"Structural and Thermal Study of Al₂O₃ Produced by Oxidation of Al-Powders Mixed With Corn Starch"

Juliana Anggono, Ph.D.

Associate Professor, Mechanical Engineering Departmen, Petra Christian University, Surabaya, Indonesia

Friday, October 30, 2009, Room 312, Rogers Bldg.
[photo]

Abstract:
The addition of corn starch to the Al flakes powder to enhance
its oxidation kinetics through pores formation to synthesize alumina
(Al2O3) via Reaction Bonding at 1400 degrees C has shown a success. Heating temperature at 1000 degrees C in air results in various size of pores left by the burn-out corn starch (corn starch decomposes at temperature 240 380 degrees C). At 1000 degrees C, there was only 0.4 wt. % Al remained unoxidized in the structure as detected by inductively coupled plasma spectroscopy (ICP-S) test. The increase in the degree of oxidation is shown by the changes in samples’ dimension and weight gain. Samples made from a mixture of Al and Al2O3 were also characterised for a comparison. Structural and thermal studies were done using scanning electron microscopy (SEM), porosimetry, and thermal expansion test (dilatometer) on samples heating at 1000 degrees C and 1400 degrees C. SEM and porosimeter identified two major pore sizes in the range of 0.3-0.4 μm and 1.7-2.7 μm which functioned as oxygen channels to the sample's interior for oxidation. Coefficient of thermal expansion (CTE) at 8x10-6 C-1 is obtained for sample after heating at 1000 degrees C. This value is the same as CTE of α- Al2O3.

Biographical Information:  

Dr. Juliana Aggono is an Associate Professor of Mechanical Engineering at Petra Christian University, one of the three major Christian Universities in Indonesia, with more than 9000 studnets.  She has recently been appointed to be Vice President for Finance at Petra.  She received her Ph.D. in Materials Science at University of Birmingham, one of the premier programs in England. She is also a dedicated follower of Jesus Christ.  Her technical presentation as well as her presentation on Petra Christian University will be a blessing to all who come.