Articoli di riviste: "Contact angle"

1

Marmur, Abraham. "Contact angle equilibrium: the intrinsic contact angle". Journal of Adhesion Science and Technology 6, n. 6 (gennaio 1992): 689–701. http://dx.doi.org/10.1163/156856192x01042.

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Kwok, D. Y., e A. W. Neumann. "Contact angle measurement and contact angle interpretation". Advances in Colloid and Interface Science 81, n. 3 (settembre 1999): 167–249. http://dx.doi.org/10.1016/s0001-8686(98)00087-6.

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Yang, S. Y., G. J. Hirasaki, S. Basu e R. Vaidya. "Mechanisms for contact angle hysteresis and advancing contact angles". Journal of Petroleum Science and Engineering 24, n. 2-4 (dicembre 1999): 63–73. http://dx.doi.org/10.1016/s0920-4105(99)00049-2.

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Wang, J. H., P. M. Claesson, J. L. Parker e H. Yasuda. "Dynamic Contact Angles and Contact Angle Hysteresis of Plasma Polymers". Langmuir 10, n. 10 (ottobre 1994): 3887–97. http://dx.doi.org/10.1021/la00022a080.

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5

Ruiz-Cabello, F. J. Montes, M. A. Rodríguez-Valverde e M. A. Cabrerizo-Vílchez. "Equilibrium contact angle or the most-stable contact angle?" Advances in Colloid and Interface Science 206 (aprile 2014): 320–27. http://dx.doi.org/10.1016/j.cis.2013.09.003.

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6

Chen, Yongjiang, e Wencheng Tang. "Determination of contact stiffness in ball screws considering variable contact angles". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 228, n. 12 (7 gennaio 2014): 2193–203. http://dx.doi.org/10.1177/0954406213516304.

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The contact angles formed at the position of each ball in ball screws are conventionally assumed to be a constant value in determination of contact stiffness. In this study, instead of being treated as pre-assumed constants, the contact angle is formulated as functions of the position angle of balls to reﬂect their distribution dependent on the operation condition and design parameters. After establishing a proper transformed coordinate system according to the ball screw mechanism, the variable contact angles and normal forces of the ball screw are predicted. Then the contact stiffness obtained by numerical calculations is validated by experiment and several characteristics arising from the variable contact angle will be discussed.

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7

Butt, Hans-Jürgen, Jie Liu, Kaloian Koynov, Benedikt Straub, Chirag Hinduja, Ilia Roismann, Rüdiger Berger et al. "Contact angle hysteresis". Current Opinion in Colloid & Interface Science 59 (giugno 2022): 101574. http://dx.doi.org/10.1016/j.cocis.2022.101574.

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8

Liu, Yong-Ming, Zi-Qing Wu, Sheng Bao, Wei-Hong Guo, Da-Wei Li, Jin He, Xiang-Bin Zeng et al. "The Possibility of Changing the Wettability of Material Surface by Adjusting Gravity". Research 2020 (27 gennaio 2020): 1–11. http://dx.doi.org/10.34133/2020/2640834.

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The contact angle, as a vital measured parameter of wettability of material surface, has long been in dispute whether it is affected by gravity. Herein, we measured the advancing and receding contact angles on extremely low contact angle hysteresis surfaces under different gravities (1-8G) and found that both of them decrease with the increase of the gravity. The underlying mechanism is revealed to be the contact angle hysteresis and the deformation of the liquid-vapor interface away from the solid surface caused by gradient distribution of the hydrostatic pressure. The real contact angle is not affected by gravity and cannot measured by an optical method. The measured apparent contact angles are angles of inclination of the liquid-vapor interface away from the solid surface. Furthermore, a new equation is proposed based on the balance of forces acting on the three-phase contact region, which quantitatively reveals the relation of the apparent contact angle with the interfacial tensions and gravity. This finding can provide new horizons for solving the debate on whether gravity affects the contact angle and may be useful for the accurate measurement of the contact angle and the development of a new contact angle measurement system.

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Kwok, D. Y., e A. W. Neumann. "Contact angle interpretation: re-evaluation of existing contact angle data". Colloids and Surfaces A: Physicochemical and Engineering Aspects 161, n. 1 (gennaio 2000): 49–62. http://dx.doi.org/10.1016/s0927-7757(99)00324-6.

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Lyashenko, Iakov A., Valentin L. Popov e Vadym Borysiuk. "Indentation and Detachment in Adhesive Contacts between Soft Elastomer and Rigid Indenter at Simultaneous Motion in Normal and Tangential Direction: Experiments and Simulations". Biomimetics 8, n. 6 (7 ottobre 2023): 477. http://dx.doi.org/10.3390/biomimetics8060477.

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In reported experiments, a steel indenter was pressed into a soft elastomer layer under varying inclination angles and subsequently was detached under various inclination angles too. The processes of indentation and detachment were recorded with a video camera, and the time dependences of the normal and tangential components of the contact force and the contact area, as well as the average contact pressure and average tangential stresses, were measured as functions of the inclination angle. Based on experimental results, a simple theoretical model of the indentation process is proposed, in which tangential and normal contacts are considered independently. Both experimental and theoretical results show that at small indentation angles (when the direction of motion is close to tangential), a mode with elastomer slippage relative to the indenter is observed, which leads to complex dynamic processes—the rearrangement of the contact boundary and the propagation of elastic waves (similar to Schallamach waves). If the angle is close to the normal angle, there is no slipping in the contact plane during the entire indentation (detachment) phase.

