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By Robert L. de Beauchamp

The Bureau of Mines reviewed aluminum chloride technology to determine the problems associated with its preparation from minerals, and to ascertain the best areas for research to solve these problems. Commercial AlC13 production processes are described and the ?state of the art? for the preparation of AlC13 from aluminous materials is evaluated. Areas for further research are indicated.

Jan 1, 1969

By H. Conrad, V. V. Damiano, G. J. London

A method is described for producing single crystals of high-purity beryllium, Be-4.37pct Cu, and Be-5.24 pct Ni. These crystals were prepared for testing in compression parallel to the [0001] by orienting and lapping to within ±3' of arc of the (0001). Microstrain testing apparatus is described along with c axis compression results for ingot purity beryllium, twelve-zone-pass material, and the above-mentioned alloys. Results show no measurable plasticity for the ingot purity material from -196" to 400°C, although some surface traces of (1122) slip was observed at 200°C and above. The twelve-zone-pass material shows substantial microstrain plasticity at 220°C with slip on (1122). Both alloys show significant plasticity at room temperature and above with slip also on (1122) planes. THE two slip systems which normally operate during the plastic deformation of beryllium in the vicinity of room temperature are:' basal slip (0001)(1120) and prism slip . Pyramidal slip with a vector inclined to the basal plane has been reported for elevated temperatures,'-a but occurs near room temperature only at very high stresses.~ A summary of the available data on the effect of temperature on the critical resolved shear stress for slip on these systems has been compiled by Conrad and Perlmutter.~ It has been postulated6'7 that one of the principal factors contributing to the brittleness of poly crystalline beryllium at temperatures below about 200°C is the difficulty of operating pyramidal slip with a vector inclined to the basal plane. Hence, detailed information on the operation of such a slip system is important to understanding the brittleness of beryllium. The operation of pyramidal slip with a vector inclined to the basal plane is best accomplished in beryllium by compressing single crystals in a direction parallel to the c axis. In such a test the resolved macroscopic shear strzss on the basal and prism planes is zero and (1012) twinning which is favored by tension along the c axis does not occur. Hence, in c axis compression of beryllium the normal deformation modes are inhibited and the operation of pyramidal slip with a vector inclined to the basal plane is favored. In the present investigation, c axis compression tests were performed on beryllium single crystal as a function of temperature (77" to 700°K), purity (commercial and twelve zone pass), and alloy content (4.37 wt pct Cu and 5.24 wt pct Ni). Presented here is a description of the test techniques employed and the gross mechanical behavior observed. A detailed analysis of the slip traces developed on the surfaces of the deformed specimens during these tests and the results of electron transmission studies of the deformed crystals are given in a separate paper.B PROCEDURE 1) Materials and Preparation. Single crystals about 1 in. diam were prepared of the following materials: commercial-purity beryllium, high-purity beryllium, and two beryllium alloys, one with 4.37 wt pct Cu and the other with 5.24 wt pct Ni. The commercial-purity single crystals were obtained by cutting specimens from large-grained ingot of Pechiney SR material, which is approximately 99.98 pct pure. The high-purity crystals were prepared by floating-zone refining (twelve passes) a rod (7 in. by 1 in, diam) of Pechiney SR grade cast and extruded beryllium. Although an absolute chemical analysis of the zone-refined material was not established, mass spectro-graphic analysis, emission spectrographic analysis, and y activation analysis indicated that it contained in atomic fractions about 5 to 10 ppm each of carbon and oxygen, 1 to 5 ppm each of nickel and iron, and about 1 to 2 ppm of copper, with the remaining residual impurities being less than 1 ppm. Further indication of the purity of this material is provided by the critical resolved shear stress for basal slip, which was approximately 300 psi. The starting material for the alloy single crystals was 1-in.-diam floating-zone-refined (six passes) rod of Pechiney SR grade beryllium. Two such rods were wrapped respectively with sufficient weight of wire of high-purity copper (99.999 pct) or nickel (99.999 pct) to yield a 5 wt pct alloy. A seventh floating-zone pass was then applied to each of the rods to accomplish the initial alloying and an eighth pass for homogenization. Analytical samples were taken from regions of the rod immediately adjacent to where the mechanical test specimens were cut; these indicated 4.37 wt pct Cu and 5.24 wt pct Ni. 2) Crystal Orientation. To avoid the occurrence of basal slip during c axis compression testing, it is necessary to load the crystals as nearly parallel to the c axis as possible. Preliminary c axis compression tests indicated that plastic flow and/or fracture occurred at stresses of the order of 300,000 psi; hence on the basis of a critical resolved shear stress for basal slip of 300 to 400 psi, the maximum crystal misorientation permitted is about 4 to 5' of arc. Since this accuracy cannot be obtained using the usual back-

