Pupak Amini | AmirKabir University Of Technology (original) (raw)
Papers by Pupak Amini
Journal of The Electrochemical Society
Two aspects of vanadium flow batteries are reviewed: electrochemical kinetics on carbon electrode... more Two aspects of vanadium flow batteries are reviewed: electrochemical kinetics on carbon electrodes and positive electrolyte stability. There is poor agreement between reported values of kinetic parameters; however, most authors report that kinetic rates are faster for VIV/VV than for VII/VIII. Cycling the electrode potential increases the rates of both reactions initially due to roughening but when no further roughening is observed, the VII/VIII and VIV/VV reactions are affected oppositely by the pretreatment potential. Anodic pretreatment activates the electrode for the VII/VIII reaction, and deactivates it for VIV/VV. Three states of the carbon surface are suggested: reduced and oxidized states R and O, respectively, both with low electrocatalytic activity, and an intermediate state M with higher activity. The role of surface functional groups and the mechanisms of electron transfer for the VII/VIII and VIV/VV reactions are still not well understood. The induction time for precipi...
ECS Transactions
The electrochemical kinetics of the VII/VIII redox reaction on carbon electrodes is enhanced by a... more The electrochemical kinetics of the VII/VIII redox reaction on carbon electrodes is enhanced by anodic treatment of the electrode and inhibited by cathodic treatment. Contrastingly, the kinetics of the VIV/VV redox reaction is inhibited by anodic treatment of the electrode and enhanced by cathodic treatment. The observed effects are attributed to oxygen-containing species on the surface of carbon electrodes and it is likely that enhancement of both VII/VIII and VIV/VV occurs on the same (meso) state of the electrode. Oxidation of this active meso state leads to inhibition of VIV/VV while reduction of the active meso state leads to inhibition of VII/VIII.We have investigated the thermal stability of VFB catholytes using a standard methodology. The induction time for precipitation of V2O5 decreases exponentially with increasing temperature or VV concentration but increases exponentially with increasing sulphate concentration. Arrhenius plots show two linear regimes, at 45–70 °C and 30...
Applied Surface Science, 2012
Commercially pure titanium samples were exposed to grit blasting and acid-alkali treatments to ob... more Commercially pure titanium samples were exposed to grit blasting and acid-alkali treatments to obtain a variety of surface compositions and morphologies. Contact roughness test and microstructural studies were employed to study the surface topography of the samples. The nature and chemical composition of surface phases were evaluated using X-ray diffraction and microanalysis techniques. Selected samples first exposed to in vitro environment were then tested to determine the surface morphology and surface microstructure. Based on the data presented in this work, it is suggested that grit blasting process utilized prior to chemical treatment stage, yields a high quality surface morphology. Such a surface morphology is expected to have superior tribological characteristics after osseointegration. Also, it appeared that the reverse sequence of processing resulted in a better biocompatibility of the product manifested by negligible amount of residual alumina on the sample surface.
Carburizing of stainless steels at low temperatures (below 500°C) develops a high content car... more Carburizing of stainless steels at low temperatures (below 500°C) develops a high content carbon layer, known for its high hardness. X-ray Diffraction investigation indicates that carburization treatment does not impact the structure of substrate; however, introduced carbon causes expansion in the carburized layer through the increase in d-spacing. Characterization of carbon concentration and hardness profiles indicate that carbon content gradually decreases while moving further into the substrate; and the origin of the increased hardness of the expanded layer arises from the super-saturated carbon content, following the solid solution strengthening theory. An area that is not well understood is in regard to the carburized layer’s relation to the substrate and the significance in their differences. Using two grades of stainless steel, AISI 316L and PH 17-4, it was observed that the carburized layer is not a separate layer, but a higher carbon content version of the substrate,
Carburizing of stainless steels at low temperatures (below 500°C) develops a high content carbon ... more Carburizing of stainless steels at low temperatures (below 500°C) develops a high content carbon layer, known for its high hardness. X-ray Diffraction investigation indicates that carburization treatment does not impact the structure of substrate; however, introduced carbon causes expansion in the carburized layer through the increase in d-spacing. Characterization of carbon concentration and hardness profiles indicate that carbon content gradually decreases while moving further into the substrate; and the origin of the increased hardness of the expanded layer arises from the super-saturated carbon content, following the solid solution strengthening theory. An area that is not well understood is in regard to the carburized layer's relation to the substrate and the significance in their differences. Using two grades of stainless steel, AISI 316L and PH 17-4, it was observed that the carburized layer is not a separate layer, but a higher carbon content version of the substrate.
Metallurgical and Materials Transactions A, 2014
ABSTRACT
Commercially pure titanium samples were exposed to grit blasting and acid–alkali treatments to ob... more Commercially pure titanium samples were exposed to grit blasting and acid–alkali treatments to obtain a variety of surface compositions and morphologies. Contact roughness test and microstructural studies were employed to study the surface topography of the samples. The nature and chemical composition of surface phases were evaluated using X-ray diffraction and microanalysis techniques. Selected samples first exposed to in vitro environment were then tested to determine the surface morphology and surface microstructure. Based on the data presented in this work, it is suggested that grit blasting process utilized prior to chemical treatment stage, yields a high quality surface morphology. Such a surface morphology is expected to have superior tribological characteristics after osseointegration. Also, it appeared that the reverse sequence of processing resulted in a better biocompatibility of the product manifested by negligible amount of residual alumina on the sample surface.
