Scientists in Germany have made lead-free detonators for reducing the environmental impact of military explosives. 

Detonators contain primary explosives which can be easily ignited by a physical or electric stimulus. They are used to trigger the explosion of more stable energetic materials in guns and hand grenades. Currently, almost all primary explosives are based on lead azide which causes concern for human health and the environment. 

Thomas Klapötke and colleagues at the Ludwig-Maximilian University of Munich made alkali metal salts as a replacement for lead azide. 'Lead is a toxic heavy metal and there are concerns about lead concentration at military training grounds,' says Klapötke. Over 90 000 hand grenades are used at these sites every year, explains Klapötke, therefore it is important to try to make the soldiers lives safer and healthier by removing toxic substances. 

Klapötke's team made a family of alkali metal salts with the energetic 5-nitrotetrazolate anion.  The salts with the harder lithium and sodium cations were found to contain crystal water, which gives them low sensitivity towards shock and friction.  The rest of the alkali metal salts form as the anhydrous species, and show increased explosive sensitivities making them more useful as prospective replacements for commonly used primary explosives.

Klapötke says that the new primary explosives are good enough for military use, however more work is needed to improve their thermally stability for use in harsh conditions such as for oil drilling. In the future we also hope to look into environmentally friendly replacements for other explosives such as perchlorates which are used as oxidisers in pyrotechnics and solid rocket boosters, he adds. 

Joseph Backofen, BRIGS Co., Herndon, US, an expert in ballistics, comments 'this work represents a clear path towards developing new energetic materials that are free from constituents deemed harmful to their users during routine work. This issue is important in primers used in rifle and pistol ammunition used in indoor training ranges by police and military personnel.'

Sarah Dixon