Analytische Chemie
Filtern
Erscheinungsjahr
Dokumenttyp
- Vortrag (2211) (entfernen)
Sprache
- Englisch (1679)
- Deutsch (514)
- Mehrsprachig (8)
- Spanisch (5)
- Französisch (3)
- Russisch (2)
Referierte Publikation
- nein (2211) (entfernen)
Schlagworte
- Nanoparticles (65)
- Concrete (64)
- Fluorescence (64)
- LIBS (62)
- Synchrotron (48)
- NDT (47)
- Zerstörungsfreie Prüfung (46)
- Ultrasound (39)
- XRF (39)
- Nanoparticle (38)
Organisationseinheit der BAM
- 8 Zerstörungsfreie Prüfung (531)
- 1 Analytische Chemie; Referenzmaterialien (497)
- 6 Materialchemie (404)
- 8.0 Abteilungsleitung und andere (148)
- 6.1 Oberflächen- und Dünnschichtanalyse (137)
- 8.2 Zerstörungsfreie Prüfmethoden für das Bauwesen (126)
- 1.4 Prozessanalytik (122)
- 8.4 Akustische und elektromagnetische Verfahren (115)
- 1.1 Anorganische Spurenanalytik (113)
- 6.3 Strukturanalytik (98)
Mycotoxins are secondary metabolites of fungi which have diverse detrimental effects on humans, animals and crops. Traceable worldwide in foods and animal feeds, these contaminants cause manifold diseases and extensive economic losses. Therefore, European legislation set maximum levels of distinct mycotoxins to minimize the risks for the buying public. But standardized food analysis techniques fail to detect masked mycotoxins, whose research increasingly moves to the fore in recent years. They are formed from detoxification metabolism of plants as well as from fungi, which conjugate for example with glucosides or dihexosides. All masked mycotoxins have one thing in common: They are not detectable with standard methods, thereby contributing to the overall exposure and pose an additional health risk for the consumer.
The dissertation work will focus on the following potential new group of masked toxins. Food safety relevant mycotoxins like zearalenone and ochratoxin A possess one or more 1,3-dicarbonyl moieties. Latter are principally able to form thermodynamically stable chelate complexes with metal cations. First investigations at BAM showed interactions between zearalenone and copper ions and it is conceivable that they possibly build a complex. Our main focus is now to identify, characterize and quantify 1,3-dicarbonyl mycotoxin metal complexes as potential candidates within the group of conjugated mycotoxins.
We will simulate processes of biotransformation and identify distinct metabolites by electrochemistry coupled to liquid chromatography/mass spectrometry (EC-HPLC-MS). The obtained knowledge contributes to a better understanding of masked mycotoxins and an improved monitoring of foods and feeds, to ensure food safety.
Titanium dioxide is one of the most studied metal oxides due to its interesting chemical, surface, electronic and (photo)catalytic properties. These properties provide this material of multisectorial applications, ranging from healthcare, photocatalysis, smart materials with self cleaning and self sterilizing properties and solar energy harvesting (photovoltaics and water photosplitting). 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 properties 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 [1,2] 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 [3]. One of the goal of SETNanoMetro is the development of design rules to tune crystal facets of TiO₂ NPs in order to optimize and control functional properties. By tuning the ratio of different facets, the functional properties would be correspondingly changed. 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 their size though hydrothermal processing of Ti(IV)-Triethanolamine complex in presence of different shape controllers (OH-, triethanolamine, fluoride). Through a careful experimental design the influence of many process parameters (pH, temperature, shape controller type and concentration) on the synthesis outcome (size, shape and polydispersity), a predictive soft model was developed. The model is able to predict reasonably well 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).
The concreting of prefabricated concrete structures can lead to insufficient bonding or even to remaining cavities. Honeycombs (aggregate clusters without cement) represent potential weakening of the structure and need to be detected non-destructively. In our study we tested the capability of ground penetrating radar (GPR) techniques for this purpose. We applied GPR in reflection mode and zero-offset profiling (ZOP) transmission mode on a precast concrete twin wall with built-in honeycombs. GPR measurements were performed as two channel measurement with ground coupled antennas with centre frequencies of 1.5 GHz and 2.6 GHz mounted to an automated scanner system.
Our findings show that ZOP transmission measurements are a more efficient method to detect voids in reinforced concrete structures compared to reflection mode measurements. This holds for both the effort needed for the measurement and the evaluation as well as the validity of the data. Honeycombs (basically representing voids) are usually characterized by strongly reduced amplitudes and earlier arrivals of the transmitted wave.
This project aims to develop capacity to produce certified reference materials (CRMs) for environmental analysis by transferring know-how between the partners and combining their skills to focus on environmental CRM production. The production process includes good manufacturing practices for processing materials, method development, the validation and application of homogeneity, stability and characterisation tests, the calculation of individual uncertainties (between-unit inhomogeneity, long term stability, characterisation) and combination of uncertainties to determine overall uncertainty of the matrix reference materials. An inter laboratory comparison registered as a EURAMET project is set as the ultimate project outcome, confirming the partners’ capabilities in applying newly acquired skills.
Due to recent advances in technical developments of NMR instruments such as acquisition electronics and probe design, detection limits of components in liquid mixtures were improved into the lower ppm range (approx. 5–10 ppm amount of substance). This showed that modern NMR equipment is also suitable for the observation of hydrocarbon samples in the expanded fluid phase or gas phase. Since Quantitative NMR spectroscopy (qNMR) is a direct ratio method of analysis without the need of calibration it was used to determine impurities in appropriate liquid and liquefied hydrocarbon isomers up to C6, which are used for preparation of primary gas standards, e.g., natural gas or exhaust gas standards. At the same time it is possible to yield structural information with a minimum of sample preparation. Thus, cross contaminations between different isomers of the observed hydrocarbons and their (NMR-active) impurities can be identified and quantified.
In general, most quantitative organic chemical measurements rely on the availability of highly purified compounds to act as calibration standards. The traceability and providence of these standards is an essential component of any measurement uncertainty budget and provides the final link of the result to the units of measurement, ideally the SI. The more recent increase in the use of qNMR for the direct assessment of chemical purity however can potentially improve the traceability and reduce the uncertainty of the measured chemical purity at a reduced cost and with less material. For example the method has beneficially been used by National Measurement institutes for recent CCQM comparisons including the CCQM–K55 series of purity studies.
Traditional ‘indirect’ methods of purity analysis require that all impurities are identified and quantified, leading to a minimum of 4 individual analytical methods (organic impurities, water, solvents, inorganic residue). These multiple technique approaches measure an array of different chemical impurities normally present in purified organic chemical compounds. As many analytical methodologies have compound-specific response factors, the accuracy and traceability of the purity assessment is dependent on the availability of reference materials of the impurities being available.
qNMR provides the most universally applicable form of direct purity determination without need for reference materials of impurities or the calculation of response factors but only exhibiting suitable NMR properties. The development of CRMs addressing qNMR specific measurement issues will give analysts compounds ideally suited for the analytical method and also provide full characterisation of qNMR related parameters to enable more realistic uncertainty budgets. These materials will give users the tools to exploit qNMR more easily and enable them to speed up analytical method development and reduce the time and financial burden of multiple analytical testing.
The design of sample flow cells, commonly used in online analytics and especially for medium resolution NMR spectroscopy (MR-NMR) in low magnetic fields, was experimentally and theoretically investigated by 1H-NMR and numerical simulations. The flow pattern was characterised to gain information about the residence time distribution and mixing effects. Both 1H-NMR imaging and spectroscopy were used to determine the characteristics of flow cells and their significance for on-line measurements such as reaction monitoring or hyphenated separation spectroscopy. The volume flow rates investigated were in the range from 0.1 to 10 ml/min, typically applied in the above mentioned applications. When compared to those commonly used in high-field NMR, the special characteristics of flow cells for MR-NMR were revealed by various NMR experiments and compared with CFD simulations. The influence of the design of the inlet and outlet on the flow pattern was investigated as well as the effect of the length of the cell. For practical use, a numerical estimation of the inflow length was given. In addition, it was shown how experiments on the polarisation build-up revealed insight into the flow characteristics in MR-NMR.
Online NMR spectroscopy is an excellent tool to study complex reacting multicomponent mixtures and gain process insight and understanding. For online studies under process conditions, flow NMR probes can be used in a wide range of temperature and pressure. This paper compiles the most important aspects towards quantitative process NMR spectroscopy in complex multicomponent mixtures and provides examples. After NMR spectroscopy is introduced as an online method and for technical samples without sample preparation in deuterated solvents, influences of the residence time distribution, pre-magnetization, and cell design are discussed. NMR acquisition and processing parameters as well as data preparation methods are presented and the most practical data analysis strategies are introduced.
Reliable analysis of chemical indicators in water, sediment and soil samples for the purpose of environmental pollution assessment poses one of the greatest analytical challenges, having in mind the complexity of sample matrix and low concentrations of pollutants. Organics (pesticides, PAHs, PCBs, etc.) and heavy metals (Hg, Cd, Ni, Pb and As) represent target parameters. Laboratories performing sampling and tests in this field regulated by respective EU directives [1], need strong support in terms of providing them with appropriate matrix CRMs enabling the process of quality control. NMIs and DIs with proven metrological capabilities for the production and certification of such materials are necessary for the provision of quality data. This project is aiming to develop capacity to produce CRMs for environmental analysis by transferring the theoretical and practical know-how between the partners and combining their skills to focus on environmental CRM production in accordance with ISO Guide 34 [2]. Production process includes good manufacturing practices for processing materials, method development and validation for homogeneity, stability and characterisation tests, characterisation of selected analytes together with additional information about matrix constituents, the calculation of individual uncertainties (between units inhomogeneity, long term stability, characterisation) and combination of uncertainties to determine overall uncertainty of the matrix reference materials. Inter laboratory comparison registered as EURAMET project is set as the ultimate project outcome, confirming the partners’ capabilities in applying newly acquired skills.
Resolving overlapping peaks of multiple components. Relative primary analytical method - Fundamental relationship of qNMR.
Troubleshooting Samples Analytics:
Impurities in products: unexpected & unwanted occurrence, unknown identity, analytical method unclear, often various analytical methods, necessary, short response time important (< 1 d), benefits: allocation of its source within hours safes cost
• Investigations planned, coordinated and documented by TSA team
• Variety of analytical methods available
In recent years, elemental imaging of biological samples using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is gaining in importance. Latest improvements regarding spatial resolution (down to 1 µm) and washout time make LA-ICP-MS particularly interesting for single cell analysis.
Many current nanomaterials can serve as contrast agents in cellular or tissue imaging, drug delivery vehicles or therapeutics, whereas others can cause toxic effects. In order to evaluate nano-bio interactions, the number of nanoparticles (NPs) inside cells as well as their localisation within cellular substructures is of particular interest.
LA-ICP-MS was used to study the NP pathway from uptake, via intracellular processing up to cell division. Fibroblast cells were incubated with different metallic NPs under varying experimental conditions. For LA analysis the cells were fixed with formaldehyde and dried.
