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Ab initio investigation of defect formation at ZrO2-CeO2 interfaces

Physical Review B 2012年第8期86卷 085407-085407页

作者： Marco Fronzi Silvia Cereda Yoshitaka Tateyama Alessandro De Vita Enrico Traversa International Center for Materials Nanoarchitectonics (MANA) National Institute for Materials Science (NIMS) Tsukuba Japan Physics Department King's College London Strand London United Kingdom International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xian Jiaotong University Xian Shaanxi China

The structural and electronic properties of low index (100) and (111) ZrO2-CeO2 interfaces are analyzed on the basis of density functional theory calculations. The formation energy and relative stability of substitutional defects, oxygen vacancies, and vacancy-dopant complexes are investigated for the (100) orientation. By comparing these results with the ones obtained in bulk structures, we provide a possible explanation for the higher experimental ionic conductivity measured at the interface.

关键词： ZIRCONIUM oxide CERIUM oxides INTERFACES (Physical sciences) CRYSTAL defects ELECTRONIC structure

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Effect of nozzle size on the surface heat transfer dynamics during cryogen spray cooling in dermatologic laser surgery

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Zhongguo Jiguang/Chinese Journal of Lasers 2012年第3期39卷

作者： Zhou, Zhifu Wang, Rui Wang, Guoxiang Guo, Liejin Chen, Bin Wang, Yueshe State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi 710049 China Department of Mechanical Engineering University of Akron Akron OH 44325 United States

Cryogen spray cooling (CSC) in conjunction with laser therapy has been the clinical standard for hypervascular lesions. In order to optimize nozzle and enhance the cooling efficiency to improve the treatment of laser surgery, an experimental system of transient cryogen spray cooling is built and eight straight-tube nozzles with different diameter and length are designed. A thin film thermocouple is directly deposited on the cooling surface to measure the surface temperature during the cryogen spray cooling. An analytical expression based on Fourier's law and Duhamel's theorem is used to calculate surface heat flux from the temperature measurements. Based on the measurements and calculations, the effect of the eight straight-tube nozzles on the heat transfer dynamics of the cooling surface and the atomization characterics are comparatively studied. Additionally, the criterion to evaluate the cooling efficiency of different nozzles is proposed, and the variation of heat extraction from the cooling surface with different spray distances by different nozzles is given.

关键词： Heat flux

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Electrochemical Treatment of Pentachlorophenol on Ni-Sb-SnO2/Ti Electrodes

Electrochemical Treatment of Pentachlorophenol on Ni-Sb-SnO2...

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2011 International Symposium on Water Resource and Environmental Protection(ISWREP 2011)

作者： Wang Yun-Hai Zhou Zhe Chen Qing-Yun Zhao Jing-Lian State Key Laboratory of Multiphase Flow Department of Environmental Science and Engineering Xi'an Jiaotong University

ISBN: (纸本)9781612843377

Nickel and antimony doped tin dioxide (NATO) coated titanium electrodes are prepared and tested for electrochemical treatment of pentachlorophenol (PCP).The effect of nickel content on the electrochemical activity is studied using PCP as target organic *** nickel content has an optimized value for the *** NATO is characterized and the relationship between activity and oxygen to tin atomic ratio is discussed.

关键词： nickel and antimony doped tin dioxide electrochemical pentachlorophenol

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Experimental study of natural convection in horizontally-positioned open-celled metal foams

Experimental study of natural convection in horizontally-pos...

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International Conference on Materials for Renewable Energy and Environment

作者： Xu, Z.G. Qu, Z.G. Zhao, C.Y. State Key Laboratory of Multiphase Flow School of Energy and Power Engineering Xi'An Jiaotong University China

ISBN: (纸本)9781612847504

Experimental study of air natural convection in horizontally-positioned copper metallic foams with open cells was conducted. Temperature distributions on the heating surface were tested under different heating power for foam samples having different porosities and pore densities. The effects of porosity and pore density on the total thermal resistance of the foam sample were quantified. It is found that the porous surface can enhance the natural convection and reduce the thermal resistance by about 20% in comparison with a smooth surface. The surface area density and mass flow rate in natural convection are affected by porosity and pore density simultaneously. When the porosity is relative small (Ε = 90%), there exits a critical value of the Gr number (turning point) for two pore densities (10ppi and 40ppi). When the Gr number is less than this critical value, the foam with a higher pore density has the lower total thermal resistance, whereas when the Gr number exceeds the turning point value, the opposite holds. If the porosity is increased to Ε = 95%, the foam with a higher pore density has the lower thermal resistance in the whole experimental range. When the porosity and pore density is the same, the foam with smaller size has the higher thermal resistance in the whole experimental range. If the size is relatively small (10010050mm), for the two pore densities studied (20ppi and 80ppi), there exits a critical value of the Gr number (turning point). The foam with a lower porosity(Ε = 90%) has the lower thermal resistance and the decrease is more obvious for the case of *** the size is relatively big(10010080mm),there exists a critical value of the Gr number (turning point) only for the case of 10ppi. When the Gr number is less than this critical value, the foam with a higher porosity (Ε = 95%) has the higher total thermal resistance, the opposite holds. While for the other two pore densities (20ppi and 40ppi), there is no turning point. The foam with a highe

关键词： Natural convection

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Optimization on ignition timing and EGR ratio of a spark-ignition engine fuelled with natural gas-hydrogen blends

Optimization on ignition timing and EGR ratio of a spark-ign...

