Nano-sizing titanium into titanium carbide by 1-chlorobutane
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TiC nanoparticles (average diameter 10–150 nm) were prepared by reacting bulk Ti powders (average diameter 20 m) with gaseous 1-chlorobutane at a relatively low temperature (1073–1273 K). 1-Chlorobutane provided the carbon atom in the TiC and the chlorine atom that assisted the shrinking of the size of the original Ti powders. The apparently simple procedure is a complex heterogeneous process combining etching, deposition, and carburization reactions.
Due to their special properties, such as high melting point, low density, extreme hardness, and high resistance to corrosion and oxidation, early transition metal carbides have many potential industrial applications.1–3 For example, they can be used in rocket nozzles and drill bits. Recently, there were reports about the potential application using early transition metal carbides as diffusion barriers for Cu metallization in microchip fabrication.4 Traditionally, transition metal carbides are prepared via high-temperature routes. For example, TiC can be synthesized by reducing TiO2 with carbon black at 2000– 2400 K.2 Recent reports have shown that it is possible to prepare TiC through reduction–carburization,5–7 gas– solid reaction,8 polymeric precursors obtained from titanium alkoxides with other organic compounds,9–11 and solid-state metathesis (SSM) methods.12,13 The last two examples are the so-called “bottom-up” strategy for the preparation of small-size materials. The strategy employs molecular precursors as the building blocks to form solid materials through chemical bond formation. To implement the strategy effectively, much chemistry knowledge is required. Another strategy is to employ the “top-down” approach. For example, bulk solid materials can be shrunk through the physical evaporation–deposition process. But this high-energy route suffers from the requirement of maintaining a vacuum environment, low production efficiency, and frequently forming highly reactive powder products. Alternatively, bulk solid materials can be shrunk through a high-energy mechanical milling process. For example, synthesis of TiC powders by this route has been reported.14,15 But the process frequently employs a long period of reaction time. Carburization of metals directly by hydrocarbons at high
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Address all correspondence to this author. e-mail: [email protected] J. Mater. Res., Vol. 17, No. 11, Nov 2002
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temperatures is a simple method to prepare metal carbides.2,8 But the process usually does not shrink and carburize the bulk metal particles effectively. For example, reacting Ti metal with methane at 1173 K for 8 h can only transform about half of the metal into the carbide.8 Here, we wish to report a simple chemical method to prepare nano-sized TiC powders by reacting bulk Ti metal powders with 1-chlorobutane at a relatively low 1073–1273 K. The reaction is a combination of etching, deposition, and carburization processes. Ti powders (2.0 g, 42 mmol) (Strem, 2N-325 mesh) or a piece of Ti foil (1 × 1 cm2, Strem
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