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By Andreas H. Vassiliou

Organic materials are major constituents of the ore in several uranium deposits. Some of these deposits have been described as "urano-organic" because, the organic materials are believed to have provided the dominant control for the accumulation and deposition of uranium and are directly and intimately intermingled with the uranium. The nature of these urano-organic deposits has been problematic in terms of (a) the origin of the associated organic materials and (b) the specific form of' occurrence of uranium. The organic materials in urano-organic deposits have been genetically related to both coal and petroleum or their progenitors or deriva-tives. Analytical data presented here (infrared, chemical. D.T.A.) suggest that coaliferous materials or related plant derivatives represent the main source of the organic fractions in practically all major urano-organic ores analyzed from the Colorado Plateau and other areas. Recognition of the specific form of occurrence of uranium in urano-organic deposits has been problematic mainly because the uranium is usually in an extremely fine-grained and disseminated state in the organic matrix. Electron microprobe and X-ray diffraction analyses presented here show that fine-grained uranium minerals, specifically uraninite or coffinite. are disseminated in the organic matrix as the predominant form of uranium in most major deposits; however. the presence of true organo-uranium compounds is also suggested for some deposits.

Jan 1, 1981

By Ali Kucuk, Bekir Karasu, Keriman Karaveli Pekkan

"Zircon (zirconium silicate) is the main opacifier of glossy, opaque, white colored, frit-based wall tile glazes. However, zirconia containing frits employed in the preparation of these glazes increase the production cost and therefore, limit zircon usage as a raw material at industrial scale. With the present study, it was searched whether borax solid wastes could be evaluated as a component in the starting relevant frit recipes. The wastes were obtained from Eti Maden Kirka Boron Company of Turkiye. Frit production, glaze preparation, application, and fast single-firing of glazed wall tiles were conducted under laboratory working conditions in Anadolu University, Department of Materials Science and Engineering laboratories. Beside standard tests applied to the final glazed wall tiles, color and gloss analyses of the fired glazes were conducted with a spectrophoto-meter and a gloss-meter. Characterization of these newly produced glass-ceramic glazes was made by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) techniques. IntroductionFrits are the indispensable constituents of most industrial glazes which mature at temperatures below 1150 °C [1]. In the traditional opaque glazes used in wall tile industry, opacity usually originates through hardening of glass matrix by adding high amounts of zirconia containing frits into the glaze batch [2]. Nowadays, researches point out that certain type of glass-ceramic layers can be alternatively employed as tile coatings lowering the use of zirconia containing expensive opaque frits. A rather high crystallization capacity of glass- ceramic glazes due to zirconia presence in glass network makes them suitable candidate as a glaze coating with a desirable micro-structure. One of the best methods to obtain an opaque glaze surface is to induce a crystal phase in the coating, whose refractive index differs significantly from that of the glassy matrix. The opacity of such coating is determined by the diffusion, refraction and reflection of light through the layer containing emerging crystals, and the degree of opacity mainly depends on the size and quantity of crystals. The development of glazes not consisting of expensive or toxic components is of special interest [3]."

Jan 1, 2008

By Shigehito Isobe

The Li-N-H system composed of LiH and LiNH2 catalyzed by titanium compound desorbs ~6 mass% hydrogen and a quite small amount of ammonia in temperature range from 150 to 250 °C under He flow atmosphere. In this work, hydrogen desorption (H-desorption) mechanism in the reaction from LiH+LiNH2 to Li2NH+H2 in a non-equilibrium condition was clarified by TDMS, TG and FT-IR analyses for the products replaced by LiD or LiND2 for LiH or LiNH2,respectively. The results suggested that H-desorption reaction progresses through two-step elementary reactions mediated by ammonia. As a next step, we carefully determined the amount of the ammonia containing in desorbed hydrogen for the Li-N-H system in a closed system from the practical point of view. The results indicated that a quite small of ammonia thermodynamically coexisted in the desorbed hydrogen in closed system, although ammonia could not be almost detected in emitted hydrogen gas by TDMS under some non-equilibrium conditions. Moreover, for understanding the role of titanium, the chemical bonding state of the titanium compounds doped as catalyst in the mixture was examined by XAFS measurement. The results indicate that the Ti atoms, which can induce catalytic effect, are in a particular chemical bonding state.

