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The adsorption of ammonia on an iron surface at ambient temperature has been investigated using Auger electron spectroscopy (AES). The effect of the electron beam on the process of the ammonia adsorption has been studied. The... more
The adsorption of ammonia on an iron surface at ambient temperature has been investigated using Auger electron spectroscopy (AES). The effect of the electron beam on the process of the ammonia adsorption has been studied. The polycrystalline iron samples precovered with different amounts of oxygen (0.15-1 ML) or sulphur (1 ML) were used. The 24 initial sticking coefficient of ammonia to oxygen precovered iron surface was estimated as s ¯5310 (independently on 0 the oxygen coverage) for the adsorption experiments without the effect of the electron beam. The strong inhibiting effect of 26 sulphur precoverage on the ammonia adsorption has been found (s ¯6.5310 ). The electron beam has favourable effect on 0 the adsorption of ammonia, and this effect increases with the oxygen coverage (one monolayer of adsorbed nitrogen atoms at the saturation state and s ¯1 for the iron surface precovered with one monolayer of oxygen). The proposed explanation is 0 the favourable effect of the electron...
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Samples of nanocrystalline iron were carburised with ethylene and next reduced with hydrogen. Both carburisation and reduction were monitored by the thermogravimetry. The obtained samples were characterised using X-ray diffraction,... more
Samples of nanocrystalline iron were carburised with ethylene and next reduced with hydrogen. Both carburisation and reduction were monitored by the thermogravimetry. The obtained samples were characterised using X-ray diffraction, high-resolution transmission electron microscopy and ferromagnetic resonance. The samples after carburisation contained cementite (Fe3C) and carbon deposit (nanofibres and nanotubes). As the result of reduction with hydrogen at 450 or 500 °C cementite was reduced to iron. A major part of carbon was also hydrogenated, only thin carbon nanotubes remained. The FMR spectra of the prepared samples were recorded at room temperature. The sample after carburisation has shown a wide FMR line with weak intensity while the resonance field has been shifted to lower magnetic field. This spectrum has been attributed to the presence of cementite. The FMR lines corresponding to samples after reduction are more intense and are connected with the presence of α-Fe nanoparti...
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This paper examines the synthesis of the ZnO/carbon spheres composites using resorcinol—formaldehyde resin as a carbon source and zinc nitrate as a zinc oxide source in a solvothermal reactor heated with microwaves. The influence of... more
This paper examines the synthesis of the ZnO/carbon spheres composites using resorcinol—formaldehyde resin as a carbon source and zinc nitrate as a zinc oxide source in a solvothermal reactor heated with microwaves. The influence of activation with potassium oxalate and modification with zinc nitrate on the physicochemical properties of the obtained materials and CO2 adsorption capacity was investigated. It was found that in the case of nonactivated material as well as activated materials, the presence of zinc oxide in the carbon matrix had no effect or slightly increased the values of CO2 adsorption capacity. Only for the material where the weight ratio of carbon:zinc was 2:1, the decrease of CO2 adsorption capacity was reported. Additionally, CO2 adsorption experiments on nonactivated carbon spheres and those activated with potassium oxalate with different amounts of zinc nitrate were carried out at 40 °C using thermobalance. The highest CO2 adsorption capacity at temperature 40 °...
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Abstract In this work, a conversion of carbon dioxide (CO2) into methane, carbon monoxide, as well as hydrogen was investigated. The TiO2/rGO photocatalysts were prepared by two steps: solvothermal method and calcination at 500, 800, and... more
Abstract In this work, a conversion of carbon dioxide (CO2) into methane, carbon monoxide, as well as hydrogen was investigated. The TiO2/rGO photocatalysts were prepared by two steps: solvothermal method and calcination at 500, 800, and 1000 °C in an argon atmosphere. The obtained samples were characterized by X-ray diffraction (XRD), UV–vis diffuse reflection spectroscopy (UV–vis/DRS), N2 adsorption-desorption and analysis of carbon content. The activity of photocatalysts was evaluated in the photocatalytic reduction of CO2. The TiO2/rGO-10 without calcination showed the highest activity toward CO2 conversion. It was found that all samples after rGO modification exhibited good activity toward H2 generation with high selectivity. The enhanced photocatalytic performance was attributed mainly to the presence of graphene due to its excellent electron transport/collection ability.
