Effects of Nitrogen Dioxide on the Oxidation of Levitated exo-Tetrahydrodicyclopentadiene (JP-10) Droplets Doped with Aluminum Nanoparticles

Abstract

Nitrogen dioxide (NO2) can significantly improve the combustion of hydrocarbon fuels, but the effect of NO2 on the ignition of fuels with energy densities enhanced by aluminum (Al) nanoparticles has not been studied. We therefore investigated the effects of NO2 on the ignition of JP-10 droplets containing Al nanoparticles initially acoustically levitated in an oxygen–argon mixture. A carbon dioxide laser ignited the droplet and the resulting combustion processes were traced in real time using Raman, ultraviolet–visible (UV–vis), and Fourier-transform infrared (FTIR) spectroscopies simultaneously with a high-speed optical or thermal imaging camera. Temperature temporal profiles of the ignition processes revealed that a 5% concentration of NO2 did not cause measurable differences in the ignition delay time or the initial rate of temperature rise, but the maximum flame temperature was reduced from 2930 ± 120 K to 2520 ± 160 K. The relative amplitudes of the UV–vis emission bands were used to deduce how NO2 affected the composition of the radical pool during the oxidation process; for example, the radicals NO, NH, and CN were detected and the OH (A 2Σ+–X 2Π) band at 310 nm was less prominent with NO2. Localized heating from a tightly focused infrared laser beam provided sufficient energy to activate chemical reactions between the JP-10 and NO2 without igniting the droplet. Raman spectra of the residue produced give information about the initial oxidation mechanisms and suggest that organic nitro compounds formed. Thus, in contrast to previous studies of hydrocarbon combustion without Al nanoparticles, NO2 was found not to enhance the ignition of an Al-doped JP-10 droplet ignited by a CO2 laser.

Unraveling the initial steps of the ignition chemistry of the hypergolic ionic liquid 1-ethyl-3-methylimidazolium cyanoborohydride ([EMIM][CBH]) with nitric acid (HNO3) exploiting chirped pulse triggered droplet merging

“…The levitator incorporates complementary in situ diagnosticsinfrared (IR), Raman (Ra), ultraviolet-visible (UV-Vis) spectroscopy, VIS/IR thermal imaging -to probe the initial oxidation processes of HILs. 25,[45][46][47][48][49][50][51][52] This is achieved by tracing the temporal evolution (kinetics) of the reactants and (functional groups of) intermediates/products formed in the oxidation processes spectroscopically and by intentionally diluting the HNO 3 reactant from WFNA down to 10% to reduce the reactivity and to slow down the speed of the initial oxidation process thus enabling the characterizations of the initial steps of the oxidation process. This is merged with the very recent computational results on the oxidation of [EMIM][CBH] by HNO 3 .…”

“…1) used in the present experiment has been discussed in detail previously. 25,[45][46][47][48][49][50][51][52]54 Briefly, in this acoustic levitator, ultrasonic sound waves with a frequency of 58 kHz are produced by a piezoelectric transducer and they get reflected from a concave plate mounted vertically upwards thus generating a standing wave. 44 The soundwaves produce acoustic radiation pressure, which allows a liquid droplet or a tiny solid particle to levitate slightly below one of the pressure minima of the standing wave.…”

Physicochemical Transformation Effect on the Relaxivity Enhancement of Iron Oxide Nanoparticles in Nuclear Medicine and MRI Imaging

“…These changes occur by coating SPION with organic acids or with a hydrophilic and biocompatible polymer [36]. They are capable of binding to a variety of biomolecules and can be used in a wide range of applications in tissue engineering and nanotechnology [59]. The average length of cubic SPIONs is 12 nm, which is the best recommended size for tissue diffusion.…”