scholarly journals Soil aeration and redox potential as function of pore connectivity unravelled by X‐Ray microtomography imaging

2021 ◽  
Author(s):  
Kristof Dorau ◽  
Daniel Uteau ◽  
Maren Hövels ◽  
Stephan Peth ◽  
Tim Mansfeldt
Keyword(s):  
Redox Potential ◽  
Pore Connectivity ◽  
Soil Aeration ◽  
X Ray

Hydrophobic Ferrocene Derivatives as Potential Standards in Electrochemistry

1997 ◽  
Vol 62 (2) ◽  
pp. 185-198 ◽  
Author(s):  
Jaroslav Podlaha ◽  
Petr Štěpnička ◽  
Róbert Gyepes ◽  
Vladimír Mareček ◽  
Alexander Lhotský ◽  
...  
Keyword(s):  
Surface Tension ◽  
Cyclic Voltammetry ◽  
Redox Potential ◽  
Diffusion Coefficients ◽  
Carbon Electrodes ◽  
X Ray Diffraction ◽  
Ferrocene Derivatives ◽  
X Ray ◽  
Special Cases ◽  
As Solubility

Ferrocene (FcH) derivatives monosubstituted by palmitoyl (1), hexadecyl (2), 1-adamantoyl (3) or 1-adamantylmethyl (4) groups were sythesized and characterized by NMR, mass and 57Fe Mossbauer spectroscopy. The structure of 1-adamantoylferrocene was determined by single-crystal X-ray diffraction. Cyclic voltammetry on gold and glass-like carbon electrodes demonstrated that the compounds can serve as electrochemical standards for special cases since their ferrocene/ferricinium redox potential remains stable and reversible, while the properties such as solubility, diffusion coefficients and surface tension are strongly solvent-dependent.

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 Characterisation of 3D printed sand moulds using micro-focus X-ray computed tomography

2019 ◽  
Vol 25 (2) ◽  
pp. 404-416 ◽  
Author(s):  
Tharmalingam Sivarupan ◽  
Mohamed El Mansori ◽  
Keith Daly ◽  
Mark Noel Mavrogordato ◽  
Fabrice Pierron
Keyword(s):  
Computed Tomography ◽  
Gas Permeability ◽  
Experimental Result ◽  
Pore Connectivity ◽  
Content Type ◽  
X Ray ◽  
3D Printed ◽  
X Ray Computed ◽  
Sand Mould ◽  
Non Destructive

Purpose Micro-focus X-ray computed tomography (CT) can be used to quantitatively evaluate the packing density, pore connectivity and provide the basis for specimen derived simulations of gas permeability of sand mould. This non-destructive experiment or following simulations can be done on any section of any size sand mould just before casting to validate the required properties. This paper aims to describe the challenges of this method and use it to simulate the gas permeability of 3D printed sand moulds for a range of controlling parameters. The permeability simulations are compared against experimental results using traditional measurement techniques. It suggests that a minimum volume of only 700 × 700 × 700 µm3 is required to obtain, a reliable and most representative than the value obtained by the traditional measurement technique, the simulated permeability of a specimen. Design/methodology/approach X-ray tomography images were used to reconstruct 3D models to simulate them for gas permeability of the 3D printed sand mould specimens, and the results were compared with the experimental result of the same. Findings The influence of printing parameters, especially the re-coater speed, on the pore connectivity of the 3D printed sand mould and related permeability has been identified. Characterisation of these sand moulds using X-ray CT and its suitability, compared to the traditional means, are also studied. While density and 3PB strength are a measure of the quality of the moulds, the pore connectivity from the tomographic images precisely relates to the permeability. The main conclusions of the present study are provided below. A minimum required sample size of 700 × 700 × 700 µm3 is required to provide representative permeability results. This was obtained from sand specimens with an average sand grain size of 140 µm, using the tomographic volume images to define a 3D mesh to run permeability calculations. Z-direction permeability is always lower than that in the X-/Y-directions due to the lower values of X-(120/140 µm) and Y-(101.6 µm) resolutions of the furan droplets. The anisotropic permeability of the 3D printed sand mould is mainly due to, the only adjustable, X-directional resolution of the furan droplets; the Y-directional resolution is a fixed distance, 102.6 µm, between the printhead nozzles and the Z-directional one is usually, 280 µm, twice the size of an average sand grain.A non-destructive and most representative permeability value can be obtained, using the computer simulation, on the reconstructed 3D X-ray tomography images obtained on a specific location of a 3D printed sand mould. This saves time and effort on printing a separate specimen for the traditional test which may not be the most representative to the printed mould. Originality/value The experimental result is compared with the computer simulated results.

