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A Search for Thermal Vacancies Forming Close Frenkel Pairs in Fe-Cr Alloys

100%
Chojcan J.
Acta Physica Polonica A
|
2001
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vol. 100
|
issue 5
723-729
EN
The room temperature Mössbauer spectra of ^{57}Fe were measured for the bcc Fe_{0.948}Cr_{0.052} solid solution quenched into water being at about 295 K from different temperatures not exceeding 1000 K, i.e. from the temperatures for which probabilities of formation of "clear" (Schottky) vacancies as well as vacancies forming the separate interstitial-vacancy (Frenkel) pairs are negligibly low. The obtained data were analysed in terms of concentration of unoccupied places in the 14-site surroundings of an ^{57}Fe Mössbauer probe in the sample. It turned out that the concentration of vacancies detected by the probe increases with temperature very rapidly - at the rate of about 10^{-4} K^{-1}. The result may suggest that the Mössbauer probe is sensitive to a possible thermal distortion of the lattice or creation of very close Frenkel pairs (the interstitial is the nearest neighbour of the vacant lattice site).
2
Content available remote

Positron Annihilation in Tektite and Hyalite

64%
Chojcan J., Sachanbiński M.
Acta Physica Polonica A
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1993
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vol. 83
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issue 3
267-271
EN
Positron lifetime spectra as well as one-dimensional angular distributions of photons coming from the two-photon annihilation of an electron-positron pair were measured at room temperature for samples of natural tektite and hyalite. The data were used for estimation of positronium characteristics in the specimens. The characteristics were analysed in terms of parameters of pores trapping the positronium atoms before their decay. In the analysis two models of the traps were taken into account, i.e. the square potential wells of spherical symmetry with barriers of finite and infinite heights. It was found that the linear dimensions of the pores resulting from these two-trap models are almost the same and they are of the order of 1 nm.
3
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Positron Annihilation in Obsidians

64%
Chojcan J., Sachanbiński M.
Acta Physica Polonica A
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1995
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vol. 88
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issue 1
103-110
EN
Positron lifetime spectra as well as one-dimensional angular correlations of positron annihilation radiation were measured at room temperature for samples of rhyolitic obsidian coming from Iceland, Italy and Armenia. The samples were of different age. One specimen (originating from Iceland) was relatively young, formed in 1980. The others were much older, collected during the 19th century. It was found that the linear dimensions of pores trapping the positronium atoms before their decay as well as the pore concentration in all old obsidians are almost the same independently of the place of their formation. Simultaneously the concentration of the pores in the young sample is about five times lower than in the old specimens. Basing on the result it is suggested to extend the study in order to find out if positron annihilation can be used for the investigation of the age of the volcanic accumulations containing obsidian.
4
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A Dilute-Limit Heat οf Solution of Aluminium in Iron Studied with ^{57}Fe Mössbauer Spectroscopy

64%
Chojcan J., Ostrasz A.
Acta Physica Polonica A
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2008
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vol. 114
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issue 6
1573-1578
EN
The room temperature ^{57}Fe Mössbauer spectra for binary iron-based solid solutions Fe_{1-x}Al_x, with x in the range 0.03 ≤ x ≤ 0.05, were analysed in terms of binding energy E_b between two Al atoms in the Fe-Al system. The extrapolated values of E_b for x= 0 were used for computation of the dilute-limit heat of solution of aluminium in iron. The results were compared with that resulting from the Miedema's model of alloys as well as those derived from the heat of formation of the system, obtained with both calorimetric measurements and theoretical calculations. The comparison shows that our Mössbauer spectroscopy findings are in good agreement with all the other results mentioned above.
5
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Nanostructure of Amber Observed by Positronium Probes

51%
Idczak R., Sachanbiński M., Chojcan J., Konieczny R.
Acta Physica Polonica A
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2015
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vol. 128
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issue 1
64-66
EN
The nanostructure of several non-crystalline amber samples of different origin was investigated with positronium atoms. It was found that the volumes of the pores observed by positronium atoms are relatively small, not greater than about 0.25 nm³ for all studied samples. Moreover, the obtained data show that the nano-porous structure of amber may be associated with its age.
6
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An Enthalpy of Solution of Silicon in Iron Studied by ^{57}Fe Mössbauer Spectroscopy

51%
Idczak R., Konieczny R., Chojcan J.
Acta Physica Polonica A
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2016
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vol. 129
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issue 3
367-370
EN
The room temperature Mössbauer spectra of ^{57}Fe were measured for Fe_{1-x}Si_x solid solutions with x in the range 0.01 ≤ x ≤ 0.05. The obtained data were analysed in terms of the binding energy E_{b} between two silicon atoms in the studied materials using the extended Hrynkiewicz-Królas idea. The extrapolated value of E_{b} for x=0 was used to computation of an enthalpy of solution H_{FeSi} of Si in α-Fe matrix. It was found that the H_{FeSi} value is negative or Si atoms interact repulsively. The result was compared with corresponding values given in the literature which were derived from experimental calorimetric data as well as with the value resulting from the cellular atomic model of alloys by Miedema.
7
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An Enthalpy of Solution of Cobalt and Nickel in Iron Studied with ^{57}Fe Mössbauer Spectroscopy

51%
Idczak R., Konieczny R., Konieczna Ż., Chojcan J.
Acta Physica Polonica A
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2011
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vol. 119
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issue 1
37-40
EN
The room temperature Mössbauer spectra of ^{57}Fe were measured for iron-based solid solutions Fe_{1-x}Co_{x} and Fe_{1-x}Ni_{x} with x in the range 0.01 ≤ x ≤ 0.05. The obtained data were analysed in terms of the binding energy E_{b} between two Co or Ni atoms in the studied materials using the extended Hrynkiewicz-Królas idea. It was found that the energy is positive or the non-iron atoms interact repulsively. The extrapolated value of E_{b} for x=0 was used for computation of the enthalpy of solution of cobalt and nickel in iron. The results were compared with our previous Mössbauer spectroscopy findings, the values resulting from the Miedema's model of alloys and the data derived from the enthalpy of formation of the Fe-Co and Fe-Ni systems, obtained with calorimetric methods. The comparison shows that the present results are in a qualitative agreement with the Miedema's model predictions and calorimetric measurements but they are at variance with the previous Mössbauer spectroscopy findings.
8
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A Study of Thermodynamic Properties of Dilute Fe-Au Alloys by the ⁵⁷Fe Mössbauer Spectroscopy

51%
Konieczny R., Idczak R., Chojcan J.
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EN
The room temperature Mössbauer spectra of ⁵⁷Fe were measured for Fe_{1-x}Au_x with the gold concentration ranging from 1 at.% till 4.8 at.%. They were analysed in terms of hyperfine parameters of their components related to unlike surroundings of the iron probes, determined by different numbers of gold atoms existing in the neighbourhood of iron atoms. Basing on the intensities of the spectrum components we determined binding energy E_b between two gold atoms in the studied materials. The latter was done for properly annealed samples using the extended Hrynkiewicz-Królas idea. It was found that the binding energy is positive or Au atoms interact repulsively. The extrapolated value of E_b for x =0 was used for computation of an enthalpy of solution of Au in Fe. Finally the obtained value of the enthalpy was used to predict the mixing enthalpy for the Fe-Au solid solutions. The results were compared with both the corresponding values resulting from the cellular atomic model of alloys by Miedema and those derived from experimental calorimetric data given in the literature.
9
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Proceedings of the 26th Polish Seminar on Positron Annihilation. Preface.

32%
Świątkowski W., Chojcan J.
Acta Physica Polonica A
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1995
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vol. 88
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issue 1
3-6
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