Measurement of dynamic wetting using phase-shifting imaging ellipsometer: comparison of pure solvent and nanoparticle suspension on film thickness profile, apparent contact angle, and precursor film length

This research investigates the effect of surface roughness, water temperature, and pH value on the wettability behaviour of copper surfaces. An electron beam physical vapour deposition technique was used to fabricate 25, 50, and 75 nm thin films of copper on the surface of copper substrates. Surface topographical analysis, of the uncoated and coated samples, was performed using an atomic force microscopy device to observe the changes in surface microstructure. A goniometer device was then employed to examine the surface wettability of the samples by obtaining the static contact angle between the liquid and the attached surface using the sessile drops technique. Waters of pH 4, 7, and 9 were employed as the contact angle testing fluids at a set of fixed temperatures that ranged from 20°C to 60°C. It was found that increasing the deposited film thickness reduces the surface roughness of the as-prepared copper surfaces and thus causing the surface wettability to diverge from its initial hydrophobic nature towards the hydrophilic behaviour region. A similar divergence behaviour was seen with the rise in temperature of water of pH 4, and 9. In contrast, the water of pH 7, when tested on the uncoated surface, ceased to reach a contact angle below 90o. It is believed that the observed changes in surface wettability behaviour is directly linked to the liquid temperature, pH value, surface roughness, along with the Hofmeister effect between the water and the surface in contact.

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Effect of surface microgeometry on pressure distribution and film thickness profile in circular contact under impact loading

Lubrication Science ◽

10.1002/ls.14 ◽

2006 ◽

Vol 18 (3) ◽

pp. 151-163 ◽

Cited By ~ 1

Author(s):

Gabriel Andrei ◽

Iulian Birsan ◽

Laurentia Andrei ◽

Douglas Walton

Keyword(s):

Film Thickness ◽

Pressure Distribution ◽

Impact Loading ◽

Thickness Profile ◽

Surface Microgeometry ◽

Effect Of Surface ◽

Circular Contact

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The Effects of Artificially-Produced Defects on the Film Thickness Distribution in Sliding EHD Point Contacts

Journal of Lubrication Technology ◽

10.1115/1.3253222 ◽

1982 ◽

Vol 104 (3) ◽

pp. 365-375 ◽

Cited By ~ 34

Author(s):

C. Cusano ◽

L. D. Wedeven

Keyword(s):

Film Thickness ◽

Contact Region ◽

Thickness Distribution ◽

Point Contact ◽

Optical Interferometry ◽

Point Contacts ◽

Thickness Profile ◽

Inlet Region

The effects of artificially-produced dents and grooves on the elastohydrodynamic (EHD) film thickness profile in a sliding point contact are investigated by means of optical interferometry. The defects, formed on the surface of a highly polished ball, are held stationary at various locations within and in the vicinity of the contact region while the disk is rotating. It is shown that the defects, having a geometry similar to what can be expected in practice, can dramatically change the film thickness which exists when no defects are present in or near the contact. This change in film thickness is mainly a function of the position of the defects in the inlet region, the geometry of the defects, the orientation of the defects in the case of grooves, and the depth of the defect relative to the central film thickness.

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Interfacial Behaviour in Ferroalloys: The Influence of Sulfur in FeMn and SiMn Systems

Metallurgical and Materials Transactions B ◽

10.1007/s11663-021-02323-2 ◽

2021 ◽

Author(s):

Sergey Bublik ◽

Sarina Bao ◽

Merete Tangstad ◽

Kristian Etienne Einarsrud

Keyword(s):

Contact Angle ◽

Interfacial Tension ◽

Sessile Drop ◽

Interfacial Properties ◽

Apparent Contact Angle ◽

Holding Time ◽

Transfer Rates ◽

Experimental Parameters ◽

Interfacial Behaviour ◽

Modelling Approach

AbstractThe present study has investigated the influence of sulfur content in synthetic FeMn and SiMn from 0 to 1.00 wt pct on interfacial properties between these ferroalloys and slags. The effect of experimental parameters such as temperature and holding time was evaluated. Interfacial interaction between ferroalloys and slags was characterized by interfacial tension and apparent contact angle between metal and slag, measured based on the Young–Laplace equation and an inverse modelling approach developed in OpenFOAM. The results show that sulfur has a significant influence on both interfacial tension and apparent contact angle, decreasing both values and promoting the formation of a metal-slag mixture. Despite the fact that sulfur was added only to the ferroalloys, most of sulfur is distributed into slag after reactions with the metal phase. Increasing the maximum experimental temperature in the sessile drop furnace also resulted in a decrease of both interfacial properties, resulting in higher mass transfer rates and intensive reactions between metal and slag. The effect of holding time demonstrated that after reaching equilibrium in FeMn-slag and SiMn-slag systems (both with and without sulfur), interfacial tension and apparent contact angle remain constant.

