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    Wyświetlanie 1-31 z 31
    Tytuł:
    Preparation, Characterization and Catalytic Properties of SBA-15-SO₃H Supported Tungstophosphoric Acid for Esterification Reaction
    Autorzy:
    Erdem, B.
    Erdem, S.
    Çıtak, A.
    Yavru, C.
    Öksüzoğlu, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/1031202.pdf
    Data publikacji:
    2017-09
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.43.Gt
    82.65.+r
    Opis:
    SBA-15-SO₃H supported tungstophosphoric acid (TPA, H₃PW₁₂O₄₀) mesoporous materials were synthesized by impregnation of TPA into the hydrothermally synthesized SBA-15-SO₃H and the catalytic performances were compared for the esterification reaction. The physical and chemical properties of the catalysts were characterized by XRD, SEM/EDX, FT-IR and N₂ adsorption/desorption techniques. The characterization results show that TPA/SBA-15-SO₃H retained the typical mesoporous structure of SBA-15-SO₃H. The experimental results indicated that TPA/SBA-15-SO₃H is a more efficient catalyst than SBA-15-SO₃H for the esterification reaction. The higher activity of TPA/SBA-15-SO₃H compared with that of SBA-15-SO₃H was consistent with the material having the low pKa value, confirming that the esterification rate was mostly dependent on the acid strength of the additional functional groups of solid acid catalyst. Accordingly, the reason for the catalytic activity difference was simply explicated by the effect of TPA, having low pKa value, affecting the pore structure and the total acidity.
    Źródło:
    Acta Physica Polonica A; 2017, 132, 3; 1041-1044
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Silicon Etching in $XeF_2$ Environment
    Autorzy:
    Knizikevičius, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/1400495.pdf
    Data publikacji:
    2013-07
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    81.65.Cf
    82.35.Gh
    82.65.+r
    Opis:
    Enhancement of silicon etching rate in $XeF_2$ environment is considered by a proposed model, which includes processes of adsorption, activation, chemical reactions, relaxation, desorption, and sputtering. The enhancement of silicon etching rate is explained by considering hydrocarbon molecules from background gas contamination in the vacuum chamber, and assuming that hydrocarbon radicals enhance the etching rate. The composition of the adsorbed layer during silicon etching in $XeF_2$ environment is calculated. It is found that hydrocarbon radicals intensify reaction of $XeF_2$ molecules with Si atoms on the surface and that this changes the kinetics of the etching rate. Using the obtained theoretical results the difference in kinetics of the etching rates of first and subsequent run is explained.
    Źródło:
    Acta Physica Polonica A; 2013, 124, 1; 137-140
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Synthesis, Structure, and Catalytic Activity of Au/Poly(ethylene terephthalate) Composites
    Autorzy:
    Mashentseva, A.
    Borgekov, D.
    Zdorovets, M.
    Russakova, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1365723.pdf
    Data publikacji:
    2014-06
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    62.23.Pq
    82.65.+r
    82.20.Pm
    Opis:
    A standard technique of electroless gold deposition was modified by changing the composition of Ag-based activation solution. This allows preparation of two types of poly(ethyleneterephthalate) (PET) track etched membranes coated entirely with gold after 1, 5, and 24 h of reaction at 4°C. After dissolving the polymer template, gold nanotubes with outer diameter of 70-80 nm were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. Reduction of p-nitrophenol to p-aminophenol by sodium borohydride was used to investigate the catalytic activity of as-prepared Au/PET membrane. All experiments were carried out for five consecutive cycles and rate constant of the pseudo-first-order reaction was calculated. It was found that Au/Ag/PET composites prepared after activation for 3 min in Ag-based solution (with potassium sodium tartrate as reducing agent) more effective catalyst (k=0.087 $min^{-1}$) was obtained when the Au/PET samples activated with ammonia silver nitrate solution (k=0.041 $min^{-1}$).
    Źródło:
    Acta Physica Polonica A; 2014, 125, 6; 1263-1266
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Temperature Dependent Catalytic Activity of Ag/PET Ion-Track Membranes Composites
    Autorzy:
    Borgekov, D.
    Mashentseva, A.
    Kislitsin, S.
    Kozlovskiy, A.
    Russakova, A.
