bluuebunny/crossref_metadata_2025 huggingface dataset:
Material Matters: Performance Standards Governing New Materials for Sports
Authors: Gelberg J. Nadine
Published: August 2016

“With a lighter but stiffer shaft and heavier clubhead the ball goes farther. Easier,” claims a 1975 advertisement for Shakespeare graphite irons. New materials such as graphite, boron, and titanium, have made sports equipment stronger yet lighter and thus more powerful. For athletes, sports have become, as the ad stated, easier. Serves over one hundred miles per hour are commonplace on the professional tennis tour, and athletes such as Tiger Woods are making par five golf holes obsolete. Sports organizations do not, however, always embrace these innovations that facilitate play. Major League Baseball retains its traditional mandate requiring only wood bats, the International Tennis Federation prohibited double strung tennis rackets, and the United States Golf Association banned asymmetrically dimpled golf balls. These technology regulations emerged to prevent the sport from becoming “easier,” protecting sport integrity.
Modeling Bicycle-Rider Vibrations: Implications for Materials Selection
Authors: Gribb Tye T. , Worzala F.J. , Gribb G.W.
Published: August 2016

Over the past several years, the number of materials routinely employed for the fabrication of major bicycle components (e.g., frame, fork, and handlebar) has increased from one (steel) to at least five (steel, aluminum, titanium, fiber-reinforced polymers, and magnesium). Historically the primary driving force for implementation of new materials in bicycle manufacture has been the almost fanatical desire to reduce the weight of the bicycle. Although weight reduction of the bicycle will continue to be important, an old design paradigm—driven mostly by the recent popularity of bicycles designed to be ridden off-road (mountain bikes)—has re-emerged: the design of bicycles that minimize the amount of road/trail shock transmitted to the rider.
Erbium-Doped Optical-Waveguide Amplifiers on Silicon
Authors: Kik P.G. , Polman A.
Published: August 2016

Thin-film integrated optics is becoming more and more important in optical-communications technology. The fabrication of passive devices such as planar optical waveguides, splitters, and multiplexers is now quite well-developed. Devices based on this technology are now commercially available. One step to further improve this technology is to develop optical amplifiers that can be integrated with these devices. Such amplifiers can compensate for the losses in splitters or other optical components, and can also serve as pre-amplifiers for active devices such as detectors.

In optical-fiber technology, erbium-doped fiber amplifiers, are used in long-distance fiber-communications links. They use an optical transition in Er3+ at a wavelength of 1.54 μm for signal amplification, and their success has set a standard of optical communication at this wavelength. Using the same concept of Er doping, planar-waveguide amplifiers are now being developed. For these devices, silicon is often used as a substrate, so that optoelectronic integration with other devices in or on Si (electrical devices, or Si-based light sources, detectors, and modulators) may become possible. Figure 1 shows an example of a silicon-based optical integrated circuit5 in which a 1 × 4 splitter is combined with an amplifying section.
Solidification Science and Engineering Practice
Authors: Flemings Merton C.
Published: August 2016

The following is an edited transcript from the 1997 David Turnbull Lectureship presentation given by Merton C. Flemings at the 1997 Materials Research Society Fall Meeting. Flemings was cited for “his contributions to the foundations and technology of solidification processing and for educating a generation of materials engineers.”
Synthesis of Novel Magnetorheological Fluids
Authors: Phulé Pradeep P.
Published: August 2016

This article focuses on the synthesis and processing of novel magnetorheological (MR) fluids. The process for preparing MR fluids typically involves introducing magnetic particles into base liquid under low shear conditions. This is followed by ball milling in the fluid with zirconia (ZrO2) grinding media for about 24 h. High-purity carbonyi iron (Fe) powders have been used for the synthesis of ironbased MR fluids while the ferrite-based MR fluids used magnetic manganesezinc ferrite and nickel-zinc ferrite powders.

Typical volume fractions of the magnetic phase that lead to MR fluids with respectable yield stresses tend to be about 0.3–0.5. Higher volume fractions, in principle, can lead to higher strength MR fluids. However, higher volume fractions tend to cause a significant, and often undesirable, increase in the “off-state” viscosity of the MR fluids. The rationale for selection and the role of different components of MR fluids are briefly discussed in the following sections.
New Functionality in Glass
Authors: Houde-Walter Susan , Green Peter
Published: August 2016

Glass serves a critical function in diverse technologies ranging from medicine to telecommunications. Fax machines and text scanners use micro-optic lens arrays made from ion-exchanged, gradedindex glass to image original documents. Data for long-distance communication by telephone or computer are transmitted in the form of modulated laser light through highly transparent glass fibers. These signals are boosted for long-haul transmission by stimulated emission in erbium-doped glass optical amplifiers. Lap-top computers use flat-panel-display glass in their liquid-crystal screens (see “Materials for Flat-Panel Displays,” MRS Bulletin, March 1996). Gall-bladder and hysterectomy surgeries have been made minimally invasive in part because of slender glass imaging endoscopes.

