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By Chai Li-yuan

Anodizing behaviors of magnesium alloys AZ31 at constant applied current, based on the electrolyte solution free of chromate or fluoride, were investigated. The anodizing process was influenced by constituents of electrolyte greatly. Therein, the oxylate salts, which led to the occurrence of the two totally different processes, played a determinant role in anodizing. They were stable and sparking process respectively. The morphology of anodizing film was observed by SEM and the structure of film was analyzed by XRD. During the stable process, a brown thin film was formed, however the sparking process led to the formation of white hard thick film. The functions of some kinds of additives, such as ammonia, glyceryl alcohol and PVP etc were also studied. Some of them had great effect on surface morphology of anodic film and some of them affected stability of anodizing process significantly.

Jan 1, 2006

By Thor Pedersen

Elkem's technologies for the processing of waste materials, dusts, sludges and other residues, are based on the use of their Multi-Purpose Furnace as the primary processing component. The Multi-Purpose Furnace? is an electric slag resistance reduction furnace equipped with a hot media, Modular Freeze Lining and Elkem's proprietary, air tight electrode seals. The oil cooled? freeze lining allows specific heat fluxes 2 to 3 times higher than furnaces lined with conventional refractory. Reduction activities taking place within the furnace are free from the reoxidation potential of infiltrated air as Elkem's electrode seals are positively gas tight. Small quantities of highly concentrated off gas of controlled composition are produced to suit the requirements of downstream processing. The high electrical thermal efficiency achieved by generating heat within the slag itself, combined with the ability to operate at high melting rates and intense power density, makes the Multi-Purpose Furnace 9 an unique implement for the design of furnace products. These characteristics are utilized in the processing example cited, "Elkem's EAF Dust Processing Technology", which combines two proven technologies in an economically feasible system for the recovery of contained metal values from K061 wastes at the same time producing a disposable slag product. The portion of the example dealing with the condensation of zinc was prepared with the assistance of Imperial Smelting Processes, Limited of Bristol, England with whom Elkem has a non- exclusive license.

Jan 1, 1990

By Mikiya Tanaka, Mikio Kobayashi, Mansour A. S. A1Ghamdi, Kenji Tatsumi, Yukinori Saiki, Hirotaka Senba

"In order to recover nickel ion in a spent electroless nickel - phosphorus alloy plating bath and, at the same time, to remove impurities such as iron and zinc, the applicability of solvent extraction with LlX84I as the extractant has been investigated using actual spent solution. Although the extraction efficiency of nickel from the spent solution is considerably lower than that from the nickel sulfate-nitrate solution, nickel in the spent solution is selectively extracted with high efficiency at the pH of 6 - 7. The extracted nickel is effectively stripped by sulfuric acid at a pH of less .than· 3. On the basis of these results, a· flowsheet for recovering nickel from the spent solution is proposed Chemical equilibrium calculations of the spent solution has shown that the complex formations of nickel with anions such as lactate and phosphonate ions become predominant in the pH range between 2 and 6. This results in the depression of nickel extraction efficiency from the spent solution as compared with that from the .nickel sulfate-nitrate solution. By combining these aqueous equilibrium calculations with the· extraction model considering the extraction stoichiometry and the aggregation of the extractant in the organic phase, the extraction behavior of nickel is quantitatively predicted.IntroductionElectroless plating is indispensable for the recent advanced industries such as the electronic and mechanical industries. Electroless plating baths are repeatedly used by supplying the metal salts; however, the accumulation of the counter anions of the metal ions, the components formed by the oxidation of the reducing reagents in the plating baths, and the metal ions as impurities dissolved from the surface of the objective materials degrades the· quality of the plating. Thus, the baths are finally treated by a precipitation method to form a large amount of metal sludge, which is disposed in dumping sites. Therefore, from the standpoints of environmental protection and resource preservation, it is highly desired to establish a recycling process of the plating baths with minimum emission. Solvent extraction seems to be one of the 'suitable methods to recover metals from the spent electroless plating baths, because the concentration of the metal ion in the baths is relatively high, which is advantageous to solvent extraction as compared with the ion-exchange and adsorption methods. Some studies about the application of solvent extraction have already been carried out using simulated spe11t electroless plating baths [1-3]."