Our results show that LA-ICP-MS is able to localise NP aggregates within cellular substructures. The NPs accumulate in the perinuclear region in the course of intracellular processing, e.g. multivesicular fusion and endosomal maturation, but do not enter the nucleus [1, 2]. A strong dependence of NP uptake on concentration and incubation time was found. Additionally, the number of NPs internalized by individual cells was determined and variations within the cell population became visible.
A new laser ablation system providing a short washout time (50 ms) together with small spot sizes (< 4 µm) and high repetition rates allows high spatial resolution applications. First results of cell imaging will be shown.
The findings demonstrate the potential of LA-ICP-MS enabling insight into NP uptake and intracellular distribution dependent on experimental parameters.
Excelling in brevity but lacking in applicability, the 2011 EU nanomaterial definition has become a source of anguish for scientists and industry alike. Repeated pleas and discussions with our own envoy have demonstrated the strength of their resolve: this definition is unlikely to change. Manufacturers of many materials (cosmetics, pigments, foodstuffs, etc.) will have to characterise and label all their products accordingly, a task still impossible for lack of a clear metrological approach towards this goal. Therefore, the onus has fallen on the scientists to come up with a practicable measurement technique allowing inexpensive classification covering large swathes of the material landscape. Small-angle X-ray Scattering (SAXS) probes the size range in question, and can - with due care - deliver a bulk-averaged volume-weighted size distribution. Like any other real-world measurement method, however, it is not (and can never be) a universal solution. This presentation will clarify the SAXS technique, provide several application examples for nanomaterial characterisation, and will detail the limitations and pitfalls that accompany its abilities. At the end of this presentation, you will have the information to judge whether the technique is amenable to your materials or not.
Thermoresponsive polymers have shown great potential in applications such as bioseparation, drug delivery and diagnostic. Only few thermoresponsive polymers that present an upper critical solution temperature (UCST) in a relevant temperature range, i.e. phase separate from solution upon cooling, have been reported so far. Moreover, the most studied UCST type polymers namely polybetaines are difficult to use under physiological conditions, which significantly restricts their potential applications. Therefore, UCST polymers with sharp and robust phase transition in physiological conditions (in the presence of salts, ions etc.) are highly needed in order to extend the range of applications of this class of polymers. Herein, a robust UCST-type copolymer of acrylamide (AAm) and acrylonitrile (AN) (poly(AAm-co-AN)) was prepared by reversible addition fragmentation chain transfer (RAFT) polymerization and its thermo-induced aggregation behavior in aqueous media was studied. At temperature below the UCST, the copolymer chains were aggregated together. The aggregate size was found to be larger with increasing AN contents and became smaller upon dilution of the copolymer solutions. While above the UCST, the copolymer chains were expanded and weekly associated in solution. The association between the copolymer chains formed smaller aggregates with increasing the AN contents or the dilution of the solutions. A model is proposed to explain such aggregation-association behavior of the Fig. 1.
Figure 1. Schematic illustration of the proposed thermos-induced aggregation behavior of the poly(AAm-co-AN) in aqueous solution.
This lecture is an introduction to ICP-MS with a double focusing magnetic sector mass analyzer. It offers fundamental background, a thorough discussion of analytical features, and state of the art information on applications. Different types of double focusing instruments also are considered. Specific topics include fundamental aspects of ICP-MS (physical properties of a double focusing instrument, operational characteristics in comparison with quadrupole instruments); analytical characteristics (spectral and non-spectral interferences, figures of merit in low and high resolution modes, blanks and memory effects, HPLC and GC interfaces), and applications (industrial including ultra-pure reagents and alloys, environmental, geological, and biomedical materials).
The presentation gave an overview of the topic, the aims and the task allocation of the M-ERA.NET founded project named “Nanohype”.
In this project four research teams working hand in hand on computational modeling, synthesis and experimental validation to design novel metal-shelled Upconversion-NP combining plasmonic interactions.
As Ph.D. student at the BAM I am responsible for the optical characterization (measurements of lifetimes, Quantum Yields and PL emissions ) of these promising novel systems.
Analytical methods require efficient and versatile strategies to measure an increasing number of analytes that can be used in conjunction with established platforms like flow cytometry. Spectral multiplexing suffers from problems such as spectral crosstalk and often requires different excitation light sources increasing instrumentation costs. Thus, the number of distinguishable reporters with intensity-based barcodes is limited. An alternative can be lifetime encoding for discrimination of fluorophores based on their fluorescence decay kinetics.
We report on the suitability of µm-sized polymer particles stained with organic dyes for lifetime encoding. These dyes are excitable at a standard laser diode wavelength and detectable within a single spectral window. For lifetime-based discrimination, these dyes display sufficiently different luminescence decay kinetics. We present the spectroscopic properties of these beads and address challenges like the limited number of detectable photons in a flow for the reliable discrimination. These studies are expected to pave the road to new applications of fluorescence lifetime multiplexing for time-domain flow cytometry.
Industrial quality control (QC) nowadays requires the visualization of surface modifications from the macro-scopic to the microscopic or even nanoscopic scale. This is a prerequisite to the evaluation of functionality and reliability, the detection of defects and their separation of artefacts. The diversity of applications ranges from low-E glazings and solar panels, micro- and optoelectronics, micro- and smart devices to sensor-on-chip and lab-on-chip systems [1]. Optical microcopy (light, confocal laser scanning, white light interference) as established QC-tool is operated at normal incidence, i.e. p- and s-polarization are undistinguishable. Either light-intensity in terms of grey scale and colour or intensity-correlated effects of phase shifts are used. In case of ellipsometry, operated at oblique incidence, p- and s-polarization matter, and amplitude ratios and phase shifts upon reflection are measured. Hence, information content must be much higher.
The visualization of surface modifications may be very challenging for coating/substrate systems of either al-most identical optical constants, e.g. transparent films on substrates of the same material, or minor film thick-ness, substance quantity and affected area, e.g. ultra-thin or island films. Ellipsometry gives access to the con-trast of intensity (I), amplitude ratio (Ψ), and phase shift (Δ) with nanometer-scaled vertical and micrometer-scaled lateral sensitivity, one is able to identify tiny changes within an unmodified surface. As both mapping ellipsometry (ME) and imaging ellipsometry (IE) are operated in the optical far-field, surface inspection is also possible on the macroscopic scale. Near the Brewster-angle of the bare, undamaged, clean, and fresh substrate, the contrast to add-on and sub-off features is superior.
Fig. 1 shows three examples of ellipsometric imaging, i.e. a thin SnO:Ni film on SiO2/Si (Fig. 1a), a dried stain of an anti-body solution on cyclo-olefin-polymer (COP) shown in Fig. 1b, and a polyimide film residue on SiO2/Si (Fig. 1c). For all of these examples, ellipsometry provides much better contrast between substrate and surface modification than optical microscopy, sometimes primarily caused by the oblique incidence (Figs. 1a and 1c), in other cases related to the phase sensitivity of ellipsometry (Fig. 1b). Other examples are laser surface modifications and the corrosion of glass. In these cases, optical microscopy and IE yield to similar results, how-ever only ellipsometry gives access to modelling.
Further investigated coating/substrate systems are 100Cr6 steel, native oxide on silicon, borosilicate glass, and the polymer polycarbonate with deposited films of graphene and ta-C:H, printed and dried pattern of liquids such as water, cleaning agents, and dissolved silicone. Besides imaging ellipsometry, referenced spectral ellipsometry (RSE) has been applied, combining the advantages of both optical microscopy (fast measurement) and ellipsometry (high sensitivity to tiny modifications).
Photoluminescence techniques are amongst the most widely used tools in the material and life sciences, with new and exciting applications continuously emerging, due to their many advantages like comparative ease of use, unique sensitivity, non-invasive character, and potential for multiplexing, remote sensing, and miniaturization. Drawbacks are , however, signals, that contain unwanted wavelength- and polarization contributions from instrument-dependent effects, which are time-dependent due to the aging of instrument components, and difficulties to measure absolute fluorescence intensities. Thus, there is a considerable need for standards for intensity, spectral, and temporal fluorescence quantities to meet the increasing need for instrument performance validation and global trends to harmonize physicochemical measurements. In this respect, instrument calibration strategies together with different types of fluorescence standards are presented as well as design concepts for robust, easy-to-use, and format-adaptable fluorescence standards useable for the determination of different fluorescence parameters and a broad variety of fluorescence techniques.
Gas sensors are an important tool in various areas for example in industrial process control as well as Gas sensors are an important tool in various areas for example in industrial process control as well as safety applications or in research. A useful gas detector should be selective, precise, stable and cost-effective. In the present research a surface based gas detection technique is investigated using the SPR effect with ellipsometric readout. This technique is called surface plasmon resonance enhanced ellipsometry (SPREE).
The sensor consists of a gold layer (40 nm) top-coated with a doped metal-oxide (M:SnOₓ,
5 nm). The coating is added by magnetron sputtering with doped targets with different doping concentrations. It could be shown that, without the top-coating, these type of sensors can detect various gases, e.g. CO, H2, O2, O3, He, N2, with sensitivities down to the ppm range (in air).
The goal of the present study is to characterize the additional coating materials in dependence of the coating conditions. With the help of the doped-metal oxide, the sensitivity increases dramatically by a factor of 100. Additionally, a selectivity for specific gases is observed which depends on the doping conditions of the coating. Changing the properties of the plasma coating process and the doping metal gives access to a variety of different layers and enables us to find the best conditions.
Permeability estimation from spectral induced polarization (SIP) measurements is based on a fundamental premise that the characteristic relaxation time (t) is related to the effective hydraulic radius (reff) controlling fluid flow. The approach requires a reliable estimate of the diffusion coefficient of the ions in the electrical double layer. Others have assumed a value for the diffusion coefficient, or postulated different values for clay versus clay-free rocks. We examine the link between t and reff for an extensive database of sandstone sampleswhere mercury porosimetry data confirm that reff is reliably determined from a modification of the Hagen-Poiseuille equation assuming that the electrical tortuosity is equal to the hydraulic tortuosity. Our database does not support the existence of 1 or 2 distinct representative diffusion coefficients but instead demonstrates strong evidence for 6 orders of magnitude of variation in an apparent diffusion coefficient that is well correlated with both reff and the specific surface area per unit pore volume (Spor). Two scenarios can explain our findings: (1) the length-scale defined by t is not equal to reff and is likely much longer due to the control of pore surface roughness; (2) the range of diffusion coefficients is large and likely determined by the relative proportions of the different minerals (e.g. silica, clays) making up the rock. In either case, the estimation of reff (and hence permeability) is inherently uncertain from SIP relaxation time.
Zur Bestimmung des Feuchtezustands und insbesondere der Belegereife von Estrichfußböden kommen in Deutschland zerstörende Prüfverfahren zum Einsatz, die eine punktuelle Probenahme erfordern. Hierbei ergeben sich immer wieder Fehlinterpretationen, da zum einen die Probenahme selbst zu einer Veränderung des Feuchtezustands führt und zum anderen, weil die Verfahren an sich mitunter ungenau sind (z.B. abhängig von der Estrichzusammensetzung). Zusammen mit vier Forschungsinstituten und dem Industriepartner Bosch wurden an der BAM zerstörungsfreie Prüfverfahren auf deren Tauglichkeit zur Estrichfeuchtemessung untersucht und mit den herkömmlichen zerstörenden Verfahren verglichen.
