Submitted by Cátia Araújo (catia.araujo@unipampa.edu.br) on 2017-01-25T12:43:50Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Efeito inibidor do tungstato de sódio e da amoxicilina em solução e em filmes de acetato de celulose na corrosão da liga de aço-carbono AISI 1020 em NaCl 0,05 molL.pdf: 3082976 bytes, checksum: 0cd5a0b855088834038b5aff2432de07 (MD5) / Approved for entry into archive by Cátia Araújo (catia.araujo@unipampa.edu.br) on 2017-01-25T12:44:16Z (GMT) No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Efeito inibidor do tungstato de sódio e da amoxicilina em solução e em filmes de acetato de celulose na corrosão da liga de aço-carbono AISI 1020 em NaCl 0,05 molL.pdf: 3082976 bytes, checksum: 0cd5a0b855088834038b5aff2432de07 (MD5) / Made available in DSpace on 2017-01-25T12:44:16Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Efeito inibidor do tungstato de sódio e da amoxicilina em solução e em filmes de acetato de celulose na corrosão da liga de aço-carbono AISI 1020 em NaCl 0,05 molL.pdf: 3082976 bytes, checksum: 0cd5a0b855088834038b5aff2432de07 (MD5) Previous issue date: 2014-02-21 / Este trabalho teve por objetivo avaliar o tungstato de sódio (Na2WO4) e a amoxicilina como inibidores de corrosão para a liga de aço-carbono AISI 1020 adicionados a um meio contendo 0,05 mol/L de Cloreto de Sódio (NaCl). Além disso, avaliar o efeito desses inibidores quando inseridos em um filme de acetato de celulose. O estudo compreendeu a exposição do metal no meio proposto, na ausência e presença de 0,005, 0,01 e 0,07 mol/L de Na2WO4, e/ou 1000, 2000 e 3000 ppm de amoxicilina inseridos ou não em filmes de 5% e 10% de acetato de celulose. Foram empregadas técnicas eletroquímicas de monitoramento do potencial de circuito aberto (PCA), espectroscopia de impedância eletroquímica (EIE) e polarização anódica. Todos os experimentos foram realizados à temperatura ambiente e em meio aerado. Quanto aos objetivos propostos pode-se concluir que: 1) As medidas de PCA para as diferentes concentrações de Na2WO4, apresentaram deslocamento dos potenciais (E) para valores mais positivos durante os 7 dias de imersão no NaCl, principalmente para 0,07 mo/L de Na2WO4, com E = - 0,407 V no 7º dia, indicando um comportamento inibidor. Para as diferentes concentrações de amoxicilina os valores de potencial não apresentaram variação tão significativa, em 1000 ppm de amoxicilina o E = - 0,560 V no 7º dia. Quando inserida a amoxicilina ao WO4-2, as concentrações melhores foram para 1000, 2000 e 3000 ppm de amoxicilina inserida em 0,07 mol/L Na2WO4, obtendo-se ao 7º dia de imersão valores respectivamente de E = - 0,380 V, E = -0,400 V e E = -,0370 V. Já para os revestimentos a base de acetato de celulose, não apresentaram valores de potencial significativos, ficando entorno de E = -0,645 V ao 7º dia. Quando inserido 2000 ppm amoxicilina e 0,07 mol/L de Na2WO4 ao filme 5 %, continuou estável ao deslocamento do potencial, 2) Por EIE demostrou-se que para 0,07 mol/L de Na2WO4 os valores de resistência aumentaram significativamente do que os demais inibidores, 3) E as curvas de polarização anódica, mostraram que para 0,07 mol/L de Na2WO4 o potencial de rompimento de filme (ERP) possuiu valores mais positivo, ERP = +0,07 V quando comparados com os demais inibidores. / This study aimed to evaluate the sodium tungstate (Na2WO4) and amoxicillin as corrosion inhibitors for carbon steel alloy AISI 1020 added to a medium containing 0.05 mol/L sodium chloride (NaCl). Moreover, to evaluate the effect of these inhibitors when inserted in a film of cellulose acetate. The study consisted of exposing the metal in the proposed environment, in the absence and presence of 0.005, 0.01 and 