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By Djona M. Gaballah I.

Selective chlorination of unroasted and roasted spent hydrorefming catalysts was studied between 300 and 600°C using the following gas mixtures : C12+CO, C12+N2 and CI2+air. Such materials contain Co, Ni and Mo compounds supported by alumina and/ or silica. They also contain variable amounts of V compounds, C, S, etc., accumulated during the life time of the catalyst. Direct oxychlorination of the C+S rich sample allows higher extraction rates than those obtained by the carbochlorination of the same roasted one. It seems that the roasting step doesn't favor the economic metals' recovery. Results of the chlorination of C+S poor spent catalysts, in the presence of CO, in the chlorinating gas mixture, or of carbon added to the sample, were comparable. Cobalt and nickel chlorides were .extracted from the chlorination residues by their dissolution with acidified water, whereas molybdenum and vanadium chlorinated compounds were recovered by selective condensation from the vapor phase. The recovery rates of valuable metals as well as the selectivity were higher for the chlorination of spent catalysts than results obtained by the hydrometallurgical processing of the same sample. Results of the scale-up of the oxychlorination of the unroasted sample confirmed those of the laboratory scale. The global recovery rates were about 88 pct of cobalt, 93 pct of molybdenum and 76 pct of vanadium. The carbochlorination was applied to the recovery of W and Ti from Denox catalyst that is a carbon and sulfur free one. Recovery rates higher than 99 pct at temperatures lower than 500 °C could be obtained. This may indicate that the chlorination process can be applied to the treatment of various industrial wastes or by-product containing transition and/or refractory metal compounds A flow - sheet for the pretreatment of these materials is proposed.

Jan 1, 1995

By Versiane Albis Leão

This work aims at the selection of an appropriate eluant for cyanide recycling using ion exchange resins. Based on a literature review as well as on experimental results, the elution of resins loaded with copper and minor amounts of iron and nickel is discussed. The resins Imac HP 555s, Amberlite IRA 900 (Rohm&Hass) and Purolite A860S (Purolite Co) were eluted using either NaCI, zinc and nickel cyanides, hydrochloric acid, sulfuric acid or acid thiourea solutions. The results indicate that saline solutions are effective only with polyacrylic resins (Purolite A860S), failing to desorb the metals, specially the nickel cyanocomplex, loaded on polystyrene-based resins. Cyanide solutions of both zinc and nickel are capable of eluting over 90% of the loaded metals. In contact with pure acid' solutions, iron precipitates onto the resin beads, as Cu(II) ferrous cyanideCu2Fe(CN)6.xH20. Thiourea is able to elute all the three metal cyanocomplexes owing to the increased solubility of copper cyanocomplexes in the presence of this complexing agent. The results demonstrate that a universal eluant is not available and the selection of the most appropriate resin-elution procedure should be based on the specific features of the system under consideration

Jan 1, 1998

By Christopher B. Vierrether

Reflected light microscopy, scanning electron microscopy, and electron microprobe analysis have been used to determine the mineralogy, phase percentages, grain sizes, textures, and partitioning of cobalt and nickel in two cobalt-nickel rich mattes. These mattes were prepared by submerged bath smelting from a flotation cobalt-nickel concentrate containing 4.8% cobalt and 5.1% nickel. The concentrate was derived from lead-zinc-copper ores of the Viburnum Trend, southeast Missouri. Eleven discrete phases have been distinguished in the matte samples, three of which contain significant cobalt and nickel. The phases are cobaltpentlandite ((Co,Ni,Fe)9S8), cobalt-bearing marmatite ((Co,Fe,Zn)S), shandite (Ni3Pb2S2), bornite (Cu5FeS4), galena (PbS), magnetite (Fe3O4), pyrrhotite ((Co,Ni,Cu,Fe)1_xS), chalcocite (Cu2S), CuPbS phase, metallic copper, and metallic silver. Cobaltpentlandite and cobalt-bearing marmatite- occur in coarse grains (50 µm) that would separate readily during grinding, but shandite contains small (5 - 10um), abundant inclusions of pyrrhotite and bornite.. Some mineralogical variations between the two matte samples were due to differing degrees of oxidation during smelting,

