Pull a silver coin out of your pocket. Look at the edge. You'll
notice a thin copper line running through the middle. That's
because the "silver" coin isn't silver at all. It's actually a
metal composite comprised of a layer of copper sandwiched
between two layers of nickel alloy, but vending machines and
telephones can't tell the difference.  The U.S. Treasury saved a
mint by replacing a precious metal with a metal composite. Now
makers of pricey metal substrate catalytic converters are trying
to use the same technology to compete with lower-cost ceramic
substrates.  The key is making the typically brittle metal
alloys used in metal converter substrates easier to fabricate.
Metal substrate converters offer automakers many advantages over
ceramics, proponents argue, such as faster "light off" (they
heat up and start catalyzing in seconds instead of minutes
because they can be made with thinner walls and have higher
thermal conductivity); better resistance to thermal shock
(allowing them to be located closer