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 ha ve employed X-ray photoelectron spectroscopy (XPS) and Auger electron spect roscopy (AES), in conjugation with sessile drop wettability tests, to exami ne the interfacial properties and surface chemistry of the systems formed b y adding liquid drops of select AI-Ti alloys to graphite substrates. A vari ety of different chemical states was revealed in the XPS results, suggestin g the formation of separate regions composed of elemental metals, alloys an d 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 anal yses were also supported by optical microscopy, scanning electron microscop y (SEM) and X-ray diffraction (XRD) studies. The combined results suggest t he 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) st ate to the (LAl-Ti + TiC) semi-liquid state. (C) 1998 Kluwer Academic Publi shers.