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By G. H. K. Pearse, R. P. Taylor

The Big Whopper, one of only four giant economic rare metal pegmatites worldwide, is set to become a producer of the highly valued lithium mineral petalite (LiAlSi4O10) used in glass, ceramics and the specialty glass-ceramics familiar as Corningware® and the new ceramic stovetops. The deposit has a strike length of 1.5 km, a width of up to 80 m and a resource, open in all directions, of 11.6 Mt, grading 25% petalite. It is amenable to open pit mining and Avalon Ventures Ltd. holds a patent on a flotation process that produces an exceptional quality petalite product. The project will also produce: superb quality Na-feldspar which, too, finds use in glass and ceramics; the unusual Rb- K-feldspar for high voltage porcelain insulators; tantalum, in high demand for electronics; lepidolite, an ore of rubidium; and mica and tin. A positive prefeasibility study has been completed and it remains only to undertake bulk sampling and a full feasibility study.

Jan 1, 2001

By Lloyd W. Trevoy

Titanium and zirconium heavy minerals occur in the tailings streams from processing plants which use the hot-water extraction process for recovery of bitumen from tar sand. In a research program conducted by Syncrude Canada Limited, the crude tailings stream was upgraded to produce quality zircon and titanium mineral products. To process the tailings through conventional upgrading equipment, bitumen residues must first be removed from the mineral grains. Then, by gravity separation, fines and coarse sand grains were removed and a 71% heavy minerals concentrate was prepared which was further separated by high-tension equipment into zircon and titanium minerals concentrates. The zircon concentrate was upgraded by gravity, magnetic and high-tension cleaning to produce a high-quality 98% zircon product. The titanium minerals concentrate was separated into rutile, leucoxene and ilmenite fractions. Heavy minerals distribution in tar sand drilling core samples has been evaluated for various locations on Syncrude Lease 17, and expected annual production levels of heavy minerals have been estimated. A preliminary evaluation has been made of the potential for zircon, leucoxene and rutile production and for further upgrading of ilmenite and leucoxene to synthetic rutile for titanium dioxide pigment production.

Jan 1, 1978

By William M. (Bill) Shaver

"The author will review the early history of shaft sinking as well as focus on the improvements made in shaft design and construction over the last fifty years (1970 to 2019) to predict how shaft sinking will change over the next fifty years and describe what the shaft sinking world might look like in 2070. INTRODUCTION It is a great honour to be one of your keynote speakers for the Fourth International Conference on Shaft Design and Construction being held in Toronto in November 2019. This is one of the opportunities we have to thank the Mining Companies of the world as well as the industries and companies we serve for their support of the mining contracting and shaft sinking business of Canada and the world at large. Many of these companies are represented here today. Without your support many of the innovations we will talk about today would not be possible. We would also like to thank all the companies that work with us in our business including all the contractors and suppliers who provide the various services we require. These include equipment manufacturers, engineering companies, project management companies and suppliers large and small who cater to our every need as quickly as possible. Without all these partners we would not be as good as we are. Many of these companies are our sponsors this week. Thank you from all of us! This is also an appropriate time to pause and think about those Shaft Sinkers we have lost and those who have been injured on our projects around the world. Please bow your head and remember the Shaft Sinkers you have worked with, who did not return home or those who returned home injured. Think about how we can continue the work of making shafts safer every day as we go forward with our projects so everyone goes home to their families safe and sound. Pause for a minute and thank you. The subject matter we have chosen to discuss today is “Shaft Sinking in the Next Five Decades”. How will the work be done, how fast will it be done, what will it cost, and why we think this may occur? It is appropriate to consider this over the next few days with this auspicious group we have assembled. Today, we will look back at all the advances that have been made over the last many years and look ahead to the future to attempt to predict what shaft sinking will look like in 2070. When I look around the room I recognize that many of us will not be around then so we need not worry about being wrong. Suffice it to say that the next 50 years will be very interesting and exciting for the shaft sinking business."

