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The present work aims to study the effect of environmental hazards, namely, temperature and humidity, on the performance and sensitivity of tracer pyrotechnic composition. The experiments showed that the different pyrotechnic compositions, aged under different conditions, are prone to become more sensitive to impact and friction. It is also revealed that aging has a negative impact on luminous intensity for which the thermal aging declined the light intensity by 38.5%, while the moisture deteriorated it by 66%, compared to the pristine composition. The thermal analysis of the aged pyrotechnic compositions demonstrated a direct correlation between the heat of reactions and the magnesium content, the primary heat source, which decreases due to the formation of metal oxides (Mg(OH)2 and MgO) during the aging process. This investigation will certainly contribute to comprehensively understanding the degradation mechanism of tracer pyrotechnic compositions, and provide information on how the physical status of materials influences the luminosity, the sensitivity, and the heat of combustion reaction.

The paper presents the results of a study on the effectiveness of few-layer graphene synthesized under SHS conditions from lignin as a modifying additive in creating composite pyrotechnic complexes based on porous silicon and calcium perchlorate. It was found that the addition of few-layer graphene (20–30 wt. %) could significantly increase the probability of the ignition of pyrotechnic compositions by laser diode (infrared) radiation (wavelength of 976 nm and power of 15 MW/m2) compared to the initial pyrotechnic compositions. Using few-layer graphene also leads to a sharp increase in sensitivity to infrared laser radiation and the initiation of explosive transformations in retrofitted pyrotechnic compositions compared to the initial pyrotechnic compositions. Due to the high productivity and low cost of the technique for synthesizing few-layer graphene, the use of composite pyrotechnic compositions modified with few-layer graphene is profitable in the actual industry. A phenomenological model of the formation mechanism of 2D graphene structures under the conditions of the SHS process is proposed.

The paper presents the results of a study on the effectiveness of few-layer graphene synthesized under SHS conditions from lignin as a modifying additive in creating composite pyrotechnic complexes based on porous silicon and calcium perchlorate. It was found that the addition of few-layer graphene (20–30 wt. %) could significantly increase the probability of the ignition of pyrotechnic compositions by laser diode (infrared) radiation (wavelength of 976 nm and power of 15 MW/m2) compared to the initial pyrotechnic compositions. Using few-layer graphene also leads to a sharp increase in sensitivity to infrared laser radiation and the initiation of explosive transformations in retrofitted pyrotechnic compositions compared to the initial pyrotechnic compositions. Due to the high productivity and low cost of the technique for synthesizing few-layer graphene, the use of composite pyrotechnic compositions modified with few-layer graphene is profitable in the actual industry. A phenomenological model of the formation mechanism of 2D graphene structures under the conditions of the SHS process is proposed. [ABSTRACT FROM AUTHOR]

It has been shown that defect-free Stone–Wales (SW) free few-layer graphene (FLG) can be obtained by carbonizing lignin under conditions of self-propagating high-temperature synthesis (SHS). The obtained few-layer graphene was used as a modifying additive for pyrotechnic compositions. It was found that the addition of 2.5 mass % of few-layer graphene synthesized from lignin to a pyrotechnic complex based on porous silicon and fluoropolymer leads to a significant increase in the combustion intensity of pyrotechnic compositions.

It has been shown that defect-free Stone–Wales (SW) free few-layer graphene (FLG) can be obtained by carbonizing lignin under conditions of self-propagating high-temperature synthesis (SHS). The obtained few-layer graphene was used as a modifying additive for pyrotechnic compositions. It was found that the addition of 2.5 mass % of few-layer graphene synthesized from lignin to a pyrotechnic complex based on porous silicon and fluoropolymer leads to a significant increase in the combustion intensity of pyrotechnic compositions. [ABSTRACT FROM AUTHOR]

