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By Bradley Stoughton

(Cleveland Meeting, October, 1912.) [SECRETARY'S NOTE.-To avoid repetition of foot-notes, references to authorities are made in this paper by means of figures, referring to a numbered list in the appendix.-J. S.] INTRODUCTION. THIS paper gives the results : first, of a research into the somewhat extensive literature of titanium; and second, of a series of original tests upon the effect of titanium on iron castings. New investigations have also been made upon the effect of titanium on steel, but I hope to treat this subject in an independent paper at some later date, and, therefore, will not discuss the experiments in detail here. The combined results of this study, which extended over a period of more than two years, can be briefly summarized as follows: 1. Steel or cast-iron, in which the titanium is properly proportioned, and which has been properly treated, is improved in strength, toughness, and durability against wear, such as, for example, the wear of railroad-rails, of steel and chilled-iron .rolls, car-wheels, etc. 2. These improvements seem to be caused, not so much by the direct effect of titanium on the metal, as by its cleansing influence in removing harmful impurities, such as oxygen and oxides, nitrogen, occluded slags, and perhaps also sulphur. It appears also to reduce segregation, which would contribute to the same end. 3. In order that its effects may be fully realized, the treatment of steel or iron with titanium must be correctly performed. There are a few simple, but essential, details to be observed; if they are neglected, the best results cannot be expected. To illustrate by an example : A series of tests on cast iron

Nov 1, 1912

By Muammer Kaya

The purpose of this review is to raise awareness about e-waste problem in the World. Whether generated at our home or our office, e-waste is most rapidly growing waste problem in the world. Even though there are conventional disposal methods (such as landfill and incineration) for e-waste, these methods have both economic and environmental disadvantages; recycling is a new waste management option which diverts end-of-life (EOL) electrical and electronic equipment (EEE) from landfill and incineration [1, 2]. Successful diversion strategy must be based on economic sustainability, technical feasibility and social support [3]. Recycling infrastructure includes transportation, collection, recovery and resale establishments. The first part of this paper describes the e-waste facts, how big is the e-waste problem and existing recycling programmes and collecting methods in the USA and EU; second part, describes various methods available to recover valuable materials (glass, plastic and metals (Pb, Cu, Al, Steel, Ni, Au, Pd, Cu etc)) in e-waste for a safe and environmental friendly disposal

Jan 1, 2009

By R. J. Baumgartner

Sustainability issues are from rising interest and importance for the mineral industry worldwide. In order to bring them into management processes and to improve decision processes, economic, ecological and social aspects of products, services or technologies have to be assessed. In this paper, the concept of integrated sustainability assessment is presented. Each aspect is assessed with quantitative or qualitative methods. The results of these ecological, social and economic sub-assessments are integrated by the means of Fuzzy Logic in order to regard preferences of decision maker and circumstances of decision situation. An example demonstrates the application of this new instrument.

Jan 1, 2005

By S. J. Aresco

The Bureau of Mines has been active in promoting the purchase of coal for Government use under specifications that define the requirements in terms of heating value of the coal, expressed in British thermal units, and the composition as shown by proximate analyses. To these, when required, are added the ash-softening temperature, the free-swelling index, and the Hardgrove grindability index. Under most of these specification contracts the bidders guarantee the quality of the coal, and that guaranteed by the successful bidder becomes the standard of his contract. The deliveries are sampled in accordance with instruction3 issued by the Bureau of Mines; the samples are analyzed in the Bureau laboratory to determine whether the coal is of the quality guaranteed by the contractor; if it is not, a price adjustment is made. Analyses of the delivered coal and tipple samples (samples collected at mine tipples as coal is being loaded into railroad cars or trucks) provide valuable data for use in evaluating future bids. In addition, the continuous sampling of coal as delivered is a check on the practical results obtained in burning the coal.

Jan 1, 1969

The following letter has been received from Professor P. A. Young, Head of the Department of Mining and Mineral Engineering at The University of Leeds, England. Extractive and process metallurgy The first annual TMS-AIME Extractive and Process Metallurgy Fall Meeting:1983 International Sulfide Smelting Symposium, will be held from 6th to 9th November, 1983, in San Francisco.

