bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bulk Metallic Glasses: At the Cutting Edge of Metals Research
Authors: Greer A. L. , Ma E. 
Published: February 2011

AbstractGlassy alloys (metallic glasses) are currently the focus of intense research in the international metals community. Setting aside elevated-temperature applications, these amorphous metals have exciting potential for structural applications. When metallic glasses were first widely studied in the 1960s, the alloy compositions then known to be quenchable into the glassy state from the liquid required high cooling rates on the order of 106 K s−1 and were consequently restricted to thin sections. The current interest in metallic glasses has its origin mainly in the increasing range of compositions that can now be cast into glasses at much lower cooling rates, permitting minimum sections of 1 mm to 1 cm or even larger. These bulk metallic glasses (BMGs) are the focus of the articles in this issue of MRS Bulletin. Our goal is to illustrate the major materials issues for BMGs, from processing to structures to properties and from the fundamental science of glasses to viable industrial applications. We hope that the articles, in providing a snapshot of a rapidly moving field, show why BMGs are attracting such intense interest and serve to highlight some challenging issues awaiting resolution.
Thermodynamics and Kinetics of Bulk Metallic Glass
Authors: Busch R. , Schroers J. , Wang W. H. 
Published: February 2011

AbstractBulk metallic glasses (BMGs) are multicomponent alloys with typically three to five components with large atomic size mismatch and a composition close to a deep eutectic. Packing in BMG liquids is very dense, with a low content of free volume resulting in viscosities that are several orders of magnitude higher than in pure metal melts. The dense packing accomplished by structural and chemical atomic ordering also brings the BMG-forming liquid energetically and entropically closer to its corresponding crystalline state. These factors lead to slow crystallization kinetics and consequentially to high glass-forming ability. This article highlights the thermodynamic and kinetic properties of BMGs and their contributions to extraordinarily high glass-forming ability. Some possible links with mechanical properties are also suggested.
Structural Aspects of Metallic Glasses
Authors: Miracle Daniel B. , Egami Takeshi , Flores Katharine M. , Kelton Kenneth F. 
Published: February 2011

AbstractA recent structural model reconciles apparently conflicting features of randomness, short-range order, and medium-range order that coexist in metallic glasses. In this efficient cluster packing model, short-range order can be described by efficiently packed solute-centered clusters, producing more than a dozen established atomic clusters, including icosahedra. The observed preference for icosahedral short-range order in metallic glasses is consistent with the theme of efficient atomic packing and is further favored by solvent-centered clusters. Driven by solute—solute avoidance, medium-range order results from the organization in space of overlapping, percolating (via connected pathways), quasi-equivalent clusters. Cubic-like and icosahedral-like organization of these clusters are consistent with measured medium-range order. New techniques such as fluctuation electron microscopy now provide more detailed experimental studies of medium-range order for comparison with model predictions. Microscopic free volume in the efficient cluster packing model is able to represent experimental and computational results, showing free volume complexes ranging from subatomic to atomic-level sizes. Free volume connects static structural models to dynamic processes such as diffusion and deformation. New approaches dealing with “free” and “anti-free” microscopic volume and coordinated atomic motion show promise for modeling the complex dynamics of structural relaxations such as the glass transition. Future work unifying static and dynamic structural views is suggested.
Porous and Foamed Amorphous Metals
Authors: Brothers Alan H. , Dunand David C. 
Published: February 2011

AbstractThis article reviews the state of the art in the field of porous amorphous metals by describing current processing techniques, mechanical properties, and potential applications. In addition to the reduction in density, the main benefit of introducing porosity in amorphous metals is the improvement in compressive ductility and energy absorption. This ductilizing effect is explained by: (1) shear-band interruption by individual pores at low porosities and (2) stable plastic bending of thin struts at higher porosities, with cellular amorphous metals displaying compressive ductilities of up to 80%.
Rheology and Ultrasonic Properties of Metallic Glass-Forming Liquids: A Potential Energy Landscape Perspective
Authors: Johnson William L. , Demetriou Marios D. , Harmon John S. , Lind Mary L. , Samwer Konrad 
Published: February 2011

