Filtern
Erscheinungsjahr
Dokumenttyp
- Zeitschriftenartikel (35)
- Beitrag zu einem Tagungsband (5)
- Buchkapitel (4)
- Beitrag zu einem Sammelband (2)
- Vortrag (2)
- Posterpräsentation (2)
- Forschungsbericht (2)
- Monografie (1)
Schlagworte
- Rheology (7)
- Nanoparticles (6)
- SEM (5)
- EDX (3)
- Haftung (3)
- High-resolution (3)
- Polysaccharides (3)
- Reinigung (3)
- Superplasticizer (3)
- T-SEM (3)
Organisationseinheit der BAM
- 7 Bauwerkssicherheit (13)
- 7.4 Baustofftechnologie (13)
- 6 Materialchemie (4)
- 8 Zerstörungsfreie Prüfung (3)
- 1 Analytische Chemie; Referenzmaterialien (2)
- 6.1 Oberflächen- und Dünnschichtanalyse (2)
- 6.5 Synthese und Streuverfahren nanostrukturierter Materialien (2)
- 8.5 Röntgenbildgebung (2)
- 1.1 Anorganische Spurenanalytik (1)
- 1.4 Prozessanalytik (1)
Paper des Monats
- ja (1)
Eingeladener Vortrag
- nein (2)
Viskosimetrische und thermophysikalische Eigenschaften umweltverträglicher Motorschmierstoffe
(2006)
The water management in proton exchange membrane fuel cells (PEMFC) is strongly influenced by the design of the gas diffusion layers (GDL). Limiting current measurements in small-scale cells operating at high stoichiometries are useful to determine the oxygen transport resistance. The oxygen transport resistance increases, once water condenses inside the GDL. In this study a new electrochemical method for voltage loss estimation of GDL induced oxygen transport losses are presented. This new method, referred to as “transient limiting current” (TLC), is compared with the literature method. TLC allows a direct estimation of oxygen transport resistance at an arbitrarily conditioned state. This study also presents a case study of liquid water visualization of a PEM fuel cell with varying GDLs types.
With the help of quasi in-situ synchrotron X-ray computed tomography and time resolved radiography measurements we investigate appearance and distribution of liquid water inside the GDLs under limiting current conditions.
Towards the standardization of biochar analysis: the COST action TD1107 interlaboratory comparison
(2016)
Biochar produced by pyrolysis of organic residues is increasingly used for soil amendment and many other applications. However, analytical methods for its physical and chemical characterization are yet far from being specifically adapted, optimized, and standardized. Therefore, COST Action TD1107 conducted an interlaboratory comparison in which 22 laboratories from 12 countries analyzed three different types of biochar for 38 physical–chemical parameters (macro- and microelements, heavy metals, polycyclic aromatic hydrocarbons, pH, electrical conductivity, and specific surface area) with their preferential methods. The data were evaluated in detail using professional interlaboratory testing software. Whereas intralaboratory repeatability was generally good or at least acceptable, interlaboratory reproducibility was mostly not (20% < mean reproducibility standard deviation < 460%). This paper contributes to better comparability of biochar data published already and provides recommendations to improve and harmonize specific methods for biochar analysis in the future.
We present a synchrotron X-ray tomographic study on the morphology of carbon fiber-based gas diffusion layer (GDL) material under compression. A dedicated compression device is used to provide well-defined compression conditions. A flat compression punch is employed to study the fiber geometry at different degrees of compression. Transport relevant geometrical parameters such as porosity, pore size and tortuosity distributions are calculated. The geometric properties notably change upon compression which has direct impact on transport conditions for gas and fluid flow. The availability of broad 3D paths, which are most important for the transport of liquid water from the catalyst layer through the GDL, is markedly reduced after compression. In a second experiment, we study the influence of the channel-land-pattern of the flow-field on shape and microstructure of the GDL. A flow-field compression punch is employed to reproduce the inhomogeneous compression conditions found during fuel cell assembly. While homogenously compressed underneath the land the GDL is much less and inhomogeneously compressed under the channel. The GDL material extends far into the channel volume where it can considerably influence gas and fluid flow. Loose fiber endings penetrate deeply into the channel and form obstacles for the discharge of liquid water droplets.