Energy-efficient condensation of steam contained in atmospheric air has emerged as a solution to the water scarcity. Academic and industrial research works that seeks to develop water collection devices with high efficiency has great relevance for the scientific community. In this work, we aim to show that modified carbon nanotubes forest can remove the condensed drops easier than a hydrophobic and a super-hydrophilic surface. In addition, this result was reached at high super saturation level which is an innovative aspect of this work. The Vertically Aligned Carbon Nanotubes (VACNTs) were grown on steel pipes. We used a CO2 laser and an O2 plasma to perform the post treatments that changed the CNTs to super-hydrophobic and super-hydrophilic, respectively. In addition, the CO2 laser treatment added a second level of roughness in the surface by etching the nanotubes walls. A polyethylene coating attached the carbon nanotubes to the substrate. We experimentally demonstrated a 24% higher vapor condensation rate at high supersaturations levels.
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Coatings are used to promote the thermal protection of metal alloys. In the aeronautical industry, the coatings used to protect the turbine blades are called Thermal Barrier Coatings (TBC). The use of NiCrAlY is an alternative as a bonding layer in coatings for turbine blades and it is possible to increase its useful life. This work aims to study the metallurgical bond between the 316-stainless steel substrate and the NiCrAlY coating which was sprayed through the High-Velocity Oxygen-Fuel (HVOF) and after irradiated by a CO2 laser beam with power of 125 W and speed of 50 mm/s. The samples were characterized by scanning electron microscopy (SEM) and the semi-quantitative analysis energy dispersive spectroscopic (EDX) showed that the chemical composition of the coating and the substrate have maintained its original stoichiometry. The line scan analysis is a technique of the EDX to analyze the diffusion between the main chemical elements of 316 steel and NiCrAlY and X-ray diffraction by identifying the alumina AL2O3 phases on the sample surface and the results showed the metallurgical bond between substrate and coating.
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