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By I. H. Pratt

The results of a study on the preparation of thin-film capacitor structures are discussed. The dietectric source material was quartz which was sputtered and deposited onto aluminum electrodes and counter-electroded to complete the metal-oxide-metal structures. This configuration was utilized to evaluate the dielectric, the device characteristics, and related process parameters. The effect of gas sputtering pressure, magnetic field strength, source-to-substrate distance, and power density on the rate of deposition is shown. Increased film thickness uniformity over a 3 by 3 in. area by optimum substrate positioning is indicated. Dielectric constant, dissipation factor, dielectric breakdown strength, insulation resistance, heat treatment, capacitance, and dissipation over the range 400 Hz to 5 MHz are reported. In the fabrication of silicon-integrated circuits, silicon dioxide has found use as a material suitable as a diffusion mask, for surface passivation of the silicon, and for protection of conductive films used for interconnections. Its use as a dielectric for thin-film capacitors in film hybrid circuits has been limited, to a degree, for lack of a compatible processing technique and because of its relatively low dielectric constant. With the recent advent of practical metal-oxide-semiconductor (MOS) field effect devices, the material is now being used to insulate the gate electrode from the conducting channel in the silicon. In this latter application, more stringent requirements have been imposed on .the oxide. A comprehensive resume of the use of silicon dioxide in integrated silicon device technology has been compiled including oxide film and bulk properties, method of oxide formations, and their applications.' A relatively new process to deposit SiO, and other dieIectrics is by rf sputtering, and the purpose of this paper is to describe the behavior of capacitors fabricated with a dielectric which has been sputtered from a quartz target and to indicate the relative effect of several of the process parameters on the film deposition. Work on rf sputtering of SiO2 and other dielectrics has been reported utilizing a triode type of sputtering system as described herein or a diode self-sustained glow discharge system. 2-8 SPUTTERING The process occurs during an electrical discharge in a gas plasma which provides the ions for acceleration to the target to produce the desired sputtering. The necessary plasma can be generated by a dc glow discharge through application of a high potential between two electrodes at approximately 2 to 10 x 10-2

Jan 1, 1969

By C. A. Stickels, C. M. Yen

Secondary recrystallization was investigated in vacuum-melted electrolytic iron to which 70 pm N was vacuum-meltedadded. The secondary texture is "near {554}<225>" for material cold-rolled 75 to 90 pct, the sharpness of the texture increasing with increased rolling reduction and with decreased annealing temperature. At reductions of 95 and 97.5 pct the secondary texture is &apos;"near {322)(296)". Both secondary orientations also exist as major components of the primary re-crystallization texture. Development of a strong "near {554) (225)" secondary texture appears to depend on the evolution of the Primary texture to a transition texture depleted in orientations near the secondary orientation before the onset of secondary growth. A variety of qualitative experinzents have been used to show that nitrogen is important in limiling primary grain growth. The presence of nitrogen does not seem essential for the establishment of a transition texture, but a loss of nitrogen during annealing may facilitate growth of grains in the secondary orientation. Secondary grains we shown to form initially at the specimen surface. This is not thought to indicate that surface energies are important in the growth process. It is proposed that the quasi-two-dimensional character of surface grains permits discontinuous growth parallel to the surface before secondary growth of interior grains is possible. An earlier study of recrystallization textures in 90 pct cold-rolled electrolytic iron showed that secondary recrystallization occurred after annealing for several days at 700C1 This type of secondary recrystallization, which had not been reported previously, results in the formation of a strong texture, best described by the indices "near {554}(225)". The purpose of the present work was to investigate the effect of various processing variables on secondary recrystallization in this material and determine the mechanism of secondary grain growth. LITERATURE REVIEW An understanding of the mechanism of a secondary recrystallization process depends on knowing: 1) how grains in the secondary orientation come to be in the primary recrystallization texture; 2) why normal grain growth does not occur; and 3) what factors determine the strength of the secondary texture. For secondary growth of grains of a particular orientation, a certain minimum fraction of the grains must be in that orientation after primary recrystallization. This requirement is apparently satisfied "naturally" in certain systems, i.e., when the primary texture obtained by rolling and recrystallizing material initially randomly oriented contains a sufficient fraction of primaries in the secondary orientation. However, in other cases, e.g., {110}<001> and {100}<001> secondary growth in silicon iron,2 it is necessary to enhance the fraction of primary grains in the secondary orientation by rolling and recrystallizing textured material. In the present case, the "near {554}<225>" orientation is contained within the spread of orientations found in the primary recrystallization texture of iron or bbc iron-base alloys. In systems where the main driving force for secondary growth is the reduction in total grain boundary energy, secondary growth is observed only when normal grain growth is minimized. Four ways in which normal grain growth can be limited are: 1) Limitation by a strong primary texture. When a very strong primary texture consisting of a single component or twin-related components develop, most primary grains are separated from one another by relatively immobile small-angle grain boundaries. The classic instance of this is secondary growth into the primary cube texture in some fcc metals. 2) Limitation by precipitates. Precipitates present in the proper volume fraction with a suitable dispersion will limit primary grain growth. The role of MnS inclusions in impeding normal grain growth in Si-Fe is well-documented.5 3) Limitation by sheet thickness. Normal grain growth slows drastically when the mean grain diameter is of the same order as the sheet thickness. This effect has been used to obtain secondary recrystallization in thin sheets of high-purity silicon iron.&apos; 4) Limitation by solute impurities. It is well-established that certain impurity elements in solution can have a large effect on grain boundary mobility.&apos; However, there does not seem to be any secondary recrystallization process in which primary grain size stabilization has been shown to be due to the drag exerted on grain boundaries by dissolved impurities. In certain systems, e.g., secondary recrystallization in silver,&apos; the means by which normal grain growth is limited has not been identified, and solute-impurity limitation might be suspected. In order to understand the factors which determine secondary texture strength in three-dimensional growth, it is necessary to examine in more detail the current picture of general secondary recrystallization processes. Following Cahn,9 it is assumed that the primary grains have a range of sizes and that secondary growth of one of the large grains in this distribution is possible when it exceeds a critical size with respect to its neighboring grains. The critical size depends on the ratio ?S/?p, where ?s is some sort of average grain boundary energy between the potential secondary and the primary grains and ?p is some sort of average grain boundary energy between primary grains. For a constant primary grain size, the critical size for secondary growth increases as ?$/?p increases. May and Turnbull5 have incorporated the

