High-Energy Mixtures

Compounds Containing Intramolecular Oxidation-Reduction Capability 

Ammonium nitrate Ammonium perchlorate Lead azide 

Note These compounds readily undergo explosive decomposition when sufficient ignition stimulus is applied. A shock stimulus is frequently needed to activate die nonionic organic molecules (such as TNT) diese compounds will frequently merely bum if a flame is applied. 

Pyrotechnic mixtures burn, but it must be remembered that these compositions—unlike most materials that undergo combustion—supply their own oxygen for combustion, through the thermal decomposition of an oxygen-rich material such 

These requirements quickly reduce the field of available materials for most energetic applications. There are few, if any, exotic chemicals that are widely used in producing energetic materials—we will discuss iron oxide, for example, at several locations in the following chapters, but other oxidizers, such as ruthenium tetroxide (RUO4), will not be discussed for reasons of cost, stability, and toxicity. 

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Warning Formulas in this book relate to mixtures, some or all of which may be highly volatile and could react violently if ignited by heat, spark, or friction. High-energy mixtures should be prepared or handled by anyone untrained in proper safety precautions work in connection with pyrotechnics and explosives... 

The desired pyrotechnic effect must be carefully considered when a fuel is selected to pair with an oxidizer for a high-energy mixture. Both the flame temperature that will be produced and the nature of the reaction products are important factors. The requirements for some of flte major pyrotechnic categories... 

The use of sulfur as a fuel in pyrotechnic compositions dates back over one thousand years, and the material remains a widely-used component in black powder, colored smoke mixtures, and fireworks compositions. For pyrotechnic purposes, the material termed "flour of sulfur" that has been crystallized from molten sulfur is preferred. Sulfur purified by sublimation - termed "flowers of sulfur" - often contains significant amounts of oxidized, acidic impurities and can be quite hazardous in high-energy mixtures, especially those containing a chlorate oxidizer [11]. 

A number of parameters related to burning behavior can be experimentally measured and used to report the "reactivity" or performance of a particular high-energy mixture [2] ... 

A variety of factors affect the ignition temperature and the burning rate of a high-energy mixture, and the chemist has the ability to alter most of these factors to achieve a desired change in performance. 

As protection against acidic impurities, high-energy mixtures will frequently contain a small percentage of a neutralizer. Sodium bicarbonate (NaHCO 3) and magnesium carbonate (MgCQj) are two frequently-used materials. The carbonate ion, CO3 reacts with H... 

Charcoal is another organic fuel, and has been employed in high-energy mixtures for over a thousand years. It is prepared by heating wood in an air-free environment volatile products are driven off and a residue that is primarily carbon remains. Shimizu reports that a highly-carbonized sample of charcoal showed a 91 3 5 ratio of C, 11, and O atoms [2]. 

Burning behavior can therefore be summarized in two words homogeneity and confinement. An increase in either should lead to an increase in burning rate for most high-energy mixtures. Note, however, that "gasless" compositions do not show the dramatic confinement effects found for "gassy" compositions. 

The requirements for a commercially-feasible high-energy mixture can be summarized as follows, keeping in mind the preceding discussions of materials and factors that affect performance... 

Successful performance of a high-energy mixture depends upon ... 

Therefore, a composition is required that will readily ignite and burn, producing the desired effect upon demand, while remaining quite stable during manufacture and storage. This is not an easy requirement to meet, and is one of the main reasons why a relatively small number of materials are used in high-energy mixtures. 

The oxidizers used in high-energy mixtures are generally ionic solids, and the "looseness" of the ionic lattice is quite important in determining their reactivity [3]. A crystalline lattice has some vibrational motion at normal room temperature, and the amplitude of this vibration increases as the temperature of the solid is raised. At the melting point, the forces holding the crystalline solid to-... 

Gonkling, John A., and Christopher J. Mocella. Chemistry of Pyrotechnics Basic Principles and Theory. 2d ed. Boca Raton, Ela. CRC Press, 2011. Covers basic chemical and safety principles, describes components of high-energy mixtures, and discusses production of smoke, sound, light, and color. 

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