LiAlH
4 would improve solid
rocket propellants if made usable.
Not LiBH
4 which is too expensive and its combustion gas toxic.
"Usable" means approximately: not pyrophoric when stored in a silo, compatible with ammonium perchlorate powder and polybutadiene while curing, insensitive to moisture, reasonably insensitive to crushing, not too sensitive to sparks, and more.
For AlH
3, this has been achieved with a very thin layer of aluminium deposited on the grains. Maybe LiAlH
4 can get the same.
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Metal
hydrides to store hydrogen: much work is invested in this topic since decades, so you're unlikely to find something new. I have two
doubts:
- If storing one hydrogen atom per lithium, or three per aluminium, is it any better to consume the hydrogen in a fuel cell, rather than oxidize the metal in a battery? It brings as many electrons, about as many volts (more with Li) and a better efficiency. It does take a depolarizer up to now, but research tries to use air for it.
- Are hydrides better than liquid hydrogen? I have a workable tank design (...provided we want to store hydrogen somewhere) that weighs only as much as the contents and keeps it for months even without a cryocooler.
http://www.scienceforums.net/topic/73798-quick-electric-machines/#entry738806my bet is that airplanes willl adopt it, cars maybe.
Difficulties of hydrides: most projects imagine to keep the metal in a tank permanently and pump hydrogen in/out, combined with a temperature swing. A little bird tells me that it takes much metal to store little hydrogen under these conditions. It may be better to
obtain a complete hydride at the filling station and give the metal back.
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At (applied) thermodynamics, this idea is simple theory (a nice concrete image of entropy and reversibility) but real
fun to experiment, and means the first progress for airships in decades, making them much more useful:
http://www.scienceforums.net/topic/70114-aerostat-buoyancy-control/find the proper set of paraffines (or salts or polyols), tinker exchangers and envelopes, observe on scales that weight changes, add optionally a big envelope to
fly the demo for real. Nice show.