A Study of an Oscillating Corner Meniscus With Phase Change Using Image Analyzing Interferometry

Volume 4 ◽  
2004 ◽  
Author(s):  
Sashidhar S. Panchamgam ◽  
Shripad J. Gokhale ◽  
Joel L. Plawsky ◽  
Sunando DasGupta ◽  
Peter C. Wayner
Keyword(s):  
Fluid Flow ◽  
Phase Change ◽  
Contact Line ◽  
Quartz Substrate ◽  
Thin Liquid Film ◽  
Adsorbed Film ◽  
Line Region ◽  
The Stability ◽  
First Time

The thickness and curvature profiles in the contact line region of a moving evaporating thin liquid film of pentane on a quartz substrate were measured for the thickness region, δ < 2.5 microns. The critical region, δ < 0.1 microns, was emphasized. The profiles were obtained using image analyzing interferometry and an improved data analysis procedure. The precursor adsorbed film, the thickness, the curvature, and interfacial slope (variation of the local “apparent contact angle”) profiles were consistent with previous models based on interfacial concepts. Isothermal equilibrium conditions were used to evaluate the Hamaker constant in-situ and to verify the accuracy of the procedures. The profiles give fundamental insights into the phenomena of phase change, pressure gradient, fluid flow, spreading, and the physics of interfacial phenomena in the contact line region. The experimental results demonstrate explicitly for the first time, with microscopic detail, that the disjoining pressure controls fluid flow within an evaporating completely wetting thin curved film and the stability of the thin film. The change in the thickness of the adsorbed film with time is demonstrated for the first time.

Experimental Determination of the Effect of Disjoining Pressure on Shear in the Contact Line Region of a Moving Evaporating Thin Film

2005 ◽  
Vol 127 (3) ◽  
pp. 231-243 ◽  
Author(s):  
Sashidhar S. Panchamgam ◽  
Shripad J. Gokhale ◽  
Joel L. Plawsky ◽  
Sunando DasGupta ◽  
Peter C. Wayner,
Keyword(s):  
Fluid Flow ◽  
Contact Line ◽  
Quartz Substrate ◽  
Thin Liquid Film ◽  
Disjoining Pressure ◽  
Dispersion Constant ◽  
Line Region ◽  
Fundamental Insight ◽  
First Time

The thickness and curvature profiles in the contact line region of a moving evaporating thin liquid film of pentane on a quartz substrate were measured for the thickness region, δ<2.5 μm. The critical region, δ<0.1 μm, was emphasized. The profiles were obtained using image-analyzing interferometry and an improved data analysis procedure. The precursor adsorbed film, the thickness, the curvature, and interfacial slope (variation of the local “apparent contact angle”) profiles were consistent with previous models based on interfacial concepts. Isothermal equilibrium conditions were used to verify the accuracy of the procedures and to evaluate the retarded dispersion constant in situ. The profiles give fundamental insight into the phenomena of phase change, pressure gradient, fluid flow, spreading, shear stress, and the physics of interfacial phenomena in the contact line region. The experimental results demonstrate explicitly, for the first time with microscopic detail, that the disjoining pressure controls fluid flow within an evaporating completely wetting thin curved film.

Use of Scanning Microphotometer to Determine the Evaporative Heat Transfer Characteristics of the Contact Line Region

1981 ◽  
Vol 103 (2) ◽  
pp. 325-330 ◽  
Author(s):  
R. Cook ◽  
C. Y. Tung ◽  
P. C. Wayner
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Heat Flux ◽  
Contact Line ◽  
Heat Transfer Characteristics ◽  
Thin Film Thickness ◽  
Thickness Profile ◽  
Line Region ◽  
Evaporative Heat Transfer

A scanning microphotometer was used to measure in situ the profile of an evaporating decane meniscus in the contact line region on a smooth inclined silicon substrate as a function of the evaporative heat flux. The use of this new experimental design to determine the effect of heat flux on the profile in the contact line region is discussed. The results support the hypothesis that fluid flow in the contact line region of an evaporating thin film results from a change in the thin film thickness profile.

