6 Materialchemie
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- 6 Materialchemie (274)
- 6.6 Physik und chemische Analytik der Polymere (91)
- 6.1 Oberflächen- und Dünnschichtanalyse (65)
- 6.3 Strukturanalytik (57)
- 6.2 Material- und Oberflächentechnologien (34)
- 6.7 Materialsynthese und Design (30)
- 6.5 Synthese und Streuverfahren nanostrukturierter Materialien (18)
- 7 Bauwerkssicherheit (15)
- 1 Analytische Chemie; Referenzmaterialien (9)
- 4 Material und Umwelt (9)
Eingeladener Vortrag
- nein (164)
Das Fügeverfahren Kleben bietet viele Vorteile, wie z.B. das Verbinden unterschiedlicher Materialklassen, geringe thermische Belastung (und damit ggf. verbundene Strukturveränderung/-schwächung) der Fügeteile und eine Lastverteilung über den gesamten Fügebereich. Die Auswahl an verfügbaren Klebstoffen und Vorbehandlungsoptionen sind dabei - wie die Applikationen auch - vielfältig. Es werden vier Applikationsbeispiele zu Referenzklebverbunden aus Edelstahl, zur Plasmaaktivierung von Niedrigenergie-Polymeren, zur Bestimmung der Haftfestigkeit von Lackierungen auf GFK und zur Wirkung von Primern vorgestellt. Einige Polymere weisen z.B. Eigenschaften auf, die eine Herstellung von festen und dauerhaft beanspruchbaren Kleb-verbindungen erschweren. Im Allgemeinen geht dies mit geringen Oberflächenenergien einher. Mittels Oberflächenvorbehandlung, z.B. durch Plasmafeinreinigung bzw. Plasmaaktivierung, können die Grenzflächen solcher Polymere - bezogen auf die Eignung als Fügeteile (Klebfestigkeit) oder als Substrat (Haftfestigkeit) – optimiert bzw. die Oberflächenenergie erhöht werden. Schnelle, zuverlässige und statistisch abgesicherte Prüfverfahren zur Ermittlung von Verbund-eigenschaften sind dabei unverzichtbar.
Das Fügeverfahren Kleben bietet viele Vorteile wie z.B. das Verbinden schwieriger Materialklassen, geringe thermische Belastung (Strukturveränderung/-schwächung) der Fügepartner und eine Lastverteilung über den gesamten Fügebereich. Die Auswahl an verfügbaren Klebstoffen und Vorbehandlungsoptionen ist dabei ebenfalls vielfältig. Einige Polymere weisen darüber hinaus Eigenschaften auf, die eine Herstellung von festen und dauerhaft beanspruchbaren Klebverbindungen erschweren. Mittels Oberflächenbehandlung, z.B. durch Plasmafeinreinigung bzw. –aktivierung, können die Grenzflächern solcher Polymere - bezogen auf die Eignung als Fügeteilpartner – optimiert werden. Schnelle Prüfverfahren zur Ermittlung von Verbundeigenschaften sind somit erforderlich.
Das Messprinzip Centrifugal Adhesion Testing Technologie verwendet die radial gerichtete Zentrifugalkraft als Belastungsgröße des zu testenden Verbunds, die durch Variation der Drehzahl gesteuert wird. Bei Erreichen der kritischen Beanspruchung trennt sich ein aufgeklebter Prüfstempel vom Substrat. Zeitgleich wird ein positionsbezogenes IR-Signal aus dem drehenden Rotor an das Basisgerät gesendet und zusammen mit der Drehzahl an die PC-Software übertragen. Für jede Probe wird die Bruchkraft berechnet und in Echtzeit angezeigt. Der Adhesion Analyser LUMiFrac® untersucht bis zu acht Prüfkörper unter identischen Bedingungen. Das neue Messprinzip erfüllt die Anforderungen von DIN EN 15870, DIN EN 14869-2, ISO 4624 sowie DIN EN 13144.
Die Multiprobentestung ermöglicht schnelle Charakterisierungen von Klebverbindungen. So kann der Effekt einer Plasmabehandlung von Bauteilen auf die Verbundfestigkeit zeitsparend bestimmt werden. Die gezielte Veränderung unterschiedlicher Plasma-Parameter, wie beispielsweise, die Plasmazusammensetzung, der Abstand vom Plasmabrenner zur Oberfläche oder die Verweildauer unter dem Brenner, beeinflußt die Festigkeit des Klebsystems und ist dem LUMiFrac direkt quantifizierbar.
Neben der Festigkeitsbestimmung von Klebverbindungen ist die Haftung von Schichtsystemen ein wichtiger Anwendungsbereich. Ergebnisse für Zug- und Scherbeanspruchung, realisiert mit unterschiedlichen Prüfkörper-Geometrien, werden vorgestellt. Ferner werden verschiedene festigkeitsbeeinflussende Faktoren, wie Prüfgeschwindigkeit oder Substratverformung bei Beanspruchung untersucht
Using magnetic materials for energy conversion as an example, this lecture shows how X-ray tomography investigations can contribute to structure elucidation in composites and solid samples. The components are tested non-destructively in order to characterize cracks, pores and other defects and their influence on the functional properties three-dimensionally and in good time in the life cycle of the material. If you combine microtomography with other methods of magnetic material characterization, you can make unique statements about the structure and the functional properties.
Using magnetic materials for energy conversion as an example, this lecture shows how X-ray tomography investigations can contribute to structure elucidation in composites and solid samples. The components are tested non-destructively in order to characterize cracks, pores and other defects and their influence on the functional properties three-dimensionally and in good time in the life cycle of the material. If you combine microtomography with other methods of magnetic material characterization, you can make unique statements about the structure and the functional properties.
Functional materials for energy conversion are important technology drivers needed for the implementation of low carbon energy. Therefore, researchers commonly focus on improving the intrinsic properties of a functional material. However, for applications, the extrinsic properties are at least as important as the intrinsic ones. Consequently, it is important to investigate and understand the external and internal structure of semi-finished products and especially defect dependent properties. The extrinsic properties may change during application and the life cycle of the material as well as through processing and molding steps.
Our studies show how X-ray tomographic (XCT) investigations can contribute to structure investigations in composites and massive samples using the example of magnetic materials for energy conversion. The components are tested non-destructively in 3D in order to localize and characterize cracks, pores, inclusions as well as other defects and their influence on the functional properties and also “in-time” during the life cycle of the material. Exsitu and in-situ experiments performed with non-destructive XCT are predestinated to follow damaging mechanisms of materials under certain load conditions, atmospheres or liquids, e.g. went through several working cycles of a functional material. By combining microtomography with other methods of magnetic and classical material characterization, unique statements about the structure and the functional properties can be made.
From the applications point of view, sometimes complex, three-dimensional geometries are needed to fully exploit the functional properties of the materials, e.g. to ensure a high surface area for heat exchange. Since many functional materials are brittle and difficult to form, shaping is often a big challenge. In principle, additive manufacturing processes offer the possibility to produce complex, porous components from poorly formable alloys.
If all stages of additive manufacturing are accompanied by X-ray tomographic imaging, the process of finding the optimal parameters for material processing can be significantly accelerated.
Based on the quality control of the initial powder material used and also investigations of the shape and arrangement of defects within the molten structure and their relationship with the melting path scanning strategy, Xray tomography has proven to be an ideal tool for additive manufacturing, even for functional materials. Overall, tomographic methods are important tools for the development of functional materials to application maturity.
Our aim is to develop a new method for full field X ray fluorescence imaging at the BAM line @ BESSY II. We will combine an energydispersive array detector for X rays with a coded aperture to get high resolution images . In coded aperture imaging , an object is projected through a mask , producing many overlapping images on the detector . The first part of the project is to perform raytracing simulations to get realistic data and to develop a reconstruction method that allows to get the Information about the investigated object out of the projected image .
We developed a new method for full field X-ray fluorescence imaging at the BAMline @ BESSY II. We combined an energy dispersive array detector for X-rays with a coded aperture to get high resolution images.
In coded aperture imaging, an object is projected through a mask, producing many overlapping images on the detector. To get the information about the investigated object out of the projected image, a decoding step is necessary.
The first part of our project was to develop the decoding algorithms. We tested the reported reconstruction with an antimask and compared the results with the performance of self-written reconstruction programs based on an iterative and a genetic algorithm. First tests were performed with raytracing simulations.
The next step was the collection of experimental data at the BAMline @ BESSY II (HZB). A test objects could be successfully reconstructed with our newly developed algorithm.
Our aim is to develop a new simple and inexpensive method for full field X-ray fluorescence imaging . We combine an energy dispersive array detector with a coded aperture to obtain high resolution images . To obtain the information from the recorded image a reconstruction step is necessary . The reconstruction methods we have developed , were tested on simulated data and then applied to experimental data . The first tests were carried out at the BAM line @ BESSY II. This method enables the simultaneous detection of multiple elements , which is important e.g. in the field of catalysis.
The industrial use of ultrashort laser pulses has made considerable progress in recent years. The reasons for this lie in the availability of high average powers at pulse repetition rates in the several 100 kHz range. The advantages of using ultrashort laser pulses in terms of processing precision can thus be fully exploited. However, high laser intensities on the workpiece can also lead to the generation of unwanted X-rays. Even if the emitted X-ray dose per pulse is low, the accumulated X-ray dose can become significant for high-repetition-rate laser systems so that X-ray exposure safety limits must be considered. The X-ray emission during ultrashort pulse laser processing was investigated for a pulse duration of 925 fs at 1030 nm wavelength and 400 kHz repetition rate. Industrially relevant materials such as steel, aluminum and glass were treated. Tungsten served as reference. X-ray spectra were recorded, and X-ray dose measurements were performed for laser treatment in air. For laser intensities > 2 × 10^13 W/cm2, X-ray doses exceeding the regulatory exposure limits for members of the public were found. Suitable X-ray protection strategies are proposed.
Ultrashort laser pulse micromachining features a high precision. By increasing the repetition rate of the applied laser to several 100 kHz, laser processing becomes quick and cost-effective and make this method attractive for industrial applications. Upon exceeding a critical laser intensity, hard X-ray radiation is generated as a side effect. Even if the emitted X-ray dose per pulse is low, the accumulated X-ray dose becomes significant for high-repetition-rate laser systems so that radiation safety must be considered.
Zinc is an essential trace element and is ingested daily by humans, partly in dissolved form. The first contact is with saliva, in which many ions are dissolved whose solubility product with zinc can be low. This could result in compounds forming, possibly in nanoparticular form, which could have different effects on the organism than pure zinc ions.
In this study, we report on the saliva stage of the artificial digestion of zinc chloride as a model substance for zinc ions. To facilitate in situ measurements, the sample is continuously passed through a small-angle x-ray scattering (SAXS) system. This custom-made machine is capable of measuring over a wide q-range and thereby able to resolve structures from around 250 nm down to the crystal structure. It is thus an excellent tool for investigating both the particle size distribution and the atomic structure of the sample.
By curve fitting, we found that shortly after addition of zinc chloride to saliva, small particles with a mean radius of 1.9 ± 0.1 nm and a distribution width of 0.6 ± 0.1 nm formed. These particles are aggregated to compact mass fractals with a fractal aggregate size of 14.7 ± 0.1 nm and a fractal dimension of 2.96 ± 0.02. Approximately 7200 single particles form each mass fractal, whose radius of gyration was found to be 36 ± 1 nm. The growth of these structures continues over the course of several weeks. To determine the compound that was formed, infrared spectroscopy was used in addition to the SAXS measurements, and zinc phosphate was identified as the product.
