Search Documents

By G. R. Purdy, J. A. Malcolm

The isothermal dendritic precipitation of y in p CuZnSn is compared with the isothermal formation of Widmanstatten a plates in p CuZn. Although both precipitates are evidently bounded by semicoherent interfaces, the dendritic shape of y evolves through smooth "sinuoidal" shape perturbations, while a-p interfaces tend to be strictly planar, or rnicroscopically faceted. An estimate of the average inter-facial free energy of cube-oriented y in p through the Mullins-Sekerka analysis indicates that it is low (of the order of 50 ergs per sq cm). Interface mication is apparently controlled by volunle dij'usion, and the observed anisotropy in growth probably results from anisotropy of inter facial free energy. Studies of the grain boundary precipitation of y in p indicate that the precipitate can grow in both $ grains, but becomes unstable with respect to the grain with which it shares a mobile semicoherent interface. Facets observed at the tips of Kurdjumov-Sacks-oriented Wid-manstatten a plates correspond to variants of an irrational hahit, near (231)0. Comparison with Hu and Smith's determination of relative interfacial free energies of a-(3 boundaries suggests that this system possesses an extremely deep o cup, which results in an ej'ective low-o zone. The possible effects of such a cup on the stability of a-p interfaces are discussed, a needles, grown during rapid continuous cooling, possess microscopically smooth interfaces, and are characterized by a high degree of' damage in the region of the boundaries. These boundaries, induced to move on tempering at 200"C, become faceted as equilibrium is approached, which seems to indicate that boundary structure and mobility in this system are dependent on the local degvee of departure from equilibrium MULLINS and sekerkal have elucidated the phase boundary stabilizing effect of surface tension. a factor not taken into account in previous treatments of morphological development. Their analysis applies to the isothermal growth of a pure spherical precipitate (planar in the limit of infinite radius) in a slightly supersaturated solution, under conditions of inter-facial local equilibrium and isotropy of interfacial free energy. More recently, several other factors which might tend to stabilize planar interfaces have received attention. These are: i) interface diffusion;4"8 and ii) slow interfacial reaction. cahn7 included a slight anisotropy in interfacial free energy, and showed that it has no stabilizing effect, but forces shape perturbations to reflect the anisotropy. shewmon4 noted that dendritic morphologies are rarely observed in solid-solid systems, and, in particular, postulated that slow interfacial reaction occurs at all boundaries between proeutectoid ferrite and austenite, except those which propagate parallel to {11 l)y planes (for Kurdjumov-Sachs [K-S] related phases). Previously, Aaronson~ had proposed interfacial reaction at the broad faces of Widmanstatten plates, and expected that the lateral motion of high-mobility incoherent ledge edges would produce planar precipitates bounded by law-mobility semi-coherent interfaces. The problem of interfacial reaction during the dif-fusional formation of precipitates has often been ignored, although it is apparent that a small component of chemical reaction must exist at any moving interface." Further, all solutions of the diffusion equations for boundary conditions corresponding to isothermal growth predict infinite growth rate at time zero, so that elements of interfacial reaction would be most easily detected at early times. However, reported deviations from diffusion control are comparatively rare," and the local-equilibrium diffusion-control model appears adequate for the description of many isothermal growth systems.'2"9 Cahn14 has treated the problem of migration of an interface which is able to reach positional energy minima, and concluded that such an interface, if subjected to a high local ther-modynamic "driving force", may migrate normal to itself without the benefit of ledges. As local equi-

