bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sample Preparation For Metallography
Authors: Gokhale Atul B. , Banerjee Sharbari 
Published: May 2012

AbstractMetallography is a highly evolved scientific field that plays a central role in materials characterization, research and development, process optimization, quality assurance, deformation studies, failure analysis, and reverse engineering. The primary means of metallographic sample preparation is mechanical in nature and consists of three distinct stages—sectioning, mounting, and grinding/polishing. However, products and procedures vary widely for different applications. This article describes how to make the most appropriate choices in performing sample preparation. A general discussion is followed by illustrative examples of four specific materials.
Kinematic Diffraction ofX‐Rays
Authors: Chen Haydn 
Published: May 2012

AbstractDiffraction by x‐rays, electrons, or neutrons has enjoyed great success in crystal structure determination. For a perfectly ordered crystal, diffraction results in arrays of sharp Bragg reflection spots periodically arranged in reciprocal space. Analysis of the Bragg peak locations and their intensities leads to the identification of crystal lattice type, symmetry group, unit cell dimensions, and atomic configuration within a unit cell. On the other hand, for crystals containing lattice defects such as dislocations, precipitates, local ordered domains, surface, and interfaces, diffuse intensities are produced in addition to Bragg peaks. The distribution and magnitude of diffuse intensities are dependent on the type of imperfection present and the x‐ray energy used in a diffraction experiment.Diffuse scattering is usually weak, and thus more difficult to measure, but it is rich in structure information that often cannot be obtained by other experimental means. Since real crystals are generally far from perfect, many properties exhibited by them are therefore determined by the lattice imperfections present. Consequently, understanding of the atomic structures of these lattice imperfections and of the roles these imperfections play is of paramount importance if these materials properties are to be exploited for optimal use.This article addresses the fundamental principles of diffraction based upon the kinematic diffraction theory for x‐rays. Nevertheless, the diffraction principles described here may be extended to kinematic diffraction events involving thermal neutrons or electrons. In practice, most x‐ray diffraction experiments are carried out on crystals containing a sufficiently large number of defects that kinematic theory is generally applicable.This article is divided into two major sections. In the first section, the fundamental principles of kinematic diffraction of x‐rays are discussed and a systematic treatment of theory is given. In the second section, the practical aspects of the method are discussed; specific expressions for kinematically diffracted x‐ray intensities are described and used to interpret diffraction behavior from real crystals containing lattice defects. Neither specific diffraction techniques and analysis nor sample preparation methods are described in this article.
Fracture Toughness Testing Methods
Authors: Landes John 
Published: May 2012

AbstractFracture mechanics is a technology that deals with the effects of a sharp crack on the load‐bearing capacity of materials and structures. It is a tool used to translate the results of laboratory fracture toughness testing into an analysis of structural safety and integrity of structural components. In this unit, the load–displacement behaviors of notched specimens are discussed and a brief description ofG,K,J, and δ is presented.
Deep Level Transient Spectroscopy
Authors: Tin Chin‐Che 
Published: May 2012

Abstract
Electrically active localized states, which give rise to defect levels, affect the electronic properties of semiconductor materials and devices. Defects can be beneficial or detrimental depending on their roles in controlling the dynamics of charge carriers in the materials. For instance, defects that give rise to deep levels help to produce semi‐insulating materials. Yet, defects have also been known to produce undesirable recombination centers detrimental to the performance of optoelectronic devices. The identification and control of defect levels are crucial in materials and electronic device development. Deep level transient spectroscopy (DLTS) is a powerful technique to characterize the defect structure of semiconductors. It has contributed much to the development of new materials and devices. Several variations of this technique have appeared since its invention, providing major improvements in both sensitivity and resolution as well as a wide range of applications. This technique can be used to characterize defects in both bulk and thin film materials, interface states of metal–insulator structures, as well as interfacial defects in devices such as field‐effect transistors and high electron mobility transistors. This paper introduces the concept underlying the DLTS technique by first describing the classical and conventional rate window method. Two major developments in data analysis using Fourier transform and Laplace transform are also presented to provide a view of the state‐of‐the‐art in DLTS.
Magnetic Moment and Magnetization
Authors: McHenry Michael E. , Laughlin David E. 
Published: May 2012

