Advances in the Science and Engineering of Functional Materials 3

Advances in the Science and Engineering
of Functional Materials
3rd Workshop between
RWTH Aachen University and Seoul National University
30th & 31st October 2014
Institute of Physical Chemistry (IPC)
RWTH Aachen University
Aachen, Germany
ii
Financial assistance is gratefully acknowledged from
International Office
BK21PLUS SNU Materials Division for
Educating Creative Global Leaders
iii
Thursday,
30.10.
Morning Session
9.00 – 9.30
Prof. Doris Klee
Vice-Rector for Human
Resources Management and
Development,
RWTH Aachen University
Greetings and Opening
Prof. Ki-Bum Kim,
Head of Department,
Materials Science and
Engineering,
Seoul National University
9.30 – 10:00
Alexander Böker
Nanoporous Ultra-thin
Membranes formed via SelfAssembly of Protein-PolymerConjugates
10.00 – 10.30
Jeong-Yun Sun
Tough Hydrogels & Stretchable
Ionics
10.30 – 11.00
Coffee Break
11.00 – 11.30
Woong-Ryeol Yu
New Electrospinning Nozzle to
Improve Jet Stability and Its
Application to Manufacture of
Multi-layered Carbon Nanofibers
11.30 – 12.00
Martin Salinga
Switching Kinetics in Phase
change Materials
12.00 – 12.30
Young-Chang Joo
Structure-property relationship
of amorphous materials for
electronic devices
12.30 – 14.00
Lunch
iv
Thursday,
30.10.
Afternoon Session
14.00 – 14.30
Regina Dittmann
From Defects to Future oxidebased resistive ReRAM
14.30 – 15.00
Miyoung Kim
Formation of nano-filaments in a
SrTiO3 thin film
15.00 – 15.30
Manfred Martin
Bulk mixed ion electron
conduction in amorphous
gallium oxide causes memristive
behavior
15.30 – 16.00
Coffee Break
16.00 – 16.30
Han-Ill Yoo
Kinetic Unmixing and
Decomposition of Ternary
Oxides under Electric Fields
16.30 – 17.00
Marjana Lezaic
Ab-initio Design of Multiferroic
Materials
17.00 – 17.30
Seungwu Han
Searching for functional oxides
using high-throughput
ab initio screening
17.40 – 18.00
Double degrees for Ph. D.
students
19.30
Conference Dinner
v
Friday, 31.10.
Morning Session
9.00 – 9.30
Doh-Yeon Kim
Future; Sustainability and Asia
9.30 – 10.00
Ulrich Simon
Electrical Characterization of
Individual Inorganic
Nanoparticles
10.00 – 10.30
Ki-Bum Kim
Nanofabrication for BioInformation Technology
10.30 – 11.00
Coffee Break
11.00 – 11.30
Norbert H. Menzler
Status of Anode-Supported
Solid Oxide Fuel Cell
Development at
Forschungszentrum Jülich –
Emphasis on Materials and
Microstructure Development of
Cells
11.30 – 12.00
Kisuk Kang
Development of Advanced
Materials for Li Rechargeable
Batteries
12.00 – 12.30
Christoph Broeckmann
Processing of Materials for
Oxygen Transport Membranes
12.30 – 13.30
Lunch
vi
List of Participants
Name
Affiliation
Email address
Prof. Alexander
Böker
DWI - Leibniz Institute for Interactive
Materials,
Forckenbeckstrasse 50, D-52056
Aachen, Germany
boker@dwi.rwth-aachen.de
Prof. Christoph
Broeckmann
Institute for Materials Application in
Mechanical Engineering,
RWTH Aachen University,
Augustinerbach 4, D-52062 Aachen,
Germany
c.broeckmann@iwm.rwthaachen.de
PD Dr. Roger A.
