Sharif Digital Repository

The properties of W-15 wt.%Cu composites were investigated by preparing two distinct composites of micrometer and nanoscale structures. Micrometer composite was produced by mixing elemental W and Cu powders and nanometer one was synthesized through a mechanochemical reaction between WO3 and CuO powders. Subsequent compaction and sintering process was performed to ensure maximum possible densification at 1000-1200 °C temperatures. Finally, the behavior of produced samples including relative density, hardness, compressive strength, electrical conductivity, coefficient of thermal expansion (CTE) and room temperature corrosion resistance were examined. Among the composites, nano-structured... 

One of the most conventional and energy efficient methods to improve the engineering properties of concrete is the utilization of waste materials and by-products. Among agricultural wastes, rice husk ash (RHA) has exhibited the greatest potential to enhance the characteristics of cement mixtures. However, the investigations on the properties and performance of RHA are slim compared to its potential advantages and few systematic studies can be found in the literature regarding parameters influencing the chemo-physical and microstructural characteristics of RHA along with its performance in cement mixtures. In this study, the effect of retention time of rice husk is systematically... 

Tungsten trioxide has been prepared by using P-PTA as a precursor on alumina substrates by spin coating method. Palladium introduced on WO 3 film via electrolysis deposition by using palladium chloride as catalytic precursor. The catalytic precursor was introduced on the series of films with different morphologies. X-ray diffractometry (XRD), Scanning electron microscopy (SEM) and XPS were applied to analyze structure and morphology of the fabricated thin films. Then we measured variation of samples' electrical conductivity of pure and Pd added films in air and diluted hydrogen. Addition of Pd resulted in a remarkable improvement of the hydrogen sensing properties of WO 3 by detection of... 

Graphene oxide platelets synthesized by using a chemical exfoliation method were dispersed in a suspension of ZnO nanoparticles to fabricate ZnO/graphene oxide composite. Formation of graphene oxide platelets (with average thickness of ∼0.8 nm) hybridized by ZnO nanoparticles (with average diameter of ∼20 nm) was investigated. The 2D band in Raman spectrum confirmed formation of single-layer graphene oxides. The gradual photocatalytic reduction of the graphene oxide sheets in the ZnO/graphene oxide suspension of ethanol was studied by using X-ray photoelectron spectroscopy for different ultra violet (UV)-visible irradiation times. After 2 h irradiation, the relative concentration of the... 

Abstract Cu-15%NbC (volume fraction) powder was synthesized using the starting powders of Cu, Nb and graphite in a high energy vibratory disc mill for 7 h of milling under argon atmosphere. A composite sample and a Cu/NbC functionally graded material (FGM) sample were produced by using the two-step press and sintering at 900 °C for 1 h under vacuum. The microstructure and physical and mechanical properties of the specimens were investigated. The field emission scanning electron microscopy, energy dispersive X-ray and X-ray diffraction analysis confirmed the synthesis of the nanostructure matrix of 18-27 nm with the nanoparticles reinforcement of 42 nm after sintering, verifying the thermal... 

In the present study, yttria stabilized zirconia (YSZ) reinforced Cu matrix composite specimens were produced by spark plasma sintering (SPS). For comparison, pure Cu specimen was also produced in the same conditions. The effect of particles content on microstructure, relative density, electrical conductivity, and Vickers hardness was evaluated. The pin-on-disk test was also performed to determine dry sliding wear behavior of specimens under different wear conditions. After sliding wear tests, the worn surfaces were examined by field emission scanning electron microscopy (FE-SEM). Microstructural study showed satisfactory distribution of reinforcement particles in copper matrix. The relative... 

Molecular level understanding of the properties of ionic liquids inside nanopores is needed in order to use ionic liquids for many applications such as electrolytes for energy storage in electric double-layer capacitors and dye-sensitized solar cells for conversion of solar energy. In this study, classical molecular dynamics (MD) simulations have been performed to investigate the radial distribution, glass transition, ionic transfer number, and electrical conductivity of the ionic liquid 1-ethyl-3-methylimidazolium hexafluorophosphate [EMIM][PF6] ionic liquid encapsulated in carbon nanotube (CNT). The effect of nitrogen as a doping element in CNT on these properties of [EMIM][PF6] was also... 

