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Methane conversion using a dielectric barrier discharge reactor at atmospheric pressure for hydrogen production

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Plasma Science and Technology 2017年第9期19卷 81-90页

作者： N kHADIR k kHODJA A BElaSRI laboratoire de Physique des Plasmas Mat6riaux Conducteurs et leurs ApplicationsUniversite d'Oran desSciences et de la Technologie USTO-MBFaculte de PhysiqueOran 31000Algeria Unite de Recherche Appliqu6e en Energies Renouvelables URAERCentre de Developpement desEnergies RenouvelablesCDER47133GhardaiaAlgeria

In the present paper, we carried out a theoretical study of dielectric barrier discharge（DBD）filled with pure methane gas. The homogeneous discharge model used in this work includes a plasma chemistry unit, an electrical circuit, and the Boltzmann equation. The model was applied to the case of a sinusoidal voltage at a period frequency of 50 kHz and under a gas pressure of 600 Torr. We investigated the temporal variation of electrical and kinetic discharge parameters such as plasma and dielectric voltages, the discharge current density, electric field, deposited power density, and the species concentration. We also checked the physical model validity by comparing its results with experimental work. According to the results discussed herein, the dielectric capacitance is the parameter that has the greatest effect on the methane conversion and H_2/CH_4 ratio. This work enriches the knowledge for the improvement of DBD for CH_4 conversion and hydrogen production.

关键词： dielectric capacitance checked methane validity herein filled figure hydrocarbons reforming

Optical and electrical conductivity properties of rare earth elements(Sm, Y, la, Er) co-doped CeO_(2)

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Journal of Rare Earths 2022年第10期40卷 1619-1627页

作者： Rabia kιrkgecit Handan OzlüTorun Fatma kιlc Dokan Esra Oztürk Institute of Science Material Science and EngineeringKahramanmaras Süt?üImam UniversityKahramanmaras46050Turkey Department of Energy System Engineering Kahramanmaras Istiklal UniversityKahramanmaras46300Turkey Department of Chemistry and Chemical Processing Technologies Kayseri UniversityKayseriTurkey Department of Metallurgical and Materials Engineering Karamanoglu Mehmetbey UniversityKaramanTurkey

In this research,un-doped CeO_(2) and Ce_(0.85)la_(0.10)MO_(0.05)O_(2)(M:Sm,Er,Y) compounds were synthesized by hydrothermal method and the multi-functional properties are *** defects were created with the additives of rare earth *** electrical and luminescence behaviors of the synthesized compounds were investigated in accord with the types of *** synthesized products were characterized by X-ray diffraction(XRD) analysis,Brunauer-Emmett-Teller(BET) measurement,UV-vis diffuse reflectance spectroscopy(DRS),scanning electron microscopy(SEM),photoluminescence(PL)spectroscopy and electrochemical impedance spectroscopic(EIS).All synthesized compounds are found to be nano-structured and have cubic *** total conductivity of all samples was ***,the total conductivity of un-doped CeO_(2),Ce_(0.85)la_(0.10)Y_(0.05)O_(2),Ce_(0.85)la_(0.10)Er_(0.05)O_(2) and Ce_(0.85)la_(0.10)Sm_(0.05)O_(2) is found to be 2.07×10^(-10),5.70×10^(-4),1.0×10^(-3) and 0.0747 S/cm,***,bandgap energy(E_(g)) of these samples calculated from UV visible absorption spectra is discussed,and the optical results show variation between 3.2 and 2.15 ***,the luminescence properties of the compounds were investigated and different emissions occur depending on the additive ***,photoluminescent emission spectra of Ce_(0.85)la_(0.10)Y_(0.05)O_(2),Ce_(0.85)la_(0.10)Er_(0.05)O_(2) and Ce_(0.85)la_(0.10)Sm_(0.05)O_(2) phosphors indicate that these phosphors have red,green and orange-red colors,respectively.

