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By J. W. Thompson

A contract stipUlating for the delivery of quantities of phosphate rock" f. o. b. mines," and stipUlating that" while this contract is in form an absolute sale for a fixed quantity in each year, it is mutually understood and agreed that the purchase is for the buyer's consumption and not for a sale; the buyer agreeing to give to seller the refusal of any surplus over and above the actual consumption. Buyer is at liberty to increase or diminish the quantity called for in any year, to the extent of not exceeding 10 per cent; provided that the quantity to be taken shall not be less than buyer's consumption; provided further that notice of such increased or diminished demand be given seller 12 months in advance of such change," is to be construed as a contract for the sale of stated quantities of rock, deliverable in approximately equal quantities during each year for the specified series of years, subject only to be increased or diminished after specified notice in any year, where the amount taken would not be les<; than the buyer's consumption, not exceeding 10 per cent, and the contract indicating that the rock was intended by both parties for consumption in the fertilizer plant of the buyer. but the quantity to be taken was not limited by the necessities of' the plant.

Jan 1, 1916

By B. Panton, J. Carvalho, E. T. Brown

High-capacity, post-tensioned anchors have found wide-spread use in initial dam design and construction, and in the strengthening and rehabilitation of concrete dams to meet modern design and safety standards. Despite the advances that have been made in rock mechanics and rock engineering during the almost 80 years in which post-tensioned anchors have been used in dam engineering, some aspects of the rock engineering design of high-capacity rock anchors for dams have changed relatively little over the last 30 or 40 years. This applies, in particular, to the calculations usually carried out to establish the grouted embedment lengths required for deep, post-tensioned anchors. These calculations which involve a number of aleatory and epistemic uncertainties, usually make simplified assumptions about the distribution and values of rock-grout interface shear strengths, the shape of the volume of rock likely to be involved in uplift failure under the influence of a system of post-tensioned anchors, and the mechanism of that failure. The resulting designs are generally conservative. These aspects of the rock engineering design of large, post-tensioned rock anchors for dams could be improved by making greater use of modern, comprehensive, numerical analyses in conjunction with 3D models of the rock mass structure, realistic rock and rock mass properties, and the results of prototype anchor tests in the rock mass concerned.

Jan 1, 2015

By Daniel Maine

Swelling clay soils have been problematic to many types of infrastructure in the United States. However, their impact on underground construction is often misunderstood. The use of swell pressures in design of initial tunnel and shaft support lacks proper guidance and is often mis-interpreted. This paper provides insight and guidance on how to implement a geotechnical investigation program to determine if swelling soil exists at a site and how it impacts the design of temporary support systems for underground projects. An example is provided for how swell pressures were incorporated into the design of an initial support system for a rib and lagging tunnel system and problems that occurred.

Jun 23, 2024

By Thomas E. Finch

Engineering mine design encompasses a range of situations, and each situation has its own range of detail and fineness. The most time consuming, and perhaps repetitive design situation involves evaluation of new or alternate mining methods. Many man years are consumed examing alternatives conjured up at all levels of the design team, from the number crunching engineer to the engineering manager. Many alternatives are intuitively disregarded, some are briefly evaluated and thrown out, and many others are started but not completed due to time constraints. All alternatives have similar input characteristics and evaluation procedures. In the design process, production requirements are known and equipment production capabilities are generated to determine the numbers and costs of an equipment type required to match a given situation. The end result is some comparative figure, typically cost per ton or yard upon which a decision is built. The similarity of input data and problem solving techniques lends design to computer solution. Computer aided equipment evaluation is not new to the mining industry. An existing and accepted technique is exemplified with the programs used by truck manufacturers. Given a haulage profile and production requirements, the number of anyone capacity, horsepower, tire size, gear ratio or similar characteristically identified truck can be determined. This information can be outputted in varying degrees of complexity and the results used with equally varying percentages of credibility by design or production engineers. Most engineers are willing to accept-the computer&apos;s effort with relief and a desire for belief. Although inherently more complex, the ultimate end of computer manipulation should be total mine design. This is an extremely large step in the evolution of mine design, and not many engineers, including the authors, believe the results would be directly applicable or necessarily correct. As with computer simulations of an operation, total computer design of mines requires such complex and lengthy input that each mine might be manually designed more quickly and cheaply. The existence of computer programs which initially evaluate a mining system or part of the system is upon us, however.

