Microscopia de força atômica in-situ de superfícies de membranas poliméricas de Nafion com nanopartículas de sílica incorporadas

• Autor(a) principal: Santos, Danielle Fernandes Amaro dos
• Data de Publicação: 2008
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/4229
• topic: Microscopia de força atômica; Polímero; In-situ; Atomic force microscopy; Polymer; In-Situ; CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA::FISICA DA MATERIA CONDENSADA

Fountains of renewable energies are occupying an important space in scientific inquiries. Within this Proton Exchange Membrane Fuel Cells (PEMFC) stand out. Studies show that the elevation of PEMFC s operation temperature results in the increase of its efficiency. Nevertheless, in these work conditions there appears to be a necessity in improving electrolyte water retention. The electrolyte traditionally used in these cells is the Nafion ® polymer. One of the ways to improve the retention of water in the polymer in elevated temperatures is the incorporation of hydrophilic particles (ex: silica). In this work atomic force microscopy was used (Atomic Force Microscopy - AFM) to characterize the surface of Nafion membranes with nanoparticles of incorporated silica through two methods ( Casting and Sol - gel ). The AFM tests were carried out in-situ to approximate the characterization conditions to the operation conditions of an electrolyte in the PEMFC. In these experiments the semi-contact method was used to avoid damage to the surface of the polymer. Samples were used without incorporated nanoparticles as a base of comparison to identify the influence of the presence of the particles in the characteristics of the surface of the electrolyte.The obtained images of the sample manufactured by the Casting method presented two distinct sides, for the sample without nanoparticles as well as for the sample with incorporated silica nanoparticles. The first side is characterized by the presence of grooves caused by the contact of the sample with the substrate of the preparation membrane. The second side for the sample without nanoparticles presents a decreased roughness compared to the same side for the Doped sample. In the sample Doped by the Casting method, its second side is characterized by two regions, the first shows a surface totally recovered by particles and the second a surface with scattered, randomly spread particles. The silica particles have an average diameter of (0.3 ± 0.1) µm. The samples manufactured by the Sol - gel method are produced from a commercial film and this film was also characterized. The images from the commercial film present two distinct sides, one with decreased roughness, not atomically flat and another with well oriented grooves. The images of the sample particles with incorporated silica through the Sol - gel method presents randomly distributed particles on the whole surface, without any significant difference between its two sides. It should be noted that the lack of grooves in one of the faces of Doped Nafion by the Sol gel method is a result of the incorporation process of the silica particles.