Jan 1, 2000

By Larry G. Twidwell, Jannette L. Chorney, Bryce D. Ruffier, Katelyn M. Lyons, Daniel W. Gaede, Ryan J. Foy, Jerome P. Downey

The Army Research Laboratory (ARL) has an interest in the recovery and processing of rare earth elements. At Montana Tech, elevated temperature chlorination of rare earth oxides is presently being investigated as a potential methods leading to the selective separation and recovery of rare earth elements from mineral ores and concentrates. After preliminary evaluation, ytterbium oxide was selected as a representative surrogate material for more extensive chlorination studies. Methods used to determine the conversion and recovery include X-ray diffraction (XRD) and inductively coupled plasma (ICP) analysis. These data have been used to establish and confirm process conditions that consistently yield high conversion efficiencies. Based on the promising results, further experimentation is underway to ascertain the metallurgical response of other rare earth oxides and carbonates to the roasting process. The end goal is to create a robust process for industrial application that has greater efficiency and reduced costs as compared to current practice.

Jan 1, 2015

By Staia. Mariana H.

Thermochemical equilibria of the heterogeneous system Ti-N-H-CI-Fe-Cr-Mo-Ni-Mn-C were calculated by using a commercial software based on the minimization of the free energy. Equilibrium calculations were done for temperatures varying between 800" and l 100°C and an initial molar relationship between reactants, a=NJTiCI,, of 0.1 to 2. The deposition process was considered to occur at atmospheric pressure. The activities of the alloying elements of the stainless steel were considered equal to their molar fractions. It was shown that for the conditions studied the substrate is no inert with respect to the gaseous phase. The existence of liquid chlorides was predicted for temperatures between 800" and 850°C and a ratio between 0.3 and 0.9. The most important metallic chlorides which appears to be present from the calculations in appreciable quantities in the gaseous phase are iron dichloride and manganese dichloride. In the low-temperatures zone and for low initial nitrogen contents, it result that the appearance of the liquid chlorides seems that partially inhibits the production of gaseous HCI. The highest deposition process efficiency calculated is obtained at a temperature 2 900°C and a N2/TiCI, ratios 2 0.7.

Jan 1, 1995

By Peter Kong

This paper provides a general discussion of atmospheric-pressure plasma generation, processes, and applications. There are two distinct categories of atmospheric-pressure plasmas: thermal and nonthermal. Thermal atmospheric-pressure plasmas include those produced in high intensity arcs, plasma torches, or in high intensity, high frequency discharges. Although nonthermal plasmas are at room temperatures, they are extremely effective in producing activated species, e.g., free radicals and excited state atoms. Thus, both thermal and nonthermal atmospheric-pressure plasmas are finding applications in a wide variety of industrial processes, e.g. waste destruction, material recovery, extractive metallurgy, powder synthesis, and energy conversion. A brief discussion of recent plasma technology research and development activities at the Idaho National Laboratory is included.

Jan 1, 2006

By Y. K. Rao

Relatively pure crystalline lead sulfate (PbSO4) can be produced by chemical vapor transport from an impure source such as the lead-acid battery paste or the roast-ore-leach-residue from a hy¬drometallurgical process-route. In a closed-reactor, transport of matter is induced by a tempera¬ture-gradient and the steady-state transfer rate can be calculated using the data on the standard free energies of formation for the species present and the pertinent binary diffusion coefficients. The present work focusses on chemical vapor transport in a tubular reactor (1.4-cm inner diameter x 10-cm long) with the source- and deposition-ends held at 850°C (T,) and 750°C (Td), respectively; PbC12(g) is the 'solvent' or 'transport agent' and NiSO4(s) placed in the source-zone -serves to maintain a sufficiently high S0,-potential such that the stability of the lead sulfate species is ensured. For the purposes of analysis, the gas-phase in the reactor is assumed to consist of eight species: H2O, PbC12, SO3, SO2. O2 HO, C12, and PbC14. The reaction between C12(g) and PbSO4(s) in the high-temperature source-zone produces PbCl2, SO2, and 02; four more reaction-equilibria in the same zone yield other species. In the low-temperature deposition-zone, reaction equilibrium involving PbC12, H2O, and SO, leads to the nucleation and growth of PbSO4 crystals; three other reaction-equilibria occur in this zone. By employing the virtual equilibrium state for the end-zones and coupling it to the Stefan-Maxwell diffusion equations for each of the gas species, the respective partial pressures for these, in the source- and deposition-zones, are computed at steady-state. From these data, the molar fluxes of PbCl2. PbCl4, and so forth, are determined. Allowing for the transport-enhancing effects of thermal convection, the net transport rate of lead (or PbSO4) is duly calculated for specified initial conditions. The predicted rates show very good agreement with measured rate data reported in the literature [ V. Plies, T. Kohlmann and R. Gruehn: Z. anorg. allg. Chem, 568, 62 (1989)

