Influence of Atmospheric Gases Present in the Pores of MCM-41 on Lifetime of Ortho-Positronium

2010 ◽  
Vol 666 ◽  
pp. 123-128 ◽  
Author(s):  
Radosław Zaleski ◽  
Michał Sokół
Keyword(s):  
Porous Material ◽  
Pore Size ◽  
Reasonable Agreement ◽  
Size Distributions ◽  
Spectroscopy Data ◽  
Atmospheric Gases ◽  
Positron Annihilation Lifetime ◽  
Pore Size Distributions ◽  
Mcm 41 ◽  
Quenching By Oxygen

The modification of the extended Tao-Eldrup model accounting ortho-positronium quenching in air is presented. Taking into account quenching by oxygen molecules adsorbed on the surface of porous material gives reasonable agreement between results of the model and the experimental positron annihilation lifetime spectroscopy data. Pore size distributions calculated using this model from the spectra for MCM 41 mesoporous sieve obtained in air, oxygen or vacuum are compared and discussed taking into account effect of ortho-positronium migration from small open pores to the larger ones. The rates of ortho-positronium quenching by air (47.2 µs-1 MPa 1), oxygen (220 µs-1 MPa-1) or nitrogen (1.7 µs-1 MPa-1) obtained from pressure dependences of the lifetimes observed in MCM 41 agree reasonably with the experimental results of other authors, if the correction for oxygen adsorbed on the surface is applied.

Ni and Cu Incorporated Mesoporous Nanocomposite Catalytic Materials

2008 ◽  
Vol 8 (2) ◽  
pp. 549-556 ◽  
Author(s):  
Asli Nalbant ◽  
Timur Dogu ◽  
Suna Balci
Keyword(s):  
Pore Size ◽  
Surface Area ◽  
Atomic Ratio ◽  
Nanocomposite Materials ◽  
Size Distributions ◽  
Hydrothermal Route ◽  
Average Pore ◽  
Pore Size Distributions ◽  
Xrd Patterns ◽  
Mcm 41

Nickel and copper incorporated MCM-41-like mesoporous nanocomposite materials prepared by the direct hydrothermal synthesis and the impregnation procedures showed highly attractive pore structure and surface area results for catalytic applications. The XRD patterns showed that characteristic MCM-41 structure was preserved for the materials synthesized following an impregnation procedure before the calcination step. The surface area of the Cu impregnated material with a quite high Cu/Si atomic ratio (0.19) was 631 m2/g. Very narrow pore size distributions with an average pore diameter of about 2.7 nm were obtained as a result of plugging of some of the smaller pores by Cu nanoballs. For lower metal to Si ratios (for instance for Ni/Si = 0.06) much higher surface area values (1130 m2/g) were obtained. In the case of nanocomposite materials synthesized by the direct hydrothermal route, MCM-41 structure was not destroyed for samples containing metal to Si atomic ratios as high as 0.12. In the case of materials containing Cu/Si and Ni/Si ratios over 0.2 wider pore size distributions and some decrease of surface area were observed.

Controlling pore size distributions of MCM-41 by direct synthesis

1996 ◽  
Vol 7 (4) ◽  
pp. 173-185 ◽  
Author(s):  
Chih Ning Wu ◽  
Tz Sheng Tsai ◽  
Chyan Neng Liao ◽  
Kuei Jung Chao
Keyword(s):  
Pore Size ◽  
Direct Synthesis ◽  
Size Distributions ◽  
Pore Size Distributions ◽  
Mcm 41

CHARACTERIZATION OF PORE SIZE DISTRIBUTIONS USING NON-NEWTONIAN FLUIDS

2020 ◽  
Author(s):  
Scott C. Hauswirth ◽  
◽  
Majdi Abou Najm ◽  
Christelle Basset
Keyword(s):  
Pore Size ◽  
Newtonian Fluids ◽  
Size Distributions ◽  
Pore Size Distributions

Preparation of P(GMA-co-EGDMA) Monolithic Columns with Adjustable Porous Properties

2014 ◽  
Vol 936 ◽  
pp. 942-949 ◽  
Author(s):  
Hao Tian Zhang ◽  
Qiu Yu Zhang ◽  
Bao Liang Zhang ◽  
Chun Mei Li
Keyword(s):  
Pore Size ◽  
Monolithic Column ◽  
Organic Polymer ◽  
Monolithic Columns ◽  
Size Distributions ◽  
Notable Effect ◽  
Pore Size Distributions ◽  
Porous Properties ◽  
Glass Tubes ◽  
First Time

Porous properties have notable effect on separating effect of organic polymer-based monolithic column. Different applications of monolithic columns require tailored pore size distributions. On account of that, P(GMA-co-EGDMA) monolithic columns were prepared with novel ternary porogenic agents. Glass tubes was chosen as polymerization mold. Moreover, factors influencing the inner pore morphology, pore size and specific surface area were investigated systematically. The results showed that the increasing of the solubility of porogenic agents and the amount of crosslinker, the decreasing of the amount of porogenic agents and temperature rising all could give rise to the decreasing of pore size. Remarkably, the effect of initiator was studied for the first time. The results showed that amount of initiator had no remarkable influence on porous properties. By controlling effect factors, P(GMA-co-EGDMA) Monolithic Columns with pore size from dozens to thousands of nanometer, which can be applied in separation of molecules with different size.

Coal pore size distributions controlled by the coalification process: An experimental study of coals from the Junggar, Ordos and Qinshui basins in China

Fuel ◽  
2017 ◽  
Vol 206 ◽  
pp. 352-363 ◽  
Author(s):  
Yong Li ◽  
Cheng Zhang ◽  
Dazhen Tang ◽  
Quan Gan ◽  
Xinlei Niu ◽  
...  
Keyword(s):  
Experimental Study ◽  
Pore Size ◽  
Size Distributions ◽  
Pore Size Distributions

A New X-Ray Scattering Method for Determining Pore-Size Distribution in Low-k Thin Films

2001 ◽  
Vol 714 ◽  
Author(s):  
Kazuhiko Omote ◽  
Shigeru Kawamura
Keyword(s):  
Thin Films ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Gas Adsorption ◽  
Size Distributions ◽  
X Ray ◽  
X Ray Scattering ◽  
Pore Size Distributions ◽  
Scattering Technique ◽  
Ray Scattering

ABSTRACTWe have successively developed a new x-ray scattering technique for a non-destructive determination of pore-size distributions in porous low-κ thin films formed on thick substrates. The pore size distribution in a film is derived from x-ray diffuse scattering data, which are measured using offset θ/2θ scans to avoid strong specular reflections from the film surface and its substrate. Γ-distribution mode for the pores in the film is used in the calculation. The average diameter and the dispersion parameter of the Γ-distribution function are varied and refined by computer so that the calculated scattering pattern best matches to the experimental pattern. The technique has been used to analyze porous methyl silsesquioxane (MSQ) films. The pore size distributions determined by the x-ray scattering technique agree with that of the commonly used gas adsorption technique. The x-ray technique has been also used successfully determine small pores less than one nanometer in diameter, which is well below the lowest limit of the gas adsorption technique.

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