bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics of Cavity Growth In Solder Joints During Thermal Cycle
Authors: Stone Donald S. , Homa Thomas R. , Li Che-Yu 
Published: March 2011

AbstractGrain boundary cavity growth in solder joints during thermal fatigue is analyzed. The stress cycle profile is estimated based on a geometrically simplified model of a ceramic chip carrier - printed circuit board assembly and a state variable equation for plastic flow in the solder.
Failure Modes of Metal Interfaces: Experimental Evidence Relating to the Effect of Chemical Species
Authors: Pashley M. D. , Pethica J. B. 
Published: March 2011

AbstractThe strength of an interface between two metal surfaces can be drastically affected by the presence of chemical species in the interface. The two surfaces may form the boundary between two grains inside a solid block of metal, the interface between a substrate and a metal film or the interface between two solid bodies brought into physical contact. Interface impurities such as oxygen atoms generally reduce the cohesion between the two surfaces. Conventional fracture experiments have difficulty in determining whether this results from a reduction in the interfacial energy, or a hardening of the interface, either of these making brittle fracture easier. The experiments which we have carried out by contacting two clean and characterised surfaces in ultra high vacuum, enable a direct study to be made of the change in interfacial energy and mechanical behaviour as a result of adsorbed species.A sharp metal point of about 1μm radius of curvature is contacted against a flat metal specimen and the force of adhesion and contact area (measured from electrical resistance) are determined. The extent of ductile or elastic behaviour of the interface can be determined from the reversibility of the contact area as a function of applied load during separation.We have shown directly from a contact experiment, that monolayer quantities of oxygen reduce the interfacial energy by a factor of three in the metal contacts studied. Interfacial ductility is only reduced by the presence of oxide layers of the order of 5nm thick.
Model Compound Approach for Polymer-Metal InterFaces: ESCA Studies
Authors: Sanda P. N. , Bartha J. W. , Silverman B. D. , Ho P. S. , Rossi A. R. 
Published: March 2011

AbstractESCA studies of two molecules which are similar in structure to the PMDA and ODA constituents of the PMDA-ODA polyimide monomer are discussed. Their interaction with in-situ evaporated Cr and Cu films are compared. The PMDA model compound interacts with Cr through the imide group, while very little interaction is observed with Cu. The ODA model compound (oxydianiline) interacts with Cr via the ether linkage and the terminal amino groups, whereas very little interaction is observed with Cu.
Interface Failure of Gold Covered SiO2 Substrate With TiW and Nb Intermediate Adhesion Layers
Authors: Liehr M. , Delrue J. P. , Herbots N. , Berghe R. Vanden , Caudano R. 
Published: March 2011

AbstractIn this paper, we report an electron microscopy study (SEM and TEM) of the Au-TiW-SiO2 structure annealed in ambient air up to 600°C. Scanning Auger microscopy has also been used to characterize the interfaces. Growth of pyramid- like structures was found to occur under heat treatment above 450°C. Volume increase and adhesion failure due to oxidation of the TiW layer and weak points in the Au top layer were found to be at the origin of this particular growth. Similar surface failures have been reported under oxidation at higher temperature for the tungsten silicide – SiO2 systems. According to the assumed growth mechanism, the necessary conditions for a pyramid growth have been defined and checked on another multilayer structure, that is the Au-Nb-SiO2 interface.
Multilayer Ceramics
Authors: Schwartz Bernard 
Published: March 2011

AbstractMultilayer ceramics (MLC) technology is the basis for several major products today, which include capacitors and packages for integrated circuits. This technology was originally developed to produce miniature capacitors for the micromodule program. When these goals were achieved, new applications in packaging were found. The MLC technology is now the building block in IBM's medium and large computers. The current state of this technology will be described. It's advancement will require improved understanding of the sciences involved in each of the process steps. Several of these technical areas will be discus-ed, particularly the relationships among the electrical properties of the materials and the performance of the package. As the dimensions become smaller, more concern will have to be shown for the defect levels. This implies improved control of material preparation and processing.
Surface Characterization by Reflection Electron Microscopy (REM)
Authors: Hsu Tung , Cowley J. M. 
Published: March 2011

