Analytische Chemie
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Airborne ultrasonic inspection is performed in through transmission, where the test piece (e.g. adhesive joint or polymer-based composite plate) is placed between the transmitter and the receiver. However, many structures with difficult shapes allow only one-sided inspection. The strong reflection of the signal from the surface overshadows the signals from the inside, so that broadband pulses are required. Thermoacoustic transmission, where the thermal energy of an electrically heated electrode is transformed into the acoustic energy of an ultrasonic wave, opens the possibility to excite broadband pulses and thus to inspect objects with one-sided access.
We present various thermoacoustic transducers consisting of an electrically conductive film on a solid substrate. The first type of transducer is a transmitter with an indium-tin-oxide electrode on a glass substrate combined with a laser Doppler vibrometer as a receiver. The second type of transducer combines thermoacoustic transmission and piezoelectric reception, having a titanium electrode as a transmitter deposited onto charged cellular polypropylene serving as a piezoelectric receiver.
Using a focusing thermoacoustic transmitter and a separate cellular polypropylene receiver, a through-transmission inspection of a 4 mm thick CFRP test piece with inserts as small as 1 mm was performed. The same emitter and a laser vibrometer as a receiver were used for a one-sided inspection of a Plexiglas block with a cross hole at 15 mm depth. A twin probe consisting of a thermoacoustic transmitter on a cellular polypropylene receiver was applied to a profile measurement on a step wedge with flat bottom holes. The smallest detected diameter of a flat bottom hole was 1 mm. Sound pressure level above 140dB was achieved with each of these transmitters. Thermoacoustic transmitters enable a step towards one-sided air-coupled ultrasonic inspection.
Im Rahmen der Lebensdauerverlängerung oder der Umnutzung von Bauwerken (z. B. Brücken, Bürogebäude oder Maste) müssen diese zum Teil neu bewertet werden. Dafür ist eine Nachrechnung für statische und dynamische Lastfälle erforderlich. Dies betrifft zum einen die Struktur selbst, die gegebenenfalls verstärkt werden muss. Aber auch die Gründung (oft Pfähle verschiedenster Typen) muss neu beurteilt werden. Nach mehreren Jahrzehnten sind jedoch für einige Bauwerke keine zuverlässigen Bestandsunterlagen verfügbar.
Eine vollständige Freilegung der Pfähle verbietet sich aus Kostengründen sowie Verlust an Widerstand gegen Zug. Lediglich der Pfahlanschluss kann visuell begutachtet werden, um Pfahlzahl, -typ und Durchmesser zu bestimmen. Für die Bestimmung der Pfahllänge müssen zerstörungsfreie Verfahren eingesetzt werden. In einer Machbarkeitsstudie wurden von den Autoren teils im Blindversuch drei Verfahren evaluiert: die klassische Pfahlintegritätsprüfung nach der Hammerschlagmethode, eine mehrkanalige Variante hierzu und das Parallel-Seismik-Verfahren. Die ersten beiden Methoden lieferten an den untersuchten Pfählen nur in Einzelfällen verwertbare Ergebnisse. Die Parallel-Seismik-Methode lieferte auch im Blindversuch an Fundamenten, bei denen die Pfahllänge dem Eigentümer bekannt war, Ergebnisse mit einer Abweichung von max. 0,5 m. Diese Toleranz lässt sich bei der Standfestigkeitsbeurteilung berücksichtigen. Die Mehrkosten des Verfahrens (anders als bei den anderen Verfahren wird ein verrohrtes Bohrloch im Boden nahe dem Pfahl benötigt) halten sich in Grenzen, wenn man es in die geotechnische Untersuchung integriert. Daher wurde es inzwischen auch in der Praxis eingesetzt. Auch liegen die Gesamtkosten für die Untersuchung deutlich unter denen für eventuell notwendigen Ersatz – oder Verstärkungsmaßnahmen, die notwendig werden, wenn keine Daten zur Pfahllänge verfügbar sind.
Der Vortrag erläutert die Ergebnisse der Machbarkeitsstudie, zeigt erste Praxisfälle und weist auf Möglichkeiten hin, das Parallel-Seismik Verfahren in Zukunft noch genauer und effizienter einzusetzen.
Der Vortrag widmet sich der Kratzbeständigkeit-Prüfmethoden und deren Bewertung und beschreibt Begriffe/Definitionen, Wirtschaftliche Bedeutung der Kratzbeständigkeit, Mess- und Prüfverfahren – allgemein (Anwendbarkeit, Messunsicherheit, Validierung), Mess- und Prüfverfahren – speziell die Erzeugung, Prüfverfahren von Einzel- und Vielfach-Kratzern, die Charakterisierung von Verkratzungen und eine zusammenfassende Bewertung im Einzelnen
Durch das alkalische Porenwassermilieu ist Stahl im Beton vor Korrosion geschützt. Unter un-günstigen Umgebungsbedingungen (Karbonatisierung, Chlorideintrag) kann die passive Deck-schicht auf der Stahloberfläche zerstört werden. Im weiteren Verlauf können sich korrosionsbe-dingte Folgeschäden, wie Risse und Abplatzungen am Bauwerk ergeben. Um notwendige Sanie-rungsmaßnahmen sind frühzeitige und weitgehend zerstörungsfrei ermittelte Informationen über das aktuelle Korrosionsverhalten der Stahlbewehrung von großer Bedeutung. Die Potentialfeld-messung ist ein etabliertes und weit verbreitetes Verfahren zur Beurteilung des Korrosionszu-standes 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.
