Wyniki wyszukiwania - BazTech

1

Localized states in nanocarbons

Kempiński W., Kempiński M., Markowski D., Łoś M.

Nukleonika

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2013

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Vol. 58, No. 3

371--373

EN

Localization phenomenon is studied in different modern nanocarbon materials: pristine C60, C60-fullerides, carbon nanotubes and graphene-based structures in the form of activated carbon fibers built of quantum dot-like basic structural units. Two experimental methods are used to define the localization and population control of spins (charge carriers) in the nanocarbon materials – electron paramagnetic resonance (EPR) and direct current (d.c.) electrical conductivity measurements. Results are discussed in the frame of the possible applications of the aforementioned materials in the molecular electronics or spintronics.

2

Determination of limit pore size distributions of porous materials from mercury intrusion curves

Cieszko M., Kempiński M.

Engineering Transactions

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2006

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Vol. 54, iss. 2

143-158

EN

The application of the capillary and chain models of pore architecture are proposed in the paper for determination of limit pore size distributions of porous materials based on the mercury intrusion curves. They estimate the range of pore sizes in the investigated material. It is proved that for a given pore size distribution, the capillary model of pore architecture, commonly used in the mercury porosimetry, and its chain model, are two limit cases of the network model of pore architecture, considered in the paper as a proper model for most real porous materials. For both limit pore architectures, the expressions describing capillary potential curves have been derived that are the basis for the procedure of determination of two limit pore size distributions. This procedure has been illustrated by determining the limit distributions for porous materials made of sintered glass beads.

3

Zastosowanie granicznych modeli przestrzeni porów do interpretacji danych porozymetrii rtęciowej

Cieszko M., Kempiński M.

Zeszyty Naukowe. Mechanika / Akademia Techniczno-Rolnicza w Bydgoszczy

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2004

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Z. 54(243)

75-88

PL

W pracy zaproponowano wykorzystanie kapilarnego i łańcuchowego modelu architektury porów do wyznaczania granicznych rozkładów wymiarów porów materiałów porowatych w oparciu o krzywe potencjału kapilarnego otrzymywane metodą wciskania rtęci. Określają one zakres występowania rozkładu wymiarów porów badanego materiału. Wykazano, że model kapilarny, standardowo wykorzystywany w porozymetrii rtęciowej, oraz model łańcuchowy są dwoma granicznymi przypadkami modelu sieciowego architektury porów dla danego rozkładu ich wymiarów. Analizę przeprowadzono w oparciu o wzory dla potencjału kapilarnego warstwy ośrodka o kapilarnej i łańcuchowej architekturze porów, dla dwustronnego wciskania rtęci.

EN

The distribution of pore diameters is the fundamental characteristics of microscopic pore space structure of porous materials. It enables one to determine basic macroscopic parameters of such materials (e.g. volume porosity, permeability or internal surface) that play important role in many physical and chemical processes appearing in permeable porous materials (e.q. filtration, transport of mass, momentum and energy, wave propagation or chemical reaction). The wide spread method of determination of pore diameters consists in the interpretation of capillary potential curves obtained from measurement of mercury intrusion into porous sample or from measurement of volume of wetting fluid (water or ethyl alcohol) removed from sample (e.g. by gas extrusion) at progressively increasing pressure. Such interpretation is based on the assumption that at increasing pressure the mercury is intrudes against the capillary forces in pores of decreasing diameter. It is equivalent to the assumption that the pore structure of real porous material can be modeled by a bundle of capillaries with random distribution of diameters. Similarly, the data obtained from fluid extrusion are interpreted. That simplified model, however, do not take into account the very common situations appearing in real porous material, where large pores are often joined with other pores by narrow necks. It unable the mercury to fulfill these large pores at pressure corresponding to their diameter. As a result the curves of pore diameter distribution determined in such way reduce the volume of large pores contained in measured material, enlarging the real volume of small pores. The purpose of this paper is to present the method of determination of limit pore size distribution in porous material based on interpretation experimental capillary potential curves obtained from the mercury intrusion measurement. It is shown that the capillary and chain models of pore architecture applied in the paper are the limit cases of the web model for a given pore size distribution and distributions obtained on the basis of these models determine the range of occurrence of pore size distributions if investigated material.

4

Zastosowanie łańcuchowego modelu struktury porów do interpretacji danych porozymetrii rtęciowej

Cieszko M., Kempiński M., Dubas M.

Zeszyty Naukowe Katedry Mechaniki Stosowanej / Politechnika Śląska

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2002

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nr 18

69-74

PL

W pracy zaproponowano wykorzystanie łańcuchowego modelu struktury porów do wyznaczania rozkładu wymiarów porów materiałów jjerowatych w oparciu o krzywe potencjału kapilarnego otrzymywane metodą porozymetrii rtęciowej. Wykazano, że rozmiary porów wyznaczone na podstawie modelu łańcuchowego są o 30 - 60 % większe od wartości wyznaczonych w oparciu o model kapilarny, standardowo wykorzystywany do interpretacji danych eksperymentalnych porozymetrii rtęciowej.

EN

In the paper the chain model of pore structure is applied to determination of pore diameters distribution in porous materials based on capillary potential curves obtained from mercury intrusion porosimetry data. It was shown that pore diameters determined from chain model of pore structure are about 30 - 60 % greater than that obtained from capillary model usually used to interpretation of mercury intrusion data.