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By Nick Holonyak

Halogen vapor-transport synthesis of Ga(As,-,Px) and its preparation into laser junctions are described. Electrical and optical properties of Ga(As,-,PX) laser junctions are discussed. The present limitations in these properties are related to material proble?vzs and the very early state of development of Ga(As,-,PX), and are discussed in this context. Inhonzogeneity problems, fluctuation of As :P ratio, and problems with deep-level contaminants are described and related to Ga(As,-,PX) junction performance. Laser junctions are demonstrated which operate to wavelengths as short as 6470 A (77°K). The prospect that Ga(As,-,P,) will operate to wavelengths perhaps 100A shorter is mentioned. IN this paper we wish to describe some of the more important features of almost 1 year of experience in the preparation and properties of Ga(As,-,P,) p-n junction lasers. Because much data so far available are far from complete, some of the results still must be considered tentative and subject to correction and revision as work on Ga(As,-,P,) crystal problems progresses. Although the electrical, optical, and device properties of Ga(As,-,P,) junction lasers are understandably of considerable interest, the work to date points out that by far the most serious problems extant and those deserving first attention are problems involving the growth, doping, and perfection of Ga(As,-,P,) crystals. One of the most formidable of these is to grow Ga(As,-,P,) sufficiently free of deep levels, either due to contaminants or to structural imperfections, to allow fabrication of laser p-n junctions which can be cooled and not suffer from "freeze-out" of carriers on deep levels (and consequent double-injection behavior). In addition to the problems of growing crystals adequately free of deep levels and generally of the highest perfection, so that the best possible laser junctions can be realized, the further goal remains of increasing the phosphorus content well beyond 40 pct in an attempt to determine the practical lower wavelength limits of laser action in the Ga(As,-,P,) system. Even though the laser junctions prepared in Ga(As,-,P,) are of importance in their own right, we have considered them at this point mainly a means to study the growth and crystal problems of the material. It can be concluded that the laser junctions now available are almost completely limited by the purity and structural deficiencies of Ga(As,-,P,) crystals, and cannot be fairly compared with, for example, GaAs p-n junction lasers until Ga(As,-,P,) crystal growth has been more extensively developed. The basis for the statements above will become evident in the following sections which describe Ga(As,-,P,) crystal and junction preparation, and laser-junction properties. G(As,-,P,) CRYSTAL GROWTH As previously reported,2 we have found it convenient to employ the halogen vapor-transport process3 for synthesizing Ga(As,-,P,) crystals for use in laser junctions. Commercially available GaAs and Gap, separately prepared by halogen vapor tranport, are sealed in the desired ratio in a quartz vessel with a quantity of column-VI donor and a small quantity of metal halide which supplies the halogen for transport. The sealed ampoule, as shown in Fig. 1, is heated at a temperature in the range from 1025" to 1100°C at the position of the source GaAs and Gap. The GaAs and Gap are simultaneously vapor-transported and deposited as Ga(As,-,P,) at one end of the ampoule

Jan 1, 1964

By Wayne W. Murdy

Since 1993, Newmont Mining has been growing through the development 'q of three major foreign mining operations with a fourth under construction. The first project, Yanacocha in Peru, began operating in October 1993. This occurred at a time when political and business risk in that country was considered high. In 1995, Newmont began operating the Muruntau joint venture in Uzbekistan. It is the first mining project of its kind in the Confederation of Independent States (CIS). In early 1996, Newmont started operating the Minahasa Mine in Indonesia. In early 1997, Newmont began construction of a $1.9-billion project in Indonesia. The company is also completing a feasibility study with its partner for the development of a gold operation in Mexico. All of these projects have been considered "risky" by most standards. Newmont has been successful in all of them through risk mitigation programs. These programs include using strong and successful in-country partners, concentrating on developing a strong national workforce with minimal expatriate employees, using World Bank, European Bank for Reconstruction and Development (EBRD) and International Finance Corp. (IFC) financing and building and maintaining strong ties with host governments.