Für diesen Versuch kamen verschiedene geophysikalische Verfahren zum Einsatz, darunter Nuklear Magnetische Resonanz (NMR), elektrische Widerstandsmessungen und Impulsradar (GPR). Es wurden neun verschiedene Estrichsorten hergestellt und während der Trocknungsphase bei Konstant-Normklima gelagert. Diese wurden sowohl zerstörend als auch zerstörungsfrei mit den o. g. Verfahren untersucht. Gleichzeitig wurden die Masseänderungen der Proben zur Bestimmung des integralen Feuchtehalts aufgezeichnet.
Die Ergebnisse zeigen zum einen, dass das Abtrocknungsverhalten von zementgebundenen Estrichen grundsätzlich unterschiedlich von dem anhydritgebundener Estriche ist. Während sich bei ersteren zügig ein deutlicher Feuchtegradient über die Höhe der Proben einstellt, verläuft dieser bei der zweiten Probengruppe sehr flach. Dies lässt sich vor allem in den NMR Daten räumlich hochaufgelöst nachvollziehen - die Datenakquise erfolgte mit einer NMR MOUSE PM 25. Ein ähnliches Bild ergibt sich auch aus den elektrischen Widerstandsmessungen, die mittels sog. Multi-Ring-Elektroden (MRE) durchgeführt wurden. MRE bezeichnen als Vertikalprofil angeordnete Ringelektroden mit einem Abstand von ca. 1-2 mm, zwischen denen jeweils Zwei-Punkt Widerstandsmessungen durchgeführt werden. Bei sehr geringen Feuchtegehalten (z.T. auch um die Belegereife) waren mit dieser Methode jedoch wegen der zu hohen Übergangswiderstände nur bedingt Messungen möglich. Im Gegensatz zu NMR und MRE sind mit dem Radarverfahren (2 GHz Antenne) keine tiefenbezogenen Aussagen möglich. Jedoch lässt sich über eine Amplitudenauswertung von direkter und an der Rückwand reflektierter Welle teilweise eine Aussage über Restfeuchtigkeit im Volumen treffen. Ebenso zeigt die Laufzeitdifferenz der beiden Wellen eine starke Abhängigkeit vom Feuchtegehalt.
In Germany there is an existing built infrastructure worth about 50 trillion Euros. The expected lifetimes of individual structures are up to 100 years. Considerable costs (annually about 35 billion Euros, the trend continues upwards) are involved in order to maintain and rehabilitate both residential as well as transportation infrastructure buildings. Most damages we observe on our built infrastructure are moisture-induced processes. Consequently reliable moisture measurement tools a highly needed for meaningful building diagnosis investigations. The optimal moisture measuring technique would be non-destructive, fast, repeatable, reliable, independent of steel in the vicinity, the surface condition or possible salt loads of the material under test. Since this is unfortunately not the case for any non-destructive method, it is often very difficult to decide for users which method to use for the particular testing problem. The only standardized methods in Germany are the “direct” and destructive Darr- and the CM tests. Although they can be highly accurate (when handled with care during the sampling), they deliver only punctual information and cannot be used for monitoring. The other, non-destructive methods are based on the change in humidity-dependent physical material properties. The underlying physics, their particular advantages and disadvantages are discussed in this paper.
The surface chemistry / functionalization of nanomaterials and microparticles largely controls the stability of these materials as well as their solubility and subsequent biofunctionalization and their interactions with biological systems. Moreover, in the case of some nanomaterials like semiconductor quantum dots or lanthanide-based upconversion nanocrystals, the ligand shell strongly affects their optical properties, e.g., via passivation of surface states and traps that favor luminescence quenching or the protection of surface atoms from quenching water molecules. This renders analytical methods for the quantification of surface groups like functionalities very important. Targets of broad interest are here amino, carboxyl, alkine and maleimide groups used for common bioconjugation reactions and typical ligands like thiols and polyethylene glycol (PEG) molecules of varying length, used for the tuning of material hydrophilicity and biocompatibility, minimization of unspecific interactions, prevention of biofouling, and enhancement of blood circulation times as well as surface-bound biomolecules like streptavidin or other biomolecules relevant e.g., for diagnostic assays. Here, we focus on simple optical methods relying on standard laboratory instrumentation, validated by method comparison and/or mass balances and present examples for their use for the characterization of different types of nanomaterials and microparticles.
Luminescence-based detection methods, ranging from fluorescence spectroscopy for photophysical and mechanistic studies over sensing applications, chromatographic separation techniques and the microarray technology with fluorescence detection to fluorescence microscopy, flow cytometry, single molecule spectroscopy, and molecular imaging to integrating sphere spectroscopy, are among the most widely used methods in the life and material sciences. This is due to e.g., their unique sensitivity enabling the detection of single molecules, potential for multiplexing, ease of combination with spatial resolution, and suitability for remote sensing. Many of these advantages are closely linked to the choice of suitable molecular and nanoscale fluorescent reporters, typically required for signal generation. This includes organic dyes without and with sensor function, fluorophore-encoded polymeric and silica nanoparticles as well as nanocrystalline systems like semiconductor quantum dots and upconversion phosphors, emitting in the visible (vis), near-infrared (NIR), and IR (infrared). Current challenges present the environment sensitivity of most fluorophores, rendering fluorescence spectra, measured intensities/fluorescence quantum yields, and fluorescence decay kinetics matrix-dependent, and instrument-specific distortions of measured fluorescence signals that need to be considered for quantification and comparability of data, particularly fluorescence spectra.
Here, current applications of luminescence-based methods and different types of reporters will be presented. In this context, suitable spectroscopic tools for the characteri-zation of the optical properties of fluorescent reporters and fluorophore-encoded microparticles, analytical tools for the determination of the surface chemistry of different types of particles, and different multiplexing strategies will be discussed.
The reliability of wheel set axle testing is of high importance because small discontinuities caused during manufacturing or rock fall impacts during operation might cause growing cracks during the operation load cycles. While most of the axles are tested by automated UT-systems today, the basic education of railway NDT operators is still manual testing providing the basic understanding and skills for the operators. In Germany it is a common rule that NDT operators in the railway branch need to refresh their knowledge and skills every five years including a refresh examination. The testing results from these exercises and from a parallel round robin test have been sampled at the DGZfP Railway Education Centre in Wittenberge for a period of about 5 years. The results of the operators written in test record sheets were compared with the “true” test crack or notch position in the axles used for examination. In this way the testing results could be categorized into “hits” and “misses” and the “hits” were further evaluated due to correct position and adequate amplitude height. Considering some thousand indications documented by the operators during the refresh examination and comparing transition bow, shaft and seat it was a highlight to see that the operators reach their best detection rate in the transition bow of the wheel axle set while this is often the most difficult part concerning the UT-echoes. Fortunately this is due to their raised awareness in the transition bow region because this is the most dangerous region with respect to fracture mechanics.
For two selected axles the experimental set up of 45° and 70° inward and outward UT-testing were also simulated showing clearly the difficulties of the UT-echoes detection of some specific test defects.
In the last two decades automated ultrasonic inspection devices took over a lot of applications that prior have been carried out using manual inspection with the evaluation of A-scans only. In parallel phased array systems have been developed and brought to the market which offer detailed and fast control over the sound field. When applying automated inspection phased array systems for UT measurements imaging of the recorded data in combination with the probe positioning data is used for the evaluation of inspections. B-Scan, C-Scan and S-Scan images are typically used with this setup.
For more sophisticated applications with linear arrays echo tomography and syntethic aperture focusing technique (SAFT) are well known methods and often applied for high resolution image reconstruction. Since channel count of phased array systems is constantly rising, matrix arrays with up to 256 elements entered the market. Signal processing in the matrix domain became 3D. Since some years the Total Focusing Method (TFM) is an additional imaging tool for these type of application. It is based on the Full Matrix Capture (FMC) using the elements of phased array probes as separate transmitters and receivers.
In this contribution we discuss the common ground of SAFT and TFM as well as the differences between these imaging tools. The combined use of automated inspection, matrix arrays and signal processing for high resolution measurements is a challenging task where a very long parameter list has to be taken into account. Under which conditions which elements of the full matrix should be taken for the reconstruction for best results?
Based on examples taken from measured and simulated echo signals it will be shown how image resolution can be optimized in dependence of different parameters like the distance between transmitters and receivers and their directivity patterns, the depth of echo source and the specimen geometry.
Ray tracing boudary value problems: simulation and SAFT reconstruction for ultrasonic testing
(2016)
The application of advanced imaging techniques for the ultrasonic inspection of inhomogeneous anisotropic materials like austenitic and dissimilar welds requires information about acoustic wave propagation through the material, in particular travel times between two points in the material. Forward ray tracing is a popular approach to determine traveling paths and arrival times but is ill suited for inverse problems since a large number of rays have to be computed in order to arrive at prescribed end points. In this contribution we discuss boundary value problems for acoustic rays, where the ray path between two given points is determined by solving the eikonal equation. The implementation of such a two point boundary value ray tracer for sound field simulations through an austenitic weld is described and its efficiency as well as the obtained results are compared to those of a forward ray tracer. The results are validated by comparison with experimental results and commercially available UT simulation tools. As an application, we discuss an implementation of the method for SAFT (Synthetic Aperture Focusing Technique) reconstruction. The ray tracer calculates the required travel time through the anisotropic columnar grain structure of the austenitic weld. There, the formulation of ray tracing as a boundary value problem allows a straightforward derivation of the ray path from a given transducer position to any pixel in the reconstruction area and reduces the computational cost considerably.
Quantification of rock structures with high resolution X-Ray μ-CT for laboratory SIP measurements
(2016)
Spectral Induced Polarization (SIP) measurements are used in many different ways to characterize natural rocks and soils. Main foci of interest are the enhanced characterization of the causes of IP-effects in clastic rocks (especially sandstones), the interactions between the matrix-fluid-system and within the electrical double layers as well as the correlation with “classical” petrophysical parameters, such as specific surface area, permeability, mercury intrusion capillary pressure (MICP) and others. Nevertheless, for all of these investigations, knowledge of the inner structure of the sample material is essential in order to create reliable and validated models as well as to interpret and to assess the data most completely. Unfortunately, many of the methods used, to get access to the inner structure of rocks are destructive (e.g. MICP, thin sectioning, etc.) and the valuable sample is lost. In addition, data is either of volume integrated nature or only available for the 2D case and the usage of sister cores does not necessarily lead to reliable results. In this paper, the authors showcase the possibilities of non-destructive and three dimensional X-ray computed tomography and of enhanced image analysis capabilities for the quantification of rock structures at the pore scale.
Permeability estimation from spectral induced polarization (SIP) measurements is based on a fundamental premise that the characteristic relaxation time (t) is related to the effective hydraulic radius (reff) controlling fluid flow. The approach requires a reliable estimate of the diffusion coefficient of the ions in the electrical double layer. Others have assumed a value for the diffusion coefficient, or postulated different values for clay versus clay-free rocks. We examine the link between t and reff for an extensive database of sandstone samples where mercury porosimetry data confirm that reff is reliably determined from a modification of the Hagen-Poiseuille equation assuming that the electrical tortuosity is equal to the hydraulic tortuosity. Our database does not support the existence of 1 or 2 distinct representative diffusion coefficients but instead demonstrates strong evidence for 6 orders of magnitude of variation in an apparent diffusion coefficient that is well correlated with both reff and the specific surface area per unit pore volume (Spor). Two scenarios can explain our findings: (1) the length-scale defined by t is not equal to reff and is likely much longer due to the control of pore surface roughness; (2) the range of diffusion coefficients is large and likely determined by the relative proportions of the different minerals (e.g. silica, clays) making up the rock. In either case, the estimation of reff (and hence permeability) is inherently uncertain from SIP relaxation time.
