bluuebunny/crossref_metadata_2025_split huggingface dataset:
Processing, X-Ray, and TEM Studies of QS87 Series 56 KΩ/Square Thick Film Resistors
Authors: Crosbie Gary M. , Johnson Frank , Donlon William T. 
Published: April 2011

ABSTRACTThick film resistors are glass/metal oxide nanocomposites used in hybrid microcircuits. These components have a small temperature coefficient of resistance that is useful in systems that experience a wide range of service temperatures. Test samples were produced by printing, drying, and firing resistor pastes in a laboratory process that simulated production conditions. The process parameters of peak firing temperature, time at peak temperature, and probe current were factors in a 23 factorial experiment that measured in-situ resistance (resistance during processing), as-fired resistance, and the temperature coefficients of resistance. As-fired resistance is shown to increase with firing time and temperature. In-situ resistance exhibited a small decrease with increasing firing temperature due to thermally-activated glass conduction at firing temperatures. The temperature coefficient of resistance measurements show that R[T] curve flattens with increasing firing time and temperature. X-ray diffraction revealed Pb-ruthenate, alumina, and Zr-silicate phases to be dispersed in the glass. Transmission electron microscopy in conjunction with energy dispersive x-ray spectroscopy revealed that the conductive phases, Pb- and CuBi-ruthenate particles, increased in size with increasing firing time and temperature. Lattice parameter measurements revealed only a small increase in the ruthenate structure. Resistance changes are attributed to increased separation of the conductive ruthenate particles by coarsening.
The Growth and Properties of Thin-Film Nano-Composites
Authors: Lewis Keith L , Pitt A M , Culus A G 
Published: April 2011

ABSTRACTNano-composites allow a materials engineering approach to be exploited to realise specific characteristics in optical thin film ensembles. For example, films can be produced with refractive indices determined by their average composition on the basis of effective medium approximations, so freeing optical designers from the constraints imposed in pure materials. A summary is presented of the progress made in a fundamental study of films based on diverse materials such as fluorides and sulphides, fabricated using molecular beam deposition techniques. The film properties (eg refractive index, surface morphology, environmental stability) are correlated with microstructure (as determined by cross-sectional TEM techniques). The enhanced properties of the films are discussed in relation to the realisation of periodically modulated graded-index structures of the type required for optical filter applications.
Crack Deflection and Interfacial Fracture Energies in Alumina/SiC and Alumina/TiN Nanocomposites
Authors: Jiao S. , Jenkins M. L. 
Published: April 2011

ABSTRACTCrack/particle interactions in Al2O3/SiC and Al2O3/TiN nanocomposites have been observed by TEM on samples containing cracks produced by Vickers indentations. No significant crack deflection by intragranular SiC particles or microcracking around nanoparticles was found. Intergranular cracks were observed to be deflected into the matrix grains by SiC particles on grain boundaries inclined to the direction of crack propagation. TiN particles were not effective in this way. These features are briefly discussed within the framework of the interfacial fracture energies. These were calculated from interfacial energies, which were determined by the measurement of grain boundary-interface dihedral angles.
Fire Retardant Polyetherimide Nanocomposites
Authors: Lee Jongdoo , Takekoshi Tohru , Giannelis Emmanuel P. 
Published: April 2011

ABSTRACTPolyetherimide-layered silicates nanocomposites with increased char yield and fire retardancy are described. The use of nanocomposites is a new, environmentally-benign approach to improve fire resistance of polymers.
Transmission Electron Microscopy and Electron Holography of Nanophase TiO2 Generated in a Flame Burner System
Authors: Turner S. , Bonevich J. E. , Maslar J. E. , Aquino M. I. , Zachariah M. R. 
Published: April 2011

ABSTRACTNanophase TiO2 (n-TiO2) particles were generated in a flame burner system under three experimental conditions. Selected individual nanoparticles were identified and characterized using selected area electron diffraction, bright-field and, in some cases, dark-field imaging to determine morphology and microstructural features. Previously unknown TiO2 particles with unusual central features were identified as rutile. Electron holography was used to characterize the central features which were found to be consistent with voids. More extensive characterization of individual particles may lead to improved understanding of n-TiO2 nucleation and growth.
Microstructure, Mechanical Properties, and High-Temperature Oxidation Resistance of Boronized γ - TiAl(Mn)
Authors: Kim S. , Yoon Y. , Kim H. , Park K. 
Published: April 2011