Im Rahmen der Lebensdauerverlängerung oder der Umnutzung von Bauwerken (z. B. Brücken, Bürogebäude oder Maste) müssen diese zum Teil neu bewertet werden. Dafür ist eine Nachrechnung für statische und dynamische Lastfälle erforderlich. Dies betrifft zum einen die Struktur selbst, die gegebenenfalls verstärkt werden muss. Aber auch die Gründung (oft Pfähle verschiedenster Typen) muss neu beurteilt werden. Nach mehreren Jahrzehnten sind jedoch für einige Bauwerke keine zuverlässigen Bestandsunterlagen verfügbar.
Eine vollständige Freilegung der Pfähle verbietet sich aus Kostengründen sowie Verlust an Widerstand gegen Zug. Lediglich der Pfahlanschluss kann visuell begutachtet werden, um Pfahlzahl, -typ und Durchmesser zu bestimmen. Für die Bestimmung der Pfahllänge müssen zerstörungsfreie Verfahren eingesetzt werden. In einer Machbarkeitsstudie wurden von den Autoren teils im Blindversuch drei Verfahren evaluiert: die klassische Pfahlintegritätsprüfung nach der Hammerschlagmethode, eine mehrkanalige Variante hierzu und das Parallel-Seismik-Verfahren. Die ersten beiden Methoden lieferten an den untersuchten Pfählen nur in Einzelfällen verwertbare Ergebnisse. Die Parallel-Seismik-Methode lieferte auch im Blindversuch an Fundamenten, bei denen die Pfahllänge dem Eigentümer bekannt war, Ergebnisse mit einer Abweichung von max. 0,5 m. Diese Toleranz lässt sich bei der Standfestigkeitsbeurteilung berücksichtigen. Die Mehrkosten des Verfahrens (anders als bei den anderen Verfahren wird ein verrohrtes Bohrloch im Boden nahe dem Pfahl benötigt) halten sich in Grenzen, wenn man es in die geotechnische Untersuchung integriert. Daher wurde es inzwischen auch in der Praxis eingesetzt. Auch liegen die Gesamtkosten für die Untersuchung deutlich unter denen für eventuell notwendigen Ersatz – oder Verstärkungsmaßnahmen, die notwendig werden, wenn keine Daten zur Pfahllänge verfügbar sind.
Der Vortrag erläutert die Ergebnisse der Machbarkeitsstudie, zeigt erste Praxisfälle und weist auf Möglichkeiten hin, das Parallel-Seismik Verfahren in Zukunft noch genauer und effizienter einzusetzen.
Der Vortrag widmet sich dem „RITZ-TEST: EVALUIERUNG UND STAND DER NORMUNG“ und beschreibt die Komponenten, Ergebnis und Messgrößen, nicht registrierende Prüfgeräte, Evaluierung Ritz-Test (Makrobereich), den Atlas der Versagensformen, Geräte für den instrumentierten Ritz-Test und die Normung des Ritz-Tests (ASTM) zur Bewertung der Haftfestigkeit“ im Einzelnen.
The basics of broadband dielectric spectroscopy were introduced in detail. The analysis of the data was discussed. As application of broadband dielectric spectroscopy the alpha-relaxation (dynamic glass transition), the chain dynamics of polymers, and the behavior of a high performance polymer were illustrated.
Presentation on recent progress in ultrasinic testing and monitoring of concrete for massive structures. First, a new instrument (LAUS) for ultrasonic echo testing of thicknesses up to 5 m is shown. A new method to provide better images of the concrete interior, Reverse Mitem Migration (RTM)is presented. Second, the use of embedded ultrasonic transducers and data processing methods borrowed from seismology to detect subtle changes in concrete are documented.
Hexagonal beta-NaYF₄ doped with 20 % Yb and 2 % Er is an efficient upconversion (UC) phosphor for the conversion of 976 nm to 845 nm, 655 nm and 540 nm light. The emission behavior of this material is strongly influenced by the particle size, surface chemistry, and microenvironment. Especially the design of nm-sized UC particles for bioanalytical applications requires reliable spectroscopic tools for the characterization of the optical properties of these materials like the UC quantum yield (QYUC) in aqueous media. The UC emission originates from multiphotonic absorption processes, rendering the QYUC excitation power density (P) dependent. The P-dependent absolute measurement of QYUC in aqueous media with an excitation wavelength of 976 nm presents a considerable challenge due to the low absorption coefficients of the UC materials and the absorption of water at this wavelength.
Here, we present the P-dependent QYUC of 21 nm, 26 nm and 31 nm-sized NaYF₄ UC particles dispersed in cyclohexane and aqueous solutions, in view of bioanalytical applications. To gain a better insight of the photonic nature of the upconversion mechanism and the quenching processes involved, the luminescence decay behavior as well as the P-dependent red-to-green luminescence intensity ratios and slope factors of the different emission bands are studied in both solvents. These results present an important step to the rational design of brighter upconversion nanoparticles.
Der Vortrag widmet sich dem „Ringversuch zur Klassifizierung von Kohlenstoffschichten mittels Ellipsometrie“ und beschreibt die experimentellen Eckdaten, die Ellipsometrie als Messmethode am Beispiel DLC auf Stahl, Proben vs. n-k Ebene vs. Ergebnisse des Ringversuches, messtechnische Bewertung des Ringversuches und normative Bewertung des Ringversuches sowie Schlussfolgerungen.
