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By B. N. Das, H. E. LaBelle, G. A. Wolf

ZnxHg1-xTe and GUPxAS1-x crystals have been grown from solution by a traveling heater method (THM). In a floating zone type fashion a solution zone sandwich of liquidus composition is made to migrate through feed material of solidus composition by a slow-speed movement of <0.25 mm per hr of the total charge through a stationary radiation or rf heater. ZnxHg1-xTe of composition 0 < x < 0.3 and GUPxAS1-x of composition 0.5 < x < 0.7 have thus been grown from their solution in liquid tellurium and gallium, respectively. A simplified analysis of heat and material transport is given. In this method, Proper adjustment of the temperature distribution along the liquid solution zone axis eliminates instability of the crystal growth front and constitutional supercooling. 1) ZnxHg1—xTe: The solid-solution telluride was grown in sealed quartz tubes at a temperature of 500 to 650°C. For first Preparations mechanical mixtures SINGLE crystals of solid solutions of III-V and II-VI compounds have been grown by various techniques from the melt, from the gaseous phase, or from solutions in of ZnTe and HgTe were used. X-ray determinations showed the resulting crystals to be homogeneous throughout their entire length, except for the end sections. The homogeneity is greatly improved by reusing the ingots obtained from first Preparations as feed material in subsequent crystal growth runs. Ingots of up to 4.5 cm have thus been obtained. 2) GaPxAs1-x: Crystals were grown in a EN crucible at a temperature of 1050°C. For first Preparation a mechanical mixture of Gap and GaAs was cemented together by a minimum amount of liquid gallium through "wet" grinding of Gap and GaAs crystals in the liquid metal and subsequent exuding of excess gallium by compacting of the charge in the EN crucible. Electron microprobe measurements using P-Ka and As-Ka radiation showed uniformity over a length of 0.4 cm. Properties of the various Preparations are described. liquid metals.&apos;-&apos; Their growth from the melt by passing a liquid zone of pseudobinary liquidus composition through a solid rod of solidus composition is generally a convenient method of growth of single crystals of solid solutions of homogeneous composition. This method loses much of its usefulness, however, if the melting point or the vapor pressure of the solid solution is high. In the case of a compound having a high melting

Jan 1, 1969

By PERCY E. BARBOUR

TWO YEARS after its organization, the Institute issued its first volume of TRANSACTIONS, covering activities that began in May, 1871, and continued through February, 1873. The preface of this first volume reads: The present volume contains the rules of the Institute, a list of members and associates, an abstract of the proceedings of the-first two years, and a number of papers selected from those proceedings. There is, therefore, nothing new in it. The papers have all been published, according to the custom of the Institute, in the Engineering and Mining Journal, and many of them have been copied into other periodicals. They are republished here, solely to enable members and associates to preserve them in convenient form. Various considerations have determined the selection of papers for this purpose. Some have been omitted at the request of the authors who, having modified the views expressed in them, naturally deprecated a republication of those views. Others have been omitted, in order not to devote too large a proportion of space to single topics, or single branches of mining or metal¬lurgy, in view of the fact that the membership of the Institute extends throughout the whole country, and represents numerous departments of these industries. Some, on the other hand, have been chosen, although not laying claim to special originality, because they contained information of importance, not easily accessible elsewhere, the presentation of which, in a form convenient for reference, was generally desired.

