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By W. E. Curran

For years the geographical isolation of the Southern iron-ore district from the great producing centers in the North and East enabled it to meet its conditions and solve its own problems without regard to the practices and policies of other districts, but during the past few years distances have been shortened, practices and wages are being standardized, and these changing conditions have brought new problems to the South. Development of Pig Iron in the South The development of the pig-iron business in the South was very slow during its early years, gained speed rapidly in the latter part of the nineteenth century, reached its peak in 1918 and was on the decline before the depression that began in the latter part of 1929. The first blast furnace in Alabama was built at Cedar Creek in 1818, the year before the state was admitted to the union. In 1830, Daniel Hillman was sent from Tuscaloosa to found an iron works in Roupes Valley, where rich pockets of brown ore were numerous. He built a forge on the site of what later became Tannehill furnace and called it the Roupes Valley Iron Works. There pots, pans, plows, and horseshoes were made of metal from his Catalon forge; shaped by a large hammer operated by water power. Daniel Hillman died in 1832 and the ironworks lay idle until 1836, when Col. Ninion Tannehill bought the property, rebuilt the forge and, using slave labor from his plantation, operated and enlarged the works. By 1845 he had built two crude furnaces and did a flourishing business in ovens, skillets and kettles, which found a good market all over the South. In 1855, the plant was sold by Colonel Tannehill to Moses Stroup, an experienced ironmaster from Pennsylvania. He tore down the old furnaces and built a new plant, the ruins of which stand today (Fig. l). This furnace plant operated continuously until it was destroyed by Northern troops in 1865. It was never rebuilt, so that the shell in the picture is the same furnace that made many tons of guns and shells for the Confederacy during the war period.

Jan 1, 1938

By C. A. Czako

INTRODUCTION In recent decades sintering and pelletizing of finely divided materials have become the primary tonnage producing modes of agglomeration. This statement is especially true in the iron and steel industry and, to a lesser degree, in the nonferrous, chemical and non-metallic minerals processing industries. In every industry the main objectives in agglomerating fines are essentially the same, namely to convert ores, minerals and chemicals of undesirable fineness into agglomerates characterized by a size consistency desirable for subsequent use or processing. Depending on the type of agglomeration process selected and the conditions maintained during agglomeration, the physical process of increasing size is complemented by a number of other unit processes. These processes can occur simultaneously, consecutively or in an overlapping manner. Some of these additional unit processes are incidental to the agglomeration operation, but at the same time can be critical, depending upon the subsequent use of the product. Accordingly, during processing, conditions have to be controlled to either suppress or enhance the extent of completion of these unit processes. The purpose of this report is to review laboratory testing as the basis for engineering modern sintering and pelletizing plants. Considering that most typical applications are for the iron and steel industry, agglomeration of ferrous materials is reviewed and discussed. When these total processes are adapted to suit non- ferrous materials, chemicals, or non-metallic substances, the over- all approach remains the same; only the processing parameters are affected as necessitated by the different nature of the materials.