Moisture measurement methods
(2016)
Moisture can cause imperfect sealings, faulty roof constructions, cracks and other kind of damages. For measuring the moisture in construction materials like concrete and screed, there are destructive(direct) and non-destructive(indirect) methods, that can be used. This presentation gives an overview and a comparison of these methods.
Die regelmäßige Überprüfung von Eisenbahnradsatzwellen auf betriebsbedingte Schädigungen ist ein fester Bestandteil des Instandhaltungskonzeptes von Eisenbahnfahrzeugen. Insbesondere bei hohen Achslasten und hohen Rotationsgeschwindigkeiten ist eine detaillierte regelmäßige Prüfung notwendig. In den letzten Jahren wurden für diese Prüfaufgabe mechanisierte Ultraschallprüfsysteme entwickelt, erfolgreich eingeführt und etabliert. Für eine Weiterentwicklung dieser Technologie stehen die Themen Erhöhung der Auflösung, Reduzierung von Oberflächen- und Störeinflüssen, Verkürzung von Prüfzeiten, Verbesserung der POD, Verlängerung von Inspektionsintervallen, Vereinfachung der Auswertung und die Möglichkeit der Durchführung von Analyseprüfungen im Vordergrund. Es werden Ansätze und neue Konzepte zur Lösung dieser Herausforderungen vorgestellt.
Der einwandfreie Zustand der Radsätze von Schienenfahrzeugen ist von größter Bedeutung für den sicheren Betrieb. Die Radsatzwellen werden durch eine große Zahl von Lastwechseln individuell unterschiedlich beansprucht. Dabei spielen viele Einflüsse wie äußere statische und dynamische Lasten, innere Lasten aufgrund von Unwuchten und inneren Spannungen und Umweltbedingungen entscheidende Rollen. Eine regelmäßige Prüfung ist daher obligatorisch. BTD entwickelt im Rahmen eines MNPQ-Projektes in Kooperation mit der BAM eine Phased Array Technik zur automatisierten Prüfung von Radsatzwellen im eingebauten Zustand. Die schwierigen Ankoppelbedingungen aufgrund der begrenzten Zugänglichkeit, der komplexen Geometrie sowie Farbschichten und Schmutz auf der Radsatzwelle stellen hierbei große Herausforderungen dar. Zu deren Bewältigung werden neben optimierten Prüfköpfen, einer in die Wasservorlaufstrecke integrierten akustischen Linse und einer speziellen Ankoppeltechnik auch Signalverarbeitungsalgorithmen eingesetzt. Die Darstellung der Signalverarbeitung ist der Schwerpunkt dieses Beitrages. Mit Hilfe von Messdatensätzen präparierter Testwellen werden verschiedene Algorithmen erprobt und hinsichtlich der Stabilität, dem Verhalten bezüglich der Ankoppelschwankungen und veränderter Wellengeometrien und der Fähigkeit zur automatischen Unterscheidung von Fehler- und Formanzeigen bewertet. Letztlich wird die beste Lösung im entwickelten Prüfsystem eingesetzt.
A comprehensive characterization of plasma modified polymer surfaces or plasma-polymerized thin films needs access to parameters as
- concentration of saturated/unsaturated carbon species (e.g. aromaticity) or other double bonds as C=N or C=O,
- branching, and
- losses of crystallinty or other degrees of structural order.
Furthermore the complex ageing phenomena of plasma modified polymers/plasma-polymers and the measurement of an in-depth distribution of chemical species are challenges for the analyst. The talk will display selected examples where such challenges have been met by using advanced methods of surface chemical analyses as Photoelectron Spectroscopy with variable excitation energy (“SyncXPS”), X-ray Absorption Spectroscopy (NEXAFS) at C, N and O K-edges and Time-of-Flight Secondary Mass Spectroscopy (ToF-SIMS) combined with Principal Component analysis (PCA).
Der Einsatz moderner Prozessanalysentechnik führt zu einer Datenflut, deren Verarbeitung und Nutzung häufig nicht ohne den Einsatz von Chemometrie zu realisieren ist. Dafür stehen zahlreiche multivariate Verfahren, wie z.B. Hauptkomponentenanalyse (PCA) und Regressionsanalyse (PLSR) für die Klassifizierung und für die quantitative Analyse zur Verfügung. Darüber hinaus können in Spezialfällen, insbesondere in der Spektroskopie, Methoden des „Indirect Hard Modeling“ eingesetzt werden. Anhand einer Industrie-relevanten Reaktion, der Hydroformylierungsreaktion zur Bildung langkettiger Aldehyde aus der Reaktion von Alkenen und Synthesegas, die sowohl im Labormaßstab als auch in einer Miniplant in Kooperation mit der TU Berlin untersucht wurde, werden Kalibrationsstrategien (Design of Experiment, DoE) und Auswertungsansätze mittels PLSR prozessbegleitender Raman Spektren dargelegt. Auf Grundlage des chemometrischen Ansatzes ist eine on-line Überwachung der Reaktion hinsichtlich der Hauptreaktanden, 1-Dodecene und 1-Tridecanal, möglich. Weiterhin konnte mittels Raman Spektroskopie die Bildung eines unerwünschten Nebenprodukts nachgewiesen werden.
A round robin test on flash thermography was organized within the scope of a standardization research project. This test gives information on reliability, comparability and efficiency of different testing situations. Data recorded on metal and CFRP test specimens with flat bottom holes (FBH) were analysed by evaluating the detectability and by calculating the signal-to-noise ratio (SNR) of the defect signatures as a function of defect parameters. For the investigation of the influence of material properties on the spatial resolution as well as on penetration depth, test specimens made of steel and copper with crossed notches and a notch ramp were constructed and investigated. Here, the minimum resolvable notch distance and the maximum detectable depth of the ramp were analysed.
Novel air-coupled ultrasonic transducer combining the thermoacoustic with the piezoelectric effect
(2016)
In recent years, there has been an increasing industrial demand for one-sided inspection of various structures by means of air-coupled ultrasonic technique. Lightweight structures based on carbon-fibre-reinforced polymers may have very complex shapes, making air-coupled transmission difficult or even impossible. The inspection of concrete structures is another example where one-sided inspection is required.
To address these challenges a new type of transducer for air-coupled pulse-echo inspection was developed, which unites two principles: thermoacoustic emission and piezoelectric reception. The thermoacoustic emitter is a titanium electrode with a thickness of several tens of nanometer. This electrode was deposited onto charged cellular polypropylene, which serves as a piezoelectric receiver. The thermoacoustic transmission is based on a transformation of the thermal energy of an electrically heated electrode into the acoustic energy of an ultrasonic wave. Thermoacoustic emitters provide resonance-free behaviour and thus extremely broadband pulses. Charged cellular polypropylene is piezoelectric due to the polarization of its cells and it is well matched to air, with a Young modulus in the order of magnitude of MPa. In this contribution we present some pulse-echo measurements with the first prototypes of the combined thermoacoustic-piezoelectric transducer.
Dual orthogonal functionality in a single material is highly desirable in many fields such as bio-imaging, sensing, coating or diagnostic and therapy. However, combining two different functionalities in a precise and controlled way is still a challenging task.
Here we present how simply dual functional hybrid nanoparticles consisting of a silica core with a fluorescent and a thermoresponsive polymeric layers can be prepared. As a first step of this work, silica core particles were coated by a fluorescent layer using surface-initiated reversible addition-fragmentation chain transfer polymerization. Afterwards, the fluorescent silica nanoparticles were completely enclosed in a switchable protective coating made of thermoresponsive poly(N-isopropylacrylamide). The thermoresponsive poly(N-isopropylacrylamide) changes its properties with varying the surroundings temperature and this behavior is reversible and controllable. To the best of our knowledge these types of hybrid dual functional core-shell-shell nanoparticles have not yet been prepared, despite the prospect of many potential applications.
Energiedispersive Röntgenspektroskopie (EDX) ist eine der meist verbreiteten Methoden zur Bestimmung der chemischen Zusammensetzung von Festkörpern und dünnen Schichten. Durch die technologische Weiterentwicklung energiedispersiver Röntgenspektrometer wurde die Leistungsfähigkeit auch im niederenergetischen Bereich unter 1 keV verbessert. Geeignete Testmaterialien zur Überprüfung der Leistungsfähigkeit im niederenergetischen Bereich in Übereinstimmung mit ISO 15632 sind kaum vorhanden und basieren hauptsächlich auf C K und F K Linien. Um gültige Resultate aus akkreditierten und zertifizierten Prüf- und Kalibrierlaboratorien in Übereinstimmung mit ISO/IEC 17025 zu gewährleisten sind regelmäßige Funktionsprüfungen der Spektrometer notwendig.
In einer Machbarkeitsstudie wurde die Eignung einer bestimmten Substanz-klasse, nämlich ionische Flüssigkeiten, als Referenzmaterial zur routinemäßi-gen Überprüfung der Energieskala, der Energieauflösung und der Spektrometer Effizienz untersucht. Es kann gezeigt werden, dass mit einer einzigen Messung an einem einzigen Referenzmaterial mehrere Geräteparameter überprüft werden können. Damit ist es im niederenergetischen Bereich möglich regelmäßige Funktionsprüfungen von Spektrometern durchzuführen, aber auch die Leistungsfähigkeit verschiedener Spektrometer zu vergleichen. Beides kann sehr effizient durch einen einfachen qualitativen Vergleich mehrerer Spektren erreicht werden. Durch die Verwendung von ionischen Flüssigkeiten als Referenzmaterial, deren Stöchiometrie genau bekannt ist bzw. zertifiziert werden kann, können eventuell sogar die gängigen Modelle zur Matrixkorrektur validiert werden. Auch wäre eine Neubewertung von Fundamentalparametern (Fluoreszenzausbeute, Massenschwächungskoeffizienten usw.) von Elementen niedriger Ordnungszahl möglich.
Scanning Electron Microscopy (SEM) represents the mostly widespread method available in analytical laboratories dedicated to the characterization of physical properties such as morphology of various solid materials from ‘micro-’ down to the nanometre scale. The use of secondary electrons excited by a sharply, nm-focussed primary electron beam enables at any modern SEM to image objects with high in-depth and lateral sensitivity, i.e. with high spatial resolution. Hence, e. g. nanoparticles (NPs) are able to be easily characterized with respect to their individual size and shape, but also to the morphology of their surface.
By preparing the nano-objects on thin membranes as electron transparent samples it is possible to perform electron microscopy in the transmission mode (TEM and TSEM). The corresponding transmission (i.e. mass-thickness) contrast reveals in-depth information, but is also well suited for dimensional measurements in the 2D projection image. Both the surface sensitive mode and the transmission one are meanwhile available at any modern SEM. If an X-ray spectrometer is attached to an electron microscope, it is possible to analyse the characteristic X-rays induced by electron bombardment. Most electron microscopes have attached an energy dispersive X-ray spectrometer (EDX) so that EDX elemental maps can be carried out. Recent technological developments of high throughput EDS detectors and their advantages regarding high-resolution X-ray analysis down to the nm range are reviewed.
