bluuebunny/crossref_metadata_2025 huggingface dataset:
Polybenzimidazoles/Phosphoric Acid Solid Polymer Electrolytes: Mechanical and Electrical Properties
Authors: Litt M. , Ameri R. , Wang Y. , Savinell R. , Wainwright J.
Published: April 2011

Poly (2,2'-(m-phenylene) 5,5'-bibenzimidazole), PBI and poly (2,5-benzimidazole), ABPBI, were cast into films and doped with phosphoric acid. Their mechanical properties were studied as a function of inherent viscosity and phosphoric acid content. The commercial PBI with an I. V. of 0.8 to 0.9 had relatively low elongation at break. It was fractionated; the higher the inherent viscosity the higher the modulus and elongation. At low phosphoric acid doping the modulus rose because a crystalline phase developed, and then dropped as more phosphoric acid was added. A second doping method produced films with high crystallinity and higher conductivity (0.02-.03 vs. 0.06-.08 S/cm) but poorer elongation than those made by doping a cast film in phosphoric acid. In order to get higher molecular weight films that could have better mechanical properties, we decided to polymerize 3,4-diaminobenzoic acid to ABPBI, an AB polymer for which I. V.'s of∼16 have been reported. After learning how to purify and polymerize the monomer, I. V.'s of 6–8 were easily obtained. Conductivities of the doped ABPBI films were as high as those of the best PBI films. With their high viscosities, the ABPBI films were much tougher and had better elongation than the doped PBI films.
A Comparative Study of Ionic Association in Poly(Ethylene Oxide)- MCF3SO3 Systems (M=Lithium and Sodium)
Authors: Frech Roger , Rhodes Christopher P. , York Shawna S.
Published: April 2011

A comparative infrared spectroscopic study of the local vibrational potential energy environment of the CF3SO3 (triflate) anion in the poly(ethylene oxide)-lithium triflate and poly(ethylene oxide)-sodium triflate systems is presented. Analysis of the crystalline stoichiometric compounds in the two systems identifies significant differences in the ionic association. Comparison of the relative percentages of the anionic species in the PEO-NaTf system at various concentrations suggests that crystalline compound formation may proceed through intermediate structures. A symmetry-based vibrational analysis is applied to the crystalline compounds.
Conductivity and Morphology of Hybrid Electrolytes Based on Blends of Pvdf With PEO-co-PPO Copolymers
Authors: Wang H.P. , Kejha J. B. , Yarovoy Y.K. , Wunder S.L.
Published: April 2011

Hybrid film electrolytes with high room temperature conductivity have been prepared by casting solutions of PVDF-HFP copolymers with PEO-PPO block copolymers and PEO oligomers followed by activation of the polymer blend films in electrolyte solutions. The morphology and conductivity of these solid electrolytes were studied as a function of concentration, molecular weight and sequence order (in the case of PPO-co-PEO-co-PPO or PEO-co-PPO-co-PEO) of the PEO and PEO-PPO copolymers, and also of the casting solvent and evaporation rate of the casting solvent. Structural studies of PVDF-HFP/PEO and PVDF- HFP/PPO-co-PEO blend films (SEM, DSC) before activation with lithium salt electrolyte may indicate the occurrence of spinodal decomposition in the films during slow evaporation of the casting solvent. As a result of spinodal decomposition, an interpenetrating bi-continuous phase may evolve with microphase separation between PVDF-HFP and PPO-PEO phases, in which the PVDF phase provides mechanical support and the PPO-PEO phase pfovides a conductive path.
Study of Polyethers/Lii Systems by Addition of Alumina Ceramic Powders Prepared by Two Synthesis Methods
Authors: Ribeiro R. A. , Silva G. G. , Mohallem N. D. S.
Published: April 2011

Composites of alumina ceramic powders prepared by co-precipitation and sol-gel methods with Lithium Iodide based polymer electrolytes are described. The polyether matrices Poly(ethylene oxide) (PEO) and block copolymer Poly(propylene glycol-ethylene glycolpropylene glycol) (Triblock) with Lil in a ratio [O]:[Li] = 20:1 are used with up to 17 wt% of α-A1203 (medium grain size). Differential Scanning Calorimetry (DSC) studies show that Tg values for PEO based composites are higher whereas those for Triblock based composites are lower than the Tg value of the polymer/salt system.

Conductivity measurements as a function of temperature show that there is no significant change in conductivity above the melting points for the electrolytes after α-A1203 powder addition (σ approximately 10−3 S.cm−l at 100°C), whereas better mechanical properties are observed for the ceramic reinforced samples. An increase in conductivity is obtained for the Triblock based composites near room temperature as a consequence of the lower melting point of these materials (26°C) in comparison to the PEO based composites (54°C).
Intercalation of Sodium-Potassium Alloys Into Graphite
Authors: Antoine L. , Gachon J.C. , Guerard D.
Published: April 2011

The intercalation, at room temperature, of the sodium-potassium eutectic into graphite is performed, in a glove box under purified argon. It leads to a high alkali metal content powder. The annealing under vacuum, at 200°C for two days leads to a pure first stage compound whose formula is NaK2C12 with a color and a structure close to that of KC8. This phase is unstable and decomposes slowly in a mixture of KC8 and free alloy. However, this free alloy, which is liquid at room temperature, remains as inclusions between the graphene layers and the compound remains as a powder which can be useful for some applications when one needs large quantities of an alkali metal “solid” at room temperature, e.g. for gas purification (it reacts with oxygen and with moisture), for rapid and intense heat provider (it burns in air and the carbon is also participating to the heating), for ionic polymerization catalyst…
Mixed Ionic-Electronic Conduction of Na-Beta-Alumina Under the Conditions of a Potentiometric CO2Sensor
Authors: Näfe H. , Gollhofer S. , Aldinger F.
Published: April 2011