Jan 1, 1921

By L. J. M. Smits

A theoretical equation is developed describing membrane potentials of shaly sands as a function of the cation-exchange capacity per unit pore volume of the rock and saturating water salinity. This equation is based on the same simple physical model as that employed earlier7 describing the electrical conductivity of shaly sands. Experiments conducted with NaCl solutions showed that the equation is obeyed, except in the case of saturated salt solutions where minor deviations were observed. A possible explanation is given for this discrepancy. As the clay content and the porosity of shales may vary appreciably, shale membrane potentials also vary. It was found that membrane potentials of shales can be calculated accurately with the aid of the same theory. Consequently, changes in membrane potentials can be accounted for by simple measurement of cation-exchange capacities per unit pore volume of both shales and shaly sands. Charts are given to facilitate interpretation of the electrochemical part of the SP in terms of cation-exchange capacities and the salinities of mud filtrate and formation water. INTRODUCTION A spontaneous potential (SP) log is a record of the way in which the electrical potential of a sonde varies as it passes down a borehole. Such variations frequently reflect rock texture, e.g., permeable beds intercalated in an impermeable series often are indicated by a sharp change in potential. Nowadays it is recognized that SP logs may be interpreted in terms of formation-water salinity and formation shaliness. The four sources of the SP are illustrated in Fig. 1. El and E4 represent streaming potentials generated by the flow of mud filtrate through mud cake opposite permeable formations and through shale, respectively. An extensive review of the literature on the evaluation of these streaming potentials is given by Lynchl and will not be discussed here. The remaining part of the SP generally is called the electrochemical potential, which is divided into two parts: a membrane potential across the shale (E3, Fig. 1) and a membrane potential in the permeable sand at the diffusion boundary between formation water and mud filtrate (E2, Fig. 1). It was found by wyllie2 that the membrane potential across the shale, E3, is the most important contribution to the electrochemical potential, the shale acting as a semi permeable membrane. When the sand is clean it does not influence the diffusion process, so E2 equals the value of the so-called liquid-liquid junction potential observed when the two solutions diffuse freely into each other. When the sand contains clay, however, this interferes with the diffusion process and affects the diffusion potential generated. The greater the proportion of clay, the stronger this effect will be. Wyllie,3 Doll4 and Poupon et al.5 took this effect into account theoretically, starting from a physical

Jan 1, 1969

By C. M. White

CITIZENSHIP is a rather abstract subject on which a great deal could be said-a subject on which a great deal is said -and still one which too many of us seldom think about and seldom work at. Too many of us engineers and business men have but a vague idea of citizenship. We think that if we go to the polls on election day and obey the laws scrupulously, with the exception of an occasional traffic violation, we are pretty good citizens and are doing our duty by our city, state, and nation. But when you think it over, that&apos;s a very passive observance of the important right of counting oneself a citizen of a country. There is nothing very positive in that attitude. There is nothing that indicates that we have sufficient interest to really go out and do a job for the -welfare of our country, forgetting any personal advantages or inconveniences that might arise. In other words, this type of voting-on-election- day, law-abiding citizenship does not keep us awake a single minute; it does not take any particular thought or require the expenditure of any time or energy.

Jan 1, 1939

By Robert H. Richards

Jan 1, 1897

By C. R. Swarts

The use of compressed air or gas in oil wells for raising crude oil to the surface has, within the last year, become a dominant factor In production engineering. Previous application of this principle was largely confined to oil wells that had been pumping for a considerable length of time. In the Seminole area, the gas-air lift has been applied to wells imniediately after natural flow has ceased and in some cases while the wells were still flowing. This early application of the gas-air lift has been watchcd with intense interest by the petroleum industry, both with respect to methods of application and mechanical installations and to the effects on immediate and ultimate production. Methods of Application The Seminole pool at its inception contained sufficient gas associated with the oil to cause natural flow. As no frce gas was found in the main productive horizon, the Wilcox sand, all the gas present was dissolved in the oil, hence the natural flowing life was short, rarely lasting over 45 days. When natural flow ceased, high fluid levels were common, and as depth and crookedness of holes were obstacles to efficient pumping, the gas-air lift was used almost exclusively in raising the oil to the surface. Because of the high gravity of the oil, 41" A. P. I., and its high gasoline content, and also because of the desire to obtain production before offset wells became productive, quantity of production was the aim of the operators and a method of flow was used whereby this aim could be fulfilled. One of the outstanding features of this method consisted in flowing the wells through the annular space between the tubing and rasing. By this means a greater quantity of fluid could be handled than by flowing through the tubing of the size in ordinary use. Wells that would produce only a few hundred barrels on the pump were by this rnethod made to produce as high as 7000 bbl. on the lift. A few days or wreks of production at that rate meant a large recovery of oil. Casing of 636 in. diameter was commonly used as a production string with a 5 3/16-in. liner set on top of the oil sand. Upset tubing for irtro-

