Lotus leaves are a typical example of superhydrophobic surface. Numerous studies have confirmed that surface morphology possessing micro-and nanoscale roughness along with a low surface energy material coating leads to apparent water contact angle (WCA) >1508. In nuclear power plants, modified 9Cr-1Mo ferritic steel is the favoured steam generator tubing material. During transit, storage and installation, SHP surface on modified 9Cr-1Mo ferritic steel can impart good corrosion resistance to retain the integrity of the specimen during operation. In this study, SHP surface of modified 9Cr-1Mo ferritic steel with a WCA of 150¡18 was successfully achieved by polishing, etching, perfluoro octyl triethoxy silane coating and baking. The WCA and contact angle hysteresis were measured. The surface morphology and the composition were characterised by atomic force microscopy and attenuated total reflection-infrared spectroscopy respectively. Superhydrophobicity and its related theories are also discussed in this paper.
Nanocrystalline CdS thin films have been prepared by the sol-gel spin-coating method. The influence of spin-coating process parameters such as, thiourea concentration (U), annealing temperature (A), rotational speed (S), and annealing time (T), and so on, on the properties of the prepared films have been studied. The experiments have been carried out based on four factor-five-level central composite designs with the full replication technique, and mathematical models have been developed using regression technique. The central composite rotatable design has been used to minimize the number of experimental parameters. The analysis of variance technique is applied to check the validity of the developed models. The developed mathematical model can be used effectively to predict the particle size in CdS nanocrystalline thin films at 95 pct confidence level. The results have been verified by depositing the films using the same condition. An ultraviolet-visible optical spectroscopy study was carried out to determine the band gap of the CdS nanocrystalline thin films. The band gap has been observed to depend strongly on particle size, and it indicated a blue shift caused by quantum confinement effects. The high-resolution transmission electron microscopy analysis showed the grain size of the prepared CdS film to be 6 nm. The main and interaction effects of deposition parameters on the properties of CdS nanocrystalline thin films also have been studied.
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