The Experts below are selected from a list of 11670 Experts worldwide ranked by ideXlab platform
Benoit Louis - One of the best experts on this subject based on the ideXlab platform.
-
assessment of the improvement of Effective Diffusivity over technical zeolite bodies by different techniques
Journal of Physical Chemistry C, 2019Co-Authors: Rogeria Bingre, Bruno Vincent, Qiang Wang, Patrick Nguyen, Benoit LouisAbstract:Technical zeolite bodies with additional porosity have been prepared with the intention to improve Effective Diffusivity. The latter has been assessed by three different techniques, combining a sim...
-
assessment of the improvement of Effective Diffusivity over technical zeolite bodies by different techniques
The Journal of Physical Chemistry, 2018Co-Authors: Rogeria Bingre, Bruno Vincent, Qiang Wang, Patrick Nguyen, Benoit LouisAbstract:Technical zeolite bodies with additional porosity have been prepared with the intention to improve Effective Diffusivity. The latter has been assessed by three different techniques, combining a simple one as uptake measurements (thermogravimetric analysis) to a more sophisticated pulsed-field gradient-nuclear magnetic resonance method. Inverse gas chromatography provided further complement to the aforementioned techniques by mimicking realistic operating conditions (temperature and flow). The three methods assessed an enhancement in the Effective Diffusivity for the samples where mesopores or macropores were created. Useful insights concerning the interactions between the binder and the zeolite were gained, showing a strong impact on the Effective Diffusivity within the catalyst body.
Rogeria Bingre - One of the best experts on this subject based on the ideXlab platform.
-
assessment of the improvement of Effective Diffusivity over technical zeolite bodies by different techniques
Journal of Physical Chemistry C, 2019Co-Authors: Rogeria Bingre, Bruno Vincent, Qiang Wang, Patrick Nguyen, Benoit LouisAbstract:Technical zeolite bodies with additional porosity have been prepared with the intention to improve Effective Diffusivity. The latter has been assessed by three different techniques, combining a sim...
-
assessment of the improvement of Effective Diffusivity over technical zeolite bodies by different techniques
The Journal of Physical Chemistry, 2018Co-Authors: Rogeria Bingre, Bruno Vincent, Qiang Wang, Patrick Nguyen, Benoit LouisAbstract:Technical zeolite bodies with additional porosity have been prepared with the intention to improve Effective Diffusivity. The latter has been assessed by three different techniques, combining a simple one as uptake measurements (thermogravimetric analysis) to a more sophisticated pulsed-field gradient-nuclear magnetic resonance method. Inverse gas chromatography provided further complement to the aforementioned techniques by mimicking realistic operating conditions (temperature and flow). The three methods assessed an enhancement in the Effective Diffusivity for the samples where mesopores or macropores were created. Useful insights concerning the interactions between the binder and the zeolite were gained, showing a strong impact on the Effective Diffusivity within the catalyst body.
Jeff T. Gostick - One of the best experts on this subject based on the ideXlab platform.
-
Measuring Effective Diffusivity in porous media with a gasket-free, radial arrangement
International Journal of Heat and Mass Transfer, 2019Co-Authors: Jeff T. GostickAbstract:Abstract A simple technique for measuring the Effective Diffusivity, and ultimately tortuosity, in porous media is presented. The method uses a custom-built apparatus, based on a radial geometry, which eliminates the need for any gaskets to seal the edge of the sample. This makes it particularly well suited for thin media such as films and layers. The experiment is based on the transient response of the oxygen concentration at the center of the sample as oxygen diffuses into an initially nitrogen filled domain from the sample perimeter. The analytical solution of Fick’s law for transient diffusion in cylindrical coordinates is fitted to the measured oxygen concentration profile to obtain the Effective Diffusivity. To validate the method, binary diffusion coefficients of N2-Air system were measured and the results show a close match and are consistent for a range of experimental parameters like flow rate and domain thickness. The classical study of diffusion in porous media based on sphere packing is revisited for further validation of the technique. The results show good agreement to the well-known Bruggeman correlation as well as to the experimental values reported in the literature. The new technique is further applied to other types of thin porous materials and the results indicate that the Bruggeman correlation generally underestimates the Effective Diffusivity of non-sphere packing.
-
In-Plane Effective Diffusivity in PEMFC Gas Diffusion Layers
Transport in Porous Media, 2016Co-Authors: Rinat R. Rashapov, Jeff T. GostickAbstract:The in-plane Effective diffusion coefficients in gas diffusion layers typically used in fuel cell electrodes were measured as a function of compression and hydrophobic polymer loading. This method was based on the transient diffusion of oxygen from air into an initially nitrogen purged porous sample and has proven to be accurate, fast, and straightforward. As anticipated, with higher compressions and higher PTFE loadings, Effective Diffusivity decreased, as a result of less pore space available for transport and because tortuosity increased. When plotted against compressed porosity, the Effective Diffusivity of untreated and treated materials for a given type of sample collapsed on top of each other, despite the simultaneous impact of PTFE loading and compression. It was possible to distinguish between the impact of PTFE and compression by plotting the data as tortuosity against compressed thickness. High compressions on the sample lead to irreversible damages to the fiber structure, resulting in decreased or unexpectedly low tortuosity. Finally, a percolation model was fitted through one of the tested materials and a reasonable agreement was observed for lower compression, but a fit to the entire data could not be achieved. This was attributed to fundamental structural changes occurring in the sample upon high compressions, an observation that helps to explain the general inability of theoretical tortuosity models to describe GDLs.
