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By Guanyong Shi, Zhihe Dou, Cong Wang, Ting'an Zhang, Hongyan Zhang

We prepared the CuCr alloy by thermit reduction-electromagnetic casting. But there are the defects such as stomata and oxide inclusions in CuCr alloy. In this paper, the existing state and distribution of inclusions and stomata in CuCr alloy are systematically analyzed. The alloy was characterized via SEM, EDS and metallographic microscope, in which the existing state and micro-structural defects of inclusions are analyzed. The results show that: there are three distinct areas: copper-rich areas, chromium-rich areas and the inclusion areas. Inclusions are mainly in the form of stomata and Al2O3 phase, mainly locating in the copper-rich phase and the interface area of chromium-rich phase and the copper-rich phase. Then, the composition of phases of the smelting slags and alloy were characterized via XRD. The results show that: the slag consists of Al2O3 and a little of Cr, the alloy consists of Cr, Cu and a little of Al2O3.

Jan 1, 2015

By P. N. Anyalebechi

The effects of application of steady and pulsed electric current on the cast microstructures of ingots of a 7050 type aluminum alloy have been experimentally investigated over a solidification rate range of 0.1-10 K/s. This involved the application of an electric current of 465-930 mA/cm2 of melt surface area to laboratory-size ingots solidified in a unidirectional manner. Within the ranges of electric current density and solidification rate investigated, the applied electric current reduced the average dendrite, grain, and second-phase particle size. It also made the size distribution of the second-phase particles more uniform. The mechanism for the observed refinement of the cast microstructure by the applied electric current is not well understood. The potential effects of heat-induced local convections, shear stress-induced fragmentation of dendrites, increased temperature gradient due to Joule heating and the thermal and constitutional supercooling engendered by Peltier, Thompson, and Joule heating are discussed.

Jan 1, 2009

By Yuzura Sato

Viscosity has been measured for various molten binary alloys of nickel with iron, cobalt and chromium in order to clarify the behavior of viscous flow of molten nickel alloys. The entire concentration range for iron and cobalt and 0-67at% of chromium content were studied. The measurement method was an oscillating cup viscometry using an alumina crucible that was precisely machined. The temperature was up to about I 880K for all the measurements. The results represented good Arrhenian relationship although some measurements included overcooled temperatures. The isothermal viscosities increased monotonously with an addition of iron and chromium into nickel. The addition of cobalt increased after stationariness. The isothermal viscosities showed concave curves. Activation energies increased monotonously by adding all the elements into nickel. These phenomena were considered to be related to the thermodynamic properties 'such as the heat of mixing and the structures of mixture melts.

Jan 1, 2003

By Norihiko Fukatsu, Takashi Iwamoto, Noriaki Kurita, Koji Katahira, Kunihiro Koide, Teruo Ohashi

"The galvanic cell-type hydrogen sensor employing CaZro.9Ino.t03-a. as the solid electrolyte was designed for the measurement of hydrogen activities in molten copper under industrial .conditions. The sensor probe consists of the cap-shaped solid electrolyte with porous platinum electrode on the inside and alumina refractory tube. The gas mixture of the composition 4%H2-0.5%02-Ar was made to flow on the inside electrode. The hydrogen sensor probe was inserted directly into molten copper and the melt was used as the outer electrode. The effect of oxygen activity gradient to EMF was eliminated theoretically by measuring the oxygen activity in the melt simultaneously with an oxygen sensor. The high stability of output and excellent response to the change of hydrogen activity were obtained over the wide range of industrial copper melting conditions.IntroductionIn the metal casting process, hydrogen easily dissolves in molten metals from water vapor in the surrounding atmosphere. Owing to the large difference in hydrogen solubility between liquid and solid metal, dissolved hydrogen becomes a cause of the defects of blowholes in castings or ingots. It is necessary to control the hydrogen content in the molten metals [l]. Using proton-conducting ceramics as a solid electrolyte, high temperature-type hydrogen sensor can be constructed [2]. SrCe03- and BaCe03-based perovskite-type oxides exhibit appreciable proton conduction under hydrogen containing atmosphere at high temperature [3-5]. A hydrogen sensor for molten aluminum using CaZro.91no.103-a. has been developed and widely used in the ·process control in the aluminum melting industry [6,7]. The same type of hydrogen sensor has also been expected in the copper melting industry. .. However, CaZro.91no.103-a shows ·not only proton but also oxide ion conduction in the high temperature and at low oxygen activies like the copper melting· conditions. Then we studied the oxide ion conduction in CaZro.91no.103-a. iit · detail [8]. From the consideration on the EMF of the galvanic cell employing this material as electrolyte, it was shown that the unknown hydrogen activity may be precisely determined from cell potential which is corrected for the effect of oxygen potential gradient And the hydrogen sensor based in this principle was constructed and tested in laboratory-scale [9,10]. We repeated the similar tests in factory-scale and developed the sensor system for practical uses [11, 12]. In this report, the structure and system of the hydrogen sensor for molten copper will be introduced first. The reliability of the sensor will then be demonstrated from the results of experiments for sensor probes carried out in TYK's laboratory."

