Surface Modification of High Explosives

Project Overview

In the laboratory, it is difficult to synthesize high explosive (HE) crystals with outlier performance from existing molecules. Therefore, it would be interesting to develop a process for functionalizing high explosive powders to improve their performance and manufacturability without sacrificing insensitivity. This project investigated atomic layer deposition as a means of applying thin film coatings to high explosive substrates (TATB in this effort) without causing the crystals to become sensitive, in the hopes of tailoring their surface chemistry and manufacturing characteristics. In this work we demonstrated the capability to deposit quality films of aluminum oxide (Al₂O₃) on TATB with controlled conformality and thickness without the TATB crystal becoming sensitive. Utilizing inverse gas chromatography and powder rheometry we were also able to demonstrate reduced particle cohesion with surface aluminum oxide coatings through increases of the basic flowability energy (BFE) from powder rheometry and decreases in surface energy from inverse gas chromatography. Through this work we were able to demonstrate a process to successfully functionalize high explosive coatings to tailor their performance and manufacturability, particularly for additive manufacturing HE and in traditional polymer bonded explosives.

Mission Impact

This work is highly impactful to laboratory missions in accelerated materials and manufacturing as well as the mission research challenge in high explosive physics, chemistry, and materials science. In this work we demonstrated a means to functionalize explosive crystals without changing their sensitivity, which is critical for improving explosives manufacturing, our understanding of explosives chemistry, and maintaining the nation's nuclear stockpile. This project could create a new program direction in explosives chemistry, physics, and manufacturing. Through this project we also investigated inverse gas chromatography (a capability that does not exist at Lawrence Livermore National Laboratory) as a technique for measuring surface properties, like surface energy. This technique could be valuable for other laboratory missions and research related to additive manufacturing (powder bed and inkjet) and energy technology (batteries, carbon nanotubess, catalysts, etc.).