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Benilov, E. S., e M. Vynnycky. "Contact lines with a contact angle". Journal of Fluid Mechanics 718 (8 febbraio 2013): 481–506. http://dx.doi.org/10.1017/jfm.2012.625.

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AbstractThis work builds on the foundation laid by Benney & Timson (Stud. Appl. Maths, vol. 63, 1980, pp. 93–98), who examined the flow near a contact line and showed that, if the contact angle is $18{0}^{\circ } $, the usual contact-line singularity does not arise. Their local analysis, however, does not allow one to determine the velocity of the contact line and their expression for the shape of the free boundary involves undetermined constants. The present paper considers two-dimensional Couette flows with a free boundary, for which the local analysis of Benney & Timson can be complemented by an analysis of the global flow (provided that the slope of the free boundary is small, so the lubrication approximation can be used). We show that the undetermined constants in the solution of Benney & Timson can all be fixed by matching the local and global solutions. The latter also determines the contact line’s velocity, which we compute among other characteristics of the global flow. The asymptotic model derived is used to examine steady and evolving Couette flows with a free boundary. It is shown that the latter involve brief intermittent periods of rapid acceleration of contact lines.

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Rakhorst, G., H. C. Van Der Mei, W. Van Oeveren, H. T. Spijker e H. J. Busscher. "Time-Related Contact Angle Measurements with Human Plasma on Biomaterial Surfaces". International Journal of Artificial Organs 21, n. 1 (gennaio 1998): 35–39. http://dx.doi.org/10.1177/039139889802100108.

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Axisymmetric drop shape analysis by profile (ADSA-P) was used to assess in time contact angle changes of human plasma drops placed on four different biomaterials. Results were related with conventional blood compatibility measurements: albumin adsorption, fibrinogen adsorption and platelet adhesion. While contact angle measurements with water are material-related but constant in time, contact angle measurements with plasma changed over time owing to protein adsorption on the solid-liquid interface. The contact medium plasma did not influence the initial contact angle. Contact angles on PDMS decreased most in time (41 degrees) and demonstrated highest levels of conventionally measured albumin and fibrinogen adsorption and platelet adhesion. PTFE, with the lowest contact angle decrease over a 500 minutes period (19 degrees), showed low fibrinogen and albumin adsorption as well as low platelet adhesion. PU and HDPE demonstrated almost similar initial contact angles with plasma and contact angle decreases (26 and 27 degrees), intermediate protein adsorption, and platelet adhesion. We conclude that biocompatibility properties of the tested materials may be more related to the behaviour of their contact angles in time, than to the initial hydrophobic or hydrophilic state.

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13

Çobanoğlu, Nur, Alper Mete Genç, Sila Övgü Korkut, Ziya Haktan Karadeniz e Matthias H. Buschmann. "Volume-independent contact angle prediction". High Temperatures-High Pressures 50, n. 4-5 (2021): 453–66. http://dx.doi.org/10.32908/hthp.v50.1021.

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The contact angle of droplets attracts attention as one of the relevant thermophysical properties describing the wettability behaviour of the fluids. The contact angle depends on the surface characteristics such as surface type and roughness as well as on the liquid type and surrounding atmosphere. This study aims to correct the error in the coefficient of the theoretical model developed for droplet shape prediction by Vafaei and Podowski [1]. The corrected model is also rearranged by non-dimensional numbers. The contact angle and the shape of water droplets for different volumes and surface types are predicted by the rearranged model and validated by experimental results. Contact angles have been over-estimated compared to experimental results because of measurement errors in geometrical parameters. It is found that the contact angle model is too sensitive to geometrical parameters. Moreover, the contact angle is found to be independent of the volume.

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Semprebon, Ciro, Glen McHale e Halim Kusumaatmaja. "Apparent contact angle and contact angle hysteresis on liquid infused surfaces". Soft Matter 13, n. 1 (2017): 101–10. http://dx.doi.org/10.1039/c6sm00920d.

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15

Ruth, Douglas. "Is contact angle a cause or an effect? – A cautionary tale". E3S Web of Conferences 146 (2020): 03004. http://dx.doi.org/10.1051/e3sconf/202014603004.

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The most influential parameter on the behavior of two-component flow in porous media is “wettability”. When wettability is being characterized, the most frequently used parameter is the “contact angle”. When a fluid-drop is placed on a solid surface, in the presence of a second, surrounding fluid, the fluid-fluid surface contacts the solid-surface at an angle that is typically measured through the fluid-drop. If this angle is less than 90°, the fluid in the drop is said to “wet” the surface. If this angle is greater than 90°, the surrounding fluid is said to “wet” the surface. This definition is universally accepted and appears to be scientifically justifiable, at least for a static situation where the solid surface is horizontal. Recently, this concept has been extended to characterize wettability in non-static situations using high-resolution, two-dimensional digital images of multi-component systems. Using simple thought experiments and published experimental results, many of them decades old, it will be demonstrated that contact angles are not primary parameters – their values depend on many other parameters. Using these arguments, it will be demonstrated that contact angles are not the cause of wettability behavior but the effect of wettability behavior and other parameters. The result of this is that the contact angle cannot be used as a primary indicator of wettability except in very restricted situations. Furthermore, it will be demonstrated that even for the simple case of a capillary interface in a vertical tube, attempting to use simply a two-dimensional image to determine the contact angle can result in a wide range of measured values. This observation is consistent with some published experimental results. It follows that contact angles measured in two-dimensions cannot be trusted to provide accurate values and these values should not be used to characterize the wettability of the system.

