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By A. U. Seybolt

In part 111' of this series it was shown that during the selective oxidation of a 3 1/4 pct Si-Fe alloy in damp hydrogen, only silica, (observed at room temperature) as low cristobalite or low tridy-mite or both, was formed as an oxidation product. In some in- „ stances where the film was fairly thin (probably well under 100A) there was some suggestion of an amorphous form of SiO2. The present investigation of oxidation rate showed that the selective oxidation of silicon-iron can be rather complicated, and apparently impossible to rationalize in an unequivocal manner. In some temperature regions, notably near 800" and 1000°C, the data seem to obey the familiar parabolic rate law. However, at intermediate temperatures complications were noted, some of which are possibly due to the order-disorder reaction in the silicon-iron solid solution. IN an earlier report' it was shown that during the oxidation of 3 1/4 pct Si-Fe alloys in H2O-H2 atmospheres only silica films were formed in the temperature range from 400° to 1000°C in hydrogen nearly saturated with water at room temperatures, or at dew points as low as -45°C. In the work to be reported here, some observations are made on the rate of oxide film formation. As in the earlier investigation, electron diffraction patterns generally showed either low tridymite or low cristobalite or both, except for some very thin films. These sometimes showed diffuse rings, presumably due to a very small crystallite size, or in a few cases, diffuse bands probably caused by an amorphous film. EXPERIMENTAL PROCEDURE Vacuum-melted silicon iron made of high-purity materials was rolled into strips 0.014 in. thick, and cut into samples 1/2 in. wide by 1 in. long. Chemical analysis showed 3.2 pct Si and 0.002 pct C. All samples were surface abraded with 600-grit paper, were solvent cleaned, and then placed in an paper,apparatus containing a "Gulbransen type"2 micro-balance. Here the gain in weight of the samples of about 5 sq cm area could be followed as a function of time during the oxidation caused by the water in atmospheres of various controlled water-hydrogen ratios. The water-hydrogen ratios can most easily be described as varying from a dew point of 0°C (PH2O-p^2 = 6.2 x 10-3 , to K (P j -40°C (PH2O/PH^= 1.3 X 10-* Most of the experiments were conducted at the 0°C dew-point atmosphere because drier atmospheres caused so little gain in weight that the accuracy of measurement was poor. Because of this, only the data obtained at PH2O,/P,,,= 6.2 x X3 will be reported. The temperature range extended from 800" to 1000°C; and most of the oxidation runs lasted for about 24 hr. The reproducibility of any reading was about ± 1 ?, but the sensitivity of the balance was about 0.2 ?. The atmosphere, flowing at 200 cm per-min, was preheated to the furnace temperature before contacting the specimen. While the gas flow caused a measurable lift on the sample, it was ordinarily sufficiently constant so that it was not an appreciable source of error. X-ray and electron diffraction checks of the samples before and after oxidation showed no evidence of preferred orientation, either on the metal samples or on the silica films formed. EXPERIMENTAL RESULTS The data obtained are summarized in Table I, and some are given in detail in Figs. 1 to 4. In the fourth column of Table I, kp refers to the parabolic rate constant in the expression (?/cm2)2 = kpt + c [1] where ? = micrograms gain in weight kp = parabolic rate constant in units r2 /cm4 t = time in minutes c = constant It will be noted that in many cases no value for kp is given; this is because in these instances the data did not obey the parabolic rate law. The silica film thicknesses given in the last columns are values calculated from the weight gain, an average tridy-mite-crystobalite density, and by assuming a perfectly plane surface. Fig. 1 shows the data plotted in the form of Eq. [I], hence a linear plot indicates parabolic behavior. It has been frequently observed in the literature that

