Coated beads and bead structures based on aluminium oxide and niobium using alginate gelation

Spherical beads consisting of 70% Al 2 O 3 and 30% niobium were produced using alginate gelation. The suspension for producing the beads contained sodium alginate as gelling agent and was added dropwise to a calcium chloride solution to serve as a solidifying agent. The beads were then coated with 100% Nb-slurry. After drying, the composite spheres were sintered in an inert atmosphere. The samples in green and sintered state were characterised using various testing methods and processed into bead structures. On the one hand, they were used as aggregates in casting slurry, whereby the matrix contained niobium in one case and pure Al 2 O 3 in the other. In addition, the beads were bonded into structures using a Nb-matrix and isostatic pressing. After sintering, electrical resistance was measured to evaluate whether coupling is possible. It was found that a matrix of Al 2 O 3 is sufficient for coupling, and thus the Nb-content can be significantly reduced.