pyrotechnics(redirected from Pyro Technic)
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pyrotechnics(pī'rōtĕk`nĭks, pī'rə–), technology of making and using fireworks. Gunpowder was used in fireworks by the Chinese as early as the 9th cent., and it was they who brought fireworks to a high stage of development. The use of fireworks for display has spread throughout the world. In many countries fireworks are used to celebrate national holidays, e.g., Independence Day in the United States and Bastille Day in France. Many combustibles and explosives and ingenious combinations of the two have been devised to produce impressive sounds and lights of many colors and to drive wheels and rockets. Fireworks are also widely used as signal devices, e.g., various colored flares and smoke grenades to denote distress or to locate targets in military operations. Powerful flares are also used in combat to illuminate enemy positions.
a branch of technology concerned with the production and application of pyrogenic compositions and various devices filled with them. Pyrotechnic compositions used for military purposes include illuminating compositions, photoflash mixtures, tracers, and signal, incendiary, and smoke compositions. Pyrotechnic compositions are used to imitate gun reports, shell bursts, and atomic explosions on the battlefield. They are also used to produce, infrared radiation.
In industry, thermite-type mixtures are used for welding rails, pipes, and electrical conductors, as well as for the production of various alloys, such as ferrochromium. Pyrotechnic compositions are used for “pumping” lasers, generating cesium plasma, and studying the upper layers of the atmosphere. Sometimes pyrotechnic compositions are used to generate gases, such as oxygen (chlorate cartridges) and hydrogen. The compounds used in the production of matches are also a type of pyrotechnic composition. Signaling compositions for emergencies are used in various forms of transportation. Pyrotechnic compositions are used in motion picture photography and in the production of fireworks.
In agriculture pyrotechnic compositions are used for the fumigation of plants (especially citrus plants), pest control, and disinfection of vegetable storehouses and wine barrels (sulfur sticks). Antihail compositions have been developed and are being used.
The basis of most pyrotechnic compositions is a binary mixture of an oxidizer and a fuel, but there are many compositions in which the fuel burns only partially because of the oxygen in the oxidizer and partially because of the oxygen in the atmosphere. High-temperature compositions utilize as fuels magnesium, aluminum, and their alloys, as well as titanium and zirconium in some cases. Organic compositions are the main fuels used in smoke compositions. Nitrates and perchlorates are the most frequently used oxidizers in pyrotechnic compositions. Metal oxides, such as Fe3O4 and MnO2, are used as oxidizers in thermite mixtures. Potassium chlorate, or Berthollet’s salt, is used as the oxidizer in smoke compositions. In addition to oxidizers and fuels, pyrotechnic compositions contain, as a rule, various additives, such as salts to color the flame, organic dyes to obtain signaling smokes, binders to impart required mechanical properties to compressed compositions, and retarders and stabilizers for safety in manufacturing and handling. The majority of pyrotechnic compositions, particularly those containing chlorates and perchlorates, possess explosive properties.
Pyrotechnic effects, particularly the rate of burning, depend on the fineness of the components, uniformity of mixing, degree of compression, and configuration of the device. Mixing the components and compressing the compositions are operations entailing fire and explosion hazards. The cardboard or metal casings are filled mostly by using conventional presses or, less frequently, a screw press or by pouring. Ignition of pyrotechnic devices is effected by ignition mixtures, black powder, a fuse, or a quick match.
The heat of combustion of pyrotechnic compositions containing oxidizers is 1.2–8.4 megajoules/kg (300–2,000 kilocalories/kg). The combustion temperature is from 400° to 3500°C. The rate of combustion of compressed compositions is from 0.5 to 20 mm/sec at a pressure of 1 kilogram-force/cm2.
REFERENCESShevchuk, M. K. Zazhigatel’nye sredstva i zashchita ot nikh. Moscow, 1961.
Likhachev, V. A. Pyrotekhnika v kino, 2nd ed. Moscow, 1963.
Vspomogatel’nye sistemy raketno-kosmicheskoi tekhniki. Moscow, 1970. (Translated from English.)
Shidlovskii, A. A. Osnovy pirotekhniki, 4th ed. Moscow, 1973.
Clark, F. P. Special Effects in Motion Pictures, New York, 1966.
Ellern, H. Military and Civilian Pyrotechnics, New York, 1968.
Lancaster, R., and T. Shimizu. Fireworks. New York, 1972.
A. A. SHIDLOVSKII