Jan 1, 1960

By John W. Weeton, Donald W. Petrasek

Relatively few metal-metal systems exist that would permit the creation of fiber-metal composites consisting of mutually insoluble constituents. It is anticipated that most high strength-to-weight ratio and high -temperature fiber composites ultimately to be produced will utilize high-strength fibers embedded in a highly alloyed matrix. An investigation was conducted to determine the effect of alloying on the tensile Properties and micro-structure of tungsten-fibey-reinforced composites. Composites were made of tungsten fibers infiltrated with copper binary alloys that contain elements of varying solubility in tungsten. Room-temperature tensile tests were made on the composites, and a metallographic study of the microstructure of the fiber-metal-matrix interfaces was conducted. It was shown that, as the depth of penetration of some alloying elements into the fiber increased, a decrease in both tensile strength and ductility of the composite results. A notch effect, due to the formation of a brittle alloy zone with the tungsten fiber, was observed and gave rise to greater reductions in tensile properties and ductility behavior than would be Predicted by a law-of-mixture relation alone. In recent years, investigators have considered combining fibrous materials with relatively weak binder materials. The interest in fiber-reinforced composites results from the fact that fibers or wires may be exceedingly strong and exhibit mechanical properties superior to those of the bulk materials from which they are derived. For example, tungsten wires drawn to less than 1 mil in diameter may have strengths of over 600,000 psi,' while steel wires ranging from 10 to 3 mils in diameter may have strengths of the order of 300,000 to over 600,000 psi.2 Both metallic and ceramic whiskers are known to have very high strengths. For example, iron whiskers have been shown to have strengths of 1.9 million psi3 and sapphire whiskers have been reported to have strengths of the order of 1.7 million psi.4 If all or part of the strengths of such fibers could be retained, subsequent to the incorporation of the fibers in an engineering material, a superior material could result. In previous work done at the Lewis Research Center, McDanels, Jech, and weeton5 demonstrated the feasibility of fabricating metal-fiber—metal-matrix composites that utilized the full strengths of the fiber and matrix materials. Tungsten fibers were combined with a copper matrix by a liquid-infiltration method such that the tungsten fibers were uniaxially oriented parallel to the tensile axis of the composite. A linear relation was established that related the tensile strength of the composite with the volume percent of the fibers. Mutually insoluble constituents were selected for the study so that the strength of the composite could be quantitatively related to the strength of the individual constituents. The fact that there are only a few metals that are mutually insoluble with tungsten, e.g., copper, silver, gold, and zinc, and that these either have low melting points, high vapor pressures, or poor oxidation resistance, makes it necessary to utilize other metals that are soluble in tungsten, where high-temperature applications are ultimately contemplated. It was anticipated that, for most practical fiber-reinforced composite materials, it would be necessary to use a fiber and metallic matrix that would have varying degrees of solubility for each other. A logical extension of the earlier work was thus felt to be a study that would determine the effects of elements that had mutual solubility with the tungsten. Numerous investigators have found that tungsten fibers may be damaged by thermal treatments or contamination of the surface of the fiber by alloying elements.6-10 On the other hand, surface treatments may improve the strength of such fibers."-" Relatively little work with composites containing tungsten fibers have been reported. The work of parikh14 has shown that kinked, short-length tungsten, steel, and molybdenum fibers could str'engthen such matrices as silver, gold, and copper. Some of the combinations of fibers and matrices studied by

Jan 1, 1964

By J. N. Roberts, K. V. Gow

In a recent review of the field of plastic deforrnation of metal single crystals, Maddin and chenl indicated the need for systematic investigations of the crystallography of the slip process with special attention to: a) The effect of the orientation of a crystal on the appearance of slip lines, b) The effect of high temperatures on the slip systems of aluminum, c) The effect of strain rate on the crystallography of slip. The present paper deals with the effect of temperature and strain rate on the mechanism of deformation of aluminum single crystals similarly oriented for single and duplex slip. The work of several investigators has shown that in aluminum at high temperatures other slip systems in addition to the predicted {I l l) <101> may operate. The most generally reported additional systems

Jan 1, 1959

United Engineering Society ARTHUR S DWIGHT J VIPOND DAVIES J V N Dorm Engineering Societies Library Board SIDNEY H BALL ALEXANDER C HUMPHRFYS GEORGE C STONE JOHN H JANEWAY Engineering Foundation Board H M BOYLSTON J VIPOND DAVIES GALEN H CLEVENGER Society for Promotion of Engineering Education WILLIAM KELLY ALLEN H ROGERS

Jan 1, 1923

By Hugh S. Spence

In the winter of 1941-42, muscovite mica was discovered by a young prospector, Justin Purdy, in the township of Mat-tawan, Nipissing District, Ontario, a few miles north of the small settlement of Eau Claire, which lies on the main Transcontinental Highway (No. 17) between Mattawa and North Bay. Muscovite had been known for many years to occur in the general Mattawa region, and various small efforts at production had previously been made by individuals working scattered deposits in the area. These minor activities, however, had never led to production of any consequence or the discovery of any important mica bodies. The Purdy finds were made in a heavily timbered, mountainous area lying about three miles north of the low-lying settled land along the highway, and in a section not hitherto prospected. The mica taken by Purdy and two partners from surface outcrops proved so remarkable in point of size of trimmed sheets that the find attracted considerable attention, and the area surrounding the three claims taken up by the prospectors was quickly blanket-staked by various interests. Though a number of other mica-bearing pegmatite dikes were found later on these stakings, none proved as rich as those on the original Purdy ground; very little commercial mica was obtained from them and attempts to develop them were short-lived. Purdy and his partners sold their initial production to dealers in Ottawa and Hull, where the Canadian mica industry long has centered. Young Purdy, unfortunately was killed in a motor accident in the early summer of 1942. His father continued mining operations for a few months and produced and sold a considerable amount of mica. In October 1942 the Purdy holdings were acquired by lnspiration Mining and Development Co. of Amos, Quebec, which had been active in staking in the area. This company formed a subsidiary, Purdy Mica Mines, Limited, to develop the property. Under the energetic management of Joseph R. Norrie, rapid progress was made, and production soon attained important proportions. Realizing from the outset the unusual character and potential value in the war effort of the Purdy discovery, the Metals Controller, Department of Munitions and Supply, at once arranged with the Department of Mines and Resources for an official geological report on the area, and also drew the attention of the War Production Board in Washington to what seemed likely to prove a highly important source of strategic-quality mica. Officials of WPB were sent up in the Summer of 1942 to inspect the property, and so impressed were they with the possibility that it might become of high