Jan 1, 1969

By Robert E. Reed-Hill, Edward R. Buchanan

A recent paper by Adams and vreeland30 describes dislocation density changes in zinc as a function of shear strain. The dislocation density was determined with the aid of an etching technique previously described by Brandt, Adams, and Vreeland.31 However, comparison of dislocation densities obtained by electron microscopy and this etching technique are not in good agreement, as will be shown below. Several zinc crystals of 99.999 pct purity were grown in air using a modified Bridgman technique.' These were annealed in air a 400°C for 1 hr and

Jan 1, 1969

By F. H. Deily

The petroleum industry has developed and utilized many aspects of rock mechanics, both in its search for petroleum and in its drilling and production operations. Geological exploration activities have been improved by knowledge of earth tectonic forces. Better understanding of seismic wave motion has contributed to a more accurate interpretation of geophysical data. Drilling activities have benefited from basic knowledge of rock strength behavior under in situ conditions. Production has been significantly increased through stimulation techniques, such as hydraulic fracturing. The ability of rock mechanics work to contribute to future petroleum activities will depend upon the development of knowledge of rock properties under greater depths and at higher pressures and temperatures.

Jan 1, 1969

By E. Miller, K. L. Komarek, M. Ettenberg

The activity of aluminum in solid Co-A1 alloys has been measured by an isopiestic technique between 850° and 1200°C from 45 to 80 at. pct Al. The activity shows a Precipitous decrease around the stoichzornetric composition of CoAl. Free energies of mixing have been calculated over a limited composition range. Considering an antistructure-vacancy defect mechanism, the degree of intrinsic disorder, a , in CoAl was related to the alunminum activity. Excellent agreement between the calculated and experimental activity curves was obtained for a = 1.25 x 10-4. ThERMODYNAMIC properties of solid aluminum-transition metal alloy are being studied in an investigation of disordering in ordered compounds. In a continuing series of investigations, activities of solid Fe-1,' Ni-A1, kd r-A13 alloys have been measured. From the results for Fe-A1 and Ni-A1, the degree of intrinsic disorder for the equiatomic compounds was calculated2 using equations derived by Wagner and chottk. From the results for Cr-A1 the degree of intrinsic disorder was calculated from equations derived by Orr.' In this paper, the results of the study of Co-A1 alloys are described. Published activity data in the Co-A1 system has been limited to liquid alloys at 1600°C.° A heat capacity study7 of stoichiometric CoAl indicated that a second-order phase transformation occurs at 790° C, attributed to an order-disorder reaction. Oelsen and Middel,' employing the calorimetric mixing of pure liquid metals, obtained heats of formation for compositions from 6 to 90 at. pct Co. Heats of formation for 50 and 78 at. pct Co alloys have also been measured by acid solution calrimetr. The Co-A1 phase diagram, as compiled by Hansen and Anderko,lo is in good agreement with more recent X-ray evidence. The method for measuring activities of aluminum in this study is essentially that employed in the studies of the Fe-1,' i-Al, and r-A13 systems. This isopiestic method entails placing cobalt specimens, in a temperature gradient, in a sealed alumina system containing a pure liquid aluminum source of fixed vapor pressure. The specimens are equilibrated, cooled to room temperature, and their final compositions determined. From the measured temperature of the specimens and the known vapor pressure of pure aluminum the activities of aluminum in the alloy can be calculated. EXPERIMENTAL PROCEDURE The cobalt was 3-mil-thick sheet of 99.9 pct purity (herritt Gordon Mines Ltd., anada). The major impurities were 0.1 pct Ni, 0.014 pct C, 0.018 pct Fe, 0.004 pct S, and 0.005 pct Cu. The aluminum metal had a purity of 99.99 pct (Aluminum Corp. of America) and all alumina parts were 99.7 pct A1,O3 (Triangle RR Grade, Morganite Refractories, Inc.) with major impurities 0.05 pct SiOz, 0.1 pct Fe203, 0.2 pct NazO, and 0.05 pCt K20. Runs 1 to 3 were made with annular cobalt specimens (12 mm ID by 21 mm OD) punched from the sheet. The specimens were deburred and degreased in carbon tetrachloride and in acetone. The samples, each weighing about 150 mg, were then positioned along an alumina rod, a in. OD by 14 in. long, separated by alumina spacers, i in. ID by | in. OD by & in. long. The lower end of the rod was placed in a hole drilled in the center of an 80-g aluminum cylinder. This assembly was put into an alumina crucible, 1+ in. ID by 13 in. OD by 3+ in. high, and the position of each sample was measured to within 50.5 mm relative to the bottom of the crucible. An alumina tube, 28.5 mm ID by 35.5 mm OD by 14 in. long, closed at the top, was slipped over the whole assembly, so that it fitted snugly into the bottom crucible. The entire reaction assembly was tied with molybdenum wire and lowered into a mullite tube, closed at the bottom. A quartz thermocouple tube, closed at one end, containing a t/Pt-10 pct Rh thermocouple, calibrated according to the specifications of the National Bureau of standards,'' was placed along the reaction assembly inside the mullite tube. The temperature of each specimen could be determined by gradually raising the thermocouple and measuring the temperature gradient along the reaction assembly. The combined error in temperature measurement and sample position resulted in a total error of Q°C in the recorded temperature of each sample. The mullite tube was sealed at the top by a water-cooled brass head, connected to a conventional glass vacuum system. The aluminum reservoir is heated to its melting point sealing the alumina system containing the samples. During this process the pressure is maintained below 0.01 li Hg. During subsequent heating to establish the proper temperature gradient and throughout the entire run the pressure is maintained below 2 1 Hg by means of a two-stage mechanical pump. Equilibration runs lasted from 4 to 6 weeks and were terminated by air cooling. The temperature of the liquid aluminum reservoir was brought below its melting point in less than 20 min. For runs 4 and 5, alloy buttons with 49 and 69 at. pct A1 were prepared from the initial high-purity metals by arc melting under purified argon. The alloy buttons were comminuted to powder with an alumina mortar and pestle until the powder passed through a 400-mesh screen, particle size 0.0014 in. Portions of this powder weighing between 50 and 200 mg were placed in small alumina trays, 25 by 15 by 5 mm, which were then

