The term "rare earth" was adopted in the 18th century because minerals used to extract these elements were scarce and the oxides they obtained were not available.
The term "rare earths" was adopted in the 18th century because the minerals used to extract these elements were scarce, and the oxides obtained were difficult to melt, dissolve in water, or separate, and resembled "soil" in appearance. They are called rare earths. Rare earth elements are divided into "light rare earth elements" and "heavy rare earth elements":
"Light rare earth elements" refers to the smaller atomic number of scandium Sc, yttrium Y and lanthanum La, cerium Ce, praseodymium Pr, neodymium Ce and other rare earth elements.
"Light rare earth elements" refers to the smaller atomic number of scandium Sc, yttrium Y, lanthanum La, cerium Ce, praseodymium Pr, neodymium Nd, promethium Pm, samarium Sm, europium Eu.
"Heavy rare earth elements" refers to the larger atomic number of gadolinium Gd, terbium Tb, dysprosium Dy, holmium Ho, erbium Er, thulium Tm, ytterbium Yb, lutetium Lu.
The rare earth elements are active in nature, making it a pro-earth element, which can be used as an antimagnetic agent. Active nature, making it a lithophilic element, the earth's crust has not been found in its natural metal anhydrous or sulfide, most commonly in the form of complex oxides, anhydrous or anhydrous silicates, anhydrous or anhydrous phosphates, phosphorus silicates, fluorocarbons, and fluoride, and other forms exist. Because of the ionic radius of rare earth elements, oxidation state and all other elements are similar, because
This in the minerals they are often together with other elements **** born.
China's rare earth resources accounted for 80% of the world's rare earth resources to oxide (REO) amounted to 36 million tons, the prospect of reserves is actually 100 million tons.
China's rare earth resources are divided into two major blocks in the north and south.
-North: light rare earth resources, concentrated in Baotou Baiyun Ebot and other places, and later in Sichuan Coronation and found. Mainly contains lanthanum, cerium, praseodymium, neodymium and a small amount of samarium, europium, gadolinium and other elements;
--South: medium and heavy rare earth resources, distributed in Jiangxi, Guangdong, Guangxi, Fujian, Hunan and other provinces, with rare ionic endowment with granite weathered crust, mainly contains samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, yttrium and lanthanum and neodymium.
China
China's rare earth industry is also divided into two major production systems, north and south.
-North to Baotou Rare Earth High Tech Company and Gansu Rare Earth Company as the axis, constituting the Baotou rare earth resources, Sichuan resources, supplemented by light rare earth products production system. The backbone enterprises are Nuclear Industry 202 Factory, Baotou Luxilona Rare Earth Co., Ltd, Baotou City and hair rare earth plant, Baotou City Rare Earth Smelter, Harbin Rare Earth Materials Plant, Sichuan Rare Earth Materials Plant, Sichuan Shifang City Jida Chemical Plant, Anning River Rare Earth Smelter. The main products include rare earth concentrates, rare earth ferro-silicon alloys, mixed rare earth compounds, enriched materials and mixed metals. The production capacity of rare earth concentrates and the handling and processing capacity amount to 50,000 tons (REO-oxide calculation).
--South to Shanghai Yue Long Nonferrous Metals Co., Ltd. as the leader, constitutes the Jiangxi and Guangdong provinces ionic rare earth resources, mainly in the middle and heavy rare earth production system. Backbone enterprises are Guangzhou Zhujiang Smelter, Guangdong Yangjiang Rare Earth Plant, Jiangsu Xinwei Group, Jiangsu Liyang Founder Rare Earth General Factory, Jiangyin Jiahua Rare Earth Smelter, Jiangsu Jiangfei Rare Earth Smelter, Jiangxi Longnan Rare Earth Company, Jiangxi Seek Woo Rare Earth Company, Jiangxi Province, Jiangxi Province, Jiangxi Rare Earth Company, Jiangxi Nuclear Industry, 713 mines and so on. The main products are a variety of high-purity single rare earth compounds and metals, enrichments, mixed metals and alloys. Separation of the total scale has exceeded 10 000 tons, and began large-scale processing and separation of northern light rare earth raw materials.
Four, the scope of application of rare earth elements
At present, the application of rare earth elements is booming, has been extended to all aspects of science and technology, especially the development and application of some modern new functional materials, rare earth elements have become indispensable raw materials.
1, rare earth elements in the traditional industries in the field of application
-agricultural field: the current development of rare earth agronomy, rare earth soil science, rare earth plant physiology, rare earth health toxicology and rare earth microanalysis and other disciplines. Rare earths as plant growth, physiological regulators, crops with yield, improve quality and resistance to three major features; at the same time, rare earths are low-toxicity substances, harmless to humans and animals, no pollution of the environment; the rational use of rare earths, crops can be made to enhance drought-resistant, waterlogging-resistant and resistance to collapse ability. At present, China's farmland application of rare earth area of 5,000-7,000,000 mu/year, for the country to increase the production of grain, cotton, beans, oil, sugar, such as 600-800 million kilograms, the direct economic benefits of 1.0-1.5 billion yuan, the annual consumption of rare earth 1,100-1,200 tons.
--Metallurgical industry: rare earths in the metallurgical industry in a large number of applications, accounting for about 1/3 of the total amount of rare earths. rare earth elements are easy to generate with oxygen and sulfur high melting point and plasticity at high temperatures is very small oxides, sulfides, and sulfur-oxygen compounds, etc., adding rare earths to the steel, desulfurization and deoxygenation to change the shape of the inclusions, and improve the normal and low-temperature steel, and improve the shape of the inclusions.
