bluuebunny/crossref_metadata_2025 huggingface dataset:
Design and Integration of ITER Divertor Components
Authors: Hirai Takeshi , Barabash V. , Escourbiac F. , Fedosov A. , Ferrand L. , Gicquel S. , Jokinen T. , Komarov V. , Martin A. , Merola M.
Published: October 2010

The ITER Divertor is aimed at exhausting the major part of the plasma thermal power including alpha power and at minimizing the helium and impurity content in the plasma. It consists of assembly of 54 divertor cassettes. Each divertor cassette has three plasma-facing components (PFCs) and one cassette body that accommodates these PFCs. The PFCs consist of the Inner and Outer Vertical targets and the Dome. The Vertical Targets directly intercept the magnetic field lines and are designed to withstand heat fluxes as high as 20 MW/m2. After the successful completion of the qualification phase, three Parties (Japan, Europe and Russia) are qualified and they are in charge of procurement of the first Divertor set. In the paper, the detail component design and the manufacturing as well as the integration of the system are reported.
Geometrical Aspects of Dislocation-Obstacle Interaction in Iron
Authors: Grammatikopoulos Panagiotis , Bacon David John , Osetsky Yuri
Published: October 2010

Experiments and atomic-scale computer simulations have shown that nano-scale voids and copper precipitates can be strong obstacles to the glide of dislocations in neutron-irradiated iron. Simulations have shown that voids are strong obstacles and that an edge dislocation climbs by absorbing vacancies at it breaks away from voids. The obstacle strength of copper precipitates is enhanced by a dislocation-induced structural transformation if they are large enough and the temperature is low enough. Most simulations have the centre of a spherical void or precipitate on the slip plane of an edge dislocation. The present work investigates how the strength of 2 and 4 nm voids and precipitates varies with the distance of their centre from the slip plane at temperatures across the range 0 to 450 K. The strength of voids is highest when their centre coincides with the slip plane, but this is not the case for small precipitates, which do not transform from the bcc structure. The strength of both type of obstacle, and the extent of climb at voids and transformation of large precipitates are not symmetric with respect to the position of their centre from the slip plane. The results are discussed in terms of the atomic mechanisms involved.
Tungsten as a Structural Divertor Material
Authors: Rieth Michael , Armstrong Dave , Dafferner Bernhard , Heger Sylvia , Hoffmann Andreas , Hoffmann Mirjam Diana , Jäntsch Ute , Kübel Christian , Materna-Morris Edeltraud , Reiser Jens , Rohde Magnus , Scherer Torsten , Widak Verena , Zimmermann Horst
Published: October 2010

Refractory materials, in particular tungsten base materials are considered as primary candidates for structural high heat load applications in future nuclear fusion power plants. Promising helium-cooled divertor design outlines make use of their high heat conductivity and strength. The upper operating temperature limit is mainly defined by the onset of recrystallization but also by loss of creep strength. The lower operating temperature range is restricted by the use of steel parts for the in- and outlets as well as for the back-bone. Therefore, the most critical issue of tungsten materials in connection with structural divertor applications is the ductile-to-brittle transition. Another problem consists in the fact that especially refractory alloys show a strong correlation between microstructure and their manufacturing history. Since physical and mechanical properties are influenced by the underlying microstructure, refractory alloys can behave quite different, even if their chemical composition is the same. Therefore, creep and thermal conductivity have been investigated using typical commercial tungsten materials. Moreover, the fracture behavior of different tungsten based semi-finished products was characterized by standard Charpy tests which have been performed up to 1100 °C in vacuum. Due to their fabrication history (powder mixing, pressing, sintering, rolling, forging, or swaging) these materials have specific microstructures which lead different fracture modes. The influence of the microstructure characteristics like grain size, anisotropy, texture, or chemical composition has been studied.
Quantitative TEM Investigations on EUROFER 97 Irradiated up to 32 Dpa
Authors: Weiss Oliver J. , Gaganidze Ermile , Aktaa Jarir
Published: October 2010

The objective of this work is to evaluate the microstructure of the neutron-irradiated reduced activation ferritic/martensitic (RAFM) steel EUROFER 97. For this purpose irradiation induced defects like defect clusters, dislocation loops, voids/bubbles and precipitates are identified by transmission electron microscopy (TEM) and quantified in size and volume density. Emphasis is put on analyzing the influence of the irradiation dose and neutron fluxe on the evolution of size and density of the defects at irradiation temperatures between 300 and 335 °C.
A first sample irradiated to a dose of 31.8 dpa was analyzed. The irradiation was carried out in the BOR 60 fast reactor of JSC “SSC RIAR” in Dimitrovgrad, within the framework of the ARBOR-1 irradiation program. To study the dose dependence in a next step the results will be compared to quantitative data on samples irradiated to a dose of 15 dpa.
The obtained quantitative data will be used for correlation of the changes in the microstructure to the changes in the mechanical properties and will serve as an input for models describing this correlation.
New Actinide Waste Forms with Pyrochlore and Garnet Structures
Authors: Livshits Tatiana , Yudintsev Sergey , Stefanovsky Sergey V. , Ewing Rodney Charles
Published: October 2010

