Synthesis of α-alumina fibre from modified aluminium alkoxide precursor

Abstract

Polycrystalline alumina fibre was successfully synthesized by pyrolysis of a preceramic fibre formed from aluminium compounds with alkoxy and chelate ligands. A mixture of ethyl 3-oxobutanoatodiisopropoxyaluminium (EOPA) and tri-sec-butoxyaluminium (SBA) was reacted with glacial acetic acid yielding a polymeric product. The IR absorptions at 630 and 700 cm-1 due to the Al-O bond changed from sharp to broad bands by treatment with acetic acid. The 27Al resonance at 35 p.p.m. increased in intensity when EOPA-SBA (7/3) was treated with 30 mol% acetic acid. An increase in the EOPA to SBA ratio 5/5 to 9/1 also raised the intensity of the signal at 35 p.p.m. The viscosity of the polymeric product increased in intensity as the amount of acetic acid increased. The viscosity of precursor increased with increasing the ratio of EOPA to SBA, and decreased with increasing measurement temperature from 45 to 75°C. The precursor polymer pyrolysed at 500°C in air was amorphous to X-rays, and crystallized in γ-alumina at 840°C. The precursor fibres were pyrolysed to yield finegrained fibres of α-alumina at 1200°C for 1 h. © 1992 Chapman & Hall.