Functionality in glass is expanding rapidly. New properties are often attributable to new defect species created by strong optical or electrical fields. For example rare-earth-doped ZBLAN glass (a commercial fluoride glass), when exposed to high peak-intensity femtosecond laser pulses, becomes phosphorescent. (See the cover of this issue.) The phosphorescence is visible to the naked eye up to 12 hours after illumination. Other compositions show similar effects. Phosphorescent glasses are transparent and may be more easily formed into contiguous films and fibers than powder or microcrystalline phosphors.
Poled Glasses
Authors: Margulis W. , Garcia F.C. , Hering E.N. , Guedes Valente L.C. , Lesche B. , Laurell F. , Carvalho I.C.S.
Published: August 2016

Glass is the most important material in optics, with uses in optical fibers, lenses, mirror substrates, and prisms. The silicate family, the prime material in this article, is well-suited for passive optical functions such as light guidance in a fiber. Because of its many desirable properties, one is tempted to use glass in active functions as well—such as in amplification and modulation of light. As early as the beginning of the 1960s, glasses doped with rare-earth ions were used as gain media for lasers. Nd:glass lasers and Erdoped fiber amplifiers are two examples of the success of the use of doped glass to perform an active optical function. The modulation and switching of light proved to be a more difficult task to perform with glass systems. Glass has very low optical nonlinearity, and the application of an electric field does little to the optical wave traveling in the material.

In 1991 Myers, Mukherjee, and Brueck submitted a polymer film on a silica substrate to a poling process, which consists of the application of high voltages at a temperature of ~300°C. After cooling to room temperature with the voltage still applied, the poled sample was illuminated with a strong infrared (ir) laser beam. As expected they found that material frequency-doubled the incoming radiation and some green light could be measured at the output. When a test was carried out to discard any contribution from the substrate to the frequency-doubled light, they discovered that it was the silica glass that was generating the green light and that they had induced a strong optical nonlinearity in silica by thermal poling. Since then poling of glasses in the context of nonlinear optics has been the subject of many publications, including the report that ultraviolet (uv) radiation can advantageously replace thermal excitation.
Semiconductor Quantum Dots
Authors: Zunger Alex
Published: August 2016

Semiconductor “quantum dots” refer to nanometer-sized, giant (103–105 atoms) molecules made from ordinary inorganic semiconductor materials such as Si, InP, CdSe, etc. They are larger than the traditional “molecular clusters” (~1 nanometer containing ≤100 atoms) common in chemistry yet smaller than the structures of the order of a micron, manufactured by current electronic-industry lithographic techniques. Quantum dots can be made by colloidal chemistry techniques (see the articles by Alivisatos and by Nozik and Mićić in this issue), by controlled coarsening during epitaxial growth (see the article by Bimberg et al. in this issue), by size fluctuations in conventional quantum wells (see the article by Gammon in this issue), or via nano-fabrication (see the article by Tarucha in this issue).
Scanning Electron-Acoustic Microscopy: Do You Know Its Capabilities?
Authors: Urchulutegui M.
Published: August 2016

Characterization of materials usually requires microscopy techniques. Some of the most useful are based on a scanning microscope and involve scanning the sample surface with a focused beam (e.g., photons, electrons, ions, etc.). For example, photoacoustic microscopy uses a laser beam, acoustic microscopy uses an ultrasound beam, and scanning electron microscopy uses an electron beam. The interaction between the material and the beam produces a signal that can be used to generate a two-dimensional image.

In scanning photoacoustic microscopy (SPAM), an intensity-modulated light beam is used to produce oscillations in the surface temperature of the sample. These oscillations induce changes in the pressure of a fluid in the photoacoustic cell as a consequence of the periodic heat conduction from the surface to the cell fluid. Subsequently many material-characterization methods have employed the same philosophy as SPAM, using a modulated beam as an excitation probe. The breadth of such techniques is due to the large number of possible excitation sources and signal detectors that have been proposed to probe the specimen response. In particular, scanning electron-acoustic microscopy (SEAM), also referred to as thermal wave microscopy, is a technique based on the utilization of a scanning electron microscope developed in 1980 and applied in recent years to material characterization. It can be considered an additional mode of scanning electron microscopy (SEM), which uses the generation of acoustic waves in the sample. Most reviews have concentrated on the application of SEAM to metals and semiconductors. However many other possibilities exist.
The Importance of New Processing Techniques in Tissue Engineering
Authors: Lu Lichun , Mikos Antonios G.
Published: August 2016

Tissue engineering offers the possibility to create completely natural tissue and replace failing or malfunctioning organs. In many cases, biocompatible, biodegradable polymers are utilized to either induce surrounding tissue and cell ingrowth or to serve as a temporary scaffold for transplanted cells to attach, grow, and maintain differentiated functions. Various processing techniques have therefore been developed to fabricate polymers with specific properties to meet the needs of a particular organ.

