Search Documents

By R. L. Bleifuss

The object of this study was to evaluate the oxidized taconites of the western Mesabi iron range and to establish a correlation between the various basic taconite types and their concentratability. The initial work included a study of the original mineralogical and stratigraphic facies of the fresh taconite and traced the oxidation and leaching patterns developed during the conversion of this material to oxidized taconite. Subsequent studies have extended this work to include the semitaconites and also the wash and heavy media ore types widely developed in the area. Each basic original mineralogical facies or taconite type produces during alteration an equivalent secondary oxidized facies which has a unique mineralogical composition and texture. These control the concentratability of the oxidized taconites. Actually the influence of the original mineralogical composition of the iron formation extends even further and determines whether the most likely product of oxidation and leaching will be a wash ore or a heavy media ore and even to the direct shipping ores where the ratio of hematite to goethite is largely determined by the original taconite type. The relationship between original taconite, oxidized taconite, semitaconites, and wash and heavy media ores is briefly summarized in Table I. The terms are not precise and in some instances tend to overlap. The table is intended to point out only the essential differences between the various materials. The original taconite was dominantly composed of mixtures of magnetite, iron carbonate, iron silicate, and quartz (chert). In a few thin stratigraphic units, hematite was present as an original constituent. The alteration of the original taconite to oxidized taconite has resulted from the circulation of ground waters through an initial fracture system related to minor structures in the iron formation. The chemical reactions have involved the oxidation and decomposition of original minerals such as magnetite, iron carbonate, and iron silicates to hematite or goethite. The alteration at this early stage is characterized by pseudomorphic replacement of the original minerals by oxidation products although retaining the major textural features of the original taconite. There was very little secondary migration of iron at this stage and the total iron content of the rock has been only slightly increased. Further alteration of this material to form a semi-taconite, a wash or a heavy media ore, involves extensive removal of silica in solution and significant redistribution of iron units. Wash and heavy media ores are developed by the growth of coarse secondary iron layers, dominantly goethite, coupled with the removal of silica in solution and decomposition of the cherty layers. This paper is concerned primarily with the materials classified as oxidized taconites which are characterized by oxidation of the original mineral constituents with little secondary enrichment. The area studied, shown on the index map, Fig. 1, extends some 30 miles along the strike of the Biwabik formation roughly from Hibbing to Coleraine. This study was greatly facilitated by the basic stratigraphic and mineralogical studies of Gruner1 and white2. The bulk of the material in this presentation represents a portion of the author's contribution to a study sponsored by the Great Northern Railway on the oxidized taconites of the western Mesabi.3 METHOD OF APPROACH A total of 106 drill holes, representing some 30,000 ft of drilling, were examined and sampled. The drill holes were logged and some 1500 composite samples were prepared for chemical analysis and bench scale metallurgical tests. These samples were analyzed for total iron and ferrous iron; and magnetite iron was determined by a standard Davis tube test at minus 200 mesh. Standard reduction roast tests using 150-gram samples of minus 10 mesh material were made on these 1500 composite samples with a mixture of H2, CO2, N2, and H2O at a temperature of 650°C. This roasted material was pulverized through 150 mesh and concentrated in the Davis tube. The iron recoveries and concentrate grades obtained on the roasted products were used to assess the concentratability of the oxidized taconites. Detailed mineralogical work was done on thin sec-

Jan 1, 1964

By A. Weiss, W. A. Coster

Jan 1, 1964

By Frederick B. Brien

For many years tin mining in Bolivia has been very important to the economy of the country. In recent years the tin content of the ore reserves has been steadily declining. An improvement in concentration efficiency is highly desirable in order to increase productivity from the present-low-grade mine ores and to allow retreatment of the many millions of tons of tailings from past operations, some of which equal the present ores in tin content. A number of investigators have been or at present are working on various phases or approaches to the problem. Gravity concentration is used in Bolivia today as it has been in the past to recover tin minerals from the mine ores. An objective of the work reported in this paper was to examine the possibility of treating present low-grade ores and sink-float tailings products, at a relatively coarse grind, in order to produce a higher grade feed material to the present gravity concentration plants. The possibility of using heavy liquids in cyclones to treat large tonnages with a minimum of outlay presented itself and is of particular interest since appropriate heavy liquids are available and with physical properties which lend themselves to simple recovery methods. Tests were carried out using a closed circuit laboratory cyclone assembly. It was desirable to determine the value of using the SG50 concept and Tromp curves for analyzing the cyclone concentration test results. The effects of entrained water on the behavior of ore particles in the cyclone were examined.

