Synthesis of nanocomposites comprising iron and barium hexaferrites

2020-02-15 00:14:01

particle reduction alpha barium hexaferrite

责任者: Pal, M.;Bid, S.;Pradhan, S.K.;Nath, B.K.;Das, D.;Chakravorty, D. 单位: Indian Assoc. for the Cultivation of Sci., Kolkata, India 来源出处: Journal of Magnetism and Magnetic Materials(J. Magn. Magn. Mater. (Netherlands)),2004/02/,269(1):42-7 摘要: Composites of nanometre-sized α-iron and barium hexaferrite phases, respectively, have been synthesized by the ceramic processing route. Pure barium hexaferrite (BaO·6Fe2O3) was first of all prepared by calcinations of the precursor oxides at a maximum temperature of 1200°C for 4 h. By subjecting the resulting powder having particle size of the order of 1 μm to a reduction treatment in the temperature range 500-650°C for a period varying from 10 to 15 min it was possible to obtain a composite consisting of nanosized barium hexaferrite and α-Fe. At reduction temperature of 650°C for a period greater than 15 min all the ferrite phase was converted to α-Fe and Ba - the particle sizes being 59.4 and 43.6 nm, respectively. These conclusions are based on X-ray diffraction and Mossbauer studies of different samples. During reduction H+ ions are introduced into the hexaferrite crystallite. It is believed that due to a tensile stress the crystals are broken up into smaller dimensions and the reduction brings about the growth of nanosized α-Fe and barium, respectively, around the hexaferrite particles. Magnetic measurements show coercivity values for the reduced samples in the range 120-440 Oe and saturation magnetization varying from 158 to 53.7 emu/g. These values have been ascribed to the formation and growth of α-Fe particles as the reduction treatment is increased. By heating the nanocomposites at a temperature of 1000°C for 1 h in ordinary atmosphere it was found that they were reconverted to the barium hexaferrite phase with a particle size ~182.3 nm. The reaction described in this study is thus reversible 关键词: barium compounds;calcination;coercive force;crystal growth;ferrites;iron;magnetic particles;Mossbauer effect;nanocomposites;particle size;powders;reduction (chemical);X-ray diffraction;nanocomposites synthesis;nanosized barium hexaferrites;nanometre-sized α-iron;ceramic processing route;calcinations;powder particle size;reduction treatment;X-ray diffraction;Mossbauer studies;reduction;tensile stress;coercivity;saturation magnetization;1200 degC;1 mum;500 to 650 degC;10 to 15 min;59.4 nm;43.6 nm;1000 degC;1 h;Fe-BaOFe2O3