High-frequency Electromagnetic Properties Of Oriented Submicron CoNi Particles And Carbonyl Iron Composites

With the applying frequency band growing higher of electronic communication systems,the working frequency of various electronic devices is increasing and the size of devices is reducing.The demands for miniaturized and low-loss antennas applying for high frequency are growing more urgent,as a distinctly important device in communication systems.Microstrip patch antennas have been concerned widely due to their low profile,easily conformal,lightweight,and easily integrated properties.Substrate materials of antennas possessing a high miniaturization factor,low-loss and a good impendence matching condition are significant for developing miniaturized microstrip patch antennas.Originally,dielectric materials with high permittivity were applied as the substrate materials of antennas.Although,these dielectric materials could reduce the size of antennas effectively,the problems of impedance mismatching and narrow applying frequency band are prominent.In order to solve these problems,magnetic substrate materials are attractive for many researchers.Distinguished from the ferrite materials,magnetic metal alloy particles are popular studied in high frequency applications recently due to their high saturation magnetization and Snoek limit value.However,using the magnetic metal alloy particles as the substrate materials of antennas possesses two major challenges that how to restrain the eddy current effect and how to improve the magnetic resonance frequency.In this paper,CoNi alloy particles were selected as the object of study to solve these problems mentioned above.The CoNi alloy particles were prepared by the polyol reduction method and the effects of the sodium hydroxide concentration and reaction time on the crystal structure and the morphology of particles were studied.The submicron CoNi alloy particles/polyurethane composites were prepared based on the optimized synthesis condition and electromagnetic parameters were studied.The results revealed that the real part of measured permeability(??)of the composite(80wt%)was 2.5 at 1 GHz,and the real part of measured permittivity(??)was only 9.5,possessing a high magnetic resonance frequency with a suppressive eddy current effect.The simulated results of a microstrip patch antenna based on the substrate material consisted of the composite at nearly 1 GHz showed that the area of the antenna reduced by 85%comparing with the conditional dielectric material(FR4),possessing a wide effective band with 220 MHz and a good impedance matching condition.In order to promote the permeability,flaky CoNi alloy particles and flaky CoNi alloy particles/polyurethane oriented composites were prepared through the planetary ball-milling and the magnetic field orientation method in this paper.The??of the flaky CoNi alloy particles/polyurethane oriented composite(80 wt%)was 3.0at nearly 1 GHz,and the domain wall resonance frequency was at around of 1 GHz.However,the permittivity improved obviously comparing with the submicron CoNi composite,going against the requirement of impedance matching.Thus,the impedance matching property of ball-milled CoNi alloy particles/polyurethane oriented composites were improved effectively using the surface oxidation method with the decrease of the permittivity.The electromagnetic properties of the flaky magnetic metal particles/polyurethane oriented composites were not only related to the fill ratio and the intrinsic property of magnetic particles,but also related to the alignment angle of flaky magnetic metal particles in polyurethane.Therefore,the flaky carbonyl iron particles coated with SiO₂ with large production were selected and the composites with various oriented angles and fill ratios were prepared using the magnetic orientation method and wire-electrode cutting method.Effects of various oriented angles on the morphology,static magnetic property and electromagnetic property of obtained composites were studied in this paper.The results revealed that the electromagnetic property and static magnetic property of composites were influenced by the angle between the vector k of the incident electromagnetic wave and the easy magnetization plane at the same fill ratio.For the same angle,the fill ratios of flaky particles could influence the rules of the electromagnetic properties of composites.