Determination of mineral surface energy using impact of rough topography

While some of the studies on the functionalization of surfaces are still in theoretical phase, it is not possible to apply them on natural surfaces which already contain some irregularities. However, progress can be made with a mineral having significant purity, crystal homogeneity, and controllable surface workability for surface treatment operations. Therefore, in this study the effects of roughness on the surface energies of natural stones were investigated by selecting a sample with a distinctive color and metamorphic origin from Mugla, Turkey. First, sample surfaces were prepared using a polishing line with five different abrasives. Three-dimensional surface scans were then performed with ZYGONewView7100 optical-profilometer and ParkSystemAFM to identify the 3D roughness of the surfaces on two different scales (micro and nano) with SPIP-software. The micro average heights (S) of the produced surfaces ranged between 0.423-1.127 µm, nano-scale 0.0806-0.173 µm, while the surface roughness ratio (Sdr) between 33.7%-40.1%, and nano-scale 5.19%-18.5%. The contact angles of the samples were measured in the presence of pure water, formamide, and diiodomethane using AttensionTheta-tensiometer. Changes in surface energy were followed by Van Oss, Good-Chaudrey approach. Young, Wenzel, Cassie-Baxter contact angle theories were tested within these calculations. It was revealed that the inconsistency in solid phase energy could not be determined at this stage, but it could be regulated by modifying the Cassie-Baxter approach. Furthermore, the percentage of air packs likely to be below the water droplet not foreseen by the previous studies was calculated as 26% up to 35% air gap on the solid/water interface