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By J. D. Sunderkötter, M. F. Stroosnijder, V. A. C. Haanappel

"TiAI-based intermetallic compounds have attracted considerable interest as structural materials for high-temperature applications due to their low density and substantial mechanical strength at high temperatures. However, one major drawback hindering industrial application arises from the insufficient oxidation resistance at temperatures beyond 700 °C. In the present contribution some general aspects of high temperature oxidation of TiAI-based intermetallics will be presented. This will be followed by a discussion of the influence of alloying elements, in particular niobium, and of the effect of nitrogen in the oxidizing environment on the high temperature oxidation behaviour of such materials.Extended AbstractIntroductionTiAI-based intermetallics are being considered as construction materials for high temperature components, e.g. in aircraft and car engines, due to their low density and substantial mechanical strength at high temperatures, see e.g. [1,2]. The best ductility can be attained with alloys consisting of y-TiAI with around 5-15 vol.% Q2-Ti3AI. However, one major hindrance to industrial application arises from the insufficient oxidation resistance at temperatures beyond 700 aG. In spite of their high aluminium content, TiAI-based intermetallics do not generally form long-lasting protective alumina scales. After longer exposure times the scales, which are initially rich in alumina, deteriorate and scales consisting of mixed alumina and titania predominate, with high growth rates similar to pure titania.It is not the intention of the present paper to present a general overview of the high temperature oxidation behaviour of TiAI based intermetallics, for which the reader is referred to the literature [3,4]. In the present contribution some general aspects of high temperature oxidation of TiAI-based intermetallics will be presented. This will be followed by a discussion of the influence of alloying elements, in particular niobium. The effect of nitrogen in the oxidizing environment on the high temperature oxidation behaviour of these intermetallics will also be considered."

Jan 1, 1996

By Marco Pasetto

The possibility to re-use marginal materials (by-products) deriving from industrial activities in the construction of road infrastructures, as total or partial substitution of natural aggregates, successfully combines demands for economy and environmental sustainability. The paper presents the results of a laboratory study, conducted at the Experimental Road Laboratory of the University of Padova, to verify the suitability of a particular type of electric arc furnace slag to be recycled in the lithic skeleton of high-performance asphalt mixes (porous asphalt, high modulus mixes, stone mastic asphalt, nonskid surfacings) for road and airport flexible pavements. the process of transformation of iron and steel slag into a product that can be used in road building is described, along with the characterisation of the mixtures, plus an analysis of the results of a wide battery of mechanical-performance tests. This study forms part of wider theoretical ? experimental research being done at the University of Padova in order to improve knowledge of the characteristics of succedaneum materials and check their possible applications in road and airport construction.

Jan 1, 2006

By Ramiro Escudero

Michoacan?s beach sands with interesting concentrations of ilmenite were studied to produce titanium by hydrometallurgical techniques. Nevertheless, among titanium species, there are different additional components of Michoacan?s beach sands which could be of interesting applications. Some of them are likely to be applied for the manufacture of nanocrystalline ceramics. Although, the most applied mineral dressing to treat these kind of sands, that contain magnetic species (i.e., ilmenite, magnetite), is a combination of gravity separation and magnetic separation, it could be of a great deal of benefit to apply the information regarding the surface characteristics of the sands? components, in order to study the application of flotation technologies to separate selectively those species with commercial value.

Jan 1, 2006

By K. R. Barrett

The cupellation of dore/lead bullion to recover precious metals is one of the oldest metallurgical processes known to man. In recent times this has been carried out in small reverberatory furnaces but the process suffers from a number of disadvantages. A new process has been developed at the Northfleet refinery of Britannia Refined Metals Ltd, which gives much improved performance. The process depends upon the injection of oxygen through a nitrogen shrouded lance at the bottom of the furnace. The lance is consumable and of unique design. Reaction rates are high giving short process time; fuel consumption is low; oxygen efficiency is high and dore recirculation is low. The new process has resulted in substantially lower operation costs.

Jan 1, 1989

By Edgar Vidal

Beryllium metal and alloys have been crucial in the advancement of technologies in space exploration, transportation, national defense, communications, energy, safety and medicine, to name a few. Beryllium is one-third lighter than aluminum and six times stiffer than steel, with unique thermal properties. Demand for this metal is expected to continue to increase as new technologies emerge, hence its efficient and safe extraction needs to be addressed. Current extraction technologies are very complex and energy intensive, but at the same time yield excellent quality metal. In order to develop new or improve current extraction methods, a detailed analysis of current and past extraction technologies must be made. This work intends to compile and interpret most of the research, development and industrial practices used in the production of beryllium, and open the field for innovative extraction methods.