Jan 1, 1982

By Albert L. Toenges

The introduction of mechanized mining in coal mines, which has speeded loading, has emphasized the importance of efficient underground transportation systems. The purpose of this investigation is to study and analyze various systems now in use, and to derive conclusions therefrom. This report may be helpful to operators who are planning new systems of transportation or who are revising present systems to increase their efficiency. This paper is the first of a series on this subject and des¬cribes some systems of transportation `utilizing rail haulage, ACKNOWLEDGMENT The information used in preparing this report was obtained through the courtesy and cooperation of the officials of the companies whose mines were studied. The descriptions of the transportation systems at the mines included herein have been checked for accuracy, and publication of the data has been approved by the executives of the several operating companies.

Jan 1, 1940

By L. J. E. Hofer

THIS BULLETIN analyzes and summarizes research at the Bureau of Mines dealing with the preparation, properties, and reactions of iron carbides in the period 1948-60, part of which was sponsored by Wright Air Development Laboratories. The objective was to develop better catalysts for the synthesis of methane and higher hydrocarbons from hydrogen and carbon monoxide. The investigations resulted in the first adequate characterization of epsilon iron carbide, which later proved to be an important intermediate in the tempering of martensite in steel. At temperatures near 170° C, the carbon in carbon monoxide reacts nearly quantitatively with finely divided alpha iron to form an iron carbide in which the metal atoms occupy the positions of the close packed hexagonal arrangement with lattice parameters of ao=2.754 A and co=4.349 A. The carbide has a composition within 2 atomic percent of that required for the formula Fe2C, a Curie point of about 370° C, a specific magnetization of 160.4 ergs per gauss-gram Fe at 50° C, and a ferromagnetic moment of 1.70 Bohr magnetons. Epsilon iron carbide can be converted to chi iron carbide by thermal treatment at 343° C for about 70 hours. The chi iron carbide so formed has a Curie point of 247° C, a specific magnetization of 142.5 ergs per gauss-gram Fe at 50° C, a ferromagnetic moment of 1.72 Bohr magnetons per iron atom, and a paramagnetic moment of 5.5 Bohr rnagnetons per iron atom. Direct synthesis of this carbide from carbon monoxide at 240° C indicates a composition within 7 atomic percent of that required for Fe2C. Chi iron carbide can be converted to cementite at 550° C in about 315 minutes. The theta iron carbide so prepared has a Curie point of 210° C, a specific magnetization of 147.3 ergs per gauss gram Fe at 50° C, a ferromagnetic moment of 1.72 Bohr magnetons per iron atom, and a paramagnetic moment of 3.9 Bohr magnetons per iron atom. Pure chi iron carbide reacts to form theta iron carbide by the elimination of free carbon. In the presence of an excess of free iron in intimate contact with the carbide, chi iron carbide reacts with the free iron to form theta iron carbide. The second reaction proceeds at an appreciable rate at 320° C and can be used to snythesize finely divided theta iron carbide with no free-carbon impurity at low temperatures. The ease of the reaction in the presence of free iron suggests that chi iron carbide is an intermediate in the tempering of epsilon iron carbide to theta iron carbide as it proceeds in steels. Experiments on carbon steel show that the magnetic moment of the iron atoms in martensite is about 2.2 Bohr magnetons per atom, a value approximately the same as that of the iron atoms in alpha iron. The Curie points of epsilon iron carbide, chi iron carbide, and theta iron carbide were found -in various specimens of tempered steel to be 10° to 20° C lower than normal values. This shift is probably the result of manganese in solid solution. Preparations of various compositions of epsilon iron carbonitrides show many effects of extensive isomorphism between epsilon iron carbide and epsilon iron nitride. The action of carbon monoxide on finely divided alpha iron at 400° C results in free carbon deposits containing filaments about 0.1 micron in diameter and several times as long. The filaments are characterized by nuclei of dense material located midway from each end of the filament. Although carbiding to near completion at 240° C over periods of about 300 hours produces a preparation containing no appreciable percentage of epsilon iron carbide, very brief periods of carbiding of the order of a minute result in the formation of detectable epsilon iron carbide even at temperatures as high as 325° C. The data indicate that epsilon iron carbide is an intermediate in the formation of chi iron carbide during its formation from carbon monoxide in the gas phase. Attempts to convert cementite to chi iron carbide by cold work increased the Curie point but did not change the X-ray powder diffraction pattern.

