			Home About us Contact

Chemical Reaction Process (chemical + reaction_process)

Distribution by Scientific Domains

Chemistry	50%

Selected Abstracts

Selective Patterned Growth of Single-Crystal Ag,TCNQ Nanowires for Devices by Vapor,Solid Chemical Reaction,

ADVANCED FUNCTIONAL MATERIALS, Issue 19 2008
Kai Xiao
Abstract We report the deterministic growth of individual single-crystal organic semiconductor nanowires of silver,tetracyanoquinodimethane (Ag,TCNQ) with high yield (>90%) by a vapor,solid chemical reaction process. Ag,metal films or patterned dots deposited onto substrates serve as chemical reaction centers and are completely consumed during the growth of the individual or multiple nanowires. Selective-area electron diffraction (SAED) revealed that the Ag,TCNQ nanowires grow preferentially along the strong ,,, stacking direction of Ag,TCNQ molecules. The vapor,solid chemical reaction process described here permits the growth of organic nanowires at lower temperatures than chemical vapor deposition (CVD) of inorganic nanowires. The single-crystal Ag,TCNQ nanowires are shown to act as memory switches with high on/off ratios, making them potentially useful in optical storage, ultrahigh-density nanoscale memory, and logic devices. [source]

Numerical simulation of model scramjet combustor flowfield

HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 5 2007
Yuan-Guang Wang
Abstract A new concept has been raised and adopted in this paper to enlarge the scope of the two-dimensional model particularly for the purpose of dealing with three-dimensional normal injection cases. Meanwhile, the method has a very good performance for its short cyclic period. The new idea was realized through special resolution with continuity equations; i.e., mass flow was directly added in the source term of the continuity equation. To prove the robustness of this illuminating method, comparisons using calculations were carried out, and the results are satisfactory. A model scramjet combustor tested on the free-jet scramjet test facility was illustrated and underwent numerical calculations with the two-dimensional program, adopting the above simplified injecting method. To simulate the chemical reaction process in the scramjet tunnel, a five-species, single-step reaction model was introduced in the calculation process. This research presents the major aerodynamic parameters and components of mass fraction distribution within the model combustor channel, which made it easy to observe and analyze the flowfield. Finally, wall pressure comparisons between the numerical and experimental results were carried out to verify the accuracy of the calculation model. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(5): 295, 302, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20159 [source]

Hard-modelled trilinear decomposition (HTD) for an enhanced kinetic multicomponent analysis

JOURNAL OF CHEMOMETRICS, Issue 5 2002
Yorck-Michael Neuhold
Abstract We present a novel approach for kinetic, spectral and chromatographic resolution of trilinear data sets acquired from slow chemical reaction processes via repeated chromatographic analysis with diode array detection. The method is based on fitting rate constants of distinct chemical model reactions (hard-modelled, integrated rate laws) by a Newton,Gauss,Levenberg/Marquardt (NGL/M) optimization in combination with principal component analysis (PCA) and/or evolving factor analysis (EFA), both known as powerful methods from bilinear data analysis. We call our method hard-modelled trilinear decomposition (HTD). Compared with classical bilinear hard-modelled kinetic data analysis, the additional chromatographic resolution leads to two major advantages: (1) the differentiation of indistinguishable rate laws, as they can occur in consecutive first-order reactions; and (2) the circumvention of many problems due to rank deficiencies in the kinetic concentration profiles. In this paper we present the theoretical background of the algorithm and discuss selected chemical rate laws. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Numerical modelling and simulation of pulverized solid-fuel combustion in swirl burners

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2009
H. Ettouati
Abstract A finite-volume numerical model for computer simulation of pulverized solid-fuel combustion in furnaces with axisymmetric-geometry swirl burner is presented. The simulation model is based on the k,,,, single phase turbulence model, considering the presence of the dispersed solid phase via additional source terms in the gas phase equations. The dispersed phase is treated by the particle source in cell (PSIC) method. Solid fuel particle devolatilization, homogenous and heterogeneous chemical reaction processes are modelled via a global combustion model. The radiative heat transfer equation is also resolved using the finite volume method. The numerical simulation code is validated by comparing computational and experimental results of pulverized coal in an experimental furnace equipped with a swirl burner. It is shown that the developed numerical code can successfully predict the flow field and flame structure including swirl effects and can therefore be used for the design and optimization of pulverized solid-fuel swirl burners. On présente un modèle numérique de volumes finis pour la simulation par ordinateur de la combustion de combustibles solides pulvérisés dans des fours munis de brûleur à tourbillon axisymétrique. Le modèle de simulation repose sur le modèle de turbulence monophasique k,,,,, et décrit la présence de la phase solide dispersée par le biais de termes-sources additionnels dans les équations de la phase gazeuse. La phase dispersée est traitée par la méthode PSIC. La dévolatilisation des particules combustibles solides et les procédés de réaction chimique homogène et hétérogène sont modélisés à l'aide d'un modèle de combustion global. L'équation de transfert de chaleur radiatif est également résolue par la méthode des volumes finis. Le code de simulation numérique a été validé en comparant les résultats des calculs par ordinateur avec des expériences pour du charbon pulvérisé dans un four expérimental équipé d'un brûleur à tourbillon. On montre que le code numérique peut prédire avec succès le champ d'écoulement et la structure de flamme y compris les effets tourbillonnaires et qu'il peut donc servir à la conception et à l'optimisation des brûleurs à tourbillons pour les combustibles solides pulvérisés. [source]