bluuebunny/crossref_metadata_2025 huggingface dataset:
Microstructural Transformations of Al2O3-TiO2 and Al2O3-ZrO2 Powders Induced by High-Energy Ball-Milling
Authors: Coste Sandrine , Bertrand Ghislaine , Coddet Christian , Gaffet Eric , Hahn Horst , Sieger H. , Rodríguez Miguel A. , Meunier Cathy , Vives Serge
Published: March 2009

Superior properties of nanostructured Al2O3 based materials, such as higher hardness and fracture
toughness, have been evidenced. In order to optimize their manufacturing, the mechanical activation
of the starting powders (Al2O3-TiO2 and Al2O3-ZrO2) was studied.
In the present work, Al2O3 powders blended with 13wt% and 44wt% of titania or 20wt% and
80wt% of yttria partially stabilized zirconia have been high-energy ball-milled using a planetary
mill, P4 (Fritsch) with steel vials and balls. The effect of the milling time and operating parameters,
such as shock energy and friction to total energy ratio, on the powder structural and microstructural
evolutions has been determined by SEM, XRD and BET.
The transformation of the metastable anatase TiO2 phase into the high pressure TiO2 II phase and
rutile phase was evidenced, simultaneously to the decrease of the alumina crystallite size, in the
Al2O3-TiO2 system. In the Al2O3-ZrO2 system, the transformation of the monoclinic phase and the
decrease of the alumina and tetragonal zirconia crystallite size have been observed.
Structure and Magnetic Properties of Strontium Hexaferrite Nanopowders Prepared by Mechanochemical Synthesis
Authors: Miclea Cornel , Tanasoiu Constantin , Miclea Corneliu Florin , Spanulescu I. , Gheorghiu Anca , Cioangher M.
Published: March 2009

Strontium hexaferrite nanopowders were prepared by mechanochemical synthesis from strontium
and iron oxides using a high energy ball mill after 50 hours of milling. The synthesis process was checked by
X-Ray diffractograms on powders milled for different times. The magnetic properties of hexaferrite
nanopowder, both compacted and dispersed in a nonmagnetic matrix were determined. Severe stresses and
structural deformations were introduced by mechanical processing, but they were eliminated, to a great
extent, by a suitable heat treatment of the milled powder at 1000 oC for one and a half hour. Coercivities as
high as 6600 Oe and specific magnetization of 65 emu/g were found for annealed noninteracting
nanopowders. Such values are very near to the theoretical values for strontium ferrite. The magnetic behavior
of such powders can be rather well described by the coherent rotation model of Stoner-Wohlfarth for an
assembly of single domain particles oriented at random. Sintered bodies of such powders produced magnets
with a high HC of 4600 Oe, a Br of 2100 Gs and an energy product maxim of approximately 1.85 MGOe.
Interparticle Potentials of Aqueous Alumina Suspensions
Authors: Moreno Rodrigo , Gutiérrez Carlos A.
Published: March 2009

In this work the rheological behaviour of aqueous alumina suspensions with solids
loadings ranging from 37 to 59 vol% is studied. A complete rheological characterisation is
performed by measuring under both controlled rate and controlled stress conditions to obtain
expanded flow curves, and by oscillatory tests to determine the elastic moduli. A commercial
polyelectrolyte was used as dispersant. The interparticle potentials are calculated considering the
electrostatic and the steric contributions. The electrostatic pair potential is estimated through the
determination of the elastic modulus, G’, the double layer thickness and the surface potential by
using a spatial particle distribution model. The consideration of the steric potential, by using a soft
spheres model, produces significant changes in the shape and values of the potential energy curves
and allows predicting the stability of suspensions that should coagulate according to the DLVO
equation. The colloidal stability and the rheological behaviour are correlated with the green and
sintered densities of Al2O3 bodies produced by slip casting.
Surface Modification of Nanopowder by Milling under Electric Discharge
Authors: Abe Hiroya , Kondo Akira , Takenaka Kosuke , Setsuhara Yuichi , Naito Makio
Published: March 2009

An apparatus which presents a mechanical milling with electric discharge is introduced.
As a model experiment, an anatase TiO2 nanopowder was processed by the method
using NH3(10%)/N2 gas. The influences of specific surface area, crystal structure, and
optical property were investigated. Relatively high specific surface areas exceeding
250m2/g were observed for all processed powders. The crystal structure and crystallinity
of TiO2 did not change by the milling with electric discharge. On the other hand,
noticeable absorption in Vis light range was observed, suggesting nitrogen doping into
the powder.
Development of Near Net Shape Forming Processes of Ceramic Parts by Colloidal Processing
Authors: Franks George V. , Chabert France , Carreras Enric Santanach
Published: March 2009

Techniques for producing near net shape ceramic components using aqueous forming
processes are reviewed. Particular focus is on three dimensional, complex shape forming by gel
casting and thin film forming by tape casting. Recent progress has been made in formulations that
rely on dispersion of submicron ceramic particles in aqueous solutions containing polymers such as
chitosan or poly vinyl alcohol and a temperature activated crosslinking agent (DHF, 2,5-dimethoxy-
2,5-dihydrofuran). These formulations can be produced to have low viscosity so that they can
either be poured or injected into complex shape molds or cast into tapes. After casting, the
suspension is heated to about 70 oC to activate the crosslinking agent. During crosslinking of the
polymer, the rheological and mechanical behavior of the suspension is changed from liquid-like to
solid-like. This allows the complex shaped bodies to be removed from the mold, dried and sintered.
The strengthening of the cast tape due to crosslinking the polymer allows it to be dried without
cracking. Rheological and mechanical behaviour, green and fired densities as well as examples of
formed components will be presented. The green bodies can be readily machined with common
high speed tool steel tools.
Packing Density and Consolidation Energy of Colloidal Particles through Pressure Filtration
Authors: Hirata Yoshihiro , Tanaka Yosuke , Sakamoto Yuko
Published: March 2009