Jan 1, 1968

By Mark Johnson, Mathew Janes

"The Resonator RD 260 Resonant Pile Driver delivers ground disturbance free, high production pile driving. The Resonator has recently been used on numerous production pile driving sites in the Netherlands and Melbourne, Australia to drive piles in sensitive areas where conventional pile drivers could not be used. Two case histories are provide in this paper which demonstrate the features and benefits of Resonant pile installation.. In the Netherlands the Resonator RD 260 was used at the Vopak Oil Storage facility in the Port of Rotterdam to install pipe and sheet pile within an active pumping gallery. The site demanded vibration free pile installation to construct a cofferdam within sensitive, highly valued assets. Access was an issue and schedule demands were stringent as shutdown windows were narrow. The RD 260 provided ground disturbance free piling immediately adjacent to fragile structures. At Vopak the only site access was using a large crane positioned over 40 m from the location of pile driving. Driving was conducted amongst 900 mm dia pipes carrying heated crude oil.In Melbourne the RD 260 was used to drive GU 18 sheet piling adjacent to light rail easements. The project was the first of many grade separations being constructed within Melbourne urban areas to lower the light rail and provide quieter rapid transit. The original trial used an RGT MR105 series vibrator but noise and vibration criteria were exceeded. The RD 260 was brought in for a trial and performed with high production and produced negligible ground vibration. Up to 17 sheet piles 14 m in length were driven in a 2.5 hour window during the trial.IntroductionThe Resonant Pile Driving method is gaining acceptance around the world as a new method to rapidly drive piles free of ground borne vibrations. The high frequency vibrator resonates the pile, essentially turning the pile into a spring, to excite the toe of the pile with high accelerations and low amplitude. High acceleration with low amplitude generates high penetration rates but the high frequency stress waves are quickly dissipated in the soil. Typically ground borne vibrations are measured at below 1 mm/sec within 1 to 5 m of the pile. The Resonant method can drive a pile next to a glass of wine, without spilling, as has been demonstrated on numerous piling sites.How Does Resonance Work?The Resonant method uses a hydraulic piston - cylinder geometry to generate high magnitude, high frequency oscillating force. This is a very different mechanism than the eccentric mass technology used in conventional and variable moment vibrators.A unique valve geometry achieves the high frequency flow switching necessary to oscillate the hydraulic piston at up to 180 Hz (10800 VPM). The valve is controlled electronically for maximum accuracy of the desired frequency. The volume of hydraulic oil delivered through the valve to the piston (flow rate) determines the amplitude while the hydraulic pressure determines the peak force."

Jan 1, 1900

Discussion of the paper of GEORGE K. BURGESS and SIR ROBERT A. HADFIELD, presented at the New York meeting, February, 1915, and printed in Bulletin No. 98, February, 1915, pp. 455 to 468. ALBERT SAUVEUR, Cambridge, Mass.-There is a definiteness and finality in the investigations that have been conducted by the Bureau of Standards and in the method of presenting the results that is most satisfactory and refreshing.. A year ago Dr. Burgess and his co-workers investigated the question of critical points in carbonless iron, and they settled the question once for all. No one can now claim that the thermal point A2 in carbonless iron does not exist. At the past meeting of this Institute in Pittsburgh, Dr. Burgess showed the worthlessness of the shrinkage clause. To my mind after his demonstration no one can again claim that the shrinkage clause renders any service. He also showed us that it was a practicable proposition to use pyrometers in steel work in order to ascertain the finishing temperatures of rails. No one can again come before this body and make the claim that it is not a practical proposition. And now Dr. Burgess shows us that steel ingots can be made in a commercial way, practically free from pipe, from segregation, aid from blow holes. It places again before us in a very clear manner the question of piped ingots and of segregation, a question which has been debated for 20 years or more. I know very well the attitude of the standpatters in the matter. They claim that most of the pipe is removed in the discard, and that if a little is left it is so thoroughly welded that it does no harm. I for one am not convinced of the soundness of the argument. I do not believe there is any one present who would claim that, given an ingot free from pipe, free from segregation, and free from blow holes, better rails will not be made out of that ingot than out of the ordinary piped or segregated metal which is used by almost all of our steel mills. In my opinion, if we give our sanction to the casting of steel in the shape of piped or segregated steel ingots, we are guilty. If we give our sanction to the rolling of rails from such metal, we are guilty. It is our duty as experts, as steel makers, and as steel consumers to make and to use the best steel obtainable on a commercial basis, for the manufacture of rails. Now, we have been shown that sound ingots can be produced from which superior rails can be made. If we do not insist upon these sound ingots, then we fail in our duty. I think that the art of casting steel ingots has advanced to such a point that the casting of steel ingots piped and segregated ought no longer to be tolerated.

Jan 5, 1915

By B. E. Shaw

This paper describes the use of the Free Piston Valve, and a simple hoist brake control system, which has been developed over the last two years, greatly improving the performance of low-pressure brake engines. The basic control system is outlined, with sections devoted to emergency trips and differential braking, and the application of the system to deep shaft hoisting is discussed.

Jan 1, 1966

By Alan B. Richards, Aleks Todoroski

The undesirable effects of blasting fumes can be controlled by minimising the amount of fume created, and by avoiding the movement of the fume plume to sensitive locations. Substantial progress has been made by the blasting industry to reduce the amount of fume typically created by blasting, but at this time no specific blast can be guaranteed to be ‘fume free’.