Der Stand der Normung im Bereich der Oberflächentechnik wird zusammengefasst. Aktuelle Normungsvorhaben zur chemischen Oberflächenanalyse, Rastersondenmikroskopie, Nanotechnologie, Oberflächenmesstechnik im Mikro- und Nanobereich, für Anwendungen von Kohlenstoffschichten sowie von Mess- und Prüfverfahren für metallische und anorganische Überzüge werden vorgestellt. Ein Ringversuch zur Klassifizierung von Kohlenstoffschichten mittels Ellipsometrie wird diskutiert. Abschließend wird das DIN-Terminologie Portal erläutert.
Fast digital radiography was used to observe the crack development during single pass bead-on-plate gas tungsten arc welding with a minifocus X-ray source and a digital detector array with 75-micrometer pixel size. The sample material were 5 mm thick AlMgSi plates. An acquisition rate of 12 frames per second and an exposure time of 40 ms per frame were used for real-time observation of the hot crack propagation during welding. The basic spatial resolution of the images is about 80 µm. A 3D laminographic reconstruction of the acquired 2D radiographic images gives access to the volumetric extent of the cracks in the welded sample. The parallel use of a high-speed camera during welding allows the real-time inspection of surface cracks. The development of surface cracks was compared with the crack’s distribution in the sample volume and these results were correlated to the used welding parameters.
SETNanoMetro, a European Seventh Framework project, seeks to develop standard synthetic routes and metrological characterisation methods for the development and production of TiO₂ nanoparticles and nano-sized coatings with highly-defined, homogeneous and reproducible characteristics, including bulk structure, size, shape and surface structure. These materials are being tested for their potential in selected technological applications, including as coatings on bone-substituting prostheses. The objective of this study was to assess how variations in morphology and chemistry of nano-sized TiO₂ coatings affect their biocompatibility in vitro.
The physico-chemical characteristics of TiO2 coatings can greatly influence their final performance. In SETNanoMetro, different deposition procedures are being set for applying films of TiO2 NPs with defined and homogenous thickness on supports of interest for the applications studied in the project. The selected substrates are the following: (i) Silica glasses for photocatalytic measurements, (ii) Ti-alloys for orthopedic and/or dental prostheses, and for cell cultures, and (iii) Conductive glasses (e.g. Fluorine doped Tin Oxide, FTO) for dye-sensitized solar cells. From the different film deposition procedures studied within the project Self-assembly of TiO2 NPs in multiple layers was selected. For this, surface modification of the substrate and of TiO2 nanoparticles (NPs) with e.g. silane coupling agents is a prerequisite. First attempts to prepare the self-assembled coating on the functionalized glass substrates seem to indicate that the functionalized NPs adhere to the substrates, even if the final coatings were not homogenous and presented agglomerates. ToF-SIMS results support this outcome.
In order to use the layer-by-layer deposition technique for the formation of TiO2 films by controlled self-assembly of the TiO2 NPs, the proper complementary moieties for the functionalization of the NPs were chosen. A first set of NPs has been produced by reaction with (3-aminopropyl)phosphonic acid (APPA) in order to functionalize the surface with free amino-groups. Then, the complementary NP set can be obtained from an aliquot of the first one, through the conversion of free surface amino-groups to aldehydes by reaction with glutaraldehyde. A proper approach for the functionalization of two types of TiO2, commercial P25 (Evonik) and SETNanoMetro-sample labelled UT001, with APPA was developed. A second set of NPs consisting of three types of TiO2 NPs, P25 and SETNanoMetro NPs (TiO2 NPs with high specific surface area > 150 m2/g and TiO2 NPs with low size < 20 nm) was functionalized with (3-aminopropyl)triethoxysilane (APTS). As for the previous set of NPs, the complementary NP set was obtained through the conversion of free surface amino-groups to aldehydes by reaction with glutaraldehyde. EDX, AES and ToF-SIMS spectra were collected and analyzed to demonstrate the presence of the surface functionalization of the different types of TiO2 NPs.
Cold neutrons are predominantly scattered at hydrogen when penetrating hydrogen-charged samples, resulting in a high image contrast between hydrogen and e.g. iron. The used radiographic set-ups consist of a neutron source, state-of-the-art scintillator screens and digital cameras. This allows monitoring diffusive hydrogen fluxes two-dimensionally with 20s temporal resolution. Such hydrogen fluxes can be quantified by using standards with known hydrogen content and similar sample thickness.
Neutron tomography generates three-dimensional models of the hydrogen distribution in steel. Such models gain new insight for damage analysis by showing the hydrogen accumulations around cracks and by enabling the hydrogen gas pressure estimation inside cracks.
The capabilities and limitations, as well as perspectives of this method will be discussed and illustrated with help of selected examples.
Bright emitters with photoluminescence in the spectral region of 800 – 1600 nm are increasingly important as optical reporters for molecular imaging, sensing, and telecommunication and as active components in electrooptical and photovoltaic devices. Their rational design is directly linked to suitable methods for the characterization of their signal-relevant properties, especially their photoluminescence quantum yield. Aiming at the development of bright semiconductor nanocrystals with emission > 1000 nm, we designed a new NIR/IR integrating sphere setup for the wavelength region of 600 – 1600 nm. We assessed the performance of this setup by acquiring the corrected emission spectra and quantum yield of the organic dyes Itrybe, IR140, and IR26 and several infrared (IR)-emissive Cd1-xHgxTe and PbS semiconductor nanocrystals and comparing them to data obtained with two independently calibrated fluorescence instruments absolutely or relatively to previously evaluated reference dyes. Our results highlight special challenges of photoluminescence studies in the IR ranging from solvent absorption to the lack of spectral and intensity standards together with quantum dot-specific challenges like photobrightening and photodarkening and the size-dependent air stability and photostability of differently sized oleate-capped PbS colloids. These effects can be representative for lead chalcogenides. Moreover, we redetermined the quantum yield of IR26, the most frequently used IR reference dye, to 1.1×10-3 in 1,2-dichloroethane DCE with a thorough sample reabsorption and solvent absorption correction.
