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By I. Filzwieser, A. Filzwieser

The Peirce Smith converter is the key metallurgical vessel in the majority of copper smelters. During the two step process, oxygen enriched air is injected through a row of tuyeres into the matte received from a primary smelting unit. Additionally, in the first step the iron content is oxidized into a fayalite slag by the addition of silica. During the second step, the remaining copper sulphide is converted into blister copper with a final sulphur content of approximately 200 ppm. The overall efficiency of this process is determined by the total reaction time, the slag quality and quantity, and the chemistry of the final blister copper. To increase the reaction kinetics during both stages, the METTOP Process Control and Regulation (MPCR) system was developed, which consists of four elements: OPC - Optical product control ACR - Automatic computer regulation GCU - Gas control unit GIS - Gas injection system The OPC system from SEMTECH records the optical spectrum emitted by the off gas flame providing immediate, detailed process information. Using this online data, additional gas can be automatically injected into the converter through a gas injection system opposite the tuyere zone. An improved oxygen distribution in the melt and the accurate determination of the process end point results in a significant reduction in the process cycle time. Furthermore, by maintaining the reaction closer to the equilibrium the final sulphur and oxygen content can be reduced compared to the conventional process. In particular, the final sulphur content can be lower than 70 ppm, eliminating the need for an oxidation step in the anode furnace.

Jan 1, 2007

By P. Su

Friction stir spot welding of a range of Mg-alloys is investigated (AZ91, AZ31, AM50 and AM60). The peak temperatures during friction stir spot welding of all Mg-alloys are close to their solidus temperatures. Also, the apparent material viscosity of Mg-alloy sheet is lower than that when Al-alloy sheet material is spot welded. This is important since it means that the widths of the stir zones forming during spot welding of Mg-alloy sheet are smaller than those when Al-alloy sheet is welded (when identical welding parameter settings are applied). These lower apparent viscosity values must be taken into account during numerical modeling of the Mg-alloy spot welding process. The efficiency of energy utilization is very low when Mg-alloy sheet is spot welded and is of the same order as that when fabricating Al-alloy sheet. The energy generation contributions of the rotating pin and the tool shoulder are investigated. When the spot welding operation is carried out without the application of a dwell period, the contribution made by the rotating pin vis-à-vis energy generation is around 66%. The contribution made by the tool shoulder increases to about 65% when a dwell period of four seconds is incorporated during the spot welding operation. This increase results from a longer contact time between the tool shoulder and material within the stir zone, The failure load during overlap shear testing increases when the bonded area and the energy input increase during spot welding. Sample failure initiates from unbonded regions and from discontinuities at the edge of the stir zone. The formation tendency of discontinuities is increased when Mg-Alloy sheet is spot welded because of the limited deformation characteristics of the base material at lower temperatures.

Jan 1, 2006

By J. B. Boisvert, W. Board, C. R. Mooney

"Traditional geostatistical modelling methods are difficult to apply to heavy-tailed deposits because the extreme positive skew of the grade distribution leads to bias. The focus here is on an innovative method of modelling the high-grade population by conditionally simulating discrete volumes (nuggets) of gold with marked Poisson and Cox processes. Capping and other ad-hoc manipulation of the assay data is not required; however, an intensity map for the point processes is required. The method is demonstrated on a dataset from an epithermal deposit and demonstrates an improvement in reducing smearing and controlling the skew of the grade distribution.RÉSUMÉ Les méthodes traditionnelles de modélisation géostatistique sont difficiles à appliquer dans des gisements dont la distribution de la teneur est à queue lourde car l’extrême asymétrie positive de la distribution de la teneur génère des biais. Dans le présent article, l’accent est mis sur une méthode novatrice de modélisation de la population à haute teneur par la simulation conditionnelle des volumes discrets d’or (pépites) au moyen de procédés marqués de Poisson et de Cox. La limite d’utilisation et d’autres manipulations ad hoc des données ne sont pas requises; toutefois, il faut une carte des intensités pour le processus ponctuel. La méthode est démontrée sur un ensemble de données d’essais provenant d’un gisement épithermal et elle montre une amélioration dans le lissage du flou et dans le contrôle de l’asymétrie de la distribution de la teneur."

