Hollow ceramic fibers are made by intercalating carbon fibers with a metal chloride and then heating the intercalated fibers in air to oxidize or burn off the carbon, leaving metal oxide fibers having generally the size and structure of the carbon fiber precursors. The fibers are then soaked in boric acid solution, briefly dried and heated at a high temperature to make hollow alumina fibers. The temperatures at which the boric acid soaked fibers are heated can be varied to produce different tube morphologies.
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