Minisymposium From Molecules to Materials

Minisymposium
From Molecules to
Materials
10./11.09.2009
Universität des Saarlandes
Dudweiler, Am Markt Zeile5
Universität
des
Saarlandes
Minisymposium
From Molecules to Materials
10./11.09.2009
Universität des Saarlandes
Dudweiler, Am Markt Zeile 5
Thursday 10.09.2009
TIME
TITLE OF THE TALK
9:00
OPENING by Guido Kickelbick and Horst P. Beck
9:15
NEW MATERIALS FOR LITHIUM ION BATTERIES – RENEWING AN OLD
STORY
Oliver Clemens, Horst P. Beck
9:45
PIGMENTS FROM THE INDUSTRIAL VIEWBASICS AND RESEARCH EXAMPLES
K. Kaufmann, Horst P. Beck
10:15
A STRUCTURE-CHEMICAL SUMMARY OF AB2O6 COMPOUNDS (A =
ME2+, B = V, NB, TA) AND THEIR PHOTOCATALYTIC PROPERTIES.
Ra, Hyun-Seup, Horst P. Beck
10:45
BREAK
11:15
RIVER MONITORING BY ONLINE MEASUREMENTS
METHODS, RESULTS AND INTERPRETATION
Christina Klein, Angelika Meyer, Horst P. Beck
11:45
RESEARCH CONTRIBUTIONS FOR A POTENTIAL RADIOACTIVE
WASTE DISPOSAL IN DEEP GEOLOGICAL CLAY FORMATIONS
Christina Möser, Ralf Kautenburger, Horst P. Beck
12:15
PHOTOCATALYTICALLY ACTIVE TIO2 JANUS NANOPARTICLES
Angelika Bachinger, Sorin Ivanovici, Guido Kickelbick
12:45
LUNCH BREAK
14:15
INVESTIGATION OF THE EFFECT OF pH, PRECURSOR
CONCENTRATION AND BONDING MODES DURING
FUNCTIONALIZATION OF TITANIA NANOPARTIOCLES WITH ORGANIC
SURFACTANTS
Mohsin Raza, Guido Kickelbick
1
Universität
des
Saarlandes
14:45
INORGANIC-ORGANIC NANOCOMPOSITES: CHEMICAL TAILORING OF
NANOPARTICLE SURFACES FOR OPTIMUM HOMOGENEITY
Bernhard Feichtenschlager, Guido Kickelbick, Thomas Koch, Silvia Pabisch,
Herwig Peterlik, Muhammad Sajjad
15:15
ADVANCED HYBRID MATERIALS IN DENTISTRY
Christoph Lomoschitz, Norbert Moszner, Peter Burtscher, Ulrich Salz, Guido
Kickelbick
15:45
BREAK
16:15
FORMATION OF POLYESTER NANOCOMPOSITES AT ELEVATED
TEMPERATURES: INCORPORATION OF TEOS, SILICA SOL AND SILICA
NANOPARTICLES
Jakob Svehla, Guido Kickelbick, Dieter Holzinger, Thomas Schmidt
16:45
POLYMER MATRIX NANOCOMPOSITES – NEW PROPERTIES IN
POLYMERS VIA NANOPARTICLES
Carsten Becker-Willinger
17:15
REGULAR PARTICLE SUPERSTRUCTURES:
SCIENCE AND ENGINEERING
Philip Born, Eoin Murray, Tobias Kraus
18:00
SCHWENKEN „ON“ DUDWEILER ZEILE 3
Friday 11.09.2009
TIME
TITLE OF THE TALK
9:00
NEW MATERIALS BASED ON BIOMINERALIZATION CONCEPTS
Ingrid M. Weiss, Magdalena Eder, Eva Weber
9:30
SCRATCHES IN AND SCRATCH RESISTANCE OF NANOPARTICLESTRENGTHENED POLYMER MATERIALS
Harald Tlatlik
10:00
FROM GAS DIFFUSION LAYERS TO GAS DIFFUSION ELECTRODES BY
ELECTRODEPOSITION
J. Mitzel, V. Keller, F. Arena, H. Natter, R. Hempelmann
10:30
BREAK
11:00
FROM INTERMETALLICS TO METAL HYDRIDES
Holger Kohlmann
2
Universität
des
Saarlandes
11:15
A NEW SAPPHIRE GAS PRESSURE CELL FOR IN SITU NEUTRON
DIFFRACTION: HYDROGENATION OF INTERMETALLICS
Nadine Kurtzemann, Horst P. Beck, Holger Kohlmann
11:40
INVESTIGATIONS OF HYDRIDES OF INTERMETALLIC PHASES LN1XEUXMG2 (LN= LA, CE, SM) VIA IN SITU DSC
Christian Reichert, Holger Kohlmann
12:00
OXIDE CATALYSTS FOR ELECTROCHEMICAL CHLORINE EVOLUTION
PREPARED BY SOL-GEL ROUTE
Ruiyong Chen, Vinh Trieu, Harald Natter, Rolf Hempelmann, Klaus Stöwe,
Wilhelm F. Maier
12:30
MICROSTRUCTURE: BASICS AND EVALUATION
Robert Haberkorn 13:00
CLOSING REMARKS
3
NEW MATERIALS FOR LITHIUM ION BATTERIES – RENEWING
AN OLD STORY
Oliver Clemens1, Horst P. Beck1
1
Institute of Inorganic and Analytical Chemistry, University of Saarland, Building C4 1,
66123 Saarbrücken, Germany
E-mail: [email protected]
Lithium ion batteries are promising candidates as energy storage materials for high
performance applications. Therefore the materials must show distinct properties, e.g.
cycling stability, high electrical and ionic conductivity, high cell voltage, etc [1]. LiMPO4
(M = Fe, Mn, Co, Ni, Mg) compounds crystallize in the olivine structure (space group
Pnma) and showed to be good candidates for the use as cathode materials in lithium
batteries, especially for Mn and Fe [2]. Although those materials show a good ionic
conductivity due to coordination sites of lithium in channels (figure 1), the electronic
conductivities of the materials are quite low. This limits the speed of lithium intercalation /
deintercalation and therefore lowers the performance of the battery cell [3].
