bluuebunny/crossref_metadata_2025 huggingface dataset:
7Li NMR study of ionically conducting glasses
Authors: Akai Tomoko
Published: April 2011

Temperature dependence of 7Li NMR was measured in 50Li20-50B203 glasses. A new method for the analysis of motional narrowing of the line width (MNLW) incorporating Kohlrasuch-Williams-Watt (KWW) function, exp(-(t/τ)β) is presented. The obtained activation parameters are compared with that from conductivity. It was shown that MNLW can be explained by the same activation energy from conductivity. It was found that electrical relaxation time was an order of magnitude smaller than that from those from NMR line width. At high temperature region, where the line is well narrowed, a residual line width was observed. It is as large as 1 kHz, and gradually decreases with the increase in temperature. It was explained that there is a mobility difference in lithium ions in this glass. These results suggest that some fraction of ions are highly mobilized in the glass.
Conductivity Enhancement of Solid Ionic Conductors (CuBr, LiI) with Dispersed Oxide Particles (TiO2, A1203) : Experiments and Percolative Transport Model
Authors: Albinet G. , Debierre J.-M. , Knauth P.
Published: April 2011

The electrical conductivity of two-phase mixtures of an ionic conductor with dispersed insulator particles is described using a percolative transport model. The difference of grain sizes, the existence and anisotropy of confined high conductivity paths near the grain interfaces are implemented by simple rules. The model is capable of simulating the two cases of ionic conductor/insulator composites : those with and those without strong interfacial interactions. The discussed experimental examples are LiI-A1203, CuBr-A1203 and CuBr-TiO2.
Mixed Ionic and Electronic Conduction in Mn/Mo Doped Gadolinium Titanate
Authors: Sprague J.J. , Tuller H.L.
Published: April 2011

Recent work has shown that Gd 2(Ti1−xMOx)2O7 (GT-Mo) exhibits high levels of mixed conduction under reducing atmospheres, making it suitable as an anode in a solid oxide fuel cell, but not as a cathode since it decomposes at high Po2. We have succeeded in extending the stability limits of GT-Mo to higher Po2 with the addition of Mn. Our earlier studies on Gd2((MoyMn1−y)xTi1−x)2O7 (GMMT) as a function of Po2,T, and composition utilizing impedance spectroscopy and x-ray diffraction are extended to include a wider range of compositions (x ≤ 0.3). In addition, a new sintering method for the GMMT material is introduced that compensates for observed materials loss and abnormal conduction behavior in previous studies. Defect models explaining the dependence of the conductivity on oxygen partial pressure, temperature, and composition are presented as well.
Electrode Kinetics of Porous La0.5Sr0.5Co0.8Ga0.2O3-δ
Authors: Yang Yuemei L. , Jacobson Allan J.
Published: April 2011

LSCGO (La0.5Sr0.5Co0.2Ga0.2O3−δ) was selected and synthesized as a cathode material for gallate-based solid oxide fuel cells (SOFC). In the present paper, the electrode polarization behavior of LSCGO was studied under various pO2and temperature conditions by a two-probe ac impedance method. A symmetric electrochemical cell: pO2, LSCGOILSGMOILSCGO, pO2, where the composition of the electrolyte LSGMO is La0.8Sr0.2Ga0.85Mg0.15O3−δ, was used in the study. Below 600°C, only semicircles due to bulk and grain boundary contributions were observed. In temperature range 700-800°C, however, a depressed and asymmetric semicircle was found in the low frequency regime (1 mHz to 1000 Hz). This low frequency feature in the impedance spectra is attributed to the electrode polarization process and can be fitted to the well-known Gerischer impedance equation. The resulting fitting parameters are used to derive surface exchange and bulk diffusion coefficients.
Conductivity Relaxation Studies On La0.5Sr0.5Co0.8Ga0.2O3−δ
Authors: Wang S. , Abeles B. , Jacobson A.J.
Published: April 2011

The surface exchange coefficient, ki, of the mixed ionic electronic conductor perovskite, La0.5Sr0.5Co0.8Ga0.2O3−δ, was determined in the temperature range 600-900°C by electrical conductivity relaxation on thin plate and long bar samples, using four probe dc conductivity measurements. The normalized conductivity could be fitted by the equation corresponding to surface limited relaxation, (σ(t) − σ1) / (σ2 − σ1) = 1 − exp(−t / Tr), where τ = l1l2 / [(l1 + l2)Γki], σ(t), σ1 and σ2 are the time dependent, initial and final conductivities, Γ is the thermodynamic factor and 21, and 212 are the lateral sides of the bar. Numerical simulation shows that the shape of the relaxation curve for the plate geometry changes only little in going from surface limited to diffusion limited transport, the change is significantly larger for the bar geometry.
Oxygen Transport in the Sr2Fe3−x, CoxOySystem
Authors: Ma B. , Balachandran U. , Mitchell B.J. , Richardson J.W. , Hodges J.P. , Jorgensen J.D.
Published: April 2011

The mixed-conducting Sr-Fe-Co oxide has potential use as a gas separation membrane. Its superior oxygen transport reveals the feasibility of using oxide membranes in large-scale oxygen separation. Sr2Fe3-xCoxOy(with x = 0.0, 0.3, 0.6, and 1.0) samples were made by solid state reaction. To understand the oxygen transport mechanism in this system, conductivity and thermogravimetry experiments were conducted at high temperature in various oxygen partial pressure environments. The oxygen diffusion coefficient was determined from the time relaxation transient behavior of the specimen after switching the surrounding atmosphere. Mobility of the charge carrier was derived from relative conductivity and weight changes. X-ray diffraction experiments were carried out on these samples to determine their crystal structures.
Synthesis of SrRuO3 by Sol-Gel Processing
Authors: Wu Y. , Zamani S. , Cao G. Z.
Published: April 2011

