bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanical and Thermal Stability of Heavily Drawn Pearlitic Steel Wire
Authors: Aernoudt Etienne , Sevillano Javier Gil , Delrue Hilde , Humbeeck Jan Van , Watté Piet , Lefever Ignace 
Published: April 2011

AbstractHaving interlamellar spacings on the nanometer scale, there is no doubt about considering heavily drawn pearlitic steel wire as a nano-layered material. This extremely fine structure is of great technical importance: indeed, as the interlamellar distance determines the onset of plastic flow, the wire can be brought to a tensile strength beyond 4000 MPa and is therefore one of the strongest materials on the market nowadays.At extremely large strains (well beyond ε = 4) and/or at moderate temperatures, the pearlitic steel loses its strength. Several possible failure mechanisms, like fragmentation of the cementite or thermal and strain-induced cementite dissolution, are put forward, but until now, there is no definite understanding of the really active mechanism.In the present work, the calorimetric differential scanning technique, in combination with thermopower measurements and the high-resolution atomic force microscopy, have turned out to be most promising tools to reveal some of the mechanisms that are responsible for the degradation of the lamellar aggregate.
Orowan-Based Deformation Model for Layered Metallic Materials
Authors: Kreidler Eric R. , Anderson Peter M. 
Published: April 2011

AbstractAn Orowan-based deformation model for layered metallic materials is presented and used to calculate the stress-strain behavior for two deformation modes. This model assumes that layer thicknesses are sufficiently small so that single rather than multiple dislocation pileups form. Deformation then proceeds by increasing the density of single dislocation pileups. Furthermore, it is assumed that the controlling stress for plastic deformation is that to propagate a tunneling dislocation loop inside an embedded elastic-plastic layer. Initially, the resolved stress required to propagate an isolated tunneling loop does not depend on whether the loop shears the layer perpendicular to an interface or stretches it parallel to an interface. At larger strains, the tunneling arrays become sufficiently dense such that local dislocation interaction changes the line energy of a tunneling dislocation. As a result, the elastic-plastic layers may exhibit modest softening when sheared or substantial hardening when stretched. When the elastic-plastic layers are embedded into a multilayered specimen with alternating elastic-only layers, no macroscopic strain softening is observed. However, the predicted macroscopic stress-strain curves for stretching and shearing are significantly different in their dependence on layer thickness.
Effects of Ductile Phase Additions on the Fracture Behavior and Toughness of DRA Composites
Authors: Ellis L. Yost , Lewandowski J. J. , Hunt W. H. 
Published: April 2011

AbstractDiscontinuously reinforced aluminum (DRA) composites have been processed to contain discrete regions of unreinforced aluminum with the objective of enhancing the damage tolerance. The effects of changes in the ductile phase size, shape and strength as well as the SiCp reinforcement distribution on the toughness were studied. The incorporation of the ductile phase can increase the crack growth resistance of the DRA composite. In such cases, stable crack propagation (i.e. R curve behavior) is observed in contrast to the behavior of the conventional DRA composite which fails catastrophically under the conditions tested. The level of toughening is affected by the size and mechanical properties of the ductile phase as well as the orientation and shape of the ductile regions with respect to the test geometry (i.e. crack arrestor vs crack divider).
Mechanical Property Data for Coated Systems-The Prospects for Measuring “Coating Only” Properties using Nanoindentation
Authors: Hainsworth S. V. , Page T. F. 
Published: April 2011

AbstractOne of the critical aspects of assessing the properties of coated systems is the prospect of being able to measure the properties of the coating in isolation of the substrate. This has led to an increase in the use of continuously-recording indentation techniques (or nanoindentation techniques) for assessing the mechanical properties of coated systems since they can be used to measure the materials response to contact deformation at a scale relevant to the coating thickness. This paper presents the results of a new method for analysing the nanoindentation loading curves for coated systems. The analysis of the loading curve uses the relationship P = Kmδ2 which describes the indenter displacement, δ, in terms of the applied load P. For each material, Km can be predicted from its modulus E and hardness H. One result is that if either of E or H is known, then the other may be calculated from the experimental loading curve. Further, the method has the potential to differentiate between the responses of the coating only, the coating and substrate in combination, and that dominated by the substrate once the load has become sufficient for cracking of the coating such that it no longer plays a significant role in supporting the applied load. In many cases, careful analysis of the loading curves allows the displacement ranges associated with these regimes to be identified. This is shown to be a powerful experimental tool for the interpretation of the mechanical properties of coated systems.
Probing Silicate/Sapphire Interfaces with AFM and Nanoindentation
Authors: Lilleodden E. T. , Zagrebelny A. V. , Ramamurthy S. , Carter C. B. 
Published: April 2011