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Ali, Moazzam, Hammas Ullah, Hamza Javaid, Nauman Naeem, Ali Turab Jafry e Huma Ajab. "Influence of Inclined Chip Angles on Dynamic Contact Angle Variations in Digital Microfluidics". MATEC Web of Conferences 398 (2024): 01022. http://dx.doi.org/10.1051/matecconf/202439801022.

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The impact of tilted angles on contact angles of water droplets in digital microfluidics was investigated. Experiments were conducted tilting the chip from 0 to 10 degrees at voltage increments of 50V from 250V to 400V DC. Both advancing and receding contact angles of the water droplets were measured at each angle and voltage combination. As the tilted angle increased from horizontal to 10 degrees, the advancing contact angle generally decreased whereas the receding contact angle increased. This trend held for all tested voltages. The changes were more pronounced at higher tilt angles above 5 degrees. Voltage was also found to influence the contact angles, with both advancing and receding angles decreasing with increasing driving voltage. The results provide insight into how tilted surface angles affect wetting properties in digital microfluidics. By understanding these relationships between contact angles, tilt angles and driving voltages, design parameters like maximum operational tilt angles before droplet pinning or instability can be better determined. The findings may assist in designing and optimizing tilted or three-dimensional digital microfluidic devices and applications.

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Pepin, Xavier, Sylvène Blanchon e Guy Couarraze. "Powder dynamic contact angle measurements: Young contact angles and effectively wet perimeters". Powder Technology 99, n. 3 (ottobre 1998): 264–71. http://dx.doi.org/10.1016/s0032-5910(98)00123-5.

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Lam, C. N. C., R. H. Y. Ko, L. M. Y. Yu, A. Ng, D. Li, M. L. Hair e A. W. Neumann. "Dynamic Cycling Contact Angle Measurements: Study of Advancing and Receding Contact Angles". Journal of Colloid and Interface Science 243, n. 1 (novembre 2001): 208–18. http://dx.doi.org/10.1006/jcis.2001.7840.

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Li, Gang. "Superhydrophobicity of Silicon-Based Microstructured Surfaces". Advanced Materials Research 989-994 (luglio 2014): 267–69. http://dx.doi.org/10.4028/www.scientific.net/amr.989-994.267.

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Here, a simple method was presented for fabricating superhydrophobic silicon surfaces. Square-pillar-array samples were fabricated on silicon substrates by using the femtosecond laser micromachining technology. We measured the static and dynamic contact angles for water on these surfaces. The contact angles and the rolling angles on the silicon surfaces were measured through an optical contact angle meter. Wettability studies revealed the films exhibited a superhydrophobic behaviour with a higher contact angle and lower rolling angle-a water droplet moved easily on the surface.

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ZHANG, XINPING, SIRONG YU, ZHENMING HE e YAOXIN MIAO. "WETTING OF ROUGH SURFACES". Surface Review and Letters 11, n. 01 (febbraio 2004): 7–13. http://dx.doi.org/10.1142/s0218625x04005925.

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This paper focuses on effects of roughness on wettability. According to Wenzel's equation, the transition of theoretical wetting contact angles is 90°, whereas many experimental results have indicated that such a transition takes place at contact angles smaller than 90°. A new model of wetting on roughness surface is established in this paper. The model indicates that the influencing factors of wetting on roughness surface include not only equilibrium contact angle θ0 and surface roughness, but also the system of liquids and solid substrates. There is a corresponding transition angle for every surface roughness, and the transition angle is lower than 90°. Surface roughness is propitious to improve the contact angle only when θ0 is lower than the transition angle. The effect of surface roughness on the contact angle increases with the increase of rE. To engineer the surface with different roughnesses, a Ti test sample is polished with sandpaper with abrasive number 350, 500, 1000 and 2000; the contact angles of water on Ti are measured by the sessile drop method. The results of the theoretical analysis agree with experimental ones.

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Wong, Ten It, Hao Wang, Fuke Wang, Sau Leng Sin, Cheng Gen Quan, Shi Jie Wang e Xiaodong Zhou. "Empirical Formulae in Correlating Droplet Shape and Contact Angle". Australian Journal of Chemistry 69, n. 4 (2016): 431. http://dx.doi.org/10.1071/ch15730.

