Browsing by Author "Motasim, M."

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Citation - WoS: 5
Citation - Scopus: 6
The Influence of Sodium Fluoride on the Dissolution Kinetics of Metallic Titanium in Citric Acid Solution Using the Rotating Disc Method
(Elsevier B.V., 2024) Motasim, M.; Aydoğan, S.; Agacayak, T.; Eker, Y.R.; El-gak, A.; Seifelnassr, A.A.S.
This study reports the effect of sodium fluoride on the dissolution kinetics of pure metallic titanium in a citric acid solution. The effects of sodium fluoride concentration, citric acid concentration, temperature, stirring speed, and disc surface area were examined. The dissolution rate of titanium increases strongly with increasing citric acid and sodium fluoride concentrations. Fluoride ions react with hydrogen ions to form hydrofluoric acid, which removes the passive layer of titanium dioxide. An increase in the concentration of NaF and acid causes the formation of a brown layer on the surface of titanium. X-ray diffraction and SEM-EDX analyses showed that the layer composition is mostly of titanium fluoride (TiF3) and titanium fluoride oxide (TiOF2). A mixed kinetic model with an activation energy of 26.4 kJ/mol can be used to explain the reaction kinetics. © 2024 Elsevier B.V.
Citation - WoS: 5
Citation - Scopus: 5
Rotating Disc Method To Study the Dissolution Kinetics of Copper Metal in Citric Acid and Hydrogen Peroxide
(Elsevier B.V., 2024) Motasim, M.; Aydoğan, S.; Ali, B.; Agacayak, T.
This study reports the kinetics of copper metal dissolution in citric acid-hydrogen peroxide solution using the rotating disc method. The effect of the concentration of citric acid as well as hydrogen peroxide, stirring speed, disc surface area, and temperature was investigated. The concentration of hydrogen peroxide (0.25–1.5 mol/L) has a strong effect on the dissolution rate (mg/min) of copper with a reaction order of 0.92, compared to a reaction order of 0.42 with respect to the concentration of citric acid (0.125–1.5 mol/L). The reaction rate is directly proportional to the disc area (A) and square root of the disc rotation speed (ω1/2), as expected from the Levich equation. The activation energy of 33 kJ/mol, in the temperature range 30-60 °C is also comparable with the values reported in previous studies. © 2024 Elsevier B.V.