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Synthesis of high‐performance thermoelectric (TE) materials with tunable compositions and nanostructures normally require sophisticated and high‐cost methods, such as high‐temperature melting and solid‐state reactions, which consume a large amount of time and energy and incur high costs. Herein, a fast, reliable, low‐cost, and environmentally friendly method, namely the vacuum‐induced method, is developed to rapidly synthesize Cu2S‐based materials with high TE performance. By mixing finely ground powders of metal‐Cu and S at room temperature, Cu2–xS compounds with a tunable x varied from 0–0.07 can be instantly formed by a quick sulfurization reaction once the mixture is placed inside a low vacuum (≈about 30 Pa and beyond). The atomic mechanism of Cu2–xS formation is studied by transmission electron microscopy, as a heterogeneous growth with the diffusion of both Cu+‐cations and S2−‐anions. In a low vacuum, the sulfur vapor is preferably attached to the copper surface with rich defected sites such as atomic vacancies, steps, and edges. The synthesized Cu2–xS powders with further plasma‐activated sintering treatment show high TE performance with ZT ≈ 1.56 around 800 K. Such a simple synthesis method may provide an effective and low‐cost way to prepare sulfides with potential applications in TE materials and solid electrolytes. [ABSTRACT FROM AUTHOR]

Abstract: The RuNiCo tri‐metallic nanocatalyst of Ru islands‐on‐nickel‐cobalt/nickel hydroxide‐cobalt hydroxide nanoparticles (Ru/NiCo/Ni(OH)2‐Co(OH)2/C) was prepared at room temperature (RT) via hydrazine hydrate reduction and galvanic replacement methods. And Ru/NiCo/Ni(OH)2‐Co(OH)2/C exhibited much higher catalytic activity in the model reaction of toluene hydrogenation than Ru/Ni/Ni(OH)2/C and Ru/Co/Co(OH)2/C due to synergistic effect of Ru, Ni and Co related species, with good stability. [ABSTRACT FROM AUTHOR]

Sliding and migration of tilt grain boundaries in a Mg–Zn–Y alloy have been investigated on the atomic scale using aberration‐corrected scanning transmission electron microscopy. Grain boundary sliding is accommodated by non‐basal dislocations moving along the grain boundary; grain boundary migration is induced by the motion of grain boundary dislocations with synchronized grain boundary diffusion. Simultaneous sliding and migration of tilt boundaries take place in both Mg matrix and long period stacking ordered phases. These results provide evidence for occurrence of grain boundary motion, which may play a role in plasticity of this kind of Mg alloys. [ABSTRACT FROM AUTHOR]

A layered ternary carbide phase, Hf2Al4C5, was successfully synthesized by spark plasma sintering method. Detailed (atomic-scale) microstructure of the ternary carbide was investigated by aberration-corrected scanning transmission electron microscopy and atomic-resolution energy dispersive X-ray spectroscopy. Hf2Al4C5 crystal grains have elongated morphologies and are characterized with a high density of stacking faults with the insertion of additional (Al4C3) or (HfC) units. Periodic stacking of Hf2Al4C5 and HfAl4C4 units along the [0001] direction is frequently observed in the Hf2Al4C5 crystal, and it leads to the formation of Hf4Al12C13, which consists of 2/3 Hf2Al4C5 unit cell and 1/2 HfAl4C4 unit cell. In addition, Z-shaped planar defects are observed in Hf2Al4C5 grains, and the formation mechanism of the Z-shaped defects was proposed as blocking effects of the Hf diffusion in Al4C3 by pre-existing {1-101} pyramidal stacking faults in Al4C3. [ABSTRACT FROM AUTHOR]

Chemical decoration of defects is an effective way to functionalize graphene and to study mechanisms of their interaction with environment. We monitored dynamic atomic processes during the formation of a rotary Si trimer in monolayer graphene using an aberration-corrected scanning-transmission electron microscope. An incoming Si atom competed with and replaced a metastable C dimer next to a pair of Si substitutional atoms at a topological defect in graphene, producing a Si trimer. Other atomic events including removal of single C atoms, incorporation and relocation of a C dimer, reversible CC bond rotation, and vibration of Si atoms occurred before the final formation of the Si trimer. Theoretical calculations indicate that it requires 2.0 eV to rotate the Si trimer. Our real-time results provide insight with atomic precision for reaction dynamics during chemical doping at defects in graphene, which have implications for defect nanoengineering of graphene. [ABSTRACT FROM AUTHOR]