Biodegradable magnesium alloys, Mg-0·8wt%Ca and Mg-10wt%Gd, have been coated with gallium-containing electrolyte using plasma electrolytic oxidation (PEO). Thus, the PEO procedure is used as a synthesis tool, to create an appropriate content in the layers. This is a first article on the examination of such layers. One part of the gallium-coated samples was additionally sealed with biodegradable poly(L-lactide-co-caprolactone) (PLLC). Gallium content, morphology and thickness of the coatings were evaluated. Special focus was set in relation to the cytotoxicity of the coating, on the two different magnesium alloys and the additional sealing with PLLC. Cytotoxicity was tested using live/dead staining of MC3T3-E1 fibroblasts and by WST-1 assay, cell differentiation by alkaline phosphatase measurement. It could be shown that the gallium-ion concentration in the PEO layer was higher for Mg-10wt%Gd than that of Mg-0·8wt%Ca, which caused a significant difference in the cytotoxic effects toward MC3T3-E1 cells. Still in all cytotoxic tests, Mg-10wt%Gd showed no to low cytotoxic levels, whereby Mg-0·8wt%Ca showed moderate results. Furthermore, it could be proved that an additional PLLC sealing benefits the cell adhesion and thus promotes the cytocompatibility of the coating.
Three methods for hardness-depth profiling were applied to a 200-nm-thick TiC film deposited onto a Ti-6Al-4V substrate. The methods were evaluated and compared with regard to their ability to detect local changes in hardness with a depth resolution on the order of a few nanometers. In the cross section method (CSM), the indentations are performed on a cross section of the sample, i.e., in a direction perpendicular to the hardness gradient. In the load-variation method (LVM) and in the constant-load method (CLM), the indentations are made in the direction of the hardness gradient, i.e., perpendicular to the as-prepared surface. In the LVM, the hardnessdepth profile is assessed using a stepwise increase of the maximum load applied to the surface. In the CLM, sublayers are removed successively by ion sputtering and hardness measurements are performed at each newly exposed surface using the same low maximum load. The CSM revealed a nearly constant hardness across the TiC film and a sharp transition from the TiC film to the Ti-6Al-4V substrate. The hardness profile obtained using the LVM and the CLM is smeared out because the recorded response is due to both the TiC film and the underlying softer Ti-6Al-4V substrate.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.