Cubic oxides with pyrochlore and garnet structures are promising matrices for long-lived
actinides immobilization. Their isomorphic capacity with respect to An and REE was determined.
To predict the long-term behavior of these matrices under their underground disposal radiation
stability of synthetic pyrochlores and garnets was studied. Most of titanate phases have the critical
(amorphization) doses close to 0.2 displacements per atom at 298 K. This value is significantly
higher for Sn- and Zr-rich pyrochlores. Corrosion behavior of the pyrochlore- and garnet-composed
matrices was investigated. The lowest actinides leach rates were observed in water and alkaline
solutions most typical for underground waste repositories. Amorphization of the phases has a low
influence on their corrosion behavior in solutions. Possibility for joint incorporation of actinides
and Tc into zirconate- and titanate-based matrices with the pyrochlore structure is discussed.
Development of New Waste Forms to Immobilize Iodine-129 Released from a Spent Fuel Reprocessing Plant
Authors: Tanabe Hiromi , Sakuragi Tomofumi , Yamaguchi Kenji , Sato Taemi , Owada Hitoshi
Published: October 2010

I-129 is a very long-lived radionuclide that is released to an off-gas stream when spent fuels are dissolved at a reprocessing plant. An iodine filter can capture I-129 in the form of AgI. However, because AgI is unstable under the reducing conditions of a geological repository and I-129 has a very long half-life, I-129 can migrate to the biosphere. These characteristics make I-129 a key radionuclide for the safety assessment of a geological disposal of radioactive wastes generated from a reprocessing plant (TRU wastes). To improve disposal safety, several new waste forms have been developed to confine I-129 for a very long period in order to reduce the leaching of I-129 from radioactive wastes. These new waste forms have technical objectives of solidifying more than 95% of I-129 into the waste form and achieving a leaching rate of less than 10-5/y. Several iodine immobilization techniques have been examined. This paper presents experimental results concerning the treatment process, leaching behavior, modeling, and related elements of these immobilization techniques.
Study of New Filters Properties for Cs-137 Vapour Capture at High Temperature
Authors: Aloy A.S. , Strelnikov A.V.
Published: October 2010

Major characteristics of two alumosilicate filters based on fly ash microspheres and porous chamotte were studied for high-temperature trapping of Cs-137 vapours.
To determine aerodynamic resistance of the filters, a test facility was designed and built to determine the aerodynamic resistance of the filters. It was shown that porous chamotte had significantly lower resistance than that of the filter based on fly ash microspheres at linear airflows up to
15 cm/sec.
Thermal treatment at 1400-15000С made it possible to increase mechanical strength of the filter based on porous chamotte factors of 1,5- 3,4, without any significant changes of other characteristics that exceeded similar parameters for the filter based on fly ash microspheres.
Microstructural Control for Improving Properties of V-4Cr-4Ti Alloys
Authors: Muroga Takeo , Nagasaka Takuya , Zheng Peng Fei , Chen J.M.
Published: October 2010

V-4Cr-4Ti alloy is an attractive candidate low activation structural material for nuclear fusion reactors. The properties of V-4Cr-4Ti during its operation strongly depend on initial microstructure, especially size and density of Ti-rich precipitates and their interaction with dislocations. This paper focuses on the effects of the precipitate states and other microstructural variables on mechanical properties of V-4Cr-4Ti alloys and the potential methods to improve the properties by microstructural control, based on Transmission Electron Microscopy.
Progressive Development for Structural Integrity Quantification of Nuclear Grade Graphite in Very High Temperature Gas Cooled Reactor Core Environments
Authors: Tsai Shuo Cheng , Hsieh Yi Tsang , Kai Ji Jung , Chen Fu Rong
Published: October 2010

Graphite is used as a moderator for high temperature gas-cooled reactor (HTGR) because the microstructure ofwithin the graphite can store defect energy (Wigner energy) induced by high-doses radiation. However, typically, there are temperature spikes associated with the random releases of enormous amount of defect energy. The irregular events of temperature spikes subsequently heat up HTGR and risk the HTGR experiencing beyond the designed-limit temperature limitsof HTGR. To further investigate the graphite-microstructure evolution subject to radiation damage, we develop a progressive method. We quantify the structural integrity of nuclear-grade graphite using High-resolution Transmission Electron Microscopy (HRTEM). In this study, the nuclear-grade graphite was first radiated by ion implantation with 3Mev C2+ to simulate the material in a very-high-temperature-gas-cooled-reactor (VHTGR)-core environment. The temperatures were controlled in the ranges of 500~1000oC. After the artificial irradiation, HRTEM analyses were proceeded to quantify the microstructure evolution and we calculated the stored energy within the microstructure of the radiated nuclear-grade graphite via Fast Fourier Transform of HRTEM images. Our results show that, at 600 oC and 3 dpa, the microstructure can store energy up to 136 (cal/g), which can heat the HTGR up to 345 oC.
General Corrosion Properties of Modified PNC1520 Austenitic Stainless Steel in Supercritical Water as a Fuel Cladding Candidate Material for Supercritical Water Reactor
Authors: Nakazono Yoshihisa , Iwai Takeo , Abe Hiroaki
Published: October 2010

