Influence of the borohydride concentration on the composition of the amorphous Fe–B alloy produced by chemical reduction of synthetic, nano-sized iron oxide particles Part II. Goethite.

Abstract

A systematic study of the effect of the NaBH4 concentration upon the composites produced by chemical reduction of nano-sized goethite (_-FeOOH) particles suspended in water is presented. Amorphous Fe–B alloys with boron contents between 2 and 8 at.% have been produced. The obtained samples were characterized by X-ray diffraction, wet chemical analyses, thermal analyses, scanning electron microscopy, transmission Mossbauer spectroscopy (TMS) and integral low-energy electronM¨ossbauer spectroscopy (ILEEMS). It was observed that the boron content of this amorphous composite sensitively depends on the borohydride concentration. The TMS analyses have shown that the contribution of the Fe1−xBx phase, which is present as a superposition of a broad sextet and a doublet, accounts for about 38% of the total spectral area. ILEEMS has further revealed that the reduction process mainly affects the surface layers of the goethite grains, without causing any changes in both particle shape and sizes.