In the current study, two pyrotechnic compositions (tracer and igniter) containing magnesium and phenolic resin have been subjected to moisture‐induced aging at 85 % relative humidity to gain better understanding of environmental needs for their long‐storage. Non‐destructive analytical methods have been explored to investigate the effect of aging at a prolonged duration on pyrotechnics properties and their thermal behavior. The degradation of these pyrotechnic compositions during aging has been assessed using X‐ray diffraction, Fourier transform infrared (FTIR) and Raman spectroscopies, and scanning electron microscopy. It is revealed that some physical changes such as the appearance of micro‐cracks on the particle surfaces and chemical modifications such as the formation of magnesium hydroxide and nitrite‐based compounds occurred during aging. These changes affect the thermal stability of these pyrotechnic compositions as found by thermogravimetric analyses, which may increase the risk of a misfire. Moreover, the FTIR and Raman spectroscopic data were coupled with two different qualitative multivariate analysis techniques, i. e. hierarchical cluster analysis (HCA) and principal component analysis (PCA) for the classification and discrimination of the spectra of the aged specimens. The obtained results demonstrated the efficiency of the adopted methodologies to easily elucidate the structural and compositional modifications that may happen within the pyrotechnic compositions during moisture‐induced aging. [ABSTRACT FROM AUTHOR]

A pyrotechnic composition containing oxidizing agents, nanocarbon and nanoaluminum additives is developed in the course of the investigation reported. The burning rate of the composition containing 80 % of ammonium nitrate, 5 % of nanoaluminum and 15 % of nanocarbon meets the requirements of a chemical gas-generating composition. It is found equal to 1.25 mm/s. The flash point of nanoaluminum amounts to 750°C, while that of the nanocarbon fuel is equal to 350°C. The laws which determine the burning of the pyrotechnic composition as a function of the nanoaluminum content are investigated. The novelty of the gas-generating composition developed in this work lies in a new mechanism of decomposition of the ammonium nitrate flowing in the confined space. In this case, the aluminum nanopowder is oxidized to aluminum oxide which accelerates the thermal decomposition of ammonium nitrate turning it completely into a gaseous state. [ABSTRACT FROM AUTHOR]

In blasting in dense urban areas and piece stone mining, the issue of organizing gentle destruction modes arises, which requires the use of pyrotechnic compositions operating in the deflagration mode. In such compositions, ammonium perchlorate, ammonium nitrate, and other nitrates are used as oxidizing agents. Magnesium is often used as fuel. In this paper, the combustion of a three-component mixture of sodium nitrate, magnesium, and carbon was studied. The latter was obtained by carbonizing a walnut shell or grinding gas mask adsorbents. The thermodynamic calculations of combustion were performed, and the combustion characteristics of the NaNO3/Mg/C mixture with a component ratio of 60/20/20 were measured. [ABSTRACT FROM AUTHOR]

A range of Mg/Sr(NO3)2/resin compositions were prepared, containing 35–60% by mass of magnesium and the particle size ranges from ≯125 to 250–300 μm. The light output was measured after consolidating the compositions into cardboard tubes. Thermogravimetric Analysis and Differential Thermal Analysis(TG/DTA) measurements were used to determine the thermal reaction process at an a!ir atmosphere. The results indicated that the compositions containing smaller magnesium particle size had a higher luminescent intensity, lower initial reaction temperature, and lower reaction peak temperature. In addition, the increase of magnesium content made the luminescent intensity increase first and then decrease, maximize at ζ(Mg) = 0.5 – 0.55 (ζ(Mg) represents the specific gravity of magnesium powder in the compositions) because of the oxygen balance (the description of oxygen balance is listed the first paragraph in 3.1). [ABSTRACT FROM AUTHOR]

