Showing 706 results for Type of Study: Research Paper
H. Ghasemi, M. A. Faghihi Sani, Z. Riazi,
Volume 4, Issue 3 (12-2007)
Abstract
Abstract: The effect of phase development on peel strength of alumina-copper metalized joint has
been investigated. The alumina-copper joint was prepared in three stages. The alumina substrate
was, first, metalized at 1500°C in H2-furnace by a new formulation. In the second step, a nickel
layer was electroplated on the metalized layer with approximately 10µm thickness. Finally, copper
strips were bonded to metalized alumina with Ag-Cu (72-28) filler metal. The peel strength of the
joint was 9.5±0.5 Kg/cm which shows approximately 30% increase in comparison to previous
works. By study of fracture surface and crack propagation path, it has been concluded that this
increase is due to the formation of more spinel phase.
A. Zakeri,, M. Sh. Bafghi, Sh. Shahriari,
Volume 4, Issue 3 (12-2007)
Abstract
Abstract: In this paper, kinetics of reductive leaching of manganese dioxide ore by ferrous ion in
sulfuric acid media has been examined. Experimental results show that increasing temperature
from 20 to 60 °C and decreasing ore particle size from −16+20 to −60+100 mesh considerably
enhance both the dissolution rate and efficiency. Molar ratios of Fe2+/MnO2 and H2SO4/MnO2 in
excess to the stoichiometric amounts were needed for successful manganese dissolution. Under the
optimum condition (ore particle size of −60+100 mesh, Fe2+/MnO2 molar ratio of 3.0,
H2SO4/MnO2 molar ratio of 2.0) manganese could be extracted with over 95% efficiency by 20
minutes leaching at room temperature. A kinetic analysis based on dimensionless time method
showed that shrinking core – ash diffusion control model fits the experimental results reasonably
well. Value of activation energy was found to be 28.1 kJ/mole for the proposed mechanism.
A. Ahmadi,, H. Sarpoolaky,, A. Mirhabibi, F. Golestani-Fard,
Volume 4, Issue 3 (12-2007)
Abstract
Abstract: Dolomite based refractories are widely used in Iranian steelmaking plants. In the
present research, wear and corrosion of refractories used in steel-making converter lining in
Esfahan Steel Company was studied. Post-mortem analysis of refractories clarified that the wear
started with oxidation of carbon followed by chemical corrosion. Iron oxide from slag reacted with
calcia, resulting in formation of low melting phase, and subsequent washout process, caused the
refractory corrosion onset from the hot face. In addition, the effect of aluminum as an anti-oxidant
and graphite on the corrosion resistance of refractory was investigated. Tar-dolomite samples
containing different amount of graphite (0, 4, 7, and 10 wt. %) were prepared in order to study
their physical properties, before and after coking. SEM micrographs employed to analyze the
microstructures to determine the effect of graphite and antioxidant on corrosion behavior of the
refractory. Results showed that oxidation process of carbon in the system was hindered and
improved corrosion resistance by introducing graphite and antioxidant into the refractory
composition.
M. Aazami, A. Khodadadi, A. Farzanegan,
Volume 4, Issue 3 (12-2007)
Abstract
Abstract: The specific rate of breakage is one of the most important factors in evaluation of
grinding process especially in ball mill. In this article the effect of ball size and feed size on
selection function were investigated using batch grinding circuit on two-iron ore anomaly (B, C)
from sangan mine in north of Iran. Eight different monosize fractions were prepared between 2000
and 500 microns, using a 2 sieve series. The specific rates of breakage (Si) were determined from
the size distributions at different grinding times, and the specific rates of breakage were compared
for three different ball diameters (25.4, 16.6 and 9.6 mm). The results showed that the breakage
function of both anomalies is normalizable (independent to the particle size) and it is independent
to the ball size. But the specific rate of breakage variate with feed size and ball size. Also optimum
size of balls for grinding of this feed obtained to be between 9.6-16.6mm.
M. Huger,, C. Gault, T. Chotard,
Volume 4, Issue 3 (12-2007)
Abstract
Abstract: A pulse-echo technique, based on ultrasonic "long-bar" mode (LBM) velocity
measurements, working up to 1700°C is described. Magnetostrictive transducers and ultrasonic
lines used in a 40-85 kHz frequency range are detailed. The conditions of choice of fundamental
parameters (frequency, line geometry, sample size) are discussed in relation with the nature and
the microstructure of the materials under test. This technique can be used to study the variations of
elastic moduli of materials at high temperature. Examples are reported concerning a wide range
of refractory materials used in steel making industry: Al2O3/C refractories used for ladles shrouds,
Al2O3-MgAl2O4 castables used for steel ladle lining, and MgO/C refractories used for basic
oxygen furnace.
