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Research history of lithium nitride

wallpapers News 2021-11-18
Research history of lithium nitride
Lithium nitride is a metal nitrogen compound with a molecular formula of Li3N. It is a purple or red crystalline solid with a light green luster in reflected light and a ruby color in transmitted light. Lithium nitride belongs to the hexagonal crystal system. In lithium nitride crystals, there is a layer of lithium and nitrogen composed of lithium and nitrogen atoms. The arrangement is that the lithium atoms are arranged in the manner of carbon atoms in the graphite crystal, and the nitrogen atoms are in the center of the hexagon formed by the lithium atoms. A lithium layer exists between the lithium and nitrogen layers. Because the ratio of lithium to nitrogen in the lithium and nitrogen layers is 2:1, which is Li2N, which does not meet the stoichiometric formula Li3N, there is a lithium layer between every two lithium and nitrogen layers.
In the lithium nitride unit cell, the distance between Li-N is 213pm, which is close to the sum of the ion radius of lithium-ion and nitrogen anion. The distance between each lithium and nitrogen layer and the adjacent lithium layer is 194pm, which indicates that the nitride Lithium is an ionic compound.
Lithium nitride was discovered as early as the end of the 19th century, and it is easily prepared by a compound reaction between elemental substances. In 1935, Zintl and Brauer first determined the hexagonal structure of lithium nitride crystals. This structure was re-determined by Rabenau and Schultz through single-crystal X-ray diffraction (XRD) in 1976.
The research on the reaction between lithium nitride and hydrogen began in the early 20th century. Daft and Miklauz discovered that lithium nitride and hydrogen reacted at 220-250°C to produce a substance composed of "Li3NH4". They continued to heat this substance and decomposed it into a substance composed of "Li3NH2" at higher temperatures (>700°C). Substances and hydrogen. Later, they and Ruff and Georges discovered that this "Li3NH4" is Li2NH + LiH, and "Li3NH2" is LiNH2 + 2 LiH.
Nowadays, lithium nitride has been applied in many fields, and the ion polarization model can be used to give a reasonable explanation for the catalytic effect of Li3N under normal pressure and high temperature and its role as a nitrogen source in solvothermal methods. Li3N, which is formed by the reaction of metallic lithium with N2 at 500 ℃, is a good catalyst for the synthesis of cBN under high temperature and high pressure. It can also catalyze the reaction of hBN under normal pressure and high temperature and is used as a synthesis of hBN and HBN in solvothermal methods. The nitrogen source of cBN.

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