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By F. McIntosh Galbraith

This paper describes the use of the magnetometer, under geological direction, in exploration of the Sudbury nickel district. The writer's experience at Falconbridge has led him to the belief that only through detailed work, and by careful correlation of both geological and geophysical results, can geophysical prospecting methods be applied successfully to mining exploration problems. It is hoped that the basic technique described in the paper will be found to have general application. Introduction Within the past 20 years, geophysical methods of prospecting have become solidly established in the field of petroleum exploration. They have not, however, been similarly adopted by the mining industry, although mining is a far older craft and should be the more advanced in its technique. While, therefore, it is almost a routine matter to have geophysical surveys performed in a new area being tested for oil, a new metal-mining district is usually teeming with prospectors and promoters long before the technical man appears on the scene. Even then, only the more primitive engineering methods are customary in the early stages of exploration. Three factors are chiefly responsible for this situation, The first is the difference between oil pools and ore deposits in their geological modes of occurrence. While most of the known metallic ore bodies have been found outcropping at the surface, petroleum deposits are characteristically buried. This does not mean that all ore deposits outcrop, but neither does it mean that we should rely on "wildcatting" to discover blind ore bodies. The second factor is the relative scale of metallic lodes and accumulations of petroleum. In areal extent, a metal-bearing vein deposit is typically a much smaller geological feature than an oil pool. Presenting a narrower target, it requires closer shooting to score a direct hit. And finally, there is the need, in mining work, for close correlation of the known local geology with geophysical observations. This becomes of increasing importance as the size of the objective diminishes. A geophysical disturbance on a large enough scale will be detected under almost any circumstances and by almost any technique; without benefit of geology, however, the significance of a local anomaly may easily be misread. Campaign at Sudbury In the Sudbury nickel district of Canada, new deposits of nickel and copper have been discovered recently by magnetic methods, under geological supervision. A campaign of exploration, designed to encompass the district eventually, was set in motion in the spring of 1935. After six years, a new and important Ore body has been discovered and its continuity established to 1000 ft. in depth; several areas have been eliminated; and a number of possibilities remain to be tested. This has been accomplished with the expenditure of less than $$I50,000-—including the cost of all diamond drilling. The responsibility for carrying out this campaign was entrusted by the company to its Geological Department, and the under

Jan 1, 1946

By J. R. Thoenen, M. C. Malamphy, G. K. Dale

THE beginning of the war and the events leading up to it precipitated a near crisis in the aluminum industry. Demands for the metal reached proportions far beyond the prewar production capacities and, in addition, the submarine menace seriously curtailed the importation of bauxite from South America, hitherto a chief source of high-grade ore. The situation required an intensive search for domestic ore to augment the reserves and in October 1941 Congress directed the Department of the Interior to investigate the extent, mode of occurrence, and quality of bauxite in the United States. In December of that year the Bureau of Mines and the Geological Survey began the search for bauxite in Arkansas, where more than 90 per cent of the domestic ore had been produced and where the greatest amount of bauxite was known to occur. The program involves the geophysical and geological investigation of the Arkansas bauxite region and the core drilling of areas considered favorable for the occurrence of bauxite deposits. Cores taken from the bauxite-kaolin zone are sampled and analyzed in the Bureau of Mines laboratory in Little Rock. The information from each of the deposits discovered is then assembled, the bauxite is graded with respect to its possible utility, tonnage estimates are made, and the whole is presented in the form of a war minerals report. Thirty-eight new bauxite deposits had been discovered and investigated at the end of the calendar year 1944, and the presence of several others had been indicated by the drilling. More than 5000 holes had been drilled throughout the bauxite region, and more than 60,000 chemical analyses had been made of samples taken from the bauxite-kaolin zone. A study of the chemical analyses led to certain general conclusions not only with regard to the chemical composition of Arkansas bauxite, but also with regard to its component minerals. Charts and diagrams based on these conclusions have been developed for practical use by the Bureau of Mines: (I) to serve as a check against laboratory analyses, (2) to present tonnage estimates of ore bodies based on mineral composition, (3) to illustrate the relationship of tonnages of bauxite to the alumina, silica, and iron content, and (4) to serve as a control for mining operations by providing a means for quick estimates of the value of the ore from a partial analysis of its chemical constituents. The use of charts and diagrams similar to those discussed in this paper is not new. The use of the trilinear diagram for studying the ultimate analyses of coals as originally proposed by Ralston in Bureau of Mines Technical Paper 93 (1915) showed that the various ranks of coal fell in different areas on the diagram and that volatile matter, calorific value and other properties could also be plotted by the use of contours. A considerable subsequent literature, largely on classification of coals, has accumulated since then, showing the utility

