Study On The Preparation Of High Peameability Ferrite Used For Anti-Electro-Magnetic-Interference From MnZn Soft Ferrite Wastes

High permeaility MnZn ferrites with broad frequency characteristic is one of the necessary functional materials in developing modern electronic information and technology, which are widely used in anti-electro-magnetic-interference materials. Large amount of MnZn ferrite wastes are produced in the manufacturing process. Huge ecnomic and environmental benefits will be produced if these wastes can be recycled and prepared to high-performance ferrites.On the basis of the former research, we used MnZn ferrite wastes as the raw material. MnZn coprecipitation powder was prepared through sulfuric acid simultaneous leaching, MnZn reduction-NH3·H2O purification and NH3HCO3 co-precipitation. Then pre-sintering, doping and milling, granulation, pressing and sintering processes, high permeaility MnZn ferrites samples were prepared.The result of this research showed that:1) Reduction process was very stict to the reductional metals. The effect of Mn-Zn metal reduction was much better than Fe powder. Purification process was harsh to the pH value. Too low or high of pH value adversed the removal of inpurities. The pH value, reaction temperature and reaction time on the purification effect were detailed studied in this research.2) Pre-sintering had a significant inpact on the composition of the powder. With the pre-sintering tempreature increasing, the grain of the powder increased and the grain size became well-distributed. But over-increasing would result in agglomerate and the powder shape would become irregular. The effect of different pre-sintering temperature and time was studied in this paper.3) Doping had a great influence on the structure of the powder and magnetic properties. Different additives had the different inpacts. MoO3,Bi2O3,SnO2,CaCO3 were studied detailed in the subject, and the best conditions for doping was obtained.4) Milling inpacted mainly on the particle size and activity of the powder. With the increased of milling time, the particle size became more and more fine and the activity was also increasing. But over-fine powder would have dscontinuous growth.5) Sintering was the most improtant factor to the properties of the ferrite. A suitable sintering temperature would obtain high permeability ferrite which owned large grain, few pores and straight grain boundaries. Appropriate heating rate and cooling rate could ensure the degree of the ferrite reaction. Sintering atmosphere would affect the phase composition of ferrite, thus affect the magnetic prorerties. So a balance sintering atmosphere must be controlled.On the basis of the optimized fomulation (Fe2O3:MnO:ZnO= 52.3: 23.3:24.4), through a variety of ferrite process, We sucessfully prepared the MnZn ferrites which the initial permeability reached 13000 and it would't reduce when the frequency got to 150KHz. This ferrite had the same properties as R15K of Hengdian East Magnetic Co., Ltd in Zhejiang.