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Showing 34 results for Copper

Alah Karam S.r., Alah Karam S.r.,
Volume 1, Issue 1 (3-2004)
Abstract

In this paper redox reaction processes and phase, formation on ternary Pb-2Sn-0.08Ca alloy utilized as insoluble lead anodes in copper electro winning cells, were investigated in 2M H__2SO__4 electrolytes, using cyclic voltammetry technique (CVA). A potential range between - 1.3V to 2.6V was chosen at various scan rates in order to study the anodic behavior and phase composition of the oxide layers on Pb-2Sn-0.08Ca alloy. Potential measurements were carried out with respect to a standard calomel electrode (SCE). The surface examination and phase composition of the lead alloy were determined by electron microscopy analysis (SEM) and x-ray diffraction technique, after- exposure to the cyclic voltammetry tests. The results indicated that the protective oxide layer (Pb0__2) formed at a much slower rate when exposed to 2M H__2SO__4 solutions, whilst its degradation due to a reduction in the applied potential occurred at a much faster rate. Hence, Pb0__2 did not remain stable, when the externally applied potential dropped below 1.SV and as a result, pitting initiated sporadically on the surface of the electrode.
Mir Habibi A.r., Rabiei M., Agha Baba Zadeh R., Moztar Zadeh F., Hesaraki S.,
Volume 1, Issue 3 (9-2004)
Abstract

ZnS : Cu phosphors were prepared by using laboratory grade chemicals through coprecipitating Cu along with ZnS using H2S and thiourea. Photo- and electroluminescence studies indicate that these phosphors have better emission characteristics compared to the phosphors in which activator is externally added. Phosphors with luminescence at ~530nrn were prepared. The difference between the characteristic properties of the samples seems to be due to formation of nanoparticles during the preparation of the samples by different methods.
Fotoohi B., No Parast M., Oliazadeh M.,
Volume 1, Issue 4 (12-2004)
Abstract

Gold deposits are varied regarding their geological and geochemical settings. Hence,their processing methods must be best organized for achieving the desired recovery of preciousmetals. In this research, two types of hard-rock gold ores, each with specific characteristics fromKouh-zar region (south of Damghan city) were subjected to mineral processing tests at thelaboratory scale. The reference (head) samples of both veins contained on average 3.5-4.5 ppmgold. According to mineralogical investigations no observable gold particles reported even inSEM analyses except for rare over-micrometer gold particles locked in the silica matrix.Therefore, the major (invisible) gold supposed to exist in sulfides" crystal structure. Flotationapplied to recover the gold interlocked within sulfides. The highest grades achieved were 49.2ppm @ R=77.61% for Baghu samples and 57.0 ppm @ R=61.00% for Darestan samples gold inthe sulfide concentrates. In the cyanidation diagnostic tests the optimum conditions of pH,particle size, cyanide concentration and leaching time were determined for both ores. High goldrecoveries (> 95%) were achievable for Baghu samples for the pH conditions between 10.5 and11, and cyanide and hydrated lime consumptions of 0.6 and 2.5 grams per kilogram of orerespectively. As it had been expected, direct cyanidation of Darestan samples (containing up to1.5% copper), couldn"t be established as an efficient procedure (due to cyanide consumption ofabout 20 times higher than for Baghu tests to achieve similar recoveries) and the preliminarycopper removal phase was determined as a necessity for better recovery of gold.
Paydar M.h., Fadaei R., Shariat M.h.,
Volume 2, Issue 2 (6-2005)
Abstract

Copper coated SiC powders having three different amounts of copper, in the range of 20-60 wt%, were prepared via electroless coating process. The produced composite powders were uniaxially cold compressed and sintered at different temperatures and times under protective atmosphere. It was found that composite Cu/SiC powders and a relatively dense copper matrix composite with a uniform distribution of SiC reinforcing particles imbedded in copper matrix can be fabricated via electroless coating method followed by conventional cold pressing and sintering process. The results also show that SiC particles have a poor wettability with copper and so liquid phase sintering of the Cu/SiC composite powders did not enhance densification of the samples. Regarding this fact, optimum sintering temperatures, which depends on copper content, was determined to be in the range of 1050-1080?C.
Rigaud M., Palco S., Paransky E.,
Volume 3, Issue 1 (6-2006)
Abstract