It is shown that, on employing a practically relevant type of a potentiometric solid state CO2sensor comprising Na-beta-alumina as solid electrolyte and Na2CO3as gas sensitive electrode, the voltage response may be remarkably affected by electronic transference. This is in contradiction to what is commonly stated in the literature about the measuring properties of such a type of a sensor. On the other hand, the observation of a non-negligible amount of electronic conduction confirms previous findings on the behaviour of Na-beta-alumina under the conditions of a CO2sensor.
New Mixed Conductors Based on Doped Layered Perovskites
Authors: Navas Carlos , Tuller Harry L. , Loye Hans-Conrad zur
Published: April 2011

A series of doped Ruddlesden-Popper phases, of general formula Sr3Ti2−xMxO7−δ (M=Al, Ga, Co), were synthesized and their electrical conductivity characterized as a function of temperature and oxygen partial pressure. For fixed-valent dopants, p-type conductivity predominates at p(O2)>10−5 atm, followed by a p(O2)-independent electrolytic regime, and n-type electronic conductivity at very low p(O2). The electrolytic regime exhibits activation energies in the range 1.7-1.8 eV. Doping with transition metals such as Co results in a very significant increase in total conductivity with a p-type conductivity at high p(O2). Furthermore, an apparent ionic regime at intermediate p(O2) is observed, characterized by high conductivity (>10−2 S/cm at 700 °C) and low activation energy (0.7 eV). This interpretation is consistent with iodometric measurements as interpreted by a defect chemical model. Other measurements are in progress to confirm this conclusion.
Investigation of Tin-Graphite Composite Anodes for Rechargeable Lithium Ion Battery
Authors: Dayalan E.
Published: April 2011

Two tin-graphite composite electrodes (27.8 % and 44.4 % tin) were evaluated for their use as high capacity anodes in rechargeable lithium ion cells. The initial charge capacities of these two electrodes were 520 mAh/g and 590 mAh/g, respectively. Cyclic voltammetry and charge-discharge cycling studies point to the alloy formation reaction between tin and lithium being the main contributing factor to the increased capacity. The capacity of these electrodes decreases with cycling but maintains considerably higher capacity than graphite electrode with same number of cycles. The development of optimized tin-graphite composite electrodes with much higher capacity than graphite electrodes looks promising.
Xps and Voltammetry Studies of Redox Behavior of Lacrl1−NixO3Electrodes
Authors: Vovk Greg , Chen Xiaohua , Mims Charles A.
Published: April 2011

Anin-situXPS and voltammetry investigation of the redox properties of LaCrj1-xNixO3(x = 0.4, 1) was carried out by incorporating the materials as one electrode in an electrochemical cell (LaCr1xNixO3|YSZ|Pd:PdO), which was directly mounted on a heated sample stage in an ultra high vacuum (UHV) chamber. Under a 0.7V cathodic bias, the perovskites reduce from formal oxidation state of Ni3+to Ni2+. This reduction is accompanied by wholesale shifts of the Cr and O core level binding energies, in keeping with the delocalized electronic states in the material. The adsorption properties of the surfaces are affected by the redox state of the surfaces; increased CO2adsorption is observed on the reduced (and therefore more basic) surface.
Mixed Conducting and Cathodic Properties of Zirconia-Nio Mixture
Authors: Park Y. M. , Choi G. M.
Published: April 2011

Absract

Stabilized zirconia-NiO mixture was chosen as a representative of ionic-electronic composite and the effect of mixture composition on the mixed conducting properties were studied. The measurements of oxygen partial-pressure dependence of conductivity and Hebb-Wagner polarization enabled to determine the electronic contribution to the total conduction in a wide composition range. In ion conduction region, electronic conductivity increased continuously with NiO content. The overpotentials of screen-printed YSZ-NiO electrode on YSZ electrolyte were measured and found to decrease with increasing NiO content and thus with the estimated electronic conductivity of porous electrode.
Iron Oxides as Anodic Materials in Li Rechargeable Batteries
Authors: Duncan M. J. , Nazar L. F.
Published: April 2011

The open framework material, CaFe204 and the isostructural solid solution phases, LiyCa1−(x+y)/2SnxFe2−xO4, where 0<y<x and O<x<0.6 have been evaluated as promising anodic materials in Li-ion batteries. These materials can be discharged to low potential, the end member CaFe2O4 attaining a discharge capacity of 800 mAh/g at a cutoff voltage of 50 mV. The capacity is enhanced on substitution of Fe3+, for Sn4+ in the framework (920 mAh/g for the composition, Li0.6Ca0.4Sn0.6Fe1.404). On introducing Sn into the structure the reversible capacity is also substantially increased compared with the parent material. Although there is a large irreversible component to the redox process during first discharge-charge, the materials can sustain a stable reversible capacity of >600 mAh/g within the voltage window of 3.0-0.005 V. The profile of the electronic density plots suggest there is no phase separation to Li/Sn alloy phases on reduction, but rather a lithium-rich, oxygen deficient Sn/Fe/oxide matrix is formed.
Titanium Dioxide and Apatite Coated Fibrous Ceramics Photocatalyst
Authors: Nonami Torn , Kato Shinji , Taoda Hiroshi
Published: April 2011