Polymer scaffolds must possess unique physical and chemical properties for specific applications and must satisfy some basic requirements for tissue engineering. These scaffolds may be implanted without cells, and the regeneration depends on ingrowth of surrounding tissue to such materials—a process known as tissue induction. Alternatively cells may be seeded into a porous polymer. The cell-polymer construct is then transplanted. In either case, one essential criterion for the scaffold is biocompatibility—that is, the polymer scaffolds and their degradation products should not invoke an adverse immune response or toxicity.

Because of the problems associated with long-term implants, such as infection, fibrous tissue formation, and the possible need for retrieval, the role of polymer scaffolds should only be a temporary one. The degradation rate is optimized to allow transplanted cells to proliferate and secrete their own extracellular matrix (ECM) while polymer scaffolds can vanish when necessary to leave enough space for new tissue growth. Biodegradability of a polymer is determined by its composition, molecular weight (MW), MW distribution, degree of crystallinity, and environmental conditions such as temperature and pH. Mechanical loading of the scaffold may affect its degradation.
Patterned Polymer Films
Authors: Balazs Anna C. , Singh Chandralekha , Zhulina Ekaterina , Gersappe Dilip , Pickett Galen
Published: August 2016

Polymer films that contain well-defined patterns can be used in a variety of novel applications. For example such films can serve as the scaffolding in fabricating organic/inorganic composites with controlled architectures. One means of forming patterned films is to anchor the ends of homopolymers onto a substrate (so that the ends are fixed and cannot move) and immerse the system in a poor solvent. The incompatibility between the polymer and solvent drives the system to phase-separate. Since the ends are immobilized however, the polymers can only escape the unfavorable solvent by clustering with neighboring chain s into distinct aggregates or “pinned micelles.” These micelles have a uniform size and spacing, and form a regular array on the surface. In this article, we use theoretical models to extend this concept and show that, by tethering copolymers—chains that contain more than one type of monomer—we can drive the system to form more complicated surface patterns. These copolymer patterns provide a handle for engineering the interaction between surfaces and thus facilitate the fabrication of novel optical devices. If the copolymer films are composed of both hydrophilic and hydrophobic domains, the surface can also be used as a template for growing biological cells with tailored shapes and sizes.
Molecular-Dynamics Simulations of Polymer Surfaces and Interfaces
Authors: Grest Gary S. , Lacasse Martin-D. , Murat Michael
Published: August 2016

From a single chain in a dilute solution to an entangled polymer melt, from bulk systems to more complex interfacial problems, computer simulations have played a critical role not only in testing the basic assumptions of various theoretical models but also in interpreting experimental results. Early computer simulations of polymers were mostly carried out on a lattice using Monte Carlo methods. This approach has led to significant progress in recent years and will continue to do so in many areas. In some cases however, for example in the study of shear, lattice models have serious limitations. For this reason and also due to the availability of more powerful computers, continuum, off-lattice polymer models have recently become popular. In this article, we review some of the recent progress in studying polymers at surfaces and interfaces using continuum models.
Silicon Carbide Electronic Materials and Devices
Authors: Capano Michael A. , Trew Robert J.
Published: August 2016

The development of SiC for electronic applications has been a subject of intense research for nearly 40 years. Much of this research is motivated by the extraordinary combination of physical properties possessed by SiC, especially in the development of SiC-based devices for specific high-temperature, high-power, or high-frequency applications that are not suitable for Si- or GaAs-based devices. During the early years of SiC research and development, a significant amount of good, fundamental research was performed, but the development of commercially available SiC-based devices was retarded by low-quality bulk materials and inadequate epitaxial processes. In the late 1980s, research at academic institutions, such as North Carolina State University, and industrial laboratories, such as Westinghouse (now Northrup-Grumman), Advanced Technology Materials, Inc. (ATMI), and Cree Research, Inc., coupled with the commercial offering of highquality SiC wafers from Cree, created an opportunity for further advancement. Improvements in epitaxial processes and device processing strategies were also realized during this time. Together these factors have enabled the fabrication of high-quality device structures and have generated increased research and funding activities in SiC electronic devices.
An Overview of SiC Epitaxial Growth
Authors: Larkin D.J.
Published: August 2016

SiC electronics research has been driven by the continued successful development of SiC technology for high-power and high-frequency semiconductor devices, and for service in high-temperature, corrosive, and high-radiation environments. The development of this technology has been accelerated by the introduction of commercially available SiC wafers, which have decreased in cost with time. The most recently demonstrated commercial SiC-based products include ultraviolet (uv)-flame sensors for terrestrial turbine engines and high-definition-television transmitter systems utilizing SiC-based transistors. Prototype microelectronic SiC devices include high-voltage Schottky rectifiers and power metal-oxide-semiconductor field-effect transistors, microwave and millimeter-wave devices, and high-temperature, radiation-resistant junction FETs (JFETs). These advancements in SiC-based device technology are attributable to both the successful development of commercially available, bulk SiC substrates and the recent advancements in SiC epitaxial layer growth technologies.
Material Matters
Authors: McTague John P.
Published: August 2016

The following is an edited transcript of the plenary lecture presented by John P. McTague at the 1996 MRS Fall Meeting on December 2,1996 in Boston.

