bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison between Thermal and Laser Annealing in Ion-Implanted Silicon.
Authors: Blosse A. , Bourgoin J.C. 
Published: March 2011

ABSTRACTN-type, 1015 −1016 cm−3 doped, Fz, Silicon has been implanted with 1 to 4 × 1012 cm−2, 100 or 300 keV, As ions. The nature and concentration of the defects has been monitored using Deep Level transient Spectroscopy as a function of the thermal treatment (in the range 500–900°C) and of the energy of the pulse (15 ns) of a ruby (0.69,μm) laser (in the range 0.3 to 0.6 J cm−2). The defects resulting from annealing by the two treatments are found to be the same. Only, for energies higher than 0.5 J cm−2, the laser treatment introduced new defects (at Ec−0. 32 eV), presumably resulting from a quenching process. Thus a laser energy below the theshold for melting and epitaxial recrystallization is able to anneal the defects produced by implantation, demonstrating that the annealing process induced by the laser pulse is not a purely thermal process but probably involves an ionization enhanced mechanism.
Modelinig of Dopant Diffusion and Associated Effects in Silicon
Authors: Fair Richard B. 
Published: March 2011

ABSTRACTResearch in the area of dopant diffusion in Si has focused on identifying the specific mechanisms and point defects involved. Recent approaches include observing the effects of diffusion and doping on oxygen precipitation, stacking fault growth or shrinkage, enhanced/retarded diffusion of one dopant in the presence of another. Very few of these studies have yielded unambiguous interpretations as a result of the indirect nature of the experiments. However, taken together we can infer the relative importance of vacancies versus Si selfinterstitials in the diffusion of each dopant species.
Interface Tribology Via Nonequilibrium Molecular Dynamics
Authors: Hoover W. G. , Hoover C. G. , Stowers I. F. , Siekhaus W.J. 
Published: March 2011

AbstractBy borrowing ideas from control theory, Nonequilibrium Molecular Dynamics incorporates temperature, stress, and heat flux directly into atomistic, time-reversible, deterministic equations of motion. We are applying this technique to studies of surface indentation, surface cutting, friction, ablation, and condensation. Here we describe simulations of the indentation and cutting processes using two-dimensional crystals composed of a few thousand particles.
Molecular Tribometry: Recent Results and Future Prospects
Authors: Alsten John Van , Granick Steve 
Published: March 2011

AbstractThe method of molecular tribometry is described. Ultrathin films of liquids are confined between parallel plates, usually of atomically smooth muscovite mica, such that the apparent area of contact equals the true area of contact. This paper consists of 5 sections. First, the phenomenon of solid lubrication by liquids is described. Second, the alternative viscous response of ultrathin liquid lubricants is described; the microviscosity is considerably enhanced over that of the isotropic liquid. Third, the critical shear strength is shown to have an extreme dependence on the normal pressure. Fourth, the materials requirements for molecular tribometry are discussed. Finally, a discussion is offered of the strengths and limitations of this new tool.
Structural Studies of Sputter-Deposited MoS2 Solid Lubricant Films
Authors: Hilton Michael R. , Fleischauer Paul D. 
Published: March 2011

AbstractThe relationship between the morphologies and crystal structures of sputter-deposited MoS2 films and their lubricating capabilities is discussed. In particular, aspects of plastic deformation processes are presented. Scanning elecron microscopy (top surface and cross sectional), transmission electron microscopy (lattice imaging and dark field), and x-ray diffraction techniques were used to characterize film structure. The asdeposited morphology, which can be described in terms of zone models, was found to influence the initial nature of the wear debris and the loadbearing capabilities of the films. In many cases a highly deformed region confined to the surface of the films was found. Applied stress was found to reorient crystallites and to induce crystallization, with the degree of both processes being related to the initial structure of the film. Criteria are presented for selecting the film type and preparation conditions to fit various applications.
Composition of Sputter Deposited MoS2 Films During Run-in in Vacuum
Authors: Ehni P.D. , Singer I.L. 
Published: March 2011

