bluuebunny/crossref_metadata_2025 huggingface dataset:
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, and

3. 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.
A Focus on Magnetism and Magnetic Materials
Authors: Herbst Jan F.
Published: August 2016

Research in magnetism has a long, redoubtable history, and one fundamental reason for its continuing productivity is the fact that advances are very often coupled intimately with progress in materials science. New materials, preparation methods, and characterization technique s continu e to provide opportunities for exploring magnetic phenomena in a progressively broader array of systems with a growing arsenal of analytical tools. Challenges to theory are often presented by discoveries on the experimental side, engendering constructive interaction which enhances our basic understanding of the materials and the physics controlling their properties. Technology invariably benefits from that ongoing process. The following series of five articles in this issue of the MRS BULLETIN aims at conveying the excitement and vitality of current work in magnetism and magnetic materials. Each author or set of author s has endeavored to provide a succinct overview of a specific area, and in combination the papers offer an informative (although certainly not exhaustive!) survey of this very active field.
MBE of Magnetic Metallic Structures
Authors: Prinz G. A.
Published: August 2016

Epitaxial growth of magnetic metals actually pre-dates epitaxial growth of semiconductors. The earliest work (1936), which reported single-crystal Fe growth on NaCl, exploited the fact that single-crystal substrates of NaCl were easy to obtain, readily cleaved, and could be cleaned in a vacuum by heating. The good lattice match between the two systems and lack of interfacial disruption upon growth permitted excellent quality single-crystal films of Fe to be grown in relatively modest vacuum. Improved vacuum techniques broadened the range of materials which could be studied, with respect to both the films and substrates. The most recent ultrahigh vacuum (UHV) techniques developed for molecular beam epitaxial growth of semiconductors, including the large array of electron-based analytical tools, have also been exploited to grow and characterize magnetic metal films.

Some requirements for these magnetic materials, such as the need for higher temperature effusion sources to generate useful fluxes of Fe, Co and Ni, and high vacuum in the presence of e-beam sources in order to avoid oxidation of the rare earths, served to stimulate new technical developments for the field in general. It is now possible to control growth to a fraction of a monolayer (ML) and even to know when one ML coverage is complete and another is beginning. The techniques have become so successful that a whole new subfield of magnetism has emerged — surface and interfacial magnetism — in which the work would be largely meaningless if one could not grow precisely characterized epitaxial magnetic metal films. Recent work has shown that it is now possible to grow single-crystal magnetic metal films on a wide variety of substrates, including insulators (oxides and salts), semiconductors, and metals.
Diluted Magnetic Semiconductors
Authors: Samarth N. , Furdyna J.K.
Published: August 2016

Diluted magnetic semiconductors (DMS) are semiconducting alloys whose lattice is partly made of substitutional magnetic ions. The most extensively studied materials of this type are the alloys, in which a fraction of the group II sublattice is replaced at random by Mn. The entire family of ternary alloys, along with their crystal structure and corresponding ranges of composition, is listed in Table I. Over the past decade, these alloys have attracted a growing scientific interest because of new fundamental effects in semiconductor physics and magnetism in these materials and because of their potential applications in optical nonreciprocal devices, solid state lasers, flat panel displays, infrared detectors, and other optoelectronic applications.

The increasing popularity of this field can be attributed to the broad variety of fascinating problems offered by the study of the alloys. To begin with, there is an interest in the semiconducting properties per se — for instance, the understanding of the electronic band structure and its variation with alloy composition. As in other ternary alloys, the band parameters and the lattice constant can be “tuned” by controlling the alloy composition, opening the door to band-gap engineering and lattice matching in the context of epitaxially grown superlattices and het-erostructures. The random distribution of Mn atoms with a well-characterized antiferromagnetic Mn-Mn exchange interaction provides an ideal system for studying fundamental questions in disordered magnetism. The sp-d exchange interaction between the spins of band electrons and the localized moments of the Mn atoms constitutes a unique interplay between semiconductor physics and magnetism. This leads to unusual magneto-transport and magneto-optic phenomena such as an extremely large Faraday rotation, giant negative magneto-resistance, and a magnetic-field-induced metal-insulator transition. Finally, the potential technological importance of DMS is also being recognized. For example, the large Faraday rotation holds promise of DMS applications as optical isolators, modulators, and circulators. We will briefly introduce some of the exciting research problems offered by the study of DMS. More detailed information is available in several extensive reviews and compendia.
Intelligent Processing of Materials
Authors: Yolken H. Thomas
Published: August 2016

