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    Wyświetlanie 1-12 z 12
    Tytuł:
    Liquation of Vycor Glasses - Study by Positron Annihilation Lifetime Method
    Autorzy:
    Jasińska, B.
    Dawidowicz, A. L.
    Radkiewicz, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/2024266.pdf
    Data publikacji:
    2001
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    78.70.Bj
    61.43.Gt
    Opis:
    Two Vycor glasses of different percentages of the components were liquated between 725 K and 950 K and leached in order to produce pores. Little intermolecular voids characterized by ortho-positronium lifetime valueτ$\text{}_{2}$≈1.5 ns were observed simultaneously. At the first stage of pore formation the intensity I$\text{}_{2}$ decreased considerably for both glasses, while at liquation temperatures higher than 825 K it increased again. The increase in I$\text{}_{2}$ resulted from changes in the properties of the bulk material. The growth ofτ$\text{}_{2}$ in this range of temperatures was also observed.
    Źródło:
    Acta Physica Polonica A; 2001, 99, 3-4; 379-384
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Aerogel IC3120 Under High Pressure Exerted Mechanically and by Nitrogen
    Autorzy:
    Gorgol, M.
    Zgardzińska, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/1033290.pdf
    Data publikacji:
    2017-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    78.70.Bj
    36.10.Dr
    61.43.Gt
    74.62.Fj
    Opis:
    Highly porous IC3120 silica aerogel was subjected to the high pressure up to 450 MPa while the positron annihilation lifetime spectra were collected. The pressure was delivered to the investigated samples in two ways: by pistons and by gas (nitrogen) penetrating the aerogel. The evolution of all PALS parameters was discussed. With the increase of the pressure, shortening of ortho-positronium lifetimes (different, depending on the pressure method introduced) was observed. Similarity between the dependence of the longest-lived o-Ps component lifetime on the pressure, for the sample affected with nitrogen molecules and pure nitrogen was observed. It suggests, that the nitrogen fills the largest free volumes of the aerogel. The pressure exerted mechanically causes much smaller decrease of free volume available for positronium. The comparison of PALS results with the electron microscopy images, obtained after removing the pressure, confirmed that more intense and lasting changes were caused by affecting the aerogel with the pistons.
    Źródło:
    Acta Physica Polonica A; 2017, 132, 5; 1531-1534
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Positron Porosimetry Studies of Template Removal from As-Synthesized MCM-41 Silica
    Autorzy:
    Zaleski, R.
    Wawryszczuk, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1812554.pdf
    Data publikacji:
    2008-05
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    78.70.Bj
    36.10.Dr
    61.43.Gt
    81.07.-b
    Opis:
    The course of template removal from MCM-41 pores was investigated by positron annihilation lifetime spectroscopy. Two methods of removal were the object of interest: a decarbonisation after standard calcination procedure and a novel procedure - pyrolysis in vacuum. The shapes of positron lifetime spectra of decarbonised sample are determined by positronium quenching caused by presence of carbon deposit on the surface. Positron annihilation lifetime spectroscopy allows also monitoring the evolution of empty space inside pores. During pyrolysis no conductive carbon is produced, so consecutive stages of template material transformation are easy to observe. In the case of pyrolysis the effect of pore emptying is obtained at temperature 500 K, lower comparing to calcination and decarbonisation (820 K).
    Źródło:
    Acta Physica Polonica A; 2008, 113, 5; 1543-1550
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Measurement and Analysis of the Positron Annihilation Lifetime Spectra for Mesoporous Silica
    Autorzy:
    Zaleski, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/2047164.pdf
    Data publikacji:
    2006-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    78.70.Bj
    36.10.Dr
    61.43.Gt
    81.07.-b
    41.75.Fr
    Opis:
    Positron annihilation lifetime spectroscopy as a technique of porous materials investigation is still under development. Both measurement conditions and lifetime spectra analysis methods have to be adapted to the requirements of positron porosimetry. If complex positron annihilation lifetime spectra of porous materials are processed, numerical methods of lifetime spectra analysis have to be used with a particular care. Among various methods of positron annihilation lifetime spectra analysis available, the most popular ones were tested implemented in programs MELT and LT. It was found, from the simulated spectra study, that a large number of counts in a spectrum is needed to obtain reliable results of analysis. Even then only an approximate solution is available. Determination of the approximation nature helps in a further interpretation of the results and in positron annihilation lifetime spectrometer setting adequate to the problem. For this purpose, a few complex spectra obtained from positron beam facility were tested. The results show a negligible influence of resolution function on long lifetime components, while the precise estimation of the background level is crucial. Also some distortions caused by imperfection of numerical analysis methods are pointed out.