AbstractIn the potential energy landscape theory of liquids, the energetic configurational landscape of a liquid is modeled using a potential energy function comprising a population of stable potential energy minima called inherent states, which represent the stable atomic configurations of the liquid. These configurations are separated by saddle points that represent barriers for configurational hopping between the inherent states. In this article, we survey recent progress in understanding metallic glass-forming liquids from a potential energy landscape perspective. Flow is modeled as activated hopping between inherent states across energy barriers that are assumed to be, on average, sinusoidal. This treatment gives rise to a functional relation between viscosity and isoconfigurational shear modulus, leading to rheological laws describing the Newtonian and non-Newtonian viscosity of metallic glass-forming liquids over a broad range of rheological behavior. High-frequency ultrasonic data gathered within the supercooled-liquid region are shown to correlate well with rheological data, thus confirming the validity of the proposed treatment. Variations in shear modulus induced either by thermal excitation or mechanical deformation can be correlated to variations in the measured stored enthalpy or equivalently to the configurational potential energy of the liquid. This shows that the elastic and rheological properties of a liquid or glass are uniquely related to the average potential energy of the occupied inherent states.
New Bulk Metallic Glasses for Applications as Magnetic-Sensing, Chemical, and Structural Materials
Authors: Inoue Akihisa , Nishiyama Nobuyuki 
Published: February 2011

AbstractSince 1988, it has been demonstrated that metallic glasses can be made in bulk form with diameters larger than several millimeters. At present, several alloy systems with maximum diameters for glass formation exceeding 1 cm are known. As a result, Zr-, Ti-, Fe-, Co-, Ni-, and Cu-based bulk metallic glasses (BMGs) are already in use for magnetic-sensing, chemical, and structural applications. In this article, recently developed BMGs with critical diameters of more than 1 cm are summarized, and some of their industrial applications are reviewed.
The Symbiosis of Light and Matter: Laser-Engineered Materials for Photo-Functionality
Authors: Livingston F. E. , Helvajian H. 
Published: February 2011

AbstractCurrent technology trends imply that further miniaturization and integration of systems are anticipated, and one approach to realizing the next generation of systems integration is the development of materials that are protean, or capable of taking on various properties; in essence, the materials properties can be selectively altered via laser excitation. The objective is that a common substrate material can be used for multiple functions. Laser direct-write material processing, because of its maskless patterning flexibility, is inherently suitable for producing localized changes in materials properties and thereby fabricating linked, integrated devices on a common substrate. The enabling of this new form of materials processing requires a light-activated protean material along with a scheme for the dynamic regulation of the laser energy for optimum laser processing on the scale of the laser spot size and for patterning speeds on the order of meters per second. The “protean material” concept and a high-fidelity laser amplitude-modulation scheme are the focus of this article.
The Collapse of the World Trade Center Towers: A Metallurgist's View
Authors: Gayle Frank W. 
Published: February 2011

This article is based on an edited transcript of a presentation given by Frank W. Gayle (National Institute of Standards and Technology) on April 12, 2007, in Symposium X at the Materials Research Society Spring Meeting in San Francisco.The NIST investigation of the World Trade Center disaster addressed many aspects of the catastrophe, from occupant egress to factors affecting the ability of the Twin Towers to remain standing after being hit by the airplanes, with the goal of gaining valuable information for future best practices in building materials, building design, and emergency response. The presentation addressed the structure of the towers, the analysis of the recovered steel, and special issues faced during the investigation. The probable collapse sequence for each of the towers was also discussed.
Importance of Nanosensors: Feynman's Vision and the Birth of Nanotechnology
Authors: Devreese Jozef T. 
Published: February 2011

In his visionary 1959 lecture at Caltech, Richard P. Feynman foresaw the potential of the ability to manipulate matter at the atomic scale. In this article, adapted from Integrated Nanosensors, MRS Symposium Proceedings Volume 952E, edited by I.K. Schuller, Y. Bruynseraede, L.M. Lechuga, and E. Johnson (2007), Jozef T. Devreese (University of Antwerp) discusses implementations of Feynman's vision in the field of nanosensors and perspectives of its further development and applications.Nanoparticles are unique tools as sensors. Particles with sizes at the nanoscale reveal physical properties that do not exist in bulk materials; these properties can operate well inside living cells. Nanosensors possess unique physical characteristics. Their sensitivity can be orders of magnitude better than that of conventional devices. Nanosensors possess such performance advantages as fast response and portability. State-of-the-art nanosensors are based on various advanced materials (quantum dots, nanoshells, nanopores, carbon nanotubes, etc.). Nanosensors furthermore allow for building an entirely new class of integrated devices that provide the elemental base for “intelligent sensors” capable of data processing, storage, and analysis. Advances can open unprecedented perspectives for the application of nanosensors in various fields, for example, as molecular-level diagnostic and treatment instruments in medicine and as networks of nanorobots for real-time monitoring of physiological parameters of a human body.
Silicon Nanomembranes
Authors: Lagally Max G. 
Published: February 2011

