Characterization of nanostructured MgAl2O4 ceramics fabricated by spark plasma sintering.

The aim of this work is to investigate the effect of sintering temperature on the properties of nanostructured spinel (MgAl 2 O 4 )fabricated by Spark Plasma Sintering (SPS). The starting material was a pure spinel (MgAl 2 O 4 ) nanopowder. The sintering was carried out at T =1300 °C, 1350 °C and 1400 °C under a pressure of 73 MPa.The samples sintered at 1300 °C exhibit a finer microstructure (mean grain size is about ~250 nm) than those sintered at 1350 °C and 1400 °C. The relative density is about 99.93% at 1300 °C, 99.63% at 1350 °C and 99.58% at 1400 °C due to the presence of some porosity in the fabricated samples. Samples sintered at 1300 °C have a good transmittance (70% at 550 nm and 78% at 1100 nm) compared to those sintered at 1350 °C and 1400 °C. Due to their high density and fine grain size, samples sintered at 1300 °C exhibit a Vickers micro-hardness Hv=18 GPa, elastic modulus E =228 GPa relatively more important than those measured on samples sintered at 1350 °C (Hv=15 GPa, E =172 GPa,) and at 1400 °C (Hv=12 GPa, E =136 GPa). They present the reverse behavior for fracture toughness k IC (1.05 MPa √m for samples sintered at 1300 °C, 1.43 MPa √m for samples sintered at 1350 °C and 2.23 MPa √m for that sintered at 1400 °C). The tribological behavior of the MgAl 2 O 4 ceramic was equally studied: the friction coefficient µ is measured and increases with sintering temperature µ =0.06, µ =0.13, µ =0.18, respectively for sintering temperature of 1300 °C, 1350 °C and 1400 °C. The wear behavior is also examined and the mass loss increases with increasing sintering temperature. [ABSTRACT FROM AUTHOR]