Analytische Chemie
Filtern
Erscheinungsjahr
- 2022 (615) (entfernen)
Dokumenttyp
- Vortrag (217)
- Zeitschriftenartikel (191)
- Posterpräsentation (89)
- Beitrag zu einem Tagungsband (59)
- Forschungsbericht (17)
- Sonstiges (15)
- Forschungsdatensatz (10)
- Buchkapitel (7)
- Dissertation (2)
- Handbuch (2)
Sprache
- Englisch (529)
- Deutsch (85)
- Mehrsprachig (1)
Schlagworte
- Fluorescence (24)
- Digitalization (22)
- Certification (20)
- Conformity assessment (20)
- COVID-19 (19)
- Digital transformation (19)
- Sensor (19)
- Calibration (18)
- Conformity assessment body (18)
- Quality infrastructure (18)
Organisationseinheit der BAM
- 8 Zerstörungsfreie Prüfung (235)
- 1 Analytische Chemie; Referenzmaterialien (215)
- 6 Materialchemie (111)
- 8.2 Zerstörungsfreie Prüfmethoden für das Bauwesen (54)
- 8.4 Akustische und elektromagnetische Verfahren (53)
- 8.0 Abteilungsleitung und andere (52)
- 1.1 Anorganische Spurenanalytik (44)
- 8.5 Röntgenbildgebung (44)
- 6.1 Oberflächen- und Dünnschichtanalyse (42)
- 1.2 Biophotonik (40)
- 6.3 Strukturanalytik (40)
- 1.8 Umweltanalytik (35)
- S Qualitätsinfrastruktur (32)
- 8.1 Sensorik, mess- und prüftechnische Verfahren (31)
- S.2 Digitalisierung der Qualitätsinfrastruktur (30)
- 1.3 Instrumentelle Analytik (28)
- 4 Material und Umwelt (27)
- 1.4 Prozessanalytik (26)
- 1.9 Chemische und optische Sensorik (21)
- 8.6 Faseroptische Sensorik (20)
- 1.7 Organische Spuren- und Lebensmittelanalytik (19)
- 6.6 Physik und chemische Analytik der Polymere (19)
- 1.5 Proteinanalytik (18)
- 1.6 Anorganische Referenzmaterialien (16)
- VP Vizepräsident (16)
- VP.1 eScience (16)
- 6.5 Synthese und Streuverfahren nanostrukturierter Materialien (15)
- 6.0 Abteilungsleitung und andere (14)
- 4.3 Schadstofftransfer und Umwelttechnologien (10)
- 4.2 Material-Mikrobiom Wechselwirkungen (9)
- 7 Bauwerkssicherheit (9)
- 9 Komponentensicherheit (9)
- 3 Gefahrgutumschließungen; Energiespeicher (7)
- 4.5 Kunst- und Kulturgutanalyse (6)
- 5 Werkstofftechnik (5)
- 3.1 Sicherheit von Gefahrgutverpackungen und Batterien (4)
- 9.0 Abteilungsleitung und andere (4)
- 5.1 Mikrostruktur Design und Degradation (3)
- 6.2 Material- und Oberflächentechnologien (3)
- 7.4 Baustofftechnologie (3)
- 7.6 Korrosion und Korrosionsschutz (3)
- 9.5 Tribologie und Verschleißschutz (3)
- 1.0 Abteilungsleitung und andere (2)
- 2 Prozess- und Anlagensicherheit (2)
- 3.5 Sicherheit von Gasspeichern (2)
- 4.1 Biologische Materialschädigung und Referenzorganismen (2)
- 4.4 Thermochemische Reststoffbehandlung und Wertstoffrückgewinnung (2)
- 5.4 Multimateriale Fertigungsprozesse (2)
- 9.4 Integrität von Schweißverbindungen (2)
- P Präsident (2)
- P.0 Präsident und andere (2)
- S.1 Qualität im Prüfwesen (2)
- 2.1 Sicherheit von Energieträgern (1)
- 2.5 Konformitätsbewertung Explosivstoffe/Pyrotechnik (1)
- 3.2 Gefahrguttanks und Unfallmechanik (1)
- 5.2 Metallische Hochtemperaturwerkstoffe (1)
- 6.7 Materialsynthese und Design (1)
- 7.1 Baustoffe (1)
- 7.3 Brandingenieurwesen (1)
- 7.5 Technische Eigenschaften von Polymerwerkstoffen (1)
- 7.7 Modellierung und Simulation (1)
- 9.2 Versuchsanlagen und Prüftechnik (1)
- 9.6 Additive Fertigung metallischer Komponenten (1)
- VP.2 Informationstechnik (1)
Paper des Monats
- ja (5)
Seit Jahren stellt die luftgekoppelte Ultraschallprüfung eine etablierte Alternative zur konventionellen Prüfung von Leichtbaukomponenten aus den Bereichen Luft- und Raumfahrt sowie Automotive dar. Im Gegenteil zur flüssigkeitsgekoppelten Prüfung in Kontakt oder im Tauchbecken ist sie weniger invasiv und bietet daher zeitliche und finanzielle Anreize.
