Superhydrophobic coating deposition

Figure 8. PM-RAIRS andXPS (inset) of superhydrophobic coatings deposited with scanning CF4/H2/He plasma (rf power = 300 W). The number of plasma treatments is indicated in the figure. (9)...

Figure 5. Optical images of water droplets ( 2 mm diameter) on a superhydrophobic coating deposited on (a) gold film, (b) Si wafer, (c) Kimwipe tissue and (d) cotton (reprinted with permission from American Chemical Society [36]).

For deposition of hydrophobic coatings, a mixture of CHVHe gases was used in the plasma. Superhydrophobic coatings were created with a Cp4/H2/He plasma. The deposited coatings were analyzed with PM-RAIRS, x-ray photoelectron spectroscopy, scanning electron microscopy (SEM, JEOL 6700 F - FESEM), atomicforce microscopy (AFM, Molecular Imaging SPM microscope with RHK controllers), ellipsometiy, and water contact angle measurements. 

Figure 8.13 (a) Morphology of the carbonaceous superhydrophobic surface deposited on wax-polymer blend coatings after sonication for 20 seconds in an ultrasonic bath. 

Lee, J.-H., Lee, S.H., Kim, D., Park,Y.S., 2013a. The structural and surface properties of carbon nanotube synthesized by microwave plasma chemical vapor deposition method for superhydrophobic coating.Thin Solid Films 546, 94. 

Figure 3 (A) Illustration of the fabrication of a highly compressible and stretchable superhydrophobic coating on polyurethane sponge through layer-by-layer deposition. (B) SEM images of the superhydrophobic coating after compression for (a) 1000 cycles, (b) 2000 cycles, (c) 3000 cycles, and (d) 4000 cycles. Reproduced from Liu etal. (2014) by permission of The Royal Society of Chemistry.

Another widely used approach in this area is a sol-gel process. In order to create surface roughness after deposition of thin films, a secondary component is included in the sol-gel deposition process which can be removed later by dissolution in hot water or sublimation. The removal of the secondary components gives porous structures. Subsequent lluorinated silane coating can render these sol-gel processed films superhydrophobic [81-83]. Microporous structures can be created through phase separation of organic polymer solutions and then used as a template for sol-gel processing of porous silica substrates. Ruorosilane treatment of these substrates produces superhydrophobic surfaces [84]. 

A number of reports have described theoretical calculations for superhydrophobic surfaces. Marmur [10] and Quere and co-workers [11,12] show the theoretical background for surface roughness. There are also many reports regarding creation of superhydrophobic surfaces using hthography [13], fractal structure of wax [14], chemical vapor deposition (CVD) of poly(tetrafluoroethylene) (PITH) [15] carbon nanotubes and web-like structures [16-18] and by coating hydrophobic silanes onto aluminum acetylacetonate [19] and so on. These micro-structured surfaces show a decrease in apparent surface free energies. 

The surface depicted in Figs 2 and 3 demonstrates distinct superhydrophobic property. The APCA was determined as (150 5)°. The drop deposited on the two-scaled relief coated with chromium is depicted in Fig. 4. 

The superhydrophobic surfaces were prepared by a dip coating procedure described elsewhere [18], based on the deposition of a silica particle/fluorinated FC735 (Acota... 

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