RU2335484C2 - Gas-making pyrotechnic compound - Google Patents

Abstract

FIELD: shooting operations.

SUBSTANCE: offered gas-making pyrotechnic compound contains an aluminum hydride powder (25÷70 wt %) and potassium perchlorate powder (30÷75 wt %). The powder has specific gas evolution of 400÷832 cm³/g, is capable to create pressure pulse of 3.0-10⁶÷13.5-10⁶ kgf/cm² · c^-1, thus temperature of ignition of powder is not higher 200°C.

EFFECT: increase of gas evolution and decrease in temperature of ignition.

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Description

The invention relates to the field of pyrotechnics and can be used in gas sources operating in a pulsed mode to obtain a mixture of gases (mainly hydrogen) of high temperature and pressure.

Gas-forming compounds are widely used in various technical means using gas energy for:

- creating a certain pressure;

- movement of actuators;

- pressurization of fuel tanks;

- filling airbags, etc.

In some cases, to ensure the operability of technical means, for example, pyro-cutters, it is necessary to create a powerful pressure pulse. Typically, such pulses are characterized by a rate of increase in pressure and have a value of the order of 10 ⁶ kgf / cm ² · s ^-1 , which actually characterizes the process of explosive transformation of the composition.

The pyrotechnic composition intended to create such a pressure pulse should have the following characteristics:

- high specific gas evolution;

- the ability to rapid (explosive) transformation, including in extruded form;

- operability in the temperature range from minus 50 ° С to plus 50 ° С with minimum quantities of substances limited by the dimensions of the structure;

- high sensitivity to the initial heat pulse (low ignition temperature), since the initiation of these compositions is often carried out by slow-burning retardants with a low combustion temperature;

- low hygroscopicity and the ability to maintain their properties for the required period of time (product warranty period).

The literature contains data on various substances (gunpowder, PTS) that can create a pressure impulse [Auxiliary systems of rocket and space technology, translation, ed. I.V. Tishunina, M., "WORLD", 1970, p. 117]. However, known substances do not meet all of the above requirements.

So, the used black (smoky) gunpowder has a pressure impulse of only 0.021 · 10 ⁶ kgf / cm ² · s ^-1 , which limits its use. Smokeless powder (0.196 · 10 ⁶ kgf / cm ² · s ^-1 ) has a higher pressure impulse, but even this material is not effective enough, especially in pressed form and at low temperatures (due to the presence of water vapor in the combustion products).

The so-called 50/25/25 DuPont mixture, which is apparently a pyrotechnic composition, is even more effective in terms of pressure impulse. In this case, the pressure pulse is 1.33 · 10 ⁶ kgf / cm ² · s ^-1 . There is no information on the formulation of this mixture.

There is also information on the composition based on ammonium and zirconium perchlorate (percentage is not given). When testing pressed samples from this composition, a pressure pulse of 4.2 · 10 ⁶ kgf / cm ² · s ^-1 was recorded. The disadvantages of this composition are the high hygroscopicity and toxicity of ammonium perchlorate.

The most promising, according to the authors of the present invention, is the use of a gas-forming pyrotechnic composition based on aluminum hydride.

This material is widely used as a high-energy additive in solid rocket fuels (TRT). For example, the following TPT composition is known, wt.% [US patent No. 3755019, class. C06D 5/06, Volume 913, No. 4, August 28, 1973]:

Aluminum hydride 5 ÷ 25 An oxidizing agent selected from the group consisting of ammonium perchlorate, sodium perchlorate, potassium perchlorate, 30 ÷ 70 ammonium nitrate, potassium nitrate, sodium nitrate Plasticized Nitrocellulose 15 ÷ 70

In this case, there is a combustion of aluminum hydride to Al ₂ O ₃ and H ₂ O, while the burning rate is several mm / s (tens of mm / s).

The closest in technical essence is a pyrotechnic composition using aluminum hydride and iron oxide [US Patent No. 3948700, class. C06B 23/00, C06B 27/00, April 6, 1976]. In this case, the inventors propose a composition for producing high temperature hydrogen, and a reaction of the type:

Fe ₂ O ₃ + 2AlH ₃ → 2Fe + Al ₂ O ₃ + 3H ₂ .

This composition contains 27.3% wt. AlH ₃ and 72.7% wt. Fe ₂ About ₃ . The reaction temperature is 3000 ° C, the specific hydrogen gas release of 300 cm ³ / g (under normal conditions: 0 ° C, 760 mm Hg).

For use as a gas-generating pyrotechnic composition capable of creating a powerful pressure pulse, this composition is not suitable, because It has a low burning rate and is not capable of rapid (explosive) transformation. The oxidizing agent Fe ₂ O ₃ , which is part of the composition, has a decomposition temperature of 1565 ° С; therefore, this composition has a rather high ignition temperature (at least 500 ° С).

