Titanium is a chemical element, chemical symbol Ti, atomic number 22, in the periodic table of chemical elements in the fourth cycle, Group IVB. Is a silver-white transition metal, which is characterized by light weight, high strength, with metallic luster, moisture-resistant chlorine corrosion. But titanium can not be used in dry chlorine, even if the temperature below 0 ℃ dry chlorine, there will be a violent chemical reaction, the formation of titanium tetrachloride, and then decomposition of titanium dioxide, or even combustion. Only when the moisture content of chlorine gas is higher than 0.5%, titanium in which to maintain a reliable stability.
Titanium is considered to be a rare metal, due to its dispersion in nature and difficult to extract. But its relatively rich, in all the elements in the tenth place. Titanium ore mainly ilmenite and rutile, widely distributed in the crust and lithosphere. Titanium is also present in almost all creatures, rocks, water bodies and soil. Extraction of titanium from the main ore requires the use of the Crow method or the Hunt method. The most common compound of titanium is titanium dioxide, which can be used to make white pigments. Other compounds include titanium tetrachloride (TiCl4) (as a catalyst and for the manufacture of smoke screens for aerial cover) and titanium trichloride (TiCl3) (for the production of catalyzed polypropylene).
Titanium has metallic luster and has ductility. Density of 4.5 g / cm3. Melting point 1660 ± 10 ℃. The boiling point of 3287 ℃. Valence + 2, + 3 and +4. The ionization energy is 6.82 eV. Titanium is characterized by a small density, mechanical strength, easy processing. The plasticity of titanium is mainly dependent on purity. Titanium more pure, the greater the plasticity. Has good corrosion resistance, not affected by the atmosphere and sea water. At room temperature, will not be less than 7% hydrochloric acid, 5% sulfuric acid, nitric acid, aqua regia or dilute alkali solution corrosion; only hydrofluoric acid, concentrated hydrochloric acid, concentrated sulfuric acid can only role it.
Titanium is an important alloying element in steel and alloys. The density of titanium is 4.506-4.516 g / cm (20 ° C) higher than that of aluminum and lower than iron, copper and nickel. But the strength is at the head of the metal. Melting point 1668 ± 4 ℃, melting latent heat 3.7-5.0 kcal / gram atom, boiling point 3260 ± 20 ℃, latent heat of vaporization 102.5-112.5 kcal / gram atom, critical temperature 4350 ℃, critical pressure 1130 atmospheric pressure. Titanium thermal conductivity and conductivity is poor, similar or slightly lower than the stainless steel, titanium with superconductivity, titanium superconducting critical temperature of 0.38-0.4K. At 25 ° C, the heat capacity of titanium is 0.126 cal / g  atoms, degree of enthalpy of 1149 cards / gram atom, entropy of 7.33 cals / gram atom, metal titanium is paramagnetic material, permeability of 1.00004 The
Titanium has plasticity, high purity titanium elongation of up to 50-60%, section shrinkage up to 70-80%, but the shrinkage strength is low (that is, the intensity of contraction). Titanium impurities in the existence of its great impact on mechanical properties, especially the gap impurities (oxygen, nitrogen, carbon) can greatly improve the strength of titanium, significantly reducing its plasticity. Titanium as a structural material has good mechanical properties, that is, by strictly controlling the appropriate impurity content and adding alloying elements to achieve.
Titanium oxide is titanium dioxide, natural TiO2 is rutile, pure TiO2 is white powder, is the best white pigment, commonly known as titanium white, cold when the white, hot when the light yellow. Previously, people mining titanium, the main purpose is to get titanium dioxide. Titanium white adhesion is strong, not easy to change from the chemical, is always white, is an excellent white paint, it has high refractive index, strong coloring, hiding power, chemical stability. Other white coatings, such as zinc white ZnO and lead white 2PbCO3 · Pb (OH) 2, do not have these excellent properties of titanium dioxide. Particularly valuable is titanium dioxide non-toxic. It has a high melting point and is used to make refractory glass , glazes, enamel, clay, and high temperature resistant laboratory utensils.
Titanium dioxide is the world's most white things, 1 gram of titanium dioxide can be more than 450 square centimeters of the area painted white. It is more than the commonly used white pigment - zinc barium white also white 5 times, it is the best paint to prepare white paint. The world as a pigment of titanium dioxide, more than a year to several hundred thousand tons. Titanium dioxide can be added to paper, making the paper white and opaque, the effect is 10 times larger than other substances, therefore, banknote paper and art paper will add titanium dioxide. In addition, in order to make the color of the plastic lighter, so that artificial silk gloss soft, and sometimes also add titanium dioxide. In the rubber industry, titanium dioxide is also used as a white rubber filler.
Titanium tetrachloride is very interesting, it is usually in the case of colorless liquid (melting point -25 ℃, boiling point 136.4 ℃), pungent odor, in the wet air will be a big white smoke - it is hydrolyzed, into White titanium dioxide hydrogel. In water is strongly hydrolyzed to partial titanic acid H ₂TiO₃. In the military, people will use titanium tetrachloride this strange temper, as an artificial aerosol. Especially in the ocean, water and more, one put titanium tetrachloride, smoke like a white Great Wall, blocking the enemy's line of sight. In agriculture, people use titanium tetrafluoride to prevent frost.