▎ 摘　　要

High brittleness is one of the Achilles' heels that limit wider application of structural ceramics. The toughness of ceramic matrix can be improved by introducing nano reinforcements randomly, however, its improvement is quite limited. Here, we propose a novel layer-by-layer stacking structure (graphene/alumina) by a molecule-level assembling method, in which the graphene nanolayers orientation could be easily tuned in ceramic matrix. As a result, the layer-by-layer ceramic nanocomposite has a dramatically improved fracture toughness of 13.71 MPa m(1/2), similar to 3.2 times of the monolithic alumina (similar to 4.34 MPa m(1/2)). At the same time, the layer-by-layer ceramic nanocomposite shows excellent electrical conductivity of 630 S/m. It is interesting that the electrical conductivity is highly sensitive to the fracture crack, which could be used as artificial intelligent helmet with self-structural integrity-monitoring and fast thermal response capabilities. This strategy paves a facile way to prepare the ultratough ceramic nanocomposites with multifunctional properties.