Jan 1, 1969

By Mark Eisner

ONE&apos;S JOB is the watershed down which the rest of one&apos;s life tends to flow write the Lynds in the first pages of their classic social study, "Middletown in Transition." Certainly engineers will confirm this statement after a check among those in their own profession with whose lives they are at all familiar. I have no hesitancy in acknowledging the truth of their observation for the men and women who are engaged in the profession of the law. It has been often remarked that American public life is overrun with members of the law profession. The highest public office in the land, that of President. has been occupied by lawyers almost to the exclusion of citizens of any of the other professions. Twenty-two Presidents of the United States out of the total of 31, were members of the bar. For the most part, members of Congress, the governors of the states, the state legislators and the mayors and other local leaders, men who occupy important positions of responsibility and public trust, have had legal training. Now this fact is no mere accident. Those who were fitted for the "job" of the practice of the law are favorably placed with respect to their participation in public life. Thus public service and public office is the watershed down which the "lawyer&apos;s" life tends to flow.

Jan 1, 1940

By E. J. Eisenach, Edward Matsen

AT the present time the Climax Molybdenum Co. is the largest molybdenum producer in the world and the operator of the largest underground mine in North America. It has grown steadily and rapidly since its beginning in 1917. Only 250,000 lb of MoS2 were produced during the first year from 1917 to 1918 when the company was formed. Operations were suspended shortly thereafter because of the lack of a market and knowledge of the uses of molybdenum. During World War I it was used as a substitute for some rare metals and for minor chemical purposes. After 5 years of intensive research and sales promotion, Climax metallurgists succeeded in finding proper applications for the newly discovered metal and the mine was reopened in 1924. Demand for molybdenum increased gradually and in 1930, 3.5 million lb of MoS2 were produced. In the meantime, research work for additional uses of molybdenum continued until it had established itself as one of the most important alloying elements in producing high quality steels. After the start of World War 11, from January 1942 to October 1953, 43 million tons of molybdenum ore were mined and 484 million lb of MoS2 were produced. Climax mine is located in Colorado, 100 miles southwest of Denver and 12 miles northeast of Leadville on the Continental Divide of the Rocky Mountains. The principal mine workings range from 11,170 to 12,000 ft in elevation. Topographically, it lies in the base of a large cirque that is surrounded by Mt. Bartlett to the north, Clinton Peak and McNamee Peak to the east and Ceresco Ridge to the south. This cirque opens to the west and to the Ten Mile Valley.

