Filtern
Erscheinungsjahr
Dokumenttyp
- Zeitschriftenartikel (62)
- Beitrag zu einem Tagungsband (30)
- Beitrag zu einem Sammelband (19)
- Forschungsbericht (3)
- Buchkapitel (1)
- Vortrag (1)
- Sonstiges (1)
- Posterpräsentation (1)
Schlagworte
- Corrosion (6)
- Corrosion testing (6)
- Deckschichtbildung (6)
- KorroPad (6)
- Korrosionsprüfung (6)
- Zinc coatings (6)
- Broadband dielectric spectroscopy (5)
- Gel-type electrolytes (5)
- Gelartige Elektrolyte (5)
- Molecular mobility (5)
- Nanocomposites (5)
- Zinkdeckschichten (5)
- Fehlstellen (4)
- Layer formation (4)
- Minderdicken (4)
- Polymers of intrinsic microporosity (4)
- ZfP an Holzbauteilen (4)
- Bauwesen (3)
- Fäulnis (3)
- Gas permeation (3)
- Holz (3)
- Korrosion (3)
- Martensitic stainless steel (3)
- Neutron scattering (3)
- Nichtrostender Stahl (3)
- PIM-1 (3)
- Pitting corrosion (3)
- Polyhedral oligomeric silsesquioxane (POSS) (3)
- Polymer-based nanocomposites (3)
- SAXS (3)
- Stainless steel (3)
- Ultraschall-Echo (3)
- Ultraschallecho (3)
- Ultraschallecho-Experimente an Probekörpern (3)
- Zerstörungsfreie Prüfung (3)
- Advanced calorimetry (2)
- Aluminium (2)
- Atmosphärische Korrosion (2)
- Boson peak (2)
- Dielectric properties (2)
- Dielectric spectroscopy (2)
- Electrical conductivity (2)
- Electrochemical potentiodynamic reactivation (2)
- Gas separation (2)
- Gas separation membranes (2)
- Grinding (2)
- Heat treatment (2)
- Korrosionsschutz (2)
- Maritime Atmosphäre (2)
- Maritime atmosphere (2)
- Nanoparticle (2)
- Nanoparticles (2)
- Neutron Scattering (2)
- POSS (2)
- Polycarbonates (2)
- Polymer of intrinsic microporosity (2)
- Polymers of Intrinsic Microporosity (2)
- Polymers with intrinsic microporosity (2)
- Polynorbornenes (2)
- Quality control (2)
- Qualitätskontrolle (2)
- Quasielastic neutron scattering (2)
- Radar (2)
- Relaxation (2)
- Salinization (2)
- Threshold (2)
- Versalzung (2)
- XANES (2)
- Zink (2)
- Abbildungsverfahren (1)
- Ablation (1)
- Abrasive belt (1)
- Absorption spectrometry (1)
- Agar (1)
- Amonium polyphosphate (1)
- Anion exchange (1)
- Artificial defect (1)
- Atmospheric corrosion (1)
- Atmospheric exposure (1)
- Austenitic Stainless Steel (1)
- Austenitic stainless steel (1)
- BDS broadband dielectric spectroscopy (1)
- Beta-relaxation (1)
- Beton (1)
- Bewehrung (1)
- Bildgebende Darstellung (1)
- Broadband Dielectric Spectroscopy (1)
- Broadband Dielectric Spectrscopy (1)
- Brücke (1)
- CHOCLAB (1)
- Calcium monofluoride (1)
- Carbon dioxide (1)
- Cathodic protection (1)
- Cavitation (1)
- Color X-ray camera (1)
- Combustibility of liquids (1)
- Compaction faults (1)
- Compound refractive lens (1)
- Corrosion resistance (1)
- Corrosivity category (1)
- Covalent Organic frameworks (1)
- Crystal Texture (1)
- Cutlery (1)
- DL-EPR (1)
- Damage (1)
- Deckschichten (1)
- Dielectric measurements (1)
- Dielectric relaxation spectroscopy (1)
- Diesel Fuel (1)
- Diffusion (1)
- Digitale Radiographie (1)
- Distribution of nanoparticles (1)
- Drop Evaporation Test (1)
- Dust explosions (1)
- EDM (1)
- EPR-Test (1)
- Electric discharge machining (1)
- Electrochemical noise (1)
- Exothermic and pressure-inducing chemical reactions (1)
- Expandable graphite (1)
- Explosive condensed substances (1)
- FT-IR (1)
- Fast Scanning Calorimetry (1)
- Fast scanning calormetry (1)
- Femtosecond (1)
- Femtosecond laser ablation (1)
- Femtosekunden (1)
- Filled rubbers (1)
- Filled thermosets and plastics (1)
- Firework display (1)
- Flammable gases and vapors (1)
- GMR (1)
- GMR-Sensor (1)
- Gas separation membrane (1)
- Gel electrolytes (1)
- Gelartige Elektolyte (1)
- Glass (1)
- Gold nanoparticles (1)
- Graphite furnace (1)
- Growth mechanism (1)
- HR-CS-MAS (1)
- Hagen (1)
- Hard coatings (1)
- Harmful effects of substances (1)
- Highly permeably polynorbornenes (1)
- Hot Cracking (1)
- ISO 11254-2 (1)
- ISO 9223 (1)
- Impact-echo (1)
- Impakt-Echo (1)
- Inelastic neutron scattering (1)
- Interfacial polarisation (1)
- Internal Surfaces (1)
- Korrosionsbeständigkeit (1)
- Korrosionsschnelltest (1)
- Korrosionsuntersuchungen (1)
- Kurzpulslaser (1)
- Laser (1)
- Laser Welding (1)
- Laser safety (1)
- Lasersicherheit (1)
- Lasertechnik (1)
- Liquid chromatography (1)
- Low-frequency impedance spectroscopy (1)
- Luftultraschall (1)
