Mesoporous rod-like SiC has been prepared by using SBA-15 as hard template and sucrose as carbon source through a vapor-solid mechanism. The material was characterized by X-ray diffraction (XRD), high resolution transmission electronmicroscopy (HRTEM) and thermalgravimetric (TG) analysis. The obtained material exhibits different morphologies, and consists of a rod-like SiC core and amorphous silica shell which is due to the excessive silica during the reaction between silica and carbon to form SiC. The diameter of the SiC nanorods are ranged from 8 to 60 nm, and the silica shell has a thickness of about 4 nm. The silica coating SiC nanorods possess more porous structure than pure SiC and in turn make it more useful in catalytic fields.

Controlling material properties at the nanoscale is a critical enabler of high performance electronic and photonic devices. A prototypical material example is VO2, where a structural phase transition in correlation with dramatic changes in resistivity, optical response, and thermal properties demonstrates particular technological importance. While the phase transition in VO2 can be controlled at macroscopic scales, reliable and reversible nanoscale control of the material phases has remained elusive. Here, reconfigurable nanoscale manipulations of VO2 from the pristine monoclinic semiconducting phase to either a stable monoclinic metallic phase, a metastable rutile metallic phase, or a layered insulating phase using an atomic force microscope is demonstrated at room temperature. The capability to directly write and erase arbitrary 2D patterns of different material phases with distinct optical and electrical properties builds a solid foundation for future reprogrammable multifunctional device engineering.

Dielectric spectroscopy is a valuable tool in physics, chemistry, biophysics, and materials science. However, there is still an argument about the typical relaxation process at low frequency, which is always masked by electrode polarization. Low-frequency dielectric measurements of water absorbed in porous titanium dioxide have been performed. The experimental results show that typical polarization at low frequency is caused by space-charge polarization. A model is proposed to explain the experimental results, which indicates that the electric field in the sample is close to 0. An effective circuit is given, and the calculation gives similar dielectric spectra to those measured in experiments, which confirms the physical model.

Charged particles exist widely in variety of technological areas as well as in nature. Even a weak charge on the particles can significantly influence their electric interaction. We investigated the phenomenon of time-dependent electric interaction between two conducting spheres in an electrostatic field. A mirror-image method was developed to analyze this system, and the fundamental role of the charges on the spheres was studied. We concluded that charges conducted to the lower sphere through the alumina tube used in our system play a main role in determining the time-dependent interaction, whereas the influence from air ions is negligible.

In this work, we performed differential scanning calorimetry (DSC) experiments to investigate the phase transition temperature and the molar enthalpy of the absorbed water confined in porous titanium dioxide. The porous titanium dioxide with three different pore size distribution and different filling fraction of the absorbed water were examined. We found that both the pore size of the examined samples and the filling fraction of the absorbed water affected the water's phase transition temperature and its molar enthalpy.

Se and MoSe2 nanoflakes are prepared in N-2 environment by hot filament chemical vapor deposition through using Se and MoO3 powders as the source materials. The structures and compositions of Se and MoSe2 nanoflakes are systemically studied by using field emission scanning electron microscope, transmission electron microscope, energy dispersive X-ray spectroscope, micro-Raman spectroscope, and X-ray photoelectron spectroscope. The results indicate that the mixing of the Se and MoO3 powders directly affects the formations and structures of Se and MoSe2 nanoflakes. When the Se and MoO3 powders are fully mixed, the Se nanoflakes are formed, however the MoSe2 nanoflakes are formed under no mixture of Se and MoO3 powders. This is due to the fact that different reactions of Se and MoO3 powders in gas environment with or without mixing the Se and MoO3 powders are generated. The study of photoluminescence properties indicates that the photoluminescence peaks are generated at about 774, 783 nm and 783, 784 nm for the Se and MoSe2 nanoflakes, respectively, which are different from the photoluminescence properties of monolayer MoSe2 nanosheet. These outcomes can enrich our knowledge of the synthesis and optical properties of two-dimensional Se-based nanomaterials and will contribute to the development of optoelectronic devices of two-dimensional Se-based nanomaterials.

