Sintering Behavior and Properties of NiFe2O4 Ceramic Inert Anode Toughened by Adding NiFe2O4 Nanopowder

NiFe2O4 ceramic inert anode for aluminum electrolysis, strengthened by adding NiFe2O4 nanopowder, was prepared via powder metallurgy method. The effects of NiFe2O4 nanopowder content on sintering behavior and properties of NiFe2O4 ceramic inert anode were studied. Linear shrinkage and scanning electron microscope (SEM) were employed to characterize the sintering property and microstructure. The results show that the sintering shrinkage degree increases gradually as increase of NiFe2O4 nanopowder content, while the sintering temperature and apparent activation energy of initial stage of sintering decrease. When nanopowder content is 40%, the sharp sintering shrinkage begins from 900 degrees C and the apparent activation energy of initial stage of sintering drops to 291.43 kJ/mol. Volume density, bending strength and fracture toughness are enhanced firstly and then decreased with the increase of nanopowder content, while the porosity and static corrosion rate display opposite tendency. The maximum value of fracture toughness is 3.12 MPa.m(1/2) with nanopowder content of 30%, which is 2.14 times that of without adding nanopowder. The toughening effect is realized by the elevated fracture surface energy, which is attributed to the enhanced grain boundary cohesive bond and the reduced porosity with addition of NiFe2O4 nanopowder.