The applied pressure and suspension height during consolidation of a 15 vol% Al2O3
suspension (0.15 μm α-Al2O3 particles, isoelectric point pH 7.8) at pH 3 - 10 in a closed
cylinder were continuously recorded using a pressure filtration apparatus. The apparent
viscosity decreased with decreasing suspension pH. The final packing density of the
dispersed acidic suspensions at pH 3.2 and 5.6 reached 62 – 63% at 19 MPa of applied
pressure. The viscous basic suspensions at pH 7.8 and 9.6 were consolidated to 52 – 54 %
density. Because of the release of the stored elastic strain energy, the height of the
consolidated Al2O3 compact increased after releasing the pressure. The energy required to
consolidate 1 cm3 of Al2O3 particles was in the range from 3.0 to 15.9 J, and became larger
for the dispersed acidic suspensions. The energy applied between two colloidal particles
during consolidation (W) was compared to the interaction energy (Ei) between two particles
in a suspension.
Multi-Scale Simulations of Rearrangement Effects and Anisotropic Behaviour during Sintering
Authors: Wonisch Andreas , Kraft Torsten , Riedel Hermann
Published: March 2009

Numerical modeling of sintering by continuum mechanical simulations is successfully
applied today to predict e.g. the distortions developing during sintering. Several examples that
demonstrate the possibilities of such simulations especially for industrial applications have been
published recently. However, there are still open questions regarding the influence of grain
rearrangement, crack formation and anisotropic starting configurations (e.g. due to prior
compaction). By using the Discrete Element Method the sintering process can be investigated on a
more fundamental mesoscopic scale. This method also considers effects due to particle
rearrangement or anisotropic configurations as well as crack developments automatically. Their
influence on various macroscopic properties like densification rate and viscosities is studied.
Suggestions how to use these insights to improve existing continuum mechanical models are given.
A Critical Assessment of Porosity Coarsening during Solid State Sintering
Authors: Exner Hans Eckart , Petzow Günter
Published: March 2009

Understanding porosity coarsening is essential for controlling the properties of sintered
materials and for producing high density or near net shape parts. As porosity is interconnected up
to relative densities in excess of 80% or even 95%, measuring, monitoring and modelling of the
growth of individual pores is relevant only at very high relative densities. This paper tries to
convey two essentials of porosity coarsening: (i) characterization of the geometry of the pore space
in the lower range of densities is possible by using stereological parameters, and (ii) coarsening of
porosity takes place during all sintering stages by various mechanisms.
Porosity coarsening has been reported in metals, ceramics and glasses. Recent and classical
approaches, experimental results with two dimensional model arrangements as well as computer
simulations of formation and opening of particle contacts are discussed. The effect of porosity
dimensions on the properties of sintered materials and measures for preventing and provoking
porosity coarsening are briefly addressed.
Microstructure-Property Relationships in Wear Resistant Alumina/SiC "Nanocomposites"
Authors: Todd Richard I. , Limpichaipanit Apichart
Published: March 2009

Alumina/SiC “nanocomposites” consist of a dispersion of SiC “nanoparticles” in an
alumina matrix with conventional grain size. The nanocomposites are much more resistant to severe
wear than pure alumina and this paper explores the mechanisms responsible by examining
microstructure-property relationships. Results correlating (i) microstructure, (ii) wear rate in a
simple abrasive wear test and (iii) quantitative analysis of the appearance of the worn surfaces, are
presented. The results show that the reduction in wear rate caused by the SiC is a consequence of
the reduction in surface pullout by brittle fracture only. For small volume fractions ( 5vol%), the
main effect of the SiC additions is to reduce the dimensions (diameter, depth) of the individual
pullouts. This is suggested to be a consequence of the change in fracture mode from intergranular in
alumina to transgranular in the nanocomposites. For greater additions of SiC nanoparticles
(10vol%), the brittle fracture responsible for the cracking is also suppressed, and it is proposed that
this is a consequence of the blocking of the formation of the long twins or dislocation pileups that
are thought to be responsible for crack initiation by intragranular SiC particles (i.e. a form of slip
homogenisation).
Melting Behaviour and Surface Structure of Glazes Containing Wollastonite and Dolomite
Authors: Kronberg Thomas , Hupa Leena , Fröberg Kaj
Published: March 2009

The influence of wollastonite and dolomite on melting behaviour and crystallization was
studied for 25 raw glazes. The melting behaviour was observed by hot-stage microscopy. The
glazes were also fired industrially both in a fast-fired gas kiln for floor tiles (50 min) and in a
traditional gas kiln for sanitaryware (25 hours). The surface composition and structure of the glazes
were studied by SEM/EDXA. The crystalline phases in the glazes were identified by XRD. Main
crystalline phases found in the glazes were wollastonite and diopside. Fusibility and surface
structure on the raw glazes containing wollastonite and dolomite as raw materials depended both on
the total content and the ratio of CaO and MgO in the glaze. Low content of alkaline earths gave
incomplete fusion, while high content gave extensive crystallization. The results can be applied to
tailor raw glaze compositions for a desired surface structure to be fired at a certain fusion
temperature.
Models, Methods & Madness: Ceramic Components Made with Highly Reactive Lithium Hydride
Authors: Broughton Duncan A. , Towndrow P.F. , Slater W.G. , Awbery R.P. , Joy Jonathan S. , Bartram K.J. , Grant D.M. , Parkes C.J. , Wade J.
Published: March 2009

