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  1. 37 Acta Physica Polonica A

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  1. 1 2018

  2. 3 2017

  3. 4 2016

  4. 3 2015

  5. 6 2014

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  1. 8 Pogrebnjak A.

  2. 7 Beresnev V.

  3. 6 Bondar O.

  4. 4 Kolesnikov D.

  5. 4 Shypylenko A.

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1
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The 5:7 Member of the Spin-Ladder Series in the Bi-Sr-Ca-Cu-O System

100%
Zaremba O., Shcherban O., Akselrud L., Gladyshevskii R., Banfi F., Giannini E.
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issue 1
42-47
EN
The crystal structure of the (Bi_{0.02}Sr_{0.39}Ca_{0.59})_{10}Cu_{17}O_{29} spin-ladder compound was determined from single-crystal X-ray diffraction data. The precursor powder was prepared from stoichiometric amounts of SrCO_{3}, CaCO_{3}, CuO, and Bi_{2}O_{3} by calcination at 820°C for 20 h and pressed to form a rod used for the crystal growth. The travelling-solvent-floating-zone method was applied in an image furnace to grow large single crystals. The composite commensurate structure was solved and refined in space group F222, Pearson symbol oF224, a = 11.340(2), b = 12.829(2), c = 19.441(3) Å, Z = 4. The composite incommensurate structure of the (Bi_{0.02}Sr_{0.39}Ca_{0.59})_{10}Cu_{17}O_{29} compound was solved and refined in the (3+1)-space group F222 (00γ), a = 11.340(2), b = 12.829(2), c_1 = 2.7773(4), c_2 = 3.8882(6) Å, q = 0.7143.
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An Icosahedral Quasicrystal as a Packing of Regular Tetrahedra

100%
Fang F., Kovacs J., Sadler G., Irwin K.
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vol. 126
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issue 2
458-460
EN
We present the construction of a dense, quasicrystalline packing of regular tetrahedra with icosahedral symmetry. This quasicrystalline packing was achieved through two independent approaches. The first approach originates in the Elser-Sloane 4D quasicrystal. A 3D slice of the quasicrystal contains a few types of prototiles. An initial structure is obtained by decorating these prototiles with tetrahedra. This initial structure is then modified using the Elser-Sloane quasicrystal itself as a guide. The second approach proceeds by decorating the prolate and oblate rhombohedra in a 3-dimensional Ammann tiling. The resulting quasicrystal has a packing density of 59.783%. We also show a variant of the quasicrystal that has just 10 "plane classes" (compared with the 190 of the original), defined as the total number of distinct orientations of the planes in which the faces of the tetrahedra are contained. This small number of plane classes was achieved by a certain "golden rotation" of the tetrahedra.
3
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Enhanced Superconductivity in Nanosized Tips of Scanning Tunnelling Microscope

100%
Samuely T., Szabó P., Komanický V., Rodrigo J., Vieira S., Samuely P.
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issue 5
1038-1039
EN
Nanosized Pb junctions exhibit superconducting correlations at magnetic fields more than an order of magnitude higher than the zero-temperature critical field of the bulk Pb. The strongly enhanced critical field is a spectacular demonstration of nanosize effect where the Meissner screening currents become ineffective for junction's tip smaller than the London penetration depth (32 nm for Pb). From the enhanced critical field we characterize the geometry of a particular junction using the variable radius pair breaking theoretical model of Suderow et al.
4
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Structure and Physicomechanical Properties of Nanostructured (TiHfZrNbVTa)N Coatings after Implantation of High Fluences of N⁺ (10¹⁸ cm¯²)

100%
Pogrebnjak A., Bondar O., Borba S., Piotrowska K., Boiko O.
Acta Physica Polonica A
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2017
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vol. 132
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issue 2
217-221
EN
New classes of high-entropy alloys, which consist of at least 5 main elements with atomic concentrations 5-35 at.%, are under great interest in modern material science. It is also very important to explore the limits of resistance of high-entropy alloy nitrides to implantation by high-energy atoms. Structure and properties of nanostructured multicomponent (TiHfZrNbVTa)N coatings were investigated before and after ion implantation. We used the Rutherford backscattering, scanning electron microscopy with energy dispersive X-ray spectroscopy, high resolution transmission electron microscopy and scanning transmission electron microscopy with local microanalysis, X-ray diffraction and nanoindentation for investigations. Due to the high-fluence ion implantation (N⁺, the fluence was 10¹⁸ cm¯²) a multiphase structure was formed in the surface layer of the coating. This structure consisted of amorphous, nanocrystalline and initial nanostructured phases with small sizes of nanograins. Two phases were formed in the depth of the coating: fcc and hcp (with a small volume fraction). Nitrogen concentration reached 90 at.% near the surface and decreased with the depth. Nanohardness of the as-deposited coatings varied from 27 to 34 GPa depending on the deposition conditions. However, hardness decreased to a value of 12 GPa of the depth of the projected range after ion implantation and increased to 23 GPa for deeper layers.
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Fabrication and Research of Superhard (Zr-Ti-Cr-Nb)N Coatings

