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Marek Wiertel, Zbigniew Surowiec, Mieczysław Budzyński and Wojciech Gac

Abstract

In this paper, results of positron annihilation lifetime spectroscopy (PALS) studies of MnFe2O4/MCM-41 nanocomposites in N2 and O2 atmosphere have been presented. In particular, the influence of manganese ferrite loading and gas filling on pick-off ortho-positronium (o-Ps) annihilation processes in the investigated samples was a point of interest. Disappearance of the longest-lived o-Ps component with τ5 present in the PAL spectrum of initial MCM-41 mesoporous material in the PAL spectra of MnFe2O4-impregnated MCM-41 measured in vacuum is a result of either a strong chemical o-Ps quenching or the Ps inhibition effects. The intensity I 4 of the medium-lived component initially increases, reaching a maximum value for the sample with minimum manganese ferrite content, and then decreases monotonically. Analogous dependence for the intensity I 3 of the shortest-lived component shows a maximum at higher MnFe2O4 content. Filling of open pores present in the studied nanocomposites by N2 or O2 at ambient pressure causes partial reappearance of the τ4 and τ5 components, except a sample with maximum ferrite content. The lifetimes of these components measured in O2 are shortened in comparison to that observed in N2 because of paramagnetic quenching. Anti-inhibition and anti-quenching effects of atmospheric gases observed in the MnFe2O4/MCM-41 samples are a result of neutralization of some surface active centers acting as inhibitors and weakening of pick-off annihilation mechanism, respectively.

Open access

K.O. Oyedotun, E. Ajenifuja, B. Olofinjana, B.A. Taleatu, E. Omotoso, M.A. Eleruja and E.O.B. Ajayi

Abstract

Lithium manganese oxide thin films were deposited on sodalime glass substrates by metal organic chemical vapour deposition (MOCVD) technique. The films were prepared by pyrolysis of lithium manganese acetylacetonate precursor at a temperature of 420 °C with a flow rate of 2.5 dm3/min for two-hour deposition period. Rutherford backscattering spectroscopy (RBS), UV-Vis spectrophotometry, X-ray diffraction (XRD) spectroscopy, atomic force microscopy (AFM) and van der Pauw four point probe method were used for characterizations of the film samples. RBS studies of the films revealed fair thickness of 1112.311 (1015 atoms/cm2) and effective stoichiometric relationship of Li0.47Mn0.27O0.26. The films exhibited relatively high transmission (50 % T) in the visible and NIR range, with the bandgap energy of 2.55 eV. Broad and diffused X-ray diffraction patterns obtained showed that the film was amorphous in nature, while microstructural studies indicated dense and uniformly distributed layer across the substrate. Resistivity value of 4.9 Ω·cm was obtained for the thin film. Compared with Mn0.2O0.8 thin film, a significant lattice absorption edge shift was observed in the Li0.47Mn0.27O0.26 film.

Open access

K. Selvarani, R. Mahalakshmi and B. Thanuja

Abstract

Co-crystals of L-phenylalanine hydrochloride (LPAHCl) were grown by slow evaporation technique in the presence of manganese sulphate and cadmium chloride. Crystallinity of the grown crystals was confirmed by single crystal X-ray diffraction. Optical transmission spectra showed very high transmittance in the entire visible region. The cut-off wavelength was observed at 250 nm for both the crystals. The optical band gap energy was found to be 4.37 eV and 4.31 eV for the grown co-crystals of LPAHCl with MnSO4 and CdCl2, respectively. The second harmonic generation of the grown crystals was confirmed by Kurtz and Perry powder SHG method and compared with KDP. The frequency dependent dielectric properties of the co-crystals were studied at different temperatures.

Open access

Mutation Breeding in Chickpea:

Perspectives and Prospects for Food Security

IMRAN M. Kozgar

Open access

D. Kalisz, S. Gerasin, P. Bobrowski, P.L. Żak and T. Skowronek

Abstract

The quality of rail steel is conditioned by its high mechanic qualities, which greatly depend on the presence of undesired nonmetallic inclusions. The paper is devoted to the segregation of components, mainly sulphur, and the formation of manganese sulphide in the process of steel solidification, at the casting rate of 100 and 500 K/min. Sulphur is a steel component which disadvantageously influences its numerous parameters. The oxide-sulphide and sulphide precipitations cause cracks and lower the strength of the material. This phenomenon was modeled with the use of author’s computer program based on Matsumiya interdendritic microsegregation model. The main assumptions of this model and thermodynamic conditions of inclusion formation during casting of steel are discussed in this paper. Two cases were analyzed: in the first one the MnS was assumed to form a pure and constant compound, whereas in the other one the manganese sulfide was precipitated as a component of a liquid oxide solution, and its activity was lower than unity. The final conclusion is that chemical composition of steel is the major parameter deciding about the formation of MnS inclusions.

