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By Marcela C. Santini, Luiz A. Teixeira

"Surface conditioning (also referred as etching) of plastics prior to metallization is generally conducted with sulfuric I chromic acid solutions. Although these baths perform well technically, the presence of Cr (VI) imposes serious operating problems of an environmental nature. The present work reports ·the results of a study of surface conditioning o(ABS using solutions based. on sulfuric acid, with hydrogen peroxide and/or nitric acid, replacing chromic acid, as oxidants. Process performance was evaluated by SEM and by the uniformity and adherence of electroless nickel coatings applied on selected conditioned samples. The results showed that the evaluated types of solutions could be optimized to perform as well as the chromic-based baths, with a much superior environmental quality.IntroductionMetallization of plastics is normally undertaken for either decorative or functional purposes. Through metallization, the specific properties of plastics such as light weight, design flexibility, and low-cost of manufacturing are enhanced by the addition of properties usually associated with metals. These include reflectiveness, abrasion resistance, electrical conductivity, and a variety of decorative effects (1).The available processes that can be used for metallization of plastics are vacuum metallization or vapoµr deposition; indirect metallization and plating (1). Plating can be sub-divided into electroless plating and electroplating. In electroless plating, metal ions in aqueous solution are deposited on the .activated plastic surface by oxi-reduction reactions without the aid of an external electric potential, forming a thin metallic layer. This electroless deposited film has two functions: (a) it provides an electrically conductive substrate that allows further coating by electroplating; and (b) provides a secure bond between the plastic substrate and the electroplated layer (1,2). In case the electroless metallic part requires an additional layer for finishing purposes, or just an increase in thickness, the part can be additionally electroplated with a· variety of metals - in most cases those are copper, nickel or chromium (3)."

Jan 1, 2000

By R. T. Hernández, I. Hilerio, A. Altamirano, M. A. Barrón

"The principal objective for finishing surfaces is to protect and/or to decorate them. This can be achieved by adding or removing material from the work surface. The addition of aggregated material is called coating or recovering. In this work, mecano-chemical techniques are investigated for surface finishing. For these techniques, barreling or polishing by the friction method will be used. These are the cleaning or finishing processes most used for great volumes of small pieces. These methods improve the surface finishing by eliminating burrs, sharp pointed, tool marks and crusts of casting. They are used to clean metallic pieces, ceramics and polymeric materials. The process is based on rubbing or friction by abrasives. The pieces are arranged in the barrel with an abrasive and an additive (water or chemical additive). The machine produces a rotating movement on the pieces. When the abrasive passes against the surfaces of the pieces, it produces an action of rubbing and impact that cleans the surfaces. The rubbing action is developed when the upper layer of the charge slides to the lower extreme when the barrel rotates. The barrel can be hexagonal or octagonal to facilitate the sliding of the charge. The barrels can be between 15 to 120 cm in length and they can have almost any diameter and velocity of rotation. There are several types of barrel: individual, multiples, and multiple compartments. The barrels are rotated using a wheel spindle or rolling pins, that the can ride horizontally or be tilted to produce an additional movement of the charge.IntroductionShot penning is a cold method in which compressive effects are induced on an exposed surface of a metallic piece, by the impact of a rain of shots directly on the surface of the metal, at great speed under controlled conditions. This differs from cleaning with the help of air, because even when shot penning cleans the surface of the metal, this function is incidental. The main purpose of shot penning is to increase the resistance of the piece to fatigue. The process has other applications: raises the tensile strength and decrease corrosion fracture."

Jan 1, 2012

The resist profile simulation is carried out using the combined data obtained. The nematic liquid crystal is clear only when a long range order exists, in the whole medium. using the Jones matrix method. Director can change from point to point and is, in general, a function of space. Details of the lens structure and of the devices fabrication and performance are described. Light from conventional light source or laser is passed through a polarizer and then incident on the specimen At the nematicisotropic, transition temperature, the medium becomes isotropic and looks clear and transparent. The transition can be approached by changing the impurity concentration or, indirectly, by tuning the temperature since the pinning strengths of the random and crystal potential have in general a different temperature dependence.