Jan 1, 2015

By R. P. van Hille, A. W. van Zyl

The BIOX® culture, aiding liberation of arsenopyrite/pyrite occluded gold, is inhibited by thiocyanate (SCN > 1 mg/L); precluding the recycling of tailings water up-stream of the bioleaching circuit. The activated sludge tailings effluent remediation (ASTERTM) process is a biological process that was developed to facilitate water recovery and treat waste water on-site (to achieve a SCN concentration < 1 mg/L) to be recycled or disposed of. The aim of this study was to investigate the effects of changing temperature and SCN loading on the SCN degradation ability of the mixed microbial population clue to seasonal temperature changes and fluctuations of SCN concentration in the waste water.

Jan 1, 2011

By James R. Hein

Manganese nodules form at the sediment surface of abyssal plains throughout the global ocean at water depths of about 4000-6500 m. The nodules form a continuum from purely hydrogenetic (all metals from seawater) to purely diagenetic (all metals from sediment pore waters), which will determine which metals of potential economic interest are enriched in the nodules. Another important factor in metal enrichment is whether diagenesis in the bottom sediment is oxic or suboxic. There are several nodule fields in the deep ocean that have received much attention with regards to economic potential, the most important being the Clarion-Clipperton zone (CCZ) in the NE Pacific, where the International Seabed Authority (ISA) has signed 12 contracts for exploration areas, each spanning 75,000 square kilometers. Those nodules are rich in nickel (mean 1.3 wt. %), copper (mean 1.1 %), and manganese (28%), with moderate amounts of cobalt (mean 0.2%), molybdenum (587 g/t), and lithium (129 g/t). A conservative estimate is that there exists 21,100 million dry tonnes of nodules in the CCZ, yielding more manganese, twice the nickel, three times the cobalt, and four times the yttrium than the entire land-based reserve base (economic plus marginally economic plus subeconomic reserves) for each metal. Total rare-earth elements (REEs) as oxides average 0.09% in CCZ nodules, a potential byproduct even at that grade because the heavy REE complement averages 26%, compared to less than 1% for the large land-based carbonatite REE deposits. The price for HREEs is much greater than for the light REEs. For comparison, the REEs in deep-ocean ferromanganese crusts are 3 to 5 times greater than nodules and the HREE complement averages 18%. Of the 12 CCZ contracts, 7 are with States (China, France, Germany, Japan, Korea, Russia, and a group of States (IOM); and 5 are with companies: G-Tec Sea Mineral Resources NV, Nauru Ocean Resources Inc. (NORI); Tonga Offshore Mining Ltd (TOML), UK Seabed Resources Ltd (Lockheed UK), and Marawa Research and Exploration Ltd. Three other nodule fields that have received attention are in the Peru Basin, which has nodules very rich in manganese (34%) and lithium (mean 311 g/t), the Penrhyn Basin (Cook Islands Exclusive Economic Zone), with nodules very rich in cobalt (mean 0.4%); and the Central Indian Ocean Basin (CIOB), where India has an exploration contract with the ISA. CIPB nodules have mean nickel, copper, and manganese contents of 1.1%, 1.0%, and 24% respectively.

May 1, 2013

By D. Campbell Mackenzie

THIS paper is submitted primarily to put on record the results of a number of experiments carried out at the Wingdam mine of Consolidated Gold Alluvials of B.C., Ltd., with the object of establishing a reliable method of concentration of &apos;wash&apos; and a maximum recovery of gold from the concentrate. It will be generally admitted that, during the last two decades, a tremendous amount of research work has been carried out, both by private companies and Government departments, with a view to improving the technique of the recovery of gold .from quartz veins or lodes. So thorough have been these investigations that milling practice at a modern quartz gold mine is almost an exact science, carried out with meticulous accuracy. In placer mining, on the other hand, very little departure from old traditional methods can be noted, with the exception perhaps of the more modern gold dredges. This may be due to the fact that the concentration of placer gravels, up to a certain point, is comparatively easy. Only a simple equipment of sluice box and riffies seems necessary where the gold is coarse and the gravel free from clay. In the early days of placer mining, when claims were rich and fairly 5hallow, nobody worried very much about fine gold; and, if clay was present, an enlarged dump box was constructed in which the gravel was subjected to a rather desultory puddling. That large quantities of gold are lost in normal placer practice is generally admitted. Some 26 years ago, I had inspectorial charge of many bucket dredges on the Ovens river, in Australia. Occasionally it was necessary for a dredge to work through its own tailing to reach a new section, and almost without exception enough gold was recovered from these tailings to defray the total cost of moving the dredge. Since those days, the technique of gold recovery in dredging has been considerably improved and it is still receiving close attention. Outside of dredge mining, most placer operations, deep or otherwise, are as they were-notorious gold losers, paying little attention to the recovery of fine gold and taking an absurd amount of time over each clean-up. In the Cariboo district of British Columbia, the alluvial gold is usual y associated with varying quantities of black sand (magnetic) and grey sand (non-magnetic); and it can be taken as axiomatic that, if you save all the black sand and grey sand, you save practically all the gold. It is on this hypothesis that we have carried out our research work and brought our recovery system up to its present highly satisfactory standard.

