Properties of tantalum

physical property

The chemical symbol TA, steel gray metal, belongs to VB group in the periodic table, atomic number 73, atomic weight 180.9479, body centered cubic crystal, common valence is + 5. The hardness of tantalum is low and related to oxygen content. The Vickers hardness of ordinary pure tantalum is only 140hv. Its melting point is as high as 2995 ℃, ranking the fifth in the elemental elements after carbon, tungsten, rhenium and osmium. Tantalum is malleable and can be drawn into thin wires to make thin foil. The coefficient of thermal expansion is very small. It only expands 6.6 parts per million for every degree of increase. In addition, its toughness is very strong, even better than copper.

CAS No.: 7440-25-7 [6]

Series: transition metals.

Relative atomic mass: 180.947 88 (12c = 12.0000)

Density: 16650 kg / M?; 16.654 g / cm

Hardness: 6.5

Element partition, 5 families, 6, D

Color: Blue Grey

Valence electron arrangement: [xenon] 4f5d6s

Atomic volume: (cm3 / mol)

ten point nine zero

Element content in seawater: (PPM) 0.00000 2

Content in crust: 1 (PPM)

Oxidation state:

Main Ta+5

Other Ta-3, Ta-1, Ta+1, Ta+2, Ta+3

Crystal structure: the cell is body centered cubic cell, each cell contains two metal atoms.

Cell parameters:

a = 330.13 pm

b = 330.13 pm

c = 330.13 pm

α = 90°

β = 90°

γ = 90°

Vickers hardness (arc melting and cold work hardening): 230hv

Vickers hardness (recrystallization annealing): 140hv

Vickers hardness (after one electron beam melting): 70hv

Vickers hardness (melted by secondary electron beam): 45-55hv

Melting point: 2995 ℃

The propagation rate of sound in it: (M / s) 3400

Ionization energy (kJ / mol)

M - M+ 761

M+ - M2+ 1500

M2+ - M3+ 2100 M3+ - M4+ 3200

M4+ - M5+ 4300

Discoverer: discovered by Swedish chemist Anders gustafar Ekberg in 1802.

Name of element: Ekberg named the element after Tantalus, the father of Niobe, Queen of Thebes in ancient Greek mythology.

Source: it mainly exists in tantalite and coexists with niobium.

It can also be used as a capacitor for electronic components.

chemical property

It has excellent chemical resistance to both hydrochloric acid and hot water. However, tantalum can be corroded in hot concentrated sulfuric acid. Under 150 ℃, tantalum will not be corroded by concentrated sulfuric acid, and only when the temperature is higher than this temperature, the corrosion thickness is 0.0004mm in 175 ℃ concentrated sulfuric acid for one year. When tantalum is immersed in 200 ℃ sulfuric acid for one year, the surface damage is only 0.006 mm. At 250 ℃, the corrosion rate increases, which is 0.116 mm per year. At 300 ℃, the corrosion rate is even faster. After soaking for 1 year, the surface is corroded by 1.368 mm. The corrosion rate in fuming sulfuric acid (containing 15% so ₃) is more serious than that in concentrated sulfuric acid. The corrosion thickness of the surface is 15.6 mm after soaking in the solution at 130 ℃ for one year. Tantalum can also be corroded by phosphoric acid at high temperature, but the reaction usually takes place above 150 ℃. After soaking in 85% phosphoric acid at 250 ℃ for one year, the surface is corroded by 20 mm. In addition, tantalum can be rapidly dissolved in mixed acid of hydrofluoric acid and nitric acid, and can also be dissolved in hydrofluoric acid. But tantalum is more afraid of strong alkali. In the caustic soda solution of 110 ℃ and 40% concentration, tantalum will be rapidly dissolved, and in the same concentration of potassium hydroxide solution, as long as 100 ℃ will be rapidly dissolved. In addition to the above conditions, the General inorganic salts can not corrode tantalum below 150 ℃. The results show that tantalum has no effect on alkali solution, chlorine gas, bromine water, dilute sulfuric acid and many other reagents at room temperature, but only reacts with hydrofluoric acid and hot concentrated sulfuric acid. Such a situation is rare in metals.

However, at high temperature, the oxide film on the surface of tantalum is destroyed, so it can react with many kinds of materials. At room temperature, tantalum can react with fluorine. At 150 ℃, tantalum is inert to chlorine, bromine and iodine. At 250 ℃, tantalum still has corrosion resistance to dry chlorine gas. When heated to 400 ℃ in chlorine gas containing water vapor, it can still keep bright. At 500 ℃, tantalum begins to corrode. Above 300 ℃, tantalum reacts with bromine, and it is inert to iodine vapor before the temperature reaches red heat. Hydrogen chloride reacts with tantalum at 410 ℃ to produce pentachloride, while hydrogen bromide reacts with tantalum at 375 ℃. When heated to 200 ℃ or lower, s can react with TA, and carbon and hydrocarbons interact with tantalum at 800-1100 ℃.