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By Otto H. Henry, J. J. Cordiano

THOUGH powder metallurgy is one of the oldest of metallurgical processes, it is in its infancy as a branch of the modern field of metallurgy. As early as 3000 B.C., the ancients produced implements and weapons of iron by reducing iron ore in a charcoal fire and forging the resultant sponge while still hot into the desired shape. Melting and casting soon superseded the powder metallurgy practice, and it was not until the turn of the twentieth century that powder metallurgy was applied to the commercial manufacture of tungsten lamp filaments. From this beginning, the use of the powder metallurgy process spread to the manufacture of porous oil-impregnated bearings, cemented carbide tools, contact points, diamond grinding wheels, clutch facings, starter brushes, resin-bonded radio cores, magnets, metallic filters, and other parts. More recently, and particularly during the present war, there has been a definite trend toward the manufacture of machine parts by this process in competition with the more conventional fabricating methods. Notwithstanding these many developments, scientific progress has been slow. While many articles on powder metallurgy have appeared in the press and various publications, there have been too few contributions to our technical societies, with the result that there is a dearth of the type of information necessary for the full development of this science. It is of primary importance that the results of research and development be freely disseminated if powder metallurgy is to realize its fullest potentialities. PURPOSE OF INVESTIGATION Excluding the refractory metal field, all commercial powder metallurgical products made by a cold compressing and sintering operation contain voids. These voids can be substantially eliminated by subsequent severe working and heat-treatment, but such practice has not proved economical in most applications. By applying heat during the compressing operation, plastic deformation of the powder particles is substantially increased, and the resultant compact or briquette is practically free of voids. However, hot-pressing has many attendant problems, which at present preclude its use in the manufacture of precision parts. The more important of these are to devise: I. A die steel capable of withstanding high pressures at elevated temperatures. 2. A high-temperature lubricant capable of preventing excessive die wear and welding of the compact to the die walls. 3. A method of retaining a neutral or reducing atmosphere in the compacting zone of the die assembly. 4. A means of ejecting the hot-pressed specimen into a neutral atmosphere until reasonably cold.

Jan 1, 1945

By P. Breidt, E. S. Greiner

THIS note reports a determination of the melting point of germanium, and the liquidus of the Ge-Ga alloys; lattice constants of the a phase are given. The alloys were prepared by melting germanium (>20 ohm-cm resistivity) and gallium (99.6 pct) in evacuated silica tubes. The materials (50 to 70 g) were heated at 1000°C, held in the liquid state for about ¾ hr, and then cooled rapidly in the tubes. Points on the liquidus were obtained by thermal analysis which consisted of obtaining time-temperature data during heating and cooling the materials in high purity graphite crucibles and a helium at- mosphere. Temperatures were determined with a Pt—Pt-Rh thermocouple protected by a silica sheath. The couple was calibrated against a National Bureau of Standards calibrated couple and also against the freezing points of copper, silver, aluminum, and the 28.1 wt pct Cu, 71.9 wt pct Ag alloy eutectic. The samples for X-ray analysis were prepared by heating small pieces of the ingots in evacuated glass or quartz tubes at temperatures between 600" and 900°C for periods ranging from 2 hr to 22 days, periods deemed sufficient for equilibrium to be attained, followed by quenching in water. The heat-treated samples were ground to powder for X-ray analysis. The lattice constants of the germanium-rich phase (a) were determined with a baok-reflection focusing camera. The X-ray reflections (331 and 422 Cr Ka, 422 and 333 Cr KB) were corrected

Jan 1, 1956

By Daniel R. Hull

In 1926 Gendersl reviewed the existing theories of this subject and stated his views in support of the gas-pressure theory. Again, in 1937, the subject was thoroughly reviewed by N. B. Vaughan3 and by Phillips and Brick,2 so that no résumé is called for here. The purpose of this paper is to describe certain observations made in the course of mill work, and to point out that they mostly tend to confirm the gas theory of Genders. Vapor Segregation There is, however, one type of inverse segregation that can be accounted for by considering the volatility of one of the constituents of an alloy. The most familiar case is ordinary brass, which is subject to a zinc enrichment of a few tenths of a per cent at the surface of a chill casting. This has been noted in 70-30 brass by Genders, and a typical example of it is given in Table 1, which represents a cylindrical billet 7 in. in diameter by 55 in. long. After lathe-turning 1/32 in. from the surface, the remaining distance to the center was sampled at six equally spaced intervals. the lead, which is essentially the same throughout, will be mentioned later. Consider a brass-mill mold, either round or rectangular in cross section, standing several feet high. It may require a minute or two for pouring. Before it is full, the metal in the lower end has partly solidified and contracted somewhat away from the mold. The initial shell of solidification follows not far behind the top of the column, even if the central portion is liquid for a long way down. There is, then, a space between metal and mold that is filled with zinc vapor. The vapor has no exit, because the liquid at the top of the rising column is not only in contact with the mold but keeps UP a fresh supply of zinc vapor, which has, perhaps, already begun to condense in the lower portion. The cycle is short. Within a minute or two after the mold is full the bar has cooled enough to condense all the zinc. Some of it may condense on the mold; it might be expected that most of it would condense there, but the mold at that time is well coated with a velvety carbon residue from the oil dressing, overlain by fluffy zinc oxide that commenced covering the inside of the mold as soon as pouring began. The clean skin of the freshly cast brass offers a preferred surface for condensation. Reabsorption is quick and inevitable. A simple experiment indicates that a surprisingly large quantity of zinc vapor is trapped in the space between mold and

