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This work aimed to produce graphene oxide with few graphene layers, a low number of defects, good conductivity and reasonable amount of oxygen, adequate for use as filler in polymeric composites. Two starting materials were evaluated: expanded graphite and graphite flakes. The method of oxidation used was the Staudenmaier one, which was tested over different lengths of time. No appreciable differences were found among the oxidation times and so the lowest oxidation time (24 h) was chosen as the most adequate. An investigation was also conducted into suitable temperatures for the reduction of graphite oxide. A temperature of 1000 ºC gave the best results, allowing a good quality material with few defects to be obtained. The reduction was also evaluated under inert and normal atmosphere. The best results were obtained when the least modified material, e. g., graphite flakes, was used as a starting material, oxidized for 24h and reduced at 1000 ºC for 30 s in a quartz ampoule under a normal atmosphere.

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The aim of this work was to investigate the effect of previous treatments at high pressures on the crystallization kinetics of monolithic samples of a Li 2 O-2SiO 2 (LS 2 ) glass. The glass transition temperature (T g ) and the temperature of the onset of crystallization (T p ) obtained by differential thermal analyses (DTA) were measured for LS 2 glass samples submitted to isostatic pressures ranging from 2.5 to 7.7 GPa during 5 min at room temperature. The observed systematic changes in T g and T p were probably related to the cracks induced by high pressure inside the monolithic samples and in its surface. Away from the cracks, the nucleation density slightly decreased as a function of pressure but along the cracks, the nucleation density was significantly higher.

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