    Zdorovets, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1402216.pdf
    Data publikacji:
    2015-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    62.23.Pq
    82.65.+r
    82.20.Pm
    Opis:
    Electroless deposition has been used to coat finely porous polyethylene terephthalate (PET) track-etched membranes with silver, forming silver nanotubes within the pores with inner and outer diameters of 60 and 100 nm. The sample's X-ray diffraction pattern shows a face-centered cubic crystalline phase of silver with the lattice constant 4.0838 nm. The average size of silver nanoclusters, as obtained from the scanning electron microscopy analysis is about 30 nm which is consistent with the X-ray diffraction results. The temperature dependent catalytic activity of prepared composites is demonstrated for two model reactions such as reduction of 4-nitrophenol (4-NP) and decomposition of hydrogen peroxide. Apparent constant rates and activation energy as well as reusability of catalysts were determined. The developed composite catalyst could be used consecutively for several runs without any damages for 4-NP reduction. For hydrogen peroxide reaction decomposition the reaction rate of the second cycle is reduced 2.4 times. Moreover, the second reuse reduced conversion of H₂O₂ to 54.7% suggests removal of active Ag centers during the first cycle of testing.
    Źródło:
    Acta Physica Polonica A; 2015, 128, 5; 871-874
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Resonant Charge Exchange in Atom Scattering on Atoms Adsorbed on Metal Surfaces
    Autorzy:
    Wiertel, M.
    Taranko, E.
    Taranko, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/2030724.pdf
    Data publikacji:
    2002-06
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    79.20.-m
    82.65.+r
    34.70.+e
    Opis:
    The ionization probability of an atom scattered from an atom adsorbed on a metal surface has been studied theoretically within the time-dependent Anderson-Newns model. The effect of the metal electron density of states, the band filling as well as the relative position of the scattered atom and adsorbed atom energy levels have been considered and the comparison with the results obtained for clean surfaces has been made.
    Źródło:
    Acta Physica Polonica A; 2002, 101, 6; 837-855
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Structure Characterization and Catalytic Properties of Cr$\text{}_{2}$O$\text{}_{3}$ Doped with MgO Supported on MgF$\text{}_{2}$
    Autorzy:
    Goslar, J.
    Wojciechowska, M.
    Zieliński, M.
    Tomska-Foralewska, I.
    Przystajko, W.
    Powiązania:
    https://bibliotekanauki.pl/articles/2043607.pdf
    Data publikacji:
    2005-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    76.30.Fc
    68.43.Fg
    82.65.+r
    Opis:
    A characterization of double oxide systems containing Cr$\text{}_{2}$O$\text{}_{3}$ doped with MgO and supported on MgF$\text{}_{2}$ was carried out. The catalysts were prepared by impregnation and co-impregnation methods and characterized by the Brunauer-Emmett-Teller method, EPR, and temperature programmed reduction. The results proved the interactions between supported oxides and the presence of spinel-like phase after treatment at 400ºC. Magnesium oxide clearly influences the catalytic activity as well as selectivity of chromium catalysts supported on MgF$\text{}_{2}$. The MgO-Cr$\text{}_{2}$O$\text{}_{3}$/MgF$\text{}_{2}$ systems were active and selective in the reaction of CO oxidation at the room temperature and in the dehydrogenation of cyclohexene.
    Źródło:
    Acta Physica Polonica A; 2005, 108, 2; 323-330
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of an Adsorbed Atom on Resonant Charge Exchange in Atom Scattering on Metal Surfaces
    Autorzy:
    Taranko, R.
    Taranko, E.
    Wiertel, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/2035749.pdf
    Data publikacji:
    2003-05
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    79.20.-m
    82.65.+r
    34.70.+e
    Opis:
    A simple model describing resonant charge transfer between the free-electron metal surface and an atom colliding with it at some distance from another adsorbed atom is presented. The negative ionization probability of a scattered atom is studied within the time-dependent Anderson-Newns model and the time-evolution operator approach. With appropriate models for the considered system, the ionization probability is shown to oscillate with the distance between the adsorbed atom and the collision point of the scattered atom with the metal surface. These oscillations are results of the indirect interaction between the adsorbed and the scattered atoms due to the coupling of both atoms with the metal energy band.
    Źródło:
    Acta Physica Polonica A; 2003, 103, 5; 483-497
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Structural Characterization of $Al_2O_3$ and $CeO_2$ Supported Ni, Co Loaded Ceramic Monolithic Catalysts
    Autorzy:
    Guldal, N.
    Baykara, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1216529.pdf
    Data publikacji:
    2014-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    81.15.-z
    81.70.-q
    82.65.+r
    Opis:
    This paper discusses structural characterizations of monolithic catalysts prepared by incorporating Ni and Co supported over a porous alumina and ceria layer by using respective nitrates and $H_2PtCl_6$ as precursors. Monolithic catalysts were synthesized by dip-coating of 400 cpsi cordierite ceramic monolithic pieces cut in 20 × 13 $mm^2$ (L× D) into appropriate solutions of metals, followed by calcination in air at 800C for 4 h. Phases of catalysts were characterized with X-ray diffraction. Morphological analysis and elemental composition were determined by scanning electron microscope and energy dispersive spectroscopy. The specific surface area analysis have been studied using the Brunauer-Emmett-Teller method. Metal contents were determined by inductively coupled plasma optical emission spectrometry.
