ANNUAL REPORT - MTA SzFKI

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defined coordination sphere was found, particularly at higher concentrations. The orientation of water molecules around the cations may be characterized by a broad distribution of Rb . . .O–H angles, peaking around the tetrahedral angle. This indicates that cations have a weak tendency to occupy a position close to one of the lone electron pairs of the O atoms. It was also found that in the rather vaguely defined hydration shell of chloride ions, six (or somewhat more) water molecules may surround each anion. However, on average, only about three of them point straight towards the anion with one of their H atoms, whereas all other hydrogens are turned away from the ion. The six neighbouring water molecules of the hydration shell can thus be separated into about three hydrogen-bonding and three (or four) non-H-bonding water molecules. Chalcogenide glasses. — The structure of sputtered amorphous Ge 2 Sb 2 Te 5 was studied by Te-, Sb- and Ge K-edge EXAFS, X-ray diffraction and, for the first time, neutron diffraction. The five datasets were modelled simultaneously by the reverse Monte Carlo simulation technique. The results obtained are thus consistent with all of the five measurements. Within the experimental errors the coordination number of Te, Sb and Ge is 2, 3 and 4, respectively. Thus, in contrast with the findings of some recent works on amorphous Ge 2 Sb 2 Te 5 all atoms satisfy the 8-N rule. Besides Te-Ge and Te-Sb bonds present in the crystalline phases Ge-Ge and Sb-Ge bonding was also found to be significant. The atomic structure of the binary AsSe, ternary (AsSe) 80 Ag 20 , (AsSe) 85 I 15 and quaternary (AsSe) 65 (AgI) 35 glasses has been studied with the X-ray and neutron diffraction. The local order was also probed with EXAFS at the Ag, As, I and Se K-edges. All experimental data were modelled simultaneously by the reverse Monte Carlo technique. Ag and I modify the structure of the host matrix (AsSe) in opposite ways. Ag atoms are preferentially covalently bonded to Se. Addition of I to AsSe decreases the connectivity of the matrix. The average coordination number in amorphous (AsSe) 85 I 15 = 2.18 ± 0.2. I atoms are covalently bonded to As atoms. Metallic glasses. — Short range order of amorphous Mg 60 Cu 30 Y 10 was investigated by X- ray and neutron diffraction, Cu and Y K-edge X-ray absorption fine structure measurements and by the reverse Monte Carlo simulation technique. We found that Mg- Mg and Mg-Cu nearest neighbour distances are very similar to values found in crystalline Mg 2 Cu. The Cu-Y coordination number is 1.1±0.2 and the Cu-Y distance is ~4% shorter than the sum of atomic radii suggesting that attraction between Cu and Y plays an important role in stabilizing the glassy state. Thermal stability and structure evolution upon annealing were also studied by differential scanning calorimetry and in-situ X-ray powder diffraction. The alloy shows a glass transition and three crystallization events, the first and dominant one at 456 K corresponding to eutectic crystallization of at least three phases: Mg 2 Cu and most likely cubic MgY and CuMgY. Borosilicate glasses. — The network structure of multi-component borosilicate based waste glasses with composition (65-x)SiO 2 .·xB 2 O 3·25Na 2 O·5BaO·5ZrO 2 , x=5-15mol% (host glass) was studied by high-Q neutron diffraction. For data analyses both the direct sine- Fourier transformation and reverse Monte Carlo simulation was applied. Several atomic partial correlation functions are displayed in Figure 2. It was established that the Si-O network consists from tetrahedral SiO 4 units with characteristic first neighbour distances r Si- O=1.60 Å and r Si-Si =3.0 Å. The boron surrounding contains two well-resolved B-O distances at 1.40 and 1.60 Å and, both 3- and 4-fold coordination are present. A chemically mixed network structure is proposed including [4] B-O- [4] Si and [3] B-O- [4] Si chain segments. The O-O and Na-O distributions suggest partial segregation of silicon and boron rich regions. The 52
