Estudo eletroquímico e computacional de inibidores voláteis de corrosão adsorvidos sobre zinco

Pós-graduação em Química - IQ

Efeito de tratamentos térmicos nas propriedades mecânicas, eletroquímicas e citotoxidade de ligas do sistema Ti-15Mo-XNb

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Preparação e caracterização estrutural, mecânica e anelástica de ligas do sistema Ti-Ta contendo oxigênio intersticial, para uso biomédico

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Obtenção de compósitos de borracha natural com resíduo industrial de couro reticulados com diferentes peróxidos

Pós-graduação em Ciência e Tecnologia de Materiais - FC

Análise da superfície de cerâmicas de dissilicato de lítio após imersão em soluções ácidas e a base de flúor

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo da corrosão em ligas de alumínio utilizadas na indústria aeronáutica

A resistência e o mecanismo de corrosão das ligas de alumínio 2024, 7010, 7050 e 7475 foram estudados em solução de NaCl. Os efeitos do tratamento térmico nas ligas, concentração de oxigênio, pH, adição de oxi-ânions e temperatura do meio constituem algumas das variáveis estudadas. Primeiramente, procedeu-se à caracterização físicoquímica dos materiais através de análise química e metalográfica, mediante microscopia eletrônica de varredura e espectroscopia de energia dispersiva. As ligas 2024, 7010, 7050 e 7475 como recebidas, recozidas e envelhecidas, revelaram a existência de partículas ternárias e quaternárias, constituídas por Al:Cu:Fe e Mg ou Zn. Também foi observado um maior número de partículas pequenas de composição variável situando-se, preferencialmente, nos contornos dos grãos. Os resultados dos ensaios de corrosão em meios aerados e desaerados indicam que o cromato é efetivo como inibidor da corrosão localizada em ambas ligas e que o molibdato somente na liga 7050. O efeito inibidor do tungstato se revela em meio desaerado e é comparativamente menor daquele observado com os outros oxi-ânions. As análises quantitativas de superfície das ligas após os ensaios de imersão indicam que ainda na presença de inibidor, se pites foram nucleados, eles crescem.

Eficiência de detergentes e EDTA na remoção da smear layer de superfícies radiculares submetidas a raspagem e aplainamento: análise através da microscopia eletrônica de varredura

A remoção da smear layer é um procedimento importante para a regeneração periodontal e para o tratamento da sensibilidade dentinária. Diversos tratamentos tem sido realizados para sua remoção, porém, mostrando resultados conflitantes ou insatisfatórios. No presente estudo nos propomos a analisar através do microscópio eletrônico de varredura a eficiência dos detergentes: lauril sulfato de sódio, Plax e de mamona assim como o EDTA 24% na remoção da smear layer. Todos os produtos testados foram aplicados com bolinha de algodão, renovada a cada 30 segundos, a qual era esfregada na superfície radicular por diferentes períodos. As fotomicrografias foram analisadas através da aplicação de um índice de remoção da smear layer por três examinadores calibrados e os resultados analisados estatisticamente. De acordo com nossos resultados pudemos chegar as seguintes conclusões: 1- a instrumentação com curetas de Gracey provocou a formação da smear layer; 2- o detergente lauril sulfato de sódio não removeu a smear layer, tendo sido o pior resultado entre os detergentes testados; 3- Os detergentes Plax e de mamona mostraram resultados semelhantes entre si e superiores ao controle negativo e ao lauril sulfato de sódio, porém, não removeram a smear layer satisfatoriamente; 4- O EDTA 24% neutro mostrou ser eficiente para a remoção da smear layer.

Scaffolds de polihidroxibutirato construídos por prototipagem rápida funcionalizados com hidroxiapatita e peptídeo osteogênico