Normalerweise wird die luftgekoppelte Prüfung mit Einzelelementschwingern in Durchschallung realisiert, wohingegen die Gruppenstrahlertechnik bereits Industriestandard im Bereich der Kontakttechnik darstellt. Die damit verbundenen Vorteile wie die aktive Fokussierung oder, die gezielte Manipulation des Einschallwinkels zur Anregung von geführten Wellen, finden im Bereich der luftgekoppelten Prüfung dabei noch wenig Anwendung.
Im Rahmen dieses Beitrags stellen wir die ersten Zwischenergebnisse des geförderten Projektes „PALUP – Phased- Array-Technik für Luftultraschall-Prüfungen“ vor. Ziel des Projektes ist die Entwicklung von Mehrelementschwingern auf Basis von zellulären Kunststoffen, die Entwicklung einer dedizierten Pulserstufe im Kilovoltbereich, sowie die nötige rauscharme messtechnische Auswertung jedes Einzelelements.
We demonstrate here using a disulfide system the first example of reversible, selective, and quantitative transformation between three crystalline polymorphs by ball mill grinding. This includes the discovery of a previously unknown polymorph. Each polymorph is reproducibly obtained under well-defined neat or liquid-assisted grinding conditions, revealing subtle control over the apparent thermodynamic stability. We discovered that the presence of a contaminant as low as 1.5% mol mol−1 acting as a template is required to enable all these three polymorph transformations. The relative stabilities of the polymorphs are determined by the sizes of the nanocrystals produced under different conditions and by surface interactions with small amounts of added solvent. For the first time, we show evidence that each of the three polymorphs is obtained with a unique and reproducible crystalline size. This mechanochemical approach gives access to bulk quantities of metastable polymorphs that are inaccessible through recrystallisation.
The fabrication of laser-generated surface structures on titanium and titanium alloys has recently gained remarkable interests, being technologically relevant for applications in optics, medicine, fluid transport, tribology, and wetting of surfaces. The morphology of these structures, and so their chemistry, is influenced by the different laser processing parameters such as the laser fluence, wavelength, pulse repetition rate, the effective number of laser pulses per beam spot area, etc. A simple way to characterize laser-generated surface structures is by means of optical microscopy (OM) or white light interference microscopy (WLIM). The latter can address the surface topography, while having a lateral resolution limit of ~(lambda)/2 (lambda = illumination wavelength). To resolve morphologies with spatial periods significantly smaller than (lambda)/2, scanning electron microscopy (SEM) is often used, taking benefit of the reduced de Broglie wavelength associated to the electrons of several keV energy. However, all the above-mentioned techniques lack the necessary depth-resolution to reveal and quantify sub-surface material modifications of these laser-generated structures. Time-of-Flight secondary ion mass spectrometry (ToF-SIMS) represents a promising surface analytical technique for studying laser-induced chemical surface alterations since the method combines a high surface sensitivity with the capability to perform a depth-profiling of the laser-affected surface zone. In this study we combine WLIM and high-resolution SEM with ToF-SIMS to fully characterize the evolution of various types of laser-generated micro- and nanostructures formed on Ti-6Al-4V alloys upon irradiation by near infrared ultrashort laser pulses (1030 nm, 925 fs) at different laser fluence levels, effective number of pulses, and at different pulse repetition rates (1 – 400 kHz). We show how this combined surface analytical approach allows to evaluate alterations in the surface chemistry and topography of the laser-generated surface structures depending on the laser processing parameters
