The Preparation And Properties Of The The Spinel Nicuzn Ferrite Nanomaterials

Nickle copper zinc ferrite soft magnetic materials is one of the main materials for multi-layer chip inductor(MLCI).The preparation of NiCuZn ferrite nanomaterials has become the trend of development at low sintering temperature and excellent properties of MLCI.The aim of this thesis focuses on the preparation of NiCuZn ferrite nanomaterials,and also investigates the relationships between microstructure and magnetic properties.Firstly, the precusor of NiCuZn ferrite was prepared by chemical co-precipitation method. X-ray diffraction(XRD) proved that the main component of the precursor was a single phase of spinel. the crystallization processes of the precursor characterized via thermogravimetry-differential scanning calorimetry(TG-DSC) indicated that the precursor still contained a little water and non-crystal materials.The microstructure and the particle size of precursor were controlled by the process condition.The particle size of sample increase with the increase of flow speed and stirring rate, while it decreases with the increase of reaction temperature. The optimum process conditions synthesised the precursor include the reaction temperature of 70℃,pH value of 10.5, the flow speed of 0.5mL/min and the stirring rate of 300rpm.Secondly, the surfactant of SDBS,PEG and PVP have been put to use in the solution of the precursor in order to obtain the nano-scaled powder.The kind,usage and using style of the surfactant were determined through the research of absorption mechanism in the interface of solid and liquid. A single surfactant and compound surfactant were chosen through the experiment results.The usage of the surfactant was determined by the critical micelle concentration(CMC) and the surfactant was put into the reactor for controlled crystallization process.The nano-scaled powder of precursor was prepared via the surfactant process. TEM photograph indicated that the precursor consists of homogeneous,discrete,spherical particles with mean particle size about 30nm.Thirdly, the calcining temperature of the precursor with nano-scaled powder has been investigated in the calcine process. The effect of calcining temperature on the magnetic properties has been explored for the optimum calcining temperature about 500℃.The precursor has been transformed into pure spinel ferrite and realised not only densification but also excellent magnetic properties calcining at 500℃from TG-DSC curves.Finally, the effect of sintering temperature on the magnetic properties of NiCuZn ferrite were investigated in the sintering process. NiCuZn ferrites with relatival sintering density of 98%, initial permeability of 200, quality factor of 150, cut-off frequency of 70 MHz were achieved at 500℃calcining temperature and 900℃sintering temperature.