A TiO2 and apatite coated fibrous ceramics photocatalyst filter has been developed. This filter has a function to absorb and decompose bacteria and various other materials. TiO2 was coated on the surface of the fibrous ceramics by a sol-gel method, then the filter was soaked in a pseudo-body solution containing excessive phosphate ion for 1 day at 37°C. In this research, it is recognized that this filter has absorbed and decomposed colon bacillus, methylene blue and acetaldehyde effectively.
Growth Characteristics of Au/SiO2 Nanocomposites
Authors: Jaeger M. D. , Soltis R. E. , Thomas J. A. , Hangas J. , Chen A. E. , Logothetis E. M.
Published: April 2011

This paper describes experimental studies of the growth morphology of Au/SiO2 nanocomposites consisting of nanometer-sized metal particles imbedded in a metal oxide, formed by the sequential deposition of metal and metal-oxide layers by RF sputtering. The materials work is aimed at the development of novel resistive-type exhaust gas constituent sensors. Using digitized images from a transmission electron microscope and an automated particle counting routine, we have measured the particle size distributions for films with varying layer thicknesses and deposition conditions. We find strong dependence of the particle size and overall composite structure on the Au and SiO2 layer thicknesses, in agreement with previous work.[1] We also identified four microstructure classes which can occur.
Structural Defects In Cerium Oxide Catalytic Support Studied by Pulsed Neutron Diffraction
Authors: Mamontov E. , Egami T. , Brezny R.
Published: April 2011

We studied the structure of coarse and nano-scale powders of CeO2 using pulsed neutron scattering. The diffraction data were analyzed using Rietveld refinement, and were also Fourier-transformed to obtain the pair-distribution function (PDF). The Frenkel type oxygen defects consisting of vacancies in the oxygen sublattice and oxygen ions in the octahedral interstitial sites of the fluorite structure were observed in cerium oxide for the first time. The interstitial oxygen ions were found to recombine with vacancies when the sample underwent thermal treatment at 1073 K. We suggest that these defects are directly involved in the oxygen storage mechanism of ceria used in automotive catalytic converters.
Palladium Supported on Alumina Catalysts Prepared by MOCVD and Impregnation Methods
Authors: Garcia G. , Vargas J.R. , Valenzuela M.A. , Rebollar M. , Acosta D.
Published: April 2011

Conventional MOCVD method has been explored to prepare Pd supported catalysts. Pd and PdO phases were found on the surface of the support. Small Pd particles about 1 to 3 nm and dispersions up to 19%were obtained by MOCVD. TPR results indicated that several surface Pd compounds are reduced. At temperatures below 25°C, PdO, the main compound, is completely converted to metallic Pd which forms hydrides. At higher temperatures, between 500 to 800°C, the reduction peaks could be attributed to Pd-support interactions and a strong support dehydroxylation. All catalysts were inactive in benzene hydrogenation and a significant conversion was only detected a temperatures above 100 °C. This was explained by the reduced accessibility of Pd sites imposed by the carbon contamination and by the Pd-Al2O3interactions.
High-Surface - Area Framework Zirconium Phosphates as Catalysts of Hexane Isomerization and Dehydroaromatization: Synthesis and Properties
Authors: Sadykov Vladislav A. , Pavlova S. N. , Zabolotnaya G. V. , Kochubey D. I. , Maximovskaya R. I. , Zaikovskii V. I. , Kriventsov V. V. , Tsybulya S. V. , Burgina E. B. , Paukshtis E. A. , Volodin A. M. , Fenelonov V. B. , Kuznetsova N. N. , Lunin V. V. , Chaikina M. V. , Agrawal Dinesh , Roy Rustum
Published: April 2011

Mechanochemical activation of solid inorganic precursors and sol-gel routes followed by hydrothermal treatment in the presence of surfactants were used to synthesize highly dispersed NZP-type complex zirconium phosphates. Genesis of samples real structure and its impact on the surface properties and catalytic performance in the reactions of hexane isomerization and dehydroaromatization have been studied.
Osteoblast Attachment on Biomaterials as a Function of Surface Charge
Authors: Marcolongo M. , Dinardo N. J. , Hickok N. , Tuan R. , Pourezzaei K. , Beard R. , Brennan D. , Heipp P. , Phan T.
Published: April 2011

Bioactive materials such as calcium phosphate ceramics and bioactive glasses enhance bone tissue formation and then bond to bone tissue. In our work, we question what particular surface feature or features of bioactive materials are responsible for the bone tissue response. In this study we have uncoupled surface charge from surface chemistry, energy, and topography and have examined osteoblast adhesion to titanium surfaces of varying surface charge. We have shown that a negative surface charge promotes osteoblast adhesion by approximately 60% over a neutral surface and that conversely, a positive surface charge inhibits osteoblast adhesion by about 20%. Continued examination of surface characteristics that control cellular responses are warranted with the eventual goal of applying those desirable surface characteristics to any structural biomaterial for bone implant or tissue engineering applications.
Functionalized Copolymers and Their Composites with Polylactide And Hydroxyapatite
Authors: Jin S. , Gonsalves K. E.
Published: April 2011

Synthetic copolymers poly(E-caprolactone-co-vinylphosphonic acid) (P(MDOVPA) and poly(E-caprolactone-co-dimethylvinylphosphoester) (P(MDOVPE)) were used to prepare composites with polylactide (PLac) and hydroxyapatite (HAp). The P(MDOVPA) was used as filler in PLac films, as it has pendant functional groups P(O)(OH)2, providing nucleation sites for the deposition of HAp in simulated body fluid. HAp growth on PLac-P(MDOVPA) film was observed by XRD. The incorporation of hydrophilic P(MDOVPE) into PLac increased the hydrophilicity of the blend. Synthetic HAp was also used to make multi-layered, alternating organic-inorganic composites with porous PLac-P(MDOVPE) blends.
Towards a Tissue Engineered Bladder Wall Patch: The Scaffold
Authors: Hilborn J. G. , Laurent A. , Mathieu H.-J. , Bisson I. , Frey P.
Published: April 2011

