bluuebunny/crossref_metadata_2025 huggingface dataset:
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.
Neutron Scattering in Materials Science: Small-Angle Neutron Scattering Studies of Polymers
Authors: Wignall George D. , Bates Frank S.
Published: August 2016

Before the application of small-angle neutron scattering (SANS) to the study of polymer structure, chain conformation studies were limited to light scattering and small-angle x-ray scattering (SAXS) techniques. These experiments were usually conducted in dilute solution, and the methodology to measure radii of gyration, virial coefficients, molecular weights, etc., was well established in the classical works of Guinier, Zimm, Debye and Kratky, who pioneered these techniques during the 1940s and 1950s. This methodology could not be applied to concentrated solutions or bulk polymers because of the difficulty of separating the intra- and inter-molecular components of the scattering function. One attempt to circumvent this difficulty was the experiment by Krigbaum and Godwin, who end-labeled polystyrene molecules with Ag atoms. When dispersed in unlabeled polystyrene, the excess x-ray scattering could in principle be analyzed to provide the end-to-end distance, though in practice the signal-to-noise ratio of the experiment was insufficient for accurately determining this parameter. To our knowledge the first suggestion to use the difference in coherent scattering lengths of deuterium (bD = 0.66 × 10−12cm) and hydrogen (bH = −0.37 × 10−12cm) to create scattering contrast between deuterated and normal (hydrogenous) molecules and provide a direct determination of molecular dimensions was made independently by at least two groups in the late 1960s. By deuterating the whole molecule, as opposed to end-labeling, this proposal increased the signal-to-noise ratio of the experiment by several orders of magnitude and made possible for the first time the practical analysis of molecular conformations in bulk polymers. Even so, such experiments could not be undertaken until the completion in Europe of the first instruments employing long wavelength neutrons and large distances between the entrance slit, sample and detector, which allowed deuterium labeling methods to be successfully applied to polymers in the early 1970s.
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.
The College-Wide Interdisciplinary Materials Science and Engineering Graduate Program
Authors: Bourell D.L. , Marcus H.L.
Published: August 2016

The college-wide interdisciplinary graduate program approach to graduate education is a viable alternative to the departmental structure for areas of study that span two or more traditional disciplines. This article will explore the nature of this organizational style using materials science and engineering as the example discipline. We will discuss the advantages and disadvantages of the graduate program approach in the light of more than 18 years of experience at the University of Texas at Austin.

The primary task of any center for higher learning is the education of students in an environment conducive to the open exchange and dissemination of ideas and knowledge. Traditionally, the university has approached this task by assembling scholars with common foundations of expertise into a collective group, the department. Besides the obvious function of providing a structured setting for the concentration of scholars with similar interests, the department also serves as the front line of faculty governance for matters including tenure, promotion, salary, resource management, and distribution. For example, course content and degree requirements are initiated at the department level. Thus the organizational structure of the college, and hence of the university, is firmly built on the traditional concept of department, a concept that has served education well.

However, there are liabilities to the departmental structure since its natural tendency is to compartmentalize knowledge with the concomitant academic provincialism. This mindset poses a particularly serious problem for a number of subject areas that are intrinsically multidisciplinary. Several examples in the field of engineering science are biomedical engineering, manufacturing and industrial engineering, nuclear engineering, environmental engineering and also materials science and engineering.
New Materials and New Challenges in Vacuum Technology
Authors: Krauss Alan R.
Published: August 2016

There are times when technological or scientific progress is blocked for want of a breakthrough in a key area, just as there appear to be instances of a problem and its solution emerging simultaneously and independently. Upon closer inspection, however, this latter happy state is usually the result of long, hard work by people who had the insight to develop a solution before their peers were aware of the existence of a problem. At the moment, there are a number of convergent events occurring in vacuum technology which in all likelihood will have as profound an effect as the development of ultrahigh vacuum (UHV) technology in the late 1960s and early 1970s. These developments may be viewed as challenges posed by the requirements of certain technologies, or as a series of breakthroughs which will lead to new opportunities. Materials and materials processing or coatings are the key factors in most of these new developments, just as new pump and seal designs, and new vacuum practice were responsible for the development of UHV (10−9–10−11 torr) technology.

