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davidqg123
gmail.comName (Japanese)
Quintero GiraldoName (Kana)
David AlbertoName
202201012646033780
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- David Quintero, Hisato Matsuya, Mana Iwai, Sho Kitano, Koji Fushimi, Hiroki HabazakiACS Applied Materials & Interfaces 16 (1) 1737 - 1748 1944-8244 2024/01/10Aluminum solid polymer capacitors are promising devices for the increased demand for power electronics applications. Nonetheless, the low breakdown voltage of commercially available catalysts (∼100 V) limits their applications. In this study, a hydroxide-film-covered high-purity aluminum was anodized at 700 V in boric acid at 85 °C, and the effect of a second hot water immersion (posthydration treatment) after anodizing on the breakdown voltage was studied as a possible future treatment to enhance the withstand voltages of solid electrolytic capacitors. The dielectric breakdown voltage of the anodized aluminum with a PEDOT:PSS coating was ∼500 V, being ∼200 V less than the anodizing voltage; however, the dielectric breakdown voltage was increased above 700 V by introducing the posthydration treatment due to the formation of a nanovoid layer above the dielectric alumina film. Our research suggests that the highly dispersed nanovoids incorporated with PEDOT:PSS avoid the current concentration at some local regions, effectively increasing the dielectric breakdown voltage. The posthydration treatment increased the leakage current by introducing physical defects in the dielectric film. However, the leakage current was reduced by a voltage sweep below the breakdown voltage after the PEDOT:PSS coating or a second anodizing process before the coating, keeping the breakdown voltage above 600 V. A promising processing route to obtain aluminum solid capacitors with high withstand voltage (600 V) found in our research is, first, dipping in hot water; second, anodizing at 700 V; then a second hot water treatment; and a second anodizing at 400 V, which keeps the capacitance invariable with a breakdown voltage enhanced.
- Quintero, D., G{\'o}mez, M.A., Casta{\~n}o, J.G., Tsuji, E., Aoki, Y., Echeverr{\'i}a, F., Habazaki, H.Surface and Coatings Technology 310 180 - 189 0257-8972 2017Spark anodizing of Ti6Al4V alloy has been performed in alkaline electrolytes containing aluminate to form wear-resistant coatings. Coatings obtained under potentiostatic conditions exhibit a better wear resistance, with a wear rate approx. 10 times lower than galvanostatic coatings, due to the formation of coatings with low porosity since potentiostatic mode controls the size of the micro-discharges. The coatings consist mainly of γ - Al2O3, whilst Al2TiO5 is present in minor proportions. For some coatings, the formation of Al6KO9.5 is observed due to the incorporation of potassium into the coating. EDS analysis shows that aluminum is the main constituent of the coatings, being mainly incorporated from the anodizing solution and homogeneously distributed into the coating. A decrease in pore density between 15 and 30% and roughness reduction of 10 to 60% was obtained with KOH and Na2WO4 additions, improving the coating wear resistance in pin-on-disc wear tests, especially by Na2WO4 addition.
- Osseointegration improvement by plasma electrolytic oxidation of modified titanium alloys surfacesDavid Alberto Quintero GiraldoJournal of materials science 2015/02/25
- Galvis, O.A., Quintero, D., Casta{\~n}o, J.G., Liu, H., Thompson, G.E., Skeldon, P., Echeverr{\'i}a, F.Surface and Coatings Technology 269 (1) 2015
- Quintero, D., Galvis, O., Calder{\'o}n, J.A., G{\'o}mez, M.A., Casta{\~n}o, J.G., Echeverr{\'i}a, F., Habazaki, H.Surface and Coatings Technology 283 210 - 222 0257-8972 2015Spark anodizing on Ti6Al4V has been performed in three alkaline solutions using different electrical parameters in order to study the coating formation. The surface features showa dependence on the shape and distribution of the electric microdischarges. In addition, the surface features and the chemical composition of the coatings are dependent on the anodizing solution employed. The tribological properties of the coatings formed are correlated with the morphology and the internal structure of the coatings. The variation of the internal structure of the coatings was evidenced by EIS analysis. Results indicate that it is possible to control the physical properties of the anodic film by an adequate selection of the process parameters. A porous structure is obtained using a solution mainly composed of hypophosphite, which exhibits a good tribological performance. Low porosity and compact structure can be obtained in the anodic film by using an anodizing solution composed of hypophosphite and metasilicate furthermore, these coatings exhibit a good corrosion protection. Highly porous structure is achieved by using an anodizing solution composed of hypophosphite and sulfate. The best wear resistances were observed in coatings formed at potentiostatic mode, as demonstrated by the results of ball-on-disc wear tests.
- Quintero, D., Galvis, O., Calder{\'o}n, J.A., Casta{\~n}o, J.G., Echeverr{\'i}a, F.Surface and Coatings Technology 258 2014