De Souza
Institute of Physical Chemistry,
RWTH Aachen University,
Landoltweg 2, D-52074 Aachen,
Germany
desouza@pc.rwthaachen.de
Prof. Regina
Dittmann
Peter Grünberg Institute (PGI-7),
Forschungszentrum Jülich GmbH,
Wilhelm-Johnen-Straße, D-52428
Jülich, Germany
r.dittmann@fz-juelich.de
Prof. Seungwu
Han
Department of Materials Science
and Engineering,
Mailstop 33-319, Seoul National
University, Seoul, Korea
hansw@snu.ac.kr
Prof. YoungChang Joo
Department of Materials Science
and Engineering,
Mailstop 33-311, Seoul National
University, Seoul, Korea
ycjoo@snu.ac.kr
Prof. Kisuk
Kang
Department of Materials Science
and Engineering,
Mailstop 33-107, Seoul National
University, Seoul, Korea
matlgen1@snu.ac.kr
Prof. Doh-Yeon
Kim
Department of Materials Science
and Engineering,
Mailstop 33-202, Seoul National
University, Seoul, Korea
dykim@snu.ac.kr
Prof. Ki-Bum
Kim
Department of Materials Science
and Engineering,
Mailstop 131-108, Seoul National
University, Seoul, Korea
kibum@snu.ac.kr
vii
Prof. Miyoung
Kim
Department of Materials Science
and Engineering,
Mailstop 33-312, Seoul National
University, Seoul, Korea
mkim@snu.ac.kr
Dr. Marjana
Lezaic
Peter Grünberg Institute (PGI-1),
Forschungszentrum Jülich GmbH,
Wilhelm-Johnen-Straße, D-52428
Jülich, Germany
m.lezaic@fz-juelich.de
Prof. Manfred
Martin
Institute of Physical Chemistry,
RWTH Aachen University,
Landoltweg 2, D-52074 Aachen,
Germany
martin@rwth-aachen.de
Dr. Norbert H.
Menzler
Institute of Energy and Climate
Research,
Forschungszentrum Jülich GmbH,
Wilhelm-Johnen-Straße, D-52428
Jülich, Germany
n.h.menzler@fz-juelich.de
Dr. Martin
Salinga
I.Institute of Physics (IA),
RWTH Aachen University,
Sommerfeldstr. 14, D-52074
Aachen, Germany
martin.salinga@physik.rwthaachen.de
PD Dr. Michael
Schroeder
Institute of Physical Chemistry,
RWTH Aachen University,
Landoltweg 2, D-52074 Aachen,
Germany
schroeder@rwth-aachen.de
Prof. Ulrich
Simon
Institute of Inorganic Chemistry,
RWTH Aachen University,
Landoltweg 1, D-52074 Aachen,
Germany
ulrich.simon@ac.rwthaachen.de
Prof. Jeong-Yun
Sun
Department of Materials Science
and Engineering,
Mailstop 33-108, Seoul National
University, Seoul, Korea
jysun@snu.ac.kr
Prof. Han-Ill
Yoo
Department of Materials Science
and Engineering,
Mailstop 33-106, Seoul National
University, Seoul, Korea
hiyoo@snu.ac.kr
Prof. WoongRyeol Yu
Department of Materials Science
and Engineering,
Mailstop 33-305, Seoul National
University, Seoul, Korea
woongryu@snu.ac.kr
1
Nanoporous Ultra-thin Membranes formed via Self-Assembly of
Protein-Polymer-Conjugates
Patrick van Rijn, Murat Tutus, Christine Kathrein, Nathalie C. Mougin,
Hyunji Park, Christopher Hein, Marco P. Schürings, and Alexander Böker
DWI - Leibniz-Institut für Interaktive Materialien, Lehrstuhl für Makromolekulare
Materialien und Oberflächen,
RWTH Aachen University, Aachen, Germany
Self-assembled membranes offer a promising alternative for conventional membrane
fabrication, especially in the field of nano-filtration. However, recent advances
pushing the developments in self-assembled membranes towards thinner
membranes with more selectivity are still limited with respect to active permeation
area, stability and responsiveness. Here we introduce a new pore-making strategy
which involves stimuli responsive protein-polymer conjugates self-assembled across
a large area of 5 cm2 using drying-mediated interfacial self-assembly. Proteins are
used as a sacrificial template which - upon denaturing - provide hydrophilic pores of
identical size. The permeation is controlled by temperature switching below and
above the lower critical solution temperature of the polymer. The membrane is
flexible and easily assembled on porous supports. A high mass transport was
measured and a size-selectivity of particles below 20 nm was determined, which is in
very good agreement with the size of protein used. This approach diversifies
membrane technology since various sizes and shapes of proteins can be used, in
addition to different responsive polymers generating a platform for “smart” selfassembled membranes.