Jan 1, 1966

By Charles L. Kimbell

Although virtually every available indicator of world mineral industry activity demonstrated a gain in 1983 relative to the 2 very poor years of 1981 and 1982, the overall prospects for future years seemed far from bright. There were significant upturns in the quantity and value of mineral commodities produced, traded, and consumed in 1983, and many nonfuel mineral prices advanced, although the price advances in current dollars in most instances barely compensated for inflation. The pattern of investment in exploration and development of new mining ventures and new plant construction reflected virtual industry-wide concern that substantial upturns in demand for mineral commodities in the near future were unlikely, at least for most large volume products. The world oil glut continued despite cutbacks in production, and substantial stocks of many other mineral commodities mitigated against growth in total productive capacity, at least among market economy nations. In these countries, development activity at both mines and plants was confined largely to programs aimed at substituting new, more efficient installations for old, uneconomic or marginally economic plants. Among the centrally planned economy countries, the pattern was somewhat different on the whole, but even there, growth in total productive capacity was evidently somewhat restrained, although it seemed questionable whether the restraint was a function of intentional planning or simply an inability to accomplish planned programs on schedule. International political events, particularly the Iran-Iraq war and the unstable situation in the eastern Mediterranean countries (Lebanon, Israel, and Syria), continued to adversely affect mineral industry activities in those areas. Similarly, the internal and international conflicts in Central America negatively influenced mineral industry operations there. In Afghanistan, it appeared that there was some upturn in the very modest mineral industry operations, but industry activities there undoubtedly continued to be affected by confrontations between the Soviets and the local citizenry.

Jan 1, 1985

By L. F. Stutzman, George Thodos

A new graphical method, which is a modification of that proposed by Buckley and Leverett', is presented for the determination of the displacing fluid saturation at breakthrough for frontal drive mechanisms. This method is applicable to all types of fluids, which may be either soluble or insoluble in the oil at reservoir and injection conditions. This adaptation has unique advantages in handling problems in which either liquids or gases are the displacing fluids. INTRODUCTION In the displacement of oil from a reservoir with water or gas injected into the formation or by the expansion of a gas cap, the determination of breakthrough or flood advance is important to define the initial and subordinate phases of the operation. Thus, the determination of the displacing fluid saturation at breakthrough is fundamental to the establishment of over-all reservoir production. Methods for analyzing this saturation and for calculating production rates have been previously reported1,'*".". All of these methods utilize the rate equation for linear flow developed by Buckley and Leverett1. xs = QT - Qn/A? (?fu/?Su) .....(1) Sp where f, represents the volumetric fraction of displacing fluid in the total flowing fluid within the reservoir as is defined by: fo = 1/1+ ku/kd µn/µn .......(2) Since the time, ?, necessary for the flood front to travel distance ?X is unknown, Eq. 1 cannot be solved directly for the determination of the breakthrough point. Therefore, it becomes necessary to solve Eq. 1 simultaneously with an equation representing a fluid bal-ance on the reservoir behind the flood front. To develop such a fluid balance equation, it has been assumed that the fluid composition is uniform in the reservoir behind the flood front. Based upon this assumption, the follow-ing equation can be derived from a material balance on the displacing fluid: x = (?X) s Dx ? x=0 [ Snx - Sn1 ] dx = QT - Qn/A? It is readily observed that the displacing fluid satura-tion behind the flood front, Snx, may be determined through the simultaneous application of Eqs. 1 and 3. Although the approach may vary, this objective re-mains the same for all of the previously mentioned graphical or analytical methods. After Sox is determined, it is then possible to calculate the gas-oil and/or water-oil ratios and the rates during the initial and subordinate phases of production, and thereby define the production history of the reservoir. In this presentation only the de-termination of Snx is considered, and the reader is re-ferred to the several texts in reservoir engineering2,4,5 for a complete discussion on the methods for establish-ing the production history of a reservoir. PROPOSED METHOD FOR DETERMINING Snx Since at any time the quantity, QT - Qn/A? is a constant, Eq. 1 may be expressed in differential form as follows: dxsn = QT - Qn/A? d (? fn/? Sn) sn .....(4) Eq. 4 may be substituted directly into Eq. 3 to obtain: ? fn/? Sn ? [ Snz - Sn] QT - Qn/A? d ( ? fn/? Sn) = QT - Qn/A? ...............(5) Eq. 5 simplifies to the expression: ? fn/? Sn ? [ Snz - Sn] QT - Qn/A? d ( ? fn/? Sn) = 1 ....(6)

