Sharif Digital Repository

[No abstract available]  

Ag and Ni are immiscible, mainly due to their large lattice mismatch. This paper reports on their nanoscale formation of solid solution at room temperature by simple reduction reactions which lead to the amorphous Ag-Ni alloy nanoparticles (ANPs) with mono-disperse distribution. Microscopic and spectroscopic studies confirmed dependence of the alloy composition on size of nanoparticles. In the presence of different ligands such as sodium citrate, polyvinyl alcohol and potassium carbonate a mixture of silver oxide and Ag-Ni ANPs was achieved. Stoichiometry of the Ag-Ni ANPs was also found to be strongly dependent on ligands of the reduction reaction and further study shows without any ligand... 

Nitinol stents are used to minimize improper dynamic behavior, low twistability, and inadequate radial mechanical strength of femoral artery stents. In this study, finite element method is used to investigate the effect of crimping and Austenite finish temperature (A f) of Nitinol on mechanical performance of Z-shaped open-cell femoral stent under crimping conditions. Results show that low A f Nitinol has better mechanical and clinical performance due to small chronic outward force, large radial resistive force, and appropriate superelastic behavior  

The effects of design parameters and material properties obtained with the ageing treatment on the mechanical performance of a z-shaped esophageal-duct nitinol wire stent under the crushing tests for clinical applications are investigated with a finite-element simulation. With 90 % crushing, low chronic outward force, high radial resistive strength and favorable superelastic behavior are attained at the segment angle of 65° and the Af temperature of 24 °C. The performance of the stent is seen to drastically vary with a change of only 1° in the segment angle  

The Finite element method was used for evaluation of the effects of material properties on the mechanical performance of the new geometry designed for the Z-shaped open-cell femoral artery self-expanding stent, made of Nitinol wire, by application of crushing force. The behavior of the stents, having two sets of properties, was compared. The stents with higher Af temperature show better clinical behavior due to lower chronic outward force, higher radial resistive strength and more suitable superelastic behavior. Model calculations show that a large change of Af temperature could exert a substantial effect on the practical performance of the stent  

Foamy Al alloy SiCp composites of different densities ranging from 0.4 to 0.7g/cm3 were manufactured by melt-foaming process, which consisted of direct CaCO3 addition into the molten A356 aluminum bath. Mechanical properties and morphological observations indicated that the three-stage deformation mechanism of typical cellular foams is dominant in the produced A356 aluminum foams. Middle-stage stress plateau shrinkage plus compressive strength and bending stress enhancements were observed in denser foams. With the same Al/SiCp ratio, energy absorption ability and plastic collapse strength of the closed-cell foams were increased with the foam density. Doubling cell-face bending effects... 

Magnesium nanopowder (MgNP) of 17 nm average size was produced by planetary ball milling of Mg (φ=229 μm) with 10 wt% NaCl (φ=406 μm) for 50 h. NaCl was omissible by dissolution in saturated KOH. Partial oxidation of MgNP occurred, however, in presence of KOH. MgNP-NaCl mixture was, therefore, used for transmission electron microscopy (TEM), scanning electron microscopy (SEM), x-ray diffraction (XRD), differential scanning calorimetry (DSC) and Sieverts equilibrium investigation. DSC analysis of ammonium perchlorate showed one endothermic and three exothermic reactions. MgNP did not noticeably affect on the initial endothermic reaction. But it decreased transformation temperatures of the... 

Corrosion of lead silicate glass (LSG) contacting 0.5 M aqueous nitric acid (HNO 3) was investigated via scanning electron microscopy, energy-dispersive spectroscopy, inductively coupled plasma analysis, and weight-loss measurement to determine the respective contributions of the ion-exchange vs. the hydrolysis reactions. The LSG having X M ≡ Pb+K+Na/Si mole ratios of less than 0.7 showed very little weight loss with no Si network deterioration. At X M > 0.7, the mechanism changed into the hydrolysis, which caused the formation of a networkless gel layer resting at the solid/liquid interface. Addition of titania (TiO 2) and zirconia (ZrO 2) had disparate effects: X M < 0.7 improved corrosion... 

Marvelous bending/straightening effects of two-way shape memory alloy (TWSMA) help their employment in design and manufacturing of new medical appliances. Constrained ageing with bending load scheme can induce two-way shape memory effect (TWSME). Scanning electron microscopic (SEM) analysis, electrical resistivity measurement (ERM) and differential scanning calorimetry (DSC) are employed to determine the property change due to flat strip constrained aging. Results show that flat-annealing prior to the aging shifts NiTi transformations temperatures to higher values. Superelastic behavior of the as-received/flat- annealed/aged samples with more adequate transition temperatures due to... 

Gold nanoparticles (AuNPs) of less than 50 nm diameter were electrodeposited from cyanide solution by pulsating electric current on modified copper and indium tin oxide (ITO) films coated on glass. Morphology, size, and composition of the deposited AuNPs were studied by X-ray photoelectron spectroscopy, atomic force microscopy, and field emission scanning electron microscopy. Effects of peak current density, pulse frequency, potassium iodide and cysteine on grain size, and morphology of the AuNPs were determined. Experiments showed that cathode current efficiency increases with the pulse frequency and the iodide ion. Size of the AuNPs increased with the current density. The number of... 