Jan 1, 2006

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

By E. Ilgar

"Deposition studies were conducted in acid copper electrolyte to determine the influence of chloride ions on cathode morphology. A statistically designed screening test was carried out in the absence and presence of 20 ppm CI- using a three factor, two level factorial design, in an electrolyte containing 36 gl'! Cu2+ and 150 gl-! H2S04, The independent variables evaluated were agitation; current density and temperature and their influence on surface roughness was determined. The copper deposited at current densities where activation was the primary control mechanism appeared similar in morphology whether stirring was used or not. The addition of 20 ppm CI- to the electrolyte gave rougher deposits under the same conditions. In the mixed control regions, considerably rougher, dendritic deposits were obtained when CI- was present. Agitation was effective in reducing the copper surface roughness both in the apparent activation and mixed control regions in the presence ofCI-. The results of this study showed that 20 ppm Cl- polarized the copper deposition at low overpotentials but caused depolarization at higher overpotentials.IntroductionChloride ion is inherently present in copper electrolyte, either as an additive or from other sources such as make up water. The behavior of the chloride ion is well documented in electrorefining operations, but its role in copper winning is less obvious. However in both cases there is evidence that cathode growth and solution chemistry are strongly influenced by its presence. The mechanism and electrochemical action of the Cl"" have been shown to be very complex, therefore a better understanding of its influence on electrocrystallization is essential for improved cathode deposit growth control. It was proposed that Cl"" polarizes the copper deposition reaction at low concentrations due to CuCI formation but depolarization occurs at higher concentrations due to the formation of a soluble CuCI2"" complex [1,2]. Franklin [3] reviewed the mechanism of additives in the electrodeposition process and proposed that the Cl"" complexed with copper, adsorbed on the cathode as an induced anion leading to an increase in the reduction rate. At cathodic overpotentials less than 100 mY, lppm NaCl had a polarizing effect, i.e. an increase in impedance of the charge transfer step. At higher Cl"" concentrations up to 100 ppm, depolarization occurred as evidenced by a decrease in impedance, which was attributed to soluble cuprous complexes [4]."

Jan 1, 1997

By Soumendra Basu, Uday Pal, Yang Yu, Srikanth Gopalan, Karl Ludwig, Deniz Cetin, Jacob Davis

"A limiting factor for Solid Oxide Fuel Cell (SOFC) performance is the oxygen reduction reaction (ORR) at the cathode surface. Changes in the surface composition and structure on annealing at 800°C has been studied, since these can influence the ORR. Idealized single crystals of cathode materials La0.8Sr0.2MnO3 (LSM) and La1-xSrxCoyFe1-yO3 (LSCF) were grown as heteroepitaxial thin films on lattice matched single crystal substrates. Changes upon heating the films to operating temperature and pressures were characterized using various synchrotron x-ray techniques. Total Reflection X-ray Fluorescence (TXRF) measurements, which probe compositional changes, were made at high temperature in real time. The LSM surfaces were found to develop manganese enrichment when heated. Highly strontium doped LSCF were found to develop strontium-rich surfaces. HArd X-ray PhotoElectron Spectroscopy (HAXPES) was used to investigate the electronic structure of the materials. Highly strontium doped LSCF precipitates a surface strontium phase that contains both oxide and carbonate contributions.IntroductionSolid oxide fuel cells (SOFCs) are chemical to electrical energy conversion devices that could potentially reshape how energy demands are fulfilled. SOFCs have a potential efficiency over 70%, fuel flexibility, low emissions, and low degradation over long time scales. Commonly, SOFCs are operated at high temperatures (above 800°C). At these temperatures expensive housing is needed to contain an operating stack as well as coatings to contain the oxidation of the metallic interconnects. Lowering the temperature of an operating device would allow for more conventional materials to be used, thus lowering overall cost. Understanding the reaction kinetics of the oxygen reduction reaction at the surface of the cathode is vital to designing a system that will perform well at lower temperatures. A commercialization goal is to reduce operating temperatures without sacrificing performance.In order to exploit the advantages of SOFCs, an understanding is needed of the surface chemical states of cations on the surface of the cathode and how this relates to the oxygen reduction reaction (ORR):"

