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By S. S. B Wang

Zirconia-based ceramic materials have potential applications in high temperature furnace insulation, hot extrusion and casting dies, pressure nozzles, cutting tools, engine parts and electronic materials. High purity and superfine powders of zirconium oxide (baddelyte) were synthesized from a solution containing zirconium oxychloride and urea under hydrothermal conditions. crystallization of the metastable tetragonal zirconia using magnesium oxide or yttrium oxide as stabilizing agents was successfully achieved. The mechanism of hydrothermal reaction to produce these powders are discussed.

Jan 1, 1989

By Jack S. McPartland

Historically, research on thiosulfate leaching of precious metals ores has been focused on processing of difficult to treat ores. Thiosulfate leaching of ores and concentrates containing sulfide minerals, copper, manganese and preg-robbing carbon constituents has been evaluated. Cyanide leaching is generally considered an efficient, environmentally acceptable means for processing of non-refractory precious metal ores, Consequently, commercial processing of finely disseminated, oxidized precious metal ores is normally accomplished using alkaline cyanide leaching. Recent changes in regulatory climate have, however, called into question the acceptability of cyanide leaching in a number of locations worldwide. In some cases where the use of cyanide is being questioned, thiosulfate leaching may provide an acceptable alternative. Developments in thiosulfate leaching of precious metal ores are reviewed in this paper.

Jan 1, 1999

By Tatsuo Inoue, Marnoru Mizuno, Toru Matsuoka, Kenichiro Abe

"The distribution of particle reinforcements and the residual stresses in metal matrix composite are simulated by considering the motion of particles and the solidification of matrix associated with temperature variation in the course of centrifugal casting process. In the analysis, a heat conduction equation including heat generation due to latent heat and also mechanical work as well as heat input from successively accumulated element on the air/metal boundary is solved by the finite element technique. After the movement of particles subjected to the centrifugal force and drag are analyzed, the residual stresses are elucidated by using a unified constitutive equation which can describe the behavior both in liquid and solid states. Results of the simulation are compared with the experimental data, and the validity and utility of the procedure is confirmed.IntroductionProcess simulation of metal matrix composite (MMC) is required to determine the mechanical properties of the materials and the efficient process and conditions of the fabrication. Properties of bonding matrix with reinforcements in the course of the processing, for example, affects the strength of the composite, while the final costs of the productions depends on the efficiency of fabrication. Therefore, the simulation of processing of MMC is prerequisite in order to clarify the mechanism to fabricate the material which has been expected to maintain high mechanical properties and the cost performance.Some techniques of processing MMC[l] have been developed so far. Among them, the centrifugal casting technique [2-5] has many attractive characteristics as processing of the MMC: The centrifugal casting technique makes the reinforcements such as particles or short fibers to be distributed in the radial direction by the centrifugal force acting on reinforcements due to the difference in density between reinforcements and matrix. Since the distribution of reinforcements affect the mechanical properties of MMC, the composite with functionally gradient mechanical properties can be provided by the centrifugal casting technique."

Jan 1, 1994

By J. W. Dini

Introduction The mission of the Materials Fabrication Division (MFD) is to provide fabrication services and technology in support of all programs at Lawrence Livermore National Laboratory (LLNL). MFD involvement is called for when fabrication activity requires levels of expertise, technology, equipment, process development, hazardous processes, security, or scheduling that is typically not commercially available. Customers are encouraged to utilize private industry for fabrication activity requiring routine processing or for production applications. MFD is .a large diversified service organization including approximately 400 full time employees. The group provides a wide variety of processes including all common machining and fabrications operations, laser and water jet cutting, electrical discharge machining, lapping, electron beam and laser welding, vacuum brazing, heat treating, forming, electroplating and metal finishing, optical polishing and grinding, vacuum coating, vacuum engineering and a variety of plastics operations. These operations occupy more than 1,250,000 square feet of floor space. For more detail on the many fabrication related services available from MFD, see Reference 1.