Jan 1, 1977

By M. Nicholas, D. M. Poole

The diameters of sessile drops have been found to increase linearly with time in five reacting binary metal systems. The spreading rates of the drops are markedly dependent on temperature and on prior alloying of the solid with the lower melting point metal, hut are independent of the drop volume, wetting atruosphere , solid-surface roughness, and prior alloying of the drop with the substrate metal. A mechanism has been suggested that relates the linear-spreading rate to lateral diffusion of the liquid-metal atoms into the solid at the drop edge. An Arrhenius- type equation has been derived that describes the temperature dependence 0) the spreading rate, and although the agreement between the actual and the predicted pre-exponen-tial terms is poor that between the activation energies is excellent and the variation in the spreading rate of copper on Ni-Cu alloys produced by different extents of alloying can be predicted with considerable accuracy. CHEMICAL interactions frequently change the wetting behavior of solid-liquid systems causing, for example, "secondary spreading1 of sessile drops beyond the size defined by the surface and interfacial tensions of the unreacted components. The kinetics of the contact-angle decreases associated with this spreading are similar for many systems, but few studies have been made with the objective of determining whether the similarities are a reflection of a common mechanism. Some workers2,3 have assumed the secondary spreading is controlled by changes in the liquid surface and liquid-solid interfacial tensions and hence by the composition of the liquid, and contact-angle changes measured by the vertical-plate technique have been used to follow the course of liquid-solid chemical reactions.4 Other processes that have been invoked to explain these time-dependent changes in specific systems include the removal of adsorbed gas from the liquid-solid interface.5 penetration of containment layers on the solid Surface,6 interdiffusion,1,7 reori-entation of the solid surface into a wettable configuration: vapor-phase transport of the liquid onto the solid in advance of the drop,9 and, from vertical-plate studies. capillary flow between oxide layers and the solid surface.10 One of the reasons for the profuseness of these suggestions may be the complexity of the contact-angle change kinetics. However, in an analysis of secondary spreading gold and copper on UC,11 it was found that the diameter of the contact area between the sessile drop and the solid surface showed a simple linear increase with time although contact-angle changes were more complex. To check whether the linearity was merely fortuitous! additional exploratory work was conducted with four reacting metal-metal systems: Au on Ni. Cu on Ni, Cu on Fe, and Ag on Au. Linear spreading was observed in every case even though the kinetics of the contact-angle changes were complex. A further detailed study of the kinetics of linear spreading of five reacting metal-metal systems has been made with the object of determining the mechanism involved. The influence of variables such as temperature, drop volume. and the initial composition of the drop on the linear-spreading rate has been measured and compared with those predicted by a number of possible mechanisms. The systems employed in this study (Cu and Au on Ni and Pt, and Ag on Au) were selected because of the availability of potentially relevant chemical and physical property data. the simplicity of their phase diagrams at the wetting temperatures, and the ease of experimentation. EXPERIMENTAL TECHNIQUES The purities of the metals used in the study were: copper, 99.9 pct; gold. 99.96 pct; nickel, 99.2 pct; platinum 99.99 pct; and silver, 99.999 pct. The wetting tests were performed in a split tantalum tube vacuum resistance furnace of a conventional design. The furnace element was held vertically and was 1 $ in. in diam and 6 in, long. Viewing ports were provided in the water-cooled chamber to enable the specimens to be observed in both the horizontal and vertical planes. The temperature in the hot zone of the furnace could be held at 1500" i 5°C for an indefinite time. The surfaces of the solid-plaque metals were ground flat on Microcut paper and both the sessile drop and substrate metals were ultrasonically cleaned in methyl alcohol prior to their insertion in the furnace. After loading, the furnace was pumped down to a pressure of 2 x 10-5 mm of mercury and degassed for 30 min at 900° to 950°C. The temperature was then increased at more than 100°C per min to that used in the wetting test. The vacuum at the wetting temperature was better than 5 x 10-5 mm of mercury. Dewetting and retraction of the drop on cooling did not occur and the contact-area diameters, therefore, were measured after solidification with a vernier traveling microscope. The diameters quoted later are arithmetic means of ten measurements. The standard error of the mean never exceeded 3 pct and was often less than 1 pct.

Jan 1, 1967

By AIME

THE wind howls almost incessantly over the mining engineers working in the near desert that is the Division of Namaqualand, the upper Atlantic coastal corner of South Africa's Cape of Good Hope Province. But when these men at the U. S.-owned mines called Nababeep South and East O'okiep (pronounced Oh-keep) tell you about their achievements, they can be heard above the wind. For their O'okiep Copper Co. Ltd. now produces over half the Union of South Africa's annual output of 30,000 tons of copper metal. Moreover, it is a very decent sample of U. S. geotechnical imagination. financial daring, and managerial skill, all operating successfully in a

Jan 1, 1947

By O?Harra B. M.

