mehrdad shahbaz | Shiraz University (original) (raw)

Papers by mehrdad shahbaz

Research paper thumbnail of CuxO Nanostructure-Based Gas Sensors for H2S Detection: An Overview

Chemosensors

H2S gas is a toxic and hazardous byproduct of the oil and gas industries. It paralyzes the olfact... more H2S gas is a toxic and hazardous byproduct of the oil and gas industries. It paralyzes the olfactory nerves, with concentrations above 100 ppm, resulting in loss of smell; prolonged inhalation may even cause death. One of the most important semiconducting metal oxides for the detection of H2S is CuxO (x = 1, 2), which is converted to CuxS upon exposure to H2S, leading to a remarkable modulation in the resistance and appearance of an electrical sensing signal. In this review, various morphologies of CuxO in the pristine form, composites of CuxO with other materials, and decoration/doping of noble metals on CuxO nanostructures for the reliable detection of H2S gas are thoroughly discussed. With an emphasis to the detection mechanism of CuxO-based gas sensors, this review presents findings that are of considerable value as a reference.

Research paper thumbnail of Effect of Ag Addition on the Gas-Sensing Properties of Nanostructured Resistive-Based Gas Sensors: An Overview

Sensors

Nanostructured semiconducting metal oxides (SMOs) are among the most popular sensing materials fo... more Nanostructured semiconducting metal oxides (SMOs) are among the most popular sensing materials for integration into resistive-type gas sensors owing to their low costs and high sensing performances. SMOs can be decorated or doped with noble metals to further enhance their gas sensing properties. Ag is one of the cheapest noble metals, and it is extensively used in the decoration or doping of SMOs to boost the overall gas-sensing performances of SMOs. In this review, we discussed the impact of Ag addition on the gas-sensing properties of nanostructured resistive-based gas sensors. Ag-decorated or -doped SMOs often exhibit better responsivities/selectivities at low sensing temperatures and shorter response times than those of their pristine counterparts. Herein, the focus was on the detection mechanism of SMO-based gas sensors in the presence of Ag. This review can provide insights for research on SMO-based gas sensors.

Research paper thumbnail of Development of new routes of severe plastic deformation through cyclic expansionextrusion process (CEE)

This paper introduces two new processing routes for a recently introduced severe plastic deformat... more This paper introduces two new processing routes for a recently introduced severe plastic deformation technique, cyclic expansion-extrusion (CEE). Two processing Routes (I and II) were experimentally performed on aluminum alloy 1050; the processed samples were investigated and compared in terms of their microstructural and mechanical characteristics. A significant improvement in mechanical properties was observed after one CEE pass via both processing routes. However, different grain structures were achieved after Routes I and II showing a more homogeneous microstructure and hardness distribution in Route II compared to Route I. In addition, compression tests of the processed samples demonstrated that Route II results in a homogeneous compressive strength. Finally, microstructure evolution during subsequent passes of this process was investigated by electron back scattered diffraction. Micro-shear bands were found as potential sites for accelerating the formation of new grains which resulted in fragmentation of the initial grains and leading to an ultrafine-grained (UFG) microstructure.

Research paper thumbnail of The Relationship between Constant Friction Factor and Coefficient of Friction in Metal Forming using Finite Element Analysis

Frictional shear stress is usually determined by utilizing the coefficient of friction or the con... more Frictional shear stress is usually determined by utilizing the coefficient of friction or the constant friction factor models. The present study deals with finite element analysis of double cup extrusion process to determine the relationship between constant friction factor (m) and coefficient of friction (µ), since the metal flow in this process is very sensitive to frictional conditions. Therefore, the Finite Element-Code Deform 2D is used which is capable of utilizing both µ and m. According to this analysis, a new equation between constant friction factor (m) and coefficient of friction (µ) is suggested. Moreover, in order to evaluate the suggested equation and to compare it with the previous equations, finite element analysis of barrel-compression test is carried out. Finite element results indicate that the new equation can accurately predict the relation between m and its equivalent μ value. The importance of converting these factors to each other is specially highlighted to introduce the frictional conditions in some professional and commercial finite element software.

Research paper thumbnail of A novel single pass severe plastic deformation technique: Vortex extrusion

Vortex extrusion (VE) is a new severe plastic deformation (SPD) method which is designed to intro... more Vortex extrusion (VE) is a new severe plastic deformation (SPD) method which is designed to introduce a specific amount of torsional strain to a material simultaneously being extruded using a specially designed stationary die. Plastic deformation characteristics of VE were analyzed by finite element analysis; processing loads, strain values as well as metal flow patterns were studied for different twist angles. Results indicated that high strain values with uniform distribution may be achieved after VE processing. Therefore, VE can be considered as a promising single pass SPD technique which can be installed on any standard extrusion equipment with no need to any additional facilities that are essential in similar method, torsion extrusion.

