Sharif Digital Repository

The microstructural characteristic of HSLA welds containing different amounts of titanium were evaluated carefully. It was observed that the microstructure of welds consisted of ferrite with mixed morphologies, and small amounts of pearlite and martensite-austenite micro-constituents. Because of insufficient time for diffusion of carbon, formation of pearlite lamellae could not be completed in the weld region. Martensite was formed from carbon enrichment of austenite during nucleation and growth of acicular ferrite and bainitic ferrite. While coarse manganese sulfide particles had weak interface strength with matrix and formed some micro-fissures; increasing titanium amount of welds... 

Roll bonding is the most important stage of the accumulative roll bonding process, which is used to produce high strength composites. The presence of a particle layer at the interface alters the bonding condition and increases the threshold reduction for the commencement of bonding. In this study, the bonding mechanism in presence of powder at the interface is analyzed and a theoretical model is proposed to predict the required threshold reduction in warm roll bonding of commercially pure aluminum sheets as a function of amount of alumina particles at the interface. The model considers the rolling parameters and the effect of amount and size of particles by defining some constants, which are... 

In the present study, the roll bonding behaviour of Al-3003/Al-4043 and Al-3003/Zn sheets were compared. The bi-layer sheets were produced by a roll bonding process at different reductions in thickness and rolling temperatures. The joint strengths of the sheets were evaluated by peel and bend testing before and after supplemental annealing treatment. The peeled surfaces were examined using a scanning electron microscope. The results indicated that the Al-3003/Al-4043 sheets were bonded with higher joint strength and lower threshold reductions in thickness with respect to the Al-3003/Zn sheets. In contrast to the Al-3003/Zn sheets, significant improvement was observed in the joint strength of... 

The age-hardening behavior and microstructure of selected samples of a Ni-Co alloy were studied using hardness testing, optical microscopy, and scanning and transmission electron microscopy. The final microstructure of the material was found to be sensitive to the temperature of the solution treatment. This approach may be used to optimize the microstructure of the alloy for different applications. © 2007 Acta Materialia Inc  

Linear and nonlinear (in both steady and transient shear flows) rheological properties of polyamide 6/acrylonitrile-butadiene-styrene (PA6/ABS) nanocomposite blends have been investigated. Characterization of nanocomposite samples morphology by scanning electron microscopy revealed that with increasing nanoclay loading, size of dispersing phase droplets decreases significantly and their uniformity improved considerably. Transmission electron microscopy observations clearly display a coexistence of intercalate and exfoliate structure for nanoclay in the polymer-blend nanocomposite. On the other hand, we see that the tactoids are collected of a few silicate layers and possibly also of a single... 

Na3MnCO3PO4 (NMCP) particles were synthesized via ball milling of Mn(NO3)2.4H2O, Na2HPO4.2H2O and Na2CO3.H2O powders. The particles were anchored onto reduced graphene oxide (rGO) sheets during hydrothermal reduction process under stirring. Materials produced were characterized by x-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), thermogravimetric (TG) measurement and galvanostatic charge/discharge tests. Results showed that dissolution of ball milling products in DI water is an effective method for separation of NMCP from byproducts. Best milling time for production of pure NMCP of minimum particle... 

Platinum nanotubes (PtNTs) are fabricated by potentiostatic electrodeposition at various overpotentials (−200 up to −400 mV versus SCE) in polycarbonate templates (PCTs) with pore diameter of 200 nm in a solution containing 5 mM H2PtCl6 and 0.1 M H2SO4. The synthesized PtNTs are characterized by field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). The electrochemical growth mechanism within nanoscopic pores and the relationship between morphological variations and kinetic parameters are investigated for the first time. It is shown that more porous structure of nanotubes forms at high overpotentials possibly due to preferably nucleation. The... 

Graphene oxide flakes are considered as potential inhibitors for different pathogenic bacteria. However, the efficacy of inhibition changes for different types and strains of bacteria. In this work, we examine Pseudomonas aeruginosa and Staphylococcus aureus, two common hospital-acquired infections, which react quite differently to graphene oxide flakes. The minimum inhibitory tests yield two distinct outcomes: stopped proliferation for S. aureus versus almost no effect for P. aeruginosa. Integrating our experimental evidence with molecular dynamics simulations, we elucidate the molecular machinery involved, explaining the behavior we see in scanning electron microscopy images. According to... 

Due to the important role of surface-related properties of NPs in their biological behavior, simple and fast methods that could precisely demonstrate accurate information about NPs' surface, structure and morphology are highly desirable. In this study a set of surface morphological nano-descriptors (size, shape, surface area, agglomeration state, curvature, corner count and aspect ratio) have been defined and extracted from Transmission Electron Microscopy (TEM) images of nanoparticles (NPs) by Digital Image Processing methods. The extracted data represent a thorough description of the surface and morphologies of NPs lying beyond their TEM images and can supply the data required for a... 