Com a evolução da engenharia tecidual novos materiais estão sendo estudados visando o tratamento de defeitos ósseos. O objetivo deste projeto foi preparar e caracterizar scaffolds a base de polihidroxibutirato (PHB), apatita e peptídeo osteogênico, osteogenic growth peptide (OGP), para aplicação em reparação óssea. Além disso, avaliar a liberação prolongada do peptídeo incorporado aos scaffolds na forma livre ou incorporado a lipossomas. Os scaffolds de PHB foram confeccionados por prototipagem rápida (PR) empregando a tecnologia Selective Laser Sintering (SLS). Posteriormente, a apatita foi incorporada in situ por meio de ciclos alternados de imersão em soluções de CaCl2 e Na2HPO4, respectivamente. Neste estudo foram selecionadas 2 marcações para o OGP, uma com 5,6-carboxifluoresceína (CF) e outra com triptofano (W), para análise de liberação prolongada. Os peptídeos foram incorporados ao sistema de liberação no momento de seu preparo. A caracterização por espalhamento de luz dos sistemas de liberação desenvolvidos mostrou que os peptídeos marcados com CF foram os melhores desenvolvidos. Portanto estes peptídeos foram adsorvidos nos scaffolds de PHB-CaP. Estudos in vitro foram realizados para avaliar o perfil de liberação do peptídeo OGP-CF do sistema de liberação controlada. A incorporação da apatita às matrizes de PHB foi confirmada por análises de microscopia eletrônica de varredura/ espectroscopia de energia dispersiva (MEV/EDS), espectroscopia na região do infravermelho (FTIR), absorção atômica, a difratometria de raios-X (DRX). Estas análises sugeriram que a principal fase precipitada foi -TCP. O sistema de liberação lipossoma/OGP-CF foi caracterizado pelas análises de dicroísmo circular e espalhamento de luz, que confirmaram a presença do peptídeo nas amostras. Após a análise da liberação, observou-se que o sistema PHB-CaP/OGP-CF obteve ...

Preparação e caracterização de vidros contendo nanopartículas de Ag

This work consists of preparation and characterization of glasses containing transition noble metals and the study of optical properties of such materials. The glasses were prepared by quenching of the glass melt followed by heat treatment and polishing of the monoliths. The structural characterization of glasses was made using differential thermal analysis, X-ray, Raman and infrared spectroscopies, while the optical properties were studied by UV-Vis and M-Lines spectroscopies. Preliminary results have shown that the color of the glasses is dependent on both concentration of silver and the melting temperature of the melt. Controlled heat treatments have been used to induce the crystallization of Ag nanoparticles within the glass. The study of crystallization was accompanied by electron microscopy and UV-Vis spectroscopy. Data from electron diffraction, as well as chemical analysis, EDX, were obtained using a transmission electron microscope. EDX data have shown that the atomic percentage of Ag is higher on the nanoparticle. X-ray diffraction was used in order to characterize the composition of the crystals and cubic AgCl was identified as the main crystallized nanophase obtained after annealing

Estudo da toxicidade de diferentes doses do Diuron (3-(3,4 -dichlorophenyl)-1,1-dimethylurea) no epitélio da bexiga de ratos wistas machos por microscopia eletrônica de varredura

Diuron (3-(3,4-Dichlorophenyl)-1,1-dimethylurea) is a substituted urea herbicide widely used on agricultural crops such as soy, cotton and sugar cane. In a previous long-term study this herbicide exerted carcinogenic activity on the urinary bladder and renal pelvis mucosa of Wistar rats and breast of mice. Also, it was shown to be carcinogenic to the mice skin in a initiation-promotion assay. In 1997, the northamerican EPA evaluated Diuron as a “known/likely” carcinogen for humans (USEPA, 2004). In a previous study developed at this laboratory, male Wistar rats treated with Diuron 2500 ppm during 20 weeks presented increased indices of cell proliferation and incidences of simple urothelial hyperplasia (HS) in the urinary bladder. Under scanning electron microscopy (SEM) severe urothelial necrosis and hyperplasia were observed. However, in that study the urinary bladders of animals exposed to lower doses of Diuron were not examined under SEM. Therefore, the possible dose-response influence of Diuron on the urothelium under SEM is not known. The present study aimed to analyze under SEM the urinary bladder of male Wistar rats exposed to 125 ppm, 500 ppm and 2500 ppm doses of Diuron through diet during 20 weeks and to compare to the previous histological findings in the same material. Under SEM, 125 ppm and 2500 ppm groups presented significantly (p<0,05) increased incidences of simple hyperplasia, i.e., 7/10 and 8/10 respectively, compared to control group and the 500 ppm group The sensitivity of SEM was higher since it detected a 45% incidence of hyperplasiaswhile the histological analysis found only 27%. Considering SEM as the gold-standard, histology showed a 44% sensitivity, 86.4% specificity, a positive predictive value of 72,7% and negative predictive value of 65,5% and accuracy of 67,5%. Scanning Electron Microscopy...(Complete abstract click electronic access below)

Produção de eletrodos em carbono vítreo monolítico e reticulado a partir da resina furfurílica dopada com cobre

The glassy carbon is a material with a huge technological evolution. Due to its lightness, biocompatibility and their thermal and electrical properties this material finds applications in several industrial fields such as electronics, medical, aerospace and chemical. In order to explore the conductive properties of glassy carbon for use as modified electrodes, the present work aims the processing of monolithic and reticulated glassy carbon with colloidal copper for use in electrochemical applications. First, the best parameters for the cure of furfuryl alcohol resin doped were established through viscosimetry measurements and pressurized differential scanning calorimetry. The analysis of the micrographs of the cured resins show that copper concentrations above 3% weight, generate higher porosity in the material. The characterizations of the monolithic and reticulated glassy carbon resulting from carbonization were performed by scanning electron microscopy (SEM), Raman and Electrochemical impedance spectroscopy, and although it was not possible to detect the presence of copper by SEM, the influence of these particles have been observed by Raman and FT-IR spectra and electrochemical behavior of the material. The decrease in conductivity of monolithic and reticulated glassy carbon in the presence of copper may be related to the defects caused by the presence of copper in the structure of the material.

