Thin foil preparation for AEM study of small metal particles in stony meteorites

Abstract

The phase transformation processes and phase equilibria of the Fe-Ni and Fe-Ni-S system at low temperature can be better understood by characterizing the microstructure and chemistry of metallic particles in stony meteorites using analytical electron microscopy (AEM) techniques. However stony meteorites have a composite nature consisting of metal particles embedded in an inherently brittle silicate matrix, which causes a differential thinning rate. The thin foil preparation of the metal particles for AEM has proved to be very difficult, and we report on the first successful specimen preparation.Materials of this type present particular difficulties in the preparation of thin foil specimens because the area of interest is limited to specific regions within the metal particles. The metal particles are usually less than 500 μm in size and the silicate matrix is inherently brittle. Moreover, the interfaces between metal particles and silicates are weak because of corrosion, depending on cooling, etc.