Research On Resistance To Thermal Shaock Performance Of NiZn Power Ferrite Material

NiZn soft magnetic ferrite is widely used as a kind of fundamental function materials in electronic information industry. This thesis aims to gain a high-performance NiZn power ferrite material which has excellent performance of resistance to thermal shock and high mechanical strength. Meanwhile we must guarantee its good magnetic properties, such as high permeability, high resistivity, high sintering density, low temperature coefficient, low magnetic loss and so on. We obtain the way to fabricate the NiZn power ferrite which has excellent performance of resistance to thermal shock and high mechanical strength by adjusting the processing conditions and selecting proper additions. At the same time, we study and analyze the reasons and theories of the performance of resistance to thermal shock and mechanical strength of NiZn ferrite. The detailed contents we study include:1. Study the basic parameters of solid phase reaction process, These parameters include the ball-milling time, the pre-sintering temperature, the sintering temperature and the rise rate of sintering temperature. These process conditions must be affirmed to make NiZn ferrite achieve its best electromagnetic properties in order to make full preparation for the following experiments. The experimental results show that when the first ball-milling time is 6h, the pre-sintering temperature is 1000 ℃, the second ball-milling time is 12 h, the sintering temperature is 1120¹130℃ and the rise rate of sintering temperature is 2℃/min, the magnetic parameters can achieve relatively better value.2. Respectively study how the composite doping Bi₂O₃-Al₂O₃, Bi₂O₃-Co₂O₃,CaO-WO₃, WO₃-Co₂O₃ will affect the magnetic parameters and micro structure of NiZn ferrite. According to the experimental results, the doping amount and the doping ratio are adjusted continuously. Meanwhile the optimum sintering temperature is determined, the experimental results can meet the engineering index: μi≥600,Bs≥400mT,tanδ/μi≤150, αμi≤0.01℃-1. Experiments indicate that adding an appropriate amount of Bi₂O₃-Al₂O₃ group can lower the sintering temperature, improve the microstucture of the material and improve its high frequency characteristics. Adding an appropriate amount of Bi₂O₃-Co₂O₃ group can maintain a high value of permeability and reduce the magnetic loss. Doping appropriate amounts of CaO-WO₃ combination can improve theresistivity of NiZn ferrites, refine the grain size and make the grain size uniform and improve the sintering density. By adding proper amount of WO₃-Co₂O₃, the nickel zinc power ferrite with good compactness and low magnetic loss can be obtained.3. Study and analyze nickel zinc ferrite materials from two aspects, thermal shock fracture and damage mechanism and mechanical strength. Talk about the factors that may influence the thermal shock and mechanical strength and establish the experimental scheme. Make research through a number of experiments. According to the experimental results, conclude the formation thermal shock crack and mechanical strength laws of the nickel zinc ferrite. The study found that selecting the appropriate sintering temperature and additives can improve the thermal shock resistance and mechanical value of strength materials. From the microscopic point of view, the changes of these conditions have a direct impact on the grain size, grain uniformity, porosity number and porosity distribution, the number and the thickness of grain boundaries, so as to change the macro properties of the material. From a thermodynamic point, the performance of thermal shock resistance of NiZn ferrite is proportional to the thermal conductivity and the thermal diffusivity.