K. Ghanbari Ahari,
Volume 5, Issue 1 (3-2008)
Abstract
Abstract: Thermodynamic computational packages MTDATA and FactSage have been used to
carry out calculations on the variation with temperature of the phases precipitated on cooling in
both oxidising and reducing conditions of a typical ladle slag composition, in the temperature
range 1700 - 900°C. The current coverage of the databases associated with the computational
packages is discussed in relation to their application to slag - refractory interaction and the
validity of the results is compared with some relevant experimental data and phase equilibrium
studies
K. Ghadarghadr Jahromi, , A. Zarei-Hanzaki, O. Golmahalleh,
Volume 5, Issue 1 (3-2008)
Abstract
Abstract: In the present investigation, the effects of thermomechanical processing parameters and
the steel chemical composition on the ultra fine ferrite formation characteristics were studied.
This was programmed relying on the capabilities of strain induced transformation (SIT)
phenomenon and applying to different grades of Si-Mn TRIP (Transformation Induced Plasticity)
steels. Accordingly, wedge shaped specimens were rolled at two different temperatures, above and
below the austenite-to-ferrite transformation temperature (Ar3). An ultra fine ferrite grain size, in
the scale of some hundred nanometers, was obtained by rolling the specimens with lower Si
content at a temperature below the related Ar3 temperature. The amount of reduction, which was
resulted in the latter microstructure, was realized to be about 55%.
H. Fattahi, M. H. Shariat,
Volume 5, Issue 1 (3-2008)
Abstract
Abstract: In chloride salt solutions, titanium alloys exhibit reasonably high pitting potentials as
high as +10 V (vs. Ag/AgCl) at room temperatures. On the other hand, anodic pitting potentials
are significantly lower in bromide solutions. In this study, pitting corrosion of commercially pure
titanium in aqueous NaBr solution of 0.1 M concentration at room temperature was studied and
the effect of an external magnetic field oriented both parallel and perpendicular to electrode
surface was investigated. Cyclic potentiodynamic and potentiostatic polarization tests were
carried out. Anodic breakdown potential of +1.45 V (vs. Ag/AgCl) obtained in the absence of
magnetic field, decreasing to +1.11 V in the presence of a 0.05 T parallel magnetic field. The
perpendicular magnetic field actually did not affect the breakdown potential. Applying of an
external magnetic field, independent of its orientation, shifted the repassivation potential
approximately 150 mV in the positive direction. SEM microscopy observations of sample surfaces
indicated that applying of magnetic field results in some variations in the pit shapes and their
sizes.
M. Rezvani, B. Eftekhari Yekta, V. K. Marghussian,
Volume 5, Issue 1 (3-2008)
Abstract
Abstract: The application of inexpensive materials such as copper, zinc, lead, iron and steel slag in
manufacturing of glass and glass-ceramic products in construction industry, lining materials as
anti-corrosion and anti-abrasion coatings in metals and etc, has led to considerable progress in
glass technology in recent years. The composition of slag glass-ceramics is mainly located in the
SiO2-Al2O3-CaO-MgO system, in which one of the most important problems is the lack of bulk
crystallization. To resolve the above-mentioned problem, the crystallization behavior of various
compositions containing different nucleating agents Cr2O3 , Fe2O3 and TiO2 in the single, double
and triple forms were studied by differential thermal analysis (DTA).The precipitated crystalline
phases was determined by the X-ray diffractometry and the micro-structural analysis was studies
using the SEM micrographs. The three point bending strength, micro-hardness and the chemical
resistance of the best composition were determined. According to the results, the resulted glassceramic
had a better specification than the stoneware floor tiles and the porcelain one, which are
considered as the two important competitors for it.
A. Ataie1,, S. Heshmati-Manesh1,, S. Sheibani1,, G. R. Khayati,y. Firozbakht,
Volume 5, Issue 1 (3-2008)
Abstract
Abstract: In this paper solid state reduction of high carbon ferrochromium-chromite composite
pellets in the temperature range of 900-1350°C was investigated. A two stage reduction
mechanism is proposed. The first stage is likely to be controlled by the chemical reaction with
activation energy of 127.2kJ/mol. In the second stage, solid state diffusion of carbon through the
reaction product layer is suggested to be rate controlling. The activation energy of this stage was
calculated to be 93.1kJ/mol. The reduction process was found to be favored by high temperatures
as well as high vacuum. The results also show that pre-milling of initial mixture has a negative
effect on the reduction degree.
