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By Gerhard Bayer

X-ray and thermoanalytical studies were carried out on the formation and stability of Ca-, Mg-and Mn-tungstate, and of the corresponding minerals scheelite and wolframite. The tungstates were synthesized by different methods: precipitation from solution, solid state reactions, displacement reactions with solutions and in the solid state. The reactivity of natural scheelite and wolframite with different salt solutions and in mixtures with other minerals was investigated.

Jan 1, 1989

By Carl W. Dalrymple

A wide variety of contaminants (heavy metals, suspended solids, colloids, oils, organics) have been successfully removed from wastewater using an electrocoagulation process. An innovative electrocoagulation system is described. This process involves a procedure which subjects dissolved and suspended wastewater contaminants to the simultaneous addition of metal ions in the presence of direct current. During the treatment process Ionic and other charged particles in the wastewater are neutralized with oppositely charged ions generating the coagulation of contaminants: The process Is called CURE, and' presented here with application to wastewaters containing mainly heavy metals.

Jan 1, 1995

By Rubén J. Sánchez Rodriguez, Carlos M. Fontes Vieira, Carlos E. Gomes Ribeiro

Ornamental compound stone are produced by industry for decades, however, few published studies describe these materials. Brazil has many deposits of stone wastes and a big potential to produce these materials. This work aims to evaluate the chemical resistance of ornamental compound stones produced with marble waste and unsaturated polyester. An adaptation of Annex H of ABNT NBR 13818:97 standard, with reagents commonly used in household products, was used. The results were compared with those obtained for natural stone used in composite production.

Jan 1, 2015

By Vaughan R. Voller

In many high temperature processes involving liquid melts the common practice is to solidify a fraction of the melt adjacent to the containment wall; a practice that can provide protection of the structural components of the process. The position, shape and transient behavior of these so called "skulls" and/or "ledges" are directly dependent on the thermal process conditions. This paper presents a model of a generic ledge process that can predict the steady shape of a ledge. Two numerical implementations are presented and compared: (1) based on a space grid of continuously deforming finite elements (2) based on a conjugate grid of fixed control volumes and deforming boundary elements.

Jan 1, 1996

By F. J. Hogan

In early 1982 Atlantic Cement Company, a wholly-owned subsidiary of Newmont Mining Corp. will come on line with a new water granulating grinding facility at Sparrows Point, Maryland to produce 800, 000 tons a year of separately ground granulated blast-furnace slag. The process and product will be unique to the United States. This paper will review some initial investigations undertaken to evaluate the cementitious properties of granulated slag. The effect of slag fineness on strength development is discussed and data is presented showing a relationship between glass content and hydraulicity and grindability of slag.

Jan 1, 1982

By Junji Shibata

It is important to recover and reuse the metal values contained in various industrial wastes in a viewpoint of environmental preservation. Most of industrial products are made through the processes to separate impurities in raw materials, solid and liquid wastes being necessarily discharged as industrial wastes. Chemical methods such as solvent extraction, ion exchange and membrane, and physical methods such as heavy media separation, magnetic separation and electrostatic separation are considered as the methods for separation and recovery of the metal values from the wastes. In this paper, some examples of the application of solvent extraction to the treatment of wastes are introduced. The treatment of solid wastes such as Ni-Co alloy scrap, Sm-Co alloy scrap, fly ash and flue dust, and liquid wastes such as plating solution, the rinse water, etching solution and pickling solution are accomplished using solvent extraction technique.

Jan 1, 1996

By Ronald L. Pariani

To date, significant advances have been made regarding the development and commercial implementation of full deposit stripping in the copper industry such as practiced at Copper Refineries, LTD in Townsville, Australia. The paper describes the history and current practice of Electrowinning (EW) plants which may be coupled with solvent extraction. The modular nature and degree of automation are described in relation to the various sizes of operations. Reference is made to the expansion capability of commercial equipment plus associated economics of the mechanical processes for producing full cathode deposits. It is recognized that the technology described may be adaptable to other nonferrous refining areas where feasible. The paper highlights the state of the art in mechanized stripping equipment as applied to current and planned SX-EW plants.