AbstractReflection electron microscopy (REM) utilizes the Bragg reflected high energy electrons to form the image of a crystal surface. Images of dislocations, atomic steps, reconstructions of surface layers of atoms and adatoms, stacking faults and twinning, superlattices, etc., have been successfully observed on a wide variety of specimens. Contrast is mainly due to diffraction and phase, which distiguished REM as a unique method for high spacial resolution and high sensitivity imaging of the surfaces of bulk specimens. REM can be effectively performed under UHV as well as under the moderate vacuum of an ordinary commercial electron microscope.
Direct Imaging of Atomic Rearrangements on Extended Gold Surfaces
Authors: Smith David J. , Marks L. D. 
Published: March 2011

AbstractRearrangements of atomic columns on extended gold surfaces have been imaged directly using a 500kV high resolution electron microscope. The (100), (110) and (111) surface profiles were all found to be highly mobile and microscopically rough, with (111) in particular developing a characteristic hill-and-valley morphology. The presence of surface steps had a marked influence on the direction of surface diffusion only for the (100) surface. The observations establish that high-resolution profile imaging can provide unique information about surface self-diffusion which is unobtainable by other techniques.
Analysis of Domain-Size Distributions in Epitaxial Growth Using Leed Angular Profiles
Authors: Saloner D. , Lagally M. G. 
Published: March 2011

AbstractAngular profiles of diffracted beams in surface-sensitive diffraction techniques can be used to establish the degree of order at the surface of crystals. Results are presented showing the sensitivity of such profiles to the growth mode of overlayer islands. A method is presented to incorporate the two-dimensional nature of the problem into the analysis and to extract finite-size effects from fundamental and superlattice beams.
Grain Boundary Structural Transformations Induced by Solute Segregation
Authors: Sickafus K. , Sass S. L. 
Published: March 2011

AbstractThe problem of solute segregation came to prominence with relation to studies of the temper embrittlement of low alloy steels. McLean and Northcott1(1948) first suggested that segregation of various elements to the grain boundaries was primarily responsible for the intergranular fracture observed in steels susceptible to this embrittlement. Direct evidence for segregation came much later with the development of surface sensitive analytical techniques, especially Auger electron spectroscopy (AES). Using AES, it was determined that impurity elements such as P, Sb and Sn, as well as alloying elements such as Ni and Cr, were highly concentrated at the fracture surfaces in embrittled steels2. It is not clear, however, why solute segregation changes the mechanical strength of the grain boundaries in these materials. Based on recent calculations, Messmer and Briant3proposed that certain solute species at a grain boundary change the chemical bonding at the interface. However, other more dramatic structural rearrangements may be possible upon segregation. Such structural changes were first suggested by the observation of facetted fracture surfaces in tellurium-doped iron alloys4. In the study presented here, it is shown that low concentrations of solute can cause changes in grain boundary structure. In particular, small concentrations of Au solute were found to cause a major change in the dislocation structure of low angle [001] Fe twist boundaries. Preliminary observations on the str ucture of a Fe-0.18 at.% Au* twist boundary were presented elsewhere5. Additional results will be presented here on the effect of changes in solute concentration and misorientation angle, θ, on this structural transformation. It is believed that these observations are evidence for the occurrence of a two-dimensional phase transformation in the grain boundary, similar to that predicted by Hart6
In Situ Hvem Studies of Electron-Beam-Driven Composition Changes in Thin Film Alloys: Displacement-Rate Gradient Effects
Authors: Okamoto P. R. , Lam N. Q. 
Published: March 2011

