U. Narkiewicz - Academia.edu (original) (raw)

Papers by U. Narkiewicz

Materials Science-poland, 2007

Magnetic properties of two FeC samples with different amounts of carbon have been studied. In bot... more Magnetic properties of two FeC samples with different amounts of carbon have been studied. In both cases, the amount of carbon was well above the mass sufficient to transform nanocrystalline iron into iron carbide (cementite). Through the dc magnetic and transmission electron microscopy (TEM) measurements it was shown that cementite nanoparticles formed agglomerates; the size distribution of these nanoparticles was very wide, and superparamagnetic-like behaviour was not observed even at room temperature.

IEEE Transactions on Magnetics

Three nanocrystalline samples of ZnO doped with MnO (with 20, 30, and 40 wt% of MnO in initial mi... more Three nanocrystalline samples of ZnO doped with MnO (with 20, 30, and 40 wt% of MnO in initial mixture) were synthesized by the wet chemical method. Previous X-ray diffraction study has found that they contained only hexagonal ZnO and cubic ZnMnO3 nanocrystals. DC magnetization study revealed a paramagnetic (PM) state above 50 K, the presence of mixed valence of Mn ions (Mn3+ and Mn4+) and an important role played by magnetic clusters influencing the behavior of the effective magnetic moment and effective interaction type. Low temperature results indicated a chain of magnetic transformation from PM to ferrimagnetic, to superparamagnetic and to blocked states. Electron spin resonance (ESR) provided additional information about magnetic relaxation of the spin clusters and possible location of separate Mn2+ and Mn4+ ions. Large magnetic inhomogeneity of our samples was evidenced, and it is the result of magnetic ions clustering, various valences of Mn ions, distribution of nanoparticle sizes, and competition of magnetic interactions.

REVIEWS ON ADVANCED MATERIALS SCIENCE

ZnO nanoparticles doped with transition metal ions are intensively studied nanomaterials, due to ... more ZnO nanoparticles doped with transition metal ions are intensively studied nanomaterials, due to their charges and the spins of electrons that provides new magnetic, optical and transport properties. They find a vast range of applications, ranging from optoelectronics to spintronics. In this context especially important is the room temperature ferromagnetism observed for ZnO doped nanomaterials, although this phenomenon is still a controversial and open topic in material science, mostly due to low reproducibility of results from samples prepared by different techniques. In the first part of this article a short review of papers using magnetometric methods to determine the magnetic characteristics of Co-doped ZnO nanomaterials is presented. Different models introduced to explain room temperature ferromagnetism (carrier mediated ferromagnetism, Co2+-oxygen vacancy pairs, blocked superparamagnetic clusters, Co2+-Zn interstitial pairs, heterogeneous distribution of magnetic ions) are ex...

Physica E: Low-dimensional Systems and Nanostructures

Abstract We have studied the magnetic properties of nanocrystals of ZnO:MnO prepared by tradition... more Abstract We have studied the magnetic properties of nanocrystals of ZnO:MnO prepared by traditional wet chemistry method. The detailed structural and morphological characterization was performed. The results of systematic measurements of AC magnetic susceptibility as a function of temperature and frequency as well as DC magnetization are reported. We observed two different types of magnetic behavior depending on the concentration doping. For samples with low nominal content (up to 30 wt% of MnO), superparamagnetic behavior was observed. We attribute the observed superparamagnetism to the presence of nanosized ZnMnO 3 phase. For nanocrystals doped above nominal 60 wt% of MnO ferrimagnetism was detected with T C at around 42 K. This magnetic behavior we assign to the presence of nanosized Mn 3 O 4 phase.

Materials Science-Poland, 2012

Decomposition of hydrocarbons was carried out on nickel and iron catalysts containing small amoun... more Decomposition of hydrocarbons was carried out on nickel and iron catalysts containing small amounts of calcium and aluminum oxides as structural promoters. Decomposition of methane, ethane and ethylene was studied under atmospheric pressure in the temperature range from 500 to 700°C. The phase composition of the obtained samples was investigated using X-ray diffraction method. The role of nickel and iron carbides in the formation of carbon deposit was discussed.

