富B-H基离子液体推进剂的设计合成及性能研究

自燃推进剂作为火箭和太空飞行器的动力核心，是航空航天领域发展的重要保障。现用自燃推进剂的主要组分是易挥发、强致癌和低能量密度的肼类化合物，开发自燃离子液体（Ionic Liquids, ILs）替代肼类物质用作绿色高能自燃推进剂具有重要的环保和战略意义。论文以设计新型富B-H基ILs推进剂为目标，合成了B-H簇基、阴阳离子共修饰型多唑B-H基自燃ILs以及绿色IL-IL双组元推进剂，系统研究ILs推进剂各项性能，对B-H基自燃ILs的研究进行了一定的创新和推进。主要研究内容如下：（1）设计合成了2类B-H簇基（[B12H12]2-和[B10H10]2-）自燃ILs。与常规B-H基自燃离子液体相比，两类推进剂在水热稳定性、密度、点火活性等方面均有很大的提升。化合物热分解温度多数可达250 oC以上。通过核磁测试和水解机理分析证实室温下[B12H12]2-和[B10H10]2-具备很好的水稳定性。常规的B-H基ILs的密度偏小（< 1.0 g·cm-3），而12种离子盐均大于1.0 g·cm-3，最高达到1.18 g·cm-3，说明簇基结构有助于提高化合物密度。两类B-H簇基离子盐的生成焓大部分均为正值。同等氧化剂/燃料（O/F）比例下，两类双组元比冲值较偏二甲肼高，且呈大比冲的O/F比例范围很宽（50% – 80%），有利于减小运行过程中推进性能损耗和简化发动机设计。[B12H12]2-离子盐与HNO3接触的点火延迟时间为4 – 16 ms，但未能与N2O4发生自燃。[B10H10]2-离子盐点火活性比[B12H12]2-离子盐更好，其与HNO3点火延迟时间达到1 ms，且能与N2O4发生自燃，点火延迟时间大多小于10 ms。（2）设计合成了6种负一价B-H簇基阴离子[B6H7]-自燃ILs。由于B-H簇阴离子的价态和分子量的降低，[B6H7]-离子盐的熔点比[B12H12]2-和[B10H10]2-离子盐低，其中4种化合物在室温下呈液态，属室温ILs的范畴。此类ILs同样具有很好的水热稳定性。由于[B6H7]-阴离子的簇状堆积单元较小，因而对于所构成的离子化合物的密度提升并不明显，但引入不饱和基团的离子化合物，密度可大于1.0 g·cm-3。[B6H7]-离子盐的生成焓均为正值。同等O/F比例下，双组元比冲值较偏二甲肼高，且呈大比冲的O/F比例范围在50% – 80%，有利于减小运行过程中推进性能损耗和简化发动机设计。[B6H7]- ILs与HNO3和N2O4接触点火延迟时间最低可达到1 ms，是迄今为止点火延迟时间最短的自燃ILs。（3）设计合成了10种多唑B-H基自燃ILs。该种ILs的设计采用阴阳离子共修饰的理念，将阴阳离子同时修饰上“着火点”B-H基团和“能量点”多唑基团，克服了以往阴阳离子单一起效的弊端。双（三唑）B-H阴离子[BTzB]--基ILs的相变温度范围是-44.9 – -57.6 oC。此类ILs的热稳定性较好，多数ILs热分解温度在250 oC左右。唑基的引入提高了ILs的密度，[BTzB]--基ILs的密度范围是1.07 – 1.16 g·cm-3。唑基的引入提高了ILs的生成焓，咪唑B-H阳离子的生成焓为440.6 – 759.2 kJ·mol-1，[BTzB]-的生成焓为24.3 kJ·mol-1。[BTzB]--基ILs生成焓范围为83.1 – 390.2 kJ·mol-1。由于粘度偏大，点火活性受到限制，点火延迟时间最低为20 ms。[BTzB]-类ILs比冲在260 s左右（氧化剂为硝酸），由于密度相对较高，密度比冲表现良好，约在360 s·g·cm-3左右。（4）设计合成了9种IL-IL型双组元推进剂。首次提出IL-IL型双组元推进剂的概念，旨在同时实现推进剂燃料和氧化剂的绿色化。ILs氧化剂是一类以NO3-作为阴离子，以咪唑或三唑阳离子为骨架的Br?nsted酸性ILs。ILs燃料是一类具有优异点火活性的[B6H7]-类ILs。ILs氧化剂在熔点（< -80 °С）和热稳定性（> 50 °С）方面均优于HNO3和N2O4。ILs燃料凝固点略高，热稳定性良好（Tg > 190 °С）。ILs氧化剂的密度在1.5 g·cm-3左右，ILs燃料的密度大于0.9 g·cm-3。三类ILs氧化剂的生成焓均为负值，ILs燃料的能量值较高（122.9 – 379.8 kJ·mol-1）。9种自燃双组元推进剂的比冲范围在182.5 - 204.0 s。O1/F组合的比冲值最高可达200 s以上。燃烧焓的范围在-2738.0 – -3011.0 J·g-1之间。比冲与燃烧焓的变化相一致。9种IL-IL型组合均能自燃，除O3/F2组合外，其它组合点火延迟时间在98 – 952 ms。尽管IL-IL组合在性能上仍有很多不足，还无法满足实际应用的要求，但是，该理念对设计新型绿色双组元推进剂具有一定的启发性。;Hypergolic propellant, as the key power of rocket and space aircraft, is an important guarantee for the development of aviation and aerospace field. As the derivatives of hydrazine (the main component of hypergol) are volatile and highly carcinogenic substances with low volumetric energy density, the research shows the environmental and strategic importance in replacing the derivatives of hydrazine with hypergolic ionic liquids (ILs). In this paper, B-H cluster-based and azole B-H based hypergolic ILs, and green IL-IL bipropellants were synthesized. Some innovations and advances were made in the study of B-H based hypergolic ILs. The research contents are as follows:(1) Two classes of B-H cluster based ([B12H12]2- and [B10H10]2-) hypergolic ILs were designed and synthesized. Compared with the conventional B-H based hypergolic ILs, the hydrothermal stability, density and ignition activity of the two ILs have been greatly improved. The thermal decomposition temperature (Td) of the compounds can reach higher than 200 oC, or even higher than 250 oC. The NMR tests and hydrolysis mechanism analysis showed that [B12H12]2- and [B10H10]2- had good water stability at room temperature. The densities of conventional B-H based ILs were relatively low (less than 1.0 g cm-3), while 12 kinds of ionic salts were more than 1.0 g cm-3, the highest of which was 1.18 g cm-3, indicating that the cluster structure was beneficial to increase the density of compounds. Most of the heats of formation (ΔHf) of B-H cluster ions were positive. At the same oxidizer/fuel (O/F) ratio, the specific impulse (Isp) values were higher than that of UDMH. And B-H cluster based hypergolic ILs exhibited a wide range of O/F combinations resulting in high performance, which was advantageous for reducing propulsion performance loss and simplifying engine design. The ignition delay times of [B12H12]2- ion salts upon contact with HNO3 ranged from 4 to 16 ms. But it could not spontaneously ignite with N2O4. The ignition delay times of [B10H10]2- ionic salts upon contact with HNO3 reached to 1 ms. And it could spontaneously ignite upon contact with N2O4 and exhibited short ignition delay times (most < 10 ms).