TEM, EELS and EFTEM characterization of nickel nanoparticles encapsulated in carbon

Nickel particles dispersed in an amorphous carbon matrix have been synthesi zed by a sonication method, and further heated at 773 K under Ar atmosphere . Both as-prepared and heated samples have been fully characterised using d ifferent techniques such as transmission electron microscopy (TEM), high re solution TEM (HRTEM), energy dispersive X-ray analysis (EDX), X-ray absorpt ion spectroscopy (XAS), electron energy loss spectroscopy (EELS) and energy filtered TEM (EFTEM). The as-prepared sample shows amorphous spherical par ticles formed by Ni2+ dispersed in a carbon matrix. After heating, the form ation of small metallic nickel nanocrystallites inside these spherical part icles is observed. The EELS spectra show a decreased oxygen content in the heated sample due to the reduction of Ni2+ in the presence of carbon. This result is also confirmed by XAS. In addition, the EELS and EFTEM analyses i ndicate that the nickel nanocrystallites are surrounded by amorphous carbon which provides some protection to the metallic nickel from oxidation.