| High-frequency electronic technology has received more attention in recent years, it has been widely used in computer, internet, communication and industry automation, so the soft magnetic cores of its transformers and inductors must have excellent high-frequency properties. Nowadays, ferrites with high resistivity and amorphous alloy strips are the main high-frequency soft magnetic materials. However, ferrites have low saturation flux intension and magnetization, it is adverse to the minimization; amorphous alloy strips have strict cooling rate, it is hard to prepare. Therefore soft materials with high saturation flux intension and magnetization, low coercivity and loss, also easy to prepare, have more advantages in many aspects. Soft magnetic composite materials (SMCs) were prepared by coating ferro-magnetic powders with high resistivity powders. Preparation and development of new SMCs has been a heat in recent study, SMCs can decrease the current loss in high frequency, and can be prepared by traditional powder metalergy method, so it will be widely used in astronomy, vihicle, electronics and many other new frontiers.Fe76Si9B10P5/Zn0.5Ni0.5Fe2O4 bulk amorphous soft composites with excellent soft magnetic properties were prepared by physical coating and spark plasma sintering (SPS) method, sintered at 487℃, with Fe76Si9B10P5 micro-powders as substrate and Zn0.5Ni0.5Fe2O4 nano-powders as coatings. Several local fine grains precipitation of α-Fe indicates the existence of local instantaneous high temperature. The sintering machenism was analyzed:there were plasmas and new discharging paths generated in the self-propagating mode, then local instantaneous high temperature formed in the interface area, besides, the tip effect of Zn0.5Ni0.5Fe2O4 nano-particles promotes the discharging process. Collision discharging also greatly promotes the discharging and plasmas formation. The preparation and densification of Fe7.6Si9B10P5/Zn0.5Ni0.5Fe2O4 composites were performed by the local instantaneous high temperature formed with the discharging heat.Besides, Fe-6.5Si/MgO bulk amorphous composites were prepared by sol-gel method and SPS technology at 600 MPa and 550℃, MgO nano-particles as insulation coating on the surface of Fe-6.5Si micro-particles. The effect of pulse current on the sintering and densification was analyzed. The pulse current promotes the bonding of MgO insulative particles, therefore the Joule heat facilitates the sintering process. The microstructure, soft magnetic properties and mechanical properties analysis of the SMCs samples with different MgO contents indicate:SMCs with moderate MgO coating have excellent soft magnetic properties, high electrical resistivity, high saturation flux intensity, low coercivity, etc. Fe-6.5Si/MgO soft composites will be used in middle or high frequency conditions with very low current loss and core loss, high mechanical properties in the future.The SMCs were more uniform and stable by sol-gel chemical coating method, the thickness of the coating is easy to control, and the comprehensive properties are more excellent. It will be widely used in high property switching power supply, generator, motor and inductor, etc. It also will have great influence on the modern industry, such as the military and the defense industry. |
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