AbstractA nanoindentation study of a calcium-aluminosilicate/α-alumina system is described. Thinfilms of CaAl2Si2O8 glass were deposited on α-alumina single crystals of {1120} and {1102} orientations by pulsed-laser deposition. These samples were then subjected to a heat treatment causing the glass to crystallize and to dewet the sapphire surface. A nanoindentation device retrofitted on an atomic force microscope was employed to probe the mechanical properties of the samples. It uniquely enables the characterization of sub-micron features such as the dewet crystallites which necessitate small displacements and exact positioning of the indenter. Strong dependencies on the crystallographic anisotropy were observed in the morphology, but less so on the mechanical properties. In addition, displacement-excursions were observed and are explained in terms of yielding in the substrate.
The Influence of Strengthening Mechanisms on Stress Relaxation in Thin Aluminum Metallization
Authors: Gorrell Jonathan , Holloway Paul , Jerman Hal 
Published: April 2011

AbstractWith the development of microelectromechanical systems there is a need for stronger aluminum thin films that resist stress relaxation. A number of strengthening mechanisms are used extensively for bulk aluminum alloys, but very few have been used to improve the performance of thin films. Pure aluminum, standard microelectronicsmetallization (A1-.04Cu-.017Si), alloy T201 (Al-.046Cu-.006Ag-.004Mn-.003Mg-.003Ti), and alloy 2090 (Al-.026Cu-.021Li-.001Zr) were electron beam evaporated or sputter deposited onto (100) silicon substrates.. Stress versus temperature and stress relaxation were measured in the films. Pure aluminum and AlSiCu alloy films exhibited plastic deformation at low stresses and low temperatures. The T201 and 2090 films exhibited residual elastic stresses at room temperature of 350 MPa and 500 MPa, and did not plastically deform until 240°C at 100 MPa stress, or 270°C at 200 MPa stress, respectively. The T201 film also showed a low stress relaxation rate. We speculate that solid solution strengthening caused the increase in strength of the T201 film, and that age hardening caused the increase in strength of the 2090 film.
Thermal Properties of Magnetron Sputtered TiN And TiAlN Thin Films on HSS
Authors: Lugscheider E. , Knotek O. , Barimani C. , Zimmermann H. , Lake M. 
Published: April 2011

AbstractIncreasing demands on production processes in terms of performance, reliability and environmental compatibility shape the specification profile for modem wear resistant coating systems. The specification of PVD coated cutting tools by the parameters hardness, wear and frictional behavior, chemical structure or chemical resistance are already known and inspected by small scale tests, e.g. pin on disc or taber abraser test. Hitherto the thermophysical properties of thin film PVD coatings were not characterized completely although the investigation of the thermal diffusivity of coated substrates give information about the thermal barrier function of the deposited coating.To determine the thermophysical properties of PVD coatings the Jenoptik Thermal Wave Inspection (TWIN) can be used. This nondestructive and contactless measuring system is based on the photothermal spectroscopy. In this paper fundamentals of the TWIN measuring technique are presented as well as first TWIN results of investigated MSIP TiN and TiAlN coated and oxidized high speed steels.
The Study of Tribological Performance and Surface Film Characterization of Bismuth Dioctyldithiocarbamate
Authors: Ligeong Chen , Junxiu Dong , Guoxu Chen 
Published: April 2011