Figure 1: structure of LiFePO4 (triphyllite) showing channels of lithium coordination
polyhedra (grey)
VO43- is of similar size as PO43- and can therefore be partially substituted in LiMnPO4
(about 20 – 30 %) [4]. This might lead to an increase of electronic conductivity due to charge
transfer interactions between Mn2+ and V5+ and to an increase of energy density (due to
possible V5+/V4+ equilibria accompanied by further lithium intercalation). The amount of
substituting PO43- for VO43- showed to be highly dependent on the octahedrally
coordinated transition metal cation, which is of high interest for our ongoing research.
[1] M. S. Whittingham, Chemical Reviews 2004, 104, 4271.
[2] A. K. Padhi, K. S. Nanjundaswamy, J. B. Goodenough, Journal of The Electrochemical
Society 1997, 144, 1188.
[3] A. Yamada, M. Yonemura, Y. Takei, N. Sonoyama, R. Kanno, Electrochemical and
Solid-State Letters 2005, 8, A55.
[4] O. Clemens, Diploma Thesis, University of Saarland, 2008.
PIGMENTS FROM THE INDUSTRIAL VIEWBASICS AND RESEARCH EXAMPLES
Kaufmann K., Beck H.P.
Institute of inorganic and analytical chemistry, University of Saarland, Campus C4.1
66123 Saarbruecken, Germany
E-mail: [email protected]
In the field of pigments qualities that affect processing play a role but so do the causes and
basics of color. Colorimetry is a crucial component of industrial testing practice, as it
provides an impartial system for assessing coloristic properties. The most commonly used
color space is the CIELAB system. The reflection spectrum serves as an analytical link
between the deducible color coordinates and the colored object.
Own research examples from the field of solid state chemistry are consulted to explain the
theoretical aspects.
Nr.
kka009
kka174
kka191
kka200
Fig. Color triangle
Compound
ZnO*SnO*TiO2
Sn2TiWO7
Bi1,95Nb0,05O3,05
Ba3(MnO4)2
L*
48.91
32,79
69,71
32,95
a*
41.44
20,90
28,84
-23,37
b*
44.21
9,70
62,04
6,40
Ca,b*
60.59
23,04
68,42
24,23
Tab. Color coordinates of some compounds
ha,b*
46.85
24,89
65,07
164,68
A structure-chemical Summary of AB2O6 Compounds (A = Me2+, B = V, Nb, Ta) and
their Photocatalytic Properties.
Ra, Hyun-Seup1, Prof. Dr. H. P. Beck1
1
Institut für Anorganische und Analytische Chemie, Universität des Saarlandes,
Fachrichtung 8.1, Campus C4.1, 66123 Saarbrücken, Germany
E-mail: [email protected]
The well known class of oxides with the general formula AB2O6 (A = Me2+, B = P5+, As5+,
Sb5+, V5+, Nb5+, Ta5+) has been intensively studied due to the potential technical applications ,
such as photocatalysis. The presented studies included the creation of a structure field map for
oxides, synthesis of missing compounds, and recording of structural data using state of the art
techniques. The obtained structure field map also allowed to distinguish between the
structural variations in these systems and revealed relationships between them.
The oxides were synthesized by classical solid state methods in appropriate environment (air,
vacuum or hydrogen). The X-ray data from powders were analyzed using the Rietveld
analysis. The structural data of AV2O6 (A = Ni, Mg, Co, Mn), ANb2O6 (A = Ni, Mg, Cu, Zn,
Co, Fe, Mn, Ca, Sn, Eu, Sr, Pb, Ba) and ATa2O6 (A = Ni, Mg, Co, Mn, Cu) were collected
and refined. The refined crystallographic data of EuNb2O6, which is isomorphous to SrNb2O6
(Spacegroup: P21/c), are described for the first time (lattice parameters: a = 7,7050(1) Å;
b = 5,5781(1) Å; c = 11,0032(1) Å; β = 90,35(1)°; V = 473,00 (1) ų).
Furthermore, the fluorination of selected compounds of this class of substances was targeted.
Unfortunately, these oxides underwent no changes under the applied fluorination techniques
and therefore no oxyfluorides could be obtained.
The photocatalytic activity of various representatives of the vanadates, niobates and tantalates
was investigated, showing a high photocatalytic activity for niobates. In addition, hydrogen
production using EuNb2O6 as photocatalytic reagent will be presented for the first time.
RIVER MONITORING BY ONLINE MEASUREMENTS
METHODS, RESULTS AND INTERPRETATION
Klein, Christina; Meyer, Angelika; Beck, Horst Philipp1
1
Institute of Inorganic and Analytical Chemistry, Saarland University, Campus C 4.1,
66123 Saarbrücken, Germany
E-mail: [email protected]
The European Water Framework Directive (WFD) requires a good ecological and
chemical status of surface waters until 2015. To achieve the objectives of this guideline the
sources of different pollution types have to be determined.