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A whole series of titania nanocomposites modified with reduced graphene oxide (rGO) was prepared using solvothermal method followed by calcination. Modification of titania with rGO has been found to lead to better photocatalytic... more
A whole series of titania nanocomposites modified with reduced graphene oxide (rGO) was prepared using solvothermal method followed by calcination. Modification of titania with rGO has been found to lead to better photocatalytic properties. The highest photocatalytic performance was obtained at calcination temperature of 600°C. Electron paramagnetic resonance/ferromagnetic resonance measurements showed oxygen defects and ferromagnetic ordering systems. The linewidth of resonance line of oxygen defects decreased linearly with calcination temperature increasing up to 600°C and an accompanying growth of mean crystallite size of anatase phase. The integrated resonance line intensity of oxygen defects depended on the calcination temperature and caused a very large increase in the intensity of resonance lines originating from oxygen defects, because inert atmosphere of calcination was enhanced by graphene presence. The occurrence of magnetic ordering system significantly influenced the pe...
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Greenhouse effect is responsible for keeping average temperature of Earth’s atmosphere at level of about 288 K. Its intensification leads to warming of our planet and may contribute to adverse changes in the environment. The most... more
Greenhouse effect is responsible for keeping average temperature of Earth’s atmosphere at level of about 288 K. Its intensification leads to warming of our planet and may contribute to adverse changes in the environment. The most important pollution intensifying greenhouse effect is anthropogenic carbon dioxide. This particular gas absorbs secondary infrared radiation, which in the end leads to an increase of average temperature of Earth’s atmosphere. Main source of CO2 is burning of fossil fuels, like oil, natural gas, and coal. Therefore, to reduce its emission, a special CO2 capture and storage technology is required. Carbonaceous materials are promising materials for CO2 sorbents. Thus multiwalled carbon nanotubes, due to the lack of impurities like ash in activated carbons, were chosen as a model material for investigation of acid treatment impact on CO2 uptake. Remarkable 43% enhancement of CO2 sorption capacity was achieved at 273 K and relative pressure of 0.95. Samples were...
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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... 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...
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The effect of an alkali treatment (potassium hydroxide) on the properties of a commercial activated carbon has been studied. The aim of the treatment was to improve the adsorption properties of the material toward carbon dioxide. In the... more
The effect of an alkali treatment (potassium hydroxide) on the properties of a commercial activated carbon has been studied. The aim of the treatment was to improve the adsorption properties of the material toward carbon dioxide. In the result of the treatment, silica contained in the raw carbon was removed and the density of the material increased. The changes in the surface chemistry were observed as well. The treatment of the activated carbon with KOH resulted in a complete removal of carboxy and lactone groups and a decrease of the general content of the acidic groups (more significant than that of basic groups). Simultaneously, the surface concentration of hydroxyl groups increased. The alkali treatment of activated carbon resulted in an increase of carbon dioxide uptake of 14% (measured using a volumetric method at 0℃). The adsorption of carbon dioxide on activated carbon has a mixed (physicochemical) character and that two types of adsorption sites are present at the surface....
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ABSTRACT The formation of metal-encapsulated carbon nanomaterials by using metallic catalysts (iron, cobalt, and nickel) has been studied. Moreover, these materials were coated with silica surface modified by... more
ABSTRACT The formation of metal-encapsulated carbon nanomaterials by using metallic catalysts (iron, cobalt, and nickel) has been studied. Moreover, these materials were coated with silica surface modified by (3-Aminopropyl)-trimethoxysilane (APTS). Each intermediate structure was confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The surface morphology of silica-coated carbon nanomaterials was analyzed by scanning electron microscopy (SEM). The modified, APTS–silica surface was additionally characterized by Fourier transform infrared spectroscopy (FT-IR), elemental (EA), and thermogravimetric analysis (TGA).
