Microstructural characteristics of Ce conversion coatings on Cf/Al composite or NiP plated Cf/Al composite

Abstract The microstructural characteristics of Ce conversion coatings on carbon fiber reinforced Al matrix (Cf/Al) composites and Ce conversion coatings on NiP plated Cf/Al composites were studied by SEM, AFM, TEM and XPS. The Ce conversion coating on the NiP plated composite does not have obvious microcracks, which can be found easily in Ce conversion coatings. The Ce conversion coating on NiP plated composite has a lower surface roughness profile arithmetic mean deviation ( R a ) than Ce conversion coating, as seen by AFM. Because of the inhomogeneity of the material surface and the different levels of deposition of Ce conversion coatings at the different sites, nonhomogeneous sites would promote microcrack formation of the Ce conversion coatings. The Cf/Al composite surface has lessuniformity than NiP plated composite, leading to more prominent microcracks. Selected area electron diffraction (SAED) patterns of Ce conversion coating could not be indexed nor matched closely to any of the oxides (Ce 2 O 3 , Ce 7 O 12 , Ce 6 O 11 ) or hydroxides (Ce(OH) 3 ) that are listed in the Powder Diffraction File maintained by Diffraction Data, but for Ce conversion coating on the NiP plated composite the data matched closely with that of CeO 2 or Ce 6 O 11 . The XPS results showed that the Ce conversion coating mainly contained both Ce 3+ and Ce 4+ species, but Ce 4+ species were the dominant oxidation state on NiP coating with Ce conversion deposition. Copyright © 2008 John Wiley & Sons, Ltd.