bluuebunny/crossref_metadata_2025_split huggingface dataset:
II-VI Blue-Green Laser Diodes: A Frontier of Materials Research
Authors: Gunshor Robert L. , Nurmikko Arto V. 
Published: August 2016

The current interest in the wide bandgap II-VI semiconductor compounds can be traced back to the initial developments in semiconductor optoelectronic device physics that occurred in the early 1960s. The II-VI semiconductors were the object of intense research in both industrial and university laboratories for many years. The motivation for their exploration was the expectation that, possessing direct bandgaps from infrared to ultraviolet, the wide bandgap II-VI compound semiconductors could be the basis for a variety of efficient light-emitting devices spanning the entire range of the visible spectrum.During the past thirty years or so, development of the narrower gap III-V compound semiconductors, such as gallium arsenide and related III-V alloys, has progressed quite rapidly. A striking example of the current maturity reached by the III-V semiconductor materials is the infrared semiconductor laser that provides the optical source for fiber communication links and compact-disk players. Despite the fact that the direct bandgap II-VI semiconductors offered the most promise for realizing diode lasers and efficient light-emitting-diode (LED) displays over the green and blue portions of the visible spectrum, major obstacles soon emerged with these materials, broadly defined in terms of the structural and electronic quality of the material. As a result of these persistent problems, by the late 1970s the II-VI semiconductors were largely relegated to academic research among a small community of workers, primarily in university research laboratories.
Conductors from Superconductors: Conventional Low-Temperature and New High-Temperature Superconducting Conductors
Authors: Larbalestier David C. , Maley Martin P. 
Published: August 2016

A useful superconducting conductor must have several properties. Some of the key properties among these are illustrated by the cross section of a Nb-47wt%Ti/Cu composite (Figure 1) which was manufactured for the dipole magnets of the Superconducting Super Collider (SSC). It represents the state of the art for conventional conductor fabrication and is thus an excellent place to start in considering what is needed for any new conductor. First among the essential properties is a high critical current density (Jc); the lower limit of useful Jc is ~104 A/cm2, but really useful values lie between 105 and 106 A/cm2. The SSC conductor achieves this at fields up to 9 T at 4.2 K, the normal temperature used for magnets cooled by liquid helium.A critical second requirement is that the superconductor be paralleled by an intimately connected good normal conductor, in this case high-conductivity Cu. One function of the Cu is to stabilize the superconductor against small temperature disturbances that lead to flux jumps that could result in local quenching of superconductivity. This requirement forces the subdivision of a given cross section of the superconductor into many filaments having a maximum diameter of no more than about 50 μm, since bigger filaments store more electromagnetic energy than can safely be deposited in the filament without locally heating it above its critical temperature (Tc). One advantage of high-temperature superconducting (HTS) materials is that they can operate at temperatures above ~10 K. Since the specific heat is a strongly increasing function at low temperatures, this permits the safe filament size to greatly increase too. The need to minimize hysteresis losses, however, often provides a separate drive to minimize the filament diameter, as in the conductor of Figure 1, where there are some 7,000 filaments which are only 6 μm in diameter. The overall Cu:Nb-Ti ratio is about 1.5:1. This represents a compromise between the need to minimize the dilution of the supercurrent density by Cu and the need to provide sufficient high-conductivity normal metal to pass the current when the magnet makes the transition from the superconducting to the normal state (a quench).
Single-Crystal Silicon: Photovoltaic Applications
Authors: Green Martin A. 
Published: August 2016

