bluuebunny/crossref_metadata_2025 huggingface dataset:
Catalysts for Emerging Energy Applications
Authors: Gates Bruce C. , Huber George W. , Marshall Christopher L. , Ross Phillip N. , Siirola Jeffrey , Wang Yong
Published: February 2011

Catalysis is the essential technology for chemical transformation, including production of fuels from the fossil resources petroleum, natural gas, and coal. Typical catalysts for these conversions are robust porous solids incorporating metals, metal oxides, and/or metal sulfides. As efforts are stepping up to replace fossil fuels with biomass, new catalysts for the conversion of the components of biomass will be needed. Although the catalysts for biomass conversion might be substantially different from those used in the conversion of fossil feedstocks, the latter catalysts are a starting point in today's research. Major challenges lie ahead in the discovery of efficient biomass conversion catalysts, as well as in the discovery of catalysts for conversion of CO2and possibly water into liquid fuels.
Aviation
Authors: Banerjee Dipankar
Published: February 2011

Aviation accounts for about 3% of the current global energy consumption of 15 terawatts (TW). The global annual growth of energy use in the aviation sector is likely to be around 2.15% and will exceed that in other transportation sectors, although land transport will continue to consume the largest amounts of fuel. Figure 1 displays the historical improvements in energy efficiency in the aviation sector. Fuel use is determined by both operational and technological factors. The former includes the passenger load factor, ground efficiencies, taxi procedures, take-off and landing paths and circuitry (actual distance traveled versus a great-circle distance), and changes in the mixture of old and new aircraft and propulsion systems with time. Technology factors, focusing on materials issues, are described in greater detail herein.
Increasing Building Energy Efficiency Through Advances in Materials
Authors: Judkoff Ron
Published: February 2011

Materials advances could help to reduce the energy and environmental impacts of buildings. Globally, buildings use about 20% of primary energy and account for 20% of atmospheric emissions. Building energy consumption emanates from a variety of sources, some of which are related to the building envelope or fabric, some to the equipment in the building, and some to both. Opportunities for reducing energy use in buildings through innovative materials are therefore numerous, but there is no one system, component, or material whose improvement alone can solve the building energy problem. Many of the loads in a building are interactive, and this complicates cost/benefit analysis for new materials, components, and systems. Moreover, components and materials for buildings must meet stringent durability and cost/performance criteria to last the long service lifetimes of buildings and compete successfully in the marketplace.
Membranes in Desalination and Water Treatment
Authors: Vainrot Nataly , Eisen Moris S. , Semiat Raphael
Published: February 2011

Membrane techniques for water treatment have been growing significantly for the last decade. Reverse osmosis, for example, is the leading seawater desalination technique. Nanofiltration membranes are used more and more for hardness removal and even to desalinate slightly polluted waters. Ultrafiltration and microfiltration membranes are used extensively mainly as membrane bioreactors in wastewater recovery. While this trend is growing, the membranes still may be improved significantly, based on new materials designed to increase the flux of water through the membranes at reduced pressures while maintaining or even improving the rejection of dissolved matter or suspended matter. Better membranes will reduce energy consumption while maintaining affordable separation properties.
Reducing Industrial Energy Use and CO2 Emissions: The Role of Materials Science
Authors: Gielen Dolf , Newman John , Patel Martin K.
Published: February 2011

Nearly one-third of the world's energy consumption and 36% of its carbon dioxide (CO2) emissions are attributable to manufacturing industries. However, the adoption of advanced technologies already in commercial use could provide technical energy savings in industry of 27–41 exajoules (EJ), along with a reduction in CO2 emissions of 2.2–3.2 gigatonnes (Gt) per year, about 7–12% of today's global CO2 emissions. Even more significant savings can be attained on the supply side if fuel switching and CO2 capture and storage are considered. However, such changes must start in the coming decade to have a substantial impact by 2050.
Nanofunctional Materials in Cancer Research: Challenges, Novel Methods, and Emerging Applications
Authors: Nagahara Larry A. , Ferrari Mauro , Grodzinski Piotr
Published: February 2011

Despite recent progress in the treatment of cancer, far too many cases are still diagnosed only after tumors have metastasized. As a result, patients with cancer face a grim prognosis and often need to endure toxic and uncomfortable whole-body chemotherapy and/or other radiation treatments with the hope that their cancers will be eliminated. If the disease can be detected early enough, statistics have shown that the burden of cancer is drastically reduced. Nanotechnology applied to cancer, by way of nanofunctional materials, is in a unique position to significantly transform the way the disease is diagnosed, imaged, and treated and is the focus of this issue of MRS Bulletin. Materials research in nanotechnology is already successfully implemented in several applications. For instance, photocatalysis using TiO2 nanoparticles is becoming the dominant method for the “self-cleaning” of material surfaces such as glass, ceramics, and fabrics. The nanomaterial carbon nanotubes is a promising candidate in sensor technology and field-emission technology. Our goal is to illustrate the promising new methods being developed in the research community and the challenges that need to be overcome in order to reach clinical utility. More importantly, we hope this issue helps educate and invoke the materials science community to tackle some of the hard issues in diagnosing and treating this disease.
Gold-Based Magneto/Optical Nanostructures: Challenges for In Vivo Applications in Cancer Diagnostics and Therapy
Authors: Melancon Marites P. , Lu Wei , Li Chun
Published: February 2011