Journal of Alloys and Compounds, 2014

ABSTRACT Nanocrystalline samples of ZnO(Mn) were characterized by X-ray diffraction to determine ... more ABSTRACT Nanocrystalline samples of ZnO(Mn) were characterized by X-ray diffraction to determine composition of the samples (ZnO, Mn3O4, ZnMn2O4 and ZnMnO3) and the mean crystalline size (between 9 and 13 nm for ZnMnO3 phases, from 24 to 47 nm for Mn3O4 phases and above 100 nm for ZnO and ZnMn2O4 phases). In this paper we report the experimental spectra of Raman scattering (from 200 to 1600 cm�1) with surface optical phonons (SOP) in range of 520–575 cm�1. The phonon of registered phases exhibits effects connected to phase concentration, while the SOP phonon mode exhibits significant confinement effect.

Polish Journal of Environmental Studies

Dyes are synthetic organic compounds that are increasingly being produced and used extensively in... more Dyes are synthetic organic compounds that are increasingly being produced and used extensively in the paper, leather, textile, plastic, cosmetic, and other industries. Approximately 70,000 ton of dyestuffs are discharged into waste streams each year by the textile industry [1]. The presence of even very low concentrations of dyes in water reduces light penetration through the water surface, precluding photosynthesis of the aqueous flora. Additionally, many dyes or their metabolites have toxic as well as carcinogenic, mutagenic, and teratogenic effects on aquatic life and humans. Hence, the removal of dyes from aquatic wastewater has became environmentally important. Various methods including photocatalysis [2], chemical oxidation [3], coagulation [4], electrochemical [5], and adsorption [6] techniques have been applied for the removal of dyes from aqueous solutions. Among these methods, adsorption has been found to be superior

Microporous and Mesoporous Materials

Acta Physica Polonica A

Due to its fascinating properties such as high surface area, very good electrical and thermal con... more Due to its fascinating properties such as high surface area, very good electrical and thermal conductivity, excellent mechanical properties, optical and electrochemical properties, graphene may be the ideal material as a substrate of nanocomposites for applications in electronics. Graphene layer can be used as a conductive matrix allowing good contact between crystallites of nanomaterials. Despite pure graphene, its composites with other species can be of interest. In this paper the results of studies on the effect of methods and parameters of synthesis, for obtaining composites graphene/Fe2O3 on their structural properties and electrical properties are presented. A series of experiments was conducted using a commercially available graphene (Graphene Nanopowder AO-3) and iron nitrate. The materials were obtained using two pressure methods: pressure synthesis in the autoclave and synthesis in the microwave solvothermal reactor. The syntheses were carried out in a solution of ethanol. The specific surface area, helium density, morphology, phase composition, thermal properties and electric conductivity of the obtained composites were investigated.

Journal of Porous Materials

Agglomerated cobalt magnetic nanoparticles coated with carbon dispersed in paraffin matrix were p... more Agglomerated cobalt magnetic nanoparticles coated with carbon dispersed in paraffin matrix were prepared. Two samples with different carbon to cobalt content (25%C-75%Co and 50%C-50%Co), dispersed at low concentration in paraffin (about 0.5%) were studied. Tempera- ture dependence of the FMR (ferromagnetic resonance) spectra were recorded in the temperature range from 90K to room temperature (RT). Both samples showed very intense

Acta Physica Polonica A, 2009

The effect of ethylene partial pressure and temperature on the hydrocarbon decomposition rate was... more 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.

MATERIALS SCIENCE-POLAND

Decomposition of ethane over cobalt nanoparticles was studied in isothermal conditions in the tem... more Decomposition of ethane over cobalt nanoparticles was studied in isothermal conditions in the temperature range 375-500 °C. The obtained products were examined using XRD and HR-TEM techniques. Carbon deposit was reduced by a flow of hydrogen in the temperature range 500-575 °C. The kinetics of hydrocarbon decomposition and carbon deposit hydrogenation were investigated using the thermogravimetry method. The values of apparent activation energies of these processes have been determined.

