Ingenieurwissenschaften und zugeordnete Tätigkeiten
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Application of 4Q-BSE detector and dedicated software enables 3D surface measurements of fracture samples in SEM. 3D surface measurement is independent from magnification and material invariant. Quantitative height measurements require careful detector adjustment and system calibration. Live 3D view allows a fast assessment of topographical features. In addition to SE and BSE imaging, 3D surface data help to analyse and interpret fracture samples.
Pre-Inca civilizations like the coastal cultures Moche and Nazca (Early Intermediate) and the inland culture Wari (Middle Horizon) were agrarian societies which supported indigenous elites of impressive wealth, power, and organization. With the expansion of the Wari Empire, the polychrome style and technique of Nazca propagated to the other cultures. High status burials, most of the Late Moche Fine Line ceramics and a large corpus of ceramics with Wari-derived decoration have been recovered in San José de Moro since 1991. The degree of transfer of procedures in this highly interactive scenario is of special interest: is there a limitation to decoration or is it adopted by the local potters also regarding the formulation of the ceramic bodies? In this context the relative amount, size and type of incorporated non-plastic inclusions as temper are important.
Deuterium permeation and cracking in duplex steels as viewed by ToF-SIMS and HR-SEM with data fusion
(2016)
Better understanding of hydrogen assisted degradation and trapping mecha-nisms requires sufficient imaging techniques for respective hydrogen-microstructure interaction studies, in particular with multi-phase metallic micro-structures [1]. The present work is focusing on the elucidation of deuterium be-havior in two austenitic-ferritic duplex stainless steels (DSS) under the assumption that deuterium behaves in many ways similarly to hydrogen [2]. For case studies standard 2205 and lean 2101 DSSs were chosen due to the extensive use of these steels in industry [3]. The analyses were conducted by using a novel in-situ permeation and Time-of-Flight secondary ion mass spectrometry (ToF-SIMS) imaging technique or by ex-situ ToF-SIMS imaging following electrochemical charging experiments. Another pioneering procedure was data fusion (including chemometry) of results of powerful laterally resolved chemical analysis and high resolution structural characterization techniques .
Results for the ex-situ observations showed a different influence of deuterium loading on the two steel grades as well as different damage mechanisms in each phase. Formation of sub-surface blisters between the ferrite and austenite were obtained in both the standard and the lean DSS. In both steels, an increased deuterium concentration was observed around deformed regions such as cracks, confirming that they originate from the presence of deuterium [4]. The formation of parallel cracks was obtained only in the austenite within the standard duplex whereas in the lean duplex the highest intensity of deuterium was obtained in the austenite along the ferrite-austenite interphase.
In comparison, application of the novel in-situ permeation technique enabled to register and record the deuterium permeation through the material and the respective saturation sequence of the two phases as well as the interfaces. Faster diffusion of the deuterium was observed in the ferrite and a direct proof for deuterium enrichment at the austenite-ferrite interface has been given [1]. The integration of the specified techniques gives a better insight into the processes leading to hydrogen induced failure. These two experimental techniques provide very valuable tools for elucidation of respective metallurgical failure mechanisms that can be used for the validation of respective numerical models for hydrogen assisted cracking (HAC).
In the present work, the influence of deuterium on the microstructure of a duplex stainless steel type EN 1.4462 has been characterized by Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) supported by scanning electron microscopy (SEM), focused ion beam (FIB), electron back scattered diffraction(EBSD) and energy dispersive x-ray (EDX) investigations. Characterization has been carried out before and after electrochemical charging with deuterium which has been used as a tracer, due to its similar behavior to hydrogen in the steel microstructure. In a first approach, the distribution of the deuterium occurring at temperatures above 58 °C has been visualized. Further it turned out that sub-surface micro blisters are formed in the ferrite-austenite interface, followed by the formation of needle shaped plates and subsequent cracking at the ferrite surface. In the austenite phase, parallel cracking alongside twins and hexagonal close packed (martensitic) regions has been observed. In both phases and even in the apparent interface, cracking has been associated with high deuterium concentrations, as compared to the surrounding undamaged microstructure. Sub-surface blistering in the ferrite has to be attributed to the accumulation and recombination of deuterium at the ferrite-austenite interface underneath the respective ferrite grains and after fast diffusing through this phase. Generally, the present application of chemometric imaging and structural analyses allows characterization of hydrogen assisted degradation at a sub-micron lateral resolution.
Considerations using silver nitrate as a reference for in vitro tests with silver nanoparticles
(2016)
Most in vitro tests regarding the cellular toxicology of nanoparticulate metals compare particle to associated metal ion exposure. However. it is also a fact. that for example silver ions are reduced by sugars or transformed to silver chloride by chloride salts which are abundant components of cell culture media. These reactions are likely to either complicate or even invalidate comparisons between effects of ions and particles. Here. we present a fast and quantitative method to determine particle formation and numbers in different cell culture media with non-destructive small-angle X-ray scattering (SAXS). Silver nitrate with a concentration of25 (.Jg Ag mL -I was dissolved for up to 24 h at 37 'C in Dulbeccos Modified Eagle Medium (DMEM) with and without 10% fetal bovine serum (FBS) and a solution ofO-glucose (4.5 (.Jg mL -1). respectively. Silver nanopartides were observed in all Solutions after 5 min. The cell culture media displayed a limited particle-growth. FBS showed an effect on the polydispersity of the generated particles but after 5 min the overall particle size was nearly equal in FBS and non FBS supplemented medium. Particles in D-glucose were precipitating after 10 min. Particulate silver concentration was between 3 and 4 (.Jg mL -1 in both cell culture media (CCM). These results should be taken into account when performing silver ion-toxicity experiments in relevant media.
Advances in scanning electron microscopy (SEM) enable the high-resolution imaging of single nanoparticles (NPs) with sizes well below 10 nm. The SEM analysis in transmission mode (T-SEM) of NPs on thin film supports has many benefits when compared to the analysis of NPs on bulk substrates. The enhanced material (mass – thickness) contrast of the T-SEM imaging mode is well suited for in-depth and, particularly valuable, to very accurate, traceable, lateral dimensional measurements of NPs. Compared to samples prepared on bulk substrates, T-SEM with energy dispersive X-ray spectroscopy (EDS) achieves a drastically improved spatial resolution of the emitted X-rays. The poor signal-to-noise ratio of the X-ray spectra emitted by a single nanoparticle (NP) can be improved by the use of high-sensitivity (high collection solid angle) silicon drift (SDD), energy-dispersive X-ray spectrometers (EDS). The EDS spectral imaging of a single NP with a spatial resolution below 10 nm has become possible. This is demonstrated by means of various examples of nanostructures. Advanced data processing of T-SEM/EDS results sets the stage for the automated classification of NPs by feature analysis. This method combines the detection of morphological structures of interest by image processing of T-SEM micrographs with the chemical classification by EDS.