bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solute-Atom Segregation at Internal Interfaces
Authors: Foiles S.M. , Seidman D.N. 
Published: August 2016

In an alloy, the equilibrium composition in the vicinity of an inhomogeneity, such as a surface or a grain boundary, will generally differ from the composition in the bulk. This was first recognized by Gibbs. This change in local composition can potentially affect the structure and mechanical properties of the boundary. As an example, experiments by Sass and co-workers have shown that the Burgers vector of the dislocations present in Fe-Au twist boundaries depends on the Au concentration at the boundary. This demonstrates that the structure does, in fact, depend on the local composition of the alloy at the interface.This article presents computer simulation studies of equilibrium segregation in binary alloys at grain boundaries, and two experimental studies of interfaces using atom-probe field-ion-microscopy (APFIM). These studies address two fundamental questions: What is the composition of the boundary region as a function of the bulk composition and temperature? What is the spatial distribution of the two species in the boundary? Note, that the comparison of experiment and calculations, where possible, is crucial. Such comparisons can provide guidance in the experimental analysis, and the comparison also provides a stringent test of the reliability of the simulation methods.This article first describes simulation and atom-probe field-ion microscope techniques and next discusses the segregation in Ni-Cu alloys to isolated edge dislocations. This is followed by a study of segregation at twist boundaries in Pt-Au alloys. Then, the segregation at an asymmetric mixed tilt-twist boundary in a Pt-Ni alloy is computed, and the results are compared with experimental atom-probe held-ion-microscopy results. Finally, the results of an atom-probe study of two-dimensional Re segregation at a twist boundary with a small tilt component in a W-Re alloy are presented.
Chemical Interfaces: Structure, Properties, and Relaxation
Authors: Ourmazd A. 
Published: August 2016

Any finite system is delimited by interfaces. In this trivial sense interfaces are ubiquitous. However, modern epitaxial techniques seek to modify the properties of materials by the creation of interfaces. “Band gap engineering,” the attempt to tailor the electronic properties of semiconductors by interleaving many dissimilar layers, is an example of this approach. Interfaces between lattice-matched, isostructural, crystalline systems, (differing only in composition) are technologically the most advanced and thus most widely used. These “chemical” interfaces are formed by the introduction of dopant impurities, or by the stacking of dissimilar materials. Chemical interfaces formed by the epitaxial growth of dissimilar materials are the subject of this article.A fundamental tenet of modern epitaxy is the tailoring of properties through control of structure. We will therefore outline how the “structure” of a chemical interface may be defined and experimentally determined. Determining the interfacial structure is a major experimental challenge, inextricably bound with our understanding of how structure affects other properties. The article will thus briefly discuss this vital link. We will conclude with an outline of the way chemical interfaces, in reality systems far from equilibrium, can relax, and how their relaxation mechanisms shed light on the fundamental properties of solids. Because the GaAs/AlGaAs system is the most technologically advanced, and to be concrete, we will illustrate the discussion by reference primarily to this system. Many of the concepts and experimental results, however, are more generally valid.
Materials Engineering and Fuel Cell Development
Authors: Steele B.C.H. 
Published: August 2016

The direct conversion of chemical energy in a fuel cell has been one of the most challenging technological problems since a simple hydrogen/oxygen fuel cell was first demonstrated 150 years ago by Groves at the London Institution. Aqueous electrolyte fuel cells have been successfully used in space to power electrical equipment in the Apollo spacecraft and in the space shuttle, but terrestrial applications have been principally limited to a few specialized military and telecommunication applications.In the original concept of a fuel cell, a primary fuel (e.g., hydrogen, hydrocarbon) is reacted with oxygen in an electrochemical cell incorporating an acid electrolyte, namely:so as to convert the free energy of oxidation (ΔG°) of the fuel to carbon dioxide and water directly into electrical energy.Fuel cells are attractive in that theoretical thermodynamic energy/fuel conversion ratios given by the appropriate value of ΔG°/ΔH° (free energy change/enthalpy change) can be very high (e.g., ~95% for H2/O2 reaction at 298 K) compared to the limitations imposed on heat engines by the Carnot cycle efficiency, (T2−T1)/T2. However, in practice it has proved difficult to realize the high electrical/fuel conversion efficiencies promised by fuel cell systems. This is caused by problems associated with the electrochemical kinetics and/or the requirement that in the Faradaic reaction both mass and electron transfer must occur in a spatially restricted region where an electrode, an electrolyte, and one of the reacting phases (usually a gas) are in intimate contact. This region is often referred to as the three-phase boundary.
Up Close: Materials Research at the Grenoble Nuclear Research Center of the French Atomic Energy Commission (CEA)
Authors: Chappert J. , Coeure P. , Rey P. , Silvent J.A. , Spitz J.P. 
Published: August 2016