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In contact angle measurements, direct identification of the contact angles from images taken from a goniometer suffers from errors caused by optical scatterings. Contact angles can be more accurately identified by the height and width of the droplet. Spherical dome is a simple model used to correlate the contact angles to the droplet shape; however, it features intrinsic errors caused by gravity-induced shape deformation. This paper demonstrates a simple method of obtaining an empirical formula, determined from experiments, to correct the gravity-induced error in the spherical dome model for contact angle calculations. A series of contact angles, heights, and surface contact widths are simultaneously collected for a large amount of samples, and the contact angles are also calculated using the spherical dome model. The experimental data are compared with those obtained from the spherical dome model to acquire an empirical formula for contact angles. Compared with the spherical dome model, the empirical formula can reduce the average errors of the contact angle from –16.3 % to 0.18 %. Furthermore, the same method can be used to correct the gravity errors in the spherical dome for the volume (calculated by height and width), height (calculated by contact angle and volume), and width (calculated by contact angle and volume), and the spherical dome errors can be reduced from –20.9 %, 24.6 %, and –4.8 % to 2 %, –0.13 %, and –0.6 %, respectively. Our method is generic and applicable for all kinds of solvent and substrates, and the derived empirical formulae can be directly used for water droplets on any substrate.

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Erbil, H. Yildirim. "Dependency of Contact Angles on Three-Phase Contact Line: A Review". Colloids and Interfaces 5, n. 1 (1 febbraio 2021): 8. http://dx.doi.org/10.3390/colloids5010008.

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The wetted area of a sessile droplet on a practical substrate is limited by the three-phase contact line and characterized by contact angle, contact radius and drop height. Although, contact angles of droplets have been studied for more than two hundred years, there are still some unanswered questions. In the last two decades, it was experimentally proven that the advancing and receding contact angles, and the contact angle hysteresis of rough and chemically heterogeneous surfaces, are determined by interactions of the liquid and the solid at the three-phase contact line alone, and the interfacial area within the contact perimeter is irrelevant. However, confusion and misunderstanding still exist in this field regarding the relationship between contact angle and surface roughness and chemical heterogeneity. An extensive review was published on the debate for the dependence of apparent contact angles on drop contact area or the three-phase contact line in 2014. Following this old review, several new articles were published on the same subject. This article presents a review of the novel articles (mostly published after 2014 to present) on the dependency of contact angles on the three-phase contact line, after a short summary is given for this long-lasting debate. Recently, some improvements have been made; for example, a relationship of the apparent contact angle with the properties of the three-phase line was obtained by replacing the solid–vapor interfacial tension term, γSV, with a string tension term containing the edge energy, γSLV, and curvature of the triple contact line, km, terms. In addition, a novel Gibbsian thermodynamics composite system was developed for a liquid drop resting on a heterogeneous multiphase and also on a homogeneous rough solid substrate at equilibrium conditions, and this approach led to the same conclusions given above. Moreover, some publications on the line energy concept along the three-phase contact line, and on the “modified” Cassie equations were also examined in this review.

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Gao, Lichao, e Thomas J. McCarthy. "Contact Angle Hysteresis Explained". Langmuir 22, n. 14 (luglio 2006): 6234–37. http://dx.doi.org/10.1021/la060254j.

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Masnok, Kriengsak, e Nobuo Watanabe. "Relationship of Catheter Contact Angle and Contact Force with Contact Area on the Surface of Heart Muscle Tissue in Cardiac Catheter Ablation". Cardiovascular Engineering and Technology 12, n. 4 (15 marzo 2021): 407–17. http://dx.doi.org/10.1007/s13239-021-00529-8.

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Abstract Purpose The aims of this study were to develop an experimental procedure for setting the catheter angle with respect to the surface of the heart muscle and the catheter contact force and to investigate the catheter contact area on the heart muscle as a function of catheter contact angle and force. Methods Visualization tests were performed for 5 contact angles (0°, 30°, 45°, 60°, and 90°) and 8 contact forces (2, 4, 6, 10, 15, 20, 30, and 40 gf). Each experiment was repeated 6 times with 2 different commercially available catheter tips. Results The morphology of the contact area was classified into rectangular, circular, ellipsoidal, and semi-ellipsoidal. The correlation between contact force and contact area was a logarithmic function; increasing contact force was associated with increased contact area. At the same contact force, the correlation between contact angle and contact area was inverse; decreasing contact angle was associated with a corresponding increase in contact area. Conclusion Both the catheter contact angle and contact force substantially impact the contact area and morphology in catheter ablation procedures.

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Restagno, Frédéric, Christophe Poulard, Céline Cohen, Laurianne Vagharchakian e Liliane Léger. "Contact Angle and Contact Angle Hysteresis Measurements Using the Capillary Bridge Technique". Langmuir 25, n. 18 (15 settembre 2009): 11188–96. http://dx.doi.org/10.1021/la901616x.

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Guo, TieNeng, Xu Hua, ZhiJie Yan e Chunsheng Bai. "Research on the elastic–plastic external contact mechanical properties of cylinder". Science Progress 103, n. 2 (aprile 2020): 003685042092781. http://dx.doi.org/10.1177/0036850420927817.

