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4 Acta Physica Polonica A

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The Kinetics of Ethylene Decomposition on Iron Catalyst

100%

Pełech I. , Narkiewicz U.

Acta Physica Polonica A

2009

tom 116

nr S

S-146-S-149

The effect of ethylene partial pressure and temperature on the hydrocarbon decomposition rate was studied. As a catalyst, a triply promoted iron catalyst (with addition of small amounts of potassium, calcium and alumina oxides) was used. The mean crystallites size was ca. 17 nm. The processes were performed using pure ethylene or ethylene-nitrogen mixture under atmospheric pressure at the temperature range from 400 to 460°C. The growth of carbon mass as a function of reaction time was measured using a thermobalance. The phase composition of the samples after ethylene decomposition was determined using X-ray diffraction technique. The reaction rate was independent of ethylene partial pressure in the range from 0.25 to 1 bar. The maximal carbon yield for given experimental conditions was estimated.

Synthesis and Characterization of ZnO Doped with Fe_{2}O_{3} - Hydrothermal Synthesis and Calcination Process

61%

Sibera D. , Jędrzejewski R. , Mizeracki J. , Presz A. , Narkiewicz U. , Łojkowski W.

Acta Physica Polonica A

2009

tom 116

nr S

S-133-S-135

The aim of the present work is to compare two methods of synthesis of nanocrystallline zinc oxide doped with iron oxide. The synthesis was carried out using microwave asssisted hydrothermal synthesis and traditional wet chemistry method followed by calcination. The phase composition of the samples was determined using X-ray diffraction measurements. Depending on the chemical composition of the samples, hexagonal ZnO, and/or cubic ZnFe_{2}O_{4} were identified. The morphology of the received materials was characterized using scanning electron microscopy. Two different structures of agglomerates were observed: a hexagonal structure (corresponding to zinc oxide) and spherical (corresponding to spinel phase). The effect of the iron oxide concentration on specific surface area and density of the samples was determined.

Surface Chemistry of Zirconia Nanopowders Doped with Pr_2O_3: an XPS Study

61%

Suchorski Y. , Wrobel R. , Becker S. , Opalińska A. , Narkiewicz U. , Podsiadly M. , Weiss H.

nr S

S-125-S-134

Zirconia nanopowders of tetragonal crystallographic structure doped with Pr_2O_3 were prepared by the microwave-assisted hydrothermal synthesis and coprecipitation method. The surface compositions were studied by X-ray photoelectron spectroscopy. The nanopowder particles appear to be inhomogeneous in their structure: for the surface region an enrichment with praseodymium is detected by X-ray photoelectron spectroscopy measurements. This allows the assumption of a core-shell-like structure of single nanopowders particles. The X-ray photoelectron spectroscopy studies confirm also Zr^{4+} and Pr^{3+} as main oxidation states of zirconium and praseodymium in the studied compounds.

Nanocrystalline ZnO Doped with Fe_2O_3 - Magnetic and Structural Properties

51%

Kuryliszyn-Kudelska I. , Hadžić B. , Sibera D. , Kilanski L. , Romčević N. , Romčević M. , Narkiewicz U. , Dobrowolski W.

nr 5

689-691

We have studied the magnetic properties of ZnO nanocrystals doped with Fe_2O_3 in the magnetic dopant range from 5 to 70 wt%. The nanocrystals were synthesized by wet chemical method. The detailed structural characterization was performed by means of X-ray diffraction and micro-Raman spectroscopy measurements. The results of systematic measurements of magnetic AC susceptibility as a function of temperature and frequency are presented. We observed different types of magnetic behavior. For ZnO samples doped with low content of Fe_2O_3, the results of low-field AC susceptibility are satisfactorily explained by superparamagnetic model including inter-particle interactions. With the increase of magnetic Fe_2O_3 content, the spin-glass-like behavior is observed.