AbstractThis article is based on the presentation given by Max G. Lagally (University of Wisconsin–Madison) as part of Symposium X: Frontiers of Materials Research on April 18, 2006, at the Materials Research Society Spring Meeting in San Francisco.Structures with nanoscale dimensions are the essence of nanotechnology. Beginning with quantum dots and buckyballs, nanostructures now include nanotubes, rods, wires, and most recently, nanomembranes: very thin, large, freestanding or freefloating strain-engineered single crystals that can variously be made into tubes or other shapes, cut into millions of identical wires, or used as conformal sheets. This article provides a brief overview of the fabrication and properties of strained-silicon nanomembranes.
Systematic Coarse Graining of Biomolecular and Soft-Matter Systems
Authors: Ayton Gary S. , Noid Will G. , Voth Gregory A. 
Published: February 2011

AbstractCoarse-grained modeling is a key component in the field of multiscale simulation. Many biomolecular and otherwise complex systems require the characterization of phenomena over multiple length and time scales in order to fully resolve and understand their behavior. These different scales range from atomic to near macroscopic dimensions, and they are generally not independent of one another, but instead coupled. That is, phenomena occurring at atomic length scales have an effect at macroscopic dimensions and vice versa. Systematic transfer of information between these different scales represents a core challenge in the field of multiscale simulation. Coarse-grained modeling works at an intermediate resolution that can bridge the very high resolution (atomic) scale to the very low resolution (macroscopic) scale. As such, a significant challenge is the development of a systematic methodology whereby coarse-grained models can be derived from their high-resolution atomistic-scale counterpart. Here, a systematic theoretical and computational methodology will be described for developing coarse-grained representations of biomolecular and other soft-matter systems. At the heart of the methodology is a variational statistical mechanical algorithm that uses forcematching of atomistic molecular dynamics data to a coarse-grained representation. A theoretical analysis of the coarse-graining methodology will be presented, along with illustrative applications to membranes, peptides, and carbohydrates.
NovelIn SituProbes for Nanocatalysis
Authors: Stierle Andreas , Molenbroek Alfons M. 
Published: February 2011

AbstractDuring the past few years, substantial effort has been devoted to developing new experimental techniques capable of delivering atomic-scale information on surfaces and nanoparticles under catalytic reaction conditions. Since the advent of surface science, pioneering experiments under highly idealized conditions have been performed (at very low gas pressures, <10−6mbar), and idealized model material systems (e.g., single crystals) have been investigated. However, understanding chemical reactions on singlecrystal surfaces close to ultrahigh vacuum does not always enable prediction of the performance of nanoparticles operating at gas pressures near or above atmospheric pressure. Therefore, thisMRS Bulletinissue focuses on the capabilities of atomic-scaleresolution, high-gas-pressure- and high-temperature-compatiblein situprobes sensitive to the structure, chemical composition, and dynamical properties of nanomaterials. It will be demonstrated how novelin situtechniques enable one to bridge the combined pressure and materials gaps from ultrahigh vacuum to atmospheric pressures and from metal single-crystal surfaces to nanoparticles or oxides.
In Situ Investigations of Chemical Reactions on Surfaces by X-Ray Diffraction at Atomospheric Pressures
Authors: Ferrer S. , Ackermann M. D. , Lundgren E. 
Published: February 2011

AbstractCatalytic reactions occurring at metal surfaces and nanoparticles have been an established research field for decades, yielding information on adsorption sites and reaction pathways under ultrahigh-vacuum conditions. Recent experimental developments have made it possible to perform well-controlled in situ surface x-ray diffraction measurements from single-crystal surfaces and nanoparticles under industrially relevant conditions. In this way, a new understanding of atomic-scale processes at surfaces and nanoparticles occurring during catalytic reactions under realistic conditions has been gained. In particular, the identification of the formation of thin oxides on model catalysts and their role in oxidation reactions demonstrates the importance of in situ probes under relevant conditions.
The Reactor-STM: A Real-Space Probe forOperandoNanocatalysis
Authors: Frenken Joost , Hendriksen Bas 
Published: February 2011

Abstract“Looking” on the other side of the pressure gap in heterogeneous catalysis is an essential step in identifying and understanding differences and similarities between the behavior of catalysts under actual operation conditions (operando) and under the nearvacuum conditions of traditional laboratory experiments. In this article, we demonstrate that real-space, atomic-scale imaging of active catalyst surfaces is possible under realistic or semirealistic reaction conditions with the reactor-STM, a scanning tunneling microscope that is fully integrated with a miniature flow reactor and housed inside an ultrahigh-vacuum system. This special-purpose instrument combines the merits of standard surface-science methods withoperandoSTM observations of model catalysts in action. We illustrate the strength of this microscope with examples of CO oxidation on platinum surfaces.
Sum Frequency Laser Spectroscopy during Chemical Reactions on Surfaces
Authors: Rupprechter Günther 
Published: February 2011

