Nano Tungsten Nitride Accelerated Preparation

Transition metal nitrides are interstitial compounds formed by nitrogen atoms inserted into metal lattices. They have high melting point, high hardness, high mechanical strength, excellent thermal stability and chemical stability. They can be used as cutting tools, wear resistant parts and high temperature resistant materials.

Nano tungsten nitride will have more remarkable advantages than tungsten carbide. Unfortunately, there is no mature production process. At present, the commonly used method is to synthesize tungsten nitride by temperature programmed reaction using WO₃ as raw material in N₂, H₂ mixture or NH₃. The disadvantages of the above methods are time consuming.

In order to improve the time-consuming disadvantage, some scholars proposed a preparation method of tungsten nitride nano powder. Tungsten nitride nano powder was synthesized by reaction in ammonia atmosphere with tungstic acid-based inorganic-organic hybrid layered compounds as precursors.

Weigh 5g H₂WO₄ and put it in a 1000ml conical bottle. Wet it with 2ml distilled water. Weigh 39G n-octylamine (0.3mol, 50ml) and 270g n-heptane (400ml). Mix them evenly. Add the mixture of n-octylamine and n-heptane into the conical bottle containing tungstic acid, stir vigorously at the side and start to be a yellow suspension. With the prolongation of time, the color of the suspension gradually fades and presents after half an hour. The white suspension was separated from solid and liquid by stirring for 24 hours and standing for 24 hours. The white suspension was washed by alcohol for 5 times (3000 r/min, 10 min) and dried at room temperature and vacuum for 30 hours. 10 g tungstate-based inorganic-organic hybrid layered compounds were obtained.

0.42g tungstic acid-based inorganic-organic hybrid layered compounds were weighed and put into the ceramic boat. The ceramic boat was put into a programmable low temperature tube electric furnace. The tube was quartz tube. The end of the quartz tube was sealed. Ar was passed through for 1 h at 100 ml/min speed. The heating began. Then the NH₃ flow rate was 120 ml/min, the heating rate was 20 ℃/min, the heating rate was 650 ℃, the holding time was 20 h, and 0.19g samples were obtained with the furnace cooling. The yield is 99%. The size of W₂N particles is about 40 nm and the surface area of BET is 8.2 m²/g.

Tungsten nitride was prepared in NH₃ by using tungstic acid-based inorganic-organic hybrid layered compounds as precursors. Tungstic acid-based inorganic-organic hybrid layered compounds were pyrolyzed in non-oxidizing atmosphere (such as Ar, NH₃). Highly active tungstic acid was obtained, which was easily nitrided with ammonia. Therefore, tungsten nitride nano-powder could be formed in a relatively short time, and tungstic acid-based inorganic-organic hybrid layers could be formed. The preparation process of these compounds is simple and can be prepared on a large scale.

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