Jan 1, 1995

By R. D. Lrwin, W. M. Mullins, S. Venugopa, J. C. Malas

"Physical models for acoustic emission (AE) are introduced and expressions are derived to predict AE activity from such parameters as applied stress, strain and strain-rate. These models are then incorporated into a visco-plastic finite-element simulation program, and the acoustic emission event rate generated during metal forming operations are predicted. Simulation results are presented for upsetting operations on a typical C-Mn type steel for various friction and die geometry conditions. The AE model predictions compare well with the limited available experimental results reported in the literature and demonstrate that AE signatures can be reliably simulated. The signatures predicted for metal forging are fairly insensitive to processing parameter changes. This suggests that AE event rate monitoring may not be well suited to process monitoring for forging. However, the size of the features is conjectured to influence the frequency content of the AE signals. Thus, since current simulations include only the ability to predict the number of events for a set of processing conditions, future work is required to simulate the duration and magnitude of acoustic events. Fourier analysis techniques may then be applied to investigate correlation with microstructural features.IntroductionThe open loop control system method for deformation processing design, as described by Malas et al. [1 ], consists of several steps in series to achieve the final design. The first step uses microstructure development models to determine the optimum deformation path to achieve the desired final microstructure. The second step, the process model, calculates the processing parameters required to achieve this deformation path. Finally, the metal-working system uses the required processing parameters to produce the part. Figure 1 shows this in block diagram form"

Jan 1, 1997

By Robert L. Stephens

"It can be argued that one of the most important property of any material is cost, since this property detennines the applications for which a material can be considered. Despite growing demand and production for commodity metals such as copper, nickel, zinc, lead, and tin, the cost of these metals has been steadily decreasing in real terms. The only way that metal miners and producers can remain financially viable in the long term is by continuing to lower their cost curve through the implementation of new metals production technologies. This paper reviews technological developments in the production of copper, nickel, zinc, lead, and tin that have or threaten to redefine the cost curves for these metals.DisclaimerThe opinions expressed in this paper the author's, and are not necessarily those held by the author's employer, Cominco Ltd.IntroductionThis meeting will discuss many novel technologies and processes for producing metals and materials with specific properties that will enhance the applications ranges for the material or will allow entirely new applications to be developed. However, in every real-world case, the cost of the new material or process is an important property that determines which applications the material or process can be used in. Other properties that are important depend on the applications.A recent press report (1) discussing the potential replacement of aluminum radiators with copper radiators in pickup trucks and sport utility vehicles provides an interesting example to reinforce the importance of cost in materials selection. In this case, the displacement of aluminum by copper is being considered because of the more favorable heat dissipation characteristics of copper. Heat dissipation has become more important due to the development of hotter-burning V-8 and V-6 engines. For this application, engineers also consider cost, weight, size, durability, and manufacturing process. The report stated that the development by the International Copper Association (ICA) of the ""CuproBraze"" manufacturing process for heat transfer products was an important development. This technology produces 845 radiators that weigh less, are more uniform in quality, and are potentially more compact. They are also expected to cost less in high production quantities than copper units produced in the past, last three to four times longer than soldered copper radiators, and the process also eliminates the use of lead solder from the manufacturing process."