Nanoparticles with a gold shell and iron core have unique optical and magnetic properties that can be utilized for simultaneous detection and treatment strategies. Several nanoparticles have been synthesized and show an ability to mediate a variety of potential applications in biomedicine, including cancer molecular optical and magnetic resonance imaging, controlled drug delivery, and photothermal ablation therapy. However, to be effective, these nanoparticles must be delivered efficiently into their targets. In this review, we will provide an updated summary of the gold-shelled magnetic nanoparticles that have been synthesized, methods for characterization, and their potential for cancer diagnosis and treatment. We will also discuss the biological barriers that need to be overcome for the effective delivery of these nanoparticles. The desired nanoparticle characteristics needed to evade these biological barriers, such as size, shape, surface charge, and surface coating are also explained.
Materials Science of High-Level Nuclear Waste Immobilization
Authors: Weber William J. , Navrotsky Alexandra , Stefanovsky Sergey , Vance Eric R. , Vernaz Etienne
Published: February 2011

With the increasing demand for the development of nuclear power comes the responsibility to address the issue of waste, including the technical challenges of immobilizing high-level nuclear wastes in stable solid forms for interim storage or disposition in geologic repositories. The immobilization of high-level nuclear wastes has been an active area of research and development for over 50 years. Borosilicate glasses and complex ceramic composites have been developed to meet many technical challenges and current needs, although regulatory issues, which vary widely from country to country, have yet to be resolved. Cooperative international programs to develop advanced proliferation-resistant nuclear technologies to close the nuclear fuel cycle and increase the efficiency of nuclear energy production might create new separation waste streams that could demand new concepts and materials for nuclear waste immobilization. This article reviews the current state-of-the-art understanding regarding the materials science of glasses and ceramics for the immobilization of highlevel nuclear waste and excess nuclear materials and discusses approaches to address new waste streams.
Ultimate Scaling of CMOS Logic Devices with Ge and III–V Materials
Authors: Heyns M. , Tsai W.
Published: February 2011

Over the years, many new materials have been introduced in advanced complementary metal oxide semiconductor (CMOS) processes in order to continue the trend of reducing the gate length and increasing the performance of CMOS devices. This is clearly evidenced in the International Technology Roadmap for Semiconductors (ITRS), which indicates the requirements and technological challenges in the microelectronics industry in various technology nodes. Every new technology node, characterized by the minimal device dimensions that are used, has required innovations in new materials and transistor design. The introduction of deposited high-κ gate dielectrics and metal gates as replacements for the thermally grown SiO2 and poly-Si electrode was a major challenge that has been met in the transition toward the 32 nm technology node since it replaced the heart of the metal oxide semiconductor structure. For the next generation of technology nodes, even bigger hurdles will need to be overcome, since new device structures and high-mobility channel materials such as Ge and III–V compounds might be needed, according to the ITRS roadmap, to meet the power and performance specifications of the 16 nm CMOS node and beyond. The basic properties of these high-mobility channel materials and their impact on the device performance have to be fully understood to allow process integration and full-scale manufacturing. In addition to thermal stability, compatibility with other materials, electronic transport properties, and especially the passivation of electronically active defects at the interface with a high-κ dielectric, are enormous challenges. Many encouraging results have been obtained, but the stringent demands in terms of electrical performance and oxide thickness scaling needed for highly scaled CMOS devices are not yet fully met. Other areas where breakthroughs will be needed are the formation of low-resistivity contacts, especially on III–V materials, and III–V materials suited for pMOS channels. An overview of the major successes and remaining critical issues in the materials research on high-mobility channel materials for advanced CMOS devices is given in this issue of MRS Bulletin.
InGaAs Metal Oxide Semiconductor Devices with Ga2O3(Gd2O3) High-κ Dielectrics for Science and Technology beyond Si CMOS
Authors: Hong M. , Kwo J. , Lin T.D. , Huang M.L.
Published: February 2011

