Lead oxide(II, IV) replacement in gasless pyrotechnic time delay compositions

Abstract. This research delves into the comparison of combustion kinetics of Al/Bi2O3, Si/Bi2O3 and Si/Pb3O4 time delay compositions. The study aims to explore compositions that exhibit combustion rates independent of pressure inside the detonator. The combustion rates of silicon (Si/Bi2O3, Si/Pb3O4) and aluminium-based composition (Al/Bi2O3) were systematically studied, revealing distinct ranges for each composition. Al/Bi2O3 exhibited rates of 30 to 130 mm/s while Si/Bi2O3 exhibited rates of 15 to 110 mm/s. Notably, the Si/Pb3O4 composition showcased the highest combustion rates, ranging from 35 to 175 mm/s. The variations in combustion rates were attributed to the unique quantitative compositions and densities of each mixture. Additionally, temperature profiles for each composition were obtained using a thin thermocouple Pt-PtRh. These profiles offer valuable insights into the thermal dynamics of the combustion process, enhancing our understanding of the energetic properties of the silicon-based mixtures. Furthermore, the investigation involved measuring the heat of combustion across a broad range of quantitative compositions. The gasless combustion of each composition was verified through Differential Thermal Analysis (DTA) and X-ray Diffraction (XRD) techniques. The determination of qualitative combustion product compositions facilitated the calculation of adiabatic temperatures. To complement the quantitative findings, Scanning Electron Microscopy (SEM) images of the combustion products were obtained, providing visual insights into the morphological characteristics of the resulting structures. The use of silicon as a common fuel in these compositions contributes to the diversification of available pyrotechnic options for time-delay detonators. This study not only expands our understanding of combustion kinetics but also highlights the potential applicability of silicon-based mixtures in the field of energetic materials.