On the thermal decomposition kinetics of graphite fluoride based on non-isothermal thermogravimetry

Aiming at the problem of uncertain mechanism of kinetics of thermal decomposition of fluorinated graphite and insufficient information of kinetic prediction, the dynamic mechanism of (CF)_n thermal decomposition reaction was analyzed by measuring multiple sets of non-isothermal thermogravimetric curves and using model-free kinetics. The thermogravimetric curve shows that (CF)_n thermal decomposition undergoes one step of weight loss, resulting in an average gas phase composition of CF_2.95. The results of kinetic analysis show that the mechanism function changes with the conversion rate: α < 0.1, the mechanism function is JMA equation f(α)=1.5(1-α)-ln(1-α)^1/3; 0.15 < α < 0.3, the mechanism function is two-dimensional Avrami-Erofeyev equation f(α)=2(1-α)-ln(1-α)1/2;0.3 < α < 0.8, the mechanism function is Šesták-Berggren equation f(α)=7.5α^1.2(1-α)2; 0.85 < α, the mechanism function is the one-dimensional Avrami-Erofeyev equation f(α)=(1-α). The recommended kinetic prediction parameter activation energy is 264.23±7.82 kJ/mol, and the pre-exponential factor is (8.70±0.21)×10¹⁴/s. In addition, the kinetic mechanism reflects the existence of carbon chain chain growth and interaction with the branching chain in the (CF)_n decomposition process, which may be an important factor in the formation of amorphous structural carbon in the reaction product.