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By Xavier Kleber, Aude Lamontagne, Veronique Massardier, Daniele Mari

"The thermoelectric power (TEP) technique was used to determine with high accuracy the strain ageing kinetics in heavily cold drawn pearlitic steel. Because of the very high sensitivity of the TEP to solute atoms, this technique allowed the strain ageing to be followed from the very first moments. The kinetics were followed during isothermal ageings performed between 20°C and 200°C for different strains. In order to avoid any ageing at room temperature, the samples were kept at -80°C immediately after cold drawing. TEP evolution versus strain highlights cementite decomposition occurring during cold drawing. During the ageing, a redistribution of the dissolved carbon atoms in ferrite occurred. The TEP increase with the ageing time was attributed to the departure of carbon atoms from ferrite (segregation to dislocations and/or carbide precipitation). The kinetics were analysed using the Johnson-Mehl-Avrami-Kolmogorov approach which enabled to determine activation energies associated with carbon atoms redistribution.IntroductionHeavily cold drawn pearlitic steel wires are commonly used as structural materials for their high strength and their acceptable ductility. However, several previous studies highlight the microstructural destabilization of pearlite mainly due to cementite decomposition during the drawing process, which induces changes of mechanical properties [1, 2]. This phenomenon was detected by several experimental techniques such as Mossbauer spectroscopy [3, 4, 5], themomagnetic analyses [6, 7], TEM [8, 9, 10] or atom probe tomography [9, 10, 11]. Nevertheless, the mechanism of cementite decomposition is still unclear. Several hypotheses were proposed in the literature. The first hypothesis relies on a strong interaction energy between carbon atoms and dislocations involving higher binding energy than that between carbon atoms and iron atoms in cementite [3]. The second hypothesis is the increase of the free energy of the interface between cementite and ferrite due to the fragmentation of cementite during deformation (Gibbs-Thomson effect) [8]. Some authors even suggest that the dissolution of cementite occur during a post-deformation ageing [12, 13]. It is worth"

Jan 1, 2013

By Johan Sundström

Anhydrous DyC13 was prepared by dehydration of DyCl3?6H20 in a fluidized bed using both batch- wise and continuous feeding. A gas mixture with varied composition of argon and HCl was used. The productivity was high, reaching values of 0.25 mol H20/m2-st during the reaction step 6- 1 and 0.062 mol H2O/m2.s during the reaction step 1-0. The product was free from hydrolytic compounds, such as DyOCI, if control of inlet gas composition versus temperature was achieved. From the results of various experiments, some relations between HCI-concentration and temperature in order to avoid hydrolysis have been deduced. The fluidization process efficiency decreases drastically after the dehydration has proceeded down to about 10 mol% of remaining water. Therefore, in a final treatment the last traces of water were removed by slowly purging gas through a packed bed. The water content could thereby be reduced to less than 1 mol%.

Jan 1, 1997

By E. Morrice

Solubility of yttrium oxide (Y203) in fluoride melts was experimentally measured in the temperature range of 998 to 1273 K and, YF3 composition in LiF.YF3 melts varying from 20 to 50 mole pct using a graphite crucible in an argon atmosphere. Solubility of oxide in the melt was found to increase with increasing temperature and YF3 composition in the melt. An expression for in XY2O3 as a function of temperature for several melts was deduced. The calculated activity coefficients of Y2O3 in the melts exhibited a negative deviation from Raoult's law.

Jan 1, 1989

By Zviad Kovziridze

It is stated that the specific character of SPHTS specimens of TiCx consists in crystal lattice strength reflecting the condition of synthesis in ?burning wave?. The use of roentgenographic and other methods of analysis allow to estimate the effect of the conditions of synthesis causing the carbon sablattice defect on the grinding intensity of TiCx -phases. The study of the kinetics of vibratory grinding of TiCx -phases in ethanol and benzene medium allows to establish high grinding intensity of the phases close to stoichiometry and the possibility of producing high dispersion powders (Ssp 4.5-6 m2/g).