The effect of cover crops on soil structure is mainly driven by root architecture

2021 ◽  
Author(s):  
Maik Lucas ◽  
Linh Nguyen ◽  
Andrey Guber ◽  
Alexandra Kravchenko
Keyword(s):  
Root System ◽  
Cover Crops ◽  
Soil Structure ◽  
Image Features ◽  
Small Scale ◽  
Pore Characteristics ◽  
Pore Connectivity ◽  
Imaging Protocol ◽  
X Ray ◽  
Wide Range

<p>Cover crops are known to increase macroporosity and pore connectivity, thus having a beneficial effect on soil hydraulic properties such as saturated hydraulic conductivity, However, cover crop species typically used encompass a variety of contrasting root architectures and their effects on small-scale pore properties are difficult to quantify.</p><p>Here we explore the influence of five different cover crops (annual ryegrass, Austrian winter pea, dwarf essex rapeseed, oats, and oilseed radish) on soil structure with X-ray µCT. Undisturbed samples were taken from an experiment with these cover crops on Kellogg Biological Station (Michigan, USA) in October 2019. Two soil columns with a diameter of 5 cm were taken in 5 - 10 cm depth from each of three replicated plots per plant species and scanned with X-ray µCT at a resolution of 18 µm.</p><p>These images will be used to characterize pore structure in terms of pore size distribution, pore connectivity. In addition, a new imaging protocol will be used, which combines existing ones with a random forest classifier to segment image features such as pores, biopores and roots simultaneously.</p><p>First, the results reveal that different cover crops indeed result in different pore characteristics.  The fibrous root system of oats leads to the highest volume of narrow macropores and increased their connectivity, while the tap root system of dwarf essex rapeseed mainly effected wide macropores.  The highly diverse root system of Australian winter pea increased a wide range of pore sizes and thus resulted in the highest visible porosity.</p><p>The current study is funded by a grant from USDA Organic Transition program</p>

scholarly journals Effect of Pore Connectivity on Li Dendrite Propagation within LLZO Electrolytes Observed with Synchrotron X-ray Tomography

2018 ◽  
Vol 3 (4) ◽  
pp. 1056-1061 ◽  
Author(s):  
Fengyu Shen ◽  
Marm B. Dixit ◽  
Xianghui Xiao ◽  
Kelsey B. Hatzell
Keyword(s):  
Pore Connectivity ◽  
X Ray

Pore connectivity across scales and resolutions

2020 ◽  
Author(s):  
Maik Lucas ◽  
Doris Vetterlein ◽  
Hans-Jörg Vogel ◽  
Steffen Schlüter
Keyword(s):  
Characteristic Size ◽  
Small Samples ◽  
Pore Connectivity ◽  
X Ray ◽  
Connection Probability ◽  
Three Samples ◽  
Different Depths ◽  
Pore Types ◽  
First Time ◽  
Joint Evaluation

<p>An important parameter to quantify pore structure and link it to soil functions is connectivity. When quantifying connectivity with X-ray microtomography (X-ray-µCT), one of the major drawbacks is that high resolution can only be achieved in small samples. In these samples, the small pores can be described, but the connectivity of larger pores cannot be quantified reasonably.</p><p>Here we explore changes in pore connectivity with changing sample size covering a range of analyzed pore diameters of more than three orders of magnitude. Soil columns with a diameter of 10 cm were taken in two different depths (0 - 20 cm and 40 - 60 cm) at different sites of an agricultural chronosequence ranging in age from 0 to 24 years. X-ray CT was used for scanning the original columns as well as undisturbed subsamples of 3 and 0.7 cm diameter. This enabled us to detect characteristic traces in certain connectivity metrics on the chronosequence, caused by different pore types and thus different processes. In detail, we determined the connection probability of two random points within the pore system, i.e. the Γ-indicator and the Euler number, χ as a function of minimum pore diameter.</p><p>Our results revealed that scale artifacts in the connectivity functions overlap with characteristic signatures of certain pore types. For the very first time a new method for a joint-Γ-curve was developed that merges information from three samples sizes, as the Γ-indicator gives highly biased information in small samples. In contrast, χ does not require such a scale fusion and is helpful to define characteristic size ranges for pore types. Overall, findings suggest a joint evaluation of both connectivity metrics to identify the contribution of different pore types to the total pore connectivity with Γ and to disentangle different pore types with χ.</p><p>For the samples of the chronosequence such an evaluation revealed that biopores mainly connect pores of diameters between 0.1 and 0.5 mm. However, this was not necessarily coupled with increasing porosity. Tillage, conversely, lead to an increase in porosity due to a shift of pores of diameter >0.05 mm towards pores of diameter >0.20 mm and therefore increased connectivity of pores >0.20 mm.</p><p>The current study is part of the DFG-Project Soil Structure (AOBJ: 628683). </p>

scholarly journals The Determination Of Diffusive Tortuosity In Concrete Specimens Using X-Ray Microtomography