An overview is given on scientific and device advances for InGaAs metal oxide semiconductor heterostructures and inversion channel metal oxide semiconductor field-effect transistors (MOSFETs), with emphasis on results using ultrahigh vacuum-deposited Ga2O3(Gd2O3) [GGO] as high-κ dielectrics. Regardless of the approaches used to deposit high-κ dielectrics on InGaAs, critical material and electrical parameters of fabricating inversion channel InGaAs MOSFETs must be ready for complementary MOS technology beyond the 16-nm node, and some of these parameters have been achieved. These parameters include low interfacial density of states; low electrical leakage currents; high-temperature (800–900°C) thermal stability for high-κ dielectrics/InGaAs heterostructures, where the amorphous oxide structure and atomically smooth and sharp interfaces are retained; and oxide scalability with a capacitance equivalent thickness of ≤1 nm. Interfacial chemical properties and band parameters, which are important for device design in the high κs/InGaAs, have been thoroughly studied. Representative enhancement-mode InGaAs MOSFETs are compared and correlated with the interfacial structures. Deposition methods and electrical characteristics of high-κ dielectrics on InGaA are discussed. The inversion channel InGaAs MOSFETs of 0.4–1.0 μm gate length have exhibited excellent device performance in terms of drain current and transconductance.
Compound Semiconductors for Low-Power p-Channel Field-Effect Transistors
Authors: Bennett Brian R. , Ancona Mario G. , Boos J. Brad
Published: February 2011

Research in n-channel field-effect transistors based upon III–V compound semiconductors has been very productive over the last 30 years, with successful applications in a variety of high-speed analog circuits. For digital applications, complementary circuits are desirable to minimize static power consumption. Hence, p-channel transistors are also needed. Unfortunately, hole mobilities are generally much lower than electron mobilities for III–V compounds. This article reviews the recent work to enhance hole mobilities in antimonide-based quantum wells. Epitaxial heterostructures have been grown with the channel material in 1–2% compressive strain. The strain modifies the valence band structure, resulting in hole mobilities as high as 1500 cm2/Vs. The next steps toward an ultra-low-power complementary metal oxide semiconductor technology will include development of a compatible insulator technology and integration of n- and p-channel transistors.
Meso- and Macroporous Ceramics by Phase Separation and Reactive Sintering Methods
Authors: Suzuki Yoshikazu , Morgan Peter E.D.
Published: February 2011

Controlled pore glasses are formed through selective etching of one phase of a spinodally decomposed borosilicate glass, an old technique that is the basis of the porous Vycor synthesis technique developed in the 1920s. This technique is receiving renewed attention as these glasses find new applications as substrates for biosensing, bioreactors, precise filtration, and chromatography. Analogous techniques are being applied to crystalline ceramics, such as directed cooling of ZrO2/MgO and MgAl2O4/Al2O3 eutectics to drive phase separation with the subsequent dissolution of one phase. Pyrolytic reactive sintering is a combination of the phase separation method and the reactive sintering method to obtain a 3D porous structure network. For example, dolomite (CaMg[CO3]2) and ZrO2 yield a uniformly porous CaZrO3/MgO composite that utilizes evolved CO2 as a “pore-forming agent.” This article gives an overview of recent developments on meso- and macroporous ceramics based on phase separation and reactive sintering technologies.
Modeling Amorphous Porous Materials and Confined Fluids
Authors: Gelb Lev D.
Published: February 2011

Many of the porous materials used in laboratory and industrial processes do not have simple regular or crystalline structures. This greatly complicates efforts to characterize them and to understand and optimize their performance for particular applications. This review surveys recent efforts to use simulation and modeling to better understand the structure and performance of several classes of materials, including phase-separated glasses, sol-gel–derived materials, templated silica materials, and activated carbons. Approaches to modeling these materials fall generally into two classes: reconstructions, which generate models based on experimental measurements, and mimetic simulations, which attempt to model the preparation of the materials. While significant progress has been made in many respects, both reconstructive and mimetic transferred currently available are often computationally intensive and not easily transferable between different classes of materials. Finally, since gas adsorption is used widely as a characterization tool for amorphous porous materials and is often the focus of the materials' application, recent developments in simulation and theory appropriate to the study of capillary phenomena in amorphous porous materials are reviewed.
Electromechanics on the Nanometer Scale: Emerging Phenomena, Devices, and Applications
Authors: Kalinin Sergei V. , Setter Nava , Kholkin Andrei L.
Published: February 2011

Coupling between mechanical and electrical phenomena is ubiquitous at the nano-and molecular scales, with examples ranging from piezoelectricity and flexoelectricity in perovskites to complex molecular transformations in redox active molecules and ion channels. This article delineates the field of nanoelectromechanics enabled by recent advances in scanning probe, indentation, and interferometric techniques and provides a unified outlook at a number of related topics, including membrane and surface flexoelectricity, local piezoelectricity in ferroelectrics and associated devices, and electromechanical molecular machines. It also summarizes experimental and theoretical challenges on the pathway to visualize, control, and manipulate electromechanical activity on the nanoscale and molecular levels.
Piezoresponse Force Microscopy: A Window into Electromechanical Behavior at the Nanoscale
Authors: Bonnell D.A. , Kalinin S.V. , Kholkin A.L. , Gruverman A.
Published: February 2011

Piezoresponse force microscopy (PFM) is a powerful method widely used for nanoscale studies of the electromechanical coupling effect in various materials systems. Here, we review recent progress in this field that demonstrates great potential of PFM for the investigation of static and dynamic properties of ferroelectric domains, nanofabrication and lithography, local functional control, and structural imaging in a variety of inorganic and organic materials, including piezoelectrics, semiconductors, polymers, biomolecules, and biological systems. Future pathways for PFM application in high-density data storage, nanofabrication, and spectroscopy are discussed.
Membrane Electromechanics in Biology, with a Focus on Hearing
Authors: Sachs F. , Brownell W. E. , Petrov A. G.
Published: February 2011

