Separation of Neighboring REElementsfrom Sm_2O_3Eu_2O_3Gd_2O_3 System by a Stepwise ChlorinationChemical Vapor Transport Reaction

The mutual separation characteristics were investigated for the neighboring Sm, Eu and Gd from their ternary oxide mixture Sm 2O 3 Eu 2O 3 Gd 2O 3 by a stepwise chlorination chemical vapor transport reaction within 6 h using AlCl 3 as complex former. The rare earth chlorides were more readily transported and concentrated in the middle temperature range of 980～1100 K and the transport efficiency was in the order of Sm≈Gd>Eu. The separation factor, expressed as molar ratio for the resulting chlorides, was 1 70 for Eu∶Sm, 1 88 for Eu∶Gd, 1 24 for Sm∶Gd in the higher temperature region, and 2 76 for Sm∶Eu, 2 83 for Gd∶Eu and 1 12 for Gd∶Sm in the lower temperature region, respectively. All results are much higher than those of the conventional wet process.

A study of the chemical composition and transport of marine aerosols over the ocean near China

In this paper the authors cite the aerosol samples collected with a KA-200 Anderson cascade Impactor and a KB-120 sampler during the first cruise of the Kuroshio investigation operated by the People's Republic of China and Japan cooperative program, from July 23 to August 21, 1987. The concentration size distributions and composition of marine aerosols over the Kuroshio area are analyzed. Neutron activation analysis is used to determine the elemental composition of the aerosols. The authors also discuss some characteristics of marine aerosols relating to long-range transport of crustal and anthropogenic elements from the continent to the remote ocean. Analytical results indicate that elements Al, Fe, Sc and Sb over this area are obviously influenced by the continent of Asia, and the size distributions are changed after long-range transport. The concentration of large particles increase. The concentrations of the elements C1 and Na are closely related to ocean conditions; the source of the elements Cl and Na is mainly the ocean. Besides coal combustion, the ocean is also a very important source for the element Se. The amount of Se is related to the distribution of marine life.

Effect of Chemical Doping on the Electronic Transport Properties of Tailoring Graphene Nanoribbons

The electronic transport properties of a molecular junction based on doping tailoring armchair-type graphene nanoribbons（AGNRs）with different widths are investigated by applying the non-equilibrium Green＇s function formalism combined with first-principles density functional theory.The calculated results show that the width and doping play significant roles in the electronic transport properties of the molecular junction.A higher current can be obtained for the molecular junctions with the tailoring AGNRs with W=11.Furthermore,the current of boron-doped tailoring AGNRs with widths W=7 is nearly four times larger than that of the undoped one,which can be potentially useful for the design of high performance electronic devices.

Preparation of Anhydrous Lutetiu m Chlorideby Chemical Vapor Transport

Anhydrous lutetium chloride, which is not easy to prepare in other ways, was prepared by chemical vapor transport (CVT) method. Lu2O3 reacted with Al2Cl6 at 300 degrees C to produce LuCl3, which was then separated from other solids by means of CVT at a temperature gradient from 400 degrees C to 180 degrees C. Residual Al2Cl6 was removed by dry Cl-2-N-2 gas at 200 degrees C. The purity of the product was > 99.9%.

Preparation of Anhydrous LnCl_3(Ln=Eu, Er, Lu) by Chemical Vapor Transport

Anhydrous lanthanide chlorides LnCl 3(Ln=Eu, Er, Lu) which are not easy to prepare in other ways were prepared by chemical vapor transport(CVT) method. Ln 2O 3 reacted with an excess of Al 2Cl 6 at 300 ℃ to produce LnCl 3. LnCl 3 reacted with Al 2Cl 6 at high temperature to form the gaseous complexes which decomposed at low temperature. LnCl 3 was then separated from other solids by controlling a proper temperature gradient. Residual Al 2Cl 6(g) was removed by the carrier of dry Cl 2 N 2 gases at 200 ℃. The yield rates are >90%, and the purity of products is >99 5%. The high purity of anhydrous lanthanide chlorides can be obtained by CVT method.

