Preparation And Microwave Absorbent Properties Of W-type Ferrite And Composite

W-type ferrite is an important class of radar absorption materials(RAM) because ofsheet structure, high natural resonant frequency and Magnetic anisotropy. But thedevelopment of W-type ferrite is restricted because RAM has a low absorption at low waveband(0~6GHz). To improve the above shortcomings, a series of research works about W-typeferrite have been developed in this thesis. W-type ferrite was prepared by sol-gel method withmetal nitrate as raw material. The structure, surface morphology and electromagneticparameters of the samples were characterized by XRD, SEM, magnetometer and vectornetwork analyzer. And the characteristics of microwave absorption at0~6GHz is mainlyresearched. Experiment results show that:(1)The pure W-type ferrite can be prepared under the condition of1200°C which lasts2hours by sol-gel method. In addition, the microwave absorption peak of the pureBaCoZnFe16O27prepared under the above condition is18dB at5GHz frequency and theabsorption bandwidth above-5dB is1GHz.(2)PTh/BaCoZnFe16O27composite materials are prepared by in situ composite method.The microwave absorption changed stronger with increasing frequency from3GHz and thereflection loss(RL) is-5db at6GHz.(3) Carbonyl iron(Fe(CO)5)/BaCoZnFe16O27composite materials prepared by differentmethod have different characteristics. The microwave absorption of composite materialsprepared by physical mixture method is similar to microwave absorption of Fe(CO)5andBaCoZnFe16O27; The microwave absorption of composite materials, which prepared bysol-gel method combined with ultrasonic resonance method, changed stronger with increasingfrequency from2GHz and the reflection loss(RL) is-10db at6GHz; Fe(CO)5can be coated by BaCoZnFe16O27with the method of coprecipitation combined with ultrasonic resonance,which avoid to oxidation at high temperature. As the result, Fe(CO)5helps to strengthenthe characteristic of microwave absorption that absorption bandwidth ofFe(CO)5)/BaCoZnFe16O27above-10dB is more than2GHz.