Jan 1, 1964

By R. W. Heins, N. Street

Recently Hiller1 reported results on the impairment of the strength of quartz glass rods through wetting, indicating that there was general agreement with the prediction of the Griffith formula in that for the liquids used the rods were weakest in water i.e. the liquid which probably had the greatest free energy of immersion. The Griffith equation predicts that the tensile stress necessary to propagate a crack of length c is where ? is the interfacial free energy, E Young's modulus. Since for a solid immersed in a liquid of surface tension ?L and contact angle 8 at the solid-liquid-gas contact, ?s - ?SL = ?L cos ? where ?s is the surface free energy of the solid. Hence comparison between ?L cos 0 and strength impairment should be possible. In a study of the usefulness of the Kuznetsov pendulum2 as a means of studying rock drillability we have determined the effects of various liquids on the pendulum hardness of Bavarian limestone. The pendulum used had diamond points (Burgess Vibro-graver), a period of 1.14 sec and a total on sample weight of 1191 g. The decline of the pendulum oscillations was recorded by a light beam on light sensitive paper carried on a kymograph. Rehbinder's expression relating hardness to amplitude attenuation as a function of time can be written In A = - (1/H) t + In Ao where A, A, = amplitude at time t and initial amplitude respectively, H = hardness parameter, and t = time. The line of best fit to the experimental points was determined using the IBM 7090 electronic computer, the computer also gave A, by extrapolation to zero time. The results for the various liquids tested are given in Table I and Fig. 1. The limestone surfaces were highly polished before testing and each reported hardness value represents the average of at least ten separate determinations of the pendulum decline curve. On each newly prepared surface the water value was again determined (also

Jan 1, 1964

By Stephen V. Thompson

Within recent years portable seismic refraction units have found their place in the industry for shallow investigations, Completely portable, relatively inexpensive and of proven accuracy, the portable refraction seismograph is an electronic tool in an electronic age. The age of electronic instrumentation has seen the development of seismic reflection and refraction equipment for deep exploration, especially in the petroleum industry. Large, expensive units, normally truck-mounted and utilizing explosives, are being used successfully for this type of sub- surface investigation. The portable seismograph utilizes the same theory for shallow work as that applied to deep refraction seismology.

Jan 1, 1964

At Great Boulder Gold Mines Ltd. a number of attempts were made to remove water soluble copper and iron salts from calcined pyritic concentrates but variou~ problems arose and the methods were abandoned.A method of rapid washing has been developed and although some problems still exist a workable process was established which resulted in substantial savings of reagents used for the cyanidation of calcine.INTRODUCTIONIn the Great Boulder flowsheet crude ore is ground in cyanide solution, then thickened, agitated and subjected to two stage filtering. Secondary filter discharge is pulped with flotation circuit water, gassed with sulphur dioxide to precipitate soluble gold and activate pyrite, and after the addition of copper sulphate and xanthate, the pyrite and tellurides are recovered by flotation. Flotation tailings are thickened and pumped to the disposal area and concentrates are calcined in Edwards roasters. Calcine is washed to remove water soluble copper and iron salts and the washings pumped to the flotation section where the copper is used as an activator. The washed calcine is cyanided and returned to the crude ore circuit via the thickeners. Solution for precipitation in the Merrill Crowe is drawn from the crude ore thickeners.Prior to the introduction of calcine washing the calcine contained 7 lb/ton copper of which approximately 60 per cent was water soluble. It also contained approximately 90 lb/tol'l of water soluble iron salts. Both the copper and...

