bluuebunny/crossref_metadata_2025_split huggingface dataset:
Links of science & Technology
Authors: Leamy Harry J. , Wernick Jack H. 
Published: August 2016

We humans have employed and improved materials for millennia, but it required the Industrial Revolution of the last century to birth the systematic, science-based development of materials. During this time, effort expended in understanding the process-microstructure-properties relationships of materials conferred great economic and military advantage upon the successful. The introduction of machine power in this era created great leverage for improvements in the strength, ductility, corrosion resistance, formability, and similar properties of materials. Response to this opportunity led to the emergence of the materials profession. Stimulated by opportunity, materials scientists and engineers of the day met many of the challenges by first understanding and then controlling the composition and microstructure of materials. In the process, they defined the materials-engineering profession and left their names as a part of its vocabulary: Martens(ite), Bain(ite), Austen(ite), Schmid, Bessemer, Charpy, and Jomminy, to name a few. In fact the understanding and control of microstructure is the hallmark of materials science and engineering. Of course the ancient art of finding, mining, concentrating, and refining materials from the earth's crust does not apply to this definition since we wish to focus on the engineeringofmaterials.Five decades ago, a new chapter in the evolution of this profession began by the invention of the transistor. This invention and the development of integrated circuitry that followed from it spawned a new era of materials achievement, again stimulated by the enormous economic and performance gains available. In this arena however, the object of the game was to completely eliminate microstructure while doing away with impurities, save for a desired few, to levels previously unimagined. Today a material thus prepared is a blank slate upon which we can write the microstructure of an integrated circuit.
Defect-Mediated Rheology of Block Copolymers
Authors: Hudson Steven D. , Amundson Karl R. , Jeon Hong G. , Smith Steven D. 
Published: August 2016

Block copolymer melts with a near-symmetric composition can microphase-separate to form a lamellar morphology where unfavorable monomeric interactions are reduced by an antiparallel layering of the polymer chains (see Figure 2, discussed later). The symmetry of such a block copolymer is the same as for small-molecule, smectic-A liquid crystals, which also exhibit (parallel or antiparallel) layering. Because of their shared symmetry, their quasistatic mechanical properties are of the same form. To lowest order, the energy of distortion of the lamellar pattern can be expressed as a sum of a compressional/dilational and a bend energy (see, for example, Reference 2):where n is a unit vector normal to the layers, and ε and ∇ n are the layer dilational and bending strain, respectively. B and K are the corresponding moduli. These have been measured only recently for block copolymers. The ratio of these moduli yields a characteristic microscopic length:which is calculated to be a fraction of the layer spacing d0.Similarities are also found in the dynamic properties of polymeric and smallmolecule smectics. These similarities are found at low strain rate and amplitude where the rheological response is controlled by their similar layered structures and associated defects. During either steady or dynamic shear, certain defect and domain motions are induced such that a steady-state alignment of the director has been observed. In this report, we discuss defect structure and how the much more viscous nature of these polymeric layered materials influences the distribution and relative population of each defect type. We also discuss how these defects can control material stress-relaxation behavior.
Polymer Adsorption
Authors: Chakraborty Arup K. , Tirrell Matthew 
Published: August 2016

Long polymer chains adsorbed onto solid surfaces are important in a wide range of applications and are relevant to many issues in biology and medicine. Adsorbed polymer layers used widely in the stabilization of colloidal suspensions, for example, are essential to the formulation of paints, coatings, printing inks, drilling needs, and ceramics processing. Adsorbed polymer layers also play a crucial role in many tribological applications such as boundary lubricants.The interfacial behavior of biological macromolecules (such as proteins) plays an important role in biomedical applications as well as in the function of living organisms. The development of biocompatible solid materials that can be used safely and efficiently in vascular and joint prostheses, catheters, artificial-heart valves and whole hearts, cardiac-arrest devices, and hemodialysis cartridges is critically important. In some instances, the adsorption of biological macromolecules onto the artificial material can lead to deleterious effects. For example, many vascular grafts and catheters fail because of thrombotic occlusion initiated by protein adsorption. Protein adsorption is also the initial subprocess that leads to plaque formation in teeth and the fouling of contact lenses. Given the central role of protein adsorption in many physiological systems, and the great benefits that could be derived by designing materials that do not adsorb biological macromolecules, understanding the interfacial behavior of biological polymers is important.The ultimate goal of research in polymer adsorption is to facilitate the manipulation of the properties of adsorbed polymer layers (or polymer-solid interfaces) so that materials with required properties can be fabricated. To take steps toward this goal, understanding how the nature of the polymer, the substrate, and other prevailing conditions (such as the type of solvent) affect the macroscopic properties of the interface is crucial.
Polymer Surface Dynamics
Authors: Granick Steve 
Published: August 2016