As only online measurements combined with hydrological data are able to distinguish
between diffuse and punctual sources of pollution we constructed several mobile
measuring stations equipped with commercial sensors and online analysers. By dint of
these instruments the concentrations and values of the following parameters are measured
continuously: nutrients (like N- and P-compounds), general parameters (like pH-value,
temperature, conductivity, turbidity, oxygen) (see fig.) and so called priority metals (like
Nickel, Cadmium). The frequency of measurements ranges from five minutes to one hour
depending on the method. All row data are stored in data loggers from where they are
automatically transferred to the central computer and thus are available at any time.
For any further interpretation of the data collected a lot of additional information such as
effluents of sewage plants, land use etc. is considered. Apart from that the concentration
curves have to be related to hydrological and meteorological data to detect the sources of
different pollution. Thereby the high temporal resolution of the measurements approves the
way of entry like interflow, surface or basic flow. The observation of general parameters
gives hints to natural circumstances within the rivers catchment areas and reflects the
sensitivity of the river against effluents and climate changes.
Thus online measurements do not only serve for a determination of the status of water
quality but they also may provide a basis for planning measures to save aquatic ecosystems.
RESEARCH CONTRIBUTIONS FOR A POTENTIAL RADIOACTIVE
WASTE DISPOSAL IN DEEP GEOLOGICAL CLAY FORMATIONS
Möser Christina, Kautenburger Ralf, Beck Horst P.
Institute of Inorganic and Analytical Chemistry and Radiochemistry,
Saarland University, Campus C4.1, 66123 Saarbrücken, Germany
E-mail: [email protected]
The deep geological disposal of high level radioactive wastes is assumed to be a way of
providing adequate protection for humans and the environment. For the safe isolation of
radioactive waste, low permeability and high sorption capacity of the geological barrier is
very important. Clay minerals play a major role in different concepts for the disposal of
high-level nuclear waste (HLW) in deep geological formations.
Natural clays can contain natural organic matter (NOM), for example humic substances.
In most aquatic systems, NOM species like humic acids (HA) can act as complexing
ligands for metal ions and may affect metal speciation and thus metal mobility. By the
formation of soluble complexes and colloids with numerous toxic heavy metals, including
radionuclides, HA can influence the migration behaviour of these pollutants in geological
clay formations.
Figure 1. The ternary system under study consisting of lanthanide ions, humic acid, clay
and important influencing factors.
In our project we analyse the sorption and desorption behaviour of the trivalent
lanthanides europium, gadolinium and terbium (as homologues of the actinides americium,
curium and berkelium) in the binary system consisting of these heavy metals and kaolinite
as model clay as well as natural Opalinus clay (from Benken, Switzerland), and in the
ternary system metal / clay / humic acid, under conditions close to nature.
The influence of the lanthanide concentration, pH-value, or different competing metal
ion concentrations on the sorption/desorption onto clay in the presence or absence of HA
was investigated. After the sorption experiments, free metal ions in the supernatant
solution were analysed by inductively coupled plasma mass spectrometry (ICP-MS).
Speciation of the lanthanide-HA complexes is performed by the hyphenation of capillary
electrophoresis (CE) with ICP-MS.
PHOTOCATALYTICALLY ACTIVE TIO2 JANUS NANOPARTICLES
Angelika Bachinger1, Sorin Ivanovici, Guido Kickelbick2
1
Institute of Materials Chemistry, Vienna University of Technology,
Getreidemarkt 9/165, 1060 Vienna, Austria
E-mail: [email protected]
2
Inorganic Solid State Chemistry, Saarland University,
Am Markt - Zeile 3, 66125 Dudweiler, Germany
E-mail: [email protected]
The light-induced redox process on the surface of anatase nanoparticles can lead to the
degradation of organic compounds. This effect is used particularly for applications in
wastewater treatment and self-cleaning of surfaces. However, the coating of organic
substrates is a challenging task, because the photocatalytic degradation process will not
prevent the substrate from damage. In the reported project anatase nanoparticles were
functionalized anisotropically with phosphonate and phosphate coupling agents featuring
different organic functionalities. One side of the particles' surface remains blank, while the
other functionalized side protects the substrate from degradation and can additionally
interact with the substrate. The anisotropic surface modification was achieved by the
Pickering emulsion method. Thus, titanium oxide nanoparticles are used to stabilize o/w
emulsions with oil-soluble organic phosphates or phosphonates. The stability of these
emulsions was optimized by varying the type of oil phase, the water-to-oil ratio, pH, and
salt concentration. 'Janus'-type nanoparticles were obtained by addition of hydrophobic
phosphonates to the oil phase of the emulsion. CP MAS NMR, FT-IR, TGA and TEM
were applied to characterize the functionalized particles. Prove for the anisotropic nature of
the nanoparticles was given by TEM analysis of poly(ethylene glycol) modified particles
with polymer-embedded gold nanoparticles. The UV-stability of the phosphonates and
phosphates was investigated by illumination of TiO2 nanoparticles modified with phenyl
phosphonic and phenyl phosphoric acid. Samples were taken in defined time intervals and
investigated by CP MAS NMR and FT-IR. It could be proved that the P-O-Ti bond is
stable under UV-illumination.
