Showing 5 results for H. Razavi
H. Razavizadeh, Ershad-Langroudi A.,
Volume 1, Issue 1 (Oct 2004)
Abstract
A new process for recovering scheelite ores comprises producing a concentrate from the ore, then leaching the concentrate with H_2SO_4 in the presence of H_3PO_4 and Na Cl at atmosphericpressure are discussed. Finely purification of the product will be described. The amounts of dissolution of tungsten in acid depend on the parameters such as time, temperature, type and concentration of acid and stilt as well as solid-liquid reaction. These factors were optimized for the result and described in details.
A. R. Kamali, S. M. M. Hadavi, H. Razavizadeh, J. Fahim,
Volume 5, Issue 2 (spring 2008 2008)
Abstract
Abstract: Production of titanium aluminides in TiO2-Al-Ca system has been investigated. For this
purpose, different compositions of raw materials were studied in a special reaction vessel. In a
special case, the non-completed reaction of TiO2 with Al and Ca resulted in the production of
granulates of titanium aluminides especially Ti3Al and other Ti – Al phases as the metallic product
and Ca12Al14O33 as the non-metallic product. Remelting of metallic granulates led to production of
TiAl ingot.
M. Ardestani,, H. Razavizadeh,, H. Arabi, H. R. Rezaie,
Volume 6, Issue 2 (Spring 2009 2009)
Abstract
Abstract:
materials can be fabricated by sintering of W-Cu composite powders. In this research W-20%wt Cu composite powders
was synthesized via a co-precipitation method. Precipitate obtained from a mixture of copper nitrate and ammonium
paratungstate (APT) in distilled water contained W-Cu compounds. This precipitate was washed, dried and calcined
at 550
of dried precipitate powder was determined by thermogravimetry (TG), differential thermal analysis (DTA) and X-ray
diffraction (XRD). The sintering of the reduced powders was investigated as a function of temperature. Relative density
of more than 98% obtained for the powders sintered at 1200
close to theoretical calculations. The hardness of the sintered powders was 320 Vickers.
W-Cu composites are widely used as contacts, heat sinks and electro discharge electrodes. These kinds of°C in air and then reduced in H2 atmosphere in order to convert to W-Cu powders. The calcination temperature°C . The corresponding electrical conductivity was too
S. H. Razavi, Sh. Mirdamadi, M. M. Hormozi,
Volume 8, Issue 1 (winter 2011 2011)
Abstract
Abstract: The aim of the present investigation is to study the physical and mechanical characteristics of dental-filling spherical high-copper and silver amalgams and to compare them with a common high-copper domestic unicompositional amalgam. In this study, cylindrical specimens were mechanically condensed according to the ISO 1559:1986 Standard in order to measure the compressive strength, Vickers hardness, static creep and dimensional change on setting. Adding more silver to the amalgam increased its compressive strength, creep resistance and reduced mercury vapor. After 1, 24 and 168h of amalgamation and Modulus of elasticity of specimen S1, the mean hardness and compressive fracture strength were significantly lower than those of . No significant differences were identified for the two alloys in the creep and dimensional changes on setting. It can be concluded that as far as the mechanical properties or corrosion resistance is concerned, the amalgam should be comprised of at least one spherical alloy.
H. Momeni, H. Razavi, S. G. Shabestari,
Volume 8, Issue 2 (spring 2011 2011)
Abstract
Abstract: The supersolidus liquid phase sintering characteristics of commercial 2024 pre-alloyed powder was studied at different sintering conditions. Pre-alloyed 2024 aluminum alloy powder was produced via air atomizing process with particle size of less than 100 µm. The solidus and liquidus temperatures of the produced alloy were determined using differential thermal analysis (DTA). The sintering process was performed at various temperatures ranging from the solidus to liquidus temperatures in dry N2 gas atmosphere for 30 min in a tube furnace. The maximum density of the 2024 aluminum alloy was obtained at 610ºC which yields parts with a relative density of 98.8% of the theoretical density. The density of the sintered samples increased to the maximum 99.3% of the theoretical density with the addition of 0.1 wt. %Sn powder to the 2024 pre-alloyed powder. The maximum density was obtained at 15% liquid volume fraction for both powder mixtures.