highly effective ability of Zr to stabilize the glass and hydrolytic properties of sodiumborosilicate host materials is argumented by the network forming role of Zr ions. Uraniumloaded glasses have been successfully prepared, and it was found that they posses good glass and hydrolytic stability. Our neutron diffraction data are consistent with a model where the uranium ions are incorporated into interstitial voids in the essentially unmodified network structure of the starting host glass. The U-O atomic pair correlation functions show a sharp peak at around 1.7 Å, and several farther smaller intensity but distinct peaks are between 2.8- 4.1 Å. Uranium ions are coordinated by 6 oxygen atoms in the 1.6-3.4 Å interval. g Si-O (r) 20 15 10 5 Si-O 0 1 2 3 4 5 6 r[Å] g Si-Si (r) 4 3 2 1 Si-Si 0 1 2 3 4 5 6 r[Å] g B-O (r) 15 10 5 B-O 0 1 2 3 4 5 6 r[Å] g O-O (r) 4 3 2 1 O-O 0 1 2 3 4 5 6 r[Å] g Na-O (r) 3 Na-O 2 1 0 1 2 3 4 5 6 r[Å] g Zr-O (r) 6 4 2 Zr-O 0 1 2 3 4 5 6 r[Å] Fig. 2. Comparison of several partial correlation functions obtained by RMC modelling for the multi-component borosilicate glasses: B5 (square), B10 (open circle), B15(crosses). Internal stress - In the frame of non-destructive testing project of supercritical water (374 ºC, 221 bar) we have tested the structural parameters of Neutron counts 1200 800 400 Fe(110) 400 C RT(25 C) e=∆d/d 0 =-∆Θ ∆ΘcotΘ (e-α*∆T)*E=95 MPa 0 39.5 40.0 40.5 41.0 41.5 42.0 42.5 2Θ Fig. 3. Neutron diffraction pattern of iron container used for supercritical water study the special containers prepared from iron. The Fe(110), Fe(200), Fe(220) Bragg-reflections were measured from room temperatures up to 400 ºC on several parts of the containers. From the shift of the peak positions - taking into consideration the thermal shift - we have determined the stresses caused by the supercritical water. Figure 3 illustrates the Fe(110) pattern taken at ambient temperature and at 400 ºC; from the data analysis 95 MPa internal stress was calculated, which is significantly lower than the expected Yield strength of 250 MPa. E-Mail: Margit Fábián Ildikó Harsányi Pál Jóvári László Kőszegi György Mészáros Viktória Mile Szilvia Pothoczki László Pusztai Erzsébet Sváb fabian@szfki.hu harsanyi@szfki.hu jovari@szfki.hu koszegi@szfki.hu meszaros@szfki.hu milev@szfki.hu pszzse@freemail.hu lp@szfki.hu svab@szfki.hu 53
Page 1 and 2:
ANNUAL REPORT 2007 RESEARCH INSTITU
Page 3 and 4: Dear Reader, It is my pleasure to h
Page 5 and 6: Key figures Permanent staff of the
Page 8 and 9: A. STRONGLY CORRELATED SYSTEMS J. S
Page 10 and 11: presented detailed study should hel
Page 12 and 13: B. COMPLEX SYSTEMS F. Iglói, R. Ju
Page 14 and 15: B.3. B.4. B.5. B.6. B.7. B.8. B.9.
Page 16 and 17: the α2 reconstruction increases on
Page 18 and 19: C.2. C.3. Kádas K, Vitos L, Johans
Page 20 and 21: C.27. Ropo * M, Kokko * K, Punkkine
Page 22 and 23: I 25 4 3 Fig. 2. Average intensity
Page 24 and 25: See also H.6. and nanostructured Pd
Page 26 and 27: Ab initio structure solution. — I
Page 28 and 29: ESA PECS 98021 Phase field modeling
Page 30 and 31: Conference proceedings E.17. Oszlá
Page 32 and 33: Fig. 1. ns-EC to s-EC transition in
Page 34 and 35: Publications Articles F.1. F.2. Bö
Page 36 and 37: G. ELECTRON CRYSTALS G. Kriza, P. M
Page 38 and 39: H. METAL PHYSICS K. Tompa, I. Bakon
Page 40 and 41: thickness can be elucidated by deco
Page 42 and 43: I. METALLURGY AND MAGNETISM L.K. Va
Page 44 and 45: temperature profile increases the s
Page 46 and 47: I.13 Kane * SN, Khinchi * SS, Gercs
Page 48 and 49: SANS. The measured 3 control rods w
Page 50 and 51: J.3. J.4. J.5. J.6. J.7. Avdeev * M
Page 52 and 53: Macromolecular Compounds (Visokomol
Page 56 and 57: László Temleitner temla@szfki.hu
Page 58 and 59: Book chapter K.22. Temleitner L, Pu
Page 60 and 61: Fig. 1 Characteristics of surface p
Page 62 and 63: M. LASER PHYSICS K. Rózsa, G. Bán
Page 64 and 65: Publications Articles M.1. Sigenege
Page 66 and 67: O. LASER APPLICATION A. Czitrovszky
Page 68 and 69: Raman spectroscopy is widely used f
Page 70 and 71: Bilateral Austro-Hungarian Cooperat
Page 72 and 73: P. FEMTOSECOND LASERS R. Szipőcs,
Page 74 and 75: Grants and international cooperatio
Page 76 and 77: E-Mail: Kárpát Ferencz optilab@t-
Page 78 and 79: y optical microscopy. While in Y 2
Page 80 and 81: Publications: Articles R.1. Földv
Page 82 and 83: S. CHARACTERIZATION AND POINT DEFEC
Page 84 and 85: groups of the Li 2 B 4 O 7 lattice.
Page 86 and 87: S.10. Lengyel K, Kovács L, Péter
Page 88 and 89: entanglement one has to find method
Page 90 and 91: T.7. T.8. T.9. Asbóth JK, Domokos
Page 92 and 93: EDUCATION Graduate and postgraduate
Page 94 and 95: Laboratory practice and seminars
Page 96 and 97: G. Dravecz (ELTE and Université de
Page 98 and 99: ⎯ K. Kamarás: Editorial Board Me
Page 100 and 101: CONFERENCES ⎯ Electrochemistry se
Page 102: TABLE of CONTENTS PREFACE 1 KEY FIG
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