INVESTIGATION OF THE EFFECT OF pH, PRECURSOR
CONCENTRATION AND BONDING MODES DURING
FUNCTIONALIZATION OF TITANIA NANOPARTIOCLES
WITH ORGANIC SURFACTANTS
Mohsin Raza1, Guido Kickelbick2
1
Institute of Materials Chemistry, Vienna University of Technology, Vienna, Austria
2
Anorganische Festkörperchemie, Universität des Saarlandes, Germany
[email protected]
In recent years TiO2 has been studied extensively as photocatalyst to deal with
environmental pollution and water purification. The light-induced redox reaction at
the surface of photocatalytic titania nanoparticles often results in the decomposition of
organic compounds. We investigated the synthesis of photocatalytically active anatase
titania nanoparticles and their surface-functionalization with molecules that interact
with the surface by different anchor groups and the change of the surface groups
under photocatalytical conditions
In a first step anatase nanoparticles were synthesized through the sol-gel method. The
obtained monodispersed particles were functionalized with sodium dodecylsulphate
(SDS), dodecyl carboxylic acid (DDA), dodecyl amine (DDAmine) and
dodecylphosphonic acid (DPA). Different concentrations of each surfactant were used
under varying pH values to optimize the conditions for surface coverage and it was
noted that pH between 2 to 3 is best for functionalizing titania nanoparticles with the
above mentioned four surfactants. The bonding modes and percentage of surface
coverage of the obtained titania nanoparticles were investigated applying FT-IR, TGA
and elemental analysis. The results show that SDS, DDA and DDAmine are bonded to
the titania surface through electrostatic interaction whereas DPA is bonded through
covalent interaction.
UV Stability of these surface modifications was investigated by exposing them to UV
photocatalytical reactor with a power of 18W for one week and 150 W for three days.
It was noted that surface functionalizations were stable under 18W and there were
some chemical alterations observed at 150 W. These surface modifications were
successfully repeated in Pickering emulsions as well to investigate anisotropic
surface-functionalization of titania nanoparticles.
INORGANIC-ORGANIC NANOCOMPOSITES: CHEMICAL
TAILORING OF NANOPARTICLE SURFACES FOR OPTIMUM
HOMOGENEITY
Bernhard Feichtenschlager1, Guido Kickelbick2, Thomas Koch3, Silvia Pabisch4,
Herwig Peterlik4, and Muhammad Sajjad3
1
Institute of Materials Chemistry, Technical University of Vienna, Austria
E-mail: [email protected]
2
Anorganische Festkörperchemie, Universität des Saarlandes, Germany
Guido: E-mail: [email protected]
3
Institute of Material Science and Technology, Technical University of Vienna, Austria
E-mail: [email protected]
4
Faculty of Physics, University of Vienna, Austria
E-mail: [email protected]
The compatibility of the inorganic phase and the organic matrix at the interface in polymer
nanocomposite materials is increased using capping agents resulting in a better dispersibility
of the inorganic nanobuilding blocks in an organic matrix. In addition to the surface-adaption
the capping agent may also contain functional groups allowing a covalent linkage to the
polymer during in situ polymerization. Many reports in literature describe the use of
compounds consisting of long alkyl chains as capping agents. However, such molecules tend
to form well ordered self-assembled monolayers, on the surface of the nanobuilding blocks. In
some cases this can lead to a decrease in dispersibility due to interparticle aggregation
phenomena.
In this work two different approaches to solve this problem were used: (i) mixing of different
coupling agents which break the ordering phenomena on the surface of the particles and (ii)
the use of different molecular structures such as polyethyleneglycol chains or flexible PDMS
chains.
Zirconia nanoparticles (22 nm equivalent diameter) and silica particles with various diameters
prepared by the Stoeber process, both with a very uniform size-distribution were used as
model systems to prove these hypotheses. The capping agents contained phosphonic acids
anchor groups for thezirconia and trialkoxysilanes for the silica systems. The organic
functionalities attached to these anchor groups were systematically varied and ordering
phenomena at the particle surface were analyzed via infrared spectroscopy studies (IR). The
dispersibility of the modified particles in organic media was investigated by dynamic light
scattering (DLS) and small angle X-ray scattering (SAXS) experiments. The particles were
used as building blocks for the preparation of nanocomposites with poly(methyl methacrylate),
polystyrene or epoxy resin formulations as polymer matrix.
The studies revealed that the higher ordered alkyl chain at nanoparticle surfaces shows a
stronger packing of the particles and a higher tendency to form aggregates in nanocomposite
systems.
ADVANCED HYBRID MATERIALS IN DENTISTRY
Christoph Lomoschitz1, Norbert Moszner2, Peter Burtscher2, Ulrich Salz2,
Guido Kickelbick3
1
Institute of Materials Chemistry , Vienna University of Technology,
Getreidemarkt 9/165-AC, 1060 Vienna, Austria
2
Ivoclar Vivadent AG,
Bendererstrasse 2, 9494 Schaan, Principality of Liechtenstein
3
Inorganic Solid State Chemistry, Saarland University,
Dudweiler Am Markt Zeile 3, 66125 Saarbrücken, Germany
E-mail: [email protected]
Polymer based fillings are successively replacing amalgam as well as glass cement fillings
in the area of dental medicine. High biocompatibility and tunable aesthetics were major
factors responsible for the high demand of polymer based fillings. Meanwhile, curing times
are in an acceptable range and drawbacks such as shrinkage during polymerization and
hardness deficiencies have been overcome by now by embedding of ceramic and/or glass
particles into the polymer. However, adhesion between the polymer and the filler or the
enamel has to be enhanced, to improve the durability and wear properties of such fillings.
Molecular adhesives, so called coupling molecules were synthesized in order to create
covalent bonds between polymer and an inorganic component (zirconia filler). Therefore,
these molecules contain a polymerizable site (methacrylate) and a moiety showing high
affinity to metal oxides (phosphoric/phosphonic acid)1 as can be seen in Scheme 1.