ABSTRACTTo improve the wear and high-temperature oxidation resistances of reactively sintered γ -TiAl(Mn) intermetallic compounds, they were boronized in the temperature range of 900 to 1100 °C for 5 to 11 hours with powder mixtures of B4C and Na2B4O7. It was found that the coating layer consisted of three sublayers, i.e., outer, middle, and inner sublayers. The outer, middle, and inner sublayers were identified as a mixture of TiB2 and TiO2, a mixture of Al2O3 and TiO2, and Ti-rich TiAl based compounds, respectively. The coating layer significantly improved the surface hardness and the wear and high-temperature oxidation resistances. The highest surface hardness (Hv ≈ 2720) was obtained at 900 °C for 11 hours. This surface hardness is much higher than that of TiAl(Mn) (Hv ≈ 400). In addition, the specimens boronized at both 1000 and 1050 °C for 9 hours showed an excellent high-temperature oxidation resistance. It is believed that the boronizing on the TiAl(Mn) intermetallics is very effective to improve the wear and high-temperature oxidation resistances.
Tensile Properties and Deformation Mechanisms in Two-Phase Titanium Aluminide Sheet Material
Authors: Appel F. , Clemens H. , Glatz W. , Wagner R. 
Published: April 2011

ABSTRACTThe mechanical properties of two-phase TiAl sheets with different compositions and microstructures were investigated over the temperature range 25–1000 °C. The microprocesses of plasticity were characterized by electron microscope observations. Particular emphasis has been paid to the mechanisms governing the deformation behavior at elevated temperatures which are relevant for the fabrication and engineering applications of structural components.
Microstructure of Massively Transformed γ-TiAl Phase Studied by High-Resolution Electron Microscopy
Authors: Abe E. , Kumagai T. , Kajiwara S. , Nakamura M. 
Published: April 2011

ABSTRACTA microstructure of the massively transformed γ-TiAl (γm) phase in a Ti-48at.%Al alloy, which was heat treated in the high-temperature α-Ti (disordered hep) single phase field (1683K), followed by ice water quenching, has been examined using high-resolution electron microscopy. The characteristic features of the microstructure originated from the α→γ massive transformation have been clarified in detail, which are as follows. (1) Extremely thin hep plates (about 0.8–2nm in thickness), which are considered to be a retained α phase, are found to exist in the γm phase. (2) Twin boundaries are found to be not flat interfaces, that is, twin interfaces are not on the exact (111) mirror plane. This situation is attributed to the existence of a number of partial dislocations at the twin boundaries. (3) Antiphase relationship between the regions either side of the thin rotated domain wall [1] is confirmed. The validity of this situation is explained by assuming that the thin rotated domain wall has been grown from a simple antiphase domain boundary. On the basis of these facts, mechanism of the α→γ massive transformation has been discussed.
Yield Stress Anomaly in B2 FeAl
Authors: Yoshimi K. , Hanada S. , Yoo M. H. 
Published: April 2011

ABSTRACTOur studies on yield stress anomaly of B2 FeAI single crystals are reviewed in this paper. A positive temperature dependence of yield stress, so-called “yield stress anomaly”, is observed in B2 FeAI in which excess vacancies are fully annealed out. Associated with the anomaly, characteristic asymmetry is found between tension and compression. While the strain-rate sensitivity is almost zero in the temperature range of the yield stress anomaly, the stress relaxation becomes significant with increasing temperature, indicating that a recovery process is thermally activated. It is ascertained by the two-surface trace analysis that slip transition from <111> direction at intermediate temperature to <100> at high temperature occurs around the peak temperature. Even at the peak temperature, in addition, operative slip vector for yielding is confirmed to be predominantly <111> by TEM. Also, it is observed that <111>-type superdislocations are frequently climb-dissociated in the temperature range of the anomaly. APB formation on {111} plane is energetically favorable, which is in agreement with the Flinn's calculation for the B2 superlattice that APB energy on {111} plane is lower than that on {110} plane. Such an anisotropy of APB energy would offer specific driving force for the climb dissociation on <111> superdislocations. On the basis of the observed results, the anomalous strengthening behavior of B2 FeAI single crystals is discussed.
Microstructure and Strengthening of Creep-Tested Cryomilled NiAl-AlN
Authors: Garg Anita , Daniel Whittenberger J. , Luton Michael J. 
Published: April 2011