Jan 1, 2006

By Teruo Tanabe

The hydrogen-absorbing materials are expected to have the following properties at moderate conditions, (a) a large capacity of hydrogen absorption, (b) the absorption rate of hydrogen is large and (c) hydrogen-absorbed materials can easily desorb hydrogen. Thus the three concepts of capacity, rate and reversibility seem to be indispensable to clarify the mechanism of hydrogen absorption by the materials. In this work, the amount of absorbed hydrogen, the absorption rate and the reversibility of hydrogen absorption- desorption reaction were measured for binary R-M systems (R = Y, La, Ce; M = Co, Ni). These experimental results were discussed by the following three physical properties that were calculated by the extended Hückel method, i.e. the density of states unoccupied by electrons, the cohesive energy and the energy fluctuation. The major results are as follows: (a) the amount of absorbed hydrogen increases with the density of states in the energy range between -9 and -4 eV, (b) the R-M compounds of which energy fluctuations are large show a large value of rate of hydrogen absorption, and (c) when the cohesive energy is large, the compound has a tendency not to easily desorb hydrogen, i.e. its reversibility is poor.

Jan 1, 2006

By K. Abe

Onahama Smelter has two green-charge reverberatory furnaces and the annual smelting capacity is 600 thousand tons copper concentrate. In addition to the concentrate, various kind of industrial wastes has been processed and utilized. First, the brick waste from converter is ground and used as raw material of castable for repairing the copper melt launders. Second, the slag containing calcium-sulfide from other foundry is fed to the reverberatory furnaces. Calcium sulfide is oxidized to CaO. The melting rate of concentrate is accelenlled and the slag loss is decreased. Third, the tip tire made of waste car tire is charged into the reverberatory furnaces as fuel. The steam of waste heat boiler for turbine generators has been increased so as to decrease the electricity cost. Fourth, the sulfur accretion from other chemical plant is blended into the copper concentrate and the sulfur is recovered as the gypsum for sale. Fifth, the processed waste oil has been utilized in the copper concentrate dryer by which the smelting capacity was increased effectively. Consequently, Onahama smelter contributes to the society by processing the wastes to the harmless slag and utilizing them as fuel through the copper smelting.

Jan 1, 1996

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 Joachim Lemke

The stainless steel sheets of permanent cathodes at Norddeutsche Affinerie (NA) were damaged by corrosion after nearly 11 years in operation. The necessary raising of the strength for stripping the copper had increased the deformation of the stainless steel blades. Current efficiency declined. After investigating the possibilities, like buying new cathodes or treating the steel surface, i.e. by sliding, a repair process was developed whereby the stainless steel sheet was exchanged. Special laser technology for cutting used blades und welding new stainless steel sheets underneath the used hanger bar was applied because the energy input into steel is the lowest of all welding methods. The new stainless steel sheet was welded with the rolling line in a horizontal direction. The achieved flatness of the repaired cathode blades amounted to less than 4mm per meter. During 11 months NA repaired nearly 36,000 permanent cathodes and put them back into operation. Repair costs were much lower than the costs of buying new ones and current efficiency increased again to more than 96% with a current density of 340 A/m².

Jan 1, 2006

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 Norbert Hort, Karl Ulrich Kainer, Carsten Blawert, Daniel Fechner