Jan 1, 1945

By F. McIntosh Galbraith

This paper describes the use of the magnetometer, under geological direction, in exploration of the Sudbury nickel district. The writer's experience at Falconbridge has led him to the belief that only through detailed work, and by careful correlation of both geological and geophysical results, can geophysical prospecting methods be applied successfully to mining exploration problems. It is hoped that the basic technique described in the paper will be found to have general application. Introduction Within the past 20 years, geophysical methods of prospecting have become solidly established in the field of petroleum exploration. They have not, however, been similarly adopted by the mining industry, although mining is a far older craft and should be the more advanced in its technique. While, therefore, it is almost a routine matter to have geophysical surveys performed in a new area being tested for oil, a new metal-mining district is usually teeming with prospectors and promoters long before the technical man appears on the scene. Even then, only the more primitive engineering methods are customary in the early stages of exploration. Three factors are chiefly responsible for this situation, The first is the difference between oil pools and ore deposits in their geological modes of occurrence. While most of the known metallic ore bodies have been found outcropping at the surface, petroleum deposits are characteristically buried. This does not mean that all ore deposits outcrop, but neither does it mean that we should rely on "wildcatting" to discover blind ore bodies. The second factor is the relative scale of metallic lodes and accumulations of petroleum. In areal extent, a metal-bearing vein deposit is typically a much smaller geological feature than an oil pool. Presenting a narrower target, it requires closer shooting to score a direct hit. And finally, there is the need, in mining work, for close correlation of the known local geology with geophysical observations. This becomes of increasing importance as the size of the objective diminishes. A geophysical disturbance on a large enough scale will be detected under almost any circumstances and by almost any technique; without benefit of geology, however, the significance of a local anomaly may easily be misread. Campaign at Sudbury In the Sudbury nickel district of Canada, new deposits of nickel and copper have been discovered recently by magnetic methods, under geological supervision. A campaign of exploration, designed to encompass the district eventually, was set in motion in the spring of 1935. After six years, a new and important Ore body has been discovered and its continuity established to 1000 ft. in depth; several areas have been eliminated; and a number of possibilities remain to be tested. This has been accomplished with the expenditure of less than $$I50,000-—including the cost of all diamond drilling. The responsibility for carrying out this campaign was entrusted by the company to its Geological Department, and the under

Jan 1, 1946

By P. R. Kalischer

In the production of alloys by powder metallurgical processes it is often necessary or desirable to include one or more cornponents that tend to form very stable oxides. Included in this group of metals are aluminum, manganese, magnesium, silicon, and a few others. In many cases it is not necessary for the sintered compact to have full density and the other physical characteristics of a cast alloy and in that event no undue precautions need be taken. If, however, it is required that the sintered part be entirely homogeneous, and have maximum density and physical properties, some method must be found to reduce the surface films of oxide, which are always present on the metals, and for the metals mentioned above this is always extremely difficult, if not impossible. since the production of high-density alloys is of particular interest to powder metallurgists, some experiments were undertaken to devise methods of reducing the refractory oxides. For this work, alloys of iron, nickel, and aluminum were chosen because aluminum oxide is one of the most stable oxides and because these alloys in the right compositions form excellent permanent magnets. All of the pertinent properties of the magnets could be accurately and delicately measured by density measuremerits and magnetic tests of sufficient scope to give a complete demagnetization curve. From such a curve the maximum coercive force, residual magnetism, and energy products could be obtained and compared with the same properties for a cast material. Any lack of homogeneity, density, or solid diffusion would be immediately apparent as a decrease in the magnetic properties. Nature and Removal of Surface Barriers The early work of the present investigation was based upon published processes.* In the published information it was claimed that by intimately mixing iron, nickel, and iron-aluminum alloy (50 Per cent Fe, So Per cent Al) powders, compressing such a mixture into the desired shape and size, and then sintering (heating to a temperature below the melting point of the component metals) in hydrogen at 1200°C. or higher, a sound, homogeneous article could be made having the desired physical size, shape, and strength, and good magnetic characteristics. However. this early work showed clearly that something in the powder compress was inhibiting diffusion and the process was almost entirely unworkable. In the initial phase of the investigation samples of iron powder, nickel powder, and iron-aluminum alloy powder were pressed into separate bars and sintered in hydrogen. Both the iron and nickel powders sintered