THE work here described had for its purpose the procuring of data from which some quantitative estimate might be made of the results obtainable by using oxygen-enriched air in roasting zinc ores on a commercial scale. The principal metallurgical advantages of using enriched air in roasting zinc ores would be: 1. The rate of roasting would be increased, with consequent gain in the capacity of the roasting furnace. 2. As less air would be required for roasting, the volume of hot gases leaving the furnace and the heat carried out of the furnace as sensible heat in these gases would be less per ton of ore roasted; partly for this reason and partly because of the increased quantity of heat generated in the furnace by the larger amount of ore that could be roasted, the consumption of fuel by the furnace would be lessened; and by the use of air sufficiently enriched with oxygen the necessity of using fuel might be entirely obviated. 3. Roaster gas having a higher SO2 content could be produced; this would make possible greater capacity and more economical operation of the sulfuric-acid plant. Certain phases of the application of enriched air to roasting can be worked out only by experimenting with a furnace of commercial, or at least semicommercial, size. Thus the precautions necessary to secure proper. distribution of heat in the furnace;1 the volume of enriched air; and the proportion of oxygen in this air, necessary to give the desired increase in roasting capacity of the furnace and in SO2 content of the roaster gases;; and the most desirable frequency of raking, thickness of

Jan 11, 1924

By G. D. Cody, D. S. Beers, B. Abeles

The thermal diffusivity (thermal conductivity divided by specific heat) of Armco iron has been measured over the temperature range 30º to 1025ºC. The results are in good agreement with the thermal diffusivity computed from published values of thermal conductivity and specific heat, except near the Curie point and at the a to y phase transition, where the measured diffusivity undergoes rabid variations. The differences observed are ascribed to a rapid variation in the electronic thermal conductivity near the Curie point, and a decrease in the lattice thermal conductivity, at the a to ? phase transition. A major difficulty in measuring the thermal conductivity of materials at high temperatures is the determination and elimination of radiation losses. It has been shown, however, that in measuring thermal diffusivity D (thermal conductivity/specific heat) radiation losses can be taken into account exactly.' In order to test the performance of a newly designed apparatus for measuring thermal diffusivity of solids,' we measured Armco iron to an accuracy of 2 pct in the temperature range 30" to 1025°C. This material was selected since both the thermal conductivity,3'4 k, and specific heat,5 C, are known accurately in this temperature range and thus the measured values of D could be compared with D computed from the pub-

Jan 1, 1962

By Malcolm Wilson

THE year 1923 was one of great importance in northern Louisiana and southern Arkansas, so far as the' development and expansion of previously discovered oil and gas fields were concerned. However, the search for new fields failed to produce a single discovery that led to important development during the period; in this respect, the year was one of discouragement to the prospector. During the winter and spring months, an especially active "wildcat" campaign was in. progress in southern Arkansas, and a large number of tests were drilled in northern. Louisiana but this activity subsided during the summer and fall. By the close of the year, only routine drilling was in effect in the fields; and only two new areas-Cotton Valley, in Webster Parish, and an area in Union Parish, La.-were showing any important activity because of favorable oil showings. Further drilling is contemplated in both of these areas, and the present feeling is that one or the other may produce the next oilfield in this territory. Briefly, the development of the Smackover field was the overshadowing event of the year. In. southern Arkansas, important development also took place in the East El Dorado, Stephens, and Irma fields; but all of these were relatively small. In northern Louisiana, many new oil wells were drilled in the Bellevue field, and many new gas wells in the Monroe field. In the old Caddo field, a large number of the deep Woodbine wells were plugged back to the "chalk rock," where a high gravity oil is obtained. In the other fields, only a few small wells were drilled. Therefore, Arkansas, furnished the real development of the year in this area. The production for the year showed a material increase over that of 1922, due, chiefly, to Smackover, and practically altogether to the Arkansas fields. In Louisiana, every field, except Caddo, Bellevue, and Elm Grove, showed slight to marked declines; while in Arkansas, El Dorado was the only field that declined throughout the year.

