Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Programa de Pós-Graduação em Química, Florianópolis, 2014.; A degradação do meio ambiente está ligada à ação direta do homem através de atividades industriais e da produção de bens de consumo que aumentam a emissão de gases nocivos e o consumo de energia. Desta forma, se faz necessário o desenvolvimento de tecnologias e de fontes de energia mais limpas e renováveis, possibilitando o desenvolvimento de economias mais sustentáveis e ambientalmente amigáveis. Neste contexto processos a plasma surgem como uma alternativa, possibilitando a geração de materiais com valor agregado como a produção de hidrogênio e de diferentes formas alotrópicas de carbono sólido. Pensando nisso, o foco principal desta dissertação, é o desenvolvimento, construção e teste de um sistema constituído de uma fonte elétrica, uma tocha de plasma AC acoplada a um reator utilizado na pirólise de um hidrocarboneto gasoso (C3H8). A tocha, a fonte elétrica e o reator foram desenvolvidos para este trabalho. O uso de capacitores e indutores na fonte elétrica para limitar a corrente foi de extrema importância para o funcionamento estável do sistema de plasma em diferentes atmosferas gasosas inclusive com a adição de vapor de água. Contudo...
This study aimed to characterize the bacterium-destroying properties of a gliding arc plasma device during electric discharges and also under temporal postdischarge conditions (i.e., when the discharge was switched off). This phenomenon was reported for the first time in the literature in the case of the plasma destruction of microorganisms. When cells of a model bacterium, Hafnia alvei, were exposed to electric discharges, followed or not followed by temporal postdischarges, the survival curves exhibited a shoulder and then log-linear decay. These destruction kinetics were modeled using GinaFiT, a freeware tool to assess microbial survival curves, and adjustment parameters were determined. The efficiency of postdischarge treatments was clearly affected by the discharge time (t*); both the shoulder length and the inactivation rate kmax were linearly modified as a function of t*. Nevertheless, all conditions tested (t* ranging from 2 to 5 min) made it possible to achieve an abatement of at least 7 decimal logarithm units. Postdischarge treatment was also efficient against bacteria not subjected to direct discharge, and the disinfecting properties of “plasma-activated water” were dependent on the treatment time for the solution. Water treated with plasma for 2 min achieved a 3.7-decimal-logarithm-unit reduction in 20 min after application to cells...
Gliding arc (glidarc) discharge is a physicochemical technique for decontamination at atmospheric pressure and ambient temperature. It leads to the destruction of bacterial phytopathogens responsible for important losses in industrial agriculture, namely, Erwinia spp., without the formation of resistant forms. We investigated the effect of a novel optimized prototype allowing bacterial killing without lag time. This prototype also decreases the required duration of treatment by 50%. The study of the time course effect of the process on bacterial morphology suggests that glidarc induces major alterations of the bacterial membrane. We showed that glidarc causes the release of bacterial genomic DNA. By contrast, an apparent decrease in the level of extractible lipopolysaccharide was observed; however, no changes in the electrophoretic pattern and cytotoxic activity of the macromolecule were noted. Analysis of extractible proteins from the outer membrane of the bacteria revealed that glidarc discharge induces the release of these proteins from the lipid environment, but may also be responsible for protein dimerization and/or aggregation. This effect was not observed in secreted enzymatic proteins, such as pectate lyase. Analysis of the data supports the hypothesis that the plasma generated by glidarc discharge is acting essentially through oxidative mechanisms. Furthermore...
We demonstrate a plasma discharge which is generated between two diverging electrodes and extended into a gliding arc in non-equilibrium condition by an air flow at atmospheric pressure. Effects of the air flow rates on the dynamics, ground-state OH distributions and spectral characterization of UV emission of the gliding arc were investigated by optical methods. High-speed photography was utilized to reveal flow-rate dependent dynamics such as ignitions, propagation, short-cutting events, extinctions and conversions of the discharge from glowtype to spark-type. Short-cutting events and ignitions occur more frequently at higher flow rates. The anchor points of the gliding arc are mostly steady at the top of the electrodes at lower flow rates whereas at higher flow rates they glide up along the electrodes most of the time. The afterglow of fully developed gliding arcs is observed to decay over hundreds of microseconds after being electronically short-cut by a newly ignited arc. The extinction time decreases with the increase of the flow rate. The frequency of the conversion of a discharge from glow-type to spark-type increases with the flow rate. Additionally, spatial distributions of ground-state OH were investigated using planar laser-induced fluorescence. The results show that the shape...