    Źródło:
    Acta Physica Polonica A; 2014, 125, 2; 281-284
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Chemically Modified Activated Carbons as Catalysts of Oxidative Dehydrogenation of n-Butane
    Autorzy:
    Malaika, A.
    Wower, K.
    Kozłowski, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1535911.pdf
    Data publikacji:
    2010-09
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    81.05.Rm
    81.65.Mq
    81.40.Gh
    82.65.+r
    Opis:
    Commercial availability and low price of light alkanes make them very attractive in many branches of industry. Potentially interesting is their use in the process of oxidative dehydrogenation leading to production of olefins. This study was undertaken to characterise the oxidative dehydrogenation of n-butane to 1,3-butadiene (important substrate in production of synthetic rubber and polyamides) taking place over the modified carbon catalysts obtained from peach stones precursor. The catalytic tests were performed in the temperature range 250-450°C at oxygen/n-butane ratio of 1:1. For the majority of the activated carbon samples studied at the lowest temperature the only product was $CO_2$. At 300°C the products of dehydrogenation of n-butane and side products appeared. With increasing temperature the amount of compounds generated increased and in the group of C4 hydrocarbons the dominant were 1-butene and 1,3-butadiene. The most effective catalyst was the sample oxidised with air, the least effective was the sample modified with ammonium peroxydisulphate.
    Źródło:
    Acta Physica Polonica A; 2010, 118, 3; 459-464
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Carbonaceous Materials Obtained from Sewage Sludge for $NO_2$ Removal under Wet Conditions at Room Temperature
    Autorzy:
    Pietrzak, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/1536471.pdf
    Data publikacji:
    2010-09
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.66.Fn
    81.05.-t
    81.05.Rm
    82.65.+r
    89.60.-k
    Opis:
    The effect of the processes of carbonisation and activation on adsorbents obtained from sewage sludge and their sorption properties towards $NO_2$ were studied. Carbonaceous adsorbents were obtained by carbonisation of sewage sludge at 600°C for four different times 30, 60, 90 and 120 min followed by activation of the carbonisates by $CO_2$ at 800°C for 60 min. Adsorption of $NO_2$ was carried out in wet air. It has been shown that by appropriate thermal and chemical treatment of sludge, mesoporous adsorbents capable of $NO_2$ removal can be obtained. The sorption abilities of the carbonised and activated samples to adsorb $NO_2$ have been shown to increase with increased time of carbonisation and reach maximum for the carbonisation maintained for 90 min. Further increase in this time causes a decrease in the adsorption abilities of the samples. The sorption properties of the carbonisates have been proved to be determined by the chemical character of the surface, while those of the activated samples - by the porous structure.
    Źródło:
    Acta Physica Polonica A; 2010, 118, 3; 487-492
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Synthesis, Characterization and Adsorptive Properties οf Organobentonites
    Autorzy:
    Jović-Jovičić, N.
    Milutinović-Nikolić, A.
    Banković, P.
    Dojčinović, B.
    Nedić, B.
    Gržetić, I.
    Jovanović, D.
    Powiązania:
    https://bibliotekanauki.pl/articles/1538150.pdf
    Data publikacji:
    2010-05
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    33.20.Ea
    61.05.cp
    68.43.-h
    78.40.-q
    82.65.-r
    Opis:
    In this paper partial and complete substitution of cations in the interlayer region of clay with different amounts of two aliphatic ammonium cations was performed with aim of synthesis of organobentonites with multipurpose adsorption properties. Domestic clay from Bogovina was submitted according to a common procedure used for the obtention of organobentonite, which comprises the following steps: grinding, sieving, Na-exchange, cation exchange and drying. The samples were characterized by X-ray diffraction and infrared spectroscopy. The incorporation of surfactant molecules into smectite structure lead to constant increase of $d_{001}$ basal spacing. IR absorption bands assigned to methyl and methylene vibrations increased with the increase of surfactant/bentonite ratio and length of aliphatic chain in surfactant molecules. Adsorptive properties of the obtained materials were in accordance with their organophylicity: the adsorption of organic dye increased while the rate of removal of $Pb^{2+}$ by adsorption decreased.
    Źródło:
    Acta Physica Polonica A; 2010, 117, 5; 849-854
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Synthesis, Characterization and Application οf Al,Fe-Pillared Clays
    Autorzy:
    Banković, P.
    Milutinović-Nikolić, A.
    Jović-Jovičić, N.
    Dostanić, J.
    Čupić, Ž.
    Lončarević, D.
    Jovanović, D.
