Band sorting based on global continuity of eigenvalues and topological properties of phononic crystals.

Band sorting is critical to obtaining physical properties from eigenvalues and eigenvectors that constitute the band diagram. We propose a band sorting method based on the global continuity and smoothness of the eigenvalues on the parameter space. Several strategies based on the connection between neighbor eigenvalues and how to sweep the parameter space are introduced to recognize level crossing degeneracies and level repulsion degeneracies.

Ultralow Thermal Conductivity and Very High Seebeck Coefficient in Two-Dimensional TeSe Semiconductor.

Emerging chalcogenide-based two-dimensional (2D) materials possess various unique yet fully explored properties and are thus considered promising candidates for next-generation optoelectronic and energy conversion applications. Here, TeSe crystals with interesting thermoelectric features were synthesized using a simple solid-state reaction. High-resolution transmission electron microscopy reveals that TeSe stabilizes in a 2D atomic structure with helical chains, resembling 2D tellurene.

3D Lithiophilic CuZrAg Metallic Glass Based-Current Collector for High-Performance Lithium Metal Anode.

Lithium metal anodes face several challenges in practical applications, such as dendrite growth, poor cycle efficiency, and volume variation. 3D hosts with lithiophilic surfaces have emerged as a promising design strategy for anodes. In this study, inspiration from the intrinsic isotropy, chemical heterogeneity, and wide tunability of metallic glass (MG) is drew to develop a 3D mesoporous host with a lithiophilic surface.

Lévy walk of quasiballistic phonons in nanowires.

Phonon transport in square-cross-section nanowires is studied using spectral Monte Carlo simulations. Our results show the evolution of the different transport regimes described by Lévy statistics as a function of the surface roughness-to-thermal wavelength ratio σ/λ. More precisely, the relationship between the Lévy index γ describing the mean free path distribution Ψ(Λ) and σ/λ is established for the classical diffusive regime, the superdiffusive regime, and the ballistic regime in the nanowire.

Cobalt-based MOF nanoribbons with abundant O/N species for cycloaddition of carbon dioxide to epoxides.

Chemical fixation of CO with epoxides is an effective option to achieve sustainable synthesis of cyclic organic carbonates. Although metal-organic frameworks (MOFs) are promising catalysts for this reaction, their low stability in aqueous solutions makes this application infeasible. In an effort to overcome this limitation, cobalt-based metal-organic framework (Co(II)MOF) nanoribbons have been prepared by coordinating the Co(II) ions with a new ligand (CHNO) full of oxygen and nitrogen moieties.

Controlled Synthesis of Perforated Oxide Nanosheets with High Density Nanopores Showing Superior Water Purification Performance.

A method for creating genuine nanopores in high area density on monolayer two-dimensional (2D) metallic oxides has been developed. By use of the strong reduction capability of hydroiodic acid, active metal ions, such as Fe and Co, in 2D oxide nanosheets can be reduced to a divalent charge state (2+). The selective removal of FeO and CoO metal oxide units from the framework can be tuned to produce pores in a range of 1-4 nm.

Understanding the Surface Reconstruction on Ternary W CoB for Water Oxidation and Zinc-Air Battery Applications.

Here, the synthesis of a series of pure phase metal borides is reported, including WB, CoB, WCoB, and W CoB , and their surface reconstruction is studied under the electrochemical activation in alkaline solution. A cyclic voltammetric activation is found to enhance the activity of the CoB and W CoB precatalysts due to the transformation of their surfaces into the amorphous CoOOH layer with a thickness of 3-4 nm. However, such surface transformation does not happen on the WB and WCoB due to their superior structure stability under the applied voltage, highlighting the importance of metal components for the surface reconstruction process.

Ternary Mo NiB as a Superior Bifunctional Electrocatalyst for Overall Water Splitting.

Transition metal borides are considered as promising electrocatalysts for water splitting due to their metallic conductivity and good durability. However, the currently reported monometallic and noncrystalline multimetallic borides only show generic and monofunctional catalytic activity. In this work, the authors design and successfully synthesize highly crystalline ternary borides, Mo NiB , via a facile solid-state reaction from pure elemental powders.

Photo-promoted in situ reduction and stabilization of Pd nanoparticles by H at photo-insensitive SmO nanorods.

Controlled synthesis of noble metal nanoparticles with well-defined size and good dispersion on supports has been a long-standing challenge in heterogeneous catalysis. Here we report a facile photo-assisted Hin situ reduction process to synthesize monodispersed Pd nanoparticles with 2-4 nm size on photo-insensitive SmO rare-earth metal oxide with nanorod morphology. Thanks to the contribution of UV irradiation, the photoelectrons generation in the SmO support accelerates the H reduction of Pd ions into Pd and stabilize the growth of very small Pd nanoparticles homogeneously dispersed on the support.

Heat conduction tuning by wave nature of phonons.

The world communicates to our senses of vision, hearing, and touch in the language of waves, because light, sound, and even heat essentially consist of microscopic vibrations of different media. The wave nature of light and sound has been extensively investigated over the past century and is now widely used in modern technology. However, the wave nature of heat has been the subject of mostly theoretical studies because its experimental demonstration, let alone practical use, remains challenging due to its extremely short wavelengths.

Heat guiding and focusing using ballistic phonon transport in phononic nanostructures.

Unlike classical heat diffusion at macroscale, nanoscale heat conduction can occur without energy dissipation because phonons can ballistically travel in straight lines for hundreds of nanometres. Nevertheless, despite recent experimental evidence of such ballistic phonon transport, control over its directionality, and thus its practical use, remains a challenge, as the directions of individual phonons are chaotic. Here, we show a method to control the directionality of ballistic phonon transport using silicon membranes with arrays of holes.

Thermal resistance at a solid/superfluid helium interface.

Kapitza in 1941 discovered that heat flowing across a solid in contact with superfluid helium (<2 K) encounters a strong thermal resistance at the interface. Khalatnikov demonstrated theoretically that this constitutes a general phenomenon related to all interfaces at all temperatures, given the dependence of heat transmission on the acoustic impedance (sound velocity  ×  density) of each medium. For the solid/superfluid interface, the measured transmission of heat is almost one hundred times stronger than the Khalatnikov prediction.