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Tytuł:
Use of Energy Summing for Selection of Coincidence Events in Positron-Lifetime Spectroscopy
Autorzy:
Bec̆vár̆, F.
C̆iz̆ek, J.
Procházka, I.
Powiązania:
https://bibliotekanauki.pl/articles/2007883.pdf
Data publikacji:
1999-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
A BaF$\text{}_{2}$ positron-lifetime spectrometer equipped with a coincidence system that represents a compromise between the traditional fast-fast and fast-slow arrangements is described. The main difference of the present configuration from both the fast-slow and fast-fast ones consists in use of a sum of the energy signals from the start and stop detectors to select the coincidence events. Quality of the spectrometer response function (≈ 150 ps FWHM for $\text{}^{22}$Na) is very close to that observed for our fast-slow configuration with the equivalent detectors but throughput of the present apparatus is increased almost by a factor of two. Moreover, the electronic scheme becomes less complicated, which has also a positive impact on its cost.
Źródło:
Acta Physica Polonica A; 1999, 95, 4; 448-454
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:
Relaxation of Free Volume in Polycarbonate and Polystyrene Studied by Positron Annihilation Lifetime Spectroscopy
Autorzy:
Cangialosi, D.
Wübbenhorst, M.
Schut, H.
Picken, S. J.
Powiązania:
https://bibliotekanauki.pl/articles/2042204.pdf
Data publikacji:
2005-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
82.35.Lr
64.70.Kb
Opis:
We present the time evolution of polycarbonate and polystyrene free volume probed by positron annihilation lifetime spectroscopy, which occurs after thermal rejuvenation above the glass transition temperature (T$\text{}_{g}$) and after plastic deformation via cold rolling. The ortho-positronium (τ$\text{}_{o-Ps}$) lifetime and its intensity (I$\text{}_{o-Ps}$) are used to characterise, respectively, size and concentration of the free volume holes. Our results suggest that the effect of plastic deformation on the polymer microstructure is far different from that of a thermally rejuvenated sample contrarily to common beliefs. In particular, plastic deformation results in an increase inτ$\text{}_{o-Ps}$ and a decrease in I$\text{}_{o-Ps}$, whereas rejuvenation above T$\text{}_{g}$ results in an increase in I$\text{}_{o-Ps}$ whileτ$\text{}_{o-Ps}$ remains unchanged. In addition, physical aging below T$\text{}_{g}$ after plastic deformation manifests as a reduction of τ$\text{}_{o-Ps}$, whereas a decrease in I$\text{}_{o-Ps}$ is observed after thermal rejuvenation. These results corroborate the idea of an amorphous-amorphous transition induced by plastic deformation.
Źródło:
Acta Physica Polonica A; 2005, 107, 4; 690-696
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analiza porównawcza struktury wewnętrznej implantów hydrofilowych oraz hydrofobowych stosowanych w chirurgii okulistycznej metodą spektroskopii czasów życia pozytonów
Comparative analysis of internal structures of hydrophilic and hydrophobic implants applied in ophthalmology by means of positron annihilation lifetime spectroscopy
Autorzy:
Chamerski, K.
Powiązania:
https://bibliotekanauki.pl/articles/134780.pdf
Data publikacji:
2015
Wydawca:
ADVSEO
Tematy:
soczewki wewnątrzgałkowe
anihilacja pozytonów
wolna objętość
wielozadaniowość
hydrofilowość
hydrofobowość
chromofory
intraocular lenses
positron annihilation
free volume
multivacancies
hydrophilicity
hydrophobicity
chromophores
Opis:
In presented work internal structures of intraocular lenses were analyzed in terms of defectiveness degree. Studies were conducted by means of positron annihilation lifetime spectroscopy method PALS. The aim of the work was determination of basic parameters describing annihilation centers in research materials, such as positron lifetime in bulk material, mean positron lifetime in the internal structure, positron trapping rate by trapping centers as well as free volumes dimensions. In obtained results differences in free volumes and positron traps concentrations between hydrophilic and hydrophobic materials were noted. Furthermore, comparison of materials with and without blue light chromophores revealed differences in positron trapping rate by multivacancy-like free spaces. Achieved results were referenced for mechanical properties of the studied materials.