The objective of the proposed technical solution is to significantly increase the gas evolution of the composition and giving it the ability to quickly (explosive) transformation in the pressed form.

The technical result achieved by using the invention is as follows:

- specific gas evolution of at least 400 cm ³ / g;

- the ability to create a pressure pulse of at least 3 · 10 ⁶ kgf / cm ² · s ^-1 in the pressed form;

- performance in the structure of the structure in the temperature range from minus 50 ° C to plus 50 ° C with minimal amounts of substance (mg);

- the ignition temperature is not more than 200 ° C;

- low hygroscopicity (less than 0.1%) and high chemical resistance over a long shelf life (at least 20 years in the product).

The task and technical result are achieved due to the fact that the known gas-forming pyrotechnic composition containing aluminum hydride and an oxidizing agent as a fuel, according to the invention, contains potassium perchlorate as an oxidizing agent in the following ratio of components, wt.%:

Aluminum hydride 25 ÷ 70 Potassium perchlorate 30 ÷ 75

The replacement of the oxidizing agent Fe ₂ O ₃ used in the prototype (decomposition temperature 1565 ° С) with potassium perchlorate (decomposition temperature 580 ° С), containing a much higher percentage of oxygen, made it possible to increase the percentage of aluminum hydride in the composition, which together led to a significant increasing the specific calorific value of the composition, the amount of hydrogen released and ensuring the ability of the composition to explosive transformation, even in pressed form.

It should be noted that when the composition is burned, a very high temperature develops (at least 3000 ° С), as a result of which the condensed products of combustion (Н ₂ О, KCl) turn into a vapor state. This significantly increases the total volume of gaseous reaction products during combustion of the composition and contributes to an increase in pressure impulse.

Experimentally selected ratio of components allows to achieve the above technical result. Experimental and calculated data are given in the table. The specific gas evolution of the combustion products of the composition is given for normal conditions (0 ° C, 760 mm Hg).

No. The content of components,% wt. Specific gas evolution, cm ³ / g (calculation) Specific calorie content, kcal / g (kJ / g) (calculation) Pressure pulse, kgf / cm ² · s ^-1 (experimental) KClO ₄ Alh ₃ H ₂ Kcl H ₂ O Total one 75 25 75 121 204 400 2.28 (9.55) 8.0 · 10 ⁶ 2 70 thirty 219 113 116 449 2.34 (9.80) 10.2 · 10 ⁶ 3 63 37 414 102 - 516 2.45 (10.26) 13.510 ⁶ four 55 45 504 89 - 593 2.09 (8.75) 13.0 · 10 ⁶ 5 fifty fifty 560 81 - 641 1.89 (7.91) 12.0 · 10 ⁶ 6 40 60 672 64 - 736 1.55 (6.49) 8.210 ⁶ 7 thirty 70 784 48 - 832 1.16 (4.85) 3.0 · 10 ⁶

Combustion of a composition with an aluminum hydride content of 37% proceeds according to the following equation:

3KClO ₄ + 8AlH ₃ = 3KCl + 4Al ₂ O ₃ + 12H ₂ ↑.

When burning compositions with aluminum hydride content of less than 37 wt.%, The combustion products can be H _2, H ₂ O, KCl, and Al ₂ O _3.

In combustion with formulations containing aluminum hydride over 37 wt.%, The combustion products can be H _2, KCl, Al and Al ₂ O _3.

For experimental testing, the claimed composition was made by mixing powders:

- aluminum hydride <10 μm;

- potassium perchlorate <40 microns.

To determine the combustion characteristics, samples with a compaction degree of 0.8–0.85 were used.

The pressure impulse was determined by burning the samples in a sealed assembly, while the maximum pressure and the time during which it was reached were determined.

The ignition temperature of the composition was determined by the DTA method.

From the data given in the table, it follows that the specific gas evolution of the claimed composition reaches 400 ÷ 832 cm ³ / g, the specific calorific value is 1.16 ÷ 2.45 kcal / g.

Compounds with aluminum hydride content of 37 ÷ 50% wt have the greatest pressure impulse. Compositions with a high content of AlH ₃ have a higher specific gas evolution, but also a lower specific calorific value, which leads to a decrease in the pressure pulse.

The ignition temperature of the claimed composition is in the range of 180 ÷ 190 ° C.

Repeatedly conducted experiments have confirmed the performance and high reliability of the claimed composition in the entire temperature range from minus 50 ° C to plus 50 ° C with a minimum composition weight of a few mg.

This composition is characterized by low hygroscopicity (less than 0.1%) and high chemical resistance during the warranty period of storage of the product (at least 20 years).

Claims (1)

A gas-forming pyrotechnic composition containing aluminum hydride powder and an oxidizing agent as a fuel, characterized in that it contains potassium perchlorate powder as an oxidizing agent in the following ratio of components, wt.%: aluminum hydride powder 25 ÷ 70 potassium perchlorate powder 30 ÷ 75