Cells are ion conductive gels surrounded by a ∼5-nm-thick insulating membrane, and molecular ionic pumps in the membrane establish an internal potential of approximately −90 mV. This electrical energy store is used for high-speed communication in nerve and muscle and other cells. Nature also has used this electric field for high-speed motor activity, most notably in the ear, where transduction and detection can function as high as 120 kHz. In the ear, there are two sets of sensory cells: the “inner hair cells” that generate an electrical output to the nervous system and the more numerous “outer hair cells” that use electromotility to counteract viscosity and thus sharpen resonance to improve frequency resolution. Nature, in a remarkable exhibition of nanomechanics, has made out of soft, aqueous materials a microphone and high-speed decoder capable of functioning at 120 kHz, limited only by thermal noise. Both physics and biology are only now becoming aware of the material properties of biomembranes and their ability to perform work and sense the environment. We anticipate new examples of this biopiezoelectricity will be forthcoming.
Nanoionics Switching Devices: “Atomic Switches”
Authors: Hasegawa Tsuyoshi , Terabe Kazuya , Sakamoto Toshitsugu , Aono Masakazu
Published: February 2011

Novel nanoionics devices, atomic switches, have been developed using a solid-electrochemical reaction to control the formation and annihilation of the metal filament between two electrodes. The switching operation can be achieved simply by the application of a bias voltage to precipitate metal atoms in a nanogap between the two electrodes or to dissolve them onto one of the electrodes. The small size of atomic switches enables rapid switching even though atomic motion is required. They also have several novel characteristics in that they are nonvolatile, consume less power, and have a simple structure and a low on-resistance. Logic gates and 1 kbit nonvolatile memory chips have been developed using atomic switches in order to demonstrate the possibilities for improving present-day electronic devices. Their characteristics also enable the fabrication of new types of electronic devices, such as high-performance programmable logic devices that may achieve a multitude of functions on a single chip.
Solid-State Materials for Clean Energy: Insights from Atomic-Scale Modeling
Authors: Saiful Islam M. , Slater Peter R.
Published: February 2011

Fundamental advances in solid-state ionics for energy conversion and storage are crucial in addressing the global challenge of cleaner energy sources. This review aims to demonstrate the valuable role that modern computational techniques now play in providing deeper fundamental insight into materials for solid oxide fuel cells and rechargeable lithium batteries. The scope of contemporary work is illustrated by studies on topical materials encompassing perovskite-type proton conductors, gallium oxides with tetrahedral moieties, apatite-type silicates, and lithium iron phosphates. Key fundamental properties are examined, including mechanisms of ion migration, dopant-defect association, and surface structures and crystal morphologies.
Exploiting New Opportunities in Materials Research by Remembering and Applying Old Lessons
Authors: Nix William D.
Published: February 2011

Recalling some of the progress that has been made in understanding the mechanical properties of materials over the past 50 years or so reveals the importance of remembering and applying old lessons when addressing new opportunities in materials research. Often, the classical lessons of the past are especially useful as a guide for thinking about new problems. Such an approach to new problems is intimately connected to the creation of simple models that capture the essential features of the phenomena involved. Experience shows that, although such efforts might not pay off immediately, they come to be useful many years later when new problems are confronted. The merit of applying old lessons to new problems is described herein by using examples from the author's career in characterizing and understanding the mechanical properties of materials. It is hoped that these lessons are sufficiently general to be applied to other areas of materials research. Problems ranging from the high-temperature creep resistance of titanium aluminides, to the residual stresses in deposited thin films, to diffusive relaxation processes in thin films, to the size dependence of the strength of crystalline materials at the nanometer scale, all provide examples of how applying lessons of the past can help to understand new problems. An effort is also made to identify new, emerging problems in materials research where the application of the lessons of the past, together with new capabilities of the future, can come together to produce a fresh understanding of material behavior.
A Mnemonic Scheme for Thermodynamics
Authors: Zhao J.-C.
Published: February 2011

A mnemonic scheme is presented to help recall the equations in classical thermodynamics that connect the four state variables (temperature, pressure, volume, and entropy) to the four thermodynamic potentials (internal energy, Helmholtz free energy, enthalpy, and Gibbs free energy). Max Born created a square to help recall the thermodynamic equations. The new scheme here separates the Max Born square into two squares, resulting in easier recalling of several sets of equations, including the Maxwell equations, without complicated rules to remember the positive or negative signs.
Nanostructured Organic–Inorganic Hybrid Solar Cells
Authors: McGehee Michael D.
Published: February 2011