Źródło:
Technical Issues; 2015, 3; 3-10
2392-3954
Pojawia się w:
Technical Issues
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positron Lifetime Spectroscopy of Nanocrystalline Copper
Autorzy:
C̆ížek, J.
Procházka, I.
Vostrý, P.
Chmelík, F.
Islamgaliev, R. K.
Powiązania:
https://bibliotekanauki.pl/articles/2007957.pdf
Data publikacji:
1999-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
79.60.Jv
Opis:
Positron lifetime spectroscopy was applied to investigate the thermal stability of nanocrystalline copper prepared by severe plastic torsion deformation. Positrons annihilating in as prepared specimens exhibited free positron component τ$\text{}_{1}$ and two defect components τ$\text{}_{2}$=164 ps and τ$\text{}_{3}$=255 ps. Evolution of the lifetimes and relative intensities of all the three components with increasing annealing temperature during step-by-step isochronal annealing up to 630°C was studied. Behaviour of positrons in nanocrystalline copper could not be interpreted in the frame of conventional 3-state trapping model due to highly inhomogeneous defect distribution. Therefore a modified trapping model was developed and applied to explain the experimental results.
Źródło:
Acta Physica Polonica A; 1999, 95, 4; 487-495
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positron Annihilation Lifetime Spectroscopy of ABS Objects Manufactured by Fused Deposition Modelling
Autorzy:
Dryzek, M.
Dryzek, E.
Powiązania:
https://bibliotekanauki.pl/articles/1033901.pdf
Data publikacji:
2017-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
61.41.+e
Opis:
Positron annihilation lifetime spectroscopy was used to study acrylonitrile butadiene styrene (ABS) specimens manufactured using fused deposition modelling to explore possibilities of identifying differences in molecular structure. The set of specimens was prepared including square tiles and long rectangular tiles (100 mm and 200 mm long) with all filament roads parallel to the longer edge. All types of tiles were produced with various infill line distance parameter resulting in different overlapping of the roads in horizontal and vertical directions. The slight increase of the ortho-positronium lifetime indicating increase of the mean free volume radius was observed for the longest tiles for which influence of weld interface is expected to be most pronounced. No differences were observed for different infill line distance parameters.
Źródło:
Acta Physica Polonica A; 2017, 132, 5; 1506-1508
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Free-Volume Studies in Polycaprolactone/Poly(propylene oxide) Urethane/Urea Membranes by Positron Lifetime Spectroscopy
Autorzy:
Ferreira Marques, M.
Gordo, P.
de Lima, A.
Queiroz, D.
Norberta de Pinho, M.
Major, P.
Kajcsos, Zs.
Powiązania:
https://bibliotekanauki.pl/articles/1812490.pdf
Data publikacji:
2008-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.41.+e
78.70.Bj
82.30.Gg
Opis:
Positron annihilation lifetime spectroscopy was used to study the free volume parameters in polypropylene oxide-based tri-isocyanate terminated prepolymer/polycaprolactone diol bi-soft urethane/urea membranes (PU/PCL) with PCL content from 5 up to 25 wt%. Positron annihilation lifetime spectroscopy measurements carried out in the temperature range 298-324 K mirrored the phase separation of the various soft and hard segments present in the membranes. The size and amount of free volume holes determined by positron annihilation lifetime spectroscopy appear to be correlated with the $CO_2$ gas permeability through the membranes.
Źródło:
Acta Physica Polonica A; 2008, 113, 5; 1359-1364
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Badanie wpływu domieszki Gd na stopień zdefektowania struktury szkła tellurowego
Studying influence of element Gd on voids degree of structure the tellurite glass
Autorzy:
Filipecki, J.
