Papers by Author: Fu Su Yen

Abstract: The traditional differential thermal analysis (DTA) techniques are employed to evaluate the kinetic behavior induced by the inter-particle relationships in a nano-particle θ-Al2O3 powder system during θ- to α- phase transformation. Discrepancies in homogeneity and inter-particle distance of the powder system may result in the diagnostic DTA profiles which can be use to evaluate the characteristics of the powder system as well as the formed α-Al2O3 particles. Based on the acknowledgement, a quasi-homogeneous transformation shows that a duration of 90 seconds is needed for one θ-crystallite to transform into one α-nucleus with a heating rate of 10 oC min-1 and fabrication of the high phase-pure and mono-sized α-Al2O3 powders is obtained.

Abstract: Pure alumina composite powders for low-temperature sintering purpose are examined. θ- and α- phase alumina particles with crystallite sizes 20 to 50 nm and 50 to 200 nm, respectively were mixed in an appropriate ratio. The composite powder can be easily sintered at temperatures as low as 1400oC, preparing high density and high pure alumina ceramics with grain size finer than 500 nm. Except the higher surface energy provided by the finer particle sizes, the performance of the powder can be attributed to the critical size phenomena occur during θ- and α- alumina phase transformation and the Furnas model that induced higher pacing density of the compact.