A novel approach to drag reduction is presented on the basis of applied positive electric potenti... more A novel approach to drag reduction is presented on the basis of applied positive electric potentials to a pipe. This has been studied by measuring the pressure drop over a 13.1 m epoxy-coated pipe made of carbon steel, through which water was flowing under conditions of constant flow rate. Potentials were applied between the pipe and the counter electrode located
ABSTRACT Piezoelectric resonator measurements show that there is a minimum of interfacial viscosi... more ABSTRACT Piezoelectric resonator measurements show that there is a minimum of interfacial viscosity of sodium hexafluorophosphate aqueous solution (approximately 1% of the bulk viscosity) at the potential of zero charge of gold electrode. Drag force measurements confirm interfacial viscosity dependence on the potential obtained from piezoelectric resonator measurements but the minimum is lower (approximately 5% of the bulk viscosity). Potential dependence of interfacial viscosity has been determined in the absence of confinement of fluid between a probe and surface what provides useful comparison to probe-based methods where confinement is inherent to the measurement and where additional model assumptions are needed to separate confinement effects. By controlling the applied potential it is possible to control the viscosity of liquid layer close to the solid interface, what increases the ability to actively manipulate a wall-bounded liquid flow field to effect a desired change.
ABSTRACT Piezoelectric resonator and drag force measurements show a decrease of interfacial visco... more ABSTRACT Piezoelectric resonator and drag force measurements show a decrease of interfacial viscosity of perchlorate and chloride aqueous solutions during polarization of gold electrode towards potential of zero charge. Though more noisy, drag force measurements have the advantage over piezoelectric technique as the former is insensitive to potential dependent adsorption, which causes distortion of data on liquid properties obtained from piezoelectric resonator measurements at more positive potentials. The shift in the potential of the viscosity minimum, obtained from drag force measurements follows the shift in the potential of zero charge (pzc) with a change in concentration. In addition, the Esin-Markov relation holds at these potentials: tenfold increase in concentration of specifically adsorbing chloride shifts the potential of viscosity minimum by -46 mV, whereas tenfold increase in concentration of weakly adsorbing perchlorate results only in the negligible shift of the potential of viscosity minimum (-4 mV).
Analysis of the admittance of quartz resonator in contact with water has shown that the viscosity... more Analysis of the admittance of quartz resonator in contact with water has shown that the viscosity-density product of water at a metallic electrode surface decreases during the positive potential scan. This decrease is more pronounced when the electrode surface is coated by a thin layer of polymer. Literature data provide evidence that the density of water in the first layer attached to the surface increases when the potential is shifted into the positive direction. It is concluded that during such potential scan the decrease of viscosity is larger than the increase of density.
... Timeresolved EQCM study Vytautas Daujotis,* Darius Jasaitis and Rimantas Raudonis Department ... more ... Timeresolved EQCM study Vytautas Daujotis,* Darius Jasaitis and Rimantas Raudonis Department of General and Inorganic Chemistry. ... The quartz supported working electrode was placed into a Teflon holder and fixed vertically to the hole at the side of a waterjacketed (20 0.05 ...
ABSTRACT This article reports on the sol-gel synthesis and characteristic properties of novel mix... more ABSTRACT 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.
The aqueous sol-gel synthesis technique for the preparation of (Pb,Sr)Sr 2 (Y,Ca)Cu 2 O 7±x (Pb-1... more The aqueous sol-gel synthesis technique for the preparation of (Pb,Sr)Sr 2 (Y,Ca)Cu 2 O 7±x (Pb-1212) and (Pb 2 ,Cu)Sr 2 (Y,Ca)Cu 2 O 8±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 (T C (onset)) observed by resistivity measurements were found to be 91 K and 75 K for Pb-1212 and Pb-3212 samples, respectively.
A novel approach to drag reduction is presented on the basis of applied positive electric potenti... more A novel approach to drag reduction is presented on the basis of applied positive electric potentials to a pipe. This has been studied by measuring the pressure drop over a 13.1 m epoxy-coated pipe made of carbon steel, through which water was flowing under conditions of constant flow rate. Potentials were applied between the pipe and the counter electrode located
ABSTRACT Piezoelectric resonator measurements show that there is a minimum of interfacial viscosi... more ABSTRACT Piezoelectric resonator measurements show that there is a minimum of interfacial viscosity of sodium hexafluorophosphate aqueous solution (approximately 1% of the bulk viscosity) at the potential of zero charge of gold electrode. Drag force measurements confirm interfacial viscosity dependence on the potential obtained from piezoelectric resonator measurements but the minimum is lower (approximately 5% of the bulk viscosity). Potential dependence of interfacial viscosity has been determined in the absence of confinement of fluid between a probe and surface what provides useful comparison to probe-based methods where confinement is inherent to the measurement and where additional model assumptions are needed to separate confinement effects. By controlling the applied potential it is possible to control the viscosity of liquid layer close to the solid interface, what increases the ability to actively manipulate a wall-bounded liquid flow field to effect a desired change.
ABSTRACT Piezoelectric resonator and drag force measurements show a decrease of interfacial visco... more ABSTRACT Piezoelectric resonator and drag force measurements show a decrease of interfacial viscosity of perchlorate and chloride aqueous solutions during polarization of gold electrode towards potential of zero charge. Though more noisy, drag force measurements have the advantage over piezoelectric technique as the former is insensitive to potential dependent adsorption, which causes distortion of data on liquid properties obtained from piezoelectric resonator measurements at more positive potentials. The shift in the potential of the viscosity minimum, obtained from drag force measurements follows the shift in the potential of zero charge (pzc) with a change in concentration. In addition, the Esin-Markov relation holds at these potentials: tenfold increase in concentration of specifically adsorbing chloride shifts the potential of viscosity minimum by -46 mV, whereas tenfold increase in concentration of weakly adsorbing perchlorate results only in the negligible shift of the potential of viscosity minimum (-4 mV).
Analysis of the admittance of quartz resonator in contact with water has shown that the viscosity... more Analysis of the admittance of quartz resonator in contact with water has shown that the viscosity-density product of water at a metallic electrode surface decreases during the positive potential scan. This decrease is more pronounced when the electrode surface is coated by a thin layer of polymer. Literature data provide evidence that the density of water in the first layer attached to the surface increases when the potential is shifted into the positive direction. It is concluded that during such potential scan the decrease of viscosity is larger than the increase of density.
... Timeresolved EQCM study Vytautas Daujotis,* Darius Jasaitis and Rimantas Raudonis Department ... more ... Timeresolved EQCM study Vytautas Daujotis,* Darius Jasaitis and Rimantas Raudonis Department of General and Inorganic Chemistry. ... The quartz supported working electrode was placed into a Teflon holder and fixed vertically to the hole at the side of a waterjacketed (20 0.05 ...
ABSTRACT This article reports on the sol-gel synthesis and characteristic properties of novel mix... more ABSTRACT 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.
The aqueous sol-gel synthesis technique for the preparation of (Pb,Sr)Sr 2 (Y,Ca)Cu 2 O 7±x (Pb-1... more The aqueous sol-gel synthesis technique for the preparation of (Pb,Sr)Sr 2 (Y,Ca)Cu 2 O 7±x (Pb-1212) and (Pb 2 ,Cu)Sr 2 (Y,Ca)Cu 2 O 8±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 (T C (onset)) observed by resistivity measurements were found to be 91 K and 75 K for Pb-1212 and Pb-3212 samples, respectively.
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