Preparation of magnetic films by new technique "ultrasound enhanced" ferrite plating

点击翻译按钮获取中文摘要

Ferrite plating invented by the investigators enables formation of ferrite films from aqueous solution. Requiring no heat treatment, the ferrite plating facilitates fabrication of ferrite film devices using non-heat-resistant substances (e.g.plastics, nano-sized multilayrs, etc.) as substrates. In this study we combined the ferrite plating with sonochemical technology to improve the crystallinity and magnetic properties of the plated films. Applying power ultrasound waves (19.5kHz, 600W) to an FeCl_2 aqueous solution at 70ﾟC,we successfully encapsulated polyacrylate spheres of two sizes, 0.25 mum and 4.5mum in average diameter, with ferrite coatings of a magnetite-maghemite mixed solution. This broke the previous lower limit (0.3mum) of the size of the particles to be encapsulated ; without application of the ultrasound waves, the ferrite coating became discontinuous or insular. Applying high frequency ultrasound waves (1.6MHz, 20W) and the above low frequency ultrasound waves simultaneously, Fe_3O_4 films were successfully improved in surface smoothness and solubility limit of Ni ions in films of NiZn ferrite (Ni_<3-x-y> Ni_x Zn_y O_4) was increased from x=0.35 to 0.42. The marked improvements are ascribed to "hot spots" and "micro-stirring" caused by collapse of cavitation bubbles in the sonicated aqueous solution.