bluuebunny/crossref_metadata_2025 huggingface dataset:
Design of a Cool Color Glaze for a Solar Reflective Tile
Authors: Ferrari Chiara , Muscio Alberto , Siligardi Cristina , Manfredini Tiziano
Published: October 2014

One of the most common materials-measures to counteract Urban Heat Island Effect can be identified in cool roof: white surface characterized by high solar reflectance and high thermal emissivity. One of the problems for the realization of cool roof is the difficult matching of white color with urban planning needs. In order to better integrate cool roofs into skylines cool colors were developed integrating pigments into cool roof surfaces. Cool roof market is actually dominated by organic based products with optimal solar performances but low durability against ageing. The use of ceramic-based products is crucial in the design of a new durable cool roof thanks to their naturally high thermal emissivity (ε=0.90) and their high chemical durability. The development of a new ceramic-based product made by a traditional porcelain stoneware tile as support, an inorganic engobe was started in the last years. In order to complete the product with a suitable glaze, eight different inorganic pigments were added to three different glazes, each one characterized by different surfaces features. Even if the addition of glazes, and pigments decrease the reflectance values of the solar reflective engobe, some promising results were achieved in this study especially regarding warm colored glazes.
Characterization of Silicate Ceramics Using Ultrasonics Test Method
Authors: Kurama Semra , Eren Gültekin Elif
Published: October 2014

Non-destructive testing techniques are widely used for testing ceramic materials. In our studies, two different types of ultrasonic test methods (A-scan and C-Scan) were investigated as non-destructive testing methods for characterization of porcelain tiles. Tiles were sintered in different temperatures to change their porosity and density properties. By changing of ultrasonic time and velocity related with samples’ some physical properties (such as bulk density, apparent density, apparent porosity (%), water absorption (%)) inspected via contact A-scan ultrasonic test method. The results show that without necessity of traditional test methods, some physical properties of ceramics can be determined by using obtained ultrasonic velocity-bulk density, apparent density, apparent porosity (%) and water absorption (%) calibration plots. Additionally, various defects were inspected in samples by using water immersion ultrasonic C-scan method. These results supported this study to obtain the information about defects’ size and place in the ceramic tiles. To support this non-destructive method results scanning electron microscope (SEM) characterization was done and images give the information about the place of the defect.
Microstructure of Ceramic Brick Contaminated by Magnesium Sulphate
Authors: Stryszewska Teresa , Kańka Stanisław
Published: October 2014

Durability of building ceramics is determined by phase composition, the presence of various admixtures and porosity structure. Insertion of salts into the ceramic materials of bricks causes a gradual loss of the original properties of the material. The studies presented in this paper relate to the impact of magnesium sulfate salts to the microstructure change of the ordinary ceramic brick treated. Two types of ceramic bricks were selected for the studies with significantly different properties of shard, which through capillary action were brought to full saturation by solutions. Determination of changes in microstructure of the test materials by the process of crystallization of salts derived from solutions and the crystallization of the corrosion products, was carried out by observation of the microstructure in SEM. In selected places, chemical analysis was performed to determine the changes in the phase composition of the test materials. As a very important factor that affects the stability of ceramic brick is its porosity, pore structure determination was performed by mercury intrusion porosimetry. Based on the received results, the categorization of pores was presented with the indication of priority place of accumulation of crystallizing salts.
Creep Testing of Refractories at Service Related Load Levels and Application for Material Simulation
Authors: Jin Sheng Li , Harmuth Harald , Gruber Dietmar
Published: October 2014

During the operation of industrial vessels at high temperatures both elastic and inelastic behaviour of refractories may occur under intense thermomechanical loads. The latter one brings about an irreversible strain, which may cause mechanical failure of refractories and be responsible for the opening of joints. Besides material failure under tensile or shear loads, creep of refractories also may contribute to the occurrence of the irreversible strains. For quantitative assessment of the thermomechanical behaviour of an industrial vessel lining by the simulations, the accurate determination and description of creep behaviour of refractories at service related load levels is of importance. In this paper, a newly developed high temperature compressive creep testing equipment is introduced. Compared with conventional creep testing machines it enables the application of higher load levels as they occur under service conditions. A general testing procedure and displacement/time curves for various temperatures and loads are shown. For simulation purposes a Norton Bailey type creep law representing strain hardening is identified from the test results. An inverse evaluation procedure is performed for this purpose which exhibits high efficiency and robustness.
Simulation of Refractory Fracture as a Tool for Advanced Material Testing
Authors: Gruber Dietmar , Jin Sheng Li , Harmuth Harald
Published: October 2014

The work presented here deals with simulation assisted evaluation of fracture testing of ordinary ceramic refractory materials. Two tests are applied. One of them, a wedge splitting test, is already established for this purpose. An inverse evaluation procedure was developed to derive more information from the test results: It enables the simultaneous determination of the specific fracture energy, the tensile strength and the Young’s modulus. Moreover specific fracture energy can also be determined in the case that the test has to be interrupted at some residual load due to relatively low material brittleness. The other test method, a laser irradiation disc test, was developed in order to determine specific fracture energy and tensile strength for fine ceramic refractory materials behaving relatively brittle. From the time elapsed until crack initiation occurs (t1) and a stable/instable transition of crack propagation takes place (t2), respectively, the tensile strength and the specific fracture energy are calculated based on a simulation of the mode I fracture behavior which applies the fictitious crack model according to Hillerborg.
Impact of Temperature and Oxygen Partial Pressure on Aluminum Phosphate in High Chrome Oxide Refractories
Authors: Bennett James P. , Kwong Kyei Sing , Nakano Jinichiro , Thomas Hugh , Nakano Anna
Published: October 2014

