Studies of post-production ageing effects in atomised aluminium powder

Abstract

The evolution of hydrogen gas from the reaction between a series of atomised aluminium powder samples and 2.5 M HCl was monitored over time. The pattern of hydrogen evolution in each case was similar in that after an initial period of slow gas production there was a rapid increase followed by slow gas production again. These studies also showed differences in the time taken to reach maximum hydrogen evolution for similarly aged powders. Lower purity aluminium powder (99.7 vs. 99.93%) or samples with a higher proportion of smaller particles reached the maximum rate of hydrogen evolution more quickly. Changes in the time taken to reach maximum gas evolution were also noted for all the powders as they aged; the time to reach a maximum generally increasing with time after atomisation. However, for each powder a short regression occurred between ca. 21 and 35 d. This suggests that changes continue to take place in the surface layer of the aluminium particulates long after atomisation has taken place.

References

1. W. D. Jones, Fundamental Principles of Powder Metallurgy, Edward Arnold, London, 1960.
2. The American Society for Metals Handbook, Volume 7, Powder Metallurgy, American Society for Metals, Ohio, 1993.
3. T. J. Carney, P. Tsakiropoulos, J. F. Watts and J. E. Castle, Int. J. Rapid Solidif., 1990, 5, 189.
4. F. A. Cotton and G. Wilkinson, Advanced Inorganic Chemistry, John Wiley and Sons, Chichester, 5th edn., 1988.
5. L. Kowalski, B. M. Korevaar and J. Duszozyk, J. Mater. Sci., 1992, 27, 2770.
6. I. Olefjord and A. Nylund, Surf. Interface Anal., 1994, 21, 290.
7. A. Nylund and I. Olefjord, Powder Metall., 1993, 36(3), 193.
8. C. E. Aumann, G. L. Skonfromick and J. A. Martin, J. Vac. Sci. Technol. B, 1995, 13(3), 1178.
9. H. E. Swanson and E. Tatge, Natl. Bur. Stand. (U.S.) Circ., 1953, No. 539, 111[JCPDS 4-787].