Jan 1, 1948

By Hugh S. Spence

In the winter of 1941-42, muscovite mica was discovered by a young prospector, Justin Purdy, in the township of Mat-tawan, Nipissing District, Ontario, a few miles north of the small settlement of Eau Claire, which lies on the main Transcontinental Highway (No. 17) between Mattawa and North Bay. Muscovite had been known for many years to occur in the general Mattawa region, and various small efforts at production had previously been made by individuals working scattered deposits in the area. These minor activities, however, had never led to production of any consequence or the discovery of any important mica bodies. The Purdy finds were made in a heavily timbered, mountainous area lying about three miles north of the low-lying settled land along the highway, and in a section not hitherto prospected. The mica taken by Purdy and two partners from surface outcrops proved so remarkable in point of size of trimmed sheets that the find attracted considerable attention, and the area surrounding the three claims taken up by the prospectors was quickly blanket-staked by various interests. Though a number of other mica-bearing pegmatite dikes were found later on these stakings, none proved as rich as those on the original Purdy ground; very little commercial mica was obtained from them and attempts to develop them were short-lived. Purdy and his partners sold their initial production to dealers in Ottawa and Hull, where the Canadian mica industry long has centered. Young Purdy, unfortunately was killed in a motor accident in the early summer of 1942. His father continued mining operations for a few months and produced and sold a considerable amount of mica. In October 1942 the Purdy holdings were acquired by lnspiration Mining and Development Co. of Amos, Quebec, which had been active in staking in the area. This company formed a subsidiary, Purdy Mica Mines, Limited, to develop the property. Under the energetic management of Joseph R. Norrie, rapid progress was made, and production soon attained important proportions. Realizing from the outset the unusual character and potential value in the war effort of the Purdy discovery, the Metals Controller, Department of Munitions and Supply, at once arranged with the Department of Mines and Resources for an official geological report on the area, and also drew the attention of the War Production Board in Washington to what seemed likely to prove a highly important source of strategic-quality mica. Officials of WPB were sent up in the Summer of 1942 to inspect the property, and so impressed were they with the possibility that it might become of high

Jan 1, 1948

By Paul M. Tyler

HISTORICAL concepts of the economics of the glass-sand industry are changing rapidly. The greatly expanded demand for glass containers combined with higher freight rates on raw materials and manufactured products have induced a migration of glass factories toward densely populated centers and the creation of new standards of place value for sub- standard sand deposits. This migration has been facilitated by the construction of pipelines to bring cheaper natural gas and liquid fuel to large cities and may be further speeded by the adoption of modern mineral dressing methods to permit economical utilization of local raw materials. Our national resources of naturally high-grade 1 silica sand are abundant, but most of the best de- posits are situated so far from large centers of population that it now costs $3.00 to $5.00 a ton to carry the sand from the mine to the optimum site for a 1 factory making beverage bottles, scientific and electrical glassware, and miscellaneous blown and pressed ware for local markets. It follows that on the basis of freight savings alone it may be economical to use material from inferior deposits closer to the factory even though the f.o.b. cost of mining and treatment may be much high

