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Tytuł:
Formation and Annealing of Micropores in Hematite
Autorzy:
Dauwe, C.
Da Costa, G. M.
Van Hoecke, T.
Segers, D.
Powiązania:
https://bibliotekanauki.pl/articles/1933484.pdf
Data publikacji:
1995-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
In iron oxide powders positrons are trapped in the surface layers and the value of the S-parameter is an indicator of the total specific surface, including external surface and internal surfaces of micropores. The evolution of micropores is followed when α-FeOOH is thermally decomposed into α-Fe$\text{}_{2}$O$\text{}_{3}$. It is shown that the micropore formation is not linked to the decomposition process, but that they also form in hematite synthesized from a ferrihydrite precursor in aqueous solution.
Źródło:
Acta Physica Polonica A; 1995, 88, 1; 119-123
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Remarks on Reconstruction of Defects Distribution by Positron Lifetime Measurements
Autorzy:
Dryzek, J.
Powiązania:
https://bibliotekanauki.pl/articles/1933485.pdf
Data publikacji:
1995-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
It is well known that the positron trapping rate obtained from positron lifetime measurements depends upon defect concentrations and trapping efficiency. If a distribution of open volume defects exists, a distribution of trapping efficiency also could be present. As an example, the calculation of trapping efficiency as a function of radius of defects in Al is presented. The correct explanation of defect size distribution obtained by positron lifetime measurements needs to introduce some additional assumptions about trapping efficiency.
Źródło:
Acta Physica Polonica A; 1995, 88, 1; 125-128
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Studies of the Cu-Mn System
Autorzy:
Nicht, E.-M.
Brauer, G.
Kajcsos, Zs.
Molnar, B.
Powiązania:
https://bibliotekanauki.pl/articles/1933529.pdf
Data publikacji:
1995-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
The superstructures Cu$\text{}_{3}$Mn and Cu$\text{}_{5}$Mn have been characterized for the first time by X-ray and differential scanning calorimetry measurements. In addition, positron lifetime measurements are presented in order to show the defect structure of these alloys. It turned out that the annealing behaviour is equal for the two different alloys and the two different deforming processes. An annealing temperature of 300°C is not sufficient to obtain a defect free state.
Źródło:
Acta Physica Polonica A; 1995, 88, 1; 205-210
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positron Annihilation Studies of the Ni-H Systems Containing Thermally Induced Crystal Lattice Defects
Autorzy:
Pająk, J.
Powiązania:
https://bibliotekanauki.pl/articles/1933538.pdf
Data publikacji:
1995-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
The interaction between hydrogen and thermally induced defects has been studied in nickel samples using the positron annihilation technique. From measurements further evidence has been found for agglomeration of vacancies and small vacancy complexes into large-size three-dimensional void-like defects in the plastically deformed and electron beam irradiated samples containing hydrogen.
Źródło:
Acta Physica Polonica A; 1995, 88, 1; 219-223
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Kinetics of the Spin-Conversion of Positronium Measured by β$\text{}^{+}$γ∆E Age-Momentum Correlation
Autorzy:
Lauff, U.
Maier, K.
Major, J.
Seeger, A.
Stoll, H.
Wesołowski, P.
Koch, M.
Bilard, I.
Abbé, J.
Duplâtre, G.
Powiązania:
https://bibliotekanauki.pl/articles/1929104.pdf
Data publikacji:
1993-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
Age-momentum correlation (AMOC) measurements provide time-resolved information on the momentum distribution of annihilating electron-positron pairs through correlated determination of Doppler broadening (∆E) of the 511 keV annihilation radiation line and positron age. In the β$\text{}^{+}$γ∆E AMOC technique implemented at the Stuttgart pelletron accelerator the start signals for the age measurements are generated when the relativistic positrons pass through a fast plastic scintillator, which has a detection efficiency close to unity. Beam-based β$\text{}^{+}$γ∆E AMOC measurements thus combine high β$\text{}^{+}$γ∆E triple-coincidence rates with low background. From a practical point of view this constitutes a major progress compared to conventional (source-based) γγ∆E AMOC measurements. The AMOC technique permits direct access to a wide variety of time-dependent processes, among them the reaction kinetics in positronium chemistry. As an example, we present a β$\text{}^{+}$γ∆E AMOC investigation of the kinetics of a spin-conversion reaction of positronium in methanol induced by the presence of a nitrosyl free-radical paramagnetic solute (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl , HTEMPO). The AMOC measurements allowed the time-resolved observation of the spin-conversion process, which had been investigated before by uncorrelated positron lifetime and Doppler-broadening measurements. It is found that within the concentration range investigated (≤ 0.1 mol/l) the spin-conversion reaction rate at room temperature depends linearly on the HTEMPO concentration with a reaction-rate constant k$\text{}_{conv}$ = (22.5 ± 0.5) × 10$\text{}^{9}$ l mol$\text{}^{-1}$ s$\text{}^{-1}$.
Źródło:
Acta Physica Polonica A; 1993, 83, 3; 349-358
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:
Positronium in Small and Large Voids in Vycor Glass
Autorzy:
Ciesielski, K.
Dawidowicz, A. L.
Goworek, T.
Powiązania:
https://bibliotekanauki.pl/articles/2007951.pdf
Data publikacji:
1999-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
The intensities of ortho-positronium components related to the pores and to small voids in the bulk were determined for a series of Vycor glasses. The ratio of "pore fraction" to the total o-Ps yield depends on the specific surface area of the porous medium. The diffusion coefficient for o-Ps was found equal to 3.7×10$\text{}^{-5}$ cm$\text{}^{2}$/s.
