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Wyświetlanie 1-3 z 3
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:
Impact of Impulse Shot Peening Parameters on Properties of Stainless Steel Surface
Autorzy:
Wiertel, M.
Zaleski, K.
Gorgol, M.
Skoczylas, A.
Zaleski, R.
Powiązania:
https://bibliotekanauki.pl/articles/1033967.pdf
Data publikacji:
2017-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.65.-b
81.20.Wk
62.20.Qp
61.72.-y
78.70.Bj
Opis:
Shot peening was applied to austenitic stainless steel 1.4541 (EN). The surface treatment was performed at various impact energies E, impact densities j and ball diameters D. This resulted in improved microhardness, which increases monotonically with the increase of E, j and 1/D. However, its changes with E and j achieve saturation at about 400 HV0.1. On the contrary, no saturation is observed in the investigated range for 1/D. In the un-shot peened 1.4541 (EN) steel, the lifetime component of low intensity was found with use of positron annihilation lifetime spectroscopy (PALS). It corresponds to positron annihilation from delocalized state of positrons in bulk. In the shot peened samples the bulk component is no longer observed. Instead, two types of defects can be identified: vacancy-like defects coupled with edge dislocations and vacancies or their small clusters (consisting 3÷5 vacancies). The results of PALS and hardness testing do not correspond very well, especially in the case of the samples shot peened with balls of varying diameters. The most probable reason for this are different depth profiles of both methods. It seems that the defects, which are responsible for the increase of static microhardness above 400 HV0.1 are located mostly below the surface layer penetrated by positrons.
Źródło:
Acta Physica Polonica A; 2017, 132, 5; 1611-1615
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
    Wyświetlanie 1-3 z 3

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