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By F. V. Lenel

Two years ago in Chicago a seminar was held on the theory of sintering of pure metal powders. As an introduction to this seminar D,.. Rhines1 gave an excellent survey of the literature on this subject, His method of presentatioll was to summarize the experimental observations on sintering and from them to develop a composite theory of sintering in which he combined all the important contributions to the theory into one organic whole. In contrast to the mechanism of sintering of pure metal powders, which, of course, al\vays takes place in the solid phase, sintering j,, the presence of a liquid phase, cannot be treated as one unified mechanism, such as the sintering mechanism of pure metals. The reason is that there are really several mechanisms depending upon the type of alloy system which is sintered and the field of its con. stitutional diagram ill which the sintering takes place, Two mechanisms have heen investigated and will be reviewed in this paper. Ill the first lnechanism the liquid is presellt during the entire time while the compacts are at the sintering temperature, In other words they are sintered between the liquidus and the solidus of the alloy system and are ~e~erogelleous during the entire sintering cycle. The second mechallism applies to alloys in which the liquid phase is formed during the sintering process, but disappears before the sintering process is completed through diffusion and formation of a solid solution. These alloys are therefore homogeneous at the end of the sintering cycle. This second mechanism is more complicated because of the two stages of sintering, the liquid and the solid, as they may be called. It is therefore not surprising that the few detailed investigations of sintering in the presence of a liquid phase have been concerned with heterogeneous sintered alloys, namely the tungsten-nickel-sinter ing which is the so-called "heavy alloy," and the cemented carbides. The mechanism of sintering of these systems is characterized by the fact that theoretical or near theoretical density is attained during sintering, while simultaneously a distinct grain growth takes place through solution of the smallest grains of the solid phase in the liquid phase and reprecipitation on the larger grains. In the first part of the survey this sintering mechanism which is called for short the heavy alloy mechanism is treated in detail. In the second part Of the survey experimental observations for the sintering of homogeneous sintered alloys where the liquid phase disappears before the completion of sintering are discussed. Much less systematic work has been done on these alloys to which the conlmercially important Porous bronzes and the iron-nickel-aluminum permanent magnet alloys belong. Emphasis will be laid throughout this survey upon the microstructural and density changes during sintcring because the Sintering mechanism can usually be described directly by these changes. Other

Jan 1, 1949

By Harvey P. Knudsen, Young C. Kim

This paper illustrates the application of geostatistics to a roll front type uranium deposit located in Wyoming. The steps involved in calculation of experimental variograms, variogram modeling, and verification of the resulting models are described in detail. The resulting spherical variogram models for grade thickness and thickness show strong geometrical anisotropies. The major axis of anisotropy for both variables is approximately parallel to the axis of the roll front and the minor axis perpendicular to the roll. This model confirms the technique of drilling "fences" across the roll front, where the drilling is much closer together than the fences along the roll.

Jan 8, 1979

By W. W. Odell

Once it was believed that anthracite or coke were the only fuels generally available and suitable for the generation of water gas, particularly so when this gas was made in the generators of standard carburetted water-gas sets such as are commonly used in the manufacture of city gas. During the past 8 years, practice has changed considerably and it is now common to find gas plants operating without anthracite or coke and using bituminous coal in the generator. This change in fuel has appreciably increased the marketability and sales of certain coal producers' products; accordingly it is of interest to coal operators and others to know the reason for this change, the present trend in practice and the adaptability of various coals for generation of water gas. This paper briefly discusses these conditions and some of the factors relating thereto. Bituminous Coal not Ideal but Cheaper than Coke In spite of many changes which have been made in both process and generating apparatus for using bituminous coal as generator fuel more efficiently, in general it is not an ideal fuel for this purpose. It is supplanting coke because it costs less; it is so much cheaper per ton delivered at the gas works that water gas made therefrom costs less per unit-volume than that made from coke, even though the quantity of generator fuel consumed per therm (100,000 B. t. u.) of gas made is greater with coal. This is the reason why so many city gas plants, as well as others, are using bituminous coal instead of coke. Conditions Favoring Change from Coke to Coal The conditions which have made it possible and feasible, as well as economical, to supplant coke with coal may be summarized as follows: (1) Changes in methods of operating and alteration in generating apparatus; (2) lowering of the calorific standards for city gas, and (3) availability

