Annual Report 2012
into Al containers with the fibers aligned vertically. The results of SANS measurements are shown in Fig.1 in the form of 2D spectra.
The alignment of fibers, which is reflected in the scattering patterns due to the anisotropic nanoscale structure, tells about the treatment effect. The enzyme and chlorine treatments appeared to have the least disruptive effect on the fiber since the spectra were isotropic, whereas just the chlorine treatment had the greatest influence. In the dry wool structure we observed a density fluctuation with spherical gyration radius ~7-9 nm corresponding to the physical diameter of long cylindrical samples. This can be identified as the micro-fibril size of the studied wool filaments. Wetting experiments on samples of mohair with mean diameter 25.3 µm and 37.3 µm were also performed. 2D SANS spectra were measured on dry samples and on samples with D2O. These results gave an indication of where and how the water molecules are attached to and detached from the wool fiber. This new knowledge will go as far as developing an understanding, at the molecular level, the influence of the wetting and drying process of wool and mohair fibers. This project was performed as a science and technology collaboration between Hungary and South-Africa.
Fig.2. 2D SANS scattering intensities of the 0.5 mm diameter tungsten samples taken from the different steps of the wire production. Temperatures of annealing: not annealed, 1420 K and
2470 K
Nanoscale morphology of tungsten wires. — Another filament structure study was related to the morphology of doped tungsten used in lighting industry. Tungsten research has a long tradition in Hungary owing to GE TUNGSRAM – a leading manufacturer of lighting products worldwide. Our SANS study focused on the nanoscale structure of wires and, in particular, on the structure-stabilizing feature of potassium doping. We investigated the potassium bubbles present in the tungsten matrix of the drawn wires to understand several qualitative and quantitative characteristics of the potassium-tungsten complex system. During the mechanical and thermal processing the potassium bubbles form a specific texture that delays the break of the wire and prolongs its life. During the wire drawing the sphere-like bubbles get elongated along the axis of the wire forming ellipsoidal and cylinder-like bubbles.
With further deformation the aspect ratio of a bubble reaches a critical value and becomes unstable: the ellipsoid splits into a row of elongated bubbles with a smaller aspect ratio. In the further steps of annealing the degree of the elongation decreases until all the bubbles adopt spherical shape. These rows of bubbles guide the grain boundary migration allowing the growth of elongated grains along the axis of the wire. This structure gives a good tensile
S-K. Neutron spectroscopy in condensed matter
strength of the wires. Analyzing the 2D SANS maps (Fig.2) of series of samples annealed at different temperatures we can determine the elongation ratio and give an accurate description of the maturation of the bubble system inside the wire during the production. Using a sophisticated 2D data treatment method we obtained the anisotropy of the scattering in a large Q range (10-5 Å-1- 10-1 Å-1) enabling us to determine the size and shape of potassium bubbles.
This lead us to understand that micro-crack formation during manufacturing of thin tungsten wires has always been presumed, and here it was finally demonstrated experimentally.
G
RANTS AND INTERNATIONAL COOPERATIONEU-FP7-CP-CSA-INFRA-2008-1.1.1 No. 226507-NMI3 – Integrated Infrastructure Initiative for Neutron Scattering and Muon Spectroscopy (J. Füzi, 2009-2012) EU-FP7 – CHARISMA – Cultural Heritage Advanced Research Infrastructures: Synergy for
a multidisciplinary approach to conservation/restoration (L. Rosta, 2009-2013)
EU-FP7-INFRASTRUCTURES-2011-1-283883, NMI3-II —Neutron Scattering and Muon Spectroscopy Integrated Initiative (L.Rosta, 2012-2015)
NAP VENEUS05 OMFB-06482/2008 Visegrád Cooperation for Development and Application of Neutron Spectroscopy Techniques in Multidisciplinary Research (L. Rosta, 2008-2011)
OTKA-A08-3 OMFB-00590/2010 Structure and dynamics of self-organized lamellar molecular systems (Mezei F. 2010-2012)
Research and Development Agreement between Wigner RCP and Helmholtz-Zentrum Berlin on Time-of-Flight Neutron Spectroscopy Techniques (L.Rosta, 2012-2014)
International Atomic Energy Agency: Project No. CRP1575, Development, Characterization and Testing of Materials of Relevance to Nuclear Energy Sector Using Neutron Beams (Gy. Török 2012-2013)
NFÜ- MAG ZRt. TÉT-0018 South-Africa, Structural Analysis of Treated Textile Fibres (Gy.