Wear of various basic refractory materials to substitute to currently used magnesia chrome bricks has been studied, measuring matte and slag penetration and dissolution, through different cup and rotary slag tests. High magnesia with and without impregnation, magnesia graphite, magnesia-alumina spinel with and without impregnation, olivine-magnesia and olivine magnesia- graphite bricks, as well as magnesia-graphite and olivine magnesia castables, have been tested. It has been shown that carbon impregnation and graphite introduction into basic refractories are feasible ways to enhance their corrosion-dissolution and penetration resistance against fayalite as well as calcium-ferrite slags. Olivine-based refractories (castables or bricks) may be considered as viable candidates to use in copper-making furnaces. At this point, evaluation of the thermo-mechanical properties of this new class of materials is still missing.
Oprea G.,
Volume 3, Issue 3 (12-2006)
Abstract

Although the flash smelting technologies use different furnace designs, the refractory linings are exposed to very similar aggressive environments and, as a result, the corrosion analysis results on one type of furnace could be generally applied to other furnaces of similar high temperature processes. Particularities regarding the different chemistries of the pyrometallurgical process and operating parameters of these furnaces could also bring particular aspects to be considered when analyzing the refractory ware and final failure in use. This paper presents a review of the existent experimental. data of corrosion analyses on refractory linings used in two particular flash furnaces for zinc-lead and respectively nickel-copper smelting. Although various modern water cooling systems are generally used to protect the refractory wall linings against corrosion by molten slag and matte, the performance of the refractory roof lining, usually used without water cooling, represents a permanent concern and the object of research studies to extend their life in service. The failure mechanisms analysed in this study are based on postmortem analyses and laboratory corrosion experiments with magnesite-chrome bricks of different chemical and mineralogical compositions. The gaseous atmosphere, usually rich in SO2 and/or CO and various metal fumes, produces irreversible microstructural changes which could shorten the life in service of the refractory lining. The experimental data proved that thermal cycling in SO2/SO3 atmospheres could bring more damage than a continuous use at relatively constant temperature, due to the magnesium and calcium sulphate formation. The laboratory experiments and postmortem analyses showed that that metal fumes at various partial pressure of oxygen would condense as oxides and react inside the pores and at the grain boundaries, contributing to the continuous deterioration of the ceramic matrix of the refractory brick lining. The mechanisms of corrosion, discussed based on laboratory experiments, were confirmed by the postmortem analyses on brick samples used in the industrial flash smelting furnaces.
A. Karimi Taheri, Kazeminezhad, A. Kiet Tieu,
Volume 4, Issue 1 (6-2007)
Abstract

Abstract: The theoretical calculation of dislocation density in different regions of a deformed workpiece of 99.99% pure copper has been carried out using different procedures consisting of Finite Element Method (FEM) and hardness measurement. To assess the validity of the results pertaining to these procedures, the dislocation density is experimentally measured utilizing the Differential Scanning Calorimetry (DSC). Comparing the predicted and experimental results, it was found that the average error in prediction of the dislocation density by the hardness measurement and FEM is 12% and 2.5%, respectively. Also, for further confirmation of the evaluated dislocation density of each region of the deformed workpiece, the annealing process was carried out and in the region of higher dislocation density, a finer grain size was observed.
Jalil Vahdati Khaki, Salman Hadji Soleimani, Mohsen Moosavi Nejad,
Volume 4, Issue 1 (6-2007)
Abstract

Abstract: The direct reduction of copper sulfide concentrate from Iranian Sarcheshme deposits with carbon in the presence of lime was investigated in the temperature range of 800-1000 ºC. The reduction kinetics was determined by means of weight loss measurements. It was found that the rate of reaction increased considerably with increasing the temperature. The kinetics was also improved when large excesses of lime and carbon were present in the mixture. The effects of catalytic additives of Na2CO3 and K2CO3 were also investigated. It was realized that the rate of reaction increased by higher concentrations of additives. X-ray diffraction analysis of reduced samples revealed that sulfur was fixed as solid CaS, and metallic copper was formed.
G. H. Akbari, M. A. Sheikhi,
Volume 4, Issue 1 (6-2007)
Abstract

