Synthesis of aluminium and titanium carbides in AlCl – TiCl4 – С system

Abstract

This paper examines how titanium carbide forms as a result of reaction of aluminium subchloride with titanium tetrachloride in the presence of carbon. The process can be described with a general equation of the following reaction TiCl4 + 2AlCl + C = TiC + 2AlCl3, which leads to the synthesis of aluminium subchloride vapours as a result of aluminium chloride reacting with metallic aluminium. It is shown that titanium carbide forms in the AlCl – TiCl4 – C system via formation of aluminium carbide 6AlCl + 3C = Al4C3 + 2AlCl3 (1), followed by reaction of aluminium carbide with titanium tetrachloride vapours Al4C3 + 3TiCl4 = 3TiC + 4AlCl3 (2). Each of the above reactions has its optimum temperature. In the case of reaction (1) and the aluminium subchloride reaction, the yield rises as the temperature increases, whereas in the case of reaction (2) it drops. The lower yield of titanium carbide as the temperature rises is the result of reaction between the formed TiC and titanium tetrachloride vapours, when free carbon precipitates at the same time contaminating the final product TiC + 3TiCl4 = C + 4TiCl3. Therefore, it would be reasonable to use two stages when synthesizing titanium carbide. Thus, aluminium carbide should be synthesized at the first stage, while the second stage should involve a reaction between aluminium carbide and TiCl4 vapours. In a laboratory experiment conducted in a flow reactor, a complete transformation of carbon into aluminium carbide would take place at 1,250 oC. At the second stage, aluminium carbide would convert into titanium carbide in 90 min at 800 oC and in 60 min at 900 oC. The described process enables to produce fine-dispersed aluminium and titanium carbides (or their mixture) to be used as inoculants.The research was carried out within the framework of the State assignment ICCT SB RAS – FRC KSC SB RAS (project № 0287-2021-0013).