Research On NiZn Power Ferrite With Resistance To Thermal Shock

This thesis focuses on the high-performance power NiZn ferrite material with mechanical strength and resistance to thermal shock. Firstly we ensure excellent electromagnetic properties, such as high permeability, high saturation magnetic flux density, high density, high resistivity, low loss, etc, which meet the requirement of technical specifications for power ferrite material. Choose the samples which meet the technical index, carries on the thermal shock and mechanical strength experiment. According to the experiment results, from two aspects of the doping and technology, research and analyze the influence factors on ferrite core about mechanism of the thermal shock and mechanical strength. Then put forward some methods to improve the mechanical strength and resistance to thermal shock for nickel-zinc-ferrite core. Topics include:1、Study the replacement of Co2+、Cu2+ and Zn2+ respectively which have a impact on nickel-zinc power ferrite about phase, magnetic parameters and microstructure. According to the experiment results, select suitable process condition, ion substitution and replace quantity, to achieve the material index. The experiment results show that, in the same replace quantity range, the change trend of Co and Cu show significantly different. Due to the transition of liquid phase sintering densification and microstructure improved and sintering, the sample replaced by Cu own higher saturated magnetic induction intensity, initial relative permeability and lower loss factor.2 、 Study the impact on nickel-zinc power ferrite magnetic parameters and microstructure through WO3, CaCO3-SiO2 composite, WO3-SiO2 composite doping respectively in the second grinding. According to the experiment results, select the appropriate process condition, the doping ions and doping amount, to meet our requirement. Adding the right proportion of WO3 can improve the sintering density, reducing the generation of porosity, grain size uniformity will be good, these will be helpful for the thermal shock performance of the sample. Adding the right proportion of CaCO3-SiO2 composite increases the thickness of the grain boundary, in order to enhance the mechanical strength and thermal shock resistant properties of the sample. Trace amounts of Bi2O3 doping, while lowering the sintering temperature, is expected to improve power ferrite microstructure.3、Firstly, thermal shock fracture and damage theory, the ferrite material strength theory has been described in these two areas, and then analyzed some of the key factors that influence both. Further, on the basis of experimental data in the third chapter, and discusses the factors that influence the mechanism of ferrite core mechanical strength and resistance to thermal shock. The establishment of micro-structural control model reveal that process condition and different doping system have a impact on pores and grain particle distribution, thereby affect the sample thermal thermal shock resistance and mechanical strength. Fine grain size distribution, low porosity materials are the preferred way to improved the thermal shock resistance and mechanical strength.