Search results for "Diffusion"
showing 10 items of 1615 documents
Investigation of water transfer across thin layer biopolymer films by infrared spectroscopy
2011
International audience; The investigation of the apparent diffusivity of water in thin layer iota-carrageenan-based films by FTIR-ATR spectroscopy clearly evidences the fundamental role of surface properties on water transfer. Water diffusivity in iota-carrageenan based biopolymer films ranges from 0.3 to 1.3 × 10−10 m2 s−1 and is thus 10–100 times lower than that in highly hydrated carrageenan gels. The surface heterogeneity and composition when fat is added strongly influence the diffusivity by modifying the liquid water absorption at the inner surface.This study of diffusing molecules in liquid state is particularly interesting to mimic situations where direct liquid water contact occurs…
Analysis and parametric sensitivity of the behavior of overshoots in the concentration of a charged adsorbate in the adsorbed phase of charged adsorb…
2003
In this work, an analysis of the parametric sensitivity of the overshoot in the concentration of the adsorbate in the adsorbed phase, which occurs under certain conditions during an ion-exchange adsorption process, is presented and used to suggest practical implications of the concentration overshoot phenomenon on operational policies and configurations of chromatographic columns and finite bath adsorption systems. The results presented in this work demonstrate and explain how the development of an overshoot in the concentration of the adsorbate in the adsorbed phase could be enhanced or suppressed by (i) varying the diffusion coefficient, D3, of the adsorbate relative to the diffusion coef…
Study of interface diffusion of Ti and TiN PVD layers by Bremsstrahlung-induced AES
1992
The influence of heat treatment in ultrahigh vacuum (UHV) on Ti and TiN layers coated by physical vapour deposition (PVD) has been studied by AES, XPS and bremsstrahlung-induced AES. It could be concluded that up to 500 o C (1 h) the Ti layer does not change significantly. At the TiN/steel substrate interface, however, a counter-diffusion of nitrogen and adventitious oxygen takes place, resulting in partial nitridation of the steel substrate and oxidation of the coating
Size Dependence of Tracer Diffusion in Supercooled Liquids
1996
We have determined by forced Rayleigh scattering the diffusion coefficients D of several photochromic tracers with van der Waals radii between 0.38 and 8 nm (the largest ones being photolabeled polystyrene micronetworks) in 10 glass-forming liquids at temperatures between the glass temperature Tg and ∼1.2Tg. The results were analyzed in terms of power law plots, D(T) ∝ T/η(T)ξ, where η is the solvent shear viscosity, and temperature shifts, D(T) ∝ T/η(T + ΔT). The shift ΔT was related with the width of the rotational correlation time distribution via the time−temperature superposition principle.
Solution Synthesis of a New Thermoelectric Zn1-xSb Nanophase and Its Structure Determination Using Automated Electron Diffraction Tomography
2010
Engineering materials with specific physical properties have recently focused on the effect of nanoscopic inhomogeneities at the 10 nm scale. Such features are expected to scatter medium- and long-wavelength phonons thereby lowering the thermal conductivity of the system. Low thermal conductivity is a prerequisite for effective thermoelectric materials, and the challenge is to limit the transport of heat by phonons, without simultaneously decreasing charge transport. A solution-phase technique was devised for synthesis of thermoelectric "Zn(4)Sb(3)" nanocrystals as a precursor for phase segregation into ZnSb and a new Zn-Sb intermetallic phase, Zn(1+delta)Sb, in a peritectoid reaction. Our …
Zur methodik thermischer diffusionsmessungen von makromolekülen in lösung
1961
Die experimentellen und theoretischen Grundlagen der Konzentrationsdiffusion, thermischen Diffusion und Thermodiffusion werden zusammengestellt. Bei der thermischen Diffusion war es bisher nicht moglich, wie bei den ubrigen Diffusionsversuchen, den Konzentrationsverlauf kontinuierlich einwandfrei zu verfolgen. Der Temperaturgradient des reinen Losungsmittels ergibt eine zu grose Anderung des Brechungsindex. Es wird daher eine Zelle beschrieben, die diesen Temperaturgradienten mittels eines Umkehrprismas eliminiert. Auserdem wird eine Vorrichtung zur Gewinnung einer scharfen Anfangsgrenzschicht zwischen Losung und Losungsmittel angegeben. Die Apparatur wird zur Messung des thermischen Diffus…
Das lösungsverhalten von polyäthylenterephthalat
1970
Das Losungsverhalten von fraktioniertem Polyathylenterephthalat wurde viskosimetrisch, durch Sedimentation und Diffusion sowie durch osmotische Messungen untersucht. Daneben wurden die durch Endgruppentitration erhaltenen Molekulargewichte ermittelt. Fur M aus Sedimentation und Diffusion ergibt sich in o-Chlorphenol bei 25°C die Viskositats-Molekulargewichtsbeziehung Die Temperaturabhangigkeit der Viskositat was in o-Chlorphenol negativ, dagegen in m-Kresol schwach positiv. Aus dem Zusammenhang [η] = f(M) wurde die ungestorte Dimension nach STOCKMAYER-FIXMAN ermittelt. Sie ist etwa σ = 1,3 mal so gros wie die zu vollig freier Drehbarkeit um die Ketteneinfachbindungen gehorende Dimension. De…
The Role of Tissue Pressure and Bulk Flow in the Formation and Resolution of Cold-Induced Edema
1976
The mechanisms responsible for the dynamics of cold-induced edema, its spread and resolution, were examined. The findings indicate that bulk flow and not diffusion should be considered as the main mechanism for the edema spreading through the extracellular spaces of the white matter.
Studies on supramolecular gel formation using DOSY NMR
2015
Herein, we present the results obtained from our studies on supramolecular self-assembly and molecular mobility of low-molecular-weight gelators (LMWGs) in organic solvents using pulsed field gradient (PFG) diffusion ordered spectroscopy (DOSY) NMR. A series of concentration-dependent DOSY NMR experiments were performed on selected LMWGs to determine the critical gelation concentration (CGC) as well as to understand the behaviour of the gelator molecules in the gel state. In addition, variable-temperature DOSY NMR experiments were performed to determine the gel-to-sol transition. The PFG NMR experiments performed as a function of gradient strength were further analyzed using monoexponential…
Transport coefficients of n-butane into and through the surface of silicalite-1 from non-equilibrium molecular dynamics study
2009
We have studied coupled heat and mass transfer of n-butane through a membrane of silicalite-1. A description of the surface was given using non-equilibrium thermodynamics, and transport coefficients were determined. Three independent coefficients were found for the whole surface: the resistance to heat transfer, the coupling coefficient and the resistance to mass transfer. These coefficients were defined in stationary state. All resistances are significant, and show that the surface acts as a barrier to transport. A new scheme was devised to find the enthalpy of adsorption, from two particular coupling coefficients, namely the measurable heats of transfer. The method yields the enthalpy of …