0.07 mol/L of Na2WO4 and/or 1000, 2000 and 3000 ppm of amoxicillin or not inserted into films 5 % and 10 % cellulose acetate. Electrochemical techniques for monitoring the open circuit potential (PCO), electrochemical impedance spectroscopy (EIS) and anodic polarization were employed. All experiments were performed at room temperature and aerated environment. As for the proposed objectives can be concluded that: 1) PCO measures for the different concentrations of Na2WO4 showed displacement of the potential (E) towards more positive values during the 7 days of immersion in NaCl mainly to 0.07 mol/L Na2WO4 with E = - 0.407 V on day 7, indicating an inhibitory behavior. For different concentrations of amoxicillin potential values showed no significant variation as in 1000 ppm of amoxicillin E = - 0.560 V on the 7th day. When inserted amoxicillin to WO4-2 concentrations were the best for 1000, 2000 and 3000 ppm of amoxicillin inserted in 0.07 mol/L Na2WO4 obtaining the 7th day of immersion values respectively E = - 0.380 V, E = -0.400 V and E = - 0370 V. As for the coatings based on cellulose acetate showed no significant potential values, getting around E = -0.645 V to day 7. When inserted amoxicillin 2000 ppm and 0.07 mol/L of Na2WO4 the film 5 % remained stable potential shift, 2) It is demonstrated that EIS to 0.07 mol/L of Na2WO4 resistance values increased significantly than other inhibitors, 3) and the anodic polarization curves showed that for 0.07 mol/L of the Na2WO4 potential breakup film (ERP) possessed more positive values, ERP = +0.07 V when compared with the other inhibitors.

Submitted by Celso Magalhaes (celsomagalhaes@ufrrj.br) on 2018-04-11T16:46:38Z No. of bitstreams: 1 2017 - Mariana Falc?o Lopes Princisval Carlos.pdf: 3027874 bytes, checksum: f7dd2c459e8918f917f701198c97f955 (MD5) / Made available in DSpace on 2018-04-11T16:46:38Z (GMT). No. of bitstreams: 1 2017 - Mariana Falc?o Lopes Princisval Carlos.pdf: 3027874 bytes, checksum: f7dd2c459e8918f917f701198c97f955 (MD5) Previous issue date: 2017-08-16 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / In this work, seven enaminoesters were synthesized, divided into three series depending on the starting amine, the series A is derived from phenethylamine, the series B of aniline and, finally, the series C derived from benzylamine. The synthesis occurred in two ways, the first being through the reaction of the ethyl acetoacetate in the presence of the corresponding amine in ethanol as solvent in the presence of p-toluenesulfonic acid and the second the amine in the presence of triethylamine and methanol as solvent, both in magnetic stirring at room temperature. The compounds were obtained as oil, with a high purity, and for some compounds separation via flash chromatography in ethyl acetate / hexane was required, yields ranging from 70-93%. The compounds were characterized by spectroscopic techniques such as Infrared and Nuclear Magnetic Resonance 1H and 13C, in addition to the refractive index. Six of the seven compounds synthesized were evaluated using electrochemical techniques of Impedance Spectroscopy Electrochemistry, Potentiodynamic Polarization and Resistance to Linear Polarization and the mass loss technique, as to the action as inhibitors of corrosion against AISI 1020 carbon steel in 0.5 mol L-1 HCl. The Molecular Modeling technique was used to better visualize the structures of the synthesized enaminoesters and, later, correlation of the inhibition efficiencies found. The theoretical parameters such as the energy of the orbitals of symmetrical boundaries and dipole moment with the results corrosion efficiency were also evaluated. In general, the enaminoesters showed good