Jan 1, 1969

By C. T. Holland

Coal mining has been an important industry in the Appalachian area for many years. This is particularly true in the northern part of the area, namely, in Pennsylvania, West Virginia, and Ohio. Also, in the south a great deal of mining activity has been carried on in Alabama, Kentucky, and southwest Virginia. Some of the by-products of this activity has been the production of mineralized water from the mines in copious quantitites. The southern Appalachians have been somewhat more fortunate in that the water there has had a considerable amount of alkalinity in it, which has to a large extent eliminated some of the more undesirable aspects of mine drainage. Northern Appalachia, including central and western Pennsylvania, the Monongahela basin in West Virginia, and the Appalachian area in eastern Ohio have not been so fortunate in that coals in those areas and the top and bottom rock have, in many cases, shown considerable quantities of pyrite, and the water does not carry the carbonates found farther south.

Jan 1, 1969

By J. O. Wheeler

"DEFINITION OF THE REGION, ITS BOUNDARIES, AND PHYSICAL AND GE'OLOGICAL CHARACTERISTICSTHIS PAPER concerns the Western Cordilleran region, embracing most of British Columbia, the southern half of Yukon Territory and the southwestern most part of the District of MacKenzie. It excludes Vancouver Island and the Queen Charlotte Islands, which are discussed in a background paper on the Pacific Continental Shelf. The region is bounded on the south by the northwestern United States, on the west by the continental shelf and Alaska, on the north by the front of the Ogilvie Mountains, on the northeast by the axis of the MacKenzie Mountains and on the east by the Rocky Mountain Trench.The region is dominated by two mountain chains that con tain icefields and glaciers: the St. Elias, Coast and Cascade Mountains in the west; the Selwyn, Pelly, Cassiar, Omineca and Columbia Mountains in the east. The Intermontane region between these mountain chains consists of lower mountains and plateaus. In the mountains, the region above the timberline and many of the steep valley-walls provide good exposures of rock, but these areas are subject to rockslides and landslides and in winter to snow avalanches. Much of the Western Cordillera was covered by ice-sheets at various times during the Pleistocene epoch. Consequently, the larger valleys in the mountains and much of the Intermontane region contain much glacial drift and alluvium and only limited exposures of rock. This same terrain in the Southern Cordillera, however, is the most favourable for agriculture. Parts of the region, particularly in the two mountain chains, are heavily forested. Elsewhere, the forest cover is less, with grassland prevailing in the south and tundra in the north."

Jan 1, 1969

By Harrison R. Cooper

With problems of diminishing ore grades and increasing cost of facilities, the mineral industry is acutely aware of the needs for improving beneficiation processes. Industry and universities are directing intensive technical effort to develop- ment of techniques with potential for using digital computers in automation and process analysis. The main problem of early attempts at on-line computer process control methods was that of economics. Now, with new advances in analysis and modeling making practical application economically important, it appears that minerals beneficiation is on the threshold of a significant jump in operating technology. In reviewing this work, particular note was taken of research and development applied to fundamental processes and the significant areas of effort where operations research techniques are used for process applications leading to the current state-of-the-art. Development of data automation and on-line control methods for process industries is deferred to the next section of this volume. This section deals with computer-facilitated mathematical-modeling development and reviews this work in conjunction with associated prior fundamental research leading to development of the methods. Flotation The 1960 state-of -the -art in flotation modeling was com- piled by Arbiter and Harris in the volume, 50th Anniversary of Froth Flotation, edited by Fuerstenau1. Many workers in the field of flotation initiated their research through flotation models, and this effort has led to use of simulation and operations re search methods employing computer techniques to facilitate advance of this work. The flotation model of Imaizumi and Inoue, published with supporting data in 1962, was expanded in 1968 with the objective of developing a basis for process automation.2,3 The fundamental work of Woodburn and Loveday in 1965 has led to techniques applicable to flotation circuit design optimization.4 This analysis is described in this volume by Woodburn in conjunction with King, Buchalter, and Piper. Niemi5,6 derived models for dynamics of a flotation circuit which were employed in developing a model describing

