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By Forrest K. Pence

Bentonite deposits are known to occur in Texas within the Jackson group of formations. This group represents the uppermost Eocene age sediments found in the coastal plain area of Texas. It outcrops across this area of the state in a narrow band of some 4 to 20 miles width. The outcrop pattern roughly parallels the present Gulf of Mexico shore line and is some 100 miles inland from the Texas shore, Fig 1. The principal bentonite deposits are found in the areas where this outcrop pattern cuts across the south-central Texas counties of Karnes, Gonzales, and Fayette. In these deposits, the better quality bentonite is found in the lower or bottom layers of the volcanic ash deposits in which they occur. Some of these better quality benton-ite~ develop very light colors upon firing and therefore justify their being classified as "white firing." The deposits in Karnes and Gonzales Counties apparently occur in commercial quantity, whereas the white firing strata so far uncovered in Fayette County have been too thin to be classified as yet as "commercial." A study of the ceramic properties of the weathered ash in Gonzales and Karnes Counties was reported in 1941.' Commercial development of the deposit in Gonzales County, 7 miles east of Gonzales, Texas. was started earlier by the Max B. Miller Co. for the purpose of marketing the material as a bleaching clay, and this operation has developed to very sizable proportions. In recent years, this company has offered a specially selected grade of the Gonzales material as a suspending agent in glaze slips. The white firing property especially adapts the material to use in white cover coat enamels. The strata in the deposit are practically horizontal and consist from top to bottom of approximately 2 ft of soil overburden, 10 ft of brown bentonite, 2 ft of coarse white bentonite, and 4 ft of waxy white bentonite overlying a he grained sandstone. The & being made in the quarry is approximately one-half mile in length. Only the bottom 4 ft of waxy bentonite is being recovered, the upper layers being stripped and wasted, Fig 2. It may appear somewhat surprising that the very bottom strata appears to have been the one most completely altered. To confirm this, samples from top to bottom of the various strata were studied microscopically by R. F. Shurtz. Professor of Ceramic Engineering, University of Texas. His interpretation is to the effect that the lower part of the seam was deposited at a much earlier date than the top, and that the lower part was chemically altered to a considerable extent before the upper part of the seam was laid down. The conclusion to be derived from these examinations may be stated briefly to he that the alteration in these strata or parts of strata has proceeded independently of the alteration in other parts of the strata during a considerable geological period. The presence of gypsum and iron stain throughout all of the strata indicates that alteration is now proceeding more or less uniformly throughout. It is contended that the alteration of the original ash to montmorillonite is not a result of the presently operating processes. A deposit which occurs approximately 7 miles southeast of Falls City and just south of the village of Casta-howa, has been explored and leased by J. R. Martin, of San Antonio. Mr. Martin has conducted mining and marketing operations in bentonite for a period of many years and asserts that the white firing strata found in this deposit occurs in commercial quantities. His pit, which is shown in Fig 3, exposes 2 ft of soil overburden, approximately 5 ft of white bentonite having coarse texture, and approximately 5 ft of waxy white bentonite which in turn overlies a brown sandy clay. Here, as in the Gonzales deposit, the most completely altered portion is found at the bottom of the seam, as per following report of microscopic examination by Mr. Shurtz. Sample No. 1: This sample was taken from the top stratum which is one foot thick. It is grayish in color and it contains visible fossilized plants. The color is probably the result of fine carbonaceous material in the rock. Under the microscope the sample is seen to consist of glass and feldspar; the amount of glass predominating. Both these substances are slightly altered. No montmorillonite or other clay mineral can be identified definitely; however, the products of the slight alteration mentioned are probably montmorillonite or mineral gel. Sample No. 2: This sample was taken from the stratum second from the top. This stratum is fourteen inches thick. The sample is light gray. It shows numerous veinlets of greenish translucent material ranging from one-eighth inches wide down to the limit of visibility with the unaided eye. It has the smooth, sub-conchoidal fracture characteristic of some bentonites. Microscopically the sample consists mainly of aggregates of clay minerals. The birefringence of the aggregates is lower than would be expected if the