Long before 1993, the journey from New York City to San Francisco, across the continent, and from New York City to London, across the sea, will be made between the sunrise and sunset of a summer day. The railway and the steamship will be as obsolete as the stagecoach. And it will be as common for the citizen to call for his dirigible balloon as it now is for his buggy or his boots. Electricity will be the motive power, and aluminium or some lighter metal will be the material of the aerial cars, which will navigate the abyss of the sky.

John J. Ingalls

“Remarkable Changes in Everyday Life”(1893)
Material Matters
Authors: Diol Sabrina J.
Published: August 2016

Through my interdisciplinary graduate work, I have attended conferences organized by various professional societies such as the Materials Research Society (MRS), American Physical Society (APS), Optical Society of America (OSA), and American Chemical Society (ACS). I have also participated in some of their employment workshops and have searched their websites for employment resources. This article elaborates on information and services that professional societies and organizations can provide to ease employment search for their student membership.

Career Workshops. These workshops provide excellent guidance, especially for students initiating their employment search. Obviously, the best ones are conducted by people who recruit PhD graduates. I attended an employment workshop organized by the American Institute of Physics (AIP) during the 1995 MRS Fall Meeting. An extremely dynamic hightechnology industrial recruiter conducted the workshop. The mock interviews, mininetworking groups, and resume and cover letter critique involved audience participation and were highly effective. I strongly recommend such a workshop. On the other hand, I have also been frustrated with workshops in which speakers did not have a technical PhD background since I often found their suggestions unsuitable.

Employment Database. A website with current job postings mainly for PhD graduates is extremely useful. The National Academy of Science (http://www2.nas.edu) is among the few sources for this. The critical issue in this case is to have a well-maintained site with frequent updates and a search engine. Another alternative, which we have been using at the University of Rochester, is to circulate job postings via electronic mail. Again, timeliness is the key issue.
Remarks on the Evolution of Materials Science
Authors: Mullins William W.
Published: August 2016

The following is an edited version of the Von Hippel Award address, given by recipient W.W. Mullins at the 1995 MRS Fall Meeting. Mullins received the Materials Research Society's highest honor “for pioneering and profound contributions to the understanding of grain boundary motion, morphological stability, the structure of surfaces and interfaces, and flow and diffusion as stochastic phenomena.” Mullins is University Professor Emeritus of Materials Science and Engineering at Carnegie-Mellon University.
Magneto-optic Recording Materials
Authors: Suzuki Takao
Published: August 2016

With significant developments in laser and semiconductor industries, optical-storage technology has successfully emerged into the consumer marketplace and more recently into the computer-based data-storage marketplace as well. For computer-based data storage and other purposes, the first generation of the International Standards Organization (ISO) standard 5-1/4-in. magneto-optic (MO) drive (325 Mbytes × 2/double-sided) was introduced in 1988 and the 3.5-in. drive (128 Mbytes) in 1991. Since then progress has been remarkable in capacity and data-transfer rate as well as cost/performance ratio, and the so-called 2X (650 Mbytes × 2 per 5-in. double-sided disk) and 3X (1 Gbyte × 2 per 5-in. double-sided disk) drives are now in the marketplace. Also a remarkable product called the MiniDisc (2.5 in.), the first recordable optical system for both the consumer and the data market, utilizes data compression and direct overwrite schemes.

The solution for increasing the capacity is by no means simple since the new technology must accommodate many factors. One of the key factors is backward compatibility. This feature is important to removable media because the customer expects new products to be compatible with their previous investments in data stored on older generation media. Another key factor is cost. The sales price ($/Mbyte) must be significantly lower than prior generations of optical-storage products and alternative storage systems (e.g., removable hard disks).

To increase the capacity in optical-storage media, several solutions are possible: short-wavelength lasers, magnetically induced super resolution (MSR), pulse width modulation (PWM), volumetric recording, land/groove recording with crosstalk cancellation, partial-response channels, banding of data, and higher numerical aperture objective lenses.
Erasable Phase-Change Optical Materials
Authors: Yamada Noboru
Published: August 2016

Almost all stones on a lane will become glassy if they are melted and quenched. They will become transparent and quite different in appearance from before vitrification. This visible change constitutes the recording of information. We might refer to the stone as “1 bit.” If the vitrified stone is subsequently kept at a high temperature under its melting point, it will lose its transparency and turn back to the appearance it had before melting and quenching. Thus the “1 bit” is erased. This is the simple mechanism of an erasable phase-change optical memory. In practical systems, a laser beam focused into a diffraction-limited spot is used for recording. This enables the spatial size of the “1 bit” to be very small (of submicron order) so that the recording density is very high.

