Search Documents

By Serdar Aksu, Fiona M. Doyle

"CMP will be an essential process in the production of integrated circuits containing copper interconnects. This study aims to improve our mechanistic understanding of the role that organic chelating agents might play in the reactive slurries used in copper CMP. Copper dissolution behavior in EDTA arid glycine was first examined by producing potential-pH diagrams for the copper-water-EDTA and copper-water-glycine 'systems. The results of potentiodynamic polarization experiments were then considered in light of these diagrams. . In-situ polarization experiments were conducted to gain insight into the electrochemistry of copper during dynamic polishing in slurries prepared from EDT A and glycine.IntroductionCopper has recently started to replace aluminum as the interconnect metal in integrated circuits. Copper interconnection offers faster and more reliable integrated circuits due to its higher electrical conductivity and superior electromigration resistance (1). The damascene method is used to form multilevel interconnects in the manufacture of integrated circuit devices with copper metallization (2, 3). Copper is deposited by CVD or electroplating into vias and trenches etched in the interlayer dielectric (IDL), over a diffusion barrier usually made from titanium, tantalum or their nitrides. Chemical mechanical planarization (CMP) then prepares the wafer for the next deposition step, by removing excess copper and planarizing the surface. During CMP, the wafer is rotated and pressed against a rotating platen covered with a polishing pad. Chemically active slurries containing submicron size abrasive particles (Si02, Al20 3, ceria, diamond, etc.) are applied. Both the mechanical action of the abrasive particles and the chemical action of slurry constituents remove material from the wafer surface. Planarization results because material is removed faster from protruding regions on the surface than from recessed regions. Since CMP can globally planarize .the entire wafer, it has become one of the key technologies for producing integrated circuits with copper metallization."

Jan 1, 2000

By Vaughan R. Voller

"Numerical methods for dealing with a temperature dependent conductivity are discussed. An approach based on a local application of a Kirchhoff transformation at the discrete level is presented. The application of this transformation - that does not require any inversion- is demonstrated on solving a two-dimensional test problem.IntroductionMuch is said in the recent literature on the modeling necessity of obtaining appropriate thermo-physical properties; in particular the requirement to account for properties that are ""strong"" functions of the depended variables, e.g., Temperature. Of course obtaining appropriate thermo-physical properties serves no purpose unless they can be accurately integrated into a discrete numerical calculation. The purpose of this paper is to examine how temperature dependent conductivities that exhibit discontinuities or rapid changes can be handled in a numerical code.The discussion will be made in the context of a control volume finite element method [1]. After a brief outline of control volume finite element fundamentals basic methods of dealing with discontinuous or rapidly changing thermal conductivity are discussed. This is followed by the presentation of the recently proposed local Kirchhoff method [2,3], The paper concludes with an investigation of the performance of the various conductivity schemes in solving two dimensional problems. This testing clearly shows the advantages (accuracy and implementation) in using the local Kirchhoff method."

Jan 1, 2001

By Bora Derin

The synthesis of titanium diboride (TiB2) by carbothermal reductions of TiO2 and B2O3 was investigated. For this aim, TiO2, B2O3 and carbon black powders were dried, weighed out and mixed in stoichiometric molar proportions (TiO2:B2O3:C = 1:1:5). The experiments were carried out in a graphite resistance furnace in argon media using different range of temperature (1400- 1700 °C) and time (0 and 15 min). The phase analyses observation of the products were examined by using XRD.

Jan 1, 2008

"Depletion of known ore reserves and increased demand for precious metals have caused a revolution in biohydrometallurgical processing technology for gold recovery. Known ore deposits and future discoveries are most likely to be lower grade sulfide ores that can be difficult to recover with current leaching technology. Future metal recovery operations will increasingly use bio-oxidation techniques.Bacteria are an integral part of mineral cycling and mineral transformation in nature. Although biological processes are recognized as part of the mineralization and oxidation reactions in some ore deposits, they have only recently been applied to enhancing metal recovery in hydrometallurgical procedures. This paper explores the traditional metallurgical application of biological leaching and oxidation reactions and reviews the complete range of bacteria available for metal recovery systems. Pre-treatment of ores with bacteria improves metal recoveries in tank leaching systems and shows promise for heap leaching methods.IntroductionThere is no longer any question that bacteria playa natural role in the on-going transformation of some ore deposits (1,2). As applied to sulfide ores, a few strains have been specifically identified that exhibit a natural leaching potential (3). These bacteria can be isolated from waters and soils in old mining districts where they contribute to continuing leaching and pollution problems in acid drainage and heavy metal solubilization. Sulfur and iron bacteria as well as many heterotrophic strains have also been found in ore deposits and sedimentary rocks at depths up to 2000 meters (4). Their presence in both ore deposits and processed ores shows the microbial association with natural leaching and the potential role that bacteria can play in the development of new leaching technology."