Jan 1, 1927

By William P. Kimball, Morris Cohen

This paper deals with the calculation of the composition of the infinitesimal trace of alloy that transfers from the liquid to the solid state at each temperature during the equilibrium solidification of a binary solid solution, and which thereby enables the compositions of the coexisting liquid and solid phases to follow along the liquidus and solidus lines respectively during the cooling. A general expression for the composition (6) of the liquid-to-solid transfer at each temperature has been derived: d= Zlxl(xl - P) + Zsxs(P - xs)/Zl(xl - P) + Zs(P - xs) [1] where ZL and Zs are the slopes of the liquidus and solidus lines at the given temperature, Xl and 28 are the compositions of the stable liquid and solid phases at the same temperature, and P is the composition of the alloy under consideration. The 6 equation is valid for the process of equilibrium heating as well as cooling, and may be applied to vapor-to-liquid, vapor-to-solid, liquid-to-liquid, and solid- to-solid transfers if the corresponding equilibrium diagrams are known. The d-versus-temperature curves for two alloys P1 and P2 are shown in Fig. I. In each case, the liquid-to-solid transfer has the same composition as the stable solid phase only at the temperature of the beginning of solidification, and has the same composition as the stable liquid phase only at the temperature of the completion of solidification. At each intermediate temperature, the composition of the liquid-to-solid transfer differs by a finite amount from those of the two coexisting phases. Therefore, during equilibrium cooling, the transfers must merge into the solid phase from the liquid without forming a transition phase; otherwise the condition of equilibrium would be violated. At any given temperature during solidification, the composition of the liquid-to-solid

Jan 1, 1941

By E. F. Loiseau

(Read at the Philadelphia Meeting, February, 1878.) UNTIL June, 1868, it had not been attempted, either in this country or abroad, to manufacture by mechanical means, from anthracite coal-dust, artificial fuel for domestic use. Several attempts had been made to utilize coal-waste by converting it into a fuel for manufacturing purposes, but none of the processes were original, and they were merely applications of the well-known European processes and machinery, slightly modified by American ingenuity and mechanical skill. With one exception all those attempts have been failures. The great difficulty in the application of European processes and machinery has always been the limited production, and the excessive cost of the manufactured product, as compared with the cost of mining and preparing the ordinary anthracite coal for the market. The only serious and intelligent attempt to manufacture, on a large scale, artificial fuel for manufacturing purposes, has been made by the Anthracite Fuel Company, whose works are erected at Fort Ewen, near Rondout, New York. This company, organized under the auspices of the Delaware and Hudson Canal Company, had to go through the usual course of difficulties, breakages, and disappointments, which seems to be the lot of every new industry. Thanks, however, to the energy and perseverance of Mr. L. L. Crounsse, a gentleman of means, from Washington, D. C., the enterprise succeeded, and it is to-day established on a permanent basis. In order to increase the production, and to reduce its cost, the Anthracite Fuel Company was compelled to change most of its plant, and to erect more powerful machinery, producing lumps of a larger size, almost twice the size of the lumps made previously by the same company. This increase in the size of the lumps has been resorted to in Europe as well as in this country, in order to increase