Jan 1, 1969

By A. F. Crawley

The density and viscosity of 1iquid thallium have been measured by absolute methods to temperatures of about 200° and 150°C, respectively, above the melting point. These new data reported, especially density data, do not closely confirm previous work. Density p, in g per cu Cm, is shown to vary linearly with temperaluve t, in °C, according to the equation p = 11.658 - 1.439 X l0-3t. The viscosity data obey the well-known Andrade equation nv1/3 = A exp C/vT , the constants A and C for thallium having values of 2.19 x A and 79.648, respectively. This paper reports some new data for the density and viscosity .of liquid thallium. Measurements of these fundamental physical properties were undertaken as part of a continuing research program at the Mines Branch, Department of Energy, Mines and Resources, Ottawa. Canada. A literature search has revealed that data are so scarce that there could not be a consensus on the true values of the density and viscosity of liquid thallium. To be more specific, there exists only one set of viscosity data' and only two acceptable sets of density data,273 one of which is limited in scope.3 In Liquid Metals Handbook,3 another density study is reported but indications of impurities in the thallium render the results suspect. In this situation, further careful experimentation was required to realize the true density and viscosity of thallium. EXPERIMENTAL METHODS Density. Densities were determined using a graphite pycnometer. The technique and its accuracy have been discussed in earlier papers.4'5 It is considered that experimental data can be obtained which are accurate within +0.05 pct, all sources of random and systematic errors having been evaluated. Density results for thallium were identical whether measured under an atmosphere of argon or a vacuum of 5 x 10-6 torr and, for the most part, the argon atmosphere was used. Viscosity. Viscosity measurements were made in an oscillational viscosimeter by an absolute method—the liquid metal being held in a closed graphite cylinder. Design and operation of the apparatus, constructed in this laboratory, have previously been discussed.6 For thallium, runs were made under a vacuum of about 2 x 10-6 torr. To evaluate viscosity coefficients from the various experimental parameters, the mathematical analysis of Roscoe7 was used. Measurements of the necessary parameters and the accuracy of these measurements have also been discussed.6 The cylinder dimensions were corrected for the anisotropic expansion of graphite, as discussed for density measurements.4,5 It is well-known that thallium oxidizes rapidly and hence a newly machined surface quickly tarnishes in air. The oxide film, however. is nonadherent and is easily removed by rubbing or by solution in water. Hence, immediately before use, both density and viscosity charges were immersed in water, wiped dry, and quickly transferred to the apparatus which was then rapidly evacuated. Specimens removed after determinations were only slightly tarnished and there was no other evidence that tarnishing affected the results. For example, the sharpness of the specimen edges from the containing vessels indicated complete filling by the liquid metal. Thallium of 99.999 pct purity was used in this investigation. Because of its high toxicity care was exercised in handling this material. For example, the melting procedure to prepare machinable ingots was carried out in an open, well-ventilated area, while protective gloves were always worn when handling the solid metal. RESULTS AND DISCUSSION Density. Measurements were made over a tempera-ture range of about 200°C above the melting point. The results are listed in Table I and plotted in Fig. 1. From the graph it is evident that the relation between density and temperature is linear. Such a relation has been observed before in this program for other metals and alloys475 and elsewhere by other workers. A least-squares analysis of experimental data gives the equation: pT1 = 11.658 - 1.439 x 10-3t where p = density in g per cu cm and t = temperature in "C. In Fig. 1, together with the present results, the data of Schneider and Heymer2 in the corresponding temperature range have also been plotted. Evidently, the two sets of data do not agree well, the results of Schneider and Heymer being about 0.6 pct higher. Viscosity. Viscosity data were obtained from the melting point, 303.5°C, up to 457.5"C. The data are listed in Table I and in Fig. 2 the plot of these results demonstrates a smooth curvilinear relation between

Jan 1, 1969

By Boris J. Kochanowsky, Burke O. Trafton

Because of the strict requirements on the quality of limestone that are dictated by the users, the operator was compelled to find new approaches to produce a product of uniform and acceptable quality. The raw material is controlled and monitored every two minutes by a special computer in order to ensure its quality. The required minimum and maximum quality constraint had an adverse effect on performance and consequently cost. In order to improve this performance, a Monte Carlo simulation model was developed and tested for the optimal truck allocation. The input data is based upon the distribution of equipment performances and costs.