Jan 3, 1924

By AIME AIME

THE John Fritz Gold Medal for 1929 was presented to Herbert Hoover at the Executive Mansion on April 25, at a luncheon given by Mr. Hoover to present and past members of the Board of Award, preceding medalists, and presidents and secretaries of the American societies of Civil, Mining and Metallurgical, Mechanical, and Electrical Engineers. The presentation party of forty engineers which gathered at the White House, from all parts of the United States, was made up of past presidents of the four senior national engineering societies that established the John Fritz Medal and included five men who had received the medal in previous years. These former medalists were Edward Dean Adams, J. J. Carty, J. Waldo Smith, Elmer A. Sperry and Ambrose Swasey. This medal is the highest honor bestowed by these four national engineering societies, having a membership of 60,000. It is awarded not oftener than annually for "notable scientific or industrial achievement, without restriction on account of nationality or sex." In accordance with custom, the award to Mr. Hoover was made tentatively and without announcement in October, 1927, and was formally con- firmed and announced one year later.

Jan 1, 1929

By Frederic P. Dewey

The improvement in leaching introduced by the Russell process has stimulated the development of processes for refining lixiviation-sulphides. In the early days several processes for dealing with the sulphides were proposed, and some of them were tried more or less ; but the business finally settled down to sending the sulphides to the smelters, although this was known to be both troublesome and expensive. In 1891 Mr. C. A. Stetefeldt* introduced at the Marsac mill, Park City, Utah, an unpatented process, built up out of the general fund of information available. It consisted in matting the sulphides, grinding, roasting, grinding again, and dissolving the copper out in diluted sulphuric acid, then melting the silver and crystallizing the bluestone. It did not yield fine bullion, hence the bullion had to be refined as well as parted; besides, there was some loss. This process was thoroughly tried at the Marsac refinery and then a year's run was made, the net result of which was that it did not prove sufficiently better than the sending of the sulphides to the smelters to warrant its substitution for that practice. In 1893 the Dewey-Walter Refining Company undertook the refining of the Daly sulphides in the Marsac refinery by the sulphuric acid process, upon which two United States patents ? have been issued to the writer. Naturally, difficulties were encountered in starting a new process, and most of 1893 was taken up in getting it into smooth working order; but in 1894 a run was started, in which all the regular sulphides produced by the

Jan 1, 1897

By Claus Goetzel

THE object of this investigation was to determine whether silver alloys could be used instead of the currently employed insert of high-expansion AVERAGE COEFFICIENT PER DE G. C. OVEN RANGE 20° To 200° C. Pure aluminum '31.6 X 10-6 Cast low-expansion Si-Cu-Ni-Al piston alloy 20.0 X 10-6 High-expansion austenitic Cu-Ni cast iron 19.3 X 10-6 Cast steel (0.25-0.35 C, 0.10-1.0 Mn) 12.6 X 10-6 Cast iron (3.15 total C, 2.16 Si) 12.8 X 10-6 Pure silver 18.9 X 10-6 austenitic ferronickel alloy, to reduce the wear of ring grooves in light metal pistons. A typical example of a piston containing a ferronickel insert is shown in Fig. 1. The high coefficient of expansion of silver made it worthy of consideration, while the small size of the insert would render it use feasible in Germany as an emergency in is- tire. The coefficients of linear expansion of several metals and alloys are as shown in the table above. Obviously the melting point of the insert must be high enough to prevent it from melting when the light alloy is cast around it. This imposes a lower limit of about 850° C. for the solidus of the silver alloy. Pure silver melts at about 961° C., so that the Fin. 1.-PISTON CONTAINING tolerable depression in the solidus is rather FERRONICKEL INSERT. small. To avoid deformation of the insert during use a Brinell hardness number of at least 60 appears necessary.

Jan 1, 1937

By S. Skowronski

PURPOSE OF INVESTIGATION Since cuprous chloride melts at 418° C., boils at 954° C. to 1033° C.,1 and is known to be volatile at a much lower temperature, the presence of chlorine in any form in or on copper to be melted has always been looked upon by copper refiners as a possible source of-serious copper loss. Although this fact has been known for some time, the copper literature contains little or no information regarding it and the field seems .never to have been properly investigated from a metallurgical standpoint. According to Greenawalt,2 cupric chloride, CuCl2, when ignited gives cuprous chloride; therefore cuprous chloride is always formed when copper enters into reaction with chlorine at a high temperature. Cuprous chloride melts somewhat below a dull red heat, and does not volatilize in closed vessels, even if strongly heated, but if heated in the air it goes off as a white vapor. Hofman3 gives the melting point of cuprous chloride

