A general design platform for ionic liquid ions based on bridged multi-heterocycles with flexible symmetry and charge

A conceptual design platform for new ionic liquids with variable heterocycles, bridges, symmetry, and charge was developed using simple alkylation, click, and ionic liquid chemistries and demonstrated with 1-(2-(5-tetrazolidyl)ethyl)-3-(5-1H-tetrazolyl)methylimidazolium and its conversion into room-temperatureionic liquids as cation or as anion

Ionic Liquid-Based Routes to Conversion or Reuse of Recycled Ammonium Perchlorate

New, potentially green, and efficient synthetic routes for the remediation and/or re-use of perchlorate-based energetic materials have been developed. Four simple organic imidazolium- and phosphonium-based perchlorate salts/ionic liquids have been synthesized by simple, inexpensive, and nonhazardous methods, using ammonium perchlorate as the perchlorate source. By appropriate choice of the cation, perchlorate can be incorporated into an ionic liquid which serves as its own electrolyte for the electrochemical reduction of the perchlorate anion, allowing for the regeneration of the chloride-based parent ionic liquid. The electrochemical degradation of the hazardous perchlorate ion and its conversion to harmless chloride during electrolysis was studied using IR and 35Cl NMR spectroscopies.</p

Capillary Extraction of the Ionic Liquid [Bmim][DCA] for Variable Flow Rate Operations

The ionic liquid [Bmim][DCA] is a propellant candidate in a standalone electrospray thruster or in a dual-mode propulsion system consisting of a chemical system and an electrospray system. Since limited published data exists for [Bmim][DCA], the electrospray characteristics are relatively unknown . Emission testing of the ionic liquid has been conducted to characterize the [Bmim][DCA] electrospray plume for both an external flow titanium needle and internal flow capillary. Mass spectrometric, retarding potential, and angle distribution measurements were collected for the positive polarity ions emitted from [Bmim] [DCA] wetted emitters with nominal extraction voltages between ~1 kV to ~2.5 kV. The titanium needle operate d at a sizably reduced liquid flow rate in comparison to the capillary. As such, only the major species of Bmim⁺ ([Bmim][DCA]) n with n=0, 1 were identifiable in the quadrupole measurement range of 0 - 1000 amu and were formed at or near the needle potential. A typical needle angle distribution was found in these measurements. For the capillary emitter, flow rates from 0.27 nL/s to 2.18 nL/s were used to investigate corresponding alterations in the electrospray beam. The aim of the investigation was to ascertain the ability to tune or dial-in an electrospray thruster to specific ion or droplet sizes and thus specific performance levels. Unlike the limited species observed from the needle emission, the capillary measurements indicated the presence of n=0,1,2,3,4 cation species with large mass droplet contributions. The lowest flow rates indicated the highest levels of ions in the measurement range of 0-1000 amu with a mix of large mass droplets. For increasing flow rate, species \u3c 500 amu ceased to exist leaving only the n=2,3,4 species mixed with large mass droplets in the electrospray beam. All ion species exceeded the quadrupole mass range at the upper flow rates. Ions emitted from the capillary were formed at levels below the emitter potential. Ohmic losses in the ionic liquid are likely the cause for the less energetic ions. Angular distribution measurements indicated broadening of the beam current and mass distribution for increasing flow rate

Ignition Evaluation of Monopropellant Blends of HAN and Imidazole-Based Ionic Liquid Fuels

Potential dual-mode monopropellant/electrospray capable binary mixtures of hydroxyl ammonium nitrate with ionic liquid fuels [Bmim][NO₃] and [Emim][EtSO₄] are synthesized and tested for monopropellant ignition capability in a micro reactor setup. The setup is benchmarked using 30% hydrogen peroxide solution decomposed via silver catalyst. Results show similar trends, but variance in the quantitative data obtained in literature. A parametric study on the geometry of the sample holder that contains the catalyst material in the reactor shows a large variance leading to the conclusion that quantitative data may only be compared to the exact same geometry. Hydrazine decomposition was conducted on unsupported iridium catalyst. The same trends in terms of pressure rise rate during decomposition (~160 mbar/s) are obtained with unsupported catalyst, but at 100⁰C instead of room temperature for tests conducted on supported catalysts in literature. Two catalyst materials were tested with the novel propellants: rhenium and iridium. For the [Bmim][NO₃]/HAN propellant, rhenium preheated to 160⁰C yielded a pressure slope of 26 mbar/s, compared to 14 mbar/s for iridium and 12 mbar/s for no catalyst at the same temperature. [Emim][EtSO₄]/HAN propellant shows slightly less activity at 160 o C preheat temperature, yielding a pressure slope of 20 mbar/s, 4 mbar/s, and 2.5 mbar/s for injection onto rhenium, iridium, and the thermal plate, respectively. Final results indicate that desirable ignition performance may potentially be obtained by using a supported rhenium catalyst, since the pressure slopes obtained with the new propellants on unsupported catalyst lie between that of hydrazine on iridium at 50⁰C and room temperature

Dual-Mode Propellant Properties and Performance Analysis of Energetic Ionic Liquids

Imidazole-based energetic ionic liquids capable of dual-mode chemical monopropellant or bipropellant and electric electrospray rocket propulsion are investigated. A literature review of ionic liquid physical properties is conducted to determine an initial set of ionic liquids that show favorable physical properties for both modes, followed by numerical and analytical performance simulations. Of the ionic liquids considered in this study, [Bmim][dca], [Bmim][NO₃], and [Emim][EtSO₄] meet or exceed the storability properties of hydrazine and their electrochemical proper ties are comparable to [Emim][Im], the current state-of-the-art electrospray propellant. Simulations show that these liquids do not perform well as chemical monopropellants, having 10-22% lower specific impulse due to their lack of oxidizing species. The ionic liquids show acceptable bipropellant performance when burned with standard oxidizers, having specific impulse 6-12% lower than monomethylhydrazine and nitrogen tetroxide combination. Considering these ionic liquids as a fuel component in a binary monopropellant mixture with hydroxyl ammonium nitrate shows 1-3% improved specific impulse over some green monopropellants, while retaining a higher molecular weight, reducing the number of electrospray emitters required to produce a given thrust level. More generally, ionic liquids with oxidizing anions perform well as chemical monopropellants while retaining high molecular weight desirable for electrospray propulsion mission