bluuebunny/crossref_metadata_2025_split huggingface dataset:
Neutron Vibrational Spectroscopy of the H5O2+ Ion and Its Deuterated Analog in Phosphotungstic Acid Hexahydrate
Authors: Maliszewskyj N. C. , Udovic T. J. , Nicol J. M. 
Published: April 2011

AbstractHeteropolyacid hydrates of the general form H3PM12O40. nH2O are of interest to researchers in areas such as proton conductivity and catalysis. The water molecules in these hydrated acids reside in the interstitial volume between the large Keggin anions and can, under certain conditions, complex with the acidic protons to form stable cations such as the “dioxonium” ion (H5O2+). We have used incoherent inelastic neutron scattering (IINS) measurements of dodecatungstophosphoric acid hexahydrate (H3PW12O40 · 6H2O) to obtain the vibrational density of states spectrum of H5O2+ stabilized by the PW12O403− Keggin anions. Spectra were measure for fully hydrogenated and fully deuterated ions in order to determine the relative merit of previous assignments of the normal mode vibrations.
Special Hysteresis Effects in N2-Sorption and Mercury-Porosimetry Measurements
Authors: Giesche Herbert 
Published: April 2011

AbstractModel pore structures were prepared from dispersions of submicron monodispersed silica particles by a sedimentation process. Ordered dense sphere packing structures were observedwith scanning electron microscopy. Nitrogen sorption- as well as Hg-porosimetry measurements confirmed the calculated values of the pore openings in those structures. In Hgporosimetry measurements a two step extrusion curve was observed, when the pore system was only partially filled during the intrusion process. This two step curve was not observed in case the pore system was filled with mercury to more than 95% during the intrusion run. The mercury porosimetry results can be interpreted in terms of the coexistence of octahedral and tetrahedral voids (pores) in the examined sphere packing structure and their special arrangement within the structure (connectivity). Two models will be described to explain thegeneral occurrence of hysteresis in Hg-porosimetry. The actual pore geometry is shown to have a profound influence on the hysteresis shape as well as a change in the contact angle (constant within each measurement) can result in totally different hysteresis curves. Nitrogen adsorption and desorption measurements on the same powders did not reveal any fine structure within the hysteresis range.
Synthesis, Characterization, and Reactivity of Feitknechtite
Authors: Luo J. , Segal S. R. , Wang J. Y. , Tian Z. R. , Suib S. L. 
Published: April 2011

AbstractThe synthesis of Mg2+ doped β-MnOOH which is known as feitknechtite is reported. Feitknechtite is a layered material having the Cd12 structure. The characterization of Mg2+ doped feitknechtite was done with X-ray powder diffraction, elemental analysis, energy dispersive X-ray analysis, scanning electron microscopy, alternating current (AC) impedance, Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, average oxidation state titrations of manganese, and acidity measurements. The formation of feitknechtite is related to the MnO4−/Mn2+ ratio used in the synthesis. Feitknechtite can be converted to synthetic birnessite or octahedral layer birnessite (OL-1) which is a precursor to the 6.9 Å tunnel structure material todorokite.
Si3N4 Whisker Upper Layer Formation on a SiC-Al2O3 Porous Body
Authors: Toro P. , Pérez A. , Baeza G. , Piderit G. , Rojas P. 
Published: April 2011

AbstractA thin upper layer on a SiC-A12O3 porous substrate was formed by spray deposition of a Si-C composite or SiC fine powder 55.0 wt% total powder suspension. The formation of a compact layer of Si3N4 whisker or a SiC smaller pore size than the porous substrate was obtained under thermal treatment up to 1400°C for 3–4 h in a nitrogen or argon gas environment, respectively. SEM microstructure observations and a qualitative (DRX-EDAX) analysis of both sintered porous bodies were performanced to confirm the nature of both layers.
Nanochannel Glass Replica Membranes for Parallel Patterning Applications
Authors: Pearson D. H. , Tonucci R. J. , Eddy C. R. 
Published: April 2011