AbstractIn this study, bismuth dioctyldithiocarbamate has been synthesized, and Its tribological behaviors, such as friction-reducing ability, antiwear property and extreme pressure performance have been respectively evaluated with a ring-on-block test rig and a fourball machine. In addition to correlate its tribological behaviors with the film formed on the metallic rubbing surface under boundary lubrication conditions, surface analyses have been conducted to characterize the surface film by means of Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy(XPS) and energy dispersion of X-ray (EDX).Test results show the additive compound can effectively improve the friction and wear of the rubbing couples. On the other hand, EDX confirmed the presence of carbon, oxygen, sulfur, nitrogen, bismuth and iron on the surface; AES revealed their depth distribution of atomic concentration percentages. Whereas XPS further disclosed that the composition of the surface film was composed of organic and inorganic species including iron sulfide and sulfate, metallic bismuth, bismuth oxide and sulfide etc. which are conducive to the reduction of friction and wear.
The Mechanics of a Free-Standing Strained Film / Compliant Substrate System
Authors: Freund L. B. 
Published: April 2011

AbstractThe deformation of film/substrate systems due to a through-the-thickness distribution of mismatch strain is discussed for cases when the layers are thin, compliant and freestanding. The connection between substrate curvature and mismatch strain is reviewed within the framework of small strains and small deflections. These results are applied to determine the second-order correction to the Stoney formula and to note the connection between mismatch strain distribution and curvature history. Then, for small strains but large deflections, it is observed that a symmetric system with equi-biaxial mismatch strain can undergo a bifurcation in deformation mode. It is also shown that the bifurcation response is sensitive to system imperfections. Finally, the critical condition for introduction of an interface misfit dislocation in an epitaxial system is established, thereby extending the Matthews-Blakeslee criterion to the case of free-standing compliant systems.
Stress Determination in Thermally Grown Alumina Scales Using Ruby Luminescence
Authors: Renusch D. , Veal B. W. , Koshelev I. , Natesan K. , Grimsditch M. , Hou P. Y. 
Published: April 2011

AbstractBy exploiting the strain dependence of the ruby luminescence line, we have measured the strain in alumina scales thermally grown on Fe-Cr-Al alloys. Results are compared, and found to be reasonably consistent with strains determined using x-rays. Oxidation studies were carried out on alloys with compositions Fe - 5 Cr - 28 Al and Fe - 18 Cr - 10 Al (at. %, bal. Fe). Significantly different levels of strain buildup were observed in scales on these alloys. Results on similar alloys containing a “reactive element” (Zr or Hf) in dilute quantity are also presented. Scales on alloys containing a reactive element (RE) can support significantly higher strains than scales on RE-free alloys. With the luminescence technique, strain relief associated with spallation thresholds is readily observed.
Investigation of The Elastic Modulus of Sol-Gel Derived Titania Using Three-Point Bending Tests
Authors: Jämting Å. K. , Bell J. M. , Swain M. V. 
Published: April 2011

AbstractThere is increasing interest in the use of sol-gel derived films in tribological applications, and this necessitates an understanding of the mechanical properties of these films. Few investigations into the mechanical properties of sol-gel films have been undertaken, and in this study we have concentrated on measurement of the elastic modulus of sol-gel derived titania films as a preliminary stage in a full investigation of stress in sol-gel deposited thin films. Sol-gel films are often very thin and in order to understand the influence of the substrate on the measured elastic modulus, we have used a multiple coating technique to deposit titania films of increasing thickness on various substrates. A three point bending apparatus is used to measure the elastic modulus. The three-point bending apparatus has very low load and displacement measuring capabilities as is required for the very thin sol-gel films. Measurements of the compositional uniformity of the films have been performed using RBS, and this has been combined with film thickness measurements to determine the film porosity. This information ensures that the measured properties relate to intrinsic film properties. The results of all these measurements will be presented.
A Model of Cleavage Fracture along Metal/Ceramic Interfaces
Authors: Lipkin D. M. , Beltz G. E. , Clarke D. R. 
Published: April 2011

AbstractWe propose a mechanism by which cleavage-type crack growth along a metal/ceramic interface could proceed concomitantly with significant plastic dissipation in the metal. The large strain gradients in the immediate vicinity of the crack tip are postulated to lead to extensive local hardening. A simple, continuum-based model is used to identify a characteristic length scale ahead of the crack tip, within which the material can not plastically deform subject to the cracktip stress field. An analytical expression is derived for the crack-tip shielding afforded by the plastic zone. The coupling between the plastic dissipation and the ideal work of fracture is found to be synergistic, with slight variations in Griffith energy affecting order-of-magnitude changes in toughness. These results suggest a possible mechanism for a number of interfacial fracture phenomena observed in thick- and thin-film metal/ceramic systems, including segregation-induced interfacial embrittlement, the ductile-to-brittle transition, and stress corrosion cracking.
Determination of Burgers Vector of Screw Dislocations in 6H-SiC Single Crystals by Synchrotron White Beam X-Ray Topography
Authors: Si W. , Dudley M. , Carter C. , Glass R. , Tsvetkov V. 
Published: April 2011