Most great technological advances initially required finding a solution to materials problems, a fact that is not very often recognized. The development of nuclear energy is no exception to this rule. The fuel in the reactor core, cladding of the fuel, and structures which support the core or which carry the coolant are, indeed, subjected to extreme conditions of radiation flux, temperature, pressure, and corrosion. In order to achieve safe, industrial reactors, the French Atomic Energy Commission (CEA) had to build an enormous program in materials research and development from the ground floor. At present, CEA has reached a very high level of knowledge and expertise through excellent scientific teams and exceptional equipment.In its present industrial phase, the French Nuclear Program still requires considerable effort in research, but it does enable the nation's industry to take advantage of the CEA's materials capabilities. In accordance with its mission to facilitate the utilization of research results, the CEA launched research and development programs in different non-nuclear industries where its research could find new applications.Since its creation in 1955, the Grenoble Nuclear Research Center (CEN-G), one of the five civilian centers of the CEA, has concentrated a great part of its research on basic (solid-state physics) and applied aspects (nuclear metallurgy). This double orientation, in which basic research is used as a basis for applied research, is an original feature of the CEN-G.
Studies of Ion Transport in AgCl and AgBr
Authors: Jacobs P.W.M. 
Published: August 2016

Silver chloride and silver bromide, like sodium chloride and sodium bromide, are ionic crystals with the rock-salt structure, but despite the similarity in the crystal radii of Ag+ (1.29 Å) and Na+ (1.16 Å) the properties of these silver halides are very different from those of the corresponding sodium salts. Much of this difference is due to the filled 4d shell in the electron configuration of Ag+, which is responsible for the higher polarizability of Ag+ (2.37 − 2.44 Å3) than Na+ (0.41 Å3 and for the tendency of Ag+ to undergo quadrupolar deformation.Associated with the high polarizability of Ag+ are the large van der Waals cation-cation and cation-anion interactions in AgCl and AgBr and the consequent high cohesive energies of these silver salts (9.26 eV and 9.12 eV, respectively). Bear in mind, however, that the large van der Waals coefficients that result from empirical fitting of two-body model crystal potentials to crystal properties may be partly due to the model attempting to simulate features of the real crystal which the model does not really include, such as many-body interactions. That such many-body interactions are important in AgCl and AgBr is evident from the large violations of the Cauchy relation between the elastic constants, C12 = C44, which ought to hold when each ion is at a center of cubic symmetry and the inter-ionic forces are derivable from two-body potentials.
Determining the Origin and Age of Metal Artifacts
Authors: Wayman Michael L. 
Published: August 2016

Metallography is undoubtedly one of the most useful techniques for addressing the numerous questions posed by archaeologists about metal artifacts. The most frequent questions include:∎ What is the nature of the metal or alloy which the object is made of?∎ Where did the object and/or its raw materials originate?∎ What technologies were employed in producing the object?∎ How old is it?Many aspects of a metal artifact's history are imprinted in its microstructure (i.e., the structure of the material as revealed under the microscope after appropriate surface preparation). The artifact has a story to tell and the role of the archaeometallurgist is to read and translate the story by studying and interpreting the microstructure. In most cases it is productive to supplement the information obtained from optical microscopy by using other analytical techniques. This will be illustrated below.Although it is frequently not possible to obtain definitive answers to the above questions, this does not necessarily mean that the analysis has served no useful purpose. For example, it may be just as important to demonstrate what an artifactis notas to prove what itis. Eliminating some of the possible identifications may be a valuable contribution.Consider the first question: What material is the artifact made of? It is normally essential to perform elemental analyses in order to identify the material. Nevertheless, metallography is a useful first step in answering this particular question. Furthermore, the specimen prepared for optical microscopy can be used without further preparation for other analytical techniques (such as electron probe microanalysis) which can yield an elemental analysis. As will be demonstrated in the following case studies, metallography is of great value in assessing the forms of impurities in metallic materials. This is highly useful information which elemental analysis cannot provide.
A Perspective on Welding Science
Authors: Cieslak M.J. , Jellison J.L. 
Published: August 2016

Welding science is an interdisciplinary field involving metallurgy and materials science, heat, fluid, and mass transfer, and arc and plasma physics to name a few. Three areas of welding science have been the focus of much research the past few years as welding scientists attempt to understand the phenomena responsible for producing fusion welds with acceptable service properties. Broadly defined, these areas are:1. physical and numerical modeling of the heat and fluid flow during fusion welding,2. understanding the microstructural evolution during solidification and cooling of welds, and3. welding of advanced materials.This short review will focus on these fusion welding research themes to provide the reader with a flavor of the work in progress at several major government, industry, and university laboratories.Much of both the experimental and theoretical studies that have advanced the understanding of fusion welding processes revolves around delineating the roles of mass, momentum, and energy transfer. The earliest models of fusion welding processes were analytical models of heat transfer by conduction. These models not only excluded much of the physics of the process, but assumed point or linear heat sources. Nevertheless, these models provided useful insight about the interplay between power and weld speed, particularly regarding weld pool shape. Also, although quantitative predictions of weld pool shape were generally inaccurate, predicted thermal contours and cooling rates away from the fusion zone were useful in understanding the extent of heat-affected zones.
Chemical Vapor Deposition Techniques
Authors: Besmann T.M. , Stinton D.P. , Lowden R.A. 
Published: August 2016