100%
Bondar O., Postolnyi B., Kravchenko Y., Shypylenko A., Sobol O., Beresnev V., Kuzmenko A., Zukowski P.
Acta Physica Polonica A
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2015
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vol. 128
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issue 5
867-870
EN
This work presents the results of (Zr-Ti-Cr-Nb)N superhard coatings research. The samples were fabricated by the vacuum-arc deposition method (Arc-PVD). Structure, composition and properties of these coatings were studied. The study of coatings was carried out using scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction. Hardness measurements and adhesion tests were performed. The coatings thickness was up to 6.2 μ m, nanocrystallites sizes ranged from 4 to 7.3 nm. Values of hardness and cohesive strength were H=43.7 GPa and L_{C}=62.06 N, respectively. The optimal conditions for coating deposition were found.
6
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Electrochemical Formation and Microstructure of Porous Gallium Phosphide

80%
Treideris M., Simkiene I., Selskis A., Balevicius Z., Babonas G.
Acta Physica Polonica A
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2011
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vol. 119
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issue 2
131-134
EN
Electrochemical formation and microstructure of porous GaP have been investigated. Nanostructured porous GaP layers of thickness up to ≈ 20 μm were fabricated on n-type (111)-oriented crystalline c-GaP substrates. Studies of microstructure of porous GaP in dependence on electrolyte type and regimes of technological procedure have been carried out by scanning electron microscopy. The samples were characterized by spectroscopic ellipsometry in visible and near UV spectral range. The investigations have shown that the structure and optical response of porous GaP can be efficiently controlled by technological procedure of electrochemical formation. The shape and dimension of pores can be varied from nanometer-scaled cylindrical pores to GaP nanorods.
7
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Investigation of Nanoscale TiN/MoN Multilayered Systems, Fabricated Using Arc Evaporation

80%
Pogrebnjak A., Bondar O., Abadias G., Eyidi D., Beresnev V., Sobol O., Postolnyi B., Zukowski P.
Acta Physica Polonica A
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2015
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vol. 128
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issue 5
836-840
EN
Using the vacuum-arc evaporation method we fabricated periodic multilayered TiN/MoN structures with different bilayer periods λ ranging from 8 to 100 nm. We found that molybdenum nitride and titanium nitride layers grown on steel show local partial epitaxy and columnar growth across interfaces. A molybdenum-titanium carbide interlayer was evidenced between the substrate and the multilayer. Molybdenum nitride and titanium nitride layers contain small (5÷30 nm) grains and are well crystallized with (100) preferred orientation. They were identified as stoichiometric fcc TiN and cubic γ-M₂N. Non-cubic molybdenum nitride phases were also detected. The hardness of the obtained structures achieved great values and maximal hardness was 31÷41.8 GPa for the multilayered structure with a 8 nm period. Hardness of the obtained coatings is 25÷45% higher in comparison with the initial single-layer nitride coatings, plasticity index of multilayered structure is 0.075.
8
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Effects of Nanoparticle Geometry and Temperature on the Structural Evolution in FeCo Nanoalloys