AbstractIndividual screw dislocations along the [0001] axis in 6H-SiC single crystals have been characterized by means of Synchrotron White Beam X-ray Topography (SWBXT). The magnitude of the Burgers vector was determined from: (1) the diameter of circular diffraction-contrast images of dislocations in back-reflection topographs, (2) the width of bi-modal images associated with screw dislocations in transmission topographs, (3) the magnitude of the tilt of the lattice planes on both sides of dislocation core in projection topographs, and (4) also the magnitude of the tilt of the lattice planes in section topographs. All of the four methods showed reasonable consistency. The sense of the Burgers vector can also be deduced from the abovementioned tilt of the lattice planes. Results revealed that in 6H-SiC a variety of screw dislocations can be found with Burgers vector magnitude ranging from 1c to 7c (c is the lattice constant along [0001] axis). This work demonstrates that SWBXT can be used as a quantitative technique for detailed analyses of line defect configurations.
Applications of Soft X-Ray Fluorescence Spectroscopy in Materials Science
Authors: Callcotit T.A. , Jia J.J. , Zhou L. , Ederer D.L. , Terminello L.J. , CARLISLE J.A. , Perera R.C.C. , Samant M.G. , Himpsel F.J. , Arakawa E.T. 
Published: April 2011

AbstractSoft x-ray fluorescence spectroscopy provides an element and angular momentum selective measure of the valence band density of states in complex materials. Results are presented demonstrating the use of SXF both as a means of solving materials problems and as a means of increasing our fundamental understanding of low energy excitation processes in various types of materials. As examples of materials applications, we discuss the L2,3 spectra of Si in various environments, and describe radiation damage studies in Beryl. Fundamental new insights are provided by the study of SXF spectra excited near an x-ray threshold. For such excitation, recent work demonstrates that an electronic Raman scattering process can greatly modify the normal fluorescence spectrum. We discuss near threshold studies of graphite, h-BN and NiS to demonstrate that the nature of the electronic excitation processes differs dramatically in various classes of materials and provides important new insights into their properties.
Photoelectron Angular Distributions Of Ultrathin NI/CU(001) Films
Authors: Mankey G.J. , Subramanian K. , Stockbauer R.L. , Kurtz R.L. 
Published: April 2011

AbstractWe present measurements of the evolution with film thickness of the 3d electronic states at the Fermi energy of ultrathin Ni films. The morphology and thickness of the films is determined from x-ray photoelectron spectroscopy. x-ray photoelectron diffraction and x-ray magnetic linear dichroism using synchrotron radiation. Photoelectron angular distributions were measured using an ellipsoidal mirror analyzer. Even at submonolayer Ni coverages, the 3d electronic states exhibit bulk-like properties. This is attributed to the short screening length of electrons in metals, the localization of the 3d electrons, the similarity of the Ni and Cu ion cores, and finally the interaction with the underlying fcc periodic potential.
Correlation Of Magnetic Dichroism in X-Ray Absorption and Photoelectron Emission using Ultrathin Magnetic Alloy Films
Authors: Tobin J.G. , Goodman K.W. , Mankey G.J. , Willis R.F. , Denlinger J.D. , Rotenberg E. , Warwick A. 
Published: April 2011

AbstractWe have begun a program to characterize magnetic alloy overlayers using both magnetic x-ray circular dichroism (MXCD) and magnetic x-ray linear dichroism (MXLD). This will allow a direct comparison of MXCD-absorption and MXLD-photoelectron emission. First results from the Advanced Light Source will be presented.
Domain Structure and Transient Photoconductivity in Ordered Ga0.47In0.53As Epitaxial Films
Authors: Ahrenkiel S. P. , Ahrenkiel R. K. , Arent D. J. 
Published: April 2011