Jan 1, 1937

By Linlin Tong, Xiangling Song, Guobao Chen, Zhenan Jin, Hongying Yang

Biooxidation of a high arsenic-bearing refractory gold ore was investigated to determine the arsenic removal efficiency by the cultured bacteria and to examine the effect of biological pretreatment on subsequent gold cyanidation. The biooxidation pretreatment process utilizes the ability of adapted acidophilic bacteria to oxidize pyrite and arsenopyrite and release the encapsulated gold. The released gold can be efficiently extracted by the subsequent cyanidation process. The biooxidation experiments were conducted with cultured bacteria using various sizes of agitation tanks. Leaching results showed that over 96.26 % arsenic extraction could be obtained from this ore after 6 days of bioleaching with continuous stirred tank reactor (CSTR). Gold extraction during the cyanidation process was increased from 29.35% to 96.71% after biological pretreatment. The content of arsenic in the biooxidation residue was reduced to below 0.3%. The transformation process of As was considered as [AsS]2- ? As (?) ? As (?) during the biological pretreatment.

Jan 1, 2014

By M. O. Pekguleryuz, D. S. Aydin

The high temperature oxidation and ignition resistance of Mg-(0-6) wt% Nd alloys have been investigated via isothermal and continuous heating experiments conducted in air atmosphere. Alloy composition is observed to be effective in low levels (~ 0.5 %) in the ignition temperature (Ti) of the alloys; the Ti of pure Mg increased from 630 °C to 770 °C with 0.5 wt% Nd addition. However, no noteworthy improvement was achieved with further additions up to 6 wt% Nd. The initial microstructure was observed to determine the oxide structure on the surface due to the differing oxidation behavior of the phases (a-Mg + Mg12Nd intermetallics). It has been found that the formation of a Nd-depleted region at the subsurface due to extensive Nd oxidation at the oxide/intermetallic interface lowers the protective ability of the oxide scale.

Jan 1, 2015

By M. R. Khalesi, S. Bellec, C. Bazin, D. Hodouin

This paper proposes a classification model to predict the split coefficient of gold ore particles as a function of the particle size and gold content. The model is calibrated and validated using data obtained from the sampling of an industrial grinding circuit. Model calibration is based on a complete simulation of the circuit and involves parameters related to the gold grain distribution in the ore as well as a grinding and liberation model. Since cyanide is added into the studied grinding circuit, assumptions related to gold dissolution in the mills are made to allow simulation results which reflect industrial behaviour patterns.

Jan 1, 2011

By Takayuki Takasugi, Naoya Masahashi, Yasuyuki Kaneno, Satoshi Semboshi, Yusuke Kadoi