Advanced materials can provide specialized properties, or combinations of properties, that cannot be obtained in conventional materials. However, advanced materials generally require unusual processing operations in order to achieve their unique microstructures and the resulting greatly improved properties. These materials also tend to be expensive because of the high value added by unusual processing operations that may be labor intensive. Because the relationships among the processing parameters, microstructure, and resulting material properties and performance are not fully understood, and because the microstructure is difficult to control, reproducibility in these materials is often unsatisfactory. A very promising direction toward overcoming these difficulties involves intelligent processing of materials, a computer-based approach to automatically controlling the evolution of microstructure during processing.

In a conventional automated materials processing system, automation involves utilizing sensors to monitor process variables such as temperature and pressure. Data from these sensors are compared with preset values automatically in order to maintain these values with control devices. Nevertheless, the microstructure and properties often experience significant variations. The variations are detected after the fact either by destructive analysis in a quality control laboratory or by nondestructive evaluation (NDE) at the end of the manufacturing process.

In contrast, an intelligent processing system utilizes a new class of NDE sensors to characterize the microstructure of the material in real time. Moreover, the real-time data plus data from conventional process variable sensors are transmitted to a computerized decision maker.
On-Line NDE for Control and Modeling of Ceramic Processing
Authors: McClung R.W. , Johnson D.R.
Published: August 2016

The high-temperature structural properties of ceramics make them unique candidates for application in such systems as advanced gas turbines and other heat engines. Of concern, however, is the variability in fast fracture strength of structural ceramics which is due, in part, to the sensitivity of ceramics to very small (e.g., 20–50 μm) critical flaws and the difficulty in detecting and characterizing this type of flaw by nondestructive examination (NDE) techniques.

The flaw sensitivity of ceramics and the typically wide variation in flaw sizes result in the situation illustrated in Figure 1, which is a frequency distribution of fast fracture strengths for a hypothetical structural ceramic with characteristic strength of 350 MPa and Weibull modulus of 5. The strength requirement, 250 MPa, for a particular application is shown. In this illustration, a significant fraction of the population of ceramic parts, 17%, has a strength below the 250 MPa requirement.

The situation illustrated in Figure 1 is typical of structural ceramics today: although in many cases the average properties of a specific ceramic may be suitable for the intended use, a significant fraction of the parts made of that material will be unsuitable. The unacceptable parts are, of course, very difficult to distinguish from the rest of the population.
Atomic-Scale Simulation in Materials Science
Authors: Baskes Michael , Daw Murray , Dodson Brian , Foiles Stephen
Published: August 2016

Realistic simulation of the atomic-scale properties of complex systems has long been a goal of scientists interested in the behavior of condensed matter. Until recently, the role of atomistic simulation techniques has been to address rather idealized problems in statistical mechanics. Treatment of more realistic materials has been uncommon not because suitable approaches toward simulating such materials were unknown, but rather because the computer power available was inadequate. Recently, major advances have occurred in the complexity of systems subject to atomistic simulation, primarily due to a dramatic increase in availability of computer power. These new capabilities have driven the development of atomic-scale descriptions of real materials accurate enough for atomistic simulation of a wide range of specific materials science problems.