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SAE 2011 World Congress and Exhibition

作者： Hu, Erjiang Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an 710049 China

In this paper, 20%H2 (20% hydrogen in natural gas-hydrogen blends, by volume) is selected as the test fuel, and the ignition timing and EGR ratio are adjusted to optimize the performance, combustion, and emissions of a natural gas-hydrogen engine. An experimental investigation on the effect of ignition timings, EGR ratios on combustion behaviors and emissions of a spark-ignition engine fuelled with natural-gas and hydrogen blends was conducted. When increasing the ignition timing at specified EGR ratio, engine power output will give its peak value at MBT timing. Large EGR introduction decreases engine power output and increases combustion duration. Effective thermal efficiency shows an increasing trend at the small EGR ratio and a decreasing trend with further increasing EGR ratio. With advancing the ignition timing, the flame development duration is increased, and the rapid combustion duration and total combustion duration are decreased. All of these three kinds of combustion duration are increased with the increase of EGR ratio. HC concentration is decreased and NOx concentration is increased with advancing the ignition timing while CO emission varies little with the ignition timing. NOx concentration is decreased with the increase of EGR ratio. HC emission is increased with the increase of EGR ratio. CO and CO2 emissions show little variations with the EGR ratio and ignition timing. Based on the above analysis, a MAP containing ignition timings and EGR ratios for 20%H2 fuel blend is presented, and this will provide the reference and guidance to engine designers and engineers. In addition, through optimizing ignition timing and EGR ratio, high efficiency and low emission spark-ignition engine can be realized fueled with natural gas-hydrogen blends. Copyright © 2011 SAE International.

关键词： Natural gas

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Exhaust recovery of vehicle gasoline engine based on organic rankine cycle

Exhaust recovery of vehicle gasoline engine based on organic...

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SAE 2011 World Congress and Exhibition

作者： Zhang, Xinxin Zeng, Ke Bai, Sujuan Zhang, Ying He, Maogang State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an Shaanxi 710049 China

When the global energy consumption continues to increase, the research hotspot in the field of internal combustion engine (ICE) is how to improve the fuel utilization efficiency to achieve the energy saving. But as far as the engine efficiency is concerned, it has been very difficult to improve the fuel utilization efficiency after the Gasoline Direct-Injection (GDI) and Homogeneous Charge Compression Ignition (HCCI) technology were adopted. In this study, the exothermic distribution of fuel was studied detailedly when a TOYOTA 8A-FE gasoline engine operated at different working conditions through conducting steady-state experiment. Only one third of fuel's chemical energy is converted into effective work by engine, the rest is released to the environment in the form of waste heat generated from cooling and exhaust gas. But except the waste heat that has to be released to the environment according to the second law of thermodynamics, the rest can be theoretically utilized. If the waste heat of the vehicle engine can be recovered, the engine efficiency will be evidently improved. Results on the exergy analysis show that the exergy in the exhaust gas is about 45-70% and it will evidently increase with the increase of engine load and revolution. So it will have a good effect on exhaust recovery when the engine has a heavy load. Considering the character of exhaust gas, the Organic Rankine Cycle(ORC) is adopted to recover the waste heat of engine's exhaust gas. The thermodynamic performances of the cycle were analyzed and R113 was determined to be the working fluid. The experimental exhaust gas recovery system used to testify the aforementioned theoretical calculation was designed and established. The system consists of exhaust gas simulation device, expander, condenser, dynamometer, pump and data acquisition and processing system. In experiment, the performance parameter and power output of the Organic Rankine Cycle were measured. The expander show a high isentropic ef

关键词： Recovery

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Photocatalytic reforming of formic acid with simultaneous hydrogen production under visible light over CdS sensitized Na2Ti 2O4(OH)2

Photocatalytic reforming of formic acid with simultaneous hy...

