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1
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Positron Annihilation Studies of Polyethylene-Carbon Black Composites

100%
Kostrzewa M., Michno Z., Majcherczyk T.
Acta Physica Polonica A
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1995
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vol. 88
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issue 1
193-198
EN
Results of investigations of the angular correlation of annihilation radiation and positron annihilation lifetime measurements are presented for polyethylene-carbon black composites. The inhibition of positronium formation due to the carbon black introduction is evidenced by a decrease in intensities of the narrow component in angular correlation of annihilation radiation curves and of the longest-lived components in positron annihilation lifetime spectra. A qualitative interpretation of the data in terms of the free-volumes model is proposed.
2
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Test Measurements of Modernized Version of Two-Detector Doppler Spectrometer

100%
Baranowski A., Kostrzewa M., Szuszkiewicz M.
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vol. 95
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issue 4
439-447
EN
Basing on the electronic analogue modules in adding and subtracting branches of pulses, a modernized two-detector Doppler spectrometer has been constructed using only one multichannel analyser. Doppler spectra for Al, Ni, Ag have been measured. ACARFIT computer program was used to compare the Doppler and angular correlation of annihilation radiation results.
3
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Positron Lifetime in Hostaphan

100%
Kostrzewa M., Bujnarowski G., Kluza A., Szuszkiewicz M.
Acta Physica Polonica A
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2006
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vol. 110
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issue 5
615-620
EN
Positron lifetime measurements in hostaphan RNK, used for encapsulation of ^{22}Na positron sources, were performed. It was found that the parameter of positron lifetime spectra in hostaphan RNK differ markedly from those for other forms of polyethylene terephthalate. The maximum penetration depth of positrons from RNK hostaphan amounts 0.42 mm. The information gained in the present study is of great importance for experimenters using hostaphan RNK for encapsulation of positron sources.
4
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Studying of Nickel Alloys with 1 at.% of Ge, Zn, In, Zr and Pb by Positron Annihilation Methods

100%
Baranowski A., Kostrzewa M., Szuszkiewicz M.
Acta Physica Polonica A
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2001
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vol. 99
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issue 3-4
329-336
EN
The measurements of cold rolled nickel alloys with 1 at.% of Ge, Zn, In, Zr, Pb and additionally Ti and Sb by positron lifetime and Doppler broadening techniques have been done. Monovacancies were a dominating type of defects in the alloys. The authors of the present paper connect the differences between the annihilation parameters of the investigated samples with the existence of the vacancy-impurity atom pairs. A direct proportionality between the vacancy lifetime and the product of vacancy-impurity binding energy and atomic radius of impurity atom has been found.
5
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Positron Annihilation with Electrons of Admixture Atoms in Some Binary Nickel Alloys

100%
Baranowski A., Kostrzewa M., Szuszkiewicz M.
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EN
Weighted difference curves have been shortly presented as a proper tool allowing to analyze in another way two-detector Doppler spectra regarding positron annihilation with admixture electrons in some nickel alloys. The analysis of low and middle momentum parts of Doppler spectra for investigated alloys reflects the annihilation of positrons with admixture electrons. There is no distinct signal of annihilations with admixture electrons from the positron lifetime data for well-annealed samples.
6
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On the Structural Phase Transition in a Perovskite-Type Diaminopropanetetrachlorocuprate(II) NH₃(CH₂)₃NH₃CuCl₄ Crystal

88%
Czupiński O., Ingram A., Kostrzewa M., Przesławski J., Czapla Z.
Acta Physica Polonica A
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2017
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vol. 131
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issue 2
304-310
EN
Chemical preparation, differential scanning calorimetry and thermal stability differential thermal gravimetry studies, positron annihilation lifetime investigations, optical observations as well as electric properties of the NH₃(CH₂)₃NH₃CuCl₄ crystal are presented. On the basis of the differential scanning calorimetry response the structural phase transition of the first order was observed at 436 K. The enthalpy and entropy of the phase transition are equal to 1120 J/mol and 2.57 J/(mol K), respectively. Differential thermal analysis and thermogravimetric analysis studies confirmed the phase transition at 436 K and one can conclude the chemical and thermal stability of the compound up to about 480 K. Optical observations showed a continuous change of colour from yellow to dark brown above the phase transition to 436 K. Dielectric measurements showed a significant increase of conductivity upon approaching the phase transition regions, with a significant increase above the phase transition temperature. An activation energy dependent on the temperature range, and different for each particular phase, is obtained from measurements of complex impedance.
7
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Cet in Solidifying Roll - Thermal Gradient Field Analysis

76%
Kania B., Jędrzejczyk D., Wołczyński W., Guzik E., Wajda W., Kostrzewa M.
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issue 1
8
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Influence of the Reforging Degree on the Annihilation of the Segregation Defects in the Massive Forging Ingots

76%
Kowalski J., Wołczyński W., Pstruś J., Pawlak S., Kostrzewa M., Martynowski R.
Archives of Metallurgy and Materials
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2011
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issue 4
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