Formation of alumina nanofibers in carbon-containing coflow laminar diffusion flames

Nano-fibrous materials have attracted continuing research interest because of potential applications due to their unique properties. We report, for the first time, formation of alumina nanofibers in carbon-containing coflow diffusion flames with pure oxygen support, using trimethylaluminum vapor as the precursor. The alumina nanofibers were non-crystalline, typically 2–10 nm in diameter and 20–210 nm in length. No alumina nanofiber formation was found in flames supported by air. Neither was alumina nanofiber formation found in flames with pure H2H2 as fuel. Thermophoretic samples showed that the nanofibers were formed in the region past the maximum temperature zone of the flame. The experimental data suggest that the alumina nanofibers were formed from gas-phase aluminum-containing species in the flame. Gas-phase carbon-containing species such as CO were probably crucial to the formation of the alumina nanofibers.