Jan 1, 1969

By M. J. Kovalik

Lower Sunnyside seam coal from Utah was blended with various proportions of char and high-temperature coke to improve the quality of the coke obtained from carbonizing this coal. The Hanson 5-pound carbonizer was used as a "screening test" for the larger scale Bureau of Mines-American Gas Association (BM-AGA) tests, which were correlated with industrial production. Eighteen carbonization tests were made in the BM-AGA 13-inch retort, with a coal charge of about 90 pounds; the cokes were evaluated by the standard ASTM tumbler test. Carbonization of blends containing char and coke breeze yielded less fissured and blockier cokes of significantly higher ASTM I-inch tumbler indices as compared with the value for the straight Sunnyside coal. It was found that the simultaneous addition of char and coke breeze yielded stronger cokes than that obtained by the addition of either one of these additives. Addition of a small proportion of Pocahontas No. 3 or Sewell coal to an optimum blend improved the resulting coke strength further.

Jan 1, 1969

By Alton B. Cook

Data are presented to show oil vaporization resulting from the passage of natural gas through a sand-packed tube saturated with synthetic reservoir oils. The Bureau of Mines performed 13 experiments, using reservoir oils synthesized with base crude oils of approximately 22°, 35°, and 45° API, at 100°, 175°, or 250° F and 1,100, 2,600, or 4,100 psia. It has been determined that the amount of vaporization is significant if proper conditions exist. These experiments show that oil vaporization depends on pressure, temperature, volatility of the oil, and amount of gas cycled. Increases in each of these conditions increase the volume of oil vaporized.

Jan 1, 1969

By Peter F. Mataich

The phosphate mining industry is a highly competitive one, one in which survival depends on the plant's ability to produce at costs equal to, or below, the competition. The solution toward getting costs down is usually one of scaling up the plants to get the most tons through at the lowest possible cost. Control of these plants has been an art. Few of them are well instrumented because until a few years ago reliable instrumentation was non-existent. International Minerals and Chemical Corporation was a pioneer in applying computer techniques to ore reserves analysis and mine planning and the success in these areas led to the question of whether we could not extend the advantages of computer processing into the plant itself. There was a great deal of doubt on the operator's end that this could be done successfully because of the lack of instrumentation and the fact that plant control was largely an art that was learned only after many years of experience. However, in 1965 the instrumentation picture began to look up and the new generation of process computers just coming on the market were considerably lower in cost than the previous ones. A preliminary study of the installation costs and the probable benefits that could be realized from computer control convinced us that a process control computer should be seriously considered for a new phosphate mining plant which was being designed.

Jan 1, 1969

By P. J. Dean

This Paper contains a comprehensive survey of the known electron-hole radiative recombination mechanisms in the family of III-V compounds. Because of space limitations, the luminescence properties of each III- V compound are not reviewed separately and exhaustively. Instead, the different known types of recombination processes are discussed in turn and exemplified with reference to the III- V compound in which they were first recognized, or are best understood. Electron-hole recombinations usually occur predominantly at impurities or lattice defects either introduced de1iberately or inadvertently present, but radiative intrinsic interband electron-hole recombinations, which occur in perfect crystals, have been observed. Recombination processes which involve the participation of impurities or lattice defects ("extrinsic" recombinations) considered include transitions in which a) free carriers recombine with carriers trapped at impurities ("free to bound" transitions) , b) electrons bound at donor impurities recombine with holes trapped at acceptor impurities ("donor-acceptor pair" recombinations), C) excitons bound to charged or neutral donor or acceptor impurities recombine radiatively (both "resonance" and "two-electron" "bound exci-ton" transitions have been observed), d) excitons bound to neutral donor or acceptor impurities recombine non-radiatively (an example of an "Auger" recombination), and e) excitons bound to impurities with the same number of valence electrons as the host atom which they replace ("isoelectronic " traps) recombine radiatively. In addition, Auger recombination processes involving one or more free carriers have been observed. These extrinsic processes all involve impurities which are present as point defects. Some apparently well-authenticated examples of the recombination of excitons bound to complex impurity-lattice defect centers including nearest-neighbor donor-acceptor pairs are also discussed. Identificalions of the transitions involved in stimulated emission from the direct gap III-V compounds are briefly reviewed. Although the examples of these recombination mechanisms are selected from the III-IV compounds ia this review, these processes have quite general relevance in semiconducting crystalline solids; irrdeed most of them have also been identified in the 11- VI compounds and elernental semzconductors. THE development of crystal growth and purification techniques in recent years and concurrent advances in the understanding of physical processes in solids has accelerated the development of a wide variety of solid-state electronic devices of proven utility. These de- vices are generally used for switching or amplifying operations in electrical circuits. Most solid-state circuit elements are very photosensitive. This photo-sensitivity is generally undesirable and the single-crystal chip forming the active portion of the solid-state device is mounted in an opaque container. The photosensitivity is made use of in phototransis-tors and photodiodes, which are among the most sensitive detectors of electromagnetic radiation particularly in the near infrared.' In these devices, light is converted into electrical power. The solid-state lamp utilizes the inverse effect, namely the conversion of electrical power into light. There is an increasing tendency to use single-crystal diodes rather than the earlier electroluminescent cells in which the active material is present as a powder embedded in a suitable dielectric.' The radiation is emitted at a rate far in excess of the thermal equilibrium rate for the frequencies and temperatures involved; i.e., luminescence occurs. The development of practically efficient solid-state lamps is at an early stage compared with solid- state circuit elements or even photodetectors. Considerable progress has been made in recent years, however.3 The present review is devoted to a survey of the radiative recombination processes in the semiconducting compound crystalline solids formed from elements in groups I11 and V in the periodic table. These materials exhibit the full range of known recombination processes in solids. In fact many of these processes were discovered in 111-V semiconductors. Nonradiative recombination processes, which control the lutninescence efficiency, are also discussed. Luminescence is efficiently excited in semiconductors through processes which produce large excess concentrations of free electrons and holes in the energy bands of the crystal. Transitions induced by lattice defects or impurities usually predominate in the recombination process. By contrast, luminescence in the conventional fluorescent lamp is excited by optical absorption at the luminescent impurity center itself (the activator) and/or at a second type of impurity center (the sensitizer). This latter type of photoluminescence process, occurring in doped ionic crystals with wide band gaps, is outside the scope of this review.4 I) ENERGY BAND DESCRIPTION OF ELECTRON STATES IN CRYSTALS The energy band description of the energy states available to an electron in a crystal forms the basis of our understanding of the empirical division of crystalline solids into metals, semiconductors, and insulators in accordance with their electrical and optical properties.' Nonmetallic crystals have a finite energy gap between the highest energy band which is

