Growth of hematite nanowire arrays during dense pentlandite oxidation

Abstract

A simple synthesis method is proposed for producing aligned and uniform single-crystal one-dimensional hematite (α-Fe₂O₃) nanostructures on pentlandite. Pentlandite is the most common terrestrial iron-nickel sulfide and the principal ore mineral of nickel. In this study, a pentlandite sample was synthesized from pure components Fe, Ni and S. Oxidation makes the chemical potential of iron reduce more than that of nickel. Iron migrated rapidly to the surface of dense pentlandite and was oxidized preferentially to form an oxide layer. Several micrometers long α-Fe₂O₃ nanowires grown along the [110] direction were achieved. The ordered oxygen vacancies which lie parallel to the growth direction were observed. Hematite (α-Fe₂O₃) and magnetite including Ni (Ni_xFe_3−xO₄) are major components of the oxide layer. Three kinds of morphology are included in this layer: nanowires, dense and porous oxides. The Ni-rich pentlandite coexists with NiS, hexagonal pyrrhotite (Fe_1−xS) and/or godlevskite (Ni₇S₆). This work provides a new strategy to inexpensively and efficiently synthesize nanostructures directly from ore minerals.