Figure 1 shows a transmission-electron-microscope (TEM) photograph of an actual optical disk. The elliptical smooth areas are recording marks in the amorphous state that were formed by high-power and short-duration laser irradiation. The shortest mark length is about 0.5 μm. The area surrounding the amorphous marks is in the crystalline state and consists of small grains. The two states differ from each other in optical properties such as refractive indices and optical absorption coefficients. Accordingly when the bits are illuminated with low-intensity laser light, the reflected light from the amorphous and crystalline regions is different and may be detected as information signals.

The amorphous marks are erased by heating above the glass-transition temperature by laser irradiation, but with lower power than is used in the case of recording.
Multiple Scattering Probes of Disordered Materials
Authors: Weitz D.A. , Pine D.J.
Published: August 2016

A large class of materials of great technological importance and scientific interest are highly disordered on length scales comparable to, or larger than, the wavelength of light. As a consequence of this disorder, these materials are often composed of a large number of regions with different indices of refraction, separated by interfaces that are abrupt on the scale of the wavelength of light. Each of these interfaces refracts or scatters light, making these materials quite opaque optically. Even in the absence of absorption, the strong scattering precludes the direct transmission of light rays through the material. This greatly complicates the study of these materials.

Examples of these disordered materials abound. Many are complex fluids; colloidal suspensions and other dispersions such as foams and emulsions often consist of particles or droplets whose diameters are comparable to the wavelength of light. Unless they are very dilute, these dispersions are typically highly opaque. Other materials consist of solid grains of similar sizes without the surrounding fluid. For example, most ceramics are composed of oxide grains sintered together; the voids between the grains lead to the large number of interfaces, and hence to the strong scattering and opaque appearance commonly associated with these materials. Similarly, many porous materials also possess a high density of voids that scatter light; filters, oxide catalyst supports, and even rocks are all optically opaque because of the strong scattering. Sand and other unconsolidated granular materials are also opaque in part because of the large number of interfaces that scatter light.
Materials Science in the Electron Microscope
Authors: Ross Frances M.
Published: August 2016

This issue of the MRS Bulletin aims to highlight the innovative and exciting materials science research now being done using in situ electron microscopy. Techniques which combine real-time image acquisition with high spatial resolution have contributed to our understanding of a remarkably diverse range of physical phenomena. The articles in this issue present recent advances in materials science which have been made using the techniques of transmission electron microscopy (TEM), including holography, scanning electron microscopy (SEM), low-energy electron microscopy (LEEM), and high-voltage electron microscopy (HVEM).

The idea of carrying out dynamic experiments involving real-time observation of microscopic phenomena has always had an attraction for materials scientists. Ever since the first static images were obtained in the electron microscope, materials scientists have been interested in observing processes in real time: we feel that we obtain a true understanding of a microscopic phenomenon if we can actually watch it taking place. The idea behind “materials science in the electron microscope” is therefore to use the electron microscope—with its unique ability to image subtle changes in a material at or near the atomic level—as a laboratory in which a remarkable variety of experiments can be carried out. In this issue you will read about dynamic experiments in areas such as phase transformations, thin-film growth, and electromigration, which make use of innovative designs for the specimen, the specimen holder, or the microscope itself. These articles speak for themselves in demonstrating the power of real-time analysis in the quantitative exploration of reaction mechanisms.

The first transmission electron microscopes operated at low accelerating voltages, up to about 100 kV. This placed a severe limitation on the thickness of foils that could be examined: Heavy elements, for example, had to be made into foils thinner than 0.1 μm. It was felt that any phenomenon whose “mean free path” was comparable to the foil thickness would be significantly affected by the foil surfaces, and therefore would be unsuitable for study in situ. However, technology quickly generated ever higher accelerating voltages, culminating in the giant 3 MeV electron microscopes. At these voltages, electrons can penetrate materials as thick as 6–9 μm for light elements such as Si and Al, and 1 μm for very heavy ones such as Au and U.
Low-Energy Electron Microscopy
Authors: Tromp Ruud M.
Published: August 2016

For surface science, the 1980s were the decade in which the microscopes arrived. The scanning tunneling microscope (STM) was invented in 1982. Ultrahigh vacuum transmission electron microscopy (UHVTEM) played a key role in resolving the structure of the elusive Si(111)-7 × 7 surface. Scanning electron microscopy (SEM) as well as reflection electron microscopy (REM) were applied to the study of growth and islanding. And low-energy electron microscopy (LEEM), invented some 20 years earlier, made its appearance with the work of Telieps and Bauer.

