Conductive polymer coatings for anodes in aqueous electrowinning

This article discusses the potential application of electrically conductive polymers as protective coatings for permanent lead anodes employed in aqueous electrowinning processes. Also presented are results from a preliminary study of the performance of two intrinsically conductive polymers (polyaniline and poly 3,4,5-trifluorophenylthiophene [TFPT]) under mild copper electrowinning conditions as conductive and protective coatings on anodic surfaces. The laboratory results indicated that using lead alloy anodes coated with TFPT merits continued research. For more information, contact A.M. Alfantazi, the University of British Columbia, Department of Metals and Materials Engineering, Vancouver, Canada, V6T 1Z4; (604) 822-8745; fax (604) 822-3619; e-mail alfantaz@interchange.ubc.ca.     

The commercialization of the FENIX iron control system for purifying copper electrowinning electrolytes

The FENIX Hydromet Iron Control System was installed at Western Metals Copper Ltd.’s Mt. Gordon Operations in Queensland, Australia. The system uses a novel and patented ion-exchange resin to selectively remove iron from copper electrolyte at the solvent extraction/electrowinning plant. At Mt. Gordon, the system delivered significant savings in reagent consumption (acid and cobalt sulfate for electrowinning and lime for neutralization of the raffinate bleed) and has the potential to deliver higher current efficiencies in copper electrowinning, leading to increased copper production. For more information, contact D.B. Dreisinger, University of British Columbia, Department of Metals and Materials Engineering, Vancouver, Canada V6T 1Z4; (604) 822-4805; fax (604) 822-3619; e-mail drei@interchange.ubc.ca.     

Casting defects in low-pressure die-cast aluminum alloy wheels

Defects in automotive aluminum alloy casting continue to challenge metallurgists and production engineers as greater emphasis is placed on product quality and production cost. A range of casting-related defects found in low-pressure die-cast aluminum wheels were examined metallographically in samples taken from several industrial wheel-casting facilities. The defects examined include macro- and micro- porosity, entrained oxide films, and exogenous oxide inclusions. Particular emphasis is placed on the impact of these defects with respect to the three main casting-related criteria by which automotive wheel quality are judged: wheel cosmetics, air-tightness, and wheel mechanical performance. For more information, contact B. Zhang, the University of British Columbia, Department of Materials Engineering, #401B, 6350 Stores Road, Vancouver, BC, Canada V6T 1Z4; (604) 827-5345; fax (604) 822-3619; e-mail bzhang@cmpe.ubc.ca.     

Exfoliation corrosion of aluminum alloys and their protection by coatings with metal-filled primers

Exfoliation corrosion (EC) is shown to represent a special type of stress corrosion which develops under the surface of aluminum high-alloyed alloys like 16T and B95T1. Protection against EC by using common paint coatings (PCs) is ineffective. Indoor tests demonstrate that EC can be almost completely suppressed by using PCs with zinc-filled primers (ZFPs). After 2-year tests in sea tropics, common PCs do not prevent the appearance and development of EC. At the same time, samples protected by PCs that involve ZFP EP-057 demonstrate the total absence of EC including bare surface areas up to 5 and even 10 mm wide where the coating has failed. Similar results are obtained in 6-year tests in north sea atmosphere. Potentiodynamic studies of different protection schemes confirm the electrochemical protection mechanism of aluminum alloys against EC by using ZFPs. It is shown that ZFPs can also be used during maintenance works. The advantages of metal-filled primers based on polyurethane over those based on epoxy resin are shown.Translated from Zashchita Metallov, Vol. 41, No. 1, 2005, pp. 40–51.Original Russian Text Copyright © 2005 by Sinyavskii, Kalinin, Gladyshev, Yakimova.     

The scale-up and design of pressure hydrometallurgical process plants

This article reviews more than 45 years of experience in the scale-up of pressure hydrometallurgical processes, from the pioneering collaboration between Sherritt and Chemical Construction Company to current process development by their successor, Dynatec Corporation. The evolution of test work is discussed, from traditional pilot-plant operations using semicommercial equipment to small scale or minipiloting with equipment several thousand times smaller than commercial units. Nickel, uranium, zinc, and gold processes have been developed and successfully implemented in worldwide operations treating a variety of feed materials, including concentrates, ores, and mattes. Data on test work duration and the ramp-up of commercial plants are presented. For more information, contact B. Vardill, Dynatec Corporation, Metallurgical Technologies Division, 8301-113 Street, Fort Sas-katchewan, Alberta T8L 4K7, Canada; (780) 992-8190; fax (780) 992-8100; e-mail wvardill@mettech.dynatec.ca.     