Źródło:
Acta Physica Polonica A; 1999, 95, 4; 483-486
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positron Trapping Model in Fine Grained Sample
Autorzy:
Dryzek, J.
Powiązania:
https://bibliotekanauki.pl/articles/2007999.pdf
Data publikacji:
1999-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
In the paper we consider the positron trapping model in the sample where the spherical particles were immersed in the medium. The radius of the particles was small enough to take into account the diffusion of positrons. We present the exact solutions of the model for two cases, when transition of the positrons from the particle to the medium was neglected and when it was taken into consideration. The theoretical calculations were applied to description of the positron annihilation in the copper sample where the recrystallization process took place.
Źródło:
Acta Physica Polonica A; 1999, 95, 4; 539-545
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positron Annihilation in Deformed and Hydrogenated Pd-23%atcu Alloy
Autorzy:
Pająk, J.
Szatanik, R.
Szuszkiewicz, M.
Powiązania:
https://bibliotekanauki.pl/articles/2008180.pdf
Data publikacji:
1999-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
Peak coincidence counting rate and positron lifetime spectra for deformed by cold-rolling, and annealed by four hours in the temperature 973 K, hydrogen free and hydrogenated PdCu with 23% Cu samples, in the temperature range from room temperature to about 720 K were measured. It was found that hydrogen improved to tempered samples creates defects that are annealed to the temperature about 525 K. In the cold-rolled up to deformation degree of 50% samples, hydrogen is trapped at defects, probably vacancies, forming H-V complexes, that become disappearing in the vicinity of the temperature at 350 K.
Źródło:
Acta Physica Polonica A; 1999, 95, 4; 637-640
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Measurements of Positrons Lifetimes in Corroded Nickel
Autorzy:
Pietrzak, R.
Szatanik, R.
Szuszkiewicz, M.
Powiązania:
https://bibliotekanauki.pl/articles/2008182.pdf
Data publikacji:
1999-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
An attempt was undertaken at making use of a technique of taking measurements of lifetimes of positrons emitted from $\text{}^{22}$Na source to investigate corroded nickel. It was found that after corrosion in HCl vapours mean positrons lifetime, the second component of positrons lifetimes as well as its intensity rise along with the corrosion time.
Źródło:
Acta Physica Polonica A; 1999, 95, 4; 647-651
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Study of Positron Properties in Quartz Crystals and Synthetic Silica Glass
Autorzy:
Anwand, W.
Brauer, G.
Hasegawa, M.
Dersch, O.
Rauch, F.
Powiązania:
https://bibliotekanauki.pl/articles/2024077.pdf
Data publikacji:
2001
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
The monoenergetic positron beamline "SPONSOR" at Rossendorf has been used to investigate the positron behaviour in a naturally grown Brasilian quartz, two synthetic quartz crystals of different origin, and synthetic silica glass. The measurements allow us to obtain the positron diffusion length of free positrons and Bloch para-positronium, if formed, in these materials. In addition, hydrothermal treatment of a synthetic quartz has been used to introduce hydrogen into the crystal up to a certain depth. The presence of hydrogen is found to influence the formation of para-positronium. The depth distribution of hydrogen has been measured independently by nuclear reaction analysis, and will be discussed in comparison with the results deduced from the positron studies.
Źródło:
Acta Physica Polonica A; 2001, 99, 3-4; 321-328
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Algorithm for Shifting Positron Annihilation Spectra
Autorzy:
Dryzek, J.
Polak, A.
Powiązania:
https://bibliotekanauki.pl/articles/2024230.pdf
Data publikacji:
2001
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
We present a simple procedure which allows us to shift the positron annihilation spectra, e.g., the Doppler broadening spectrum of the annihilation line. That is especially required when we wish to compare different spectra obtained with a spectrometer with the reduction of background. As an application of the obtained algorithm we present the studies of positron annihilation in carbon material samples.
Źródło:
Acta Physica Polonica A; 2001, 99, 3-4; 355-361
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Study of Defects in GeTe and (GeTe)$\text{}_{1-x}$(AgBiTe_2)_x Solid Solutions by Positrons
Autorzy:
Misheva, M.
Avramova, I.
Plachkova, St.
Djourelov, N.
Powiązania:
https://bibliotekanauki.pl/articles/2025145.pdf
Data publikacji:
2001
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
Positron lifetimes and Doppler broadening of the annihilation line measurements were performed to study the vacancy type defects in polycrystalline GeTe and (GeTe)$\text{}_{(1-x)}$(AgBiTe$\text{}_{2}$)$\text{}_{x}$ (x=0,0.03,0.05,0.1,0.15,0.2, and 1) solid solutions. The values of lifetimes obtained are explained as due to positron and positronium saturated trapping at vacancies and vacancy clusters. The interdependence between mean positron lifetime and hole concentration is discussed.
Źródło:
Acta Physica Polonica A; 2001, 99, 3-4; 423-428
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of Annealing on Free-Volume Properties of Poly(ethylene Terephthalate) Studied by Positron Annihilation
Autorzy:
Misheva, M.
Djourelov, N.
Seganov, I.
