Originally posted by Norman L. Reitzel on rec.pyrotechnics
Well, there are more sources of energy than transferring electrons. The
particular reaction of which you are speaking forms an intermetallic
compound (Nickel Aluminide) where the nickel and aluminum are covalently
bonded. However, the crystal lattice for nickel aluminide is quite a bit
more compact and regular than for either aluminum or nickel alone. The
energy you are seeing is called the lattice energy, and comes from the
increased bonding that occurs when the dense nickel-aluminum crystals are
formed.
Incidentally, the reason that aluminum is so great in pyrotechnics is
because aluminum oxide has -extremely- high lattice energy. Think about
the product, aluminum oxide, and you will find that it is -really- hard,
and used for abrasives. This hardness (and density) come from the same
place, the density and bonding energy of the aluminum-oxygen lattice.
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