The Microstructure and Mechanical Properties of Silicon Carbide Containing Graphene Nanoplatelets Sonicated for Different Times

Abstract

Graphene platelets (GPLs) are widely preferred as a second phase to improve the properties of advanced technology ceramics thanks to their excellent mechanical properties. However, their agglomeration tendency requires the application of dispersion processes before mixing with matrix powders. Sonication is the most commonly used technique for the dispersion of GPLs. In this study, the effects of adding GPLs prepared at different probe-sonication times such as 1, 2, 4 and 6 h on the microstructure and mechanical properties of spark plasma sintered (SPS) silicon carbide (SiC) were investigated. Scanning electron microscopy (SEM) examinations and size measurements revealed that the size of GPLs decreased with increasing sonication time. However, the reduction in the size of the GPLs was very low up to the 2 h sonication time and became more pronounced at the GPLs prepared at 4 and 6 h sonication times. Raman analyses indicated that dispersions of GPLs agglomerates increased as well as defects and/or disorders in their structures with increasing sonication time. However, the thickness of the well-dispersed GPLs obtained at the 2 h sonication time did not change when the sonication time was increased to 4 and 6 h. The highest increment in the fracture toughness of SiC matrix in both the throughplane (//) and in-plane (٣) directions was achieved with the addition of GPLs sonicated for 2 h among the GPLs prepared at different sonication times. The higher contribution of 2 h sonicated GPLs to fracture toughness than non-sonicated and 1 h sonicated GPLs was associated with their more homogeneous distribution in the matrix microstructure, while higher toughness values they provided compared to 4 and 6 h sonicated GPLs could be explained by the positive effect of their higher lateral size and aspect ratio. GPLs have improved the fracture toughness of SiC matrix with the help of bridging and deflection toughening mechanisms.

Keywords

• graphene platelets (gpls)
• sonication time
• fracture toughness
• silicon carbide