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Thermal analysis in thin-film fluid regions of rectangular microgroove

Thermal Science ◽

10.2298/tsci160114288g ◽

2018 ◽

Vol 22 (2) ◽

pp. 899-897

Author(s):

Xiaohong Gui ◽

Xiange Song ◽

Baisheng Nie

Keyword(s):

Thin Film ◽

Heat Transfer ◽

Heat Flux ◽

Contact Angle ◽

Film Thickness ◽

Flux Distribution ◽

Total Heat ◽

Heat Flux Distribution ◽

Total Heat Transfer ◽

Thin Film Thickness

The effects of contact angle and superheat on thin-film thickness and heat flux distribution occurring in a rectangle microgroove are numerically simulated. Accordingly, physical, and mathematical models are built in detail. Numerical results indicate that meniscus radius and thin-film thickness increase with the improvement of contact angle. The heat flux distribution in the thin-film region increases non-linearly as the contact angle decreases. The total heat transfer through the thin-film region increases with the improvement of superheat, and decreases as the contact angle increases. When the contact angle is equal to zero, the heat transfer in the thin-film region accounts for more than 80% of the total heat transfer. Intensive evaporation in the thin-film region plays a key role in heat transfer for the rectangle capillary microgroove. The liquid with higher wetting performance is more capable of playing the advantages of higher intensity heat transfer in thin- film region. The current investigation will result in a better understanding of thin- -film evaporation and its effect on the effective thermal conductivity in the rectangle microgroove.

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Apparent contact angle of oleic acid and triolein on a reverse osmosis membrane in SC-CO2 environment

The Journal of Supercritical Fluids ◽

10.1016/j.supflu.2021.105470 ◽

2021 ◽

pp. 105470

Author(s):

Karina Araus ◽

Eileen Santos ◽

Ricardo Couto ◽

Feral Temelli

Keyword(s):

Contact Angle ◽

Oleic Acid ◽

Reverse Osmosis ◽

Apparent Contact Angle ◽

Reverse Osmosis Membrane ◽

Co2 Environment

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Modelling of Partially Wetting Liquid Film Using an Enhanced Thin Film Model for Aero-Engine Bearing Chamber Applications

Volume 2C: Turbomachinery ◽

10.1115/gt2020-15845 ◽

2020 ◽

Author(s):

K. Singh ◽

M. Sharabi ◽

R. Jefferson-Loveday ◽

S. Ambrose ◽

C. Eastwick ◽

...

Keyword(s):

Thin Film ◽

Contact Angle ◽

Film Thickness ◽

Liquid Film ◽

Flow Rate ◽

Operating Conditions ◽

Film Model ◽

Thin Film Model ◽

Wide Range ◽

Aero Engine

Abstract In the case of aero-engine, thin lubricating film servers dual purpose of lubrication and cooling. Prediction of dry patches or lubricant starved region in bearing or bearing chambers are required for safe operation of these components. In the present work thin liquid film flow is numerically investigated using the framework of the Eulerian thin film model (ETFM) for conditions which exhibit partial wetting phenomenon. This model includes a parameter that requires adjustment to account for the dynamic contact angle. Two different experimental data sets have been used for comparisons against simulations, which cover a wide range of operating conditions including varying the flow rate, inclination angle, contact angle, and liquid-gas surface tension coefficient. A new expression for the model parameter has been proposed and calibrated based on the simulated cases. This is employed to predict film thickness on a bearing chamber which is subjected to a complex multiphase flow. From this study, it is observed that the proposed approach shows good quantitative comparisons of the film thickness of flow down an inclined plate and for the representative bearing chamber. A comparison of model predictions with and without wetting and drying capabilities is also presented on the bearing chamber for shaft speed in the range of 2,500 RPM to 10,000 RPM and flow rate in the range of 0.5 liter per minute (LPM) to 2.5 LPM.

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Moving contact lines and dynamic contact angles: a ‘litmus test’ for mathematical models, accomplishments and new challenges

The European Physical Journal Special Topics ◽

10.1140/epjst/e2020-900236-8 ◽

2020 ◽

Vol 229 (10) ◽

pp. 1945-1977 ◽

Cited By ~ 3

Author(s):

Yulii D. Shikhmurzaev

Keyword(s):

Contact Angle ◽

Mathematical Models ◽

Contact Line ◽

Dynamic Contact Angle ◽

Dynamic Contact ◽

Dynamic Wetting ◽

Line Speed ◽

Moving Contact ◽

New Challenges ◽

Litmus Test

Abstract After a brief overview of the ‘moving contact-line problem’ as it emerged and evolved as a research topic, a ‘litmus test’ allowing one to assess adequacy of the mathematical models proposed as solutions to the problem is described. Its essence is in comparing the contact angle, an element inherent in every model, with what follows from a qualitative analysis of some simple flows. It is shown that, contrary to a widely held view, the dynamic contact angle is not a function of the contact-line speed as for different spontaneous spreading flows one has different paths in the contact angle-versus-speed plane. In particular, the dynamic contact angle can decrease as the contact-line speed increases. This completely undermines the search for the ‘right’ velocity-dependence of the dynamic contact angle, actual or apparent, as a direction of research. With a reference to an earlier publication, it is shown that, to date, the only mathematical model passing the ‘litmus test’ is the model of dynamic wetting as an interface formation process. The model, which was originated back in 1993, inscribes dynamic wetting into the general physical context as a particular case in a wide class of flows, which also includes coalescence, capillary breakup, free-surface cusping and some other flows, all sharing the same underlying physics. New challenges in the field of dynamic wetting are discussed.

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