Jan 1, 2006

By D. Kennis

"Union Miniere Precious Metal's (UMPM's) Hoboken Business Unit has a long tradition in complex Pb-Cu metallurgy, focussing on the recovery of precious metals from various types of secondary and recyclable materials. Although the old flow sheet, based on a traditional sinter plant, blast furnace, and lead refinery process was a very complete flow-sheet with the capability of dealing with almost every impurity, the weaknesses became clear:1. old and costly technology,2. too many unit operations,3. too much internal recycling, and4. dependency on concentrates for the sintering process.To maintain the competitiveness of the Hoboken Business Unit, the project ""Smelter 2000"" was born. This project represents a breakthrough in metallurgical processes and technology. A modem smelting technology was chosen together with the development of a new process. A lead-copper process combining lead slag and blister copper production, carried out in an ISASMEL T vessel, was the key to simplifying the Hoboken flowsheet. ISASMEL T smelting technology was chosen for its flexibility towards feed characteristics and process parameters.The new smelter was commissioned at the end of 1997. Although there were a lot of problems due to the high degree of technical innovations in the process, the new smelter came to design capacity within 1 year after start-up. During this period, however, UMPM had, a very difficult time because of the extreme clear-cut nature of going from the old to the new flowsheet.After two and a half years of operation, the new flowsheet has proven to fit with the strategy of UMPM, focussing on treating secondary Pb-Cu materials and a broad range of recyclable feeds such as electronic scrap (E-scrap) and catalysts. Together with the new Precious Metals Plant, efficient logistics, recognised world class sampling practices and a customer-focussed commercial organisation, UMPM Hoboken can definitely be considered reborn."

Jan 1, 2000

By Vladyslav M. Sokolov

The cost effective and environmentally friendly recycling technology was developed and tested. It enables utilization of the fine nickel-base superalloy scrap in a form of heavily oxidized scarfing granulates. The process of granulates generation was discussed in details. Their properties were investigated. The results of literature search showed anticipated sufficient improvement of the properties of cast iron by its alloying with the elements from the scarfing granulates. The novel alloying approach is based on the two stage reduction operation. Firstly thegranulates were partially reduced in a solid state by their exposure with powdery carbon at the range of 1550 ? 1700°C. Then the gotten product was efficiently introduced into liquid iron since it has a form of fine natural agglomerates for arranging the optimal conditions for reduction of the granulates. The thermodynamic evaluation demonstrates higher reduction efficiency of carbon and silicon dissolved in iron than of the same elements in a form of the separate phases. The considered process partially provides itself by energy since the reaction of reduction of the chromium oxide by silicon dissolved in liquid iron has exothermal character. The mostly complete extraction of Ni was received. The sufficient reclamation of Cr was gotten at the same time.

Jan 1, 2006

By F. A. Fasoyinu

The mechanical properties of yellow brass (C85800), high strength yellow brass (C86300), and high manganese brasses (C99700 and C99750) cast in permanent molds have been studied. The tensile properties as well as fracture and impact toughness of these alloys are strongly dependent on the chemical composition. Alloys and/or compositions exhibiting relatively high zinc equivalent often exhibited high ultimate tensile strength and yield strength with significant reduction in ductility (% elongation). In order to achieve optimum properties with a good balance between strength and ductility, a calculation of the zinc equivalent before alloy preparation can be useful.

Jan 1, 1999

By S. Y. Tan

As CMOS devices are scaled down into nano-region, SiO2 dielectric is approaching its physical and electrical limits. High-k material has been investigated widely in recent years, and gate oxide take place growth oxide with Hf-based below 45nm gate length technology node has been shown. The phenomenon of interfacial property between bulk silicon and gate dielectric materials (HfO2 and HfSiO) was focused. A comparison of capacitance-voltage (C-V) characteristic of gate insulator was presented. Furthermore, the electrical property and thermal stability of high-k dielectric materials at various post deposit anneal (PDA) temperatures were established. The X-Ray diffraction technique was (XRD) utilized to analyze crystallization of the thin films, and the X-ray photoelectron spectroscopy (XPS) was applied for surface chemical bounding energy to identify the silicon and dielectric layers. Results show that HfSiO films have exhibited a superior performance on both thermal stability and electrical performance.