"With the development of new heat resistant magnesium alloys, the automotive industry has introduced several parts to the drive train. The rising number of large magnesium components will result in a higher quantity of automotive post consumer scrap and the changing legislation will force car manufacturers to take magnesium recycling into consideration. So far post consumer scrap has not been used for magnesium alloy production. Quite a reasonable amount of automotive scrap is likely to end up in a mixed light metal shredder fraction. The separation of mixed magnesium scrap according to several alloys is complex. Therefore secondary magnesium alloys made from blended post consumer scrap would be useful. For this work a matrix of potential recycling alloys was prepared by chill casting and high pressure die casting. The materials were investigated for their microstructure, mechanical properties, heat resistance and corrosion properties. The results will be presented in this paper.IntroductionWithin the last ten to fifteen years several heavy magnesium parts have been assembled in passenger cars, such as gear box housings and crank cases [1, 2]. Reasons are the lately developed new heat resistant alloys and the increasing responsibility of automotive manufacturers to reduce the vehicles weight and thereby CO2 emissions. The latter is pushed by international legislation [3, 4]. The rising quantity of magnesium in automobiles will result in an increasing amount of so called post consumer scrap at the end of the vehicles life.So far magnesium recycling was done only for clean scrap that is free from impurities, contaminations and sorted according to a chemical composition or a single alloy respectively [5- 15]. The latter is also called class 1 scrap and mainly consists of sprues and runners from magnesium die casters [15, 16]. For the upcoming automotive post consumer scrap the materials quality strongly depends on the way end of life vehicles are treated. By proper dismantling of old cars, the bigger magnesium components could be collected and possibly treated similar to class 1 scrap [15]. Up to date automotive manufacturers have no uniform recycling system for end of live vehicles. Most probably a considerable quantity of old cars will be shredded. The resulting light metal shredder fraction will contain aluminium and magnesium scrap, both from several alloys. A separation of mixed magnesium and aluminium scrap is feasible according to [17]. Other authors claimed that the grade of separation of magnesium from aluminium is still not sufficient for a proper industrial recycling process of magnesium post consumer scrap [15, 16]. If an automatic sorting is possible it will probably be very expensive [18]. Therefore, so far the main use of post consumer scrap has been the steel desulphurisation and aluminium production [15]. The use of post consumer scrap for magnesium alloy production has been considered already by [15] and [16] but some problems have to be approached."

Jan 1, 2008

By A. J. Rigby

Current practices employing porous plugs to inject nitrogen into molten copper during primary smelting are described. Nitrogen stirring increases heat transfer to the bath, eliminates temperature stratifications, and improves efficiency during the steps of desulfurization and deoxidation. The opportunity to use porous plugs as the means to introduce reducing gases to deoxidize copper is also discussed. Previously reported laboratory results using porous plugs, which point to very high utilization efficiencies of hydrogen when used as the reducing gas, are again reviewed. Advances in the design of the porous plug, and the introduction of a system enabling external replacement of plugs is also discussed.

Jan 1, 1999

By Manuel Alvarado, David Nemir, Jan Beck

"Thermoelectric generation using special N-doped and P-doped semiconductors is well known as a means for direct heat energy to electrical energy conversion without the need for moving parts. The technology is used today in niche markets for low level electricity production and has been proposed as a scalable means for capturing large scale energy from waste heat streams. The choice of geometry of the thermoelements and conductors is critical to the successful implementation of a waste heat recovery system in order to manage losses due to Joule heating and diffusive heat flows. This paper describes a simulation study to define the performance impact of different aspect ratios for the active thermoelements and the electrical interconnect. The use of a finite element model that incorporates the intercoupled heat and electrical energy flows highlights some of the issues impacting scalability.IntroductionThermoelectric phenomena arise out of the intercoupled electrical and thermal currents in a material. A two-element thermoelectric generator is depicted in Figure 1. It is constructed by connecting an N-type thermoelement and a P-type thermoelement in electrical series, with both elements in thermal parallel between a heat source and a heat sink. The electrical series connection is made by attaching conductors as shown. Ideally, these series connection elements will be both good thermal conductors and good electrical conductors.The two element generator in Figure 1 is disposed between two thermal reservoirs: the heat source, which furnishes heat energy; and the heat sink, which absorbs heat energy. Heat energy flux Q, flows from the heat source to the heat sink, driven by the temperature difference between the source and the sink. As depicted in Figure 1, when a resistive load, R, is attached, electrical current, I, may be extracted from the thermoelectric generator and furnished to the load. The N-type and P-type thermoelements, are the active portions that do the actual conversion of heat energy to electrical energy. Although thermoelements may be built using conductors such as bismuth and antimony, higher efficiency thermoelectrics are built using heavily doped semiconductors. Thermoelectric devices are generally formed by connecting many pairs (couples) of N and P type thermoelements in electrical series and in thermal parallel. A commercially available module having 127 couples (254 elements) is shown in Figure 2."

