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By Rainer Schmid-Fetzer

"Isothermal solidification can be used to form strong bonds at low temperature which remain solid at much higher temperatures. The exploitation of this principally known technique for new high temperature processing steps and applications in electronic assemblies is the aim of this study. Three basically different variants of this bonding process are given. A comprehensive metallurgical screening is performed and the feasibility of binary material systems is given on a quantitative scale. Very attractive systems are spotted that have never been studied before. Detailed examples for the realization of bonding with complex ternary and multilayer systems are given. A highly innovative example is the chip stack or wafer to wafer bonding of unmetallized Si or SiC at 250°C. The proposed bond remains stable above the melting point of Si and enables entirely new semiconductor manufacturing steps. An improved die bonding process was proposed and verified experimentally.1. IntroductionIsothermal solidification can be applied to form strong bonds at relatively low temperature which remain solid at higher temperatures. The general principle of this type of joining processes is illustrated in Fig. 1. An interlayer of a low melting component, Lo, is provided as a foil or a thin film coating between the high melting joint components, Hi. The assembly is heated under moderate pressure to the bonding temperature, T 8 , and a liquid filler forms, either because the melting point of Lo is exceeded or due to a eutectic reaction between Lo and Hi. This molten filler initiates a rapid interdiffusion or reaction diffusion between Lo and Hi and the subsequent approach to an equilibrium state results in isothermal solidification. The solid phases formed at T 8 in the joint region exhibit a remelt temperature above T8 •"

Jan 1, 1996

By C. A. Young

The remediation of cyanide (CN-) and nitrate (NO)-) anions in mine and agricultural waters by various photolytic methods has been reviewed and investigated. Photolytic methods such as direct photolysis, homogenous photolysis, and heterogeneous photocatalysis are briefly described and compared. Results and discussions show that each method has certain advantages and disadvantages. For each method, Eh-pH diagrams prove useful for determining reaction mechanisms. Preliminary results obtained for cyanide oxidation and nitrate reduction show that homogeneous photolysis can be superior due to faster kinetics than the other methods. The photolytic methods were individually, not simultaneously, tested and compared. Differences in concentrations of products were obtained and attributed to differences in photoconversion efficiencies and other inherent characteristics of .the photolytic methods. Various reaction mechanisms are proposed in accordance with the literature as well as measurements obtained from solution analysis using ion selective electrodes and ion chromatography .

Jan 1, 1995

By Ralph H. Nafziger

The Bureau of Mines, in cooperation with the Idaho National Engineering Laboratory, has electroslag melted a V-5Ti-5Cr alloy using a fused CaF2, flux. The alloy is a candidate for use in future fusion reactors. One objective of this research was to evaluate the feasibility of the electroslag melting process in separating simulated radioactive isotopes from the V alloy to demonstrate recyclability. Small amounts of Ca, Y, and Mn were added as surrogates for radioactive isotopes. Results showed that this vanadium alloy can be electroslag melted satisfactorily. The impurities added intentionally were removed or decreased successfully. Among the major alloying constituents, Cr was retained but there were some Ti losses. The latter may be controlled with process refinements. This research suggests that the electroslag melting process could be a suitable method for recycling V alloys after use in future fusion reactors, or for processing other reactive metal alloys with more immediate applications.

Jan 1, 1996

By Luis M. Chia

The direct dissolution of zinc in an organic solution of di-(2-ethylhexyl) phosphoric acid (D2EHPA) and kerosene was studied. The objective was to gain a better understanding of the fundamentals involved in the anodic step of the galvanic stripping process. Results showed that metallic zinc does dissolve spontaneously at ambient temperature by an electrochemical mechanism and the presence of additional oxygen activated the process. When oxygen was removed by prior nitrogen sparging, dissolution did not occur indicating a depolarizing cathodic reaction is necessary. The concentration of water in the organic also affected the rate of dissolution. A factorially designed experiment was made using four variables at two levels selected by evaluating results from previous screening tests. D2EHPA concentration, surface area and agitation were all found to be significant for the values chosen. Temperature was less significant and it was found that zinc dissolution is probably a diffusion or mixed controlled process, as indicated by the calculated activation energy of 6 kcal/mole.

Jan 1, 1995

By André L. B. Bittencourt

The copper content in the waste slag represents the greatest loss in the process of Caraíba Metais' Smelter. By identifying the variables responsible for copper stabilization in the slag, a minimization on these losses is expected, producing a granulated waste slag with a copper content lower than 0.7%. Statistics resourses such as control charts, Pareto's diagram and correlations curves were applied for the data obtained in the first semester of 1992. The magnetite and the calcium oxide contents in the slag of the Flash Smelter Furnace were most prominent variables. Some operational changes introduced during and after this investigation have shown good results.

