THERMOGRAVIMETRIC CHARACTERIZATION OF GELCAST ALUMINA COMPOSITES

Gelcasting is a new method for forming advanced ceramics based on obta ining intermediary gels promoted by polimerization ''in situ'' within the ceramic slurry. Gelcast composites of an ALCOA A-1000 alumina and the copolymer obtained using acrylamide and N,N'-metylenebisacrylamide as monomers were characterized by thermogravimetry. Polymer distribut ion was determined by thermogravimetric analysis of small size specime ns that were taken from different parts of the alumina composites form ed in different shapes. Derivative thermogravimetry was used to identi fy the resulting polymerization stage within the gelcast body, as well as to study the influence of mold materials and operating conditions. All the composites show an even distribution of the polymer in the bu lk, which enables machining in the green state and obtaining high dens ity alumina bodies after sintering.