J. SONG et al.: THERMAL REACTION PROCESSES AND CHARACTERISTICS OF AN Al/MnO2 PYROTECHNIC ... 327–333 THERMAL REACTION PROCESSES AND CHARACTERISTICS OF AN Al/MnO 2 PYROTECHNIC CUTTING AGENT BASED ON RESIDUE ANALYSES TERMI^NO REAKCIJSKI PROCESI IN LASTNOSTI PIROTEHNI^NEGA REZALNEGA SREDSTVA Al/MnO 2 NA OSNOVI ANALIZE OSTANKOV Jiaxing Song 1 , Tao Guo 1* , Wen Ding 1 , Miao Yao 1 , Xiaonan Zhang 1 , Junyi Huang 1 , Fengli Bei 2 , Zhongshen Yu 1 , Feilong Liu 3 , Xiang Fang 1 1 College of Field Engineering, Army Engineering University of PLA, Nanjing 210007, China 2 School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China 3 331104 Troop of PLA, Nanjing, 210001, China Prejem rokopisa – received: 2019-06-09; sprejem za objavo – accepted for publication: 2019-12-01 doi:10.17222/mit.2019.125 The pyrotechnic cutting performance of an Al/MnO2 mixture was carried out via an onset experiment. In order to understand the thermal reaction processes of the sample, both the oxide component (MnO2) and the mixture were tested by simultaneous thermal analysis. The chemical reaction processes were analysed based on residue analysis. There was an obvious combustion flame during the thermal reaction of the Al/MnO2 pyrotechnic cutting agent, and the flame could melt through the steel target easily, which meant Al/MnO2 thermite mixture had a good pyrotechnic cutting performance. Thermal reactions between Al and MnO2 had several chemical processes, including two thermal decompositions process of MnO2 and thermite exothermic reactions. As for the main exothermic reaction, the measured heat release was about 323.9J g –1 in the temperature range from 547.8 °C to 641.6 °C before the Al melt. The reaction products were mainly MnO (manganosite) and Al2O3. Keywords: simultaneous thermal analysis, pyrotechnic cutting agent, manganese dioxide Avtorji v ~lanku na osnovi izvedenih preizkusov poro~ajo o pirotehni~nih lastnostih me{anice prahov Al in MnO2.D ab i razumeli termi~no reakcijske procese vzorca, so izvedli simultano termi~no analizo tako oksidne komponente (MnO2), kot tudi me{anice. Kemijske reakcijske procese so analizirali s pomo~jo analize ostankov. Nastal je o~iten plamen med termi~no reakcijo pirotehni~nega rezalnega sredstva Al/MnO2 in posledi~no je plamen zelo lahko enostavno raztalil oz. preluknjal jekleni vzorec (plo{~o), kar pomeni da ima izbrana termitna me{anica Al/MnO2 dobre pirotehni~ne sposobnosti za rezanje. Reakcija med Al in MnO2 je potekala v dveh fazah: s termi~nim razpadom MnO2 in z eksotermi~nimi reakcijami. Glavna eksotermi~na reakcija je potekala med 547,8 °C in 641,6 °C {e preden je pri{lo do taljenja Al. Pri tem procesu so avtorji izmerili spro{~anje toplote na pribli`no 323,9 J·g –1 . Reakcijska produkta sta bila v glavnem MnO (manganozit) in Al2O3. Klju~ne besede: simultana termi~na analiza, pirotehni~no rezalno sredstvo, manganov dioksid 1 INTRODUCTION Thermite, as a kind of energetic material, is com- posed of two components: fuel and oxidizer, which could be used as the pyrotechnic cutting agent. 1,2 Usually, magnesium (Mg) and aluminium (Al) powder can be chosen as the fuel. For instance, as for Mg/CuO thermite mixture, Hosseini reported that the particle size of the metal oxide would significantly affect the thermal behaviour of the thermite system. 3 In fact, compared with Mg powder, the volumetric combustion heat of Al powder is much higher than that of Mg powder. 4 Besides, Al has the advantages of high energy density, lower cost, many more resources and a lower melting temperature than that of Mg powder, theoretically. So, Al-based thermite is one of the most widely used energetic ma- terials for many applications, such as explosives, electric igniters, welding and propellants. 5–8 As for the oxidizer, there are so many metallic or non-metallic oxides to be used in a thermite system, such as Fe 2 O 3 , NiO, I 2 O 5 ,B i 2 O 3 and CuO. Hu synthesized pollen-like porous Fe 2 O 3 via a template method, then the Fe 2 O 3 was combined with Al powder to prepare the Al/Fe 2 O 3 thermite energetic composite. 