SOL-GEL PROCESSING OF REFRACTORY COMPOUNDS IN ALUMINA-BARIA SYSTEM

Barium hexa-aluminate refractory fibres were obtained by a sol-gel pro cessing route. Aluminium chlorohydrate Al-2(OH)(5)Cl . 2.5H(2)O was us ed as the aluminium precursor and barium salts as barium precursors. I t was found that the gels obtained had a structure similar to alumina gels, with a network that consisted mainly of Al-O groups; the barium species were trapped in the network or absorbed by the Al-O group matr ix. The gels or gel fibres could be heat treated at 1200-1400 degrees C to form the desired crystalline phases. During sintering, phase segr egation and crystallisation of transitional phases such as tribarium a luminate 3BaO . Al2O3 and barium monoaluminate BaO . Al2O3 occurred. T he microstructure and constitution of the phases formed at different s tages were evaluated.