AbstractWear tests were performed under ultra high vacuum conditions in a ball-onflat configuration on magnetron sputtered and triode sputtered MoS2 films on 440C steel substrates. The issue of material loss versus deformation of the film was investigated using energy dispersive x-ray microanalyses for mass loss determinations and Michelson interferometry to measure the deformation of the tracks. Significant deformation without material loss was found in the first 10 passes. Surface composition of the tracks and the transfer film on the ball was determined by Auger electron spectroscopy. The S/Mo ratio wasfound to increase and the O/Mo ratio was found to decrease with increased sliding distance.
Microstructure and Wear Characterization of Selflubricating Al2O3 - MoS2 Composite Ceramic Coatings
Authors: Koshkarian K.A. , Kriven W.M. 
Published: March 2011

AbstractComposite ceramic coatings of alumina (A1203) containing some molybdenum disulfide (MoS2) were electro-codeposited on to Al metal substrates by a combination of anodic sparks deposition of A1203 and electrophoresis of MoS2. The microstructures were characterized by XRD, XPS, SEM, EDS, SNMS,TEM, SAD and relative wear resistance measurements. The coatings consisted mostly ofa-A1203 with some γ and βpresent as well. The coatings were porous and microcracked. SEM showed them to consist of circular “splats” which had rapidly crystallized from the molten state in areas ofdielectric breakdown in the coating. In the TEM the microstructure was seento contain “sets” of parallel, elongated grains having a single crystallographic orientation. The grains were separated by dislocated, low angle grain boundaries or microcracks. The sets intersected at irregularly curved interfaces and were mechanically interlocked. Quantitative SNMS indicated that up to 26 wt% MoS2 was incorporated in coatings fabricated from 5g\1 solutions. SEM\EDS as well as TEM\SAD\EDS identified 1-3μm particles of MoS2 incorporated into the 5g\1 solution derived coatings. These coatings exhibited a 50% lower wear rate than pure alumina coatings deposited under the same conditions.
The Evaluation of Materials for Tribological Applications
Authors: Winer Ward O. 
Published: March 2011

AbstractThe goal of tribo-material development is to produce materials which can beused to construct tribo-elements for use in mechanical systems and which will perform in a predictable manner. Tribo-element performance is critical in determining mechanical system reliability. In addition, tribo-elements are among the most severely taxed mechanical system elements, and require a high level of geometric accuracy and stability. Because of the wide variety of operating variables and environments, there are no universal test procedures to determine the efficacy of materials for tribological applications. Tribo-material evaluation is complex, important, and not well understood.This paper discusses the primary environmental operating variables for different tribo-elements, the rationale for their importance and will survey how they are normally included in tribo-material evaluation. The paper will also distinguish between tribomaterial evaluation for known well defined applications as compared with the evaluation of potential tribo-materials for which the relevant application is unknown. The objective of the material scientist, in either situation, is to select and use the evaluation program involving minimum time and cost consistent with generating results leading to design decisions with confidence.The role and nature of the many available “bench tests” will be discussed as will be the role and sophistication of thorough tribo-system simulation.As in many areas of materials development, it is appropriate for tribo-material development to paraphrase the well known adage; “the proof of the tribo-material is in the using.”
The Bonding of Fluorinated and Hydrogenated Ethers to Metal Surfaces: A Surface Science Approach to Tribology
Authors: Walczak M.M. , Leavitt P.K. , Thiel P.A. 
Published: March 2011

AbstractWe report a surface science study of fluorinated and hydrogenated ethers adsorbed at a metal surface. Fluorinated ethers bond less strongly to ruthenium surfaces than the hydrogenated analogs, both for atomically-smooth and atomically-rough surfaces. For the hydrogenated ethers, 0.03 to 0.17 monolayers undergo decomposition, while fluorinated ethers do not decompose significantly.
Molecular Contact Pressure in Tribology
Authors: J.M. Georges , J.L. Loubet , A. Tonck , Lyon Ecole Centrale De 
Published: March 2011

