Medium caliber munitions are currently detonated through the use of impact-sensitive (stab) detonators. Stab detonators are mechanically activated by forcing a firing pin through the closure disc of the device and into the stab-initiating mixture (NOL-130). Current stab mixtures, as well as primer and igniter compositions, contain hazardous materials such as lead styphnate, lead azide, barium nitrate, antimony sulfides, and tetrazene. Alternative impact-initiated devices (IID) that do not use lead or other environmentally hazardous materials are critically needed.
The objective of this project was to develop new IIDs that do not contain hazardous materials and that have performance characteristics similar to or an improvement over the current stab compositions through the use of environmentally acceptable, energetic, sol-gel-coated, flash metal multilayer nanocomposites.
A precision energetic foil of metal multilayers (flash metal) and a ceramic-based energetic sol-gel coating that uses nontoxic and nonhazardous components such as ferric oxide and aluminum metal were investigated for use in alternative IIDs. The flash metal serves as the precision igniter and the energetic sol-gel functions as a low-cost, nontoxic, nonhazardous booster in the ignition train. The multilayer foils are produced using magnetron physical vapor-sputtering techniques and are composed of metals such as titanium, aluminum, and zirconium. Both the multilayer and sol-gel technologies are versatile, commercially viable processes that enable the manipulation of properties such as stab sensitivity and energy output. In all cases, these compositions were modified with the clear intent of minimizing environmental and health concerns while maintaining performance.
This project detailed the stab ignition, small-scale sensitivity, and energy release characteristics of bimetallic Al/Ni(V) and Al/Monel energetic nanolaminate free-standing films. The influence of the engineered nanostructural features of the multilayers was shown to be strongly correlated with both stab initiation and small-scale energetic materials testing results. Structural parameters of the thin films found to be important include the bi-layer period, total thickness of the film, and presence of coating aluminum layers. Live lead-free M55 stab detonators were prepared using energetic nanolaminate as the stab mix, cyanuric triazide as the transfer charge, and an Army formulation for the output charge. These lead-free detonators were demonstrated to have the acceptable stab sensitivity as is required in current M55 detonators. There was evidence that replacement of the current NOL-130 stab mix by compact powders of energetic multilayers does not affect the performance of the stab detonator.
The development of environmentally benign IIDs will result in the removal of hazardous and toxic components associated with their manufacturing, handling, and use. This will lead to improved worker safety during manufacturing as well as reduced exposure for Service personnel. The alternative IIDs may be applicable to a wide range of other devices such as small caliber ammunition and sub-munitions. (Project Completed - 2006)