Three types of samples were scanned to observe their microstructure, not only surface structure but internal one as well. The samples were industrial copper matte, industrial fayalite slag, and laboratory-treated (doped) copper matte. The XCT results managed to show all the sought differences, e.g. glassy structure, microcracks and distribution of inclusions. Samples are described in Sibarani, D., Hamuyuni, J., Luomala, M., Lindgren, M., Jokilaakso, A., 2020. Thermal Conductivity of Solidified Industrial Copper Matte and Fayalite Slag. Heat Transfer Utilization in Pyrometallurgy. To get this dataset, please contact fairdata-pas@gtk.fi. Preview dataset found at https://doi.org/10.23729/eb1eeec0-8fd9-4ce9-a1c2-76792d7103e5

2020