Jan 3, 1954

By S. G. Dixit, A. K. Biswas

The flotation and adsorption behavior of ilmenite, monazite and zircon have been studied with sodium oleate as the collector and pH as the principal variable. The maxima in the flotation and adsorption properties of any of the above minerals fall within similar pH ranges. The bell shaped pH versus adsorption magnitude (r) curve is explained on the basis of collector concentration (Co and the concentration of hydroxyl ion (COH-) acting as the depressant. An equation of the type: 1 =KiCor~K2 Coh-/Coi-is proposed to account for the experimental data. The beach sand deposits along the sea coast in Southern India contain ilmenite, monazite, zircon, rutile and sillimanite as valuable minerals while quartz, garnet, shells and traces of hornblende form the gangue. A typical composition of the deposits is reported to be as follows:&apos; Ilmenite 75%, Zircon 4-6%, Rutile 3-4%, Monazite 2 - 4%, Garnet 2 - 5% and the rest 8 -10%. Selective flotation of beach sand constituents has been reported by many workers.2-4 The fatty acid soaps have been invariably used as collectors. It is seen that all the valuable constituents of the beach sand are efficiently floated by soap collectors such as sodium oleate. In order to selectively float the beach sand constituents, it is necessary to use some depressants such as sodium silicate.3 The physicochemical parameters that govern the flotation of these minerals are yet to be studied in detail. In the present article, the findings on the parallel studies on the flotation and adsorption of the systems — ilmenite-sodium oleate, monazite-sodium oleate and zircon-sodium oleate — are being reported. In these correlative studies on adsorption and flotation of beach sand minerals, ilmenite (FeTiO3), monazite (Ce, Dy, Nd) PO4 and zircon (ZrSiO,) have been selected because they represent three important

Jan 1, 1970

By R. G. Treuting, W. C. Ellis

D. Whitwham, M. Mouflard, and P. Lacombe (British Council Research Fellow, Labratoire du Professor Chaudron, Vitry-sur-Seine; Inqenieur de Recherches, Labratoire de Vitry; and Maitre de Recherches, Labratoire de Vitry, Professeur Adjoint de Metallurgie, Ecole des Mines, Paris)—The authors&apos; work is of great interest in bringing out the geometrical relations existing between twinned lattices, and for the notion of a coincidence super lattice developed from this. We should like to point out that a similar idea was put forward by Friedel8 in his book on the subject of lattice merohedrism "merihedrie réticulaire:"—When two crystals A and B are twinned with respect to a mirror plane, there exists a common superlattice, "réseau periode," which is independent of the contact surface between the two crystals. The volume V of this superlattice is a simple multiple of the volume v of the lattice of crystals A, or B, (Fig. 5). This "multiple cell" is defined by the twin plane (p q r) and a row of atoms [h k l] normal to this plane, the base being taken as the smallest unit (two-dimensional) of this plane. Two cases must be considered. First when the multiple cell, as defined, has no atom site at its center nor at the center of its faces other than (p q r), v the twinning index is defined by —. In the second v case, when one of the two above conditions does not v apply, then the twinning index is V 2v A more intuitive definition of the twinning index would be the proportion of atoms of C, which would coincide with those of C1 when the C, lattice is imagined to extend on the other side of the contact surface. In the case of cubic crystals, the twinning index

Jan 1, 1952

By Ralph C. Flow

In Cleveland County, North Carolina, 1 ½ miles south of Kings Mountain, Foote Mineral Co. operates an open pit for the production of spodumene, feldspar, mica and commercial stone. Spodumene concentrate is sent to Foote Mineral&apos;s Sunbright, Va., plant and to other customers. Exton, Pa. and New Johnsonville, Tenn., plants produce lithium com- pounds sold to the oil industry for multipurpose lithium-base greases, to the metal industry as welding flux, to the air conditioning market and to the glass industry. Ceramic-grade spodumene, feldspar, and mica concentrates go to other processing companies from the Kings Mountain plant. Waste amphibolite is delivered to a neighboring quarry operation. Geology and exploration of the deposit have been described by T. L. Kesler, Chief Geologist of Foote Mineral Co., in the September 1961 MINING ENGINEERING. Measured ore reserves as published at that time were 20.7 million tons. The ore deposit consists of a series of lithium-bearing pegmatites enclosed in amphibolite and mica schist wall rocks. The general strike of the pegmatites is northerly, and in the southern part of the pit, they dip slightly towards the west. The largest body being mined has a fairly uniform thickness of about 200 ft. Other pegmatites in the pit area range from 20 to 100 ft in thickness. Minerals in the pegmatites are 20% spodumene, 32% quartz, 6% muscovite, 41 % feldspar and 1 % trace minerals.