Jan 1, 2019

By Nicolas Gatelier, Sophie Laurent, Thierry You

Hard-rock caverns for hydrocarbon storage are a very particular type of underground facility controlled not only by local administrative and regulatory constraints that can be very specific, but also by the possible risks of geotechnical or geomechanical failure. Each such facility throughout the world is a prototype that needs to be adapted to very different site conditions. The straight forward application of design methodologies from relatively similar fields (mines, tunnels) can be very useful, but risks holding back the scientific and technical improvements needed by an engineering industry in full development. Here we look at various case histories and at problems that have been raised where recent attempts at standardization would appear to have been ill adapted, and where storage designers, through experience and judgment, may still provide innovative engineering solutions.

Jan 1, 2015

By M. Cossette, V. H. Tran

"How can the durability of asphalt pavement be doubled without increasing highway budgets? Asphalt containing asbestos can provide the desired performance with additional costs being made up by longer life. The addition of a low percentage of asbestos to an asphalt mix permits a higher asphalt content without any consequent loss in stability. It is mainly the higher asphalt content that provides improved performance and durability, although the fibrous reinforcement plays a key role in preventing the propagation of micro-fissures. As well, several international studies show that, thanks to the latest production techniques, no environmental hazards need be incurred.RésuméComment doubler la durée des chaussées d'asphalte sans augmenter les budgets de voirie? L’asphalte contenant de l'amiante peut offrir les performances souhaitées et l'augmentation des couts initiaux peut être rapidement compensée par une durée prolongée. L’addition d'une faible teneur en amiante courte il l'enrobe de bitume permet des teneurs en bitume plus élevées sans subir une perte de stabilité en conséquence. C'est principalement la teneur accrue en bitume qui assure un améliorations propriétés physiques et une augmentation des performances mécaniques, ainsi qu'on prolongement de la durée. Cependant, le renforcement fibreux joue un rôle clef en prévenant la propagation éventuelles micro-fissures. Les nouvelles techniques évitent tous risques environnementaux"

Jan 1, 1991

By G. Stokreef, B. R. Davis, M. Kadiyski, T. LeBel, Alvear Montenegro, R. Parra, V. Montenegro

A drop tower and methodology were developed to study the impact of mineralogy on the flash combustion behaviour of copper concentrates. Reaction shaft conditions of a flash furnace were simulated using a drop tower reactor and different molar ratios of oxygen gas to sulphur in the feed. Five feeds were tested in the drop tower including pure minerals chalcopyrite and pyrite as well as two mineralogically distinct copper concentrates and a blend of the two. The behaviour of each of these five feeds were evaluated through analysis of the solid combustion products for elemental sulphur, mineralogy and particle size. Desulphurization curves for each of the feeds were produced. It is thought that the desulphurization behaviour of pure minerals can be used to estimate the behaviour of a concentrate and that a blending recipe could be developed, which can optimize the chemical and mineralogical inputs to the flash furnace and guide operations on the optimum furnace conditions. Overall, the drop tower has proven to be a useful tool for studying flash combustion processes. Experimental results suggest that mineralogy has a significant impact on the conditions required for the production of matte with consistent grade. This finding is especially significant for custom smelters, which may see several different blends in a day. INTRODUCTION Flash furnace smelting is a continuous feed, batch tap, pyrometallurgical process that is used to produce copper matte from copper sulphide concentrates. Dried concentrate(s), silica flux, and secondary materials are blended to a target chemical composition, typically given by the Cu/S ratio, before processing. This fine, dried feed is dispersed throughout the heated furnace reaction shaft with an O2-enriched reaction gas. The particles heat up in the shaft of the furnace, ignite and undergo reactions that pre-oxidize the iron sulphide and some of the impurities in the feed. Oxidation reactions in the shaft of the furnace desulphurize the feed and produce an SO2-containing off gas. The reacted particles fall into the furnace settler and separate into a Cu-rich matte and an iron-silicate slag, while the SO2-containing off gas is carried out of the furnace for heat and dust recovery, as well as H2SO4 production. Some concerns during operation of the furnace are dusting, over or under oxidation of the feed, and a stable flame.