Mechanochemistry is increasingly used for synthesizing various materials including metal organic compounds and cocrystals. Although this synthesis approach offers a fast and pure synthesis in high yields, there is a lack in understanding the mechanisms of milling reactions. The necessary data can only be obtained in in situ experiments, which were only recently established for milling reactions. Herein, we present a novel setup enabling a combined in situ investigation of mechanochemical reactions using synchrotron XRD and Raman spectroscopy.
The specific combination allows to study milling processes comprehensively on the level of the molecular and crystalline structure and thus obtaining reliable data for mechanistic studies. Besides well-known MOFs like ZIF-8, the formation process of new metal phosphonates and model cocrystals could be studied in detail. The syntheses pathway of the different compounds could be revealed. The results prove that the presented method combination is applicable for a wide range of materials and will provide the necessary understanding to tune and optimize mechanochemically synthesized compounds.
Starting out from Flory`s most probable Distribution concept, correct and incorrect evaluations of SEC measurements are discussed. Using the correct mode, polyesters prepared by irreversible and reversible polycondensation methods were studied. Polyesters of α,ω−alkanediols and isophthalic acid or polyesters of diphenols and sebacic acid were prepared by three different irreversible polyconcensation methods. Formation of cyclic oligo and polyesters was monitored by MALDI-TOF mass spectrometry and dispersities were measured by SEC. The results are compared with the theories of Flory and Odian.
Eqilibrated polyesters were prepared by reversible polycondensation of ethyl 6-hydroxycaproate or by alcohol-initiated ring-opening polymerization of ε-caprolactone. Various catalysts were compared. The influence of dilution and of di- or multifunctional initiators was evaluated. Furthermore, equilibrated polylactides were prepared from L- or meso-lactide at 120, 160 and 180°C. A fast even-odd equilibration was discovered in addition to reversible cyclization and intermolecular transesterification. The influence of these different equilibration mechanisms on the dispersity was investigated. The preparative and theoretical consequences are discussed.
2PM FlySCAN: Innovative approach for wide field high resolution imaging of skin tissue volumes
(2016)
Two Photon Microscopy (2PM) is an innovative Technology for high resolution imaging of human skin in vivo and ex vivo. Up to now the method is limited by its interdependence between the field of view and the attainable resolution. The new FlySCAN Technology overcomes these boundaries and enable images sizes of many millimeters by resolutions in the submicrometer range revealing very specific information on clinically and biologically relevant tissue and cell structures. The advantages of the new approach are demonstrated by excellent in vivo and ex vivo tissue images.
Mechanische Eigenschaften von Materialien im Mikro- und Nanobereich werden heute mit der Instrumentierten Eindringprüfung bestimmt. Das Verfahren ist bereits umfangreich in der DIN EN ISO 14577 Teil 1-4 genormt. Im Ergebnis des EU EMRP Projekts Dynamic mechanical properties and long-term deformation behavior of viscous materials (MEPROVISC)“ wurden die zwei neuen Normprojekte für die Instrumentierte Eindringprüfung „Linear elastische dynamische Eindringprüfung“ und „Eindringkriechen und zeitabhängige Eigenschaften“ vorgeschlagen und mit deren Bearbeitung im ISO/TC 164/SC3 Hardness Testing begonnen.
Ausgehend von der Darstellung der wesentlichen Ergebnisse des Projekts MEPROVISC werden die Grundzüge der neuen Normen in Bezug auf Kalibrierung, Methodik, Auswertung und Bestimmung der Messunsicherheit erläutert. Weiterhin werden die Möglichkeiten der aktiven Mitarbeit an diesen Normprojekten aufgezeigt.
Purity statements of high purity materials serving as primary standards by GDMS.
Primary standards are materials known for their total purity and therefore appropriate to realise the link with the International System of Units (SI). The realisation and dissemination of primary standards is of fundamental importance for comparability of measurement results through traceability in all fields of chemical analysis.
To serve as a primary standard for element determination the total purity of a high purity material needs to be measured. In order to achieve a sufficiently small uncertainty (i.e. < 0.01%) this involves determining all possible impurity contributions and to subtract their sum from the ideal purity of 100%.
GD-MS has the potential to reduce the effort for purity determination, as a fast sensitive multi-element analysis without extensive sample preparation. Similar to other solid sampling techniques, glow discharge
requires calibration link the measured signal and the content of the impurities in the matrix.
The use of the concept Relative Sensitivity Factors (RSFs) provides good approximations especially for high purity materials. However, it only works with a wide uncertainty of the results.
