EFFECT OF ORGANIC-LIGANDS USED IN SOL-GEL PROCESS ON THE FORMATION OFMULLITE

The preparation of mullite by the sol-gel method using organic polyden tate ligands and the effect of the raw materials and organic polydenta te ligands on the formation of mullite were investigated. Two series o f samples were prepared using tetraethoxyorthosilicate (TEOS) and alum inum nitrate nonahydrate, or dibutoxyethylacetoacetatoaluminum (Al(OBu )(2)(AcAcEt)) as the silica and alumina sources, respectively, and usi ng ethylene glycol (EG), 1,3-propanediol (PD), 1,3-butanediol (BD), 2- methyl-2,4-pentanediol (MPD), diethlene glycol monoethyl ether (DEME) and ethoxyethanol as the ligands. When the alumina source was aluminum nitrate nonahydrate, mullite was apt to appear in the order of EG > P D > MPD. When Al(OBu)(2)(AcAcEt) was the alumina source, the tendency toward the appearance of mullite crystalline phase was EG > ED > DEME > MPD. Between the two alumina sources, aluminum nitrate nonahydrate g ave mullite much easier than Al(OBu)(2)(AcAcEt). These relationships w ere discussed from the viewpoints of the coordination ability of the l igands and the miscibility between the silica and alumina.