A sulfuric-acid process with near-zero SO2 gas emissions

A sulfuric-acid process has been developed that is able to handle low and variable SO₂ concentrations with practically zero SO₂ emissions (less than 3 ppm). The plant comprises two stages—a single-bed converter contact plant and a modified tower plant. Acids of 95–98% and/or oleum with up to 32% free SO₃ can be produced in the first stage. Off-gas of the first stage is piped to the second stage, where the SO₂ is converted to near nontracability while producing 76% strong acid. It is then returned to the contact plant to produce stronger acid or oleum. This process does not generate any additional disposable waste. For more information, contact T. Keilpart, Process Engineering Associates, 707 Redway Lane, Houston, Texas, 77062; (281) 488-6633; fax (281) 488-2456; e-mail PEA@net1.net.     

The mineralogical transformation of a polymetallic sulfide ore during partial roasting

A partial desulfurization roasting process has been tested on a typical copper-zinc sulfide concentrate in a Nichols Herreshoff monohearth pilot furnace. In this process, the sulfur is partially removed and iron, to a certain degree, is preferentially oxidized. The mineralogical characterizations of the reaction products at different residence times enable the recognition of a sequence of reactions and various textural relationships during the roasting. The testing showed that a controlled desulfurization at a temperature as low as 650°C can lead to the decomposition of chalcopyrite, resulting in the formation of discrete particles of Cu₂S having a size ranging from five to 20 micrometers or more. For more information, contact L. Evrard, Universite Catholique de Louvain, Department of Materials and Processes Sciences, Place Sainte Barbe 2, B-1348 Louvain-la-Neuve, Belgium; +32-10-472-488; fax +32-10-472-488; e-mail evrard@pcim.ucl.ac.be.     

Pressure leaching las cruces copper ore

A hydrometallurgical process was developed for treating the Las Cruces massive sulfide-ore deposit located near Seville, Spain. A two-stage countercurrent leach process, consisting of an atmospheric leach and a pressure leach, was developed to effectively leach copper from the copper-bearing minerals and to generate a solution suitable for the subsequent solvent-extraction and copper-electrowinning operations. The results of batch and continuous miniplant tests are presented. For more information, contact W.D. Vardill, Dynatec Corporation, Metallurgical Technologies Division, 8301-113 Street, Fort Saskatchewan, Alberta, T8L 4K7 Canada; (780) 992-8190; fax (780) 992-8100; e-mail wvardill@mettech.dynatec.ca.     

Effect of directional solidification process on microstructure and stress rupture property of a hot corrosion resistant single crystal superalloy

The influences of different directional solidification processes, i.e., the high rate solidification(HRS) and liquid metal cooling(LMC), on microstructure and stress rupture property of DD488 alloy were investigated. The DD488 alloy was directional solidified by both HRS and LMC processes. The microstructure and stress rupture properties at 980 ℃/250 MPa were investigated by using optical microscopy(OM), scanning electron microscopy(SEM), electron microprobe analyzer(EPMA), transmission electron microscopy(TEM) and stress rupture testing. The results indicated that the LMC process refined the primary dendrite arm and decreased the microporosity volume fraction and solidification segregations of Cr and Co in as-cast DD488 alloy. After standard heat treatment of 1,260 ℃/4 h, AC(air cooling) + 1,080 ℃/4 h, AC + 870 ℃/24 h, AC, the γ′ morphology in LMC alloy was more cuboidal than that in HRS alloy, and the γ′ volume fraction of LMC alloy was higher than that of HRS alloy. The stress rupture life at 980 ℃/250 MPa of HRS alloy was 76.8 h, and it increased to 110.0 h in LMC al oy. The LMC process increased the stress rupture life due to the higher γ′ volume fraction, more perfect rafting structure and finer interfacial dislocation networks.     

Nickel hydroxide precipitation from aqueous sulfate media

Hydrometallurgical processing of laterite ores constitutes a major industrial and R&D activity in extractive metallurgy. In some of the process flowsheets, nickel hydroxide precipitation is incorporated. For these operations, the optimization of nickel hydroxide precipitation is important to assure efficiency and product quality. The main objective of this investigation was to study and improve the precipitation characteristics of Ni(OH)₂ in a sulfate system using supersaturation controlled precipitation. For more information, contact George P. Demopoulos, McGill University, Department of Mining, Metals and Materials Engineering, M.H. Wong Building, 3610 University, Montreal, Quebec, H4L 3Y9, Canada; (514) 398-4755, ext. 0266; fax (514) 398-4492; e-mail george@minmet.lan.mcgill.ca.     