- Magnetic flux leakage (1)
- Mass loss (1)
- Materialbearbeitung (1)
- Materials processing (1)
- Matrimid (1)
- Membrane (1)
- Membrane polymers (1)
- Metallic coatings (1)
- Methane removal (1)
- Methane total oxidation (1)
- Methyl group rotation (1)
- Microporous polymers (1)
- Mobiles Röntgen (1)
- Multiple-pulse damage (1)
- NDT (1)
- NDT of Wood (1)
- Nano structure (1)
- Nanocomposite (1)
- Nanodielectrics (1)
- Nanoparticle formation (1)
- Ni-Base Alloy (1)
- Nondestructive (1)
- Normung (1)
- Oberfläche (1)
- Oberflächenbehandlung (1)
- Ochratoxin A (1)
- PE-HD Sorption (1)
- Particles (1)
- Passivität (1)
- Permeation (1)
- Physical ageing (1)
- Physical aging (1)
- Polarisation (1)
- Polycapillary optic (1)
- Polyhedral oligomeric silsesquioxanes (1)
- Polymer (1)
- Polymer clay nanocomposites (1)
- Polymer of intrisic microporosity (1)
- Polymerbasierte Nanokomposite (1)
- Polymers (1)
- Polynorbornes (1)
- Polystyrene (1)
- Prüfmethoden (1)
- Rapid corrosion test (1)
- Reaction products (1)
- Reconstruction (1)
- Reference defect (1)
- Round-robin experiment (1)
- S on 1-LIDT (1)
- SAFT (1)
- SIP (1)
- Scannende Systeme (1)
- Schleifen (1)
- Schneidwaren (1)
- Separation membranes (1)
- Silicon impurities (1)
- Small-angle X-ray scattering (1)
- Solar cell (1)
- Solid-phase extraction (1)
- Sound pressure (1)
- Spannglied (1)
- Spectral induced polarization (1)
- Spektroskopie (1)
- Stress corrosion Cracking (1)
- Streuflussprüfung (1)
- Surface (1)
- Surface treatment (1)
- Synchrotron radiation (1)
- Synergy (1)
- Synthetic aperture focusing technique (SAFT) (1)
- Tandem mass spectrometry (1)
- Testing methods (1)
- Textile (1)
- Thermoplastic elastomers (1)
- TiMgN (1)
- Ultraschallecho-Verfahren (1)
- Ultrasonic echo (1)
- Verfleckungen (1)
- WAXS (1)
- Wine (1)
- X-ray fluorescence (1)
- X-ray micro beam (1)
- X-ray photoelectron spectroscopy (1)
- X-ray refraction (1)
- Xerogel (1)
- ZfP (1)
- Zirconium (1)
- corrosion invetsigations (1)
- gel-type electrolytes (1)
- pnCCD (1)
- zinc coatings (1)
- Überzüge (1)
Organisationseinheit der BAM
- 7 Bauwerkssicherheit (30)
- 6 Materialchemie (21)
- 6.6 Physik und chemische Analytik der Polymere (18)
- 7.5 Technische Eigenschaften von Polymerwerkstoffen (18)
- 7.6 Korrosion und Korrosionsschutz (12)
- 6.5 Synthese und Streuverfahren nanostrukturierter Materialien (6)
- 6.1 Oberflächen- und Dünnschichtanalyse (3)
- 1 Analytische Chemie; Referenzmaterialien (1)
- 1.1 Anorganische Spurenanalytik (1)
- 1.4 Prozessanalytik (1)
Eingeladener Vortrag
- nein (1)
Polymers of intrinsic microporosity exhibit a combination of high gas permeability and reasonable permselectivity, which makes them attractive candidates for gas separation membrane materials. The diffusional selective gas transport properties are connected to the molecular mobility of these polymers in the condensed state. Incoherent quasielastic neutron scattering was carried out on two polymers of intrinsic microporosity, PIM-EA-TB(CH3) and its demethylated counterpart PIM-EA-TB(H2), which have high Brunauer–Emmett–Teller surface area values of 1030 m2 g-1 and 836 m2 g-1, respectively. As these two polymers only differ in the presence of two methyl groups at the ethanoanthracene unit, the effect of methyl group rotation can be investigated solely. To cover a broad dynamic range, neutron time-of-flight was combined with neutron backscattering. The demethylated PIM-EA-TB(H2) exhibits a relaxation process with a weak intensity at short times. As the backbone is rigid and stiff this process was assigned to bendand-flex fluctuations. This process was also observed for the PIM-EA-TB(CH3). A further relaxation process is found for PIM-EA-TB(CH3), which is the methyl group rotation. It was analyzed by a jump-diffusion in a three-fold potential considering also the fact that only a fraction of the present hydrogens in PIM-EATB(CH3) participate in the methyl group rotation. This analysis can quantitatively describe the q dependence of the elastic incoherent structure factor. Furthermore, a relaxation time for the methyl group rotation can be extracted. A high activation energy of 35 kJ mol-1 was deduced. This high activation energy evidences a strong hindrance of the methyl group rotation in the bridged PIM-EA-TB(CH3) structure.