Jan 1, 1950

By J. L. Kenty, J. P. Hirth

The concept of a critical super saturation, below which the nucleation rate is essentially zero and above which it is essentially infinite, is discussed with reference to vapor-solid nucleation. The necessary and sufficient conditions deduced for observations of this type of behavior are: 1) the nucleation rate must exhibit a sharp dependence on super saturation, 2) the growth rate must be sufficiently large that nuclei become observable in the time period of the experiment, and 3) the number of highly preferred nucleation sites must be small. Experiments reveal that the nucleation of silver on sodium chloride is visually detectable at all experimentally accessible super saturations and does not exhibit critical nucleation behavior. Failure to observe a critical super saturation is attributed to the insensitivity of nucleation rate to supersaturation as a consequence of the particular values of the contact angle and the surface free energy for this system. THE concept of a critical supersaturation, below which the nucleation rate is essentially zero and above which it is essentially infinite, arises naturally in homogeneous nucleation theory. Experimentally this type of behavior has been found by Volmer1 and others for water and other low surface tension liquids, as reviewed by several authors.2'3 The same type of behavior has been predicted and observed for heterogeneous nucleation of solids by Yang et al.4 and others,596 as also recently reviewed.2,7,8 In the work reported here on the heterogeneous nucleation of silver on NaC1, however, no critical super-saturation was found. Similar observations have been made recently for other systems.9-11 These results led to a reexamination of nucleation theory which revealed that there are conditions for which critical behavior is not predicted, either for homogeneous or heterogeneous nucleation. Although heterogeneous nucleation is of primary importance in this paper, some insight into critical behavior for such a case can be gained by considering homogeneous nucleation. Accordingly both types of nucleation theory are reviewed briefly. The requisite conditions for critical supersaturation behavior are then considered. The experimental results for the nucleation of silver on NaCl are presented and interpreted in terms of the theoretical presentation. REVIEW OF NUCLEATION THEORY There are essentially two approaches to nucleation theory, the so-called classical theory involving the concepts of bulk thermodynamics, and the statistical mechanical theory in which nuclei are regarded as macromolecules. The classical theory is based on the work of Volmer and Weber12,13 and Becker and. Doring14 and has been extended by Pound et al.15 The crucial assumption in the classical theory is that the small clusters or nuclei can be characterized by the same thermodynamic properties as those of the stable bulk phase. Thus, the nuclei are assumed to have a surface free energy, y, and a volume free energy of formation (relative to the vapor phase), ,, identical to that of the bulk. For deposition under low super-saturation conditions, the nuclei are large and this assumption is satisfactory. However, in many cases of interest, the nuclei contain only a few atoms and this assumption is highly questionable. The statistical mechanical models originated, for the specific case of a dimer as the critical nucleus, with the work of Frenkel16 and were extended later to larger sizes by Walton,17,18 Hirth19 and, more recently, Ht Zinsmeister. These models describe the nucleus in terms of a partition function, the estimation of which is tractable for clusters of 2 to 10 atoms, but extremely difficult for clusters larger than 10 atoms. Although the classical and statistical mechanical models are expected to apply for the limiting cases of large and small nuclei, both are uncertain for intermediate sizes. In this paper we shall treat only the classical model, recognizing that it is exact only for large nucleus sizes and regarding it as a phenom-enological description for small nucleus sizes. When analyses of experimental data using bulk properties show the nucleus size to be small, the resulting parameters should be regarded as largely empirical parameters describing the relative nucleation potency of the system. Considerable justification for the continued use of classical theory is provided by its general success in predicting nucleation behavior as a function of supersaturation and temperature. We emphasize that the qualitative features of the statistical mechanical models, particularly the critical super-saturation behavior that is central to the present work, are the same as those of the classical model. Of course, potential energy terms and surface partition functions replace the volume and surface energy terms of the latter model. The most recent versions of classical nucleation theory have been extensively reviewed.2,3,7 so that only the results are presented here. For homogeneous nucleation of a condensed phase from the vapor phase, the volume free energy change is ?Gv=vrT = =^ln£ [1] where v is the molecular volume of the condensing species. The supersaturation ratio,

