Howell Joshua H, Canfield Brian K, Costa Lino, Rhodes James E, Terekhov Alexander, Moeller Trevor M
Computational and Experimental Aerospace Research Lab (CEAR), University of Tennessee Space Institute, 411 B. H. Goethert Pkwy, Tullahoma, Tennessee 37388, United States.
Center for Laser Applications (CLA), MS 35, University of Tennessee Space Institute, 411 B. H. Goethert Pkwy, Tullahoma, Tennessee 37388, United States.
J Phys Chem B. 2024 Oct 31;128(43):10661-10674. doi: 10.1021/acs.jpcb.4c04319. Epub 2024 Oct 21.
Ionic liquids (ILs) have proven extremely useful for a wide variety of roles, including as propellants for electrospray thrusters (ETs), due to their unique physical and chemical properties, as well as the potential tunability of those properties, through chemical engineering. However, there is a lack of literature exploring the effects of IL properties on ET operation. This paper presents experimental results investigating key physical properties of the common ILs 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMI-TFSI), 1-butyl-3-methylimidazolium trifluoromethanesulfonate (BMI-TFO), EAN, and Bmpyr-DCA not provided by manufacturers or reported in the literature, namely, their electrochemical stability windows (ESWs) and contact angles. Cyclic voltammetry experiments were employed to define the ESW of each IL, which is necessary for long-term ET operation while avoiding chemical breakdown. Contact-angle measurements were also conducted to study the wettability of the ILs on glass surfaces to be used for ET thruster substrates [Howell, J. H.; . 2023, 122, 103799]. In addition, an analytical discussion is presented using established parametric relationships and scaling laws to examine the effects of relevant IL physical properties, such as surface tension and ion molecular weights, on ET performance. The results demonstrate the relative impact of IL properties on important ET figures of merit such as thrust density, power density, and specific impulse, which provide key insights into the future development of novel ILs specifically tailored for use as ET propellants.
离子液体（ILs）已被证明在多种应用中非常有用，包括作为电喷雾推进器（ETs）的推进剂，这得益于其独特的物理和化学性质，以及通过化学工程对这些性质进行潜在调节的可能性。然而，目前缺乏探索离子液体性质对电喷雾推进器运行影响的文献。本文展示了实验结果，研究了常见离子液体1-乙基-3-甲基咪唑双（三氟甲基磺酰）亚胺（EMI-TFSI）、1-丁基-3-甲基咪唑三氟甲磺酸盐（BMI-TFO）、EAN和Bmpyr-DCA的关键物理性质，这些性质制造商未提供，文献中也未报道，即它们的电化学稳定窗口（ESWs）和接触角。采用循环伏安法实验来确定每种离子液体的电化学稳定窗口，这对于电喷雾推进器的长期运行同时避免化学分解是必要的。还进行了接触角测量，以研究离子液体在用于电喷雾推进器基板的玻璃表面上的润湿性[豪厄尔，J. H.；. 2023, 122, 103799]。此外，本文还进行了分析讨论，使用已建立的参数关系和缩放定律来研究相关离子液体物理性质，如表面张力和离子分子量，对电喷雾推进器性能的影响。结果证明了离子液体性质对重要的电喷雾推进器性能指标，如推力密度、功率密度和比冲的相对影响，这为专门设计用作电喷雾推进器推进剂的新型离子液体的未来发展提供了关键见解。
