In-operando thermophysical properties and kinetics measurements of Al-Zr-C composites

This work investigates the combustion velocity, thermophysical properties, and reaction activation energies of Al-Zr-C nanolayered composite microparticles undergoing gasless high-temperature propagation after preparation via additive manufacturing. High-speed videography and pyrometry of the reaction event were used to analyze two Al-Zr-C samples with varied stoichiometry. Combustion velocity of the Al-Zr-C composites was ~0.3–0.5 cm/s and varied inversely with the Al content in the system. The Al-Zr-C composites also exhibited auto-oscillations during the propagation event which were characterized to have temperature fluctuations of ~50–100 K with a periodicity of ~1 Hz. Temperature data collected via color ratio pyrometry was used to measure the thermal profile in-operando. Temperature maps were used to estimate the thermal diffusivity of the samples to be ~2 × 10−6 m2/s on the leading edge of the reaction front with a >30x increase in thermal diffusivity on the trailing edge. The activation energy for the Al-Zr-C composites was estimated to be ~30–35 kJ/mol under reacting conditions. This work ultimately demonstrates an accessible measurement methodology that could be used to estimate thermophysical changes in materials for generalized modeling purposes and confirms the functionality of the materials to create conductive pathways after reaction.