References
[1] N.C. Mougin, P. van Rijn, H. Park, A.H.E. Müller, A. Böker Adv. Funct. Mater. 2011, 21, 2470.
[2] P. van Rijn, N.C. Mougin, D. Franke, H. Park, A. Böker Chem. Commun., 2011, 47, 8376.
[3] P. van Rijn, N.C. Mougin, A. Böker Polymer, 2012, 53, 6045.
[4] P. van Rijn, H. Park, K. Özlem Nazli, N.C. Mougin, A. Böker Langmuir, 2013, 29, 276.
[5] P. van Rijn, M. Tutus, C. Kathrein, N.C. Mougin, H. Park, C. Hein, M.P. Schürings, A. Böker Adv.
Funct. Mater. 2014, doi: 10.1002/adfm.201401825.
2
Tough Hydrogels & Stretchable Ionics
Jeong-Yun Sun
Department of Materials Science and Engineering,
Seoul National University, Seoul, Korea
Hydrogels are used as scaffolds for tissue engineering, vehicles for drug delivery,
actuators for optics and fluidics, and model extracellular matrices for biological
studies. The scope of hydrogel applications, however, is often severely limited by
their mechanical behaviour. Most hydrogels do not exhibit high stretchability; for
example, an alginate hydrogel ruptures when stretched to about 1.2 times its original
length. Some synthetic elastic hydrogels have achieved stretches in the range 10–
20, but these values are markedly reduced in samples containing notches. Most
hydrogels are brittle, with fracture energies of about 10 Jm-2, as compared to 1,000
Jm-2 for cartilage and 10,000 Jm-2 for natural rubbers. Intense efforts are devoted to
synthesizing hydrogels with improved mechanical properties; certain synthetic gels
have reached fracture energies of 100–1,000 Jm-2.
We have reported the synthesis of a new hydrogel from polymers that form ionically
and covalently crosslinked networks. Although such gels contain 90% water, they can
be stretched beyond 20 times their initial length, and have fracture energies of 9,000
Jm-2. Even for samples containing notches, a stretch of 17 is demonstrated. We
attribute the gels’ toughness to the synergy of two mechanisms: crack bridging by the
network of covalent crosslinks, and hysteresis by unzipping the network of ionic
crosslinks. Furthermore, the network of covalent crosslinks preserves the memory of
the initial state, so that much of the large deformation is removed on unloading. The
unzipped ionic crosslinks cause internal damage, but are healed by re-zipping. These
gels serve as model systems to explore mechanisms of deformation and energy
dissipation, and expand the scope of hydrogel applications.
Furthermore, as a new application, we have proposed a class of devices enabled by
hydrogel conductors that are highly stretchable, fully transparent to light of all colors,
and capable of operation at frequencies beyond 10 kHz and voltages above 10 kV.
We have created a transparent actuator that can generate large strains, and a
transparent loudspeaker that produces sound over the entire audible range. The
electromechanical transduction is achieved without electrochemical reactions.
3
New Electrospinning Nozzle to Improve Jet Stability and Its
Application to Manufacture of Multi-layered Carbon Nanofibers
Woong-Ryeol Yu
Department of Materials Science and Engineering and
Research Institute of Advanced Materials,
Seoul National University, Seoul, Korea
A new nozzle system for the efficient production of multi-layered nanofibers through
electrospinning is reported. Developed a decade ago, the commonly used coaxial
nozzle system consisting of two concentric cylindrical needles has remained
unchanged, despite recent advances in multi-layered, multi-functional nanofibers.
