Research On Nizn Power Ferrite Material With Resistance To Thermal Shock

This paper aims to gain a high performance of power NiZn ferrite which has high thermal shock resistance and high mechanical strength. For power ferrite, it is required to has high initial permeability, high saturation magnetic induction intensity, high resistivity, high Curie temperature and low loss, etc. In views of the above technical indicators, this paper in the case of priority to meet excellent electromagnetic properties, thermal shock and mechanical strength of the power of nickel zinc ferrite. The study found that the way of oxides doping, sintering process, in which commonly affected material electromagnetic properties, thermal shock and mechanical strength, etc. This paper will study from the following several aspects: firstly, to study the mixed oxide doping on the influence of the magnetic performance; secondly, to study the influence of presintering and sintering process on the material microstructure; thirdly, to study the common mechanism of mechanical strength, heat shock resistance on the materials performance. Specific include the following contents:Firstly, researched the effect of the way of Bi2O3 doping on the magnetic material. In this paper we have comparative studied the first ball mill doping, secondary ball mill doping and different methods of Bi2O3 doping. The study found that: the mixed with 0.1 wt % + 0.2 wt %, can get better electromagnetic performance. We also studied the different influence of the way of WO3 doping, finally Bi2O3 and WO3 doping were studied, the influence of the composite doping of Bi2O3, WO3, SiO2 and CaO. By improving the proportion of compound doped oxide, we have optimized the microscopic characteristic of the material, improved the performance of the material, then we have got a method of preparation of high performance heat shock power ferrite.Secondly, studied the influence of sintering process to the magnetic properties and microscopic characteristics of nickel zinc ferrite, and then known the relations between sintering process and the thermal shock performance and mechanical strength. This thesis also studies the influence include the presintering temperature, sintering temperature, heating rate, holding time and ball milling time on the micro morphology of the nickel zinc ferrite materials, finally determined the best preparation process of high performance of power heat shock nickel zinc ferrite.Thirdly, combining the theory of thermal shock and its experimental method, based on the previous experimental samples of thermal shock experiments, summarized causes of crack and mixed mode and oxide types, and summarized their rules. Study found that: properties significantly enhanced by improving presintering temperature, thermal shock performance, and mechanical strength; From microscopic perspective, medium grain size(10μm ~ 20μm), uniform grain size, low porosity, and the reasonable air distribution are the key to obtain high performance heat shock power ferrite.