AbstractThis paper is a part of a long-term study of the physics of boundary lubrication. In this regime, the shape and pressure of the film are controlled by two phenomena: first, the elastic or plastic deformation of the substrate, and second, the physical state of the film. Three physical states can be detected: the condensed solid, granular and colloidal states. A new piece of apparatus, allowing the continuous and simultaneous measurement of static and dynamic forces, displacement and current voltage between a sphere and a plane, is used to determine surface forces and rheological properties of the film. The viscous and elastoplastic behavior of the interface is given by a transfer function. The lubricant we studied was calcium dialkylbenzenesulfonate solution containing encapsulated calcium carbonate and dissolved in pure dodecane (volume fraction 5.10-). While a pure dodecane solution behaves like a Newtonian fluid, with its bulk viscosity, the colloidal solution shows an increase of the viscosity near the steel surfaces suggesting adsorption. After 8 hours, each steel surface is covered with a layer, which includes an almost complete “monolayer” of calcium carbonate particles, with some incomplete layers on top of it. During indentation of the layer the repulsive forces vary exponentially with the thickness of the layer. This result is consistent with two effects: the consolidation of the layer during the process and scaling factors such as the Hill number (a/D).
Universal Aspects of Brittle Fracture, Adhesion, and Atomic Force Microscopy
Authors: Banerjea Amitava , Smith John R. , Ferrante John 
Published: March 2011

AbstractThe universal relation between binding energy and interatomic separation was originally discovered for adhesion at bimetallic interfaces involving the simple metals Al, Zn, Mg, and Na. We show here that the same universal relation extends to adhesion at transition metal interfaces. Adhesive energies have been computed for the low index interfaces of Al, Ni, Cu, Ag, Fe, and W using the Equivalent Crystal Theory (ECT) and keeping the atoms in each semi-infinite slab fixed rigidly in their equilibrium positions. These adhesive energy curves can be scaled onto each other and onto the universal adhesion curve. We have also investigated the effect of tip shape on the adhesive forces in the Atomic Force Microscope (AFM) by computing energies and forces using the ECT. While the details of the energy-distance and force-distance curves are sensitive to tip shape, all of these curves can be scaled onto the universal adhesion curve. This means that although absolute magnitudes of adhesive forces in the AFM cannot be determined without knowing the geometry of the tip, the shape of the force-distance curve is universal, at least for distances changing normal to the substrate.
Nondestructive Evaluation for Materials Characterization
Authors: Green Robert E. 
Published: March 2011

AbstractIn recent years classical nondestructive testing techniques for detecting macroscopic defects have been augmented by more sophisticated nondestructive evaluation methods for characterizing the microstructure and associated physical and chemical properties of materials. This paper will briefly describe several such nondestructive evaluation methods developed in the Center for Nondestructive Evaluation (CNDE) at The Johns Hopkins University.
Gel Point Determination in Curing Polydimethylsiloxane Polymer Networks by Longitudinal Ultrasonic Waves
Authors: Shefer A. , Gorodetsky G. , Gottlieb M. 
Published: March 2011

AbstractThe formation of well characterized poly-dimethylsiloxane networks has been studied by means of an acoustic interferometer. The hydrosilation reaction used to form these networks was followed by infra red spectroscopy. The relative changes in velocity of the ultrasonic longitudinal waves propagating through the system are found to be very sensitive to gelation and to the density of crosslinks. Due to our simultaneous kinetic and ultrasonic studies it was possible to relate the changes in acoustic properties of the curing system directly to the cure state.
Laser-Ultrasonics for Materials Characterization
Authors: Monchalin J.-P. , Aussel J.-D. , Héon R. , Bussière J. F. , Bouchard P. 
Published: March 2011

AbstractSeveral material properties and microstructural features can be determined or monitored by measuring ultrasonic velocity and/or ultrasonic attenuation. Conventional techniques which use piezoelectric transducers for generation and reception have several limitations, in particular in the case of materials at elevated temperature, of samples of complex shapes, and in regard to the detection bandwidth. These limitations are eliminated by laser-ultrasonics, a technique which uses lasers for generation and detection of ultrasound. Following a review of the various principles and methods used for generation and detection, we discuss the use of laserultrasonics for velocity and attenuation measurement. Examples of application to various materials are presented.
Ultrasonic Real-Time Monitoring of Slip Cast Cake Thickness
Authors: Jarman David , Gesing Adam J. , Farahbakhsh Bahram , Burger Gene , Huchins David , Mair H. D. 
Published: March 2011