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2011 MRS Spring Meeting

作者： Tang, Wendong Jing, Dengwei Guo, Liejin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi 710049 China

ISBN: (纸本)9781618395238

The present work reports the renewable hydrogen production by an anaerobic photocatalytic reforming of formic acid over CdS sensitized Na 2Ti2O4(OH)2 nanotubes, the Na 2Ti2O4(OH)2 nanotube was prepared and charactered by X-ray diffraction, UV-visible absorption, transmission electron microscopy, etc. The activity of the catalyst in formic acid was investigated. The greatest photocatalytic reforming activity of formic acid occurs as the formic acid initial concentration is 20 v.%. A probable mechanism for the photocatalytic reforming process was proposed and discussed. © 2011 Materials Research Society.

关键词： Cadmium sulfide

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Performance of a domestic refrigerator using TiO2-R600a nano-refrigerant as working fluid

Performance of a domestic refrigerator using TiO2-R600a nano...

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作者： Bi, Shengshan Guo, Kai Liu, Zhigang Wu, Jiangtao State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi 710049 China

In this work, an experimental work was investigated on the nano-refrigerant. TiO2-R600a nano-refrigerants were used in a domestic refrigerator without any system reconstruction. The refrigerator performance was then investigated using energy consumption test and freeze capacity test. The results indicate that TiO2-R600a nano-refrigerants work normally and safely in the refrigerator. The refrigerator performance was better than the pure R600a system, with 9.6% less energy used with 0.5 g/L TiO2-R600a nano-refrigerant. Thus, using TiO2-R600a nano-refrigerant in domestic refrigerators is feasible. © 2010 Elsevier Ltd. All rights reserved.

关键词： Refrigerators

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The effect of substrates and anodes on microbial fuel cell performance

The effect of substrates and anodes on microbial fuel cell p...

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International Symposium on Water Resource and Environmental Protection (ISWREP)

作者： Wang, Yun-Hai Xi, Huan Lin, Feng-Jiao Wang, Bai-Shi Chen, Qing-Yun State Key Laboratory of Multiphase Flow Department of Environmental Science and Engineering Xi'an Jiaotong University Xi'an China

ISBN: (纸本)9781612843377

In a single chamber microbial fuel cell (MFC), the gas diffusion electrode was employed as cathode. Different organic substrates including starch, glucose and drainage from a hotel were used as fuel to generate electricity. Glucose resulted the best electricity production and the highest COD removal ratio. Nickel foam and carbon cloth were employed as anodes and their effect on MFC performance was discussed. The results indicated that nickel foam could enhance the electricity generation, but suffered an anodic corrosion to form nickel phosphate. The MFC internal resistance was 940 Ω with nickel foam as anode while 640 Ω with carbon cloth as anode. The maximum power output on nickel foam is 190 mW m-2. The coulomb efficiency reached up to 90%. The possible mechanism was discussed based on the anodes characterization results. © 2011 IEEE.

关键词： Anodes

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TiO2-SnO2:F interfacial electronic structure investigated by soft x-ray absorption spectroscopy

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Physical Review B 2012年第12期85卷 125109-125109页

作者： Coleman X. Kronawitter Mukes Kapilashrami Jonathan R. Bakke Stacey F. Bent Cheng-Hao Chuang Way-Faung Pong Jinghua Guo Lionel Vayssieres Samuel S. Mao Department of Mechanical Engineering University of California at Berkeley Berkeley California 94720 USA Environmental Energy Technologies Division Lawrence Berkeley National Laboratory Berkeley California 94720 USA Advanced Light Source Lawrence Berkeley National Laboratory Berkeley California 94720 USA Department of Chemical Engineering Stanford University Stanford California 94305 USA Department of Physics Tamkang University Tamsui Taiwan Republic of China International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Shaanxi 710049 People's Republic of China

The electronic structure of the titanium dioxide (TiO2)-fluorine-doped tin dioxide (SnO2:F) interface is investigated by soft x-ray absorption spectroscopy using synchrotron radiation. The measurements probe the site- and symmetry-selected unoccupied density of states and reflect the interaction between an early transition-metal-oxide (d0) semiconductor and a post-transition-metal-oxide (d10) degenerate semiconductor. The distinct interfacial electronic structure of TiO2-SnO2:F is established by contrasting spectra with those for anatase and rutile TiO2, SnO2:F, and ZnO-SnO2:F and CdO-SnO2:F interfaces. Oxygen 1s absorption spectra, which relate to the O 2p partial density of states of the conduction band, indicate that the interface is associated with a reduction in Ti d-O p orbital hybridization and an alteration of the TiO2 crystal field. These observations are consistent with measured titanium 2p absorption spectra, which in addition provide evidence for distortion of long-range order around the cation site in the interfacial TiO2. The TiO2-SnO2:F interface is a functional component of a number of optoelectronic devices, perhaps most notably within the anode structure of solar cell architectures. In nonequilibrium conditions, such as those found in operating solar cells, interfacial electronic structure directly influences performance by modifying, for instance, the quasi-Fermi level electrons and the potential distribution at the transparent electrode.

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