corrosion efficiency, excess by the compound derived from hydroxylaniline. All presented corrosion inhibition efficiency with mixed inhibitor characteristics. However, the compounds that did not present substituents and those that contain electron donor group (OCH3) stood out as inhibitors, highlighting the compound EN1, which presented efficiency of 92% of inhibition of the corrosion by the technique of Resistance to Polarization Potentiodynamics and 98% by the technique of mass loss after 24h of immersion. The efficiency was shown to be dependent on the concentration in the synthesized compounds, that is, the corrosion inhibition efficiency increases with XXIII increasing inhibitor concentration, and that the adsorption phenomena of the compounds studied obey the Langmuir isotherm. Thus, the synthesized, especially the not substituted, enaminoesters can be considered as promising corrosion inhibiting agents for acidic AISI 1020 carbon steel. / Nesta disserta??o, foram sintetizados sete enamino?steres, divididos em tr?s s?ries de acordo com a amina de partida, sendo a s?rie A derivada da fenetilamina, a s?rie B da anilina e, por ?ltimo, a s?rie C derivada da benzilamina. A s?ntese ocorreu de duas formas, sendo a primeira atrav?s da rea??o do acetoacetato de etila na presen?a da amina correspondente em etanol como solvente, na presen?a de ?cido p-toluenossulf?nico e, a segunda, a amina na presen?a de trietilamina e metanol como solvente, ambas em agita??o magn?tica ? temperatura ambiente. Os compostos foram obtidos em forma de ?leo, com alto grau de pureza, sendo necess?ria para alguns compostos a separa??o via cromatografia flash em acetato de etila/hexano, os rendimentos variaram na faixa de 70-93%. Os compostos foram caracterizados por t?cnicas espectrosc?picas de Infravermelho e Resson?ncia Magn?tica Nuclear 1H e 13C, al?m de ?ndice de refra??o. Seis dos sete compostos sintetizados foram avaliados por t?cnicas eletroqu?micas de Espectroscopia de Imped?ncia Eletroqu?mica, Polariza??o Potenciodin?mica e Resist?ncia a Polariza??o Linear e, por ensaio de perda de massa, quanto ? a??o como inibidores de corros?o frente a a?o carbono AISI 1020 em solu??o de HCl 0,5 mol L-1 . Modelagem Molecular foi utilizada para melhor visualiza??o das estruturas moleculares dos enamino?steres sintetizados e, posterior, correla??o das efici?ncias de inibi??o encontradas. Os par?metros te?ricos como a energia dos orbitais de fronteiras sim?tricos e momento dipolar foram calculados e, apenas os valores de momento dipolar correlacionaram com os resultados experimentais da efici?ncia anticorrosiva. De forma geral, os enamino?steres apresentaram boa efici?ncia anticorrosiva, com exce??o do composto derivado da hidr?xianilina (EN6). Todos apresentaram efici?ncia de inibi??o ? corros?o com caracter?sticas de inibidores mistos. Por?m, os compostos que n?o apresentaram substituintes e os que cont?m grupo doador de el?trons (OCH3) se destacaram como inibidores mais eficientes, dando destaque ao composto EN1, que apresentou efici?ncia de 92% de inibi??o da corros?o, pela t?cnica de Resist?ncia a Polariza??o Potenciodin?mica e 98% pela t?cnica de perda de massa ap?s 24 h de imers?o. XXI A efici?ncia se mostrou dependente da concentra??o nos compostos sintetizados, ou seja, a efici?ncia de inibi??o da corros?o aumentou com o aumento da concentra??o dos inibidores. Os fen?menos de adsor??o dos compostos estudados, apenas o EN1 obedece ? isoterma de Langmuir e os restantes a Langmuir modificada. Com isso, os enamino?steres sintetizados, especialmente os n?o substitu?dos, podem ser considerados como promissores agentes inibidores da corros?o para o a?o carbono AISI 1020 em meio ?cido.