Gasifiers are reaction vessels used to process carbon feedstock such as coal and/or petcoke at elevated temperature, high pressure, and in a reducing atmosphere (low oxygen partial pressure) to form CO and H2, called synthesis gas or syngas. Syngas is used as a fuel in power generation or as a feedstock material in chemical production. By-products of the gasification process include unreacted carbon, gases such as CO2 and H2S, and slag formed from mineral impurities or organic metallic compounds in the carbon feedstock that liquefy during gasification. In the gasifier, slags interact with the high chrome oxide refractory liner, causing wear and eventual failure of the refractory lining by two primary means - spalling (structural and chemical) and chemical dissolution. Failure of the refractory lining causes the gasifier to be shut down for repair, with increased service time identified by users as important for greater usage of gasification as an industrial process. Phosphate additions to high chrome oxide refractories have been found to increase service life during commercial service by reducing spalling and lowering chemical dissolution of the refractory liner. The mechanism of how they improve service life is not well understood. The microstructure and physical properties of high chrome oxide refractories with and without phosphate additions removed from a commercial gasifier after approximately eight months of exposure to a coal slag are evaluated in this report, with the emphasis on evaluating slag/refractory interaction in refractory pores. Details of the investigation are presented and possible mechanisms of how phosphate additives improve wear resistance discussed.
Microstructures and Corrosion Mechanisms in MgO-C Bricks in Contact with High-Basicity and FeO-Rich Slags
Authors: Benavidez Edgardo , Brandaleze Elena , Musante Leonardo , Galliano Pablo
Published: October 2014

The MgO-C bricks are extensively used as lining work on different steel containers. Due to the high temperatures of the process, these refractories are subjected to severe wear and corrosion processes, principally in the area of contact with the slag. These slags have variable contents of CaO, SiO2, Al2O3, MgO and FeO, varying in composition according to the process stage. In this paper, cup tests were performed at 1650 °C during 2 hours in air, using two commercial MgO-C bricks. They were put in contact with two different grades of slags, one with high basicity (HB) and the other rich in FeO (RF). The corrosion degree suffered by the refractory materials were analyzed and compared. Microstructural observations were performed in order to postulate the probable corrosion mechanisms acting on each material. The results establish that, in the case of HB slag, the attack is carried mainly through the filler region (matrix). In the case of RF slag attack, it is observed that Fe is the main specie that diffuses through the matrix area of the bricks, and to a lesser extent through MgO grains. In both cases, the quality of the raw material used in manufacturing each refractory bricks, be playing an important role in the corrosion degree.
Multiphysics Modelling Applied to Refractory Behaviour in Severe Environments
Authors: Blond Eric , Merouki Tarek , Schmitt Nicolas , de Bilbao Emmanuel , Gasser Alain
Published: October 2014

It is a common practice to design refractory linings with the help of thermal computations, thermochemistry analyses and strong workman know-how. Their mechanical design is often limited to simple thermo-elastic computations. Sometimes computations are refined considering non-linear mechanical behaviour, even if corrosion often induces additional chemical strain and strong change in service of the mechanical behaviour of the refractory. The aim of this presentation is to briefly recast the irreversible thermodynamic framework in order to underline the implications of some basic thermodynamic concepts in term of refractory behaviour modelling. Then, the use of these concepts to develop fully 3D finite element simulations accounting simultaneously for thermal, mechanical and chemistry phenomena will be illustrated on the particular case of SiC-based refractory. Comparison between long duration oxidation test at high temperature and model prediction allows the validation of the proposed approach. Then, an extension to the industrial case of refractory lining in Waste to Energy plant will be illustrated. The interest of taking into account the thermo-chemo-mechanical coupling effects is shown.
Synthesis of Inorganic Polymers Using a CaO-Al2O3-FeO-SiO2 Slag
Authors: Kriskova Lubica , Machiels Lieven , Jones Peter Tom , Blanpain Bart , Pontikes Yiannis
Published: October 2014

The focus of the present paper is to investigate the effect of the activating solution on the structure and mechanical properties of inorganic polymers synthesised from a slag resembling the vitrified residue from a Waste-to-Energy plasma installation. The slag consists of (in wt.%) 22 CaO, 12 Al2O3, 34 SiO2 and 20 Fe2O3 and the activation solution was 50:50 mass ratio NaOH and sodium silicate, with the NaOH solution molarities varying from 2 M to 10 M. The synthesised slag was almost completely amorphous due to the rapid cooling, with only traces of magnetite and quartz. The inorganic polymers were prepared by mixing the slag, sand and activation solution. In all cases, heat was generated during sample preparation and its amount increased with the activating solution strength. After 90 days, the compressive strength of the samples activated with 6 M or higher NaOH solutions was similar, approximately 88 MPa. For NaOH activation solutions with molarities lower than 6 M, the compressive strength was lower, both at early as well as late curing times. SEM and EPMA analysis revealed-between undissolved particle remnants-a distinct binder phase, composed of (in wt.%) 18.9±2.5 CaO, 11.5±0.1 Al2O3, 40.3±2.1 SiO2, 15.8±1.2 FeO, 5.1±1.9 Na2O and 3.7±0.6 MgO. In conclusion, the present study showed that the CaO-Al2O3-FeO-SiO2 vitrified residue could be converted into a stable inorganic polymer having reasonably high mechanical strength, when activated with a mixture of sodium silicate and sodium hydroxide solution with a molarity of at least 4 M.
Studies of Natural and Accelerated Carbonation in Metakaolin-Based Geopolymer
Authors: Pouhet Raphaëlle , Cyr Martin
Published: October 2014