Stepwise Chlorination-Chemical Vapor Transport Reactions for Bastnaesite Concentrate

Vapor phase extraction and mutual separation of rare earth (RE) elements from bastnaesite concentrate were investigated using stepwise chlorination chemical vapor transport reactions mediated by vapor complexes LnAl n Cl 3 n +3 (Ln=RE elements). The bastnaesite was heated to 800 K and chlorinated between 800～1300 K with C+Cl 2+SiCl 4 to remove CO 2, SiF 4 and high volatile chlorides. At the temperature of 1300 K for 6 h, the resulted RE chlorides were chemically transported and mutual separated with the vapor complexes while CaCl 2 and BaCl 2 were remained in the residues. Significantly different CVT characteristics were observed for gradually decreased and wave form temperature gradients.

Laser Radiation Influence on Transport Phenomena in a Biotissue

Different mechanisms of laser radiation influence on the chemical transport inside a biotissue are investigated. The average size of speckles existing inside a biotissue and the radiation intensity in them are estimated experimentally. Gradient forces and forces caused by the thermal expansion acting on the micro-volume inside a tissue as result of an irregular light field are calculated at different average light intensities including therapeutic. Using theoretical simulation taking into account nonequilibrium light absorption in structural elements of biotissue it has been obtained that the coherent light influences on the chemical transport more strongly in comparison with the incoherent one.

Relationship between disorder,magnetism and band topology in Mn(Sb_(1-x)Bi_(x))_(2)Te_(4) single crystals

We investigate the evolution of magnetic properties as well as the content and distribution of Mn for Mn(Sb_(1-x)Bi_(x))_(2)Te_(4) single crystals grown by large-temperature-gradient chemical vapor transport method.It is found that the ferromagnetic MnSb_(2)Te_(4) changes to antiferromagnetism with Bi doping when x≥0.25.Further analysis implies that the occupations of Mn ions at Sb/Bi site Mn_(Sb/Bi) and Mn site Mn_(Mn) have a strong influence on the magnetic ground states of these systems.With the decrease of Mn_(Mn) increase of Mn_(Sb/Bi),the system will favor the ferromagnetic ground state.In addition,the rapid decrease of T_(C/N) with increasing Bi content when x ≤0.25 and the insensitivity of T_(N) to x when x> 0.25 suggest that the main magnetic interaction may change from the Ruderman-Kittel-Kasuya-Yosida type at low Bi doping region to the van-Vleck type in high Bi doped samples.

Simulation of Tropospheric Ozone with MOZART-2:An Evaluation Study over East Asia

Climate changes induced by human activities have attracted a great amount of attention. With this, a coupling system of an atmospheric chemistry model and a climate model is greatly needed in China for better understanding the interaction between atmospheric chemical components and the climate. As the first step to realize this coupling goal, the three-dimensional global atmospheric chemistry transport model MOZART-2 (the global Model of Ozone and Related Chemical Tracers, version 2) coupled with CAM2 (the Community Atmosphere Model, version 2) is set up and the model results are compared against observations obtained in East Asia in order to evaluate the model performance. Comparison of simulated ozone mixing ratios with ground level observations at Minamitorishima and Ryori and with ozonesonde data at Naha and Tateno in Japan shows that the observed ozone concentrations can be reproduced reasonably well at Minamitorishima but they tend to be slightly overestimated in winter and autumn while underestimated a little in summer at Ryori. The model also captures the general features of surface CO seasonal variations quite well, while it underestimates CO levels at both Minamitorishima and Ryori. The underestimation is primarily associated with the emission inventory adopted in this study. Compared with the ozonesonde data, the simulated vertical gradient and magnitude of ozone can be reasonably well simulated with a little overestimation in winter, especially in the upper troposphere. The model also generally captures the seasonal, latitudinal and altitudinal variations in ozone concentration. Analysis indicates that the underestimation of tropopause height in February contributes to the overestimation of winter ozone in the upper and middle troposphere at Tateno.

Numerical Simulation of CO_2 Concentrations in East Asia with RAMS-CMAQ

The regional air quality modeling system RAMS-CMAQ(Regional Atmospheric Modeling System and Models-3 Community Multi-scale Air Quality) was developed by incorporating a vegetation photosynthesis and respiration module(VPRM) and used to simulate temporal-spatial variations in atmospheric CO2 concentrations in East Asia,with prescribed surface CO2 fluxes(i.e.,fossil fuel emission,biomass burning,sea-air CO2 exchange,and terrestrial biosphere CO2 flux).Comparison of modeled CO2 mixing ratios with eight ground-based in-situ measurements demonstrated that the model was able to capture most observed CO2 temporal-spatial features.Simulated CO2 concentrations were generally in good agreement with observed concentrations.Results indicated that the accumulated impacts of anthropogenic emissions contributed more to increased CO2 concentrations in urban regions relative to remote locations.Moreover,RAMS-CMAQ analysis demonstrates that surface CO2 concentrations in East Asia are strongly influenced by terrestrial ecosystems.