Jan 1, 1964

By D. A. Dukelow, K. Li, G. C. Smith

Decarburization in the Fe-C system by oxygen top blowing has been studied in laboratory -scale experiments. It is shown that equilibrium models fail to explain or predict either the course of refining or endpoint conditions, giving results which either are incompatible with the chemistry of the system or do not satisfy material balance requirements. Also the path of decarburization was found to vary even for heats made under apparently identica1 conditions. A promising approach to analyzing the decarburization results is to relate oxygen efficiency fm carbon removal to bath carbon content. This relationship for Fe-C heats shows the same range of oxygen efficiencies as is obtained in pilot-plant and commercial heats using hot metal-scrap charges. This implies that oxygen transfer is primarily controlled by the decarburization reaction itself, independent of other refining reactions. Therefore, it should be possible to study separately decarburization and slag-metal reactions. DECARBURIZATION is probably the most important reaction in steelmaking. Not only is it a main reaction in the refining of iron to steel but it also provides the stirring action in the bath necessary for the diffusion processes to proceed at reasonable rates so as to make a steelmaking process practical. Kinetics of decarburization in the open-hearth process has been a subject of investigation for many years.&apos;-B It is generally accepted that at steelmaking temperatures the rate of homogeneous C-0 reaction is extremely high and cannot constitute a rate-controlling step. Diffusion of oxygen through a boundary film in the metal phase has been suggested by arken&apos; as rate-determining. Recently, Larsen and sordah16 concluded from experiments in a laboratory furnace that, with oxygen supplied from air or combustion gases, the rate of "steady-state" carbon boil is controlled essentially by a diffusion process of O2, Co2, or H2O through a film of nitrogen above the slag surface. Displacing this diffusion film by a stream of nearly pure oxygen produced a ten-fold increase in the rate of carbon boil with the rates of slag-metal oxygen transfer, bubble nucle-ation, and other steps all apparently able to keep pace. In the top-blown basic oxygen process, however, the transport of oxygen takes a more direct route. and the state of bath agitation is much more turbulent than in the open-hearth process. In addition, direct contact of the gas with the metal phase provides opportunity for direct oxidation of carbon. It is likely that the rate-limiting factor for the decarburization reaction will be different. However, only a few descriptive discussions of the subject have been reported in the literature.10-l2 Studies of the decarburization kinetics based on plant or pilot-plant data are necessarily complicated and are influenced by other refining reactions which occur simultaneously. In order to investigate the mechanism of decarburization, experiments have been conducted in which carbon-saturated iron melts were top-blown with pure oxygen over a range of conditions. It is hoped that this study will form a foundation on which a more basic understanding of this important reaction may be built. EXPERIMENTS One group of blowing experiments was made in a standard 200-lb induction furnace and another group in a 500-lb induction furnace. The furnaces were modified to the general shape of a basic oxygen furnace by adding a rammed refractory cone section to the regular crucible body. Crucible and cone were of high MgO (95 pct) material. A water-cooled lance, 1/2 in. in diam and threaded at one end to take a nozzle, was used for blowing oxygen. The lance with its water and oxygen lines was supported on a cantilever arrangement so that it could be moved up, down, or sideways. Oxygen of 99.5 pct purity was supplied from a cylinder and metered through a rotameter equipped with pressure and temperature gages. Another pressure gage was located at the top of the lance. A schematic diagram of the assembly is shown in Fig. 1. Before each experiment, a weighed amount of ingot iron, containing 0.02 pct C, < 0.01 pct Si, 0.10 pct Mn, 0.019 pct P, and 0.015 pct S, was charged in the furnace and melted down by induction heating. Graphite was then added to the molten charge until it became saturated. When the temperature of the charge reached the desired level, the lance was lowered to a predetermined height above the bath