Jan 1, 1978

By A. B. Kinzel

IT is with sincere appreciation and a deep sense of responsibility that I accept the honor of delivering the Howe Memorial Lecture. In our time metallurgical research has delved into phenomena ever more complex in character, so that much of this work must be done by organized teams. We, of the Union Carbide and Carbon Research Laboratories and the Electro Metallurgical Co., are truly a team and the lecture which is to follow is due largely to a few of the outstanding members of that team here cited and well known to you in their own right: John Lamont, whose work deserves special recognition, Walter Crafts, William Forgeng, William Binder, Robert Fowler, and David Swan. Thus it is a fitting pleasure to accept this honor for the research institution which I represent. Henry Marion Howe was truly inspirational and his breadth of view was such that he could use either the method of rigid proof or implied mechanism to further the broad understanding. But perhaps his outstanding characteristic was his sound judgment and his ability to weigh observations. The following is replete with observations and judgment as to their implication. We would like to feel that it is the type of dissertation which Howe, himself, would have enjoyed. Chromium carbides in stainless steel have, in a sense, been a key to the progress of the stainless steel industry. Brearley&apos;s first stainless steel, containing approximately 0.30 pct C, was successful because it differed from previous Fe-Cr alloys in that the carbides were present in such amount and form as to provide the stainless and cutting properties. Again, the 12 pct Cr die steels with a carbon content of 1.5 pct or more achieved their properties by virtue of the form and distribution of the chromium carbides. In the straight chromium steels with from 12 to 25 pct Cr, chromium carbide amount and distribution are once more the determinants with respect to physical properties and corrosion resistance. In each of the cases just cited the role of the carbide is in essence similar to that of iron carbide in carbon steel and this story is so well known that we need not dwell on it. In the austenitic stainless steels, the chromium carbide plays only a minor positive role with respect to mechanical properties, and for corrosion resistance the objective is to achieve maximum homogeneity. Thus the tendency has been to ever lower the carbon and correlatively the chromium carbide content of the austenitic steels. Today stainless steels with carbon less than 0.03 pct are beginning to find their true place, and this is being aided in major degree by our Company&apos;s introduction of a new type of ferrochromium having negligible carbon. The role of carbon in these austenitic steels has long been recognized, and a truly enormous amount of research has been devoted to the subject. Much has been learned about corrosion resistance, but the attack on the problem from the point of view of carbide precipitation and the nature thereof has left much to be understood. Because of its fundamental importance to the future of stainless steels, further study of the mechanism of carbide formation in austenitic steels is of interest. In the 18-8 Cr-Ni steels, which are typical of the austenitic class of steel, carbon is soluble in the aus-tenite to the extent of approximately 0.15 pct at 1832°F (1000°C). The solubility becomes less with decreasing temperature, so that at 1652°F (900°C) the solubility limit is approximately 0.06 pct, at 1472°F (800°C) it is about 0.03 pct, and at 932°F (500°C) it is approximately 0.01 pct. Obviously this is the ideal situation for the classical precipitation phenomenon. It is true that, in a sense, 18-8 austenite resulting from annealing is in a metastable state, and the phenomenon of ferritic precipitation from this austenite should be considered. However, in a so-called fully austenitic 18-8 steel this is secondary with respect to the carbides and can be neglected. A wide variety of chromium carbides is known. Only one chromium carbide, Cr,,C,,, frequently referred to as Cr,C, has been found in unmodified low carbon 18-8 steel. This, fortunately, simplifies the study of the precipitation phenomena. For this study an A.I.S.I. type 304 stainless steel of commercial quality was selected. Analysis showed C 0.07 pct, Mn 0.49 pct, Si 0.33 pct, Ni 9.34 pct, Cr 18.91 pct, and N 0.033 pct. As expected with this composition the steel was homogeneous after annealing except for a few pools of ferrite, which were disregarded in that their location was not coincident with subsequent carbide precipitation areas. On corrosion testing the steel was normal and typical of good commercial quality. Specimens 1/2xlx4 in. were annealed and subjected to precipitation heat treatment for 100 hr at 100" temperature intervals from 1000° to 1500°F and for ten selected intervals ranging from 5 min to 64 hr at 1300°F. These blocks were then cut into small pieces for metallographic studies. The first problem