Jan 1, 2017

By Ernest L. Corp

First in a projected series on the use of flexible liners for support of underground mine openings, this report presents information obtained from an extensive review of the literature on this subject. It also includes results of some preliminary test work by the Bureau of Mines. Investigations thus far indicate that flexible liners offer numerous advantages over rigid-type sup-ports, By deforming in the direction of the applied stress, the stresses are redistributed from the liner to the surrounding material. The corresponding buildup of passive resistance in the direction of diametric extension causes an equalization of stresses around the liner, thereby enabling the liner to carry loads in a more efficient manner. However, additional experimental data are needed to establish design criteria that will permit maximum utilization of the flexible liner concept in mining. Testing of small-scale models, accompanied by measurement of free-field stresses in material surrounding the model, is recommended as the most suit-able approach to the problem. The experimental procedures necessary to such an approach are outlined in detail and a statistical design for the experiments is proposed. The report also describes a device developed by the Bureau for measuring free-field soil pressures to 1,000 psi and a technique for evaluating the response of the device.

Jan 1, 1967

By Yimin Zhu, Dezhou Wei, Haijun Liang, Zhifu Zhou

It has been fairly well established by many experiments that Thiobacillus ferrooxidans (T. ferrooxidans), also named Acidithiobacillus ferrooxidans(Kelly and Wood, 2000),can depress the floatability of pyrite. However, the mechanisms governing the process have not been known completely. In the present investigation, wettability and electrokinetic studies were carried out to examine the surface chemical changes on pyrite before and after interaction with T. ferrooxidans or its secretions. Attachment of T. ferrooxidans to pyrite was observed using a scanning electron microscope. The results of experiments showed that, under certain conditions, T. ferrooxidans and its secretions would obviously change the surface electricity of pyrite and result in the iso-electric point of pyrite shifting notably. However, the surface wettability of pyrite hardly changed and its hydrophobicity increased little after interaction with T. ferrooxidans and its secretions. Based on the results of the present investigation it can be reasoned that the depression of floatability of pyrite is due to the reduction of surface free energy, rather than the increase of surface hydrophilicity of pyrite. The decrease of surface free energy weakens the attachment of collector to pyrite; during the process bacterial protein plays the most important role and the bacterial chemotaxis strengthens the effect.

Jan 1, 2003

By S. Veeramasuneni

The sign of the surface charge for alkali halides in their saturated brines has been established from non equilibrium electrophoresis measurements and on this basis the flotation response of alkali halides was explained based on the adsorption of oppositely charged collector colloids by heterocoagulation. These surface charge results for alkali halides are generally as expected from simplified lattice ion hydration theory with some exceptions, specifically LiF, KCI, NaCl, KBr, RbBr, KI, and Rbl .The presence of natural oxygen defect states in the crystal lattice and the inaccuracies involved in the gaseous ion hydration free energy values used appear, in past, to be responsible for these deviations. The presence of natural oxygen defect states in KCI, KBr, RbBr, and Rbl as characterized by UV Nis absorption, was found to account for their anomalous surface charge. Further, other positively charged alkali halides, LiF, NaCl and KI, were found to be free of oxygen defect states. Nevertheless, oxygen defects can be created in these alkali halides to make them negatively charged and has been demonstrated for NaCl. Such negatively charged NaCl can be readily floated with positively charged amine collector colloids thus confirming the surface charge/collector colloid adsorption theory.

Jan 1, 1996

By D. M. Thayer

Laboratory and pilot plant investigations have indicated that copper recoveries of 50% can be achieved with fine grinding and flotation of a copper reverberatory furnace slag, Microscopic and microprobe studies indicate that the recoverable copper is in the form of matte, chalcocite, and metallic copper; the percentage of copper in particles appearing to be copper-free was from 0.23 - 0.54%.

Jan 1, 1969

By M. R. Geer

The ever-increasing need to guard against stream pollution has intensified interest in the problems of handling and disposing of flotation tailing. Therefore, the Bureau of Mines investigated the possibility of using crushed washery refuse to adsorb the free water in thickened flotation tailings on a bench scale and then in a pilot plant because the conventional methods of disposing of coal flotation tailings--impounding them or filtering them so they are dry enough to be conveyed to the refuse dump--are sometimes either impractical because of space limitations or costly because of low filter capacity. Most of the refuse samples tested were of similar mineralogical composition and exhibited similar water retention capability. The amount of crushed refuse required to adsorb the water in a particular tailing was influenced greatly by the fineness of the solids in the tailing and hence the percentage of solids to which it could be thickened. The ratio of crushed refuse to tailing solids required to provide a mixture dry enough to be carried on an inclined conveyor belt varied from 2.4 to 6.4. Several chemical agents that were tested were very effective in turning the free water in tailings into a stable gel. Fly ash also was very effective in adsorbing water.