Jan 1, 1878

By J. Fred, Johnson

THIS TALK is a digest of some of the information contained in tables, one on practices and one on costs of shaft sinking, in Bulletin 357 of the U. S. Bureau of Mines written by E. D. Gardner, Supervising Engineer of the Bureau at Tucson, and myself. The table of practices contains information on 43 shafts and the table of costs contains information on 25 shafts. These various shafts were sunk between 1917 and 1930 so they may be termed modern practice with costs applicable in the United States, Canada and Mexico. In the compilation of this material the statistics on shafts which were concreted have been eliminated, as these figures were entirely out of line with corresponding figures for timbered shafts. It is my experience that where costs are divided between sinking and concreting the tendency is to load the costs onto the larger item of concreting. Thus a shifting of costs making an addition of 10 per cent in concreting costs may suffice to make a deduction of 40 per cent in sinking costs. Fine work is done (on the books) and everybody is happy. Most shafts are sunk with three shifts of men per day. Each shift consists of men who are miners, muckers, or timbermen, as chance may call for during their shift. Where pumping or high fixed costs do not necessitate three shifts it is cheaper to sink on two shifts. It is desirable for speed and economy in any case to work out a cycle of operations for each 24 hours. In this way men are hired for their ability as machinemen, muckers, or timbermen; they know exactly what to do and there is no passing the buck to the next shift.

Jan 1, 1933

By P. Payson

Intergranular corrosion in corrosion-resistant chromium-nickel steels has been widely discussed in the last few years. So far as the author knows, nothing has been published which definitely shows that this tendency can be eliminated, although suggestions have been made that a remedy is possible if certain specifications are satisfied. Strauss, Schottky and Hinnüberl suggested an increase in chromium content to an extent that would prevent the impoverishment of chromium on carbide precipitation sufficient to cause impaired corrosion resistance in the matrix. Pilling2 suggested an increase in nickel, so that the stability of the austenite matrix would be increased. Aborn and Bain3 say that "intergranular attack—may be eliminated by preventing carbide precipitation (e. g., by lowering the carbon content or somehow raising its solubility) or by precipitating it permanently under conditions which will not remove chromium from solid solution so drastically at any points." In a later paper Aborn and Bain4 state that many different metallic elements, tungsten, vanadium, copper, aluminum, molybdenum, titanium and zirconium, have been added in small percentages to increase the stability of these alloys, but that it has been reported that according to the copper sulfate test these added elements act only to retard the intergranular corrosion. and that increased nickel and chromium contents have similar effects. Newell5 showed that the lower the quenching temperature before reheating, the less severe was the intergranular attack.

Jan 1, 1932

By A. C. Richardson

Troughs or launders are probably the oldest machines used for ore concentration, and their development was suggested no doubt by the natural segregation and stratification of materials that take place in the bed of a stream. Trough washers for coal cleaning were first used in France and Germany about one hundred years ago and have been used in some form or other ever since. The early launders were intermittent or batch machines, and only comparatively recent developments have made them continuous. The chief disadvantage of early launder systems as applied to coal has been that when a satisfactorily clean coal was produced the loss of good coal in the refuse was excessive. Other disadvantages have been the large quantities of water and the great lengths of troughs necessary to treat moderate tonnages of feed. One of the most widely used types of trough washers is the Rheolaveur, which has been developed in the last 25 years. Fig. 1 shows a more or less standard arrangement for fine coal. In this there are four trouglis placed one below the other and sloped a few degrees from the horizontal. Rheo-boxes or draws are provided at intervals in the bottom of the trough for the removal of material deposited from the stream. These draws are spaced substantial distances apart. Some of the rheo-boxes are provided with upward currents of water to modify the horizontal current stratification. In operation it is the function of the first two troughs to remove all refuse material and permit only clean coal to be discharged over the end. In order to accomplish this, large quantities of coal are drawn through the rheo-boxes. The third and fourth troughs are used to recover the coal discharged through the boxes of the first two troughs as a middling product and to discharge a clean refuse. The middlings are returned to the first launder and are usually about equal to 40 per cent of the raw coal being fed to the launder. In considering launder processes, one would reason that the conditions of extreme crowding under which stratification takes place in a flowing stream should effect complete separation in a single pass down a launder.

