Showing 9 results for Saatchi
Saatchi, A. Najafi- Zadeh, M. R. Rahimipour,
Volume 14, Issue 1 (1-1994)
Abstract
M. Monir-Vaghefi, A Saatchi and J.hejazi,
Volume 15, Issue 1 (7-1994)
Abstract
In this work the effects of various methods of agitation on the properties of electroless Ni-P-MoS2 composite coatings were investigated. Magnetic stirring as well as purging the solution with gas (Air, Oxygen, Nitrogen) were used. Plating rate, chemical composition, MoS2 distribution, and hardness of the deposit were measured. Topography of coating was studied with metallography and scanning electron microscopy. It was concluded that purging the solution with air produced optimum results, i.e. high rate of deposition, uniform distribution of MoS2 particles and appropriate surface morphology.
M. H. Fathi, Gh. Feizi, Sb. Moosavi, Gh. Gahanshahi, M. Salehi, A. Saatchi and V. Mortazavi,
Volume 20, Issue 1 (7-2001)
Abstract
Hydroxyapatite coatings have been used on metallic substrates in a variety of applications, including modifying the surface of human implants, bone osseointegration and biological fixation. In this paper, the effects of various kinds of metallic substrate on clinical and pathological results of in vivo tests are presented. Four kinds of endodontic implants i.e, stainless steel, cobalt base alloy, plasma sprayed hydroxyapatite coated stainless steel, plasma sprayed hydroxyapatite coated cobalt base alloy were prapared and implanted in mandibular canine of
cats. After a healing period of 4 months, investigation by SEM and histopathological interpretation and evaluation showed significant differences in tissue response and osseointegration between coated and non-coated metallic implants. It was concluded that the results were affected by the kind of metallic substrate .
Keywords: Hydroxyapatite coating, Dental endodontic implant, Osseointegration, Corrosion, Stainless steel,
Cobalt base alloy
A. Saatchi, H. Yan, and S. J. Harris,
Volume 20, Issue 1 (7-2001)
Abstract
Zinc was electrodeposited from an acidic sulphate solution on commercial steel sheet substrates galvanostatically at 10, 20, and 100 mA/cm2. The steel substrates had an average roughness number of 1.34 microns and a high percentage of its grains had their (111) planes parallel to the plate surface. During electrodeposition at 10 mA/cm2, on some specimens, there was an intense potential fluctuation around –870 mV vs Saturated Calomel Electrode (SCE). During this period zinc hydroxide precipitated on the surface. After a certain time, the potential dropped to –1020 for zinc deposition. Zinc nuclei were seen to precipitate from zinc hydroxide. Increasing current density changed nucleation mode from progressive to instantaneous, and also changed the size, morphology, and texture of zinc deposits.
Keywords: Zinc Electroplating, Current Density, Morphology, Orientation
M. Shamanian, A. Saatchi, M. Salehi and T. H North,
Volume 21, Issue 2 (1-2003)
Abstract
The metallurgical and mechanical properties of Ti6Al4V/(WC-Co) friction welds have ben investigated. The microstructure close to the bondline comprised a mixture of acicular and equiaxed α plus β phases. The diffusion of elements in the welded specimens has been detected. The fracture strengths of Ti6Al4V/(WC-Co) friction welds markedly improved when the cobalt content in the (WC-Co) carbide substrate increased.
During the three-point bend testing of Ti6Al4V/WC-6wt.%Co welds, the crack initiated at the bondline region at the periphery of the weld and then propagated into the brittle (WC-6wt.%Co) substrate, while with the Ti6Al4V/WC-11 wt.%Co and Ti6Al4V/WC-24wt.%Co welds, the crack initiated and propagated at the bondline region.
Keywords: Friction welding, Ti6Al4V alloy, Cemented tungsten carbide, Microstructure, Fracture strength
K. Raeissi, A. Saatchi and M. A. Golozar,
Volume 23, Issue 2 (1-2005)
Abstract
On electropolished steel at low current densities, morphology and texture of electrodeposited zinc were investigated. Zinc coating is consisted of hexagonal crystallites laid on each other to produce packets. These packets are of different sizes and are stacked in different orientations to construct a homogeneous coating on steel substrate. This coating does not have texture, i.e., it has a random texture. With increasing current density, the morphology changes completely as each grain attains a special orientation. In this case, coating has a strong basal plane (0002) along with low angle planes (1013 and 1014). Coating obtained on mechanically polished surfaces consists of individual packets of zinc crystals, which are near each other with different
orientations. These coatings have a higher density of basal plane (0002) in comparison to electropolished surfaces. The morphology and texture variations with cathodic polarization and surface preparation of steel are due to their effect on nucleation and growth.
F. Shahriari, F. Ashrafizadeh, A. Saatchi,
Volume 31, Issue 2 (Dec 2012)
Abstract
Although titanium has been recognized for its excellent bio-compatibility with human tissues and good corrosion resistance in some specific environments, little attention has been paid to the surface enrichment of the components by titanium. In this paper, titanium diffusion coating was formed on the surface of Ni-based alloy B-1900 via pack cementation technique and the microstructure of the coatings obtained was studied. Diffusion titanizing was carried out via pack cementation technique at 850 and 950 C for 3 hours in a mixture of commercially pure titanium, Al2O3 and NH4Cl powder. Microstructure, phase composition and concentration profile of the coatings were examined using optical and electron metallography, X-ray diffraction, and glow discharge optical spectroscopy. The results showed that Ti2Ni and AlNi2Ti were the main constituents of the coating. The formation mechanism of the coatings was also evaluated.
A. Fattah-Alhosseini, A. Saatchi, M.a. Golozar, K. Raeissi, B. Bavarian,
Volume 32, Issue 2 (Dec 2013)
Abstract
In this study, effect of potential on composition and depth profiles of passive films formed on 316L stainless steel in 0.05 M sulfuric acid has been examined using X-ray photoelectron spectroscopy (XPS). For passive film formation within the passive region, four potentials -0.2, 0.2, 0.5, and 0.8 VSCE were chosen and films were gown at each potential for 60 min. XPS analysis results showed that atomic concentration of Cr and Fe initially increase (E < 0.5 VSCE) and then decrease with potential. This decrease is due to surface dissolution of the Fe and Cr oxides. For both alloying elements, Ni and Mo, no obvious change in atomic concentration was showed. Results indicated that at higher potentials, before entering transpassive region, oxidation of Cr3+ to Cr6+ is happened.
M. Rezazadeh, R. Emadi, A. Saatchi, A. Ghasemi, M. Rezaeinia,
Volume 35, Issue 3 (Journal of Advanced Materials-Fall 2016)
Abstract
Simultaneous application of mechanical pressure and electrical charge on powder samples in spark plasma sintering process, has resulted in a sample with a density close to the theory. In the present study, a thermal-electrical-mechanical coupled finite element model of spark plasma sintering system using multi-objective optimization algorithm is proposed to optimize the mold variable. The simulation performed for Si3N4-SiO2 (1:1 mol) specimen has good agreement with the experimental results. Multi-objective genetic algorithms was used for optimization of mold design in order to maximize the temperature of sample core and minimize the mises stress in the mold. The results show that the optimized dimensions cause 8% increase in sample temperature and about 18% decrease in temperature difference between mold surface and sample core. This leads to better uniformity in the porosity distribution of final sample.