The preparation of synthetic pressed powder samples by different modifications of liquid and powder doping used for the determination of both metallic and none-metallic impurities are described. Efficient determination of metallic impurities by GD-MS via differential and absolute measurements with a significantly reduced target uncertainty of 20 % for absolute measurements using liquid doped pressed powder calibration could be achieved. The determination of impurities has been evaluated by independent analytical methods such as HR-ICP-MS, ETAAS; CGHE and combustion analysis
The presentation will give an overview on non-destructive testing techniques being developed at the Federal Institute for Materials Research and Testing, Germany (BAM). This includes ultrasonic methods, ground penetration radar, Laser-Induced Breakdown Spectroscopy (LIBS), infrared thermography, pile testing, sensor technology and building scanner. A focus of the talk will be ultrasonic methods, which are well established in various aspects of concrete testing. They are used for imaging the interior geometry of constructions, estimation of concrete strength or monitoring lab investigations. However, so far the detection of distributed damages, especially in an early stage, has been almost impossible. The arrival of new technologies as embedded transducers and sensitive data processing techniques adopted from seismology has opened new field of work. Recent research has been focused to detect changes in concrete elements induced by stress, temperature, moisture or chemical attacks by permanent monitoring. Techniques as Coda Wave Interferometry can resolve changes in ultrasonic velocity in the order of 1*10-5. In addition, many researchers believe that the investigation of nonlinear effects can be used to characterize damages. The presentation will give a wrap up of ultrasonic techniques currently used in practice. This will include echo based methods as multi-channel/multi-offset imaging of structural elements using commercial and prototype devices. Imaging methods as SAFT and RTM will be shortly discussed. The focus will be on the emerging techniques used for monitoring. New types of sensors will be presented as well as the devices used in laboratory and field applications. Insight will be given on the various influence factors on ultrasonic signals and various ways of feature extraction and data processing. The results of lab experiments will be shown to demonstrate the detection of various kind of damages from mechanical load, ASR, corrosion to fatigue. The experiences with our first installations in real constructions (bridges, tunnel) will also be presented.
Under the assumption of local thermal equilibrium, a numerical algorithm is proposed to find the equation of state for laser-induced plasmas (LIPs) in which chemical reactions are permitted in addition to ionization processes. The Coulomb interaction in plasma is accounted for by the Debye–Hückel method. The algorithm is used to calculate the equation of state for LIPs containing carbon, silicon, calcium, chlorine, nitrogen, and argon. The equilibrium reaction constants are calculated using the latest experimental and ab initio data of spectroscopic constants for the molecules N2, C2, Si2, CN, Cl2, SiN, SiC, CaCl, CaCl2 and their positive and (if existed) negative ions. The algorithm is incorporated into a fluid dynamic numerical model based on the Navier–Stokes equations describing an expansion of LIP plumes into an ambient gas. The dynamics of LIP plumes obtained by the ablation of SiC, CaCl2, solid silicon, or solid carbon in an ambient gas containing N2 and Ar is simulated to study formation of molecules and molecular ions. A particular attention is paid to formation of anions Cl−, Cl2−, Si2−, C2−, CN−, and SiN− in LIPs.
Integrating fluorescent probes with sensing matrices presents a major challenge because usually, when confined in a rather rigid matrix, fluorophores tend to behave completely different than for instance in the molecular state in solution. The lecture reviews the major strategies that have been devised recently to circumvent such issues with special focus on the works carried out in this field by BAM’s Chemical and Optical Sensing Division. Moreover, it will be shown that by using certain strategies not only can the response behavior be retained but synergistic effects can even endow the hybrid with a much better performance than the probe molecule alone.
Macrocycle-containing fluorescent probes continue to be one of the most popular classes of indicator molecules for the sensitive optical detection of ionic inorganic analytes, in particular metal ions, since the first integration of crown ether building blocks into chromophoric π systems more than 30 years ago. However, whereas a large multitude of such probes have been described for operation in organic or mixed aqueous environments, the step to realistic analytical media such as water samples, aqueous food extracts or body fluids is still scarce. On one hand, this is due to considerably low complex stability constants for instance for alkali and alkaline-earth metal ions. On the other hand, many classes of organic dyes that show favourable spectroscopic properties and ion-induced responses in organic solvents are not soluble in neat aqueous media and/or exhibit only significantly quenched fluorescence, even if transition metal ions are binding strongly to the receptor unit. A way to circumvent such problems in a rather simple manner is the steric incorporation of fluorescent probes into mesoporous silica nanomaterials. The local polarity in such pores, whether nascent or modified appropriately with functional silanes, resembles much more a quasi-organic environment while at the same time allowing for free diffusion of water and its cargo.
Two examples of powerful hybrid signalling systems will be presented, utilizing charge transfer-type indicator molecules that show inferior sensing properties in their molecular state. One example discusses mercury(II) determination over an extended concentration range and the other discusses silver(I) and mercury(II) discrimination simply on the basis of photophysical effects retained in the hybrid materials.
Since more than 20 years, optical spectroscopic techniques, in particular fluorescence-based methods, are on the rise in many different areas of chemical and biochemical analysis, with no end being in sight.1,2 Advances in miniaturization and remote applications on one hand and ground-breaking developments in microscopy and laser-based high-throughput instrumentation on the other hand have fuelled these developments substantially.3,4 At the core of utmost of these applications however is not only the instrument, but a small entity that is able to absorb and emit photons and thus to report on the actual (bio)chemistry that is going on in a particular sample of interest.5,6 Besides intense research on various types of luminescent particles (e.g., quantum dots and carbon dots) and proteins, dye chemistry has thus seen its revival and the number of publications dealing with the design, synthesis and application of new fluorescent dyes as probes, stains, labels or indicators is still continuing to grow.
