Gas Conditions (gas + condition)

Distribution by Scientific Domains


Selected Abstracts


Order-Disorder Phase Transition in Type-I Clathrate Cs8Sn44,2,

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 26 2007
Andreas Kaltzoglou
Abstract The clathrate compound ,-Cs8Sn44,2 has been synthesized from its elements under inert gas conditions and has been characterized by single-crystal and powder X-ray diffraction. At room temperature, it crystallizes with cubic symmetry [a = 24.256(3) Å, space group Iad, Z = 8] and adopts a 2,×,2,×,2 superstructure of the type-I clathrate and a high ordering of the vacancies (,) in the Sn framework. Single crystals of ,-Cs8Sn44,2 reversibly transform at 90 °C to the high-temperature , form with primitive symmetry [a = 12.135(1) Å, space group Pmn, Z = 1] and a lower ordering of the defects. Differential thermal analysis corroborates the reversible character of the phase transition, which occurs with an enthalpy change of approximately 0.38 J,g,1. An atom-migration mechanism describing the order-disorder transition involving spiro-connected six-membered rings only (scsr mechanism) is proposed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]


Simple models for evaluating effects of small leaks on the gas barrier properties of food packages

PACKAGING TECHNOLOGY AND SCIENCE, Issue 2 2003
Donghwan Chung
Abstract A detailed theoretical analysis and calculations were made for providing a simple and explicit means to evaluate the effects of small leaks on the barrier properties of food packages. Small leaks, such as pinholes and channel leaks, were approximated as cylindrical pores with diameters of 50,300,,m. The first part of the current study proposes a simple mathematical model based on Fick's law of diffusion, which accounts for both the gas leakage across small leaks and the gas permeation across package walls. The model uses an effective permeability that depends on leak dimensions, type of diffusing gas, type of packaging material and gas conditions around the leak ends. In the second part of the study, three practical cases are presented to illustrate the application of the proposed model in examining the significance of leaks. These demonstrate in a simple and explicit manner that for LDPE packages: (a) leaks affect the oxygen transfer more than the water vapour transfer; (b) leak effects are more significant at lower storage temperatures; and (c) that for high gas barrier packages, the effect of leaks is very important and should not be neglected. The model can be also used to arrive at conclusions about the significance of leaks in other packaging situations (e.g. other than LDPE packaging materials) and to correct the shelf-life estimation of gas- and water vapour-sensitive foods for errors from package leaks. Copyright © 2003 John Wiley & Sons, Ltd. [source]


High Productive Deposited Mo Layers for Back Ohmic Contacts of Solar Cells

PLASMA PROCESSES AND POLYMERS, Issue S1 2009
Jens-Peter Heinß
Abstract In the paper, thin molybdenum (Mo) layers produced by magnetron sputtering [state of the art in production for photovoltaic applications (PV)] are compared with those produced by high-rate electron beam (EB) deposition technology. Stainless steel and borofloat glass served as substrate materials. Mo layers deposited by DC-magnetron sputtering were produced as a reference and investigated by analysis of structure and specific electrical resistance. Alternative layers prepared by high-rate EB-deposition with a rate up to 240,nm·s,1 were characterised by inquests of mechanical properties, sheet resistance and cell efficiency. A strong dependency of specific electrical resistance on residual gas conditions was determined. The specific electrical resistance dropped from 18 to 11,µ,·cm. Compactness of Mo layers increased with implementation of plasma activation. The layer formation became denser and comparable to the magnetron sputtered Mo layers. [source]


Vapor-phase elemental mercury adsorption by Ca(OH)2 impregnated with MnO2 and Ag in fixed-bed system

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2010
Y. J. Wang
Abstract The ability of three sorbents (untreated Ca(OH)2, MnO2 -impregnated Ca(OH)2 and Ag-impregnated Ca(OH)2) removing the elemental mercury had been studied using a laboratory-scale fixed-bed reactor at 80 °C under simulated fuel gas conditions. The adsorption performance of the three sorbents was compared by mercury removal efficiency and adsorption capacity. The effect of acid gases such as HCl and SO2 on the mercury removal was investigated and presented in this article. The results showed that the mercury removal by Ca(OH)2 was mainly controlled by physical mechanisms. In the case of Ca(OH)2, the presence of both SO2 and HCl promoted the Hg0 removal, and compared HCl with SO2, HCl had a higher mercury removal than SO2. Ca(OH)2 impregnated with MnO2 had a slightly higher mercury removal than the original Ca(OH)2, but it was beneficial for mercury speciation. The presence of both SO2 and HCl promotes the Hg0 removal greatly, which was adsorbed by Ca(OH)2 impregnated with MnO2. The Ca(OH)2 impregnated with MnO2 adsorbed more than 50% total Hg due to the occurrence of chemisorptions. The mercury removal by Ca(OH)2 impregnated with Ag was the highest. The reason might be that mercury integrated with silver easily that could produce silver amalgam alloy. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]