Jan 1, 1953

By Robert C. Merritt

This report describes laboratory as well as pilot heap leaching investigations of low-grade sandstone ores from Wyoming, New Mexico, and Colorado. Sodium carbonate-bicarbonate solutions containing sodium hypochlorite extracted up to 86, 54, and 16 percent U308 from Wyoming, New Mexico, and Colorado ores, respectively. Ammonium carbonate-bicarbonate solutions containing sodium hypochlorite were less effective at leaching these ores. Acid leach in replicate pilot plant testing resulted in U308 extractions of 96, 88, and 81 percent from the Wyoming, New Mexico, and Colorado ores. The development of cost-effective processes for extracting uranium from low-grade ore is essential to the assurance of a continuing domestic supply of uranium.

Jan 1, 1977

By L. F. Heising

The Bureau of Mines evaluated 42 composite samples from selected Michigan-Wisconsin iron formations by reductive roasting-magnetic separation and flotation at minus 325 mesh. Samples having poor to marginal response on initial examination by conventional methods were reevaluated by finer grinding, by reagent suite modifications, and by selective flocculation-desliming techniques. Results ranged from excellent on Menominee Range samples to relatively on Gogebic Range ores. Marquette Range samples ranged from responsive to nonresponsive, depending upon grain size and mineral association.

Jan 1, 1967

By C. T. Anderson

In July 1947, the U. S. Bureau of Mines, in cooperation with the Air Materiel Command, started an investigation of zirconium alloys with the object of determining the suitability of such alloys for high-temperature applications. This report covers the preliminary study of about 25 zirconium-rich alloy systems with respect to preparation, fabrication, tensile properties, metallographic structures; constitution, and heat resistance. Obviously, each system could not be investigated thoroughly, and this publication can be regarded only as a first approach. The more promising individual alloy systems will be studied in greater detail and reported in subsequent publications. The study of zirconium alloys on such a scale has been made possible by the U.S. Bureau of Mines developments in the past 5 years On producing zirconium metal. This basic process is similar to that developed by Kroll for producing ductile titanium metal and consists essentially of reducing zirconium chloride by means of molten magnesium. The Northwest Electrodevelopment Laboratory at Albany, Oreg., has produced several thousand pounds of ductile metal in this manner and has a pilot plant producing over 300 pounds of metal per week. Alloys were prepared by melting Bureau of Mines zirconium and the best available grade of alloying element in graphite, with suitable provisions for preventing oxidation. The ingots were quartered longitudinally and sheath-swaged at 850° c. to 3/8-inch diameter rod. Two of those rods were send to Wright Field for room-temperature and 1,200° F. tensile properties. The remaining two sections were used for metallographic, hardness, heat-treatment, and heat-resistance studies. The salient features of this investigation are summarized in table 1.