关键词： Cerium oxide Co-doping Conductivity Luminescence Oxygen vacancy Rare earth elements

Investigation of magnetic, optical and electrical properties of la_3Ba_3Cu_6O_(14) synthesized by molten flux method

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Journal of Rare Earths 2015年第12期33卷 1341-1347页

作者： k.Agilandeswari A.Ruban kumar Department of Chemistry Auxilium College School of Advanced Sciences VIT University

The great deal of novel rare earth based semiconducting lanthanum barium copper oxide la3Ba3Cu6OI4 （LBC-336） were synthesized by low temperature molten salt synthesis （MSS） due to ＂dissolution precipitation mechanism＂. Here, we reported one pot synthesis of product by direct precipitation from a molten kOH-NaOH mixnare at 450 ℃ and single phase la3Ba3Cu6014 with tetragonal crystal system. The particle size of 140-200 nm were observed in both PXRD pattern and HRSEM micrographs and it showed a cubic morphology. The semiconducting nature was extracted from various parameters like optical band gap （1.8 eV）, AC conductivity （0.70 eV）, DC conductivity （0.70 eV）, and also Hall effect parameters like the charge carrier concentration values n=6,0x 1026 m-3 and it proved as a p-type semiconductor. The electrical phase trasition temperature from ferroelectric to antiferroelec- tric system （Tin=420 k） and anti-ferroelectric - paraelectric system （depolarization temperature Ta=673 k） which attributed to the space charge polarization contributed to the conduction mechanism. The magnetic phase transitions were from ferromagnetic to ferrimagnetic system （Curie temperature （Tc=70 k）） and it led to soft magnetic material and also held good for superconductor appli- cation upto 70 k.

关键词： molten flux synthesis band gap phase transitions semiconductor superconductors rare earths

Dielectric, piezoelectric, and ferroelectric properties of lanthanum-modified PZTFN ceramics

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International Journal of Minerals,Metallurgy and Materials 2014年第10期21卷 1019-1027页

作者： Arvind kumar S.k.Mishra Research and Technology Development Centre Sharda University Dr. Harisingh Gour University

Specimens of Pb1-1.5xlax（Zr0.53 Ti0.47）1-y-zFeyNb2O3 （x = 0, 0.004, 0.008, 0.012, and 0.016, y = z = 0.01）（PZTFN） ceramics were synthesized by a semi-wet route. In the present study, the effect of la doping was investigated on the structural, microstructural, dielectric, piezoelectric, and ferroelectric properties of the ceramics. The results show that, the tetragonal （space group P4mm） and rhombohedral （space group R3c） phases are observed to coexist in the sample at x = 0.012. Microstructural investigations of all the samples reveal that la doping inhibits grain growth. Doping of la into PZTFN improves the dielectric, ferroelectric, and piezoelectric properties of the ceramics. The hys- teresis loops of all specimens exhibit nonlinear behavior. The dielectric, piezoelectric and ferroelectric properties show a maximum response atx 〉 0.012, which corresponds to the morphotropic phase boundary （MPB）.

关键词： ceramics lanthanum doping dielectric properties piezoelectricity ferroelectricity Rietveld refinement hysteresis loops

Numerical simulation of the effect of gold doping on the resistance to neutron irradiation of silicon diodes

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Journal of Semiconductors 2015年第1期36卷 47-51页

作者： k.Bekhouche N.Sengouga B.k.Jones laboratory of Metallic and Semiconducting Materials (LMSM) Université de Biskra 07000 Biskra Algeria Department of Physics Lancaster University Lancaster LA5 9LX UK

We have carried out a numerical simulation of the effect of gold doping on the electrical characteristics of long silicon diodes exposed to neutron irradiation. The aim is to investigate the effect of gold on the hardness of the irradiated diodes. The reverse current voltage and capacitance voltage characteristics of doped and undoped diodes are calculated for different irradiation doses. The leakage current and the effective doping density are extracted from these two characteristics respectively. The hardness of the diodes is evaluated from the evolution of the leakage current and the effective doping density with irradiation doses. It was found that diodes doped with gold are less sensitive to irradiation than undoped ones. Thus gold appears to stabilise the electrical properties on irradiation. The conduction mechanism is studied by the evolution of the current with temperature. The evaluated activation energy indicates that as the gold doping or irradiation dose increases, the current switches from the basic diffusion to the generation-recombination process, and that it can even become ohmic for very high gold densities or irradiation doses.