Upset resistance dissimilar welding of aluminium and copper narrow rods was performed. Effect of the interface characteristics was studied on the joint mechanical and electrical properties. Upset resistance welding (URW) was successful for production of joints with high strength and electrical conductivity between aluminium and copper rods. Reaction layer at the joint interface was composed of the Al2Cu cellular phase and lamellar eutectic structure of α-Al and Al2Cu. Enhancement of the welding current and decrease in the upset force increased the reaction layer thickness and strength of the joint. URW had no significant detrimental effect on the electrical conductivity of the weld zone.... 

In order to fabricate nanofiber scaffold for bone tissue engineering, electrospinning technique was employed. This technique produces nanofiberous scaffold supporting cell adhesion, migration, and proliferation. Here, we developed a novel conductive scaffold from poly-caprolactone, gelatin, and poly aniline/graphene nanoparticles. In this study, co-electrospinning was utilized to fabricate composite electrospun scaffold. The effect of polyaniline/graphene (PAG) nanoparticles on the mechanical properties and electrical conductivity of this hybrid scaffold was investigated. The result showed that PAG nanoparticles enbance both mechanical properties and electrical conductivity of the scaffolds.... 

Cu-CNT composites were fabricated by a flake powder metallurgy method, and their microhardness, electrical conductivity, frictional and wear properties were investigated. Homogenous distribution of CNTs in fine-grained Cu matrix was obtained using this process. Microhardness increased with the addition of CNT vol% up to 8% to the Cu matrix, while the conductivity decreased to 79.2 IACS %. Results showed that CNTs play a major role in improving wear resistance by forming a CNT-rich film that acts as a solid lubricant layer. In the synthesized composites, Cu- 4 vol% CNT composite exhibited the best wear and friction properties. The dominant wear mechanisms for the Cu-CNT composites were... 

Partial substitutions of Pr and Ce are known to suppress the superconducting state in REBa2Cu3O7-δ systems. We have substituted Ce for Gd in Gd1-xCexBa 2Cu3O7-δ compounds with x = 0.0-0.6 by the standard solid-state reaction technique. X-ray diffraction (XRD) experiments are performed and their results are refined by the Rietveld method. XRD analysis shows a predominantly single-phase perovskite structure with few impurity phases. Our resistivity results show that, by increasing the Ce content, Tc decreases, the transition temperature width increases, and in the normal state a metal-insulator transition (MIT) occurs at x c = 0.12. The normal state resistivity of the samples and their slopes... 

Application of organic−inorganic nanocomposite membranes for water treatment is exceptionally growing owing to their tunable functionalities in addition to their enhanced permeation and antifouling propensity. In the present work, novel nanocomposite polyethersulfone (PES) membrane was synthesized using antimony-doped tin oxide (ATO) nanoparticles (NPs) via phase separation technique. It was found that the modified PES-ATO nanocomposite membranes exhibited significantly higher fouling resistance and larger permeate flux recovery ratio when tested with oil sands produced water than unmodified PES membranes. Furthermore, the PES-ATO membranes provided 40% more organic matter removal compared... 

Polyamide 6 (PA6)/carbon nanotube (CNT)/conductive carbon black (CCB) nanocomposites with the incorporation of physical and chemical dispersants were prepared via melt blending method to examine the synergistic enhancement of electrical conductivity. Investigation of modified CNT with octadecyl triphenyl phosphonium chloride (OTPC-CNT) as physical dispersant was performed by Fourier transform infrared, nuclear magnetic resonance, Raman spectroscopy, and thermogravimetric analysis. Morphological, electrical, rheological, and mechanical properties of PA6/CNT/CCB nanocomposites were examined by field emission scanning electron microscopy, transmission electron microscopy, digital insulation... 

SnO2 is considered as one of the high specific capacity anode materials for Lithium-ion batteries. However, the low electrical conductivity of SnO2 limits its applications. This manuscript reports a simple and efficient approach for the synthesis of Sb-doped SnO2 nanowires (NWs) core and carbon shell structure which effectively enhances the electrical conductivity and electrochemical performance of SnO2 nanostructures. Sb doping was performed during the vapor-liquid-solid synthesis of SnO2 NWs in a horizontal furnace. Subsequently, carbon nanolayer was coated on the NWs using the DC Plasma Enhanced Chemical Vapor Deposition approach. The carbon-coated shell improves the Solid-Electrolyte... 

