ANALYSIS OF THE INFLUENCE OF SURFACE ROUGHNESS AND NANOPARTICLE CONCENTRATION ON THE CONTACT ANGLE
Igor Seicho Kiyomura1; Francisco Nascimento2; Alex Cunha1; Elaine Maria Cardoso1
1 UNESP - University Estadual Paulista; 2 USP - University of são Paulo
doi:10.20906/CPS/COB-2015-1550
Resumo
In the past few years, the scientific community has been researching the effects of the promising interaction between high thermal conductivity nanoparticles and a base fluid, the so-called nanofluids, first presented by Choi (1995). These nanoparticles of metals or metal oxides, diluted in base fluid, are used to enhance the heat transfer properties of a fluid and are currently being employed in different areas, in particular, microelectronics and microcooling for producing compact and miniaturized equipment. Nanofluids, in the boiling process, can modify the characteristics of the heating surface and the physical properties of the base fluids, interfering directly on the mechanisms of formation and detachment of vapor bubbles. Thus, some issues must be better understood such as the role of nanoparticle deposition on the wettability and how to control the deposition process, before applying this technique in macro and micro scales devices. In this study, the effect of surface roughness and nanoparticle concentration on the contact angle was analyzed. The tests were carried out on copper surfaces with different roughness values, corresponding to a smooth surface (polished using an aluminum-oxide abrasive compound, corresponding to Ra = 0.03 µm) and a rough surface (polished using #600 emery paper, corresponding to Ra = 0.16 µm). The nanostructures were produced by maghemite nanoparticle deposition, with different mass concentration (0.29 and 2.9 g/l), via the evaporation process of Fe2O3-deionized water nanofluid. After the deposition process, the surfaces were submitted to metallographic, roughness, and wettability analysis. This paper mainly focuses on the variation of contact angle and wettability, due to the microstructural change caused by the roughness and nanoparticle deposition process.
Palavras-chave: Nanofluids; nanostructured surfaces; contact angle; wettability; roughness