Toughening of MgAl2O4 spinel/ Si3N4 nanocomposite fabricated by spark plasma sintering

The main objective of this work is to compare the hardness, fracture toughness, and optical transparency of MgAl₂O₄ spinel (magnesium aluminate), MgAl₂O₄ spinel/ Si₃N₄ nanocomposite, and the heat-treated spinel/Si₃N₄ nanocomposite. For this purpose, the commercial spinel nanopowder and the laboratory-made spinel/ Si₃N₄ nanocomposite powder were sintered using spark plasma sintering (SPS). A heat treatment at 1000?°C for 4?h was carried out on the as-sintered nanocomposite. The field emission scanning electron microscopy (FESEM), Energy dispersive X-ray (EDX) mapping, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Nanoindentation, and Vickers microhardness analyses were used to determine microstructure, elemental analysis, functional group, hardness, and indentation toughness of the samples. The results showed that the hardness and toughness of the heat-treated sample are more than those of the as-SPSed nanocomposite as much as 15.7% and 25.7%, respectively. Also, the values of optical transmission of the nanocomposite sample in the visible range (400–800?nm) and infrared region (800–2000?nm) were lower than those of pure spinel.