Jan 1, 1950

By Dany Racine, Daniel Marceau, Denis Laroche, Dmitry Lukovnikov

Carbon base materials play a critical role in the performance of Hall-Héroult cell. The determination of their thermo-physical properties is of primary importance for modeling and designing complete cell systems. However, overcoming the associated experimental hurdles is complex and often underestimated. Of them are the Poisson’s ratio measurements and the continuous oxidation/burning of the materials at temperatures above 200°C. The novel procedure developed in this research is based on the Gleeble® 3800 system. Its vacuum chamber allows test with a chosen atmosphere at temperature of more than 1000°C. Young’s modulus, Poisson’s ratio and the coefficient of thermal expansion values can all be adequately measured using a single test. Cylindrical carbon samples (: 50mm, L: 100mm) were tested in the modified system at temperatures ranging from room to 950°C without any trace of oxidation. The resulting values were also in good agreement with literature data for a specific graphite material.

Jan 1, 2015

By John Jiang, Brian R. Hart, Stamen S. Dimov, Aparup Chattopadhyay, Barun K. Gorain

"This paper presents a systematic approach to metallurgy diagnostics using an integrated gold deportment methodology developed for complex refractory gold and copper-gold ore bodies. Quantification of gold deportment for these ore bodies is a challenging task due to reasons such as lower grades, high variability of visible and invisible gold content in different sulphides and iron oxide phases, significant presence of disseminated and composite carbonaceous matters along with associations of various copper sulphide phases. Some case studies are presented in this paper to demonstrate the value of a high confidence gold deportment methodology in developing insights for problem diagnostics and to identify opportunities for metallurgical improvements. A holistic approach involving different fields of expertise is critical for successful development and delivery of solutions for complex ore bodies.INTRODUCTION Studies were initiated on various complex ore deposits and also on samples representing various process streams. These complex copper-gold single refractory, double and triple refractory gold ores are mainly composed of silicates and/or carbonates with moderate amounts of clay and mica, along with minor amounts of sulphides and organic carbonaceous matter. Variable proportions of visible gold and “invisible gold” (sub-microscopic gold) were noted in different mineral phases for various ore types and process stream samples. Invisible gold commonly occurs as solid solution or as colloidal-sized particles in different sulphides and other phases for different refractory ores. The dominance of invisible gold and presence of highly preg-robbing along with finely disseminated carbonaceous matters adversely affects gold recovery in flotation and leach circuits for most of these double and triple refractory ores. This paper discusses applications of an integrated gold deportment technique developed for different types of gold and copper-gold ores, namely, complex copper-gold, double and triple refractory gold ores (Chattopadhyay & Gorain, 2014; Chattopadhyay et al., 2016). Various process streams from flotation and gold leaching circuits were investigated. Different concentrates and tailings samples from flotation circuits whereas feed and discharges from pressure oxidation (POX) and carbon-in-leach (CIL) residues were used from gold processing circuits."

Jan 1, 2017

By T. R. Kostecki, J. Hirschi

"Analytical engineering design is based upon a trial-and-error iterative and deterministic process. Within this process, the engineer obtains some estimated values, plugs them into de facto closed-form equations, and receives output, which is expected to be a single number that serves as the basis for the design. This number is typically a factor of safety, or some other equivalent strength-stress ratio. This provides the engineer with a quick and relatively quantitative design methodology. This can create problems however, because in mining applications, the actual in situ system is highly variable, complex and often chaotic, which can lead to potentially incorrect conclusions that result in unsafe designs. A more appropriate and reliable approach is a probabilistic analysis for engineering design. This process is used widely in civil and other engineering disciplines, but is often overlooked for applications in coal mine design. Additionally, it seems the amount of past studies using this approach, especially in coal mine design, are rather limited. Considering how the probabilistic approach can account for uncertainty in parametric values and how unpredictable a mining design can be, the authors believe that this approach has potential in mining. This paper will focus on a summary of past studies related to probabilistic analysis in coal mine pillar design and provide recommendations for future work that could improve design reliability. INTRODUCTIONFeasibility and fundamental design procedures for excavations often start with an assessment of mine openings, pillar design, and the surrounding structure by using a deterministic approach with closedform solutions (ex. Bienawski, Obert-Duvall). These are reliable methods, but designers know that the inputs in these closed-form solutions are estimates at best and do not incorporate any degree of uncertainty. This is therefore not an optimal design procedure.A more appropriate design should incorporate some uncertainty because of the chaotic and variable nature of geology and mining conditions in general. In an attempt to account for uncertainty, a probabilistic approach can be adopted, which accounts for deviations in variables and provides a more optimum design solution. By applying a probabilistic approach, a designer can look at multiple failure scenarios at the same time instead of using the same deterministic design over and over."

