【作者】 王天放；

【导师】 李疏芬；

【作者基本信息】 中国科学技术大学 ， 物理化学， 2008， 博士

【摘要】 燃烧是能源利用的一种主要形式，随着经济的发展，对于能源的需求日益加剧。而且，随着行业的不断增加和细化分类，对于燃料的性能方面的要求也不断增多，这些性能主要包括燃料本身的稳定性、机械性能、能量密度，以及燃烧的稳定性、燃速、特征信号和产物的污染性等。推进剂是一种由含能材料组成的燃料，主要应用于航天飞行器，曾一度以高能作为其首要目标进行了大量的研究工作。而随着航空航天技术的不断发展，对于航天器在运行中的轨道微调，包括编队飞行，航天飞机与空间站的对接和卫星的变轨等，又要求研发出燃烧稳定、可控性好、低燃速的推进剂，同时具有低感度和低污染的优点。本论文针对这一目标，选择了若干种新型燃料体系，并对其热分解及燃烧机理进行了深入的探讨。本论文由两大部分组成。第一部分是对新型高能固体燃料体系GAP／B组分的热分解及对推进剂燃烧特性的影响进行了相关实验和理论计算研究。主要探讨了硼作为高能燃料组分的优缺点以及改性方法，高能黏合剂GAP的热分解和燃烧机理分析，并对GAP／B基的固体燃料的性能进行了一定的实验探索。第二部分是实验研究了新型浆态燃料体系Al／H₂O的组分和添加剂对燃料燃烧机理的影响。主要研究了纳米铝粉和水、聚丙烯酰胺在燃烧过程中的作用机理，及非晶态纳米硼／钴合金、硝酸铵（AN）、奥克托金（HMX）和六硝基六氮杂异戊兹烷（CL-20）等添加剂对燃料燃烧性能的影响。此外，对作为微推力推进剂的燃料、Al/H₂O基燃料的助燃剂和稳燃剂的甲基丙烯酸甲酯（MMA）的贫燃燃烧反应机理进行了深入的实验研究。特别是首次将同步辐射光电离分子束质谱技术应用到了含能聚合物热分解的研究，第一次提出了GAP（Glycidyl Azide Polymer）详细热分解机理，第一次对贫燃低压条件下MMA／O₂／Ar预混火焰进行了研究，得到了反应机理以及火焰中物质碎片的浓度分布，为建立MMA燃烧反应的动力学模型提供了有价值的数据，提出了可适合不同需求的Al／H₂O基推进剂的较好配方，具有一定的创新性。通过上述研究，本论文得到了如下的研究结果：（1）综述了GAP／B和Al／H₂O基燃料的研究进展，包括基本的性质、燃烧特性、提高燃料性能的方法等。（2）提出了一种准确测定硼粉中硼含量的方法，并对市售的硼粉进行了测定，其中的杂质成分含量应用原子吸收光谱（AAS）和高频电感耦合等离子谱（ICP）方法进行测量。给出了两种简单易行而且效果良好的包覆处理硼粉的方法，即重结晶法和中和沉淀法，包覆剂选择为AP和LiF，通过DSC和点火实验初步检测了包覆的效果，并将包覆过的硼粉应用于推进剂的配方中，结果显示使用了LiF／AP双层包覆硼粉的推进剂样品体现出较好点火和燃烧性能。（3）采用激光散射（GPC）的方法原位表征了缩水甘油叠氮聚醚（GAP）样品的数均和质均分子量，分别为3981和5497，分散度为1．38，校正了提供方所给数据。（4）应用溶剂挥发的方法制备了GAP包覆B的燃料样品B^GAP，并对包覆效果进行了实验测试。应用TG／DTG和原位升温傅立叶变换红外光谱的方法研究了未固化的GAP和GAP包覆的硼粉(B^GAP)在常压空气和氮气条件下的热分解，并应用Kissinger方法对第一步——氮消除反应的动力学常数进行了计算。结果显示，B^GAP与纯GAP的热分解过程存在着不同，主要表现在更低的起始温度和反应中检测到的不同的基团；二者在空气中的自由能均比氮气中的低，而且B^GAP热分解第一步的自由能比纯GAP的低，说明B确实改变了GAP的热分解机理，而且新的反应路径过渡态具有较低的能量。应用同步辐射VUV光电离分子束质谱研究了低压条件下，GAP在惰性气体Ar中的热分解，结果显示GAP的热分解开始于70℃，生成物基本为低分子量物质，NH₃在低温时生成较少，而在高温时含量大幅度增加，许多中间体和自由基通过测量光电离效率谱（PIE）而被确认，其中包括在之前的研究中未见报导的叠氮基团（N₃）和GAP单体。同时还首次提出了某些热分解生成物的电离能范围，如vinyloxy radical，acetylcyanide，3-azide propylene等。GAP的裂解机理表明，GAP发生均裂反应后，生成的自由基又发生自由基反应、分子间交联反应、加成反应或H转移反应等，然后再进一步反应生成最终产物。运用Gaussian 03量化计算的方法B3LYP／6-31G（d）∥G2，计算了GAP热分解重要步骤氮消除反应的路径，得到反应物、中间物和产物的结构和能量信息。（5）根据物理化学中反应平衡的概念，应用最小自由能法计算了GAP在绝热条件下的燃烧产物组成和温度，结果显示燃烧温度为1475K，产物摩尔分数为：0．2238N₂+0．2842C+0．1402CO+0．1200CO₂+0．0219CH₄+0．3220H₂+0．0067H₂O。（6）制备了一系列高硼含量的推进剂样品，其中分别含有未包覆的B和B^GAP，黏合剂包括常用的端羟基聚丁二烯（HTPB）和GAP。对其点火、燃烧、能量、残渣成分等进行了实验研究，发现用GAP包覆硼粉对提高推进剂的燃烧特性具有明显的改善效果，较合适的包覆比为1：0．3。（7）对Al／H₂O基燃料进行了一系列详细的实验研究。首先，对不同粒度的铝粉作为燃料组分的可能性进行了探讨，结果显示含有纳米级铝粉的样品具有最佳的点火性能。