Jan 1, 1988

By P. Koskinen

Outokumpu Oy has 30 years' experience in nickel production. It is mainly based on the technology developed within the company. The production chain starts from the mines reaching to the high-grade cathode nickel and the stainless steel manufacturing. As a multi-metal producer Outokumpu has the advantage to exploit from nickel raw materials also other valuable metals and intermediate products which can be processed at the company's various plants. The main source of nickel concentrate is nowadays the Enonkoski Mine started up in early 1986. It is the most modern mine in Finland being provided with the latest Finnish high-tech systems. Nickel concentrates are smelted at the Harjavalta Works using Outokumpu's internationally well-known flash smelting method. Also nickel containing residues and secondaries' are used as raw materials. The high-grade nickel matte from the smelter is then refined at the nickel refinery in a hydrometallurgical process, which was also developed by the company's own research staff. These processes have been continually improved and capacities gradually enlarged to 18 000 mtpy of cathode nickel. Besides plating, melting and superalloying purposes part of the nickel ends in stainless steel at the Tornio Works. The production was started in 1976 and has reached an established position on the European market.

Jan 1, 1988

By P. J. Uggowitzer, K. Steinhoff, A. Wolf

"With the increasing acceptance of the Thixoforging process in the last few years, also the technical and commercial requirements for this forming technology and its components increased. So far, a great deal of work has been done in the development of an efficient process and control design. However, less attention has been paid to the development of new specifically tailored aluminum wrought alloys for this specific manufacturing process. · In this paper a new AlMgSi-alloy (A6082), optimized for the Thixoforging process, is presented. In the first part, the technical potential of the new alloy is specified by its microstructural evolution and flow characteristics in the semi-solid state. In the second part, the mechanical properties of thixoforged components of different conventional AlMgSi-alloys a (e illustrated · and compared to the new alloy.IntroductionSemi-solid metalworking, also known as semi-solid forming, is a hybrid manufacturing method that incorporates elements of both casting and forging. The key to the process relies on the peculiar flow behavior of slurries containing non-dendritic solid, which was first studied at the MIT by Flemings et al. [i], in the early 1970s. It was discovered, that if an alloy is uniformly stirred during freezing, discrete rounded particles of solid are formed rather than the normal dendrites, and the slurry is highly fluid (-5 Pas) up at least 50% solid. In addition, these slurries posses thixotropic flow characteristics: the viscosity is dependent on sheare rate and time. The more vigorously they are stirred, the more fluid they become. However, on standing the viscosity recovers and the material stiffens (-106 Pas).The semi-solid forming process exploits this phenomenon. In a first step, the required non-dentritical- microstructure is obtained by mechanical or electromagnetic stirring during primary solidification of the alloy. The stirred slurry is generally fully solidified as a feedstock billet and - in a second process step - reheated above the solidus temperature into the semi-solid state. In this condition, the thixotropic properties permit the material to be handled by robotic devices and transferred to a die (Thixocasting) or subjected to- a forming process by means of forging (Thixoforging). Owing to the shear stress which acts on the semisolid material during forming operation, the viscosity of the material is reduced attaining so the desired fluid-like flow characteristics."

Jan 1, 2000

By Nils Eivind Kamfjord, Roar Jensen, Ingeborg Solheim

"SINTEF has carried out several pilot scale silicon process experiments in the past, but always with an open off gas system. In order to test the possibilities in running a semi closed furnace operation, a new off gas hood has been designed and tested. The off gas hood is designed to collect all off gases to gain insight into the phase compositions in the off gas and at the same time have the opportunity to monitor and maintain the charging/stoking of the furnace. The furnace hood has regulation and control of the air inlet into the combustion zone in two different heights. The off gas temperature and composition was continuously monitored and analyzed during the experiment. In order to expand the knowledge on NOx- formation in silicon metal production, such information is vital.IntroductionBecause of the negative environmental impact, the attention towards all kinds of NOX emissions increases in Norway. The authorities’ demand towards better surveillance and control of emissions increases as well.Earlier and new industrial measurements in FeSi- and Si-metal furnaces reveal quite high NOX-emission. The measurements also show that the NOX formation (mainly as thermal NOX) is distinct connected to the formation of dust (SiO?SiO2) in the combustion chamber above the furnace surface, when the temperature is high and the access to N2/O2 is good. This means that stoking, charging and temperature straight above the furnace surface is important factors for the NOX formation."

