bluuebunny/crossref_metadata_2025_split huggingface dataset:
Growth and Structural Studies of Thin Films in the Mo-Bi-O System
Authors: Depero L. E. , Sangaletti L. , Zocchi M. , Rizzi G. A. 
Published: April 2011

AbstractIn the present contribution an X-ray diffraction (XRD) study of thin films in the Mo-Bi-O system is reported. The samples were grown by MOCVD on A12O3substrates. Several thin films have been grown starting from a Mo:Bi ratio in the two metallorganic precursors ranging from 6:1 to 1:1, thus obtaining films constituted by MoO3and Mo-Bi-O layers with different thicknesses. The effect of the underlying Mo-Bi-O layer on the preferred orientation of the MoO3layer, which is found in the samples with a high Mo:Bi ratio in the precursors, is discussed. Moreover, an equation is proposed relating the percentage of the phase constituting the film, as given by the Rietveld leastsquares procedure, and the film thickness. Thus it is shown that the growth rate of the pure MoO3film is much higher than that of the Mo-Bi-O oxide film. A tentative explanation can be given by considering a possible growth inhibiting action by Bi in this system.
Sol-Gel Route To Oxygen Ion Conductors in Thin Film Form
Authors: Pell J. W. , Delak K. M. , Loye H.-C. zur 
Published: April 2011

AbstractThe oxygen-ion conducting Aurivillius phases Bi2Cu0.1V0.9O5.35 and Bi2Nb0.3V0.7O5.5 were synthesized as bulk powders by the sol-gel method, and gave single-phase powder X-ray diffraction patterns at calcination temperatures as low as 450 °C. Crack-free films of both materials were spin-coated onto quartz, platinum, and silver substrates and heat-treated in a twostep firing process. The effects of different process parameters were investigated.
Optical Indices of Tin-Doped Indium Oxide and Tungsten Oxide Electrochromic Coatings
Authors: Von Rottkay K. , Rubin M. , Ozer N. 
Published: April 2011

AbstractThin films of tin-doped indium oxide are widely used for transparent conductors. One application of ln203:Sn (ITO) is transparent contacts for electrochromic electrodes. Optical design of electrochromic devices requires knowledge of the optical constants for each layer from the near ultraviolet and visible to the mid infrared. Determination of the optical constants of the electrochromic layer cannot be made in isolation; a complete device or at least a half-cell including a layer of ITO is required to change the optical state of the electrochromic material. Measurements on ITO were made using variable-angle spectral ellipsometry, and spectral transmittance and reflectance. A series of structural models were fit to this data. The problem is complicated because of inhomogeneity in the films, variability in the manufacturing process, and sensitivity to environmental conditions. The spectral dependency was modeled by a single Lorentz oscillator and a Drude free-electron component. This data was then used as the basis for a model to extract the optical constants for a tungsten oxide electrochromic film.
Grain Growth Simulation of [001] Textured YBCO Films Grown on (001) Substrates with Large Lattice Misfit: Prediction of Misorientations of the Remaining Boundaries
Authors: Rodriguez Julio C. , Ling S. , Tsap J. , Chan Siu-Wai 
Published: April 2011

AbstractWe employed a Monte Carlo technique to simulate the effect of (1) the anisotropic grain boundary energy in the film and (2) the large misfit between the film and substrate on the grain growth of [001] textured Yba2Cu3Ov7-x (YBCO) films. In terms of remaining grain boundaries of certain misorientations, the simulation results concur with the experimental observation of preferred grain orientations of YBCO on various substrates, such as (001) MgO and (001) Yttria stabilized Zirconia (YSZ). Three factors were identified to influence the grain growth of these [001] tilt boundaries in the simulation and could help to elucidate the origin of special misorientations observed experimentally. These are (1) the depth of local minima in boundary energy vs. misorientation curve, (2) the number of possible combinations of coincidence epitaxy (CE) orientations contributing to the exact misorientation for each of the high angle but low energy (HABLE) boundaries, and (3) the number of possible combinations of coincidence epitaxy CE orientations within the angular ranges near each of the HABLE boundaries.
Structure, Mechanical Properties, and Thermal Transport in Microporous Silicon Nitride Via Parallel Molecular Dynamics
Authors: Omeltchenko Andrey , Nakano Aiichiro , Kalia Rajiv K. , Vashishta Priya 
Published: April 2011