Water as side effect of reinforcing boehmite filler Local changes in anhydride cured epoxy resin
(2019)
Nanocomposites offer wide opportunities for lightweight constructions and enable reduction of weight and volume. Beside macroscopic toughening nanoparticle reinforced polymers show a soft interface around boehmite (AlOOH) filler nanoparticles. A related strong interaction between boehmite and the anhydride cured resin system is widely suspected in literature but not determined by structural Analysis. Determination of the molecular structure is important to allow simulations approaching the real system and predict future reinforcing effects.
DRIFT (diffuse refletance infrared fourier transformed) spectra of the boehmite reinforced anhydride cured epoxy show significant changes in the molecular structure compared to the neat polymer. Further investigations of the interactions between the single components of the resin system and the boehmite filler pointed out reactions between released water released from the boehmite filler and the anhydride hardener or amine accelerator. This leads to the discussion of competing polymerisation mechanisms that highly influence the polymer properties. Ongoing experiments and literature research approve that this impact of water is able to locally change the stoichiometrie, alter the curing mechanism or support an inhomogeneous crosslink density.
Visualisierung von mikro- und nanoskalierten Oberflächenstrukturen mittels abbildender Ellipsometry
(2019)
In den letzten Jahren hat die Einbindung der abbildenden Ellipsometrie in die Gruppe der optischen Verfahren zur Oberflächencharakterisierung ein enormes Potential bei der Analyse von topologischen Strukturänderungen gezeigt. Der dabei abgebildete Kon-trast wurde typischerweise auf Änderungen im Brechungsindex, Absorptionseffekte oder Schichtdickenänderungen zurückgeführt. In späteren Studien wurde festgestellt, dass auch andere Faktoren, wie etwa die Krümmung der Oberfläche oder Kanten von Struktu-ren einen signifikanten Einfluss auf die Messung der ellipsometrischen Paramater haben. Um diese Effekte aus der ellipsometrischen Messung extrahieren zu können, wird auf die Analyse der Müller-Matrix zurückgegriffen.
In dem hier vorliegenden Beitrag wird gezeigt, wie die Müller-Matrix-Imaging Ellipsomet-rie (MM-IE) zur Charakterisierung von Oberflächenstrukturen verwendet werden kann. Dazu werden mikro- und nanoskaliert gekrümmte Oberflächen zunächst mit verschiede-nen Referenzmethoden, wie Rasterelektronenmikroskopie (SEM), Lichtmikroskopie (OM), Weißlichtinterferenzmikroskopie (WLIM) und Rasterkraftmikroskopie (AFM) vali-diert erfasst. Der anschließende Vergleich mit den Ergebnissen der Müller-Matrix-Ima-ging-Ellipsometrie ermöglicht eine Korrelation der zugrunde liegenden Strukturphäno-mene mit den ellipsometrischen Daten. In diesem Artikel wird das Prinzip an drei industriell relevanten Strukturgruppen demonstriert: Sub-Mikropartikel, Mikropartikel und sub-mikroskalierte Vertiefungen.
Visualisierung von mikro- und nanoskalierten Oberflächenstrukturen mittels abbildender Ellipsometrie
(2019)
In den letzten Jahren hat die Einbindung der abbildenden Ellipsometrie in die Gruppe der optischen Verfahren zur Oberflächencharakterisierung ein enormes Potential bei der Analyse von topologischen Strukturänderungen gezeigt. Der dabei abgebildete Kon-trast wurde typischerweise auf Änderungen im Brechungsindex, Absorptionseffekte oder Schichtdickenänderungen zurückgeführt. In späteren Studien wurde festgestellt, dass auch andere Faktoren, wie etwa die Krümmung der Oberfläche oder Kanten von Struktu-ren einen signifikanten Einfluss auf die Messung der ellipsometrischen Paramater haben. Um diese Effekte aus der ellipsometrischen Messung extrahieren zu können, wird auf die Analyse der Müller-Matrix zurückgegriffen.
In dem hier vorliegenden Beitrag wird gezeigt, wie die Müller-Matrix-Imaging Ellipsomet-rie (MM-IE) zur Charakterisierung von Oberflächenstrukturen verwendet werden kann. Dazu werden mikro- und nanoskaliert gekrümmte Oberflächen zunächst mit verschiede-nen Referenzmethoden, wie Rasterelektronenmikroskopie (SEM), Lichtmikroskopie (OM), Weißlichtinterferenzmikroskopie (WLIM) und Rasterkraftmikroskopie (AFM) vali-diert erfasst. Der anschließende Vergleich mit den Ergebnissen der Müller-Matrix-Ima-ging-Ellipsometrie ermöglicht eine Korrelation der zugrunde liegenden Strukturphäno-mene mit den ellipsometrischen Daten. In diesem Artikel wird das Prinzip an drei industriell relevanten Strukturgruppen demonstriert: Sub-Mikropartikel, Mikropartikel und sub-mikroskalierte Vertiefungen.
View into the depths of copolymer microstructure by a special approach of LC-MS data evaluation
(2019)
It is a well-known story that copolymers beside their molar mass distribution (MMD) can exhibit a functionality type distribution (FTD), a copolymer composition distribution (CCD), a monomer sequence distribution (MSD) and additionally different topologies within one sample. This is and will remain a challenge for analysts.
First a very short overview will be given concerning the common liquid separation techniques for polymers (SEC, LAC, LCCC, GELC) coupled to soft ionization mass spectrometric methods like MALDI and ESI-MS with focus on their limitations. For very broadly distributed samples or chemical very similar species the superposition of different separation mechanisms in chromatography is unavoidable or the separation efficiency cannot be optimized.
Different ionization probabilities and species of the same nominal mass with completely different structures are just two problems of mass spec of complex polymer mixtures.
Subsequently, different examples will be shown how these limitations in some cases could be outsmarted.
First example will be the separation of statistical EO-PO copolymers of different chemical compositions by end group functionality and the quantification of end group fractions over the whole CCD. Here an UP-LCCC / ESI-TOF-MS coupling is applied.
Further for different kinds of polymers it will be shown how it could be realized to obtain information on small isobaric/isomeric topological heterogeneities by coupling UP-SEC / ESI-TOF-MS.
All results are based on the data processing of reconstructed ion chromatograms of single mass traces of complex ESI-MS spectra.
Polymers with intrinsic microporosity are promising candidates for the active separation layer in gas separation membranes. Here, by means of inelastic neutron scattering, the vibrational density of states (VDOS) and the molecular mobility were investigated for PIM-1, the prototypical polymer with intrinsic microporosity. The results are compared to data measured for a more conventional high-performance polyimide used in gas separation membranes (Matrimid).
The measured data show the characteristic low frequency excess contribution to the VDOS above the Debye sound wave level, generally known as the Boson peak in glass-forming materials. In comparison to the Boson peak of Matrimid, that of PIM-1 is shifted to lower frequencies. This shift is discussed considering the microporous, sponge-like structure of PIM-1 as providing a higher compressibility at the molecular scale than for conventional polymers.
Elastic fixed window scans were measured on a neutron backscattering spectrometer to have an overview about the molecular dynamics at a time scale of ca. 1 ns. The temperature dependence of the estimated mean squared displacement shows a step-like increase in the temperature range from 100 K to 250 K indicating the onset of some molecular mobility. The nature of this motional process was analyzed in detail by quasielastic neutron scattering combining Time-of-Flight and backscattering where the data are discussed with regard to both the q- and the temperature dependence.
Polymers with intrinsic microporosity are promising candidates for the active separation layer in gas separation membranes. Here, by means of inelastic neutron scattering, the vibrational density of states (VDOS) and the molecular mobility were investigated for PIM-1, the prototypical polymer with intrinsic microporosity. The results are compared to data measured for a more conventional high-performance polyimide used in gas separation membranes (Matrimid).
The measured data show the characteristic low frequency excess contribution to the VDOS above the Debye sound wave level, generally known as the Boson peak in glass-forming materials. In comparison to the Boson peak of Matrimid, that of PIM-1 is shifted to lower frequencies. This shift is discussed considering the microporous, sponge-like structure of PIM-1 as providing a higher compressibility at the molecular scale than for conventional polymers.
Elastic fixed window scans were measured on a neutron backscattering spectrometer to have an overview about the molecular dynamics at a time scale of ca. 1 ns. The temperature dependence of the estimated mean squared displacement shows a step-like increase in the temperature range from 100 K to 250 K indicating the onset of some molecular mobility. The nature of this motional process was analyzed in detail by quasielastic neutron scattering combining Time-of-Flight and backscattering where the data are discussed with regard to both the q- and the temperature dependence.
Thermosetting materials are gaining increasing attention in many structural composite applications. However, the incorporation of inorganic nanoparticles (NPs) into polymer matrix is a promising approach to enhance their functional characteristics, and thus, to enable the development of thermosets advanced application. It has been shown that Boehmite Alumina (BA) used as nanofillers can improve different parameters of polymers. This NPs can be easily tailored enabling desirable interactions with a big range of polymers. However, the overall effect of nanofiller depends on many factors, therefore, making it hard to predict the resulted performance of nanocomposites. In the current contribution we would like to discuss the impact of Boehmite NPs on two different epoxy resin nanocomposite systems with the focus on the possible influence mechanisms of this nanofiller.
As the first system, UV curable Cycloaliphatic-Epoxy Oligosiloxane (CEOS) resin/Boehmite nanocomposites were investigated by FTIR, TGA, DSC and T-SEM. It was observed that incorporation of BA leads to the reinforcement of glass transition (Tg) and overall thermal stability indicating the attractive interactions between BA and CEOS network. In addition, an increase in epoxy conversion of CEOS was concluded for nanocomposites assuming that particles are involved in UV polymerisation processes.
The second epoxy/Boehmite nanocomposite is based on the bisphenol-A-diglycidyl ether (DGEBA) cured with methyl tetrahydrophtalic acid anhydride (MTHPA). Thermomechanical as well as nanomechanical properties of this material were investigated by DMTA and IR spectroscopy and the advanced Intermodulation AFM, respectively. In contrast to the first system, it was found that BA leads to a decrease of Tg and crosslink density of the polymer while the young’s modulus of the composite and local stiffness of polymer matrix increase significantly.
As a result, the versatile role of Boehmite was detected depending on the investigated systems. Based on the obtained results, the parameters indicating property-efficient epoxy/Boehmite system are suggested.
Im Vortrag wird die Problematik Mikroplastik eingeführt und ein Probenset aus dem Mittelmeer mit ersten Ergebnissen besprochen. Die Alterung von Polymeren im Umweltkontext sowie Möglichkeiten der Analyse von Polymeralterungsfortschritten werden diskutiert. Die thermoanalytische Methode mit Zersetzungsgasanalytik (TED-GC-MS) wird eingeführt und deren Einsatzmöglichkeiten in der Thematik umrissen.
Secondary fluorescence is an inevitable effect that has to be taken into account in any algorithm for quantitative electron probe microanalysis (EPMA) as an additional correction. Moreover, secondary fluorescence worsens spatial resolution of EPMA. Secondary fluorescence is excited both by characteristic radiation and by the X-ray continuum. In most cases the correction is small. There are, however, cases, e.g. the determination of low heavy metal concentration in a light matrix, where the contribution of secondary fluorescence exceeds 10% of the measured X-ray line intensity.