Jan 2, 1919

By D. L. Martin, E. R. Parker

DURING the heat-treatment of silver specimens for tensile tests it was observed that the bars blistered and became brittle when heated in a hydrogen atmosphere. [ ] To check this unexpected result, a wide variety of commercial silvers were heated in hydrogen at 850°C, Only a few of the materials developed blisters, the most severe of which is the tube pictured in Fig. I. The microstructure of a cross section of the tube is shown in Fig, 2. The embrittlement is extremely severe at the edge; the blisters result from the severe deforma- [ ] tion of the surface material by large underlying gas pockets, The effects resulting from hydrogen embrittlement of silver have been observed by numerous investigators over a long time1,2,3 although it was only recently that a clear explanation was offered ,4 However, the damage resulting from hydrogen embrittlement has not been generally recognized; and it is of advantage to know more about this phe-

Jan 1, 1943

By C. C. McDermond

In reviewing petroleum development in Venezuela during the year 1936, it is well to bear in mind certain factors that affected progress, although not directly connected with the oil industry itself. At the start of the year, when the present Federal Administration took over the reins of government, reaction against the former regime resulted in some popular uprisings. Although these were entirely political in character, they were not without their effect on the oil industry itself. Such popular agitation really ended with a short general strike in Caracas, Maracaibo and other cities during June, these strikes being based on demands for certain changes in government policies. The strikes were duly investigated and their motives taken into consideration by the executive power or by Congress, and during the year many of the civil, political and administrative laws have been revised. In June and December, however, it was necessary to suspend activities in drilling and production work, particularly in the Lake Maracaibo Basin area. In June a strike caused a five-day shutdown in the main producing fields and on Dec. 14 labor difficulties resulted in a shutdown that continued to the end of the year, which necessitated suspension of all drilling and production in the Lake Basin area and curtailment of shipments to deep-water terminals. Actually, the strike lasted for a period of 42 days, until Federal intervention brought the dispute to a close with minor wage increases to workers hut with no loss of initiative or independence on the part of the oil companies. Operations in eastern Venezuela were not affected by the labor disturbances, production and exports having been reduced in December only in the Lake Basin fields. Well Completions On Jan. 1, 1937, a total of 3384 wells had been completed throughout Venezuelan fields, as compared with 3094 on Jan. 1,1936. Of these wells, 2005 were producers. The 290 completions effected during 1936 were by the following operating companies: Lago Petroleum Corporation, 123 completions; Dutch Shell group, 104; Standard Oil Company of Venezuela, 46; Mene Grande Oil Co., 15; British Controlled Oilfields, Ltd., 2.

Jan 1, 1937

By V. F. Parry, E. O. Wagner

This paper summarizes investigations during 1949 on three pilot plants for drying low-rank fine coal by entrapment in hot gases. Detailed operating results on processing seven coals having moisture ranging from 24 to 62 pet, formulas and data for calculating performance of large units, and general conclusions on the problem of drying fine coal are presented. THIS paper presents a summary of investigations by the Coal Branch of the Bureau of Mines during 1949 on the removal of internal moisture from low-rank coals by processing them in the entrained and fluidized state. A paper on this subject, giving a summary of the early work, was presented at the 1949 AIME annual meeting1 and gave a the- oretical discussion of the time and heat required to dry various sizes of low-rank coal. The investigations on two pilot plants were presented in the foregoing paper. During 1949, three additional pilot plants were built to study phases of the drying problem and to investigate different techniques of handling fine coal in the entrained and fluidized state. The present paper gives operating data on the new units and presents detailed data on the drying of seven coals having bed moisture ranging from 62 to 24 pct. The problem of removing surface moisture from fine coal is principally one of heat exchange and dispersion of the coal particles so that heat can reach the liquid moisture to permit evaporation, and it does not involve the factors of size and time of contact to any great extent. If enough heat can reach the surface of the particles at temperatures higher than 250°F, moisture evaporates almost instantly, and the factors of time and size are of secondary importance compared with the factors of heat balance and dispersion of the coal. Therefore, it does not appear to be necessary to employ a fluidized bed when removing surface moisture, and the most efficient process would be one in which the coal particles are entrained in a hot gas stream of optimum temperature traveling at a velocity that causes the particles to disperse into a low-density phase. When low-rank coals are dried, the fluidized bed is necessary to provide control of time of contact. This is done by adjusting the superficial velocity which controls the density or dispersion of the particles. The density of beds having fluidized properties suitable for drying low-rank coals appears to range from about 5 up to about 15 lb per cu ft. When the density is below 5 lb per cu ft, which represents a low-density phase, optimum conditions for removal of surface moisture should be found, and this requires superficial velocities of about 15 fps. The problem of removing bed moisture from low-rank coals involves consideration of size of coal, temperature, mass flow, heat balance, pressure, time of contact, and method of dispersing the coal in the heating mediums. The experimental work presented here gives data on these factors. Coal sizes up to 1/2 in. x 0 were dried with hot gases having initial temperatures ranging from 1900° to 2400°F. Coal