Impact of Precursor Levels and Global Warming on Peak Ozone Concentration in the Pearl River Delta Region of China

The relationship between the emission of ozone precursors and the chemical production of tropospheric ozone （03） in the Pearl River Delta Region （PRD） was studied using numerical simulation. The aim of this study was to examine the volatile organic compound （VOC）- or nitrogen oxide （NO~ =NO＋NO2）- limited conditions at present and when surface temperature is increasing due to global warming, thus to make recommendations for future ozone abatement policies for the PRD region. The model used for this application is the U.S. Environmental Protection Agency＇s （EPA＇s） third-generation air-quality modeling system; it consists of the mesoscale meteorological model MM5 and the chemical transport model named Community Multi-scale Air Quality （CMAQ）. A series of sensitivity tests were conducted to assess the influence of VOC and NO~ variations on ozone production. Tropical cyclone was shown to be one of the important synoptic weather patterns leading to ozone pollution. The simulations were based on a tropical- cyclone-related episode that occurred during 14-16 September 2004. The results show that, in the future, the control strategy for emissions should be tightened. To reduce the current level of ozone to meet the Hong Kong Environmental Protection Department （EPD） air-quality objective （hourly average of 120 ppb）, emphasis should be put on restricting the increase of NOx emissions. Furthermore, for a wide range of possible changes in precursor emissions, temperature increase will increase the ozone peak in the PRD region; the areas affected by photochemical smog are growing wider, but the locations of the ozone plume are rather invariant.

Middle-High Latitude N_2O Distributions Related to the Arctic Vortex Breakup

The relationship of N2O distributions with the Arctic vortex breakup is first analyzed with a probability distribution function （PDF） analysis. The N2O concentration shows different distributions between the early and late vortex breakup years. In the early breakup years, the N2O concentration shows low values and large dispersions after the vortex breakup, which is related to the inhomogeneity in the vertical advection in the middle and high latitude lower stratosphere. The horizontal diffusion coefficient （Kyy） shows a larger value accordingly. In the late breakup years, the N2O concentration shows high values and more uniform distributions than in the early years after the vortex breakup, with a smaller vertical advection and Kyy after the vortex breakup. It is found that the N2O distributions are largely affected by the Arctic vortex breakup time but the dynamically defined vortex breakup time is not the only factor.

Highly crystalline ReSe2 atomic layers synthesized by chemical vapor transport

Two-dimensional (2D) anisotropic rhenium diselenide (ReSe2) has attracted lots ofattention due to its promising applications in electronics and optoelectronics. However,controlled synthesis of high quality ultrathin ReSe2 remains as a challenge.Here we developed an approach for synthesizing high quality 2D ReSe2 flakes witha thickness down to monolayer by chemical vapor transport (CVT) through carefullytuning the growth kinetics. The atomic structures and anisotropy of theobtained ReSe2 flakes were intensively characterized with scanning transmissionelectron microscope and angle-resolved polarized Raman spectroscopy. Fieldeffecttransistors fabricated on the CVT-grown ReSe2 flakes showed n-typesemiconducting behavior with an on/off current ratio of 105 and a mobility up to
5 cm2 V−1 s−1, which is comparable to mechanically exfoliated flakes and isobvious higher than the samples synthesized with other approaches. This study notonly make high quality 2D ReSe2 easily accessible for both fundamental and applicationexplorations but also sheds new lights on the chemical synthesis of otheranisotropic 2D materials.

A Safe and Brief Way for Preparing Anhydrous LnCl_3 (Ln=Sc, Y, La to Lu)

Anhydrous lanthanide chlorides LnCl 3 (Ln=Sc, Y, La to Lu except for Pm), which are difficult to prepare in other ways, were prepared by chemical vapor transport (CVT) process. Rare earth oxide reacted with Al 2Cl 6 at 300℃ to produce LnCl 3, which was then separated from other solids by means of CVT at a temperature gradient from 400 to 180℃. Residual Al 2Cl 6 (g) was removed by carrier of dry N 2 gas at 200℃. The yielding rates were >90%, and the purity of products was >99.5%.

