Few-layered graphene - Si3N4 nanocomposites prepared by Spark Plasma Sintering: Microstructure and properties

Abstract

The Spark Plasma Sintering of few-layer-graphene (FLG)-Si₃N₄ powders, prepared by the chemical vapor deposition of carbon from methane, produces dense nanocomposites for samples with up to 24.9 vol% of carbon. The samples are characterized by several techniques including Raman spectroscopy, scanning and transmission electron microscopy. The reorganization of the FLG islands/films into FLG nanoplatelets is avoided if moderate amounts of sintering additives are used, therefore minimizing liquid phase formation. A novel microstructure with FLG films at the grain boundaries of Si₃N₄ is obtained for a sample with very high carbon content. This sample shows high electrical conductivity (15.7 S/cm), moderate fracture strength (320 MPa) and SENB toughness (3.8 MPa.m^1/2), low microhardness (5.6 GPa) and low friction coefficient against a WC-Co ball due to the formation of a carbon tribofilm in the contact. Controlling the carbon content and the FLG microstructure (platelets and/or films) gives properties that may fit different applications.