80%
Yalçin M., Mekhrabov A., Akdeniz M.
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vol. 125
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issue 2
600-602
EN
Effects of nanoparticle size (2.0-6.0 nm) and shape (spherical and cubic) on structural characteristic of atomic ordering processes and order-disorder transformation in B2-type ordered equiatomic-FeCo nanoalloys have been studied by combining electronic theory of alloys in the pseudopotential approximation with Ising-type Hamiltonian site exchange Monte Carlo simulation method. Structural evolutions in amorphous nanoparticles (2-6 nm) of Fe_{50}Co_{50} alloy have been utilized via molecular dynamic simulations from room temperatures to 1700 K temperatures. It has been shown that disordering starts at surface and propagates into volume of nanoparticles with increasing temperature. FeCo nanoparticles with critical dimensions more than 5 nm have order-disorder transformation behavior almost similar with bulk B2-FeCo alloys irrespective of their shape. Molecular dynamic analyses indicate that short- and medium-range ordered atomic structures exist in quenched Fe_{50}Co_{50} nanoparticles at room temperature. Deformed bcc structures and deformed icosahedron structures are most probable atomic configurations for 2, 4, 6 nm particles of Fe_{50}Co_{50} nanoalloy.
9
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ZnO Thin Films Synthesized by Sol-Gel Process for Photonic Applications

80%
Znaidi L., Touam T., Vrel D., Souded N., Ben Yahia S., Brinza O., Fischer A., Boudrioua A.
Acta Physica Polonica A
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2012
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vol. 121
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issue 1
165-168
EN
Undoped and aluminum-doped ZnO thin films are prepared by the sol-gel process. Zinc acetate dihydrate, ethanol and monoethanolamine are used as precursor, solvent and stabilizer, respectively. In the case of Al-doped ZnO, aluminum nitrate nonahydrate is added to the precursor solution with an atomic percentage equal to 1 or 2 at.% Al. The multi thin layers are prepared by spin-coating onto glass substrates, and are transformed into ZnO upon annealing at 550°C. Films with preferential orientation along the c-axis are successfully obtained. The structural, morphological, and optical properties of the thin films as a function of aluminum content have been investigated for different elaboration parameters (e.g. layer number) using X-ray diffraction, atomic force microscopy, scanning electronic microscopy. Waveguiding properties of the thin films have been also studied using m-lines spectroscopy. The results indicate that our films are monomodes at 632.8 nm with propagation optical loss estimated around 1.6 dB/cm.
10
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Influence of Annealing on Optical Properties of ZnO Nanorods Obtained by the Microwave-Assisted Hydrothermal Process

80%
Materska P., Witkowski B., Godlewski M.
Acta Physica Polonica A
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2016
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vol. 130
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issue 5
1202-1204
EN
Optical properties of ZnO nanorods (of different sizes, grown on two different substrates) are investigated. Nanorods were grown using microwave-assisted hydrothermal process on gallium nitride or silicon substrate. To initiate nanorods growth on a silicon substrate ZnO nucleation layer was used. ZnO nanoseeds were deposited by atomic layer deposition. For GaN substrate an epitaxial relation was observed. For both substrates nanorods show a hexagonal structure, expected for wurtzite ZnO. Results of nanorods annealing are discussed.
11
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Van Der Waals Density Functionals for Graphene Layers and Graphite

80%
Birowska M., Milowska K., Majewski J.
Acta Physica Polonica A
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2011
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vol. 120
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issue 5
845-848
EN
In this communication, we present results of theoretical studies of various systems where Van der Waals interaction plays a considerable role. In the first-principle calculations performed in the density functional theory framework we implement novel functionals accounting for Van der Waals forces and employ to the test cases of graphite and graphene layers. It turns out that this approach provides a solution to the long standing problem of overbinding between graphene layers in bulk graphite, giving the distance between the carbon layers in excellent agreement with experiment. In graphene bilayers, Van der Waals functionals lead to energetic barriers for A-B to A-A ordering of graphene bilayers that are by a factor of two smaller than the barriers obtained with standard functionals. It may be of crucial importance, particularly, if one uses atomistic ab initio methods as a starting point for multi-scale modeling of materials and for determination of effective potentials.
12
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Structural and Electronic Properties of Functionalized Graphene

80%
Milowska K., Birowska M., Majewski J.
Acta Physica Polonica A
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2011
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vol. 120
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issue 5
842-844
EN
In the present paper, we study the effects of functionalization of graphene with simple organic molecules OH, and NH_2, focusing on the stability and band gaps of the structures. We have performed DFT calculations for graphene supercells with various numbers of the attached molecules. We have determined adsorption energies of the functionalized graphene mono- and bilayers, the changes in the geometry, and the band structure. We observe the characteristic effects such as rehybridization of the bonds induced by fragments attached to graphene and opening of the graphene band gap by functionalization. We have also studied the dependence of the adsorption energies of the functionalized graphene on the density of the adsorbed molecules. Our calculations reveal that the -OH and -NH_2 groups exhibit the strong cohesion to graphene layers. Further, we determine the critical density of the OH fragments which lead to the opening of the band gap. We also show how to engineer the magnitude of the band gap by functionalizing graphene with NH_2 groups of various concentrations.
13
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Multicomponent (Ti-Zr-Hf-V-Nb)N Nanostructure Coatings Fabrication, High Hardness and Wear Resistance