Jan 1, 1970

By R. H. Jamison

A relatively new haulage system is described. Employed by the Delmant Fuel Co.. the "Full Dimension" system provides an uninterrupted flow of coal from a loader or continuous miner at the face to the main line transportation system. This system is said to provide a higher percentage of recovery as well as additional safety and production. Delmont Fuel Co. is employing a comparatively new system of transportation known as a Full Dimension system. Cne of these systems has been in operation for a year at the company's 10-B Mine as a part of a conventional section. A second was installed at the No. 10 mine in late 1960 to handle the production of a Colmol in a pillar section. SYSTEM COMPONENTS A Full Dimension system is a haulage system that provides an uninterrupted flow of coal from a loader or continuous miner at the face to the main line transportation system. The equipment required for this system consists of a series of interconnected chain conveyors that are mobile and articulated. They will retract or extend a sufficient distance for the development of a five-entry system; or, in the Colmol pillar section, it provides reach of 210 ft in all directions from the section belt. The components of this system are: l)One 160-ft chain line placed in tandem with the belt conveyor. It has a self-propelled drive, is 20 in. wide and 9 in. deep. Moving this conveyor requires the assistance of a loading machine or cutting machine. 2) One 40-ft piggyback that discharges along the entire length of the 160 ft chain conveyor. 3) A mobile bridge carrier, which is a self-propelled conveyor with four wheel steer and four wheel drive, twenty-eight feet long, it delivers coal to the receiving end of the piggyback. Axles steer individually making possible almost lateral movement. 4) Another 40-ft piggyback, duplicate of item 2 that delivers coal along the entire length of item 3 (mobile bridge carrier). 5) A second mobile bridge carrier, similar to the first, which deliver coal to the piggyback (item 4). 6) A third 40-ft piggyback, duplicate of items 2 and 4. This pig is attached to the loading machine and delivers its coal along the length of the second mobile bridge conveyor. Since the original preparation of this paper, the Delmot Fuel Co. has been able to eliminate the 160-ft chain conveyor. This was accomplished by connecting the outby piggyback directly to a loading machine with an extended boom. The loading machine loads directly onto the belt. This change has resulted in a substantial reduction in moving time and greatly increased flexability. A single trailing cable powers the entire string of equipment. It is attached to the side of the equipment in such a way as to keep it off the ground and afford maximum protection. The tramming rate of this equipment is 90 fpm. The conveyor capacity in a conventional section at Delmont's mines is 7.5 tpm and in the Colmol section is 5.5 tpm. This regulation is a simple function of conveyor speed. To visualize operation of this equipment, it would be well for me to touch briefly on local conditions in the Upper Freeport seam in which we mine. (Also, see the photographs of some of the equipment in use.) DELMONT'S TOPOGRAPHY The Delmont Fuel Co. operates two mines in this seam in Westmoreland County, Pa. The No. 10 mine, which was opened in about 1912, is now almost worked out. Depending on economics in the industry, it has a life of two to four years on a declining production basis. A year ago a new drift mine was opened which is called No. 10-B. It is about two miles from the cleaning plant and is connected thereto by an overland belt conveyor. The new mine is being developed at a rate calculated to take up the slack as the old mine plays out. The Upper Freeport seam averages 4.2 ft in thickness in the area of the Delmont mines. It carries 4 in. of boney coal at the top of the seam and a middle man of from 2 to 4 in. We mine just above a 1-in. slate parting which has 4 to 6 in. of highly laminated coal beneath it. This material normally makes a very firm bottom. The roof varies from dark shale to sand rock and 36-in. bolts are placed on 4-ft centers for roof support. All working places are driven 20 ft wide on development and 25 ft wide on retreat. Selection of mobile chain conveyor equipment when it became available, was a very natural move for Delmont Fuel to make, because chain conveyors and piggybacks had been in use at the company's mines for about 12 years. Grades in the new mine

Jan 1, 1961

By R. R. Knuckey

Having been associated with the operation of the de Vooys process for coal, which has treated 13,000,000 tons per annum, and recognizing the process as of value in ore sorting, Huntington, Heberlein and Co. Ltd. (Great Britain) in 1936 made an examination of all other existing methods. In none of the pioneer applications had recognition been given to the necessity for maintaining certain conditions that are essential for sorting certain ores if a truly efficient separation by gravity alone is to be assured. Consequently, in 1936-1937 Huntington, Heberlein and Co. Ltd., with Pearson, employing certain ideas connected with the de Vooys application, commenced the development of a separator that would allow conformance with optimum conditions in the zone where separation is effected. Later, Holt and Wade added to the value of the original application by Wuensch, Rakowsky and others, whose conceptions are being successfully operated today. Meantime, Trostler had enhanced the value of the original H-H. process by improvements that are now embodied in operating plants, and today the process incorporates an improved apparatus and a stable medium that produce the optimum conditions for separation. These conditions are: 1. Elimination of disturbing currents in the separating zone; 2. Reduction to a minimum of medium-density differences throughout the separating zone; 3. Stable medium of minimum viscosity to permit the unretarded fall of mineralized particles; 4. Removal of products of separation with minimum disturbance to the separating zone. Design of Separator The H-H. sink-and-float separator consists of a pyramidal tank in which the separation actually takes place, connected at the bottom with an inclined bucket elevator. The tank and the elevator are filled with medium to within a few inches of the top of the tank. Medium is fed into the separator at a variety of points, according to the type of ore being treated, and it is withdrawn from the separator at two points: (1) together with the float product, by means of a variable-speed addle, at the surface of the medium, and (2) by flowing over an adjustable weir cut in the side of the elevator casing. The prepared ore is fed onto the surface of the medium. The intermediate paddles, which revolve at a slow speed of 2 to 5 r.p.m., move the floating ore across the bath from feed end to float-discharge end. The ore, which is heavier than the medium, sinks below the sweep of the addles and reaches the boot of the bucket elevator, which discharges it without disturbance of the separating zone. These arrangements for withdrawing medium from the separator allow the use of minimum flows, which connote minimum