Electronic conductive oxide SrRuO3has been synthesized by sol-gel processing. Various precursors were tested and four different processing methods were developed. Stable SrRuO3sols were obtained using these four processing methods with various precursors. It was found that partial hydrolysis of strontium precursors was required to achieve a cross-condensation of ruthenium and strontium, so as to obtain a single phase SrRuO3perovskite at relatively low temperatures. The stable sols were either poured into petri-dishes to form xerogels or dip-coated on substrates to form thin films. Single phase SrRuO3perovskite was obtained after heat-treatment at 800 °C or higher temperatures. TGA/DTA, XRD and SEM were applied to characterize sol-gel derived SrRuO3ceramic powders and films.
Electrical Conductivity of Zirconia-Mn Oxide Mixture
Authors: Kim J. H. , Choi G. M.
Published: April 2011

Mn2O3 was added to YSZ (8 mol% yttria- doped zirconia) either to form solid solution or two-phase (Mn2O3 and Mn2O3 doped-YSZ) mixed-conducting oxide. The electrical conductivity was measured between 600 and 1000°C in air using 4-probe d.c. method in a wide composition range to determine composition-dependent conductivity. Up to 12 mol% MnO1.5 addition, the conductivity decreases and the activation energy increases. With further increase of MnO1.5 content, the conductivity of composite begins to increase slowly and then increases rapidly after 30 mol% due to the interconnected, conductive Mn2O3 particles. Above 35 Mol% MnO1.5 content, the activation energy is nearly the same as that of Mn2O3. Hysteresis behavior shown in the conductivity of composite also provides the evidence of percolation by MnO1.5.
Grain Boundary Conductivities of 0.58% Y203 Doped CeO2 Thin Films
Authors: Tian Chunyan , Chan Siu-Wai
Published: April 2011

We have prepared Y2O3 doped CeO2 thin films on various substrates using electron beam evaporation. Both polycrystalline and single crystal-like textured films were shown by x-ray diffraction and transmission electron microscopy analyses. AC impedance spectroscopy was used to study the electrical properties of the films. The ionic conductivities of the films are dominated by grain boundaries, and higher as compared to that of a bulk material having the same dopant concentration sintered at 1500°C. The grain boundary conductivities of the films were investigated with regard to grain size, grain boundary impurity segregation, space charge on grain boundaries, and grain boundary misorientations. The contribution of grai boundary misorientation to the resistance of the grain boundary is considered to be negligible with respect to those of the impurity layer and space-charge layers. The grain boundary resistance may originate from the oxygen vacancy depletion in the space-charge layers.
Supercapacitors and Batteries
Authors: Goodenough J.B. , Lee Hee Y. , Manivannan V.
Published: April 2011

Comparisons are made between the material requirements for supercapacitor electrodes and the cathode of a lithium-ion battery. The performances of the battery cathodes Li1+xFe2(SO4)2(PO4) and Li1+5 VMoO6 are compared to those for supercapacitor electrodes operating with 5.3 M H2SO4, Nafion 117, or 2 M KCl aqueous solution at pH 6.7. The use of a KCl aqueous electrolyte at mild pH allows stabilization of amorphous, hydrated electrode materials such as a-MnO2nH2O that are not stable in 5.3 M H2SO4 or with Nafion 117. However, the larger K+ ion appears to reduce by a factor of three the theoretical capacity attainable with H+ ions.
Photocatalysis Using Semiconductor Nanoclusters
Authors: Wilcoxon J.P. , Thurston T.R.
Published: April 2011

We report on experiments using nanosize MoS2 to photo-oxidize organic pollutants in water using visible light as the energy source. We have demonstrated that we can vary the redox potentials and absorbance characteristics of these small semiconductors by adjusting their size, and our studies of the photooxidation of organic molecules have revealed that the rate of oxidation increases with increasing bandgap (i.e. more positive valence band and more negative conduction band potentials). Because these photocatalysis reactions can be performed with the nanoclusters fully dispersed and stable in solution, liquid chromatography can be used to determine both the intermediate reaction products and the state of the nanoclusters during the reaction. We have demonstrated that the MoS2 nanoclusters remain unchanged during the photooxidation process by this technique. We also report on studies of MoS2 nanoclusters deposited on TiO2 powder.
Silica-Copper Molybdate Catalysts Prepared by Sol-Gel and Impregnation Methods: Reactivity and Spectroscopic Studies
Authors: Canevali C. , Morazzoni F. , Scotti R. , Cauzzi D. , Predieri G. , Moggi P.
Published: April 2011

Silica-copper molybdates prepared by sol-gel and impregnation methods were tested as catalysts in the oxidation of propene at 400°C, both in a pulse and in a flow reactor. Their catalytic activity is connected to their structural features, as revealed by electron paramagnetic resonance (EPR) and X-ray diffraction (XRD) characterization.
Manipulation of Catalyst Structure for Molybdenum Trioxide by Chemical Etching
Authors: Zeng H.C.
Published: April 2011