Cu–Ti alloy wires doped with and without a small amount of Ni were fabricated by over-aging and using intense drawing procedures. For both the Cu–Ti alloys with and without Ni doping, the over- aged microstructure was occupied fully with a coarse lamella of Cu solid solution and β-Cu4Ti plates precipitated discontinuously by grain boundary reactions. The full-lamellar microstructure was developed much more rapidly by aging in multi steps at 873 K to 723 K rather than by isothermal aging at 723 K. Ni doping in Cu-Ti alloy was also effective to accelerate the formation of the lamellar microstructure. When drawing the over-aged alloy with inferior hardness but superior electrical conductivity, the strength increased steadily and eventually exceeded that for the wires drawn from the peak-aged alloy. In addition, the electrical conductivity of the wires drawn from the over-aged alloy was always much greater than that from the peak-aged alloy. Eventually, the procedure of over-aging, followed by intense drawing, could enhance both the strength and electrical conductivity of Cu-Ti alloys, whichever they contain a small amount of Ni or not, rather than the conventional peak-aging and drawing process. INTRODUCTION Cu-based alloy wires, which have an excellent combination of strength and electrical conductivity, have attracted extensive attention for highly mechanically stressed electrical devices, such as conductive lead wires and wires in suspension springs. Cu-Be alloys are widely used for such electrical components owing to their combination of strength and electrical conductivity among industrial Cu-based alloys. However, since beryllium is potentially toxic and also a rare element, substitute materials for Cu-Be alloys have been searched for several decades. Age-hardenable Cu–Ti based alloys have been proposed as candidates because their mechanical and physical properties are comparable to those of Cu-Be alloys; however, their electrical conductivity is inferior (Datta & Soffa, 1976; Soffa & Laughlin, 2004). In order to satisfy the requirement of downsizing and streamlining electrical devices, further improvement of the mechanical and electrical properties of Cu–Ti alloy wires is needed. Age-hardenable Cu–Ti alloys, which contain approximately 3 to 6 at.% Ti, are typically prepared using a solid solution treatment above 1100 K and then aging at a moderate temperature of 700 K to 800 K. It has been revealed that the microstructural events during aging progress as follows (Soffa & Laughlin, 2004): (1) compositional modulation of the parent supersaturated Cu solid solution in an initial aging stage (Laughlin & Cahn, 1975), (2) continuous nucleation and growth of fine needle-shaped precipitates of metastable β’-Cu4Ti with a tetragonal structure in a peak-aged stage, and (3) discontinuous precipitation of cellular components laminating the plates of a terminal Cu solid solution and stable β-Cu4Ti with an orthorhombic structure at the grain boundaries in an over-aging stage. It has been also accepted that the highest number density of dispersed fine β’-Cu4Ti needles should contribute to maximal strengthening. On the other hand, decease of the strength in the over-aging stage occurs due to the replacement of the fine β’- Cu4Ti needles with cellular components containing coarse β-Cu4Ti plates, while the electrical conductivity is significantly enhanced due to the depletion of solute Ti in the Cu matrix. This suggests that a combination of strength and electrical conductivity for age-hardenable Cu-Ti alloys is in a trade-off relationship, and that innovative improvement of both properties might be limited to tuning the aging conditions.

Jan 1, 2019

By F. E. Lathe

INTRODUCTION THE present study, based largely upon phase equilibrium diagrams and other theoretical considerations but nevertheless addressed primarily to the practical metallurgist, has been undertaken with a view to discovering what light can be thrown upon the role of alumina in slags. According to Liddell (23), "alumina apparently acts as .a base if much silica is present, as an acid if the silica is low, always as a nuisance." Newton and Wilson (26) state that .alumina "is never added intentionally, as it makes the slag viscous, and is generally an undesirable constituent of slags". Camp and Francis (3) sum up their views by saying, "alumina is seldom used intentionally as a flux, but it is present in nearly all raw material, hence unavoidable". One has only to read The Function of Alumina in Slags, by Henrich (I3), and the very extensive discussion that followed the presentation of his paper, to realize that, before the days of phase equilibrium diagrams, it was a very serious question indeed as to whether alumina should be calculated as a basic, acid, or neutral constituent. Opinions then differed widely, as well they might; today, even though no categorical answer can be given to the question raised, the function of alumina can be at least partly clarified by a study of the fundamental work done by the Geophysical Laboratory in Washington and by certain universities in both America and Europe. It will be a source of gratification to Canadian metallurgists and ceramists to know that work of this type is now under way in the recently organized Physical and Crystal Chemistry Section of the Mines Branch, Ottawa, and that results of practical value have in fact already been obtained.

Jan 1, 1951

By C. A. Pickles

Microwaves are being applied industrially in a number of fields and possess a number of potential advantages that could be applied in extractive metallurgy. Microwave heating has a number of unique characteristics, which distinguish it from the conventional heating methods. In microwave heating, the absorption of energy occurs at the molecular or atomic level and therefore the heat is generated within the material itself. In conventional heating, the exterior temperature is usually higher than the interior, but with microwave heating, the temperature gradient is inverted and thus the interior temperature can be much higher than that of the surface. The energy densities in microwave systems can be relatively high and this in combination with the low thermal conductivities of oxide ores, can lead to very high internal heating rates. In this research, the application of microwave energy for the reduction of a nickeliferous silicate laterite ore has been investigated. The real and imaginary permittivities are the two fundamental properties which determine the microwave absorption characteristics of a material and these were measured for the ore, both with and without carbon additions using the cavity perturbation technique. The microwave heating and reduction experiments were performed in a 0 to 2 kW CTC microwave system. The effects of power input, processing time, sample mass and charcoal additions on the microwave absorption were investigated. Then reduction experiments were performed and the nickel grade of the magnetic concentrate and the nickel recovery in the concentrate were determined.