Jan 1, 1941

By Daniel R. Hull

In 1926 Gendersl reviewed the existing theories of this subject and stated his views in support of the gas-pressure theory. Again, in 1937, the subject was thoroughly reviewed by N. B. Vaughan3 and by Phillips and Brick,2 so that no résumé is called for here. The purpose of this paper is to describe certain observations made in the course of mill work, and to point out that they mostly tend to confirm the gas theory of Genders. Vapor Segregation There is, however, one type of inverse segregation that can be accounted for by considering the volatility of one of the constituents of an alloy. The most familiar case is ordinary brass, which is subject to a zinc enrichment of a few tenths of a per cent at the surface of a chill casting. This has been noted in 70-30 brass by Genders, and a typical example of it is given in Table 1, which represents a cylindrical billet 7 in. in diameter by 55 in. long. After lathe-turning 1/32 in. from the surface, the remaining distance to the center was sampled at six equally spaced intervals. the lead, which is essentially the same throughout, will be mentioned later. Consider a brass-mill mold, either round or rectangular in cross section, standing several feet high. It may require a minute or two for pouring. Before it is full, the metal in the lower end has partly solidified and contracted somewhat away from the mold. The initial shell of solidification follows not far behind the top of the column, even if the central portion is liquid for a long way down. There is, then, a space between metal and mold that is filled with zinc vapor. The vapor has no exit, because the liquid at the top of the rising column is not only in contact with the mold but keeps UP a fresh supply of zinc vapor, which has, perhaps, already begun to condense in the lower portion. The cycle is short. Within a minute or two after the mold is full the bar has cooled enough to condense all the zinc. Some of it may condense on the mold; it might be expected that most of it would condense there, but the mold at that time is well coated with a velvety carbon residue from the oil dressing, overlain by fluffy zinc oxide that commenced covering the inside of the mold as soon as pouring began. The clean skin of the freshly cast brass offers a preferred surface for condensation. Reabsorption is quick and inevitable. A simple experiment indicates that a surprisingly large quantity of zinc vapor is trapped in the space between mold and

Jan 1, 1941

By Paul Rhedey

Various commercial pelroleum cokes were heat-1,reated at temperatures between 500° and 1500°C, in a nitrogen atmosphere, in laboratovy induction furnaces. The rate of tenlperature rise was varied betzveen 10" and 300°C per min, or the green cokes were flash-calcined, orv a combination of heating rates was used. Changes in the rate of heating had only negligible effects on the degree of' calcination as characterized by mean crystallite thickness and the chemical properties of the calcined coke. The physical structure of the cake was however significantly affected when rate of heating during calcination exceeded 50°C per min over the temperature range of 600° to 900°C. Surface-accessible porosily increased with the .rate of temperature rise, and this was accompanied by a change in pore size distribution. Source and properties of the green coke also had an influence on the structure of the calcined coke. The evidence presented suggests a similar mechanism of porosity development in petroleuiiz coke during calcination in industvial equiplnenl, such as rotary kilns. An increase in surface accessible povosity incveased the pitch binder requirement when the coke was used as aggregate in Soderberg paste. A correlation was established between calcined coke porosity and paste binder requiremenl. ManY results have been published on the changes of properties of petroleum coke during calcination, such as chemical composition, real density, electrical resistivity, crystallite and pore structure. The correlation of these properties with temperature of calcination and time at maximum temperature has been rather well established in both laboratory and pilot plant experiments. Surprisingly little attention has been given however to the effect of calcination conditions, such as rate of temperature rise or furnace atmosphere, on the chemical and structural properties of the calcined coke. It has been observed that petroleum coke, when calcined in industrial equipment, acquires higher porosity and lower real density than those attainable in laboratory furnaces at apparently identical calcina- tion temperature and soaking time. This paper describes a study of the effect of rate of heating during calcination on calcined coke properties using green petroleum cokes of different volatile matter, hydrogen, and sulfur content. An attempt was made to correlate the changes in coke structure with the flowability of anode paste of the type normally used in aluminum reduction cells. EXPERIMENTAL Petroleum Cokes Used. In the study of release of volatile matter and sulfur during calcination and the effect of rate of heating on calcined coke properties two delayed cokes of different sulfur contents were used. The results of analysis of the green cokes are given in Table I. In the study of the effect of flash calcination thirty-six commercial petroleum cokes from twelve different refineries were used with a range of properties shown in Table 11. Calcination Conditions. Calcination experiments were carried out in a laboratory induction furnace. In each run a 200-g sample of dry green coke sized to 10 by 65 Tyler mesh was calcined in a graphite crucible. The crucible containing the sample was placed in the middle of a stack of eight others filled with metallurgical coke to reduce temperature gradients within the sample. Temperature was measured by two Pt, Pt-10 pct Rh thermocouples and controlled by a Celectray instrument. The two couples generally agreed within 5°C. In the study of volatile matter and sulfur release the samples were heated to temperatures in the range of 500" to 1500°C at a rate of 10°C per min in a nitrogen atmosphere and held at the final temperatures for 30 min. In the study of the effect of heating rate on calcined coke properties the desired rates between 10' and 300°C per min were obtained by manually adjusting the power input. Flash calcination was carried out by dropping 100 g of the green coke into the graphite dish preheated to the calcination temperature. Because of the small heat capacity of the furnace the coke was introduced in 20-g portions at a time. For this purpose a 2-in.-long nipple between two 1-in. gate valves installed on the top flange of the furnace served to provide a gas seal while feeding coke to the furnace. It was estimated that the temperature of the coke reached that of the furnace at a rate of approximately 1000°C per min. Holding time at final temperature was also 30 min. Calcined Coke Proper- Determined. Porosity was determined on 20 by 35 Tyler mesh samples using an Aminco-Winslow mercury pressure porosimeter with an operating range of 1.8 to 3000 psi absolute pressure (100 to 0.05 p pore diameter range).' Apparent density was obtained by the mercury poro-simeter. It represents a particle density of the 20 by

