Fabrication and characterization of aluminum hybrid composites reinforced with silicon nitride/graphene nanoplatelet binary particles

In this study, pure aluminum was reinforced with pure silicon nitride (varying from 1 to 12 wt%), pure graphene nanoplatelets (changing from 0.1 to 0.5 wt%), and their hybrid form (silicon nitride/graphene nanoplatelets) by using powder metallurgy method. The results show that Vickers hardness increased to 57.5 +/- 3 HV (Al-9Si(3)N(4)) and 57 +/- 2.5 HV (Al-0.1GNPs) from 28 +/- 2 HV (pure aluminum). Similarly, ultimate compressive strength of the pure silicon nitride and pure graphene nanoplatelet-reinforced aluminum composite was improved to 268 +/- 6 MPa (Al-9Si(3)N(4)) and 138 +/- 4 MPa (Al-0.5GNPs) from 106 +/- 4 MPa (pure aluminum), respectively. Interestingly, the highest Vickers hardness, ultimate compressive strength, and ultimate tensile strength of aluminum-silicon nitride-graphene nanoplatelet hybrid composites were determined as 82 +/- 3 HV (Al-9Si(3)N(4)-0.5GNPs), 334 +/- 9 MPa (Al-9Si(3)N(4)-0.1GNPs), and 132 MPa (Al-9Si(3)N(4)-0.1GNPs), respectively. The Vickers hardness (for Al-9Si(3)N(4)-0.5GNPs), ultimate compressive strength (for Al-9Si(3)N(4)-0.1GNPs), and ultimate tensile strength (for Al-9Si(3)N(4)-0.1GNPs) improved similar to 193%, similar to 215%, and similar to 47% when compared to pure Al, respectively. Above 9 wt% silicon nitride and 0.1 wt% graphene nanoplatelets content, an adverse effect was observed due to the agglomeration of silicon nitride and graphene nanoplatelets in aluminum matrix composites. Also, energy-dispersive X-ray and scanning electron microphotographs confirmed the presence of both silicon nitride and graphene nanoplatelets and uniformly distributed in the aluminum matrix.