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By Dart Wantland, C. A. Heiland

There once was a little kid, whose lot was a very tough one until he grew up. His parents did not have much in common; from all indications, it is probable that the child was not wanted. His father Geology and his mother Physics separated shortly after his birth, which occurred during the World War amid a smoke screen of mathematics. He was kicked around a great deal. His parents could not agree on a name, and they finally christened him "Geophysics," for short. His relatives insisted that the name should be "Geophysical Prospecting," "Geophysical Exploration" or "Exploratory Geophysics"; though the youngster has grown up by now, this battle is still going on. His father did not think the child would amount to much until he began to show some unexpected talents, which were acquired, no doubt, from his mother Physics. His progress caused his father no little worry, and he began to wonder whether his offspring would help him in his business when he grew up or would set up shop in competition with the old man. His aunt Petroleum watched his growth with benevolent interest; his uncle Mining remained rather skeptical and cousin Civil Engineering not only assumed the attitude of the man from Missouri but was not much convinced even after he had been shown. Making a long story short, the kid decided that he had to stand on his own feet and get along as best he could. Having come from a good family he possessed some outstanding characteristics such as resourcefulness and a reasonable amount of business ability. He therefore decided that it would be to his advantage to follow in his father's and mother's footsteps as much as possible, and develop the good qualities of both. As a result, the youngster did fairly well for himself, and his relatives decided that it might be to their advantage to be on better terms with him. Father Geology had come to the conclusion that the boy could be very helpful to him and now wanted him to live in his house. His mother, who had brought him through the teething and measles stages, felt quite capable of bringing up the boy without the help of his father; and, as the fairer sex will do, would confide to a neighbor every now and then that his

Jan 1, 1940

By C. A. Heiland

THERE once was a little kid, whose lot was a very tough one until he grew up. His parents did not have much in common; from all indica-tions, it is probable that the child was not wanted. His father Geology and his mother Physics separated shortly after his birth, which occurred during the World War amid a smoke screen of mathematics. He was kicked around a great deal. His parents could not agree on a name, and they finally christened him "Geophysics," for short. His relatives insisted that the name should be "Geophysical Prospecting," "Geophys-ical Exploration" or "Exploratory Geophysics"; though the youngster has grown up by now, this battle is still going on. His father did not think the child would amount to much until he began to show some unexpected talents, which were acquired, no doubt, from his mother Physics. His progress caused his father no little worry, and he began to wonder whether his offspring would help him in his business when he grew up or would set up shop in competition with the old man. His aunt Petroleum watched his growth with benevolent interest; his uncle Mining remained rather skeptical and cousin Civil Engineering not only assumed the attitude of the man from Missouri but was not much con-vinced even after he had been shown. Making a long story short, the kid decided that he had to stand on his own feet and get along as best he could. Having come from a good family . he possessed some outstanding characteristics such as resourcefulness and a reasonable amount of business ability. He therefore decided that it would be to his advantage to follow in his father's and mother's foot-steps as much as possible, and develop the good qualities of both. As a result, the youngster did fairly well for himself, and his relatives decided that it might be to their advantage to be on better terms with him. Father Geology had come to the conclusion that the boy could be very helpful to him and now wanted him to live in his house. His mother, who had brought him through the teething and measles stages, felt quite capable of bringing up the boy without the help of his father; and, as the fairer sex will do, would confide to a neighbor every now and then that his

