Nanocrystal Growth in Thermally Treated Fe 75 Ni 2 Si 8 B 13 C 2 Amorphous Alloy
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IRON-BASED amorphous alloys have been a focus of considerable scientific interest in recent times. Their main features are isotropic physical and mechanical properties. The addition of metalloid amorphizers like B, Si, P, or C and the substitution of Fe by Co or Ni (or a mixture of both) enhance their glass-forming ability,[1,2] although boron-free soft magnetic alloys have been prepared recently with magnetic properties similar to those of conventional boron-containing Fe-based alloys.[3] Recently, commercial, soft magnetic nanocrystalline materials have been successfully obtained by crystallization of the amorphous precursors.[4,5] These materials are characterized by a microstructure of nanocrystals embedded into an amorphous matrix, exhibiting superior soft magnetic and mechanical properties to both amorphous and macrocrystalline magnetic alloys.[6–8] The functional properties of these materials are highly dependent on their microstructure,[9,10] including the degree of crystallization and the nanocrystal size. The control of the crystallization process and the degree of crystallization would allow for tailoring of the material properties to particular needs. Both iron and iron-based nanostructured materials have been successfully synthesized in recent times, attracting considerable interest. Monodisperse iron nanoparticles[11,12] and nanorods[13–15] have been synthesized both in a solution DRAGICA M. MINIC´, Professor, and VLADIMIR A. BLAGOJEVIC´, Research Scientist, are with the Faculty of Physical Chemistry, University of Belgrade, Belgrade 11000, Serbia. Contact e-mail: dminic@ffh.bg.ac.rs DUSˇAN M. MINIC´, Research Scientist, is with the Military Technical Institute in Belgrade, 11001 Belgrade, Serbia. BOHUMIL DAVID and TOMA´Sˇ ZˇA´K, Senior Research Scientists, NADEˇZˇDA PIZU´ROVA´, Research Scientist, are with the Institute of Physics of Materials, Academy of Sciences of Czech Republic, Brno 61662, Czech Republic. Manuscript submitted January 13, 2012. Article published online April 5, 2012 3062—VOLUME 43A, SEPTEMBER 2012
and on a substrate, and it was observed that these materials exhibit different properties than the bulk iron: lower melting temperature and superparamagnetic behavior.[11,13] Iron nanorods arrays also exhibit high coercivity and high remanence, which makes them interesting for potential magnetic recording applications.[14] Palumbo and Barrico[16] conducted modeling of primary iron crystal growth in a Fe85B15 amorphous alloy and found a reasonable agreement between the calculated and experimental DSC curves, although it was shown that continuous heating requires more detailed treatment of nucleation. Stergioudis et al.[17] found that Ni affects crystallization of Fe75-xNixSi9B16 (x = 1 to 4) amorphous alloy strongly, changing the morphology of the resulting crystal grains. Kim et al.[18] studied the growth direction and velocity of the a-Fe(Si) crystalline phase during crystallization of Fe80Si8B12 amorphous alloy; they found that dendritic growth occurs in the {111} direction and that
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