Titanium dioxide is produced in two main forms. The main form is pigment grade titanium dioxide, which accounts for more than 98% of the total output. Titanium dioxide pigments take advantage of the excellent light scattering properties of titanium dioxide in applications that require white opacity and brightness. The other production form of titanium dioxide is ultrafine (nanometer materials) product. This form of titanium dioxide can be chosen when different properties such as transparency and the maximum UV absorption are required (e.g. sunscreen).
Titanium dioxide has the functions of absorption, band gap and electrical conductivity. It is because of these functions that titanium dioxide products are used in many industrial products and consumer goods, including paints, coatings, adhesives, paper, plastics and rubber, printing inks, coated fabrics and textiles, as well as ceramics, building fabrics, roofing materials, cosmetics, toothpastes, soaps, water treatment agents, pharmaceuticals, food pigments, automotive products, sunscreen, catalysts, and so on.
Nano titanium dioxide is widely used in sunscreen cosmetics because of its strong ability to absorb and resist ultraviolet rays.
Compared with the same dose of organic anti-ultraviolet agent, the absorption peak of nano titanium dioxide in ultraviolet region is higher; moreover, nano titanium dioxide has a blocking effect on ultraviolet rays in medium and long wavelength regions, which is unlike organic anti-ultraviolet agent that only has shielding effect on ultraviolet rays in medium wavelength region or long wavelength region. Especially because of its fine particles, the finished products have high transparency and visible light can pass through them. The skin whiteness will look natural when adding nano titanium dioxide into cosmetics, which overcomes the opacity of some organics or pigment grade titanium dioxide and the unnatural skin whiteness. Due to these advantages, nano TiO2 has been widely valued and gradually replaced some organic anti-UV agents. Now it has become a physical shielding anti-ultraviolet agent with superior performance in sunscreen cosmetics.
Titanium dioxide is a kind of very important photocatalyst, and the band gap size of titanium dioxide has a great influence on the optical properties and photocatalytic activity.
The band gap width of anatase titanium dioxide is 3.20 eV, and 290-400 nm ultraviolet radiation is required to excite the valence band electrons to the conduction band, which is equivalent to using only 3-5% of solar visible light (400-800 nm).
Therefore, it is a challenge for photocatalytic materials to make full use of light energy to improve the light response between visible light regions. At present, optimizing the preparation process and improving the material structure are two feasible methods.
Titanium dioxide has the properties of semiconductors. TiO2 electrical conductivity increases rapidly with the increase of temperature, and it is also very sensitive to hypoxia.
The dielectric constant and semiconductor properties of rutile titanium dioxide are very important to electronic industry, because they can be used to produce ceramic capacitors and other electronic components.
For example, rutile titanium dioxide is still an electrical insulator at 20 ℃, but its conductivity increases 107 times when heated to 420 ℃. A slight reduction in oxygen content has a special effect on the electrical conductivity. The electrical conductivity of TiO2 is less than 10-10s/cm according to the chemical composition, while the conductivity of TiO1.9995 is as high as 10-1s/cm.