Sharif Digital Repository

In this paper, the effects of type and amount of various secondary carbides on the microstructure and cutting performance of Ti(C0.7N0.3)-12Co system have been investigated. Nine alloys with different amounts of WC, Mo2C and Ta0.7Nb0.3C additives were studied, using scanning electron microscopy (SEM), Vickers hardness (HV), transverse rupture strength (TRS) and continuous turning tests. Alloys including Mo2C and WC presented finer carbonitride grain structure, as well as higher wear resistance resulting from their higher hardness and highly solution hardened binder phase. © 2006 Elsevier Ltd. All rights reserved  

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... 

In present work, an attempt has been made to investigate the wear behavior of particle reinforced composites based on one of the proper magnesium alloys. The SiCP/QE22 composites and QE22 unreinforced specimens were produced via the powder metallurgy route. The volume fractions of SiC particles with three different shapes, i.e. sharp, blocky and round, were selected in the range of 10-25 vol.%. The dry sliding tests were conducted on unreinforced matrix and SiCP/QE22 composites using pin-on-disk apparatus, according to ASTM G99-95a standard. The applied loads were selected as 3, 5 and 20 N. The tests were carried out under sliding speeds of 0.5 and 1.2 m/s. In all tests, the sliding... 

We have studied the phase formation of a CoSi2 layer by solid-state reaction of ternary Co/WxTa(1-x)/Si(1 0 0) systems. The effect of cosputtered WxTa(1-x) nanometric interlayers, with different values of x (0, 0.25, 0.5, 0.75 and 1), on the degree of texturing of a CoSi2 layer and disilicide formation of the refractory metals has been investigated. The annealed samples, in a temperature range of 400-1000 °C, were analysed by x-ray diffraction, sheet resistance measurement, scanning electron microscopy, and energy-dispersive x-ray techniques. Using W0.25Ta0.75 and W interlayers, the best (1 0 0) texture of the CoSi2 layer with a thermal stability in the range of 900-1000 °C was produced. In... 

In FeCo fine particles, induced anisotropy has a considerable contribution in increasing the coercivity. We have prepared Fe0.7Co0.3 fine particles by the borohydride method in the presence of various magnetic fields in the range 0 ≤ H0 ≤ 2 kOe. We have studied and analysed the factors affecting the induced anisotropy and magnetic structure of these particles by the use of SEM, XRD and vibrating sample magnetometer. It was found that heat treatment, and also the presence of a magnetic field of about 1 kOe during the grain growth, result in the maximum coercivity of Fe 0.7Co0.3 fine particles. The value of magnetic field intensity should be such that it causes formation of oriented atomic... 

Alkoxides are the most common precursors used for the production of alumina nanopowders. These materials are, however, expensive and corrosive. This paper introduces a new method for the production of alumina nanopowders by rapid cooling of a synthetic caustic sodium aluminate solution (Bayer liquor), followed by calcination in the presence of a surface-stabilizing agent like 1,2-dihydroxy-3,5-benzene disulfonic acid disodium salt (Tiron). The powders produced are characterized by differential thermal analysis, XRD, transmission electron microscopy, scanning electron microscope, and Brunauer-Emmet-Teller. A nanopowder of α-alumina with an average crystallite size of 27.7 nm and an average... 

Denim jeans have consistently been fashionable around the world. This fabric inspired strong opinions from historians, teenagers, and movie stars, and has acquired different styles throughout the years. Most jeans today are stonewashed; this technique first become popular in 1970. Now, in addition to pumice stones, enzymes are used on the cotton fabrics to create the stonewashed look. Nowadays, plasma treatment is a cost-effective and environment-friendly process which is able to modify the properties of the fabric surface in order to achieve this effect. Plasma surface treatment changes the properties of the fabric up to a limited depth (several molecular layers), leaving the bulk... 

In this work, cavitation during creep in AA7075-T76 was simulated employing a probabilistic cellular automata scheme. Two-dimensional cellular automata coupled with the governing equations for cavity growth were utilized to define the size and distribution of cavities during creep. Both diffusion and strain-controlled mechanisms were taken into account while the first and second neighboring cells were considered for determination of the cavity growth as well as to generate the initial microstructure. Moreover, uni-axial creep experiments on AA7075-T76 were carried out under different temperatures and applied stresses including 170 MPa at 150 °C and 150 MPa at 160 °C. The microstructural... 

Copper slag (CS) is an industrial by-product, which is commonly disposed in engineered landfills. Prior studies have successfully incorporated CS as an aggregate phase in cementitious materials. However, the alkali-activated material (AAM) incorporating CS has been scarcely studied. Specifically, the elevated temperature behavior of AAM with CS has not been investigated previously. The present paper aims to study the effects of elevated temperature treatment on the mass loss and residual strength of alkali-activated slag mortars incorporating 0–100% (by volume) of CS with an incremental step of 20% instead of natural sand. The mass loss, compressive and flexural strengths, and microstructure... 

The fabrication of TixNi1-x shape memory films using simultaneous magnetron sputtering from two separate, elemental targets was investigated. The films were deposited at room temperature and then annealed at 500 °C to achieve the shape memory effect. The influence of sputtering parameters such as power ratio to the targets (to control the composition) and Ar gas pressure (to control the film structure) were studied. It was found that the Ar gas pressure had a critical influence on the shape memory effect of the films. Characterization of the films was carried out by energy dispersive X-ray spectroscopy in a scanning electron microscope (to measure the film composition and uniformity), in... 