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Calcination and microwave-assisted hydrothermal processing of precipitated zirconium dioxide are compared. Characterization of synthesized products of these two technologies is presented. The infiuence of thermal treatment up to 1200oC on... more
Calcination and microwave-assisted hydrothermal processing of precipitated zirconium dioxide are compared. Characterization of synthesized products of these two technologies is presented. The infiuence of thermal treatment up to 1200oC on the structural and spectroscopic properties of the so-obtained zirconium dioxide is examined. It was found that initial crystallization of material inhibits the crystal growth up to the 800oC (by means of XRD and TEM techniques), while the material crystallized from amorphous hydroxide precursor at 400oC, exhibits 26 nm sized crystallites already. It was found using the TG technique that the temperature range 100–200oC during the calcination process is equivalent to a microwave hydrothermal process by means of water content. Mass loss is estimated to be about 18%. Based on X-ray investigations it was found that the initial hydroxide precursor is amorphous, however, its luminescence activity suggests the close range ordering in a material.
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Magnetic properties of the Fe2O3/ZnO nanocomposites determined by SQUID ac/dc magnetization study and ferromagnetic resonance technique will be reviewed. Samples with stoichiometric formula nFe2O3/(1 − n)ZnO, where the composition index n... more
Magnetic properties of the Fe2O3/ZnO nanocomposites determined by SQUID ac/dc magnetization study and ferromagnetic resonance technique will be reviewed. Samples with stoichiometric formula nFe2O3/(1 − n)ZnO, where the composition index n changes from 0 to 1, have been synthesized using two methods: traditional wet chemical route followed by calcination and microwave assisted hydrothermal process. The obtained nanocomposites have been characterized by various techniques – XRD, SEM, TEM, and Raman spectroscopy. Special consideration will be devoted to SQUID dc magnetometry of n = 0. 30 nanocomposite. It will be shown that the obtained results concerning the temperature dependence of magnetization in ZFC and FC modes as well as magnetization in external magnetic fields could be interpreted in terms of superparamagnetic or spin glass phase model.
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Terbium doped zirconium dioxide was successfully synthesized using microwave hydrothermal method. The powder is strongly agglomerated and has mean crystallite size around 6 nm. The density of obtained powders is significantly lower than... more
Terbium doped zirconium dioxide was successfully synthesized using microwave hydrothermal method. The powder is strongly agglomerated and has mean crystallite size around 6 nm. The density of obtained powders is significantly lower than density of bulk zirconium dioxide indicating the existence of zirconium and dopant hydroxides remaining after the hydrothermal process. The effect of terbium on morphology, phase composition, specific surface area and density of the samples was determined.
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ABSTRACT
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Nanocrystalline iron has been carburised to form iron carbide. The ir on samples contained small amounts of additives (Al 2O3, and CaO) to avoid sintering. The carburisation process was carried out in a thermobalance, at 580 C, at... more
Nanocrystalline iron has been carburised to form iron carbide. The ir on samples contained small amounts of additives (Al 2O3, and CaO) to avoid sintering. The carburisation process was carried out in a thermobalance, at 580 C, at atmospheric pressure, under a flow of CH4/H2 (2:1). The carburisation process was stopped at several stages by cooling under gaseous nitrogen and the samples analysed by XRD. The average crystallit e size of iron nanoparticles has been determined as a function of the degree of carburisation. Based on t he recently presented nucleation model, the size distribution of iron nanocrystallites has been determined .
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ABSTRACT Fine particles of Fe2O3/ZnO were synthesized by wet chemical method. The morphological and structural properties of the mixed system were investigated by scanning electron microscopy, X-ray diffraction and X-ray photoelectron... more
ABSTRACT Fine particles of Fe2O3/ZnO were synthesized by wet chemical method. The morphological and structural properties of the mixed system were investigated by scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The major phase was determined to be the cubic spinel phase of γ-Fe2O3 maghemite with mean crystalline size of about 20 nm together with small amounts of hexagonal ZnO and ZnFe2O4. The magnetic properties of the material were investigated by ferromagnetic resonance (FMR) in the temperature range from liquid helium to room temperature. An asymmetric and very intense FMR signal was recorded exhibiting strong shift to low magnetic fields with decrease in temperature. Analysis of the FMR spectra in terms of two separate line components indicates the presence of strongly anisotropic interactions.
Research Interests: Condensed Matter Physics, Materials Science, Quantum Physics, Scanning Electron Microscopy, Magnetic field, and 11 moreMagnetic Properties, Ferromagnetic Resonance, X ray diffraction, Scanning Electron Microscope, Room Temperature, Spinel, Structural Properties, Ferromagnetism, X Ray Photoelectron Spectroscopy, Fine Particles, and maghemite
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Magnetic resonance study of six samples consisting of carbon encapsulated nickel nanoparticles or carbon nanotubes ended with such nickel nanoparticles was carried out at room temperature. Samples of Ni/C were prepared by carburization of... more
Magnetic resonance study of six samples consisting of carbon encapsulated nickel nanoparticles or carbon nanotubes ended with such nickel nanoparticles was carried out at room temperature. Samples of Ni/C were prepared by carburization of nanocrystalline nickel by ethylene (C2H4) and methane (CH4). Hydrocarbons decomposition on nickel nanoparticles was done at temperatures 500, 600 and 700°C. Magnetic resonance spectra of samples designated as CH4/500, CH4/600, CH4/700, C2H4/500, C2H4/600 and C2H4/700 were obtained by Bruker E 500 spectrometer. The integrated intensities of the resonance spectra were correlated with the carburization conditions (temperature, type of hydrocarbon) during samples preparation. A core-shell model of the investigated samples allowed rough estimation of appropriate shell sizes.
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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... 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.
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ABSTRACT Magnetic chitosan nanocomposites have been synthesized on the basis of metal (Fe, Co, Ni)-encapsulated carbon nanomaterials. The organic layer was identified using Fourier transform infrared spectroscopy and elemental analysis.... more
ABSTRACT Magnetic chitosan nanocomposites have been synthesized on the basis of metal (Fe, Co, Ni)-encapsulated carbon nanomaterials. The organic layer was identified using Fourier transform infrared spectroscopy and elemental analysis. The functionalized nanomaterials were employed to remove metal ions: cadmium, copper, nickel, lead and zinc from aqueous solutions. Their adsorption capacities were studied by the batch procedure. The concentration of cations extracted was determined by inductively coupled plasma mass spectrometry. The influence of different parameters (pH, amount of the support studied, contact time) on the cation extraction was investigated. The studies demonstrated excellent ability of copper and lead adsorption, and satisfactory adsorption of other ions applied by the supports studied. The nanocomposites with complexed cations can be easily removed from water with the help of an external magnet. They can then undergo regeneration in an acidic environment and can be reused in the analogous process repeatedly.
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Two samples of the binary magnetic system of nanoparticles containing Fe 3 O 4 -35% of weight, Fe 3 C-29% of weight and C-36% of weight (carbon) in PTMO block PET polymer at low concentrations of 0.5% and 0.3% have been prepared. The... more
Two samples of the binary magnetic system of nanoparticles containing Fe 3 O 4 -35% of weight, Fe 3 C-29% of weight and C-36% of weight (carbon) in PTMO block PET polymer at low concentrations of 0.5% and 0.3% have been prepared. The temperature dependence of the FMR resonance field has been investigated. It has shown the evidence of the matrix critical points. In all temperature ranges, especially at high temperatures, the FMR spectra are dominated by the signal from the Fe 3 O 4 oxide. For both samples the fitting procedure has been done by using the Lorentzian lines. The influence of temperature on the FMR resonance line has an extraordinary character near the matrix critical points (mechanical or magnetic interactions). It is suggested that using the FMR method might be very fruitful in studying the critical points of the matrix or in investigations of the intermolecular interactions.
Three samples with various Fe 3 C/C ratios have been prepared by the carburisation of iron with ethyl-ene or an ethylene–hydrogen mixture. Carburisation was controlled with thermogravimetry. After carburi-sation, the samples were... more
Three samples with various Fe 3 C/C ratios have been prepared by the carburisation of iron with ethyl-ene or an ethylene–hydrogen mixture. Carburisation was controlled with thermogravimetry. After carburi-sation, the samples were characterized using XRD and scanning electron microscopy. XRD measure-ments have shown the presence of the Fe 3 C (cementite) phase only. The mean size of cementite crystallites estimated using Scherrer's equation was in the range of 40–46 nm. Ferromagnetic resonance (FMR) absorption signals were investigated at room temperature. In all samples an asymmetric, very broad, and intense FMR line shifted toward low magnetic field was recorded. The linewidth, intensity, and position of the resonance field depended strongly on carbon concentration. With increasing carbon concentration the linewidth and integrated intensities of the FMR spectra decreased, and the resonance line shifted towards higher magnetic fields. The separation of granules from each other b...