bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cement Based Encapsulation Experiments for Low-radioactive Phosphate Effluent
Authors: Sugaya Atsushi , Horiguchi Kenichi , Tanaka Kenji , Akutsu Shigeru 
Published: February 2009

AbstractDevelopment work has been carried out for several years on the cementation of phosphate waste from the Tokai Reprocessing Plant Solvent Waste Treatment Facility. The phosphate waste consists of mainly NaH2PO4 at a concentration of approximately 440g/&#8467;, and has a pH of approximately 4. During attempts to encapsulate this waste in cement the phosphate species interfere with the hydration reaction and retard the setting of the cement and reduce the strength of the wasteform. To mitigate these detrimental effects, pretreatment of the phosphate waste with Ca(OH)2 prior to cementation has been investigated at small scale.
The effect of pre-treating the waste with various amounts of Ca(OH)2, specified by the Ca(OH)2/ NaH2PO4 molar ratio, was investigated under a range of mixing conditions. The viscosity of the pre-treated waste simulant was recorded and an optical microscope was used to identify the presence of small crystals formed during pre-treated. Cementation of pre-treated phosphate waste simulant was also investigated using various conditions to assess the effects of changing the waste loading, mixing temperature and water/cement ratio. The dimensional stability and strength of the resulting cemented waste was assessed up to 28 days.
Results from the trials show that pre-treatment of the waste simulant with Ca(OH)2 is particularly sensitive to the Ca(OH)2/ NaH2PO4 molar ratio and mixing temperature. These two factors strongly affect the rheology of the pre-treated waste and the acceptability for subsequent cementation. An optimum Ca(OH)2/ NaH2PO4 molar ratio was found to exist and the importance of controlling the waste temperature during pre-treatment was explained.
Cementation trials were performed using the pre-treated phosphate waste simulant and slag cement. It has been shown that pre-treated phosphate waste may be encapsulated in slag cement where the wasteform achieved compressive strengths exceeding 10 MPa after 28 days curing at waste loadings exceeding 13wt% (given as a % weight of cement wasteform represented by the NaH2PO4 in the untreated waste).
Demonstration trials of pre-treatment and encapsulation will be executed at full scale in the future.
Analysis of Electrochemical Performance of Single Step Co-fired Solid Oxide Fuel Cell (SOFC) Analyzed Using Polarization Model and Impedance Spectroscopy
Authors: Yoon Kyung Joong , Gopalan Srikanth , Pal Uday B. 
Published: February 2009

AbstractAnode-supported planar solid oxide fuel cell (SOFC) was successfully fabricated by a single step co-firing process. The cell comprised of a porous Ni + yittria-stabilized zirconia (YSZ) anode support, a porous and fine-grained Ni + YSZ anode active layer, a dense YSZ electrolyte, a fine-grained porous Ca-doped LaMnO3 (LCM) + YSZ composite cathode active layer, and a porous LCM cathode current collector layer. The cell was tested between 700˜800oC with humidified hydrogen (97% H2+3% H2O) as fuel and air as oxidant. The measured maximum power densities were 1.42W/cm2 at 800°C, 1.20W/cm2 at 750°C, and 0.87W/cm2 at 700°C. The cell was also tested at 800oC with various compositions of oxidant, and cell parameters including the area specific ohmic resistance, exchange current density, and anodic and cathodic limiting current densities were determined using the polarization model and impedance spectroscopy.
Transport Through Electrophoretically Deposited CuMn1.8O4 Spinel Coatings on Crofer Interconnects
Authors: Huang Wenhua , Gopalan Srikanth , Pal Uday B. , Basu Soumendra 
Published: February 2009

AbstractDense and well-adhered CuMn1.8O4 spinel oxide coatings were successfully deposited on Crofer 22 APU stainless steel substrates by a cost effective electrophoretic deposition technique. Coated and uncoated Crofer substrates were oxidized for 120 hours in air at 800°C. A diffusion model was developed for the oxidation of the coated alloys, which predicted para-linear oxidation kinetics. The effective diffusivities in the coating and in the thermally grown oxide were calculated to be 2×10-15 cm2/s and 2.5×10-16 cm2/s respectively, at 800°C. Area specific resistances (ASR) of thermally cycled samples at 800°C did not show a significant difference compared to the isothermally oxidized sample for the same total oxidation time, suggesting good coating adherence. The ASR of the coated alloys is projected to be around 3.8×10-2&#937;cm2 after 50000 at 800°C in air, making them excellent candidates for interconnect applications for solid oxide fuel cells operated at 800°C or lower.
SPEEK-based Composite Membranes for Direct Methanol Fuel Cells
Authors: D'Epifanio Alessandra , Mecheri Barbara , Weise Christoph F , Greenbaum Steve , Traversa E , Licoccia Silvia 
Published: February 2009