Jan 1, 2014

By Kazuteru Tozawa

Surface tension, density and viscosity coefficient of acidic copper sulfate solutions simulating electrolyte solution for electrolytic production of copper have been measured and are summarized as a function of the solution composition and temperature. Nickel sulfatc is taken to be a representative coexisting sulfate that affects the physical properties of the copper sulfate electrolyte solution. The sulfates in the solutions, including sulfuric acid, increase the physical properties under consideration. Gelatin, representing organic additives for electrolyte solution, was found to sensitively affect the surface tension of the solution at low concentration of up to 200mgIL. The surface tension was markedly lowered by the addition of gelatin and the increasing concentration of gelatin led to a more pronounced decrease in the observed values. The surface tension gradually increases with time after addition of gelatin and the increase is enhanced by higher acid concentration and higher temperature. The observed change in the surface tension is considered to reflect the preferential adsorption of gelatin to the bubble-solution interface and the decomposition of gelatin due to hydrolysis to form various molecules having smaller molecular weights.

Jan 1, 2003

By Mehdi Asgharifar, Rouzbeh Sarrafi, Radovan Kovacevic

"The surface treatment of aluminum alloys using atmospheric-pressure of low intensity DC plasma arc discharge is investigated in terms of surface properties. With respect to the conventional surface treatment processes for aluminum alloys mostly based on chemical etching or sand blasting, this process is very environmentally friendly and cost-effective. The effect of two processing parameters, the current and the plasma torch scanning speed, on the surface morphology is studied by using a scanning electron microscope. The effects of cathode spots within the tested range of process parameters are determined, and the limiting factors of the process (such as surface cracking) are discussed. The topographical studies of the treated surfaces have suggested potential enhancement of surface properties for different applications, such as preparing surface for painting and adhesive bonding.IntroductionIn the last decade the aluminum alloys are finding broad applications in automotive industry. In order to successfully execute the joining process of aluminum alloys such as arc welding, laser welding, and adhesive bonding, there is a need to remove oxides for welding and texture the surface for bonding along the join line. A number of surface treatment techniques such as chemical etching, sand blasting, and plasma treatment have been used by industry. It is shown [1] that plasma surface treatment is characterized as environmentally friendly, lower cost, and easier to control process. Bogaerts et al. [1] mention that when an adequately high potential difference is applied between cathode and anode, electrons are accelerated toward anode by an electric field coming in collision with gas atoms. The gas breaks down into positive ions and electrons, giving rise to gas discharge. The DC electrical discharges used in industrial plasma sources can be related to their location on the voltage-current curve as shown in Figure 1.It is generally believed that dark discharges other than coronas, and arc or torch plasmas are not very good candidates for surface treatment because oflow or high power density and active species flux. However, the glow discharge plasma is used for plasma surface treatment applications because of its proper power density and active-species flux [2]. Our objective is to investigate the feasibility of using low intensity DC plasma arc discharge as a surface treatment method without damaging the cathodic non-thermionic workpiece."

Jan 1, 2011

By Susumu Okabe

Top blow injection has been applied to continuous copper smelting and converting by Mitsubishi Materials Corporation since 1974. In this process, injected feeds are captured by and dispersed in the molten bath immediately and effectively, and the reaction is enhanced by the agitation of the bath. The continuous motion of the molten bath, however, may cause severe damage of furnace lining materials, if the injection is not controlled and the furnace is not designed properly. In order to suppress refractory wear, especially at the bath line, surface wave of the molten bath should be moderated. A cold model study was carried out with water bath in a cylindrical vessel and the physical model was derived which correlates the oscillation of gas jet impingement on the bath surface and the surface wave. It was found that a half of the proper frequency of the gas jet impingement coincides the proper frequency of the surface wave.