Jan 1, 1947

By R. R. Knuckey

Having been associated with the operation of the de Vooys process for coal, which has treated 13,000,000 tons per annum, and recognizing the process as of value in ore sorting, Huntington, Heberlein and Co. Ltd. (Great Britain) in 1936 made an examination of all other existing methods. In none of the pioneer applications had recognition been given to the necessity for maintaining certain conditions that are essential for sorting certain ores if a truly efficient separation by gravity alone is to be assured. Consequently, in 1936-1937 Huntington, Heberlein and Co. Ltd., with Pearson, employing certain ideas connected with the de Vooys application, commenced the development of a separator that would allow conformance with optimum conditions in the zone where separation is effected. Later, Holt and Wade added to the value of the original application by Wuensch, Rakowsky and others, whose conceptions are being successfully operated today. Meantime, Trostler had enhanced the value of the original H-H. process by improvements that are now embodied in operating plants, and today the process incorporates an improved apparatus and a stable medium that produce the optimum conditions for separation. These conditions are: 1. Elimination of disturbing currents in the separating zone; 2. Reduction to a minimum of medium-density differences throughout the separating zone; 3. Stable medium of minimum viscosity to permit the unretarded fall of mineralized particles; 4. Removal of products of separation with minimum disturbance to the separating zone. Design of Separator The H-H. sink-and-float separator consists of a pyramidal tank in which the separation actually takes place, connected at the bottom with an inclined bucket elevator. The tank and the elevator are filled with medium to within a few inches of the top of the tank. Medium is fed into the separator at a variety of points, according to the type of ore being treated, and it is withdrawn from the separator at two points: (1) together with the float product, by means of a variable-speed addle, at the surface of the medium, and (2) by flowing over an adjustable weir cut in the side of the elevator casing. The prepared ore is fed onto the surface of the medium. The intermediate paddles, which revolve at a slow speed of 2 to 5 r.p.m., move the floating ore across the bath from feed end to float-discharge end. The ore, which is heavier than the medium, sinks below the sweep of the addles and reaches the boot of the bucket elevator, which discharges it without disturbance of the separating zone. These arrangements for withdrawing medium from the separator allow the use of minimum flows, which connote minimum

Jan 1, 1947

By Pradeep K. Rohatgi, Clyde M. Adams

Structures produced upon solidification of the eu-tectic composition (33 wt pct Cu) aluminum copper alloy have been examined as a function of freezing rate dfs /d? , the rate of change of fraction solid (fs) with time (8). Slow (dfs/d? = 0.0016 sec-1), intermediate (dfs/d? = 0.02 sec-1) and rapid (dfs/d? = 0.4 to 7.30 sec-1) freezing rates were used. The lamellar Al-Cual2 eutectic is arranged in the form of rod-shaped colonies at rapid freezing rates. The colonies are aligned parallel to the direction of heat flow, whereas the lamellae within the colonies are aligned at various angles, as high as 90 deg, to the direction of heat flow. The colony spacing (C) is proportional to the square root of inverse freezihg rate. The relationship is C = 15.5(dfs/d?)-1/2 where C is in µ and 8 is in sec. The ratio of colony spacing to lamellar spacing is greater than 20.0 and increases with a decrease in the freezing rate. A duplex dendritic structure is produced at intermediate freezing rates. A fine lamellar eutectic is arranged within the dendrites (exhibiting side branches at an angle close to 60 deg from the main stem) and a coarse irregular eutectic appears in the interdendritic regions. The duplex eutectic structure is also produced at slow freezing rates. However, at slow freezing rates there is a Platelat of CuAl2, along the center of the main stem of each dendrite and the other lamellae are arranged perpendicular to the central platelet. THE eutectic between CuA12 and a! aluminum has been reported to freeze in a lamellar form by several workers.'-3 chadwick4 has measured the interlamel-lar spacing as a function of growth rate. Kraft and Albright2 have reported on irregularities in the lamellar structures, and have proposed growth models which account for the formation of faults during solidification. In certain instances the lamellar eutectic has been found to exist in colonies. The colony formation315 has been attributed to the breakdown of a planar liquid-solid interface due to rejection of impurities. The aim of the present work is to study the structures produced from the eutectic aluminum-copper alloy under relatively fast solidification rates, such as encountered in casting and welding operations. The solid-liquid interface presumably remains planar under conditions of slow unidirectional freezing which produce lamellae aligned parallel to the direction of heat flow. The local growth velocities are the same over the entire interface and are equal to the rate of growth of the all-solid region. The spacing between the eutectic lamellae is inversely proportional to the square root of the growth rate of the all-solid region. Under the freezing conditions used in the present study, the solid-liquid interface is cellular or dendritic and the local growth velocities are different in the different regions of the interface. The relationship between the growth rate of the all solid region and the local growth velocities varies with the location and the shape of the interface. The growth rate of the all-solid region is, therefore, an inadequate parameter to describe the eutectic micro-structures which depend upon the local growth velocities. For this reason the structures have been examined as a function of freezing rate, dfs/d?, where fs is the fraction solidified at time 0. The freezing rate was varied by a factor of 4000. The relationship between the freezing rate, dfs/d?, and the growth velocit of the all solid region depends upon the specimen geometry and the shape of the interface. EXPERIMENTAL PROCEDURES The A1-33 pct Cu alloy used throughout this study was made in an induction furnace, using electrolytic copper and aluminum of commercial purity (99.7 pct), the primary impurities being silicon (0.12 pct), iron (0.14 pct), and zinc (0.02 pct). Three ranges of freezing rates were investigated: 1) A spectrum of rapid freezing rates (ranging from 0.40 to 7.30 sec-1) was obtained in arc deposits made on 2-in. thick cast plates of the eutectic alloy. The arc was operated at constant power and was made to travel at constant velocity on the surface of the plate that was in contact with the chill surface during solidification. The pool of liquid metal formed under the moving tungsten arc solidified rapidly by heat extraction through the unmelted plate. Conditions of unidirectional heat flow were achieved near the fusion zone interface, especially in the center of the arc deposits. The great advantage of the arc technique is that rapid cooling and freezing rates can be varied in a qualitative way. The correlation between the arc parameters and the solidification rate is given by the following relationship:6-8