Jan 1, 2015

By L. M. Burman

The phase-boundary pressure required to maintain a natural hydrocarbon fluid in a single phase must be considered in planning the recovery of reservoir liquids by miscible-phase processes. The change in the phase-boundary pressure at reservoir temperature that results when a light component or a mixture of light components is added to a reservoir fluid is an especially important consideration. The cricondenbar pressure (maximum phase-boundary pressure) and the critical pressure are unique correlated pressures that have been utilized to calculate the change in phase-boundary pressure that may result when the composition of a reservoir liquid is altered by an additive. In this study one reservoir oil and three gas-condensate fluids are used as examples. Correlations pertaining to the critical and cricondenbar states in chapters 4 and 5 of Bureau of Mines Monograph 10 (3)5 were used to demonstrate how butane and lighter components added to these reservoir fluids affect their phase-boundary pressures.

Jan 1, 1962

By Jr. Reed

Cassiterite was discovered in Coosa County, Ala. in 1880 by Judge John S. Bentley. Since that time intensive surface prospecting has revealed the presence of cassiterite in pegmatite bodies that occur in a zone about 20 miles long and 3 miles wide. Numerous trenches and test pits and several shafts were sunk, and one attempt was made to nine and concentrate the cassiterite commercially. The problem of a domestic tin industry and the question of the extent of the Alabama tin deposits have long been of public interest and concern. The deposits have been examined by numerous geologists and several governmental agencies, including the Geological Survey of Alabama, the Geological Survey and the Bureau of, Mines. of the Department of Interior, and others. The Bureau of Mines and the owners of the properties, Charles A. Dean and Robert A. Russell, investigated the Coosa County tin deposits under a cooperative agreement from October 1, 1948, to June 10, 1949. Sixteen hand trenches totaling 527 linear feet and 33 machine trenches totaling 6,780 linear feet were dug. Two shafts wore sunk for a total of 72 feet, and 44.4 feet of drifting was done. Thirty-one diamond-drill holes totaling 2,776 feet were drilled.. Four hundred thirty samples, representing 1,192.6 linear feet, were taken for assay and wore analyzed by the Southern Experiment Station at Tuscaloosa, Ala.

Jan 1, 1950

By Andersan dos Santos Paula

O objetivo deste trabalho foi avaliar a influência da potência do laser Yb:vidro a fibra, no que diz respeito a extensão dos efeitos estruturais promovido e a possibilidade de corte de uma chapa de NiTi equiatômica austenítica com evidência de encruamento. Após a tentativa de corte a laser, a caracterização foi realizada através de microscopia óptica, microscopia eletrônica de varredura (MEV) / espectroscopia de energia dispersiva de Raios X (EDS) e análise de nanoindentação instrumentada. De acordo com os resultados obtidos pode-se observar que nenhum dos parâmetros de corte a laser usados nos 3 cortes distintos foi suficiente para promover o seccionamento da chapa, bem como revelou evidências de recristalização em conjunto a uma significativa oxidação superficial na zona termicamente afetada.

Aug 16, 2017

By Antonio Fabiano de Oliveira

Estudos de laminação com revestimento de cromo e influência nas propriedades foram realizados com o objetivo de aumentar a produtividade dos cilindros. Para tal, foram utilizados cilindros cromados para laminação de chapas de cobre, com amostragem da técnica de réplica epoxy. A compreensão da correlação entre microestrutura e propriedades do material é objeto de grande interesse e, ao mesmo tempo, necessário para aplicação prática na laminação a frio, combinando revestimento e produtividade. O objetivo da pesquisa atual é comparar as propriedades tribológicas do cobre antes e depois da laminação, no cilindro de trabalho e chapa, com e sem revestimento de cromo.

