Survey of conditions to produce metal-boron amorphous and nanocrystalline alloys by chemical reduction

Chemical reduction synthesis (CRS) has been employed to produce binary and ternary M-B (M = Fe, Co, Ni and Mn) alloys of different structural arrangem ents: amorphous and amorphous/nanocrystalline alloys, the latter comprising nanometric crystalline particles embedded in an amorphous matrix. The opti mum concentrations to obtain amorphous alloys are 0.1 M (100 ml, metallic s alt) and 0.2 M (250 ml, reductor: NaBH4) as deduced from X-ray diffraction and room temperature Mossbauer spectroscopy. If equal concentrations and ae rosol droplets are used, the amorphous/nanocrystalline structure is the lar gest fraction produced. From the variation of pH we predict the feasibility and optimisation of the reduction process, in particular, reaction mass yi elds. In some cases, the alloys have one or two peaks in the AC susceptibil ity at temperatures < 200 K. (C) 2001 Elsevier Science B.V. All rights rese rved.