Search results

1

Soft X-Ray Diffraction up to Wavelengths of 6.0Å Becomes Feasible at ID1 of ESRF

100%

Carpentier P., Boesecke P., Bois J., Chesne M., Fanchon E., Kahn R., Stuhrmann H., Vicat J.

Acta Physica Polonica A

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2002

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vol. 101

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issue 5

603-612

EN

Recent experiments carried out at the Anomalous Scattering Beamline ID1 of ESRF are described which show that a cold helium atmosphere provides optimal conditions for protein crystallography with soft X-rays at wavelengths up to 6Å. Image plates are suitable detectors for this wavelength range. The improvement with respect to earlier experiments is considerable. This observation opens the way to the use of anomalous dispersion at the K-edge of light elements, like phosphorus, sulphur, chlorine and calcium. Moreover, there is an interest to use the strong anomalous dispersion of some heavy elements such as uranium (110 anomalous electron units at its M_V edge) to solve large biological structures. The methods of multiwavelength anomalous diffraction and diffraction anomalous fine structure find new resonant labels which are wide spread in living matter and materials.

2

Cryocrystallography of Biological Macromolecules

100%

Schneider T. R.

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EN

X-ray diffraction experiments on crystals of biological macromolecules, especially when carried out on highly intense synchrotron beam lines, frequently suffer from radiation damage. Performing such experiments at cryogenic temperatures virtually eliminates radiation damage thus producing higher quality diffraction data and often making previously intractable problems feasible. In the following article the most important experimental aspects of low temperature diffraction experiments on macromolecular crystals will be discussed.

3

Magnetisation and Hydrogenation of Mg/Ni Multilayers

63%

Pacanowski S., Marczyńska A., Dawczak-Dębicki H., Jabłoński B., Szymański B., Smardz L.

Acta Physica Polonica A

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2018

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vol. 133

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issue 3

617-619

EN

In this contribution we have studied magnetisation of Mg/Ni multilayers (MLs) to characterise the alloing effect near interfaces. The layered structure was characterised by standard X-ray diffraction. The MLs were deposited by UHV magnetron sputtering onto naturally oxidised Si(100) substrates. Results showed, that due to Mg-Ni alloy formation near interfaces the magnetizations of the MLs were strongly reduced. Effective "dead" Ni layer thickness was estimated as 1.2 nm at room temperature (RT). Furthermore, hydrogen absorption kinetics at a pressure of about 1000 mbar was studied at RT in Pd covered Mg/Ni MLs using four-point resistivity measurements. Results showed that the fastest initial rise in resistance in the first 9 s was observed for d_{Ni}=3.5 nm.

4

Automatic System for Crystallographic Data Collection and Analysis

63%

Minor W., Cymborowski M., Otwinowski Z.

Acta Physica Polonica A

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2002

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vol. 101

|

issue 5

613-619

EN

During the last 10 years the rate of new protein structures determined by X-ray crystallography has risen about tenfold. The use of high flux sources was instrumental in this growth. There are numerous advantages of using synchrotron radiation for protein crystallography: rapid data collection, use of micro-crystals and the ability to conduct measurements at wide range of wavelengths. The rate-limiting step is often the ability to analyze and back up a fast stream of data produced by a multi-module CCD detector. The goal of the newly developed HKL-2000 package is to integrate all computational activities that have to be performed during the data collection experiment. The Graphical Command Center of HKL-2000 organizes and forwards the data collection parameters to the display, indexing, strategy, simulation, refinement, integration, scaling, and merging tasks. Data acquisition can become a part of data processing (or vice versa), which includes indexing, integration, scaling, and even phasing. The increase in internet band width will provide an opportunity to remotely interact with the experimental setup and perform the synchrotron experiment from the home laboratory.

5

Optimization of Azimuthal Scan Procedure for Absolute Structure Determination

63%

Grochowski J., Serda P.