Jan 1, 1970

By H. A. Bourne, E. L. Haden, D. R. Reichmuth

A circumferential-toothed bit with novel tooth form gave improved penetration performance. In this design the exterior flank of all teeth were vertical when in rolling contact with the hole bottom. Rock chips were generated by the interior flank of the tooth displacing the rock inwardly and downslope toward the center of the hole. A unique two-cone laboratory bit assembly enabled evaluation of numerous cone and tooth configurations. Some of the variables investigated, in addition to weight on bit, rotary speed and rock type, were tooth interference, percent tooth, hole bottom angle, attack angle and relief angle. Most tests were conducted dry on a brittle synthetic sandsone or a ductile quarried limestone. Tooth configurations were found to be more significant in the ductile material. This was attributed to the deeper tooth penetration before rock failure. These studies showed that the attack angle (angle beween interior flank of the tooth and rock surface) was the controlling variable; changing the tooth configuration from the assymetric or semi-wedge to the more conventional symmetric or wedge form reduced penetration performance; and penetration performance of circumferential-type cutters was directly proportional to rotary speeds up to 200 rpm. INTRODUCTION Much of the published literature on rock-chisel interactions describe experiments wherein symmetrical wedges are vertically loaded or impacted against a smooth rock surface.1-6 are is usually taken to insure that the indentation is not made near the edge of the rock specimen less erroneous data be obtained. The literature describes relatively few studies in which the investigator deliberately attempted to take advantage of an edge or free surface. In contrast, anyone who chips ice or breaks up a concrete sidewalk almost always works near an edge. Chisel "indexing," which has been considered by some investigator1,2,6,7 makes limited application of an edge or free surface. Probably the best documented investigation into applying this idea to drilling was that of Drilling Research Inc. at Battelle Memorial Institute.' Their "annular wing" percussion bit consisted of paired asymmetric chisels oriented so as to produce and move chips to the center of the hole. They predicted that the lowest energy requirement for chip generation would be achieved with a stepped hole bottom having a median angle of 45" to the horizontal. Results from limited tests showed that approximately 50 percent of the rock fragments were large and semi-circular in shape, as would be expected by a chisel impact near an edge. The remaining 50 percent were fine chips produced by the chisels in re-establishing the steps or ledges. Initial penetration rates with this bit were high, but they rapidly decreased. This was the result of excessive tooth wear caused by the constant friction on the gauge surfaces. The basic idea — circumferentially placed asymmetric chisels — still appears to have merit. If the concept could be applied to a rolling cutter bit, two of the shortcomings of the fixed chisel design could be overcome: (1) reduction in tooth friction, and (2) greatly increased cutter surface. Adapting asymmetric chisels to cutters rolling on an inclined hole bottom is restricted by bit geometry. The basic elements of roller rock-bit construction prevents the practical attainment of a 45" hole bottom angle. Nonetheless, experimentally it was considered desirable to investigate the influence of hole bottom angle to at least 40". This paper describes the laboratory studies conducted in evaluating the circumferential-toothed roller cutter rock bit. EXPERIMENTAL APPARATUS AND PROCEDURE BIT ASSEMBLY The cost of constructing a sufficient number of conventional three-cone rock bits to investigate circumferential cutter performance was prohibitive. Instead, a novel two-cone laboratory assembly which used an external bearing system was designed and constructed. The external bearings made it possible to alter the journal bearing angles and thus allow a wide flexibility in cutter configuration. Fig. 1 shows the laboratory bit assembly, the various bearing mount plates and the appropriate roller cutters for drilling shallow holes having hole bottom angles of 0, 10, 20, 30 or 40". The bit was limited to a drilling depth of 1 1/2 in. at the gauge teeth and a hole diameter of 43/4 in. This more or less intermediate size bit was chosen because it gave a more realistic match between bit teeth and the rock than would a microbit. Also, the rock sample size required was convenient and easy to obtain. CIRCUMFERENTIAL CUTTERS The tooth configuration used in our initial studies is shown in the upper half of Fig. 2. All cutters used in this series had the same tooth form — 43" included tooth angle, 2" positive relief angle and a horizontal tooth flat width of 1/32 in. Each cone cuts alternate rows except for the gauge row. The row-to-row spacing in view was 1/4 in. Static loading tests conducted earlier with asymmetrical chisels had been used to establish this spacing. These tests showed energy requirements for chip production increasing rapidly as the distances to the edge increased beyond