Chemical vapor deposition (CVD) is one of the few deposition processes in which the deposited phase is produced in situ via chemical reaction(s). Thus the vapor source for CVD can consist of high vapor pressure species at moderate temperatures and yet deposit very high-melting phases. For example, pure TiB2, which melts at 3225°C, can be produced at 900°C from TiCl4, BC13, and H2.Chemical vapor deposition and its variants such as low pressure CVD (LPCVD), plasma-assisted CVD (PACVD), and laser CVD (LCVD) have been active areas of research for many years. Recent review articles have contained extensive lists of the phases deposited by CVD, which include most of the metals and many carbides, nitrides, borides, silicides, and sulfides. The techniques have found increased acceptance as commercial methods for the fabrication of films and coatings which are fundamental to the semiconductor device and the high-performance tool bit industries. They have been used to prepare multiphase-multilayer coatings, stand-alone bodies, and fiber-reinforced composites. As the demand increases for more complex and sophisticated materials, it is expected that CVD will play a still larger role.In CVD a solid material is deposited from gaseous precursors onto a substrate. The substrate is typically heated to promote the deposition reaction and/or provide sufficient mobility of the adatoms to form the desired structure. Chemical vapor deposition was performed for the first time when early humans inadvertently coated cooking utensils with soot from the campfire. In this CVD process, hydrocarbons generated by the heated wood pyrolyzed on the utensil surface, depositing carbon.
Crystal Growth
Authors: Gentile A.L. , Elwell D.F. 
Published: August 2016

Crystal growth is a vital and fundamental part of materials science and engineering, since crystals of suitable size and perfection are required for fundamental data acquisition and for practical devices such as integrated circuits.The word “crystal” comes from the Greek and means “congealed by cold.” The term was originally applied to ice crystals and to crystalline quartz found in such locations as the Alps and thought, at one time, to be some permanently frozen form of water. As a crystallization process, crystal growth extends throughout recorded history—the crystallization of salt from sea water may have preceded pottery-making as the oldest method for controlled phase transformation of materials.The crystallization of salts such as sodium carbonate was known to the Egyptians, and the process of purification by recrystallization from aqueous solution was described by Greek and Roman writers before the Christian era. The “father” of crystal growth, however, is generally considered to be the English scientist, Robert Boyle, who in 1672 described experiments relating the form of crystals to impurities and changes in growth rate. Boyle believed in the healing powers of crystals, part of the mysticism which has had a strong revival in recent times. We understand that crystals are particularly valued for enhancing the ability of the third eye to perceive auras, but are unable to offer warranted samples.Recognition as the “founder” of the theory of crystal growth is normally given to the American J. Willard Gibbs, who in 1878 published a seminal work on phase transformations, including a theory of the energy to generate a crystal nucleus and of the equilibrium form of crystals.
Growth of Single Crystal Fibers
Authors: Feigelson Robert S. 
Published: August 2016

Single-crystal fibers represent perhaps one of the most underexplored areas of material science. Despite some early interest and excitement 30 years ago, the lack of immediate applications led to a decline in research activity, and until recently, little was known about their growth behavior and properties. During the past few years single-crystal fiber research has been revived and preliminary results have stimulated considerable interest in the scientific community.At present, the most extensive and broadly based single-crystal fiber program is at Stanford University, where the focus has been on studying fibers for optical applications. This program emerged from a desire to combine the light-guiding properties of fiber geometries with the unique physical properties of crystalline materials, as was done during the last decade for glass fiber applications. Such materials could lead to a range of novel devices with higher efficiencies than possible in bulk crystals. But single-crystal fiber growth technology may have an even broader applicability. While single-crystal fibers of semiconductor, superconductor, and high strength materials could play an important role in future device applications, an important current use for the single-crystal fiber growth technology is in preparing single crystals of a wide variety of materials for property evaluation. Fiber crystals may have much higher crystalline perfection than bulk crystals of the same composition, making them useful for studying the intrinsic properties of a material and for improving device performance. Other areas of interest which have been identified include metastable phase formation and the growth of oriented ferroic domain and multiphase structures.
Photonic Materials: Introduction
Authors: Glass Alastair M. 
Published: August 2016

