For EELS measurements hexagonal narrow mesh copper grids were used. Sections were examined in a LEO 912 AB transmission electron microscope (Zeiss, Oberkochen, Germany) with in-column energy filter, operated with a LaB6 cathode and an acceleration voltage of 80 kV for conventional imaging and 120 kV for EELS. Micrographs and EELS were recorded with a slow scan dual speed CCD camera Sharpeye (Tröndle, Moorenweis, Germany), operated by iTEM software (Soft Image System, Münster, Germany).