AbstractAn ultrasonic method was developed for real-time monitoring of cake thickness during the casting of an alumina slip. The technique uses pulse-echo ultrasound to measure the time of flight and hence the thickness of the cast layer. Variations on the method are applicable to both production process control and to the fundamental studies of slip casting process kinetics.
Nondestructive Depth Profiling of a Diffuse Interface
Authors: Sinclair Anthony N. , Dickstein Phineas , Graf Michael A. 
Published: March 2011

AbstractA numerical solution of the one-dimensional wave equation is used to find the characteristics of wave propagation in a non-homogeneous medium. The solution is used to determine the magnitude and phase of the reflection coefficient at a diffuse interface. The result is found to be strongly dependent on sonic frequency. Comparison is made between theoretical calculations and measurements of the reflection coefficient at a copper-to-nickel diffusion bond.
Neutron Diffraction Measurements of Strain and Texturre in Welded Zr 2.5 wt.Z Nb Tube
Authors: Holden T. M. , Hosbons R. R. , Root J. H. , Ibrahim E. F. 
Published: March 2011

AbstractThe axial and tangential components of residual strain have been measured through the region of an electron beam weld in Zr 2.5 wt.% Nb tube. Marked changes in grain orientation in the tube occur as far away as 10 mm from the weld-centre. In particular a large fraction of the grains which had an [0002] direction aligned tangentially in the original tube were reoriented with this direction aligned axially. These grains showed high (5 x 10-4) tensile strain. Compressive strains (-5 to - 10 x I0-4) were measured in the region 5 - 10 mm from the weld-centre in those grains with [1010] directioný aligned axially. The hoop straint vary from tensile (maximum 5 x 10-4) to compressive (maximum -5 x 10-4) as a function of distance from the weld centre.
Determination of Thermally and Mechanically Induced Internal Stresses in Metal-Matrix Composites by X-Ray Methods
Authors: Yazici Rahmi , Bagnoli K. E. , Bae Y. 
Published: March 2011

AbstractIn this study the progression of thermally and mechanically induced internal strains (stresses) in metal-matrix composites was investigated by X-ray methods. The materials studied were whisker-reinforced 2124 Al-SiC(w) and 6061 Al- SiC(w) composites. X-ray diffractometry was used to measure thermally induced stresses on samples cycled from ambient to 280°C. Significant variations in residual stress values were observed in the matrix depending on the location and direction of the measurements with respect to the whisker orientation. The determined stress states of the as-processed and the thermally cycled samples were evaluated with continuum models. The microstrains in composites induced during processing and tensile loading were also investigated by nondestructive means. Individual grains of the matrix were analyzed by rocking-curve measurements using a modified X-ray doublecrystal diffractometer. The relationship between the plastic deformation induced by applied loads and the progression of the microstrain/excess-dislocation values was determined.
X-Ray Diffraction for Nondestructive Characterization of Polycrystalline Materials
Authors: Ruud C. O. , Weedman S. D. 
Published: March 2011

AbstractX-ray diffraction has long been the mainstay for materials characterization in the laboratory. This characterization includes the determination of phase composition, residual stress, microstrain, grain size, and crystallographic texture of polycrystalline metals, ceramics, and minerals. The analytical capabilities of XRD techniques have been expanded recently by the application of computer control to data collection and processing. These capabilities include the identification of irregularities in metals and ceramics that are caused by processing and fatigue damage, as well as the apriori prediction of processing anomolies. While the above applications have been largely restricted to the laboratory, the possibility for exploitation of the nondestructive nature of x-ray diffraction for inprocess evaluation of materials is now being realized. The availability of computer-controlled position-sensitive x-ray detectors can now provide rapid, non-contacting, in-process interrogation of materials. The examples of nondestructive characterization illustrated in this paper will be those that can be used for process control and/or damage assessment.
Acoustoelastic Determination of the Fourth Order ODF Coefficients and Application to R-Value Prediction
Authors: Daniel D. , Sakata K. , Jonas J. J. , Makarow I. , Bussiere J. F. 
Published: March 2011