Jan 1, 1994

By M. S. Moats

The treatment of oxidized residues of zinc with high iron content continues to present a technical challenge in both the steel and zinc industries. Two main problems are commonly identified and include high treatment costs and environmental concerns about contaminated, iron-bearing residuals. A new approach to this problem is described in which selective separation of the iron and zinc into salable products may be potentially feasible. The waste material is first leached to give a solution having an approximate concentration of 110 g/l Zn, 15 g/1 Fe and 40 g/1 H2SO4 and other impurities such as Pb, Cd, Cu and Sb. A suitable organic, such as D2EHPA, is used to load the majority of the iron. The aqueous phase is then acceptable for zinc electrowinning after standard solution purification. The novel step in the flow sheet is the efficient recovery of the ferric iron from the organic solvent using a solid metal to reduce the iron to the ferrous state. The Fe+2 is easily stripped into an aqueous phase in a relatively pure form, suitable for use in water treatment. Process parameters and possible flow sheet designs are described and discussed.

Jan 1, 1995

By Wenxian Zhu, Xuema Li, Patrick R. Taylor

"Experiments were performed in a non-transferred arc, thermal plasma flow reactor to investigate the synthesis of ultra fine boron nitride (BN) powder from the reaction system of boron oxide (Bz03), methane (CH4), ammonia (NH3) and hydrogen (H2). Argon (Ar) and nitrogen (N2) were used as plasma gases. The thermodynamics and kinetics of the synthesis reactions were examined and a chemical reaction mechanism was proposed. The powders produced under certain operating conditions had high purity and good conversions. All the products were extremely fine powders (< 30nm) and were uniform in size distribution. The powder products were analyzed by chemical and physical characterization. The effects of the reaction variables on the conversions from B203 to BN and the purity of the products were investigated.IntroductionIn the past few decades, boron nitride (BN) has attracted a great deal of interest because of its excellent thermal, chemical and electrical properties (1-4) It has a high thermal stability and thermal conductivity. Chemically, it is very stable and is not wetted by most molten metals and slag. It is also an excellent low loss insulator. Since hexagonal boron nitride (h-BN) is light in weight, strong and easily fabricated, it has applications in a variety of specialized high temperature areas, such as a high temperature lubricant, crucibles for molten metals, thermocouple protection tubes, break rings for horizontal continuous casting of steel, and friction reducing coatings. In cubic form, boron nitride is one of the hardest materials known, second only to diamond, and it is an excellent material for tools in which the use of carbon based materials is limited by oxidation or reaction with metals."

Jan 1, 1998

By V. Ramachandran

In view of the increasing environmental regulations that have been promulgated in the last 30 years, non-ferrous smelters and refineries have learnt to handle effectively the process waste streams that need to be bled from the system for impurities&apos; control The cations of concern are copper, lead, zinc, cadmium, mercury, thallium, nickel, silver, sodium and potassium. Anionic species of arsenic and selenium also need to be addressed, Sulfates and chlorides-not a major concern at present-have come under scrutiny in the recent past. The current paper reviews several treatment options with reference to a) types of waste streams processed b )process chemistry c)discharge options and recovery of treated water and d) sludge disposal The long term goal of any smelter and/lor refinery should be to achieve zero liquid discharge from the plant. Methods to obtain zero discharge are discussed.

Jan 1, 2003

By Kafui Nyavor

The indirect, and the direct contact mechanisms of bacteria oxidation of sulfides were studied using Thiobacillus ferrooxidans and pyrite. The aim was to determine which of the two generally aeeepted mechanisms played a dominant role, if any, during acid mine drainage (AMD) formation from the oxidation of sulfide minerals. The results show that at a pH of 4.5 where T. ferrooxidans are quite active, but where initial chemical oxidation of pyrite to Fe2+ is limited, the bacteria were unable to directly oxidize pyrite to any significant extent. Whereas, in the presence of Fe2+, T. ferrooxidallS assisted oxidation of pyrite by the indirect mechanism was observed and sustained over the pH and Eb range where the bacteria is active. The results lead to the conclusion that the direct contactmechanism of pyrite oxidition by T. ferrooxidans is insignificant. The predominant, and possibly the only, pathway involves the indirect bacteria oxidation of available Fe2+ to Fe3+, which in turn oxidizes FeS2 to generate additional Fe2+ and acidity in a cyclic process.