Jan 1, 2012

By Zengjie Wang

Investigation on hydrochloric acid leaching of the ilmenite from Panzhihua, China was carried out to prepare synthetic rutile. The leaching parameters were optimized to obtain high content of TiO2 in the products. The experimental data suggest that an optimum leaching can be realized with 30% acid, a solid/liquid ratio of 1/4 at 95°C for 4h, and ore ground for -400 mesh size. After the acid leaching, an additional alkaline leaching process using hot NaOH solution was performed, and then the products was in grain form followed by heat treated at 900°C for 2h in order to extract Si and increase the particle size of synthetic rutile. The final product has a high content of TiO2 (about 95%), a low content of chlorine consuming elements (total CaO+MgO =0.07%) and a suitable particle size distribution for chlorination process.

Jan 1, 2008

By L. Filip

The roast-leach-electrowinning (RLE) process for zinc was modified to treat two typical complex concentrates containing zinc, lead, copper, gold and silver. Laboratory testwork results indicated that the optimum roasting temperature ranged from 700 to 800°C, in order to produce acceptable residual sulfur levels. The calcined concentrate was subjected to a three-stage leach sequence. The resulting leach solution was purified by hematitic precipitation and directed to the recovery of copper and zinc by solvent extraction and electrolysis. Alkaline smelting and subsequent electrolytic purification recovered the lead and precious metals from the leach residue. A flowsheet was developed based on the laboratory testwork results, and demonstrated in a large-scale pilot plant. The recoveries produced during the pilot plant operation ranged from 90 to 92% for zinc and copper, 85% for lead and 90% for gold and silver, respectively.

Jan 1, 1999

By Bradford C. Wesstrom

The extraction of metals from Copper Refinery Slimes may involve many different processes. This paper describes the use of pressure leaching for decopperizing of copper refinery slimes at the El Paso Refinery. Process equipment will be described, along with the process chemistry, unit operations and unit processes associated with the decopperizing process. Copper contained in the raw slimes ranges from 15-35%. After autoclaving less than 1 % copper remains.

Jan 1, 2000

By Keizo Uematsu, Satoshi Tanaka, Nozomu Uchida, Ronne Hendrajaya

"The influence of microstructural defects on strength in Si3N4 is reviewed. The presence of cracks, pores and inclusions greatly affects the strength of Si3N4. The micron order crack size and distribution were quantified by micrographic technique. The observed defect size was range from 4 µm to 28 µm.The density of defect increases as the defect size decreases. The correlation between defects size and density was better represented on the logarithmic graph. The correlation was linier. IntroductionFracture in ceramics materials occurs from. In order to understand the relationship between strength and defects, it is necessary to examine the fracture process quantitatively.1In this study, the micrographic technique is used to determine the defects size and distribution in Si3N4. The observed data will be used to predict the material strength by using fracture mechanics rnodel.2Experimental ProcedureThe sintered Si3N4 specimens ( SNl, Japan Fine Ceramics Center) were sliced into 1mm thick . The both sides of specimen surface were polished into by using diamond slurries with particle size down to 2µm. The final thickness was 0.045 mm. The optical microscope (NIKON OPTIPHOT02-POL) was used to observed the internal defects with transmission mode. The reflection mode was used to determine the surface defects, so that the internal defect could be distinguished from surface defect. The measurement and counting was taken on the micrograph and the longest part of the defect was measured as the defect size. The size density distribution of internal defect is taken."

