bluuebunny/crossref_metadata_2025_split huggingface dataset:
Infrared Optical Materials: Where Do We Stand?
Authors: Klocek Paul 
Published: August 2016

The usefulness of infrared (IR) radiation has been recognized for many years and is today the basisof an expanding technology. The development of the laser, particularly the IR laser, has further fueled this technology expansion. Optical materials have always played a critical role in IR technology, primarily as transmissive and reflective optical components. Often, the lack Of an adequate IR optical material has delayed the implementation of applications Until appropriate materials or quality of materials were developed. While the developed material may satisfy the basic requirements of the application, often its other physical properties and/or cost are not desirable. The limited number of IR optical materials combined with the growing humber of applications has kept their development essential to our technological growth.This paper reviews some current research and developmen t trend s in IR optical materials primarily for transmissive components. These IR components include geometric optics, windows and domes, optical fibers, high energy laser optics, and coatings. The emphasis is on optical materials for applications involving wavelengths in the 2-14 μm region.Intrinsic AttenuationIntrinsic attenuation defines the fundamental limits to light propagation in a transmissive material. It is composed of electronic or bandgap absorption, lattice vibration or multiphonon absorption, and Rayleigh and Brillouin scattering. Bandgap absorption results from the promotion of an electron from the valence to the conduction band by direct absorption of a photon or indirectly involving a phonon and the appropriate change in k-vector. The onset of absorption occurs at photon energies greater than or equal to the bandgap.
Defects in Ceramic Oxides
Authors: Nowick Arthur S. 
Published: August 2016

The topic that I am attempting to cover easily requires a whole book to do it justice. To deal with it in a short article, I will focus on a few basic principles that dominate the behavior of defects in oxides and then present some examples taken from well-studied and relatively well-understood materials.The study of defects in oxides differs from the study of defects in metals and alloys or in semiconductors in several important ways. First, oxides generally have very high melting points so that intrinsic point defect concentrations at temperatures below ~1500°C are usually negligibly small. Second, an oxide does not always maintain the composition at which it was fabricated, as alloys do, but can exchange oxygen with the ambient atmosphere, according to the ambient partial pressure of oxygen, P(O2). Thus, the stoichiometry, and accordingly the defect concentration, can be controlled by annealing in a specific P(O2) atmosphere. Third, and most important, oxides have a high degree of ionicity so that most point defects possess an effective charge. The consequences of this fact are far reaching; some of them are as follows:1. In a binary oxide, e.g. a metal oxide (MO), there are two sublattices. The diffusion of cations and of anions proceeds each on its own sublattice, involving different point defects. Accordingly, cation and anion diffusion rates can be very different and, in fact, usually are.
Polymer Gels, Materials That Combine Liquid and Solid Properties
Authors: Winter H. Henning 
Published: August 2016

We are accustomed to thinking of matter as being in one of three states: solid, liquid, or gas. Nature, however, has provided us with a marvelous intermediate state, the gel. Industrial applications are just beginning to explore the advantageous gel properties as adhesive, superabsorber, damper, membrane, toner, catalyst support, etc. Gels are good adhesives since they combine the surface wetting property of liquids with the cohesive strength of solids. Strong adhesion and damping properties suggest gels as a binder in composite materials. For example, the car of the future may operate at a much reduced noise level due to a thin layer of gel in its body. Widespread technical applications have not yet materialized because, until recently, it was difficult to measure gel behavior. This has changed, and as a consequence, gels can now be manufactured with reproducible properties.What the many possible types of gelation processes have in common is that molecules connect into a three-dimensional network structure. Junctions between molecules form as chemical bonds (cross-links) or physical associations (such as crystalline or glassy domains, hydrogen bonds, etc.). The molecular architecture determines the gel properties in ways which have yet to be explored. Typical parameters are the monomer building block, molecular size, branching, chain stiffness, cross-link functionality, and solvent content.
Polymer Materials Science: Novel Synthesis and Characterization of Supermolecular Structures
Authors: Frank Curtis W. 
Published: August 2016

The two feature articles in this issue present numerous contrasts, but both reflect the vitality of research in polymer science today. David Tirrell and co-authors paint a picture of how the techniques of molecular biology may be applied to the synthesis of novel “proteinlike” polymers with control over molecular weight, composition, and stereoregularity that is unprecedented in the realm of traditional polymer chemistry. Wolfgang Knoll turns his attention to ultrathin polymer films with thicknesses comparable to molecular chain dimensions and demonstrates how evanescent wave optical methods may be used to provide spectroscopic as well as imaging information on the characterization of these “restricted geometry” systems.Both authors address the issue of supermolecular structure, whether approached from the synthetic or physical chemical viewpoints. Tirrell describes a series of target polymers, expressed by genetically engineered microorganisms, which may provide a fundamental understanding and control over chain folding, a critical morphological feature governing solid-state behavior of synthetic polymers. Knoll analyzes the fundamentals of evanescent wave optical methods for interrogating the molecular organization in polymer films that have considerable potential in electronic or photonic applications.
Environmental Protection: Charting a New Course: 1991 MRS Spring Meeting Plenary Address
Authors: Lingle Stephen A. 
Published: August 2016

