Microstructure and Fracture Mechanism Investigation of Porous Silicon Nitride-Zirconia-Graphene Composite Using Multi-Scale and In-Situ Microscopy.

ABSTRACT: Silicon nitride-zirconia-graphene composites with high graphene content (5 wt.% and 30 wt.%) were sintered by gas pressure sintering (GPS). The effect of the multilayer graphene (MLG) content on microstructure and fracture mechanism is investigated by multi-scale and in-situ microscopy. Multi-scale microscopy confirms that the phases disperse evenly in the microstructure without obvious agglomeration. The MLG flakes well dispersed between ceramic matrix grains slow down the phase transformation from ? to ?-Si₃N₄, subsequent needle-like growth of ?-Si₃N₄ rods and the densification due to the reduction in sintering additives particularly in the case with 30 wt.% MLG. The size distribution of Si₃N₄ phase shifts towards a larger size range with the increase in graphene content from 5 to 30 wt.%, while a higher graphene content (30 wt.%) hinders the growth of the ZrO₂ phase. The composite with 30 wt.% MLG has a porosity of 47%, the one with 5 wt.% exhibits a porosity of approximately 30%. Both Si₃N₄/MLG composites show potential resistance to contact or indentation damage. Crack initiation and propagation, densification of the porous microstructure, and shift of ceramic phases are observed using in-situ transmission electron microscopy. The crack propagates through the ceramic/MLG interface and through both the ceramic and the non-ceramic components in the composite with low graphene content. However, the crack prefers to bypass ceramic phases in the composite with 30 wt.% MLG.

SUBMITTER: Liao Z 

PROVIDER: S-EPMC7911286 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature