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By Ali Unal, Ali I. Kahveci

Alcoa developed a fractional crystallization process some 30 years ago as a method to purify aluminum. Depending on the purity of feed metal, it has been commercially used to make 3N7-6N purity aluminum. As an extension of this technology, Alcoa has experimented with purifying various aluminum alloy scrap for the purpose of recycling. Purified aluminum alloy scrap can be reused for making the same alloy. This presentation will discuss Alcoa fractional crystallization technology and its application to alloy scrap processing. Process capabilities and the partitioning of eutectic and peritectic impurities during fractional crystallization will be discussed for the alloy systems investigated.

Jan 1, 2000

By C. H. Quan

Solvent extraction tests were carried out on a rare earth chloride solution derived from monazite processing to determine the effect of extractant and diluent on the distribution coefficients between organic and aqueous phases, and the separation factor between rare earths. The extractants were 20% by volume di-2-ethyl-hexyl phosphoric acid (DZEHPA) or 2-ethyl-hexyl phosphonic acid (Ionquest® 801). Four Shellsol diluents were tested ranging from nil to 100% aromatic content. D2EHPA gave the highest rare earth extraction for a given pH but was less selective than Ionquest. The geometric mean separation factor between adjacent rare earths varied from 2.41-2.56 for D2EHPA to 2.62-3.01 for Ionquest. The nil-aromatic diluents (Shellsol 2037 and 2358) gave better separation factors in Ionquest but, in D2EHPA, were slightly inferior to the 100% aromatic diluent Shellsol AB. Yttrium behaved as a pseudo-heavy rare earth with a distribution coefficient lying between Ho and Er, as expected from its ionic radius.

Jan 1, 1992

By M. Nilmani, J. Sofra

The transverse distributions of the solids discharge velocity and mass flux at the discharge end of vertical and inclined lances were measured in order to detennine the transverse distributions of the axial momentum flux, which is a dominant factor influencing the penetration behaviour of particles into melts during submerged injection. The effects of gas velocity (10 - 30 m/s), solids loading (5 - 10), lance length (0.15 - 1.0 m), lance inclination (vertical downward - horizontal) and particle density (2500 - 8900 kg/m3 ) were investigated, while the lance diameter and particle size were fixed at 10 mm and 220 µm respectively. The particle velocities and mass fluxes were measured by image analysis of particles illuminated in a laser-generated light sheet aligned vertically through the axis of the lance at the discharge point. The particle discharge velocity profiles for vertical downward flows were synunetrical about the centre-line of the lance, with the maximum velocities occurring at the centre-line. The velocities increased with increasing gas velocity, increasing lance length and decreasing particle density in accordance with previous observations. The transverse mass flux profiles were also synunetrical for vertical downward flows, however at the lower gas velocities the peaks in the profiles were displaced from the centre-line of the lance by a fractional diameter of about 0.15. The particle discharge velocity profiles become increasingly asynunetric as the lance orientation was changed from vertical to horizontal, with higher particle velocities present near the top wall of the lance. The mass flux profile also became asyrrunetric as the horizontal orientation was approached, however in this case, the profile became biased towards the bottom of the lance. The effect was much more pronounced for a gas velocity of 10 m/s than for 30 m/s, showing the relatively stronger gravitational influence as the velocity was reduced.

Jan 1, 1996

By Ahmad Ghahreman, James McNeice

Separation of rare earth elements (REE) is often achieved by acid leaching of mineral concentrates followed by subsequent solvent extraction (SX), to purify individual rare earth metals (REM). Cerium, the most abundant REE, is usually the largest component of these ores. Demand for less prevalent REE, such as praseodymium and dysprosium; have led to a market saturation and price collapse of cerium. One method of improving the economics of REE separation is to remove cerium from solution prior to SX. This is accomplished via the oxidation of cerium (III) to cerium (IV), which precipitates as cerium hydroxides. This study probes the efficacy of four oxidants; hydrogen peroxide, sodium hypochlorite, potassium permanganate, and Caro’s Acid with the goal of improving cerium removal whilst minimizing REE and reagent losses. The effect of oxidant type and dosage, pH, cerium concentration, and temperature on the kinetics of the process will be discussed.

Mar 1, 2018

By A. G. Jackson, Mark D. Benedict, Steven R. LeClair, Yang Cao, David M. Conrad

"Electronic Prototyping (EP) represents a new and powerful medium that many in science and technology view as the research paradigm of the future. Actually, EP has many handles, sometimes referred to as simulation-based design involving more long term objectives such as virtual reality, but regardless of the 'spin', the direction of EP is an enhanced visual paradigm to enable a new set of tools for engineers and scientists alike. Tools to not only automate, visualize and compute otherwise intractable problems but to enable augmentations of our ability to perceive that which is interesting and new -""a virtual version of a process"" [1] prodding us on the pathways of materials and process discovery.IntroductionActually there are many reasons to apply sensors to materials, such as smart or adaptive materials/structures, and new materials synthesis/processing [1], only some of which are motivated by improved product quality and/or productivity. Although U.S. Air Force applications of sensors to materials processing represent but one of many perspectives, hopefully it is a perspective which will engender new ideas and insights in addressing future challenges in materials research. To provide context and establish need for future sensor applications in materials processing, we will utilize on one of several Air Force vistas or '21st-Century' objectives."

Jan 1, 1997

The physico-chemical principles of chloride hydrometallurgy are reviewed to rationalise the complex chemistry in chloride-based processes for metal sulphides in terms of the predicted Eh-log[Cl-] relationships, measured changes in activity of H+, Mz+, Cl- and solubility of Ag(I), Cu(I), Cu(II), Pb(II), Ni(II), Au(III), Sb(III) and Bi(III). These changes reflect the nature of chemical speciation, competing effect of hydration/hydrolysis and chloro-complexation,composite effect of increasing acid and/or salt concentration and decreasing water activity. Rate data for the dissolution of PbS and ZnS in HCl containing Fe(III) or Cu(II) are compared and contrasted to highlight the effect of acid and chloride concentration, water activity, and the nature of oxidant. It is shown that LiCl, NaCl and HCl influence the kinetics of oxidative PbS leaching based on their effect on solubility of PbCl2 co-precipitated with elemental sulphur on the mineral surface. Evidence for the beneficial effect of Cu(II) in sulphide leaching is discussed.

Jan 1, 2003

By Junji Shibata

The waste acid mixture whose main component is phosphoric acid, is discharged from the etching process in the liquid crystal production industry. In order to separate impurity acids from the phosphoric acid, trioctyl phosphate (TOP) is used as an extractant. TOP can extract acetic and nitric acids selectivity. The extraction and stripping operations are carried out for the acid mixture by beaker-scale experiments and countercurrent multistage operations with mixer-settler equipment. TOP selectively extracts the acetic and nitric acids in the acid mixture. From the results of the McCabe-Thiele analysis obtained by beaker-scale tests, the extraction for acetic and nitric acids are approximately 100%, respectively, by 6-stage extraction with a phase ratio (A/O) of 0.4. On the other hand, almost all of acetic and nitric acids are stripped with water from the organic phase by 4-stage stripping with a phase ratio (A/O) of 1.0. About 95% of acetic and 98% of nitric acids can be removed from the acid mixture without extracting phosphoric acid in case of the mixer-settler equipment operation. There are several steps such as slicing, lapping, chemical etching and mechanical polishing in the silicon wafer production process. The chemical etching step is necessary to remove any damaged layer caused in the slicing and lapping steps. The typical etching liquor is the acid mixture comprising nitric acid, acetic acid and hydrofluoric acid. The waste acid is treated by a neutralization method with a high alkali cost and balky solid residue. A solvent extraction method is applicable to separate and recover each acid. Acetic acid is first separated from the waste liquor using 2-ethlyhexyl alcohols as an extractant. Then, nitric acid is recovered using TBP (Tri-butyl phosphate). Finally hydrofluoric acid is separated with TBP solvent extraction. The expected recovered acids in this process are 2mol/L acetic acid, 6mol/L nitric acid and 6mol/L hydrofluoric acid. The yields of this process are almost 100% for acetic acid and nitric acid. On the other hand, it is important to recover and reuse the metal values contained in various industrial wastes from a viewpoint of environmental preservation. Most industrial products are made through processes to separate impurities in raw materials, solid and liquid wastes being necessarily discharged as industrial wastes. Chemical methods such as solvent extraction, ion exchange and membrane separation, and physical methods such as heavy media separation, magnetic separation and electrostatic separation are considered as the methods for separation and recovery of the metal values from the wastes. Some examples of the application of solvent extraction to the treatment of wastes such as Ni-Co alloy scrap, Sm-Co alloy scrap, fly ash and flue dust, and liquid wastes such as plating solution, the rinse solution, etching solution and pickling solution are introduced.

Jan 1, 2003

By H. Kandemir

An experimental study of the bacterial oxidation of naturally occurring high-purity sulphide minerals (FeS2, Fe1-xS, Cu5FeS4, ZnS) is presented using a mesophilic strain of T. ferrooxidans. As well as metal analyses and solution pH, partitioning of sulphide sulphur into elemental sulphur and sulphate has been monitored as a function of leach time. Partially oxidized sulphide substrates have been characterized, at regular time intervals, by X-ray diffraction methods and extracellular organic compounds reporting into leach solution .have been identified by thin layer -chromatography.

Jan 1, 1985

By D. M. Hausen

Multiple drill sections through many of the numerous breccia pipes in the American Eagle copper deposit at Copper Creek, Arizona, have been evaluated by means of alteration and geochemical data. Contoured plots indicate vertically plunging, concentric, cylindrical shells of alteration and mineralized rock that are similar in structure, geometry, magnitude and petrology to the San Manuel-Kalamazoo Deposit, located about 14 miles to the southwest. Both deposits are similar in dimension and consist of multiple, irregular, rod-shaped injections of porphyry into a granodiorite host. Analogous to the San Manuel-Kalamazoo Deposit, most of the porphyry plugs are oriented parallel to the cylindrical axis of the "ore shell". A continuously mineralized, elliptical shell, inferred from deep drilling, is capped by a flatter zone of copper mineralization. Above this flat zone, copper-bearing fluids were channeled upward along conduits that correspond with quartz-sericite "breccia pipes". At depth, zones of sericite and K-feldspar alteration products exhibit conformable relationships with the copper deposition. A "bullet-shaped" ore shell, with a nearly vertical axis, is proposed to explain the conformable zones of altered and mineralized rock. The "nose" or top of the "bullet" is 1800 to 2300 feet below the surface, and structurally controlled in part by steeply dipping Hi and ENE faults. If correct, this model suggests that the vertical ore shell may extend to great depth.

