Pyrotechnic heat sources

Fireworks are a part of die field of civilian pyrotechnics (Greek pyr, fire techne, art) the rest of the field is railway fusees and torpedoes. Military pyrotechnics includes lights for signals and illumination, noise makers for training, heat sources, smokes, and some minor rocket effects. Many of the same formulas and devices are used in both fields with the military devices more sturdily built... 

Thermal batteries are a special class of reserve batteries which take advantage of the long-term stability intrinsic to many interfaces when both the active material and the electrolyte are solid state, at least until activation. The stability is attributable to the very low diffusion coefficients of electrolyte ions in the solid state for the chosen electrolyte systems. These batteries are fully assembled with electrolyte present, but the electrolyte remains a solid nonconductor until it is melted by rapid heating from a pyrotechnic heat source. 

By far the most important colored smokes are those in which the dyestuff is gradually evaporated from a mixture of dye and a pyrotechnic heat source. This involves the selection of suitable dyes and of cool-buriing, gas-forming mixtures, which melt and evaporate the dye with a minimum of destruction. However, the recovery may be no more than one-third of the amount of dye in the formulation. 

In a manner that closely parallels the creation of aerosols for obscuration or signaling, one can also form aerosols of definite chemical entities. As a rule, the substance that is to be evaporated and recondensed is mixed with the heat- and gas-producing pyrotechnic mixture. Exceptionally, the evaporated substance derives from a chemical chaise within the heat-producing system. Arrangements where a gaseous heat source or gas itself furnishes a physically separate dispersing force fall under a subject treated in the next chapter on nonspecific gases. 

By insulation, heat transfer can be slowed down and attenuated, and in a pyrotechnic device, the heat itself can he gradually released though rarely slowly enough to make much difference. Also, these schemes are of little help when the heat transfer must be fast and still not excessive as to temperature. If we add the requirement that certain devices must be functional and effective at extremes of ambient temperatures, at least between —65 and +160°F as in certain power sources described below, the problem only becomes solvable by compromise. One could devise auxiliary heat sources activated through... 

A commercially available, practical pyrotechnic heat source is the fully enclosed, primer-activated cartridge, a type of which is described in patents by Bennett. of zinc, barium chromate, and... 

At low ambient temperatures, dry cells and other galvanic cells lose their faculty to give their nominal current output. Pyrotechnic heat sources can be employed to remedy this deficiency. Experimentally, one such system consists of cheap, easily molded, relatively cool burning pellets, inserted into metal tubes, which are immersed in the electrolyte. The pellets consist of fine iron powder and sulfur in the proportion 70/30 (theory 64/36 calc. 250 cal/g). They are easily ignited and while expanding in a semiliquid state, glow at bright red heat... 

The requirement for a specified quantity of calories to be delivered and therefore exactly measured is the exception rather than the rule in the applications of pyrotechnic heat production. How-evCTj with the mounting interest in the basic behavior of pyrotechnic heat sources and their relation to radiant output, dissemination, and other objectives, the question of how many calories a fuel or a mixture delivers is frequently in the mind of the modern practitioner. Heat output has the advantage that (as with physical constants) it often can be measured exactly. However, as has been emphasized pieviously, the number of calories as such is only one of the factors that determine usefulness or efficacy of a mixture. 

Magnesium and aluminum are the most important pyrotechnic fuels in quantity of consumption as well as in effectiveness for creating light and heat. Magnesium, since its introduction into fireworks about 1865, has been in the forefront of the development of radiation effects— white and colored, visible, ultraviolet, and infrared, while aluminum, used pyrochemically since about 1895, has been primarily a heat source in the thermite process but has also taken an increasing part in light production such as in flash charges. 

Adiabatic Ignition of Propellants, Pyrotechnic Compositions, etc. When ign of a subst is effected in a highly insulated condition with no gain of heat from or loss of heat to the system, it is called adiabatic ignition. The ign can be initiated by a spark, flame, incandescent wire, etc and the heat developed by these sources must be taken into consideration when calculating the heat of expin or deton from experimental data... 

Chlorate. Potassium chlorate, [CAS 3811-04-9], chlorate of potash, KCIO, white solid, soluble, mp about 350°C, powerful oxidizing agent, and consequently a fire hazard with dry organic materials, such as clothes, and with sulfur upon heating oxygen is liberated and the residue is potassium chloride formed by electrolysis of potassium chloride solution under proper conditions, Used (l)m matches, (2) in pyrotechnics, (3) as disinfectant, (4) as a source of oxygen upon heating, (Hazardous Use of potassium perchlorate is recommended instead )... 

A pyrotechnic composition is a substance or mixture of substances designed to produce an effect by heat, light, sound, gas or smoke or a combination of these, as a result of non-detonative self-sustaining exothermic chemical reactions. Pyrotechnic substances do not rely on oxygen from external sources to sustain the reaction. 

All the halates decompose on heating, nsually above their melting point. In the presence of a transition metal catalyst snch as Mn02, the decomposition of KCIO3 to chloride and oxygen starts at 70 °C and is the source of pure oxygen in laboratory preparation. In a series of the halates with the same cation, the thermal stability decreases in the seqnence of [103] > [0103] > [Br03] . Potassinm chlorate is used in the mixtnre of safety matches, in pyrotechnic formulations, and as intermediates in the prodnction of perchlorates. 

Thus, in order to produce colored light, besides needing the color species, a source of energy is necessary. In pyrotechnics, the energy is typically thermal energy (heat). 

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