Acta Physica Polonica A

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1997

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vol. 91

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issue 5

961-968

EN

The paper describes the application of the azimuthal scan technique for absolute structure determination using X-ray anomalous dispersion. A diffraction pattern with rotation around the scattering vector provides information about various anisotropic effects: absorption, extinction and multi-beam interaction. Recording of azimuthal scans for Friedel pairs is proposed as an alternative to single reflection measurement. Several factors affecting the smoothness of the azimuthal scan curves are discussed and a procedure for eliminating various sources of errors, involving a Fourier filtering, is proposed in order to increase feasibility of chiral discrimination.

6

Synthesis of Highly Porous SrTiO₃ Materials

63%

Mizera A., Drożdż E., Łańcucki Ł.

Acta Physica Polonica A

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2018

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vol. 133

|

issue 4

873-875

EN

Strontium titanate is a perovskite with a great potential to act as an anode material for solid oxide fuel cells. The requirements for these materials concern not only electrical but also microstructural properties. The strontium titanate with regular pore structure can exhibit lower flow resistance compared to random pore distributed materials. Several methods of synthesis (with addition of various organic agents) allowed obtaining materials with regular/irregular pore structure. Regardless of synthesis methods all materials showed high porosity (above 40 vol.%). Additionally it was found that three-dimensionally ordered macroporous structure collapsed after sintering at 1200°C whereas macro-mesoporous structure of P-123 modified strontium titanate had persisted.

7

Growth and Characterization of Titanium Doped Spinel Crystals

51%

Gritsyna V., Kazarinov Y., Kobyakov V., Lytvynov L.

Acta Physica Polonica A

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2018

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vol. 133

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issue 4

774-777

EN

MgAl₂O₄ (magnesium aluminates spinel, MAS) single crystals doped with titanium ions obtained by the Verneuil method were non-uniformly colored along of the growth crystallographic direction. The crystals were characterized measuring lattice parameter, optical absorption spectra and relative concentration of impurity atoms (Ti, Mn, Cr, and Fe) in different spots of grown Ti:MAS boule. There was observed the correlation of the intensity of absorption band at 800 nm to the relative concentration of iron supporting the identification of this band with charge transfer transition in complexes Ti⁴⁺+Fe²⁺ → Ti³⁺+Fe³⁺. The new resonant structure at the wavelength of 470 nm was found and tentatively identified with the Fano resonance in the complexes formed by lattice defects and impurity ions.

8

Structural Studies of Titanium Oxide Multilayers

51%

Karwasz G., Miotello A., Zomer E., Brusa R., Kościelska B., Armellini C., Kuzmin A.

Acta Physica Polonica A

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2005

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vol. 107

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issue 6

977-982

EN

Multilayers of titanium oxide on conductive glasses (silica, covered with indium/tin and tin oxides) were obtained by different methods (from suspension, by sol-gel, by vacuum sputtering). X-ray diffraction and positron annihilation depth-resolved characterization of these samples are presented. The data allow us to determine optimal deposition parameters, in order to obtain the anatase phase, important in practical applications in photoelectrochemical cells.

9

Effect of Doping on Ga_{1-x}Al_{x}As Structural Properties

51%

Bąk-Misiuk J., Domagała J., Paszkowicz W., Trela J., Żytkiewicz Z. R., Leszczyński M., Regiński K., Muszalski J., Härtwig J., Ohler M.

Acta Physica Polonica A

|

1997

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vol. 91

|

issue 5

911-917

EN

The microstructure of Ga_{1-x}Al_{x}As layers was studied using methods of high resolution diffractometry and topography. Mapping out the reciprocal space in the vicinity of 004 reciprocal lattice points shows a difference in diffuse scattering between doped and undoped layers. This result is attributed to a difference in a point-defect density. From the measurements of lattice parameters at different temperature it was found that the thermal expansion coefficients for the doped layers are higher than for the undoped ones. This phenomenon is attributed to the change of the anharmonic part of lattice vibrations by free electrons or/and point defects.