Jan 1, 2000

First, a classification of the various primary sources of feed materials for the production of cobalt is presented from a mineralogical point of view : sulfides, arsenides, sulfo-arsenides and oxide minerals. Each of these cate- gories will be characterized by its behaviour towards concentration methods, taking account of the presence of the associated minerals of other metals and of the nature of the gangue minerals. Then, for each category of cobalt bea- ring ores, typical flowsheets of treatment will be presented and discussed and the characteristics of the cobalt concentrates produced will be under- lined having in view their subsequent processing by pyro - and (or) hydrome- tallurgical methods.

Jan 1, 1988

By B. Nowak

For sources with an iron-to-vanadium ratio of far above 1, it is proposed to leach in acid and to oxidize under autoclave conditions. During this oxidation process, it is experimentally shown that divalent iron contained in this solution will be oxidized to trivalent iron, whereas free acid contained will be consumed by this reaction. In case no acid is present or already fully consumed, a solid consisting of ferric compounds and an iron-vanadium-co-precipitate will form that can be filtered from the solution. If choosing the right reaction conditions, this filter cake has an iron-to-vanadium ratio of close to 1, whereas the liquid remainder is almost vanadium free. This precipitate, identified as FeVO4, 1.1 H2O, can be processed by conventional technologies such as caustic leaching, or probably salt roasting or reduction with aluminum, yielding common marketable products.

By S. Abe

Various copper anodes to be electrorefined were subjected to a heat treatment comprising annealing at a temperature in the range of 700 °c to 1,000 °c followed by a slow cooling preferably on the order of about 150 °c, and using these heat treated anodes , a series of dissolution experiments were conducted under conventional electrorefining conditions. The results obtained have indicated that the above annealing/slow cooling process dramatically improves the dissolution activity regardless of the type of anodes. As an example, passivation times of l to 3 minutes in a standard test have been increased to more than 80 minutes by this innovated heat treatment. Other advantages sterning from the improved anodic activity include reduced electrical short circuiting which results in substantial labor effort in the tankhouse, reduced energy requirement, and reduced cost of processing anode slimes because the amount of anode slimes is reduced. In addition, this process gives rise to a dramatic change in the nature of anode slime layer formed in such a way that a comparable final cathode copper product can be achieved even from high-impurity copper starting material.

Jan 1, 1987

By K. Osseo-Asare

Third phase formation, the separation of a solvent extraction organic phase into two liquids, is generally attributed to the limited solubility of the extracted complexes in the hydrocarbon diluents. Much of the research on third phase fomiation, therefore, emphasizes experiments designed to establish the stoichiometry of the species responsible for the limited solubility. This work offers a different approach, based on the recognition that the solvent extraction third phase, in fact, corresponds to the middle phase in a microemulsion fluid system. Using the tri-n-butylphosphate (TBP)-diluent-water-electrolyte system as a model system, current concepts of microemulsion phase behavior are utilized to develop a general framework for interpreting and predicting the patterns of phase behavior in solvent extraction systems.

