Rimantas Raudonis

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 PREPARATION AND CHARACTERIZATION OF NOVEL MIXED-METAL COBALTATES-ALUMINATES

This article reports on the sol-gel synthesis and characteristic properties of novel mixed neodymium and neodymium-yttrium cobaltates and cobaltates-aluminates (NdCoO3, NdCo0.75Al0.25O3, NdCo0.5Al0.5O3, NdCo0.25Al0.75O3, (Nd0.5Y0.5)CoO3, (Nd0.5Y0.5)Co0.75Al0.25O3, (Nd0.5Y0.5)Co0.5Al0.5O3, and (Nd0.5Y0.5)Co0.25Al0.75O3). The polycrystalline powders were characterized by powder X-ray diffraction (XRD) analysis, Fourier transform-infrared (FT-IR) spectroscopy, and scanning electron microscopy (SEM). Single-phase solid solutions NdCo1-xAlxO3 and (Nd0.5Y0.5)Co1-xAlxO3 were obtained after annealing precursor gels for 10 h at 1000°C. From the results obtained, it could be concluded that the NdCo1-xAlxO3 and (Nd0.5Y0.5)Co1-xAlxO3 solids are composed of spherical grains with uniform size (from 100 to 500 nm). The surface morphology changes slightly with substitution of cobalt by aluminium and neodymium by yttrium. With increasing amount of aluminium the crystalline particles formed with more pronounced agglomeration. The possible application of synthesized compounds as blue cobalt-based pigments was suggested.

Reduction in pressure drop for pipe flow due to applied electric potentials to the pipe

For all forms of transport of fluids in pipes, there is loss of pressure due to the friction. It has been shown that an electrical potential applied to the pipe wall can reduce water flow friction. Piezometric pressure loss over the 13.1 m slanting epoxy coated pipe made of steel, through which water was flowing, decreased when pipe was exposed to positive DC-potentials in the range 0.6–1.6 V. Maximum reduction was 2% with an applied potential of 1.0 V. Results from full scale experiments in a hydroelectric power plant (12.5 MW, 85 GWh) show that head loss decreased from 45.9 m to 39.8 m at maximum flow rate after 2.5 years of exposure to 1.1 V. Similar results for the head loss in another power plant (28 MW, 116 GWh) were 17.5 and 17.2 m, respectively, after 9 months of exposure to this DC-potential. The positive polarization of the pipes was noticeable throughout the whole length of the pipe.

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.

Synthesis of lead-based 1212 and 3212 superconductors by an aqueous sol-gel method

The aqueous sol-gel synthesis technique for the preparation of (Pb,Sr)Sr2(Y,Ca)Cu2O7±x (Pb-1212) and (Pb2,Cu)Sr2(Y,Ca)Cu2O8±x (Pb-3212) superconductors using two different complexing agents, namely 1,2-ethanediol and tartaric acid was studied. The phase transformations, composition and micro-structural features in the polycrystalline samples were studied by powder X-ray diffraction analysis (XRD), infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). XRD analysis of the ceramic samples obtained by calcination of Pb-Sr-Y-Ca-Cu-O acetate-glycolate precursor gels in air, for 10 hours at 800°C and at 825°C, showed the presence of homogeneous Pb-1212 and Pb-3212 crystallites as major phases. The XRD patterns of the ceramics obtained from Pb-Sr-Y-Ca-Cu-O acetate-tartrate precursor gels, however, showed multiphasic character. The critical temperature of superconductivity (TC (onset)) observed by resistivity measurements were found to be 91 K and 75 K for Pb-1212 and Pb-3212 samples, respectively.