AbstractThis article explores theories describing magnetic dipole moments and magnetization, including the origin and coupling of magnetic dipole moments and their addition to yield a magnetization. In particular, we define field quantities and magnetic dipole moments. This is followed by discussion of the atomic origins of dipole moments, magnetization and dipolar interactions, and magnetization in superconductors. The coupling of magnetic dipole moments is discussed in the context of mean field and exchange theories. This allows for the definition of ferromagnetism, antiferromagnetism, and ferrimagnetism. The microscopic magnetization and domains are finally discussed.
Magnetotransport in Metals and Alloys
Authors: Bass Jack 
Published: May 2012

AbstractElectronic transport properties are fundamental to the classification of materials. The behaviors of the electrical resistivity ρ, the thermal conductivity κ, and the thermopowerSare used to define whether a material is a metal, a semiconductor, or an insulator. Studies of how ρ, κ, andSvary with impurity content (alloying), magnetic fieldB, sample size, deformation, and so on, provide insight into the nature of current carriers and how they are scattered. Studies of magnetoresistance, the variation of ρ withB, can yield additional information about electronic structure, the current carriers, and their scattering. In systems involving magnetic metals, ρ(B) has technical applications to magnetic sensing and memory. The Hall effect and the thermopowerScan often be used to infer the sign of the charge of the majority current carriers, and the thermal conductivity κ, while closely related to ρ, can manifest differences that contain significant information. The Hall effect in semiconductors also finds use in sensors, but in metals it is smaller and usually of more interest for the physical insight it can provide into both nonmagnetic and magnetic metals. Changes with magnetic field in the thermal conductivity and thermoelectric coefficients of metals are usually small and difficult to measure. They have provided useful information about physical phenomena such as many‐body contributions to thermoelectricity and giant magnetoresistance in granular alloys and magnetic multilayers but are much less studied than the resistivity and Hall effect. Transport and magnetotransport measurements of metals and alloys are made over a wide range of temperatures extending from the lowest achievable temperature to the liquid state.This article focuses on four measured quantities in solid metals and alloys in the presence of a temporally constant and spatially uniform magnetic fieldB—the electrical resistanceR, the Hall resistanceRH, the thermal conductanceK, and the thermopowerS. The basic theory underlying these quantities applies also to liquid metals and alloys. The discussion begins with definitions and general information, including how to relate the measured quantities to the fundamental properties ρ, the Hall coefficientR0, κ, andS. These are followed by a brief description of the behaviors of ρ, κ, andSin zero magnetic field. Many more quantities than these four can be defined and measured, some of which have provided important information about metals. A few are briefly discussed.
Techniques for Corrosion Quantification
Authors: Frankel Gerald S. 
Published: May 2012

AbstractCorrosion, the environmental degradation of materials, is a problem for many applications of materials, particularly for metals. Accurate evaluation of the susceptibility of a material to corrosion in a given environment and improvements made through, for instance, protective coatings or the addition of corrosion inhibitors to the environment are critical for successful utilization of materials in aggressive conditions. A number of techniques, both electrochemical and nonelectrochemical, have been developed to allow detailed characterization of the corrosion response and accurate prediction of component degradation. In this chapter several techniques are described, with an emphasis on electrochemical methods. These techniques use a fundamental understanding of corrosion kinetics as well as sensitive instrumentation to allow quick and informative assessments of corrosion rates. The Tafel technique using potentiodynamic polarization data also provides information about the rate‐limiting processes, the tendency toward passivity, and the likelihood for passivity breakdown by localized corrosion. However, it is not suitable for field monitoring. Linear polarization is simple, rapid, and very well suited for field monitoring of corrosion rates. The Tafel slopes must be known for accurate determination of corrosion rate, or they can be estimated with little resulting error. Electrochemical impedance spectroscopy is a powerful laboratory tool, particularly for resistive environments and coated metals. This chapter provides the principles, practical aspects, and problems associated with each technique. Some common nonelectrochemical methods are also discussed.
Ultraviolet Photoelectron Spectroscopy
Authors: Himpsel F. J. 
Published: May 2012

