MICROWAVE AND RHEOLOGICAL PROPERTIES OF HIGH-LOADED SILCOTIN 25/R-10 SILICONE COMPOSITE WITH SiO2 NANOPOWDER (TARKOSIL)

Radio-absorbing materials for electromagnetic compatibility and reduction of electromagnetic wave reflections are used in radio electronic equipment. In the practical application of materials in the form of coatings and gaskets, it is important to take into account the mechanical properties due to possible joint changes in microwave and mechanical characteristics. The effect of the introduction of silicon dioxide (tarkosil) nanopowder on the microwave characteristics and rheological properties of a highly filled composite based on the silicone binder SilcoTin 25 and microparticles of carbonyl iron grade P-10 has been studied. The samples were made according to the method of obtaining highly filled composites with a content of 80 wt. % of micro-powder P10, previously tested for various grades of carbonyl iron. Microwave measurements were performed using the transmission/reflection method in a coaxial cell using S-parameters with the calculation of reflection, transmission, and absorption coefficients in the "lumen" mode of a 2 mm thick layer without a metal substrate. The frequency measurement range is 0.5 ‒ 18.0 GHz. It has been shown that the administration of tarkosil (1 ‒ 3 wt. %) in a composite with micro-powder P10 leads to an ambiguous restructuring of the balance of absorption, reflection and transmission. With a moderate change in absorption, an increase in reflection is observed. The dielectric and magnetic tangents of the loss angle, as well as the modulus of the normalized impedance, are calculated from the frequency dependences of the complex values of the dielectric ε* and magnetic μ* permittivity. It is shown that the increase in reflection is mainly associated with a deterioration in impedance matching while maintaining significant magnetic losses. 

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