bluuebunny/crossref_metadata_2025_split huggingface dataset:
Applications of Synchrotron Surface X-Ray Scattering Studies of Electrochemical Interfaces
Authors: You Hoydoo , Nagy Zoltán 
Published: August 2016

Aqueous-solution/solid interfaces are ubiquitous in modern manufacturing environments as well as in our living environment, and studies of such interfaces are an active area of science and engineering research. An important area is the study of liquid/solid interfaces under active electrochemical control, which has many immediate technological implications, for example, corrosion/passivation of metals and energy storage in batteries and ultracapacitors. The central phenomenon of electrochemistry is the charge transfer at the interface, and the region of interest is usually wider than a single atomic layer, ranging from a monolayer to thousands of angstroms, extending into both phases.Despite the technological and environmental importance of liquid/solid interfaces, the atomic level understanding of such interfaces had been very much hampered by the absence of nondestructive, in situ experimental techniques. The situation has changed somewhat in recent decades with the development of the largely ex situ ultrahigh vacuum (UHV) surface science, modern spectroscopic techniques, and modern surface microscopy.However in situ experiments of electrochemical interfaces are difficult, stemming from the special nature of these interfaces. These are so-called buried interfaces in which the solid electrode surface is covered by a relatively thick liquid layer. For this reason, the probe we use in the structural investigation must satisfy simultaneously two conditions: (1) the technique must be surface/interface sensitive, and (2) absorption of the probe in the liquid phase must be sufficiently small for penetration to and from the interface of interest without significant intensity loss.
Transport of Gases in Porous Membranes
Authors: Sotirchos Stratis V. , Burganos Vasilis N. 
Published: August 2016

The capability of membranes to affect differently, both qualitatively and quantitatively, the transport rates of chemical species of dissimilar chemical structure through their interior space renders them attractive for use in many separation problems. Extensive research efforts have thus been undertaken on the preparation and characterization of membrane materials and the study of the transport processes involved in their use in separation applications. The study of the transport of gaseous species through the pore space of porous membranes and the analysis and understanding of the mechanisms that are involved in this process are a very important, if not the most important, element in the development of membranebased separation processes.The resistance that a gaseous species encounters as it is transported through the pore space of a porous membrane is a function of its molecular properties, of its interaction with the material that makes up the walls of the pores, and of the membrane pore structure. Gaseous transport in pores can take place through various mechanisms, whose contribution to the overall transport rate of a particular species is, in general, determined by the strength of the interactions of the molecules of that species with the pore walls and by the relative magnitudes of three length scales that characterize the molecular size, the distance between pore walls, and the density of the fluid in the pore space.
Dense Palladium and Perovskite Membranes and Membrane Reactors
Authors: Ma Yi Hua 
Published: August 2016

The development of high-temperature processes and tighter environmental regulations requires utilization of efficient gas-separation processes that will provide high fluxes, high selectivity of separation, and the ability to operate at elevated temperatures. Dense inorganic membranes and membrane reactors are especially well suited for high-temperature reactions and separations, due in part to their thermal stability and high separation selectivity (in theory, infinite). Furthermore, membrane reactors offer an inherent advantage of combining reaction, product concentration, and separation in a single-unit operation for the improvement of process economics and waste minimization.The classification of membrane reactors can either be by membrane material and geometry or by the configuration of the reactor. Porous and dense membranes in both tubular and disk forms have been used for membrane reactors. The membrane can either be catalytically active (catalytic membrane reactor [CMR]) or simply act as a separation medium. In the latter case, the catalyst is packed in the reactor, whose walls are formed by the membrane (packed-bed membrane reactor [PBMR]). In addition, if the membrane is also catalytically active, the reactor is called a packed-bed catalytic membrane reactor (PBCMR).The principal materials from which porous inorganic (ceramic) membranes are made are alumina, zirconia, and glass. Alumina and zirconia membranes are usually asymmetric and composite, with a porous support (0.5–2.0 mm thick) for mechanical strength and one or more thin layers for carrying out separations.On the other hand, glass membranes, such as Vycor and microporous glass, have symmetric pores. Materials commonly used as the porous support are alumina, granular carbon, sintered metal, and silicon carbide.
Separation of Volatile Organic Compounds from Water by Pervaporation
Authors: Baker R.W. 
Published: August 2016