The carbonation of Portland-cement-based materials involves the reaction between atmospheric CO2 and calcium ions in the pore solution. The formation of calcium carbonate is responsible for a decrease in the pH of the pore solution from 12.5 to 9, thus leading to the depassivation of steel reinforcements and their possible corrosion, and can also lead to efflorescence (white crystals formed on the surface). In metakaolin-based geopolymer activated by sodium silicate, in which calcium is almost non-existent, the presence of CO2 will lead to the formation of sodium carbonates. Since geopolymer can be carbonated, the risk of corrosion or efflorescence needs to be assessed. A pH study of the geopolymer pore solution showed a very fast decrease compared to OPC, with almost total carbonation after only 14 days. In natural atmospheric CO2 conditions, it was found that the formation of sodium carbonate did not lead to a decrease of the pH to below a value around 9, thus limiting the risk of corrosion by depassivation of reinforcement, but the large amount of carbonate suggested a significant risk of efflorescence. A study of accelerated carbonation performed under an atmosphere of 50% CO2 highlighted the formation of sodium bicarbonate resulting in a lower pH of the pore solution and a much larger amount of product formed. Finally the study of efflorescence carried out by semi-immersion tests in natural or accelerated conditions confirmed the different nature of the crystals formed (sodium carbonate or bicarbonate) but showed no significant impact on the amount of carbonated products. This study thus demonstrates that the accelerated carbonation test had very limited usefulness, given the rapidity of the natural reaction. Furthermore, it was found that this test did not reproduce reality as it led to different reaction products.
Different Treatment Application of Illite Clay for Low Temperature Ceramics
Authors: Sedmale Gaida , Sperberga Ingunda , Rundans Maris , Grase Liga
Published: October 2014

Impact of chemical treatment by alkali of raw, dehydroxylated at 600 °C and intensively milled illite clay on structure, phase composition and some properties of sintered at lower temperatures ceramic materials were studied using DTA, X-ray diffraction (XRD), as well as scanning electron microscopy (SEM) and mercury intrusion porosimetry. DTA and XRD results show that alkaline activation of illite clay by sodium hydroxide leads to the slight structural changes of illite characterized by structural water losses showed from DTA and negligible decrease of illite and kaolinite, as well dolomite diffraction peaks on XRD. Additional treatment, intensive milling and in particular dehydroxylation, contributes to the considerable changes in intensities of all effects on DTA-curves, especially for dehydroxylation endo-peak. It is shown that chemical treatment promotes the formation of rather amorphous and homogenous structure of sintered at 600°C respective ceramic samples and leads to the growth of the compressive strength.
Addition of Ammonium Molybdate in Geopolymer Formulation
Authors: Vidal Laëticia , Joussein Emmanuel , Absi Joseph , Rossignol Sylvie
Published: October 2014

Geopolymers are inorganic materials obtained by the alkaline activation of aluminosilicate sources. The ammonium molybdate could be used as a complexant for silica in order to complex the siliceous species in the alkaline solution. According to this, the aim of this work is to control the siliceous species and to understand the role of ammonium molybdate as a complexing agent acting on the formation of the different networks. To do this, additions of ammonium molybdate (up to 0.32% molar) in the silicate solution were realized along the formulation of geopolymer using two metakaolins. The results highlight that the addition of ammonium molybdate in geopolymer results in a decrease of the shrinkage at high temperature. Moreover, X-ray diffraction data and SEM after calcination show that geopolymers without ammonium molybdate form two phases (KAlSi2O6 and KAlSiO4) while with additions of molybdate, there were only the phase KAlSi2O6 associated with Al2O3 doped Mo and K2Mo2O7. Finally, SEM observations show that additions of ammonium molybdate seem to favor crystallization. The results allow to evidence the role of molybdate in the control of the polycondensation reaction in order to influence the formation of specific network
Targeted Use of SPS Method for Improvement of Thermoelectrics
Authors: Bulat Lev Petrovich , Nefedova Irina Alexandrovna , Pshenay-Severin Dmitry Alexandrovich
Published: October 2014

Use of spark plasma sintering (SPS) allows improving thermoelectric figure of merit Z of bulk nanothermoelectrics but required parameters of SPS process for achievement of best Z can be defined only empirically. In the present study the finite elements method for investigation of electric and thermal processes which occur in volume and on boundaries of sintering particles is applied. As a geometrical model a structural cell of a sintered sample, containing contact “a truncated cone - a plate” has been chosen. Temperature distributions in the volume of a sample depending on amplitude, on-off time ratio and duration of impact of the electric current has been obtained for solid solution based on bismuth telluride using the energy balance equation and the equation of electric current continuity. Under certain conditions nonlinear and nonlocal processes start to arise. The calculated temperature distributions at different sintering conditions were comparing with empirically defined experimental parameters that lead to improved value of Z. The comparison allows formulating recommendations to achieve best conditions of SPS process for increase of Z. The present method can be used for management of SPS fabrication process for different application, not only for thermoelectrics.
Biogas Reforming for Hydrogen Production: Performance of Ni/La-Ce-O Catalysts
Authors: Pino Lidia , Vita Antonio , Italiano Cristina , Fabiano Concetto , Laganà Massimo , Recupero Vincenzo
Published: October 2014