Journal of The Electrochemical Society
Two aspects of vanadium flow batteries are reviewed: electrochemical kinetics on carbon electrode... more Two aspects of vanadium flow batteries are reviewed: electrochemical kinetics on carbon electrodes and positive electrolyte stability. There is poor agreement between reported values of kinetic parameters; however, most authors report that kinetic rates are faster for VIV/VV than for VII/VIII. Cycling the electrode potential increases the rates of both reactions initially due to roughening but when no further roughening is observed, the VII/VIII and VIV/VV reactions are affected oppositely by the pretreatment potential. Anodic pretreatment activates the electrode for the VII/VIII reaction, and deactivates it for VIV/VV. Three states of the carbon surface are suggested: reduced and oxidized states R and O, respectively, both with low electrocatalytic activity, and an intermediate state M with higher activity. The role of surface functional groups and the mechanisms of electron transfer for the VII/VIII and VIV/VV reactions are still not well understood. The induction time for precipi...
ECS Transactions
The electrochemical kinetics of the VII/VIII redox reaction on carbon electrodes is enhanced by a... more The electrochemical kinetics of the VII/VIII redox reaction on carbon electrodes is enhanced by anodic treatment of the electrode and inhibited by cathodic treatment. Contrastingly, the kinetics of the VIV/VV redox reaction is inhibited by anodic treatment of the electrode and enhanced by cathodic treatment. The observed effects are attributed to oxygen-containing species on the surface of carbon electrodes and it is likely that enhancement of both VII/VIII and VIV/VV occurs on the same (meso) state of the electrode. Oxidation of this active meso state leads to inhibition of VIV/VV while reduction of the active meso state leads to inhibition of VII/VIII.We have investigated the thermal stability of VFB catholytes using a standard methodology. The induction time for precipitation of V2O5 decreases exponentially with increasing temperature or VV concentration but increases exponentially with increasing sulphate concentration. Arrhenius plots show two linear regimes, at 45–70 °C and 30...
Applied Surface Science, 2012
Commercially pure titanium samples were exposed to grit blasting and acid-alkali treatments to ob... more Commercially pure titanium samples were exposed to grit blasting and acid-alkali treatments to obtain a variety of surface compositions and morphologies. Contact roughness test and microstructural studies were employed to study the surface topography of the samples. The nature and chemical composition of surface phases were evaluated using X-ray diffraction and microanalysis techniques. Selected samples first exposed to in vitro environment were then tested to determine the surface morphology and surface microstructure. Based on the data presented in this work, it is suggested that grit blasting process utilized prior to chemical treatment stage, yields a high quality surface morphology. Such a surface morphology is expected to have superior tribological characteristics after osseointegration. Also, it appeared that the reverse sequence of processing resulted in a better biocompatibility of the product manifested by negligible amount of residual alumina on the sample surface.
Carburizing of stainless steels at low temperatures (below 500°C) develops a high content car... more Carburizing of stainless steels at low temperatures (below 500°C) develops a high content carbon layer, known for its high hardness. X-ray Diffraction investigation indicates that carburization treatment does not impact the structure of substrate; however, introduced carbon causes expansion in the carburized layer through the increase in d-spacing. Characterization of carbon concentration and hardness profiles indicate that carbon content gradually decreases while moving further into the substrate; and the origin of the increased hardness of the expanded layer arises from the super-saturated carbon content, following the solid solution strengthening theory. An area that is not well understood is in regard to the carburized layer’s relation to the substrate and the significance in their differences. Using two grades of stainless steel, AISI 316L and PH 17-4, it was observed that the carburized layer is not a separate layer, but a higher carbon content version of the substrate,
Carburizing of stainless steels at low temperatures (below 500°C) develops a high content carbon ... more Carburizing of stainless steels at low temperatures (below 500°C) develops a high content carbon layer, known for its high hardness. X-ray Diffraction investigation indicates that carburization treatment does not impact the structure of substrate; however, introduced carbon causes expansion in the carburized layer through the increase in d-spacing. Characterization of carbon concentration and hardness profiles indicate that carbon content gradually decreases while moving further into the substrate; and the origin of the increased hardness of the expanded layer arises from the super-saturated carbon content, following the solid solution strengthening theory. An area that is not well understood is in regard to the carburized layer's relation to the substrate and the significance in their differences. Using two grades of stainless steel, AISI 316L and PH 17-4, it was observed that the carburized layer is not a separate layer, but a higher carbon content version of the substrate.
Metallurgical and Materials Transactions A, 2014
ABSTRACT
Commercially pure titanium samples were exposed to grit blasting and acid–alkali treatments to ob... more Commercially pure titanium samples were exposed to grit blasting and acid–alkali treatments to obtain a variety of surface compositions and morphologies. Contact roughness test and microstructural studies were employed to study the surface topography of the samples. The nature and chemical composition of surface phases were evaluated using X-ray diffraction and microanalysis techniques. Selected samples first exposed to in vitro environment were then tested to determine the surface morphology and surface microstructure. Based on the data presented in this work, it is suggested that grit blasting process utilized prior to chemical treatment stage, yields a high quality surface morphology. Such a surface morphology is expected to have superior tribological characteristics after osseointegration. Also, it appeared that the reverse sequence of processing resulted in a better biocompatibility of the product manifested by negligible amount of residual alumina on the sample surface.