A new method for surface functionalization of inherently reactive polymers such as polyesters has been developed. It is based on the direct nucleophilic attack on the ester group in the polyethyleneterephtalate backbone by the acid moiety of polyacrylic acid (PAA) catalyzed by titaniumisopropoxide. The PAA grafted surfaces were characterized by X-ray photoelectron spectroscopy to demonstrated the presence of a thin grafted layer rendering the substrates hydrophilic. Subsequent acid group activation using N-ethyl-N'-(3-dimethylaminopropyl) carbodiimide hydrochloride allowed for in-situ collagen immobilization rendering the surfaces cell adhesive. Human smooth muscle and urothelial cells successfully seeded these surfaces, reaching confluence after 7 days.
Sintering Behavior and Mechanical Properties of Hydroxyapatite-Zirconia Composites
Authors: Silva Viviane V. , Domingues Rosana Z.
Published: April 2011

The elaboration of composite materials has been considered one possibility to improve mechanical properties of bioactive phases based on hydroxyapatite used for medical implants. Ceramic and polymeric materials have been tested as the other phase. The aim of this study is to evaluate the sintering behavior and the mechanical properties (compressive strength, modulus of resiliency and microhardness) of hydroxyapatite-zirconia (ZH) composites prepared by precipitation method. Powders of hydroxyapatite-zirconia (ZH) composites, with 40 vol % of zirconia content, and pure hydroxyapatite (HA) as well as pure ZrO2- CaO (ZO) were sintered at 900, 1100 and 1200°C in air at a pressure of 700 MPa for 3 hours, using uniaxial pressing. The products obtained at 1100 and 12000 C are dense, with density values over 91% of the theoretical ones. Experimental results indicated that the sinterization process can be described as admitting a bi-modal structure for ZH composites consisting of a sphere of ZO embedded into a matrix of HA. In this structure the matrix is consider to sinter faster. Intermediate values (between those of pure phases of HA and ZO) of compressive strength and modulus of resiliency were found for ZH composites, suggesting that these composites have potential applications as implant materials.
Peptide Coated Titanium Rods Show Increased Bone Formation in a Rat Femur Model
Authors: Ferris D.M. , Moodie G.D. , Dimond P.M. , Ehrlich M.G. , Valentini R.F.
Published: April 2011

In vitro, groups have demonstrated that peptide modified surfaces influence short and long term cell responses like attachment, shape and function via cell receptors known as integrins. These receptors translate information to the nucleus via sets of complex signaling pathways. Little is known about the ability of these surfaces to influence the inherently complex in vivo environment, however. The present study was designed to evaluate the quality and quantity of new bone formed in response to gold coated titanium rods modified with the peptide sequence Arg-Gly-Asp-Cys (RGDC). Quantitative histomorphometric analysis of histologic sections perpendicular to the implant long axis showed a thicker (P < 0.01) shell of new bone formed in response to peptide modified implants (26.2 microns ± 1.9 vs. 20.5 microns ± 2.9) as early as 2 weeks. Mechanical pull-out testing conducted at 4 weeks revealed the average pull-out force of peptide modified rods was 38% greater than gold control rods. The significant difference in the thickness of new bone formed around the implant was maintained at 4 weeks (32.7 microns ± 4.6 vs. 22.6 microns ± 4.0). These results demonstrate the feasibility of developing peptide coated biomaterials designed to elicit a host response at the cell receptor level.
Development of Vascular Substitutes
Authors: Nerem Robert M.
Published: April 2011

A long-term objective of many involved in blood vessel research is the development of a small diameter vascular substitute which can be used in coronary bypass graft surgery. If these efforts are to be successful, there are critical functional characteristics which must be achieved. In recent years many of those interested have turned their attention to tissue engineering, and over the past decade some progress has been reported. The results of some of these efforts are briefly reviewed here. Included is the strategy of the Georgia Tech team and recent results which demonstrate that in vitro mechanical stimulation of smooth muscle cell-seeded tubular collagen constructs induces a remodeling with the result that the associated material properties are considerably enhanced.
The Biology of Corrosion and Wear Debris from Orthopedic Implants
Authors: Jacobs Joshua J. , Glant Tibor T.
Published: April 2011

Bone loss (osteolysis) following total joint arthroplasty has been a subject of increasing concern in the orthopedic research community. Depending on the distribution and severity, bone loss can lead to aseptic loosening, periprosthetic fracture and formidable reconstructive problems at revision surgery. Bone loss is believed to be primarily a response to particulate wear and corrosion debris derived from the prosthetic materials. Phagocytosed particulates activate macrophages and osteoblasts (and perhaps fibroblasts) to produce factors which stimulate osteoclastic bone resorption and reduce osteoblastic bone formation. To investigate the responses of these cells to particulate corrosion and wear debris, in vitro studies have been performed by measuring factors at both the molecular and cellular levels that may trigger, maintain and/or regulate particulate biomaterial-induced pathologic bone resorption. The biological effect of a particulate species depends upon their size, concentration (number) and composition, in the order listed. Particulate wear debris of phagocytosable size (less that 10 micrometers) activate macrophages, fibroblasts and osteoblasts more effectively that those of larger sizes. As a response to phagocytosed particulates, i) macrophages produce a number of cytokines (interleukins such as II-1, II-6, TNF-alpha) and prostaglandins, which may act either in an autocrine fashion or further stimulate cells present in the periprosthetic tissue; ii) fibroblasts secrete active forms of metalloproteinases; and iii) osteoblasts have diminished collagen type I synthesis. Taken together, particulate corrosion and wear debris provoke a series of biological responses which generate an active microenvironment around prosthetic components. Strategies to modify the host response to particulate degradation products have emerged from these in vitro studies. These strategies may provide pharmacotherapeutic solutions to this important clinical problem.
Phase Inversion Dynamics of PLGA Solutions Related to Drug Delivery
Authors: Mchugh A.J. , Graham P.D. , Brodbeck K.J.
Published: April 2011