Here, we demonstrate a core-cut nozzle system, in which the exit pipe of the core
nozzle is removed such that the core fluid can form an envelope inside the shell
solution. This configuration effectively improves the coaxial electrospinning behavior
of two fluids and significantly reduces the jet instability, which was proved by finite
element simulation. The proposed electrospinning nozzle system was then used to
fabricate bi-, tri-, and tetra-layered carbon nanofibers.
4
Switching kinetics in phase change materials
Martin Salinga
I. Physikalisches Institut IA,
RWTH Aachen University, Aachen, Germany
Phase change materials are essential ingredients for next-generation electronic
memory devices and reconfigurable electronics for their ability to be switched
between states with very different resistivity within nanoseconds upon electrical
excitation, while being stable over many years otherwise. It is these materials’
characteristic combination of electronic excitability of their amorphous phase and
their unconventional structural transformations that makes this seeming contradiction
possible. Thorough experimental investigations of both phenomena allowed us to
gain deeper insights into the fundamental properties of this family of materials.
Recently the crystallization kinetics could be traced back to an extremely high fragility
of the undercooled liquid phase. A comprehensive model including the quenching
rate dependence of the glass formation and relaxation processes in the glass
managed to explain the different experimental observations reported in literature. Our
investigations of transient effects in electrical excitation of phase change materials
concentrate on the changes around the threshold for resistivity breakdown in the
amorphous phase. The discussion of the results from both studies give guidance to
experimentalists and theoreticians aiming for a fundamental understanding of the
physics of phase change materials.
5
Structure-property relationship of amorphous materials for
electronic devices
Young-Chang Joo
Department of Materials Science and Engineering,
Seoul National University, Seoul, Korea
Amorphous materials have been actively applied in electronic devices, due to their
unique properties originated from disordered atomic structure distinct from crystalline
materials. However, such devices suffer from the reliability issues originated from
their phase instability, and it is crucial to characterize and tune the phase stability for
the development of stable devices. In this study, mechanical stress analysis was
utilized to detect the structural changes and phase stability in amorphous films and to
predict the device functionalities.
The crystallization kinetics of the amorphous phase change materials were explored;
crystallization temperature (Tx), glass transition temperature (Tg), super-cooled liquid
region (Tx - Tg) of amorphous Ge2Sb2Te5 (GST) films doped with various elements.
Besides, the viscosity and the fragility were also determined. Doping effects on the
thermal stability and atomic mobility show successful matching with phase change
RAM characteristics; data retention and SET speed, respectively. The novel in-situ
measurement of mechanical stress and resistance were conducted to correlate two
phenomena.
Amorphous In-Ga-Zn-O (a-IGZO) is an active material for TFT, experiences phase
instability originated from interfaces. Surface-to-volume ratios of the a-IGZO film were
varied by thickness variation and the thickness dependence of the phase stability of
a-IGZO are discussed.
6
From defects to future oxides-based resistive ReRAM
Regina Dittmann
Peter Grünberg Institute (PGI-7),
Research Centre Jülich, Jülich, Germany
Flash memories and DRAM are ubiquitous today. However, a potential leap beyond
the limits of Flash (with respect to write speed, write energies) and DRAM (with
respect to scalability, retention times) emerges from redox-based switching effects
encountered in a large variety of metal oxides (ReRAM). Although first commercial
memories based on Ta2O5 thin films are available since 2013, the microscopic details
of the switching and failure mechanism are only rarely understood so far. Oxygen ion
transport and redox reactions on the nanoscale provide the essential mechanisms. In
contrast to most other applications of oxide thin films, point defects as well as
extended defects promote the switching processes and their presence is prerequisite
for a reliable device performance. The presentation will cover the current
understanding of the microscopic switching processes and the role of defects
extracted from a broad variety of spectroscopic investigations of resistively switching
oxide devices. Furthermore, we will discuss its implications on the device
performance such as switching time, switching power and retention time.
