Bulk high purity hafnium.
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|Bulk high purity hafnium.|
Description supplied by the source:
This sample is a newer generation of the industrial van Arkel-de Boer process, and it shows both clear differences and similarities to the more commonly-seen 'iodide-process' bar. This hafnium is produced and sold in bulk pails/barrels as >99.99% melt stock- it was difficult to refine hafnium reliably to this purity in the past, due to its 'getter' characteristics, very high melting point, and chemical similarity to other refractory metals, and the Arkel-de Boer process was used at very high expense for critical applications where this level of purity was needed. This newer material is proportionally much less expensive due to refinements in the process. The older crystal bars take a lot of electricity to create, a dedicated reaction vessel, and already-purified raw material, and a decent amount of time; all of these factors contributed to their cost. However, this crystal bar looks as if it was grown on an electrode placed against a wall; the ends are clearly mechanically chopped to remove it, but in the center of the bar, the hollow channel for the electrode is visible, and the 'bar' is only a half cylinder, with no evidence of being chopped in half. In addition, and unfortunately for the collector, the crystal structure of this hafnium is starkly different from other crystal bar- the individual crystal grains are quite small and less developed, and the overall structure is more homogeneous; this would imply a shorter and hotter growth period, with less time for the individual crystals to slowly develop and grow outward from the electrode.
Source: Ethan Currens
Contributor: Ethan Currens
Acquired: 21 March, 2008
Text Updated: 2 April, 2008