Although metallic nanoparticles play an important role in the area of nanotechnology, a coherent mechanistic explanation for the evolution of the particles during their chemical synthesis has not yet been provided in many cases. To gain a profound understanding of the growth mechanism of colloidal nanoparticles, new approaches using Small Angle X-Ray Scattering (SAXS) combined with X-ray absorption near-edge structure (XANES) are presented. This combination allows for insights into two prominent syntheses routes of gold nanoparticles (GNP): The 'slow' reaction using sodium citrate (30-90 min) as a reducing agent and the 'fast' reaction employing NaBH4 (within few seconds). In the first case data derived with the coupled XANES and SAXS suggests a four-step particle formation mechanism. For the second system a time resolution in the order of 100-200 ms was achieved by coupling a common laboratory SAXS instrument with a microstructured mixer, which allows data acquisition in a continuous-flow mode. The results indicate a coalescence driven growth process. Based on the capabilities to deduce the size, number and polydispersity of the particles, the results of both methods enable the development of mechanistic schemes explaining the different phases of particle formation and growth, thus providing a basis for improved control over the synthesis processes.
A great challenge in the production of nanoparticles with defined sizes and properties is to control their growth in situ. We developed a dedicated combined small-angle X-ray scattering (SAXS) and X-ray absorption spectroscopy (XAS) setup to monitor nanoparticle formation in solution. The capabilities of simultaneously deriving particle sizes and oxidation states of atoms/ions are illustrated for the formation of spherical gold nanoparticles by the reduction of hydrogen tetrachloroaureate (HAuCl4). Particles with initial radii of 4.60 ± 0.10 nm and final radii of 5.67 ± 0.10 nm were produced in a levitated droplet with a volume of 4 µL. An ethylene oxide/propylene oxide triblock copolymer PEO-PPO-PEO (Pluronic F-127) functions as reducing agent and colloidal stabilizer. XANES shows in situ how the gold was reduced in the droplet from Au(III) to Au(0), and simultaneously SAXS recorded the size distribution of the formed nanoparticles. It is shown that the final particle number is reached quickly. Thereafter, only the particles sizes increase. Comparison of XANES and SAXS shows that the quantity of Au(0) is higher than the quantity of gold located in the nanoparticles while the particles are growing. Finally, all the Au(0) is found in the nanoparticles. We tentatively attribute this finding to the pseudo crown ether effect of the polymer surfactant that kinetically stabilizes gold atoms when formed from gold ions within their protecting cavity. A simple burst mechanism for the gold nanoparticle formation is the consequence. The possibility of an inhomogeneous particles structure with an enhanced density near the particle surface is discussed.
Compact pnCCD-based X-ray camera with high spatial and energy resolution: a color X-ray camera
(2011)
For many applications there is a requirement for nondestructive analytical investigation of the elemental distribution in a sample. With the improvement of X-ray optics and spectroscopic X-ray imagers, full field X-ray fluorescence (FF-XRF) methods are feasible. A new device for high-resolution X-ray imaging, an energy and spatial resolving X-ray camera, is presented. The basic idea behind this so-called 'color X-ray camera' (CXC) is to combine an energy dispersive array detector for X-rays, in this case a pnCCD, with polycapillary optics. Imaging is achieved using multiframe recording of the energy and the point of impact of single photons. The camera was tested using a laboratory 30 µm microfocus X-ray tube and synchrotron radiation from BESSY II at the BAMline facility. These experiments demonstrate the suitability of the camera for X-ray fluorescence analytics. The camera simultaneously records 69696 spectra with an energy resolution of 152 eV for manganese Kα with a spatial resolution of 50 µm over an imaging area of 12.7 × 12.7 mm². It is sensitive to photons in the energy region between 3 and 40 keV, limited by a 50 µm beryllium window, and the sensitive thickness of 450 µm of the chip. Online preview of the sample is possible as the software updates the sums of the counts for certain energy channel ranges during the measurement and displays 2-D false-color maps as well as spectra of selected regions. The complete data cube of 264 × 264 spectra is saved for further qualitative and quantitative processing.