Jan 1, 1968

By W. G. Pfann

Under certain conditions, a molten zone can be made to move through a solid by impressing a stationary temperature gradient across the solid. This phenomenon can be utilized in fabricating semiconductive devices, growing single crystals, joining, boring fine holes in solids, measuring diffusivities in liquids, small scale alloying, and purification. Fundamentals and exemplary applications are outlined. ANEW aspect of the travel of a molten zone through a solid is considered in this paper. Whereas, in previously described zone melting techniques,'-' zones were usually caused to move by changing the position or temperature of a heat source, in the present technique a zone is made to move by impressing a temperature gradient across it. For example, a thin layer of molten A1-Si alloy, sandwiched between two silicon slabs having a temperature gradient normal to the layer, will travel through the hotter slab. One feature of temperature gradient zone melting, as this technique will be called here, is that zones of unusually small dimensions can be maintained. This leads to such diverse uses as have been listed in the abstract. In this paper fundamentals of the movement of a molten zone in a temperature gradient, and some practical applications thereof, are outlined. Assumptions The movement of a molten zone through a solid body of solvent substance in which a temperature gradient exists will be discussed. The length of the zone will be its dimension in the direction of motion. The direction of the temperature gradient will be toward the region of higher temperature. To be considered is a binary or higher order solute-solvent system in which the concentration of solute in the molten zone is sufficient to produce a lowering of the freezing temperature of the solvent which is at least of the order of the temperature range impressed on the charge. While we discuss primarily molten zones in a solid matrix, the principles are applicable to solid or vaporous zones in a solid matrix, a requirement being that the diffusivity in the zone be substantially greater than in the matrix. Diffusion of solute into the surrounding solid will be assumed negligible. In general, its presence will not basically alter the conclusions to be drawn. For illustration, a system represented by the partial constitutional diagram of Fig. la will be discussed, in which k, the distribution coefficient defined in the figure, is constant and less than unity. However, the technique is applicable to any solute- solvent system in which one component lowers the melting point of another component. Movement of a Molten Zone in a Temperature Gradient Consider, in the system AB of Fig. 1, where B is designated the solute and A the solvent, the effect of sandwiching a thin layer of solid B between blocks of solid A and placing the whole in a temperature gradient such that the temperature of the layer is above the lowest melting temperature of the system. Surrounded by an excess of A, the layer will dissolve A, becoming molten, and expand in length." As so- lution of A continues, at both interfaces, the mean solute concentration in the zone will move to the right in Fig. la, until at temperature T, the liquid at the cooler interface reaches the liquidus concentration C,. Solution of A thereupon ceases because the liquid T1 is saturated with A. The liquid at the hotter end of the zone, being at temperature T2, is not saturated with A at concentration C1. Hence solution of A continues there and concentration C2 is approached. A concentration gradient therefore is set up in the zone, causing A to diffuse toward the cool end and B toward the hot end. As a result, the liquid at the cool interface becomes supersaturated and a layer of crystalline A containing concentration kc, of B in solid solution freezes. Since a source of A

Jan 1, 1956

By Robert S. Baker

It has been demonstrated in the laboratory by A. J. Phillips1 that a transformation or conversion from beta directly to alpha may take place in a brass of 61 to 62.5 per cent copper content. The completion of the transformiation is dependent on a rapid rate of cooling from the all-beta field through the alpha + beta range to the alpha field. Phillips states that in a slowly cooled alloy containing 62 per cent copper and 38 per cent zinc the copper content of the beta is progressively decreased from 62 to 56 per cent by precipitation of alpha. Rapid cooling tends to prevent the separation of alpha with a copper content of more than 62 per cent by reducing to a minimum the time required for passing through the alpha + beta range. Upon crossing beyond the (alpha + beta) (alpha) boundary to the all-alpha region below, the material is transformed from beta to alpha. It, is essential that there be no change in composition. Phillips obtained his results by quenching a 62:38 copper-zinc alloy from 850" C. in iced brine at -8" C. No reference to the occurrence of this transformation in a manufacturing process has been found in the literature. An investigation of the microstructures of a number of hot forgings made from leaded brass rods yielded one forging in which this striking conversion from beta to alpha had occurred. The purpose of this paper is to describe the transformation and certain conditions under which it may occur during the hot pressing of brass. The conversion was noted in a shape forged from a leaded brass rod, the composition of which was: Cu, 60.26 per cent; Zn, 37.86; Pb, 1.88. In this study the lead content was disregarded and the alloy was considered to be equivalent to an alloy of 61.40 per cent copper and 35.60 per cent zinc (9812 parts = 100 parts). The possibility that the lead might obstruct or accelerate the precipitation of alpha was not studied. The lead appears as black globules in the photomicrographs and has a negligible solubility in the alloy.

Jan 1, 1932

By G. Pizzi, G. M. Ciucci, G. L. Chierici

The use of the material balance equation to estimate the volume of hydrocarbons originally present in a reservoir, whose producing mechanism is partly due to water drive, has been discussed in the literature by several authors. There is no general agreement upon the possibility of obtaining reliable results by this method. Gas reservoirs in contact with an active aquifer are considered in this paper. Theoretical considerations based on the cybernetic principle of uncertainty (which states that the internal structure of a system cannot be uniquely determined from its observed external behavior) lead to the conclusion that the volume of gas originally present in a reservoir of this type cannot be uniquely determined from its past history. The range of values which encompasses the actual value of the reserves varies from case to case and must be determined by either numerical or analogical methods. Results obtained for six gas fields are reported. All these fields were produced with small fluctuations in their production rates, as is common practice for gas reservoirs; no gas storage fields were considered. Results obtained show that reserves values in a range of 1 to 2, associated with appropriate aquifers, allow the matching of the reservoir past history with mean-square deviations less than the experimental errors involved in pressure and produclion measurements. Similar results have been found in several other partial water drive gas reservoirs. From these results it is concluded that gas reserves cannot be uniquely determined from the past performance of partial water drive reservoirs, at least in cases where the reservoir has been submitted to small fluctuations in the production rates, and pressure data of normal accuracy are available. INTRODUCTION A number of authors have analyzed the problem of estimating the reserves originally present in a partial water drive reservoir from its past pressure-production performance. Literature which deals with this subject can be grouped, according to their conclusions, as follows. 1. A reliable value for the reserves can be obtained even if reservoir data (pressure and cumulative production) are affected by errors within the normal range.'-' 2. A reliable value for the reserves can be obtained only if reservoir data are very accurate'- or if past production performance has been subjected to abrupt variations in the production rate."' 3. No unique value for the reserves can be obtained from reservoir past production performance. This conclusion has been based upon theoretical considerations" and verified in several field cases. The purpose of this paper, which deals only with partial water drive gas reservoirs, is to test the above conclusions against actual field cases. Some theoretical considerations on this problem are also presented. THEORETICAL CONSIDERATIONS As the behavior of a gas reservoir communicating with an aquifer depends on both the aquifer and the reservoir characteristics, the physical system to be studied is the combined gas reservoir plus aquifer. The information which is available for studying the performance of such a system is the well production rates and bottom-hole pressures, all given as functions of time. The external behavior of the reservoir-aquifer system is therefore described by 2n input variables (Gp, Wp,) and n output variables (p,), n being the number of wells in the reservoir. In reservoir engineering it is common practice to consider the reservoir as a whole, disregarding the internal distribution of pressures and of producing wells. This practice is equivalent to substituting the above multi-variable system with a single-variable system, where the average reservoir pressure is the only output variable and the cumulative production G,(t) and W,(t) are the input variables. The internal structure of such a system, defined by initial gas reserves G, aquifer shape and dimensions, boundary conditions and petrophysical parameters distribution throughout the aquifer, is unknown. Therefore, from a cybernetic point of view the system is a "black-box It has been demonstrated" that for a blackbox the indetermination principle holds. Accordingly, the number of different internal structures (or set of parameters) which can account for the observed external behavior is infinite. As a consequence, the initial reserves cannot be uniquely determined from the reservoir past performance. When W,(t) is known, the determination of G from