Zr O2
X = C,O
O
O
O
P
O
X
n
HO
HO
P
O
X
n
O
O
O
Scheme 1: Phosphorous coupling molecules – yellow: polymerizable site
Modification of zirconia was carried out under mild conditions in order to conserve the
polymerizable moiety. Bonding of the phosphate/phosphonate moiety could be evidenced
by means of IR, 31P MAS NMR and XPS. Due to its amphiphilicity, only the
phosphoric/phosphonic acid head group interacts with the surface and the alkyl chains and
polymerizable moiety respectively are pointing away from the surface. Thermogravimetric
measurements proved that the coverage of the particles used were between 50 and 100 %
of a theoretically dense monolayer. Furthermore it was shown that coupling molecules
containing a long alkyl spacer (C5 or C10) reveal an orientation on the particle surface.
Nitrogen sorption measurements displayed that the hydrophobic character of the modified
surfaces increases with increasing alkyl spacer length, which is accounted for the pending
alkyl chains from the particles.
References
(1)
P. H. Mutin, G. Guerrero and A. Vioux, J. Mater. Chem. 2005, 15, 3761-3768.
FORMATION OF POLYESTER NANOCOMPOSITES AT ELEVATED
TEMPERATURES: INCORPORATION OF TEOS, SILICA SOL
AND SILICA NANOPARTICLES
Jakob Svehla1, Guido Kickelbick2, Dieter Holzinger3, Thomas Schmidt3
1
Institute of Material Chemistry, Vienna University of Technology,
1060 Vienna, Austria
2
Inorganic Solid State Chemistry, Saarland University,
66125 Saarbrücken, Germany
2
Tiger Coatings GmbH & Co. KG, 4600 Wels, Austria
E-mail: [email protected]
Inorganic-organic nanocomposites are an important new materials class in which the solgel process is often applied for the formation of the inorganic moiety. Commonly used
polymerization techniques, such as radical polymerization, can be easily combined with
the sol-gel process due to its mild reaction conditions and the vast possibilities for tailoring
size and morphology of the inorganic moiety. However specific polymer classes, e.g.
polyesters, require much higher reaction temperatures (in the case of polyesters between
150 and 250°C) which leads to changes in the sol-gel reaction mechanisms. Therefore
different processing technologies have to be applied if sol-gel modified polyesters are
targeted.
In this report we reveal a systematic study on the modification of polyester formulations by
the incorporation of tetraethylorthosilicate (TEOS) prehydrolysed silica sol and silica
nanoparticles. The resulting inorganic-organic hybrid materials showed increased
molecular weights and molecular weight distributions compared to neat polyesters.
Reactions of residual silanol and/or ethoxy groups of the silica phase with polyester
components led furthermore to branching of the polymer chains. Transmission electron
microscopy (TEM) revealed a highly dispersed inorganic phase in the organic matrix.
Rheologic investigations of neat and cured hybrid resins showed moreover enhanced
viscosities compared to non-modified polyesters.
POLYMER MATRIX NANOCOMPOSITES – NEW PROPERTIES IN
POLYMERS VIA NANOPARTICLES
Carsten Becker-Willinger
INM – Leibniz Institute for New Materials, Campus D2 2, D-66123 Saarbrücken,
Germany
E-mail: [email protected]
One area of scientific interest in the Program Division “Nanomers” at INM is the
development of polymer matrix nanocomposites suitable for optical and engineering
applications. In order to understand the structure property relationships concerning
mechanical, thermomechanical and thermal properties polymethacrylate nanocomposites
containing silica nanoparticles with a particles size d90 < 15 nm have been investigated.
The silica nanoparticles have been surface modified prior to use in order to achieve
compatibility with the polymer matrix and to avoid particle agglomeration. Acetoxypropyltrimethoxy-silane and methacyloxy-propyltrimethoxy-silane have been used as
surface modifiers. The polymethacrylate matrix has been synthesized starting from the
monomer mixture in presence of the pre-dispersed particles. Unmodified silica
nanoparticles have been dispersed for comparison. Transmission electron microscopy on
ultramicrotomed thin slices revealed that a quite homogeneous particle distribution over
the matrix could be obtained in case of surface modified nanoparticles. This result could
also confirmed by small angle x-ray scattering showing also a fractal dimension of 3.1 in
the Porod region which indicates that the primary particles possess a sharp phase boundary
to the polymer matrix. No indication of a distinct interfacial layer could be observed. Three
point bending measurements revealed that the elastic modulus increase in dependence on
the filler content corresponds well to the classical mixing rules described e.g. by the Kerner
equation. The maximum strength showed the expected decrease in dependence on
increased filler content according to the Nielsen model for spherical particles. Dynamic
mechanical thermal analysis gave some indication about the existence of immobilized
polymer segments on the particle surface in the case of silica surface modified with
methacryloxy-propytrimethoxy-silane where a covalent bonding could be assumed. In this
case an increase in glass transition temperature of about 35 °C has been detected for the
system containing 10 vol.-% silica compared to the unfilled polymethacrylate matrix.
REGULAR PARTICLE SUPERSTRUCTURES:
SCIENCE AND ENGINEERING
Philip Born, Eoin Murray, Tobias Kraus
Leibniz Institute for New Materials (INM)
Campus D2 2, 66123 Saarbruecken, Germany
E-mail: [email protected]
Nanoparticles form regular superstructures – but only under certain conditions.
Superstructures are an interesting, interface-dominated material class, and we would like to
prepare them in macroscopic quantities. It is also fundamentally interesting when and why
particles arrange into regular structures. Our group therefore analyzes particle assembly
processes. We observe the processes in situ while varying process parameters and
interparticle potentials. The resulting particle agglomerates are structurally characterized
ex situ. This yields process-structure-correlations that we use to improve particle
deposition techniques and to further the basic understanding of interacting particle systems.
Figure 1: Supraparticles formed from gold nanocrystals.