Jan 1, 2005

By Dale A. Sketchley

The objective of Quality Assurance and Quality Control programs on advanced exploration projects is to ensure that data from sampling, assaying, and recording of geological observations are of high integrity for the purpose of obtaining reliable mineral resource and reserve estimates. National Instrument 43-101 Standards of Disclosure for Mineral Projects states that all scientific and technical reports must be prepared and certified by a Qualified Person in accordance with professional and industry standards following Mineral Exploration Best Practices Guidelines and Definitions, and Guidelines of the CIM Standards on Mineral Resources and Reserves. Additional information is given in Companion Policy 43-101CP and Technical Report Form 43-101F1. Although the Qualified Person must discuss and describe the Sampling Method and Approach; Sample Preparation, Analyses, and Security; and Data Verification; there is little specific information in the guidelines on Quality Assurance and Quality Control programs. Examples from the Oyu Tolgoi Cu-Au Project are given for optimizing sampling protocols, following proper sample preparation procedures, safeguarding sample shipments through chain of custody, ensuring quality of assaying with Round Robin monitoring programs, verifying transcribed data, and validating data with check assays to ensure high integrity for resource and reserve estimation. Oyu Tolgoi, also known as Turquoise Hill, is in the South Gobi desert, Mongolia, about 550 km south of the capital city of Ulaanbaatar, and 875 km northwest of Beijing, China. The project covers a major copper-gold system, which consists of the South West, South, Central, and Far North deposits, comprising high sulphidation and porphyry mineralization with oxide, supergene, and hypogene ore types. Exploration is done by multiple diamond drill rigs, and samples are prepared on-site and shipped to laboratories in Mongolia, Canada, and Australia for further preparation and analysis.

May 1, 2003

By F. Guo

"The leaching kinetics of zinc sulphide concentrate was studied under total pressures ranging from 0.3 MPa to 0.5 MPa and leaching temperatures ranging from 358 K to 378 K. The apparent activation energy of leaching reaction under different total pressures was calculated. The results show that for the extraction of zinc at low-temperature pressure leaching is controlled by an interfacial chemical reaction. This was supported mineralogical analysis of the leaching residue. The kinetic equation for low-temperature pressure leaching of zinc sulphide concentrate was further established by quadratic regression on the basis of shrinking core model.INTRODUCTIONThe Roast-Leach-Electrowinning Process (RLE) is the primary route for zinc production and responsible for more than 85% of the total zinc production (Souza et al., 2007). During the roasting of zinc concentrates, fugitive SO2 causes pollution. The prevention of SO2 emissions from the RLE process can be one of the challenges to this technology (Deller, 2005). In the 1980s, the Zinc Pressure Leach (ZPL) process changed the concept of zinc hydrometallurgy, in which zinc sulphide concentrate is directly leached at approximately 423 K and approximately 0.7 MPa oxygen overpressure and the sulphidic sulphur is oxidized into elemental sulphur so that the pollution by SO2 is completely avoided. Since 1981, five zinc plants have adopted the ZPL process either for expansion by integration with existing roasting facilities, or for the production of zinc without any roasting at all (Collins et al. 1994; Barth et al. 1998). The innovation of the ZPL process has made the zinc industries more competitive although it needs an autoclave. The direct leaching technology of zinc is still in development."

Jan 1, 2012

By Tom Demorest

SMART is an association of mining companies that meet regularly to coordinate the technology development needed by the mining industry. Since 1995, the member companies and institutions have directed research and influenced the manufacturers and suppliers to improve surface mining technology and services. SMART actively supports learning seminars, collaborative research projects, and user groups. Members of SMART include some of the major surface mining companies in North America and Australia. These companies have recognized the value that collaboration can bring to the needs of individual organizations as well as the global mining industry.