Among the various classes of dyes available as bright fluorophores for a wavelength range that is compatible with many (bio)analytical applications and the respective instrumentation, in particular pyrrolic dyes that do not belong to the classical porphyrins or phthalocyanines have received strong attention recently. Starting perhaps with the revival of the traditional boron-dipyrromethene laser dye ca. 15 years ago,7 these so-called BODIPYs have developed into a colourful spectrum of different derivatives.8 However, the interest in expanding the range of pyrrole-containing π-systems beyond BODIPYs has also constantly increased and has brought about several other pyrrole-based ring systems such as diketopyrrolopyrroles9 or dipyrrolonaphthyridinediones which possess a favourable brightness and other interesting properties. The present contribution will give a critical overview of the field, pinpointing advantages and prospects as well as discussing potential aspects of improvement with an emphasis on the chemical sensing and the longer wavelength range.
Multiplexed bead-based array formats play an increasingly important role in analytical laboratories. Due to the high surface-to-volume ratio, fast reaction kinetics and modular assay design, these sensor formats are applied in clinical diagnostic, drug development and classical biosensors with great success.
As the spherical platform, researchers utilize micron sized particles made from polymeric or silica material. Such beads are commercially available from vendors such as BD or Luminex. However, we have encountered several problematic issues which accompany these platforms: first, bigger sized beads, which are required for particle handling reasons, are difficult to prepare with high monodispersity - a key requirement for cytometric application. Second, plain beads, made from either polymer or silica, have each several disadvantages such as inferior scattering properties in case of silica or limited flexibility for coupling strategies in the case of latex beads.
In order to overcome this problem, we have developed a versatile core-shell (CS) platform which consists of a polymeric core with a structurally controlled silica shell. In our approach, the core building block can be easily prepared with high yields and high monodispersity in a dispersion polymerization from approximately 500 nm to 1.3 µm. Then, silica is coated in a classical sol-gel process to protect the core with a stable yet modifiable surface (see SEM image in Figure 1, platform). Here, we combine ideal scattering properties and easy preparation of the polymeric core with the chemical flexibility of a silica surface. Moreover, the additional shell domain adds density to the composite, which makes particle handling feasible also for nanometer sized beads.
In this contribution we present proof-of-principle results of competitive immunoassays with fluorescence detection using our CS beads – each performed in mix-and-read fashion without washing steps. All sizes are applicable in cytometric read-out which and can be used for size encoding (see Set 1 to 3 in Figure 1, size encoding). However, further multiplexing for a set of at least 20 parameters can be achieved by swelling hydrophobic dyes into the core. To the same time, precise tuning of the surface with mixed silane layers allowed us to improve the selectivity towards small molecules in competitive immunoassays significantly (see example in Figure 1, Application). We believe that our platform allows researchers to gain access to superior assay performance in combination with a low-threshold approach for the synthesis of the spherical platform.
Im Nachlass Adelbert Chamissos, der in der Staatsbibliothek zu Berlin aufbewahrt wird, finden sich einige Zeichnungen – Lineamente – deren Inhalt rätselhaft ist. So ist nicht klar, was diese Zeichnungen darstellen und in welchem Zusammenhang sie entstanden sind. Die wenigen Aufschriften lassen weder eine eindeutige Identifizierung noch Datierung zu. Erste naturwissenschaftliche Untersuchungen widmen sich der Entstehungsgeschichte dieser Zeichnungen, der verwendeten Materialien und dem Auffinden möglicher Referenzen, um die Objekte in das Werk Chamissos einzuordnen.
Wilson´s disease, a rare genetic disorder of the copper metabolism, causes the copper accumulation in various organs, leading to manifold hepatic, neurological and psychiatric symptoms. To study the elemental distribution, human Wilson´s disease liver samples were analyzed by means of LA-ICP-MS. Results demonstrated an inhomogeneous copper and iron distribution in human liver with hotspots of very high intensities. Both elements were quantified by an external calibration using matrix-matched standards made of gelatin, showing concentrations up to several thousand micrograms per gram. Additionally, results were validated by means of synchrotron radiation based μXRF at the BAMline at BESSYII (Helmholtz-Zentrum Berlin).
Core capability tables list the skills and experiences, which at least partially are needed to successfully carry out a specific analytical task within the IAWG. The required skills and experiences, so-called core capabilities (CC), are identified for each analytical procedure. The summarized CC tables are listed in the appendix of each report on the corresponding key comparison or pilot study. These CC tables enable us to demonstrate that we have the analytical procedure we claim under control by means of other Key Comparison, which do not exactly meet the claimed calibration and measurement capability. This is especially important for: a) fields where no Key Comparison is available, b) Revision of CMC claims or c) when a participation in a Key Comparison was not possible.
Applications of fibre reinforced plastic (FRP) composites in modern industries are increasing due to their considerable advantages such as light weight and excellent mechanical properties. Accordingly, importance of operational safety of modern structures made of advanced composites by ensuring the material quality has led to increasing demands for development of non-destructive evaluation (NDE) systems. In the context of a European project entitled “Validated Inspection Techniques for Composites in Energy Applications” (VITCEA), the aim is to develop and validate traceable procedures for novel NDE techniques with contrasting damage detection capabilities in energy related applications such as wind and marine turbine blades, nacelles, oil and gas flexible risers. Accordingly, VITCEA focuses on optimization of ultrasonic tests (UTs) for quantitative defect detection and quality characterization of FRP structures. In this context, the present study describes the ultrasound field in heterogeneous composite materials. The theoretical predictions are compared with simulation results obtained from CIVA a software package dedicated to NDT simulations based on the asymptotic ray theory.
