Published 6 issues per year
ISSN Print: 2150-766X
ISSN Online: 2150-7678
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ON GAS RELEASE BY THERMALLY-INITIATED FULLY-DENSE 2Al·3CuO NANOCOMPOSITE POWDER
ABSTRACT
A recently developed model for low-temperature exothermic reactions in nanocomposite Al-CuO thermites described the evolution of an alumina layer growing between Al and CuO and changes in its diffusion resistance as critically affecting ignition of the composite reactive material. The model was successful in describing ignition of individual composite particles in a CO2 laser beam. However, it was unable to conclusively predict ignition of the same powder particles coated onto an electrically heated filament. In this work, ignition of fully-dense 2Al·3CuO nanocomposite powder prepared by arrested reactive milling was studied using a modified electrically heated filament experiment, located in a miniature vacuum chamber. Thin layers of the powders coated on a nickel-chromium filament were ignited at heating rates between 200 and 16,000 K/s. The ignition was accompanied by both optical emission and pressure signals. The pressure signals occurred before emission, with increasing delay at higher heating rates. Ignition temperatures were only slightly affected by the heating rate. The results are interpreted proposing that the low-temperature redox reaction produces a metastable CuOl−x phase with 0 < x ≤ 1 which releases oxygen upon heating. It is shown that despite a relatively small heat release, the low-temperature reactions in nanocomposite thermites are important as producing destabilized, partially reduced oxides that decompose with gas release upon heating. In the present experiments, the gas release changed thermal properties of the powder coating, reducing the efficiency of heat exchange with the supporting filament and thus enabling its thermal runaway and ignition.
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Williams Rayon A., Schoenitz Mirko, Dreizin Edward L., Validation of the Thermal Oxidation Model for Al/CuO Nanocomposite Powder, Combustion Science and Technology, 186, 1, 2014. Crossref
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Williams Rayon A., Patel Jaymin V., Dreizin Edward L., Ignition of Fully Dense Nanocomposite Thermite Powders by an Electric Spark, Journal of Propulsion and Power, 30, 3, 2014. Crossref
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Abraham Ani, Zhong Ziyue, Liu Ruodong, Grinshpun Sergey A., Yermakov Michael, Indugula Reshmi, Schoenitz Mirko, Dreizin Edward L., Preparation, Ignition, and Combustion of Mg·S Reactive Nanocomposites, Combustion Science and Technology, 188, 8, 2016. Crossref
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Shaw William L., Dlott Dana D., Williams Rayon A., Dreizin Edward L., Ignition of Nanocomposite Thermites by Electric Spark and Shock Wave, Propellants, Explosives, Pyrotechnics, 39, 3, 2014. Crossref
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Mursalat Mehnaz, Huang Ci, Julien Baptiste, Schoenitz Mirko, Esteve Alain, Rossi Carole, Dreizin Edward L., Low-Temperature Exothermic Reactions in Al/CuO Nanothermites Producing Copper Nanodots and Accelerating Combustion, ACS Applied Nano Materials, 4, 4, 2021. Crossref