Densification, hydrogen retention, microstructure, and mechanical properties of ε-ZrH2- monolith fabricated by high-pressure spark plasma sintering

The sintering of zirconium hydride (ZrH2-x) without hydrogen atmosphere faces the challenge of thermal dehydrogenation problem, which is overcome by the high-pressure spark plasma sintering (HPSPS) technique in this study. The application of high pressure remarkably reduces the initial densification temperature and effectively restrains the thermal dehydrogenation of ZrH2-x in SPS. Under 500 MPa loading, ε-ZrH1.72 monolith with high densification (96.62%) and high hydrogen density (6.04 × 10 22 atoms H/cm3) is sintered at a relatively low temperature of 700 °C for only 5 min. Meanwhile, the grain growth of ZrH2-x is very limited. The Young's modulus and hardness of the sintered ε-ZrH1.72 are 58.68 GPa and 2.61 GPa respectively. Compared with the directly hydrided ε-ZrH2-x, the sintered ε-ZrH1.72 has a more uniform hardness distribution and improved fracture toughness of 3.19 MPa m1/2. This study provides a valuable reference for the sintering of other easily decomposable materials.