Hafnium has been successfully alloyed with iron , titanium , niobium , tantalum , and other metals.
Hafnium carbide is the most refractory binary composition known, and the nitride is the most refractory
of all known metal nitrides (m.p. 3310C). At 700 degrees C hafnium rapidly absorbs hydrogen to form
the composition HfH1.86.
Hafnium is resistant to concentrated alkalis, but at elevated temperatures reacts with oxygen, nitrogen,
carbon , boron , sulfur , and silicon. Halogens react directly to form tetrahalides.
Uses
Because the element not only has a good absorption cross section for thermal neutrons (almost 600 times
that of zirconium), but also excellent mechanical properties and is extremely corrosion-resistant, hafnium
is used for reactor control rods. Such rods are used in nuclear submarines.
Hafnium is used in gas-filled and incandescent lamps, and is an efficient getter for scavenging oxygen
and nitrogen.
Handling
Finely divided hafnium is pyrophoric and can ignite spontaneously in air. Care should be taken when
machining the metal or when handling hot sponge hafnium.
Exposure to hafnium should not exceed 0.5 mg/hr. (8 hour time-weighted average - 40-hour week).
Costs
The price of the metal is in the broad range between $100/lb and $500/lb, depending on purity and
quantity. The yearly demand for hafnium in the U.S. now exceeds 100,000 lb.
Sources: CRC Handbook of Chemistry and Physics and the American Chemical Society.
Last Updated: 12/19/97, CST Information Services Team
Hafnium