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Diffusion-reaction compromise the polymorphs of precipitated calcium carbonate

Particuology 2013年第3期11卷 301-308页

作者： Han Wang Wenlai Huang Yongsheng Han EMMS Group State Key Laboratory of Multiphase Complex SystemsInstitute of Process EngineeringChinese Academy of Sciences Graduate School of Chinese Academy of Sciences

Diffusion is seldom considered by chemists and materialists in the preparation of materials while it plays an important role in the field of chemical engineering. If we look at crystallization at the atomic level, crystal growth in a solution starts from the diffusion of ions to the growing surface followed by the incorporation of ions into its lattice. Diffusion can be a rate determining step for the growth of crystals. In this paper, we take the crystallization of calcium carbonate as an example to illustrate the microscopic processes of diffusion and reaction and their compromising influence on the morphology of the crystals produced. The diffusion effect is studied in a specially designed three-cell reactor. Experiments show that a decrease of diffusion leads to retardation of supersaturation and the formation of a continuous concen- tration gradient in the reaction cell, thus promoting the formation of cubic calcite particles. The reaction rate is regulated by temperature. Increase of reaction rate favors the formation of needle-like aragonite particles. When diffusion and reaction play joint roles in the reaction system, their compromise dominates the formation of products, leading to a mixture of cubic and needle-like particles with a controllable ratio. Since diffusion and reaction are universal factors in the preparation of materials, the finding of this paper could be helpful in the controlled synthesis of other materials.

关键词： Calcium carbonate Shape control Crystallization Diffusion Compromise

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NO EmissionCharacteristics of Hydrothermally Pretreated Antibiotic Mycelial Dreg Combustionin a Drop Tube Reactor

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Energy Procedia 2014年 61卷 743-746页

作者： Dachao Ma Guangyi Zhang Chinnathan Areeprasert Gan Lina Kunio Yoshikawa State Key Laboratory of Multiphase Complex Systems Institute of Process Engineering Chinese Academy of Sciences Beijing 100190 China Department of Environmental Science and Technology Tokyo Institute of Technology Kanagawa 226-8502 Tokyo Japan

Antibiotic mycelial dreg (AMD) is one of typical industrial wastes with high moisture and nitrogen contents which are difficult to be dealt with. The previous works demonstrated that the hydrothermal pretreatment is feasible for removing moisture and nitrogen contents from AMD so as to upgrade this waste into solid biofuel. Nevertheless, the NO emission characteristics of its combustion are still unknown and needed to be tested. The present work was aimed to clarify this understanding in a laboratory drop tube reactor under the temperature of 1273K. The raw AMD, the hydrothermally pretreated AMD and coal were respectively supplied into the reactor for combustion. The concentration of NO in the flue gas for different samples were measured and compared to evaluate the emission performance of the fuels. Compared to raw AMD, the NO emission of mono-combustion of hydrothermally pretreated AMD was dramatically reduced, whose reduction rate was above 30%. In order to investigate the mechanism of NO reduction, some analyses using Thermo Gravimetric Analyzer (TGA), X-ray Photoelectron Spectroscopy (XPS) and others were performed to reveal the properties of the raw AMD, hydrothermally pretreated AMD and coal. It was shown that the intermediates produced from releasing volatile maters act as reductants for the reduction of NO. The hydrothermal pretreatment can control the NO emission.

关键词： Hydrothermal pretreatment NO emission Antibiotic mycelial dreg

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Study on the recovery of ionic liquids from dilute effluent by electrodialysis method and the fouling of cation-exchange membrane

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Science China Chemistry 2013年第12期56卷 1811-1816页

作者： BAI Lu WANG XiaoLiang NIE Yi DONG HaiFeng ZHANG XiangPing ZHANG SuoJiang Beijing Key Laboratory of Ionic Liquids Clean Process State Key Laboratory of Multiphase Complex SystemsInstitute of Process Engineering Chinese Academy of Science College of Chemistry and Chemical Engineering University of Chinese Academy of Sciences

With the wide application of ionic liquids(ILs)in various fields,developing efficient techniques to recover ILs from effluent is an urgent demand for the cost reduction and the environmental *** this study,an electrodialysis(ED)method was used to recover 1-butyl-3-methylimidazolium chloride([Bmim]Cl)IL from aqueous solution as model *** influences of initial IL concentration and applied voltage on the current efficiency,removal ratio,desalination ratio,membrane flux and specific energy consumption during the ED process were *** was found that the removal ratio and desalination ratio increases with the increasing of initial IL concentration and applied *** current efficiency decreases with the increasing of initial IL concentration and the current efficiency reached the maximum value of 94.3%at 25 ***,as the applied voltage increases,the membrane flux increases and the specific energy consumption ***,the fouling of cation-exchange membrane was also discovered after the desalination of *** deposits on the surface or into the membrane which is probably caused by[Bmim]+was characterized by scanning electron microscopy,elemental analysis and Fourier transform infrared.