By A. D. Hughes

A relatively small area in Malaya, about 200 miles long by 40 miles wide, is the most important source of tin in the world. Some tin is recovered in other parts of the peninsula. Of the tin mined, 98 pct is recovered from alluvial deposits. From 1935 to 1941 the average annual world production of tin was 190,000 tons. The average annual production from Malaya during the same period was 62,000 tons or about one third of the total. Other producing countries, in order of importance, were the Netherlands East Indies 34,000 tons, Bolivia 30,000, Belgian Congo, Nigeria, Siam, Burma, China, and a few others with smaller amounts. The serious shortage of tin during the war period was due to the fact that the Japanese were occupying Malaya, Netherlands East Indies, Siam, Burma, and China which, together, formerly were producing 65 pct of the world supply. Because of the importance of tin in the world economy, and because of the fact that little is generally known in this country regarding the methods of recovering the tin in Malaya, it is believed that a short description of the industry, as carried on there, may be of interest to many of the readers. In addition you may be interested in the effect of the Japanese occupation, subsequent recovery of the properties and conditions existing at that time. The Malay Peninsula lies at the southeast tip of Asia. Singapore, a British colony, is situated on a small island at the southern end of the peninsula. It is a city of nearly a million population, an important world port, the site of a large British naval base and of one of the tin smelters. The Federation of Malaya consists of nine states, plus Penang, Malacca, and other small areas formerly part of the Straits Settlements, and it now covers the entire peninsula. The civil administration is controlled by the British. A constitution was adopted recently after reaching agreement with the Malay Sultans of the various states, who retain control of religious matters. The Capital is at Kuala Lumpur, a city of about 200,000 population, 250 miles north of Singapore and about half way to Penang. The country covers an area of 51,000 square miles, an area about equal to that of Florida and about one third that of California. It has a population of about seven million consisting of Malays, Chinese, East Indians, and a relatively small number of Europeans. The principal products are tin and rubber. There are over three million acres of planted rubber. The country is not self-supporting agriculturally as about one third of the necessary food supplies is imported. Rice is the principal food of the Asiatic population and some of the recent unrest is caused by a shortage of rice and the consequent high price. Good highways have been built through the settled part of the country. A railway, Government owned, extends from Singapore northward through the entire peninsula. The climate is tropical but health conditions are good for a tropical country. I was in Malaya from 1939 until January 1942, during the time of the simultaneous air attacks on Pearl Harbor, Manila, Hongkong, and Singa-

Jan 1, 1950

By Bernhard Blumenthal

A melting process was developed by which high purity electrolytic uranium crystals can be converted into sound ingots without serious contamination. Careful preparation of the crystals, melting in a high vacuum, and directional solidification led to a metal of better than 99.993 wt pct purity. The metallographic examination showed a substantially clean metal with only residual amounts of a second phase which responded to heat treatment. The density of high purity uranium is 19.05 g per cu cm. FOR the study of the fundamental properties of uranium and its alloys, a base metal of high purity is needed, and an investigation was started at Argonne several years ago to examine various methods of preparing high purity uranium. Early success was achieved by the fused salt electrolysis process in preparing high purity metal in crystal form,' and the problem became that of melting the crystals into ingots without contamination. The electrolytic crystals contained a few ppm of heavy metals, less than 15 ppm C, and large quantities of potassium and lithium in the form of trapped fused salt electrolyte. On melting in vacuo in magnesia or urania crucibles, the metal picked up considerable quantities of carbon and some iron, copper, and silicon but lost most of the potassium and lithium. It was not metallographically clean, and much research work was necessary to determine the optimum melting conditions for minimum contamination. This work has resulted in the development of a melting procedure by which sound ingots can be prepared with only a limited contamination by carbon. In the section entitled "Melting of the Electrolytic Metal," the equipment and processes that have been developed for melting the electrolytic crystals are described in detail. The "Metallography" section is devoted to the metallography of high purity uranium, and the section "Density of High Purity Uranium" contains the first property measurement on high purity uranium—a density determination. Melting of the Electrolytic Metal Apparatus—Melting and Vacuum Equipment: Uranium may be melted in either resistance or induction-type electric furnaces. Resistance heating was found to be preferable to induction heating for melting down the electrolytic crystals, for several reasons: Although induction heating permits fast heating, this advantage cannot be utilized when crucibles with limited thermal shock resistance are used. Temperature control of induction-heated melts is poor, and the stirring effect increases the rate of contamination of the melt from the crucible, slag, or the furnace atmosphere; liquation and controlled solidification are difficult to carry out. Because of these objections, resistance heating was chosen. A 10 kw Globar resistance furnace of low heat capacity permitted uniform heating of a uranium charge to its melting point in 45 min. The furnace was insulated with a removable aluminum shield so that, after melting and removal of the shield, the furnace could be quickly cooled to room temperature. The furnace was equipped with an apparatus for directional solidification; see Fig. la. The crucible was suspended in the center of the furnace; and when the melting was complete, the crucible was slowly lowered into the cold end of the furnace tube. Solidification took place upward from the bottom; and when the rate of lowering was small, a sound ingot free from sink holes and shrinkage cavities was produced. To remove the large quantities of gas contained in the electrolytic crystals, melting in a high vacuum is mandatory. While, from the standpoint of contamination, melting in a highly purified argon atmosphere appeared feasible, lithium and potassium removal proved less efficient under such conditions. Also, a vacuum-melted ingot has a cleaner surface than one melted in an inert atmosphere. The vacuum system must be of very high pumping speed and leak tight so that a vacuum of less than 2x10-7 mm Hg is attainable when the system is pumped down cold. The system must have a high pumping speed, so that the pressure maximum which may rise to 1x10-4 mm during heating can be quickly reduced