7
Formation of nano-filaments in a SrTiO3 thin film
Miyoung Kim
Department of Materials Science and Engineering,
Seoul National University, Seoul, Korea
Resistive switching memory (ReRAM) attracted considerable attention due to its
scientific implications and technological potential for non-volatile memory and related
applications. We investigate microstructures of a SrTiO3 thin film to elucidate
atomistic origin of unipolar resistive switching, for which we employ in-situ
transmission electron microscopy together with electron energy-loss spectroscopy.
Interestingly, it is revealed that there exists preferred orientational relationship
between the filaments and the neighboring SrTiO3 grains, which indicates that the
filaments are generated in specific grain boundaries. Additionally, co-generation of
Ruddlesden-Popper (RP) structure is often observed in the vicinity of the filament
structure. Morphology and crystal structure of the filaments are further examined
during repeated in-situ SET and RESET operation. This work provides insight on the
evolution of nano-filaments in oxides.
8
Bulk mixed ion electron conduction in amorphous gallium
oxide causes memristive behavior
Yoshitaka Aoki,a Carsten Wiemann,b Vitaliy Feyer,b Hong-Seok Kim,c
Claus Michael Schneider,b,d Han Ill-Yooc and Manfred Martina,c
a
Institute of Physical Chemistry,
RWTH Aachen University and JARA-FIT, Aachen, Germany.
b Peter Grünberg Institute (PGI-6) and JARA-FIT,
Research Centre Jülich, Jülich, Germany.
c Department of Materials Science and Engineering,
Seoul National University, Seoul, Korea.
d Fakultät für Physik and Center for Nanointegration Duisburg-Essen (CENIDE),
Universität Duisburg-Essen, Duisburg, Germany.
In thin films of mixed ionic electronic conductors sandwiched by two ion-blocking
electrodes, the homogeneous migration of ions and their polarization will modify the
electronic carrier distribution across the conductor, thereby enabling homogeneous
resistive switching. Here we report non-filamentary memristive switching based on
the bulk oxide ion conductivity of amorphous GaOx (x~1.1) thin films. We directly
observe reversible enrichment and depletion of oxygen ions at the blocking
electrodes responding to the bias polarity by using photoemission and transmission
electron microscopies, proving that oxygen ion mobility causes memristive behaviour.
The shape of the hysteresis I-V curves is tunable by the bias history, as found in the
mathematically derived memristor model. This dynamical behaviour can be attributed
to the coupled ion drift and diffusion motion and the oxygen concentration profile
acting as a state function of the memristor.
Y. Aoki et al., Nat. Commun. 5:3473 doi: 10.1038/ncomms4473 (2014)
9
Kinetic Unmixing and Decomposition of Ternary Oxides in
Electric Fields
Jakyu Chun,a Manfred Martina,b and Han-Ill Yooa
a Department
of Materials Science and Engineering,
Seoul National University, Seoul, Korea
b Institute of Physical Chemistry,
RWTH Aachen University, Aachen, Germany
A general expectation is that in a uniform oxygen activity atmosphere, cationelectrotransport induces a ternary or higher oxide, e.g., AB1+O3+, to kinetically
unmix unless the electrochemical mobilities of, say, A2+and B4+ cations are identically
equal, and eventually to decompose into the component oxides AO and BO 2 once
the extent of unmixing exceeds the stability range of its nonmolecularity . It has,
however, earlier been reported [Yoo et al., Appl. Phys. Lett., 2008, 92, 252103] that
even a massive cation electrotransport induces BaTiO3 to neither unmix nor
decompose even at a voltage far exceeding the so-called decomposition voltage Ud,
a measure of the standard formation free energy of the oxide (| G f |=nFUd) in classic
Gibbs sense. Here, we report that as expected, NiTiO3 unmixes at any voltage and
even decomposes if the voltage applied exceeds seemingly a threshold value larger
than Ud. We demonstrate experimentally that the electrochemical mobilities of Ni2+
and Ti4+ should be necessarily unequal for unmixing, Also, we show theoretically that
equal cation mobilities appear to be a sufficiency for BaTiO3 only for a
thermodynamic reason. The kinetic meaning of the decomposition voltage is
elucidated in comparison with the thermodynamic decomposition voltage in the
original Gibbs sense.