AbstractIn situ high-voltage electron microscopy (HVEM) observations have shown that the highly-focused electron beams normally employed for HVEM irradiation experiments can cause large chemical composition changes in the irradiated zone of thin film alloys during elevated temperature irradiations. The driving force for the process comes primarily from the radial gradients in displacement rates generated by the beam. Hence, the rate of change in composition exhibits a strong dependence not only on the temperature and beam intensity, but also on the spatial characteristics of the beam profile. This dependence on beam shape and size poses previously unrecognized problems, particularly for HVEM studies of the effects of dose-rate on radiation-induced phenomena that are sensitive to alloy composition. Moreover, composition changes driven by radial gradients in the displacement- rate occur at increasingly rapid rates as the beam diameter is reduced. Hence, at higher voltages, beam-induced composition changes occurring during analysis may become a serious problem, even at relatively low temperatures, for microchemical analysis techniques, such as EDX and EELS, which employ far smaller diameter electron beams than those used for irradiation purposes in the HVEM.
Structural Changes of a σ = 51 Tilt Boundary in Germanium During High Temperature Creep
Authors: Skrotski W. , Wendt H. , Carter C. B. , Kohlstedt D. L. 
Published: March 2011

AbstractThe incorporation of lattice dislocations into a 16° [011] tilt bound-ary in Ge bicrystals has been analyzed with high-resolution and conventional transmission electron microscopy techniques. Dislocations in subgrain boundaries produced during high-temperature creep, knit into the high-angle grain boundary. As these lattice dislocations are absorbed, the structure changes along the grain boundary from one subgrain to the next. Analysis of the boundary structure by lattice-fringe imaging demonstrates that the secon-dary dislocations which accomodate the deviation from the coincidence orien-tation do not have primitive DSC Burgers vectors.
Exafs Studies of Ion Implanted Bismuth
Authors: Kunoff E. M. , Dresselhaus M. S. , Kao Y. H. 
Published: March 2011

AbstractMagnetorefiection and preliminary Rutherford Backscattering channeling experiments indicate that point defects induced in the bismuth lattice by ion implantation are largely annealed out during the implantation process due to its low melting temperature of 271.3°C. These experiments also show that the implanted ions cause long range strains in the crystal. Single crystal bismuth samples have been implanted at low temperatures (from 273°K down to 77°K) with 75 As to a total fluence of 5 × 1016/cm2 at energies ranging from 50 keV to 200 keV to yield an approximately constant arsenic profile from the sample surface to a depth of 625 Å. To study the local environment of the implanted As ions, EXAFS measurements have been made at the Cornell High Energy Synchrotron Source (CHESS). From these data, we obtain a comparison of the As nearest neighbor distances in samples implanted at different temperatures. We discuss the effect of sample temperature during implantation on these properties. This work represents the first use of EXAFS to characterize annealing of implantation-induced lattice defects during the process of ion implantation.
Rutherford Backscattering and Channeling Studies of Laser Annealed, Nitrogen Implanted and Non-Implanted Single Crystal Austenitic Stainless Steel.
Authors: Whitton J. L. , Laursen T. , Nilson J. A. , Nip Wing , Mitchell I. V. , Plattner H. H. , Swanson M. L. 
Published: March 2011

AbstractIon backscattering and channeling of 2.0 MeV He+ has been used to observe the effects of excimer laser annealing on unimplanted and nitrogen implanted single crystal austenitic stainless steel. The laser annealing was done either in air or in flowing helium. In general, laser annealing resulted in a significant increase in lattice disorder of both unimplanted and implanted specimens. Laser annealing in helium atmosphere caused a near-surface decrease of disorder in the implanted specimens with, however, a higher dechanneling rate at greater depths. Channeling with nuclear reaction analysis shows that the as - implanted nitrogen occupies octahedral interstitial sites as evidenced by flux peaking along the <110> axis and a decreased signal along the <100> axis. A similar effect is observed after laser annealing in a helium atmosphere.
Tin-Doping Induced Defects in GaAs Films Grown by Molecular Beam Epitaxy
Authors: Chen S. H. , Enquist P. , Carter C. B. 
Published: March 2011

