In recent years, extensive investigations have focused on the study and improvement of supercapacitor electrode materials. The electric devices produced with these materials are used to store energy over time periods ranging from seconds to several days. The main factor that determines the energy storage period of a supercapacitor is its self-discharge rate, i.e., the gradual decrease in electric potential that occurs when the supercapacitor terminals are not connected to either a charging circuit or electric load. Self-discharge is attenuated at lower temperatures, resulting in an increased energy storage period. This paper addresses the temperature-dependence of self-discharge via a systematic study of supercapacitors with nominal capacitances of 1.0 and 10.0 F at DC potentials of 5.5 and 2.7 V, respectively. The specific capacitances, internal resistances, and self-discharge characteristics of commercial activated carbon electrode supercapacitors were investigated. Using cyclic voltammetry, the specific capacitances were determined to be 44.4 and 66.7 Fg−1 for distinct carbon electrode supercapacitors. The self-discharge characteristics were investigated at both room temperature and close to the freezing point. The internal resistances of the supercapacitors were calculated using the discharge curves at room temperature. The microstructures of the electrode materials were determined using scanning electron microscopy.

Magnesium is an important base material for non-permanent implants, even though its corrosion rate in the human body is usually elevated for most applications. In order to reduce that rate, polymer coatings can be a better option than heavy-metal containing Mg alloys. In this work, random copolymers of PMMA and PMAA were synthesized and used for coating pure Mg by simply immersing Mg coupons into a diluted copolymer solution. It has been shown by SEM analysis and quantitative adsorption analysis that the copolymers have adsorbed onto the Mg surface. All the coated materials presented a lower corrosion rate than the uncoated Mg, reaching close to 100% reduction for most of the copolymer up to 6 hours of testing. The copolymers with 5, 8 and 13% of PMAA in their composition showed the best performances as corrosion controllers.

GONSALVES, T. C. Synthesis of planned copolymers for the coating of metallic magnesium and its alloys. 2019. 81 p. Dissertation (Master of Science)