VO2 (B) nanosheets were prepared by a liquid-phase exfoliation from VO2 (B) bulk. The lithium storage properties of VO2 (B) nanosheets as capacity cathode materials for rechargeable lithium secondary batteries were investigated. It was found that the nanosheets with the thickness of several nanometers and width of tens of nanometer had a preferential growth direction along [001] orientation. By comparing with VO2 (B) bulk, the VO2 (B) nanosheets showed a higher initial discharge capacity and a slower capacity fading rate. The reasons for these phenomena were discussed and analyzed.

Vanadium pentoxide nanorods assemblies were synthesized by a microwave-assisted hydrothermal synthesis, combined with subsequently annealing treatment. The structure and morphology of the nanorods were characterized by XRD, FESEM and HRTEM, and the electrochemical properties of the electrodes made from the V2O5 nanorods were investigated. The V2O5 nanorods with an average diameter of 100 nm and lengths up to several micrometers are almost parallel distributed in the assemblies. The V2O5 nanorods assemblies exhibit an initial discharge capacity of 330 mA hg(-1) at a current density of 50 mA g(-1), which is very higher than that of the separated V2O5 nanorods. The V2O5 nanorods assemblies also show a lower capacity fading rate in comparison with the separated V2O5 nanorods. A low polarization of the charge transfer reaction and a high diffusion rate of lithium ion inside the electrode composed of the paralleled nanorods are considered responsible for the enhanced capacity. (C) 2015 Elsevier Ltd. All rights reserved.

Interaction, polarization, and charges or electric field distribution of conducting spheres in applied electric field are in many fields including electrorheological fluids, electrophoresis, and electrical engineering. A system with two equipotential conducting spheres in an applied uniform electric field is analyzed by image method. A new method is put forward to calculate the image charges distribution when using image method, which ensures the validity of image method to analyze equipotential cases. An apparatus is constructed to measure the force experimentally as well. Results show that the distribution of electric field and electric interaction are different with the case not equipotential.

Three visible imaging diagnostic systems have been installed on EAST tokamak for several different diagnostic purposes. One is a high-speed camera system that can be operated to study edge plasma phenomena with a maximum recording speed of 16 kfps and a minimum exposure time of 1 µs. The other two systems have color cameras that are used by machine operators to monitor the discharge process including plasma shape, position, movement, and interaction with the device wall. A newly developed wide-view optics subsystem has been introduced into the imaging diagnostic system to transmit the plasma visible light to the outside of the device so that the camera can be installed outside, ensuring the safe and reliable functioning of the imaging diagnostic system. To match the optics, upgrades of the imaging acquisition and storage subsystem have been made to obtain both high temporal and high spatial resolutions in plasma imaging. In this paper, the design and results obtained during operations of the new visible imaging diagnostic systems are described using images of EAST tokamak plasma discharges during the recent plasma campaign.

An electrothermochromic VO2 nanoparticles film based on a Ag nanowires heater was prepared. The infrared performance of the film can be dynamically regulated and controlled by an applied voltage with high stability and reversibility. The film can overcome the high T-c limit of VO2 in practical applications and can be built on flexible substrates.

The Raman vibrational spectra of water inside mesoporous silicate are measured in a temperature range of 100 <= T <= 303 K. It is found that the Raman spectrum of confined water becomes more different from that of bulk water with the decrease of water content in pores. For samples with high water content in pore, the main peak position of the Raman spectrum of water changes abruptly in a narrow temperature range. However, when water content decreases down to 20%, the red shift of the main peak of the Raman spectrum is continuous with temperature decreasing. At the same time, its temperature-dependence is the same as that of bulk amorphous ice.

The multiple scattering method is used in calculating the electric field distribution for the systems composed of spheres. According to the calculation result, we propose a new mechanism of the electrorheological effect and show that the yield stress induced by this mechanism exhibits the typical characteristics of that observed in experiments.

Optically efficient cerium and terbium doped lanthanide fluoride (La1−x−yCexTby)F3 nanocrystals with different doping concentrations have been synthesized by a hydrothermal route in the presence of ethylenediamine tetraacetic acid disodium salt (EDTA). The results showed that the formation of nanocrystals with different morphologies depends on terbium ion Tb3+ doping concentration, but independent of cerium ion Ce3+ doping concentration. With increase in Tb3+ doping concentration, the morphologies of nanocrystals evolved from a spherical shape to a plated-like one. In addition, both the photoluminescence quantum yield (PL QY) and the fluorescence lifetime of nanocrystals increased with the increase in Ce3+ doping concentration in cerium and terbium co-doped system. The PL QY reached up to 55%, and the lifetime up to 7.3ms. Transmission electron microscopy (TEM), X-ray diffraction (XRD), selected area electron diffraction (SAED), X-ray fluorescence (XRF), energy dispersive spectroscopy (EDS), ultraviolet–visible (UV–vis) absorption, photoluminescence (PL) and infrared (IR) spectroscopies were employed to characterize the properties of nanocrystals. The growth mechanism of nanocrystals with different morphologies and optical properties of nanocrystals with different doping concentrations were investigated.

