In situ Reaction Synthesis of Needle-like Macroporous Mullite Supports

The needle-like structured porous mullite ceramic membrane supports were prepared us- ing kaolin,Al_2O_3 and Al(OH)_3 as raw materials by in situ reaction sintering.Al_2O_3/kaolin and Al(OH)_3/kaolin mixtures with different contents of AlF_3 additives were selected,respectively.The effects of different aluminium resources and doping amount of the additives on the needle like struc- tured macroporous mullite support formation were investigated.Results show that topaz is formed prior to the formation of needle-like mullite and the needle-like mullite formation is closely related to the topaz content in samples.Formation mechanism of needle-like mullite is vapor-solid reaction mechanism.The needle-like structured porous mullite support with porosity of more than 35% and average pore size of 1.5μm is more easily prepared using the Al(OH)_3/kaolin mixture as raw materials,and it's quantity increases with the AlF_3 content increasing.