Comparative study of the rheological behaviors of Mxenes-PAG and Alumina-PAG nanofluids

Comparative study of the rheological behaviors of Mxenes-PAG and Alumina-PAG nanofluids

• Autor
• Eliel Wellington Marcelino
• Co-autores
• Luis Fernando Grespan Setz , Sydney Ferreira Santos , Humberto Naoyuki Yoshimura
• Resumo

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  This work considered Mxenes nanosheets of Ti₃C₂Tx synthesized at the UFABC laboratory and obtained through a chemical etching of in-situ HCl in the 3D structure Ti₃AlC₂. Conversely, the Alumina nanostructures used in this work were obtained from the company Cabot® and they are commercially named FAL100. The PAG oil (Polyalkylene Glycol) was obtained from the company Montreal®, named PAG-46. For the characterization of Mxenes and Alumina nanostructures, SEM images and confocal microscope images were obtained. The nanofluids were prepared through the dispersion of a mass fraction of 0.1wt.% of MXenes and Alumina into PAG oil by a sonication process to obtain a homogeneous and dispersed mixture. The mixture was stirred for a period of 15 minutes at 1000RPM before the sonication process for 2h to obtain dispersed and homogeneous nanofluids. The nanofluid samples contained a volume of 16ml which were poured into a concentric cylinder device of a rotational rheometer to obtain the flow and viscosity curves. The shear rate range varied in a ramp mode from 0 to 1000s^-1 for 180 seconds, with fixed temperatures of 20°C, 30°C, and 40°C. For the fixed temperature of 20°C, at shear rates from 250s^-1 to 1000s^-1, the flow curve results showed that Mxenes-PAG nanofluid had the same shear stress levels as Alumina-PAG nanofluid. Conversely, for lower shear rates, below 250s^-1, the Alumina-PAG demonstrated a shear stress of around 5% smaller than the Mxenes-PAG. For lower shear rates, below 250s^-1, the average viscosity level of Alumina-PAG was 12.5% smaller than the viscosity level of Mxenes-PAG. For higher shear rates the viscosity curves of Mxene-PAG and Alumina-PAG nanofluids were essentially the same. At the fixed temperature of 30°C, the Mxenes-PAG and Alumina-PAG nanofluids demonstrated similar behavior for the flow and viscosity curves, over the shear rate range from 600s^-1 to 1000s^-1. Conversely, at lower shear rates, Mxenes-PAG nanofluid showed about 4% less shear stress and 3% less viscosity than Alumina-PAG nanofluid. Finally, at the fixed temperature of 40°C the viscosity and shear stress levels for pure PAG were smaller than nanofluids during the whole shear rate range. The Mxenes-PAG nanofluid showed smaller viscosity and shear stress than Alumina-PAG nanofluid for higher and lower shear rate ranges. Overall, the behavior of the pure PAG at all temperatures demonstrated flow and viscosity curves with a Newtonian behavior. The addition of nanostructures in the PAG oil for obtaining the Mxenes-PAG and Alumina-PAG nanofluids showed no changes in the initial Newtonian behavior of the base fluid at all tested temperatures. The pure PAG sample, without the addition of nanostructures, showed higher shear stress and viscosity than nanofluid samples, indicating that the addition of nanostructures in PAG oil can reduce the viscosity and shear stress of the PAG oil for the entire temperature range except for 40°C. This is because the nanostructures remain deposited in the nanofluid with a lower kinetic energy until 30°C. When thermal energy increases for the temperature to reach 40°C, the nanostructures tend to demonstrate a higher mobility within the nanofluid due to a higher kinetic energy. Conversely, for the pure PAG at 40°C there is no nanostructures, thus its viscosity and shear stress is decreased.

• Palavras-chave
• Nanofluid, Mxenes, Rheology, Alumina
• Modalidade
• Comunicação oral
• Área Temática
• Materiais Funcionais Avançados