9 According to Hu’s results, pollen-like Al/Fe 2 O 3 thermite mixture has good compatibility with both Hexogen (RDX) and Octo- gen (HMX), but it is not compatible with Hexa- droitrohexazoiso-woods Alkyl (CL-20) and Glycidyl Azide Polymer (GAP) based on the results of TG-DSC tests. Al/NiO nanothermite film has been synthesized and prepared via integrating a colloidal crystal template and magnetron sputtering, and it shows a uniform structure and homogeneous density with greatly im- proved interfacial contact between the fuel and the oxidizer on the nanoscale. 10 A. M. Hobosyan 2 chose I 2 O 5 as an oxidizer to prepare nanostructure energetic materials. The experiments showed that the nanostruc- tured Al/I 2 O 5 energetic materials have a pressure Materiali in tehnologije / Materials and technology 54 (2020) 3, 327–333 327 UDK 67.017:544.016.2:546.71 ISSN 1580-2949 Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 54(3)327(2020) *Corresponding author's e-mail: guotao3579@126.com (Tao Guo) discharge value of 43.4M Pa/g, which is twice that of the purchased commercial micro-level I 2 O 5 particles. L. Glavier11 and his co-authors reported four kinds of thermite powder mixtures and their burning rate performances and over-pressure generation, Al/Bi 2 O 3 , Al/MoO 3 , Al/CuO and Al/PTFE. 11 They observed that the Al/Bi 2 O 3 powder mixture has the fastest burning rate, while Al/PTFE has the slowest velocity, and Al/CuO thermite mixture could generate the highest pressure peak. CuO, as an oxidizer, is one of the most widely used in the thermite system. Unlike other oxidizers, CuO has a thermal decomposition process with gaseous oxygen release when heated. This unique property has a great influence on the reaction mechanism of the Al/CuO thermite system. Sui prepared an Al/CuO nanothermite composite with a layer-by-layer structure, and they found that the thermite reaction between Al and CuO nanoparticles was initiated, at the onset temperature, by the interactions of Al and CuO nanoparticles at the contacting surface of the two reactive layers. 12 Then, the thermal-decomposition of CuO occurs, followed by the subsequent migration of oxygen into the Al layer. The thermite reaction was maintained by the gas-solid reaction between the Al nanoparticles and oxygen. As for the thermal decomposition properties of oxi- dizers, the characteristics of MnO 2 are similar to CuO. The process and kinetics of the thermal decomposition of MnO 2 have been reported. The results showed that there are two main reactions during the thermal decompo- sition, MnO 2 Mn 2 O 3 Mn 3 O 4 . 13,14 According to Fisher’s famous report, the theoretical calculation reaction heat of 4Al+3MnO 2 is higher than that of the Al+CuO system.15 Recently, the thermal properties and kinetics of Al/ -MnO 2 nanostructure thermite have been reported, and its heat release was approximately 1150J g –1 . 16 Al/MnO 2 nanothermite, as a kind of additive, has been added into propellants as well as explosives. 17,18 Besides, a pyrotechnic cutting agent is an important use for thermites. As for pyrotechnic cutting agent, a large dosage of Al/MnO 2 nanothermite, for example more than ten grams of sample, will lead to a sudden explosion because of the high energy density and the fast reaction speed, and the prices of nanomaterials are usually much higher than those of micron-level materials. In addition, the pre- paration process of micron-level thermite is simple and effective. Therefore, technical staff and industries prefer to use micron-level components rather than nano-level thermites in engineering applications, at present. In this paper we report and analyse the pyrotechnic cutting performance of Al/MnO 2 pyrotechnic cutting agent mixture at the micron-level scale, and the morphologies and phase characteristics of the sample are tested by field emission scanning electron microscope (FE-SEM), X-ray diffraction(XRD) and simultaneous thermal analysis. In the end, the reaction products are collected and tested. Based on residue analysis, the possible chemical reaction is analysed. 