Combustion Characteristics and Thermochemistry of Selected Silicon-Based Compositions for Time-Delay Detonators

This study investigates the combustion characteristics of silicon-based time-delay compositions with bismuth(III) oxide (Bi2O3), antimony(III) oxide (Sb2O3), and lead(II,IV) oxide (Pb3O4) to identify formulations with pressure-independent burn rates. Unlike conventional pyrotechnic compositions, silicon-based mixtures offer an improved energy density and reduced sensitivity to pressure variations. The linear combustion rate of the compositions was determined for a wide range of silicon contents and for different compaction pressures. Experimental results show that burn rates range from 8 mm s⁻1 to 195 mm s⁻1, depending on the metal oxide type and silicon content. The highest rate (195 mm s⁻1) was observed for Si/Pb3O4 at 30 wt.% silicon, while Si/Sb2O3 had the lowest (10 ÷ 35 mm s⁻1). The calorimetric heat of combustion varied between 1200 J g⁻1 and 1400 J g⁻1, with adiabatic combustion temperatures reaching 2200 K, calculated from this heat. DTA and XRD confirmed the condensed-phase combustion, forming reduced metal phases and silicon oxides. SEM and EDS revealed a porous residue structure. This work introduces a novel approach to time-delay compositions using silicon as a primary fuel. It shows that specific silicon oxide–metal systems maintain stable combustion for different loading pressures and advance pyrotechnic formulations for safer and more efficient industrial and defense applications.