Török 2011-2013)
P
UBLICATIONSArticles
1. Nagy G, Pieper* J, Krumova* SB, Kovács* L, Trapp* M, Garab* G, Peters* J; Dynamic properties of photosystem II membranes at physiological temperatures characterized by elastic incoherent neutron scattering. Increased flexibility associated with the inactivation of the oxygen evolving complex; Photosynth Res; 111, 113-124, 2011 2. Rosta L, Len A, Pépy G, Harmat* P, Nano-scale morphology of inclusions in tungsten
wires – a complex SANS study; Neutron News; 23, 13-16, 2011
3. Szakál A, Czifrus* S, Marko M, Füzi J, Rosta L, Cser, L; Optimization of focusing supermirror neutron guides for low gamma-background; Nucl Instr Meth A; 634, S130-S133, 2011
Annual Report 2012
4. Cser L, Krexner* G, Markó M, Szakál A; Neutron holography – a brief history and overview; Neutron News; 23, 17-20, 2012
5. Fábián M, Sváb E; Uranium surrounding in borosilicate glasses from neutron- and X-ray diffraction and reverse Monte Carlo modeling; Neutron News; 23, 9-12, 2012
6. Kasztovszky* Zs, Rosta L; How can neutrons contribute to Cultural Heritage Research?;
Neutron News; 23, 25-28, 2012
7. Mezei F, Russina* M, Káli Gy; Neutron diffraction for long pulse neutron sources;
Neutron News; 23, 29-31, 2012
8. Nagy G, Szabó* M, Ünnep R, Káli Gy, Miloslavina* Y, Lambrev* PH, Zsiros* O, Porcar* L, Rosta L, Garab* G; Modulation of the multilamellar membrane organization and of the chiral macrodomains in the diatom Phaeodactylum tricornutum revealed by small-angle neutron scattering and circular dichroism spectroscopy; Photosynth Res;
110, 71-79, 2012
9. Posselt* D, Nagy* G, Kirkensgaard* JJK, Holm* JK, Aagaard* TH, Timmins* P, Rétfalvi* E, Rosta L, Kovács* L, Garab* Gy; Small-angle neutron scattering study of the ultrastructure of chloroplast thylakoid membranes – periodicity and structural flexibility of the stroma lamellae; Biochim Biophys Acta – Bioenergetics; 8, 1220-1228, 2012 10. Saerbeck* T, Klose* F, Le Brun* AP, Füzi J, Brule* A, Nelson* A, Holt* SA, James* M;
Polarization "Down Under": The polarized time-of-flight neutron reflectometer PLATYPUS; Rev Sci Instr; 83, 081301/1-12, 2012
11. Török Gy, Lebedev* V, Vinogradova* L; Structural and conformational properties of polymeric stars with fullerene centre in solutions by SANS; Procedia Chemistry; 4, 154-163, 2012
Articles in Hungarian
12. Rosta L, Nyolcvan éves a neutron (Eighty years from the discovery of neutron, in Hungarian); Nukleon; 5(4), 1-5, 2012
13. Rosta L, Neutronkutatások Magyarországon (Neutron research in Hungary, in Hungarian); Nukleon; 5(5), 1-5, 2012
Conference proceedings
14. Franklyn* CB, Török Gy; Use of small angle neutron scattering to study various properties of wool and mohair fibres; In: Proc. Applications of Nuclear Techniques Eleventh International Conference (12–18 June 2011 Crete, Greece); AIP Conf Proc;
1412, 93-97, 2011
15. Russina* M, Mezei F, Kali Gy; First implementation of novel multiplexing techniques for advanced instruments at pulsed neutron sources; J Phys Conf Ser; 340, 2012