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- 2012 (7) (entfernen)
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- Water transport (2)
- Articular cartilage (1)
- Chemical safety (1)
- Data matching (1)
- Dispersion (1)
- Explosion propagation limits (1)
- FIB/SEM imaging (1)
- Gas diffusion layers (1)
- Histology (1)
- Instrumentation for neutron sources (1)
A method for the determination of safety properties for micro reactors and micro structured components is presented.
Micro structured reactors are not inherently safe but the range of safe operating conditions of micro reactors are
extended since the explosion region is reduced. The λ/3 rule was demonstrated to be applicable to micro scale
tubes for stoichiometric mixtures of ethane–oxygen and ethane–nitrous oxide. Furthermore first results from an investigation concerning detonation propagation through a micro reactor of non-ideal geometry are shown. Initial
pressure investigated is ranging from low pressure up to 100 kPa.
Synchrotron X-ray radiography and tomography investigations of a custom-made polymer electrolyte membrane fuel cell optimised for visualisation purposes are presented. The 3D water distribution and transport pathways in the porous carbon fibre gas diffusion layers (GDLs) were investigated. The authors found that water is not only moving from the GDL into the channel, but can also take the opposite way, that is, from the channel into free pore space of the GDL. Such movement of water into the opposite direction has been subject of speculations but has so far not yet been reported and might bring new insights into the general water transport behaviour, which might give new aspects to the general description of water transport processes and influence modelling assumptions to describe the process taking place in the GDL.
By means of synchrotron X-ray computed tomography, model composites consisting of silica and styrenebutadiene rubber were studied with a very high spatial resolution. By our analysis technique we were able to determine the nano- and micro dispersion from the experimental results by our numerical analysis. These results are discussed with respect to crucial advantages of the generically 3-dimensional tomography technique as compared to 2-dimensional methods. Our quantitative analysis of the 3d images demonstrates that in the case of our model composites the filler dispersion is good, independent on the filler concentration. Our new 3-dimensional results evidence that considering only 2-d pictures may lead to ambiguities that can lead to wrong conclusions.
A new high-resolution detector setup for neutron imaging has been developed based on infinity-corrected optics with high light collection, combined with customized mounting hardware. The system can easily be installed, handled and fitted to any existing facility, avoiding the necessity of complex optical systems or further improved electronics (CCD). This is the first time optical magnification higher than 1:1 has been used with scintillator-based neutron detectors, as well as the first implementation of infinity corrected optics for neutron imaging, achieving the smallest yet reported effective pixel size of 3.375 µm. A novel transparent crystal scintillator (GGG crystal) has been implemented with neutrons for the first time to overcome limitations of traditional powder scintillators (Li6/ZnS, Gadox). The standardized procedure for resolution measurements with the Modulation Transfer Function (MTF) is summarized to facilitate comparison between instruments and facilities. Using this new detector setup, a resolution of 14.8 µm with a field of view of 6 mm × 6 mm has been achieved while maintaining reasonable count times. These advances open a wide range of new possible research applications and allow the potential for additional future developments.
Perforated gas diffusion layers (GDLs) of polymer electrolyte membrane fuel cells (PEMFCs) were investigated by means of in-situ synchrotron X-ray radiography during operation. We found a strong influence of perforations on the water distribution and transport in the investigated Toray TGP-H-090 GDL. The water occurs mainly around the perforations, while the holes themselves show varying water distributions. Some remain dry, while most of them fill up with liquid water after a certain period or might serve as drainage volume for effective water transport.
The study was aimed at demonstrating a true cellular resolution for articular cartilage using synchrotron radiation-based X-ray microcomputed tomography (SR-µCT) with a sample-specific optimization of the phase contrast. The generated tomographic data were later used to prepare a matching histological sample from the full volume specimen.
We used highly coherent and monochromatic X-rays from a synchrotron source to image a tissue sample of bovine articular cartilage after deparaffinization. Phase contrast enhancement was achieved by using five different sample to detector distances for the same X-ray energy. After tomography, the sample was re-embedded into resin while retaining a dedicated sample orientation for subsequent sectioning and polishing, which was conducted until a previously defined spatial position was achieved. The protocol for resin embedding was developed to inhibit morphological changes during embedding. Giemsa staining was applied for better structural and morphological discrimination. Data from tomography and lightmicroscopy were exactly matched and finally compared to results from FIB/SEM imaging. Image detail was achieved at a single cell resolution. Image detail was achieved at a single cell resolution, which has been estimated to be 0.833 µm/voxel in the tomographic data.
SR-µCT with optimized phase contrast properties represents a method to investigate biological tissues in certain areas of interest, where true cellular resolution or enhanced volumetric imaging is needed. In this study, we demonstrate that this method can compete with conventional histology using light microscopy but even surpasses it due to the possibility of retrieving volumetric data.