scholarly journals Effects of Surface Tension on the Stability of Surface Nanobubbles

2021 ◽  
Vol 9 ◽  
Author(s):  
Yongcai Pan ◽  
Bing He ◽  
Binghai Wen
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
State Dependence ◽  
Detection Methods ◽  
Hydrophilic Surface ◽  
Surface Tensions ◽  
Saturation Degree ◽  
Gas Saturation ◽  
Variable Surface ◽  
The Stability

The existence of surface nanobubbles has already been confirmed by variable detection methods, but the mechanism of their extraordinary stability remains unclear and has aroused widespread research interest in the past 2 decades. Experiments and theoretical analyses have tried to account for these stabilities such as the very long lifetime, very high pressure and very small contact angle. Attractive hydrophobic potential was applied to complement the pinning-oversaturation theory and successfully explain the survival of surface nanobubbles in undersaturation environment by some researchers. However, the survival of nanobubbles on hydrophilic surface still requires sizeable oversaturation. In this paper, we introduce the variable surface tensions, namely Tolman-dependence and state-dependence, and show that they effectively promote the stability of nanobubbles. The decrease in surface tension can lead to larger contact angle and even make the nanobubbles survivable on the highly hydrophilic surface. In Tolman-dependence, the changing rate in the contact angle evolution slows down, which is more obvious when the bubble size is close to the Tolman length. The contact angle is also getting larger in the state-dependence, and the increase of the gas saturation degree is beneficial to the stability of surface nanobubbles. With the gas saturation ratio of 3, the bubbles on the quite hydrophilic surface can also be stable, while grow up on the hydrophobic surface. The variable surface tensions weaken the need of saturation degree for the surface nanobubbles’ stability.

Enhancement on CO2 Bubble Absorption in MDEA Solution by TiO2 Nanoparticles

2013 ◽  
Vol 631-632 ◽  
pp. 127-134 ◽  
Author(s):  
Shu Hong Li ◽  
Yi Ding ◽  
Xiao Song Zhang
Keyword(s):  
Thermal Conductivity ◽  
Surface Tension ◽  
Mass Fraction ◽  
Kinematic Viscosity ◽  
Absorption Rate ◽  
Surface Tensions ◽  
Mechanical Agitation ◽  
Maximum Enhancement ◽  
Nanoparticles Concentration ◽  
The Stability

TiO2-N-methyldiethanolamine(MDEA)-H2O nanofluids were prepared by dispersing TiO2 nanoparticles in the 50wt% (mass fraction) MDEA solution. The stability of nanofluids was studied by the method of absorbance. Only with mechanical agitation, the nanofluids can keep stable at least 48 h without any dispersant. The surface tensions; kinematic viscosities and thermal conductivities of the MDEA solution were measured at the temperature of 20 °C when the TiO2 na-noparticles concentration was 0.05wt%, 0.2wt%, 0.4wt% and 0.8wt%. The results show that they all increase with increasing concentration of the nanoparticles. The maximum enhancement of the surface tension, kinematic viscosity and thermal conductivity is 0.6 %, 4.6 % and 5.9 % respectively at the concentration of 0.8 wt%. The influence of nanoparticles on CO2 bubble absorption in the MDEA solution was studied. It can be found that the CO2 absorption rate can be enhanced by 1.95%, 6.53%, 7.79%, 11.54% when the TiO2 nanoparticles concentration is 0.05wt%, 0.2wt%, 0.4wt% and 0.8wt% respectively. The possible mechanisms for the phenomena in experiments and related results are also explained.

Film flow over heated wavy inclined surfaces

2010 ◽  
Vol 665 ◽  
pp. 418-456 ◽  
Author(s):  
S. J. D. D'ALESSIO ◽  
J. P. PASCAL ◽  
H. A. JASMINE ◽  
K. A. OGDEN
Keyword(s):  
Surface Tension ◽  
Stokes Equations ◽  
Fluid Layer ◽  
Bottom Topography ◽  
Marangoni Effect ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Inclined Surfaces ◽  
Variable Surface ◽  
The Stability

The two-dimensional problem of gravity-driven laminar flow of a thin layer of fluid down a heated wavy inclined surface is discussed. The coupled effect of bottom topography, variable surface tension and heating has been investigated both analytically and numerically. A stability analysis is conducted while nonlinear simulations are used to validate the stability predictions and also to study thermocapillary effects. The governing equations are based on the Navier–Stokes equations for a thin fluid layer with the cross-stream dependence eliminated by means of a weighted residual technique. Comparisons with experimental data and direct numerical simulations have been carried out and the agreement is good. New interesting results regarding the combined role of surface tension and sinusoidal topography on the stability of the flow are presented. The influence of heating and the Marangoni effect are also deduced.