Chemical etching method has been frequently used in defect investigation for crystalline materials in solid-state chemistry / physics and fundamental materials research. Recently, we apply this technique into catalytic materials fabrication. In this work, crystalline catalysts of orthorhombic MoO 3 have been prepared via a vapor phase deposition method and their crystallographic structure has been affirmed by XRD and FTIR investigations. A chemical etching method has been developed for restructuring these thermally processed catalysts. Using a 0.1 M NaOH etchant, {001} and {100} plane areas of the catalysts can be significantly increased while surface steps, ledges, and terraces are created upon this etching. Moreover, alternate crystal plane combinations of either {100} and {010}, or the {001} and {010} are observed on crystal edges and rectangular etch pits in the basal planes {010}. Technological merits and the processing parameters of this new method have also been identified. Following the findings of the current work, it is believed that the chemically carved surface structures may be crucial for certain MoO 3-involving catalytic reactions.
Combinatorial Screening of Anode and Cathode Electrocatalysts for Direct Methanol Fuel Cells
Authors: Reddington Epok , Yu Jong-Sung , Sapienza Anthony , Chan Benny C. , Gurau Bogdan , Viswanathan Rameshkrishnan , Liu Renxuan , Smotkin Eugene S. , Sarangapani S. , Mallouk Thomas E.
Published: April 2011

Progress in several important electrochemical technologies, including batteries, fuel cells, sensors, and electrosynthesis, is currently materials-limited. A common feature of all electrode reactions is the imbalance (i.e., loss or generation) of ions at the electrode surface. We describe in this paper a method by which excess ions in the electrode diffusion layer can be imaged, and used to identify the best electrode materials from a combinatorial array of compositions.

Although in principle this method can be applied to many electrochemical problems, we have focused on finding better electrocatalysts for direct methanol fuel cells (DMFCs). The DMFC performs two half-cell reactions: oxidation of methanol, and reduction of oxygen. Two of the most important problems in DMFCs are the poor performance of the electrocatalysts, and the crossover of methanol from the anode to the cathode side of the cell. An ideal situation would be the simultaneous development of two new catalysts: an anode that oxidizes methanol at low overpotential, and a “methanol-tolerant” cathode that reduces oxygen without oxidizing methanol.

Based on previously developed rules for predicting the activity of ternary alloy catalysts (Ley, et al., J. Electrochem. Soc. 1997, 144, 1543), we began searching quaternary combinations of noble metals for the anode, and ruthenium selenide-type materials for the cathode reaction. The anode and cathode reactions generate and consume protons, respectively, creating a substantial pH gradient at the electrode surface. Changes in local pH are imaged by means of an appropriate fluorescent indicator: Ni-PTP for the anode and Eosin Y for the cathode. DMFC testing confirms the utility of the screening method, in that a Pt/Ru/Os/Ir quaternary catalyst was substantially superior to the best binary and ternary catalysts prepared under similar conditions.
Synthesis and Characterization of a New Family of Microporous Zirconium Silicates
Authors: Bern David S. , Bedard Robert L. , Broach Robert W. , Leon-Escamilla E. Alejandro , Gisselquist Jana L. , Plutht Joe
Published: April 2011

A family of microporous zirconium-silicate framework materials designated as UZSi (UOP zirconium silicates) has been synthesized and structurally characterized. A general hydrothermal synthesis approach yielded a variety of known and novel zirconium-silicate topologies consisting of ZrOa23(oct) and SiO20(tet) units. A novel microporous framework (UZSi-9, Na2ZrSi3O9·x H2O) has been synthesized and structurally characterized. This framework contains A- and A-propeller units, which can also be found in the framework of the compositionally similar UZSi-1 1 (Na2ZrSi3O9·x H2O). Both UZSi-9 and UZSi-II adsorb and desorb water with a Type I microporous isotherm.
Synchrotron Infrared Microspectroscopy for Assessment of Mutagenicity of Metal Implants
Authors: Zhang Miqin , Holman Hoi-Ying N. , Ferrari Mauro , Hunter-Cevera Jennie C.
Published: April 2011

A major concern in the development and implementation of metal implants for the clinical use is the assessment of material-induced mutagenesis. In this study we used synchrotron microspectroscopy in the mid-infrared region (4000-400 cm1 ) to non-invasively assess the in situ human cell responses to metal surfaces. Specifically we examined the subtle genetic aberrations of cells as they responded to a range of metals commonly used in metal prosthetic devices. Relative band intensities and band intensity ratios for functional groups of biomolecules that are inherent to the experimental system were examined. The molecular components of the biomolecules as they were perturbed by the interactions with metals were investigated. These results demonstrate the potential use of synchrotron FTIR microspectroscopy to screen the mutagenicity of metal implants.
Early Osteoblast Attachment, Spreading, and Focal Adhesions on RGD Coated Surfaces
Authors: Moodie G.D. , Ferris D.M. , Hertzog B.A. , Wimmer N. , Morgan H. , Chen C.Y. , Mathiowitz E. , Valentini R.F.
Published: April 2011

Cells recognize and interact with the extracellular matrix (ECM) through heterodimeric receptors known as integrins. The objective of our work is to immobilize integrin-stimulating peptides to bone-contacting implants in order to control cellular activity and response.

We have previously demonstrated that cysteine (C) containing peptides self-assemble onto gold-coated substrates. Investigations have focused on the RGD (Arg-Gly-Asp) peptide sequence since it is found in several bone ECM proteins. Gold was first coated onto glass coverslips by evaporation and the peptide was applied in a 0.22 mM solution. Contact angle and surface plasmon resonance verified RGDC peptide attachment and formation of a monolayer.

Rat calvarial osteoblasts isolated from six-day-old rat pups were used from passages one to three. Cell attachment at 20 minutes is 100% greater on RGDC than on CG (control peptides) or plain gold surfaces. Cells on RGDC also stain positively for vinculin, a protein which is present in focal adhesions (functional structures into which integrins assemble) whereas surfaces without integrin stimulating peptides do not. Scanning electron micrographs show cells to be more spread and have more processes at 20 minutes, 1, 3, and 24 hours on RGDC. Live video images of these surfaces from zero to three hours after plating confirmed earlier and greater cell spreading on RGDC.

