Fabrication of β- and β-Al2O3 tubes by pressureless powder packing forming and salt infiltration

Abstract

A new forming method, pressureless powder packing (PLPP), was studied to fabricate the β- and β′′-Al2O3 tubes. Alkali sources were infiltrated into the pores of α-Al2O3 tube preforms that had been prepared by the PLPP forming method. The composition for the synthesis of β′′-Al2O3 phase was Na2O · 0. 138Li2 · 4.4Al2O3. The β′′-Al2O3 fraction of calcined and sintered bodies was increased with the increase of calcination temperature, and phase formation was largely affected by the type of starting α-Al2O3. Large particle size and narrow size distribution of fused α-Al2O3 resulted in uniform green microstructure that enhanced the homogeneity of alkali salts after infiltration, which was very important for the β′-Al2O3 formation. Sintered microstructure was uniform in all specimens but further development was required for density improvement.