AWE is a world center of excellence in lithium hydride technology and has 50 years of
experience in research, characterisation and manufacture of lithium hydride artifacts. Because of its
affinity for water, lithium hydride is handled under ultra-dry conditions, in argon or nitrogen filled
glove boxes. Even when handled with extreme care though it still picks up traces of moisture in the
gas atmosphere and the resulting material, when fabricated into shapes, continually outgasses very
low levels of hydrogen.
Lithium hydride is a pale grey polycrystalline solid, compacted to less than 100% theoretical density.
The generation of hydrogen gas is a major concern as it may be fielded in sealed metal containers
that are susceptible to attack by hydrogen. For this reason, the outgassing has been the subject of
intensive study. It is therefore surprising that its chemical properties are not better understood,
properties that are fundamental to developing a model of the materials ageing behaviour.
This paper will present our current research investigating the mechanisms of hydrogen outgassing,
enhancing specific analytical techniques to probe the unique chemistry, and using our knowledge to
improve resultant ceramic components.
Powder Injection Moulding (PIM) of Mesophase Carbon with Water-Based Binders
Authors: Gruhl Michael , Derfuss B. , Rottmair Christian , Volek Andreas , Singer Robert F.
Published: March 2009

Since there are no net-shape techniques for complex parts made of mesophase carbon
available yet, this work focuses on a powder injection moulding (PIM) approach. The single biggest
problem to overcome here is the overlap of debindering and pyrolysis/sintering of mesocarbon
when using conventional binders, causing high porosity and cracks. Water-based binders with agar
as gelling agent can avoid this problem effectively by removing the binder in an optimized drying
step. The subsequent sintering can then be carried out at high heating rates, leading to better
densification and good mechanical properties. Furthermore, the dependency of the rheological
properties of the water-based feedstock on its water content is investigated.
Electrophoretic Deposition as Shaping Technique - A CAM Approach
Authors: Zeiner Johannes , Nold Alexander , Clasen Rolf
Published: March 2009

Electrophoretic deposition (EPD) is a potential-enhanced technique for fabricating near-netshaped
geometries. Its advantage is the independence of particle velocity from particle size so
that optimum package densities are achieved by using powder mixtures. If the deposit is
formed on a membrane that is located between the two electrodes, aqueous suspensions can
be used because the formation of bubbles caused by the electrolytic decomposition of water
and the deposition are separated in space. Combining EPD with a CAM system, any structure
can be individually near-netshaped. In the present study, the geometry for an electrode for the
use with a CAM system is theoretically developed by simulating the distribution of the
electric field in EPD and finally fabricated in order to investigate its deposition properties.
First of all, spot-wise deposits are fabricated on a membrane so that theoretical predictions
and experimental results can be compared. Secondly, a translative motion of the electrode
along the membrane is controlled by a CAM system. The so fabricated two-dimensional
structures are rectangles and circles whereas the fineness as well as the structural integrity are
investigated. This approach will be further developed in future to enable the fast fabrication of
individual geometries with excellent green body properties.
A New Fabrication Method of Porous Ceramics Using Unidirectional Solidification
Authors: Ueno Shunkichi , Lin Li Ming , Nakajima Hideo
Published: March 2009

A new fabrication method of porous ceramics using unidirectional solidification was proposed in this
paper and the role of silica additive on the formation of porous alumina structure was discussed. A
porous alumina was formed by unidirectional solidification process that was conducted using floating
zone melt method in hydrogen atmosphere at normal pressure. The effect of silica additive on the
porosity and the pore size of the solidified samples was examined. The porosity of the solidified
samples increased with increase of silica contents. On the other hand, the pore size decreased with
increase of silica content. The average pore size of 10% and 20% silica added samples were 0.396
mm and 0.184 mm, respectively.
Synthesis of Highly Monodispersed Core/Shell Mesoporous Silica Spheres
Authors: Yano Kazuhisa , Nakamura Tadashi , Nozaki Hiroshi , Suzuki Noritomo , Akimoto Yuusuke
Published: March 2009

Particle size development of monodispersed mesoporous silica spheres (MMSS) was investigated by
laser scattering measurement, TEM and XRD in situ. Smaller particles suddenly appeared after the
commencement of the experiment, then growing homogeneously to larger particles. It is assumed that
residual silica precursors in solution preferentially reacted with existing particle surface silanol,
preventing generation of new particles. This leads to the formation of monodispersed particles. Based
on the mechanism, monodispersed mesoporous silica spheres with core/shell structure have been
newly synthesized.
Processing and Properties of Porous Al2O3 by Slurry Foaming Combined with Gelcasting
Authors: Ha Jung Soo , Lim Byong Gu
Published: March 2009