Jan 1, 1998

By K. Watling

Vibrational spectra of surface and solution compounds formed during cyclic voltammetry of a gold electrode in a deoxygenated 0.01 mol dm-3 NaCN solution have been examined using surface-enhanced Raman scattering (SERS) spectroscopy. The presence of cyanide at the electrode surface was indicated by Raman bands characteristic of the carbon-nitrogen stretch, CN.. Chemisorption of cyanide on the gold surface was evidenced by the presence of vibrational modes due to gold-carbon stretching, AuC, and gold-carbon-nitrogen bending, AuCN. Prior to the disappearance of the surface cyanide stretch band, a limiting value of the CN was obtained, the same as the value reported for adsorbed cyanide. Effects upon the voltammetry and vibrational modes of surface species due to additions of silver and lead to the gold-cyanide system have been observed.

Jan 1, 2003

By G. A. Bala

As part of ongoing research to define mechanisms of microbial enhanced oil recovery (MEOR), this work describes the activity of Bacillus l1chen1formis JF-2 (ATCC 39307) Mosurfactant against crude oils with varying compositions. Surfactant based MEOR improves oil recovery by lowering the oil/brine interfactal tension (IFT) therefore permitting oil to be displaced or solub1lized into the aqueous phase.? MEOR is an Enhanced Oil Recovery (EOR) process which allows for the introduction of chemical and miscible fluids, in the form of microbial metabolic end-products, through the injection of microorganisms into the reservoir or stimulation of indigenous reservoir microbial populations. These microorganisms represent a replenishable in situ source of acid, gas, biopolymer, solvent, or surfactant products which can be. supported and manipulated by the addition of simple and inexpensive nutrients to enhance the recovery of oil. Microbially mediated surfactant production represents one mechanism of MEOR. Bacillus licheniformis JF-2. has been used in a mode 1 MEOR system based on Berea sandstone cores (permeabilly .85 to 400 md) to examine surfactant based MEOR of medium to heavy crude oils (API gravity 38.1° to 17.5°). Enhanced oil recovery was achieved with all oils tested using either cell free culture supernatants or microbial suspensions as injectants with no detrimental effect to the oil. Spatial distribution of cells following mf?crobtal flooding was analyzed with scanning electron microscopy. Data indkate complete distribution of cells with a predominance of organisms located distal to the point of injection. There appears to be no sign:if1cant recovery trend with respect to oil composition.. The biosurfactant produced by Bacillus lichen1form1s JF-2 lowers the interfacial tension of all oils tested equally well.

Jan 1, 1991

By H. Y. Sohn, Joshua E. Ramos, Moo Eob Choi

"A new technology for ironmaking based on direct gaseous reduction of iron ore concentrate is under development. This technology would drastically lower CO2 emission and reduce energy consumption by nearly 38% of the blast furnace requirements. Experiments were performed using iron oxide concentrate at 1150oC in a bench-scale facility, which was the highest temperature that could be reached in the facility. The reduction extent was determined at residence times of 3.5 - 5.5 seconds in which the reduction extent approached 43% with 0% excess H2 and 95% with 860% excess H2. Separate kinetics measurements showed that the rate is much faster at 1200 - 1400 oC. Experiments were also carried out using syngas (mixtures of H2 + CO). About 90% reduction in 3.5 seconds with 860% excess hydrogen contained in the syngas demonstrated sufficiently fast reduction for a suspension process and the feasibility of usingsyngas instead of pure hydrogen.IntroductionDespite the improvements in the modern blast furnace (BF) process, it suffers from many drawbacks. The process requires the feed in the form of sinters or pellets and high-grade coking coal. Thus, BF iron production is projected to decrease gradually [1]. The main factors for this are the environmental regulations [2] and the high capital investment cost.A large number of new ironmaking technologies have been developed or are under development [3]. Most of these processes, however, are not sufficiently intensive to replace the blast furnace because they cannot be operated at high temperatures due to the sticking and fusion of particles. Therefore, a new technology is under development for producing iron directly from fine concentrates by a gas-solid suspension technology, which would reduce energy consumption by about 38% of the amount required by the blast furnace and drastically lower environmental pollution, especially CO2 emission, from the steel industry."