2 EXPERIMENTAL PART 2.1 Materials and equipments Al powder, Shanghai Naiou Nano Technology co., LTD., purity >99.9 %, average particle size 5 μm; MnO 2 powder, Shanghai Naiou Nano Technology co., LTD., purity >99.9 %, average particle size 5 μm; Anhydrous ethanol, AP, Shanghai Jiuyi Chemical Reagent co., LTD. All the reagents were used directly without any further treatment or purification. The Al/MnO 2 pyrotechnic cutting agent mixture phase and chemical components were characterized using XRD analysis (Bruker, D8 Advance, Germany). The morphologies, particle size and mixing quality of the components and Al/MnO 2 pyrotechnic cutting agent mixture were characterized by FE-SEM analysis (HITACHI High-Technologies corporation, S-4800 II, Japan). The investigation of thermal behaviour was carried out based on the TG-DSC (NETZSCH STA 449F3, Germany) analysis, and the heating rate was 10 °C min –1 in a corundum crucible, covering the tem- perature range from room temperature to 900 °C in a N 2 atmosphere with a velocity of 30 mL min –1 . 2.2 Sample preparation The Al/MnO 2 pyrotechnic cutting agent mixture was prepared through the use of the ultrasonic mixing method. Prior to the mixing process, 30.0 g of Al powder and 70.0 g of MnO 2 powder (mass fraction ratio of Al/MnO 2 about 3:7) were immersed in anhydrous ethanol with magnetic stirring separately for 30 min. Then, both mixed liquids were sonicated for 30 min, primarily in a sonic bath (Hechuang, KH3200E). Next, the ethanol solution of Al was slowly and homo- geneously added into the ethanol solution of MnO 2 . The suspension was ultrasonically dispersed and magnet- ically agitated for several times until the ethanol was almost evaporated to dryness under ambient conditions. After the ultrasonic mixing operation, the slurry was dried at 60 °C for 12 h under vacuum. The thermite mixture was poured into a firework torch. The torch was prepared from PVC pipe scrap. 2.3 Pyrotechnic cutting experiment Figures 1a and 1b are the diagram and photograph of the pyrotechnic cutting onset experiment, respectively. The ignition device was installed on the top of Al/MnO 2 pyrotechnic cutting agent and was sparked by electric firing. Before ignition, the 3-mm steel plate was set on the upper part of pyrotechnic cutting agent. The distance between the surface of the pyrotechnic cutting agent and the steel plate was about 3 cm. The process of ignition and combustion was recorded by a camera. J. SONG et al.: THERMAL REACTION PROCESSES AND CHARACTERISTICS OF AN Al/MnO2 PYROTECHNIC ... 328 Materiali in tehnologije / Materials and technology 54 (2020) 3, 327–333 3 RESULTS AND DISCUSSION 3.1 Pyrotechnic cutting performance Figure 2 shows the process of the Al/MnO 2 pyro- technic cutting agent combustion experiment to test its pyrotechnic cutting performance. The Al/MnO 2 pyro- technic cutting agent was ignited electrically. As shown in Figure 2a, the colour of the fire is white at the beginning of the pyrotechnic cutting agent combustion. Then so much thermite mixture is ignited because of the self-propagation reaction, and the fire becomes saffron yellow in a very short time, Figure 2b. The flame heats directly on the lower surface of the steel plate. Next, the steel plate is melted through suddenly, and according to Figure 2c, the height of the flame is about 100 cm, so there must be a certain pressure on the steel plate before melting through. In Figure 2d, the height of the flame still high, about 100 cm, which means that the com- bustion of the Al/MnO 2 pyrotechnic cutting agent could last for some time, about several seconds. In the end, the height of flame gradually becomes