Effect of CeO2 addition on the properties and microstructures of ZTA ceramics through hot isostatic press sintering
Loading...
Date
2016-06
Authors
Lee Wei Kean
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
The effect of CeO2 addition on the properties and microstructures of zirconia toughened alumina (ZTA) ceramic composites were investigated in this study. The composition of CeO2 was varied from 0 wt.% to 7.0 wt.%. The starting materials was mixed continuously for 8 hours and dried in oven at 90 ºC for 24 hours. The mixture is then subsequently hydraulically pressed into cylinder mould at 300 MPa to formed pellets. The pressed samples were sintered in the hot-isostatic pressing (HIP) at 1600oC for 20 minutes soaking time. For Vickers hardness, the value increased from 1575.7 HV (0 wt.% CeO2) to 1711.3 HV (5.0 wt.% CeO2) and followed by a decline by sample with 7.0 wt.% CeO2 to 1569.0 HV. The highest Vickers hardness obtained at 5.0 wt.% CeO2 sample which also have the highest bulk density (4.48 g/cm3) and lowest percentage of porosity (0.37%). Meanwhile for fracture toughness values, it has similar trend like Vickers hardness. The fracture toughness increase from 5.11 MPa.√m (0 wt.% CeO2) to 5.73 MPa.√m (5.0 wt.% CeO2). The value then decreased rapidly from 5.73 MPa.√m (5.0 wt.% CeO2) to 5.23 MPa.√m (7.0 wt.% CeO2). HIP sintering used in the study greatly reduced the percentage of porosity and hence improve the hardness and fracture toughness. Results of SEM micrographs showed that, the addition of CeO2 produced an elongated grains formed from the presence of CeAl11O18 as secondary phase. Secondary phase play vital role in affecting the fracture toughness; higher percentage of the elongated phase will give higher fracture toughness. In overall, sample of ZTA-5.0 wt.% CeO2 is the best composition with optimum properties.