Study on Imaging Arsenic Aggregates in Porous Media by X-Ray Difference Micro-Tomography

2011 ◽  
Vol 356-360 ◽  
pp. 2362-2366
Author(s):  
Dao Ping Peng ◽  
Tao Huang ◽  
Chun Xiao Meng
Keyword(s):  
Porous Media ◽  
Background Noise ◽  
3D Visualization ◽  
Pore Space ◽  
Fluvial Sediments ◽  
X Ray ◽  
The Media ◽  
Micro Tomography ◽  
Grain Surface ◽  
Post Deposition

In order to investigate the change of internal structure of porous media caused by arsenic deposition, X-ray difference micro-tomography was used to characterize the distribution of arsenic aggregates within porous media by scanning a series of arsenic samples prepared in the laboratory and arsenic-rich fluvial sediments from the Río Loa in Chile. After image processing, background noise in the tomograms was reduced and arsenic information was enhanced. Then the processed images were used to generate 3D spatial distribution datasets of arsenic in the media. Tools like Avizo6 and Blob3D were used to reconstruct and visualize the 3D datasets. 3D visualization showed that arsenic accumulated in the pore space and grain surface; arsenic aggregates of different sizes had distinctly different morphologies, which small aggregates tended to be spherical while big aggregates were relatively flat. These results show that difference micro-tomography can be used to observe the pre- and post-deposition structure of porous media, without any destruction to the samples.

scholarly journals An X-ray computed micro-tomography dataset for oil removal from carbonate porous media

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Tannaz Pak ◽  
Nathaly Lopes Archilha ◽  
Iara Frangiotti Mantovani ◽  
Anderson Camargo Moreira ◽  
Ian B. Butler
Keyword(s):  
Porous Media ◽  
Oil Removal ◽  
X Ray ◽  
X Ray Computed ◽  
Micro Tomography

scholarly journals Pore formation during dehydration of a polycrystalline gypsum sample observed and quantified in a time-series synchrotron X-ray micro-tomography experiment

Solid Earth ◽  
2012 ◽  
Vol 3 (1) ◽  
pp. 71-86 ◽  
Author(s):  
F. Fusseis ◽  
C. Schrank ◽  
J. Liu ◽  
A. Karrech ◽  
S. Llana-Fúnez ◽  
...  
Keyword(s):  
Time Series ◽  
Pore Space ◽  
Three Dimensional ◽  
Internal Stresses ◽  
Micro Computed Tomography ◽  
X Ray ◽  
Computer Codes ◽  
Micro Tomography ◽  
Effective Drainage

Abstract. We conducted an in-situ X-ray micro-computed tomography heating experiment at the Advanced Photon Source (USA) to dehydrate an unconfined 2.3 mm diameter cylinder of Volterra Gypsum. We used a purpose-built X-ray transparent furnace to heat the sample to 388 K for a total of 310 min to acquire a three-dimensional time-series tomography dataset comprising nine time steps. The voxel size of 2.2 μm3 proved sufficient to pinpoint reaction initiation and the organization of drainage architecture in space and time. We observed that dehydration commences across a narrow front, which propagates from the margins to the centre of the sample in more than four hours. The advance of this front can be fitted with a square-root function, implying that the initiation of the reaction in the sample can be described as a diffusion process. Novel parallelized computer codes allow quantifying the geometry of the porosity and the drainage architecture from the very large tomographic datasets (20483 voxels) in unprecedented detail. We determined position, volume, shape and orientation of each resolvable pore and tracked these properties over the duration of the experiment. We found that the pore-size distribution follows a power law. Pores tend to be anisotropic but rarely crack-shaped and have a preferred orientation, likely controlled by a pre-existing fabric in the sample. With on-going dehydration, pores coalesce into a single interconnected pore cluster that is connected to the surface of the sample cylinder and provides an effective drainage pathway. Our observations can be summarized in a model in which gypsum is stabilized by thermal expansion stresses and locally increased pore fluid pressures until the dehydration front approaches to within about 100 μm. Then, the internal stresses are released and dehydration happens efficiently, resulting in new pore space. Pressure release, the production of pores and the advance of the front are coupled in a feedback loop.

scholarly journals Imaging of colloidal deposits in granular porous media by X-ray difference micro-tomography

2007 ◽  
Vol 34 (18) ◽  
Author(s):  
Jean-François Gaillard ◽  
Cheng Chen ◽  
Susa H. Stonedahl ◽  
Boris L. T. Lau ◽  
Denis T. Keane ◽  
...  
Keyword(s):  
Porous Media ◽  
X Ray ◽  
Granular Porous Media ◽  
Micro Tomography ◽  
Colloidal Deposits

Acoustic Wave Propagation in Saturated Porous Media

2013 ◽  
Author(s):  
Aliaksei Pazdniakou ◽  
Pierre M. Adler
Keyword(s):  
Porous Media ◽  
Wave Propagation ◽  
Acoustic Wave ◽  
Good Precision ◽  
Saturated Porous Media ◽  
Acoustic Wave Propagation ◽  
Lattice Spring Model ◽  
The Media ◽  
Micro Tomography ◽  
Computational Resources