Jan 1, 1941

By Warren E. Wilson

PRESENT-DAY design of launders is essentially an art depending to a marked degree upon the experience of the designer, whose problem is that of determining the dimensions of a conduit that will transport the pulp within the physical limitations of the plant and in the most economical manner. This paper has been prepared in an effort to place launder design upon a more scientific basis. A method is developed from elementary principles and presented in a form that may be used directly by the designer in determining launder dimensions.. The equations that are developed are believed to represent an advance over older ones, in that they give due consideration to all the pertinent variables, either including them in the analysis or showing that they may be neglected within the limits of applicability of the equations. Experimental data from several sources are used in evaluating the coefficients that are not determined in the mathematical analysis. On the basis of the material presented, it is concluded that launders may be designed with a much greater degree of accuracy than previously believed possible, when due consideration is given to all the factors involved in the problem. However, a great deal of work still remains to be done in the laboratory before a complete answer to all the questions in launder design can be made available. HISTORY OF LAUNDER DESIGN Among the references1-11 are cited accounts of many experiments that have been conducted in an effort to advance the knowledge of the flow of liquid-solid mixtures in flumes and pipes. With three notable exceptions, this work was carried on in such a manner that the results have limited value in solving the general problem, since not all the pertinent variables were measured and controlled. The exceptions are found in the works of Blue,6 Gilbert,7 and Blatch,11 who exercised great care in controlling and measuring all the significant quantities involved in the experimentation. It is notable that much of the work done by men directly connected with the mineral industries1-4 lacks somewhat in completeness, owing apparently to preconceived notions concerning the factors that determine the flow. For example, many measurements on flow in pipes and flumes carrying liquid-solid mixtures determined only the slope and percentage of solids, with no mention of size of particles, depth of flow, roughness of channel or specific gravity of solids. Material in current handbooks8,9 and textbooks is based largely on the experimental work cited above. Although most discussions of the topic-include statements that the results to be obtained by using the data presented are limited by the fact that all variables have not been considered, it is

Jan 1, 1943

By d&apos, John C. Entremont

Pure iron was inductively melted in small refractory crucibles and optical pyrometer and immersion thermocouple readings were simultmzeously taken. The resulting emissivities of the liquid iron surface obtained were found to be greatly affected by both the gaseous atmosphere and geometrical changes in the physical setup. Quantitative values for these effects are indicated. FOR many applications in both the laboratory and plant, optical pyrometry is still the best means of measuring temperatures in the incandescent range. A prerequisite in evaluating the correct temperature is a good value of the emissivity of the surface. To obtain the emissivity from the tabulated values of the literature can be very confusing and often far from correct. There are many reasons for these difficulties, and it is not within the scope of this paper either to enumerate or to discuss them all. Its purpose is to show quantitatively how several factors affect the apparent emissivities obtained from experimental measurements on liquid iron surfaces. The black body is the reference state for the quantitative values of emissivities and is defined1 as a body which absorbs all radiation incident on it, reflecting none; such a surface emits more radiation per unit area per unit time than any surface which reflects any radiation, and is given a value of unit emissivity. All bodies having reflective power thus have emissivities less than unity and are considered nonblack or grey bodies. The ratio of the radiant energy emitted by the flat, nonblack surface to that of a perfectly black surface of equal area and temperature is the emissivity of the surface. The above definitions are applied to flat, polished, opaque surfaces, very seldom encountered in actual measurements, and for this reason many authors have suggested that the word "emittance" be used for real bodies rather than emissivity. The emittance has reference to the material and its configuration rather than to its properties in the idealized state. Recent observations of molten iron in a small refractory crucible indicate that not only the configuration of its surface but the geometrical arrangement of its surrounding and the nature of the surrounding atmosphere have a pronounced effect on the emittance. Neglect of changes in such conditions may lead to errors as large as 40°C at 1600°C. Thus it is suggested that the term "apparent emissivity" be used and that it be recognized that its value pertains to a particular experimental arrangement only. As a result of not recognizing these differences in emissivities, which are obtainable from changes in the physical setup of an observation, many investigators have incorrectly quoted their values as those of the emissivities of particular materials rather than as an apparent emissivity for their particular arrangements. As a consequence, values of the emissivity of liquid iron ranging from 0.3 up to 0.55 are found in the literature. In an effort to establish an accurate optical temperature scale for liquid iron solutions in which de-oxidation studies were to be carried out, it was observed that the temperature relationship, obtained by simultaneously taking immersion thermocouple

