Effectiveness of Microwave Absorption by Refractory Powders Depending on Particle Sizes

Abstract

The efficiency of microwave absorption of metallic refractory compounds at 2.45 and 9.53 GHz is studied. It is ascertained that electromagnetic absorption is influenced by the grain size of absorbing particles: when it increases by 10 times, the absorptivity of ZrC, ZrSi₂, HƒC, TaN, HƒN, ZrN, and NbC particles becomes higher by a factor of 7 and that of SiC, NbSi₂, WC, B₄C, MoSi₂, and VN particles only by a factor of 2 to 4. It is connected with the physical properties of each compound: magnetic permeability (sign and value), thermal EMF factor (sign and value), and the active component of AC resistance. It is shown that violation of stoichiometry (namely, the formation of nonmetal vacancies) increases the effectiveness of microwave absorption while the formation of replacement phases does not change the nature of interaction between the microwave field and substance. It is established that the morphology of particles with the same sizes does not influence the efficiency of microwave absorption. It is proved that the measurement of absorption in weak fields can be used for nondestructive inspection of refractory metallic compounds.