ANALYSIS OF FLY-ASH DEPOSITION ON NICKEL

The surface chemical composition, particle size and shape of fly-ash deposits formed on a nickel surface have been investigated by using the surface sensitive techniques of X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and energy dispersive analysis of X-rays (EDAX). The XPS studies showed that Ni is well dispersed in the ash deposit mainly as oxide/hydroxide, chloride and sulphate. Argon-ion sputtering depth profiling also showed that the NiCl2 and NiSO4 content decreased below the surface, with reduction to sulphide occurring for the latter. EDAX analyses of the ash deposit samples indicated the strong presence of Ni and Cl with trace-element quantities of Fe, Si, S, Ca and K. SEM photomicrographs of ash deposits showed them to consist typically of irregularly shaped 10-50-mu-m particles.