Jan 10, 1962

By George F. Kunz

THE recently discovered occurrence of diamonds near Murfreesboro, Pike county, Ark., was brought to. our attention by Mr. Samuel W. Reyburn (Trustee for Messrs. C. S. Stifft, A. D. Cohn, August Zinsser, Jr., and himself, owners of the property), through whose courtesy we investigated the locality of the deposit. Prospecting with the diamond-drill is now in active progress ; but mining operations on a large scale have not yet been ordered. Geology.-The geology as well as the petrography of this interesting locality has been well described by Messrs. J. C. Branner and R. N. Brackett.1 Briefly summarized, the igneous rock in which the diamonds are found is a vitreous peridotite, forming a stock or volcanic neck, which has broken up through the Carboniferous and Cretaceous quartzites and sandstones. After an extensive period of erosion, during which an unknown portion of the neck and presumably a previously existent volcanic cone have been removed, the surface was covered with thin beds of Post-Tertiary conglomerate. The volcanic intrusion was accompanied by the formation of several small dikes of a rock much like that of the main body. One of these dikes cuts across the stock, while another cuts the Cretaceous sandstone, but is overlain by the conglomerate, thus giving a datum for the period of intrusion. So far as known, there was little, if any, metamorphism of the country-rock by the igneous magna, which probably followed an approximately vertical course, so that a more or less vertical extension downward of the igneous body to indefinite depths may be expected.

Mar 1, 1908

By D. Cox, M. J. Duggin, L. Zwell

The carbides of approximate composition and Mn have been studied using X-ray diffraction techniques. Those carbides of the type (Fe,Aln)zC ave isostructural with cementite. The cell pararmeters a and c have minimum values at approximately 10 at. pd substitution of manganese for iron; no satisfactory explanation has yet been found for this phenomenon. The carbide fFeMn4)C has a monoclinic unit cell whose dimensions are close to those of ,11,15Cz A neu-troip-dij~ractiot~ study of (F&apos;eAlrz4)C~ reveals that, like MnsCZ, it is isostructural with Pd5Bz. The iron and manganese atoms occupy the palladium atom sites, while the carbon atoms were found to have the same atomic coordinates as the hovon atoms. A neutrorr-diffraction study of indicates that the carbon-atom positions are very close to those occupied in (Fez.,ll/lr~,.3)C. In both carbides studied, tlre iron and manganese atomzs were found to be essentially randomly distributed, although, in the case of (Fe,.811fn1.2)C, it is possible that there may be a slight preference of manganese atoms for- the general (d) positions and a corresponding slight preference of iron atoms for the special (c) positions. It has been found that a complete range of solid solution exists between Fe3C and Mn3C at 1050°C,I although Mn3C becomes unstable when the temperature is reduced to 95O0C,&apos; and can only be retained by rapid quenching. It is also known that a complete range of solid solution exists from Fe5Cz to M~SC~,~ although the stability range of carbides of the type (Fe,Mn)sCz as a function of the relative proportions of iron and manganese is not known. X-ray examinations of Oh-man&apos;s carbide3 and Spiegeleisenkristall,~ which have the approximate compositions (Fe3.67Mnl.33)C2 and (Fe3-,Mn,)C, where x lies between 0.4 and 1, respectively, have been made. The following carbides have also been studied: ] The lattice parameters determined during these investigations are listed in Table I. It is seen that carbides of the type (Fe,Mn)sCz have a monoclinic unit cell while carbides of the type (Fe,Mn)3C have an orthorhombic unit cell. It is evident that the variation of lattice parameters with manganese content is not linear for carbides of the type (Fe,Mn)3C. The coordinates of the atoms in (Fe2.7Mno.3)C have recently been determined by single-crystal analysis., The fractional atomic coordinates have been shown by Fasiska and jeffrey to be in good agreement withj those deduced from an earlier analysis of Fe3C by Lipson and etch.&apos; However, it was impossible to determine whether iron and manganese atoms occupied ordered positions because of the small difference between the atomic scattering factors of iron and manganese. The atomic positions in Mn5Cz (Refs. 8 and 9) and Fe5C2 (Refs. 7 and 8) have been obtained only by comparisons made with the isostructural compounds P~SB~.&apos; Since X-ray diffraction techniques were used in these investigations, accurate positioning of the carbon atoms, which have a low atomic scattering factor, was difficult. No attempt has been made to determine the atomic positions in the other carbides previously studied. It was felt that an investigation of the lattice parameters of a number of intermediate carbides of the types (Fe,Mn)sCZ and (Fe,Mn)& would be of interest. It seemed likely that a neutron-diffract ion study of such carbides would indicate whether ordering occurred between the iron and manganese atoms because of the large difference between the neutron-scattering cross sections of iron and manganese. It also seemed probable that such an investigation would provide a determination of the atomic coordinates of the carbon atoms. I) EXPERIMENTAL DETAILS Specimens, each weighing approximately 20 g, were carefully prepared according to the following proportions: The components were 500-mesh powders of 99.995 pct purity iron and spectroscopically pure carbon and a 200-mesh powder of 99.995 pct purity manganese. The component powders were intimately mixed by prolonged shaking, then each specimen was inserted into a spot-welded cylindrical container of tantalum foil, whose end was closed but not sealed. Each specimen in its envelope was then sintered at 1050° C for 24 hr in a thin-walled evacuated quartz capsule, such a time having been previously found sufficient for equilibrium to be attained.&apos; Each specimen was then quenched in order to attempt to retain the high-temperature phase, as the literature indicates that transformations may occur on cooling. Debye-Scherrer X-ray photographs were taken of each specimen using a 114.6-mm-diam camera, Fig. 1, patterns 2 to 6. The exposure time was 6 hr using filtered iron radiation at a tube voltage of 40 kv and a tube current of 12 ma.

