Showing 17 results for Type of Study: Technical Note
I. Ebrahimzadeh, Gh.h. Akbari,
Volume 6, Issue 1 (3-2009)
Abstract
Abstract: Horizontal continuous casting is widely used to produce semi-finished and finished metallic products.
Homogeneity in metallurgical characteristics and mechanical properties in such products is of importance. In the
present work microstructure and mechanical properties of a horizontal continuous cast pipe have been studied.
Microstructural features were investigated by an optical microscope equipped with image analyzer and SEM was used
to characterize precipitates. Tensile behavior, impact strength and hardness variations were the mechanical properties
which were studied. Results showed that microstructure and mechanical properties had diversities in different parts of
the pipe and distinct differences were observed between upper and lower parts of the pipe. A meaningful correlation
was found in microstructure and mechanical properties in different parts of the component.
M. J. Tafreshi1, M. Fazli2,
Volume 6, Issue 2 (6-2009)
Abstract
Abstract:
fabricated. Modifications carried out in different parts of the old system in order to control most
of the growth parameters with more accuracy. The fabricated system was used to grow sapphire
single crystals with almost 10 mm in diameter and 50 mm in length. The crystallinity and
structure of the grown crystals were characterized by computer aided single crystal X-ray
diffraction technique.
A Verneuil system, more sophisticated than a conventional one, has been designed and
M. Ardestani,, H. Razavizadeh,, H. Arabi, H. R. Rezaie,
Volume 6, Issue 2 (6-2009)
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
A. Bahrami, M. R. Hosseini, M. Pazouki,
Volume 6, Issue 4 (12-2009)
Abstract
Abstract:
point of view. In this study, a shaking-table was used for concentrating a manganese ore sample from the Ghasem Abad
area in Kerman, Iran. Experiments were designed by using L
The influence of each variable and their interactions on the operation of the device was studied. The variables under
investigation were: table slope, table frequency, water flowrate, feed rate, and particle size. The manganese
concentrate grade, recovery, and separation efficiency were used as response variables. It was shown that water
flowrate, table slope, feed rate, and particle size are the significant variable on concentrate grade while, all the
variables influence manganese recovery. Also, water flowrate, table slope, and table frequency have an important
effect on manganese separation efficiency. Finally, three mathematical models were presented to predict the values of
each response variables.
Among all gravity concentration methods, the shaking-table is the most effective one from the metallurgical8 Taguchi design with five variables, each in two levels.
M. Nusheh*, H. Yoozbashizadeh,
Volume 7, Issue 2 (6-2010)
Abstract
Abstract:
the competition between the precipitation of cobalt ions and evolution of hydrogen gas on the cathode surface during
the reduction process in a sulfate bath, investigation on the mechanism of metal precipitation is of great importance.
In the present work, study on the kinetics of cobalt electrowinning and the mechanism of the involved reactions have
been carried out. The obtained results, confirm the mechanism of cobalt precipitation by depletion of hydroxides. The
effects of temperature and scan rate parameters were studied on electrowinning of cobalt by cyclic voltammetry
technique. The diffusion coefficient and rate constant of the reactions were measured and calculated by performed
experiments.
Nowadays cobalt is mostly produced through the electrowinning process of sulfate solutions. Regarding to
A. m. Hadian, B. Nazari,
Volume 7, Issue 3 (8-2010)
Abstract
ABSTRACT
Dolomite refractories have a good production potential in Iran
due to the existence of high-quality dolomite ore in many regions of the country, particularly in Isfahan and Hamedan. The basic problem associated with the production and use of this type of refractories is inherent tendency to hydration of calcined dolomite. One of the methods to overcome this problem is to increase the amount of magnesia in doloma. This study focuses on the use of Iranian dolomite to produce magnesia –doloma (mag-dol) refractory with high resistance to hydration and corrosion. It was found that addition of 20wt% magnesite to dolomite would result in capsulating of CaO by MgO that protects doloma from further hydration
H. Rafiee*,, S. Rastegari, H. Arabi, M. Mojaddami,
Volume 7, Issue 4 (10-2010)
Abstract
Abstract:
activity gas diffusion process has been investigated in this research. Effects of coating temperature and aluminum
concentration in powder mixture on formation mechanism were studied using optical and scanning electron
microscopes, EDS and X-ray diffraction (XRD) techniques. For this purpose two different packs containing 1 and 2
wt% aluminum powder, were used for coating the samples at two temperatures, 850ºC and 1050ºC. The ratio of Al to
activator was kept constant in both packs. By increasing the Al content in high activity powder mixture, the
concentration of diffused Al increased in the coating layers, and the thickness of coating increased. At 1050ºC as the
rate of diffused Al to the interdiffusion zone increased, this zone gradually transformed to outer coating phases. At
850ºC coating formed by inward diffusion of Al, but at 1050ºC it was initially formed by inward diffusion of Al followed
by outward diffusion of Ni.