    Powiązania:
    https://bibliotekanauki.pl/articles/1808061.pdf
    Data publikacji:
    2009-04
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.05.C-
    61.43.Gt
    61.46.-w
    68.43.-h
    82.65.+r
    Opis:
    Al,Fe-pillared clay was synthesized from domestic clay from Bogovina according to a common procedure: grinding, sieving, Na exchange, pillaring, drying and calcination. Two synthesized samples differing only in calcining conditions were prepared. Phase composition and textural properties of the starting clay and synthesized pillared clays were characterized using X-ray diffraction and physisorption of nitrogen. Catalytic tests were performed using sample with better textural properties being the one submitted to milder calcining conditions. Catalytic wet peroxide oxidative degradation of aromatic compounds phenol and tartrazine on the synthesized catalyst was confirmed showing better efficiency in the case of tartrazine.
    Źródło:
    Acta Physica Polonica A; 2009, 115, 4; 811-815
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    EPR characteristics of activated carbon for hydrogen production by the thermo-catalytic decomposition of methane
    Autorzy:
    Więckowski, A.
    Najder-Kozdrowska, L.
    Rechnia, P.
    Malaika, A.
    Krzyżyńska, B.
    Kozłowski, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1158900.pdf
    Data publikacji:
    2016-09
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    33.35.+r
    61.66.Hq
    76.30.-v
    82.30.Lp
    82.65.+r
    88.30.ej
    Opis:
    The electron paramagnetic resonance (EPR) method was used to characterize samples of activated coal before and after reactions of the catalytic decomposition of methane and ethanol at temperatures of 1023 K (750°C), 1123 K (850°C) and 1223 K (950°C). The EPR parameters: spectroscopic splitting factor g, peak-to-peak linewidth ΔBₚₚ, and spin concentration c were measured. During the ethanol-assisted catalytic decomposition of methane carbon-located-spin radicals are partially transformed into oxygen-located-spin radicals.
    Źródło:
    Acta Physica Polonica A; 2016, 130, 3; 701-704
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The Influence of the Au Nanoparticles Dimension on the Photocatalytic Performances of $TiO_2-Au$ Porous Composites
    Autorzy:
    Melinte, G.
    Baia, M.
    Georgescu, D.
    Baia, L.
    Iancu, V.
    Diamandescu, L.
    Popescu, T.
    Cotet, L.
    Barbu-Tudoran, L.
    Danciu, V.
    Simon, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1491327.pdf
    Data publikacji:
    2012-01
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    81.05.Rm
    81.07.Wx
    82.80.Ej
    68.37.Lp
    82.65.+r
    82.50.Hp
    Opis:
    The influence of Au nanoparticles dimension on the photocatalytic performances of the $TiO_2$ aerogels-Au composites was evaluated. Structural and morphological peculiarities of the $TiO_2$ aerogel, unloaded and loaded with 5 and 22 nm Au nanoparticles, were studied by transmission electron microscopy technique, X-ray diffraction and $N_2$-sorption measurements. UV-Vis diffuse reflectance measurements were performed to determine the band gap energies. The photocatalytic activity was evaluated by monitoring the salicylic acid photodegradation. It was found that the Au nanoparticles promote the anatase phase crystallization and produce the decrease of the specific surface area and band gap energy values. The porous composite with the smallest Au nanoparticles dimension exhibits the best photocatalytic performances.
    Źródło:
    Acta Physica Polonica A; 2012, 121, 1; 208-210
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Desorption Activation Energy of $SiBr_2$ Molecules according to Steady-State Approximation
    Autorzy:
    Knizikevičius, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/1365355.pdf
    Data publikacji:
    2014-05
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    81.65.Cf
    82.20.Db
    82.20.Pm
    Opis:
    The chemical etching of intrinsic and n-type polycrystalline silicon in $Br_2$ ambient is considered. The theoretically calculated dependences of silicon etching rates on pressure of $Br_2$ molecules at different temperatures are compared with experimentally measured ones. The reaction and desorption activation energies are evaluated. It is found that activation energy of Si + $Br_2$ → $SiBr_2$ reaction for intrinsic silicon is equal to (1.82 ± 0.24) eV, and decreases to (1.45 ± 0.24) eV when n-type silicon films are used. Desorption activation energy of $SiBr_2$ molecules for intrinsic silicon is equal to (1.94 ± 0.17) eV, and decreases to (1.51 ± 0.17) eV when n-type silicon films are used. Desorption of $SiBr_2$ molecules is an etching-rate limiting process at high pressure of $Br_2$ molecules.
