Atomic‐Scale Observation of Irradiation‐Induced Surface Oxidation by In Situ Transmission Electron Microscopy

Abstract

Irradiation of materials with high energy particles can induce structural transitions or trigger chemical reactions. Understanding the underlying mechanism for irradiation-induced phenomena is of both scientific and technical importance. Here, CdS nanoribbons are used as a model system to study structural and chemical evolution under electron-beam irradiation by in situ transmission electron microscopy. Real-time imaging clearly shows that upon irradiation, CdS is transformed to CdO with the formation of orientation-dependent relationships at surface. The structural transition can always be triggered with a dose rate beyond 601 e/Ųs in this system. A lower dose rate instead leads to the deposition of an amorphous carbon layer on the surface. Based on real-time observations and density functional theory calculations, a mechanism for the oxidation of CdS to CdO is proposed. It is essentially a thermodynamically driven process that is mediated by the formation of sulfur vacancies due to the electron-beam irradiation. It is also demonstrated that the surface oxidation can be suppressed by pre-depositing a conductive carbon layer on the CdS surface. The carbon coating can effectively reduce the rate of sulfur vacancy creation, thus decreasing defect-mediated oxidation. In addition, it isolates the active oxygen radicals from the ribbon, blocking the pathway for oxygen diffusion

Oxidation behavior of cobalt nanoparticles studied by in situ environmental transmission electron microscopy

“…(2) The electron beam may have enhanced the diffusion of Co also through the knock-on effect [30], thus promoting oxidation. (3) Electron beam irradiation may have assisted the decomposition of O 2 into atomic oxygen, and thus enhanced oxidation [23,33,34]. The high-energy electrons directly induced the ionization and disassociation of molecular oxygen in the microscope column and on the NP surfaces.…”

Phase and defect evolution in uranium-nitrogen-oxygen system under irradiation

“…The efficiency of energy generation and utilization systems depends on material property changes influenced by microstructure evolution under extreme operating conditions. Particularly in environment where materials are subjected to a flux of energetic neutrons and charged particles, degradation of mechanical properties [1,2], corrosion/oxidation resistance [3][4][5][6][7], and thermal conductivity [8][9][10] have been associated with defect generation, and compositional redistribution in the microstructure. Energetic particles can knock atoms out of their lattice site and create point defects (vacancies, interstitials).…”

Filming nanodroplet running and jetting mediated by nanoscale solid-gas and solid-liquid interface

“…In the experiments we observed the evolution of voids that was categorized into the nucleation, growth, and coalescence processes. It has been documented that the voids would be formed through the thermal heating 28 , local stress concentrators caused by extended defects (e.g., dislocations and grain boundaries) 29 , Kirkendall effect 30 and atomic displacement induced vacancy zones 31 . The e-beaminduced temperature rise was normally in the range of several degrees 32,33 , indicating that heating did not dominate the formation of voids.…”