Jan 1, 1964

By H. F. Webster, C. G. Dunn

Rolling md annealing procedures are described for developing the (110) preferred orientation in tantalum for use as a thermionic-emission materinl where electrodes of a uniform high work function are needed. The development of a (110) [001] annealing texture is also reported. A preferential growth process due to low (110) gas-metal surface energy is considered in explanation of the observed growth of (110) grains. ThE growth of (110)-oriented grains in thin strips of rolled zone-refined tantalum, previously discussed briefly,&apos; is reported together with more recent information on the formation of a (110)[001.] annealing texture, i.e., one where the [001] direction of each grain lies close to the rolling direction. The development of tantalum sheet with a (110) preferred orientation (position of [001 ] directions unspecified) is of importance as a thermionic-emission material in thermionic-energy converters. Since therm ionic-emission properties of cesium-coated crystals vary over a wide range depending on (hkl) a2-7 a single (hkl) preferred orientation is more useful than either several preferred orientations or none. Furthermore, the (110) preferred orientation yields the highest thermionic-emission density for a cesium coverage of less than a monolayer.5-7 A consideration of the stability of the grain structure needed at high operating temperatures suggests that the preferred orientation itself should be produced by annealing processes. Information on annealing textures in tantalum, however, is rather limited. Pugh and Hibbard 8 obtained (111)[112] and (lll)[112] components in a 1400°C recrystallization texture in 95 pct cold-rolled foil; these components were enhanced on annealing at 2500°C. Muller9 rolled 99.97 Ta to 90 pct reduction in thickness in the final stage and noted only a slight sharpening of the rolling texture, with some intensification of the (111)[112] component upon annealing at 1200°C. The experimental procedure followed in the present work stemmed from the idea of using possible differences in (hkl) surface energies to provide a small driving force for growth of grains having the lowest (hkl) surface energy.l0* This would mean using high-purity tantalum processed into thin sheet form and annealed at high temperatures either in a noncontaminating atmosphere or in one producing additional sample purification. EXPERIMENTAL Zone-Refined Tantalum. National Research Corp. tantalum in the form of 1/8-in.-diam rod and of 99.98 purity (53 ppm 0, 15 ppm N, and 8 ppm C) was zone-melted four times. The traversing speed was 4 mm per min. Such treatment increased the resistance ratio, R293k/R20K , where R293K is the resistance of the specimen at 20°C and R20K the re-resistance at liquid-hydrogen temperature, from a value of 25 for the initial rod to 175 for the zone-refined rod (the increase in the resistance ratio provides a measure of purification11,12). Part of a zone-refined rod was rolled unidirec-tionally to a strip 0.003 in. thick and 0.28 in. wide. Samples were given anneals in the range 1300" to 2100°C using ac conduction heating in an oil-free vacuum system. Recrystallization to small grains appeared to be complete at 1300°C. Large grains were formed at higher temperatures, but these were not entirely strain-free, some grains showing asterism in Laue X-ray patterns and some displaying a range in orientation. Part of the difficulty was caused by thermal expansion of the tantalum strip as it was held between fixed supports. However, in a different arrangement with the tantalum freely suspended in a tantalum can, high-frequency induction heating in vacuo at about l0-6 Torr produced

Jan 1, 1964

By Philip Lindstrom

Retreat mining, using yielding steel friction props, over a seven-year period has been successful at a uranium mine operated by Hecla Mining Company in southeast Utah. The support system allow good roof control, maximum profit, complete extraction, and good ventilation. Unusual subsidence observations were made in that some of the surface was raised rather than lowered, Longwall mining, commonly practiced in European coal mines, has a potential of broader application because of mechanization possibilities and better roof control and ventilation at greater depths.

Jan 1, 1964

By J K. Irwin

The authors discuss the application of drum and friction hoists under modern conditions and give four examples of friction hoists proposed for various applications. The paper concludes with a summary of the advantages and limitations of friction hoists relative to drum hoists. Introduction T H~ introduction of the multiple-rope friction hoist m the late 1940&apos;s has complicated the se-lection of the right hoist for a given job. Once such considerations as rope safety factor, drum to rope ratio, hoisting distance, tons per hour and/or service duty have been decided upon, the selection of a drum hoist is relatively simple. We now ask our-selves "which hoist -drum or friction? (See Figure 1 and Figure 2). When a friction hoist is a possibility we are immediately concerned with how many ropes to use, whether to hoist balanced or counter-balanced, whether a friction hoist will be flexible enough for the application and, of course, what the relative costs will be.

Jan 1, 1964

By Avnulf Muan, Egil Aukrust

Activity-composition curves jor cobalt oxide and manganese oxide in solid solutions with spinel-type structure have been determined by studying the equilibrium between the spinel phase and a coexisting solid-solution phase in the tewzperature range 1100" to 1400"C. Within limits of experimental error, the system displays the behavior of a regular solution. The excess integral free energy of mixing is represented by the equation . The standard free energy of formation of cobalt manganite, CoMn,O,, from the oxide components COO mzd Mn2OS at 1200°C is calculated to be -8.6 kcal. AMONG the technologically and theoretically most important oxide phases are those which crystallize with the same structure type as the mineral MgO . A120,. Although the name spinel originally was used only for this mineral, the term is generally used today to designate the whole group of oxide phases with this same structure type. It is in this wider meaning that the term is being used in the present paper. The previous literature on spinels is very extensive. There are two aspects of spinels which have attracted particular attention: the structure, including the nature and distribution of the cations present, and the physical properties (electric, magnetic). The status of knowledge in these fields has been well-summarized in recent review articles.1&apos;2 By contrast, thermodynamic properties of spinels are virtually unknown. Delineation of the activity-composition curve over the whole composition range of a solid-solution series with spinel-type structure is the objective of the present work. The system at elevated temperatures (>1000"C) constitutes such a series. The activity-composition curves for this system can be calculated from a study of the equilibrium between the above spinel solid solution and a solid solution (Co,Mn)O with sodium chloride-type structure. Data for the latter solid solution have become available recently.3 The system, in contact with metallic CO at 1200°C, obeys Raoult&apos;s law. The determination of the activity-composition curve for the spinel phase is based on the following relations. Consider the reduction-oxidation equilibrium for cobalt ions according to the equation: Because it is impossible in practice to measure single activities of electrically charged constituents, we will treat the equilibria in terms of electrically neutral components. Eq. [I] can then formally be written as follows: where and the activities of cobalt oxide in the (Co,Mn)O and the spinel solid-solution phases, respectively, K is a constant at constant temperature, and Pa is the oxygen pressure of the gas phase. The numerical value of K can be determined from a determination of the oxygen pressure P& for the equilibrium coexistence of Cos04 and COO in the binary system Co-0. Under these circumstances be set equal to 1, and hence K = [Po Eq. [3] can therefore be written