Jan 1, 1938

By C. A. Heiland, Dart Wantland

There once was a little kid, whose lot was a very tough one until he grew up. His parents did not have much in common; from all indications, it is probable that the child was not wanted. His father Geology and his mother Physics separated shortly after his birth, which occurred during the World War amid a smoke screen of mathematics. He was kicked around a great deal. His parents could not agree on a name, and they finally christened him "Geophysics," for short. His relatives insisted that the name should be "Geophysical Prospecting," "Geophysical Exploration" or "Exploratory Geophysics"; though the youngster has grown up by now, this battle is still going on. His father did not think the child would amount to much until he began to show some unexpected talents, which were acquired, no doubt, from his mother Physics. His progress caused his father no little worry, and he began to wonder whether his offspring would help him in his business when he grew up or would set up shop in competition with the old man. His aunt Petroleum watched his growth with benevolent interest; his uncle Mining remained rather skeptical and cousin Civil Engineering not only assumed the attitude of the man from Missouri but was not much convinced even after he had been shown. Making a long story short, the kid decided that he had to stand on his own feet and get along as best he could. Having come from a good family he possessed some outstanding characteristics such as resourcefulness and a reasonable amount of business ability. He therefore decided that it would be to his advantage to follow in his father's and mother's footsteps as much as possible, and develop the good qualities of both. As a result, the youngster did fairly well for himself, and his relatives decided that it might be to their advantage to be on better terms with him. Father Geology had come to the conclusion that the boy could be very helpful to him and now wanted him to live in his house. His mother, who had brought him through the teething and measles stages, felt quite capable of bringing up the boy without the help of his father; and, as the fairer sex will do, would confide to a neighbor every now and then that his

Jan 1, 1940

By I. A. Violic, L. D. Cruz, M. A. Solari

In Exxon's Los Bronces Expansion Project in Chile, a stochastic simulation is performed to resolve the complex decision problem of matching the mine to mill system capacities from both technical and economic standpoints. The unique combination of weather conditions at the mine and the 30-km (18.6 mile) belt conveyor network for ore transport to the mill necessitates this analysis in the planning phase to optimize the design capacity of the system. Appropriate statistical distributions of major equipment performance, snow storm duration, power outage, etc., are developed from actual mine local records and manufacturers' specifications. The interactions of operational constraints including ore storage capacities, number and sizes of individual equipment, ore variations, and mine and mill production rates are studied more realistically than in a traditional planning approach. Details of the computer modeling and typical results of simulation studies are discussed.

