bluuebunny/crossref_metadata_2025_split huggingface dataset:
Irradiation of Plastics: Damage and Gas Evolution
Authors: Evans D. , Crook M.A. 
Published: August 2016

There have been many studies (see for instance Reference 1) directed at quantifying the effects of ionizing radiation on polymers. Mainly these studies have focused on assessing the degradation of mechanical properties. In addition to changes in mechanical properties, a mixture of gases results from the irradiation of polymeric compounds. The amount of gas produced is related to the total absorbed dose while the type of gas is independent of dose and is related only to polymer structure. For many polymers, hydrogen is the major component in the gaseous mixture but polyesters and anhydride-cured epoxide resins are a notable exception.Some problems associated with radiation damage may be further complicated when the irradiation temperature is in the cryogenic range. When materials are irradiated at low temperatures (<150 K), the release of volatile degradation products is delayed and occurs—possibly very rapidly and exceeding normal diffusion rates—only when the polymer is warmed. The rapid release of gaseous degradation products could occur as a result of warming a superconducting magnet that has been resin bonded and irradiated at low temperatures during operation. Radiation damage-related problems may be summarized as follows: (1) changes in short-term mechanical properties, (2) production of gases and low-molecular-weight species, and (3) longer term and geometrical effects (unknown) of trapped gases on electrical and mechanical properties.This article considers mechanisms of radiation-induced damage and relates the chemical structure of the polymer to the rate of damage accumulation. Changes in electrical properties measured on irradiated polymers are generally small, and mechanical damage is generally more significant than changes in electrical characteristics. However all such reports are a result of electrical measurements on thin films and do not consider the effects of trapped gases on long-term electrical properties in bulk specimens.
Defects in Liquid-Crystalline Polymers
Authors: Kléman M. 
Published: August 2016

The properties of imperfections (or defects) of the atomic or molecular order in condensed matter can be conveniently described under two headings: (1) Topological properties—Defects break a specific symmetry of the ordered system at a local scale, that is, along a point defect, a line defect (a dislocation or a disclination), or a surface defect (a wall). (2) Elastic properties—Defects are sources of two types of distortions of the order: long-range distortions, which depend crucially on the broken symmetry but also on the material constants, and short-range distortions in the “core” region of the defect where the order parameter of the ordered phase is broken. These distortions are irreversible in the sense that defects appear during plastic deformation (in solids) or rheological flow (in liquid crystals).To illustrate this classification, let us recall the example of dislocation lines in solids. These defects break translational symmetries (henceforth a dislocation is defined topologically by the translation b it breaks, the so-called Burgers vector). They are at the origin of rather weak, long-range, internal distortions and stresses that depend on the elastic constants (in the region of the good crystal) and rather strong, short-range distortions and stresses in the “core” region, implying a complete rearrangement of the molecular order. These stresses are different in the static and dynamic states, and the shape of the dislocation line, as well as its size, etc., depend on the history of the sample.In this article, we will focus on defects in liquid-crystalline polymers. A synthetic polymer that displays mesomorphic order (intermediate between crystalline and liquid) is usually made of units that are themselves mesogenic and that align coherently when in contact.
Morphology and Dynamic Interaction of Defects in Polymer Liquid Crystals
Authors: O'Rourke Mary Jane E. , Thomas Edwin L. 
Published: August 2016