Jan 1, 1964

By D. A. Shock

Utilizing the technology developed for oil well stimulation by hydrofracing, a disposal system which permanently fixes the waste has been proven. Large quantities of radioactive waste can be processed by a single well system making this method an attractive method for permanent radioactive waste disposal. The system depends on locating a relatively thick formation of impermeable, but easily fracturable rock such as a shale, creating a horizontal fracture, pumping the waste into the fracture in a form which will subsequently solidify and seal the fracture from the well system. The paper presents the theoretical considerations from creating and extending horizontal fractures and how these considerations were used in designing a waste disposal system which is now operating.

Jan 1, 1964

By Y. Nakada, B. Chalmers

The work-hardening behavior of surface layers of aluminum and gold single crystals was investigated by alternately deforming and then removing a thin surface layer by electropolishing or by etching. Aluminum crystals exhibited lower flow stresses after the surface removal; gold crystals did not. Abrasion of surface eliminated easy glide in both gold and aluminum crystals. By alternately deforming and removing the surface layer, it was shown that the abraded crystals work-harden preferentially under the abraded layer. It is suggested that this phenomenon is caused by the difficulty of propagating dislocations through the abraded layer. It has been demonstrated in numerous cases&apos;-3 that the plastic behavior of metals in either single-crystal or polycrystal form is sensitive to the environment and to the condition of the surface; it has also been reported4-6 that single crystals of some metals, when deformed in tension, exhibit more work hardening near the surface than in the interior. A third type of effect that has been attributed to the special part played by the surface in plastic deformation is the influence of the dimensions of the specimen on the various parameters that define its plastic-deformation characteris- tics.?-&apos;&apos; Many of these experiments were made on aluminum, on which an oxide film is always present under available experimental conditions; many of the effects have been attributed to the oxide film, either in terms of its higher elastic moduli, which would cause local stress redistribution, or its higher strength, which would oppose the escape of dislocations at the surface of the metal. On the other hand, it has been suggested II,12 that the mere presence of a surface should be sufficient to produce the observed results. A rigorous examination of this question could, in principle, be carried out by comparing the behavior of aluminum with its oxide film with that of the same material without oxide. This experiment would present great difficulties. The most practical alternative is to compare aluminum with gold, which has no crystalline surface film at room temperature, and to study the effects of various surface treatments on gold. The experiments described in this paper fall into two groups, the objectives of which were to determine 1) whether single crystals of gold shared the property of aluminum that the removal of a surface layer after some plastic deformation reduced the flow stress for further deformation and, since the result of this was negative, 2) whether a surface treatment could be found that caused gold to behave in this way. I) EXPERIMENTS AND RESULTS All the tests described below were carried out on single crystals of about 6 by 6 mm cross section and of sufficient length to provide a gage length of about 10 cm.