High-resolution micrographs (SEM, TSEM, TEM) and corresponding X-ray elemental maps on various representative nanoparticles, but also layered samples prepared in cross-section, will be presented and discussed. The importance of selecting the best suited analysis conditions will be highlighted. Also other, often challenging, topics such as sample preparation and image data processing will be critically addressed by practical examples. Further analytical techniques able to be employed at an electron microscope, like cathodoluminescence (CL) or micro-X-ray fluorescence (µXRF) will be briefly surveyed.
A novel direct sampling ionization scheme for ambient mass spectrometry is presented. Desorption and ionization is achieved by a quasi-continuous laser induced plasma in air. Since there are no solid or liquid electrodes involved the ion source does not suffer from chemical interferences or fatigue originating from erosive burning or from electrode consumption. A laser plasma was ignited under ambient conditions in front of a modified TOF MS atmospheric pressure interface, using a high repetition rate DPSS laser operating at 532 nm and 26 kHz and an aspherical lens with a focal length of 8 mm. Emission spectroscopy (40-1100 nm) and time resolved studies on specific plasma parameters revealed insight into the physical and chemical plasma properties. Plasma ignition can be performed in rare gases and under ambient conditions. The hot plasma zone was kept at a certain distance from the sample region. Thus, effective collisional cooling seemed to prevent thermal fragmentation. Every single spark generates a shockwave, providing new reactive species, which expands concentrically from the hot region. Under ambient conditions primary charge carriers (ions and electrons) as well as VUV radiation initialize reaction cascades equivalent to other ambient ionization methods, such as DART or DBD. Mass spectra of polar/nonpolar hydrocarbons, sugars, pharmaceuticals and natural biomolecules in food were observed. Comprehensive emission spectroscopic measurements and time resolved electron current studies revealed insight into some plasma properties, such as the emitted high energetic radiation and the time evolution of the expanding plume.
Lanthanide-doped photon upconversion nanoparticles (UCNPs) exhibit many advantages compared to Stokes-shifted luminescent probes (organic dyes, quantum dots). Due to the upconversion process, the limitations of photobleaching, autofluorescence and low penetration depths in tissue shown by classical fluorescent probes are avoided. This makes UCNPs particularly useful for applications in complex biological samples. Sensing of intracellular pH is of particular interest in biomedical research since structure and function of biomolecules strongly depend on the concentration of protons in their environment.
Dual orthogonal functionality in a single material is highly desirable in many fields such as bio-imaging, sensing, coating or diagnostic and therapy. However, combining two different functionalities in a precise and controlled way is still a challenging task.
Here we present how simply dual functional hybrid nanoparticles consisting of a silica core with a fluorescent and a thermoresponsive polymeric layers can be prepared. As a first step of this work, silica core particles were coated by a fluorescent layer using surface-initiated reversible addition-fragmentation chain transfer polymerization. Afterwards, the fluorescent silica nanoparticles were completely enclosed in a switchable protective coating made of thermoresponsive poly(N-isopropylacrylamide). The thermoresponsive poly(N-isopropylacrylamide) changes its properties with varying the surroundings temperature and this behavior is reversible and controllable. To the best of our knowledge these types of hybrid dual functional core-shell-shell nanoparticles have not yet been prepared, despite the prospect of many potential applications.
Polydimethylsiloxane (PDMS)is one of the most appearing
contamination of medical devices.Dedicated analysis of PDMS on surfaces necessary, but the lack of calibration samples provides a bottle neck. There is a demand for metrological tools ensuring traceable and reliable analysis of mass deposition and of the chemical species of
contaminants. Photoelectron spectroscopy (PES) and reference-free GIXRF can be used to qualify bench top instrumentation.
Comparison of PES data and GIXRF data enable the establishment of a traceability chain.
In the course of miniaturizing modern technology down to the molecular scale, understanding the materials behavior has to be investigated and deviations from the bulk that might arises from confinement effects has to be understood. Here, a combination of nano-sized relaxation spectroscopies (Broadband dielectric spectroscopy (BDS) and Specific heat spectroscopy (SHS); employing AC nanochip calorimetry) were utilized to investigate the glassy dynamics of ultra-thin films of blends of Poly (vinyl methyl ether) (PVME) / Polystyrene (PS) 50:50 wt-%, which are miscible bulk (thicknesses: 8nm - 200nm, film thickness was controlled by ellipsometry, film topography by AFM). Both methods are sensitive to different probes; where SHS senses entropy fluctuations while BDS measures dipole fluctuations. For BDS measurements, a recently developed nano-structured electrode sample arrangement is employed; where ultra-thin films are spin-coated on an ultra-flat highly conductive silicon wafer, sandwiched between a wafer with nanostructured SiO2 nano-spacers with heights between 35 nm and 70 nm. The method was applied for film thicknesses up to 50 nm. For thicker films, the samples were prepared between crossed electrodes. It was proven that, for 50 nm films, both contact methods will lead to identical results. By measuring the dynamic Tg in dependence of the film thickness, SHS showed that the Tg of the whole film was strongly influenced by a nanometer-thick surface layer at the polymer/air interface due to a self-assembling process [1]. The dynamic Tg obtained from the SHS measurements decrease with decreasing film thickness, evidencing the importance of a mobile surface layer at the polymer/air interface for the glass transition of the whole film. Compared to the SHS results, the BDS measurements show a completely different behavior. At high temperatures, the temperature dependence of the relaxation times of the films follows that of bulk-like PS/PVME; obeying the VFT-law. With decreasing temperature, the temperature dependence deviates from the VFT to an Arrhenius law; where the apparent activation energy decreases with decreasing film thickness. This is the first example where confinement induced changes were observed by BDS for ultra-thin films. All results were analyzed in details in a comprehensive discussion.
Thiols have a high binding affinity to noble metals and semiconductor (SC) materials. Thiol ligands enable size control and tuning of the surface during the synthesis of nanoparticles (NP), significantly influence their physico-chemical and optical properties, and allow for their bioconjugation via further functional groups. Thus, simple, inexpensive, robust, and fast methods for the quantification of thiol groups and the characterization of thiol-modified or - stabilized nanomaterials including polymers are of considerable importance.
Emissive nanoparticles (NP) are of ever increasing importance in nanotechnology, optical industries, and life sciences. Applicationrelevant properties determining particle performance and biocompatibility depend mainly on surface functional groups or ligands. Coating with polyethylene glycol (PEG) ligands enhances hydrophilicity and biocompatibility of nanomaterials, and enables subsequent binding of biomolecules. Hence, PEGylated particles must be carefully engineered and monitored with simple and fast methods.
Spray drying is a widely used process step in ceramic technology to
convert fine grained raw powders to free-flowing granules. Type and
amount of the organic additives (dispersants, binders and plasticizers)
define viscosity and stability of the slurry, the granulate structure and
the compaction behaviour.
Alumina and Zirconia powders were characterized with regard to
particle size, shape and specific surface area (BET). Zeta-potential
measurements by Stabino® were used to investigate the effect of
different dispersants on slurry stability. Unfortunately, this method is
restricted to suspensions with less than about 30% by weight of solid
content. The multi-sample analytical centrifuge LUMiSizer® overcomes
this problem. This device enables analysis of the separation behaviour
of suspensions over a wide range of solid content. On the basis of
position and time resolved photometric detection of transmitted light,
it is possible to determine the instability index, the sedimentation
velocity, and the sediment height in dependence of type and amount
of organic additives at various centrifugal accelerations. Additional
information is obtained from the shape of the transmission profiles.
Based on LUMiSizer® measurements, suitable additive concentrations
were derived. Thereby, the number of investigations by viscometry and
spray drying experiments can be significantly reduced.
Finally, it was possible to produce alumina, zirconia and ZTA aqueous
slurries with up to 80 weight-% of solid. The optimized suspensions
were successfully spray dried and the resulted granules show good
compaction behaviour.
The surface modification of nanometer- and micrometer-sized particles with polyethylene glycol (PEG) ligands of varying length is a very common strategy to tune their hydrophilicity and biocompatibility, minimize unspecific interactions, improve biofunctionalization efficiencies, and enhance blood circulation times. Nevertheless, simple methods for the quantification of PEG ligands are rare. This is similarly true for the spectroscopic characterization of lanthanide-doped upconverting nanoparticles (UCNPs), novel near infrared (NIR)-excitable nonlinear fluorescence reporters for bioanalysis and theranostics, providing background-free multiple narrow emission bands in the visible and NIR, excellent photostability, and long luminescence lifetimes.
We present here a simple method for the determination of the number of PEG ligands on nanomaterials and screening methods for the fast identification of nonradiative deaction pathways in UCNPs.
Fluorescent particles like nm- and m-sized polymeric beads doped or labeled with different types of fluorophores and nanocrystalline systems like quantum dots and upconversion phosphors emitting in the visible (vis), near-infrared (NIR), and IR (infrared) region are of increasing importance as fluorescent reporters for bioanalysis and medical diagnostics. The assessment and comparison of material performance and the development of rational design strategies for improved systems requires suitable spectroscopic tools for the determination of signal-relevant optical properties and analytical tools for the determination of the number of surface groups, ligands, biomolecules and /or fluorophores per bead. In this respect, suitable spectroscopic tools for the characterization of the optical properties of such materials like photoluminescence quantum yields and brightness values and the determination of their surface chemistry are introduced. This includes integrating sphere setups for absolute measurements of fluorescence quantum yields of liquid and solid, transparent and scattering materials in the wavelength region of 350 nm to 1600 nm at varying excitation power densities for the study of multi-photon processes and simple optical assays, validated by comparison with established analytical techniques relying on different detection principles. Here, different examples for the optical and analytical characterization of different types of nanoscale reporters are presented.
Since the advent of industrial computed tomography (CT), this new analysis method has been used also for the investigation of objects of cultural heritage and art. CT provides the possibility to determine the inner and outer surfaces and to investigate the material structure without causing damage to the valuable objects.
In this talk I will present examples of measurements performed at BAM, which demonstrate what CT can do for objects of diverse materials and for different objectives.
Eight different screed types are tested including two different sample heights of 35 and 70 mm. The moisture of the four cement based and four sulphate based screeds are monitored during hydration and evaporation. All samples are stored in a climatic chamber at 23° C and 50 % relative humidity. Embedded sensors like temperature arrays, humidity sensor arrays, and multi-ring electrodes are embedded in the samples to yield a detailed moisture evolution with high depth resolution. Furthermore, nuclear magnetic resonance is used to quantify the water content at different depths. This multi-sensor approach allows a comprehensive monitoring of the moisture and its gradient in the different screed samples. This yields a deeper insight into the hydration, moisture convection, and diffusion processes.
