The effect of different graphene nanoplatelets addition on mechanical, thermal and electrical properties of sialon ceramics

SiAlON ceramics have a wide range of application areas such as aviation, automotive and defense industries thanks to their superior properties. In addition, improvements in mechanical, thermal and electrical properties of SiAlONs leads to new application areas as well as longer service life. When the graphene nanoplatelets (GNPs) with excellent mechanical, thermal and electrical properties are added as a second phase to the ceramic matrices, they dramatically improve the properties of the material. However, different mechanical, thermal and electrical performances have been obtained in different studies even when same/close amounts of GNPs were added to the same matrix. The most important reason for this is the use of GNPs having different properties from each other. In this study, four different GNPs with different platelet size, thickness (number of platelets) and size/thickness ratios were added to SiAlON matrix and composites were sintered in spark plasma sintering (SPS) furnace. The microstructures, mechanical properties such as hardness, fracture toughness and friction coefficient and also thermal, electrical conductivities of GNP-SiAlON composites were compared. Additionally, to reduce the thickness, microfluidization technique was applied in 1, 2, 4 and 8 cycle numbers to one of the GNPs used during the study. The effects of different cycle numbers on the GNPs dimensions and thicknesses and also on the mechanical properties of the matrix were investigated. It was determined that the highest increment in the mechanical properties, thermal and electrical conductivity of the SiAlON was achieved by GNPs with larger platelet size, higher size/thickness ratio and thinner structure. Keywords: SiAlON, GNP, Platelet size, Thickness (Number of platelets), Microfluidization.