Jan 1, 2000

By Drew Sinha

Success of the environmentally benign semiconductor manufacturing depends on the cost-effective integration of the principles of reduce, recover, reuse and recycle from source material to final product disposal. Increasing demand combined with current shortage of polysilicon provided unique opportunities to recover the silicon waste, caused by various defects, in wafer manufacturing process. Current practices relating to recovery and reuse of waste silicon produced, from crystal growth process to finally polished and epitaxially deposited silicon wafer, at Mitsubishi Silicon America is presented. Future plan to recycle the process generated silicon fines produced during the intermediate steps of the wafer manufacturing process such as grinding, slicing, lapping and polishing is also discussed.

Jan 1, 1998

By Joon H. Jang

At a selected pH, hydrothermal oxidation of chalcopyrite was carried out under controlled F+,, at elevated pressures and temperatures (172-200°C) by balancing the rate of oxygen injection against the rate of consumption. Chalcopyrite was converted to covellite (CuS) and digenite (CU1.8S) with rejection of iron and sulfur to the solution. Covellite forms in the first stage, followed by nucleation and growth of digenite in the second stage. The effects of rapid and slow injection of stoichiometric quantities of oxygen are compared. Both the covellite and digenite form a porous layer occupying the same volume as the original chalcopyrite grain. An electrochemical kinetic model is presented to correlate the observed results.

Jan 1, 1993

The oxidation of zinc vapour plays a very important part in the operation of the Imperial Smelting Process. The kinetics of the reoxidation of zinc vapour by carbon dioxide and water vapour onto quartz and zinc oxide substrates is qualitatively understood and this pertains to the conditions found as the gases are being transferred from the furnace to the splash condenser. However, re-oxidation also occurs in the shaft of the furnace where the solid substrates are sinter and metallurgical coke. It was found that there was a threefold increase in the rate of oxidation on sinter, compared to quartz and a 30 to 300 increase in rate on the coke. This was attributed to the high surface area offered by these materials.

Jan 1, 2003

By J. D. Budai, D. H. Lowndes, D. P. Norton, D. K. Christen, B. C. Chakoumakos, J. R. Thompson, B. C. Sales

"Artificially-layered structures, consisting of (Sr,Ba,Ca)CuO2 layers in the tetragonal, ""infinite layer"" crystal structure, have been grown by pulsed-laser deposition. Superlattice chemical modulation is observed for structures with SrCuO2 and (Sr,Ca)CuO2 layers as thin as a single unit cell (~3.4 Å). In addition, novel thin film superconductors were formed by using the constraint of epitaxy to stabilize SrCuO2/BaCuO2 superlattices in the infinite layer structure. Using this approach, two new structural families, Ba2Srn-1CUn+l O2n+2+ d) and Ba4Srn-1CUn+3O2n+6+ d, have been synthesized which superconduct at temperatures as high as 70 K. These results represent not only the synthesis of new structural families of superconductors, but also demonstrate that pulsed-laser deposition and epitaxial stabilization can be effectively used to engineer artificially-layered thin-film materials.Advances in the understanding of epitaxial thin-film growth of the cuprates have heightened interest in creating artificially layered superconductors.(1-3) The layered structure of the copper oxide superconductors opens the possibility of forming novel materials by carefully controlling the epitaxial growth of sub-units of the crystal structures. Thin-film growth methods offer unique opportunities for the atomic engineering of new high-temperature superconducting (HTSc) materials through the ability to form artificially layered crystal structures.(4,S) Moreover, the surfaces of single-crystal substrates provide an ""atomic template"" that can be used to stabilize epitaxial films in metastable crystal structures.An important development in forming new HTSc compounds by artificially-layered epitaxy has been the epitaxial growth of (Sr,Ca)CuO2 films in the so-called infinite layer structure.(6-17) This material, which can be considered the parent compound of all of the copper oxide superconductors, has a relatively simple, layered structure consisting of CUO2 planes separated by planes of alkaline earth elements.(18) Bulk synthesis of (Sr,Ca)CuO2 with the tetragonal, infinite layer structure generally requires the use of high pressure and high temperature bulk processing techniques.(19-24) However, recent experiments show that this metastable compound can be epitaxially stabilized at less than atmospheric pressure, resulting in the growth of tetragonal (Sr,Ca)CuO2 single crystal thin films of the infinite layer defect perovskite structure by pulsed-laser deposition (PLD) over a wide range of growth conditions.(6-17)"