In particular, aluminum is emerging as a material which may replace stainless steel for applications where the ultimate in vacuum is required. By suitable treatment, pure aluminum and aluminum alloys can be made to produce static outgassing rates more than 10 times lower than stainless steel. Systems capable of reaching a base pressure in the extremely high vacuum (XHV) range of 10−12–10−13 torr, such as those described in this issue by H. Ishimaru, are now commercially available.
Coatings for Improved Vacuum Materials
Authors: Moriyama K.
Published: August 2016

For the past 10 years, reactively deposited films of titanium nitride, TiN, have been applied to cutting tools such as drills, hob cutters, and endmills. A nominal film thickness of 2–4 μm has been shown to give excellent resistance to abrasion and corrosion and to extend tool life three times or more. This is attributable to the physical properties of TiN, which include microhardness of 1,800 kg/mm2 and surface friction approximately one-third that of high-speed tool steel. Corrosion resistance is realized from the dense, fine-grain equiaxed structure of the inert TiN film. Additional applications range from decorative use based on its goldlike appearance to use as a diffusion barrier in semiconductor devices.

More recently, TiN has found application as a high quality coating for components used in ultrahigh vacuum (UHV and XHV) system apparatus and especially in high energy particle accelerators. This article discusses the application of TiN coatings to ultrahigh vacuum systems and high energy particle accelerators.

The native oxides which form on stainless steel and aluminum tend to be porous and trap large amounts of water vapor and other gases. These trapped gases can be partially removed by vacuum baking, although for particle beam devices in which beam-induced desorption is at least as important as the thermal outgassing rate, an extensive beam-conditioning process is required to get rid of the final vestiges of trapped gas. The oxide surfaces have low sticking coefficients for the adsorption of incident gas molecules, but the oxides have much higher secondary electron yields than the clean metals and consequently have very high beam-induced desorption rates.
Vacuum Systems for Synchrotron Light Sources
Authors: Schuchman J.C.
Published: August 2016

Synchrotron light sources are electron storage rings that produce synchrotron radiation by accelerating electrons in a circular storage ring. The synchrotron light (photon beam) is then used to irradiate various sample materials for basic and applied research in such fields as solid state physics, biology, chemistry, surface science, and technology.

The electron storage ring must provide an ultrahigh vacuum environment for the electron beam to minimize electron residual gas collision which would shorten the beam-lifetime. This article will discuss the design of electron storage ring vacuum systems and materials, and how the choice of materials can affect the machine design.

A typical electron storage ring is shown in Figure 1. It consists of an injector (linac and booster), transport system, storage rings, and experimental photon beam lines. These machines vary in size from a few meters in circumference for a compact light source used for x-ray lithography, to a few hundred meters in circumference for high energy physics.

The vacuum system for an electron storage ring is an all-metal ultrahigh vacuum system. The operating pressure is in the low 10−9 torr range with stored electron beam, and 10−10 torr without beam.

Certain unique vacuum problems must be faced in electron storage ring design: photon-stimulated gas desorption, power dissipation in the chamber walls, impedance changes due to changes in the chamber cross section, conductance limitations, accurate placement of the chamber, and all of those sundry problems associated with a large bake-able all-metal UHV system. Some of these characteristics are illustrated schematically in Figure 2. Two excellent papers that address many of these issues have been written by N. Mistry (system design) and H. Wiedemen (impedances and instabilities).
High Tc Oxide Superconductors
Authors: Maple M. Brian
Published: August 2016

This issue of the MRS BULLETIN is devoted to high Tc superconductivity. It is the sequel to a previous series of articles on the same subject which appeared in the MRS BULLETIN in January 1989. While the articles in the January 1989 issue emphasized the families of high Tc superconducting oxides known at that rime, as well as novel processing techniques and thin films, the papers in this issue focus on the physical properties of high Tc oxide superconductors.