The vast majority of solar cells used in the field are based on single-crystal silicon. There are several reasons for this. First, by using this material, photovoltaic manufacturers can benefit from the economies of scale of the much larger microelectronics industry, where crystalline silicon also dominates. Since lower-quality silicon is acceptable for solar cells, cell manufacturers are able not only to benefit from large production volumes, but also to use off-grade material. The relatively high efficiencies that result from this material, its excellent reliability in the field, its almost complete lack of environmental problems, and recent laboratory progress strengthen the position of this technology.Although there had been earlier work with what might be termed “cast multicrystalline silicon,” the first efficient crystalline silicon cells were reported in 1954. These cells displayed energy conversion efficiencies of about 6%, a substantial improvement over what had been previously demonstrated. Performance improved rapidly through the 1950s, with efficiencies up to about 15% demonstrated in the early 1960s. By this time, their use on spacecraft had become the major commercial purpose of the cells, with reliability a more important attribute than efficiency. The technology then stabilized for a decade. In the early 1970s, another burst of activity pushed the performance of laboratory cells to about 17%. At about this time, a simple processing sequence was developed, based on screen printing the metal contacts to the cell. Anisotropic chemical etching of the silicon to produce surface texture to reduce reflection loss was also implemented, to give the cell structure shown in Figure 1.
Status of Computational Fluid Dynamics and Its Application to Materials Manufacturing
Authors: Sawada Ikuo , Tanaka Hiroyuki , Tanaka Masahiro 
Published: August 2016

Computational fluid dynamics was born principally in the aerospace field as a method for fluid flow and heat transfer research methods following experimental and analytical approaches. Along with progress in the cost performance of computers, computational fluid dynamics is now establishing itself as a tool to improve production processes and product quality in the steel, nonferrous metals, glass, plastics, and composite materials industries.Materials manufacturers use computational fluid dynamics for diverse purposes:1. Reduction in experimental conditions and costs;2. Detailed analysis of mechanisms with multifaceted information unobtainable through experimentation;3. Universal tool for scale-up; and4. Evaluation of novel processes.It can be readily imagined that accuracy, flexibility, and other requirements of computational fluid dynamics should vary with specific applications.Fluids generally observed in materials manufacturing processes are molten materials such as metal, glass, and plastics, and gases for stirring and refining. In the flow of such fluids, materials quality and process characteristics are governed by the following:1. Transport phenomena in the bulk region (where fluid flow is normally turbulent);2. Chemical reaction at interfaces;3. Transport phenomena in boundary layers near the interfaces; and4. Complex coupled phenomena (heat transfer, diffusion, chemical reaction, phase transformation like solidification, free surface, electromagnetic force, and bubble flow).
Emerging Technologies for Reuse of Lignocellulosic Materials: Recycling Our Disposed Wood and Paper
Authors: Laufenberg Theodore L. 
Published: August 2016

“Lignocellulosic materials” refer to the organic matter produced by plants on the Earth in the form of grasses, shrubs, agricultural crops, and trees. Worldwide, this plant growth (also called biomass) serves two sustaining functions for our planet: it degrades carbon dioxide to oxygen and it has been the origin or storage media of all non-atmospheric carbon. Leaving aside the related critical issues of fossil fuel depletion and global warming/cooling, lignocellulosic materials growing on the surface also serve many commercial purposes: food production, fuel sources, structural materials for housing and industry, paper products, and chemicals.Although lignocellulosic materials represent a sustainable resource base, the expanding use of paper and wood products has caused the developed countries to reevaluate the use and recovery of these natural biopolymerics. This issue of the MRS Bulletin explores some of the intricacies surrounding the recovery and reuse of these biomaterials. The applications for materials research are by no means exhaustively covered in these articles. Instead we illuminate the critical issues facing the paper recycling community and the technologies being applied to this resource to create marketable materials.
Paper Recycling: Definitions and Developments
Authors: Mulligan Daniel B. 
Published: August 2016

