Few-layered-graphene/zirconia composites: Single-step powder synthesis, spark plasma sintering, microstructure and properties

Abstract

The chemical vapor deposition of carbon is performed onto a commercial yttria-stabilized zirconia (3YSZ) powder bed. This produces few-layered-graphene (FLG) film uniformly covering the 3YSZ grains, without the manipulation of any pre-existing nanocarbon in the form of graphene platelets. The powders are then consolidated by spark plasma sintering, producing specimens where FLG is located along the grain boundaries of the 3YSZ matrix, which is below 0.3 μm in grain size. The samples are characterized by Raman spectroscopy, X-ray photoelectron spectroscopy, scanning and transmission electron microscopy. The pure 3YSZ exhibits higher toughness and fracture strength compared to composites, but the trend is that their toughness increases upon the increase in carbon content. Crack-deflection and crack-bridging are observed. The composites are electrically conducting with a percolation threshold between 1.48 and 1.98 vol.% of carbon, reflecting the continuous nature of the FLG film over very long distances.