Jan 1, 1928

By Raymond O. Ladoo

FUSED quartz is a glass made by the fusion of nearly pure silica. Some confusion in terminology exists but in the trade today "fused quartz" generally refers to the perfectly transparent colorless product made from rock crystal whereas "fused silica" is a white, translucent product made from silica sand. Vitrified silica is the term preferred by purists for all quartz glass, but it lacks the definiteness of -the trade terms. Since the raw materials, methods of production, and properties of the finished products arc different for the two types, the trade terms are preferred. As fused quartz is amorphous, it-physical properties differ greatly from those of quartz crystal. Lacking crystallographic directions and having no piezo-electric properties, fused quartz. of course, has no value for the making of radio oscillator plates; but it does have other valuable and unique properties. Perhaps the &apos;best known and most useful properties are its extremely low coefficient of expansion and its ability to transmit short-wave ultraviolet radiant energy. Crystal quartz not only has an aver-

Jan 1, 1947

By O. P. Arora, M. Metzger, G. R. Ramagopal

Single-phase aluminum containing 0.0001 to 0.06 pct Cu was studied in strong acid, mainly through observations of hydrogen evolution. The strong influence of copper was exerted almost entirely through the imposition after a certain delay time of an auto-catalytic localized-corrosiott reaction. Additions of cupric ion to the acid produced lower accelerations. The significance of the quantity and distribution of copper was discussed, and the implications for intergranular corrosion and neutral chloride pitting were indicated. AN investigation of intergranular corrosion in single-phase high purity aluminum exposed to hydrochloric acid indicated the copper content of the metal to have an influence on corrosion at lower levels than previously suspected.&apos; The work reported here was a closer examination of the action of copper but dealt with general corrosion to gain the advantage of having a continuous measure of corrosion through the volume of hydrogen evolved, the reduction of hydrogen ion to hydrogen gas being the principal or only cathode reaction in strong hydrochloric acid. Previous work on the hydrochloric acid corrosion of aluminum was sometimes insufficiently structure-conscious and the need for care in evaluating it arises from the low solubility of the iron impurity,&apos; and of some alloying elements, and the known or possible presence in many of the compositions studied of second phases leading to greatly increased corrosion rates.3 These increases are attributed to the presence of low hydrogen-overvoltage cathodes provided by the second phase.3&apos;4 For the present single-phase work, a few studies which used high-purity base material and small copper additions5-&apos; provide the essential information most unambiguously. The corrosion rate was shown to be increased markedly by the introduction into the acid of small quantities of the ions of copper (and of certain other metals) which cement on the aluminum and provide cathodes of low overvoltage.5 When there was sufficient copper in the aluminum, the same result was produced during the course of corrosion leading to a rate which increased with time as the reaction was stimulated by one of its products (autocatalytic reaction). In 2N (7pct) HC1, an accelerating rate was observed at 0.1 pct Cu but not at 0.01 pct.5,7 The present work dealt with corrosion rate and morphology and their correlation with the quantity and distribution of copper catalyst for copper contents from 0.0001 to 0.06 pct. PROCEDURE A lot of high-purity aluminum containing 0.0021 pct Cu, 0.001 pct Fe and 0.003 pct Si (Alloy A) was alloyed with copper to yield aluminum containing 0.014 pct Cu (B) and 0.06 pct Cu (C). Later it was found necessary to include the lower copper Alloy K which contained 0.0001 pct Cu, 0.0004 pct Fe and 0.0004 pct Si. The upper limit for any other element can be confidently estimated as 0.0005 pct. No element other than copper appears to be present in quantities sufficient to have an effect on general corrosion as great as the observed effect of the copper in A, B, and C. The only other heavy metal detected by spectrographic examination was silver (< 0.0001 pct). The acid was made up from a selected lot of 37 1/2 pct CP hydrochloric acid containing 0.1 ppm heavy metals (mainly Pb), 0.05 ppm Fe, and < 0.008 ppm As and from water distilled from 1 megohm-cm demineralized water and believed to have contained negligible quantities of heavy metals influencing corrosion. Acid strength was adjusted to within 0.05 pct HCl of the stated value by using precision specific gravity measurements. Test blanks 10 by 41 mm were sheared from 1.65-mm cold-rolled sheet. Edges were finished by filing. The blanks were annealed in air at 645°C for 24 hr in alundum boats and rapidly water quenched. The anneal is thought to have produced a substantially homogeneous solid solution—for iron, copper, or silicon, for example, the annealing temperature was 200°C or more above the solvus-and the quench is considered to have preserved the high-temperature structure except for the condensation of lattice vacancies into dislocation loops.&apos; The 0.06 pct Cu alloy did not appear unstable in respect to slow precipitation reactions at room temperature since two pairs of tests failed to show significant differences between specimens heat treated 3 1/2 years earlier and specimens heat treated 1 or 2 days before.

