Estudo das propriedades de pastilhas e fios supercondutores do sistema BSCCO dopados com compostos nanoparticulados de cálcio

• Ano de defesa: 2014
• Autor(a) principal: Nogueira, Natacha Andréia [UNESP]
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Estadual Paulista (Unesp)
• Palavras-chave em Português: Supercondutores; Fios; Raios X - Difração; Microestrutura; Superconductors
• Link de acesso: http://hdl.handle.net/11449/110884

The present work was designed to test the addition of a little proportion (1 wt,%) of two calcium compounds, calcium silicate and calcium e o zirconate, in the preparation of Bi:2212 silver sheathed wires, which were successfully tested in processing of melt-textured pellets and were observed in the microstructure in function of the use calcium compound. Three heat treatments with nearby values to the maximum temperatures, but slightly different were applied to the wires in O2/Ar atmosphere using the partial-melting method. Analysis of X-ray diffraction performed in the removed powder from the ceramic core of treated wires showed the predominance of the Bi:2212 phase, despite of the presence of a multiphasic character for the samples. Thermogravimetry and differental thermal analysis were performed in the ceramic powders used to prepare the wires. Observations of longitudinal and cross sections of the wires performed in a scanning electron microplate presence of the superconductiong phase accompanied by more or less segregation of phase rich in copper. The treatments with higher maximum temperatures are more effective to improving the superconducting properties that were evaluated that were evaluated using tranport and megnetic measurements. The critical temperatures were higher that 100K. The critical current densities obtained by transport measurments ranged from 3.44/cm2 (reference wire treated up 880ºC) to 38.8A/cm2 (wire with addition of CaSiO3) treated up 883ºC), this higher value is related to microstructure with addition of CaSiO3 treated up 883ºC), this higher value is related to microstructure with a higher proportion of microplates and smaller proportion of segregated phase. The critical current density determined by magnetization produced much higher values because they are based on a critical model, the Bean Model. The same wire observed like the better in electrical measurements also also showed higher values when...