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Wyszukujesz frazę "positron lifetime spectroscopy" wg kryterium: Wszystkie pola

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    Wyświetlanie 1-13 z 13
    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:
    Investigation of PCM Microcapsules with Paraffin Filling by Positron Lifetime Spectroscopy
    Autorzy:
    Zgardzińska, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/1402636.pdf
    Data publikacji:
    2015-05
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    78.70.Bj
    62.23.Pq
    61.80.Fe
    61.72.-y
    61.46.-w
    81.07.Nb
    64.70.Nd
    82.35.Pq
    Opis:
    Positron annihilation lifetime spectroscopy was applied to investigate the microcapsules composed of n-eicosane (filling material) and polysiloxane polymer (shell) in the range of temperatures 123-333 K. Pure components of microcapsules were also investigated as a base for interpretation of the measurement results. The temperature of phase transitions in microcapsules was determined. It showed the appearance of a rotary phase, which is not present in pure n-eicosane. In the considered material, two types of free volume have been identified. The sizes of free volumes able to accommodate Ps were estimated using standard models. On the basis of the o-Ps intensities, the content of polysiloxane in microcapsules was estimated as about 40%. Internal structure of the microcapsules (morphology) was observed by scanning electron microscopy.
    Źródło:
    Acta Physica Polonica A; 2015, 127, 5; 1536-1539
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    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:
    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:
    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:
    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:
    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:
    A new approach to the presentation of the positron annihilation lifetime spectroscopy results, n-alkanes
    Autorzy:
    Zgardzińska, B.
    Standzikowski, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/1057935.pdf
    Data publikacji:
    2017-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    36.10.Dr
    78.70.Bj
    82.30.Gg
    Opis:
    The standard form of the positron annihilation lifetime spectroscopy results presentation are two plots of o-Ps lifetime and intensity as a function of external factor, e.g. temperature, pressure. Both o-Ps parameters change (stepwise) when in the medium phase transitions occur. For a more complete picture of the structural changes occurring in the matter we suggest to use an additional plot, in the coordinates, (τ₃, I₃). The hydrocarbons are selected to show the advantages following from the presentation of the results in the intensity-lifetime (INTI) plot.
    Źródło:
    Acta Physica Polonica A; 2017, 132, 5; 1496-1500
    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:
    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:
    Positron Annihilation Lifetime Spectroscopy and Dielectric Measurements of Natural Kaolinite and Kaolinite Intercalated by Potassium Acetate
    Autorzy:
    Leluk, K.
    Orzechowski, K.
    Jerie, K.
    Baranowski, A.
    Słonka, T.
    Głowiński, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/2047141.pdf
    Data publikacji:
    2006-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    91.60.-x
    77.22.-d
    78.70.Bj
    Opis:
    Intercalation of clay minerals consists in inserting of guest molecules into interlayer area. It results in expanding the interlayer distance and changes of physical and chemical properties of the material. Dielectric spectroscopy, positron annihilation lifetime experiments, X-ray, and thermoanalysis were jointly applied to investigate the structural changes accompanying intercalation.
    Źródło:
    Acta Physica Polonica A; 2006, 110, 5; 621-629
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Hydrolytic Degradation of Poly(L-Lactide-co-Glycolide) Studied by Positron Annihilation Lifetime Spectroscopy and Other Techniques
    Autorzy:
    Pamuła, E.
    Dryzek, E.
    Dobrzyński, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/2047148.pdf
    Data publikacji:
    2006-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    82.35.-x
    82.35.Lr
    78.70.Bj
    61.18.Fs
    82.56.Ub
    83.85.Jn
    68.37.Ps
    Opis:
    Changes of the poly(L-lactide-co-glycolide) structure as a function of degradation time in phosphate-buffered saline for 7 weeks were investigated by gel permeation chromatography, differential scanning calorimetry, nuclear magnetic resonance ($\text{}^{1}$H NMR), and positron annihilation lifetime spectroscopy. Surface properties as wettability by sessile drop and topography by atomic force microscopy were also characterized. Chain-scission of polyester bonds in hydrolysis reaction causes a quite uniform decrease in molecular weight, and finally results in an increase in semicrystallinity. Molecular composition of the copolymer and water contact angle do not change considerably during degradation time. Atomic force microscopy studies suggest that the copolymer degrades by "in bulk" mechanism. The average size of the molecular-level free volume holes declines considerably after one week of degradation and remains constant till the sixth week of degradation. The free volume fraction decreases as a function of degradation time.
    Źródło:
    Acta Physica Polonica A; 2006, 110, 5; 631-640
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Porosity of Silica Monoliths with Tailored Mesopores of Ink-Bottle Shape Determined by Nitrogen Adsorption and Positron Annihilation Lifetime Spectroscopy
    Autorzy:
    Sienkiewicz, A.
    Kierys, A.
    Gorgol, M.
    Zaleski, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/1033934.pdf
    Data publikacji:
    2017-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    81.05.Rm
    68.43.-h
    81.70.-q
    78.70.Bj
    36.10.Dr
    Opis:
    The comparison of pore size distributions obtained with the use of two porosimetric methods: low temperature nitrogen sorption (LN2) and positron annihilation lifetime spectroscopy (PALS), was performed for porous silica monoliths. Four investigated samples were prepared under various synthesis conditions. Nitrogen sorption showed the presence of bottle-shaped pores in all investigated samples. In addition, it seems that the presence of methanol during synthesis influences porosity to a greater extent than organic additives. Quite good agreement between the LN2 and PALS results was observed only for the silica monolith synthesized with β-cyclodextrins as pore directing agent. The biggest discrepancy in the results obtained from these two techniques was observed for the silica gel synthesized with no additives. The origin of such discrepancies, taking into account the shape of pore size distribution and deficiencies of data analysis techniques, is discussed.
    Źródło:
    Acta Physica Polonica A; 2017, 132, 5; 1568-1571
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-13 z 13

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