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By E. H. Snow, B. E. Deal

Instability effects in semicanductor devices have long been attributed to the motion of charges on or within oxide layers on the surface. These effects are of critical importance in metal-insulator-semiconductor MIS) field-effect devices. For this reason, the capacitance-voltage or the conductance-voltage characteristic of these devices can be used as a sensitive detector to study charge transport and polarization effects in the oxide or insulator. A review is given of the results of such studies of thermally grown SiO2 as well as of other insulating films of importance in silicon technology. Three types of effects are distinguished. The first of these is the drift of mobile cations within the dielectric, examples being thermally grown SiO, which is often contaminated with sodium ions, and a variety of other glasses in which the mobile ions are a part of the glass composition. The second effect is a dipole-type polarization which occurs in phosphosilicate glass films obtained by reacting P2O5 with thermally grown SiO2. The third effect involves the transfer of charges between the dielectric and the silicon electrode. This occurs in silicon nitride and other deposited dielectrics. It is concluded that MIS studies have provided a powerful technique joy the study of charge transport and polarization effects in insulating films. The knowledge gained from these studies has led to an understanding of surface effects on conventional transistors and diodes as well as making possible stable MIS transistors. THE metal-insulator-semiconductor field-effect transistor is conceptually the oldest type of active semiconductor device.' The earliest attempts at making this device were frustrated because of high surface state densities at the interface between the semiconductor and the gate insulation.' However, by using a silicon substrate with thermally produced silicon dioxide as the gate insulation, this problem was solved and metal-silicon dioxide-silicon devices with good characteristics were made as early as 1960. 3 Yet it was still over 5 years before these devices became a commercial reality. This delay was largly due, not to surface states, but to stability problems associated with polarization effects within the insulating layer which caused the threshold voltage of the device to drift under temperature and bias treatments. The solution to these problems has not only made possible stable MIS devices, but it has added immensely to our understanding of failure mechanisms in conventional bipolar transistors and has added to the reliability of ali types of planar devices. In this review, we shall first describe the effects of various types of polarization phenomena on MIS device characteristics. Then, since thermally grown SiO, is by far the most important insulator used in these devices, we shall review historically the type of instabilities which have been observed in thermal oxides, the attempts at understanding and eliminating them, and the present status of the problem. We shall then turn our attention to the various deposited insulators which have been used, including lead glasses, phosphosilicate glass, vapor-deposited silicon oxide, and silicon nitride. Interestingly enough, many of these materials show polarization effects which are quite different from those generally observed in thermally grown SiO2. THE EFFECTS OF POLARIZATION PHENOMENA ON MIS CHARACTERISTICS The simplest MIS device and the one which has been most frequently used in the study of polarization effects is the MIS capacitor. Two modifications of this structure with single- and double-layer dielectrics are illustrated in Figs. l(a) and (b), respectively. The capacitance of this structure as a function of voltage applied to the metal gate electrode is plotted in Fig. 2 for the case of an n-type silicon substrate. When the silicon surface is accumulated (positive bias) the measured capacitance is just that of the insulating layer C. When the surface is inverted (negative bias), the capacitance is that of the insulator and a silicon depletion layer in series CoCs/(Co + Cs). Indicated on the horizontal axis of Fig. 2 is the voltage VT at which the silicon surface becomes strongly inverted. This voltage corresponds to the threshold or turn-on

Jan 1, 1969

By A. B. T. Werner, J. J. Schanz

A survey of the world's sources and markets for natural graphite and some predictions of future trends are presented here. The authors feel that there is no indication of major changes in sources of graphite over the next few years, but it is possible that the importance of domestic graphites as opposed to foreign carbons may increase in the more distant future. U.S. consumption of natural graphite, which has been in general decline for the past six years, and will probably continue downhill with the virtual disappearance of some markets. However, other markets such as bearings, brake linings and crucibles will probably grow. Natural graphite is the name given to all the naturally occurring mineral forms of carbon that crystallize in the hexagonal system. Natural graphite~ are generally divided into three broad classifications that are based on physical rather than chemical differences — crystalline flake, Ceylon amorphous and other amorphous. Crystalline flake graphites occur as thousands of small individual flakes disseminated throughout the ore and closely resemble shiny black fish scales. Ceylon amorphous graphite is mined from narrow veins of almost pure mineral. It is produced in lump form and often has a coarse platy or needlelike structure. Other amorphous graphites include all those that are extremely fine-grained and have a crystalline structure that is not visible under normal circumstances. In the primary raw material markets, the graphite's country of origin is also important. Crystalline flake graphites may, for example, be of the Alabaman, Bavarian or Madagascan types; Ceylon amorphous graphite may have originated in Montana or Ceylon; and other amorphous graphites may come from Mexico, Hong Kong or Korea. The distinctions between the graphites from each particular locality are small yet important, for the country of origin will signify certain inherent physical characteristics and will often give an idea of the amount of graphitic carbon contained in the shipment in question. .In certain instances, however, even this is not enough, since the actual mine at which the graphite is produced may have to be known before its true commercial value can be ascertained. Thus, the Madagascar flake graphite shipped from the Sahalambo mines of the Societe des Graphites de la Sahanavo is a thick flake which is known to be especially suited for use in crucibles, while the dull black earthy amorphous material formerly mined at Cranston, R.I., was ideal for stove polish. Synthetic, artificial, electric furnace and manufactured are terms used to describe graphites made from coke. These graphites will be considered in this paper only to the extent that they enter competition with natural graphite. DOMESTIC SOURCES OF NATURAL GRAPHITES Natural graphites have been produced from mines in Alabama, Alaska, California, Georgia, Montana, New Jersey, New York, North Carolina, Pennsylvania, Rhode Island, Texas and other states. The exception is the crystalline minerals resembling Ceylon graphite that have come from Montana and the amorphous meta-anthracites from Rhode Island. All the products mined have been flake graphite. In 1960, production was reported only in Texas and Pennsylvania. The Alabama graphite deposits of flake in quartz-mica schists are found southeast of Birmingham in a narrow belt that extends for about 60 miles southwest from Delta in Randolph County to Verbena in Chilton County. Since the long-run prospects for Alabama graphites appear to be fairly bright, especially if regular production of high quality output becomes possible, regional ore reserves of all kinds, including indicated and inferred, are estimated to be of the order of 25 million tons. Of this amount, 14 million tons are of the weathered variety. Alabama graphites are favored by their relative ease of mining, and by the fact that special methods of milling have been developed at the larger properties. In addition, the steady rise in ocean freight rates for Madagascar graphites, the tendency among crucible manufacturers to use flakes of a smaller size, and the possibility of producing other salable byproducts in addition to the graphite are favorable to Alabama producers. Against

