm; to obtain higher values, the blocks of foam glass are glued, which further complicates the technology for obtaining the material as a whole.

In an article by Barsukov B.C. “Integrated Protection of Special Shielded Rooms” [Special Technique Magazine, No. 1, 2000], the results of a comparative analysis of some radioprotective materials, including foam glass, are presented. In this paper, it is noted that the most effective problem of creating environmentally safe protected rooms is solved using materials that are special wide-band absorbers made in the form of ceramic plates and foam glass. The use of integrated protective panels provides both electromagnetic, acoustic and environmental protection. It is noted that the foam glass obtained with a carbon-containing blowing agent has a radio absorption at a frequency of 4 GHz in the range from 0.2 to 5 dB / cm.

Known radar absorbing material based on a polymer dielectric binder [RU 2355081, IPC H01Q 17/00, 05/10/2009], containing microgranules, the matrix material of which is transparent to the radiation of the radio wave range, characterized in that it additionally contains substances that absorb electrical and magnetic components of radio wave radiation in the composition of the microspheres, with each type of microspheres contains only one substance selected from the group consisting of ferrite, copper, fulleron C ₇₀ , evenly distributed the entire matrix material in the form of clusters. The disadvantage of this absorber is that it is obtained on the basis of epoxy resin (ES), which is a combustible material. The use of ES is very limited, since during curing under industrial conditions a certain amount of sol fraction remains in them - a soluble residue that can cause serious damage to health. When not cured, epoxies are fairly toxic and can also be harmful. In addition, it is technologically difficult to achieve uniform distribution in the entire volume of nanoclusters, which is not explained in this patent.

Closest to the proposed solution by technical nature is [RU 2375793, IPC H01Q 17/00, 10.12.2009] a material representing foam glass obtained by the interaction of silicate glass and a carbon-containing blowing agent - silicon carbide in an amount of from 1 to 35 wt.%. The claimed foam glass is characterized by the following radiophysical properties at a frequency of 100 GHz: absorption coefficient from 6 to 19 dB / cm and reflection coefficient from -24 to -12 dB. Known technical solution has several disadvantages. The claimed foam glass has a high density (more than 450 kg / m ³ ), which impairs its radiophysical properties. The claimed strength of the material (up to 10 MPa) complicates the manufacturing technology of elements of various geometric shapes, which is necessary to increase the efficiency of absorption of electromagnetic waves. The manufacturing process is carried out at high temperatures (920-930 ° C), which is accompanied by high energy consumption. In the manufacture of this foam glass, silicon carbide is used, which is scarce and more expensive compared to other carbon-containing blowing agents. In addition, the amount of introduced silicon carbide is up to 39 wt.%, Which is quite expensive.

The objective of the invention is to increase the absorption coefficient, mechanical strength, while maintaining a low reflection coefficient.

The technical result is achieved by the fact that a porous glassy material comprising more than 85 wt.% Glass phase contains a crystalline phase in the form of quartz in an amount of 5 to 14.5 wt.% And a size of less than 0.5 μm, and carbon black is used as a blowing agent. the amount of 0.5 wt.%.

Concrete example

The mixture for the manufacture of glass granules contains silica-containing material, soda ash and dolomite. As a silica-containing material, take raw materials with a silicon oxide content of at least 83% and a fraction size of less than 0.1 mm, with the following ratio of components, in wt.%: Silica-containing material - 61-68; soda ash - 19-23; dolomite - 13-16. The mixture is prepared by mixing materials in the indicated proportions, followed by compaction on a roller press (or on a disk granulator, or extruder). The resulting compacted charge has increased chemical activity at the stage of silicate formation and glass formation, due to the finely dispersed silica-containing material and its close contact with other components of the charge, primarily with soda ash.

The heat treatment of the compacted charge in the temperature range 900–950 ° C makes it possible to obtain glass granulate, the phase composition of which, according to X-ray phase analysis, is represented by the glassy phase and a small amount of residual silica. The crushed glass granulate to a specific surface area of not less than 5000 cm ² / g is mixed with 0.5 wt.% Gas-forming agent - soot and foaming at temperatures of 800-850 ° C.

The invention is illustrated in the table, which shows the results of physico-mechanical and radiophysical measurements of the obtained samples.

As can be seen from the table, the foam obtained on the basis of glass granulate has increased strength characteristics: 1.4 times the strength value of the analogue and 2 times the strength value for foam glass obtained on the basis of cullet. In this case, the radiophysical properties of the foam glass surpass those of the analogue.

Claims (1)

Material for absorbing electromagnetic waves, containing a porous glassy material comprising more than 85 wt.% Glass phase, characterized in that the porous amorphous material contains a crystalline phase in the form of quartz in an amount of from 5 to 14.5 wt.% And a size of less than 0.5 microns and as a blowing agent use soot in an amount of 0.5 wt.%.