Porous ceramics are essential for a variety of technical applications such as thermal
insulators, filters, catalyst supports, gas sensors, bone graft substitutes, etc. Of numerous processing
methods, the slurry foaming method is advantageous in producing porous ceramics with a cellular
structure with high degrees of shape complexity and control of pore size and connectivity. It
combines foaming and setting of a ceramic slurry. The gelcasting employing in situ polymerization of
organic monomers is superior to other setting methods utilizing thermal gelation of agar, carrageenan,
gelatine, starch, or egg white in green strength and machinability. Previously unusual acrylic (or
acrylate) monomer was used to produce porous Al2O3 and hydroxyapatite. In the present work,
porous Al2O3 was prepared by the slurry foaming method with acrylamide monomer, commonly used
in gelcasting for producing dense ceramics. The foaming and gelation behavior was investigated with
the parameters such as the type and concentration of surfactant (i.e. foaming agent), solid loading,
and the concentrations of initiator and catalyst. The density, porosity, microstructure, and strength of
the resulting samples were characterized.
Microwave-Material Interaction in Oxide Ceramics with Different Additives
Authors: Willert-Porada Monika , Negahdari Zahra , Gerdes T. , Müller Achim , Paneerselvam M.
Published: March 2009

A systematic study upon microwave (2.45 GHz frequency) and conventional heating (resistance
heating furnace) was undertaken on porosity, grain growth and densification of commercial grade
Al2O3-ceramics doped with MgO (aliovalent doping), with ZrO2 (grain boundary pinning) and with
additives promoting elongated grain growth (LaAlO 3 and La2O3, AlPO4). Processes accompanied
by a strong non-equilibrium situation, e.g., dissolution, segregation, vacancy formation, are
influenced by the presence of the microwave field during heat treatment, visible on microstructure
differences of microwave as compared to conventionally sintered samples. Regular grain growth is
almost not affected by the microwave field, but the on-set of exaggerated grain growth and pore
coalescence is delayed and occurs at higher density as compared to conventional sintering. Such
microstructure differences seem to be more pronounced if the surface to volume ratio of the
samples is low, therefore volumetric heating has a larger contribution to transport phenomena as
compared to small samples.
Microwave Assisted Modification and Coating of Carbon Materials
Authors: Wolf Hannes , Pajkic Z. , Willert-Porada Monika
Published: March 2009

In this work, a fluidized bed process for microwave plasma assisted CVD of metals,
metal carbides and metal nitrides on carbon and graphite materials is presented. Boron coated
graphite produced in this reactor was found to show increased specific capacity and electrical
conductivity compared to uncoated graphite when used as anode in lithium ion-battery. Parameters
for uniform coating of carbon fibers with aluminum based ceramics were found for decomposition
of trimethylaluminum precursor in a microwave plasma.
Production Scale m3 Batch Furnace for Hybrid-Heating and Microwave Sintering
Authors: Gerdes T. , Willert-Porada Monika , Park Ho Seon , Schmidt A.
Published: March 2009

Production scale inert atmosphere microwave sintering has not been successful yet, mainly because
of lack of suitable equipment. For sintering in air microwave furnaces are available at different
industrial scale, e.g., gas-microwave hybrid heated batch kilns or microwave “adiabatic casket”
tunnel kiln [1]. Inert atmosphere furnaces require vacuum and gastight coupling of microwave
energy. In the State of the Art technology, microwave-coupling windows represent a heat sink
inside the sintering furnace. Although, radiation heat loss at temperatures > 1600 °C can be reduced
by using a thermally insulating casket inside the microwave furnace, heat loss and temperature
gradients caused by the microwave transparent windows are still not acceptable. Therefore, a new
concept was developed assisted heating in inert atmosphere sintering furnaces, enabling high power
microwave coupling by means of high temperature resistant antennas [2]. This paper presents
microwave sintering results of commercial powder metallurgical (PM)-parts, details of the antenna
system and the processing technology.
Development of Elastico-Luminescent Nanoparticles and their Applications
Authors: Xu Chao Nan , Li C. , Imai Y. , Yamada H. , Adachi Y. , Nishikubo K.
Published: March 2009

Recently we have proposed that stress distribution of a subject can be visualized by
utilizing a novel mechanoluminescence phenomenon that can give intense visible light emission by
application of mechanical stress. As the luminescence intensity is proportional to the time-variation
of strain energy in the elastic region, we call it elastico-luminescence. In order to realize a high space
resolution in such visualization for stress distribution, we aim to develop strong elastico-luminescent
nanoparticles, such as a controlled structure of α-SrAl2O4:Eu (monoclinic phase). The processing of
the nanoparticles, the property and the applications will be reported in the present work.
Fracture Resistance of Ceramics: Direct Measurements
Authors: Gogotsi George
Published: March 2009

Fracture resistance of ceramics is evaluated by flaking off the specimen edge and chip
scar surfaces are examined. The fracture resistance characteristic was calculated from the results of
direct measurements that did not make use of linear fracture mechanics concepts, which is typical of
conventional fracture toughness test methods. A fracture resistance test method termed the edge
fracture (EF) method is discussed. This method is built upon measuring the flaking resistance FR on
indentation of the specimen. The FR values for homogeneous elastic ceramics are proportional to the
KIc ones determined by the SEVNB method. Flaking resistance vs chip size relationships (R-lines)
are derived. Data analysis was built upon statistically reliable measurements on advanced alumina,
zirconia, scandia, and silicon nitride ceramics.
Non Conventional Synthesis of Monoclinic Celsian from Ba-Exchanged Zeolite A: Study of the Effect of Residual Na and Forming Pressure
Authors: Ferone C. , Pansini M. , Andreola Fernandanora , Barbieri Luisa , Siligardi Cristina , Manfredini Tiziano
Published: March 2009