Jan 1, 1992

By K. Fagerlund

In this work, the rate of dissolution, melting behaviour and phase separation of silica flux with molten slag and matte were investigated. Mutual dissolution between high-grade matte and silica was chemically determined. Silica dissolution rates ,in various iron silicate slags was determined using the rotating rod method. The reaction and separation phenomena of slightly oxidised chalcopyrite samples and cuprous sulphide-magnetite mixtures with silica sand were examined all about 1350°C. The samples were water quenched, and polished specimens were studied and analysed using a light optical microscope ,and a scanning electron microscope with energy dispersive spectrometer. The silica dissolution rate in slag was found to increase with decreasing silica content and increasing ferric iron content. The reaction rate of silica sand' with matte was found to increase with increasing oxidation degree and magnetite content of matte:

Jan 1, 1998

By Yu-ichi Kanbe

It becomes more important to control the composition of inclusions with increasing the demand for quality of products in terms of cleanliness. Along with the development of refining technology to make inclusions harmless, a study was made to develop how to predict the quality of final products. At first, observations of a number of defects revealed that the defects were caused by inclusions larger than 100 m in diameter. Therefore it is required to detect relatively large inclusions in steel, whose existence is quite rare, to identify the quality. In order to estimate the maximum size of inclusions in a given sample, the method with statistics of extreme values has been applied for continuously cast (CC) slabs, hot-rolled coils and cold-rolled coils of type 304 stainless steel. For the CC slabs the diameter of inclusions, which were analyzed to be mostly silicate with globular shape, in the specimens was measured. For the coils, the width of inclusions was measured at the unit section perpendicular to rolling direction because it corresponds to the diameter assuming that the width of globular inclusions does not vary with rolled. Then maximum inclusion diameter in a specimen was calculated. As a result, the obtained values in the rolled coils are larger than in the slabs. This may imply that the measurement with the coils gives the values closer to the truth. Besides, the measurement with the coils is even faster than with the slabs due to its simplicity of preparation of the specimens.

Jan 1, 2006

By Susumu Okabe

Top blowing lances are employed by the Mitsubishi Continuous Copper Converter for the continuous supply Of reaction gases into moken bath. In order to minimize the refractory wear caused by the interaction between the furnace lining and the melt splash. optimum furnace design and blowing condition are? required. An empirical equation obtained by the physical model study enables the estimation of the splashing rate on a vel1ical plane at a certain distance from the lance.

Jan 1, 1996

By K. Dzieciol

The paper presents a study about three image correlation methods ?common cross-correlation, mutual information and phase-correlation ? applied to characterize microstructures reconstructed with X-ray tomography. It is shown that phase correlation is not only the fastest, but also the most sensitive method for detection of similar microstructure features, cavities in the present case. A new image correlation indicator is proposed, which takes into account both the phase shift and the amplitude of similar features in compared images. Some preprocessing aspects related to the tomographic reconstruction and filtering out of characteristic noise are also discussed.

Jan 1, 2009

By Dachun Liu, Yifu Li, Baoqiang Xu, Yongnian Dai, Bin Yang

"The removal of impurity arsenic from crude tin is one of the major problems in the process of tin refining. Through a thermodynamic analysis on vacuum refining process of crude tin, the vapor pressure of impurity arsenic under different temperatures can be obtained, which demonstrates that it is possible to separate tin and arsenic by the vacuum refining process. This paper attempts to verify the behaviors of impurity arsenic. The experiment result shows that through vacuum distillation, crude tin with 0.16% arsenic can be refined from crude tin with 0.96% arsenic, and about 50% impurity arsenic can be collected in the form of metallic arsenic.PrefaceThe crude tin obtained by the reduction process is insufficiently pure for most applications, even smelting from tin concentrate. Arsenic is a common impurity in crude tin and also one of the predominant elements to affect tin performance. Arsenic is a poisonous metal that has long been linked to an increased risk of cancers, diabetes, thickening of the skin, diseases of the liver and digestive complications, so there is a mandatory limit on the amount of arsenic (<0.015%) in tinfoil wrapper and tin layers for food packaging. Arsenic causes a poor appearance and plasticity, and increases viscosity. The impurities content of crude tin fluctuate over a wide range; a lot depends on composition of tin ore concentrate, treatment method and technological process before reduction smelting. And the content range of arsenic is usually 0.5~4%, but it is higher in some factories."

Jan 1, 2012

By Stavros A. Argyropoulos, Henry H. Hu

"The assimilation of exothermic additions in liquid metals exhibit an array of unique coupled heat, mass and momentum transport phenomena. These phenomena are further complicated by the presence of a moving boundary.This paper describes a) A mathematical model which simulates the complex phenomena, and b) An extensive verification of the mathematical model. The SIMPLER algorithm was employed to solve numerically the pertinent partial differential equations. The computational results indicated that the exothermic heat of mixing led to a rapid increase in temperature around the moving boundary, which produced an enhanced convective flow in the liquid phase. The intensification of fluid flow around the moving boundary resulted in an acceleration of the melting process.Verification of the model was carried out in two contexts. The first was, in a low temperature physical model consisting of ice immersion in different sulfuric acid solutions. In this physical model, both temperature and velocity measurements were carried out. The model results were compared with experimental measurements and they were found to be in excellent agreement. The second context employed high temperatures, involving the assimilation of silicon in high carbon liquid iron. The model was also applied to predict fluid flow, heat and mass transfer for these high temperature experiments and a good agreement was obtained.In addition new dimensionless heat transfer correlations that quantify these complex phenomena will be presented."

