Abstract:
Al2O3 is one of the most used ceramic oxides that finds a lot of structural applications. The thesis explores a low temperature sintering route of alumina through the addition of sintering additives that employ a hybrid liquid and solid-state sintering enhancements that can potentially promote sintering at relatively low temperatures. The sintering additives used are primarily mixtures of CuO and TiO2 in different combinations. The basis of study was made initially on the interaction of alumina with CuO, added in amount of 1wt%, 3wt%, 5wt% and 8wt%. Afterwards the study of addition of TiO2 was observed in the Al2O3- CuO system mentioned earlier. It was observed that the densification of Al2O3 improved upon the addition of these two aids, in comparison to pure alumina sintered at same temperature(s). The mechanical properties of the sintered pellets were also studied for both the systems and a comparative study was established. It was revealed that the hardness increased by the addition of TiO2 in Al2O3-CuO system. The best results for mechanical properties were obtained for the samples containing a 5wt% of copper oxide. CuO enhanced densification via the formation of a liquid phase at alumina-alumina grain boundaries which enhanced densification kinetics, while the addition of TiO2 creates vacancies in the Al2O3 lattice which promotes solid state sintering. A combination of these two phenomena is expected to promote sintering and densification at relatively lower temperatures, used for sinter alumina conventionally. Upon the addition of the two, densification increased leading to an increase in micro-vickers hardness values from 17.5 GPa to 31.5 GPa at 1300 0C, and from 21.38GPa to 45.66 GPa at 1400 0C. While the compression at 1300 0C of Al2O3- CuO system was 2.284 GPa while upon the addition of TiO2 its value increased to 6.29 GPa. At 1400 0C the value increased from 4.003GPa to 8.34GPa. Further, in alumina multiphase system CuO- TiO2- ZrO2 were added and studied. The optimized concentration i.e 5wt% CuO- TiO2, was considered and ZrO2 (1wt% and 5wt%) was added. The results showed drastic decrease in the densification and mechanical properties of alumina.
