Pore structure and its impact on CH4 adsorption capability and diffusion characteristics of normal and deformed coals from Qinshui Basin

2015 ◽  
Vol 10 (1) ◽  
pp. 94 ◽  
Author(s):  
Shou qing Lu ◽  
Yuan ping Cheng ◽  
Wei Li ◽  
Liang Wang
Keyword(s):  
Pore Structure ◽  
Qinshui Basin ◽  
Diffusion Characteristics ◽  
And Diffusion ◽  
Adsorption Capability

The Effect of Leaching on the Pore Structure of Cement-Based Grouts for Use in Nuclear Fuel Waste Disposal

1990 ◽  
Vol 212 ◽  
Author(s):  
M. Onofrei ◽  
M. N. Gray ◽  
D. Breton ◽  
G. Ballivy
Keyword(s):  
Pore Structure ◽  
Total Porosity ◽  
Cementitious Materials ◽  
X Ray ◽  
Diffusion Characteristics ◽  
Deep Geological Disposal ◽  
Porosity And Permeability ◽  
Nuclear Fuel Waste ◽  
And Diffusion

ABSTRACTResearch on the longevity of cement-based grout materials for sealing a deep geological disposal vault is an important aspect of the Canadian and other nuclear waste management programs. These studies include assessments of the chemical durability of cement grouts, and the effects of leaching and phase transformation on the long-term hydraulic and diffusion characteristics of grouts.This paper presents the results of laboratory studies carried out to assess the effects of leaching of cement phases on the pore structure of hardened grouts. Measurements of mercury intrusion and scanning electron microscopy with energy dispersive x-ray analysis, have been used to investigate the changes in pore structure of both a reference grout (90% Type 50 cement, 10% silica fume, water-to-cementitious materials ratio between 0.4 and 0.7) and ALOFIX-MC (a fine cement product of Japan), as a function of leaching time.The work discussed here reveals that the porosity of hardened grout does change during leaching, but within limits that depend on grout composition and initial porosity. The results confirm that the materials have the potential to self-seal and maintain their performance for longer periods than those currently predicted by longevity models.Our studies of the porosity and permeability of grouts suggest that pore size distribution rather than total porosity is the more important parameter in determining longevity.

Organic Heterojunctions for Photovoltaic Applications: C60 Growth on Pentacene

2010 ◽  
Vol 1263 ◽  
Author(s):  
Rebecca Ann Cantrell ◽  
Paulette Clancy
Keyword(s):  
Atomic Scale ◽  
Short Axis ◽  
Energy Functions ◽  
Potential Energy Functions ◽  
The North ◽  
Diffusion Characteristics ◽  
Static Energy ◽  
Semi Empirical ◽  
Organic Heterojunctions ◽  
And Diffusion

AbstractUsing atomic-scale Molecular Dynamics (MD) and energy minimization techniques in conjunction with semi-empirical MM3 potential energy functions, we consider the adsorption of a C60 molecule on a series of hypothetical pentacene structures that vary only in the tilt of the angle that the short axis of the pentacene molecules makes with the underlying surface (the long axis lying essentially flat, as on a metal substrate). Important relationships were discovered between the angle adopted by the short axis of pentacene on the surface, φ1, and the adsorption and diffusion characteristics of C60. Static energy calculations show that there is a transition of the deepest energy minima from between the pentacene rows at low values of φ1 to within the rows at high values of φ1, where φ1 is the angle the pentacene short axis makes with the surface. MD confirms this trend by the predominant residence locations at the extreme φ1 values. Furthermore, MD results suggest that the C60 traverses the pentacene surface in the east-west direction for lower φ1 values (φ1 ≤ 40°) and in the north-south direction for higher φ1 values (φ1 ≥ 70°). Taking both static and dynamic results together, the most favorable tilt angles for mono-directional nanowire growth should occur between 70° and 80° off-normal.

scholarly journals Experimental and Simulation Studies on Adsorption and Diffusion Characteristics of Coalbed Methane

Energies ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 3445 ◽  
Author(s):  
Donghyeon Kim ◽  
Youngjin Seo ◽  
Juhyun Kim ◽  
Jeongmin Han ◽  
Youngsoo Lee
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Coalbed Methane ◽  
Equilibrium Time ◽  
Diffusion Characteristics ◽  
Adsorbed Methane ◽  
Cbm Production ◽  
Lump Coal ◽  
And Diffusion

Coalbed methane (CBM) content is generally estimated using the isotherm theory between pressure and adsorbed amounts of methane. It usually determines the maximum content of adsorbed methane or storage capacity. However, CBM content obtained via laboratory experiment is not consistent with that in the in-situ state because samples are usually ground, which changes the specific surface area. In this study, the effect of the specific surface area relative to CBM content was investigated, and diffusion coefficients were estimated using equilibrium time analysis. The differences in adsorbed content with sample particle size allowed the determination of a specific surface area where gases can adsorb. Also, there was an equilibrium time difference between fine and lump coal, because more time is needed for the gas to diffuse through the coal matrix and adsorb onto the surface in lump coal. Based on this, we constructed a laboratory-scale simulation model, which matched with experimental results. Consequently, the diffusion coefficient, which is usually calculated through canister testing, can be easily obtained. These results stress that lump coal experiments and associated simulations are necessary for more reliable CBM production analysis.

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