Jan 1, 2009

By Mikiya Tanaka

This paper outlines our attempt to establish a recycle process of nickel in the spent baths and waste rinse water of electroless nickel plating plants using solvent extraction and solvent-impregnated support, Solvent extraction studies of nickel from actual spent baths revealed that (i) nickel is efficiently extracted by a hydroxyoxime extractant such as LIX84I at a pH greater than 6 and is readily stripped with sulfuric acid, and (ii) the mixtures of LIX63 and acidic organophosphorus extractants (D2ERP A, PC88A, and Cyanex 272) enhanee the nickel extraction efficiency to a sufficient degree without pH adjustment, but at the same time, reduce the stripping efficiency. The application of acidic organophosphorus extractants to selectively remove impurity metal ions (iron and zinc) from a real spent bath before extracting nickel lead to the finding that PC88A and Cyanex 272 effectively remove iron and zinc without pH adjustment leaving nickel in the raffinate. The removal of nickel from the waste rinse water was also studied. Solvent-impregnated supports with a macroporous resin and oil sorbents made of natural kapok fiber and synthetic fiber as supports were applied using D2EHPA and LIX860 as the extractants. During the batch operation, nickel is removed with a high efficiency without pH adjustment. During the column operation, however, the effective removal is hindered by (i) the dissolution of the nickel-D2EHPA complex into the aqueous phase in the high loading region, and (ii) the slow removal rate of the LIX860-impregnated support.

Jan 1, 2003

By J. D. Miller

Gold adsorption from cyanide solutions by activated carbon has been studied at great length during the past decade. Findings from past research are reviewed and discussed with respect to structural features of various carbons, including carbon black, activated carbon, graphite and diamond.

Jan 1, 1991

By Roger W. Lee

The commissioning of the prototype Imperial Smelting Furnace (ISF) in 1950 was a technological breakthrough in the pyrometallurgical smelting of zinc and provided significant advantages over the existing retort processes. However, for most zinc concentrates the electrolytic zinc process continued to be more economic. Therefore, the Imperial Smelting Process (ISP) specialised in smelting zinc and lead concentrates that were less amenable for treatment by either the electrolytic zinc process or the lead blast furnace. Subsequently, improved mineral processing techniques led to a decrease in the availability of these concentrates so the treatment of secondary materials in the ISP assumed greater importance. This was facilitated by the development of techniques such as hot briquetting and tuyere injection. In 2002 over 1 million tonnes of zinc and 400,000 tonnes of lead were produced by the ISP. However, in the 2002-3 the economics of the Process became extremely difficult because of low metal prices and increased operating costs. This resulted in the closure of four ISP smelters in 2003 and two in 2005. Nevertheless, two new ISP smelters are scheduled for commissioning in China in 2006 where local economic conditions continue to favour the process. The economics of the process are examined particularly in respect of smelter margin and operating costs. The need to increase the smelter margin means that the future of the process will be closely linked to its ability to consume secondary materials and an examination will be made of its potential for conversion to 100% secondary operation. Apart from a reduction in raw materials costs, a substantial reduction in operating costs would ensue from not operating sinter and sulphuric acid plants.