Jan 1, 2000

By Hideo Nakae, Hideki Yamaura, Toshiaki Kimura

"In 1968 J. N. Reding et al. suggested processes for fabricating composites. According to their patent, decompression atmosphere, which occurs during the reaction between magnesium and oxygen and/or nitrogen in the closed system, causes the spontaneous infiltration of melt into narrow spaces such as ceramic preforms. However, they did not report the proof of this phenomenon or the industrial manufacturing method. Therefore, this research measured the pressure change among SiC particles surrounding molten aluminum. As a result, the pressure reduction during the Mg reaction was identified. Moreover, the existence of Mg3N2, which improves the wettability between Al alloy melt and SiC particles on the interface, was observed on the surface of particles. Applying these two phenomena, a new process for the manufacturing of cast discontinuously reinforced aluminum composites (DRA) was developed. This new method is expected to produce DRA without additional pressure.IntroductionWith the increasing demands for light-weight materials in the automotive and aerospace industry in recent years, ceramic particulate reinforced aluminum matrix composites called DRA (Discontinuously Reinforced Aluminum Composite) have been receiving significant attention because of its lightness, superior abrasion resistance, high heat conductivity and low thermal expansion [1-3]. Consequently, DRA was considered for electronic parts such as heat-sinks or a base for power semiconductors, and began to be applied for automotive parts including brake drums, discs, cylinder liners, pistons and so on [4- 6]. However, high machining cost is one of the significant barriers to widespread use ofDRA. One solution to this problem is the adoption of cast DRA that can be produce to near-net shape, reducing machining cost."

Jan 1, 2000

By F. E. Wagner, L. J. Cabri, Y. G. Safonov, N. S. Bortnikov, A. D. Genkin, J. Friedl, G. N. Gamyanin

"A multidisciplinary investigation (including INAA, SIMS, EPMA, and Mossbauer Spectroscopy) was used to characterize gold in four of the largest Siberian mesothermal sulfide gold deposits. These are the Olympiada (""'750 metric tons gold) and Veduga (estimated at 75-100 metric tons gold) deposits in the Enisei Mountain Range and the Nezhdaninskoye (z500 metric tons gold) and Sentachan deposits in the Verchoyansk-Kolyma area. It was found that some of the mineralization is refractory in all four deposits, largely due to the occurrence of ""invisible"" gold in arsenopyrite as well as within pyrite, but with a lesser concentration. The gold concentration and its distribution varies considerably both within and between arsenopyrite grains, with implications for processing options such as heap leaching. The ore most likely to be amenable to heap leaching is the oxidized ore of the #4 orebody of the Olympiada deposit, but further quantitative mineralogical investigations are recommended for this orebody's sulfide ore and for the ores of the Nezhdaninskoye deposit. Following a full mineralogical characterization, it is possible that economic viability will depend on a combination of pre-concentration with or without pre-treatment, followed by heap leaching of some tailings products.Acknowledgements· The Russian authors performed this study under an ""Eco res"" Project which was financially supported by the Ministry of Science and New Technology of the Russian Federation. C.J. Stanley wishes to thank John Spratt and Terry Williams for help with EPMA. F.E. Wagner acknowledges the Deutsche Forschungsgemeinschaft for a grant supporting the Mossbauer studies. L.J. Cabri is grateful to the following: M. Beaulne, D. Carson and J.H.G. Laflamme for technical support, K.E. Haque for technical comments, and D.M. Hausen and W. Petruk for editorial suggestions."

Jan 1, 1997

By Emil B. Milosavljevic, Ljiljana Solujic

Cyanide is exceptionally reactive, and in typical gold/silver processing liquors, cyanide may be transformed into various species and forms depending on the mineralogy of the ore and chemical make-up of the process water. The exact speciation and relative concentrations depend on the Eh and pH values, as well as the free CN concentration in the system. Very good cyanide balances can be achieved by the judicious selection of the analytical techniques used. The choices an analyst has to make (which analytical methods to use and which ones to avoid) in order to gain better understanding of cyanide speciation and balances in a particular system under investigation will be discussed. Examples of cyanide balances obtained for the laboratory scale tests (agitated leach and column tests) will be presented and discussed.

Jan 1, 1999

By N. V. Gorelikova

A new type of zirconium mineralization has been recognized in the Devonian volcanic rocks from an orogenic depression in the Central Kazakhstan. The most characteristic features of this deposit are the fine-grained nature of the zirconium mineralization, an unusual texture of the zirconium ores, and a close association of zirconium with phosphorus in the ores. Zircon grains form fine globular aggregates with the features of hexagonal crystal habit. In addition to crystalline zircon, the ores contain metacolloidal zircon, similar to hydrozircon. The morphological and textural features of the zirconium ores suggest that the deposition of ore deposits took place at a low temperature from colloidal solutions. It is believed that this deposit should be considered to be a new type of zirconium mineralization that is related to low-temperature hydrothermal processes.