Dark ground optical microscopy, electron microscopy, and protein release rate studies have been used to quantify the effects of formulation changes on the phase inversion dynamics and in vitro drug release properties of an injectable PLGA-based drug delivery system. Gel growth rates and water influx rates are determined from plots of the square of the respective front with time. Results show that additives that increase the solution gelation rate and produce finger-like void morphologies result in higher initial release rates. Conversely, additives that slow the rate of gelation dramatically reduce the initial drug release rate and lead to a more dense sponge-like morphology.
Novel pH-Sensitive Hydrogels with Peg-Tethered Chains for Oral Delivery of Calcitonin
Authors: Torres-Lugo M. , Peppas N.A.
Published: April 2011

Major challenges in oral delivery of peptides include the need to overcome gastric and intestinal degradation. pH -Sensitive hydrogels are suitable candidates for oral drug delivery of peptides due to their ability to respond to their environment. We have developed a new type of hydrogel composed of poly(methacrylic acid) grafted with poly(ethylene glycol) which can be used as drug delivery carriers for salmon calcitonin. These hydrogels were prepared by free radical solution polymerization and were molecularly designed to contain poly(ethylene glycol) tethered chains promoting mucosal adhesion and providing calcitonin protection, as well as methacrylic acid moieties, which act as calcium binders leading to epithelial cell junction opening. Solutions of approximately 0.1 mg/ml of salmon calcitonin were used to load the protein into the gels at pH = 7 and constant ionic strength of 0.1 M.In vitrorelease studies were performed at pH=7 and 37 °C, while keeping an ionic strength of 0.1 M. Calcitonin release was achieved. The release behavior was explained in terms of diffusional theories.
Small-Angle Neutron Scattering of Bilayer Vesicles Made with Synthetic Phospholipids
Authors: Trevino S. F. , lvkov Robert , Matyas Gary R. , Lebeda Frank J.
Published: April 2011

We have used Small-Angle Neutron Scattering to investigate the structure of bilayer lipid membranes in aqueous solution. The lipids consist of equimolar concentrations of two molecules DMPG and DMPC (see text). The structures consist of solvent filled cores surrounded by shells composed of the lipid bilayers. In particular the radii of the core and shell thickness are measured as a function of lipid concentration and temperature. Other features which reveal themselves are vesicle forming ability of the lipids, additional larger structures and inter-vesicle interactions at large vesicle concentrations. The study is motivated by the possible use of these systems as delivery vehicles for various beneficial therapeutic compounds.
Production of Zirconium-Based Glassy Alloy Wires by Melt Extraction Method and Their Mechanical Properties
Authors: Katsuya A. , Inoue A.
Published: April 2011

Glassy Zr65Al10Ni10Cu15 wires were produced in the diameter range up to about 310 µm by a melt extraction method using a copper wheel in an argon atomospher The grass transition temperature (Tg) and crystallization temperature (Tx) are 652K and 757K, respectively, and the temperature interval of the supercooled liquid, ΔTx(=Tx-Tg) is 105K, in agreement with those for the corresponding melt-spun ribbon. The wires have a nearly real circular cross section and good mechanical properties.
On the Effect of Al on the Formation of Amorphous Mg-Al-Cu-Y Alloys
Authors: Ohnuma M. , Linderoth S. , Pryds N. , Eldrup M. , Pedersen A. S.
Published: April 2011

The bulk amorphous alloy (Mg1-xAlx)60Cu30Y10 has been studied, in particular the influence of Al concentration on the glass forming ability and on the various transition temperatures. The amorphous single phase has been obtained for x up to 0.07 by casting into a wedge-shaped copper mold. The amorphous alloys were investigated by differential scannning calorimetry (DSC). All the specimens with x = 0 - 0.07 show a clear glass transition. The crystallization temperature decreases with increasing Al concentration, while the temperatures of the glass transition, melting and solidification change only slightly. The DSC measurements show that for Al contents below 0.05 the first exothermic peak which corresponds to crystallization, consists of two overlapping peaks. To clarify the origin of the splitting of the first exothermic peak, the crystallization process of Mg60Cu30Y10 alloy has also been studied by x-ray diffraction.
Continuous Amorphization of Zr-Based Alloys by Controlled Mechanical Intermixing
Authors: Wilde G. , Sieber H. , Perepezko J. H.
Published: April 2011

Binary Zr-(Cu, Ni, Al) alloys were mechanically intermixed by cold-rolling stacks of elemental foils. The results indicate that solid-state amorphization is initiated if the grain size of the Zr-Cu and Zr-Ni alloys falls below a critical value. Amorphization was not observed for the Zr-Al alloy. These results are in accordance to the predictions of a model for solid-state amorphization. The comparison with the results on a quaternary Zr-Cu-Ni-Al alloy indicate the influence of multicomponent alloying on the glass-forming ability of Zr-rich alloys by mechanical working.
Characterization of Gas Atomized Cu48Ti34Zr10Ni8 Amorphous Metal Powder
Authors: Foley J. C. , Sordelet D. J. , Lograsso T. A.
Published: April 2011

