Metallic cerium received the greatest demand in the form of dioxide. Most of it is used for the production of polishing powders. They go to the bleaching and polishing of mirrors, mineral lenses, chemically resistant glasses; possess good suspension qualities, high efficiency and purity of processing.
Surfaces after work do not contain scratches and damage. The raw material in Russia for the production of powders is loparite concentrate, which is supplied from the Kola Peninsula.
Historical information
The element of cerium acquired its name in honor of the planet Ceres. It was discovered almost simultaneously by the German chemist M. G. Klaproth and two Swedish colleagues V. Hiesinger and J. J. Berzelius in the nineteenth century. The mineral was called cerite, and the chemical element was called cerium. The structure of the atom is shown in the photo.
The chemist K. G. Mozander isolated cerium in its pure form in 1839, and the American chemist W. F. Gillebrand obtained cerium in the form of metal using electrolysis. Cerium is a metal of nuclear energy. It is used as a hot zone material.
Lanthanide metal properties
The chemical element cerium is a light rare-earth element; it belongs to the third group in the periodic table. It has a light gray color with an atomic mass of 140.12 and a melting point of about 1000 degrees Celsius. The metal has a high activity and in the compounds shows two valencies 3+ and 4+. It actively reacts with nitrogen, hydrogen and oxygen. The interaction with hydrogen begins at room temperature and is accompanied by the release of heat. The more active the reaction, the higher the temperature.
The metal is able to dissolve in diluted acids with the release of hydrogen. One of the special properties of cerium is its violent reaction with zinc, which proceeds instantly and ends with an explosion. In air, a metal forms a coating of a very thin oxide film. The element ignites at a temperature of more than 300 degrees Celsius, turning into dioxide. This is a yellow powder substance. When it is calcined in hydrogen, trivalent cerium oxide is obtained, which, when reacted with alkali, becomes tetravalent. Cerium is a malleable and viscous metal. It easily rolls and when heated is drawn into the wire. It depends on the pressure. During compression, a significant decrease in volume occurs and the electrical resistance decreases. This exceptional phenomenon is explained by the appearance of tetravalent ions in the electron cloud.
Deposits of Cerium Ores
Pure cerium minerals do not exist in nature. Most of all it contains:
- bastnesitis. The ore consists of yellow, red or brown crystals. Deposits in the United States and China contain most of the world's cerium reserves. Known deposits of bastnesite ores are also found in Vietnam and Afghanistan;
- monazite. It is a brilliant yellow-brown mineral. Its deposits are concentrated in Brazil, Austria, Malaysia, Thailand, the USA and South Africa. Monazite sand placers are found along the shores of the seas, lakes and rivers of many countries;
- loparite ores. They are the main source of metal cerium in Russia. The main field is located on the Kola Peninsula.
Polishing powders
The basis for them is cerium dioxide. They are produced in Russia in two brands:
- Optipol is a semi-universal powder. The composition perfectly demonstrates its properties when working with crystals, ceramics, flat parts of crown glass mirrors, display, automotive, borlant and chemically resistant glasses.
- "Ftoropol" is a universal powder. It consists of finely divided crystalline particles having a brown tint.They are polished with optical glasses (rangefinder lenses, periscopes, binoculars), various mirrors, lenses for glasses, photo masks, plates for semiconductors, stones for jewelry and jewelry. The basis of the powder is a mixture of oxyfluorides and rare earth oxides.
World prices for cerium
Important cerium products on the market consist of alloys, oxides, carbonates, acetates, and some other compounds. The price of metal cerium is determined by the type of product and its purity. The cost of cerium dioxide, whose purity is 99.99%, per kilogram is equal to 29.5 US dollars.
The powders used for polishing of the Ftoropol brand cost about 8, and Optipol costs about $ 6 per kilogram. The price of cerium mischmetal is from 14 to 18 dollars per kilogram. On the Russian market, cerium oxide costs about 17,000, and electrolytic cerium is $ 90 per kilogram.
The use of cerium in domestic industry
For the first time in 1884 a patent was obtained for the use of cerium. Metal began to be used in gas-burning lamps to increase the brightness of the flame of fixtures. Currently, it is widely used:
- with small additives to alloys that crack, forging, rolling improves, sheets, pipes and rods are easily obtained. Metal contributes to the modification of alloys of iron, magnesium, aluminum, structural steels, increasing their strength and corrosion resistance;
- as an additive to cast iron. Thereby increasing fluidity, improving the machinability of castings and physico-mechanical properties;
- in the oil and chemical industries, they are used as a catalyst accelerating the reaction time;
- in magnetic thermometers;
- in atomic engineering use glasses containing cerium. Under the influence of radiation, they do not fade and protect personnel;
- it is part of the most effective Polirit powder for polishing mirror and optical glass;
- an alloy of cerium with iron is used as artificial flint for lighters;
- used for cooking colored glasses having a shade of yellow to orange;
- One of the important global areas of application of cerium is manifested in the verification of exhaust gases from motor vehicles. This element helps to remove sulfur dioxide from them. The cerium introduced into the catalysts significantly improves and stabilizes the work when the structure of the exhaust mixtures changes;
- added for the manufacture of very hardened refractory materials ;
- used for the production of solid-state powerful batteries, which are designed for electric vehicles, computers, cell phones, film and cameras;
- in medicine they treat and prevent symptoms of motion sickness. In dentistry, cerium steel and ceramics are used.
Cerium Technology
During the processing of concentrates containing rare-earth metals, at the initial stage, light elements are separated from heavy elements and only then the necessary metal is released. Cerium is obtained from ores, more often, from monazite according to the following technology:
- precipitated from a nitrate solution cerium hydroxide;
- filter the pulp;
- drying the precipitate;
- calcined the resulting oxide.
With this technology, cerium dioxide powder is recovered. In its pure form, metal is mined by melt electrolysis. Then it is smelted and formed into ingots.
Instead of a conclusion
Mineral lenses are replaced by plastic ones. They are much lighter and more resistant, and in the manufacture of low-cost. In global markets, the demand for mineral glass has changed. The Russian manufacturer did not stand aside. This has contributed to lower demand for products made from cerium metal. Domestic manufacturing plants have to focus on a different market.
They switched to the production of powders for polishing liquid crystal television screens and monitors. The main consumer was Southeast Asia. In addition, Russian products also enter the domestic market, satisfying the demand for cerium powders. They are used for navigation technology of aviation, navy and defense. In addition, cerium metal is used for the manufacture of optical coatings, and it is also used in the production of fluorescent lamps and ceramics.