10

Influence of Isomorphic Atom Substitution on Lattice Anisotropy of Thallium Dichalcogenide Layered Mixed Crystals

51%

Gasanly N.

Acta Physica Polonica A

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2006

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vol. 110

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issue 4

471-477

EN

Compositional variation of the lattice parameters of TlBX_2-type (B = Ga or In and X = S or Se) mixed crystals with monoclinic structure were studied by X-ray diffraction technique. The lattice anisotropy (c/b) of these mixed crystals changes linearly with substitution of the atoms located both at the centers and the vertices of the corresponding BX_4 tetrahedra. A brief survey of the important features of the effect of isomorphic atom substitution on the lattice anisotropy and the unit cell volume of TlBX_2-type mixed crystals with layered structure was presented.

11

Dendrite Growth in Selector-Root Area of Single Crystal CMSX-4 Turbine Blades

51%

Bogdanowicz W., Tondos A., Krawczyk J., Albrecht R., Sieniawski J.

Acta Physica Polonica A

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2016

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vol. 130

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issue 4

1107-1109

EN

The single crystal turbine blades made of CMSX-4 nickel-based superalloy were studied. The turbine blades were obtained by the Bridgman technique with withdrawal rate of 5 mm/min. The samples, cut-off from root part of blades and containing the fragment of the selector, were studied. The effect of selector geometry on the dendrites growth and defects formation in the selector-root area of the blade were analyzed. The Laue diffraction, scanning electron microscopy, and X-ray diffraction topography were applied. It was found that, during crystallization of the selector, the dendrite cores, after reaching the surface of mould, may bend, if the angle between dendrite cores and the mould surface was equal to 12°. When the angle was equal to 24° the growth of dendrites has been stopped. It can be stated that the defects, which appeared in the selector were inherited by the root part.

12

Magnetic Anisotropy of UFe_{10-x}Ni_{x}Si_{2} Intermetallic Alloys

51%

Drzazga Z., Suski W., Wochowski K., Wójcik J., Winiarska A.

Acta Physica Polonica A

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2000

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vol. 98

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issue 5

555-560

EN

The magnetic anisotropy in UF_{10-x}Ni_{x}Si_{2} series has been studied by torsion magnetometry and initial ac magnetic susceptibility measurements in the temperature range of 77-293K. The effective anisotropy constant changes with Ni content showing some increase for intermediate concentration. An increase in magnetic anisotropy energy at low temperatures is due to the uranium sublattice ordering. Magnetic anisotropy behaviour in UFe_{2}Ni_{8}Si_{2} is influenced by an additional enhancement of the 3d sublattice connected with the ordering Fe magnetic moments.

13

Absolute Structure Determination in Absence of Heavy Scatterers

51%

Grochowski J.

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EN

Methods of absolute structure determination for molecules containing only light atoms (C, H, N, O) are discussed in the paper. This experimentally difficult problem has a direct application in the structure determination of naturally originated compounds and modern chiral drugs. Several experimental methods of absolute structure determination like electron diffraction, multiple X-ray diffraction and X-ray anomalous scattering techniques are briefly discussed and compared. An application of dedicated azimuthal scan method for the case of hexamethylenetetramine is given as an illustration of this technique.

14

Solid Solutions of Oxide Crystals as Substrates for Epitaxial Layer Depositions

51%

Berkowski M., Fink-Finowicki J., Aleksijko R., Diduszko R., Byszewski P., Kikalejshvili-Domukhovska R.

Acta Physica Polonica A

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2006

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vol. 109

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issue 4-5

457-463

EN

We present results of investigation on growth of solid solution crystals with perovskites and K_2NiF_4 structures used as substrates for epitaxy. Perovskite single crystals with no twins and crystals with K_2NiF_4 structure with the lattice parameter in the range 3.876-3.819Å and 3.754 to 3.688Å, respectively, can be grown. Here preliminary results on investigation on growth of other solid solution crystals with the lattice constant from 3.946 to 3.688Å are also presented thus covering the whole interesting range for depositing oxide materials. These crystals can be grown by the Czochralski method that secures their high structural quality. Discussed crystals are resistant to reaction with the deposited oxide layers.