Jan 1, 1956

NEW MEMBERS The following list comprises the names of those persons who became members during the period Jan. 10, 1919, to Feb. 10, 1919. ADAMS, FRANCIS SPEARMAN, Supt., Power Dept., Anaconda Copper Min. Co.; Anaconda Mont. ALDERSON, G. E., Min. & Met. Engr 1317 Sloane Ave., Lakewood, Ohio. BENJOVSKY, T. D., Min. Engr., Cons. & Constr 2045 Vine St., Denver, Colo. BROPHY, OSCAR, Met 1523 S. Broad St., Philadelphia, Pa. BUTTRAM, FRANK, Chief Geol., Fortuna Oil Co., 424 Liberty National Bank Bldg., Oklahoma City, Okla. COCHRAN, R. B., Mine Supt., The Teziutlan Copper Co., Aire Libre Puebla., Mexico. CONNAR, T. C., Civ. & Min. Engr. & Geol.; Chief Engr., Zanesville Coal Co., Zanesville, Ohio. DAVE, E. O Capt., Co. A, 212th Engineers, Camp Devens, Mass. FOLEY, CHARLES B., Electro-Met., Martin Rockwell Corpn., 347 Madison Ave., New York,. N. Y. HOSFORD, WILLIAM F., Asst. Tech. Supt., Western Electric Co., Inc., Hawthorne Station, Chicago, Ill. HOSTER, M. T., Supt., French Creek Mines, E. & G. Brooke Iron Co., St. Peters, Pa. KAWASAKI, SHIGETARO, Chief Geol., Geological Survey of Chosen, Government General of Chosen, Keijo. Korea.

Jan 3, 1919

By J. J. Tietien, R. O. Clough

A technique previously used to prepare alloys of InAs1-xPx and GaAsl-x Px, miry: the gaseous hydrides arsine and phosphine, has been extended to grow single -crystalline GaAs 1-x Sb x by replacing the phos-phine with stibine. Procedures were developed for handling and storing stibine which now make this chemical useful for vapor phase growth. This represents the first time that this series of alloys has been grown from the vapor phase. Layers of P -type GaSb and GaSb-rich alloys have been grown with the carrier concentrations comparable to the lowest ever reported. In addition, a p-type alloy containing 4 pct GaSb exhibited a mobility of 400 sq cm per v-sec which is equivalent to the highest reported for GaAs. RECENTLY, interest has been shown in the preparation and properties of GaAs1-xSbx alloys, since it was predicted1 that for compositions in the range of 0.1 < x < 0.5, they might provide improved Gunn devices. However, preparation of these alloys presents fundamental difficulties. In the case of liquid phase growth, the large concentration difference between the liquidus and solidus in the phase diagram, at any given temperature, introduces constitutional supercooling problems. It is likely that, for this reason, virtually no description of the preparation of GaAs1-xSbx by this technique has been reported. In the case of vapor phase growth, problems are presented by the low vapor pressure of antimony, and the low melting point of GaSb and many of these alloys. In previous attempts1 at the vapor phase growth of these materials, using antimony pentachloride as the source of antimony vapor, alloy compositions were limited to those containing less than about 2 pct GaSb. This was in part due to the difficulty of avoiding condensation of antimony on introducing it to the growth zone. A growth technique has recently been described2 for the preparation of III-V compounds in which the hydrides of arsenic and phosphorous (AsH3 and pH3) are used as the source of the group V element. With this method, GaAs1-xPx and InAs1-xPx have been prepared2&apos;3 across both alloy series with very good electrical properties. Since the use of stibine (SbH3) affords the potential for effective introduction of antimony to the growth apparatus, in analogy with the other group V hydrides, this growth method has been explored for the preparation of GaAs1-xSbx alloys. In addition to GaSb, these alloys have now been prepared with values of x as high as 0.8. In the case of GaSb, undoped p-type layers were grown with carrier concentrations equivalent to the lowest reported in the literature. Thus it has been demonstrated that, with this growth technique, all of the alloys in this series can be prepared. EXPERIMENTAL PROCEDURE A) Growth Technique. The growth apparatus, shown schematically in Fig. 1, and procedure are virtually identical to that described2 for the growth of GaAs1-xPx alloys, with the exception that phosphine is replaced by stibine.* HCl is introduced over the gallium boat to *Purchased from Matheson Co., E. Rutherford,N+J. transport the gallium predominantly via its subchlo-ride to the reaction zone, where it reacts with arsenic and antimony on the substrate surface to form an alloy layer. The fundamental limiting factors to the growth of GaAs1-xSbx alloys from the vapor phase, especially GaSb-rich alloys, are the low melting point of GaSb (712°C) and the low vapor pressure of antimony at this temperature (<l mm). Thus, relatively low antimony pressures must be employed, which, however, imply low growth rates. To provide low antimony pressures, very dilute concentrations of arsine and stibine in a hydrogen carrier gas were used. Typical flow rates (referred to stp) were about 4 cm3 per min of HC1 (0.06 mole pct)+ from 0.1 to 1 cm3 per min of ASH, (0.002 to 0.02 mole pct), and from 1 to 10 cn13 per min of SbH3 (0.02 to 0.2 mole pct), with a total hydrogen carrier gas flow rate of about 6000 cm3 per min. Although no precise data on decomposition. kinetics exist, it is known4 that stibine decomposes extremely rapidly at elevated temperatures. However, the high linear velocities attendent with the high total flow rate (about 2000 cm per sec) delays cracking of the stibine until it reaches the reaction zone and prevents condensation of antimony in the system. To improve the growth rates of the GaSb-rich alloys, growth temperatures just below the alloy solidus are main-

