We continue to review some of the most important materials in heat treatment and metallurgy.
Tantalum (chemical symbol: Ta)
Tantalum is a shiny blue-gray, ductile metal (Fig. 1) that is chemically nonreactive, making it very resistant to corrosion attack. It has the fourth-highest melting point of any metallic element, and it was used for light-bulb filaments until being replaced by tungsten starting in 1909. For cost reasons, tantalum is often used as a substitute for platinum.
Tantalum was discovered in 1802 by Swedish chemist Anders Gustaf Ekenberg in minerals found in Ytterby, Sweden. Partly deaf from a childhood infection and blinded in one eye by an exploding flask, perhaps his greatest contribution was the discovery of the talent of his student Jöns Jacob Berzelius, a Swedish chemist considered to be one of the founders of modern chemistry. It was first thought that Ekenberg had only discovered an alternate form of niobium, an element immediately above it on the periodic table and chemically similar to tantalum. In 1866, however, Swiss chemist Jean Charles Galissard de Marignac showed that tantalum and niobium were two distinct elements. Tantalum was named after the mythological figure Tantalus, a son of the Greek god Zeus.
In 1922, Clarence W. Balke discovered that oxidized tantalum made a good rectifier of alternating current and it soon found use in radio receiving sets and capacitors. Since then the use of tantalum in the electronics and chemical industries has increased steadily.
Tantalum capacitors have the highest capacitance per unit volume compared to similar devices. Some of its most common uses today are in electrolytic capacitors and miniaturized electronics. Capacitors made from tantalum can be found in a range of products, such as automotive electronics, laptop computers, mobile phones and tablets. Tantalum is also used for electronic sound filters and as a barrier against copper diffusion in semiconductors.
Since tantalum is also biologically inert, it is used in surgical instruments, implants, clips and prosthetics. Alloyed with carbon, tantalum is used in making carbide tools for metalworking equipment.
Tantalum’s most important contribution to metallurgy is as an addition to nickel-based superalloys to improve their mechanical properties at high temperatures, hot corrosion resistance and longevity. Nickel-based superalloys are the predominant materials in the hot section of gas turbine engines and comprise approximately 50% of the weight of high-performance aircraft engines.
Here are some interesting facts about tantalum.
- Atomic number: 73
- Atomic weight: 180.94788
- Melting point: 3290 K (3017°C or 5463°F)
- Boiling point: 5731 K (5458°C or 9856°F)
- Density: 16.4 grams per cubic centimeter
- Phase at room temperature: Solid
- Element classification: Metal