Golis, E.
Kotynia, K.
Chamerski, K.
Powiązania:
https://bibliotekanauki.pl/articles/168534.pdf
Data publikacji:
2015
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Ceramiki i Materiałów Budowlanych
Tematy:
szkła tellurowe
defekty
anihilacja
spektroskopia czasów życia pozytonu
tellurite glasses
defects
annihilation
positron lifetime spectroscopy
Opis:
Materiałem badawczym było szkło tellurowe. Badaniom poddano szkło bazowe TeO2-P2O3-ZnO-LiNbO3 oraz szkło domieszkowane gadolinem (TeO2-P2O3-ZnO-LiNbO3)(Gd2O3). W celu dokonania analizy własności strukturalnych wykorzystano metodę pomiarów czasów życia pozytonów PALS (Positron Annihilation Lifetime Spectroscopy). W proponowanej metodzie możliwa jest identyfikacja defektów strukturalnych trudnych do wychwycenia innymi tradycyjnymi metodami pomiarowymi. Przeprowadzone badania wykazały istnienie dwóch składowych czasów życia pozytonów τ1 i τ2. W oparciu o model dwustanowy obliczono parametry wychwytu pozytonów, które pozwalają wyciągnąć wnioski o charakterze i stopniu zdefektowania badanych szkieł tellurowych.
The tellurite glass such as: TeO2-P2O3-ZnOLiNbO3 as a reference glass and (TeO2-P2O3-ZnO-LiNbO3)(Gd2O3) has been studied. The positron lifetime PALS (Positron Annihilation Lifetime Spectroscopy) was used to analyze the structural properties of tellurite glasses. The proposed method, can identify structural defects which are difficult to capture by other traditional methods. The study showed the existence of two components τ1 and ττ. The basis of the two-state model parameters were calculated capture of positrons, which allow you to draw conclusions about the nature and degree of defect studied tellurite glasses.
Źródło:
Szkło i Ceramika; 2015, R. 66, nr 1, 1; 17-19
0039-8144
Pojawia się w:
Szkło i Ceramika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Free Volume of PVA/SSA Proton Exchange Membrane Studied by Positron Annihilation Lifetime Spectroscopy
Autorzy:
Gomaa, M.
Hugenschmidt, C.
Dickmann, M.
Abdel-Hamed, M.
Abdel-Hady, E.
Mohamed, H.
Powiązania:
https://bibliotekanauki.pl/articles/1033241.pdf
Data publikacji:
2017-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
82.47.Gh
78.70.Bj
Opis:
Humidity control and water management in polymer electrolyte membranes for fuel cells are still of high importance to improve the fuel cells' efficiencies. In this study, poly (vinyl alcohol) (PVA)was crosslinked using 15 wt% sulfosuccinic acid (SSA) by a solution casting method and additionally thermally crosslinked at 100°C. Positron annihilation lifetime spectroscopy was used to study the mean free volume size and the distribution at different humidity. A slight decrease in the free volume was found up to a relative humidity of 30% whereas it increases strongly for a relative humidity of more than 30%. The volume of the voids duplicates from 0.036 to 0.078 nm³ by changing the relative humidity from 30 to 80%. Thermogravimetric analyzer was used to determine the thermal stability of the membrane. From thermogravimetric analyzer data, it was found that the PVA with 15 wt% SSA membrane are chemically stable up to 200°C.
Źródło:
Acta Physica Polonica A; 2017, 132, 5; 1519-1522
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Gas filling of SBA - 15 silica micropores probed by positron annihilation lifetime spectroscopy (PALS)
Autorzy:
Gorgol, M.
Zaleski, R.
Kierys, A.
Powiązania:
https://bibliotekanauki.pl/articles/147961.pdf
Data publikacji:
2013
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
SBA-15 porous silica
positron annihilation
Opis:
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.
