History
Anders Gustaf Ekeberg discovered niobium in 1802, but many chemists
thought niobium and tantalum were one and the same. Some felt that perhaps
tantalum was an allotrope of niobium. Later, Rose, in 1844, and Marignac,
in 1866, showed that niobic and tantalic acids were two different acids.
The word Tantalum comes from the Greek word "tantalos" meaning "father of
Niobe" (Greek mythology, (tantalum is closely related to niobium in the
periodic table) the first relatively pure tantalum was produced by von
Bolton in 1907.
Fabrication
Tantalum works similar to copper in forming operations it can be
cold-formed in both the grain direction and in the cross grain direction.
It can be spun, drawn, and hydro-formed. Like copper, it work-hardens and
when this occurs, it requires annealing in inert gas or a vacuum before
further working. If annealed in the presence of hydrogen I any amount
embrittlement will occur. An Electron Beam can weld tantalum or if care is
taken by TIG. The welds are strong and can be stress-relieved by
annealing. Welded tantalum can be further formed and even drawn.
Applications
Tantalum has gained wide acceptance for use in electronic components,
chemical equipment, missile technology, and nuclear reactors. The
electronics industry consumes the majority of tantalum produced for
capacitors. Other industries concerned with corrosion, especially the
chemical processing industry are accounting for an increasingly larger
percentage of the market. Tantalum can be used to fabricate valves for
corrosive liquids and to manufacture heaters for acids and heat shields
for rocket motors. It is also used as a component of ion implanters in the
manufacture of semiconductors. Also, because tantalum does not have a low
neutron absorption cross-section it is used for radiation shielding.
Tantalum mill products are used in the fabrication of corrosion resistant
process equipment including reaction vessels, columns, bayonet heaters,
shell and tube heat exchangers, diaphragms and orifices. The metal offers
excellent "getter" properties, making it popular in vacuum tubes to absorb
products of out-gassing upon heat up of the tube components. It is also
used to getter potential contaminants of niobium and its alloys as well as
titanium during vacuum heat-treating operations. Tantalum is used in
vacuum furnaces where very high temperatures must be attained and where
there can be no residual oxygen or hydrogen present during the cycle.
Special Qualities of Tantalum Products:
Corrosion Resistance
Tantalum is almost completely immune to attack by acids and liquid metals.
It equals glass in resistance to acids and it is impervious to liquid
metals up to 1650°F. Few chemicals such as hydrofluoric acid, fuming
sulfuric acid, and strong alkalis will begin to break through tantalum's
corrosion barrier. This ability to resist practically everything has won
tantalum favor among manufacturers of chemical equipment, instruments,
heating elements, and surgical implants.
Thermal Conductivity
Tantalum conducts heat better than the nickel alloys, ductile irons, and
stainless/high temperature steels. Therefore, tantalum has become the
efficient heat transfer surface, especially in acidic or corrosive
environments. The corrosion-proof surfaces of tantalum remain smooth and
clean under conditions that foul or scale so-called acid resistant
materials.
Melting Point: 5425°F (2996°C)
Of the refractory metals, tantalum is outranked only by tungsten at 6170°F
and rhenium at 5732°F. The high temperature strength of tantalum, combined
with its workability, has resulted in the fabrication of superior heat
shields, heating elements, electrodes, and other high temperature parts.
"Getter" Characteristics
Tantalum absorbs surrounding gases and vapors extremely well at elevated
temperatures. Electronic tube manufacturers have long-recognized the
ability of tantalum to maintain high vacuum inside the tubes.
"Valve Action"
Tantalum forms highly stable anodic films and combined with its acid
resistance can be used in the manufacture of rectifiers, capacitors,
lightning arrestors and surge suppressors.
Material Forms
H Cross Company can supply tantalum products in wire, rod, ribbon, strip,
sheet and foil forms at 99.95% purity and in wire, strip and ribbon at
99.995% purity for specialized applications such as filament materials. We
also handle 90/10 tantalum tungsten products in wire, strip, ribbon, sheet
and foil forms for higher strength at high temperatures. Please
email or call with your specific requirements. |