Jan 1, 2019

By Robert B. Parsons

"The budget that was tabled by Finance Minister MacEachen on November 12, 1981 will result in a major tax reform of Canada's income and sales tax systems, the likes of which have not been witnessed by taxpayers since 1971. All segments of the economy will be affected one way or another by the far-reaching budget proposals; the mining industry did not escape untouched.Important changes will be introduced which will alter some of the fundamentals of structuring mineral resource ventures in Canada. This month, Tax Notes examines these changes, and also summarizes the other highlights of this key federal budget.IntroductionFinance Minister MacEachen's budget, with its lower personal tax rates, loophole plugging and tax shelter bashing, represents the biggest shakeup in our tax system since tax reform in 1971. In his budget, presented in the House of Commons on November 12, Mr. MacEachen proposed substantially lower tax rates for middle and upper income individuals, with the top federal and provincial tax rate dropping to about 50%, but in return he eliminated most of the opportunities for individuals, and corporations, to reduce or defer taxes through a wide variety of tax shelter and tax planning mechanisms.Although many of those budget proposals that dealt with the resource industries focused on the implementation of the September 1, 1981 agreement reached by the federal and Alberta governments concerning the National Energy Program (see Tax Notes in the December 1981 issue of the Bulletin), the budget also contained some proposed amendments that would have significant implications for investment in the mining industry.This month, Tax Notes examines these latter proposals, and also summarizes very briefly those budget proposals which are not unique to the resource sector."

Jan 1, 1982

By Yue hua Hu, Wei Sun, Pan Chen, Li Wang, Runqing Liu, Central South University

"The flotation separation of muscovite from quartz was investigated using mixed sodium oleate/dodecylamine (NaOL/DDA) collectors. The flotation experiments were conducted on single minerals and their collecting performances were studied by means of adsorption amounts and molecular dynamics simulation. Flotation results show that muscovite presents good floatability while quartz exhibits poor floatability in alkaline condition. Adsorption amounts show that both NaOL and DDA can absorb onto surfaces of muscovite and quartz in presence of mixed surfactants. Molecular dynamics simulation indicates that DDA plays an important role in the adsorption of mixed surfactants on these two mineral surfaces. The molecules of mixed NaOL/DDA are arranged in a rigid and well-ordered packing on muscovite (001) surface. Only a few DDA adsorb on quartz directly, and rest DDA and NaOL molecule exist near by the quartz surface, forming a hydrophilic cylinder-like structure. This study may provide guidance for the flotation mechanism and application of mixed anionic/cationic collectors.INTRODUCTIONIn the past decades, there has been an ever-increasing demand for muscovite (KAl2(Si3Al)O10(OH)2) because of its potential applications in cosmetics, construction and metallurgy industries (Barlow & Manning, 1999). Besides, muscovite is an important carrier for some rare metals, including vanadium, titanium and lithium (SsuerrN, 1979). Quartz (SiO2) occurs as the main gangue mineral in muscovite ores, which results in a low purity of muscovite and limits its wide applications. Therefore, there is an urgent need for the beneficiation of low grade muscovite ores. Many studies remove quartz by screening and gravity separation in virtue of their differences in shape, hardness and density. However, these methods undergo poor efficiency in case of small particle size (below 50µm) of muscovite and quartz (Liubakka, Sullivan, Lamphere, Corradi, & Dykhuis, 2011; Santos, Franca, & Ogasawara, 2011)."

Jan 1, 2016

By H. J. Ni, M. Y. Huang, S. W. Chen

The effects of several fluxes on purification, microstructures and properties of A00 aluminium have been studied. The experimental results and analyses indicate that many cracks and large porosities exist in the surface film above the melt purified by C2Cl6 and that the film is floe and mostly composed of AhO3 and pure aluminum, which carries many carbon particles and AlCh not fully volatilized. And then over 50% of the all-melting residue is pure aluminum, which is one of the major reasons for high melting loss. Moreover, because of a mass of gas bubbles and a state of seethe, there exist many inclusions which size is under l0µm in the microstructure of A00 aluminum purified with C2Cl6 or fluxes containing C2Cl6- With this purifying method, the aluminum crystal grains are extended along the radius that was observed firstly and the average crystal size of A00 aluminum are about 100µm~150µm. In addition, small size inclusions have little affected on tensile strength and micro inclusions under l0µm have little affected on elongation.