Jan 1, 1962

By J. E. Johnson

OF the many items of information necessary to the successful management of the blast-furnace, few are more important than knowledge of the location and movement of the stock-line: whether the furnace is full and has. been kept so; whether the stock is settling regularly or slipping; and, if slipping, how often it has slipped, at what times, and how far at each time. To obtain these data, a man is sometimes stationed at the top of a. pair of mechanically-filled furnaces, simply to watch and gauge them by hand in the old-fashioned way. - A more recent practice is the suspension of test-rods from ropes leading over pulleys to the ground-level, where the ropes are wound on small drums with graduated peripheries and provided with crank-handles, whereby the skip-man or some other person can quickly and conveniently gauge the position of the stock-line in the furnace. I believe the credit for this great improvement belongs to Messrs. McClure & Phillips of Sharon, Pa., who were, as far as I know, the first to apply it, and who have a patent for it. The valuable indications gained by application of the Uehling pyrometer to the down-comer are Dot to be ignored; but the information thus furnished is somewhat indi¬rect, and there is no scale for the translation of "top-tempera¬tures " into " feet down." Moreover, this apparatus as a whole is delicate, and the cost of its installation and maintenance is high. If the record furnished by the Uehling pyrometer is not in the most desirable form, the test-rods, on the other hand, give no record at all, except through the memory, or notes of a man who, to say the least, is not gauging continuously, and who may omit to report an improperly low stock-line, if it be due to a fault of his own.

Mar 1, 1905

By Frank Foote, E. R. Jette

Precision lattice-constant measurements have been widely used in the study of cubic solid solutions but as yet have been rarely applied to noncubic solid solutions. (See, however, references I and 2.) With the high precision at present attainable in the measurement of lattice constants, the X-ray method should be readily applicable to noncubic solid solutions. In the work reported here, hexagonal close-packed magnesium was used as the solvent and either lead, bismuth or gold as the solute. In the magnesium-lead and magnesium-bismuth systems the a and c lattice constants were determined as a function of composition, densities were calculated from these lattice-constant data, these theoretical densities were compared with those directly measured and the solid solubility limit was determined on quenched specimens over a considerable range of temperature. In the magnesium-gold system, the solid solubility is very small but we have obtained an indirect check on the solubility limit previously reported. Materials and Preparation oF the Alloys The magnesium used was obtained from the Aluminum Company of America and was 99.987 per cent pure. Impurities as reported On the label were: Fe, Al, 0'004 per cent; Si, 0.009 per cent; Zn, trace; Cu, Pb, nil. The bismuth was Merck's analytical grade, minimum purity 99.95 per cent. Maximum impurities as listed on the label were: Fe, 0.008 per cent; Pb, 0.010 per cent; Ag, 0.010 per cent; Cu, 0.005 per cent; Sn, 0.003 per cent; Sb, 0.00; As, 0.000; S, 0.01 per cent. The gold was purified by double precipitation with sulphur dioxide. The lattice constants of these three metals have been previously reported.3 The lead used was test lead, silver free and with a maximum of 0.10 per cent heavy metal impurities. The lattice constant 01 this lead has been measured and found to be 4.94057 ± 0.00016 at 25°C. The alloys were prepared by melting together weighed amounts of the constituent metals in magnesia-lined alundum crucibles under an atmosphere of hydrogen purified by passing over magnesium heated to 500°C. The magnesia lining prevented contamination 01 the alloys with aluminum. Vacuum melting could not be used because of the volatility of magnesium. A high-frequency induction furnace was used for the melting operation and the stirring action of the current resulted in thorough mixing of the constituents. The melts were allowed to freeze in the crucible, the ingots obtained weighed about 10 grams. An extremely thin white film formed on the surface of the melts, sometimes covering only a part of the exposed surface. The ingots were filed clean, placed in small iror crucibles with close-fitting lids and indi. vidually sealed into Pyrex glass tubes Before sealing off, the tubes were alter

