Showing 4 results for Khosravi
M. Khosravi Saghezchi, H. Sarpoolaky, F. Heshmatpour,
Volume 5, Issue 2 (spring 2008 2008)
Abstract
Abstract: Lead-containing glass borosilicate was synthesized by Sol-gel technique using
metalalkoxids such as tetraethyleorthosilicate (TEOS), Al-sec-butoxide and trimethyl borate. The
sol containing TEOS converts to gel during drop wise addition of Al-alkoxide while inorganic lead
salt was added in the last stage of gelation to prepare the alcogels. The specimens were dried at
room temperature to set then heated at 600°C quickly to avoid crystallization preparing a glass
containing 63 wt% lead oxide. The influence of pH on absorption behavior of the sols studied by
UV visible technique so the characteristic of the gel, alcogel and xerogel were studied in the
different acidic concentrations. The UV spectrums show that the higher the acidity of the
hydrolysis stages, the higher the absorbance. The results showed the sample with 63 wt% lead was
found fully amorphous. Microstructure and phase analysis of the glass powders were investigated
by X-ray diffraction (XRD), X-ray fluorescence (XRF) and scanning electron microscopy (SEM)
equipped with EDS analysis.
M. Khosravi Saghezchi, R. Ajami, M. Biazar Markie, H. Sarpoolaky,
Volume 12, Issue 4 (December 2015)
Abstract
A comparing study on formation and microstructure features of aluminum titanate is investigated through both solid-state and sol-gel processes. Aluminum titanate formed by firing at 1350ºC and 1450ºC for 4h in solid-state process. In the sol-gel process formation of submicron sized particles is followed by addition of sucrose into the transparent sol. XRD analysis was confirmed the formation of aluminum titanate at 1400ºC in lower duration of calcination (3h) without any additives in the sol-gel process. In this work 2wt% MgO is added to the samples as the additive for forming acceleration of aluminum titanate. The influence of MgO addition and heat treatment are studied on phase formation and microstructure development of aluminum titanate in both procedures. Additive optimizes aluminum titanate formation at lower temperatures (1300-1350ºC). Phase and microstructure studies of Mg containing samples optimally show significance in aluminum titanate formation.
R. Niazi, E. Tohidlou, H. Khosravi,
Volume 17, Issue 3 (September 2020)
Abstract
The effects of erbium (Er) addition at various weight percentages (0-0.6 wt.% at an interval of 0.2) on the microstructural characteristics, tensile response and
wear properties of as-cast Al-7.5Si-0.5Mg alloy were evaluated. The microstructure of samples was examined by X-ray diffraction, optical microscopy and scanning electron microscopy. The obtained results demonstrated that the incorporation of erbium obviously decreased the α-Al grain size and eutectic Si, and altered the Si morphology from plate to semi-globular. Further addition of erbium (> 0.2 wt.%) did not alter the eutectic morphology and size. Moreover, the Al
3Er phase was also observed in the eutectic region after modification. Out of the erbium contents used, 0.2 wt.% erbium showed the best influence on the tensile and wear properties. Compared with those of unmodified specimen, the values of ultimate tensile strength and elongation were enhanced by 31% and 39%, respectively with the introduction of 0.2 wt.% erbium. Additionally, a remarkable enhancement in the wear properties was observed with the addition of 0.2 wt.% erbium.
Zahra Rousta, Esmaeil Tohidlou, Hamed Khosravi,
Volume 18, Issue 1 (March 2021)
Abstract
This study deals with the effects of erbium (Er) addition on the microstructural evolution and tensile properties of Al-Mg2Si in-situ metal matrix composites. The morphology of primary Mg2Si and eutectic phases were observed in details using optical microscope and scanning electron microscopy (SEM). The results showed that the increase of Er content has a slight effect on the size and morphology of primary Mg2Si phases, but the eutectic structure evolves from the coarse structure into the fine one. Also, with Er addition the eutectic mixtures of Al and Mg2Si with fibrous morphology has been developed instead of the flake like Al-Mg2Si eutectic microstructure. Meanwhile, Al3Er phase was observed in the samples containing Er. The ultimate tensile strength (UTS) of the composite changes under the various content of Er. The maximum strength was found at the 0.6 wt% Er with the fine eutectic microstructure. The study of SEM micrographs from the fracture surface of composites revealed that Er addition changes the fracture mode from brittle to ductile one with fine dimples. The mechanism of microstructural evolution was discussed in details.
