Sharif Digital Repository

A simple and low-cost electrochemical deposition method is used to prepare reduced graphene oxide/polypyrrole/Cu2O-Cu(OH)2 (RGO/PPy/Cu2O-Cu(OH)2) ternary nanocomposites as the electrode material for supercapacitor application. First, graphene oxide-polypyrrole (GO/PPy) nanocomposite is electrochemically synthesized on Ni foam by electro-oxidation of pyrrole monomer in an aqueous solution containing GO and Tiron. Subsequently, the GO/PPy film is converted to the corresponding reduced form (RGO/PPy) by an effective and eco-friendly electrochemical reduction method. Then, a thin layer of Cu2O-Cu(OH)2 is formed on RGO/PPy film by chronoamperometry. The RGO/PPy/Cu2O-Cu(OH)2 nanocomposite is... 

Synthesis of efficient, low-cost, and stable bifunctional electrocatalysts with earth-abundant resources for electrochemical water electrolysis is a challenging subject for large-scale energy conversion processes. Herein, we report a high-performance electrocatalyst based on vanadium oxysulfide/cobalt-cobalt sulfonitride (VOS/Co-CoSN) for oxygen and hydrogen evolution reaction (OER and HER). The Co-CoSN film was synthesized on a copper sheet (CS) by a facile electrodeposition method. Then, VOS was electrochemically grown onto the Co-CoSN@CS electrode at various deposition times. At the optimal deposition time (300 s), the obtained VOS-300/Co-CoSN catalyst was studied for OER and HER in... 

The development of a nonenzymatic glucose sensor working in real human body conditions through a noninvasive sampling approach has attracted considerable attention. Hence, this work focuses on the development of a new nonenzymatic glucose sensor based on flower-like Au nanostructures (F-AuNTs) and graphene oxide (GO) as a supporting matrix. The F-AuNTs-GO hybrid was synthesized by simple drop casting of the GO suspension onto the graphite sheet (GS) followed by electrodeposition of F-AuNTs on GO nanosheets at 3 V in a two-electrode system. The electrocatalytic activity of the F-AuNTs-GO/GS sensor toward glucose electrooxidation was initially evaluated in a 0.1 M buffer phosphate solution (pH... 

Synthesizing efficient electrode materials for water splitting and supercapacitors is essential for developing clean electrochemical energy conversion/storage devices. In the present work, we report the construction of a ruthenium cobalt oxide (RuCo2O4)/Ti3C2Tx MXene hybrid by electrophoretic deposition of Ti3C2Tx MXene on nickel foam (NF) followed by RuCo2O4 nanostructure growth through an electrodeposition process. Owing to the strong interactions between RuCo2O4 and Ti3C2Tx sheets, which are verified by density functional theory (DFT)-based simulations, RuCo2O4/Ti3C2Tx MXene@NF can serve as a bifunctional electrode for both water splitting and supercapacitor applications. This electrode... 

Polyaniline/graphene oxide (PANI/GO) co-doped with Zn2+ and Fe3+ was synthesized via a simple and low cost one-step chronoamperometry method on stainless steel (SS) as the substrate. The Fe3+-Zn2+-PANI/GO nanocomposite is characterized using X-ray diffraction as well as Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and field emission scanning electron microscopy. Also, cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy are used to study the electrochemical performance of the as-prepared electrode materials. Significantly, the Fe3+-Zn2+-PANI/GO nanocomposite exhibits a specific... 

Polyaniline/graphene oxide (PANI/GO) co-doped with Zn2+ and Fe3+ was synthesized via a simple and low cost one-step chronoamperometry method on stainless steel (SS) as the substrate. The Fe3+-Zn2+-PANI/GO nanocomposite is characterized using X-ray diffraction as well as Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and field emission scanning electron microscopy. Also, cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy are used to study the electrochemical performance of the as-prepared electrode materials. Significantly, the Fe3+-Zn2+-PANI/GO nanocomposite exhibits a specific... 

Iron‑vanadium oxysulfide (Fe-VO-S) nanostructures with different Fe:VO atomic ratios are synthesized by a facile and low cost electrochemical deposition method. The synthesis of the various samples is confirmed by the physicochemical characterizations such as Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM). For different Fe-VO-S nanostructures, the correlation between the physicochemical and the electrochemical properties is investigated. It is found that the Fe:VO atomic ratio has an important effect on the structure and size of the resulted particles.... 