The liquid crystal phase is an anisotropic mesophase, intermediate in order between the liquid and crystal phases. Liquid crystals have less translational order than crystals and more rotational order than isotropic liquids. The liquid crystal phase does not support finite shear stresses and thus behaves like a fluid. Molecules that display a liquid crystal phase are referred to as mesogenic. Mesogenic molecules exhibit shape anisotropy: either large length to diameter ratio (needlelike) or large diameter to thickness ratio (disklike). Because of their shape anisotropy, all liquid crystals display orientational order of their molecular axes.Until 1956, all known examples of liquid crystals were low molecular weight compounds. Robinson was the first to identify liquid crystallinity in a liquid crystalline polymer (LCP) as the explanation for “a birefringent solution” of a polymeric material, poly-y-benzyl-L-glutamate, in chloroform, previously observed by Elliott and Ambrose. Chemists soon discovered that LCPs may be readily synthesized by covalently stitching small mesogenic units (e.g., rigid monomers) together into a chain using short flexible spacers. Mainchain or sidechain liquid crystal polymers may be formed (Figure 1). An example of a polymer molecule possessing a liquid crystal phase is shown in Figure 2. Liquid crystals may be thermotropic, where liquid crystallinity is exhibited over a range of temperatures, or lyotropic, where nonmesogenic solvent molecules are present in addition to the mesogens, and liquid crystallinity is observed over a range of concentrations as well.
A Non-Periodic Lattice Model for Crystals inNephila clavipesMajor Ampullate Silk
Authors: Thiel Brad L. , Viney Christopher 
Published: August 2016

Defects play a significant role in determining the physical and thermodynamic behaviors of a material. This precept can be especially helpful when one attempts to interpret the engineering properties of a biological material in the context of its complex, hierarchical microstructure. An excellent example of an impressive engineering material used by nature is silk, which has a composite microstructure assembled from one or more protein polymers. Spiders, aided by several million years of evolution, have succeeded in producing a polymer fiber [major ampullate silk (MAS)] with a strength-to-weight ratio exceeding that of nearly all synthetic materials. Even the exceptions—specialty fibers such as carbon, silica, and some variants of Kevlar—pale in comparison when toughness (energy required to bring about failure) is taken into account; they are relatively brittle and lack the viscoelastic extensibility of MAS. When one considers that spiders produce this naturally biodegradable material under ambient conditions and with an aqueous solvent, the feat becomes even more impressive. It is clear that the spider could be an excellent instructor in both polymer processing and microstructural design.where the α-carbon is bonded to a functional “R” group that distinguishes the monomer as being one of the 20 commonly occurring natural a-amino acids.
Adhesion of Polymers
Authors: Brown Hugh R. 
Published: August 2016

The adhesion of a polymer to itself, to a different polymer, or to an inorganic material can often be one of its most important properties. Adhesives are normally polymers, but then so are nonstick coatings. Clearly, polymer adhesion can vary from very strong to extremely weak. Adhesion is a sufficiently complex and broad area that there are a range of approaches to its understanding. My approach here is one that attempts to bridge between the mechanics of crack propagation and the atomic-scale processes that occur at a crack tip. I will not be concerned with the details of the interface chemistry and its modification. The interface chemical approach is very useful in many practical situations but is often very specific to particular systems. Adhesion (or perhaps its inverse) can be considered a failure property. We can only measure the adhesion between two items by breaking the joint between them. I will be mainly concerned with failure by crack propagation using a fracture-mechanics approach.I will first consider the general question of the effects of bulk mechanical properties on adhesion and then describe some recent work on fracture mechanics of biomaterial interfaces as it relates to polymer glasses. I will then change the focus to the scale of the polymer chain to consider local processes involved in adhesion.
High-Temperature Applications of Intermetallic Compounds
Authors: Pope David P. , Darolia Ram 
Published: August 2016

One of the greatest challenges currently facing the materials community is the need to develop a new generation of materials to replace Ni-based superalloys in the hot sections of gas-turbine engines for aircraft-propulsion systems. The present alloys, which have a Ni-based solid-solution matrix surrounding Ni3Al-based precipitates, are currently used at temperatures exceeding 1100°C, which is over 80% of the absolute melting temperature. Since Ni3Al melts at 1395°C and Ni at 1453°C, it is clear that significantly higher operating temperatures, with the attendant improvements in efficiency and thrust-to-weight ratio, can only be attained by the development of an entirely new materials system. This problem is a primary reason for the current high level of interest in high-temperature intermetallic compounds.The development of such a material system has important implications for national defense and for spin-offs to civilian technology, as well as for the economy and balance of payments. Obviously it would be a boon to any economy to have these new materials developed domestically, as was the case in the United States for the currently used single-crystal technology applied to Ni-based superalloys. As an example, the aerospace industry is one area where the United States is still the undisputed world leader, with net exports of $29 billion in 1989, twice that of any other U.S. industry.
Plasma Processing of Advanced Materials
Authors: Collins George , Rej Donald J. 
Published: August 2016