Jan 1, 2006

By M. D. Crites

As part of a multi-year program for assessing the viability of chrome-free refractories in copper smelting, converting and refining furnaces, dynamic corrosion tests have been conducted on a series of refractories from the magnesia-alumina system, using a ferrous silicate slag. The corrosion rates of the test refractories are compared with those of a reference mag-chrome brick, and recommendations are made for more in-depth evaluations of the more corrosion-resistant materials.

Jan 1, 1999

By R. Cheng

The kinetics of the solvent extraction of ythium from HCl solution with mono-2-ethyl hexyl phosphonic acid mono-2-ethyl hexyl ester (HEHEHP) have been studied using a rotating diffusion cell (RDC). The effects of rotation speed, pH, ymium and extractant concentrations and temperature on the rate of extraction were examined. The rate of extraction of ythium appears to be controlled by an interfacial reaction of metal ion and extractant. The concentration of the latter is determined mainly by diffusion through the membrane. The contributions of the rates of diffusion in the diffusion layer, diffusion in the membrane and chemical reaction at the interface to the overall rate have been calculated on the basis of a kinetic model.

Jan 1, 1992

By Y. K. Rao

The direct reduction of lead sulfide with carbon in the presence of lime was investigated at several temperatures and under two different inert gas atmospheres. The catalyzed reduction kinetics were determined both with a nitrogen atmosphere and a helium-rich helium-nitrogen atmosphere. The reduction kinetics under the latter were d-ecidedly superior to those under the former. The differences-were interpreted in terms of faster diffusion rates in a helium medium and-synergistic effects.

Jan 1, 1983

By Richard L. Kerr

The U.S. aluminum recycling industry has experienced rapid growth in both its size and importance over the past two decades. Secondary recovery now makes up about one-third of total U.S .. aluminum supply compared with ]9 percent, of a much smaller total in the early 1970's. This growth has occurred in part because recycled metal performs as well as new aluminum in most applications, and because it provides major savings in production costs and natural resource utilization. In addition, the recycling industry has played a critical role in greatly expanded -production and reclamation of aluminum beverage cans. Recycled metal makes up over half of the content of aluminum sheet used: to manufacture beverage cans. In future years, both the-production and reclamation of aluminum cans are likely to rise in foreign markets, thus providing the industry with opportunities for further growth. Recyclers may also play a larger role in supplying auto producers who are using increasing amounts of aluminum in passenger cars and trucks. However, in order to take advantage of this growing market, an efficient infrastructure for collection of scrap and production of metal must be developed.

Jan 1, 1995

By M. W. Wadsley

Despite the convenient subdivision of extractive metallurgy into hydro- and pyro- divisions, many flowsheets contain both types of process. When complex materials are used as feed, combinations of hydro- and pyro-metallurgical processes are even more common. Hydrometallurgy is used to treat many by-products and waste-products. (Bio-metallurgical processes may be considered to be a sub-set of hydro-metallurgical processes.) Combinations of the different processes in the Australian metallurgical industry are described. Selected international examples demonstrate that the use of combked processes is not a unique. Antipodean phenomenon. The motives for selection of combined pyre- and hydro-metallurgical processes in a flowsheet are examined.

Jan 1, 1994

By Xiaojie Gao, Jingshe Li, Chengsong Liu, Haiyan Tang

In order to clarify the reaction between MnO-SiO2 oxides with low FeO content and Fe-Mn-Si alloy, two diffusion couples were produced by the new method using confocal scanning laser microscopy (CSLM). The interface of the alloy and oxide, content of Mn and Si in the alloy near the interface, size distribution and composition of the particles which precipitated in the alloy were observed and analyzed using the electron probe microanalysis (EPMA). Results show that though the FeO content in the oxides decrease to 1% which is lower than the equilibrium with the molten steel at 1873K, the diffusion of oxygen from oxide to alloy still exists during the heat treatment at 1473K and causes shorter Particle Precipitated Zone (PPZ) and Manganese Depleted Zone (MDZ) normally for the reduction of diffusion flux of oxygen.

Jan 1, 2015

By Helena Byrdziak

KGHM Polska Miedz S.A. is a significant European copper producer with production of 447,000 mtpy, operating three underground mines and three smelters. The company has been involved for years in environmental activity, which was stimulated not only by the company itself, but by the development of environmental regulations as well. The first set of regulations, concerning water protection, was' established in Poland' in 1974, while a comprehensive environmental law was passed in 1980. This law in general requires industry to submit all data of environmental significance to the local authorities. Based on this data, they establish limits concerning emissions into the air, water and ground, the amount of wastes produced and the means of their disposal. A company has to pay fees for each tonne of emitted substances and stored wastes. When the emission of a substance exceeds the limit, the company has to pay a penalty which is about ten times higher than the fees. This approach in general is effective because it forces companies toward: reduction of their emissions. The problem is that the law is constantly subject to change and is becoming not only more restrictive but is involving more and more bureaucracy.

