#CC #paper on how #space satellites produce #alumina that can deplete the ozone layer upon reentry. “Satellites burn up at the end of service life during reentry, generating aluminum oxides as the main byproduct. These are known catalysts for chlorine activation that depletes ozone in the stratosphere. We present the first atomic-scale molecular dynamics simulation study to resolve the oxidation process of the satellite’s aluminum structure during mesospheric reentry, and investigate the ozone depletion potential from aluminum oxides.” #environment
on 02024-11-19#paper on #gelcasting #alumina and zirconia #ceramics #materials with #gelatin and polyethylene spheres to add porosity. Presumably you could use paraffin spheres too, which would be cheaper and maybe improve thixotropy. Something somewhat hydrophilic, not easily water-soluble, and burnable-out might work better still. (Lecithin?)
on 02015-08-15this chapter of “Novel Colloidal Forming of Ceramics” discusses #gelcasting #alumina #ceramics by adding hexanedioic acid to dechelate calcium ions from calcium phosphate that had been chelated by sodium hexametaphosphate and trisodium citrate, polymerizing #alginate #materials into a gel. The usual song and dance about ball mills, vacuum degassing, dissolving alginate for days, and so on, but basically their main problem was that it was gelling too damn fast, which is why they came up with this chelation nonsense to slow it down.
on 02015-08-15#Abstract about #Gelcasting 50% (by weight) #alumina #materials with 1% (by weight) #alginate and 1.8% (by volume) calcium phosphate. This seems particularly interesting to me for #3D printing because alginate gels fast when there’s enough ionic calcium present, which can be controlled by temperature.
on 02015-08-15Galip Sarper Koçlar’s master’s thesis #paper on #gelcasting of #alumina #ceramics #materials with #gelatin and #carrageenan gum. He got best results with 5% by weight gelatin, or 1.7% by weight carrageenan, which resulted in significantly lower fired hardness but higher fired compressive strength than the gelatin, and all his trials were with 47–53% alumina, which reached 95.8% after firing at 1550°, and a bit of Dolapix dispersant. 17.5% linear shrinkage. In English, not Turkish, although it’s kind of broken English. The introduction has the best #survey of gelcasting I’ve found so far. Apparently #acrylamide (and, I guess, other similar binders) needs 30–60 minutes to gel in the mold. He also mentions existing “natural gelcasting” processes for technical ceramics using “starch, ovalbumin, chitosan, alginades [sic; should be #alginate], #gelatin, carragenan [sic] gum and [sic] etc.”, and agarose, with the disadvantage being lower green strength.
on 02015-08-15