Exploring Green Pyrotechnic Formulations and Primary Explosives with 1,3,4-Oxadiazole-Based Micro and Submicron Energetic Coordination Polymers

Abstract

Alkali and alkaline-earth metal incorporated 5,5′-dinitramino-3,3′-azo-1,3,4-oxadiazole (H₂DNAO) based Energetic Coordination Polymers (ECPs), namely dipotassium 5,5′-dinitramino-3,3′-azo-1,3,4-oxadiazole(K₂DNAO), dicesium 5,5′-dinitramino-3,3′-azo-1,3,4-oxadiazole(Cs₂DNAO) and barium 5,5′-dinitramino-3,3′-azo-1,3,4-oxadiazole(BaDNAO) are synthesized for the first time. Synthesized ECPs are thoroughly characterized using infrared spectroscopy (IR), elemental analysis (EA), thermogravimetric analysis and differential scanning calorimetry (TGA-DSC), field emission scanning electron microscopy (FE-SEM), and dynamic light scattering (DLS), UV–vis spectroscopy. All ECPs are also confirmed by single-crystal X-ray diffraction technique (SC-XRD). The micro-ECPs exhibit excellent densities (1.98–2.80 g cm⁻³), insensitivities (IS: 25-40 J; FS: 240-360 N), and good thermal stabilities (T_d: 182–212 °C). K₂DNAO and Cs₂DNAO show good detonation performance (VOD:7460-7893 m s⁻¹; DP: 27.5-30.6 GPa), respectively. To further investigate sub-micron-energetics, three sub-micron ECPs are prepared from their micro counterparts using ultrasonication method, demonstrating significant improvement in thermal stability (T_d: 194–221 °C) but are highly sensitivity (IS: 2-15J; FS: 40-360N). Burning tests of two experimental formulations using micro K₂DNAO and Cs₂DNAO demonstrate their potential in green pyrotechnic applications. Interestingly, the submicron-counterparts show remarkable initiating capability. Considering their ease of synthesis, and safety profile, these materials can be effectively transported in their microform and can be rapidly converted into submicron-form on demand, making them suitable for pyrotechnic applications.