Tantalum (Ta)
As mentioned on the previous pages on niobium, these two metals are usually found together. It was identified in
1802 by the Swedish chemist, Ekeburg, who found the tantalum oxide ores so difficult to dissolve that he called
the metal after the mythical Greek "Tantalus."
Tantalum is one of the most corrosion resistant materials available. The first ductile tantalum was developed in
1905 and until 1922, most applications were limited to certain instruments, particularly surgical.
Tantalum forms very stable anodic oxide films which make excellent electronic capacitors. For example, an
oxide film provides both corrosion resistance and the dielectric properties that give the electrical flow "valve"
action needed in a capacitor.
Tantalum comes principally from tin slags, and tantalite and columbite ores. Tantalite-rich ores are being mined
in Canada.
What are some of tantalum's applications?
Mill products such as sheet are made into corrosion resistant chemical equipment such as bayonet heaters, vapor
condensers, multi-tube heat exchangers, thermowells, rupture diaphragms and orifices.
Tantalum plugs are used to repair perforations in glass-lined steel equipment. Tantalum components are used in
sulfuric acid concentrators, in temperature controllers for chromium plating and in distillation and condensation of
acids and acidic chemicals.
Many surgical applications have been opened to tantalum because it is inert to body fluids and tissues. It is used
for surgical implants, for suture wire, cranial repair plates and for wire gauze for abdominal muscle support in
hernia repair surgery.
Tantalum carbide is added to some grades of cemented carbides to make hard carbide cutting tools which have a
low coefficient of friction and a high resistance to mechanical shock. The back cover lists some of the major uses
of tantalum and tantalum alloys.
Isn't its corrosion resistance a factor in many applications?
Tantalum's inertness to many chemicals has fostered its use as a corrosion resistant material in severe acid
environments. It is resistant to sulfuric, hydrochloric, and nitric acids, organic chemicals and many liquid metals.
Thus it is used in heat exchangers, spargers and reaction vessels in organic reactions, particularly when corrosive
inorganics are involved.
Applications are determined by inertness to chemical attack at moderate temperatures, reactivity at high
temperatures, good strength and ductility and by the dielectric properties of its electrolytic oxide film.
Are tantalum capacitors widely used?
The electronic industry is a major market for high purity tantalum, particularly for capacitors. Tantalum
capacitors provide higher volumetric capacitance efficiency than other capacitor materials and perform better at
both low and high temperatures.
Also, tantalum combines with certain gases at elevated temperatures and will release some of these gases when
heated in a vacuum to a higher temperature. This property is extremely useful in electronic tubes. And, good
high temperature strength, low vapor pressure and the gettering effect have made tantalum an important metal in
special-purpose vacuum tubes where it removes residual gases. It can be formed and welded into anodes and
grids, which are cleaned easily in strong acids. However, capacitors are the major electronic use of tantalum and
the development of higher-capacitance powders has broadened the field of application. With these powders, less
is needed to make a unit of a given capacitance rating; high capacitance permits miniaturization.
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Tantalum capacitors operate in computers and military hardware, color television sets, radios and cell phones.
What about tantalum alloys?
Tantalum alloys that have good high temperature strength are used in many aerospace products. However, all
tantalum alloys oxidize rapidly and surface coatings are required for elevated temperature service in oxidizing
environments.
Tantalum and niobium alloy with each other and with nickel, cobalt, chromium, tungsten and many other
elements. Tantalum alloys have good fabricating characteristics.
With such a high melting point, how is it fabricated?
The high melting point and reactivity of tantalum prevents its consolidation to near finished shape by casting.
Thus, many fabricated shapes start from powders. However, the technology of powder metallurgy has advanced
to such a high state that there is no loss of flexibility. In fact, even if tantalum did have a lower melting point,
PM processing would still be used because of other advantages.
Tantalum powder can be compacted mechanically or isostatically. Compacting presses are used for
smaller shapes such as bars, which are resistance sintered. Isostatically pressed shapes can be either resistance or
induction sintered.
Tantalum ingots up to 1600 Kilograms (3500 lbs.) are made by arc or electron beam melting of compacted and
sintered bars. Electron beam melted ingots are noted for their high purity, excellent ductility and good
weldability.
PM bars or melted ingots are extremely ductile. They can be cold rolled into sheet and foil and can be formed
and drawn into many shapes.
Tantalum can be lap or seam welded, TIG welded and electron beam welded. It is used in multi-tube heat
exchangers in corrosive environments in the chemical industry. It is also used to clad steel and copper pipe and to
line chemical reaction vessels.
Tantalum uses
Electrolytic capacitors
Heat exchangers
Bayonet heaters
Thermometer wells
Vacuum tube filaments
Chemical process equipment
High temperature furnaces components
Crucibles for handling molten metal and alloys
Cutting tools
Aerospace engine components
inerts Surgical implants
Alloy additive in superalloys
