The Influence of Al_2O_3 and TiO_2 Additions on the Sintering Behavior of Partial Reaction Bonding Silicon Nitride

摘要

To compare the influence of Al_2O_3 and TiO_2 on the sintering behavior of partial reaction bonding silicon nitride (RBSN) and post densification behavior, different amounts of Al_2O_3 or TiO_2 have been added into Si-Si_3N_4-Y_2O_3 system. The results indicated that a high amount of Al_2O_3 addition inhibited the reaction bonding process, a lower nitridation degree was obtained, while TiO_2 has limited influence on nitridation, only slightly decreased nitration degree with increasing TiO_2 addition. After post sintered at 180CC, a density ranging from 2.31 to 3.09g/cm~3 were obtained with additions of Al_2O_3 and TiO_2, much larger than the one without them. The linear shrinkage of post-sintered samples was strongly promoted with high Al_2O_3 content, but it was irrelevant with the amount of TiO_2. The highest bending strength of 523MPa can be obtained with addition of 6wt% Al_2O_3. TiO_2 transformed into TiN which located at grain boundary interfaces, restraining the grain growth of β-Si_3N_4 and leading to an inferior flexural strength after post sintered at 1800°C.