High-pressure spark plasma sintering and mechanical properties of dense uranium hydride consisting of β-UH3 and UH2

Abstract

Uranium hydride (UH_3-x) has the nature of physical disintegration and thermal decomposition. In this study, dense UH_3-x consisting of β-UH₃ and UH₂ is synthesized via high-pressure spark plasma sintering (HPSPS) under high-temperature exceeding conventional thermal dehydrogenation thresholds. The implementation of 700 MPa uniaxial pressure during sintering effectively suppresses thermal decomposition (β-UH₃ → α-U). Sintering temperatures above 600 °C are essential to achieve full densification and crack mitigation. Significantly, an unreported β-UH₃ → UH₂ phase transition is discovered, providing novel insights into metastable phase evolution within the U-H system and establishing a direct synthesis pathway for UH₂. Finally, the mechanical properties of dense UH_3-x are experimentally measured.