scholarly journals Principles of positron porosimetry

Nukleonika ◽  
2015 ◽  
Vol 60 (4) ◽  
pp. 795-800 ◽  
Author(s):  
Radosław Zaleski
Keyword(s):  
Numerical Analysis ◽  
Pore Size ◽  
Pore Volume ◽  
Unique Feature ◽  
Positron Lifetime ◽  
Review Article ◽  
Empirical Parameter ◽  
Positron Annihilation Lifetime

Abstract The paper deals with positron porosimetry (PP), which is based on positron annihilation lifetime spectroscopy (PALS). The numerical analysis of positron lifetime spectra for PP is more demanding than in most of other applications of PALS. The resulting intensity distributions of ortho-positronium (o-Ps) lifetimes are interpreted in terms of the extended Tao-Eldrup (ETE) model, which provides the dependence between the o-Ps lifetime and pore size. Additionally, the relation between the intensity of an o-Ps component and the pore volume allows obtaining pore size distribution (PSD). The value of the empirical parameter Δ, which is dependent on material, can be estimated from the temperature dependence of an o-Ps lifetime. The most unique feature of PP among other techniques that allow determination of PSDs is its ability to perform measurements in almost any conditions. This makes this method suitable for various in situ studies. In this review article, both the capabilities and the limitations of PP are discussed. The methods to overcome some of the limitations are presented.

Preliminary Positron Lifetime Results on Free Volumes in Cyclodextrins

2010 ◽  
Vol 666 ◽  
pp. 99-102 ◽  
Author(s):  
Maria Fatima Ferreira Marques ◽  
A.M.G. Moreira Da Silva ◽  
P.M. Gordo ◽  
Z. Kajcsos
Keyword(s):  
Positron Annihilation ◽  
Free Volume ◽  
Positron Lifetime ◽  
Positron Annihilation Lifetime Spectroscopy ◽  
Positron Source ◽  
Lifetime Component ◽  
Positron Annihilation Lifetime ◽  
Long Lifetime

Positron annihilation lifetime spectroscopy was used to study the free-volume parameters in various pure -, - and -cyclodextrins samples and, in the case of β-cyclodextrin, with inclusion of S-carvone and thymoquinone. The results clearly indicate the presence of long lifetime components related to Ps-formation. The data show that the addition of S-carvone to β-cyclodextrin results in a decrease of o-Ps lifetime that we ascribe to a reduction of free volume holes from 81.8 to 63.7 Å3. The long lifetime component disappears when thymoquinone is added to -cyclodextrin, indicating this substance acts as an o-Ps quencher. For all samples studied, a decrease in the long lifetime component values was observed with increasing source in situ time, a result that might be attributed to the irradiation of the sample by the 22Na positron source.

scholarly journals Full-scale pore size distribution features of uranium-bearing sandstone in the northwest of Xinjiang, China

2021 ◽  
Vol 8 (5) ◽  
pp. 202036
Author(s):  
Sheng Zeng ◽  
Hao Li ◽  
Ni Zhang ◽  
Bing Sun ◽  
Jinzhu Li ◽  
...  
Keyword(s):  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Pore Volume ◽  
Gas Adsorption ◽  
Full Scale ◽  
Uranium Recovery ◽  
Distribution Features ◽  
Pore Types

As an important nuclear fuel, uranium in sandstone uranium deposits is mainly extracted by in situ leaching. The porosity of sandstone is one of the important indexes determining in situ leaching efficiency. Moreover, the microscopic pore size distribution (PSD) of the uranium-bearing layer has an important effect on porosity. It is necessary to feature the pore structure by various techniques because of the different pore types and sizes in the uranium layer. In this paper, combined with nitrogen gas adsorption, nuclear magnetic resonance techniques and scanning electron microscopy, the full-scale PSD features of uranium-bearing sandstone in the northwest of Xinjiang are effectively characterized. The results show that pores structure of uranium-bearing sandstone include dissolution pores ( d ≤ 50 nm), intergranular pores (50 nm < d ≤ 200 µm) and microfractures. Intergranular pores of 60 nm and 1 µm are the significant contributors to pore volume. The effects of the pore volume of two pore types (dissolution pores and intergranular pores) on the porosity of uranium-bearing sandstone are analysed. The results show that intergranular pores have the greater influence on the porosity and are positively correlated to the porosity. Dissolution pores have little effect on the porosity, but it is one of the key factors for improving uranium recovery. Moreover, the greater the difference of PSD between sandstones, the stronger the interlayer heterogeneity of uranium-bearing sandstone. This kind of interlayer heterogeneity leads to the change of permeability in the horizontal direction of strata. It provides a basis for a reasonable setting of well type and well spacing parameters.

