Effect of organic additives on the properties of sol-gel spun alumina fibres

High alumina fibre mats (Al2O3–4 wt.% SiO2) were prepared with and without organic additives (lactic acid and PVA) using a sol-gel spinning technique. As the organic content increased, surface roughness after calcination increased, phase transition was retarded and the strength of the fibres decreased. The effect of lactic acid was more pronounced than PVA probably because of the formation of aluminium lactate resulting in an increase in its decomposition temperature as compared to PVA. Variations in heating schedules used in the calcination of alumina fibre had a significant effect on phase transition and properties of alumina fibres. It was found that at very low (60°C/h) and very high (400 and 600°C/h) heating rates the strength and handleability of the fibres decreased. Fibres having good strength (1.2 GPa) and handleability were obtained using a heating rate of 240°C/h.