The Effect of Carbon Black Additions on Electromagnetic Wave Absorption of Fe 73 Si 16 B 7 Nb 3 Cu 1 Base P/M Sheets
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1118-K07-11
The Effect of Carbon Black Additions on Electromagnetic Wave Absorption of Fe73Si16B7Nb3Cu1 Base P/M Sheets Sun-I Kim, K. Y. Sohn, W. W. Park School of Nano Engineering, Inje University, 607 Obang-dong, Gimhae, Gyeongnam 621-749, Republic of Korea
ABSTRACT Melt-spun Fe73–Si16–B7–Nb3-Cu1 (at%) amorphous strip was pulverized and then crystallized to obtain nano-grain structure at 540℃ for 1h under a nitrogen atmosphere. Carbon black of 0.1~ 1wt% and its dispersant were mixed with the nano-grain structured Fe-based powder for 1h via ball milling for 1h. The mixture was tape-cast with a polymer-based organic binder, and dried at 100℃ to make a thin sheet. The microstructure and electromagnetic wave absorption properties of the sheet were investigated using a network analyzer. As a result, the properties of electromagnetic wave absorption were improved by the increase of dielectric loss, which was mainly caused by the increase of complex permittivity with the addition of carbon black. INTRODUCTION Recently, the use of electronic devices such as electric home appliances and wireless telecommunication systems has been rapidly increased. These devices give off harmful electromagnetic waves, which cause a malfunction to others by the electromagnetic interference. In addition, it becomes a serious menace to our health by increasing the temperature of human body [1-2]. Therefore, the demand for EM wave shields and the interest in electromagnetic wave absorber are dramatically growing to overcome these problems. The ferrite, sendust and permalloy have been widely used as conventional EM wave absorbing materials. However, the permeability of the conventional alloys generally decreases at a high frequency due to the law of Snoek’s limit [3]. Hence new materials that have a high permeability in a range of gigahertz have been required. The Fe73Si16B7Nb3Cu1 nanocrystalline P/M alloys have excellent permeability. Especially, as they were insulated with electrical insulation such polymer binder, they have a high electrical resistance, which enables to lower eddy current at a high frequency [4-5]. According to the reported studies [6-8], various dielectric and conductive materials have been added to the magnetic materials in order to enhance a complex permittivity. Among the effective additives, carbon black powder was reported as a good material which can improve the EM wave absorption properties. Thus, the thin EM wave absorption sheets with different sized carbon black powders were fabricated, and the absorption properties of nanocrystalline P/M sheets has been analyzed closely in this study.
EXPERIMENTAL PROCEDERE Fe73Si16B7Nb3Cu1 (at %) soft magnetic amorphous strip was made via rapid solidification process, and then the strip was pulverized using a jet mill and an attrition mill to obtain flakeshaped powder. After ball milling, the powder was classified using a series of sieves to collect a powder with sizes under 53 m(- 270 mesh), and then got average thickness of powders were 6m and sizes were 50m. The Fe-bas
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