Four samples of Ba-exchanged zeolite A, bearing 0.27, 0.43, 0.58 and 0.74 meq/g Na residual
amounts, were thermally treated in the temperature range 200-1500 °C for times up to 28 hours.
The same samples were pressed at 30 and 60 MPa to manufacture cylindrical pellets, which were
thermally treated at 1300 °C for 5 hours. Thermally treated materials were characterized by room
temperature XRD. The sequence of thermal transformations that Ba-exchanged zeolite A undergoes
(zeolite ® amorphous phase ® hexacelsian ® monoclinic celsian) and the strong mineralizing
action developed by Na are confirmed. Pressing the Ba-exchanged zeolite A powder-like samples to
obtain cylindrical pellets is found to expedite the sluggish final phase transition hexacelsian ®
monoclinic celsian. The optimum residual Na content of Ba-exchanged zeolite A to be transformed
into monoclinic celsian is assessed to range between 0.27 and 0.43 meq/g.
Combustion Synthesis of α-Si3N4 Powder under Low Nitrogen Pressure
Authors: Chang Chih Wei , Chung Shyan Lung
Published: March 2009

A combustion synthesis reaction has been developed for the α-Si3N4 powder under low
nitrogen pressure. Si and solid state nitrogen source were used as the reactants, and ammonium
halide powders were added as a catalytic agent. These powders were mixed and pressed into a
cylindrical compact and wrapped up with an ignition agent (i.e., Ti + C). The synthesis reaction was
triggered by combustion of the igniting agent. The product as synthesized is composed mostly of
α-phase and in the form of agglomerated fine particles (0.1-1 μm in diameter). The effects of the
additives and other experimental parameters on the process were investigated and a possible
reaction mechanism was also proposed.
In Situ Ultrahigh Vacuum Transmission Electron Microscope Investigations of Dynamical Changes of Nanostructures on Silicon
Authors: Chen Lih Juann , Wu Wen Wei , Liu C.H.
Published: March 2009

In situ ultrahigh vacuum transmission electron microscope (TEM) is a powerful tool to
investigate the dynamic changes of nanostructures on silicon. By observing growth and phase
transitions in situ, understanding of their mechanisms can be used to model relevant processes. With
the precise knowledge of the changes occurred on an atomic level, accurate control of the growth
process can be achieved. The dynamical changes occurred on the nano scale are often unexpected,
which also underscores the importance of the approach. In this presentation, we highlight two
examples to demonstrate the unique capability of in situ TEM to study the dynamical changes. The
examples include collective movement of Au nanoparticles and directed movement of Au-Si
droplets on Si bi-crystal.
Magnetic Mapping - A Way to Test and Understand Current Flows in Thin and Bulk Superconductors
Authors: Granados X. , Iliescu S. , Bozzo B. , Bartolome E. , Puig Teresa , Obradors X. , Amorós J. , Carrera M.
Published: March 2009

Nondestructive testing of superconducting blocks and thin films is a worth point in their
development and their industrial production. The most intrinsic characteristic to be tested is the
critical current, so is the maximum current can be carried in the superconducting state. The
measurement of the current flowing through the samples could be done by direct transport
experiments but this means using specific samples, and only the mean current may be found.
Distribution of current density in the sample is more relevant because it yields the map of inhomogeneity
of the samples, and its effect in the current density distribution.
Magnetic measurements have been developed by Hall scanning and magneto-optical effect,
allowing the mapping of the component of the magnetic field perpendicular to a surface of the
sample created by the current distribution. By solving the inverse Biot-Savart problem a map of
current densities can be obtained. We will present the status of the magnetic measurements obtained
by exploring superconducting bulks and tapes magnetized by an external field and the magnetic
map generated by the current carried through superconducting wires.
MgB2 Composite Superconductors Made by Ex Situ and In Situ Process
Authors: Kováč Pavol , Hušek I. , Melišek T.
Published: March 2009

Generally, two basic routes called as in-situ and ex-situ process are used for composite
MgB2 wires now. Mentioned processes have been used for making of single-core composite wires.
The applied heat treatment parameters influence the microstructure of MgB2 phase, critical
temperature and critical current density, but it has also decisive effect on the MgB2/metal reaction.
It was found that the transport current densities are much more sensitive to the used sheath material
than critical temperatures. The main factors limiting the transport current density are cracks
introduced by deformation and porosity caused by the boron diffusion in ex-situ and in-situ wires,
respectively.
Preparation and Properties of Advanced MgB2 Wires and Tapes
Authors: Goldacker Wilfried , Schlachter Sonja I.
Published: March 2009

Only five years after the discovery of superconductivity in MgB2 first wires and tapes are
used in technical applications. Different companies started to produce conductors with length above
1 km and to demonstrate their feasibility for different applications with small demonstrator coils.
However, the physical and technical performance of these conductors is still significantly below the
potential of this material and furthermore MgB2 conductors stand in strong competition with
technical NbTi wires. This contribution gives a review about different approaches of MgB2
conductor development, about conductor performance and the potential for further improvements.
Preparation of Partial-Melted Sm-Ba-Cu-O Bulk Superconductor
Authors: Imao Hiroya , Matsumoto Kousuke , Kishida Satoru
Published: March 2009