Surface Science, 1996

The segregation of nitrogen, phosphorus, sulphur and carbon in iron causes the formation of Fe-X-... more The segregation of nitrogen, phosphorus, sulphur and carbon in iron causes the formation of Fe-X-X bonds on the surface. The system metal (Fe(111),Mo(100))-carbon has been studied using the AES method. The bonds Fe-C observed for lower surface coverages were transformed to Fe-CC bonds for higher coverages and the interaction between iron atoms and carbon atoms decreased. In the case of molybdenum the two different adsorption states were observed without a formation of CC bonding. The enthalpy of segregation for both adsorption states for iron and molybdenum has been determined using the Langrnuir-McLean equation. The enthalpy of carbon segregation at the first adsorption state (lower carbon coverages) was-140 and-68 kJ/mol for Fe(lll) and Mo(100) surfaces, respectively, and for the second adsorption state-60 and-47 kJ/mol, respectively. The further increase of the carbon surface concentration caused the formation of 3D graphite on the Fe(111) surface and of carbide-like compounds on the Mo(100) surface.

Journal of Physics and Chemistry of Solids, 2016

Acta Physica Polonica A, 2009

Nanocrystalline samples of ZnO(Fe) were synthesized by wet chemical method. Samples were characte... more Nanocrystalline samples of ZnO(Fe) were synthesized by wet chemical method. Samples were characterized by X-ray diffraction to determine the sample composition and the mean crystalline size. Low-frequency Raman modes were measured and assigned according to confined acoustic vibrations of spherical nanoparticles. Frequencies of these vibrational modes were analyzed in elastic continuum aproximation, which considers nanoparticle as homogeneous elastic sphere.

Acta Physica Polonica A, 2008

Nanocrystalline samples of ZnO(Fe) were synthesized by wet chemical method. Samples were characte... more Nanocrystalline samples of ZnO(Fe) were synthesized by wet chemical method. Samples were characterized by X-ray diffraction to determine composition of the samples (ZnO, Fe2O3, ZnFe2O4) and the mean crystalline size (8-52 nm). In this paper we report the experimental spectra of the Raman scattering (from 200 to 1600 cm-1). Main characteristics of experimental Raman spectrum in 200 to 1600 cm-1 spectral region are: sharp peak at 436 cm-1 and broad two-phonon structure at ≈1150 cm-1, typical of ZnO; broad structure below 700 cm-1 that has different position and shape in case of ZnFe2O4 or Fe2O3 nanoparticles.

Materials Science-poland, 2007

Magnetic properties of two FeC samples with different amounts of carbon have been studied. In bot... more Magnetic properties of two FeC samples with different amounts of carbon have been studied. In both cases, the amount of carbon was well above the mass sufficient to transform nanocrystalline iron into iron carbide (cementite). Through the dc magnetic and transmission electron microscopy (TEM) measurements it was shown that cementite nanoparticles formed agglomerates; the size distribution of these nanoparticles was very wide, and superparamagnetic-like behaviour was not observed even at room temperature.

IEEE Transactions on Magnetics

Three nanocrystalline samples of ZnO doped with MnO (with 20, 30, and 40 wt% of MnO in initial mi... more Three nanocrystalline samples of ZnO doped with MnO (with 20, 30, and 40 wt% of MnO in initial mixture) were synthesized by the wet chemical method. Previous X-ray diffraction study has found that they contained only hexagonal ZnO and cubic ZnMnO3 nanocrystals. DC magnetization study revealed a paramagnetic (PM) state above 50 K, the presence of mixed valence of Mn ions (Mn3+ and Mn4+) and an important role played by magnetic clusters influencing the behavior of the effective magnetic moment and effective interaction type. Low temperature results indicated a chain of magnetic transformation from PM to ferrimagnetic, to superparamagnetic and to blocked states. Electron spin resonance (ESR) provided additional information about magnetic relaxation of the spin clusters and possible location of separate Mn2+ and Mn4+ ions. Large magnetic inhomogeneity of our samples was evidenced, and it is the result of magnetic ions clustering, various valences of Mn ions, distribution of nanoparticle sizes, and competition of magnetic interactions.