When light is absorbed in organic semiconductors, bound electron–hole pairs known as excitons are generated. The electrons and holes separate from each other at an interface between two semiconductors by electron transfer. It is advantageous to form well-ordered nanostructures so that all of the excitons can reach the interface between the two semiconductors and all of the charge carriers have a pathway to the appropriate electrode. This article discusses charge and exciton transport in organic semiconductors, as well as the opportunities for making highly efficient solar cells and for using carbon nanotubes to replace metal oxide electrodes.
Synthesis and Processing of Organic Materials in Supercritical Carbon Dioxide
Authors: McCluskey Georgia E. , Lee Jin-Kyun , Sha Jing , Ober Christopher K. , Watkins Scott E. , Holmes Andrew B.
Published: February 2011

Carbon dioxide (CO2) is arguably the most high-profile molecule of recent times. Although much of its bad press comes from environmental concerns associated with greenhouse gas emissions, there exists the possibility to harness this abundant resource for application to the synthesis and processing of useful materials. This article describes a selection of recent successes in using supercritical carbon dioxide (scCO2) as a solvent for polymerizations. Further, the uses of compressed CO2 as a processing tool in the fabrication of materials for applications such as coatings and biomaterials are discussed. Finally, the application of scCO2 to photolithography is demonstrated, with particular focus on CO2 as a processing solvent for the patterning of organic electronic devices.
Atomistic Simulations of Dislocations in Confined Volumes
Authors: Derlet P.M. , Gumbsch P. , Hoagland R. , Li J. , McDowell D.L. , Van Swygenhoven H. , Wang J.
Published: February 2011

Internal microstructural length scales play a fundamental role in the strength and ductility of a material. Grain boundaries in nanocrystalline structures and heterointerfaces in nanolaminates can restrict dislocation propagation and also act as a source for new dislocations, thereby affecting the detailed dynamics of dislocation-mediated plasticity. Atomistic simulation has played an important and complementary role to experiment in elucidating the nature of the dislocation/interface interaction, demonstrating a diversity of atomic-scale processes covering dislocation nucleation, propagation, absorption, and transmission at interfaces. This article reviews some atomistic simulation work that has made progress in this field and discusses possible strategies in overcoming the inherent time scale challenge of finite temperature molecular dynamics.
Recent Advances in Bulk Crystal Growth
Authors: Fornari Roberto , Roth Michael
Published: February 2011

The growth of high-quality single crystals remains a challenging endeavor of materials science. Crystals of suitable size (from fiber crystals with diameters of tens of micrometers up to crystalline ingots or blocks with volumes up to 1 m3) and perfection (free from precipitates, inclusions, and twins with good uniformity and low concentration of dislocations) are required for fundamental research and practical implementation in microelectronic circuits, electro-optic switches and modulators, solid-state lasers, light-emitting diodes, sensors, and many other devices. In this introductory article of this issue of MRS Bulletin, we describe the two main challenges of today's crystal growth, namely (1) the production of well-established crystalline materials with improved structural perfection and larger size at a lower cost and (2) the bulk growth of new categories of materials with extreme thermodynamic characteristics, such as a very high melting point, high melting dissociation pressure, incongruent phase diagram, and anisotropic segregation. The subsequent six articles provide examples of how the crystal growers took up these challenges, which led to new experimental approaches and technological advances.
Advanced Structural Materials and Cladding
Authors: Allen T. , Burlet H. , Nanstad R.K. , Samaras M. , Ukai S.
Published: February 2011

Advanced nuclear energy systems, both fission- and fusion-based, aim to operate at higher temperatures and greater radiation exposure levels than experienced in current light water reactors. Additionally, they are envisioned to operate in coolants such as helium and sodium that allow for higher operating temperatures. Because of these unique environments, different requirements and challenges are presented for both structural materials and fuel cladding. For core and cladding applications in intermediate-temperature reactors (400–650°C), the primary candidates are 9–12Cr ferritic–martensitic steels (where the numbers represent the weight percentage of Cr in the material, i.e., 9–12 wt%) and advanced austenitic steels, adapted to maximize high-temperature strength without compromising lower temperature toughness. For very high temperature reactors (>650°C), strength and oxidation resistance are more critical. In such conditions, high-temperature metals as well as ceramics and ceramic composites are candidates. For all advanced systems operating at high pressures, performance of the pressure boundary materials (i.e., those components responsible for containing the high-pressure liquids or gases that cool the reactor) is critical to reactor safety. For some reactors, pressure vessels are anticipated to be significantly larger and thicker than those used in light water reactors. The properties through the entire thickness of these components, including the effects of radiation damage as a function of damage rate, are important. For all of these advanced systems, optimizing the microstructures of candidate materials will allow for improved radiation and high-temperature performance in nuclear applications, and advanced modeling tools provide a basis for developing optimized microstructures.
Graphite, Ceramics, and Ceramic Composites for High-Temperature Nuclear Power Systems
Authors: Bonal Jean-Pierre , Kohyama Akira , van der Laan Jaap , Snead Lance L.
Published: February 2011