Jan 1, 1987

By Yuzuru Sato

Viscosity has been measured for various molten binary alloys of nickel with iron, cobalt and chromium in order to clarify the behavior of viscous flow of molten nickel alloys. The entire concentration range for iron and cobalt and 0-67at% of chromium content were studied. The measurement method was an oscillating cup viscometry using an alumina crucible that was precisely machined. The temperature was up to about 1880K for all the measurements. The results represented good Arrhenian relationship although some measurements included overcooled temperatures. The isothermal viscosities increased monotonously with an addition of iron and chromium into nickel. The addition of cobalt increased after stationariness. The isothermal viscosities showed concave curves. Activation energies increased monotonously by adding all the elements into nickel. These phenomena were considered to be related to the thermodynamic properties such as the heat of mixing and the structures of mixture melts.

Jan 1, 2003

By John C. Taylor

With growing emphasis on energy conservation and increased concern over the presence of heavy metals in the environment, it is fortunate that most metals are readily recycled. In this respect, metals have a significant advantage over plastics and similar materials used as metal substitutes. For many years a secondary industry has processed scrap copper, nickel, lead and zinc to produce refined metal which has, to varying degrees, influenced the price and displaced the production of primary metal. This paper reviews some of the challenges the industry will face and the changes in process technology which will be required as pressure mounts to increase the amount of metal recycled. In the case of most base metals, this will have an impact on primary metal production; as the tonnage of metal recycled increases, the requirement for primary production, or new metal, will depend more and more on the growth in consumption.

Jan 1, 1993

By A. Haxhiaj, E. Haxhiaj

"The paper has as a studying object the issue of effective management of gasses’ heating and dusts in reductive melting process in lead (Pb) metallurgy. It also analyses the issue related to the usage and recycling of dusts and gasses in all pyro-metallurgical processes of technical lead production. The paper contains the analysis of technological process of separation of humidity, gasses, and dusts of valuable remainders in “Trepça” plant. Paper has the results of theoreticalexperimental studying, analytical and graphical of gasses thermal balance depending on height and composition of load, and the coke quantity on load for reductive melt in “Water-Jacket” furnaces. With thermal balance, having into consideration all parameters of heat in entry and exit depending on aforementioned factors we aimed to optimize the parameters of the process, keeping the attention to the minimization of energy consumption, and the overall influence on environment.1. IntroductionThe upper part of the furnace which is the study point of this paper lies from the reactions zone of Water-Jacket furnace and it also includes the furnace neck. In this zone has been elaborated the zonal material balance referenced third in the row. The separation of humidity, dusts, gases and lead with gases depends on many parameters like temperature, load composition, and height of load inserted in the furnace, and also the height of preheating zone in Water-jacket furnace. Lead oxidizes in reaction zone of the furnace and exhales with gases like dusts and small particles after which falls in worthy storage of Trepça plant and has negative effects in environment, and economic stability of reductive melting process of Water-jacket furnace. Thermal balance of gases in this zone depends on many factors; height and load composition, coke quantity in a load. The calculation has been done as the standard methodology of thermal calculation is done; moreover, by using a computer for mathematical models which enables very accurate results. We must emphasize that acquired and used heat in reaction zone and melted materials is calculated in others studies, so their influence in preheating zone is assumed."

