Electromagnetic Wave Absorption Characteristics of Half Carbonized Powder-Type Magnetic Wood

A new technique for designing the material composition for a powder-type magnetic wood to achieve a specific matching frequency for an electromagnetic wave absorber is proposed and validated experimentally. The complex permittivity of the wood powder is changed by heating the powder-type magnetic wood until the surface is carbonized (referred to as half- carbonized) and has a conductive property. The changed complex permittivity of the wood powder alters the frequency at which peak absorption takes place. The experimental results for this study show that the electromagnetic wave absorption characteristics of the half- carbonized Mn-Zn ferrite powder-type (40 volume%) magnetic wood can be controlled by adjusting the processing temperature. The correct matching frequency and an acceptable bending strength are achieved if the material is processed at 250°C. The powder-type magnetic wood boards used in these experiments satisfy JIS standards for wood surface materials in terms of bending strength. The results from our studies can be used to design indoor powder-type magnetic wood wave absorbers with a specified absorption frequency.