Microstructural Parameters for Modelling of Superconducting Foams

Abstract

Superconducting YBa2Cu3Oy (YBCO) foams were prepared using commercial open-cell, polyurethane foams as starting material to form ceramic Y2BaCuO5 (Y-211) foams which are then converted into superconducting YBCO by using the infiltration growth process. For modelling the superconducting and mechanical properties of the foam samples, a Kelvin-type cell may be employed as a first approach like done in the literature for pure polyurethane foams. However, for a refined model of a superconducting foam sample, the real sample structure must be considered. Thus, a proper description of the specific microstructure of the superconducting YBCO foams is required. A variety of parameters including the cell size and shape, the window size and shape, the length and shape of the foam struts or ligaments and the respective angles of intersection are used to describe the real foam structure. To obtain a set of reliable data, YBCO foam samples were investigated using optical microscopy, SEM and electron backscatter diffraction (EBSD). The detailed investigation of the foam microstructure reveals not only the differences to the polymeric foams used as base material, but also gives insight to details of the infiltration growth process via the increased surface amount in a foam sample.