Ceramics International | 2021
Pressureless densification of HfB2-based ceramics using HfB2 powders by borothermal reduction
Abstract
Abstract Using boron and SiC as additives, the pressureless densification of HfB2 powders synthesized by borothermal reduction with water-washing process was studied. The water-washing HfB2 powders showed good sinterability (relative density: 96.2%), due to the small grain size with the in-situ boron impurities, whereas the microstructure of the sintered sample was coarsened with average grain size of 10.19\xa0±\xa04.12\xa0μm. After adding 5\xa0wt% boron, the relative density was improved (98.7%) and the grain size was reduced (4.68\xa0±\xa01.17\xa0μm). In order to further inhibit the grain growth, enhance densification and mechanical properties, 20\xa0vol% SiC was added. Finally, fully dense HfB2-based ceramics (relative density: 99.9%) with small grain size of 3.45\xa0±\xa00.88\xa0μm were fabricated by the combination of boron and SiC. The Vickers’ hardness and fracture toughness of HfB2 with additions of boron and SiC were 18.27\xa0±\xa01.95\xa0GPa and 3.33\xa0±\xa00.16\xa0MPa\xa0m1/2, respectively.