    Źródło:
    Acta Physica Polonica A; 2006, 110, 5; 729-738
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Positron Annihilation Lifetime Spectroscopy Study of the Formation of Mesoporous Materials from the Zeolite Precursor
    Autorzy:
    Bosnar, S.
    Bosnar, D.
    Gržeta, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/1196124.pdf
    Data publikacji:
    2014-03
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    78.70.Bj
    81.05.Rm
    61.43.Gt
    Opis:
    In this work, positron annihilation lifetime spectroscopy was used for the structural characterisation of porous materials prepared from amorphous zeolite precursors acting as the starting materials and hexadecyltrimethylammonium bromide acting as a mesoporous template. The best fits of the obtained lifetime spectra provide a four-component exponential decomposition. The lifetime values of the long-lived components point to the presence of mesoporous voids. Infrared and X-ray analyses show that the obtained materials consist partly of a crystalline zeolite structure.
    Źródło:
    Acta Physica Polonica A; 2014, 125, 3; 775-777
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Testing the Extended Tao-Eldrup Model. Silica Gels Produced with Polymer Template
    Autorzy:
    Śniegocka, M.
    Jasińska, B.
    Wawryszczuk, J.
    Zaleski, R.
    Deryło-Marczewska, A.
    Skrzypek, I.
    Powiązania:
    https://bibliotekanauki.pl/articles/2043364.pdf
    Data publikacji:
    2005-05
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    78.70.Bj
    61.43.Gt
    Opis:
    The temperature dependence of o-Ps lifetime in the pores calculated from extended Tao-Eldrup model was compared to the experimental data, collected for a set of silica gels synthesized using the polymer template technique. For the sample with average pore radii 2.0 nm rather good agreement between the model and experiment was found. For the sample with narrow pores (near 1.0 nm) the lifetime spectrum was complex. Except the range of highest temperatures the lifetimes are far from model calculations.
    Źródło:
    Acta Physica Polonica A; 2005, 107, 5; 868-873
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Nanoporosity of Polymer Sorbents and Membrane Materials as Seen by PALS and Low Temperature Gas Sorption
    Autorzy:
    Shantarovich, V.
    Bekeshev, V.
    Kevdina, I.
    Yampolskii, Yu.
    Bermeshev, M.
    Belov, N.
    Powiązania:
    https://bibliotekanauki.pl/articles/1033916.pdf
    Data publikacji:
    2017-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    78.70.Bj
    61.43.Gt
    Opis:
    The limits of application of positron annihilation lifetime spectroscopy and low temperature gas sorption for studying nanoporosity of polymer sorbents and membrane materials are discussed relying on the results previously obtained by the authors. For the two methods, limitations are determined by different factors: the dispersion of the material is essential for low temperature gas sorption, while concentration of nanopores of given size is important for positron annihilation lifetime spectroscopy. The both methods came out to be a useful addition to each other in the studies of micropores and mesopores.
    Źródło:
    Acta Physica Polonica A; 2017, 132, 5; 1548-1551
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Controlled Porosity of MCM-41 Obtained by Partial Blocking of Pores by Silicon Oil
    Autorzy:
    Gorgol, M.
    Krasucka, P.
    Goworek, J.
    Zaleski, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/1033928.pdf
    Data publikacji:
    2017-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    78.70.Bj
    36.10.Dr
    61.43.Gt
    68.43.-h
    Opis:
    Partial blocking of mesopores in the ordered MCM-41 silica by DC550 silicon oil was proposed as a preparation method of the material with controlled porosity and fixed pore size. The porosity of the samples with various content of DC550 was examined with the use of low temperature nitrogen sorption and positron annihilation lifetime spectroscopy. It was shown that the oil blocks the primary pores by forming the plugs near its entrances, but also partially locates in the interparticle spaces. The comparison of the results obtained from both investigation techniques was used to make the first attempt to obtain the calibration of ortho-positronium intensity, depending on pore volume. This is necessary to improve the utility of positron annihilation lifetime spectroscopy as a porosimetric technique. The need to take the migration of positronium to larger free volume into account is discussed.
    Źródło:
    Acta Physica Polonica A; 2017, 132, 5; 1559-1563
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The Influence of the Temperature on Positron Annihilation Lifetime Spectra in Porous Sol-Gel Glass Doped with Ag Nanoparticles
    Autorzy:
    Gorgol, M.
    Jasińska, B.
    Reisfeld, R.
    Levchenko, V.
    Powiązania:
    https://bibliotekanauki.pl/articles/1196126.pdf
    Data publikacji:
    2014-03
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    78.70.Bj
    36.10.Dr
    65.60.+a
    61.43.Gt
    Opis:
    Silver nanoparticles with continuous size distribution from 10 to 20 nm were incorporated into porous glass produced using sol-gel technique. Positron annihilation lifetime spectroscopy was used to compare obtained material with an undoped reference glass. The positron annihilation lifetime spectroscopy measurement were made in a broad temperature range (from - 180C to 200°C). The experimental lifetime values were compared with the predictions of the extended Tao-Eldrup model of the temperature range. Experimental results for the reference material were in agreement with the model, except for a small discrepancy at low temperatures. In doped material substantial changes and non-monotonous temperature dependences of intensity and lifetime values were observed. Heating the material to 200C resulted in reorganization of the material structure.
