In-situ synthesis of Medium-Entropy (HfZrTi)B2 Ceramic Composite from Initial Oxide Powders

Abstract

In the current work, the B2 medium-entropy, ceramic composite (HfZrTi)B2 was in situ synthesized through reactive spark plasma sintering (RSPS) at 2000 °C and at two loadings of B4C powder, 10 minutes. The obtained specimens were described based on the microstructure, relative density, hardness, and fracture toughness. The data show that the increase in the B4C content significantly enhances the reduction reaction of the oxide precursors, therefore, leading to the formation of the (HfZrTi)B2 phase to a higher degree. The lattice-parameter calculations provided a value of 14.7668 A of the stoichiometric composition and a value of 3.14985 A of the sample with the increased B4C content, which has validated the insertion of a larger lattice distortion in the sample with the higher B4C content. Additionally, the specimen with higher B4C also obtained a lower porosity of 12.9% and a hardness value of 10.6 Gpa, as compared to the other specimen with lower B4C loading, which had a porosity of 17.7% and a hardness of 9.4 Gpa. The fracture toughness could not be measured due to relatively high porosity.