The advent of multi-component metallic alloys, which exhibit relatively good glass forming ability, has opened opportunities for processing metallic glasses into thick cross section components. The relatively good glass forming ability is important because conventional processing techniques (e.g., casting, extrusion and rolling) may be used to fabricate useful shapes while retaining the excellent engineering properties of an amorphous structure. In particular, the favorable processing characteristics of bulk amorphous alloys are the low cooling rates which can be exercised to yield an amorphous structure and the operating temperature range between the glass transition temperature (Tg) and the crystallization temperature (Tx). Current work is focused on developing a processing strategy that will allow us to fabricate even larger cross section amorphous alloys than are currently achievable by casting methods. The technique involves producing high pressure gas atomized (HPGA) Cu48Ti34Zr10Ni8 powders and consolidating them at temperatures above Tg, but below Tx. Thermal analysis of atomized powders by DSC provides details of the influence of powder particle size, which is related to cooling rate during atomization. The results of experiments characterizing the thermal and kinetic behavior of Cu48Ti34Zr10Ni8 powders indicate that short processing times are required to retain the amorphous structure during consolidation in the temperature regime between Tg and Tx.
Formation of Glassy Spinodals in Bulk Metallic Glasses
Authors: Guo W. H. , Leung C. C. , Kui H. W.
Published: April 2011

When a eutectic alloy melt is undercooled well below its liquidus T1, liquid state phase separation occurs. The liquid morphologies can be frozen by subsequent crystallization. It was found that for Pd82Si18 when rapid quenching is also employed, ore of the phase-separated liquids after solidification is amorphous. The undercooled specimen is in bulk form with a diameter of ∼ 5 mm.
Effect of Small Amounts of B and C Additions on Glass Formation and Mechanical Properties of a Zr-Base Alloy
Authors: Liu C. T. , Pike L. M. , Chen N. G.
Published: April 2011

The effect of B and C additions up to 0.4 at. % on glass formation and mechanical properties of a Zr-base alloy Vitreloy 105 was studied using various techniques. All alloys were prepared by arc melting and drop casting. Boron additions increase the glass forming ability by lowering Tm and increasing Tg. Carbon additions only lower Tm but not affect Tg. B and C additions occupy free space and do not harden the glass phase.
Exelfs of Metallic Glasses
Authors: Ito Y. , Alamgir F. M. , Jain H. , Williams D. B. , Schwarz R. B.
Published: April 2011

The feasibility of using extended energy-loss fine structure (EXELFS) obtained from ∼1 nm regions of metallic glasses to study their short-range order has been examined. Ionization edges of the metallic glasses in the electron energy-loss spectrum (EELS) have been obtained from PdNiP bulk metallic glass and Ni2P polycrystalline powder in a transmission electron microscope. The complexity of EXELFS analysis of L- and M-ionization edges of heavy elements (Z>22, i.e. Ni and Pd) is addressed by theoretical caluculations using an ab initio computer code, and its results are compared with the experimental data.
Microforming of Mems Parts with Amorphous Alloys
Authors: Saotome Yasunori , Zhang Tao , Inoue Akihisa
Published: April 2011

Microformability of new amorphous alloys in the supercooled liquid state and microforming techniques for the materials are shown. In the supercooled liquid state, the materials reveal perfect Newtonian viscous flow characteristics and furthermore exhibit an excellent property of microformability on a submicron scale. As for microforming techniques, microforging and micro extrusion of amorphous alloys are introduced in addition to the fabrication method of micro dies of photochemically machinable glass. As a result, amorphous alloys are expected as one of the most useful materials to fabricate micromachines.
Thermal Stability of Bulk Metallic Glasses. Influence on Mechanical Properties
Authors: Pelletier J. M. , Jacquemard Y. , Perez J. , Bathie R. Perrier de la
Published: April 2011

Two Zr-base bulk metallic glasses were investigated in the present work. DSC experiments were performed at different heating rates (dT/dt). Evolution of the characteristic temperatures, glass transition and onset of crystallisation, were determined as a function of dT/dt. Evolution of shear elastic modulus and internal friction are measured as a function of temperature and resulting microstructural evolution; these evolutions are related to variation of the atomic mobility.
Residual Stresses in Bulk Metallic Glasses due to Differential Cooling or Thermal Tempering
Authors: Ustundag E. , Clausen B. , Hanan J. C. , Bourke M. A. M. , Winholtz A. , Pekers A.
Published: April 2011

Due to their very low thermal conductivities and large thermal expansion values, bulk metallic glasses (BMGs) undergo differential cooling during processing. Large thermal gradients are generated across a specimen leading to residual stress buildup. A thin surface layer contains compressive stresses balanced by tension in the middle. Such stresses can not only influence the mechanical behavior of BMGs, but they can also lead to problems during manufacturing of large or intricate components. Analytical and finite element modeling was used to predict the values and distribution of such stresses as a function of processing conditions. Neutron diffraction measurements were then performed on model specimens which included crystalline phases as “strain gages”. It was shown that significant stresses, on the order of several hundred MPa, can be generated in BMGs. Modeling and diffraction results are presented and their implications discussed.
Thermodynamics and Glass Forming Ability from the Liquid State
Authors: Desre P. J.
Published: April 2011

