In situ high-temperature TEM observation of material escape from a surface of CoFeNi/Cu/ZrAlO composite into the amorphous carbon layer

Abstract

We observed the moment of material escape from a surface of CoFeNi/Cu/Zr(Al)O2 composite into the amorphous carbon layer when we studied the phase transformation of the structure using in situ transmission electron microscopy (TEM) technique at 800°C. To protect the top surface of the TEM specimen against focused-ion beam process damage, the specimen had been coated with an amorphous carbon layer, a thin Pt film and a W protective layer. During our high-temperature experiments at 800°C, we detected that the CoFeNi nanoparticles moved from the surface of the TEM specimen into the amorphous carbon layer. A porous amorphous carbon layer had a large impact on the visualization of this phenomenon. Liquid-like behavior of the CoFeNi phase, which possessed some crystalline order, was detected before the material escaped from the surface. After heating, the carbon layer became tightly packed with small particles and single atoms. The majority of the particles in the carbon layer were in the size range of 1–4nm. The particles were assigned to the CoFeNi, FePt, and W phases. The CoFeNi particles escaped directly from the specimen surface, while the FePt and W particles were formed in the carbon layer during heating as a result of atomic reactions. The single atoms observed in the carbon layer were attributed to the heavy elements Pt and W.