Jan 1, 2006

By Jean-Luc Beaudoin

"In addition to the actual energy consumed, billing is dependent on the peak load and the power factor. The lower the power factor goes, the higher will be the penalty the consumer pays. The principles of a power factor regulator, the two ways of improving the power factor and methods for calculating the capacitor values required will be described.The rate structure of the utility company is founded on three cornerstones: the energy consumed during a given period of time and two penalties imposed when the power factor is low or the power demand is high. Even though the normal consumption of a customer might be 10 kW, with a peak demand of 20 kW only once a month, the wiring and associated equipment at the input to the customer's plant will have to accommodate this peak demand. The power company has no means of forecasting these demands and cannot therefore provide the additional equipment necessary. So it exacts a penalty, and the customer must take all possible steps to avoid these peak power demands. This can be accomplished by using an automatic peak load regulator which will selectively disconnect the loads which are not essential in the operation of a plant .The principles of such a controller will be described.Principles of power factor regulatorsThe operating principles of a power factor regulator will now be described. It might be asked why the power factor of an electrical installation in a mine, or a factory, should be corrected at all, but there is a simple answer. In addition to the actual energy consumed, the billing is dependent on the peak load and the power factor. The lower the power factor goes, the higher will be the penalty the consumer pays."

Jan 1, 1982

By C. Barnett

"A description of the Geco orebody has been given by W .L. Brown and R.C.E. Bray (1). The mill flowsheet and equipment were described by M.J.S. Bennett, D. Wild and C. Lawton (2). Mill capacity is now 4, 150 tons per operating day of copper, silver, zinc and lead ore. A recent flowsheet has been published in the - Canadian Mining Manual (1966).Soon after the start of production in September 1957, it became apparent that large tonnages of sand would be required by the mine for backfill pruposes. Initial experimental work on the preparation of sand fill from the flotation tailings was begun in late 19 59. Cyclones of local manufacture, in a variety of sizes, were tested quite successfully. There were, however, several obvious advantages with some of the custom-built cyclones and a recommendation was obtained from the Techniquip Company. A single Krebs D-10-B cyclone was tested experimentally in 1960.INITIAL TESTWORKExperimental results showed that with our relatively coarse grind (in the order of 53 % minus 200 mesh) 75 - 80% of the flotation tailings could be recovered as backfill sand with one stage of treatment. Percolation rates of four inches per hour were obtained with cyclone inlet pressures in the range of 20 - 25 psi and feed densities of 20 - 23% solids."

Jan 1, 1968

By T. Bhambhani, O. Yavuzkan, D. R. Nagaraj

"Cu ore bodies commonly contain oxide Cu at the surface, with sulfide Cu content increasing with depth. The recovery of oxide Cu minerals by flotation is a longstanding challenge in the minerals industry, especially for high acid-consuming ores which would not be economical for direct acid leaching. Current practice of oxide Cu recovery involves sulfidization (often using controlled potential sulfidization or CPS) using NaSH (or Na2S) followed by flotation using traditional sulfide collectors. CPS has shown to improve recovery of oxide Cu but has the following limitations: a) HSE issues with NaSH, b) high consumption of NaSH, and c) inability to recover certain oxide Cu minerals because they are refractory to sulfidization. The oxide Cu flotation is further complicated by the presence of certain non-sulfide gangue minerals which adversely impact both recovery and selectivity.Over the past eight decades, numerous collectors have been proposed and evaluated for the direct flotation (i.e. without sulfidization) of oxide Cu minerals, the most researched of which is alkyl hydroxamate. While there are numerous publications dealing with the fundamentals of interaction of alkyl hydroxamates with single minerals, there are few publications which discuss the practical aspects of alkyl hydroxamate use in ore flotation, particularly their use with sulfidizing agents. Case studies in this paper include methods to identify optimum combinations of sulfidizing agents and oxide collectors to maximize recovery for various types of ores. It was observed that some ores do not require any sulfidization, while others require at least partial sulfidization to improve efficacy of AHX. Depending upon the ore type and mineralogy, recovery improvement in the range of 5 to 15% units, over and above that achieved with CPS, has been observed with the use of AHX. For ores requiring high dosages of NaSH, it was shown that AHX can be used to reduce the NaSH consumption significantly. The challenges associated with the presence of non-sulfide gangue minerals in oxide copper ores are included, and the use of modifiers to alleviate the associated problems and enhance the performance of AHX is discussed."