For secondary fluorescence correction the measured X-ray line intensity has to be divided by the correction factor (1+I_flchar/I_p +I_flcont/I_p )≈(1+I_flchar/I_p )(1+I_flcont/I_p ) in order to get those intensity I_p, which is excited only by the primary electrons. I_flchar and I_flcont mean the calculated characteristic and continuums fluorescence intensities. In order to get the intensity of fluorescence radiation, the absorption of the exciting radiation in the specimen, the photoionization probability and the self-absorption of the emitted line must be calculated. The critical quantity is the X-ray yield of the exciting atoms in case of fluorescence by characteristic radiation and the bremsstrahlung yield of the specimen in case of continuum fluorescence. In the former case it is reasonable to apply the same physical model to calculate I_flchar and I_p.
Secondary fluorescence is an inevitable effect that has to be taken into account in any algorithm for quantitative electron probe microanalysis (EPMA) as an additional correction. Moreover, secondary fluorescence worsens spatial resolution of EPMA, as discussed once more in two recent papers. Secondary fluorescence is excited both by characteristic radiation and by the X-ray continuum. In most cases the correction is small. There are, however, cases, e.g. the determination of low heavy metal concentration in a light matrix, where the contribution of secondary fluorescence exceeds 10% of the measured X-ray line intensity.
For secondary fluorescence correction the measured X-ray line intensity has to be divided by the correction factor (1+I_flchar/I_p +I_flcont/I_p )≈(1+I_flchar/I_p )(1+I_flcont/I_p ) in order to get those intensity I_p, which is excited only by the primary electrons and enables the determination of specimen composition. I_flchar and I_flcont mean the calculated characteristic and continuums fluorescence intensities. In order to get the intensity of fluorescence radiation, the absorption of the exciting radiation in the specimen, the photoionization probability and the self-absorption of the emitted line must be calculated. This can be performed in a straightforward way. The critical quantity is the X-ray yield of the exciting atoms in case of fluorescence by characteristic radiation and the bremsstrahlung yield of the specimen in case of continuum fluorescence. In the former case it is reasonable to apply the same physical model to calculate I_flchar and I_p.
Most industrial nanoparticles have non-spherical shapes and also possess polydisperse size distributions, and due to their agglomeration/ aggregation state are difficult (or even impossible) to be addressed individually. Further, driven by regulatory purposes related to the identification of a material as a nanomaterial, the accurate measurement of the smallest dimension of a (nano)particulate material makes the analysis even more complex.
In the first phase of the EU Project nPSize - Improved traceability chain of nanoparticle size measurements (https://www.bam.de/Content/DE/Projekte/laufend/nPSize/npsize.html), the efforts are focused on synthesis of nanoparticles of well-defined, non-spherical shape. Following candidates of reference materials (CRM) with certifiable particle size (distribution) are under characterization with respect to their homogeneity and stability: (i) titania nanoplatelets (10-15 nm thickness x 50-60 nm lateral), (ii) titania bipyramides (~60 nm length x 40 nm width), (iii) titania acicular particles (100 nm length x 15-20 nm width; aspect ratio 5.5/6), (iv) gold nanorods (~10 nm width x 30 nm length), and (v) gold nanocubes (~55 nm x 55 nm x 55 nm).
Measurement of nanoparticle size (distribution) becomes a challenging analytical problem when non-spherical nanoparticles must be accurately measured. Most industrial nanoparticles have not only non-spherical shapes but also possess polydisperse size distributions, and due to their agglomeration/aggregation state are difficult (or even impossible) to be addressed individually. Moreover, driven by regulatory purposes related to the identification of a material as a nanomaterial, the accurate measurement of the smallest dimension of a (nano)particulate material makes the analysis even more complex.
In the first phase of the EU Project nPSize - Improved traceability chain of nanoparticle size measurements (https://www.bam.de/Content/DE/Projekte/laufend/nPSize/npsize.html), the efforts are focused on synthesis of nanoparticles of well-defined, non-spherical shape. Following candidates of reference materials (CRM) with certifiable particle size (distribution) are under characterization with respect to their homogeneity and stability: (i) titania nanoplatelets (10-15 nm thickness x 50-60 nm lateral), (ii) titania bipyramides (~60 nm length x 40 nm width), (iii) titania acicular particles (100 nm length x 15-20 nm width; aspect ratio 5.5/6), (iv) gold nanorods (~10 nm width x 30 nm length), and (v) gold nanocubes (~55 nm x 55 nm x 55 nm).
We developed a setup for time- and lateral-resolved X-ray absorption fine structure (XAFS) spectroscopy. A dispersive element is placed behind the sample to investigate. The broadband incoming beam transmits the sample, is then dispersed and finally collected by a position sensitive detector. This allows the recording of a whole X-ray absorption near edge structure (XANES) or extended X-ray absorption fine structure (EXAFS) spectrum in a single shot. The dispersive element is a Si(111) crystal, bent by means of a so called wafer bender, developed in house. Our setup is very flexible, easy to adjust and allows a time resolution down to one second which can be used to follow chemical reactions with dynamics on this time scale.
X-ray absorption fine structure (XAFS) spectroscopy is a powerful and widely used tool for material characterization. It is non-destructive, element-sensitive and requires no long-range order of the sample, making it suitable for the investigation of amorphous phases. XAFS includes the X-ray absorption near edge structure (XANES) and the extended X-ray absorption fine structure (EXAFS), providing information about the electronical state of the absorbing atom and the spatial order of the neighboring atoms respectively.
Our new approach presented here is derived from the classical dispersive XAFS setup. The aim is to have a scanningless, stable and reproducible setup for applications, in which dynamic processes occur in the second time scale.
A broad polychromatic beam passes through the sample and is dispersed afterwards by a convexly bent Si (111) crystal. All energies are reflected under different angles and thus spatially separated, allowing a position sensitive detector to record a spectrum over the energy range of the incoming beam in a single shot.
Tests of this setup were performed at the BAMline @ BESSY-II (Berlin, Germany) with different metal foils. First in situ measurements comprised the investigation of the early stages of the zinc(II)2-methylimidazolate (ZIF-8) crystallization. This topic of metal-organic-frameworks (MOF) research is of interest for medical applications. Structural changes with a time resolution of 1 s could be followed. The second dimension of the broad beam can be used for a lateral resolution.
Nanocomposites are extremely versatile due to their physicochemical properties, which differ significantly from bulk homopolymers. One of the inorganic nanomaterials which are increasingly used as a filler in polymer matrices is boehmite, typically used as an inexpensive flame retardant. Here, it is used as a nanofiller in polycarbonate and polyamide, expecting to improve their mechanical properties. For industrial use boehmite is obtained by the solvothermal method, resulting in a layered nanomaterial, whereas naturally it occurs as single crystals with the size of <100µm. In this work we are obtaining and isolating boehmite crystals by a bottom-up method, in which a reaction between aluminum nitride and sodium hydroxide. Obtaining boehmite as microcrystals is necessary for its analysis and characterization, as well as to investigate its interaction with polymer matrices at the polymer/particle interface. Here, the obtained particles in polymer matrices are characterized with differential scanning calorimetry and thermogravimetry analysis.
Nanocomposites are extremely versatile due to their physicochemical properties, which differ significantly from bulk homopolymers. One of the inorganic nanomaterials which are increasingly used as a filler in polymer matrices is boehmite, typically used as an inexpensive flame retardant. Here, it is used as a nanofiller in polycarbonate and polyamide, expecting to improve their mechanical properties. For industrial use boehmite is obtained by the solvothermal method, resulting in a layered nanomaterial, whereas naturally it occurs as single crystals with the size of <100µm. In this work we are obtaining and isolating boehmite crystals by a bottom-up method, in which a reaction between aluminum nitride and sodium hydroxide. Obtaining boehmite as microcrystals is necessary for its analysis and characterization, as well as to investigate its interaction with polymer matrices at the polymer/particle interface. Here, the obtained particles in polymer matrices are characterized with differential scanning calorimetry and thermogravimetry analysis.
In contrast to microplastics, little is known about nanoplastics (1 to 100 nm). In order to make the dectecability of nanoplasics more reliable, we started to develop nanoplastic reference materials. This project also aims to anser the question of how the single chain conformation of bio(polymers) changes in contact with nanoplastics. Small-angle X-ray and neutron scattering methods are suitable methods for studing this topic. Recently the soft and hard interactions between polystyrene nanoplasics and human serum albumin corona was investigated with small-angle neutron scattering. Here we concentrate on small-angle X-ray scattering as our favorite method to study how (bio)polymers change their conformation in contact with nanoplastics. The scattering of bovine serum albumin in its native state can be detected easily. The scattering pattern of this biopolymer changes dramatically when its globular stucture changes to a coil structure. Modeling of chain conformations and the calculation of the scattering pattern is relatively easy to perform. Numerous model calculations will be provided to predict the changes of conformation of single bio(polymer) chains when in conatact with nanoplastics. These predictions will be compared with recent experimenal results from in situ measurments of bio(polymers) in contact with nanoplastics. The impact of temperature, polymer concentration and salt on the single-chain conformation changes will be discussed.
The European Commission's recommendation on the definition of nanomaterial [2011/696/EU] is broadly applicable across different regulatory sectors and requires the quantitative size Determination of constituent particles in samples down to 1 nm. A material is a nanomaterial if 50 % or more of the particles are in the size range 1-100 nm. The implementation of the definition in a regulatory context challenges measurement methods to reliably identify nanomaterials and ideally also nonnanomaterials as substance or product ingredient as well as in various matrices.
The EU FP7 NanoDefine project [www.nanodefine.eu] addressed these challenges by developing a robust, readily implementable and cost-effective measurement strategy to decide for the widest possible range of materials whether it is a nanomaterial or not. It is based on existing and emerging particle measurement techniques evaluated against harmonized, material-dependent performance criteria and by intra- and inter-lab comparisons. Procedures were established to reliably measure the size of particles within 1-100 nm, and beyond, taking into account different shapes, coatings and chemical compositions in industrial materials and consumer products. Case studies prove their applicability for various sectors, including food, pigments and cosmetics.
A main outcome is the establishment of an integrated tiered approach including rapid screening (Tier 1) and confirmatory methods (tier 2), a decision support flow scheme and a user manual to guide end-users, such as manufacturers, in selecting appropriate methods. Another main product is the “NanoDefiner” e-Tool which implements the flow scheme in a user-friendly software and guides the user in a semi-automated way through the entire decision procedure. It allows a cost-effective selection of appropriate methods for material classification according to the EC's nanomaterial definition and provides a comprehensive report with extensive explanation of all decision steps to arrive at a transparent identification of nanomaterials as well as non-nanomaterials for regulatory
purposes.
Polymers of intrinsic microporosity (PIMs) have recently emerged as novel materials for a broad range of high-performance applications from gas separation to electronic devices. The very rigid, contorted polymer chains show only limited molecular mobility and therefore pack inefficiently giving rise to intrinsic microporosity with pore sizes generally smaller than 1 nm resulting in BET surface areas larger than 700 m2/g. Using conventional thermal analysis techniques, no glass transition temperature (Tg) of PIMs could be unambiguously detected up to now. Employing fast scanning calorimetry (FSC) based on a one chip sensor, decoupling the time scales responsible for the glass transition and the thermal decomposition is a reliable strategy to overcome this limitation. The FSC device is capable to heat and cool a small sample (ng-range) with ultrafast rates of several ten thousand K/s. Evidence of a glass transition is obtained for a series of PIMs with different chain rigidities. Local small-scale fluctuations are held responsible for the glass transition of highly rigid PIMs rather than segmental motions as in conventional polymers.
A central challenge to ensure the sustainable production and use of nanotechnologies is to understand and effectively control the risks along the industrial innovation value chain. Knowledge about nanotechnology processes and nanosafety issues (hazards, fate, risk...) is growing rapidly but the effective use of this knowledge for risk management by market actors is lagging behind.
