Low temperature synthesis and sintering of mechanochemically activated ZrB2 and ZrB2 based ceramic and improved mechanical properties

This work covers synthesis of ZrB2 powder by citrate gel method, producing ZrB2 and ZrB2 based composites by pressureless sintering at low temperatures, mechanochemical activation of powders and mechanical characterization of samples.Pure ZrB2 was obtained 1500 ? C by citric acid gel method with 1.6 m2/g surface area and dXRD: 60 nm crystallite size. Citric acid/cation mole ratio was determined as an important parameter on the formation of single phase zirconium diboride. By changing these parameters, the formation temperature of ZrB2 was reduced down to 1350 ? C by mechanical activation of gels.The effect of mechanical activation on powders was examined by peak broadening of XRD data. The crystallite size of nonactivated to activated powder was changed whereas the lattice strain was increased.The sintered density of mechanochemically activated zirconium diboride without sintering aids was reached 86%at 1750 °C and the hardness of these samples was calculated as 4.8 GPa under load of 9.8 N. The addition of second Fe into zirconium diboride was obtained sintered density 99.9%. at 1750 ?C. Non-activated ZrB2-ZrO2 has 57%sintered density at 1750 °C however; activated one was reached up to 91%. The hardness values of these samples were varied from 1.65 to 14.95 GPa.