Jan 1, 1958

By N. Kinoshita, Y. Inada

The authors have proposed and discussed storage of low temperature materials such as LNG, LPG and frozen food in rock caverns. In this case, as the rock mass around the caverns will receive effects of low temperature, it is necessary to consider the thermal behavior and the stability of caverns. In this study, strength and deformation characteristics obtained by the uniaxial tension test and the compression test at low temperatures were discussed. Using the results, temperature and stress distribution around caverns when LNG was stored, were analyzed. Then thermal behavior of the rock mass around caverns was discussed. Die Autoren haben Lagerung von Niedertemperatur-Materialien wie LNG, LPG und tiefgefrorenen Nahrungsmitteln in Felskavernen vorgeschlagen und diskutiert. Da in diesem Fall die Felsmasse um die Kavernen den Effekten der niedrigen Temperatur ausgesetzt ist, ist es erforderlich, das Thermalverhalten und die Stabilität der Kavernen zu berücksichtigen. In dieser Untersuchung wurden Stärke-und Deformationseigenschaften, die durch ein-axialen Spannungstest und Kompressionstest bei niedrigen Temperaturen erhalten wurden, diskutiert. Mit diesen Ergebnissen wurden Temperatur- und Stressverteilung um die Kavernen bei Lagerung von LNG analysiert. Dann wurde das Thermalverhalten der Felsmasse in der Umgebung der Kavernen diskutiert. Les auteurs proposent et discutent l'entreposage de matériaux à basse température, tels que le GNL, le GPL et des aliments congelés, dans des cavités rocheuses. Comme, dans ce cas, la masse rocheuse entourant la cavité subit les effets des basses températures, il est nécesaire d'étudier le comportement thermique et la stabilité des cavités. Dans cette étude, les auteurs discutent des caractéristiques de résistance et de déformation, obtenues par essai de tension uniaxial et essai de compression à basse température. En se servant des résultats, ils analysent la répartition de la température et des pressions autour des cavités, lors du stockage de GNL. Ils discutent ensuite le comportement thermique de la masse rocheuse autour des cavités.

Jan 1, 2003

By A. H. Warner, G. A. Morrison

"INTRODUCTION The brown-iron ores of the Western Highland Rim of Tennessee extend north and south across the State for 115 miles. Many prospects of iron ore are known in this area.The district is credited with an output of 8 million tons of washed ore prior to 1930. Records on past shipments of ore indicates that the grade was probably 45 to 50 percent iron, 0,7 to 1.25 percent phosphorus, and 10 to 21 percent insoluble.As part of a survey of the iron resources of the Appalachian area, the Bureau of Manes began exploration .of the Churchwell and Robinette properties April 16, 1945, and continued until July 25, 1945, during which time 122 feet of test pits were sunk and 667 feet of churn drilling was completedPROPERTY AND ACCESSThe Churchweil property and that part of the Robinette tract north of U. S. Highway 64 are reported to be owned by the heirs of William Millsaps.The Churchwell property is northeast of Waynesboro, the county seat of Wayne County (fig. 1), and is east of Forty-Eight Creek, between Duggar Branch on the north and Little Forty-Eight Creek on the south.The property is reached from Waynesboro by traveling U. S. Highway 64 east 8 miles to Forty-Eight Creek, thence north on a secondary road 2 miles, to where Little Forty-Eight Creek joins it, thence by an old logging road up the hill half a mile to the property.The Robinett tract lies 1 mile southeast of the Churchwell and is reached by traveling east from Waynesboro on U. S. Highway 64 and a distance of 6.7 miles, and then turning left on an old logging road and following the ridge 2 miles to the prospect."

Oct 1, 1946

By A. I. A. Salama

The CANMET Western Research Centre (CWRC) has developed a hydrocyclone model simulation of dewatering and fine particle separation circuits. The simulation is based on an existing empirical model. Utilizing a cyclone manufacturer’s published data, some modifications have been developed and integrated into the model. Feed stream characteristics, cyclone mechanical dimensions, and operating conditions are used in the CWRC modelling simulation. The computer results are presented in 3D graphs and corresponding 2D maps showing the cyclone mass recovery, percent solids by mass in underflow and overflow, and cut size as functions of the cyclone apex diameter and cyclone throughput (i.e., inlet pressure or pressure drop). Results of the computer simulation have been used in the economic feasibility and design of several dewatering circuits in oil sand plants.