A major surge of activity is underway to understand the dynamics of polymer chains at interfaces. This stands in contrast to the situation a generation ago when much of polymer-materials research revolved around understanding dynamics in the bulk (isotropic) state. Building in part on earlier studies that had been somewhat neglected, striking new findings have been obtained. The new methods and equipment include surface-specific spectroscopies; advanced, in situ time-resolved methods to determine surface structure and composition; and the surface-forces apparatus for measuring adhesion and interfacial rheology. Also, older methods (such as contact angle) have been revitalizated and applied to new problems. Theoretical calculations and molecular-dynamics simulations are also emerging.Appreciation is growing that scientific understanding is possible of these systems that are so complex and, often, so far from equilibrium. Polymer surfaces are becoming recognized as an area with many opportunities to do exciting and useful surface science, particularly regarding kinetics, diffusion, surface chemistry, and other rate-dependent processes.The engineering significance is that while polymers and plastics-based applications are rooted in our economic life, too often the technologies and formulations are empirically derived. One tends to take plastics and their communication with adjoining materials for granted. A molecular understanding is needed so that better design can emerge by rational extension.During the course of these new activities, the community of polymer science has rubbed shoulders with and has thereby become increasingly integrated with other disciplines-colloid science, surface science, biomedical science, and microelectronics, to cite a few examples. When dealing with interfaces, one's parochial materials interests quickly become generalized.
Ion-Beam Analysis of Polymer Surfaces and Interfaces
Authors: Kramer Edward J. 
Published: August 2016

Ion-beam analysis of chemical composition as a function of depth is by now well-established for inorganic materials and is an important method of investigating growth of thin films. It has been applied to polymers much more recently, perhaps because fairly obvious problems with radiation damage discouraged workers in this field initially. Ion-beam analysis has developed, however, into a analytical tool that complements other methods, such as x-ray photoelectron spectroscopy and neutron reflection, very well. The purpose of this short article is to give the reader an introduction to its current uses in polymers.The ion beams of ion-beam analysis are typically highly energetic (1–5 MeV) beams of 4He++. While other beams are used, for example, 3He and 15N, alpha particle beams are used in the vast majority of experiments reported in the literature. Two major categories of experiments are carried out with such beams. Rutherford backscattering (RBS) spectrometry to detect heavy elements in the polymer and forward recoil spectrometry (FRES) (also known as elastic recoil detection) to detect the isotopes hydrogen and deuterium. The basic principles for each method are similar.
Substrate Engineering With Plastic Buffer Layers
Authors: Schowalter Leo J. 
Published: August 2016

The advantage that epitaxy offers the electronics and optoelectronics industries is that it allows the possibility of producing precisely controlled layers of very high crystal quality. Heteroepitaxy of different materials offers the promise of tailoring device layers in clever ways that nature did not intend. However unlike fruit juices, nature has made it difficult to epitaxially combine different materials. As the preceding articles have clearly pointed out, it is very difficult to obtain smooth epitaxial layers that are free both of defects and strain when there is a lattice mismatch between the layers and their substrates.As already discussed in this issue, a uniform network of dislocations at the interface between a flat, uniform epitaxial layer and its substrate can completely relieve strain in the majority of the epitaxial layer. This would be a satisfactory situation for many devices so long as the active region of the device could be kept away from the interface. The problem is how to introduce the dislocations in an appropriate way. When an epitaxial layer has a larger lattice parameter than the underlying substrate, a misfit dislocation running along the interface represents a plane of atoms that has been removed from the epitaxial layer. (One would insert a plane of atoms if the epitaxial lattice parameter was smaller. For simplicity however we will continue to assume that the epitaxial layer has a larger lattice parameter.) It is not possible for a whole half plane of atoms, bounded by the dislocation at the interface and the substrate edges along the two sides, to be removed at once. The boundary between where the extra plane of atoms has been removed and where the epitaxial layer has not relaxed yet will represent a threading dislocation. This threading dislocation would continue to move as the size of the misfit dislocation along the interface grows. Ideally it moves all the way out to the substrate edge and vanishes there while the misfit dislocation along the interface would end up extending from one side of the substrate to the other. However other dislocations and other kinds of defects can effectively pin the threading dislocation resulting in an epitaxial layer with many threading dislocations. Unfortunately these threading dislocations are generally detrimental to most kinds of devices. It is precisely this high density of threading dislocations that limits applications of many heteroepitaxial layers.
Applications of Intermetallic Compounds
Authors: Westbrook J.H. 
Published: August 2016