Jan 1, 2009

By R. G. Henley

Mount Isa copper concentrate was combusted in a laminar-flow furnace. The conditions simulated those likely to be encountered in flames in flash smelters of the Outokumpu (air as oxidant) and INCO (oxygen as oxidant) types. The range of conditions studied was as follows: T 400-1400°C, 02 0-100%, SO2 0-95% for residence times up to 0.23 s. The distribution of sulfur, arsenic and lead between the particles and the gas phase was studied. Combustion was very rapid provided the concentrate was adequately dispersed, i.e., no agglomerates. The importance of the latter is discussed. It was possible to oxidize 80% of the sulfur present in the con¬centrate after only 0.1 s reaction time at 1000°C in an atmosphere contain¬ing 8.5% 02 and 12.5% SO2. Best volatilizations (90% of the As, 52% of the Pb) were obtained under localized conditions attained in an air-type flame. Average volatilizations were: air-type flame, As 50%, Pb 32%; oxygen-type flame, As 40%, Pb 30%. The substitution of oxygen for air reduced the arsenic volatilization. The products of combustion were mainly cuprospinel and cuprite; small inclusions of elemental copper were found in some of the particles. At high temperatures, there was a loss of copper due to vaporization of CU( g) CuO kg) (g)

Jan 1, 1983

By W. John Rankin

Professionals, technical and non-technical, working in the mineral and metal commodity industries need to understand the concept of sustainability and its implications for the industry. Undergraduate courses have not done this well in the past. Much has been written in this field, and there have been great advances in understanding. However, much of what has been published is superficial and sometimes misleading, and there is as yet no coherent, single account that can serve as an introduction or overview for mineral industry graduates. This paper presents an outline which can guide readers in developing an understanding of the topic and its relevance to their work. Key references are provided, particularly those accessible on the internet, which will serve to introduce the reader to the important principles and understandings. The guide should also be useful to academics preparing students to work in the minerals and metal production sectors.

Jan 1, 2010

By W. John Rankin

The finite and non-renewable nature of mineral resources poses unique challenges for sustainability: How can mineral and material needs of society be satisfied indefinitely? How can the benefits of exploitation of minerals best be captured for present and future generations? How can the environmental problems caused by large scale mining and processing best be ameliorated? These issues are rarely addressed, or if so only incidentally, in traditional courses in geology, mining, metallurgy and materials yet addressing them will increasingly be a major role for professionals in the minerals and materials industry and related sectors and agencies. This paper describes a framework for examining these and other sustainability issues related to meeting future material needs from non-renewable resources. The framework may be useful for educational purposes, either as the basis of a dedicated subject or by including the elements of it throughout a traditional course in relevant subjects.

Jan 1, 2014

By Thomas P. Battle

Modern-day direct reduction of iron first developed as a small-scale, low capital and operating cost alternative to the blast furnace. Since commercialization of continuous DR technology in the late 1960s, the market for the products of direct reduction has grown to more than 74 million tonnes in 2012. The initial advantages of DR plants over BF facilities have grown over the years, for several reasons, including the increased size of DR modules, lower energy and emissions (particularly CO2), along with the flexibility to use a number of different reductants. The development of DR technology over the past forty years will be emphasized in this presentation, including recent developments that allow for even more direct sustainability comparisons with the iron blast furnace – and even combine the two technologies for improved synergies. Also briefly discussed will be the possibilities of using direct reduction for non-ferrous ores.