Numerical tools were developed which are able to address acoustic wave propagation in dry and saturated porous media. Lattice methods, namely the lattice Boltzmann method (LBM) and the lattice spring model (LSM), can be successfully used for this purpose. The media are discretized by elementary cubes which can be obtained by computed micro-tomography [1]. Numerical results with a good precision can be obtained even for coarse geometry discretizations. Reasonable computational resources are necessary to obtain the results. The program codes can be parallelized in order to work with large samples.

scholarly journals Pore formation during dehydration of polycrystalline gypsum observed and quantified in a time-series synchrotron radiation based X-ray micro-tomography experiment

2011 ◽  
Vol 3 (2) ◽  
pp. 857-900 ◽  
Author(s):  
F. Fusseis ◽  
C. Schrank ◽  
J. Liu ◽  
A. Karrech ◽  
S. Llana-Fúnez ◽  
...  
Keyword(s):  
Time Series ◽  
Pore Space ◽  
Three Dimensional ◽  
Internal Stresses ◽  
Micro Computed Tomography ◽  
X Ray ◽  
Computer Codes ◽  
Micro Tomography ◽  
Effective Drainage

Abstract. We conducted an in-situ X-ray micro-computed tomography heating experiment at the Advanced Photon Source (USA) to dehydrate an unconfined 2.3 mm diameter cylinder of Volterra Gypsum. We used a purpose-built X-ray transparent furnace to heat the sample to 388 K for a total of 310 min to acquire a three-dimensional time-series tomography dataset comprising nine time steps. The voxel size of 2.2 μm3 proved sufficient to pinpoint reaction initiation and the organization of drainage architecture in space and time. We observed that dehydration commences across a narrow front, which propagates from the margins to the centre of the sample in more than four hours. The advance of this front can be fitted with a square-root function, implying that the initiation of the reaction in the sample can be described as a diffusion process. Novel parallelized computer codes allow quantifying the geometry of the porosity and the drainage architecture from the very large tomographic datasets (6.4 × 109 voxel each) in unprecedented detail. We determined position, volume, shape and orientation of each resolvable pore and tracked these properties over the duration of the experiment. We found that the pore-size distribution follows a power law. Pores tend to be anisotropic but rarely crack-shaped and have a preferred orientation, likely controlled by a pre-existing fabric in the sample. With on-going dehydration, pores coalesce into a single interconnected pore cluster that is connected to the surface of the sample cylinder and provides an effective drainage pathway. Our observations can be summarized in a model in which gypsum is stabilized by thermal expansion stresses and locally increased pore fluid pressures until the dehydration front approaches to within about 100 μm. Then, the internal stresses are released and dehydration happens efficiently, resulting in new pore space. Pressure release, the production of pores and the advance of the front are coupled in a feedback loop. We discuss our findings in the context of previous studies.

scholarly journals Assessment of Geometrical and Transport Properties of a Fibrous C/C Composite Preform Using x-ray Computerized Micro-tomography: Part I. Image Acquisition and Geometrical Properties

2005 ◽  
Vol 20 (9) ◽  
pp. 2328-2339 ◽  
Author(s):  
Olivia Coindreau ◽  
Gérard L. Vignoles
Keyword(s):  
Pore Space ◽  
Three Dimensional ◽  
Internal Surface ◽  
Carbon Composite ◽  
Internal Surface Area ◽  
X Ray ◽  
Geometrical Properties ◽  
Original Algorithm ◽  
Micro Tomography

Raw and partially infiltrated carbon–carbon composite preforms have been scanned by high-resolution synchrotron radiation x-ray computerized micro-tomography. Three dimensional high-quality images of the pore space have been produced at two distinct resolutions and have been used for the computation of geometrical quantities: porosity, internal surface area, pore sizes, and their distributions, as well as local and average fiber directions. Determination of the latter property makes use of an original algorithm. All quantities have been compared to experimental data with good results. Structural models appropriate for ideal families of cylinders are shown to represent adequately the actual pore space.

X-ray micro tomography in the scanning electron microscope

1978 ◽  
Vol 36 (1) ◽  
pp. 106-107 ◽  
Author(s):  
W. Brünger
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Target Surface ◽  
The Body ◽  
X Rays ◽  
Cross Sectional ◽  
X Ray ◽  
Micro Tomography ◽  
Scanning Electron

Reconstructive tomography is a new technique in diagnostic radiology for imaging cross-sectional planes of the human body /1/. A collimated beam of X-rays is scanned through a thin slice of the body and the transmitted intensity is recorded by a detector giving a linear shadow graph or projection (see fig. 1). Many of these projections at different angles are used to reconstruct the body-layer, usually with the aid of a computer. The picture element size of present tomographic scanners is approximately 1.1 mm2.Micro tomography can be realized using the very fine X-ray source generated by the focused electron beam of a scanning electron microscope (see fig. 2). The translation of the X-ray source is done by a line scan of the electron beam on a polished target surface /2/. Projections at different angles are produced by rotating the object.During the registration of a single scan the electron beam is deflected in one direction only, while both deflections are operating in the display tube.

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