The Fabrication of ZrO2-ZrC Microspheres by Internal Gelation and Carbothermal Reduction Process

ZrO2-ZrC (ZrCO) ceramic microspheres were fabricated by combination of internal gelation and carbothermal reduction process. The internal gelation broth containing carbon powders was prepared and stored at room temperature of 25 degrees C to form a precursor of microspheres. By dropping droplets of the broth into hot silicone, the gel microspheres would solidify within a few seconds by decomposition of hexamethylenetetramine (HMTA). The dispersability of the carbon powders in the broth is the key factor to producing ZrCO microspheres with uniform density distribution, as zirconium carbides are generated by the direct reduction of ZrO2 with carbon. The ZrCO ceramic microspheres fabricated with various mass ratio of ZrO2 and ZrC have good sphericity and no cracks through optimizing washing and heat treatment process.