Jan 1, 2010

By A. G. Jackson, Rand R. Biggers, John D. Busbee, Iman Maartense, David P. Lubbers, David C. Liptak

"This paper describes the application of Raman Spectroscopy for characterizing superconducting YBCO thin film parameters. Attenuation of the substrate Raman spectrum as a function of material deposited is established. Also a correlation between film quality and Raman spectrum is explored. The identification and discrimination of superconducting and non-superconducting phases of YBCO is presented. The critical temperature (Tc) of a film as a function of its oxygen content is also established using Raman peak ratios. These results provide significant implications toward the use of Raman Spectroscopy for in situ monitoring and control of the PLD process. Film quality can be controlled via optimization of film oxygen content and reduction of improper YBCO phases. Film thickness can be controlled by monitoring the response of the substrate material. Also the PLD process can be studied and modeled using this powerful observation tool.IntroductionSuperconductors are materials that possess unique characteristics when cooled to sufficiently low temperatures. Below a material's critical temperature (Tc) it exhibits zero resistance to current flow. One such material, yttrium barium copper oxide (YBCO) has a critical temperature of approximately 92° K. Due to its high critical temperature YBCO is being aggressively researched for many possible applications, because of high current carrying capability and strong pinning of flux lines.YBCO in the 123 form is a ceramic material that was discovered in February, 1987. Its unit cell structure is shown in Figure 1 [ 1,2]."

Jan 1, 1997

By Dirk Bergmann

During the spray forming process, a continuous molten metal stream is atomized by impinging high speed inert gas jets. In the generated spray cone, the resulting metal droplets are rapidly cooled by the huge temperature difference to the surrounding gas phase and thereby partly solidified during flight. After a certain flight and residence time inside the spray cone, the droplets impinge onto the solid substrate and form the product (deposit) by compaction. Material properties of this preform strongly depend on several process parameters and especially on the thermal and kinetic state of the deposited droplets at the point of impingement. Smaller droplets may cool very fast due to their low mass and impinge onto the product in a completely solidified state as solid metal powder particles. Larger droplets with big mass contain a higher amount of thermal energy and impact during the state of phase change or still as completely liquid. It is obvious, that a certain amount of liquid content in the droplets is needed for forming a homogeneous deposit. Therefore, the thermal history of metal droplets during flight in the spray cone is of great importance for overall process modelling and control. Modelling the effects of the impinging droplet mass on the formation and heat balance of the deposit, the thermal conditions of the droplet stream need to be temporary and spatially averaged at different locations. Averaging may be achieved in different ways, giving alternative results. A first method is averaging over the droplets total enthalpy which consists of the thermal content and the remaining latent heat of fusion within the droplets. A second method may yield the average over the heat content and the solid fraction separately. Results of these two methods depend on the application and the kind of information which one wants to achieve and show some deviations, which will be discussed in terms of consolidation and energy conservation of the deposit.

Jan 1, 1999

By Reza Rahimi, M. Nili Ahmadabadi

"Because of high cost and shortage of primary resources of Ni-base superalloys, revert alloys can be used as a part of charging materials for production of superalloys ingots. The current study is based on recycling of IN738LC, a Ni-base superalloy, using 30% and 50% reverted alloy and balanced amount of virgin raw materials. Therefore, it has been attempted to cast an alloy with references to standard chemical composition and mechanical properties. After charging and casting in vacuum melting furnaces, chemical composition verification and non-destructive tests (i.e. Penetration and Radiography Tests), quality of samples were evaluated at elevated temperature by stress-rupture test. Results acquired from chemical composition and mechanical test indicate that cast ingots using 30% and 50% reverted alloy is reliable and consistent with the quality control requirements.IntroductionIn recent years, there have been many fluctuations in cost and availability of raw materials which are extremely determining in Ni-base superalloys production. Accessibility to the high purity metals such as Cobalt, Molybdenum, Tantalum, Niobium and etc. have been problematical during the past decades. Therefore, shortages of critical raw materials beside the economical considerations motivated the alloy suppliers and investigators to study and find alternate sources such as reclamation and recycling of scraps [1].There are a lot of reasons for the necessity of recycling; perhaps the most justifiable one is that consumers themselves produce scraps. For example, the weight of a finished superalloy product could be less than one-third of the cast alloy weight and in the case of complicated machined parts; this portion may reach to one-tenth [2]. High values of constituents, reduction of energy consumption and environmental concerns have all strengthened the obligation of recycling in Ni-base superalloys.Because of the high degree of risk in usage of improper materials for production of turbine blades, a delicately controlled program for recycling is needed. Depending on the type of scraps, this program can define the recycling procedure, required instruments, allowable percentage of scrap for usage and finally confidence level of the process."