Fireworks are constructed of powder and other materials that can readily release light and heat by oxidation reaction. Pyrotechnic compositions are highly susceptible and readily result in explosive decomposition. Fireworks have led to numerous accidents during their manufacture, storage, and display. Water as an impurity affects the decomposition properties of fireworks, and consequently influences their emission safety. This research focused on the thermal stability of multiple tubes of propellant, effect pieces, and propellant mixed with water using differential scanning calorimetry (DSC) and thermokinetic analysis. The thermokinetic method was employed to determine the apparent activation energy and predict the long-term stability of dry and humid propellants. According to the predicted results, the decomposition of dry and humid propellants was severely limited after 30 days at an isothermal condition of 80 °C. However, the DSC tests indicated that water could substantially influence the heat release, emission ability, and sensitivity of the propellant. The exothermic peak for the humid propellant was ca. 275 °C, which was lower than dry propellant of 318 °C. The water visibly diminished the heat emitted from and peak intensity of the propellant. Insufficient energy supply might result in lower emission height, and lower exothermic onset temperatures in wetted propellant could lead to faulty ignition times. Therefore, contact with water (that could lead to water infiltration) should be avoided to increase the probability of successful launching and ignition. [ABSTRACT FROM AUTHOR]

The burning rate of pyrotechnic composition of implosive thruster is measured by optical fiber speed-measuring technique, and the effects of the proportion of components and the main charge density on burning rate are studied. The pressure exponent of burning rate is measured by closed-bomb test. The results show that the burning rates of pyrotechnic compositions with different proportions are different at initial stage and are tend to be the same at later stage, and the burning rate increases first and then de­creases with the increase in main charge density. The maximum burning rate of pyrotechnic composition can reach 800 m/s at the density of 1.45 g/cm ’. The pressure exponent of burning rate is 0. 736 4 in the test pressure range. It shows that the pyrotechnic composition can burn stably in a certain pressure range and can satisfy impulsive thrust requirement. [ABSTRACT FROM AUTHOR]

The applicable legislative framework for pyrotechnic articles as regards the placing on the market and use of these products safely is regulated both at national level (Law 319/2006 on Safety and Health at Work with subsequent amendments, Law 126/1995 on the regime of explosive materials and Technical implementation rule, with subsequent amendments), and at European level (through Directive 2013/29 / EU) which states the principles to be applied for insurance the legality for performing operations with explosive materials, the sale, handling and use of pyrotechnic articles, as well as the registration and authorization to carry out the operations with them, in order to avoid personal injury, damage to property or damage to the environment. Thus, according to the regulations in force pyrotechnic articles are classified into different categories depending on the level of risk, taking into account their place of use and destination (in accordance with Article 5 of the Technical Implementation Rule 126/1995 on the regime of explosive materials). Also, pyrotechnic articles are products that present a specific risk to the supplier due to the mode of operation and the quantity / content of the pyrotechnic composition involved, and the possession, marketing and use of such products whose security quality is not legally guaranteed are the object of unlawful actions or the source of risk factors that may affect the security of individuals, material assets and the environment. Also, a number of technical information and data related to security parameters (NEC, safety distances) must be taken into account on the basis of pyrotechnic articles which must be scientifically determined using highperformance equipment to get verosimiles results. [ABSTRACT FROM AUTHOR]

The aim of the study was to develop methods to reduce the penetration ability of the flame front and red-hot striking elements that propagate in the confined space of mines. In the article is considered a method for localizing explosions of a methane-dust mixture in coal mines, by creating an aqueous barrier (increased density) in the propagation path of the flame front and incandescent particles, using a high-energy pyrotechnic composition based on nanoaluminum. The optimal pyrotechnic composition contents of ammonium nitrate - 50%, smokeless powder - 45%, magnesium - 3% and nanoaluminum - 2%. This composition punched the target to a depth of 6.5 mm with a barrier thickness of 50 mm. Water cannon with a nozzle with a diameter of 80 mm, allows to localize the spread of the flame front. [ABSTRACT FROM AUTHOR]