Jan 1, 2011

By A. Alvarez

In this work, mesophilic and thermophilic cultures have been used in the presence of silver as a catalyst. Chalcopyrite and byproducts of bioleaching were characterized in order to: a) obtain information about the kinetics control of the process, and b) explain the different behaviour observed during the mineral attack. With thermophilic microorganisms (68°C and Norris medium as nutrient) the reaction stopped at approximately 65% copper extraction, with and without Ag ion addition as a catalyst. The remaining chalcopyrite appears surrounded by hydronium jarosite (with ammonium ion in substitution in the "alkaline site"), goethite and elemental sulphur. With mesophilic cultures (35°C and 9K medium as nutrient) the reaction stopped at approximately 25% copper extraction (without Ag) and approximately. 85% extraction (with Ag). In both cases, the remaining chalcopyrite was surrounded by agglomerates of ammonium jarosite (with hydronium ion substitution in the "alkaline site") and some iron oxides and/or hydroxides.

Jan 1, 1999

By Ronald J. McGregor

An overview or precious metals project development and start-up, which emphasizes the process decision. Logic which determines process flowsheet, project economics, and training required to train new operators for start-up. The process decision required to successfully develop a precious metals project requires a blending of test data, environmental considerations and operations experience. Decisions to use Merrill-Crowe or carbon adsorption/ electrowinning/replating, fixed pad or multi-use pad {in heap leach) are dependent not only on technology but also on ability to train new operators. The market for experienced operators is acutely depleted and almost all new operators will have to be "home grown". Experience from the Brewer project in South Carolina as well as other projects put together in the West will be discussed.

Jan 1, 1989

Korea has about 68 hundreds million tons of limestone's reserves. Still, high-Ca2+ limestone containing more than 52% calcium oxide makes up for about 12% only; hence the need for securing and effectively developing limestone. The best solution is to manufacture precipitated calcium carbonate (PCC). The synthesis of PCC using high-Ca2+ limestone has several advantages including the efficient development of resources and easing the import dependence on PCC. The first step is the selection of suitable limestone for the synthesis of PCC. In this study, formation age was decided as the primary key point, with its effect on calcination, hydration, and synthesis of aragonite investigated. Results showed that the yield of aragonite increased when newer limestone was used. On the other hand, neither the activity and bulk density of quicklime nor the particle size of aragonite was affected by the formation age, although special values were registered following each formation age. Moreover, the bulk density of quicklime and particle size of aragonite tended to increase with decreasing activity. This result is different from that of the other experiment. Therefore, a suitable method for measuring the activity of quicklime for use in the manufacture of PCC must be established.

Jan 1, 2006

By Fiseha Tesfaye, Pekka Taskinen

"A thermodynamic study of the equilibrium phase assemblage AgBi3S5-Bi2S3-S was made by an EMF-technique, using the RbAg4l5 solid electrolyte. The ternary phase was synthesized from the pure Ag2S and Bi2S3 in an evacuated silica ampoule and grinded into powder and mixed with appropriate compositions of B12S3 and S, in a series of experiments, for pressing in to pellets. The pellets were assembled to form the galvanic cells Pt (-) | Ag ] RbAg4ls | AgBi3S5+ Bi2S3 + S + (C) I Pt (+). The EMF-measurements were made in the temperature range 299 - 460 K.In this paper, thermodynamic functions of the ternary phase AgBi3S5 (pavonite) have been determined. The agreement between the obtained results and the literature values were established.IntroductionThe complex group of ore minerals constitutes from trace amounts to a major proportions of sulfosalts. Although the sulfosalts rarely form massive ore bodies, they are commonly associated with rich sulfide ore minerals for the base and precious metals and widely distributed in a metal poor sulfide minerals [1]. For instance, Ag-bearing sulfosalts are encountered in ore minerals for the production of the base metals and are common sources of silver. Nevertheless, thermodynamic properties of the sulfosalts are poorly known.Reliable thermochemical data are essential for quantitative modeling of the chemical behavior of the sulfosalts in equilibrium with sulfides, which in turn would promote the optimization of complex minerals treatment and extractive metallurgy of the valuable metals."

Jan 1, 2012

By Zhong g. Shui-ping

A new type Pb-Ag (0.8wt%)-Bi (0~5.0wt %) alloy used as anode in electrowinning of zinc from sulphuric acid electrolytes was prepared. The electrochemical properties of this ternary lead alloys have been tested and compared with those of Pb-Ag (0.8wt %) anodes used in industry. Results show the anodic overpotential decreases with the increasing of Bi content in the alloys. When the content of Bi was 1.0 wt% and 5.0 wt%, the anodic overpotential is about 40?50 mV and 60?80 mV lower than that of Pb-Ag (0.8wt %) alloy, respectively. The formation of oxide layers on the surface of these alloys was traced by LSV methods and the composition of the anodic oxide layers was characterized by XRD and SEM analysis. The surface layer on the two type anodes examined is mainly composed of a?PbO2 and ß?PbO2. But different structure of the surface layer was observed, Pb-Ag (0.8wt%)-Bi (1.0wt %) has a more fine-grained structure as compared to Pb-Ag (0.8wt %). But the film on Pb-Ag (0.8wt%)-Bi (3.0wt %) alloy is rather friable, cracked and not tightly attached to the anode.

