Research about pressureless sintering of milled powder zrb2 based ceramic with carbon

This study was about Zirconium diboride powders with a 2 wt% of graphite, the mixture was grounded at different time in Argon atmosphere, with high energy ball milling. The as-purchased powder was milled from micrometer size, until nanoparticles. Then were product specimens with uniaxial press and after with isostatic press. The green bodies were sintered without external pressure at different temperatures, from 1800°C until 2100°C. The effects of initial particle size and carbon on densification, microstructure were investigated. Even if the operating conditions were not totally developed in controlled atmosphere, so there were problem of oxidation due to high reactivity of nanoparticles. Graphite is an effective process control agent for HEBM and removes the oxides present in the specimens, to promote with vacuum, the sintering at lower temperature. Relative density increased from ~71% for not milled powders at 1800°C, to 98% for 180 minutes milled powders at 2100°C.