Jan 1, 1967

At 8 o&apos;clock on the evening of Thursday, July 25th, the special train chartered by the Provincial Government for the Institute&apos;s use, pulled out of Toronto. Ten parlor cars and two dining cars made up the train. The culinary arrangements were under the personal supervision of Mr. McConkey, of Toronto. [ ] The Hon. Frank Cochrane, Minister of Mines, Lands and Forests, was the efficient host of the party. He was assisted by the Hon. Dr. Pyne, Minister of Education, and by Mr. T. W. Gibson and Dr. W. G. Miller. On arriving at Cobalt, the delegates were met by the following Committee Mr. A. A. Cole, representing the T. & N. 0. Railway; Messrs. R. W. Leonard and D. B. Rochester, deputies from the Cobalt Chamber of Mines ; Messrs. Run¬ning and Martin, from the Cobalt City Council; Messrs. McLeod and Ferland,

Jan 1, 1907

By Robert F. Mehl

THE mechanical behavior of metals and alloys is presumably conditioned by two factors; namely, the crystalline symmetry and the interatomic forces. Considerable attention has been given to the first of these factors through the recent advances in X-ray technique. It is the purpose of the present paper to call attention to the importance of the second of these factors, to point out promising methods of investigation, and to present some pertinent data. Plastic deformation takes place by slip along atomic planes.1 This slip may be inhibited in a number of ways: by the interatomic forces of cohesion which bind the atoms rigidly in a lattice structure, which in pure metals is usually of high symmetry; by lattice distortion caused by solid solution formation or by mechanical strain; by the intercrystalline boundaries where slip is restrained, probably by the non-registration of the atom planes in adjacent crystallites;2 and by the presence of small hard particles which serve to "key" the slip along the atom planes.3 In pure metals, and perhaps also in solid solutions, the atom planes of easiest slip are those exhibiting the greatest density of atomic population and the greatest interplanar distance4 and apparently can now be predicted from the analysis of the lattices. Concerning the interatomic forces, which resist this slip by holding the atoms firmly together, little is known. Most textbooks on physical metallurgy, following the work of Bottone,5 correlate the hardness of the pure metals with the atomic volume,

Jan 1, 1928

The Library of the above-named Societies is open frond 9 A.M. to 10 P.M., except on holidays. It contains about 70,000 volumes and 90,000 pamphlets, including sets of technical periodicals and the publications of scientific and technical societies. Members of the Institute, with few exceptions, are forced to spend a portion of their time in localities isolated front sources of information. To these the Library, through Its Library Service Bureau, can render valuable service through correspondence; letters requesting information will receive especial attention. The Library is prepared to furnish references and photographic copies of articles on mining and metallurgical subjects; to determine the existence of mining neaps, and to furnish general information on the geology and mineral resources of all countries. All communications should he made as definite as possible so that the information received may be what is desired and not include collateral matter which may not be of interest. The time spent in searching for such collateral matter will be saved, and the information will be, sent more promptly and in more usable shape.

