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Spalanie mieszanin metali z polimerami fluorowęglowymi

Cudziło S.

Wiadomości Chemiczne

2001

[Z] 55, 7-8

715--749

The main aim of the paper is to overview recent works dedicated to miscellaneous aspects of combustion process of metal- fluorocarbon polymer formulations. In order to systematise the collected data, the article is divided into sections discussing consecutively: mechanism of the combustion process and factors determining the linear burning rate, thermal decomposition of the mixtures, their sensitivity to mechanical, thermal and laser stimuli, emission characteristics of the flame accompanying combustion, problems concerning their stability and ageing process, and their application forms of military interest. Metal-fluorocarbon polymer compositions are heterogeneous high-energetic materials in which the burning rate is strongly dependent on the metal particle sizes (f) and the concentration of metal (x) in the mixture. The oxidation reaction of metal particles is considered to occur from the surface of each particle and propagates towards its centre. If the total burning surface area of the metal particles is small, the reaction completes at far downstream of the propellant burning surface. Therefore the heat flux feedback from the gas phase to the front of the combustion wave and, consequently, the burning rate rise when x increases and f decreases. By using metals that melt down at a temperature below the PTFE decomposition temperature (770 K), it is also possible to facilitate the initiation and propagation of the combustion wave in the compositions in question. Applying different methods of thermal analysis to study the decomposition of PTFE in the presence of some metals, it has been shown that an addition of Mg, Al, Al3Mg4, Ti, B, Zr causes the purely endothermic decomposition of PTFE in nitrogen and argon to develop exotherms with onsets in the temperature range 740(770 K. As the amount of a metal increases these exotherms enlarge whereas the decomposition endotherm is reduced in size. Size of Mg particles and its concentration in a MTV mixture affects not only the burning rate and decomposition parameters, but also the sensitivity of the mixtur. MTV compositions seem to be quite sensitive to impact and their sensitivity increases with increasing burning rate. On the other hand, they have low sensitivity to friction and do not produce a hazardous response while being heated under typical cookoff conditions. PTFE is an exceptionally good oxidiser in composition designed for producing high radiation output in the IR region. MTV compositions display functional relation between stoichiometry and specific intensity of radiation in 2-3-mm and 3-5-mm bands. With rising weight fraction of Mg up to 60 % the specific intensity increases. For values of x>60 %, the radiation output decreases. Infrared tracking flares are the main direction of military applications of MTV formulations. The latest patent in the field claims an IR-emitting flare composition comprising about 54/58 % of Mg and the remainder a mixture of PTFE and polytrifluorochloroethylene in substantially equal amount. This mixture is superior to prior-art flares. Ageing of MTV is caused by the reaction of magnesium with water into magnesium hydroxide and hydrogen. This reaction continues until all Mg is converted into Mg(OH)2. The burning characteristics, the maximum pressure and in particular the burning time are changed with respect to unaged pellets. These changes greatly affect the performance of the compositions. Because of important advantages of MTV mixtures as a relative high caloric output, strong radiant output, generation of multiphase reaction products, low gas output, these compositions are used as igniters for solid rocket motors and other pyrotechnics. A general conclusion that can be made on the basis of the papers is that metal rich compositions (containing 60(65 % Mg) perform better than other ones. Finally metal-PTFE formulations are a perfect solution for composite pyrotechnic mixtures in which presence of oxygen is undesirable. Such a situation takes place in compositions producing clouds rich in soot particles or in smoke-generating mixtures based on red phosphorus.

Military applications of neural networks

Świątnicki Z.

Biuletyn Wojskowej Akademii Technicznej

1999

Vol. 48, nr 11

183-190

The main applications of neural networks in military systems were described. The idea of neurocomputer was shown. Application of neural networks in military robots was presented. The main tasks of neural networks in military systems were discussed.

W pracy omówiono podstawowe wojskowe zastosowania sieci neuronowych. Opisano ideę neurokomputera. Zostało zaprezentowane wykorzystanie sieci neuronowych do konstrułowania robotów wojskowych. Przedstawiono próbę klasyfikacji zadań realizowanych przez sieci neuronowe.