bluuebunny/crossref_metadata_2025 huggingface dataset:
Perturbed-Angular-Correlation Spectroscopy: Renaissance of a Nuclear Technique
Authors: Catchen Gary L.
Published: August 2016

During the past decade, perturbed-angular-correlation (PAC) spectroscopy has emerged as an important technique in several areas of materials science. PAC spectroscopy is used to measure the effects of local fields at well-defined lattice sites in a crystal. These measurements can provide unique information about the structures, kinetics, and energetics associated with point defects, the mechanisms of phase transitions, and the strengths and symmetries of chemical bonds of atoms on surfaces and at interfaces. In what follows, I describe the PAC technique in the context of several examples of these applications and I comment on the historical evolution of this spectroscopy.

Hyperfine Interactions

The field of hyperfine interactions encompasses spectroscopic techniques that use the electric and magnetic nuclear moments to measure the specific extranuclear environment of the nuclear moments. Examples of these techniques are nuclear-magnetic-resonance (NMR), nuclear-quadrupole-resonance (NQR), electron-paramagnetic-resonance (EPA), muon-spin-rotation (MSR), Mössbauer-effect (ME), and perturbed-angular-correlation (PAC) spectroscopies. Each of these techniques is well-suited to certain types of measurements but useless for others. For example, NMR spectroscopy can be particularly useful for measuring chemical shifts associated with nuclei of atoms that are major constituents of crystalline solids. However, nuclear electricquadrupole interactions associated with some NMR-active nuclei are not only difficult to measure but they often obscure much of the chemical-shift information by producing spectral-line broadening. PAC spectroscopy can be used to accurately measure the nuclear electric-quadrupole interactions at the sites of nuclei of atoms that are trace dopants in crystals. But the PAC technique is insensitive to the effects of local charge distributions that produce the NMR chemical shifts. ME spectroscopy can be used to measure both of these effects as well as nuclear magnetic-dipole interactions. However, ME measurements are often only practical on crystals that have one of several elements as a major constituent, that is, either Fe or Sn. In addition, the ME sensitivity depends on temperature, and the NMR and EPR sensitivities also depend on temperature. However, the PAC measurement is independent of temperature, which can be a great advantage for studying phenomena such as phase transitions.
Smart, Very Smart, and Intelligent Materials
Authors: Newnham Robert E.
Published: August 2016

One of the qualities that distinguishes living systems from inanimate matter is the ability to adapt to changes in the environment. Smart materials have the ability to perform both sensing and actuating functions and are, therefore, capable of imitating this rudimentary aspect of life. Poled piezoelectric ceramics, for instance, are capable of acting as both sensor and actuator. External forces are detected through the direct piezoelectric effect, and a response is elicited through the converse piezoelectric effect, in which a voltage of suitable phase, frequency, and amplitude is applied to the same ceramic.

In this special issue, emphasis is placed on actuators, with articles on piezoelectric, electrostrictive, magnetostrictive, and shape memory materials. This is not to say that sensor materials are any less important; it is simply a matter of space. Optical fiber sensors, chemical sensors, thermistors, micromachined semiconductors, and other smart materials deserve special issues of their own.

Smart materials can be conveniently subdivided into passively smart materials that respond to external change without assistance, and actively smart materials that utilize a feedback loop enabling them to both recognize the change and initiate an appropriate response through an actuator circuit.

Zinc oxide varistors are passively smart materials capable of self-protection against high voltage breakdown. When struck by lightning, the ceramic varistor loses most of its electrical resistance, and the current is bypassed to ground. The resistance change is reversible, and acts as a standby protection phenomenon.
Sensors, Actuators, and Smart Materials
Authors: Trolier-McKinstry S. , Newnham R.E.
Published: August 2016

The field of electronic ceramics includes components as diverse as Mn-Zn ferrites, lead zirconate titanate transducers, ZnO varistors, and Al2O3 or cordierite-based packages for integrated circuits. An overview of electroceramics is given in Figure 1, which depicts schematically the types of electronic and ionic phenomena of interest. Many of the materials pictured utilize some bulk property of the ceramic, such as the presence of ferroelectric of ferrimagnetic dipoles, electronic or ionic conductivity, or a phase transition to provide a useful function. In other materials, extraordinary responses can be engineered by suitably tailoring the thickness and properties of a grain boundary phase. Varistors, barrier layer capacitors, and PTC thermistors, for example, all rely on the preparation of semiconducting grains and insulating grain boundaries to create properties that cannot be found in single crystals. In a similar way, some of the porous ceramics utilized in humidity sensors rely on surface properties rather than on a bulk response to detect changes in the ambient humidity (Kulwicki, 1992). Finally, in materials for insulators or substrates, all of the otherwise interesting phenomena must be eliminated. With the exception of the last category, all of the phenomena depicted in Figure 1 can be utilized in ceramic sensors. While sensing and actuating materials are currently a fraction of the overall multibillion-dollar electroceramics market, the percentage is expected to grow as more and more devices are made “smart.”

