Graphene-Si3N4 nanocomposites: powder synthesis, Spark Plasma Sintering, microstructure and properties
BERRAIS A. 1, WEIBEL A. 1, CHEVALLIER G. 1,2, ESVAN J. 3, ESTOURNES C. 1, LAURENT C. 1
1 Université Toulouse 3 / CIRIMAT, Toulouse, France; 2 CNRS / PNF2, Toulouse, France; 3 Toulouse INP / CIRIMAT, Toulouse, France
The dispersion of graphene in a ceramic matrix can lead to composites with interesting physical and mechanical properties [1-4]. Samples are usually prepared by methods that involve mixing a ceramic powder with more or less defective graphene agglomerates, followed by consolidation by sintering. This results in a microstructure where platelets of a few layers of graphene (few-layered-graphene - FLG) are dispersed as discrete particles in the ceramic matrix.
However, it is possible to prepare graphene-ceramics powders without mixing, by subjecting a powder bed to a heat treatment causing the decomposition of a carbonaceous gas, which results in the formation of a deposit of few-layer-graphene (FLG), with typically 1-8 layers, around the ceramic grains. Moreover, the microstructure after sintering then consists of a continuous FLG film, located along the matrix grain boundaries, unlike the samples prepared by a mixing route.
Graphene-Si3N4 powders and samples sintered by Spark Plasma Sintering are studied by techniques including carbon assays, Raman and XPS spectroscopy, scanning and transmission electron microscopy. The role of the presence of FLG on densification, electrical conductivity, microhardness and mechanical reinforcement will be presented and discussed. This method is by nature versatile and results obtained for FLG-MgO , FLG-Al2O3  and FLG-3Y/ZrO2  nanocomposites will be presented.
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