Search results for "Aqueous solution"
showing 10 items of 1610 documents
Preparation of mixed oxides MNdO3, with M=Cr, Fe. Comparison of several methods
1993
Abstract Different methods for the formation of NdCrO3 and NdFeO3, having the perovskite-like structure, were studied including the ceramic method, simultaneous precipitation of hydroxides and simultaneous crystallization from aqueous solutions of nitrates. Preparation of mixed oxides from hydroxides simultaneously precipitated lowered the temperature and time required for their formation. In the case of NdCrO3 the formation process from hydroxides and nitrates occurred through the chromate, NdCrO4, without intermediate decomposition of the precursor to metal oxides, which lead to the mixed oxide by 600°C.
Studies on various reactor configurations for coupling photocatalysis and membrane processes in water purification
2002
General aspects and perspectives of heterogeneous photocatalysis for the treatment of polluted aqueous effluents are presented. Some experimental results obtained by using various configurations of photocatalytic membrane reactors (PMRs) are reported. The configurations studied were: (i) irradiation of the cell containing the membrane, with three sub-cases: (i1) catalyst deposited on the membrane; (i2) catalyst in suspension, confined by means of the membrane; (i3) entrapment of the photocatalyst in a PSF membrane; (ii) irradiation of the re-circulation tank and catalyst in suspension confined by means of the membrane. In the case “(i)”, a preliminary investigation of membrane stability und…
Electrochemical Determination of the Fe(III)/Fe(II) Ratio in Archaeological Ceramic Materials Using Carbon Paste and Composite Electrodes
2002
A method for determining the iron(III)/iron(II) ratio in ceramic materials based on microsample attachment to graphite/polyester composite electrodes is presented. This quotient is of considerable interest for determining the nature and firing conditions of the original materials in archaeological ceramics. The electrochemistry of iron in ceramic materials in acetic/acetate and Na2EDTA aqueous solutions is described in terms of reductive dissolution processes of iron(III) materials and oxidative dissolution processes of iron(II) ones. The iron(III)/iron(II) ratio is determined from peak area measurements in linear scan voltammograms performed in 0.10 M acetic/acetate buffer (pH 4.70) and 0.…
Effect of NaClO disinfection/cleaning on passive films on AISI 316L
2020
Abstract 316 L stainless steel samples were passivated in NaClO containing solutions in order to simulate disinfection processes. Passive films were grown at the open circuit potential by immersion in NaClO aqueous solutions at different concentrations and temperature in order to understand how exposure to aggressive environments could affect subsequent corrosion resistance of SSs. In the attempt to study the passive film growth mechanism, in-situ Open Circuit Potential measurements were performed in the same growth solutions. Photoelectrochemical and impedance investigation of passive films was carried out in order to link their solid state properties with their corrosion behaviour.
Synthesis, characterization and magnetism of monodispersed water soluble palladium nanoparticles
2008
Water soluble, monodispersed Pd nanoparticles with a narrow particle size distribution have been successfully synthesized by controlled reduction of [PdCl4]2−. The resulting aqueous colloids are stable over extended periods of time and can be prepared at high nanoparticle loading (20 g/L of Pd) with no agglomeration. The size of the nanoparticles can be reduced from the nanometer (ca. 3.5 nm) to the sub-nanometer size range (ca. 0.9 nm). Detailed magnetic characterization indicated that the larger, 3.5 nm nanoparticles show ferromagnetic properties at room temperature, while the sub-nanometric ones lose this magnetic behavior.
A tensiostatic study of the anodic behaviour of tungsten in acid solutions
1975
Abstract Tensiostatic anodization of tungsten has been studied in 1 N solutions of H 2 SO 4 , HClO 42 , HNH 2 SO 3 and HCl at 25 °C. For several voltage values, the curves of current vs . time and open-circuit voltage vs . time have been obtained. All results indicate that the oxide films produced during the polarization are slowly dissolved in the acid solutions. The HCl, and to a lesser extent the HNH 2 SO 3 solutions, show a more aggressive behaviour. For values of the applied voltage above about 50 V, gas evolution begins. In the case of HCl solutions, the gas is Cl 2 and the electrode is rapidly corroded.
RGB video electrochemistry of copper electrodeposition/electrodissolution in acid media on a ternary graphite:copper:polypropylene composite electrode
2019
Abstract Galvanostatic copper electrodeposition and electrodissolution on graphite:copper:polypropylene composite electrodes in acidic media have been investigated to extend the technological applicability of ternary composites. Both electrochemical processes were monitored by RGB video electrochemistry. The analysis of digital images allowed the color changes on the electrode surface to be investigated. We estimate the growth rate of the copper layer in two different electrode geometries. The relatively high resistance of this composite causes a gradient of the electric resistance along the electrode involving a non-homogeneous electrodeposit growth in CuSO4/H2SO4 aqueous solutions. Copper…
Damping by Bulk and Shear Viscosity of Confined Acoustic Phonons for Nanostructures in Aqueous Solution
2007
International audience; A nanoparticle in aqueous solution is modeled as a homogeneous elastic isotropic continuum sphere in contact with an infinite viscous compressible Newtonian fluid. The frequencies and damping of the confined vibrational modes of the sphere are calculated for the material parameters of a CdSe nanoparticle in water and a poly(methyl methacrylate) nanosphere in water. Although the effects of viscosity are found to be negligible for macroscopic objects, for nanoscale objects, both the frequency and damping of the vibrational modes are significantly affected by the viscosity of the liquid. Furthermore, both shear viscosity and bulk viscosity play an important role. A mode…
Traversing Phase Fields towards Nanosized Beta Tricalcium Phosphate
2013
The difficulty of beta tricalcium phosphate (β-TCP) crystallization in aqueous media opens the question whether β-TCP can be produced using an alternative pathway. Amorphous calcium phosphate (ACP) is metastable in an aqueous environment and prefers a more stable apatite phase. Others have transformed a crystallized calcium deficient hydroxyapatite (Ca-def HAp) into β-TCP, but automatic transformation from ACP to Ca-def HAp followed by transformation to β-TCP has not been addressed. This work shows the formation of Ca-def HAp after different aging times of ACP and the subsequent transition to β-TCP. An amorphous phase with a Ca/P ratio of 1.5 was synthesized, rinsed, filtered and excess flu…
Abatement of 1,1,2,2-tetrachloroethane in water by reduction at silver cathode and oxidation at boron doped diamond anode in micro reactors
2012
The treatment of aqueous solutions of 1,1,2,2-tetrachloroethane was performed by anodic oxidation at boron doped diamond (BDD), cathodic reduction at silver and coupled processes. Experiments were performed in macro and micro reactors with an interelectrode distance lower than 100. μm. Drastically higher abatements of the chlorinated compound and current efficiencies were obtained in microdevices that, furthermore, allowed to perform the electrolyses with low cell voltages in the absence of supporting electrolyte. When reduction and oxidation processes were carried out simultaneously in the microreactor, a higher abatement of pollutants was obtained with the same amount of the passed charge…