Mesh-on-lead anodes for copper electrowinning

ELTECH System Corporation has developed and patented a Mesh-on-Lead™ (MOL™) (Mesh-on-Lead and MOL are trademarks of ELTECH Systems Corporation) anode for primary copper electrowinning operations. Over the past five years, ELTECH has demonstrated the MOL concept with full-scale anodes at several premier commercial tankhouses. During these demonstrations MOL anodes exhibited numerous performance advantages relative to standard Pb-Ca-Sn anodes, including reduced power consumption due to lower oxygen evolution over-potential, improved cathode quality, minimized lead sludge generation, eliminated cobalt addition as a result of stabilized lead substrate, and improved current efficiency due to reduced short circuiting. For more information, contact Michael Moats, ELTECH Systems Corporation, 625 East Street, Fairport Harbor, OH 44077; (440) 357-4074; fax (440) 357-4077; e-mail msm@eltechsystems.com.     

Synthesis and characterization of polyimides from triphenylamine-based diamine monomers with thiophene or trifluoromethyl side group

Triphenylamine-based novel diamine monomers with side group, such as 4-(2,2′-bithiophenyl)-4′,4″-diaminotriphenylamine (2TTPA) and 4-(3,5-bis(trifluoromehyl)phenyl)-4′,4″-diaminotriphenylamine (6FTPA) were prepared and used for polyimide synthesis. 4-Bromo-dinitrotriphenylamine (BrTPA), prepared from 4-bromoaniline and 1-fluoro-4-nitrobenzene, was reacted with 2,2′-bithiophenene-5-boronic acid (2TBB) or 3,5-bis(trifluoromethyl)benzeneboronic acid (6FBB), followed by hydrogenation to afford 2TTPA and 6FTPA, respectively. After characterization by FT-IR, ¹H-NMR, EA and melting point analyzer, the triphenylamine-based dimaines were utilized to prepare polyimides with 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) or 2,2-bis-(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA). The polymers were characterized by FT-IR and ¹H-NMR. Thermal, optical and electrical properties were also evaluated by DSC/TGA, UV–vis/photoluminescence spectrometery and cyclic voltammetry (CV), respectively. The 6FDA–6FTPA polyimide exhibited high glass transition temperatures (291 °C), high thermal stability (>488 °C) and light blue emission (480 nm) with very good solubility even after imidization.     

Diagnostic microbeam technology in gold ore processing

This treatise offers a brief but comprehensive glimpse of how microbeam analytical techniques have been applied over the last 20 years to resolve problems in gold ore processing. It covers only those techniques that are being used on a routine basis to study gold occurrences in plant samples. To facilitate the readers’ understanding, the microbeam techniques are introduced (and assessed) from a problem-solving point of view. These microbeam techniques form an intricate part of the comprehensive mineralogical and analytical approach used to establish on a direct and quantitative basis the occurrence of gold in tailings. Gold deportments determined by microbeam analytical techniques will identify opportunities for optimization and provide realistic targets for reducing the gold content in tailings streams. This approach has been applied in a number of gold operations, with the ultimate benefit of improved gold recovery. For more information, contact S. Chryssoulis, AMTEL, 205-100 Collip Circle, London, Canada N6G 4X8; (519) 858-5037; fax (519) 858-5038; e-mail amtel@skynet.ca.     

Using mineralogy to optimize gold recovery by flotation

Gold is an important by-product of many porphyry copper ore deposits. Precise mineralogical characterization of the unfloated gold in what is typically very low grade (i.e., <0.1 g/t Au) flotation tails provides a clear picture of the carriers and causes for gold losses in these large tonnage operations, thereby identifying the means to reduce such losses. Analyzing quantitative gold deportments in flotation tails enables the carriers of unfloated gold to be ranked, the most appropriate carrier identified, and test work designed to address specific causes of gold losses. Typically, 10–20% of the gold in the tails can be recovered without additional grinding or by regrinding a rougher or cleaner scavenger concentrate. For more information, contact S. Chryssoulis, Amtel, 100 Collip Circle, Suite 205, London, Ontario, Canada N6G 4X8; (519) 858-5037; fax (519) 858-5038; e-mail amtel@skynet.ca.     