Open access

M. Kupková, M. Hrubovčáková, M. Kabátová and M. Kupka

Abstract

Elemental iron and manganese powders were blended to form mixtures containing 25, 30 and 35wt.% Mn. Mixtures were compressed into prismatic bars and sintered. Some of the bars were repressed and resintered. Compared to a bar pressed and sintered once, the bar pressed and sintered twice possessed a higher relative density, a higher bending stiffness, and a grid microindentation data set with a lower variance. Bars were immersed in Hank's solution for eight weeks. After this procedure, the bending stiffness were found reduced for all bars except for those pressed, sintered and only repressed, the bending stiffness of which remained unchanged. The repressing has most likely closed up throats connecting the clusters of pores with the free surface of a bar, reducing thus a surface area exposed to a corrosive attack. The resintering has opened up those throats, the electrolyte could fill accessible pores and corrosion weakened the near-surface material, reducing thus a bar's bending stiffness.

Open access

Bożena Gołębiowska, Grzegorz Rzepa and Adam Pieczka

). Studies on manganese oxide minerals VI. Thallium in some manganese oxides. American Mineralogist , 47 , 1461-1467. Czerny, J. (1992). Hydrothermal mineralization phenomena in Karniowice Travertine near Cracow. Mineralogia Polonica , 23 , 3–13. Daiyan, Ch., Guanxin, W., Zhenxi, Z., & Yuming, Ch. (2003). Lanmuchangite, a new thallium (hydrous) sulphate from Lanmuchang, Guizhou Province, China. Chinese Journal of Geochemistry , 22 (2), 185-192. Gołębiowska, B., Pieczka, A., Rzepa, G., Matyszkiewicz, J., & Krajewski, M. (2010). Iodargyrite from Zalas

Open access

Petr Dostál and Pavel Kovář

ABSTRACT

Clonal plants are very often among the first species to establish during primary succession. They may rapidly capture available space due to efficient vegetative propagation, but the question arises whether they may also rely on seed bank or seed rain during expansion and recovery after a possible disturbance. This question becomes increasingly important in extreme conditions of industrial deposit investigated in this study. We explored the two aforementioned seed sources in a clonal grass Calamagrostis epigejos within an ecotoxicologically stressed environment - abandoned tailings containment (former sedimentation basin) - from manganese-ore mining. Density of seeds found in seed rain was 617 seeds m-2, and in soil seed bank 220 seeds m-2, based on an autumn survey. Soil seed pool was almost depleted until the following spring as only 13 seeds m-2 were present. This pattern contrasted with the capacity of C. epigejos to build a persistent soil seed bank as shown by a burial experiment. Seed rain was thus identified to be the sole reliable seed source that may assist in recovery of this species after a possible disturbance

Open access

Małgorzata Rajfur, Małgorzata Anna Jóźwiak and Andrzej Kłos

Abstract

Due to their occurrence in very different conditions and high resistance to physical and chemical factors, algae are pioneers colonising new environments and their sorption properties are used in biomonitoring and water remediation. The efficiency of the process of heavy metal sorption in algae used for in situ tests depends on abiotic factors, such as the chemical composition of water. Freshwater algae Spirogyra sp. were used in tests. Algae were exposed in the laboratory in manganese chloride solutions with various contents of other cations, including heavy metals and macronutrients. It has been shown that some heavy metals may desorb manganese bound to the surface of algae as a result of ion exchange in the following sequence: Cd2+ < Mn2+ ≈ Zn2+ < Cu2+. It has been also found that the competitiveness of sorption of cations naturally present in the alga environment versus Mn2+ cations changes in the sequence Na+ < Ca2+ < H+, defined for the concentrations referring to the cation unit charge. The results of tests were compared to the results of dried sea algae Palmaria palmata analyses.

Open access

Monika Wałęsa-Chorab, Adam Gorczyński, Damian Marcinkowski, Zbigniew Hnatejko and Violetta Patroniak

) modified π -conjugated bis(terpyridine)s and their Zn(II) based metallo-polymers. Macromol. Rapid Commun . 29, 1679-1686. DOI: 10.1002/ marc.200800377. 6. Wałęsa-Chorab, M., Stefankiewicz, A.R., Ciesielski, D., Hnatejko, Z., Kubicki, M., Kłak, J., Korabik, M.J. & Patroniak V. (2011). New mononuclear manganese(II) and zinc(II) complexes with a terpyridine ligand: Structural, magnetic and spectroscopic properties. Polyhedron , 30, 730 737. DOI: 10.1016/j.poly.2010.12.032. 7. Béziau, A., Baudron, S.A., Guenet, A. & Hosseini, M.W. (2013