Jan 1, 1964

By E. J. Rapperport, M. F. Smith

A presentation of the W-Ru constitution diagram is given. Techniques utilized in the determination of phase boundary values include electron micro-probe analysis of two-phased alloys and diffusion couples, as well as normal metallographic and X-ray methods. The primary features of the diagram are: 1) a terminal solid solution of ruthenium in tungsten with a maximum solubility of 23 at. pct Ru at 2300°C; 2) a terminal solid solution of tungsten in ruthenium with a maximum solubility of 48 at. pct W at 2205°C; 3) a o phase of maximum breadth about 6 at. pct based on the composition W3Ru2 which forms peritectically from the melt at 2300°C, and which decomposes eutectoidally at 1667 °C to form a twigs ten and 0 ruthenium; 4) a eutectic at 45 at. pct Ru and 2205°C with the products being o plus ß ruthenium. THE W-Ru diagram has previously been studied only in a cursory fashion. Raub and alter&apos; obtained a 1400°C isotherm in which they observed no intermediate phases, and on which they established the limits of solubility as 36.5 at. pct W in ruthenium and about 1.5 at. pct Ru in tungsten. In addition, Obrowski2 found a o phase forming peritectically from the melt and existing only above 1650°C. Below this temperature the phase was presumed to decompose eutectoidally. The present work finds the diagram as given in Fig. 1. I) EXPERIMENTAL PROCEDURE The materials used for alloy preparation in determining the W-Ru constitution diagram were 99.9 pct pure ruthenium powder supplied by Baker Chemical Co., and 99.9 pct pure tungsten powder from General Electric Co. Typical analyses of these elements are given in Table I. Initial alloys at 10 at. pct intervals were prepared from the metal powders by the following method. Powders sufficient for 25 g of the alloys were weighed out with an accuracy of 0.1 mg and blended mechanically. After blending, the powders were compacted, in a steel die, at approximately 30,000 psi. The compacts were sintered in an electric vacuum furnace in order to remove adsorbed gases and to achieve partial densification prior to arc-melting. Vacua of 10-4 mm Hg or less were maintained in sintering as the furnace temperature was raised to approximately 2000°C. Sintering times ranged from 10 to 20 hr. The sintered compacts were arc-melted under a protective atmosphere of purified helium. Melting was conducted on a water-cooled copper hearth, utilizing a nonconsumable tungsten electrode. In the melting process, each alloy was turned over and re-melted on opposite sides from four to six times to ensure complete melting and to eliminate gross in-homogeneities. The arc-melter used had a vacuum capability of 5 X 10-6 mm Hg, and a leak rate of about 20 -liters per hr. Chemical analysis techniques for refractory metal-platinum group metal combinations are not well-established; therefore, composition control and determination depended principally upon weight-loss observations and calculations. This consisted in weighing each alloy after sintering and after arc-melting, and calculating the maximum and minimum composition values, assuming the total weight losses to be first all tungsten, and then all ruthenium. Since composition uncertainty was directly related to weight loss, care was taken to minimize losses in handling, compacting, and melting. Prior to homogenization and equilibration the as-arc-melted alloys were analyzed in several

Jan 1, 1964

By Leonard R. Weisberg

The general properties of diffusion in GaAs are reviewed. A total of .fourteen atoms have been studied to date, and activation energies for eleven reported are (in ev): Ga (5.6), As (lo), Zn (2.49), Cd (2.43), Sn (2.5). Mn (2.75). S (4.0). Se (4.2). Ag (0.33), Cu (0.52). and Li (1.0). The dijfusion of the first eight atoms, as measured by Goldstein using radiotracer techniques, established the principle of sub lattice diffusion for both host and impurity atoms, since atoms substituting for gallium have lower activation energies than those substituting for arsenic. The diffusion constant of interstitial copper has been determined for the first time by Hall and Racette using heavily doped p-type samples in which interstitial copper predominates. The anomalous behavior of zinc, which has an abrupt diffusion front and a strong dependence on zinc concentration, has recently been quantitatively explained in terms of an interstitial-substi-tutional equilibrium-diffusion mechanism. Lithium and silver diffuse mainly interstitially, while the diffusion of phosphorus is complicated by the continual formation ofGap. Junction-migration measurements indicate diiferent results than radiotracer techniques, and this is one problem that still remains, together with discrepancies in cadmium-diffusion results, and an unexplained dependence of impurity diffusion on arsenic pressure. BESIDES the usual insights into the behavior of atoms in solids, studies of diffusion in semiconductors have additional importance for device applications. In fact, the amount of diffusion studies performed on a semiconductor might serve as a simple barometer of its technological importance. Thus, the information accumulated for GaAs is not yet quite comparable to that for germanium or silicon, but considerable knowledge is available. The diffusion of at least fourteen atoms has been investigated for GaAs, and the diffusion constants have been determined for eleven of these. Interesting results were found for GaAs that elucidated problems not previously solved for germanium or silicon. For example, the interstitial-diffusion constant for the very fast diffusant, copper, was first measured in GaAs. Also, solutions for interstitial-substitu-tional equilibrium diffusion in extrinsic material were provided first for GaAs, although they are ap- plicable to germanium, silicon, and other semiconductors. Studies in GaAs firmly established the concept of sublattice diffusion, which should have application in many different compound systems. The purpose of this paper is to review briefly the general state of knowledge concerning diffusion in GaAs. First some general aspects of diffusion will be covered, and next attention will be given to the results mentioned above. Diffusion in GaAs has been measured both by radiotracer and junction-penetration techniques, and some discussion will be given of differences in the two sets of results. The comprehensive work of oldsteinl-&apos; has served as the primary reference for the diffusion of well-behaved substitutional atoms in GaAs. Since a review has recently been presented of many of these reults, details of the diffusion data will not be repeated. Neither will any discussion be given of the experimental techniques of diffusion measurements, except to note here, in passing, the simplicity and effectiveness of the precision lapping device employed by Goldstein.&apos; I) EXPERIMENTAL RESULTS AND DISCUSSION A) Summary of Experimental Results. Diffusion constants D = Do exp(E/kT) have been determined for eleven atoms in GaAs: a,&apos; AS,&apos; n,&apos;" Cd,&apos;" n,&apos; n,8 s, e,&apos; Ag,O CU," and i." These results are summarized in Table I. In addition, diffusion was investigated for phosphorus,4&apos;12 germanium,I3 and ilicon,&apos; but Do and E were not determined. Radiotracer techniques were used for most of the studies except for lithium, where a combination of chemical and electrical techniques was employed, and germanium and silicon, where junction-migration techniques were applied. The diffusion of zinc, manganese, sulfur, and tin was also measured using junction migration.13&apos;14 Goldstein demon-