Biogas, a renewable source of CH4 and CO2, is used for hydrogen generation by tri-reforming reaction; the reaction is a combination of CO2 reforming, steam reforming and partial oxidation of CH4 in a single catalytic step.Several Ni/La-Ce-O mixed oxides, prepared by combustion synthesis, were used as catalysts. The experimental tests, carried out with synthetic biogas at 800°C with a gas hourly space velocity (GHSV) of 30000 h-1, were aimed to study the influence of different parameters (amount of La doping, Ni load and feed composition) on the catalysts activity and stability. The synergic effect of nickel-lanthana-surface oxygen vacancies of ceria influences the samples activity.
An Investigation into the Effect of Ferroelectricity of BaTiO3 on the Photocatalytic Activity in Dye Decolourisation
Authors: Cui Yong Fei , Briscoe Joe , Dunn Steve
Published: October 2014

We use BaTiO3 as a model photocatalyst to investigate the effect of ferroelectricity on catalytic activity against photocatalytic decolourisation of Acid Black 1. We find that there is a strong relationship between the degree of ferroelectric nature of the BaTiO3 and the catalytic activity. When Ag is photodeposited onto BaTiO3 to produce a modified BaTiO3, the higher tetragonal material content shows the highest photocatalytic efficiency even though there is a reduced surface area due to heat treatment. This change in the performance of the catalyst is associated with improvements in charge carrier separation due to the internal space charge layer formed in a ferroelectric due to the internal dipole.
Scanning Hall Probe Imaging of LaFe13-xSix
Authors: Lovell Edmund , Morrison Kelly , Pereira Andre M. , Caplin David , Gutfleisch Oliver , Cohen Lesley F.
Published: October 2014

Magnetocaloric materials with a Curie temperature near room temperature are of interest for application in high-efficiency solid state cooling. There are several promising families of materials including the LaFe13-xSix system which offers large magnetocaloric entropy change, low magnetic and thermal hysteresis, and tunability of the metamagnetic transition by introduction of interstitial hydrogen or partial substitution on the La or Fe sites. There is a large amount of literature on the properties and mechanism of the magnetocaloric effect in this material system, and more recently our group and several other groups have discussed the origins of the dynamics of the metamagnetic transition and its relation to magnetic hysteresis. Nevertheless, although extremely informative in other systems, there has been little spatially resolved information concerning the nature of the magnetic transition in this system. Here we use scanning Hall probe imaging to study LaFe13-xSix polycrystalline samples with x=1.2 prepared by induction melting to resolved the local static and dynamic magnetic properties. We find that the local properties of the magnetic transition are governed by chemical inhomogeneity rather that demagnetization effects associated with sample geometry.
Several Approaches to Bipolar Oxide Diodes with High Rectification
Authors: Grundmann Marius , Schein Friedrich Leonard , Karsthof Robert , Schlupp Peter , von Wenckstern Holger
Published: October 2014

We report on advances in the fabrication of high quality bipolar heterodiodes with oxideelectrodes. The highest rectification above 1010 is obtained for a structure from a-ZCO/ZnO/ZnO:Alon Al2O3 (a-ZCO: amorphous ZnCo2O4). Rectification better than 106, a value larger than reportedfor all previous attempts, is obtained for our a-ZCO/a-ZTO (a-ZTO: amorphous zinc tin oxide), a-NiO/ZnO and CuI/ZnO diodes. The ZCO/ZnO has been used as gate in JFETs with ZnO as channel.The bipolar diodes open the field of oxide semiconductor electronics to applications in photovoltaics.
Nitrogen Doped and Functionalized Carbon Materials as Supports for Catalysts in Electro-Oxidation of Methanol
Authors: Lázaro M.J. , Alegre C. , Nieto-Monge M.J. , Sebastián D. , Gálvez M.E. , Pastor E. , Moliner R.
Published: October 2014

The objective of this work is to study the behavior of Nitrogen-doped carbons as supports of catalysts for the electro-oxidation of methanol. Two carbon materials have been considered: a) carbon xerogels (CXG), highly mesoporous, whose porosity and pore size distribution are easily performed during the synthesis method; b) carbon nanofibers (CNF), which have a high electrical conductivity, good behavior in high temperature conditions and resistance to acid/basic media. Meanwhile, a commercial carbon black (Vulcan XC72R) which is commonly used in manufacturing of electrocatalysts fuel cells was used for comparison. Nitrogen was introduced into the CXG during the synthesis process, what is commonly referred as doping, by including melamine as a reactant. In contrast, N-groups were created over CNF by post-treatment with: ammonia (25%), urea (98%), melamine (99%) and ethylenediamine (99.5%), with a carbon: nitrogen molar ratio 1:0.6. N-containing carbon materials were characterized by elemental analysis, nitrogen adsorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), SEM-EDX and TEM to determinate the amount and forms of nitrogen introduced. Pt-catalysts were prepared by the microemulsion method. The influence of the nitrogen doping and functionalization on the catalytic behavior in the electrochemical oxidation of methanol was evaluated by different physicochemical and electrochemical analysis.
Improved Durability and Cost-Effective Components for New Generation Direct Methanol Fuel Cells - DURAMET Project
Authors: Aricò A.S.
Published: October 2014