Powiązania:
https://bibliotekanauki.pl/articles/2025732.pdf
Data publikacji:
2001
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
The effect of annealing on free-volume properties of poly( ethylene terephthalate) was studied using a set of samples annealed for two hours in air at eight temperatures between 80ºC and 220ºC. The fractional free-volume in the samples was estimated from ortho-positronium lifetime and its relative intensity. The variations of fractional free-volume and of the macroscopic specific volume with annealing temperature were compared. The variation of the pore volume probability density functions with the annealing temperature was found. The interdependence between S- and W-parameters was also discussed.
Źródło:
Acta Physica Polonica A; 2001, 99, 3-4; 429-433
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Some Aspects of Positronium Interaction with Elementary Free Volumes in Polymers
Autorzy:
Shantarovich, V. P.
Powiązania:
https://bibliotekanauki.pl/articles/2025763.pdf
Data publikacji:
2001
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
This paper contains a discussion of original and recently published results on positronium annihilation lifetime studies of elementary free volumes in the group of polymer glasses. The results are used for indication of non-homogeneity of these materials and give some basis for considering a connection of the long-lived component intensities I$\text{}_{3}$(I$\text{}_{4}$) with concentrations N$\text{}_{3}$(N$\text{}_{4}$) of elementary free volumes and, in this way, with fractional free volume.
Źródło:
Acta Physica Polonica A; 2001, 99, 3-4; 487-495
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positron Irradiation Effects on Positronium Formation in Polycarbonate Sduring a Positron-Annihilation Experiment
Autorzy:
Suzuki, T.
Kondo, K.
Hamada, E.
Ito, Y.
Powiązania:
https://bibliotekanauki.pl/articles/2025767.pdf
Data publikacji:
2001
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
The positron-irradiation effect on polycarbonate during a positron-annihilation lifetime spectroscopy experiment was investigated using different intensities of $\text{}^{22}$Na positron sources andγ-irradiated samples. The decrease in I$\text{}_{3}$ was larger for a larger intensity of positron sources. In the case of a weak source (≈ 140 kBq), I$\text{}_{3}$ did not change with the elapsed time for non-irradiated samples. However, for 1 MGy irradiated samples, I$\text{}_{3}$ measured with the weak source increased with the elapsed time. This can be attributed to a decrease in the radicals induced in the irradiated samples by γ-irradiation. In order to explain the change in I$\text{}_{3}$ measured at room and liquid-nitrogen temperatures, several effects, such as radicals, cross-linking, structure change, and charging, need to be considered. Also, it is difficult to explain the change in I$\text{}_{3}$ using only one of these effects.
Źródło:
Acta Physica Polonica A; 2001, 99, 3-4; 515-521
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ortho-Positronium Annihilation in Room Temperature Ionic Liquids
Autorzy:
Hirade, T.
Powiązania:
https://bibliotekanauki.pl/articles/1030029.pdf
Data publikacji:
2017-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
Very new phenomena have been found in room temperature ionic liquids, e.g. oscillation of positronium (Ps) bubble. It is almost impossible to see this kind of phenomenon in usual molecular liquids. The Ps bubble oscillations in N,N,N-trimethyl-N-propylammonium bis(trifluoro-methanesulfonyl)imide (TMPA-TFSI), N-methyl-N-propylpiperidinium bis(trifluoromethane-sulfonyl) imide (PP13-TFSI) and 1-ethyl-3-methylimidazolium thiocyanate (EMIM-SCN) were successfully observed. Even though the Ps bubble size is smaller for EMIM-SCN, the oscillation frequency of the Ps bubble at 10°C above the melting temperatures was quite similar for the other room temperature ionic liquids. Hence, the Ps bubble oscillation is, probably, caused by the repulsive force initiated by the ionic structures in room temperature ionic liquids that can remain at 10-15°C above the melting temperatures.
Źródło:
Acta Physica Polonica A; 2017, 132, 5; 1470-1472
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positron Lifetime Measurements of Subsurface Region in Aluminium Alloy and Aluminium Alloy Composite after Dry Sliding
Autorzy:
Dryzek, E.
Powiązania:
https://bibliotekanauki.pl/articles/2043305.pdf
Data publikacji:
2005-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
This paper presents positron lifetime studies of the subsurface region of AK12 aluminium alloy and Al$\text{}_{2}$O$\text{}_{3}$-particle-reinforced AK12 aluminium alloy composite after sliding against steel in the pin-on-disc machine. The defect depth profile detected in the AK12 alloy extended up to 300μm but for the composite AK12 the range of this profile was significantly shortened to less than 90μm. The positron lifetime dependence on depth evidences a steep gradient of defect concentration near the surface. The subsurface zones have been also examined using scanning electron microscopy.
Źródło:
Acta Physica Polonica A; 2005, 107, 5; 753-760
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positron Annihilation in Medical Substances of Insulin
Autorzy:
Pietrzak, R.
Szatanik, R.
Powiązania:
https://bibliotekanauki.pl/articles/2043341.pdf
Data publikacji:
2005-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
Positrons lifetimes were measured in medical substances of insulin (human and animal), differing as far as the degree of purity and time of their activity in the organism are concerned. In all of the cases the spectrum of positron lifetime was distributed into three components, with the long-life component ranging from 1.8 to 2.08 ns and the intensity taking on values from 18 to 24%. Making use of Tao-Eldrup model, the average radius of the free volume, in which o-Ps annihilated, and the degree of filling in the volume were determined. It was found that the value of the long-life component for human insulin is higher than that of animal insulin. Moreover, the value of this component clearly depends on the manner of purification of the insulin. It was also noticed that there occurs a correlation between the value of this component and the time after which it begins to be active in the organism, as well as the total time of its activity.