Jan 1, 1951

By E. O. Wagner, V. F. Parry

This paper summarizes investigations during 1949 on three pilot plants for drying low-rank fine coal by entrapment in hot gases. Detailed operating results on processing seven coals having moisture ranging from 24 to 62 pet, formulas and data for calculating performance of large units, and general conclusions on the problem of drying fine coal are presented. THIS paper presents a summary of investigations by the Coal Branch of the Bureau of Mines during 1949 on the removal of internal moisture from low-rank coals by processing them in the entrained and fluidized state. A paper on this subject, giving a summary of the early work, was presented at the 1949 AIME annual meeting1 and gave a the- oretical discussion of the time and heat required to dry various sizes of low-rank coal. The investigations on two pilot plants were presented in the foregoing paper. During 1949, three additional pilot plants were built to study phases of the drying problem and to investigate different techniques of handling fine coal in the entrained and fluidized state. The present paper gives operating data on the new units and presents detailed data on the drying of seven coals having bed moisture ranging from 62 to 24 pct. The problem of removing surface moisture from fine coal is principally one of heat exchange and dispersion of the coal particles so that heat can reach the liquid moisture to permit evaporation, and it does not involve the factors of size and time of contact to any great extent. If enough heat can reach the surface of the particles at temperatures higher than 250°F, moisture evaporates almost instantly, and the factors of time and size are of secondary importance compared with the factors of heat balance and dispersion of the coal. Therefore, it does not appear to be necessary to employ a fluidized bed when removing surface moisture, and the most efficient process would be one in which the coal particles are entrained in a hot gas stream of optimum temperature traveling at a velocity that causes the particles to disperse into a low-density phase. When low-rank coals are dried, the fluidized bed is necessary to provide control of time of contact. This is done by adjusting the superficial velocity which controls the density or dispersion of the particles. The density of beds having fluidized properties suitable for drying low-rank coals appears to range from about 5 up to about 15 lb per cu ft. When the density is below 5 lb per cu ft, which represents a low-density phase, optimum conditions for removal of surface moisture should be found, and this requires superficial velocities of about 15 fps. The problem of removing bed moisture from low-rank coals involves consideration of size of coal, temperature, mass flow, heat balance, pressure, time of contact, and method of dispersing the coal in the heating mediums. The experimental work presented here gives data on these factors. Coal sizes up to 1/2 in. x 0 were dried with hot gases having initial temperatures ranging from 1900° to 2400°F. Coal

