Darius Jasaitis

Characterization of sol–gel process in the Y–Ba–Cu–O acetate–tartrate system using IR spectroscopy

Abstract Systematic investigation of sol–gel process in the Y–Ba–Cu–O acetate–tartrate system was performed using IR spectroscopy. Different values of synthesis parameters (temperature and duration of inorganic polymerization reactions, evaporation temperature and evaporation time during gelation) were used, and significant influence in some cases on superconducting characteristics of the oxide ceramics of composition YBa 2 Cu 4 O 8 was observed. Characterization by IR spectroscopy and thermogravimetric analysis, revealed the difference of local homogeneity in the precursor gels prepared under different evaporation regimes during gelation process. In addition, the explanation of the possible hydrolysis and condensation reactions in the sol state has been suggested.

Sol–gel preparation and characterization of manganese-substituted superconducting YBa2(Cu1−xMnx)4O8 compounds

In this work the effect on the structural and superconducting properties of YBa2Cu4O8 (Y-124) of replacing Cu by Mn was studied. Multimetallic oxide powders with the composition of YBa2(Cu1−xMnx)4O8 (x=0.00, 0.01, 0.02, 0.03, 0.04 and 0.05) have been prepared by a simple aqueous sol–gel method at an oxygen pressure of 1 atm starting from an aqueous mixture of the metal acetates. Homogeneous gels were achieved by complexing copper ions by tartaric acid before the gelation process. Thermal decomposition of the gels was studied by thermogravimetry. Effects of manganese substitutions on the properties of compounds were studied by X-ray powder diffraction, TG analysis, IR spectroscopy and resistivity measurements. These data indicated that the transition temperature of superconductivity drastically decreases upon Mn substitution, and that superconductivity is lost at 3% of Mn substitution level. XRD measurements showed that the structure of the Y-124 phase is also largely affected even at low manganese-substitutional levels.

The mechanism of electroreduction of silver cyanide complexes in aqueous electrolytes—I. Time-resolved EQCM study

Using a quartz supported silver electrode in potential step experiments, simultaneous measurements of current and electrode mass responses have shown that in parallel to electroreduction of silver cyanide complexes from water solutions the oxidation of electrolyte species occurs. In conjunction with the results of published studies an assumption is made that the adsorbed cyanide is the species which is oxidized.

Sol-gel synthesis and study of neodymium substitution effects in Co-Al-Nd-O system with possible applications as novel inorganic pigments

AbstractIn the present work, the formation of cobalt aluminium spinel (CoAl2O4) as well as novel cobalt neodymium-aluminates with nominal compositions of CoAl1.75Nd0.25O4, CoAl1.5Nd0.5O4 and CoAlNdO4 by an aqueous sol-gel process and the sinterability of the products are investigated. The metal ions, generated by dissolving starting materials of metals in the diluted acetic acid were complexed by 1,2-ethanediol to obtain the precursors for the mixed metal ceramics. The phase purity of the synthesized compounds was characterized by powder X-ray diffraction analysis and infrared spectroscopy. The microstructural evolution and morphological features of the products were studied by scanning electron microscopy and atomic force microscopy, which together with the optical characterization of these new compounds showed that the sol-gel-derived materials could be successfully used as effective cobalt-based ceramic pigments.

Sol-Gel Derived Ferrites: Synthesis and Characterization

In the present work, the sinterability and formation of nanosized yttrium iron garnet (Y3Fe5O12), yttrium perovskite ferrite (YFeO3), cobalt, nickel and zinc iron spinel (CoFe2O4, NiFe2O4 and ZnFe2O4, respectively) powders by an aqueous sol-gel processes are investigated. The phase purity of synthesized nano-compounds was characterized by powder X-ray diffraction analysis (XRD). The microstructural evolution and morphological features of obtained transition metal ferrites were studied by scanning electron microscopy (SEM). The possible application of these nanosized transition metal ferrites as ceramic pigments was demonstrated.