Jan 1, 1969

By E. Breinan, M. Salkind

Al3Ni whiskers were chemically extracted from unidirectionally solidified Al-A13Ni eutectic ingots, bent into loops, and heated for 0.1 to 10 hr at 320°, 415", and 510°C. The initial strains ranged from 0.003 to 0.055. In all cases, permanent plastic deformation was noted after heat treatment. The deformation consisted of relatively uniform bending at low stresses and temperatures and short times and kinking followed by fracture at high stresses and temperatures and long times. After kinking, the whisker segments adjacent to the kinks were found to have straightened, which is evidence of a dislocation condensation mechanism. The range of temperatures and strains at which time dependent plastic deformation was found indicates that creep of whiskers probably plays a role in the creep of A13Ni whisker-reinforced aluminum. WHISKERS may be defined as nearly perfect single crystals which exhibit high strength. Because they can support high stresses at relatively low strains, they have been successfully employed in reinforcing metals at both ambient and elevated temperatures. In studying the creep behavior of A13Ni whisker-reinforced aluminum at elevated temperatures,1,2 it was noted that the composites exhibited measurable creep deformation. This investigation of the creep relaxation of individual A13Ni whiskel, extracted chemically from the composite was initiated to determine if creep of whiskers could con. "bute to the overall creep of the composite material. Many observations of plastic deformation of metal and halide whiskers have been made. Brenner3-8 noted that copper, silver, and iron whiskers exhibited heterogeneous plastic deformation at room temperature when strained beyond their yield points. Gyulai9 and Gordon10 observed plastic deformation of relatively large (>3 µ) NaCl and KC1 whiskers, although the smallest, most perfect whiskers were completely elastic. Eisner" noted plastic deformation and microcreep of iron and silicon whiskers at room temperature after straining beyond the yield point. Whiskers reported to exhibit creep at stresses below the yield point were zinc1'-" and Silicon.15 Cabrera and price" observed some zinc whiskers which crept at room temperature after a short incubation period but then stopped creeping after a short time. Because some of their specimens exhibited no creep, they concluded that those whiskers that crept were relatively imperfect. Pearson, Reed, and Feldman15 observed similar creep behavior of silicon whiskers at 800°C. They also concluded that creep of the whiskers was a result of imperfections in their crystals. Brenner16 observed delayed failure of A12O3 whiskers at elevated temperatures but found no evidence of plastic deformation up to 2030°C (99 pct of E.EREINAN and M.SALKIND,JuniorMembers AIME,are Research Scientist and Chief, respectively, Advanced Metallurgy Section, United Aircraft Research Laboratories, East Hartford, Conn. Maunscript submitted April 5, 1968. IMD the melting temperature). Brenner also noted7 that some copper and iron whiskers exhibited delayed kinking above 350°C while others did not. One can conclude from these observations that small relatively perfect whiskers could exhibit completely elastic behavior during sustained elevated-temperature loading of composites. Since A13Ni whiskers tested in both bending and tension were found to exhibit no evidence of plastic deformation at room temperature'7'18 this study was initiated to determine whether or not creep of A13Ni whiskers occurred at the elevated temperatures at which creep in the composites was observed. Whiskers were chemically extracted from ingots of unidirectionally solidified A1-A13Ni eutectic, constrained in bending to various elastic strains and heat-treated. The bending constraints were removed after heat treatment and the amount of permanent set was taken as a measure of the time-dependent plastic deformation. EXPERIMENTAL PROCEDURES Ingots of eutectic Al-A13Ni containing nominally 6.2 wt pet Ni were unidirectionally solidified at approximately 11 cm per hr using a process described elsewhere.19,20 The starting materials were 99.99 pct pure. Cylindrical sections cut from the center of each ingot were placed in a 3 pct aqueous solution of hydrochloric acid and the whiskers were extracted as described previously.17 The whiskers nearest the surface were blackened somewhat due to overexposure to the acid while the center of the ingot was being dissolved These partially attacked whiskers were discarded. An intermediate zone of silver-gray-colored whiskers was collected and stored in methanol for use in relaxation experiments. Individual long pieces of A13Ni whiskers were placed on Fisher Precleaned Microscope Slides. These normally straight whiskers were bent elastically into arcs or loops of varying radii by manipulating their ends with a slender probe. The mass attraction between the whisker and the probe was sufficient to cause the whisker to follow the probe. The whiskers were retained in the elastic bend by the surface tension of a fine residual film on the slides. By using long whiskers, the action of the surface tension on the unlooped ends of the whisker allowed high elastic strains to be maintained in the loops. After each whisker was bent, a photomicrograph was taken for use in measuring the bending strain. The range of strains studied was 0.003 to 0.055. The bent whiskers were then encapsulated in Pyrex tubes at pressures between 10"6 and 5 x 10"6 mm of mercury and heat-treated at 320°, 415°, and 510°C (respectively 53, 61, and 70 pct of the peritectic decomposition temperature). After each heat treatment, the liquid film on the slides was found to have dried, but the whiskers were held in their original shapes by a residue on the slide. The minimum radius of curvature of each bent whisker was measured before and

