Use of Energy Summing for Selection of Coincidence Events in Positron-Lifetime Spectroscopy

Bečvář, F.; Čı́žek, Jakub; Procházka, I.

doi:10.12693/aphyspola.95.448

Cited by 14 publications

(1 citation statement)

References 3 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Subsequently, the samples were isochronaly annealed with the effective heating rate of 1 K/min. A PL spectrometer described in [3,4] with the timing resolution of 150 ps (FWHM 22 Na) at a coincidence count rate of 80 counts/s was used. XRD studies were carried out with the aid of XRD7 and HZG4 (Seifert-FPM) powder diffractometers using Cu K a radiation.…”

Section: Methodsmentioning

confidence: 99%

Thermal Stability of Ultra Fine Grained Copper Prepared by High Pressure Torsion Using Various Pressures

Čı́žek

Procházka

Kužel

et al. 2003

JMNM

View full text Add to dashboard Cite

Two samples of ultra fine grained copper were prepared by high pressure torsion using two different pressures of 3 GPa and 6 GPa. The higher pressure resulted in an ultra fine grained structure with a smaller grain size and higher density of defects compared to the sample prepared with the lower pressure. We compared thermal stability of ultra fine grained structure for both samples. Microstructure investigations were performed by positron lifetime spectroscopy combined with X-ray diffraction and transmission electron microscopy. Firstly microstructure of the asprepared samples was characterized. Subsequently the samples were subjected to isochronal annealing and evolution of microstructure with annealing temperature in both samples was compared. We have found that the sample prepared using the higher pressure exhibits a lower thermal stability.

show abstract

Section: Methodsmentioning

confidence: 99%

Thermal Stability of Ultra Fine Grained Copper Prepared by High Pressure Torsion Using Various Pressures

Čı́žek

Procházka

Kužel

et al. 2003

JMNM

View full text Add to dashboard Cite

show abstract

Positron Lifetime Study of Reactor Pressure Vessel Steels

Čı́žek

Procházka

Kočík

et al. 2000

phys. stat. sol. (a)

View full text Add to dashboard Cite

Positron lifetime (PL) study of several reactor pressure vessel (RPV) steels is presented. VVER-440 type Cr±Mo±V, VVER-1000 type Cr±Mo±Ni±V and A533-B RPV steels were included in the investigation. It was found that positrons annihilate from delocalized state or trapped at dislocations (lifetime % 150 ps) in all specimens. In the case of Cr±Mo±V and Cr±Mo±Ni±V RPV steels a small fraction of positrons may be trapped at misfit defects at the vanadium carbide±matrix interface. The conventional trapping model (CTM) failed in the interpretation of measured PL spectra due to the strongly non-uniform spatial distribution of dislocations in the samples. Therefore, the modified trapping model (MTM) was developed in the present work. Contrary to the CTM, the MTM takes into account the non-uniform distribution of dislocations and it provides a self-consistent interpretation of measured PL spectra. The specific trapping rate n D 0:36 Â 10 À4 m 2 s À1 was determined by comparison of the mean dislocation density obtained from PL spectra using the MTM and that measured by TEM. The component arising from positrons trapped at screw dislocations and the component coming from positrons trapped at edge ones were separated in the PL spectra. This approach allowed us to obtain a measure of fraction of screw and edge dislocations in the samples. J. C Ï iÂz Ïek et al.a As: 0.008 wt%, Co: 0.009 wt%. b Solute Al: 0.012 wt%.

show abstract

Positron-Lifetime Investigation of Thermal Stability of Ultra-Fine Grained Nickel

Prochzka

Cieslar

et al. 2002

phys. stat. sol. (a)

View full text Add to dashboard Cite

Thermal stability of ultra-fine grained (UFG) nickel (mean grain size 114 nm) prepared by high pressure torsion was studied by means of positron-lifetime spectroscopy (PLS) combined with TEM. The experimental results obtained by PLS are interpreted using the diffusion trapping model, which allows for determination of important physical parameters characterizing the specimens. The microstructure of the material studied is strongly inhomogeneous. The grain interiors with low dislocation density are separated by distorted regions with high numbers of dislocations. We have found that positrons are trapped at dislocations inside the distorted regions and in the microvoids situated inside the grains. Structure evolution with increasing temperature was studied in details using isochronal annealing of the specimen. We have found that recovery of the UFG structure involves the abnormal grain growth followed by further recrystallization in the whole volume of samples. It was shown that PLS is sensitive to structure changes, caused by the magnetostriction phenomenon.

show abstract

Use of Energy Summing for Selection of Coincidence Events in Positron-Lifetime Spectroscopy

Cited by 14 publications

References 3 publications

Thermal Stability of Ultra Fine Grained Copper Prepared by High Pressure Torsion Using Various Pressures

Thermal Stability of Ultra Fine Grained Copper Prepared by High Pressure Torsion Using Various Pressures

Positron Lifetime Study of Reactor Pressure Vessel Steels

Positron-Lifetime Investigation of Thermal Stability of Ultra-Fine Grained Nickel

Contact Info

Product

Resources

About