Jan 1, 1997

By L. A. Neumeier

The Bureau of Mines evaluated the properties and anisotropy in properties of rolled Zn-Cu and Zn-0.12 pct Ti-Cu alloys with various copper additions to 1.25 pct. The alloys were rolled cold and at various hot-rolling temperatures to reductions as high as 92 pct after breakdown rolling. The properties are extremely sensitive to various combinations of composition, rolling temperature, and rolling reduction, Zn-Cu alloys can develop good creep resistance, but they are inferior in that respect to Zn-Ti-Cu alloys. For alloys either with or without the titanium addition, cold-rolling results in recrystallization of the matrix and rejection of copper from solution, causing poor hardness, tensile, and creep properties, but high ductility. Peak tensile strengths develop when the alloys are rolled in the range 320° to 400° F, Best creep resistance for Zn-Cu alloys requires higher rolling temperatures when copper content is increased. Creep resistance is best for Zn-Ti-Cu alloys with about 0.75 to 1.0 pct CU rolled near 480° F. Some copper is soluble in the TiZn15 phase, which forms into "stringers" during rolling. The possible contributions to creep behavior of factors such as distribution of second-phase particles, grain size, and preferred orientation are discussed.

Jan 1, 1970

By Feida Wu, Yuhang Liu, Huimin Gao, Yuhan Song, Zhi Liu, Zijie Ren

In the process of quartz purification by calcination water quenching, the different expansion rates of gangue minerals and quartz were used to produce cracks or remove fluid inclusions, which is conducive to subsequent purification. However, the role and mechanism of calcination-water quenching are still lacking in research. In this paper, the position of calcinationwater quenching in gangue quartz purification process was adjusted and the removal effect of calcination-water quenching process at different nodes in the process was explored. The results show that the purification effects of grinding-calcinationwater quenching-classification-acid leaching process and grinding-classification-acid leaching-calcination-water quenching process were relatively good. The main reason is that calcined water quenching can make quartz produce cracks, which are more rough. At the same time, calcined water quenching is located after grinding, which has a larger specific surface area, pore volume and pore diameter, and has a strong adsorption capacity for acid solutions.

Nov 2, 2023

By Norman Miskelly

Substantial progress has been made over the last ten years in the development of uniform national and international standards covering the definition, estimation and public reporting of mineral resources and mineral reserves. Agreement between the major participating countries has been reached, which include the requirement that a Competent Person prepares and approves publication of mineral resources and reserves. Most national regulatory organizations have accepted the new standards and have included them in the rules that must be followed by mining companies operating under their jurisdiction. These developments are the result of a concerted effort on the part of professional societies, national regulatory agencies, international organizations, and many dedicated individuals. The historical development of these standards is summarized in this paper. Accepted definitions of mineral resources and mineral reserves are discussed, as well as the definition and role of the Competent Person. Additional effort is needed before the international standards are fully understood, accepted and followed by mining companies, regulatory agencies, the investment community and the general public. Steps being taken toward development of a Mineral Reserves International Reporting Code Template (International Template) that will be available for all countries to use in deriving their specific country reporting codes, are outlined

Jan 1, 2003

By Carl Tom Blevins

Resin was first introduced to U. S. mines in 1971 and first produced in 1973. The original polyester roof bolt resin was very expensive and limited to a single cartridge size and a single slow gel time. Early resin applications were limited to very difficult ground conditions. Today approximately 80% of the over 100 million roof bolts installed in U.S. mines, tunnels, and construction projects employ polyester roof bolt resin. The industry has evolved from hand packing samples for trial testing to producing enough resin, if converted to a .9 inch (22.9mm) diameter cartridge, to encircle the world at the equator approximately three (3) times each year. Manufacturing and design improvements allow for a more consistent product with a wide range of applications at a price that is approximately 30% below our 1974 sales price. An inflation adjusted dollar buys six (6) times more resin in 2006 than in 1974. Modern gel times range from a few seconds to over 15 minutes. Viscosity is matched to bolt type and drilling machine characteristics. Multiple cartridge diameters and a wide range of cartridge lengths are offered by two operating companies. Resin manufacturers have also gone through a period of restructuring and change to meet the challenges of the mining industry. DuPont Fasloc has become Fasloc, Inc., a stand-alone company. Celtite became Fosroc then Minova, as it is known today. During this transformation, several manufacturers have either discontinued production or were absorbed. The industry led the development of the chemical grouting materials specifications contained in ASTM F432-95, Standard Specifications for Roof and Rock Bolts and Accessories. A history of the industry will be presented within a discussion of the evolution of the strength index, speed index, cartridge volume, class designation, and product marking requirements of ASTM F432-95.