By George S. Ansell, John B. Hudson, Stephen A. Koffler

The permeability of hydrogen through the a phase of palladium has been measured by a low pressure permeation technique under conditions such that bulk diffusion was the rate-controlling process. The observed permeability is described by the equation: J = 1.80 x 1O-3 P½exp(-3745)/RT) cc(stp)/sec/cm2/en over a range of hydrogen pressure, P, from 2.9 x 10-5 m Hg to 5.0 x 10-3 cm Hg, and over a temperature range, T, from 300" to 709°K. The fact that the permeability shows a square root dependence on pressure and a reciprocal dependence on thickness was taken as evidence that bulk diffusion, rather than surface reactions, was the rate-controlling process. The permeability data were used in conjunction with the solubility data of Salmon et al., to determine the diffusivity of hydrogen through palludium as: D = 4.94 x 10-3 exp(-5745/RT) cm2/sec There was no influence of sub structural defects observed over the temperature range employed. From the permeability data obtained, coupled with grain size measurements, it was concluded that the ratio of grain boundary diffusivity to bulk diffusivity was less than 105 over the range of temperature investigated. THE diffusive mass transport of hydrogen in the a phase of palladium has been studied previously by numerous investigators.' In spite of the large amount of attention this system has received, there is not good agreement between the results obtained in different investigations.' This is due in part to the fact that the mass transport was surface-limited during some of these studies, rather than being diffusion-controlled3-5 The reason for the disagreement in other cases is not clear. These studies made use of such techniques as rate of absorption from solutions6 and gases,' electrochemical potential,8 time lag,' and permeation10,11 to determine the mass transport behavior. Of these, the gas permeability technique is the only method which allows an easy test to determine if diffusion is the rate-controlling mechanism, thus eliminating the uncertainty regarding the limiting transport processes inherent in the other techniques. The two most recent permeability studies are those of Toda10 and Davis." Toda determined the permeability of hydrogen in the a phase of palladium over the temperature range from 170" to 290°C, and over the pressure range from 36 to 630 mm Hg utilizing a steady-state gas-permeability technique. Toda's result was: J = 1.41 x 10-3 P½ exp(-3220/RT) where J = specific permeability in cc(stp)/sec/cm2/cm, P½ = square root of the inlet pressure in (cm Hg)½, R = Universal gas constant, and T = temperature in deg Kelvin. Davis11 also employed a steady-state gas-permeability technique over the temperature range from 200" to 700°C and over the pressure range from 0.02 to 760 mm Hg. His result for the permeability of hydrogen in the a phase of palladium was: J = 3.15 x 10-3 P½ exp(-A440/RT) In the range of overlapping temperature for these two investigations, the values of the specific permeability calculated from the above two equations differ by a factor of about 1.8. In the present investigation, the permeation of hydrogen in the a phase of palladium was determined over a wide temperature range, 27" to 436oC, and over the pressure range from 2.9 x 10-5 to 5.0 x 10-3 cm Hg. This temperature range overlaps that of the previous investigations of Toda and Davis, but also covers the lower temperature range which has never before been investigated. The lower pressure range used here avoided the interaction between the dissolved hydrogen atoms observed at higher hydrogen concentrations.' MATERIALS The as-received palladium specimens were cold rolled from a casting and were supplied as 5.08 cm discs of 0.508 and 0.762 mm thickness. According to J. Bishop and Company specifications, the composition of the discs was 99.95 pct Pd, the balance being Cu, Ag, Au, and Ir. In order to obtain samples of varying grain size, the as-received discs were then heat treated. Sample 1 was treated for eight minutes in a nitrogen atmosphere at 810°C and then air-cooled. Sample D was heated first to 550°C in helium. The helium atmosphere was then immediately replaced by hydrogen and the temperature was slowly raised to 1220°C and held for 22 hr. The sample was then cooled to 550°C where the hydrogen was replaced by helium and the disc was further furnace-cooled to room temperature. Sample H was given the same heat treatment, only with hydrogen substituted for helium below 550°C. The reason that hydrogen was not used throughout the entire annealing cycle for samples D and H was to prevent the distortion encountered by low-temperature cycling in hydrogen observed by Darling." After these heat treatments were completed, the

Jan 1, 1970

By AIME AIME

FOUR separate groups of conveyors are installed in the Morenci Reduction Works as follows: (1) Ore-handling conveyors from the primary crushing plant to the coarse ore bin, from the coarse-ore bin to the secondary crushing plant, and from the secondary crushing plant to the ore bin in the concentrator plant. (2) Conveyors in the mill section of the concentrator plant. (3) Conveyors handling concentrate from the filter plant to the bedding plant, and from this plant to the smelter. (4) Conveyors handling flux and custom ore in the smelter crushing plant and to the bin at the bedding plant.