Jan 1, 1996

By Xiang (Frank) Chen, Mikhail A. Sokolov, Randy K. Nanstad

"Nickel-base Alloy 617 is being considered as a structural material for application in the secondary heat exchanger of the New Generation Nuclear Plant, a very high temperature gascooled reactor. Thermal aging of Alloy 617 plate and welds is being performed with tensile, Charpy impact, and fracture toughness tests conducted at temperatures to 950°C. Results of testing for thermal aging to 5,300 h have been obtained and are presented; varying effects of thermal aging temperature and time on fracture toughness are observed. The 9Cr-1MoV (Grade 91) ferritic steel is a candidate for structural applications in the sodium fast reactor. Fracture toughness testing of unaged Grade 91 steel has been performed to evaluate specimen size effects in preparation for future testing of the material in the thermally aged condition. Results for material in the mill-annealed and heat treated conditions are presented and show that this heat of Grade 91 steel does not indicate a small specimen bias on the fracture toughness Master Curve reference temperature.IntroductionThe behavior of advanced engineering materials will be a critical factor in the performance of Generation IV reactors. In the case of materials utilized for reactor internals and pressure vessels, the effects of irradiation and long time thermal aging are major issues. The environmental conditions for some of the Gen IV reactors are generally beyond present day reactor technology, requiring new experimental data as well as analytical predictions of expected behavior of candidate materials at conditions for which there are only sparse or no experimental data. The radiation environments and several key materials issues for some Gen IV systems are summarized in Section 5 of [l] as a starting point for modeling and microstructural analysis of Generation IV materials. More detailed descriptions of materials research and development needs and recommended activities for the SCWR, VHTR, and GFR are provided in references [2, 3, 4], respectively. Mansur, et. al. provide an interesting comparison of materials needs for Generation IV reactors to corresponding needs for fusion reactors and spallation neutron sources in [5]. The two primary candidate reactor systems currently undergoing significant research and development by the U.S. Department of Energy (DOE) are the New Generation Nuclear Plant"

Jan 1, 2012

By Mariana H. Staia

The present communication reports the results obtained by applying different concentration methods, at laboratory level, to the black sands from Estado Bolivar, Venezuela, with the aim of obtaining an adequate ilmenitic concentrate for the subsequent chlorination process. Sizing analysis was performed and plasma emission spectroscopy method was used to determine the chemical composition. It was found that from the two hydrogravimetric methods used, the Humphrey spirals is much more effective than Wilfley tables, leading to a 85% recovery. The most convenient particle size group for these concentration methods was the one corresponding to ASTM 40-140 mesh. When magnetic concentration was applied to the concentrate, obtained as a product from Humphrey spiral, a recovery of ilmenite more than 90% was obtained in the first step. It has been shown that the ore would respond to the separation techniques employed, giving individual minerals: ilmenite, zircon and silica as concentration products.

Jan 1, 1995

By Richard A. Leiby

The recycling of lead-acid batteries in the United States has become a challenge as to how to balance ever increasing environmental regulation and cost with efficient operations. East Penn&apos;s captive secondary lead smelter has developed into a recycling facility producing lead, polypropylene, sulfuric acid, ammonium bisulfite, and non-hazardous discard slag. The emphasis has been to design a facility to comply with environmental regulations, to eliminate wastes, and to produce products, while at the same time, continuing to supply the company&apos;s battery manufacturing raw material needs.

Jan 1, 1993

By Beate Ina Jenssen

Ferric iron removal from the nickel electrolyte at Glencore Nikkelverk AS in Kristiansand, Norway, is achieved by precipitation of iron hydroxide followed by filtration, and it is desirable to improve filtration properties of the precipitated iron hydroxide in order to decrease the filtration time. The effect of increasing the residence time from the current 45 min to 75 min and temperature from 65 °C to 90 °C on the filtration properties of the precipitated iron hydroxide (akaganéite) was studied by simulating the industrial process conditions in a continuous reactor setup operating at steady state, using ferrous-containing process solution as feed material. It was possible to decrease the filter cake resistance by both increasing residence time and temperature, but temperature gave the most pronounced effect and reduced the filter cake resistance by one order of magnitude.