Jan 1, 2001

By U. Meyer, A. Alonso, P. Banios

The sampling of cathodes has changed with the introduction of the ISA-process in copper refineries. A Jernkontoret joint working group of refineries and rod plants from both primary and recycled copper plants has been investigating whether the actual sampling of cathodes is representative for this type of cathodes. As a first stage, samples were sent to the members of the working group with the objective to find an easy basis for a comparison of the results of the next stages. All samples show the same tendency for nearly all elements. In some cases, there may exist differences in calibration and for some elements the detection limits are too high, especially when Optical Spectrometry is used. In the second stage, discs were compared with melted samples to answer the question whether the punching of discs is sufficient for the quality control of the cathode. The analyses of the discs represent fairly well the cathode quality. There are differences between cathodes from different crops. Three punches are sufficient to determine the cathode quality. Finally, samples from various lots of cathodes were compared with samples from the rod produced from these cathodes. The impurity content of the rod corresponds to the impurity content of the cathode.

Jan 1, 2000

By Kang Wan, Lei Tang, Jianchao Li, Jieyu Zhang, Minqi Sheng, Jifang Xu

"The viscous flow phenomenon in slag close to the liquidus temperature was considered. A simple approach that liquidus temperatures of melt could be derived from viscosity data was employed. The potential of this method for estimating the liquidus temperatures of pure water and binary alloy was demonstrated. The liquidus temperatures of the CaO-Alz03 based slags obtained from the second derivative method depends upon the number of viscosity values available at different temperature intervals. The results indicated that plots start deviating from the straight-line behavior at temperature as expect, and the second derivatives show the break points at a certain temperature, which is the liquidus temperature. Comparisons among the present observations as well as the characteristic temperature of the selected slags, which measured by the hemisphere method and DSC, indicated that it is possible to get a reasonable idea of estimate the liquidus temperatures from activation energies for viscous flow.IntroductionThe liquidus temperature of slag, which has a significant effect on the kinetics of chemical reactions and the slag-metal separation, is extremely important for metallurgical operations. Experimental measurements of the liquidus temperatures of slags are difficult, since slags invariable supercool. In addition, behavior of a single constituent in a multi-component slag is different in different circumstances due to its interaction with other constituents. Hence, it is essential to study the liquidus temperature of each particular slag resulting from a special process. Usually, the compositions of the slags aimed to the single liquid region of the phase diagram. However, the phase diagram of many slag systems, which back often to the 1950's, involves considerable uncertainties. Many liquidus temperatures are given as dotted lines in Slag Atlas [1]. Disagreements between the phase diagram and the reality have been found [2]."

Jan 1, 2013

By Godwin M. Beene

Large scale mining operations started in Zambia in 1913 and rapidly expanded during the post 1930 period with the opening of several mining and processing plants on the present Zambian Copperbelt. As a consequence of poor tailings dumps design methods at the start of the mines, and in view of stringent Government Legislation pertaining to environment in the recent years, Nkana Mine has developed a unique method of dump construction at its current tailings depository, Tailings Dam 15A. This method has enabled the revegetation of the dump retaining walls while construction is still in progress, a situation which was not possible on the older dumps. Cowdung has proved to be a superior fertilizer for providing plant nutrients on the tailings. The new method of dump walls construction and walls rainwater runoff drainage system has almost eliminated tendency of gully formation which is common on older dumps, as rainfall on the Zambian Copperbelt comes in intense thunderstorms. The decanted water from the dump is discharged to the natural environment in a controlled fashion after ensuring that it meets the Zambian Government Statutory requirements.