M. Kazemi Pour, S. Sharafi,
Volume 5, Issue 1 (3-2008)
Abstract
Abstract: Hardfacing is one of the most useful and economical ways to increase the service life of
components subjected to abrasive wear. Iron based hardfacing alloys have long been considered
as candidate coatings for wear-resistant applications in industry. In the present work two layer of
Fe-34Cr-4.5C%wt hardfacing alloy was deposited on ASTM A36 carbon steel plates by SMAW
method. The microstructure consists of large primary and eutectic M7C3 carbides, metastable
austenite and small amount of secondary carbides. The microstructure was analyzed by optical
and scanning electron microscopes. In the same condition of size, shape, distribution and volume
fraction of carbides the as-welded matrix changed to martensite, tempered martensite and ferrite
by heat treatment processes. The wear resistance was measured by pin-on-disk method under loads
of 5, 10 and 20N and for sliding distance of 1500m. The results showed that the as-welded sample
with austenitic matrix has the most and the ferritic matrix specimen has the least wear resistance.
The predominate mechanisms for mass losses were determined to be micro-cutting, microploughing.
C. Dehghanian, Y. Mirabolfathi Nejad,
Volume 5, Issue 1 (3-2008)
Abstract
Abstract: Despite having a number of advantages, reinforced concrete can suffer rebar corrosion
in high–chloride media, resulting in failure of reinforced concrete structures. In this research the
corrosion inhibition capability of the mixture of calcium and ammonium nitrate of steel rebar
corrosion was investigated in the simulated concrete pore solution. Cyclic polarization and
Electrochemical Impedance Spectroscopy (EIS) techniques were applied on steel concrete pore
solution containing 2 weight percent sodium chloride (NaCl). Results show that such mixtures had
higher inhibition efficiency than calcium nitrate alone. The optimum concentration of the inhibitor
mixture was determined to be 45 mgr/lit.
N. Hatami,, R. Babaei, P. Davami,
Volume 5, Issue 2 (6-2008)
Abstract
Abstract: In this study an algorithm for mold-filling simulation with consideration of surface
tension has been developed based on a SOLA VOF scheme. As the governing equations, the
Navier-Stokes equations for incompressible and laminar flows were used. We proposed a way of
considering surface tension in mold-filling simulation. The proposed scheme for surface tension
was based on the continuum surface force (CSF) model we could confirm the remarkable
effectiveness of the surface tension by experiment which concluded in very positive outcome.
A. R. Kamali, S. M. M. Hadavi, H. Razavizadeh, J. Fahim,
Volume 5, Issue 2 (6-2008)
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. Khosravi Saghezchi, H. Sarpoolaky, F. Heshmatpour,
Volume 5, Issue 2 (6-2008)
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.
A. Hassani, R. Ravaee,
Volume 5, Issue 2 (6-2008)
Abstract
Abstract: To ensure the rail transportations safety, evaluation of fatigue behavior of the rail steel
is necessary. High cycle fatigue behaviour of a rail steel was the subject of investigation in this
research using fracture mechanics. Finite element method (FEM) was used for analyzing the
distribution of the stresses on the rail, exerted by the external load. FEM analysis showed that the
maximum longitudinal stresses occurred on the railhead. To find out about the relation of crack
growth with its critical size, and to estimate its lifetime, the behaviour of transverse cracks to rail
direction was studied using damage tolerance concept. It revealed that transverse crack growth
initially occurred slowly, but it accelerated once the crack size became larger. Residual service
life was calculated for defective segments of the rails. In addition, allowable crack size for
different non-destructive testing intervals was determined the allowable crack size decreased as
the NDT intervals increased.
A. Allahverdi, E. Najafi Kani, S. Esmaeilpoor,
Volume 5, Issue 2 (6-2008)
Abstract
Abstract: The use of alkali-activated cementitious materials especially over the past decades has
significantly been increased. The goal of this research is to investigate the effects of silica modulus
and alkali concentration on alkali-activation of blast-furnace slag. In this research, the most
important physical characteristics of cementitious systems, i.e. the 28-day compressive strength
and final setting time, were studied by changing influencing parameters such as silica modulus,
i.e. SiO2/Na2O, (0.44, 0.52, 0.60, and 0.68) and Na2O concentration (4, 6, 8 and 10% by weight of
dry binder) at a constant water-to-dry binder ratio of 0.25. Final setting time of the studied
systems varies in the range between 55-386 minutes. The obtained results show that systems cured
at an atmosphere of more than 95% relative humidity at room temperature exhibit relatively high
28-day compressive strengths up to 107 MPa.
