Properties of titanium

Titanium is a metal chemical element, chemical symbol Ti, atomic number 22, in the chemical element periodic table in the fourth cycle, IVB group. It is a silvery white transition metal, characterized by light weight, high strength, metallic luster and resistance to wet chlorine corrosion. However, titanium can not be used in dry chlorine gas. Even if the temperature is below 0 ℃, there will be violent chemical reaction to form titanium tetrachloride, which will be decomposed into titanium dichloride and even burned. Only when the water content of chlorine is higher than 0.5%, titanium can maintain reliable stability in it.  

Titanium is considered to be a rare metal because it is dispersed in nature and difficult to extract. It is relatively rich in all elements. Titanium ore is mainly ilmenite and rutile, widely distributed in the crust and lithosphere. Titanium also exists in almost all organisms, rocks, water and soil. Extraction of titanium from the main ore requires the Kroll or hunt process. The most common compound of titanium is titanium dioxide, which can be used to make white pigments. Other compounds include titanium tetrachloride (TiCl4) (used as catalyst and smoke screen as air cover) and titanium trichloride (TiCl3) (used to catalyze the production of polypropylene).

physical property

Titanium has metallic luster and ductility. The density is 4.5 g / cm3. The melting point is 1660 ± 10 ℃. Boiling point 3287 ℃. The valence is + 2, + 3 and + 4. The ionization energy is 6.82 ev. Titanium is characterized by low density, high mechanical strength and easy processing. The plasticity of titanium mainly depends on its purity. The purer the titanium, the greater the plasticity. It has good corrosion resistance and is not affected by atmosphere and sea water. At normal temperature, it will not be corroded by hydrochloric acid below 7%, sulfuric acid below 5%, nitric acid, aqua regia or dilute alkali solution; only hydrofluoric acid, concentrated hydrochloric acid and concentrated sulfuric acid can act on it.

Titanium is an important alloy element in steel and alloy. The density of titanium is 4.506-4.516 g / cm3 (20 ℃), which is higher than that of aluminum and lower than that of iron, copper and nickel. But the specific strength is the first of all metals. [8] Melting point 1668 ± 4 ℃, melting latent heat 3.7-5.0 kcal / g atom, boiling point 3260 ± 20 ℃, latent heat of vaporization 102.5-112.5 kcal / g atom, critical temperature 4350 ℃, critical pressure 1130 ATM. The thermal conductivity and conductivity of titanium is poor, which is similar to or slightly lower than that of stainless steel. The superconductivity of pure titanium is 0.38-0.4k. At 25 ℃, the heat capacity of titanium is 0.126 cal / G [9] atom · degree, the enthalpy is 1149 cal / g atom · degree, and the entropy is 7.33 cal / g atom · degree. Titanium is a paramagnetic material with a permeability of 1.00004.

Titanium has plasticity. The elongation of high-purity titanium can reach 50-60%, and the reduction of area can reach 70-80%, but the shrinkage strength is low (i.e. the strength produced during shrinkage). The existence of impurities in titanium has great influence on its mechanical properties, especially interstitial impurities (oxygen, nitrogen, carbon) can greatly improve the strength of titanium and significantly reduce its plasticity. As a structural material, titanium has good mechanical properties by strictly controlling the appropriate impurity content and adding alloy elements.