Jan 1, 1970

By John Eash

DURING recent years nickel has had an increasingly important role as an alloying element in the copper-tin bronzes. Nickel additions not only produce better casting alloys but also make alloys whose properties can be varied by precipitation hardening; thus leading to increased commercial application of copper-nickel-tin alloys. Recent investigations have indicated a decrease in the solubility of tin in the alpha phase as the annealing temperature is lowered and as the nickel content is increased within certain limits. A further change caused by the nickel additions is produced in the excess phase of the copper-tin bronzes. The alpha plus delta eutectoid is replaced by a clear precipitated constituent in the alloys containing up to 15 per cent tin and not less than 1 per cent nickel. This paper has a dual purpose. The first is to present a new determination of the alpha-phase boundary in alloys containing from 0 to 20 per cent nickel, together with the liquidus and solidus temperatures above that field. The second purpose is to give the equilibrium conditions existing in alloys exceeding the alpha phase containing up to 31 per cent tin and 5 per cent nickel, so that the disappearance of the alpha plus delta eutectoid constituent may be explained. After considering the earlier investigations of the related alloy systems and the experimental procedure used in this investigation, the alloys will be discussed in groups as separate quasibinary systems containing constant amounts of nickel. The systems considered contain 0, 1, 2, 3, 5, 10 and 20 per cent nickel. The straight copper-tin system was reinvestigated in order to establish a foundation on which to build the remaining material. The 1 per cent nickel alloys studied give the relations existing in the region of the eutectoid transformation between the copper-tin system and the 2 per cent nickel copper-tin system which has been investigated in detail. The thorough examination of the latter system was made since 2 per cent of nickel is representative of the commercial additions to the cast bronzes and also because it is sufficient to produce

Jan 1, 1932

By L. C. Kern

This paper presents information on the use of a new propping agent (malleable aluminum particles) which has been used successfully for producing high-conductivity fractures. The conductivity of a packed fracture depends on the width of the fracture as well as the permeability of the propping material. It is significant that the flow capacity of a propped crack is often increased many fold by propping the crack with a sparse distribution of particles. However, the flow capacity of a sparsely propped crack can be limited by two phenomena: (I) crushing of the propping particles, and (2) embedment of the propping particles in the formation walls. Malleable aluminum particles exhibit interesting properties which tend to overcome these limitations. As high loads are applied to the particles they will deform slightly, rather than shattering. The deformation results in a greater bearing area against the formation wall. This reduces the stress on the particle and reduces particle penetration into the formation. The behavior of aluminum particles under load and the bearing capacities of serveral formation rocks have been measured in the laboratory. By properly using these data, as explained in this paper, the flow capacities of aluminum-propped cracks can be calculated for a variety of conditions. Aluminum particles have been used successfully in the field to prop fractures. Where high-conductivity fractures were needed, the aluminum-propped fractures have given greater well stimulation than could have been expected for conventional fracturing processes. INTRODUCTION The purpose of a hydraulic fracture treatment is to create a conductive channel from the wellbore out into the oil or gas formation. The word conductive is emphasized because we believe that the fracture conductivity (flow capacity) is one of the most important factors influencing fracturing results. Previous papers have pointed out the additional well stimulation that can sometimes be achieved by increasing fracture conductivity. Several years ago, we investigated in some detail the effect of fracture conductivity on productivity increases to be expeced from vertical fractures. Both electrical analog and theoretical studies of unsteady-state flow behavior were made. A discussion of the electrical analog equipment and some of the results of the study were given in a previous paper&apos; by Dyes, Kemp and Caudle. Further details were given recently by McGuire and Sikora.5 Fig. 1 shows the remarkable influence of relative fracture flow capacity and length on well stimulation. Briefly, the study indicates the following. 1. High-permeability formations require high-conductivity cracks for best results. 2. The longer the crack, the higher the fracture conductivity required for best results. 3. If the conductivity of the crack is very large compared to the formation (i.e., flow is not being limited by crack conductivity), then the longer the fracture, the better will be the results. Judging from recently published articles,1,314 there is current interest in methods for obtaining high fracture conductivities. Hence, we would like to present in this paper a discussion of a new fracture propping process (use of aluminum particle) which we have used successfully to obtain highly conductive fractures. There are several factors which influence the conductivity of a propped crack. Conventional fracturing techniques frequently result in a crack completely packed with fracturing sand. For such conditions, the crack conductivity is the product of the width of the packed fracture and the permeability of the propping material. It is significant that a large increase in conductivity sometimes can be obtained by propping with particles which are distributed sparsely (less than a