Jan 1, 1938

By G. Abowitz, R. B. Gordon

The velocity of sound, mass density, and thermal expansion coefficient were measured in dilute lead, tin, zinc, bismuth, cadmium, indium, and potassium amalgams as a function of composition. Measurements in the Hg-TI system extended ovev the wider range of composition, 0 to 40 at. pct TI. The sonic velocity was measured as a function of temperature. The calculuted adiabatic compressibility in all cases was found to decrease much more rapidly than would be expected on the basis of a linear variation with composition. An interpretation of the results is given in terms of changes in the Debye characteris -tic temperature of mercury on alloying and a possible change in the bonding of mercury itself. If a liquid is considered as an isotropic elastic medium, the phase velocity of a longitudinal elastic wave traveling in the liquid is given by where K is the bulk modulus, G the shear modulus, and d the mass density. G can be neglected for liquids of ordinary viscosity, i.e., approximately 1CT2 poise, because the shear stress component is relaxed essentially at once. That is, for liquids of ordinary viscosity and at frequencies of the applied stress up to several hundred megacycles, the relaxation time of the shearing process is much shorter than the period of the applied stress. Eq. [I] then reduces to The adiabatic rather than the isothermal compressibility is measured at the megacycle frequencies used in ordinary ultrasonic velocity measurements. The sonic velocity and compressibility have been determined for many organic liquids and aqueous eletroltes,' and the results have been interpreted in terms of existing theories for these fluids. The velocity of sound and compressibility are important parameters in theories of the liquid state. For example, equations of state have been proposed relating the free volume of liquids to the acoustic velocity.3 Comparatively very little work has been done on the acoustic properties of liquid metals and alloys. leppa,' orddon, and several other investigators

Jan 1, 1963

By Woolf, W. G.

Filtration of hot (60°C) supersaturated zinc sulphate solution (sp gr 1.540) from slimy leach residues at the electrolytic zinc plant of Sullivan Mining Co., Kellogg, Idaho, is de- scribed. Separation of liquids and solids in the finished leach is by Burt filters modified to meet conditions of high-acid, high-density process for electrolytic zinc. Operating characteristics of the Burt filter on this pulp are presented.

Jan 1, 1950

By Michael Tenenbaum, C. C. Brown

IN recent years, the importance of slag control in basic open-hearth operations has been universally recognized. To effect such control during the working period of the heat, methods have been developed to measure or estimate slag oxidation and slag basicity. While satisfactory rapid chemical methods have been developed to determine slag oxidation, no completely adequate method of evaluating basicity has yet been provided. The most generally accepted control methods of measuring slag basicity are based on visual estimates. While considerable benefit may be derived from such estimates, the need for some measurable indication of slag basicity has become increasingly apparent. In a recent paper, Philbrook and Jolly[$] suggested a promising technique for making the basicity determination. Their method consists of measuring the pH of a mixture of powdered open-hearth slag and distilled water. It was found that a relation could be established between the slag basicity and the alkalinity of the water mixture as measured by the hydrogen-ion concentration. The general procedure followed in making the measurements and the considerations involved in constructing the original curves are given in the paper of Philbrook and jolly and need not be repeated. It is the purpose of this paper to discuss some of the factors considered in applying the pH measurements to actual slag control and to present some of the results of its application. FACTORS INVOLVED IN MEASURING pH OF WATER-SLAG MIXTURES To facilitate the application of the pH control system, it was desirable that no alteration be made in the routine methods of sampling and crushing the furnace slag. Some of the factors considered before establishing a curve to relate slag basicity with the pH reading are reviewed individually in the following paragraphs. EFFECT OF COOLING RATE Under actual operating conditions there can be considerable variation in the tem¬perature of the piece of slag crushed for the pH determination. To determine whether variations in crushing temperature or in cooling rate would affect the pH reading, a series of four samples was prepared from each of two separate slags. These samples represented conditions far more extreme than would actually be encountered. To obtain these samples, a thick pancake of slag was poured. One piece of this pancake was crushed immediately after it had solidified. Another piece was water-quenched and then crushed. A third piece was allowed to air-cool to room temperature before crushing. The fourth sample was prepared from a chilled slag. This sample was poured onto a heavy inclined steel plate at the