Jan 1, 1988

By Jari Aromaa, Antti Kekki, Olof Forsén

"The deposition of copper on inert substrate depends on the number of active sites that will react at certain overpotential. The critical overpotential depends on surface morphology, surface film resistance and additives on cathode surface. The effects of surface properties on copper nucleation and growth rates were studied for used stainless steel blanks from several tankhouses. The surfaces of the blanks were characterized with electrochemical and mechanical methods. Electrochemical deposition tests were done at current density of 300 A/m2 for 10, 30 and 60 seconds. The nucleation density and copper coverage were estimated using image analysis. The surface film resistance did not correlate with copper growth. Increasing surface roughness correlated with lower copper growth.IntroductionStainless steel cathode blanks in copper electrorefming are usually made of AISI 3 I6L type steel. They have a typical lifetime over 10 years. During use the surface will collect deposits and become rough due to wear and corrosion. These factors can affect the nucleation and growth of copper. The nucleation and deposition of copper on inert substrate depends on the number of active sites that will react at certain overpotential. The critical overpotential can depend on surface film resistance, surface morphology, and additives adsorbed on cathode surface.The deposition potential of metallic ions on a foreign substrate is usually higher than the deposition potential on the electrode made of the same metal due to crystallographic substrate/metal misfit [I]. If the substrate has traces of the depositing metal they will be preferential growth sites. For a smooth deposit a large number of simultaneous nuclei is necessary. However, excessive nucleation density can lead to porous deposits [2]. Surface films of good conductivity are needed for dense nucleation and small nuclei. On cathode blanks the number of active sites increases with increasing surface film conductivity [3-5] and/or surface film porosity [6]. On AISI 3 I6 L stainless steel a more resistive oxide has been found to limit favourable sites for copper nucleation and more conductive film promoted high-density copper nucleation [7]. Also Urda-Kiel et al. have concluded that thicker oxide layers on AISI 304 stainless steel resulted in lower nucleation [8]. Increase in overpotential or current density activates more and more of the potential nucleation sites and this can be seen as higher number of nuclei [9] or smaller average distance between nuclei [10]."

Jan 1, 2012

By Thomas J. Keefe, O&apos

The effects of cobalt, B-naphthol, glue and antimony on the polarization behavior of zinc sulfate electrolyte were investigated. It was found that B-naphthol was beneficial in reducing the detrimental effects of cobalt while antimony and excess glue were each harmful. Since the nu cl eat ion over potential was insensiti1ve to coba1t, other regions of the polarization curve were used to indicate electrolyte balance. The low? current density area occurring in the reverse or anodic sweep direction was? often an indicator when an ?unstable condition existed. The two parameters evaluated were the degree of inflection in the polarization curve in the low current density region during scanning and the rate of current rise observed when the sample was potentiostated at -0.781 Volts (SHE). Using this technique, a two-additive system was shown to be desirable to control cobalt and antimony containing electrolytes. The structure of the deposits was examined using scanning electron microscope techniques.

Jan 1, 1985

By Salustio s. Guzman

The standard .free energies of formation of tin chlorides were estimated with reviewed and estimated basic thermodynamic data, and measured reversible potentials for the disproportionation of tin dichloride into metallic tin and tin tetrachloride. Values for cºp, Sº, Hº?-Hº 298, -(Gº - Hº298) /T,.Hºf, Gºf, and log Kp are given in tabular form, these estimations are compared with estimations reported in the literature.

Jan 1, 1985

By George Kazonich

The high costs and environmental problems associated with making iron and steel in the United States is driving the development of new technologies to replace the blast furnace. A prototype reactor incorporating rocket technology was designed and built. This rapid rate reactor was operated successfully and consistently made iron metal. Minus 325-mesh magnetite particles could be reduced to iron metal in less than 50 ms in a high temperature flow through reactor. Iron product was recovered inside the reactor and in a downstream cyclonic separator. The results of typical operation and how parametric changes affected the reduction of iron ore concentrates are discussed.

