Chemical Synthesis of Hexacelsian and Celsian Powders
W. M. Kriven,* S. J. Lee
U.S. Air Force Office of Scientific Research, 49620-96-1-0464

Hexacelsian (BaO.Al2O3.2SiO2) powder is chemically synthesized by a solution-polymerization route employing PVA solution as a polymeric carrier. A fine, amorphous-type hexacelsian powder with an average particle size of 0.8 ?m and a BET specific surface area of 63 m2/g is prepared by a ball-milling for 12 h after calcination of 800C for 1 h. A densified hexacelsian is obtained through sintering at 1550?C for 2 h under an air atmosphere. The reconstructive transformation between hexacelsian and celsian occurs during annealing at 1590?C for times of 72 h. A volume contraction of 5.6% is accompanied by the reconstructive transformation.

Synthesis and Characterization of Ce3Si5O12N Powder
W. M. Kriven,* D. K. Kim
South Korean Government Fellowship

Ceramic Ce3Si5O12N powders are chemically synthesized by the Pechini method in a nitrogen atmosphere, using cerium nitride and Ludox AS-40. After calcination at 1350C in a tube furnace under Ar atmosphere, a pure powder is obtained. Crystallinity is examined by XRD analysis and the decomposition behavior of the powder precursor is investigated by thermogravimetric (TGA) and differential thermal analysis (DTA). For characterization of powder synthesized, Fourier transform infrared spectroscopy (FTIR), Auger electron spectroscopy (AES), particle size distribution, specific surface area, chemical analysis, and density measurement are carried out.