Dislocation and pores in mullite from diphasic gels

摘要

Stoichiometric mullite prepared from the reactions of nanometer-sized pscudo-bochmite and acidic-catalysed silica gel has non-sinterable pores and dislocations. The formation of the pores is accompanied by densification and reactions of the diphasic alumino-silicate gel matrix. These pores tend to be faceted and show low-index crystallographic planes, (110) and (211). After heat treatment at (ge) 1400(degrees)C for 24 hr. Dislocations are identified by weak- beam, dark-field, and 2-beam techniques, that show basically three types: one with Bergers vector 001 and is pure screw or a mix: the others may have 210 or 131 Bergers vector. The possible atomic models near last two dislocations are proposed. But the direct observation needs more TEM work.