Abstract
In this investigation, a novel process for the synthesis of nano-ZrO(2) powders based on high-temperature mechanochemical technology (HTMT) in a short process is proposed and HTMT nano-ZrO(2) enhancement mechanism as an additive on the properties of B(4)C ceramics was systematically investigated. ZrO(OH)(2) was used as a precursor, and ZrO(2)-B(4)C composites were prepared by optimizing the ball milling temperature and time in combination with the hot-press sintering technique. The results demonstrated that the high-temperature mechanical force causes the transition temperature of ZrO(2) from monoclinic to tetragonal crystal system to be decreased to 500 °C. The ZrO(2) treated by high-temperature ball milling at 600 °C/6 h exhibits lower microstress, higher crystallinity, and a particle size of only about 9.12 nm. HTMT nano-ZrO(2) effectively controls the size of in situ generated ZrB(2) particles in B(4)C ceramics, reduces interfacial porosity and grain coarsening, and promotes densification of B(4)C ceramics compared to commercially available nano-ZrO(2). With the addition of 4 wt% HTMT nano-ZrO(2), the composite showed optimal comprehensive properties: relative density of 99.75% (2.57 g/cm(3)), fracture toughness of 4.74 MPa/m(1/2), flexural strength of 266.61 MPa, Vickers hardness of 31.14 GPa, and fracture mode with mixed mechanism of through-crystallization and along-crystallization.