Abstract: Ball mills are used in the last stage of ore processing for grinding raw materials. Forged 70Cr2 alloy steel and Austempered Ductile Iron (ADI) balls are materials from which grinding balls are made for Sarcheshmeh Copper Plant (SCP) ball mills. In the present study wear and impact properties of these two kinds of balls have been investigated. Some balls randomly were selected as samples. They were cut to investigate the cross section under optical and scanning electron microscopes. The microstructure of the sample balls was studied and quantitative measurements of microstructural features were performed. The hardness of different parts of cross sections of balls was measured. The wear resistance of the balls was measured by Pin on Disc method. Repeated dropt test was employed to evaluate impact resistance of the balls. The microstructure of ADI balls consisted of bianitic matrix with graphite nodules and some retained austenite and martensite. Micro cracks and porosities in the cast structure were frequently observed. In the case of forged steel balls the microstructure composed of tempered martensite in outer area and bianitic structure with some tempered martensite in central areas. The wear and impact resistance of forged steel balls were markedly higher than those of ADI balls. The difference was consistent with the differences between the microstructures of the two kinds of balls. Cast structure with microcracks and shrinkage porosities in ADI balls gives rise to lower impact resistance.
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.
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.
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

Seyyed Masood Bagheri , Jamal Zamani, Ali Mehdipour Omrani,
Volume 6, Issue 4 (12-2009)
Abstract

Abstract: The purpose of this study is to produce scarf joint through explosive welding process (EXW). The scarf weld is a process in which the final bond interface is oblique. With applying the explosive welding technique, this joint can create a metallic bond between similar or dissimilar metals. In this study, chamfered end of aluminum and copper plates were joined explosively and named scarf joint, employing changes in chamfered angle at different stand-off distance and explosive loading. The geometry of scarf joint enables consideration of both flyer and base plate thickness and explosive loading and the effects on mechanical properties of interface such as bond shear strength and micro-hardness can be investigated. Mathematical models developed for the interface properties of scarf joint to make relationship between the bond shear strength and explosive loading ratio. To check the adequacy of developed models, mechanical properties of interface, such as bond shear strength, predicted and compared with actual values in explosive cladding process. The results show reasonable agreement with theoretical predictions. Consequently, mathematical model which is based on scarf joints, can predict bond shear strength of cladding metals under desired explosive loading and flyer plate thickness
B. Tolaminejad, A. Karimi Taheri, H. Arabi, M. Shahmiri,
Volume 6, Issue 4 (12-2009)
Abstract

Abstract: Equal channel angular extrusion (ECAE) is a promising technique for production of ultra fine-grain (UFG) materials of few hundred nanometers size. In this research, the grain refinement of aluminium strip is accelerated by sandwiching it between two copper strips and then subjecting the three strips to ECAE process simultaneously. The loosely packed copper-aluminium-copper laminated billet was passed through ECAE die up to 8 passes using the Bc route. Then, tensile properties and some microstructural characteristics of the aluminium layer were evaluated. The scanning and transmission electron microscopes, and X-ray diffraction were used to characterize the microstructure. The results show that the yield stress of middle layer (Al) is increased significantly by about four times after application of ECAE throughout the four consecutive passes and then it is slightly decreased when more ECAE passes are applied. An ultra fine grain within the range of 500 to 600 nm was obtained in the Al layer by increasing the thickness of the copper layers. It was observed that the reduction of grain size in the aluminium layer is nearly 55% more than that of a ECA-extruded single layer aluminium billet, i.e. extruding a single aluminium strip or a billet without any clad for the same amount of deformation. This behaviour was attributed to the higher rates of dislocations interaction and cell formation and texture development during the ECAE of the laminated composite compared to those of a single billet
Z. Ghaferi, K. Raeissi, M. A. Golozar,, A. Saatchi, S. Kabi,
Volume 7, Issue 4 (10-2010)
Abstract

Abstract:

current densities. Electrochemical impedance spectroscopy (EIS) results showed that the codeposition mechanism of

tungsten in Ni-W deposition is the reduction of tungsten oxide which changed to the reduction of tungsten-containing

ion complexes at higher current densities. In Co-W electrodeposition, the tungsten codeposition takes place via

reduction of tungsten oxide, although, the role of tungsten-containing complexes at higher current densities cannot be

ruled out. The surface morphology of Ni-W coatings was crack-free and was strongly dependent on deposition current

density. In addition, higher grain size and lower tungsten content were obtained by increasing the current density. In

Co-W coatings, no obvious variation in surface morphology was observed except for the fine cracks appeared at

higher current densities. In this system the grain size remained almost constant with increasing current density. The

microhardness values of Ni-W and Co-W coatings decreased due to the increase in the grain size and/or decrease in

tungsten content.