A series of model steels containing copper levels up to 0.48wt%, nickel up to 0.22wt% and silicon levels of 0.52wt% were oxidised in air at 1050 and 1150??C, and in a CO2-N2 mixture at 1250??C for times of up to 3 hours. The scaling kinetics were measured and the behaviour of copper-rich phase formation at the scale/metal interface was investigated. When oxidised at 1050/1150??C, significant quantities of copper-rich phase were observed for most model steels. The relatively high oxidation rate under these conditions led to the rapid development of a copper-rich layer with little copper diffusing into the metal. However, when oxidised at 1250??C, the copper-rich phase did not form for a significant amount of time; and for some model steels, not at all. This was attributed to the considerably lower oxidation rate and the fact that more copper was found to have diffused into the metal. Alloying additions of nickel and silicon were found to be beneficial in reducing the amount of copper-rich phase measured at the scale/metal interface under the conditions investigated at 1150??C and 1250??C. This occurred because nickel and silicon addition promoted the occlusion of copper-rich phase into the scale. Copper enrichment during oxidation was modelled using a numerical description of the diffusion processes involved. Predictions of the time for commencement of copper-rich phase formation at 1250??C were in close agreement with observation. Agreement between predicted and observed copper-rich layer thickness was less successful under conditions where occlusion was significant, and the measured thickness varied non-uniformly with time. The cracking susceptibility of the model steels was examined using a hot compression test. Oxidation was performed in air at 1050, 1150 and 1250??C and most specimens were compressed at 1050??C. The amount of cracking was found to increase with the amount of copper-rich phase precipitated at the scale/metal interface during oxidation. In general, nickel addition reduced the amount of cracking at all temperatures; and under some conditions prevented cracking altogether. Silicon reduced or completely suppressed cracking when the subscale formed was liquid. The beneficial effects of nickel and silicon addition were attributed to their effect of promoting copper occlusion.

The effect of initial microstructures of an 0.05 wt.% C low carbon steel, acicular ferrite (AF), Bainite (B), polygonal ferrite (PF), fine polygonal ferrite (FPF), and a microstructure produced by direct strip casting (DSC) (termed SC), on the deformation and recrystallization behaviour of cold rolled low carbon (LC) steel, was investigated. The initially prepared samples with the initial microstructures were cold rolled to 50, 70 and 90% reductions, then annealed isothermally in the temperature range 580 ??? 680 oC. The microstructures and textures produced by deformation and annealing were studied by optical microscopy, XRD, TEM, SEM and EBSD. The initial microstructures were characterized mainly by optical microscopy and EBSD. Using EBSD, the ferrite grain size of the AF, B and SC samples was considerably larger than that found by optical microscopy with a large fraction of low angle grain boundaries (LAGBs) observed within prior austenite grains. All samples exhibited a very weak texture close to random. After cold rolling, the microstructures of AF and SC contained shear bands with PF and FPF generating deformation bands. For AF and SC, the pearlite phase was more extensively elongated in rolling direction compared with PF and FPF. After 90% cold rolling reduction, PF, FPF and SC consist mainly of the texture component and AF and B . It was found that FPF recrystallized most rapidly followed by B, PF and AF with SC recrystallizing orders of magnitude more slowly due to the solution drag caused by its uniformly distributed higher Mn content. Very strong (???-fibre) texture was generated in cold rolled PF followed by FPF, with AF, SC and B generating very weak textures. The texture evolution during annealing 90% reduction PF was examined in further detail. The behaviour of nucleation and grain growth provides strong evidence of orientated nucleation as the dominant factor for CRA texture development in this material.