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Based on Hertz contact theory, an elastic-plastic contact mechanics model of outer cylinder under different contact angles of axis is proposed. The relationship among contact angle, load and contact deformation, contact stiffness and contact area is established. The finite element method is used to simulate the elastic-plastic contact process of the cylinder. The influence of the load and radius of the cylinder model on the contact deformation and the contact stiffness is compared and analyzed under different contact angles. The error of the analysis results of the finite element and the mechanical model is within 9%. On this basis, the influence of contact deformation, contact area and contact angle on the contact stiffness of the outer cylinder in elastic and plastic stage is explored. The results show that in the stage of elastic and plastic deformation, the amount of contact deformation and contact area increase with the increase of load. The contact stiffness decreases with the increase of contact angle and increases with the increase of cylinder radius. The amount of contact deformation decreases with the increase of cylinder radius, and tends to constant gradually. In the elastic stage, the contact stiffness increases with the increase of load. The contact area decreases with the increase of contact angle and increases with the increase of cylinder radius. In the plastic stage, the contact stiffness is constant with the increase of load, and the contact area is independent of contact angle and cylinder radius.

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Huang, X. B., X. X.W., J. J. Song, C. G. Bai, R. D. Zhang e M. J. Zhou. "Contact angle of water on iron ore fines: Measurement and analysis". Journal of Mining and Metallurgy, Section B: Metallurgy 51, n. 1 (2015): 33–40. http://dx.doi.org/10.2298/jmmb140903010h.

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The relative contact angle (?RCA) for seven iron ore fines was measured by using Washburn Osmotic Pressure method under laboratory conditions. By choosing cyclohexane as the reference that can perfectly wet iron ore particles, the relative contact angles were measured and varied from 57? to 73?. With the volume % of goethite (?G) as the variable, a new model for relative contact angle was developed. The expected relative contact angle for pure goethite is about 56?, while that for goethite free samples is about 77?. Physical properties, such as surface morphology (SMI) and pore volume (Vpore) can influence the relative contact angle. The ?G can be expressed as a function of SMI and VPore. Thus, we inferred that the relative contact angle is a function of ?G for the iron ores used. The measured relative contact angles were found to be in good agreement (Radj 2 >0.97) with the calculated ones based on the research from Iveson, et al. (2004). Comparing with the model developed by Iveson et al.(2004), the new model for contact angle proposed in this paper is similar, but more detailed with two meaningful physical parameters. The modification of physicochemical properties on iron ores would be another topic in the further study on granulation.

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ZORN, Justyna, e Michał WASILCZUK. "THE EFFECT OF THE EXPOSURE-IN-OIL ON THE CONTACT ANGLE OF THE POLYMERS FORMING SLIDING LAYERS IN HYDRODYNAMIC BEARINGS". Tribologia 269, n. 5 (31 ottobre 2016): 219–27. http://dx.doi.org/10.5604/01.3001.0010.6702.

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Polymers used as the sliding layers of hydrodynamic thrust bearings are typically thermoplastics characterized by relatively high values of contact angles when compared with metals. Metals, including Babbitt, or other bearing alloys, are characterized by low values of the contact angles. The lower the angle, the better the surface is wetted. Plastics used in tribological pairs to ensure a lower coefficient of friction, that is, for example, polytetrafluoroethylene (PTFE) or its composites, have several times higher contact angles compared to the bearing alloys. The research described below shows the effect of the exposure-in-oil contact angle of the polymer layer applied on a hydrodynamic sliding bearing. The conducted study showed the beneficial effects of oil on the reduction of the contact angle.

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Uilk, Janelle M., Ann E. Mera, Robert B. Fox e Kenneth J. Wynne. "Hydrosilation-Cured Poly(dimethylsiloxane) Networks: Intrinsic Contact Angles via Dynamic Contact Angle Analysis". Macromolecules 36, n. 10 (maggio 2003): 3689–94. http://dx.doi.org/10.1021/ma021154x.

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Chen, H., T. Tang e A. Amirfazli. "Fabrication of polymeric surfaces with similar contact angles but dissimilar contact angle hysteresis". Colloids and Surfaces A: Physicochemical and Engineering Aspects 408 (agosto 2012): 17–21. http://dx.doi.org/10.1016/j.colsurfa.2012.04.015.

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Shupe, Todd F., Chung Y. Hse e Wan H. Wang. "An Investigation of Selected Factors that Influence Hardwood Wettability". Holzforschung 55, n. 5 (19 settembre 2001): 541–48. http://dx.doi.org/10.1515/hf.2001.087.

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Summary Wettability of sanded and non-sanded transverse and tangential sections of 22 southern hardwoods species was judged by measurement of contact angles using phenol formaldehyde resins. As expected, contact angle values on transverse sections were higher than those on tangential sections for both sanded and non-sanded surfaces. On sanded surfaces, hackberry had the highest mean contact angle (64.7°), and black oak had the lowest mean contact angle (50.1°). On non-sanded surfaces, winged elm had the highest mean contact angle (59.1°), and sweetgum had the lowest mean contact angle (45.9°). In addition, 4 of the 22 species (southern red oak, sweetgum, white oak, and post oak) were selected to investigate the effect of oven-drying, air-drying, and free-drying on wettability. The mean transverse contact was 2.1°–29.0° and 5.1°–31.5° higher than radial and tangential values, respectively. The contact angle pattern typically displayed for a given species and plane was generally oven-dry > air-dry > freeze-dry. The species pattern for most methods and planes was: sweetgum > white oak > post oak > southern red oak. White oak and post oak gave similar contact angle values.