Ongoingin vitroexperiments are investigating the long-term response of osteoblasts to RGDC and other immobilized peptides in terms of differentiation, matrix production, and integrin expression.
In Vitro Biocompatibility Testing of Collagen-Calcium Phosphate Composites Using Human Bone Derived Osteoblasts
Authors: Lawson A.C. , Oyama M. , Emerton M.E. , Francis M.J.O. , Simpson A.H.R.W. , Czernuszka J.T.
Published: April 2011

Human bone derived osteoblasts were cultured on collagen-calcium phosphate composites. The ability of the substrates to support cell attachment, proliferation and bone formation was assessed using histochemical staining for alkaline phosphatase activity and immunolocalisation of transforming growth factor- β1and type 1 collagen. The effect of calcium phosphate phase and crystal size was investigated and the calcified samples compared with uncalcified collagen. Osteoblasts adhere to the collagen-calcium phosphate composites and express a mature osteoblast phenotype in vitro. Cell adhesion was greater on unmineralised collagen than on the mineralised composites, however, these cells were less differentiated. The presence of larger crystals seemed to have a detrimental effect on the cells, reducing proliferation and alkaline phosphatase activity. There was no discernible difference between the effect of hydroxyapatite and octacalcium phosphate on the cells.
Prospects for Chemical Control and Engineering of Organically Modified Ceramics
Authors: Rankin Stephen E. , McCormick Alon V.
Published: April 2011

Hydrolytic polycondensation of silicon alkoxides and organically modified alkoxides shows promise as a route to new materials for medicine. Mathematical models of this polymerization accelerate the development of these materials and processes for their production. With a reliable model, one can rapidly explore a wide variety of options for controlling material properties. Here we describe a model for kinetics of sol-gel copolymerization of a simple pair of ethoxysilanes: (CH3)3Si(OC2H5) and (CH3)2Si(OC2H5)2. We then describe how reactor configuration alone can be used to control of polymer structure by choosing how to mix the reactants. An example is shown of maximizing homogeneity at any reactor residence time of interest in the model copolymer system by using the time of addition of the faster-reacting monomer.
Porosity Evolution in Electrosurgical Blade Coatings
Authors: Konesky Gregory
Published: April 2011

During Electrosurgery, Radio Frequency (RF) electrical power is applied to a cutting surface which cauterizes the incision. The desiccation of surrounding tissue results in hemostasis and surgery without bleeding. In the case of localized heavy bleeding, a coagulation process is employed using modulated RF power. However, substantial amounts of desiccated tissue may stick to the blade, undoing the achieved hemostasis, and possibly worsening the situation. To prevent this, various electrosurgical blade coatings have been developed to both permit the flow of RF power through the coating, and prevent desiccated tissue from sticking to it.

PolyTetraFluoroEthylene (PTFE) is a commonly used electro- surgical blade coating that undergoes substantial surface morphology changes during use, eventually leading to failure. Highly conductive Diamond-Like Nanocomposite (DLN) electrosurgical coatings have been developed with the requisite non-stick characteristics and enhanced durability.

After a brief review of electrosurgical fundamentals, the underlying mechanisms of operation of these two coating materials are compared. In the case of PTFE, establishment and evolution of porosity in the coating is essential to the flow of RF power, yet ultimately leads to long term degradation. Alternate conduction mechanisms for DLN coatings are considered.
Production and Characterisation of a Collagen-Calcium Phosphate Composite for Use as a Bone Substitute
Authors: Lawson A.C. , Czernuszka J.T.
Published: April 2011

A composite for use as a bone substitute has been produced by the precipitation of calcium phosphate onto a collagen matrix. A collagen sheet is used as a membrane separating reservoirs of calcium and phosphate ions. The ions diffuse through the membrane and calcium phosphate precipitation occurs on and within the collagen matrix.

Composites containing octacalcium phosphate or hydroxyapatite have been produced by varying the precipitation pH. If the correct balance of phosphate and calcium ion concentrations is achieved, precipitation occurs through the entire cross-section of the collagen sheet, giving a composite microstructure analogous to bone. The composite stiffness increases with increasing mineral content, reaching 2.8 GPa with 39 wt % mineral, when measured dry.
Development of a Multiple-Lumen Nerve Cuff Utilizing Growth Stimulant Patterns for Controlled Regeneration
Authors: Chen Y.S. , Miller C. , Greer M.H. , Quinones M. , Greer R.T.
Published: April 2011

Silicone rubber multiple-lumen (ML) nerve cuffs were used for side-by-side comparisons of the effectiveness of two varieties of nerve growth stimulants (collagen gel and a gel mixture of collagen, fibronectin, and laminin) for regenerating cables across a 15 mm gap in 10 adult Sprague-Dawley rats. The filling pattern of the six tubes of the multiple-lumen portion of the cuff alternated with the collagen gel and the gel mixture of collagen, fibronectin, and laminin. After an 8 week implantation period, 53% (32 of 60) of the 0.5 mm diameter lumens displayed successful cable regeneration for both material fillings. The ML cuff experiments demonstrate the ability to bridge a 15 mm gap in the sciatic nerve of the rat by 8 weeks for relatively small diameter conduits in ML cuffs loaded with two varieties of growth stimulants. A more advanced organization including a smaller acellular region fraction and a higher vascularity is seen in the cables from the mixture-filled lumens compared to those in the cables from the collagen-filled lumens.
Interfacial Fracture Toughness of a Plasma Sprayed Hydroxyapatite Coating Used for Orthopedic Implants
Authors: Sugimura Y. , Spector M.
Published: April 2011