Jan 1, 1994

By B. Q. Li, Y. Shu, K Lynn

"This paper discusses the effects of magnetic field and internal radiation on the melt flow and solidification morphology during solidification processing of oxide crystals for optoelectronic and remote sensing applications. The numerical solution of the integral differential equation characterizing the internal radiation and the magnetohydrodynamic equations describing the magnetic and transport phenomena is obtained by applying the combined discontinuous and continuous finite element method. The results show that both internal radiation and an externally applied magnetic field can have important effects on the melt flow and solidification behavior during the melt processing of oxide materials.IntroductionOptical single crystals are widely used in optical and electronic devices. These crystals are often grown from high temperature oxide melts under strictly controlled conditions. As in the well-known single crystal growth processes for semiconductor wafers, thermal gradient in the melt is a major contributing fuctor to the oxide melt pool. Unlike the semiconductor single crystal growth processes, however, the oxide melt is semitransparent and internal thermal radiation plays an important role in redistributing the thermal energy in the melt pool. Our recent experience with pilot-scale plant measurements also shows that the oxide melt is electrically conducting, although its electrical conductivity is considered much lower than the liquid metal or semiconductor melt.The fact that the oxide melt is absorbing and emitting in the thermal radiation frequency range makes it difficult to study the thermal energy transport in the melt pool. This is because thermal radiation is governed by a hyperbolic differential equation, which is different from those describing the transport processes in liquids. Also, our understanding of how thermal radiation interacts with other transport mechanisms such as convection and conduction is rather limited at point in time, in particular in high temperature oxide melts for optical single crystal processing."

Jan 1, 2004

By J. T. I. Poijärvi

The smelter off-gas cleaning and the weak acid treatment at Outokumpu Harjavalta Metals Oy are presented and described in this paper. The smelter consists of the copper and nickel smelters and the acid plant of three separate acid plants two of which are double contact and one single plant and of one liquid sulphur dioxide plant. The preliminary cooling and flue dust separation of the smelter off-gases from the copper and nickel flash smelting furnaces and converters in the waste heat boilers and in the hot electrostatic precipitators are described. The final cooling and cleaning of the gases in the scrubbers at the sulphuric acid plant and the treatment of the weak acid in the vacuum and in the submerged combustion evaporators for the removal of impurities are pre¬sented as well as the treatment of the condensates from the evaporators. The attention is paid to the generation of sulphur trioxide in the smelter off-gas and to the treatment of that in the weak acid bleed-off and to the utilization of the treated acid.

Jan 1, 1992

By Thomas Gliick, Jianming Lu, David Dreisinger

"The recovery of manganese from the Boleo project of Baja Mining is via an acid oxidation and acid reduction process in seawater. Manganese as manganese dioxide is leached into solution as manganese sulphate with the addition of sulphur dioxide gas as a reductant and then precipitated as a manganese carbonate. The use of the manganese carbonate intermediate to produce electrolytic manganese metal (EMM) has been extensively studied. The manganese carbonate can be used in place of natural (MnC03) or reduced ores (MnO) of manganese as a feed to the EMM plant. Manganese carbonate can be dissolved in spent electrolyte from manganese plating, followed by purification using ammonium sulphide precipitation of minor elements and then electrowinning in a selenium free process. The results of small cell testing of manganese electrowinning are reported.IntroductionThe Boleo Project of Baja Mining is a greenfields development currently under construction approximately 5 km north of the town of Santa Rosalia, Baja California Sur, Mexico. The Boleo property is held by the Mexican company, Minera y Metalurgica del Boleo S.A. de C. V. (MMB). MMB is owned 70% by Baja Mining Corp. and 30% by a consortium of Korean companies consisting of KORES - Korea Resources Corporation, LS Nikko Copper, Hyundai Hysco, SK Networks and lljin Copper.The Boleo deposit has Measured and Indicated resources of264.7 million tonnes grading 1.50% copper equivalent (CuEq) & Inferred resources of 159.9 million tonnes grading 1.15% CuEq. The calculation of copper equivalent is based on a combination of metal prices and predicted metallurgical recoveries (Table I). The metallurgical recoveries have been confined by extensive bench and pilot plant testing. Proven and probable reserves are available at Boleo to provide for more than a 30 year mine life. Initially, 25 years of mine life and 23 years of process plant operation have been scheduled in the February 2010 Technical Report Update (www.sedar.com)"