Jan 1, 2006

By M. Oliazadeh

The present study was performed to develop a process for solvent extraction of molybdenum and cobalt from an acidic solution generated by an electrodeposition process of nanocrystalline cobalt alloys. Solvent extraction is a common practice in hydrometallurgical and refining processes to produce metals; however its application for separation of molybdenum and cobalt from this specific solution is new, because molybdenum and cobalt are not commonly associated together in nature. Five commercial organic extractants were examined for extraction of cobalt and molybdenum from synthetic acidic solutions with pH ranging from 1 to 5. Preliminary results showed that at pH 2, any of the Cyanex 923, Alamine 336, Aliquat 336 and Hostarex A327 could be used to extract 99% of molybdenum from solutions, while from pH 3 to 5, Aliquat 336 was able to extract about 100% of molybdenum. Cobalt extraction, on the other hand, varied from 15% to 23% at pH 3 and 30% to 53% at pH 2 using different extractants. Based on results obtained, Aliquat 336 was applied on mixed solutions of cobalt and molybdenum at various pHs. The results showed that molybdenum could be extracted as much as 99% from a mixture of molybdenum and cobalt at acidic pHs, while less than 1% of cobalt was separated at pH 2 to 4 simultaneously.

Jan 1, 2003

By José D. T. Capocchi

Viscosity of liquid lead, tin, and Pb-Sn alloys has been measured by the rotational viscometer method in the temperature range from 50 K above their respective liquidus temperature to 823 K. The results are accurate to within ±1.0 %. The variation of viscosity with temperature followed the Arrhenius-type equation µ = µo.exp(Q/RT). The composition dependence of the isothermal viscosity and the activation energy for viscous flow have not shown anomalous changes at the eutectic composition of the Pb-Sn system.

Jan 1, 2000

By Mike Adams

Comprehensive pilot testwork has been conducted on BHP Billiton's Ravensthorpe nickel laterite deposit over a fifteen-month period at Lakefield Oretest. Some 228 tonnes of ore were processed in a beneficiation pilot-plant comprising scrubbing, attrition scrubbing, screening and thickening over sixteen pilot runs with an average mass closure of 99.2%. This produced a suitable feed for hydrometallurgical piloting over seven runs covering 1,680 hours of operation. The integrated EPAL® (enhanced pressure acid leach) circuit comprised a limonite pressure acid leach front end discharging into a saprolite atmospheric leach circuit and subsequently to induced jarosite precipitation, counter-current decantation, iron removal, mixed hydroxide precipitation, and manganese removal. The pilot plant met its key objectives in demonstrating the flowsheet's technical viability, and generating raw data inputs for the project feasibility study. Rapid, intensive data capture, collation and reporting helped solve key flowsheet issues. The pilot plant also demonstrated its value as a risk management tool in the resolution of numerous engineering, metallurgical and materials selection issues at a manageable scale. A disciplined approach to experimental planning, operation and management was a significant contributor to the overall success of the campaign. Keywords: Ravensthorpe, Nickel, Piloting, Beneficiation, Pressure, Leach

Jan 1, 2004

By Pinakin Chaubal

An analysis of the blast furnace and the low-pressure shaft DR furnace is carried out by redefining the reaction zones. The concept of a characteristic reaction gas temperature (CRGT) is introduced and the two reactors are compared and contrasted using some recent process developments with an aim to develop a platform for further synergistic innovations.

Jan 1, 2006

By Seyed Mohammad Taghavi

In this report, the efficacy of different factors such as temperature of reaction, time of reaction and depth of bed are investigated in a process of recovery of zinc oxide from zinc ore concentration residues in a fluidized bed furnace. Under optimum conditions, there was more than 93.5% zinc oxide in products.

Jan 1, 2006

By C. G. Anderson, L. G. Twidwell

"Throughout the world, there are many orebodies or materials which have significant value but also contain arsenic, antimony, and mercury. As regulations on the transport, exposure, disposition and emission of these elements have become more stringent; it has become increasingly more difficult to derive the values from the resources. This paper outlines the fundamentals of alkaline sulfide hydrometallurgy and its successful application to arsenic, antimony and mercury bearing ores, concentrates, by-products, and other materials.Fundamental Alkaline Sulfide HydrometallurgyHydrometallurgical methods can be employed for treatment of gold, arsenic, antimony, tin and mercury containing materials, concentrates and ores as well as complex ones containing any number of metals. The alkaline sulfide system is one of these and is essentially a mixture of sodium sulfide and sodium hydroxide. This is a unique hydrometallurgical system as it is a very selective lixiviant for the distinct leaching of tin, gold, antimony, arsenic and mercury [1-7]. Worldwide, it is employed industrially in the CIS, China and the United States for the production of antimony [8-15].As an example, when the system is applied to an arsenic containing material like orpiment, As2S3, a solution of sodium thioarsenite is formed. This is illustrated as:"