AbstractThe fourth order orientation distribution function (ODF) coefficients of textured low carbon steel sheets were determined nondestructively from the anisotropy of the velocity of Lamb (So) and SHO plate waves measured using electromagnetic acoustic transducers (EMATs). The three coefficients (C411, C412, C413) are calculated from five velocity measurements made in three directions in the rolling plane of the sheet using the Hill approximation by an iterative numerical method. The coefficients were also determined from Young's modulus measurements based on a resonance technique and are compared to those obtained ultrasonically. The comparison with coefficients determined from X-ray diffraction pole figures permits adjustment of the C411 coefficient and then very good agreement is obtained. The plastic strain ratios (R-values) of the steel samples are predicted from the adjusted coefficients using a series expansion method based on the Taylor theory of crystal plasticity. These are compared with experimental measurements and again good agreement is displayed.
X-Ray Absorption Spectroscopic Studies of Catalytic Materials
Authors: Via G. H. , Sinfelt J. H. , Meitzner G. , Lytle F. W. 
Published: March 2011

AbstractX-ray absorption spectra (XAS) contain information in the LIII near-edge region on filling of the absorber d-band, and in the extended fine-structure region on the physical environment of the absorber. We report here an evaluation of the effect on platinum LIII edges of preparation in clusters with a high fraction of Pt atoms at the surface. We also report the effects on platinum and rhenium LIII edges from addition of copper. These effects are surprisingly small.We have also re-evaluated extended x-ray absorption fine-structure spectra (EXAFS) of platinum and rhenium in alumina-supported platinum-rhenium bimetallic catalysts. A novel feature of this new analysis was the requirement that interatomic distances, coordination numbers, and Debye-Waller type factors maintain certain physically necessary relationships among themselves. This procedure decreased the number of free variables and increased the amount of information returned by the analysis.
Time-Resolved X-Ray Absorption Spectroscopy: Strengths and Limitations
Authors: Fontaine A. , Dartyge E. , Itie J. P. , Jucha A. , Polian A. , Tolentino H. , Tourillon G. 
Published: March 2011

AbstractX-ray Absorption Spectroscopy has proved to be a powerful tool to elucidate a huge number of questions in materials science. Great interest exists in time-resolved experiments achieved with extreme energy resolution and energy scale stability to take a full benefit of the strong correlation between the stereochemical environment of the absorbing atom and the exact shape and position of the absorption edge.Fast energy dispersive X-ray spectroscopy allows in-situ observations with data collected in a short time. Nowadays the main limitation concerns very low-concentration samples since It is no longer possible to use the dispersive geometry because detection of the signal via the decay channels is no more possible.
Reflection-Extended-X-Ray-Absorption-Fine-Structure Spectroscopy at the Carbon K-Edge
Authors: Long G. G. , Black D. R. , Tanaka D. K. 
Published: March 2011

AbstractThe carbon K-edge Reflection-Extended X-Ray Absorption Fine Structure (refl-EXAFS) spectra from graphite, diamond and glassy carbon have been investigated. There is good phase shift transferability between the two well-known bonding types in diamond and graphite, provided that appropriate inner potential corrections to the K-edge energy E. are made. The model spectra from diamond and graphite were used to investigate the nature of glassy carbon. It was found that, for the particular form of glassy carbon used in this study, the bonding more closely resembled sp3 than sp2. This result is preliminary pending our evaluation of the influence of surface oxygen.
Dispersive X-Ray Synchrotron Studies of Pt-C Multilayers
Authors: Rodricks B. , Lamelas F. , Medjahed D. , Passos W. Dos , Smither R. , Ziegler E. , Fontaine A. , Clarke R. 
Published: March 2011

AbstractWe demonstrate the simultaneous acquisition of high-resolution x-ray absorption spectra and scattering data, using a combination of energy-dispersive optics and a twodimensional CCD detector. Results are presented on the optical constants of Pt and on the reflectivity of a platinum-carbon multilayer at the LIII absorption edge of Pt.