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Mao-Gang, Gong, Liu Yuan-Yue e Xu Xiao-Liang. "A new model for the formation of contact angle and contact angle hysteresis". Chinese Physics B 19, n. 10 (ottobre 2010): 106801. http://dx.doi.org/10.1088/1674-1056/19/10/106801.

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Koch, Brendan M. L., A. Amirfazli e Janet A. W. Elliott. "Modeling and Measurement of Contact Angle Hysteresis on Textured High-Contact-Angle Surfaces". Journal of Physical Chemistry C 118, n. 32 (4 agosto 2014): 18554–63. http://dx.doi.org/10.1021/jp504891u.

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Saketi, Pooya, Juha Hirvonen, Yuli Lai, Christian Ganser, Christian Teichert, Joakim Järnström, Pedro Fardim e Pasi Kallio. "Automated Drop-on-Fiber contact angle measurement using a microrobotic platform". Nordic Pulp & Paper Research Journal 29, n. 2 (1 maggio 2014): 225–31. http://dx.doi.org/10.3183/npprj-2014-29-02-p225-231.

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Abstract Measuring contact angles on single fibers enables the separation of structural factors from surface chemistry factors. Current Drop-on-Fiber (DOF) contact angle measurement methods for natural fibers generally, and for pulp/paper fibers specifically, present a number of challenges. These are manipulation and mounting of the microscale fibers, straightening natural fibers to produce repeatable axisymmetric droplet conformation, measuring the droplet volume excluding the fiber volume and also human errors due to manually performed tasks. This paper presents a novel method to measure contact angles in DOF systems and overcome the above mentioned challenges using microrobots. The proposed microrobotic platform is capable of handling natural and synthetic fibrous materials in microscale, and dispensing probe liquid droplets down to 12 nl. It measures contact angle values using computer vision and a droplet-profiledetection algorithm. It reports the contact angle values as a function of volume of the droplet. The paper validates the capabilities of the proposed platform by applying three commonly used probe liquids: deionized water, ethylene glycol and diiodomethane for measuring contact angles on glass and pulp fibers. Finally, the results are compared with a picoliter contact angle measurement approach.

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35

Hennig, A., K. J. Eichhorn, U. Staudinger, K. Sahre, M. Rogalli, M. Stamm, A. W. Neumann e K. Grundke. "Contact Angle Hysteresis: Study by Dynamic Cycling Contact Angle Measurements and Variable Angle Spectroscopic Ellipsometry on Polyimide". Langmuir 20, n. 16 (agosto 2004): 6685–91. http://dx.doi.org/10.1021/la036411l.

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B, Guo. "Effect of Fluid Contact Angle of Oil-wet Ceramic Fracture Proppant on the Water Flow from Sandstones to Proppant Packs". Petroleum & Petrochemical Engineering Journal 6, n. 1 (2022): 1–9. http://dx.doi.org/10.23880/ppej-16000295.

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Ceramic fracture proppants are extensively used for enhancing oil and gas well productivity in low-permeability reservoirs. Previous work reported attracting-oil-repelling-water (AORW) property of oil-wet proppants at the faces of fractures. Because of lack of method for measuring contact angle of proppant packs, the terms water-wet proppant and oil-wet proppant were defined on the basis of observations of liquid droplets on the surfaces of proppant packs without quantitative measurement. An innovative method was developed in this study to determine the contact angles of fracture proppant packs. The effect of oil contact angle of oil-wet fracture proppant pack on the competing water/oil flow from sandstone cores to the packs was investigated. It was found that, for a given fracture proppant pack, the sum of the water contact angle and oil contact angle measured in the liquid-air-solid systems is less than 180 degrees, i.e., the two angles are not supplementary. This is believed due to the weak wetting capacity of air to the solid surfaces in the liquid-air-solid systems. Both water and oil contact angles should be considered in the classification of wettability of proppant packs. Fracture proppant packs with water contact angles greater than 90 degrees and oil contact angles significantly less than 90 degrees can be considered as oil-wet proppants. Reducing oil contact angles of oil-wet proppants can increase capillary force, promote oil imbibition into the proppant packs, and thus improve the AORW performance of proppants. Fracture proppant packs with water contact angles less than 90 degrees and oil contact angles less than 90 degrees may be considered as mixed-wet proppants. Their AORW performance should be tested in laboratories before they are considered for well fracturing operations.

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Wang, Ming, e Boyun Guo. "Effect of Fluid Contact Angle of Oil-Wet Fracture Proppant on the Competing Water/Oil Flow in Sandstone-Proppant Systems". Sustainability 14, n. 7 (23 marzo 2022): 3766. http://dx.doi.org/10.3390/su14073766.