AbstractSulfonated polyether ether ketone (SPEEK)-based composite membranes doped with 23 and 50 wt% of hydrated tin oxide (SnO2·nH2O) were prepared and characterized for Direct Methanol Fuel Cell (DMFC) applications . The composite membranes were characterized in terms of ion exchange capacity (IEC), tensile tests, water uptake measurements, electrochemical impedance spectroscopy (EIS), and Pulsed-field-gradient spin-echo nuclear magnetic resonance (PFGSE NMR) spectroscopy. The body of results indicated the involvement of hydrated tin oxide in the proton conduction mechanism, the inorganic phase providing additional paths between the water clusters for proton transport. NMR measurements evidenced that SnO2·nH2O particles not only facilitate the proton transport but also hinder water diffusion. Therefore, due to the selectivity of SnO2·nH2O for proton diffusion, the filler effect was found to be also beneficial for the reduction of methanol crossover through the SPEEK membrane and for improving the performance of the SPEEK membrane when used as electrolyte in a DMFC test station.
Electrochemical preparation of nanostructured TiO2 as anode materials for Li ion batteries
Authors: Duan Huanan , Chen Xiangping , Gnanaraj Joe , Liang Jianyu 
Published: February 2009

ABSTRACTTiO2 is an attractive anode material for Li-ion batteries due to its high capacity, high mechanical stability during Li intercalation/deintercalation process, limited side reactions with the electrolyte, low cost, and environmental friendliness. In this study, titanium hydroxide gel films were prepared in acidic aqueous solutions of TiOSO4, H2O2 and KNO3 by potentiostatic cathodic electrosynthesis on various copper substrates, including planar Cu foil, mechanically polished planar Cu foil, and Cu nanorod arrays grown on Cu foil. Crystalline TiO2 films were obtained by heat treating the electrodeposited titanium hydroxide gel films at 500 oC in argon atmosphere. The morphology and microstructure of the TiO2 films were characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD). SEM results showed that after deposition, each Cu nanorod has been covered by a layer of TiO2 gel, forming a core-shell structure. The effects of Cu nanorod arrays on the morphology and the electrochemical property of the TiO2 deposits were discussed.
Reduction of bis(Oxalato)Borate on a High Surface Area Carbon Electrode
Authors: Flynn John , Schlaikjer Carl 
Published: February 2009

ABSTRACTLithium bis(oxalato)borate (LiBOB) has gained widespread interest as an electrolyte salt for lithium ion batteries because of its high conductivity, low cost, thermal stability, and adequate solubility in many organic solvents [1]. Cyclic voltammetric data taken on platinum [2] and carbon [3] indicate electrochemical stability over a wide potential range.We show that bis(oxalato)borate (BOB) can be reduced at about 1.75 volts anodic to lithium, by discharging electrolytes at low current density (0.1 mA/cm2) on high surface area carbon electrodes containing a mixture of acetylene and Ketjen carbon blacks. The evidence includes discharge profiles and 11B NMR data. The behavior of discharge plateaus indicates that BOB is reduced to a soluble species with electrolytic properties, and the appearance of a broad 11B NMR peak in the electrolyte indicates that the reduced species undergoes extensive exchange.
Development of Ultrahigh Surface Area Porous Electrodes using Simultaneous and Sequential Meso- and Micro-structuring Methods
Authors: Maddox Franchessa , Cook Catherine , McKenzie Leigh , O'Neil Brenda , Junkin Elizabeth A. , Redden Christopher , Basu Soumen , Bakker Martin G. , Småtts Jan-Henrik , Lindén Mika 
Published: February 2009