This study introduces a new method for evaluating the adhesion strength of a coating on a substrate. The interfacial fracture toughness, Γi is used to assess the work per unit area required to separate an interface. Γi is measured for the as-received specimens of hydroxyapatite plasma sprayed on Ti-6A1-4V substrate. Calculation of the interfacial fracture toughness requires that the elastic modulus of the coating to be known. The Young's modulus of the plasma sprayed hydroxyapatite is assessed using a bend test. The effect of aqueous environment on the interfacial fracture toughness is also investigated.
Novel Approaches to Microporous Membrane-Based Controlled Release
Authors: Farrell Stephanie , Sirkar Kamalesh K.
Published: April 2011

Membrane-reservoir controlled release systems have been used for the delivery of a wide variety of therapeutic agents. Drug permeation is typically achieved by a solution-diffusion type of mechanism from a loaded reservoir region through a liquid-filled pore, and the rate of release is generally dependent on membrane porosity, tortuosity, and surface area. We have exploited the partition coefficient (between the reservoir liquid and the pore liquid phases) as an additional rate-controlling mechanism, and we have also extended the applications of membrane-reservoir systems to include delivery of microstructures such as liposomes.

If the fluid that fills the pore of the membrane is chosen to be immiscible with the liquid in the reservoir phase, the drug partitions between the two phases at the interface between the reservoir and the pore. The partition coefficient may be exploited to provide rate control by reducing the driving force for diffusion across the fluid-filled membrane pore. The performance of this type of system is evaluated using benzoic acid in an organic reservoir phase, diffusing through water-filled membrane pores. Both hydrophilic and hydrophobic membrane materials were investigated. A hydrophilic membrane material afforded the advantage of a more stable water-filled pore phase.

Controlled delivery of liposomal structures may also be achieved using a porous membranereservoir device. The pores of the membrane must be large enough to permit the passage of the liposomes, which are transported by simple Brownian motion. This concept is demonstrated using a porous polycarbonate membrane system, which was chosen to minimize interaction between the membrane and the liposomes.
Fast X-ray Measurement System for Structural Study in Zr60Al15Ni25 Supercooled Liquid
Authors: Sato S. , Matsubara E. , Waseda Y , Zhang T. , Inoue A.
Published: April 2011

A fast x-ray measurement system adopting the geometry of the Debye-Scherrer camera in combination with an imaging plate has been developed for the structural study of supercooled liquid. We carried out the anomalous x-ray scattering (AXS) measurement as well as the ordinary x-ray diffraction measurement with this system in Zr60Al15Ni25 supercooled liquid at 720K above the glass transition temperature (693K). A whole diffraction profile of very good counting statistics that even fits to the AXS analyses is obtained for a very short time (≅600s). The analyses of scattering data observed in the Zr60Al15Ni25 supercooled liquid for various annealing times in this system provide us information on a change of local atomic structures in the liquid state.
Compositional Dependence of Thermal Stability and Soft Magnetic Properties for Fe-Al-Ga-P-C-B Glassy Alloys
Authors: Mizushima T. , Makino A. , Yoshida S. , Inoue A.
Published: April 2011

Structure, glass forming ability and soft magnetic properties for Fe-Al-Ga-P-C-B glassy alloy system were investigated in the compositional range of Fe from 69 to 78 at%, (Al+Ga) from 2 to 12 and (P+C+B) from 17 to 28. The saturation magnetization (σ5) rises gradually with increase of Fe concentration. The maximum value of 70K for supercooled liquid region (ΔTx=Tx-Tg, Tx: crystallization temperature, Tg: glass transition temperature:) and the maximum thickness of 180 μm for glass formation (tmax,) are found in the composition range around Fe=70at% and (Al+Ga)=7at%. The highest permeability (μc) of 20,000 at 1kHz and the lowest coercive force (Hc) of 2 A/m at the sample thickness of 30 μm can be also obtained at this composition. It was ascertained that the composition regions to yield the maximum glass forming ability and lowest magnetostriction were in agreement with that in which the most excellent soft magnetic properties were yielded. This results allow us to assume that the excellent soft magnetic properties for this glassy alloy system in the limited composition range are presumably due to high structural homogeneity resulting from significantly high glass-forming ability.
Fracture in Bulk Amorphous Alloys
Authors: Horton J. A. , Wright J. L. , Schneibel J. H.
Published: April 2011

The fracture behavior of a Zr-based bulk amorphous alloy, Zr-10 Al-5 Ti-17.9 Cu-14.6Ni (at.%), was examined by transmission electron microscopy (TEM) and x-ray diffraction forany evidence of crystallization preceding crack propagation. No evidence for crystallizationwas found in shear bands in compression specimens or at the fracture surface in tensile specimens.In- situ TEM deformation experiments were performed to more closely examine actualcrack tip regions. During the in-situ deformation experiment, controlled crack growth occurredto the point where the specimen was approximately 20 μm thick at which point uncontrolledcrack growth occurred. No evidence of any crystallization was found at the crack tips or thecrack flanks. Subsequent scanning microscope examination showed that the uncontrolledcrack growth region exhibited ridges and veins that appeared to have resulted from melting. Performing the deformations, both bulk and in-situ TEM, at liquid nitrogen temperatures (LN2) resulted in an increase in the amount of controlled crack growth. The surface roughness of the bulk regions fractured at LN2temperatures corresponded with the roughness of the crack propagation observed during the in-situ TEM experiment, suggesting that the smooth-appearing room temperature fracture surfaces may also be a result of localized melting.
Mechanism for Light Emission During Fracture of a Zr-Ti-Cu-Ni-Be Bulk Metallic Glass: Temperature Measurements in Air and Nitrogen
Authors: Gilbert C. J. , Ager J. W. , Schroeder V. , Ritchie R. O.
Published: April 2011

