A forming technique to produce spherical ceramic beads using sodium alginate as a precursor binder phase

The purpose of this study was to improve the forming techniques and parameters for producing spherical ceramic beads using sodium alginate as a sacrificial template. This process has the potential of producing beads for applications such as stress-wave propagation of granular media, beads for milling, catalyst support, and encapsulation of drugs, as well as water filtration. This simple, inexpensive, and environmentally friendly approach to producing spherical ceramic beads using bead-forming equipment occurs when a flat-tipped needle produces droplets that cross-link, forming green bodies upon contact with CaCl₂ solution. An exchange of ions takes place where sodium alginates substitute their Na⁺ for Ca²⁺ to form semirigid bodies. Spherical ceramic beads using 50 wt% alumina suspension with 0.04 wt% polyacrylate dispersant are produced when: the viscosity of the slurry is below 0.3 Pa·s, the surface tension of the gelling solution is below 50 mN·m, and the distance of the nozzle tip to the reacting solution is ~3 cm. This approach for producing ceramic beads using alginates will allow its use for any type of ceramic material, changing its chemical composition, and controlling the microstructure and shape of the beads.