The age of nuclear power originated with the gas-cooled, graphite-moderated reactor in the 1940s. Although this reactor design had intrinsic safety features and enjoyed initial widespread use, gas-cooled reactor technology was supplanted by higher power density water-cooled systems in the 1960s. However, the next-generation reactors seek enhanced power conversion efficiency and the ability to produce hydrogen, best accomplished with high-temperature gas-cooled systems. Thus, international interest in gas-cooled reactor systems is reemerging. Although the materials systems of these reactors are fairly simple, the reactor environment, particularly its high temperatures and intense irradiation, present extreme challenges in terms of material selection and survivability. This article provides a brief review of materials issues and recent progress related to graphite and ceramic materials for application in gas-cooled nuclear reactor environments. Of particular interest are the drastic, irradiation-induced microstructural evolution and thermophysical property changes occurring as a result of energetic neutron irradiation, which significantly impact the performance and lifetime of much of the reactor core. For “nuclear” graphite, the performance and lifetime not only are closely related to the irradiation environment but also are dramatically affected by the specifics of the particular graphite: manufacturing process, graphitization temperature, composition (amount of coke, filler, etc., depending on where it was mined), and so on. Moreover, the extreme environmental challenges set down by this next generation of fission nuclear plants have driven the development and application of ceramic composites for critical components, pushing beyond upper temperature limits set by metallic alloys used in previous generations of nuclear reactors. The composite material systems of particular interest are continuous carbon-fiber composites and newly developed radiation-resistant silicon carbide fiber composites.
Mechanical Regulation of Cells by Materials and Tissues
Authors: Thomas Wendy E. , Discher Dennis E. , Prasad Shastri V.
Published: February 2011

Over the last dozen years, studies at the cell and tissue level have demonstrated that the function and fate of all cells, stem cells in particular, are affected by the collective physical properties of their microenvironments. Meanwhile, biophysical studies at the single molecule level have taught us a great deal about how mechanical forces affect the structure and function of proteins involved in the assembly of cells into tissues. Together, these molecular, cellular, and tissue studies provide insight into the process and importance of mechanotransduction, which is the process by which mechanical forces are transduced into biological signals. This insight should motivate biomimetic approaches to better control cell fate and tissue function.
Functional Tissue Engineering Through Biofunctional Macromolecules and Surface Design
Authors: Moroni Lorenzo , Habibovic Pamela , Mooney David J. , van Blitterswijk Clemens A.
Published: February 2011

Tissue engineering is a rapidly developing discipline that has already entered the clinics and will tremendously change patient management in the near future. The aim of classical tissue engineering is to heal damaged or diseased tissues and organs through the combination of cells, biological factors, and porous biomaterials. The resulting, engineered tissue must possess appropriate functional properties to replace or supplement the targeted tissue. This is still a challenge to overcome before tissue-engineered products can be considered a complete success. Classical tissue engineering approaches rely on the use of mature cells expandedin vitroand transplanted alone or seeded in passive 3D scaffolds, which can lead to the loss of cellular phenotype and production of nonfunctional extracellular matrix. An emerging strategy involves the design of bioactive 3D scaffolds with instructive properties able to recruit cellsin situand direct tissue formation. Here, we present and discuss recent efforts to achieve smart scaffolds encompassing macromolecular biofunctionalization and surface design.
Polymer Behavior at the Air-Water Interface
Authors: Gargallo Ligia
Published: February 2011

This article reviews polymer behavior at the air-water interface with a focus on the Langmuir technique and spreading processes to gain insight into this interface. The influence of the solvent and the water subphase on some polymer monolayers is discussed. The surface pressure–area isotherms (π–A) are described in terms of the chemical structure and the hydrophilic-hydrophobic balance of selected polymeric systems, with an emphasis on the behavior of the specific diblock copolymer films at the air-water interface. In some cases, molecular dynamic simulation studies can be used to visualize the organization and orientation of polymers at the air-water interface and to identify the main molecular interactions involved in such processes.
Shape and Biomechanical Characteristics of Human Red Blood Cells in Health and Disease
Authors: Diez-Silva Monica , Dao Ming , Han Jongyoon , Lim Chwee-Teck , Suresh Subra
Published: February 2011

The biconcave shape and corresponding deformability of the human red blood cell (RBC) is an essential feature of its biological function. This feature of RBCs can be critically affected by genetic or acquired pathological conditions. In this review, we highlight new dynamicin vitroassays that explore various hereditary blood disorders and parasitic infectious diseases that cause disruption of RBC morphology and mechanics. In particular, recent advances in high-throughput microfluidic devices make it possible to sort/identify healthy and pathological human RBCs with different mechanobiological characteristics.
Electronic Properties of Organic-Based Interfaces
Authors: Kronik Leeor , Koch Norbert
Published: February 2011