Jan 1, 1964

By J R. O Walli

Large production shafts can be successfully sunk through the ubiquitous Blairmore formation of southern Saskatchewan by employing the freezing process and by the installation of a cast iron tubbing lining. Although the freezing technique for shaft sinking and the use of cast iron tubbing to preserve the shaft are new to the North American continent, these procedures have been employed in Europe for the past eighty years. More than 200 shafts, covering a wide variety of ground conditions, have been sunk by the freezing process, and most of these have been lined with cast iron tubbing. The No. 1 shaft of International Minerals and Chemical Corporation, near Esterhazy, Saskatchewan, comprises the first major example in Canada of the employment of European methods to overcome extremely difficult ground conditions. The Blairmore formation was solidified by the deep freezing process, employing a lithium chloride solution as the refrigerant, with input temperatures ranging to -55°F

Jan 1, 1964

By d&apos, Kathleen J. Amico

THIS summary appears in Minerals Yearbook volumes I and III, which cover mineral production in the United States, its island possessions, the Canal Zone, and the Commonwealth of Puerto Rico, as well as the principal minerals imported into and exported from the United States. The several commodity and area chapters contain further details on production. A summary table comparing world and U.S mineral production also is included.

Jan 1, 1964

Gold was determined directly in eight different mill cyanide solutions, by atomic absorption spectroscopy in an acetylene-air flame. Some of the mill solutions were diluted with water to bring them into the most sensitive absorption region (5-50 p.p.m. Au) whereas those solutions with very low gold content &#171;2 p.p.m.) were concentrated by evaporation.Calcium was complexed with ethylene diamine tetra-acetic acid (EDTA) to avoid the undesirable effect of a precipitate on atomization.When added to standard gold solutions, EDTA had no effect on absorption, nor did any of the impurities common in mill cyanide solutions.Known amounts of gold, ranging from 2 to 30 p.p.m., were added to mill solution&apos;aliquots and recovered to within 100 &#177; 2&#183;5 per cent. For duplicate determinations under normal worKing conditions, standard deviation was 1&#183;32 p.p.m.Excellent agreement was found between atomic absorption gold values and accurate fire assay values.INTRODUCTIONAtomic absorption spectroscopy has been shown to offer a rapid and accurate method for the determination of trace amounts of a number of metal ions. In the field of primary metallurgy atomic adsorption has been used for routine determinations of lead, copper, silver, zinc, cadmium and iron in a variety of raw materials and intermediate products.The scope of atomic absorption spectroscopy was reviewed recently by Willis (1963).The noble metals silver, gold, platinum, rhodium and palladium were determined by atomic absorption from chloride solutions by Lockyer &#183;and Hames (1959). In their determination of gold down to 1 p.p.m., they found no interference from the noble metals, nor from considerable excess...

