Laser ignition of energetic complexes: impact of metal ion on laser initiation ability

Abstract

Laser ignition of explosives is believed to be a safe and reliable initiation method to trigger the reaction of energetic materials. Energetic complexes including most primary explosives are a class of important explosives. The determinant of the laser initiation threshold of energetic complexes is still unclear. The coordination metal ions have a significant influence on the properties of energetic complexes. However, the effect of metal ions on the laser ignition ability has not attracted enough attention. To inspect the influence of alkali and alkaline earth metal ions on the laser initiation ability of energetic complexes, sodium(I) (1), potassium(I) (2), magnesium(II) (3), calcium(II) (4), and barium(II) (5) containing energetic complexes based on the ligand 4,4′,5,5′-tetranitro-2,2′-biimidazole (TNBI) were prepared. The crystal structures and thermal behaviors of four new complexes (1, 3, 4, and 5) were characterized. Laser initiation tests were carried out using different laser energy densities. TNBI and all complexes could be initiated and they all exhibited deflagration processes. It is found that the initiation delay times have a definite relationship with the metal ion type. Two alkali metal-containing complexes were easy to initiate, followed by the ligand TNBI, whereas the alkaline earth metal-containing complexes showed longer initiation delay times.