Research History of Lithium Nitride

Lithium nitride preparation

Lithium nitride can be prepared by directly reacting elemental nitrogen and lithium. It is usually prepared by burning lithium in pure nitrogen. Whether in the laboratory or in industry, this method is the best way to prepare lithium nitride. Commonly used methods. In addition, nitrogen can also be introduced into liquid sodium dissolved with metallic lithium, and the lithium nitride prepared by the latter has a higher purity.

method one

The method uses metal lithium and pure nitrogen to directly react at high temperature, and the purity of the product can reach 95% to 99%.

Preparation device:

1—Nitrogen bottle; 2—Cooling pipe; 3—Electric furnace; 4—Rubber stopper;

G—Reaction tube; J—U-shaped tube; K—reverse bottle;

L—wash gas bottle; M—glass cock

Pass the nitrogen through a U-shaped tube containing phosphorus pentoxide and a quartz tube containing red hot copper chips to fully deoxidize. Then the nitrogen gas is passed through the potassium hydroxide drying tube and the scrubber of concentrated sulfuric acid to further remove the water. The reaction tube is an iron tube with a length of 90 cm and an inner diameter of 5 cm. The tube is equipped with a small iron plate and a large iron plate. There is a resistance wire heating outside the tube and a thermocouple to measure the temperature.

First, pass nitrogen into the reaction tube (note: the preparation of the reaction, the reaction and the end of the reaction are always in nitrogen). The temperature is gradually increased to 200°C in order to drive out the air and moisture in the reaction tube. After the reaction tube is cooled, a freshly cut 0.5 cm size lithium particle is added to the small plate for deoxygenation and dehydration. Add 10 to 12 lithium particles of the same size as the reactant in the large plate. After ventilation for 1 hour, the temperature was slowly raised to 450°C. After the reaction is over, slowly open the stopcock and gradually reduce the pressure of nitrogen. After the reaction tube is cooled to room temperature, the lithium nitride product is taken out.

Method Two

In this method, a zirconia crucible is used as a container, and the reaction is carried out at a high temperature of 800 DEG C to obtain lithium nitride crystals.

Preparation device:

a—Zirconium oxide crucible; b—iron crucible; c—porcelain tube; d—reaction apparatus

a is a zirconia crucible coated with a layer of molten lithium fluoride (melting point 840°C). Put a in an iron protective crucible b, and then put the two together in a high-temperature porcelain tube c. Cover the porcelain tube with a glass lid and seal it. The glass cover is connected with a three-way piston, which can be vacuumed or gas can be introduced. There is a serpentine tube at the periphery of the seal between the glass cover and the porcelain tube for cooling water.

Scrape the surface of the lithium in an argon operation box, cut into small pieces, and put it into crucible a under the protection of argon. After sealing the porcelain tube, evacuate and vent nitrogen, and repeat the operation many times. If you want to prepare larger lithium nitride crystals, you can start nitriding at 400°C, and dilute the pure and dry nitrogen with 20% (volume fraction) of high-purity argon, and then gradually increase the temperature to 800°C to obtain nitrogen. Lithium.

Research History of Lithium Nitride

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. Dafert 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 into a substance composed of "Li3NH2" at higher temperatures (>700°C). Substances and hydrogen. Later, they, Ruff and Georges discovered that this kind of "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 at 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 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.

Overview of Lithium Nitride Li3N Powder

Li3BN2 is a metal nitrogen compound with the molecular formula Li3N. It is the only stable alkali metal nitride. It is a purple or red crystalline solid, with a high melting point, a light green luster under reflected light, and a ruby color under transmitted light. Long-term exposure to the air will eventually produce lithium carbonate. The chemical properties of alkaline metal nitrides are extremely limited. Among binary compounds, only lithium nitride is stable and easy to prepare (sodium nitrite and potassium nitride can only be prepared under more extreme conditions).