AbstractNanochannel glass replica membranes are thin metallic films containing patterned arrays of uniform, nanometer-scale voids whose sizes, positions, geometric patterns, and packing densities may be controlled to a high degree. These membranes have been prepared from refractory and noble metals and are well suited for use as shadow masks in a variety of substrate patterning applications. Here we describe their use in the sub-micron, parallel patterning of Si and GaAs by materials deposition and reactive-ion etching respectively.
High-Pass Optical Filters Based on Gold-Coated Nanochannel Glass Materials
Authors: Rosenberg A. , Tonucci R. J. 
Published: April 2011

AbstractWe have fabricated high-pass optical filters from thin nanochannel glass (NCG) wafers coated with sputtered and evaporated gold films. The near-infrared (IR) transmission spectra of these filters have a sharp cutoff at a wavelength that scales linearly with the channel diameter, as expected for hollow metallic waveguides. Cutoff wavelengths approaching 1 μm have been achieved to date using NCG materials with sub-micron channel diameters. The spectra are dominated by a strongly resonant transmission peak just above the cutoff wavelength, where the peak transmission can be as much as twice that predicted based on the geometrical open area of the NCG structure. The NCG wafers were typically less than 20 μm thick, and the Au films ranged in thickness up to 600 nm.
Effect of Preparation Parameters on the Microporous Structure of Ni/SiO2 Catalysts
Authors: Castillon F. E. , Bodganchikova N. , Fuentes S. , Avalos M. 
Published: April 2011

AbstractIn this work we report the synthesis of Ni/SiO2 catalysts promoted by group 2 (IIA) cations (calcium and barium) which are currently used as hydrogenation catalysts. The effect of the preparation parameters aging, base agent, and type of cation, on the surface area of catalysts is evaluated. Catalysts were prepared by precipitation of the precursor silicic acid, along with nickel nitrate and calcium and barium carbonates, with NaOH, NH4OH and Na2CO3as precipitating agents. Catalysts were characterized by diffuse reflectance spectra (DRS) and by BETsurface area measurements. Results are discussed in terms of solgel chemistry (1).
Vanadium Molecular Sieve, Vapo-5: Preparation and Electrochemical Characterization
Authors: Bedioui F. , Briot E. , Devynck J. , Balkus K. J. 
Published: April 2011

AbstractThe vanadium containing molecular sieve VAPO-5 was characterized by using cyclic voltammetry. The as-synthesized and calcined samples contain loosely bound VO2+ species that can be removed by immersion in the aqueous electrolyte solution. The steady-state cyclic voltammograms of VAPO-5 reveal two distinct reversible V(5+)/V(4+) processes centered at Eeq(I) = 0.11 V/SCE and Eeq(II) = −0.07 V/SCE. These processes have been proposed to arise from framework vanadium located at structurally distinct sites V-O-T (T = Al or P).
Synthesis and Surface Modification of Deagglomerated Superparamagnetic Nanoparticles
Authors: Lesniak Christoph , Schiestel Thomas , Nass Riüdiger , Schmidt Helmut 
Published: April 2011

AbstractA method for the preparation of aminosilane coated, chemically stable, agglomerate-free superparamagnetic iron oxide nanoparticles (ferrites, e.g. Fe3O4 and γ-Fe2O3) has been developed. These nanocomposite particles posess core-shell structure. The well crystallized core particles are prepared by precipitation from aqueous salt solutions (primary particle size 10 nm). The surface modification of the weakly agglomerated core particles with aminosilane (e.g. γ-aminopropyl- triethoxysilane) leads to deagglomerated particles, covered by a thin polymerized aminosilane shell. A strong dependency of the particle/agglomerate size on the silane/iron oxideratio as well as on the disintegration time was found. A ratio of aminosilane to iron oxide of 0.8 (weight ratio) and a disintegration time of 72h result in overall particle sizes in the range of 10–15 nm. After surface modification, aminogroups are present on the particle surface (IEP of 9.5). The particles show superparamagnetic behaviour (saturation magnetization 68 EMU/g) and aqueous suspensions are stable against agglomeration. A desorption of the coating in aqueous suspensions (pH 3 to 11) is not observed.
Physics and Electrochemistry of Oxide Growth
Authors: Sikora Elzbieta , Macdonald Digby D. 
Published: April 2011