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Ceramic fracture proppants are extensively used for enhancing the recovery of fossil energy and geothermal energy. Previous work has reported the attracting-oil-repelling-water (AORW) property of oil-wet proppants at the faces of fractures. Because of the lack of a method for measuring the contact angle of proppant packs, the terms water-wet proppant and oil-wet proppant were defined based on observations of liquid droplets on the surfaces of proppant packs without quantitative measurement. An innovative method was developed in this study to determine the contact angles of fracture proppant packs. The effect of the oil contact angle of the oil-wet fracture proppant pack on the competing water/oil flow from sandstone cores to the packs was investigated. It was found that, for a given fracture proppant pack, the sum of the water contact angle and oil contact angle measured in the liquid–air–solid systems is less than 180°, i.e., the two angles are not supplementary. This is believed to be due to the weak wetting capacity of air to the solid surfaces in the liquid–air–solid systems. Both water and oil contact angles should be considered in the classification of wettability of proppant packs. Fracture proppant packs with water contact angles greater than 90° and oil contact angles significantly less than 90° can be considered as oil-wet proppants. Reducing oil contact angles of oil-wet proppants can increase capillary force, promote oil imbibition into the proppant packs, and thus improve the AORW performance of proppants. Fracture proppant packs with water contact angles less than 90° and oil contact angles less than 90° may be considered as mixed-wet proppants. Their AORW performance should be tested in laboratories before they are considered for well fracturing operations.

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Terpiłowski, Konrad, Lucyna Hołysz, Diana Rymuszka e Robert Banach. "Comparison of contact angle measurement methods of liquids on metal alloys". Annales Universitatis Mariae Curie-Sklodowska, sectio AA – Chemia 71, n. 1 (24 maggio 2016): 89. http://dx.doi.org/10.17951/aa.2016.71.1.89.

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<p>The paper presents the studies of metal wettability using two methods: the sessile droplet and immersion ones. Based on the measured contact angles, there was calculated apparent surface free energy from the acidic–basic approach and the contact angle hysteresis. The advancing contact angles measured using the immersion method exhibit a little higher values than those measured by the sessile droplet method. The application of the immersion method leads to obtaining higher contact angle hysteresis. Both methods give different values of contact angles but they can be applied independently for estimation of metal surface wettability.</p>

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Li, Ri, e Yanguang Shan. "Contact Angle and Local Wetting at Contact Line". Langmuir 28, n. 44 (24 ottobre 2012): 15624–28. http://dx.doi.org/10.1021/la3036456.

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40

Rusanov, Anatoly I. "Effect of contact line roughness on contact angle". Mendeleev Communications 6, n. 1 (gennaio 1996): 30–31. http://dx.doi.org/10.1070/mc1996v006n01abeh000565.

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41

Collet, P., J. De Coninck, F. Dunlop e A. Regnard. "Dynamics of the Contact Line: Contact Angle Hysteresis". Physical Review Letters 79, n. 19 (10 novembre 1997): 3704–7. http://dx.doi.org/10.1103/physrevlett.79.3704.

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42

Kwok, D. Y., T. Gietzelt, K. Grundke, H. J. Jacobasch e A. W. Neumann. "Contact Angle Measurements and Contact Angle Interpretation. 1. Contact Angle Measurements by Axisymmetric Drop Shape Analysis and a Goniometer Sessile Drop Technique". Langmuir 13, n. 10 (maggio 1997): 2880–94. http://dx.doi.org/10.1021/la9608021.

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43

Tyowua, Andrew Terhemen, e Stephen Gbaoron Yiase. "Contact Angle Hysteresis – Advantages and Disadvantages: A Critical Review". Reviews of Adhesion and Adhesives 8, n. 1 (1 marzo 2020): 47–67. http://dx.doi.org/10.7569/raa.2020.097302.

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The existence of contact angle hysteresis – the difference between the values of the advancing and receding contact angles – is evident in nature (e.g. sticking of rain drops to car windscreens and window panes) and many industrial processes (e.g. surface coating, spraying, and dyeing of fabrics). This phenomenon is often viewed as a nuisance, but it is advantageous in many processes including dip and spin coating, spraying, and painting. With the early theoretical framework of Thomas Young, Robert Wenzel, and A. B. D. Cassie and S. Baxter, describing the wettability of solid surfaces and by extension contact angle, contact angle hysteresis has been deeply investigated. We review here the various ways of measuring contact angle and, consequently, contact angle hysteresis as well as related theoretical models. The successes and limitations of these models are highlighted. We conclude with the advantages and disadvantages of contact angle hysteresis whose presence in many processes is often considered as a nuisance, especially when "coffee stain" forms from the evaporation of a volatile liquid drop containing nonvolatile components.

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Khlayboonme, S. Tipawan, e Warawoot Thowladda. "Effects of Air Exposure Time and Annealing Temperature on Superhydrophobic Surface of Titanium Dioxide Films". Key Engineering Materials 751 (agosto 2017): 137–42. http://dx.doi.org/10.4028/www.scientific.net/kem.751.137.

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TiO2 thin films coated on glass substrates for self-cleaning applications were prepared by sol-gel dip-coating technique. The influence of annealing temperature and air exposure time on wettability was investigated by a water contact-angle measurement. Thermal annealing at temperatures of 100, 200 and 300 °C in air were conducted to the films. Surface morphology of the films was observed by FE-SEM. Elemental distribution and optical properties were examined by EDX mapping and UV-Vis transmission spectroscopy, respectively. Atomic bonding was confirmed by FTIR. The contact angle reached a maximum when the films were annealed at 200 °C. The contact angles of the as-synthesized films were 61.4±2.7°. During storage in air for 20 days, the contact angles increased to 143.1±2.1°. The films were further reannealed with 100 °C for 20 min, the contact angles were enhanced to 153.1±1.3°. The association of contact angle among the surface morphology, elemental distribution and atomic bonding of the films will be discussed.