The Super-Critical Water-cooled Reactor (SCWR) has been designed and investigated because of its high thermal efficiency and plant simplification. As the operating temperature of supercritical water reactor will be between 280°C and 620°C with a pressure of 25MPa, the selection of materials is difficult and important. The PNC1520 austenitic stainless steel developed by Japan Atomic Energy Agency (JAEA) as a nuclear fuel cladding material for a Na-cooled fast breeder reactor. The corrosion data of PNC1520 in supercritical water (SCW) is required but does not exist. The purpose of the present study is to research the corrosion properties for PNC1520 austenitic stainless steel in supercritical water. The supercritical water corrosion test was performed for the standard PNC1520 (1520S), the Ti-additional type of PNC1520 (1520Ti) and the Zr-additional type of PNC1520 (1520Zr) by using a supercritical water autoclave. In view of general corrosion, 1520Zr may have larger possibility than 1520S and 1520Ti to adopt a supercritical water reactor core fuel cladding.
P and Al Diffusion Process for Thin Si Wafers Studied by SEM and EDX
Authors: Ochoa-Martínez Efrain , Merchan Alejandro , Romero Rocío , Gabas Mercedes , Martínez Lourdes , Martín Francisco , Leinen Dietmar , Ramos-Barrado José Ramón
Published: October 2010

The aim of this study is to optimize processes suitable for production of extremely thin cells focusing in two of the solar cell fabrication steps: P and Al diffusion for pn junction and BSF formation respectively. SEM analysis has been used to monitor BSF junction uniformity and EDX to determine composition of the diffused Al layer formed by screen-printing. The influence of the preparation conditions is studied in order to avoid the formation of an eutectic Al-Si alloy, that is the responsible for the bow of thin wafers. Phosphorus deposition has been carried out by spray coating, a technique that allows in-line implementation and reduces manipulation of the cell. Samples were prepared on 250 and 100 μm silicon wafers, comparing various mixtures of H3PO4 as precursor, the resulting emitters were characterized measuring their surface resistivity and analyzing surface composition by XPS and FTIR.
Investigation of Thin Film Solar Cells on CdS/CdTe Base with Different Back Contacts
Authors: Khrypunov G. , Meriuts A. , Klochko H. , Shelest T. , Khrypunova A.
Published: October 2010

The peculiarities of photo-electric processes in thin film CdS/CdTe solar cells (SC) with different back electrodes (Cu/Au, ITO, Cu/ITO) have been studied. As it was established by capacitance – voltage (C – V) characteristics, the potential barrier heights for CdTe/Cu/Au and CdTe/ITO were 0.3 eV and 2.2 eV, respectively. The concentrations of charge carriers near back contact consisted 91020 m–3 and 21021 m–3, respectively. A high carrier concentration and high potential barrier of the ITO back contact caused the tunnel – recombination mechanism of the charge transport. The investigations of CdS/CdTe/ITO SC spectral photosensitivity testify a negative impact of the developed grain-boundary surface of the base layer on the processes of diffusion and separation of non-equilibrium current carriers generated by short-wave radiation. It is shown that the deposition of Cu nanolayer before the deposition of ITO films give stable efficiency 10 % for bifacial CdS/CdTe solar cells.
17.0% Aperture Area Module Efficiency Using Large mc-Si Metal-Wrap-Through Cells
Authors: Weeber Arthur W. , Bennett Ian J. , Tjengdrawira Caroline , Lamers Machteld W.P.E. , Mewe Agnes A. , Romijn Ingrid G. , de Jong Paul C.
Published: October 2010

An integrated cell and module technology based on metal-wrap-through (MWT) cells has been developed and demonstrated. 243 cm2 large and 160 µm thin multicrystalline silicon MWT cells were made with a best cell efficiency of 17.9%. From 36 cells with an average efficiency of 17.8% a full-size module was made with an efficiency of 17.0% (aperture area). The module was made using a conductive rear-side foil with conductive adhesive for the interconnection. The module was constructed using a dedicated module manufacturing line that is designed to be able to work with extremely thin cells and provide a high through-put of one 60 cell module per minute.
Study and Design for High Thermoelectric Properties for AgxTeyTlz Compound with First Principle Band Calculation
Authors: Funashima Hiroki , Hamada Noriaki
Published: October 2010

Recently it was reported that AgxTeyTz shows extremely low thermal conductivity, and high power generating efficiency as a thermoelectric conversion material[1]. We evaluate the seebeck coefficient on basis of the first principles calculations. The electronic band structure calculation is performed using all-electron full-potential linearized augmented plane-wave method(FLAPW) within the local density approximation(LDA). The seebeck coefficent is analyzed by Bloch-Boltzmann equation. In this paper, we find that AgTeTl and AgTe2Tl3 are better thermoelectric material among AgxTeyTlz.
Optimizing Quantum Dot Solar Concentrators with Thin Film Solar Cells
Authors: van Sark W.G.J.H.M. , De Mello Donegá Celso , Schropp Ruud E.I.
Published: October 2010

Quantum dots are proposed as luminescent species in luminescent solar concentrators in combination with thin film silicon solar cells. As both tuning absorption and emission properties of quantum dots is possible by adapting process conditions, as well as tuning the band gap of thin film silicon solar cells, an optimum combination is expected to exist for which the conversion efficiency of the whole device is maximum. As a first step we have employed ray-tracing modeling to determine the efficiency of a luminescent concentrator using several quantum dots and heteronanocrystals with varying Stokes’ shift and absorption cross sections. A maximum efficiency of 5.9% is found for so-called Type II heteronanocrystals.
AlGaAs/GaAs Photovoltaic Cells with InGaAs Quantum Dots
Authors: Lantratov Vladimir M. , Mintairov Sergey A. , Blokhin Sergey A. , Kalyuzhnyy Nikolay A. , Ledentsov Nikolay N. , Maximov Maxim V. , Nadtochiy Alexey M. , Pauysov Alexey S. , Sakharov Alexey V. , Shvarts Maxim Z.
Published: October 2010