Jan 1, 1984

By Nicholas J. Grant, John S. Benjamin

A series of composite alloys containing a high volume of NiAl, Ni3Ah or CoAl, bonded with 0 to 40 vol pct of a ductile metal phase, were prepared by powder blending and hot extrusion. The binder metals were of four types: pure nickel or cobalt, near saturated solid solutions of aluminum in nickel and cobalt, type 316 stainless steel, and niobium. Sound extrusions were obtained in almost all instances. Studied or measured were the following: interaction between the alunzinides and the binders, room-temperature modulus of rupture values, 1500° and 1800°F stress rupture properties, hardness, structure, and oxidation resistance. Stable structures can be produced for 1800°F exposure, with interesting high-temperature strength and good high-temperature ductility. Oxidation resistance was excellent. A large number of experimental investigations have been made of the role of structure on the properties of cermets and composite materials. Gurland,1 Kreimer et al.,2 and Gurland and Bardzil3 have indicated the preferred particle size in carbide base cermets to be about 1 µ, with a hard phase content of 60 to 80 vol pct. The optimum ductile binder thickness was noted to be 0.3 to 0.6 µ.1 Complete separation of the hard phase particles by the binder is important in reducing the severity of brittle fracture.' The purpose of the present study was to produce structures comparable to the conventional cermets, using a series of relatively close-packed intermetal-lic compounds rather than carbides as the refractory hard phase, and to study the effects of binder content and composition on both high- and low-temperature properties. The selected intermetallic compounds were particularly of interest because of the potential they offered in yielding room-temperature ductility. The highly symmetrical structures are known to possess high-temperature ductility and room-temperature toughness. Based on a ductile binder, the alloys were prepared by the powder-metallurgy route to avoid melting and subsequent alloying of the matrix, and were extruded at relatively low temperatures. It was expected that the composite alloy would retain useful ductility. In contrast, infiltration and high-temperature sintering led to alloying of the matrix and to decreased ductility. The systems Ni-A1 and Co-A1 were selected for this study. In the Ni-A1 system the compounds NiA1, having an ordered bcc B2 structure, and Ni3Al(?1), having an ordered fcc L12 structure, were chosen. In the system Co-A1 the intermetallic compound CoAl with an ordered bcc B2 structure was used. ALLOY PREPARATION The intermetallic compounds, see Table I, were prepared by using master alloys of Ni-A1 and CO-A1, with additions of either cobalt or nickel to achieve the desired compositions. The master alloy in crushed, homogenized form, was melted with pure nickel or cobalt in an inert atmosphere, cold copper crucible, nonconsumable tungsten arc furnace. The resultant intermetallic compounds were homogenized at 2192°C in argon, crushed, and dry ball-milled in a stainless mill to -100 and -325 mesh for the Ni-A1 compounds and to -325 mesh for the CoAl compound. Finer fractions were separated for some of the composite alloys. Several ductile binders were utilized. These included Inco B nickel, 5µ ; pure cobalt, 5 µ, from Sher-ritt Gordon Mines, Ltd.; fine (-325 mesh) niobium hydride powder; fine (15 µ) type 316 stainless-steel powder; and near-saturated Ni-A1 and Co-A1 solid-solution alloys, also in fine powder form. The niobium hydride was decomposed above about 700°C in processing of the compacts in vacuum to produce niobium powder. The Ni-7.1 pct A1 and the Co-5.3 pct A1 solid-solution alloys were prepared from pure nickel or cobalt and pure aluminum by nonconsumable tungsten arc melting under an inert atmosphere. The ingots were homogenized, lathe-turned to fine chips, and dry ball-milled in air to -325 mesh powder. These solid-solution alloys are designated NiSS and CoSS; see Table I. Subsequently the hard and ductile phases were dry ball-milled as a blend. Experiments clearly established the need to coat the hard particles with the ductile binder to optimize subsequent hot compaction by extrusion. Ordinary dry mixing usually resulted in nonhomogeneous alloys which were quite brittle. Conventional cermets are consolidated by liquid phase sinteiing or infiltration, which resulis in undesirable and uncontrolled alloying of the binder phase. For this study, a loose (unsintered) powder-extrusion process was emploved, minimizing reactions between binder and hard particle, thereby permitting much greater control of composition and structure. The constituent powders were first mixed in the desired

Jan 1, 1967

By David A. Martin

Resource based companies have been inundated with changes in government tax legislation during the past few years. To cope, capital investment planning analysts have turned almost completely to computer simulation modeling to react quickly enough to determine the effect on their companies' major investment projects and on the projected financial picture of the companies. This paper will examine various royalty and tax structures as applied to coal, oil and gas, and minerals in the U.S. and Canada with particular emphasis on recent changes in the Canadian tax scene and their implications to capital project economic evaluation in other parts of the world.

Jan 1, 1977

By John Chipman

IN the manufacture of rimming steel-which constitutes the bulk of the world's production of mild steel-the factors that determine the quality of the product are very closely associated with the pouring and solidification of the steel in the ingot mold. The behavior of the metal in the mold is, on the one hand, the resultant of the complex processes through which the liquid metal has passed, and, on the other, it is an indication of the probable behavior of the ingot during subsequent rolling and finishing operations. A detailed study of the mechanism of solidifica-tion of rimming ingots ought to yield information that will be useful iii controlling the structure of the ingot and the quality of the ultimate product. The first step in such a study is to determine the rate at which the solid shell of the ingot forms from the liquid metal in the mold. A knowledge of the rate of solidification will make it possible to correlate observations of rimming action and gas evolution with studies of the structure, porosity, and segregation within the ingot. Thus, if the metal in the mold is observed to fall, let us say one minute after pouring, the portion of the structure associated with this fall will lie located in the part of the ingot that is solidifying at that particular moment. The knowledge that the ingot solidifies to a depth of ¾ in. in the first minute enables us to locate in the ingot the structural features corresponding to the observed fall. Conversely, the blowhole condition associated with a rising or growing ingot will be found in the part of the ingot that is solidifying at the time the phenomenon occurs. The time required for the complete solidification of an ingot has long been a matter of speculation. It is of considerable practical importance in connection with charging and heating in the soaking pits. Too rapid handling of the ingot through heating and rolling processes has been thought to be associated-with excessive pipe and other internal defects, so that a further object of this investigation was to attempt to estimate the time required for complete solidification, or the minimum practical time within which the subsequent operations can be performed with the minimum hazard.

