Search

We report results of magnetic hysteresis scaling of minor loops for hollow Fe3O4 submicron particles with variable diameter of 400–720 nm. As in the case of bulk ferromagnetic materials, a power-law scaling with an exponent of ∼1.5 was found to universally hold true between hysteresis loss and remanence of minor loops, although the magnetization process is significantly different from a bulk ferromagnet where irreversible Bloch wall displacement plays a crucial role. The minor-loop coefficient decreases with inner/outer diameter ratio and is almost independent of temperature above T = 30 K. The behavior of the coefficient indicates that a mobility of a magnetic vortex under magnetic fields increases with increasing a inner/outer diameter ratio of a hollow sphere and is weakly temperature dependent. The results suggest that the coefficient can be a sensitive indicator of the particle geometry for vortex spherical particles. [ABSTRACT FROM AUTHOR]

In this work, we studied the residual micro lattice strain of an onyx sample, which is a micro- to the cryptocrystalline variety of the mineral quartz SiO2. That the investigation has been carried out using in-situ stress experiments with the time-of-flight neutron diffraction method. The aim of the study is to investigate residual lattice strains and pressure directions in the sample using time-of-flight neutron diffraction, which is a powerful tool for the study of the residual strain behavior in bulk materials, like geological rock samples containing large grains. The residual strain was detected in different sample directions turning the sample in steps of 30° by 180° around the cylindrical z-axis. These experiments have been performed at the time-of-flight neutron strain diffractometer EPSILON, situated on the pulsed neutron source IBR-2M of the Joint Institute for Nuclear Research in Dubna, Russia. The results of this study will provide insights into the compressional and tensional residual strain of the crystallographic lattice planes, and will have implications for our understanding of the tectonic history of this region. These different strains are arranged in the sample by a sinusoidal distribution in radial directions. [ABSTRACT FROM AUTHOR]

Iron-containing oxides are the most important functional substance class and find a tremendous variety of applications. An attractive modern application is their use in biomedical technologies as components in systems for imaging, drug delivery, magnetically mediated hyperthermia, etc. In this paper, we report the results of the experimental investigation of submicron Y3Fe5O12 garnet particles obtained in different sizes by solution combustion synthesis (SCS) using glycine organic fuel to discuss the interdependence of peculiarities of the crystal and magnetic structure and size's influence on its functional magnetothermal performance. A complex study including Mössbauer and Raman spectroscopy accompanied by X-ray diffractometry, SEM, and measurements of field and temperature magnetic properties were performed. The influence of the size effects and perfectness of structure on the particle set magnetization was revealed. The ranges of different mechanisms of magnetothermal effect in the AC magnetic field were determined. [ABSTRACT FROM AUTHOR]

Exploring two-dimensional anode materials that can utilize the storage capacity and diffusion mobility of Li ions is at the heart of lithium ion battery (LIB) research. Herein, we report the results of ab initio electronic structure calculations on the storage capacity and diffusion mobility affinities of Li ions adsorbed onto nondefective and defective MXene V2C monolayers. It is found that Li ions strongly chemisorb on the two sides of the V2C surface with a preferential adsorption site at the hollow center of the honeycomb structure. The binding profile and open-circuit voltage calculations reveal that the Li/V2C structure exhibits a specific capacity as high as 472 mA h g−1 at the Li2V2C stoichiometry, a value relatively high compared with those of the typical anode materials including graphite (372 mA h g−1). Furthermore, the diffusion barrier of a Li ion over the V2C surface is identified to be no more than 0.1 eV, which is a few times smaller than that of graphene and graphitic anodes. In addition, during the lithiation and delithiation processes, the change in the lateral lattice is quite small, only about a 2% increase at the full lithiation of Li2V2C, implying a good cycling performance. Importantly, these intriguing findings are very robust against the intrinsic structural and atomic defects including local point vacancies and biaxial compressive and tensile strains. More specifically, the presence of a monovanadium vacancy enhances the binding energy up to 3.1 eV per Li ion, which is about a 30% enhancement compared with the defect-free Li/V2C structure, and reduces the activation barrier by about 2 meV; meanwhile, these binding and diffusion mobility features can be improved even more when the lattice constant of the V2C monolayer is expanded. These results thus suggest that MXene V2C could be a promising anode material with high capacity and high rate capabilities for next generation high-performance LIBs. [ABSTRACT FROM AUTHOR]

The evaporation of high purity silicon ingot was performed in Ar, N2, and air atmospheres using a power electron accelerator. The obtained powders with primary particle sizes of 10–500 nm were investigated using Brunauer–Emmett–Teller analysis (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence measurement, and Raman spectroscopy. The structure and photoluminescence properties of Si(Ar) nanopowder obtained at a large quenching rate differ substantially from those of Si(Ar) and Si(N2) obtained at a smaller quenching rate. Photoluminescence peaks in the visible region of the spectrum are detected at room temperature for the Si(Ar) nanopowders. [ABSTRACT FROM AUTHOR]