Jan 1, 1999

By Paul-Dominique Oudenne

This paper reviews the experience gained by CMI NESA over the last thirty years for the treatment of arsenical and antimonical bearing concentrates and other complex metallurgical by-products. The importance of preliminary mineralogical characterization is emphasized as a preliminary step for the success of the roasting. Stage selective roasting appears as an attractive and efficient route for the treatment of complex concentrates. Numerous examples will be given for confirmation of such thermal treatment.

Jan 1, 2006

By Jian Li, S. Penttila, W. Zheng

"Materials selection for Gen IV supercritical water reactor in-core components faces major challenges due to severe operating condition. Beside high-temperature mechanical properties, SCC and general corrosion resistance of commercially available materials are also major focuses in recent research. Recent reports suggest that certain types of surface modifications are beneficial to SCW corrosion resistance. In this study, the effects of surface modifications are investigated, and possible mechanisms for improved corrosion performance are discussed.IntroductionThe current Canadian pressure-tube supercritical water reactor (SCW) design specifies a core outlet temperature of 625°C under 25 MPa of pressure, with peak cladding temperature as high as 850°C. Challenges in materials selection include high-temperature mechanical properties, corrosion resistance, SCC resistance and radiation damage. Most of the SCW corrosion test results available are below 730°C. Early work by Allen [1] summarized the corrosion resistance of alloy groups including Ni-based super alloys, stainless and ferritic/matensitic (F/M) steels that can potentially be used for SCW reactors. F/M steels can only be used at low temperature sites (e.g. down stream piping). At 500°C and 25 MPa, F/M steels develop a thick but mechanically stable oxide layer. However, the long term stability of the surface oxide layer is largely unknown. Ni-based alloys appear to form very thin surface oxide, however pitting was observed in the vicinity of some intermetallic precipitates [2-5], and dissolution of major alloying components could pose significant problems for down stream piping [6]. In addition, concerns of Helium formation due to Ni transmutation prevented this alloy group to be used as fuel cladding. The corrosion resistant austenitic stainless steels (e.g. 316L) are found to be susceptible to localized corrosion such as pitting, intergranular attack and stress corrosion cracking (SCC) [7]."

Jan 1, 2012

By Zheng Wei, Jian Cheni, Zhenliang Weng, Wei Liang, Hongbo Zhu, Jinhui Peng, Linqing Dai, Qianxu Ye

"By testing the dielectric constant and the dielectric loss factor of concentrated Dahongshan, mill scale, anthracite and light-burned dolomite in different frequency and temperature, and by studying the temperature-rising characteristics of the materials in the microwave field of 2.45GHz in frequency, the research in the paper shows that to reach at 1250°C under the same condition -2KW the microwave power and 30g the mass --the time concentrated Dahongshan takes is 330s, whereas the millscale is 855s and the anthracite is 820s. About the last one, the higher the temperature is, the stronger the absorptivity is. After the temperature has rose to 400°C, the anthracite's absorptivity increases dramatically. The result of the research would serve as the foundation of the further study on making direct reduced iron by microwave heating.1. IntroductionUnder the microwave fields, materials' dissipation of dielectric bodies would generate thermal effect. Therefore, the dielectric constant and the dielectric loss factor are closely related to materials' ability of absorbing microwave energy-the larger the dielectric constant and the dielectric loss factor are, the stronger the material's ability of absorbing microwave energy is, and the better the thermal effect would be[1-2]. In order to research how to make reduced iron from iron ore fines by microwave heating deeply and systematically, the test of raw materials' dielectric constants and dielectric loss factors are of the essence. What's more, because a mineral' conductivity is influenced by its components and crystal structure[3], it is necessary to study different materials' different temperature-rising characteristics; hence such studies would provide theoretical foundation of further research."

Jan 1, 2012

By T. Lezhava

A new reactor model with rotating cathodes has been developed where various forms (dendrite, spongy) of metal depositions and their uninterrupted removal are accomplished by the realization of high current densities and low energy consumption. At the same time in contrast with the existing methods a high quality metal powder may be obtained from concentrated electrolytes without any specific organic or inorganic additives, which allows raising the intensity of the process. The reactor can be used for electrowinning of metals with low adhesive capacity (Pb, Ag, Cu, Zn, Ni, Co, etc.) and the powders. The obtained products may be utilized in general metallurgy as well as in powder metallurgy.