o
10
Ab-initio Design of Multiferroic Materials
Marjana Ležaić
Peter Grünberg Institute,
Research Centre Jülich, Jülich, Germany
Multiferroic materials display a simultaneous ferroelectric and magnetic order and are
currently one of the spots of high interest in spintronics investigations. The reasons
are numerous possible applications such as 4-bit memory and a possibility of electric
field controlled magnetization (or magnetic field controlled electric polarization).
Designing novel multiferroics with predefined desired properties is not an easy task,
due to an essential incompatibility of the physics driving the two functionalities,
ferroelectricity and magnetism. In the few materials that do possess a non-zero net
magnetisation along with a ferroelectric polarisation in a single phase, the problem
usually encountered is the low magnetic ordering temperature.
This talk will be dedicated to understanding the difficulties and to possible ways of
circumventing them, within a framework of ab-initio multiferroics design [1].
Furthermore, some applications of both bulk and of multicomponent layered
multiferroic systems will be discussed [2,3].
[1] Phys. Rev. B, 83, 024410 (2011)
[2] Nature Materials 9, 649 (2010)
[3] Phys. Rev. Lett. 111, 077601 (2013)
11
Searching for functional oxides using high-throughput ab initio
screening
Kanghoon Yim, Yong Youn, and Seungwu Han
Department of Materials Science and Engineering,
Seoul National University, Seoul, Korea
In this talk, I will present our recent efforts to identify functional oxides appropriate for
specific application targets, utilizing the high-throughput ab initio screening. First, we
try to find candidate dielectric materials that can be used in next-generation memory
(DRAM or FLASH) and logic (CPU) devices, based on the digital database of energy
gap, dielectric constant, and defect formation energies for a large collection of binary
and ternary oxides available on ICSD. Second, we try to identify ideal dopants for
ZnO when the material is used for electronic or energy devices. For these ends, we
develop a series of automation codes that can carry out ab initio computation of bulk
and defect properties of oxides efficiently and reliably.
12
Future; Sustainability and Asia
Doh-Yeon Kim
Department of Materials Science and Engineering,
Seoul National University, Seoul, Korea
At the beginning of 20th century, the world population was 1.6 billions. It has been
increased dramatically during last 100 years so that nowadays we are 7.3 billions.
This means that overall situation for human-being has been greatly improved, and
this is mainly due to the development of science and technology driven by
Europeans. Particularly, the industrial revolution stemmed from the invention of
steam engine has greatly changed the world. Why the industrial revolution happened
in Europe(Britain) rather than in Asia(China)? And then, will Asia be remained as a
follower rather than first-mover in future? In this talk, I’d like to discuss the
sustainability of modern civilization and the future role of Asia for all human-being.
13
Electrical Characterization of Individual Inorganic
Nanoparticles
Ulrich Simon
Institute of Inorganic Chemistry,
RWTH Aachen University, Aachen, Germany
Inorganic nanoparticles (NP) including metals, metal oxides, and chalcogenides
exhibit size dependent electrical properties. This makes such NP promising for
applications e.g. in energy conversion, information storage, or sensing devices.
However, most of these applications rely on the integration of a multitude of NP
instead of single ones. Thus, several applications utilize the integral properties of
ensemble of NP, rather than the distinct properties of the individual nanoscale
building blocks.
In order to take full advantage of the nanoscale size for ultimate miniaturization,
experimental techniques are required that allow analyzing the properties of individual
particles in an environment that approaches the conditions to be applied for the
desired application.