Jan 1, 1941

By Frank Foote, E. R. Jette

Precision lattice-constant measurements have been widely used in the study of cubic solid solutions but as yet have been rarely applied to noncubic solid solutions. (See, however, references I and 2.) With the high precision at present attainable in the measurement of lattice constants, the X-ray method should be readily applicable to noncubic solid solutions. In the work reported here, hexagonal close-packed magnesium was used as the solvent and either lead, bismuth or gold as the solute. In the magnesium-lead and magnesium-bismuth systems the a and c lattice constants were determined as a function of composition, densities were calculated from these lattice-constant data, these theoretical densities were compared with those directly measured and the solid solubility limit was determined on quenched specimens over a considerable range of temperature. In the magnesium-gold system, the solid solubility is very small but we have obtained an indirect check on the solubility limit previously reported. Materials and Preparation oF the Alloys The magnesium used was obtained from the Aluminum Company of America and was 99.987 per cent pure. Impurities as reported On the label were: Fe, Al, 0'004 per cent; Si, 0.009 per cent; Zn, trace; Cu, Pb, nil. The bismuth was Merck's analytical grade, minimum purity 99.95 per cent. Maximum impurities as listed on the label were: Fe, 0.008 per cent; Pb, 0.010 per cent; Ag, 0.010 per cent; Cu, 0.005 per cent; Sn, 0.003 per cent; Sb, 0.00; As, 0.000; S, 0.01 per cent. The gold was purified by double precipitation with sulphur dioxide. The lattice constants of these three metals have been previously reported.3 The lead used was test lead, silver free and with a maximum of 0.10 per cent heavy metal impurities. The lattice constant 01 this lead has been measured and found to be 4.94057 ± 0.00016 at 25°C. The alloys were prepared by melting together weighed amounts of the constituent metals in magnesia-lined alundum crucibles under an atmosphere of hydrogen purified by passing over magnesium heated to 500°C. The magnesia lining prevented contamination 01 the alloys with aluminum. Vacuum melting could not be used because of the volatility of magnesium. A high-frequency induction furnace was used for the melting operation and the stirring action of the current resulted in thorough mixing of the constituents. The melts were allowed to freeze in the crucible, the ingots obtained weighed about 10 grams. An extremely thin white film formed on the surface of the melts, sometimes covering only a part of the exposed surface. The ingots were filed clean, placed in small iror crucibles with close-fitting lids and indi. vidually sealed into Pyrex glass tubes Before sealing off, the tubes were alter

Jan 1, 1941

By Hiroshi Oikawa, A. G. Guy

Recent experimental evidence has shown that it is often incorrect to neglect the reactions occurring at an interface with respect to the diffusion reactions. By introducing reaction-rate constants and k for the transfer of components 1 and 2 between the a and b phases, a phenomenological description has been devised for the coupled processes of diffusion and in-terfacial reaction. An illustrative example has been analyzed with the aid of a suitable computer program. The results indicate that for kab values on the order of 10'1 cm per sec and Ð values of about 10¯10 sq cm per sec, the interfacial reactions are significant during the first 10 2 to l0 6 sec of a diffusion experiment. Among the observable effects of the interfacial reactions in this case appear to be the burying Kirkendall markers and an anomaly in the initial shifting of these markers. THE study of diffusion between two phases is especially important because of its direct connection to phase transformations. For example, the transformation of austenite to ferrite involves diffusion in the a and ý phases and also an interfacial reaction (trans formation) at the a/? interface. If ferrite and aus-tenite are the two members in a diffusion couple, the same two reactions occur during the diffusion process. The numerical values obtained for the diffusion coefficients and interfacial-reaction constants from diffusion experiments can then be employed to predict phase-transformation behavior. Refinement of the calculations of phase transformation is also suggested by the present method for treating two-phase diffusion. In the recent paper by Nolfi et al.' only the solute com ponent is considered in the interfacial reaction accompanying a phase transformation. The present analysis demonstrates that both components must be considered. It is generally recognized that reactions of some kind must occur at the interface in a two-phase diffusion couple, but usually it is assumed that the interface reaction occurs so rapidly that its effect on the overall process is unobservable because the slower diffusion process determines the kinetics of the process. However, Seith and Heumann 2 pointed out that effects of the interfacial reaction should always occur in the early stages of diffusion, and recently Eifert et al. 3 have shown that interfacial reactions influence the composition and motion of the interface in a/ß Al-Cu diffusion couples during the entire course of prolonged, high-temperature treatments. A general procedure for handling the combined processes of interfacial reaction and diffusion in a binary, two-phase system is to introduce kinetic coefficients for the interface reactions and to develop the system of equations governing the interlinked processes of diffusion and interface reaction. The resulting equations, although not amenable to solution in closed form, can be usefully manipulated by a digital computer. INTERFACIAL REACTIONS IN TWO-PHASE DIFFUSION Consider the general case of diffusion between two solid solutions, a and ß, which are adjacent phases in a binary system, Fig. 1. Two semiinfinite bars having compositions c1 and c0ß are jointed at x = 0. If concentrations are expressed in volume fraction,4