Jan 1, 2008

By Yong Xian, Zhaohui Sun, Honggang Zhong, Qijie Zhai, Jie Sun

Vacuum refining is admitted as an effective means to remove impurities in the process of alloy smelting. In this paper, Orthogonal and single factor experiments were carried out to investigate effects of multiple factors, such as superheat degree of the melt, degassing time and vacuum degree, on the vacuum refining process. The results showed that the best removal rate of oxygen and nitrogen is up to 82.71% and 61.3%, respectively, due to high vacuum degassing efficiency. It is found that the superheat degree is minimal impact on the deoxidization rate, in addition, nitrogen removal is controlled by the degassing time. The inclusions exist in the AlV55 alloy are mainly composed of oxides and vanadium-nitrogen compounds.

Jan 1, 2015

By Toshihiko Emi

The quest for cleaner steel is driven by increasingly stringent requirements from the manufacturing and construction industries. Key issues are the occurrence and removal of inclusions; These are discussed in the context of the unit processes of deoxidation, refining, transfer and casting of molten steel. Process thermodynamics and kinetics are also discussed. Recent progresses achieved and problems yet to be solved are elaborated, and an integration of the unit processes into a system to produce extra clean, steels with better performance is presented.

Jan 1, 1999

By D. Ducharme, J. Lenz

Operation of the Kidd electrolytic zinc plant commenced in 1972 with a cellhouse capacity of 105,000 tonnes of zinc cathode. The original cellhouse layout consisted of 42 parallel rows for a total of 588 cells. As leaching capacity increased, the cellhouse was expanded to 630 cells. Zinc cathode was manually stripped from plant start-up until the development of a mobile automated stripping system in 1994. Machine development continued until a second unit was placed in production in 1996, from which point, 60 % of the cellhouse was being stripped with the automated system. The final phase of the project was implemented in 1999 with the commissioning of two more automated strippers. This paper describes the implementation of the automated stripping system and its impact on cellhouse productivity.

Jan 1, 2000

By John J. Jonas, Sang-Hyun Cho, Ki-Bong Kang

"The recrystallization behavior of Nb micro alloyed steels containing Cr, Mo, Ni and Ti. was studied using hot torsion testing with the aim of modeling the recrystallization processes and the mean flow stress taking into account the microstructural behavior during hot rolling. The kinetics of static and metadynamic recrystallization were characterized and appropriate expressions were formulated for the recrystallization kinetics. These are shown that the recrystallization kinetics depend on steel composition and the processing conditions. The stress-strain curves were determined in order to derive new equations for the peak stress, peak strain, mean flow stress and softening kinetics. The peak strain is influenced by the presence of alloying elements; their addition, which has a solute drag effect, retards the rate of grain boundary motion, shifting the peak to the right. The addition of Nb to the steel results in a significant increment in the activation energy for hot deformation, and Mo has smaller effect than Nb, but Cr has the opposite effect. It was also found that the deformation activation energy in these steels was not altered by the addition of Ni. The rate of metadynamic recrystallization increases with strain rate and temperature and is observed to be independent of strain, in contrast to the observations for static recrystallization.The mean flow stress (MFS) calculations, based on the Sims analysis, are then compared with the predictions of a model based on an improved Misaka mean flow stress equation in which solute effects, strain accumulation, as well as the kinetics of static and metadynamic recrystallization are accounted for. Good agreement between the measured mean flow stresses, which is obtained from the mill logs of POSCO Kwangyang #3 HSM (hot strip mill), and 'predicted ones is obtained over the whole range of rolling temperatures. The results demonstrate that dynamic recrystallization followed by metadynamic recrystallization, supported by the unexpected load drops, sometimes occurs for the rolling schedules studied in the present analysis."

Jan 1, 2001