May 1, 2009

By Norman A. Grant

"Location and Transportation FacilitiesTHE BEAVERLODGE area of North Saskatchewan is on the north side of lake Athabasca, 500 air miles northeast of Edmonton.The main Eldorado operation and townsite are on the north •side of Beaverlodge lake, which is immediately north of lake Athabasca and is separated from it by only a mile long portage at Lodge bay. The once famous town of Goldfields. Saskatchewan, and the Box property of the Consolidated Mining and Smelting Company of Canada, Limited, are located on lake Athabasca nine mines from Beaverlodge townsite.Previously, all Eldorado freight was delivered by barge at the Lodge Bay portage, hauled across the portage, and across Beaverlodge lake by small Northern Transportation Company barges, which involved many handlings.In 1952 the port of 'Bushell' was established at Black bay. This is a particularly snug harbour, well protected from the main body of the lake and with good foundations for docking facilities. A Butler building, 300 ft. by 60 ft., and tank farms provide storage at the port. A •road from Bushell to the main Beaverlodge operation, a distance of twelve miles through rugged terrain, was built by the Saskatchewan Government. The cost was shared by the Saskatchewan Government, the Federal Government, and Eldorado and other mining companies.Along this road are located the properties of several enterprising mining companies and near the midpoint lies the ambitious budding town of Uranium. This road has made portaging unnecessary and palletized freight loaded at Waterways, Alta., is now loaded directly on trucks at Bushell and delivered to the point of consumption."

Jan 1, 1953

By Seong-Taek Lim

Recently, 7xxx aluminum alloys have been evolved into new variants for thick semiproducts which have low amount of 2nd phases and low quench sensitivity. Commercial 7xxx alloys, especially in the thick forgings made of big ingots, often entail microstructural inhomogeneities and concurrent poor mechanical properties due to limited heating ranges and slower quench cooling. In this study, high strength aluminum alloy 7175 and 7050 are adjusted as an attempt to control the equilibrium phases (M-, T- and S-phase) to have optimum microstructure for the thick forging applications. The effects of the relative content of (Zn, Mg, Cu) on the evolutions of the coarse equilibrium phases, hardening response and resultant mechanical properties are investigated. Equilibrium phases (M,T,S) are evolved depending on the constitutional effect, primarily the change of Zn:Mg ratio, and cooling rate following solutionizing. The formation of the T- and S-phases is effectively controlled, and M-phases are homogeneously precipitated in the adjusted (dilute and high Zn:Mg ratio) alloys. It provides extended heating range and lower quench sensitivity than conventional alloys. The attempts ensure the microstructural homogeneity and improved properties, and is expected to be uniquely applicable in 7xxx thick forgings.

Jan 1, 2004

By Zara Hosseini

?Microseismicity ?Seismic Systems ?Intrinsically Safe and Explosion Proof Seismic System ?Case studies: ?Gas Drainage Optimization ?Fault Identification ?Conclusion Seismic Event ?Occurrences in which energy is released in the rockmass creating a series of seismic waves propagating throughout the rockmass ?Can cause a Fall of Ground or CoalBurst Factors creating Seismicity: ?Mining at Depth ?High stress zones ?Major geological structures ?Mining practices and strategies ?Mining activities i.e. drilling and blasting

Aug 1, 2013

By Horst Konig

This paper illustrates that, with the application of new processes, smaller steel plants using local raw materials can be economical and advisable. It also introduces the problems connected with the direct reduction processes, which use non-coking coal or gas as reducing agents, and which are employed in connection with conventional reduction to produce excellent results. Electric smelting is also discussed, and some practical examples of operating plants are given.

Jan 1, 1970

We report the studies of Proton-Exchange Membrane Fuel Cells (PEM FC) and hydrogen storage materials at McMaster University for the last 14 years. From the initial investigation of ionic conduction mechanism to the revelation of the origin of non-Arrhenius temperature dependence, as well as the synthesis and characterization of high temperature polymer electrolytes, both experimental and theoretical works have been compiled for the fuel cell membranes. In addition to the discovery of suppressed ionic conduction in Electrode-Membrane Assembly (EMA) and novel hydrocarbon PEMs based on micro-emulsion, the first evidence of hydrogen adsorption saturation by carbon nano-tubes was also achieved, which has been the bottleneck for the application of PEM FC. Prior to our study, a number of controversial publications have claimed the hydrogen capacity of these materials to be between 0.1 to 10.0 wt.%, and none demonstrated a plateau of adsorption with pressure that is consistent with monolayer saturation. Others suggested that the tube bundle structure is opened under high pressure to enable higher adsorption on newly uncovered surfaces, but received no confirmation. Using our home made high-pressure instrument with in-situ electrical probes, we found that a plateau is nearly achieved at about 300 atm in the room temperature isotherm, and that nanotube bundles actually compress with pressure instead of splitting, using in-situ electrical measurements.

Jan 1, 2005