Rare Earths for Science
The Ames Laboratory has been actively involved in the preparation of very pure rare earth metals since the early 1940s, when Dr. Frank H. Spedding and his group of pioneers developed the ion-exchange process. Their technique separates the "fraternal fifteen" plus yttrium and scandium. As a result of this process and subsequent work, high-purity oxides are available from which high-purity rare earth metals can be prepared. In most cases, the rare earth oxides are first converted to their respective fluorides and then reduced metallothermically on a kilogram scale, using pure calcium metal specially sublimed for this purpose.
All videos are available through the Ames Laboratory Youtube Channel.
Arc casting of intermetallics may sound mundane, however, depending on the solidification behavior of the constituents inhomogeneity, defects, and other physical phenomena may result. Above is an example of solidification segregation that generates stress in a casting.
The modified AB alloy is used for metal hydride hydrogen storage. Upon solidification the Sn is partially rejected and increases in concentration in the remaining liquid. Upon completing solidification there is a great deal of internal stress in the ingot. As the ingot cools further the stress is relieved.
Atomization of metal requires high pressure gas and specialized chambers for cooling and collecting the powders without contamination. The critical step for morphological control is the impingement of the gas on the melt stream.
The video is a color video of a liquid metal stream being atomized by high pressure gas.
Melt-spinning is a method used for producing amorphous ribbon, which can then be converted to powder. The quality of the ribbon is controlled by several processing factors.
This video shows the melt stream, melt pool, and ribbon formation in slow motion.