Abstract
A brief overview of ultraviolet photoelectron spectroscopy (UPS) and related techniques is given. This technique measures the occupied electronic states in solids and at surfaces. In its angle‐resolved version, it provides the complete information about electrons in solids. After discussing the underlying physics, a variety of applications in materials science are illustrated. Practical questions are addressed as well.
Ellipsometry
Authors: Arsov Lj. , Ramasubramanian M. , Popov B. N. 
Published: May 2012

Abstract

Ellipsometry, also known as reflection polarimetry or polarimetric spectroscopy, is a classical and precise method for determining the optical constants, thickness, and nature of reflecting surfaces or films formed on them. Ellipsometry derives its name from the measurement and tracking of elliptically polarized light that results from optical reflection. Typical experiments undertaken with this technique consist of measuring the changes in the state of polarization of light on reflection from the investigated surfaces. Hence, ellipsometry finds applicability in a wide variety of fields such as physical and chemical adsorption, corrosion, electrochemical and chemical formation of passive layers on metals, oxides, polymer films, semiconductor growth and microelectronics, biology, medicine, and immunological reactions. The main strength of this technique lies in its capability not only to allow
in situ
measurements and provide information about the growth kinetics of thin films but also simultaneously to allow the determination of many or all of the optical parameters necessary to quantify the system. Spectroscopic ellipsometry allows the accurate and swift characterization of optical constants and reflectivity for single and multilayer coatings with film thicknesses of from 0.1 nm to 30 μm. Phase‐modulated ellipsometry is more sophisticated and was developed in recent years thanks to the advent of computer control and multichannel detectors. Other configurations of ellipsometers for special purposes are tailored for qualification and online production control, photovoltaic applications and testing of solar cells, single or multiwavelength monitoring, and
in situ
film growth allowing the precise control of film deposition processes.
Impulsive Stimulated Thermal Scattering
Authors: Rogers John A. , Maznev Alex , Nelson Keith A. 
Published: May 2012

AbstractImpulsive stimulated thermal scattering (ISTS) is a purely optical, noncontact method for characterizing the acoustic behavior of surfaces, thin membranes, coatings, and multilayer assemblies, as well as bulk materials. The method has emerged as a useful tool for materials research in part because (1) it enables accurate, fast, and nondestructive measurement of important acoustic (direct) and elastic (derived) properties that can be difficult or impossible to evaluate in thin films using other techniques; (2) it can be applied to a wide range of materials that occur in microelectronics, biotechnology, optics, and other areas of technology; and (3) it does not require specialized test structures or impedance‐matching fluids which are commonly needed for conventional mechanical and acoustic tests. Further, recent advances in experimental design have simplified the ISTS measurement dramatically, resulting in straightforward, low‐cost setups, and even in the development of a commercial ISTS photoacoustic instrument that requires no user adjustments of lasers or optics. With this tool, automated single‐point measurements, as well as scanning‐mode acquisition of images of acoustic and other physical properties, are routine.ISTS, which is based on transient grating (TG) methods, is a spectroscopic technique that measures the acoustic properties of thin films over a range of acoustic wavelengths. This article focuses only on ISTS measurement of acoustic motions in thin films. It begins with an overview of other related measurement techniques. It then describes the ISTS acoustic data and demonstrates how it can be used to determine (1) the stress and flexural rigidity in thin membranes; (2) the elastic constants of membranes and supported films; and (3) the thicknesses of single or multiple films in multilayer stacks.
Electron Paramagnetic Resonance
Authors: Eaton Gareth R. , Eaton Sandra S. 
Published: May 2012