A new ternary nanocomposite based on graphene oxide (GO), polypyrrole (PPy) and vanadium pentoxide (V2O5) is obtained via one-step electrochemical deposition process. Electrochemical deposition of V2O5, PPy and GO on a stainless steel (SS) substrate is conducted from an aqueous solution containing vanadyl acetate, pyrrole and GO to get V2O5/PPy/GO nanocomposite. Characterization of the electrode material is carried out by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM). The electrochemical performance of the as-prepared nanocomposite is evaluated by... 

In this work, nanostructured composites of Cr2O3-graphene oxide (Cr2O3/GO) with conducting polymers; polyaniline (PANI) and polypyrrole (PPy) with the shape of cauliflower were synthesized via s simple and low cost one-step chronoamperometry method. The structures and morphologies of the resulting ternary nanocomposites were characterized by using Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The electrochemical capacitive properties of the prepared nanocomposites were evaluated by using cycle voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The... 

The development of electrode materials with simple preparation, favorable price, excellent electrocatalytic activity, and stability are some of the most important issues in the field of electrochemistry. Herein, we prepared Ni–Co/Ni–Co–O–P cotton flower like on a copper sheet (CS) by a convenient, efficient, and scalable electrodeposition method. The Ni–Co/Ni–Co–O–P was employed as effective binder free electrode material in two different applications such as electrocatalytic water splitting and acetaminophen (APAP) sensor. Remarkably, the Ni–Co/Ni–Co–O–P@CS exhibits low overpotentials of 310 and 90 mV at 10 mA cm−2 for oxygen and hydrogen evolution reactions in alkaline media, respectively.... 

An approach composed of the thermodynamics-based dislocation model and the Taylor theory is used to investigate the evolution of microstructure and flow stress during high-pressure torsion (HPT). The incremental temperature rise is considered through the modelling of HPT. The temperature can affect the annihilation of dislocations and thus the dislocation density. The model predicts the dislocation density, sub-grain size and flow stress during HPT. The modelling results are compared with the experimental data and the modelling results without considering the incremental temperature rise. A remarkable agreement is observed between the modelling results with considering the temperature rise... 

Two-internal variable thermodynamics model is presented to investigate the evolution of microstructure and flow stress during severe plastic deformation. Previous studies have shown that due to heterogeneous distribution of dislocations during severe plastic deformation, the use of multivariable models is needed. In this regard, a two-internal variable model is presented. In the present paper, the dislocation densities in the subgrain boundaries and interiors are considered as internal variables. The model uses general laws of thermodynamics and describes the evolution of the dislocation densities on the basis of parameters such as the self-diffusion activation energy and the stacking fault... 

Recent investigations have shown that the steady state grain size of severely deformed materials is dependent on the stacking fault energy. In this paper, a model is presented to investigate such a dependency which uses thermodynamics based calculations. The present model shows that the relationship between the steady state grain size and the stacking fault energy of material is in power law form, directly. Furthermore, the model shows that the steady state grain size has an exponential relationship with the self-diffusion activation energy and a decrease in the self-diffusion activation energy increases the steady state grain size. The model predictions are in good agreement with the... 

The main goal of high-pressure torsion (HPT) process is to reduce the grain size. Experiments have shown that this aim is achievable, but there is a limit in reducing the grain size. The present paper investigates this limit through a thermodynamics-based model. However, this was investigated by other researches through dislocation density-based model. At first, the validity of the model in description of the limiting grain size obtainable by HPT of different materials is examined. Then, the influence of inherent material parameters is investigated. Finally, the present results are compared with those obtained by equal channel angular pressing. © 2019, © 2019 Institute of Materials, Minerals... 

The strength evolution during the processing/cycling of the metal matrix composite through accumulative roll bonding (ARB) as a severe plastic deformation method is studied by performing a twofold model. It is shown that the strength evolution during cycling consists of two parts: monolithic-like behavior and composite-like behavior. The contribution of each behavior is obtained. The particle effectiveness is at the lowest value at the beginning of the cycling and reaches its highest during the final cycles. It is shown that there is a critical strain at which monolithic-like behavior initiates to decline. The process also shows a minimum strain at which composite-like behavior dominates. ©... 

SnS2-SnO2 nano-heterostructures are synthesized with two different precursors of thioacetamide (TAA) and thiourea (TU) at various solvent ratios (SR) of ethanol and water by using a facile, economical, scalable, and cost-effective solvothermal method. The obtained products have been characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), and Brunauer–Emmet–Teller (BET) techniques. It is found that different precursors and various SR values have an influence on the composition and morphologies of the prepared nanostructures, leading to variation in capacitive behavior of the fabricated electrodes....