Jan 1, 1945

By Stefan S. Kapusniak, Nichol Riggott, Stephen F. Smith

Stability investigations have been carried out in a number of major coal mining tunnels in the U.K. using various instrumentatcon techniques. The paper describes these instrumentation methods and presents results from studies in several tunnels. Both long and short term stability aspects are discussed. Prediction of tunnel stability is examined in relation to tunnel support requirements. Computer simulation techniques are used along with actual underground measurements to identify tunnel design parameters for influencing choice of support and prediction of long term stability.

Jan 1, 1984

By J. F. Mahoney, P. B. Hobsbawn, N. Arbiter, C. C. Harris

Current trends in flotation applications are reviewed and effects of increased cell sizes and automation of circuits considered. The role of laboratory and pilot plant investigations in establishing design criteria and project feasibility are assessed and illustrated.

Jan 1, 1978

By J. M. Uys, T. B. King

WalSH, Chipman, King, and rant' have measured the water content (as hydrogen) of actual steel-making slags. An average water content of 290 ppm was found for basic open-hearth tapping slags and 114 ppm for acid open-hearth slags. Upon equilibration of these slags at 1550°C with a 25 pct H20-75 pct Nz atmosphere, the water content increased to about 410 and 300 ppm for the basic and acid slags, respectively. Walsh et al. concluded that an acid slag was thus relatively far removed from equilibrium, and that basic slags showed a closer approach to equilibrium, with the water vapor in the furnace atmosphere. Herasymenko2 contended that these conclusions were unjustified, as the oxygen pressure used in the equilibration experiments, ;bout 5 x X atm, was quite different from that found in the furnace. Consequently, during the experiments the slag composition would have changed due to oxidation of ferrous iron. As an extension of Walsh's work and to attempt to clarify this matter, the solubility of water in a basic open-hearth slag was measured as a function of oxygen pressure. Similar measurements were also made on synthetic silicates in the "Fe0"-Fe203-SiO, system. The experimental technique has been described previously by Walsh et a1.l and Uys and King.3 Samples of the basic open-hearth finishing slag, contained in 10-cc platinum crucibles, were equilibrated at 1550°C with atmospheres of different oxygen pressure but constant water-vapor pressure, Ph~o = 0.192 atm. Calculations, as well as measurements, indicate that this figure approximates the water pressure of the combustion gases in a steam-atomized, oil-fired open hearth. Oxygen pressures in the open hearth can vary from 10"2 atm in the combustion gases to between l0-' and 10" atm in the steel bath. The former figure depends on the combustion practice and the latter on the carbon content and temperature of the bath. The oxygen pressure of the slag should lie somewhere between these extremes and is expected to be closer to that of the steel bath than that of the combustion gases. Oxygen pressures were therefore varied between 10" and 6 x l0 atm. At the lowest pressure the slag "puffed up" when quenched (indicating possible loss of water) so experiments were not conducted at lower oxygen pressures. The results are shown in Fig. 1, which includes the water content of the slag "as sampled". The results show that the water content of the slag increased appreciably on equilibration with water vapor at 0.192 atm pressure and that the water solubility apparently decreases with increased oxygen pressure. The solubilities found are comparable to those of the Li20-Ca0-Si02 system.3 Work with synthetic slags in the "Fe0"-Fe203-SiOz system was performed at 1500" C, with Ph20 = 0.192 atrn and for oxygen pressures varying between 10"2 and 10-lo atm. Samples for chemical analysis were prepared as described by Larson.4 The results are shown in Fig. 2. Some low-silica melts tested at low oxygen pressures "puffed up" when quenched and analyzed less than 100 ppm water; these results are not included in Fig. 2. The melts containing 40 mol pct silica also showed a tendency to "puff up" during the quench, when they were tested at the lowest oxygen pressure. These results indicate that, at constant silica content, the solubility of water decreases somewhat with increased oxygen pressure. The effect is, however, small considering the wide range of oxygen pressures studied. Also, at constant oxygen pressure (above about lom5 atm) the solubility increases