Jan 1, 1950

Jan 1, 1925

By J. R. O’Connor

Stimulated emission from Nd+3 in yttrium uanadate fYVOJ is reported. Single crystals of YVO4:Nd, obtained from Linde Col-p., have improved substantially in the last several months. Pulsed thresholds of YVO, laser rods are now approximately 2 to 3 5, cowparable to tliose for YAG:Nd. Yttrium uanadate crystalli~es irz a space group similar to zircon. All rare-earth vanadates have this structure. Rare-earth ions sucll as Nd+3 which substitutes for Y+3, aye situated irz a strong tetragonal crystal field which lacks inversion symmetry. This condition increases the p&apos;robability of the parity-forbidden f — f transitions. Yttrium anadate has strong absorption bands beyond -1000A. These are clue to Y-O, V-O charge transfer and molecular transitions. Under 2537 and 3660A irradiation pure YVO, fluroresces u bright yel-LOLO. This fli&orescence is corrzpletely quenched in YV04:Ncl crystals. This and other evidence of energy trut~sjer from the lattice is repovted. Optzcul atz 1user pvope 1-ties o! YI&apos;U4:E[t are brieJy described. THIS paper describes some of the optical and laser properties of Nd+3- and Eu+3-doped yttrium orthovana-date (YVO4). It reports laser action for the first time in this low-symmetry host. For some time we have pursued a research program concerning laser hosts&apos; wherein the rare-earth (RE) ion is situated at a site of low crystal symmetry so as to increase the probability of radiative transitions. Single crystals of doped and undoped YV04 are grown from iridium crucibles in an oxyhydrogen gas-fired furnace by a modified Czochralski technique.&apos; This material crystallizes in a D4li tetragonal space group of the zircon (ZrSiO,) type.3 All RE vanadates have the same structure and form solid solutions with YVO4. Therefore, it will be possible to investigate a variety of cross-pumped laser systems, as in the case of yttrium aluminum garnet (YAG).4 At present, ~d&apos;~-doped YAG is one of the most efficient solid-state lasers.5 Accordingly, most of the material to follow will compare the properties of YV04 to those of YAG. Fig. 1 shows the relative transmission of YAG and two types of YVO4. "Pure" YVO4 has a normal absorption edge and is colorless. A second type has a broad absorption peaking near 4200A and is yellow. Rubin and Van uitert6 suggest the yellow material is slightly reduced. Samples of each type are being investigated by electron spin resonance,7 but these studies are so far inconclusive. The pulsed laser threshold is much lower in the yellow material than in the colorless. Therefore, the absorption at 3500 to 5000.4 transfers energy to the Ndi3 ions. Photons of wave length between 2000 and 4500A cause undoped YVO4 to fluoresce at 4800, 5250, 5460, 5540, and 5750A. This emission, previously reported by Brixner and Abramsom,8 is partially quenched by EU&apos;~ and completely quenched by Ndt3 at room temperature due to energy transfer from the lattice to the RE ions. At low temperatures, some lattice fluorescence is present. This implies that the energy-transfer process is in part phonon-assisted. Although the YVO, single crystals used in this work were prepared from Y2O3 containing less than 0.01 pct rare-earth impurities, there is aopossibility that emission lines between 4800 and 5750A are due to dysprosium, terbium, and so forth. However, these lines are not observed in other compounds, prepared from Y2O3, such as YP04, Y2MoO6, and so forth. Furthermore, extensive absorption measurements on our "pure" YV04 single crystals between 0.4 and 5.0 failed to reveal any characteristic rare-earth lines. Fig. 2 compares the absorption spectra of Ndt3-doped YAG and YVO4from 0.6 to 1.0 . The Ndt3 absorptions are labeled according to free ion, R-S coupling. These term designationsQ are appropriate for YAG:Nd. They appear to be inappropriate for YV04:Nd. In YVO, neodymium must substitute for yttrium. The yttrium site is situated In a strong tetragonal field, where point symmetry is (42m) or possibly lower.1° However, the reduced splitting of the Stark components of the YV0,:Nd spectrum implies that the NdT3 ion is in a cubic site. The only plausible explanation for this discrepancy is that the Ndt3 ion is in a low-symmetry site, lacking inversion symmetry, so that a substantial admixture of 4f and 5d wave functions occurs. In this case, R-S coupling is not valid and J is no longer a good quantum number." Consistent with this view, the 4~ metastable level of YV04:Nd has an oscillator strength larger and a

Jan 1, 1968

[United Engineering Society ARTHUR S. DWIGHT J, VIPOND DAVIES J, V, N. DORR Engineering Societies Library Board SYDNEY H. BALL ALEXANDER C, HUMPHREYS GEORGE C, STONE JOHN H, JANEWAY Engineering Foundation Board H. M. BOYLSTON J. VIPOND DAVIES GALEN H, CLEVENGER Society for Promotion of Engineering Education WILLIAM KELLY ALLEN H. ROGERS]