Direct Methanol Fuel Cells (DMFCs) have been postulated as suitable systems for power generation in the fields of portable power sources, remote and micro-distributed energy generation, and auxiliary power units (APU). The main objective of the DURAMET project ((http://www.duramet.eu) is to develop cost-effective components for DMFCs with enhanced activity and stability in order to reduce stack costs and improve performance and durability. The project concerns with the development of DMFC components for application in auxiliary power units and portable systems.
Ceria Based Materials with Enhanced OSC Properties for H2 Production by Water Splitting Reaction
Authors: Pappacena Alfonsina , Boaro Marta , Šolcová Olga , Trovarelli Alessandro
Published: October 2014

A novel surfactant-assisted synthesis method was developed in our laboratory to enhance the oxygen storage capacity (OSC) and the thermo stability of a TWC catalyst based on zirconia and rare earth oxides. The same procedure was used to prepare ceria-zirconia compositions with different amount of ceria, either undoped or doped with La and Nd. The potential use of these materials in a two steps solar thermochemical water splitting cycle for the production of H2 was investigated. For this proposal the O2 release of the materials was measured through thermogravimetric analysis in N2 at 1573K. Then all prepared compositions were subjected to an aging treatment at temperature above 1573K in air or in N2 flow and their activity in producing H2 via water splitting at 1073K was evaluated with respect their structural evolution. The results obtained highlight that the reactivity depends on the temperature and atmosphere of the treatments and on the composition. The best result was obtained for the ceria rich composition treated at 1573K in N2 and for the corresponding doped composition treated in air.
RADON Operational Experience in High-Temperature Treatment of Radioactive Wastes
Authors: Stefanovsky Sergey V. , Myshkin Yuri V. , Adamovich Dmitri V. , Beliy Michael D.
Published: October 2014

FSUE Radon deals with collection, transportation, treatment, conditioning, and interim storage and final disposal of conditioned low-and intermediate-level radioactive wastes (LILW) as well as radiation monitoring, decontamination and environmental remediation of Moscow and Moscow area. Liquid LILW with high salinity is subject to vitrification at the Radon full scale vitrification plant using a cold crucible inductive melting (CCIM) at temperatures of 1150-1200 °C. The bench-scale cold crucible based unit is used for research works and feasibility study on new promising ceramic and glass-ceramic waste forms based on incinerator slag and ash. Solid and liquid organic LILWs are treated in a plasma shaft furnace with liquid slagging at temperatures of 1400-1500 °C. Molten slag is solidified in containers yielding a glass-crystalline material with high chemical durability and strong mechanical integrity suitable for safe long-term storage and disposal in both interim repositories and underground sites. One of the promising methods for LILW treatment is application of thermochemical reactions – self-propagating high-temperature synthesis (SHS) with high energy release which is considered as a potential technology for treatment of spent ion-exchange resins, silts and grounds and some specific wastes.
Behavior at High Temperature of Metallic Liners (Ta, Nb) Used in the Sandwich Cladding Material of the GFR
Authors: Charpentier Ludovic , Balat-Pichelin Marianne
Published: October 2014

The Gas-cooled Fast-Reactor (GFR) is one of the system developed in the frame of the 4th generation of nuclear plants. The helium coolant may contain some residual oxidizing impurities that can oxidize the cladding material. A sandwich material with a metallic layer (Ta or Nb) inserted between two sheets of SiC/SiC composite is a promising cladding system of the nuclear fuel to support mechanical strengths, to retain fission products without blocking the neutrons. Nevertheless SiC may support active oxidation with production of gaseous SiO and CO and sublimation in accidental conditions for temperatures above 2000 K, so the aim of the following study is to firstly investigate the oxidation resistance of the metallic liner in extreme conditions, alone and then covered by the SiC/SiC composite. The High Pressure and Temperature Solar Reactor (REHPTS) was implemented at the focus of the 6 kW Odeillo solar furnace in order to reproduce in helium atmosphere the sudden and huge temperature increase that can occur in the case of a nuclear accident. XRD and SEM enabled to observe that the high temperature exposure favored the (211) preferential orientation of tantalum and that the amorphization of niobium occurs above 1500 K. Such changes may impact the properties of the cladding elements. Some sandwich materials made of one plate of metal covered with a SiC/SiC composite were also tested and a carburation of the metallic plates at 2200 K was observed.
Depleted Uranium as Hydrogen Storage Material
Authors: Yamawaki Michio , Arita Yuji , Yamamoto Takuya , Nakamori Fumihiro , Ohsawa Kazuhito
Published: October 2014

Large amounts of depleted uranium kept as uranium fluoride or solid form after enrichment of natural uranium is sought to be utilized in the form of UNiAl intermetallic compound for hydrogen absorber. First principles calculation on UNiAl hydride has been performed in this study to predict the change of the crystal structure and the lattice constants with varying the hydrogen content. The results of the calculations have supported the experimental trends, suggesting that the present approach is promising in predicting the better hydrogen absorber based on depleted uranium.
Xenon Ion Irradiation Effects on a Ni-Base Ni-17Mo-7Cr Alloy
Authors: Huang He Fei , Li De Hui , Yan Long
Published: October 2014

