In this study, the evolution of structure and the relationship between microstructure and corrosion behavior of the Ti-6Al-4V ELI (Extra Low Interstitial) alloy was investigated in Ringer&amp / #8217 / s solution at 37 &plusmn / 0.1 oC. Initially, different heat treatments were performed in order to obtain several microstructures which were / Widmanst&auml / tten &amp / #945 / for furnace cooling (FC), basket-weave &amp / #945 / for air cooling (AC), martensite (&amp / #945 / &#039 / ) for water quenching (WQ) from 1060 oC, and aged martensite for ten hours at 500, 600, 700, 800, 900 oC. The microstructural characterizations were done by using SEM and X-ray Diffraction technique. Finally, the corrosion tests were accomplished in Ringer&amp / #8217 / s solution and NaF added Ringer&amp / #8217 / s solution by using open circuit potential and anodic polarization techniques, respectively. The results showed that vanadium element removal from martensite phase and unit cell volume increase were detected during aging due to the replacement of vanadium with titanium atoms. According to the alloying element distribution throughout the microstructure, the passive film formation due to equilibrium corrosion conditions was better in FC specimen than AC and WQ specimens. But during anodic polarization, the stability of the film in high Cl- ion concentration medium was more resistant to dissolution for WQ and aged specimens. As a result, the alloying element distribution underneath the passive film seemed to have an important role on the film formation and its stability. However, in non-equilibrium conditions, the passive film formation tendency due to the addition of NaF at 0.2M decreased because of the detrimental effects of F- ions.

Submitted by Maike Costa (maiksebas@gmail.com) on 2017-03-21T13:19:09Z No. of bitstreams: 1 arquivototal.pdf: 2398658 bytes, checksum: 37469752b2f4c25b709db170a9ae08b0 (MD5) / Made available in DSpace on 2017-03-21T13:19:09Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2398658 bytes, checksum: 37469752b2f4c25b709db170a9ae08b0 (MD5) Previous issue date: 2014-06-18 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The transport of materials trough dental enamel has been regarded as dependent on diffusion which doesn´t infiltrate the nanopores of normal dental enamel normal, being these materials considered as above the threshold for enamel nanopores (MATEN). In this in vitro study, applied the electrokinetic flow (EKF) to infiltrated the MATEN into the dental enamel pores mature of unerupted permanent human teeth. It were tested an aqueous solutions with refractive index of 1.56 (Thoulet’s solution) by 5h and a infiltrant resin ICON® by three different times (1; 1,5 and 2 h), both with pH higher than the critical pH of enamel, applying 5V in both cases. Dental enamel ground sections were mounted on customized microfluidic chips made of poly-methyl-siloxane and submitted to EKF. A pre-infiltration with 1 mM KCl solution by 2 h and 1V. Three samples were infiltrated by 1.56 Thoulet´s solution and eight samples were infiltrated using infiltrant resin. Histological sites (n = 30) in Thoulet´s group were analyzed for water birefringence before and after infiltrated. The sample of resin group were subsequently exposed to in vitro demineralization by 192h. The depth of hybrid layer was analyzed by fluorescence and polarizing microscopy. The analysis of mineral volume by radiomicrography was performed in infiltrated histological sites (n = 30) and not infiltrated histological sites (n = 30), before the infiltrated and after demineralization, always hydrated. The negative birefringence of histological points (n = 30) in water, before infiltration of Thoulet’s solution (mean of -22.47 x 10-4) was significantly lower than after the infiltrated of Thoulet’s solution 1.56 (mean of – 51.7 x 10-4) (p < 0.00001; ANOVA; effect size = 6.69). Depth of enamel hybrid layer ranged for 640 m to 1430 m (mean of 760 m). The hydrated minerals volumes of infiltrated parts before demineralization were similar to after demineralization (p = 0.123; T test) while the not infiltrated parts presented similar hydrated mineral volumes after demineralization (p < 0.00001; effect size = 3.263). It is concluded that EKF was successful in infiltrating MATEN in enamel pores, without enamel etching, resulting in a new hybrid layer model and a huge increase in infiltration compared to diffusion, opening new opportunities for scientific innovation and with potential clinical applications in Dentistry. / O transporte de materiais através do esmalte dentário tem sido baseado no processo de difusão, os quais não infiltram os nanoporos do esmalte dentário humano normal, uma vez que são considerados materiais com dimensões acima do limite dos poros do esmalte (MDALPE). Neste estudo, in vitro, aplicou-se o fluxo eletrocinético (FEC) para a infiltração dos MDALPE nos poros do esmalte dentário maduro de dentes humanos permanentes não irrompidos. Foram testados solução aquosa de Thoulet com índice de refração (n) = 1,56, por 5 h e resina infiltrante ICON® por três tempos diferentes (1; 1,5 e 2h), ambos com pH acima do valor crítico do esmalte, aplicando 5 V em ambos os casos. Cortes por desgaste de esmalte dental foram inseridos em chip microfluidicos customizados feitos de poli-metil-siloxano e submetidos ao FEC. Uma infiltração prévia com KCl 1mM foi realizada em cada amostra por 2 h, usando 1V. Três amostras foram infiltradas com solução Thoulet n= 1,56 e oito amostras foram infiltradas com resina infiltrante. Pontos histológicos (n = 30) do grupo da solução Thoulet foram analisados quanto à birrefringência em água antes e após a infiltração. As amostras do grupo da resina foram posteriormente submetidas à desmineralização in vitro por 192 h. A profundidade da camada híbrida foi determinada pela microscopia de fluorescência e de luz polarizada. A análise do volume mineral através da radiomicrografia foi realizada em pontos histológicos nas áreas infiltrada (n = 30) e não-infiltrada (n = 30), antes da infiltração e após a desmineralização, sempre hidratados. A birrefringência negativa de pontos histológicos (n = 30) em água, antes da infiltração da solução de Thoulet (média de -22,47 x 10-4) foi significativamente menor que a birrefringência após a infiltração com a solução de Thoulet n = 1,56 (média de -51, 7 x 10-4) (p < 0,00001, ANOVA; tamanho do efeito 6,69). A profundidade da camada híbrida no esmalte variou de 640 m a 1430 m (média de 760 m). Os volumes minerais (hidratados) dos pontos infiltrados antes da desmineralização foram similares àqueles após a desmineralização (p = 0,123; teste T pareado), enquanto os pontos não infiltrados apresentaram volumes minerais (hidratados) menores após a desmineralização (p < 0,00001; teste T; tamanho do efeito de 3,263). Conclui-se que a técnica do FEC foi aplicável, com sucesso, ao transporte de MDALPE, nos poros do esmalte, sem ataque ácido, resultando em um novo modelo de camada híbrida como também num aumento expressivo da infiltração resinosa se comparada com a difusão, abrindo novas oportunidades para inovação científica e com potencial de aplicações clínicas em odontologia.