Jan 1, 1988

By Carla Lupi, Mauro Pasquali

"Photographic technology is based on light sensitivity of silver halides that, because of silver properties, are capable of forming photographic images. Photographic laboratories and hospital departments because of digital photographic systems less use this technology today. Nevertheless recovery of silver is still advantageous because environmental problems related to Ag ions danger to biological system. Many processes have been studied to treat silver containing photographic bath: cementation, chemical precipitation and electrowinning. In this work, after preliminary voltammetric tests, a batch electrometallurgical process has been studied to completely deplete the silver containing photographic fixing baths. The effect, of silver concentration in the electrolyte, varying over the range 0,2-1 g/L, bath stirring and current density ranging from 10 to 500 A/m2 on process yield and deposit quality, has been investigated. Introduction Photographic wastes, electronic scrap and spent catalysts constitute the main sources of materials for silver recycling. Among those silver secondary sources, the photographic discharged material could be still important and useful, even if photographic laboratories and hospital departments, because of digital photographic systems, less use photographic technology. Several processes have been developped in order to recover silver used in the field of photography from both photographic solutions and scrap film paper[1-5]. Fixing solutions are very complex baths but, because of silver position in the electromotive series, electrolysis could represent an advantageous method for silver recovery. Electrolysis produces high purity silver without generating new pollutants, while the fixer can be reused: obviously it is necessary to purge off a portion of this solution in order to avoid the excessive build up of other deleterious compounds into solution. A tested recovery method was constituted by the dissolution of silver from X-ray films with concentrated nitric acid. Internal electrolysis and external electrolysis methods were carried out using a steel electrode as cathode and a copper electrode as anode [6]. Silver recovery from photographic chemical solutions has been also performed in a special cell [7]: the solution is supplied to the bottom of a non-agitated cell having a vertically elongated form and including a central anode enclosed by a cathode. An other study discloses the use of an electrolytic cell comprising at least one anodic compartment and one cathodic compartment: the solution is treated in the cathodic compartment and then recycled in the anodic one [8]. A more recent work proposes the use of zirconium cathode for the recovery of silver from photographic fixing solution [9]: studies carried out by cyclic voltammetry showed that about 98% of total Ag can be recovered with an electrical efficiency close to 92%."

Jan 1, 2008

By P. R. Taylor

Diamond films have been successfully formed in an inductively coupled plasma (ICP) chemical vapor deposition (CVD) system from several gas mixtures: CH,-H,, C2112-112, and C2112-112-02' Our previous thermodynamic study indicated that the substrate temperature could be lowered by the presence of oxygen species at moderate system pressures (0.3-0.5 atm) and that higher volumetric growth rates required a high temperature source and a moderate pressure system in CVD processing. The principal experimental results were consistent with the thermodynamic predictions. The deposited films were characterized by laser Raman spectroscopy, scanning electron microscopy, and X-ray diffraction. The films were well faceted and uniform, with the growth rates over 10 pm/hr on molybdenum substrates. The crystal size ranged between 1 and 2 microns for a two hour experiment. It was possible to decrease the substrate temperature to below 800 °C in this system.

Jan 1, 1995

By Tomas Astorga

APEC, the Asia Pacific Economic Cooperation is the forum of 21 countries having approximately 56% of the total world income, and over 45% of global trade. In 1997, APEC economies produced 67% of the world copper output, 55% of gold, and over 45% of other base metals. Mining in APEC captures more than 60% of the total mining investment in the world. New and emerging economies are now appearing in the demand scenery, such as China. New trends in the international environmental regulations are posing questions related to the use of copper in different industrial and consumption applications. These may have a strong impact on future trade of copper. New applications are also appearing based in new technology fields. The paper examines the growth potential of the copper market in main consumer ad highly populated economies of APEC, incorporating analysis of various interrelated factors. It also analyses the outlook of the copper supply. Its conclusions point to the need to implement demand outlook models. Finance and economic reforms will open important avenues for trade growth in basic metals, particularly copper. Changes in the consumption patterns of highly populated countries will add to better perspectives of copper demands. The recovery of a fast pace of economic growth in the APEC region will bring new demands for copper, especially as a consequence of high tech applications. More extended policies focused in the need for developing energy efficiency programs and schemes will add to this picture.

Jan 1, 1999

By Guillermo J. Román

The precipitation of copper and zinc as cements from a copper alloys' spent pickling solution has been studied at laboratory and pilot scale, with the objective of designing an economic process to recover both metals and render a solution to be either recycled to the pickling process or treated in a standard fashion and produce a non-hazardous sludge. The sulfuric acid spent pickling solution already containing copper and zinc was used first to dissolve another solid residue originated in the copper alloys foundry to neutralize part of the acidity. The resulting enriched solution was treated separately with two reductants,; sodium borohydride and iron powder varying pH and excess of reductant under constant agitation. Under the best conditions, precipitation of over 95 percent of zinc and copper was achieved together with the reduction of lead and cadmium contents respectively. A process for the combined residues treatment is proposed.