The quality of polycrystalline and single-crystal bulk and thin-film materials has improved to the point where researchers can now make reliable measurements of many physical properties representative of the intrinsic behavior of these materials. As a result, a broad spectrum of important issues such as the nature of the electronic structure, the type of superconducting electron pairing, the magnitude and temperature dependence of the superconducting energy gap, the behavior of fluxoids in the vortex state, etc., can be addressed meaningfully. Presently emerging is a consistent picture of the physical properties of the high Tc oxides, which will form the foundation to eventually developing an appropriate theory for the normal and superconducting states of these remarkable materials.
Magneto-Optical Storage Materials
Authors: Greidanus Frans J.A.M. , Zeper W. Bas
Published: August 2016

Magneto-optical (MO) recording combines the advantages of optical recording and magnetic recording. It offers very high storage densities, it is a noncontact technique, and it allows an unlimited number of read/write cycles. Although the potential of magneto-optical recording was recognized nearly 25 years ago, suitable materials did not exist at that time. Since then, substantial efforts have been made optimizing existing materials and searching for new ones. In 1973 an important development was started by Chaudhari et al., who discovered amorphous GdCo with perpendicular magnetic anisotropy as a possible MO recording material. Today amorphous ternary rare-earth (RE) transition-metal (TM) alloys like GdTbFe and TbFeCo are the recording layers in the MO disks which appear on the market. Although these materials show good recording performance, they also exhibit some drawbacks, mainly caused by their susceptibility to oxidarion and corrosion. However, two new classes of suitable MO materials with good oxidation resistance are emerging.
Materials for Future High Performance Magnetic Recording Heads
Authors: Jagielinski Tomasz
Published: August 2016

Recording in the 1990s will be high density, high frequency, in-contact recording on high coercivity media. Today's state-of-the-art head materials, NiFe, Sendust and amorphous alloys, will be used in some applications. However, layered structured and artificial superlattices will become the key head technologies of the future. Use of advanced preparation techniques will allow “true” materials engineering and the fabrication of devices to incredibly accurate specifications.

These very high density recording systems will require optimal inter-play between all the components—media, head, and head/media interface. Future media will be very smooth, high coercivity, large moment thin films. The head/media spacing will be less than 50 nm, and recording at more than 100 MHz will be required. Single-track heads will be replaced by very narrow track-width multitrack devices in high data rate recorders. Thin film heads will provide the answer to most of the problems of large recording fields and high frequency response. These changes will define new requirements for head materials, some of which cannot be met by currently used materials. Conventional ferrite heads will not be found in high performance recording systems; thin film inductive and magnetoresistive (MR) heads (Figure 1) will be widely used. Thin films, metals and alloys, both crystalline and amorphous, layered structures and artificial superlattices will be the key head technologies in the future. New material preparation technologies, MBE (molecular beam epitaxy), MOCVD (molecular chemical vapor deposition), sputtering, and ion beam deposition are becoming increasingly available and less expensive. These methods will be used to fabricate future devices to incredibly accurate specifications.
Thin Film Recording Media
Authors: Judy Jack H.
Published: August 2016

The rapidly growing demand for magnetic information storage systems at lower cost and higher capacity has driven the magnetic recording industry to accelerate development of thin film magnetic recording media. The ultimate recording density depends on the bit transition lengths, as shown in Figure 1 for various media, and on signal-to-noise ratio, which is proportional to the number of particles per bit. Longitudinal thin film media bit transition lengths are limited by thickness, magnetic properties, and zig-zag magnetic domain microstructures at the transitions, whereas in perpendicular media the principal limitation is the diameter of the grains. The recent development of quasi-particulate longitudinal and perpendicular thin film media indicates that areal bit densities substantially exceeding 109 bits/inch2 will be achieved in the future.