    Źródło:
    Acta Physica Polonica A; 2014, 125, 5; 1240-1243
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Subdiffusion with External Time Modulation
    Autorzy:
    Wojnar, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/1812233.pdf
    Data publikacji:
    2008-09
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    05.40.Jc
    05.70.Ln
    82.39.Rt
    87.18.Hf
    89.65.Gh
    89.65.Lm
    Opis:
    A subdiffusion process, similar to a Zeldovich-Kompaneets heat conduction process, is defined by a nonlinear diffusion equation in which the diffusion coefficient takes the form D=a(t)f^n, where a=a(t) is an external time modulation, n is a positive constant, and f=f(x, t) is a solution to the nonlinear diffusive equation. It is shown that a Zeldovich-Kompaneets solution satisfies the subdiffusion equation if a=a(t) is replaced by the mean value of a. Also, a solution to the subdiffusion equation is constructed that may be useful in description of biological, social, and financial processes.
    Źródło:
    Acta Physica Polonica A; 2008, 114, 3; 607-611
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Spatially Resolved Chemistry on Bimetallic Surfaces
    Autorzy:
    Behm, R. J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1968689.pdf
    Data publikacji:
    1998-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.16.Ch
    68.10.Jy
    82.65.-i
    Opis:
    The local chemical properties of bimetallic surfaces, which are often drastically different from those of each of the components, will be discussed. Using CO adsorption as a probe molecule it will be shown for two model systems, Au/Pd(111) and Pt/Ru(0001), that their chemical properties depend decisively on the local surface structure and that the correct interpretation of area integrating spectroscopic and kinetic data obtained from such surfaces requires detailed knowledge of their (defect) structure and of the distribution of the different components in the surface layer. It will further be shown that information on the local chemical properties of specific structural elements such as monolayer islands and monolayer island edges, and specific surface ensembles can be gained by applying high resolution scanning tunneling microscopy imaging and area integrating spectroscopic techniques in combination to bimetallic surfaces whose morphology and composition is varied in a systematic and controlled way. Based on experimental results adsorption on a monolayer A / substrate B system is suggested as a model for gaining information on the modifications in chemical properties of AB alloy surfaces due to metal-metal interactions.
    Źródło:
    Acta Physica Polonica A; 1998, 93, 2; 259-272
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Chemisorption Isotherms for Ising Anderson Hamiltonian
    Autorzy:
    Taranko, E.
    Cardenas, R.
    Taranko, R.
    Fedyanin, V. K.
    Powiązania:
    https://bibliotekanauki.pl/articles/1931807.pdf
    Data publikacji:
    1994-12
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    68.45.-v
    82.65.My
    Opis:
    The adsorption isotherms for Ising-Anderson type model Hamiltonian describing the chemisorbed system was calculated. The submonolayer coverage of the substrate surface was considered on the equal footing together with the electronic characteristics of the chemisorbed adatoms in a self-consisting manner. The resulting adsorption isotherms depend in explicit way on the electronic parameters describing the chemisorbed adatoms and substrate metal.
    Źródło:
    Acta Physica Polonica A; 1994, 86, 6; 917-927
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Rayleigh's Distribution, Wigner's Surmise and Equation of the Diffusion
    Autorzy:
    Wojnar, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/1400185.pdf
    Data publikacji:
    2013-03
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    05.40.Jc
    05.70.Ln
    82.39.Rt
    87.85.gj
    89.65.Gh
    89.65.Lm
    21.10.-k
    Opis:
    After summaries on Rayleigh's distribution and Wigner's surmise, the time evolution of Rayleigh-Wigner's statistics is studied and a suitable diffusion type equation is proposed. Also the variance and kurtosis of time evolution of Rayleigh's distribution are calculated. Obtained results may be useful in description of physical, social and biological processes.
    Źródło:
    Acta Physica Polonica A; 2013, 123, 3; 624-628
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Negatively and Positively Polarized Hydrogen Adspecies on Thin Platinum Films
    Autorzy:
    Nowicka, L.
    Wolfram, Z.
    Duś, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/1892305.pdf
    Data publikacji:
    1992-01
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    82.65.-i
    73.60.Aq
    Opis:
    Hydrogen adsorption on thin platinum films under isothermal conditions within the temperature and pressure intervals 78-298 K and 10$\text{}^{-10}$-10$\text{}^{-2}$ Torr has been studied measuring simultaneously surface potential (SP) and pressure (P), by means of a sensitive, short response time apparatus. Two forms of hydrogen deposit of different electrical character have been distinguished. The first one arising at the beginning of adsorption decreases the surface potential, the second one following it increases the SP due to positively polarized adspecies formation. This positively polarized form is inhomogeneous as concerns binding energy. Hydrogen uptake associated with the decrease of SP becomes larger with increase of temperature. It seems that this β¯ form of the adsorbate stabilizes the positively polarized adspecies on the surface.
    Źródło:
    Acta Physica Polonica A; 1992, 81, 1; 117-124
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Steering and Locking of Discrete Solitons in Optical Waveguide Arrays
    Autorzy:
    Peschel, U.