This study is mainly devoted to the establisment of relations between easy glass forming ability of some multicomponent liquid alloys and strong heteroatomic bonding in connection with nucleation. The chemical short range order in typical liquid bulk glass formers as Zr-Ni-AI is evaluated from a statistical model and presented as Cowley's order parameters versus concentration. The effect of the nature and of the number of components on the chemical contribution to the liquid-crystal interface energy and on the Gibbs energy of crystallisation is analysed and discussed. A specific mechanism of nucleation based on a distribution of concentration fluctuations in the undercooled liquid is proposed. This homophase fluctuation mechanism, which is thermodynamically and kinetically justified, leads to a lower preexponential factor in the expression of the frequency of nucleation as a function of the number of components. Furthermore, this frequency of nucleation can be strongly lowered by an augmentation of the energy barrier of nucleation depending on the nature and the number of components in the liquid phase.
The Kinetic Investigation of the Deposition of Alumina and Aluminosilicates from Mixtures of SiCl4, AlCl3, CO2, and H2
Authors: Nitodas Stephanos F. , Sotirchos Stratis V.
Published: April 2011

The codeposition of alumina, silica, and aluminosilicates from mixtures of silicon tetrachloride, aluminum trichloride, carbon dioxide, and hydrogen is investigated in this study. Chemical vapor deposition experiments are carried out in a hot-wall reactor of tubular geometry coupled with an electronic microbalance. In order to elucidate some aspects of the codeposition process, the deposition of pure alumina and pure silica from mixtures of silicon tetrachloride and aluminum trichloride, respectively, with CO2 and H2, is also investigated. Among the most interesting findings of our study is that the presence of AIC13 has a catalytic effect on the incorporation of silica in the deposit, leading to codeposition rates that are higher than the deposition rates that are obtained when only one of the two chlorides (SiCI4 or A1C13) is present in the feed
Silicon Nitride Coatings Formed using the Selective Area Laser Deposition (SALD) Technique
Authors: Sun Lianchao , Shaw Leon L. , Marcus Harris L.
Published: April 2011

In this paper, the Selective Area Laser Deposition (SALD) technique was used to deposit silicon nitride material from the gas phase. Tetramethylsilane (TMS) and ammonia were chosen as precursors for silicon and nitrogen respectively. Effects of processing temperatures and gas ratios of TMS to total pressure (PTMS+ PNH3) on the relative amounts of silicon nitride and the growth kinetics were studied. Further, surface morphology and electrical properties of the deposits were also examined. It is found that the as-deposited materials are mainly composed of amorphous phases and the heat-treated samples (at 1500°C for 8hrs) consist of α-Si 3N4, α-SiC and β-SiC. The amount of αz-Si3N4decreases with the increase of the TMS pressure. The volume growth rate of deposits also increases with the TMS pressure. The apparent activation energy for these processes is estimated as 1 OOkJ/mol.
Zirconia Coatings Deposited by Inductively Coupled Plasma Assisted CVD
Authors: Colpo P. , Ceccone G. , Leclercq B. , Salvatore P. , Rossi F.
Published: April 2011

Thin films of zirconia have been deposited by an Inductively Coupled Plasma Assisted CVD (ICP-PACVD) reactor from tetra (tert-butoxy)-zircon precursor diluted in Ar and O2gas mixture. An independent RF generator is used to control carefully the substrate negative bias voltage during the deposition. Zirconia thin films, with thickness up to 10 microns were deposited on Si (100) polished wafers under different plasma conditions. Correlation between deposition parameters, and microstructure has been established showing that the ion bombardment has a large influence on the coating characteristics. In particular, the possibility of tailoring mechanical properties of the films by controlling the applied DC bias voltage is discussed.
CCVD: Low-Cost Vapor-Deposition of Thin Films in Open Atmosphere
Authors: Schmitt Jerome J.
Published: April 2011

The new, patented Combustion Chemical Vapor Deposition (CCVD) process holds promise for low cost, high throughput manufacturing of thin film ceramic coatings with composition and microstructure tailored for specific applications in electronic, optic, anti-corrosion and anti-wear applications. The flame-based CCVD process is an open-air, non-vacuum, environmentally friendly process with the ability to produce coatings of equal or superior quality to those produced by conventional vacuum-based methods. Capital and operating costs for CCVD coating systems are significantly lower than, for example, conventional CVD and PVD technologies. As an open-atmosphere process, ccvD can be easily implemented in a continuous production line environment, avoiding the need for vacuum load-locks. MicroCoating Technologies has used CCVD to deposit over 60 different inorganic materials onto a variety of substrates ranging from metals and polymers to ceramics. Multi-layered films of complex composition have been achieved with excellent stoichiometric control. We review the CCVD process and characteristics of representative coatings
Carbon Film Synthesis on the Water by Excimer Laser Irradiation
Authors: Hidai H. , Tokura H.
Published: April 2011

Water was used as a substrate and carbon films were obtained from methane gas on the water by ArF excimer laser. The film was analyzed by a SEM, elementary analysis, Raman spectrum and FT-IR. Moreover synthesized position of the film was studied.
Photo Chemical Modification of the ZnSe Surface
Authors: Stepanenko Victor M.
Published: April 2011

Photon stimulated reaction of chlorine at ZnSe surface was observed at room temperature in the photon range from 4 eV to 12 eV. Estimated quantum efficiency is about 1, depending on the photon range and gas pressure. The study of reaction products was performed with AES, XPS and SEM with Energy Dispersion Analysis. A model based on photon stimulated diffusion of dissociated gas atoms is dicussed. Comparison to C12/GaAs and XeF2/Si systems was made.Effective laser ablation of the ZnCI2 films deposited with masks was exploited for direct patterning. The ultimate resolution obtained was restricted with diffraction limit,
Diamond-Like Nanocomposite Films Fabricated in an Acetylene Atmosphere by Ion Beam Assisted Deposition: XPS Analysis
Authors: Wang Paul W. , Sulak Jodi L. , Ding Xing-Zhao , Zhang Fu-Ming , Liu Xiang-Huai
Published: April 2011