Jan 1, 1917

By G. F. Jenkins

The word asbestos is a broad term that has been accepted and applied to a number of fibrous mineral silicates found in nature. They are incombustible and can be separated by mechanical means into fibers of various lengths and thicknesses, but differ in chemical composition and other properties. It is generally recognized that there are six varieties of asbestos; the finely fibrous form of serpentine known as chrysotile, and five minerals of the amphibole group, i.e., amosite (not fully recognized as a mineral species name but accepted in asbestos terminology), anthophyllite, crocidolite, tremolite and actinolite. (Figs 1-4.) Physical and Other Properties The structures of asbestos fibers have been studied intensely in recent years. X-ray diffraction patterns 1 to 15 have been used as a means of identification and classification. The amphibole group structures have been fairly well established while the serpentine group has been the subject of many investigations during the past six years. Low-angle X-ray scattering techniques5 have shown that the chrysotile fibrils are "hexagonally close packed" and parallel to each other, having cross-sectional diameters varying from 180Å* units to 300Å units, while the amphibole fibers are many times larger in cross section. The electron micrographs of chrysotile asbestos (Figs 1-4) have also indicated that the fibrils might be in the form of a hollow tube. This point has been the subject of considerable controversy by a number of investigators.7 to 16 Density measurements17 made on a sample of high quality Arizona fiber did not indicate that the fiber had a hollow tube structure; however, the so-called "sheet structure" of the fibril could be distorted in such a way that it gives the appearance of a hollow tube in the electron microscope. It is of interest to quote one investigator, F. L. Pundsack,17 in this connection: Although the empirical composition of chrysotile is 3MgO.2SiO2.2H20, the true unit cell[#] composition is best represented as Mg12(OH)16Si8O20. This cell has dimensions of a= 5.3Å, b = 9.2 Å, and c = 14.6 Å where the "a" direction is the fiber axis. The calculated density of this unit is 2.56 g/cc, a value in close agreement with experimentally determined density values for chrysotile. The exact manner in which the unit cells of asbestos are stacked together to build up a single fiber of chrysotile is not known, but from various

Jan 1, 1960

By J. W. Downey, A. E. Dwight, R. A. Conner

THE MgCu2 type Laves phase has been observed in the thorium-osmium and thorium-iridium systems. Two alloys corresponding to ThOs2 and ThIr, were prepared by arc melting a 5-g charge in a water-cooled copper. crucible. Both alloys were very brittle. X-ray diffraction patterns were obtained using filtered Cu and Co radiation with a Straumanis-type DeBye-Scherrer camera. The a,, values as shown in Table I were obtained by a Nelson-Riley extrapolation. The structure belongs to space group Oh7-Fd3m. Relative intensities for each of these compounds were calculated on the assumption that 8 thorium atoms occupy (a) positions and 16 osmium or irid-ium atoms occupy (d) positions. The calculated intensities are the product of the Lorentz-polarization factor, the multiplicity factor and F&apos;, the structure factor, neglecting the absorption and temperature

Jan 1, 1959

By George Bell

THE mine and milling plant of Demonstration Gold Mines, Ltd., is near the city limits of Baguio, Mt. Province, P. I. The mine road connects with the main highway to Manila. The nearest railway point is near sea level, approximately 40 miles distant. The Baguio district is very mountainous and has one of the heaviest rainfalls in the world. It is therefore difficult to maintain roads or to impound tailings and mine dumps. All supplies are trucked into the district direct from Manila or the nearest railway point, which means uncertain deliveries and high freight rates. Installation of equipment is difficult and costly. The average elevation at the mine is 4000 ft. and the climatic condi-tions.are ideal except for a three months rainy season. The company generates its own power for mining and milling opera-tions with three 400-hp. Ruston Diesel engines direct connected to 250-kw. General Electric alternating current generators. Labor conditions have been excellent, although at present social security laws are causing some unrest. Labor receives a higher average wage rate in this district than other labor in the Islands. The com-pany also furnishes free living quarters, hospitalization and work-men&apos;s compensation. Taxation has been reasonable up to the present time, but some of the new mining legislation may make it difficult to operate and pay dividends. The future depends largely upon the continuation of $35 gold and the political outcome in the Islands.

Jan 1, 1939

The Library of the above-named Societies is open from 9 A.M to 10 P. M. except on holidays. It contains about 70,000 volumes and 90,000 pamphlets, including sets of technical periodicals and publications of scientific and technical societies. Members of the Institute, with few exceptions, are forced to spend a portion of their time in localities isolated from sources of information. To these the Library, through its Library Service Bureau, can render valuable service through correspondence; letters requesting information will receive especial attention. The Library is prepared to furnish references and photographic copies of articles on mining and metallurgical subjects; to determine the existence of mining maps, and to furnish general information on the geology and mineral resources of all countries. All communications should he made as definite as possible so that the information received may he what is desired and not include collateral matter which may not be of interest. The time spent in searching for such collateral matter will be saved, and the information will be sent more promptly and in more usable shape.

