* Zirconium is a member of the transition metals family:
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ZIRCONIUM / Zr / 40
A hard, lustrous, silvery metal that strongly resists corrosion
through formation of an oxide layer. As with aluminum, however,
powdered zirconium, which is black, burns easily. It is also found
in an amorphous, powdered form. Five isotopes are found in nature:
Zr<90/40> / 52%
Zr<92/40> / 17%
Zr<94/40> / 17%
Zr<91/40> / 11%
Zr<96/40> / 3%
All are stable, except possibly Zr<96/40>, which some suspect has a
half-life of about 3E17 years.
atomic weight: 91.224
abundance: 18th
density: 6.506 gm/cc
melting point: 1,852 C
boiling point: 4,377 C
valence: 2 3 4
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Although zirconium is a very common element, twice as common as copper, its usage is limited compared to its availability, with production in the hundreds of thousands of tonnes a year. Zirconium oxide (ZrO2) or "zirconia" has a high melting point and is used in heat-resistant crucibles, ceramics, and abrasives. Zirconia-based compounds are also used in cosmetics, antiperspirants, and food packaging. The compound zircon, ZrSiO4, makes up a range of cheap gemstones, with different colors depending on impurities. Most zirconium is mined as zircons, with most of the output as zircons as well -- only a few thousand tonnes of zirconium is produced each year as pure metal. It does have military use as an incendiary.
Zirconium metal is used for components in nuclear reactors since it resists heat and corrosion, and does not absorb neutrons. Zircaloy alloy -- 98% zirconium, 1.5% tin, plus traces of iron, chromium, and nickel -- is used as cladding for reactor fuel elements. The corrosion resistance of zirconium metal also makes it useful for chemical processing and medical implants, and its heat resistance makes it useful for spacecraft that have to reenter the Earth's atmosphere. Zirconium is also used as an alloying element to create high-grade stainless steels.
