scholarly journals Stability of frozen water droplets on highly hydrophobic porous surfaces: Temperature effects

2019 ◽  
Vol 469 ◽  
pp. 864-869 ◽  
Author(s):  
Stella M.M. Ramos ◽  
Christophe Pirat ◽  
Cécile Cottin-Bizonne
Keyword(s):  
Temperature Effects ◽  
Water Droplets ◽  
Porous Surfaces ◽  
Highly Hydrophobic

Wetting Mode Transition of Water Droplets by Electrowetting on Highly Hydrophobic Surfaces Coated with Two Different Silanes

2012 ◽  
Vol 41 (1) ◽  
pp. 23-25 ◽  
Author(s):  
Tsutomu Furuta ◽  
Munetoshi Sakai ◽  
Toshihiro Isobe ◽  
Sachiko Matsushita ◽  
Akira Nakajima
Keyword(s):  
Mode Transition ◽  
Water Droplets ◽  
Hydrophobic Surfaces ◽  
Highly Hydrophobic

scholarly journals Experimental Investigation on the Wind-driven Runback Motion of Water Droplets over Solid Surfaces with Different Wettabilities

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Liqun Ma ◽  
Zichen Zhang ◽  
Hui Hu
Keyword(s):  
Solid Surface ◽  
Contact Angles ◽  
Aircraft Icing ◽  
Water Droplets ◽  
Elastic Materials ◽  
Lotus Leaf ◽  
Liquid Lubricant ◽  
Measurement Results ◽  
Porous Surfaces ◽  
Ice Adhesion

Aircraft icing is widely recognized as one of the most serious weather hazards to flight safety. Specially designed hydro-/ice-phobic coatings are currently undergoing development for aircraft icing mitigation. It was found that hydro-/icephobic coatings would delay the ice accretion iover airframe surfaces so that the impacted supercooled water droplets could be blown away by the airflow from the airframe surface before being frozen into ice. It is of fundamental importance to understand the wind-driven runback behavior of water droplets over surfaces treated with different coatings, since the corresponding knowledge would be very helpful and essential to develop more efficient anti-/de-icing systems for aircraft icing protection. With the rapid development of surface engineering, a series of specially designed surface coatings succeed in icing mitigation using airflow to remove the remained water. While various hydro-/ice-phobic coatings/surfaces have been developed in recent years, the “state-of-the-art” icephobic coatings/surfaces can be generally divided into three categories, i.e., 1). Lotus-leaf-inspired superhydrophobic surfaces (SHS) with micro-/nano-scale surface textures to achieve very high contact angles (typically > 150°); 2). Pitcherplant-inspired slippery liquid infused porous surfaces (SLIPS) with a layer of liquid lubricant (which is immiscible with water) being sandwiched between ice and solid substrate materials; and 3). Icephobic elastic materials/surfaces with deformable structures/surfaces. SHS has a water droplet contact angle (CA) larger than 150° and a sliding angle (SA) less than 10° . SHS always has a hierarchical structure which is similar to the lotus leaf, and water droplets on SHS appear as water beads which can easily roll off the surface by wind or gravity before frozen. Another strategy to reduce ice adhesion strength to a solid surface is to use a layer of liquid lubricant, which is immiscible with water, between ice and the solid surface. The use of such lubricated surfaces was investigated as early as 1960s, and has gained increasing attentions again recently with the introduction of a concept called Slippery Liquid-Infused Porous Surfaces (SLIPS). SLIPS concept is inspired by the Nepenthes pitcher plants, which have evolved highly slippery, liquidinfused micro-textured rim to capture insects. SLIPS surfaces were not only found to be able to suppress ice/frost accretion by effectively removing condensed moisture even in high humidity conditions, but also exhibit at least an order of magnitude lower ice adhesion than most SHS coatings. More recently, elastic materials/surfaces, such as Polydimethylsiloxane or PDMS in short, which would be structurally deformed/altered dynamically upon applying extra mechanical stress, have also been suggested for icing mitigation. Elastic materials display ultra-low adhesion to ice due to their low work of adhesion and liquidlike deformability, while maintaining good mechanical durability due to their solid-like rigidity. It is found that water droplets would not only be more readily rebounding away from the surface after impingement, but also be able to roll away before frozen due to the hydrophobicity of PDMS. Considering the differences in wettabilities and mechanisms of water repellency, it is necessary to have a systematic understanding of how efficient the surfaces are when the aerodynamic force is applied to remove the adhered water droplets. In the present study, a comprehensive experimental campaign was conducted to characterize the transient runback behaviors of wind-driven water droplets over the surfaces of test plates coated with different hydro-/icephobic coatings (i.e., SHS, SLIPS and PDMS). A high-resolution Particle Image Velocimetry (PIV) system was used to achieve quantitative measurements of the velocity field of the airflow around the wind-driven water droplets on the test surfaces with different wettabilities. With the detailed PIV measurements of the airflow field around the runback water droplets and the droplet profiles, the aerodynamic forces and the adhesion forces acting on the water droplets were estimated. While Fig. 1 shows the experimental setup used in the present study, Fig. 2 to Fig. 3 given some of the typical measurement results. More measurement results and comprehensive analysis and discussions will be provided in the full version of this research paper.

Immobilizing a Drop of Water: Fabricating Highly Hydrophobic Surfaces that Pin Water Droplets

Nano Letters ◽  
2008 ◽  
Vol 8 (4) ◽  
pp. 1241-1245 ◽  
Author(s):  
Adam Winkleman ◽  
Gilad Gotesman ◽  
Alexander Yoffe ◽  
Ron Naaman
Keyword(s):  
Water Droplets ◽  
Hydrophobic Surfaces ◽  
Highly Hydrophobic

Dynamics of water droplets detached from porous surfaces of relevance to PEM fuel cells

2006 ◽  
Vol 300 (2) ◽  
pp. 673-687 ◽  
Author(s):  
A. Theodorakakos ◽  
T. Ous ◽  
M. Gavaises ◽  
J.M. Nouri ◽  
N. Nikolopoulos ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Pem Fuel Cells ◽  
Water Droplets ◽  
Porous Surfaces

Characterization of carbides in M50NiL

1991 ◽  
Vol 49 ◽  
pp. 606-607
Author(s):  
L. S. Lin ◽  
K. P. Gumz ◽  
A. V. Karg ◽  
C. C. Law
Keyword(s):  
Temperature Effects ◽  
Base Composition ◽  
Lattice Parameter ◽  
Control Surface ◽  
Carbide Formation ◽  
Particle Sizes ◽  
Low Carbon ◽  
Fee Structure ◽  
Heat Treated

Carbon and temperature effects on carbide formation in the carburized zone of M50NiL are of great importance because they can be used to control surface properties of bearings. A series of homogeneous alloys (with M50NiL as base composition) containing various levels of carbon in the range of 0.15% to 1.5% (in wt.%) and heat treated at temperatures between 650°C to 1100°C were selected for characterizations. Eleven samples were chosen for carbide characterization and chemical analysis and their identifications are listed in Table 1.Five different carbides consisting of M6C, M2C, M7C3 and M23C6 were found in all eleven samples examined as shown in Table 1. M6C carbides (with least carbon) were found to be the major carbide in low carbon alloys (<0.3% C) and their amounts decreased as the carbon content increased. In sample C (0.3% C), most particles (95%) encountered were M6C carbide with a particle sizes range between 0.05 to 0.25 um. The M6C carbide are enriched in both Mo and Fe and have a fee structure with lattice parameter a=1.105 nm (Figure 1).

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