Charcoal-containing microwave electromagnetic radiation absorbers with relief surface

Abstract

A new technology for manufacturing microwave electromagnetic radiation (EMR) absorbers characterized by a geometrically inhomogeneous surface is presented. The novelty of the presented technology lies in the use of radiotransparent polymer forms with hemispherical depressions of the same volume, which are the component for the formation of the surface layer of absorbers. The technology consists in filling these molds with a mixture of powdered activated (birch) charcoal and the binder in the liquid phase and further drying it in the forms. Compared with analogues, the developed technology is characterized by low complexity of reproduction. Most of the time required to implement the presented technology is associated with the drying process of a mixture of powdered activated birch charcoal and a binder. The experimentally established patterns of changes in the values of electromagnetic radiation reflection and absorption coefficients in the frequency range 1.0–28.0 GHz of the absorbers manufactured in accordance with the presented technology are provided, depending on the type of binder contained in them (polyvinyl acetate aqueous solution, gypsum aqueous solution, polyurethane mastic). It was determined that the most effective of the EMR absorbers studied in the course of establishing the indicated patterns are those ones that contain an aqueous solution of polyvinyl acetate. Electromagnetic radiation absorption coefficient values in the frequency range 1.0–28.0 GHz of such absorbers vary from 0.75 to 0.99. In addition, the mass per unit area of such absorbers is 1.5–2.0 times less than the mass per unit area of absorbers containing an gypsum aqueous solution or polyurethane mastic. Microwave EMR absorbers manufactured using the presented technology are characterized by higher mechanical strength, as well as lower cost compared to analogues and are recommended for use in the creation of anechoic chambers.