Preparation And Research Of Magnetic Shielding Material For Low Freouency

The main research contents of the thesis are to settle the difficulty of electromagnetic shielding (magnetic shielding for low frequency) on the basis of summarizing present development of electromagnetic shielding material, which broadens frequency dimension of electromagnetic shielding material to attain the goal of wide-band electromagnetic shielding. First of all, the thesis systematically analyse electromagnetic shielding theory and it gets precise analytic equation of electromagnetic shielding effectiveness by analyzing. On the basis of this, it is to analyse magnetic shielding for low frequency and double layer magnetic shielding effectiveness model. And it is educed that double layer structure of layer magnetic shielding is able to increase shielding effectiveness obviously. On the basis of shielding theory of layer composite structure, the thesis compiles the software of analysing material shielding effectiveness. The software can analyse shielding effectiveness of multiform shielding material and different kinds of material. Then it can get theoretical solution by simulating and calculating. Secondly, the thesis devises magnetic shield effectiveness testing flatform and implements to measure low-frequency magnetic shielding effectiveness of material. The thesis develops actual testing system. It has function of automatic measuring and automatic analysis. And it has the characteristic of high degree of precision, highly active and fast. Lastly, magnetic soft magnetic alloy film is plated on aluminum film with high shielding effectiveness by electrochemical treatment method, which let material have shielding effectiveness in low-band (<100KHz). Thereby it broadens frequency dimension of electromagnetic shielding material. Soft magnetic alloy film is non-crystalline by x-ray analyzing. It is compact between alloy film and basal body. Grain of the surface is very fine and grain size can be smaller than 40nm. The non-crystalline soft magnetic alloy film has a very little coercive force. Primary relative permeability of the sample attains to 8705 and soft magnetic performance is very good. Electromagnetic shielding effectiveness of the material attains to 70dB and low-frequency magnetic shielding effectiveness attains to 11dB.