Mechanism of pH variation and H2O2 generation in water exposed to pulsed discharge plasma

Positive and negative pulsed discharge plasma is generated above test liquid containing NaCl in Ar atmosphere, and the spatiotemporal variation of pH value in the liquid is visualized by a colorimetric method using bromothymol blue. Furthermore, polarity effects on H 2 O 2 generation are examined by electrochemical calculation and a colorimetric method using titanium sulfate. When the positive pulsed discharge plasma is generated, the pH value of the liquid is decreased by H + generation through the dissociation of H 2 O + , formed by the charge exchange reaction between Ar + and H 2 O, while the pH value of the vicinity of an earthed electrode is increased by OH - generation through the electrolysis of water. When the negative pulsed discharge plasma is generated, the pH value of the liquid is increased by OH - generation and H + reduction, respectively, through the reaction of hydrated electrons with H 2 O and H + , while the pH value in the vicinity of the earthed electrode is decreased by H + generation through the electrolysis of water. The generation of H 2 O 2 is found to be promoted when the positive pulsed discharge plasma is generated, and this increase rate of H 2 O 2 is in approximate agreement with the calculated generation rate of H 2 O 2 , which is produced from OH generated by electrolysis

A multi-scale study on the bubble dynamics of cryogenic cavitation

This study aims to construct a multi-scale cavitation model for unsteady cryogenic cavitation CFD. Many elementary physical processes of bubbles (i.e, nucleation, growth/shrink, evaporation/condensation, coalescence/fission, collapse, bubblebubble interaction, bubble-turbulence interaction, and so on) emerge in cryogenic cavitation where some of the processes have not been understood well. In this paper, we mainly focused the molecular processes in homogeneous liquid-vapor nucleation with noncondensable gas solution by using Molecular Dynamics (MD) method. Bubble nucleation in liquid oxygen including helium, nitrogen, or argon was simulated. Molecular interaction was given by Lennard-Jones potential, and basically, each potential parameter was defined so that a saturation curve obtained by MD data was consistent with an experimental value. In the case that helium was impurity, a bubble nucleus was formed by density fluctuation at a lower concentration while a cluster constituted with helium molecules formed a bubble nucleus at a higher concentration, and the nucleation point becomes closer to the saturation point of pure oxygen when helium molecules form clusters. On the other hand, in the case that nitrogen or argon was the impurity, the above-mentioned clustering was not observed clearly at a concentration where helium made clusters, and these impurities have weaker action to make clusters and cavitation bubble nuclei compared with helium.http://deepblue.lib.umich.edu/bitstream/2027.42/84285/1/CAV2009-final102.pd

Structural characterization of mist chemical vapor deposited amorphous aluminum oxide films using water-free solvent

Excellent quality amorphous aluminum oxide (AlOx) thin films have been obtained by atmospheric pressure solution-processed mist chemical vapor deposition (mist-CVD) technique at 400°C using water-free solvent. X-ray fluorescence investigations verified the formation of AlOx film by the mist-CVD. X-ray diffraction, X-ray photoelectron spectroscopy, ellipsometry and X-ray reflectivity analyses revealed that the synthesized amorphous AlOx films have bandgap of 6.5 eV, refractive index of 1.64 and mass density of 2.78 g/cm3. These values are comparable to those reported for high-quality amorphous Al2O3 thin films deposited by atomic layer deposition method