The paper presents technologies of reducing the technological environmental impact of man-made space launch vehicles (SLV) based on controlled descent and trajectories of deorbiting the spent stages, burning of the separated nose fairing halves and tail section in the atmosphere. Controlled descent of a spent stage is accomplished due to the installation of an active on-board recovery system that uses unexpended remnants of the liquid components of propellant in the tanks. The burning of the fairing and tail section is based on the introduction of pyrotechnic compositions in their designs. Practical possibility of implementing this technology is shown taking the SLV Soyz-2.1.b space rocket as an example. It makes it possible not only to provide a solution to the basic environmental requirements, but also to improve the performance characteristics of the SLVs, move to a new technical level of their designing and operation. Using the technology of gasification of liquid residual propellants allows controlled descent of separating SLV stages with the scatter of impact points less than1 km, displacement of the impact range to 15% and increasing the mass of the payload due to the maneuver of the SLV lower stage to the intended impact area to 5% of the initial payload mass. The mass of additional equipment required for the implementation of this technology can be up to 3-5% of the dry structure of the SLV separating part.

Abstract A conceptual approach to improve the safety of rocket-space activity is presented, including minimization of space debris returning from space. The main idea is to eliminate hazards of uncontrolled re-entry of detachable rocket design elements after finishing their mission with the use of the energy of pyrotechnic thermite reaction to disrupt these parts made of composite polymeric material, i.e., carbon fiber reinforced polymer. As an example, the payload fairing half is considered, the conditions for its descent in dense layers of the atmosphere are calculated. Results reveal that depending on the entrance velocity, the target object or completely burn out, or the additional heat source is required for its full destruction. It is proposed that pyrotechnic composition to be installed on the object could serve as additional heat source to provide its combustion or fine dispersion during the atmospheric re-entry phase of the descent trajectory. The possible pyrotechnic compositions to be used are presented and discussed. Highlights • Re-entry conditions for detachable rocket elements are calculated. • At entrance velocity 2 km/s the additional heat source is required for destruction. • Thermal modelling reveals pyrotechnic composition to be additional heat source. • Amount of pyrotechnic charge to disrupt composite polymeric material is estimated. [ABSTRACT FROM AUTHOR]

Analytical and experimental studies conducted at Semenov Institute of Chemical Physics for investigating the use of pyrotechnic compositions, i.e., thermites, to reduce the risk of the fall of thermally stable parts of deorbiting end-of-life LEO satellites on the Earth are described. The main idea was the use of passive heating during uncontrolled re-entry to ignite thermite composition, fixed on the titanium surface, with the subsequent combustion energy release to be sufficient to perforate the titanium cover. It is supposed, that thus destructed satellite parts will lose their streamline shape, and will burn out being aerodynamically heated during further descending in atmosphere (patent FR2975080). On the base of thermodynamic calculations the most promising thermite compositions have been selected for the experimental phase. The unique test facilities have been developed for the testing of the efficiency of thermite charges to perforate the titanium TA6V cover of 0.8 mm thickness under temperature/pressure conditions duplicated the uncontrolled re-entry of titanium tank after its mission on LEO. Experiments with the programmed laser heating inside the vacuum chamber revealed the only efficient thermite composition among preliminary selected ones to be Al/Co 3 O 4 . Experimental searching of the optimal aluminum powder between spherical and flaked nano- and micron-sized ones revealed the possibility to adjust the necessary ignition delay time, according to the titanium cover temperature dependency on deorbiting time. For the titanium tank the maximum temperature is 1100 °C at altitude 68 km and pressure ~60 Pa. Under these conditions Al/Co 3 O 4 formulations with nano-Al spherical particles provide the ignition time to be 13.3 s, and ignition temperature as low as 592±5 °C, whereas compositions with the micron-sized spherical Al powder reveal these values to be much higher , i.e., 26.3 s and 869±5 °C, respectively. The analytical and experimental studies described in this paper provide a portion of the basic information required for the development of pyrotechnic device to reduce the risk of the fall of thermally stable parts of deorbiting end-of-life LEO satellites on the Earth. [ABSTRACT FROM AUTHOR]

