Preparation of long alumina fibers by sol-gel method using malic acid

The precursor sol of alumina was prepared by sol-gel method with aluminum nitrate and malic acid as raw materials. The effects of content of malic acid and polyvinylpyrrolidone (PVP) on sol spinnability were explored. The gel fibers with above 80 cm in length were obtained by mixing aluminum nitrate, malic acid and PVP on mass ratio of 10:3:1.5. Thermogravimetry-differential scanning calorimetry (TG-DSC), Fourier transform infrared (FTIR) spectrum, X-ray diffractometry (XRD), and scanning electron microscopy (SEM) were used to characterize the properties of the gel and ceramic fibers. The alumina fibers with a smooth surface and about 20 μm in diameter were obtained by sintering at 1 200 °C, and their main phase was indentified to be α-Al2O3.