This study aims to design a novel inserted welding tool to friction stir spot weld SS400 low carbon steel sheets of 4mm thickness. In order to enhance the efficiency of frictional heat generation and to enhance the quality of the welding spot, the welding tool based on a cylindrical tungsten carbide and is inserted by a SS400 low carbon cylinder. The welding apparatus composed of a vertical milling machine and a welding platform that can keep the load between tool and workpiece constant. The plunge load is 8kN and there's no inclination angle on the tools. Welding temperature and the tool plunge depth are measured by thermelcouples and a displacement meter. ¡@¡@At the tool rotational speed of spindle of 900rpm and welding for 60 seconds, the temperature rising rate of the tools with 5 mm and 10 mm inserted material are 5.28 times and 6.31 times greater than the one without insert. While they are 1.36 and 1.42 times greater than at 1200rpm.At the tool rotational speed of spindle of 900rpm and welding for 300 seconds, themaximun welding temperature the tools with 5 mm and 10 mm inserted material can reach are 59¢J and 412¢J higher than the one without insert. While they can reach 35.6¢J and 197.6¢J greater than at 1200rpm. According to the tensile test, the shear failure loads of clad steel plates increase 11.3kN and 15.5kN by using tools with 5 mm and 10 mm inserted material at 900rpm for 60 seconds, and increase 7.6kN and 18.3kN by using tools with 5 mm and 10 mm inserted material at 1200rpm.

In this study, a novel assembled-type tool was used to weld SS400 low-carbon steel plate using the friction stir spot welding. The welding tool was made of tungsten carbide embedded a circular rod made of the low-carbon steel. The superiority of this embedded material not only could effectively promote the interface temperature of the joint, but also the thickness of stir zone. Compared to previous studies, this novel tool can significantly improve the manufacturing cost and the trimming time. The welding apparatus composed of a vertical milling machine and a welding platform. The operating conditions of welding were as followings: the diameter of embedded material, the welding speed, and the vertical load. During the welding process, the interface temperature of the joint, the tool plunge depth, and the vertical load were simultaneously measured by the K-type thermocouple, a displacement sensor, and a load cell. Experimental results revealed that the interface temperature, the thickness of the stir zone, and the tensile strength of the welding joint was proportional to the diameter of the embedded material. The best welding condition is the embedded material diameter of 10mm, the vertical load of 8kN, the welding speed of 1200rpm, and the welding time of 100 seconds.

In this research, corrosion behaviour of A36 carbon steel under engineered disbonded coating was investigated in sulphuric acid solutions containing sodium chloride and iron (III) sulphate. Scanning electron microscopy (SEM) and x-ray diffraction (XRD) analyses were carried out to study the morphology and phase composition of corrosion products formed on the carbon steel surface. The results of the SEM analysis showed that only general and pitting corrosion occurred on the carbon steel surface with the engineered crevice. The size of the pits increased as the sulphuric acid and sodium chloride concentrations increased. Moreover, the corrosion products had an open, irregular and loose structure at the pits mouth. The loose and open structure of the corrosion products facilitates diffusion of chloride ions, oxygen, water and contaminants into the carbon steel surface. In contrast, the corrosion products had a very compact and continuous structure outside the pits which provided a good protection against further corrosion. The x-ray diffraction analysis showed that the corrosion products layer mainly consisted of lepidocrocite (γ-FeOOH), goethite (α-FeOOH) and iron sulphide (FeS) on the crevice edges. The Pourbaix diagram of iron in sulphuric acid solution at room temperature indicates that iron sulphide is formed on the metal surface at different pH values. The akaganeite (β-FeOOH) diffraction peak was not identified in any spectrum which could be due to the low concentration of chloride ions in the solutions. Furthermore, the number of lepidocrocite peaks decreased as the sulphuric acid concentration increased from 10 g l-1 to 50 g l-1. The lepidocrocite is dissolved in the presence of sulphuric acid, and the dissolved ion acts as an oxidant to the metal and hence lower lepidocrocite peaks are identified. Electrochemical noise measurement (ECN) testing was also performed to investigate the corrosion process occurring on the carbon steel surface with the engineered crevice. The results of the ECN measurements showed that current increased during first few minutes and then decreased slightly. Also, the coupled potential did not change after an initial shift in negative direction. The low current flowing through the carbon steel electrodes and the constant potential showed that the crevice corrosion did not develop. These results imply that the crevice corrosion may not occur on the carbon steel surface in acidic solutions containing chloride ions.

