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1
Content available Principles of positron porosimetry
Zaleski R.
Nukleonika
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2015
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Vol. 60, No. 4, part 1
795--800
EN
The paper deals with positron porosimetry (PP), which is based on positron annihilation lifetime spectroscopy (PALS). The numerical analysis of positron lifetime spectra for PP is more demanding than in most of other applications of PALS. The resulting intensity distributions of ortho-positronium (o-Ps) lifetimes are interpreted in terms of the extended Tao-Eldrup (ETE) model, which provides the dependence between the o-Ps lifetime and pore size. Additionally, the relation between the intensity of an o-Ps component and the pore volume allows obtaining pore size distribution (PSD). The value of the empirical parameter Δ, which is dependent on material, can be estimated from the temperature dependence of an o-Ps lifetime. The most unique feature of PP among other techniques that allow determination of PSDs is its ability to perform measurements in almost any conditions. This makes this method suitable for various in situ studies. In this review article, both the capabilities and the limitations of PP are discussed. The methods to overcome some of the limitations are presented.
2
Content available Positron annihilation lifetime spectroscopy study of roller burnished magnesium alloy
Zaleski R., Zaleski K., Gorgol M.
Nukleonika
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2015
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Vol. 60, No. 4, part 1
789--794
EN
The effect of roller burnishing on Vickers’ hardness and positron lifetimes in the AZ91HP magnesium alloy was studied. The microhardness increases with an increase in the burnishing force and with a decrease in the feed. The comparison of various methods of analysis of positron annihilation lifetime (PAL) spectra allowed identification of two components, which are related to solute-vacancy complexes and vacancy clusters, respectively. It was found that the increase in microhardness was related to the increase in the concentration of vacancy clusters.
3
Nieniszczące badania warstwy wierzchniej stali metodą wykorzystującą anihilację pozytonów
Zaleski K., Zaleski R.
Przegląd Mechaniczny
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2013
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nr 2
37--40
PL
Właściwości warstwy wierzchniej są bardzo ważną cechą elementów maszyn. W pracy przedstawiono wyniki badań doświadczalnych warstwy wierzchniej stali C45 i 100Cr6 metodami wykorzystującymi anihilację pozytonów Badane próbki były obrabiane metodą nagniatania wibracyjnego. Obróbka nagniataniem powodowała powstawanie ściskających naprężeń własnych w warstwie wierzchniej próbek. Badania anihilacji pozytonów były prowadzone metodą rozkładu kątowego promieniowania pochodzącego z anihilacji dwufotonowej pozytonów oraz spektroskopii czasów życia pozytonów Na podstawie wyników badań stwierdzono, że naprężenia własne w warstwie wierzchniej badanych stali mają wpływ na parametry anihilacji pozytonów.
EN
Properties of the surface layer are very important feature of machine elements. In the paper the results of the surface layer study by positron annihilation methods have been presented for 45C and 100Cr6 steels. Tested samples were treated by vibratory shot peening. The shot peening treatment created compressive residual stresses in the surface layer of the samples. Angular distribution of the two-quanta annihilation radiation and positron annihilation lifetime spectroscopy were used in the study. Results of the experiment revealed, that various residual stresses in the surface layer of the tested steels reflect in different positron annihilation parameters.
4
Content available Ortho-positronium migration in mesopores of MCM-41, MSF and SBA-3
Zaleski R., Błażewicz A., Kierys A.
Nukleonika
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2013
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Vol. 58, No. 1
235-240
EN
Three materials: MCM-41, MSF and SBA-3 with a very similar pore diameter but different lengths of cylindrical pores were investigated using the nitrogen sorption method and positron annihilation lifetime spectroscopy. The size of primary pores and interparticle spaces obtained by both methods is similar. However, volume ratios between the discussed kinds of pores found by the above-mentioned methods differ significantly. Such discrepancy is the result of both ortho-positronium migration and the inaccessibility of the pores for nitrogen. Comparing the results of nitrogen sorption and positron annihilation lifetime spectroscopy allows us to estimate that connectivity between the primary pores and the interparticle spaces is the highest in MCM-41 and lowest in SBA-3.
5
Content available Gas filling of SBA - 15 silica micropores probed by positron annihilation lifetime spectroscopy (PALS)
Gorgol M., Zaleski R., Kierys A.
Nukleonika
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2013
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Vol. 58, No. 1
229-233
EN
Positron annihilation lifetime measurements were conducted in situ while two gasses (nitrogen and oxygen, respectively) were introduced into the SBA-15 porous silica sample. Slow changes in lifetime spectra were observed during a long lasting gas interaction with the sample. Introduced gases slowly filled the free volumes, starting from the smallest ones, especially small micropores. In the presence of a gas, the rate of change of ortho-positronium (o-Ps) and unbound positron intensity was larger than the rate of change of lifetime. This suggests the existence of an additional process, which reduces the number of ortho-positronium atoms due to the interaction with the gas. Moreover, the process of filling pores with gas was slower than the process of emptying them while the gas was pumped out.