Jan 1, 1963

By Howard A. Meyerhoff

Nonmetallic rock and mineral products are so diversified that any generalizations regarding the industries based upon them are of doubtful value and can be misleading. They are geared to every phase of the national economy and respond sensitively and immediately to any economic change, but the responses vary with the individual products. They are also affected by political and competitive factors to a degree that is disconcerting and, at times, ruinous to operators, owners, and stockholders of mineral properties. It is not unusual to find these special factors functioning in reverse of general trends insofar as individual products are concerned. As this summary is being written in the final weeks of 1949 production statistics for the year are not complete, but it is obvious that few, if any, new production records will be set, and that 1949 level, will, in general, be lower than those of 1948. The decline in output is not alarming and reflects in large part the tendency of users, who have been finding sources of supply more dependable to rely on prompt deliveries rather than on inventories to meet immediate needs. Except for the government's program of stock piling which, insofar as it has worked at all, is of more direct interest and benefit to foreign than to domestic producers, industrial inventories have been further reduced, and the neater balance between production and consumption has freed capital for the manufacturer and has cut down the serious hazard of substantial inventory losses. There are no quantity products and only a few special products that cannot be supplied in quick response to current demands. Normal development of a few nonmetallic industries has been retarded by the government's unpredictable application and irrational interpretation of antitrust laws, and by extension of preferential tariffs to new countries and new products. Synthesis is likewise a potent threat. in certain fields, but otherwise it is difficult to make a review of 1949 read much differently from a review of 1948. Changes have been qualitative rather than quantitative, except for a few operations that have been pinched out by the relentless competition that characterizes many of the industrial mineral industries.

Jan 1, 1950

By Toshimi Yamane

The internal friction of cold-worked titanium iso-thermally annealed at temperature below the recrystallization temperature was measured. The internal friction was calculated from the half width of a resonance curve of the specimen which was vibrated transversally by the electromagnetic method. The experimental results were as follows: 1) The specimens annealed for a long time at temperature below the re crystallization temperature after cold working have the strain-amplitude dependent internal friction. 2) The internal friction increased by the cold working was decreased during the isothermal annealing. The reason of decrease of the internal friction is considered to be caused by the annihi-lation of lattice defects. 3) There is a linear relation between logQt-1/Q0-1 and (1/T)2/3 below the recrys-tallization temperature, where Q0-1 is the internal friction standing 24 hr at the room temperature after cold rolling, Qt-1 is the internal friction annealed at T°K for t min. 4) The hardness of the cold-worked titanium does not change by the annealing at 300°C for a long time but decreases by annealing at 400ºand 460°C. METALS, when cold worked, show sharp changes in physical and mechanical properties' The internal friction of cold-worked metals increases sharply and has a maximum value1,2 connected with working de- grees. The increased internal friction of cold-worked metals is recovered by annealing. This phenomenon is the well known effect called Köster effect. The recovery of the internal friction occurs earlier than the changes in tensile properties, hardness, or X-ray diffraction, and is very sensitive to the structure of a metal. The mechanism of the recovery at a temperature lower than the recrystallization temperature is being considered variously by many investigators: there are such views as the annihilation of dislocations by smith,' the rearrangement of dislocations mentioned by Nowick,4 and interaction of dislocation with point defects.5 Smith and Nowick also considered the interaction but it is so difficult for them to explain the rearrangement mechanism systematically, it being not considered a special model; therefore, we do not explain it quantitatively. Experiments measuring the recovery of the internal friction of cold-worked metals were performed by Gordon and Nowick6 on NaCl, and by Smith on copper. In addition, there are many studies, particularly those of measurements on copper by other investigators. There are comparatively many investigations on aluminum and iron which are the cubic system,'-' but only a few on metals of the hexagonal system.10 In view of this, I investigated cph titanium at room temperature and measured the internal friction after annealing isothermally at temperature lower than the recrystallization temperature. SAMPLES AND EXPERIMENTAL METHOD samples for the experiment were cut from a 6-mm titanium plate. The long direction of samples was

