Mechanism of microwave-initiated ignition of sensitized energetic nanocomposites

Alibay, Zaira; Kline, Dylan J.; Rehwoldt, Miles C.; Biswas, Prithwish; Herrera, Steven; Wang, Haiyang; Zachariah, Michael R.

doi:10.1016/j.cej.2021.128657

Cited by 13 publications

(6 citation statements)

References 52 publications

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“…The volumetric power absorbed by MnO x nanoparticles is in the range of 5–10 GW/m 3 , which gives the total heat absorbed per MnO x nanoparticle of 0.7 pW. Compared to absorption with other microwave sensitizers, such as nTi, the absorption of MnO x particles is 2 orders of magnitude lower than nTi, which also leads to a much longer ignition delay time for MnO x . To better understand the thermochemistry in fabricated nAl/MnO x thermites, differential scanning calorimetry and T-jump ignition tests were conducted.…”

Section: Resultssupporting

confidence: 56%

“…Microwave radiation incident on a material can lead to dielectric heating, arc discharge, and ionization of the gaseous species, which in turn can be employed to modulate combustion performance. , Dielectric heating is expected to be the initiator to thermally driven reactions and would occur before gaseous species are released. This dielectric heating is expected to be a primary contributor in overcoming the reaction activation barrier and regulating the ignition event . Research on microwave stimulation of metal particles (often used as fuels) have demonstrated that the dielectric (native oxide) coating on metals can dramatically increase electromagnetic (EM) absorption in otherwise microwave insensitive particles. , This led to the design of architectures where nTi coated with TiO 2 /TiN was used to stimulate microwave ignition in energetic materials …”

Section: Introductionmentioning

confidence: 99%

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Microwave Stimulation of Energetic Al-Based Nanoparticle Composites for Ignition Modulation

Alibay

Olsen

Biswas

et al. 2022

ACS Appl. Nano Mater.

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Although electromagnetic stimulation promises safe and controlled ignition of energetic materials, ultraviolet (UV) to infrared (IR) wavelength sources experience significant photon attenuations in energetic materials. Conversely, radiation in microwave frequencies is recognized for instantaneous volumetric heating capabilities. However, many energetics are poor microwave heaters, and to accelerate the heating, recent efforts focused on adding microwave susceptors that do not participate in the energetic reaction. This is the first effort to demonstrate that nanoscale aluminum (nAl)/manganese oxide (MnO x ) can be rapidly heated at rates ∼104 °C/s under microwave radiation without addition of inert microwave susceptors. Detailed analysis of nanoscale MnO x was performed via X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The samples of MnO x at different loadings of nAl were three-dimensionally (3D) printed into composite films and tested with a microwave applicator at a 2.45 GHz frequency. Infrared thermometry experiments showed that with an increase in MnO x content the heating rate in the samples increases by orders of magnitude. Computational modeling based on the dielectric and thermophysical properties of the materials showed that an electric field is the dominant mechanism accounting for ∼96% of the heating of the nAl/MnO x composites at microwave frequencies. The microwave ignition mechanism was deconvoluted via high-speed IR imaging, in situ time-of-flight mass spectroscopy (TOFMS), temperature-jump (T-jump), and thermogravimetric analysis/differential scanning calorimetry (TGA/DSC) analysis. The results show that microwave stimulation can effectively heat and control ignition in nAl-based thermites with MnO x , where the oxidizer acts dually as a microwave susceptor and an ignition driver.

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Section: Resultssupporting

confidence: 56%

Section: Introductionmentioning

confidence: 99%

Microwave Stimulation of Energetic Al-Based Nanoparticle Composites for Ignition Modulation

Alibay

Olsen

Biswas

et al. 2022

ACS Appl. Nano Mater.