We report on the response of a monolithic high Tc transition-edge bolometer to about 3 mmWave for the first time. The detector structure consisting of 400-nm YBa2Cu3O7-x(YBCO) film on buffered yttria stabilized zirconia substrate without any coupled antenna, shows bolometric type responsivity to the 3-mmWave radiation at its transition temperature. The YBCO thin film Ce0.9La0.1O2 buffer layer are both fabricated by the metal-organic deposition method. The meander line pattern of the bolometer is designed for obtaining maximum absorption and responsivity possible when the polarized radiation of the source is aligned with the pattern. Meander lines are 50 micrometers wide and 1.5-mm long. We... 

In this study, an attempt has been made using different concentrations of rare-earth (RE) elements Yb, Gd in Ni–Zn spinel ferrite to examine the magneto-optical and electrical conductivity analysis of the prepared samples. RE doped Ni–Zn ferrite with composition Ni0.5Zn0.5YbxGdxFe2-xO4 (where, x = 0.00, 0.20, 0.40, 0. 60, 0.80 and 1.00) were prepared by one step sol-gel self-ignition approach. XRD and FESEM were used to examine the formation of a single-phase and variations in the grain size with the increasing contents of RE elements in Ni–Zn ferrite NPs. FTIR confirmed the vibrational studies of the RE doped spinel ferrite. The saturation magnetization, remanence, and coercivity elucidated... 

In this study, an attempt has been made using different concentrations of rare-earth (RE) elements Yb, Gd in Ni–Zn spinel ferrite to examine the magneto-optical and electrical conductivity analysis of the prepared samples. RE doped Ni–Zn ferrite with composition Ni0.5Zn0.5YbxGdxFe2-xO4 (where, x = 0.00, 0.20, 0.40, 0. 60, 0.80 and 1.00) were prepared by one step sol-gel self-ignition approach. XRD and FESEM were used to examine the formation of a single-phase and variations in the grain size with the increasing contents of RE elements in Ni–Zn ferrite NPs. FTIR confirmed the vibrational studies of the RE doped spinel ferrite. The saturation magnetization, remanence, and coercivity elucidated... 

Choosing the appropriate ion exchange membrane in vanadium redox flow batteries plays an important role in achieving optimal system performance. In this article, the implementation of commercial cation exchange membranes (Nafion 115, Nafion 117, and Nafion 212), anion exchange membranes (FAP 450 and QA-PFE), and the combination of them are investigated. In this regard, the effects of membrane type, thickness, electrical conductivity, and the transfer of vanadium species at different current densities are examined carefully. In addition, the influences of the flow rate and the concentration of electrolytes are investigated using a comprehensive developed model. The model predictions are... 

Herein, a series of superhydrophobic thin polyacrylic resin-coated carbon black (CB)/hexagonal boron nitride (h-BN)@Fe3O4/cellulose composite papers with good flexibility, low density (~0.67 g/cm3), high electrical conductivity (~0.065 S/cm), good thermal conductivity (0.462 W.m−1. K−1), and with water contact angle (WCA) of 153° were successfully fabricated by a facile dip-coating/spraying method. The CB-BN@Fe3O4 distribution in cellulose matrix provided high electrical conductivity in the in-plane and thickness directions. The electrical conductivity in both in-plane and thickness directions increased by increasing the number of vacuum-assisted dip-coating cycles. Moreover, these... 

Polyamide 6 (PA6)/carbon nanotube (CNT)/conductive carbon black (CCB) nanocomposites with the incorporation of physical and chemical dispersants were prepared via melt blending method to examine the synergistic enhancement of electrical conductivity. Investigation of modified CNT with octadecyl triphenyl phosphonium chloride (OTPC-CNT) as physical dispersant was performed by Fourier transform infrared, nuclear magnetic resonance, Raman spectroscopy, and thermogravimetric analysis. Morphological, electrical, rheological, and mechanical properties of PA6/CNT/CCB nanocomposites were examined by field emission scanning electron microscopy, transmission electron microscopy, digital insulation...