LEEM and TEM have many things in common. Unlike STM and SEM, they are direct imaging techniques, using magnifying lenses. Both use an aperture to select a particular diffracted beam, which determines the nature of the contrast. If the direct beam is selected (no parallel momentum transfer), a bright field image is formed, and contrast arises primarily from differences in the scattering factor. A dark field image is formed with any other beam in the diffraction pattern, allowing contrast due to differences in symmetry. In LEEM, phase contrast is the third important mechanism by which surface and interface features such as atomic steps and dislocations may be imaged. One major difference between TEM and LEEM is the electron energy: 100 keV and above in TEM, 100 eV and below in LEEM. In LEEM, the imaging electrons are reflected from the sample surface, unlike TEM where the electrons zip right through the sample, encountering top surface, bulk, and bottom surface. STM and TEM are capable of ~2 Å resolution, while LEEM and SEM can observe surface features (including atomic steps) with -100 Å resolution.
Defects in Intermetallic Compounds: How Do They Differ From Those in Ordinary Metals?
Authors: Sun Y.Q.
Published: August 2016

Just as in ordinary metals, defects in intermetallic compounds fall into three basic categories: point defects (vacancies, substitutional and interstitial atoms), line defects (dislocations), and planar defects (stacking faults, interfaces, grain boundaries). Also like ordinary metals, many important physical and chemical properties of intermetallic compounds are governed by the presence of these defects and the effects on them from temperature, composition, chemical environment, elastic stress state, and so on.

What ultimately distinguishes an intermetallic compound from ordinary metals is its superlattice crystal structure. A two-dimensional analogue of the actual three-dimensional superlattice structure is shown in Figure 1a where the superlattice (unit cell marked by full lines) is made up of two identical sublat-tices (unit cells marked by dotted lines). A property of the sublattice is that it is exclusively occupied by one atom species, and accordingly sublattices are named after the atoms that occupy them, for example, the A and B sublattices in Figure 1a. In three dimensions, a super-lattice may consist of several sublattices. For example, the L12 superlattice of Ni3Al consists of four interpenetrating cubic sublattices, one occupied by Al atoms (Al sublattice), the other three by Ni atoms (Ni sublattices). When the sub-lattices are occupied exclusively by their designated atoms, the crystal is said to be fully ordered. The crystal will be partially ordered if a certain fraction of the sublattice sites is taken up by atoms that would otherwise sit at other sublattices; this fraction is used to describe the degree of long-range order.
Progress Toward Crystalline-Silicon-Based Light-Emitting Diodes
Authors: Canham Leigh
Published: August 2016

The semiconductor silicon is the dominant material in microelectronics and is one of the best-studied materials known to humanity. Its inability to emit light efficiently is therefore well documented. Nevertheless, a “holy grail” of semiconductor materials research has for decades been the realization of an efficient Si light-emitting diode (LED). Such a device would enable optoelectronic circuitry to be based entirely on silicon and would revolutionize VLSI technology since the other required Si-based devices (detectors, waveguides, modulators, etc.) have already been demonstrated. Although this holy grail has proved elusive, the 1990s have heralded greatly renewed interest and optimism in the development of such devices for both the visible and near-infrared spectral ranges. Dramatic progress is at last being made. This review focuses, in a somewhat chronological manner, on the progress of specific approaches to realizing crystalline structures of high radiative efficiency, and the materials constraints involved.
Spin-Polarized Quantum Fluids and Solids
Authors: Bedell Kevin S. , Silvera Isaac F. , Sullivan Neil S.
Published: August 2016

The spin-polarized phases of the quantum fluids and solids, liquid 3He, solid 3He, and spin-aligned hydrogen have generated considerable excitement over the past fifteen years. The introduction of high magnetic fields (B ∼ 10–30 T) in conjunction with low temperatures (T ≲ 100 mK) has given rise to opportunities for exploring some of the new phases predicted for these materials. There is a broad range of physical phenomena that can be accessed in this regime of parameter space—unconventional superfluidity, unusual magnetic ordering, Bose-Einstein condensation and Kosterlitz-Thouless transitions, to name a few. This is most surprising since this plethora of complicated states of matter are present in some of the most uncomplicated materials. The rich variety of phases found in these materials are all examples of collective phenomena of quantum many-body systems, and they serve as prototypes for developing an understanding of magnetism and order/disorder processes in other systems, and for the design and characterization of new materials.
Environmental Stability of Polymers
Authors: Atkins Thomas , Batich Chris
Published: August 2016