Light emitted during rupture of Zr41.2Ti13.8Cu12.5 Ni10Be22.5 (at%) bulk metallic glass has been investigated. Charpy V-notch specimens fractured in a pendulum impact apparatus were used to excite light emission. Spectra acquired from rupture in air exhibited a single broad peak and were fit to a blackbody temperature of ∼3175 K. In nitrogen, however, light emission was no longer visible to the eye. In this case, the captured light was at least four orders of magnitude less intense, and spectra were shifted to the red with an effective blackbody temperature of ∼1400 K. Fracture surfaces generated in both air and nitrogen exhibited local melting, providing further evidence of intense heating during fracture. Based on these observations we argue that the intense light emission in air is associated with pyrolysis of fresh material exposed during rupture. Results were compared to preliminary observations of light emission from ribbons of a Zr57Nb5Ni12.6Cu15.4Al10 (at%) glass.
Equilibrium Thermodynamics Near the Glass Transition - The Conceptual Application of the Limiting Fictive Temperature
Authors: Wilde G. , Perepezko J. H.
Published: April 2011

The enthalpy, entropy, specific heat, specific volume and the equilibrium shear viscosity of the deeply undercooled melt of the bulk glass forming alloy Pd40Ni40P20 have been determined as functions of temperature. The concept of limiting fictive temperature was applied to the entire set of measurements in order to allow for a valid comparison of the data based upon the respective equilibrium values. The comparison of the equilibrium properties shows that a proposed hierarchy of stability limits does not apply for this alloy. The results also indicate that the glass temperature as defined by the limiting fictive temperature does not depend on the property under observation.
Synthesis and Properties of Ferromagnetic Bulk Amorphous Alloys
Authors: Inoue A. , Zhang T. , Koshiba H. , Itoi T.
Published: April 2011

Since an amorphous phase in Au-Si system was synthesized for the first time by rapid solidification in 1960[1], a large number of amorphous alloys have been prepared by various rapid solidification techniques. As the main amorphous alloy systems, one can list up the noble metal-, Fe-, Co-, Ni-, Ti-, Zr-, Nb-, Mo-, lanthanide(Ln)-, Al- and Mg-based alloys. Among these alloy systems, Fe-[2], Co-[2] and Al-[3]based amorphous alloys have been used in application fields of magnetic and high specific-strength materials. Thus, Fe- and Co-based amorphous alloys have gained the most important position as engineering amorphous alloys. When special attention is paid to Fe-based amorphous alloys, Fe-P-C alloys were synthesized in 1967[4] as the first Febased amorphous alloy. Subsequently, engineering important (Fe,Co)-Si-B amorphous alloys have been developed in 1974[5][6], followed by the formation of (Fe,Co,Ni)-(Cr,Mo,W)-C in 1978[7], (Fe,Co,Ni)-(Zr,Hf) in 1980[8] and then (Fe,Co,Ni)-(Zr,HfNb)-B amorphous alloys in 1981[9]. The (Fe,Co)-Si-B amorphous alloys have been used in many application fields as soft magnetic materials[2]. However, after 1981, nobody have succeeded in finding a new amorphous alloy in Fe- and Co-based systems by rapid solidification from liquid phase. Besides, all these amorphous alloys have serious disadvantages that high cooling rates above 105 K/s are required for glass formation and the resulting sample thickness is limited to less than about 50 μm[ 10]. Great efforts have been devoted to find Fe- and Co-based amorphous alloys with a high thermal stability of supercooled liquid against crystallization and a high glass-forming ability (GFA). Very recently, we have succeeded in finding new ferromagnetic bulk amorphous alloys with critical sample thicknesses ranging from I to 15 mm in Fe-(AI,Ga)-(P,C,B,Si)[11]-[14], (Fe,Co,Ni)-(Zr,IHf,Nb)- B[15]-[17], (Fe,Co)-(Zr,Hf)-(Nb,Ta)-(Mo,W)-B[18], (Fe,Co)-Ln-B[19] (Ln=lanthanide metal) and (Nd,Pr)-Fe-Al[20]-[22] systems. In this review, we present the formation, thermal stability, mechanical strength and magnetic properties of these new ferromagnetic bulk amorphous alloys.
Oxygen Distribution in Zr-Based Metallic Glasses
Authors: Ping D. H. , Hono K. , Inoue A.
Published: April 2011

This paper reports the atom probe analysis results of the oxygen dissolved in the as-cast amorphous and crystallized Zr65Cu15Al10Pd10 and Zr65Cul17.5Ni10Al17.5 alloys. Impurity oxygen ranging from 0.1 to 1 at.% is dissolved uniformly in the as-quenched Zr65Cu15A110Pd10 and Zr65Cu17.5Ni10Al7.5 amorphous alloys even though the oxygen is not added intentionally. When the Zr65Cu15Al10Pd10 alloy is crystallized, oxygen redistribution occurs; it is rejected from the primary Zr2 (Cu, Pd) crystals and partitioned in the subsequently crystallized phases. Oxygen atoms are enriched in some of the crystalline phases up to approximately 4 at.%, and virtually no oxygen is dissolved in the remaining amorphous phase. In the partially crystallized Zr65Cu17.5Ni10Al7.5 alloy, fine oxygen enriched particles containing ∼ 15 at.%O have been detected in direct contacted with crystalline grains. This work demonstrates that oxygen redistribution occurs during the crystallization reaction, thereby influencing the kinetics of crystallization.
Simulation of Stress Distribution and Mechanical Response of Metallic Glasses
Authors: Kogure Y. , Doyama M.
Published: April 2011