Jan 1, 2016

"Line Creek Resources Ltd. produces three million clean tonnes per year of metallurgical and thermal coals for the international market. The mining operation, which is located in the mountains of southeastern British Columbia, produces coal from four pits by conventional truck and shovel methods.The South Pit, which has been in operation since J982, has a benched highwall 490 m in height. Shallow dipping coal seams at the base of the syncline formation will be exposed in the highwall over the next four years of pit life. The first of these seams, which will measure 500 m in final highwall length, was exposed in J994. An auger, powered by a 1250 hp engine capable of cutting 2.2 m diameter holes, was brought on site in J994 and has proven to be a successful means of recovering coal from the J3 m thick seam.This paper covers the background to the selection of an auger mining method to recover highwall reserves together with the geotechnical and methane considerations for this approach.IntroductionLine Creek Resources Ltd., a wholly owned subsidiary of Manalta Coal Ltd., owns and operates the Line Creek mine. The operation which consists of four active pits, a processing plant, and rail loadout is located in the southeastern coal fields of British Columbia. Figure 1 shows the general area.The coal bearing sequence at the mine is preserved on the east and west limbs of a major syncline. Up to twelve mineable coal seams, ranging in thickness from 2 m to 15 m are contained in the formation. Within the pits the seams are stratigraphically consistent and structurally undisturbed, except for small-scale thrust faults that create multiple repeats of the seams."

Jan 1, 1995

By W. M. Moon, Hugh G. Miller, C. -S. So

"Digital image processing and enhancement techniques have been applied to airborne gamma ray spectrometry data from Sudbury, Ontario. These results have been correlated and compared with the available geological maps to evaluate their usefulness for identifying lithological units. Digital processing allows the correlation of various data sets, and different combinations of images can be tested and viewed as a composite image. Composite images with pseudocolours provide an opportunity to analyze and correlate information that is not otherwise apparent in individual images. Principal component analysis has been applied to the gamma ray spectrometry data to evaluate their efficacy and relative information contents of the measured and computed data. The results of this study indicate that the combined radioelements image (obtained by combining the radioelement image and the ratio images) is effective for defining areas of relative concentration of a specific element in near surface materials. Furthermore, the composite radioelements image (produced by combining three separate radioelement images) and composite principal components image reflect large-scale lithological variations. IntroductionThe Sudbury area is a unique geological structure located in the southern Canadian Shield (Fig. 1). Because the area hosts economically significant nickel-copper deposits (Pye et al., 1984), it has been surveyed in great detail by geological and geophysical methods. In order to obtain meaningful geological infonnation about the Sudbury area, several studies have been carried out with the application of innovative mathematical techniques for geophysical modelling, and attempts have been made to integrate the multisensor geophysical data available for the area (e.g. Gupta et aI., 1984; Moon et al., 1988; Singh et al., 1993). The main objective of this paper is to apply digital image processing and enhancement techniques to airborne ganuna ray spectrometry data in order to determine their usefulness for regional geological mapping."

Jan 1, 1994

By V. Nudo, R. del Villar, A. R. Laplante

"Fine iron ore recovery from the tails of Les Mines Quebec Cartier was investigated using Reichert trays and spirals. The effect of feed rate, density and splitter setting on the performance of rougher, cleaner and recleaner stages of a 2DS tray assembly was determined using 2- and 3- factorial experimental designs. The tray concentrate, assaying 27% Fe, was further upgraded by spiral to yield a concentrate assaying 55% Fe. Further laboratory scale testing showed this material to be easily upgraded to 65-66% Fe with high Fe recoveries.This paper presents the metallurgical results of the three tray stages. The model used to predict the performance of a full recovery circuit is then described. Simulation results are presented and their reliability assessed. Finally, an economic evaluation of the proposed scavenging circuit is summarized.INTRODUCTIONThe Mount Wright plant (UWP), located near Fermont, Quebec, processes daily 130,000-150,000 tonnes of iron ore assaying between 27 and 33% Fe, to upgrade it with three stages of 44.5 cm pitch GEC spirals to 66% Fe, while rejecting approximately 80,000 tonnes assaying between 6 and 11% Fe (1-3). Heavy liquid separation (at 3. 3 g/mL) of the plus 37 µm fraction (+400 mesh) of the tails reveals that a significant fraction of the iron is in the sink product, below 150 pm (100 mesh), as shown in Table 1. Also shown is the iron grade of the sink and float fractions. The high grade of the fine sink indicates that hematite ls well liberated below 105 µm (150 mesh), as previous studies have shown (4,5). The iron grade of the floats is very low in the fine size range, but increases with increasing size above 105 pm, because of incomplete liberation. Overall, two thirds of the plus 37 µm iron ls in the sink product, which constitutes less than 10% of the total tail."

