Physical Properties

1) Relative density

Among the commonly used white pigments, titanium dioxide has the smallest relative density. Among the white pigments of the same quality, titanium dioxide has the largest surface area and the highest pigment volume.

2) Melting point and boiling point

Since the anatase type transforms into a rutile type at high temperature, the melting point and boiling point of anatase titanium dioxide do not actually exist. Only rutile titanium dioxide has a melting point and boiling point. The melting point of rutile titanium dioxide is 1850 ° C, the melting point in air is (1830 ± 15) ° C, and the melting point in oxygen-rich is 1879 ° C. The melting point is related to the purity of titanium dioxide. The boiling point of rutile titanium dioxide is (3200±300)°C, and titanium dioxide is slightly volatile at this high temperature.

3) Dielectric constant

Since titanium dioxide has a high dielectric constant, it has excellent electrical properties. When determining some physical properties of titanium dioxide, the crystallographic direction of titanium dioxide crystals should be considered. The dielectric constant of anatase titanium dioxide is relatively low, only 48.

4) Conductivity

Titanium dioxide has semiconductor properties, its conductivity increases rapidly with temperature, and it is also very sensitive to oxygen deficiency. The dielectric constant and semiconductor properties of rutile titanium dioxide are very important to the electronics industry, and these properties can be used to produce electronic components such as ceramic capacitors.

5) Hardness

According to the Mohs hardness scale, the rutile titanium dioxide is 6-6.5, and the anatase titanium dioxide is 5.5-6.0. Therefore, in the chemical fiber extinction, the anatase type is used to avoid abrasion of the spinneret holes.

6) Hygroscopicity

Although titanium dioxide is hydrophilic, its hygroscopicity is not very strong. The rutile type is smaller than the anatase type. The hygroscopicity of titanium dioxide has a certain relationship with the size of its surface area. Large surface area and high hygroscopicity are also related to surface treatment and properties.

7) Thermal stability

Titanium dioxide is a material with good thermal stability.

8) Granularity

The particle size distribution of titanium dioxide is a comprehensive index, which seriously affects the performance of titanium dioxide pigments and product application performance. Therefore, the discussion of hiding power and dispersibility can be directly analyzed from the particle size distribution.

The factors affecting the particle size distribution of titanium dioxide are complex. The first is the size of the original particle size of hydrolysis. By controlling and adjusting the hydrolysis process conditions, the original particle size is within a certain range. The second is the calcination temperature. During the calcination of metatitanic acid, the particles undergo a crystal transformation period and a growth period, and the appropriate temperature is controlled to make the growth particles within a certain range. The last is the pulverization of the product. Usually, the modification of the Raymond mill and the adjustment of the speed of the analyzer are used to control the pulverization quality. At the same time, other pulverizing equipment can be used, such as: universal mill, jet mill and hammer mill.

Crystal structure

Titanium dioxide has three crystalline forms in nature: rutile, anatase and brookite. Plate titanium type belongs to orthorhombic crystal system, which is an unstable crystal form. It is converted into rutile type at above 650 °C, so it has no practical value in industry. The anatase type is stable at room temperature, but it is converted to rutile at high temperature. Its transformation strength depends on the manufacturing method and whether there is an inhibitor or accelerator added during the calcination process.

It is generally believed that the crystal transformation hardly occurs below 165 °C, and the transformation occurs rapidly when it exceeds 730 °C. The rutile type is the most stable crystalline form of titanium dioxide, with a dense structure and higher hardness, density, dielectric constant and refractive index than the anatase type. Both rutile type and anatase type belong to the tetragonal system, but have different lattices, so the X-ray images are also different. The diffraction angle of anatase type titanium dioxide is located at 25.5°, and the diffraction angle of rutile type is located at 27.5°. The rutile-type crystals are slender, prismatic, and usually twinned; while the anatase-type crystals are generally approximately regular octahedrons.

Compared with the anatase type, the rutile type is smaller and denser than the anatase type because its unit lattice is composed of two titanium dioxide molecules, while the anatase type is composed of four titanium dioxide molecules. Great stability and relative density, therefore high refractive index and dielectric constant and low thermal conductivity.

Among the three isomers of titanium dioxide, only the rutile type is the most stable, and only the rutile type can be obtained by thermal conversion. Natural brookite is converted to rutile type at temperatures above 650°C, and anatase can also be converted to rutile type at around 915°C.

Chemical Properties

The chemical properties of titanium dioxide are extremely stable, and it is a kind of acidic amphoteric oxide. It hardly reacts with other elements and compounds at room temperature, and has no effect on oxygen, ammonia, nitrogen, hydrogen sulfide, carbon dioxide, and sulfur dioxide. It is insoluble in water, fat, dilute acid, inorganic acid, and alkali, only soluble in hydrogen. Fluoric acid. However, under the action of light, titanium dioxide can undergo continuous redox reactions and has photochemical activity. This kind of photochemical activity is particularly obvious under the irradiation of ultraviolet rays, and this property makes titanium dioxide not only a photosensitive oxidation catalyst for some inorganic compounds, but also a photosensitive reduction catalyst for some organic compounds.

Emergency treatment: Isolate the leaked contaminated area and restrict access. It is recommended that emergency personnel wear dust masks (full face masks) and general work clothes. Avoid dust, carefully sweep up, put in a bag and transfer to a safe place. If there is a large amount of leakage, cover it with plastic sheeting or canvas. Collect and recycle or transport to waste disposal site for disposal.

Titanium dioxide (or titanium dioxide) is widely used in various structural surface coatings, paper coatings and fillers, plastics and elastomers, and other uses include ceramics, glass, catalysts, coated fabrics, printing inks, roofing and flux. According to statistics, the global demand for titanium dioxide in 2006 reached 4.6 million tons, of which the coating industry accounted for 58%, the plastic industry accounted for 23%, the paper industry 10%, and the other 9%. Titanium dioxide can be prepared from ilmenite, rutile or titanium slag. There are two production processes for titanium dioxide: sulfate process and chloride process. The sulfate process is simpler than the chloride process, and can use low-grade and relatively cheap minerals. Today, about 47% of the world's production capacity uses the sulfate process, and 53% of the production capacity is the chloride process.