EC4SafeNano (European Centre for Risk Management and Safe Innovation in Nanomaterials and Nanotechnologies) promotes a harmonized vision of expertise in risk assessment and management for the public and private sectors to enable the safe development and commercialization of nanotechnology.
EC4SafeNano is operated together by major European risk institutes with the support of numerous associated partners, gathering all stakeholders involved in Nanomaterials and Nanotechnologies (regulators, industry, society, research, service providers...).
In a case study the surface chemical transformations upon 2 different ageing procedures (long-term UV irradiation or swimming pool water) of a representative set of titanium dioxide nanoparticles has been investigated. The materials have been analyzed by various analytical techniques. Each method addresses different aspects of the complex endpoint surface chemistry. The multi technique approach allows evaluation of the capabilities and limitations of the applied methods regarding their suitability to address the endpoint surface chemistry and their sensitivity to identify even small surface chemical transformations.
Results:
- To obtain a comprehensive picture, it is insufficient to concentrate on a single analysis technique.
- By using time-of-flight secondary ion mass spectrometry (ToF-SIMS) in combination with principal component analysis (PCA) it was possible to identify even subtle changes in the surface chemistry of the investigated materials.
- A general trend that was observed for the UV-aged samples is the decrease of organic material on the nanomaterial surface.
This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 723623.
The Dark Side of Science
(2019)
The Joint Summer School of the two Marie Skłodowska-Curie Innovative Training Networks (ITN) “BioCapture” and “GlycoImaging”, funded by the EU within the Horizon 2020 framework programme, which are both devoted to the development of new methods for cancer biomarker and cancer cell detection, will take place at the Adlershof Campus of BAM. 19 Early stage researchers of both projects will convene, discuss their own science and plan future collaborative research. Training in scientific writing (instructor: Luita Spangler, Free University of Berlin), an employability workshop (Antti Kapanen, University of Applied Sciences Berlin) and first contacts with the “dark side of science” (Brian R. Pauw, BAM) will complement the programme of the summer school.
The movement of the macroscopic magnetic moment in ferromagnetic systems can be described by the Landau-Lifshitz (LL) or Landau-Lifshitz-Gilbert (LLG) equation. These equations are strictly valid only at absolute zero temperature. To include temperature effects a stochastic version of the LL or LLG equation for a spin density of one per unit cell can be used instead. To apply the stochastic LL to micromagnetic simulations, where the spin density per unit cell is generally higher, a conversion regarding simulation cell size and temperature has to be established. Based on energetic considerations, a conversion for ferromagnetic bulk and thin film systems is proposed. The conversion is tested in micromagnetic simulations which are performed with the Object Oriented Micromagnetic Framework (OOMMF). The Curie temperatures of bulk Nickel, Cobalt and Iron systems as well as Nickel thin-film systems with thicknesses between 6.3 mono layer (ML) and 31ML are determined from micromagnetic simulations. The results show a good agreement with experimentally determined Curie temperatures of bulk and thin film systems when temperature scaling is performed according to the presented model.
Titanium dioxide is one of the most studied metal oxides due to its chemical, surface, electronic and (photo)catalytic properties, providing this material of multisectorial applications ranging from healthcare, photocatalysis, smart materials with self cleaning and self sterilizing properties and solar energy harvesting. However it is difficult to correlate the functional properties of TiO2 nanomaterials to the properties at single nanoparticle level due to the high polydispersity in shape, size and surface features of the currently available TiO2 nanoparticles (NPs). Although intensive experimental and theoretical studies have been conducted on the reactivity of different surfaces of metal oxides such as TiO2 much less attention is paid on the dependence of functional properties, like photocatalytic activity, dye adsorption, open circuit potential and fill factor in dye sensitized solar cells, on crystal facets in different orientations. One of the goal of SETNanoMetro project was the development of design rules to tune crystal facets of TiO2 NPs in order to optimize and control functional properties. In the present work we have developed a series of design rules in order to obtain sets of anatase TiO2 NPs with low polydispersity and to tune their shape and size by hydrothermal processing of Ti(IV)-
Triethanolamine complex in presence of different shape controllers. Through a careful experimental design, a predictive soft model was developed. The model is able to predict the synthesis outcome allowing to tune the shape factor from 5 (prisms) to 1.5 (bipyramids) to 0.2 (platelets). This allows to control the main crystal facets exposed ranging from (100) to (001). Due to the dependence of functional properties of nanomaterials on shape distribution and not only size, the availability of NPs sets with uniform and well defined and tunable shapes can be of paramount relevance in order to produce reference nanomaterials for shape measurement.
We present the synthesis of monodisperse monometallic Ni nanoparticles (NPs) and bimetallic NiCu respectively NiCo NPs. The NPs were investigated using SAXS, STEM, EDX, and XANES, showing that the NPs are size tunable and stable while the surface is not entirely covered. Nickel NPs have exhibited immense potential as important catalyst for the Sabatier reaction, i.e. converting waste to energy via transformation of CO2 into CH4.
Nanoparticles (NP) have become important materials for a variety of chemical technologies. The enhanced surface-area-to-volume ratio of NPs, making them excellent for use as catalyst, in analytical assays, and for antimicrobial applications.
Nickel NPs have exhibited immense potential as important catalyst for the Sabatier reaction, i.e. converting waste to energy via transformation of CO2 into CH4, and could replace the rare earth elements such as Ru, PT, or Rh. In this work we describe the solvothermal synthesis of monometallic and bimetallic nickel nanoparticles.
Monodisperse monometallic Ni NPs were synthesized using Oleylamin as solvent and reducing agent. The nanoparticles were investigated using small angle scattering (SAXS), scanning transmission electron microscopy (STEM) and energy dispersive X-ray spectroscopy (EDX), showing that the NPs are stable while the surface is not entirely covered. However, Ni has a high propensity to undergo oxidation, and becoming deactivated by coke formation. Hence, we further explore the preparation of bimetallic NPs, where a second metal is added to stabilize the Ni.
Bimetallic Cu-Ni NPs were synthesized by simultaneous solvothermal reduction. These bimetallic NPs exhibit excellent catalytic properties are promising candidates to be used as catalysts for efficient energy storage.
Nanoparticles (NPs) have become important materials for a variety of chemical technologies. The enhanced surface-area-to-volume ratio of NPs, making them excellent for use as catalyst, in analytical assays, and for antimicrobial applications.
Nickel NPs have exhibited immense potential as important catalyst for the Sabatier reaction, i.e. converting waste to energy via transformation of CO2 into CH4, and could replace the rare earth elements such as Ru, PT, or Rh. In this work we describe the solvothermal synthesis of monometallic and bimetallic nickel nanoparticles.
Monodisperse monometallic Ni NPs were synthesized using Oleylamin as solvent and reducing agent. The nanoparticles were investigated using small angle scattering (SAXS), scanning transmission electron microscopy (STEM) and energy dispersive X-ray spectroscopy (EDX), showing that the NPs are stable while the surface is not entirely covered. However, Ni has a high propensity to undergo oxidation, and becoming deactivated by coke formation. Hence, we further explore the preparation of bimetallic NPs, where a second metal is added to stabilize the Ni.
Bimetallic Cu-Ni NPs were synthesized by simultaneous solvothermal reduction. These bimetallic NPs exhibit excellent catalytic properties are promising candidates to be used as catalysts for efficient energy storage.
Absorption edge tomography is a method which exploits the sudden change of the attenuation coefficient, when the photon energy crosses the absorption edge of an element. The beamline BAM line at BESSY II, which is operated by the Federal Institute for Materials Research and Testing, can provide a monochromatized beam in a photon energy range from 5 keV up to 80 keV with a bandwidth of 2%. Together with the microtomography setup, this enables differential tomography sensitive to any element with N >= 24 (Cr) by using an appropriate K- or L-edge in this range. Here, a polymer filament embedding metal organic framework (MOF) was prepared and used for 3D printing. Absorption edge tomography at the copper K edge was employed to perform a non-destructive 3D characterization of the microstructure of the embedded MOF. Data fusion was then used to determine the size distribution of the embedded MOF.
Absorption edge tomography is a method which exploits the sudden change of the attenuation coefficient, when the photon energy crosses the absorption edge of an element. The beamline BAM line at BESSY II, which is operated by the Federal Institute for Materials Research and Testing, can provide a monochromatized beam in a photon energy range from 5 keV up to 80 keV with a bandwidth of 2%. Together with the microtomography setup, this enables differential tomography sensitive to any element with N >= 24 (Cr) by using an appropriate K- or L-edge in this range. Here, a polymer filament embedding metal organic framework (MOF) was prepared and used for 3D printing. Absorption edge tomography at the copper K edge was employed to perform a non-destructive 3D characterization of the microstructure of the embedded MOF. Data fusion was then used to determine the size distribution of the embedded MOF.
Synchrotron based absorption edge tomography for the analysis of 3D printed polymer embedded MOF
(2019)
Absorption edge tomography, also known as differential tomography at absorption edges, is a method which exploits the sudden change of the attenuation coefficient, when the photon energy crosses the absorption edge of an element. Synchrotron radiation is the best source for absorption edge tomography, because of its small bandwidth, high intensity and easily adjustable photon energy. The synchrotron beamline BAMline at the synchrotron radiation facility BESSY II in Berlin, which is operated by the Bundesanstalt für Materialforschung und -prüfung (BAM), provides a monochromatized beam in a photon energy range from 5 keV up to 80 keV with a bandwidth of 2%, when the double multilayer monochromator is used. Together with the microtomography setup, this enables differential tomography with submicron resolution at the K edge of the elements from chromium up to the lanthanides, and up to uranium, when the L edges are used as well.
In this work, metal organic frameworks (MOFs) embedded in polymer are characterized using differential tomography. MOFs are microporous structures of metal ions, coordinated by organic linker molecules, that can be used in a broad field of applications, especially in gas storage and catalysis. In this work, polymer embedded MOFs were extruded into filaments, which were subsequently used for 3d-printing to profit from the specific properties of the MOFs in polymeric materials combined with the arbitrary shapes provided by 3d-printing. For the extrusion, different polymer classes like ABS, polyester- and polyetherurethanes, as well as different MOFs (ZIF-8, ZIF-67, HKUST-1) were used to create MOF containing filaments with a nominal diameter of 3.0 mm. Differential tomography at the edges of the Zn, Co, and Cu was then used to find the distribution of the corresponding MOF in the filament and to analyze the shape of the inclusions.
In recent years, the improved understanding of the formation of laser-induced periodic surface structures (LIPSS) has led to an emerging variety of applications that modify the optical, mechanical and chemical properties of many materials. Such structures strongly depend on the laser beam polarization and are formed usually after irradiation with ultrashort linearly polarized laser pulses. The most accepted explanation for the origin of the structures is based on the interference of the incident laser radiation with electromagnetic surface waves that propagate or scatter at the surface of the irradiated materials. This leads to an intensity modulation that is finally responsible for the selective ablation in the form of parallel structures with periods ranging from hundreds of nanometers up to some micrometers. The versatility when forming such structures is based on the high reproducibility with different wavelength, pulse duration and repetition rate laser sources, customized micro- and nanometric spatial resolutions, and the compatibility with industrially relevant processing speeds when combined with fast scanning devices. In this contribution, we review the latest applications in the rapidly emerging field of surface functionalization through LIPSS, including biomimetic functionalities on fluid transport, control of the wetting properties, specific optical responses in technical materials, improvement of tribological performance on metallic surfaces and bacterial and cell growth for medical devices, among many others.