Morphology-controlled Tantalum Diselenide Structures as Self-optimizing Hydrogen Evolution Catalysts

Metallic layered transition metal dichalcogenides(TMDs)nanomaterials based on Group 5 transition metals are attracting substantial interests as alternative catalysts for hydrogen evolution reaction(HER).However,controllable preparation of tantalum diselenide(TaSe2)remains challenging,which has hindered the exploration on its application in HER.Herein,we develop a facile method named surface-assisted chemical vapor transport(SACVT)for controllable synthesis of TaSe2 plates and nanobelts,by regulating the molar ratio of selenium to tantalum and reaction temperature.Unique quasi-arrays and self-supported structure help TaSe2 nanobelt own more active sites and higher ability of charge transfer,so it is superior to TaSe2 plate in electrocatalytic HER.Interestingly,they both exhibit the ability to optimize their morphologies upon cycling for dramatically improved and robust electrocatalytic performance.The selfoptimized structures can increase the effective active surface by exposing more active sites on the basal-planes and edges,shorten the interlayer electron-transfer pathways at a thinned domain,and accelerate the charge transfer,which mainly derive from high basal-plane activity and weak interaction between layers of metallic TaSe2.This work provides a reliable way for controllable synthesis of different TaSe2 structures,motivating further efforts to explore new high-efficiency catalysts in the large family of metallic TMDs for electrochemical energy conversion.

Growth, characterization, and Raman spectra of the 1T phases of TiTe_(2), TiSe_(2), and TiS_(2)

High-quality large 1T phase of TiX_(2)(X = Te, Se, and S) single crystals have been grown by chemical vapor transport using iodine as a transport agent. The samples are characterized by compositional and structural analyses, and their properties are investigated by Raman spectroscopy. Several phonon modes have been observed, including the widely reported A_(1g) and E_(8) modes, the rarely reported E_(u) mode(-83 cm^(-1) for TiTe_(2), and -185 cm^(-1)for TiS_(2)), and even the unexpected K mode(-85 cm^(-1)) of TiTe_(2). Most phonons harden with the decrease of temperature, except that the K mode of TiTe_(2) and the E_(u) and “A_(2u)/Sh” modes of TiS_(2) soften with the decrease of temperature. In addition, we also found phonon changes in TiSe_(2) that may be related to charge density wave phase transition. Our results on TiX_(2) phonons will help to understand their charge density wave and superconductivity.

Facile and fast growth of high mobility nanoribbons of ZrTe5

Recently, ZrTe5 has received a lot of attention as it exhibits various topological phases, such as weak and strong topological insulators, a Dirac semimetal, a three-dimensional quantum Hall state, and a quantum spin Hall insulator in the monolayer limit. While most of studies have been focused on the three-dimensional bulk material, it is highly desired to obtain nanostructured materials due to their advantages in device applications. We report the synthesis and characterizations of ZrTe5 nanoribbons. Via a silicon-assisted chemical vapor transport method, long nanoribbons with thickness as thin as 20 nm can be grown. The growth rate is over an order of magnitude faster than the previous method for the bulk crystals.Moreover, transport studies show that the nanoribbons are of low unintentional doping and high carrier mobility, over30000 cm2/V·s, which enable reliable determination of the Berry phase of π in the ac plane from quantum oscillations. Our method holds great potential in growth of high quality ultra-thin nanostructures of ZrTe5.

Carbon agent chemical vapor transport growth of Ga2O3 crystal

Beta-type gallium oxide（β-Ga2O3） is a new attractive material for optoelectronic devices. Different methods had been tried to grow high quality β-Ga2O3 crystals. In this work, crystal growth of Ga2O3 has been carried out by chemical vapor transport（CVT） method in a closed quartz tube using C as transport agent and sapphire wafer as seed. The CVT mass flux has been analyzed by theoretical calculations based on equilibrium thermodynamics and 1D diffusional mass transport. The crystal growth experimental results are in agreement with the theoretical predictions. Influence factors of Ga2O3 crystal growth, such as temperature distribution, amount of C as transport agent used, have also been discussed. Structural（XRD） and optical（Raman spectroscopy, photoluminescence spectrum） properties of the CVT-Ga2O3 crystal are presented.