The irradiation effects of a new nickel-base alloy (Ni-17Mo-7Cr) has been investigated by using 1 MeV Xe20+and 7 MeV Xe26+ions irradiation with displacement damage range from 0.33 to 6.6 dpa. The transmission electron microscopy and nanoindentation were employed to study respectively the microstructural evolution of thin-foil specimens and nanoindentation hardness changes of bulk specimens. In case of 0.33 dpa, high number density of nano-scale black spots were observed in thin-foil specimens. High-resolution transmission electron microscopy images revealed that these black spots are some rounded solute clusters and dislocation loops. As far as the ion dose of 3.3 and 6.6 dpa, the black spots were replaced with linear-like defects which were proved to be some Ni, Mo and Cr-enrichment regions. In addition, nanoindentation results for bulk specimens showed an evident hardening phenomenon in irradiated Ni-17Mo-7Cr alloys, compared to the unirradiated specimen. The irradiation induced defects may be responsible for the hardening of Ni-17Mo-7Cr alloys.
Behavior of Fuel and Structural Materials in Severely Damaged Reactors
Authors: Sato Nobuaki , Krishima Akira , Sasaki Takayuki
Published: October 2014

To study the fuel debris treatment at Fukushima Daiichi NPP, information on the behaviour of fuel and structural materials in severely damaged reactors, i.e., oxides and metals of uranium and zirconium is essential. Since sea water was introduced to the reactors, situation of fuel debris became different from that for TMI case. In this paper, phase relations of uranium and zirconium oxides were analyzed by powder XRD method at high temperatures. By the heat-treatment of the mixture of UO2 and ZrO2 (U:Zr=1:1) under 10 torr air, UO2 was oxidized to U3O8 over 800 oC, The UO2 like phase appeared again at 1350 oC which may be caused by the decomposition of U3O8. The oxidation behavior of the UO2-ZrO2 system was also investigated by using solid solution sample with different U/Zr ratios under different steam and oxygen pressures. The oxidation of the UO2-ZrO2 mixture seemed to be suppressed with decreasing U/Zr ratio. The behavior of fuel materials in the presence of seawater was also discussed as well as that for other structural materials.
Two Terminal Non-Volatile Memory Devices Using Diamond-Like Carbon and Silicon Nanostructures
Authors: Alotaibi Sattam , Gabrielyan Nare , Paul Shashi
Published: October 2014

This work illustrates a novel device for storing electronic charge and works as a non-volatile memory device. It is fabricated using an industrial technique and consists of silicon nanostructures and diamond like carbon (DLC) as a memory element and an ultra-thin barrier layer respectively. Both the silicon nanostructures and the DLC have been deposited by plasma enhanced chemical vapour deposition (PECVD) technique. The nanostructures are sandwiched between two DLC layers. To understand the ability of silicon nanostructures to store electronic charge current-voltage (I-V) and current-time (I-t) measurements were carried out. The memory effect is noted as the difference between the two electrical conductivity states (low ‘‘0’’ and high ‘‘1’’).
Switching in Polymer Memory Devices Based on Polymer and Nanoparticles Admixture
Authors: Alhalafi Z.H. , Paul Shashi
Published: October 2014

In this paper, a non-volatile memory device based on a blend of metal oxides (Known as NiO) and polymer has been investigated. These devices have shown to display memory effects; a marked difference in electrical conductivity between the ‘on’ and ‘off’ states. However, the exact mechanism under-pinning these two conductivities states are not very clear. The structures used in investigation are metal-admixture-metal (MAM) and metal-insulator-semiconductor (MIS) devices. Also, glass and p-types silicon (100 orientations) with a pre-prepared Ohmic back contact were used for the MAM and MIS substrates respectively. This work will address some of the questions in regard to the electrical bistability shown by polymer memory devices.
Microwave Measurements of Surface Resistance and Complex Conductivity of NdBaCuO Films
Authors: Mazierska Janina , Leong Kenneth , Ledenyov Dimitri , Rains Adam , Zuchowski Nina , Krupka Jerzy
Published: October 2014

Typically microwave properties of High Temperature Superconducting films are defined in terms of surface resistance Rs computed from Q-factor measurements obtained using one of resonant techniques. While NdBaCuO films are known to have higher TC and JC than YBaCuO films, not much is known about their loss at high frequencies. In this paper we report on microwave properties of NdBaCuO films of varying quality and thickness based on measurements with a 25GHz sapphire Hakki Coleman resonator and computations using two approaches: the surface resistance and the complex conductivity as primary variables for rigorous electromagnetic solutions.
High Critical Currents in Single Grain YBa2Cu3Oy Bulk Superconductors Produced by Infiltration-Growth
Authors: Nakazato Kenta , Muralidhar Miryala , Inoue Kazuo , Koblischka Michael R. , Murakami Masato
Published: October 2014

