Due to peculiar properties like thermal and electrical conductivity, alloyability, malleability and so on, copper is widely used as reference material for a great number of industrial components, such as heating/cooling devices and electronics. When copper is in contact with a water flow, it could become crucial to control its surface wetting properties to enhance efficiency in such devices. With this aim, copper surfaces were functionalized by deposition of hybrid, nanostructured layers to achieve advanced water repellence, e.g. superhydrophobicity. First, alumina nanoparticles obtained by sol-gel routes were deposited to form a thin gel layer, which, after treatment in boiling water, turned into a nanostructured boehmite coating with a peculiar flower-like morphology. Two sol-gel syntheses of Al2O3 nanoparticles were attempted, namely in water and in isopropyl alcohol. This latter revealed to be able to provide a better organized nanostructured coating with higher superhydrophobicity after chemical grafting of a fluoroalkylsilane moieties with respect to the water-based one. The further analyses of XPS spectra confirmed these circumstances. Moreover, the effect of thermal treatment temperature on surface morphology were also evaluated. After formation of the gel film, the surfaces were heat-treated at either 200, 300 or 400°C. SEM investigations showed that flower-like boehmite prevailed when T <= 300°C, while at T = 400°C CuO microwires grew, displacing boehmite itself. Even though all coated samples displayed superhydrophobic behavior, the 400°C-treated surface was extremely brittle, while the 200°C-treated sample could perfectly withstand ultrasonic treatment with no loss in superhydrophobicity. These results suggest that it is necessary to strictly control both the synthesis of coatings precursors and the processing variables when copper surfaces modifications leading to advanced water repellence have to be designed.
Sol-gel routes in different media to obtain nanostructured, superhydrophobic coatings on copper surface
Veronesi Federico;Raimondo Mariarosa;Blosi Magda;Boveri Giulio;
2017
Abstract
Due to peculiar properties like thermal and electrical conductivity, alloyability, malleability and so on, copper is widely used as reference material for a great number of industrial components, such as heating/cooling devices and electronics. When copper is in contact with a water flow, it could become crucial to control its surface wetting properties to enhance efficiency in such devices. With this aim, copper surfaces were functionalized by deposition of hybrid, nanostructured layers to achieve advanced water repellence, e.g. superhydrophobicity. First, alumina nanoparticles obtained by sol-gel routes were deposited to form a thin gel layer, which, after treatment in boiling water, turned into a nanostructured boehmite coating with a peculiar flower-like morphology. Two sol-gel syntheses of Al2O3 nanoparticles were attempted, namely in water and in isopropyl alcohol. This latter revealed to be able to provide a better organized nanostructured coating with higher superhydrophobicity after chemical grafting of a fluoroalkylsilane moieties with respect to the water-based one. The further analyses of XPS spectra confirmed these circumstances. Moreover, the effect of thermal treatment temperature on surface morphology were also evaluated. After formation of the gel film, the surfaces were heat-treated at either 200, 300 or 400°C. SEM investigations showed that flower-like boehmite prevailed when T <= 300°C, while at T = 400°C CuO microwires grew, displacing boehmite itself. Even though all coated samples displayed superhydrophobic behavior, the 400°C-treated surface was extremely brittle, while the 200°C-treated sample could perfectly withstand ultrasonic treatment with no loss in superhydrophobicity. These results suggest that it is necessary to strictly control both the synthesis of coatings precursors and the processing variables when copper surfaces modifications leading to advanced water repellence have to be designed.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
