Fabrication Of Element With MI Effect Based On Co-rich Amorphous Ribbon

In all amorphous materials, Co-based amorphous alloy exhibits highest permeability, lower coercive force and nearly zero magnetostriction coefficient. Co-based amorphous alloy can be used as magnetic sensitive materials in magnetic sensors, current sensors, high frequency switching power supply and also magnetic amplifier. Especially, magnetic sensors based on Co-based amorphous alloys are widely applied in the fields of navigation, communication and geological examination due to its high sensitivity, large measuring range, low power consumption and high signal-to-noise ratio. However, soft magnetic properties of Cobalt-based amorphous alloy are closely related to the factors such as compositions and microstructure. Therefore, it has important academic and application values to research and prepare Co-based amorphous alloys with superior soft magnetic properties,In this dissertation, the effect of preparation paramenters such as speed and pressure, Mo addition and thermal treatment methods on magnetic properties of the CoFeSiB system have been investigated. In addition, MI magnetic sensors with amorphous ribbons were fabricated and the response of MI magnetic sensors to the external magnetic field under different driving frequencies was tested.XRD, TEM and DSC were used to analyze the crystal structure and thermo-stability of the as-quenched amorphous ribbons. The magnetic properties of amorphous ribbons and characterists of MI magnetic sensors were measured by VSM, B-H loop tracer and impedance analyzer. Main conclusions of this dissertation are as follows:(1) Soft magnetic amorphous ribbons with nominal composition Co67Fe4Si14.5B14.5were fabricated by the melt-spinning technique using a copper drum250mm in diameter. The ribbons with the dimension20μm in thickness and0.8mm in width were fabricated by the drum rotating at35m/s and the argon pressure of20kPa. The as-quenched Co67Fe4Si14.5B14.5amorphous ribbons display excellent soft magnetic properties and the coercive force, saturation magnetization and effective permeability (1kHz、1A/m) were1.52A/m，61.3emu/g and14556, respectively.(2) With the increasing of Mo, saturation magnetization of as-quenched (Co0.942Fe0.o58)71-xSi6.4B22.6Mox (x=0～5) amorphous ribbons monotonically decreases from72.4emu/g (x=0) to28.6emu/g (x=5). With the addition of Mo2%, the amorphous ribbons display the minimal coercive force and the maximal effective permeability. In addition, glass transition temperature (Tg) and also super-cooled liquid region (ATx) increase monotonically with increasing Mo addition, which suggests that adding Mo element can improve the formation ability of the amorphous alloy.(3) The effect of magneto-thermal treatments on magnetic properties of Co67Fe4Si14.5B14.5and (Co0.942Fe0.058)71-2Si6.4B22.6Mo2amorphous ribbons were investigated. Compared with conventional thermal annealing, magneto-thermal treatments are effective in improving soft magnetic properties. During longitudinal magneto-thermal treatment, amorphous ribbons not only release innerstress but also induce magnetic anisotropy which is consistent of shape anisotropy axis. The saturation magnetization and effective permeability of the Co67Fe4Si14.5B14.5ribbon annealed in the longitudinal magnetic field increased by about7.7%to65.917emu/g and by9.2%to15892, repectively, while the coercive force decreased by43.4%to0.86A/m. For the (Co0.942Fe0.058)71-2Si6.4B22.6Mo2amorphous ribbons, the soft magnetic properties of the ribbons were also obviously improved after magneto-thermal treatments. In addition, the saturation magnetization and effective permeability of the(Co0.942Fe0.058)71-2Si6.4B22.6Mo2ribbon annealed in the longitudinal magnetic field increased by about40.15%to80.99emu/g and by65.52%to12510, repectively, while the coercive force decreased by48.39%to0.64A/m.(4) MI magnetic sensors with the cores of Co67Fe4Si14.5B14.5and (Co0.942Fe0.058)71-2Si6.4B22.6Mo2amorphous ribbons were fabricated by filling mold of glue and winding enameled wires. In the lower frequencies, MI magnetic sensors with the cores annealed in longitudinal magnetic field perform sensitive response in external magnetic field. Under the driven frequencies of31kHz, the MI magnetic sensor with the core of Co67Fe4Si14.5B14.5amorphous ribbon after longitudinal magnetic field annealing, has shown the maximum value sensitivity of332%/(A-m-1).