Źródło:
Acta Physica Polonica A; 2005, 107, 5; 852-856
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Performance of a High-Resolution Digital Positron-Lifetime Spectrometer
Autorzy:
Bečvář, F.
Čížek, J.
Procházka, I.
Powiązania:
https://bibliotekanauki.pl/articles/1812465.pdf
Data publikacji:
2008-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
This work describes a digital positron-lifetime spectrometer based on two ultrafast digitizers. Performance of the digital spectrometer in conditions of a routine measurement is compared with an analogue setup connected to the same detectors. It was found that engagement of the digital setup leads to an improvement of timing resolution (FWHM for $\text{}^{22}Na$) from 169 ps for the traditional analogue setup to 146 ps for the digital setup. The coincidence count rate for 1.2 MBq $\text{}^{22}Na$ source is 75-80 coinc./s for both configurations. These results clearly demonstrate the advantages of the digital timing over the traditional analogue setup.
Źródło:
Acta Physica Polonica A; 2008, 113, 5; 1279-1284
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Nanopores in Silica Aerogels
Autorzy:
Šauša, O.
Iskrová, M.
Majerník, V.
Krištiak, J.
Jesenák, K.
Vargová, M.
Powiązania:
https://bibliotekanauki.pl/articles/1812550.pdf
Data publikacji:
2008-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
The size of nanopores in thermally treated samples of silica aerogels was determined by ortho-positronium lifetime measurements at room temperature. The annealing of samples in the temperature region of 300-800°C does not make substantial changes in pore size felt by positronium. The annealing at higher temperatures from an interval of 800-1050°C causes shrinkage of the samples reducing the pore size to 1-15 nm. The macropores vanish at temperature treatment at 1000°C and the positron annihilation is not affected by oxygen from air.
Źródło:
Acta Physica Polonica A; 2008, 113, 5; 1517-1522
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positron Annihilation Study of Defects in the Cage-Type Uranium Compound
Autorzy:
Rubaszek, A.
Powiązania:
https://bibliotekanauki.pl/articles/1336614.pdf
Data publikacji:
2014-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
The electron and positron properties of the $UIr_2Zn_{20}$ compound of the Fd-3m cage-type crystal structure are studied. The characteristics for the perfect crystal are compared with their counterparts in the elements containing Ir and Zn vacancy. The presence of the vacancy hardly influences the electron charge density around individual atoms. In contrast to electrons, the positron is strongly localized inside the vacancy and the transfer of positron charge is observed. The positron lifetime, τ, appears to be strongly sensitive to the presence and type of the vacancy. Furthermore, this parameter calculated for the perfect crystal is very close to the experimental value for Zn. Here the theoretical values of τ depend on the approach applied to the electron positron (e-p) correlations.
Źródło:
Acta Physica Polonica A; 2014, 125, 3; 737-740
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positron Annihilation Methods by Use of LSO Scintillators
Autorzy:
Hirade, T.
Oka, T.
Powiązania:
https://bibliotekanauki.pl/articles/1339992.pdf
Data publikacji:
2014-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
$Lu_2SiO_5$:Ce (LSO) scintillator is one of the scintillators used for positron emission tomography because of its high efficiency of gamma-ray detection. We tried to use LSO for positron annihilation lifetime and age-momentum correlation measurements because the high efficiency is needed to reduce the positron irradiation effect during measurements. The high efficiency with reasonable time resolution was successfully obtained by use of the dynode signals from photomultiplier tubes.
Źródło:
Acta Physica Polonica A; 2014, 125, 3; 825-828
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Comparison of Different Theoretical Models of Positron Lifetime Spectra for Polymers
Autorzy:
Kansy, J.
Powiązania:
https://bibliotekanauki.pl/articles/1812531.pdf
Data publikacji:
2008-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
The same reference positron lifetime spectra of polyurethane, measured in temperature range 112 to 390 K, were analyzed with three theoretical models: the "conventional" model with three exponential decay component of discrete values of lifetimes, a model with one discrete exponential component and two "packages" of exponentials with log-normal distribution of annihilation rates, and a model considering positronium slow localization, positronium internal relaxation as well as "delayed" formation of positronium. It turns out that the two latter models fit to the experimental data with the same excellent quality, in spite of the fact that in both models the ratio of intensities related to para-positronium and ortho-positronium was constrained to be as 1:3.
Źródło:
Acta Physica Polonica A; 2008, 113, 5; 1397-1407
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positron Annihilation in Steel Samples Deformed by Uniaxial Tension
Autorzy:
Rudzińska, W.
Szuszkiewicz, M.
Bujnarowski, G.
Kluza, A.
Powiązania:
https://bibliotekanauki.pl/articles/1812548.pdf
Data publikacji:
2008-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
Angular distributions of the positron annihilation quanta were measured for steel ST2 SAL samples deformed by uniaxial tension up to different deformation degrees. The dependences of the S parameter on the relative elongation of the samples are presented. The positron annihilation data for steel are compared with the results obtained previously for polycrystalline iron samples deformed by uniaxial tension up to different deformation degrees in the proportionality and limited proportionality regions.
Źródło:
Acta Physica Polonica A; 2008, 113, 5; 1507-1510
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Defect Profile Induced by Friction and Wear Processes Detected by Positron Annihilation Method
Autorzy:
Dryzek, J.
Dryzek, E.
Cleff, B.