Jan 1, 1928

By R. R. French

Investigations were conducted by the lndiana Geological Survey for some dry methods of bene-ficiating low-grade gypsum ore. Seventy-two batch and continuous flow tests were performed with a roller mill, rod mill, pebble mill, electronic color sorter, electrostatic separator, and an air separator. Approximately 650 size analyses and 550 chemical analyses were performed during the investigation. Batch samples were tested by the Survey, and most of the continuous flow tests were handled by com-mercial laboratories. INTRODUCTION Although many companies producing gypsum have been interested in dry beneficiation, very little information has been published in the past. One of the most comprehensive investigations was reported by the Canadian Department of Mines.5 Other reports of interest have been published by the Canadian Department of Mines,&apos; the South Australian Department of Mines,2 and the U.S. Bureau of Mines.3 Some beneficiating practices, such as hand picking, selective mining, crushing and screening, milling, and air classifying, were already in use in the Canadian industry prior to MacPherson&apos;s investigations.5 MacPherson examined the effect of tabling, air separation, screening, flotation, electrostatic separation, calcining, washing, and various types of milling, in his efforts to eliminate dolomite, limestone, and small amounts of silica and clay from the gypsum ore. RAW MATERIAL Gypsum and anhydrite occur within the lower part of the St. Louis Limestone (Mississippian) in southwestern Indiana. Gypsum in single beds 10 or more ft thick occur at Shoals, Martin County; near Freedom, Owen County; near Bloomfield, Greene County; and in the Devonian strata of LaPorte County. Only the Shoals deposit has been exploited commercially. The western edge of the Shoals deposit is contaminated by a continuous bed of shale, about 1 1/2 to 2 ft thick, near the top of the evaporite and by thin continuous strata or irregular masses of carbonate rock. The low-grade material used in these investigations was obtained from the waste pile of the National Gypsum Co.&apos;s plant at Shoals. The waste ore averaged about 67.4% gypsum and was contaminated by various amounts of shale, dolomite, and limestone. All the material had been previously crushed and screened to minus 1 1/4 to plus 3/8 in. X-ray analyses of powdered, sedimentated, gly-colated, and heat-treated samples of the shale showed that it was composed of slightly structurally disordered illite, Fe-rich chlorite, and very finegrained disseminated silt. The clays and silt were partly cemented with carbonate material. Light-gray argillaceous limestone and gray or brown porous dolomite made up most of the carbonate rock contamination. Crushing Characteristics: The rate unweathered gypsum, carbonate rock, and shale reduce in size was determined by crushing handpicked samples in a rod mill and screening at minus 100 mesh (.0059 in.). Fig. 1 graphically represents the data. These data indicate that carbonate rock should be relatively easy to separate from gypsum, but that shale should be difficult to separate from gypsum by differential crushing. Controlled Samples: Eight rod mill tests of hand-picked samples of mixed gypsum and shale and mixed gypsum and carbonate rock were made. Sample weight and crushing weight were standardized, but the scalping screen size was varied from 3 to 10 mesh (.265 to .0787 in.) in order to obtain the optimum purity and recovery. The data obtained from the tests (see Table I) illustrate that the relatively hard carbonate rock allows appreciable beneficiation (13.6 to 18%), but the low strength gypsum and shale allows only minimal separation (3.1 to 7.5%).* Semi control led Samples: During the investigation considerable slaking of the shale was noted when the ore was subjected to alternate wetting and drying. As demonstrated in laboratory tests, as much as 76% shale can be removed by two cycles of wetting and drying in a 48-hour period with subsequent screening at .265 in. Five ore samples, stockpiled and weathered, were screened, rod-mill crushed and rescreened at .157 or .187 in. with excellent results (Table 11).

Jan 1, 1967

By Jack M. Jodrey, Neil D. Donnell, O&apos

Bituminous sands of the Lower Cretaceous McMurray Formation in northern Alberta constitute the ore for the surface mining operation at Syncrude Canada Ltd. These sediments represent a complex succession of fluvial, estuarine and marine depositional environments. Grade prediction is realized through a combination of geological interpretation, computer modeling, and reference to past mining experience. Accurate forecasts of feed grade permit reliable predictions of volumes for removal to meet budgeted synthetic crude oil production. This planning facilitates efficient allocation of mining equipment and resources. The feed grade to the Extraction Plant is monitored at various points along the delivery system.

Jan 1, 1985

By P. K. Koh, L. S. Birks, J. M. Siomkajlo

Direct identification in situ of x and a phase precipitates in stainless steel is possible with the electron probe microanalyzer. Although particles in the 1 p size range are too small to yield absolute percent composition, the relative % Crfi Mo ratio can be used to distinguish the two phases with better than 95 pct confidence. Wet chemical analysis of extracted residues gives Cr/Mo ratios in good agreement with electron probe results extrapolated to the 4 to 5 p size range. WHEN stainless steels are subjected to extended heating in the temperature region around 1600°F, precipitation of the brittle 0 or x phases may occur and impair the properties of the material. Identi-

