From Droplet Growth to Film Growth on a Heterogeneous Surface: Condensation Associated with a Wettability Gradient

Zhao, Hong; Beysens, Daniel

doi:10.1021/la00002a045

Cited by 159 publications

(161 citation statements)

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“…In this stage, due to significant numbers of coalescences events of large drops, the growth law exponent of the mean drop radius R becomes unity (Fig. 4), which is in agreement with a growth law as R ∼t 1/(D d −Ds) [32,33]. Here D d = 3 is the drop dimensionality and D s = 2 is the surface dimensionality.…”

Section: Resultssupporting

confidence: 74%

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Water condensation on zinc surfaces treated by chemical bath deposition

Narhe

González-Viñas

Beysens

2010

Applied Surface Science

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a b s t r a c tWater condensation, a complex and challenging process, is investigated on a metallic (Zn) surface, regularly used as anticorrosive surface. The Zn surface is coated with hydroxide zinc carbonate by chemical bath deposition, a very simple, low-cost and easily applicable process. As the deposition time increases, the surface roughness augments and the contact angle with water can be varied from 75 • to 150 • , corresponding to changing the surface properties from hydrophobic to ultrahydrophobic and superhydrophobic. During the condensation process, the droplet growth laws and surface coverage are found similar to what is found on smooth surfaces, with a transition from Cassie-Baxter to Wenzel wetting states at long times. In particular, it is noticeable in view of corrosion effects that the water surface coverage remains on order of 55%.

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Section: Resultssupporting

confidence: 74%

“…At this stage, the surface coverage saturates around a value that depends on the apparent contact angle according to [33] …”

Section: Resultsmentioning

confidence: 99%

Water condensation on zinc surfaces treated by chemical bath deposition

Narhe

González-Viñas

Beysens

2010

Applied Surface Science

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“…2. The data [11] where ε 2 ∞ is plotted versus contact angle shows that this value corresponds to an average contact angle φ ≃ 90 • . We thus use the data calculated for this particular value of φ.…”

Section: Experimental: Determination Of the Characteristics Of A Dew mentioning

confidence: 96%

“…The shape of the drop is no more a spherical cap. In this case ε 2 ∞ becomes dependent on the hysteresis, and since the hysteresis effects are stronger for small contact angles [11], ε 2 ∞ becomes higher as φ is smaller. This dependence will be used in section 3 to determine the contact angle.…”

Section: Introductionmentioning

confidence: 96%

Coherent light transmission by a dew pattern

Nikolayev

Sibille

Beysens

1998

Optics Communications

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We study both theoretically and experimentally the transmission of coherent light by a drop pattern (dew). The theory is based on the Kirchhoff scalar approach to diffraction. The polarization of the diffracted wave in the zero diffraction order is analyzed separately. The intensity in the zero diffraction order in the far zone is an oscillatory function of the drop size. These oscillations are observed with a pattern of water drops growing on glass. The model allows the evolution of the important parameters of the drop pattern (average radius and surface coverage) to be obtained from the light intensity in the zero diffraction order. IntroductionDepending on the wettability of the surface on which vapor condenses, dew forms a transparent film or a diffuse assembly of droplets. The knowledge of the properties of dew, "breath figures" or, generally speaking, dropwise condensation, opens a vast field of applications ranging from high-technology processes of film growth [1] to soil desinfection in agronomy [2], sterilization in pharmacology [3] and water recovery in dew condensers [4]. The optical properties of dew have received considerable attention from the scientists who studied the natural physical effects (see, e.g. [5,6]) and from those who are interested in industrial applications [7,8].The morphology and kinetics of dew formation were investigated extensively both theoretically and experimentally (see e.g. [9,10] and refs. therein). Its growth can be characterized by several physical values, the most important of which are the mean radius a of the drops and the surface coverage ε 2 , which is the fraction of surface area covered by the projections of the drops on the surface.Two regimes of growth can be identified. At the beginning of the condensation process the drops grow independently, a follows a power law a ∼ t µ 0 , where t is the elapsed time, and the surface coverage increases. When the temperature of the substrate is kept constant, µ 0 = 1 3 . When the drop radius becomes large enough, coalescences between drops occur and the exponent changes to another value µ = 3µ 0 . The growth is then self-similar and the surface coverage reaches a saturation value Email address: vadim.nikolayev@cea.fr (Vadim S. Nikolayev) ε 2 ∞ as well as all the statistical characteristics of the drop pattern, except a . When the surface is ideally smooth and clean ε 2 ∞ ≈ 0.55 independently of the wetting properties (characterized by the contact angle φ, see Fig. 1). For a nonideal surface, the pinning of the contact lines by the surface heterogeneities leads to a hysteresis of the contact angle, i.e. to a significant difference between the advancing and receding contact angles. The shape of the drop is no more a spherical cap. In this case ε 2 ∞ becomes dependent on the hysteresis, and since the hysteresis effects are stronger for small contact angles [11], ε 2 ∞ becomes higher as φ is smaller. This dependence will be used in section 3 to determine the contact angle. In the analysis below, the drops are considered ...

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“…Zhao and Beysens found no directed movement of such small droplets, but a different growth behaviour at the ends of the gradients. 16 With a growing droplet size, they observed that the centre of gravity of the droplet moved towards the more hydrophilic end of the gradient. Superhydrophobicity is an increasingly studied phenomenon since the easy generation of superhydrophobic surfaces would open up many new possibilities for industrial applications.…”

Section: Wettability Effectsmentioning

confidence: 99%

Surface-chemical and -morphological gradients

2008

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Surface gradients of chemistry or morphology represent powerful tools for the high-throughput investigation of interfacial phenomena in the areas of physics, chemistry, materials science and biology. A wide variety of methods for the fabrication of such gradients has been developed in recent years, relying on principles ranging from diffusion to time-dependent irradiation in order to achieve a gradual change of a particular parameter across a surface. In this review we have endeavoured to cover the principal fabrication approaches for surface-chemical and surface-morphological gradients that have been described in the literature, and to provide examples of their applications in a variety of different fields.

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From Droplet Growth to Film Growth on a Heterogeneous Surface: Condensation Associated with a Wettability Gradient

Cited by 159 publications

References 0 publications

Water condensation on zinc surfaces treated by chemical bath deposition

Water condensation on zinc surfaces treated by chemical bath deposition

Coherent light transmission by a dew pattern

Surface-chemical and -morphological gradients

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