Jan 1, 1999

By S. Peng, Vaughan R. Voller

"Free boundary problems are a common occurrence in materials processing operations. An important example is the filling of material into molds. This paper looks at filling problems associated with polymer processing, in particular Resin Transfer Molding (RTM) and Compression Molding. A general, single governing equation is developed which on numerical solution provides predictions for the position of the polymer front in the mold during filling. Both fixed and deforming finite element solutions are developed. Application to polymer filling test problems reveal that the fixed and deforming grid scheme are accurate and compare closely with each other.IntroductionProblems arising from the analysis of material processing operations often involve the tracking of a moving boundary, on which a balance conditions needs to be met, or the locating of a free surface that defines the solution domain. Material processing examples of so called ""free and moving boundary problems"" include; the tracking of solidification/melting fronts[l], the tracking of the metal/gas interface during the filling of a mold[2] and location and shape of a skull (freeze line) in a melting furnace[3].Computational solution of free and moving boundary problems usually fit into one of two classes, viz.1. Fixed grid scheme: In which the spatial domain is covered by a fixed grid (mesh) of node points and the solution uses an auxiliary variable (e.g. a local liquid fraction) to track the moving boundary or locate the free surface.2. Deforming grid scheme: In which the grid in the spatial domain is continuously deformed (or adapted in a steady state problem) such that a specified set of grid points lie on the moving boundary or the free surface.Details on the basic underlying features in these two classes of solution can be found in the excellent monograph by Crank [4]."

Jan 1, 1994

By Hideki Minoura

"Two novel electrochemical techniques for the preparation of highly crystallized CdS film have been presented. One is cathodization of a conductive substrate in an acidic chemical bath containing cadmium salt and thioacetamide, where electroreduction of proton at small current densities induces a growth of highly crystallized CdS thin films, whose growth is not disturbed by the reactions in the solution phase. The other technique is electoreduction of aqueous Cd2+— SCN complex. An advantage of this technique lies in no formation of solid particles in the bulk, of the bath.IntroductionIn recent years much attention has been paid to materials preparation by solution processing because of its advantages in lowering the cost as well as the stress to the environment, as compared to the conventional gas phase techniques which unavoidably require high temperature and/or vacuum. We have been trying to explore novel techniques for preparing functionalized compound semiconductors by aqueous solution process. Semiconductors which we have been mainly focusing on are CdS and ZnO, which are important semiconductors finding applications in various devices. In the present paper, some of the techniques that we have recently established for the preparation of highly crystallized CdS will be presented.Methods of the CdS film processing in solution phase (wet process), which have been reported so far can be divided into two major groups; one is chemical bath deposition (CBD) in alkaline solution containing Cd2+ and thiourea 1)4) and the other is electrodeposition (ED) in acidic solution containing Cd2+ and thiosulfate ions - 5)-8) or organic solutions containing dissolved sulfur 9)-11)."

Jan 1, 2000

By A. A. Hejja

The effect of composition on electrical conductivity, viscosity and liquidus temperature of the slags was investigated in the temperature range of 1300" to 1450°C. The synthetic slags containing CaO, MgO, SiO,, A1,0, and FeO were similar to those employed in the electric furnace smelting of sulphide Cu-Ni concentrates containing PGM (Platinum Group Metals) from the Merensky Reef of South Africa. FeO and SiO, were found to affect the viscosity and conductivity the most while liquidus temperature depended on MgO content in addition to these. The activation energy for electrical conduction was found to vary from 67 to 159 kJ/mol and that for viscosity from 125 to 209 kJ/mol. Optimization of the slag composition was attempted on the basis of opposite trend of the viscosity-electrical conductivity relationship with slag composition.

Jan 1, 1994

By Khalid Hattar, Alexander McGinnis, Buchheitm Thomas, Paul Kotula, Luke Brewer

"Understanding the effects of extensive radiation damage in structural metals provides necessary insight for predicting the performance of those metals considered for application in the extreme radiation environment. Predicting mechanical performance after long term radiation exposure is of great importance to extending the life of current nuclear reactors and for developing future materials for the next generation of reactors. A combination of finite element modeling, nanoindentation, and TEM characterization were used to rapidly determine the microstructure and mechanical properties influences of ion irradiation on a standard 3 l 6L stainless steel sample. The results of this study found that ion irradiation and small scale mechanical property testing can be used to characterize extensive levels of radiation damage structure, only when significant consideration is given to ion irradiation depth, surface roughness and polishing condition, the irradiation temperature, and many other experimental parameters.IntroductionFor either the success of next generation nuclear reactors or the extension of current nuclear reactors significantly beyond their designed lifetimes, research is needed into the degradation of the microstructure and mechanical properties governing the performance of the reactor alloys exposed to extreme environments. Although the exact dose and temperature of these nuclear reactor plans may vary, the cladding and other structural components will be exposed to greater dose and at elevated temperatures. To acco=odate these severe exposures, established cladding materials are being testing to longer exposure and new alloy compositions are being considered. [1-3] For neutron test facilities to reach 100 dpa level, exposure times often span several years, significantly limiting the down-select process of potential new materials for extreme radiation environments. Ion irradiation has been used as a technique to provide a look at the effect of irradiation damage on materials in a significantly shorter time frame. Previous work using proton irradiation provides a deep, broad, and relatively uniform defect profile compared to heavy ion irradiation; however, using this type of radiation still requires weeks to months to reach the 100 dpa level. [4] In this research, we investigated the feasibility of using heavy ion (nickel) irradiation and small scale mechanical testing to provide in a few days a first order screening technique for potential alloys that are being considered for advanced testing."

