Abstract The study on the inactivation of Escherichia coli (E. coli) bacteria in water flowing continuously in a treatment system based on two different reactors is presented. The bacteria inactivation is achieved in a water volume of 500 mL inoculated with an E. coli concentration of 1.45×103 bacteria/mL using combined treatment with ozone and ultraviolet (UV) radiation. Inoculated water firstly is introduced to cylindrical reactor supplied with ozone at a concentration of 1000-1100 ppm and, subsequently, transferred to a rectangular geometry reactor subjected to UV radiation with an energy per volume of 1.44 J/mL. Inactivation efficiency of E. coli bacteria in the water of 99.32% was attained in a total treatment time of 180 seconds.

Abstract Experimental investigation about methylene blue degradation in aqueous solution applying several Advanced Oxidation Processes such as O3, O3/H2O2, O3/UV and O3/UV/H2O2 was accomplished. Methylene blue treatment consisted in evaluating the degradation of an initial concentration of 22 ppm in 500 ml of aqueous solution. The contaminant degradation efficiencies were analyzed considering parameters such as: treatment time, three different pH values for the solution and O3 and H2O2 as oxidizing reagents. The discoloration of the samples was examined throughout the experimental each 10 minutes. Using O3/UV/H2O2 (10 ppm) with an initial 7 pH and a treatment time of 60 minutes the highest degradation efficiency of 98% was achieved.

It is reported the design, construction and initial tests of a three cell flying capacitor inverter (TCFCI) in a half-bridge configuration. The device operates at a 200 kHz frequency which leads to a voltage output at 12.5 kHz presenting an acceptable response in an open-loop configuration. These features outdo those reported in the current multilevel converter literature. The TCFCI is driven by pulse width modulation, following a phase shift (PS-PWM) control strategy, in order to generate a steady AC voltage signal. This inverter is used to excite a dielectric barrier discharge cell (DBDC) intended for cold plasma generation at room pressure. Some results obtained for two different kinds of atmosphere, helium and argon, are presented. All the system having been tested, early recorded voltage and current waveforms, are included. Finally, three methods for calculating the related electric efficiency of the discharge cell are discussed.

Pure nitrogen, 30% argon/70% nitrogen, 50% argon/50% nitrogen, 70% argon/30% nitrogen plasma immersion ion implantation (PIII) processes onto aluminium samples has been performed at 2 to 6 kV negative bias and 50 to 150 us pulse widths, the sample temperature being established at 400 °C. Incident fluencies of ~10(18) atoms/cm² were used to investigate the diffusion behaviour and AlN phase formation in the samples. X-ray diffraction (XRD) shows the formation of the cubic phase of AlN with both pure nitrogen and all the mixtures whereas the hexagonal phase becomes apparent only in the 50% mixture and in pure nitrogen. The characteristic peak of AlN has also been determined by Raman spectroscopy. The microhardness was found to be always maximal with the 50% nitrogen 50% argon mixture.

Samples of pure Titanium were treated by means a PIII process using a dense DC glow discharge with different mixtures of nitrogen-oxygen and oxygen pure. The surface of treated samples was analyzed by means of different techniques such as X-ray diffractometry, Scanning Electron Microscope, Vickers Microhardness tester and profilometer. We conclude that the modified surface is formed by TiN0.26 diffused into TiO2 in rutile phase, forming a uniform layer up to 10 μm in thickness and whose resultant microhardness is almost five times greater than that of untreated titanium. Some control over the superficial parameters is taken by varying the proportion of nitrogen-oxygen at a pressure of 1x10-2 Torr (~1.33 Pa), obtaining a thicker layer, a harder surface or a reduced roughness. The identified phases have biocompatible properties, which provide interest in the bioengineering field.

One alternative application in the decomposition and destruction of volatile organic compounds (VOCs) by a silent plasma dielectric barrier discharge (DBD) has been successfully accomplished. For this purpose, we have designed and constructed two pairs of cells, of rectangular and circular geometries, 333.96 cm³ each cell, and a similar second pair of 62.25 cm³ each one. Resonant inverters for low (3.3 kHz) and high (100 kHz) frequencies were also designed and applied to these cells. The specification of the main physical parameters of each cell contemplates: i) a first order degradation ratio of the compound, and ii) air breakdown at atmospheric pressure as a function of the carrying gas. The power consumed by the cells during the discharges was computed both theoretically and experimentally by Manley's method. The equipment was applied to the degradation of toluene, which has been degraded by an oxidation process in air-oxygen and argon-oxygen gas mixtures at atmospheric pressure within the cells. The destruction efficiency was measured as a function of the initial concentration. When air is used as an oxidant, a clear formation of solid products on the walls of dielectric glass plates has been observed, such deposits being polymeric in nature. These deposits seem to be responsible for a decline in the degradation efficiency of the treated compounds.