Organic-based interfaces can possess a range of surprising electronic properties that are of intense interest from both the basic science and the applied research points of view. In this issue of MRS Bulletin, we provide state-of-the-art overviews of selected topics involving three complementary aspects of the electronic properties of organic-based interfaces: the nascent electronics technologies that would gain from improved understanding and control of such interfaces; the novel properties that organic-based interfaces may possess; and the experimental and theoretical challenges afforded by such studies.
Van der Waals Interactions Between Organic Adsorbates and at Organic/Inorganic Interfaces
Authors: Tkatchenko Alexandre , Romaner Lorenz , Hofmann Oliver T. , Zojer Egbert , Ambrosch-Draxl Claudia , Scheffler Matthias
Published: February 2011

Van der Waals (vdW) interactions play a prominent role in the structure and function of organic/organic and organic/inorganic interfaces. Their accurate determination from first principles, however, is a notoriously difficult task. Recently, a surge of interest in modeling vdW interactions has led to promising theoretical developments. This article reviews the state-of-the-art of describing vdW interactions by density-functional theory with respect to accuracy and practicability. The performance of the different methods is demonstrated for simple systems, such as rare-gas dimers and small organic molecules. The nature of binding at organic/inorganic interfaces is then exemplified for the perylene-3,4,9,10-tetracarboxylic-3,4,9,10-dianhydride (PTCDA) molecule at surfaces of coinage metals. This fundamental system is the best-characterized organic molecule/metal interface in experiment and theory. We emphasize the crucial importance of a balanced description of both geometry and electronic structure in order to understand and model the properties of such systems. Finally, the relevance of vdW interactions to the function of actual devices based on interfaces is discussed.
Organic Electronics at the Interface with Biology
Authors: Owens Róisín M. , Malliaras George G.
Published: February 2011

The emergence of organic electronics represents one of the most dramatic technological developments of the past two decades. Perhaps the most important frontier of this field involves the interface with biology. The “soft” nature of organics offers better mechanical compatibility with tissue than traditional electronic materials, while their natural compatibility with mechanically flexible substrates suits the nonplanar form factors often required for implants. More importantly, the ability of organics to conduct ions in addition to electrons and holes opens up a new communication channel with biology. In this article, we consider a few examples that illustrate the coupling between organic electronics and biology and highlight new directions of research.
Phase Transitions in Thin Block Copolymer Films
Authors: Kramer Edward J.
Published: February 2011

David Turnbull's experiments and theoretical insights paved the way for much of our modern understanding of phase transitions in materials. In recognition of his contributions, this lecture will concentrate on phase transitions in a material system not considered by Turnbull, thin diblock copolymer films. Well-ordered block copolymer films are attracting increasing interest as we attempt to extend photolithography to smaller dimensions. In the case of diblock copolymer spheres, an ordered monolayer is hexagonal, but the ordered bulk is body-centered cubic (bcc). There is no hexagonal plane in the bcc structure, so a phase transition must occur as n, the number of layers of spheres in the film, increases. How this phase transition occurs with nand how it can be manipulated is the subject of the first part of my presentation. In the second part of the talk, I show that monolayers of diblock copolymer spheres and cylinders undergo order-to-disorder transitions that differ greatly from those of the bulk. These ordered 2D monolayers are susceptible to phonon-generated disorder as well as to thermal generation of defects, such as dislocations, which, while they are line defects in 3D, are point defects in 2D. The results are compared to the theories of melting of 2D crystals (spheres) and of 2D smectic liquid crystals (cylinders), a comparison that will allow us to understand most, but not all, of the features of these order-disorder transitions that occur as the temperature is increased.
Overview of the Natural Space Environment and ESA, JAXA, and NASA Materials Flight Experiments
Authors: Edwards David L. , Tighe Adrian P. , Eesbeek Marc Van , Kimoto Yugo , de Groh Kim K.
Published: February 2011

Space environmental effects on materials are very severe and complex because of the synergistic interaction of orbital environments such as high-energy radiation particles, atomic oxygen, micrometeoroids, orbital debris, and ultraviolet irradiation interacting synergistically, along with thermal exposure. In addition, surface degradation associated with contamination can negatively impact optics performance. Materials flight experiments are critical to understanding the engineering performance of materials exposed to specific space environments. Likewise, the spacecraft designer must have an understanding of the specific environment in which a spacecraft will operate, enabling appropriate selection of materials to maximize engineering performance, increase mission lifetimes, and reduce risk. This article will present a methodology for assessing the engineering performance of materials baselined for a specific spacecraft or mission. In addition, an overview of the space environment, from low Earth orbit to interplanetary space, will be provided along with an overview on the effects of the space environment on materials performance. The majority of this article is devoted to materials flight experiments from the European Space Agency (ESA), the Japan Aerospace Exploration Agency (JAXA), and from the National Aeronautics and Space Administration (NASA). Some of the experiments reviewed include ESA's Materials Exposure and Degradation Experiment on the International Space Station (ISS), JAXA's Micro-Particles Capturer and Space Environment Exposure Device experiments on the ISS Service Module and on the ISS Japanese Experiment Module Exposed Facility, and NASA's Long Duration Exposure Facility satellite and the Materials International Space Station Experiment series flown on the exterior of ISS.
Mechanistic Studies of Atomic Oxygen Reactions with Polymers and Combined Effects with Vacuum Ultraviolet Light
Authors: Tagawa Masahito , Minton Timothy K.
Published: February 2011