With the northeastern United States leading the way, tipping fees paid to landfill owners for solid waste disposal have increased as much as 533% since 1980. Fueled by the rapidly diminishing number of available landfills, these rates are expected to go only higher, adding to the public's frustration. Local, state, and federal officials are seeking solutions to mitigate the problem and the public outcry.In an address at the May 14,1990 Waste-paper I Conference, James B. Malloy, president and chief operating officer of Jefferson Smurfit Corporation and Container Corporation of America, stated: “The bottom line is that our industry, not only in the U.S., but also around the world, must continue to strive for sensible waste reduction at the source as well as total integration of waste management options. In cooperation with, not in conflict with, the public sector we can continue to be positive, constructive participants in the search for workable solutions to the municipal solid waste challenge.”Recycling is part of the solution. Paper, which contributes up to 40% of solid waste, offers an obvious solution (see Figure 1). The focus on recycling must remain high, encouraging the public to collect and sort waste paper as well as purchase recycled material. What follows is a description of some attempts to inject order into this otherwise complex issue.
Engineered Porous Materials
Authors: Schaefer Dale W. 
Published: August 2016

Rustum Roy recently observed that, operating from a finite number of elements, materials science faces an over-supply problem, too many scientists, and too few elements. Like all Malthusian dilemmas, relief is unlikely within the assumptions. Materials scientists, however, enjoy opportunities to develop new materials through morphological engineering of traditional substances. Carbon, after all, provided a century of progress for polymer chemists and a revolution in the manufacturing world. The trend from atomic- to molecular- to chain-level engineering can obviously be extended to mesostructure engineering and beyond. The tailoring of porosity is an example of such an extension.This issue of the MRS Bulletin examines the concept of engineered porosity from three perspectives. Smith, Hua, and Earl discuss characterization based on classic gas adsorption and more recent NMR and scattering methods. Two articles, one by Harold and Lee, and the other by Fain, look at the pore structure requirements for important applications, reactive separations and gas separation. Finally, the materials science of engineered porosity is discussed in four articles. Even describes emulsion-derived foams in which surface-active species impose micron-scale structure that is retained during polymerization. Shapovalov broadly reviews methods to introduce porosity in metals. Durian discusses recent work on relaxation phenomena in aqueous foams. Finally, I review the factors that control structure in mesoporous aerogels.
Catalysis with Inorganic Membranes
Authors: Harold M.P. , Lee C. , Burggraaf A.J. , Keizer K. , Zaspalis V.T. , de Lange R.S.A. 
Published: August 2016

Catalytic inorganic membranes are among the most challenging and intriguing porous materials. Consisting of a thin film of mesoporous or microporous inorganic material deposited on a macroporous material, catalytic membranes are multifunctional materials that must be engineered for both chemical and physical properties. New approaches to carrying out chemical reactions are possible by tailoring the membrane catalytic activity and selectivity, permselectivity, and other thin film properties. Readers are referred to several recent reviews of inorganic membranes, in particular, Zaspalis and Burggraaf, Armor, Gellings and Bouwmeister, Hsieh, Stoukides, and Tsotsis et al.Inorganic membranes are most conveniently classified according to pore size (see introductory article). Of particular importance is the ratio of the pore size to the molecular mean free path (MFP). Decreasing pore dimensions lead to increased selectivity with corresponding loss of permeability.Macroporousmembranes have a pore size much larger than the MFP, leading to molecular (bulk) diffusion or viscous flow. Knudsen diffusion dominates in themesoporousregime, where the pore size is comparable to the MFP. In addition, surface diffusion of the molecules along the pore walls may contribute, leading to an enhanced flux of the adsorbed species along the walls. Themicroporousregime is encountered when the pore size is comparable to the molecules. This regime makes possible much higher permselectivities, which depend on both molecular size and specific interactions with the solid. Finally, in dense membranes, molecular transport occurs through a solution-diffusion mechanism, which also involves specific interactions between the solute and membrane.
Characterization of Porous Solids
Authors: Smith Douglas M. , Hua Duen-Wu , Earl William L. 
Published: August 2016

