Papers by Keyword: Sendust

Abstract: A low-cost composite electromagnetic wave absorber made of sendust dispersed in resin was developed that does not contain any rare metals. In this study, spherical sendust particles with average particle sizes of approximately 5 and 20 μm were dispersed in polystyrene resin at volume ratios in the range 2040 vol% to broaden the absorption frequency bandwidth at frequencies above 10 GHz. The optimal volume ratios of sendust with average particle sizes of approximately 5 and 20 μm were found to be approximately 30 and 35 vol%, respectively. Electromagnetic wave absorbers can be flexibly designed by controlling the volume ratio of spherical sendust particles in resin.

Abstract: To design an electromagnetic wave absorber with good absorption properties at frequencies above 1 GHz, the frequency dependences of the relative complex permeability μr*, the relative complex permittivity εr*, and return loss were investigated for the composite made of both sendust (an alloy of Al 5%, Si 10%, and Fe 85%) and aluminum particles dispersed in polystyrene resin. It was found that the frequency dependence of μr* for this composite can be changed by adjusting the particle size of aluminum and the volume mixture ratio of sendust and aluminum. Therefore, a flexible design of an absorber with good absorption characteristics was proposed based on the ability to control μr*. The composite made of both sendust and aluminum was found to exhibit a return loss of less than −20 dB in the frequency range of not only several GHz but also around 20 GHz if appropriate volume mixture ratio and particle size were selected.

Abstract: The effects of the particle size of sendust, which is an alloy of Al 5%, Si 10%, and Fe 85%, on the absorption characteristics of composite electromagnetic wave absorbers made of polystyrene resin and sendust were investigated in the frequency range from 1 to 40 GHz. The size of sendust particles was varied between approximately 5 and 20 m. A metal-backed single-layer absorber made of 20 m sendust particles absorbed more than 99% of electromagnetic wave power at frequencies above 20 GHz. Meanwhile, a composite made of 5 m particles exhibited a return loss of less than −20 dB in the frequency range of not only several GHz but also above 30 GHz. In addition, the relative complex permeability r* was shown to be controlled by adjusting the particle size of sendust, and an electromagnetic wave absorber with a flexible design was proposed.

Abstract: Composite electromagnetic wave absorbers made of a soft magnetic material (permalloy or sendust) and polystyrene resin were investigated [1]. The volume mixture ratio of magnetic material was varied in the range from 18 vol% to 75 vol%. The composites with the low volume mixture ratio of soft magnetic material absorbed more than 99 % of electromagnetic wave power in the frequency range from 1 GHz to 10 GHz. The values of the real part
r’ of the relative complex permeability
r * for both magnetic materials were less than unity at frequencies above approximately 6 GHz as the volume mixture ratio of magnetic material increased. This result suggests the possible realization of an electromagnetic wave absorber that can operate above 10 GHz.

Abstract: The frequency dependences of the complex permeability μ r*, complex permittivity ε r*, and return loss were investigated for composite electromagnetic wave absorbers made of soft magnetic materials (permalloy or sendust) and polystyrene resin. For permalloy, two types of particle shape were used: grain-type or flake-type. The volume mixture ratio of magnetic materials was varied in the range from 40 % to 70 %. The values of the real part μ ’ and imaginary part μ ” of μ r * increased with increasing mixture ratio of magnetic materials. The frequency dependence of μ r * for flake-type permalloy composite was similar to that for sendust composite. All absorbers showed the absorption of electromagnetic waves in the frequency range above 1 GHz.