NEW MATERIALS BASED ON BIOMINERALIZATION CONCEPTS
Ingrid M. Weiss1, Magdalena Eder1, Eva Weber1,2
1
INM – Leibniz Institute for New Materials, Program Division Biomineralization, Campus
D2-2, D-66123 Saarbrücken, Germany; E-mail: [email protected]
2
Saarland University, Molecular Plant Biology - Prof. Bauer, Saarland University, Campus
A2-4, D-66123 Saarbrücken, Germany
The INM Program Division "Biomineralization" aims to develop new materials by taking
advantage of the hierarchical order which is attributed to native biological materials. In
Nature, functional materials are built following a bottom-up approach from the nano- to the
micron regime, with the tallest trees of more than 100 m in height. The inspiration comes
from emerging concepts in mollusc shell and nacre biomineralization based on chitin selfassembly and glycosyltransferases such as the mollusc chitin synthase, a molecular myosin
motor.1,2 The last decade of research in biomineralization demonstrated that amorphous
mineral precursors play a key role in the functional assembly of composite materials such
as the aragonitic mollusc shells, calcitic sea urchin spines (CaCO3), and bone
(hydroxyapatite).3,4
Current challenges in biomineralization research are discussed on the example of speciesspecific thickness of ~ 0.5 µm aragonite platelets within a periodic layer-by-layer
structures of chitin and silk-like proteins in nacre-type biominerals. We proved the
presence of covalently attached, hydrophobic amino acid side chains in the chitin matrix of
mollusc bivalve shells. The accumulation of the modified chitin matrix at the interface can
quantitatively be demonstrated by the critical aggregate concentration of the purified chitin
matrix, which is approximately by an order of magnitude smaller than that of pure chitin.
Our finding suggests an active role of such chemically modified chitooligosaccharides in
creation of a defined interface and guidance of the periodic matrix textures, which would
result in unique material properties of natural mollusc shells.5
We see Biology, in general, and biomineralization gene products (proteins, glycans), in
particular, as powerful fabrication tools for new materials. Exploring their function in
heterologous environments will enable us to transfer the most successful concepts from
chemical nanotechnology towards renewable functional materials for multiple applications
and environmental benefit.
___
References:
1
Weiss IM, Schonitzer V, Eichner N, Sumper M. 2006. The chitin synthase involved in marine bivalve
mollusk shell formation contains a myosin domain. FEBS Lett 580(7):1846-1852.
2
Weiss IM, Kaufmann S, Heiland B, Tanaka M. 2009. Covalent modification of chitin with silk-derivatives
acts as an amphiphilic self-organizing template in nacre biomineralisation. Journal of Structural
Biology 167(1):68-75.
3
Addadi L, Politi Y, Nudelman F, Weiner S. 2008. Biomineralization design strategies and mechanisms of
mineral formation: Operating at the edge of instability. In: Novoa JJ, Braga D, Addadi L, editors.
Engineering of Crystalline Materials Properties. Netherlands: Springer. p 1-15.
4
Weiner S, Mahamid J, Politi Y, Ma Y, Addadi L. 2009. Overview of the amorphous precursor phase
strategy in biomineralization. Frontiers of Materials Science in China 3(2):104-108.
5
Ashby MF. 2008. The CES EduPack Database of Natural and Man-Made Materials. Cambridge, U.K.:
Granta Design.
SCRATCHES IN AND SCRATCH RESISTANCE OF
NANOPARTICLE-STRENGTHENED POLYMER MATERIALS
Harald Tlatlik
INM – Leibniz Institute for New Materials, Campus D2 2, D-66123 Saarbrücken,
Germany
E-mail: [email protected]
Scratch-resistant, organic coatings are already in everyday use. They offer advantages over
other coating techniques like the simple, versatile, and gentle methods of application and
the possibility to include so-called third functions (colour, transparency, dirt-repellence, ...),
just to name a few.
A modern and promising way to enhance the scratch resistance is the integration of nanosized, inorganic particles into the polymer matrix. But unfortunately, the relationship
between basic materials' properties and the scratch behaviour is largely unexplored, both
without and with incorporated nano particles.
The fundamental question of this project is: What is the relationship between the scratch
resistance of a polymer surface over length scales and its chemical composition and
microstructure? In particular, the influence of the glass transition temperature on the
groove formation and on the groove's “self-healing” behaviour at different length scales is
still unclear. Especially, the mechanisms of the nano particles leading to scratch-resistant
effects is hardly investigated and thus poorly understood. Beyond that, the effect of the
surface's structural features like roughness or distance between the nano particles is not
well known.
Concretely, two problems will be investigated:
•
Is the deformation of the polymer coating during scratching exclusively borne by
the relative movement of the coils (viscous flow)? Or do additional bond breakages
within the macromolecules play an import role for the deformation process?
•
Is the dramatic enhancement of scratch resistance by inorganic nano particles due
to their high hardness or are they rather fixing the macromolecules by chemical
bonds? What about synergetic effects between macromolecules and particles
exceeding the fixation?
In my talk I will introduce the possible mechanisms that lead to the enhanced scratch
resistance by nano particles and present an experimental strategy to answer the questions
above. Additionally, I will present first experimental investigations of scratching on the
nanometre scale, elucidating the high dynamics of the scratched polymer surface.
FROM GAS DIFFUSION LAYERS TO GAS DIFFUSION
ELECTRODES BY ELECTRODEPOSITION
J. Mitzel1, V. Keller2, F. Arena1, H. Natter1, R. Hempelmann1
1
Institute of Physical Chemistry, Saarland University, Am Markt-Zeile 3, 66125
Saarbrücken, Germany
E-mail: [email protected]
2
present address: Frankenallee 29, 60327 Frankfurt am Main, Germany
A new method for the preparation of electrocatalysts in gas diffusion electrodes (GDE) out
of a precursor layer by pulsed electrodeposition has been developed.
