Vacuum Drying for Ultrafine Alumina Powders

Abstract

It is well known that the drying of liquid-borne powders will create agglomerates and the problem of agglomeration is particularly acute in the nanoscale range. To eliminate/mitigate the agglomeration problem, in this study, a vacuum drying technique was used for drying the colloid solution with θ-Al₂O₃ ultrafine particles. For comparison purposes, other drying methods including oven drying, microwave drying, and freeze drying were also applied for drying of the same kind of colloid solution. The results indicate that the redispersibility, which is closely related to the degree of agglomeration, of the dried powders obtained from vacuum drying is better than that obtained from freeze drying. More surprisingly, results showed that the dried powders obtained from the vacuum drying assisted by microwave heating has the redispersibility close to 100%.

Keywords:

• Microwave drying
• Ultrafine alumina powders
• Vacuum drying

ACKNOWLEDGMENT

The authors express their sincere appreciation to the director, Professor Fu-Su Yen, and his staff of the Particulate Materials Research Center of National Cheng Kung University for their great help in providing θ-Al₂O₃ powders and for technical support in measurements. The financial support granted by the National Science Council of Taiwan under contract number NSC 97–2221-E-006–224 is also greatly appreciated.

Notes

^a Additional ultrasonic energy was applied for diluted suspension.