Jan 1, 1942

By S. Weinig, E. S. Machlin

THE mechanism of the martensitic transformation has been the subject of a remarkable number of papers in recent years.' Because the task of evaluating all the available theories is a formidable one, the authors will confine themselves merely to the presentation of results of an experimental investigation of the habit orientation, lattice relations, magnitude and direction of average transformation shear strain, and orientation of subband markings for a single variant of the possible habit systems in an 11 pct Mo-Ti alloy. It is hoped that these data will assist in the establishment of a rigorous theory for the mechanism of the martensitic transformation. Experimental Procedure Specimen Preparation: A sample, approximately 1/2 x 1/4 x 1/4 in., was cut from a double arc-melted ingot composed of commercial-process A titanium and high purity molybdenum (nominally, 11 pct Mo). It was capsuled in evacuated Vycor at 10.-3 mm Hg subsequent to a double argon wash and homogenized for 48 hr at 1100°C. After a direct quench into H2O at room temperature, a large-grained specimen resulted, which, by X-ray diffraction and metallographic means, was subsequently shown to be in the body-centered-cubic phase, ß. Two adjacent, approximately perpendicular faces were polished and the ends of the specimen were ground parallel in a V-block. Fiducial lines were inscribed at 45" to the common edge of the polished surfaces in order that they would be perpendicular to the habit traces of the subsequently formed a plates.2 The specimen was then compressed between the ground ends in a Buehler press to stress induce the transformation ß to a'. Experimental Measurements: The habit-plane orientation, the orientation of subband markings, the orientation relation between the parent ß and the product a', and the transformation strain for the same plate were determined. To further establish the nature of the subbands, one surface was repol-ished and etched. The bands in the a' were still visible and were found to be optically anisotropic under polarized light. Back-reflection Laue patterns were obtained from the ß matrix and from a region comprising both a' plates and adjacent ß matrix (a Cu target was used). By superposition of the two X-ray diffraction patterns, it was possible to obtain a tentative orientation relationship between the two phases. This result was confirmed by a pattern taken after the specimen was rotated to make the basal-plane pole of the hexagonal a' phase strike the film. This necessitated cutting the specimen to expose the a' plate in the new position relative to the X-ray beam. Analysis of Experimental Measurements On the basis of the aforementioned X-ray patterns, the orientation between parent and product

Jan 1, 1955

By Robert Keeney

AT the beginning of the use of the electric furnace, for the manufacture of calcium carbide and ferro-alloys, experimental work was conducted in it upon the production of steel from iron ore. Stassano performed two series of experiments in Italy, the first1 during the years 1898 to 1902, and the second2 in 1908. For many years steel and wrought iron have been produced directly from ore on a small scale in the forge, crucible, and reverberatory furnaces; but the difficulties attending the operation of these combustion processes have prevented their adoption to any great extent. The combustion

Jan 2, 1914

By Roderick K. Davey

Introduction in any business, it is essential that we select those alternatives which are not only technically feasible, but will be the most profitable to the business m terms of corporate objectives Some of the studies and activities requiring support of financial analysis to select the alternatives which most closely satisfy the management objectives and technical considerations are as follows 1 ) Cutoff grade determination. 2) Ore reserve estimation. 3) Production forecasts (long- and short-term) for an operating mine, development of a new mine, or expansion of an existing mine. 4) Evaluation of haulage alternatives. 5) Evaluation of equipment.

Jan 1, 1979

By J. B. Newsom

IN the September 1936 issue of MINING AND METALLURGY the pioneer work of boring a 5-ft. shaft to a depth of 1125 ft. at the Idaho Maryland mine in California was described. Later, a Bureau of Mines Information Circular (No. 6923) gave additional data. In re¬cent months still further progress has been made in this technique through the sinking of a 5 1/2-ft. shaft for Pickands, Mather & Co. at their Zenith mine, Ely, Minn. The present work was done with new carefully designed equipment and several experienced men so that progress, as shown below has been much better:

Jan 1, 1938

By H. M. Woodrooffe

Three of the world's largest phosphate deposits are located in the USSR. These have an estimated reserve of 2,600 million short tons of elemental phosphorus. The best known lies in the Khibiny Massif, an alkalaic rock formation some 600 square miles in area with mountain peaks rising to an altitude of 3300 ft above the surrounding terrain. The Khibiny Massif is north of the Arctic Circle in the Kola Peninsula at a latitude of 67° 30' north and a longitude of 35° 30' east. It is connected by rail to Murmansk, 100 miles northwest, and Leningrad, 900 rail miles south.