Jan 1, 2003

By K. Oraee

Proven and probable coal reserves in Iran are estimated to be in excess of 5 Billion tons while the annual coal production is a mere 2 Million tons. Underdevelopment of the industry has proved higher production levels to be impossible, despite growing demand for energy supplies. The existences of numerous legislation are thought to have a detrimental effect on coal mining activities to the extent that some business entities have become uneconomical in many areas. This paper provides an analysis of the prevailing mining laws, policy making, legal frameworks and obstacles. It also outlines some other obstacles enshrined in the law and also highlights areas where foreign direct investment should be encouraged. The costs of lost opportunities are then estimated. The paper concludes by demonstrating that deregulations, amendments and in some cases complete abolishment of the incumbent legislations governing the coal mining industry will greatly enhance development of the industry. The analysis provided in this paper together with the results obtained, can prove useful to macro-economic policy makers both at local and national levels.

Feb 27, 2013

By Fermont F. Clarke, Others, Paul Zinner

"INTRODUCTION The Edison mine comprises workings on two irregular spodumene-bearing pegmatite dikes which outcrop near the town of Keystone in the southern portion of the Black Hills of South Dakota. The Bureau of Mines conducted an investigation of the Edison mine as part of a comprehensive study of the lithium mineral-production possibilities in the Black Hills area. The work was undertaken during the Second World War, when the demand for certain lithium salts and compounds exceeded the then small productive capacity of the industry.During the course of the project, the Bureau of Mines completed 13 diamond core-drill holes, aggregating 2,114.5 feet of drilling. Twenty-six cannel samples were taken from the main Edison shaft, and 13 miscellaneous samples were obtained to permit analysis of the efficiency of phases of mining and sorting operations. Metallurgical tests were made by the Bureau of Mines to investigate the feasibility of beneficiating spodumere-bearing ores from the Edison mine. 3/"

Apr 1, 1948

By C. E. Golson

Modern concrete technology emphasizes the basic qualities required of an acceptable aggregate: it must be clean, sound, homogeneous, and of a size gradation resulting in a concrete of the desired physical qualities at a minimum cost. In the case of coarse aggregates, crushing, scrubbing, and screening will usually provide the required material, although beneficiation is often necessary in order to eliminate unsound or deleterious fractions. Beneficiation is also applicable to fine aggregates,( but the processes most often employed are washing, classification, and dewatering.

Jan 1, 1959

Electricity supply constraints in SA are increasingly challenging mines to operate more energy efficiently without reducing production output. Mining compressed air systems are well known to be operated inefficiently and are also a major power consumer. Two available and proven technologies can be applied on new and existing mines to replace or and optimise available compressed air facilities and achieve meaningful reductions in electrical power consumption; ? Hydro powered drilling and mining is significantly more energy efficient than compressed air and provides drilling rates that are twice as fast. ? Stope drilling systems using compressed-air or water drills allow further energy savings. The technologies are discussed and a broad strategy to selectively apply these them together is presented.

Jan 1, 2008

By J. A. Taylor, R. J. Fowell

Abstract: The amount of published literature pertaining to the field of rock mechanics has increased markedly in recent years. Whilst computer applications aid our understanding of the mechanisms of pillar instability, the applications do not take into account the effect of time; thus the determined pillar factor of safety has limited meaning. A more realistic approach would be to consider pillar stability in terms of time to failure. However such an approach would require a reasonable estimate of the in-situ pillar mass strength and a validated methodology linking the time to failure with in-situ pillar mass strength and the geometric layout of the working. Résumé: Le volume de bibliographie au sujet de la mécanique des roches a augmenté considérablement ces derniêres années. Alors que des modeles informatiques aident a la compréhension des mécanismes d'instabilité de pilliers, ces modèles ne prennent pas en compte les effets du temps; ainsi, la determination du coefficient de surete du pillier a un sens limité. Une approche plus réaliste devrait considérer la stabilité du pillier en fonction du temps de défaillance. Cependant une telle approche exigerait une estimation raisonnable de la resistance du massif rocheux du pillier ainsi qu'une méthodologie qui lie le temps de défaillance avec la résistance in-situ du massif rocheux du pillier et la géometrie de l'excavation souterraine. Zusammenfassung: Die Anzahl der Veröffentlichungen auf dem Gebiet der Felsmechanik ist in jüngster Zeit sehr gestiegen. Computerprogramme sind wertvoll um den Mechanismus der Pfeilerunbeständigkeit zu verstehen, aber sie vernachlässigen den Zeiteffekt. Daher haben die errechneten Sicherheitsfaktoren der Pfeiler nur begrenzte Bedeutung. Eine realistischere Bewertung wäre, die Stabilität der Pfeiler auf Grund der Zeit bis zum Verfall zu beurteilen. So ein Verfahren würde eine Schätzung der in-situ Gebirgsfestigkeit und eine validierte Methologie, die die Zeit zum Verfall in Abhängigkeit der in-situ Pfeilerfestigkeit und der geometrischen Auslage der Grube zusammenbringt, brauchen.