No description available.

The effect of initial microstructures of an 0.05 wt.% C low carbon steel, acicular ferrite (AF), Bainite (B), polygonal ferrite (PF), fine polygonal ferrite (FPF), and a microstructure produced by direct strip casting (DSC) (termed SC), on the deformation and recrystallization behaviour of cold rolled low carbon (LC) steel, was investigated. The initially prepared samples with the initial microstructures were cold rolled to 50, 70 and 90% reductions, then annealed isothermally in the temperature range 580 ??? 680 oC. The microstructures and textures produced by deformation and annealing were studied by optical microscopy, XRD, TEM, SEM and EBSD. The initial microstructures were characterized mainly by optical microscopy and EBSD. Using EBSD, the ferrite grain size of the AF, B and SC samples was considerably larger than that found by optical microscopy with a large fraction of low angle grain boundaries (LAGBs) observed within prior austenite grains. All samples exhibited a very weak texture close to random. After cold rolling, the microstructures of AF and SC contained shear bands with PF and FPF generating deformation bands. For AF and SC, the pearlite phase was more extensively elongated in rolling direction compared with PF and FPF. After 90% cold rolling reduction, PF, FPF and SC consist mainly of the texture component and AF and B . It was found that FPF recrystallized most rapidly followed by B, PF and AF with SC recrystallizing orders of magnitude more slowly due to the solution drag caused by its uniformly distributed higher Mn content. Very strong (???-fibre) texture was generated in cold rolled PF followed by FPF, with AF, SC and B generating very weak textures. The texture evolution during annealing 90% reduction PF was examined in further detail. The behaviour of nucleation and grain growth provides strong evidence of orientated nucleation as the dominant factor for CRA texture development in this material.

A series of model steels containing copper levels up to 0.48wt%, nickel up to 0.22wt% and silicon levels of 0.52wt% were oxidised in air at 1050 and 1150??C, and in a CO2-N2 mixture at 1250??C for times of up to 3 hours. The scaling kinetics were measured and the behaviour of copper-rich phase formation at the scale/metal interface was investigated. When oxidised at 1050/1150??C, significant quantities of copper-rich phase were observed for most model steels. The relatively high oxidation rate under these conditions led to the rapid development of a copper-rich layer with little copper diffusing into the metal. However, when oxidised at 1250??C, the copper-rich phase did not form for a significant amount of time; and for some model steels, not at all. This was attributed to the considerably lower oxidation rate and the fact that more copper was found to have diffused into the metal. Alloying additions of nickel and silicon were found to be beneficial in reducing the amount of copper-rich phase measured at the scale/metal interface under the conditions investigated at 1150??C and 1250??C. This occurred because nickel and silicon addition promoted the occlusion of copper-rich phase into the scale. Copper enrichment during oxidation was modelled using a numerical description of the diffusion processes involved. Predictions of the time for commencement of copper-rich phase formation at 1250??C were in close agreement with observation. Agreement between predicted and observed copper-rich layer thickness was less successful under conditions where occlusion was significant, and the measured thickness varied non-uniformly with time. The cracking susceptibility of the model steels was examined using a hot compression test. Oxidation was performed in air at 1050, 1150 and 1250??C and most specimens were compressed at 1050??C. The amount of cracking was found to increase with the amount of copper-rich phase precipitated at the scale/metal interface during oxidation. In general, nickel addition reduced the amount of cracking at all temperatures; and under some conditions prevented cracking altogether. Silicon reduced or completely suppressed cracking when the subscale formed was liquid. The beneficial effects of nickel and silicon addition were attributed to their effect of promoting copper occlusion.