Jan 1, 1937

By Otto Henry

THE purpose of this investigation was to determine the equilibrium diagram of the lithium-magnesium pair as a first step in studying the possible usefulness of these alloys as ultra-light structural materials. REVIEW OF THE LITERATURE The behavior of lithium towards magnesium was first investigated by Masing and Tammann.(I)? In order to prevent oxidation the alloys were made in iron tubes under an atmosphere of hydrogen; temperatures were measured with a glass-protected thermocouple. These investigators found that lithium and magnesium form two series of solid solutions separated by a miscibility gap between 85 and 95 per cent magnesium; that the alloys with 81 and 95 per cent magnesium showed a homogeneous structure under microscopic examination, while the alloy with 89 per cent magnesium contained two distinguishable crystallites; that the curve indicating the beginning of crystallization rises from the melting point of lithium to that of magnesium; and that no compounds of lithium and magnesium are formed. The equilibrium diagram was not plotted because no definite data were obtained for determining the solidus and the posi-tion of the miscibility gap in the solid state. The difficulties encountered in this investigation were: (1) that it was necessary to heat them as high as the melting point of magnesium in order to obtain homogeneous melts; at such temperatures the alloys attacked the glass protecting the thermo-couple; and (2) that at temperatures above 400° C. the lithium united

Jan 1, 1934

By Charles Will Wright

THE economy as well as the living standards of a country depends largely upon adequate supplies of raw materials at reasonable prices. Geological and climatic conditions responsible for the occurrence of commercial minerals and the growth of raw agricultural and forest products are so varied in different parts of the world that no country can be self-sufficient. The world is rapidly shrinking because of improvement in transportation facilities, but populations are steadily increasing and so are the needs for a greater production of raw materials and for their more equitable distribution. Too many barriers between nations prevent free access to the main sources of supply of the raw materials vital to neighboring nations and it is just such barriers that are often the cause of friction and even war. The International Trade Organization is doing a commendable job in helping to. break down barriers and to reduce friction, and we should now find ways to facilitate access to these sources of supply and encourage more efficient and greater production of the raw materials so urgently needed throughout the world. This cannot be done by individual selfish governmental agencies, influenced as they are by politics, nor by socialistic governments attempting to nationalize industries. It can be done efficiently only by the free individual through private enterprise properly protected against adverse governmental action. This protection can be supplied by the World Bank.

Jan 1, 1948

By Maurice Cook

A procedure of obtaining specimens of lead, tin, and cadmium with a moderately equiaxed structure and a smooth surface suitable for etching without grinding and polishing is described; the advantages of general oblique illumination (as opposed to vertical illumination) in the photomicrography of pure metals .are stated. Using these methods, a statistical study of the changes brought about in deformed lead, on annealing, has been made. The common mode of structural change was found to be recrystallization. Cases of growth of one original grain into another were rare; but if a totally recrystallized specimen was annealed above 200° C., a few large grains appeared and spread over the whole area, except for a certain number of small grains which remain unabsorbed. The temperature needed to produce structural change in lead was found to be lower, the greater the degree of deformation. With tin, an extension of 28 per cent. caused practically no recrystallization at ordinary temperatures, but recrystallization occurred if the specimen was heated to 100° C. In cadmium at low temperatures, the grain size decreased in marked manner as the deformation increased; but at high annealing temperatures, the grain size was comparatively independent of the degree of deformation. THE structural changes in metals brought about by annealing following a deformation at a low temperature has been the subject of many investigations. No less than eleven metals and alloys have been studied in some detail; namely, aluminum,1 tungsten,2 iron,3 copper,4 gold,5