Instrumentação eletrônica para experimentação do modelo Bouncer Ball dissipativo

In our experiments, we studied the classical dynamic of a particle in vertical motion subject to a constant gravitational field and the partial shock with an elastic wall with oscillatory motion located below the particle. The motion of the particle was confined to the vertical direction by a glass guide tube, which was initially evacuated, allowing viscous drag forces to be disregarded. The time between impacts, as well as the time between the reference phase of the movement of the base and the moment of impact and the period of oscillation of the base will be acquired by a hardware and software to obtain the phases space to be compared later with the description of the system through mapping discrete variables via the 'particle velocity immediately after shock 'and' phase of the movement of the base at the instant of shock 'obtained by computer simulation. This requires developing an electronic analog system followed by Digital implemented in reconfigurable logic, more specifically a sequential machine able to discriminate the impact with the metal base from the impacts of the glass guide tube, based on the frequency spectrum of the response of the microphone to these different impacts

Estudo de temperatura de plasma de álcool através de espectroscopia de emissão natural radical C2*

Non-intrusive methods of diagnosis, such as spectral analysis of the radiation emitted by the system, have been used as a viable alternative for determining the temperature of combustion systems. Among them, the determination of temperature by natural emission spectroscopy has the advantage of requiring relatively simple experimental devices. Once Chemiluminescent species are formed directly in the excited state, the collection and recording of radiation emission spectrum is enough to determine the temperature (CARINHANA, 2008). In this study we used the process of making direct comparisons between the experimental spectra obtained in the laboratory from the plasma of alcohol, and the theoretical spectra plotted from a computer program developed at the IEAv. The objective was to establish a fast and reliable method to measure the rotational temperature of the radical C2*. The results showed that the temperature of the plasma, which in turn can be taken as the rotational temperature of the system, is proportional to the pressure. The temperature values ranged from ca. 2300 ~ 2500 K at a pressure of 19 mmHg to 3100 ~ 3500 K for the pressure of 46 mmHg. The temperature values are somewhat smaller when we consider the theoretical spectrum as a Lorentzian curve. The overlap of the spectra was better when using the profile curve, but still were not exactly superimposed. The solution to improve the overlap of the theoretical with the experimental spectra is the use of a curve that has the convolution of two profiles analyzed: Lorentzian and Gaussian. This curve is called the Voigt profile, which will also be implemented by programmers and studied in a next work

Determinação de temperatura de chamas por espectroscopia de espécies quimioluminescentes

In a combustion process involving fossil fuels, there is the formation of species Chemiluminescent, especially CH*, C2* and OH*, whose spontaneous emission can be used as a diagnostic tool. In the present work, mapping and determination of the rotational temperature of the species CH* produced in flames on a burner fueled by Liquefied Petroleum Gas (LPG) was carried out. This study is part of a project involving the characterization of supersonic combustion in scramjets engines, whose study has been conducted in the hypersonic shock tunnel IEAv laboratories. The technique used was the natural emission spectroscopy, which has as main advantage of being non-intrusive. The rotational temperature determination was made using the Boltzmann method, whose principle is to relate the emission intensity of the species to the temperature by means of spectroscopic constants established.The temperature values were determined from the analysis of electronic bands AX and BX of the radical CH*. In order to confirm the results of flame temperatures obtained by the natural emission technique, was also used the technique of line reversal sodium. The results of both techniques showed that the temperature of the flames investigated is about 2500K a 2700K

Espectroscopia de infravermelho e suas aplicações

Infrared spectroscopy (IR spectroscopy) explores the infrared region of the electromagnetic spectrum. Like any other spectroscopic technique, it can be used to identify a compound or the composition of investigate a sample. Spectroscopy (IR) is a very important technique in qualitative chemical analysis, widely used in the chemistry of natural products, organic synthesis and transformations. In this work we study of the theoretical foundations of infrared spectroscopy, the different vibration modes, experimental techniques, and the identification and characterization of solids. Were studied as applications: their use in thermograph and remote sensing satellites