Powiązania:
https://bibliotekanauki.pl/articles/1933487.pdf
Data publikacji:
1995-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
The positron annihilation studies of defect profile in Cu samples whose surfaces were exposed to the friction and wear processes are presented. The values of the S-parameter and its dependences on the depth from the Cu surface are the functions of the value of the load applied in the sliding contact between two metals. It indicates possibilities of applying the presented measurement method in the industry.
Źródło:
Acta Physica Polonica A; 1995, 88, 1; 129-133
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Annihilation of Positrons in Fe-Ni Alloys
Autorzy:
Szuszkiewicz, S.
Powiązania:
https://bibliotekanauki.pl/articles/1933545.pdf
Data publikacji:
1995-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
The effect of positron polarization on annihilation characteristics for ferromagnetic alloy samples, Fe$\text{}_{64}$Νi$\text{}_{36}$, Fe$\text{}_{63}$Νi$\text{}_{37}$, Fe$\text{}_{25}$Νi$\text{}_{75}$ and Fe$\text{}_{50}$Νi$\text{}_{50}$, has been studied. It was observed that the global two-quantum annihilation rate depends on mutual orientation of positron beam direction and the sample magnetization. The observed changes of the rate are opposite to the ones which could be expected from the effect of mutual orientation of positron and electron spins on positron backscattering. They can be explained as a result of changing of the relation between 3γ- and 2γ-annihilation probabilities.
Źródło:
Acta Physica Polonica A; 1995, 88, 1; 237-239
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Resonance Trapping of Positrons in Solids
Autorzy:
Dryzek, J.
Powiązania:
https://bibliotekanauki.pl/articles/1929062.pdf
Data publikacji:
1993-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
Basing on a new approach to the calculations of the positron trapping rate, an attempt ',was made to explain the prevacancy effects observed in positron annihilation measurements in metals. The defect in the calculation is represented by a complex potential: the real part of it is responsible for the scattering and the imaginary part - for the trapping of incoming positrons. It is shown that the resonance trapping of the positron s-wave and p-wave at low temperature and d-wave and f-wave in prethermal regions provide substantial contributions to the trapping rate of positrons. The calculations were done for the point defect and for the dislocation, taking into account the thermal distribution of the positron energy and the thermal expansion of the crystal lattice. The resonance trapping of positrons could be responsible for prevacancy effects in metals and could help to solve some problems in the study of positron annihilation.
Źródło:
Acta Physica Polonica A; 1993, 83, 3; 293-296
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positron Annihilation in Internally Oxidized Copper
Autorzy:
Misheva, M.
Nancheva, N.
Feschiev, N.
Powiązania:
https://bibliotekanauki.pl/articles/1929106.pdf
Data publikacji:
1993-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
The positron lifetimes in internally oxidized polycrystalline copper, annealed at different temperatures, were measured. It was found that the dispersed alumina particles act as positron traps. Estimation of concentration of defects was made in the frames of the trapping model.
Źródło:
Acta Physica Polonica A; 1993, 83, 3; 365-369
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positron Annihilation in Helium Charged Ni Samples
Autorzy:
Pająk, J.
Rozenfeld, B.
Powiązania:
https://bibliotekanauki.pl/articles/1929108.pdf
Data publikacji:
1993-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
The angular correlation curves of annihilation quanta and isochronal annealing curves for the plastically deformed nickel samples charged with helium have been measured. The results indicate that helium is effectively trapped at crystal lattice defects and is released from them at the temperature below 350 K.
Źródło:
Acta Physica Polonica A; 1993, 83, 3; 371-374
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Effect of Visible Light Irradiation on Positronium Formation in Polyethylene at Low Temperature
Autorzy:
Ito, Y.
Hirade, T.
Hamada, E.
Suzuki, T.
Powiązania:
https://bibliotekanauki.pl/articles/2007996.pdf
Data publikacji:
1999-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
The effect of visible light exposing on the ortho-positronium formation in polyethylene was studied. Lifetime spectra of positrons in polyethylene were measured in the temperature range between 50 K and 370 K. It was observed that the visible light quenches the enhancement of ortho-positronium intensity (I$\text{}_{3}$) at lower temperature than ca. 250 K - the glass transition temperature of polyethylene. On the other hand, the lifetime of ortho-positronium component (τ$\text{}_{3}$) was not affected by the presence of the visible light.
Źródło:
Acta Physica Polonica A; 1999, 95, 4; 533-538
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Pal Application To the Study of Sorption Mechanism in Polymers - Capillary Effects
Autorzy:
Ito, Y.
Shimadzu, A.
Ikeda, K.
Powiązania:
https://bibliotekanauki.pl/articles/2008001.pdf
Data publikacji:
1999-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
The positron annihilation lifetime technique can be applied to the study of the sorption mechanism in polymers in a quite unique way. In our previous experiments it had been shown that τ$\text{}_{3}$ and I$\text{}_{3}$ of polymers show a V-shaped dependence as a function of the contact with vapors. The decreasing part of the V-shaped dependence had been attributed to the Langmuir-type sorption, and the increasing part to delayed occurrence of the Henry-type sorption. But since there was some doubt that a capillary effect, i.e. the vapor to be sorbed is deposited in between the polymer membranes, might be involved in the increasing part, we performed a careful experiment to avoid the capillary effect. We have performed further experiments in a careful condition to avoid the capillary effect, and have observed the same V-shape as before. Thus our interpretation of the V-shaped dependence has been established. Furthermore, in another example it is shown a case where the capillary effect is observed. This latter case is an example how positron annihilation lifetime can distinguish the real sorption and false sorption (capillary effect).
