Linking pore network structure derived by microfocus X-ray CT to mass transport parameters in differently compacted loamy soils

Soil Research ◽  
2019 ◽  
Vol 57 (6) ◽  
pp. 642
Author(s):  
Arjun Baniya ◽  
Ken Kawamoto ◽  
Shoichiro Hamamoto ◽  
Toshihiro Sakaki ◽  
Takeshi Saito ◽  
...  
Keyword(s):  
Mass Transport ◽  
Coordination Number ◽  
Structural Parameters ◽  
Network Connectivity ◽  
Pore Network ◽  
Gas Diffusion ◽  
Transport Parameters ◽  
X Ray ◽  
Surface Areas ◽  
X Ray Computed

Mass transport in soil occurs through the soil pore network, which is highly influenced by pore structural parameters such as pore-size distribution, porosity, pore tortuosity, and coordination number. In this study, we visualised the networks of meso- and macro-pores (typical pore radius r ≥ 10 μm) using microfocus X-ray computed tomography (MFXCT) and evaluated pore structural parameters of two loamy soils from Japan and New Zealand packed at different degrees of compaction. The effect of compaction on pore structural parameters and relationships between pore structural parameters and measured mass transport parameters were examined. Results showed a clear influence of compaction on pore structural parameters, with the MFXCT-derived mean pore radii and pore tortuosities decreasing and the mean pore coordination number increasing with increasing dry bulk density. Especially, pores with r > 80 µm became finer or were not well formed due to compaction. The MFXCT-derived pore structural parameters were not well correlated with the equivalent pore radii from measured water retention curves. However, volumetric surface areas and pore-network connectivity-tortuosity factors derived from MFXCT allowed a fair prediction of several important mass transport parameters such as saturated hydraulic conductivities, soil-gas diffusion coefficients, and soil-air permeabilities. Further studies are needed to link micro-pores with radii smaller than the X-ray CT resolution to meso- and macro-pores visualised by X-ray CT to improve the prediction of mass transport parameters in soil.

3D Structural Imaging of Porous GDL of a Fuel Cell

2011 ◽  
Author(s):  
Seung-Gon Kim ◽  
Sang-Joon Lee
Keyword(s):  
Fuel Cell ◽  
Structural Parameters ◽  
Gas Diffusion ◽  
Polymer Electrolyte Fuel Cell ◽  
Structural Imaging ◽  
Freezing And Thawing ◽  
X Ray ◽  
Freeze And Thaw ◽  
X Ray Computed ◽  
External Light Source

Synchrotron X-ray computed tomography was employed to measure the volume variation of gas diffusion layer (GDL) for polymer electrolyte fuel cell (PEFC). The study was conducted using 3D reconstruction (or a 3D rendering software) of orthoslice images. Especially, the temporal variation of structural parameters such as porosity was measured under freeze and thaw cycles. The freezing and thawing cycle were generated using a CRYO-system and an external light source alternatively. As a result, the structural parameters such varied significantly between the successive freeze/thaw cycles and irreversible change was also observed.

scholarly journals Effect of long-term irrigation and tillage practices on X-ray CT and gas transport derived pore-network characteristics

Soil Research ◽  
2019 ◽  
Vol 57 (6) ◽  
pp. 657
Author(s):  
Karin Müller ◽  
Nicola Dal Ferro ◽  
Sheela Katuwal ◽  
Craig Tregurtha ◽  
Filippo Zanini ◽  
...  
Keyword(s):  
Gas Transport ◽  
Greenhouse Gas Emission ◽  
Structural Characteristics ◽  
Network Connectivity ◽  
Total Porosity ◽  
Pore Network ◽  
Transport Parameters ◽  
X Ray ◽  
Tillage Practices

The gas transport parameters, diffusivity and air-filled porosity are crucial for soil aeration, microbial activity and greenhouse gas emission, and directly depend on soil structure. In this study, we analysed the effect of long-term tillage and irrigation practices on the surface structure of an arable soil in New Zealand. Our hypothesis was that topsoil structure would change under intensification of arable production, affecting gas exchange. Intact soil cores were collected from plots under intensive tillage (IT) and direct drill (DD), irrigated or rainfed. In total, 32 cores were scanned by X-ray computed tomography (CT) to derive the pore network >30µm. The cores were then used to measure soil-gas diffusivity, air-permeability and air-filled porosity of pores close to the resolution of the X-ray CT scans, namely ≥30µm. The gas measurements allow the calculation of pore-network connectivity and tortuosity parameters, which were compared with the CT-derived structural characteristics. Long-term irrigation had little effect on any of the parameters analysed. Total porosity tended to be lower under IT than DD, whereas the CT-derived porosity was comparable. Both the CT-derived mean pore diameter (MPD) and other morphological parameters, as well as gas measurement-derived parameters, highlighted a less developed structure under IT. The differences in the functional pore-network structure were attributed to SOC depletion and the mechanical disturbance through IT. Significant correlations between CT-derived parameters and functional gas transport parameters such as tortuosity and MPD were found, which suggest that X-ray CT could be useful in the prediction of gas transport.