关键词： silicon diodes gold doping numerical simulation

Critical parameters near the ferromagnetic-paramagnetic phase transition in la_(0.67–x)Y_xBa_(0.23)Ca_(0.1)MnO_3 compounds(x=0.10 and x=0.15)

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Journal of Rare Earths 2015年第3期33卷 263-270页

作者： Mounira Abassi N.Dhahri J.Dhahri k.Taibi E.k.Hlil laboratory of Condensed Matter and Nanosciences University of Monastir 5019 Tunisia Institut Néel CNRS and Joseph Fourier university B.P.166 38042 Grenoble France Institut Néel CNRS et Université Joseph Fourier BP 166 F-38042 Grenoble cedex 9 France

The critical properties of the mixed manganite la0.67–x Y x Ba0.23Ca0.1Mn O3 with x=0.10 and x=0.15 around the paramagnetic（PM）-ferromagnetic（FM） phase transition were investigated through various techniques. These involved modified Arrott plots, kouvel-Fisher method and Widom scaling relation. Magnetic data, analyzed in the critical region, using the above methods, yielded the critical exponents for（x=0.10） la0.57Y0.10Ba0.23Ca0.1Mn O3（β=0.312±0.002 and γ=1.147±0.003 at T C=299.23±0.05 k）. Moreover, the estimated critical exponents of（x=0.15） la0.52Y0.15Ba0.23Ca0.1Mn O3 were β=0.286±0.004 and γ=0.943±0.002 at T C=289.53±0.06 k. The critical exponents＇ values were close to the theoretical values of 3D-Ising model and tricritical mean-field model. These results suggested that the present composition should be close to a tricritical point in the la0.67–x Y x Ba0.23Ca0.1Mn O3 phase diagram. Expressing the field dependence as ΔS M∝H n allowed us to establish a relationship between the exponent n and the critical exponents of the material and to propose a phenomenological universal curve for the field dependence of ΔS M.

关键词： perovskite manganites phase transition entropy critical properties rare earths

Influence of bismuth on magnetism and magnetocaloric properties of laFe_(11.6)Si_(1.4) intermetallic compound

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Journal of Rare Earths 2015年第7期33卷 740-745页

作者： A.Boutahar k.Zehani L.Bessais H.lassri E.k.Hlil LPMMAT Hassan II University-Casablanca Faculty of Science Ain Chock BP 5366 Maarif-Casablanca Morocco ICMPE-CMTR UMR CNRS 7182 2-8 H. Dunant St 94320 Thiais France Néel Institue CNRS and Joseph Fourier University

Crystal structure, magnetic properties and magnetocaloric effects （MCE） of la1-xBixFe1 1.4Si1.6 （x=0.0 and 0.1） compounds were investigated by X-ray diffraction and magnetization measurements. The la1-xBixFe11.4Si1.6 compounds presented a cubic NaZnx3 type structure. First, the magnetization behavior and the magnetic transition were analyzed in terms of landau theory. Then, Bi substitution for la in la1-xBixFe11.4Si1.6 compounds led to a decrease in magnetic entropy change （-△SM^max） but an increase in Curie temperature （Tc） significantly. The significant increase of Tc by Bi substitution from 202.5 to 256 k for x=0.0 and x=0.1 respectively was attributed to an increase in the Fe-Fe exchange interactions. Moreover, magnetocaloric effect was calculated in terms of isothermal magnetic entropy change. The maximum values of （-△SM^max ） of la1-xBixFe11.4Si1.6 for x=-0.0 and 0.1 compounds were found to be, respectively, 22.56 and 4.36 J/（kg.k） under an applied magnetic field change of 5 T. For the same applied magnetic field （μ0H=5 T）, the relative cooling power （RCP） values were found to vary between 487 and 296 J/kg.

