Effect of gaseous phase on the behavior of boron carbide during the heating process

Abstract

Silicon carbide and boron carbide are used in various fields of industry owing to their high levels of physicochemical properties and hardness.In the absence of special additives, these materials are usually sintered at elevated (2000~ and above) temperatures.The materials based on silicon carbide in which binding agents form at relatively low temperatures (1500~ with the participation of a gaseous medium (atmosphere) are finding wide application.In view of this, it was of interest to explore the possibility of using a similar technological route for boron carbide also. For this purpose, we studied the behavior of boron carbide during heat treatment in a carbonaceous particulate charge consisting of a mixture of coke and quartz sand.It is known that the gaseous phase in the C--Si02 system consists of CO, C02, and SiO [i]; besides this, the gaseous phase of the aforementioned charge contains nitrogen and traces of oxygen.The information available on the behavior of boron carbide in various gaseous media is quite limited.In the atmosphere of pure oxygen [2], oxidation of boron carbide starts at 600~ and the oxidation rate increases at 800-i000~ thereafter, it decreases and at 1200-1300~ it abruptly increases once again due to the formation of liquid B20s and its vaporization. Besides this, the formation of volatile lower oxides of boron is also possible.