What is pure metal?
The gold, silver, copper, iron, tin, etc. we come into contact with in life are called metals. Gold: 24K pure gold jewelry with few impurities is called pure gold, pure copper is called copper, and aluminum is also very pure. Its signs, such as gold, 99% mark has more gold content, other content is less, it is also very high to achieve high purity Difficult: There are four 9, five 9, six 9, the few that can reach six 9 in the world, are used in semiconductors. It is remarkable that gold reaches four nines, and the rest are impurities. For example, pure silver and pure copper are marked with four nines, which is 99.99%. The subsequent figures are not labeled, and the rest are impurities.
The characteristics of pure metals have a fixed melting point. For example, the melting point of copper is 1083 degrees Celsius, and gold is more than 900. Both have a fixed melting point. The gloss of the metal is yellow, the silver is white, the copper is purple. characteristic.
The process of making pure metal can be summarized into two types.
The first is to obtain a pure metal compound by precipitation, solvent extraction, ion exchange, etc., and then reduce it to pure metal. Such as pure metal titanium, often TiCl4 is purified by distillation and then reduced to pure sponge titanium.
The second is to obtain crude metal and then purify it into pure metal. There are two types of purification methods: chemical purification and physical purification.
Chemical purification methods include electrolytic refining, oxidation refining, chlorination refining, disproportionation metallurgy, and so on.
Physical purification methods mainly include zone purification, distillation, distillation refining, drawing single crystals, vacuum refining, and the like.
Drawing a single crystal is a method of using a seed crystal or an autogenous seed crystal to pull a single crystal out of a melt to obtain a purified metal. The physical purification method has simple equipment, convenient operation, and less reagent pollution, which can be used as the final purification method. The chemical purification method has great flexibility and selectivity, but often has the disadvantage of reagent contamination, and is widely used in pre-purification and intermediate purification. But in production, the two methods are often used in conjunction with each other. At present, ultra-high-purity germanium with a purity of 12 "9" can be prepared, and 7 "9" or more high-purity silicon, arsenic, gallium, and indium can be prepared. These high-purity metals are used as materials for the semiconductor industry.
The detection methods of pure metals include activation analysis, atomic absorption spectrometry, fluorescence spectrophotometry, mass spectrometry, chemical spectroscopic analysis and gas analysis.
The ionization concentration in a semiconductor can be determined by measuring the Hall coefficient, and the purity of ultrapure gallium can be determined by measuring the residual resistivity.
Nanjing Kirin Scientific Instrument Group Co., Ltd.