We studied the different carrier kinetic mechanisms involved into the interband absorption of quantum dots (QDs) by photocurrent spectroscopy. It was shown that in vertically coupled InGaAs QDs an effective carrier emission, collection and separation take place due to minizone formation. The possibility for the incorporation of vertically-coupled QDs into solar cells (SC) without any deterioration of structural quality of the p-i-n-junction has been shown. Due to the additional absorption of solar spectrum in QD media and the subsequent effective separation of photogenerated carriers, an increase (~1%) in short-circuit current density (Jsc) for the QD
SC-devices has been demonstrated. However the insertion of QDs into intrinsic region reduced the open circuit voltage (Voc) of such devices. Moving the QD array in the base layer as well as including the Bragg reflector (BR) centered on 920 nm resulted in increase of the Voc. Moreover an improved absorption in the QD media for SC with BR led to further increase of Jsc (~1%). The efficiency for QD SCs at the level of 25% (30 suns AM1.5D) has been demonstrated.
Material and Design Requirements for Advanced Concentrators
Authors: Pitz-Paal Robert , Lüpfert Eckhard
Published: October 2010

Concentrating solar collectors direct the sunlight towards a focus point or focus line.
Relevant parameters are the fidelity of the concentrator with respect to its ideal parabolic shape, its
stiffness under wind and gravitational loads, the angular accuracy of the tracking and the solar
weighted specular reflectance of the reflector. Additional aspects refer to the long term durability
and ease of cleaning of the reflector surface. Solar concentrators require lower geometrical
precision than astronomic apparatus. Therefore, more cost effective designs are possible by using
up the overall acceptable error budget to a level that collection efficiency of the reflected sun rays is
still very efficient. Understanding the impact of the different parameters describing the quality of
the concentrator with respect to system performance and cost is necessary for an advanced and
efficient concentrator design.
DLR has recently developed guidelines to measure the most relevant concentrator characteristics in
its qualification center QUARZ. This paper presents the relevant parameters of mirrors for
concentrating solar collectors and discusses their economic impact.
New Method to Characterize Phase Change Materials
Authors: Palomo Del Barrio Elena , Dauvergne Jean Luc
Published: October 2010

A method for thermodynamic characterization of shape-stabilized PCM based on onesingle sample and one-single experiment has been proposed. The simplicity of the experimental device is comparable to that of the T-History method. However, instead of simple energy balances as in T-History method, a numerical heat transfer model is used to retrieve the whole set of parameters/functions characterizing the PCM from temperature measurements at one-single point within the PCM. An efficient inversion technique has been proposed for that. Its most striking feature is that it allows non-parametric identification of the enthalpy-temperature function in an easy way. Such a function is retrieved by solving a problem of moving sources estimation by inversion of a linear heat conduction model.
Test Facility for Absorber Specimens of Solar Tower Power Plants
Authors: Geimer Konstantin , Sauerborn Markus , Hoffschmidt Bernhard , Schmitz Mark , Göttsche Joachim
Published: October 2010

The Solar-Institute Jülich (SIJ) has initiated the construction of the first and only German solar tower power plant and is now involved in the accompanying research. The power plant for experimental and demonstration purposes in the town of Jülich started supplying electric energy in the beginning of 2008. The central receiver plant features as central innovation an open volumetric receiver, consisting of porous ceramic elements that simultaneously absorb the concentrated sunlight and transfer the heat to ambient air passing through the pores so that an average temperature of 680°C is reached. The subsequent steam cycle generates up to 1.5 MWe. A main field of research at the SIJ is the optimization of the absorber structures. To analyze the capability of new absorber specimens a special test facility was developed and set up in the laboratory. A high-performance near-infrared radiator offers for single test samples a variable and repeatable beam with a power of up to 320 kW/m² peak. The temperatures achieved on the absorber surface can reach more than 1000°C. To suck ambient air through the open absorber - like on the tower - it is mounted on a special blower system. An overview about the test facility and some recent results will be presented.
Building Integration Solutions for CPV
Authors: Chemisana Villegas Daniel
Published: October 2010

For building integration, concentrating photovoltaic systems (CPV) can offer a host of advantages over conventional flat panel devices, the most notable being: a higher electrical conversion efficiency in the PV cells, better use of space, ease of recycling of constituent materials, and reduced use of toxic products involved in the PV cells’ production process. However, the viability of building-integrated concentrating PV systems (BICPV) is dependent on their ability to offer a comparative economic advantage over flat panel photovoltaic technologies whose market prices are decreasing from day to day (<1.8 € / Wp) and which offer other advantages such as ease of replacement of structural elements.
A comparative analysis is presented of the main existing CPV systems’ suitability for use in buildings, in which the different challenges specific to integration of each system are discussed. The systems are categorised by type of concentration technology and concentration factor. Two further sets of BICPV systems are proposed, one refractive and one reflective, which we consider well adapted for use in buildings in that they are cost and space efficient, structurally practical and conserve architectural harmony.
A CPV System Based on NIR Reflecting Lamellae Integrated into a Greenhouse: Optimizing of Optics
Authors: Sonneveld Piet , Swinkels Gert Jan
Published: October 2010

