scholarly journals Facile construction of a polydopamine-based hydrophobic surface for protection of metals against corrosion

RSC Advances ◽  
2017 ◽  
Vol 7 (19) ◽  
pp. 11528-11536 ◽  
Author(s):  
Nan Wei ◽  
Yueyue Jiang ◽  
Ye Ying ◽  
Xiaoyu Guo ◽  
Yiping Wu ◽  
...  
Keyword(s):  
Metal Surfaces ◽  
Hydrophobic Surface ◽  
Water Droplets ◽  
Protection Of Metals

Metal surfaces with a hydrophobic feature, which could prevent percolation of water droplets and improve their capability against corrosion, arouse extensively interest.

scholarly journals Heterogeneous freezing of water droplets containing kaolinite particles

2011 ◽  
Vol 11 (9) ◽  
pp. 4191-4207 ◽  
Author(s):  
B. J. Murray ◽  
S. L. Broadley ◽  
T. W. Wilson ◽  
J. D. Atkinson ◽  
R. H. Wills
Keyword(s):  
Cooling Rate ◽  
Surface Area ◽  
Clay Mineral ◽  
Constant Temperature ◽  
Hydrophobic Surface ◽  
Supercooled Liquid ◽  
Stochastic Approach ◽  
Solid Particles ◽  
Rate Coefficients ◽  
Water Droplets

Abstract. Clouds composed of both ice particles and supercooled liquid water droplets exist at temperatures above ~236 K. These mixed phase clouds, which strongly impact climate, are very sensitive to the presence of solid particles that can catalyse freezing. In this paper we describe experiments to determine the conditions at which the clay mineral kaolinite nucleates ice when immersed within water droplets. These are the first immersion mode experiments in which the ice nucleating ability of kaolinite has been determined as a function of clay surface area, cooling rate and also at constant temperatures. Water droplets containing a known amount of clay mineral were supported on a hydrophobic surface and cooled at rates of between 0.8 and 10 K min−1 or held at constant sub-zero temperatures. The time and temperature at which individual 10–50 μm diameter droplets froze were determined by optical microscopy. For a cooling rate of 10 K min−1, the median nucleation temperature of 10–40 μm diameter droplets increased from close to the homogeneous nucleation limit (236 K) to 240.8 ± 0.6 K as the concentration of kaolinite in the droplets was increased from 0.005 wt% to 1 wt%. This data shows that the probability of freezing scales with surface area of the kaolinite inclusions. We also show that at a constant temperature the number of liquid droplets decreases exponentially as they freeze over time. The constant cooling rate experiments are consistent with the stochastic, singular and modified singular descriptions of heterogeneous nucleation; however, freezing during cooling and at constant temperature can be reconciled best with the stochastic approach. We report temperature dependent nucleation rate coefficients (nucleation events per unit time per unit area) for kaolinite and present a general parameterisation for immersion nucleation which may be suitable for cloud modelling once nucleation by other important ice nucleating species is quantified in the future.

scholarly journals Dust removal from a hydrophobic surface by rolling fizzy water droplets

RSC Advances ◽  
2020 ◽  
Vol 10 (34) ◽  
pp. 19811-19821 ◽  
Author(s):  
Bekir Sami Yilbas ◽  
Ghassan Hassan ◽  
Hussain Al-Qahtani ◽  
Saeed Bahatab ◽  
Ahmet Z. Sahin ◽  
...  
Keyword(s):  
Removal Rate ◽  
Hydrophobic Surface ◽  
Dust Removal ◽  
Liquid Droplets ◽  
Water Droplets

Here, environmental dust cleaning from an inclined hydrophobic surface by rolling liquid droplets has been studied and the influence of fluid droplets on the dust removal rate has been examined.