-
Effective Diffusivity in partially saturated carbon fiber gas diffusion layers effect of through plane saturation distribution
International Journal of Heat and Mass Transfer, 2015Co-Authors: Pablo A Garciasalaberri, Gisuk Hwang, Marcos Vera, Adam Z Weber, Jeff T. GostickAbstract:Abstract The Effective Diffusivity of gaseous species in partially-saturated finite-size porous media is a valuable parameter for mathematical modeling of many processes, but it is difficult to measure experimentally. In this work, the Effective Diffusivity of carbon-fiber gas diffusion layers (GDLs) used in polymer electrolyte fuel cells (PEFCs) was determined by performing lattice Boltzmann (LB) simulations on X-ray tomographic reconstructions of invading water configurations. Calculations on dry GDLs were in close agreement with previous experimental data; the Effective Diffusivity was reduced by the addition of PTFE due to the loss of pore volume and the higher tortuosity of transport paths. The effect of water saturation was significantly larger. It was found that the resistance of water to gas transport was extremely dependent on the saturation distribution through the porous medium, particularly the peak saturation, and not just the average saturation as is typically considered in the literature. Through-plane diffusion was dramatically limited in materials with high-peak local saturations, even at low average saturation levels. No significant limitations were observed for diffusion in the material plane. The computed results demonstrate the strong sensitivity of finite-size porous media to local conditions, highlighting the difficulties of applying volume-averaged continuum-scale modeling techniques to micro-scale materials.
-
a method for measuring in plane Effective Diffusivity in thin porous media
International Journal of Heat and Mass Transfer, 2015Co-Authors: Rinat R. Rashapov, Fariha Imami, Jeff T. GostickAbstract:Abstract A new experimental technique for measuring the in-plane components of the Effective Diffusivity tensor of thin porous materials is presented. The method is based on the transient diffusion of oxygen from air into a porous sample initially purged with nitrogen. The oxygen concentration is measured at a fixed location in the sample with time and the response is fitted to an analytical solution of Fick’s law for one-dimensional, transient diffusion. As validation, it was confirmed that this method reproduced the theoretical value of oxygen Diffusivity in nitrogen within 1% when no sample is present. Effective diffusion coefficients were measured for a variety of thin fibrous graphite paper materials typically used in fuel cell electrodes. The sample holder was designed to allow varying degrees of compression, thereby changing the porosity and tortuosity of the material. As expected the Effective Diffusivity drops with compression, not only due to a decrease in porosity but also to a large increase in tortuosity. The present method provides accurate, fast, and repeatable measurements, is applicable to electrically conductive materials where brine conductivity is difficult to interpret, uses a simple sample holder, an off-the-shelf oxygen sensor, and involves only air and nitrogen gas. The obtained values were in excellent agreement with comparable results in the literature, yet with a much more direct method.
Qiang Wang - One of the best experts on this subject based on the ideXlab platform.
-
assessment of the improvement of Effective Diffusivity over technical zeolite bodies by different techniques
Journal of Physical Chemistry C, 2019Co-Authors: Rogeria Bingre, Bruno Vincent, Qiang Wang, Patrick Nguyen, Benoit LouisAbstract:Technical zeolite bodies with additional porosity have been prepared with the intention to improve Effective Diffusivity. The latter has been assessed by three different techniques, combining a sim...
-
assessment of the improvement of Effective Diffusivity over technical zeolite bodies by different techniques
The Journal of Physical Chemistry, 2018Co-Authors: Rogeria Bingre, Bruno Vincent, Qiang Wang, Patrick Nguyen, Benoit LouisAbstract:Technical zeolite bodies with additional porosity have been prepared with the intention to improve Effective Diffusivity. The latter has been assessed by three different techniques, combining a simple one as uptake measurements (thermogravimetric analysis) to a more sophisticated pulsed-field gradient-nuclear magnetic resonance method. Inverse gas chromatography provided further complement to the aforementioned techniques by mimicking realistic operating conditions (temperature and flow). The three methods assessed an enhancement in the Effective Diffusivity for the samples where mesopores or macropores were created. Useful insights concerning the interactions between the binder and the zeolite were gained, showing a strong impact on the Effective Diffusivity within the catalyst body.
Patrick Nguyen - One of the best experts on this subject based on the ideXlab platform.
-
assessment of the improvement of Effective Diffusivity over technical zeolite bodies by different techniques
Journal of Physical Chemistry C, 2019Co-Authors: Rogeria Bingre, Bruno Vincent, Qiang Wang, Patrick Nguyen, Benoit LouisAbstract:Technical zeolite bodies with additional porosity have been prepared with the intention to improve Effective Diffusivity. The latter has been assessed by three different techniques, combining a sim...
-
assessment of the improvement of Effective Diffusivity over technical zeolite bodies by different techniques
The Journal of Physical Chemistry, 2018Co-Authors: Rogeria Bingre, Bruno Vincent, Qiang Wang, Patrick Nguyen, Benoit LouisAbstract:Technical zeolite bodies with additional porosity have been prepared with the intention to improve Effective Diffusivity. The latter has been assessed by three different techniques, combining a simple one as uptake measurements (thermogravimetric analysis) to a more sophisticated pulsed-field gradient-nuclear magnetic resonance method. Inverse gas chromatography provided further complement to the aforementioned techniques by mimicking realistic operating conditions (temperature and flow). The three methods assessed an enhancement in the Effective Diffusivity for the samples where mesopores or macropores were created. Useful insights concerning the interactions between the binder and the zeolite were gained, showing a strong impact on the Effective Diffusivity within the catalyst body.