Polymers, the main ingredient of plastics, constitute the fastest-growing sector of materials—having been introduced only in this century. Their application, however, is plagued by inappropriate use and resulting premature failure. Conversely, polymers are also being attacked as indestructible contributors to the waste stream. Although objective discussion of their merits is complicated by the enormous financial interests involved, it is clear that their rapid use with a short-term experience base has led to many problems. On the positive side, they are amenable to good theoretical and experiential understanding because of the excellent organic and physical chemistry background underlying the field. Hence, we can expect to see even more widespread use of polymers and hopefully fewer problems, as our knowledge base grows, is disseminated, and is applied. This article will address the current field of polymer environmental stability and summarize a few select areas where major technical efforts are being directed.
CdTe Thin-Film Solar Cells
Authors: Suntola T.
Published: August 2016

Cadmium telluride is currently the most promising material for high efficiency, low-cost thin-film solar cells. Cadmium telluride is a compound semiconductor with an ideal 1.45 eV bandgap for direct light-to-electricity conversion. The light absorption coefficient of CdTe is high enough to make a one-micrometer-thick layer of material absorb over 99% of the visible light. Processing homogenous polycrystalline thin films seems to be less critical for CdTe than for many other compound semiconductors. The best small-area CdTe thin-film cells manufactured show more than 15% conversion efficiency. Large-area modules with aperture efficiencies in excess of 10% have also been demonstrated. The long-term stability of CdTe solar cell structures is not known in detail or in the necessary time span. Indication of good stability has been demonstrated. One of the concerns about CdTe solar cells is the presence of cadmium which is an environmentally hazardous material.
Modeling the Processing of Aluminum Alloys
Authors: Shercliff H.R. , Myhr O.R. , Tjøtta S.
Published: August 2016

The production and use of aluminum alloys involves a wide range of processing and fabrication methods. For a number of reasons discussed in this article, process modeling has an increasingly important role in all areas of production. This article reviews some process modeling activities in aluminum processing. The aims of the review are to (1) describe the current state of research in two major processing areas, (2) establish the principal motivations in the aluminum industry for undertaking process modeling, and (3) to identify generic research issues most in need of attention. This review is not intended to be exhaustive, but considers only selected processes, based on work in Norwegian laboratories with which the authors are most familiar. There is considerable parallel modeling activity worldwide in industry and academia which will not be discussed here. The case studies selected are sufficient, however, to illustrate all the main points of the review.

A recent review of materials process modeling identifies a number of recurring themes which indicate the commercial reasons why process modeling is undertaken in various industries. They may be summarized as modeling to (1) develop new or scaled-up processes, (2) reduce the number of trials, (3) optimize an existing process, and (4) improve quality by reducing product variability.

So the overriding concerns in industry are improving productivity and quality, and reducing costs. Modeling is also important from the point of view of model based real-time control of processes, but developments in this area are at present limited to relatively slow processing operations. Models are also important tools for both industry and academia to improve scientific understanding of materials processing. Within a company, modeling serves as a means to assemble know-how about the company's processes, raising the level of training of the workforce and making it possible for people to learn a process quickly.
Micromorphology and Macromorphology of Recycled Fiber and Wood
Authors: Stokke Douglas D.
Published: August 2016

The versatility of wood as a raw material is emphasized by the realization that the mass of wood consumed annually in the United States is nearly that of the combined total U.S. consumption of aluminum, plastics, cement, and steel (Figure 1). Partly as a result of the enormous quantities consumed, many wood and paper products also make up significant fractions of the materials disposed in landfills, despite accelerated recycling efforts, notably those of the paper industry. With a target recycle rate of 40% by 1995, the paper industry will make further progress in alleviating some of the disposal problems, but additional efforts to recycle wood and wood-fiber-based materials into other types of products will also be needed. Many of these opportunities have been described. A common denominator in these utilization schemes is to consider how the morphology of secondary wood-based materials may limit their use, and how the morphological characteristics of recycled fiber and wood may influence the properties of the materials produced from them. These considerations suggest, at least partly, a materials science approach to the utilization of recycled fiber and wood, particularly for the fabrication of wood-based composites.
Up Close: New Jersey Advanced Technology Center for Surface-Engineered Materials: An Experiment in Research Management
Authors: Smith D.A.
Published: August 2016

The Advanced Technology Center for Surface Engineered Materials (ATC-SEM) is a bold experiment in research management. Scientists from its five member institutions work independently within a central framework for overall planning and for the allocation of resources. Access to areas of expertise beyond the compass of the individual institutions more than offsets the logistical problems inherent in the distributed nature of the organization.

ATC-SEM had its origins in 1988 as one of a number of Advanced Technology Centers established by a grant from the New Jersey Commission on Science and Technology after approval of the Jobs, Education, and Competitiveness Bond Act. All the ATCs are dedicated to improving the competitiveness of New Jersey's industry through the application of technology.