    Źródło:
    Acta Physica Polonica A; 2014, 125, 3; 778-781
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Positrons and Positroniu m in Grainy and Porous Solids
    Autorzy:
    Kajcsos, Zs.
    Liszkay, L.
    Duplâtre, G.
    Varga, L.
    Lázár, K.
    Pál-Borbély, G.
    Beyer, H.
    Lohonyai, L.
    Caullet, P.
    Patarin, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/2025110.pdf
    Data publikacji:
    2001
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    78.70.Bj
    36.10.Dr
    61.43.Gt
    Opis:
    Systematic investigations have been performed using positron annihilation techniques on micrograins of crystalline powders (e.g., MgO, Al$\text{}_{2}$O$\text{}_{3}$, SiO$\text{}_{2}$) and on various zeolites (e.g., silicalite 1, Na-X, Na-Y, ZSM-5, mordenite) aiming at a better under standing of the formation and decay of the long-lived ortho-positronium states. The techniques were lifetime spectroscopy, Doppler-effect measurements and the recording of the full energy distribution of the annihilation radiation. The influences of heat treatment, sample evacuation and presence of gases were investigated. Lifetimes over 130 ns and o-Ps fractions of about 30% were found. A strong correlation of positron annihilation technique data with a water content of the samples was evidenced. Possible pictures of the formation and decay of ortho-positronium in porous media are discussed.
    Źródło:
    Acta Physica Polonica A; 2001, 99, 3-4; 399-406
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Positron and Positronium Trapping in Heat Treated Zeolites (Ceramics), the Effect of Swift Heavy Ion Irradiation
    Autorzy:
    Major, P.
    Kajcsos, Zs.
    Liszkay, L.
    Zalán, P.
    Kosanović, C.
    Bosnar, S.
    Subotić, B.
    Lázár, K.
    Skuratov, V.
    Havancsák, K.
    Gordo, P.
    Ferreira Marques, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1812537.pdf
    Data publikacji:
    2008-05
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    78.70.Bj
    61.43.Gt
    36.10.Dr
    61.80.Jh
    Opis:
    A systematic study of zeolite precursor gels, zeolites, and products of their recrystallization to ceramics was carried out in presence of various alkali ions. The investigation of radiation damage induced by high-energy ion beam irradiation with swift heavy ions (Bi ions at 670 MeV energy with $4×10^{12}$ ion/$cm^2$ fluence) was also included. The shortening of lifetimes found after irradiation in ceramics might probably be ascribed to interactions of o-Ps with free radicals and other quenching agents created through the ion irradiation. These lifetime-shortening interactions probably partly hide the o-Ps trapping in free volume sites.
    Źródło:
    Acta Physica Polonica A; 2008, 113, 5; 1441-1446
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Positronium Trapping in Porous Solids: Means and Limitations for Structural Studies
    Autorzy:
    Kajcsos, Zs.
    Liszkay, L.
    Duplâtre, G.
    Varga, L.
    Lohonyai, L.
    Pászti, F.
    Szilágyi, E.
    Lázár, K.
    Kótai, E.
    Pál-Borbély, G.
    Beyer, H. K.
    Caullet, P.
    Patarin, J.
    Azenha, M. E.
    Gordo, P. M.
    Lopes Gil, C.
    de Lima, A. P.
    Ferreira Marques, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/2042216.pdf
    Data publikacji:
    2005-05
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    36.10.Dr
    78.70.Bj
    61.43.Gt
    Opis:
    Positron annihilation techniques are used for the structural investigation of solids but the interpretation of results in grainy and porous media is still unclear. A unique picture can be obtained assuming that the dominant process is Ps trapping in competing "extended free volume" sites. In samples with a large amount of free volumes near-saturation Ps trapping will rule the lifetime pattern, and very long lifetimes of over 100 ns might arise from o-Ps trapped in mesopores. It is shown that lifetime parameters must be corrected for the 3γ/2γ counting efficiency ratio. The results demonstrate the high sensitivity of Ps to mesopores in zeolites but also that Ps-trapping poses limitations on the applicability of lifetime to structural investigation in porous systems. The evolution of the lifetime spectra upon changes in the sample and measuring conditions should be considered in a complex way, observing not only changes in some selected components but in the whole lifetime pattern simultaneously.
    Źródło:
    Acta Physica Polonica A; 2005, 107, 5; 729-737
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-12 z 12

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