A. Ghahremaninezhad

In Situ Electrochemical Analysis of Surface Layers on a Pyrrhotite Electrode in Hydrochloric Acid Solution

The present study considers the electrochemical dissolution of pyrrhotite electrodes in 1 M HCl solution. Conventional electrochemical techniques as well as electrochemical impedance spectroscopy (EIS) and in situ Mott-Schottky analysis have been applied for surface studies during the anodic dissolution of the electrode. EIS results showed the formation of two distinct surface layers on the electrode. The first layer forms during sample preparation and is stable up to around 600 mV vs saturated calomel electrode (SCE). The second layer starts to form at high anodic potentials (>670 mV vs SCE). Electrochemically active dissolution of the pyrrhotite occurs between the formation potential of the two surface layers (600-670 mV vs SCE). Mott-Schottky plots showed that both of the layers are n-type semiconductors with quite different donor densities. Moreover, the second surface layer is less conductive than the first and thus hinders the dissolution current more effectively. Three different equivalent electrochemical circuits were modeled for different dissolution potential ranges and the model regression results was compared to the experimental results of the EIS.

Electrochemical and corrosion behaviour of stainless steels 316L and 317L in chloridised ammonium sulphate solution

Abstract The corrosion of stainless steel alloys 316L and 317L in chloridised ammonium sulphate solution at 100°C and varying pH was investigated. Alloy 316L was found to be an adequate material for use in naturally aerated solution within the pH range of 5·4–7·4. At low potentials (<0·23 V) and a high potential (0·75 V), alloy 317L shows better performance. It also exhibits better pitting resistance at high potential, however, in the potential range of 0·23–0·45 V, alloy 316L shows better corrosion resistance. The dissolution of the Mo oxide species is proposed to be the reason for the weak performance of alloy 317L in the potential range of 0·23–0·45 V. On a examiné la corrosion des aciers inoxydables 316L et 317L dans une solution chlorée de sulfate d’ammonium à 100°C et à pH variable. On a trouvé que l’alliage 316L était un matériel adéquat pour utilisation dans une solution aérée naturellement dans la gamme de pH de 5·4 à 7·4. Aux faibles potentiels (<0·23 V) et à potentiel élevé (0·75 V), l’alliage 317L montrait une meilleure performance. Il exhibait également une meilleure résistance à la corrosion par piqûres à potentiel élevé. Cependant, dans la gamme de potentiel de 0·23–0·45 V, l’alliage 316L montrait une meilleure résistance à la corrosion. On propose la dissolution d’une espèce d’oxyde de Mo comme étant la raison pour la faible performance de l’alliage 317L dans la gamme de potentiel de 0·23–0·45 V.

The Pt/Ni Modified TiO2 Nanotubes and its Catalytic Activity Toward Glucose

The catalytic activity of Pt/Ni/TiO2 nanotubes electrode toward glucose has been studied. Fabrication of Pt/Ni nanostructures was done in a single-bath solution through electrochemical pulse method by changing the deposition potential between -0.3 and -4 V vs. SCE, respectively. The resulting modified electrode represented high conductivity due to the effective presence of metallic components and uniform surface area caused by dispersion of Pt and Ni nanostructures. The scanning electron microscopy images also confirmed that a large amount of metals colonies were well-dispersed at the edge of the TiO2 nanotubes. In addition, the Pt/Ni TiO2 nanotubes modified electrode exhibited an excellent performance in cyclic voltammetry results by changing the concentration of glucose. The proposed electrode had a wide linear range up to 13 mM with the detection sensitivity of 230 μAmM−1 cm−2 respectively. The experiment results also revealed that the electrode exhibited good selectivity with no interference from other oxidable species.

GROWTH BEHAVIOR OF THE ELECTRODEPOSITED Co-Ni ALLOY NANOWIRES

The Co-Ni alloy nanowires were electrodeposited into porous anodic aluminum oxide (AAO) templates. At the first, highly ordered AAO templates were synthesized by two-step anodizing of aluminum to increase pore ordering. Arrays of nanowires with diameter about 30 nm and length about 5000 nm were electrodeposited by alternating current. The composition and structure property of nanowires were investigated by EDX, SEM and TEM techniques. It was found that nanowire composition was related to ions concentration in solution and it was shown that at the optimum potential range of electrodeposition (17-19 V), a change at the potential was shown no strong effect on chemical composition of nanowires. It was observed that nano pores were filled continuously and so nanowires were dense with uniform composition in nanowire length.