scholarly journals Образование пузырька на гидрофобной поверхности

2020 ◽  
Vol 90 (6) ◽  
pp. 886
Author(s):  
С.И. Кошоридзе ◽  
Ю.К. Левин
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Surface Energy ◽  
Gibbs Energy ◽  
Surface Charge ◽  
Double Electric Layer ◽  
Surface Tension Coefficient ◽  
Electrostatic Energy ◽  
Spontaneous Generation ◽  
The Stability

The paper investigates the formation of charged equilibrium nanobubble on smooth hydrophobic water - solid interface. Expressions are given for change the Gibbs energy of the system taking into account the capillary Kelvin formula, the electrostatic energy of the double electric layer at the bubble-water boundary and the surface energy. It is shown that the dependence of the Gibbs energy on the radius of nanobubble have a minimum, which indicates the possibility of spontaneous generation of these nanostructures. The dependence of Gibbs energy on the contact angle, as well as water salinity and surface tension coefficient of water is investigated. Calculated surface charge required for the stability of nanobubble.

scholarly journals THE THEORETICAL RESPONSE OF LIVING CELLS TO CONTACT WITH SOLID BODIES

1922 ◽  
Vol 4 (4) ◽  
pp. 373-385 ◽  
Author(s):  
Wallace O. Fenn
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Solid Surface ◽  
Flat Surface ◽  
Living Cells ◽  
Point Of View ◽  
Solid Surfaces ◽  
Surface Tensions ◽  
Solid Bodies ◽  
Fluid Cell

The theoretical behavior of a hypothetical fluid cell in contact with flat and curved solid surfaces is discussed from the point of view of surface tension. An equation is derived for calculating the equilibrium position of the cell on a flat surface in terms of the surface tensions between the cell and the plasma, the plasma and the solid surface, and the solid surface and the cell. It is shown that the same equilibrium is predicted from consideration of the contact angle between the cell and the solid body. The relative surface energy has been calculated at various stages in the ingestion of a solid particle by a fluid cell four times as large in diameter, and it is thus shown that no particle will be ingested until the surface tensions are such that the cell would spread to infinity on a flat surface of the same substance. Here again the same equilibrium is predicted from considerations of the contact angle. The adhesiveness of blood cells to solid substances is shown to be a pure surface tension phenomenon, but in most reactions between living cells and solid bodies the fluidity of the protoplasm is also a factor of prime importance. The frequent occurrence of adhesiveness as a property of cells in contact with solid bodies is due in part to the fact that, by so adhering, the surface area of the cell not touching the solid is decreased.

scholarly journals A pH-Responsive Foam Formulated with PAA/Gemini 12-2-12 Complexes

2021 ◽  
Vol 5 (3) ◽  
pp. 37
Author(s):  
Hernán Martinelli ◽  
Claudia Domínguez ◽  
Marcos Fernández Leyes ◽  
Sergio Moya ◽  
Hernán Ritacco
Keyword(s):  
Surface Tension ◽  
Dynamic Surface Tension ◽  
Foam Formation ◽  
Ph Responsive ◽  
Dynamic Surface ◽  
X Ray ◽  
Equilibrium Surface Tension ◽  
Potential Applications ◽  
The Stability ◽  
Air Interfaces

In the search for responsive complexes with potential applications in the formulation of smart dispersed systems such as foams, we hypothesized that a pH-responsive system could be formulated with polyacrylic acid (PAA) mixed with a cationic surfactant, Gemini 12-2-12 (G12). We studied PAA-G12 complexes at liquid–air interfaces by equilibrium and dynamic surface tension, surface rheology, and X-ray reflectometry (XRR). We found that complexes adsorb at the interfaces synergistically, lowering the equilibrium surface tension at surfactant concentrations well below the critical micelle concentration (cmc) of the surfactant. We studied the stability of foams formulated with the complexes as a function of pH. The foams respond reversibly to pH changes: at pH 3.5, they are very stable; at pH > 6, the complexes do not form foams at all. The data presented here demonstrate that foam formation and its pH responsiveness are due to interfacial dynamics.

scholarly journals Influence of moisture content on the contact angle and surface tension measured on birch wood surfaces