Im Rahmen des EMPIR-Projektes NanoXSpot (Nanometre X-Ray Focal Spot Measurement) werden rückführbare Messverfahren zur Bestimmung der Brennfleckgröße und -form von Röntgenröhren mit Submikrometerauflösung (100 nm – 20 µm) entwickelt, die die Grundlage für die Erarbeitung eines Standardentwurfes bilden. Der Standardentwurf wird bei CEN TC 138 (Non-destructive testing) WG 1 (Radiographic testing) eingereicht und mit ISO und ASTM harmonisiert. Zur Untersuchung der entwickelten Methoden (Brennfleck-CT, Fit-Prozedur für Strichgruppenkörper) und des im Projekt NanoXSpot neu entworfenen Testkörpers, NxS, wurde ein Ringversuch durchgeführt. Dabei wurde sowohl der angestrebte Überlappungsbereich mit EN 12543 Teil 5 (Messung der effektiven Brennfleckgröße von Mini- und Mikrofokus-Röntgenröhren) und ASTM E 2903 (Standard Test Method for Measurement of the Effective Focal Spot Size of Mini and Micro Focus X-ray Tubes) für Brennflecke >5 µm als auch Brennflecke <5 µm untersucht. Im Mittelpunkt standen dabei Stabilität und Wiederholbarkeit der entwickelten Methoden zur Bestimmung der Brennfleckgröße. In diesem Beitrag werden die Ergebnisse des durchgeführten Ringversuches vorgestellt und diskutiert, um Schlussfolgerungen und Empfehlungen für die Vorbereitung eines erweiterten Ringversuchs mit Partnern und Stakeholdern abzuleiten.
Even though we often do not knowingly recognize them, nanoparticles are present these days in most areas of our daily life, including food and its packaging, medicine, pharmaceuticals, cosmetics, pigments as well as electronic products, such as computer screens. The majority of these particles exhibits a core-shell morphology either intendedly or unintendedly. For the purpose of practicability, this core-shell nanoparticle (CSNP) morphology is often assumed to be ideal, namely a spherical core fully encapsulated by a shell of homogeneous thickness with a sharp interface between core and shell material. It is furthermore widely presumed that all nanoparticles in the sample possess the same shell thickness. As a matter of fact, most real CSNPs deviate in several ways from this ideal model with quite often severe impact on how efficiently they perform in a specific application.
The topic of this cumulative PhD thesis is the accurate characterization of the actual morphology of CSNPs by advanced X-ray analytical techniques, namely X-ray photoelectron spectroscopy (XPS) and scanning transmission X-ray microscopy (STXM). A special focus is on CSNPs which deviate from an ideal core-shell morphology. In the paper from 2019 nanoparticle shell thicknesses are extracted from the elastic-peak intensities in an XPS spectrum based on an ideal particle morphology. This happens for a series of CSNP samples comprising a poly(tetrafluoroethylene) (PTFE) core and either a poly(methyl methacrylate) (PMMA) or polystyrene (PS) shell. The same paper as well as the paper from 2020 demonstrate for the first time, that the analysis of the inelastic background in an XPS spectrum of CSNPs can identify and quantify the heterogeneity of the shell and the incomplete encapsulation of the core.
The result from an XPS experiment is always an average across a large nanoparticle ensemble. Deviations from an ideal morphology within a single particle of the sample cannot be assessed separately. As opposed to that, a spatial resolution of 35 nm enables STXM to visualize the interior of single CSNPs which exhibit a sufficient X-ray absorption contrast between core and shell material. In the paper from 2018 a STXM analysis is demonstrated based on the example of the PTFE-PS CSNP samples already mentioned in the previous paragraph.
In the publication from 2021 (Ca/Sr)F₂ core-shell like nanoparticle ensembles for the practical use in, among others, antireflective coatings are investigated. These nanoparticles do not possess a sharp interface between core and shell material, which is why a shell thickness determination as described in the second paragraph is inappropriate. Instead, in-depth profiles of the chemical composition are obtained by XPS experiments based on synchrotron radiation with variable X-ray photon energy to elucidate the internal morphology of the particles. Additionally, theoretical in-depth profiles of Ca and Sr XPS peak intensities are simulated, in order to facilitate the interpretation of the experiments. Thus, an enrichment of CaF₂ at the particle surface was determined, which could hardly have been assessed by any other analytical technique. Because this kind of non-destructive depth profiling by XPS is very demanding, more than usual effort is spent on gapless documentation of the experiments to ensure full reproducibility.