Jan 1, 2006

By BLAllEY STEVENS

(Canal Zone Meeting, November, 1910.) I. INTRODUCTION. TEH object of this paper is to show how igneous intrusion is governed by definite mechanical laws. A distinction is made between dikes and fissures, and the various characteristics of intrusions are explained on an exact scientific basis. The modification of rock-stresses by intrusion is then considered and extensive isostress regions are recognized. Finally, a complete classification of intrusions is constructed covering all pos-sible cases. The generalizations of observed data, taken from Geikie's Textbook of Geology, conform to the laws of intrusion herein stated, and the deductions based upon these laws. No authority, however, is quoted for the type which I have named a corrugated intrusion. Its existence is a necessary deduction from the laws of intrusion, and even the entire absence of examples in technical publications cannot disprove its reality. In all probability, corrugated fissures would have remained undiscovered, but for the working of mineral veins. As intrusions of tabular form are seldom worked for commercial purposes, it has been left for theory to anticipate the discovery of corrugated dikes. In the light of these laws of intrusion and the corresponding laws of fissures,1 there seems to be a remarkable uniformity of stress-distribution in rocks at moderate depths. This renders .possible the mathematical calculation which should help us to approximate exact science in this and kindred branches of applied geology.

Jan 1, 1911

By J. E. Harris, J. A. Whiteman, A. G. Quarrell

The graphitizing reaction has been studied in a number of Fe-C-Si alloys in the temperature range 550° to 725°C. The TTT relationships exhibit "C" curve behavior except where nuclei, either foreign or graphite itself, are present before the start of the reaction. It is suggested that the rate -controlling process is diffusion of carbon through ferrite. For the reaction to proceed at the observed rate it is calculated that the matrix surrounding the particles must deform plastically; experimental evidence for this deformation is presented. It is well-established that the decomposition of austenite to pear lite occurs at a maximum rate at an intermediate temperature.l-5 This "C curve" be- havior, which has been reported in a number of other systems,5-10 is a consequence of the relatively low rate of nucleation of the pearlite at small degrees of undercooling of the austenite. The cemen-tite phase in the pearlite is, in turn, metastable with respect to graphite and if steels are held for prolonged periods at elevated temperatures decomposition of the pearlite occurs. It is difficult to predict the shape of the subcriti-cal graphitization TTT (time, temperature, transformation) diagram for, in this case, undercooling does not occur. However, the free-energy change for the reaction does decrease with increasing temperature" (Fig. 1) and it is thus anticipated that the rate of nucleation will fall as the temperature approaches that of the eutectoid. In addition, a decreasing growth rate with increasing temperature is predicted in some circumstances with pure Fe-C alloys. However, apparently similar conditions exist for first-stage graphitization in the austenite range (malleabilization) but no evidence for C curve behavior has been presented in the extensive liter-