Jan 1, 2012

By F. Chabchoub

A mathematical model has been developed to study the influence of process variables on the horizontal Ohno continuous casting process. The model simulates the heat transfer and fluid flow in a wide plate ingot of pure tin. A two dimensional numerical analysis based on a control-volume finite difference approach, the Semi-Implicit Method for Pressure-Linked Equations algorithm (SIMPLER), and an Enthalpy Transforming Model was used. The shape and position of the solid-liquid interface were calculated at different casting speeds, ingot thicknesses, and cooling device characteristics, as well as various mould temperatures. Results of the mathematical model were compared with

Jan 1, 1992

By W. D. Cho

Fast dissolution of nonmetallic inclusions such as alumina particles in molten slags has been required in secondary steelmaking -ladle and tundish - to minimize the amount and the size of nonmetallic inclusions in steel products. In the present work, the dissolution behavior of alumina particles in molten CaO-A12O3 and CaO-A12O3-SiO2 slags at the temperatures between 1450 and 1550°C have been investigated in terms of kinetics and mechanism. Alumina particles were added directly into the slags and the variation of the particle size with time was determined using optical and electron microscopies. The conventional types of slag for ladle and tundish were included in the dissolution study. The effects of Al2O3, Siq, CaF2 and MgO contents on the dissolution rate of alumina particles have also been determined. The diffusion boundary layer between alumina particle and bulk slag phase has been observed and analyzed using SEM and EDS. Based on the analysis of kinetic data and the boundary layer, the dissolution mechanism has been discussed.

Jan 1, 2002

By Baokuan Li, Qiang Wang, Zhu He

"A mathematical model has been developed to investigate the magnetohydrodynamic (MHD), thermal, and solidified behavior in electroslag remelting process. Based on the finite volume method, a multiphase coupling MHD approach is employed to investigate the droplet formation as well as movement in molten slag under the action of an alternating current. The VOF formulation is adopted for interface tracking. The electrical potential method is adopted for the electric current and magnetic field. The Electromagnetic force and Joule heating are recalculated at each time step and then is implemented in the momentum and energy equations as a source term, respectively. Moreover, solidification of the metal is described by an enthalpy-based formulation, while the mushy zone is treated as a porous medium with porosity equal to the liquid fraction. The model is used to investigate the effect of electrode tip shape on MHD, thermal, and solidified behavior and provide valuable information.IntroductionElectroslag remelting (ESR) process has been used widely to produce high-performance alloys dedicated to critical application, such as hot work tool steels, nickel base alloys, the manufacture of components in aerospace and landbased turbines, etc. Figure 1 shows a schematic diagram of ESR process including a consumable electrode, a molten slag pool, a liquid metal pool, a solidified ingot, and a water-cooled mold. Alternating or direct current flows from the electrode to the water-cooled baseplate through the high resistivity calcium-fluoride-based molten slag which result in Joule heating and Electromagnetic force (EMF). Part of the Joule heating melts the electrode and the droplets travel through the slag and accumulate the liquid metal pool. The electrode is continuously advanced into the slag as it melts to build up an ingot of improved structure and composition by controlled solidification and chemical refinement. The metallurgical properties of the remelted ingot are really related to the solidification structure, which strongly depends on magnetohydrodynamic, thermal, and solidified behavior in the molten slag, liquid metal pool, and mushy zone."