Pervaporation is a membrane process used to separate liquid mixtures. Separation is achieved by a combination of evaporation and membrane permeation. As a result, the process offers the possibility of removing dissolved volatile organic compounds (VOCs) from water, dehydrating organic solvents, and separating mixtures of components with close boiling points or azeotropes that are difficult to separate by distillation or other means.A schematic diagram of the pervaporation process is shown in Figure 1. In the example shown, the feed liquid is a solution of toluene in water which contacts one side of a membrane that is selectively permeable to toluene. The permeate, enriched in toluene, is removed as a vapor from the other side of the membrane. The driving force for the process is the difference in the partial vapor pressures of each component in the feed liquid and the permeate gas. This driving force can be increased by raising the temperature of the feed liquid to increase its vapor pressure or by decreasing the permeate gas pressure. The permeate gas pressure can be adjusted by using a vacuum pump, but industrially the most economical method is to cool and condense the vapor. Condensation spontaneously generates a vacuum. The permeate vapor pressure is then determined by the temperature of the permeate condenser and the composition of the permeate liquid generated by cooling and condensing the permeate vapor.Pervaporation membranes are made by coating a thin layer of selective polymer material onto a microporous support.
Medical Materials for the Next Millennium
Authors: Hench Larry L. 
Published: August 2016

The following article is an edited transcript of the Von Hippel Award address, given by recipient Larry L. Hench at the 1998 MRS Fall Meeting on December 3, 1998. Hench received the Materials Research Society's highest honor for “pioneering accomplishments in the field of glass and ceramics, including the demonstration of the first bioactive glass called Bioglass® and subsequent expansion of the field, demonstration of the feasibility of encapsulating nuclear waste products in glass/ceramic matrices, and development of sol-gel processing to produce ultrahigh-purity optical and dielectric materials with controlled microstructures.”The problem our Society faces as we head into the next millennium is that our average age expectancy has increased to a very attractive number of years but our bodies begin to deteriorate long before then. With the use of antiseptics, anti-biotics, and vaccinations during this Century, we have increased our survival rate considerably, as shown in Figure 1. The average age expectancy has increased to the mid-70s for many countries. However, as we pass the age of 30, our bodies begin to deteriorate. The quality of our connective tissues, particularly our skeletal tissues that hold us upright, begins to decline. The volume of bone that Supports us decreases with time, and for at least some of us, the weight our bones have to bear increases with time. The net effect is that the strength of bone degrades with age, causing the probability of fracture to increase (Figure 2). lf we integrate the area under the curve in Figure 1 from 60 years onward to 90 years, multiply it by the couple of billion people on earth, and then multiply that by the fraction of people subject to bone failure (Figure 2), we have a catastrophic repair problem facing society.
Environment-Assisted Intergranular Cracking
Authors: Scully J.R. 
Published: August 2016

Intergranular separation in polycrys-talline materials involves breaking metallic bonds along grain boundaries in response to stress. The surfaces created in this manner expose the grain facets on either side of the original boundary, as shown in Figure 1. This mode of fracture often occurs at much lower fracture stress and energy than cracking by ductile processes through the interior of grains. The exposure of specific materials to certain environments and stress can promote this low-energy, intergranular mode of separation, even when fracture of the same material in vacuum would occur along a ductile transgranu-lar path. Three types of environment-assisted intergranular cracking can occur in a wide variety of alloy/environment systems: intergranular stress-corrosion cracking (IGSCC), intergranular hydrogen embrittlement, and intergranular liquid-metal embrittlement.Figure 1 shows an example of IGSCC. This type of cracking is a pervasive problem in many technological applications, leading to extensive repairs, loss of service function, and safety concerns. IGSCC occurs in the weld-heat-affected zones of stainless-steel pipes in high-purity primary coolant waters within nuclear power plants, and in nickel-based alloys utilized as heat-exchanger tubing when exposed to the high-purity primary as well as secondary coolant waters in power plants. It is also seen in Al-based alloys used for fuselage skins and structural components in military and commercial aircraft when exposed to humid atmospheric conditions. Ferrous alloys used in the oil and gas industry are also susceptible. For instance, IGSCC of mild steels used in buried gas-transmission pipelines is a widespread international problem, leading to explosions when leaking natural gas ignites.
Lasing in Rare-Earth-Doped Semiconductors: Hopes and Facts
Authors: Gregorkiewicz T. , Langer J.M. 
Published: August 2016

