Studies On Coated Ferrite Composite And Its Magnetic Properties

In this thesis, a packaged structure for a composite of cenospheres (CS) coated with spinel ferrite and M-type barium ferrite was designed. A packaged structure for a composite of tetrapod-shaped ZnO whisker coated with spinel ferrite was synthesized successfully via co-precipitation method. The influence of synthesis conditions for the performances of the package structure, which consisted of composition, morphology and magnetic properties, was investigated by using XRD, SEM, EDS, and VSM techniques.From the results, it was shown that the well packaged structure of spinel ferrite-CS and M-type barium ferrite-CS composite could be obtained by co-precipitation. The phase of BaFe12O19 existed in the packaged structure of composite became purer with decrease Fe/Ba molar ratio. With increasing calcination temperature, the magnetic performances, which consisted of specific saturation magnetization Ms,remnant magnetization Mr and coercivity Hci, were improved for the CoFe2O4-CS. When the calcining temperature was higher than that of 900℃, the magnetic performances of the package structure of spinel ferrite-CS decreased. With increasing calcination temperature, the magnetic performances, which consisted of specific saturation magnetization Ms and remnant magnetization Mr, increased gradually. However, along with increasing calcination temperature, the coercivity Hci of BF-CS increased at start and then decreased. The maximum of Hci for BF-CS appeared when calcined at 1000℃.The well-packaged structure of spinel ferrite-ZnO composite with tetrapod-shap can be obtained by co-precipitation. The increase of drop-time to some extent is in favor of enhancing the content of the composite coating. The increase of drop-temperature or calcining temperature to some extent is in favor of enhancing the packaged structure of coated composite,the crystallinity and particles size. With increasing calcination temperature, the magnetic performances, which of specific saturation magnetization Ms of NiFe2O4-ZnO increased firstly and then decreased. The the maximum of specific saturation magnetization Ms was attained for NiFe2O4-ZnO calcined at 1000℃. However, along with the increasing of temperature, the magnetic performances, which consisted of remnant magnetization Mr,the coercivity Hci, decreased gradually. The well package structure of CoxNi(1-x)Fe2O4-ZnO composite with tetrapod-shap can be obtained via elementary gallimaufry, and the consisted of composition and magnetic properties, were controlled by changing the Co/Ni molar ratio.