This article will review magnetic phenomena relevant to thin film recording media, describe macromagnetic and micromagnetic characterization techniques, survey the development of state-of-the-art thin film media, correlate micromagnetics with magnetic properties, media noise, and recording performance, and discuss future requirements of longitudinal and perpendicular thin film recording media.

Ferromagnetic and ferrimagnetic thin films exhibit a nonlinear, multivalued, and hysteretic relationship between the magnetic dipole moments per volume or magnetization M and the magnetizing field intensity H as shown in Figure 2 for the component of M in the direction of H.
Artificially Layered Superconductors
Authors: Schuller Ivan K. , Guimpel J. , Bruynseraede Y.
Published: August 2016

The study of Artificially Layered Superconductors (ALS) started more than 20 years ago with the search for unusual and/or high temperature superconductivity in a variety of metal-semiconducting layers. Renewed interest was motivated by the advent of novel preparation techniques that allow control of layer thicknesses close to interatomic distances. In this way layered superconductors can be used as model systems to study a variety of physical phenomena, prepare structures with improved properties and discover novel metastable phases which do not exist in nature. Examples of these studies include: a diversity of dimensional transitions, interaction between superconductivity and magnetism, interaction between superconductivity and electron localization, enhancements of critical fields and critical currents, and the study of incommensurate systems.

Recent developments in high temperature ceramic superconductors further increase the importance of studies of Artificially Layered Superconductors. The newly discovered ceramic superconductors are structurally layered and therefore many of their properties will also be determined by this structure. Because of this, particularly in the search for the mechanism of superconductivity, it is important to understand which properties are a consequence of the layered nature of the material and which are due to the presence of some unusual, yet undetermined physical phenomena.

What makes Artificially Layered Superconductors especially attractive for investigation? The main reason rests on the fact that the characteristic lengths which determine the superconducting properties, i.e., the coherence length and penetration depth, are quite long in conventional low temperature superconductors.
Excimer Laser Drill for Multilayer Printed Circuit Boards: From Advanced Development to Factory Floor
Authors: Bachmann Friedrich
Published: August 2016

A novel excimer laser process has been developed for generating cylindrical via holes with an aspect ratio of about one. The fabrication process is being successfully run on a production line for a highly miniaturized printed circuit board used for the multichip module in the new Siemens 7500 H 90 mainframe computer. The process is outstanding in terms of reliability and reproducibility. To the best of our knowledge, this is the first that that excimer lasers have been put into large-scale use in an industrial environment.

Since signal delay times for chips have decreased much more rapidly than delay times for packaging, the computing speed of high-speed computers is restricted by the packaging techniques used. Therefore, further development of packaging technology became a prime objective for those developing high-performance computers. Packaging delay times had to be reduced drastically to keep up with increasingly shorter chip delay times. This, in effect, meant that a greater packaging density had to be implemented.

A novel planar packaging technique has lead to considerable progress in solving this problem. This technique has been described in detail elsewhere. A key component in this technology is a multichip module, which can take in each of 16 areas, either an LSI module with 320 leads or 9 MSI modules with 52 leads as “bare” ICs. This means that a micro-wiring printed circuit board of this kind can accomodate between 16 (LSI) and 144 (MSI) chips. This article describes how these printed circuit boards are manufactured.

As the specifications (Table I) show, blind vias 80 μm in diameter at a pitch of 0.5 mm have to be made in a 16-layer printed circuit board. It is intended that these blind vias will provide the through-contact for neighboring layers. The excimer laser plays a major role in this process.
Polymer Ionics
Authors: Ratner Mark A. , Shriver D.F.
Published: August 2016

The preparation, utilization, and understanding of high polymers represents one of the great triumphs of chemistry and materials science in the 20th century. Synthetic polymers have traditionally been used as structural materials and electrical insulators. Biopolymers often exhibit interesting electrical response phenomena. A recent article in the MRS BULLETIN, for example, discussed piezoelectric properties of both synthetic and biopolymer systems. The newer, synthetic electroactive polymeric materials, however, represent one of the most exciting current areas of polymer materials science.