A plasma, commonly referred to as the “fourth state of matter,” is an ensemble of randomly moving charged particles with a sufficient particle density to remain, on average, electrically neutral. While their scientific study dates from the 19th century, plasmas are ubiquitous, comprising more than 99% of the known material universe. The term “plasma” was first coined in the 1920s by Irving Langmuir at the General Electric Company after the vague resemblance of a filamented glow discharge to a biological plasma.Plasmas are studied for many reasons. Physicists analyze the collective dynamics of ions and electron ensembles, utilizing principals of classical electromagnetics, and fluid and statistical mechanics, to better understand astrophysical, solar, and ionospheric phenomenon, and in applied problems such as thermonuclear fusion. Electrical engineers use plasmas to develop efficient lighting, and high-power electrical switchgear, and for magneto-hydrodynamic (MHD) power conversion. Aerospace engineers apply plasmas for attitude adjustment and electric propulsion of satellites. Chemists, chemical engineers, and materials scientists routinely use plasmas in reactive ion etching and sputter deposition. These methods are commonplace in microelec tronics since they allow synthesis of complex material structures with submicron feature sizes. A substantial portion of the multi-billion-dollar market for tooling used to manufacture semiconductors employs some form of plasma process. When compared with traditional wet-chemistry techniques, these dry processes result in minimal waste generation. Plasmas are also useful in bulk processing—for example as thermal sprays for melting materials.While the quest for controlled thermonuclear fusion dominated much of plasma research in the 1960s and 1970s, in the last 20 years it has been the application of plasmas to materials processing that has provided new challenges for many plasma practitioners. It is not surprising that the guest editors and several of the authors for this issue of MRS Bulletin come from a fusion plasma-physics background.
Modification of Polymeric Surfaces With Plasmas
Authors: Coates Don M. , Kaplan Stephen L. 
Published: August 2016

As adaptable as polymeric materials are in their many applications to our daily lives, the need exists to tailor the polymer surfaces to provide even more flexibility in regard to their uses. Plasma treatments offer an unprecedented spectrum of possible surface modifications to enhance polymers, ranging from simple topographical changes to creation of surface chemistries and coatings that are radically different from the bulk polymer. Furthermore plasma treatments are environmentally friendly and economical in regard to their use of materials.Plasma processing can be classified into at least four categories that often overlap. These are the following: (1) surface preparation by breakdown of surface oils and loose contaminates, (2) etching of new topographies, (3) surface activation by creation or grafting of new functional groups or chemically reactive, excited metastable species on the surface, and (4) deposition of monolithic, adherent surface coatings by polymerization of monomeric species on the surface. Key features of these processes will be briefly discussed, with a rudimentary introduction to the chemistries involved, as well as examples. Focus is placed on capacitively coupled radio-frequency (rf) plasmas (see Figure 1 in the article by Lieberman et al. in this issue of MRS Bulletin) since they are most commonly used in polymer treatment.
Materials Processing With Thermal Plasmas
Authors: Boulos Maher , Pfender Emil 
Published: August 2016