Jan 1, 1995

By Pinakin C. Chaubal

Today?s steel industry is in a vibrant and resurgent mode. This transformation has been in the making for some time now. Over the last few decades, the industry was steadily transforming itself into becoming a high tech industry. New technology was adopted, efficiencies were enhanced, lean manufacturing concepts were brought in and a strong customer focus was developed. Today?s mills employ sophisticated instrumentation, computerized monitoring, on-line smart systems etc. driving processes that are producing at rates of many tons/minute. All this is not possible without judiciously using the latest available technologies in various fields and developing a more sophisticated work force. Prof. Sohn has been a pioneer in driving the concept of process engineering in process metallurgy. In this paper the focus is on some aspects of process engineering ? primarily process modeling - as applied to iron and steelmaking processes. Examples are shown to demonstrate how problems have been addressed. Some thoughts on future directions are presented.

Jan 1, 2006

By Pinakin C. Chaubal

Today?s steel industry is in a vibrant and resurgent mode. This transformation has been in the making for some time now. Over the last few decades, the industry was steadily transforming itself into becoming a high tech industry. New technology was adopted, efficiencies were enhanced, lean manufacturing concepts were brought in and a strong customer focus was developed. Today?s mills employ sophisticated instrumentation, computerized monitoring, on-line smart systems etc. driving processes that are producing at rates of many tons/minute. All this is not possible without judiciously using the latest available technologies in various fields and developing a more sophisticated work force. Prof. Sohn has been a pioneer in driving the concept of process engineering in process metallurgy. In this paper the focus is on some aspects of process engineering ? primarily process modeling - as applied to iron and steelmaking processes. Examples are shown to demonstrate how problems have been addressed. Some thoughts on future directions are presented.

Jan 1, 2006

By Pinakin C. Chaubal

Today?s steel industry is in a vibrant and resurgent mode. This transformation has been in the making for some time now. Over the last few decades, the industry was steadily transforming itself into becoming a high tech industry. New technology was adopted, efficiencies were enhanced, lean manufacturing concepts were brought in and a strong customer focus was developed. Today?s mills employ sophisticated instrumentation, computerized monitoring, on-line smart systems etc. driving processes that are producing at rates of many tons/minute. All this is not possible without judiciously using the latest available technologies in various fields and developing a more sophisticated work force. Prof. Sohn has been a pioneer in driving the concept of process engineering in process metallurgy. In this paper the focus is on some aspects of process engineering ? primarily process modeling - as applied to iron and steelmaking processes. Examples are shown to demonstrate how problems have been addressed. Some thoughts on future directions are presented.

Jan 1, 2006

By Pinakin C. Chaubal

Today?s steel industry is in a vibrant and resurgent mode. This transformation has been in the making for some time now. Over the last few decades, the industry was steadily transforming itself into becoming a high tech industry. New technology was adopted, efficiencies were enhanced, lean manufacturing concepts were brought in and a strong customer focus was developed. Today?s mills employ sophisticated instrumentation, computerized monitoring, on-line smart systems etc. driving processes that are producing at rates of many tons/minute. All this is not possible without judiciously using the latest available technologies in various fields and developing a more sophisticated work force. Prof. Sohn has been a pioneer in driving the concept of process engineering in process metallurgy. In this paper the focus is on some aspects of process engineering ? primarily process modeling - as applied to iron and steelmaking processes. Examples are shown to demonstrate how problems have been addressed. Some thoughts on future directions are presented.

Jan 1, 2006

By Kumar M. Lyer

The channel reactor for ferrous and nonferrous processing has been modeled as a combination of ideal reactors. Cold model studies simulated the counter-current flow of slag and matte (or metal) with high-strength submerged gas injection. A composite model has been developed which describes the mass transfer between the two liquid phases, including the transfer of minor elements. The residence time for the matte droplets in the matte/slag emulsion is compared with the settling rates for the matte droplets in the slag to determine their relative importance in the mass transfer between matte and slag. The governing equations for mass transfer have been developed using correlations for the mass-transfer coefficients in the continuous and dispersed phases. An application of this scheme to a typical copper smelting system is presented.

Jan 1, 1993