Jan 1, 1987

"This paper discusses the use of risk assessment and risk management techniques within the Australian underground coal mining industry, within the context of geotechnical risk. The industry works within a pro-active, “enabling” legislative framework, where companies and management apply a range of risk assessment tools as part of their everyday management processes. Different geotechnical risk factors and approaches are reviewed, together with application examples – ranging from mine planning and design, operations, and accident investigations.A particularly powerful resource in each of the above stages of geotechnical management is the RISKGATE system. RISKGATE is an assembled “body of knowledge” structured under different topics across the Australian coal industry, of which three topic areas address rock mechanics issues for both the underground and surface mining sector. This paper will provide an overview of RISKGATE in the context of risk-based rock mechanics applications in underground coal mining."

Jan 1, 2015

By Bern Klein, A. Tugba Cebeci, Libin Tong

"Sensor based sorting faces two main challenges related to limited capacity/throughput and the ability of sensors to accurately discriminate based on estimated grades. This paper is aimed at improving sensor discrimination. Sensors have the ability to measure more than a single response. X-ray fluorescence (XRF) can detect and provide concentration information about a range of elements. Similarly, electromagnetic sensors (EMs) can generate magnetic susceptibility and conductivity responses over a range of frequency levels. The sensors thereby provide a response signature rather than a simply a single response that is a proxy for a metal grade. Furthermore, integrating sensor responses can improve the discrimination of metal bearing rock from waste. A study was conducted on a gold ore to assess sortability using XRF and EM sensors. A multi-variable regression approach was used to develop models that included a range of responses. Correlations improved significantly when compared to single response correlations. The approach showed that both positive and negative correlations contributed to the improved correlations. Stepwise regression simplified the models and showed that 2nd order interaction effects can be important. The approach also showed that combining different responses can improve discrimination accuracy. An important outcome of the study was that an ore that had been consider not to be sortable was determined to be sortable through the application of an approach that used the sensor responses in a more intelligent manner.INTRODUCTIONMining is aimed at recovering valuable minerals from their host rocks. Many methods are used to recover valuable minerals, and finding efficient and cost-effective ways is the key in research and production. . Ore sorting technology is fitting this definition. It not only discards waste rocks away from the concentrator but also recovers metal bearing ore particles that could be lost to the waste dump. The benefits of ore sorting include increased energy efficiency and reduced water and reagent usage in the downstream operations (Bamber, 2008; Gunson, Klein, Veiga, & Dunbar, 2012; Mazhary & Klein, 2015; Robben, Wotruba, Robben, von Ketelhodt, & Kowalzcyk, 2013)."

Jan 1, 2016

By M. Takebayashi, K. Takenaka, S. Matsubara, T. Yoneyama

The cathode production of Toyo Smelter and Refinery, owned by Sumitomo Metal Mining Co., Ltd. reached 450,000 tons per year in 2016 with three tank houses. Niihama tank house commenced operations in 1919 with conventional sheet cathode technology. Approximately 100 years of operation experience and the technical development enabled that the current density of Niihama tank house and the Toyo tank house #1 increased to 320 A/m2. These operation techniques were utilized at the Toyo tank house #2 which started in 2005, and its current density reached up to 350 A/m2 with permanent cathode technology. In order to achieve high current efficiency under condition of 350 A/m2 operation at Toyo tank house #2, continued efforts had been made to verticality of anodes and permanent cathodes. To improve verticality of anodes and cathodes, reduction of short circuit ratio by changing the shape of the anode, optimizing the anode pressing machine and off-line process for rectifying the distortion of permanent cathodes was carried out. In addition, concentration control of electrolyte and expansion of Ni removing ability from the electrolyte prevented passivation. Finally, more than 96% of the current efficiency was stably confirmed. INTRODUCTION Today, Toyo Smelter and Refinery of Sumitomo Metal Mining operates three tank houses in Japan, namely, Toyo tank house #1, Toyo tank house #2, and Niihama tank house with a total capacity of 450,000 metric tons of copper cathodes. Figure 1 shows the trend of cathode copper production and the current density at three tank houses over the last 10 years. Cathode production by Toyo Smelter and Refinery reached 450,000 tons per year in 2016 with three tank houses.