ABSTRACTVery high surface area nanostructured metal electrodes are of interest as efficient current collectors. For thin film devices, the nanostructured metal can be grown in place using electrodeposition or electroless deposition. For larger devices metal electrodes structured at more than one length scale are desirable. Self-assembling surfactant templates are a versatile method of generating a range of nanostructures. As we report here, electrodeposition of nickel, cobalt and copper from liquid crystalline solutions of Triton X-100 produces a number of nanostructures, with significant surface area increases. Electrodeposition into templates with microstructure has proven more demanding. Oil-in-water Microemulsions of Tween surfactants and soy oil, produce micrometer scale structures, however measured nickel surface area does not scale with sample thickness. The method is also not robust, and was found to give microstructures only for nickel and cobalt. Experiments show that under our conditions a combination of nickel metal, nickel acetate and nickel/detergent microstructures are formed.
Grain Refinement for Strengthening in Fe3Al-based Alloys Through Thermomechanical Processing
Authors: Kobayashi Satoru , Takei Akira , Takasugi Takayuki 
Published: February 2009

AbstractA thermomechanical process (TMP) for grain refinement was performed in bulk Fe3Al-based alloys containing ˜10% volume fraction of κ-Fe3AlC precipitates. In the TMP, κ particles play an important role in reducing the inhomogeneity of recrystallization due to the matrix orientation. The grain size was refined to ˜20 μm by optimizing the κ particle size. A fine-grained and pancake/recovered microstructure fabricated by the TMP showed more than 1200 MPa tensile strength and 8% tensile ductility at room temperature in air. The tensile strength of this material was higher than those of conventional wrought Fe3Al alloys at temperatures between room temperature and 500 °C, and the specific tensile strength was as high as that of the Ti-6Al-4V alloy at temperatures above 400 °C.
Ab Initio Study of Elastic Properties in Fe3Al-based Alloys
Authors: Friák Martin , Deges Johannes , Stein Frank , Palm Martin , Frommeyer Georg , Neugebauer Jöerg 
Published: February 2009

AbstractFe3Al-based alloys constitute a very promising class of intermetallics with great potential for substituting austenitic- and martensitic steels at elevated temperatures. A wider use of these materials is partly hampered by their moderate ductility at ambient temperatures. Theoretical ab initio based calculations are becoming increasingly useful to materials scientists interested in designing new alloys. Such calculations are nowadays able to accurately predict basic material properties by needing only the atomic composition of the material. We have therefore employed this approach to explore (i) the relation between chemical composition and elastic constants, as well as (ii) the effect transition-metal substituents (Ti, W, V, Cr, Si) have on this relation. Using a scale-bridging approach we model the integral elastic response of Fe3Al-based polycrystals employing a combination of (i) single crystal elastic stiffness data determined by parameter-free first-principles calculations in combination with (ii) Hershey's homogenization model. The ab initio calculations employ density-functional theory (DFT) and the generalized gradient approximation (GGA). The thus determined elastic constants have been used to calculate the ratio between the bulk B and shear G moduli as an indication of brittle/ductile behavior. Based on this approach we have explored chemical trends in order to tailor mechanical properties. Using this information we have cast a selected set of Fe3Al-based ternary alloys, obtained for these the elastic constants by performing impulse excitation measurements at room as well as liquid nitrogen temperature and compared them with our theoretical results.
Ultrasonic Vacuum Chill Casting and Hot Rolling of FeAl-based Alloys
Authors: Šíma Vladimír , Málek Přemysl , Kozelský Petr , Schindler Ivo , Hána Petr 
Published: February 2009

AbstractAn ultrasonic device was designed to fabricate relatively small vacuum chill castings of FeAl-based alloys with improved microstructure. A special hot-rolling procedure preventing thermal shocks was used for the thermomechanical treatment of cast alloys.The efficiency of ultrasonic vacuum casting is manifested by improved microstructure of hot-rolled iron aluminides Fe – 40 at.% Al with addition of C or Zr and B or Zr and B with 1 wt.% of Y2O3 particles.
Grain Refinement of γ-TiAl Based Alloys by Inoculation
Authors: Gosslar Daniel-Hendrik , Güenther Robert , Hartig Christian , Bormann Rüediger , Zollinger Julien , Steinbach Ingo 
Published: February 2009

AbstractA significant grain refinement is achieved for a Ti-45Al (at.%) alloy via the addition of a novel Ti-Al-TiB2 master alloy. This refinement is attributed to a low lattice mismatch of TiB2 with the primary solidifying phase and its thermodynamic stability. Model calculations allow for the prediction of the grain size as a function of cooling rate, alloy constitution and particle size distribution and content. However, the model predictions are smaller than the experimentally observed grain size since the fraction of effective particles is overestimated.
Application of the Fluorine Effect to TiAl-Components
Authors: Donchev A. , Pflumm R. , Schütze M. 
Published: February 2009

