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Crystalline zinc oxide (ZnO) particles with different morphologies have been synthesized by the hydrothermal method under the magnetic field. It is found that the magnetic field influences the nucleation and growth of ZnO crystals. ZnO crystals obtained under high pulsed magnetic field were more uniform and well integrated.

Nanocrystal MnO2 was successful synthesized by hydrothermal method under pulsed magnetic field. The effect of pulsed magnetic field on the nucleation and growth of MnO2 was studied by XRD and SEM analysis. It was found that the morphology of MnO2 has been changed comparing without magnetic field. However, there were no different phases presented when pulsed magnetic field was applied.

Nanocrystalline CO 3 O 4 particles were successfully synthesized by hydrothermal method under pulsed magnetic field. The effect of magnetic field and aging time on the morphology and microstructure were examined. Different morphologies were observed from SEM images for the samples fabricated with or without pulsed magnetic field. The pulsed magnetic field made CO 3 O 4 sphere compact and more smooth surface. The hollow sphere morphology and refined grain of CO 3 O 4 were formed after aging process.

ZnO has the richest family of nanostructures among all materials, both in structures and in properties [ 1]. It has attracted great interest because of its potential high-tech applications. It is well known that synthesis technology is very important for getting desirable microstructure and properties. With the development of nano-technology, ZnO particles with various morphologies have been successfully synthesized. Although various synthetic methods of ZnO nanoparticles, such as growth from solution, hydrothermal growth, and thermal evaporation, have been much researched. That's mostly focused on modifying the synthesis conditions and difficult to control the microstructure and properties of synthesized materials. To solve this problem, we try to apply magnetic field in synthesis process to find new way [2]. Here we report the pulse magnetic field is applied in the hydrothermal process of ZnO particles' fabrication.The essential reaction for synthesis of ZnO particles is as following:Zn(CH3COO)2 +2NH3 . H20 � 2CH3COONH4 +ZnO .J., +H20(1) All chemicals used in this work were analytical grade reagents. Samples were prepared using the following procedures: The mixture of ammonia and zinc acetate solution was stirred for 15 minutes, then transferred into a 25 ml Te flon-lined stainless steel autoclave. The autoclave was heated and maintained at 180°C for 4 hours with or without 4 T pulsed magnetic field, respectively. Then, the autoclave was cooled down naturally to room temperature. The precipitates were filtered off and washed with distilled water and ethanol several times. Finally, the particles were dried at 60°C for 10 hours.X-ray diffraction (XRD) patterns for as-synthesized zinc oxide particles were detected by a D/max-3C X-ray diffract meter equipped with Cu Ku radiation (A = 1.5406 A) to observe the phase purity. The morphology and size of the ZnO particles were further observed by field emission scanning electron microscopy (FE-SEM, JEOL JSM-6700). Fig. 1 is X-ray diffraction patterns for the ZnO particles obtained by hydrothermal method with and without magnetic field, respectively.20 o o N o 40 a) 4T 60 80 2Theta(deg.) 100 20 N o 40 60 80 2Theta(deg.) b ) OT 100 Fig. 1. XRD patterns of as-synthesized ZnO particles obtained under magnetic field of: (a) 4 T, ( b ) 0 T 978-1-4244-6644-3/10/$26.00 ©2010 IEEE 642