Article ID Journal Published Year Pages File Type
1625671 Journal of Alloys and Compounds 2007 12 Pages PDF
Abstract

Amorphous Fe–B alloys can be prepared at room temperature by reduction with borohydride of iron-oxide particles in suspension. By varying the borohydride concentration, amorphous Fe–B alloys with boron contents between 2 and 13 at.% have been produced by reduction of synthetic (nano-sized particles) and natural (micro-sized) hematite (α-Fe2O3) using sodium borohydride (NaBH4). The results presented in this paper were obtained from a systematic study of the effect of borohydride concentration on the resulting reaction products using a variety of experimental techniques, such as X-ray diffraction, wet chemical analyses, thermal analyses, scanning electron microscopy, transmission Mössbauer spectroscopy (TMS) and integral low-energy electron Mössbauer spectroscopy (ILEEMS). Three distinct NaBH4 concentrations have been applied. Beside unreacted hematite, amorphous Fe1−xBx alloys have been identified from the TMS spectra recorded at various temperatures between 15 K and room temperature. The amount of Fe1−xBx increases strongly with increasing NaBH4 concentration, and for a given concentration with increasing specific surface area (SSA). Thermal analyses have suggested that for any given reduction condition, the boron content x in the formed amorphous alloy has a bimodal distribution. This is found to be consistent with the finding that the contribution of the Fe1−xBx phase to the total Mössbauer spectra consists of a superposition of a broad sextet and doublet. ILEEMS has further revealed that especially the surface layers of the hematite grains are affected by the reduction processes.

Related Topics
Physical Sciences and Engineering Materials Science Metals and Alloys
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