关键词： ionic liquid electrodialysis membrane effluent recovery

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Double layered,one-pot hydrothermal synthesis of M-TiO_2(M=Fe^(3+),Ni^(2+),Cu^(2+)and Co^(2+)) and their application in photocatalysis

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Science China Chemistry 2013年第12期56卷 1783-1789页

作者： CHEN YingYing XIE YongBing YANG Jun CAO HongBin LIU Hui ZHANG Yi National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology Key Laboratory of Green Process and Engineering Institute of Process Engineering Chinese Academy of Sciences State Key Laboratory of Multiphase Complex Systems Institute of Process Engineering Chinese Academy of Sciences University of Chinese Academy of Sciences

A double layered, one-pot hydrothermal method was adopted in this work to prepare transition metal ions （Fe3＋, Ni2＋, Cu2＋ and Co2＋） doped TiO〉 The morphology and chemical properties of TiO2 and the status of metal ions were characterized with XRD, TEM, BET, UV-Vis and XPS analysis. TEM images show that the obtained TiO2 was very uniform with an average particle size of 10.4 nm. XPS, TEM and XRD results show that transitional metals were doped onto TiO2 in the form of ions. Photocatalytic decomposition of oxalic acid under UV illumination and methylene blue degradation under visible light on these materials were conducted, respectively. The results reveal that Cu2＋-TiO2 and C02＋-TiO2 showed a highest activity under UV and visible light illumination, respectively, and they were both more active than commercial P25 TiO2. With this special design of double layers, the hydrolysis of titanium precursor in the system with water can be easily controlled and metal ions are simply doped. This strategy can be further applied to synthesize metal ion doped TiO2 using various metal precursors with controllable amounts, and thus lead to better optimization of highly active photocatalyst.

关键词： double layered hydrothermal synthesis metal ions doped Ti02 photocatalysis

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Synthesis of CdS/CNTs photocatalysts and study of hydrogen production by photocatalytic water splitting

Synthesis of CdS/CNTs photocatalysts and study of hydrogen p...

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作者： Wang, Xixi Liu, Maochang Chen, Qingyun Zhang, Kai Chen, Jie Wang, Meng Guo, Penghui Guo, Liejin International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Shaanxi 710049 China

A series of CdS and CdS/CNTs photocatalysts were successfully prepared by hydrothermal method and they were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), UV-visible optical absorption spectra (UV-Vis), etc. By studying their photocatalytic properties, it is found that, for CdS, photocatalysts prepared in appropriate alkaline environment presented higher hydrogen production activity, reaching 794.6 μmol h-1 g-1;the photocatalytic activity of CdS was obviously enhanced by combining it with CNTs via a special two-step hydrothermal method, and the corresponding hydrogen production rate reached 1.771 mmol h-1 g -1;the photocatalytic activity was further improved by loading co-catalyst NiS, achieving 12.13 mmol h-1 g-1. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

关键词： Cadmium sulfide

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ZnS/ZnO heterojunction as photoelectrode: Type II band alignment towards enhanced photoelectrochemical performance

ZnS/ZnO heterojunction as photoelectrode: Type II band align...

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作者： Guo, Penghui Jiang, Jiangang Shen, Shaohua Guo, Liejin International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Shaanxi 710049 China

Heterojunction structures are attracting lots of attention for enhancing the electron injection across the interface. The ZnS/ZnO one-dimensional heterojunction film was firstly prepared via a chemical sulfidization following hydrothermal reaction. The heterostructure was characterized as ZnS(blende)/ZnO(wurtzite) shell-core nanorods via XRD, SEM and TEM. A type II band alignment structure of ZnS/ZnO composite was synthesized via a temperate condition proved by PLS and XPS. The values for valence band offset (VBO) and conduction band offset (CBO) were calculated to be 0.96 eV and 1.25 eV, respectively. The special electron structure in the heterojunction helped reduce the energy barrier height at the interface and enhance the separation of photo-generated carriers. Thus, the photoelectrochemical performance was highly improved, and a photocurrent density of 380 μA/cm2 at 0.9 V (vs. Ag/AgCl) was obtained. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

关键词： Heterojunctions

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Synthesis of uniform ZnO/ZnS/CdS nanorod films with ion-exchange approach and photoelectrochemical performances

Synthesis of uniform ZnO/ZnS/CdS nanorod films with ion-exch...

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作者： Jiang, Jiangang Wang, Meng Ma, Lijing Chen, Qingyun Guo, Liejin State Key Laboratory of Multiphase Flow in Power Engineering International Research Center of Renewable Energy Xi'An Jiaotong University Shaanxi 710049 China

The uniform ZnO/ZnS/CdS core-shell nanorod film was synthesized by a two-step ion-exchange method. The crystal structure, morphology, composition and optical property of as-prepared films were characterized by X-ray diffraction (XRD), Raman, Scanning electron microscope (SEM), Transmission electron microscope (TEM), Energy dispersive X-ray Detector (EDX) and UV-vis techniques. The results showed that the ZnO nanorod arrays can be used as sacrificial templates to synthesize uniform ZnS layer and further transform into CdS by simple ion-exchange approach. The CdS content in the films can be adjusted easily by changing the reaction temperature. The intimate contact between core and shell can be observed by high-resolution TEM image, which decrease the crystal boundary potential barrier and then facilitate the photogenerated charges transfer between the different phases. In this experiment, the ZnO/ZnS/CdS nanorod films were used in the photoelectrochemical (PEC) hydrogen production. And it is found that the film prepared at 70 C (first step) and 100 C (second step) gives a maximum photocurrent density and photo conversion efficiency. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

关键词： Cadmium sulfide

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Fabricating CdS/BiVO4 and BiVO4/CdS heterostructured film photoelectrodes for photoelectrochemical applications

Fabricating CdS/BiVO4 and BiVO4/CdS heterostructured film ph...

