Combined in situ microstructural study of the relationships between local grain boundary structure and passivation on microcrystalline copper

Abstract

In situ Electro-Chemical Scanning Tunneling Microscopy (ECSTM) and Electron Back-Scatter Diffraction analysis of the same local microstructural region were combined to study the relationships between grain boundary (GB) type and structure and passivation on microcrystalline copper in 0.1 M NaOH aqueous solution. The results show that, for high angle random boundaries, passivation in the Cu(I) oxidation range is characterized by a decrease of the depth of GB edge region due to the formation of a passive film locally thicker than on the adjacent grains and thus to anodic oxidation being locally less efficient since it consumes more copper at the grain boundaries. For 3 CSL boundaries, the Cu(I) passivation efficiency was observed to be dependent on the local structure of the boundaries. A transition from more to less efficient passivation was observed for a deviation angle of 0.4-0.5° of the {111} GB plane with respect to the perfect geometry of an ideal coherent twin boundary. This transition would result from the effect on the local anodic oxidation properties of an increased density of misfit dislocations accommodating the increased deviation of the boundary plane from the exact CSL plane.

In situ scanning tunneling microscopy study of 2-mercaptobenzimidazole local inhibition effects on copper corrosion at grain boundary surface terminations

“…The decrease of the GB depth is consistent with the local accumulation of reaction products, more important in the GB region because of the locally higher reactivity. Such a local GB behavior has been observed by ECSTM for copper passivated in 0.1 M NaOH(aq) and attributed to a locally thicker Cu(I) passive oxide film formed in the GB regions[24,25,64]. In 10 mM HCl(aq) + 1 mM MBI, the electrochemical response is indicative of a passivation-like behavior not observed in the absence of MBI.…”

Local Effects of Organic Inhibitor Molecules on Passivation of Grain Boundaries Studied In Situ on Copper

“…The experiments were performed with microcrystalline samples obtained by cryogenic rolling after freezing in liquid nitrogen of highpurity cast electrolytic tough pitch copper. [22][23][24][25][26]65,66,[81][82][83] In order to ensure the relatively smaller grain size necessary for the microstructure to be included in the STM field of view, the annealing treatment for full recrystallization of the samples was limited in time and temperature of 1 min and 200°C, respectively. The resulting samples showed no preferential grain orientation, i.e.…”

“…Early-stage intergranular dissolution of copper in the active state and transient dissolution during passivation have been studied in situ at the nanometric scale using electrochemical scanning tunneling microscopy (ECSTM). [22][23][24][25][26] Surface GB terminations assigned to coherent twins showed weaker dissolution, both in active and passive states, than GB edges assigned to other CSL or random boundaries. Combining ECSTM with electron back-scatter diffraction (EBSD) characterization of the same local GB sites, the passivation behavior of coherent twins was found to depend on the deviation angle of the GB plane from its perfect {111} orientation with a transition from more to less efficient passivation for a deviation angle of 0.4°-0.5°2 6 For random boundaries, passivation in the Cu(I) oxidation range was characterized by a decrease of the depth of GB edge region due to the formation of a passive film locally thicker than on the adjacent grains, and thus to anodic oxidation being locally less efficient since consuming more copper at the grain boundaries 26 A practical approach to mitigate and control metals and alloys corrosion in aggressive environments is by using corrosion inhibitors.…”

Quantifying Local Atomic Distortions in UO2 Grain Boundaries: Correlation with Energetic and Electronic Properties

“…Materials in practical use are typically polycrystalline, comprising multiple single-crystalline grains, whose interfaces form grain boundaries (GBs). As inherent planar defects, GBs introduce mismatched lattices and excess volumes, significantly affecting the material’s properties and behavior, including thermal and electrical conductivity, , corrosion resistance, , migration, and solute segregation. , To facilitate the design of next-generation materials with improved or novel properties, it is essential to establish quantitative relationships between the structure of GBs and their properties.…”