AbstractElectron paramagnetic resonance (EPR), also known as electron spin resonance (ESR) or electron magnetic resonance (EMR), is the method of choice for characterizing unpaired electrons in materials. With proper attention to experimental methods, EPR can provide quantitation of the concentrations of unpaired electrons and characterize the chemical environment of the spin. It is routinely applied to solid or liquid samples. Cryogenic temperatures may be needed to observe transition metal ions with rapid electron spin relaxation.
Extrusion Foaming of a Preceramic Silicone Resin with a Variety of Profiles and Morphologies
Authors: Wolff Friedrich , Ceron Nicolat Bruno , Fey Tobias , Greil Peter , Münstedt Helmut 
Published: May 2012

AbstractPreceramic foams with a variety of profiles and morphologies were fabricated by a continuous foam extrusion process based on a single‐screw extruder. A methyl silicone resin was used as the preceramic polymer and carbon dioxide as the foaming agent. Variations of the foam morphology were achieved by changing the key process parameters carbon dioxide content, foaming pressure, and foaming temperature. Samples of different porosities, cell densities, pore sizes, and pore size gradients were obtained. From these results, conditions for the fabrication of particular foam structures can be derived. Various foam profiles as rods, tapes, and tubes were extruded and pyrolysed into ceramic foams.
Plasticity Mechanisms in Sub‐Micron Al Fiber Investigated by In Situ TEM
Authors: Mompiou Frédéric , Legros Marc 
Published: May 2012

AbstractSub‐micron Al fibers have been tested mechanically in situ in a transmission electron microscope. Their plastic behavior appears to be strongly sensitive to their initial dislocation content. We report here observations on fibers that were obtained by a chemical etching of a eutectic alloy where isolated and stable sources operate. The strength of sources in fibers of different size has been directly measured. We show that the increase of the yield stress with decreasing fiber size can be directly attributed to the increase of the source strength.
Reversible Lithium Storage with High Mobility at Structural Defects in Amorphous Molybdenum Dioxide Electrode
Authors: Ku Jun H. , Ryu Ji Heon , Kim Sun Ha , Han Oc Hee , Oh Seung M. 
Published: May 2012

AbstractThis work demonstrates that structural defects in amorphous metal oxide electrodes can serve as a reversible Li+ storage site for lithium secondary batteries. For instance, molybdenum dioxide electrode in amorphous form (a‐MoO2) exhibits an unexpectedly high Li+ storage capacity (up to four Li per MoO2 unit), which is larger by a factor of four than that for the crystalline counterpart. The conversion‐type lithiation is discarded for this electrode from the absence of Mo metal and lithium oxide (Li2O) in the lithiated a‐MoO2 electrode and the retention of local structural framework. The sloping voltage profile in a wide potential range suggests that Li+ ions are inserted into the structural defects that are electrochemically nonequivalent. This electrode also shows an excellent cycle stability and rate capability. The latter feature is seemingly due to a rather opened Li+ diffusion pathway provided by the structural defects. A high Li+ mobility is confirmed from nuclear magnetic resonance study.
Nitroxide Radicals@US‐Tubes: New Spin Labels for Biomedical Applications
Authors: Rivera Eladio J. , Sethi Richa , Qu Feifei , Krishnamurthy Ramkumar , Muthupillai Raja , Alford Michael , Swanson Michael A. , Eaton Sandra S. , Eaton Gareth R. , Wilson Lon J. 
Published: May 2012