Nanomaterials are a relatively new class of materials for which a regulatory framework still has to be established and regulators require comprehensive datasets of well characterized nanomaterials for the implementation. Especially information about the surface chemistry of nanoparticles is crucial, since it largely determines their biological and environmental fate. How the surface chemistry changes under relevant ageing conditions is of particular interest, because exposure will normally occur not to the pristine material but to a nanoform that underwent some kind of transformation.
In this talk, first a short overview about the contributions of division 6.1 to multiple European-funded projects will be presented, in which surface analytical techniques are used to improve the physical-chemical characterization of nanomaterials. Secondly, a study investigating the surface-chemical transformations of a representative set of titanium dioxide nanoparticles is discussed in more detail. The ageing has partly been performed at the BAM division 7.5, and the surface chemistry was analyzed using time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS). By analyzing the complex mass spectra with principal component analysis (PCA), it was possible to identify even subtle changes that occur upon ageing.
An overview of the activities in the field of surface and microbeam analysis at BAM-6.1 is given with focus on physico-chemical characterization at the nanoscale. Ideas of potential joint activities are presented: structural and chemical analysis of graphene, deposition techniques for nanoparticles, EBSD on steel for a broader range of methods, instruments and types of steel, soft X-ray Analysis of low-Z materials, analysis of mesoporous thin films, etc.
The cleaning of black carbon covered Italian marble and limestone sculptures is a challenging task for restorers and scientists, especially when black soot is penetrated into the porous surface of a stone.
Numerous sculptures of the Bode-Museum underwent two domestic fires at the repository in Berlin in May 1945, where soot damaged the surface of these artworks. Promising results in removing black layers were achieved by the application of modified gels to artificially weathered and sooted Carrara marble mockups. However, transferring the cleaning method to original samples requires a cautious proceeding with respect to short-term and long-term implications. To understand physico-chemical reactions, the analytics of gel-treated marble surfaces is of essential importance.
Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS) and Auger electron spectroscopy (AES) were used to gain insights into surface chemistry and the distribution of chemical groups or fragments and enable a deeper understanding of the functionality of the applied gels and of the efficiency of tested cleaning processes. Depth profiling by ToF-SIMS is introduced as a tool to study the penetration behavior of applied cleaning chemicals.
The contribution presents the analytical methods, their possibilities and challenges, and summarizes initial results of this study.
The exploration of metal phosphonates has gained great interest during the last decades, because of their structural diversity. They are promising candidates for a variety of applications ranging from adsorbance to electrocatalysis. The knowledge of the Crystal structure is significant for assigning a coordination polymer for a specific function. We investigated the influence of the fluorination degree of the organic linker on the Crystal packing, the interlayer distance, and the hydrophobicity of the resulting compounds. With fluorinated and nonfluorinated benzylphosphonic acids as starting materials in mechanochemical synthesis, four novel cadmium benzylphosphonates were obtained. Their structures were solved from powder X-ray diffraction.
Polymers at interfaces play a major role in a broad variety of applications ranging from engineering purposes (for instance polymer based nanocomposites) to high tech implications (for instance light emitting diodes).
Here, thin films with thicknesses down to few nanometers are prepared on different substrates as model systems for polymer composites. The thin films are investigated by a combination of surface analytical and volume sensitive methods. As surface analytical methods atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and contact angle measurements (CAM) are employed. As volume sensitive broadband dielectric spectroscopy (BDS), specific heat spectroscopy (SHS), and ellipsometry are used. Especially attention is paid to understand the glass transition behavior of thin films because the glass transition is the key phenomenon determines the application of polymers also in thin films.
To understand the glass transition behavior of thin films, which is controversially discussed in literature, a three layer model is discussed. Firstly, a mobile surface layer is assumed at polymer air interface of the film due to missing of segment/segment interactions. Secondly, in the middle of the film a bulk-like layer should be expected. Thirdly, for polymers having non-repulsive interactions with the substrate an irreversibly adsorbed layer is expected to be formed. Due the adsorption the molecular mobility of the segments in this layer is slowed down. What is measured for the glass transition of thin films is a complicated average of all of these effects. The different layers are hardly to address separately. Therefore, in the presentation especially model systems are selected and investigated to verify the layer model.
Ellipsometry has become a powerful measurement tool in semiconductor industry since the sixties of the last century.
Early standardization activities focused exclusively on SiO2/Si (ASTM F 576-01, SEMI 3624). The first generic standard dealing with ellipsometry is DIN 50989-1:2018 Ellipsometry – Part 1: Principles. Standardization is a prerequisite for accreditation according to DIN EN ISO/IEC 17025 and the evaluation of uncertainty budgets.
Die gemeinsame Forschungsstrategie der Bundesoberbehörden zur Nanotechnologie wurde 2016 veröffentlicht. Die darin enthaltenen Aufgaben wurden von den Bundesoberbehörden vielfältig bearbeitet. Diese Präsentation gibt einen Überblick über die Projekte, die von der BAM bis 2019 bearbeitet wurden/werden und sich in den Rahmen der Forschungsstrategie einordnen.
Im Vortrag wird der Ansatz zur Aufklärung von Adsorptionsprozessen, die in der Wasserphase stattgefunden haben, mittels Thermogravimetrie und Zersetzungsgasanalyse vorgestellt.
Es wird allgemein gezeigt wie TGA zur Charakterisierung von Aktivkohleoberflächen genutzt werden kann und welche Unterschiede sich in verschiedenen Adsorbat-Systemen zeigen. Im Detail wird die thermische Zersetzung von adsorbiertem Carbamazepin an drei verschiedenen Aktivkohlen präsentiert.
In diesem Beitrag wird gezeigt wie mit Thermogravimetrischen Analysen (TGA) Aktivkohleoberflächen charakterisiert werden können. Außerdem wie TGA mit Zersetzungsgasanalyse zur Untersuchung von Adsorbat-Systemen (Carbamazepin an drei verschiedenen Aktivkohlen) zur Aufklärung von Adsorptionszuständen genutzt werden kann.
Porous materials play an important role in several fields of technology, especially for energy applications like photovoltaics, electrolysis or batteries. The activity of porous films is affected by properties like porosity, film thickness, chemical composition of the material as well as the crystallinity of the framework. The complex morphology of such porous films constitutes a challenge for modern analytical techniques and requires approaches employing the combination/complementation of data of different analytical methods. In this contribution we characterize thin mesoporous iridium-titanium mixed oxide film properties by spectroscopic ellipsometry (SE).
Mesoporous iridium oxide - titanium oxide (IrOx-TiOx) films were prepared via dip-coating of a solution containing a triblock-copolymer as structure-directing agent, an iridium precursor as well as a titanium precursor in ethanol. Deposited films with different amounts of iridium (0 wt%Ir to 100 wt%Ir) were synthesized and calcined in air. The thin films were analyzed with SE using the Bruggeman effective medium approximation (BEMA) for modelling. The results were compared with electron probe microanalysis (EPMA) as part of a combined SEM/EDS/STRATAGem Analysis.
Bacterial biofilms have the capacity to develop and thrive in virtually all circumstances and surfaces, even in the most challenging environmental conditions. The pervasive and recalcitrant existence of biofilms renders them to be a significant safety risk and economical encumbrance in a wide array of industries and technologies, and therefore is a priority area of research.
It is essential to develop an improved understanding of the mechanisms implicated during biofilm formation, such as in the case of the diffusion of bacterial-secreted extracellular electron transporters, which are purported to play an important role during biocorrosion by exoelectrogenic bacteria. Hence, a fundamental understanding of electron transfer mechanisms between bacteria and extracellular electron acceptors will contribute insight to our understanding of charge transport and chemistry at the biofilm – external insoluble electron acceptor interface.
In the present work, Attenuated Total Reflection - Fourier transform-infrared (ATR-FTIR) spectroscopy has been coupled to electrochemical techniques for the nondestructive, in situ spectro-electrochemical monitoring of biofilms in real-time. Shewanella sp. have been selected for this investigation due to their adaptable exoelectrogenic respiratory capacities and their notable ability to reduce metals via several different mechanisms of extracellular electron transfer mechanisms, including self-secreted flavin shuttles. Gold-thin film model substrates have been used due to their inert nature and for their ability to permit precise manipulation of the substrate surface polarization. Additionally, hydrogels comprised of calcium cross-linked alginate have been used to mimic the architectural features of extracellular polymeric substances which are integral to a bacterial biofilm, to allow the study of electron-transporting flavin molecules in an artificial biofilm. The results will demonstrate patterns of diffusion, akin to how flavins would diffuse in a naturally occurring biofilm, and how polarization affects this process. Furthermore, insight will be gained on how the redox behavior of flavins can influence the development and evolution of a biofilm.
This interdisciplinary approach should shed light on bacterial electron transfer mechanisms which could contribute towards emerging technologies which seek to better understand such mechanisms for novel antifouling strategies, renewable energies, and bioremediation.
Zinc oxide (ZnO) nanoparticles find manifold applications, most prominently in photovoltaics, where their unique optical properties are exploited. Particularly important are their band gap energy of 3.37 eV, which can be widely tuned through doping, and a large exciton binding energy of 60 mV. As a wide-bandgap II-VI semiconductor, the optical band gap energy and fluorescence energy become size-dependent when moving to particle radii of a few nanometers.
To gain a deeper insight into this issue, we report on a microwave-assisted, size-selective synthesis of pure ZnO nanoparticles. By hydrolysis of the metal precursor in presence of a strong base at temperatures exceeding the solvent’s boiling point, the reaction is dramatically accelerated, and narrowly dispersed, spherical particles are yielded within seconds – instead of hours at lower temperatures. The determination of their size distributions in high resolution using small-angle x-ray scattering (SAXS) allows for a precise mapping of the optical properties (UV/Vis absorption and fluorescence) to particle size.
We observed that the mean particle radii increase from 2.6 ± 0.1 nm with increasing synthesis temperature from 125 °C to 200 °C. This is accompanied by a red shift of the optical band gap and the fluorescence energies, the latter of which can be seen in Figure 1. Thus, undoped ZnO nanoparticles with narrow size distributions and pre-defined size as well as optical properties can be obtained through a microwave-assisted synthesis.
Simulational tools are applied to investigate the physical properties of nanoparticles.
For the description of radioactive gold nanoparticles, particles scattering simulations are performed with the Geant4 monte carlo simulation toolkit.
The temperature dependent behaviour of the magnetization dynamics of different magnetic nanoparticles are simulated with the object oriented micormagnetic framework (OOMMF).
It is a well-known story that copolymers beside their molar mass distribution (MMD) can exhibit a functionality type distribution (FTD), a copolymer composition distribution (CCD), a monomer sequence distribution (MSD) and additionally different topologies within one sample. Nowadays a wide range of different analytical separation techniques and multi-detection possibilities are available.
The challenge consists in a clever combination of these techniques coordinated with the heterogeneity to be investigated.
A number of applications will be presented from e.g. topology elucidation of branched EO-PO “academic” copolymers to copolymer composition of partially broadly distributed progressively tailored “industrial relevant” copolymers consisting of e.g. polyamides, polycarbonates and polysiloxanes.
Multidimensional separation techniques will be demonstrated with focus on mass spectrometric detection techniques (ESI-/MALDI-TOF-MS) coupled online or semi-online to prior separation.
Extraction of true, 3D shape (and size) of non-spherical nanoparticles (NPs) is associated with Errors by conventional 2D electron microscopy using projection images. Significant efforts within the ISO technical committee TC 229 ‘Nanotechnologies’ are aimed at establishing accurate TEM and SEM measurement of NP size and shape as robust, standard procedures. Study groups have been organizing inter-laboratory comparisons on well-selected NP systems according to the market needs, such as aggregated titania nano-powder for which size and shape distribution of primary crystallites of irregular shape must be measured accurately. To be noticed is e. g. the fact that the measurement procedure allows only manual selection of the particles clearly distinguishable for analysis as well as manual definition of the contour of the imaged NPs.
