TY  - JOUR
A1  - Shashev, Yury
A1  - Kupsch, Andreas
A1  - Lange, Axel
A1  - Müller, Bernd R.
A1  - Bruno, Giovanni
T1  - Improving the visibility of phase gratings for Talbot-Lau X-ray imaging
JF  - Materials testing : Materialprüfung ; materials and components, technology and application
N2  - Talbot-Lau interferometry provides X-ray imaging techniques with significant enhancement of the radiographic contrast of weakly absorbing objects. The grating based technique allows separation of absorption, refraction and small angle scattering effects. The different efficiency of rectangular and triangular shaped phase gratings at varying detector distances is investigated. The interference patterns (Talbot carpets) are modeled for parallel monochromatic radiation and measured by synchrotron radiation. In comparison to rectangular shapes of phase gratings much higher visibility is obtained for triangular shapes which yield enhanced contrast of a glass capillary test specimen.
KW  - Talbot-Lau interferometry
KW  - phase grating
KW  - synchrotron imaging
KW  - visibility
KW  - X-ray refraction
Y1  - 2016
U6  - https://doi.org/10.3139/120.110948
SN  - 0025-5300
VL  - 58
SP  - 970
EP  - 974
PB  - Hanser
CY  - München
ER  - 
TY  - JOUR
A1  - Tötzke, Christian
A1  - Gaiselmann, G.
A1  - Osenberg, M.
A1  - Arlt, T.
A1  - Markötter, H.
A1  - Hilger, A.
A1  - Kupsch, Andreas
A1  - Müller, B. R.
A1  - Schmidt, V.
A1  - Lehnert, W.
A1  - Manke, Ingo
T1  - Influence of hydrophobic treatment on the structure of compressed gas diffusion layers
JF  - Journal of power sources : the international journal on the science and technology of electrochemical energy systems
N2  - Carbon fiber based felt materials are widely used as gas diffusion layer (GDL) in fuel cells. Their transport properties can be adjusted by adding hydrophobic agents such as polytetrafluoroethylene (PTFE). We present a synchrotron X-ray tomographic study on the felt material Freudenberg H2315 with different PIPE finishing. In this study, we analyze changes in microstructure and shape of GDLs at increasing degree of compression which are related to their specific PTFE load. A dedicated compression device mimicking the channel-land pattern of the flowfield is used to reproduce the inhomogeneous compression found in a fuel cell. Transport relevant geometrical parameters such as porosity, pore size distribution and geometric tortuosity are calculated and consequences for media transport discussed. PTFE finishing results in a marked change of shape of compressed GDLs: surface is smoothed and the invasion of GDL fibers into the flow field channel strongly mitigated. Furthermore, the PTFE impacts the microstructure of the compressed GDL. The number of available wide transport paths is significantly increased as compared to the untreated material. These changes improve the transport capacity liquid water through the GDL and promote the discharge of liquid water droplets from the cell. (C) 2016 Elsevier B.V. All rights reserved.
KW  - Gas diffusion layer
KW  - Synchrotron tomography
KW  - Compression
KW  - Hydrophobic treatment
KW  - Water transport
Y1  - 2016
U6  - https://doi.org/10.1016/j.jpowsour.2016.05.118
SN  - 0378-7753
SN  - 1873-2755
VL  - 324
SP  - 625
EP  - 636
PB  - Elsevier
CY  - Amsterdam
ER  -