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Estudo da viscosidade dinâmica de nanofluidos de grafeno aplicados à hipertermia terapêutica
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Advisor(s)
Abstract(s)
Os nanofluídos à base de grafeno têm vindo a ganhar relevo em aplicações biomédicas de transferência térmica controlada. Este trabalho teve como objetivo avaliar a viscosidade dinâmica de nanofluídos de grafeno em função da temperatura e da fração volúmica, considerando a sua adequação à hipertermia terapêutica. Prepararam-se amostras em diferentes fluidos base, tendo a parafina sido selecionada para ensaios aprofundados. As amostras centrifugadas e não centrifugadas foram caracterizadas por UV-Vis, FTIR, densidade e viscosidade entre 15 e 55 °C.
Nas amostras não centrifugadas, observou-se que, para frações volúmicas até 0,30 %, a viscosidade diminui exponencialmente com a temperatura, enquanto para concentrações superiores ocorre uma inversão da tendência, originando um comportamento em “U” com valores mínimos entre 30 °C e 35 °C. Por outro lado, nas amostras centrifugadas, verificou-se uma diminuição contínua e exponencial da viscosidade em todo o intervalo de temperaturas e frações volúmicas, comportamento semelhante ao observado para a parafina pura. A comparação com os modelos teóricos e empíricos evidenciou que estes não reproduzem adequadamente o comportamento experimental. Já os modelos semiempíricos revelaram-se os mais adequados para descrever os dados obtidos, sendo a análise em função da temperatura aquela que apresentou o melhor ajustamento.
Graphene-based nanofluids have gained increasing relevance in biomedical applications involving controlled heat transfer. This work aimed to evaluate the dynamic viscosity of graphene nanofluids as a function of temperature and volume fraction, assessing their suitability for therapeutic hyperthermia. Nanofluids were prepared using different base fluids, with liquid paraffin being selected for detailed testing. The centrifuged and non-centrifuged samples were characterized by UV-Vis spectroscopy, FTIR, and measurements of density and viscosity within the temperature range of 15 to 55 °C. In the non-centrifuged samples, it was observed that for volume fractions up to 0.30 %, viscosity decreased exponentially with temperature, while at higher concentrations an inversion of the trend occurred, resulting in a “U-shaped” behavior with minimum values between 30 °C and 35 °C. Conversely, the centrifuged samples exhibited a continuous exponential decrease in viscosity across all temperatures and volume fractions, showing a behavior similar to that of pure paraffin. The comparison with theoretical and empirical models showed that they do not adequately reproduce the experimental behaviour. In contrast, the semi-empirical models proved to be the most suitable to describe the obtained data, with the temperature-dependent analysis providing the best fit.
Graphene-based nanofluids have gained increasing relevance in biomedical applications involving controlled heat transfer. This work aimed to evaluate the dynamic viscosity of graphene nanofluids as a function of temperature and volume fraction, assessing their suitability for therapeutic hyperthermia. Nanofluids were prepared using different base fluids, with liquid paraffin being selected for detailed testing. The centrifuged and non-centrifuged samples were characterized by UV-Vis spectroscopy, FTIR, and measurements of density and viscosity within the temperature range of 15 to 55 °C. In the non-centrifuged samples, it was observed that for volume fractions up to 0.30 %, viscosity decreased exponentially with temperature, while at higher concentrations an inversion of the trend occurred, resulting in a “U-shaped” behavior with minimum values between 30 °C and 35 °C. Conversely, the centrifuged samples exhibited a continuous exponential decrease in viscosity across all temperatures and volume fractions, showing a behavior similar to that of pure paraffin. The comparison with theoretical and empirical models showed that they do not adequately reproduce the experimental behaviour. In contrast, the semi-empirical models proved to be the most suitable to describe the obtained data, with the temperature-dependent analysis providing the best fit.
Description
Keywords
Dynamic viscosity graphene nanofluids rheological models therapeutic hyperthermia Grafeno Hipertermia terapêutica Modelos Reológicos Nanofluídos Viscosidade dinâmica