low in Figure 2e. Besides, as shown in Figures 2c to 2e, there is a lot of smoke during the combustion. The whole process lasts about 35 s. Figure 3 presents the results of the Al/MnO 2 pyro- technic cutting agent combustion experiment, which could verify its pyrotechnic cutting performance. As shown in Figures 3a and 3b, there is apparently a burnt hole in the steel plate, and there is a deposit of molten steel around the hole. In order to quantify the pyro- technic cutting performance, we measured the hole in Figures 3c and 3d. The hole is shaped like a short strip. The width is about 1.0 cm and the length is about 3.5 cm. In order to understand the phenomenon of the com- bustion experiment, we made further research on the component and pyrotechnic cutting agent. 3.2 TG-DSC results Figure 4 presents the results of the TG-DSC tests. The black line is the DSC curve in the range of room temperature to 900 °C while the blue line is the TG curve. J. SONG et al.: THERMAL REACTION PROCESSES AND CHARACTERISTICS OF AN Al/MnO2 PYROTECHNIC ... Materiali in tehnologije / Materials and technology 54 (2020) 3, 327–333 329 Figure 1: Pyrotechnic cutting onset experiment of: a) setting diagram, b) experiment photo Figure 3: The result of the Al/MnO 2 pyrotechnic cutting agent combustion experiment Figure 2: The Al/MnO 2 pyrotechnic cutting agent combustion experiment Before the temperature reached 500 °C, there is no obvious signal in either the DSC curves or TG curves, which means that there is no chemical reaction. Figure 4a is the TG-DSC results of the MnO 2 component. In the temperature range 500 °C to 600 °C, a rapid mass loss appears in the TG curve, about –8.5 %, and the endo- thermic peak A appears in the DSC curve with heat release –197.1J g –1 , which means the first thermal decomposition of MnO 2 . As the temperature continues to rise, there is no endothermic or exothermic signal with the smooth TG curve. But when the temperature rises to 730 °C, the second mass loss signal appears in the TG curve, about –0.9 %, the heat release is about –57.4 % (Endothermic Peak B). Figure 4b is TG-DSC results of the Al/MnO 2 pyrotechnic cutting agent. In the temperature range of 500 °C to 600 °C, due to the thermal decomposition per- formance of the MnO 2 component, there is also a rapid mass loss in the TG curve, about –4.3 %, and there is no endothermic signal but an apparent exothermic peak (Exothermic Peak C) with 323.9J g –1 heat release. As is generally known, Al powder will not decompose in this temperature range. As the mass fraction of Al powder added is about 30 %, the theoretical mass loss should be reduced by about –5.9 % if all of MnO 2 in pyrotechnic cutting agent is decomposed. But in fact, the experimen- tal measurement value of the mass loss is only –4.3 %. It means that only part of the MnO 2 component undergoes the first thermal decomposition and the rest directly reacts with Al powder in the solid state. According to the law of conservation of mass, the oxygen element only transfers between MnO 2 and Al powder, so the part of thermite reaction will not show a mass change. As for the thermal decomposition product, according to the position of the peak point of exothermic peak C, the most intense reaction point (peak C) appears after the mass reduction is completed in the TG curve, which means the thermal decomposition product involves in the thermal chemical reaction. Therefore, between 500 °C and 600 °C, there are at least three intertwined reactions. They are the first thermal decomposition reaction of MnO 2 , the thermite reaction of MnO 2 with Al and the reaction between decomposition products of MnO 2 with Al. Peak C is the main reaction with a lot of gaseous oxygen release, which could be the main reason why in Figure 2c and 2d the height of thermite flame is so high. Gaseous oxygen has a good combustion-supporting effect. It could greatly increase the combustion tempera- ture