    Lederer, F.
    Morandotti, R.
    Aitchison, J. S.
    Eisenberg, H.
    Silberberg, Y.
    Powiązania:
    https://bibliotekanauki.pl/articles/2015072.pdf
    Data publikacji:
    2001-01
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    42.65.Tg
    42.65.Wi
    42.82.Et
    Opis:
    By operating an AlGaAs waveguide array at the half band gap, we experimentally demonstrate basic features of discrete systems, which do not appear in the corresponding continuous counterpart - the slab waveguide. Under selected initial conditions, we observed nonlinearly induced locking of an initially moving soliton to the input waveguide. If the power is even higher, originally locked beams start to move again, but in a direction opposite to the initial tilt.
    Źródło:
    Acta Physica Polonica A; 2001, 99, 1; 57-65
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Chemisorption Theory at Submonolayer Coverages: Influence of the Dynamic Hopping on the Electronic Characteristics
    Autorzy:
    Cardenas, R.
    Taranko, E.
    Taranko, R.
    Fedyanin, V.
    Powiązania:
    https://bibliotekanauki.pl/articles/1891892.pdf
    Data publikacji:
    1991-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.20.-r
    82.65.My
    Opis:
    The influence of the dynamic hopping term included in the Newns-Anderson Hamiltonian on the electronic structure of the chemisorbed layer at different coverages rates is investigated. It is shown that this additional interaction can destroy the initial symmetry of the Newns-Anderson model or restore this symmetry in the initial negative asymmetric case. The coverage dependence of the adatom electron charge is also studied for the case of hydrogen chemisorption on a model transition metal surface.
    Źródło:
    Acta Physica Polonica A; 1991, 80, 5; 731-743
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Charge Transfer Dynamics in Atom-Metal Surface Collisions
    Autorzy:
    Wiertel, M.
    Taranko, R.
    Taranko, E.
    Powiązania:
    https://bibliotekanauki.pl/articles/2011189.pdf
    Data publikacji:
    1999-12
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    79.20.Rf
    78.70.-g
    82.65.Pa
    Opis:
    We study the charge exchange in atom-metal collisions in the framework of the generalized time-dependent Anderson-Newns model. The electron correlations and correlated hopping are treated within the mean-field approximation. The resulting one-particle model with an effective spin-dependent atom-surface coupling is used to study the charge transfer in scattering of Na and Li atoms on metal surfaces. It is shown that the effective occupation dependent atom-surface coupling influences mainly the expectation values for producing positive, neutral, and negative particles for small work functions and high atom velocities. It is also shown that the temperature dependence of these expectation values is more visible, especially for magnetic solutions.
    Źródło:
    Acta Physica Polonica A; 1999, 96, 6; 769-783
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Interaction of Hydrogen with Vanadium Layers Preadsorbed on Tungsten Field Emitter Tip
    Autorzy:
    Błaszczyszyn, R.
    Wachowicz, E.
    Błaszczyszynowa, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1968928.pdf
    Data publikacji:
    1998-05
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    79.70.+q
    82.65.My
    Opis:
    Interaction of hydrogen with vanadium layers preadsorbed on a thermally cleaned tungsten field emitter was studied at room temperature and 78 K through measurements of the total work function changes. An increase in the work function followed by its slight decrease at higher exposure can be understood taking into account the possibility of negatively (β$\text{}^{-}$) and positively (β$\text{}^{+}$) polarized adspecies formation on thin vanadium layer. This process leads to vanadium hydride formation. The work function results suggest that hydrogen diffusion into the vanadium layer is meaningful at room temperature. Thermal desorption of hydrogen adsorbate carried out within the temperature range 409-461 K from thin vanadium layer (Θ$\text{}_{V}$ = 40) provided a value of 127 ± 6 kJ/mol for the activation energy for desorption.
    Źródło:
    Acta Physica Polonica A; 1998, 93, 5-6; 763-773
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Nonlinear Characterization of Safranin O Dye for Application in Optical Limiting
    Autorzy:
    Balaji, G.
    Rekha, R.
    Ramalingam, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1505339.pdf
    Data publikacji:
    2011-03
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    42.70.Jk
    42.65.-k
    82.35.-x
    Opis:
    The optical nonlinearity of safranin O dye in methanol solution at different concentrations and as a solid film with polymethylmethacrylate (PMMA) has been studied using cw Nd-YAG laser at 532 nm as the source of excitation. The optical responses were characterized by measuring the intensity dependent refractive index $(n_2)$ of the medium using the Z-scan technique. The open aperture Z-scan trace of the dye in solution and solid sample displayed saturable absorption. The closed aperture Z-scan trace of the dye exhibited a negative (defocusing) nonlinearity. The nonlinear refractive index was found to vary with concentration. Optical limiting characteristics of the dye at various concentrations in solution were studied. The nonlinearity appears to be of thermal origin.