Jan 1, 1999

By M. Tomita

One of the most essential factors for a custom smelter to strengthen its competitive power is to Improve its comparative standing in purchase of concentrates from the world market. It is especially critical for Japanese smelters who depend almost 90% of their raw materials on import. In order to accomplish this breakthrough, the development of the new technology which enables us to treat concentrates containing higher Impurities is inevitable. Nippon Mining Company Ltd. made an intensive research on processing complex ore for three years from 1979, and successfully developed an original hydrometallurgical process to treat converter dust for eliminating impurities from the copper smelting circuit. The commercial plant was constructed at the Saganoseki Smelter & Refinery in 1982, and its nine years operation has been satisfactorily proven the advantages of the technology. The concept of this process and its operational performance are discussed.

Jan 1, 1992

By N. El-Kaddah, J. W. McKelliget

"A mathematical model for the analysis and design of hybrid plasma reactors for advanced materials synthesis is presented. The model is based upon a solution of the electromagnetic vector potential equation and is capable of predicting the two-dimensional velocity, temperature, and electromagnetic fields as well as the reaction kinetics inside the reactor for any axi-symmetric coil configuration. The model is used as a computer aided design tool for the design of hybrid plasma reactors consisting of a conventional DC torch augmented by an RF induction coil and it is demonstrated that the hybrid system possesses superior characteristics for materials synthesis over conventional DC or RF systems. The coupling between the RF and DC components is found to affect both the temperature field and the flow field and to have a significant effect on the reaction kinetics and on materials recovery. The model is used to study the thermal decomposition of silicon tetrachloride as a function of reactor design and operating parameters and it is demonstrated that through a CAD approach it is possible to significantly improve the operation of materials synthesis systems.IntroductionIn recent years there has been growing interest in the use of the inductively coupled plasma for chemical synthesis as a way of meeting the increasing demand for high quality, high performance materials for use in critical applications/l/. Although the basic feasibility of this approach has been demonstrated in the laboratory/2,3/ there still exists a number of operational problems that adversely affect system performance for some applications. In particular, the recirculation and back flow effects that arise from the electromagnetic forces in the plasma can result in the repulsion of the reactants from the hot plasma core and their subsequent deposition on the walls of the reactor. Another operational problem arises from the fact that the energy dissipated in the plasma has to compensate for the heat losses to the environment by conduction, convection, and radiation in order to maintain the ionization of the plasma and, hence, the stability of the plasma may be affected by the presence of the reactants and their products."

Jan 1, 1988

By Reinhard F. Dobner

After a short introduction about the HK&apos;s secondary smelter process and explanations concerning the anodes produced the regulation and buffering of bleed will be described and the principles of technology for processing of bleed will be presented. Modernization aspects, especially installation equipment, and the different types of evaporators used will be described in detail. Besides, experience made with acid-resistant materials - stainless steel, enamel, plastics - will be reported. Environmental aspects such as water and air pollution will be outlined briefly and in conclusion the quality of products obtained as well as quality control will be presented.

Jan 1, 1997

By R. M. Westcott

A two-electrode, direct current, slag resistance furnace (SRF) has been constructed and operated to selectively reduce the zinc and lead contents of non-ferrous slags. The experimental SRF is equipped with multiple methods of gas/solids injection for both mixing and reaction. A computer is used to position the electrodes and for data acquisition. A geometric factor correlation was previously developed at Columbia University for calculating the electrical resistance on the basis of furnace geometry and slag conductivity. The experimental SRF was used to test this correlation.

Jan 1, 1994

By Cindy L. Williams

"The Blue Star subdistrict in the Carlin Trend, Nevada, includes multiple mines with 33.9 t Au in reserve and past production totaling 89 .1 t Au. The deposits are characterized by zoned alteration mineralogy and gold grades. From orebody centers outward the zones include: 1) a silicified core with erratic gold grade; 2) adjacent mill-grade (> 1.37 Au git) intense quartz-sericite-pyrite alteration; 3) enveloping leach-grade (0.21 Au g/t to 1.37 Au git) weaker sericite-kaolinite-quartzpyrite alteration; 4) surrounding decarbonatized and intensely argillized waste and leach grade ore; 5) pervasively decarbonatized waste rock; and 6) peripheral waste with weak decarbonatization and local propylitic alteration. Zoned alteration extends as much as 1500 m beyond orebodies.Understanding Blue Star subdistrict zoned alteration assemblages and gold grades has increased geologists' ability to provide practical and economically significant information to geotechnical engineers, mine planners and drill and blast personnel. Alteration influences geotechnical pitslope design because each assemblage has distinct rock strength. Geotechnical engineers use three-dimensional models of incompetent alteration types as a foundation for pit-slope design. In the drill and blast cycle, hard and soft alteration types require modified practices (powder column, blast hole spacing, delay design etc.) for optimum blast energy distribution. Further, geotechnically instable alteration types require careful blast procedures to prevent backbreak whic~ damages ultimate walls. In addition to mine planning and mining applications, zoned alteration assemblages extending beyond orebodies provide a useful exploration guide. Metallurgical character also varies with alteration type. Intensely quartz-sericite-pyrite altered or silicified ore has relatively high partical-size dependency and poor leach recoveries. Moderately sericite-kaolinite-quartz-pyrite altered rock, in contrast, shows little size dependency and good leach recoveries.The author sincerely thanks L. Schutz, P. Williams, C. Clode, W. Trudell, P. Herrera, M.DKunkel, M. Goings and numerous other Newmont geologists, metallurgist, engineers and support staff who made this paper possible."