We prepared SmBa2Cu3Oy (SmBCO) superconducting bulks by partial melting growth
with a top seed. From the results, we found that the SmBCO bulks prepared by melting process
showed good superconductivity, where the critical temperature Tc and the temperature transition
width ΔT of the bulk were 94K and about 1K, respectively. The as-prepared bulks required annealing
at 500°C for 24h to improve the superconductivity. However, the characteristics of the bulks may be
improved by more detailed study, for example optimum preparation and annealing conditions.
Logic Operation of SFQ Circuit Elements Made of YBCO Junctions
Authors: Tarutani Y. , Tsubone K. , Wakana H. , Adachi S. , Ishimaru Y. , Nakayama K. , Oshikubo Y. , Horibe O. , Tanabe K.
Published: March 2009

YBa2Cu3O7-x(YBCO) ramp-edge junction technologies have been developed for
fabricating high-operating-temperature SFQ(Single Flux Quantum) circuits. The Ic(critical current)
spread that is the key parameter for integrating junctions could be decreased to 8% for a
1000-junction array that was formed on a groundplane. The background technologies that enabled
this uniform junction characteristic are precise control of the counter-electrode deposition-conditions
and deposition of the extremely smooth multiplayer that showed the roughness as small as 2 nm.
Based upon these ramp-edge junction technologies, oxide SFQ-circuit-elements were fabricated and
their logic operations were investigated. SFQ circuit elements such as a confluence buffer, a set-reset
flipflop, and a toggle flipflop have been fabricated and their logic operations were measured by using
an SFQ-dc converter. Both toggle flipflops that have one output and two outputs have been
fabricated. These circuits could be operated up to the temperature of near 60 K under finite operating
margins. These experimental results enable us to further develop fuctional and much more integrated
SFQ circuits.
kA-Class High-Current HTS Conductors and Windings for Large Scale Applications
Authors: Leghissa Martino , Hussennether Volker , Neumüller Heinz Werner
Published: March 2009

Multistrand conductors with kA-class current capacity are a key requirement for many
large scale applications of HTS in power engineering and magnet technology. Siemens has
developed a cabling technology for continuously transposed conductors (CTC) for transformer and
generator applications with critical current up to 1.2 kA at liquid nitrogen temperature. For
technical issues of coil winding several demonstrator coils were fabricated in solenoid and racetrack
geometry. The current capacity of the CTCs and of the coils are in agreement with model
calculations considering magnetic field distributions within the conductor and coils, respectively.
To account for mechanical loads during operations such as Lorentz forces and centrifugal forces
robust conductors are required. We constructed dedicated devices in order to study the performance
of continuously transposed conductors in coil-like geometry.
Development of an HTS Power Cable Based on YBCO Tapes
Authors: Mukoyama S. , Yagi M. , Kashima N. , Yamada Yutaka , Shiohara Yuh
Published: March 2009

Many technical problems need to be developed in order that a high temperature
superconducting (HTS) cable will use in a real power network. A second-generation HTS tape
(YBCO coated conductor) has potential of making its AC loss lower than that of a BSCCO tape
because the superconducting layer of a YBCO tape is thinner than that of a BSCCO tape. Moreover,
cost of a YBCO tape will become less than that of a BSCCO tape in future because quantity consumed
of costly component (such as silver) in a YBCO tape is less than that in a BSCCO tape. Considering
these, an HTS power cable that using YBCO tapes will become an economical choice compared with
a conventional XLPE cable or a BSCCO HTS cable.
HTS power cables using YBCO tapes have been developed in the Japanese national projects. HTS
conductors were fabricated by Furukawa and YBCO tapes were manufactured by ISTEC SRL and
Chubu Electrical Power Company, and these properties were measured.
Status and Prospects of HTS Synchronous Machines
Authors: Neumüller Heinz Werner , Klaus G. , Nick W.
Published: March 2009

Up to now most of the efforts for developing HTS technology have been directed
to devices for grid applications. However, HTS synchronous machines as motors and
generators become more and more interesting within the world-wide development programs.
Replacing the copper winding of the rotor by an HTS one and introducing an iron-less aircore
stator winding the very compact HTS machine has less than half the weight and volume,
higher efficiency and an excellent operational behavior when compared to the conventional
devices. These features make HTS rotating machines very attractive for e.g. ship drives and
industrial applications for the processing industry and power generation in power plants and
wind parks. World-wide, HTS machines have already demonstrated their advantages and
technical feasibility. The prototypes are ranging from the 5 MW low-speed high-torque
propulsion motor to the high-speed 3600 rpm 4 MVA HTS generator. Feasibility studies
clearly show the financial benefits when introducing high-efficient HTS wire based rotors
into a large scale power generator systems. At present, most of the industry driven activities
take place in the United States, Germany, Japan and Korea and are mainly directed towards
applications aboard ships. Further potential applications as well as the technical and economic
benefits will be discussed.
Long Length MgB2 Conductors for Industrial Applications
Authors: Malagoli A. , Grasso Giovanni , Vignolo Maurizio , Tumino Andrea , Braccini V. , Bernini Cristina , Tropeano M. , Siri A.S. , Nardelli Davide , Modica Marco
Published: March 2009

In spite of the relatively short time dedicated to the development of MgB2 conductors since its
discovery in 2001, a remarkable progress has been already achieved in terms of critical current
density, homogeneity of the conductors and reproducibility of the results over long lengths. Unlike
other HTS and LTS materials, MgB2 conductor processing is more open to a number of
improvements and modifications that help in making it more attractive for several DC and AC
applications. Up to now our work has been focused on the improvement of the production capacity
in order to allow for the assembly of large prototype magnets to test the capability of MgB2 to
maintain the present level of performance over very long lengths. Long MgB2 tapes of about 1600
m with superconducting and mechanical properties suitable for making low field magnets are
already available. Presently we are focusing on the enhancement of the irreversibility field. This
would open the possibility of using MgB2 also for high field applications.
Preparation of Strontium Vanadate Sr3V2O8 as Additive to Bi-Based Superconductors
Authors: Rubešová K. , Sýkorová Dagmar
Published: March 2009