ABSTRACTThe mechanical grinding of prealloyed NiAl powder in liquid nitrogen (cryomilling) results in an intermetallic matrix composite where micron sized particle free aluminide cores (grains) are surrounded by thin mantles comprised of nanometer sized A1N particles and NiAl grains. Under high temperature, slow strain rate conditions both compressive and tensile creep testing have shown that the mechanical strength of hot extruded cryomilled NiAl approaches the levels exhibited by advanced NiAl-based single crystals and simple Ni-based superalloys. Transmission electron microscopy of cryomilled materials tested between 1100 and 1300 K revealed little, if any, dislocation structure within the mantle regions, while the NiAl cores contained subgrains and dislocation networks after testing at all strain rates between 10-4 and 10-8 s-1. These and other microstructural observations suggest that creep strength is the result of a fine NiAl grain/subgrain size, the inability of dislocations to move through the mantle and stabilization of the microstracture by the A1N particles.
An Explanation of the Small Strain-Rate Sensitivity of Ni3Al
Authors: Sun Y. Q. 
Published: April 2011

ABSTRACTBased on the superkink model, an explanation is given in this paper for the small strain-rate sensitivity of the anomalous yield stress of Ni3Al. The yield stress is proposed to be the stress needed to destabilise the average superkinks and it varies inversely with superkink height. The yield stress is insensitive to the strain-rate because the superkink height is controlled by the rate at which the superkink widens and is not directly related with the superkink propagation speed.
Dislocation Structures in Ni3(Al, Hf)
Authors: Kruml T. , Viguier B. , Bonneville J. , Spätig P. , Martin J. L. 
Published: April 2011

ABSTRACTSingle crystalline specimens of Ni74.8Al21.9Hf3.3 were subjected to compression tests at different temperatures. Thin foils for transmission electron microscopy observations were prepared from several specimens deformed within and above the yield stress anomaly domain. The dislocation microstructure was studied. The weak beam imaging and image simulation techniques followed by anisotropie elasticity calculations were used for the determination of antiphase boundary energies in both cube and octahedral planes, resulting in values of 237 mJm-2 and 252 mJm-2 respectively. The comparison of the present results with data taken from literature shows the influence of Hf on mechanical properties, dislocation microstructures and APB energies.
Stress response by the strain-rate change in binary, stoichiometric Ni3AI single crystal
Authors: Demura M. , Hirano T. 
Published: April 2011

ABSTRACTThe strain-rate dependence of flow stress in single crystals of binary, stoichiometric Ni3Al was studied in the temperature region of the yield stress anomaly. Below 400 K, the steady-state flow stress was found to be independent of strain rate, though it changed temporarily when the strain rate was changed. The strain-rate insensitivity can be explained by assuming that the flow stress is controlled by the multiplication/immobilization of mobile dislocations.
The Mechanical Behavior and Deformation Mechanisms of Nb-Al-V Alloys
Authors: Tappin D. K. , Horspool D. N. , Smith L. S. , Aindow M. 
Published: April 2011

ABSTRACTA series of Nb-Al-V alloys containing 20–40 at. % V and 10–25 at. % Al have been investigated. The phase distributions in the alloys indicate that Al promotes the formation of the A15 phase whilst V stabilises a B2 phase. Room temperature compression testing revealed that the B2 is inherently ductile such that for the alloys with less than 40% by volume of the A15 phase, strains of over 50% were obtained easily. The 2% offset yield stresses of these alloys did not vary significantly with composition, being 1.2±0.1GPa in each case. TEM studies were used to show that the deformation in the B2 phase occurs predominantly by the glide of screw-type super-partial dislocations with b=l/2<111> on {110} and {112}. In some alloys this dislocation activity was preceded by the formation of pseudo-twins, via a martensitic shear transformation.
Laves Phase-Based Materials: Microstructure, Deformation Modes and Properties
Authors: Kumar K. S. 
Published: April 2011