Jan 1, 1963

FINAL REPORT OF' THE COMMITTEE OF THE AMERICAN INSTITUTE OF MINING AND METALLURGICAL ENGINEERS W. E. FOHL, Chairman J. W. PAUL J. M. RAYBURN C. A. WARNER JOHN B. CORRIN C. E. KREBS JOHN H. WILSON A. W. HESSE M. M. LEIGHTON H. I. SMITH [Accepted and Committee discharged with thanks, April 27, 1928.] Regulations recommended for the location, drilling, casing, protection, operation, plugging and filling, and abandonment of natural gas and petroleum wells; having for their objectives the protection of life and property by prevention of intrusions of oil and gas into workable coal beds, and the conservation of oil and gas resources in territory not underlain with workable coal beds. ARTICLE I DEFINITIONS SEC. 1. For the purpose of these regulations, definitions are as follows: Well.-A bore hole drilled for the purpose of developing natural gas or petroleum, or a bore hole producing natural gas or petroleum. Well Operator.-Any person, persons, firm, partnership, corporation, company or association that proposes to, or does drill, operate or abandon a well as herein defined. Coal Operator.-Any person, persons, firm, partnership, corporation, company or association that proposes to, or does operate a coal mine in territory known or reputed to be underlain with oil or gas-bearing strata. Coal Owner.-Any person, persons, firm, partnership, corporation, company or association, other than a Coal Operator as herein defined, that owns coal lands in territory known or reputed to be underlain with oil or gas-bearing strata. State Mining Department.-The duly constituted authorities of a state having jurisdiction over coal-mining operations, and oil and gas operations as herein provided. Plat.-A map, drawing or print made in accordance with the provisions of these regulations. Casing.-The pipe commonly used in wells drilled for natural gas and petroleum. Oil and Gas.-Synonyms, respectively, for Petroleum and Natural Gas.

Jan 1, 1928

By Ernest A. Kaarsberg

This paper presents the results of studies of the elasticity of some isotropic and anisotropic rock samples based on longitudinal- and shear-wave pulse velocity measurements. Experimental evidence from velocity measurements on isotropic steel samples is also presented to show, within error limits, that any two of the elastic constants required to completely describe the elasticity of an isotropic solid can be obtained from any two of the following four velocity measurements: longitudinal "rod,' "plate," extended medium (infinite medium equivalent), or shear wave. Measurements of three of these velocities in an approximately isotropic basaltic rock sample are used to illustrate this application to this type of rock. For the anisotropic study, a suite of Colorado oil shale samples is used. These rocks exhibited transverse isotropy. The five elastic constants required to completely specify this type of anisotropy are obtained from longitudinal- and shear-wave pulse velocity measurements made in directions parallel, perpen-dicular, and at 45° to the bedding plane. Density, velocity, and elastic modulus relationships among these shales are also given. Duvall 1 has described a method for determining the elastic constants of isotropic and, in two cases, anisotropic rock samples. This method is based on ultrasonic pulse techniques and on resonance-frequency measurements of rock samples in the shape of rods (diamond drill cores). Rock samples, however, are not always available in rod form. When this is the case, other methods can be used to study their