This paper presents the results of an experimental study of the ignition and combustion of pyrotechnic compositions based on microsized and ultra-nanosized aluminum particles in a model two-zone gas generator using water as oxidizer. The flow of combustion products from the gas generator was video recorded, and the condensed products sampled behind the nozzle exit were studied by chemical and particle-size analyses. It was found that the replacement of microsized aluminum particles by ultra-nanosized particles in the samples led to a ≈17% decrease in the active aluminum content in the condensed phase, a 10-15% increase in the efficiency of the process in the gas generator (completeness of conversion of the pyrotechnic composition to combustion products), and a factor of about three decrease in the ignition delay. [ABSTRACT FROM AUTHOR]

This paper presents the experimental study of ignition and combustion of micro- and nanoparticles of aluminum diboride as part of pyrotechnic energy-saturated compositions in a gas generator with an air afterburner chamber and the thermodynamic calculations of combustion of pyrotechnic compositions based on aluminum diboride in air. The discharge of the combustion products from the afterburner chamber is recorded on video. It is shown that replacing micron aluminum diboride by powdered diboride with a mass-average diameter of particles equal to ≈270 nm in the pyrotechnic composition and increasing the pressure in the afterburner chamber cause the combustion efficiency in air to increase by 5-20%. [ABSTRACT FROM AUTHOR]

In order to understand the effects of gaseous production on the acoustic radiation characteristics of underwater pyrotechnic combustion, the pyrotechnic combustion pressure-time curves are plotted using a closed bomb and then maximum pressure is used to calculate the quantity of gaseous products. The results show that among the four pyrotechnic compositions with different gas productions, overall sound pressure level (OASPL) and 1/3 octave band sound pressure level (SPL) in composition #4 which has the highest nozzle gas flow, shortest period of bubble formation and largest maximum bubble diameter, reached 165.1 dB and 163 dB respectively, which were 6 dB and 10 dB higher than the corresponding minimum values. During underwater pyrotechnic combustion, bubbles were formed at the nozzle of the combustion device and thus generated low-frequency noise. The increased gas production resulted in a shorter bubble formation period, a larger number of bubbles, and larger bubble diameter, which destabilize the fluid during bubble formation, improve the prone of bubbles to coalescence and breakup, and increase the sound pressure level. [ABSTRACT FROM AUTHOR]

High-speed photography was used to study bubble movement characteristics during underwater pyrotechnic combustion. The results show that bubble behaviors include bubble formation at the nozzle, departure from the nozzle, bubble coalescence, and bubble breakup. Compared with cavitation bubbles and fluidization bubbles, the nozzle bubbles formed during underwater pyrotechnic combustion feature larger diameters, up to centimeters, and darker, and more irregular shapes. During large bubble coalescence, two bubbles approach each other, generate a channel for transfer of mass and heat, and finally coalesce. The bubbles contain high-temperature gases and solid residues generated during pyrotechnic combustion, which lead to non-uniform forces on the bubble surface and make the bubbles more prone to breakup. Because of the high-temperature solid grains, the surrounding liquid vaporizes to form bubbles. [ABSTRACT FROM AUTHOR]

The volume changing characteristics of the bubble produced by the pyrotechnic composition combustion underwater are the research foundation of the underwater combustive sound source. In order to analyze the characteristic of the acoustic radiation and phenomenon of the pyrotechnic composition combustion underwater, the high speed photography was used to study the behavior of the bubble at exit, which was generated by the pyrotechnic composition combustion underwater. A new calculative method about volume of the bubble which was based on AutoCAD was put forward, then, their velocity and changing acceleration were obtained. Results showed that the maximum changing speed and changing acceleration of the volume for bubble is respectively 1. 62 X 10-4 m³/s and 1. 93 x 10-2 m³/s², respectively. And these results could be considered as solid references for mathematic model and composition design in near future. [ABSTRACT FROM AUTHOR]