In an previous research project a new type of greenhouse with an integrated concentrated photovoltaic system (CPV) was developed which has an integrated filter for reflecting the near infrared radiation (NIR) to the greenhouse and exploiting this radiation in a solar energy system. The performance of the system was promising. In this study further optimalisations of the CPV system are made to avoid the large construction for solar tracting. Hereto all parts will be integrated into the greenhouse. The NIR-reflector material is carried out as a NIR-reflective lamllea system and the CPV–module is mounted into the ridge. In this paper the results of the optimization process of the CPV system based on NIR reflecting lamellae is presented. The optimization process is based on a maximal total annual electricity production and is performed with a ray tracing model and actual radiation data. Results show that the optimization of the lamellae greenhouse can be seen from a theoretical and a practical point of view. Theoretically, the number of lamellae for the investigated concept must be high (>100) and focus with a generic focal length of 3.5 m and glazing bars must be avoided. Then the maximal annual electricity output can be over 26 kWh/m². In practice, mechanical restrictions, plant conditions and costs will determine the implementation. The proposed CPV-system has positive side-effects like reducing the heat load (and need for cooling) during summer and blocking of the direct radiation which can be harmful for some crops. With this, the feasibility of the system depends greatly on local conditions which require a tailor-made economical analysis.
Structural Characterization of Nano-Crystalline Mg2Si Prepared by Ball Milling
Authors: Ioannou Maria , Hatzikraniotis Euripides , Lioutas Christos B. , Paraskevopoulos Konstantinos M. , Kyratsi Theodora
Published: October 2010

In this work, nano-crystalline Mg2Si powder was prepared by ball milling and structural studies vs ball milling time are presented. The identification of the phases of the materials and the evaluation of their purity were performed using Powder X-ray diffraction (PXRD). Crystallite size evolution during ball milling was followed by PXRD and single line analysis, based on Scherrer equation. Transmission Electron microscopy (TEM) observations and IR Reflectivity measurements were used for the investigation of nano-features and confirmation of the PXRD results.
Thermoelectric Iron Oxides
Authors: Kajitani Tsuyoshi , Nozaki Tomohiro , Hayashi Kei
Published: October 2010

P- and N-type thermoelectric iron oxides were developed. The p- and n-type thermoelectric iron oxides were based on delafossite-type CuFeO2 and spinel-type Fe3O4, respectively. The dimensionless figure of merit, ZT, of the bulk p- and n-type iron oxides were 0.15 and 0.10 at 1200K, respectively. The ZT values were improved by the introduction of nano-voids. The physical properties of these iron oxides are structurally unique because of the triangular, or “Kagome,” arrangement of FeO6 octahedra. The delafossite-type CuFeO2 becomes anti-ferromagnet at temperatures less than 20K. The inverse spinel-type Fe3O4 is a ferrimagnet　at room temperature. In both crystals, the iron ions are assumed to be in the high-spin state.
Modular Combustor-Radiator for Micro-TPV System Application
Authors: Chou Siaw Kiang , Yang W.M. , Li Jun
Published: October 2010

The micro combustor is a key component of a micro thermophotovoltaic (TPV) system. In order to maximize the power output, a high wall temperature and uniform distribution along the combustor wall are desirable. Compared to the cylindrical structure, a modular TPV system has been developed with the advantages of easier fabrication and assembly. Three kinds of micro combustors with widths of 1.0 mm, 1.5 mm and 2.0 mm have been experimentally studied. The results indicate that the wall temperature decreases with the increase of width due to the weakened heat transfer between the wall and the hot gases. Other parameters affecting the performance of the micro combustor have also been studied. For the first time, a SiC porous foam was inserted in the micro combustor to enhance both the preheating of the inlet mixture and the heat transfer between the hot gases and the wall, thereby increasing the wall temperature. An increase of 80-90 K has been obtained along the wall of the micro planar combustor with SiC as porous media. This enhanced performance translates to an increase of 33% in radiation energy density.
Interface and Surface Modification of ZnO Induced by Hydrogen and Nitrogen and their Impact on Optical Properties
Authors: Giangregorio Maria M. , Bianco Giuseppe Valerio , Sacchetti Alberto , Capezzuto Pio , Losurdo Maria , Bruno Giovanni
Published: October 2010

In this contribution, we address two critical and interesting aspects from both fundamental and technological point of views, which are the polarity of ZnO and the interface reactivity and stability to hydrogen and nitrogen. The effects of atomic hydrogen and nitrogen produced by radiofrequency (r.f. ,13.56 MHz) H2 and N2 plasmas and of temperature on the optical, compositional and structural properties of Zn- and O-polar ZnO have been studied. It is found that Zn-polar ZnO is highly reactive with atomic hydrogen while O-polar ZnO is almost inert. Conversely, both polarities react with nitrogen, with the O-polar ZnO showing a larger reactivity toward N-atoms than the Zn-polarity.
Iron Pnictide Thin Film Hybrid Josephson Junctions
Authors: Seidel Paul , Schmidl Frank , Grosse Veit , Döring Sebastian , Schmidt Stefan , Kidszun M. , Haindl Sylvia , Mönch I. , Schultz Ludwig , Holzapfel B.
Published: October 2010