关键词： NaZn13 itinerant-electron metamagnetic transition magnetocaloric effects rare earths

Progression of injectivity damage with oily waste water in linear flow

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Petroleum Science 2014年第4期11卷 550-562页

作者： Jin Lu Wojtanowicz Andrew k InPetro Technologies Inc. 9800 Centre Parkway#860HoustonTX 77036USA Craft & Hawkins Department of Petroleum Engineering Louisiana State UniversityPatrick F.Taylor HallRoom 2160BBaton RougeLA 70803USA

Numerous laboratory experiments and field cases show that even very small amount of oil in injected water can cause severe injectivity damage. Although injectivity decline caused by oil droplets has been studied experimentally, there is still lack of an easy-to-use and widely accepted model to predict the decline behavior. In this work, we developed an analytical model to predict the time-dependent progress of the water permeability reduction in linear flow by analyzing experimental data obtained from linear core flooding. The model considers mass transfer of the oil phase from the produced water to the rock due capture effects by dispersion, advection and adsorption inside the rock. As the captured oil saturation increases, permeability reduces following the relative permeability drainage relationship. The reduction stabilizes when the oil saturation comes to an equilibrium value controlled by oil droplet size and injection velocity. The model is calibrated using published experimental data from prolonged core floods with oil- contaminated waste water. Theoretical runs of the model replicate all the effects known from experimental observations. Resulting from the model is a distributed change of permeability vs. time and distance from the point of injection that can be converted to the overall injectivity damage.

关键词： Produced water injection injectivity decline permeability damage linear flow model,filtration model

Deduction and Validation of an Eulerian-Eulerian Model for Turbulent Dilute Two-Phase Flows by Means of the Phase Indicator Function-Disperse Elements Probability Density Function

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Chinese Journal of Chemical Engineering 2000年第3期8卷 189-202页

作者： Santiago laín Ricardo Aliod MVT-UST Fachbereich Ingenieurwissenschaften Martin-Luther-UniversitatHalle-WittenbergD-06099Halle(Saale)GermanyFluid Mechanica DepartmentE.U.Politecnica de Huesca.University of ZaragozaCarretera Zaragoza km.6722071 HuescaSpain

A statistical formalism overcoming some conceptual and practical difficulties arising in existing two-phase flow (2PHF) mathematical modelling has been applied to propose a model for dilute 2PHF turbulent Hows. Phase interaction terms with a clear physical meaning enter the equations and the formalism provides some guidelines for the avoidance of closure assumptions or the rational approximation of these terms. Continuous phase averaged continuity, momentum, turbulent kinetic energy and turbulence dissipation rate equations have been rigorously and systematically obtained in a single step. These equations display a structure similar to that for single-phase flows. It is also assumed that dispersed phase dynamics is well described by a probability density function (pdf) equation and Eulerian continuity, momentum and fluctuating kinetic energy equations for the dispersed phase are deduced. An extension of the standard k-e turbulence model for the continuous phase is used. A gradient transport model is adopted for the dispersed phase fluctuating fluxes of momentum and kinetic energy at the non-colliding, large inertia limit. This model is then used to predict the behaviour of three axisymmetric turbulent jets of air laden with solid particles varying in size and concentration. Qualitative and quantitative numerical predictions compare reasonably well with the three different sets of experimental results, studying the influence of particle size, loading ratio and flow confinement velocity.

关键词： two-phase flow turbulence phase indicator function pdf ensemble average jet