Free Volume Determination of Azobenzene−PMMA Copolymer by a Pulsed Low-Energy Positron Lifetime Beam with in-Situ UV Illumination

2004 ◽  
Vol 37 (21) ◽  
pp. 8035-8042 ◽  
Author(s):  
John Algers ◽  
Peter Sperr ◽  
Werner Egger ◽  
Laszlo Liszkay ◽  
Gottfried Kögel ◽  
...  
Keyword(s):  
Free Volume ◽  
Positron Lifetime ◽  
Low Energy ◽  
Volume Determination ◽  
Uv Illumination

The measurement of the hydraulic permeability of saturated soil in situ . II

1953 ◽  
Vol 216 (1124) ◽  
pp. 72-89 ◽  
Keyword(s):  
Pore Size Distribution ◽  
Pore Size ◽  
Potential Distribution ◽  
Hydraulic Permeability ◽  
Two Dimensional ◽  
Capillary Fringe ◽  
Isotropic Media ◽  
Two Dimensional Flow

After a brief description of a new sand-tank laboratory and equipment for studying problems of the flow of fluids in porous materials, the remainder of the paper is devoted to an account of the application of a part of this equipment to a study of the flow of water between a pair of wells, such as is required for the determination of the permeability of the sand by the method described in part I. The potential distribution about the wells is found to conform sufficiently well with theory to justify the application of the analysis of part I, the interference due to the confining walls being satisfactorily negligible. The perturbation of the water table inseparable from the imposition of a potential difference between the wells is found not to invalidate the results based on an assumption of two-dimensional flow, while the corrections on account of the presence of a capillary fringe and a surface of seepage are satisfactorily made by adding to the measured depth of water in the well an increment equal to about half the thickness of the capillary fringe. The end correction for non-penetrating wells is also sufficiently well made by an addition to the measured depth of water; the magnitude of the correction is given for isotropic media for a well system of the dimensions used here, and the method of applying it to anisotropic media is indicated. The two-well method is used to estimate the permeability of the sand, which is then discussed in relation to the pore-size distribution. The elucidation of the permeability profile in a succession of strata is then discussed. Finally, techniques suited to work in the field are described, and a few preliminary fields results are quoted.

scholarly journals Determination of permeability of overconsolidated clay from pressuremeter pressure hold tests

2018 ◽  
Vol 55 (4) ◽  
pp. 514-527
Author(s):  
Lang Liu ◽  
David Elwood ◽  
Derek Martin ◽  
Rick Chalaturnyk
Keyword(s):  
Regression Analysis ◽  
Numerical Analysis ◽  
Laboratory Testing ◽  
Constant Pressure ◽  
Creep Effect ◽  
In Situ Conditions ◽  
Sample Recovery ◽  
Horizontal Permeability

A method was developed to interpret the horizontal permeability (kh) from pressuremeter pressure hold tests (PHTs) of approximately 3 min duration. The method relies on a regression analysis of the numerical analysis simulating the consolidation of clay under a constant pressure boundary during undrained expansion. The method was applied to a series of PHTs performed in deep clay formations in the Seattle area. The interpreted permeabilities are thought to be more representative of in situ conditions than those determined by laboratory testing by virtue of reduced disturbance during sample recovery and preparation. Results could be improved with a further exclusion of the creep effect on PHTs.

Pore Size Determination of TEMPO-Oxidized Cellulose Nanofibril Films by Positron Annihilation Lifetime Spectroscopy

2011 ◽  
Vol 12 (11) ◽  
pp. 4057-4062 ◽  
Author(s):  
Hayaka Fukuzumi ◽  
Tsuguyuki Saito ◽  
Shinichiro Iwamoto ◽  
Yoshiaki Kumamoto ◽  
Toshiyuki Ohdaira ◽  
...  
Keyword(s):  
Pore Size ◽  
Positron Annihilation ◽  
Positron Annihilation Lifetime Spectroscopy ◽  
Oxidized Cellulose ◽  
Size Determination ◽  
Cellulose Nanofibril ◽  
Positron Annihilation Lifetime

High-Temperature CO2 Capture Using MgO/γ-Al2O3 Materials as Adsorbent

2012 ◽  
Vol 476-478 ◽  
pp. 1811-1814 ◽  
Author(s):  
Xin Fu
Keyword(s):  
High Temperature ◽  
Pore Size ◽  
Pore Volume ◽  
Co2 Adsorption ◽  
In Situ Ftir ◽  
N2 Adsorption ◽  
Carbonate Species ◽  
Adsorption Desorption ◽  
Co2 Adsorbent

CO2 adsorbent, MgO/γ-Al2O3, was prepared by impregnation methods. The structure and surface properties of the prepared materials were characterized by XRD, N2 adsorption-desorption, in situ FIIR and CO2-TPD techniques. The results indicated that the surface area, pore size and pore volume of materials decreased with the introduction of MgO. Their capacity for CO2 adsorption could be significantly improved when the MgO loading increased from 0 to 10 wt %. CO2-TPD and in-situ FTIR showed that the materials have three basic sites which can react with CO2 to form bicarbonate, bidentate carbonate and monodentate carbonate species.

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