Jan 1, 2012

By Jr. Foot

The Bureau of Mines, U.S. Department of the Interior, investigated flotation methods for recovering fluorite and byproduct beryllium from the Fish Creek deposit of Nevada. The preferred method includes (l) fluorite rougher and cleaner flotation, (2) de sliming at 20 micrometers, (3) muscovite flotation, (4) silicate flotation, (5) hypochlorite wash of silicate concentrate, and (6) beryllium rougher and cleaner flotation from the silicate concentrate, Laboratory results showed that over 94 pct of. the fluorite was recovered in a concentrate containing 96 pct CaFz. Beryllium flotation produced .concentrates .containing in excess of 5 pct BeO with recoveries over 70 pct. A 1.00-lb/h continuous flotation unit was constructed to demonstrate this procedure,

Jan 1, 1985

An EAF dust generated in a Swedish steel mill has been leached in hydrochloric acid at The solution obtained has been subjected to purification by cementation followed by precipitation of zinc with sodium carbonate. The thermal decomposition of the precipitate was studied using thermal analysis and X-ray diffraction. The results show that during the calcination of the precipitate three different reactions occur. The decomposition of the solid phases Zn5(CO3) (OH)6, CaZn(CO3)2 and CaCO3 occur completely at 370°C, 560°C and 940°C respectively, yielding a final product containing 61.9% ZnO and 38.1% CaO. Methods to minimize calcium and manganese in the final product are discussed.

Jan 1, 2003

By Yasuhiro Konishi

Hydrolytic stripping is the process in which metal ions are simultaneously stripped from a loaded cation-exchange solvent extractant and precipitated as oxides or hydroxides. Hydrolytic stripping is usually effected by contacting the loaded organic phase with water at elevated temperatures. The possibility of using hydrolytic stripping to prepare ceramic powders with controlled size and morphology is now being evaluated for different systems, using carboxylic acid extractants. As part of this work, mathematical models were developed to describe the kinetics of nucleation and growth of nickel ferrite particles. This paper describes the development of the models, along with estimation of key parameters appearing in the rate equations from experimental data.

Jan 1, 1990

By R. H. Crist

Reactive components of algal cell walls include uronic and alginic acids: In addition, many marine species have half ester sulfate groups which function as fixed anions. Associated metals vary with the media, eg., Ca and Mg in fresh water (FV) and Na, Ca, Mg in seawater. . These metals readily exchange with aqueous phase protons or metal cations. A plot of the total amount of metal cations displaced by protons vs .. pH shows one inflection at pH 4 for FV algae and' in addition a second inflection at pH 2, 3 for marine algae. The first inflection is interpreted as. Indicating the cations associated with carboxyl groups ,and the ,second with half ester ?Sulfate groups. The exchange capacities of various aigal ,species vary widely. When FV algae is placed in a Pb2+ solution,- the amount of Pb2"' deposited on the algae is. Equivalent to the. Total Ca2?, Mg2, and H+ displaced? thereby confirming the ion exchange mechanism. Ion exchange equilibrium constants are reported for the displacement of ca2+ from Vaucheria. With Mg2+, sr2+, Cd2+, Pb2+_ and Na+ as well as the reverse reactions. Cd2+ can .be removed partially from algae by precipitating it as CdS or Cd(OH) 2 Pb2+ and Cu2+ are also partially removed as the hydroxides. Rates of reaction for various alkali hydroxides decrease with increasing .unhydrated cation radius. It is concluded that theory is useful in predicting viable applications for algae in pollution abatement.

Jan 1, 1991