Rare earth elements are the general names of rare earth elements in lanthanides, including scandium Sc, yttrium Y and lanthanum La, cerium Ce, praseodymium Pr, neodymium nd, promethium Pm, samarium Sm, europium Eu, gadolinium Gd, terbium Tb, dysprosium Dy, holmium Ho, erbium Er and promethium in lanthanides.

The term "rare earth" has been used since18th century. At that time, minerals used to extract such elements were very scarce, and the oxides obtained were difficult to melt, dissolve in water and separate, and their appearance resembled "soil", so they were called rare earth. Rare earth elements are divided into "light rare earth elements" and "heavy rare earth elements":

"Light rare earth elements" refer to scandium Sc, yttrium Y, lanthanum La, cerium Ce, praseodymium Pr, neodymium Nd, promethium Pm, samarium Sm and europium Eu with smaller atomic numbers.

"Heavy rare earth elements" are gadolinium Gd, terbium Tb, dysprosium Dy, holmium Ho, erbium Er, thulium Tm, ytterbium Yb and lutetium Lu with large atomic numbers.

Two. Rare earth resources and reserves

Because of the activity of rare earth elements, it becomes pro-MagmaElemental, and its natural metal anhydrous or sulfide has not been found in the earth's crust. The most common forms are complex oxides, hydrated or anhydrous silicates, hydrated or anhydrous phosphates, phosphosilicates, fluorocarbons and fluorides. Because the ion radius and oxidation state of rare earth elements are similar to those of all other elements, because

In minerals, they often appear together with other elements.

China's rare earth resources account for 80% of the world's rare earth resources, reaching 36 million tons in terms of oxide (REO), and its prospective reserves are actually 654.38+billion tons.

China's rare earth resources are divided into two parts: north and south.

—— North: Light rare earth resources, concentrated in Baotou Baiyun Ebote and other places, were later discovered in Mianning, Sichuan. It 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, occur in the weathering crust of granite as rare ions, mainly containing samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium and ytterbium.

China's rare earth industry is also divided into two major production systems: North and South.

-In the north, with Baotou Rare Earth Hi-Tech Company and Gansu Rare Earth Company as the axis, a production system of light rare earth products has been formed, with Baotou rare earth resources as the mainstay and Sichuan resources as the supplement. The backbone enterprises include 202 Nuclear Industry Factory, Baotou Luxirona Rare Earth Co., Ltd., Baotou Hefa Rare Earth Factory, Baotou Rare Earth Smelter, Harbin Rare Earth Material Factory, Sichuan Rare Earth Material Factory, Sichuan Shifang Jida Chemical Plant and Anning River Rare Earth Smelter. The main products are rare earth concentrates, rare earth ferrosilicon alloys, mixed rare earth compounds, concentrates and mixed metals. The production capacity, treatment and processing capacity of rare earth concentrate reached 50,000 tons (calculated by reach oxide).

—— Shanghai Yuelong Nonferrous Metals Co., Ltd. is the leader in the south, which constitutes the medium and heavy rare earth production system in Jiangxi and Guangdong provinces, mainly based on ionic rare earth resources. Key enterprises include Guangzhou Pearl River Smelter, Guangdong Yangjiang Rare Earth Factory, Jiangsu Xinwei Group, Jiangsu Liyang Fangzheng Rare Earth General Factory, Jiangyin Jiahua Rare Earth Smelter, Jiangsu Jiangfei Rare Earth Smelter, Jiangxi Longnan Rare Earth Company, Jiangxi Xunwu Rare Earth Company, Jiangxi Rare Earth Company and Jiangxi Nuclear Industry 7 13 Mine. The main products are various high-purity single rare earth compounds and metals, concentrates, mixed metals and alloys. The total separation scale has exceeded 10 000 tons, and the large-scale processing and separation of light rare earth raw materials in the north has begun.

Fourth, the application scope of rare earth elements

At present, the application of rare earth elements is developing vigorously, which has extended to all aspects of science and technology, especially the development and application of some new modern functional materials. Rare earth elements have become indispensable raw materials.

1. Application of Rare Earth Elements in Traditional Industries

-Agriculture: At present, there are rare earth agronomy, rare earth pedology, rare earth plant physiology, rare earth health toxicology and rare earth trace analysis. As a plant growth and physiological regulator, rare earth has three characteristics: increasing yield, improving quality and resisting stress. At the same time, rare earth is a low toxic substance, which is harmless to people and animals and has no pollution to the environment; Rational use of rare earth can enhance the drought resistance, waterlogging resistance and lodging resistance of crops. At present, the application area of rare earth in farmland in China is 50-70 million mu/year, accounting for 600-800 million kg of grain, cotton, beans, oil and sugar. Direct economic benefit10-1500 million yuan, annual consumption of rare earth 1 100- 120.

-Metallurgical industry: Rare earths are widely used in metallurgical industry, accounting for about 1/3 of the total rare earths. Rare earth elements easily react with oxygen and sulfur at high temperature to generate oxides, sulfides and sulfur-oxygen compounds, with high melting point and low plasticity. Adding rare earth into molten steel can play the role of desulfurization and deoxidation, change the shape of inclusions, improve the toughness and fracture of steel at room temperature and low temperature, reduce the hot brittleness of some steel, and improve the machinability of heating and the firmness of welded parts.

