Formation of β-zirconia and γ-zirconia nano-particles from α-zirconia by mechanical activation

The phase transformation of zirconia and formation of beta-zirconia and gamma-zirconia nano-particles from alpha-zirconia by mechanical activation were studied. alpha-zirconia powder (with monoclinic structure) for 2-150 h and 40:1-60:1 ball-to-powder weight ratio (BPWR) was ball milled. The effect of milling variables on this process such as BPWR and milling duration was also investigated. Structural evaluations were analyzed using X-ray diffraction and a scanning electron microscope (SEM). Results showed, however the phase transformation of alpha-zirconia to beta-zirconia (with tetragonal structure) at 1250 degrees C after eight hours was not performed, beta-zirconia and gamma-zirconia (with cubic structure) could be achieved by ball milling of alpha-zirconia at room temperature. Results shown that alpha to beta phase transformation began after two hours milling and completed after 48 h. Moreover, alpha to gamma phase transformation completed after 150 h milling with 40:1 BPWR. In addition, using Williamson-Hall equation indicated that the particle size of zirconia powder was reduced down to 30 nm and obtained the equilibrium point after 48 h milling. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.