Indium Indium
Indium is a metal element, English name: Indium, element symbol In, belongs to the IIIA group of metal elements, atomic number: 49, relative atomic mass: 114.8, melting point 156.61 °C, boiling point 2060 °C. Relative density 7.31 g/cm³. Indium is a silvery white metal with a slightly light blue luster, the texture is very soft, can be scratched with nails, strong plasticity, good ductility, can be pressed into pieces. Indium metal at room temperature is not oxidized by air. Indium is slightly radioactive, so contact with skin and ingestion should be avoided. The content of indium in the earth's crust is 1×10^ (-5), although it also has independent minerals, such as indium sulfate (CuInS2), indium thioite (FeInS4), indium ore [In(OH)3], etc., but the amount is very small, indium is mainly homogeneous in iron amphibolite (the content of indium is 0.0001% to 0.1%), hematite, galena and other polymetallic sulphide ores. In addition, tin ore, black tungsten ore, and ordinary horn amphibolite also contain indium. Indium metal is widely used in aerospace, radio and electronics industry, medical, defense, high-tech, energy and other fields.
Indium discovery and industrial development
【A Brief History of the Discovery of Indium】
Indium was discovered in 1863 by Reich and Richter in Germany while studying sphalerite by spectroscopy.
The discovery of indium is due to the discovery of the element thallium, after the discovery and acquisition of thallium, Riich, a professor of physics at the Freiberg School of Mines in Germany, was interested in some properties of thallium and hoped to get enough metals for experimental study. He began searching for the metal in 1863 in the zinc mines produced in Himmelsfüst. The main components of this ore are arsenic-containing pyrite, sphalerite, chalcite, silica, manganese, copper and a small amount of tin, cadmium and so on. Reich believes it may also contain thallium. Although the experiment took a lot of time, he did not get the desired element. However, he obtained a grass-yellow precipitate of unknown composition and thought it was a sulfide of a new element.
This hypothesis can only be proved by using spectroscopic analysis. However, Reich was colorblind and had to ask his assistant H.T. Richter to conduct spectral analysis experiments. Richter succeeded in his first experiment, when he found an indigo-blue bright line in a spectroscope that did not match the two blue bright lines of cesium, and named it indium from the Greek word "indikon" (indigo). The two scientists co-signed a report on the discovery of indium. The separation of the metal indium was done by both of them. They first isolated the chloride and hydroxide of indium, reduced it to metal indium on charcoal using a blowpipe, and exhibited it at the French Academy of Sciences in 1867.
【Indium Industry Development】
The industrial production of indium began in the early 1920s. In recent years, the global demand for indium has grown rapidly. Since 2003, it has been increasing at a rate of 5-10% per year. Before 2008, the global fine indium production showed a trend of increasing year by year, and after 2008, due to the strengthening of resource protection in various countries in the world, the supply of indium gradually decreased.
With the deepening of people's understanding and research on indium, indium currently plays a very important role in the fields of information, aerospace, energy, military industry and medicine and health, in flat panel displays, alloys, semiconductor data transmission, aerospace products and solar cell manufacturing. Especially with the rapid development of the IT industry, the demand for ITO films or ITO glass (ITO target production accounts for more than 70% of the global indium consumption) is increasing, as well as various new liquid crystal displays such as notebook computers, TVs and mobile phones, as well as contact screens and building materials (ITO target production accounts for more than 70% of the global indium consumption), which has an important impact on the market status of indium.
It is precisely because of the rapid development of the indium industry that the global indium resources are very limited. In recent years, countries have begun to strengthen their reserves of indium.
【Development of Indium Industry in China】
China's indium resources reserves are relatively rich, domestic production capacity is mostly used for export, in the past two years, with the formulation of the state's export quota for indium, the price of indium at home and abroad continues to hang upside down, domestic indium exports are getting less and less, and the title of the main exporting country is gradually disappearing. Due to the relatively low price of indium abroad, Japan, the main consumer of indium, has now stopped purchasing from China, and South Korea has gradually replaced China's position.
The development of China's indium industry started late, and there are still many problems such as unbalanced development and incomplete structure of the indium industry. Such as: indium ingot production is large, the use of small amount; mainly to produce crude indium and fine indium, deep processing products industrialization and industrialization has not been a breakthrough; high-purity indium, ITO target materials, indium-containing semiconductor materials and other high-tech, high-value-added products have not been able to form market competitiveness, the output is very small, a large number of imports from abroad. Therefore, adjusting the industrial structure and continuously carrying out scientific and technological innovation is an important direction for the development of China's indium industry.