AbstractThe surface specificity of vibrational sum frequency generation (VSFG) spectroscopy allows one to characterize adsorbed and reacting molecules on catalyst surfaces while the catalyst functions at high pressure and high temperature. VSFG spectroscopy can be carried out in different modes, including scanning, broadband, time-resolved, and polarization-dependent, and has been applied to various active surfaces. Single-crystal and nanoparticle model catalysts have mostly been used, which are typically prepared under ultrahigh vacuum, but applications to powder materials have been reported recently. In this article, the fundamentals and technical aspects of VSFG are summarized, and its benefits are illustrated by case studies of elementary processes of heterogeneous catalysis.
Polymer Nanocomposites
Authors: Winey Karen I. , Vaia Richard A. 
Published: February 2011

AbstractPolymer nanocomposites (PNCs)–that is, nanopar ticles (spheres, rods, plates) dispersed in a polymer matrix–have garnered substantial academic and industrial in terest since their inception, circa 1990. This is due in large part to the incredible promise demonstrated by these early efforts: PNCs will not only expand the per form ance space of traditional filled polymers, but introduce completely new combinations of properties and thus enable new applications for plastics. Low volume additions (1–5%) of nanopar -ticles, such as layered silicates or carbon nanotubes, provide property enhancements with respect to the neat resin that are comparable to those achieved by conventional loadings (15–40%) of traditional fillers. The lower loadings facilitate proc essing and re duce component weight. Most important, though, is the unique value - added properties not normally possible with traditional fillers, such as reduced permeability, optical clarity, self - passivation, and increased re sis tance to oxidation and ablation. These characteristics have been transformed into numerous commercial suc cesses, including automotive parts, coatings, and flame retardants. This issue of theMRS Bulletinprovides a snapshot of these exemplary successes, future opportunities, and the critical scientific challenges still to be addressed for these nanoscale multiphase systems. In addition, these ar ticles provide a perspective on the current status and future directions of polymer nanocomposite science and technology and their potential to move beyond additive concepts to designed ma te rials and devices with prescribed nanoscale composition and morphology.
Strategies for Dispersing Nanoparticles in Polymers
Authors: Krishnamoorti Ramanan 
Published: February 2011

AbstractControlling the dispersion of nanoparticles in polymeric matrices is the most significant impediment in the development of high-perform ance polymer nanocomposite ma te rials and results primarily from the strong interpar ticle interactions between the nanopar ticles. This review examines the theoretical and experimental strategies employed in developing appropriate chemical and physical methods to achieve controlled dispersion of nanopar ticles. Methods to characterize the state of dispersion, including force and electron micros copy, and scattering, electrical, and mechanical spectroscopy, are considered with special emphasis on achieving quantitative meas ures of the dispersion. Some of the outstanding issues, such as long-term aging and the implication for the dispersion of nanopar ticles, development of high-throughput methods for rapid screening, and methods for in-line monitoring, are also discussed.
Transparent Conducting Oxides for Photovoltaics
Authors: Fortunato Elvira , Ginley David , Hosono Hideo , Paine David C. 
Published: February 2011

AbstractTransparent conducting oxides (TCOs) are an increasingly important component of photovoltaic (PV) devices, where they act as electrode elements, structural templates, and diffusion barriers, and their work function controls the open-circuit device voltage. They are employed in applications that range from crystalline-Si heterojunction with intrinsic thin layer (HIT) cells to organic PV polymer solar cells. The desirable characteristics of TCO materials that are common to all PV technologies are similar to the requirements for TCOs for flat-panel display applications and include high optical transmissivity across a wide spectrum and low resistivity. Additionally, TCOs for terrestrial PV applications must use low-cost materials, and some may require device-technology-specific properties. We review the fundamentals of TCOs and the matrix of TCO properties and processing as they apply to current and future PV technologies.
Epitaxial Growth of III-V Nanowires on Group IV Substrates
Authors: Bakkers Erik P. A. M. , Borgström Magnus T. , Verheijen Marcel A. 
Published: February 2011

AbstractSemiconducting nanowires are emerging as a route to combine heavily mismatched materials. The high level of control on wire dimensions and chemical composition makes them promising materials to be integrated in future silicon technologies as well as to be the active element in optoelectronic devices.This ar ticle reviews the recent progress in epitaxial growth of nanowires on non-corresponding substrates. We highlight the advantage of using small dimensions to facilitate accommodation of the lattice strain at the surface of the structures. More specifically, we will focus on the growth of III-V nanowires on Group IV substrates. This approach enables the integration of high-perform ance III-V semiconductors monolithically into mature silicon technology, since fundamental issues of III-V integration on Si such as lattice and thermal expansion mismatch can be overcome. Moreover, as there will only be one nucleation site per crystallite, the system will not suffer from antiphase boundaries.Issues that affect the electronic properties of the heterojunction, such as the crystallographic quality and diffusion of elements across the heterointerface, will be discussed. Finally, we address potential applications of vertical III-V nanowires grown on silicon.