The first step in this method is the coating of a commercial carbon fiber paper (gas
diffusion layer, GDL) with a precursor layer by airbrush, serigraphy or with a coating
knife. For these procedures a dispersion of carbon black in an alcoholic solution of Nafion
and precursor salts is used with different viscosities. After drying the thickness of the
precursor layer averages 5 to 30 µm. The precursor ions were electrochemically deposited
in-situ out of this precursor layer [1-3]. The electrocatalysts prepared in this way have a
high degree of catalyst utilization due to the fact that they are located on electroactive sites.
Due to recent improvements of these methods [4, 5] the in-situ electrodeposition of catalyst
nanoparticles with diameters down to 2 nm is possible.
The structural characterization of the electrocatalysts is done by XRD and TEM, which
yield the catalyst particle size and distribution. The catalyst nanoparticles are well
dispersed, hardly any agglomerates can be observed. For the electrochemical
characterization mainly cyclovoltammetry is used. The electrochemically active surface
area can be calculated from the hydrogen desorption or CO oxidation peak. Different
measurements in a fuel cell testing station like voltage current and stoichiometric
characteristics were made also.
Not only the electrodeposition parameters must be optimized. Also a special morphology
of the carbon fiber substrate is required to obtain well distributed, very small and thus very
active catalyst nanoparticles.
[1]
[2]
[3]
[4]
[5]
R. Hempelmann, M.-S. Löffler, H. Schmitz, H. Natter and J. Divisek, EP 1 307 939
B1, 2001
M.-S. Löffler, H. Natter, R. Hempelmann and K. Wippermann, Electrochimica
Acta 48, 3047-3051 (2003)
K. Wippermann, K. Klafki, J. Mergel, M.-S. Löffler, H. Natter und R.
Hempelmann, Proc. Electrochem. Soc. 31, 518 – 529 (2005)
R. Hempelmann, V. Keller, M. Lopez, H. Natter, EP 0700 3516.7 (2007)
R. Hempelmann, V. Keller, H. Natter, DE 102 007 033 753.3 (2007)
FROM INTERMETALLICS TO METAL HYDRIDES
Holger Kohlmann
FR 8.1 Inorganic Solid State Chemistry, Saarland University, Am Markt Zeile 3,
66125 Saarbrücken, Germany
E-mail: [email protected]
Metal hydrides have attracted interest in recent days because of their use in hydrogen storage
and in electrochemical applications, such as in nickel-metal hydride rechargeable batteries [1].
Many fundamental properties of this class of compounds are just as fascinating [2], as will be
outlined in this talk by giving examples from all classes of metal hydrides, ranging from ionic
over covalently bonded to metallic interstitial hydrides.
Synthesis by solid state, solid-gas or solution methods in general yields powders, i. e.
single crystal methods for structure solution are not applicable. Due to the more favorable
scattering of hydrogen for neutrons than for X-rays, structural characterization is performed
by neutron diffraction. The potential and limitations of modern neutron powder diffraction
methods will be discussed.
The incorporation of hydrogen into intermetallic compounds often changes their
physical properties considerably. Metal-insulator transitions and inducing cooperative
magnetism occurr frequently, i. e. hydrogen may be used to tune eletrical, optical and
magnetic properties [2].
Structural investigations unveil an unusual wealth of close structural relationships
between intermetallics and their hydrides. Some of them can be interpreted as manifestation
of intercalation reactions and order-disorder transitions, in other cases, more complicated
mechanisms are suggested [3]. These findings call for in situ investigations of the
hydrogenation of intermetallics, in order to explore reaction pathways experimentally.
[1] A. Züttel, Hydrogen storage methods, Naturwissenschaften 2004, 91, 157-172
[2] H. Kohlmann, Metal Hydrides, in: Encyclopedia of Physical Sciences and Technology (R.
A. Meyers, Ed.), Academic Press, 3rd edition, 2002, Vol. 9, 441-458
[3] H. Kohlmann, Wasserstoff als strukturdirigierendes Element in Metallhydriden,
Habilitation thesis, Saarland University, 2008
A NEW SAPPHIRE GAS PRESSURE CELL FOR IN SITU NEUTRON
DIFFRACTION:
HYDROGENATION OF INTERMETALLICS
Nadine Kurtzemann1, H.P. Beck2, Holger Kohlmann1,
1
FR 8.1 Inorganic Solid State Chemistry, Saarland University, Am Markt Zeile 3,
66125 Saarbrücken, Germany, E-Mail: [email protected]
2
FR 8.1 Inorganic and Analytical Chemistry and Radiochemistry, Saarland University
Building C 4.1, 66123 Saarbrücken, Germany
Detailed studies of the processes during hydrogen uptake
allow the identification of intermediates and reaction
pathways. These essential informations will help to
understand better hydrogen storage materials, hydrogen
induced rearrangements in intermetallics resulting for
example in hydrogen embrittlement, and technical processes
such as HDDR (hydrogenation, disproportionation,
desorption and recombination). Therefore it was aimed to
develop a new gas pressure cell for such in situ neutron
powder diffraction experiments to explore the hydrogenation
(deuteration) of intermetallics. However, commonly used gas
pressure cells have disadvantages, e.g. due to hydrogen
embrittlement and unwanted reflections of the container
material. Using a single crystal sapphire tube these problems
can be overcome because of the chemical inertness of this material and due to the fact that
proper orientation of the sapphire avoids the interference of its single crystal reflections. At
present a maximum hydrogen pressure of 80 bar and a temperature range from room
temperature up to about 300°C can be attained using a heat gun. With this equipment first
in situ measurements of palladium rich hydrides were successfully performed with the
neutron powder diffractometer D20 (ILL, Grenoble) proving the general feasibility of such
studies. For the future it is planned to increase the accessible temperature and pressure
range which is necessary for example to study HDDR systems. Therefore we intend to
apply a laser for heating and to control the pressure externally. Moreover it is possible to
enhance the design of the cell for other solid-gas reactions or to use it as gas flow cell.