As discussed in the introduction to this issue, smart materials are capable of sensing a change in the environment and responding in a useful way.
A Concept of a “Virtual Production Line” Produced by Integrating Databases and Models of Materials
Authors: Iwata Shuichi
Published: August 2016

One of the requirements for an intelligent system is to construct a virtual reality in the computer. For materials development, the “reality” is a laboratory or a production line used to improve some aspect of a material by changing its composition, processing parameters, service conditions, etc. In the case of information in libraries, the reality is a search that uses a thesaurus and bibliographic (fact) databases. The greatest barrier faced by users of materials information is that of accessing necessary information through both a librarian's view and a scientific/technological expert's view. One of the objectives of a virtual production line is to reduce this barrier through user-friendly interfaces.

In designing materials, two typical approaches are combined to solve a given problem. The first is a top-down approach, in which a number of requirements are resolved to a set of possible and practical solutions for satisfying these requirements to a certain level. Almost all alloy development has followed such an approach. The second approach is a bottom-up approach, where different materials properties are described on the basis of underlying theories, preferably using first principles and fundamental data. But the vast number of possible materials makes the bottom-up approach unrealistic on its own. Instead, semi-empirical approaches are needed to bridge the gap between ad hoc data sets for practical applications and results produced by the bottom-up approach using fundamental data and first-principle calculations.
Microstructural Aspects of Materials for Nondestructive Long-Pulse High-Field Magnets
Authors: Embury J.D. , Hill Mary Ann , Spitzig W.A. , Sakai Y.
Published: August 2016

The development of high-field magnets for pulsed-field applications is the subject of considerable research activity throughout the world. Induced field strengths in excess of 30 T can be produced only as pulses generated by the discharge of energy, e.g., from a capacitor bank into a resistive solenoid. A variety of electromagnetic design issues relate to the pulse duration, field strength, and volume of the coil; however, from the viewpoint of materials selection and coil design, there are two salient property requirements: (1) high electrical conductivity to minimize the temperature rise due to the flow of current in the coil, and (2) high mechanical strength to resist the Lorentz forces exerted during the pulse. Such forces can result in catastrophic failure, as illustrated in Figure 1, because the coil is, in essence, stressed in the manner of an internally pressured cylindrical vessel. At lower stresses, plastic distortion of the coil is observed.
Implications of Amalgam and Ceramic Degradation in the Oral Environment
Authors: Anusavice Kenneth J. , Söderholm Karl-Johan , Grossman David G.
Published: August 2016

Recent breakthroughs in materials science and technology have led to improved dental restorative ceramics, metals, and resin-based composites. These breakthroughs have been most important since one of the major controversies during this period has centered on allegations of the physiological risks of mercury released from amalgam restorations. Dental amalgams have been used in the United States since 1832, yet not a single well-documented case of dental patient toxicity to mercury from amalgam restorations has been reported in the scientific literature.

A particularly extreme position has been adopted by the Swedish government, which has proposed the progressive elimination of amalgam as a dental restorative material by 1997. Among the materials that have been considered as the most biocompatible alternative to amalgam are dental ceramics. New ceramic products and technologies have gained considerable acceptance in Sweden even though their safety and efficacy have not been fully established.

Although dental ceramics constitute a much more costly alternative than some other materials, they offer the advantages of esthetics, inertness, durability, low thermal conductivity, and low diffusivity, as compared with amalgams. Although ceramics are generally considered to be inert in the oral cavity, there are certain phenomena associated with their use that may cause significant surface degradation of these materials and subsequent physiological side effects.
Overview of Cast Multicrystalline Silicon Solar Cells
Authors: Watanabe Hiroyuki
Published: August 2016

Worldwide environmental problems such as the greenhouse effect and acid rain have been caused by the human race's continuous reliance on the combustion of petroleum for fuel.

Solar energy, which is clean and practically unlimited, is expected to be a desirable alternate energy source to conventional power supplies, and demand for the photovoltaic system has increased throughout the world, especially in Europe and the United States.

Photovoltaic cells are probably the most effective method for capturing solar energy, since they are easy to use and are the most effective means of directly generating electricity.

Many kinds of solar cells have been developed in past years, especially since the first oil crisis in 1973. Among them, solar cells from cast multicrystalline silicon (also refereed to as (cast) polycrystalline silicon or semicrystalline silicon) are considered to be one of the most promising types, capable of achieving both high efficiency and low cost.

In 1975, Wacker proposed a new manufacturing method for silicon substrates, using the casting method. Since then, many organizations have been involved in the research and development of multicrystalline ingots and solar cells using multicrystalline silicon substrates.

