Positronium Thermalization Process in Nanoporous Materials and its Influence on the Shape of PALS Spectrum

A new method of analysis of PALS spectra of porous materials is proposed. The model considers both the thermalization process of positronium inside the pores and the pore size distribution. The new model is fitted to spectra of mesoporous silica MCM-41 and MSF. The resulting parameters are compared with parameters obtained from fitting the “conventional” models, i.e. a sum of exponential components with discrete or/and distributed lifetimes.

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A New Method of Calculating Pore Size Distribution: Analysis of Adsorption Isotherms of N2 and CCl4 for a Series of MCM-41 Mesoporous Silicas

Journal of Colloid and Interface Science ◽

10.1006/jcis.2001.7715 ◽

2001 ◽

Vol 241 (1) ◽

pp. 127-141 ◽

Cited By ~ 16

Author(s):

Masako Hakuman ◽

Hiromitu Naono

Keyword(s):

Pore Size Distribution ◽

Pore Size ◽

Size Distribution ◽

Adsorption Isotherms ◽

Mesoporous Silicas ◽

New Method ◽

Distribution Analysis ◽

Mcm 41

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Coal Fly Ash Derived Silica Nanomaterial for MMMs—Application in CO2/CH4 Separation

Membranes ◽

10.3390/membranes11020078 ◽

2021 ◽

Vol 11 (2) ◽

pp. 78

Author(s):

Marius Gheorghe Miricioiu ◽

Violeta-Carolina Niculescu ◽

Constantin Filote ◽

Maria Simona Raboaca ◽

Gheorghe Nechifor

Keyword(s):

Fly Ash ◽

Pore Size Distribution ◽

Pore Size ◽

Size Distribution ◽

Coal Fly Ash ◽

High Surface ◽

Industrial Applications ◽

Mixed Matrix Membranes ◽

Co2 Removal ◽

Mcm 41

In order to obtained high selective membrane for industrial applications (such as natural gas purification), mixed matrix membranes (MMMs) were developed based on polysulfone as matrix and MCM-41-type silica material (obtained from coal fly ash) as filler. As a consequence, various quantities of filler were used to determine the membranes efficiency on CO2/CH4 separation. The coal fly ash derived silica nanomaterial and the membranes were characterized in terms of thermal stability, homogeneity, and pore size distribution. There were observed similar properties of the obtained nanomaterial with a typical MCM-41 (obtained from commercial silicates), such as high surface area and pore size distribution. The permeability tests highlighted that the synthesized membranes can be applicable for CO2 removal from CH4, due to unnoticeable differences between real and ideal selectivity. Additionally, the membranes showed high resistance to CO2 plasticization, due to permeability decrease even at high feed pressure, up to 16 bar.

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Probe material choice for nuclear magnetic resonance cryoporometry (NMRC) measurements of the nano-scale pore size distribution of unconventional reservoirs

Energy Exploration & Exploitation ◽

10.1177/0144598718802475 ◽

2018 ◽

Vol 37 (1) ◽

pp. 412-428

Author(s):

Feng Zhu ◽

Wenxuan Hu ◽

Jian Cao ◽

Biao Liu ◽

Yifeng Liu ◽

...

Keyword(s):

Nuclear Magnetic Resonance ◽

Magnetic Resonance ◽

Pore Size Distribution ◽

Porous Materials ◽

Pore Size ◽

Size Distribution ◽

Geological Samples ◽

Nano Scale ◽

Chloride Hexahydrate ◽

Nuclear Magnetic

Nuclear magnetic resonance cryoporometry is a newly developed technique that can characterize the pore size distribution of nano-scale porous materials. To date, this technique has scarcely been used for the testing of unconventional oil and gas reservoirs; thus, their micro- and nano-scale pore structures must still be investigated. The selection of the probe material for this technique has a key impact on the quality of the measurement results during the testing of geological samples. In this paper, we present details on the nuclear magnetic resonance cryoporometric procedure. Several types of probe materials were compared during the nuclear testing of standard nano-scale porous materials and unconventional reservoir geological samples from Sichuan Basin, Southwest China. Gas sorption experiments were also carried out on the same samples simultaneously. The KGT values of the probe materials octamethylcyclotetrasiloxane and calcium chloride hexahydrate were calibrated using standard nano-scale porous materials to reveal respective values of 149.3 Knm and 184 Knm. Water did not successfully wet the pore surfaces of the standard controlled pore glass samples; moreover, water damaged the pore structures of the geological samples, which was confirmed during two freeze-melting tests. The complex phase transition during the melting of cyclohexane introduced a nuclear magnetic resonance signal in addition to that from liquid in the pores, which led to an imprecise characterization of the pore size distribution. Octamethylcyclotetrasiloxane and calcium chloride hexahydrate have been rarely employed as nuclear magnetic resonance cryoporometric probe materials for the testing of an unconventional reservoir. Both of these materials were able to characterize pore sizes up to 1 μm, and they were more applicable than either water or cyclohexane.

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