Jan 1, 1964

By S. Floreen

Measurements have been mode of the effects of tempering and austenitizing heat treatments, the work-hardening characteristics, and the effects of test temperature and strain rate on the properties of a low-carbon Fe-18 pet Ni martensitic alloy. In many respects the alloy behaved quite similarly to cold-worked iron. One notable quality was the excellent ductility at temperatures as low as 20°K. Many of the qualities of the maraging steels could he related to the properties of the Fe-Ni matrix. THE 18 pet Ni maraging steels have demonstrated that unusual combinations of strength and toughness may be obtained by age hardening a low-carbon Fe-Ni martensite matrix.&apos; These properties must, to some extent, reflect the properties of this Fe-Ni matrix, and therefore an understanding of the properties of this matrix is a prerequisite to a complete understanding of the steels. There have been several recent studies of Fe-Ni-C martensites, but not much attention has been paid to alloys with very low carbon contents. At low carbon levels the crystal structure of these alloys is essentially bee.2 Electron transmission microscopic examination of a 20 pet Ni binary alloy showed martensite platelets separated by low angle boundaries.3 Plastic deformation of the low-carbon alloys has been shown to proceed by wavy glide.4 The hardness of these martensites is typically RC 28, and their yield strengths are 70 to 80 kg per sq mm.2, 5 Their ductility is excellent. Room-temperature tensile elongations of 18 pet and reductions of area of 70 pet have been observed in an Fe-18 pet Ni binary alloy.5 These observations have provided a qualitative understanding of the flow characteristics of these alloys. To date, however, no thorough study of their properties has been made. In particular, it is not known to what extent the deformation characteristics of low-carbon martensites are similar or dissimilar to those of pure iron or other bee metals. The present work was undertaken to provide more detailed information on the flow characteristics of a low-carbon Fe-18 pet Ni martensite. PROCEDURES, RESULTS, AND DISCUSSION Materials. A 40-lb heat of the Fe-18 pet Ni alloy used in this study was made by vacuum-induction melting. The charge materials were electrolytic iron and electrolytic nickel. A carbon boil was used to achieve deoxidation. After the boil the heat was refined by additions of 0.1 wt pet Ti and Al. These additions are commonly used in the maraging steels to keep the carbon and nitrogen contents in solid solution at a minimum. After casting, the heat was

Jan 1, 1964

By G. B. Craig, G. L. Montgomery

A simple technique has been developed which reveals glide dislocations in zone-refined aluminum as etch pits. The technique has been tested quantitatively by making dislocation counts on aluminum single crystals deformed in pure bending. The method has the advantage of being insensitive to the orientation of the surface under examination. A number of etchants which will reveal dislocations in annealed aluminum have been reported.&apos;-&apos; These etchants apparently depend on decoration of the dislocations by an impurity (probably iron) and cannot, therefore, be used to reveal fresh glide dislocations. In addition, it is unlikely that screw dislocations will be etched because of their small attraction for impurity atoms. Amelinckx6 has reported that glide dislocations located along slip traces can be revealed by fluo-rated aqua regia. This work indicated that dislocations themselves, irrespective of decoration by impurity atoms, are responsible for the etch pits. However, as a result of additional etching experiments, Wyon and Marchin7 concluded that dislocations alone are not sufficient to explain the localization of etch pits on slip lines in aluminum using chemical etch-pitting techniques. In addition, their results show that glide dislocations are revealed only on surfaces approximately parallel to a (100) axis and that not all slip systems are attacked. These observations have been confirmed by the present authors. The technique described in this article is insensitive to the orientation of the surface, and reveals dislocations on all glide systems. Fig. 1 shows a deformed region in the neighborhood of a scratch. Dislocations can be seen along three slip traces. In the present work, single crystals of zone-refined aluminum are polished for from 2 to 5 min in a chemical polishing reagent held at 100°C, as described by Herenguel and second:&apos; H2Sol 60 pct H3PO4 30 pct HNO3 10 pet The samples are then coated with a thin oxide film by annealing in air at 450°C for 1 hr and cooling in the furnace. After deformation, dislocation etch pits are developed by immersing the specimen in the same polishing solution which is now held at a temperature of 50°C. The formation of small hydrogen bubbles indicates that etching has occurred. The sample is immediately removed from the solution. Prolonged etching results in enlargement of the pits and, in regions of high dislocation density, the overlapping and loss of resolution of individual pits. It is the experience of the authors that contact with iron will ruinously contaminate the reagent. With careful etching, dislocations separated by half a micron can be resolved optically and the method has been shown to be sufficiently sensitive to reveal dislocations produced during the pre-easy glide region of deformation, Fig. 2. A few examples of glide-dislocation configurations, as revealed by this technique, are shown in Figs. 1 to 4.

Jan 1, 1964