The well-fitted Langmuir adsorption isotherms suggested that the CV adsorption was monolayer adsorption. In the thermodynamic study, the negative Δ G indicated that the adsorption of CV on the surface was spontaneous and the positive Δ H suggested that the reaction was endothermic. The adsorption capacity of both increased with increasing pH and temperature. It was also indicated by the larger slope of adsorption lines as a function of SSA. Owing to the larger surface site density, the saturated adsorption amount of α-quartz was larger than that of α-cristobalite. As two common SiO 2 polymorph minerals in soil and sediments, α-quartz and α-cristobalite have been studied for the effects of their surface heterogeneity on adsorption behaviors toward crystal violet (CV) by batch adsorption experiments in different specific surface areas (SSAs) and at different pH values and temperatures, as well as by X-ray photoelectron spectroscopy (XPS) investigation. The diversity in the crystal structure of SiO 2 polymorphs might lead to the heterogeneity in their surface microstructures and properties. They play an irreplaceable role in the whole geochemistry and environment processes. The nanohardness of the WL is much higher than that of the bulk material due to oxide hardening.Silica minerals are a kind of important minerals and widespread on the earth’s surface. The white layer shows less crystal plastic deformation than the bulk material, and refined grains with random orientation can be found in the WL. The upper portion of the WL consists of primarily the solid solution phase (Cu + Ni + Zn)-FCC, while Ti 2O 3 and Nitinol austenite phases dominate the lower portion of the WL. The white layer of Nitinol by EDM is a crystalline structure instead of the traditionally believed amorphous solid. The WL by wire-EDM exhibits a porous and non-uniform bi-layered structure. This work focuses on a comprehensive investigation on the crystallography, compositions, and properties of the white layer using transmission electron microscopy (TEM), X-ray diffraction (XRD), electron backscatter diffraction (EBSD), and nanoindentation.
The machined surface integrity is critical to product performance such as fatigue, corrosion, and wear, yet few studies have conducted a thorough investigation of the machined surface integrity, in particular white layer (WL). Wire electric discharge machining (wire-EDM) is an alternative process to machine Nitinol SMAs. Nitinol shape memory alloy (SMA) is very challenging to machine by conventional mechanical cutting.