Jan 1, 1993

By N. M. Komkov

The main operation of obtaining zinc from sulfide raw materials by hydrometallurgical technologies is the oxidation roasting of zinc concentrates in fluidized bed furnaces. The technical-economic parameters are determined by the parameters of the roasting process, which depend on the composition of the initial raw materials, the temperature of the bed and on other factors. The predetermined roasting temperature is maintained due to the change of specific efficiency as well as to the quantity of the heat removed from the bed. The efficiency of caissons depends at a high degree on the composition and the thickness of the accretion formed on the surface of the caissons. Forecasting the roasting results is impossible unless we know the mechanism of the accretion formation. The aim of the present paper is the thermodynamic analyses of the behavior of the charge compositions under roasting and the determination of the potential mechanism of the accretion formation. The thermodynamic analyses show that under conditions of the oxidation roasting the thermodynamic probability of the formation of zinc sulfate is higher than the probability of the oxide formation until a temperature of 873°K is reached. The thermodynamic probability of the formation of the lead sulfate is higher than the probability of oxide formation in the entire temperature range of roasting. The probability of formation of ferrites and silicates of zinc decreases only insignificantly the sulfate stability. The results of the investigation of the accretions composition formed under roasting of concentrates with particle sizes less than 0.02 um (60%), containing 65% of sphalerite (ZnS), 12% of pyrite and chalcopyrite (FeS2 and CuFeSz2 each, 3% of galenite (PbS), 7% of silica and other non-ore minerals, have shown that the composition of accretion varies depending on the depth of the accretion layer. The accretions on the caissons and the thermo-siphons consist mostly of zinc sulfate (more than 50%). The accretions of forchamber consist mostly of zinc oxide. They also contain ferrites and silicates. The formation of the sulfate zinc accretion in the cold parts of the fluidized bed furnace (the caissons and thermo-siphons) may be explained by a lower temperature on the surface and probably by a catalytic influence of the present oxides in the formation of S02 and sulfates. The nature of the structure of the accretion in the hotter parts of the furnace may supposedly be explained by the formation of elemental vaporous zinc during roasting.

Jan 1, 2003

By J. E. Dutrizac

A mineralogical study of a weak acid leach residue from the Clarksville zinc plant of Savage Zinc Inc. was carried out. The study focused on Pb and Cd as these elements most significantly impact on the environmentally acceptable disposal of the residue. The residue consists of major amounts of bassanite, zinc ferrite and various Zn-Pb-Fe-Cd silicate species. Also present are lesser quantities of PbSO4, sphalerite, Fe2O3 quartz, Mn-Pb-Fe oxides, SrS04, (Pb,Sr)SO4 iron gel-silica gel, jarosite and Ti oxide. The principal Cd carriers are the zinc ferrite, which contains up to 9.00% Cd and likely accounts for -45% of the total Cd content of the residue, and the various silicate species which contain up to 6.97% Cd and account for about 45 % of the total Cd. The sphalerite is a minor Cd carrier containing an average of 0.35 % Cd and accounting for -5 % of the total Cd; the other carriers contribute only trace amounts to the total Cd content. The major Pb carriers are PbS04, Pb-bearing silicates and Mn-Pb-Fe oxides. Minor proportions of the total 1.09% Pb content of the residue are carried by SrS04 and (pb,Sr)S04' Trace Ph carriers include the iron gel-silica gel, Fe-Zn-AI oxide and bassanite. The residue after the toxicity characteristic leaching procedure (TCLP) is mineralogically very similar to the initial weak acid leach residue; the amounts of calcium sulphate are approximately the same in the two products. The principal Cd and Pb carriers are also the same as those noted in the initial residue, except that some dissolution and reprecipitation of Pb-Sr sulphate takes place. That the residue fails the TCLP test is likely a consequence of the superficial dissolution of Pb and Cd from species such as PbS04 or Zn-Pb-Fe-Cd silicate.