Jan 1, 1969

By J. F. Smith

ELASTIC constants of yttrium and eleven of the rare earth elements have been measured. This has been accomplished by measuring the propagation velocities of ultrasonic pulses. The velocity measurements were made by noting the elapsed time between an applied pulse and the appearance of successive echoes. The pulse-echo technique has become relatively common, and the basis of the measurement is outlined in several standard tests, e.g., Heuter and Bolt.1 Two important assumptions are made when using this method for the determination of elastic moduli. First, the pulse is assumed to propagate as a plane wave. To justify this assumption, the cross section of the test specimen should be large compared to the wave length of the transmitted pulse. For these measurements on the rare earth elements the minimum cross section wave length ratio was about 20. A second assumption which must be made when using polycrystalline specimens is that the grains are sufficiently numerous and randomly oriented so that the specimen may be approximated as elasti-cally isotopic. The grain size in the as-cast specimens which were used is believed to be sufficiently fine for this approximation, and the degree of preferred orientation is believed to be small. Supporting this viewpoint is the fact that elasticity measurements by the pulse-echo technique on as-cast specimens of other metals give results which are in satisfactory agreement with values obtained by other techniques. Hence, it is believed that the measured elasticity values for the rare earth elements are not apt to be seriously in error due to the assumption of elastic isotopy. The apparatus used in this determination was a modified Sperry Reflectoscope with a precisely calibrated time base circuit. Piezoelectric transducers were used both to generate the pulse and to detect the echoes. X-cut quartz crystals were used for the longitudinal modes, and Y-cut quartz crystals were used for the shear modes. Frequencies of 2.25 and 5 megacycles per sec were employed. Most of the specimens were 2.5 to 5.0 cm in length. Results Table I is a tabulation of the measured propagation velocities of longitudinal waves and of shear waves, together with densities obtained by Sped- ding, Daane, and Herrmann2 from lattice parameter measurements. The shear modulus, Poisson's ratio, and Young's modulus were calculated from the data in Table I through use of the following relationships: µ = pv32 [1] s=2-(vb/vs)2/2[1-(vb/vs)2] [2] and Y= 2µ(l+s) [3] where s is the shear modulus, Y is the Young's modulus, s is Poisson's ratio, p is the density, V0 is the longitudinal wave velocity, and v, is the shear wave velocity. The calculated quantities are shown in Table 11. Compressibility values can be computed from the relationship and the computed values may be compared with measured values obtained by Bridgman.8 Table III lists the data for such a comparison. The agreement is satisfactory, being particularly good for neodymi- um and gadolinium, poor for samarium, and intermediate for the other elements. Some variation is expected since Bridgman's measurements are isothermal, whereas the present measurements are adiabatic. In addition there may be some effect due to small variations in purity. Though most of the rare earth metals measured by Bridgman and all of the metals used in the present measurements were prepared at this laboratory, minor purity variations might exist since the samples came from different lots. Also, any imperfections such as dislocations, vacancies, voids, grain boundaries, microcracks, etc., should contribute to the volume change of a com-

Jan 1, 1958

By G. Stuart Jenkins

Conditions at the properties of the Consolidated Coal Co. had reached a point where improvements were almost impractical. The mines, sunk years ago, had shafts and entries so small as to preclude the use of large mine cars. A radical change was necessary in the type of mining and also in the type of mine to accommodate such haulage units. After due consideration, the company decided to enter the field of trackless mining, utilizing belt conveyors and chain-flight conveyors, the belt conveyors to take the long haul, and the chain-flight conveyors to be used for gathering. It was decided not to sink a shaft, hut to drive a slope on an inclination of 17½°, which the company believes to be about the limit on which coal can be carried on a belt without rolling back unduly. Sinking the Slope It was decided, in sinking the slope, to make an opencut until rock was reached, which was some 65 ft. below the surface, and then to drive the slope through an inclined tunnel from that point. In making the open-cut, the schedule called for the removal of about 25,000 cu. yd. of clay, holding the banks on an inclination of one and a half to one, the thought being to make this cut in a minimum of time, put in a reinforced concrete slope, and then back-fill. Difficulty was experienced because the clay was of a sort that was called "subsiding base" material by contractors visiting the job. In other words, a "squeeze" occurred, the pressure causing the floor of the cut to move up just as it does in many mines where the coal is underlain by thick fire clay and inadequate pillars have been left. It was necessary to move the waste banks back from the edge of the cut 700 or 800 ft., and even then the floor could not be controlled, the result being that almost 100,000 cu. yd. of clay was handled before the rock was reached. A concrete slope was then rapidly constructed, using 95 tons of special-shaped reinforcing iron. The floor of this slope was made 30 in. thick at the bottom, and 17 in. thick at the top, the sidewalls being 18 in.