Bulk YBa2Cu3Oy “Y-123” superconductors with high critical current density (Jc) have been grown by infiltrating a Ba3Cu5Oy “Y-035” liquid source into a Y2BaCuO5 “Y-211” precursor block. Magnetization measurements showed that similar Tc (onset) values and large variation in self-field critical currents were observed when the samples were isothermally grown at different temperatures. We then adapted slow cooling process for the samples 27 mm in diameter and 5 mm in thickness using the growth profile which was optimized on the basis of isothermal growth conditions. The specimens cut from various locations of a large bulk material showed the uniform and sharp superconducting transition with Tc (onset) around 93.2 K. Jc values at 77 K and 0T was in the range of 150 - 175 kA/cm2. Such high Jc values could be obtained without refining the particle size of Y-211 secondary phase. Atomic force microscopy measurements revealed that uniform nanosized secondary Y-211 particles are embedded in the Y-123 matrix, which led to a dramatic improvement of the critical current performance at 77 K.
Hybrid Energy Harvesting Using Electroactive Polymers Combined with Piezoelectric Materials
Authors: Cornogolub Alexandru , Cottinet Pierre Jean , Petit Lionel
Published: October 2014

Electroactive polymers (EAP) are relatively soft and flexible materials, easy to integrate and able to undergo large deformations by applying an electric field (usually some 10 V/μm). This coupling between strain and electric field (quadratic by nature) as well as particular mechanical properties have already been used advantageously to design actuators. As energy harvesters, EAP have also shown good abilities by providing energy densities up to 0.4 J/g/cycle (generator integrated in a shoe). Moreover, they present some advantages over other techniques as electromagnetic or piezoelectric as they have low resonance frequency response and high elasticity which enable them to be used in situations where large displacements are available. The main drawback of EAP as energy harvesters is that they don't experience direct coupling between strain and electric field, such as the piezoelectric effect. It is therefore essential to use an external electrical polarization source in order to create energy cycles induced by the EAP capacitance variations when it is subject to external stress. The goal of this work is to combine the EAP and piezoelectric materials using the advantages of both, for a hybrid energy harvesting. Different possible configurations and their performances are studied and a comparison with existing techniques is made.
Residual Thermal Stress of Spinell Based-Ceramic Infiltrated with Glass Rich in Lanthanum
Authors: da Silva Paula Cipriano , dos Santos Claudinei
Published: October 2014

Ceramic composites developed for glass infiltration in ceramic substract has as main advantage the reduction of fabrication temperatures of ceramic parts compared to the solid state sintering. In this work, spinell based-ceramics infiltrated with glass rich in lanthanum, aiming applications in dental ceramics, were developed and studied. Pre-sintered spinell substrates with porosity of 10, 15 and 20% were infiltrated with glass at temperature 1120°C-120min, using heating and cooling rate of 10°C/min. The composites present relative density superior 98.6% in every investigated condition, and X-ray diffraction indicated the phase MgAl2O4, as unique crystalline phase detected. Hardness Vickers varying between 850-1000HV and fracture toughness varying between 3.0 to 4.5MPa.m1/2 were obtained for composites with variation of intergranular phase quantity. The evaluation of residual thermal stress indicates that compressive thermal stress are generated in every composition varying from 70-90MPa, for compositions containing between 10 to 20% of infiltrated glass, respectively. Theoretical calculations indicate that the excellent quantity of inter-granular phase infiltrated must be 17%, for obtaining better resistance to crack propagation in this material.
Fluctuations in Frequency Composition of Neural Activity Observed by Portable Brain Intention Detection Device
Authors: Shoureshi Rahmat A. , Aasted Christopher M.
Published: October 2014

As part of the goal of developing wearable sensor technologies, we have continued the development of a headset system for monitoring activity across the primary motor cortex of the brain. Through the combination of electroencephalography (EEG) and near-infrared spectroscopy (NIRS), the headsets are capable of monitoring event-related potentials and hemodynamic activity, which are wirelessly transmitted to a computer for real-time processing to generate control signals for a motorized prosthetic limb or a virtual embodiment of one or more limbs. This paper focuses on recent observations that have been made regarding the frequency content of EEG data, which we believe is responsible for the high performance we have previously reported using artificial neural networks to infer user’s intentions. While the inference engine takes advantage of frequency content from 0-128 Hertz (Hz), distinct fluctuations in alpha (8-13 Hz), beta (13-30 Hz), and gamma (30-100 Hz) frequency bands are human-observable across varying upper limb motor exercises when observed at the group level. In addition to prosthetic limbs, this technology is continuing to be investigated for application in areas including pain treatment, robotic arm control, lie detection, and more general brain-computer interfaces.
Anti-Reflective Porous Silicon Features by Substrate Conformal Imprint Lithography for Silicon Photovoltaic Applications
Authors: Blayney G.J. , Zaradzki C. , Liu Y. , Mohd-Azmi M.A. , Guy Owen James
Published: October 2014

Silicon photovoltaic cells require anti-reflection treatments in order to minimise optical losses and improve cell efficiencies. Commercially, the silicon surface is textured using a chemical etchant followed by the addition of an anti-reflective coating to further suppress reflectivity. We present a process using metal assisted etching to create porous silicon features capable of reducing reflectivity to less than 5%. A method for producing porous silicon using Substrate Conformal Imprint Lithography (SCIL) has been developed in order to pattern the nanoscale anti-reflective structures onto silicon wafers.
Nondestructive Evaluation of Photoelectrical Properties of a PVT Grown Bulk 15R-SiC Crystal
Authors: Liaugaudas Gediminas , Jarašiūnas Kęstutis , Tsavdaris Nikolaos , Sarigiannidou Eirini , Chaussende Didier
Published: October 2014