(2) Six kinds of [B6H7]- ILs were designed and synthesized. Due to the lower valence state and molecular weight, the melting points of [B6H7]- ionic salts were lower than that of [B12H12]2- and [B10H10]2- ionic salts. Four compounds were liquid at room temperature and belonged to the category of room temperature ILs. Such ILs also showed good hydrothermal stability. Because the cluster-like stacking units of [B6H7]- anions are small, the density of the ionic compounds is not significantly increased, but the ionic compounds with unsaturated groups can be denser than 1.0 g cm-3. The ΔHf values of [B6H7]- ions were positive. At the same O/F ratio, the Isp values were higher than that of UDMH, and the O/F ratio with high specific impulse ranged from 50% to 80%, which is beneficial to reducing propulsion performance loss and simplifying engine design during operation. The ignition delay times of [B6H7]- ILs upon contact with HNO3 or N2O4 could reach 1 ms, which is the shortest ignition delay time so far.(3) Ten mutil-azole B-H based hypergolic ILs were designed and synthesized. The design of mutil-azole B-H based hypergolic ILs adopted the concept of anion-cation co-modification, which modifies anions and cations on both "ignition point" B-H group and "energy point" azole group simultaneously, overcoming the disadvantages of single anion-cation effect in the past. The transition temperature range of mutil-azole B-H based ionic liquid is -44.9 ? -57.6 oC. The thermal stability of these ILs is good, and the Td of most ILs are around 250 oC. The densities of ILs were increased by the introduction of azole group, ranging from 1.07 to 1.16 g cm-3. The ΔHf values of ILs were increased by introducing azole groups. The ΔHf of the cations varied from 440.6 to 759.2 kJ·mol-1 and that of [BTzB]- was 24.3 kJ·mol-1. The ΔHf of [BTzB]--based ionic liquid ranged from 83.1 to 390.2 kJ·mol-1. Because of the high viscosity, the ignition activity was limited, and the lowest value of the ignition delay time is 20 ms. The Isp values were about 260 s (oxidizer is nitric acid). Because of their relatively high densities, the specific impulse performance is good, about 360 s g cm-3.(4) Nine IL-IL bipropellants were designed and synthesized. The concept of IL-IL bipropellant was proposed for the first time, aiming at greening propellant fuel and oxidizer. IL oxidizers are a kind of Br?nsted acidic ILs with NO3- as anion and imidazolium or triazolium as cation. IL fuel is a class of [B6H7]--based ILs with excellent ignition activity. IL oxidizers are superior to HNO3 and N2O4 in melting points (< 80 oC) and thermal stabilities (> 50 oC). The freezing points of IL fuels were slightly higher and the thermal stabilities were good (Tg > 190 oC). The densities of IL oxidizers were around 1.5 g cm-3, and the densities of IL fuels were greater than 0.9 g cm-3. The ΔHf values of the three IL oxidants are all negative, and that of the IL fuels are high (122.9 - 379.8 kJ·mol-1). The Isp of 9 kinds of hypergolic bipropellants varied from 182.5 to 204.0 s. The heats of combustion (ΔHc) ranged from -2738.0 to -3011.0 J g-1. The change of Isp was consistent with the change of ΔHc. All the nine IL-IL combinations can spontaneously ignite, and IDs of the other combinations varied from 98 to 952 ms except for O3/F2. Although IL-IL combinations still have many deficiencies in performance and can not meet the requirements of practical application, this concept has some inspiration for the design of new green hypergolic bipropellant.