Jan 1, 1963

By Ken-ichi Hirano, B. L. Averbach, Morris Cohen, N. Ujiiye

The influence of plastic deformation in compression on the self-diffisivity of a iron has been measured in the temperature range of 742º to 885°C. The diffusivity is enhanced in proportion to the strain rate, but this dependence decreases with increasing temperature. The magnitude of the strain is relatively unimportant in this connection. Strain rates from 0 to -2 x 10-3 sec-1 were investigated, with a corresponding increase in diffusivity up to 3 x 103 times. The results are analyzed in terms of vacancy diffusion and the excess vacancies introduced during dejornzntion. It is concluded that grain boundaries are the main vacancy sinks in polycrystalline iron and that the vacancy lifetime is therefore dependent on the grain size. A typical vacancy lifetime at 800°C with a nzean grain-boundary intercept of 0.3 cm is of the order of 1 sec. LATTICE imperfections are considered to be the dominant mechanism of diffusion in close-packed crystals. Vacant lattice sites are usually the most important defect, but the enhancement of diffusion along grain boundaries and other short-circuiting paths has been well documented. Inasmuch as plastic straining produces a variety of defects, it would be expected that the application of stresses sufficient to cause plastic flow during a diffusion run might result in an increase in the self-diffusivity. Enhanced self-diffusion in a iron under compressive creep has been observed by Buffington and Cohen' and subsequent coworkers.2 Lee and Maddin3,4 have also found an enhancement in the self-diffusivity of silver single crystals undergoing torsional deformation. On the other hand, Darby, Tomizuka, and Balluffi5 have not observed any significant diffusion increase in single crystals of silver deformed either in tension or in compression, although the results in this case may have been affected by the occurrence of recrystallization. With poly crystalline silver, however, Forestieri and Girifalco6 have found en- hanced diffusion during compressive creep. A small decrease in the self-diffusivity of zinc single crystals under compressive loading has been reported,7 but the applied stresses in these experiments were too low to cause appreciable plastic deformation. For the cases in which enhanced diffusion has been found, a number of common effects have been noted. Usually, the ratio of the diffusivity during straining, Ds, to the diffusivity in the unstrained condition, D,, varies linearly with the strain rate, and does not seem to be a function of the plastic strain, at least up to ? = 0.2. Values of Ds/Du of the order of 100 have been reported'-4 but the enhancement decreases with increasing diffusion temperature. The activation energy for diffusion decreases markedly with increasing strain rate and approaches a level of roughly one-half the unstrained value. Most of the current explanations of these observations assume that excess vacancies are generated by the deformation, but rather large concentrations of excess vacancies and/or long lifetimes are required by these theories.',',',' Since the original work on iron, there has been an important improvement in the compressive-loading technique.2 The early data were also analyzed without taking into account the motion of the coordinate system in the specimens undergoing plastic deformation. This problem has now been solved by a number of investigators (see Refs. 11, 12, and the appendix of the present paper). Consequently, the strain-diffusion runs on iron for the Ds measurements were repeated and extended over wider ranges of temperature and strain rate. In addition, the original diffusivity data9 on the unstrained iron have been corrected for the divergence of the beam in the counting system and new data points have been added, resulting in somewhat different values for the self-diffusi-vities in a iron.10 The new values for Du are used in this paper. A comparison of Ds and Du confirms the large enhancement in the self-diffusivity of iron during compressive creep, as previously reported.',2

