feni软磁合金吸波材的设计与制备.docx

优秀毕业论文 精品参考文献资料 ABSTRACTAB ABSTRACT AB STRACT The aim of this dissertation iS to provide theoretical evidence and practical applications for researching and developing new type electromagnetic wave absorbers． This investigation will show several disadvantages in the traditional types of applied electromagnetic wave absorbing materials whose wave absorbers are ferrite or SiC powders：narrowing the absorbing frequency bands，enlarging their thickness，and weakening the effectiveness of their absorption．In order to make substitutions for traditional types of electromagnetic wave absorbers．for the first time a“shell-core’’ structure theoretical model will be outlined and discussed．After considering material applications and the relationships of microstructure versus electromagnetic characteristics，‘shell—core”structure composite powders，the new type wave absorbers which possess FeNi3，Y一(Ve，Ni)and Fe304 phases and were prepared by using the method of“mechanical alloying+oxidation+re—crystallizing heat treatment”will be described．The microstructure of the“shell．core”structure composite powders was studied by means of modem material analyzing techniques， including XRD，MFM，FEG-SEM，EDS，and SO on．It Was proved that the complex magnetic permeability benefitS from the increasing average crystal grain size，the decreasing magnetic domain width and wall thickness ofthe new type wave absorbers； the“shell layer’’which possesses Fe304 phase call be effective to reduce complex electric permittivity．Two kinds of single·-layer and double-·layer flat type composites contained within the“shell—core”structure composite powders whose grain granularity WaS under lOktm were manufactured． These new types of electromagnetic absorbing materials，aS well as the absorbing mechanism will be deeply analyzed．The double—layer absorbing physical model “match leading layer+electromagnetic dissipation layer’will be discussed and evaluated by theoretical calculations of absorbing effectiveness(AE)on flat typ