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Characterization of Defects in Titanium Created by Hydrogen Charging

100%
Hruška P., Čížek J., Knapp J., Melikhova O., Havela L., Mašková S., Lukáč F.
Acta Physica Polonica A
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2017
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vol. 132
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issue 5
1606-1610
EN
Hydrogen interaction with vacancies in α-Ti was investigated employing positron lifetime spectroscopy combined with ab initio theoretical modeling of vacancy-hydrogen complexes. Ab initio modeling revealed that multiple hydrogen atoms up to 7 can be trapped at vacancies in the α-Ti lattice. Trapped H atoms are located close to the nearest neighbor tetrahedral sites around the centre of vacancy. Lifetimes of positrons trapped at vacancies associated with various numbers of hydrogen atoms were calculated. Positron lifetime measurement of H-loaded α-Ti samples revealed that phase transition into the hydride phase introduced dislocations. Vacancies were created by H loading as well and agglomerated into small vacancy clusters.
2
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Ferromagnetic Resonance in CdTe:Cr Single Crystals Containing Dopant-Related Macrodefects

76%
Popovych V. D., Kuzma M., Skop N., Stefaniuk I., Cieniek B.
Acta Physica Polonica A
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2017
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vol. 132
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issue 1
34-38
EN
We study CdTe:Cr single crystals grown by the physical vapor transport method from pre-synthesized (Cd,Cr)Te alloys with 5 at.% of chromium nominal content. Macrodefects in the form of (111)-oriented thin platelets of dopant-related second phases were detected by scanning electron microscopy patterning of the chemically treated surfaces of the crystals. Magnetic properties of the crystals were investigated by ferromagnetic resonance using X-band Bruker spectrometer (9.43 GHz). Their ferromagnetic resonance spectra show several broad lines, which position depends on the orientation of the sample in relation to the external magnetic field in spectrometer. The angular dependences of ferromagnetic resonance spectra are interpreted in the frame of shape anisotropy of ferromagnetic resonance of the planar defects embedded in a weak magnetic CdTe matrix.
3
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Impact of Impulse Shot Peening Parameters on Properties of Stainless Steel Surface

64%
Wiertel M., Zaleski K., Gorgol M., Skoczylas A., Zaleski R.
Acta Physica Polonica A
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2017
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vol. 132
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issue 5
1611-1615
EN
Shot peening was applied to austenitic stainless steel 1.4541 (EN). The surface treatment was performed at various impact energies E, impact densities j and ball diameters D. This resulted in improved microhardness, which increases monotonically with the increase of E, j and 1/D. However, its changes with E and j achieve saturation at about 400 HV0.1. On the contrary, no saturation is observed in the investigated range for 1/D. In the un-shot peened 1.4541 (EN) steel, the lifetime component of low intensity was found with use of positron annihilation lifetime spectroscopy (PALS). It corresponds to positron annihilation from delocalized state of positrons in bulk. In the shot peened samples the bulk component is no longer observed. Instead, two types of defects can be identified: vacancy-like defects coupled with edge dislocations and vacancies or their small clusters (consisting 3÷5 vacancies). The results of PALS and hardness testing do not correspond very well, especially in the case of the samples shot peened with balls of varying diameters. The most probable reason for this are different depth profiles of both methods. It seems that the defects, which are responsible for the increase of static microhardness above 400 HV0.1 are located mostly below the surface layer penetrated by positrons.
4
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Local Pseudoelastic Behaviour and Surface Characteristics of N Ion Implanted NiTi Shape Memory Alloy

64%
Levintant-Zayonts N., Kwiatkowski L., Swiatek Z., Brzozowska J.
Acta Physica Polonica A
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2017
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vol. 132
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issue 2
210-216
EN
The main goal of the proposed paper is to present the results of the nitrogen ion implantation effects on mechanical and corrosion properties of NiTi shape memory alloy. Local pseudoelasticity phenomena of NiTi were determined using the ultra-low load applied system. The load-penetration depth curves show that lower nitrogen fluence improves mechanical properties in the near surface layer but higher ion fluence leads to degradation of pseudoelasticity properties. Corrosion resistance of NiTi in the Ringer solution was evaluated by means of electrochemical methods. The results of potentiodynamic measurements in the anodic range for implanted NiTi indicate a decrease of passive current density range in comparison with non-treated NiTi, without any signs related to Ni release. The results of impedance measurements recorded at the corrosion potential show a capacitive behaviour for all samples without clear predominance of one of them. It can be explained by the fact that this result concerns the first stage of corrosion exposition. It is shown that nitrogen ion implantation leads to formation of modified surface of improved physicochemical properties.
5
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Concentration of radiation displacement defects in BSO and BGO crystals irradiated by electrons or neutrons

64%
Potera P.
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EN
This work is devoted to the calculation of the concentration of radiation displacement defects (RDD) in bismuth germanate and bismuth silicate crystals as a function of particle energy (electrons and neutrons). Energy dependencies of RDD concentrations are discussed in comparison with results for other complex oxide crystals. The obtained results show that for the case of electron irradiation the radiation hardness of BSO and BGO should be similar to other oxide crystals, but for neutrons is drastically smaller. Additionally, for the neutron irradiation, the efficiency of the production of defects in the oxide sublattice is drastically smaller than for other oxide crystals.
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