Jan 1, 1963

By R. A. Graham, R. W. Rohde, J. R. Holland

In a shock wave compression study of a martensitic Fe-30 pct Ni alloy, Graham, Anderson, and Holland' found a region of unusual compressibility extending from a few kilobars up to about 20 kbars. This region was characterized by a continuously decreasing shock wave velocity with increasing stress. In this note, we report the results of a study initiated to determine the source of this unusual compressibility. In earlier shock-loading experiments on martensitic Fe-30 pct Ni, Loree et a1.' determined that a phase change occurred at about 80 kbars. Subsequently, Bowden and elly found that samples of a similar material shock-loaded at about 100 kbars experienced a martensite-to-austenite transition. Their crystal-lographic analysis showed the transition was a direct reversal of the established martensite system to the austenite phase. The shock loading in the present experiments was accomplished by precisely controlled plane impact between two discs of the sample material. This configuration created a state of uniaxial strain in the two the front of a projectile which was accelerated to various velocities. Planarity between the impacting discs was controlled to 5 x 10-4 rad, and impact velocities were measured to 0.5 pct. From a knowledge of the Hugoniot relationships of the material and the impact velocity, the shock-wave stress can be calculated. Samples were shocked at 18, 50, 70, and 100 kbars. The specimen discs shocked at 18 and 50 kbars were instrumented with quartz gages to observe the stress time profile. A more detailed description of the experiment has been given previously.4 The shock-loaded specimens were recovered intact by decelerating them in a catcher filled with soft wood. Discs of Fe-30 pct Ni nominally 12.7 mm thick and 64 mm in diam were cut from bar stock. Chemical analysis of the material provided the following composition in weight percents: 29.5 Ni, 0.50 Mn, 0.21 Si, and 0.10 C, with traces of Cr, Cu, Mo, Al, and Co. The discs were austenitized at 650° C for 2 hr at a pressure of less than l0-' torr, and furnace-cooled. Martensite was then produced by quenching the discs at -196" and holding 168 hr. The initial martensitic structure formed is shown in Fig. l(a). Typical microstructures of samples shock-loaded at 18 and 100 kbars are shown in Figs. l(b) and l(c). The banded structure with the austenite regions running parallel to the shock propagation direction was characteristic of samples shock-loaded at all stresses. No such banding was found in samples that were not shock-loaded. Comparison of Figs. l(b) and l(c) shows that, although under the optical microscope the two microstructures are quite similar, the martensite plates of the specimen shocked at 100 kbars etched in a distinctly different manner. This unique etching behavior of martensite in samples shock-loaded above the 80 kbar transition point has also been observed by Leslie el al.' These investigators determined from X-ray and electron microscope studies that fcc martensite, similar in appearance to normal bcc martensite, had been formed under shock loading. A quantitative determination of the amount of austenite present after shock loading was made by X-ray techniques. Both the methods of Lindren' and Miller' were utilized. The results are shown in Table I. The error limits are those experimentally observed from two independent analyses of each sample and represent the precision of the experiment. The absolute error, which should be similar for each sample, is believed to be about 10 pct. It is seen that as the shock stress increases the amount of austenite present also increases. On the basis of the X-ray and microscopic observations, we conclude that shock loading below the 80 kbar ersal will initiate a martensitic reversal: the amount of reversal that occurs increases with in-

