An Order–Disorder Transition in Surface Complexions and Its Influence on Crystal Growth of Boron-Rich Nanostructures

Controlled fabrication of boron-rich nanostructures was achieved by manipulating the processing temperature: high-temperature processing (1400–1500 °C) produced mainly tabular platelets with parallel twinning cross sections, whereas low-temperature processing (1100–1200 °C) facilitated the growth of star-shaped nanowires with cyclic twinning cross sections. This study revealed that this growth habit transition was related to the structural order of the adsorbed Ba atoms in nanoscale surficial films, which is a type of surface complexion (stable equilibrium phase-like surface states). It is demonstrated that an order–disorder transition in these surface complexions can play a critical role in determining the growth habits of crystals

Microstructural Evolution of a Cu and θ‑Al₂O₃ Composite Formed By Reduction of Delafossite CuAlO₂: A HAADF-STEM Study

In situ reduction of bulk, polycrystalline copper­(I) aluminate (CuAlO₂) results in the formation of an intimate two-phase mixture of metallic Cu and θ-alumina. The microstructure of a partially transformed region was studied at the atomistic scale using high-angle angular-dark-field scanning transmission electron microscopy (HAADF-STEM). The observations were consistent with a topotactic transformation mechanism whereby deintercalation of the Cu atoms occurs sequentially at the edges of the Cu⁺ atomic layers of the CuAlO₂ delafossite structure. The Cu forms faceted nanoislands that exhibit an orientation relationship with the θ-alumina matrix. There is also concomitant outward diffusion of oxygen, and it is suggested that the θ-alumina is formed by the consolidation of the layers of Al–O octahedra of the delafossite structure, with some local rearrangement of the Al³⁺ ions. This model is supported by the observed continuity of the Al–O layers between the parent CuAlO₂ and θ-alumina, together with the orientation relationship <i>(0003)­CuAlO</i>₂//<i>(402̅)­θ-alumina</i>

Hyperdislocations in van der Waals Layered Materials

Dislocations are one-dimensional line defects in three-dimensional crystals or periodic structures. It is common that the dislocation networks made of interactive dislocations be generated during plastic deformation. In van der Waals layered materials, the highly anisotropic nature facilitates the formation of such dislocation networks, which is critical for the friction or exfoliation behavior for these materials. By transmission electron microscopy analysis, we found the topological defects in such dislocation networks can be perfectly rationalized in the framework of traditional dislocation theory, which we applied the name “hyperdislocations”. Due to the strong pinning effect of hyperdislocations, the state of exfoliation can be easily triggered by 1° twisting between two layers, which also explains the origin of disregistry and frictionlessness for all of the superlubricants that are widely used for friction reduction and wear protection

Zeolite Structural Confinement Effects Enhance One-Pot Catalytic Conversion of Ethanol to Butadiene

The one-pot conversion of ethanol to butadiene is a promising route for butadiene production; however, simultaneous attainment of high butadiene productivity and high butadiene selectivity is challenging. Here, zeolite-confined bicomponent Zn–Y clusters were constructed and applied as robust catalysts for ethanol-to-butadiene conversion with a state-of-the-art butadiene productivity of 2.33 g_BD/g_cat/h and butadiene selectivity of ∼63%. Structural confinement effects are responsible for the enhanced butadiene production efficiency via a multiple-step cascade reaction

Seeded Mineralization Leads to Hierarchical CaCO₃ Thin Coatings on Fibers for Oil/Water Separation Applications

Like their biogenic counterparts, synthetic minerals with hierarchical architectures should exhibit multiple structural functions, which nicely bridge the boundaries between engineering and functional materials. Nevertheless, design of bioinspired mineralization approaches to thin coatings with distinct micro/nanotextures remains challenging in the realm of materials chemistry. Herein, a general morphosynthetic method based on seeded mineralization was extended to achieve prismatic-type thin CaCO₃ coatings on fibrous substrates for oil/water separation applications. Distinct micro/nanotextures of the overlayers could be obtained in mineralization processes in the presence of different soluble (bio)­macromolecules. These hierarchical thin coatings therefore exhibit multiple structural functions including underwater superoleophobicity, ultralow adhesion force of oil in water, and comparable stiffness/strength to the prismatic-type biominerals found in mollusk shells. Moreover, this controllable approach could proceed on fibrous substrates to obtain robust thin coatings, so that a modified nylon mesh could be employed for oil/water separation driven by gravity. Our bioinspired approach based on seeded mineralization opens the door for the deposition of hierarchical mineralized thin coatings exhibiting multiple structural functions on planar and fibrous substrates. This bottom-up strategy could be readily extended for the syntheses of advanced thin coatings with a broad spectrum of engineering and functional constituents