Jan 1, 2014

By Susanne Pignolet-Brandom

Fourteen samples of crushed Duluth Complex rock were characterized by the QEM?SEM automated scanning electron microscope image analysis system to evaluate the application of the system to mining waste rock characterization. The system can reliably distinguish the iron sulfides, the copper-iron sulfides and the nickel-iron sulfides. Calcite was distinguished from all other minerals except fluorite. The volumetric abundances were verified by comparing elemental abundances calculated using the QEM"SEM volumetric percentages and appropriate mineral compositions with elemental abundances determined by standard laboratory procedure. The pH and sulfate concentrations of rinse water from laboratory leach experiments correlated well with the mineralogical data.

Jan 1, 1989

By Natasa Mitevska

The statistical analysis of the slag composition influence on copper losses to discard slag in the reverberatory furnaces No.1 and No.2 in the RTB BOR, Copper Smelter and Refinery (Yugoslavia) is presented in this paper. The model for the slag basicity calculation is determined, and connected to the copper distribution coefficients between the matte and slag phase. The influence of all components on the slag structure is also illustrated.

Jan 1, 2003

By Alan J. Hurd

"New insights into the development of microstructure in sol-gel films have recently been revealed by several diagnostic techniques, including imaging ellipsometry, ""chemical imaging"" by fluorescent tracers, light scattering from capillary waves, and finite-element modeling. The evolution of porosity during the continuous transition from dilute sol to porous solid in restricted geometries such as films and fibers is becoming clearer through fundamental understanding of evaporation dynamics and capillarity.IntroductionWith sol-gel processing, the full flexibility of solution chemistry can be exploited to make ceramic films and fibers with well controlled compositional characteristics. No less important is the ability to tune porosity and connectivity for specific applications such as optical and electrical coatings and membranes. Since the chemical and physical factors that determine the microstructure are not entirely understood, new diagnostics applied to sol-gel processing are welcome.Sol-gel films and fibers are distinguished by processing that takes a sol through continuous stages of increasing concentration and connectivity of a solid precursor. The liquid carrier is usually volatile or, at least, volatilizable through heat treatment. During deposition through states of increasing solids concentration, this sol might gel, as in bulk sol-gel processing, however, the gel state may be a fleeting transient that quickly empties of liquid. Nevertheless, the structures formed in solution during this stage influence the structure of the final solid. In particular, porosity is likely to be a remnant of networks formed in the sol-to-gel transition. Here we report on experiments whose goal is to discover the factors involved with porosity development."

Jan 1, 1994

By Jun Iwai, Osamu Takai, Yasushi Inoue, Hiroyuki Sugimura

"Infrared reflection absorption measurement was performed during plasma-enhanced chemical vapor deposition of silicon dioxide films at room temperature. Hydrocarbon contaminants adsorbed onto growing film surface are oxidized by oxygen radicals in plasma resulting functional groups which include C=O and C-O bondings. These groups exist only near the surface and are hydrolyzed rapidly after exposure to air.IntroductionRecently low-temperature silicon dioxide (SiO2) deposition has been in a growing industrial demand in pa1ticular, polymelic substrates such as polycarbonate and polyethylene telephthalate, which have poor heat resistance, need low process temperature (near room temperature) in coating of SiO2 which is a suitable material to improve optical and mechanical properties of polymenc products. Plasma enhanced chemical vapor deposition (PECVD) using organosilicon reactants is one of the most promising technique for lowering process temperature, so that it has been extensively studied1-12. In the present; however, hydrocarbon contaminants and a plenty of Si-OH termination in Si-O-Si networks tend to exist in the films, which degrade mechanical, optical and electrical properties of the films. It is necessary to understand the deposition mechanism at, low temperature in order to solve the problems. We have studied the low-temperature PECVD of Si02 by spectroscopic diagnosing techniques such as optical emission and mass analysis6-7, 11- 12Infrared reflection absorption spectroscopy (IR-RAS) has been a well-established technique for characterization of thin films on metals as· well as on semiconductors and insulators13-17. In this paper, we report on' the surface reaction of room-temperature PECVD of Si02by using in situ IR-RAS."

Jan 1, 2000