Photocatalysts that are used for waste water treatment are often suspended in the waste water during processing and then must be removed from the water after treatment. To reduce the post-degradation expenses and time, separation is facilitated by an immobilization process. The effect of immobilized TiO2 geometries on the photocatalytic behavior of the photocatalyst is investigated in this work. Powder, fiber, film, and network-shaped TiO2 nanocatalysts were produced by using different templates. The cellulose fiber and ceramic templates were used as substrates for fiber and film/network geometry production. The products were characterized by x-ray diffraction (XRD),... 

Presence of bubbles affects quality of the lead silicate glass (LSG) samples. This paper presents the most recent results obtained on formation and collapse of bubbles in LSG melts. Main sources of the bubbles are dissolved gases and redox reactions. A foamy layer full of bubbles rapidly forms at top of the molten phase. Effect of viscosity and density of the melt on content and ascension rate of the bubbles are investigated. Number and mean diameter of the bubbles and thickness of the top bubbly layer are calculated from gas volume measurements and image analysis via J software  

Synthesis and immobilization of Au nanoparticles (AuNPs) was performed on transparent fluorine-doped tin oxide (FTO) substrate by pulse electrodeposition method. The method was cost effective, simple and capable of producing nanoparticles strongly attached to the substrate. Effects of several influencing factors such as duty cycle, pulse frequency, current density, solution concentration, deposition period and annealing procedure on the optical properties of AuNPs-FTO electrode were investigated. AuNPs-FTO electrodes were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and UV-Vis absorption analysis. Controllability... 

Pd 2+-doped TiO 2 thin films with mesoporous structure were produced on quartz substrate by sol-gel dip coating. The structural, morphological and optical properties of the film were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), transmission electron microscopy (TEM), atomic force microscopy (AFM) and UV/vis transmittance spectroscopy. By increasing the Pd 2+ concentration from 0 to 6 mol%, the crystallites appeared solely as the anatase phase and their average sizes decreased from 10.5 to 7.1 nm. Addition of Pd 2+ also resulted in increasing of the specific surface area and decreasing of the pore size of the layer. The transmittance of the films decreased in the... 

The influence of milling and subsequent annealing on nickel-ferrite phase formation was investigated by X-ray diffraction (XRD). Microstructure and magnetic properties of NiFe 2O 4 were determined by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and vibration sample magnetometry (VSM). Single phase nanosized nickel-ferrite was obtained by 30 h mechanical alloying (MA) and subsequent annealing at 600 °C for 1 h. Magnetic properties of the milled powder were extensively affected by the annealing temperature. Considerable growth of the particles and necking by sintering resulted from annealing at 1000 °C  

TiO2 thin films with mesoporous structure were deposited on quartz substrate by sol-gel dip coating. The structural, morphological and optical properties of the films were characterized by X-ray diffraction (XRD), simultaneous thermal analysis (STA), Fourier transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET), atomic force microscopy (AFM), transmission electron microscopy (TEM) and UV/Vis transmittance spectroscopy. Crystallization of the anatase phase was initiated at 300°C. Its transformation to the rutile phase occurred at 700°C. Anatase and rutile crystallites initially sized 3.2 and 15.3nm, respectively. The anatase phase was under tension; but the rutile phase was... 

In this work, the effect of addition of ZrO2 to TiO2 and catalyst geometry on photocatalytic properties of the nanocomposite TiO2/ZrO2 was investigated. The traditional use of powdery photocatalyst for the degradation of organic compounds has post-treatment problems which means much higher time and costs. A novel method to minimize these problems is immobilization by insertion onto an inert substrate. Several geometries of TiO2–10%ZrO2 (T-10Z) nano-photocatalysts (powder, fiber, film, and network-shaped) were produced using different templates. The products were characterized by X-ray diffraction, field emission scanning electron microscopy, Brunauer–Emmett–Teller, and diffuse reflectance... 

In this research, ball milling of magnesium fillings with NaCl, KCl and urea was investigated as a simple way to produce Mg nanoparticles. Effects of feed geometry and milling time on crush mechanism and product size were determined. Optical, scanning and transmission electron microscopes were used to study the morphology of the products. Spherical charge particles were milled under argon atmosphere with 10 wt% cuboidal NaCl at 250 rpm for 50 h. With ball to powder ratio of 10:1, the average diameter of the product was 17 nm. Addition of NaCl changed the breakage mechanism from ductile–ductile to ductile–brittle, reduced particle size, stopped agglomeration and prevented the undesirable... 

In this study, the effect of adding 5–12.5 wt% CuO to TiO2 on photocatalytic properties of the nano-composite TiO2/CuO was investigated. The products were characterized by X-ray diffractometer, SEM, Brunauer–Emmett–Teller (BET), and DRS. BET-specific surface area of the TiO2/CuO composites was lower than that of the pure TiO2. Incorporation of CuO into TiO2 shifted absorption spectra to the visible region. As the CuO content increased from 0 to 12.5%, a clear decrease in optical band gap from 2.95 to 2.30 eV was observed. The photocatalytic performance was determined by methyl orange degradation and cyanide photo-oxidation under ultraviolet irradiation. However, the excessive incorporation... 

Stent implantation has been regarded as a major strategy to solve gastrointestinal diseases such as biliary obstruction during the last decade. The application of nitinol superelastic stents has been recently considered for minimising such problems as restenosis after stent implantation, the ability to low stent twist, unsuitable dynamic behaviour and inadequate strength radial of stent. In the present article, the effects of material properties on mechanical performance of Z shaped nitinol wire stent under crushing test for clinical applications are studied by finite element modelling. Nitinol stent shows better mechanical and clinical performance after applying 90% crushing, less chronic...