Entity

Time filter

Source Type

Curitiba, Brazil

Sucharski G.B.,Federal University of Parana | Pukasiewicz A.G.M.,Federal Technological University of Parana | Vaz R.F.,Institutos Lactec | Paredes R.S.C.,Federal University of Parana
Soldagem e Inspecao | Year: 2015

HVOF thermal spray process produces coatings with low porosity and low oxide content, as well as high substrate adhesion. Small variations on the parameters of the HVOF process can generate coatings with different characteristics and properties, which also is chemical composition depended of the alloy. FeMnCrSi alloy is a cavitation resistant class of material with a great potential for HVOF deposition use. The main goal of this article is to study the influence of some HVOF parameters deposition, as standoff distance, powder feed rate and carrier gas pressure on three different alloys. FeMnCrSi experimental alloys with some variations in nickel and boron content were studied. Taguchi experimental design with L9 orthogonal array was used in this work. Porosity, oxide content, tensile adhesion strength and microhardness of the coatings were evaluated. The results indicated that all factors have significant influence on these properties. Chemical composition of the alloys was the most important factor, followed by the carrier gas pressure, standoff distance and powder feed rate. The addition of Ni, produces coatings with lower levels of oxide content and porosity. An experiment with improved parameters was conducted, and a great improvement on the coating properties was observed. © 2015, Universidade Federal de Uberlandia. All rights reserved. Source


Mazur M.M.,Federal University of Parana | Braganc M.D'O.G.P.,Federal University of Parana | Portella K.F.,Federal University of Parana | Ribeiro S.,Institutos Lactec | And 3 more authors.
Ceramica | Year: 2016

The mechanical strength and the dielectric properties of ceramic insulators are essential properties to support the electricity distribution networks. However, both the moisture and the pollutant content in the atmosphere may become harmful and cause failures in the power supply by increasing its electrical current leakage. The insulating glazing has high affinity with the resulting water from the interaction of the glass surface with atmosphere. In this study, the deposition of aluminum nitride films was carried out on the glazed samples of ceramic electrical insulators, via pulsed DC magnetron sputtering plasma, and with a mixture of argon and nitrogen gas and Ti on pin type insulators for 15 kV voltage class. The morphology of the films and the performance of insulators were measured by SEM-FEG/EDS, AFM, maximum RMS leakage current and degree of hydrophobicity. The performance of deposited films by the degree of hydrophobicity measured in samples reduced from CM6 to CM4 with AlN, and CM7 to CM3 with Ti layer. The maximum RMS leakage current measured with and without the insulating film based on nanometric Ti was higher in devices without the protection, reaching measured values of 5 mA and with shutdown of computerized measuring system (after 3 days in Sauípe and 3 months in Pituba) as a consequence of having overcome the short circuit withdrawal period laid down in software (surges exceeding 300 mA). With the deposition of the films in 7 insulators, changes in two of these, with peaks of maximum leakage current achieving 2.4 mA, in the field were observed. Most insulators analyzed had the variations in RMS leakage current between 0.2 and 2 mA in the measurement period, in adverse conditions of weather (rain and different wind speeds). Source


Fernandes N.T.D.,Programa de Pos Graduacao em Desenvolvimento de Tecnologia | Demonti R.,Programa de Pos Graduacao em Desenvolvimento de Tecnologia | Demonti R.,Federal University of Parana | De Andrade J.,Programa de Pos Graduacao em Desenvolvimento de Tecnologia | And 5 more authors.
2015 IEEE 13th Brazilian Power Electronics Conference and 1st Southern Power Electronics Conference, COBEP/SPEC 2016 | Year: 2015

Lead acid batteries are still broadly used in stand alone photovoltaics. The main concerns within the use of this type of batteries are high cycling and the prolonged undervoltage state, which leads to sulfation. This work proposes a method of reverting the battery sulfation and reducing the gases formation using a three-step battery charger. A bidirectional converter in which the output current is pulsed with both magnitude and width controllable is implemented. Those pulses are used together with constant current profiles in order to increase charge acceptance and, by that, reduce the gases formation and potentially increase the battery life. © 2015 IEEE. Source


Freire C.A.,Federal University of Parana | Souza-Bastos L.R.,Federal University of Parana | Chiesse J.,Federal University of Parana | Tincani F.H.,Federal University of Parana | And 9 more authors.
Environmental Science and Pollution Research | Year: 2015

Iguaçu River is the second most polluted river of Brazil. It receives agrochemicals and contaminants of urban and industrial sources along its course. A multibiomarker approach was employed here to evaluate the health of a small characin (Astyanax spp.) at two sites along the river, sampled during a dry (autumn) and a rainy (spring) season. Biomarkers were condition factor and somatic indices (gonads and liver); genetic damage (comet assay and micronucleus test); enzyme activities such as hepatic catalase (CAT) and glutathione S-transferase (GST), lipoperoxidation (LPO), branchial and renal carbonic anhydrase (CA), acetylcholinesterase (AChE) in the muscle and the brain, histopathology of the liver and gills, and concentrations of polycyclic aromatic hydrocarbons (PAHs) in bile. There were no consistent differences in biomarker responses between the two study sites. Some biomarkers revealed greater potential impact in the rainy season, when increased amounts of contaminants are washed into the river (combined CAT inhibition and LPO increase, CA upregulation). Other biomarkers, however, revealed potential greater impact in the dry season, when contaminants potentially concentrate (GST induction, AChE inhibition, and liver histopathological alterations). Although of a complex nature, field experiments such as this provide rich data for monitoring protocols and assessment of general risk of exposure to pollutants of river systems. © 2015, Springer-Verlag Berlin Heidelberg. Source


Braganca M.O.G.P.,Federal University of Parana | Braganca M.O.G.P.,Institutos Lactec | Portella K.F.,Institutos Lactec | Bonato M.M.,Federal University of Parana | And 2 more authors.
Construction and Building Materials | Year: 2016

Concretes with 1% nano-Fe3O4 addition aged for 300 days in chloride and sulfur dioxide chambers were analyzed by multiple technics and the performance results were evaluated by impedance spectroscopy and cyclic voltammetry. They exhibited a higher electrochemical stability because of the absence of passive film breakdown and an enhanced electrical resistance to charge transfer. The better properties were resulted from a more homogeneous microstructure produced by the byproducts of the reaction between the cement hydrates and the added nano-material. They were supposed be accumulated in pores and voids. © 2016 Published by Elsevier Ltd. Source

Discover hidden collaborations