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0 pointskragen3y ago0 comments

my candidate list of high-density fillers from dernocua (sorry for markdown) is

- Osmium: [US$13000/kg][8], 22.65 g/cc, or possibly iridium at more than twice that price

- Tungsten: [US$30/kg][9], 19.3 g/cc

- Tungsten carbide? Not sure what it costs but its density is 15.6 g/cc.

- Lead scrap: 95¢/kg, 11.3 g/cc

- Steel scrap: [21¢/kg][10], 7.9 g/cc

- Magnetite: [10¢/kg][11] [or so][12], 5.2 g/cc

- Quartz (as construction sand): 3¢/kg, 2.6 g/cc

- Water: [.06¢/kg][22] or so, 1 g/cc

[8]: https://www.metalary.com/osmium-price/ [9]: https://www.metalary.com/tungsten-price/ [10]: https://www.usgs.gov/centers/nmic/iron-and-steel-scrap-stati... [11]: https://www.usgs.gov/centers/nmic/iron-ore-statistics-and-in... [12]: https://stockhead.com.au/resources/barry-fitzgerald-why-magn... [22]: http://www.scientificamerican.com/article/israel-proves-the-...

this is my approximation of the pareto frontier; that is, each of the items on the list is conjectured to be cheaper than everything that's denser than it is, and denser than everything that's cheaper. corrections are welcome

i was thinking baryta (46¢/kg, 4.48 g/cc), mercury, litharge, minium, cinnabar, cupric oxide (US$3.90/kg, 6.315 g/cc), zinc oxide (US$29/kg, 5.6 g/cc), and manganese dioxide (5.026 g/cc) might be interesting in this context too

i hadn't thought of your suggestion of galena (just cinnabar) and generally i'm skeptical of metal sulfides because of their tendency to produce hydrogen sulfide; i don't think that's an issue with those two. litharge, minium, and mercury are a lot more worrisome toxicologically

i don't have solid pricing information for mercury, litharge, minium, cinnabar, or galena, and i'd be interested

tungsten is probably more chemically inert for medical purposes than a lot of these

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scythe3y ago

Density alone is a weak parameter. For photons with energy below 200 keV — that is, most of them — the attenuation is proportional to Z^2, so barium with atomic number 56 is four times as attenuating as nickel with atomic number 28, and lead with atomic number 82 is about twice as effective as barium — all of this before you account for density.

I've done a bit of searching for materials myself. Barium is mined as barite (BaSO4) or witherite (BaCO3), not baryta (BaO*xH2O, caustic), and USGS lists the price of barite as $180/t, or $0.20/kg.

You also have a K-edge effect, which prompted me to wonder whether you can easily produce barium zirconate from the respective ores, which are both cheap — BaZrO3 (sg ~5.5) is not currently manufactured (Zircon sand was <$1/kg until a COVID-related shortage). But at this point I decided I was overthinking it.

kragenOP3y ago

baryta is barite, not baria. baria is not just caustic but also toxic and prone to produce dangerous peroxides

i think the price i cited for it is retail, locally

i was interested in density for psychological effects when i made the list

thanks for the tip about barium zirconate; it sounds very promising. how about lead zirconate?

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