Multicrystalline silicon substrates contain many kinds of defects compared to single-crystal silicon substrates, so the efficiency of multicrystalline silicon solar cells has been inferior to that of single-crystal cells. Recent research on multicrystalline silicon solar cells has resulted in substantial improvements and in the demonstration of high-efficiency cells.
Recent Progress in Amorphous Silicon Solar Cells and Their Technologies
Authors: Hamakawa Y. , Ma W. , Okamoto H.
Published: August 2016

A big barrier impeding the expansion of large-scale power generation by photovoltaic (PV) systems was the high price of solar cell modules, which was more than $50/Wp (peak watts) by 1974. Therefore, cost reduction of solar cells is of prime importance. To achieve this objective, tremendous R&D efforts have been made over the past ten years in a wide variety of technical fields, from solar cell materials, cell structure, and mass production processes to photovoltaic systems. As a result, more than an order of magnitude in cost reduction has been achieved, and the module cost has come down to less than $5/Wp in a firm bid for the large-scale market. Two phases of technological innovation can be identified. The first innovation in progress is based on low-cost polycrystalline technologies applicable to well-developed single-crystalline silicon solar cell fabrication processes. The second remarkable innovation is a-Si:H (hydrogenated amorphous silicon) technology, which we will discuss.

We open our discussion with a brief overview of the present status of a-Si solar cell R&D efforts, with some new insights in device physics. Next, we discuss some new approaches and key technologies for improving solar cell efficiency with stabilized performance using new materials such as a-SiC:H (amorphous silicon carbide), μc-SiC:H (microcrystalline silicon carbide), and a-SiGe:H (amorphous silicon germanium). Also, the progress of conversion efficiency in various types of amorphous silicon solar cells is surveyed and summarized.
Nanocrystalline Thin-Film PV Cells
Authors: Grätzel Michael
Published: August 2016

In a conventional p-n junction photovoltaic cell, made, for example, from silicon, the semiconductor assumes two roles at the same time: It harvests the incident sunlight and conducts the charge carriers produced under light excitation. In order to function at a good efficiency, the photons have to be absorbed close to the p-n interface. Electron-hole pairs produced away from the junction must diffuse to the p-n contact where the local electrostatic field separates the charges. To avoid charge carrier recombination during the diffusion, the concentration of defects in the solid must be small. This imposes severe requirements on the purity of the semiconductor material, rendering solid-state devices of the conventional type expensive.

We have developed a new molecular photovoltaic system for solar light harvesting and conversion to electricity. It is based on the spectral sensitization of a thin ceramic membrane by suitable transition-metal complexes. The film consists of nanometersize colloidal titanium dioxide particles sintered together to allow for charge carrier transport. When derivatized with a suitable chromophore, these membranes yield extraordinary efficiencies for the conversion of incident photons into electric current, exceeding 90% for certain transition metal complexes within the wavelength range of their absorption band. In this article, we discuss the underlying physical principles of these astonishing findings. Exploiting this discovery, we have developed a new type of photovoltaic device whose overall light-to-electric-energy conversion yield is 12–15% in diffuse day-light and 10% under direct (AM1.5) solar irradiation.
Stochastic Modeling of Grain Structure Formation in Solidification Processes
Authors: Rappaz Michel , Gandin Charles-André
Published: August 2016

Besides the numerical tools which have been developed for solving the continuity equations in materials processing, the prediction of microstructures and defects in such processes is becoming an important step in assessing the quality, and ultimately the mechanical properties, of the final products. Because the typical length scales associated with the process and with the microstructure differ widely (typically a factor of 104), special techniques have to be used when coupling the macroscopic and microscopic levels. This contribution will briefly present some of the modeling tools recently developed for solidification. The trend is now to replace deterministic models used over the last 20 years by stochastic approaches which directly generate computed micrographs. Among those, Monte Carlo techniques originally developed for the grain growth in solids were adapted to the solidification of alloys, and cellular automata models specifically take into account the dendrite growth mechanisms.
Long Wavelength Laser Diode Reliability and Lattice Imperfections
Authors: Chu S.N.G.
Published: August 2016

Reliable long wavelength laser diodes emitting in the 1.30−1.55 μm regime with an expected operating life greater than 25 years for optical fiber communication applications are now fabricated using a combined heavy screening and accelerated aging process. For a given laser structure, the reliability of the devices depends intricately on both the crystalline perfection of the complex buried-heteroepitaxial semiconductor structures as well as the qualities of structures external to the semiconductor, such as electrical contact, dielectric coating, bonding, and packaging structures external to the semiconductor. The former (crystalline perfection) determines the intrinsic property of the laser, while the latter qualities (electrical contact, etc.) determine the contact resistance, parasitic capacitance, heating, and mechanical and thermal stresses to which a packaged laser device is subjected during operation. Since device heating and external stresses both degrade laser performance and accelerate permanent damage—through processes such as crystalline defect formation, current leakage path development, and doping profile redistribution—a reliable laser device, therefore, requires both a perfect semiconductor structure and also a high-quality external structure. Realistically, however, this may not be easily achievable, especially when a development program is limited in resource and time. Proper choice of the critical material issues in a development process becomes crucial to the success of the program.
Unit Operations for Improving the Bulk Properties of Recycled Fiber
Authors: Silveri Luigi
Published: August 2016

Over the past few years, recycling within the pulp and paper industry has been brought sharply into focus. The primary motivating factors for this have been the crisis in the landfills, of which paper is the largest component, the ensuing legislation, greater public awareness of recycling as an issue, and a desire to recycle more.