Rare earth is used as graphite nodulizer and nucleating agent to inhibit harmful elements in cast iron, improve the quality of castings and greatly improve the mechanical properties of castings. It is mainly used in four aspects: ingot mould, roller, cast pipe and special-shaped parts.

The application in non-ferrous alloys has a good effect on all kinds of non-ferrous metal-based alloys and improves the physical and mechanical properties of the alloys. Aluminum, magnesium and copper are the most widely used series.

-Petrochemical field: Rare earth molecular sieve cracking catalyst for petroleum cracking industry is characterized by high activity, good selectivity and high gasoline yield. Rare earths are widely used in this respect.

-Glass industry: Rare earth has three applications in the glass industry: glass coloring, glass decoloring and preparation of glass with special properties. Rare earth oxides used for glass coloring include neodymium (pink with purple luster) and praseodymium glass is green (making filters). Cerium dioxide can oxidize yellow-green ferrous iron in glass to trivalent and decolorize it, avoiding the toxicity of arsenic oxide in the past, and neodymium oxide can also be added for physical decolorization. Rare earth special glasses such as cerium glass (radiation protection glass) and lanthanum glass (optical glass).

-Ceramic industry: Rare earths can be added to ceramics and porcelain glazes to reduce glaze cracks and make them shiny. Rare earths are mainly used as pigments for ceramics. Because rare earth elements have unfilled 4f electrons, they can absorb or emit light with different wavelengths in ultraviolet and visible infrared regions, and the emission range of each light region is small, resulting in softer and purer color, novel tone and good smoothness of ceramics. Such as yellow, purple, green, pink, orange, brown, black and so on. Rare earth oxides can be used to make high-temperature resistant transparent ceramics (used in laser and other fields) and high-temperature resistant crucibles (metallurgy).

Electric light source industry: Rare earth, as the luminescent material of fluorescent lamps, is an energy-saving light source, characterized by good light efficiency, good light color and long service life. Compared with incandescent lamps, it can save electricity by 75-80%.

2. Application of rare earth elements in high-tech industries

Luminous materials of displays: yttrium and europium in rare earth elements are the main raw materials of red phosphors, which are widely used in color TVs, computers and various displays. At present, China's annual output of red powder for color TV sets is 300-400 tons, and that for computer monitors is 50- 100 tons, so as to meet the domestic demand of 35 million color picture tubes and nearly one million monitors.

Magnetic materials: neodymium, samarium, praseodymium, dysprosium, etc. It is the main raw material for manufacturing modern super permanent magnet materials. Their magnetism is 4- 10 times higher than that of ordinary permanent magnet materials, and they are widely used in high-tech fields such as television, electroacoustic, medical equipment, maglev train, military industry and so on. According to experts' prediction, by the end of this century, the output value of such materials will reach $3.5 billion. NdFeB permanent magnet materials with independent intellectual property rights developed by Nankai University in our city belong to this category, and are currently being industrialized in cooperation with Jianda Group.

—— Hydrogen storage materials: MMNi5(MM is mixed rare earth metal) and LaNi5, intermetallic compounds of rare earth and transition elements, which are excellent hydrogen absorption materials and are called hydrogen sponges. Its most successful application is the manufacture of secondary batteries-metal hydride batteries, that is, nickel-hydrogen batteries. Its equal volume charge capacity is twice that of the widely used nickel-cadmium battery at present, and its charge-discharge cycle life and output voltage are the same as those of the nickel-cadmium battery, but there is no cadmium pollution. Nankai University in our city has great advantages in the research and development of hydrogen storage materials. Through the 863 project, Heping Bay Company started the industrialization of Ni-MH battery.

-Laser materials: Rare earth ions are the most important activators of solid laser materials and inorganic liquid laser materials, among which Nd3+-doped laser materials are the most studied. Besides substrates such as YAG and YAP glass, laser materials with high rare earth concentration can be called special application materials.

-Precision ceramics: Yttrium oxide stabilized pick is a kind of structural ceramics with excellent performance, which can be used to make knives and scissors for various special purposes; It can be used to manufacture automobile engines, because it has the advantages of high thermal conductivity, low expansion coefficient, good thermal stability, high engine horsepower, fuel saving and so on, and does not reduce the labor intensity at 65438 0650℃.

-Catalysts: In addition to making petroleum cracking catalysts, rare earths are widely used in many chemical reactions. For example, rare earth oxides such as LaO3, Nd2O3 and Sm2O3 are used for dehydrogenation of cyclohexane to benzene, and LnCoO3 is used for catalytic ammoxidation to nitric acid instead of platinum. It is also used as a catalyst for synthesizing isoprene rubber and cis-polybutadiene rubber.

In order to solve the current urban air pollution problem, CH and CO in automobile exhaust should be oxidized to reduce NOX. Rare earth elements are the main raw materials of automobile exhaust purification catalysts. Our chemical research institute has a strong advantage in this respect, which can promote the formation of an automobile exhaust purifier product.

-HTS materials: Recent studies show that many single rare earth oxides and some mixed rare earth oxides are important raw materials for HTS materials. Once HTS materials are put into practical use, the whole world will undergo earth-shaking changes. At present, China has made a major breakthrough in the research of rare earth superconducting materials.