Extracting silica and alumina from low-grade bauxite

Deposits of bauxite ores near aluminum smelters often possess an excessively high percentage of silica. Development of such high-silica ores would be beneficial to alumina producers. Therefore, unique industrial and operational experience in the field of high-silica bauxite processing was gained at the Russian National Aluminium-Magnesium Institute, St. Petersburg, pilot plant with the consecutive extraction of silica and alumina from low-grade ores. This article describes the chemistry, processing-unit operations, and results obtained from this process. For more information, contact V.L. Rayzman, 3356 Barnard Way, #206, Santa Monica, California 90405; (310) 399-3048; e-mail viktorayzman@yahoo.com.     

The development of a fluidized bed process for the heat treatment of aluminum alloys

Heat treating of aluminum alloys is often necessary to achieve the mechanical properties required for a part. With conventional furnaces, though, the heat-treating process requires several hours and manufacturers have traditionally utilized off-line, batch heat-treating operations. The long cycle times required for heat treating with conventional systems go contrary to lean manufacturing where the goal is to reduce the time a part spends in the factory. The fluidized bed technology offers rapid heating rates and excellent temperature control that allows one to significantly reduce the time required for heat treating by an order of magnitude. Technomics developed a fluidized bed conveying system that allows the manufacturer to bring the heat-treating system in-line with the casting or forging operation, obtaining a true lean manufacturing process. For more information, contact Jay Keist, Technomics, LLC, 17200 Medina Road, Plymouth, MN, 55447; (763) 383-4720; fax (763) 383-4717; e-mail jaykeist@rapidheattreat.com.     

Impurity control and removal in copper tankhouse operations

During copper smelting, most of the undesirable impurities such as Pb, Sb, Bi, and As are only partially removed by oxidation. When white metal and blister copper are in equilibrium, these impurities are distributed mainly into the copper phase, from which their removal is difficult. When copper dissolves during electrorefining in a copper tankhouse, these impurities are continuously released from the anodes either as insoluble phases (slimes), which fall to the bottom of the cell, or as dissolved species in the electrolyte, the transfer of which to the cathode must be inhibited. This article presents impurity control methods in copper tankhouse operations with traditional and newly developed processes. It also summarizes the technologies demonstrated for removal of impurities from electrolyte that prevent them from being recycled in the copper smelting and refining circuit. For more information, contact Shijie Wang, Phelps Dodge Refining Corporation, 850 Hawkins Blvd., El Paso, TX 79915; (915) 775-8836; fax(915) 775-8352; e-mail swang@phelpsdodge.com.     

Carbon nanotubes and other fullerene-related nanocrystals in the environment: A TEM study

Carbon nanotubes and other fullerene-related nanocrystals are ubiquitous in the atmospheric environment—both indoor and outdoor. In fact, these nanostructures have been observed even in a 10,000 year-old ice core sample, indicating their natural existence in antiquity, probably as natural gas/methane combustion products. Similar carbon nanotubes and complex carbon nanocrystal aggregates are observed to be emitted from contemporary combustion sources such as kitchen stoves (natural gas and propane), water heater and furnace exhaust vents, natural gas-burning (electric) power plants, and industrial furnace operations, among others. These observations have been made by collecting nanoparticulates and nanocrystal aggregates on carbon/formvar and silicon monoxide/formvarcoated 3 mm grids that were examined with a transmission-electron microscope. This study begins to establish an environmental context for considering the potential impact of future nanostructured particles on human health. For more information, contact L.E. Murr, the University of Texas at El Paso, Department of Metallurgical and Materials Engineering, El Paso, Texas 79968; (915) 747-6929; fax (915) 747-8036; e-mail fekberg@utep.edu.     

Tip-based nanomanufacturing by electrical, chemical, mechanical and thermal processes

Nanomanufactured products with higher complexities in function, materials, scales and their integration demand an increasing need for advanced manufacturing tools. It is driven by applications such as ultra-dense memory, individualized biomedicine and drug delivery, molecular reading and sorting, and nanoscale circuitry. The tip-based nanomanufacturing (TBN) platform represents a potent gamut of processes for such applications - performing various nanoscale manufacturing operations including machining, depositing, patterning, and assembling with in situ metrology and visualization. This keynote paper presents a comprehensive overview of TBN processes based upon “nanotool tips” applying electrical, electrochemical, mechanical, electromagnetic and other forces to perform manufacturing operations.     

汽车弹簧摇臂自动化传递模的研制

汽车底盘弹簧摇臂是一种结构复杂的厚板冲压件,要实现自动化传递模生产方式困难很大,本文将7工序模具安装在6,100mm长的压机工作台上,实现了紧凑型结构设计的目标,并在正拉伸与反拉伸一次性成形方法和模具新型材料研发上有所创新。