In reality, recycling has always been a significant part of papermaking. On a worldwide basis, about one third of the fiber supply is recycled fiber (Table I). A further significant portion of the fiber supply comes from the use of residues from sawmills and other woodworking operations; thus, in the strictest sense, the recycled content is even higher.

The amount of recycled paper that is used varies from 45–50% for Japan and Continental Europe, which have limited forest resources, to about 10% for Canada and Scandinavia, which are rich in forest resources.

In the United States, the recycle rate is about 26% and increasing. Estimates of future usage vary, but the industry as a whole is moving toward a recycle rate close to about 40% or higher by the end of the decade.

It is important to understand the effect that recycling has on fiber properties and also the effect that adding recycled pulp can have on the final sheet properties. To arrive at this, it is worthwhile to review the main aspects of the recycling process and how the process affects pulp properties.
Chemical Products from Lignocellulosics
Authors: Glasser Wolfgang G.
Published: August 2016

Lignocellulosics represent that mass of organic matter produced by land-growing plants in the form of trees, shrubs, and agricultural crops. Lignocellulosics are renewable, and they sustain living conditions on our planet by recycling carbon dioxide to oxygen. Lignocellulosics serve the planet as a carbon sink. Chlorophyll is the essential catalyst and sunlight the necessary energy source that drive this carbon dioxide reduction to an organic mass that varies little from the carbon-to-oxygen ratio of carbon monoxide.

There is, however, no distinct “lignocellulose” molecule. Instead, nature has found it necessary to formulate a multiphase material consisting of cellulose, hemicelluloses, and lignin. The composition of this multiphase material can be likened to a fiber-reinforced organic glass where cellulose serves as lightweight fiber, lignin serves as a continuous (glassy) matrix, and hemicelluloses serve as coupling agents. The overall composition suggests that there is 35–45% cellulose, 25–35% hemicelluloses, 20–25% lignin, and various minor constituents.

In chemical terms, cellulose is a linear homopolysaccharide with a high degree of crystallinity. It consists of 1,4-β-linked D-glucopyranose units connected in syndiotactic fashion (on alternating sides of the main chain). Cellulose molecules in nature occur with molecular weights exceeding 2 million. Hemicelluloses, by contrast, are branched heterosaccharides of lesser molecular weight. They rarely exceed 20,000 daltons. Hemicelluloses are either rich in glucomannan chains (softwoods), or they consist primarily of branched xylans (hardwoods and annual crops). The chemical composition of hemicelluloses is extraordinarily similar to cellulose (i.e., polyanhydro-pyranoside), but their morphological structure is vastly different.
Bandgap and Defect Engineering for Semiconductor Holographic Materials: Photorefractive Quantum Wells and Thin Films
Authors: Nolte David , Melloch Michael
Published: August 2016

Bandgap engineering of thin semiconductor layers and defect engineering combine to form photorefractive (PR) quantum well structures. PR quantum wells are semi-insulating thin films useful for dynamic holography and other coherent and incoherent optical applications. As materials for thin-film dynamic holography, they have high nonlinear-optical sensitivity and high speed.

The PR effect translates a spatially varying irradiance, from the interference of two or more coherent light beams, into a refractive index grating. The multiple-step PR process begins with photoexcitation of charge carriers, followed by transport and trapping of charge at deep defects. The trapped space-charge generates electric fields that alter the refractive index of the material through the electrooptic effect. The same laser beams that generate the gratings diffract from the gratings, leading to a rich variety of multiple-beam effects, such as two-wave and four-wave mixing.

Because the PR process involves several distinct physical parameters, such as carrier mobility and electrooptic coefficients, optimized performance requires a coincidence of favorable properties in a single material. Rather than relying on coincidence, bandgap engineering of multiple layers of semiconductors provides a way to individually tune the separate material pa rameters. Likewise, defect engineering in semiconductors provides flexibility in the choice of defects, their concentrations, and degree of compensation. Bandgap and defect engineering combined make custom designed PR materials possible.
The Future of the Materials Initiative, National Laboratories, and Technology Policy
Authors: Bromley D. Allan
Published: August 2016

Following D. Allan Bromley's plenary lecture at the 1991 MRS Fall Meeting, the MRS Bulletin conducted a telephone interview with him on December 27. The following is an edited version of that interview. Bromley is Assistant to the President for Science and Technology and also Director of the Office of Science and Technology Policy (OSTP). His plenary address is published in the Bulletin's Material Matters column this month.

