▎ 摘　　要

Si3N4 composites with 3 and 5 wt% of graphene nanoplatelet (GNP) additions were prepared by spark plasma sintering. We used both commercially available GNPs and thinner few-layer graphene nanoplatelets (FL-GNPs) prepared by further exfoliation through ball milling with melamine addition. We found that by employing thinner FL-GNPs as filler material a 100% increase in the fracture toughness of Si3N4/3 wt% FL-GNP composites (10.5 +/- 0.2 MPa m(1/2)) can be achieved as compared to the monolithic Si3N4 samples (5.1 +/- 0.3 MPa m(1/2)), and 60% increase compared to conventional Si3N4/3 wt% GNP composites (6.6 +/- 0.4 MPa m(1/2)). For 5 wt% filler content the increase of the fracture toughness was near 50% for both GNP and FL-GNP fillers. The hardness of the composites decreased with increasing GNP content. However, composites reinforced with 5 wt% of FL-GNPs displayed 30% higher Vickers hardness (12.8 +/- 0.2 GPa) than their counterparts comprising conventional GNP fillers (9.8 +/- 0.2 GPa). We attribute the enhanced mechanical properties obtained with thinner FL-GNPs to their higher aspect ratio leading to a more homogeneous dispersion, higher interface area, as well as smaller pores in the ceramic matrix