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1
Content available remote Badanie procesów azotowania i redukcji w układzie nanokrystaliczne żelazo-amoniak-wodór
Wilk B., Arabczyk W.
Przemysł Chemiczny
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2014
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T. 93, nr 6
1036-1040
PL
Badano procesy azotowania nanokrystalicznego żelaza oraz redukcji otrzymanych nanokrystalicznych azotków żelaza mieszaninami azotującymi o różnym składzie chemicznym w temp. 350°C w stanach kwazirównowagowych. Wykazano znaczne odstępstwa zachowania nanokrystalicznego układu Fe-NH3-H2 od otrzymanych przez Lehrera zależności dla materiałów grubokrystalicznych. Stwierdzono istnienie zjawiska histerezy dla zależności stopnia zaazotowania żelaza od potencjału azotującego w stałej temperaturze. Izoterma procesu redukcji nanokrystalicznych azotków żelaza przebiega powyżej izotermy procesu azotowania nanokrystalicznego żelaza w obszarze potencjałów azotujących, w których zachodzi reakcja chemiczna. W tych obszarach azotujących w procesach azotowania i redukcji trwale istnieją obok siebie dwie fazy stałe: α-Fe(N) + γ’-Fe4N lub γ’-Fe4N + ε-Fe3-2N. W redukcji nanokrystalicznego azotku żelaza w temp. 350°C w obszarze potencjałów azotujących 0,0036-0,0020 Pa-0,5 stwierdzono współistnienie 3 faz stałych: α-Fe(N) + γ’-Fe4N + ε-Fe3-2N.
EN
Com. Fe catalyst for NH3 synthesis was nitrided with NH3-H2 mixts. at 350°C. The nitriding resulted in formation of stable Fe(N), Fe4N and Fe2-3N phases. After redn., the area of the Fe2-3N phase was extended.
2
Content available remote Magnetic characterization of nanocrystalline iron samples with different size distributions
Typek J., Zolnierkiewicz G., Pelka R., Kielbasa K, Arabczyk W, Guskos N.
Materials Science Poland
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2014
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Vol. 32, No. 3
423—429
EN
Nanocrystalline iron was obtained by fusing magnetite and promoters. The oxidized form was reduced with hydrogen and passivated (sample P0). The average nanocrystallite size in sample P0 was d(P0) =16 nm and the width of size distribution was s(P0) = 18 nm. Samples of nanocrystalline iron with narrower diameter ranges and larger and smaller average crystallite sizes were also synthesized. They were: sample P1 (d(P1) = 28 nm, s(P1) = 5 nm), sample P2 (d(P2) = 22 nm, s(P1) = 5 nm), sample P3 (d(P3) = 12 nm, s(P1) = 9 nm). These four samples were studied at room temperature by dc magnetization measurements and ferromagnetic resonance at microwave frequency. Correlations between samples sizes distributions (average size and width of the sizes) and magnetic parameters (effective magnetization, anisotropy field, anisotropy constant, FMR linewidth) were investigated. It was found that the anisotropy field and effective magnetization determined from FMR spectra scale linearly with nanoparticle sizes, while the effective magnetic anisotropy constant determined from the hysteresis loops decreases with nanoparticle size increase.
3
Content available remote Przemiany fazowe podczas procesów azotowania nanokrystalicznego żelaza
Moszyński D., Moszyńska I.
Przemysł Chemiczny
|
2013
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T. 92, nr 7
1332-1335
4
Content available remote Badanie procesu azotowania katalizatora żelazowego
Kiełbasa K., Wilk B., Arabczyk W.
Przemysł Chemiczny
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2013
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T. 92, nr 5
859-861
5
Content available remote Characterization of carbon deposit with controlled carburization degree
Helminiak A., Mijowska E., Arabczyk W.
Materials Science Poland
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2013
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Vol. 31, No. 1
29-35
EN
Promoted nanocrystalline iron was carburized in a differential tubular flow reactor with thermogravimetric measurement of mass changes. The carburization process was carried out in the presence of pure methane under atmospheric pressure at 650 °C to obtain different carburization degrees of the sample. The carburized iron samples were characterized by the X-ray diffraction, high-resolution transmission electron microscope in the energy-dispersive X-ray spectroscopy mode, thermoprogrammable oxidation, and Raman spectroscopy. As a result of the methane decomposition on the nanocrystalline iron the following nanocrystalline products were observed: iron carbide Fe3C, graphite, iron and nanotubes. The crystallinity of the samples increased with the carburization degree.
6
Content available remote Thermal stability of nanocrystalline iron
Wrobel R. J.
Materials Science Poland
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2012
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Vol. 30, No. 1
63-69
EN
Nanocrystalline iron was obtained by reduction of magnetite doped with structural promoters at 773 K and characterized by various methods i.e. thermal desorption of gases (BET), X-ray diffraction (XRD) and inductively coupled plasma atomic emission spectroscopy (ICP-AES). Crystallite size distribution was determined using a novel method based on a phenomenon unique to nanomaterials, i.e. the dependence of the crystallite phase transition on the size of the crystallites. Thermal treatment of the nanocrystalline iron in a hydrogen atmosphere at 1073 K revealed that it is thermally unstable. The parameters of the log-normal crystallite size distribution were d0 = 15.3 nm, s = 0.35 and d0 = 23.5 nm, s = 0.17 for iron treated at 773 K and 1073 K, respectively. The corresponding average crystallite sizes determined from the Scherrer formula were 18 nm and 24 nm, respectively. The size distribution of the sintered materials clearly shows that the thermal stability is a function of the size of the crystallites, i.e. the smallest crystals are the least thermally stable. However, no increase in the contribution of crystallites above 35 nm has been observed. Application of this phenomenon combined with the determination of crystallite size distribution enables fine-tuning of the crystallite size distribution.
7
Content available remote Badanie kinetyki utleniania nanokrystalicznego żelaza parą wodną
Pelka R., Arabczyk M.
Przemysł Chemiczny
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2011
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T. 90, nr 5
974-977
8
Content available remote Zjawisko histerezy procesów azotowania i redukcji w układzie nanokrystaliczne żelazo-amoniak-wodór
Moszyńska I., Moszyński D., Arabczyk W
Przemysł Chemiczny
|
2009
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T. 88, nr 5
526-529
9
Content available remote The influence of iron nanocrystallite size on a nitriding process rate
Pelka R., Glinka P., Arabczyk W.
Materials Science Poland
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2008
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Vol. 26, No. 2
349--356
EN
In the course of nitriding process of nanocrystalline iron promoted with aluminum and calcium oxides, nitrides such as Fe4N and Fe3-2N were fabricated. The process rate was studied making use of a flow differential tubular reactor with thermogravimetric measurement of mass changes. Nanocrystalline iron was reduced under hydrogen atmosphere at 500 oC and 800 oC. Average crystallite sizes determined by the XRD method after reduction performed at 500 oC as well as at 800 oC and after passivation were 18 and 42 nm, respectively. The nitriding process rate as well as catalytic ammonia decomposition rate were limited by the ammonia dissociative adsorption rate on the surface of iron and were dependent on the ratio of the crystallite surface area to crystallite volume. Obtained results were explained based on the adsorption range model.
10
Content available remote Technology of the nanocarbon materials preparation
Narkiewicz U.
Polish Journal of Chemical Technology
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2005
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Vol. 7, nr 3
87-94
EN
The technology of the nanocarbon materials preparation by the catalytic decomposition of hydrocarbons on nanocrystalline iron is described. Among different methods of nanocarbon materials preparation, this one, based on the catalytical gas-solid reaction can be recommended as a simple, inexpensive, easy to control and easy to process scale up-grading. The use of nanocrystalline iron as a raw material enables carrying out the process in the kinetics area of the reaction, when diffusion is not limiting. There is no need to apply special conditions, as high pressure or vacuum, laser ablation or high temperatures (the process can be carried out with good efficiency in the temperature range from 350 to 550°C). Depending on the process conditions, different forms of nanocarbons can be obtained (amorphous carbon, carbon nanofibers or nanotubes).
11
Content available remote Carburisation of nanocrystalline iron with ethylene
Narkiewicz U., Kucharewicz I., Arabczyk W., Lenart S.
Materials Science Poland
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2005
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Vol. 23, No. 4
939--946
EN
The carburisation of nanocrystalline iron with ethylene has been studied. The carburisation processes were carried out under atmospheric pressure, under the flow of pure ethylene or ethylene-hydrogen mixture at a constant temperature in the range of 310-550 °C. The process was controlled using a spring thermobalance and cathetometer, with the accuracy of 0,1 mg. The phase composition of the samples after carburisation was determined by means of X-ray diffraction (XRD). As a result of the carburisation of nanocrystalline iron with ethylene, the formation of iron carbide Fe3C occurs, followed by the formation of carbon deposits. Under a C2H4/H2 gas mixture, these two reaction steps can be separated, while under pure ethylene the reactions are much faster and the simultaneous formation of iron carbide and carbon deposits is observed. Depending on temperature and on the carburisation degree, various forms of carbon deposits can be observed using TEM: spherical, helicoidal, and nanotubes. The diameter of these carbon forms is below 100 nm.
12
Content available remote Zastosowanie metod termograwimetrycznych do badania reakcji w układzie ciało stałe-faza gazowa
Arabczyk W., Narkiewicz U., Konicki W., Wróbel R., Bay B., Woźniak R.
Przemysł Chemiczny
|
2003
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T. 82, nr 3
207-210
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