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Hussain S.,Chongqing UniversityChongqing | Hussain S.,National Engineering Research Center for Magnesium AlloysChongqing | Liu T.,Chongqing UniversityChongqing | Liu T.,National Engineering Research Center for Magnesium AlloysChongqing | And 5 more authors.
Sensors and Actuators, B: Chemical | Year: 2017

Wurtzite zero dimensional ZnS nanospheres and random-shaped nanoparticles successfully synthesized via a low temperature hydrothermal route. The formation of nanostructures is attributed due to PVP and thiourea and discussed in details. The as-prepared nanostructures were characterized by XRD, EDS, SEM and HRTEM. Based on experimental results, a plausible growth mechanism is also proposed along with crystal structure of ZnS. The gas–sensing properties of as–prepared ZnS products are tested using efficient substrate sensors via an intelligent gas testing system. Both at room and 100–400 °C temperature, high response and selectivity towards formaldehyde than other gases is observed. Comparative studies of ZnS nanostructures for different concentrations of formaldehyde gas and definite sensor-stability for different gases is studied, as well. © 2016 Elsevier B.V.

Kotobuki M.,National University of Singapore | Song S.,National University of Singapore | Song S.,Chongqing UniversityChongqing | Takahashi R.,Hokkaido University of Science | And 2 more authors.
Journal of Power Sources | Year: 2017

Li5La3Ta2O12 (LLTa) is a promising solid electrolyte for all-solid-state batteries due to its high stability in contact with Li metal, however, low Li ion conductivity of LLTa has restricted its application. In this study, improvement of the Li ion conductivity of LLTa solid electrolyte by substitution of Ge4+ for Ta5+ is studied because the improvement is thought to be achieved by increase of charge carrier concentration caused by the substitution of low valence Ge4+ for high valence Ta5+. The Ge substitution shrinks a lattice of cubic LLTa due to small ion radius of Ge4+ (0.530 Å) compared with Ta5+ (0.640 Å). The Li ion conductivity of LLTa is improved by the Ge substitution. The highest bulk and total Li ion conductivities are obtained in Li5.25La3Ta1.75Ge0.25O12 prepared by spark plasma sintering at 1100 °C and the values are 1.3 × 10−4 and 8.4 × 10−5 S cm−1 at 28 °C, respectively. The lithium transference number of the Ge-substituted LLTa determined by Hebb-Wagner (HW) polarization method is ≈ 1. Also, it is verified that the new solid electrolyte is stable in a potential range of 0–10 V vs. Li/Li+, indicating that the Ge-substituted LLTa is a promising solid electrolyte for all-solid-state battery application. © 2017 Elsevier B.V.

Shen L.,Chongqing UniversityChongqing | Zhou J.,Chongqing UniversityChongqing | Ma X.,Chongqing UniversityChongqing | Lu X.Z.,Hong Kong Polytechnic University | And 4 more authors.
Journal of Materials Processing Technology | Year: 2017

The temperature field and thermal cycling characteristics of a cast-steel matrix die of automobile crankshaft were predicted. The hot forging die was divided into three temperature regions, i.e., surfacing temperature fluctuation region (0–3 mm in thickness), near surfacing temperature gradient region (3–20 mm in thickness) and matrix temperature balanced region (above 20 mm in thickness), and their temperatures were distributed in high, medium and low-tempered temperature zones respectively. The influences of temperature distribution on the microstructure and mechanical properties of the forging die before and after service were studied. The tempered martensite of strengthened layer decomposed and the coarse grain appeared after service. The protruding part of the ribbed slab was easy to propagate fatigue crack, leading to significant decreasing of tensile strength and impact properties. The tempered martensite and lower banite increased in transition layer, the mechanical properties under high temperatures decreased obviously. The strengthening of hardened structure in weld zone was reduced and the coarse grain structure disappeared, this enabled the performance of the weld zone was more stable than the cast-steel matrix layer and the transition layer. © 2016 Elsevier B.V.

Sun Q.,Chongqing UniversityChongqing | Zhang X.,Chongqing UniversityChongqing | Shu Y.,Chongqing UniversityChongqing | Tan L.,Chongqing UniversityChongqing | Liu Q.,Chongqing UniversityChongqing
Materials Letters | Year: 2016

Deformation twinning is one of the most important strain accommodation mechanisms for deformed hexagonal materials. The stacking faults inside the twin may act as obstacles to hinder the subsequent motion of the dislocations and accordingly influence the mechanical properties of materials. In the present work, two types of basal stacking faults within the {101¯2} deformation twin in a deformed magnesium alloy have been studied by high-resolution transmission electron microscopy. It has found that one ends of the basal stacking faults are usually bounded by the incoherent twinning boundaries. According to this experimental feature, the possible formation mechanisms of such basal stacking faults will be discussed. © 2016 Elsevier B.V.

Sun Q.,Chongqing UniversityChongqing | Zhang X.Y.,Chongqing UniversityChongqing | Yin R.S.,Chongqing UniversityChongqing | Ren Y.,Chongqing UniversityChongqing | Tan L.,Chongqing UniversityChongqing
Scripta Materialia | Year: 2015

Using high-resolution transmission electron microscopy, we characterized the interfacial structure of {101¯3} twinning boundaries (TBs) in deformed cobalt, and found that TBs consist of {101¯3} TBs, {101¯1¯} TBs, basal-pyramidal (BPy) and pyramidal-basal (PyB) interfaces. The existence of {101¯1¯} TBs, BPy and PyB interfaces is responsible for the deviation of the actual {101¯3} TB from the theoretical twinning plane. Correspondingly, the migration of TBs attributed to the glide of twinning disconnections is discussed. © 2015 Acta Materialia Inc.

