Anomalous electroless polyol deposition of FeNi powders and films

Abstract

Nanostructured FeNi powders and films were synthesized by reducing the metal acetates in refluxing ethylene glycol (EG). The chemistry of anomalous deposition of Fe and Ni was investigated for this polyol process. Unlike conventional polyol process in which the reaction solution was neutral, strong alkaline condition achieved by using NaOH was indispensable in the synthesis of FeNi. If NaOH was absent, the metal salts in EG solution tended to precipitate as a complex having FeNi(EG)2 structure, and little reduction took place. The addition of NaOH caused the reduction of metal precursors to metals, resulting in film deposition on substrate and powder precipitation in solution. In solution the formation of Fe(OH)2 led to the disproportionation of Fe(II) and increased the yield of Fe. However, Ni(OH)2, another product of NaOH-induced reaction, inhibited the reduction of Ni(II) to Ni. In the vapor phase of this refluxing system, film deposition took place in an Fe-rich environment with the participation of FeNi(EG)2. This generated complex was further reduced by EG vapor to preferentially dissociate metal Fe. As a result, high Fe concentration film could be obtained by vapor deposition. © 2001 The Electrochemical Society. All rights reserved.