Formation mechanism of an aluminide coating on a nickel base superalloy IN738LC via a single step high
M. Farzalipour Tabriz, M. Ghassemi Kakroudi*,
Volume 7, Issue 4 (10-2010)
Abstract
Abstract: Cordierite-Mullite based kiln furnitures are widely used in fast-firing of ceramic products because of their low thermal expansion which confer them a very good ability to thermal shock resistance. Difference in CTE of constituent phase can develop damage during thermal cycling due to internal stresses. Increase in industrial competitiveness leads to the development of new means for extending refractory life and increasing reliability of industrial tools so investigations regarding the structuralmechanical behaviour of refractory systems are becoming essential. In this paper, Thermo-mechanical design of commercial Cordierite-Mullite based kiln furniture was investigated by using finite element method (FEM) and possible solutions for improvement of working life have been considered. The results indicated that the change of the kiln furniture geometry can decrease the maximum thermomechanical stress in study conditions which can prolong the refractory service life. Obtained results indicate the existence of an optimal thickness for the section under maximum thermo-mechanical stress. Increasing filet radius of ring region from 3 to 9 mm decreases thermo-mechanical stress value from 113 to 93 MPa.
M. J. Tafreshi, B. Dibaie, M. Fazli, M. Alidaie,
Volume 8, Issue 1 (3-2011)
Abstract
M. R. Parsa, M. Soltanieh,
Volume 9, Issue 2 (6-2012)
Abstract
In this research, the nickel oxide was dissolved in cryolite at temperatures of 880, 940 and 1000°C. In order to reduce the nickel oxide, aluminum was added to the salt. Simultaneously the nickel oxide was reduced and Al3Ni2 intermetallic compound was formed. In the duration intervals of 2.5-40 minutes samples of the salt and metallic phases were taken. The variation of the nickel content in metallic and salt samples was determined by the AAS. The results indicate that increasing the temperature and duration has a positive effect on the reduction process and Al3Ni2 intermetallic compound formation. The nickel content in the metallic sample has its highest amount at 1000°C in 10 minutes. Furthermore, practical results of the studies of nickel content variations in metallic and salt samples confirm the data obtained from theoretical calculations.
Dr Mohammad Reza Sarmasti Emami,
Volume 9, Issue 3 (9-2012)
Abstract
This paper presents an experimental and theoretical investigation of the causes of corrosion of stack in a cement plant. In this paper, information related to metallic stack failures are given in the form of a case study in Neka Cement Plant, Mazandaran, Iran. Heavy corrosion attacks were observed on the samples of stack. The failure can be caused by one or more modes such as overheating, stress corrosion cracking (SCC), hydrogen embrittlement, creep, flame impingement, sulfide attack, weld attack, dew point corrosion, etc. Theoretical calculations and experimental observations revealed that, the corrosion had taken place due to the condensation of acidic flue gases in the interior of stack. Also, the chemical analysis of the corrosion deposits and condensates confirmed the presence of highly acidic environment consisting of mostly sulfate ions.
A. Amirkaveei, A. Saidi,
Volume 9, Issue 4 (12-2012)
Abstract
Thermal explosion mode of combustion synthesis was used to fabricate TiAl-Al2O3 and TiAl-Ti2AlC-Al2O3 composites from elemental powder mixtures of TiO2, Al and C and characterized by XRD and Scanning Electron Microscopy (SEM) coupled with Energy-Dispersive Spectroscopy (EDS). The experimental results showed that thermite reaction of Al with TiO2 caused TiAl-Al2O3 composite formation. By adding carbon powder to the thermite mixture, ternary carbide Ti2AlC and TiAl-Ti2AlC-Al2O3 composite were formed. With low carbon in thermite mixture, direct formation of Ti2AlC without intermediate TiC was observed. After TiAl formation, Ti2AlC precipitated from molten TiAl in the vicinity of carbon particles. SEM micrographs show that addition of carbon to thermite mixture changes the microstructure to a laminated form with plate-like grains.