Therefore we developed and evaluated methods which allow us to study the
electrical properties of individual metal, metal oxide and chalcogenide NP either in a
nanoelectrode (NE) configuration [1] or by means of a flexible nanomanipulator (NM)
set-up [2]. In this report we will introduce our recent results on the charge transport
properties of individual sub-20 metal NP in a lithographically fabricated NE and of
sub-micron sized metal oxide and chalcogenide NP contacted in a NM set-up, which
exhibit resistive switching properties and which therefore are considered promising
for resistive memory devices.
[1] M. Manheller, S. Karthäuser, R. Waser, K. Blech, U. Simon, J. Phys. Chem. C,
2012, 116, 20657-20665; N. Babajani, P. Kowalzik, R. Waser, M. Homberger, C.
Kaulen, U. Simon, S. Karthäuser, J. Phys. Chem. C, 2013, 117 (42), 22002–22009
[2] J. Timper, K. Gutsmiedl, C. Wirges, J. Broda, M. Noyong, J. Mayer, T. Carell, U.
Simon, Angew. Chem. Int. Ed., 2012, 51 (30), 7586-7588
14
Nanofabrication for Bio-Information Technology
Ki-Bum Kim
Department of Materials Science and Engineering,
Seoul National University, Seoul, Korea
The fabrication of nanometer scale features such as quantum dots and quantum
wires in a controllable and economically viable manner is one of the essential
requirements for the production of future ultra-high-density electronics, photonics,
magnetic, and biological sensors and devices. In this talk, I will discuss a new
method of patterning nanometer-scale periodic structures with much improved
throughput by employing the various crystalline lattice images available in high
resolution transmission electron microscopy (HRTEM) which is named as AIPEL
(Atomic Image Projection Electron-beam Lithography).
Then, I will change the subject to the nanopore fabrication by utilizing the same
transmission electron microscope. The demonstration of single molecule sequencing
with biological nanopores, most notably α-hemolysin protein that spontaneously
embedded themselves in a lipid bilayer, greatly accelerates the work to mimic this
structure in solid-state. Accordingly, various methods were proposed to form sub-10
nm, preferably down to 2 nm scale nanopore on the membrane structure utilizing
either ion beam or electron beam perforation. These structures were interposed
between cis- and trans-liquid chambers and successfully utilized to monitor the flow
of DNA molecules by measuring the ionic current between cis- and trans-chambers.
While these works presented interesting results, namely, demonstrating the transport
of single stranded DNA through the nanopore when an electrical bias is applied, the
scientific information one could harvest from these experiments is quite limited. Most
importantly, the translocation time is too fast to obtain the information on the types of
bases. In order to analyze the base types (namely, A, T, G, C), which is separated
only 0.34 nm, it is important to design a structure where the translocation of DNA
through the pore is well controlled. Recently, our group, in collaboration with the
members of IBM, reported the formation of multiple nanopore structure by utilizing
electron beam lithography and atomic layer deposition (ALD) with the pore size less
than 10 nm. More importantly, this structure has built-in gate electrode, just like MOS
transistors for semiconductor device, and can control the transport of ions. It is
expected that this device can also be utilized to control the transport of DNA and
other bio-molecules.
15
Status of Anode-Supported Solid Oxide Fuel Cell Development
at Forschungszentrum Jülich – Emphasis on Materials and
Microstructure Development of Cells
Norbert H. Menzler
Institute of Energy and Climate Research IEK-1,
Research Centre Jülich, Jülich, Germany
The presentation gives an overview about the status of anode-supported solid oxide
fuel cell (ASC) development at Forschungszentrum Jülich. The ASC is based on a
tape-cast Ni(O)-8YSZ support and screen printed functional layers like anode
(Ni(O)/8YSZ), electrolyte (8YSZ), diffusion barrier (GDC) and mixed ionic-electronic
conducting LSCF cathode. State-of-the-art single cells obtain current densities of
approx. 1.3A/cm² at 0.7V and 700°C. In stack environment approx. 0.8A/cm² can be
reached. By introducing thin-film electrolytes and barrier layers applied by e.g. solgel-technique or physical vapor deposition even higher current densities can be
realized.
