In Situ Graded Ceramic/Reduced Graphene Oxide Composites Manufactured by Spark Plasma Sintering

The present work merges two key strategies for the manufacturing of advanced ceramics, in particular, the development of functionally graded materials (FGMs) and the addition of graphene-based fillers into a ceramic matrix. A silicon nitride/reduced graphene oxide FGM composite is produced, in one step, from a single powder composition using the spark plasma sintering (SPS) technique with an asymmetric setting of the punches and die to create a continuous temperature gradient along the cross section of the powder compact. A deep microstructural and mechanical characterization has been done across the specimen thickness. The FGM composite exhibits bottom-top gradients in both the matrix grain size (150% increase) and alpha-phase content (89 -> 1%). The FGM bottom surface is 10% harder than the top one and, on the other hand, the latter is 15% tougher. The presence of reduced graphene oxide sheets homogeneously distributed within the ceramic composite reduces the mechanical gradients compared to the monolithic silicon nitride FGM, although allows reaching a maximum long-crack toughness value of 9.4 MPa center dot m(1/2). In addition, these graphene-based fillers turn the insulating ceramics into an electrical conductor material.

Automated summary

The study successfully combines two key strategies for manufacturing advanced ceramics, developing functionally graded materials and adding graphene-based fillers to a ceramic matrix. A silicon nitride/reduced graphene oxide FGM composite is produced using spark plasma sintering (SPS) technique. The FGM composite exhibits gradients in matrix grain size and alpha-phase content, and the presence of graphene-based fillers reduces mechanical gradients compared to monolithic silicon nitride FGM.