INVESTIGATIONS OF HYDRIDES OF INTERMETALLIC PHASES
LN1-XEUXMG2 (LN= LA, CE, SM) VIA IN SITU DSC
Christian Reichert, Holger Kohlmann
FR 8.1 Inorganic Solid State Chemistry, Saarland University, Am Markt Zeile 3,
66125 Saarbrücken, Germany
E-mail: [email protected]
In order to investigate the hydrogenation properties of the ternary systems Ln1-xEuxMg2 (Ln=
La, Ce, Sm), in situ DSC presents a highly effective tool, because of its ability to monitor
reaction enthalpies. Contrary to batch reactions, a wider range of parameters can be controlled
in one experiment.
LnMg2H7 and EuMg2H6 are known in literature as salt-like hydrides, with the former having
the largest capacity of hydrogen storage of all Laves phases. The work concentrates on the
corresponding ternary systems Ln1-xEuxMg2H7-x. Substitution of Eu in EuMg2 by Ln and of
Ln by Eu in LnMg2 takes place, up to 50% and 20% respectively, and follows the rule of
Végard. The hydrides are prepared directly via hydrogenation of those Laves phases. High
pressure and slow heating favors ternary hydrides, while low pressure and fast heating leads
to the corresponding binary hydrides. Yet, the hydrides are yield as amorphous powders.
Therefore, main effort is finding experimental conditions, among which well crystallized
products form.
Finally, the structure, magnetic and luminescence properties of those hydrides shall be
explored.
OXIDE CATALYSTS FOR ELECTROCHEMICAL CHLORINE
EVOLUTION PREPARED BY SOL-GEL ROUTE
Ruiyong Chen1, Vinh Trieu1, Harald Natter1, Rolf Hempelmann1,*,
Klaus Stöwe2, Wilhelm F. Maier2
1
2
Institute of Physical Chemistry, Saarland University, 66123 Saarbrücken, Germany
Institute of Chemical Engineering, Saarland University, 66123 Saarbrücken, Germany
E-mail: [email protected]
Chlor-alkali electrolysis is one of the most energy consuming industrial processes in the
world.[1] It is highly desirable to develop new electrocatalysts to reduce the electrode
overpotential. RuO2-based oxides coated onto metal substrate are being successfully
employed as electrocatalysts over the past 40 years.[2-4] For the mixed oxide materials, the
homogeneity in microstructure is crucial in achieving the synergistic effects among the
multi-components. In this aspect, sol-gel technique possesses special advantages compared
to the conventional thermal decomposition preparation method. A homogeneous M-O-M’
network is formed by the successive and overlapped hydrolysis and condensation reactions
of molecular precursors. The versatile sol-gel technique also allows the fabrication of
coating, thin film structures onto various substrates with flat or complex geometric shape,
and the control in coating structures and morphologies.
The structural characterization of the electrocatalysts was carried out by X-ray diffraction,
Raman microscopy and scanning electron microscopy. The electrocatalytic performance of
the coatings and the dependence on the chemical composition, coating surface
morphologies and crystallite size were investigated by means of cyclic voltammetry,
chronopotentiometry and impedance spectroscopy.
References:
[1]
[2]
[3]
[4]
I. Moussallem, J. Jörissen, U. Kunz, S. Pinnow, T. Turek, J. Appl. Electrochem. 2008,
38, 1177-1194.
O. de Nora, Chem. Eng. Technol. 1970, 42, 222-226.
H.B. Beer, Brit. Patent 1 147 442, 1965.
S. Trasatti, Electrochim. Acta 2000, 45, 2377-2385.
Microstructure: Basics and Evaluation
Robert Haberkorn
Universität des Saarlandes, Anorganische Festkörperchemie,
Dudweiler, Am Markt Zeile 3, 66125 Saarbrücken, Germany
Abstract
X-ray diffraction of a polycrystalline matter causes coherently scattered intensity with more
or less distinct peaks. The width and shape of such a peak is caused by the setup of the radiation, the goniometer, sample preparation and intrinsic properties of the matter. The intrinsic
properties of the matter, like crystallite size, microstrain, strain of other types or stacking fault
densities, are also called microstructural effects. All the other effects together may be called
instrumental broadening.
Programs using pattern decomposition or Rietveld analysis model the width and shape of
peaks by any angle dependency. Common programs, like DBWS [1], apply simple angle dependencies without physical meaning. More sophisticated programs, like FormFit [2], use
separate models for instrumental broadening and microstructure and enable extensive evaluation of microstructural effects [3]. A rather new method, the fundamental parameters approach, implemented in programs like Topas [4], calculate for each peak the width and shape
caused by instrumental broadening from goniometer radius, slit widths, monochromator setup
and other measurable parameters.
[1] Wiles D. B., Young R. A.; J. Appl. Cryst. 14 (1981) 149.
[2] Haberkorn R.; ErlRay – A program package to evaluate X-ray powder pattern, Dudweiler,
2004.
[3] Cheary R. W., Coelho A. A., Cline J. P.; J. Res. Natl. Stand. Technol. 109 (2004) 1-25.
[4] Topas V2.1; General profile and structure analysis software for powder diffraction data,
User Manual, Bruker AXS, Karlsruhe 2003, Germany.