排序方式: 共有12条查询结果,搜索用时 281 毫秒
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S. Majid Ghahari Alison J. Davenport Trevor Rayment Thomas Suter Jean-Philippe Tinnes Cristiano Padovani Joshua A. Hammons Marco Stampanoni Federica Marone Rajmund Mokso 《Corrosion Science》2011,53(9):2684-2687
Pitting corrosion of stainless steel has been investigated with high-resolution in situ X-ray microtomography. The growth of pits at the tip of stainless steel pins has been observed with 3D microtomography under different conditions of applied current and cell potential. The results demonstrate how pits evolve in stainless steel, forming a characteristic “lacy” cover of perforated metal. In addition, it is shown how the shape of pits becomes modified by MnS inclusions. 相似文献
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Corrosion protection of AA7449-T7951 friction stir welds by laser surface melting with an Excimer laser 总被引:1,自引:0,他引:1
Cristiano Padovani Alison J. Davenport Brian J. Connolly Stewart W. Williams Eirian Siggs Amela Groso Marco Stampanoni 《Corrosion Science》2011,53(12):3956-3969
The corrosion protection afforded by laser surface melting (LSM) AA7449-T7951 friction stir welds was investigated. LSM produced melting of the constituent particles and formation of a homogeneous 3–5 μm thick layer. Electrochemical tests showed a reduction in cathodic reactivity after LSM. The breakdown potentials, however, did not change significantly, indicating an anodically reactive surface. In situ and ex situ observation after immersion in 0.1 M NaCl showed that LSM reduced the depth attack in the weld region (particularly the HAZ), affording sacrificial protection to the substrate. Delamination of the treatment can occur during corrosion propagation. 相似文献
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Sergey Gorelick Joan Vila-Comamala Vitaliy Guzenko Rajmund Mokso Marco Stampanoni Christian David 《Microelectronic Engineering》2010,87(5-8):1052-1056
We present a fast and reliable fabrication method of dense, periodic and high aspect ratio PMMA and metallic nanostructures. Biased lines are directly exposed by a 100 keV electron beam in thick layers of polymethyl-methacrylate (PMMA) resist to produce polymer mold which is later used to grow Au high aspect ratio structures by electroplating. Dense PMMA and Au nanostructures with aspect ratios >11 were manufactured in 520 nm and with aspect ratios >12 in ~1 μm thick layers of PMMA. This method was successfully applied to produce various X-ray optics devices, such as beam shaping condensers, Fresnel zone plates and diffraction gratings. The performance of a beam shaper was tested at 10 keV photon energy showing a good diffraction efficiency of 10%. 相似文献
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Philipp Schneider Thomas Krucker Eric Meyer Alexandra Ulmann-Schuler Bruno Weber Marco Stampanoni Ralph Müller 《Microscopy research and technique》2009,72(9):690-701
Recent evidence suggests a close functional relationship between osteogenesis and angiogenesis as well as between bone remodeling and bone vascularization. Consequently, there is a need for visual inspection and quantitative analysis of the bone vasculature. We therefore adapted and implemented two different vascular corrosion casting (VCC) protocols using a polyurethane-based casting resin in mice for a true three-dimensional (3D), direct, and simultaneous measurement of bone tissue and vascular morphology by micro-computed tomography (μCT). For assessment of vascular replicas at the level of capillaries, a vascular contrast perfusion (VCP) protocol was devised using a contrast modality based on a barium sulfate suspension in conjunction with synchrotron radiation (SR) μCT. The vascular morphology quantified using the VCP protocol was compared quantitatively with the results of a previously established method, where the vascular network of cortical bone was derived indirectly from cortical porosity. The presented VCC and VCP protocols have the potential of serving as a valuable method for concomitant 3D quantitative morphometry of the bone tissue and its vasculature. Microsc. Res. Tech. 2009. © 2009 Wiley-Liss, Inc. 相似文献
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Christoph AppelJohn Mantzaras Rolf SchaerenRolf Bombach Andreas InauenBeat Kaeppeli Bernd HemmerlingAnna Stampanoni 《Combustion and Flame》2002,128(4):340-368
The gas-phase ignition of fuel-lean hydrogen/air mixtures over platinum was investigated experimentally and numerically in laminar channel-flow configurations. Experiments were performed at atmospheric pressure in an optically accessible catalytic channel combustor established by two Pt-coated parallel plates, 300 mm long (streamwise direction) and placed 7 mm apart (transverse direction). Planar laser induced fluorescence (PLIF) of the OH radical along the streamwise plane of symmetry was used to monitor the onset of homogeneous ignition, one-dimensional Raman measurements (across the 7-mm transverse direction) provided the boundary layer profiles of the major species and temperature, and thermocouples embedded beneath the catalyst yielded the surface temperature distribution. Computations were carried out using a two-dimensional elliptic fluid mechanical model that included multicomponent transport and elementary homogeneous (gas-phase) and heterogeneous (catalytic) chemical reaction schemes. Four homogeneous and three heterogeneous reaction schemes were tested in the model against measured homogeneous ignition characteristics. The differences between measured and predicted homogeneous ignition distances could be substantial (ranging from 8% to 66%, depending on the particular hetero/homogeneous schemes) and were ascribed primarily to the homogeneous reaction pathway. Sensitivity analysis indicated that the discrepancies induced by the gas-phase schemes originated either from the presence of heterogeneously-produced water due to its effectiveness as collision partner in the chain terminating reaction H + O2 + M = HO2 + M, or from an overall overprediction of the radical pool in the preignition zone. The heterogeneous schemes had significant differences in their surface coverage and radical fluxes, but these variations had practically no impact on homogeneous ignition. Sensitivity and reaction flux analyses have shown that this was attributed to the ability of all heterogeneous schemes to capture the measured mass-transport-limited fuel conversion and to the relative insensitivity of homogeneous ignition on the magnitude of the heterogeneous radical fluxes, provided that all radical adsorption reactions (OH, H, and O) were included in the heterogeneous schemes. 相似文献
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Reto Flückiger Federica Marone Marco Stampanoni Alexander Wokaun Felix N. Büchi 《Electrochimica acta》2011,56(5):B963
In polymer electrolyte fuel cells (PEFCs), condensation of water within the pore network of the gas diffusion layers (GDL) can influence the gas transport properties and thus reduce the electrochemical conversion rates. The use of X-ray tomographic microscopy (XTM), which allows for a resolution in the order of one micrometer is investigated for studying ex situ the local saturation in GDL's. The strength of XTM is the high spatial resolution with simultaneous contrast for water and carbon, allowing for non-destructive 3D-imaging of the solid and the contained water. The application of this method for imaging the ex situ water intrusion into the porous network of GDLs is explored using absorption and phase contrast methods. It is shown that the inhomogeneous filling behavior of GDL materials can indeed be visualized with sufficient resolution. For Toray paper TGP-H-060 the local saturation was measured as function of the water pressure. The results, evaluated in 1D, 2D and 3D show a liquid water retention effect at the denser layers near the surface. A comparison with established capillary pressure functions is presented. Altogether, the results show the potential of the XTM-method as a tool for studying the liquid water behavior in PEFC on a microscopic scale. 相似文献