another #video #toread about aluminum-foil #batteries by #Thoisoi, who turns out to be Polish or Estonian, not Russian. He uses stainless-steel window screens as the cathode current collector, because it’s an #aluminum-air battery; in one case he adds a layer of graphite conductive spray paint to the screen. Additionally he’s going to use activated carbon for the cathode, sprinkling it on the epoxy-coated graphite-coated fine stainless-steel mesh, then pressing it in a jugaad five-tonne hydraulic press at 100° for 40 minutes, though he says you could just leave it for 12 hours at room temperature. In the end he has eight cathodes, four with a coarser mesh; the dry cathodes measure as only 8Ω or so on a non-autoranging multimeter. He’s making pouch cells with a food-bag hot sealer, which melts sheets of polyethylene (LDPE) together with a hot wire. His anode is 8-layer-thick aluminum foil. As an electrode separator, he uses a wet paper towel, and sandwiches the anode between two cathodes, I suppose to keep air from getting to it. Weirdly, he seals the pouch cell in plastic, so I’m not sure how the air is going to get to the cathodes. One of the cells uses 20mℓ o an electrolyte made from 5g NaCl and 5g NaHCO₃ #materials in 100mℓ of water, giving 0.75V which rapidly declines. On injecting 10mℓ 10% NaOH into the bag with a syringe, it perks up to 1.6V. Short-circuit current is 750mA, but he needs two in series (measuring 2.60V on the multimeters) to dimly light a red LED, suggesting an “internal resistance” of hundreds of ohms. With the NaOH he thinks its shelf life is only a few hours; his batteries were dead in four hours of playing his CD player.
I thought he was going to explain the results he got from different cathode geometries, but he never does. Also he never reports the power output of the battery or explains how the air is supposed to get in.
on 02026-01-14#video by #Thoisoi on making metal foam #materials. Very low quality text-to-speech audio (in particular, missing all the quantitative information!) and a significant amount of talking-head filler and stock-footage filler, and he spends a bunch of time talking about misleading relationships between metals’ density and chemical properties. He finally starts making hydrogen-blown aluminum foam at 10'20" after some fake video of typing a Google search by melting calcium into it at supposedly 760° in his furnace, but the crucible and alloy don’t glow, so that must be the wrong temperature. Some footage of reacting calcium granules with water and setting them afire. He adds titanium hydride as a hydrogen source, mixing it into the alloy with a quartz tube as it’s starting to decompose, so that the hydrogen will dissolve in the aluminum.
But that didn’t work, so he tried again without adding any calcium beforehand, then adds the calcium granules once the aluminum was already melted; this time, when he adds the hydride, the aluminum starts to foam immediately, but only foams a little.
On a third trial, he lowered the furnace temperature to 700° (but the aluminum and crucible are still not glowing) and got slightly better foam, but still pretty bad, more like sourdough bread than a sponge.
I suspect the calcium is to reduce the surface tension of the aluminum, because the alloy wets the crucible more, but it doesn’t seem to have worked very well.
He bought some commercial aluminum foam samples, which weighed 0.27g/cc, but didn’t bother to test its material properties quantitatively.
on 02025-03-25