Jan 1, 1962

By Wallace Ralston

The East Texas area includes the northeast 38 counties of the state of Texas. It covers all, and extends beyond, the borders of what is commonly described as the East Texas Basin. It is one of the most important oil and gas-producing areas of the Mid-Continent Province. It includes four important oil fields—Van, East Texas, Cayuga and Long Lake— and the recent extension of Rodessa field into Cass County, Texas, may prove to be of major size. Four commercial gas fields are in this area— Bethany, Waskom, Cayuga and Long Lake. Up to January, 1936, all of the oil has been produced from the Upper Cretaceous formations, and most of that from the basal member, the Woodbine sand. Gas is produced from both the Upper and Lower Cretaceous formations. Development in Fields East Texas Field.—This field continued to dominate the drilling and production situation throughout the United States. There were 4036 wells completed in this field during 1935; that is, 365 more wells than were completed during 1934. Drilling activity was due to close spacing of wells and the addition of 10,000 acres to the field. The field is now drilled to a density of one well to 6½ acres, which is certainly more wells than necessary for economic production of the field. The close spacing of wells is due mostly to the type of proration, which is per well allowable based on a potential test, and does not take acreage into consideration, and also to the numerous small acreage tracts such as town lots and excess strips. The field now has 19,519 producing wells. The allowable production for the field during 1935 was 161,118,659 bbl.; estimated production, including illegal or "hot oil," was 174,200,150. The illegal production of oil gradually decreased throughout the year, until an estimated low was reached of 20,500 bbl. daily during the months of November and December. The price of oil remained at $1.00 per barrel throughout the year. As stated, about 10,000 acres were added to the field during the year, making a total of 128,000 productive acres. There is a possibility that

Jan 1, 1936

By Thomas R. Scotese

A rock mechanics instrumentation and monitoring program was implemented during pillar extraction at Gulf Mineral Resources&apos; Mt. Taylor Mine, the deepest uranium mine in the U.S. Three types of monitoring were employed: (1) drift convergence around stopes (using a portable tube extensometer), (2) stress changes in pillars (using vibrating wire stressmeters in horizontal boreholes), and (3) load changes in haulageways under stopes (using vibrating wire load cells in jack stands). Results include convergence-time graphs, convergence contour maps, stress-time graphs, a stress increase contour map, load-time graphs, and abutment load limit maps. Major factors influencing results include (1) size of pillars around the extraction area, and (2) presence and orientation of a major fault adjacent to one extraction area. These factors, combined with pillar extraction, produced evidence of load transfer over 120 m from a stope measuring only 55 m x 45 m. Vertical stress increases of 7 to 17 MPa (1000 to 2500 psi) within 60 m of the stope were obtained using the stress- meter manufacturer&apos;s method. The fault apparently prevented load transfer in the down-dip direction but increased load transfer in the up-dip direction. Convergence rates of up to 1.3 cm/day (0.5 in/day) were measured at two stations. Instruments were generally reliable despite adverse underground conditions. The instrumentation and monitoring program at Mt. Taylor provided a warning system against ground control problems and a characterization of ground behavior for future development and extraction of pillars. Recommendations are made for future mining and instrumentation practices.

Jan 1, 1984

By Charles P. Williams

The lead-bearing area of Missouri has been subdivided, geographically, into the Southeastern, the Central, and the Southwestern

By G. L. Oldright, F. W. Schroeder

Very great changes were made in the dimensions of the smelting hearths of the furnaces in the period from about 1800 to 1906, the length increasing from about 11 to 116 ft., and the width from 8 to 19 ft. During this time the tonnage smelted increased from about 9 to 250 tons per 24 hr., and the tons of charge smelted per ton of coal increased from 0.77 to 4.3. Dr. Mathewson3 noted no great difference in the "fuel ratio" (i. e., the amount of charge smelted per ton of coal) as the furnace at Anaconda was increased in length by stages from 85 to 116 ft. (The percentage of copper in the slag, however, was lowered from 0.42 to 0.36 per cent. The other components of the slag were not given.) Lump coal fired on grates was the fuel used during this period. The practice in operating the furnaces over such a length of time naturally varied considerably, and there were differences in composition and nature of the charge, yet it may he considered that the improvements made were due largely to increases in the size of the furnace used. Doubtless some credit should be given to improvements in operating technique, like changes in the methods of firing the lump coal. However, the greater part of the advance was probably due to factors influencing the