The Collision Behavior of Droplets Splitted from a Droplet that Rebounded on Super-Hydrophobic Surface

2015 ◽  
Vol 723 ◽  
pp. 968-971 ◽  
Author(s):  
Zheng Yong Huang ◽  
Jian Li ◽  
Fei Peng Wang ◽  
Huan Huan Xia ◽  
Mao Chang Li
Keyword(s):  
Contact Time ◽  
Hydrophobic Surface ◽  
Reynolds Numbers ◽  
Elastic Collision ◽  
Water Droplets ◽  
Water Contact ◽  
Ice Accumulation ◽  
Pollution Flashover ◽  
Water Accumulation ◽  
Spreading Time

Droplet rebounding on super-hydrophobic surfaces is critical to suppress pollution flashover (i.e. enhancement of pollution flashover-voltage) and to reduce ice accumulation on insulators. This paper presents a novel way to reduce water accumulation on surface via the elastic collision between droplets splitted from a droplet that has rebounded from super-hydrophobic surface. The water-mass that contacted with surface will be reduced resultantly. The influence of hydrophobicity of the surface on contact time and spreading time of water droplets are discussed. The collision behavior between the splitted droplets is indicated by the surface charge that was induced by the rebounding droplets on super-hydrophobic surface. Experimental results show that the super-hydrophobic surface endows water droplets with shorter contact time, spreading time than those values obtained on a bare glass. Specific Web and Reynolds numbers can lead to the elastic rebounding between water droplets, delaying the water contact with the super-hydrophobic surface. The contact electrification between the rebounded droplet and the super-hydrophobic surface renders the droplet charged, thus determines the collision behavior of the splitted droplets that born from the rebounded droplet.

Study on Discharge of Separated Water Droplets in DC Field

2011 ◽  
Vol 130-134 ◽  
pp. 3276-3279
Author(s):  
Zong Xi Zhang ◽  
Shan Feng Yin
Keyword(s):  
Electric Field ◽  
Hydrophobic Surface ◽  
Electrical Equipment ◽  
Water Droplets ◽  
Surface Flashover ◽  
Voltage Drops ◽  
Flashover Voltage ◽  
Dc Electric Field ◽  
Water Drops ◽  
And Migration

With the accelerating construction of strong smart grid, and the grid voltage level rising, performance requirements for the electrical insulation of electrical equipment also continue to increase. In terms of the advantages of RTV on antifouling, RTV-based paints coated insulator coating capacity of its flash tolerance can significantly increase, mainly due to RTV coating hydrophobic hydrophobicity and migration. But when the hydrophobic surface is in the fully wet, many small drops of water in the surface will be gathered into big drops of water, and these large droplets will distort the surface electric field of the medium. So the flashover voltage of the hydrophobic surface’s separated water droplets under DC electric field are analyzed comparatively in this paper, while some influencing factors such as different medias and volume of water drops, are introduced in specific experiments, and their effects on the flashover voltage are analyzed; under DC electric field experiment on the surface of hydrophobic and hydrophilic surface flashover voltage drops separation characteristics were studied.

scholarly journals Formation of double emulsion micro-droplets in a microfluidic device using a partially hydrophilic–hydrophobic surface

RSC Advances ◽  
2021 ◽  
Vol 11 (56) ◽  
pp. 35653-35662
Author(s):  
Ampol Kamnerdsook ◽  
Ekachai Juntasaro ◽  
Numfon Khemthongcharoen ◽  
Mayuree Chanasakulniyom ◽  
Witsaroot Sripumkhai ◽  
...  
Keyword(s):  
Flow Rate ◽  
Frequency Ratio ◽  
Encapsulation Efficiency ◽  
Double Emulsion ◽  
Hydrophobic Surface ◽  
Water Droplets ◽  
Oil In Water ◽  
Rate Ratios ◽  
Frequency Ratios ◽  
Ratio Range

(a) Droplet encapsulation efficiency & inner and outer diameters of water-in-oil-in-water droplets at various frequency ratios and flow rate ratios and (b) Images of water-in-oil-in-water droplets over a frequency-ratio range of fr = 0.73–1.30

Macroporous Silicone Sheets Integrated with Meshes for Various Applications

2019 ◽  
Author(s):  
Gen Hayase ◽  
Shin-ichiro M. Nomura
Keyword(s):  
Acetic Acid ◽  
Hydrophobic Surface ◽  
Ammonia Solution ◽  
Water Droplets ◽  
Composite Sheet ◽  
Oil Separation ◽  
Giant Vesicle ◽  
Silicone Gels

Flexible macroporous silicone gels were prepared using methyltrimethoxysilane and dimethyldimethoxysilane as co-precursors via a two-step reaction catalyzed by acetic acid and ammonia solution. A sheet-shaped material was integrated with the gel by immersing the mesh in the sol during the reaction. The mesh reinforced sheet having a thickness of several millimeters was resistant to bending and pulling and easy to handle. The composite sheet was used for various applications such as water-oil separation, manipulation of water droplets by adsorption on the hydrophobic surface, and preparation of giant vesicle dispersion.