Źródło:
Acta Physica Polonica A; 1999, 95, 4; 546-550
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Void Shapes and o-Ps Lifetime in Molecular Crystals
Autorzy:
Jasińska, B.
Kozioł, A. E.
Goworek, T.
Powiązania:
https://bibliotekanauki.pl/articles/2008032.pdf
Data publikacji:
1999-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
The size and shape of the free volume in molecular crystals was estimated from crystallographic data. The o-Ps lifetime values were calculated from respective models and compared with the experimental data. The best agreement for channel-like voids has been obtained for the value of DR parameter equal 0.19 nm. The threshold value of radius allowing Ps trapping in the void was found to be (0.12-0.13) nm.
Źródło:
Acta Physica Polonica A; 1999, 95, 4; 557-561
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Influence of Deformation and Chemical Composition on Elementary Free Volumes in Glassy Polymers
Autorzy:
Shantarovich, V. P.
Novikov, Yu. A.
Suptel, Z. K.
Oleinik, E. F.
Boyce, M. C.
Powiązania:
https://bibliotekanauki.pl/articles/2008185.pdf
Data publikacji:
1999-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
A relation between positronium annihilation characteristics and concentration of elementary free volumes is considered for the case of positronium formation before its localization. We estimated the diffusion coefficient of nonlocalized positronium (≈10$\text{}^{-4}$ cm$\text{}^{2}$/s). The positron annihilation lifetime studies of uniaxial compression and annealing of some glassy polymers revealed variations of the shape of elementary free volumes size-distributions.
Źródło:
Acta Physica Polonica A; 1999, 95, 4; 659-662
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positron Lifetime Studies of the Subsurface Zones Created under Dry and Lubrication Conditions
Autorzy:
Dryzek, J.
Dryzek, E.
Powiązania:
https://bibliotekanauki.pl/articles/2024223.pdf
Data publikacji:
2001
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
We present the measurement of the positron lifetime spectra in the subsurface zones in copper samples with surfaces damaged in dry and lubrication conditions. We observe that close to the damaged surface the single vacancies were present, but deeper in the sample treated in the dry condition the vacancy clusters were detected. A zone with dislocations was located deeper than the zone with the vacancies and their clusters.
Źródło:
Acta Physica Polonica A; 2001, 99, 3-4; 351-354
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Application of a Pulsed Slow-Positron Beam to Low-Density Polyethylene Film
Autorzy:
Hamada, E.
Oshima, N.
Katoh, K.
Suzuki, T.
Kobayashi, H.
Kondo, K.
Kanazawa, I.
Ito, Y.
Powiązania:
https://bibliotekanauki.pl/articles/2024257.pdf
Data publikacji:
2001
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
A pulsing system for a slow-positron beam was applied to study the region near the surface of low-density polyethylene film using positron-annihilation lifetime measurement. The lifetime and intensity of ortho-positronium near the surface were measured as a function of the incident positron energy (1.6-9.1 keV). The size of intermolecular spaces in the surface region (~ 1500 nm) was larger than that in the bulk region. This tendency was especially strong in the region around 200 nm below the surface. On the other hand, the intensity of ortho-positronium decreased at lower incident positron energies, which was attributed to a decrease in the density of the spur electrons and/or an increase in the number of reemitted positrons from the surface.
Źródło:
Acta Physica Polonica A; 2001, 99, 3-4; 373-378
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Defects in Some Hydrogenated Metallic Materials Studied by Positrons
Autorzy:
Mikhalenkov, V. S.
Powiązania:
https://bibliotekanauki.pl/articles/2024976.pdf
Data publikacji:
2001
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
The measurements of angular correlation of annihilation radiation and positron lifetime were performed to study defects in commercial stainless steel and nickel subjected to deformation and electron irradiation. It follows from variation of S-parameter derived from angular correlation of annihilation radiation spectra that hydrogen charging of Fe-Cr-Ni-Mn austenite steel results in appearance of modest amount of vacancies which agglomerate into small clusters during annealing at low temperatures. Electron irradiation produces much more defects, so that subsequent hydrogenation does not add much to their concentration. The major part of defects anneals out gradually to 700 K. The residual part is preserved up to 950 K. This fact testifies to bonding state of vacancies. Nickel of 3N purity was prepared in three initial states, i.e. cold-rolled and hydrogenated before and after deformation. In an initial state all samples contain, along with simple defects, vacancy clusters. Their size and concentration are much larger in hydrogenated samples, as compared with merely cold-rolled one. Annealing above 400 K causes growth of cluster size and decrease in their concentration. At 500 K clusters are observed to disappear in cold-rolled sample, while in the sample hydrogenated after deformation they survive to 600 K.
Źródło:
Acta Physica Polonica A; 2001, 99, 3-4; 415-422
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Long-Time Aging Behaviour of the Alloy Al-2024 Characterized by Positron Annihilation Spectroscopy
Autorzy:
Nicht, E.-M.
Brauer, G.
Tempus, G.
Powiązania:
https://bibliotekanauki.pl/articles/2025039.pdf
Data publikacji:
2001
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
The reconstruction of the precipitation structure after solution treatment has been investigated by positron annihilation spectroscopy. In this study the behaviour of samples taken from an aircraft "Airbus 300", being in operation for 18 years, is compared to a reference material supplied by Alcoa. The results of position annihilation spectroscopy show that there are no significant differences in both materials. This finding is in agreement with the results obtained from other methods within the scope of the general research program which points to a materials behaviour as predicted for a safe operation of this type of aircraft.