15

Structure of CaPs Coatings Electrophoretically Deposited on NiTi Shape Memory Alloy

51%

Dudek K., Goryczka T.

Acta Physica Polonica A

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2016

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vol. 130

|

issue 4

1053-1055

EN

The surface of NiTi shape memory alloys applied as long-term implants has been modified by protective calcium phosphates (CaPs) coatings, with the objective of improving the biocompatibility of this material. The calcium phosphates such as hydroxyapatite Ca₅(PO₃)OH (HAP) and β-tricalcium phosphate β-Ca₃(PO₄)₂ (β-TCP) were deposited by electrophoretic deposition. In order to improve the adhesion, the deposited samples were vacuum-sintered at wide range of temperature from 500°C to 1000°C for 2 h. The studies revealed that applied sintering conditions did not change the structure of CaPs. The coatings consisted of HAP with hexagonal structure (P63/m) and β-TCP with rhombohedral structure (R-3c). Changes in lattice parameters for CaPs coatings after deposition and sintering were refined by the Rietveld method.

16

Surfactant Effect on Synthesis of Nanocrystalline La_xSr_{1-x}MnO_3 by Hydrothermal Method

51%

Sin W., Wong K., Li P.

Acta Physica Polonica A

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2007

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vol. 111

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issue 1

165-171

EN

Crystalline La_xSr_{1-x}MnO_3 was prepared by a hydrothermal route in the presence of surfactant. The cationic surfactant of cetyltrimethylammonium bromide as a template is used to regulate the nucleation and crystal growth. The as-synthesized product was characterized by X-ray diffraction and transmission electron microscopy. Nanosized and uniform rod-like monocrystals of La_xSr_{1-x}MnO_3 were obtained. Their magnetic properties were studied using a vibrating sample magnetometer. Our results reveal that the use of surfactant helps to lower the processing temperature and to speed up the formation and crystallization of La_xSr_{1-x}MnO_3. The surfactant also provides us an additional means of controlling the nanocrystalline size and maintaining the stoichiometry of the as-prepared nanocrystallites.

17

Structure of Chitosan-ZnO Layers Electrophoretically Deposited on NiTi Shape Memory Alloy

45%

Goryczka T., Kokoszka A., Kowalski P., Łosiewicz B.

Acta Physica Polonica A

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2016

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vol. 130

|

issue 4

1056-1058

EN

The surface of NiTi shape memory was modified by deposition of chitosan-ZnO thin film. The electrodeposition process was carried out at room temperature at voltage-time conditions: 10 V/30 s, 10 V/300 s, 20 V/30 s, or 20 V/300 s. Structure of the obtained coatings was studied by means of grazing incidence beam X-ray diffraction. Distribution of the zinc oxide particles in the chitosan matrix was observed with use of scanning electron microscopy. It was found that depending on the electrodeposition parameters, the structure of the obtained chitosan-ZnO coatings varies from amorphous to coarse-grained.

18

Structural Properties of Co and CoFe Electrodes Forming a Magnetic Tunnel Junction

45%

Gładczuk L., Pankowski P., Paszkowicz W., Dłużewski P., Wójcik M., Przysłupski P.

Acta Physica Polonica A

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2007

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vol. 111

|

issue 1

135-140

EN

The M_1/MgO/M_2 trilayer tunnel magnetoresistance systems are studied by means of X-ray diffraction, NMR, and transmission electron microscopy techniques. As M_1 and M_2 electrodes we used Co, Fe, and CoFe layers. The growth mechanism and structural quality of both electrodes and of the epitaxial MgO barrier forming the magnetic tunnel junctions are experimentally examined. It is shown that the crystallographic coherence of magnetic tunnel junctions across the MgO barrier is significantly disturbed by imperfect crystal structure of magnetic electrodes. The NMR results indicate a difference in short-range order between bottom and top electrodes.