An inter-laboratory exercise on titania NPs (pure anatase, grown by hydrothermal synthesis) of well-defined non-spherical shape, i.e. bipyramidal, has been recently started within ISO/TC 229 under similar conditions as for the irregular shaped titania. In the TEM micrograph the particles tracked manually according to the measurement protocol. Overlapped particles were allowed to be considered, as long as they are clearly distinguishable. One decisive NP selection criterion was to analyze only those NPs with a roundness value below 0.7, i.e. the NPs laying on the support foil and, hence, with projection areas clearly deviating from perfect circles (R=1). The overall evaluation (for 15 labs) of the size descriptors (area, Feret, minFeret, perimeter) and shape descriptors (aspect ratio, roundness, compactness, extent) by analysis of variance is just to be finished and included in ISO/WD 21363 Nanotechnologies -- Protocol for particle size distribution by transmission electron microscopy.
The successful off-line coupling of asymmetrical flow field flow fractionation (AF4) and capillary electrophoresis (CE) for Separation of nanoparticles (NPs) with different surface coatings was shown.
Two mixtures of polystyrene nanoparticles (PS-NPs) with comparable core sizes (20 nm and 50 nm) but different coatings (no coating/carboxyl-coated) were studied. Separation in either method resulted in non-baseline resolved or non-separated peaks. In contrast, two-dimensional off-line coupling of AF4 and CE resulted in clearly separated regions in their 2 D plots and can obviouly improve separation resolution.
Nowadays, different nanoparticles have been developed for commercial applications. However, since data on toxicity are barely available, their increasing application in cosmetic products, food and their release in the environment might cause severe problems. Since a range of physical, chemical, and biological characteristics of NPs are closely related to particle size and surface functionalization, precise separation and surface groups quantification is essential to acquire an in-depth understanding of their properties.
In this work, the performance of asymmetrical flow field flow fractionation (AF4) and capillary electrophoresis (CE) for the separation of nanoparticles (NPs) with different sizes, coatings, and coating densities was investigated and optimized.
For the first time, a two-dimensional off-line hyphenation of both techniques (AF4-CE) was developed. The results clearly demonstrated, that AF4-CE hyphenation can significantly improve the separation resolution and reduce the peak broadening in CE. Also, for the first time, CE was employed to determine the coating density of NPs and the results were in good agreement with the values acquired with conductometric titration.
3D coherence scanning interferometry (CSI) is anoptical, non-contact and rapide measurement technique using a defined bandwidth of white light at normal incidence. White light interference microscopy (WLIM) providest here-dimensional surface topometry data up to a resolution of 0.4 µm lateral and 0.1 nm vertical. Three operating modi, surface, films and advanced films, enable measurements of step heights, roughness, wear volume, cone angle, surface pattern and layer thickness. Traceability to SI system is ensured by certified standards (PTB/NIST) within a DAkkS DIN EN ISO/IEC 17025:2018 accredited lab.
Small-angle scattering (SAS) offers a reliable route to characterize the nanostructure of large amounts of material with a minimum of tedium, for example, easily extracting size distributions and volume fractions. There are a variety of analysis programs available while the evaluation of SAS measurements has been dominated by the classical curve fitting approach. SASfit represents such a classical curve fitting toolbox: it is one of the mature programs for SAS data analysis and has been available and used for many years. The latest developments will be presented and a scattering function of a mass fractal model of branched polymers in solution is provided as an example for implementing a plug-in.
Alternatively to classical curve fitting, part two presents the latest developments of the user-friendly open-source Monte Carlo regression package McSAS. The form-free Monte Carlo nature of McSAS means, it is not necessary to provide further restrictions on the mathematical form of the parameter distribution: without prior knowledge, McSAS is able to extract complex multimodal or odd- shaped parameter distributions from SAS data. The headless mode is presented by an example of operation within interactive programming environments such as a Jupyter notebook.
Despite abundant evidence of the occurrence of microplastics (MP) – these are particles smaller 5 mm – in aquatic environments, little is known about the accumulation of plastic in terrestrial environments, especially in soils.
Possible major input pathways could be the use of plastic mulching, the use of compost, sewage sludge or residues from biogas facilities as fertilizers, as well as littering in urban areas. To estimate the MP pollution, the development of reliable, fast methods for sampling, sample preparation, and detection is needed. The obtained data must be representative of the sampled environmental compartment and measurements from different environmental compartments must be comparable. A first breakthrough is an application of ThermoExtractionDesorption-Gas Chromatography-MassSpectrometry (TED-GC-MS) for the detection of MP, including tire abrasives. This method allows the determination of mass content within a few hours and only a minimum of sample preparation for samples from aquatic environments is needed.
However, in contrast to filtrate samples from aquatic environments, sediment or soil samples need an enrichment of MP. Whereas MP concentration from marine sediments can be obtained by floatation and density Separation techniques using NaCl solutions, the extraction or separation from soils proves to be more difficult, as plastic particles are often part of organo-mineral aggregates within the soil matrix.
The aim of this study is the development of a practicable processing guideline for representatively taken soil samples in order to concentrate microplastics, without complex and time-consuming treatment steps. Dispersants or detergents can be applied to decompose the soil matrix, but each preparation step carries the risk of crosscontamination of the sample and prolongs the preparation procedure.
For this reason, we choose ZnCl2-solution with a density of 1.7 g/cm3, which include the densities of relevant MP types (0.9-1.7 g/cm3). It was tested to achieve both, disaggregation and separation as it decomposes organic material and dissolves carbonates. Also, ZnCl2 is inert to the precipitation of undesirable salts and Carbonates during the process of density separation, as polytungstate solution does. ZnCl2 can be reused after stepwise filtering (7 µm, 1.5 µm, 0.7 µm). Thus, disposal costs can be reduced. Efficiency and reproducibility of the sample preparation as well as the degradation behavior of MP under the present conditions were demonstrated with model samples.
Real sampling campaigns were conducted at several agricultural sites and floodplains in south-west Germany. The sampling was performed according to practice for soil sampling, using adequate sampling strategies (pattern of sampling, number of field samples, homogenization, etc). The lab sample was fractioned into three size classes (5-100 µm, 100-1000 µm, and 1-5 mm). The identification and determination of mass fraction were done using TED-GC-MS.
For inorganic/polymer nanocomposites a so-called Rigid Amorphous Phase (RAF) is formed in the interfacial region by adsorption of polymer segments onto the nanoparticles. The segmental dynamics of RAF is expected to be altered, as compared to the pure matrix, which might percolate into the entire system, affecting the overall nanocomposite properties. A combination of two relaxation spectroscopy techniques (Broadband Dielectric Spectroscopy (BDS) and Specific Heat Spectroscopy (SHS) in a form of Temperature Modulated DSC (TMDSC)) as well as Fast Scanning Calorimetry (FSC) was employed to investigate the structure and molecular mobility of nanocomposites based on Epoxy and Layered Doubled Hydroxides with different nanoparticle content.
First, BDS investigations proved the existence of a process, which is present only for nanocomposites, assigned to the dynamics of polymer segments within RAF. Second, the amount of RAF was quantified by analyzing the change of specific heat capacity step of nanocomposites, comparing to the pure material.
Thirdly, the glass transition of nanocomposites was studied with FSC, applying high heating rates (500-10 000 K/s). Considering that all techniques probe essentially the same molecular process, an activation plot was constructed, delivering a complete picture of the molecular mobility and structure of the polymer nanocomposites including RAF.
For inorganic/polymer nanocomposites a so-called Rigid Amorphous Phase (RAF) is formed in the interfacial region by adsorption of polymer segments onto the nanoparticles. The segmental dynamics of RAF is expected to be altered, as compared to the pure matrix, which might percolate to the entire system, affecting the overall nanocomposite properties. A combination of two relaxation spectroscopy techniques (Broadband Dielectric Spectroscopy (BDS) and Temperature Modulated DSC (TMDSC)) as well as Fast Scanning Calorimetry (FSC) was employed to investigate the structure and molecular mobility of nanocomposites based on Epoxy and Layered Doubled Hydroxides with different nanoparticle content. First, BDS investigations proved the existence of a process, which is present only for nanocomposites, assigned to the dynamics of polymer segments within RAF. Second, the amount of RAF was quantified by analyzing the change of specific heat capacity step of nanocomposites, comparing to the pure material. Thirdly, the glass transition of nanocomposites was studied with FSC, applying high heating rates (0.5-10 kK/s). Considering that all techniques probe essentially the same molecular process, an activation plot was constructed, delivering a complete picture of the molecular mobility and structure of the polymer nanocomposites including RAF.
Crystalline molecular materials with mechanical flexibility are promising for technological development. This is particularly true for the development of advanced materials with optoelectronic and biomedical applications. While a growing number of mechanically flexible crystalline molecular materials are being reported,1 they remain scarce. At present, most discoveries are serendipitous, as limited design strategies are currently known. Amongst these strategies Desiraju et. al. suggested that elastic materials must contain herringbone structures.2 For plastic crystals, the so-called ‘shape-synthon’ strategy has been developed, in which weak non-covalent interactions are introduced into structures to facilitate mobility of molecules.3 This includes formation of slip planes. Generally, these models have performed very well at predicting and rationalizing the mechanical properties of new materials. Recently, however, a family of one-dimensional covalent networks (coordination polymers; CPs) has been described, which show mechanical elasticity. With drastically different structural chemistry, these systems do not seem to adhere to the currently established rules. Herein, we present the first such system: a plastically bendable crystal of a 1D CP, [Zn(-Cl)2(3,5-Cl2Py)2]n (where 3,5-Cl2Py = 3,5-dichloro pyridine). This CP crystallizes in a tetragonal, and can therefore be bent over two major faces to acute angles without fracturing. We conducted bending and indentation experiments to quantify the mechanical properties of the CP crystal. This was complimented by Vibrational (Raman and Terahertz) spectroscopy and theoretical calculations for deeper understanding of molecular level structural deformation.
This report describes a standard operation procedure for dispersion of nanomaterials in liquids prior to toxicological or ecotoxicological testing. Main factors, who determine the state of agglomeration and aggregation of ENMs after dispersion are specific energy input, particle concentration and fluid composition. The method was validated in two round robin tests, where two typical nanomaterials (a nanopowder and a nanodispersion) were investigated. One main result arising out of the data comparison was that only those participants, who were able to follow the instructions in the SOPs completely, received similar results regarding particle size and zeta potential. The SOP is easy to adapt for other types of nanomaterials. The results provide the standardization process and were presented at DIN working group.
Advanced wastewater treatment by the application of activated carbon is used to eliminate organic micropollutants in large scale wastewater treatment plants. However, underlying adsorption processes are unclear. On the one hand, compositions of wastewater differ and are very complex. On the other hand, activated carbons have physicochemical properties which impair investigations on adsorption mechanisms, since they are non-graphitic, non-graphitizable and have a highly disordered microstructure. This leads to their large surface areas and internal pore structure but also implies heteroatoms and functional groups. These are not easily accessible for research but affect the adsorption of organic micropollutants. Thermogravimetric analysis and evolved gas analysis can provide valuable insights into these kinds of systems. First, pyrolysis makes functional surface groups accessible, e.g. through decarboxylation, which facilitates characterisation of activated carbons. Second, adsorbates can be investigated by thermal desorption or decomposition, depending on the sorption conditions of the organic micropollutants. Single component systems as well as multi component systems with competing organic background matter are compared for various activated carbons. Surprising distinctions in the adsorption mechanisms will be presented.