2021 ◽  
Author(s):  
Rami Benkreif ◽  
Fatima Zohra Brahmia ◽  
Csilla Csiha
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Moisture Content ◽  
Solid Wood ◽  
Contact Angles ◽  
Surface Moisture ◽  
Wood Coatings ◽  
The Relationship ◽  
Wood Surfaces

AbstractSurface tension of solid wood surfaces affects the wettability and thus the adhesion of various adhesives and wood coatings. By measuring the contact angle of the wood, the surface tension can be calculated based on the Young-Dupré equation. Several publications have reported on contact angle measured with different test liquids, under different conditions. Results can only be compared if the test conditions are similar. While the roles of the drop volume, image shooting time etc., are widely recognized, the role of the wood surface moisture content (MC) is not evaluated in detail. In this study, the effect of wood moisture content on contact angle values, measured with distilled water and diiodomethane, on sanded birch (Betula pendula) surfaces was investigated, in order to find the relationship between them. With increasing MC from approximately 6% to 30%, increasing contact angle (decreasing surface tension) values were measured according to a logarithmic function. The function makes possible the calculation of contact angles that correspond to different MCs.

Osteoconductivity of Superhydrophilic Ti- and Zr-Alloy for Biomedical Application

2016 ◽  
Vol 879 ◽  
pp. 2524-2527
Author(s):  
Masazumi Okido ◽  
Kensuke Kuroda
Keyword(s):  
Contact Angle ◽  
Water Contact Angle ◽  
Strong Influence ◽  
Biomedical Application ◽  
Hydrophobic Surface ◽  
Hydrophilic Surface ◽  
Water Contact ◽  
Zr Alloy ◽  
Zr Alloys

Surface hydrophilicity is considered to have a strong influence on the biological reactions of bone-substituting materials. However, the influence of a hydrophilic or hydrophobic surface on the osteoconductivity is not completely clear. In this study, we produced super-hydrophilic and hydrophobic surface on Ti-and Zr-alloys. Hydrothermal treatment at 180 oC for 180 min. in the distilled water and immersion in x5 PBS(-) brought the super-hydrophilic surface (water contact angle < 10 (deg.)) and heat treatment of as-hydrothermaled the hydrophobic surface. The osteoconductivity of the surface treated samples with several water contact angle was evaluated by in vivo testing. The surface properties, especially water contact angle, strongly affected the osteoconductivity and protein adsorbability, and not the surface substance.

Electrohydrodynamic stability: Taylor–Melcher theory for a liquid bridge suspended in a dielectric gas

2002 ◽  
Vol 452 ◽  
pp. 163-187 ◽  
Author(s):  
C. L. BURCHAM ◽  
D. A. SAVILLE
Keyword(s):  
Surface Tension ◽  
Dielectric Constant ◽  
Electric Fields ◽  
Liquid Bridge ◽  
Numerical Solutions ◽  
Specific Conductivity ◽  
Axisymmetric Deformation ◽  
Aspect Ratios ◽  
The Stability ◽  
Theory And Experiment

A liquid bridge is a column of liquid, pinned at each end. Here we analyse the stability of a bridge pinned between planar electrodes held at different potentials and surrounded by a non-conducting, dielectric gas. In the absence of electric fields, surface tension destabilizes bridges with aspect ratios (length/diameter) greater than π. Here we describe how electrical forces counteract surface tension, using a linearized model. When the liquid is treated as an Ohmic conductor, the specific conductivity level is irrelevant and only the dielectric properties of the bridge and the surrounding gas are involved. Fourier series and a biharmonic, biorthogonal set of Papkovich–Fadle functions are used to formulate an eigenvalue problem. Numerical solutions disclose that the most unstable axisymmetric deformation is antisymmetric with respect to the bridge’s midplane. It is shown that whilst a bridge whose length exceeds its circumference may be unstable, a sufficiently strong axial field provides stability if the dielectric constant of the bridge exceeds that of the surrounding fluid. Conversely, a field destabilizes a bridge whose dielectric constant is lower than that of its surroundings, even when its aspect ratio is less than π. Bridge behaviour is sensitive to the presence of conduction along the surface and much higher fields are required for stability when surface transport is present. The theoretical results are compared with experimental work (Burcham & Saville 2000) that demonstrated how a field stabilizes an otherwise unstable configuration. According to the experiments, the bridge undergoes two asymmetric transitions (cylinder-to-amphora and pinch-off) as the field is reduced. Agreement between theory and experiment for the field strength at the pinch-off transition is excellent, but less so for the change from cylinder to amphora. Using surface conductivity as an adjustable parameter brings theory and experiment into agreement.

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