Yang Q.,Chongqing UniversityChongqing | Yang Q.,Guizhou University | Chen H.,Guizhou Normal University | Li B.,Chongqing UniversityChongqing
Archives of Environmental Contamination and Toxicology | Year: 2015

An investigation was performed to identify the sources of arsenic (As) and heavy metals in house dust and to assess the associated human health risks in the vicinity of phosphorus (P) mining in Guizhou, China. The concentrations and spatial distributions of mercury (Hg), As, cadmium (Cd), lead (Pb), iron (Fe), copper (Cu), manganese (Mn), and P in 23 house dust samples from the study area were determined. Greater concentrations of As and Pb were found compared with values in other investigations in various countries. Pollution sources were identified using multivariate statistical analysis. As, Pb, Mn, and Hg pollution was mainly attributed to mining activities, and Mn and Cd levels were largely associated with automobile emissions. The dominant wind direction and the distance of the residence from the mining region were found to play an important role in element distributions. A health risk assessment showed that As and Pb should be paid more attention, although the noncancer risks of the studied elements were within the safe range and the cancer risks of As and Cd are within the acceptable range under present conditions. © 2014 Springer Science+Business Media New York.

Zhou C.,Chongqing UniversityChongqing | Li M.,Chongqing UniversityChongqing | Hu Z.,Chongqing UniversityChongqing | Yin H.,Chongqing UniversityChongqing | And 2 more authors.
Journal of Crystal Growth | Year: 2016

In this study, a novel motion mode for crystals during growth, i.e., 2D translation, is proposed. Numerical simulations of flow and mass transfer are conducted for the growth of large-scale potassium dihydrogen phosphate (KDP) crystals subjected to the new motion mode. Surface supersaturation and shear stress are obtained as functions of the translational velocity, distance, size, orientation of crystals. The dependence of these two parameters on the flow fields around the crystals is also discussed. The thicknesses of the solute boundary layer varied with translational velocity are described. The characteristics of solution flow and surface supersaturation distribution are summarized, where it suggests that the morphological stability of a crystal surface can be enhanced if the proposed 2D translation is applied to crystal growth. © 2016 Elsevier B.V.

Wang T.,National University of Singapore | Yu Z.,Chongqing UniversityChongqing | Hoon D.L.,National University of Singapore | Huang K.-W.,King Abdullah University of Science and Technology | And 2 more authors.
Chemical Science | Year: 2015

Phosphine-catalyzed highly enantioselective γ-additions of 5H-thiazol-4-ones and 5H-oxazol-4-ones to allenoates have been developed for the first time. With the employment of amino-acid derived bifunctional phosphines, a wide range of substituted 5H-thiazol-4-one and 5H-oxazol-4-one derivatives bearing heteroatom (S or O)-containing tertiary chiral centers were constructed in high yields and excellent enantioselectivities. The reported method provides facile access to enantioenriched tertiary thioethers/alcohols. The mechanism of the γ-addition reaction was investigated by performing DFT calculations, and the hydrogen bonding interactions between the Brønsted acid moiety of the phosphine catalysts and the "C=O" unit of the donor molecules were shown to be crucial in asymmetric induction. This journal is © The Royal Society of Chemistry.

Cao K.,Zhejiang University | Kuang M.,Chongqing UniversityChongqing | Zhang Y.,Chongqing UniversityChongqing | Liu J.,Zhejiang University | And 2 more authors.
Materials Research Bulletin | Year: 2016

Nanostructure is believed to produce great benefits for anode materials in lithium ion batteries (LIBs) by enhancing lithium ion transfer, accommodating large volume change and increasing surface area. Whether the nanostructure (especially the porous nanostructure) could be well held during charging/discharging process is one of the most commonly concerned issues in LIBs research. The dynamic evolution of birnessite manganese dioxides nanosheets during lithiation process is investigated by in-situ transmission electron microscopy (TEM) for the first time. The TiO2@MnO2 core-shell nanowires are used as the anode and Li metal as the counter electrode inside the TEM. Interestingly, the lithiation process is confirmed as MnO2 and Li converting to Li2O and Mn. The original porous structure of the nanosheets is hard to preserve during lithiation process due to lithiation-induced contact flattening. © 2016 Elsevier Ltd. All rights reserved.

Li T.,Chongqing UniversityChongqing | Zeng W.,Chongqing UniversityChongqing | Zhang Y.,Chongqing UniversityChongqing | Hussain S.,Chongqing UniversityChongqing
Materials Letters | Year: 2015

Abstract We report the synthesis of novel nest-like MoO3 hierarchical structures with nanobelts as building blocks via a facile hydrothermal process. A comparison study reveals that an enhanced gas sensing performance for the sensor made of nanobelt-assembled nest-like MoO3 towards ethanol occurs over that of the monodispersed MoO3 nanobelts. The improved gas sensing properties are mainly attributed to the well-aligned nanoporous structures with a less stacking configuration, which provides sufficient nano or micro reaction rooms for chemical reaction as well as effective diffusion channels for gases. © 2015 Elsevier B.V.

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