A. Moosavi, A. Aghaei,
Volume 5, Issue 2 (6-2008)
Abstract
Abstract: Auto-ignited gel combustion process has been used for producing a red hematite-zircon
based pigment. The combustible mixtures contained the metal nitrates and citric acid as oxidizers
and fuel, respectively. Sodium silicate (water glass) was used as silica source for producing zircon
phase. X-Ray Diffractometery, Electron Microscopy and Simultaneous Thermal Analysis were used
for characterization of reactions happened in the resulted dried gel during its heat-treatment.
L* a* b* color parameters were measured by the CIE (Commission International de I'Eclairage)
colorimetric method. This research has showed that solution combustion was unable to produce
coral pigment as the end product of combustion without the need for any further heat treatment
process.
William L. Headrick,, Alireza Rezaie, William G. Fahrenholtz,
Volume 5, Issue 2 (6-2008)
Abstract
gasification (BBLG). One particularly harsh application is linings for gasifiers used in the
treatment of black liquor (BL). Black liquor is a water solution of the non-cellulose portion of the
wood (mainly lignin) and the spent pulping chemicals (Na2CO3, K2CO3, and Na2S). Development
of new refractory materials for the black liquor gasification (BLG) application is a critical issue
for implementation of this technology. FactSage® thermodynamic software was used to analyze
the phases present in BL smelt and to predict the interaction of BL smelt with different refractory
compounds. The modeling included prediction of the phases formed under the operating
conditions of high temperature black liquor gasification (BLG) process. At the operating
temperature of the BLG, FactSage® predicted that the water would evaporate from the BL and that
the organic portion of BL would combust, leaving a black liquor smelt composed of sodium
carbonate (70-75%), potassium carbonate (2-5%), and sodium sulfide (20-25%). Exposure of
aluminosilicates to this smelt leads to significant corrosion due to formation of expansive phases
with subsequent cracking and spalling. Oxides (ZrO2, CeO2, La2O3, Y2O3, Li2O, MgO and CaO)
were determined to be resistant to black liquor smelt but non-oxides (SiC and Si3N4) would oxidize
and dissolve in the smelt. The other candidates such as MgAl2O4 and BaAl2O4 were resistant to
sodium carbonate but not to potassium carbonate. LiAlO2 was stable with both sodium carbonate
and potassium carbonate. Candidate materials selected on the basis of the thermodynamic
calculations are being tested by sessile drop test for corrosion resistance to molten black liquor
smelt. Sessile drop testing has confirmed the thermodynamic predictions for Al2O3, CeO2, MgO
and CaO. Sessile drop testing showed that the thermodynamic predictions were incorrect for ZrO2.
M. Divandari,, H. Arabi, H. Ghasemi Mianaei,
Volume 5, Issue 3 (9-2008)
Abstract
Abstract: Thermal fatigue is a stochastic process often showing considerable scatter even in
controlled environments. Due to complexity of thermal fatigue, there is no a complete analytical
solution for predicting the effect of this property on the life of various components, subjected to
severe thermal fluctuations. Among these components, one can mention car cylinder, cylinder head
and piston which bear damages due to thermal fatigue. All these components are usually produced
by casting techniques. In order to comprehend and compare the thermal fatigue resistance of cast
Al alloys 356 and 413, this research was designed and performed. For this purpose, several
samples in the form of disc were cast from the two alloys in sand mould. The microstructures of the
cast samples were studied by light microscopy in order to choose the samples with the least
amounts of defects for thermal fatigue tests. The results of thermal fatigue tests showed that the
nucleation of microcracks in Al-356 alloy occurred at shorter time relative to those occurred in Al-
413 alloy under the same test conditions. In addition, the density of micro-cracks in Al-356 alloy
was more than that of Al-413 alloy. The results of fractography on 356 alloy indicated that the
cracks were generally nucleated from inter-dendritic shrinkage porosities and occasionally from
the interface of silicon particles with the matrix. The growth of these micro cracks was along the
dendrite arms. Fractography of 413 alloy fracture surfaces showed that nucleation of microcracks
was often associated with silicon particles.