Jan 12, 1972

By W. H. Gunniss

When the copper smelters were built, in Montana, all of the refractory products which were used in their construction were shipped in from Eastern factories. It was apparent that if a material suitable for the manufacture of these products could be found within the State, a saving of freight could be effected and a new industry built up. Prospecting for such materials was started and experiments were made with samples from numerous deposits. Considerable effort and funds were expended in an attempt to manufacture silica brick from Dillon quartz, a light colored sandstone that is found near Dillon, Mont., on the Oregon Shortline railroad. As a brick material the Dillon quartz was a failure, but it has proved very satisfactory as a silica cement. It is now being used in laying silica brick and for reverberatory furnace bottoms. A bed of quartzite that is particularly suited to the manufacture of high-grade silica brick was finally discovered at Browns Spur, 6 miles west of Anaconda. The material from this deposit is now being used in the manufacture of the Anaconda silica brick, which have gained a wide reputation for heat-resisting and lasting qualities. The analysis of an average sample of this quartz is: SiO2, 96.7; Fe2O3, 0.3; Al208, 2.5; CaO, 0.3 per cent. The very low percentage of fluxing ingredients makes this a most refractory material. All of the Anaconda silica brick are hand molded. Various types of brick machines have been tried, but the hand-mold process proved the best suited to the manufacture of silica brick from this material. The silica is first put through a jaw crusher and is then dumped into wet pans, where 4 per cent. of lime paste is added, to produce a bond. Without the lime the material would not be plastic enough to mold. After a few minutes' grinding in the wet pans the material is conveyed to the molder, who forces it into the molds by hand. The brick are then dumped on pallets and placed in the drier, where they are left. until dry enough to be set in the kilns. Some of the brick are re-pressed before being dried. They are burned about five days, in round down-draft kilns. It is not necessary to have as much heat in the kilns as the brick will be subjected to when in use in the furnaces. Montana refractories are used in smelters throughout the West. Prospecting for fire clays was also carried on. After experimenting with clays from several different deposits, it was found that a mixture of

Jan 1, 1914

By M. A. Bryant, J. C. Goodwin, T. B. Faddies, L. D. Kornze

The Mercur Gold Mine is located 56 km (35 air miles) southwest of Salt Lake City in north central Utah; In July 1981 Getty Mining Company made the decision to put Mercur into production. The first gold bar was poured in April 1983. This paper provides details on: 1) the history of the camp, 2) past production, 3) geology of the deposit, 4) the exploration and development program, 5) ore reserve estimates, 6) detailed geologic pit mapping, 7) production blasthole sampling techniques and 8) the use of geostatistics (kriging) in handling assays and gold extractions to produce the required mill feed.

Jan 1, 1985

By George W. Mitchell

THE property of Eureka Corp. Ltd. is located in the approximate geographic center of Nevada, 2 miles from Eureka, the county seat. The great sources of power, the Colorado, Snake, and Salmon Rivers and the rivers of northern California, are 300 to 500 miles distant, and no lines serve areas closer than 150 miles. Fuel for diesel and steam generation is available in Utah, 300 to 400 miles to the east. Eureka's railhead is 80 miles north where two trunk lines cross the county. A spur line serves Ely, 77 miles east. Good highways connect Eureka to the railheads.

Jan 8, 1953

By Horace C. Knerr

It has been shown that the resistance to corrosion of duralumin sheet is greatly influenced by the quenching medium used in heat treatment, or, more specifically, by the rate of cooling during quenching. The severity of corrosive attack after exposure to salt-water spray increases in .the following order: The tensile strength, yield point and elongation are only slightly affected by the quenching medium, as shown in Table 1. Tensile test requirements: yield stress, 25,000 lb. per sq. in. minimum; ultimate stress, 55,000 lb. per sq. in. minimum; elongation in 2 in., 18 per cent. minimum.

Jan 1, 1931

By F. W. von Batchelder

The principles of microradiography and their application practically coincided with the discovery of X-rays. These principles were first used in the metallurgy field by Heycock and Neville1 in a study of the dendrite structure of alloys of Au-Na, Au-A1, Cu-A1, and Ag-A1. The method was introduced in the USA by clark2 after a visit to France. Scores of papers have been written, and a very complete bibliography on this subject was compiled by the Eastman Kodak company. Although a number of papers have discussed X-ray

Jan 1, 1959

By T. B. Armstrong

Electrical energy conservation sees that service facilities are operated only when needed and that production equipment is operated under an optimum condition. Specific energy consumption (kw-hr per tonne) is not regularly recorded for comminution circuits because of variations in ore characteristics and the low grinding efficiency (0.1 to 2.0%) of the equipment. Improved data acquisition can produce meaningful results. Particle size monitor systems and density gauges permit comparison of energy (kw-hr) and production (tonne) for a "fixed" condition. Finding the operating condition producing the lowest unit energy consumption provides a target for an effective energy management program.

Jan 1, 1982