Ni-W and Co-W alloy nanocrystalline coatings were electrodeposited on copper substrate at different

S. H. Razavi, Sh. Mirdamadi, M. M. Hormozi,
Volume 8, Issue 1 (3-2011)
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.
M. R. Zamanzad-Ghavidel,, K. Raeissi, A. Saatchi,
Volume 9, Issue 2 (6-2012)
Abstract

Abstract: Nickel was electrodeposited onto copper substrates with high {111} and {400} peak intensities. The grain size of coatings deposited onto the copper substrate with a higher {111} peak intensity was finer. Spheroidized pyramid morphology was obtained at low current densities on both copper substrates. By increasing the deposition current density, grain size of the coating was increased for both substrates and eventually a mixed morphology of pyramids and blocks was appeared without further increase in grain size. This decreased the anodic exchange current density probably due to the decrease of surface roughness and led to a lower corrosion rate.
Z. Shahri, S.r. Allahkaram,
Volume 9, Issue 4 (12-2012)
Abstract

Metal matrix composite coatings reinforced with nano-particles have attracted scientific and technological interest due to the enhanced properties exhibited by these coatings. Cobalt/hexagonal boron nitride nano-composite coatings were prepared by means of the pulse current electroplating from a chloride electrolyte on copper substrates and a comparison was made with the pure cobalt in terms of structure and tribological properties. Effects of particles concentration (5-20 gL-1) and current density (50-200 mA cm-2) on the characterization of electroplated coatings were investigated via X-ray diffraction analysis, energy dispersive spectroscopy and Vickers micro-hardness. Moreover, the tribological behavior was studied using pin-on-disc method. The results showed that cobalt/hexagonal boron nitride nano-composite coatings have higher hardness, wear resistance and lower friction coefficient than pure cobalt and the plating parameters strongly affect the coating’s properties
Z. Shahri, S. R. Allahkaram,
Volume 10, Issue 4 (12-2013)
Abstract

Metal matrix nano composite coatings possess enhanced properties such as corrosion and wear resistance. This paper aims to study the corrosion behavior of pure Co and Co-BN nano composite coatings deposited with different particles concentration (5-20 g L-1) on copper substrates using electroplating technique. Morphology and elemental compositions of the coatings were investigated by means of scanning electron microscope (SEM) equipped with an energy dispersive spectroscopy (EDS). The corrosion behavior was analyzed in a 3.5 wt% NaCl via polarization and impedance techniques. The results obtained in this study indicate that the co-deposition of BN nano particles improved corrosion resistance of electrodeposited cobalt coatings.
A. Nikfahm, I. Danaee, A. Ashrafi, M. R. Toroghinejad,
Volume 11, Issue 2 (6-2014)
Abstract

In this research accumulative roll bonding process as sever plastic deformation process was applied up to 8 cycles to produce the ultrafine grain copper. Microstructure of cycle 1, cycle 4 and cycle 8 investigated by TEM images. By analyzing TEM images the grain size measured below 100 nm in cycle 8 and it was with an average grain size of 200 nm. Corrosion resistance of rolled copper strips in comparing with unrolled copper strip was investigated in acidic (pH=2) 3.5 wt. % NaCl solution. Potentiodynamic polarization and EIS tests used for corrosion resistance investigations. The corrosion morphologies analyzed by FE-SEM microscopy after polarization test and immersion for 40 hours. Results show that the corrosion resistance decreased up to cycle 2 and increased after rolled for forth time. The corrosion degradation was more intergranular in cycle 2 and unrolled counterpart. It was more uniform rather than intergranular type in cycle 8. Corrosion current density in unrolled sample (2.55 µAcm -2 ) was about two times of that in cycle 8 (1.45 µAcm -2 ). The higher corrosion rate in cycle 2 in comparison with others was attributed to unstable microstructure and increase in dislocation density whereas the uniform corrosion in cycle 8 was due to stable UFG formation

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