The interface of aluminum and MgAl2O4 formed naturally during high-temperature oxidation of an aluminum–magnesium alloy was observed in high resolution in a bid to investigate heterogeneous nucleation of aluminum grains on MgAl2O4 particles. Scanning electron microscopy at an ultra-high magnification of 200,000× has clearly detected a thin intermediate layer of about 50 nm, which is conventionally too small to be detected by the microscopy, between aluminum and MgAl2O4. An electron-transmitting specimen was fabricated exactly on the layer in the same chamber without moving it for further sampling. Chemical analyses show that the intermediate layer is composed of aluminum and oxygen, i.e., Al2O3, which means that the thin Al2O3 layer prevents the direct contact of aluminum and MgAl2O4.
- High-resolution image
- Focused ion beam