Jan 1, 2003

By D. F. Scott

The purpose of this study was to determine if miners are at risk from exposures to chemicals used in the mining industry, and determine the nature and sources of the illnesses and injuries. The authors reviewed the Mine Safety and Health Administration?s (MSHA) Employment and Accident, Injury, and Illness database and identified 2,705 cases of chemical-related injuries and illnesses that were reported to MSHA from 1999-2006, involving 66 different chemicals. The main source (cause) of chemical-related cases was acids/alkalis (about 39%). The primary nature (effect) of chemical-related cases was chemical burns (about 57%). The job classification where workers incurred the most chemical-related injuries and illnesses was cleaning plant operator/media operator/boney preparation plant operator/crusher worker. The number of nonfatal days lost did not change significantly and overall, the incidence rate of chemical-related cases decreased by 36%. Chemical burns accounted for a large number of injuries; mining companies should carefully examine their personal protective equipment (PPE) requirements, training methods, and safety culture to insure that their workers are protected.

Jan 1, 2009

By Hideo Ando, Yuka Satou, Tatsuya Ishitake

Whole-body vibration occurs when the body is supported on a surface which is vibrating. Occupational exposures to whole-body vibration mainly occurs in the transportation industry, but also in association with other industrial process. Epidemiological studies have frequently indicated an elevated health risk for the spine in workers exposed to whole-body vibration. With regarding to train or bus operators, a fall of drivers’ wakefulness level because of fatigue is often pointed out. This decrease in wakefulness results in an increase of the occurrence of accidents. However, a study of how whole-body vibration affects people's level of wakefulness has not been done. To test the hypothesis that exposure to whole-body vibration has a certain effects on level of wakefulness, the change of a subjective wakefulness level and changes of electroencephalogram (EEG) were observed under experimental exposure to short-term whole-body vibration. Methods Subjects are ten healthy male university students, with an average age of 20.7 ± 1.8 years old, and they are all nonsmokers. Using the equipment (CV-300, AKASHI) of whole-body vibration generator, we consider an exposure environment of actual driver work, so that set the frequency and the acceleration level as 10 Hz and 0.6ms-2 r.m.s.. The subjects were exposed to whole-body vibration in the seated position and exposure time was fixed for 12 minutes. Subjective wakefulness level was evaluated using the questionnaire of VASS (Visual Analog Sleepiness Scale) and KSS (The Kwansei Gakuin Sleepiness Scale). For the electroencephalogram (EEG) measurement, it was equipped with the electrodes based on the International ten-twenty electrode system (C3-A2, O1-A2, O2-A1). EEG activity in the alpha frequency band (8 – 12 Hz) is one of the most typical physiological indicator which represent the transition from wakefulness to sleepiness. AAT (Alpha Attenuation Test) which repeats three times each opened and closed eye for 1 minute was performed in a seating position with directions of the researcher in the beginning, in the middle and in the end of exposure to whole-body vibration. For analysis, power spectral analysis was conducted over the last 6 min of EEG, and wakefulness levels were defined as the ratio of mean alpha power during eyes closed versus eyes opened. The laboratory was kept at room temperature (21 ± 1.0 degrees C), humidity was 50 ± 5%, noise level was 63.6 dB (A) eq, and illumination 510 lx. Each experiment was started around 10:00 am to minimize the effect of biorhythm.

