Contribution of in-situ experiment in a high resolution/analytical electron microscope to materials science.

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A new specimen-heating holder for use of in-situ experiments in an electron microscope was developed. This holder allows observation at near-atomic resolution of phenomena which occur at temperatures as high as 177 3K.Also, it allows elemental analysis from nanometer scale area. Various unsolved problems in materials science have been attacked using this powerful new tool as is descibed in the following :1) Solid-Liquid Reactions (Melting, Solidification and Liquid-Phase Sintering)Melting and solidification processes of Al (metals) and alumina (ceramics) were observed and the atomic structure of the solid-liquid interfaces were analyzed. In Al melting initiates at the crystal surface. The solid-liquid interface in Al is atomically rough, while that in alumina is flat. Reactions between solid Fe and molten Zn were also observed for the first time by TEM.2) Solid-Solid Reactions (Grain Boundaries and Interfaces)It was observed that a grain boundary in Cu-Ga intermetallics vibrates strongly. The vibration depends on temperature and accelerating voltage of the electron microscope. It is suggested that the vibration is induced by point defects. Reaction between Au and Si surface was observed at near-atomic resolution. Surface of Si becomes clean after Au melts on the surface of Si, even it was initially covered with a native oxide. As a result, surface reconstruction took place.3) Solid-Gas Reactions (Oxidation and Reduction)When silica is reduced the Si/silica interface vibrates strongly.