Jan 11, 1924

By M. G. Driessen, H. E. Criner

Possible applications of cyclone thickeners for: (1) clarification of the washery water and, (2) recovery of fine coal from the plant bleed. The paper shows: (1) that it is possible to remove all particles including the very finest, from the circulating water, thus obtaining a closed water system and, (2) that reduction of the ash content of the solids of the plant bleed is feasible by means of cyclone thickeners. Performance data for different size cyclones is given in the form of graphs.

Jan 1, 1950

The State School of Mines, University of Utah, is this year giving-a four weeks' course for prospectors-Jan. 8 to Feb. 3, 1917-covering the fundamentals of geology, mineralogy, mining and the metallurgical treatment of ores. There will be 36 lectures of 1 hr. each and about 20 laboratory periods, each 3 hr. in length. It is the purpose of the School of Mines to make the course entirely a practical one, and purely theoretical considerations will be omitted. The laboratory work is designed to supplement the lectures and-to give those taking the course a working knowledge of the principles involved. In order to bring the course within the reach of all, no laboratory fees will be charged, and the only fee will be a nominal one for registration in the University, of $1.00, but it is expected that those who attend will be genuinely interested in the work.

Jan 2, 1917

By George L. Porter

Mr. President and Gentlemen of the Institute of Mining Engineers: . Unofficially representing the people of the vicinage, it is my pleasant duty to welcome you to the city of Bridgeport, to the valley of the Naugatuck, to the State of Connecticut. The importance and wide-reaching influences of the investigations for which your Institute is organized, the beneficial results which have directly and indirectly blessed mankind from your and kindred studies, the distinguished position which has been achieved in the scientific world by the Institute as a society, and the personal reputation which is the proper recognition of the ability and knowledge of its individual members, assure all that in attempting to honor you we are ourselves honored. In the republic of knowledge no fictitious rewards dignify the incompetent and the ignorant—the attested success of inventions and discoveries in the workshop of nature differentiates her real citizenship. Your present place of meeting is wisely selected ; for this senti-

Jan 1, 1895

By Donald W. Gentry, John F. Abel

This paper presents some of the results of a rock mechanics instrumentation program designed for, and implemented at. longwall panel 4N at the York Canyon Mine near Raton, New Mexico. The objective of this particular instrumentation program was to determine the response of the rock mass to longwall mining of a thick coal seam utilizing shield-type supports. Measurements were made in the rock along the ground surface, above the coal seam, in the coal seam, and immediately below the coal seam. Longwall test panel 4N had a total developed length of 762 m (2500 ft) and a face width of 168 m (550 ft), [Fig. 1]. The seam mining height in the panel area was approximately 3 m (10 ft). The average depth of overburden above the panel is 107 m (350 ft) although it ranges from 73-134 m (240-440 ft). Roof support at the face was provided by 116 Hemscheidt 320 HSL shields. These shield-type supports weigh 11.4 metric tons each.

