XPS study of finely dispersed iron powders modified by radiation-grafted acrylamide

Abstract

X-ray photoelectron spectroscopy was used to investigate structural peculiarities of the modifying layer obtained by means of radiation grafting of acrylamide (AA) on the surface of finely dispersed iron powder (FDIP) with a stabilizing coating based on oleic acid and isophytol. Judging by the information obtained on the grafting degree of AA, the highest grafting degree has been attained with water used as the monomer solvent (direct technique). The reasons for the grafting failure while using ‘the hydroperoxide technique’ have been discussed. Based on the XPS data, the mechanism of AA grafting from water solution to the surface of FDIP with a stabilizing coating has been proposed. The grafting process has been assumed to be associated with the formation of linear chains, including several types of reactive N- and O-containing groups at the active sites of the FDIP stabilizing layer. Such active sites are presumably represented by Fe(III), which are the central atoms of the complex compounds on the outer surface of the stabilizing coating. Polyacrylamide-grafted chains with hydrophobic radicals and a set of polar groups replace some of the monomer ligands around Fe(III) in the process of grafting. This process is most likely followed by the formation of chelate structures. The use of a chemical derivatization technique has provided insight into the nature of the peaks in the region of 284 eV in the C 1s spectra. The appearance of these peaks results from the formation of ‘quasi-graphite’ structures by isolated CC bonds present in a closely packed, highly oriented, stabilizing coating of iron powders under study. Copyright © 2000 John Wiley & Sons, Ltd.