80%
Pogrebnjak A., Beresnev V., Kolesnikov D., Bondar O., Takeda Y., Oyoshi K., Kaverin M., Sobol O., Krause-Rehberg R., Karwat C.
Acta Physica Polonica A
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2013
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vol. 123
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issue 5
816-818
EN
First results in the field of synthesis and research of the multicomponent (Ti-Zr-Hf-V-Nb)N nanostructured coatings are presented in the paper. Influence of processes of spinodal segregation and mass-transfer on single-layered or multilayered crystal boundary (second phase) forming were explored. Superhard nanostructured coatings were investigated before and after annealing at the temperature 600°C using unique methods (slow positron beam, proton microbeam particle induced X-ray emission-μ, Rutherford backscattering-analysis, scanning electron microscopy with energy dispersive X-ray spectroscopy, X-ray diffraction analysis was performed using DRON-4 and nanoindentor). Diffraction spectra were taken point-by-point, with a scanning step 2Θp=0.05 to 0.1°. We detected that positron trapping by defects was observed on the nanograins boundaries and interfaces (vacancies and nanopores which are the part of triple and larger grain's boundary junction). The 3D distribution maps of elements obtained by the proton microbeam (particle induced X-ray emission-μ) together with the results obtained by slow positron microbeam gave us comprehensive information about physical basis of the processes, connected with diffusion and spinodal segregation in superhard coatings.
14
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Photocatalytic Properties of Mechanochemically Synthesized Nanocrystalline ZnAl_2O_4 and CdSe

80%
Kostova N., Eliyas A., Fabián M., Achimovičová M., Baláž P.
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vol. 126
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issue 4
967-970
EN
Nanocrystalline powders of ZnAl_2O_4 and CdSe were prepared via mechanochemical synthesis. Powder slurries were coated as thin films on SiO_2 thin layer chromatography (TLC) sheet by capillary method. The photocatalytic activity of the film coating was tested in a self-made gas-phase flat-plate continuous-flow photocatalytic reactor with toluene as model air contaminant. The tested nanocrystalline ZnAl_2O_4 turned out to be poor oxidation photocatalyst under UV irradiation. CdSe displays considerable photocatalytic activity under visible light, where TiO_2 is inactive. The nonconventional one-step mechanochemical route to ZnAl_2O_4 and CdSe synthesis offers several advantages compared to traditional processing routes, including low-temperature solid state reactions at ambient temperature, absence of organic templates contamination and low expenses.
15
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Effect of Iron Atoms on the Properties οf Silicon Cage Clusters

80%
Mahtout S.
Acta Physica Polonica A
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2013
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vol. 124
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issue 4
688-694
EN
In this work, we have systematically studied the effect of iron atoms on the structural, electronic, and magnetic properties of silicon cage clusters in the range size of 19 to 24 atoms, using the density functional theory implemented in the code SIESTA. A new behaviour in the structural, electronic, and magnetic properties of the doped silicon clusters is obtained. We find that the encapsulation of one-Fe atoms within silicon clusters lead to stable Fe encapsulated Si clusters when compared to the clusters with the same size of pure silicon. However, the clusters stabilities leads to a decrease when the number of Fe atoms in substitution increase in the clusters. It is seen that the Fe doped silicon clusters have large HOMO-LUMO gap for spin up electrons while those with spin down electrons have a very small HOMO-LUMO gap. The silicon clusters which are not magnetic in their pure state become magnetic after the substitution of Fe atoms and the magnetic moments of different structures increase when the number of Fe atoms increase in the clusters.
16
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Synthesis and Characterization of ZnO Doped with Fe_{2}O_{3} - Hydrothermal Synthesis and Calcination Process