By Emmanuel N. Zevgolis

After the Krupp-Renn process was shown to be unsuitable for treatment of the Greek nickeliferous laterites, the LM process was developed. It involved roasting reduction up to metallic iron in a Rotary Kiln (R/K) and smelting in an Electric Furnace (E/F). Ferronickel (with 15% Ni) produced in the E/F, was upgraded to 90-95% Ni in an 02 converter. Raw Ni was then electrolyzed to pure Ni. The LM process was not applied for very long however, due to various problems. So, the Larco process was developed, i.e., pre-reduction in R/Ks, smelting of the calcine in E/Fs for ferronickel production (15% Ni) and enrichment to 20% Ni, in an O2 converter. Until now, many technological improvements have been invented and applied or adjusted to the process, which have made it a fully reliable and competitive one. sohe of the improvements were the invention and application of a new granulation process for liquid ferronickel, the modification of the existing R/Ks, E/Fs and converters and the design of new ones, and others that are described in the paper. Keywords: Ferronickel, metallurgy, laterites, LM process, Larco process

Jan 1, 2004

By Musa Karakus

The sedimentary iron ores of Alsace-Lorraine, France have very high phosphorous contents that average 0.7% and are as much as 2.19% P. Ores from the Tucquegnieux and Joeuf mines have been studied by cathodoluminescence microscopy, X-ray diffraction, scanning electron microscopy, and electron microprobe analysis in order to fully characterize the mineralogy, size, shape, and distribution of the deleterious phosphate grains. The phosphorous occurs as collophane, a carbonate fluorapatite, in ten morphological forms, most abundantly as microcoprolites, but also as intraclasts, concentric layers, and cortices in ooids, phosphate replaced ooids and bioclasts, phosphatiC shells, fossil infillings and internal molds, fish teeth, phosphatiC laminae, and cements between the goethite ooids. About 95% of the phosphate grains are sufficiently large that relatively fine grinding fol&apos;lowed by reverse flotation would be expected to be effective in significantly diminishing the phosphorous content of the concentrates.

Jan 1, 1989

By P. A. Botha

Most sinter producers prefer to use a range of iron ores with the aim to optimize their sinter blends. ISCOR is however limited to the use of ore from two deposits, namely Sishen and Thabazimbi. Only sinter produced from Sishen ore is described in this report. The Sishen iron ore deposit provides high-grade hematite ore with a mean iron content of 65 per cent. Three major ore types are developed: massive, laminated and conglomeratic. The main ore mineral is hematite with minor to trace amounts of quartz, mica, phosphates and, in places, carbonates. A sinter product is characterized by its mineralogical composition and metallurgical properties. The production rate also plays an important role in the economic evaluation of sinter quality. Sinter-pot tests were conducted with varying basicities, given as the ratio of CaO to SiO:< and coke content. The results of these tests were characterized by mineralogical and metallurgical methods. Basicity of a sinter mix directly influences the mineralogical composition and metallurgical properties. The content of calcium ferrite and calcium silicate increases with increasing basicity, thereby increasing the reducibility and cold strength of the sinter product. Experiments performed during this study provided a model for the optimization of the sinter mix with respect to its mineralogical and metallurgical parameters.

Jan 1, 1991

By Kuniaki Murase, Tetsuji Hirato, Koji Nitta, Yasuhiro Awakura

"The redox behavior of copper species in an ""ammonium imide"" room temperature molten salt was examined in order to clarify the applicability of the salt to the electroplating media of various metals. Trimethyl-n-hexylammonium bis(trifluoromethanesulfonyl)- amide (TMHA-Tf2N), having an electrochemical window of 5.6 V (50 °C), and corresponding copper(II) salt were synthesized. In TMHA-Tf2N media monovalent copper ion, Cu(I), was stable and Cu metal was oxidized, or corroded, in the presence of Cu(II) species. Cathodic electrodeposition of copper metal and anodic dissolution of it were, thus, one-electron reaction and their current efficiencies were almost 100%.IntroductionElectrodeposition of metals from aqueous solutions is an important soft process for manufacturing thin-film materials, surface finishing, and extractive metallurgy. However, the electrodeposition of base metals, such as zinc, chromium, and nickel, from aqueous media inevitably accompanies hydrogen evolution, which lowers the cathodic current efficiency of metal deposition. Since the electrodeposition of aluminium, titanium, and rare earths from aqueous media is actually impossible due to their largely negative redox potentials, nonaqueous media such as aprotic organic solvent and high-temperature molten salts have been employed for the electrodeposition of these metals. Room temperature molten salts (RTMS),1, 2) or room temperature ionic liquids, have also been developed as a promising electrolytes for the electrodeposition of base metals. In this field, chloroaluminates of alkylpyridinium or alkylimidazolium cation have been well investigated for aluminium3) or alluminium-alloy4-5) electroplating media. On the other hand, in order to avoid high hygroscopicity arising from the use of aluminium chloride, attempts have been made to combine the alkylimidazolium cations with fluorine-containing hydrophobic anions, e.g. BF4-,6) CF3SO3- (TfO-),7) (CF3SO2)2N- (Tf2N-),8) and H(HF)n-ions,9) and investigated for electrodeposition media.'°) Recently, a new series of RTMS consisting of tetraalkylammonium cations and Tf2N- anion, sometimes abbreviated as TFSI- anion, was found independently by MacFarlane et al.11, 12) and Matsumoto et al. 13) This type of RTMS, which is commonly named ""ammoniumimide"" salt, has a wide electrochemical window of ca. 5 V and, thus, the RTMS seems to be suited for practical application as a solvent for the electrodeposition process. In this paper, we report the electrochemical behavior of copper species in an ammoniumimide RTMS, trimethyl-n-hexylammonium bis(trifluoromethanesulfonyl)amide (TMHA-Tf2N)."