Semiconductors doped with rare-earth (RE) elements have attracted a lot of attention as alternative materials for producing electrically pumpe d semiconductor lasers whose emission wavelength is very weakly dependent on temperature. This prospect is especially attractive in the case of indirect-gap Silicon, whose photonic applications as the material for light emitters still remain more of a hope than a reality. In view of a desirable emission wavelength at 1.5 μm, a lot of research has concentrated on Si:Er (see Coffa et al. for a recent review). It is generally recognized that doping with Er ions presents one of the most promising approaches to Silicon photonics. However, despiteintensive investigations, stimulated emission has not been conclusively demonstrated for Si.Er or for any other RE-doped semiconductor. This is in striking contrast to optical amplifiers and lasers based on various erbium-doped glasses. In this article, which builds on recent articles in MRS Bulletin on Silicon photonics, we will address the issues relevant to efficient light generation by semiconductors doped with RE elements in general, and specifically by Si:Er-based structures.The intraimpurity electronic structure of RE ions is dominate d by electron-electron and spin-orbit interactions within the 4f shell. In the case of Er3+, they produce separated J-multiplets with 4I15/2 and 4I13/2 as the ground and the lowest-lying excited states, respectively. Due to the effective Screening of 4f electrons by the outer electron Shells, the host has a very limited influence and changes only slightly the relative positions of the levels. Depending on a particular site symmetry, the even terms of the crystal field split the free-ion J-multiplets into the Stark components typically by several meV for the ground State. The energy-level diagram of an Er3+ ion in a cubic crystal field is shown in Figure 1, where the energy transfer paths relevant for Si:Er are also schematically indicated. The odd terms of the crystal field potential admix the states of opposite parity to the 4f11 configuration of the Er3+ ion, thereby introducing a certain degree of electric-dipole strength into the otherwise forbidden intra-4f-shell transitions. This effect enhance s slightly the magnetic-dipole strength of the 4I15/2 ↔ 4I13/2 transition and is host- and site-dependent. There-fore, Er-related center s of different microstructure can be fairly easily identified.
Spectral Data Storage Using Rare-Earth-Doped Crystals
Authors: Maniloff Eric S. , Johnson Alan E. , Mossberg Thomas W. 
Published: August 2016

Conventional optical data-storage techniques, such as magneto-optic disks and CD-ROMs, record a single bit of information at each particular substrate location. In order to produce the gigabyte-class storage substrates demanded by today's computers using such conventional technologies, access to tens of billions of individual material locations is required. This brute-force approach to optical data storage has produced impressive results. However, there is increasing interest in methods for more efficiently accessing storage materials. One approach is to record multiple bits at a single storage-material location. This can be accomplished by multiplexing the bits spectrally, using differing optical frequencies to record data bits. It has been realized for over 20 years that when certain materials are cooled to appropriate temperatures, typically below 20 K, the possibility of spectrally multiplexing large numbers of bits in a single material location arises. Although this approach, known as spectral hole-burning, has been proposed as a data-storage mechanism, to date it has primarily been used as a tool to study material properties. Rare-earth-doped crystals have been demonstrated to have properties that lend themselves to a variety of different spectral hole-burning-based data-storage applications. In this article, we will review the principles of spectral hole-burning, discuss some specific material systems in which spectral hole-burning is of particular interest, and describe methods for producing high-capacity, high-data-rate spectral memories.Spectral hole-burning, and spectral memories based on spectral hole-burning, depend on a material property referred to as inhomogeneous absorption line broadening. Materials exhibiting this property contain active atoms or molecules that individually respond to (absorb) very specific frequencies of light, but the collective response of all of the material's active atoms or molecules covers a spectral region that is broad compared with the response of a particular active atom or molecule. Inhomogeneous absorption line broadening is caused by local variations in the structure of the host, which in turn lead to variations in the electronic levels of the active atoms or molecules. The absorption linewidth of an individual absorber is referred to as the homogeneous linewidth Γh, and the absorption width of a collection of inhomogeneously broadened absorption centers is referred to as the inhomogeneous linewidth Γi. Application of monochromatic light to such a material has the effect of exciting only a very small subset of active absorbing atoms—those residing in the illuminated spatial volume within a homogeneous width of the exciting light's specific frequency. If the frequency of the imposed light is shifted, a different subset of active absorbing atoms in the illuminated volume responds.
Materials Science of the Cell
Authors: Wirtz D. , Evans E. 
Published: August 2016

Living cells are formidably complex systems that perform highly coordinated tasks which relate multiple biochemical and biophysical inputs to cell activities. Cell tasks may include not only adhesion and spreading, receptor-ligand mediated signal transduction, division, growth and programmed death, but also cell-type-dependent functions such as the environmental barrier provided by skin cells. These various cellular activities, often performed simultaneously or in a hierarchical order, involve hundreds of membrane, cytoplasmic, and extracellular proteins, ions, and small molecules, which interact with one another by means of regulated forces.For instance, cell migration requires the coordination of membrane extension and retraction, cytoskeletal gelation-contraction-dissolution, the formation of focal adhesions at the front of the cell, and detachment of these adhesions at the rear of the cell. These processes involve not only cytoskeletal polymers and motor proteins (which provide the cell with the necessary motor forces and passive mechanical resistance to sustain both cell movement and cell integrity), but also specific membrane proteins (“cell receptors”) to promote intimate contact between the cell and its extracellular milieu. Nevertheless, despite the critical function of cell migration in wound healing, immune response, cancer metastasis, and embryogenesis, the fundamental mechanisms of this phenomenon are not well understood.One of the steps limiting our understanding of cellular activities such as cell migration has been the lack of fundamental theory, backed by experimental methods, to monitor and characterize cellular processes quantitatively, noninvasively, and in real time.
Bounded Rationality and Materials Selection
Authors: Arunachalam V.S. , Bhaskar R. 
Published: August 2016