    Źródło:
    Acta Physica Polonica A; 2011, 119, 3; 359-363
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Second Harmonic Generation in AlGaAs Nanowaveguides
    Autorzy:
    Rutkowska, K.
    Duchesne, D.
    Volatier, M.
    Arès, R.
    Aimez, V.
    Morandotti, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/1493258.pdf
    Data publikacji:
    2011-10
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    42.82.Et
    42.65.Ky
    42.79.Nv
    42.70.Mp
    78.67.Uh
    Opis:
    In this paper, we investigate semiconductor nanowaveguides (i.e. ridge waveguides with core-widths narrower than 1 μm) intended to act as novel optical light sources through nonlinear wavelength/frequency conversion. In particular, numerical calculations have been performed in order to design suitable photonic devices (fabricated in the AlGaAs/GaAs platform) capable of high efficiency second harmonic generation. Particular interest has been dedicated to the effective conversion of optical signals from 1520-1600 nm (the third telecom window) down to 760-800 nm. We demonstrate that the output wavelength (resulting from modal phase-matching) can be dynamically tuned by proper adjustment of the temperature and/or geometrical parameters of the waveguides. In addition, by changing the waveguide width it is also possible to modify the device dispersion characteristics, giving the possibility to work in the region of anomalous dispersion and thus allowing for the generation of temporal solitons.
    Źródło:
    Acta Physica Polonica A; 2011, 120, 4; 725-731
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    An Enthalpy of Solution of Cobalt and Nickel in Iron Studied with $\text{}^{57}Fe$ Mössbauer Spectroscopy
    Autorzy:
    Idczak, R.
    Konieczny, R.
    Konieczna, Ż.
    Chojcan, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1506574.pdf
    Data publikacji:
    2011-01
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    76.80.+y
    82.60.Lf
    65.40.G-
    Opis:
    The room temperature Mössbauer spectra of $\text{}^{57}Fe$ were measured for iron-based solid solutions $Fe_{1-x}Co_{x}$ and $Fe_{1-x}Ni_{x}$ with x in the range 0.01 ≤ x ≤ 0.05. The obtained data were analysed in terms of the binding energy $E_{b}$ between two Co or Ni atoms in the studied materials using the extended Hrynkiewicz-Królas idea. It was found that the energy is positive or the non-iron atoms interact repulsively. The extrapolated value of $E_{b}$ for x=0 was used for computation of the enthalpy of solution of cobalt and nickel in iron. The results were compared with our previous Mössbauer spectroscopy findings, the values resulting from the Miedema's model of alloys and the data derived from the enthalpy of formation of the Fe-Co and Fe-Ni systems, obtained with calorimetric methods. The comparison shows that the present results are in a qualitative agreement with the Miedema's model predictions and calorimetric measurements but they are at variance with the previous Mössbauer spectroscopy findings.
    Źródło:
    Acta Physica Polonica A; 2011, 119, 1; 37-40
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Atomic Force Microscopy of Instabilities and Reorganization of Langmuir-Blodgett Films
    Autorzy:
    Takamoto, D. Y.
    Ter-Ovanesyan, E.
    Schwartz, D. K.
    Viswanathan, R.
    Chiruvolu, S.
    Zasadzinski, J. A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1968761.pdf
    Data publikacji:
    1998-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    82.65.Dp
    Opis:
    The atomic force microscope was used to show that Langmuir-Blodgett films are unstable to reorganization via a folding mechanism by which uniformly thick films spontaneously form holes and multilayer steps. These bilayer step defects originate at isolated sites and quickly spread to cover the entire film. The defects retain the sixfold symmetry of the underlying molecular lattice; after sufficient time, straight edges begin to form and the entire film is comprised of high islands with straight edges aligned with sixfold symmetry. The kinetics of the reorganization depend strongly on the chain length of the fatty acid used and the nature of the substrate. The results suggest that the reorganization is driven by an interconversion of strained, asymmetric monolayers to unstrained, centrosymmetric bilayers.
    Źródło:
    Acta Physica Polonica A; 1998, 93, 2; 373-382
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Temperature Dependence of a Dielectric Relaxation in Weakly Polar Ferrofluids
    Autorzy:
    Rajňák, M.
    Kurimský, J.
    Dolník, B.
    Cimbala, R.
    Paulovičová, K.
    Kopčanský, P.
