About Niobium Metal and Tantalum Metal


Niobium is a rare and refractory metal, with steel gray luster, a melting point of 2,467°C and a density of 8.6g/cm3. For the excellent low-temperature plasticity, it can be processed into various semi-finished products through the cold stress. With high-temperature resistance and high strength, it still has enough strength, plasticity and thermal conductivity above the temperature of 1,000°C. It has superior superconductivity at low temperatures. Its resistance is close to zero if it is at the temperature of about minus 260°C. Below the temperature of 150°C, it is resistant to atmospheric corrosion and chemical corrosion. At room temperature, niobium metal powder is insoluble in many acids and salts, but soluble in hydrofluoric acid and an acidic solution of fluorine ions as well as the concentrated alkali solution. It not only is prone to the hydrogen embrittlement, but also can generate a stable oxide film when is anodized. In natural minerals, tantalum exists in symbiosis with niobium. There are many minerals containing niobium and tantalum, which are pyrochlore, columbite-tantalite, fergusonite, niobium ilmenite rutile, red spar and the placer of niobium tantalate. Some steelmaking slag and tin-smelting slag are also important sources for refining niobium. Whether it is niobium mine or tantalum mine primarily depend on the ratio of niobium and tantalum.

Tantalum was found in 1802, with Ta as element symbol, the name originating from Greece mythical King of the wealth Tantalus. Tantalum is almost completely free from corrosion, so it makes important contributions to the repair of the body in surgery: to replace the bones (such as the skull); to be made of foil or wire so as to connect broken nerve; to be woven mesh so as to be used to bind up the abdominal muscles.

Tantalum is a grayish metal with slightly blue. Due to its various special features and a wide range of application areas, it is known as the generalist of “metals Kingdom”.

Tantalum has very hard texture with hardness up to 6-6.5, as well as density of 16.6. Its melting point is up to 2,996°C, behind only tungsten and rhenium, ranked third. Tantalum has excellent ductility so that it can pull into a filament, or make into a thin foil. Meanwhile, it has low thermal expansion coefficient, with only expansion of 6.6 per million per degree Celsius. In addition, its toughness is very strong and is superior to copper.

Tantalum has very good chemical properties too. Tantalum metal powder is highly resistant to corrosion. In both cold and hot conditions, it has no reaction with hydrochloric acid, concentrated nitric acid and “aqua regia”. Soaked into sulfuric acid at the temperature of 200°C for a year, surface of tantalum is only damaged about 0.006mm. Experiments have shown that, tantalum does not react with alkaline solutions, chlorine, bromine water, dilute sulfuric acid, as well as many other medicaments at room temperature; only reacts with hydrofluoric acid and hot concentrated sulfuric acid. This is relatively rare property of the metal.

Tantalum is widely applied for its characteristics. For the equipments used for the production of various inorganic acids, tantalum can be used to replace stainless steel so as to improve service life more than dozens of times. In addition, tantalum can replace the precious metal platinum used in the past in the chemical, electronic and electrical industries, etc., so the cost greatly reduces.

In addition, tantalum is an important element to refine super steel, corrosion-resistant steel and heat-resistant steel alloy, but also special material required to develop rockets, spacecraft, jet aircraft and other space technology. A non-magnetic alloy made of tantalum and tungsten is widely used in the electrical industry. Especially tantalum carbide made of tantalum and carbon has great hardness, which is comparable to that of diamond even at high temperatures. Tools made of it can cut many hard alloys at high speed; drill bits made of it can substitute for the most hard alloy or diamonds. Therefore, tantalum is considered as “vitamins” in smelting.

In modern medicine, tantalum can also play an important role. Studies have shown that tantalum has no harm to the human body, and the body’s muscles can also grow on it, medically called that “bio-compatibility”. Doctors use the characteristic of tantalum to repair broken skull and cracks and coloboma of limb fractures. Meanwhile, tantalum can also be made into filaments one-tenth thinner than human hair, as a suture for visceral surgery using, or embedded artificial eyeball. This tantalum wire can even replace muscle tendon and nerve fibers. Medical scientists firstly use the tantalum plate to make artificial ears and suture them on the head; then transplant skin from the legs. Over a period of time, new skin graft looks good, so people can almost not make out that they are artificial tantalum ears.