The vulnerabilities inherent in choosing an innovative material for a design can make for technological catastrophe. The points of weakness are not dependent on the technical nature of the innovation, but instead are intrinsic to human problem-solving and decision-making. We present a computational approach for managing and containing this fallibility using ideas from cognitive science and artificial intelligence, in particular, understanding how the boundedly rational behavior of humans and organizations leads to specific kinds of errors that affect the choice and use of materials.Materials choice in an industrial setting is often the result of a long chain or network of circumstances whose origins lie in many domains—from traditional engineering practice to the very latest innovation, from the commercial to the technical. In turn, every materials-selection decision has a long chain of consequences that are difficult to compute. This lengthy chain of consequences of a single decision gives rise to numerous points of error. What is particularly troublesome about these errors is not that they arise because of incomplete scientific engineering knowledge, but rather that they occur in spite of the fact that all (or at least, almost all) of the technically relevant information is available and sometimes even known to the technical personnel on the project. We will illustrate this approach by using a historical example of a major materials failure. Advances in database-systems design present an opportunity for integrating the ontology of material attributes with properties data. This may enable the design of more appropriate validation procedures required in proving a material for an artifact.
Enhancing the Operating Life and Performance of Lead-Acid Batteries via Grain-Boundary Engineering
Authors: Palumbo G. , Erb U. 
Published: August 2016

Although conventional lead-acid batteries are considered a rather mature technology, significant research and development efforts are currently under way to enhance their performance and operating life. These efforts are being driven by the demands of both the automotive and stationary (or standby) market sectors. Both major markets have need of lead-acid batteries with higher energy density or reduced size and weight; however, the automotive sector is also driven to mitigate the cycle-life reduction of its “starter, lighting, and ignition” (SLI) batteries that results from rising “under the hood” temperatures in modern automobiles.The operating and cycle lives of leadacid batteries are limited by the resistance of the positive Pb-alloy electrodes to intergranular-degradation processes (i.e., corrosion, cracking, and creep). Figure 1 shows an example of near-through-wall cracking and some inter-granular corrosion (grain-dropping at surface) observed in a Pb-lwt%Sb positive battery grid following approximately four years of service. In addition to the breaching of grid electrical continuity by corrosion and cracking processes (as indicated in Figure 1), the relatively high homologous temperature of operation for lead-acid batteries (i.e., >0.6 Tm, where Tm is the melting temperature) promotes intergranular-creep processes that result in dimensional changes in the electrodes over time (i.e., grid “growth”); this causes adjacent plates to short, leading to reduced battery capacity.
Materials for Advanced Flywheel Energy-Storage Devices
Authors: DeTeresa S.J. 
Published: August 2016

Flywheels are mechanical devices that store kinetic energy in a rotating mass. A simple example is the potter's wheel. For energy storage and conversion, an efficient method to exchange energy with a flywheel device is by converting the energy between mechanical and electrical forms. Typically a flywheel designed to perform this type of energy exchange is a combination of a motor and a generator. Energy is transferred into the device for storage by using it as a motor to consume electrical energy and spin the mass. This energy can be recovered with an efficiency exceeding 80% by using the flywheel as an electrical generator. Although the concept of storing energy in a rotating mass is an ancient idea, the relatively recent advent of advanced fiber-composite materials offers the potential for improved energy storage and conversion using rotating electromechanical devices.The achievable energy density (energy/weight) of a simple flywheel design, such as that shown schematically in Figure 1, is proportional to the specific strength (strength/density) of the material. The particular type of composite flywheel shown in this figure is composed entirely of circumferentially wrapped fiber. Although other designs have been suggested and constructed, this version is the most common for energy-storage applications. As discussed in the earliest papers on the subject, such as the article by Post and Post, the proportionality between energy density and specific strength favors the use of fiber composites. The remarkable combination of mechanical properties and low density achieved with fiber composites has made them attractive and nearly essential for aerospace applications.