A new setup for fast spatially resolved measurements of elemental trace amounts under total reflection conditions using a new colour X-ray camera is described. Samples prepared on conventional total reflection X-ray fluorescence (TXRF) reflectors were measured at BESSY II synchrotron. A spatial resolution of 50 × 50 µm² was obtained, while the required time for the investigation of a 10 × 10 mm² sample is 30 seconds. The set-up is up to 350 times faster than conventional X-ray fluorescence systems for elemental traces. The major components of the X-ray camera are polycapillary optics and a pn-CCD chip with an active area of 13 × 13 mm². This area is divided into 264 × 264 pixels of 48 × 48 µm². A full X-ray spectrum with a resolution of 152 eV @ 5.9 keV and a chip temperature of 246 K is recorded for each pixel. The chip has a read-out rate of 400 Hz.
Superglassy polymers with a large fractional free volume have emerged as novel materials with a broad range of applications, especially in the field of membrane separations. Highly permeable addition-type substituted polynorbornenes with high thermal resistance and chemical stability are among the most promising materials. The major obstacle for extending the practical membrane application is their strong tendency to physical aging, leading to a partial decline in their superior transport performance over time. In the present study, broadband dielectric spectroscopy with complementary X-ray scattering techniques were employed to reveal changes in microporous structure, molecular mobility, and conductivity by systematic
comparison of two polynorbornenes with different numbers of trimethylsilyl side groups. Their response upon heating (aging) was compared in terms of structure, dynamics, and charge transport behavior. Furthermore, a detailed analysis of the observed
Maxwell−Wagner−Sillars polarization at internal interfaces provides unique information about the microporous structure in the
solid films. The knowledge obtained from the experiments will guide and unlock potential in synthesizing addition-type polynorbornenes with versatile properties.
We report on the trace analysis of copper and iron impurities in multicrystalline silicon wafers with the microbeam X-ray fluorescence (µ-XRF) technique. The efficiency of solar cells, which are based on multicrystalline silicon wafers, is strongly influenced by minor contamination with metals such as copper and iron. Application of compound refractive lenses (CRLs) in µ-XRF allows versatile two-dimensional mapping of relevant contaminations and localization of their sites of deposition. In this context, the measured bulk average limit of detection (LOD) was one picogram of iron and copper per gram of silicon. We suggest that µ-XRF is a valuable tool for non-destructive spatial (3D) quantification of metal impurities in a wide range of materials and devices whose functioning could be critically affected by impurities.
The mechanism of action of zirconium permanent modifiers on graphite surfaces was investigated in order to understand its influence on the analytical signal in atomic and molecular absorption spectrometry (AAS/MAS). For this, the molecule formation of CaF was studied, which is used for the indirect analytical determination of fluorine in high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS-GFMAS). The kinetics of this reaction was established by monitoring its molecular spectrum at different atomisation temperatures. An Arrhenius plot showed a pseudo-first order reaction with respect to fluorine (n = 1). An intermediate state was isolated, and its structure was elucidated by spectroscopic methods: scanning electron microscopy with energy dispersive X-ray spectroscopy (SEMEDX), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XANES and EXAFS), and Raman microspectroscopy. We propose here a mechanism, where ZrO2 acts as a heterogeneous catalyst: after a pyrolytic step, an intermediate state of ZrO(OCaF) is activated, and at higher temperatures, CaF(g) is released from the zirconium-coated graphite surface. No evidence of the formation of zirconium carbide was found. Consequently, as the CaF formation is catalysed by a heterogeneous catalyst, surface modifications with ZrO2 nanoparticles and ZrO xerogels were investigated in order to increase the surface area. Their influence was evaluated in the molecule formation of CaF, CaCl, CaBr, and CaI. Graphite furnace modification with zirconium oxide nanoparticles proves to be the best choice for fluorine analysis with a signal enhancement of more than eleven times with respect a non-coated graphite furnace. However, the influence of zirconium modifications in the analytical signals of Cl, and I is lower than the F signals or even negative in case of the Br. Understanding zirconium modifiers as heterogeneous catalysts offers a new perspective to AAS and MAS, and reveals the potential of surface analytical methods for development of improved permanent modifiers and graphite furnace coatings.