AbstractMolecular dynamics simulations are performed to investigate structure, mechanical properties, and thermal transport in amorphous silicon nitride under uniform dilation. As the density is lowered, we observe the formation of pores below ρ = 2.6 g/cc and at 2.0 g/cc the largest pore percolates through the entire system. Effects of porosity on elastic constants, phonons and thermal conductivity are investigated. Thermal conductivity and Young's modulus are found to scale as ρ1.5 and ρ3.6, respectively.
Ab Initio Investigation of Grain Boundary Sliding
Authors: Payne M. C. , Francis G. P. , Molteni C. , Marzari N. , Deyirmenjian V. , Heine V. 
Published: April 2011

AbstractWe are using total energy pseudopotential calculations to carry out an extensive investigation into grain boundary sliding in a number of different systems, in order to understand, at microscopic level, the fundamental mechanisms responsible for this process.In this paper we present results for the sliding process at the ∑ = 5(001) twist grain boundary in germanium, chosen as a typical covalently bonded material, and contrast them with preliminary results obtained for the ∑ = 5 (001) twist grain boundary in aluminium, a typical metal.
Defect Structure of β NiAl Using the BFS Method for Alloys
Authors: Bozzolo Guillermo , Amador Carlos , Ferrante John , Noebe Ronald D 
Published: April 2011

AbstractThe semiempirical BFS method for alloys is generalized by replacing experimental input with firstprinciples results thus allowing for the study of complex systems. In order to examine trends and behavior of a system in the vicinity of a given point of the phase diagram a search procedure based on a sampling of selected configurations is employed. This new approach is applied to the study of the/3 phase of the Ni-Al system, which exists over a range of composition from 45–60 at. % Ni. This methodology results in a straightforward and economical way of reproducing and understanding the basic features of this system. At the stoichiometric composition, NiAl should exist in a perfectly ordered B2 structure. Ni-rich alloys are characterized by antisite point defects (with Ni atoms in the Al sites) with a decrease in lattice parameters. On the Al-rich side of stoichiometry there is a steep decrease in lattice parameter and density with increasing Al content. The presence of vacancies in Ni sites would explain such behavior. Recent X-ray diffraction experiments suggest a richer structure: the evidence, while strongly favoring the presence of vacancies in Ni sites, also suggests the possibility of some vacancies in Al sites in a 3:1 ratio. Moreover, local ordering of vacant sites may be preferred over a random distribution of individual point defects.
Monte-Carlo Studies of Bosonic van der Waals Clusters
Authors: Meierovich M. , Mushinski A. , Nightingale M. P. 
Published: April 2011

AbstractIn a previous paper [1], we developed a form of variational trial wave function and applied it to van der Waals clusters: five or less atoms of Ar and Ne modeled by the Lennard-Jones potential. In addition, we tested the trial functions for a hypothetical, light atom resembling Ne but with only half its mass. We did not study atoms such as He4 with larger de Boer parameters, i.e., systems in which the zero point energy plays a more important role relative to the potential energy. This is the main purpose of the present paper. In fact, we study clusters to the very limit where the zeropoint energy destroys the ground state as a bound state. A simple picture of this un-binding transition predicts the power law with which the energy vanishes as the de Boer parameter approaches its critical value and the power of the divergence of the the size of the clusters in this limit. Our numerical results are in agreement with these predictions.
Film Effects On Ductile/Brititle Behavior In Stress-Corrosion Cracking
Authors: Zhang Tong-Yi , Chu Wu-Yang , Xiao Ji-Mei 
Published: April 2011

AbstractThe present work analyzes the effects of a passive film formed during stress corrosion cracking on ductile/brittle fracture behavior, considering the interaction of a screw dislocation with a thin film-covered mode III crack under an applied remote load. Exact solutions are derived, and the results show that the crack stress field due to the applied load is enhanced by a harder film or abated by a softer film. The critical stress intensity factor for dislocation emission from the crack tip is greatly influenced by both the stiffness and thickness of the filn. A dislocation is more easily to be emitted from the crack tip if the covered film has a shear modulus larger than that of the substrate. The opposite is also true, i.e., a softer film makes dislocation emission more difficult. Both phenomena become more significant when the film thickness is smaller.
R-Curve Response Of Silicon Carbide Whisker-Reinforced Alumina: Microstructural Influence
Authors: Sun E. Y. , Hsueh C. H. , Becher P. F. 
Published: April 2011