Jan 1, 1969

By John M. Karpinski, David S. Cahn

A new device based on a constant rate of loading has been developed for the compression testing of green and dry pellets. This device has a lower test variation for green pellets than the existing constant deformation rate tester. While the test variations for dry pellets are similar for both types of machine, the new tester is sensitive enough to measure dry pellet deformations of 15 µ in. for cyclic loading studies. In the study discussed here, the compressive load at which a pellet breaks proved to be a normally distributed random variable, and the load-deformation relationship was found to be linear for dry pellets but not for green pellets. The paper emphasizes the need for a standardized test procedure throughout the industry. For many years the green and dry compressive strengths of pellets have been considered as possible criteria of pellet performance during induration. Little attention, however, has been given to standardizing the unfired pellet compressive strength test or to determining the characteristics of this test. The purpose of this study was to compare the constant deformation rate test with constant loading rate

Jan 1, 1969

By Jaakko Kajamaa

Neutron diffraction was applied to determine sheet textures by the transmission method. Cold-rolled and recrystallized copper sheets were investigated. The amount of cube texture was determined for three compositions, in which the phosphorus content was, respectively, 0, 0.005, and 0.03 wt pct. The heat treatment was in every case 8 sec at 650°C. In the two latter cases the cube texture was prevented. In addition a comparison with the X-ray diffraction transmission method was made with the 96 pct cold-rolled copper sheet. Outer parts of both (111) pole figures can be considered to be rather identical. This is seen from the fact that the intensity ratio ITD/120" was 0.45 for neutron diffraction and 0.40 for X-ray diffraction. Differences between the methods were discussed in detail. Features peculiar to neutron and X-ray diffraction in texture studies were listed and compared. In this work neutron diffraction was applied to determine sheet textures. Specifically, it was desired to ascertain whether this method can be used to reveal differences when compared to other methods. In addition, the amount of the cube texture in copper sheets was determined as a function of phosphorus content. Previous applications of neutron diffraction to texture problems include the following: nickel wires,' wire of some bcc metals,' and uranium bars.3 In the neutron diffraction technique the greatest difference is in the sample—its method of production and its volume. A sample needs no treatment and its volume is roughly 105 times larger than the volume of an X-ray diffraction sample. The cold-rolled sheet was investigated both by neutron diffraction and by X-ray diffraction, because it is expected that, due to large number of defects, possible differences in the results of the two methods would be revealed. It is a well-known fact that X-ray lines show broadening when cold-worked. Analysis has shown that this is based chiefly on small crystalline size, micro-stresses, and/or faults.4'5 Neutrons are sensitive to the above-mentioned disturbing factors as well, but circumstances in diffraction are different from the X-ray case. Because the sample represents a larger volume, the result is an average over that volume. In addition, it can be assumed that the sample has preserved its original structure, because it needs no special preparation. The particular limitation of neutrons is the relatively low neutron intensity available from nuclear reactors. This decreases the resolution as compared to the X-ray diffraction methods. Furthermore, absorption mainly reduces diffracted X-ray intensity, while multiple scattering effects, i.e., secondary extinction, disturb neutron diffraction. SO neutrons and X-rays behave in a different way when interacting with matter. As in other structural investigations, one can utilize this difference in texture studies as well. One cold-rolled and three recrystallization textures in copper sheets were investigated by neutron diffraction. The samples were produced at the Outokumpu copper factory to the specifications shown in Table I. The paper is divided into five parts. The first deals with the theory of the measurement. In the second, experimental procedures are described. Results are presented in the third part. Both cold-rolled and re-crystallized samples are studied. Discussion is in the fourth part, and finally in the fifth part some conclusions are drawn. 1) THEORETICAL CONSIDERATIONS Properties peculiar to neutron diffraction are the following: a) the scattering length varies greatly between one element and another; b) many of the elements do not absorb neutrons appreciably. In this connection it is of primary interest to know the interaction of neutrons with lattice imperfections. As with X-rays this problem leads to diffraction analysis of deformed and recrystallized metals. From the physical point of view the main difference is that neutrons are scattered by nuclei (magnetic scattering is not considered here), whereas X-rays are scattered by electrons. The features peculiar to neutron and X-ray diffraction methods in texture studies are listed in Table 11. Pole figures are an important tool in performing structural analysis of deformed or recrystallized metal. Present texture research technology requires pole figures which are as precise as possible. The choice between these two methods depends on the technical information which is required. The X-ray diffraction transmission technique may give results which are not necessarily representative of the average physical state of the sample. Although foil samples normally contain enough crystallites for diffraction, they may not necessarily represent the whole structure. An example of this problem is the frequently observed difference between the "surface" and the "inside" texture of a sample. The production of foil samples may disturb the original structure of the parent material. The selection and orientation of the foil from the sample is quite arbitrary. Normally, a highly deformed piece of metal has several texture components. Different components are deformed in a slightly different manner. This is a re-

