Browsing by Author "Kan, SW"

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Electromagnetic wave absorption behavior of NiZn-ferrite prepared via hydrothermal method
(2005)
Peng, CH
;
Wang, HW
;
Kan, SW
;
Chen, SY
;
材料科學與工程學系
Ni0.5Zn0.5Fe2O4 ferrite powders were synthesized by a hydrothermal method. The nanoparticles of these materials were mixed with a thermal-plastic polyurethane (TPU) polymer in order to form a suitable composite for electromagnetic wave absorber in a frequency range from 2.0 to 15.0 GHz. The effect of particle size on the reflection loss was investigated by comparing nanosized and microsized powders. The reflection loss as a function of frequency (f), thickness of the absorber(d), the real and imaginary part of permittivity (epsilon' / epsilon") and the real and imaginary part of permeability (mu'/mu") were obtained by calculation using the Bruggeman effective medium theory. The effect of Co2+, Cu2+, and Mg2+ on the reflection loss was also studied.
Microwave absorbing materials using Ag-NiZn ferrite core-shell nanopowders as fillers
(2004-12-01)
Peng, CH
;
Wang, HW
;
Kan, SW
;
Shen, MZ
;
Wei, YM
Silver nanoparticles coated with Ni0.5Zn0.5Fe2O4 spinel ferrites, forming a core-shell structure, were synthesized by utilizing hydrothermal method at different ferrite/silver ratio (ferrite/silver = 6/1, 4/1, 2/1, 1/1, 1/6) and introduced into polyurethane matrix to be a microwave absorber. The complex permittivity (epsilon', epsilon") and permeability (mu', mu") of absorbing composite materials consisted of ferrite/silver core-shell nanopowders and polyurethane were measured in the frequency range of 2-15 GHz. The reflection loss and matching frequency were calculated from measured data using theory of the absorbing wall for different ferrite/silver ratios. It was found that the matching frequency for reflection loss exceeded a satisfactory -25dB at 9.0 GHz for using NiZn ferrite as a filler shifts to higher frequencies (10.9-13.7 GHz) as the ferrite/silver ratio of core-shell nano-filler decreased from 6/1 to 2/1. The present result demonstrates that microwave absorbers using ferrite/silver core-shell filler can be fabricated for the applications over 9 GHz, with reflection loss more than-25 dB for specific frequencies, by controlling the ferrite/silver ratio of the core-shell nano-fillers in the composites. (C) 2004 Elsevier B.V. All rights reserved.