AbstractThe oxidation resistance of TiAl-alloys can be improved by several orders of magnitude by fluorine doping of the surface zone of the material. The oxidation mechanism changes from the formation of a thick mixed oxide scale to a protective alumina layer. This fluorine treatment influences only the surface region of the components so that the bulk properties are not affected. Recent results achieved with TiAl-components showed the potential of a fluorine treatment for the use of TiAl in several high temperature applications. Turbine blades for aero engines made of TiAl were treated with fluorine by different methods and their performance during high temperature oxidation tests in air is shown. Further on by selective local fluorination a structured oxide scale develops on TiAl above 800°C. A simple high temperature activation cause the formation of areas covered by a thin alumina layer alternating with a thick mixed oxide scale where no fluorine was applied before oxidation. The aim is to reproduce a shark-skin pattern (tiny parallel ridges) on the surface in order to minimize the aero dynamic resistance of turbine blades rotating in a gas flow. Different methods used for this attempt and the corresponding results are also presented.
Processing, Microstructure, and Thermal Expansion Measurements for High Temperature Ru-Al-Cr B2 Alloys
Authors: Hashimoto Yutaka , Okamoto Norihiko L. , Acosta Manuel , Johnson David R , Inui Haruyuki 
Published: February 2009

AbstractThe B2 intermetallic compound RuAl has a melting temperature above 2000 °C and is a candidate for high temperature structural applications. A large extension of the B2 phase field is found in the Ru-Al-Cr system as was documented by the characterization of arc-melted and heat treated alloys. Two compositions consisting of Ru-35Al-19Cr and Ru-20Al-38Cr (at. %) were directionally solidified in an optical floating zone furnace. Depending upon the processing conditions, single phase, polycrystalline, B2 microstructures could be produced. The coefficient of thermal expansion (CTE) was measured from room temperature to 1250 °C for the Ru-20Al-38Cr alloy, and an average value of 11×10-6 K-1 was found. Additionally, the thermal conductivity was measured as 27 W/mK at room temperature for the Ru-20Al-38Cr B2 alloy and as 89 W/mK for binary RuAl.
Thermodynamic Re-Assessment of the Co-Nb System
Authors: He Cuiyun , Stein Frank , Palm M. , Raabe Dierk 
Published: February 2009

AbstractA new thermodynamic assessment of the Co-Nb system is presented. All experimental phase diagram data available from the literature have been critically reviewed and assessed using thermodynamic models for the Gibbs energies of the individual phases (Thermo-Calc). Compared to previous assessments more elaborate models for the description of the C14 and C36 Laves phases and for the μ phase were employed. Thereby a calculated phase diagram is obtained which satisfactorily agrees with the experimental data.
Surface structure modification of Ni3Al foil catalysts by oxidation-reduction treatment
Authors: Jang Jun Hyuk , Xu Ya , Demura Masahiko , Wee Dang Moon , Hirano Toshiyuki 
Published: February 2009

AbstractA two-step treatment, oxidation in air followed by reduction in hydrogen, was carried out to modify the smooth Ni3Al foil surface into Ni particles supported on the oxide structure. The surface structure significantly changed depending on the oxidation temperature. A layer of granular NiO formed on the outer surface and inner oxide zone (IOZ) over Ni3Al foil surface after oxidation at 973 K. The IOZ was a mixture of Al and Ni oxides. In contrast, a large amount of faceted NiO particles formed on the outer surface after oxidation at 1173 K. Beneath the NiO particles, NiAl2O4 thin layer formed on IOZ over Ni3Al foil surface. And then, these NiO was selectively reduced to Ni after reduction treatment, constituting an oxide supported Ni particles structure. These results suggest that it is possible to modify the surface structure of Ni3Al foils simply by oxidation-reduction treatment.
Direct Modeling of the Simultaneous Flow of Compressible Atomizing Gas Jets and a Weakly Compressible Liquid Intermetallic Stream During Gas Atomization
Authors: Tong Mingming , Browne David J. 
Published: February 2009