Jan 6, 1918

By W. C. Hagel

Previous inuestigators have repovted unusually low H* and Do values for self-dzf@szon in certazn bcc metals, e.g., chromium nnd y -uvanium. It has been postulated that this is nn experimental crl -tetion for the existpnce of a four -atom ring meclzanzsm, mid there could be. zmpovtant theoretrcal Implicatlons. By utilizing a precise sectioning technique with Cr51 as the tracer, self-dzffi-lsion measurements in large grains of 99.99-pct Cr were extended from 1200° fo 1600"C. A least- squares analysis of the data yields that D 0.280 exp (-73,20U/RT) cm2 sec-&apos;. These AH* and Do unlues are not anomalous; there is little reason to believe that n vacancy mechanism is not opevatiue. Apparent differences at lower temperatures may result from preferential diffusion along short-circuititing paths and/or sample contamination. WITH continued technological effort, chromium and chromium-base alloys should ultimately become useful high-temperature structural materials. Accurate measurements of self-diffusion coefficients in the pure metal are necessary for a quantitative understanding of sintering, grain growth, creep, and other related rate processes. However, two conflicting determinations have been reported.* Using an Since careful diffusion studies normally yield Do values ranging from 0.1 to 10 cm2 sec-l, the Paxton-Gondolf results require independent experimental corroboration before an undue amount of speculation arises to explain the apparent anomaly. As discussed by Nowick6 and clearly shown by Hoffman and Turn-bull7 for self-diffusion in silver, a low AH* and Do can arise from preferential diffusion along grain boundaries or other short-circuiting paths. The most reliable data come from high-temperature measurements where volume effects predominate. Following a precise sectioning technique developed for determining silver diffusion in the intermetallic compound AgMg8 and cation diffusion in the corundum oxide Cr2O3,9 the purpose of this study was to measure true volume diffusion in high-purity, large-grain samples at higher temperatures than considered previously. Another point of interest is the frequent proposal10-12 that chromium undergoes an allotropic transformation between 1375" and 1800°C where the diffusion data might then show a discontinuity. I EXPERIMENTAL 1) Sample Preparation. The highest purity (99.997 pet) Cr currently available is produced by reduction of chromium tri-iodide. Three pounds of the resulting crystal bar were shipped in a sealed container with a complete chemical analysis from the vendor.* In conformity with the procedure used for

Jan 1, 1962

By J. C. Fisher, J. H. Hollomon, David Turnbull

Understanding of the diffusion problem has recently been furthered by the analysis of Birchenall and Meh1.l They pursued the problem of the variation of the diffusion coefficient with composition for non-ideal solid solutions. Their analysis follows the tradition of Wagner,l Jost, Dehlinger, and Darken & who assumed the net flux of diffusing material to be proportional to the gradient of a quantity related to free energy. The basic assumption in Birchenall and Mehl&apos;s formulation of the problem is that the net flux of diffusing material is proportional to a thermodynamic activity gradient. To estimate the applicability of the derived relations, they corrected the diffusion coefficients of carbon in austenite by utilizing Smith&apos;s6 activity data for carbon, and the diffusion coefficients for zinc in copper with activity data computed from the vapor pressure measurements of Har-greaves.&apos; The corrected coefficients for carbon were virtually independent of carbon concentration. For the diffusion of zinc in copper a moderate variation of diffusion coefficient with concentration remained after the correction. The problem of diffusion can be formulated in another way than that used by Birchenall and Mehl. The method is that of chemical rate theory and has been used by Eyring and his coworkers8,9 as well as by Eyring and Zwolinskilo in a discussion to Birchenall and Mehl&apos;s paper. As yet the method has not been applied to substitu-tional solid solutions. On the basis of their assumptions, Eyring and Zwolinski derived a relation between the diffusion coefficient and activity that is identical with that of Dehlinger and Darken but which does not correct for the variation of the diffusion coefficient with concentration as well as does the relation derived by Birchenall and Mehl. It was thought that the theory of diffusion would be more complete if the inconsistency between the two analyses could be rationalized and if diffusion in substitu-tional alloys were analyzed on the basis of the concepts of the chemical rate theory. Chemical Rate Theory According to the theory of absolute reaction ratess the reaction +..... +X, Eq I is viewed as taking place in two steps. First the reactants A1, A², . . . A; combine to form an activated complex M with which they are in equilibrium: A1 + A1+ . . . + A=M. Eq 2 Second the activated complex decomposes to give the products XI, XZ, . . . Xi: M?X, + X²+ . . . +Xi Eq g It has been showns that the number of activated complexes decomposing per unit volume per unit time is given by the expressiont kT -h CM † The transmission coefficient has been taken as unity.