Experimental Study of Evaporation in the Contact Line Region of a Thin Film of Hexane

1985 ◽  
Vol 107 (1) ◽  
pp. 182-189 ◽  
Author(s):  
P. C. Wayner ◽  
C. Y. Tung ◽  
M. Tirumala ◽  
J. H. Yang
Keyword(s):  
Liquid Film ◽  
Contact Line ◽  
Thin Liquid Film ◽  
Bulk Composition ◽  
Transport Processes ◽  
Shear Stresses ◽  
Strong Function ◽  
Thickness Profile ◽  
Line Region ◽  
Curvature Gradient

The transport processes in the contact line region (junction of evaporating thin liquid film, vapor, and substrate) of stationary steady-state evaporating thin films of hexane with various bulk compositions were studied experimentally. The substrate temperature distribution and liquid film thickness profile were measured, analyzed, and compared with previous results on other systems. The results demonstrate that small changes in the bulk composition significantly alter the characteristics of the transport processes in the contact line region. The curvature gradient at the liquid-vapor interface is a strong function of evaporation rate and composition. Concentration and temperature gradients give interfacial shear stresses and flow patterns that enhance contact line stability.

Novel Environmental Control Chamber for FT-Raman Spectroscopy: Study of in situ Phase Change of Sulfur

1997 ◽  
Vol 51 (1) ◽  
pp. 101-107 ◽  
Author(s):  
H. G. M. Edwards ◽  
D. W. Farwell ◽  
J. M. C. Turner ◽  
A. C. Williams
Keyword(s):  
Raman Spectroscopy ◽  
Phase Change ◽  
Monoclinic Phase ◽  
Environmental Control ◽  
Atmospheric Conditions ◽  
Spectroscopy Study ◽  
Ft Raman Spectroscopy ◽  
The Stability ◽  
Ft Raman

The adaptation and construction of an environmental chamber suitable for FT-Raman spectroscopy is described for the recording of Raman spectra of specimens at temperatures from 25 to 125 °C while exposed to different controlled synthetic atmospheric conditions. Test spectra were obtained from sulfur to illustrate the stability and applications of the system. The α rhombic/β monoclinic phase change in sulfur was monitored as a function of time, and bands sensitive to this phase change have been identified.

scholarly journals In-Situ Kinetic Investigation of Calcium Aluminate Formation

Ceramics ◽  
2018 ◽  
Vol 1 (1) ◽  
pp. 175-197 ◽  
Author(s):  
John Salasin ◽  
Claudia Rawn
Keyword(s):  
Calcium Aluminate ◽  
Sol Gel ◽  
Ambient Conditions ◽  
X Ray Diffraction ◽  
Direct Crystallization ◽  
Crystalline Materials ◽  
The Stability ◽  
First Time ◽  
Kinetic Equilibrium

Rapid in-situ non-ambient X-ray diffraction represents a powerful tool for characterizing the evolution of crystalline materials in real time. The calcium aluminate system and formation of Ca12Al14O33 (C12A7) is particularly sensitive to processing conditions. This report characterizes the kinetic pathways to thermodynamic equilibrium as a function of atmosphere (ambient, dry, and vacuum) and reactant heterogeneity (as-received, milled, and sol-gel reactants). When reactants are heterogenous (as-received and milled), intermediary phases of Ca3Al2O6 (C3A) and CaAl2O4 (CA) are observed as the route to C12A7 formation and Ca5Al6O14 (C5A3) is only observed as a decomposition product of C12A7. When reactants are heterogenous, C12A7 is only thermodynamically favorable under ambient conditions due to the stability provided by hydration. When reactants are homogenous (sol-gel), direct crystallization of C12A7 from an amorphous precursor is observed at low temperature regardless of atmosphere defining C12A7 as the kinetic equilibrium. These findings accurately define the heterogenous formation pathways and report for the first time the formation of C12A7 under a carbon-free vacuum environment.