Źródło:
Acta Physica Polonica A; 2001, 99, 3-4; 441-445
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigations into the Influence of Hydrogen and Defects on the Spectra of Lifetime of Positrons in Palladium
Autorzy:
Pietrzak, R.
Szatanik, R.
Smiatek, W.
Powiązania:
https://bibliotekanauki.pl/articles/2025753.pdf
Data publikacji:
2001
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
The influence of interstitial hydrogen concentration and structural defects caused by quenching of palladium, begun at different temperatures up to the temperature of liquid nitrogen or by stretching by external forces, on spectra of lifetimes of positrons in this metal was investigated. It was found that the spectra of positron lifetimes in the examined systems are best described by their distribution into two components. On the basis of the two-state model of annihilation, the conclusion was drawn that the initial temperature from which quenching of palladium is commenced and also the relative elongation, which is caused by external forces, markedly influence the concentrations and sizes of defects in the sample.
Źródło:
Acta Physica Polonica A; 2001, 99, 3-4; 455-463
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Comments on the Effect ofγ-Irradiation on Positronium Formation in Polymers at Low Temperatures
Autorzy:
Shantarovich, V. P.
Hirade, T.
Kevdina, I. B.
Gustov, V. W.
Oleinik, E. F.
Powiązania:
https://bibliotekanauki.pl/articles/2025760.pdf
Data publikacji:
2001
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
Quantitative description of the effect of γ-irradiation of PE and PMMA on positronium formation on the trapped electrons at low temperatures is suggested. The consideration shows that, at least in these substances, the number of the trapping centers is probably enough to localize all ortho-positronium, and therefore the intensity of the long-lived positronium component is dependent mostly on the probability of Ps formation but not on the number of the trapping centers.
Źródło:
Acta Physica Polonica A; 2001, 99, 3-4; 497-501
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positron Annihilation in Pure and Hydrogenated Palladium Deformed by Uniaxial Tension
Autorzy:
Rudzińska, W.
Pająk, J.
Szymański, Cz.
Szatanik, R.
Powiązania:
https://bibliotekanauki.pl/articles/2025764.pdf
Data publikacji:
2001
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
Angular distributions of the positron annihilation quanta were measured for pure and hydrogenated palladium samples deformed by uniaxial tension up to different deformation degrees. The relative difference curves, and the values of the R parameter characterizing the dimensions of defects trapping the positrons, were determined. It was found that for relative elongations ranging from 1.9 to 3.5%, in both the pure and hydrogenated palladium, the positrons are trapped in defects larger than vacancy clusters. The values of the R parameter for pure palladium samples elongated up to 0.39, 0.77, and 1.5% indicate a dominant role of smaller defects, like the vacancy clusters.
Źródło:
Acta Physica Polonica A; 2001, 99, 3-4; 479-486
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Some Aspects of Free Volume Studies in Molecular Substances Using Positron Annihilation Experiments
Autorzy:
Shantarovich, V. P.
Suzuki, T.
Djourelov, N.
Shimazu, A.
Gustov, V. W.
Kevdina, I. B.
Powiązania:
https://bibliotekanauki.pl/articles/2042187.pdf
Data publikacji:
2005-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
Positron annihilation lifetime spectroscopy is accepted now as a method for the studies of elementary free volumes (free volume holes) in solids, in polymers in particular. The aim of this paper is to discuss some problems, the difficulties on the way of this application and to illustrate them by several examples obtained by the authors.
Źródło:
Acta Physica Polonica A; 2005, 107, 4; 629-634
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Crystallization Process in Porous and Nonporous Vycor Glass
Autorzy:
Jasińska, B.
Dawidowicz, A. L.
Pikus, S.
Powiązania:
https://bibliotekanauki.pl/articles/2042215.pdf
Data publikacji:
2005-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
Three stages of thermal and chemical processing of Vycor glass were carried out. Raw material, the glass with small and big pores was studied. In each stage of study various crystallinity degrees of investigated material were obtained. The relation between crystallinity degree and the intensity of o-Ps components was determined. In nonporous material a high correlation between o-Ps intensity and crystallinity degree was found. In porous material the decrease in total o-Ps intensity can be a measure of the crystallinity degree.
Źródło:
Acta Physica Polonica A; 2005, 107, 5; 724-728
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positron Annihilation in Defected Monocrystalline Gold Samples
Autorzy:
Pająk, J.
Rudzińska, W.
Szuszkiewicz, M.
Garłowska, M.
Powiązania:
https://bibliotekanauki.pl/articles/2043340.pdf
Data publikacji:
2005-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
Angular distribution of the positron annihilation quanta was measured for monocrystalline gold samples, oriented in (110) and (111) directions. The samples were deformed by elongation for different deformation degrees. The S and W parameters as a function of deformation degree of the sample were determined. It was found that the dynamics of the dislocations and vacancy generation during the sliding of some crystallographic planes, depends on the crystallographic direction.
Źródło:
Acta Physica Polonica A; 2005, 107, 5; 848-851
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positron Annihilation in Polycrystalline Metals Deformed by Uniaxial Tension
Autorzy:
Rudzińska, W.
Pająk, J.
Szuszkiewicz, M.
Bujnarowski, G.
Kluza, A. A.
