Maico Taras da Cunha

Estudo do comportamento eletroquímico do benzotriazol e benzimidazol na oxidação do aço inoxidável tipo ABNT 304

This work reports a study of the inhibiting action of benzotriazole (BTAH) and benzimidazole (BZM) on the corrosion of 304 austenitic stainless steel (SS) in 4.5 mol/L H2SO4. All solutions were prepared with analytical degree reagents and highly purified water. The concentrations used were: [BTAH]= 1x10-5 mol.L-1 and [BZM]= 1x10-3 mol/L. The experiments were carried out at a room temperature of 26 ± 2°C. Open circuit potential (OCP), anodic potentiostatic polarisation curves (AP), electrochemical impedance spectroscopy (EIS) and optical microscopy (OM) were used in the experiments. The results of OM for BTAH + BZM showed a corrosion-inhibiting synergic effect for 304 SS. The OCP measures in the presence of BTAH, BZM or BTAH+BZM indicate an increase in corrosion potential (Ecorr), suggesting that BTAH, BZM and BTAH+BZM acted as anodic corrosion inhibitors. AP curves in the presence BTAH and BZM, individually, suggested catalytic corrosion action for 304 SS, but in the presence of BTAH+BZM, inhibitor corrosion was observed. The results of the experiments were confirmed by EIS diagrams obtained in Ecorr.

A corrosão do aço inoxidável austenítico 304 em biodiesel

Fuel distribution uses 304 stainless steel containers for the storage of biofuels, however, there are few reports in the literature about the corrosive aspects this steel in biodiesel. The objective of this research is to study the corrosive behavior of 304 austenitic stainless steel in the presence of biodiesel, unwashed and washed, with aqueous solutions of citric, oxalic, acetic and ascorbic acids 0,01 mol L-1, and compare with results obtained for the copper (ASTM D130). The employedtechniques were: atomic absorption spectrometry (AAS) and optical microscopy (OM). The results of EAA showed a low rate of corrosion for the stainless steel, the alloys elements studied were Cr, Ni and Fe, the highest rate was observed for the chrome, 1.78 ppm / day in biodiesel with or without washing. The OM of the 304 steel, when compared with that of copper, has a low corrosion rate in the 304 steel/biodiesel system. Not with standing, this demonstrates that not only the 304 steel, but also the copper, corrodes in biodiesel.

Electrochemical behavior of indole for AISI 430 stainless steel in changing the media from 1 mol L-1 H2SO4 to 1 mol L-1 HCl

The adsorption of organic substances in metals and in different media has been attributed to different effects, such as the carbon chain size, type or number of heteroatom in the molecule structure, reactivity, the steric effect, among others. The objective of this work is to study the electrochemical indole behavior for AISI 430 stainless steel (SS), when changing the study media from H2SO4 1 mol L-1 to HCl 1 mol L-1. The experimental techniques used are as follows: the open-circuit potential, anodic and cathodic potentiodinamic polarization, electrochemical impedance spectroscopy, optical microscopy and scanning electron microscopy. These results suggest that the adsorption of indole in the presence of SO4-2 is lower than in the medium containing Cl-, which is justified by the indole action as a weak acid, because it has only a single pair of electrons, which is displaced and takes part in the π-electron aromatic system; thus the first step of the indole reaction in acid media is the protonation and generation of an indole cation.

Estudo do comportamento eletroquímico de azóis para o aço inoxidável AISI 430 em H2SO4 1 mol L-1

Corrosion is an undesirable process that occurs in metallic materials. Studied was the effect of inhibiting Benzotriazole (BTAH), Benzimidazole (BZM) and Indole in different concentrations for the stainless steel (SS) AISI 430 in H2SO4 1 mol L-1. The techniques employed this research were: anodic potenciostatic polarisation, electrochemical impedance spectroscopy, optical microscopy and scanning electron microscopy. The curves of anodic polarisation showed that BTAH, BZM and Indol act as corrosion inhibitors for 430 SS, at concentrations of 1x10-3 and 5x10-4 mol L-1, but do not inhibit corrosion for concentrations equal to or less than 1x10-4 mol L-1. The in-crease of the efficiency in relation to the inhibitory substances studied followed this order: Indol <BZM <BTAH. The anodic polarization curve results were supported by electrochemical impedance spectroscopy, and microscopic analysis.

Study of TiO2 Hybrid Solar Cells with Natural Dyes

Celulas solares sensibilizadas por corante (CSSC) sao dispositivos que aproveitam a luz do sol para gerar energia e possuem na composicao um oxido semicondutor e um fotossensibilizador adequado. Devido ao custo elevado, a pesquisa por novos materiais aplicados nas celulas solares desperta grande interesse. Este trabalho tem como objetivo estudar celulas solares hibridas de interface FTO/TiO2/corante produzidas com diferentes fotossensibilizadores naturais de baixo custo, extraidos em solucao etanoica acidificada, de diferentes produtos naturais: ameixa, uva, urucum e berinjela. As tecnicas de caracterizacao utilizadas foram: Espectroscopia na regiao do ultravioleta-visivel (UV-VIS), Espectroscopia na regiao do Infravermelho por Transformada de Fourier (IV-TF), medidas do Potencial de Circuito Aberto em funcao do tempo (Eca), curvas Fotocronoamperometricas (FCA) e Curvas de Densidade de Fotocorrente em funcao do Potencial (j-E). Os corantes testados nas CSSC apresentaram caracter de fotossensibilidade, com adsorcao nos filmes de TiO2 e absorcao maxima na regiao do visivel. A CSSC com melhores parâmetros fotovoltaicos foi empregando-se o corante extraido da ameixa, gerando uma celula solar com ƞ = 0,12±0,03, Eca = 572±12 mV, FF = 0,57±0,01 e jcc = 0,40±0,09 mA cm-2.

