Researches about nanomaterials related to properties such as superhydrophobicity, self-cleaning, corrosion and scratching resistance can be directly related to the materials' wettability. This characteristic is quantified by the contact angle made between the surface and a water droplet, in which angles above 90 degrees are considered to be hydrophobic and those above 150 degrees, superhydrophobic. The focus of this work was the development of a superhydrophobic self-cleaning surface, using silica nanoparticles with a particle diameter around 400 nm to 800 nm (produced via sol-gel, referring to the classic Stöber method) functionalized with perfluorooctyltriethoxysilane (POTS) on a polymeric substrate polymethyl methacrylate (PMMA). Four different surface treatment conditions were analyzed: untreated, treated with non-functionalized silica nanoparticles, treated only with POTS and treated with silica nanoparticles functionalized with POTS. For this last condition, a static water contact angle of (150.0 ± 0.44) degrees and a dynamic water contact angle of (7.5 ± 0.38) degrees were obtained, which is a typical value of a superhydrophobic surface. However, the surface treated with POTS alone had a contact angle of 115 degrees. The high contact angle value was due to the low surface energy obtained, which was of (1.45 ± 0.02) dyn/cm. The modified superhydrophobic surface revealed a superior self-cleaning performance by freely rolling spherical water drops on the non-wettable solid surface. The stability of the modified surface has been proven by water jet impact.

This work aims to study the influence of cutting parameters (cutting speed, feed rate, cutting depth and tool cutting edge angle) regarding surface roughness and burr formation during the milling of a mixed structure comprised of titanium and carbon fiber (stack). The parameters were varied from maximum to minimum, just as the tool cutting edge angle of the insert, through a full factorial design with 32 trials. The analyses were performed by measuring the surface roughness and burr size along with metallographic analyses through optic microscopy and scanning electron microscopy. The results showed that the surface roughness was higher for carbon fiber and burr size was higher for titanium. There were a number of tests with delamination of the carbon fiber, and the best cutting parameters to minimize surface roughness and burr formation were tool cutting edge angle of 45º, a feed rate of 0.028 mm/tooth, cutting depth equal to 0.26 mm and cutting speed equal to 150 m/min.

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