Thin films of iron pnictides open the way for fundamental experiments on superconductivity in this material. Thus we started to develop tunneling and Josephson junctions with pnictide film electrodes. Different preparation methods for Josephson junctions were investigated and the first results are presented. Resistive measurements show a high superconductive transition temperature of about 20 K even for the La-1111 electrode after patterning and preparation of the tunneling window. The hybrid junctions were completed with a PbIn counter electrode and normal conducting gold layers as barriers.
Investigation of Fluctuating Diamagnetism and Spin Dynamics in SmFeAsO1-xFx Superconductors
Authors: Prando Giacomo , Carretta Pietro , Lascialfari Alessandro , Rigamonti Attilio , Sanna Samuele , Romanò Laura , Palenzona Andrea , Putti Marina , Tropeano Matteo
Published: October 2010

The superconducting iron-pnictides SmFeAsO1-xFx (x = 0.15 and x = 0.2) are studied by means of 19F-NMR spectroscopy and SQUID magnetometry. Fluctuating diamagnetism above Tc is briefly examined, stressing the analogy with the phenomenology in underdoped cuprates. The 19F relaxation rate allows us to infer an indirect magnetic coupling between Sm3+ moments, possibly involving conduction electrons in FeAs bands, with no appreciable effects on crossing the superconducting transition temperature. A comparison between the superconducting samples and the insulating SmOF, often present as spurious phase in SmFeAsO1-xFx pnictides, is also carried out. Relevant differences in the spin dynamics features are found.
Pathways towards P-Type Oxide Layers for Optoelectronic Applications
Authors: Szyszka Bernd , Polenzky Christina , Loebmann Peer , Goetzendoerfer Stefan , Elsaesser Christian , Koerner Wolfgang
Published: October 2010

State of the art optoelectronic applications such as thin film solar cells, flat panel displays, and light emitting diodes suffer from the non-availability of p-type oxide materials on the industrial scale. Novel technologies such as transparent electronics, UV light emitting diodes, and improved thin film solar cells using wide band gap p-type oxide layers as front contact will be available once p-type oxide layers with proper layer and interface properties can be obtained on an industrial scale.
In this paper, we report on our progress towards p-type oxide layers for industrial applications. We address the first principles density functional theory modeling of ZnO based layers where a pathway towards p-conductivity is seen taking the nitrogen doping of grain boundaries into account.
The second part of the paper is on the synthesis of p-type Delafossite layers such as
CuCr1-xAlxO2:Mg by Sol-Gel and CuCrO2 by hollow cathodes gas flow sputtering. We report on the deposition processes and film properties obtained. Both methods reveal p-type conductivity by means of Seebeck-coefficient measurements.
The Effect of Oxygen Distribution Inhomogeneity and Presence of Higher Borides on the Critical Current Density Improvement of Nanostructural MgB2
Authors: Prikhna Tetiana , Gawalek Wolfgang , Savchuk Yaroslav , Serga Maxim , Habisreuther Tobias , Soldatov Alexander , You Shu Jie , Eisterer Michael , Weber Harald W. , Noudem Jacques G. , Sokolovsky Vladimir , Karau Friedrich , Dellith Jan , Wendt Michael , Tompsic Mikhael , Tkach Vasiliy , Danilenko Nikolay , Fesenko Igor , Dub Sergey N. , Moshchil Vladimir , Sergienko Nina , Schmidt Christa , Litzkendorf Doris , Nagorny Peter , Sverdun Vladimir , Vajda Istvan , Kósa Janos
Published: October 2010

MgB2-based nanostructural materials with rather high oxygen concentration (5-14 wt.%)
and dispersed grains of higher borides (MgB12, MgB7) high-pressure (2 GPa or 30 MPa) synthesized
(in-situ) or sintered (ex-situ) demonstrated high superconducting characteristics (critical current
density, jc, up to 1.8-1.0106 A/cm2 in the self magnetic field and 103 in 8 T field at 20 K, 3-1.5105
A/cm2 in the self field at 35 K, upper critical field up to HC2 = 15 T at 22 K, field of irreversibility
Hirr =13 T at 20 K). The additives (Ti, SiC) and synthesis or sintering temperature can affect the
segregation of oxygen and formation of oxygen-enriched Mg-B-O inclusions in the material
structure, thus reducing the amount of oxygen in the material matrix as well as the formation of
higher borides grains, which affects an increase of the critical current density. The record high HC2
and Hirr have been registered for the material high-pressure (2 GPa) synthesized from Mg and B at 600 oC having 17% porosity and more than 7 wt.% of oxygen. The attained values of the critical
current, AC losses and thermal conductivity make the materials promising for application for fault
current limiters and electromotors. The structural and superconducting (SC) characteristics of the
material with matrix close to MgB12 in stoichiometry has been studied and the SC transition Tc=37
K as well as jc= 5×104 A/cm2 at 20 K in the self field were registered, its Raman spectrum
demonstrated metal-like behavior.
A Multiband Model for LaO1-xFxFeAs
Authors: Murguía-Romero Gabriela , Orozco Susana , Ortiz María de los Ángeles , Méndez-Moreno Rosa María , de la Mora Pablo
Published: October 2010

Based on electronic structure calculations using WIEN2k code for the iron oxypnictide
LaO1-xFxFeAs a multi-band model is proposed. Within the BCS framework a generalized Fermi
surface with overlapping bands is introduced. s-wave pairing symmetry and different doping values
are considered. This model is used to describe some properties of iron-based oxypnictide
superconductors as function of the coupling parameter as well as other relevant parameters of the
model. In order to get numerical results the experimental data of LaO1-xFxFeAs with several doping
concentrations provide the input of this work.
Seawater Magnetohydrodynamics Power Generator / Hydrogen Generator
Authors: Takeda Minoru
Published: October 2010