Jan 1, 1995

By Barry T. Kilbourn

A dominant characteristic of many derivatives of the lanthanides is stability at high- temperatures. Combine this with novel solid-state behavior under those conditions and there is the potential for new materials that can not only improve existing applications but also help create new technologies. These property themes will be traced through new uses ranging from efficient energy generation and raw material conversion to control of environmental emissions and temperature measurement. Conducting ceramics, methane conversion catalysts, sulfur oxide capture agents and phosphor hosts will be described. Some categories will account in the future for significant lanthanide consumption whereas others will remain commercially negligible but technologically vital. All uses will illustrate the versatility of those elements inappropriately termed rare.

Jan 1, 1992

By R. K. Amankwah

The ability of Streptomyces viridosporus in sorbing heavy metals from wastewater has been investigated. It was found out that the biomass of the soil microorganism could be used in sorbing Pb2+, Cu2+, Zn2+ and Ni2+ ions from acidic solutions of metal ion concentration between 10 and 100 ppm. Over 99% of Pb2+ and 88% of Cu2+ ions were sorbed from wastewater of concentration 10 ppm with Ni2+ and Zn2+ recording values below 50% for a contact period of 4 hours. The quantity of metal ions sorbed per gram of biomass from the wastewater was in the order Pb2+ > Cu2+ > Ni2+ > Zn2+ and this is related to their electronegativities. Biosorption was sensitive to variations in pH and in the range investigated; metal binding was optimum at 5.5. About 63% antimony was also sorbed from dilute cyanide solution.

Jan 1, 2003

By Migen Dibra

Antitrust and competition laws are designed to protect the free markets and promote competition in order to assure a dynamic and efficient economy and to provide competitive prices for quality products and services. They apply to mergers and acquisitions as well as to joint ventures especially among competitor companies who possess market power and these include collaborations on research and development. If it is determined that these actions are likely to substantially prevent or lessen competition the courts might dissolve, stop, alternate them, etc. Two new factors affect this process today: The role of new technologies and the markets globalization. They both have a considerable effect on the way these laws are interpreted by the courts and on their eventual amendments in order to reflect the new reality. A new applied technology and the globalization separately or together may change the factors that determine how anticompetitive a merger or acquisition between competitors may be and may also serve as a basis for amending the antitrust and competition laws. In this paper, a short review of the recent mergers and acquisitions of various companies has been carried out along with an abridged analysis of the current antitrust and competition laws in USA, Canada and European Union in the view of their capacity to handle the new reality. Some related court decisions are also examined and several examples are given in order to illustrate the influence of new technologies and globalization in interpreting the existing laws and on their amendment possibilities.

Jan 1, 2006

By Satya Ganti, Bryan Turner, Bill Davis, Veeraraghavan Sundar

This work presents a three dimensional microstructural analysis of medium carbon steels, based on serial sectioning using optical microscopy. The microstructural phases considered here are ferrite and pearlite. Typically conventional 2D microscopy is used to analyze these phases (ASTM E112-13 in Standard test methods for determining average grain size. ASTM International, West Conshohocken, PA, 2013), with eddy current (Khan et al. in J Mater Process Technol Freitas et al. in Mater Sci Eng A 527(16):4431–4437, 2010) as alternatives. Medium carbon steel samples were heat treated in a furnace and either slowly cooled in the furnace, or cooled at higher rates. This resulted in different pearlitic microstructures in the samples. The analysis was conducted with Robo-Met.3D®, a fully automated metallography system for serial sectioning. Based on optical microscopy, volume cubes of hundreds of microns on edge were imaged and reconstructed to conduct grain size and phase volume analysis. The system proved capable of collecting image data with high fidelity, and controlled slice thickness in an automated manner. The resultant dataset was useful in visualization and analysis of pearlite and ferrite phases in steel samples.

