Embed Size (px)
Citation preview
Minisymposium
From Molecules to Materials
10./11.09.2009
Universität des Saarlandes Dudweiler, Am Markt Zeile5
Universität des Saarlandes
1
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 VIEW-
BASICS 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
Universität des Saarlandes
2
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 NANOPARTICLE-STRENGTHENED 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
Universität des Saarlandes
3
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 LN1-
XEUXMG2 (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 EVALUATIONRobert Haberkorn
13:00 CLOSING REMARKS
NEW MATERIALS FOR LITHIUM ION BATTERIES – RENEWING AN OLD STORY
Oliver Clemens1, Horst P. Beck1
1Institute 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) VO4
3- 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 PO4
3- 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 VIEW- BASICS 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.
Fig. Color triangle
Nr. Compound L* a* b* Ca,b* ha,b* kka009 ZnO*SnO*TiO2 48.91 41.44 44.21 60.59 46.85 kka174 Sn2TiWO7 32,79 20,90 9,70 23,04 24,89 kka191 Bi1,95Nb0,05O3,05 69,71 28,84 62,04 68,42 65,07 kka200 Ba3(MnO4)2 32,95 -23,37 6,40 24,23 164,68
Tab. Color coordinates of some compounds
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
1Institut 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
1Institute 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 1Institute of Materials Chemistry, Vienna University of Technology,
Getreidemarkt 9/165, 1060 Vienna, Austria E-mail: [email protected]
2Inorganic 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
1Institute of Materials Chemistry, Vienna University of Technology, Vienna, Austria 2Anorganische Festkörperchemie, Universität des Saarlandes, Germany
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
1Institute of Materials Chemistry, Technical University of Vienna, Austria E-mail: [email protected]
2Anorganische Festkörperchemie, Universität des Saarlandes, Germany Guido: E-mail: [email protected]
3Institute of Material Science and Technology, Technical University of Vienna, Austria E-mail: [email protected]
4Faculty 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
1Institute of Materials Chemistry , Vienna University of Technology, Getreidemarkt 9/165-AC, 1060 Vienna, Austria
2Ivoclar Vivadent AG, Bendererstrasse 2, 9494 Schaan, Principality of Liechtenstein
3Inorganic 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.
ZrO2O
O
n
XP
OHOH
O
X = C,O
O
O
n
XP
OO
O
ZrO2O
O
n
XP
OHOH
O
X = C,O
O
O
n
XP
OO
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 sol-gel 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. Acetoxy-propyltrimethoxy-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
1INM – Leibniz Institute for New Materials, Program Division Biomineralization, Campus D2-2, D-66123 Saarbrücken, Germany; E-mail: [email protected]
2Saarland 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 self-assembly 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 species-specific 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 nano-sized, 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
1Institute of Physical Chemistry, Saarland University, Am Markt-Zeile 3, 66125 Saarbrücken, Germany
E-mail: [email protected] 2present 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] R. Hempelmann, M.-S. Löffler, H. Schmitz, H. Natter and J. Divisek, EP 1 307 939
B1, 2001 [2] M.-S. Löffler, H. Natter, R. Hempelmann and K. Wippermann, Electrochimica
Acta 48, 3047-3051 (2003) [3] K. Wippermann, K. Klafki, J. Mergel, M.-S. Löffler, H. Natter und R.
Hempelmann, Proc. Electrochem. Soc. 31, 518 – 529 (2005) [4] R. Hempelmann, V. Keller, M. Lopez, H. Natter, EP 0700 3516.7 (2007) [5] 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
1Institute of Physical Chemistry, Saarland University, 66123 Saarbrücken, Germany 2Institute 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] I. Moussallem, J. Jörissen, U. Kunz, S. Pinnow, T. Turek, J. Appl. Electrochem. 2008,
38, 1177-1194. [2] O. de Nora, Chem. Eng. Technol. 1970, 42, 222-226. [3] H.B. Beer, Brit. Patent 1 147 442, 1965. [4] 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 radia-tion, 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 de-pendencies without physical meaning. More sophisticated programs, like FormFit [2], use separate models for instrumental broadening and microstructure and enable extensive evalua-tion of microstructural effects [3]. A rather new method, the fundamental parameters ap-proach, 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.
