Dielectric relaxation due to heterogeneous structure in moist wood |
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Authors: | Hiroyuki Sugimoto Ryosuke Takazawa Misato Norimoto |
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Institution: | (1) Advanced Wood-based Material Technology Group, Materials Research Institute for Sustainable Development, National Institute of Advanced Industrial Science and Technology (AIST), 2266-98 Anagahora, Shimoshidami, Moriyama-ku, Nagoya 463-8560, Japan;(2) Daiken Kogyo, Okayama 702-8045, Japan;(3) Department of Mechanical Engineering, Doshisha University, Kyotanabe 610-0321, Japan |
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Abstract: | Dielectric properties in three main directions for hinoki wood (Chamaecyparis obtusa) specimens conditioned at various levels of relative humidity were measured in the frequency range from 20 Hz to 10 MHz over
the temperature range from −150°C to 20°C. Three relaxations were observed in the specimens conditioned at high levels of
relative humidity. The relaxation in the highest frequency range was ascribed to the motions of adsorbed water molecules.
The relaxation in the middle frequency range remained unchanged by the ethanol–benzene extraction of specimens. The relaxation
location was independent of measuring directions. The relaxation in the lowest frequency range was not detected in the specimens
impregnated with methyl methacrylate (MMA). This result suggested that the relaxation was due to electrode polarization. The
Cole-Cole circular arc law applied well to two relaxations recognized in the specimens impregnated with MMA. The relaxation
magnitude in the middle frequency range was extremely large, and the distribution of relaxation times was very narrow. These
characteristics suggested relaxation of the Maxwell-Wagner type resulting from the interfacial polarization in the heterogeneous
structure, which included adsorbed water with large electrical conductivity within the insulating cell walls. |
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Keywords: | Dielectric relaxation Heterogeneous struc-ture Adsorbed water Cole-Cole circular arc law Methyl methacrylate |
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