Molecular dynamics simulation of the metallic glasses has been done. The embedded atom method potential function for copper is used to express the atomic interaction. The stress distribution in the glassy state is evaluated from specific volume occupied by single atom and local density in divided cells. The displacements of individual atom under the shear stress are calculated and the correlation between the displacements and the atomic volumes are investigated.
Corrosion Resistant Coatings for High Temperature Applications
Authors: Besmann T. M. , Haynes J. A. , Cooley K. M. , Vaubert V. M. , Lee W. Y.
Published: April 2011

Efforts to increase efficiency of energy conversion devices have required their operation at ever higher temperatures. This will force the substitution of highertemperature structural ceramics for lower temperature materials, largely metals. Yet, many of these ceramics will require protection from high temperature corrosion caused by combustion gases, atmospheric contaminants, or the operating medium. This paper discusses examples of the initial development of such coatings and materials for potential application in combustion, aluminum smelting, and other harsh environments.
Kinetics of Copper Chemical Vapour Deposition from Cu(hfac)VTMS
Authors: Heerdt M. L. H. Ter , Van Der Put P.J. , Schoonman J.
Published: April 2011

A new model, based on irreversible reactions, is used to describe surface kinetics in copper Chemical Vapour Deposition. The mechanism proposed includes a reduction reaction with hydrogen parallel to the well-known disproportionation reaction of Cu(hfac)VTMS. This reduction reaction, not easily modelled by Langmuir-Hinshelwood-type models, appears to be important only at sufficiently high hydrogen partial pressures. The rate constants of the precursor adsorption reaction and the disproportionation reaction are low, probably caused by the dissociation included in these reactions.
Chemical Vapor Deposition (CVD) of Parylene Films using Liquid Source Delivery
Authors: Xu Chongying , Baum Thomas H.
Published: April 2011

Parylene-N films were formed on silicon substrates at a substrate temperature of −20 °C and pressures from 4 - 7 torr via liquid source precursor delivery. [2.2 ] Paracyclophane, the precursor of parylene-N, was dissolved in an organic solvent and delivered into a vaporizer / pyrolysis unit. The solution was vaporized at ∼ 200 °C and its vapor was cracked at ∼ 700 °C to generate the reactive morromeric species. Films were grown by condensation and polymerization, and analyzed by infrared (FTIR), thermogravimetric analysis (TGA) and X-ray diffraction (XRD) analysis. These analyses indicated the formation of parylene-N films without detectable solvent contamination or incorporation into the polymeric films.
Boron-Doped Diamond Films for Electrochemical Applications
Authors: Martin Heidi B. , Smith Bridget A. , Angus John C. , Landau Uziel , Anderson Alfred B.
Published: April 2011

Diamond electrodes possess unique chemical stability, a very wide potential window of water stability, and low background currents. These properties give rise to numerous possible applications, for example, electrosynthesis and electrodestruction reactions at extreme potentials and environmental conditions and as a sensor electrode in aggressive environments. Furthermore, the study of semiconducting diamond electrodes promises to lead to greater understanding of the surface chemistry of diamond and of electronic levels and surface states in doped diamond. In this paper the reactivity of diamond electrodes and their use in a molten salt environment, as a sensor element, and for characterizing diamond are discussed.
Low Stress Under Bump Metallizations for Direct Chip Attach
Authors: Su P. , Korhonen T. M. , Hong S. J. , Korhonen M. A. , Li C. Y.
Published: April 2011

In order to use a flip chip method for bonding the Si chip directly to an organic substrate, compatible under bump metallization (UBM) must be available. Conventional schemes with a copper-based solderable layer are not well compatible with the high-tin solders (such as eutectic Pb-Sn) used with organic substrates. This is due to the rapid reaction between Sn and Cu which depletes the UBM of copper. Ni-based schemes exhibit slower reaction with the solder and have been identified by the semiconductor industry as preferable replacements to Cu-based UBM's. However, Ni-containing metallurgies are often associated with high stresses, which results in poor practical adhesion between the silicon chip and the metallization, leading to interfacial failure during fabrication or service. In this research, several nickel-containing UBM schemes are studied experimentally. Stress measurements are made for each metallization before patterning of UBM pads. An optimal Ni concentration for the UBM is suggested based on the results from this study.
Physical Behavior of Fluorine Atoms in the Fabricated Transparent SiO2 Thin Film at Room Temperature
Authors: lizuka H , Murahara M
Published: April 2011

This paper describe the growth of a transparent SiO2 thin film performed by using Xe2• excimer lamp at room temperature. In this study, NF., and O2 mixture gases was employed as a reaction gas. A silicon substrate was placed in a reaction chamber, which was filled with NF3 and O2 mixture gases. The mixture gases were exposed to the Xe2• excimer lamplight, and SiF4 and NO2 gases were produced by photochemical reaction. Subsequently SiF4 adsorbed onto the Si substrate. SiO2 was formed by oxidation reaction between SiF4 and NO2. These processes occur spontaneously, and SiO2 film is grown. The refractive index of fabrication SiO2 thin film is 1.32. By annealing at 200°C, the refractive index of this filn was increased to 1.44. Further increase in the annealing temperature, resulted in a higher refractive index and lower density of fluorine atoms.
Thickness Effect on Cracking Phenomena and Mechanical Properties of Submicron Glass Thin Films Deposited on a Polymer Substrate
Authors: Yanaka M. , Kato Y. , Tsukahara Y. , Takeda N.
Published: April 2011