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“…Ammonia borane (AB) and other chemical hydrides − possess higher enthalpy of oxidation than commonly employed metallic or metalloid fuels in solid-state propellants such as Al, Ti, Si, and Mg, − on both a gravimetric and molar basis (Figure ). Owing to its high gravimetric hydrogen content (19.6%) and low hydrogen generation temperature, AB has found considerable interest in the hydrogen storage application communities as has investigation of its dehydrogenation mechanism. − However, for its application in solid-state propellants, complete oxidation of the constituent boron in addition to hydrogen is essential to exploit its high energy content.…”

Section: Introductionmentioning

confidence: 99%

Rerouting Pathways of Solid-State Ammonia Borane Energy Release

et al. 2021

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Ammonia borane (NH3BH3, AB) represents a promising energy-dense material for hydrogen storage and propulsion; however, its energy release mechanisms on oxidation by solid-state oxidizers are not well understood. In this study, through in situ time-of-flight mass spectrometry supported by attenuated total reflection-Fourier transform infrared spectroscopy and density functional theory calculations, we investigate the fundamental reaction mechanisms involved in the energy release from solid-state AB with different chemical oxidizers. We show that the reaction of AB with oxidizers like KClO4 is mediated by [NH3BH2NH3]+[BH4]− (DADB) formation, resulting in its kinetic entrapment into low-energy BNH x clusters that are resistant to further oxidation, thus limiting complete energy extraction. In contrast, with an ammonium-based oxidizer such as NH4ClO4, the presence of NH4 + ions enables AB to follow an alternative reaction pathway forming [NH3BH2NH3]+[ClO4]− rather than DADB, thus inhibiting the formation of BNH x species and facilitating its complete oxidation. This alternative reaction route causes the AB/NH4ClO4 system to exhibit remarkably higher energy release rates over that of AB/KClO4 (∼27x) and the standard Al/NH4ClO4 propellant (∼7x).

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“…Furthermore, a recent experimental study on microwave ignition of n-Ti/poly(vinylidene fluoride) energetic suggested that ignition is mainly due to electric field absorption of the oxide shell. 23 1.2. Thermally Switchable Microwave Absorption.…”

Section: Introductionmentioning

confidence: 99%

“…Consequently, the authors proposed that microwave absorption was mostly induced by the electric field component, causing formation of localized hot spots within the oxide shell due to a thermal runaway instability. Furthermore, a recent experimental study on microwave ignition of n-Ti/poly(vinylidene fluoride) energetic suggested that ignition is mainly due to electric field absorption of the oxide shell …”

Section: Introductionmentioning

confidence: 99%

Smart Electromagnetic Thermites: GO/rGO Nanoscale Thermite Composites with Thermally Switchable Microwave Ignitability

Barkley

Lawrence

Zohair

et al. 2021

ACS Appl. Mater. Interfaces

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This effort demonstrates the development of a novel, graphene oxide nanoscale thermite composite with thermally tunable microwave ignitability. A model thermite system containing nanoscale aluminum and nanoscale iron(II) oxide in a stoichiometric ratio (30/70 wt %) was combined with sheets of graphene oxide (GO) or reduced graphene oxide (rGO) using an immiscible two-fluid sonication and tape casting process. The samples were microwave irradiated within a singlemode resonant microwave cavity to determine the microwave ignition delay. Neat thermites were found to ignite after 4.34 s of microwave illumination, whereas 30 wt % rGO thermite composite ignition delay was an order of magnitude shorter (0.43 s). For most samples (4 of 6 trials), it was found that application of a 30 wt % GO coating inhibits microwave ignition of the thermite. Thermal treatment of the GO thermite composite led to switching of thermites from unignitable to ignitable with microwave field application as short as 0.24 s due to GO reduction. Optimum heat treatment time and GO content are explored with SEM, DSC/TGA-MS, Raman, and XPS deconvolution. This effort demonstrates the use of GO and rGO addition to achieve thermally switchable microwave ignitability to electromagnetically shield or enhance nanoscale energetic ignition by microwave energy.

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Mechanism of microwave-initiated ignition of sensitized energetic nanocomposites

Cited by 13 publications

References 52 publications

Microwave Stimulation of Energetic Al-Based Nanoparticle Composites for Ignition Modulation

Microwave Stimulation of Energetic Al-Based Nanoparticle Composites for Ignition Modulation

Rerouting Pathways of Solid-State Ammonia Borane Energy Release

Smart Electromagnetic Thermites: GO/rGO Nanoscale Thermite Composites with Thermally Switchable Microwave Ignitability

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