Síntese e estabilidade coloidal de nanofluidos (NF) aquosos de óxido degrafeno (GO) e propriedades reológicas de NF aquosos de poliacrilamida - GO

• Ano de defesa: 2017
• Autor(a) principal: Jesús Andrés Nuncira Valencia
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; UFMG
• Palavras-chave em Português: Estabilidade coloidal; Nanofluidos de GO; Propriedades reológicas; Poliacrilamidas parcialmente hidrolisadas; Acrilamida; Copolímeros; Coloides; Reologia; Engenharia quimica
• Link de acesso: http://hdl.handle.net/1843/BUOS-AUUKLX

Graphene oxide (GO) is a carbon nanomaterial (CNM) that exhibits excellent thermal, electrical and mechanics properties. Due to this, GO is a potential material for a wide range of applications in science and technology such energy industry, and it ca be use for production of nanocomposites or nanofluids (NF). In this research work, the efforts were focused in three aspects: 1. to produce GO nanosheets with high structural and morphological quality trough acid treatment using the modified Hummers method; 2. to evaluate the colloidal stability of GO dispersions as a function of aging time and; 3. to study the influence of GO on rheological responses when added in polymer solutions withacrylamide/acrylic acid copolymer (AMcoAA) as the base matrix. Structural and morphological characterization of GO were made by transmission electron microscopy (MET), scanning electron microscopy (SEM), atomic force microscopy (AFM), thermogravimetric and its corresponding derivate (TGA/DTG), Fourier transform infrared (FTIR) and Raman spectroscopy, elemental composition analysis (CHN) e X-ray diffraction (XRD). These characterizations allowed to confirm the lamellar and multilayer of GO nanosheets, besides the insertion of structural defects in the surface of the CNM as a result of acid treatment. UVVIS spectroscopy, dynamic light scattering (DLS) and electrophoretic mobility () were used to study the colloidal stability of GO when dispersed in water for 90 days. Results obtained allowed to observe the high colloidal stability of GO when in aqueous suspension, evidenced by the small decrease in absorbance (4%), the high surface charge (-64,2 mV) and the considerable decrease in apparent particle size (43.5%). Finally, rotational and oscillatory rheology measurements performed at different experimental conditions, allowed to analyze the interaction between AMcoAA and GO. The GO influence on polymeric system viscosity showed,mainly, that in systems with high salinity concentrations, counterions as disruptive agents between AMcoAA and GO interactions, impeding or limiting the electrostatic interactions between them.