Jan 1, 1928

By Robert Forsyth

As the latest plant on a large scale, the new Bessemer works of the North Chicago Rolling Mill Company, at South Chicago, presents some features of interest to steel-makers, I have ventured to lay before the Institute a short description of that plant, and some* remarks upon the practice there. At the time the South Chicago works were designed the adoption of the basic process in this country seemed imminent. Experience in Europe had demonstrated the perfect success of the process technically, and the question of its commercial value was one which, for any particular works, would have to be settled by its special advantages for procuring the necessary ores and basic materials. Under the circumstances, it was thought best at South Chicago to so arrange the plant as to allow the introdnction of the basic whenever it became advisable, and to make such other changes from the standard type of Bessemer plant as the state of the art seemed to demand and to foreshadow. As the use of metal direct from the blast furnace, while generally condemned by experts here, was in such successful practice in Europe (particularly in connection with the basic process), there was no doubt about its feasibility, while its economy in fuel and labor made it especially attractive to the Western manufacturer. It was accordingly decided to build a direct-metal plant adapted to the basic process. The ingots made were to be rolled into rails at one heat, and were to be of such size (12 inches square and long enough for three and four rails) as to be readily and quickly handled by the rolling machinery proposed. This small size of ingots, and the large number cast from each heat of 10 tons, made it necessary to provide a good deal of room in the casting-pit—much more than in any previons plant—and to put down extra facilities for handling ingots. To meet the delays incident to the basic process—to insure that one vessel should be always blowing if necessary, and to provide opportunity for current repairs to linings, etc.—it was decided that three vessels should be used, and, to properly concentrate the work of

Jan 1, 1884

Jan 1, 1923

By Harry H. Power

WORK of the Committee on Education of the Petroleum Division has been under way for approximately-one year. Although some progress has been made, further activities of the Committee are necessary in order to discuss mutual problems more thoroughly by a unified group interested primarily in this field of specialization.

Jan 1, 1944

The following list comprises the names of those persons who became members during the period May 10, 1916, to June 10, 1916: ARCHIBALD, JOHN CHRISTIE, Min. Engr., Supt. of Cyanide Plant, Guanajuato Reduction Mines, Guanajuato, Mex. BRUNEL, FRANK P., Cons. Min. Engr Mitchell & Brunel, Ajo, Ariz. CALVERT, WILLIAM ROBERT, Cons. Geol. ...225 Kearns Bldg., Salt Lake City, Utah. CHAMPION, J. R., Supt The Yak Mining, Milling & Tunnel Co., Leadville, Colo. CHARLES, LAVERN JOHN, Construction Engr., Elephant Butte Dam, Elephant Butte, N. M. CHASTEL, ANDRE, Min. Engr., Societe Miniere & Metallurgique de Penarroya, 12, Place Vendome, Paris, France. CHRISTIE, WALLACE H., Vice-Pres. and Mgr., Alt. Bert Gold Dredging Co., 604 Mission St., San Francisco, Cal. CLARK, RONALD ..Hardinge Conical Mill Co., 120 Broadway, New York, N. Y.