Jan 1, 1965

By Joseph Hays

MORE years ago than I care to admit I conferred the title of "combustion engineer? upon my-self since nobody else would confer it. I thought at the time, and for some, years thereafter, that my field was limited to the precincts where the fuel was being burned, but I found that I could stand in the door of the furnace room and hear distressed heat units calling for help all over the plant. Some of them were over-worked, others were compelled to do useless work, and still others, anxious to render a proper account of themselves, were not permitted to do any sort of work at all and were utterly wasted. The combustion engineer has something to do at that interesting occasion when the heat unit is being born in the furnace, but his responsibility does not end there. He must follow the little fellow throughout the entire period of its hectic existence in the plant and see that it gets a fair chance and a square deal everywhere. I fear that the general impression of the combustion engineer's duties is much as mine was in the beginning; that his job is limited to the implements and processes incident to the specific operation of converting fuel into active, heat energy and of applying it to the boiler, the still, or what-not, with the least possible waste. But is it not true that a heat unit saved in a remote corner of the plant means just as much to the fuel account as another saved at the furnace? And if nobody else is looking after the heat units out on the range why should the combustion engineer spend all of his time hanging around the corral? If combustion engineer is not a broad enough title to cover the man in charge of a general heat unit rescue campaign call him any-thing else you please. The job is all that counts. The name means nothing. A skunk by any other name would smell as bad. The greatest field I have ever found for general "heat rescue" work is the oil refinery. In refining we first put heat into the oil and then take it away from the vapor. The greatest heat losses occur during the cooling operation, but there are losses, many of them preventable, either wholly or partly, at every step of the several processes in oil refining.

Jan 3, 1928

By P. A. Davies

Paper presented at the conference: Risk assessment in the extractive industries, held in Exeter, UK, 23-24 March 1994, and first published London: IMM, 1994, preprint volume, 11pp., 15 refs. Hazards such as vibration, dust emission and fragment projection can result in an area called the Danger Zone being set around a blasting site. Traditionally Danger Zones have been set solely on the basis of consequences (e.g. based on the maximum distance of rock projection or expected ground vibration plus a defined safety margin). Advances in risk assessment and its growing acceptance as a safety management tool have led to the setting of Danger Zones based on both consequences and frequency of occurrence. This allows distances to be optimised on the basis of acceptable risk levels rather than the potential consequences of infrequent events. The setting of a flyrock Danger Zone is used to demonstrate a risk-based approach compared with a traditional consequence approach

Aug 1, 1995

By M. Roy, Y. Roux, R. McIvor

"La Compagnie Minière Québec Cartier at Port Cartier. Quebec, utilizes six parallel wet grinding open circuit ball mills to grind iron ore concentrate for the pellet making process. In an attempt to improve grinding efficiency, a mix of 605 25 mm (1 in.) and 405 38 mm (1 ½ in.) grinding balls was charged to mill D while the opposite mix was used in all the other mills. Because media costs were higher for mill D, it was necessary to find out if the smaller balls provided a net economic benefit. Therefore, a test program was undertaken to determine the relative efficiency of the charge in mill D compared to the other grinding mills. Mill F was chosen for comparative efficiency measurements.The first problem was to choose a suitable definition of grinding efficiency. In management's view, previous attempts to quantify milling performance using population balance modelling were ineffective because they were unable to relate breakage rate functions to grinding circuit economical in any meaningful way. Work index analysis was also not favoured because of a number of complicating effects, including the fineness of the feed and product streams and open circuit grinding.It was decided to adopt a recent innovative approach which had been successfully applied to closed-circuit ball milling. For ""functional performance analysis of ball milling"" (McIvor et al., 1990; McIvor et al., 1991), a size criterion is first chosen to define ""fines·' and ~'coarse particles"". In this case 45 microns (325 mesh) was chosen to distinguish fines from coarse material. The relative grinding efficiency of each ball mill environment would then be ~e cumulative grinding (disappearance) rate of coarse (plus 45 nucrons) material per kilowatt hour of energy applied to the coarse material in the mill, divided by the grindability (measured in the laboratory) of the coarse material in the mill feed.Because the disappearance rate of coarse particles is also the production rate of fines, the following equation can be written for the efficiency of the mill environment, Effe, as defined above:"

Jan 1, 1994

By R. G. Mallon, R. L. Braun

Primary copper-sulfide ore deposits that are well below the water table can be chemically mined by in-situ high-pressure leaching. The leaching is accomplished by pumping oxygen gas into the bottom of a large underground flooded column of rubblized ore. Part of the injected oxygen dissolves under the high hydrostatic pressure in the column. With a high enough injection rate, the excess oxygen gas induces a convective circulation of oxygenated solution within the rubble column, which transports dissolved oxygen throughout the system. At elevated temperatures, this results in a relatively rapid dissolution of the copper minerals. A method of calculating the leaching rates is presented. The calculation is done by means of a finite-difference computer code that couples all of the processes relating to copper leaching, convective circulation, and the injection, dissolution, and consumption of oxygen. Results of the calculation for a typical case show that over 70% of the copper can be extracted in less than six years with good efficiency in oxygen utilization.

