Degree of improvement over pre-project conditions
Primary high explosives (primaries) are used in small quantities to generate a detonation wave when subjected to flame, heat, impact, electric spark, or fiction. Detonation of the primaries is required to initiate the secondary boosters, main charge explosives, or propellants. In the early seventeenth century, toxic mercury fulminate was first made and has been used since as an initiating primary. Lead azide and lead styphnate, identified in 1907, are the only viable replacements because of their higher performance and better thermal stability, but their deleterious effects on the environment and human health have made their replacement essential.
Although substantial research efforts have been devoted to the search for new environmentally-friendly (green) primary explosives, this still unsolved problem became a “holy-grail” for energetic materials scientists. Dr. Huynh at Los Alamos National Laboratory recently ended this long-standing search with her discovery of four series of green primaries. Unlike the existing primaries, these green primaries have controlled explosive sensitivities that prevent unexpected accidents. Furthermore, upon detonation, they do not release toxic residues that contaminate the environment and cause harmful effects to human beings.
With available alkaline (Na+), alkaline earth (Ca2+), and organic cations (ammonium (Amm), hydrazonium (Hyzm), sodium (Na+), potassium (K+), magnesium (Mg2+), calcium (Ca2+), nitrosocyanaminium (NCAm), 5-amino-1-nitroso-1,2,3,4-tetrazolium (ANTm), 1,5-diamino-4-nitroso-1,2,3,4-tetrazolium, and 1,2,5-triamino-1,2,3-triazolium (TATm)) as partners, four series of 5-nitrotetrazolato-N2-ferrate hierarchies have been prepared which provide a plethora of green primaries with diverse initiating sensitivities and explosive performance. They are ready to replace not only toxic lead primaries but also thermally unstable primaries and poisonous agents.
Cationic partners
5-Nitrotetrazolato-N2-ferrate hierarchies
Dr. Huynh’s discovery meets all the requirements of modern primary explosives including insensitivity to light, sufficient sensitivity to give reliable detonation, thermal stability, and chemical stability. More importantly, they do not contaminate the atmosphere and do not deposit toxic residue into the environment. Dr. Huynh’s discovery was recognized as one of the R&D 100 international winners of 2006.
Beneficial effects beyond the facility to EHS field and larger community
Besides lead toxicity, the impact sensitivity of lead azide can never be desensitized because it is as sensitive to impact when it is wet as when it is dry. One millimeter long crystals of lead azide are vulnerable to spontaneous explosion due to internal crystal stresses. Among currently existing primaries, lead styphnate has the worst electrostatic discharge sensitivity (0.0002 J) which is 1250 times more susceptible to be set off than that of a normal human activity (0.25 J) can be.
Owing to high risk of accidents due to extreme sensitivities that are impossible to suppress, all production of lead primaries has long been abandoned in the U.S. However, we are still facing these unmanageable sensitivities and the toxicity of lead while handling, loading, and utilizing imported lead primaries. More seriously, poisonous particulates in the air, from processing lead primaries, and toxic residues, from depositing lead metal upon detonation, continue to contaminate the environment and pose health-risks to human beings, respectively.
Green primaries can be easily and safely prepared from commercially available iron salts and high nitrogen ligands in water. These aqueous reactions are astoundingly advantageous because (1) the resulting primaries are quantitatively precipitated owing to their insolubility in water, (2) the explosive sensitivities of these green primaries are completely suppressed by the water solvent, and (3) the aqueous solvent leftover contains innocuous byproducts (NaCl or NH4Cl and NaNO3 or NH4NO3). As a consequence, personnel are not threatened by exposure to hazardous chemicals and toxic lead, and they do not need to worry about unanticipated accidents.
To summarize, these new green primaries have the following benefits: (1) elimination of exposure to human beings both from harmful reagents and toxic lead, (2) saved lives from unexpected accidents, (3) elimination of need to install specialized equipment, (4) reduced liability insurance, (5) diminished expensive waste disposal. Most importantly, these iron green primaries deposit nontoxic residual products (iron, nitrogen, water, and carbon dioxide) into the environment upon detonation.
These iron green primaries are the only known technologically advanced materials that meet all current criteria for green primary explosives including (1) insensitivity to moisture and light; (2) sensitivity to initiation but not too sensitive to handle and transport; (3) thermal stability to more than 250 °C; (4) chemical stability for extended periods; (5) no toxic metals such as lead, mercury, silver, barium or antimony; and (6) no perchlorate, which may be a possible teratogen and has adverse effects on thyroid function.
Advancement with regulators and the general public
The invention of iron green primaries opened up a unique area of molecular energetic explosives research that has been internationally recognized and has already led to world-wide pursuit. It will enable regulators used to regulate all lead primaries in the future, and, potentially, to outlaw their use to prevent humans from further lead intake and to eliminate anxiety caused by the unexpected detonation of lead primaries.