Oct 30, 2017

By H. D. B. Wilson, D. T. Anderson

"Canadian sulphide deposits generally have characteristic compositions. Metal associations in ore deposits and in igneous rocks are similar.Nickel: sulphur ratios, copper-nickel ratios, and nickel :cobalt ratios in copper-nickel sulphide ores are characteristic for most orebodies. Nickel, as sulphide, is highest in ores associated with ultrabasic rocks, whereas copper is highest in ores associated with gabbros. Cobalt is relatively constant. The metal ratios in copper-nickel ores are due, first, to the composition of the related igneous rock or magma; second, to the partition ratios of the metals into the sulphides when separating from the silicate rock or magma; and third, to the conditions at the time of deposition. Each factor is discussed and the evidence indicates the Frood orebody is a magmatic segregation in place and Falconbridge is an injected sulphide melt. Many Canadian orebodies containing copper, zinc, or lead also have relatively constant compositions. •Copper and zinc are concentrated in gabbro and diorite, and copper-zinc ores in northwestern Quebec are spatially related to gabbros and diorites. The same three factors con-trolling metal ratios in. copper-nickel deposits should control the metal ratios in copper-zinc deposits if the metals come from the gabbro-diorite intrusions.The ratios of base metals in common sedimentary rocks are not similar to the ratios in orebodies. Base metal elements are mobilized during high-grade metamorphism, but much fundamental research is needed before the relation between metamorphism and ore deposits can be established on a sound basis. The distribution of elements in sulphide orebodies suggests that cop-per, zinc, and lead are deposited simultaneously .in relatively constant proportions rather than successively in a paragenetic sequence. Zoning may be due to different ratios of metals being deposited under changing temperature, pressure, and chemical environment, or may be the result of other processes."

Jan 1, 1959

By Daniel J. Schulze

Abstract-Eclogite is an important source of diamond in the upper mantle, but is more localized than peridotite. Using eclogitic minerals in kimberlite and diamond exploration is also more problematic than using the well-known peridotite-derived indicator minerals Cr-pyrope and magnesiochromite. The problems include color similarities between orange garnets from eclogites, Cr-poor megacrysts, and crustal garnets, chemical similarities with Cr-poor megacryst suite garnets (specifically elevated Na2O contents), and low abundance of eclogite garnet xenocrysts in most known kimberlites. Chemical screens must be used carefully to distinguish between varieties of orange garnets in exploration samples. For example, most orange garnets of crustal origin have >22 wt% FeO, with mantle eclogite garnets having lower values. Na2O-bearing garnets from the Cr-poor megacryst suite can be distinguished from Na2O-bearing garnets from diamondiferous eclogites by the elevated TiO2 contents of the former. The low abundance of eclogite garnet xenocrysts in kimberlites worldwide, however, may dictate that use of eclogite garnets in diamond exploration in most cases be restricted to advanced stages of kimberlite exploration and evaluation of kimberlite diamond potential. Crpyropes, Mg-ilmenites and Cr-rich chromites are more useful than eclogitic garnets in most stages of diamond exploration. If orange garnet xenocrysts are sought in a kimberlite exploration program, those from the Cr-poor megacryst suite will be more useful than eclogite derived garnets, due to the typical great abundance of the former, although they carry no information of the diamond potential of the host kimberlite.