Coating materials are nowadays often required to deliver not only sufficient barrier performance and suited optical appearance but a broad range of other functional properties. The incorporation of inorganic nanoparticles (NPs) is known to improve many key characteristics and provide new functionalities in polymer materials. Presented work aims to prepare and characterize an organic-inorganic coating material designed to bring together advantageous properties of hybrid materials and reinforcement effect delivered from the inorganic NPs embedment.
Siloxane-based hybrid resins hold great advantages as coating materials as their properties can be tuned between those of polymers and those of glasses, thus, the compositions with superior thermal and mechanical properties can be achieved. We used Cycloaliphatic Epoxy Oligosiloxane (CEOS) resin as a polymeric matrix where the network formation was achieved by UV induced cationic polymerisation. Boehmite Alumina (BA) nanoparticles were added to CEOS resin as a reinforcing agent and resultant material was processed into films either by bar-coating or by spin-coating depending on further characterization procedure. Two different types of BA NPs, hydrophilic and organophilic, were used in order to assess the impact of particles surface on the resin characteristics. CEOS synthesis by condensation reaction was confirmed using 13C and 29Si NMR. Changes in CEOS photocuring process, resulting from particles incorporation, were monitored by real-time IR spectroscopy. At the same time, the thermal behaviour was evaluated by DSC and TGA methods. Morphology of the coatings was investigated by means of SEM operated in transmission mode.
It was observed that BA presence increased the epoxy conversion degree and glass transition temperature. Material formulations providing best film characteristics were determined with regard to the particle type and loading. Compared to the hydrophilic nanoparticles, organophilic BA NPs yield superior overall performance of the foils.
Dose enhancement by gold nanoparticles (AuNP) was shown to increase the biological effectiveness of radiation damage in biomolecules and tissue. Most of the current studies focus on external beam therapy on combination with AuNP. Here we present a Monte-Carlo study (Geant4) to characterise radioactive AuNP. Radioactive ¹⁹⁸Au emits beta and gamma rays and is considered for applications with solid tumours. To effectively apply ¹⁹⁸AuNP their energy deposit characteristics have to be determined in terms of intrinsic and extrinsic properties e.g. AuNP diameter, AuNP density, and their clustering behaviour. After each decay process, the energy deposit, inelastic scattering events, kinetic energy spectrum of secondary particles within the AuNP themselves and in a spherical target volume of water up to 1 μm radius were determined. Simulations were performed for AuNP radii ranging from 2.5 nm to 20 nm radius, different cluster sizes and densities. The results show an increase of the energy deposit in the vicinity of the AuNP up to 150 nm. This effect nearly vanishes for distances up to one micron. For the case of AuNP clusters and the same activity, the enhancement of the energy deposit increases with the relative gold mass percentage and therefore can be adjusted by changing AuNP radius or clustering behaviour.
Dose enhancement by gold nanoparticles (AuNP) was shown to increase the biological effectiveness of radiation damage in biomolecules and tissue. Most of the current studies focus on external beam therapy on combination with AuNP. Here we present a Monte-Carlo study (Geant4) to characterise radioactive AuNP. Radioactive 198 Au emits beta and gamma rays and is considered for applications with solid tumours. To effectively apply 198 AuNP their energy deposit characteristics have to be determined in terms of intrinsic and extrinsic properties e.g. AuNP diameter, AuNP density, and their clustering behaviour. After each decay process, the energy deposit, inelastic scattering events, kinetic energy spectrum of secondary particles within the AuNP themselves and in a spherical target volume of water up to 1 μm radius were determined. Simulations were performed for AuNP radii ranging from 2.5 nm to 20 nm radius, different cluster sizes and densities. The results show an increase of the energy deposit in the vicinity of the AuNP up to 150 nm. This effect nearly vanishes for distances up to one micron. For the case of AuNP clusters and the same activity, the enhancement of the energy deposit increases with the relative gold mass percentage and therefore can be adjusted by changing AuNP radius or clustering behaviour.
This presentation reviews current and expected developments in the field of laser-induced periodic surface structures (LIPSS, ripples). These surface nanostructures are a universal phenomenon and can be generated on almost any material by irradiation with intense linearly polarized radiation. LIPSS are formed in a “self-ordered” way and are often accompanying laser material processing applications. The structures can be produced in a single-step process and enable surface functionalization through the adaption of optical, mechanical and chemical surface properties. Their spatial periods typically range from several micrometers down to less than 100 nanometers, exhibiting a clear correlation with the polarization direction of the laser radiation used. Various types of LIPSS have been classified, relevant control parameters were identified, and material specific formation mechanisms are analyzed for different types of inorganic solids, i.e., metals, semiconductors, and dielectrics, through time-resolved optical experiments and theoretical simulations. Special attention will be paid to a comparison of the currently available formation theories for LIPSS with a discussion of their respective strengths and weaknesses. Currrently explored applications featuring surface functionalization in the fields of optics, surface wetting, medicine, and tribology will be discussed.
Laser-induced periodic surface structures (LIPSS, ripples) are a universal phenomenon that can be observed on almost any material after the irradiation by linearly polarized laser beams, particularly when using ultrashort laser pulses with durations in the femtosecond to picosecond range. During the past years significantly increasing industrial and research activities have been reported in the field of LIPSS, since their generation in a single-step process provides a simple way of nanostructuring and surface functionalization towards the control of optical, mechanical or chemical surface properties. In this contribution the mechanisms of formation and current trends and applications of LIPSS are reviewed, including the colorization of technical surfaces, the control of surface wetting properties, the mimicry of the natural texture of animals, the tailoring of surface colonization by bacterial biofilms, the advancement of leadless medical pacemakers, and the improvement of the tribological performance of nanostructured metal surfaces.
Laser-induced periodic surface structures (LIPSS, ripples) are a universal phenomenon that can be observed on almost any material after the irradiation by linearly polarized laser beams, particularly when using ultrashort laser pulses with durations in the femtosecond to picosecond range. During the past years significantly increasing industrial and research activities have been reported in the field of LIPSS, since their generation in a single-step process provides a simple way of nanostructuring and surface functionalization towards the control of optical, mechanical, biological, or chemical surface properties. In this contribution the mechanisms of formation and current trends and applications of LIPSS are reviewed, including the colorization of technical surfaces, the control of surface wetting properties, the mimicry of the natural texture of animals, the tailoring of surface colonization by bacterial biofilms, the advancement of leadless medical pacemakers, and the improvement of the tribological performance of nanostructured metal surfaces.
The 44th Meeting of the Versailles Project on Advanced Materials and Standards (VAMAS) Steering Committee has just taken place at NIST in Boulder (CO, USA). BAM participates with significant contributions in Technical Working Areas on nanoparticle and surface chemistry characterization, but also has positioned itself to new global material challenges and trends in the developement of advanced materials and their characterization, such as thermal properties, self-healing materials, and micro- and nanoplastic.
High performance polymers of intrinsic microporosity (PIMs) have emerged as novel materials with broad applications from gas separation to electronic devices. Sufficiently rigid, even contorted polymer chains show only limited molecular mobility, therefore undergo inefficient packing and give rise to intrinsic microporosity with pore size generally smaller than 1 nm and BET surface areas larger than 700 m2/g. Further performance optimization and long-term stability of devices incorporating PIMs rely on our understanding of structure-processing-property relationships and physical aging, in which glass transition plays a key role. Up to now no glass transition temperature (Tg) of PIMs could be detected with conventional thermal analysis techniques before degradation. Decoupling the time scales responsible for the glass transition and the thermal decomposition is a reliable strategy to overcome this. This was achieved by employing fast scanning calorimetry (FSC) based on a chip sensor, which is capable to heat and cool a small sample (ng-range) with ultrafast rates of several ten thousand K/s. FSC provides definitive evidence of glass transition of a series of PIMs with a special consideration on the chain rigidity. The determined glass transition temperature of these PIMs follows the order of the rigidity of their backbone structures. FSC provides the first clear-cut experimental evidence of the glass transition of PIM-EA-TB with a Tg of 663 K, PIM-1 of 644 K and PIM-DMDPH-TB of 630 K at a heating rate of 1Χ104 K/s. Local fluctuations are featured in glass transition of highly rigid PIMs. As conformational changes are prevented by the backbone rigidity, the glass transition must rather be assigned to local small scale fluctuations.
Der Vortrag gibt den aktuellen Stand der Normung im Bereich der Oberflächentechnik insbesondere der Oberflächenanalytik und der Oberflächenmess- und -prüftechnik wider. Vorgestellt wird der Status technischer Berichte, Normenentwürfe und Normen u.a. zur Bewertung von Auflösung und Schärfe mit strahlbasierten Methoden im Nanometer- und Mikrometerbereich, zur Messung von Schichtdicken und Nanopartikeln in kritischen Dimensionen einschließlich Größen- und Formverteilungen mittels REM, zur Messung der Schichtdicke von Nanomaterialien und zur Klassifizierung von Kohlenstoffschichten mittels Ellipsometrie, zur Standardisierung der Ellipsometrie, zur Kalibrierung von Konfokalmikros-kopen für die Formmessung, zur linear elastisch dynamischen instrumentierten Eindringprüfung, zur Messung der flächenbezogenen Masse mittels AAS und ICP, zur Schichtpotentialmessung von Mehrfach-Nickelschichten, zur Schichtdicken und Flächen-widerstandsbestimmung sowie zur Bestimmung der Schichthaftung mittels Zentrifugentechnologie.
Neuartige Materialien, die bekannte (Werk-)Stoffe mit neuen Funktionalitäten ausstatten, spielen eine zunehmend wichtige Rolle im Bereich der Materialforschung und -prüfung. Das Spektrum neuartiger Materialien reicht von der gezielten Oberflächenfunktionalisierung und -strukturierung makroskopischer Materialien, dünnen Beschichtungen bis hin zu mikro- und nanoskaligen Kompositmaterialien und funktionalen Materialien an der Schnittstelle zur Biologie, Biotechnologie, nachhaltige Energiespeicherung und Sensorik. Dabei bieten neuartige Materialien die Chance, Werkstoffe und Produkte mit erweiterter oder verbesserter Funktionalität zu erhalten und Sicherheit bereits im Designprozess zu berücksichtigen. Durch dieses breite Anwendungsspektrum und die Herausforderungen, die solche Materialien für die Sicherheit in Chemie und Technik mit sich bringen, sind diese in allen Themenfeldern der BAM repräsentiert (Material, Analytical Sciences, Energie, Infrastruktur und Umwelt).
Die Aufgaben der BAM erstrecken sich dabei von der Herstellung von Referenzmaterialien für Industrie, Forschung und Regulation, über die Erstellung von standardisierten Referenzverfahren für nachhaltige Messungen im Umwelt- und Lebenswissenschaftsbereich bis hin zur Bereitstellung von belastbaren und zitierbaren Referenzdaten. Durch die genaue Charakterisierung neuartiger Materialien können potentiell problematische Substanzen identifiziert und deren Risiken besser abgeschätzt werden. In diesem Beitrag werden einige aktuelle Beispiele aus diesen Bereichen vorgestellt.
The test material EDS-TM001 together with an accompanying software package, “EDS spectrometer check”, have been made available in 2009 by BAM to be employed by EDS (energy-dispersive X-ray spectrometer) users to check the performance of an EDS with a SEM. With EDS-TM001/002 test material, this periodical check is simplified to the acquisition of only one 10 kV spectrum. The software “EDS spectrometer check” is destined to evaluate automatically this spectrum and determine the EDS performance in terms of energy resolution and calibration, as well as possible alteration of low-energy efficiency due to detector contamination. Energy resolution can be compared with the specified values according to the international ISO standard ISO 15632:2012.