Photoelectrochemical Behavior of the Cell FTO/TiO 2 /CeO 2 /N719 Obtained from the Pechini and Precipitation of Cerium Oxide Methods

Renewable energy sources have received much attention in recent years due to concerns about global climate and environmental changes. Solar energy appears to be a promising alternative, especially dye-sensitized solar cells (DSSC), which, according to the literature, can achieve a power conversion efficiency in excess of 11%, depending on the semiconductor oxide used in their fabrication. The aim of this paper is to investigate the performance of DSSCs using cerium oxide (CeO2), titanium oxide (TiO2), and commercial dye N719. CeO2 was obtained using the Pechini and precipitation methods. The characterization techniques employed were x-ray diffraction, Raman spectroscopy, scanning electron microscopy, ultraviolet–visible spectroscopy, dynamic light scattering, and photoelectrochemical measurements. The results indicate that the efficiency of the DSSC CeO2/TiO2 obtained using the precipitation method was about 20% higher than that of the DSSC TiO2.

Influência do Método de Obtenção de Partículas de Nb 2 O 5 Empregadas em Células Solares Sensibilizadas por Corante Compostas de TiO 2 /Nb 2 O 5

The niobium pentoxide (Nb 2 O 5 ) is a semiconductor capable of prevent the efficiency loss by recombination in dye sensitized solar cells (DSSC) given the high energy gap. The aim of this study is to investigate the performance of DSSC containing Nb 2 O 5 obtained by Pechini method and hydrothermal synthesis, mixed with TiO 2 nanoparticles. The characterization techniques used were X-ray diffraction (XRD), scanning electron microscopy (SEM), dynamic light scattering (DSL) and potentiodynamic polarization under power light incidence of 100 mWcm -2 . XRD confirmed obtaining orthorhombic structure niobium pentoxide tested for both methodologies, the SEM showed the best distribution of the oxide obtained by hydrothermal synthesis efficiency was calculated from the current density-potential curves (j-v) confirming the higher efficiency for this sample, about 20% higher. DOI: 10.5935/1984-6835.20160064

Corrosion characterization of phosphated carbon steel treated with benzotriazole

Purpose – The purpose of the paper is to show the corrosion effect of benzotriazole in comparison with iron phosphate (PFe) coating as a sealer for the PFe layer in carbon steel paint pre-treatment and to show its ecological advantages as a more environment-friendly inhibiting compound than PFe. Design/methodology/approach – Samples of carbon steel (SAE 1010) were phosphated in two baths, one containing iron PFe and PFe and BTAH (PFe + BTAH). Anodic potentiostatic polarization curves and electrochemical impedance spectroscopy were used to evaluate the corrosion resistance of phosphated carbon steel in 0.1 molL−1 H2SO4, 0.5 molL−1 NaCl and 0.1 molL−1 NaOH. The phosphate layers obtained were analyzed by infrared spectroscopy. Surface observation by scanning electron microscopy (SEM) showed that the PFe and PFe + BTAH layers are deposited as crystals with granular morphology. The electrochemical results showed that the PFe + BTAH coating was more effective in corrosion protection of the carbon steel. Finding...

Study of Copper Electrodeposition in Alkaline Medium Using Pulsed Current

The electrodeposition of copper and its alloys from cyanide alkaline solutions is widely employed in industry to obtain high quality copper layers on ferrous and non-ferrous metals substrates. New processes of copper electroplating, from cyanide free baths, have been considered an alternative solution regarding the new environmental requirements. This work has a main objective to study the electrodeposition of copper ions from an alkaline cyanide-free bath, stabilized by two different complexing agents for the Cu 2+ ions: ethylenediamine and sodium citrate. In this study, the following techniques were employed: pulsed current, quartz microbalance, potentiodynamic and galvanostatic polarizations, forced convection using the rotating disk electrode, optical and electronic scanning microscopy. The current modulation influence was registered through quartz microbalance measurements. Results revealed that the use of pulsed current in sodium citrate and ethylenediamine media produced good results in the cathodic current and the copper deposit morphology.

Estudo da Eletrodeposição de Cobre em Meio Alcalino com uso de Corrente Pulsada

A eletrodeposicao de cobre e suas ligas a partir de solucoes alcalinas cianetadas e muito utilizada industrialmente para obtencao de camadas de cobre de alta qualidade sobre substratos ferrosos e nao ferrosos. Novos processos de eletrodeposicao do cobre, isentos de ions cianeto, tem sido uma alternativa as novas exigencias ambientais. Este trabalho tem como objetivo principal estudar a eletrodeposicao de ions de cobre a partir de um banho alcalino isento de ion cianeto, estabilizado por dois diferentes agentes complexantes para os ions de Cu 2+ , a etilenodiamina e o citrato de sodio. Neste estudo foram empregadas as seguintes tecnicas: corrente pulsada, microbalanca de quartzo, polarizacoes potenciodinâmica e galvanostatica, conveccao forcada empregando eletrodo de disco rotatorio, microscopias optica e eletronica de varredura. Relacionou-se a influencia da modulacao de corrente atraves de medidas de microbalanca de quartzo. Os resultados mostram que a aplicacao de corrente pulsada, nos meios de citrato de sodio e etilenodiamina, revelaram boa eficiencia quanto corrente catodica e a morfologia dos depositos de cobre. DOI: 10.5935/1984-6835.20140019