Jan 1, 2019

By Eiichi Sato, Koichi Kitazono, Hiroshi Masuda, Kenta Higane

"The present study investigated the low-temperature creep mechanisms in ultrafine-grained (UFG) aluminum manufactured by accumulative roll bonding. UFG aluminum with grain size 0.39 µm showed steady state creep even at room temperature under low stresses as confirmed by the creep curves in the strain rate–strain plot. The low-temperature behavior was divided into four regions by three distinctive stresses, sI, sII and sIII: sI (=45 MPa) is denoted as the micro-yielding stress with which dislocations start movement, sII (=85 MPa) the dislocation-multiplication stress above which dislocations multiply with creep deformation, and sIII (=171 MPa) the conventional yield stress above which macroscopic plastic strain is generated. During low-temperature creep, below sI, negligible plastic strain is generated. Between sI and sII, creep deformation with stress exponent 2.5 occurred, which is accommodated by dislocation absorption into grain boundary and grain boundary sliding, similarly to the low-temperature creep of HCP metals. Between sII and sIII, creep deformation with stress exponent 7.0 occurred, whose mechanism is similar to the low-temperature creep of coarse-grained aluminum. Above sIII, power-law breakdown occurred.INTRODUCTIONIt is well understood that the creep deformation brings about at high homologous temperatures (T/Tm) of >0.4, where Tmis the melting point, with diffusion processes. Recently, the importance of aluminum is increasing for cryogenic temperature parts such as a metallic liner or a cap in high pressure-hydrogen vessels, and the presence of creep behavior in aluminum at room temperature has become recognized (Matsunaga, 2013;Kassner, 2015).In HCP metals and alloys, especially intitanium, steady-state creep behavior appears at room temperature with apparent activation energy of1/10 of that for self-diffusion(Neeraj, 2000; Matsunaga, 2009).On the other hand, Kassner (2015) claims that aluminum shows creep behavior at room temperature with apparent activation energy of 4/5of that forself-diffusion, but never reaches the steady state. We should note that it is derived from the data obtained from short-term creep tests of few hour, and Matsunaga (2013) already claimed the presence of steady state in room temperature creep in aluminum with activation energy of 1/5of that for self-diffusion.The mechanisms for low temperature creep are considered different between HCP and FCC metals: in HCP metals, grain boundary sliding is observed and is thought to accommodate piled-up dislocations at grain boundaries through absorbing them. The so-called slip-induced grain boundary sliding occurs with low number of activated slip systems(Matsunaga,2009).On the other hand, in FCC metals, many activated slip systems bring about work hardening with dislocation cell structure formation. In the initial stage of creep, it results in primary creep (Kassner, 2015), but Matsunaga (2013) claimed that once the annihilating of a cross-slipped dislocation to another reaches balance, steady state is established. It has been, however, strongly required to show more convincing experimental verification for the presence of steady state in FCC metals at low temperature."

Jan 1, 2018

By P. C. Sui

Numerical investigation and parametric simulations of the coupled electrical conduction and mass diffusion in the GDL of a PEMFC are reported. The coupled transport is solved using a 2D, "under-the-rib" computational domain for the cathode GDL. The current density on the GDL/catalyst layer interface, which constitutes one of the boundary conditions for the GDL domain and reflects the activation overpotential in the catalyst layer and the ohmic loss in the membrane, is solved iteratively using a novel numerical algorithm. A parametric study is performed to investigate the effects on current density distribution of various operating conditions such as oxygen concentration and membrane resistance, and of design factors such as GDL geometry, anisotropic transport properties, and deformation under the land area. The results show that the current density distribution under the land area can be dominated by either electron transport or mass transport, depending on the operating regime.

Jan 1, 2005