    Timko, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1032784.pdf
    Data publikacji:
    2017-04
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    47.65.Cb
    77.22.Ch
    77.22.Gm
    82.70.Dd
    Opis:
    In this paper, we report on the temperature dependent broadband dielectric response of a ferrofluid based on transformer oil and magnetite nanoparticles covered with oleic acid molecules. For that purpose the method of dielectric spectroscopy has been chosen in the frequency range from 20 Hz up to 100 kHz. The experiments were carried out on thin film ferrofluid samples confined in a glass plate capacitor containing indium tin oxide (ITO) plate electrodes. The obtained complex permittivity spectrum shows a pronounced dielectric dispersion in the low frequency range. Taking into account the ferrofluid composition we associate this relaxation with ion impurity polarization at the nanoparticle-oil interface. The strong temperature dependence of the relaxation process has been found when conducting the experiments in the temperature range from 298 K to 358 K. The relaxation time of the revealed process exhibits a typical Arrhenius behavior. Based on the conducted experiments and analysis, we propose some reasonable practical applications of the studied ferrofluid in the field of electrical engineering.
    Źródło:
    Acta Physica Polonica A; 2017, 131, 4; 943-945
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Generation of Fe₃O₄ Nanoparticle Aggregates in a Ferrofluid Driven by External Electric Field
    Autorzy:
    Kurimský, J.
    Rajňák, M.
    Cimbala, R.
    Paulovičová, K.
    Timko, M.
    Kopčanský, P.
    Kolcun, M.
    Kosterec, M.
    Kruželák, L.
    Powiązania:
    https://bibliotekanauki.pl/articles/1032151.pdf
    Data publikacji:
    2017-04
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    47.57.J-
    47.65.Cb
    77.22.Jp
    77.22.Ch
    82.70.Dd
    Opis:
    In the paper the experimental study of magnetic nanoparticle aggregation in a transformer oil based ferrofluid driven by an external electric field is reported. The studied ferrofluid was composed of the magnetite nanoparticles, oleic acid surfactant, and transformer oil. Generally, it is considered that superparamagnetic nanoparticles do not interact in the absence of external magnetic field. In the paper we present an experimental observation of the particle assembly formation in a direct current external electric field by optical microscopy. During the observation no external magnetic field was applied. A diluted low-polarity ferrofluid drop on a glass surface was exposed to the external static inhomogeneous electric field. It is assumed that induced dipole-dipole interaction and subsequent dielectrophoretic motion give rise to the electrohydrodynamic flow in the fluid after a certain time period. As a result, a visible particle chain was formed at the drop electrical equator. This demonstration is expected to contribute to the understanding of the streamer formation and electrical breakdown in transformer oil based ferrofluids.
    Źródło:
    Acta Physica Polonica A; 2017, 131, 4; 907-909
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Ultrasound Frequency Analysis of a Magnetic Fluid in Low-Intensity External Magnetic Field
    Autorzy:
    Kurimský, J.
    Rajňák, M.
    Cimbala, R.
    Dolník, B.
    Tóthová, J.
    Paulovičová, K.
    Timko, M.
    Kopčanský, P.
    Kolcunová, I.
    Petráš, J.
    Džmura, J.
    Balogh, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1032764.pdf
    Data publikacji:
    2017-04
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    43.58.+z
    43.60.+d
    47.65.Cb
    82.70.Dd
    83.80.Hj
    Opis:
    This work deals with an interaction of a magnetic fluid of a dielectric nature with a magnetic field by means of ultrasound waves measurements and analysis. Ultrasound analysis is known as a non-destructive inspection tool often used in technical diagnostics, moreover, it has numerous applications in medicine and biology, too. We report the low-frequency ultrasound analysis of a dielectric magnetic fluid in a low-intensity external static magnetic field. The studied magnetic fluid was composed of a transformer oil and dispersed magnetite nanoparticles coated with oleic acid. Experiments were carried out by using an ultrasonic testing cell. The cell was exposed to a magnetic field of 50 mT in both parallel and perpendicular direction to the waves propagation. A through-transmission mode measurement was applied, where two fixed narrow-band transducers with completely shielded crystal for maximum RFI/EMI immunity (Physical Acoustic R15I-AST, the resonant frequency 150 kHz) served as a transmitter and a receiver. In this way we carried out the measurement of the frequency-dependent ultrasonic response to a rectangle calibrating signal of 5 μs pulse width. Digitized signals were recorded for further analysis. We present the frequency domain analysis of the low-frequency ultrasound in magnetic fluid. The frequency spectrum in magnetic fluid colloidal system was calculated by the Fourier transformation method. Results show that there is a frequency shift in the amplitude-frequency spectrum caused by the step-up magnetic field. The higher the magnetic field, the higher the frequency of the peaks. The effect of particle aggregation in magnetic field on the ultrasound wave propagation is discussed in the paper.
    Źródło:
    Acta Physica Polonica A; 2017, 131, 4; 910-912
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-31 z 31

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