Many synthetic ionic polymer materials are known; perhaps the first were the polyelectrolytes and crosslinked ion exchange materials. These are materials whose backbone contains charges of one sign, balanced by small counter ions of the opposite sign. Such polyelectrolytes have found very important applications in analytical chemistry, water purification, and chemical processing.

Complexes, in which salts are dissolved in neutral polymer hosts, have until recently received less attention. The area of polymer/salt complexes became extremely active following the work of P.V. Wright, who first clearly showed that polyethylene oxide (PEO) is an excellent polymer host for a number of salts, and that the resulting solid polymer/salt complexes are electrical conductors. M. Armand broadened the investigation of electrical properties of polymer/salt complexes and pointed out that these materials might be useful in electrochemical devices, especially batteries.

This article will discuss the formation, properties, behavior, and applications of polymer electrolytes and mixed conductors—that is, polymeric materials in which charge is transported either by ions or by ionic and electronic charge motion. Our concentration will be on solvent-free materials—materials in which no small molecule solvents are present. There is substantial interest, and substantial progress, in the area of solvent-swollen polymer electrolytes.
Using Analytical Electron Microscopy to Design Radiation Resistant Steels for Fusion Applications
Authors: Maziasz P.J. , Klueh R.L. , Rowcliffe A.F.
Published: August 2016

The Fusion Reactor Materials Program in the United States began in about the mid-1970s, in a world sensitized to energy production needs by the 1973 Arab Oil Embargo. In the program's early stages, materials problems were recognized to be as important as any of the other problems facing this new energy technology. The effects of irradiation on the behavior of materials to be used in the first-wall and blanket structure were of particular concern. Today, although the economic and political realities that define energy needs have changed, fusion energy still remains an important part of our vision for a better future. Global environmental effects such as the “greenhouse effect” from increased CO2 in the atmosphere and acid rain, coupled with safety concerns about fission reactors, make fusion very attractive as a clean and safe energy source.

Over the past 10 years, the range of candidate materials for structural application in fusion reactors has expanded to include new martensitic and ferritic steels with reduced activation characteristics, vanadium alloys, ceramics, and composite materials. However, because austenitic stainless steels are easily fabricated, nonmagnetic, reasonably strong and tough, commercially available, and familiar, they also remain as candidate materials for fusion. They have also been extensively studied for use in various fission reactor systems as well. The austenitic and stainless properties of Fe-Cr-Ni alloys and steels were discovered during 1900–1915. Commercial grades like AISI types 304 and 316 stainless steels were developed prior to World War II. The effects of irradiation on materials have been studied since 1942, when Eugene P. Wigner anticipated that fission fragments and energetic neutrons would damage crystalline materials by displacing atoms to create point defects (vacancies and interstitials).
Linus Pauling Addresses MRS in San Diego
Authors: Chianelli R.R.
Published: August 2016

On Wednesday, April 26, 1989 at 6:00 p.m. Linus Carl Pauling, research professor, delivered the Plenary Address for the MRS Spring Meeting held in San Diego, California. He was introduced by John Baglin, Past President of MRS with the following words: “Linus Pauling…scientist, philosopher, and a thinker, whose fearless, pioneering research has made and continues to make vital and fundamental contributions to the sciences of chemistry, physics, mineralogy, biology and medicine. His work, frequently controversial, has stimulated thought and debate and research, promoting, indeed, the healthiest kind of scholarly activity within these many disciplines.”

With these thoughts and many more in my head 1 set out for the airport the previous afternoon to pick up Linus Pauling. I was about to meet someone who had deeply affected my scientific career from my early days as an undergraduate through the most important and fundamental aspects of 15 years of research. I was aware of almost all of Pauling's prizes and awards, but I couldn't quite remember what he won his second Nobel Prize for (he won the Nobel Peace Prize in 1962 for presenting a petition to the Secretary-General of the United Nations to ban atom bomb tests), and it was while I was wondering about this that Linus Pauling walked toward me after exiting the airport security gate.
Surface Structural Techniques Applied to Interfaces
Authors: Robinson I.K.
Published: August 2016

An interface is an internal surface, the boundary between two media which may be crystalline, amorphous solid, or liquid. Its close similarity with a surface, a solid-vacuum boundary, suggests that many of the powerful techniques available for studying surfaces might be applied to the interface structure problem. The extent to which this is possible is the subject of this article.