Properties of Indium: The physical and chemical properties of indium
【Physical properties of indium】
Indium, melting point 156.61 °C, boiling point 2060 °C, relative density of 7.31g/cm³, is silvery white and slightly light blue luster of the metal, the texture is very soft, with nails can easily leave scratches on its surface, strong plasticity, good ductility, can be pressed into pieces. Pure indium rods can make a squeaking sound when bent. Liquid indium can infiltrate glass and will adhere to the surface of contact leaving black marks. Liquid indium has excellent fluidity and can be used to cast high-quality quantity castings. Indium is less volatile than zinc or cadmium, but can be sublimated when heated in hydrogen or vacuum. Indium, with weak radioactivity, avoids direct contact as much as possible during use. Natural indium has two main isotopes, one of which is In-113 as a stable nuclide and In-115 as β- decay.
【Chemical properties of indium】
At room temperature, indium metal is not easily oxidized by air, from room temperature to the melting point (156.61 °C), at about 100 °C, indium begins to oxidize, the surface forms a very thin oxide film, when the temperature is higher, it can react with oxygen, halogen, sulfur, selenium, tellurium, phosphorus, indium can form amalgam with mercury. Under intense heat (temperature above 800 ° C), indium burns to form indium oxide, and the flame is blue-red.
Large pieces of indium metal do not react with boiling water and alkali, but powdered indium can interact with water to form indium hydroxide. Indium has a slow effect with cold dilute acids, and is easily soluble in hot inorganic acids, acetic acids, and oxalic acid. Indium can form alloys with many metals (especially iron, and indium with iron is significantly oxidized).
Indium has three valence states of +1, +2 and +3, the main oxidation states are +1 and +3, trivalent indium is stable in aqueous solution, and monovalent compounds are usually disproportionated when heated. The main compounds are In2O3, In(OH)3, InCl3, when combined with halogens, can form a halide and a trihalide, respectively.
Indium forms covalent bonds in its compounds. Some indium salt solutions have low electrical conductivity, and generally electrolytically processed indium is usually operated with cyanide, sulfate, sulfamate and fluoroborate.
【Indium compounds】
Indium can form compounds with +1, +2 and +3 valences, of which the main indium compounds are +3 valences, such as In2O3, InCl3, InN. Indium carbides cannot be stable at room temperature, but ternary carbides have been reported, such as Mn3InC, (Ln) 3InC and so on. Concentrated indium perchlorate, indium sulfate and indium nitrate solutions are highly viscous.
Indium's organic compounds include trimethylindium (Me3In), triphenyl indium (Ph3In), etc., trimethyl indium and triethylindium (Et3In) are prone to spontaneous combustion in air. For a short time, Me2InClO4 at 0 °C is stable in water.
Indium carnet (C5H5In) is the only organic derivative of indium in the +1 oxidizing state, which is a moisture-stable, oxygen-sensitive pale yellow crystal.
【Coordination polymer】
In(III.) and rigid dicarboxylic acids (1,3-isophthalic acid and 1,4-naphthalenediic acid), four compounds [In_2(OH)_2(1,3-BDC)_2(2,2'-bipy)2](1), HIn(1,3-BDC)_2•2DMF (2), In(OH)(1,4-NDC)•2H_2O (3) and HIn(1,4-NDC)_2•2H_2O•1.5DMF (4).
In(III.) and flexible dicarboxylic acids (1,4-benzenediacetic acid, trans-1,4-cycloadipic acid and 4,4'-diphenyl etherdicarboxylic acid), under different solvothermal conditions, three compounds (Me_2NH_2) were obtained [In(cis-1,4-pda)2](5), In(OH)(trans-1,4-chdc)(6) and In(OH)(oba)•DMF•2H_2O (7).
In(III.) and optically-polarized D-camphoric acid (D-H_2Cam) synthesized a 3D indium coordination polymer with a single chiral structure InH(D-C_(10)H_(14)O_4)_2(8) under solvothermal conditions.
In(III.) and nitrogen-containing azeclic carboxylic acids (2-pyridinecarboxylic acid and 2,3-pyrazinedicarboxylic acid), two compounds were synthesized under solvothermal conditions In_2 (OH)_2(2-PDC)_4(9) and HIn(2,3-PDC)_2(10).