AbstractRising fracture resistance with crack extension (R-curve response) can lead to improvements in the mechanical reliability of ceramics. To understand how microstructures influence the R-curve behavior, direct observations of crack interactions with microstructural features were conducted on SiC whisker-reinforced alumina. The contribution of the dominant toughening mechanisms to the R-curve behavior of these composites is discussed using experimental and theoretical studies.
Fracture Of Particulate Composites With Strong Or Weak Interfaces
Authors: Lekatou A. , Faidi S.E. , Lyon S.B. , Newman R.C. 
Published: April 2011

AbstractThe tensile fracture of glass-bead/epoxy composites has been studied using a large number of glass volume fractions (q) from 0 to 0.25. Absorption of water from a saturated NaCl solution was used to destroy interface adhesion. The strength of the dry composites decreased up to q = 0.15, then became constant. The strength of the wet composites showed a plateau around q = 0.12, then an abrupt drop between 0.12 and 0.15, then became nearly constant. It is possible that the abrupt drop in strength occurs at the percolation threshold. However, electrical measurements on similar composites prepared with conducting (silver-coated) beads showed that the applicable percolation threshold (qc) was ≥ 0. 16, in agreement with the observation of anomalous water uptake only for q ≥ 0.18. It is concluded that the abrupt drop in strength occurs below qc, and is due to large finite interface clusters (or rather the more planar parts of such clusters) acting as nuclei for a progressive matrix fracture process. The plateau around q = 0.12 is due to favourable fibre-like interactions of smaller interface clusters, and gives the highest normalized (wet/dry) strength of about 0.9.
Micromechanical Behavior Of Polymer Interface Reinforced With Copolymers
Authors: Wang Q. , Chiang F. P. , Guo L. , Rafailovich M. , Sokolov J. 
Published: April 2011

AbstractThe fracture toughness of interface reinforced with dps-b-dpmma copolymer between immiscible polymers of PS and PMMA is tested by asymmetric double cantilever beam. The local deformation field at the interfacial crack tip is determined by the technique of SIEM. Normal and tangential crack opening displacements are calculated. A weak singularity is shown to exist near crack tip. Direct observation on the fracture process inside an environmental scanning electron microscope shows the large effect of mode mixity.
Synthesis And Characterization Of Nine Metal Nitrides
Authors: Wade Travis , Crooks Richard M. 
Published: April 2011

ABSTRACTWe demonstrate a simple electrochemical method suitable for preparing precursors for nine different metal-nitride ceramics. These precursor powders were calcined in flowing NH3 or Ar to yield metal-nitride ceramic powders. This electrochemical synthetic technique was applied to Al, Ga, Mo, Nb, Ni, Ti, V, W, and Zr and resulted in a nitride of each of these metals. The calcination conditions determined the resulting phase, composition, and morphology of the product. The ceramic materials were characterized primarily by powder XRD.
Flame Synthesis Of High Purity, Nanosized Crystalline Silicon Carbide Powder
Authors: Keil D. G. , Calcote H. F. , Gill R. J 
Published: April 2011

ABSTRACTSelf-propagating flames in pure silane-acetylene mixtures produce silicon carbide (SiC) powder and hydrogen as main products. Through precise control of the stoichiometry of the reactant gas mixture, it has been possible to produce white SiC at high yields. Characterization of such powders by TEM has shown that the nascent powder consists of polycrystalline hexagonal plates with a narrow size distribution (40 ± 7 nm diameter). Infrared spectroscopy of powders indicate microcrystalline SiC and little bound hydrogen. Chemical analysis by the ANSI method showed the powder to be >96 wt % SiC with an impurity of silica (3.9 weight %) due to air exposure of the powder. Traces (0.1 to 0.2 weight %) of both free carbon and free silicon were found. Metal impurities detected by SIMS were typically low: less than 10 ppba for aluminum, sodium, titanium and vanadium. Boron was observed at 10 ppma. Like the oxygen, the boron impurities are probably associated with exposure of the powders to the atmosphere.
High-Pressure, High-Temperature Synthesis of Superhard Boron Suboxide
Authors: Hubert H. , Garvie L. A. J. , Leinenweber K. , Buseck P. R. , Petuskeyt W. T. , McMillan P. F. 
Published: April 2011