Jan 1, 1951

By A. C. Losekamp, R. M. Fincel, J. B. Conway

TANTALUM like several other metals exhibits a great affinity for or reactivity with certain gases. Tested in atmospheres which are not completely pure this metal becomes contaminated by certain impurities (notably nitrogen, oxygen, and hydrogen) with a resultant change in various properties. Well-known are the drastic changes in hardness, ductility, and electrical resistivity. Also previously recorded are the distortions of the lattice1,2 accompanying the increased content of oxygen and nitrogen in tantalum. This pronounced affinity for certain gases along with the significant property variations thereby produced makes it necessary to observe additional experimental precautions in making various property determinations with tantalum. Some recent measurements of the linear thermal-expansion characteristics of tantalum have made this point quite emphatically. Failure to observe the greatest precautions in reducing the contaminating influence has led to some extremely distorted results. Not only does such operation lead to different heating and cooling curves during the thermal-expansion measurements, but upon cooling to room temperature the sample is found to have suffered a permanent (actually semipermanent since the specimen can be returned to its original length by a 3-hr degassing treatment in vacuum at 2300°C) elongation. In addition, subsequent heatings will not follow the initial heating curve unless the expansion measurements are based on the actual specimen length at the beginning of the heating cycle. These thermal-expansion measurements were made by positioning the specimen horizontally at the longitudinal midpoint of a 20-in.-long, 4-in.-diam resistively heated tungsten tube furnace. The specimens were in the form of 20-mil sheet formed into a sharp U-shape about 0.3 in. in width and 0.3 in. in depth. Fiducial marks in the form of 0.010-in. holes drilled at either end of the 2.5-in.-long sheet specimens were viewed by a paired filar micrometer telescope system mounted on an Invar bar on the top of the furnace. Tests were made in helium with temperatures measured by a Pt/Pt-lORh thermocouple to 1000°C; above 1000°C temperature was measured by means of an optical pyrometer sighted into a black-body hole drilled into the specimen-holding fixture in the vicinity of the specimen. Previous tests with black-body holes drilled in a 0.25-in.-diam rod specimen had confirmed the temperature uniformity between specimens and specimen-holding fixture in this furnace. A typical thermal-expansion curve for arc-cast tantalum in helium is shown in Fig. 1 for the case where no attempt is made to remove all the impurities from the cover-gas atmosphere. The initial heating curve appears smooth and has a shape characteristic of all metals. However, it is known that the sample begins absorbing impurities at temperatures above 1000°C which are sufficient to distort the lattice and lead to specimen lengths which are somewhat larger than would be obtained in the absence of contamination. During the cooling cycle the expansion curve is seen to be significantly different from the heating curve. This is due to the impurity content causing a semipermanent (i.e., permanent until the impurities are removed by vacuum degassing) deformation which will not allow the speci-

Jan 1, 1965

By Richard I. Petritz

A brief review of today's processing of integvated circuits is given. The major trends in the development of advanced integvated electronics are identified as 1) the broadening of the integvated circuit concept to a large class of circuit function, 2) the processing of more complex circuits within relatively small chips of silicon, and 3) the processing of very large electronic functions on complete slices of silicon. This latter trend, called array technology, is then developed in detail. Emphasis is given to defining the key tech-nological problems. Current progress being made is illustrated. THIS paper will endeavor to identify the major trends in advanced integrated electronics technology. One of these, array technology, will be developed in some detail. The array technology discussion will identify the key problem areas. Since it is the scope of the entire meeting' to present specific progress in the science and technology of integrated electronics, we shall indicate general directions being explored rather than discuss comprehensively solutions to the problems. In order to set the stage for the discussion of future trends in integrated-electronics technology, let us briefly compare the processes by which circuits are fabricated through discrete-device technology with that of integrated circuits technology. The reader is referred to the December 1964 issue of Proceedings of IEEE2 for a comprehensive review of integrated electronics. The article3 by Jay Lathrop is an excellent discussion of integrated-circuits technology. A discussion of the history of semiconductor technology is contained in Ref. 4. A) Current Status of Integrated Electronics. Fig. 1 (top) shows the process by which circuits are constructed from discrete devices. Key points are: 1) Slices containing large numbers of transistors or diodes are processed separately. 2) The slices are scribed into small chips (on the order of 15 mils on a side is about as small as can be conveniently handled) each chip containing one transistor. 3) Each device is specified separately—circuit -function specs are derived largely from device specs. 4) Circuits are formed by connecting together the discrete devices. 5) The number of circuit connections required is approximately equal to the number of devices. 6) There are potentially many more discrete devices per inch2 of semiconductor—only our lack of ability to handle them in discrete form prevents us from going to several orders of magnitude higher density iin Fig. 1, 400,000 transistors are discussed at 1.5 mils on a side). The bottom part of Fig. 1 illustrates the integrated circuit process. Key points are: 1) On the same slice of silicon, transistors, diodes, and resistors are processed grouped to do a complete circuit function. 2) While still in slice form, the components are interconnected into circuit functions by an evaporation process, eliminating the need for separate interconnection steps later. Dramatic improvements in cost and reliability are realized. With a simple flash of metalization thousands of interconnections are reliably made. 3) The slices are scribed into chips which contain complete circuit functions. 4) The circuit functions are specified-not each component in the circuit. This important point was missed by some of the early opponents to integrated circuitry. They argued that, with device yields at x pct, integrated circuit yields would be pct, where n is the required number of devices to make a circuit. This argument leads to extremely low yields for integrated circuits. The fallacy of the argument is that in integrated circuits each device is not specified separately. Furthermore, since a device is forever integrated into a specific circuit function, it need meet only the requirements for that particular function. Discrete devices, on the other hand, are tightly specified so that they can be applied to a variety of circuit functions. 5) Extremely high packing densities are achievable because one need only make the basic devices as large as the circuit demands. Their size is not dictated by handling requirements. A current example

