Role of Niobium on the Passivation Mechanisms of TiHfZrNb High-Entropy Alloys in Hanks' Simulated Body Fluid.

A family of TiHfZrNb high-entropy alloys has been considered novel biomaterials for high-performance, small-sized implants. The present work evaluates the role of niobium on passivation kinetics and electrochemical characteristics of passive film on TiHfZrNb alloys formed in Hanks' simulated body fluid by analyzing electrochemical data with three analytical models. Results confirm that higher niobium content in the alloys reinforces the compactness of the passive film by favoring the dominance of film formation and thickening mechanism over the dissolution mechanism.

Porosity modeling in a TiNbTaZrMo high-entropy alloy for biomedical applications.

High-entropy alloys (HEAs) have attracted great attention for many biomedical applications. However, the nature of interatomic interactions in this class of complex multicomponent alloys is not fully understood. We report, for the first time, the results of theoretical modeling for porosity in a large biocompatible HEA TiNbTaZrMo using an atomistic supercell of 1024 atoms that provides new insights and understanding.

Simulation of Structure and Properties in Ni-Based Superalloys: Haynes282 and Inconel740.

The electronic structure, interatomic bonding, and mechanical properties of two supercell models of Ni-based superalloys are calculated using ab initio density functional theory methods. The alloys, Haynes282 and Inconel740, are face-centered cubic lattices with 864 atoms and eleven elements. These multi-component alloys have very complex electronic structure, bonding and partial-charge distributions depending on the composition and strength of the local bonding environment.

Temperature-Dependent Properties of Molten LiBeF Salt Using Molecular Dynamics.

Molten lithium tetrafluoroberyllate (LiBeF) salt, also known as FLiBe, with a 2:1 mixture of LiF and BeF is being proposed as a coolant and solvent in advanced nuclear reactor designs, such as the molten salt reactor or the fluoride salt cooled high-temperature reactor. We present the results on the structure and properties of FLiBe over a wide range of temperatures, 0-2000 K, from high-throughput molecular dynamics simulation using a supercell model of 504 atoms. The variations in the local structures of solid and liquid FLiBe with temperature are discussed in terms of a pair distribution function, coordination number, and bond angle distribution.

Effect of AlO Seed-Layer on the Dielectric and Electrical Properties of Ultrathin MgO Films Fabricated Using Atomic Layer Deposition.

Metal/insulator/metal (M/I/M) trilayers of Al/MgO/Al with ultrathin MgO in the thickness range of 2.20-4.40 nm were fabricated using sputtering and atomic layer deposition (ALD).

High-Performance All-Inorganic CsPbCl Perovskite Nanocrystal Photodetectors with Superior Stability.

All-inorganic perovskites nanostructures, such as CsPbCl nanocrystals (NCs), are promising in many applications including light-emitting diodes, photovoltaics, and photodetectors. Despite the impressive performance that was demonstrated, a critical issue remains due to the instability of the perovskites in ambient. Herein, we report a method of passivating crystalline CsPbCl NC surfaces with 3-mercaptopropionic acid (MPA), and superior ambient stability is achieved.

Self-Assembled Metal Molecular Networks by Nanoconfinement.

Quasi-two-dimensional (2D) metal molecular networks (MMNs) often exhibit a nanoconfinement effect and high degree of anisotropy, which are highly diverse in their mechanical, electronic, and magnetic functionalities. Here we report an interfacial self-assembly of mechanically robust 2D MMNs, in which 3d transition metals are interconnected via molecular thiol bridges. The Langmuir-Schäfer assembled freestanding 2D nanosheets exhibit highly desired anisotropic charge transport and spin susceptibility, in which light and magnetic field induced charge transfer regulates the electronic interactions.

Magnetic properties of core-shell nanoparticles possessing a novel Fe(ii)-chromia phase: an experimental and theoretical approach.

Room-temperature ferrimagnetic and superparamagnetic properties, and the magnetic interactions between the core and shell, of our iron-incorporated chromia-based core shell nanoparticles (CSNs) have been investigated using a combination of experimental measurement and density functional theory (DFT) based calculations. We have synthesized CSNs having an epitaxial shell and well-ordered interface properties by utilizing our hydrothermal nanophase epitaxy (HNE) technique. The ferrimagnetic and superparamagnetic properties of the CSNs are manifested beyond room temperature and magnetic measurements reveal that the exchange bias interaction between the antiferromagnetic (AFM) core and ferrimagnetic (FiM) shell persists close to ambient temperature.

The Ti AlC MAX Phase as an Efficient Catalyst for Oxidative Dehydrogenation of n-Butane.

Dehydrogenation or oxidative dehydrogenation (ODH) of alkanes to produce alkenes directly from natural gas/shale gas is gaining in importance. Ti AlC , a MAX phase, which hitherto had not been used in catalysis, efficiently catalyzes the ODH of n-butane to butenes and butadiene, which are important intermediates for the synthesis of polymers and other compounds. The catalyst, which combines both metallic and ceramic properties, is stable for at least 30 h on stream, even at low O :butane ratios, without suffering from coking.

Effect of an Interfacial Layer on Electron Tunneling through Atomically Thin AlO Tunnel Barriers.

Electron tunneling through high-quality, atomically thin dielectric films can provide a critical enabling technology for future microelectronics, bringing enhanced quantum coherent transport, fast speed, small size, and high energy efficiency. A fundamental challenge is in controlling the interface between the dielectric and device electrodes. An interfacial layer (IL) will contain defects and introduce defects in the dielectric film grown atop, preventing electron tunneling through the formation of shorts.

Experimental and theoretical investigation of a mesoporous K(x)WO3 material having superior mechanical strength.

Mesoporous materials with tailored properties hold great promise for energy harvesting and industrial applications. We have synthesized a novel tungsten bronze mesoporous material (K(x)WO3; x ∼ 0.07) having inverse FDU-12 type pore symmetry and a crystalline framework.

Synergistic Strain Engineering Effect of Hybrid Plasmonic, Catalytic, and Magnetic Core-Shell Nanocrystals.

Hybrid core-shell nanocrystals, consisting of distinct components, represent an emerging functional material system, which could facilitate synergistic coupling effects via integrating drastically different functionalities. Here we report a unique strain engineering effect induced by phase transformation between plasmonic core and magnetic shell materials, which leads to a facile surface reconstruction of bimetallic core-shell nanocrystals to enhance their synergistic magnetic and catalytic properties. This advancement dramatically results in two orders of magnitude enhancement in magnetic coercivity and significant improvement in catalytic activity.

Multiferroicity of carbon-based charge-transfer magnets.

A new type of carbon charge-transfer magnet, consisting of a fullerene acceptor and single-walled carbon nanotube donor, is demonstrated, which exhibits room temperature ferromagnetism and magnetoelectric (ME) coupling. In addition, external stimuli (electric/magnetic/elastic field) and the concentration of a nanocarbon complex enable the tunabilities of the magnetization and ME coupling due to the control of the charge transfer.

Densification of a continuous random network model of amorphous SiO2 glass.

We have investigated the mechanism of densification of a nearly perfect continuous random network (CRN) model of amorphous SiO2 (a-SiO2) glass with 1296 atoms and periodic boundary conditions. The model has no under- or over-coordinated atoms and small bond length and bond angle distributions. This near-perfect model is systematically densified up to a pressure of 80 GPa using ab initio constant-pressure technique.