Jan 1, 1961

H. RIES, Ithaca, N. Y.-The part of Mr. Fiske&apos;s paper that interests me especially is that portion dealing with the raw materials, and the tests that were applied to the raw materials in order to determine their value in advance, if possible, because that, I believe, is a step in the right direction. For a number of years I have done my best to persuade different consumers of clay to develop standard methods for testing raw materials. We have in this country a large variety of clays which can be used for a great many different purposes, but in many cases the consumers either have no standard methods for determining the value of those clays in. advance, or if they have they do not publish them; consequently it often puts the clay miner at a disadvantage. If, for example, manufacturers of different types of refractory materials would state publicly just what physical tests their raw materials have to meet, it would, I believe, help them to find more easily the materials that they are looking for, and the clay producer would also be benefited. It would also encourage him to have his clays tested in advance, so that samples could be accompanied by certificates of physical tests that would be of convenience to the manufacturer. At the present time, in this country there are certain types of clay which seem to be rather scarce. There apparently are not many deposits of clay that are exactly suited for the manufacture of zinc refractories. So, too, there are not many deposits of clay that are suited for the manufacture of glass-pots, or the blocks for glass tank furnaces, or clays that can be used for graphite crucibles. Now, in many cases, no standard series of tests has been developed. I am also gratified to see that Mr. Fiske considers the tensile strength. tests of value. Some years ago the American Ceramic Society appointed a committee to draw up a series of recommendations covering standard tests. These recommendations were especially for the use of State geologists and the U., .S. Geological, Survey. Among the tests that were considered was the tensile-strength test, which Mr. Fiske has mentioned in his paper. Unfortunately, a majority of the committee turned it down, and the test was therefore not officially approved, but two of us, who formed the minority, believed in it. Since then the other members of the Committee have come to see that that is an important test to make and Mr. Fiske has emphasized it in his paper.

Jan 1, 1918

By Shozo Saito, P. A. Beck

Mettrllographic and X-ray diffraction study of Cb-Co alloys in the Composition range of 7 to 33 nt. pct Cb, after annealing at 1175 °&apos;, showed that near 25 al. pct Cb on MgNi,-lype hexagonal Laves Phaseexists in a narrow composition range, and that an MgCl- type cubic Laves Phase occurs between approximately 27 and 32.6 ut. pd Cb. Lattice parameter and density measures indicated that, in both phases. the deviations from proper Loves sloichimetry result from the substitution of cobalt atoms for some 0f the columbium atoms. Tlle same phases occurant 1000&apos;C, together with an additional phase of unknown structure, which appears between the hexagonal Laves phase and the cobalt-bose terminal solid solutions KOSTER and Schmid&apos; identified a phase corresponding to the composition VCo,, and more recently the crystal structure of this phase has been determined.&apos; In the Ta-Co system Korchynsky and Fountain recently found two intermediate phases at the composition Taco,, one of them metastable. In contrast to the V-Co and the Ta-Co systems, in the Cb-Co system no intermediate phase has been found4 at the composition CbCo,. The present investigation was undertaken in order to reexamine the question of the existence of such a phase. EXPERIMENTAL PROCEDURE Twelve alloys were prepared by arc-melting in a water-cooled copper crucible under helium atmosphere. Electrolytic cobalt and 99.9 pct pure colum-bium powder have been used as starting materials. It was found that melting losses can be reduced by compressing the colunlbium powder in the form of thin pellets before melting. For the alloys used the melting losses were not higher than 1 pct. The intended compositions of all alloys and the chemical analyses of three of them are given in Table I. Specimens from all alloys were annealed in evac- uated fused silica tubes at 1175°C for 3 days and quenched in cold water. A second set of specimens of most alloys was annealed at 1000°C for 7 days and then quenched in cold water. The annealed and quenched specimens were examined metallographically, using the following etchant: 60 pct glycerine +20 pct H,NO, + 10 pct HF + 10 pct water. Powder specimens for X-ray diffraction were prepared by crushing annealed solid specimens in a mortar. Alloys containing 27.3, 28, 29.7, and 32.6 at. pct Cb annealed at either 1175" or 1000°C were very brittle and it was found unnecessary to reanneal the powders. However, alloys containing 24.8 at. pct Cb, or less, especially those annealed at 1000°C, were much less brittle and re-annealing was required to remove the strains present in the crushed powders. In each case reannealing was done at the same temperature at which the corresponding solid specimens were annealed and it, too, was followed by quenching in cold water. In many instances X-ray diffraction patterns were also taken of the polished and etched solid specimens and compared with the corresponding X-ray diffraction patterns obtained with powders. The X-ray diffraction patterns were taken with an asymmetrical focusing camera, using CrK radiation. For precision lattice parameter measurements some X-ray diffraction patterns were taken with a symmetrical focusing camera, again using CrK radiation. EXPERIMENTAL RESULTS A microscopic examination of the alloys annealed at 1175°C revealed that the alloy containing 25.5 at. pct Cb was composed of a single phase, but that the 24.8 at. pct Cb alloy did contain a small amount of a second phase, identified by means of X-ray diffraction as having a fcc structure, undoubtedly the terminal solid solution based on cobalt. Apart from the few very weak lines corresponding to this minor phase, the X-ray diffraction patterns of these alloys could be well interpreted in terms of a MgNi,-type hexagonal Laves phase structure. The indexing of the X-ray diffraction pattern, Table 11, yas based on the lattice parameter values a, = 4.740A and c,