ABSTRACTIntermetallic compounds with the AB2 stoichiometry can exist with the C14, C15 or C36 structures, otherwise called Laves phases. In the past, single-phase Laves compounds, particularly Mg-containing binary compounds, have been examined to obtain an understanding of the dislocation structures as well as their mobility; alternately, effort has also been expended in examining the polytypic transformations that occur in such Laves phases. More recently however, Laves phases and polyphase alloys containing the Laves phase have been examined with the intent of developing structural alloys for elevated temperature applications. Specifically, alloys based on the Cr-Group IV(Ti, Zr, Hf) and Group V (Nb, Ta) elements as well as the ternary V-Hf-Nb system have been the focus of several investigations. Physical and mechanical properties have been measured, and microstructure has been characterized as a function of heat treatment. Deformation modes have been re-examined in detail. New ideas based on synchroshear have been put forth to explain the polytypic transformations that occur in these systems, and have been extended to also explain twinning and slip. Earlier observations are first summarized and then these recent advances are reviewed and the potential for these materials is assessed.
Y2O3 Morphology in an Oxide Dispersion Strengthened FeAl Alloy Prepared by Mechanical Alloying
Authors: Inkson B. J. , Threadgill P. L. 
Published: April 2011

ABSTRACTThe microstructure of an oxide dispersion strengthened FeAl (Zr,B) alloy, manufactured by mechanical alloying then extrusion, has been examined by HREM. Y2O3 is dispersed throughout the FeAl matrix as particles, ranging in size from 5nm upwards, which are effective in pinning the bulk dislocations. Although in the main the observed oxide particles are irregular in morphology, a significant minority of particles exhibit faceted surfaces. In particular, the facets of the Y2O3 particles are observed to coincide with {100}B2, {110}B2 and {112}B2 planes of the surrounding bulk FeAl matrix. In addition, HREM imaging reveals uncoupled 1/2<111>FeAl superpartial dislocations lying a few nanometres from some of the FeAl - Y2O3 interfaces.
Solution and Precipitation Hardening in Carbon-Doped Two-Phase γ-Titanium Aluminides
Authors: Appel F. , Christoph U. , Wagner R. 
Published: April 2011

ABSTRACTA two-phase titanium aluminide alloy was systematically doped with carbon to improve its high temperature strength. Solid solutions and precipitates of carbon were formed by different thermal treatments. A fine dispersion of perovskite precipitates was found to be very effective for improving the high temperature strength and creep resistance of the material. The strengthening mechanisms were characterized by flow stresses and activation parameters. The investigations were accompanied by electron microscope observation of the defect structure which was generated during deformation. Special attention was paid on the interaction mechanisms of perfect and twinning dislocations with the carbide precipitates.
Void Morphology in Polyethylene/Carbon Black Composites
Authors: Marr D.W.M. , Wartenberg M. , Schwartz KB. , Agamalian M. M. , Wignall G. D. 
Published: April 2011

ABSTRACTA combination of small angle neutron scattering (SANS) and contrast matching techniques is used to determine the size and quantity of voids incorporated during fabrication of polyethylene/carbon black composites. The analysis used to extract void morphology from SANS data is based on the three-phase model of microcrack determination via small angle x-ray scattering (SAXS) developed by W. Wu12 and applied to particulate reinforced composites.
Compatibilizers made from Copolymers that Exhibit Strong Interactions
Authors: Bauer Barry J. , Liu Da-Wei 
Published: April 2011

ABSTRACTRandom copolymers of poly(methyl methacrylate-d8) (PMMA) and poly(methacrylic acid) (PMAA) were synthesized and blended with polyethylene oxide (PEO), and SANS was used to estimate the strength of interaction between the various polymer pairs. The addition of PMAA greatly reduced the scattering of the blend, giving a large negative Flory-Huggins interaction parameter. Copolymers of the type PMAA-g-PS, PMAA-r-PS, PMMA-g-PS, and PMMA-r-PS (g = graft, r = random) were used as compatibilizers for the melt blending of mixtures containing 80% PS and 20% PEO. Random copolymers containing half PMMA and half PS or half PMAA and half PS were ineffective compatibilizers while graft copolymers of these polymers produced a much finer dispersion of PEO in PS when blended at 190°C. Graft copolymers made with 90% PS were different, however, with PMMA grafts having only a small effect, while PMAA grafts having a large effect. Random and graft copolymers of PS and PMMA were also used to compatibilize blends of PS and PMMA. The results were similar to the same compatibilizers with blends of PS and PEO, with the graft copolymer causing a finer dispersion.
Melt-Processable Block Copolyimides
Authors: Hunt Craig L. , VanKirk Terre L. , Kumar Sai R. 
Published: April 2011