Jan 1, 1979

By E. H. Herron, J. H. Perry

Mathematical simulation of reservoir behavior may be used to help understand reservoir processes and to predict reservoir behavior, thereby leading to the most economically desirable form of exploitation. In addition, simulation can be used as a tool for reservoir description to learn more about the physical nature of the reservoir and the mode of primary recovery. This use is essential in most reservoir studies and represents one of the more significant applications of simulation. Prediction of reservoir behavior provides information concerning displacement efficiency, optimum well locations, and the comparison of alternative producing processes. Since oil, water and gas all commonly occur in many reservoirs, a simulation that takes into account the simultaneous flow of three immiscible phases is a prerequisite for obtaining such information. Furthermore, a simulation that describes this flow in two dimensions provides the capability of evaluating combination gas- and water-drive reservoirs with either an areal or a cross-sectional description. Many reservoir problems require such a simulation. The objective of the research described here was to develop a mathematical model and associated computer program for accurate, efficient, and economical prediction of the reservoir flow of three phases in two-dimensional geometry. Several authors have discussed multidimensional reservoir simulation of two phases.l-3 Gottfried et al.' presented an analy- sis of three-phase simulation in one dimension. Fagin and Stewart" and Garrett6 have discussed the simulation of three-phase flow in two dimensions, but their solution techniques were different from the method discussed in this paper. In particular, previous models and computer programs have usually involved either fewer capabilities or inefficient and less rigorous descriptions resulting in limited applicability. In the following sections, we present a description of the model, an evaluation of the method, and the application to reservoir problems. Additional and supporting material is presented in the Appendix. The Three-Phase Model General Description The three-phase model consists of the mathematical description of the flow of oil, water and gas in a reservoir. Conceptually this description considers flow in all three space dimensions, but in the subject simulator it is assumed that no flow occurs in the third dimension. The model includes the effects on reservoir behavior of fluid and rock compressibility, viscosity, gravity, capillary pressure, relative permeability and gas solubility. Within the two-dimensional restriction, the reservoir considered may be completely heterogeneous and anisotropic. The differential equations governing multiphase, multidimensional flow in a reservoir are too complex to be solved analytically, so they are approximated by a system of finite difference equations and solved

Jan 1, 1970

By E. L. Corp, J. C. Johnson, W. G. Pariseau, M. Poad, M. E. Fowler

This paper describes a comprehensive geomechanics case study of a full¬scale test stope at the Carr Fork Mine. The mine is owned by Anaconda Miner¬als Company and is located near Tooele, Utah. Large diameter blast holes were used in a new method known as blast hole post-fill (BHPF). The new design proved highly successful in contrast with earlier experience with vertical crater retreat (VCR) stopes. The main geomechanics objective was the estab¬lishment of a design procedure for optimizing stope and pillar dimensions with respect to productivity and recovery. An integrated three-part approach consisting of mine measurements, laboratory testing and finite element calcu¬lations was taken. Independent correlations of 0.88 and 0.89 between calculated and measured displacements and between estimated and observed yield :ones substantiate the finite element design approach using UTAH-II. Subse¬quent stope and pillar design analyses indicate that doubling of the original stope width at 50% extraction is quite possible without sacrifice of safety or stability.

Jan 1, 1984

By L. C. Glenn

The account of oil and gas production in Tennessee, and of the geological factors related to such production, as given by the writer' a few years ago needs to be supplemented by brief statements as to production and development to bring it up to date. Activity in searching for favorable geological structures or in drilling given areas has never been comparable to the intensive work done in states of large production. It is not possible, therefore, to prepare a statement giving the details that may be readily available in such states, but instead one must be content with more general statements. In the past 10 or 12 years there has been a moderate amount of drilling for both oil and gas widely scattered over the state. Of much of this there is no available record. Morgan, Clay, Scott and Pickett counties have had more oil-drilling activity than any other counties, and likewise they have had almost all of the oil production. In Scott and Morgan counties production centers about Sunbright and Glenmary, the oil coming from the St. Louis limestone at a depth of 1200 to 1500 ft. Wells usually are small but generally hold up well. In Clay, Pickett, Fentress, Overton, Macon and Sumner counties there is a large area in which there are many small structural domes, some of which have been drilled. Wells vary from a few barrels to several hundred flush production and last for some years. The oil comes from porous weathered zones, mostly in the Trenton division of the Ordovician, though some comes from lower horizons beneath one or more bentonite beds that serve as horizon markers and are known as the "pencil cave." Wells recently drilled in the Central Basin and in the Western Highland Rim have been dry or have had only shows of oil. The horizons tested are also usually Ordovician in the Central Basin and usually either Ordovician or Mississippian; occasionally also Devonian on the Highland Rim. In the Gulf Embayment area of West Tennessee there has been but little activity. A well near Ridgely said to be over 2200 ft. deep is supposed to have entered Upper Cretaceous sands and clays in the lower

