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We report the dynamics of the gold–silicon eutectic reaction in limited dimensions were studied using in situ transmission electron microscopy and scanning transmission electron microscopy heating experiments. The phase transformation, viewed in both plan-view and cross-section of the film, occurs through a complex combination of dislocation and grain boundary motion and diffusion of silicon along gold grain boundaries, which results in a dramatic change in the microstructure of the film. The conversion observed in cross-section shows that the eutectic mixture forms at the Au–Si interface and proceeds into the Au film at a discontinuous growth rate. This complex process canmore » lead to a variety of microstructures depending on sample geometry, heating temperature, and the ratio of gold to silicon which was found to have the largest impact on the eutectic microstructure. The eutectic morphology varied from dendrites to hollow rectangular structures to Au–Si eutectic agglomerates with increasing silicon to gold ratio.« less

Defect production and growth in CrFeCoNi, a single-phase concentrated solid solution alloy, is characterized using in situ electron irradiation inside a transmission electron microscope operated at 400–1250 kV and 400 °C. All observed defects are interstitial-type, either elliptical Frank loops or polygonal (mostly rhombus) perfect loops. Both forms of loops in CrFeCoNi exhibit a sublinear power law of growth that is > 40 times slower than the linear defect growth in pure Ni. Lastly, this result shows how compositional complexity impacts the production of Frenkel pairs and the agglomeration of interstitials into loops, and, thus, enhances the radiation tolerance.

Abstract Alane (AlH ₃ ) is a unique energetic material that has not found a broad practical use for over 70 years because it is difficult to synthesize directly from its elements. Using density functional theory, we examine the defect‐mediated formation of alane monomers on Al(111) in a two‐step process: (1) dissociative adsorption of H ₂ and (2) alane formation, which are both endothermic on a clean surface. Only with Ti dopant to facilitate H ₂ dissociation and vacancies to provide Al adatoms, both processes become exothermic. In agreement, in situ scanning tunneling microscopy showed that during H ₂ exposure, alane monomersmore » and clusters form primarily in the vicinity of Al vacancies and Ti atoms. Moreover, ball milling of the Al samples with Ti (providing necessary defects) showed a 10 % conversion of Al into AlH ₃ or closely related species at 344 bar H ₂ , indicating that the predicted pathway may lead to the direct synthesis of alane from elements at pressures much lower than the 10 ⁴  bar expected from bulk thermodynamics.« less