Jan 1, 1968

By A. S. Usrnani

Due to both turbulence and the highly variable geometry of castings, a realistic numerical simulation of the metal flow is prohibitvely expensive with current technology. However, when the chief purpose is to achieve realistic thermal fields a precise How simulation is not necessarily required. In this paper we assume a laminar flow regime and obtain the flow field by solving the incompressible Navier-Stokes Equations using a velocity-pressure segregated semi-implicit finite element method. The free metal surface is predicted by advecting a pseudo-concentration function via the computed How field. This involves an explicit finite element solution of a pure advection equation. The thermal field is calculated by solving the convective-diffusive energy equation by an explicit finite element method using the computed flow field and the location of the free surface. All the advection terms are discretized using a Taylor-Galerkin method. The interface between the metal and mould is modelled using special interface elements. The model is demonstrated by solving practical example problems. The results show that a sharp thermal front is maintained during the course of filling without excessive diffusion. The heat diffusion in the mould can be controlled by varying the metal mould heat transfer coefficient.

Jan 1, 1994

By C. B. Manula

This report is volume 7 of an eleven-volume final report for a Grant completed by The Pennsylvania State University for the Bureau of Mines to develop a dynamic general purpose computer simulation model for underground coal mining. The simulator developed under the Grant has a wide range of possible applications in the design and evaluation of underground coal mining systems from the standpoints of health and safety, productivity, and mine environment. The Master Design Simulator consists of nine free-standing function-oriented subsystem models linked together into an integrated, comprehensive model of an entire mining system. The subsystems comprising the Master Design. Simulator include geology and reserves, methane generation, roof support, subsidence, production, rail haulage, cost, water generation," and ventilation. This volume of the final report describes the Rail Haulage subsystem of the Master Design Simulator. This subsystem can be used as a free standing model or can be linked to the Production subsystem to provide rail haulage capability. Complex rail haulage systems can be realistically simulated with this model. This report includes complete instructions for operating the subsystem as well as a program listing. In addition, a case study is included which illustrates the application of the subsystem when linked to the production subsystem.

Jan 1, 1974

By R. V. Lundquist

Lime-soda sinters, made and processed for recovering alumina and soda, consisted of several types of compound structures differing from the ideal dicalcium silicate and sodium aluminate. Many or these compound structures were causes for low alumina recovery and contributed to the relation or leach slurries. Presence or free lime, whether in the sinter or released by hydrolysis of sinter compounds, contributed to relation of leach slurries. Free lime tends to establish the initial viscosity assumed by a leach slurry. Previous investigations by the Bureau of Mines (1, 4)4/ and by other laboratories (5) have demonstrated the technical applicability of the lime-soda sinter process to the recovery of alumina from aluminum silicate materials. The basic concept of the process is sintering aluminum silicate materials with limestone and soda ash for the production of dicalcium silicate and sodium aluminate and then extracting the sodium aluminate by leaching the sinter in causticized liquors. Alumina is precipitated from the pregnant liquors by carbonating with carbon dioxide. Reaction in the sintering operation may be represented by the following simplified equation: A1203?SiO + 2CaCO3 + Na2C03 = 2Ca0?SiO + Na20?Al203 + 3C02

Jan 1, 1960

By A. J. Forney

This report summarizes the findings of methods of treating caking coals in a fluid bed to destroy their caking properties. In batch tests it was found that several coals, including those with a free-swelling index greater than 8, could be decaed at temperatures from 400° to 425° C with a fluidizing gas composed of inert gas or steam containing 0.2 percent oxygen and a minimum residence LS,-;,' of 5 minutes. When treatment decreased the free-swelling index from about 8 to 1-1/2 or lower, the resulting treated coal was noncaking. In a continuous unit with continuous feed and discharge of coal, slightly more severe conditions were required to decake the coal. For 18- to 100-mesh coal a temperature of 430° to 440° C and an oxygen-to coal ratio of 0.4 cubic foot of oxygen per pound of coal feed was necessary. Finer mesh sizes required lower oxygen-to-coal ratios. In tests using air only as the fluidizing medium and treatment temperatures well below the softening range, the caking properties of 150- to 200-mesh coal were destroyed in 30 to 40 minutes of residence time at 200° C. Coarser sizes of 18 to 48, 48 to 100, and 100 to 150 mesh required longer residence time.