Jan 1, 2008

Electrocrystallization studies were conducted in a concentrated acid-copper electrolyte to determine the influence of chloride ions and glue on copper nucleation and on the structure of thin copper layers. Electrochemical experiments allied to SEM and XRD examination were performed to characterize the mechanism of nucleation in the presence of additives at 65°C. Results indicated that most of the copper nucleation from a 83 g dm-3 Cu2+ solution, with 140 g dm-3 of H2SO4 is achieved in a matter of milliseconds, Although the presence of chloride and glue, at the concentration levels tested, does not seem to substantially modify the nucleation mechanism, the morphology, nuclei density and the copper film structure and orientation are changed by the presence of additives and by electrolyte stirring.

Jan 1, 1999

By Jean Frenay

Bacterial leaching tests have been carried out on Portugese pyritic ores containing zinc, copper, lead and silver as valuable elements. Both indigenous and isolated strains of Thiobacillus ferrooxidans were used. During the tests the factors pH, Eh and dissolved oxygen were measured and related to the leaching activity of the bacteria. Different means to estimate or determine the real bacteria concentration were examined. The influence of nutrient media and particle size has been evaluated. The role of galvanic couples was studied by electrical linking of mineralogical samples of pyrite, sphalerite and chalcopyrite. Leach residues were examined by optical microscopy to follow the mineralogical alterations during the leaching. The results show a rather good leaching of the sphalerite. However, the dissolution of copper from chalcopyrite is much more difficult, 50 % recovery never being obtained.

Jan 1, 1985

By M. Frades, C. Frías, G. Díaz, A. B. Mejías

"In recent years, zinc recovery from flue dusts and other industrial wastes has been increased, offering to the market a large tonnage of secondary zinc oxides, which can not be processed directly to render high quality zinc because of the hazardous impurities and halogens content.The ZINCEXTM Technology has been commercially applied for more than thirty years and represents the most suitable solution to deal with secondary or crude zinc oxides due to its flexibility, simplicity, and cost-efficiency, allowing production of SHG electrolytic zinc and pure zinc sulfate salts thanks to the flexibility and selectivity of the zinc solvent extraction unit regarding to get rid of impurities.A dual plant able to produce electrolytic zinc and crystallized zinc sulfate has been engineered to provide a flexible and profitable solution to zinc market. A description of the study and the relevant achievements is presented in this paper.IntroductionZinc is a valuable commodity in the marketplace and can be recycled again and again and still maintain its physical and chemical properties. Zinc recycling offers both environmental and economic benefits such as reducing volumes of material that end up in landfills, saving energy by reducing the need for mining and smelting, and relieving environmental impact on the land and water, and conserving zinc ore [1].The supply of zinc able to be re-processed will be increasing from year to year according to secondary materials enter the recycling stream, and as a result, more recycled zinc will become available in the market. Thus, some existing zinc refineries are implementing an annexed treatment line to process secondary oxides in conjunction with primary zinc concentrates [2].The galvanized steel scrap is normally recycled in electric arc furnaces or in basic oxygen furnaces, which generates a large tonnage of zinc-bearing flue dusts (EAFD). Around one million ton EAFD is yearly produced at the USA and the EU, respectively. The flue dusts are treated commercially by pyrometallurgical ways such as waelz kilns, electrothermic furnaces, etc, to yield secondary zinc oxides that can not be processed directly to render high quality zinc because of the hazardous impurities and halogens content [3]."

Jan 1, 2008