ABSTRACTA multianvil device was used to investigate the formation of BxO phases produced in the 2 to 10 GPa pressure range with temperatures between 1000 and 1800 °C.Amorphous and crystalline B and BP were oxidized using B2O3 and CrO3. Using powder X-ray diffraction and parallel electron energy-loss spectroscopy (PEELS), we were unable to detect graphitic or diamondstructured B2O, reported in previous studies. The refractory boride B6O, which has the α-rhombohedral boron structure, is the dominant suboxide in the P and T range of our investigation. PEELS with a transmission electron microscope was used to characterize the boron oxides.
Thermodynamic Modeling of Atomic Bonding in Covalent Cx(BN)1-x Alloys
Authors: Akkerman Z. L. , Efstathiadis H. , Smith F. W. 
Published: April 2011

ABSTRACTThe results of the application of the free energy model (FEM) to the atomic bonding in covalent network Cx(BN)1-x alloys are presented. The high values of C-C and B-N bond energies strongly favors chemical ordering and phase separation of carbon and boron nitride. Only at temperatures of the order of the melting points are equilibrium bonding configurations including CB and C-N bonds expected to be present. Two types of structure based on either sp3 (tetrahedral) or sp2 (trigonal) configurations with different short and long range ordering are possible in the alloys. The tetrahedral structure will consist of separate clusters of diamond-like carbon and cubic boron nitride. For the hexagonal structure planar bonding causes instead two-dimensional clusters to be present. The weak interlayer bonding makes thermodynamically possible the formation of alternating graphite and BN layers. Special physical properties of the alloys connected with this ordering may be expected.
synthesis of crystalline carbon nitride by chemical vapor deposition
Authors: Zhang Yafei , Li Hulin , Xue Qunji 
Published: April 2011

ABSTRACTCrystalline carbon nitride films have been synthesized in a rf plasma assisted hot filament chemical vapor deposition system. Large crystalline grains up to ∼10 μm in size as well as film-like regions are observed in the morphology of the films. β-C3N4with two groups of lattice parameters ( one is consistent with the theoretical value and the other is 3% smaller) in the deposited films on polycrystalline Ni substrate has been revealed by x-ray diffraction spectrum (XRD). No Raman shift peaks have been found evidently by Raman scattering measurement, but some presently unknown diffraction peaks appeared in the XRD spectrum. It is proposed that there are possible unknown structures of crystalline C-N in the films. Heteroepitaxial growth of crystalline β-C3N4has also been tried via a buffer layer of α-SiC on Si (100) substrate. The XRD pattern of a film show that there are only two main peaks at 2.79 Å and 1.87 Å corresponding to the (200) and (300) crystalline planes of the theoretical β-C3N4The two main peaks indicate heteroepitaxial growth along the (100) direction of β-C3N4.
Adhesion Evaluation of TiN and (Ti, Al)N Coatings on Titanium 6Al-4V
Authors: James R. D. , Paisley D. L. , Gruss K. A. , Parthasarthi S. , Tittmann B. R. , Horie Y. , Davis R. F. 
Published: April 2011

ABSTRACTTo assess the adhesion of nitride coatings on metals, titanium 6% aluminum 4% vanadium substrates were coated with titanium nitride (TiN) using both cathodic arc and electron beam evaporation. Titanium aluminum nitride ((Ti, Al)N) was also deposited using cathodic arc evaporation. The interfaces of the coated samples were loaded in tension using a high speed shock wave which caused spallation either at the interface, in the coating or in the metal. Scanning acoustic microscopy analysis of the spalled samples detected delaminations at the interface in the samples deposited by cathodic arc evaporation. DYNA2D modeling of plate impact spallation experiments revealed the tensile adhesion strength for TiN deposited by both techniques was ≈ 2.0 GPa. The tensile adhesion strength for (Ti, Al)N was less than 1.5 GPa.
Synthetic, Characterization and Decomposition Studies of Indium Sulfide Precursors
Authors: Schluter Rodney D. , Luten Henry A. , Rees William S. 
Published: April 2011