Lithium nitride belongs to the hexagonal crystal system. In the lithium nitride crystal, there is a layer of lithium and nitrogen composed of lithium and nitrogen atoms. Lithium atoms are arranged in graphite crystals like carbon atoms, and nitrogen atoms are located in the center of the hexagon of lithium atoms. There is a lithium layer between the lithium nitrogen layers. Since the ratio of lithium to nitrogen in the lithium nitrogen layer is 2:1, that is, Li2N (does not meet the stoichiometric formula Li3N), there is a lithium and nitrogen layer between every two lithium layers. In the unit cell of lithium nitride, the distance between Li-N is 213 pm, which is close to the sum of the ion radii of lithium ions and nitrogen anions. The distance between each lithium nitrogen layer and the adjacent lithium layer is 194pm,

At room temperature, metal lithium can partially form lithium nitride when exposed to air. Lithium forms lithium nitride in a nitrogen stream, which is 10-15 times faster than lithium in the air, and then all lithium becomes lithium nitride. On the contrary, it is difficult for other alkali metals to form nitrides. For example, sodium nitrite can only be prepared by depositing an atomic beam on sapphire at low temperature and decomposing it under slight heating. Lithium nitride is easily hydrolyzed to produce lithium hydroxide and ammonia, especially fine powdered lithium nitride, which will burn violently when heated in air. Therefore, lithium nitride must be processed in an inert atmosphere (such as nitrogen). Used as a nitriding agent in organic reactions, as a reducing agent and nitrogen source in inorganic reactions.

Lithium nitride has been discovered since the end of the 19th century and is easily prepared by combining elements. The research on the reaction between lithium nitride and hydrogen began in the early 20th century. Daft and Miklauz discovered that lithium nitride reacts with hydrogen at 220-250°C to form a substance composed of "Li3NH4". They continue to heat the substance at higher temperatures (>>; 700°C) to produce "Li3NH2" and hydrogen.

Lithium nitride Li3N powder application

Lithium nitride is prepared by the direct reaction of elemental nitrogen and lithium, usually by burning lithium in pure nitrogen. In laboratories and industry, this method is the most commonly used method for preparing lithium nitride. Alternatively, nitrogen can be injected into liquid sodium dissolved in lithium metal to produce purer lithium nitride. Lithium nitride has many applications, as shown in the figure below:

1. Solid electrolyte

Lithium nitride is a fast ion conductor, and its conductivity is higher than other inorganic lithium salts. Many studies have been conducted on the use of lithium nitride as a solid electrode and battery cathode material.

2. Fast ion conductor

A series of lithium fast ion conductors were prepared based on lithium nitride. As a fast ion conductor material, it should have higher decomposition voltage, lower electronic conductivity, higher ion conductivity and better chemical stability.

3. Preparation of Boron Nitride from Lithium Nitride

Lithium nitride (Lin3) is a catalyst for the synthesis of (boron nitride) CBN under high temperature and high pressure. Lithium nitride catalyzes the conversion of Bn to CBN and the reaction of B4C and NH4A under normal pressure and high temperature. It can also be used as a nitrogen source for solvothermal reaction with Bbr3 to generate Bn and CBn. In addition to being used as a solid electrolyte, lithium nitride is also an effective catalyst for converting hexagonal boron nitride into cubic boron nitride.

4. Preparation of lithium difluorosulfinate from lithium nitride.

Lithium difluorosulfide (LIN(SO2F)2, hereinafter referred to as LIFSI) is an electrolyte with broad application prospects. LiFSI has suitable conductivity, high thermal stability and electrochemical stability

5. Preparation of Cubic Boron Nitride from Lithium Nitride

Preparation of lithium boron nitride (Li3BN2). Li3BN2 is an important catalyst for the synthesis of cubic boron nitride superhard materials and has been used in the industrial production of cubic boron nitride synthesis. The hardness of cubic boron nitride is lower than that of diamond, but diamond cannot be used for the grinding of ferrous metals, so cubic boron nitride is currently the best grinding material for ferrous metals and their alloys.

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