The U.S. Environmental Protection Agency (EPA) is one of several agencies that serve as members of the Federal Coordinating Council of Science, Engineering, and Technology. In this role, EPA chairs the Environmental, Safety, and Health Work Group of the Committee on Materials. One of the primary purposes of the Committee on Materials is to strengthen the government-industry:university partnership in materials research. Strengthening and building this partnership is also one of the goals of the Materials Research Society. You bring together an interdisciplinary group of scientists and engineers from industry, government, and academia to exchange ideas on the forefront of materials research.A recent National Research Council report, Materials Science and Engineering for the 1990s: Maintaining Competitiveness in the Age of Materials, identified six major science and engineering initiatives. One of these six initiatives was the environment. I believe that we will see, over the next few years, a major thrust in materials research to develop environmentally benign or “environmentally friendly” materials—materials that are less toxic and less polluting and do not deplete scarce natural resources, materials that have longer useful lives, and materials that can be recycled and require less energy to manufacture.
Load-Bearing Ordered Intermetallic Compounds—A Historical View
Authors: Cahn Robert W. 
Published: August 2016

Chemical combination among metals has been studied for a long time. In the early days, chemists had much difficulty in understanding how metals could combine at all among themselves, often in several different proportions, since this often seemed to be at variance with elementary notions of valency. Indeed, in the last century a distinction was proposed between daltonides and berthollides, the former being compounds with simple ratios of the numbers of constituent atoms… consistent with Dalton's atomic theory!… the latter, called after a skeptical French chemist, being the name reserved for compounds with a wide composition range which scarcely seemed explicable on any reasonable atomic model. A few nostalgic souls still employ these distinctions.An early classic on the subject was a book published by two Italian chemists in 1918. British metallurgist C.H. Desch also wrote a monograph on intermetallic compounds in 1914 (the year when the name “physical metallurgy” was first proposed, and the chemical bias of metallurgy shifted toward a physical one), and he declared that “attempts to form a theory of the constitution of intermetallic compounds… have been comparatively unsuccessful.” When he returned to the subject 20 years later, he felt much more cheerful about the state of the theory because in the meantime Hume-Rothery had introduced the concepts of atomic size factor, electron/atom ratio, and electronegativity (a concept also associated with the name of Linus Pauling) into the discussion of intermetallic phases, or compounds. Today, a battery of sophisticated physical concepts is used to make sense of both binary and multielement intermetallic compounds and they are no longer regarded as chemical anomalies.
Designing Interfaces in Inorganic Matrix Composites
Authors: Cornie James A. , Argon Ali S. , Gupta Vijay 
Published: August 2016

The key to controlling and predicting the properties of metal matrix composites lies in understanding and controlling the interface. When properly designed, the interface between reinforcing fibers and the matrix or protective coating can act as a mechanical fuse through a controlled delamination mechanism.Controlled delamination, in effect, results in the decoupling of fibers from early damage due to stress concentrations in the vicinity. The delamination event must precede the crack bridging and frictional pull-out mechanisms that have been so effectively demonstrated in ceramic matrix composites. The delamination event, therefore, is the necessary precondition, and so analysis of composite toughening must start with a definition of the conditions for interface debonding.This decoupling can be expressed in terms of cohesive strength of the interface, shear strength of the interface, and fiber fracture stress. In a related but alternative manner, debonding can be expressed in terms of the intrinsic work of fracture of the interface as compared to the transverse work of fracture of the fiber.
An Evaluation of the Interface Tensile Strength–Toughness Relationship
Authors: Gupta Vijay 
Published: August 2016

Mechanical properties of interfaces between dissimilar or similar materials (e.g., grain boundaries) have become the focal point of research in several fields, including composite materials (metal, ceramic and intermetallic matrix composites), tribology, and solid state devices. This is not surprising because the interfaces between dissimilar materials are sites for mechanical stress concentrations and often nucleate the overall failure process.Interfaces of interest in composite materials exist between fibers and their diffusion barrier coatings or between the fibers and the surrounding matrix material. In the field of tribology, interfaces exist between various types of functional (magnetic, conducting, optical, electrical), protective (thermal barrier, corrosion, wear resistant), or decorative coatings and their underlying substrates. And, finally, metal/ceramic interfaces are of interest in multilayer devices and magnetic disks and head technology. In all the above applications, mechanical properties of the interface (tensile and shear strength, toughness, etc.) often control the overall functionality of the coated part. Therefore, improving the mechanical properties of the interface for a prolonged life of the coated part is of fundamental interest. However, in ceramic and metal matrix composites, where the fiber/coating interface is used to deflect impinging cracks from the matrix, it is often desirable to impair the strength of the interface.
Fiber Coatings Derived from Molecular Precursors
Authors: Fischer H. Eric , Larkin David J. , Interrante Leonard V. 
Published: August 2016