This article focuses on mechanistic aspects of hyperthermal atomic oxygen reactions with polymers, which are the major contributor to material degradation in low Earth orbit. Due to the importance of well-controlled experiments in the understanding of the reaction mechanisms, ground-based experimental results obtained by a hyperthermal atomic oxygen beam generated by laser detonation facilities are mainly surveyed. Combined effects of atomic oxygen and vacuum ultraviolet (VUV) light on fluorinated polymers are also described. Such combined effects of hyperthermal atomic oxygen and VUV light are important not only from a fundamental point of view but also for engineering purposes (i.e., methodology for ground-based space environmental simulation). The VUV-sensitive polymers, poly(methyl methacrylate), and Teflon fluorinated ethylene-propylene do not show significant synergistic effects. Instead, the effect of combining atomic oxygen and VUV light produces erosion of the polymer that is the sum of the erosion caused by atomic oxygen and UV light acting individually. The experimental results suggest that material erosion in a complicated space environment may be quantitatively predicted if the erosion yields caused by the individual action of atomic oxygen and VUV light are known.
From Diatom Biomolecules to Bioinspired Syntheses of Silica- and Titania-Based Materials
Authors: Kröger Nils , Sandhage Kenneth H.
Published: February 2011

Amorphous silica is (next to CaCO3) the second most abundant biologically produced inorganic material. A certain group of photosynthetic microalgae, called diatoms, forms complex 3D silica architectures (frustules) containing regularly arranged nanoscale features (pores, channels, protuberances). Recently, biomolecules involved in diatom silica formation have been characterized, and first insights into their structure-function correlations have been obtained. This has spurred the development of synthetic (bio)polymers capable of directing thein vitroformation of silica and other inorganic materials from aqueous precursor solutions under mild conditions. Here we present a summary of current insight into the mechanism of silica formation by diatom biomolecules and provide examples of synthetic (bio)polymers for the formation of silica and titania materials with complex structures.
Cellulose Biocomposites—From Bulk Moldings to Nanostructured Systems
Authors: Berglund Lars A. , Peijs Ton
Published: February 2011

Cellulose biocomposites are widely used in industry as a low-cost engineering material with plant fiber reinforcement. However, chemical and microstructural heterogeneity causes low strength, low strain-to-failure, high moisture sensitivity, and odor and discoloration problems. Efforts toward improved performance through fiber orientation control, increased fiber lengths, and biopolymer use are reviewed. Interfacial strength control and moisture sensitivity are remaining challenges. As an attractive alternative reinforcement, high-quality cellulose nanofibers obtained by wood pulp fiber disintegration can be prepared at low cost. These nanofibers have high length/diameter ratios, diameters in the 5–15 nm range, and intrinsically superior physical properties. Wood cellulose nanofibers are interesting as an alternative reinforcement to more expensive nanoparticles, such as carbon nanotubes. Nanopaper and polymer matrix nanocomposites based on cellulose nanofiber networks show high strength, high work-of-fracture, low moisture adsorption, low thermal expansion, high thermal stability, high thermal conductivity, exceptional barrier properties, and high optical transparency. The favorable mechanical performance of bioinspired foams and low-density aerogels is reviewed. Future applications of cellulose biocomposites will be extended from the high-volume/low-cost end toward high-tech applications, where cellulose properties are fully exploited in nanostructured materials.
Physics of Oxides for Future Devices
Authors: Scott James F.
Published: February 2011

Ferroelectric oxides underwent a renaissance in the 1980s and 1990s, driven by the success in commercializing thin-film ferroelectric random-access memory devices (FRAMs) for applications such as the SONY PlayStation 2 memory board. Materials scientists gravitated into this new field from magnetic oxides and from high-Tcsuperconductivity. But as the FRAM prospects wane and neither dynamic random-access memory devices nor FLASH memory has been replaced, we now require new directions for materials research on oxides. In this article, I outline briefly four new directions for ferroelectric oxide research: something old—ferroelectrically induced ferromagnetism and multiferroic switching; something new—THz emission from oxide ferroelectrics; something borrowed—Heisenberg-like switching of domains in nanoferroelectrics; and something blue—ZnO light-emitting devices. Magnetoelectricity—the linear coupling of polarization and magnetization—was theoretically predicted by Igor Dzyaloshinskii in 1957 and measured experimentally by Astrov two years later. It did not produce commercial devices. Although a flurry of new work occurred in the 1970s, emphasizing boracites—mostly by Hans Schmid in Geneva, no materials were found that exhibited large effects at room temperature. In the past decade, the search has been renewed, emphasizing rare earth systems such as Tb manganites.
Better batteries for electric vehicles
Authors: Wu Corinna
Published: February 2011

Improved battery technology, innovative recharging strategies, and generous financial incentives are making electric vehicles more attractive to consumers than ever before.