Powiązania:
https://bibliotekanauki.pl/articles/2043362.pdf
Data publikacji:
2005-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
Angular distributions of the positron annihilation quanta were measured for polycrystalline samples deformed by uniaxial tension up to different deformation degrees. The S parameter as a function of the W parameter was determined. The data obtained for samples elongated up to different elongation degrees indicate that in the proportionality and limited proportionality regions the changes in the physical properties of samples are governed mainly by generation of vacancies and formation and kinetics of transformations of vacancy clusters occurring first of all on the grains of monocrystallites. In the region of plastic deformations the dominant defects are dislocations and vacancies and their aggregates generated due to the formation and movement of the dislocation of the primary and secondary slip. The positron annihilation data are corroborated by the results of the resistometric and tensometric measurements in the proportionality and limited proportionality regions.
Źródło:
Acta Physica Polonica A; 2005, 107, 5; 857-863
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positron Annihilation Studies of the Subsurface Zone in Aluminium Alloys
Autorzy:
Dryzek, E.
Dryzek, J.
Powiązania:
https://bibliotekanauki.pl/articles/2047123.pdf
Data publikacji:
2006-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
The paper presents positron lifetime studies of the subsurface region of the aluminium cast AK64 alloy containing silicon as a main alloying element after sliding against stainless steel in the pin-on-disc tester. The subsurface zone of the depth exceeding 150μm has been detected. The scanning electron microscopy revealed only the plastically deformed region occurring at the depth up to ca. 50μm and cracks at the depth less than 30μm. The comparison with the results obtained for the AK12 alloy containing almost a twice higher amount of silicon demonstrates the influence of the hard silicon rich particles on the total depth of the subsurface zone. A higher amount of hard particle prevents to some extend the propagation of defects inside the material.
Źródło:
Acta Physica Polonica A; 2006, 110, 5; 569-575
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positron Annihilation in Metals Defected by Action of the Tensile Force
Autorzy:
Rudzińska, W.
Pająk, J.
Szuszkiewicz, M.
Bujnarowski, G.
Kluza, A. A.
Powiązania:
https://bibliotekanauki.pl/articles/2047160.pdf
Data publikacji:
2006-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
Results of experimental investigations of uniaxially elongated mono- and polycrystalline samples of several metals (Fe, Ta, Pd, Ag, and Au), performed using the positron annihilation methods, are reviewed. The dependences of the S-parameters and positron lifetimes on the relative elongation of the samples were presented. The data obtained for polycrystalline samples indicate that in the proportionality and limited proportionality regions the changes in the physical properties are governed mainly by generation of vacancies and by kinetics of formation and transformations of vacancy clusters occurring first of all on the grain boundaries of monocrystallites. In the region of plastic deformations the dominant defects are dislocations and vacancies and their aggregates generated due to the formation and movement of the dislocations of the primary and secondary slip. In the case of monocrystalline samples it was found that the dynamics of the dislocations and vacancy generation during the sliding of some crystallographic planes depends on the crystallographic direction.
Źródło:
Acta Physica Polonica A; 2006, 110, 5; 691-699
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Melting Process of the Sn-45 wt.% In and Sn-77 wt.% In Alloys as Viewed by Positron Annihilation
Autorzy:
Rudzińska, W.
Szuszkiewicz, M.
Powiązania:
https://bibliotekanauki.pl/articles/2047161.pdf
Data publikacji:
2006-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
The temperature dependences of the positron annihilation parameters F and R were determined for Sn-45 wt.% In and Sn-77 wt.% In alloys. The obtained results enabled to verify the vacancy and the quasicrystalline models of the melting process. It was found that for metals transforming into the liquid state from the structures different than the close packed structure, the melting transition are hardly explainable in terms of the vacancy model of melting. The strong trapping of positrons in metallic liquids is an indication of the presence of microvoids (vacancy clusters) or microcrystals containing defects more immense than vacancies. The share of these positron trapping centers in the volume of metallic liquids is constant or decreases with increasing temperature. The obtained results demonstrate the particular applicability of the positron annihilation method for studies of defect kinetics in metallic liquids.
Źródło:
Acta Physica Polonica A; 2006, 110, 5; 701-708
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Variable-Energy Positron Annihilation as Highly Sensitive Nanoporosimetry for Porous Thin Films
Autorzy:
Ito, K.
Kobayashi, Y.
Powiązania:
https://bibliotekanauki.pl/articles/2042214.pdf
Data publikacji:
2005-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
78.55.Mb
Opis:
Positron annihilation was applied to measuring critical pore sizes in various materials. In recent years, positron annihilation with a variable-energy positron beam has emerged as a powerful tool for the investigation of porous thin films synthesized as low-k dielectrics, high performance gas sensor materials, and so on. This paper is a brief overview of recent progress in nanopore characterization of thin films by means of positron annihilation with a description of several important issues relevant to positron annihilation.
Źródło:
Acta Physica Polonica A; 2005, 107, 5; 717-723
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positron Annihilation in Cotton Cellulose
Autorzy:
Golonka, P.
Mayer, J.
Dryzek, E.
Powiązania:
https://bibliotekanauki.pl/articles/2024232.pdf
Data publikacji:
2001
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
42.70.Jk
Opis:
The changes of the cotton fibre microstructure as a result of annealing at temperatures from 20ºC to 300ºC were investigated by positron lifetime spectroscopy and differential scanning calorimetry. The aim of the paper was to examine the cotton cellulose thermal degradation process.
Źródło:
Acta Physica Polonica A; 2001, 99, 3-4; 363-367
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
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