| MnZn ferrites have been widely used in electronics and communications fields. As the main part of ferrite absorbing agent, MnZn ferrite powder has excellent electromagnetic-wave absorption property. This thesis proposed a new synthetic method of MnZn ferrites powder firstly. It also studied the influence of magnetic powder and sintering atmosphere on the properties of MnZn ferrites.(1)MnZn ferrite powder was synthesized by low-temperature solid state reaction. Mn-Zn ferrite powder was synthesized at 900℃ without pulverization by adding a moderate amount of hydrophilic carbon fiber in the mixture of the raw materials. Effects of carbon fiber and synthesis condition on the magnetic property for the samples were investigated by Vibrating Sample Magnetometer. The particle diameter increases with the amount of carbon increasing. However, excessive addition of carbon fiber deteriorates the magnetic performance of the ferrite powder. The spinel phase purity reaches the maximum with the addition of 0.5wt% carbon. On the other hand, the ferrite powder with high magnetic performance and high reaction rate of raw material powder was obtained when the carbon addition reaches to 0.64wt%. There, the optimum amount of the carbon addition is 0.64wt%. For the Mn Zn ferrite powder with different formula, the optimum synthesis temperature, sintering time and amount of carbon fiber addition should be determined by further more experiments.(2) The high permeability MnZn ferrite cores were synthesized by using ferrite powders with high spinel ratio. The effects of carbon fiber and synthesis condition on the magnetic properties of MnZn ferrite cores were investigated. The addition of carbon fiber accelerates solid phase reaction, promotes grain growth and densification, and effectively exhausts air flow. On the other hand, it also leads to abnormal grain growth and lattice distortion. Appropriate sintering temperature and partial pressure of oxygen can improve the magnetic of the sample.The spinel MnZn ferrite powder was successfully synthesized under 900 oC with the addition of carbon fiber, which has an important significance in the field of absorbing materials. Effect of powder on the properties of MnZn ferrite cores was also studied in this thesis. This work is meaningful for further research in synthesis of high permeability MnZn ferrite. |