Jan 1, 1995

By W. Petruk

The behaviour of galena, chalcopyrite and tetrahedrite during floration of a fine-grained base metal ore from New Brunswick was investigated by image analysis study of the mill concentrates and tailings. The minerals were analyzed to determine the grades and recoveries as related to free and unliberated mineral grains and their size distributions. The results show that only 37 wt % of the galena was liberated but 88 wt % of the free galena was recovered, indicating good mill performance for the lead. The lead recovery was 65 wt %, with the main loss due to unliberated galena. Most of the unliberated galena lost to mill tailings is so fine-grained that galena liberation and Pb recovery would not improve significantly by re-grinding. Chalcopyrite liberation was 56 wt % but only 75 wt % of the free chalcopyrite was recovered. Copper recovery was 45 wt %, with the chalco-pyrite loss in the mill tailings being both as large free grains, and as small and large unliberated grains. It was calculated that copper recoveries could be improved about 8 to 10 wt % by changing the concentrator operations and by regrinding. Concentrator operations hive already been modified and copper recoveries have improved about 5 wt %. About 29 wt % of the silver was lost to tailings mainly as both free and unliberated, large and very small, Silver-bearing tetrahedrite grains. It was calculated that about 25 wt % of the silver in the tailings might be recovered by improved milling conditions and by regrinding.

Jan 1, 1981

By N. Kanari

The kinetics of oxychlorination of MgO by Cl2+O2 was studied in the temperature range of 850 °C - 1025 °C, using thermogravimetric analysis. The effects of C12/02 ratio, gas velocity, temperature and partial pressure of reactive gases on the reaction rate were investigated. The oxychlorination process was characterized by an apparent activation energy of about 214 kJ/mol. The reaction orders with respect to C12+O2. C12 and O2 at 950 °C were about 0.65.0.98, and -0.37, respectively. Some data about oxychlorination kinetics of MgO, Cr2O3, and MgCr2O4 contained in chromite were compared. Efficiency of using oxychlorination for the removal of iron oxides contained in magnesia was demonstrated.

Jan 1, 1999

By Pengfu Tan

In order to understand and control the formation of dioxins and furans in iron ore sinter plants and to possibly avoid expensive end-of-pipe removal stages, thermodynamic calculations on the stability of PCDD/Fs have been combined with sinter process modeling by means of kinetic simulations and computational fluid dynamics. Three thermodynamic databases of PCDD/Fs, derived using the Group Additivity approach and two computational molecular modeling methods, MNDO and PM3, respectively, combined with the SGTE database have been used to model the PCDDIF formation and the PCDD/F isomer distributions in iron ore sintering. The results show very similar conditions for the PCDD/F formation using the different databases. Concerning the isomer distributions of toxic PCDD/Fs, the calculated data derived from the MNDO method showed optimum agreement with measured values from industrial furnaces. The thermodynamic calculations also proved that the isomer distributions found in combustion processes are equilibrium values, while the concentration ratio of PCDDs and PCDFs in the wind boxes does not represent an equilibrium state. A CFD model of iron ore sintering was developed including the kinetics of 15 relevant chemical reactions with the aim of describing the temperature fields and the gas flow patterns in the sintering bed. On the basis of these information and experimental observations reported in the literature possible pathways for the PCDD/F formation in sinter plants have been identified: PCDD/Fs are formed in the critical temperature region of 250 to 450°C below the combustion zone, are then carried downwards with the gas and condensed close to the bottom of the sinter bed. Transported to the discharge end with the solid mixture, they are again released into the gas phase when the flame front approaches the bottom. PCDD/Fs are also formed in the last wind boxes when the hot off-gases cool down and reach the critical temperature range. Consequently, methods to reduce the dioxin formation reactions are proposed including inhibitor addition to the sinter feed and off-gas quenching.

Jan 1, 2003

By J. M. Demarthe

MINEMET RECHERCHE (IMETAL Group, formerly Le Nickel-Penarroya-Mokta) has studied on a laboratory scale and patented a new process to recover metal values -copper- from sulphide ores and concentrates. It combines a cupric leaching, solvent extraction and copper sulphate electrowinning according to the main following steps - A direct and selective leaching of copper sulphide ores or concentrates at atmospheric pressure with cupric chloride to form cuprous and ferrous chlorides and elemental sulphur. Pyrite remains in the sulphur residue. - The leach solution is separated into two parts -In the first one, air is injected to precipitate iron as goethite. The oxidation step can be easily realized at atmospheric pressure by maintaining an excess of cuprous and-ferrous chlorides in the liquor. Copper is extracted from the second part as cupric ion by an LIX reagent. Direct injection or air in the mixing chamber maintains good extraction conditions, so that only one mixer settler is required. - Iron, in the form of ferrous ion, is not coextracted. - Copper is stripped from the organic phase, transferred into a sulfuric phase and sent to sulphate electrowinning cells, which are now conventional in copper metallurgy. - Only electricity and air are required. After a feasibility study, the next step will be to develop it on a pilot and commercial scale.