Jan 1, 1934

By J. T. Norton, Joseph Gurland

IN spite of the extended use and high state of practical development of the cemented tungsten carbides, the structure of these alloys is still a matter of considerable controversy. The characteristic high rigidity and rupture strength of sintered compacts have been attributed to a continuous skeleton of tungsten carbide grains, formed during the sintering process. This view is based mainly on the work of Dawihl and Hinnuber,1 who reported that a sintered compact of 6 pct Co maintained its shape and some of its strength after the binder was leached out with boiling hydrochloric acid. After leaching, only 0.04 pct Co was reported to remain in the compact. They also showed that the assumed increasing discontinuity of such a skeleton, as the cobalt content is increased, could be made to account for the observed discontinuous increase of the coefficients of thermal expansion, the loss of rigidity, and the impaired cutting performance of alloys of more than 10 pct Co. Contradictory evidence was cited by Sanford and Trent,' who mentioned that a sintered compact was destroyed by reacting the binder with zinc and leaching out the resulting Zn-Co alloy. The skeleton theory also does not account for the observed change of strength of sintered compacts as a function of cobalt content. If the skeleton is responsible for the strength, the latter would be expected to decrease with increasing binder content. Actually, the strength increases and reaches a maximum around 20 pct Co. In addition, tungsten carbide is brittle and undoubtedly very notch sensitive. The highest value found in the literature for the transverse rupture strength of pure tungsten carbide prepared by sintering is 80,000 psi.3 herefore, such a skeleton does not easily account for a rupture-strength value of 300,000 psi and higher, commonly found in sint.ered tungsten carbide-cobalt compacts. In view of the conflicting data present in the literature, experiments were undertaken to determine whether the sintering of tungsten carbide-cobalt alloys leads to the formation of a carbide skeleton or whether the densification behavior and the properties of cemented compacts are consistent with a structure of isolated carbide grains in a matrix of binder metal. The specimens were prepared from powders of commercial grade. Tungsten carbide powder ranged in particle size from 0 to 5x10-4 cm. Mixtures of tungsten carbide and cobalt were ball milled in hexane for 48 hr in tungsten carbide lined mills. After milling, the specimens were pressed in a rectangular die (1x1/4x1/4 in.) at 16 tons per sq in. NO pressing lubricant was used. Sintering of the tungsten carbide-cobalt compacts was carried out in a vertical tube furnace equipped with a dilatometer (Fig. I), by means of which the change of length of the powder compacts could be followed from room temperature to 1500°C. An atmosphere of 20 pct H, 80 pct N was maintained inside the furnace. Decarburization of the samples was prevented by the presence of small rings of graphite inside the furnace tube. The temperature of the sample was measured by a platinum-platinum-rhodium thermocouple, which also was part of a temperature control system able to maintain a constant temperature within ±100C. Pure tungsten carbide compacts were prepared by sintering the carbide without binder or by evaporating the binder from sintered compacts in vacuum at 2000°C. Since complete densification of these samples was not desired, they were sintered only to 60 or 80 pct of the theoretical density of tungsten carbide. The specimens were prepared for metallographic examination by polishing with diamond powders and etching with a 10 pct solution of alkaline potassium ferricyanide. Cobalt etches light yellow and the carbide gray. The amount of porosity is exaggerated since it is difficult to avoid tearing out carbide particles, especially from incompletely sintered samples. Experimental Observations A number of specific experiments were carried out in order to study some particular aspect of the sintering problem. The details of these experiments, together with their results, are as follows: Electrolytic Leaching: The binder was removed by electrolytic leaching from sintered tungsten carbide-cobalt compacts for the purpose of determining the continuity of the carbide phase. The method used was based on the work of Cohen and coworkers4 on the electrolytic extraction of carbides from annealed steels. If the sample is made the anode, using a 10 pct hydrochloric acid solution as the electrolyte, the binder is dissolved, but the rate of solution of tungsten carbide is negligible. A current density of 0.2 amp per sq in. was applied. As shown in Fig.