Bulletin: You have obviously managed to sustain excellent relations with the administration while also being an effective spokesperson for science. During your term in office, both the FCCSET (Federal Coordinating Council for Science, Engineering, and Technology) and PCAST (President's Council of Advisers on Science and Technology) committees have been revitalized. Could you briefly describe the impact of their increased effectiveness?

Bromley: I think the best way to do that is to indicate what they're doing now. The FCCSET was established in 1976 at the same time that the OSTP was put in place through joint action of the administration and Congress. The charge to the Council was that of integrating and coordinating issues that transcend the boundaries of any single agency, so it focused on interdisciplinary and multi-agency programs. In the early days, however, it did not function as had been intended because the members were at too low a political level. Decisions reached in the Council could, later in the budget process, be disowned by more senior people in the agencies. Having recognized that problem and with strong support from President Bush, I was able to reconstitute the FCCSET so that its members now consist of secretaries or deputy secretaries from all the relevant agencies, as well as heads of independent agencies like EPA, NSF, and NASA.
Pulsed Laser Deposition History and Laser-Target Interactions
Authors: Cheung Jeff , Horwitz Jim
Published: August 2016

The laser, as a source of “pure” energy in the form of monochromatic and coherent photons, is enjoying ever increasing popularity in diverse and broad applications from drilling micron-sized holes on semiconductor devices to guidance systems used in drilling a mammoth tunnel under the English Channel. In many areas such as metallurgy, medical technology, and the electronics industry, it has become an irreplaceable tool.

Like many other discoveries, the various applications of the laser were not initially defined but were consequences of natural evolution led by theoretical studies. Shortly after the demonstration of the first laser, the most intensely studied theoretical topics dealt with laser beam-solid interactions. Experiments were undertaken to verify different theoretical models for this process. Later, these experiments became the pillars of many applications. Figure 1 illustrates the history of laser development from its initial discovery to practical applications. In this tree of evolution, Pulsed Laser Deposition (PLD) is only a small branch. It remained relatively obscure for a long time. Only in the last few years has his branch started to blossom and bear fruits in thin film deposition.

Conceptually and experimentally, PLD is extremely simple, probably the simplest among all thin film growth techniques. Figure 2 shows a schematic diagram of this technique. It uses pulsed laser radiation to vaporize materials and to deposit thin films in a vacuum chamber. However, the beam-solid interaction that leads to evaporation/ablation is a very complex physical phenomenon. The theoretical description of the mechanism is multidisciplinary and combines equilibrium and nonequilibrium processes. The impact of a laser beam on the surface of a solid material, electromagnetic energy is converted first into electronic excitation and then into thermal, chemical, and even mechanical energy to cause evaporation, ablation, excitation, and plasma formation.
Novel Materials Applications of Pulsed Laser Deposition
Authors: Cotell Catherine M. , Grabowski Kenneth S.
Published: August 2016

The successful use of pulsed laser deposition (PLD) to fabricate thin film superconductors has generated interest in using the technique to deposit thin films of other materials. The compositional fidelity between laser target and deposited film and the ability to deposit films in reactive gas environments make the PLD process particularly well suited to the deposition of complex multicomponent materials. Cheung and Sankur recently provided an excellent review of the PLD field, including a table of over 100 elements, inorganic and organic compounds, and

superlattices that have been laser evaporated. Over 75 of these materials were deposited as thin films.

The goal of this article is to provide an introduction to some of the newer applications of PLD for thin film fabrication. Four classes of materials are highlighted: ferroelectrics, bioceramics, ferrites, and tribological materials. Ferroelectric materials are structurally related to the high-temperature superconducting oxides and therefore are a direct extension of the recent superconducting oxide work. Bioceramics are dissimilar in structure and application to both ferroelectrics and superconducting oxides, but they are complex multicomponent oxides and, therefore, benefit from the use of PLD. Ferrites, also complex, multicomponent oxides, represent another exciting, but only lightly explored opportunity for PLD. In contrast, tribological materials are typically neither complex nor multicomponent. Nevertheless, interesting structures and properties have been produced by PLD. A few of the more important ones will be discussed. These different types of materials demonstrate the diversity of capabilities offered by PLD.
Materials Manufacturing
Authors: Eagar Thomas W.
Published: August 2016

The behavior of successful manufacturing companies has changed in response to the accelerating pace of technological development in recent years. Manufacturing firms are under greater pressure than ever to bring new products and processes to market rapidly, with lower costs and higher quality than achieved in the past. In addition, the establishment of a global economy no longer dominated solely by the United States has required firms to expand their outlooks and horizons. Successful firms must take a multinational view, understanding and serving local customer needs while maintaining the efficiency of a global enterprise. This requires greater flexibility in manufacturing and distributing new products.