Optimization of Droplet Generation by Controlling PDMS Surface Hydrophobicity

2004 ◽  
Author(s):  
Lung-Hsin Hung ◽  
Abraham P. Lee
Keyword(s):  
Hydrophobic Surface ◽  
Surface Hydrophobicity ◽  
Droplet Generation ◽  
Hydrophilic Surface ◽  
Water Droplets ◽  
Pdms Surface ◽  
Oil In Water

This paper presents an optimized method for droplet generation in PDMS microchannels. With controllable PDMS surface hydrophobicity and hydrophobicity recovery, alternative component droplets can be generated as anticipated. Different surface hydrophobicity results in different droplet generation patterns. Monodispersed water-in-oil and oil-in-water droplets are generated from hydrophilic and hydrophobic surface respectively. Nearly hydrophilic surface (30°<θ<50°) results in long-tailed droplets and less hydrophilic surface (70°<θ<80°) results in stream mixing. Discussion of methods to loss and recovery hydrophobicity of PDMS also included.

Anti-Icing Property of the Prepared Super-Hydrophobic Octadecyltrichlorosilane (OTS) Film by Phase Separation Method

2013 ◽  
Vol 663 ◽  
pp. 331-334
Author(s):  
Liang Ge ◽  
Jin Yuan Yao ◽  
Hong Wang ◽  
Gui Fu Ding
Keyword(s):  
Contact Angle ◽  
Phase Separation ◽  
Heterogeneous Nucleation ◽  
Hydrophobic Surface ◽  
Separation Method ◽  
Surface Wettability ◽  
Nucleation Theory ◽  
Ice Formation ◽  
Water Droplets ◽  
Hydrophobic Surfaces

In this paper, we prepared an octadecyltrichlorosilane(OTS) super-hydrophobic film using phase separation method to demonstrate the anti-icing property of super-hydrophobic surfaces. We investigated the super-hydrophobicity of the surface in -5°C environment, as well as the icing process of water droplets on the surface which proceeded at the temperature low to -15°C. We found that the prepared OTS film retained its super-hydrophobicity in the -5°C environment by the measurement of contact angle. It was observed that the icing progress of water droplets on the super-hydrophobic surface was greatly retarded. Based on the classical heterogeneous nucleation theory, it concluded that the ice formation is directly related to the surface wettability. This research would be beneficial to the preparation of anti-icing films.

STUDY OF LEIDENFROST MECHANISM IN DROPLET IMPACTING ON HYDROPHILIC AND HYDROPHOBIC SURFACES

2013 ◽  
Vol 21 (04) ◽  
pp. 1350028 ◽  
Author(s):  
SEOL HA KIM ◽  
JUN YOUNG KANG ◽  
HO SEON AHN ◽  
HANG JIN JO ◽  
MOO HWAN KIM
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Hydrophobic Surface ◽  
Bubble Nucleation ◽  
Hydrophilic Surface ◽  
Water Droplets ◽  
Time Resolved ◽  
Droplet Dynamics ◽  
Different Shapes ◽  
Time Resolved Imaging

Water droplets, 2 mm in diameter, were allowed to fall freely onto hydrophobic and hydrophilic heated surfaces, and their impacts were imaged using high-speed cameras to investigate the droplet dynamics and heat transfer. As the heating power increased, the water droplets evaporated faster, eventually hovering over the surface due to the formation of a boiling film when the Leidenfrost point (LFP) was reached. The heat transfer from the surface into the droplet was evaluated, and LFP transition phenomena were investigated using time-resolved imaging of both side and bottom views. The hydrophilic surface showed a higher heat transfer rate and a higher LFP than the hydrophobic surface did. Furthermore, the droplet dynamics revealed very different shapes depending on the surface wettability; vigorous bubble nucleation and growth was observable for the hydrophilic surface, but not the hydrophobic surface. The rebound behavior of the droplets was analyzed based on the droplet free energy, including kinetic, potential, and surface energy terms.

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