Banca de QUALIFICAÇÃO: EDSON SILVA DO NASCIMENTO

Study of sintering and anodic oxidation in the production of a niobium electrolytic capacitor

niobium electrolytic capacitor, sintering, anodic oxidation.

In this work, an alternative to current tantalum electrolytic capacitors on the market was studied, due to their high cost. Niobium was used for this, since it is a potential substitute for this application, as it is lighter and cheaper than tantalum. They belong to the same group on the periodic table and thus have many similar physical and chemical properties. Niobium is used in several technologically important applications and Brazil has the largest reserves in the world, around 96%. These electrolytic capacitors have high specific capacitance, that is, they can store high amounts of energy in small volumes compared to other types of capacitors. This is the main attraction of this type of capacitor, as there is a growing demand in the production of capacitors with an increasingly high specific capacitance, due to the miniaturization of various electronic devices, such as GPSs, televisions, computers, cell phones and many others.. The production route of the capacitor was made by powder metallurgy. The initial niobium poder was first characterized by XRD, SEM and laser particle size to then be sieved into particle size 400mesh. The powder was then compacted at pressure of 100MPa and sintered at 1400, 1450 and 1500°C using two sintering time 30 and 60min. After sintering, the samples underwent an anodic oxidation process (anodization), where a thin surface layer of niobium pentoxide is created over the entire surface of the sample. An electronic circuit was created so that the anodizing of the samples was controlled throughout this process. The variables of the anodizing process greatly influenced the formation of the film, and consequently, the electrical properties of the capacitor. The samples were then characterized by means of electrical measurements of capacitance, dissipation factor and ESR (equivalent series resistance). Sintering modifies the porosity of the samples, influencing the results of electrical measurements. The best results were obtained for the sintering temperature of 1400°C with the baseline of 60 minutes.