This study surveyed the amount of dissolved aluminum, reflectance of aluminum surfaces, and thicknesses of the anodic oxide films after electropolishing under conditions of several solution temperatures and current densities. Based on results obtained when phosphoric-sulfuric acids were used on pure aluminum A1050, we assessed electropolishing effects on surface structures and specular glosses. Results show the optimum conditions for electropolishing of pure aluminum: current density at 60 °C that is greater than 0.113 A/cm2 and greater than 0.151 A/cm2 at 80 °C. Moreover, electropolishing of pure aluminum with current density 0.151 A/cm2 at 80 °C can provide flat, smooth surfaces having both high reflectance and specular gloss, creating almost no anodic film.
The relationship between the activation energy, crystallinity, and morphology of UV-irradiated multi-walled carbon nanotubes (MWCNTs) was systematically investigated. Using total UV energy as an index, MWCNTs were irradiated with ultraviolet light at 254 nm and 185 nm. The activation energy of the MWCNTs was 320 kJ/mol prior to irradiation and 154 kJ/mol after irradiation with 16174 J/cm2 of total UV energy. In addition, the value of the IG/ID ratio for the MWCNTs was 7.12 prior to irradiation and 3.63 after irradiation with 16174 J/cm2 of total UV energy. Transmission electron microscopy (TEM) observations showed that the outer layers of the MWCNTs were increasingly etched away and the linearity of the graphite layer was lost as the total UV energy increased. In addition, when the total UV energy exceeded 10856 J/cm2, the hollow structure of the MWCNTs was completely lost. It was therefore found that, as the energy of the incident ultraviolet light increases, the activation energy of MWCNTs decreases, the crystallinity deteriorates, and the morphology changes. Furthermore, it was demonstrated that the level of total UV energy exposure can be used as an indicator of the morphology, activation energy, and crystallinity of UV-irradiated MWCNTs.
To develop a safe and environmentally friendly passivation treatment, the pitting resistance of Type 304 stainless steels, which were finished with different polishing methods and then passivated in H2O2 solutions under various conditions, were examined by measuring their pitting potentials in deaerated 3.5 %NaCl. Results show that pitting potentials were strongly dependent on the surface polishing conditions. A remarkable increase in pitting potential was attained on an electro-polished surface. The highest resistance to pitting was obtained on a surface treated in 3.5 %H2O2 at 25 °C for 2 h. The steels treated under this condition showed extremely high pitting potential of 1075 mV(vs. Ag/AgCl(sat. KCl)) in 3.5 %NaCl, but they showed no change in pitting potential after immersion in aerated 3.5 %NaCl for 100 d.