Claire M. Grégoire

Hydrogen chlorine (HCl) is an important combustion intermediate during plastic (municipal waste) and composite propellant (aerospace) combustion, but the understanding of its high‐temperature chemistry is still evolving. In this study, the pyrolysis of 0.5% HCl in Ar was investigated behind reflected shock waves in a shock tube at temperatures ranging from 2290 to 3490 K and pressures from 0.7 to 3.6 atm. A laser source was set to access the R(8) transition line of H ³⁵ Cl in the fundamental band near 3.3 µm at the specific wavelength of 3045.06 cm ⁻¹ . Numerical predictions using chemical kinetics mechanisms from the literature did not capture well the decomposition behavior of HCl in our conditions. According to these models, the most sensitive reaction HCl + M H + Cl + M (M = Ar) could be isolated, and its rate constant was retrieved from the experimental measurements. A pressure dependence was observed over the range of pressures covered. The present study measured the bimolecular reaction rate of the title reaction ( k _{1.5 atm} in cm ³ ·mol ⁻¹ ·s ⁻¹ , T in K, R = 1.987 cal·mol ⁻¹ ·K ⁻¹ ) as: valid near 1.5 atm, as well as ( k _{in cm ³ ·mol ⁻¹ ·s ⁻¹ ): and ( k >2 atm in cm ³ ·mol ⁻¹ ·s ⁻¹ ): suitable for conditions below 1 atm and above 2 atm, respectively. A generalized overall equation for the unimolecular reaction HCl H + Cl was obtained and is described as k all in (s ⁻¹ ). Finally, the results indicate that the measurements at pressures up to 3.6 atm in the present study were sufficient to determine that the title reaction is in its high‐pressure limit.}

During a thermal runaway, Lithium-ion battery cells are subjected to a large increase in temperature, which will vaporize and potentially thermally degrade their liquid electrolyte. The formation of gas in the battery cell will increase the pressure until the flammable gases vent and potentially lead to a fire incident. While the pyrolysis chemistry of the electrolyte components has been studied near atmospheric pressure, the effect of pressure has not been investigated. This study was undertaken to better understand the effect of pressure on the thermal dissociation of two common linear electrolyte components, diethyl carbonate (DEC) and ethyl methyl carbonate (EMC). The pyrolysis of DEC and EMC was studied in the gas phase, in 99.75% He/Ar, and was carried out at high temperatures and for pressures near 5.5 atm. The time-resolved CO formation was measured using a quantum cascade laser, providing a unique experimental dataset. A detailed chemical kinetics analysis was performed to understand the effect of pressure on DEC and EMC, with CO time-history results obtained in similar conditions at near-atmospheric pressure for DEC and EMC serving as baselines for comparison. Numerical predictions using detailed chemical kinetics mechanisms from the literature were carried out, and reaction pathways at different pressures were highlighted to emphasize the effect of pressure on the pyrolysis chemistry.

Bis(2,2,2-trifluoroethyl) carbonate (BtFEC) is a fire suppressant candidate for the use of lithium-ion batteries (LIBs). It is known that the electrolyte components in LIBs are highly flammable, making them susceptible to igniting, whether this is due to a manufacturing fault or an abuse of the LIB itself. To address this risk, the efficiency of BtFEC as a fire suppressant was investigated experimentally in a high-temperature combustion environment, allowing for further refinement and validation of the model. Using a shock tube, BtFEC combustion properties were measured experimentally behind a reflected shock wave, capturing OH* chemiluminescence to assess ignition delay times (IDT) as well as CO time-history profiles through the implementation of laser absorption spectroscopy. Both pyrolysis and oxidation conditions were captured with three equivalence ratios (ϕ = 0.5, 1.0, and 1.5) for a temperature range of ∼1200-1650 K at near-atmospheric pressures. In addition, key species measurements were taken using a microflow reactor (MFR) with a controlled temperature profile associated with Fourier transform infrared spectroscopy (FTIR). Key species investigated were BtFEC, CO, CO₂, CHF₃, CF₂O, C₂F₆, and HF for the temperatures range of 800-1300 K. MFR measurements allowed for a new set of measurements by which to validate the model compared to the previous study [Mathieu et al. Proc. Combust. Inst. 2023, 39, 499] where the first assembly of the model used CO time-history, IDT, and laminar flame speed measurements. Refinement of the model was carried out with new high-level calculations as well as sensitivity, rate-of-production, and reaction pathway analyses using recent reaction rate updates from the literature. The modifications led to improvements in the level of agreement between the kinetic modeling and the new experimental data.