Jan 1, 1953

By D. A. Stevenson, R. A. Burmeister

Single-phase silver antimony telluride has been prepared by zone-melting techniques using initial compositions of A new phase appears upon prolonged annealing of this material, but the reaction does not appear to be a simple eutectoid decomposition. A complete analysis of the phase equilibria is complicated by the slow kinetics involved. The Hall coefficient, magneto -resistance, electrical resistivity, and Seebeck coefficient are all sensitive to the presence of second phases. The low Hall mobilities measured for single-phase material indicate that the usual band theory is inadequate to explain the observed transport properties in the system. Density anomalies of up to 2.5 pet between measured and theoretical density were observed but are not conclusive evidence for a defect structure. COMPOSITIONS in the Ag-Sb-Te system have been studied previously by several investigators.1"18 The interest in this system arises from potential thermoelectric applications of alloys on the Ag2Te-Sb2Tes vertical section. Although the composition corresponding to the formula AgSbTe, has received most attention, it has been found to consist of more than one phase.7'8 A thorough understanding of the properties of this heterogeneous material has been impeded by both lack of knowledge of the properties of the homogeneous phases comprising it and the problem of analysis of transport properties in an inhomogeneous system. The present work describes the preparation of the homogeneous ternary phase and the corresponding electrical properties of both homogeneous and heterogeneous material. MATERIAL PREPARATION Most specimens for this investigation were prepared by encapsulating the elements in evacuated quartz tubes after which they were melted and homogenized in the liquid state. The ambient temperature was then dropped to 500°C and the resulting ingot zone melted. The growth rate, width of zone, stoichiometry, and number of passes have an effect on the resultant microstructure. Grains several centimeters in length were easily produced by this method. Other solidification techniques were also used, including uniform slow cooling of the entire specimen and rapid freezing. The microstructures of specimens produced by these techniques frequently differed appreciably from similar compositions prepared by zoning. A variety of nonequilibrium microstructures characterized by long needlelike particles resulted from the rapid-freeze method. PHASE EQUILIBRIA The lack of information on phase equilibria is a major difficulty associated with a comprehensive study of the Ag-Sb-Te system. Considerable confusion has resulted from the use of the formula AgSbTe, to identify the cubic ternary intermediate phase even though it has been established that material of this stoichiometry normally contains AgzTe as a second phase.798 In this paper, silver antimony telluride will denote the cubic ternary intermediate phase comprising the major portion of AgSbTe,. The term "single phase" will denote material which consists of only the cubic phase (as evidenced by metallographic examination and X-ray diffraction) and the term heterogeneous will describe multiphase material containing AgzTe, SbzTe3, or other phases in addition to the cubic phase. The single-phase material may actually contain a variety of inhomogeneities—gradual changes in composition on a macroscopic scale, localized fluctuations in composition, clusters or other products of early stages of the precipitation process, and a variety of point and line defects—all of which will not be detected by the present techniques for determining homogeneity. Single-phase material has been prepared from compositions close to 59 mole pct SbzTe3 21 (this notation refers to the location on the Ag,Te-Sb2TeS vertical section). Zone widths of =2 cm and growth rates 51.2 cm per hr were used. The single-phase region at elevated temperatures extends off the vertical section to a composition which can be expressed approximately as Ag,,SbzgTes,.9 The latter two compositions as well as AgSbTe, are represented in the conventional Gibbs triangle in Fig. 1. It is not presently possible to ascribe exact values to the limits of the single-phase region on a given isotherm or vertical section due to the extremely

Jan 1, 1964

By G. L. F. Powell

TURNBULL and Cech1 reported undercooling small droplets (approximately 50 mp in diam) of a large number of metals by approximately 0.18 TE (TEoK = the equilibrium freezing point). This was considered to be the undercooling for homogeneous nucleation in

Jan 1, 1968