ABSTRACTThe synthesis, characterization and decomposition of several indium thiolates containing the bulky substituted aryl ligand 2,4,6-i-Pr 3C6H2 (Ar′) or the internally chelating ligands 2-CH3O,5-CH3C6H3 (Ar″) and o-C6H4CH2N(CH3)2 (Ar"‘) are described. Two synthetic methods have been utilized: metathesis reactions between lithium thiolates and the appropriate metal halides and the addition of elemental metal to diaryl disulfides. The thermal decomposition of each indium precursor results in the formation of 1n2S3, based on thermogravimetric data. The homoleptic compound In(SAr′)3 can be isolated as a yellow oil. This liquid precursor has been derivatized by the reversible formation of acetonitrile and tetrahydrofuran adducts. Although, the molecule exists as a monomer in both adducts, the coordination number of the metal and he orientation of the ligands are markedly different. The internally chelating In(SAr″)3 and In(SAr.″′)3 adopt contrasting dimeric and monomeric structures respectively.
A Carbon Drug Delivery System for Lithium
Authors: Maleki H. , Ila D. , Zimmerman R. L. , Jenkins G. M. , Poker D. 
Published: April 2011

AbstractLithium was introduced into pyrolyzed phenolic resins by dissolving lithium nitrate (5, 10, and 15% by mass) in a resol precursor. Impregnated specimens were pyrolyzed at 500°C, 575°C, and 650°C in inert atmosphere. After pyrolysis, samples were placed in 5 ml of phosphate buffered saline solution, refrigerated at 5°C, for various Li release times. Inductively coupled plasmaatomic spectroscopy was used to analyze these solutions, which were tested every 24 hours for 5 days; another set was tested after 60 days. Samples containing 5% lithium salt, fired to 500°C, released Li+at a lower rate than those fired at higher temperature. At the early stages of exposure to saline, samples fired at 575°C and 650°C released Li+at a higher rate, which fell to that of 500°C samples after many days. After leaching, nuclear reaction analysis using alpha radiation, with an exposure time of I hour, allowed us to analyze [Li+] and gradient up to 121μm below the surface. This indicates that a smaller [Li+] remains in 650°C samples than in those fired at 575°C and 500°C. For 500°C samples, [Li+] near the surface was lower than that for samples fired at 575°C and 650°C. This indicates that 500°C samples release Li+from near the surface, whereas samples fired at higher temperature release Li+from deep below the surface, probably because of higher permeability. Li+release rates of samples fired at 500°C and below 650°C follow a simple diffusion law, with diffusivities between 1017and 10-18m2/s. Li+rate may controlled over long time by a multilayered sprayed precursor with variable concentration.
Prediction of New Fingerprints of Ordering in GaInP2 Alloys
Authors: Franceschetti Alberto , Wei Su-Huai , Zunger Alex 
Published: April 2011

AbstractUsing ab initio all-electron methods, we investigate the evolution of effective masses, deformation potentials and pressure coefficients with the degree of long-range order in spontaneously ordered Ga0.5In0.5P alloys. We find that (i) the electron effective mass in the ordering direction increases significantly with the degree of order, while the effective mass in the perpendicular direction decreases; this produces a strong anisotropy of the electron effective mass which is not present in the disordered alloy; (ii) the band-gap deformation potential for (001) epitaxial strain decreases with increasing degree of order, reflecting the extent of the ordering-induced Γ - L coupling; (iii) the band-gap pressure coefficient decreases from 8.4 meV/kbar in the disordered alloy to 6.6 meV/kbar in the ordered CuPt structure; interpolation to partial degrees of order leads to good agreement with recent high-pressure experiments.
Pattern Formation by Changing V/III Ratio During Growth of GaAs by Movpe
Authors: Paul Shashi , Shivashankar S. A. 
Published: April 2011

AbstractRode pointed out that periodically-disturbed surface morphology can occur on epilayers grown on slightly misoriented substrates. Johnson and Legg investigated Rode's prediction in Metalorganic Vapour Phase Epitaxy (MOVPE) of AIGaAs at fixed V/III ratio, but no report is available on the faceting as a function of V/III ratio in epilayers of GaAs grown by MOVPE. We have therefore investigated faceting, as function of V/III ratio, during the growth of GaAs by MOVPE at atmospheric pressure, and have found that faceting in epilayers, grown by MOVPE, is not only dependent on misorientation angle but also on the V/III ratio. These layers have characterized by optical microscopy, SEM, photoluminescence(PL), and Hall ineasuremwnts. Direct correlation between surface morphology and near-band-edge PL has been observed. Mirror-like smooth morphology was obtained at a relatively low V/Ill ratio (≈ 15); faceting occur as a ratio is gradually is increased to about 25 and beyond. On the basis of our study, we believe the dimensions of faceting on micrometer scale can be tailored by varying the V/III ratio. These patterns can be utilized in the fabrication of optoelectronic and transferred electron devices, large scale integration of the later being possible.