Investigation of excess carrier dynamics in a 15R-SiC bulk layer grown by physical vapour transport (PVT) on 15R-SiC substrate has been carried out using pump-probe techniques: an interband carrier injection by a picosecond laser pulse and measuring the induced absorption and diffraction of a probe beam. For this task, differential transmittivity (DT) and light induced transient grating (LITG) techniques were used. Room temperature carrier lifetime varied in the 3 ns 8 ns range at excess carrier densities above ΔN0 = 7×1017 cm-3 and was ascribed to the recovery time of optically recharged carrier traps, and their activation energy of Ea = 75 meV was determined. The presence of recharged traps caused the injection-dependence of the diffusion coefficient D, whereby its value dropped below 0.1 cm2/s at ΔN0 < 1×1018 cm-3 and gradually increased up to 0.7 cm2/s at higher injections. At elevated temperatures (300 K < T < 700 K), when the traps are thermally activated, the diffusivity increased up to ~ 1.5 cm2/s and was independent on ΔN0. The overgrown layer parameters were comparable to those of the used 15R PVT seed.
Polarization Engineering of Al(Ga)N/GaN HEMT Structures for Microwave High Power Applications
Authors: Rennesson Stephanie , Lecourt Francois , Defrance Nicolas , Chmielowska Magdalena , Chenot Sébastien , Lesecq Marie , Hoel Virginie , Okada Etienne , Cordier Yvon , de Jaeger Jean Claude
Published: October 2014

The aim of this paper is to optimize the epitaxial layer structure of an AlGaN/GaN high electron mobility transistor (HEMT) for high power density at high frequency. The idea is to play on the polarization engineering with the different layers of the epitaxial stack. The influence of the cap and barrier layer thicknesses, the aluminum content in the barrier and the insertion of an AlGaN buffer layer are studied through the electron gas density, electron mobility and sheet resistance. This permits to find out the best trade-off in order to satisfy the requirements for high performances.
Synthesis and Characterization of (3-Aminopropyl)Triethoxysilane-Modified Epitaxial Graphene
Authors: Burwell Gregory , Teixeira Sofia , Castaing Ambroise , Guy Owen James
Published: October 2014

Electrochemical immunosensor devices comprise of an antibody immobilised onto a semiconducting or conducting substrate. The use of epitaxial graphene in immunosensors allows for the detection of an antigen specifically bound to the immobilised antibody by monitoring the current modulation of lithographically fabricated graphene channel devices. Multilayer epitaxial graphene (MEG) was produced on semi-insulating 4H-SiC(0001) substrates by annealing at 1700°C at 1x 10-5 mbar using a graphite cap. Thickness and morphology of the graphene was studied using Raman spectroscopy, XPS, AFM, and SEM. Selective areas of graphene were targeted for modification by adding a protective window of PMMA. In order to immobilise the antibody to the graphene substrate, an amine-terminated surface is required. (3-aminopropyl) triethoxysilane (APTES), is used to achieve amine termination, which is itself bound to a hydroxyliated graphene surface. Hydroxylation was achieved using Fenton chemistry and changes in surface hydrophobicity are confirmed using contact angle measurements. Attachment of APTES to the hydroxyl terminated graphene channel was confirmed using cyclic voltammetry (CV), XPS, and Raman spectroscopy. This functionalization method can be used to attach any antibody to the graphene substrate that can bind to an amine group. This platform is therefore easily adaptable for the fabrication of a range of immunosensor devices for the detection of different biomarkers.
Injury Characteristics in the German Professional Male Soccer Leagues After a Shortened Winter Break
Authors: Fünten Karen aus der , Faude Oliver , Lensch Jochen , Meyer Tim
Published: November 2014

Context:

The winter break in the top 2 German professional soccer leagues was shortened from 6.5 to 3.5 weeks in the 2009–2010 season.

Objective:

To investigate whether this change affected injury characteristics by comparing the second half of the 2008–2009 (long winter break) with the equivalent period in the 2009–2010 season (short winter break).

Design:

Prospective cohort study.

Setting:

German male professional soccer leagues.

Patients or Other Participants:

Seven professional German male soccer teams (184 players in the 2008–2009 season, 188 players in the 2009–2010 season).

Main Outcome Measure(s):

Injury incidences and injury characteristics (cause of injury, location, severity, type, diagnosis), including their monthly distribution, were recorded.

Results:

A total of 300 time-loss injuries (2008–2009 n = 151, 2009–2010 n = 149) occurred. The overall injury incidence per 1000 soccer hours was 5.90 (95% confidence interval = 5.03, 6.82) in 2008–2009 and 6.55 (5.58, 7.69) in 2009–2010. Match injuries per 1000 hours were 31.5 (25.0, 38.0) in the first season and 26.5 (20.2, 32.7) in the second season; the corresponding training values were 2.67 (2.08–3.44) and 3.98 (3.19–4.95), respectively. The training injury incidence (incidence rate ratio = 1.49 [95% confidence interval = 1.07, 2.08], P = .02) and the risk of sustaining a knee injury (incidence rate ratio = 1.66 [1.00, 2.76], P = .049) were higher in 2009–2010 after the short winter break; the incidence of moderate and severe injuries (time loss >7 days) trended higher (incidence rate ratio = 1.34 [0.96, 1.86], P = .09).

Conclusions:

Shortening the winter break from 6.5 to 3.5 weeks did not change the overall injury incidence; however, a higher number of training, knee, and possibly more severe injuries (time loss >7 days) occurred.