EDS-TM is a synthetic material consisting of a 6 μm thick layer of C, Al, Mn, Cu and Zr deposited on a steel (EDS-TM001) or silicon (EDS-TM002) substrate. The chemical composition of EDS-TM was chosen such as to give nearly equal intensities of the low energy lines in a 10 kV spectrum, thus, making it very sensitive against spectrometer efficiency changes. New results and gained experiences will be presented.
When the FWHM of the X-ray lines in the EDS-TM spectrum are determined, the spectrum Background must be subtracted accurately. The applied physical background subtraction procedure is robust and considers the transmission of the detector window. While the previous version considers only Moxtek AP windows, the new software version includes selection of silicon nitride window and the case of windowless detector.
Oxidation effects on the functionality and formation of laser-induced periodic surface structures
(2019)
In the last decades, the formation of laser-induced periodic surface structures (LIPSS) has been widely studied, not only to stablish a general understanding of the main mechanisms present during the irradiation with ultrashort laser pulses, but also to identify the main processing parameters for its fabrication on various technical materials. However, an important and almost always present effect that is typically set aside is the material oxidation during or after the laser processing. Usually, this leads to optical, chemical, structural and mechanical alterations that are seldomly studied in detail. Therefore, in this work we present a study that includes the formation of LIPSS on Ti6Al4V alloy for tribological applications were different oxidations layers are involved.
The material characterization using different techniques, such as energy dispersive X-ray analyses (EDX), X-ray photoelectron spectroscopy (XPS), micro Raman spectroscopy (µ-RS), and depth-profiling Auger electron microscopy (AEM), and other techniques, confirms the formation of a non-negligible superficial oxide layer – strongly dependent on the specific processing parameters. We perform tribological experiments on laser irradiated samples oxidized by alternative ways to have a comparison on its friction performance. The obtained results show significant differences that depend directly on the thickness and the quality of the oxidized layer. This may open a fertile research area until now barely explored with clear impact on LIPSS based applications.
The characteristics of TiO2 coatings can greatly influence their final performance in large-scale applications. In the present study self-assembly of TiO2 nanoparticles (NPs) in multiple layers was selected as a deposition procedure on various substrates. For this, the main prerequisite constitutes the surface modification of both NPs and substrate with e.g. silane coupling agents. A set of functionalized TiO2 NPs has been produced by reaction with either (3- aminopropyl)triethoxysilane (APTES) or (3-aminopropyl)phosphonic acid (APPA) to functionalize the NP surface with free amino-groups. Then, the complementary functionalized NP set can be obtained from an aliquot of the first one, through the conversion of free surface amino-groups to aldehydes by reaction with glutaraldehyde (GA). Several types of TiO2 NPs differing in size, shape and specific surface area have been functionalized. FTIR, TGA, SEM/EDS, XPS, Auger electron spectroscopy (AES) and ToF-SIMS analyses have been carried out to evaluate the degree of functionalization, all the analytical methods employed demonstrating successful functionalization of TiO2 NP surface with APTES or APPA and GA.
Materials with a high acid resistance are required in different important infrastructures. Examples include repair systems for sewer structures, where biogenic sulfuric acid corrosion is the major degradation mechanism. Low-calcium alkali-activated materials (AAMs) have been repeatedly observed to exhibit high acid resistance. However, the reasons for the high acid resistance of these materials were not fully under¬stood until recently, and the use of highly alkaline activator solutions to produce AAMs appears to hamper their commercial uptake. These issues have been tackled by characterising one-part AAMs and studying their alteration when exposed to sulfuric acid.
One-part AAMs were synthesized by mixing blends of solid silica and sodium aluminate with water, and subsequent curing at 60–80 °C. Acid resistance testing was performed according to DIN 19573, i.e. exposure to sulfuric acid at pH = 1 for 70 days. Characterisation of the cured and the acid-exposed materials was done by XRD, ATR-FTIR, SEM as well as 29Si, 27Al and 1H MAS NMR spectroscopy, including cross-polarisation and double-resonance methods.
Materials synthesized from industrial silicas were gel-zeolite composites, containing a substantial amount of unreacted ‘excess’ silica, while materials synthesized from rice husk ash were fully amorphous, containing ‘excess’ hydrous alumina. The sulfuric acid resistance of mortars based on these binders conformed to the requirements of DIN 19573 for sewer repair applications. The high acid resistance was caused by precipitation of silica gel at the mortar–solution interface, inhibiting further degradation. The presence of alumina gel may inhibit bacterial activity, potentially further improving performance in sewer environments.
The phase assemblage of silica/sodium aluminate-based one-part AAMs can be adjusted via choice of the silica starting material. Properly designed materials exhibit excellent acid resistance, caused by precipi¬tation of silica gel which protects subjacent regions, and they may also inhibit bacterial activity.
Laser-induced periodic surface structures (LIPSS, ripples) with ~500–700 nm period were produced on titanium alloy (Ti6Al4V) surfaces upon scan processing in air by a Ti:sapphire femtosecond laser. The tribological performance of the surfaces were qualified in linear reciprocating sliding tribological tests against balls made of different materials using different oilbased lubricants. Extending our previous work, we studied the admixture of the additive 2-ethylhexyl-zinc-dithiophosphate to a base oil containing only anti-oxidants and temperature stabilizers. The presence of this additive along with the variation of the chemical composition of the counterbodies allows us to explore the synergy of the additive with the laseroxidized nanostructures.
In arid sun-exposed environments, rock-inhabiting fungi dominate microbial communities on rock surfaces. Fungi are known to enhance rock weathering, although the exact mechanisms are not completely understood. These natural processes can be simulated by reproducible experimental systems. Particularly attractive are genetically amenable rock-weathering fungi, where certain traits can be knocked-out to identify weathering-relevant functions. Here, we studied the effect of the rock-inhabiting fungus Knufia petricola A95 and its melanin-deficient mutant (ΔKppks) on the weathering of a Fe-bearing olivine. We examined the olivine dissolution kinetics and looked at the olivine-fungus interface. For the former we inoculated olivine powder with the fungus in batch and mixed flow reactors and analysed the medium solution by ICP-OES, for the latter biofilm-covered olivine sections from flow-through reactors were analysed by FIB-TEM.
In general olivine dissolution was lower when olivine was incubated without fungi: the abiotic olivine dissolution rates were lowest and the surface of the abiotically reacted olivine sections showed no etching. Various chemical analyses show Fe (oxyhydr)oxide precipitation on top of the abiotically reacted olivine, indicating its role in inhibiting olivine dissolution. Both the wild type (WT) and ΔKppks solubilised and bound significant amounts of Fe released by olivine dissolution. Fe (oxyhydr)oxide precipitation was thus reduced, explaining the enhanced olivine dissolution in their presence. Particularly efficient at preventing Fe precipitation were attached WT cells: the inhibition of olivine dissolution almost completely disappeared. The attachment capacity of the WT is most likely caused by the production of WT-specific extracellular polymeric substances. Our presented experimental systems allowed the precipitation of Fe (oxyhydr)oxides and included a rock-inhabiting fungus and thus simulated weathering processes relevant to natural ecosystems.
Metal phosphonates are metal-organic compounds consisting of a metal core and a phosphonate ligand. Depending on the nature of the ligand, metal phosphonates appear in different structures covering the range from molecular compounds to three-dimensional networks. Due to their structural diversity, the chemistry of metal phosphonates has gained great interest during the last decades. Metal phosphonates can be used for various applications as gas storage and separation, magnetism, and energy conversion. Especially transition metal phosphonates are promising candidates as electrocatalysts. Mechanochemistry is a versatile approach for green and fast synthesis of pure substances. By milling the reactants, various organic, inorganic, and metal-organic compounds can be obtained in high yields. Here, we present the synthesis of different new metal phosphonates obtained by grinding of metal acetates with respective phosphonic acids. By varying the ratio of the reactants, we are able to determine the composition of the final products. The addition of small amounts of liquid to the grinding process tends to increase the product’s crystallinity. The crystal structures of the new compounds were determined from powder X-ray data.
The occurrence of microplastic particles (MP) in nearly each environmental compartment but especially in water is well documented in an increasing amount of publication within the last few years. However, a comprehensive understanding of MP occurrence, sources and pathways in the environment as well as effects of MP on the environment is still unclear. Many of the studies are not compatible, because they used different sampling, sample preparation and detection techniques, resulting in a very broad variation and very different dimension of archived results. Hence a useful avoiding strategy for reduction the MP entry in the environment is not possible. Furthermore, the existing methods are often very time consuming, need user knowledge and labour force, which is often not acceptable for the routine monitoring of an action or sanction.
The call for harmonised methods become loud and louder and promising efforts are done in this area. However, the scientific discussion is often focus on advantages and disadvantages of detection tools and sample preparation, less initiative is given to the sampling strategy. That is a pity, because every environmental scientist knows, a good analytical result depend on a good sampling strategy.
The sampling of water seems on the first view easy because the sampling process include already an up concentration of the MP by means of sieves and filters. However, this filtering of water is often limited by filter cake on the sieves, consisting of high amount of natural particular matter. Hence often a small water volume is filtered, which will not own a representative amount of trait carriers or complex sieves cascades are used, which need a high technical equipment.
Recently we presented a fast thermoanalytical method for the detection of polymers fractions in water samples. This method, thermo-extraction desorption gas chromatography mass spectrometry (TED-GC-MS) can analyse MP in water filtrates without sample preparations within 2-3 hours. Advantageous is the additional analysis of rubber particles from tires beside the MP. In order to come even faster we now start to develop new sampling strategies, which should be use for different water systems. It is intended to reduce the effort in the field and to elongate times for sampling to obtain a representatives result without random effects.
In the present presentation we will show first result using a sedimentation box for sampling of MP from surface water. Advantages and disadvantages will be discussed and comparison to data from conventional fractionated filtration will be given.
New reference material candidates for traceable size measurement of nonspherical nanoparticles
(2019)
Size measurement of nanoparticles (NP) becomes a challenging analytical problem when non-spherical shapes must be traceably measured. However, most industrial NPs have irregular shapes and broad size distribution making it often more complex to follow European regulatory to identify a material as a nanomaterial according to which accurate measurement of the smallest dimension and its size Distribution is necessary.
The European research project nPSize - Improved traceability chain of nanoparticle size measurements aims to fill this gap by developing potential non-spherical reference nanoparticles, measurement procedures and physical modelling to improve the traceability chain, comparability and compatibility for NP size measurements between different methods. Therefore, new model NP with well-controlled shape has been synthesized and are supposed to be systematically characterized using the traceable methods scanning/transmission electron microscopy, atomic force microscopy and small angle X-ray scattering.
Following NP candidates are under investigation with respect to their homogeneity and stability: (i) titania nanoplatelets (10-15 nm thickness x 50-100 nm lateral), (ii) titania bipyramides (~60 nm length x 40 nm width), (iii) titania acicular particles (100 nm length x 15-20 nm width; aspect ratio 5.5/6), (iv) gold nanorods (~10 nm width x 30 nm length), and (v) gold nanocubes (~55 nm x 55 nm x 55 nm). In addition, sample preparation procedures as well as measurement analysis procedures with evaluation of appropriate measurands and descriptors for each material class and method are being developed to support standardization. To underpin the traceability of the size measurement of nonspherical NP, physical modelling of the signals in e.g. electron microscopy techniques will be used and in combination, the implementation of machine learning is aimed to facilitate measurement Analysis procedures, especially regarding the accurate thresholding/segmentation of the NPs.