| 研究実績の概要 |
I studied the kinetics of grain/grain/melt triple junctions of Σ9 grain boundaries (GBs) in Si through seeded experiments. A series of experimental methods have been developed to achieve this goal, which include: (1) A procedure for cutting Si seeds with accurate tilting angles; (2) Modification of in situ observation furnace for better temperature control; (3) A new method fixing the seeds on quartz plates enabling good seed alignment throughout experiments; (4) A treatment for fragile as-grown samples has been developed to create fine surface without cracking for subsequent SEM and EBSD analysis.
I have found some interesting phenomena: (1) Three out of four symmetric Σ9 GB types studied were frequently twinned during experiments. Only type-2 Σ9 GBs were stable and less twinned; (2) Type-2 Σ9 GBs did not develop groove at solid/melt interface when the deviation from perfect one was low. However, a type-2 Σ9 GB with a deviation of 4.8° was found developing interfacial groove during growth. The results suggest that the formation of interfacial groove may depend on the energy of the participating GBs. The more a Σ9 GB deviates from a perfect one, the higher the GB energy, and, as a result, the GB groove develops at solid/melt interface due to different kinetics at the triple junction; (3) Σ19a GBs were also observed growing stably during directional solidification. This type of GBs is generated by twinning and capable of developing interfacial grooves with large enough deviation.
Other relative results about Si and Si-Ni alloy have been published or presented.
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