Jan 1, 1949

By David Turnbull, J. H. Hollomon, J. C. Fisher

Understanding of the diffusion problem has recently been furthered by the analysis of Birchenall and Meh1.l They pursued the problem of the variation of the diffusion coefficient with composition for non-ideal solid solutions. Their analysis follows the tradition of Wagner,l Jost, Dehlinger, and Darken & who assumed the net flux of diffusing material to be proportional to the gradient of a quantity related to free energy. The basic assumption in Birchenall and Mehl&apos;s formulation of the problem is that the net flux of diffusing material is proportional to a thermodynamic activity gradient. To estimate the applicability of the derived relations, they corrected the diffusion coefficients of carbon in austenite by utilizing Smith&apos;s6 activity data for carbon, and the diffusion coefficients for zinc in copper with activity data computed from the vapor pressure measurements of Har-greaves.&apos; The corrected coefficients for carbon were virtually independent of carbon concentration. For the diffusion of zinc in copper a moderate variation of diffusion coefficient with concentration remained after the correction. The problem of diffusion can be formulated in another way than that used by Birchenall and Mehl. The method is that of chemical rate theory and has been used by Eyring and his coworkers8,9 as well as by Eyring and Zwolinskilo in a discussion to Birchenall and Mehl&apos;s paper. As yet the method has not been applied to substitu-tional solid solutions. On the basis of their assumptions, Eyring and Zwolinski derived a relation between the diffusion coefficient and activity that is identical with that of Dehlinger and Darken but which does not correct for the variation of the diffusion coefficient with concentration as well as does the relation derived by Birchenall and Mehl. It was thought that the theory of diffusion would be more complete if the inconsistency between the two analyses could be rationalized and if diffusion in substitu-tional alloys were analyzed on the basis of the concepts of the chemical rate theory. Chemical Rate Theory According to the theory of absolute reaction ratess the reaction +..... +X, Eq I is viewed as taking place in two steps. First the reactants A1, A², . . . A; combine to form an activated complex M with which they are in equilibrium: A1 + A1+ . . . + A=M. Eq 2 Second the activated complex decomposes to give the products XI, XZ, . . . Xi: M?X, + X²+ . . . +Xi Eq g It has been showns that the number of activated complexes decomposing per unit volume per unit time is given by the expressiont kT -h CM † The transmission coefficient has been taken as unity.

Jan 1, 1949

The Telfer Project, one of the world&apos;s newest gold mines, is located about 300 km (190 miles) northeast of the Mt. Newman iron ore project in the northern part of Western Australia. The first mineral claims were staked in 1972; and by mid-1975 ore reserves of 3. 8 million mt (4. 19 million st) of 9.6 g per mt (0. 28 oz per st) ore had been indicated. It is interesting to note that Newmont spent more than 10 years and A$10 million in Australia for extensive mineral exploration before finding the Telfer deposit, and then spent approximately A$3 million in exploration and feasibility engineering on Telfer. Including this A$3 million, a total of A$27 million was spent to complete construction of the mine, village, gold treatment plant and associated roads, airport, water and services. Over 50% of the capital cost is in the metallurgical facility, or approximately A$10, 000 per ton per day. All economically significant gold mineralization at Telfer occurs in a series of layered quartz-limonite reefs in which the former pyrite has been oxidized to limonite to a depth of 100 m (330 ft). The most important gold reef occurs at the base of the siltstone-shale horizon within the enclosing sandstone dome -like structure. At the Main Dome structure the dipping ore horizons will be mined to a vertical depth of about 60 m (200 ft) by open-cut methods. The waste-to-ore ratio is approximately 12:1. Eventually 44 million mt (48. 5 million st) of ore and waste will be mined. Mining of the waste is by contract; however, the ore and a thin layer of waste is company-mined. Dilution from mining the geological ore reserve is about 10%. The ore is completely oxidized and the gold occurs free within the reef, material as discrete particles of varying but mainly fine grain size. Most of the gold is "free milling"; that is, over 50% of the gold is coarse enough to be recoverable by gravity concentration. Two duplex mineral jigs receive the two cyclone underflows from the grinding circuit. The rougher jig concentrate is up-graded on a continuous strake from which the concentrate is tabled to produce a final free gold product. Jig tailings are returned to the ball mill and the concentrates are amalgamated. Gold amalgam is pressed, retorted, and melted into gold bars. The gravity gold recovery circuit is the same as was used in many of the gold mills in California in the 1930s.

Jan 1, 1981