Experimental Evaluation of Marangoni Shear in the Contact Line Region of an Evaporating 99+% Pure Octane Meniscus

2007 ◽  
Vol 129 (11) ◽  
pp. 1476-1485 ◽  
Author(s):  
Sashidhar S. Panchamgam ◽  
Joel L. Plawsky ◽  
Peter C. Wayner
Keyword(s):  
Thin Film ◽  
Fluid Flow ◽  
Intermolecular Interactions ◽  
Contact Line ◽  
Disjoining Pressure ◽  
Operating Conditions ◽  
Working Fluid ◽  
Quartz Surface ◽  
Experimental Conditions ◽  
Line Region

Image analyzing interferometry was used to study the spreading characteristics of an evaporating octane meniscus (purity: 99+%) on a quartz surface. The thickness, slope, and curvature profiles in the contact line region of the meniscus were obtained using a microscopic data analysis procedure. The results obtained for the octane were compared to that of pure pentane (purity: >99.8%) under similar operating conditions. Isothermal experimental conditions of the menisci were used for the in situ estimation of the retarded dispersion constant. The experimental results for the pure pentane demonstrate that the disjoining pressure (the intermolecular interactions) in the thin-film region controls the fluid flow. Also, an imbalance between the disjoining pressure in the thin-film region and the capillary pressure in the thicker meniscus region resulted in a creeping evaporating pentane meniscus, which spreads over the solid (quartz) surface. On the contrary, for less pure octane, the intermolecular interactions between octane and quartz had a significantly different contribution for fluid flow, and hence, the octane meniscus of lower purity did not creep over the quartz surface. As a result, we had a stationary, evaporating octane meniscus. Using the experimental data and a simple model for the velocity distribution, we evaluated the Marangoni shear in a portion of the stationary, evaporating octane meniscus. An extremely small change in the concentration due to distillation had a significant effect on fluid flow and microscale heat transfer. Also, it was found that nonidealities in small interfacial systems, i.e., the presence of impurities in the working fluid, can have a significant effect on the thickness of the adsorbed film, the heat flux, the spreading characteristics of an almost pure fluid, and, therefore, the assumptions in modeling.

Microscale Temperature Measurements Near the Contact Line of an Evaporating Thin Film in a V-Groove

2009 ◽  
Author(s):  
C. P. Migliaccio ◽  
H. K. Dhavaleswarapu ◽  
S. V. Garimella
Keyword(s):  
Thin Film ◽  
Contact Line ◽  
Quartz Substrate ◽  
Constant Heat Flux ◽  
Electrical Heating ◽  
Thin Film Evaporation ◽  
Meniscus Shape ◽  
Liquid Feeding ◽  
Line Region ◽  
Balance Analysis

Thin-film evaporation of heptane in a V-groove geometry is experimentally investigated. The groove is made of fused quartz, and electrical heating of a thin layer of titanium coated on the backside of the quartz substrate provides a constant heat flux. The effects of liquid feeding rate on the temperature suppression in the thin-film region and on the meniscus shape are explored. High resolution (∼6.3 μm) infrared thermography is employed to investigate the temperature profile in the thin-film region, while a goniometer is used to image the meniscus shape. An approximate heat balance analysis is used to estimate the fraction of total meniscus heat transfer which takes place in the contact line region.

Contact line instability in spontaneous spreading of a drop on a solid surface

2001 ◽  
Vol 428 ◽  
pp. 171-183 ◽  
Author(s):  
P. NEOGI
Keyword(s):  
Solid Surface ◽  
Contact Line ◽  
Dynamic Contact ◽  
Contact Lines ◽  
Large Curvature ◽  
Line Region ◽  
The Stability ◽  
Dynamic Contact Line ◽  
Wetting Kinetics ◽  
Kinetics Of

The wetting kinetics of a drop on a solid surface is measured by observing the movement of the contact line, which is often seen to be unstable, showing a scalloped profile. Many factors have been cited, which, although they can cause instability, can also be eliminated from the experiments, but still the instabilities appear. The basic shape of a spreading drop has a large curvature localized in the vicinity of the contact line as determined by microscopy. It is shown here using linear stability analysis that this curvature can destabilize the contact line region. When the drop profile is disturbed from a basic thickness of h to h + h′, there are two contributions from h′ in the form of added Laplace pressure. One of these is commonly accounted for in the stability analyses. The other is not, and occurs only if the basic shape has a curvature, and the drop has a large curvature near the apparent dynamic contact line, but only for a wetting liquid. This is why instability is not reported in the case of spreading of drops of non-wetting liquids. It also explains why instability gives rise to the changed spreading kinetics of drops that are sometimes reported in the literature, and suggests that as larger curvatures are expected in forced spreading those cases are probably accompanied quite frequently by unstable contact lines.

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