An Investigation of Methyl Viologen Functionalized Reduced Graphene Oxide: Chitosan as a Support for Pt Nanoparticles Towards Ethanol Electrooxidation

Mehri-Saddat Ekrami-Kakhki,Nahid Farzaneh,Sedigheh Abbasi,Hadi Beitollahi,Seyed Ali Ekrami-Kakhki 대한금속·재료학회 2018 ELECTRONIC MATERIALS LETTERS Vol.14 No.5

In this research, graphene oxide was prepared by a modified Hummers’ method, and then functionalized with 1, 1′-dimethyl-4, 4′-bipyridinium dichloride (MV), and chitosan (CH) to get a MV–RGO–CH support. Pt nanoparticles were preparedon this support to get Pt/MV–RGO–CH catalyst. The morphology and microstructure of Pt/MV–RGO–CH catalyst werecharacterized with transmission electron microscopy image and X-ray diffraction analysis. The electrocatalytic activity ofthe prepared catalyst towards ethanol oxidation was investigated by carbon monoxide stripping voltammetry, cyclic voltammetry,and electrochemical impedance spectroscopy techniques. The effects of some experimental parameters such as scanrate, ethanol concentration, and temperature were investigated for ethanol electrooxidation at Pt/MV–RGO–CH catalyst. Durability of the catalyst was also investigated. The electrocatalytic performance of Pt/MV–RGO–CH catalyst for ethanoloxidation was compared with those of Pt/CH and Pt/MV–RGO catalysts. The higher electrocatalytic performance of Pt/MV–RGO–CH than Pt/CH and Pt/MV–RGO catalysts towards ethanol electrooxidation indicated that Pt/MV–RGO–CHcould be a promising catalyst for application in direct ethanol fuel cells.

Evaluation of the Progressive Collapse of the Reinforced Concrete Frames Considering the Soil–Structure Interaction: Parametric Study Based on the Sensitivity Index

Seyed Ali Ekrami Kakhki,Ali Kheyroddin,Alireza Mortezaei 한국콘크리트학회 2022 International Journal of Concrete Structures and M Vol.16 No.5

In this essay, to investigate the progressive collapse of the reinforced concrete (RC) frames, a nonlinear static pushdown analysis was performed with column removal scenarios from the first story. At first, a numerical model was simulated and verified with the experimental model in SeismoStruct software without soil–structure interaction (SSI). Afterward, the foundation, soil, and the RC frame were modeled simultaneously in FLAC software and verified with the numerical model of the SeismoStruct software. Furthermore, the effect of SSI was studied on the progressive collapse of RC frames based on the sensitivity index (SI). The sensitivity index is defined as the ratio of the residual capacity under gravity loading of the structure by removing the column to the value of the undamaged structure. The results showed that by considering SSI, the sensitivity index decreases. Then, a parametric study of the framed structures (thickness of the foundation) and substructures (soil density, soil types, soil layers, and the soil saturation conditions) was performed to evaluate the progressive collapse-resisting capacity based on the sensitivity index. The results showed that by considering SSI, with an increase in the soil density and decrease in the groundwater level, the conditions would be better for preventing progressive collapse. It was also shown that rock and silty sands (SM), compared to other studied soil types, and SM and silty sands—silty clay with low plasticity—silty sands (SM-CL/ML-SM), compared to other studied soil layers, are better for preventing progressive collapse.

Statistical Analysis of the Electrocatalytic Activity of Pt Nanoparticles Supported on Novel Functionalized Reduced Graphene Oxide-Chitosan for Methanol Electrooxidation

Mehri-Saddat Ekrami-Kakhki,Sedigheh Abbasi,Nahid Farzaneh 대한금속·재료학회 2018 ELECTRONIC MATERIALS LETTERS Vol.14 No.1

XCThepurpose of this study is to statistically analyze the anodic currentdensity and peak potential of methanol oxidation at Pt nanoparticlessupported on functionalized reduced graphene oxide (RGO), usingdesign of experiments methodology. RGO is functionalized with methylviologen (MV) and chitosan (CH). The novel Pt/MV-RGO-CH catalystis successfully prepared and characterized with transmission electronmicroscopy (TEM) image. The electrocatalytic activity of Pt/MV-RGOCHcatalyst is experimentally evaluated for methanol oxidation. Theeffects of methanol concentration and scan rate factors are alsoinvestigated experimentally and statistically. The effects of these twomain factors and their interactions are investigated, using analysis ofvariance test, Duncan’s multiple range test and response surface method. The results of the analysis of variance show that all the main factors andtheir interactions have a significant effect on anodic current density andpeak potential of methanol oxidation at α = 0.05. The suggested modelswhich encompass significant factors can predict the variation of theanodic current density and peak potential of methanol oxidation. Theresults of Duncan’s multiple range test confirmed that there is asignificant difference between the studied levels of the main factors.