Jan 1, 1961

By E. I. Larsen, E. F. Swazy, F. R. Hensel

High strength, high-conductivity copper-base alloys have found considerable use in the resistance welding and electrical industry in the form of castings, forgings, or wrought products. There are a number of parts utilized by these industries which would lend themselves to manufacture by powder metallurgical methods provided the required physical and electrical properties are obtainable with such methods. The present paper describes the results of a study of certain copper-base powder metallurgical products susceptible to precipitation hardening. Copper Powders The general types of commercially available copper powders are flake, spherical and electrolytic. Micrographs of these three types are shown in Figs. I, 2 and 3. The difference in particle shape is pronounced and obvious. The type of powder used is determined, or at least indicated, by the final properties desired in the finished article. The type of powder employed during the present investigation was electrolytic powder shown in Fig. 3, and was chosen because of its particular adaptability to the work described in this Paper. The screen and chemical analyses of this powder are shown in Table I. In the preparation of compacts of high electrical conductivity, the purity of the copper powder is of importance in addition to other factors, such as density and the state of internal stresses. These variables were studied briefly by pressing a number of compacts to various pressed densities, sintering them for one hour in hydrogen at 975OC and repressing. The size of the finished compacts was 1/4, by % by 8 in. The time interval from the application to the termination of pressure was approximately 20 sec. Some of the compacts were annealed before testing. The results are listed in Figs. 4 to 8, inclusive. In Fig. 4 the curves of pressed density vs. compacting pressure, and sintered density versus compacting pressure show the typical direct relationship of pressure and density. Compacting pressures exceeding about 30 tons per sq. in. result fiequently in expansion during sintering for the type of powder used. Fig. 5 indicates that variations in the initial pressed density within the range of about 5 to 6 grams per c, c., affect only slightly the pressure required to obtain a

Jan 1, 1946

By E. I. Larsen, E. F. Swazy, F. R. Hensel

High strength, high-conductivity copper-base alloys have found considerable use in the resistance welding and electrical industry in the form of castings, forgings, or wrought products. There are a number of parts utilized by these industries which would lend themselves to manufacture by powder metallurgical methods provided the required physical and electrical properties are obtainable with such methods. The present paper describes the results of a study of certain copper-base powder metallurgical products susceptible to precipitation hardening. Copper Powders The general types of commercially available copper powders are flake, spherical and electrolytic. Micrographs of these three types are shown in Figs. I, 2 and 3. The difference in particle shape is pronounced and obvious. The type of powder used is determined, or at least indicated, by the final properties desired in the finished article. The type of powder employed during the present investigation was electrolytic powder shown in Fig. 3, and was chosen because of its particular adaptability to the work described in this Paper. The screen and chemical analyses of this powder are shown in Table I. In the preparation of compacts of high electrical conductivity, the purity of the copper powder is of importance in addition to other factors, such as density and the state of internal stresses. These variables were studied briefly by pressing a number of compacts to various pressed densities, sintering them for one hour in hydrogen at 975OC and repressing. The size of the finished compacts was 1/4, by % by 8 in. The time interval from the application to the termination of pressure was approximately 20 sec. Some of the compacts were annealed before testing. The results are listed in Figs. 4 to 8, inclusive. In Fig. 4 the curves of pressed density vs. compacting pressure, and sintered density versus compacting pressure show the typical direct relationship of pressure and density. Compacting pressures exceeding about 30 tons per sq. in. result fiequently in expansion during sintering for the type of powder used. Fig. 5 indicates that variations in the initial pressed density within the range of about 5 to 6 grams per c, c., affect only slightly the pressure required to obtain a