Jan 1, 1997

By Daniel J. Schulze

Eclogite is an important source of diamond in the upper mantle, but is more localized than peridotite. Using eclogitic minerals in kimberlite and diamond exploration is also more problematic than using the well-known peridotite-derived indicator minerals Cr-pyrope and magnesio-chromite. The problems include color similarities between orange garnets from eclogites, Cr-poor megacrysts, and crustal garnets, chemical similarities with Cr-poor megacryst suite garnets (speci?cally elevated Na2O contents), and low abundance of eclogite garnet xenocrysts in most known kimberlites. Chemical screens must be used carefully to distinguish between varieties of orange garnetsin exploration samples. For example, most orange garnets of crustal origin have >22 wt% FeO, with mantle eclogite garnets having lower values. Na2O-bearing garnets from the Cr-poor megacryst suite can be distinguished from Na2O-bearing garnets from diamondiferous eclogites by the elevated TiO2contents of the former. The low abundance of eclogite garnet xenocrysts in kimberlites worldwide, however, may dictate that use of eclogite garnets in diamond exploration in most cases be restricted to advanced stages of kimberlite exploration and evaluation of kimberlite diamond potential. Cr-pyropes, Mg-ilmenites and Cr-rich chromites are more useful than eclogitic garnets in most stages of diamond exploration. If orange garnet xenocrysts are sought in a kimberlite exploration program, those from the Cr-poor megacryst suite will be more useful than eclogite derived garnets, due to the typical great abundance of the former, although they carry no information of the diamond potential of the host kimberlite.

Jan 1, 1997

By F. Hassani, D. O’Donnell, M. Momayez, P. Guevremont

Shotcrete is a practical and economical support system in many Canadian underground mines. Although shotcrete technology has gained acceptance in the mining industry, there are some problems that have emerged with respect to quality assessment and thickness measurement of the liner. This paper presents recent tests performed with miniature seismic reflection technology (MSR) developed and patented at McGill University primarily for thickness measurement of this heterogeneous liner. MSR is also capable of providing information regarding the quality of shotcrete in terms of its mechanical properties such as modulus of elasticity and Poisson’s ratio. Work was performed on site in an underground mine in Ontario, Canada. This paper also presents the results from laboratory tests performed on fiber-reinforced and non-reinforced shotcrete panels that were used to assess the P-wave velocity in both materials. The results of these tests were used in a second site investigation. The NDT thickness measurements showed good agreement with direct thickness measurement such as coring. In addition, the MSR technology has the advantage of being more accurate and more affordable compared to other non-destructive testing (NDT) systems in the market.

Jan 1, 2002

By Gisele Ferreira de Lima

Magnésio e suas ligas são promissores para armazenagem de hidrogênio devido à alta eficiência, boa reversibilidade, baixo custo e segurança. Entretanto, hidretos à base de Mg apresentam cinéticas de ab/dessorção lentas, temperaturas de operação muito altas, e alta reatividade ao ar para aplicação práticas. A moagem de alta energia (HEBM) combinada com o uso de catalisadores têm produzido nanocompósitos à base de Mg com cinéticas mais rápidas. Recentemente, processos termomecânicos e de deformação plástica severa (SPD) têm sido investigados para produzir nanocompósitos em volume com melhor resistência ao ar (processo de ativação) e que podem ser facilmente fabricados em escala industrial. No presente trabalho, amostras 2Mg-Fe foram misturadas com CNT (0-5%p.) por HEBM, e em seguida processadas por extrusão a quente (termomecânico) a 300oC e/ou laminação a frio (SPD) a temperatura ambiente. Pós com 0%p a 5%p. de CNT mostraram padrões de DRX muito similares indicando similares nanoestruturas. Todas as amostras puderam ser laminadas, mas somente amostras com menos que 2,0%p. de CNT puderam ser extrudadas, e submetidas pela combinação de extrusão-laminação. As propriedades cinéticas, medidas pelos métodos Sieverts e DSC, foram piores para as extrudadas, intermediárias para as extrudadas/laminadas e melhores para as somente laminadas. Nessas últimas, os picos de Bragg mostraram baixa intensidade e textura favorável ao longo de (002) no Mg, que possivelmente explicam esses resultados. Quanto maiores foram as quantidades de CNT melhores foram as propriedades (cinética e temperatura de dessorção).

Aug 8, 2018