Mechanical Property and Oxidation Behavior of Self‐Reinforced Si ₃ N ₄ Doped with Re ₂ O ₃ (Re=Yb, Lu)

Abstract

In this work, self‐reinforced silicon nitrides with β‐Si 3 N 4 seeds doped with Re 2 O 3 (Re=Yb, Lu) were investigated. Firstly, the two kinds of seeds were obtained by heating α‐Si 3 N 4 powder with Yb 2 O 3 or Lu 2 O 3 , respectively. Then the self‐reinforced silicon nitride ceramics were prepared by HP‐sintering of α‐Si 3 N 4 powder, Re 2 O 3 as additive, and the as‐prepared seeds. Oxidation test was carried out at 1400°C in air for 100 h with thermogravimetry analysis (TGA) measurement. Mechanical properties, scanning electronic microscopy microstructures, and X‐ray diffraction patterns were measured before and after oxidation. The results indicated that the introduction of the seeds doped with Re 2 O 3 (Re=Yb, Lu) could obviously increase the toughness and keep the room temperature and high‐temperature strength of the ceramics at high values. After oxidation, the crystalline phase in grain boundary changed and the mechanical properties decreased. TGA showed a parabolic weight gain and the oxidation mechanism was discussed.