Jan 1, 1976

By Guy Deschênes

Thiourea solutions can be used as leach liquors to treat gold ores or slimes. It is also efficient to elute resins or strip solvents that were loaded in cyanides solutions. The hydrogen pressure reduction is a practical step to recover gold and silver from leach solutions, and strips and eluates without any destruction of thiourea. It is a critical point because these processes have to consider the recycling of the liquors to be irore economical. The effect of temperature, pressure, acidity, compotation of the solution and the nature of catalysts on pressure reduction by hydrogen were investigated. An electranetallurgical study was? carried out to investigate the mechanism. The composition of the products was studied by different analytical methods. The process shows a good selectivity to precipitate gold and silver in a thiourea solution containing iron and copper. Gold and silver concentrations can be decreased to 0.2 ppm and 0.1 ppm at respectively 70 KPa H2 and 28°C. No decomposition of thiourea was evident during the tests. Metals such as nickel powder or platinum activate the reaction and improve the reduction.

Jan 1, 1989

By S. Ozbilen

"Al-Li binary alloys with nominal Li contents of0.15, 1.1and2.8 (in wt%) were aged naturally at room temperature for two months, aged at low temperatures ( 65 and 1 OOEC) for up to 2 months and aged artificially at 190EC for 4 days after water quenching to 25EC following solutionizing at 530EC for 20 minutes. Ageing behavior of these binary alloys were studied by Vicker's Hardness measurements and DSC thermal analysis. Thermal analysis results indicate the formation of GP zones of Al-Li system in Al-2.8wt%Li binary alloy. In the same alloy, rapid quenching from one phase region (a) gives rise to precipitation of small o' particles in a matrix (a) with still high supersaturation. During ageing of this alloy below lOOEC an additional transformation, i.e., GP zone formation occurs proceeding at a very high rate which is described on the basis of the theoretical analysis for the quenched Al-Li system proposed by Khachaturyan et al [6]. Ageing at temperatures below 11 OEC takes place slowly by the formation of small d' particles of lower thermal stability than the quenched-in d precipitates in addition to GP zones resulting in an increase in hardness compared to water quenched samples. During artificial ageing, GP zones transform by dissolution to d' precipitates while d' particles already in the microstructure coarsen during under aged condition at which hardness increases with time till peak aged condition.IntroductionIn binary Al-Li alloys the d' (Al3Li) fully coherent internally ordered inetastable phase of Li2 structure with a=0.4038d [1-5] forms homogeneously between 120 and 190EC before the formation of stable d' (A!Li) phase and cause the superior mechanical properties. This is due to an appreciable age hardening effect resulting because of the d' precipitation during ageing [1]. The response of d' to decomposition and its formation kinetics have been studied previously and it is believed that the decomposition of the a-supersaturated solid solution occurs in a two stage process; i.e., a 6 d' (Al3Li) 6 d(A!Li). Khachturyan et al [6] theoretically investigated precipitation of the d' phase and gave an interpretation of the transformation paths of the quenched Al-Li alloys. They predict that the disordered supersaturated solid solution congruently orders, and then the uniformly ordered solution decomposes into ordered regions that differ in Li-content. Finally, ordered d' phase forms in the disordered matrix."