AbstractThe encapsulation of nitroxide radicals within ultrashort (ca. 50 nm) single‐walled carbon nanotubes (US‐tubes) is achieved. Tempo‐ and Iodo‐Tempo@US‐tubes are characterized by thermogravimetric analysis (TGA), X‐ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Electron paramagnetic resonance (EPR) spectra display characteristic signals due to the detection of the spin probes within the US‐tubes. Longitudinal proton relaxivities (r1) of both nitroxide@US‐tubes samples are 7 to 13 times greater than the free nitroxide radicals in solution, giving relaxivities comparable to the clinical contrast agent (CA) Magnevist. In addition, transverse proton relaxivities (r2) show unprecedented proton relaxation enhancement in comparison to any other reported nitroxide radical‐based system or the clinically approved T2 CA, Resovist, under the same conditions. T2‐weighted magnetic resonance imaging (MRI) phantom images show that the encapsulation of nitroxide radicals within the US‐tubes produces good contrast enhancement due to their high r2 relaxivities. The nitroxide radicals@US‐tube agents are a new promising class of spin probes for MRI and electronic paramagnetic resonance imaging (EPRI) labeling, tracking, and diagnosis.
Charge Density Dependent Nongeminate Recombination in Organic Bulk Heterojunction Solar Cells
Authors: Rauh Daniel , Deibel Carsten , Dyakonov Vladimir 
Published: May 2012

AbstractApparent recombination orders exceeding the value of two expected for bimolecular recombination have been reported for organic solar cells in various publications. Two prominent explanations are bimolecular losses with a carrier concentration dependent prefactor due to a trapping limited mobility and protection of trapped charge carriers from recombination by a donor–acceptor phase separation until re‐emission from these deep states. In order to clarify which mechanism is dominant temperature‐ and illumination‐dependent charge extraction measurements are performed under open circuit and short circuit conditions at poly(3‐hexylthiophene‐2,5‐diyl):[6,6]‐phenyl‐C61 butyric acid methyl ester (P3HT:PC61BM) and PTB7:PC71BM (poly[[4,8‐bis[(2‐ethylhexyl)oxy]benzo[1,2‐b:4,5‐b′]dithiophene‐2,6‐diyl][3‐fluoro‐2‐[(2‐ethylhexyl)carbonyl]thieno[3,4‐b]thiophenediyl]]) solar cells in combination with current–voltage characteristics. It is shown that the charge carrier density n dependence of the mobility μ and the recombination prefactor are different for P3HT:PC61BM at temperatures below 300 K and PTB7:PC71BM at room temperature. Therefore, in addition to μ(n), a detrapping limited recombination in systems with at least partial donor–acceptor phase separation is required to explain the high recombination orders.
Preparation of Highly Ordered Nitrogen‐Containing Mesoporous Carbon from a Gelatin Biomolecule and its Excellent Sensing of Acetic Acid
Authors: Mane Gurudas P. , Talapaneni Siddulu N. , Anand Chokkalingam , Varghese Shaji , Iwai Hideo , Ji Qingmin , Ariga Katsuhiko , Mori Toshiyuki , Vinu Ajayan 
Published: May 2012

AbstractNovel nitrogen‐containing mesoporous carbon with well‐ordered pores (NMC‐G) and high basicity is synthesized using a low‐cost single‐molecule precursor, gelatin biomolecule, and SBA‐15 as a template via nanocasting method. The obtained materials are thoroughly characterized. It is found that the prepared materials have excellent textural properties such as high specific surface areas, huge pore volumes, and large pore diameters. The pore diameter of the materials can also be controlled with a simple adjustment of the pore diameter of the hard templates. The C/N ratio of the samples is calculated to be ≈6.01, which is slightly higher than that observed for mesoporous carbon nitride samples. X‐ray photoelectron spectroscopy (XPS) reveals the presence of sp2 hybridized carbon in aromatic ring structure attached to amino groups. The materials could adsorb a huge quantity of CO2. The sensing capability of the materials with different pore diameters for different adsorbates including ethanol, acetic acid, aniline, toluene, and ammonia is also investigated. Among the materials with different pore diameters studied, the material with the highest basicity and the largest pore diameter (NMC‐G‐150) showed excellent sensing performance with a high selectivity of adsorption for acetic acid molecule.