AbstractHeavily Sn-doped GaAs films have been grown by molecular-beam epitaxy and found to contain single-crystal Sn particles situated in the near-surface region of the epilayer GaAs. The morphology and chemical composition of the particles have been examined by using cross-section transmission electron microscopy combined with energy-dispersive x-ray spectroscopy. Different growth conditions were used to study the Sn-particle formation and high-resolution transmission electron microscopy was used to investigate microstructures. The observations are discussed in terms of several models previously proposed for these phenomena.
Characterization of Emitter-Collector Shorts by Anodization, Voltage Contrast Sem, and Tem
Authors: Carim A. H. , Sinclair R. , Stacy W. T. 
Published: March 2011

AbstractChemical anodization and voltage contrast scanning electron microscopy (VC-SEM) have been used to identify electrically faulty structures in a bipolar test array. Direct comparison of these techniques was achieved by examining the same emitters with each method. VC-SEM is shown to be a useful technique for delineating E-C shorts because of its nondestructive and purely electrical nature. Further investigations by transmission electron microscopy revealed dislocations in many short-circuited emitters and occasionally in unshorted devices. This confirmed prior observations that crystallographic defects in silicon devices may sometimes be, but are not always, electrically active.
Positron Annihilation Studies of Vacancy Formation in Tungsten, Chromium, and Niobium
Authors: Smedskjaer L. C. , Loper G. D. , Chason M. K. , Siegel R. W. 
Published: March 2011

AbstractVacancy formation was studied in the refractory bcc metals, tungsten, chromium, and niobium, using the positron annihilation spectroscopy Doppler broadening technique, between room temperature and the respective melting temperatures, under ultra-high vacuum conditions. Temperatures were measured by optical and infrared pyrometry, a W(Rh) thermocouple, and the power delivered to the sample, with calibrations against known melting temperatures. For W, a trapping-model analysis of the data from the temperature range 300–3633 K yielded a vacancy formation enthalpy of 3.76 ± 0.39 eV. For Cr, a similar fit to the data from 296–2049 K yielded a vacancy formation enthalpy of 2.0 ± 0.2 eV. The results are discussed in relation to previous vacancy formation and self-diffusion studies. Measurements on Nb as a function of temperature and oxygen content are also presented.
Small Angle X-Ray Scattering (Saxs) Study of Coarsening Kinetics in an Aluminum-Lithium Alloy
Authors: Spooner Stephen 
Published: March 2011

AbstractCoarsening kinetics was studied in a A190. 6 Li9. 4 alloy aged at 100°C, 128°C, 165°C, 178 ° C, and 209 °C. The time-dependent behavior of the average precipitate radius followed t1/3 behavior. The precipitate/ matrix interfacial energy obtained from analysis of the kinetic constant was 0.015 J/M2 and was largely independent of temperature. The scattering curves exhibit interparticle interference which prevents us from calculating a particle size distribution.
Influence of Aggregates on the Strength and Elastic Modulus of High Strength Mortars Containing Microsilica
Authors: Dingsøyr E. , Mosberg T. , Young J. F. 
Published: March 2011

AbstractThe strength development of mortars made with a high strength paste containing microsilica was investigated as a function of aggregate type and
content. Strength could be modelled using composite theory; the predicted strengths of the paste and aggregate component reflected the influence of
the cement-aggregate bond. Scanning electron microscopic examinations gave a qualitative idea of the extent of bond failure, which correlated satisfactorily with the predicted behavior. The modulus of elasticity for SiC mortars could be predicted well by Hirsch's model or the aggregate model.
Optimized High Strength Mortars: Effects of Chemistry, Particle Packing, and Interface Bonding
Authors: Roy Della M. , Nakagawa Zenbe-E , Scheetz Barry E. , White Elizabeth L. 
Published: March 2011