As the business environment for materials manufacturing changes, so too does our measure of materials performance. Traditionally, materials scientists and engineers have emphasized processing, structure and properties, and the way they come together to produce performance of a product in a given application. However, as shown by Figure 1, there are several additional dimensions to performance. In particular, successful commercial performance depends not only on the physical properties of the material but also on our ability to shape it into a useful object in an economical and timely manner. Without shape, the product cannot serve its intended function, and without economical production, the product's usefulness is limited to fewer, higher value applications. Achieving more rapid and more consistent commercial success from advanced materials requires emphasizing not only the process by which the material is made but the process by which the material achieves its geometry and function, while at the same time maintaining the ability to bring these materials to market rapidly at an economical price. Indeed, the cost delay in commercializing a new material can be the key to success or failure.
Materials in Electronic Manufacturing: Electronic Packaging
Authors: Pfahl Robert C.
Published: August 2016

Electronic packaging involves using an appropriate combination of conductive and dielectric materials to electrically interconnect and mechanically support electronic components in a reliable and cost-effective manner. Since the invention of the integrated circuit in 1959 and mass wave-soldering in 1958, the vast majority of electronic packaging has involved a planar substrate to which semiconductor devices in protective packages are attached by melting eutectic solder. The planar substrates or printed circuit boards (PCBs) were invented in 1940, but their widespread implementation was limited until the invention of mass soldering. PCBs use conventional epoxy-glass dielectric material with mass patterned conductive traces of copper, but alternative materials have been used for either enhanced electrical performance or lower product cost.
Aqueous Surface Chemistry and Corrosion of Minerals
Authors: Casey W.H. , Eggleston C. , Johnsson P.A. , Westrich H.R. , Hochella M.F.
Published: August 2016

Nature is generous with complexity. The number of thermodynamic variables necessary to describe even simple stream chemistry can easily number to a hundred. Nevertheless, research on Earth materials remains exciting because of the vastness of geologic time and the huge scale of global processes. For example, even simple ion-exchange experiments have profound implications when considered in the context of global cycling of elements. Sodium exchange from seawater onto the 1.83 × 1016 g of river-borne clays removes 20–30% of the yearly sodium addition to the ocean. Research on Earth materials, although complex, is rewarding through the scale of the potential result.

The surface chemistry of minerals is important for understanding natural mineral transformations and also because surface reactions help control the migration and degradation rates of pollutants in natural waters. These pollutants range from organic herbicides and pesticides, which leak past reactive soil horizons into groundwaters, to acid rain and heavy-metal leaching from mine tailings, sewage sludge, or coal fly ash. The importance of characterizing mineral surface chemistry is clear when one considers that 0.5 to 2% of usable groundwater in the United States is thought to be contaminated.

This article reviews some simple surface chemistry of oxide and silicate minerals in water. We focus on the kinetics of mineral corrosion because this subject is interesting to both geochemists and materials scientists. The surface properties that make some solid oxides relatively inert to acid corrosion, for example, are also manifested in the rates of natural mineral weathering.
Materials Science of the Earth's Deep Interior
Authors: Navrotsky A. , Weidner D.J. , Liebermann R.C. , Prewitt C.T.
Published: August 2016

Man has walked on the moon, sent probes to or near the surfaces of Mars and Venus, and dispatched vehicles to fly near comets, asteroids, and the outer planets and their moons. In contrast, a journey to the center of the Earth remains as unattainable and fictional as in Jules Verne's day. We know the interior of our planet from several types of evidence: direct sampling of rock brought to the surface by geologic process from depths no greater than 200 km, remote sensing especially by seismology (the study of natural or anthropogenic sound waves passing through the Earth), inferences from the chemistry of meteorites and from other geochemical arguments, and laboratory and computational simulations of the conditions at depth. The laboratory study of Earth materials at high temperatures and pressures is the subject of this review. In a sense, the basic question of deep earth geophysics is a peculiar sort of inverse problem in materials science; rather than determining the properties of a given material, one seeks to find materials, under constraints of natural elemental abundances, which have properties consistent with seismological and other geophysical observations.

What are the “hard facts” about planet Earth as a material system? Its radius and mass are well constrained, as are pressure and density as a function of depth (see Figure 1). Its vertical temperature distribution is less well known, but it is clear that the interior is hot, with temperatures in the mantle reaching perhaps 3000 K and in the core perhaps 6000–7000 K.
Response of a Material: From Single Ions to Experimental Times and Fluences
Authors: Brown W.L. , Ourmazd A.
Published: August 2016

The preceding article by Davies treated the behavior of single ions as they slow down in a solid, colliding with atoms of the solid and often transferring enough energy to initiate atomic displacement cascades. For a 200 keV As ion with a speed ~108 cm/s and a range in Si of ~ 2 × 10−5 cm, the cascade is completed in less than 10−12 s. The small volume excited in the cascade relaxes over 15 decades or more in time in a series of increasingly deliberate steps. The experimental evidence for most of these decades is indirect. No probes with sufficient spatial and time resolution exist to examine the spatial and temporal evolution of collision cascades created by individual incident ions. The first few decades in time have been followed in metals by molecular dynamics (MD) calculations and also approximated by continuum theory. The results of MD calculations for 5 keV cascades in Ni are shown in Figure 1. The behavior is in-terpreted as indicative of local “melting,” consistent with the concept of a “thermal spike” in the material. Extension of MD calculations to times of nanoseconds and longer is still prohibitively expensive in computer time, and application to covalently bonded systems, where the interatomic forces are much more complex than in metals, has not yet been reported.

