EDS and EELS using a TEM-FEG microscope

Abstract

The combination of energy-dispersive X-ray spectroscopy, electron energy-loss spectroscopy and high-resolution electron microscopy provides a very powerful approach to characterizing advanced materials, EDS, EELS and HREM capabilities of an Hitachi HF-2000 FEG fitted with a Noran High-Purity Ge Explorer EDS system, a Gatan Model 666 PEELS and a Gatan Model 694 Retractable Slow-Scan CCD camera have been employed to study the microstructure at the nanometer scale of several materials such as WC-Co thermal-sprayed coatings and Ni/Ti multilayers. HVOF (high-velocity oxy-fuel) thermal-sprayed coatings display a microstructure which is very different from the starting powder due to complex physical and chemical modifications that occur during the spraying process. In particular, the matrix of the coating is no longer only composed of Co, but also of W and C. The simultaneous use of EDS and EELS spectroscopy allowed the quantification of these three elements in the matrix and the characterization of their distribution in the microstructure. The performance of Ni/Ti multilayers for neutron optics can be significantly improved by modifying the layer structure. A systematic EDS, EELS and HREM study of the structure and composition of thin Ni and Ti films with progressive addition of carbon and hydrogen has been made. It is shown that gradual reorientation and smaller grain size in the Ni layers lead to better defined interfaces and that hydrogen incorporation into the Ti layers improves the neutron reflectivity.