In the past 10 years of development the focus has been lying firstly on choosing the
best materials combinations with respect to single layer physical, mechanical and
electrochemical characteristics but also on their interactions during manufacturing
and operation. Subsequently, the layers micro-structures were optimized with respect
to electrochemical functionality. Here parameters like particle size, porosity,
thickness, layer integrity and so on play key roles to obtain high-power-density longterm stable cells. By optimizing all layers by means of chemistry and microstructure
drastically enhanced current densities were reached. By doing so even 3A/cm² at
700°C and 0.7V are realistic.
Besides cell optimization all other SOFC stack components like the steel for the
bipolar plates, the glass-ceramic sealant, the metal protection layers and the cell
contact materials have been optimized in house.
Meanwhile Jülich operates the longest ever run planar stack which in August 2014
has reached an operation time of 7 years while degrading moderately with respect to
loss of voltage. But the degradation of less than 1%/1000h is still too high for
stationary applications (operation times 40-80,000h). By introducing a plasmasprayed protection layer onto the bipolar plates the degradation can be reduced to
about 0.3%/1000h. Such kind of stack currently is running since 31,000h.
Finally, in spring 2014 a 20kW el SOFC system which was developed, built and
operated in Jülich has been shut down after ~ 7.000h of operation with natural
gas/LNG and ambient air. With this system the applicability oft he Jülich SOFC stack
design has been proven.
16
Development of Advanced Materials for Li Rechargeable
Batteries
Kisuk Kang
Department of Material Science and Engineering,
Seoul National University, Seoul, Korea
Lithium rechargeable batteries have been widely used as key power sources for
portable devices for the last couple of decades. Their high energy density and power
have allowed the proliferation of ever more complex portable devices such as cellular
phones, laptops and ipads. For larger scale applications, such as batteries in electric
vehicles (EVs) or power tools or large energy storage systems (EESs), higher
standards of the battery, especially in term of the rate (power) capability, energy
density, cost-effectiveness and cycle stability are far more strictly required. However,
current Li rechargeable battery technology has yet to improve significantly to meet
those requirements. In this presentation, I will introduce our approaches to address
these issues and some accomplishments that have been made in my research
group.
17
Processing of Materials for Oxygen Transport Membranes
Anke Kaletsch, Simone Herzog, Ewald Pfaff, Christoph Broeckmann
Institute for Materials Application in Mechanical Engineering,
RWTH Aachen University, Aachen, Germany
Mixed ionic and electronic conducting (MIEC) materials like the perovskite
Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) are used for high temperature oxygen transport
membrane (OTM). MIEC materials show selective oxygen conductibility at elevated
temperatures of around 800 °C – 900 °C and can be used in several technical
applications where oxygen is needed at a high temperature level, for example in the
iron and steel industry, the chemical industry or for oxyfuel combustion in coal fired
power plants. Different design concepts for membranes are going to be developed
actually, based either on planar MIEC plates or tubular pipes. In both concepts the
ceramic components need to be produced in a robust process that can be transferred
easily to an industrial scale. In case of a planar design a tape casting process is
developed. Tubes are produced by cold isostatic pressing (CIP) followed by sintering
in air atmosphere. The membranes need to be integrated into the entire plant design,
thus a gas- and vacuum tight joining technology is needed, usually between the
ceramic membrane and connecting sleeves or frames made of metallic high
temperature alloys. A special brazing technology, called reactive air brazing (RAB)
has been developed for this purpose. Although MIEC materials mainly are optimized
regarding high oxygen flux and high thermodynamic stability, a minimum mechanical
strength is needed in order to survive mechanical load cases dominated by static
forces, creep and thermal shocks. Therefore particular testing methods have been
developed to characterize the mechanical properties of membrane materials.