Jan 1, 1970

By J. D. Price, W. M. Bertholf

A. C. RICHARDSON*—First of all, [ think that the paper represents a lot more work, study, and correlation than has been indicated by the brief talk by Mr. Price. I like the way he started out and described the areas from which the samples were obtained, the locations of the washing plants, the available tonnages, and other background information with which to evaluate the data he submitted later on. Then I like the way in which he described the various types of washing plants, the tonnages handled and the difficulties of the washing problems; showing the amount of material that lies close to the specific gravity at which the washing separation is made. Later he gave figures from washing plant operations showing recoveries and cleaning efficiencies. He then discussed his own plant at Pueblo. It is the same old plant, I think, that I worked around a good many years ago. It is unusual to find a plant treating nearly 5000 tons of coal a day on tables. But this table plant is, I believe, more efficient than is indicated by the figures that Mr. Price gave. To determine the efficiency of a cleaning operation or to compare it with another it is necessary to consider the quantity and character of the material close to the specific gravity at which the separation is made. It is not fair, I believe, to penalize the table operation by something like 4 pct of out-of-place-material as he has done here. The variety and difficulty of the coals that he has to wash, the continuous shift and change in their composition make a very difficult cleaning problem and the table performance is excellent. I believe that the information in this paper will be of interest and value to anyone operating or planning to build a coal cleaning plant in this or other areas; particularly where the cleaning of fine coal is a problem. The data may be used for comparative purposes in determining the relative efficiencies of other cleaning plant separations. E. D. HAIGLER*—What is a Baum jig? J. D. PRICE (authors' reply)—A Baum-type jig is one in which the pulsations of the water is secured by means of a pulsating air current applied on top of the water. I imagine you are all familiar with the old plunger-type jig which is in effect a U tube in which a plunger on one side of the U, moving up and down, causes a corresponding pulsation on the far side of the jig. In the Baum jig, the pulsating air current is applied on the surface of the water on one side of the U tube of the jig and gives a corresponding pulsation on the other. It is also commonly known as a pneumatic jig. The control of the rise and fall of the water in the jig body proper is under much better control than it is in any of the other type jigs. Mr. Richardson could enlarge on that feature, for I know that he has had considerable experience with these jigs. A. C. RICHARDSON—You have asked how to control a Baum-type jig. The pulsations in a Baum jig can be modified and regulated to a marked degree by the amount of water admitted to the jig and by the adjustments of the valve which regulates the manner in which air is admitted. The number of pulsations per minute is controlled by the number of cycles of the air valve. Thirty to forty cycles per minute is a good speed for large jigs treating coarse sizes of cod. With an air valve it is possible to modify the time-velocity curve of the pulsating water to some extent which in turn determines the action in a jig bed. Within limits the following parts of the air valve cycle may be regulated: (1) the rate and period of air admission, (2) the period of air expansion, (3) the rate and period of air exhaust, and (4) the period of air compression. The rate and period of air admission determines the acceleration of the water at the beginning of the pulsion stroke and the amplitude of the stroke. The period of air expansion, after inlet port is closed, is one in which the water has reached the desired velocity, positive acceleration reduced, and the bed held in a mobile condition. The rate and period of the air exhaust can be adjusted to modify the degree of suction and so modify the manner in which the particles in the bed stratify. The compression period, alter the exhaust port closes and before the intake port opens may be used to advantage in retarding the downward velocity of water during the suction stroke. An ideal jig stroke is one in which during the up stroke the bed is lifted slowly in a mass and opens up like an accordian with the bottom layers dropping away first. With the bed open and mobile the particles adjust themselves according to their hindered settling rates. During the down stroke, while the bed is still open the particles of high specific gravity are accelerated toward the bottom layers. It is possible to approach this stroke with all types of jigs but it is less difficult to approximate it with a Baum jig.

Jan 1, 1950

By L. S. Darken

It has long been recognized that the driving force in an isothermal diffusion process may be regarded as the negative gradient of the chemical potential (partial molal free energy) of the diffusing substance. This equivalence is exactly analogous to the fact that a mechanical force is the negative gradient of the potential energy. Nernstl in 1888 expressed these driving forces in terms of osmotic pressure, which is directly related to the chemical potential and free energy. The relationship between the diffusivity, mobility and activity coefficient of electrolytes in aqueous solution has been developed in great detail by Onsager and FuossZ with results which have recently been confirmed experimentally by Harned and Nuttall. This interpretation of the driving force in isothermal diffusion has been discussed earlier by the author,4,5 who pointed out4 that "for a system of more than two components it.is no longer necessarily true that a given element tends to diffuse toward a region of lower concentration even within a single phase region"; departure from the behavior of an ideal solution may be so great that the concentration gradient and the chemical potential gradient, or activity gradient, may be of different sign, thus giving rise to "up hill" diffusion. Since, in the discussion of that paper,4 some skepti- cism as to the validity of this conclusion was expressed, it seemed desirable to adduce experimental evidence to support it. Evidence of such diffusion in nonmetallic systems has already been reported. For example, it was observed by Hartley" in a series of experiments in which sodium chloride diffused from a saturated solution in about 5 pct acetone in water into a solution virtually free of salt but with essentially the same acetone concentration. Specifically, a wine glass containing crystalline salt and saturated solution was totally immersed in a large glass cylinder containing the acetone-water solution without salt; the difference in specific gravity was such as to prevent convection. Diffusion of salt was accompanied by a marked depletion of acetone in the wine glass; after 3 days the acetone concentration decreased from 5.37 pct at the top of the glass, where the salt concentration was low (0.93 pct), to 1.84 pct at the bottom where the salt concentration was high (21.64 pct). This "uphill" diffusion was found to be such that the partial pressure (activity) of acetone was essentially equalized throughout the system when a steady state gradient of sodium chloride was maintained. In order to demonstrate the existence of such diffusion in metals, a series of four weld-diffusion experiments was made. In these measurements pairs of steel of virtually the same carbon content, but differing markedly in alloy content, were welded at the end and held at 10500 C for about two weeks. Subsequent analysis showed that carbon had diffused so as to produce an inequality