AbstractWe examine the influences of spontaneous atomic ordering and the associated subvariant domain structure on the transient photoconductivity in epitaxial Ga0.47In0.53As films grown by MOCVD on InP 2°-<110>. Ultra-high frequency photoconductivity decay is used to measure carrier lifetimes in ordered and disordered material following excitation with a YAG laser. Ordered material shows an extended lifetime of 18–186 gis that decreases with incident power. Strongly ordered material showed two CuPt-B subvariants in TEM diffraction patterns and images. Ordering in the first 0.5 μm of growth consists of a fine, interwoven structure with the subvariants closely associated. The subvariants then segregate into imperfectly ordered columnar superdomains that form a mosaic in the film plane with numerous order/order interfaces. In addition, order/disorder interfaces form within and adjacent to the partially ordered superdomains. We attribute the extended transient photoconductivity lifetime in ordered samples to trapping effects that result from the subvariant domain structure.
Depth-Sensitive Strain Analysis of a W/Ta/W Trilayer
Authors: Malhotra S. G. , Rek Z. U. , Yalisove S. M. , Bilello J. C. 
Published: April 2011

AbstractThe high-resolution x-ray diffraction technique was used to determine the entire strain tensor as a function of x-ray penetration depth in a 400 nm W/Ta/W trilayer, which consisted of 150 nm W, 100 nm Ta, and 150 nm W. The strain tensor was calculated in a laboratory reference frame to determine the variation of in-plane strains, εxx, and εyy, and the normal strain εzz as a function of x-ray penetration depth. Two different methods were then used to determine the strains εxx, εyy, and εzz in each layer of trilayer, and both indicated that the strain states in the W layers were fe same, and that the strains εxx and εyy. in the W and Ta layer were the same magnitude. The difference between the Ta and W arose witK the normal strain, εzz, and was due to a Poisson contraction effect. The average residual stresses in the trilayer were determined with the HRXRD data, and also with sin2ψ and a substrate curvature technique, double-crystal diffraction topography. All three techniques indicated that the average biaxial stress in the trilayer was ∼1.0 GPa.
Thin-Film Deposition Via Pulsed Laser Ablation
Authors: Panayotov V. G. , Kelly M. C. , Gomlak G. G. , Birdwhistell T. L. T. , Koplitz B. D. 
Published: April 2011

AbstractWe report on a novel experimental approach for thin-film deposition via pulsed laser ablation. A combination of design features including the incorporation of original sample manipulation methods as well as enhanced analytical capabilities allow for experimental control and flexibility for thin-film deposition studies of a variety of materials. Here, the application is illustrated with a study of 532 nm pulsed laser ablation and subsequent deposition of CdTe.Conditions have been found that produce a mildly energetic ablation plume, and the average kinetic energies for the neutral and ionic ablation species in the plume have been determined to be approximately 2 and 11 eV, respectively. It has been shown that in the presence of an electric field the ionic species can be diverted away from the detector (and subsequently from the eventual deposit). Thin film deposits clearly reveal an increase in the number of sub-micron particles when direct ablation ions contribute to the deposition. The possibility for extraction of ablation ions and preparation of ablation plumes of neutrals only has been clearly demonstrated.
Structural and Surface Morphology Changes in CuInSe2 Thin Films as a Function of Cu/In Ratio
Authors: Fons P. , Niki S. , Yamada A. , Tweet D. J. 
Published: April 2011

AbstractDue to its high near bandedge absorption, CuInSe2 is considered to be one of the most promising solar cell materials. As CuInSe2 films are usually grown by metastable processes, the Cu/In ratio often deviates from the ideal ratio of unity. To investigate the structural and morphological changes induced by such stoichiometric variations we have grown a series of epitaxial CuInSe2 epitaxial thin films with varying Cu/In ratios by molecular beam epitaxy on GaAs(001) substrates from elemental sources at a growth temperature of 450° C. Overall structural, microstructural and surface morphological changes were observed by X-ray diffraction, transmission electron microscopy, and atomic force microscopy, respectively. It was observed that as films deviated from stoichiometry, twinning occurred preferentially on the anion {1 · 1 · 2} planes.