Jan 1, 1998

By William Petrul

Image analysis studies were performed on mill products from laboratory flotation tests of the Zn-Pb ore from the Faro deposit in Yukon, Canada, to determine mineral liberations at specific grinds and to predict recoveries at optimum flotation conditions. The minimum and optimum grinds for liberating sphalerite and galena were predicted from size analysis data for the minerals in large ore pieces, and determined by image analysis studies of the mill products. The determined optimum grinds are about 2 Tyler mesh sizes larger than predicted because sane of the fine grained sphalerite and galena occurs in interstices between coarser grained pyrite and is liberated when the pyrite grains are broken apart. Materials balance calculations were performed on the analyzed values for the liberated and unliberated sphalerite and galenaa to determine their distributions in the mill products. The laboratory flotation tests recovered 74% of the sphalerite and 83% of the galena in Zn and Pb concentrates respectively. The mineral evaluation study indicates that the optimum recovery for sphalerite and galena are 85 and 83% respectively. The company is currently recovering 80% 'of the sphalerite and 82% of the galena.

Jan 1, 1989

By Riyad N. Ahmad-Bitar, Shadia J. Ikhmayies

"CdS/CdTe solar cells were built by depositing a 200 nm layer of Sn02:F on glass substrates by the spray pyrolysis (SP) technique, a 500 nm CdS:In layer by the same technique and a 1-1.5 µm CdTe layer by vacuum evaporation. The cells were CdCh heat-treated in nitrogen atmosphere for 30 minutes at 350 -.C. The photoluminescence (PL) spectra were measured at the CdS/CdTe interface for two cells with different values of the CdTe layer's thickness at temperature T = 60 K. A deconvolution peak fit was performed from which it is found that the peaks are characteristic of the solid solution CdSxTei-x· The parabolic relation that relates the bandgap energy with the composition was used to estimate x, where xis [S]/([Te]+[S]) and [Te], [S] are the concentrations of Te and S atoms respectively. The results show that the interface is smooth and the change of the bandgap occurs gradually.IntroductionCdS/CdTe heterojunctions represent a combination of materials promising various applications, and for solar energy conversion in the first place [1]. In photovoltaic cells the CdS material acts as a wide bandgap window. Direct bandgap CdTe with high optical absorption coefficient is used as an absorber [1]. Solar cells with efficiencies of 10 to 16% have been obtained with CdTe grown by close space sublimation, electrodeposition, vacuum evaporation and rf sputtering methods [2]. In this work the CdTe layer was prepared by vacuum evaporation because it results with films of minimum impurities, while the Sn02:F and CdS:In layers were deposited by the spray pyrolysis technique because it is a low cost method which enables intentional doping and large area thin films."

Jan 1, 2011

By T. Wang, R. G. Reddy, D. Mantha

"A new eutectic LiN03-NaN03-KN03-KN02 quaternary molten salt system was calculated using thermodynamic modeling. The eutectic temperature was predicted to be 100°C. The melting point and heat capacity of the salt eutectic composition were determined using DSC. The experimentally determined melting point is in excellent agreement with the predicted value. The melting point is more than 124°C lower than that of the KN03-NaN03 solar salt. The density of the molten salt was experimentally determined as function of temperature. Using the density, heat capacity and the melting point, thermal energy storage density and gravimetric storage density of the quaternary molten salt were calculated and compared with that of solar salt. The larger storage density value of this molten salt indicates that this salt has a better energy storage capacity for solar power generation systems.IntroductionMolten salts have been used as thermal energy storage media for solar energy applications. Nitrates are being used in the solar energy applications for their low melting point, low unit cost, high heat capacity, high thermal stability, negligible vapor pressure and high energy storage density [l]. Solar salt (NaN03/KN03: 60/40) is the most popular thermal energy storage medium which is currently being used with the freezing point of 221 ·c [2]; another ternary system HITEC® which contains NaN03, KN03 and NaN02 has freezing point of 141°C [3]. Newer nitrate salt mixtures are being studied and projected as potential candidates for thermal energy storage (TES) and heat transfer (HT) applications. Based on these favorable features, molten salt can work directly as the energy storage medium below 500°C [l]. Development and synthesis of newer molten salt mixtures with freezing point lower than those currently used for thermal energy storage applications is necessary for sustained utilization of solar energy. The approach to develop lower freezing point molten salt mixtures is by the prediction of new eutectic mixtures and also by the development of new nitrate compounds."

