Tungsten for radiation shielding use
blog.prusa3d.com
blog.prusa3d.com
Maybe get the kids to look into using Magnetorquers to get some spin on and half shield with this product .. and you now have a platform for directional gamma ray detection | mapping.
( Gamma counts coming from "over there" will decrease whenever "over there" is masked by the partial shielding )
There are other apps, but that one springs to mind.
The detector part (doped crystals + scintillation sensors) is fundamentally undirectional - those pesky gamma come in from any direction.
One side has to be shielded to bias the reading (use Tungsten perhaps) .. and by rotating the entire satellite the shielding direction changes - you now have a bulk data stats analysis challenge, do particular orientations align with counts (at various energy levels) rising or falling.
As alway, have a fiddle with a ground based setup first.
now see, if we do that, then you're ruining the one chance I have of being the exact right person to go to space to fix the thing.
Depending on your environment and the sensitivities of what you're shielding, you might need one or the other, and possibly both.
Disclaimer: I'm not a nuclear physicist. I learned this while researching for a hard-sci-fi novel I'm working on.
But it is only 15% by volume... So to the casual observer, this material is mostly plastic.
So I think the casual observer would notice that. But also means with thar price per KG.
Pure tungsten on the other hand is very good and can even shield beta particles
that is depressing
Tungsten is ok
https://pubmed.ncbi.nlm.nih.gov/29300000/
don't confuse government power with wisdom; in many ways they are opposites
it should be heavier than lead; lead is only 11.3 g/cc, tungsten is 19.3, 75% tungsten would be 14.5, but then the other 25% is petg with sp.gr. ≈ 1 so you should actually get a density of 14.7
but i struggle to imagine cases where using tungsten is a more cost-effective option than using lead and making the object 9% bigger? they cite 'various medical applications' but tungsten isn't exactly ideal for permanent body contact either
oh actually they say it's 75% tungsten by mass, not volume, so it's only 4 g/cc, and so its attenuation (at 140keV) is only 18% of lead's (by volume)
copper might be an alternative that is less toxic than lead and less expensive than tungsten
I was thinking weights to fit specific items. Model railway wagons, for example, need to be weighted and balanced to operate smoothly, but you have significant size constraints. I threw a bunch of tungsten weights inside a small locomotive to give it extra tractive effort.
That said, no metal dust is very nice. Solid lead might be safer than tungsten powder. Maybe you could make an iodinated polymer or use a barium cement.
- 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
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.
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?
You'd likely do better just machining it out of steel (5g/cm³, and much cheaper)
Err, they make it sound like ordinary lead is the best choice? The article's point is that additive manufacturing is a workaround for tungsten's difficult material working properties. But: lead foil, you can simply bend it with your hands, into any shape you want. And apparently it's much thinner.
But the tungsten costs many times more, and is also much harder unlike lead which is soft and easily worked, which is why radiation shielding is still overwhelmingly made of lead. In applications where its toxicity is a problem, it's used encapsulated inside another inert material.
If you need complex parts, this could be an excellent choice.
Idk what the confusion here is. Maybe you are unfamiliar with machining?
I can't explain everything in every comment. You can research the materials if you want to understand the discussion in more context.
Tbh I have no idea how you came away thinking I said lead is hard. "also difficult". "this" is the material that is the center point of the discussion. Context, yo.
(i actually had the impression that working lead on a lathe was very easy indeed due to its softness, but i've never tried doing it myself, and my bachelor's degree from youtube is worth what i paid for it)
i think you may have misunderstood something in the comment you were replying to yourself
A little bit of lead in steel will increase machinability, but only a teeny amount. Similar to adding a small bit of phosphorus.
It's also hard to hit dimensions in lead, and if you do hit them, the second the temperature changes you'll lose them. Additionally, whatever you make can't see any stress, or the part is donezo.
Idk if you've ever handled lead - but considering you can bend thick sheets of it by hand and melt it on your stove, I'm sure you can imagine the kind of issues you might have integrating expensively machined chunks of it in to hot high pressure environments with moving parts.
Even though lead is cheap and this filament is expensive, actually getting the lead to shape by machining or working it is also a costly process. 3d printing has a sort of cost ceiling. Once a part is designed, all of the real work is done. For fabrication and machining - once the part is designed the work has only begun.
What might look like a small and simple combination of geometric shapes can cost thousands to machine.
I'd rather spend 500 on filament and a day's engineering labor on a part than the same day's engineering, 100$ of lead, and 1k or more on manufacturing. Not to mention the lead times on machined parts can be wild.
maybe an exception is that petg's maximum elastic strain is larger than lead's
Of course the petg in there is a limiting factor, but even plain petg is an order of magnitude better than lead at retaining its shape under a wide range of loads. You can print gears for lathes in petg! And they last years! (If you're wondering why you might do this - it's a good idea to have a cheap point of failure on devices that have enough power to rip themselves to shreads.)
Not to mention this is only v1 of the material. We could see exotic plastics that are far more heat resistant like PEEK get a secondary filler for niche radioactive usecases.
(at such low filler loadings the tungsten will change the modulus of elasticity very little)
petg does have higher yield stress than pure lead (53 megapascals vs. what https://nickelinstitute.org/media/1771/propertiesofsomemetal... says is 17 megapascals) but there are lead alloys that are in the same range of yield stress, including regular lead-tin solder. but they won't last if you try to make change gears out of them precisely because they're harder than petg
by the same token, though, i think you're going to get a lot of springback and long-term distortion out of petg you aren't going to get with lead
I did not, in fact, come away thinking lead is hard. I did, however, explain and spell out for you how @kragen probably did so; I'm not sure how I can make it any more clear.
you seemed to be saying that this filament might be a better alternative to lead sometimes, but i couldn't tell when that might be. pure tungsten is clearly a better choice sometimes, for example because it shields better than lead, is harder, is denser, and is more refractory, but none of those seems to be true of this filament
from your other comment at https://news.ycombinator.com/item?id=35206874 it looks like you're saying that, although this composite is inferior to lead in those ways, it's easier to print
For the right application, there are some good wins here.
what do you think about copper-filled or baryta-filled filaments as cheaper alternatives
maybe this is wrong but i feel like both tungsten and copper are in the 'if you have it embedded in your body you are going to need surgery to get it out before you get gangrene' while lead and baryta are not
or just print it?
It's a bit of a no brainer.
Even if you just want a shielding layer, the convenience of this will win out on low volume parts.
The other high-melting metals near it in the periodic table all fall down on one or more of those properties. Osmium, for instance, is rather expensive, mined in only very small quantities, and reacts with air to form highly-toxic osmium tetroxide.
> In the staining of the plasma membrane, osmium(VIII) oxide binds phospholipid head regions, thus creating contrast with the neighbouring protoplasm (cytoplasm). Additionally, osmium(VIII) oxide is also used for fixing biological samples in conjunction with HgCl2. Its rapid killing abilities are used to quickly kill live specimens such as protozoa. OsO4 stabilizes many proteins by transforming them into gels without destroying structural features. Tissue proteins that are stabilized by OsO4 are not coagulated by alcohols during dehydration.
> OsO4 will irreversibly stain the human cornea, which can lead to blindness. The permissible exposure limit for osmium(VIII) oxide (8 hour time-weighted average) is 2 µg/m3. Osmium(VIII) oxide can penetrate plastics and food packaging, and therefore must be stored in glass under refrigeration.