Chemically-activated combustion synthesis of TiC-Ti composites

The self-propagating high-temperature synthesis (SHS) of titanium carbide-titanium (TiC-Ti) composites from elemental powders in the presence of boosters (i.e., Teflon) is studied. Specifically, the dual role played by the polymer, i.e., as reaction promoter and as carburising agent, is investigated. The combustion temperature and velocity of the propagating front increase as the amount of booster added to the mixture is augmented. Correspondingly, the amount of titanium in the end product decreases, thus demonstrating that the polymer directly participates in the carburization process. However, when Teflon is considered as a carbon source for partial substitution of graphite, the dependence of temperature and wave velocity on the ratio between carbon produced by Teflon and the total amount of carbon, displays a maximum. Accordingly, the carburization process is enhanced. Furthermore, it is shown that upon a proper change of the carbon and titanium (C/Ti) ratio, TiCx-Ti composites containing Ti metal in the range of 0-25 wt.% can be prepared. Generally, the composite is constituted by carbide grains surrounded by titanium, which acts as a binder. Finally, the compound TiF3 was found to be an intermediate species which triggers the Teflon activated combustion synthesis of TiCx-Ti composites. (C) 2003 Elsevier B.V. All rights reserved.