Uniform layers of ZnO nanostructures were formed on quartz and alumina substrates through a simple vapor phase transport (VPT) method without any catalyst or buffer layer by making proper growth conditions. The effect of substrate on morphology, crystalline structure and photoluminescence spectra has been investigated. Scanning electron microscopy images revealed that morphlogical grwoth depends on used substrate, aligned rods with flower-like bundels and entangled rods are vertically aligned rods on the quartz and alumina substrates, respectively. X-ray diffraction studies showed that grown films on the quartz substrates possess stronger c-axis orientation compared to those on the alumina... 

In this study, different concentrations of ascorbic acid (50, 100 and 200 μg/mL) were added to the liquid phase of a calcium phosphate cement (CPC). The cements were immersed in simulated body fluid (SBF) for different intervals and physical, physicochemical and mechanical properties of them were evaluated. The release of added ascorbic acid from CPCs into the SBF solution was also studied. From the results, both setting time and injectability of CPC decreased by adding ascorbic acid, however the compressive strength was sharply increased before soaking in SBF solution. But, the compressive strength values of all cements (with or without ascorbic acid) soaked in SBF solution for more than 7... 

Carbon nanotubes with unique physical and mechanical properties have shown great potential for biological applications, including tissue engineering and mimicking the structure and properties of human bones. In the present work, sol-gel synthesized nanocomposite powder of multi-wall carbon nanotube/hydroxyapatite characterized using field-emission scanning electron microscopy, transmission electron microscope, X-ray diffraction, Fourier transform infra-red spectroscopy and thermal analyses. The results show homogenous dispersion of nanotube in well-crystallized hydroxyapatite ceramic matrix. Scanning electron microscopy and transmission electron microscope observations show the sodium... 

In this research, a finite element model was developed in order to simulate the two-step residual stress distribution of a thermal barrier coating system, considered to be used in diesel engine cylinder head, with a real roughness and real porosity. Two steps including the bond coat and the top coat deposition processes were taken into account. The real geometry of coating layers, including the roughness and the porosity, was also considered based on a scanning electron microscopy image. Then, effects of the convective heat transfer coefficient and initial substrate and substrate/bond coat preheating temperatures on the residual stress were studied. Obtained results illustrate that the... 

Nanosecond lasers of different intensities were pulsed into sputter-deposited amorphous thin films of near equiatomic Ni/Ti composition to produce partially crystallized highly sensitive R-phase spots surrounded by amorphous regions. Scanning electron microscopy having secondary and back-scattered electrons, field emission scanning electron microscopy, optical microscopy and X-ray diffraction patterns were used to characterize the laser treated spots. Effect of nanosecond pulse lasering on microstructure, morphology, thermal diffusion and inclusion formation was investigated. Increasing beam intensity and laser pulse-number promoted amorphous to R-phase transition. Lowering duration of the... 

Accumulative roll bonding (ARB) is used as a novel method to produce particle reinforced metal matrix composites (MMCs). Roll bonding of the sheets with layers of powder on their surfaces is the main stage in this process and it has been found that quality of the bonding has an important role in properties of the product. In this work, the behavior of alumina particles layer at interface during the rolling is investigated and the effects of particle size and amount of particle at interface on bonding of the commercial pure aluminum sheets are also studied. The results of peeling test indicate that presence of the powder at interface reduces the bond strength. However, it is shown that by... 

The main purpose of this study is to prepare and characterize hydroxyapatite (HA)-10%wt bioglass (BG) composite nanopowders and its bioactivity. Composites of hydroxyapatite with synthesized bioglass are prepared at various temperatures. Suitable calcination temperature is chosen by evaluating of the phase composition. X-ray diffraction (XRD), Transmission electron microscopy (TEM) and Scanning electron microscopy (SEM) techniques are utilized to characterize the prepared nanopowders. The bioactivity of the prepared composite samples is evaluated in an in vitro study by immersion of samples in simulated body fluid (SBF) for predicted time. Fourier transformed infrared (FTIR) spectroscopy and... 

Considerable researches have been focused on zinc-iron (Zn-Fe) alloy coatings due to their superior characteristics among zinc alloy electrodeposits in recent years. The corrosion behavior of these coatings depends on the phase structure and morphology of the Zn-Fe deposits. In this work the effects of pulse plating variables such as current density, off-time, frequency and pulse modes on the morphology and phase structure of Zn-Fe deposits was studied by scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectrometry (EDS) analysis. The corrosion behavior of these coatings was measured by means of polarization curves and Neutral salt spray tests. It was shown... 

In this study a novel Pt/Ni nanostructure consisting of nano-bushes and nanocubes was fabricated onto TiO 2 nanotubes. The scanning electron microscopy images showed that a large amount of well-dispersed nano-architectures had uniformly covered all over the surface which made an electrode with high surface area. It was obviously seen that the nanocube structures mainly consists of Ni had been grown on top of each other while the Pt colonies represented bush-like structures. As a non-enzymatic glucose biosensor, the Pt/Ni TiO 2 nanotubes modified electrode exhibited an excellent performance. The proposed biosensor had two linear ranges for detection of glucose from 0 to 0.12 mM (correlation... 

Nanocrystalline hydroxyapatite (nHA) of 50 nm average diameter and length to diameter ratio of >3 was synthesized by biomimetic method. Non-isothermal sintering improved densification behavior and mechanical properties of apatite to 0.88 maximum fractional density, 70MPa bending strength, 148MPa compressive strength and 2.53GPa microhardness at sintering temperature of 1250°C. Higher sintering temperatures resulted in the decomposition of the apatite and in-situ biphasic calcium phosphate HAP/TCP formation. This process lowered apatite densification and weakened mechanical properties of the sintered specimen. Transmission electron microscopy (TEM), x-ray diffraction (XRD) and field emission...