Catalytic ignition of ionic liquids for propellant applications

Shamshina, Julia L.; Śmiglak, Marcin; Drab, David M.; Parker, T. Gannon; Dykes, Hiram W. H.; Salvo, Roberto Di; Reich, Alton

doi:10.1039/c0cc02162h

Cited by 60 publications

(31 citation statements)

References 16 publications

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“…19À24 It was recently found that a set of three different solvatochromic probes is sufficient to determine precise α, β, and π* (the dipolarity/ polarizability) À values of ILs. 19À23 The dissolved solvatochromic 4 shows the high hydrogen bonding accepting ability of the azolate anion and therefore the high probability of hydrogen bonding. The fact that the α parameter is considerably higher for [Bmim]5AT than for [Bmim]4Ni-Im indicates higher strength of interaction in [Bmim]5AT due to its superior electron density in the nitrogenrich ring.…”

Section: Lettermentioning

confidence: 99%

Peculiar Behavior of Azolium Azolate Energetic Ionic Liquids

Pogodina

Metwalli

Müller‐Buschbaum

et al. 2011

J. Phys. Chem. Lett.

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b S Supporting Information I onic liquids (ILs) are liquids formed by ions whose properties are tuned by the cation/anion combination. A great variety of possible cation/anion combinations drives the development of novel ILs and allows flexibility in tailoring ILs for specific applications. Azolium azolates possess superior energy density and therefore are targeted for propulsion and explosives applications. 1À4 However, the fundamental physical properties of these ILs and their full potential are not yet explored.Common ILs, which have already been widely studied, possess an organic cation and an inorganic anion. Azolium azolates consist of an organic azolium cation and an organic azolate anion; that is, the anion has the structure of an aromatic planar rich in nitrogen ring, which may lead to specific behavior of ILs. It is already accepted that ILs are complex fluids and show structuring in their liquid phases. Experimental 5,6 and theoretical 7 evidence suggests that ILs are heterogeneous on the nanoscale with polar and apolar domains in the bulk liquid, which makes them similar to bicontinuous microemulsion but with orders of magnitude lower length scales. 7,8 Our first thermorheological studies in a wide temperature range of the two ILs with inorganic anions (Scheme 1, [Bmim]BF 4 and [TMP]Tos) revealed that both ILs are characterized by broad multimodal spectra of relaxation times and show cooperative dynamics and structural heterogeneity. 9 However, the degree of this structuration depends strongly on the molecular structure of the ILs and the strength and types of interand intra-ion interactions. Present research has been undertaken to explore the effect of azolate anion structure on the physical properties of ILs, specifically on their glassy dynamics and ion interactions, utilizing rheology, X-ray scattering, UV/vis absorption, and ab initio calculations. We have studied four ILs (Scheme 1), three of which shared the same 1-butyl-3-methylimidazolium ([Bmim]) cation. Figure 1 shows a T g -scaled Arrhenius representation of IL viscosities. (Here we use calorimetric glass-transition temperature T g .) The viscosity growth spans over 12 decades in the studied broad temperature range up to T g . The [Bmim]5AT exhibits higher viscosities in comparison with the other three ILs in the accessed temperature range. Note that the experimental viscosity of [Bmim]5AT at room temperature is η exp = 5 Pa 3 s, which exceeds the η-value calculated from ion dimensions (COSMO program) by an order of magnitude η cal = 0.45 Pa 3 s (table, Supporting Information). This indicates strong interactions between ions and possible structuration of [Bmim]5AT. ABSTRACT:We present studies of molecular dynamics and interactions in azolium azolate energetic ionic liquids (ILs) by utilizing a variety of physical methods. We observe peculiar rheological behavior for these ILs, which deviates from the one expected for molecular glass-formers. Major peculiarities include high elasticity in the low-frequency zone, peculiar van Gurp plots, and...

