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Liu C.,Chongqing University | He C.,Chongqing University | He C.,Chongqing Academy of Metrology and Quality Inspection | Xie T.,Chongqing University | Yang J.,Chongqing University
Fullerenes Nanotubes and Carbon Nanostructures | Year: 2015

Graphene (reduction of graphite oxide, rGO) was successfully prepared by using ammonia solution (NH3·H2O) as a reductive agent. The molecular structure and electrochemical properties of rGO were characterized by FTIR, XRD, Raman, SEM, EIS, and cyclic voltammetry (CV). The electrochemical sensing of chromium (Cr(VI)) at graphene-modified electrode (rGO/GCE) was investigated by differential pulse cathodic stripping voltammetry. The result showed that the charge transfer resistance of [Fe(CN) 6]3-/4- at rGO/GCE was 75.02 Ω·cm2 decreased by about nine times comparing as that of GCE. The reduction peak potential of Cr(VI) at rGO/GCE was shifted positively by 116 mV and the peak current increased by about eight times. Meanwhile, the detection limit was 1.5 × 10-7 mol/L. It was worth noting that the synthesis of rGO by reducing GO with NH3·H2O was more friendly to environment and human health relative to hydrazine hydrate (NH 2-NH2·H2O) or other poisonous reductants. © 2015 Copyright © Taylor & Francis Group, LLC.

Hu G.-H.,Chongqing University | Hu G.-H.,Chongqing Academy of Metrology and Quality Inspection | He W.,Chongqing University | Wang K.,Chongqing Changshou Electrical Power Bureau
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2011

Online monitoring of distribution transformer harmonic loss is an important approach to providing decision-making for the determination of the high-loss transformer and ensuring the transformer economic operation. circuit model is introduced to improve the transformer harmonic additional loss model and the accuracy of the algorithm is effectively improved by using the ratio of winding loss and eddy current loss to compensate transformer core loss caused by harmonics. Based on which, online monitoring system for transformer harmonic additional loss is designed. System host controller adopts DSP2812 which can detect transformer operating parameters and supply real-time data for monitoring transformer harmonic additional loss through serial port. The system software is developed by object-oriented Visual C + + 6.0, including data display module, serial port operation module and transformer parameters setting module. The analysis of the experiment indicates that the result of monitoring system is correct.

Wu G.,Hubei University | Chen M.-H.,Hubei University | Liao J.,Chongqing Academy of Metrology and Quality Inspection
Diamond and Related Materials | Year: 2016

Microwave plasma chemical vapor deposition (MPCVD) has gained increasing attention as a feasible and effective way to produce large, high-quality, single-crystal diamonds. However, the growth of polycrystalline diamond on the periphery of the seed crystal and the cracking generated by the internal stress during the growing process lead to significant decline of the quality and integrity of the CVD diamond, thus increasing the difficulty of synthesizing large diamond layers. Although optimized growth parameters and refined substrate holders have been employed by some researchers to improve the periphery quality of CVD diamond layers, more research needs to be done in this area. In this study, we used a specially designed substrate holder with a circular recess, in which the seed crystal was placed. By designing substrate holders with different recess depths and a seed crystal with different side-surface crystallographic orientations, we aimed to determine the influence of the recess depths and the crystallographic orientation of seed sides on the growth quality according to polarizing microscope, laser Raman spectroscopy, UV fluorescence imaging, and photoluminescence (PL) mapping measurements. The results demonstrate that as the recess depth increases, the amount of polycrystalline diamonds and the internal stress on the periphery are controlled effectively. The crystalline quality is improved, and the growth rate is decreased. In addition, compared to the periphery with {100} seed sides, the periphery with {110} seed sides displays better crystalline quality, lower internal stress, and fewer polycrystalline diamonds after growth, which is probably due to the intrinsic nature of the growth steps propagating on the {100} diamond surface and the effect of nitrogen atoms on the growing process in the diamond lattice. © 2016 Elsevier B.V. All rights reserved.

Yu X.,Chongqing Academy of Metrology and Quality Inspection | Zeng W.,Chongqing University
Journal of Materials Science: Materials in Electronics | Year: 2016

The manner how nano building blocks assemble into hierarchical architectures exerts a tremendous influence on gas-sensing property of the metal oxides. Herein, we focus on tuning the 1D SnO2 rectangular nanorods into 3D hierarchical nanoflowers by manipulating the concentration of surfactant (citric acid) as well as the period of hydrothermal process, and then investigate their gas-sensing performance. Nanostructures assembled by short, unordered and well-ordered rectangular nanorods were successfully fabricated, corresponding to infant, abnormal and blooming SnO2 nanoflowers, respectively. In comparison, sensor based on blooming SnO2 nanoflowers exhibited significantly enhanced gas response to ethanol than the other two, not only in terms of the sensitivity but also the response/recovery time, which may be mainly attributed to the sufficient diffusion channel and exposed surface provided by finely dispersed nanorods in the blooming nanoflowers. © 2016 Springer Science+Business Media New York

Miao R.,Chongqing University | Yu X.,Chongqing Academy of Metrology and Quality Inspection | Zeng W.,Chongqing University
Materials Letters | Year: 2016

Nanomaterials with three-dimensional architectures, frequently exhibiting novel functional properties, have attracted considerable attention of the researchers. In current work, we have successfully synthesized the NiO flower-like microspheres with abundant nanoparticles adhering to the petals via a facile hydrothermal method. Interestingly, it is found that the excellent gas sensing properties of the samples towards ethanol are likely attributed to the well-aligned porous architectures as well as great amounts of nanoparticles adhering to the petals, considered as active sites. Meanwhile, we also elaborated a distinctive growth mechanism of such a unique architecture and a plausible gas sensing mechanism, respectively. © 2016 Elsevier B.V. All rights reserved.

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