Regular Article

Study on the phase evolution and element migration of vanadium oxide during the nitridation process

¹ College of Materials Science and Engineering, Chongqing University, Chongqing, PR China
² Chongqing Key Laboratory of Vanadium-Titanium Metallurgy and Advanced Materials, Chongqing University, Chongqing, PR China

^* e-mail: diaojiang@163.com

Received: 9 November 2020
Accepted: 23 March 2021

Abstract

In this paper, a series of nitriding experiments were carried out to investigate the phase evolution and element migration in the nitriding process. The results show that it undergoes a low temperature reducing stage firstly. High valent vanadium oxides are reduced to V₂O₃ between room temperature and 770 °C. In Ar atmosphere, V₂O₃ reacts with C to form VC in the temperature interval of 770 °C∼1080 °C. In N₂ atmosphere, V₂O₃ reacts directly with N₂ and C to form VN in the interval of 670 °C∼1050 °C. During 1050 °C∼1270 °C, part of the VN obtained in the previous reaction stage will react with C to form VC. High temperature is beneficial to the removal of impurity element sulfur. The volatilization of alkali metal elements in the pellet mainly occurs between 670 °C and 1270 °C. However, there are about 20% of sodium and potassium remain in the nitriding product. The volatile alkali metal vapor would react with other gases at the furnace cover to form a white sediment and deposits on the cover. The sediment mainly consists of Na₂CO₃, K₂CO₃, Na₂SO₄, K₂SO₄, KCl, etc.