Dispositivos microfluídicos: uma nova ferramenta para preparação de fibras de grafeno e derivados

• Ano de defesa: 2020
• Autor(a) principal: Rocha, Jaqueline Falchi da
• Orientador(a): Castro e Silva, Cecilia de Carvalho
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso embargado
• Idioma: por
• Instituição de defesa: Universidade Presbiteriana Mackenzie
• Palavras-chave em Português: fibras de grafeno; óxido de grafeno; microfluídica
• Área do conhecimento CNPq: CNPQ::ENGENHARIAS
• Link de acesso: https://dspace.mackenzie.br/handle/10899/28458

Due to the distinctive mechanical, optic, thermal and electric properties of graphene, it has been gaining global attention from a lot of researchers for the development of nanofibers, which present superior properties with respect to the carbon fibers, with the higher values reported of tensile strength and Young modulus, 130 GPa and 1,1 TPa, respectively. However, the biggest challenge resides in preparing the graphene fibers in a scalable way, in a continuous manner and maintaining its unique properties. In this regard, it is crucial the development of new technologies to surpass these difficulties. In this way, the present work shows the employment of 3D flow focalization of microfluidic devices, based on ceramics, using LTCC (Low Temperature Cofired Ceramics) technology for the development of graphene oxide fibers. The GO was synthesized by the modified Hummers method and characterized by the Raman spectroscopy technique. The wet spinning technique was used for preliminary studies of the formation of fibers, to optimize parameters such as ideal concentration of GO dispersion, flow rate of GO dispersion and coagulating agents. The optimized condition for the formation of GO fibers with appropriate mechanical stability was achieved for a GO dispersion of 5 mg mL-1, with an inlet flow of 2.5 mL min-1 using a hexadecyltrimethylammonium bromide coagulant bath (CTAB ) (0.5 mg mL-1). The fibers formed by the conventional wet spinning method showed satisfactory electrical conductivity after reduction with two-stage heat treatment (annealing at 300oC in an Ar / H2 atmosphere for 30 minutes, followed by microwave treatment, 100 W of power for 2 seconds), reaching electrical conductivity values of 1.19x104 ± 2.38 S m-1. The tests for obtaining GO fibers using the 3D ceramic-based microfluidic device with channel dimensions 43.63 mm long and 1.43 mm wide, showed great effectiveness for making long fibers (50 cm). In addition, the device was able to modulate the diameter of the fibers due to the ratio between the flow of GO dispersion by the flow of CTAB solution, making it possible to obtain fibers from 89 to 22 μm of diameter. The microfibers of GO, with an average size of 7 cm in length and 90 μm in diameter, presented to support weight of 6.02 ± 0.81 g before breaking. The 3D hydrodynamic microfluidic focusing device showed potential for the development of microfibers from other two-dimensional materials.