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Water-Sorption Effects near Grain Boundaries in Modified MgO-Al₂O₃ Ceramics Tested with Positron-Positronium Trapping Algorithm

100%

Klym H., Ingram A., Shpotyuk O., Hadzaman I., Chalyy D.

Acta Physica Polonica A

2018

vol. 133

issue 4

864-868

Water-sorption processes near grain boundaries in the MgO-Al₂O₃ ceramics prepared at different temperatures were studied using positron annihilation lifetime spectroscopy. Numerical values of three- and four-component treatment of spectra were used for study of physical- and chemical-sorption processes in the MgO-Al₂O₃ ceramics. To apply mathematical approach in the form of positron-positronium trapping algorithm into three-component treatment of positron annihilation lifetime spectra it was shown that physical-adsorbed water did not modify positron trapping sites near grain boundaries in water-immersed MgO-Al₂O₃ ceramics and localized mainly in nanopores. The chemically-adsorbed water modifies structural extended defects located near grain boundaries that accompanied them by void fragmentation at water desorption.

On the Structural Phase Transition in a Perovskite-Type Diaminopropanetetrachlorocuprate(II) NH₃(CH₂)₃NH₃CuCl₄ Crystal

100%

Czupiński O., Ingram A., Kostrzewa M., Przesławski J., Czapla Z.

Acta Physica Polonica A

2017

vol. 131

issue 2

304-310

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.

Physico-Chemical and Biological Properties of Arsenic Sulfide (As_{55}S_{45}) Nanosuspension Prepared by Milling

86%

Bujňáková Z., Shpotyuk O., Sedlák J., Pastorek M., Turianicová E., Baláž P., Ingram A.

vol. 126

issue 4

902-906

Nanosuspension based on melt-quenched arsenic sulfide of nominal As_{55}S_{45} composition was prepared by nanomilling and tested as potential anticancer drug. Polyvinylpyrrolidone was used as steric stabilizer and inhibitor of agglomeration. Individual nanoparticles had average size of 192 nm (determined by photon cross-correlation spectroscopy) and had several times better dissolution ability in comparison with bulk As_{55}S_{45}. Effect of nanomilling is shown to be associated with formation of arsenic sulfide crystalline nanoparticles and free-volume entities located at the interface between nanoparticles and surrounding matrix as it follows from positron annihilation measurements. Cytotoxicity tests were performed using human melanoma cell line Bowes and confirmed high toxicity of the studied nanosuspension.

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3 Acta Physica Polonica A

1 2018

1 2017

1 2014

3 Ingram A.

2 Shpotyuk O.

1 Baláž P.

1 Bujňáková Z.

1 Chalyy D.

1 Czapla Z.

1 Czupiński O.

1 Hadzaman I.

1 Klym H.

1 Kostrzewa M.

1 Pastorek M.

1 Przesławski J.

1 Sedlák J.

1 Turianicová E.

Search results

Water-Sorption Effects near Grain Boundaries in Modified MgO-Al₂O₃ Ceramics Tested with Positron-Positronium Trapping Algorithm

On the Structural Phase Transition in a Perovskite-Type Diaminopropanetetrachlorocuprate(II) NH₃(CH₂)₃NH₃CuCl₄ Crystal

Physico-Chemical and Biological Properties of Arsenic Sulfide (As_{55}S_{45}) Nanosuspension Prepared by Milling