As Davies has noted, the atoms of the cascade rapidly lose their high vibrational excitation to atoms in the surrounding material, and in only a few picoseconds the system cools. This constitutes a very rapid thermal quench—slower only than the quench associated with deposition of individual atoms (or small atomic clusters) on a cold substrate. The quench may produce a small volume of material with a different phase than its surrounding. For example, a small volume of “hot” Si atoms may be highly disordered and may quench to produce a small amorphous Si region in a crystalline Si matrix.
Ion-Assisted Surface Processing of Electronic Materials
Authors: Picraux S.T. , Chason E. , Mayer T.M.
Published: August 2016

Why are low-energy ions relevant to the surface processing of electronic materials? The answer lies in the overriding trend of miniaturization in microelectronics. The achievement of these feats in ultrasmall architecture has required surface processing capabilities that allow layer addition and removal with incredible precision. The resulting benefits of greater capacity and speed at a plummeting cost per function are near legendary.

The ability of low-energy ions to enhance the precision of surface etching, cleaning, and deposition/growth processes (Figure 1) provides one basis for the interest in ion-assisted processes. Low-energy ions are used, for example, to enhance the sharpness of side walls in plasma etching and to improve step coverage by metal layers in sputter deposition. Emerging optoelectronic applications such as forming ridges for wave-guides and ultrasmooth vertical surfaces for lasers further extend piesent requirements, and low-energy ions again provide one tool to help in this area of ultraprecise materials control. Trends associated with the decreased feature size include the movement from wet chemical processing to dry processing, the continuing need for reductions in defect densities, and the drive toward reduced temperatures and times in process steps.

How do the above trends focus interest on studies of low-energy ion-assisted processes? In current applications, these trends are driving the need for increased atomic-level understanding of the ion-enhancement mechanisms, for example, in reactive ion etching to minimize defect production and enhance surface chemical reactions.
High-Temperature Superconductors 1992: Bringing the Materials Under Control
Authors: Larbalestier David C.
Published: August 2016

As I write, it is about six years since Bednorz and Müller sent off their amazing paper reporting superconductivity at about 30 K for a mixed phase sample in the La-Ba-Cu-O system. After an incubation period of a few months, during which only a handful of people paid any attention, the community suddenly woke up (literally overnight) to the realization that the discovery was genuine, when Kitazawa (Tokyo University) and Chu (University of Houston) confirmed the result at the 1986 Fall Meeting of the Materials Research Society. No need to repeat the stories of the next frantic couple of years: the Nobel Prize for the discovery, the tantalizing prospect of another prize for understanding the superconducting mechanism, the almost limitless prospects of new superconducting technologies which appeared in article after article, designed not just for scientists and engineers, but for the general public at large. Now, six years later, perhaps some perspective on the high-temperature superconductivity discoveries is possible.

At the fundamental science level, the discoveries have indeed been spectacular. Many layered structures based on the CuO2 sheets have been discovered. The first advance was the Tokyo group's discovery of the structure and composition of the superconducting phase La2-xBaxCuO4-δ, where x is optimally about 0.15. Then came the Alabama/Houston discovery of superconductivity at 92 K in YBa2Cu3O7-δ, followed rather quickly by the discoveries of 110 K superconductivity in the Bi-Sr-Ca-Cu-O (BSCCO) system at Tsukuba and then 125 K in the Tl-Ba-Ca-Cu-O (TBCCO) system by the Arkansas group.
Control of Composition and Microstructure in High-Temperature Superconductors at the Atomic Level by Molecular Beam Epitaxy
Authors: Eckstein J.N. , Bozovic I. , Klausmeier-Brown M.E. , Virshup G.F. , Ralls K.S.
Published: August 2016

The idea of engineering the detailed microstructure of materials by controlling the chemical synthesis process at an atomic level is particularly interesting for high-temperature superconductors (HTS) and many other oxide compounds. The prospect of integrating such materials as superconductors, ferroelectrics, and compounds with interesting magnetic properties into samples with atomic precision and perfect heterojunctions would seem to open the door to many novel possibilities. These materials, while complex, fundamentally have planar crystalline structure, and thus allow for the possibility of molecular and even atomic layer engineering. The “zoology” of phases that has been discovered in the study of naturally occurring HTS compounds is by now quite complex and illustrates this theme. While CuO2 planes are universally important for superconductivity, there is much more flexibility and variety in the other kinds of layers that act to complete the crystal structure. Examples of such “other” layers include alkaline earth oxides like SrO and BaO, copper oxide “chain” layers and rock-salt-like (BiO)2 bilayers, to name a few important ones. Moreover, families of very similar polytype phases have also been identified, in which members of each family differ principally in the number of copper oxygen planes within each formula unit.