In this section, we will outline several of the techniques used to simulate the microscopic behavior of an atomistic system. The first method introduced for atomistic simulation was the molecular dynamics technique, in which Newton's equations of motion for the individual atoms are integrated numerically for given interatomic and external forces. One of the first uses of this technique was the study, by Fermi, Pasta, and Ulam, of randomization of vibrational energy in a one-dimensional chain of atoms. Although the results of this initial application were to some extent unsatisfactory, the molecular dynamics technique has since been applied to a wide range of problems in the statistical mechanics of condensed media.
Three Dimensional X-Ray Computed Tomography in Materials Science
Authors: Kinney J.H. , Johnson Q.C. , Bonse U. , Nichols M.C. , Saroyan R.A. , Nusshardt R. , Pahl R. , Brase J. M.
Published: August 2016

Imaging is the cornerstone of materials characterization. Until the middle of the present century, visible light imaging provided much of the information about materials. Though visible light imaging still plays an extremely important role in characterization, relatively low spatial resolution and lack of chemical sensitivity and specificity limit its usefulness.

The discovery of x-rays and electrons led to a major advance in imaging technology. X-ray diffraction and electron microscopy allowed us to characterize the atomic structure of materials. Many materials vital to our high technology economy and defense owe their existence to the understanding of materials structure brought about with these high-resolution methods.

Electron microscopy is an essential tool for materials characterization. Unfortunately, electron imaging is always destructive due to the sample preparation that must be done prior to imaging. Furthermore, electron microscopy only provides information about the surface of a sample. Three dimensional information, of great interest in characterizing many new materials, can be obtained only by time consuming sectioning of an object.

The development of intense synchrotron light sources in addition to the improvements in solid state imaging technology is revolutionizing materials characterization. High resolution x-ray imaging is a potentially valuable tool for materials characterization. The large depth of x-ray penetration, as well as the sensitivity of absorption crosssections to atomic chemistry, allows x-ray imaging to characterize the chemistry of internal structures in macroscopic objects with little sample preparation. X-ray imaging complements other imaging modalities, such as electron microscopy, in that it can be performed nondestructively on metals and insulators alike.
Liquid Crystalline Polymers
Authors: Windle Alan
Published: August 2016

Not much more than a decade ago, the plastics industry viewed itself as a mature branch of the heavy chemical industry. Its raison d'être was the mass production of four or five main-line polymers, and profits were equated to tonnage output, plant efficiency, and clever downstream processing such as film blowing. The chemistry was essentially simple and the monomer, of course, cheap. There was, however, a spark of new thinking. A trend was developing toward the design and manufacture of more complex, more expensive polymers, with special properties which could command a special price. Such products would sell advanced scientific know-how, not just engineering expertise which could all too easily be exported to the major oil producers in the form of a polymer plant.

Designing particular molecules to achieve desired properties is now a major theme of polymer producers. There is a move toward increasing the aromatic content of polymer backbones to achieve greater levels of chemical and thermal stability, while the development of new cross-linking systems remains as chemically intensive as ever. It is, however, the introduction of liquid crystalline polymers which, above all, has exploited the principles of molecular design, while at the same time challenging our understanding in a new area of polymer science.

A polymer is “liquid crystalline” where the chains are sufficiently rigid to remain mutually aligned in the liquid phase although the perfect positional periodicity of a crystal is no longer present. In other words there is a long-range orientational order without long-range positional order (Figure 1). Structurally, therefore, the phase is intermediate between a crystal and a liquid leading to the use of the term mesophase. Where the liquid crystalline phase forms on melting the polymer, it is known as thermotropic, but where it is achieved by solvent addition it is called Inotropic. Increasing temperature, or solvent concentration, will eventually lead to the reversion of the liquid crystal phase to the normal isotropic polymer melt.
Electrically Conductive Polymers
Authors: Wnek Gary E.
Published: August 2016

Polymeric materials are typically considered as insulators, and in fact important applications do rely on their poor conductivity— e.g., electrical cable insulation and charged dielectric films (electrets, electrical analogs of magnets), the latter finding use in microphones. Research in the last decade, however, has lead to the discovery of polymeric materials with extremely high conductivity, approaching that of copper. This brief article will highlight recent work in the synthesis, processing and applications of these novel materials.

