Showing 5 results for M. Zandrahimi
A. Poladi, M. Zandrahimi,
Volume 5, Issue 3 (Summer 2008 2008)
Abstract
Abstract: Austenitic stainless steels exhibit a low hardness and weak tribological properties. The
wear behaviour of austenitic stainless steel AISI 316 was evaluated through the pin on disc
tribological method. For investigating the effect of wear on the changes in microstructure and
resistance to wear, optical microscopy and scanning electron microscope were used. The hardness
of the worn surfaces was measured with a micro-hardness tester. Worn surfaces were analyzed
through X-ray diffraction. Results showed that with increasing the sliding distance and applied
load, the austenite phase partially transformed to ά martensite, and there was no trace of ε phase
detected. Due to the formation of probably hard and strong martensite phase, as the sliding
distance and applied load increased, the hardness and the wear resistance of the material was
increased. Wear mechanism was on the base of delamination and abrasion.
M. Pirhadi Tavandashti, M. Zandrahimi, B. Akbari,
Volume 6, Issue 1 (winter 2009 2009)
Abstract
Abstract: Nanoparticles exhibit a high reactivity and strong tendency towards agglomeration. In this study, aluminum
oxide (alumina) nanoparticles were characterized by gas adsorption (BET), transmition electron microscopy (TEM)
and photon correlation spectroscopy (PCS) techniques to assess the agglomeration of the particles. There is a good
correlation between the BET and TEM measurements but PCS was larger in the mean and median size and with a
degree of agglomerates being detected. Some agglomeration was evident, but most of the particles existed as discrete
objects as observed in the (HR) TEM images which were in good agreement with the agglomeration factor.
A. Rezvanifar, M. Zandrahimi,
Volume 7, Issue 1 (winter 2010 2010)
Abstract
Abstract:
powerful method for the characterization of microstructures of crystalline materials in terms of crystallite size and
dislocation structures. In this paper the effect of the sliding on the microstructure of A356 in the as-cast and heat
treated conditions are studied, The X-ray phase analysis shows that with increasing applied load, the dislocation
density is increased, whereas the crystallite size is decreased. It was found that heat treatment raised dislocation
density during wear. The screw or edge character of dislocations in worn specimens were determined by analyzing the
dislocation contrast factors, it was demonstrated that the character of the prevailing dislocations in high loads is
nearly pure screw.
Diffraction peak profile analysis has recently been developed to such an extent that it can be applied as a
B. Akbari, M. Pirhadi Tavandashti, M. Zandrahimi,
Volume 8, Issue 2 (spring 2011 2011)
Abstract
Abstract: Most properties of nanoparticles are size-dependent. In fact, the novel properties of nanoaprticles do not prevail until the size has been reduced to the nanometer scale. The particle size and size distribution of alumina nanoparticle, as a critical properties, have been determined by transmission electron microscopy (TEM), photon correlation spectroscopy (PCS), surface area analysis (BET) and x-ray diffraction peak broadening analysis. The particle size was found to be in the range of 5-95nm. Cumulative percentage frequency plot of the data extracted form TEM images indicates that particle size distribution obeys the log-normal function. The TEM images also reveal that particles are spherical in shape and loosely agglomerated. Comparing of the XRD and TEM results shows that the particles are single-crystal. The HRTEM images also verify that the particles have a single-crystal nature. In comparison, there is a good correlation between the BET, XRD and TEM measurements other than PCS that is sensitive to the presence of the agglomerates.
M. Zandrahimi, A. Rezvanifar,
Volume 9, Issue 1 (march 2012 2012)
Abstract
Abstract: Cold working performed before an aging treatment has a significant effect on size and amount of precipitate produced. This could be caused by the increase in defect density, such as vacancies and dislocations. In this research, the Al-Cu-Si alloy was solution-treated, wear-tested and then artificially aged for a period of 1–5 h. Changes in the amount of precipitate, in the lattice parameter of the matrix, and in the precipitates are measured by X-ray diffraction and then calculated.It was observed that performing a wear test before the aging treatment was done significantly increased the amount of precipitate, while wear rate decreased.