Jan 1, 1949

By A. F. Crawley

The densities of some liquid Pb-Sb alloys up to 11 wt pct Sb and Pb-Sb-& alloys up to 10 pct Sb/10 pct Sh have been determined by a pycnometric technique over a temperature range of about 130°C above their melting points. The data given are accurate within 0.05 pct. Density is shown to vary linearly with temperature , and equations relating these quantities have been formulated. Molar volumes calculated from the density data indicate that volumetric deviations from ideal mixing are undetectable within the limits of experimental error. A continuing research program into some fundamental physical properties of liquid metals is being pursued at the Mines Branch, Department of Energy, Mines and Resources, Ottawa, Canada. This work has received support from the Canadian Zinc and Lead Research Committee in cooperation with the International Lead and Zinc Research Organization. This paper, which reports some density data for Pb-Sb and Pb-Sb-Sn alloys, follows previous work from this laboratory on lead, tin, and Pb-Sn alloys.' Of previous data from others, Greenaway2 and Sato and Munakata3 have reported results on Pb-Sb alloys. No previous work has been published on the ternary Pb-Sb-Sn alloys, reported here. EXPERIMENTAL METHOD Densities were measured by a pycnometric technique which has been described in detail and appraised for accuracy in earlier Mines Branch reports.475 Fig. 1 shows the densitometer with the pycnometer in position for a run. The pycnometer is also shown in some detail. The pycnometer of dense, high-purity graphite, about 14 cu cm in volume, was carefully machined to a uniform, smooth finish. The height was measured by a depth micrometer and the diameter by fitting precision gage blocks between steel balls.' In each case several readings were taken, and the final results were considered accurate within 0.01 pct. The resulting volumetric uncertainty together with small inaccuracies in the coefficients of linear expansion of graphite lead to a maximum systematic uncertainty in the method of ±0.03 pct. As shown in Fig. 1, the pycnometer lid is a threaded cap. Thus, the charge, a cylinder of the alloy, can easily be inserted and the solidified metal can readily be removed after a run. The dimensions of the cylindrical charge are chosen to ensure that, once molten, the metal will not only fill the pycnometer completely but will discharge an excess into the excess-metal float chamber. AS the temperature is increased above the melting point, the volume of metal in the excess chamber increases until the system has equilibrated at the desired temperature. At this point, the excess chamber is moved to one side by twisting the shaft F, leaving a fixed volume of liquid metal in the pycnometer. This volume of fluid is readily calculated using measured coefficients of linear expansion of the graphite which expands anisotropically. The associated weight of fluid is determined as the weight of the solidified metal removed after the furnace has cooled down. Alloys were prepared from 99.997 pct Pb, 99.999 pct Sn, and 99.999 pct Sb, being melted by an electric furnace in a graphite crucible and poured into graphite molds. Several density specimens of the same nominal size were machined from each ingot, and, by comparing specimen weights, relative differences in specimen composition resulting from segregation in the ingots could be detected. In this way, segregation was found to have occurred in Pb-Sb alloys at compositions beyond the eutectic (11.2 pct Sb) and this

Jan 1, 1969

By E. C. Truesdale, Gerald Edmunds

A few years ago H. M. Cyr, working in the Research Laboratories of The New Jersey Zinc Co., produced a few pounds of zinc1 of such purity that no other elements were detected in it by spectrographic analysis, using the facilities then available. This zinc contained less than one ten-thousandth of one per cent of metallic impurities.&apos; During the decade that followed upon the laboratory production of this "spectro-graphically pure" zinc, commercial developments brought about the production of large tonnages of zinc of purity exceeding 99.99 per cent, and today zinc of 99.999 per cent purity is produced and marketed as "chemically pure" zinc. Typical analyses of present supplies of high-purity zinc are given in Table 1. Table 1.—Typical Analyses Percentnge by Weight Sum of Zinc Fe, Ib1 Fe Cd 1A1 cd Special High Grade*.......... 0.007b 0.005b 0.005b none O.OIOb C.P. (chemically pure)......... < 0.0002 0.0005c 0.000052 S.P. (spectrographically pure).. <0.0002d <0.00005d a A.S.T.M. Standard Specification for Special High Grade Slab Zinc (A.S.T.M. Designation: B 637). b Maximum. &apos; Fe chemically determined. Pb and Cd are spectrographically determined. d Differences between composition of C.P. and S.P. zinc are discussed later in this paper. The availability of commercial tonnages of special high-grade zinc has been the basis for the development of the zinc-base die-casting alloy industry which, in the year 1936, consumed one-eighth of the zinc used in the United States for all purposes. This and the C.P. and S.P. grades have given impetus to scientific investigations into the properties of pure

Jan 1, 1939

By E. C. Truesdale, Gerald Edmunds

A few years ago H. M. Cyr, working in the Research Laboratories of The New Jersey Zinc Co., produced a few pounds of zinc1 of such purity that no other elements were detected in it by spectrographic analysis, using the facilities then available. This zinc contained less than one ten-thousandth of one per cent of metallic impurities.&apos; During the decade that followed upon the laboratory production of this "spectro-graphically pure" zinc, commercial developments brought about the production of large tonnages of zinc of purity exceeding 99.99 per cent, and today zinc of 99.999 per cent purity is produced and marketed as "chemically pure" zinc. Typical analyses of present supplies of high-purity zinc are given in Table 1. Table 1.—Typical Analyses Percentnge by Weight Sum of Zinc Fe, Ib1 Fe Cd 1A1 cd Special High Grade*.......... 0.007b 0.005b 0.005b none O.OIOb C.P. (chemically pure)......... < 0.0002 0.0005c 0.000052 S.P. (spectrographically pure).. <0.0002d <0.00005d a A.S.T.M. Standard Specification for Special High Grade Slab Zinc (A.S.T.M. Designation: B 637). b Maximum. &apos; Fe chemically determined. Pb and Cd are spectrographically determined. d Differences between composition of C.P. and S.P. zinc are discussed later in this paper. The availability of commercial tonnages of special high-grade zinc has been the basis for the development of the zinc-base die-casting alloy industry which, in the year 1936, consumed one-eighth of the zinc used in the United States for all purposes. This and the C.P. and S.P. grades have given impetus to scientific investigations into the properties of pure

Jan 1, 1939

By John A. Wolfe

The brightest spot in the mineral economy of the Philippines is the rapid development of reserves and production of copper. If economic conditions remain favorable and the political climate is encouraging, production of this metal should increase at a rate of 25% per year for several years, long enough to rank this country as one of the major copper producers of the world. In 1965 the copper content of the Philippine concentrates was approximately 60,000 tons. It should total about 80,000 tons in 1966. A major part of the increase will come from the rich Lepanto mine located in Mountain Province, North Central Luzon. Daily production of ore increased from 1200 to 2000 tons at the end of 1965. The ore, consisting of enargite and luzonite, averages nearly 3% copper and 0.12 oz. of gold per ton. It is an under- ground operation with a cutoff grade of 2%. The ore is associated with extensive silicification under a volcanic cap rock. Further expansion to increase ore production to 2600 tpd is under way.