To quantify the moisture in concrete, RFID based humidity sensors are embedded. Passive high frequency, ultra-high frequency RFID tags as well as active Bluetooth sensors are tested. After concreting, all sensors measure the corresponding relative humidity to monitor the concrete moisture. Two case studies are performed, embedding in an existing construction, i.e. the duraBASt test bridge, and embedding in cement based mortar in the laboratory. As basis for robust and long-life sensors in alkaline concrete, different casing materials are tested. Furthermore, signal strength measurements and their sensitivity to different moisture levels are performed.
Pollen represent one major cause for human allergic diseases. Currently the characterization and identification of pollen is time-consuming since it mainly relies on the microscopic determination of the genus-specific pollen morphology. A variety of new analytical approaches, like Raman - and fluorescence spectroscopy have been proposed in order to develop fast and reliable pollen identification. Recently matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was initially applied for the rapid investigation of such complex biological samples. Taxonomic differences and relations of single pollen grains could be identified.
Both commercially available lyophilized pollen and fresh pollen acquired from biological samples collected in parks and in the Botanical Garden Berlin in the years 2013-2015 were investigated. The samples were prepared by formic acid extraction in the gas phase and spotted with HCCA matrix. A variety of new approaches, like a newly developed MALDI target with micrometer sample spots sizes, were tested for their suitability. The obtained mass spectral data were investigated by principal component analysis (PCA).
The applicability of MALDI-TOF mass spectrometry for the classification of pollen according to their taxonomic relationships was proven. Specifically, chemical differences in the mass spectra at the levels of plant order, genus and in many cases even of species could be identified. Based on these results, further investigations have been undertaken to optimize the sample preparation for the classification of single pollen grains in mixtures of pollens. A novel MALDI-target design was developed to enhance the phenotypic information of pollens in their mass spectra. The combination of mass spectral patterns and multivariate statistics provide a powerful tool for the investigation of structural correlations within mixtures. The results can be used to improve the reconstruction of taxonomic relations of single species in various mixtures and might be useful for the development of a fast routine method to identify pollen based on mass spectrometry.
Characterization of bio-molecular surfaces and liquids by means of reference-free X-ray spectrometry
(2016)
An increasing field of application for X-ray spectrometry and related analysis techniques is the investigation of tailor made functional surfaces modified by organic molecules. For a detailed understanding and further development of such functionalized surfaces, a quantitative determination of the surface density of molecular species or even specific functional groups is required. By means of reference-free X-Ray Fluorescence (XRF) spectrometry such customized surfaces can be analyzed quantitatively, when using specific marker elements. A chemical analysis of molecular bonds can be accomplished by X-Ray Absorption Spectroscopy in the Near-Edge region (NEXAFS). Especially in the soft X-ray range an access to relevant light elements like carbon C, nitrogen N and oxygen O is possible. Especially, the characterization of liquids and solid-liquid interfaces aiming at the determination of bio-molecular moieties (functional groups) is of great interest. The characterization of such systems requires the analysis of bio-molecules in their liquid environment. For the understanding of (biomolecular) reactions and binding processes the verification and quantification of biomolecule immobilization is essential. However, the analysis in the soft-X-ray range involves a higher experimental effort. In this contribution various successful applications of the characterizations of organofunctionalized surfaces, solid-liquid interfaces and liquids containing bio-molecular species by means of reference-free X-ray spectrometry will be presented. The experiments were performed at the plane-grating monochromator beamline (PGM-U49) in the soft X-ray range at the synchrotron radiation facility BESSY II. Using calibrated instrumentation and a quantification approach based on atomic fundamental parameters a quantitative access without any calibration sample or reference material is possible. In a complementary analysis by X-Ray Photoelectron Spectroscopy (XPS) and fluorescence measurements based on laserexcitation in the optical light spectrum the functional-group density of silane monolayers were determined. Here, the nitrogen atoms of the head-group of the label molecule employed could be used as specific marker for the reference-free quantitative XRF analysis and is used for traceable calibration of XPS and fluorescence spectroscopy. Furthermore, a novel UHV-compatible liquid-cell developed to investigate liquids and solidliquid interfaces will be presented. Protein attachment at the solid-liquid interface was investigated by detection of the characteristic N1s→π*(O=C-N) amide bond resonance in the N K-edge NEXAFS by using ultra-thin epoxy-functionalized SiC-windows.
Safe innovation & sustainable production with MNMs need that we:
Understand risks and benefits (diagnostic, assessment)
Identify and implement risk reduction strategies (manage)
Communicate on residual risks (acceptance)
Huge knowledge on characterization, hazards, diagnostic (science)
Little effective use of it for operational risk management (expertise)
Objectives of the centre:
Bridge the gap between research and application (public, private),
Bridge the gap between knowledge on risks and risk management,
Balance between Science and Appliance,
in a sustainable way:
Efficient & Sustainable structure
Collective, harmonized, shared expertise
EU scale, internationally connected.
In recent years, elemental imaging of biological samples using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is gaining in importance. Recent improvements regarding spatial resolution (down to 1 µm) and washout time make LA-ICP-MS particularly interesting for single cell analysis.
Many current nanomaterials can serve as contrast agents in cellular or tissue imaging, drug delivery vehicles or therapeutics, whereas others can cause toxic effects. In order to evaluate nano-bio interactions, the number of nanoparticles (NPs) inside cells as well as their localisation within cellular substructures is of particular interest.
LA-ICP-MS was used to study the NP pathway from uptake, via intracellular processing up to cell division. Fibroblast cells were incubated with different metallic NPs under varying experimental conditions. For LA analysis the cells were fixed with formaldehyde and dried.
Our results show that LA-ICP-MS is able to localise NP aggregates within cellular substructures. The NPs accumulate in the perinuclear region in the course of intracellular processing, e.g. multivesicular fusion and endosomal maturation, but do not enter the nucleus [1, 2]. A strong dependence of NP uptake on concentration and incubation time was found. Additionally, the number of NPs internalized by individual cells was determined and variations within the cell population became visible.
A new laser ablation system providing a short washout time (50 ms) together with small spot sizes (< 4 µm) and high repetition rates allows high spatial resolution applications. First results of cell imaging will be shown.
The findings demonstrate the potential of LA-ICP-MS providing insight into NP uptake and intracellular distribution dependent on experimental parameters.
Here, we present an overview of the research activities of division Biophotonics concerning the design and (bio)analytical application of molecular and nanoscale functional chromophores for e.g., biomarker analysis including methods for the reliable determination of their application relevant properties. This includes the absolute determination of their brightness and photoluminescemce quantum yield, determining the signal size from the material side, as well as the development of fluorescence standards for such measurements and instrument calibration strategies, thereby providing important prerequisites for the comparison of material performance, the mechanistic understanding of nonradiative decay channels, and the rational design of new optical reporters. Moreover, for particle-based systems, ranging from nm-sized semiconductor quantum dots to m-sized polymeric and silica beads, simple optical methods and assays for the assessment of their surface chemistry are presented, which enable the quantification of the number of total and derivatizable surface functionalities, ligands per particle and particle-bound biomolecules. In addition, validation concepts for such methods are introduced utilizing method comparisons, multimodal and cleavable probes.
There is an increasing interest in optical reporters like semiconductor quantum dots and upconversion nanocrystals with emission > 800 nm for bioanalysis, medical diagnostics, and safety barcodes. Prerequisites for the comparison of material performance, the mechanistic understanding of nonradiative decay channels, and the rational design of new nanomaterials with improved properties are reliable fluorescence measurements and validated methods for the assessment of their surface chemistry. The latter is of special relevance for nanocrystalline emitters, where surface states and the accessibility of emissive states by quenchers largely control accomplishable photoluminescence quantum yields and hence, signal sizes and detection sensitivities from the reporter side. Here, we present the design of integrating sphere setups for the excitation power density-dependent absolute measurement of emission spectra and photoluminescence quantum yields in the wavelength region of 350 to 1600 nm and results from spectroscopic studies of semiconductor quantum dots and upconversion nanocrystals of different size and surface chemistries in various environments. Subsequently, examples for simple approaches to surface group and ligand analysis are presented.
Measuring the moisture state of screeds is critical for floorers in order to prevent structural damages of bottom coverings. Typically destructive tests are carried out on small samples delivering only punctual information. We tested several non-destructive testing methods in terms of sensitivity in the critical low moisture range and observed substantially different drying behavior for the two tested cement based and calcium-sulphate based screed samples. Our findings are supported by moisture gradient measurements using the nuclear magnetic resonance technique.
In this contribution, two large-area EDS detectors were tested according to the procedure proposed by Procop et al. (2015). In a first step, the optimal working distance (WD) in the two different SEM chambers was determined by moving the sample stage in the Z direction and monitoring the count rates at a magnification of 10,000 and a field of view of 25.6 µm. The WD at which the highest intensity was measured was selected as the optimal position, corresponding to the crossover between the EDS detector optical axis and electron beam optical axis. Next the Cu Kα peak was measured at different relative EDS positions while it was partially removed from the fully inserted position. The spectrum at each location was collected for 10 sec using the highest pulse rate and intermediate current to minimize pile up effects. The ‘inverse squared normalized intensities vs. relative EDS position’ used to extract the true detector – specimen distance shows a non-linear relationship even at the minimal relative positions, which indicates shadowing due to obstruction or use of an unsuitable and/or off-centered collimator. The normalized count rates measured as a function of the EDS distances, results in a too low GCE (too low true solid angles) for both tested detectors. The source of losses of signal was shadowing caused by collimators.
Since the first LC/ ESI-MS experiment of the Nobel prize winner John B. Fenn in 1984, the coupling of liquid chromatographic to mass spectrometric techniques gained a continuous rapid development.
The lecture will give a general survey of different LC separation techniques as size exclusion chromatography (SEC), liquid adsorption chromatography (LAC), liquid chromatography at critical conditions (LCCC) and gradient elution liquid chromatography (GELC) combined with Matrix assisted Laser Desorption Ionization (MALDI) respectively Electrospray Ionization (ESI) Time of Flight (TOF) mass spectrometry.
Often the deficiencies of stand-alone methods can be bridged. LC, blind to structural information needs mass spectrometry as one of the most powerful detectors able to give detailed information on e.g. the repeat units, functionalization or copolymer composition of the chromatographic separated constituents. A separation prior to MS reduces the polydispersity which is one of the reasons for failing of MS. Also problems with different ionization probabilities in complex mixtures can partly be overcame.
On the basis of different examples on- and offline coupling principles will be compared and the pros and cons of both mass spectrometric techniques will be discussed.
Recently, MALDI imaging techniques in coupling with chromatography have become interesting e.g. for visualization of copolymer composition.
Die Bestimmung der chemischen Zusammensetzung einer Oberfläche und deren Quantifizierung mit wichtig für die Qualitätssicherung vieler industrieller Produkte und Materialien. Die chemische Beschaffenheit von Oberflächen bzw. Grenzflächen muss genau kontrolliert werden um die Produktqualität zu garantieren. Diese Prüfung ist oft auch für individuelle Prozessschritte durchzuführen.
Referenzmaterialien sind unverzichtbar, wenn es darum geht, die Richtigkeit und Zuverlässigkeit von Messergebnissen zu gewährleisten. Falsche Messwerte können zu erheblichen Mehrkosten führen. Referenzmaterialien gewährleisten die Rückführung von Messergebnissen auf anerkannte Bezugsgrößen (Standards), dienen der Ermittlung der Messunsicherheit von analytischen Verfahren und wer-den zur Kalibrierung verwendet. Für zertifizierte/akkreditierte (ISO 9000 und ISO 17025) Prüf- und Kalibrierlaboratorien ist der Einsatz von Referenzmaterialien in der Qualitätssicherung obligatorisch.