Jan 7, 1916

By H. I. Aaronson, C. Wells

Configurations of ferrite crystals have been found in a plain carbon steel which appear to have resulted from the nucleation of new ferrite crystals at the interphase boundaries of previously formed crystals despite the high carbon concentrations which necessarily develop at these boundaries. This phenomenon has been termed sympathetic nucleation. An attempt has been made to reconcile the occurrence of sympathetic nu-cleation with current nucleation theory. THIS investigation is one of a series on the formation of proeutectoid ferrite from austenite. From the viewpoint of chemical composition, this reaction consists of the nucleation and diffusional growth of crystals of carbon-poor ferrite within a matrix of carbon-rich austenite. The austenite adjacent to the austenite-ferrite boundaries will be greatly enriched in carbon, approximately to the value of the y/(a + y) equilibrium curve or its metastable extrapolation at the temperature of transformation. Those areas of austenite appreciably farther removed from the growing ferrite, on the other hand, will be relatively unaltered in composition, especially at the earlier stages of transformation. Since rates of nucleation are considered to decrease exponentially with decreasing supersaturation,&apos; the frequency with which ferrite nuclei appear at austenite-ferrite boundaries should be negligible in relation to that at which they form in other regions of the austenite. During this investigation, however, many groupings of ferrite crystals have been found which appear to have resulted from the nucleation of ferrite at austenite-ferrite boundaries. This phenomenon has been given the name of sympathetic 71.1tcleation. A number of micrographs of morphological configurations caused by sympathetic nucleation will be presented, after which an explanation for this reaction will be proposed in terms of current nucleation theory. Some of the structures to be considered are composed of bainite, an aggregate of ferrite and carbide, rather than of ferrite. Since ferrite and bainite differ only in that bainite forms under conditions which result in the nucleation of carbides behind the advancing austenite-ferrite boundaries,&apos; it will usually be unnecessary, for the purpose of this paper, to distinguish between the two reaction products. All studies were performed on an electric furnace steel (obtained from the Vanadium Alloy Steel Co.) containing 0.29 pct C, 0.76 pct Mn, 0.25 pct Si, 0.005 pct P, and 0.007 pct S. The alloy was cast as a 150 Ib, 7x7 in. cross section ingot and forged into bars 2x2 in. in cross section. These bars were homogenized for 48 hr at 1250°C in an Endo-Gas atmosphere. The depth to which decarburization penetrated during this heat treatment was determined by chemical and microscopic analyses and the affected metal was removed by machining. Specimens for isothermal transformation studies were cut from the remaining material; most of these specimens were 1/2x1/4X1/16 in., though some with a thickness of 1/32 in. were prepared for use at the shorter reaction times and lower reaction temperatures. Specimens were austenitized for 30 min at 1300°C, isothermally reacted for various times at temperatures ranging from 775" to 475 "C, and then quenched in iced water. The austenite grain sizes within individual specimens ranged from ASTM Nos. 1 through —4. A commercial heat-treating salt which was continuously deoxidized by an immersed graphite crucible served to minimize the loss of carbon during austenitizing; thick covers of powdered graphite and immersed graphite rods effectively prevented decarburization in the lead pots employed for the isothermal reaction treatments. The heat-treated specimens were sectioned and mounted in Bakelite. Following the completion of standard grinding and mechanical polishing procedures, the specimens were electrolytically polished with a Buehler-Waisman apparatus and etched in 2 pct nital. Experimental Results Rules of Evidence for Sympathetic Nucleation—On the basis of observations made on a single plane of polish, one precipitate crystal may be considered to have been sympathetically nucleated at the inter-phase boundary of another precipitate crystal when the following conditions are fulfilled: 1) The sympathetically nucleated crystal is not in contact with a grain boundary or a subboundary in the matrix phase. 2) The shape, size, and location of the crystal at whose boundary sympathetic nucleation occurred (hereafter termed the base crystal) and the crystal formed by sympathetic nucleation substantially pre-clude the possibility that the plane of polish em-ployed may have concealed the fact that both crys-tals actually nucleated at a grain boundary or a sub-boundary in the matrix phase.

Jan 1, 1957

By K. Stout, L. Friel

Some rock mechanics theorists believe that if a hydraulically placed backfill can be introduced in a stoped out area, which will minimize wall closure by taking high stresses across the fill with minimum compaction, then heavy ground and rock burst phenomena will be minimized. The paper will discuss a large scale laboratory project when fill strength was increased over four times by the head vibrated method and up to well over 20 times by the double placed, cemented, vibrated head method when compared to conventionally placed fills. The only preconditioning of the 60% solids by weight slurry was the addition of cement in some tests.

Jan 1, 1983

By R. A. Harrington

THE structure of anodic films formed on aluminum and other metals under varied conditions is not well known despite the wide use of such films both as protective coatings and as the dielectric medium in elec-trolytic condensers. The present work was undertaken as a survey of the possibilities of electron diffraction in the investigation of anodic films, especially in comparing the properties of anodic films formed under dif-ferent sets of conditions and subjected to various subsequent treatments. In addition, an effort has been made to compare surface films formed on aluminum by anodic treatment with surface films formed by heating, immersion in chemicals, etc, The electron diffraction method in many cases has been successfully applied to the study of thin surface films. Its principal advantage is that it can be used without removing the films from the base material upon which they have been formed. The low penetrating power of electrons, in the "reflection" diffraction method which has been used in this work, prevents the appearance of diffraction patterns from substances at depths greater than about 100 Angstrom units (10-6 cm.). Different investigations of the structure of anodic films have shown widely varying results, depending on the methods used in preparing the films. Apparently under some conditions these films are crystalline and under other conditions they are amorphous, and it has been difficult to say which type of structure will be found in any particular case. Schmid and Wassermann&apos;s&apos; X-ray diffraction patterns of eloxal? films show two broad, diffuse bands, which these investigators attribute to finely divided cubic y-Al2O3-§ Burgers, Claassen, and Zernicke3 obtained sharp X-ray