The multiple cracking progress in thin SiOx films deposited on polyethylene terephthalate (PET) substrates during tensile tests were investigated. Five kinds of specimens with different SiOx film thicknesses of 43, 67, 90, 120 and 320 nm were prepared. With the appropriate estimation of the residual strain in the film, the crack onset stress was found to be nearly proportional to the minus one-half power of the thickness. After the cracking is sufficiently developed, on the other hand, thinner specimens showed higher crack density than thicker ones. In order to predict the multiple cracking progress, stress distributions in the cracked films were calculated both by the elastic-plastic finite element analysis and modified shear lag analysis. The prediction, under the assumption of the unique stress criterion, explained reasonably well the multiple cracking progress obtained in the experiments.
Nitrogen-Induced Nanocrystallinity of CVD Diamond Films on Ti-6Al-4V Alloys
Authors: Catledge Shane A. , Vohra Yogesh K.
Published: April 2011

Microwave plasma chemical vapor deposition (CVD) was used to grow nanocrystalline diamond films by adding nitrogen to a high density plasma defined by a high operating pressure (125 Torr) and high methane feedgas concentration (15% in a balance of hydrogen). Films grown at these conditions but without nitrogen exhibited well-faceted, high phase purity crystalline diamond while those grown with added nitrogen showed a nanocrystalline structure and were an order of magnitude smoother. The nitrogen-induced nanocrystalline films are believed to be comprised predominantly of diamond nanocrystallites in a matrix of tetrahedral amorphous carbon. The films were characterized by Raman spectroscopy, grazing-angle x-ray diffraction, surface profilometry, nano-indentation, electron microscopy, and pin-on-disc tribometry. In contrast to standard CVD conditions, the high density plasma results in adhered films on Ti-6AI-4V substrates even at substrate temperatures of 850°C. We present plasma optical emission spectroscopy results which are correlated with changes in the Raman spectra and the film microstructure. The hardness of the films (∼90 GPa), their low rms surface roughness (27 nm), and their good adhesion to the substrate makes these films potentially useful for tribological applications.
13C NMR Spectroscopy of Amorphous Hydrogenated Carbon and Amorphous Hydrogenated Boron Carbide
Authors: Braddock-Wilking Janet , Lin Shiu-Han , Feldman Bernard J.
Published: April 2011

We report the 13C NMR spectra of amorphous hydrogenated carbon and boron carbide. The amorphous hydrogenated carbon spectra consist primarily of a sp2 carbon peak at 40 ppm and a sp3 carbon peak at 140 ppm and are in reasonable agreement with recent theoretical calculations of Mauri, Pfrommer, and Louie, but there are some noteable discrepancies. The amorphous hydrogenated boron carbide spectra are very different from that of amorphous hydrogenated carbon, showing two sharp lines at 135 and 170 ppm at low boron concentrations and an intense, broader line at 15 ppm at high boron concentrations. We suggest the two sharp lines at 135 and 170 ppm could be due to carbon atoms in boron-containing aromatic rings, and the broader line at 15 ppm as due to carbon atoms in boron carbide icosahedra. These lines provide evidence of nanocrystalline structure imbedded in an amorphous hydrogenated boron carbide matrix.
Synthesis of Crystalline Structures of CNx, Thin Films Deposited on Sapphire, Quartz and Alumina Substrates
Authors: Alexandrescu R , Cireasa R. , Crunteanu A. , Cojocaru C. S. , Morjan I. , Kumar A. , Vasiliu F.
Published: April 2011

Carbon nitride films raise current interest for their potential applications as ultrahard materials. We report on the formation of crystalline CN structures in films deposited at 248 nm on different substrates (sapphire, quartz, alumina) using the laser-induced CVD method and a gas mixture containing ethylene/nitrous oxide and ammonia as carbon and nitrogen source, respectively. The structural and morphological properties of the films were characterized by different analytical techniques (SEM, TEM, TED and XPS).
Novel Uses of Boron Phosphide Films
Authors: Waddell Ewan
Published: April 2011

Plasma Assisted Chemical Vapour Deposition (PACVD) deposited films of Boron Phosphide (BP) are known to be very effective in protecting the 8-11.5μm band IR substrate materials germaniurn and zinc sulphide from solid and liquid particle erosion encountered in high speed flight. This paper describes the results obtained by protecting the 3-5μm band substrate material silicon and the 8-11.5μm band substrate material zinc selenide. In addition, results are presented which show that germanium can be very effectively protected from the corrosive effects of salt fog.
Static Dissolution of Uo2 in Interstitial Boom Clay Water
Authors: Lemmens K. , Cachoir C. , Iseghem P. Van
Published: April 2011

Static dissolution experiments were performed with unirradiatcd UO2 in Boom Clay water. The objectives were (1) to measure the solubility of uranium species in Boom Clay water, with UO2 as the solid phase, and (2) to assess the impact of dissolved organic matter and carbonate concentration on this solubility. The tests were supported by calculations with geochemical codes to indicate possibly solubility controlling solid phases. The tests were performed in anoxic and reducing conditions, at 20 and 25°C. The following conclusions could be drawn: (1) Within 2 months in anoxic conditions, the uranium concentrations appear to approach saturation. (2) The “near-saturation” concentrations are between 2.4 and 7.8× 10−7 M. (3) The influence of the carbonate concentration and humic acids on the uranium concentration was apparently small, but the interpretation is hampered by pH and Eh variations. (4) The concentrations tend to be higher than the concentrations found in literature for similar Eh and/or pH conditions; this can probably be explained by small differences in experimental conditions. (5) The measured “near steadystate” uranium concentration in the real clay water agrees relatively well with the solubility calculated for uraninite. (6) Addition of sulfide species reduced the rcdox potential, but not the uranium concentrations, except in real Boom Clay water.