of the flame, which is one of the reasons why the steel plate is melted. Besides, the participation of ga- seous oxzgen will increase the speed of combustion and increase the combustion pressure. The high temperature causes the surface of the steel sheet to melt, while the high combustion pressure causes the steel sheet to be perforated. Around 660 °C, the endothermic peak (D) appears on the DSC curve. According to the properties of Al pow- der, the endothermic peak (D) is caused by the melting heat absorption of Al powder, about –38.4J g –1 . With the increase of temperature, between 760 °C and 900 °C, the DSC curve has two signals, and endo- thermic peak E and exothermic peak F, respectively. The main reason for the appearance of the endothermic peak E is the further thermal decomposition, which does not undergo the thermite reaction. The further thermal decomposition will also be released gaseous oxygen with a mass reduction, about –0.2 %. The exothermic peak F appears after the endothermic peak E, which might be the second thermite reaction between the further thermal decomposition products and the melted Al powder. There is no obvious mass change in the second thermite reaction according to the law of mass conservation. 3.3 XRD results In order to figure out the phase of the thermal decom- position products, an adequate amount of MnO 2 sample is calcinated in a muffle furnace, and the calcination temperature is 700 °C and 900 °C, respectively, with 3 hof thermal insulation, respectively, with the product J. SONG et al.: THERMAL REACTION PROCESSES AND CHARACTERISTICS OF AN Al/MnO2 PYROTECHNIC ... 330 Materiali in tehnologije / Materials and technology 54 (2020) 3, 327–333 Figure 4: Results of TG-DSC tests: a) MnO 2 component, b) Al/MnO 2 pyrotechnic cutting agent removed after cooling. The XRD spectrum of MnO 2 and its thermal decomposition products are shown in Figure 5. After 700 °C calcinations, the XRD diffraction peak and the characteristic peak of the product (the red spectrum) are consistent with Mn 2 O 3 (JCPDS PDF 41-1442), and after 900 °C calcinations, the XRD diffraction peak and the characteristic peak of the product (the blue spectrum) are consistent with Mn 3 O 4 (JCPDS PDF 24-0734). After the TG-DSC experiment, the residues of Al/MnO 2 pyrotechnic cutting agent sample were collected, which should be the reaction products. The residues of the Al/MnO 2 sample in crucible, mainly grey-green solid substances, are shown in Figure 6. The reaction products of the Al/MnO 2 pyrotechnic cutting agent are tested by XRD, as shown in Figure 6. The main components of the products are Al 2 O 3 and MnO, instead of Mn or Mn 3 O 4 . MnO, as a common manganese oxide, is grey-green. According to a previous research report, the oxides in the metal elemental manganese are only MnO and Mn 3 O 4 , and the amount of MnO will continue to increase if the temperature is above 800 °C. 19 In our experiment the sample is heated up to 900 °C. In addition, due to the thermite reaction occurrence, the products are mainly MnO, which is consistent with the grey-green colour and the XRD spectrum. So, the chemical reaction equation of the Al/MnO 2 pyrotechnic cutting agent should be as follows: 2Al + 3MnO 2 MnO+Al 2 O 3 (1) 3.4 SEM results As shown in Figure 7, the morphology of MnO 2 powder and the microstructure of the Al/MnO 2 pyro- technic cutting agent before and after the thermal reac- tion are observed by FE-SEM. Figure 7a is a FE-SEM image of MnO 2 powder, and the microstructure of the MnO 2 is an irregular sheet or block with distinct edges and corners. Figure 7b is a FE-SEM image of the Al/MnO 2 pyrotechnic cutting agent before the thermal reaction. The spherical particles are Al powder with a 5-μm particle size, and there is no obvious agglome- ration. The distribution is more dispersed, and the irregular sheet or block sample is MnO 2 . From the picture, there is no reaction at normal