Thermal plasmas in which the plasma state approaches local thermodynamic equilibrium may be produced by high-intensity arcs (current I > 100 A) or by radio-frequency (rf) discharges at high-power densities and at pressures exceeding 10 kPa (0.1 atm). In such plasmas, electron and heavy-particle temperatures are identical, and particle densities are only a function of the temperature (chemical equilibrium).Thermal-plasma technology has passed through a drastic transition stage from primarily space-related activities in the 1960s to a more and more materials-oriented focus in the 1980s and 1990s, and thermal-plasma processing of materials is now attracting increasing interest for industrial applications.Thermal-plasma processing of materials however must be viewed in the context of much broader technology trends, some of which are visible today. There is no question that materials and materials processing will be one of the most important technical issues as we approach the turn of the century. This trend will not be restricted to the development of new materials but will also include the refining of materials, the conservation of materials (by hard facing, coating, etc.), and the development of new processing routes that are more energy-efficient, more productive, and less damaging to our environment. Thermal-plasma processing is already playing an important role in these developments. Its potential for developing new materials-related technologies is increasingly recognized, and many research laboratories all over the world are engaged in advancing the frontiers of our knowledge in this exciting field. As a result of these efforts, thermal-plasma processing has emerged as a powerful technology that is finding numerous industrial applications.
Electroceramic Thin Films Part II: Device Applications
Authors: Auciello Orlando , Ramesh Ramamoorthy 
Published: August 2016

Ferroelectric thin films have experienced tremendous development in recent years due to the advent of sophisticated film-synthesis techniques and an increase in the understanding of the related materials science and integration of films into various novel devices. Major advances in ferroelectric thin-film synthesis and characterization were addressed last month in the June MRS Bulletin. This volume is dedicated to selective device issues and applications.Ferroelectric materials can be used to fabricate capacitors for integration into nonvolatile ferroelectric random-access memories (NVFRAMs) and as high di-electric layers for capacitors with high capacitance for manufacturing planar dynamic random-access memories (DRAMs). Ceramic conductors can be applied to ohmic, voltage-dependent, and thermally sensitive resistors; fast-ion conductors; and humidity and gas sensors. Piezoelectricity is being exploited in micromachines such as accelerometers, displacement transducers, and actuators such as those required for inkjet printers, for video-recording head positioning, and for micromachining. Pyroelectricity can be utilized in the fabrication of high-sensitivity room-temperature infrared detectors while electro-optic activity can be used in color-filter devices, displays, image-storage systems, and optical switches for integrated optical systems. These applications of electroceramic thin films are only part of a more extensive list.
Glass Substrates for Flat Panel Displays
Authors: Moffatt Dawne M. 
Published: August 2016

One material exists in most types of flat panel displays that are used in high information content applications, from liquid crystal displays to electroluminescent displays. This material is glass, something we all use daily. As a substrate, glass plays a significant role in the manufacture and function of flat panel displays (FPDs). In the case of active-matrix liquid crystal displays (AMLCDs), the semiconductor-based thin-film transistors (TFTs) or diodes are fabricated on the active glass substrate. In addition, AMLCDs require color-filter structures consisting of dyed or pigmented resins built upon the passive plate of an AMLCD cell. For plasma and electroluminescent display panels, the glass provides the surface upon which are deposited phosphors, conductive lines, and dielectrics.The excellent properties of glass make it the substrate of choice in FPDs. It is the only material that can meet the demanding requirements of high-information-content FPD manufacturing processes and operation. Glass' transparency is an obvious requirement. For all types of displays, the rigidity of glass also plays a important role because it adds overall mechanical integrity and strength.One of the most important attributes of glass in terms of the display manufacturing process is its thermal stability. Glass substrates, particularly those made of “hard” or high temperature glasses, can be processed at elevated temperatures with minimal deformation. In addition, the dimensional precision required in the alignment of various display components is maintained throughout the specific manufacturing processes.
Observation of Vortices in Superconductors
Authors: Bonevich J.E. , Harada K. , Matsuda T. , Tonomura A. 
Published: August 2016