The phase evolution and properties of strontium vanadate Sr3V2O8 were investigated
using different method of preparation: solid state reaction and two wet-route techniques (colloidal
route and sol-gel method - polymerized complex route). DTA/TG study showed decomposition
temperatures of starting materials and helped to choose processing temperatures. XRD analysis was
used to determine phase evolution. Solid state reaction sample contained a small amount of Sr3V2O8
as soon as after the first calcinations, but 100% of Sr3V2O8 did not appear until whole procedure
was finished. Colloidal route turned out as an inconvenient method for preparation of pure phase.
The final colloidal route sample contained 80% of Sr3V2O8, residual volume corresponded to
Sr10V6O25. The most progressive phase evolution was detected in the sol-gel route. Raman an FTIR
spectroscopy detected evolution of the first amount of Sr3V2O8 after gel heating at 250°C for 2
hours. The pure strontium vanadate was prepared after heating at 800°C for 2 hours.
MgB2 Films, Fibres and Heterostructures Grown by an Innovative Hybrid Physical-Chemical Vapor Deposition Technique
Authors: Orgiani Pasquale , Cui Y. , Chen J. , Ferrando V. , Pogrebnyakov A.V. , Redwing Joan M. , Li Qi , Xi X.X.
Published: March 2009

In order to grown epitaxial magnesium diboride MgB2 films, fibers and heterostructures,
an hybrid physical-chemical vapour deposition (HPCVD) technique was developed, which
combines physical vapour deposition (PVD) with chemical vapour deposition (CVD).
The superconducting and normal-state properties of the MgB2 films are determined by the film
thickness. Above 3000Å, a Tc of 41.8 K, a ρ0 of 0.28 μΩ·cm, and a residual resistance ratio RRR of
over 30 were obtained. A carbon-containing metal-organic precursor was added to the carrier gas to
achieve carbon doping. As the amount of carbon in the film increases, the resistivity increases, Tc
decreases, and the upper critical field increases dramatically as compared to clean films. The selffield
Jc in the carbon doped film is lower than that in the clean film, but Jc remains relatively high to
much higher magnetic fields, indicating stronger pinning. The carbon doping approach can be used
to produce MgB2 materials for high magnetic-field applications. We report on structural and
superconducting properties of round MgB2 coated-conductor fibers on SiC fibers. The coating is
polycrystalline and composed of elongated crystallites. The pure MgB2 fiber shows a zero
resistance Tc of 39.3K. The carbon-alloyed fibers show a high upper critical field of 55T at 1.5K
and a high irreversibility field of 40T at 1.5 K. The result demonstrates great potential of MgB2
coated conductors for superconducting magnets. We also report structural and transport proprieties
of MgB2/MgO and MgB2/AlN multilayers. The epitaxial MgB2/MgO/MgB2 trilayers were grown
in-situ in the HPCVD system, while MgB2/AlN/MgB2 trilayers were deposited using an ex-situ
process. The results are promising for all-MgB2 planar Josephson junctions.
Interband Pairing Interaction in Magnesium Diboride Probed by Tunneling Spectroscopy
Authors: Schneider Rudolf , Geerk Jochen , Zaitsev Alexander G. , Heid Rolf , Bohnen K.P. , von Löhneysen H.
Published: March 2009

We report on the study of the interband pairing interaction in the two-band
superconductor MgB2 by tunneling spectroscopy using thin film tunnel junctions. The films
were deposited in situ by an approach comprising a conventional planar B sputter gun and a
special homemade Mg evaporator providing a high vapor pressure. For the tunneling
experiments sandwich-type crossed-strip tunnel junctions with a native MgB2 oxide as the
potential barrier and Al, In or Pb counterelectrodes were prepared. Voltage-dependent
differential conductance measurements revealed estimates of the barrier thickness and height
of 1.5 nm and 1.6 eV, respectively, and allowed us to determine the phonon-induced
structures in the tunneling density of states of the phonon-mediated superconductor MgB2.
The analysis of the reduced density of states using the standard single-band Eliashberg
equations yielded an effective electron-phonon spectral function accounting for the smaller
energy gap. A further analysis involving ab-initio LDA calculations and the two-band
Eliashberg equations revealed that the dominant feature in the effective spectral function, a
strong peak at 58 meV, was mainly due to the interband pairing interaction.
Application of Laser Technique on the Formation of Superconductive Layer on the Bulk of Press Formed Bi System - Evaluation of Mechanical Properties of the Treated Bulk
Authors: Miyazawa Hajime , Hotta Katsuyoshi , Shimizu Hiroyuki , Morita Mitsuaki , Hirose Haruo
Published: March 2009