Jan 4, 1967

By MCA Woolsey

(Butte. Meeting, August, 1913.). IN metallurgical circles it is known widely, but somewhat vaguely, that the ease of: reduction of metallic oxides depends largely on the way they have been prepared. It is likewise known that different forms of carbon have different and greatly varying reducing powers. It is the purpose of this paper to show somewhat more definitely and scientifically these facts. Some years ago the writer published an account of pyrometric determinations of the reduction- temperature of zinc oxides variously prepared and of several kinds.1 In said paper it was shown that the temperature it which zinc oxide evolves zinc according to the equation Zn0. +&apos; C = Zn + CO depends upon the ;nature of:., the.&apos; two reacting bodies. The determinations bad a range of accuracy of from 2° to. 6° C.,whereas differences were found to. amount to an extreme. of 90° C. :.86 the differences are real ones and must have, definite cause. The equation of boiling water, (H20)4 = 4 (H2O) has a fixed temperature for equilibrium of 100° C. at 760 mm. pressure. , In general, all equations. reacting e in .the liquid or the gaseous phase have-well-defined constant physical conditions which govern the equilibrium point and reaction velocities. In a reaction where we have one or more solid phases, the temperature conditions requisite for the unbalancing of the stable system are found to vary. These variations are due to the fact that in a solid there is a very complex molecule and it is not, a question solely of the tearing away of two interlocked atoms, but also of the destruction of a complex molecule containing hundreds, or possibly thousands, of smaller molecules.

Jan 7, 1913

By E. H. Hamilton, H. C. Vacher

The limiting concentrations of carbon and oxygen which may CO-exist at equilibrium in liquid iron are important in determining the degree to which liquid steel may be refined before it is deoxidized. Most refining processes depend upon the oxidation of a highly carburized iron which invariably results in contaminating the steel with oxygen. The oxygen thus introduced presents many problems to the refiner, who in turn has attempted to rid the steel of this impurity by deoxidation witch elements such as manganese, silicon and aluminum. The importance of the limiting concentrations of carbon and oxygen is accentuated in view of a number of recent researches which have indicated in many instances the existence of relations between oxide inclusions and dissolved oxygen and physical properties and chemical behavior of steel. The determination of the equilibrium concentrations of carbon and oxygen existing in iron under steelmaking conditions is obviously of fundamental importance. It has been generally assumed that the product of the equilibrium concentrations of carbon and oxygen in liquid iron is a constant and that this product is directly proportional to the carbon monoxide pressure in equilibrium with the liquid iron. Hertyl.2 has computed values for this product based on open-hearth data which are all in the neighborhood of 0.01 to 0.03 (per cent. FeO X per cent. C) for temperatures in the vicinity of 1550" to 1600" C. and one atmosphere pressure. Kinzel and Egan % have attempted to determine the value of this product by exposing liquid iron to carbon monoxide at one atmosphere pressure. The value reported by them was 0.0005 at 1550" C. In order to apply certain equations to the rate of carbon elimination in the open-hearth process, Feild4 found it necessary to assume a value of 0.0102 at 1580" C. for this

Jan 1, 1931

By STEPHEN L. GOODALE

THE question indicated in this title was put by letter to a number of my friends working in various industries, who have charge of young metallurgical graduates. The replies were almost unanimous in stating that the college training should cover in the most .thorough manner possible those sciences which are the fundamentals - of engineering. Mathematics, physics, mechanics, electricity, chemistry, physical chemistry, and their applications to actual problems of life were mentioned in most of the letters I received. Some writers added also business law, economics,. and finance. One reply expressed it: "These subjects, well founded, mixed with good judgment, well applied, should enable the .young man to carry on the art of life successfully." One answer stated frankly what is really wanted: "As much as possible.&apos; &apos; This writer mentioned .the sciences as being very important, but he wishes men &apos; to be trained in metallurgy also, and he concedes the omission of some advanced chemistry and physic&apos;s to secure the metallurgy. He emphasized particularly. the a we. desirability of work in college to development&apos; He concludes his letter with a repetition of his slogan that what is wanted is as much as is possible.