Innovation / inventiveness / originality of solutions, methods and project in general
Primary explosives are sensitive high explosives used in initiating devices, such as primers and detonators for commercial and military applications. Successful detonations of secondary explosives or propellants are accomplished by suitable sources of initiation energy that is transmitted directly from the primaries, or through secondary explosive boosters. Reliable initiating mechanisms are available in numerous forms of primers and detonators depending upon the nature of the secondary explosives. In addition, the technology of initiation devices used for military and civilian purposes continues to expand owing to variations in initiating method, chemical composition, quantity, sensitivity, explosive performance, and other necessary built-in mechanisms.
Unfortunately, all existing primary candidates suffer from instability and excessive sensitivity. In addition, they release poisonous particulates that can be inhaled and toxic residues that can also be absorbed. Currently, none of them simultaneously meet the six green primary criteria: (1) insensitivity to moisture and light; (2) sensitivity to initiation but not too sensitive to handle and transport; (3) thermal stability to at least 200 °C; (4) chemical stability for extended periods; (5) no toxic metals such as lead, mercury, silver, barium or antimony; and (6) no perchlorate, which may be a possible teratogen and has adverse effects on thyroid function. Clearly, new approaches are needed.
Developing qualified primaries is much like searching for effective drugs or creating efficient catalysts. Energetic materials chemists manipulate chemical functionality to obtain desirable sensitivity and choose molecular backbones to improve explosive performance. Pharmacologists try different building blocks to search for effective treatments and change substituents on parent compounds to minimize side effects. Coordination chemists judiciously select metals as well as ligands to design inexpensive catalysts and then fine-tune reaction conditions to maximize products. Fundamentally, most scientific researchers operate on the same principles to accomplish different missions.
Given the advanced development of initiation devices and the current criteria for green primaries, the keys to success in developing green primaries include not only skill and knowledge but also flexibility and creativity to address the tradeoffs among safety, sensitivity, performance, stability, and non-toxicity. Dr. Huynh’s advanced approach is based on the chemical nature of currently-used primaries in order to overcome this long-standing problem.
Existing primary explosives include organic compounds, metastable-innerstitial-composites (MICs), and coordination complexes. The major disadvantages of organic compounds are that (1) they are susceptible to being degraded by boiling water, (2) they are unstable in moisture, and heat; (3) they darken rapidly by exposure to sunlight; (4) they contain perchlorate; and (5) they undergo molecular elimination followed by intra-molecular rearrangement. Mixtures of aluminum nanoparticles and heavy metal oxides (MICs) are known to have appropriate sensitivity. However, instability toward atmospheric oxygen and moisture, safety concerns during large scale production, and residual heavy metal contaminations have prevented their adoption as lead primary replacements. The thermally stable cationic coordination complexes have desirable properties, but their perchlorate content makes them unacceptable.
A systematic assessment of existing primary explosives clearly reveals limitations for organic compounds, from inadequate thermal stability to decomposition upon exposure to heat or light. MICs are undesirable due to air oxidation of nanoaluminum particles, and existing coordination complexes are disadvantaged by their anionic perchlorate partners. Based on this analysis, Dr. Huynh concluded that a coordination complex anion or anions charge compensated by environmentally benign cations such as NH4+ or Na+ would make superior primary explosives.
Integration with other facility activities; management and employee acceptance
1. The preparation of the green primary explosives is quite simple and straight forward; hence, no specialized equipment and safety engineering are unnecessary.
2. During production, these green primary explosives possess absolutely no sensitivity and toxic particulates, so investment in expensive manipulators and air purification systems is not required.
3. Throughout the aqueous production, employees never have to worry about being exposed to poisonous fumes and severe conditions such as high temperature and pressure.
4. More importantly, these iron green primaries can be chemically tailored to give a plethora of primaries with diverse initiating sensitivity and explosive performance. The availability of customizable, truly-green primaries has the potential of hastening the replacement of lead primaries.
Operating efficiency and/or cost savings over pre-project conditions
1. Once formed, these green primaries are quantitatively precipitated and analytically pure without the need for purification and re-crystallization. Hence, their production is quite cost-effective.
2. Owing to their insensitivity when the green primaries are wet with water, and to their controllability when dry, liability insurance to cover events due to unexpected explosions can be altogether eliminated.
3. Since the sensitivities of these green primary explosives can be completely suppressed by water, and their chemical compositions do not contaminate the air, expensive personal protective gear and special equipment can now be avoided.
4. Since the production of these green primaries does not generate any hazardous waste solvents, their manufacture eliminates the costs of waste disposal. All of the waste is non-hazardous aqueous waste that contains non-toxic salts.
LA-UR-06-8413
Please see attached document for the chemical structures.