Jan 1, 2014

By Rameshwar Sreenivasan

This paper presents a sustainability analysis of Selective Laser Sintering (SLS) from an energy standpoint. Data of electrical power consumed by the system over an entire build were acquired using a LabVIEW 8.6 circuit. The power drawn by individual subsystems was also measured, and an energy balance was performed. These data were then used to arrive at a Total Energy Indicator of the process with the help of a specific type of Environmental and Resource Management Data (ERMD) known as Eco- Indicators, which indicates the level of sustainability of the process.

Jan 1, 2010

By Jyri Talja, Shaolong Chen, Hannu Mansikkaviita

"Drying (water removal) prior to smelting is always economically feasible. Unnecessary heating of vapour can thus be eliminated resulting in savings of5-15 MUSD every year.Thermodynamically removal of one ton of water out of copper concentrate at 100 °C (with 10 % moisture) requires approximately 3150 MJ/tH2o, consisting of heating of the water (377 MJ), heating of the concentrate (509 MJ) and water evaporation (2260 MJ). This is quite independent of the selected drying technology. In reality some more heat is needed as higher temperature is practiced to enhance the drying performance and to reduce the equipment size.Major nominator in drying energy efficiency is amount of gases, which depends greatly on the drying technology. Dryers based on direct heating with fossil fuels have high gas flow rates, and thus they require additional energy of about 1400-1600 MJ/tH2o, compared to indirect modemsteam drying at 250-400 MJ/tH2o.Significant benefits in energy consumption (900-1300 MJ/tH2o) with additional potential for a bonus profit of 2-4 MUSD/y year, together with full elimination of some 40 000 tpy CO2 per mid-size dryer is available by selecting sustainable, energy efficient steam drying.IntroductionRemoval of water from the concentrate is very energy intensive thus having a significant environmental impact. However, drying prior to smelting is always economically feasible and very often viable also from the perspective of process operations. This environmental impact of drying can, however, be decreased or even fully eliminated with proper selection of the drying technology.Energy incorporated in drying consists always of a number of phases like liquid (water), solids (concentrate) and gases (water vapour, purging I dilution air, combustion gases). Each phase is heated to a specific temperature during the drying process.Heating of water, heating of the concentrate and water evaporation consumes more or less the same amount of energy despite of the drying technology (3150 MJ per ton of water). In conventional drying this amount of energy is achieved by combustion of fossil fuels wirg subsequent CO2 emission. Alternatively, chemical energy derived from sulphide smelting can be utilized in a form of steam thus generating zero emission ofCO2, in modem steam drying."

Jan 1, 2012

By Krishna Parameswaran

This paper illustrates sustainability considerations in copper hydrometallurgy using examples of practices at ASARCO LLC, an integrated U.S. primary copper producer. Using the classic Brundtland Commission development of sustainable development, i.e., “development that meets the needs of the present without compromising the ability of future generations to meet their own needs,” the paper discusses how copper hydrometallurgical processes can be sustainable. The examples used to illustrate sustainable development and related concepts include: water conservation opportunities in milling and leaching operations; implementing green chemistry and promoting product stewardship in the electrorefining of copper.

By Krishna Parameswaran

This paper discusses sustainability considerations in primary copper smelting using selected examples of practices at ASARCO LLC, an integrated U.S. primary copper producer. Using the classic Brundtland Commission definition of sustainable development, i.e., “development that meets the needs of the present without compromising the ability of future generations to meet their own needs,” the paper discusses how copper mining and smelting practices can be made sustainable. The examples used to illustrate sustainability considerations include: (1) adoption of flash smelting; (2) emission reduction and process improvement associated with anode refining of blister copper and the converter retrofit project, and (3) preliminary research findings on alkali treatment of copper smelting slags and copper mine tailings.