Electromagnetic interference shielding effectiveness and microwave absorption of ferrite-polymer composite using Ni0.32Cu0.08Zn0.6Fe2O4 ferrite

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In order to solve the influence of electromagnetic interference to electronic devices, the ferrite-polymer composite was prepared. The spinel ferrite composition Ni0.32Cu0.08Zn0.6-ferrite was prepared by usual ceramic method, after that crack the calcinated NiCuZn ferrite, then it was ball milled for 2 h, 4 h, 6 h, 8 h, 10 h, 12 h, 14 h, subsequently, and dried for 24 h. The X-ray diffraction (XRD) pattern of the powders indicated that the spinel ferrite powders were obtained without any impurities phase. By use the Laser particle size analyzer and SEM, it can obtain the average size of the particles gradually decreased from 12.55 μm to 5.54 μm with the ball milling time increase from 2 h to 14 h. The complex permittivity, complex permeability and electromagnetic shielding properties of ferrite-polymer composites prepared with the ferrite ratio of 80% in paraffin matrix have been investigated in 1 MHz-1 GHz frequency range by using Agilent E4991A RF impedance analyzer. All the parameters μ', μ", ε' and ε" of the composites are found to have a trend of decrease with the ferrite ball milling time increased in most of the frequency range. The electromagnetic shielding effectiveness (SE) calculate by the electromagnetic parameters was decreased with the ferrite ball milling time increase, and increased with the frequency increase that have a maximum value approach to 3.75 dB at the frequency of 1 GHz and thickness of 10 mm. In this frequency range (1 MHz-1 GHz), the reflection loss and multiple reflection loss are much lower than the absorption loss, that is to say, the SE are mostly determined by the absorption loss.

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