Jan 1, 2000

By M. J. Collins

A hydrometallurgical process has been tested at the Sherritt Research Centre for separation of zinc, lead, copper and precious metal values from the zinc oxide fume leach residue stockpiled at the HBM&S operations in Flin Flon, Manitoba. Zinc is found primarily as zinc femte and sphalerite in the residue, lead as lead sulphate and jarosite, and copper as sulphide and jarositic compounds. Gypsum and siliceous gangue are significant diluents. The separation process includes hot acid, atmospheric and reducing (sulphur dioxide) leaching; zinc, copper and lead flotation; and atmospheric iron removal steps. Zinc is recovered to a high strength zinc sulphate solution and to a zinc sulphide concentrate suitable for feed to a roaster or to a zinc pressure leach plant; lead to a high grade lead sulphate concentrate suitable for feed to a lead smelter, and copper to a high grade copper sulphide concentrate suitable for feed to a copper smelter. Precious metals are divided between the zinc, lead and copper concentrates.

Jan 1, 1993

By Yang Guangqing, Shao Jiugang, Zhang Jianliang, Wan Dan, Fu Yuandi, Guo Hongwei

"Resource of metallurgical coke is becoming scarce, and although coke can be partially replaced by pulverized coal injection, there are many restrictions for further increase in coal ratio. Mixed charge of ore and lump coal from top to replace more coke was studied in this paper. Softening-melting property of the burden was affected by charge of lump coal. Softening-melting properties of mixed charge of ore and coke, mixed charge of ore and lump coal were tested respectively. Results show: the property of the burden mixed with coke is superior to the burden mixed with lump coal; lump coal would not deteriorate softening-melting property of the burden and some of them can even improve softening-melting property of the burden. Top charge of lump coal would not deteriorate softening-melting process, and this should be a new way to increase coal consumption to decrease coke rate.IntroductionThe blast furnace is still the predominant process for the reduction of iron ore and will probably remain so for the next decades. Metallurgical coke is becoming scarce and expensive, so the cost of hot metal can be decreased by reducing the consumption of metallurgical coke[l]. Coke can be partially replaced by pulverized coal injection, currently the highest rate of pulverized coal reached 266kg/tHM, most of blast furnace PCR is about 150kg/tHM, and it is very difficult to further increase of PCR. Nut coke is charged into blast furnace mixed with iron ore, not only for improving utilization of metallurgical coke, but also for lowering the coke rate. Presently the majority of blast furnaces in the world use nut coke although its amount is very different: from 10-20 to 70--100 kg/tHM and more[2-4].The effect ofnut coke in blast furnace is extensively researched, and the main conclusions recommend: to improve gas permeability of cohesive layer in blast furnace, to promote reduction of iron burden, protect metallurgical coke from the solution in the shaft due to higher reactivity of nut coke. There is no special requirement for the strength of nut coke[5-8]. Nut coke is also used for sintering fuel, which may lead to the shortage of the nut coke charging into blast furnace. So lump coal mixed with iron ore is considered to be charged into the blast furnace, not only to reduce the cost of grinding coal, but also to increase the use amount of coal."

Jan 1, 2013

By L. J. Davies

Refractories usage in furnaces for the extraction of nickel from both sulphides and lateritic ores is reviewed. Recent changes in raw materials and basic brick qualities developed to meet the increasing demands of existing and new processes are outlined. Examples of used brick examinations to establish mechanisms of wear are given. The importance of physical and chemical properties are discussed. The use of simulative laboratory testing to aid in refractories development and selection is described.

Jan 1, 1988