Der Vortrag beschäftigt sich mit den materialwissenschaftlichen Aspekten des Buchdrucks. Hierbei geht es weniger um die Darstellung und Erklärung der unterschiedlichen Druckverfahren (Hochdruck, Tiefdruck, Flachdruck und Durchdruck), diese werden nur am Rande gestreift, um die Vielfalt der unterschiedlichen Drucktechniken darzulegen. Vielmehr beschäftigt sich der Vortrag mit den Materialien, d.h. Druckfarben, die sich dann tatsächlich auf dem Schriftträger analysieren lassen. Unterschiedliche Drucktechniken (und Effekte) erfordern unterschiedliche Materialzusammensetzungen - diese werden innerhalb des Vortrags diskutiert.
Electromagnetic waves with frequencies between 0.1 and 10 THz are described as THz-radiation (T-ray). The ability to penetrate dielectric materials makes T-rays attractive to reveal discontinuities in polymer and ceramic materials. THz-Time Domain Spectroscopy Systems (THz-TDS) are available on the market today which operates with THz-pulses transmitted and received by optically pumped semiconductor antennas. In THz-TDS the travelling time (ToF) and shape of the pulse is changed if it interacts with the dielectric material and its inherent disconti-nuities. A tomogram of the object under the test can be reconstructed from time of flight diffraction (ToFD) scans if a synthetic focusing aperture (SAFT) algorithm is applied. Otherwise, planar discontinuities like cracks in plastics or delaminated lay-ers in composites can be abstracted as layers located at any angle in relation to the outer sample surface direction. A tomogram from the scanned sample can then be reconstructed in case the interactions of electromagnetic pulses with the existing in-herent interfaces are detectable and a model is assumed which describes the device under the test as multilayer structure composed of thin layers with different dielec-tric properties.
A short description of both the SAFT – and Optical Layer algorithm for the recon-struction of the inherent structure is initially given. Measurements on representative samples with a variety of artificially produced small and large scale. Reconstructed tomograms are presented to discuss and evaluate the benefits and limits of the two different reconstruction approaches.
X-ray backscatter imaging is a well established NDT technique to inspect complex objects using only a single-sided access. In difference to conventional transmission X-ray radiography, the X-ray backscatter imaging utilizes the scattered radiation caused by the Compton scattering effect. In order to achieve high backscatter intensities from a test object, it is necessary to optimize the backscatter system parameters namely the angle between source and slit camera, the slit collimator system, the shielding between source and scatter camera, and the type of detector. In addition, the scatter phenomena in to the investigated object need to be understood.
In this contribution, we present a Monte Carlo model McRay which considers all relevant single and multiple interactions of photons and electrons. This model can be used to simulate back scatter techniques. It allows not only calculating the scatter image for a given experimental setup but also registering the spectrum of the detected scattered photons. Both aspects are important to understand the imaging process, to interpret the results, and to optimize the backscatter camera investigated here. Additionally experimental results will be presented and compared with simulations.
In this contribution, we discuss the influence of scattered radiation on materials’ effective attenuation coefficients at higher X-ray energies. The selected X-ray spectra for the dual-energy experiments correspond to 3 MV and 7.5 MV acceleration potential of the used betatron. Experiments were performed on a test phantom containing step wedges of different low- and high-Z materials. We evaluated the ratio between low- and high-energy X-ray attenuation coefficients quantitatively based on simulated poly-energetic high-energy X-ray source spectra and the detector sensitivity using the “analytical Radiographic Testing inspection simulation tool” (aRTist) developed at BAM. Furthermore, the influence of scattered radiation is evaluated using an efficient Monte-Carlo simulation. The simulation results are compared quantitatively with experimental investigations. Finally, important applications of the proposed technique in the context of aviation security are discussed.
Modelling becomes more and more important in modern NDE. It is increasingly used to optimize techniques for complex applications, to support the preparation of written procedures, and for education purposes. To describe the complete chain of RT, the model includes simulating all necessary properties of X- or Gamma-ray sources, the interaction of photons with material with special attention to scattered radiation, the detection process, and the complete geometrical RT setup handling arbitrary parts or constructions. Depending on the given inspection problem and the influencing factors that should be addressed by the simulation, an appropriate physical model has to be chosen to describe the underlying interaction mechanisms. The simulator aRTist combines analytical and Monte Carlo methods to efficiently model the radiation transport such that transmission as well as scatter techniques can be modelled. In this contribution we focus on Monte Carlo simulation of scatter contribution within aRTist. Examples for RT/tomographic applications and back-scatter techniques are presented to demonstrate the usability of the presented simulation tool for a broad range of radiological applications.
A model is presented that employs a unified approach for
simulating the photon energy spectra for transmission and direct
beam targets composed of arbitrary homogeneous materials. In order
to achieve this, a detailed model of electron transport within the
target is employed. The validity of the developed model is shown
through comparisons with Monte Carlo simulations as well as
measurements for a number of different configurations.
For the last 20 years active thermography has developed into a standard method in non-destructive material testing. It has become possible to detect defects such as cracks, voids, or even material inhomogeneities. Until now, it is still difficult to quantify subsurface or hidden defects in size due to the diffusive nature of heat flow within a solid. Facing this issue, lockin thermography and other photothermal techniques have been established. They are based on exciting a sample periodically (e.g. with a halogen lamp), causing a controlled periodical heat flow and thereby representing strongly damped thermal waves. These techniques make use of interference and reflection of thermal waves which allow enhancing depth resolution.
