Enhanced Nanostructure Dynamics on Au(111) with Adsorbed Sulfur due to Au-S Complex Formation

Control of Silver Micro-Flakes Sintering and Connection Properties of Epoxy-Based Conductive Adhesives by the Effectiveness of Binder Chemistry

Bonding materials with high thermal and electrical conductivity and reliable resistance to thermal stress are required. The authors have been conducting fundamental research on sintering-type bonding, in which metal micro-fillers are low-temperature sintered in the resin-bonded type electrically conductive adhesives (ECAs), as a new bonding technology, with the aim of easing thermal stress through the resin binder. This study investigated the influence of the kind of additive diluent in epoxy-based ECAs containing silver (Ag) micro-flakes on the microstructure development in the adhesives and the connection properties to metal electrodes. As a result, the sintering of Ag micro-flakes was observed to proceed in the adhesive once cured at 150 °C and by post-annealing at 250 °C. Furthermore, the sintering behavior varied greatly depending on the kind and composition of the binder additive diluent, with corresponding changes in electrical conductivity and connection characteristics with metal electrodes. Additionally, electrode surface conditions affected the connection performance. These findings are valuable for designing sintering-type bonding using resin-bonded ECAs, optimizing interfacial interactions between binder chemicals and metals.

Electrocatalytic Reduction of Nitrogen to Ammonia: the Roles of Lattice O and N in Reduction at Vanadium Oxynitride Surfaces

Vanadium oxynitride and other earth-abundant oxynitrides are of growing interest for the electrocatalytic reduction of nitrogen to NH₃. A major unresolved issue, however, concerns the roles of lattice N and lattice O in this process. Electrochemistry and photoemission data reported here demonstrate that both lattice N and dissolved N₂ are reduced to NH₃ by cathodic polarization of vanadium oxynitride films at pH 7. These data also show that ammonia production from lattice N occurs in the presence or absence of N₂ and involves the formation of V≡N: intermediates or similar unsaturated VN surface states on a thin vanadium oxide overlayer. In contrast, N₂ reduction proceeds in the presence or absence of lattice N and without N incorporation into a vanadium oxide lattice. Thus, both lattice N and N₂ reduction mechanisms involve oxide-supported V surface sites ([V]_O) in preference to N-supported sites ([V]_N). This result is supported by density functional theory-based calculations showing that the formation of V≡N:, V-N═N-H, and a few other plausible reaction intermediates is consistently energetically favored at [V]_O rather than at [V]_N surface sites. Similar effects are predicted for the oxynitrides of other oxophilic metals, such as Ti.