Jan 1, 1946

By C. C. Clark, J. S. Iwanski

The purpose of this investigation was to study mi-crostructural changes that take place in a commercial nickel-chromium-iron alloy, such as Incoloy "901," over long periods of time at temperatures up to 13 50°F and to correlate such changes with creep-rupture properties. of the alloy. In the course of the investigation, some microstructural changes were observed which correspond to microstructural alterations found in previous studies of Inconel "X." Microstructural phases have been identified in both alloys with the aid of electron and X-ray diffraction and an electron probe microanalyzer. The materials used in this investigation were from commercial heats of the following chemical composition: Pct Cr Pct Ni Pct Mo Pct Fe Pct Cb Incoloy "901" 12.51 43.67 5.72 Bal. -Inconel "X" 14.61 73.44 - 6.61 1.02 Pct A1 Pct Ti Pct Mn Pct Si Pct C Incoloy "901" 0.10 2.46 0.46 0.24 0.05 Inconel "X" 0.70 2.43 0.51 0.36 0.04 Long-term creep-rupture tests were conducted on Incoloy "901" at temperatures of 1000°, 1200°1 and 1350°F. A summary of these results is shown in Table I along with the results of a long-term creep-rupture test conducted on Inconel "X" at 1500°F. The heat treatments given the specimens are also shown in Table I. When the creep-rupture results on Incoloy "901" are compared with shorter-tertn data, there is no evidence of any undue deterioration of the creep-rupture strength with time, nor is the elongation decreased more than would be expected from the influence of time alone. INCOLOY "901" PHASE IDENTIFICATION Microscopic examination of the Incoloy "901" specimens reveals a dark etching grain boundary constituent in the specimen which was under test for about 11,500 hr at 1000°F. This grain boundary constituent was seen to increase in size as the test temperature was increased to 1200" and 1350°F, Figs. 1, 2, and 3. Simultaneously, an acicular structure of definite crystallographic orientation appears within the grains of the 1350°F specimen, Fig. 3. Under examination with the electron microscope, a fine precipitate is observed in the 1200 °F specimen. Fig. 4. It becomes considerably larger in the 2850-hr 1350°F specimen, Fig. 5. In a few areas the precipitated particles have been replaced by, or transformed to, small needles or platelets. After 7380 hr at 1350°F, Figs. 3 and 6, the needles are much larger and have replaced nearly all of the fine precipitate. X-ray diffraction studies detected the presence of hexagonal Laves phase and hexagonal n phase (Ni,Ti) in the 1350°F specimens, Table 11. Only the Laves phase was detected by X-ray diffraction in the 1200°F specimen and none was detected in the 1000°F specimen. In this latter specimen, however, the small quantity of precipitate in the grain boundaries (presumed to be Laves phase) precludes its detection by X-ray diffraction. Composition of the hexagonal Laves phase is not yet known, although its diffraction

Jan 1, 1960

By H. Becke, D. Stolnitz, D. Flatley, W. Kern

Zinc difhsions in gallium arsenide having surface concentrations as low as 5 x 10&apos;&apos; atoms per cu cm have been attained. A multiple-difhsion sequence is employed during which zinc enters the gallium arsenide from a silicon dioxide film in a solid-to-solid diffusion step. The technique is illustrated for the case of a zinc surface concentration of -1 x 1017 atoms per cu cm and a junction depth of 1.2 p. Radiotracer measurements of -0.1-p layers of gallium arsenide are used to delineate the resulting profile. A diffusion coefficient for zinc in pyrolytically deposited silicon dioxide is reported. ZINC is frequently used as an acceptor impurity in gallium arsenide. As examples, p-n junctions are formed using zinc-diffused layers in solar cells, lasers, and varactor diodes. For these purposes surface concentrations of 10&apos;&apos; to over loz0 zinc atoms per cu cm are desired and readily obtained from a vapor source. Diffusion of zinc into gallium arsenide to yield surface concentrations of about 1017 atoms per cu cm, however, is more difficult. For instance, oldstein&apos; reports that large changes in the vapor density of zinc produce only small changes in surface concentration. Such low surface concentrations are necessary in forming the diffused base of a gallium arsenide double-diffused n-p-n transistor in order to obtain an adequate emitter efficiency. An alternative approach to zinc diffusion which can provide reduction in surface concentration of several orders of magnitude is the introduction of the diffusant from a solid source. This can be conveniently accomplished by using oxide films of the type generally employed for selective diffusion masking. Such oxides also serve to prevent the dissociation of the gallium arsenide surface at the high temperatures of diffusion. DIFFUSION PROCEDURE Fig. 1 illustrates the diffusion sequence which is employed for obtaining zinc surface concentrations in the range from 5 x lom to 1 X 10" atoms per cu cm. The description of technique will be given for the instance of -1 x 1017, which is typically utilized in double-diffused gallium arsenide transistor investigations at this laboratory. Tin- or germanium-doped gallium arsenide wafers drawn from crystals grown by horizontal Bridgman or Czochralski techniques are used, with bulk concentrations ranging from 1 to 3 X 10" carrier atoms per cu cm. Each wafer is chemically polished on the (iii) arsenic face using a mixture of five parts concentrated sul-furic acid, one part water, and one part 30 pct hydrogen peroxide at room temperature, followed by rinsing in deionized and quartz-distilled water. Pyrolytic silicon dioxide was chosen as the oxide coating because of the high quality of the films obtainable, the ease of their preparation, and the excellent control over film thickness and uniformity.

Jan 1, 1964

By Jay N. Fairbanks, Richard G. Robinson

This paper discusses a computer program and related formulas for fire fighting responses by coal mine personnel. The computer will interpret the mine air analysis, print reports, and provide relevant graphs allowing quick and accurate responses to coal mine fires.

Jan 1, 1983