Diamond-like nanocomposite (DLN) film, by embedding the diamond-like carbon into an amorphous SiO2 network, is a special class of modified diamond-like carbon (DLC) coating, which shows many excellent properties and potential applications. In this work, DLN films were fabricated in an acetylene atmosphere by ion beam assisted deposition. However, in order to understand the mechanical and electronic properties of the DLN film separation of the sp3 carbon bond from sp2 bond is necessary, because the former determines the hardness and the latter is related to the optical gap and electrical conductivity. Here we report the effect of the annealing on the relative concentrations of sp3 and sp2 hybrids in the film by using the XPS technique to decompose the C ls signal into sp3 and sp2 components. The XPS results clearly indicate that the distribution of the sp3 and sp2 C species is modified by thermal annealing at 700 °C. More sp3 species accumulate at the interface and gradually decrease towards the film surface.
Deposition and Etching of Amorphous Carbon Films Prepared by ECR-Plasma-Enhanced Benzene Chemical Vapor Deposition
Authors: Chen Xiao-Hua , Tolbert Laren M. , Ning Z. Y. , Hess Dennis W.
Published: April 2011

Amorphous hydrogenated carbon thin films have been deposited from benzene vapor in a microwave electron cyclotron resonance (ECR) plasma enhanced chemical vapor deposition (CVD) system. Plasma enhanced dissociation and reaction of benzene were monitored by mass spectrometry. Deposited films were characterized by Fourier transform infrared spectroscopy and fluorescence spectroscopy. The effect of the deposition rate on the film density and plasma etch resistance was also studied. The etch resistance of deposited carbon film is higher than the conventional resist Novolac.
Quantitative Analysis of Raman Spectra from Diamond Like Carbon: Calibration Transfer
Authors: Rosenblum S. S. , Davis Kevin L. , Tedesco James M.
Published: April 2011

We report on Raman studies of diamond-like carbon (DLC) films; in particular, we report on the instrumentation and methodology required for comparing Raman measurements taken on different Raman analyzers. Raman spectroscopy has taken on an increasingly important role in materials processing because of its capability of performing non-destructive, in situ characterization of thin films. In particular, noncrystalline carbon coatings have become ubiquitous as protective layers on everything from machine tools to hard disk drives. As tolerances on coating properties begin to play an important part in determining device failure, Raman spectroscopy has found ever greater application as a quality control/quality assurance tool. However, use of Raman as an analytical tool has been hampered by the inability to quantitatively compare spectra obtained with different Raman analyzers. By using automated, robust calibration protocols on both the wavelength and intensity axes, we have demonstrated cross-instrument calibration transfer of DLC films.
The effect of silicon on thermal stability and wear behavior of diamond-like carbon films
Authors: Wu Weng-Jin , Hon Min-Hsiung
Published: April 2011

The diamond-like carbon (DLC) films added with silicon content from Oat% to 19.2at% were deposited using R.F. PECVD. By increasing the annealing temperature the groups of CHn and Si-H in FTIR spectra of the deposited films decrease because of hydrogen evolution, whereas the intensity of C=O and Si-O peaks increases due to oxidation. From Raman spectra, the observable shoulder of D band occurs at 400°C and 500°C respectively, which indicates that the addition of silicon improves the thermal stability of DLC films. A pin-on-disk wear test was conducted to investigate the wear behavior of the DLC films. DLC film with small amount of silicon addition has a lower friction coefficient (0.01) than the undoped one(0.1). Raman analysis showed that in wear test the graphitization of pure DLC film occurs at the initial stage whereas for the silicon containing DLC, graphitization of wear debris or transferred film was not observed after the wear test.
Sorption of Uranium(6+) and Neptunium(5+) by Surfactant-Modified:Natural Zeolites
Authors: Prikryl James D. , Pabalan Roberto T.
Published: April 2011

Experiments were conducted to determine the ability of surfactant-modification to enhance the ability of natural zeolites to sorb U(6+) and Np(5+). Natural zeolite material, comprised mainly of clinoptilolite and treated with the cationic surfactant exadecyltrimethylammonium-bromi(le (IDTMA), was reacted with U(6+) and Np(5+) solutions open to the atmosphere and having a range of radionuclide concentration, pH, and NaCI concentration. The results indicate surfactantmodification of the zeolite enhances its ability to sorb U(6+), particularly at pHs greater than six where U(6+) sorption on unmodified zeolite is typically low due to formation of anionic U(6+) aqueous carbonate complexes. In contrast, there is little enhancement of Np(5+) sorption onto surfactant-modified zeolite. The presence of chloride anions in solution makes surfactantmodification less effective. The enhanced sorption of U(6+) is interpreted to be due to anion exchange with counterions on the external portion of a surfactant bilayer or admicelles.
Thermochemistry of Hf-Zirconolite, CaHf Ti2O7
Authors: Putnam Robert L. , Navrotsky Alexandra , Woodfield Brian F. , Shapiro Jennifer L. , Stevens Rebecca , Boerio-Goates Juliana
Published: April 2011

The formation enthalpy, - 3752.3 ± 4.7 kJ·mol−1, of Hf-zirconolite, CaHfTi2O7, was obtained using high temperature oxide-melt solution calorimetry. Combined with heat capacity data obtained using low temperature adiabatic calorimetry we report the heat capacity (Cp) and the standard molar formation energetics (ΔH°f. elements, Δ S°T, and ΔG°f. elements)for Hf-zirconolite from T = 298.15 K to T = 1500 K. Comparison of Hf-zirconolite with Zr-zirconolite is made.