By H. H. Kellogg

A model of the slag-fuming process for recovery of zinc oxide fume from lead blast furnace slags, adapted to solution by a digital computer, is presented. The model incorporates the variaticm with time of the following: the fuming of zinc and lead, the change in the ferrous-ferric ratio in the slag, the transfer of sulfur to and from the slag, the temperature of the liquid slag, the temperature of the gases and fume which exit to the flue, the heat losses to the water jackets, and the amount of frozen slag on the water jackets. The assumptions which underlie the model-some of which are but crude approximations—are discussed. Despite some obvious shortcomings, the model simulates faithfully many of the important features of practical slag-fuming operations. The behavior of the model is compared with the operation of the American Smelting and Refining Co. fumzace at El Paso, Tex. The model is used to predict the effects on performance of changes in the coal rate, the temperature of the secondary air, and the composition of the coal. THE fuming of lead blast furnace slag for recovery of zinc oxide is standard practice today, and it has been the subject of several previous attempts at mathematical process analysis.&apos;-&apos; The mathematical process model described in this paper incorporates many of the features from the earlier studies, but it is a far more complete and realistic representation of the commercial process in that the following additional features have been included: the fuming of lead as well as zinc; the transfer of sulfur between slag and gas; the addition of slag feed in batches, over a period of time; tapping of the final slag over a period of time; the change of slag temperature with time. The additional features of the present model add greatly to the mathematical complexity, but this difficulty has been obviated by programming the model for solution by a digital computer. The IBM 7094 computer solves the model for one operating cycle of the fuming furnace in less than 1 min. It is doubtful if the same calculations could be completed with the aid of a desk calculator in less than a month. The computer program, written in the Fortran IV language, is too lengthy for presentation here.* Instead, this paper As shown in the sections which follow, it does simulate with remarkable faithfulness most of the known behavior of the industrial process. On the other hand, the model contains several gross simplifications of both the chemistry and heat balance, necessitated by the lack of more exact knowledge. In addition to these known weaknesses, it is not unlikely that those more intimately acquainted with industrial practice than the author will find other additions to or modifications of the model which will improve its utility and reliability. CHEMISTRY In brief outline, the present model treats the fuming furnace as two units, A and B, in series. In A the batch of slag reacts with the continuous stream of air (primary and secondary) and fuel injected at the tuyeres, to produce a stream of hot, reduced gases containing zinc vapor. The zinc content of both the slag and the product gas changes with time because of the batch nature of the process. Unit A is called the "lower furnace" in this paper; physically, it is considered to be that part of the fuming furnace which lies below the charge port. In B, the "upper furnace", the product gas from A is burned with the stream of "tertiary" air, to produce zinc oxide fume. The performance of B also depends on time because of the time dependence inherited from the product gas of A. The rate behavior in the lower furnace determines the important features of the process—the rate of elimination of zinc and lead from the slag, and the amount of fuel required for this purpose. Bell, Turner, and peters&apos; published the first useful model of the lower furnace. They employed the assumption that, at any instant of time, the slag and reduced gas reach a state of equilibrium, according to the reactions: They cited only indirect evidence in support of their assumption of slag-gas equilibrium, yet several more recent laboratory studies of the activity of zinc oxide in slags4-8 have produced evidence which supports their view. On first acquaintance it seems unlikely that a high-output "rate" process like slag fuming would even approach an equilibrium state. The author, in an earlier study,&apos; established, however, that the gas-slag interface in a fuming furnace was capable of such high mass-transfer rates that a close approach to equilibrium between gas and slag was quite probable. In devising the present model it was decided to assume a state of equilibrium between slag and gas at the outset, and then to modify this assumption as necessary in order to make the model agree with the be -havior of the actual process. Up to this time the assumption remains a part of the model, since no behavior

Jan 1, 1968

By Joseph Lindmayer, Karl M. Busen

If silicon is in contact with silicon oxide, a heterojunction is formed which induces an inversion layer ("channel"). Influences of impurities and structural parameters on the channel are discussed. There seems to be no relation between surface damage in silicon and the channel. Phosphorz~s doping of the silicon oxide has no pronounced effect on the channel. Channels which were well above the range predicted by the heterojunction model were related to the action of H* at the silicon/silicon oxide interface. Channels which were well below tlze range predicted by the heterojunc-tion model were related to a transition region in the oxide adjacent to the interface. In support of the assumed transition region and the H+ are the ex-periments described on the paper. Furthermore, the concept of metastable OH groups in silzca, known from other publications, has been used to explain certain channel characteristics by the formation and the accommodation of hydrogen in the silicon oxide. THE electrical characteristics of a semiconductor device in many cases are influenced by the conditions of its surface. Because these conditions often are changing with temperature, time, ambient, or other parameters, numerous attempts have been undertaken to stabilize them by suitable processes. Several years ago Atallal studied the silicon/silicon dioxide interface and since then increasing attention has been given to the silicon dioxide as a means to stabilize silicon surfaces. This led to the evolution of the planar silicon devices where oxide layers are used to protect places at which the junctions are intersecting the surface. The formation of the oxide layers on silicon can be carried out by a variety of processes: high-temperature thermal oxidation (exposing the silicon surface to oxidizing agents such as 02, HzO, COz), evaporation of SiOz, or anodic oxidation of silicon. Originally the oxides were considered able to "passivate" the silicon surface and it was understood that they 1) protected the surface against any influence from the ambient and 2) stabilized surface conditions which were necessary for proper device performance. It soon was realized that the second quality was not always obtainable: Atalla and Tannenbaum showed that, in the process of forming a layer on doped silicon by thermal oxida- tion, electrically active impurities in the silicon near the interface are redistributed, thus giving rise eventually to the formation of unwanted charge distributions. The degradation of planar junctions during reoxidation of silicon was observed by Barson et a. Surface studies with silicon planar junction structures indicated that the breakdown voltage depended on the kind of procedure which was applied during or after oxidation.*" Yamin and worthinge report on charge storage and dielectric properties of SiOz films at elevated temperatures. Another influential parameter on the silicon surface is discussed by Lindmayer and usen,&apos; namely the appearance of a surface potential on silicon as a consequence of the heterojunction formed by the silicon/silicon oxide interface. In the present paper the influence of impurities and structural parameters in silicon oxide in connection with the heterojunction is a particular object of our investigations. I) EXPERIMENTAL The material used was 10 ohm-cm p-type silicon slices with either damaged surfaces (mechanically lapped or polished) or damage-free surfaces (chemically polished). The majority of the slices were oxidized for 1 hr and 20 min at 1250°C in a steam + oxygen atmosphere generated by passing O2 through HzO at 90°C (wet oxygen). This led to oxide layers of about 9000 A. On some slices oxide layers were grown in pure oxygen (dry oxygen). By a photoresist process a set of 20 by 200 mil windows was then etched out from the oxide layer. The pattern of the windows is shown in Fig. 1. In a subsequent process n-type pockets with surface concentrations between 2 x 10" and 5 x 10" cm"3 were formed by phosphorus diffusion. This allowed ohmic contacts between the silicon surface and tungsten probes which for electrical measurements were placed into two adjoining windows and