Jan 1, 1976

By George McIvor, Bill Thompson, Don Whitmore, Brad Rhude

"In 1972 Manitoba Hydro decided to develop the hydro electric potential of the Nelson River. This program included the construction of the Jenpeg Generating Station at the point where the channel of the Nelson River discharged into Cross Lake. The Jenpeg station serves two primary functions: 1) Provides a control structure for the regulation of Lake Winnipeg.2) Acts as a 126,000 kilowatt hydraulic generating station."

Jan 1, 1992

By D. Brady

When deciding to deploy rescue teams underground the decision makers need to be able to determine that there won?t be an explosion whilst the rescue teams are underground. Previously general body concentrations in areas likely to be travelled were compared to explosive limits on a one off basis with no formal process looking at trends or other areas. A new approach is being adopted that takes into account the rate of change of gas concentrations with triggers set to enable a withdrawal of personnel prior to a possible explosion and influences such a barometric pressure changes. This paper explains the rationale behind the changes made and the advantages and implications of adopting such an approach.

Jan 1, 2012

By Peter O. Wilkinson

Ascot Racecourse in the UK is a major international venue for horseracing. The racecourse is being redeveloped to provide entirely new public facilities. The development includes the construction of a new grandstand. A site investigation was earned out comprising mainly cone penetration testing. The site is underlain by the Bagshot Formation, comprising predominately cohesionless deposits of medium dense becoming dense, silty fine to medium sand, containing occasional layers of clay. Shallow foundations would present uncertainty regarding total and differential movement; hence a piled foundation solution was chosen using a continuous flight auger (CFA) piling system. The possibility that piles may found either directly on or within the influence of cohesive material suggested uncertainty regarding toe resistance. In order to measure shaft friction, an instrumented preliminary test pile was undertaken. The results were compared to published correlations of cone and shaft resistance. This approach resulted in a net saving in terms of pile length which resulted in optimum value engineering and hence a cost saving to the client.

Jan 1, 2006

By A. Sainato, S. J. Schatzel, D. M. Hyman, J. C. LaScola

The Bureau of Mines determined the gas contents of 135 oil shale samples obtained from approximately 630 ft of core drilling. Drilling was done within a projected mining zone of the Cathedral Sluffs Mine, located in the Piceance Basin of western Colorado. Methane contents were determined by the modified direct method, which can measure the volumes of several gases released from or reacted with mine rock without destructive sample treatment. Over the duration of the test, nitrogen was largely unreactive, CO2 increased slightly, oxygen decreased markedly, and methane increased more than the total increase of all contained gases. The gas volumes were normalized per unit sample mass and are given in cubic centimeters per gram. Common time irzdices for test duration of 3, 40, and 125 days were used to compare methane desorption among samples. The means of the sample populations for these indices were 0.0316, 0.114, and 0.195 cm3/g, respectively. These quantities are lower than those reported in a Bureau emissions study at the Horse Draw Mine in the Piceance Basin. Oil shale samples that were gas enriched beyond the mean methane contents frequently contained bitumens and pyrite.