Jan 1, 1940

By G. S. Hume

The total production of crude oil in Canada showed only a small improvement in 1936 over 1935, but developments of great importance took place in Alberta on the west flank of the Turner Valley field in the foothills southwest of Calgary. These have led to renewed activity in drilling such as has not been experienced for many years, and undoubtedly this will result in a very considerable increase in the oil production during 1937.

Jan 1, 1937

By D. H. Forbes, I. B. Cadoff, H. M. Manasevit

Single-crystal silicon films have been obtained on several natural crystal faces of BeO using the thermal decomposition of silane and the hydrogen reduction of silicon tetrachloride. From an analysis of X-ray diffraction data it was determined that the following film-substrate orientation relationships exist: (111) Si 11(0001) BeO, (111) Si 11(1011) BeO, (100) Si 11f1010) BeO. and (110) Si 11(1010) BeO. An analysis of the crystallographic relationships between the film and substrate indicates that a match occurs between the silicon atoms in the film and the berylliuni ion sites in the substrate. This correspondence is in agreement with previous work on the deposition of silicon on sapphire.1-3 silicon on spinel: and tungsten on sapphire. The high resistivity, thermal conductivity, and radiation resistance of beryllium oxide make it an important substrate material for the deposition of thin films of silicon or other semiconductors. The importance of semiconductor-insulator composites to the field of integrated microelectronics has been well-documented in the case of silicon on sapphire.'-' The successful growth of large-area single-crystal silicon on an insulator, sapphire, was first reported in 1963.1,2 Since that time studies have been made of the crystallographic relationships between the deposited film and the sapphire substrate. On the basis of the observed relationships, a model has been proposed relative to the crystallographic requirements for epitaxy between the semiconductor film and the metal oxide substrate.3 It is proposed in this model that epitaxy is the result of a match between atoms of the deposited film and the metal ion sites of the substrate plane. This match is not limited to a 1 to 1 correspondence between sites in the two lattices. Sub- sequent studies of the deposition of silicon on spinel4 and tungsten on sapphire5 have yielded data which support this model. On the basis of this previous work it was felt that silicon on BeO should also fit this model. In the present study, the choice of substrate orientation was limited to the natural faces of synthetic BeO crystals. Of the faces available, the (0001) plane seemed the most favorable for epitaxial growth. EXPERIMENTAL PROCEDURE Silicon films were deposited from silane and silicon tetrachloride in the apparatus shown in Fig. 1. The hydrogen ambient gas was purified by passage either through a DEOXO unit, molecular sieves, and a liquid nitrogen cold trap, or through a heated Pd-Ag thimble. The gas was then mixed with the silicon source materiai and passed over the substrate which lies on a spacer above an inductively heated silicon pedestal. The following deposition conditions were used: a hydrogen flow rate of 3 liters per min with silane and silicon tetrachloride concentrations of 0.2 mole pct and a pedestal temperature of 1175" * 5°C as observed with an optical pyrometer assuming an emissivity of 1.0. Deposition was preceded by a 15- to 30-min hydrogen-etch period conducted at a temperature of 1275°C (obs). Adherent silicon films from 2 to 10 u were grown on the various BeO faces. The substrates were synthetically grown beryllium oxide single crystals ranging from 5 to 10 mm in

Jan 1, 1967