Numerical Investigation of the Progressive Collapse of the Reinforced Concrete Wall-Frame Structures Considering the Soil–Structure Interaction

Seyed Ali Ekrami-Kakhki,Ali Kheyroddin,Alireza Mortezaei 한국콘크리트학회 2023 International Journal of Concrete Structures and M Vol.17 No.4

In this essay, the progressive collapse resistance of the reinforced concrete wall-frame structures was evaluated with and without considering the soil–structure interaction. The vulnerability of the frames against progressive collapse was investigated with the middle column removal scenario from the first story, based on the sensitivity index. To evaluate the effects of soil–structure interaction, the wall-frame structures along with the soil (hard soil) and foundation were simultaneously modeled in FLAC software and compared with the frames in Seismostruct software. The results showed that the sensitivity index decreased by considering the soil–structure interaction in the wall-frame structures. Afterward, a parametric study of the structures (foundation thickness) and substructures (soil types, soil densities, soil saturation conditions and soil layers) was performed. The results showed that with an increase in thickness of the foundation, the sensitivity index increased, and therefore, the condition of the structure would be more critical against progressive collapse. It was found that high groundwater levels in the subsoil can reduce its bearing capacity and lead to the damage to the structure. In addition, it was determined that by changing the substructure soil type from type 4 (Clay-MC) to type 1 (Rock), the use of layer 1 (SM) and layer 2 (SM-CL/ML (Very hard clay)-SM), and the soils with high density, the condition of the structures is better to prevent progressive collapse.

Microstructure and Mechanical Properties of Dual Phase Steels, with Different Martensite Morphology, Produced During TLP Bonding of a Low C-Mn Steel

Abolfazl Fazaeli,Aliakbar Ekrami,Amir Hossein Kokabi 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.5

In this research, production of ferrite - martensite dualphase Steels with different martensite morphology was considered during transient liquid phase bonding of a low carbon steel. The steel was bonded using an iron base interlayer with melting point of 1443 K and 40 μm thickness. Bonding process carried out at 1473 K, under pressure of 0.5MPa, at different holding time of 10, 20, 30 and 40 minutes. Microstructural studies of joint region showed that isothermal solidification completed at the bonding time of 40 minutes. Microstructure of joints made at the bonding time of 10, 20, and 30 minutes consists of two distinct region, athermal and isothermal solidified zones. Microstructure of these zones was studied and chemical composition of these zones was determined by EDS. Joints made with bonding time of 40 minutes were homogenized at 1008 K and then cooled into cold water to produce dual phase ferrite and martensite microstructure with different martensite morphology. According to shear test results, it was found that the shear strength of ferrite - fibrous martensite microstructure is greater than those with ferrite - continuous martensite and ferrite - blocky martensite microstructure.

An Investigation on the Fatigue Fracture of P/M Al-SiC Nanocomposites

Ghasemi Yazdabadi, H.,Ekrami, A.,Kim, H. S.,Simchi, A. Springer Science + Business Media 2013 Metallurgical and materials transactions. A, Physi Vol.44 No.6

Microstructural Characteristics of a Cast IN718 Superalloy Bonded by Isothermal Solidification

Majid Pouranvari,Ali Ekrami,Amir-Hossein Kokabi,한흥남 대한금속·재료학회 2013 METALS AND MATERIALS International Vol.19 No.5

Isothermal solidification is a key feature of transient liquid phase bonding which prevents the formation of deleterious intermetallic phases in the joint centerline and results in bonds with improved mechanical performance. This paper discusses the metallurgical characteristics and mechanical properties of an as-cast IN718 superalloy bonded by diffusion-induced isothermal solidification of Ni-7Cr-4.5Si-3.2B-3Fe (wt%)filler metal. After transient liquid phase bonding of as-cast IN718 at 1000 °C for 60 min, a bond exhibiting a solid solution microstructure with joint efficiency of 72% in terms of shear strength was obtained. The joining process was effectively able to prevent the formation of hard and brittle nickel and chromium borides, which typically lead to critical problems in brazing. The formation of Nb-rich Laves phase, which is well known as a major issue in the fusion welding of IN718, was not observed. The bonding time,which governs the extent of isothermal solidification, was a critical parameter for controlling the mechanical properties of the joints in terms of shear strength and hardness distribution across the bond.

Effect of Helicobacter Pylori eradication on patients with ITP: a meta-analysis of studies conducted in the Middle East

Seyed Mohammad Sadegh Pezeshki,Najmadin Saki,Mehran Varnaseri Ghandali,Alireza Ekrami,Arshid Yousefi Avarvand 대한혈액학회 2021 Blood Research Vol.56 No.1

Background Immune thrombocytopenia (ITP) is a bleeding disorder. Helicobacter pylori is a Gram-negative bacterium that is presumed to be associated with ITP and therapeutic response of patients. To evaluate the effect of H. pylori eradication on platelet count of ITP patients, we analyzed the studies conducted on the association between H. pylori infection and response to therapy in ITP patients in Western Asia focusing on the Middle East region. Methods A systematic search of databases (PubMed/Medline, ISI Web of Science, Cochrane Central) and Google Scholar search engine results was conducted up until January 2020. The keywords included in the search were Helicobacter pylori and/or H. pylori, ITP and/or immune thrombocytopenia. Results Seven studies comprising a total of 228 H. pylori-infected patients (193 with successful eradication) were included in this study. The association between H. pylori eradication and ITP was expressed as odds ratios (OR) and 95% confidence intervals (CI). The findings showed that patients who received eradication treatment for H. pylori infection had significantly higher OR (OR, 8.83; 95% CI, 2.03‒38.35; P =0.004) than those in the non-eradicated group. Conclusion Our results indicate a significant therapeutic effect of H. pylori eradication on the platelet count of patients with chronic ITP. Given the inherent limitations of this study, including the small number of patients, further studies with more patients are recommended.