Progress in the synthesis and engineering of advanced porous materials demands better pore structure characterization. The analysis of pore structure is complicated by (1) the wide range in pore sizes observed, from molecular (<1 nm) to macroscopic (>1 mm) dimensions, (2) complex pore shapes and connectivities, (3) chemical and physical heterogeneities, and (4) pore structure changes that can occur during characterization.The required pore structure information varies with application. Bulk density and the pore-size distribution are needed for thermal insulation. In this case, the dimension of interest is the so-called hydraulic radius since, for small pores, the gas-phase conductivity is proportional to the mean hydraulic radius to the mean free path. A few large but isolated pores will significantly affect conductivity but will go undetected in typical gas-absorption methods. In contrast, for separations, bottlenecks control performance. For transport, such as migration through geologic formations, both the pore-size distribution and pore connectivity are important. For adsorption, surface area and pore size are the relevant factors. Finally, the conventional concepts of pore structure lose meaning as the pore size approaches molecular dimensions, typical of adsorbents and gas-separation membranes.
John von Neumann and Materials Science
Authors: Seitz Frederick 
Published: August 2016

I presume that many of you will be surprised to learn that John von Neumann, a great mathematician, and a remarkable man, had even a passing interest in materials science since his name is usually associated with work in function theory, mathematical logic, the mathematical foundations of quantum mechanics, game theory, and of course with the development of computer logic. Actually, he was deeply interested in the evolution of materials science and technology, and he played an important role in giving prominence to materials science at a critical time in its evolution. But first let me tell you a little about his life.John von Neumann was born in Budapest, Hungary, in 1903 into a prominent business family. His mathematical genius was recognized early by his high school teacher, Lázsló Ratz, who insisted that he receive special tutoring since mathematical geniuses tend to flower early. He became a close and, indeed, a lifetime friend of a slightly older fellow student, Eugene Wigner, who was inspired by the same mathematics teacher. The two of them frequently wandered home together after school, with von Neumann providing a tutorial on some aspect of mathematics while Wigner, who had a comparably brilliant mind, absorbed everything. The two students had different personalities, but shared a great love of mathematics.Von Neumann was never a narrow genius. He soaked up knowledge of all kinds rapidly and was exposed to much because the von Neumann family dinner gatherings were devoted to discussions of technical, historical and cultural affairs, as well as business. This great versatility in interests was a characteristic trademark of von Neumann‘s entire life.
Materials and the Environment
Authors: Weissman Suzanne H. , Sekutowski Janine C. 
Published: August 2016

We co-organized the first MRS technical symposium dealing with the environment at the 1991 Spring Meeting in Anaheim, California. Entitled “Environmentally Conscious Materials Processing,” the symposium dealt with waste minimization, pollution prevention, alternative materials and processes, recovery and recycling, and chemical sensors for process stream monitoring. This symposium captured much interest among the press and the materials community. Because of the growing interest in the environment, the MRS Bulletin asked us to guest edit this special issue that deals with the interrelated areas of materials science and the environment.In recent years, environmental concern has heightened in the United States and around the world. Public concern was greatly raised by increased environmental awareness incidents such as the accident in Bhopal, India, and the oil spill in Alaska by the Exxon Valdez. As a result, U.S. companies are more concerned with public acceptance of their operations. In addition, manufacturers have been subject to increasingly stringent environmental legislation. Federal, state, and local legislation currently regulate air emissions, water discharges, occupational exposure, and treatment and disposal of various hazardous chemicals. In addition, the Montreal Protocol, an international agreement signed by the United States, regulates the production and use of halogenated organic compounds now known to deplete the Earth's ozone layer. Associated with these stringent environmental regulations are increasing waste-associated costs. Waste disposal costs are increasing at an annual rate of about 10%.
The Changing Paradigm for Business Success in Advanced Materials and Components Manufacturing
Authors: Barnett B. , Bowen H.K. , Clark K. 
Published: August 2016