It is generally agreed that the mechanical performance of continuous fiber-reinforced composites will depend to a large extent on the nature of the interface between the fiber and the matrix. In the case of many inorganic composites, compositional and/or morphological gradients can arise over an extended region between the matrix and reinforcing fiber as a result of processing conditions, mechanical forces, or chemical interactions. The term “interphase” has been applied to such a region.There have been numerous theoretical and experimental treatments of this subject in an effort to quantify the stress and strain in the interphase region, and to correlate the presence of such forces with the mechanical performance of the attendant composites. Much of the experimental work has emphasized controlling the nature of the interphase through careful control of the processing conditions or by the introduction of special interface layers, often by applying a coating to the reinforcing fiber prior to incorporating it into the matrix.
Imaging with Surface Spectroscopies
Authors: Kelley Michael J. 
Published: August 2016

A little more than 20 years ago we learned how to direct photons, electrons, or ions a few keV or lower energy onto a surface and measure the energy or mass distribution of backscattered or emitted species. By arranging conditions so that the bombarding or detected species is strongly attenuated by matter, the information obtained is restricted to not more than the outermost several atomic layers. We then learned how to infer the composition, chemical state, and (sometimes) the molecular structure of the surface from these spectra. So began the era of “alphabet soup.” The ensuing decades brought several things:■ The commercial availability of major surface spectroscopies. Even if not totally user friendly, they aren't outright hostile and work for most people on most days. Instrument makers seeking increased sales volume will continue to improve their ease of operation and reliability.■ The scrutiny of most materials and structures. There is reliable literature about the very large majority of applications. We know where to begin interpretation and what are the major pitfalls. We have little excuse for the egregious errors we sometimes still make.■ Many good research groups. When something really new comes along (e.g., the high temperature superconductors), the correct understanding of the data is worked out quickly enough to use it as a tool, guiding research and development.■ The seeming reluctance, outside certain specialized areas, of the materials community to integrate surface spectroscopies into other than basic research. Expense is often cited as a barrier, but this is hardly credible when the daily cost of top-notch spectroscopy isn't more than twice typical industrial researcher internal billine rates.
The Federal Budget in the Executive Branch
Authors: Post Robert L. 
Published: August 2016

This is the second of a short series on the federal budget process. Here, we will focus on how the science budget is set inside the Executive Office of the President. The main players here are the Office of Management and Budget (OMB) and the Office of Science and Technology Policy (OSTP).The budget process for a given fiscal year starts in the agencies. For example, the fiscal year 1991 budget request to Congress was put together by the agencies during the winter, spring and summer of 1989. In the Department of Energy (DOE) for example, budget requests are obtained from the field offices. Typically, these requests are an exercise in optimism, founded on the time-honored notion that you are certain to get nothing if you don't at least ask.In any event, DOE headquarters staff, after receiving these requests, pare down the totals in a process not unlike that followed within the OMB. This can resuit in weeping and gnashing of teeth at the field offices even at this early stage. While not generally appreciated, OMB staff can often do much of their budget cutting work before even receiving the formal budget request by a judicious combination of friendly advice, jawboning or more extreme measures which this writer will not go into. (On a more positive note, previous administration guidance—e.g., a planned doubling of the National Science Foundation (NSF) budget in five years, or a commitment to a given schedule for space probes, satellites, etc., in the case of NASA—can largely “hard wire” the budget process before the budget submission to OMB).
The Physics of Complex Materials: Macroscopic Approaches
Authors: Cladis P.E. 
Published: August 2016