The ATM-SEM is administered through Associated Institutions for Material Sciences (AIMS) which has six member institutions, five of which are universities. AIMS also administers other multicampus programs in New Jersey, including the New Jersey NASA space grant consortium and a SEMATECH Center of Excellence. The hallmark of each program is a collaborative effort which transcends the capabilities of any of the individual campuses. The consortium member institutions span the private, public, and industrial sectors and comprise the New Jersey Institute of Technology, Princeton University, Rutgers (the State University of New Jersey), Stevens Institute of Technology, the University of Medicine and Dentistry of New Jersey, and David Sarnoff Research Center (an independent contract research center).
Membrane Gas Separation Principles
Authors: Fain D. E.
Published: August 2016

Some industrial processes require the separation of gas or vapor mixtures. Methods for separating the mixtures vary from separation by diffusion to separation by distillation. Many of the methods, such as distillation, are energy intensive. Membranes can reduce the energy required to produce a desired separation. Because of their corrosion resistance and high temperature applications, engineered inorganic membranes can significantly increase the efficiency of many of these processes. The magnitude of the separation factor, available operating conditions, enrichment, yield, and cost of the membranes play a large role in determining whether membranes can be more economical than other methods of separation. These factors have to be evaluated on a case-by-case basis.

Martin Marietta Energy Systems' Office of Technology Transfer conducted a preliminary market survey with the assistance of the University of Tennessee and commercial marketing experts in inorganic membranes. The survey assumed that membranes could be made with permeabilities a factor of 3 larger and with cost per unit area a factor of 3 smaller than is currently available. The results indicated that active implementation of such technology could expect to achieve the following results:

• $2 billion dollar per year sales market,

• $16.6 billion increase in the national GDP,

• $2 billion improvement in the balance of trade, and

• 6 quads per year decrease in energy use.
Some Materials Concerns in Nuclear Waste Management
Authors: Hunter Regina L.
Published: August 2016

The U.S. Environmental Protection Agency (EPA) has determined that deep geologic disposal is appropriate for three types of radioactive waste generated in the United States: spent fuel, high-level waste, and transuranic waste. Spent fuel is nuclear fuel that has been discharged from a reactor after irradiation. High-level waste (HLW) is the highly radioactive material that remains after the reprocessing of spent fuel to recover uranium or plutonium. Transuranic (TRU) waste is any waste material contaminated with more than 100 nCi/g of elements having atomic numbers greater than 92 and half-lives longer than 20 years. Spent fuel and HLW can result from either commercial or governmental activities, although no commercially generated spent fuel has been reprocessed since 1972. TRU waste results primarily from the design and manufacture of nuclear weapons, not from nuclear power plants.

The physical characteristics of TRU waste differ substantially from those of spent fuel and HLW. This imposes different requirements on materials associated with containment and isolation, so TRU waste will be discussed separately from spent fuel and HLW Because all three are judged to be particularly dangerous to human beings and the environment, the EPA standard requires a demonstration of adequate 10,000-year performance of geologic repositories for these radioactive wastes. The U.S. Department of Energy (DOE) is responsible for implementing the standard by designing, siting, and building the repositories.

This article briefly describes TRU waste, HLW, and spent fuel and the two repositories currently planned by DOE. It con cludes by offering some observations on materials compatibility among waste, container materials, and host rock.
Ion-Beam-Induced Amorphization of Complex Ceramic Materials—Minerals
Authors: Wang L.M. , Ewing R.C.
Published: August 2016

As early as 1893, mineralogist W.C. Broegger recognized the first example of the transition from the crystalline to aperiodic (amorphous) state in minerals and defined the term “metamikte.” Metamict minerals were considered to be one of three classes of amorphous materials (porodine and hyaline being the other two), but distinguishable as phases that were originally crystalline, as evidenced by well-developed crystal faces. The amorphous state was determined on the basis of a characteristic conchoidal fracture and optical isotropy. There was no mention of radiation damage as a potential cause. In 1914, Hamberg first suggested that metamictization is a radiation-induced, periodic-to-aperiodic phase transition caused by alpha-decay of the constituent radioactive uranium and thorium. In the late 1930s, Stackelberg and Rottenbach tried to test this hypothesis directly by bombarding a thin slab of zircon with alpha particles. Although unsuccessful, the experiment must have been one of the first in which an “ion beam” was used to “modify” a material. After this early effort, there was little research on metamict minerals, and they remained a mineralogical curiosity.

R.C. Ewing's interest in this topic began in the early 1970s. Since then, there has been a continuing research program using modern analytical techniques on minerals that have received α-decay doses up to 1026α-decay events/m3over geologic time periods up to 109years. As an example, electron diffraction patterns have shown that naturally occurring zirconolites (CaZrTi2O7) containing varying concentrations of thorium oxide (up to 19 wt% ThO2) are amorphized to different degrees depending on their age and the resulting α-decay event dose (Figure 1).