Jan 1, 1966

By K. L. Ludeke

For many reasons it appears that deep-rooted, perennial shrubs offer potential for improved stabilization and provide maintenance-free vegetative cover to harsh sites where perennial grasses have not been successful. The very fact that a drought-adapted shrub has a massive root system that can use moisture from a greater volume of mineral waste soil materials suggests that long-range arid environment resource development may be greatly enhanced by utilization of desirable forage shrubs. An effort is underway to assemble information and plant materials of promising species from many arid regions of the world. Surprisingly, many of the better plants for arid sites are quite high in protein content, and with proper management, breeding, and selection may prove to be very desirable livestock feed. Advancements in arid-land solid waste stabilization hold favorable promise for many industries that mine and mill in arid regions for effective reclamation of disturbed areas. Particularly exciting is the possibility of establishment of high density maintenance-free vegetative cover of climax vegetation that reclaims the disturbed area back to its original land use. Because of high shrub productivity, stabilization potential, nutritional quality, and reclamation success, greater use should be made of shrubs in disturbed land reclamation associated with mining and milling operations in harsh arid environments.

Jan 1, 1984

By Linge H. G

The effect of sodium pyrophosphate and several polyacrylate deflocculants (Freevis 502, 528, 529 and 532; and Maxfloc 1015) on the gold loading on Calgon GRC22 and Norit R035l5 carbons was tested and found to be insignificant in a pulp free enviroument. These deflocculants can therefore be used in plants processing viscous gold pulps without fear of fouling the carbon.

Jan 1, 1990

G. K. BURGESS, ? Washington, D. C.-At the Bureau of Standards it was decided, in order to study the high-aluminum end of these curves, that efforts should be made to prepare pure aluminum, and the promise of getting aluminum, practically free from the two elements that have such great effect in very small quantities, namely, silicon and iron, and which

Jan 12, 1919

By M. Manrique, S. A. Pirzada, P. R. Taylor

A thermal plasma-assisted laminar flow reactor was used to evaluate the kinetics of converting alumina to sodium aluminate in flight. Free energy minimization calculations were used to determine experimental conditions. The experimental variables included alumina particle size, alumina/sodium nitrate molar ratio, temperature and residence time. A mathematical model for the conversion was developed and validated. Experimental and mathematical results are presented.

Jan 1, 1998

The materials used for pump construction vary according to the nature of the solution handled. The pump materials in use are the result of extended experiment and are all giving satisfactory results. Research is still in progress, particularly with stainless steel and rubber lining, both of which show considerable promise. Following are the materials used: For tank-room acid, carrying about 100 grams per liter free sulphuric acid, hard lead is used. Stainless steel is under investigation. Duriron is satisfactory, but requires very careful handling to prevent mechanical breakage. For pulps containing low acid (10 grams per liter), abrasive solids, ferric iron, copper, etc. pumps are made of hard lead. Stainless steel is satisfactory. For pulps containing no acid but carrying abrasive materials and copper, bronze is used. Pulps containing acid (10 grams per liter), copper, iron and nonabra-sive solids require lead pumps. Rubber linings are under investigation. Clear neutral solutions containing copper are handled in bronze pumps; neutral solutions free of copper, acid, abrasive material, etc., in iron or bronze. The hard lead used contains 13 per cent antimony. The stainless steel has the following analysis: Cr, 20.0 per cent; Ni, 7.0; C, 0.25; W, 4.0; Cu, 2.0.

Jan 1, 1937

Arkansas Geological Survey, Rooms 443-447 State Capitol, Little Rock, Ark George C Branner, State Geologist A list of available publications will be sent upon request Publications issued by the U. S Bureau of Mines, U S Geological Survey and Oklahoma Geological Survey, pertaining to' Arkansas, are also available through this Survey office. Annual Reports may be had for the following years. 1890, 3147, 1891, 81 35; 1892, $1 10 Other available publications: The slates of Arkansas, by A H. Purdue, with a bibliography of the geology of Arkansas by John C Branner (1909), $1.10, Coal mining in Arkansas, pt 1, by A A Steel (1910), 3175, An outline of the physical features of Arkansas, by George C Branner (1927), free, An outline of the metallic minerals of Arkansas, by George C Branner, free, Bulletin 3, The geology of the Arkansas Paleozoic Area, by Carey Croneis (1930), $3 20, Bulletin 4, St Peter and older Ordovician sandstones of northern Arkansas, by A W Giles (1930), $1 95, Bulletin 5, A geomagnetic survey of the bauxite region of Arkansas, by Noel H Stearn (1930), 80 cents, Information Circular 1, A barite deposit in Hot Spring County, by B Parks and George C Branner (1932), $1, Information Circular 2,

Jan 1, 1933