Typical polymers, the oxidant (or “dopant”) used to create carriers, and room temperature conductivities are given in Table I. A key feature shared by these materials is delocalized (at least over a few repeat units) π-electron density. Such unsaturated polymers facilitate carrier generation because of the ability for resonance derealization of the resulting radical ions, which can also offer good intramolecular carrier mobility. In addition, the geometry of π-orbitals allows for good orbital overlap and encouragesintermolecular carrier transport.

That the polymer chains are considerably shorter than typical sample dimensions indicates that intermolecular transport is dominant, especially in view of the disorder observed in most conducting polymer systems. However, as the number of defects (crosslinks, “twists” which inhibit conjugation) decreases, it might be anticipated that carriers can travel greater distances along a chain before a (presumably) higher activation energy, inter molecular electron transfer becomes necessary, thus affording higher conductivity. Indeed, it has been recently reported that samples of very high quality, oriented polyacetylene, when treated with iodine,exhibit conductivities approaching that of copper at room temperature.
Ferroelectric Ceramics for Dielectric Electromechanical and Pyroelectric Applications
Authors: Schulze Walter A. , Gururaja Turuvekere R.
Published: August 2016

The growth of integrated circuit applications has been a strong influence in the expansion of markets for ferroelectric ceramics. Ferroelectrics perform three major functions in circuits:

1. They store energy with a high volume efficiency,

2. They have very useful large changes in impedance with frequency, and

3. They transduce between various energy forms and electrical signals.

For many years commercial ferroelectric ceramics have been dominated by the barium titanate and lead zirconate titanate (PZT) systems. A tremendous research effort has been dedicated to these systems with very interesting studies still progressing on basic understanding, reproducibility, and modifications to utilize inexpensive electrodes. Processing studies are also seeking to reduce the size of devices and develop new transducing and sensing applications. The need to reduce cost and to fulfill specific applications is creating demands for new materials. Much of this effort has centered on lead-based systems referred to as relaxor ferroelectrics.

The areas of application of ferroelectrics are narrowed in this review by eliminating the interfacial (grain-grain boundary) devices and electro-optic applications discussed in “Electronic Ceramic Thin Films” by Bruce Tuttle in this issue. Also, this article can only cover a small fraction of the information indicated by the title.
Plasma Synthesis of Ceramic Powders
Authors: Phillips D.S. , Vogt G.J.
Published: August 2016

Condensation from plasmas has been shown to yield very fine, high purity powders from even the most refractory materials. Elementary particles in these powders are often single crystals, as fine as 50 nm diameter. These particles vary widely in agglomeration state; in some systems they are essentially independent, while in others hard agglomerates as large as several microns are observed. In this article the geometric aspects of reactor design which are thought to influence these powder structures are reviewed, along with three case studies in powder microstructure. Finally, the structure of the “typical” plasma powder is compared with expectations from alternative preparation routes.

The development of new, energy-efficient processing strategies for ceramic fabrication has become a rapid growth field over the last ten years. Most of these strategies rely on minimizing diffusion requirements during densification by improving both the chemical homogeneity and the initial density of the powder compact to be consolidated; both requirements dictate unusual care in the synthesis of the starting powders. In the oxide systems most extensively studied to date, the required powders can often be produced by precipitation from aqueous solutions and/or emulsions. In the carbide and nitride systems widely envisaged for the next generation of structural applications, these techniques are difficult and gas-phase synthesis routes appear more attractive. In fact, even the leading practitioners of the precipitation arts write enthusiastically of aerosol synthesis methods for the oxides.
Up Close: MIT's Ceramics Manufacturing and Process Integration Laboratory
Authors: Pober Richard L. , Thomson Elizabeth A.
Published: August 2016

In a relatively short period of time ceramics have become the key elements to a variety of new technologies, including integrated circuit substrates, artificial limbs, turbocharger rotors, and, of course, superconductors. By and large, however, they have not met their potential. Though advances in basic research are responsible for the breakthroughs so far, no extensive work has been done to establish the manufacturing paradigms necessary for the production of reliable, reproducible materials.