19

Study of solid-solution hardening in binary aluminium-based alloys

38%

Draissia M., Debili M.-Y.

Open Physics

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2005

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vol. 3

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issue 3

395-408

EN

Solid-solution formation in binary aluminium-based alloys is due essentially to the combined effects of the size and valence of solvent and solute atoms, as expected by the four Hume-Rothery rules. The lattice parameter of aluminium in the solid solution of the sputtered Al−Fe films is [Al-a (Å)=4.052−6.6×10−3Y]. The increasing and decreasing evolution of the lattice parameter of copper [Cu-a (Å)=3.612+1.8×10−3Z] and aluminium [Al-a (Å)=4.048−1.6×10−3X] in the sputtered Al-1.8 to 92.5 at. % Cu films is a result of the difference in size between the aluminium and copper atoms. The low solubility of copper in aluminium (<1.8 at % Cu) is due to the valences of solvent and solute atoms in contrast with other sputtered films prepared under similar conditions, such as Al−Mg (20 at. % Mg), Al−Ti (27 at. % Ti), Al−Cr (5at. % Cr) and Al−Fe (5.5 at. % Fe) where the solubility is due to the difference in size.

20

Microstructure Analysis of Nanocrystalline Powders by X-ray Diffraction

38%

Louër D., Audebrand N.

Acta Physica Polonica A

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2002

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vol. 102

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issue 1

45-56

EN

The use of X-ray diffraction line profile analysis for the study of nanocrystalline powders is described. The fundamentals of the theory are presented in terms of crystallite/domain size, size distribution, lattice distortion, dislocation density and stacking faults. Line profile parameters and the methods of pattern fitting introduced to overcome the diffraction-line overlap problem are described. The approaches based of the integral breadth of the measured line profiles and the Fourier method are discussed. In addition, simplified approaches are also commented. Representative examples are selected to illustrate various cases of microstructure, such as nanomaterials with strain-free spherical nanocrystallites, strain-free crystallites with anisotropic crystallite shape, anisotropic crystallites with microstrains and spherical crystallites with dislocation densities and crystallite size distributions.

Refine search results

Soft X-Ray Diffraction up to Wavelengths of 6.0Å Becomes Feasible at ID1 of ESRF

Cryocrystallography of Biological Macromolecules

Magnetisation and Hydrogenation of Mg/Ni Multilayers

Automatic System for Crystallographic Data Collection and Analysis

Optimization of Azimuthal Scan Procedure for Absolute Structure Determination

Synthesis of Highly Porous SrTiO₃ Materials

Growth and Characterization of Titanium Doped Spinel Crystals

Structural Studies of Titanium Oxide Multilayers

Effect of Doping on Ga_{1-x}Al_{x}As Structural Properties

Influence of Isomorphic Atom Substitution on Lattice Anisotropy of Thallium Dichalcogenide Layered Mixed Crystals

Dendrite Growth in Selector-Root Area of Single Crystal CMSX-4 Turbine Blades

Magnetic Anisotropy of UFe_{10-x}Ni_{x}Si_{2} Intermetallic Alloys

Absolute Structure Determination in Absence of Heavy Scatterers

Solid Solutions of Oxide Crystals as Substrates for Epitaxial Layer Depositions

Structure of CaPs Coatings Electrophoretically Deposited on NiTi Shape Memory Alloy

Surfactant Effect on Synthesis of Nanocrystalline La_xSr_{1-x}MnO_3 by Hydrothermal Method

Structure of Chitosan-ZnO Layers Electrophoretically Deposited on NiTi Shape Memory Alloy

Structural Properties of Co and CoFe Electrodes Forming a Magnetic Tunnel Junction

Study of solid-solution hardening in binary aluminium-based alloys

Microstructure Analysis of Nanocrystalline Powders by X-ray Diffraction