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作者： Jiang, Jiangang Wang, Meng Li, Rong Ma, Lijing Guo, Liejin State Key Laboratory of Multiphase Flow in Power Engineering International Research Center of Renewable Energy Xi'An Jiaotong University Shaanxi 710049 China

The photoelectrochemical (PEC) properties of heterostructured CdS/BiVO 4 and BiVO4/CdS film electrodes on conducting glass for hydrogen production under visible light were investigated. These two types heterostructured film electrodes were prepared using spin coating method and ultrasonic spray pyrolysis method. The structural analyses of the prepared films were determined by using XRD, SEM, EDX and UV-vis. Photoelectrochemical measurements were carried out in a convenient three electrodes cell with 0.5 M Na2SO3 aqueous solution. In order to investigate band gap influence of electrode PEC property, a series ITO/Cd1-xZn xS/BiVO4 and ITO/BiVO4/Cd1-xZn xS (x = 0 ∼ 1) film electrodes were also synthesized. After PEC test, a maximum photocurrent density from ITO/CdS/BiVO4 film electrode was confirmed. The maximum photocurrent density, 3 times and 113 times as that of single CdS film electrode and single BiVO4 film electrode, respectively. Incident photon to current conversion (IPCE) of as prepared film electrodes were measured and the value were 65% (ITO/CdS/BiVO 4), 22% (single CdS film) and 10% (ITO/BiVO4/CdS) at 480 nm with 0.3 V external bias. Comparison with ITO/BiVO4/CdS electrode and single Cd1-xZnxS electrodes, the heterostructured ITO/CdS/BiVO4 electrode can effectively suppress photogenerated electron-hole recombination and enhance light harvesting. Therefore, the ITO/CdS/BiVO4 electrode gave the maximum photocurrent density and IPCE value. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

关键词： Bismuth compounds

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Denoising method of X-ray phase contrast DR image for TRISO-coated fuel particles

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Particuology 2013年第6期11卷 695-702页

作者： Min Yang Jianhai Zhang Fanyong Meng Sung-Jin Song Xingdong Li Wenli Liu Dongbo Wei School of Mechanical Engineering and Automation Beijing University of Aeronautics School of Mechanical Engineering Sungkyunkwan University State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChinese Academy of Sciences National Institute of Metrology

TRISO （tristructural-isotropic） fuel is a type of micro fuel particles used in high-temperature gas-cooled reactors （HTGRs）. Among the quality evaluation methods for such particles, inqine phase contrast imaging technique （PCI） is more feasible for nondestructive measurement. Due to imaging hardware limitations, high noise level is a distinct feature of PCI images, and as a result, the dimensional measurement accuracy of TRISO-coated fuel particles decreases. Therefore, we propose an improved denoising hybrid model named as NL P-M model which introduces non-local theory and retains the merits of the Perona-Malik （P-M） model. The improved model is applied to numerical simulation and practical PCI images. Quanti- tative analysis proves that this new anisotropic diffusion model can preserve edge or texture information effectively, while ruling out noise and distinctly decreasing staircasing artifacts. Especially during the process of coating layer thickness measurement, the NL P-M model makes it easy to obtain continuous contours without noisy points or fake contour segments, thus enhancing the measurement accuracy. To address calculation complexity, a graphic processing unit （GPU） is adopted to realize the acceleration of the NL P-M denoising.

关键词： TRISO-coated fuel particle X-ray phase contrast imaging Image denoising Partial differential equation Non-local means

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Experimental study on loop heat pipe with flat evaporator at different tilt angles

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Hsi-An Chiao Tung Ta Hsueh/Journal of Xi'an Jiaotong University 2013年第5期47卷 38-43页

作者： Long, Yan Wei, Jinjia Lü, Xiao State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

To realize highly efficient heat dissipation of electronics, a loop heat pipe (LHP) with a flat evaporator was designed to study its operation characteristics at the tilt angles of 0°, 30°, 45°, 60°, 90° with an improved evaporator structure and a well arranged pipes which can reduce heat loss due to back conduction and improve inner flow performance. The results show that the LHP with inclination has a lower power to start up than the horizontal one, and at the same heat load, the operation temperature of the evaporator is much lower and the system is easier to reach a steady state with less temperature oscillations. However, there is slight difference in operating performance for the LHP at different title angles. The thermal resistance decreases with an increase in the heat load and a steady state occurs at last. The thermal resistance is larger for the horizontal case than that for the inclination case at the same heat load. The thermal resistances are very different at different tilt angles at low heat load, but the difference is small at high heat load.

关键词： Thermal load

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