The techniques to be discussed in this article include low energy electron diffraction (LEED), medium energy ion scattering (MEIS), x-ray diffraction, and x-ray reflectivity. (The most widely used method, transmission electron microscopy (TEM), is the subject of a separate article in this issue of the MRS BULLETIN.) To summarize what we will find, surface methods were developed to be nonpenetrating in order to have surface sensitivity. This works against us in the interface situation by requiring the use of extremely thin samples, at least on one side of the interface. This means special handling of samples in some cases and raises the possibility of artifac-tual results. Of the three methods, x-ray diffraction is the most penetrating and least surface sensitive; it probably has the greatest potential for widespread use in interface science.

This article defines structure as “atomic structure” for this purpose: we are interested in the coordinates of atoms at the interface and their relation to bulk structures on one or both sides. For this reason, we will consider only interfaces that are crystalline on at least one side. Since crystals are by far our strongest structural reference point, much less can be said about other interfaces. We will also consider the morphology of an interface, defined as the boundary of the crystal(s) that demarcates the interface, also at the atomic level. This is most apparent in the form of interface roughness. The roles of strain and misfit dislocations in interface formation, also studied by these techniques, are outside the scope of this article.
Structure and Energy of Grain Boundaries in Metals
Authors: Merkle K.L. , Wolf D.
Published: August 2016

The investigation of structure-property correlations is a rather complex endeavor not only because interfacial Systems are intrinsically inhomogeneous, with chemical composition and physical properties differing from the surrounding bulk material, but also since three different aspects of the geometrical structure are involved — namely the macroscopic, microscopic, and atomic structures. As outlined in the Guest Editors' introduction, in addition to the choice of the materials which form the interface, five macroscopic and three microscopic degrees of freedom (DOFs) are needed to characterize a single bicrystalline interface. The importance of the atomic structure at the interface as well as the local interfacial chemistry, extrinsic (i.e., impurity segregation) or intrinsic (for example, via interfacial reactions or space-charge phenomena), greatly add to the task's complexity.

Grain boundaries (GBs) in pure metals represent ideal model Systems for investigating the strictly geometrical aspects of structure-property correlations for the following three reasons. First, the complexity due to the myriad of possible choices of materials combinations forming the interface is avoided, enabling a focus on the different roles of the three distinct geometrical aspects of the structure. Second, because GBs are bulk interfaces, dimensional interface parameters (such as the modulation wavelength in strained-layer superlattices, or the thickness of epitaxial layers) do not enter into the problem. Finally, the GB energy is thought to play a central role in various GB properties, such as impurity segregation, GB mobility and fracture, GB diffusion and cavitation, to name a few. A better understanding of the correlation between the structure and energy of GBs, therefore, promises to offer insights into more complex structure-property correlations, as well.
Up Close: The Department of Materials, University of Mons, Belgium
Authors: Wautelet M.
Published: August 2016

The State University of Mons was established in 1965, at the heart of an old industrial region of South Belgium. Since that time, the role of the University emerged as a source of new ideas for the region. The Department of Materials was founded in 1988, developing from the identification of various groups and their expertise in the materials science field. The goal of the Department of Materials is “to arrange and promote researches in this field. The Department will also work at improving education in Materials Science.” The Department will continue existing contacts and promote new contacts with regional, national, and international industries, and its experimental facilities are accessible to all interested researchers.

The members of the Department of Materials belong to the Faculties of Science and Medicine of the State University of Mons. They form an interdisciplinary group, including physicists, chemists and biologists—experimentalists and theoreticians.