Jan 1, 1965

By Howard Eavenson

PRIOR to 1907 nearly all coke was made in beehive ovens, and most of the gas produced was made in the old-style gas retorts, and while there were a few coke plants in southern West Virginia, southwest Virginia and Kentucky operating on high-volatile coals the proportion of the total product made by them was small and was usually used locally. The greater part of the coke made, and the coal gas produced, came from the Pittsburgh seam of western Pennsylvania and northern West Virginia-which was then regarded as the standard coking and gas coal of the coun, try, and the best coal available anywhere for these purposes. With the advent of the by-product oven and the building of coke plants at the furnaces, the restriction of the use of one grade of coal for making coke was removed and the use of mixtures of low-volatile and high-volatile coals began. The change in the locations of the coke plants removed the necessity of using Connellsville coal and also made sources of gas available to the public utilities other than of their own manufacture. Most of the first oven plants were built at points distant from the Connellsville region and this afforded an opportunity for the use of coals from the southern Appalachian fields, which were at approximately equal distances from the ovens. Since that time development has been made on a number of seams of coal of great purity in southern West Virginia, southwestern Virginia and eastern Kentucky, which have been largely used for cokemaking, gas and other metallurgical purposes where low amounts of ash, sulfur and phosphorus are determining factors. These coals are much lower in the objectionable elements than the best of the coal from the Pittsburgh seam, or than any northern coal, and in by-product ovens produce coke that is not excelled for any purpose by any coal mined in this country, and is equaled very seldom. Coal from several of these seams is shipped in great quantities without beneficiation and is lower in ash and sulfur than the best washed product from any seam mined in the north.

Jan 1, 1932

By C. J. Huffman

MAGNESIUM alloy tubing and hollow shapes are finding increasingly wider usage in practical applications today. Square and rectangular tubing and hollow shapes find [ ] greater diversification in use than standard round tubing. Typical applications are roller conveyors, ladder rungs, spools, furniture, tank car loading tubes, athletic equipment, and business machine parts. In general, the amount of tubing and hollow shapes produced represent a minor portion of the magnesium extrusion business. The magnesium alloys in which tubing and hollow shapes are being produced together with typical properties are presented in Table I. MI A alloy is a low cost alloy possessing good welding and stress corrosion characteristics together with moderate formability and corrosion resistance. It is widely used for low strength applications. AZ31 B, alloy is used for moderately stressed applications and possesses good corrosion resistance and formability with fair welding characteristics. AZ61 A alloy has slightly higher physical properties than AZ31 B alloy together with good formabil- [ ] ity and corrosion resistance but slightly poorer welding characteristics. AZ80 A, ZK60 A-F, and ZK60 A-T5 alloys are used where the maximum in physical properties is required. AZ80 A alloy possesses fair corrosion resistance but with formability and welding characteristics inferior to&apos; the other alloys. ZK60 A-F and ZK60 A-T5 alloys, while only recently offered for com¬mercial use, are finding favor due, to the higher permissible extrusion rates. These alloys possess greater toughness than AZ80 A alloy and, while of moderate formability at room temperature, are very formable at 300° to 500°F. The major portion of tubing and hollow shape production at the present time is in AZ3I B alloy. Magnesium alloy tubing is commercially available in the as-extruded condition or, in the case of ZK60 A-T5, in the as-extruded and aged

Jan 1, 1951

By G. W. Brock

Experiments in the form of aging of overstrained tension specimens and elevated temperature tension testing, have been carried out on recrystallized arc-cast molybdenum. The aging behavior of molybdenum was found to be strongly dependent on the degree of plastic strain present in the lattice: the reason for this being the low solid solubility for the common interstitial elements in molybdenum. GEORGE W. BROCK, formerly Research Associate, Department of Theoretical and Applied Mechanics, University of Illinois, Urbana, III., is Research Associate, Department of Engineering Sciences, IBM Research Center, Yorktown Heights, N. Y. Manuscript submitted January 19, 1961. IMD THE term strain aging is familiar in connection with the recovery of the yield point in mild steel after tensile overstraining, and there are other instances where it is known to exert an appreciable effect on mechanical properties. For example, steel exhibits a greater tensile strength at mildly elevated temperatures than at room temperature and serrated stress-strain flow curves occur under certain conditions. It has been known for a number of years that the phenomenon of strain aging is directly connected with the presence of carbon and nitrogen in the lattice; and extremely small amounts of either element are sufficient to produce the effect. In this study, the aging behavior of overstrained tensile specimens of recrystallized molybdenum has

Jan 1, 1962

By G. F. Bolling

Single crystals of each metal were deformed at 77°K and heated at constant rates, variously in the range 0.125" to 4o°Kper min from 77" to -390oK, while being monitored in an X-ray diffractometer. Changes in diffraction-peak heights and line breadths were used to ascertain the temperature ranges of recrystalliza-tion. The results were subjected to the analysis of nicholas&apos; in order to obtain the rate-controlling activation energies,Q. In this analysis no recourse to a separate and distinct nucleation stage is required and the results of studying recrystallization proved consistent with the hypothesis of a constant number of nuclei or equivalent hypotheses. The values Pb = 5.5 ± 0.5 keal per mole Zn ~ 7.5 Sn - 5 Bi - 9. 5 correspond for lead, zinc, and tin to activation energies obtained elsewhere for grain boundary migration, and for bismuth and lead to previous studies of re-crystallization by Barrett.6 This correlation allows the conclusions that interference from recovery was minimal and that the observed recrystallization rates in these pure metals are effectively governed by grain boundary migration. Good agreement was not found between the results of this kind of study in zone-refined aluminum and previous work; and supplementary isothermral experiments involving hardness tests and metallography did not resolve the discrepancy. Nevertheless, at least a range,Q = 11.5 ± 2 keal per mole, can be assigned to the activation energy for boundary migration in aluminum. An experimental study of one aspect of the recrystallization process is presented here for four metals of different crystal structure. The metals chosen for study were all zone-refined to reduce impurity effects, but the attendant high purity presented a difficulty. For any reasonably high driving force a "re-crystallization temperature", TR, is in the range of 0.25 T,, where T, is the absolute melting point, and study was therefore restricted to lower temperatures. An X-ray technique under constant heating-rate conditions adequate above 90°K was devised for the study; in consequence, a newer type of analysis following Nicholas1 had to be used to obtain quantitative information about activation energies. The standard methods of studying recrystallization have involved the comparable analyses of Johnson and Mehl2 and Avrami3 which are reviewed by Burke and Turnbull.* The general analysis4 which is applied only to isothermal studies using any of various investigative techniques states:

Jan 1, 1968