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Chen, Shuai, Jiadao Wang e Darong Chen. "Wetting Behaviors of an Underwater Oil Droplet on Structured Surfaces". MRS Advances 1, n. 10 (2016): 667–73. http://dx.doi.org/10.1557/adv.2016.168.

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ABSTRACTIn this study, the wetting behaviors of an underwater oil droplet on structured surfaces were investigated using molecular dynamics simulations and experiments. The wetting states and contact angles of the underwater oil droplet on different hydrophobic surfaces were simulated. The simulation results showed that there were three kinds of equilibrium states on the pillar surfaces: the Wenzel, cross, and Cassie states. Moreover, the equilibrium state of the underwater oil droplet transformed from a Wenzel to Cassie state when the water contact angle decreased. The contact angle of the underwater oil droplet increased as the water contact angle decreased. Furthermore, the wetting behaviors of the underwater oil droplet on rough polytetrafluoroethylene and silicon surfaces were studied in experiments. The experimental results also indicated that the contact angle of the underwater oil droplet increased as the water contact angle decreased, which corresponded well with the simulation results.

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Liao, Neng Tung, e Jen Fin Lin. "A New Method for the Analysis of Deformation and Load in a Ball Bearing With Variable Contact Angle". Journal of Mechanical Design 123, n. 2 (1 luglio 1999): 304–12. http://dx.doi.org/10.1115/1.1357163.

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The contact angle of a ball in a ball bearing is conventionally assumed to be a constant value in the mechanism analysis; in reality, this is not true. This assumption is made for the purpose of simplifying calculations, but the real elastic deformation produced at the position of each ball due to the acting force varying with the contact angle is unable to be considered. This study tries to establish a simple, three-dimensional expression for the elastic deformation at different position angles in terms of the geometry of the contact surface at the inner and outer races. Simply using the Newton method when the bearing deformations in the radial and axial directions are available can solve the contact angle as a function of position angle. Several characteristics arising from the variable contact angle will be discussed.

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HUANG, F. L., Q. F. WEI, W. Z. XU e Q. LI. "PREPARATION AND CHARACTERIZATIONS OF PTFE GRADIENT NANOSTRUCTURE ON SILK FABRIC". Surface Review and Letters 14, n. 04 (agosto 2007): 547–51. http://dx.doi.org/10.1142/s0218625x07009827.

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Superhydrophobic materials have been extensively studied because of their wonderful array of properties and applications. In this study, normal and superhydrophobic surface of silk fabric have been prepared via deposition of different shapes of PTFE nanostructure using magnetron sputter coating. The effects of PTFE sputter coating on surface morphology and surface chemical properties were characterized using atomic force microscopy (AFM) and ATR-FTIR (attenuated total reflection-Fourier transform infrared spectroscopy). The wettability of the fabric was characterized through measuring the surface contact angle by drop shape analysis apparatus and dynamic contact angle by Wilhelmy technique. As evaluated by water contact angle measurements, all the treatments resulted in a significant enhancement in the hydrophobicity of silk fabric, while larger sputtering pressures brought bigger PTFE nanoparticles, which led to higher contact angles. The results have also revealed that alternant working pressures, could bring gradient nanostructures which generated both high contact angle and less contact angle hysteresis.

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ESIPOVA, N. E., S. V. ITSKOV e V. D. SOBOLEV. "CONTACT ANGLE HYSTERESIS ON SOLID CRYSTALLINE SURFACES". Коллоидный журнал 85, n. 2 (1 marzo 2023): 158–66. http://dx.doi.org/10.31857/s0023291222600602.

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The article presents the results of experimental studying the hysteresis of water contact angles at crystalline surfaces. Receding and advancing contact angles and their hysteresis at hydrophilic and hydrophobic substrates with different surface structures (silica, mica, and calcite) have been studied under the action of an external pressure applied to the three-phase contact line of a sessile air bubble. Hysteresis of the contact angles has been observed on hydrophobized samples of silica and mica. The anchoring of the three-phase contact line (pinning) facilitates a change in the contact angles under the applied external pressure. When the three-phase contact line moves along the hydrophilic surfaces of silica and mica no marked changes in the advancing and receding contact angles are observed, and the hysteresis is actually absent. The stable pinning observed on the polished surface of a calcite crystal brought in contact with water leads to the appearance of contact angle hysteresis and hydrophilization of the calcite surface, with the hydrophilization being related to structural displacements in the crystal lattice.

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Marmur, Abraham. "The Contact Angle Hysteresis Puzzle". Colloids and Interfaces 6, n. 3 (4 luglio 2022): 39. http://dx.doi.org/10.3390/colloids6030039.

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This short review explains the essence of the theory of contact angle hysteresis. It emphasizes the controversial points and discusses the shortcomings of contact angle hysteresis measurements. The review ends with conclusions regarding the improvements that are required to make these measurements useful for the characterization of surface wettability.

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Chibowski, Emil, e Fernando Gonzalez-Caballero. "Interpretation of contact angle hysteresis". Journal of Adhesion Science and Technology 7, n. 11 (gennaio 1993): 1195–209. http://dx.doi.org/10.1163/156856193x00051.

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