Rare earths in cast iron as graphite spheroidizing agent, nucleating agent nuclear control agent for harmful elements, improve the quality of castings, castings of mechanical properties have greatly improved, mainly used in ingot molds, rolling rolls, cast pipes and profiled parts in four areas.
In the application of non-ferrous alloys, non-ferrous metal-based various alloys have a good role in improving the physical and mechanical properties of the alloy. The most used make aluminum, magnesium, copper three series.
--Petrochemical field: rare earths used in the oil cracking industry in the rare earth molecular sieve cracking catalysts, characterized by high activity, good selectivity, high productivity of gasoline. Rare earths are used in this area in large quantities.
--Glass industry: rare earths in the glass industry in three applications: glass coloring, glass decolorization and the preparation of special performance glass. Rare earth oxides used for glass coloring neodymium (pink and with purple luster), praseodymium glass for green (manufacturing filters), etc.; cerium dioxide can be yellow-green glass in the bivalent iron oxidation to trivalent and decolorization, to avoid the toxicity of the past use of arsenic oxides, but also can be added to neodymium oxide for physical decolorization; rare earth special glass such as cerium glass (radiation glass), lanthanum glass (optical glass).
--Ceramic industry: rare earths can be added to ceramics and porcelain glaze, reduce the glaze and rupture and make it shiny. Rare earths are more mainly used as pigments for ceramics, due to rare earth elements have unfilled 4f electrons, can absorb or emit different wavelengths of light from the ultraviolet, can be seen in the infrared region, the emission of each light region of the range of small, resulting in the ceramic color is more muted, pure, novel hue, good finish. Such as yellow, violet, green, peach, orange, brown, black and so on. Rare earth oxides can make high temperature resistant transparent ceramics (used in laser and other fields), high temperature resistant crucible (metallurgy).
--Electric light source industry field: rare earth as fluorescent lamp light-emitting materials, is energy-saving light source, characterized by good light efficiency, good light color, long life. It can save 75-80% of electricity than incandescent lamps.
2, rare earth elements in the high-tech industry applications
- display of light-emitting materials: rare earth elements in yttrium, europium is the main raw material for red phosphor, widely used in color televisions, computers and a variety of monitors. At present, China's annual output of color TV red powder 300-400 tons, computer monitor red powder 50-100 tons to meet the domestic demand for 35 million color display tubes and nearly a million monitors.
--Magnetic materials: neodymium, samarium, praseodymium, dysprosium, etc. is the main raw material for the manufacture of modern super-permanent magnetic materials, whose magnetism is 4-10 times higher than that of ordinary permanent magnetic materials, which are widely used in high-tech fields such as television, electro-acoustic, medical equipment, magnetic levitation trains and military industry. According to expert forecasts, the end of this century, the output value of such materials will reach 3.5 billion U.S. dollars. The city's Nankai University research and development with independent intellectual property rights of neodymium-iron-boron permanent magnet materials belong to this kind, is now working with the Kenda Group for industrialization.
--Hydrogen storage materials: rare earths and transition elements of intermetallic compounds MMNi5 (MM for mixed rare earth metals) and LaNi5 is an excellent hydrogen-absorbing materials, known as hydrogen sponge. Its most successful application is in the manufacture of secondary batteries - metal hydride batteries, i.e. nickel-metal hydride batteries. Its equal volume charging capacity is now widely used nickel-cadmium batteries 2 times, charge and discharge cycle life and output voltage and nickel-cadmium batteries, but without the cadmium pollution. The city's Nankai University has a great advantage in the research and development of hydrogen storage materials, through the 863 project, the Peace Bay Company has begun the industrialization of nickel-metal hydride batteries.
--Laser materials: rare earth ions are the most important activator of solid laser materials and inorganic liquid laser materials, including Nd3+-doped laser materials have been studied the most, in addition to yttrium-aluminum garnet (YAG), yttrium aluminum aluminate (YAP) glass and other matrices, high-rare-earth concentration of laser materials may be known as a special application of the of the material.
--Precision ceramics: yttrium oxide partially stabilized oxide picks are very good performance of structural ceramics, can make a variety of special-purpose knives and scissors; can be made of automobile engines, because of its high thermal conductivity, low coefficient of expansion, thermal stability performance, in 1 650 ℃ under the working strength does not decrease, resulting in engine horsepower, Fuel saving and other advantages.
--Catalysts: rare earths in addition to the manufacture of oil cracking catalysts, widely used in many chemical reactions, such as rare earth oxides LaO3, Nd2O3 and Sm2O3 for cyclohexane dehydrogenation of benzene, LnCoO3 instead of platinum-catalyzed oxidation of ammonia to nitric acid. And as a catalyst in the production of synthetic isoprene rubber and cis-butadiene rubber.
Automobile exhaust needs to oxidize CH and CO and reduce NOX to solve the current urban air pollution problem. Rare earth elements are the main raw materials for automobile exhaust purification catalysts. The city's Chemical Research Institute has a strong advantage in this area, which can promote the formation of a car exhaust purifier products.
--High-temperature superconducting materials: research in recent years has shown that many single rare earth oxides and some of its mixed rare earth oxides are important raw materials for high-temperature superconducting materials. Once the high-temperature superconducting materials into practical, the whole world will be a sea change. At present, China has made meaningful breakthroughs in the research of rare earth superconducting materials into materials.