Diffusion induced atomic islands on the surface of Ni/Cu nanolayers

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Composition, morphology and electrical transport properties of Co-Pb electrodeposits

Bath compositions were elaborated for the codeposition of Co and Pb by taking into account the chemical compatibility of Co2+ and Pb2+ with the appropriate anions. Electrolytes containing either acetate, chloride or nitrate anions were tested, but only the acetate bath proved to be appropriate for the preparation of compact Co-Pb films. Deposits were obtained with constant current, with constant potential or by using various current and potential pulses in order to investigate the possibility of multilayer formation. The variation in deposit composition as a function of the deposition parameters was elucidated by using cyclic voltammetry, current transient measurements and gravimetry. X-ray diffraction (XRD) patterns recorded for two-pulse plated deposits revealed a nanocrystalline structure with grain sizes in the range 5 to 20 nm. The XRD peaks could be well indexed to pure face-centered cubic Co and Pb, indicating that the Pb codeposited with Co is not dissolved in Co but is segregated. Both the d.c.-plated and the two-pulse plated deposits exhibited anisotropic magnetoresistance without an indication for a noticeable giant magnetoresistance contribution. This means that the observed magnetoresistance arises from spin-dependent electron scattering events dominantly within the sufficiently large Co regions and not along electron paths between two Co regions via the Pb regions. Low-temperature resistivity measurements revealed a superconducting transition slightly below that of pure Pb. This may be ascribed to a proximity effect: the ferromagnetic Co grains suppress somewhat the superconductivity of the Pb phase due to the nanoscale phase mixture of the two constituents

Designing the color of hot-dip galvanized steel sheet through destructive light interference using a Zn-Ti liquid metallic bath

The color of hot-dip galvanized steel sheet was adjusted in a reproducible way using a liquid Zn-Ti metallic bath, air atmosphere, and controlling the bath temperature as the only experimental parameter. Coloring was found only for sample s cooled in air and dipped into Ti-containing liquid Zn. For samples dipped into a 0.15 wt pct Ti-containing Zn bath, the color remained metallic (gray) below a 792 K (519 C) bath temperature; it was yellow at 814 K, violet at 847 K, and blue at 873 K. With the increasing bath temperature, the thickness of the adhered Zn-Ti layer gradually decreased from 52 to 32 micrometers, while the thickness of the outer TiO2 layer gradually increased from 24 to 69 nm. Due to small Al contamination of the Zn bath, a thin (around 2 nm) alumina-rich layer is found between the outer TiO2 layer and the inner macroscopic Zn layer. It is proven that the color change was governed by the formation of thin outer TiO2 layer; different colors appear depending on the thickness of this layer, mostly due to the destructive interference of visible light on this transparent nano-layer. A complex model was built to explain the results using known relationships of chemical thermodynamics, adhesion, heat flow, kinetics of chemical reactions, diffusion, and optics

Mágneses ellenállást mutató perovszkitok és spinellek vizsgálata Mössbauer-spektroszkópiával, mágneses és röntgendiffrakciós módszerekkel = Mössbauer spectroscopic, magnetic and x-ray diffraction studies of some perovskite and spinel materials possessing magnetoresistivity

I. Kutatásunk legfontosabb eredménye, hogy összefüggést tudtunk felmutatni a vizsgált kobaltát perovszkitok lokális elektromos és mágneses szerkezete és az általuk mutatott mágneses ellenállás között. Sikerült felvázolni a La0.8Sr0.2Co1-yFeyO3 (0 < y < 0,3) perovszkitok mágneses fázisdiagramját, részletesen elemezni tudtuk a különböző fázisok természetét, valamint a lantánionok európiummal való cseréjével megállapítottuk a ritkaföldfém lokális elektromos állapotát. Egy újabb kísérletsorozat során elkészítettük, karakterizáltuk és megvizsgáltuk a La1-xSrxFe0.025Co0.975O3 (0 < x < 0,25) összetételű perovszkitokat is. Eredményeink alapján megállapítottuk, hogy a mágneses ellenállás kiváltó oka a vizsgált perovszkitokban a nanoméretű elektromos-mágneses fázisszeparáció lehet. II. A pályázat másik kutatási témájának keretén belül növények vasfelvételi mechanizmusait vizsgáltuk Mössbauer-spektroszkópia segítségével uborka és búza felhasználásával. Bizonyítottuk az ún. I. stratégiai csoportba tartozó növények redukción alapuló vasfelvételi mechanizmusát és rámutattunk a Cd vasfelvételt (és transzportot) gátló hatásaira. Emellett biomineralizációs és szintetikus folyamatokban képződő jarozitok szerkezetét tanulmányoztuk PXRD és Mössbauer-spektroszkópiai módszerekkel. UV-látható spektrofotometria és Mössbauer-spektroszkópia alkalmazásával megvizsgáltuk a növényélettani szempontból jelentős indol-3-ecetsavnak a vas(III)-mal történő reakcióinak mechanizmusát és kinetikáját. | I. Our primer finding is that we were able to correlate the observed local electronic and magnetic properties of the investigated cobaltate perovskite samples with their magnetoresistance. We presented the magnetic phase diagram of La0.8Sr0.2Co1-yFeyO3 (0 < y < 0.3) perovskites, and we analyzed the nature of the depicted magnetic phases. Moreover, by replacing the lanthanum ions with europium, using 151Eu Mössbauer spectrometry we have determined the local electronic structure of the rare-earth cation, as well. We have also prepared and characterized La1-xSrxFe0.025Co0.975O3 (0 < x < 0.25) samples and performed several experiments on them. Due to our results, we were able to determine the possible source of the magnetoresistance of the investigated family of perovskites, being the nanosize electronic-magnetic phase separation. II. In the second part of the project, the iron-uptake mechanisms of plants were investigated by Mössbauer spectroscopy, using cucumber and wheat as model plants: direct evidence for the strategy I iron-uptake mechanism was given and the inhibitory effects of Cd on the iron-uptake and transport were demonstrated. The structure of jarosites formed during biomineralization and synthetic processes were studied with the help of PXRD and Mössbauer spectroscopy. The mechanism and the kinetics of the reaction of the plant hormone indole-3-acetic acid with iron(III) was discussed in detail using UV-Vis spectrophotometry and Mössbauer spectroscopy

A 222Rn-nek mint egy természetes myomjelzőnek alkalmazása környezeti vizsgálatokban

Application of Rn-222 as a natural tracer in environmental studie

Larmor precession and debye relaxation of single-domain magnetic nanoparticles

The numerous phenomenological equations used in the study of the behaviour of single-domain magnetic nanoparticles are described and some issues clarified by means of qualitative comparison. To enable a quanti- tative application of the model based on the Debye (exponential) relaxation and the torque driving the Larmor precession, we present analytical solutions for the steady states in presence of circularly and linearly polarized AC magnetic fields. Using the exact analytical solutions, we can confirm the insight that underlies Rosensweig’s introduction of the "chord" susceptibility for an approximate calculation of the losses. As an important conse- quence, it can also explain experiments, where power dissipation for both fields were found to be identical in "root mean square" sense. We also find that this approximation provides satisfactory numerical accuracy only up to magnetic fields for which the argument of the Langevin function reaches the value 2.8