Some of the cost isn't just from using the equipment, but because you'll have some evaporation from melting in vacuum. He says at the start of the article that Sacks started with a kilogram of beads:
>After melting from both sides and a lengthy cool down period (plus a couple of "ouch, where are my gloves" moments) Sacks' iridium was consolidated into a block a little over 2" square and less than 1/2" thick, weighing 1.7 pounds. It's startlingly heavy, distinctly more so than a similar sized tungsten block (which would be about 15% lighter and about 10,000% cheaper).
If true, the melt lost 22.7% of the mass, which is pretty painful. Google is saying iridium is about $167,000 per kilo right now! I assume they've got a cold trap on the vacuum line, and recovered some of the difference in weight as fine iridium dust, but the rest is going to end up coating the inside of the vacuum chamber.
If they routinely melt platinum-group metals, I wonder how often they scrap the entire chamber to melt it down and recover the evaporate.
Normally all furnaces or vacuum chambers where precious metals may evaporate have their walls covered with some metallic foil, e.g. aluminum foil (while the worked metal is heated at very high temperatures by the electron beam, the walls remain much colder), on which the precious metals lost during heating will condense.
After a production batch, the metallic foil is replaced and the used foil is chemically processed and almost 100% of the precious metals are recovered.
Some of the cost isn't just from using the equipment, but because you'll have some evaporation from melting in vacuum. He says at the start of the article that Sacks started with a kilogram of beads:
>After melting from both sides and a lengthy cool down period (plus a couple of "ouch, where are my gloves" moments) Sacks' iridium was consolidated into a block a little over 2" square and less than 1/2" thick, weighing 1.7 pounds. It's startlingly heavy, distinctly more so than a similar sized tungsten block (which would be about 15% lighter and about 10,000% cheaper).
If true, the melt lost 22.7% of the mass, which is pretty painful. Google is saying iridium is about $167,000 per kilo right now! I assume they've got a cold trap on the vacuum line, and recovered some of the difference in weight as fine iridium dust, but the rest is going to end up coating the inside of the vacuum chamber.
If they routinely melt platinum-group metals, I wonder how often they scrap the entire chamber to melt it down and recover the evaporate.