Research paper thumbnail of CuxO Nanostructure-Based Gas Sensors for H2S Detection: An Overview

Chemosensors

H2S gas is a toxic and hazardous byproduct of the oil and gas industries. It paralyzes the olfact... more H2S gas is a toxic and hazardous byproduct of the oil and gas industries. It paralyzes the olfactory nerves, with concentrations above 100 ppm, resulting in loss of smell; prolonged inhalation may even cause death. One of the most important semiconducting metal oxides for the detection of H2S is CuxO (x = 1, 2), which is converted to CuxS upon exposure to H2S, leading to a remarkable modulation in the resistance and appearance of an electrical sensing signal. In this review, various morphologies of CuxO in the pristine form, composites of CuxO with other materials, and decoration/doping of noble metals on CuxO nanostructures for the reliable detection of H2S gas are thoroughly discussed. With an emphasis to the detection mechanism of CuxO-based gas sensors, this review presents findings that are of considerable value as a reference.

Research paper thumbnail of Effect of Ag Addition on the Gas-Sensing Properties of Nanostructured Resistive-Based Gas Sensors: An Overview

Sensors

Nanostructured semiconducting metal oxides (SMOs) are among the most popular sensing materials fo... more Nanostructured semiconducting metal oxides (SMOs) are among the most popular sensing materials for integration into resistive-type gas sensors owing to their low costs and high sensing performances. SMOs can be decorated or doped with noble metals to further enhance their gas sensing properties. Ag is one of the cheapest noble metals, and it is extensively used in the decoration or doping of SMOs to boost the overall gas-sensing performances of SMOs. In this review, we discussed the impact of Ag addition on the gas-sensing properties of nanostructured resistive-based gas sensors. Ag-decorated or -doped SMOs often exhibit better responsivities/selectivities at low sensing temperatures and shorter response times than those of their pristine counterparts. Herein, the focus was on the detection mechanism of SMO-based gas sensors in the presence of Ag. This review can provide insights for research on SMO-based gas sensors.

Research paper thumbnail of Development of new routes of severe plastic deformation through cyclic expansionextrusion process (CEE)

This paper introduces two new processing routes for a recently introduced severe plastic deformat... more This paper introduces two new processing routes for a recently introduced severe plastic deformation technique, cyclic expansion-extrusion (CEE). Two processing Routes (I and II) were experimentally performed on aluminum alloy 1050; the processed samples were investigated and compared in terms of their microstructural and mechanical characteristics. A significant improvement in mechanical properties was observed after one CEE pass via both processing routes. However, different grain structures were achieved after Routes I and II showing a more homogeneous microstructure and hardness distribution in Route II compared to Route I. In addition, compression tests of the processed samples demonstrated that Route II results in a homogeneous compressive strength. Finally, microstructure evolution during subsequent passes of this process was investigated by electron back scattered diffraction. Micro-shear bands were found as potential sites for accelerating the formation of new grains which resulted in fragmentation of the initial grains and leading to an ultrafine-grained (UFG) microstructure.

Research paper thumbnail of The Relationship between Constant Friction Factor and Coefficient of Friction in Metal Forming using Finite Element Analysis

Frictional shear stress is usually determined by utilizing the coefficient of friction or the con... more Frictional shear stress is usually determined by utilizing the coefficient of friction or the constant friction factor models. The present study deals with finite element analysis of double cup extrusion process to determine the relationship between constant friction factor (m) and coefficient of friction (µ), since the metal flow in this process is very sensitive to frictional conditions. Therefore, the Finite Element-Code Deform 2D is used which is capable of utilizing both µ and m. According to this analysis, a new equation between constant friction factor (m) and coefficient of friction (µ) is suggested. Moreover, in order to evaluate the suggested equation and to compare it with the previous equations, finite element analysis of barrel-compression test is carried out. Finite element results indicate that the new equation can accurately predict the relation between m and its equivalent μ value. The importance of converting these factors to each other is specially highlighted to introduce the frictional conditions in some professional and commercial finite element software.

Research paper thumbnail of A novel single pass severe plastic deformation technique: Vortex extrusion

Vortex extrusion (VE) is a new severe plastic deformation (SPD) method which is designed to intro... more Vortex extrusion (VE) is a new severe plastic deformation (SPD) method which is designed to introduce a specific amount of torsional strain to a material simultaneously being extruded using a specially designed stationary die. Plastic deformation characteristics of VE were analyzed by finite element analysis; processing loads, strain values as well as metal flow patterns were studied for different twist angles. Results indicated that high strain values with uniform distribution may be achieved after VE processing. Therefore, VE can be considered as a promising single pass SPD technique which can be installed on any standard extrusion equipment with no need to any additional facilities that are essential in similar method, torsion extrusion.