Due to the vast diversity of nanoparticles differing in material, composition and shape, a measurement procedure cannot unalteredly be transferred from one sample to another. Nevertheless, because the papers in this thesis present a greater depth of reporting on the experiments than comparable publications, they constitute an important guidance for other scientists on how to obtain meaningful information about CSNPs from surface analysis.
Here, we present a study on agarose thin-film samples that represent a model system for the exopolysaccharide matrix of biofilms. Povidone-iodide (PVP-I) was selected as an antibacterial agent to evaluate our x-ray photoelectron spectroscopy (XPS)-based methodology to trace specific marker elements, here iodine, commonly found in organic matrices of antibiotics. The in-depth distribution of iodine was determined by XPS analyses with variable excitation energies and in combination with argon gas cluster ion beam sputter cycles. On mixed agarose/PVP-I nanometer-thin films, both methods were found to solve the analytical task and deliver independently comparable results. In the mixed agarose/PVP-I thin film, we found the outermost surface layer depleted in iodine, whereas the iodine is homogeneously distributed in the depth region between this outermost surface layer and the interface between the thin film and the substrate. Depletion of iodine from the uppermost surface in the thin-film samples is assumed to be caused by ultrahigh vacuum exposure resulting in a loss of molecular iodine (I2) as reported earlier for other iodine-doped polymers.
A large and increasing number of scientific domains pushes for high neutron imaging resolution achieved in reasonable times. Here we present the principle, design and performance of a detector based on infinity corrected optics combined with a crystalline Gd3Ga5O12 : Eu scintillator, which provides an isotropic sub-4 μm true resolution. The exposure times are only of a few minutes per image. This is made possible also by the uniquely intense cold neutron flux available at the imaging beamline NeXT-Grenoble. These comparatively rapid acquisitions are compatible with multiple high quality tomographic acquisitions, opening new venues for in-operando testing, as briefly exemplified here.
Morpho-Chemical Characterisation of Me-TiO2 Nanoparticles for Enhanced Photocatalytical Activity
(2022)
The conversion of solar energy into electricity and solar fuels is of crucial importance for a green and sustainable future. Water splitting using semiconductor photo-catalysts is considered a sustainable method to produce clean hydrogen (H2) fuel. Nevertheless, H2 photo-production efficiency remains still low, although extensive research works to understand better the mechanisms of the Hydrogen Evolution Reaction (HER) and the Oxygen Evolution Reaction (OER) are being carried out. In this respect, TiO2 is a key photoactive material, usually employed with a co-catalyst deposited onto the surface to enhance charge carriers’ separation and catalyze surface charge transfer reactions. The deposition of a co-catalyst on the TiO2 nanoparticle surface represents one successful way to enhance the activity of the photocatalyst through a modification of its surface and redox properties. In this context, high-resolution scanning electron microscopy coupled with elemental analysis by energy-dispersive X-ray spectroscopy (EDS) is fundamental for studying and understanding the effect of the nanoparticle morphology on the functional properties of shape-controlled TiO2 crystals (bipyramides, platelets, and elongated particles). Different types of metal-semiconductor combinations, TiO2 shapes and dopant metals (Ag, Pt, etc) and metal concentrations will be discussed.
microscopy (AFM), or X-ray reflectometry. For the additional determination of thin film composition, techniques like X-ray photoelectron spectroscopy (XPS) or mass spectrometry-based techniques can be used. An alternative non-destructive technique is electron probe microanalysis (EPMA). This method assumes a sample of homogenous (bulk) chemical composition, so that it cannot be usually applied to thin film samples. However, in combination with the thin film software StrataGEM, the thickness as well as the composition of such films on a substrate can be determined.
This has been demonstrated for FeNi on Si and SiGe on Al2O3 film systems. For both systems five samples with different elemental composition and a reference were produced and characterised by Korean research institute KRISS using inductively coupled plasma mass spectrometry (ICP-MS), Rutherford backscattering (RBS), and transmission electron microscopy (TEM). These samples were used for an international round robin test.
In 2021, a new and open-source thin film evaluation programme called BadgerFilm has been released. It can also be used to determine thin film composition and thickness from intensity ratios of the unknown sample and standards (k-ratios).
In this contribution, we re-evaluated the data acquired for the FeNi and SiGe systems using the BadgerFilm software package and compared the resulting composition and thickness with the results of the established StrataGEM software and other reference methods. With the current evaluation, the BadgerFilm software shows good agreement with the composition and thickness calculated by StrataGEM and as the reference values provided by the KRISS.