temperature, which means the two components can coexist. Figure 7c is a FE-SEM image of the product after the thermal reaction. The eggshell structure in the red circle in the Figure 7c is the Al 2 O 3 layer formed by the oxi- dation of the surface of Al powder. As the temperature increases, the molten Al breaks out from the wrapped Al 2 O 3 film and participates in the reaction, leaving the Al 2 O 3 shell. The increase in the thickness of the shell is due to the partial adhesion of Al to the initial Al 2 O 3 layer during the rupture process, resulting in an increase in thickness. In addition, it can be seen from the Figure 7c that the irregular angular or block structure of the origi- nal MnO 2 disappears and is replaced by the smoother particles on the inner surface of the red square in the Figure 7c. The reaction products are agglomerated due J. SONG et al.: THERMAL REACTION PROCESSES AND CHARACTERISTICS OF AN Al/MnO2 PYROTECHNIC ... Materiali in tehnologije / Materials and technology 54 (2020) 3, 327–333 331 Figure 5: XRD spectrum of MnO 2 and its thermal decomposition products Figure 6: Results of reaction products: a) residues in crucible, b) the XRD spectrum to the high temperature and the chemical reaction. The small sphere in Figure 7c is the Al 2 O 3 product after the Al powder reaction, and the volume is significantly smaller than the Al-Al 2 O 3 ball before the reaction. 4 CONCLUSIONS In paper, the pyrotechnic cutting performance of Al/MnO 2 thermite is reported. It can burn a 3-mm steel plate with a hole that is 3.5 cm long and 1 cm wide in 35 s. Firstly, the thermal decomposition performance of MnO 2 was verified by TG-DSC and XRD. In order to explain the combustion phenomenon, an Al/MnO 2 thermite sample was tested by TG-DSC. A large amount of MnO 2 in the Al/MnO 2 thermite system decomposes and releases gaseous oxygen, while the rest of MnO 2 reacts with the Al powder, a solid phase reaction. At the same time, according to the position of the peak (A), thermal decomposition product Mn 2 O 3 is alsoinvolved in a thermite reaction. Gaseous oxygen has a good com- bustion-supporting effect. It could greatly increase the combustion temperature of the flame, which is one of the reasons why the steel plate is melted. Besides, the participation of gaseous oxygen will increase the speed of combustion and increase the combustion pressure. The high temperature causes the surface of the steel sheet to melt, while the high combustion pressure causes the steel sheet to be perforated. According to the image and the XRD spectrum of the reaction products in the crucible, a lot of grey-green solid substances should be MnO rather than Mn. It means that the chemical reaction equation of the Al/MnO 2 thermite system is 2Al+3MnO 2 3MnO+Al 2 O 3 . Finally, the morphology of the MnO 2 powder and the microstructure of the Al/MnO 2 thermite before and after the reaction are observed by FE-SEM. The microstructure of MnO 2 is an irregular sheet or block, with distinct edges and corners. As the tempe- rature increases, the molten Al breaks out from the wrapped Al 2 O 3 film and participates in the reaction, leaving the Al 2 O 3 shell. Acknowledgement The financial support from the National Natural Science Foundation of China (General Program. Grant No.51673213) and National Science Fund for Distinguished Young Scholars (Project No.51704302) are gratefully acknowledged. 