Although some research activities involve more than one group, they can be arranged according to either the nature of materials (thin films, polymers, surfaces, quasi-one-dimensional conductors, bio-materials) or methods of preparation (laser irradiation, chemical vapor deposition, electron evaporation) and characterization (electron and x-ray diffraction, spectrophotometry, FTIR, micro-Raman, electrical conductivity, surface analytical techniques).
The Unique Electronic Properties of the Silver Halides
Authors: Brown Frederick C.
Published: August 2016

The modern photographic emulsion is an extremely sensitive detector of light quanta. In fact, high speed black-and-white film (which consists mainly of microcrystalline grains of AgBr or AgBrI suspended in gelatin on an inert base) ranks with the photomultiplier tube as capable of detecting a very few individual light quanta. Exposure times can vary from minute fractions of a second to hours. Unlike the multiplier tube, the photographic emulsion also responds well to relatively high light flux, that is, film can have wide exposure latitude. In many respects such as sensitivity, latitude, resolution, etc., film sets the pace as new multiplier tubes and charge-coupled devices are developed.

Of course, the high sensitivity of film comes about because light absorbed within an emulsion grain causes a latent image to be formed (usually on the surface), which then renders the entire grain developable. The tabular grains of a modern high speed emulsion are largely triangular or hexagonal single-crystal platelets approximately 10 ü across and 0.1 ü thick. Such a grain will contain about 109 silver atoms, and it can be sensitized by a few molecules of gold sulfide or other additives adsorbed on its surface.

In the concentration speck theory of the latent image, light is absorbed throughout the grain, but this energy is transported by the motion of electrons to a sensitivity center usually on the surface where the latent image is formed.
The Improbability of the Photographic Process
Authors: Slifkin Lawrence
Published: August 2016

The very high sensitivity of silver halide photographic emulsions is the result of a surprisingly high quantum efficiency in the formation of the latent image, combined with a large amplification of the stored optical signal upon photographic “development.” The efficient formation of the latent image can be traced to the effects of an unusual set of physical properties of silver bromide and silver chloride, involving the electron energy band structure, the dynamics of photoelectrons, the nature and mobilities of the ionic point defects, and the existence of a sub-surface electric field.

Despite the current availability of a wide variety of optical recording systems, the standard silver halide photographic emulsion continues to offer a unique combination of sensitivity, resolution, tone quality, convenience, and economy. This article will outline the physical processes that operate in forming the image. It will emphasize the unusual set of properties of silver bromide and silver chloride that are involved, and that impart to the process its extraordinary efficiency. Only black-and-white images will be considered, but the same basic imaging process is involved in color photography as well.

This discussion is, of necessity, brief and often qualitative, but more complete treatments of the scientific aspects of the photographic process can be found in the other articles in this issue of the MRS BULLETIN, as well as in the bibliography.
Microscopic Analysis in Archaeology
Authors: Stevenson C. , Prior C.
Published: August 2016

The papers in this edition of the MRS BULLETIN were among those presented during a workshop entitled “SAS Interfaces '87: Microscopy for the Archaeologist.” The workshop was sponsored by the Society for Archaeological Sciences at the 52nd annual meeting of the Society for American Archaeology held in Toronto, Ontario, May 1987. The Society for Archaeological Sciences is an interdisciplinary professional society for researchers involved in the broad spectrum of physical science applications to archaeology in order to promote interaction among scientists interested in different aspects of common research problems.

Archaeometry, i.e., “archaeological science,” is concerned with the physical analysis of archaeological materials and the application of techniques from the laboratory sciences to the objectives and needs of archaeology. It includes such activities as compositional analysis, reconstruction of past technologies and processes, remote sensing, paleo-environmental reconstruction, and of course, isotopic and other chronometric dating methods. Such techniques alone, however, yield results that mean little without appropriate application to anthropological problems. The chief concern of archaeologists is to choose the most appropriate analysis method to achieve results that are useful in interpreting cultural behavior. To that end, laboratory analysts need to be aware of the interests and concerns of archaeologists, and archaeologists need to be able to understand the technical advances in archaeometry to incorporate them into their research.