Jan 1, 1997

By A. D. Neuman, C. C. Davis, M. R. Lopez, A. C. Martinez, T. A. Nothwang, S. L. Voit

"One of the thrust areas for the Global Nuclear Energy Partnership (GNEP) program is the development of actinide bearing fuels for transmutation in a fast reactor. Mixed Oxide (MOX) fuel has an extensive fast reactor irradiation history and thus is being considered for use as a baseline composition from which minor actinides (MA) can be incorporated for use as a transmutation fuel. This study involves characterization of precursor powders and pellets to be inserted into the Advanced Test Reactor in Idaho. These pellets will have three compositions: one standard MOX composition, (U80Pu20)O1.98, and two compositions of MA-MOX with oxygen to metal ratios (O/M) of (U75Pu20Am3Np2)O1.98 and (U75Pu20Am3Np2)O1.95. The precursor powders, which consisted of, highly enriched uranium oxide, HEUO2, depleted uranium oxide, DUO2, neptunium oxide, NpO2, americium oxide, AmO2, and plutonium oxide, PuO2, were characterized using a field emission gun scanning electron microscope (FEG-SEM) for particle morphology, size, and size distribution prior to pellet production.IntroductionThe Global Nuclear Energy Partnership (GNEP) was created in order for “fuel-cycle supplier” nations to provide assured supplies of nuclear fuel to “fuel-cycle customer” nations. The customer nations would utilize the fuel for electricity generation and subsequently return it to the supplier nation after it is spent. This spent fuel would then be reprocessed by the supplier nation in order to recycle the actinide constituents, mainly uranium and plutonium, in advanced nuclear power reactors, and thus reducing waste volumes [1, 2]. Nuclear materials would also be strictly controlled through the International Atomic Energy Agency. One of the thrust areas for the GNEP program is the development of these actinide bearing fuels for transmutation in a fast reactor under the U.S. Advanced Fuel Cycle Initiative (AFCI) in order to transmute long-lived transuranic actinide isotopes into shorter-lived fission products [3]."

Jan 1, 2008

By S. V. Subramanian

The tool material and the machine design for high speed machining are well advanced over the last decade but the steel design has lagged behind. The paper examines the design of steel in order to control the sliding tribology for high speed machining under dry machining conditions. In high speed machining of steel, accelerated chemical wear of the tool occurs once atomic contact is established at the tool-chip interface, resulting in poor tool life even with high performance tools such as cubic boron nitride. Recent research has confirmed the occurrence of nanocrystalline grains in the interfacial layer of the chip at the tool-chip contact. The volume percentage of grain boundary is increased significantly (10 to 30%) as the nanocrystalline grain size is decreased well below 30 nm. The solubility of tool material into the nanocrystalline grain boundary is two or three orders of magnitude greater than in the crystal lattice. Further the kinetics of diffusion in the grain boundary is seven or eight orders of magnitude greater than in the crystal lattice. Enhanced nanocrystalline grain boundary diffusion occurring in the interfacial layer at the tool-chip contact causes the accelerated chemical wear. Significant improvement in tool life could be achieved by engineering glassy oxide inclusions in steel, designed to self-lubricate the tool-chip interface in-situ at higher cutting speeds. Thus the control of sliding tribological condition at the tool-chip interface is key to suppress nanocrystalline layer formation at the tool-chip contact and hence prevent accelerated chemical tool wear. Sulfide inclusions are designed essentially to promote chip fracture. In addition, sulfide inclusions are designed to act as a diffusion barrier at the tool-chip interface. The application of inclusion engineering concepts to enhance the tool life in high speed machining will be demonstrated with a suitable case history.

Jan 1, 2006