Just what is an intermetallic compound? An intermetallic compound is a true compound of two or more metals that has a distinctive structure in which the metallic constituents are in relatively fixed abundance ratios and are usually ordered on two or more sublattices, each with its own distinct population of atoms. Often substantial or complete disorder may be obtained as a result of a low ordering energy or the intervention of some external agency—for example, extreme cooling rates or radiation. Deviations from precise stoichiometry are common on one or both sides of the nominal atomic ratio, necessitating some misordering and/or the introduction of vacancies. Usually metal-metalloid compounds such as silicides, arsenides, or tellurides are also included in the category since the phenomenology of most such compounds is similar to that of metal-metal compounds. More than 25,000 distinct intermetallics are now known.To many, intermetallic compounds (IMCs) are classed as “exotics” or “advanced materials.” Such categorization should apply only to the recent interest in their potential use as monolithic high-temperature structural materials. Actually IMCs have been used for thousands of years in an astonishing range of applications exploiting not only their mechanical properties but their chemical, electrical, magnetic, optical, and semiconducting properties as well. Most readers will be surprised to learn that they carry within their own bodies (dental fillings) or on their persons (jewelry or pocket lighters) IMCs for which selection and processing are uniquely appropriate to those applications. The economic impact of IMCs is as unappreciated as the diversity of their applications. Some are regularly produced in quantities of 1,000s of tons per year while others, although not in tonnage production, are key factors in devices with billion-dollar markets.
Metallurgical and Chemical Applications of Intermetallics
Authors: Westbrook Jack H. 
Published: August 2016

Practical metallurgical application of intermetallic compounds (IMCs) occurred more than 3,000 years before they were recognized as distinct entities in alloys. Pliny, The Elder (A.D. 23–79) recorded in his encyclopedia a then old practice: the use of mercury both to recover gold from sands and other dispersed sources, and to gild less-noble metal objects. In both cases, the key factor is the formation of a Au-Hg intermetallic compound (amalgam) stable at room temperature but readily decomposable on heating to produce solid gold. An illustration of the Au-recovery process, reproduced from Ercker (1574) appears in Figure 1. Use of the amalgam processes for silver apparently occurred later. Bronze mirrors were silver-coated with the amalgam process by the Chinese in the second century B.C., and silver was recovered from crushed sulfide ores using mercury in the famous Potosi process (1566, but probably known much earlier).The key properties of intermetallics that make possible their diverse applications in chemical and metallurgical processes are their high melting points relative to one or all of their constituent elements, their often sharply defined composition, their brittleness, and their controllable reactivity/stability–that is, systems can be chosen such that a stable intermetallic forms easily at room or low temperatures that is nonetheless readily decomposable at a higher temperature. Once the intermetallic forms however, a useful physical property (e.g., hardness or conductivity) or chemical property (oxidation, sulfidation, corrosion resistance, nonsticking quality, etc.) may be that which is ultimately exploited in use.We will review these two classes of applications using representative examples from both process metallurgy and chemistry.
Use of Plasma Processing in Making Integrated Circuits and Flat-Panel Displays
Authors: Gottscho Richard A. , Barone Maria E. , Cook Joel M. 
Published: August 2016

The ever-shrinking dimensions of microelectronic devices has mandated the use of plasma processing in integrated circuit (IC) factories worldwide. Today the plasma-processing industry has grown to over $3 billion in revenues per year, well in excess of predictions made only a few years ago. Plasma etching and deposition systems are also found throughout flat-panel-display (FPD) factories despite the much larger dimensions of thin-film transistors (TFTs) that are used to switch picture elements (pixels) on and off. Besides the use of plasma in etching and depositing thin films, other processes include the following: removal of photoresist remnants after development (descumming), stripping developed photoresist after pattern transfer (ashing), and passivating defects in polycrystalline material. Why are plasma processes so prevalent?In etching, plasmas are used for high-fidelity transfer of the photolithographically defined pattern that defines the device or circuit. More generally, plasma provides the means to taper sidewalls. In Si processing, the sidewalls must be nearly vertical to obtain high density integration and faster performance. However in making FPDs, sidewalls are tapered to obtain uniform step coverage and reduce shorting. In deposition, plasmas are used to enable processing at low temperature. For both etching and deposition, only plasma processing provides an economically viable means for processing large area substrates: 300 mm for Si and more than 550 × 650 mm for FPDs. It is the ability to scale uniform reactant generation to larger areas that sets plasma apart from beam-based processes that might otherwise offer the desired materials modifications. The nonequilibrium characteristics of plasma further distinguish this processing method. Energetic electrons break apart reactant precursors while ions bombard the surface anisotropically.
Materials in Active-Matrix Liquid-Crystal Displays
Authors: Hanna Jun-ichi , Shimizu Isamu 
Published: August 2016