The goal of this issue of the MRS BULLETIN, with its focus on the physics of complex materials, is to point out some of the fascinating features, both fundamental and applied, of complex materials: liquid crystals and polymers. Over the past 20 years, we have witnessed impressive advances in the understanding of liquid crystals and polymers on all fronts—physics, chemistry, materials research, and applications.Physicists are interested in the fundamentals of a phenomenon. Our assumption is that once we understand how the pieces of a System work, the understanding of how the whole System works immediately follows. However, those of us who have been involved in materials physics research quickly learn that complexity generates rules of its own on scales much larger than the microscopic scale of the molecules involved. Some-times these rules are beautifully simple and elegantly described, but most often they are not. The following articles high-light some important current research in the domain of complex materials, particularly for liquid crystals and polymers.Contributing to this special issue are: Pierre-Gilles de Gennes; J. William Doane; Wolfgang Meier and Heino Finkelmann; Paul Keyes; Patrick Oswald, John Bechhoefer and Francisco Melo; and Walter Zimmerman. They give us their current thinking on polymers in shear, novel electro-mechanical effects observed in polymeric liquid crystals, and how liquid crystals in a solid polymer matrix make useful high-speed color displays.
Innovative Processing Techniques for Intermetallic Matrix Composites
Authors: Stoloff N.S. , Alman D.E. 
Published: August 2016

Although intermetallics based on aluminum or silicon tend to have a very attractive combination of low density and excellent oxidation resistance, they suffer from lack of adequate creep strength and, in most cases, from inadequate ductility and toughness. It has been recognized for several years that an approach which could simultaneously solve both problems, without degrading other properties, is to utilize the intermetallics as matrices for composite materials. The consequence has been an explosion of interest in two-phase intermetallic-based alloys.With the exception of some early work by Seybolt, intermetallic matrices have been utilized for composites only for the past five to six years; the first published reference to systematic studies of fibrous composites dates from the proceedings of an MRS meeting in December 1986. The published literature is much sparser than, for example, that on ceramic matrix composites, which have been under development for a much longer period. Nevertheless, an appreciable number of intermetallic matrices have been reinforced with fibers or particles.Because of the relatively high melting points and extreme brittleness of most intermetallic compounds utilized as matrices, as well as other significant advantages, enormous effort has been devoted to powder metallurgical techniques. In this category we include reactive sintering of elemental or elemental plus prealloyed powders, reactive hot pressing, reactive HIPing, injection molding, the XD process, dynamic compaction of powders, mechanical alloying, the powder cloth method, and, of course, traditional hot pressing techniques.
Neutrons and Materials Science
Authors: Axe John D. , Hayter John B. , Pynn Roger 
Published: August 2016

This issue of the MRS BULLETIN is devoted to the technique of neutron scattering and its role in materials characterization. Compared with electrons and x-rays, the other major scattering probes, neutrons seem exotic and expensive. Why then are they so important? This article will address this question generically, with a few specific examples. Subsequent articles will address in greater detail a few of the more prominent techniques that are important for materials scientists.We will begin by reviewing why scattering methods are used to study structure, when for many materials it is possible to employ electron microscopy (where, of course, the images are reconstructed from the interference among the scattered waves). One reason is that direct imaging often tells very little about the relationship between an observed structure and the material properties that derive from it. Figure 1, for example, shows a stereo image of a colloidal latex which is clearly crystalline. The stereo view of the same material in the melt seems random to the eye. If many thousands of such images are taken, however, and the number of pairs of particles separated by a given distance are plotted against the separation (this is the so-called pair distribution function), it is found that certain separations are highly probable, while others are equally improbable. In the systems of Figures 1 and 2, the pair distribution functions are not very different (particularly for separations up to several interatomic distances), and it is this function which governs the thermodynamic properties of the material.
Microstructure and Fracture Resistance of Metal/Ceramic Interfaces
Authors: Evans A.G. , Rühle M. 
Published: August 2016

Metal-ceramic interfaces play an important, sometimes controlling, role in composites, multilayer substrates, capacitors, electron tubes, and automotive power sources. Often bonding and adhesion between the ceramic and metal are critical to the components' performance. Interface geometry and chemistry play a dominant role in determining the mechanical and electrical integrity of composites. Furthermore, unique properties may be developed from multilayer ceramic-metal structures.Systematic studies of metal-ceramic interfaces started in the early 1960s. Such studies were directed toward identifying general rules that govern bonding and interface behavior both theoretically and experimentally, including the thermodynamics of interfacial reactions and crys-tallographic relationships, and toward evaluating atomistic structure at the interface. This article summarizes results concerning the interrelation between atomistic structure and the macroscopic fracture resistance of metal-ceramic interfaces. More details are published in a recent conference proceedings.Determining atomistic structures of metal-ceramics interfaces is, in general, complicated since the two materials that have to be matched exhibit different atoms (ions) and possess different crystal symmetries, crystal structures, and lattice parameters. The adjacent lattices are not commensurate, the two different structures can be described as being just quasiperiodic. However, examples exist where the lattice mismatch is small, and both components possess the same lattice symmetry. Ag/MgO and Nb/Al2O3interfaces are examples that serve as model systems for experimental studies as well as theoretical calculations. The interfaces can be formed either by diffusion-bonding, internal oxidation, or epitaxial film growth.