AbstractHigh strength mortars have been prepared utilizing optimized particle packing, reactive substituents to modify the chemistry- and addition of superplasticizers. Otherwise the processing techniques were conventional. The compressive strengths of one prototype material after curing at temperatures from 38 C to 250 C were above 70 MPa. The strengths were particularly high at 175 C (195 MPa) where excellent bonding had developed; one chemically modified material reached 245 MPa. The specimens cured at 175 and 250 C (after a lower temperature precure) developed their strengths rapidly, having reached essentially full strength by 7 days. At lower curing temperatures the strength increased with time, apparently still increasing at 56 days (106 MPa) for the materials cured at 38 C. Modified mixtures were prepared using different proportions of silica fume, MgO, different ratios of sand to fine components, and different sand mineralogy and other admixture proportions for rheological optimization. Microhardness, dynamic Young's modulus, density, and permeability were measured in addition to strength. Matrix chemistry and sand mineralogy and proportions affected the strength. Matrix-aggregate bond was very important. The above types of cementitious materials have potential importance for applications where they may be exposed to extreme conditions and to temperature cycling.
High Strength Autoclaved Mortars
Authors: Baggott R. , Sarandily A. 
Published: March 2011

AbstractAutoclaved cement-silica mortars having flexural strengths of up to 57 MPa were prepared by pressing and casting methods of fabrication. It was found that the Griffith dependence of strength upon the size of the largest flaw, the modulus of elasticity and the surface energy was applicable. The relative contributions of these three parameters were evaluated and it was established that although the maximum flaw was the dominant factor in a specific material, surface energy changes were responsible for major strength differences associated with water-solid ratios or variations in the preparation method. Preliminary studies identified the various microstructural features that operated as Griffith's flaws.
A Contribution to the Modelling of the Corrosion Process for HLW Glasses
Authors: Conradt R. , Roggendorf H. , Scholze H. 
Published: March 2011

AbstractAn evaluation of a broad set of HLWg lass corrosion data implies that adequate corrosion models must also take into account kinetics slower than √t. Solubility limits may not give a sufficient explanation for these cases. Before all, the long term leach rates are not infinitely small. A proposal is made how “slow” kinetics can be included in a model.
The Effect of Groundwater Flow on Release Rate Behavior of Borosilicate Glass
Authors: Apted M. J. , Adiga R. 
Published: March 2011

AbstractA simple open-system model is used to evaluate the effect of groundwater flow on borosilicate glass dissolution. With appropriate assumptions, the mass balance equation is: dc/dt=R-kfc;R=k(ceq-c)where c is the concentration of dissolved species i, t is time, kf is the flushing frequency (i.e., volumetric flow rate divided by fixed pore volume), and R is the normalized rate of dissolution. A first-order dependence of R on departure of c from the equilibrium saturation concentration, Ceq, is also assumed. Results from steady-state (dc/dt = 0; c = css = constant) static and dynamic flow tests on a borosilicate glass at 90°C were used to calculate R and the dissolution rate constant, k, as a function of flow rate. The calculated results of the model are in good agreement with independent measurements.There are three important conclusions. First, even the slowest flow rate used (0.1 ml/hr) corresponds to a high flow rate with respect to the intrinsic dissolution rate of the glass and expected repository flow conditions. Second, previous release models that scale radionuclide release rate directly to solubility concentration may overestimate release at high flow rates. This is because previous models fail to account for the pronounced decrease in steady-state solution concentration at the solid interface with increasing flow rate. Third, increased flow rate accelerates the glass dissolution rate without changing the reaction mechanism. This effect is attributable to constant replenishment of undersaturated solution at the glass surface and an apparent increase in the dissolution rate constant with increasing flow rate.
Surface Film Characterization of Corroded HLW Glass Specimens
Authors: Bart Gerhard , Aerne Ernst T. , Grauer Rolf , Linder Hanspeter , Z'berg Doris , Zwicky Hans U. 
Published: March 2011

AbstractIn a joint Japanese, Swedish, Swiss HLW glass characterization programme, interactions of real waste glass specimens with possible burial system components are studied. The report describes the glass surface analytical work performed at the Swiss Federal Institute for Reactor Research (EIR) during the first completed phase of the programme.