> First the basalt is melted at a temperature of 1,400 °C (2550 °F). The molten rock is then extruded through small nozzles for the production of filaments of basalt fibers.
As a 3D-printer user, I flinched.
As a 3D-printer user, I flinched.
Putting 3d printing concepts on the table, though, you could definitely see something like a sintered bed printer using a laser to print it, but then you wouldn't get anything close to the standard FDM style print.
- balance an exothermic reaction (self-propagating high-temperature synthesis) to occur just after leaving the nozzle
- externally apply the heat with laser or plasma arc etc
The limit of externally applying heating is when the heat flux has to be so high that some material vaporizes and pops. An exothermic reaction within the material overcomes this limitation.
But I don't think we'd end up with the basalt being very filamentous.
If instead the binder and precursor can melt, react, and expand into a solid that precipitates out because of a super high melting point, the expansion will ensure that you get a fully dense part that can be machined back down.
That's still quite a bit cozier than nylon or PET, of course.
These temperatures make it a significantly trickier engineering problem; ideally, your nozzle would retain its shape at those temperatures despite containing a lot of pressure, not be corroded by the lava you're squeezing through it, not be abraded by any zircon grains that snuck into your melt, and not oxidize on the outside from the temperature when it's exposed to air. I'm pretty sure you could make a zirconia nozzle work if it was thick enough, but I don't think ruby, sapphire, or diamond would last very long. Probably something like inconel would also work, but I don't think 304 or 316 would.
I'd bet inconel and other high temperature alloys would be eroded very quickly, anything that's fluxed enough to melt below 1000C is going to be extremely corrosive. Hot molten sodium hydroxide levels of corrosive. Fun to think about though, a serious materials challenge for sure.
Felsic lavas (and magmas) which melt at those temperatures do not typically contain a lot of alkali oxides, but they do contain some. See https://en.wikipedia.org/wiki/Calc-alkaline_magma_series#/me... However, ferrous and quasi-ferrous alloys like inconel are among the best choices for alkali corrosion. For example, table 4 in Birgitte Stofferson's dissertation https://orbit.dtu.dk/en/publications/containment-of-molten-n... gives an inconel corrosion rate of 1.06 mm per year in molten NaOH at 600°, which happens through oxidation from oxygen dissolved in the melt. Monel 500 corroded only 5.06 mm per year at 700°.
If you were trying to keep a 100μm hotend aperture within a ±10% tolerance, you could start with a 95μm aperture and replace the hotend when the aperture had expanded to 110μm. At 1mm/year those 15μm would be 5 days of printing time, which seems like a usable hotend lifetime. Presumably printing in lava rather than 100% NaOH would extend the lifetime further.
> Basalt Woven Textile has high corrosive and chemical resistance to the influence of a corrosive media: salt solutions, acid solutions and particularly alkali liquids. The specific strength of basalt fiber exceeds the strength of alloyed steel by a factor of 2,5 and the strength of glass fiber by a factor of 1,5. Heat-insulating items made from basalt fiber combined with inorganic binding agents may be used by temperatures up to 700°С. In addition there is a range of compositions consisting of basalt rocks that have a higher thermal stability – up to 800°С.