In the study of the application of a laser technique on the bulk of press formed Bi system, the
authors have reported that a superconductive layer can be obtained underneath the laser melted layer.
In a continuing series of this study, this paper deals with the mechanical properties of the bulk laser
treated. Superconductive powder of Bi system, 2223 phase was pressed to form a disk specimen of
2 mm thick and 10 mm at 29 MPa to 196 MPa. Then a CO2 laser beam of output power 6 W to 9 W
was scanned linearly in air to melt the surface of the specimen to be subjected to the evaluation of
hardness and fracture strength. The experimental results showed that the values of microvickers
hardness of superconductive layer and melted layer are 135 and 105 respectively while that of the
specimen as press formed is as low as 45. The fracture strength of the laser treated specimen was
increased to 34 N from 15 N. The mechanical properties obtained deserve non sensitive handling in
a practical use of the treated bulk.
Basic Characteristics of the Single Layer Type Microwave Absorber in X Band Using Superconductor Powder
Authors: Hotta Katsuyoshi , Shimizu Hiroyuki , Watanabe Y. , Hirose Haruo
Published: March 2009

The purpose of this study is to examine the basic characteristics of the single layer type microwave
absorber in X band. Samples were produced from Bi system (2223) superconductor powder and
metallic powder and inserted into a wave guide system where the complex reflection intensity was
measured (The short circuit method) by using the vector network analyzer[1].
As the result, at the room temperature (300K), the reflection loss is apt to increase with increasing
the content of the Bi system superconductor powder. Furthermore, the measured value of the
reflection loss agreed with the value calculated from the complex permittivity εr* .
At liquid nitrogen temperature (77K) where the superconductor powders are in the superconducting
state, some differences occurred between the calculated value and the measured one of the reflection
loss.
For the metallic powders, copper powder showed good agreement between the calculated and the
measured of reflection loss.
For the magnetic material, it was concluded that the theoretical formula under consideration of
complex permeability μr* should be derivated.
Use of Electric Discharge Sintering for Elaboration of Diamond Tools
Authors: Raychenko O.I. , Istomina T.I. , Morozova R.O. , Morozov I.A. , Derev'yanko O.V.
Published: March 2009

A number of installations for electric discharge sintering of powder materials is
developed. There are installations in which energy is delivered by following currents:
1) superposition of the direct and alternating (with frequency up 7900 Hz) currents, 2) alternating
current (50 Hz). The sintering is carried out in conductive (graphite) moulds. The sintering is
often done in thermal and electric insulator moulds (for example, ceramic on Si3N4 base, asbestos
cement). At sintering of metal-diamond composition in insulator moulds metallic electrodespunches
(steel) are used. Such a variant of sintering allows one its duration to short from ~900 s
down to ~60–150 s. This ensures complete safety of dimensions and operating characteristics of
diamond grains. The technologies of various diamond elements for tools for treatment of glasses
and soft stones (stone saws, tools in forms of tablets, rings). The preliminary pressure which is
applied to powder sample simultaneously with current was equal to ~10 MPa (~100 kg/cm2). The
end pressure was equal to ~100 MPa (~1000 kg/cm2). The current density was equal to ~700–
1200 A/cm2. Tests of diamond tablets (diamond 20/14 mkm, binder 80 % Cu+20 % Sn) at
grinding of glass had shown: the abrasivity of tablets with common diamonds is equal to ~50
g/(cm2 min), and abrasivity in case with diamonds annealed in hydrogen is equal to ~70 g/(cm2
min).
Vacuum Thermionic Energy Conversion Based on Nanocrystalline Diamond Films
Authors: Koeck F.A.M. , Garguillo J.M. , Smith John R. , Tang Y.J. , Bilbro G.L. , Nemanich Robert J.
Published: March 2009

Vacuum thermionic energy conversion achieves direct conversion of heat into electrical
energy. The process involves thermionic electron emission from a hot surface and collection of the
electrons on a cold surface where the two surfaces are separated by a small vacuum gap. Results
are presented which indicate that nanocrystalline diamond films could lead to highly efficient
thermionic energy conversion at temperatures less that 700°C. A critical element of the process is
obtaining a stable, low work function surface for thermionic emission. Results are presented which
establish that N-doped diamond films with a negative electron affinity can exhibit a barrier to
emission of less than 1.6 eV. Films can be deposited onto field enhancing structures to achieve an
even lower effective work function. Alternatively, nanocrystalline diamond films prepared with S
doping exhibit field enhanced thermionic emission and an effective work function of ~1.9 eV. The
field enhanced structures can reduce the effect of space charge and allow a larger vacuum gap. The
possibility of a low temperature nanocrystalline diamond based thermionic energy conversion
system is presented.
Shape Memory Alloys for Biomedical Applications
Authors: Hannula Simo Pekka , Söderberg Outi , Jämsä Timo , Lindroos V.K.
Published: March 2009

NiTi
shape memory alloy (SMA) products appeared to the medical markets in 1980’s,
their global market being more than US$ 130 billion in 2002. In most medical applications material
must be biocompatible. NiTi
offers the bodytemperature
activated shape memory effect (SME),
superelasticity (SE) and the damping capacity, which all can be applied in medical use. The dental
arch wires and stents are benefiting from SE. The NiTi
vena cava filters obtain their umbrella
shaped mesh when SMEactivated.
Generally the NiTi
tubes and guidewires are applied in the
minimally invasive medical procedures and in the interventional radiology. There are numerous
steerable, hingeless, kink resistant, highly flexible clinical instruments that may provide constant
force. NiTi
is used for the dental implants and the attachments of the partial dentures and for the
orthopaedics. In the latter one the main applications are the clamps for connecting bone fractures or
parts for e.g. the spinal bentcalibration
bar. Miniaturization has enabled small SMAactuators
that
are applicable in active endoscopes with allround
bending and in actuators for kidney or heart
pumps. The main risks using NiTi
are the insecure fatigue life and possible cytotoxicity.