Jan 6, 2006

By A. Totani, S. Nakajima, H. Okazaki

The phase diagram for the SnTe-SnSe system has been studied in the temperature range from 300° to 900°C by differential thermal and quenching techniques. The X-ray measurements were made on quenched specimens. High-temperature diffraction was also made to study the phase transition in SnSe. The system is proved to be of a eutectic type in which no intermetallic compound exists. The eutectic point is at the composition SnTeo.55 Seo.45. the eutectic temperature being 755°C. Solid solubility limits are SnTeo.6Seo.r and SnT eo. 3s Seo.6s at the eutectic temperature, and change almost linearly to SnTeo.aaSeo.lz and SnTeo.18 Seo.az as temperature decreases to 300°C. It was shown that the SnSe phase has a phase transition of the second order at about 540°C and that the transition temperature decreases with increase of the SnTe content. THERMOELECTRIC properties of tin telluride (SnTe) and tin selenide (SnSe) have been studied extensively in recent years. The variation of physical properties with composition could be of interest if these compounds form an appreciable crystalline solution. The purpose of present investigation is to confirm the formation of crystalline solution or intermetallic compound, if any, and to establish the phase diagram for this system. The crystal structure of SnTe is NaCl type with a cubic unit cell1 (a = 6.313A). The crystal of SnSe having an orthorh2mbic unit cellz (a = 11.496, b = 4.1510, and c = 4.4437A) is isomorphous with tin sulfide (SnS) which has a distorted sodium chloride structure. It has been known that SnSe has a phase at at 540°C; the transition has been assumed to be of the second order. As far as we know, only two studies on the SnTe-SnSe pseudobinary system have been reported. The conclusion obtained in these papers is that, in the composition regions near SnTe and SnSe, the system forms a crystalline solution of the SnTe structure and the SnSe structure, respectively, and that, in the intermediate region, both phases coexist. However, neither the variation of the solid solubility vs the temperature nor the liquidus and solidus were investigated. Hence present writers have attempted to determine the phase diagram of the system by differential thermal analysis (D.T.A.) and X-ray diffraction. EXPERIMENTAL Sample Preparation. Starting materials, SnTe and SnSe, were prepared by the direct fusion of commercially available high-purity (99.999 pct) elements. Stoichiometric amounts of each couple Sn-Te or Sn-Se were weighed into a clear fused silica ampule. After evacuation to a pressure below 10-3 mm Hg, the am- pule was sealed, and annealed at 900°C for 5 hr. The melt was quenched in water. X-ray analysis confirmed the formation of a single phase of SnTe or SnSe. The other samples, SnTel-,Sex were synthesized from these SnTe and SnSe by mixing them in the required ratio, followed by annealing at 900°C and quenching. These samples were used directly for D.T.A. For X-ray measurements, samples were annealed at 700°, 600°, or 500°C for 100 hr or at 300°C for 150 hr, and then quenched in water. It was found that the lattice constants of the SnTe phase annealed for 150 hr at temperatures above 500°C did not differ from those annealed for 100 hr at the same temperatures. However the X-ray phase analysis showed that at 300°C the annealing for 150 hr was necessary to attain a true equilibrium state. D.T.A. The solid-liquid equilibrium temperature was determined from D.T.A. measurements. The sample was sealed in an evacuated silica tube and molybdenum powders sealed in an another tube were used as a reference material. The sample and the reference tube were placed in a nickel block and were heated from room temperature to 900°C at a rate of 3°C per min and then cooled down at the same rate to 600°C. Thermocouples for these measurements were Pt-Pt. Rh (10 pct) and the error of temperature measurements was within + l0C. D.T.A. curves were obtained on a two-pen recorder and an automatic controller (PID type) was used for the program of heating and cooling. When temperature reaches the solidus from the low-temperature side, there appears an endothermic peak. The solidus temperature was determined by extrapolation of the straight portion of the starting flank of this peak to the base line. In a similar way, the liquidus temperature was determined from an exothermic peak on D.T.A. cooling curve. In the case of supercooling, if any, its degree can be estimated from the magnitude of the abrupt temperature rise. X-Ray . X-ray powder patterns were taken by a diffractometer using CuK, radiation. Since the SnSe crystal is cleaved easily, the powders become flaky when SnSe-rich samples are ground in an agate

Jan 1, 1969