Jan 1, 2012

By Makoto Ohtsuka

The ternary Ni2MnGa intermetallic compound is an intelligent material which has both a ferromagnetic property and a shape memory effect (SMB), The use of the shape memory alloy films for an actuator of micro-machines is very attractive because of its large recovery force, The purpose of the present study is to investigate the effects of fabrication conditions and to clarify the relationships between these properties and fabrication conditions of the Ni-Mn-Ga films, The Ni-Mn-Ga films with a thickness of nearly 5 um were deposited with a radio-frequency magnetron sputtering apparatus using a NisoMn2sGa25 or Nis2Mn24Ga24 target. They were heat-treated at various temperatures between 873 and 1273 K for homogenization and ordering and then cooled in a furnace, The composition of the films depended on the sputtering power. The as-deposited films were crystalline and had columnar grains, After the heat treatment the grains widened and the grain boundary became indistinct with the increasing heat treatment temperature, The martcnsitie transformation temperature of the heat-treated films increased with increasing nickel content. Furthermore the effect of plastic deformation and constraint aging on SME is also investigated, After plastic deformation, the two-way SME was shown through the martensitie transformation and its reversion, The intensity of X-ray diffraction peaks from stress-induced martensitie phase was found, The constraint-aged films also showed the two-way 5MB by thermal cycling,

Jan 1, 2003

By A. Perillo

The process, realized in. the Kivcet furnace, can convert continuously lead concentrates, residues and secondary lead bearing materials into a lead bullion free of sulphur and a discardable slag. The lead recovery can be up to 99%. The long experience of about three years at Portovesme demonstrates the capability of the furnace to smelt a very. high range of lead raws without interruption of the operation. The operating costs are very competitive in comparison to the traditional technology. The work place and environment are clean and new tight regulations for the? hygiene control are met. The Kivcet furnace can be considered as consisting of three parts (reaction shaft, waste gas shaft and electro-furnace) connected with a common hearth. The technical basis of the furnace construction is the application of a number of design elements .which have mostly been used before in designs of industrial furnaces, such as open hearth furnace, refining furnace and other furnaces dealing with liquid meta1s. Refractory wear in the reaction shaft with typical pattern from watercooling soon has been stabilized and since maintained. No deformation of the furnace shell and no leakage of metal or s:l:ag through the bottom is? appeared after three years' operations.

Jan 1, 1990

By Shizhe Liu, Bing Li, Heng Wang, Zuxin Zhao

In this paper, cyclic voltammetry and chronoamperometry have been applied to investigate the effects of Nd2O3 concentration on the anode effects, critical potential for the anode effects and Nd2O3 reduction in LiF-NdF3-Nd2O3 melts at 950℃. The results show that the oxidation peaks in the potential of about 2.7V are attributed to the oxygen ions oxidation and the peak current density increases with Nd2O3 concentration increase from 0 to 0.5wt%. The critical potential caused the anode effects shifts to 0.3V more positive value as Nd2O3 content in the melts decreases from 0.01wt% to 0.5wt%. The cyclic votammograms on W electrodes in the LiF-NdF3-Nd2O3 melts present two pairs of reduction and oxidation peaks, indicating that the reduction of Nd ions in the LiF-NdF3-Nd2O3 melts in two steps rather than one step.