6
Content available Positron annihilation study of iron oxide nanoparticles in mesoporous silica MCM-41 template
Surowiec Z., Wiertel M., Zaleski R., Budzyński M., Goworek J.
Nukleonika
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2010
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Vol. 55, No. 1
91-96
EN
The subject of investigation were the samples obtained by impregnation of MCM-41 template with an aqueous solution prepared from Fe(NO3)3ź9H2O. As a result of such a procedure, iron oxides deposits on MCM-41 were formed. The Mössbauer studies revealed an occurrence of Fe3O4 nanocrystallites in the both ferri- and superparamagnetic states. Almost 80% small particles exist in a paramagnetic state. The positron annihilation lifetime spectroscopy (PALS) spectra were measured in air or in vacuum. The long-lived ortho-positronium (o-Ps) components and their intensities are time dependent due to air molecules interaction with iron oxide nanocrystallites and silica walls surfaces. The adsorption of air on the nanocrystallites surface causes a total screening of their surface and a raise of the o-Ps lifetime values. Observed anti-quenching effect is a result of competition of two phenomena: practically switching off a pick-off mechanism related to interaction of o-Ps with magnetite nanoparticles and considerably weaker usual quenching by paramagnetic oxygen molecules.
7
Content available Positron annihilation lifetime spectroscopy study of thermal processing and rehydration of dry leek (Allium porrum L.)
Zaleski R., Wawryszczuk J., Sobczak K.
Nukleonika
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2010
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Vol. 55, No. 1
73-78
EN
New application of positron annihilation lifetime spectroscopy (PALS) to development of food processing techniques is tested. Dehydrated leeks were an object of the study. Three experiments were performed consisting of evacuating air and volatile compounds from the sample, applying thermal treatment and rehydrating the sample. Distinct changes in positron lifetime spectra allowed the monitoring of alterations in the sample structure. The most likely origin of the particular components present in the spectra was able to be proposed from these data. Changes of the components were ascribed to the various processes occurring in the samples.
8
Rola pomiarów związków furanu w ocenie procesów cieplnych zachodzących w izolacji celulozowej
Słowikowska H., Słowikowski J., Zaleski R.
Energetyka
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2009
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nr 6
349-353
PL
Na podstawie literatury przedmiotu i wyników własnych badań omówiono rolę pomiarów koncentracji związków furanu w próbce oleju, pobieranej z pracującego transformatora, w ocenie intensywności i lokalizacji przegrzań miejscowych izolacji celulozowej. Wskazano ponadto na rolę podstawowego związku furanu, jakim jest 2-furfural (2FAL), w oszacowaniu stopnia „zużycia” zwojowej izolacji papierowej.
EN
Discussed is the role, on the basis of specialized technical literature and the authors’ own reasearch results, of furane compounds concentration measurements in oil samples drawn from working transformer, in the assessment of intensity and localization of local overheats in cellulose insulation. Moreover, indicated is the role of a basic furane compound which is 2-furfural (2FAL) in assessment of paper turn insulation „wear-out” degree.
9
Podstawy oceny opłacalności modernizacji transformatorów
Malewski R., Subocz J., Szrot M., Płowucha J., Zaleski R.
Energetyka
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2006
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nr 12
884-891
PL
Przedstawiono generalne uwarunkowania rynkowe, które stymulują rewitalizację majątku sieciowego przedsiębiorstw dystrybucyjnych oraz produkujących energię elektryczną. Zaprezentowano najważniejsze metody pozwalające dokonać kompleksowej oceny stanu technicznego oraz przeanalizowano główne techniczno-ekonomiczne składniki kosztów modernizacyjnych, które mogą wspomagać proces decyzyjny w zakresie zarządzania populacją transformatorów. Decyzja o wymianie bądź modernizacji transformatora stanowi istotny czynnik przy planowaniu budżetu przedsiębiorstwa. Podjęcie racjonalnej decyzji wymaga wykonania specjalistycznych badań stanu technicznego transformatora.
EN
Described are general market conditions stimulating revitalization of power network assets belonging to distribution companies and electric power firms. Presented are the most important methods allowing to carry out the technical state complex evaluation and analysed are main technical and economical modernization cost elements which can help in decision processes concerning transformer population management. Deciding whether to replace or only modernize the transformer is a vital thing when you plan your company budget but it needs carrying out the transformer technical state specialized tests.
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