REVIEWS ON ADVANCED MATERIALS SCIENCE

ZnO nanoparticles doped with transition metal ions are intensively studied nanomaterials, due to ... more ZnO nanoparticles doped with transition metal ions are intensively studied nanomaterials, due to their charges and the spins of electrons that provides new magnetic, optical and transport properties. They find a vast range of applications, ranging from optoelectronics to spintronics. In this context especially important is the room temperature ferromagnetism observed for ZnO doped nanomaterials, although this phenomenon is still a controversial and open topic in material science, mostly due to low reproducibility of results from samples prepared by different techniques. In the first part of this article a short review of papers using magnetometric methods to determine the magnetic characteristics of Co-doped ZnO nanomaterials is presented. Different models introduced to explain room temperature ferromagnetism (carrier mediated ferromagnetism, Co2+-oxygen vacancy pairs, blocked superparamagnetic clusters, Co2+-Zn interstitial pairs, heterogeneous distribution of magnetic ions) are ex...

Physica E: Low-dimensional Systems and Nanostructures

Abstract We have studied the magnetic properties of nanocrystals of ZnO:MnO prepared by tradition... more Abstract We have studied the magnetic properties of nanocrystals of ZnO:MnO prepared by traditional wet chemistry method. The detailed structural and morphological characterization was performed. The results of systematic measurements of AC magnetic susceptibility as a function of temperature and frequency as well as DC magnetization are reported. We observed two different types of magnetic behavior depending on the concentration doping. For samples with low nominal content (up to 30 wt% of MnO), superparamagnetic behavior was observed. We attribute the observed superparamagnetism to the presence of nanosized ZnMnO 3 phase. For nanocrystals doped above nominal 60 wt% of MnO ferrimagnetism was detected with T C at around 42 K. This magnetic behavior we assign to the presence of nanosized Mn 3 O 4 phase.

Materials Science-Poland, 2012

Decomposition of hydrocarbons was carried out on nickel and iron catalysts containing small amoun... more Decomposition of hydrocarbons was carried out on nickel and iron catalysts containing small amounts of calcium and aluminum oxides as structural promoters. Decomposition of methane, ethane and ethylene was studied under atmospheric pressure in the temperature range from 500 to 700°C. The phase composition of the obtained samples was investigated using X-ray diffraction method. The role of nickel and iron carbides in the formation of carbon deposit was discussed.

Journal of Alloys and Compounds, 2014

ABSTRACT Nanocrystalline samples of ZnO(Mn) were characterized by X-ray diffraction to determine ... more ABSTRACT Nanocrystalline samples of ZnO(Mn) were characterized by X-ray diffraction to determine composition of the samples (ZnO, Mn3O4, ZnMn2O4 and ZnMnO3) and the mean crystalline size (between 9 and 13 nm for ZnMnO3 phases, from 24 to 47 nm for Mn3O4 phases and above 100 nm for ZnO and ZnMn2O4 phases). In this paper we report the experimental spectra of Raman scattering (from 200 to 1600 cm�1) with surface optical phonons (SOP) in range of 520–575 cm�1. The phonon of registered phases exhibits effects connected to phase concentration, while the SOP phonon mode exhibits significant confinement effect.

Polish Journal of Environmental Studies

Dyes are synthetic organic compounds that are increasingly being produced and used extensively in... more Dyes are synthetic organic compounds that are increasingly being produced and used extensively in the paper, leather, textile, plastic, cosmetic, and other industries. Approximately 70,000 ton of dyestuffs are discharged into waste streams each year by the textile industry [1]. The presence of even very low concentrations of dyes in water reduces light penetration through the water surface, precluding photosynthesis of the aqueous flora. Additionally, many dyes or their metabolites have toxic as well as carcinogenic, mutagenic, and teratogenic effects on aquatic life and humans. Hence, the removal of dyes from aquatic wastewater has became environmentally important. Various methods including photocatalysis [2], chemical oxidation [3], coagulation [4], electrochemical [5], and adsorption [6] techniques have been applied for the removal of dyes from aqueous solutions. Among these methods, adsorption has been found to be superior

Microporous and Mesoporous Materials

Acta Physica Polonica A

Due to its fascinating properties such as high surface area, very good electrical and thermal con... more Due to its fascinating properties such as high surface area, very good electrical and thermal conductivity, excellent mechanical properties, optical and electrochemical properties, graphene may be the ideal material as a substrate of nanocomposites for applications in electronics. Graphene layer can be used as a conductive matrix allowing good contact between crystallites of nanomaterials. Despite pure graphene, its composites with other species can be of interest. In this paper the results of studies on the effect of methods and parameters of synthesis, for obtaining composites graphene/Fe2O3 on their structural properties and electrical properties are presented. A series of experiments was conducted using a commercially available graphene (Graphene Nanopowder AO-3) and iron nitrate. The materials were obtained using two pressure methods: pressure synthesis in the autoclave and synthesis in the microwave solvothermal reactor. The syntheses were carried out in a solution of ethanol. The specific surface area, helium density, morphology, phase composition, thermal properties and electric conductivity of the obtained composites were investigated.