Jan 1, 1969

By AIME AIME

WHEN a local man has attained high position in business and civic affairs at home, his fellow citizens feel elated if his attainments are given recognition in the form of election to office in an organization of national scope. Eugene Ainsworth White, a new Director of the Institute, is one of the must prominent citizens of Tacoma, where for the past thirteen years he has managed the Tacoma Smelter of the American Smelting and Refining Co. A list of the civic duties he has carried with distinction would be a long one; for recent years it would show that he has been chairman of the Community Chest, vice-president of the Chamber of Commerce. and a member of the Pierce County Taxation Bureau.

Jan 1, 1945

By H. L. Tedrow

FACED with a scarcity of labor in its operations at Alma, Colo., the London Mines and Milling Co. has been employing women for several months in its sorting and crushing plant. The results so far obtained indicate that women can be used successfully and to good advantage on a number of various jobs around the surface plant of an ordinary mine. Eight women are now employed as sorters to pick waste out of the ore as it passes by them on a sorting belt. After a short period of breaking in they have become adept at their work and are doing better work than that formerly done by the class of labor obtainable. They are continually warned and instructed, particularly from the standpoint of safety and their physical strength.

Jan 1, 1942

By J. Chipman, N. J. Grant, B. M. Shields

The vacuum tin-fusion method of analysis for hydrogen, developed by Carney, Chipman, and Grant, has been modified to permit the analysis of the evolved gases for hydrogen by means of a thermal conductivity cell. A properly prepared sample can be analyzed in 10 min with a probable error of ±0.12 ppm. A study of various methods for storage of hydrogen samples shows that samples can be safely held in a dry ice-acetone bath as long as six days. Storage in liquid nitrogen is necessary for samples to be held one week or more. HE vacuum tin-fusion method, as developed by I- Carney, Chipman and Grant,' is the only analytical procedure which has shown promise of being fast enough for use in the control of hydrogen during steelmaking. It was felt that further simplification and faster speed of operation could be effected by the use of thermal conductivity measurements for analysis of the gases evolved in the tin-fusion method. The application of conductivity measurements to the tin-fusion method is possible because: 1—the evolved gas is essentially a mixture of hydrogen, nitrogen and carbon monoxide with a hydrogen content usually over 50 pct, 2—the evolved gas is collected at a relatively low pressure, and 3— the thermal conductivities of CO and N2 are practically identical while that of hydrogen is very much greater. The major part of this research program was devoted to the construction and calibration of a vacuum tin-fusion apparatus which analyzes the evolved gases for hydrogen by means of a thermal conductivity cell. The second phase of the problem was associated with the development of a procedure for storage of samples prior to analysis. With the rapid quenching method for hydrogen sampling,' which seems to be the most practical for steel mill use, it is necessary that the samples be stored safely during the interval between sampling and analysis if the hydrogen content of the molten metal is to be maintained in the supersaturated solid samples. The thermal conductivity bridge has been used for a number of years in the analysis of certain gas mixtures. An elementary discussion of the theory and practice of gas analysis by thermal conductivity measurements is given by Minter.3 A more comprehensive discussion of the theory and of the various measuring circuits is presented by Daynes.' A complete knowledge of the theory and properties of the thermal conductivity of gases and gaseous mixtures can be gained by a study of the standard textbooks on the kinetic theory of gases."' The existing data on the thermal conductivity of single gases are reviewed by Hawkins: that for a number of binary gas mixtures by Daynes' and Lindsay." The thermal conductivity method may be applied to the determination of the composition of a binary mixture if: 1—the thermal conductivity of the mixture varies monotonically with composition, and 2— the two gases have measurably different thermal conductivities. The greater the difference between the two gases, the greater the sensitivity of the method.10 he method is applicable to the analysis of multicomponent mixtures when all of the gases in the mixture except one have nearly the same thermal conductivity. Fortunately, the mixture of hydrogen, nitrogen, and carbon monoxide evolved by the tin-fusion analysis' falls in this latter classification. The thermal conductivities of nitrogen and carbon monoxide are practically equal; and the thermal conductivity of hydrogen is approximately seven times that of the other two. Therefore, the thermal conductivity of a gaseous mixture of hydrogen, nitrogen, and carbon monoxide at known temperature and pressure can be related directly to the percentage of hydrogen in the mixture by suitable calibration. Usually the thermal conductivity of a mixture of gases is measured at atmospheric pressure where the thermal conductivity is independent of pressure over a wide pressure range. At very low pressures (below 1 mm Hg), the thermal conductivity of gases varies with the pressure. This phenomenon has been utilized in the Pirani vacuum gage for the measurement of pressures in the range of 10" to 10-0 mm of mercury.= Very little has been published concerning the variation of thermal conductivity with pressure at intermediate pressures between 1 mm Hg and 1 atm. However, preliminary measurements indicated that the thermal conductivities did vary with pressure over the range of pressures (up to 10 mm Hg) at which gases are delivered from the vacuum pump. Therefore, the calibration of the thermal conductivity cell had to be planned to include the effects of both gas composition and pressure. Such a calibration chart is shown in Fig. 4. Most industrial applications of the thermal conductivity method of gas analysis have used a compensated Wheatstone bridge circuit containing two

Jan 1, 1954

By R. M. Briney

A RETURN to nonwar conditions characterized the year 1946. The acquisition and forced use, under Government auspices, of low-grade and uneconomic ores, both foreign and domestic, ceased in 1945, but there was some carry-over into the early months of 1946. The world shipping situation delayed the procurement of some foreign ores, but conditions were improving by the end of the year. No actual shortage of any important alloy was experienced, hence the industry was able to make prompt shipment of orders placed. Price levels of ferroalloys, which had remained virtually constant through the war years, were forced upward, with increases on specific products as conditions necessitated. Standard ferroman-ganese and low-carbon ferrochrome were notable exceptions in that their price did not change. No new ferroalloy smelting plants were constructed. The Defense Plant Corp.. sold the works at Ashtabula, Ohio, to the Electro Metallurgical Co. A new type of ferroalloy furnace was described at the Birmingham meeting of the Electrochemical Society. Known as the "Elkem Rotary Furnace" it is distinguished by a rotating shell. The whole furnace, including shell, refrac-