This great richness of structure sets a pattern that invites the imagination to devise new materials and heterostructures and has motivated the development of synthesis techniques that control growth at the level of the submolecular—atomic layers. For instance, with adequate control of the growth process, highly metastable phases, such as Bi2Sr2Ca7Cu8O20, can be synthesized and their properties measured.
Critical Current Properties and Microstructures of Ag-Sheathed Bi-Based Superconducting Wires
Authors: Kato T. , Hikata T. , Ueyama M. , Sato K. , Iwasa Y.
Published: August 2016

Since the first report of superconductivity in the Bi-Sr-Ca-Cu-O (BSCCO) system by Maeda et al., an enormous quantity of material work has been reported on the Bi system. The Bi-2223 phase exhibits a zero-resistivity temperature of around 110 K and this is the highest critical temperature outside the 125 K critical temperature found in the Tl-Ba-Ca-Cu-O system. The layered BSCCO phases cleave easily, making it possible to align grains by a deformation process.

The powder-in-tube method is one of the fabrication processes that permits grain alignment and the achievement of high critical current density. This tendency is particularly strong for the 2223-BSCCO phase.

In this paper, we report on the relation between the critical current density (Jc) and the microstructure in silver-sheathed Bi-Pb-Sr-Ca-Cu-0 (2223) wires produced by the powder-in-tube method.
Old and New World Spanish Majolica Technology
Authors: Olin Jacqueline S. , Myers J. Emlen
Published: August 2016

Majolica pottery is an earthenware covered with lead glaze opacified and whitened by adding a small percentage of tin oxide. The technology of majolica production, a Muslim contribution, was introduced into Spain and then diffused to the Western Hemisphere in the course of colonization very soon after the Spanish arrival in Mexico in 1521. (See Table I for Majolica production sources and excavation sites.)

In the 1980s there were two references on the organization of majolica production in both Spain and the New World. Descriptions of the layouts of the potters' workshops, of the sources of the clays, how the kilns were used, and how the glazes were made are taken from historical and ethnographic sources. These authors also discuss the interesting and important effect of the presence of Italian potters in both Seville and the New World. However, little has been written based on archaeologically excavated material from Seville, the main source of supply to the New World, or from known Puebia or Mexico City production.

In the 1970s a project involving neutron activation analysis of Spanish majolica ceramics was developed through the cooperative efforts of Malcolm Watkins and Richard Ahlborn of the National Museum of American History, Charles Fairbanks of the University of Florida, and Jacqueline Olin. Neutron activation analysis provides precise simultaneous determination of the concentrations of up to 35 elements. Two chemically distinct groups of ceramics were identified among sherds excavated at New World sites. They could be stylistically divided between Spanish and Mexican production with some important exceptions.
Quantitative Rutherford Backscattering from Thin Films
Authors: Chu W.K. , Langouche G.
Published: August 2016

Rutherford backscattering spectrometry (RBS) is probably one of the most frequently used techniques for quantitative analysis of composition, thickness, and depth profiles of thin solid films or solid samples near the surface region. It has evolved in the past few years from an obscure nuclear technique into a major materials characterization technique. This is primarily due to its simplicity, versatility, and the amount of information it can produce in a short time. Because of its quantitative feature, RBS analysis often serves as a standard for other techniques. The purpose of this article is to introduce the topic to a broad community of materials researchers. Readers who want a more rigorous treatment of the topic for utility purposes can refer to a monograph.

In the early 1960s, several of the low-energy atomic and nuclear physics laboratories started to use their accelerators to do research in solid-state physics. This activity opened up a fertile interdisciplinary area called ion-solid interaction, which impacts materials research significantly.
Scanning Probe Microscopy of Thin Films
Authors: Hues Steven M. , Colton Richard J. , Meyer Ernst , Güntherodt Hans-Joachim
Published: August 2016

Atomic force microscopy (AFM) was invented in 1986 by Binnig, Quate, and Gerber as “a new type of microscope capable of investigating surfaces of insulators on an atomic scale.” Stemming from developments in scanning tunneling microscopy (STM), it became possible to image insulators, organic and biological molecules, salts, glasses, and metal oxides — some under a variety of conditions, e.g., ambient pressure, in aqueous or cryogenic liquids, etc. In 1987, Mate and co-workers introduced a new application for AFM where atomic-scale frictional forces could be measured. Likewise, in 1989, Burnham and Colton used the AFM to measure the surface forces and nano-mechanical properties of materials. Today, there are many examples of using AFM as a high-resolution profilometer, surface force probe, and nanoindentor. Several new imaging techniques have been introduced; each depending on the type of force measured, e.g., magnetic, electrostatic, and capacitative. Because of the diverse nature of the field and instrumentation, the names “scanned probe microscopy” and “XFM” (where X stands for the force being measured, e.g., MFM is magnetic force microscopy) have been adopted.