The use of manmade materials progressed rather slowly until the science and technology of metals, refractories, and glass burst forth in the mid-1800s and continued its infancy through the first decades of the 20th century. In fact, much of the scientific wherewithal in industrial nations focused on the development of manmade materials from the standpoint of properties and fabrication processes. From the discipline of metal physics, which emerged in the 1930s, and from the scientific activities in ceramics, polymers, and electronic materials that blossomed in the 1940s and 1950s, a science and engineering base was established, enabling advanced materials and components to be fabricated, often for specific end-user applications. The molecular engineering of crystals, for example, has its roots in von Hippel's studies of dielectric materials at the Massachusetts Institute of Technology, which began in the 1930s. In this time frame, society, which had primarily used such materials as wood, gypsum, clay, copper, zinc, lead, and iron, turned to a broader set of materials to meet new uses. These new applications required an understanding not only of the composition of matter, but of novel and difficult processes as well. Research specialties broadened.From the late 1950s to the present, the knowledge base for materials and components has exploded. In this period, the scientific and technological field of endeavor—materials science and engineering (MS&E) — evolved from a collection of discrete, disparate arts and crafts with varied amounts of science and practitioners who generally did not stray from their own specialties to a more diffuse field where researchers take a broader approach to materials research and practice.
GaAs Integrated Circuit Manufacturing
Authors: del Alamo Jesús A. 
Published: August 2016

In the mid 1980s, reports of exciting progress from GaAs integrated circuit (IC) performance from R&D laboratories world-wide portrayed a rosy future for GaAs. Now, in the early 1990s, true to their reputation, GaAs ICs are still largely the stuff of the future. In fact, deployment of GaAs ICs in real systems has been disappointingly slow. In 1985, the commercial GaAs IC market was forecast to reach $800 million by 1990. The actual figure was only $142 million. To put this number in perspective, it represents less than 0.4% of the total Si IC merchant market.In a recent survey of the GaAs industry, Kato explored the causes for GaAs troubles, with startling findings. The issue certainly does not seem to be a performance one because GaAs ICs are sufficiently ahead of alternative technologies. Material quality is not a problem either. Extremely high-quality 3 in. and 4 in. GaAs wafers are now on the market at reasonable prices. On the other hand, several serious deficiencies center around IC manufacturing. The price of the final GaAs ICs is perceived as not competitive with alternative technologies. This is rooted in the low yields and poor repeatability of the manufacturing lines. A great contribution to cost is time-consuming functionality testing, particularly for analog products. For MMICs (monolithic microwave integrated circuits) in particular, final testing can easily become the bottleneck of the entire fabrication process. There is also much uncertainty about reliability. This might explain to a large extent the low customer confidence in the technology. Kato reports that fundamental technical problems in making GaAs ICs are still believed to remain.
Nuclear Magnetic Resonance Spectroscopy of Geological Materials
Authors: Stebbins Jonathan F. 
Published: August 2016

From the earliest days of extractive metallurgy, materials scientists and geoscientists have shared common ground. Experimental approaches, such as phase equilibrium and structural studies, are often similar, as are the questions asked in attempts to connect microscopic fundamentals to technologically desired or naturally observed bulk properties. The actual materials studied by both groups are often similar or even identical, such as silicate ceramics and glasses, magnetic oxides, and crystals based on the perovskite structure.Nuclear magnetic resonance (NMR) was applied to solid-state physics shortly after the technique was invented in 1946. Even at the start, many of the samples placed in magnets in physics laboratories were large single crystals of naturally occurring minerals such as gypsum (CaSO4 · 2H2O) and fluorite (CaF2), perhaps borrowed from mineralogist colleagues. In the last 10 years, however, applications to both the earth and materials science have rapidly expanded because of improvements in both technological capabilities and basic theory. Only work on inorganic materials will be discussed here, although 13C NMR studies have proved very useful in characterizing the complex, often inseparable mixtures of large organic molecules found in soils, kerogen, and coal. I will not attempt to thoroughly review the broad and fast growing literature in inorganic applications. Instead, I have chosen examples, primarily from our recent studies, to illustrate the scope of what is and will become possible.Several recent books clearly introduced the basic concepts of solid-state NMR, and applications to crystalline and glassy silicates as well as NMR at high temperature have been reviewed recently.