So far, only the temporal component of the light source was modified to achieve a defined vertical heat flow – In contrast, we propose a novel technique in which we are able to control both: time and space. This technique enables us to exploit the possibilities of coherent thermal wave shaping. We achieve that by combining a spatial light modulator (SLM) with a high power laser. This approach allows us to launch a set of individually controlled and fully coherent high energy thermal waves into the sample volume. That means, we intentionally use wave propagation throughout the sample’s material in both - vertical and lateral direction.
As one possible application, we use a thermal waves’ interference effect of two phase shifted wave patterns to detect the position of hidden defects. The wave patterns are positioned with a certain distance and a 180° phase shift to each other creating an amplitude depletion zone right in the middle of the two patterns. When a defect is brought unsymmetrically into the depletion zone, the lateral heat flow is disturbed. If the sample is now moved through the depletion zone, a defect can be easily characterized. Exciting periodically while controlling simultaneously phase and amplitude enables us to have a defined thermal wave propagation throughout the sample which means thermal waves can be controlled almost like acoustical or optical waves. This offers the opportunity to transfer known technologies from wave shaping techniques to thermography methods.
Der Vortrag widmet sich Haftung und Haftfestigkeit bezüglich Grundlagen, Einflussgrößen sowie Prüfverfahren und beschreibt die Punkte: Generische und spezifische Motivation, Einflussgrößen auf Haftfestigkeit und Haftung von Beschichtungen, Prüfverfahren zur quantitativen Bestimmung der Haftfestigkeit und zur qualitativen Klassifizierung bzw. semi-quantitativen Bewertung der Haftung im Einzelnen.
Production of inorganic RM
(2016)
Beschrieben wird anhand von Beispielen die Vorgehensweise der BAM bei der Zertifizierung von Referenzmaterialien
Durch den Einsatz von eingebetteten faseroptischen Sensoren können Bauteile überwacht und frühzeitig Informationen über Materialveränderungen gewonnen werden. Um die Zuverlässigkeit eines solchen Sensors gewährleisten zu können, ist es wichtig, die korrekte Funktion des Sensors im Verbund mit einer Werkstoff-Matrix on-line und in-situ überwachen zu können. Im Rahmen des DFG-Projekts FAMOS² (FAser-basierter Magneto-Optischer SchichtSensor) wurde ein selbstdiagnose-fähiger Schichtsensor entwickelt, welcher mit Hilfe einer magnetostriktiven Aktorschicht validiert werden kann. Durch eine Kombination aus PVD (physical vapour deposition) und ECD (electro-chemical deposition) wird die Aktorschicht auf faseroptischen Sensoren haftfest abgeschieden. Ein äußeres Magnetfeldes dehnt die Aktorschicht und damit auch die Faser reversibel. Diese Dehnung führt zu einer Verschiebung der Bragg-Wellenlänge, welche direkt mit der Stärke des zu messenden Magnetfeldes korreliert. Ein etwa 100 Nanometer dünnes PVD-Schichtsystem aus Chrom und Kupfer dient zunächst als Haftvermittler zwischen Glasfaser und ECD-Schicht. Um eine rotationssymmetrische Schichtabscheidung zu erhalten, erfolgt während der PVD-Beschichtung eine Rotation der Faser. In einem klassischen Watts-Elektrolyten wird dann im zweiten Schritt die eigentliche etwa 30 Mikrometer dicke ECD-Aktorschicht auf die PVD-Schicht abgeschieden. Reine Ni-Schichten werden mit NiFe-Legierungen verglichen.
Die Geometrie der Faser stellt für die Herstellung und Charakterisierung der Schichten auf der einen Seite eine besondere Herausforderung dar, bietet aber zugleich auch neue experimentelle Möglichkeiten. So kann ggf. die Entstehung von Spannungen in der Schicht während der ECD-Abscheidung in-situ verfolgt werden, indem die Wellenlängenverschiebung aufgrund der Dehnung des Bragg-Gitters optisch gemessen wird. Die Anpassung der Beschichtungsverfahren an die Fasergeometrie sowie die Charakterisierung und die Eigenschaften der ECD-Schicht werden diskutiert. Insbesondere wird auf den Elastizitätsmodul der Aktorschicht eingegangen, wobei Werte aus der Nanoindentation und dem 2-Punkt-Biegeversuch mit der beschichteten Faser als Biegebalken verglichen werden.
Within the scope of a DIN INS project, a flash thermography round robin test that evaluates reliability, comparability, and efficiency of different testing situations was organized. The results give information about the detectability of defects, e.g. depending on their size and depth, the evaluation methods and the materials used. Besides, the influences of equipment and parameters used by the participants on the results were analysed. All of the quantitative results as well as the feedback given by the participants will be presented in a DIN committee in order to contribute to a flash thermography standard.
The duraBASt area at the highway intersection “Köln-Ost” is a large test field for road testing. It includes the duraBASt test bridge which is ca. 66 m long and 14.25m broad. This bridge is part of the “road in the 21st century” project and is equipped with several sensors for structural health monitoring. This feasibility study is realised to construct intelligent bridges in the future. Quantities like temperature, strain, moisture, corrosion, etc. are measured by embedded sensors. In the presented work, the focus lays on passive RFID-based sensors. The communication and energy supply is realised by a mobile transmitter through the concrete cover. Hence, no cables or batteries are required. The sensors are design to withstand in the alkaline environment in concrete. Thus, moisture and corrosion are detectable for several decades.