The new Ceramics Manufacturing and Process Integration Laboratory (CMPIL) at the Massachusetts Institute of Technology was conceived to address this need. As a logical extension of the science-based Ceramics Processing Research Laboratory (CPRL), also at MIT, the CMPIL will “test” fundamental ideas as they relate to ceramics manufacturing. The goal is to create a hands-on “research factory,” complete with manufactured product, to make an impact on manufacturing productivity and teach students, staff, and visiting scientists the principles that control ceramics manufacturing systems. Other thrusts include developing innovative processing techniques and collecting operating data that will ultimately be transferred to industry.
Fundamentals of X-Ray Photoemission Spectroscopy
Authors: Grunthaner F.J.
Published: August 2016

Rapid progress in the development of new electronic materials and the steady maturation of silicon-based technologies has resulted in a host of novel electronic devices in which the active region of the structure is confined to an interface or a surface. The chemical, electronic, and physical characterization of surfaces and interfaces in semiconductors and insulators is of critical importance to manufacturing process control as well as to the fundamental electron physics and materials science which support microelectronic device research.
Up Close: The Ion Beam Materials Laboratory at Los Alamos National Laboratory
Authors: Tesmer J.R. , Parkin D.M. , Maggiore C.J.
Published: August 2016

The new Ion Beam Materials Laboratory (IBML) is a Los Alamos National Laboratory (LANL) resource devoted to the characterization and modification of surfaces through the use of ion beams. IBML was developed and designed in response to a large number of recognized research needs ranging from archaeology to the Strategic Defense Initiative and from basic research to semiconductor development. Most recently, the IBML has been used in research on high temperature superconductors. The IBML was dedicated in February 1987 when the 3 MV tandem accelerator reached operational status.

Beginning with an existing accelerator facility built to support nuclear physics, Los Alamos researchers added materials science capability and started to demonstrate the power of ion beam techniques as they apply to many of the Laboratory's research activities. These efforts led to a growing interest in ion beams by fellow researchers and caught the attention of LANL management. By the fall of 1984, a clear grassroots case—which was supported by the Laboratory's Center for Materials Science (CMS)—was made for developing a modern ion beam facility, which included capabilities for materials modification and analysis. The $1.7-million IBML was funded with Laboratory-wide resources in the spring of 1985 and was charged with supporting Laboratory-wide programs.
Up Close: Center for Materials Science at Los Alamos National Laboratory
Authors: Parkin Don M.
Published: August 2016

Los Alamos National Laboratory (LANL) has extensive and diverse activities and programs in materials science and engineering. The Center for Materials Science (CMS) was established to promote scientific collaboration and scientific excellence in materials research and engineering throughout the Laboratory and with individuals and institutions outside the Laboratory. The Center's objective is to enhance the Laboratory's materials science and technology contributions to the nation's defense, energy, and scientific missions.

Consistent with its main objective, Laboratory resources supply the principal funding for CMS programs. Additional funding for individual scientific research programs conducted by CMS members comes directly from outside sources.