Jan 1, 1940

By F. Weinberg

Measurements have been made of solute segregation during dendrilic growth by using radioactive solute elements and ,measuring the activity of den(12-ites cut from decanted specimens. This has been done for both lead awl tin based binary alloys contaitzing the following solute additions: Ag, T1204, was dependet on ko, the equilibrium distribution coefficient in the following way Fay k &apos;c 0.1, C/C 0.6; for k0 >0.1. 0.6 <c,/c,< I. Qualitative obse?-vations were madc of dendritic segregation, by using autoradiographic techniques, for the Sn + Ag110 and Sn + Tlo4 systems. The observation were found to he in general agreement with the measurements ofCA/Co. Autoradiographic were also obtained of scctiolccl delzr11-iie stalks. These indicated that the stalks had a substructure, dclileated by solute corzetlt?atio?zs nlolg the substructure walls. A new dendrite growth direction <JI2> is reported for tila. SOLUTE segregation in dilute binary alloys has been investigated by Pfann,&apos; Smith, Tiller, and Rut-ter,&apos; and others. They considered the case of a slowly advancing plane solid interface, and derived expressions for the distribution of solute in both solid and liquid during solidification. To determine these expressions, they assumed no diffusion in the solid and either complete mixing in the liquid:&apos; or diffusion controlled solute movements in the liquid without any convective mixing.&apos; The present investigation considers solute segregation during dendritic growth, in which case the solid-liquid interface is not plane, and the growth rates are rapid. Segregation under these growth conditions has not been treated mathematically, because of the relative complexity of the system. It has been suggested by Chalmer, on the basis of preliminary results, that an alternative to the diffusion and heat flow controlled conditions during growth is &apos;diffusionless" dendritic growth in which solid is formed with the same composition as the liquid. He suggests this type of growth may depend upon a solvent-solute relationship that permits some solid solubility without excessive increase in internal energy, as is the case for solutions of tin in lead. On the other hand, Montariol,4 and others, have shown experimentally that some segregation does occur during dendritic growth in metals using etching and radioactive tracer techniques to indicate the concentrations of the solute. The present investigation was undertaken to determine, both qualitatively and quantitatively, the extent of solute segregation associated with dendritic growth in a series of binary alloys, as a function of solute concentration. PROCEDURE The solvent materials used were Vulcan Electrolytic tin (99.997 pct purity) and Tadanac lead (99.998 pct purity). The solute materials were Zn, Sn, and Sb (better than 99.998 pct purity), Ag and Co (99.5 pct purity), and T1 (Fisher "purified" metal sticks). Activation of the solute metals was carried out in the reactor at Chalk River, Canada. Master alloys were prepared by induction heating from the radioactive solute metal and the pure solvent, under argon, in graphite crucibles. Pieces of these alloys were then added to the solvent to give the required solute concentration. Dendrites were grown in essentially the same manner as that described by Weinberg and Chalmer, , in which controlled orientation single crystals were grown dendritically in horizontal graphite boats, and the liquid decanted. The crystals were grown and decanted in an atmosphere of tank argon. Before decanting, a sample of the liquid was drawn up in a glass tube and allowed to solidify rapidly. The orientations of the single crystals were such that <loo> was parallel to the growth direction, and (100) in the horizontal plane for lead, and [1101 and (110) respectively for tin. With these orientations long dendrite stalks formed along the bottom of the boat in the dendrite direction (<100> for lead and [I101 for tin) from which secondary branches grew. Only these secondary branches, which grew freely in the liquid from the dendrite stalk to the liquid surface, were used in the measurements. Accordingly, effects due to substrates and oxides on the surface of the liquid need not be considered. In order to measure the solute concentration C, of the dendrites, individual dendrite stalks were cut from the decanted specimens, remelted, and formed

Jan 1, 1962