2015 ◽  
Vol 60 (2) ◽  
pp. 1115-1119 ◽  
Author(s):  
Z. Ranachowski ◽  
D. Jóźwiak-Niedźwiedzka ◽  
P. Ranachowski ◽  
M. Dąbrowski ◽  
S. Kudela ◽  
...  
Keyword(s):  
Random Walk ◽  
Three Dimensional ◽  
Micro Ct ◽  
Connectivity Analysis ◽  
Pore Connectivity ◽  
Cement Ratio ◽  
X Ray ◽  
Water To Cement Ratio ◽  
Random Walk Simulation

Abstract The paper presents a method of pore connectivity analysis applied to specimens of cement based composites differing in water to cement ratio. The method employed X-ray microtomography (micro-CT). Microtomography supplied digitized three-dimensional radiographs of small concrete specimens. The data derived from the radiographs were applied as an input into the application based on the algorithm called ‘random walk simulation’. As the result a parameter called diffusive tortuosity was established and compared with estimated porosity of examined specimens.

Nondestructive Microscopy Test on Damage of Waterproof Material in Underground Engineering

2015 ◽  
Vol 645-646 ◽  
pp. 900-905
Author(s):  
Qing Guo Wang ◽  
Qi Xin Yang ◽  
Ya Jun Jiang ◽  
Juan Yang
Keyword(s):  
Alkaline Solution ◽  
Corrosive Medium ◽  
Underground Engineering ◽  
Pore Connectivity ◽  
X Ray ◽  
Microstructure Changes ◽  
Groundwater Environment ◽  
Naoh Solution ◽  
Alkaline Groundwater

The microstructure changes of acrylate spray-on waterproof material in alkaline groundwater environment were tentatively studied with X-ray microscopy (XRM), and the validity of deciding the failure of the material was explored in paper. Regarded NaOH solution with pH=12 as corrosive medium, after the immersion in the alkaline solution, spray-on waterproof material was scanned with XRM, and the structure was characterized with some indexes such as porosity and pore connectivity. The results show that when the waterproof material is immersed in alkaline solution for some time, the surface of the material becomes uneven, the overall porosity falls and the pore connectivity rises. It is feasible to study on the failure of waterproof material in underground engineering with XRM.

Micro-/Mesoporous Polymer-Derived Ceramic Structures Using Molecular Porogens

2017 ◽  
Vol 742 ◽  
pp. 310-316
Author(s):  
Thomas Konegger ◽  
Herwig Peterlik ◽  
Rajendra K. Bordia
Keyword(s):  
Systematic Investigation ◽  
Oxide Ceramic ◽  
Pore Connectivity ◽  
Asymmetric Membranes ◽  
X Ray ◽  
Energy And Environment ◽  
X Ray Scattering ◽  
Polymer Derived Ceramic ◽  
Mesopore Structure ◽  
Separation Of Gas Mixtures

Micro-and mesoporous ceramics demonstrate promising properties for applications in energy-and environment-related fields. Due to their high thermal and chemical stability, they are particularly suited for separation in harsh thermal or chemical environments, e.g. as membrane materials for the separation of gas mixtures. In this work, we present the use of a preceramic poly(vinyl)silazane in combination with organic molecular porogens for the generation of micro-/mesoporous non-oxide ceramic structures. Microporosity is generated during the pyrolytic conversion process, while the addition of molecular porogens, to be removed during the heat-treatment, enables further control of the micro-/mesopore structure. A systematic investigation of various porogens showed the suitability of polystyrene for this purpose. Based on these findings, the pore structure and pore connectivity of polysilazane/polystyrene-derived structures were evaluated using gas physisorption and small angle X-ray scattering techniques. This material was further investigated by preparing asymmetric membranes consisting of micro-/mesoporous polysilazane/polystyrene-derived layers on porous ZrO2/TiO2 supports. The potential for gas separation applications was then demonstrated by single-gas permance evaluation of the generated structures at temperatures up to 300 °C.

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