Jan 1, 1930

By D. T. Peters, S. Floreen

The age hardening behavior of an Fe-8Ni-13Mo alloy was studied after the matrix had been varied to produce either ferrite, cold u~orked ferrite, or nzassive nzartensite. The aging behavior of the cold worked ferrite and murtensite structures were very similar. The martensite aging kinetics were much different from those observed in earlier studies of aging of maraging steels, even though the martensite wzatri.r had the same dislocation structure as those found in maraging steels. The results suggest that the previously observed precipitation kinetics of maraging steels ?nay have been controlled by the nucleation be-haviov, which in turn were dictated by the alloy compositions and the resultant identities of the precipitating phases. IT is well known that the rate of precipitation from solid solution depends not only on the degree of super-saturation, but also on the density and distribution of dislocations in the matrix structure. These imperfections often act as nucleation sites, and may also enhance atomic mobility. &apos;Thus, the presence of dislocations is important since the type and distribution of precipitates may be determined by them. The precipitate density and morphology in turn affects the mechanical properties of the alloy. A number of studies have been devoted to the precipitation characteristics in various types of maraging steels.&apos;-" These are iron-base alloys containing 10 to 25 pct Ni along with other substitutional elements such as Mo, Ti, Al, and so forth, that are used to produce age hardening. The carbon contents of these steels are quite low, and carbide precipitation is not believed to play any significant role in the aging reactions. After solution annealing and cooling these alloys generally transfclrm to a bcc lath or massive martensite structure characterized by elongated martensite platelets that are separated from each other by low angle boundaries, and that contain a very high dislocation den~it~.~~~~~~~~-~~ Age hardening is then conducted at temperatures on the order of 800" to 1000°F to produce substitutional element precipitation within the massive martensite matrix. Most of the aging studies to date have revealed several common traits in these alloys, regardless of the particular identity of the precipitation elements. Generally hardening has been found to be extremely rapid, with incubation times that approach zero. The agng kinetics, at least up to the time when reversion of the martensite matrix to austenite begins to predominate, frequently follow a AX/~~ = ktn type law, where x is hardness or electrical resistivity, t is the time, and k and n are constants. The values of n are frequently on the order of 0.2 to 0.5, which are well below the idealized values of n based on diffusion controlled precipitate growth models. Finally, the observed activation energy values are typically on the order of 30 kcal per mole, and thus are well below the nominal value of about 60 kcal per mole found for substitutional element diffusion in ferrite. The common explanation of these observations is that the precipitation kinetics are controlled by the massive martensite matrix structure. Thus, the absence of any noticeable incubation time has been attributed, after ~ahn," to the fact that the precipitate nucleation on dislocations may occur without a finite activation energy barrier. The low values of the activation energy are generally assumed to be due to enhanced diffusivity in the highly faulted structure. If this explanation that the precipitation kinetics are dominated by the matrix structure is correct then one should observe a distinct difference in lunetics between aging in a martensitic matrix and aging the same alloy when it has a ferritic matrix. Such a comparison cannot be made with conventional maraging compositions, but could be made with the alloy used in the present study. In addition, the ferritic structure of the present alloy could be cold worked to produce a high dislocation density so that one could determine whether ferrite in this condition would age similarly to martensite. EXPERIMENTAL PROCEDURE The composition of the alloy used in this study was 8.1 pct Ni, 13.0 pct Mo, 0.10 pct Al, 0.13 pct Ti, 0.012 pct C, bal Fe. The alloy was prepared as a 40 lb vacuum induction melt. The heat was homogenized and hot forged at 2100°F to 2 by 2 in. bar, and then hot rolled at 1900°F to $ in. bar stock. The aging lunetics were followed by Rockwell C hardness and electrical resistivity measurements. Samples for hardness testing were prepared as small strips approximately 2 by $ by 4 in. thick. Electrical resistivity was studied on cylindrical samples approximately 2 in. long by 0.1 in. diam. The method for making the alloy either martensitic or ferritic was based on the fact that the alloy showed a closed y loop type of phase diagram. At high temperatures, above approximately 24003F, the alloy was entirely ferritic. Small samples on the order of the dimensions described above remained entirely ferritic after iced-brine quenching from this temperature. In practice, a heat treatment of 1 hr in an inert atmosphere at 2500°F followed by water quenching was used to produce the ferritic microstructure. These samples were quite coarse grained and usually en-

Jan 1, 1970

The Second Pan-American Scientific Congress will be held under the auspices of the United States Government in Washington, D. C., Dec. 27, 1915, to Jan. 8, 1916. The organization officers are John Barrett, LL. D., Director General of the Pan-American Union, Secretary General; Glen Levin Swiggett, Ph. D., Assistant Secretary General; the headquarters of the Congress are the Pan-American Union, Washington, D. C. The program of the Congress is divided into nine main Sections, which are given below with the name of the Chairman of each Section: 1. Anthropology, William H. Holmes, B. S., Smithsonian Institution, Washington. 2. Astronomy, Meteorology, and Seismology, Robert S. Woodward, Ph. D., Carnegie Institution, Washington, D. C. 3. Conservation of National Resources, Agriculture, Irrigation and Forestry, George M. Rommel, B. S., Bureau of Animal Industry, Department of Agriculture, Washington, D. C. 4. Education, P. P. Claxton, LL. D., Bureau of Education, Washington, D. C.

Jan 12, 1915

By Sam Harlan

At intervals during the past several years the oil industry has been confronted with the problem of forestalling crises in its affairs. These crises have been reduced to periods of depression which, fortunately, the industry has been able to survive. Under the existing competitive practices which control the producing division of the industry it apparently has been proved that the best efforts logically to curtail development and producing operations are inadequate for effecting a true production balance and the consequent stabilization of prices. The industry is awakening to the fact that the situation warrants revolutionary thought and at this time it is looking for a permanent solution of its problem in a general plan for unit development and operation such as the one first proposed by Henry L. Doherty. Mr. Doherty&apos;s proposal was designed not only as a means for stabilizing the industry as a whole, but its principles involve very definite potential benefits for the average individual operator and royalty owner as participants in pooled projects. The benefits to these individuals would be derived from maximum recovery, the maximum utilization of natural energies, the minimization of development and operating costs, enhanced values of leases and royalties through improved efficiencies and ultimate yields, improved earnings through stabilized crude oil prices, etc. This plan was revolutionary to the industry&apos;s practices and at the time was rejected, but it now appears that the development and operating policies for new properties are continually approaching the ideal of the original plan. Oil companies are constantly extending their efforts to improve all factors that have a bearing on the costs and efficiencies of their operations. These efforts may, in some degree, be a normal outgrowth of the industry&apos;s progress, but the forced consideration of market conditions, the growing appreciation of the importance of regulating operations for maximum ultimate economies and the depreciation of the old principle of maximum flush at any cost, come from a new school of thought which has been stimulated by the immediate pressure of overproduction and