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Section: Lettermentioning

confidence: 99%

Peculiar Behavior of Azolium Azolate Energetic Ionic Liquids

Pogodina

Metwalli

Müller‐Buschbaum

et al. 2011

J. Phys. Chem. Lett.

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“…EILs based on 2-hydroxyethyl hydrazine were found to be thermally stable and less hazardous than hydrazine [12]. One such EIL, hydroxyethylhydrazinium nitrate (HEHN), was found to be a suitable candidate for the replacement of hydrazine-based monopropellants [13]. Although HEHN was not hypergolic at room temperature with nitric acid, hypergolicity may be imparted by suitable measures, such as the addition of water and acetone, and catalysing the oxidizer with 1 to 3 mole percent nickel nitrate, along with preheating the fuel and oxidizer to 394 K [14].…”

Section: Introductionmentioning

confidence: 99%

Ignition Delays of Mixtures of the Non‐Hypergolic Energetic Ionic Liquid Hydroxyethylhydrazinium Nitrate Blended with Unsymmetrical Dimethylhydrazine

Swami

Senapathi

Srinivasulu

et al. 2019

Propellants Explo Pyrotec

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The study deals with the investigation of energetic ionic liquids capable of serving as both monopropellants and bipropellants on a single mission. Various blends of the monopropellant hydroxyethylhydrazinium nitrate (HEHN), which was found to be non‐hypergolic with red fuming nitric acid (RFNA) and white fuming nitric acid (WFNA) under ambient conditions, were formulated with known hypergols to impart hypergolicity and to reduce the viscosity and surface tension of pure HEHN. Considering the miscibility and the ignition delays of the chosen hypergols, unsymmetrical dimethylhydrazine (UDMH) was chosen as the candidate for combustion characterization through measurement of ignition delays. UDMH‐HEHN blends containing a minimum of 30 % and 40 % UDMH by weight were found to be hypergolic with RFNA and WFNA, respectively. Meticulous experiments were conducted to measure the ignition delays in a drop test setup, equipped sequentially with a high‐speed camera, which was primarily utilized to observe the physico‐chemical events governing ignition, as well as an optoelectronic diagnostic setup, which was utilized to segregate the physical and chemical ignition delays. Standard hypergolic propellants were chosen to compare the veracity of the data from the optoelectronic diagnostics setup with those obtained using a high‐speed camera. The hypergolic blend containing 60 % UDMH was found to be the best candidate, owing to its low ignition delay of 5.8 ms with RFNA, 80 % lower vapor pressure compared to UDMH, and 30 g‐s/cm3 higher predicted vacuum density specific impulse than UDMH with IRFNA.

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“…There have been several general reviews published on protic ionic liquids, with a few provided here . Specifically, within the space community, protic ionic liquids (and related salts) are being proposed as chemical thruster propellants, with several candidates, including hydroxylammonium nitrate, ammonium dinitramide, and 2‐hydroxyethylhydrazinium nitrate (HEHN), being considered.…”

Section: Introductionmentioning

confidence: 99%

Dissociation pathways of protic ionic liquid clusters: Alkylammonium nitrates

Patrick

Annesley

2019

J Mass Spectrom

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Protic ionic liquids are promising candidates for many applications, including as spacecraft propellants. For both fundamental interest and understanding clustering and dissociation during electrospray‐based propulsion, it is useful to explore the dissociation pathways of protic ionic liquid clusters, as well as the factors affecting the relative contributions of each pathway to the observed MS/MS spectra. With that said, most of the published reports on ionic liquid cluster dissociation have focused on aprotic ionic liquids. The purpose of the current work is to explore the dissociation pathways (eg, loss of amine, nitric acid, or ion pair) of alkylammonium nitrates using energy‐resolved collision‐induced dissociation. Here, it was found that, in general, protic ionic liquids have multiple dissociation pathways—namely, protic ionic liquids can lose their neutralized cation (here, an alkylamine) or neutralized anion (here, nitric acid)—in addition to the ion pair dissociation familiar to aprotic salt and aprotic ionic liquid clusters. In general, increasing the basicity of the cation (here, through increasing the degree of alkylation) decreases the propensity to follow these alternative pathways. Interestingly, increasing the cluster size has a similar effect: as cluster size increases, nitric acid loss decreases. These results will help better model and design protic ionic liquids for electrospray‐based spacecraft propulsion and help provide a better understanding for the general behavior of protic ionic liquids versus aprotic ionic liquids within mass spectrometers.

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Catalytic ignition of ionic liquids for propellant applications

Cited by 60 publications

References 16 publications

Peculiar Behavior of Azolium Azolate Energetic Ionic Liquids

Peculiar Behavior of Azolium Azolate Energetic Ionic Liquids

Ignition Delays of Mixtures of the Non‐Hypergolic Energetic Ionic Liquid Hydroxyethylhydrazinium Nitrate Blended with Unsymmetrical Dimethylhydrazine

Dissociation pathways of protic ionic liquid clusters: Alkylammonium nitrates

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