Jan 1, 1969

By William C. Peters

"A large proportion of the earth's surface is blanketed by young sedimentary formations and by recent lava flows. How many Guanajuatos lie concealed beneath the rhyolitic capping of the Sierra Madre of Mexico? How many Kirkland Lakes are under the drift cover of the Canadian Shield? How many Wilunas are still hidden by the alluvium of the desert of Western Australia? How many ore deposits lurk underneath the basalt-covered plateaus of the Columbia River region? If erosion at Goldfield, Nevada, had stopped 100 feet higher, probably no ore would have been exposed. How many Goldfields are still awaiting discovery?" --Hugh Exton McKinstry, 1948

Jan 1, 1969

By Howard S. Avery

The wear resistance of an alloy in heavy mill liner sections may be quite different from that of the same alloy in small balls and other light sections. This fact was established by means of a well standardized laboratory test that was validated for ball mill service. The salient properties of mill liner alloys, including austenitic manganese steels, medium alloy hardenable steels, and abrasion resistance cast irons are described, critically compared, and quantitatively ranked in terms of mill liner service. Where they are tough enough the high-chromium and other martensitic cast irons (e.g. Ni-Hard) promise maximum economy, but their section sensitivity is a limitation. To overcome this an extensive research program studied over a hundred experimental alloys, ranking them for heavy section abrasion resistance by means of the laboratory test. Computer analysis of the results provided a parabolic formula in terms of composition, the apexes of the parabolas providing optimum wear resistance. From the extensive family of parabolas one apex was selected for intensive study in experimental liners, pilot plant production, development of quality controls, and finally full scale production. This is a 19% chromium iron critically alloyed with nickel and molybdenum and hardened by heat treatment. It has excellent resistance to various types of abrasion, but its chief advantage is in heavy mill liner sections, where it has about 25% better abrasion resistance than the best of the quality controlled chilled Ni-Hards. It is also tougher. After production problems were solved, a number of ball and rod mill tests were arranged on a guaranteed performance basis. Two of these, representing about 138,000 pounds of mill liner castings, have recently confirmed in service the superiority that was predicted by the laboratory tests.

Jan 1, 1969

Reports on process control computer projects at the Kamioka Plant are summarized from the Japanese technical literature (see references). Fluidized Bed Roaster and Sulfuric Acid plant1 A small process control computer (Yokogawa CCS-200 with an OKITAC 5090P 8K central processor) was installed in the Kamioka smelter in the summer of 1964. A year-and-one-half installation project followed, which successfully brought the roaster and acid converters under computer control. The process plant consisted of two 130 RPD fluosolids roasters and two Monsan to acid units. The roasters are charged with lead-zinc concentrates with SO2 from the roaster processed to sulfuric acid. The computer system provides the following functions: 1) log data from the plant--the input is taken from 50 analog signals, 130 high-low digital alarm points, and 50 analog high- low alarm points; 2) set-point control on 18 control loops; 3) direct digital control (DDC) on eight control loops for which conventional controllers were difficult to adapt due to abnormal loop characteristics or delay times; 4) execution of a safe shut-down procedure

Jan 1, 1969