Ionischen Flüssigkeiten (IL) sind vielversprechende Kandidaten für die Verwendung als Referenzmaterial in oberflächenanalytischen Verfahren wie Energie-dispersive Röntgenspektroskopie (EDX) und Röntgenphotoelektronenspektroskopie (XPS). In zwei Machbarkeitsstudien wurde eine geeignete Klasse von ILs als Referenzmaterial getestet:
Für die Anwendung in EDX wurde die Eignung von ILs als Referenzmaterial zur routinemäßigen Überprüfung der Energieskala, der Energieauflösung und der Spektrometer-Effizienz untersucht. Es kann gezeigt werden, dass mit einer einzigen Messung an einem einzigen Referenzmaterial mehrere Geräteparameter überprüft werden können. Damit ist es im niederenergetischen Bereich möglich, regelmäßige Funktionsprüfungen von Spektrometern durchzuführen, aber auch die Leistungsfähigkeit verschiedener Spektrometer zu vergleichen
Für Die Anwendung in XPS wurde die Eignung von ILs als Referenzmaterial zur Bestimmung der Transmissionsfunktion T(E) von Photoelektronenspektrometern getestet. Dazu wurde die Auswertesoftware UNIFIT entsprechend adaptiert und erlaubt nun T(E) anhand der bekannten Stöchiometrie der IL zu ermitteln. Es wird gezeigt, dass durch die Verwendung ausgewählter ILs als Referenzmaterial die Genauigkeit der Quantifizierung von XPS Daten unter Nutzung einer experi-mentell bestimmten T(E) wesentlich verbessert werden kann.
One of the more difficult tasks for structural health monitoring is the continuous evaluation of the stability and load capacity of the building materials. This knowledge can be won, e.g., by taking material samples at the examining place with the drawback of partly destroying the structure. To avoid this, modern sensor and communication technologies offer promising methods for non-destructive testing. To address the tasks for monitoring of concrete structures, in the presented study, different sensors were combined with RFID transponders and embedded in concrete components.
The effect of a nanometre confinement on the molecular dynamics of liquid crystals was studied by broadband dielectric and neutron spectroscopy. As confining host the molecular sieve Al-MCM-41 (Si/Al=60) with a mean pore diameter of 3 nm was selected. As guest the liquid crystals 8CB and E7 were chosen where the latter does not crystallize but undergoes a glass transition forming a nematic glass.
Dielectric spectroscopy shows that for the confined systems one relaxation process is observed. Ist characteristic relaxation time is much lower compared to that of the bulk. No signature of the Phase transition characteristics of the bulk liquid crystal is detected. The temperature dependence of the relaxation time of this relaxation process has to be described by the Vogel-Fulcher-Tammann equation and thus shows similarities to glassy dynamics.
The vibrational density of states measured by neutron spectroscopy (IN6, ILL; TOFTOF, MLZ) Shows excess contributions with respect to the Debye density of states (boson peak). For the confined systems the low frequency contributions of the boson peak are suppressed, an effect which is also found for conventional glass forming systems.
In addition elastic scans were carried out at the backscattering spectrometer (BS) IN10 at ILL. Such measurements provide an overview about the temperature dependence of the microscopic dynamics.
Assuming a Gaussian form for the elastically scattered intensities the effective mean square displacement was calculated. For the nanoconfined samples the mean square displacement is strongly reduced in comparison to the bulk. Also these measurements show the signature of a glass Transition indicated by a change in the temperature dependence of the mean square displacement. For confined E7 the extracted glass transition temperature is shifted by more than 20 K to higher temperatures.
Broadband inelastic neutron scattering was carried out by combining time-of-flight (IN6, ILL; TOFTOF, MLZ) and backscattering (IN10, ILL; SPHERES, MLZ) experiments in the time domain.
The time dependence of the incoherent intermediate scattering function Sinc(q,t) shows two Relaxation processes which were quantitatively analyzed by fitting the KWW function to the data. The process at shorter times shows a close similarity the methyl group rotation found for polymeric systems. The process at longer times was assigned to glassy dynamics. The obtained data are compared in detail in their temperature dependence to the dielectric results.
Der Grad der Finite-Elemente-Diskretisierung wird vom Verhältnis der Details zur Objektgröße bestimmt. Die Diskretisierung eines großen Objektes mit vielen kleinen Details führt zu einer hohen Anzahl an Elementen bzw. Knotenpunkten. Die Berechnung solcher Körper erfordern nicht nur sehr hohe Rechenzeit, sondern was die Berechnung unmöglich macht, ist der sehr hohe Speicherbedarf. Mit Hilfe eines Ersatzkörpers wird dieses Problem umgangen.
Many engineering structures are made of composite materials or metal foam. To simulate the deformational behaviour of these structures often requires a high number of discretisation elements. This in turn yields a very large system of linear equations that are extremely time and memory consuming or practically impossible to solve. It is therefore desirable to find an approach to overcome this obstacle.
The Berlin Main Station was built between 2000 and 2006. At the occasion of the 10th anniversary after the Berlin Main Station was officially opened to train traffic, a view back on eight years of monitoring was given. For the period of the construction with different load cases, the monitoring system was required by the Railway Authorities (Eisenbahnbundesam, EBA) to survey differential vertical displacements between neighbouring supports of the glas roof and the partially prestressed middle bridges. 128 sensors were installed.The data was published in the Internet with access restricted to the BAM scientists and the owner of the station, the German Railways DB AG.
The paper addresses the “Conventional Single-Sample vs. Multiple-Sample Hardness Testing: Hardness Testing Machine vs. Centrifuge” and the follow points are discussed in more detail: Principle of the centrifuge test, components of the centrifuge test, indenter geometries, microscopic measurement of Brinell and Vickers indents, and hardness testing: conventional vs. centrifuge.
Active thermography has been developed into a well-established non-destructive testing method and is used to detect cracks, voids, or material properties. The spatial-temporal structure of the external heating: spatially: planar (e.g., halogen lamp) or local (e.g., focused laser), and temporally: pulsed (e.g., flash lamp) or periodical (e.g., halogen lamp), has led to different testing modalities, as for instance flash and lock-in thermography. In this work, we combine a high-power laser with a spatial light modulator (SLM) allowing us to merge all degrees of freedom into a spatially and temporally controlled heat source. This approach allows us to launch a set of individually controlled and fully coherent high-energy thermal waves into the sample volume. As one possible application, we demonstrate the interference of two phase shifted thermal wave patterns in order to detect the position and depth of hidden defects, which is still a challenging task in thermographic and photothermal techniques. The patterns are positioned with a certain distance and a phase shift of pi to each other, creating an amplitude depletion zone that is centered between them. Now, when a defect is brought into the depletion zone, the destructive interference is disturbed and the defect can be recognized. This approach means that we intentionally exploit the vertical and lateral propagation directions of the thermal waves. In a more general view, controlling simultaneously control of phase and amplitude of a set of thermal waves enables us to have a defined propagation of the thermal wave field within the sample, which means that thermal waves can be controlled almost like acoustical or optical waves. However, in contrast to optical or acoustical waves, thermal waves are highly damped due to the diffusive character of the thermal heat flow and therefore limited in penetration depth in relation to the achievable spatial resolution. Nevertheless, the coherence length of thermal waves can be chosen in the mm-range for modulation frequencies below 10 Hz which is perfectly met by present SLM technology. Eventually, this offers the opportunity to transfer known technologies from wave shaping techniques to thermography methods and to exploit the possibilities of coherent thermal wave shaping.
In recent years, the optimization of the imaging stations at research reactors and especially the further development of the neutron detectors allowed the measurement of hydrogen distributions with increasing spatial and temporal resolution at lower detection limits at the same time. Hydrogen has compared to iron a high total neutron cross section, which allows with basic radiographic methods the visualization of hydrogen in two and three dimensions inside the microstructure of components. This enables the in situ measuring of hydrogen mass flows inside cm thick steel samples with a temporal resolution of 20 s as well as the quantitative measurement of hydrogen accumulations at the crack’s inner surfaces in hydrogen embrittled iron samples. For the first time, we detected directly gaseous hydrogen in the crack cavities and we could measure the gas pressure. This new quality of the information on a micrometer scale allows new insights for the analysis of damage mechanisms, e.g. of hydrogen embrittlement. Further, this method is non-destructive and provides local information in situ and in three dimensions with a spatial resolution of 20-30 µm, which is not accessible with common methods as e.g. thermal desorption spectroscopy.
In this contribution, we show examples that demonstrate the spatial and temporal resolution of the neutron radiography and tomography method in order to visualize and quantify hydrogen accumulations at cracks. The measurements were performed at the research reactor BER II of HZB in Berlin and at the FRM II reactor of the neutron source Heinz Maier-Leibnitz in Garching.
The paper addresses the ‘Determining the influence of preparation and measurement conditions on bonding strength using CAT-Technology’ and the follow points are discussed in more detail: Motivation, CAT – Technology, Influence of bonding area on bonding strength, Influence of storing & measurement temperatures and Influence of substrate thickness and coating support.
The comprehensive knowledge of material properties as engineered and the material behavior in use is of huge importance for the functionality and reliability of processes and products. Hence, the accurate determination of material properties is a prerequisite for the applicability of a given material. Nowadays, macroscopic product features are originated by material properties on the microscopic and nanoscopic scale. This is a general challenge for uncertainty budgets in measurement and testing based on a conformity assesment.
Testing labs accreditated according to DIN EN ISO/IEC 17025 have to meet these demands. This paper focuses on the measurement of physical quantities (measurand with value and unit) and on the testing of material properties (qualitative, semi-quantitative or quantitative characteristics) of solid state materials. For both measurement and testing, the expression of uncertainty according to GUM is essential. Regarding the object/sample one has to subdivide in surface and bulk features, from the measurement/testing point of view destructive vs. nondestructive procedures have to be distinguished. Moreover, direct mesurement/testing and model-based determination of quantities/properties of interest require different approaches regarding the expression of uncertainty. For surface quantities and properties as discussed here, further considerations have to be made with respect to localized (lateral extension, native or artificial) or stratified (homogeneity and isotropy) material features vs. mapping (integration area) and imaging (lateral resolution and field of analysis) specifications of the measurement/testing procedure.
The concept of uncertainty budgets and the expression of uncertainty is introduced and discussed in more detail for the nondestructive model-based determination of thickness by spectroscopic ellipsometry (SE), the destructive determination of adhesion by means of centrifugal adhesion testing (CAT). It is shown that the expression of uncertainty for these examples and real materials requires different approaches resulting in either quantitity values with unit or qualitative/quantititative attributes with calculated/estimated uncertainties in agreement with GUM.
Economic industrial spray drying of ceramic slurries aims for as high as possible solids content. Investigated slurries of up to 80 wt% solids content were analyzed regarding stability while staying processable for granule production via spray drying.