The compounds α-lead oxide (α-PbO) and β-lead oxide (β-PbO) were purchased from Merck co. and used for thermal investigations in laboratory. The compound was heated in a thermogravimeter at different temperature, from 25 to 400 °C. The used gas atmosphere was O2. The received products were investigated by X-ray diffraction (XRD) technique. The received product Pb3O4 was confirmed by XRD. The textures of two different morphologies of α-PbO, β-PbO and the product Pb3O4 is investigated by scanning electron microscope (SEM) and transmission electron microscope (TEM) techniques. © 2018, Faculty of Metallurgy. All rights reserved  

The Co nanowires were electrodeposited in polycarbonate membrane (PCT). SEM, TEM and XPS techniques were used to characterize the morphology, structure and size of nanowires as well as chemical composition. The influence of different mediums was studied on the optical absorption of dispersed cobalt nanowires. The absorption spectrum of cobalt nanowires in water showed a broad shoulder at 290 nm, but in ethanol solution it was not observed in the visible region of the spectra up to 200 nm. Cobalt nanowires dispersed in methanol presented a peak at 236 nm. We attribute the data to oxidation of cobalt in water and low dielectric constant of methanol relative to ethanol and water. We found... 

Design of nanoparticle synthesis by inert-gas condensation process was studied according to the mechanisms and kinetics of nucleation and growth in the vapor phase. The effect of process parameters, e.g., source temperature, evaporation rate, and the inert-gas pressure, on the particle size and particle shape was examined at the example for silver and copper-tin alloy. The synthesized nanopowders had near spherical shape with particle size range from 10 to 60 nm dependent on the processing condition. Scanning and transmission electron microscopy (SEM and TEM) analyses showed that the crystallites are subunits of larger agglomerate particles, and relatively large particles display crystal... 

This research focused on fabrication of various carbon nanofibers (CNFs) from electrospun Polyvinyl alcohol (PVA) by utilization of iodine (I2) and cadmium acetate dihydrate (Cd) as stabilizers. Moreover, the influence of carbon nanotube (CNT) incorporation on structure and morphology of CNFs was investigated. In this regard, PVA and PVA-Cd solutions were individually prepared and electrospun. The resulting nanofibers were treated in I2 vapor and then carbonized. In the case of CNT incorporation, oxidized CNTs were first scattered in PVA and PVA-Cd solutions and then electrospun, iodinated and carbonized in the same conditions as mentioned above. It was found that the I2, Cd and their... 

In this study, we explored the growth kinetics of the Al-Fe intermetallic (IM) layer at the joint interface of the St-12/Al-5083 friction stir lap welds during post-weld annealing treatment at 350, 400 and 450 C for 30 to 180 min. Optical microscope (OM), field emission gun scanning electron microscope (FEG-SEM) and transmission electron microscope (TEM) were employed to investigate the structure of the weld zone. The thickness and composition of the IM layers were evaluated using image analysis system and electron back-scatter diffraction (EBSD), respectively. Moreover, kernel average misorientation (KAM) analysis was performed to evaluate the level of stored energy in the as-welded state.... 

Ternary nanocomposites of polypropylene/polyamide 6/layered silicate were prepared through three different processing procedures. X-ray diffraction and transmission electron microscopy were used to study the nanostructure of the samples, and tensile and impact strength measurements were conducted to assess the mechanical properties. It was shown that processing route has a significant effect on the delamination of clay platelets. Fully exfoliated nanostructure was achieved through a certain two-step processing route. Compatibilization of the blends affected microstructure as well as nanostructure. Mechanical properties were affected by changing the processing route, to a great degree.... 

An efficient method has been developed to synthesize well-aligned multi-walled carbon nanotubes (MWCNTs) on a conductive Ta substrate by chemical vapor deposition. Free-standing MWCNTs arrays were functionalized through electrochemical oxidation with the formation of hydroxyl and carboxyl functional groups. Facile template-free electrochemical routes were then developed for the shape-selective synthesis of less-common Au nanostructures, including flower, sphere, dendrite, rod, sheet, and cabbage onto the aligned MWCNTs at room temperature. Especially, among all the synthesis methods for Au nanocrystals, this is the first report using electrochemical technique to synthesize wide variety... 

VO2(picolinichydrazone) complex as a catalyst was stabilized on a SBA-15 mesoporous silica as a catalytic support by using (3-chloropropyl)triethoxysilane as a connector. SBA-15 is nanoporous and has a high ratio of surface area to volume. The immobilization of a metal–Schiff base complex to the surface area of SBA-15 can improve its catalytic effects by increasing the catalytic surface area. Unlike homogeneous catalysts, heterogeneous catalysts can be recovered and reused several times without any significant loss of catalytic activity. A vanadium–Schiff base complex-functionalized SBA-15 was synthesized by covalency connected by a pre-synthesised VO2(picolinichydrazone) complex to... 

Finemet bulk soft magnetic alloy was fabricated by spark plasma sintering of the milled ribbons. The amorphous melt-spun ribbons were milled for 36min by high energy vibrational mill and then sieved to separate particles smaller than 125μm. The size distribution of particles was determined by a laser diffraction particle size analyzer. Spark plasma sintering was carried out at super-cooled liquid region for short times of 7 and 21min. The structure of bulk samples was characterized using X-ray diffraction, scanning electron microscopy, differential scanning calorimetry and transmission electron microscopy techniques. The magnetization and coercivity of samples were measured using SQUID... 

In this research, Araldite 2011 has been reinforced using different weight fractions of Reduced Graphene Oxide (RGO). Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) analyses were conducted and it has been shown that introduction of the RGO greatly changes the film morphology of the neat adhesive. Uni-axial tests were carried out to obtain the mechanical characteristics of the adhesive-RGO composites. It has been observed that introducing 0.5 wt% RGO enhances the ultimate tensile strength of the composites by 30%. In addition, single lap joints using neat adhesive and adhesive-RGO composites were fabricated to...