Electron holography was originally proposed as a means of improving the resolution of the transmission electron microscope (TEM). And within the last decade dramatic improvements in coherent field-emission electron sources, coupled with TEM instrumentation, have allowed the promise of holography to come to fruition. These improvements in TEM resolution notwithstanding, it has been the application of holography techniques and coherent-beam imaging to the investigation of magnetic and electric fields that has sparked the interest of materials scientists. Electron holography is a unique tool for probing phenomena in the microscopic world because all the information about the object is contained in the hologram (both the electron wave's amplitude and phase), whereas conventional microscopy records only the intensity. It is in this sensitivity to the phase that materials scientists can observe the true potential of electron holography.Electromagnetic phenomena in a wide range of materials systems have been observed via electron holography; domain structures in magnetic particles and electric fields in p-n junctions are just two examples. Furthermore, fundamental physical properties, such as the existence of the vector potential predicted by Aharonov-Bohm (the AB effect), have been conclusively demonstrated by electron holography. For more information, interested readers are referred to several reviews of electron holography.
The Quartz-Crystal-Microbalance Study of Protein Binding on Lipid Monolayers at the Air-Water Interface
Authors: Okahata Y. , Ebara Y. , Sato T. 
Published: August 2016

Interactions of proteins with cell membranes are of great interest in studies such as molecular recognition at cell surfaces. A monolayer lipid film at the airwater interface is useful in cell-surface modeling. Studies in binding behavior of proteins from a solution with a lipid monolayer have been reported by using variousin situtechniques: surface-tension measurements, fluorescent-labeling techniques, radio-labeling techniques, fluorescence reflection methods, surface plasmon resonance, and surface-force measurements. These methods have potential applications in the observation of protein bindings. However, they require large, expensive equipment forin situmeasurements and present difficulties for quantitatively obtaining the amount of protein adsorbed and the time frame for both binding and dissociation processes.In this article, we discuss a new, easyin situtechnique to detect interactions of adsorbed proteins with a phospholipids monolayer through the use of a Langmuir film balance on which a quartz-crystal microbalance (QCM) is horizontally attached to the lipid monolayer from the air phase (see Figure 1). QCMs are known to be very sensitive mass-measuring devices because their resonance frequency decreases with an increase of a given mass on a QCM at the nanogram level. Adsorption and penetration behavior of proteins can be observed quantitatively from the frequency changes (ΔF) of the QCM on the monolayer and the surface-pressure changes (Δπ) of the monolayer responding to the addition of proteins. The amount of adsorbed proteins (Δm) wasalso obtained from the frequency changes after lifting and drying the sample in air.Recently, QCMs have become popular tools for detection of bioactive compounds such as odorous and bitter substances, and for measurement of protein adsorption, immuno-assays, DNA hybridization, enzyme reactions, and cell growth.
Deterministic Chaos Theory and Its Applications to Materials Science
Authors: Markworth Alan J. , Stringer John , Rollins Roger W. 
Published: August 2016

Over the past 30 years or so, some fascinating new developments have taken place in a field that is now called “nonlinear science.” These developments have been of such magnitude that historian Alan Beyerchen concluded “There is every reason to believe that the westernized world is in the early stages of an intellectual transformation of major proportions, perhaps as significant as the emergence of the modern worldview in the fifteenth through seventeenth centuries.”These new developments are rooted in work conducted by mathematician Jules Henri Poincaré around the turn of the century. He carried out some calculations regarding planetary orbits and demonstrated the possibility of erratic or “chaotic” dynamical behavior. What is particularly interesting about such behavior is that it is exhibited bydeterministicsystems, that is, systems that have no stochastic (noisy) character of any kind. Little was done with Poincaré's findings until the 1960s when new work in nonlinear science, based on numerical models, led to the discovery of amazingly complex behavior that can be exhibited even by very simple deterministic systems. Since that time, the discipline has grown enormously and has been applied in practically every area of science and engineering, as well as in other diverse areas such as the financial market, political science, economics, and even Adlerian psychology.