Preliminary stability examinations were carried out on the one hand via zeta potential measurements and on the other hand by optical centrifuge analysis for determination of suitable additive type, quantity and composition while even allowing the detection of potential side effects. The processability of the slurry for spraying has primarily been quantified by viscosity measurements.
Early spray dried granules turned out to have internal voids and/or hard shells leading to defective sinter bodies and low density. Focusing on the root of these voids, the “hollow hard granules”, a controlled destabilization and flocculation was initiated by weakening electrostatic repulsion and approaching the isoelectric point. Destabilization, quantifiable by optical centrifugation, leaded to a change in speed of clarification as well as packing density, influencing movement speed of the phase boundary and the final height of the sediment, respectively. For sufficient destabilization, the solids content needed to be reduced in order to keep the viscosity suitable for the following spray drying procedure.
The versatile controlled destabilization of the ceramic slurry finally leaded to a significantly reduced fraction of hollow granules featuring a sinter body of higher density with smaller pores and a narrower pore size distribution, additionally this destabilization approach has shown to be transferrable with excellent results to zirconia and even ZTA (zirconia toughened alumina) composite materials.
Durch das alkalische Porenwassermilieu ist Stahl im Beton vor Korrosion geschützt. Unter ungünstigen Umgebungsbedingungen (Karbonatisierung, Chlorideintrag) kann die passive Deckschicht auf der Stahloberfläche zerstört werden. Im weiteren Verlauf können sich korrosionsbedingte Folgeschäden, wie Risse und Abplatzungen am Bauwerk ergeben. Um notwendige Sanierungsmaßnahmen sind frühzeitige und weitgehend zerstörungsfrei ermittelte Informationen über das aktuelle Korrosionsverhalten der Stahlbewehrung von großer Bedeutung. Die Potentialfeldmessung ist ein etabliertes und weit verbreitetes Verfahren zur Beurteilung des Korrosionszustandes der Bewehrung in Stahlbetonbauwerken. Mit Hilfe dieses Verfahrens können Bereiche aktiv korrodierender Bewehrung zerstörungsfrei lokalisiert werden. In der Regel kommt diese Messmethode bei der Detektion chloridinduzierter Korrosion zum Einsatz.
Reference-free XRF is a SI traceable technique for the
determination of the mass deposition (mass per unit area) of elements in films on the nano- and micro scale. The method is radiometrically calibrated instrumentation (PTB@BESSY II, Germany) and based on reliable knowledge of all relevant atomic fundamental, experimental and instrumental parameters. No calibration sample or reference materials are necessary. The approach had been validated in the CCQM-P140 pilot study and the K129 key comparison by determination of mole fractions in Cu(In,Ga)Se2 thin films.
The certified reference material BAM-L200, a nanoscale stripe pattern for length calibration and specification of lateral resolution, is described. BAM-L200 is prepared from a cross-sectioned epitaxially grown layer stack of AlxGa1-xAs and InxGa1 xAs on a GaAs substrate. The surface of BAM-L200 provides a flat pattern with stripe widths ranging down to 1 nm. Calibration distances, grating periods and stripe widths have been certified by TEM with traceability to the length unit. The combination of gratings, isolated narrow stripes and sharp edges of wide stripes offers a plenty of options for the determination of lateral resolution, sharpness and calibration of length scale at selected settings of imaging surface analytical instruments. The feasibility of the reference material for an analysis of the lateral resolution is demonstrated in detail by evaluation of ToF-SIMS, AES and EDX images. Other applications developed in the community are summarized, too.
BAM-L200 fully supports the implementation of the revised International Standard ISO 18516 (in preparation) which is based on knowledge outlined in the Technical Report ISO/TR 19319:2013.
FLiMFlow – Recent achievements in flow cytometry with lifetime detection and lifetime-encoded beads
(2016)
Flow cytometry is a widespread technique in biological research and clinical applications. Two different directions are currently of importance in development of new methods in this field. Whereas analyses in research become increasingly complex and require a growing number of simultaneously detectable codes and fluorescent labels, also low-cost methods and portable devices are needed in routine application.
Lifetime encoding could present an alternative to common spectral multiplexing. On the one hand, it addresses the need for additional codes by combining spectral and lifetime multiplexing. On the other hand, using only lifetime encoding could help to reduce instrument costs by keeping the number of excitation sources and detectors low.
Here, we report on our recent progress in employing dye-stained lifetime-encoded polymer microparticles as a model system for lifetime encoding in flow cytometry. The discrimination of two lifetime codes was achieved with two bead sets. Moreover, the simultaneous detection of a spectrally different ligand fluorescence signal could be demonstrated.
In vivo detailed spatial distribution of TiO2 NPs was here investigated for the first time using a 2D chemical imaging analysis based on Confocal Raman Spectroscopy. The invertebrate nematode C. elegans was employed as prototypical model of living organism. Rod, bipyramidal and quasi-spherical engineered TiO2 NPs with different primary particle sizes and agglomeration states were prepared, characterized and then administered to nematodes. Exploiting the typical fingerprint of TiO2 in the Raman spectrum, we monitored the biodistribution of NPs inside the worm using a non-invasive, label-free method. The high spatial resolution chemical imaging and the specificity of the Raman technique in the localization of TiO2 NPs helped in the design of behavioral C. elegans studies aimed at elucidating the relationship among the size, shape, and agglomeration state of NPs and their ability to induce specific toxic effects.
Evaluation of electron microscopy techniques for the purpose of classification of nanomaterials
(2016)
One current and much-debated topic in the characterization of nanomaterials (NM) is the implementation of the recently introduced recommendation on a definition of a nanomaterial by the European Commission. According to this definition, a material is a NM when for 50% or more of the particles in the number size distribution, one or more external dimensions is in the size range 1 nm-100 nm. The European NanoDefine Project was set up to develop and validate a robust, readily implementable and cost-effective measurement approach to obtain a quantitative particle size distribution and to distinguish between NMs and non-NMs according to the definition.
All currently available sizing techniques able to address nanoparticles were systematically evaluated. It was demonstrated that particle sizing techniques like: analytical centrifugation, particle tracking analysis, single-particle inductively coupled plasma mass-spectrometry, differential electrical mobility analysis, dynamic light scattering, small angle X-ray scattering, ultrasonic attenuation spectrometry, but also gas adsorption analysis based on the BET-method can be applied for a screening classification. However, the quality of the results depends on the individual material to be classified. For well-dispersed, nearly spherical (nano)particles most of the sizing techniques can be applied in a quick and reliable way. In contrast, the classification of most real-world materials is a challenging task, mainly due to non-spherical particle shape, large polydispersity or strong agglomeration/aggregation of the particles. In the present study it was shown that these issues can be resolved in most cases by electron microscopy as a confirmatory classification technique.
Electron microscopy techniques such as TEM, STEM, SEM or TSEM (transmission in SEM) are capable of assessing the size of individual nanoparticles accurately. Nevertheless the challenging aspect is sample preparation from powder or liquid form on the substrate, so that a homogeneous distribution of well-separated (deagglomerated) particles is attained. The systematic study in this work shows examples where the extraction of the critical, smallest particle dimension - as the decisive particle parameter for the classification as a NM - is possible by analysing the sample after its simple, dry preparation. The consequences of additional typical issues like loss of information due to screening of smaller particles by larger ones or the (in)ability to access the constituent particles in aggregates are discussed.
By means of practical examples the inherent statistical evaluation of the particle size is highlighted together with all its pitfalls such as setting of a suitable threshold for delimitation of the particle .
Ein kurzes Blick in die Computertomographie (CT) im Rahmen des RT3 Kurs der DGZfP ist gegeben.
Die Radontransformation ist bildlich erklärt, und die Grundlagen der Technik mit Vergleich zu der Radiographie sind auch erwähnt. Die typische Rekonstruktionsfehler und deren Beseitigung sind behandelt. Am Ende Beispiele der Anwendungen der CT sind gegeben, aus der zerstörungsfreie Prüfung, der Materialwissenschaft und der Metrologie.
We present the results of a machine learning (ML)- inspired data fusion approach, applied to multi-sensory nondestructive testing (NDT) data. Our dataset consists of Impact-Echo (IE), Ultrasonic Pulse Echo (US) and Ground Penetrating Radar (GPR) measurements collected on large-scale concrete specimens with built–in simulated honeycombing defects. In a previous study we were able to improve the detectability of honeycombs by fusing the information from the three different sensors with the density based clustering algorithm DBSCAN. We demonstrated the advantage of data fusion in reducing the false positives up to 10% compared to the best single sensor, thus, improving the detectability of the defects. The main objective of this contribution is to investigate the generality, i.e. whether the conclusions from one specimen can be adapted to the other. The effectiveness of the proposed approach on a separate full-scale concrete specimen was evaluated.
Neutronenbeugung hat verschiedenste Anwendungen, die auf die eigenartigen physikalischen Eigenschaften der Neutronen berühen.
Während die Beugungstechniken wie z.B. die klassische Pulverbeugung, die Kleinwinkelstreuung und die Texturanalyse besonders für die Materialcharakterisierung nutzbar sind, setzt sich die Neutronenbeugung als zerstörungsfreies Verfahren für Eigenspannungsanalyse extrem relevant ein.
Allerdings sind nur wenig die Leute, die die Neutronenbeugung in der ZfP Community benutzen. Dieser Vortrag hat das Ziel die Interesse an der Nutzung von einem solchen Grossgerätwerkzeug aufzuwecken und ein Paar impactvolle Anwendungsbeispiele einiger Techniken zu zeigen.
Die Bestimmung mikroskopischer mechanischen Eigenschaften von Kompositen (MMC oder CMC), sowie der Mapping von Eigenspannungsfelder in Komponenten werden bearbeitet.
Es wird gezeigt, dass Neutronenbeugung grundsätzlich eine zerstörungsfreie Methode für beide die Materialcharakterisierung und die Komponentenintegrität ist, die hohes Potentiell hat, zum Verfahrensportfolio der zerstörungsfreier Prüfung zu gehören.
Boron oxide glasses usually show low glass transition temperature Tg due to the three-fold oxygen coordination of boron. Adding of alkali and alkaline earth oxides to the glass composition will not decrease but increase Tg due to a change in boron coordination from trigonal to tetrahedral, known as the boron anomaly. Only for higher fractions of alkali oxides, non-bridging oxygens (NBO) are progressively formed in competition with tetrahedrally coordinated boron, which leads to a decrease in viscosity.
ln contrast to this well-known behavior of alkali oxides (R2O), there is little known about adding H2O to borate glasses. The present work therefore aims in shedding light on the rheological properties of hydrous soda lime borate glasses with particular focus on the role of water. For doing so, we determined Tg as a function of Na2O and H2O content using differential thermal analysis (DTA) backed up by micropenetration viscosity measurements. Results show that water decreases Tg for all glasses and water concentrations under study (< 8 wt.% total water). Obviously, water mostly causes the formation of NBO having no significant influence on boron coordination as seen for alkaline.
Affinity extraction is one of the most powerful separation methods. Regarded to be indispensable in some research fields, such as proteomics, the application in other fields is still scarce or even waning. Many researchers fear the perceived complexity, cost and unreliability of this approach. The presentation gives a broad overview of the most important methods and discusses some important points for their implementation. Having considered these aspects, it should be easier to establish an affinity separation approach to resolve challenging analytical questions.