Jan 1, 2012

By Chunyang Guan, Jilai Xue, Jun Zhu, Qiaochu Liu

"Al-Sc Alloys have showed many advanced properties for a wide range of industrial application, which is usually produced using thermal reduction process. This work is aimed to develop an electrochemical process to make Al-Sc alloy using industrial Hall aluminum reduction cells. The experiments have been carried out in a lab cell where NaF/AlF3-Al2O3-LiF as electrolyte, Sc2O3 as raw material, and liquid aluminum as cathode were used at operating temperature of 950 °C. The resulting Al contained 0.2 - 0.5 wt.% Sc that is the common range in its content for advanced applications. However, a small fraction of Sc was found from thermal reduction at Al melts interface. SEM-EDS and ICP-AES analysis showed a uniformed distribution of Sc at varying locations of the Al-Sc alloy sample. In addition, a higher Sc content in Al-Sc alloy can be obtained with introducing ultrasound through the cathode than that without it.IntroductionIn recent years, scandium has been investigated as an alloying element for aluminum alloys. With addition of a small amount of Sc, Al alloys can improve the strength, weld ability, resistance to re-crystallization and corrosion resistance [1-3]. Due to their advanced properties and potential applications, the demand for Al-Sc alloys will increase in the future. However, the difficulties in reduction technologies and the high costs in production process may limit their expansion in application areas.The current major method of producing Al-Sc alloys is to mix Sc into Al by melting Al-Sc master alloy. This alloying process has several technical problems, such as easy segregating and heavy burning loss, etc. The price of Sc metal or starting material is also high, so the mixing process is an expensive alloying method. Molten salt electrolysis is alternative method to prepare RE metal and RE alloys [4, 5]. It also can reduce the segregation of alloying elements. Sc2O3 is an ideal material as raw material with low price and decomposition voltage. Some work has proved that Al-Sc alloys can be obtained by electrolysis Sc2O3 directly in cryolite [6-8], or CaCl2 molten salt [9]."

Jan 1, 2012

By H. Y. Sohn, S. PalDey

"A new chemical synthesis process for the preparation of intermetallic compounds has been developed. It involves the vapor-phase reduction of mixtures of constituent metal chlorides by magnesium vapor to produce intermetallic compounds in the form of fine powder. The advantages of the process include (a) the use of inexpensive raw materials, (b) low reaction temperatures, and (c) products in the form of fine particles. Titanium and nickel aluminides were prepared by this method. The effect of AlCl/TiCl3 partial pressure ratio on the formation of different titanium aluminides was studied. A two-phase mixture containing 80 mol % of TiAl and 20 mol % of TiA13 formed at an AlC13/TiC13 ratio of 10. The amount of TiA13 was maximized to 72 mol% at an AlC13/TiC13 ratio of 16. The maximum conversion of the limiting chloride TiCl3 was 94 % . In the case of nickel aluminides, NiAI, NiAl3, and Ni2Al3 were formed by reducing mixtures of NiC12 and A1Cl3 vapors. The effect of the partial pressure ratios AlCl3/NiC12 and Mg/NiC12 on the formation of nickel aluminides was studied. The maximum content of NiAl obtained was 98 mol % . At the AlC13/NiC12 ratio of 19, a two-phase mixture of 17 mol% of NiAl and 83 mol% of NiA13 was produced. The product particles were very fine in the size range of 0.05 to 0.2 µm.A. IntroductionIntermetallic compounds are attracting much attention [1]. Titanium and nickel aluminides have attracted a great deal of attention from the aerospace as well as automobile industries because of their potential for high-temperature application (e.g., low density, good oxidation resistance, and high-temperature strength retention [2, 3]). Gamma TiAl and two-phase (TiAl and Ti3Al) alloys [4] are used for gas turbine engine rotational components as well as automobile exhaust valves. TiAl3 is one of the most extensively investigated aluminum-rich intermetallics. Nickel aluminides are attractive because of their low densities, relatively high melting point and good high-temperature strength properties. For example, Ni3Al shows increasing rather than decreasing yield strength with increasing temperature [5]."

Jan 1, 1998