AbstractThe growth of the passive film on tungsten in phosphate buffer solution has been described in terms of the Point Defect Model (PDM). The steady-state current and passive film thickness have been measured as a function of voltage, with the film thickness being obtained from an analysis of capacitance and reflectance data. The observed data cannot be accounted for by the High Field Model (HFM) in its classical form, but can be understood in terms of the PDM. Diagnostic criteria that have been derived from the PDM were used to identify the majority charge carriers in the passive film. The Point Defect Model was employed, together with Mott- Schottky analysis to explore the crystallographic defect structures of the passive films, whereas their electronic structures have been studied using photoelectrochemical impedance spectroscopy (PEIS). The experimental results demonstrate that these structures are strongly coupled with the vacancies acting as the dopants.
Aqueous and Surface Chemistry of Calcium - Metal Hydroxides in High pH Environments
Authors: Cocke David L. , Yousuf M. , Mollah A. , Hess Thomas R. , Lin Tien-Chih 
Published: April 2011

AbstractMixed hydroxides of calcium, zinc, cadmium and lead have been recently identified in the high pH environments of hydrating cement. FTIR, XRD, SEM, and SPM have been used to characterize these systems. A chemical equilibrium model of the early hydration of a zinc-doped cement/water system, Na-K-Ca-Zn-H-SO4-OH-Zn(OH)2-Zn(OH)3-Zn(OH)4-H2O, has been developed to better understand the mechanism of the surface formation of calcium hydroxyzincate (CHZ). The model is based on Pitzer's semi-empirical method for calculation of ion-activity coefficients at high ionic strength. The Pitzer parameters for Na+-Zn2+,Na+-Zn2+- and have been evaluated, and the results successfully predict the equilibria (solubilities) of Na2SO4-ZnSO4-H2O, NaOH-Zn(OH)2-H2O and KOH-ZnO-H2O systems. The chemical model clearly demonstrates that the formation of CHZ on the calcium-silicahydrate (C-S-H) surface is critically controlled by the Ca2+ ion concentration as well as pH of the pore water system. The results of this study suggest that the growth of CHZ is preceded by surface complex formation. Sequential charge control and sequential structure development have been used to discuss the surface selectivity of these compounds and their control of cement hydration.
Reactive Sputter Deposition of Superhard Polycrystalline Nanolayered Coatings
Authors: Sproul William D. 
Published: April 2011

AbstractNanometer-scale multilayer nitride coatings, also known as polycrystalline nitride superlattice coatings, such as TiN/NbN or TiN/VN with hardnesses exceeding 50 GPa, are deposited by highrate reactive sputtering. The high hardness is achieved by carefully controlling several deposition parameters in an opposed cathode, unbalanced magnetron sputtering system: the target power, the reactive gas partial pressure, the substrate bias voltage and current density, and the substrate rotation speed. Target power controls the deposition rate and the thickness for each layer in conjunction with the reactive gas partial pressure at each target, which also affects the composition of each layer, and the substrate rotation speed. Split partial pressure control is necessary when each layer requires a different partial pressure to be stoichiometric. Fully dense, well-adhered coatings with the highest hardness are deposited when the negative substrate bias exceeds -130 V and the substrate ion current density is 4–5 mA cm−2. The work on polycrystalline superlattice coatings is being extended into oxide systems. Oxide coatings can now be sputter deposited using pulsed dc power, which prevents arcing on both the target and the substrate. Pulsed dc power along with partial pressure control of the reactive gas leads to significantly higher deposition rates for the oxide films compared to sputtering with conventional rf power.
Mechanics Of Interfacial Crack Propagation In Microscratching
Authors: Boer Maarten P. de , Nelson John C. , Gerberich William W. 
Published: April 2011

AbstractA new probing technique has been developed to test thin film mechanical properties. In the Microwedge Scratch Test (MWST), a wedge shaped diamond indenter tip is drawn along a fine line, while simultaneously being driven into the line. We compare microwedge scratching of Zone 1 and Zone T thin film specimens of sputtered W on SiO2. Symptomatic of its poor mechanical properties, the Zone 1 film displays three separate crack systems. Because of its superior grain boundary strength, the Zone T film displayed only one of these - an interfacial crack system. Using bimaterial linear elastic fracture mechanics, governing equations are developed for propagating interfacial cracks, including expressions for strain energy release rate, bending strain, and mode mixity. Grain boundary fracture strength information may be deduced from the Zone 1 films, while adhesion may be inferred from the Zone T films.
Time Dependent Deformation During Indentation Testing
Authors: Lucas B. N. , Oliver W. C. , Pharr G. M. , Loubet J-L. 
Published: April 2011

