The dissolution of Al2O3 and MgO inclusions in synthetic CaO‐Al2O3‐MgO slags have been investigated in situ with a confocal scanning laser microscope (CSLM). The dissolution mechanisms were elucidated by using analytical‐rate expressions. A set of parameters is introduced to distinguish between reaction control and diffusion control of the dissolution process. It was found that whereas Al2O3 inclusion dissolution rates are limited by diffusion, MgO dissolution appears to be limited by surface reaction. For both Al2O3 and MgO, the dissolution rate and the apparent activation energy increased when the slag composition was slightly shifted away from the saturation limit of the dissolving species in the phase diagrams.

Argon ion milling was used to transfer the pattern of sparse 12 nm iron oxide nanoparticles into underlying thin films of Pt and magnetic tunnel junction stacks and quantify their etching rates and morphological evolution. Under typical milling conditions, Pt milled at 10 nm min−1, while the isolated particles of iron oxide used for the mask milled at 5 nm min−1. Dilute dispersions of nanoparticles were used to produce the sparse nanomasks, and high resolution scanning electron microscopy (SEM) and atomic force microscopy were used to monitor the evolution of etched structures as a function of milling time. SEM measurements indicate an apparent 20% increase in feature diameter before the features began to diminish under additional milling, suggesting redeposition as a limiting feature in the milling of dense arrays. Simulations of the milling process in nanoparticle arrays that include redeposition are consistent with this observation. These simulations predict that an edge-to-edge spacing of 3 nm in a dense array is feasible, but that redeposition reduces the final structure aspect ratio from that of the masking array by as much as a factor of two.