To carry out its responsibilities, CMS has accepted four demanding missions:

1. Build a core group of qualified and established materials scientists and solid state physicists.

2. Promote and support top-quality, interdisciplinary materials research programs at Los Alamos.

3. Strengthen the interactions of materials scientists at Los Alamos with the external materials science community.

4. Establish and maintain modern materials research facilities in a readily accessible, central location.

The core group of CMS members has a broad charter to advance materials science and technology in directions expected to have long-term impact on LANL's mission. The acting director is Don M. Parkin. In addition to the director, six members presently constitute the CMS. James L. Smith heads an experimental effort in superconductivity.
Oxynitride Glasses
Authors: Loehman Ronald E.
Published: August 2016

Research on oxynitride glasses has expanded considerably since the first systematic compositional investigations were begun some ten years ago. This review will briefly introduce that work with an emphasis on more recent developments. Also included is some discussion of the applications of oxynitride glasses in both bulk and thin film form. The literature review is selective, however, and the recently developed phosphorus oxynitride glasses are only briefly mentioned. For more detailed information on earlier work on silicon oxynitride glasses see the reviews by Jack and Loehman. For discussions of phosphorus oxynitride glasses see Marchand, Peng and Day, and Rajaram and Day.

The development of bulk oxynitride glasses has been closely associated with research on Si3N4and other nitrogen-containing ceramics. The initial discovery that large amounts of nitrogen can be incorporated in silicate glasses originated with analyses of glassy grain boundary phases in Si3N4that was hot-pressed or sintered with different additives to promote liquid phase formation at the processing temperature. (Some applications of oxynitride glasses take advantage of that close connection to Si3N4. See Applications of Oxynitride Glasses below.) Later, systematic study of the bulk oxynitride glasses showed that nitrogen incorporation increases density, hardness, glass transition temperature and fracture toughness, and, to a certain extent, decreases the thermal expansion coefficient. Nitrogen additions also tend to lower glass solubility in aqueous solutions.
Halide Glasses
Authors: Moynihan Cornelius T.
Published: August 2016

The term “halide glass” refers to glasses in which the anions are from elements in Group VIIA of the periodic table, namely, F, Cl, Br and I, as opposed, for example, to “oxide glasses,” such as silicates, borates, phosphates, etc. Two known single component halide melts are glassforming, BeF2and ZnCl2, but the majority of halide glasses are multicomponent. Practical interest in halide glasses has been generated almost entirely by their optical properties, which cannot be duplicated in a more conventional oxide glass. Barriers to the practical deployment of halide glasses have their origin in materials properties in which they can be markedly inferior to oxide glasses, e.g., mechanical strength, resistance of the melt to crystallization, chemical durability, etc.

In the past decade there has been considerable and accelerating research activity in the area of halide glass science and engineering. Halide glass research up to 1980 has been reviewed by Baldwin et al. and oxide and halide glasses for laser applications have been compared by Weber. Four international symposia on halide glass science and engineering have been held in the period 1982–1987, the proceedings of the last two of which have been or will be shortly published. The proceedings of a 1986 NATO-sponsored meeting on halide glasses have also been published in book form.
Multidisciplinary Graduate Programs in Materials
Authors: Johnson Herbert H.
Published: August 2016

What constitutes a strong multidisciplinary program in materials? Does a strong multidisciplinary program require strong disciplines? What are the differences (if any) between interdisciplinary, multidisciplinary, crossdisciplinary, and transdisciplinary programs? Are thrust areas essential components of a good multidisciplinary program? What is the role of central facilities in multidisciplinary research and education? Are there intrinsic differences between the activities of graduate students in multidisciplinary and single-investigator programs? Is peer review appropriate and, equally important, feasible for large multidisciplinary programs?

This family of questions is of increasing interest and some concern in both the academic and funding segments of the national materials community. It does not appear to be a major issue in either the industrial or national laboratory arenas, where the funding practices, organizational patterns, and in some respects the research and development goals, are different from those in the research universities. An essential distinction is the presence of a formal education component in the graduate materials programs in the universities. However, in discussions of academic materials research programs, both funder and (regrettably) fundee occasionally relegate purely educational aspects to the background.

Multidisciplinary and block-funded programs are a steadily increasing fraction of the total research support in materials available to universities. Some 30 years ago virtually all university research in materials-related subjects was supported through single-investigator grants.