Design of Composite Electromagnetic Wave Absorber Made of Fine Spherical Metal Particles Dispersed in Polystyrene Resin

摘要

For the purpose of designing electromagnetic wave absorbers which can operate at frequencies above 1 GHz, the ability to control the relative complex permeability μr/* and the relative complex permittivity εr/* for the composite made of fine metal particles dispersed in polystyrene resin was investigated. Method to calculate μr/* for sample made of dispersed metal particles having the distribution of the size is proposed. In order to clarify the effect of particle shape on μr/* and εr/*, samples made of dispersed non-spherical aluminium particles in polystyrene resin were prepared and the values of μr/* and εr/* were compared. Moreover, in order to clarify the effect of particle size on μr/* and e* , samples made of dispersed spherical particles of copper with the size of several micro meters were prepared. The calculated value of μr/* using the proposed formula considering the size distribution was more in agreement with the measure value compared with that calculated using formula applicable to single particle size. Proposed formula was also applicable to calculation of μr/* with multiple kinds of average particle size. Moreover, the calculated value of μr/* was qualitatively in agreement with the measured value for the samples with different shape or size. The measured values of μr/* for the composite made of the mixture of copper particles with two kinds of average particle size were in agreement with the calculated values. Thus, it was found that the values of μr/* and absorption characteristics can be controlled by the particle size distribution, the particle shape, or mixing ratio of particles with different average particle size.