In today's world of increasing office automation and computer-aided personal-communications systems, display devices play a very important role as person-machine interfaces. Above all, high-definition, full-color flat-panel displays will be key devices in the near future when processing huge amounts of information—including pictorial images via computer networks and telecommunication systems that transcend the present limitations of time and place—will be possible.Passive-matrix liquid-crystal displays (LCDs) represent the most widely used choice for portable display devices. Figure 1 illustrates the essential components and operating principle of a typical LCD. Each pixel is addressed by the top- and bottom-line electrodes of the cell based on information signals, producing a light image. By installing a color filter of red, green, or blue for each pixel, full-color images can be displayed. However, the essential problems of crosstalk among pixels and low response speed become serious with an increase in the number of pixels, resulting in a low contrast ratio and failure of the display to keep up with the signals.
Materials and Manufacturing Issues for Color Plasma Displays
Authors: Weber Larry F. , Birk Jane D. 
Published: August 2016

Recent demonstrations of color-plasma displays with exceptional image quality and performance that meet and in some cases exceed that of cathode-ray tubes (CRTs) have resulted in a renewed interest in this 25-year-old technology. The tremendous market potential for large-area plasma displays for both home-entertainment and computer applications now appears to be an attainable goal. This new generation of plasma displays features full color capability, high brightness and contrast ratio, wide viewing angles, and rapid refresh rate. The success of today's plasma displays is the result of the integration of advancements in driver electronics and the materials and processes used in the fabrication of the plasma-display structures.Using color-plasma technology, two-inch-thick direct-view displays can be made that are up to 60 inches in diagonal. During the past several months, numerous articles have appeared in the media announcing major investments in facilities and technology for largescale manufacturing of these large-area plasma displays. Table I lists the companies committed to plasma-display research and development. Additional advancements in materials, processes, and electronics will be required to achieve high-volume, low-cost manufacturing.
Magnetic Recording Head Materials
Authors: Brug James A. , Anthony Thomas C. , Nickel Janice H. 
Published: August 2016

The materials used in magnetic recording heads have recently received a tremendous amount of attention. This has been the result of a fortunate set of circumstances. Ever-increasing demands for information storage, especially for graphics-intensive applications, have necessitated unprecedented increases in disk-drive areal densities. Combined with this are recent discoveries in the area of magnetoresistive materials, enabling the design and fabrication of much more sensitive recording heads. The end result is a flurry of activity that has come to dominate the field of magnetics. This article will explore choices for magnetoresistive read head materials, with an emphasis on the materials challenges.The recording heads that are used in high-performance disk drives typically consist of separate magnetoresistive read and inductive write heads (see Figure 1) where previously a single inductive head performed both functions. Separation of the two heads allows each to be optimized for their individual function, an essential factor in enabling disk drives to contain gigabytes of storage. The write head is the simpler of the two, consisting of a U-shaped ferromagnet surrounding a set of coils. The ends of the ferromagnet are the magnetic poles defining the write gap. When current passes through the coils, a field bridges the gap, setting the orientation of the magnetization in the media. Information is stored by changing the polarity of the current in order to write a pattern of magnetic domains in the media. The materials used in write poles will be reviewed in the section, Write Head Materials.
Evolution of Ge Precipitate Morphology in Al
Authors: Dahmen U. 
Published: August 2016

Static electron microscopy provides views of microstructures frozen in time. For many problems, such snapshots give a clear picture of the material's characteristics after a particular processing step, but for other problems it is the evolution of the microstructure itself, its mechanisms and kinetics, that are important to understand. For this class of problem, in situ electron microscopy is an indispensable tool because it can provide real-time dynamic observations of processes, showing, for example, where dislocations nucleate, how a particle grows, by what mechanism and how fast an interface migrates. The major limitation to such experiments is that foils must be extremely thin to be electron transparent. The proximity of the free surfaces can have a strong effect on the dynamic equilibrium. For that reason, high-voltage electron microscopes are particularly useful for in situ TEM experiments. The greater penetration depth of high energy electrons makes it possible to observe processes in foils that are thick enough to avoid the dominant influence of the surfaces.This article will describe some experiments in which the dynamic behavior of precipitates in a simple alloy system was examined during in situ temperature cycling in order to understand the effect of bicrystal anisotropy on the characteristics of interface motion.