5 REFERENCES 1 D. D. Dlott, Thinking Big (and Small) about Energetic Materials, Materials Science and Technology, 22 (2006) 4, 463–473, doi:10.1179/174328406X83987 2 A. M. Hobosyan, K. S. Martirosyan, Iodine Pentoxide Nano-rods for High Density Energetic Materials, Propellants Explosives Pyrotechnics, 42 (2017) 42, 506–513, doi:10.1002/prep.201600220 3 S. G. Hosseini, A. Sheikhpour, M. H. Keshavarz, and S. Tavangar, The effect of metal oxide particle size on the thermal behavior and ignition kinetic of Mg-CuO thermite mixture, Thermochim Acta, 626 (2016), 1–8, doi:10.1016/j.tca.2016.01.005 4 L. H. Shen, G. P. Li, Y. J. Luo, K. Gao,Z. Ge, Preparation and characterization of Al/B/Fe2O3 nanothermites, Science China Chemistry, 57 (2014) 6, 797–802, doi:10.1007/s11426-013-5050-2 5 Y. Shi, G. Jian, M. R. Zachariah, Electrospun Nanofiber-Based Thermite Textiles and Their Reactive Properties, ACS Applied Materials & Interfaces, 4 (2012) 12, 6432–6435, doi:10.1021/ am3021125 6 N. H. Yen, L. Y. Wang, Reactive Metals in Explosives, Propellants Explosives Pyrotechnics, 37 (2012) 2, 143–155, doi:10.1002/ prep.200900050 7 C. Rossi, A. Esteve, P. Vashishta, Nanoscale Energetic Materials, Journal of Physics and Chemistry of Solids, 71 (2010) 2, 57–58, doi:10.1016/j.jpcs.2009.10.015 8 M. R. Weismiller, J. Y. Malchi, R. A. Yetter, T. J. Foley, Dependence of Flame Propagation on Pressure and Pressurizing Gas for an Al/CuO Nanoscale Thermite, Proceedings of the Combustion Institute, 32 (2009) 2, 1895–1903, doi:10.1016/j.proci.2008.06.191 9 X. L. Hu, X. Liao, L. Q. Xiao, X. X. Jian, and W. L. Zhou, High- Energy Pollen-Like Porous Fe2O3/Al Thermite: Synthesis and Properties, Propellants Explosives Pyrotechnics, 40 (2015)6 , 867–872, doi:10.1002/prep.201500046 10 C. P. Yu, W. C. Zhang, R. Q. Shen, 3D ordered macroporous NiO/Al nanothermite film with significantly improved higher heat output, lower ignition temperature and less gas production. Materials & Design, 110 (2016) 15, 304–310, doi:10.1016/j.matdes.2016.08.002 11 L. Glavier, G. Taton, J. M. Ducere, Nanoenergetics as pressure generator for nontoxic impact primers: Comparison of Al/Bi2O3, Al/CuO, Al/MoO3 nanothermites and Al/PTFE, Combustion and Flame, 162 (2015) 5, 1813–1820, doi:10.1016/j.combustflame. 2014.12.002 J. SONG et al.: THERMAL REACTION PROCESSES AND CHARACTERISTICS OF AN Al/MnO2 PYROTECHNIC ... 332 Materiali in tehnologije / Materials and technology 54 (2020) 3, 327–333 Figure 7: FE-SEM images of samples: a) MnO 2 powder, b) Al/MnO 2 agent mixture before thermal reaction, c) Al/MnO 2 agent mixture after thermal reaction 12 H. Sui, L. Lesergent, J. Z. Wen, Diversity in Addressing Reaction Mechanisms of Nano-Thermite Composites with a Layer by Layer Structure, Advanced Engineering Materials, 20 (2017) 3, 1700822, doi:10.1002/adem.201700822 13 W. M. Dose, S. W. Donne, Manganese dioxide structural effects on its thermal decomposition, Materials Science Engineering B, 176 (2011) 15, 1169–1177, doi:10.1016/j.mseb.2011.06.007 14 J. X. Song, X. Fang, T. Guo, A novel process of thermal decom- position of MnO2 nanorods, Russian Journal of Physical Chemistry A, 92 (2018) 9, 1742–1747, doi:10.1134/S0036024418090273 15 S. H. Fischer, M. C. Grubelich, A Survey of Combustible Metals Thermites and Intermetallics for Pyrotechnic Applications, Defense Technical Informantion Center, 1996, doi:10.2514/6.1996-3018 16 J. X. Song, X. Fang, Thermal Properties and Kinetics of Al/alpha-MnO2 Nanostructure Thermite, Journal of Brazilian Chemical Society, 29 (2018) 2, 404–411, doi:10.21577/0103- 5053.20170154 17 N. N. Zhao, C. C. He, Preparation and Characterization of super- thermite Al/MnO2 and Its Compatibilities with the Propellant Components, Chinese Journal of Explosives and Propellants. 35 (2012) 6, 32–36, doi:10.14077/j.issn.1007-7812.2012.06.018 18 S. Elbasuney, Novel Colloidal Nanothermite Particles (MnO2/Al) for Advanced Highly Energetic System, Journal of Inorganic and Organometallic Polymers and Materials, 28 (2018) 1793–1800, doi:10.1007/s10904-018-0823-x 19 T. Kengo, O. Yoshito, Enhancement of the Catalytic Activity by an Ion Product of Sub- and Supercritical Water in the Catalytic Hydration of Propylene with Metal Oxide, Industrial & Engineering Chemistry Research, 43 (2004) 10, 2345–2348, doi:10.1021/ ie030805q J. SONG et al.: THERMAL REACTION PROCESSES AND CHARACTERISTICS OF AN Al/MnO2 PYROTECHNIC ... Materiali in tehnologije / Materials and technology 54 (2020) 3, 327–333 333