AbstractConstant loading rate/load indentation tests (1/P dP/dt) and constant rate of loading followed by constant load (CRL/Hold) indentation creep tests have been conducted on high purity electropolished indium. It is shown that for a material with a constant hardness as a function of depth, a constant (1/P dP/dt) load-time history results in a constant indentation strain rate (1/h dh/dt). The results of the two types of tests are discussed and compared to data in the literature for constant stress tensile tests. The results from the constant (1/P dP/dt) experiments appear to give the best correlation to steady-state uniaxial data.
Stress Distribution in Si Under Patterned thin Film Structures
Authors: Wong S. P. , Huang L. , Guo W. S. , Cheung W. Y. , Zhao Shounan 
Published: April 2011

AbstractWe have employed the infrared photoelasticity (PE) method to study the stress distribution in Si substrates under patterned thin film structures such as thermal oxide layers partially covered by metal films and oxide layers with long trench openings. It is demonstrated that a lot of information on the two dimensional stress distribution in the substrate under patterned thin film structures can be obtained from PE experiments. The capability, limitation, and further development of the PE method for semiconductor applications are discussed.
Tribology Studies of Organic Thin Films by Scanning Force Microscopy
Authors: Bar G. , Rubin S. , Parikh A. N. , Swanson B. I. , Zawodzinski T. A. 
Published: April 2011

AbstractUsing the micro-contact printing method we prepared patterned self-assembled monolayers (SAMs) consisting of methyl-terminated alkanethiols of different chain lengths. The samples were characterized using lateral force microscopy (LFM) and the force modulation technique (FMT). In general, higher friction is observed over the short chain regions than over the long chain regions when a low or moderate load is applied to the scanning force microscopy (SFM) tip. For such cases the high friction (short chain) regions are also “softer” as measured by FMT. At high loads, a reversal of the image contrast is observed and the short chain regions show a lower friction than the long chain regions. This image contrast is reversible upon reduction of the applied load.
Near-Plastic Threshold Indentation and the Residual Stress in Thin Films
Authors: Houston J. E. , Michalske T. A. 
Published: April 2011

AbstractIn recent studies, we used the Interfacial Force Microscope in a nanoindenter mode to survey the nanomechanical properties of Au films grown on various substrates. Quantitative tabulations of the indentation modulus and the maximum shear stress at the plastic threshold showed consistent values over individual samples but a wide variation from substrate to substrate. These values were compared with film properties such as the surface roughness, average grain size and interfacial adhesion and no correlation was found. However, in a subsequent analysis of the the results, we found consistencies which support the integrity of the data and point to the fact that the results are sensitive to some property of the various film/substrate combinations. In the present paper, we discuss these consistencies and show recent measurements which strongly suggest that the property that is being probed is the residual stress in the films caused by their interaction with the substrate surfaces.
An Analysis of Void Nucleation In Passivated Interconnect Lines Due to Vacancy Condensation and Interface Contamination
Authors: Gleixner R. J. , Nix W. D. 
Published: April 2011

AbstractNucleation of voids due to vacancy condensation in passivated aluminum lines is analyzed within the context of classical nucleation theory. A discussion of sources of hydrostatic tensile stress in such lines provides a reasonable upper limit of 2 GPa. The void nucleation rate is then calculated at various sites within the line. Results suggest that nucleation rates are far too low to account for observed rates of voiding. Void nucleation at a flaw at the line/passivation interface is then considered as an alternative nucleation mechanism. Such flaws may be created by contaminants introduced during fabrication of the line. In this case, nucleation is feasible at greatly reduced stresses, well within the observed values. Furthermore, a simple model of void growth indicates that a fast atomic transport path, such as a grain boundary, must intersect the void for an appreciable growth rate. These results suggest that void nucleation in aluminum interconnect lines occurs at flaws at the sidewall of the line and that stress-induced and electromigration-induced voiding can be controlled by eliminating interfacial contamination.
Relationship Between The Void and Hillock Formation and The Grain Growth in Thin Aluminum Films
Authors: Kononenko O. V. , Matveev V. N. 
Published: April 2011

