Evaluation of Critical Parameters for the Fabrication of Metal Hollow Spheres Using an Alginate‐Based Sol–Gel Process

Abstract

This study focuses on the fabrication of metal hollow spheres using an alginate‐based sol–gel technology in combination with a freeze‐drying process. The mixing routine for the metal slurry is investigated. Critical processing parameters, influencing the yield of intact spheres such as the aging time in the reaction solution and in water as well as the freezing time and the rotation of the spheres during freezing are evaluated with statistical design of experiments. A customized debinding regime is developed with a heating rate of 0.1 K min−1 in critical temperature ranges and a maximum temperature of 350 °C. For the fabrication of hollow metal spheres with additions of 1.0 wt% potassium alginate, the optimum aging time in Ca(OH)2‐reaction solution is 4 min (4C) and the spheres are only to be rinsed with purified water (0 W). Furthermore, the rotation of the spheres (+R) during freezing significantly contributes to the increased yield of 80.2%, which is significantly higher as compared to the previous studies. Sintered spheres have a compressive strength of 159 MPa with a corresponding strain of 42%.