Jan 1, 2014

By I. G. L. Sinclair

The Selbaie deposit is located in northern Quebec. It is comprised of three distinct, but genetically related, Cu-Zn-Ag ore bodies which also contain economically significant amounts of Au. The deposits are Archean in age and volcanogenic in origin. At Selbaie, ore microscopy has been employed to aid in planning of ore beneficiation methods and to monitor the ongoing performance of the concentrator. Examples of both types of study are described. Early in the life of the mine, excessive amounts of Zn appearing were found to be appearing in the Cu concentrate. Microscopic examination of concentrates showed that this was being caused by the presence of coatings of supergene chalcocite on sphalerite grains. Fine coatings of supergene galena and chalcopyrite were also observed on some sphalerite grains. The presence of Ag and Au in the ores makes an important contribution to the revenue of the mine. The various modes of occurrence and mineralogical relationship of these two metals are described and discussed. Monitoring of the ongoing concentrating process at selbaie is done by qua-litative and quantitative examination of products collected at various points along the circuit. Causes of such problems as excessive loss of metals to the tailings or inefficient recovery of individual metals, can often be identified and possible solutions proposed.

Jan 1, 1989

By E. Ozberk

The copper and nickel smelting industries are important contributors to the technical and economic well-being of Canada while some of the smelters are among the largest sources of sulphur dioxide emissions in Canada. A review of the operations in six smelters - Falconbridge Limited, Falconbridge, Ontario; Hudson Bay Mining and Smelting Co. Limited, Flin Flon, Manitoba; Inco Limited, Copper Cliff, Ontario and Thompson, Manitoba; Noranda Mines Limited, Horne Division, Noranda, Quebec and Gaspe Mines Division, Murdochville, Quebec - have shown that about 80% of the total sulphur input to these smelters was emitted to the atmosphere in 1980. A simultaneous review of the existing and emerging technologies which can directly or indirectly reduce the sulphur dioxide emissions indicated that it is possible to reduce the emissions to below 20% of the sulphur input to these smelters. This can be achieved by varying degrees of modifications to the smelting operations and installing sulphur fixation facilities at significant costs which may increase the metal production costs. This would consequently make the competitiveness of the Canadian copper and nickel producers more difficult in the already tough world metals market.

Jan 1, 1983

By Q. Chen

The magnetic properties and phase evolution of Nd-lean and/or boron-rich melt- extracted ribbons of Nd98Fe90.2xBx, where x = 6 through 11, have been studied using XRD, DTA, TMA, and VSM. The off-stoichiometric Nd2Fe14B compositions cause additional phases to be present after crystallization and affect the magnetic properties obtained. The crystallization temperature of this alloy series rises with the increasing) boron content. In addition to Nd2Fe14B and a-Fe, Fe3B is detected. It is found that increasing the boron content reduces B, within this composition range. The magnetic properties are directly associated with the relative magnetic phase content in the samples.

Jan 1, 1997

By B. Manana

In heap leaching, the oxidative dissolution of value minerals encapsulated deep within large particles cannot be fully understood on the basis of the bulk solution conditions relative to variable solution conditions near the mineral surface. In the present study, the diffusion of the oxidising species through inner particle pores is simulated in a model apparatus that separates an inert platinum electrode under controlled reduction potential from the bulk solution through narrow pores of varying length. The Cu-NH3 system was selected as a model system and Cu(II)/Cu (I) as the redox couple of interest. Platinum probes inserted in the pores allowed the measurement of varying redox potentials along the pore length. Results showed that in a 10 mm pore, there exists a narrow (0.5 mm) zone near the reduction surface that is depleted of the oxidant and in which its supply is strongly diffusion limited, even if it is in abundance in the bulk solution. The consistent presence of this narrow diffusion region across all experimental results indicated that the transportation of the reduced species away from the reaction surface had the most significant influence on the potential variations within the pore. This was further supported by the minimal effect of varying concentrations of both Cu(II) and dissolved oxygen on the solution potential within this region.

By E. Fregeau-Wu

The major obstacle in recycling steelmaking slags to the blast furnace is their phosphorus content. Removal of the phosphorus, which is primarily associated with the silicate and phosphate phases, would allow for greater recycle of these slags for their iron, manganese, and lime contents. Calculations show that separation of the silicates from the oxide phases would remove nearly 90% of the phosphorus from the slag. The variable grain size of the as-received slag made liberation by fine grinding difficult. Therefore, slow-cooling experiments were undertaken to improve the grain size distribution. The grain size distributions were determined using in-situ image analysis. The samples were ground to their apparent liberation size and high gradient magnetic separation was used to separate the magnetic oxides from the nonmagnetic silicates and phosphates. Liberation analysis and modeling was performed on selected separation products for discussion of benefication characteristics.

Jan 1, 1995