Mar 1, 2018

By Lijuan Li, Xin Xia, Junjun Huang, Qijie Zhai, Xiang Jiang

"Some experiments with different temperatures (1173, 1223, and l273K) and different annealing times (3, 4, 5, 6min) were carried out on cold-rolled plate of Fe-36Ni invar alloy. The microstructure and the mechanical properties were observed and tested respectively, and the fracture morphology was observed by SEM. The results show that with increasing of the temperature and the annealing time, the austenite grains gradually grow up accompanied by a small amount of annealing twin crystals, meanwhile, its plasticity and toughness are improved, and it is typical ductile fracture under the condition of tensile failure. After annealed at l223K, the invar alloy has better comprehensive properties than that at the other annealing temperatures, and the grains size is more uniform. Furthermore, when the annealing time is 4min, the invar alloy has the best comprehensive properties.IntroductionAs we known, most metals and alloys expand with increasing temperature. More than one hundred years ago (in 1897), Guillaume observed that Fe-Ni alloy with face-centered cubic (fcc) crystal structure, consisting of36%Ni, showing a very small thermal expansion coefficient below the ferro-to-paramagnetic transition, the thermal expansion coefficient around room temperature( <2 X 1O-6K-1 compared to most metallic materials which have a thermal expansion coefficient of 10-20 X 1O-6K-1) [1,2]. Since then, the subject has attracted many researchers, and various alloys with low thermal expansion coefficients have been developed. These alloys, generally known as ""invar alloys"", are in demand where dimensional changes due to variation in temperature must be minimized and where high stability is required [3, 4]."

Jan 1, 2012

By Robert E. Moore

Renewed interest in olivine refractories has led to efforts to characterize them employing modern techniques of experimentation and data analysis. Initial studies have focused on determination of physical and thermophysical properties. Special equipment for the determination of thermal shock resistance and creep behavior have been constructed. Optimal compositions for maximizing various properties are being identified using appropriate statistical techniques. The overall goal is to develop response surfaces for each of a selected group of engineering design and use properties. Development of ?olivine Refractories? in the United States The term "olivine refractories" is used here because it does appear that domestic deposits of this rock will be the focus of renewed interest and "olivinell is the preferred term in this country. There are extensive deposits of high quality olivines extending through parts of Georgia. North Carolina and in the state of Washington. The eastern olivines are much more localized and extensively altered compared to the western materials. The Washington olivines exist as massive rock deposits in the Twin Sisters mountain area northeast of Seattle and their inaccessi-bility has slowed efforts to develop them. The North Carolina olivines have been used in steel plant applications since the 1930&apos;s. Geologists use the term "olivine" to describe assemblages of ortho-silicates. 2RO.SiO2, wherein the RO may be MgO. FeO. MnO. etc. When the RO consists essentlally of MgO and FeO. the material is called dunite and. as such, is synonymous with "refractory olivine." Refractory olivines utilizing North Carolina materials were developed for brick products by Birch and Harvey in this country around the mid-1930&apos;s. (I) Their work was completely independent of that of V. M. Goldschmidt and co-workers who used massive dunites located in Denmark. (2) These deposits are currently being mined by A/S Olivine of Denmark for the manufacture of a rather complete line of brick shapes for use in steel-plant. glassplant. and cement kiln applications. Birch and Goldschmidt

Jan 1, 1982

By Toshiharu Hayashi

We prepared the water dispersed with Au particles ranging from 10 to 20 nm size by a novel wet chemical synthesis; generating seeds of Au cluster by adding a borane dimethylamine complex into chloroaureic acid (gold salt) solution, and then growing simultaneously with aminoalcohol included in the solution. As-prepared Au nano-particles with chemical surface modification were found to have some attractive performances, i.e., showing a high dispersiveness in an aqueous solution in a long time, sintering nano-particles at low temperature, and having low resistivity in the film prepared from nano-particles. In the case that smaller Au nano-particles were removed from as-prepared colloid, especially, Au thin film formed on the surface of Si plate showed the excellent value of 7.0x10-6ohm cm (reference peculiar resistance: 2.35x10-6 ohm cm).The sintering temperature was dependent on the elimination of 2-aminoethanol that modified on the surface of Au nano-particles.

Jan 1, 2006