ABSTRACTWe present here our probing research with segmented block copolyimdes derived on the basis of certain design principles to optimize performance and processability. We have shown that incorporation of relatively short blocks of rigid mesogenic segments along the backbone of flexible polyimide chains produce thermoprocessable polymeric systems which exhibit self-reinforcing characteristics.
In-Situ High Resolution Transmission Electron Microscopy of Solid-Liquid Interface of Alumina
Authors: Sasaki Katsuhiro , Saka Hiroyasu 
Published: April 2011

ABSTRACTThe atomic structure and dynamic behavior of the solid-liquid interface of alumina were observed in a transmission electron microscope (TEM). The in-situ heating experiment of the alumina powder was performed using the newly developed heating holder. The surface of alumina was partially melted at about 2000K. Molten alumina on the surface migrated along the surface and formed liquid droplets. Such droplets existed stably on the surface during observation. The solid-liquid interface was observed by high resolution electron microscopy. The layer-by-layer growth of solid was observed on the solid-liquid interface. The nucleation of the monolayer island and the progress of the atomic step were observed directly. The velocity of the step progress at the solid-liquid interface was directly measured.
Rapid Migration of Defects in Ion-Implanted Silicon
Authors: Lalita J. , Pellegrino P. , Hallén A. , Svensson B. G. , Keskitalo N. , Fatima S. , Jagadish C. 
Published: April 2011

ABSTRACTThe temperature dependence of the so-called reverse dose rate effect for generation of vacancy-type defects in silicon has been investigated using samples implanted with 1.3 MeV protons at temperatures between 70 and 300 K. The effect is found to involve a thermally controlled process which exhibits an activation energy of ∼0.065 eV, possibly associated with rapid migration of Si self-interstitials (I). Further, using a concept of dual Si ion-implants long range migration of I:s at room temperature has been studied. Annihilation of vacancy-type defects at a depth of ∼3 μm is obtained by injection of I:s from a shallow implant with sufficiently high dose.
Suppression of Boron Transient Enhanced Diffusion in SiGe HBTs by Carbon Incorporation
Authors: Lanzerotti L. D. , Sturm J. C. , Stach E. , Hull R. , Buyuklimanli T. , Magee C. 
Published: April 2011

ABSTRACTIn this paper we demonstrate, using both SIMS and transistor electrical characteristics, that substitutional carbon fractions of 0.5% in heavily doped Si0.8Ge0.2 base heterojunction bipolar transistors (HBTs) reduce both thermal diffusion and transient enhanced diffusion (TED) of boron. Furthermore we show that carbon suppresses TED of boron in carbon-free regions that surround the carbon layers.
Interface Effects on the Adhesion of Thin Aluminum Films
Authors: Schneider J.A. , Guthrie S. , Moody N.R. 
Published: April 2011

ABSTRACTDifferences in the adhesion and fracture toughness of aluminum films on sapphire due to the presence of controlled contaminants are being investigated. Adhesion is evaluated by use of nanoindentation and continuous scratch tests. A comparison was made of the properties of textured thin films of aluminum (178 to 1890 nm) that were vapor deposited onto (0001) oriented sapphire substrates. A very thin (1 nm) layer of carbon was deposited at the interface of selected samples prior to the vapor deposition of the aluminum. Spalling was observed during continuous scratch testing in specimens with carbon at the interface but not in specimens without carbon at the interface.
Texture of Gold-Palladium Couples
Authors: Chung Young S. , Evans Keenan , Glaunsinger William 
Published: April 2011

ABSTRACTThe crystal textures of polycrystalline films of gold-palladium couples on an oxidized silicon (100) substrates were investigated via x-ray diffraction (XRD) pole figures. Studies were performed on both as-deposited and thermally annealed films. Scanning electron microscopy (SEM) was used to examine the microstructures of the seed layer thin films as deposited. The {111} texture formation of gold-palladium thin film couples displayed a strong dependence on the nature of the underlying seed layer. Gold films deposited on a palladium seed layer revealed much less degree of {111} texture, than gold films deposited directly on a silicon dioxide surface. In contrast, palladium films deposited on polycrystalline gold films showed a higher degree of {111} texture, compared to palladium films deposited directly on silicon dioxide. The {111} texture of annealed gold-palladium alloy thin films was greater for palladium on gold than for gold on palladium. These results are interpreted in terms of the gold-palladium diffusion mechanism and the interaction of the condensing metals with the oxygens of the SiO2 substrate surface.