Jan 1, 2006

By Shun Myung Shin, Dong Hyo Yang

Cobalt is recovered from square type of spent lithium ion batteries (LIBs) containing 5~20 % Co, 5~7 % Li, 5~10 % Ni, 15% organic chemicals, and 7% plastics together with Cu, Al, Fe, and Mn. The waste LIB was prepared by physical treatment. After screening, the crushed LIBs were separated to +8 mesh, -8/+16 mesh, and -16 mesh powder. Among these, -16 mesh powder was selected for leaching. The leaching test was investigated at 2 M H2SO4, 6 vol.% H2O2, reaction temperature 60 ?, agitation speed 300 rpm, solid/liquid ratio 50 g/ 500 ml, reaction time 1 h. The leaching efficiency of cobalt was more than 99 % and its concentration was 24.9 g/L. For removing of impurities such as copper, iron, and aluminum in the leaching solution before cobalt solvent extraction, the impurities were eliminated by pH control with alkali solution. For selective extraction of cobalt, the aqueous phase removed impurities was equilibrated with different volumes of 0.4 M Cyanex 272 saponified of 50 %. Extraction efficiency of cobalt was about 80 % at first step. Separation coefficient (ßCo/Li) of cobalt and lithium extractions was 206.5. Over 9.0 % of pure cobalt sulfate solution was obtained after stripping with H2SO4 solution.

Jan 1, 2008

By Reimers. Jan H.

Practically all the world's lead is produced by sintering and blast furnace smelting, or the Imperial Smelting Process which is a variant of the blast furnace process. Increased coke and labour costs and strict lead emission limits have, however, made blast furnace smelting undesirable in most countries. A change-over to other lead smelting processes providing better working conditions and lower emissions is, therefore,. expected to occur once economic conditions improve and the necessary capital expenditures can be justified. The need for new lead smelting processes has long been evident and a number of new processes have been proposed 'and advanced to various stages of development. One of the new processes is already proven on commercial scale, while several others are still being tested on pilot plant scale.

Jan 1, 1983

By Eliezer Martinez-Jimenez, Gretchen T. Lapidus

"Electro-assisted reduction is an effective pretreatment to render chalcopyrite less refractory towards oxidative leaching. In this process, chalcopyrite is selectively converted to chalcocite or copper metal in an electrolytic cell under ambient conditions, while ferrous ion is leached into solution. However, the reaction velocity is hampered by the formation of a ferrous sulfide passivating layer on the solid surface, especially at elevated solid to liquid ratios. In the present work, several strategies for overcoming this problem were evaluated. On one hand, specific ligands for ferrous ion were added in order to increase its solubility and, on the other, an anode material which promotes the oxidation of the sulfide ion was chosen. Leaching tests showed citric acid to be an effective ligand for both ferrous and ferric ions and, in combination with a lead-silver anode, significantly increased the kinetics of chalcopyrite reduction and subsequent copper leaching.IntroductionAttempts to oxidize chalcopyrite at a rapid rate in aqueous solutions, below their normal boiling point, have met with difficulties because of passivation by some of its own components. An alternative line of research explores reductive pretreatment, transforming the chalcopyrite into less refractory copper phases, which can later be oxidized. A recompilation of these efforts up until 2000 was published by Dreisinger and Abed [1]. However, this practice usually requires large excesses of reducing agents, such as copper, lead, aluminum or iron, and in this last case at near-boiling temperatures, in highly"

Jan 1, 2012

By A. V. Tarasov

A flow-sheet for waste-less processing of spent lead batteries comprises mechanized separation of batteries, smelting of the metallic fraction in a kettle, electrothermal smelting of oxysulfate fraction, refining of crude lead and processing of reverts to produce commercial products. Smelting of lead-containing fraction is performed in an electrothermal furnace using a processing technology developed in the Gintsvetmet Institute and differing from conventional processes by the fact that it does not require any fluxing agent (soda); no matte is formed in the process and the amount of slag produced is minimal, because its formation depends only on the ash content of coke and the quality of battery scrap separation. The process has been patented. It has been introduced on a commercial scale in 1.8 MVA furnaces at the plant of A0 "RyazTsvetmet" (Ryazan, Russia). The process has the following main advantages as compared with conventional shaft-furnace smelting and smelting in a short-drum furnace: the process does not require technical-grade oxygen, the amount of process gas generated is minimized ensuring a decrease in lead-containing dust and sulfur dioxide emissions by 3 to 5 times per unit of lead recovered; a decrease in dust entrainment resulting in lower amounts of recycled dust; lower slag yield (a decrease from 20-25% to 3-5%); lower coke requirement (a decrease from 10-14% to 3-4%). Refining of crude lead is performed using conventional technology but there are several unique features for which know-how is available. Processing of by-products of electrothermal smelting and secondary lead refining (slag, drosses, skimmings) and ebonite fraction (crushed battery casings) is performed in a slag-fuming furnace.

Jan 1, 2002