Optical technologies have advanced dramatically in recent years. In just two decades the transparency of optical fibers has improved by four orders of magnitude. Semiconductor lasers have evolved from a new invention to highly reliable, high performance commercial devices for wide bandwidth optical communications. New approaches to higher frequency modulation, wider bandwidth transmission, more sensitive detection and optical amplification are constantly being developed. Fundamental limitations are sufficiently far removed from current capabilities that considerable further progress can be anticipated. These advances have provided the stimulus for a much broader investigation of the potential of optics in future information technologies in which optics and electronics play complementary roles. This rapidly developing field is referred to as “photonics.” Increasing attention is now being paid to applying optics to wide bandwidth switching systems and to exploring the potential of optics for image processing and computation.Past progress in optical communication can be traced largely to the dramatic progress in optical fiber and compound semiconductor materials technologies. Likewise, future opportunities in photonic switching and information processing will depend critically on the development of improved photonic materials. The future role of optics in these conventionally electronic technologies, and the extent of that role, depends on whether materials can be designed and fabricated with the required characteristics.
Material Demands for Optical Neural Networks
Authors: Anderson Dana Z. 
Published: August 2016

From the time of their conception, holography and holograms have evolved as a metaphor for human memory. Holograms can be made so that the information they contain is distributed throughout the holographic medium—destroy part of the hologram and the stored information remains wholly intact, except for a loss of detail. In this property holograms evidently have something in common with human memory, which is to some extent resilient against physical damage to the brain. There is much more to the metaphor than simply that information is stored in a distributed manner.Research in the optics community is now looking to holography, in particular dynamic holography, not only for information storage, but for information processing as well. The ideas are based upon neural network models. Neural networks are models for processing that are inspired by the apparent architecture of the brain. This is a processing paradigm that is new to optics. From within this network paradigm we look to build machines that can store and recall information associatively, play back a chain of recorded events, undergo learning and possibly forgetting, make decisions, adapt to a particular environment, and self-organize to evolve some desirable behavior. We hope that neural network models will give rise to optical machines for memory, speech processing, visual processing, language acquisition, motor control, and so on.
Physical and Technological Limitations of Optical Information Processing and Computing
Authors: Tanguay Armand R. 
Published: August 2016

Over the past four decades, the growth of information processing and computational capacity has been truly remarkable, paced to a large extent by equally remarkable progress in the integration and ultra-miniaturization of semiconductor devices. And yet it is becoming increasingly apparent that currently envisioned electronic processors and computers are rapidly approaching technological barriers that delimit processing speed, computational sophistication, and throughput per unit dissipated power. This realization has in turn led to intensive efforts to circumvent such bottlenecks through appropriate advances in processor architecture, multiprocessor distributed tasking, and software-defined algorithms.An alternative strategy that may yield significant computational enhancements for certain broad classes of problems involves the utilization of multidimensional optical components capable of modulating and/or redirecting information-carrying light wave-fronts. Such an optical processing or computing approach relies for its competitive advantage principally on massive parallelism in conjunction with relative ease of implementation of complex (weighted) interconnections among many (perhaps simple) processing elements. A wide range of computational problems exist that lend themselves quite naturally to optical processing architectures, including pattern recognition, earth resources data acquisition and analysis, texture discrimination, synthetic aperture radar (SAR) image formation, radar ambiguity function generation, spread spectrum identification and analysis, systolic array processing, phased array beam steering, and artificial (robotic) vision.
Materials Aspects of the SL Lightguide Undersea Cable Design: 1988 MRS Spring Meeting Plenary Addres
Authors: Tuminaro Raymond D. 
Published: August 2016

Starting in the 1950s, AT&T has been involved in the design, installation, and operation of undersea coaxial cable systems to provide international and inter-island telecommunication services. These systems are analog transmission systems, utilizing frequency division multiplexing to simultaneously transmit multiple channels over a single cable. With the passage of time, and in response to an ever growing demand for services, the frequency bandwidths of successive systems have been increased to accommodate the need for increased traffic density. The increases in bandwidth have been accompanied by increases in copper ohmic losses, brought about by the skin effect phenomenon, mandating ever shorter spacing between repeaters, and consequently larger numbers of repeaters for a given system length. The reliability outlook for extending coaxial cable technology beyond its present capacity, with a decrease in repeater spacing below the current value of about 9 km, is not favorable.Fortunately, we now have available optical fibers for transmission media. Unlike coaxial cable, the fiber medium is not limited by the skin effect phenomenon. Using fiber technology, we can transmit large amounts of traffic through a very small cross-sectional areas, using repeaters at infrequent intervals. Moreover, undersea fiber optical systems utilize digital (as opposed to analog) transmission, a format extremely advantageous in terms of transmission quality and the types of services that can be offered.