The synthesis of monodisperse nanocrystals is an important topic in the field of nanomaterials not only for practical applications, but also for scientific interest in fundamental research. In this feature article, we mainly focus on synthesis of monodisperse nanocrystals by a two-phase approach without the separation of nucleation and growth processes, and report some progress made recently in the observation and understanding of nucleation and growth of semiconductor nanocrystals. Firstly, a novel two-phase approach to monodisperse nanocrystals, which is different from the well-established synthesis models, is discussed. We demonstrate that the two-phase approach has a quite lengthy nucleation process, and can be applied to the synthesis of many kinds of binary monodisperse nanocrystals. Then, we provide a summary of recent research progress in the observation and understanding of nucleation and growth of semiconductor nanocrystals in one-phase and two-phase systems, and compare the nucleation and growth mechanisms of the two kinds of reaction systems. Although the lengthy nucleation process of the two-phase approach enables researchers to capture some useful information about the nucleation and growth processes, and the nucleation and growth processes have been studied by optical absorption spectra and transmission electron microscopy, there is little or no experimental data available on the atomic configurations of critical nuclei. Finally, the current difficulties and future challenges in synthesis and structural characterization of critical nuclei are presented.

The temperature dependence of the local structure of liquid Sb has been studied by x-ray absorption spectroscopy. It is shown that about 10% of the atoms with coordination of 3 and weak Peierls distortion exist in liquid Sb just above its melting point. The Peierls distortion weakens gradually with increasing temperature and vanishes at about 750 degrees C. This structural variation in liquid Sb is different from the normal liquid-liquid phase transition. This work reveals the relationship between the variation in the local structure and the change in the physical properties, such as the electrical resisitvity of liquid Sb, with temperature. The complete agreement between the measured electrical resistivity values during heating and cooling processes suggests that the structural units with the features of a rhombohedron appear above the melting point of Sb during solidification.

The surface tension and density of xBi(2)O(3)-(1-x)GeO2 (BGO) melts have been measured systematically from their respective melting points up to around 1480 K within 0.25 <= x <= 0.86. With the addition of Bi2O3, the density of this system increased smoothly with a positive curvature. Deviation of molar volume from ideality of this system melts decreased firstly, past a minimum at about x=0.4, and then increased. Partial molar volumes of Bi2O3 and GeO2 have also been calculated based on the measured density data and compared with those of a binary bismuth borate system. On increasing the content of Bi2O3, the surface tension of BGO melts increased slowly when x <similar to 0.40, past a maximum at about x=0.50, and then decreased rapidly. In addition, the temperature coefficient of surface tension remained positive within the lower content range of Bi2O3, changed sign from positive to negative at about x=0.38, and then was almost independent of the composition within the measured temperature range when the Bi2O3 content was increased further.

Colloidal CdSe and CdS quantum dots were synthesized at low temperatures (60-90 degrees C) by a two-phase approach at a toluene-water interface. Oil-soluble cadmium myristate (Cd-MA) was used as cadmium source, and water-soluble Na2S, thiourea, NaHSe, Na2SeSO3, and selenourea were used as sulfur and selenium sources, respectively. When a cadmium precursor in toluene and a selenium precursor in water were mixed, CdSe nanocrystals were achieved at a toluene-water interface in the range of 1.2-3.2 nm in diameter. Moreover, we also synthesized highly luminescent CdSe/CdS core-shell quantum dots by a two-phase approach using poorly reactive thiourea as sulfur source in an autoclave at 140 degrees C or under normal pressure at 90 degrees C. Colloidal solutions of CdSe/CdS core-shell nanocrystals exhibit a photoluminescence quantum yield (PL QY) up to 42% relative to coumarin 6 at room temperature.