Kusano, Y.; Sorensen, B.F.; Andersen, T.L.; Toftegaard, H.L.; Leipold, F.; Salewski, M.; Sun, Z.; Zhu, J.; Li, Z.; Alden, M.
Fonte: IOP PublishingPublicador: IOP Publishing
Tipo: Artigo de Revista Científica
Publicado em //2013EN
Relevância na Pesquisa
A non-equilibrium quenched plasma is prepared using a gliding-arc discharge generated between diverging electrodes and extended by a gas flow. It can be operated at atmospheric pressure and applied to plasma surface treatment to improve adhesion properties of material surfaces. In this work, glass-fibre-reinforced polyester plates were treated using an atmospheric pressure gliding-arc discharge with air flow to improve adhesion with a vinylester adhesive. The electrodes were water-cooled so as to operate the gliding arc continually. The treatment improved wettability and increased the density of oxygen-containing polar functional groups on the surfaces. Double cantilever beam specimens were prepared for fracture mechanic characterization of the laminate adhesive interface. It was found that gliding-arc treatment significantly increases the fracture resistance in comparison with a standard peel-ply treatment.; Yukihiro Kusano, Bent F Sørensen, Tom L Andersen, Helmuth L Toftegaard, Frank Leipold, Mirko Salewski, Zhiwei Sun, Jiajian Zhu, Zhongshan Li and Marcus Alden
Introduction:Candida species are responsible for about 80% of hospital fungal infections. Non-thermal plasmas operated at atmospheric pressure are increasingly used as an alternative to existing antimicrobial strategy. This work investigates the action of post-discharge region of a non-thermal atmospheric plasma jet, generated by a gliding arc reactor, on biofilms of standard strain of Candida albicans grown on polyurethane substrate. Methods Samples were divided into three groups: (i) non-treated; (ii) treated with argon plasma, and (iii) treated with argon plus air plasma. Subsequently to plasma treatment, counting of colony-forming units (CFU/ml) and cell viability tests were performed. In addition, the surface morphology of the samples was evaluated by scanning electron microscopy (SEM) and optical profilometry (OP). Results Reduction in CFU/ml of 85% and 88.1% were observed in groups ii and iii, respectively. Cell viability after treatment also showed reduction of 33% in group ii and 8% in group iii, in comparison with group i (100%). The SEM images allow observation of the effect of plasma chemistry on biofilm structure, and OP images showed a reduction of its surface roughness, which suggests a possible loss of biofilm mass. Conclusion The treatment in post-discharge region and the chemistries of plasma jet tested in this work were effective in controlling Candida albicans biofilm contamination. Finally...
Major sterilization mechanisms are related to atoms and radicals, charged
parti-cles, excited molecules, ozone, and UV radiation. The ROS (Reactive
Oxygen Species) are well known as evildoers. These species are easily created
in ambient air and water and they live long enough to reach the cell and attack
the organic matter. Test molecules conversion in dry and wet air is studied
using Dielectric Barrier Discharge (DBD) and Gliding Arc Reactors (GAR). The
effects of tem-perature and energy deposition into the media on the active
species production and then on the organic compounds degradation are presented
for two non thermal plasma reactors: DBD and GAR. Main production species
investigated are OH, O3, NOx, CO and CxHyOz by-products. It is shown from
experiment analysis that the reactive species production is quite different
from one reactor to another. GAR and pulsed DBD are two chemical processing
ways in which the temperature of heavy species in ionized gas is determinant.
By reviewing the species production obtained from both reactors, a discussion
is open about plasma decontamination.; Comment: NATO-AdvancedStudy Institute on Plasma Assisted Decontamination of
biological and Chemical Agents, Cesme-Izmir : Turquie (2007)