Study On Synthesis And Mechanism Of NiZn Ferrite By Self-Propagating Combustion Technique

NiZn ferrite was synthesized using self-propagating high-temperature synthesis (SHS) and self-propagating low temperature synthesis (LCS). Theoretical analyses of combustion synthesis were performed in terms of SHS. The influence of ZnO content, the iron content, green density, the Nickel source, as well as doped Bi2O3, Co2O3, PbO, SiO2 and MoO3 were investigated systematically NiZn ferrite were produced by SHS under Magnetic field, which is one of the novelties of the study. The effects of magnetic field strength, change of magnetic direction, application to the stage of combustion synthesis on the performance of sample were studied individual. In terms of LCS, molar ratio of citric acid to metal ions, sol pH, the influence of sintering temperature as well as preheating temperature were investigated, respectively. Reactions temperatures were obtained by infrared radiation thermometer, The NiZn ferrite phase composition, microstructure and magnetic properties were also characterized with the help of XRD, EDS, SEM, VSM. The lattice parameter and the size of crystal were calculated by Jade5.0. These concrete works are the following:By thermodynamic calculation based on thermodynamic principle, the adiabatic temperature of combustion synthesis Ni0.35Zn0.65Fe2O4 has been calculated when different mixture of iron, iron oxides, Zinc oxide, Nickel oxide and sodium perchlorate powders. The synthesis pathways of NiZn ferrite were induced according to the relationship of free enthalpies of reaction products versus temperature, and a mechanics corresponding to the self-propagating high temperature combustion mechanism of form Ni-Zn ferrite powders were proposed.In the process of self-propagating high temperature synthesis of NiZn ferrite in normal air atmosphere, Ni0.35Zn0.65Fe2O4 was selected as the main prescriptions, with the low coercivity and high specific saturated magnetization. Ni0.35Zn0.65Fe2O4 reached the optimal performance when Fe:Fe2O3=3:1, odium perchlorate content was 23.1%, in which condition the saturated magnetization (Ms) was 68.1emu/g, coercivity was 17Oe, The initial permeability was 23.3. Ni0.35Zn0.65Fe2O4 synthesized by Ni and NiO have better magnetic properties.The effects of Bi2O3, Co2O3, PbO, MoO3 and SiO2-doping respectively on the microstructures and electromagnetic properties of Ni0.35Zn0.65Fe2O4 were investigated. The results show that Bi2O3 and PbO addition can promote the grain growth, MoO3 and SiO2 addition can increase the density of sintered product and the initial permeability of NiZn ferrites. the grain of Ni0.35Zn0.65Fe2O4 can decrease after SiO2 were doped, the size are about 1-2μm. the initial permeability of NiZn ferrites can increase 10% and 74.4% corresponding individually doped 1% SiO2 and MoO3.This paper also systematically explores the effect of the electromagnetic field on ferrite by combustion synthesis. The high saturation magnetization of Nickel-zinc ferrite can be improved by combustion synthesis in the optimum magnetic field strength of 0.5T or 1.1T. The specific saturation magnetization of products increased of 5.4% in a field of 1.12T compared those of 0T. The initial permeability of sample increased of 38% prepared in the field of 1.12T than those of 0T. When the magnetization is 1.1T, NiZn ferrite became polygonal crystal pronounced, which is due to the crystal growth. The magnetic field of 1.3T applied to different stages of combustion process were studied, He of sample were increased when the applied magnetic field; the specific saturation magnetization were not change obviously trend. The magnetic field influence on the property of NiZn ferrite is mainly determined by the property of combustion pro and the cooling process of the product after combustion. The model of heat and mass transfer process during SHS under external magnetic field had been built.Nio.35Zno.65Fe204 was synthesized by sol-gel self-propagating synthesis router. The best optimum technological conditions are the body solution pH=7.00, citric acid and metal ions of the material in a ration of 2:1, ignition temperature at 400℃and sintering temperature at 1180℃, in which condition the specific saturated magnetization (Ms) was 70.2 emu/g, coercivity was 51.6Oe. Ni0.35Zn0.65Fe2O4 was synthesized by means of sol-gel auto-combustion synthesis method using other fule, such as glycine and urea.