AbstractVoid and hillock formation during annealing was studied depending on the deposition conditions. Aluminum films were deposited onto oxidized silicon substrates by the self-ion assisted technique. The bias 0 or 6 kV was applied to the substrate during deposition. The films were then annealed in vacuum for 1 hour in the temperature range from 150° to 550°C. The structure of the films was investigated by transmission electron microscopy. The void and hillock formation was studied with optical and scanning electron microscopes.It was found that recrystallization and void and hillock formation in the films depend on the bias during deposition. Normal grain growth occurred in the films deposited without bias. Abnormal grain growth was observed in the 6 kV-films. It was also found that the mechanism of stress relaxation during thermal cycling depends on the self-ion bombardment. In the films prepared without bias, stress relaxation proceeds by diffusion creep. In the films deposited at the 6 kV bias, stress relaxation proceeds by plastic deformation.
The Fluorescence X-Ray Microprobe at the Advanced Light Source
Authors: Thompson Albert C. , Chapman Karen 
Published: April 2011

AbstractThe fluorescence x-ray microprobe beamline at the Advanced Light Source (ALS) provides a technique to study almost any sample with excellent trace element sensitivity, high spatial resolution and minimal sample damage. During the last two years, the focused spot size has been improved from 2 μm × 4 μm to 1.6 μm × 1 μm using a pair of elliptically-bent multilayer mirrors. Two sets of mirrors have been produced for operation at 8.5 keV and 12.5 keV with a bandpass (ΔE/E) of 4 %. The intensity has also increased by a factor of 20 to over 1 × 1010 photons/sec by linearly grading the multilayer coating on the mirrors and by operation of the ALS at 1.9 GeV rather than 1.5 GeV.A wide variety of samples have been studied. Some of the materials science samples that have been studied include gallium nitride samples, polycrystalline silicon solar cells, the liner material of a rocket motor and the central germanium core of an optical fiber.
An Observation of the Dimension Effect in the CKα- Spectra of the Ultra Dispersed Diamonds
Authors: Mazalov L.N. , Okotrub A.V. , Bulusheva L.G. 
Published: April 2011

AbstractThe fluorescent CKα - spectra of ultra dispersed diamonds (UDD), separated into fractions by size, were obtained. The distinction between the spectra are more pronounced in the short-wave region. A quantum-chemical calculation of the C136 diamond cluster was performed using the MNDO method. Hydrogen atoms were placed on the broken bonds of the edge carbon atoms. According to the results of the calculation, the theoretical CKα- spectra of the cluster's surface and volume were simulated. In the theoretical and experimental spectra the same tendencies are reflected if the surface carbon atoms are linked to oxygen groups.
Epitaxial Variants and Grain Boundary Structures in Heteroepitaxial Lithium Tantalate on Basal Sapphire
Authors: Bellman Robert A. , Raj Rishi 
Published: April 2011

AbstractSingle crystal heteroepitaxial ferroelectric films are desired for non-linear optical applications to maximize the electro-optic coefficient and minimize waveguide losses. In this study, lithium tantalate films were deposited on (0001) sapphire from lithium hexaethoxytantalate by chemical beam epitaxy. Characterization showed that films had nearly stoichiometric composition, epitaxial orientation, and a high degree of crystalline perfection. However, the films exhibited high optical waveguide losses. Additional characterization by TEM revealed that the films had a two dimensional grain structure with epitaxial variants related by translation and a twin orientation to the substrate. To better understand the nature of the heteroepitaxial growth of lithium tantalate on (0001) sapphire, a model was developed to explain the observed epitaxial orientations, misfit dislocation networks, and grain boundary structures of lithium tantalate on (0001) sapphire.
The Atomic Fe/Ag Exchange on Ag(100)
Authors: Langelaar M. H. , Boerma D. O. 
Published: April 2011

AbstractIn this paper we present a low-energy ion scattering (LEIS) study of the site exchange of Fe adatoms with Ag atoms from the Ag(100) surface. The time-of-flight (TOF) spectra obtained at low temperatures have been interpreted with a newly developed LEIS simulation program MATCH. After low temperature deposition (˜50 K) of Fe atoms oil the Ag(100) surface, the Fe atoms occupy adatom positions. These Fe adatoms exchange sites with Ag atoms from the first layer, starting at a temperature of 130(10) K.