Jan 1, 1967

By Richard W. Smith

There are three distinct varieties of phosphate rock, in Tennessee, known commercially as: (a) the "brown" rock, which is the residual product of the weathering and natural concentration of certain phosphatic Ordovician limestones; (b) the "blue" rock, which is an unaltered phosphatic stratum of Mississippian or Devonian age; and (c) the "white" rock, which is the result of chemical replacement and deposition. Before 1894, South Carolina and Florida had supplied most of the phosphate of the United States, South Carolina leading until that date and Florida from then until the present time. In December, 1893, the blue phosphate of Tennessee was discovered almost simultaneously on Swan Creek, in Lewis County, by two independent parties—by one as the result of a careful and systematic search for a workable deposit of the long known kidney phosphate, and by the other through mistaking it for a "bloom" of coal. Leases were taken and, with further prospecting disclosing other deposits in the region, the development progressed as rapidly as could be expected without railroad transportation. In January, 1896, Judge S. Q. Weatherly, who was interested in the development of the blue phosphate, while riding along the road south of Mt. Pleasant, noticed some slabs of a brown rock in place above the limestone. He took samples, and had them analyzed, thus discovering the high-grade brown phosphate of this district. This discovery was kept a secret until July, 1896, when mining was started at the village of Mt. Pleasant. Development proceeded rapidly, many owners obtaining their capital by the sale of their rock fences, which were largely composed of slabs of high-grade brown phosphate. The development of the brown rock, which is richer and more easily mined than the blue, caused Tennessee to advance from a poor third in production to second, surpassing the output of South Carolina, and being excelled only by Florida.

Jan 1, 1927

By William Kranz

Discussion of the paper of WILLIAM G. KRANZ, presented at the San Francisco meeting, September, 1915, and at the New York meeting, February, 1916, and printed in Bulletin No. 101, May, 1915, pp. 927 to 930. J. W. RICHARDS, So. Bethlehem, Pa.-At the present time I believe there are 35 electric steel furnaces under construction in the United States, and many more in operation. The United States Steel Corporation, for example, is putting up for one firm a plant of eight electric furnaces. The principal increase in use of the electric furnace at the present time is based on its superiority for making steel for shrapnel and for munitions of war. I understand that electric steel has been found far more reliable and suitable than ordinary steel for these purposes in Europe.

Jan 5, 1916

By John A. Dunn

Continued increase in electric power requirements for mining, brought on by higher capacity mining machines and total mechanization, emphasizes the importance of proper power system design and planning. How effective a mine operates to produce quality coal at low cost depends to a great extent on how well its power system is planned and how well it is maintained. To be planned well it must be adequate to serve all the needs of the mine, it should be safe, there should be a margin for expansion, and it should be easily maintained. In planning a power system for mining coal it is helpful to establish a reliable base for estimating loads. Since most mines are served electric power by utility, power bills for similar mine loads are useful in setting up a base for estimates.

Jan 12, 1964