Jan 1, 1987

By Takeshi Yoshikawa, Kazuki Morita, Yuichi Kato

"A composite composed of carbon fiber and a Cu-Si alloy is a promising candidate for next generation brake disc materials used in high-speed trains. The composite can be prepared by vacuum infiltration of the Cu-Si alloy into the fibrous carbon matrix. The activity of Si in the alloy plays an important role in controlling the formation of SiC; this formation is attributed to the reaction between the Si in the alloy and the carbon fiber during the infiltration process. Because Fe has strong affinity with Si, the addition of Fe is expected to decrease the activity of Si in the alloy. In the present work, the variation in the activity of Si in the alloy with the addition of Fe has been investigated by equilibrating a Cu-Fe-Si alloy with solid SiO2 and graphite under controlled CO partial pressure. The first-order and second-order interaction parameter of Fe on Si in molten Cu was determined to be -16 and 160, respectively. The negative value of the first-order interaction parameter clarified the addition of Fe to the Cu-Si alloy is effective in decreasing the activity of Si in the alloy.IntroductionIron-based materials have been commonly used for brake discs in high-speed trains. It becomes critical for brake disc materials to withstand high thermal loads with an increase in the maximum speed of high-speed trains. The fabrication of high heat-resistant, light-weight brake disc materials is then crucial for their use in next-generation high-speed trains. Carbon fiber is known to be a light-weight, high-strength material, and is considered to be a promising matrix material for use in brake discs. The Cu-Si alloy exhibits high thermal conductivity. The composite in which the Cu-Si alloy is added to the carbon fiber matrix is expected to be a high performance material for brake discs. The composite can be prepared by the infiltration of the Cu-Si alloy into the carbon fiber matrix at a temperature higher than 1700 K."

Jan 1, 2012

By Martin Hertzberg

The Bureau of Mines 8-liter flammability system was used to study the effectiveness of a variety of powdered inhibitors in preventing the propagation of explosions of coal dust or methane in air. Over 35 different chemical additives were evaluated against Pittsburgh seam pulverized coal. The least effective inhibitors were the carbonates, which required mass additions in the range of two to three parts inhibitor to one part of coal dust in order to prevent propagation. The most effective inhibitors were the derivatives of ammonium phosphate, which were effective quenching agents at additions of only one part inhibitor to four parts of coal dust. Alkali halide powders were of intermediate effectiveness. These laboratory-scale results are in good agreement with full-scale mine experiments in all cases where detailed comparisons have been made. Data were also obtained for the effectiveness of several of the same powdered inhibitors against methane-air explosions. Their relative order of effectiveness and the concentration ranges required for quenching the gas explosion are comparable to those measured for coal dust explosions. Data are also presented for the effectiveness of N2 and CF3Br addition. Some preliminary data are also presented for powder addition to methane burner flames. Those data are compared with other burner data and evaluated in terms of their relevance to explosion tests.

Jan 1, 1982

By Martin Banda, Gift C. Chisakuta, Moses Chabinga

KCM made a major modification to the Nchanga Tailings Leach Plant (TLP) changing the circuit from feeding post leach thickeners in parallel with leach discharge for solid ?liquid separation to a Counter Current Decantation (CCD) configuration utilising most of the existing equipment. The new circuit is aimed at improving copper recovery from approximately 70% to 79% through enhanced wash efficiency. The re-introduction of CCD circuit at elevated throughput of 46 000-tpd design was made possible due to the EIMCO E-Duc technology design which is an auto-dilution system that enhances solids settling rate. Commissioning (manual operation) which accommodated on-going operational requirements was phased and completed in January 2004. The circuit stabilised in subsequent months and in March alone an all time record copper recovery of 81.8% was achieved which contributed an extra 779 tonnes copper above the plant?s projected production plans. 100% of the project cost was paid back by end of April 2004 This paper discusses the work involved and the challenges faced during the re-commission

Jan 1, 2005

By Carrasco .. P. J. A., R. Parada, I. Saavedra, F. Parada, R. Parra, E. Balladares

In most of the smelters, the management of flue dust has a double objective: the control of minor elements in the anodes and the management of volatiles compounds that can cause contamination due to fugitive gas emissions. This is a special concern when high content of Va elements (As, Sb & Bi) are present in concentrates. We present the results of the experimental study to prove the principle of a novel process that recovers, via volatilization, the As, Sb and Bi in the flue dust as gaseous sulfides, due to a previous sulfidization. In the case of as control any further classical treatment for its stabilization is possible from the gas. The clean calcine can be returned to the smelter avoiding any concentration of these minor elements in the circuit. This process is now tested at pilot scale and shows better indices on carbon footprint than the classical hydrometallurgical process for flue dust.

Jan 1, 2011