Structure and mechanical properties of zirconium oxide modified with carbon nanotubes

Results of experimental investigation of mechanical properties of synthesized composite “zirconium oxide - multiwalled carbon nanotubes” are presented in this paper. Ceramic composite was produced on the basis of hydrothermal synthesis from zirconium salt solution with dispersed carbon nanotubes followed by critical point drying of hydrogel and thermal treatment of obtained aerogel. Zirconium oxide/carbon nanotubes aerogel fragments were then sintered in order to obtain bulk sample in the form of tablet by hot pressing technique. Mechanical properties of composite were investigated with microindentation system NanoTest. Experiments on single loading with different values of maximum applied load in range 100...500 mN were conducted. Elastic modulus and hardness of the composite were calculated from experimental indentation curves with standard Oliver-Pharr model. Energy dissipated into the material during indentation and energy of elastic recovery during unloading stage were calculated as areas under corresponding parts of indentation curves. It was found that composite microhardness is a power law function of indentation depth, whereas elastic modulus linearly decreases with increasing indent depth. Synthesized composite exhibits huge fraction of energy dissipated into material which increases with increasing load/indentation depth. Moreover, for all investigated values of maximum applied loads there were no cracks in the edges of indentation trace. The obtained results have shown that synthesized composite is highly effective in suppressing the cracks growth. Aforementioned regularities of mechanical behavior of composite can be linked with its phase composition as well as with presence and arrangement of carbon nanotubes in ceramic matrix.