A. M. Rashad,
Volume 10, Issue 1 (3-2013)
Abstract
The current research aims to investigate alkali-activated fly ash (AAFA) concrete/mortar modified with
granulated ground blast-furnace slag (slag). FA was partially replaced with slag at levels of 0, 5, 10 and 15%, by
weight. The workability and mechanical properties of alkali-activated concretes were studied. Drying shrinkages of
alkali-activated mortars were investigated. All results of alkali-activated FA/slag concretes/mortars were compared to
control concretes/mortars based on plain AAFA. The results indicated that the workability decreased as the slag
content increased. Mechanical strengths and drying shrinkages increased with increasing slag content
S. Mohamed, S. Jamal, M. Zafer, A. Sh. M. Yassin,
Volume 11, Issue 2 (6-2014)
Abstract
High quality GGG:Cr,Ca crystal for passive Q-switching Nd:garnet lasers has been grown by the
Czochralski method. Thermal treatment of GGG crystals co-doped with Cr4+
and Ca2+
at different temperatures is
investigated. The absorption spectra were resolved into different peaks, of modified Gaussian line-shape. Transition
from octahedral sites to tetrahedral ones is thermally activated. An optimal temperature interval for this transition was
found to be 1200-1300 ˚C. The investigated samples were used as saturable absorbers in flash-lamp pumped Nd:YAG
laser, and a pulse width of about 16 nsec was obtained
A. Nogueira, S. de Barros, L. Alves,
Volume 17, Issue 3 (9-2020)
Abstract
The construction sector is responsible for relevant environmental impacts and one of its most crucial points is the use of concrete. Geopolymers represent the most promising green and ecological alternative for common Portland cement and cementitious materials, due to its proven durability, mechanical and thermal properties. This work presents an experimental and comparative study of adhesion at the fiber-matrix interface between glass fibers and carbon fibers added to the geopolymer matrix. This analysis was performed by pull-out test, whereby it was found that the greatest efficiency was obtained by reinforcing with the glass fibers, incorporated at 2 mm in the geopolymer matrix. As results, the adhesion between the fibers and the geopolymer structure can be assessed, as well as the optimum length of application.
Chitnarong Sirisathitkul, Patchara Sukonrat, Pongsakorn Jantaratana, Thanida Charoensuk,
Volume 19, Issue 3 (9-2022)
Abstract
Repeated heat treatment on manganese-bismuth (MnBi) in a tube furnace increases the homogeneity of rare-earth-free magnets. Ferromagnetic low temperature phase (LTP) MnBi is formed after heating Mn and Bi in a ratio of 2:1 at 1000 °C for 1 h and then 400 °C for 1 h. Areas with comparable compositions of Mn and Bi are detected, but some Mn and Bi remains segregate after using this stepped heating 3 times. The subsequent annealing at 340 °C gives rise to higher magnetizations and coercivity than those using 410 °C annealing. Increasing the starting Mn:Bi ratio to 4:1 reduces the coercivity and remanent magnetization due to the increase in Mn oxidation at the expense of ferromagnetic phase.
Fabio Edson Mariani, Gabriel Viana Figueiredo, German Barragan, Luiz Carlos Castelleti, Reginaldo Teixeira Coelho,
Volume 20, Issue 3 (9-2023)
Abstract
Elevating component performance through advanced surface coatings finds its epitome in the domain of laser cladding technology. This technique facilitates the precision deposition of metallic, ceramic, or cermet coatings, accentuating their superiority over conventional methods. The application spectrum for laser-clad metallic coatings is extensive, encompassing critical components. Central to the efficacy of laser cladding is the modulation of laser parameters—encompassing power, speed, and gas flow—which decisively influence both process efficiency and coating properties. The meticulous calibration of these parameters holds the key to producing components endowed with refined attributes while ensuring the sustainable continuation of the process. As such, this study embarks on an empirical investigation aimed at transcending existing process limitations. It delves into the characterization of laser-clad WC-17Co coatings on AISI H13 and AISI 4140 steels. The importance of WC-17Co coatings lies in their capacity to enhance wear resistance, extend component life, reduce maintenance costs, and improve the performance of various industrial components across diverse sectors. On the other hand, the substrates have pivotal roles. AISI H13 is lauded for its exceptional hot work capabilities, while AISI 4140 steel is renowned for its robust strength and endurance. Through rigorous evaluation, the resultant deposited coatings offer crucial insights into the efficacy of manufacturing parameters. Employing a comprehensive suite of analytical techniques including laser confocal microscopy, Vickers microhardness assessment, and micro-adhesive wear testing, the study thoroughly characterizes the samples. The outcomes underscore the achievement of homogenous coatings marked by elevated hardness and exceptional wear resistance, thereby signifying a substantial enhancement over the substrate materials.
