The authors study the morphological evolution of magnetron-sputtered thin silver (Ag) films that are deposited on weakly interacting silicon dioxide (SiO2) substrates in an oxygen-containing (O2) gas atmosphere. In situ and real-time monitoring of electrically conductive layers, along with ex situ microstructural analyses, shows that the presence of O2, throughout all film-formation stages, leads to a more pronounced two-dimensional (2D) morphology, smoother film surfaces, and larger continuous-layer electrical resistivities, as compared to Ag films grown in pure argon (Ar) ambient. In addition, the authors’ data demonstrate that 2D morphology can be promoted, without compromising the Ag-layer electrical conductivity, if O2 is deployed with high temporal precision to target film formation stages before the formation of a percolated layer. Detailed real-space imaging of discontinuous films, augmented by in situ growth monitoring data, suggests that O2 favors 2D morphology by affecting the kinetics of initial film-formation stages and most notably by decreasing the rate of island coalescence completion. Furthermore, compositional and bonding analyses show that O2 does not change the chemical nature of the Ag layers and no atomic oxygen is detected in the films, i.e., O2 acts as a surfactant. The overall results of this study are relevant for developing noninvasive surfactant-based strategies for manipulating noble-metal-layer growth on technologically relevant weakly interacting substrates, including graphene and other 2D crystals.

Mineral carbonation is considered to be the most stable mechanism for the sequestration of CO₂. This study comprises a comparative review of the effect of ball milling on the CO₂ uptake of ultramafic/mafic lithologies, which are the most promising rocks for the mineralization of CO₂. Samples of dunite, pyroxenite, olivine basalt and of a dolerite quarry waste material were previously subjected to ball milling to produce ultrafine powders with enhanced CO₂ uptake. The optimum milling conditions were determined through selective CO₂ chemisorption followed by temperature-programmed desorption (TPD) experiments, revealing that the CO₂ uptake of the studied lithologies can be substantially enhanced via mechanical activation. Here, all these data are compared, demonstrating that the behavior of each rock under the effect of ball milling is predominantly controlled by the mineralogical composition of the starting rock materials. The ball-milled rock with the highest CO₂ uptake is the dunite, followed by the olivine basalt, the pyroxenite and the dolerite. The increased CO₂ uptake after ball milling is mainly attributed to the reduction of particle size to the nanoscale range, thus creating more adsorption sites per gram basis, as well as to the structural disordering of the constituent silicate minerals.