A seawater magnetohydrodynamics (MHD) power generator / hydrogen generator is expected to become popular with the development of superconducting technology because of low loss and high efficiency. We have designed a new helical-type seawater MHD generator using a solenoid superconducting magnet, by considering the experimental results for a helical-type MHD ship. The experimental and computational results for the helical-type generator including the results of a recent study on hydraulic characteristics are discussed.
Manufacturing Metamaterials Using Synchrotron Lithography
Authors: Moser Herbert O. , Jian Linke , Kalaiselvi Shenbaga M.P. , Virasawmy Selven , Maniam Sivakumar M. , Banas Agnieszka , Banas Krzysztof , Heussler Sascha P. , Casse Bernard Didier F. , Moos Markus , Kohler Heinz
Published: October 2010

The function of metamaterials relies on their resonant response to electromagnetic waves in characteristic spectral bands. To make metamaterials homogeneous, the size of the basic resonant element should be less than 10% of the wavelength. For the THz range up to the visible, structure details of 50 nm to 30 μm are required as are high aspect ratios, tall heights, and large areas. For such specifications, lithography, in particular, synchrotron radiation deep X-ray lithography, is the method of choice. X-ray masks are made via primary pattern generation by means of electron or laser writing. Several different X-ray masks and accurate mask-substrate alignment are necessary for architectures requiring multi-level lithography. Lithography is commonly followed by electroplating of metallic replica. The process can also yield mould inserts for cost-effective manufacture by plastic moulding. We made metamaterials based on rod-split-rings, split-cylinders, S-string bi-layer chips, and S-string meta-foils. Left-handed resonance bands range from 2.4 to 216 THz. Latest is the all-metal self-supported flexible meta-foil with pass-bands of 45% up to 70% transmission at 3.4 to 4.5 THz depending on geometrical parameters.
Au-Based Transparent Conductors for Window Applications: Effect of Substrate Material
Authors: Lansåker Pia C. , Gunnarsson Klas , Roos Arne , Niklasson Gunnar A. , Granqvist Claes Goran
Published: October 2010

Thin films of Au were made by sputter deposition onto glass substrates with and without transparent and electrically conducting layers of SnO2:In. The Au films were up to ~11 nm in thickness and covered the range for thin film growth from discrete islands, via large scale coalescence and formation of a meandering conducting network, to the formation of a more or less “holey” film. Scanning electron microscopy and atomic force microscopy showed that the SnO2:In films were considerably rougher than the glass itself. This roughness influenced the Au film formation so that large scale coalescence set in at a somewhat larger thickness for films on SnO2:In than on glass. Measurements of spectral optical transmittance and electrical resistance could be reconciled with impeded Au film formation on the SnO2:In layer, leading to pronounced “plateaus” in the near infrared optical properties for Au films on SnO2:In and an accompanying change from such two-layer films having a lower resistance than the single gold film at thicknesses below large scale coalescence to the opposite behavior for larger film thicknesses.
The Relationship of Electrical and Structural Properties of Synthetic Melanin Embedded in Matrix of Thin Films Zinc Oxide, for their Use as Electrodes in Bio-Generators
Authors: Altamirano-Juárez Delia Cristina , Hernández-Barriga José Javier , García-Pacheco Carlos
Published: October 2010

Melanin doped zinc oxide thin films were obtained using a process of soft chemistry with pH in the basic region. The electric and structural properties of these films were compared with films of un-doped ZnO obtained using the same process. Undoped films show the characteristic diffraction pattern of polycrystalline ZnO wurtzite type, while the doped films also present other signals associated to the melanin or some derived present phase of this. It is relevant because melanin is reported as amorphous material. Differences of grain size were detected and attributed to the presence of at least two existent phases in the films. Resistivity data were analyzed from the obtained values of films of un-doped ZnO and associated to the structural changes. The films have turned out to be stable in bio-generating systems of useful energy.
Extraordinary Stability of Structural and Electronic Properties of Tin Oxide Nanoparticles Formed by Soft Chemistry
Authors: Rumyantseva Marina , Zhurbina Irina , Varechkina Elena , Badalyan Siranuysh , Gaskov Alexander , Timoshenko Victor
Published: October 2010

Powders of tin dioxide (SnO2) have been prepared by two different modifications of wet chemical synthesis, i.e. (i) by conventional hydrolysis of tin chloride dissolved in aqueous ammonia solution and (ii) by precipitation from tin chloride dissolved in aqueous hydrazine monohydrate (N2H4*H2O) solution. The prepared gels were dried and then annealed at different temperatures varied from 300 to 700 oC in order to form nanocrystals. Structure and optical properties of the samples were investigated by using X-ray diffraction, transmission electron microscopy, thermoprogrammable hydrogen reduction, low temperature nitrogen adsorption method, photoluminescence, infra-red absorption, Raman spectroscopy, and X-ray photoelectron spectroscopy. The samples prepared by hydrazine-based method are characterized by surface area about 127-188 m2/g with high sintering resistance. The optical spectroscopy data revealed pure crystallinity and high defect concentration for the samples prepared by hydrazine-based method. The experimental results are discussed in view of different states of chemisorbed oxygen on SnO2 nanocrystal surfaces, which determine electronic and optical properties of the prepared samples.
Potentiostatic Deposition of Zinc Oxide on Flexible Substrate
Authors: Wong Ching Hong , Mak Chee Leung , Wong Kin Hung
Published: October 2010