80%
Sibera D., Jędrzejewski R., Mizeracki J., Presz A., Narkiewicz U., Łojkowski W.
Acta Physica Polonica A
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2009
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vol. 116
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issue S
S-133-S-135
EN
The aim of the present work is to compare two methods of synthesis of nanocrystallline zinc oxide doped with iron oxide. The synthesis was carried out using microwave asssisted hydrothermal synthesis and traditional wet chemistry method followed by calcination. The phase composition of the samples was determined using X-ray diffraction measurements. Depending on the chemical composition of the samples, hexagonal ZnO, and/or cubic ZnFe_{2}O_{4} were identified. The morphology of the received materials was characterized using scanning electron microscopy. Two different structures of agglomerates were observed: a hexagonal structure (corresponding to zinc oxide) and spherical (corresponding to spinel phase). The effect of the iron oxide concentration on specific surface area and density of the samples was determined.
17
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Synthesis and Properties of Mesoporous Maghemite

80%
Kotsyubynsky V., Hrubiak A., Moklyak V., Mohnatska L., Fedorchenko S.
Acta Physica Polonica A
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2018
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vol. 133
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issue 4
1035-1037
EN
Mesoporous maghemite (γ -Fe₂O₃), obtained by thermal decomposition of iron citrate xerogel hydrate, was investigated by X-ray diffraction, scanning electron microscopy, the Mössbauer and impedance spectroscopies and low temperature nitrogen adsorption. The influence of precursor molar concentration on the material morphology, crystalline and magnetic microstructures and electric conductivity was studied. Obtained results open up the possibility for synthesis of ultrafine γ -Fe₂O₃ with controlled structural and morphological characteristics.
18
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Effect of Thermal Treatment on the Structure and Mechanical Properties of Coatings Based on (Ti, Hf, Nb, Si)N

80%
Pogrebnjak A., Komarov F., Sobol O., Kaverina A., Shypylenko A., Karwat C.
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vol. 125
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issue 6
1312-1316
EN
Current paper presents the results of investigating of nanostructured cathode arc vacuum evaporation coatings, based on (Ti, Hf, Nb, Si)N. Several methods of the structural and elemental analysis were used: proton microbeam, nano- and micro-electron beam, X-ray diffraction analysis. To determine tribological properties (scratch resistance, adhesive and cohesive strength) of the coatings, scratch testing were conducting. Influence of thermal annealing at temperatures 300, 500, 800, 1000C on elemental composition, microstructure, residual stress, phase composition, profiles of atomic distribution in the coatings were investigated.
19
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Surface Chemistry of Zirconia Nanopowders Doped with Pr_2O_3: an XPS Study

80%
Suchorski Y., Wrobel R., Becker S., Opalińska A., Narkiewicz U., Podsiadly M., Weiss H.
Acta Physica Polonica A
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2008
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vol. 114
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issue S
S-125-S-134
EN
Zirconia nanopowders of tetragonal crystallographic structure doped with Pr_2O_3 were prepared by the microwave-assisted hydrothermal synthesis and coprecipitation method. The surface compositions were studied by X-ray photoelectron spectroscopy. The nanopowder particles appear to be inhomogeneous in their structure: for the surface region an enrichment with praseodymium is detected by X-ray photoelectron spectroscopy measurements. This allows the assumption of a core-shell-like structure of single nanopowders particles. The X-ray photoelectron spectroscopy studies confirm also Zr^{4+} and Pr^{3+} as main oxidation states of zirconium and praseodymium in the studied compounds.
20
Content available remote

Influence of Deposition Parameters and Thermal Annealing on the Structure and Properties of Nitride Coatings (TiHfZrVNb)N

80%
Pogrebnjak A., Abadias G., Chartier P., Bondar O., Yakuschenko I., Takeda Y., Krause-Rehberg R., Kolesnikov D., Beresnev V., Partyka J.
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vol. 125
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issue 6
1296-1299
EN
Results of structure, phase composition, physical and mechanical properties and tribological properties investigations of nitride high-entropy coatings (TiZrHfVNb)N are presented in the paper. Proton microbeam (μ-PIXE), X-ray diffraction method, including method of X-ray strains measurements, energy dispersive X-ray spectroscopy and scanning electron microscopy analysis, microhardness testing and nanoindentation were used. Thermal annealing (t=600°C) influence on defect profiles, structure and element distribution in the coatings was investigated. It was found that thermal treatment of coatings leads to changing of defect profiles and to element redistribution. Also we can say that it influences less on grain size changing. Investigated (TiZrHfVNb)N coatings demonstrate high values of hardness and excellent wear resistance.
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