Microscopy and electron spectroscopic study of the interfacial chemistry in Al-Ti alloy/graphite systems

The chemical and physical interaction of liquid metal surfaces with various substrates is an important, largely unexplored aspect of technology, with implications in composite science and catalysis. In the present case, we have employed X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES), in conjugation with sessile drop wettability tests, to examine the interfacial properties and surface chemistry of the systems formed by adding liquid drops of select AI-Ti alloys to graphite substrates. A variety of different chemical states was revealed in the XPS results, suggesting the formation of separate regions composed of elemental metals, alloys and carbides. Many of the specific features detected appear to depend on the various treatment properties, e.g. the temperature, bulk alloy composition, size and shape of the alloy drop and time of interaction. The surface analyses were also supported by optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) studies. The combined results suggest the induction of a strong reaction between titanium and carbon, resulting in an improvement in the wettability of the alloy with the graphite substrate and a corresponding structure transformation from the (LaAl-Ti + Al3Ti) state to the (LAl-Ti + TiC) semi-liquid state. (C) 1998 Kluwer Academic Publishers