Transparent zinc oxide (ZnO) films on flexible copper-coated polyethylene terephthalate (PET) sheet have been grown by a potentiostatic cathodic deposition technique using aqueous zinc nitrate as electrolyte. ZnO films were fabricated using different deposition parameters such as applied potential, electrolyte concentration and bath temperature. Their structural and optical properties were characterized by X-ray diffractometer, scanning electron microscope, diffuse reflectance UV-VIS spectrophotometer and photoluminescence spectrometer. The effects of these deposition parameters on the structural and optical properties of the fabricated ZnO films have been investigated. On the basis of our results, we demonstrate that high quality ZnO films have been successfully grown on flexible polymeric substrates using a low temperature potentiostatic cathodic deposition technique.
Chromogenics for Sustainable Energy: Some Advances in Thermochromics and Electrochromics
Authors: Granqvist Claes Goran , Green Sara V. , Li Shu Yi , Mlyuka N.R. , Niklasson Gunnar A. , Avendaño Esteban
Published: October 2010

Chromogenic materials are able to change their optical properties in response to external stimuli such as temperature (in thermochromic materials) and electrical charge insertion (in electrochromic materials). Below we review some recent advances for these types of materials. Specifically we first discuss the limitations of thermochromic VO2 films for energy efficient fenestration and show from calculations that nanocomposites containing VO2 can have superior properties and display high luminous transmittance and large temperature-dependent solar transmittance modulation. Even better results may be found for nanoparticles of VO2:Mg. In the second part of the paper we survey some recent progress for electrochromic devices and show that W oxide films have increased coloration efficiency when some Ni oxide is added. We also present initial results for flexible electrochromic foils produced by roll-to-roll coating and continuous lamination.
Nanostructured Metal Oxides as Cathode Interfacial Layers for Hybrid-Polymer Electronic Devices
Authors: Vasilopoulou Maria , Palilis Leonidas C. , Georgiadou Dimitra G. , Argitis Panagiotis , Kostis Ioannis , Papadimitropoulos George , Stathopoulos Nikolaos A. , Iliadis Agis , Konofaos Nikolaos , Davazoglou Dimitris
Published: October 2010

We report the use of nanostructured metal oxides as cathode interfacial layers for improved performance hybrid polymer electronic devices such as light-emitting diodes (PLEDs) and solar cells. In particular, we employ a stoichiometric (WO3) and a partially reduced tungsten metal oxide (WOx) (x<3), both deposited as very thin layers between an aluminum (Al) cathode and the active polymer layer in hybrid PLEDs and achieve improved PLED device performance reflected as an increase in the current density and luminance and a reduction of the operating voltage. On the other hand, we investigate the use of a stoichiometric tungsten oxide layer as a thin cathode interfacial layer in hybrid polymer photovoltaic cells (Hy-PVs). We demonstrate improved photovoltaic cell performance, primarily as a result of the substantial increase in the short-circuit photocurrent. The improved PLED device characteristics are attributed to enhanced electron injection that primarily results from the lowering of the effective interfacial barrier, as evidenced by photovoltaic open circuit voltage measurements, and improved electron transfer. On the other hand, the observed improvement in the hybrid solar cell performance is primarily attributed to its enhanced internal quantum efficiency, most likely due to the improved electron transport and extraction at the active layer/WO3/Al interface and the reduction of the corresponding contact series resistance. Correlation between the metal oxide surface morphology and the device performance is also investigated and will be discussed.
Optimisation of Thermochromic Thin Films on Glass; Design of Intelligent Windows
Authors: Saeli Manfredi , Piccirillo Clara , Parkin Ivan P. , Binions Russell , Ridley Ian
Published: October 2010

Theoretically thermochromic glazing has the potential to reduce energy consumption in buildings by allowing visible light for day lighting, reducing unwanted solar gain during the cooling season, while allowing useful solar gain in the heating season. In this study building simulation is used to predict the savings made by novel thermochromic glazing coatings compared to standard products, for locations with different climates. The results suggest that thermochromic glazing can have a significant energy saving effect compared to current approaches.
Transparent Conductors on Polymer Films
Authors: Fahland Matthias , Vogt Tobias , Schoenberger Alexander , Mosch Sindy
Published: October 2010

The paper will present a review of different solutions for transparent conducting electrodes on flexible substrates. The analysis of the present situation reveals a gap for low sheet resistance electrodes.
Two new approaches to the problem will be presented. The first one is a novel technology for the deposition of zinc oxide on polyethylene terephtalate film. The intention for this process is the establishment of a low cost coating in a roll-to-roll machine. Silicon was used as the dopant material with a concentration varying in different samples between 1 and 4 %. The optimum parameters provided a transparent layer with a sheet resistance of 16 Ωsqu. Metal grids are a second promising approach for achieving low sheet resistance electrodes. The combination of these grids with transparent conducting oxides (TCO) will be presented. The TCO were deposited under vacuum in a roll-to-roll coating machine. The grids were applied by aerosol jet printing and subsequent tempering of the film.