Źródło:
Nukleonika; 2013, 58, 1; 229-233
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
PALS investigations of matrix Vycor glass doped with molecules of luminescent dye and silver nanoparticles. Discrepancies from the ETE model
Autorzy:
Gorgol, M.
Jasińska, B.
Reisfeld, R.
Powiązania:
https://bibliotekanauki.pl/articles/147152.pdf
Data publikacji:
2015
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
positron annihilation lifetime spectroscopy (PALS)
porous glass
lumogen dye ROT-305
silver nanoparticles
Vycor glass
Opis:
A thermal stability of three materials: undoped reference Vycor glass, glass filled with ROT-305 red dye, and silver nanoparticles was investigated by positron annihilation lifetime spectroscopy (PALS) in a broad temperature range (from 93 to 473 K). The attempt of pore size calculations from the ortho-positronium lifetime data was performed using the extended Tao-Eldrup (ETE) model. Below room temperature, a significant decrease in lifetime values of the longest-lived component was found for all the samples. This effect could not be explained by thermal shrinkage of the material and is probably caused by interaction of -Ps with a Vycor glass matrix. The greatest discrepancy from the ETE model predictions was observed for the reference glass. Doping the base material with dye molecules and silver nanoparticles resulted in similar small decrease in this discrepancy. After reheating the samples to the room temperature, the PALS components returned to the initial values. In the temperature range of 293–473 K, quite good agreement between PALS results and the ETE model predictions was observed for the reference glass and the glass incorporated with dye molecules. The observed small discrepancy in this range could possibly be partly explained by thermal expansion of the material. For the glass doped with silver nanoparticles, a significant change in PALS parameters was observed in the temperature range from 403 to 473 K.
Źródło:
Nukleonika; 2015, 60, No. 4, part 1; 717-720
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Porosity structure in photon active glasses
Autorzy:
Jasińska, B.
Śniegocka, M.
Reisfeld, R.
Zigansky, E.
Powiązania:
https://bibliotekanauki.pl/articles/147953.pdf
Data publikacji:
2013
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
glass
ortho-positronium (o-Ps)
porosity
positron annihilation lifetime spectroscopy (PALS)
sol-gel technique
Opis:
Two kinds of photon active glasses were investigated using positron annihilation lifetime spectroscopy (PALS). Both kinds of glasses were prepared using a sol-gel technique, doped by complex of ruthenium tris bipyridyl chloride. Glasses differed from the initial matrix: the first one was prepared using silicon oxide while the second one - zircon oxide. The ortho-positronium (o-Ps) lifetime and intensities were determined from lifetime spectra. Different porosity structure concluded from PALS measurements was found in both cases. In the silica based glasses small free volumes (angstrom size) and pores (from 1 to 10 nm) existed in the material. On the contrary, in zirconia based glasses small intermolecular voids were produced in the structure only, independently of the way of material preparation.
Źródło:
Nukleonika; 2013, 58, 1; 241-244
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Surface Concentration of Defects at Grain Boundaries in Sintered Alumina Determined by Positron Annihilation Lifetime Spectroscopy
Autorzy:
Kansy, J.
Si Ahmed, A.
Liebault, J.
Moya, G.
Powiązania:
https://bibliotekanauki.pl/articles/2028969.pdf
Data publikacji:
2001-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
77.84.Bw
61.72.Mm
Opis:
Sintered alumina samples of grain diameters spanning from 1.2 to 4.5μm have been investigated by positron annihilation lifetime spectroscopy. One series of samples was produced from material containing about 150 ppm impurities (mainly SiO$\text{}_{2}$). The second one was made from material having about 2700 ppm of various elements (SiO$\text{}_{2}$, MgO, CaO). Two models of positron trapping at grain boundaries are compared: The first one relates to the diffusion-limited regime; and the other one - to the transition-limited regime of trapping. As a result the relative change of surface concentration of defects at grain boundaries is determined. Additionally, the positron diffusion constant in bulk alumina at room temperature, D$\text{}_{+}$=0.36±10 cm$\text{}^{2}$/s, is estimated.
