Browsing by Author "Georgiev M."
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Item Characterization of beryllium selenates by X-ray powder diffraction, DTA and DSC(2004-11-01) Koleva V.; Karadjova V.; Georgiev M.BeSeO4.2H2O and BeSeO4 have been studied röntgenographically: BeSeO4.2H2O forms orthorhombic / crystals with lattice constants: a = 5.843(2) Å; b = 9,790(3) Å; c = 4.692(1) Å; V = 268.4(1) Å3. The crystals of BeSeO 4 are tetragonal: a = 4.648(1) Å; c = 7.084 (3) Å; V= 153.1(1) Å3, SG I4̄. The thermal dehydration of BeSeO 4.4H2O has been studied by TG, DTA and DSC methods. The dehydration occurs in four steps and intermediate hydrates BeSeO 4.2H2O, BeSeO4.H2O and BeSeO 4.0.5H2O are formed. The enthalpies of dehydration of the observed dehydration processes have been determined. The higher value of ΔHdeh of BeSeO4.4H2O as compared to those of other metal selenate tetrahydrates is discussed in terms of the strong Be-H2O interaction. The enthalpies of formation of BeSeO 4.4H2O and BeSeO4.2H2O have been calculated. © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.Item On the formation of solid solutions of blödite- and kröhnkite-type structures. Iv. Synthesis, structural, spectroscopic and thermal investigations of Na2Co1-Xmgx(So4)2•4H2O (0 < X < 1)(2017-01-01) Georgiev M.; Marinova D.; Bancheva T.; Stoilova D.New structural, spectroscopic and thermal data on the formation and characterization of solid solutions containing cobalt blödite, Na2Co(SO4)2•4H2O, and magnesium blödite, Na2Mg(SO4)2•4H2O, are provided in this contribution. On the basis of the solubility data and X-ray powder diffraction it is found that both compounds form a continuous series of solid solutions due to their isostructureness. It is established that the lattice parameters of the solid solutions obey the Vegard rule. The infrared spectra of the blödite phases are interpreted in the light of their crystal structures. The strength of the hydrogen bonds in both hydrates and in the solid solutions is analyzed in terms of matrix infrared spectroscopy (matrix-isolated HDO molecules). The thermal behavior and phase transitions of the solid phases are studied by TG and DTA analyses. It is found that the dehydration processes occur stepwise forming thus intermediate hydrates and anhydrous compounds at 350°C.