| Recently, hollow microspheres have attracted great interest on its preparation and characteristic study due to its extensive application on catalysis, makeup, medicine, gene delivery, hydrogen production and storage, photonics, photo-electronics, rechargeable battery and etc. Whereas of all the methods to prepare hollow microspheres, template method is the most extensive one because theoretically once an appropriate template is determined, the hollow structure can be fabricated whose size, conformation and chemical compositon are controllable. Therefore, it has great value to further considerably investigate the theory and technology to prepare hollow microsphere by template method. Furthermore, as a result of significant application in electronic devices, semiconductor materials, biological engineering, optoelectronics and microwave absorbing for ZnO and ferrite, at present, the preparation of ZnO with hollow structure and ferrite materials is a research hotspot for material science, optics, electromagnetic, biology and chemistry.In this article, ZnO and CoFe2O4 hollow microspheres were manufactured by template method. Centering on the preparation of hollow sphere, this work put the emphasis on the discussion of the influence of the preparation process to the hollow structure and the appearance, and has a dissertation on the contribution of the annealing temperature to the magnetic properties of CoFe2O4 hollow spheres. The main contents of the work are as following:1. Colloidal carbon spheres were prepared by hydro-thermal method, and the structure and morphology were characterized. The particle was typical spherical, amorphous, and the size appears uniformly.2. The polycrystalline ZnO hollow spheres with wurtzite structure were acquired by template method. Processing parameters effected on the structure and shape of hollow microspheres were studied systematically. Pure ZnO hollow spheres were prepared when the sintering temperature was not less than 450℃; the size and surface topography of hollow spheres can be controlled by adjusting the stewing time of carbon template in Zn2+ ion solution. The addition of Cl- and NO3- had a significant influence on the morphology of ZnO hollow microspheres.3. The polycrystalline Co-ferrite particles with spinel structure were fabricated by hydro-thermal method. We researched the temperature and time of hydro-thermal reaction affected the structure and magnetic property of Co-ferrite particles thoroughly. The temperature played an important role of the component of Co-ferrite. With the temperature increasing, the magnetic properties of Co-ferrite enhanced; we can also modulate the magnetic parameters by changing the reaction time. We consider that the predisposing cause of the crystal nucleus growth of Co-ferrite was the hybridization of electron orbits between O2- ion and magnetic positive ion.4. Hollow microspheres of polycrystalline Co-ferrite particles with spinel structure were prepared by template method. The influence of the structure,shape and the magnetic properties of hollow spheres by changing the sintering temperature was researched in depth and detailed. The shape change of Co-ferrite microspheres would be occurred when the sintering temperature altered. When the temperature raised up to 550℃, the microspheres transformed from hollow structure to loose structure. We also found that a-Fe2O3 turned up when the sintering temperature rose to 450℃. We think the formation of Fe3+[(Co1-xFex)2+Fe3+]O4 was the main reason for the phase transition and the alteration of magnetic properties of samples. |
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