Jan 1, 1947

By Donald E. Meyer

High current-low voltage EB-gun evaporation in an oil-free ultra-high vacuum system was found to be necessary, though not sufficient, for stability (300°C, 106 v per on) of aluminium gate MOSFET's and MOS capacitors not stabilized by a phosphorous glaze. five characteristics of the equipment used: 1) Vacuum purification of the aluminum charge, 2) Ionization of the evaporant by the electron beam, 3) X-ray formation, 4) Residual gases during evaporation, and 5) Metal film structure were studied as Possibly significant in MOS fabrication. EVAPORATION of contact metals common to the semiconductor industry historically has been accomplished with oil diffusion pump systems and various resistance heated evaporant sources as dictated by the type of metal evaporated. To meet a need for greater reliability of semiconductor devices, other metallization methods were developed. A good example would be application of the moly-gold contact system to integrated circuits with deposition by RF or triode sputtering.' More recently, fabrication of stable metal-oxide-silicon devices and circuits has put new demands on metallization. The purity of the thin metal films composing MOS structures is critical, particularly at the metal-oxide interface, and ultra-high vacuum metallization using sputter-ion pumping and electron beam gun (EB-gun) evaporation are well suited for the task. At this laboratory aluminum has been the most common contact-gate metal for both MOS capacitors and MOSFET's. In the earliest work with MOS capacitors, aluminum was evaporated from wetted tungsten filaments using both diffusion pump and ion pump vacuum systems. In spite of clean oxide techniques these capacitors were unstable under bias-tempera-ture stressing. Only after a switch to EB evaporation of aluminum were stable capacitors produced. Using the same techniques it was possible to make MOSFET's with equivalent stability. Stability data for a discrete MOSFET is shown in Fig. 1. This is a "clean" oxide gate (no phosphorus stabilization or no etch back of a thicker gate) having a thickness of lOOO? thermally grown on the (111) plane. Gate length after diffusion was 0.24 mils, and the devices were hermetically sealed. Stressing conditions were 300°C and 106 v per cm applied alternately as a positive and negative field for 10 min, 50 min, and 4 hr for a total stress time of 10 hr. An initial shift in turn-on voltage of 0.1 v was detected for 10 min of positive bias. All evidence at this laboratory indicated that while EB-gun evaporation of ultra-high purity aluminum was not sufficient for 300°C stability, it did seem to be necessary. There may well then be something inherent in the EB-gun deposition used which enhanced stability, and probably no single factor existed but rather a series of factors. It is the purpose of this paper to report on some of the investigations carried out to learn more about EB-gun evaporation in ultra-high vacuum systems. EXPERIMENTAL DESCRIPTION The EB-gun was self accelerated, had a maximum power rating of 10 kw, and used a water-cooled copper crucible able to hold a 20-g aluminum charge. The electron beam was bent 180 deg and focused by an electromagnet which also provided movement of the beam across the crucible. Normal power conditions in this work were 9 kv and 300 to 600 mamp. The gun can be described as high-cur rent/low-voltage and was quite different in its mechanism of operation from EB-guns with much higher acceleration potentials. An oil-free vacuum system capable of 5 x 10- l0torr, a quartz crystal rate and thickness monitor and a quadruple mass spectrometer completed the evaporation system, Fig. 2. A typical evaporation cycle consisted of a 3 to 4 hr pumpdown to the upper l0-9 range and evaporation at l0? per sec with the pressure in the bell jar not rising above 1 x 10"7 torr. Thickness control was 5 pct or less and could be automatically monitored and controlled. Five phenomena associated with the EB evaporation and considered as possible contributors to Ma performance included a purification effect, ionization of evaporating aluminum, X-rays, constitution of vacuum ambient during evaporation, and film structure dependence upon evaporation rate. These phenomena are now discussed. Vacuum Purification. The design of the EB-gun permitted purification of the aluminum charge by vacuum outgassing. Particular features included an efficiently water-cooled copper hearth with a capacity of over 20 g of aluminum and the capability for sweeping the beam across the charge. Such capacity meant that aluminum had to be added only after about every fifth evaporation. A new charge was not required each evaporation as is necessary with filament evaporation. An oxide "scum" which appeared on the charge could be completely cleared from the top hemisphere of the charge by sweeping with the beam prior to opening the shutter. An indication of the purifying effect was obtained by a series of analytical measurements on incoming aluminum, after melting but with little vacuum out-gassing, after 30 min outgassing, and the evaporated film itself. Either a solids (spark source) mass spectrometer or an emission spectrometer were used for analyzing the aluminum charge. Analysis of the evapo-

Jan 1, 1970

By James Hyslop

MECHANIZATION of American coal mining continues to make rapid progress. Economic pressure will compel abandonment of manual methods wherever possible and will also provide the incentive needed for the improvement of machines and mining systems. However, rapid progress may be made along strictly technological lines and at the same time much slower progress in approaching maximum productivly and efficiency. One can well ask, just how efficient are mechanized mines, and to what extent is productivity affected by the mental attitude of management and workers?

Jan 1, 1946

Jan 1, 1945

Jan 1, 1911

By T. F. Witherbee

THE following calculation of heat requirement covers the working of the furnace from January 25th to February 14th, inclusive. A short time previous to the first date the furnace had been working rather badly, so that 300 lbs. of ore and 500 lbs. of limestone were taken off. Within the time mentioned the quality of the iron passed

Jan 1, 1877

By M. A. Matzkin

The Problem: There are no roads and mapping has been inadequate. There isn't a clearing large enough to accommodate a conventional airplane. Entry would consume months, yet the area must be investigated. Sustained communication is impossible except by radio. Cost in time and money for exploration would be exorbitant. . . . . . . . .

Jan 9, 1953