Źródło:
Acta Physica Polonica A; 2001, 100, 5; 737-742
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Photoluminescence and positron annihilation lifetime studies on pellets of ZnO nanocrystals
Autorzy:
Karbowski, A.
Fedus, K.
Patyk, J.
Bujak, Ł.
Służewski, K.
Karwasz, G.
Powiązania:
https://bibliotekanauki.pl/articles/148001.pdf
Data publikacji:
2013
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
photoluminescence (PL)
positron annihilation lifetime spectroscopy (PALS)
X-ray diffraction (XRD)
ZnO nanocrystals
Opis:
We explore the interrelationships between the X-ray diffraction patterns, the photoluminescence spectra and the positron lifetimes obtained from circular pellets composed of commercial ZnO nanoparticles. The experimental results are studied as a function of thermal treatment at different temperatures. X-ray diffractograms reveal the temperature- independent wurtzite phase structure of nanocrystals and show huge enlargement of ZnO grains after annealing at temperatures higher than 700 centigrade. Photoluminescence measurements exhibit two emission bands : a near band edge emission in UV (small tilde 378 nm) and a defect-related broad visible peak with a maximum in the green region ( small tilde 502 nm). The significant enhancement of the green emission at the expense of UV luminescence is observed after sample sintering at 800 and 1000 centigrade. The positron annihilation lifetime spectroscopy (PALS) is applied in order to study the thermally induced evolution of defects. The lifetime components show a step-like dependence on the thermal treatment, but do not follow exactly the variation in crystallographic phases and only vaguely follow differences in photoluminescence. The positron data indicate therefore some additional structural and/or defect changes. The possible origin of green luminescence from ZnO pellets is discussed.
Źródło:
Nukleonika; 2013, 58, 1; 189-194
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Studies of unicellular microorganisms Saccharomyces cerevisiae by means of positron annihilation lifetime spectroscopy
Autorzy:
Kubicz, E.
Jasińska, B.
Zgardzińska, B.
Bednarski, T.
Białas, P.
Czerwiński, E.
Gajos, A.
Gorgol, M.
Kamińska, D.
Kapłon, Ł.
Kochanowski, A.
Korcyl, G.
Kowalski, P.
Kozik, T.
Krzemień, W.
Niedźwiecki, S.
Pałka, M.
Raczyński, L.
Rajfur, Z.
Rudy, Z.
Rundel, O.
Sharma, N. G.
Silarski, M.
Słomski, A.
Strzelecki, A.
Wieczorek, A.
Wiślicki, W.
Zieliński, M.
Moskal, P.
Powiązania:
https://bibliotekanauki.pl/articles/147902.pdf
Data publikacji:
2015
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
environmental scanning electron microscopy (ESEM)
free volume
inverted microscopy
positron annihilation
positronium
yeasts
Opis:
Results of positron annihilation lifetime spectroscopy (PALS) and microscopic studies on simple microorganisms, brewing yeasts, are presented. Lifetime of ortho-positronium (o-Ps) were found to change from 2.4 to 2.9 ns (longer-lived component) for lyophilized and aqueous yeasts, respectively. Also hygroscopicity of yeasts in time was examined, allowing to check how water – the main component of the cell – affects PALS parameters, thus lifetime of o-Ps were found to change from 1.2 to 1.4 ns (shorter-lived component) for the dried yeasts. The time sufficient to hydrate the cells was found below 10 hours. In the presence of liquid water, an indication of reorganization of yeast in the molecular scale was observed. Microscopic images of the lyophilized, dried, and wet yeasts with best possible resolution were obtained using inverted microscopy (IM) and environmental scanning electron microscopy (ESEM) methods. As a result, visible changes to the surface of the cell me mbrane were observed in ESEM images.
Źródło:
Nukleonika; 2015, 60, No. 4, part 1; 749-753
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
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