Nature of the clay - cation bond affects soil structure as verified by X-ray computed tomography

Soil Research ◽  
2012 ◽  
Vol 50 (8) ◽  
pp. 638 ◽  
Author(s):  
Alla Marchuk ◽  
Pichu Rengasamy ◽  
Ann McNeill ◽  
Anupama Kumar
Keyword(s):  
Computed Tomography ◽  
Hydraulic Conductivity ◽  
Zeta Potential ◽  
Structural Stability ◽  
Structural Parameters ◽  
Pore Connectivity ◽  
X Ray ◽  
Clay Dispersion ◽  
X Ray Computed ◽  
Cation Ratio

Non-destructive X-ray computed tomography (µCT) scanning was used to characterise changes in pore architecture as influenced by the proportion of cations (Na, K, Mg, or Ca) bonded to soil particles. These observed changes were correlated with measured saturated hydraulic conductivity, clay dispersion, and zeta potential, as well as cation ratio of structural stability (CROSS) and exchangeable cation ratio. Pore architectural parameters such as total porosity, closed porosity, and pore connectivity, as characterised from µCT scans, were influenced by the valence of the cation and the extent it dominated in the soil. Soils with a dominance of Ca or Mg exhibited a well-developed pore structure and pore interconnectedness, whereas in soil dominated by Na or K there were a large number of isolated pore clusters surrounded by solid matrix where the pores were filled with dispersed clay particles. Saturated hydraulic conductivities of cationic soils dominated by a single cation were dependent on the observed pore structural parameters, and were significantly correlated with active porosity (R2 = 0.76) and pore connectivity (R2 = 0.97). Hydraulic conductivity of cation-treated soils decreased in the order Ca > Mg > K > Na, while clay dispersion, as measured by turbidity and the negative charge of the dispersed clays from these soils, measured as zeta potential, decreased in the order Na > K > Mg > Ca. The results of the study confirm that structural changes during soil–water interaction depend on the ionicity of clay–cation bonding. All of the structural parameters studied were highly correlated with the ionicity indices of dominant cations. The degree of ionicity of an individual cation also explains the different effects caused by cations within a monovalent or divalent category. While sodium adsorption ratio as a measure of soil structural stability is only applicable to sodium-dominant soils, CROSS derived from the ionicity of clay–cation bonds is better suited to soils containing multiple cations in various proportions.

scholarly journals Pore network structure linked by X-ray CT to particle characteristics and transport parameters

2016 ◽  
Vol 56 (4) ◽  
pp. 676-690 ◽  
Author(s):  
Shoichiro Hamamoto ◽  
Per Moldrup ◽  
Ken Kawamoto ◽  
Toshihiro Sakaki ◽  
Taku Nishimura ◽  
...  
Keyword(s):  
Network Structure ◽  
Pore Network ◽  
Transport Parameters ◽  
X Ray ◽  
Particle Characteristics

scholarly journals Investigating Evaporation in Gas Diffusion Layers for Fuel Cells with X-ray Computed Tomography

2016 ◽  
Vol 120 (50) ◽  
pp. 28701-28711 ◽  
Author(s):  
Iryna V. Zenyuk ◽  
Adrien Lamibrac ◽  
Jens Eller ◽  
Dilworth Y. Parkinson ◽  
Federica Marone ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Fuel Cells ◽  
Gas Diffusion ◽  
Gas Diffusion Layers ◽  
X Ray ◽  
Diffusion Layers ◽  
X Ray Computed

scholarly journals Microstructural differences between naturally-deposited and laboratory beach sands

2021 ◽  
Vol 24 (1) ◽  
Author(s):  
Amy Ferrick ◽  
Vanshan Wright ◽  
Michael Manga ◽  
Nicholas Sitar
Keyword(s):  
Mechanical Properties ◽  
Coordination Number ◽  
Grain Orientation ◽  
Flowing Water ◽  
X Ray ◽  
Depositional Processes ◽  
Grain Orientations ◽  
Computed Microtomography ◽  
X Ray Computed ◽  
Beach Sands

AbstractThe orientation of, and contacts between, grains of sand reflect the processes that deposit the sands. Grain orientation and contact geometry also influence mechanical properties. Quantifying and understanding sand microstructure thus provide an opportunity to understand depositional processes better and connect microstructure and macroscopic properties. Using x-ray computed microtomography, we compare the microstructure of naturally-deposited beach sands and laboratory sands created by air pluviation in which samples are formed by raining sand grains into a container. We find that naturally-deposited sands have a narrower distribution of coordination number (i.e., the number of grains in contact) and a broader distribution of grain orientations than pluviated sands. The naturally-deposited sand grains orient inclined to the horizontal, and the pluviated sand grains orient horizontally. We explain the microstructural differences between the two different depositional methods by flowing water at beaches that re-positions and reorients grains initially deposited in unstable grain configurations.

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