RECENT ADVANCES IN ENERGETIC MATERIALS IN SWEDEN, ESPECIALLY AT THE FOI

During the twentieth century, few breakthroughs occurred in energetic materials. Hexanitrobenzene was judged only 25 years ago to be the theoretically best explosive. Hexanitrohexaazaisowurtzitane (CL-20) later proved to be 20% better than octogen and 6% better than hexanitrobenzene. In the early 1990s, FOA (National Defence Research Establishment, Sweden) synthesized CL-20, enabling Sweden to purchase it from the United States. In 1995, an effective synthesis for ammonium dinitramide (ADN) was found. ADN gives much lower signature in rockets than ammonium perchlorate (AP), higher performance, and low environmental impact. Diaminodinitroethene (FOX-7) is a high explosive with lower sensitivity than TNT and similar performance to hexogen (RDX). N-guanylurea dinitramide (FOX-12) has properties similar to NC but is very insensitive and inherently more thermally stable. An FOI effort to synthetize new high energy density materials started with tetrahedral tetraazatetrahedrane (N-4), sponsored by the U.S. DoD/DARPA. This nonnatural substance was modeled by numerical quantum mechanics, and promises to have three to four times the energy of octogen. So far, the existence of this molecule has not been verified; but efforts continue. Other nitrogen clusters, such as N-8 or polymeric N-x, promise even higher yields. The pentazolate ion (N-5(-)) was successfully made at FOI by laser synthesis. With the N-5(+) counterion, synthesized by the U.S. Air Force Research Laboratory, it could form a very energetic all-nitrogen molecule. The step in energy density from octogen to N-4 is much greater than the change from black powder to high explosives, such as picric acid or trinitrotoluene, occurring in the 1870s. That change most certainly caused a complete revolution in warfare methods and weapons technology.