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Tungsten Isotope
Nov 06, 2017

Tungsten, a metal element. Atomic number 74, atomic weight 183.84. Steel gray or silver white, high hardness, high melting point, free from air erosion under normal temperature; The main purpose is to manufacture filament and high speed cutting alloy steel, super hard molds, also for optical instruments, chemical instruments. China is the world's largest depository of tungsten.

Tungsten is a metal element. Tungsten chemical symbol W, atomic number is 74, the relative atomic mass is 183.85, the atomic radius of 137 meters, the density of 19.35 g/per cubic centimeter, belongs to the periodic table 6 cycles of VIB (second) for a long period of time. In nature, tungsten is mainly a six-valent cation with an ion radius of 0.68 x 10-10m. Due to the small W6 + ion radius, electricity price is high, the polarization ability strong, easy to form the complex anion, thus tungsten is mainly in the form of complex anion (WO4) 2 -, and solution of Fe2 +, Mn2 + and Ca2 + cation form black tungsten or scheelite ore precipitation. After smelting, tungsten is silver and white luster metal, melting point is very high, hardness is very big, the vapor pressure is very low, evaporation speed is also small, chemical character also is relatively stable.

Chemical properties

Tungsten is a rare high melting point metal, and can improve the high temperature hardness of steel, belongs to the periodic table 6 cycles Ⅵ group B (2) for a long period of time. Tungsten is a kind of silver and white metal, which is shaped like steel. Tungsten has a high melting point, low vapor pressure and a smaller evaporation rate. Chemical properties of tungsten is stable, with air and water at room temperature without reaction, when heated, not any concentration of hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid and aqua regia to tungsten doesn't work, when the temperature rose to 80 °, 100 ° C, the various kinds of acid, except hydrofluoric acid, and other weak acid in tungsten. At normal temperature, tungsten can dissolve rapidly in mixed acid with hydrofluoric acid and concentrated nitric acid, but not in alkaline solution. With the presence of air, the molten base can oxidize tungsten to tungstate, and the reaction to the formation of tungstate is stronger when there are oxidants (NaNO3, NaNO2, KClO3, PbO2). High temperature can be combined with oxygen, fluorine, chlorine, bromine, iodine, carbon, nitrogen and sulfur, but not with hydrogenation.

There are five kinds of tungsten isotopes in nature, which have a very long half-life and can therefore be considered stable isotopes. All these isotopes can be decayed into hafnium through alpha decay. So far could measure the half-life is 180 w, it has a half-life of 1.8 x in 1018, other isotope has not been observed natural decay, the half-life of forced degradation: T1/2 > 8.3 years, 182 w, 184 w, T1/2 > 29 years, 185 w, T1/2 > 13 years, 186 w, T1/2 > 27 years. So far their half-life is only theoretical. On average, alpha decay occurs twice a year in a gram of 180W. This element has found four isotopes, three of which are likely to be slightly radioactive. They are 182W, 186W, 183W.

Tungsten currently has 27 artificial radioactive isotopes, the most stable of which is 181W, its half-life is 121.2 days, the half-life of 185W is 75.1 days, the half-life of 188W is 69.4 days, and the half-life of 178W is 21.6 days. The half-life of other radioactive isotopes is under 24 hours, most of them less than 8 minutes.

There are a dozen main tungsten mines, China has two main kinds; Wolframite (tungsten and iron tungstate) and white tungsten (calcium tungstate).

1. Black tungsten ore (FeMn) WO4. It has dark grey, reddish brown, light brown, brown and iron brown. Semi - metallic luster, metallic gloss and resin gloss. Usually leaf shaped, curved flaky, granular and dense; There are also some thickened plates, pointed columnar crystals, often with white quartz in the form of the veins in granite and its adjacent rock cracks. Hardness 5-5.5, proportion 7.1-7.5. The differential fracture. Crispy, weak magnetism. Wolframite is the main raw material for refining tungsten and producing tungstate acid salts. The traditional process USES alkali fusion method.

2. White tungsten mine CaWO4. The color is gray, and there are brown, green and light red. Grease sheen. It is a dipyramidal pseudooctahedral or plate-like crystal, which can be seen with oblique streaks. Some crystals are crust, kidney, granular and dense. Hardness is 4.5 5; The proportion of 5.9 6.2. Sexual embrittlement, shell or differential fracture. When illuminated by fluorescent lamp, white tungsten ore can emit beautiful light blue fluorescence.

The above tungsten minerals can be used for reelection (shaking bed, jigging, etc.), flotation, chute, and heavy sand, etc., to get the concentrate of black tungsten concentrate or white tungsten concentrate

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