AbstractThe authors have developed a new atomization model enabling direct numerical simulation of the simultaneous flow of compressible atomizing gas jets and a weakly compressible liquid metal stream. It has been used to simulate the atomization of a Ni-50wt.%Al melt stream by argon gas jets in a closed-coupled atomizer. The 2D simulation results show that the presence of the liquid intermetallic stream significantly influences the field variables, particularly the aspiration pressure. At the gas plenum pressure used, the gas nozzles are choked and hence the gas flow upstream of the tip of the liquid delivery tube is not influenced by the presence of the liquid intermetallic stream, whereas the downstream gas flow is affected. Significant differences between model predictions assuming either incompressible or compressible gas are reported. Besides the atomization of liquid intermetallic stream by argon gas, this unified atomization model is available for use to simulate a variety of different twin-fluid atomization processes.
Physical and Mechanical Properties of Single Crystals of Co-Al-W Based Alloys with L12 Single-Phase and L12/fcc Two-Phase Microstructures
Authors: Inui Haruyuki , Tanaka Katsushi , Kishida Kyosuke , Okamoto Norihiko L. , Oohashi Takashi 
Published: February 2009

AbstractSingle-crystal elastic constants of Co3(Al,W) with the cubic L12 structure have been experimentally measured by resonance ultrasound spectroscopy at liquid helium temperature. The values of all the three independent single-crystal elastic constants and polycrystalline elastic constants of Co3(Al,W) experimentally determined are 15~25% larger than those of Ni3(Al,Ta) but are considerably smaller than those previously reported. Two-phase microstructures with cuboidal L12 precipitates being well aligned parallel to <100> and well faceted parallel to {100} are expected to form very easily in Co-base superalloys because of the large value of E111/E100 and cij of Co3(Al,W). This is indeed confirmed by experiment. Values of yield stress obtained for both [001] and [¯123] orientations of L12/fcc two-phase single crystals moderately decrease with the increase in temperature up to 800°C and then decrease rapidly with temperature above 800°C without any anomaly in yield stress. Slip on {111} is observed to occur for both orientations in the whole temperature range investigated.
Microstructural Investigations of the Unusual Deformation Behavior of Nb2Co7
Authors: Stein Frank , Palm Martin , Frommeyer Georg , Jain Padam , Kumar Sharvan , Siggelkow Lisa , Grüner Daniel , Kreiner Guido , Leineweber Andreas 
Published: February 2009

AbstractUsually, single-phase intermetallics in bulk form can easily be crushed into powder by hammering. It was therefore quite a surprise when we found that a bulk sample of the monoclinic intermetallic compound Nb2Co7 could be extensively deformed at room temperature without shattering or fracturing. In a previous paper, results of microhardness, compression, tensile and bending tests were provided and discussed [1]. In order to understand the observed unusual deformation behavior of this intermetallic phase, its hitherto unknown crystal structure has been studied and the microstructure of undeformed and deformed samples has been analyzed in the present investigation by light-optical, scanning electron and transmission electron microscopy.
Single-phase specimens deformed at very different strain rates (hammering and conventional compression testing) both show the occurrence of microcracks along grain boundaries which, in compression-deformed specimens, are strongly localized in extended shear bands oriented approximately 45° to the compression axis. The grains adjacent to the microcracks are heavily deformed whereas, away from the sheared regions, the samples remain free of any indication of plastic deformation.
Composition Dependence of the Hardness of Laves Phases in the Fe-Nb and Co-Nb Systems
Authors: Voß S. , Stein F. , Palm M. , Grüner D. , Kreiner G. , Frommeyer G. , Raabe D. 
Published: February 2009

AbstractSingle-phase Fe-Nb and Co-Nb Laves phase alloys were produced by arc melting and levitation melting. By casting the levitation melted alloys in a preheated mould and subsequent slow cooling to room temperature, solid rods of 15 mm in diameter and about 100 mm length of the brittle Laves phases were obtained. Within the extended homogeneity ranges of the NbFe2 and NbCo2 Laves phases, the Vickers hardness was measured in dependence on composition. The results show that the hardness has a maximum at the stoichiometric composition in both systems, indicating defect softening. Nanoindentation measurements on a Co-Nb diffusion couple confirm the dependence of the hardness on composition. In addition, these measurements indicate that the crystal structure of the Laves phase polytype – cubic or hexagonal – seems to have no effect on the hardness. Indentation fracture toughness KIC-IF data for the different polytypes of the Laves phases were evaluated from the Palmquist cracks originating from the edges of the Vickers indentations.