Jan 1, 1930

"The earth is the Lord&apos;s and the fullness thereof." Science knows no national boundaries, knows no country. These views might be taken as premises for a discussion of the development of the mineral resources of the world. Yet how far man is removed from such broadminded ideals! In this day of jealousy and dread, of political machinations and statesmen&apos;s maneuverings, of rantings and crass ravings against fellow-beings, man&apos;s attitudes towards God&apos;s gifts are but the measure of the smallness of man. That the exploitation of mineral wealth should be for the common good, none will deny, but what is meant by "common"? Is it for the common good of The Pennsylvania State College, Pennsylvania, the United States of America, or the world? If man is big enough and honest enough to state categorically that by "common," as used in the context above, is meant that the utilization of the mineral wealth should be for the mutual benefit of all mankind, and that all concerned strive to see that such a viewpoint is executed, then there is brighter hope for the future. It is to be hoped that the world may have at least a few years or possibly a generation of peace. What can be done in these years to work towards the ultimate goal of human improvement? The work of statesmen in the drafting of international agreements and the easing of small frictions which appear between nations, as they

Jan 1, 1950

By G. D. Rieck, M. M. P. Janssen

Chemical diffusion coefficients and heats of activation for diffusion in the NizAh fy), NiAl (6), and Ni3A1 (E) intermetallic phases and the solid solution of aluminum in nickel (( phase) were calculated from layer growth experiments. No finite diffusion coefficient for the NiAl3 ((3) inter metallic phase could be calculated. The values of the diffusion coefficients are dependent both on the method of calculation and the type of diffusion couple. The heat of activation for diffusion in the y phase was found to be 47 kcal per mole in the temperature range oj 428" to 610°C. Heats of activation of 41, 12, and 48 kcal per mole were found for diffusion in the 6, E, and ( phases, respectively , in the temperature range of 655" to 1000°C. Experiments with markers in the diffusion zone demonstrate a very pronounced Kirkendall effect. It appears that only aluminum atoms take an active part in the diffusion process during the formation of the 0 and y phases at temperatures of about 600°C. During the formation of the 6, E, and < phases at higher temperatures only nickel atoms are moving. It is suggested that the great stability of the intermetallic compounds in the Ni-A1 system governs the Kirkendall effect. SOME factors controlling layer growth during inter-diffusion in the Ni-A1 system (phase diagram, see Fig. 1) were studied by Castleman and Seig1e.l&apos;~ They found the NiA1, ((3) and NiAl3 (y) intermetallic compounds to appear in the diffusion zone of Ni-A1 couples at annealing temperatures of 400" to 625°C; the NiAl (6) and Ni3A1 (E) intermetallic compounds appeared in y-Ni couples at annealing temperatures of 800" to 1050°C. These authors carefully examined metallographically Ni-A1 couples after 340 hr annealing at 600°C. Besides the (3 and y phases they found very thin layers of the 6 and E phases. ~n~erman~ and Castleman and Froot4 observed a much more rapid growth of the 5 and E phases at 600°C in Ni-A1 couples in case a crack was present at the /3-A1 interface. Numerous layer thickness measurements carried out by Castleman and Seigle on the y phase prove that the layer growth of this phase obeys the parabolic law after a certain transient period. From this they concluded that the layer growth of the y phase is controlled by volume diffusion. The growth of the 13, 6, and E phases appeared to be volume-diffusion-controlled also. The authors estimated that at 600°C and at atmospheric pressure Dp was 1.8 x lo-"ll sq cm per sec, D, 9.1 x 10" ™ sq cm per sec, Qp 27 kcal per mole, and Qy 31 kcal per mole. The present work was carried out to obtain more quantitative data about the kinetics of growth of the phases of the Ni-A1 system and the reactions that occur during the formation of these phases. Because in this system the diffusion process results in the formation of several distinct intermetallic compounds, the current term reaction diffusion is used in the title of this paper. In order to obtain layers of the fl phase compound of uniform thickness, a new technique for preparing diffusion couples was developed. The kinetics of growth of the y phase in 6-Al, E-Al, and Ni-A1 diffusion couples was studied at different temperatures. The kinetics of growth of the 6, c, and ( phases in Ni-y, Ni-6, and Ni-c diffusion couples was also studied at different temperatures. The calculation of the diffusion coefficients Dp and Dy by Castleman and Seigle are critically considered in this paper; by means of a revised method of calculation more reliable val-ues of , and Dg were found. These values are in good agreement with the values of the diffusion coefficients obtained by the method of Boltzmann-Matano. From the temperature dependence of the diffusion coefficients the heats of activation for diffusion were calculated by means of an Arrhenius-type equation. The investigation of the Kirkendall effect has been used to obtain information about the ratio of the intrinsic diffusion coefficients of the separate atoms5 and the mechanism of diffusion. Moreover porosity as a result of a distinct Kirkendall effect would be of practical importance in connection with the bonding of diffusion coatings. The analyses of the diffusion couples were carried out by metallographic methods. The values of the concentrations at the phase boundaries and the concentration profile in each of the phases, which are needed for the calculation of diffusion coefficients, were obtained by electron-pro be X-ray microanalysis. EXPERIMENTAL PROCEDURE A) Materials for Diffusion Couples. The intermetallic compounds 6 (50 at. pct Ni) and E (74 at. pct Ni) were prepared from the pure metals by high-frequency induction melting in argon atmosphere. Use was made of aluminum wire (99.99 wt pct Al) and nickel sheet (99.95 wt pct Ni). The 6 and E phase melts and the nickel shiet (thickness 0.1 and 0.5 mm) used for preparing diffusion couples were annealed for 64 hr at 1200°~ for homogenization and grain coarsening (final crystal size 1 to 3 mm). composition and homogeneity of the intermetallic compounds were checked by mi-crohardness measurements and X-ray diffraction. From the 6 and E phase melts discs of 0.5 mm thickness were prepared by means of a water-cooled rotat-

Jan 1, 1968