Journal of Porous Materials

Agglomerated cobalt magnetic nanoparticles coated with carbon dispersed in paraffin matrix were p... more Agglomerated cobalt magnetic nanoparticles coated with carbon dispersed in paraffin matrix were prepared. Two samples with different carbon to cobalt content (25%C-75%Co and 50%C-50%Co), dispersed at low concentration in paraffin (about 0.5%) were studied. Tempera- ture dependence of the FMR (ferromagnetic resonance) spectra were recorded in the temperature range from 90K to room temperature (RT). Both samples showed very intense

Acta Physica Polonica A, 2009

The effect of ethylene partial pressure and temperature on the hydrocarbon decomposition rate was... more 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.

MATERIALS SCIENCE-POLAND

Decomposition of ethane over cobalt nanoparticles was studied in isothermal conditions in the tem... more Decomposition of ethane over cobalt nanoparticles was studied in isothermal conditions in the temperature range 375-500 °C. The obtained products were examined using XRD and HR-TEM techniques. Carbon deposit was reduced by a flow of hydrogen in the temperature range 500-575 °C. The kinetics of hydrocarbon decomposition and carbon deposit hydrogenation were investigated using the thermogravimetry method. The values of apparent activation energies of these processes have been determined.

Surface Science, 1996

The segregation of nitrogen, phosphorus, sulphur and carbon in iron causes the formation of Fe-X-... more The segregation of nitrogen, phosphorus, sulphur and carbon in iron causes the formation of Fe-X-X bonds on the surface. The system metal (Fe(111),Mo(100))-carbon has been studied using the AES method. The bonds Fe-C observed for lower surface coverages were transformed to Fe-CC bonds for higher coverages and the interaction between iron atoms and carbon atoms decreased. In the case of molybdenum the two different adsorption states were observed without a formation of CC bonding. The enthalpy of segregation for both adsorption states for iron and molybdenum has been determined using the Langrnuir-McLean equation. The enthalpy of carbon segregation at the first adsorption state (lower carbon coverages) was-140 and-68 kJ/mol for Fe(lll) and Mo(100) surfaces, respectively, and for the second adsorption state-60 and-47 kJ/mol, respectively. The further increase of the carbon surface concentration caused the formation of 3D graphite on the Fe(111) surface and of carbide-like compounds on the Mo(100) surface.

Journal of Physics and Chemistry of Solids, 2016

Acta Physica Polonica A, 2009

Nanocrystalline samples of ZnO(Fe) were synthesized by wet chemical method. Samples were characte... more Nanocrystalline samples of ZnO(Fe) were synthesized by wet chemical method. Samples were characterized by X-ray diffraction to determine the sample composition and the mean crystalline size. Low-frequency Raman modes were measured and assigned according to confined acoustic vibrations of spherical nanoparticles. Frequencies of these vibrational modes were analyzed in elastic continuum aproximation, which considers nanoparticle as homogeneous elastic sphere.

Acta Physica Polonica A, 2008

Nanocrystalline samples of ZnO(Fe) were synthesized by wet chemical method. Samples were characte... more Nanocrystalline samples of ZnO(Fe) were synthesized by wet chemical method. Samples were characterized by X-ray diffraction to determine composition of the samples (ZnO, Fe2O3, ZnFe2O4) and the mean crystalline size (8-52 nm). In this paper we report the experimental spectra of the Raman scattering (from 200 to 1600 cm-1). Main characteristics of experimental Raman spectrum in 200 to 1600 cm-1 spectral region are: sharp peak at 436 cm-1 and broad two-phonon structure at ≈1150 cm-1, typical of ZnO; broad structure below 700 cm-1 that has different position and shape in case of ZnFe2O4 or Fe2O3 nanoparticles.