之后，应用离线裂解GC／MS检测了单组分添加剂聚丙烯酰胺（PAM）水溶液在300℃，450℃和600℃时的闪速裂解，结果显示液相产物中检测到很多易燃的物质，特别是确认了一些含氮的环状物质，如1，2，4-Triazine-3，5（2H,4H）-dione，5-Nitro furfural semicarbazone，Hexadecanamide等，被认为会在燃烧条件下释放出较高的能量促进燃烧。而气相产物仅仅在600℃时才被检测到，而且均为可燃的小分子。FTIR的结果显示在裂解后的残留物中焦炭含量会随着温度的升高而增多。PAM的加入在很大程度上增加了推进剂的燃速，提高了能量，并大幅度降低了压强指数，与空白配方相比，降了约60％。（8）制备了纳米B／Co的非晶态合金添加剂，进行了XRD和SEM实验，结果显示其粒度在21nm左右，将其添加入Al／H₂O基础配方中，发现对提高推进剂的燃速及能量特性具有较为明显的作用，与空白配方相比，在1MPa的氩气环境里分别提高了4．52mm·s^-1和718．53J·g^-1。在氩气环境中，添加固体推进剂常用的氧化剂，包括AP、HMX、RDX、CL-20等，对Al／H₂O推进剂的燃烧未见明显改进作用，反而提高了点火阈值，使燃速和能量特性下降，文中提出了“竞争反应机制”的观点，即在严格的氩气环境里，氧化剂和Al存在着对于点火药产生的热量的竞争，需要能量特性更优秀的氧化剂作为添加剂。（9）应用同步辐射光电离分子束质谱研究了贫燃平面预混MMA／O₂／Ar在低压（2．67kPa）氩气环境中的燃烧，检测并确认了约42种中间体和自由基，并给出了大部分物质的摩尔分数分布曲线，提出了可能的反应机理。C₃H₂O被首次发现在整个燃烧中起到关键作用，它参与生成了许多中间体和产物。（10）通过一系列实验研究，提出了单一氩气条件下较好的Al／H₂O基推进剂配方以适应不同的需求，配方一：nano—Al+1wt％PAM水溶液+5wt％B／Co+少量MMA（<5wt％），体现出高能、低压强指数、较高燃速、燃烧稳定、突出的铝燃烧效率的特性；配方二：nano—Al+3wt％PAM水溶液+5wt％B／Co+MMA（>5wt％），具有高能、高压强指数、高燃速、较高的铝燃烧效率的特性，其中m_Al：m_H2O=1:1。更多还原

【Abstract】 Combustion is a main path for energy utilization. Nowadays, along with the boom of economy, the demands for energy is becoming increasingly intensifying, which lead to the requirements for the specific characteristics of different fuels, including the combustion stability, insensitivity, mechanical property, energy density, burning rate, characteristic signals, exhaust pollutions etc., aiming at adapting various applications. Propellant is a kind of fuels composed of energetic materials, and applies to provide the aerospace crafts with propulsion energy. The previous researches were once used to focusing on making propellants exhibit high-energy performances, and there is a great deal of relevant references. Whereas, together with the rapid development of aerospace technology, some new needs has arisen besides the demands for high specific impulse, for example, the increasingly developed micro-propulsion systems that are used to fulfill the requirements of maintaining the formate and tracking for spacecrafts, the abutting joint between space shuttle and space station, the orbit transfer of satellites, and so forth. These demands ask for the development of propellants with high combustion stability, outstanding controllability and low burning rate, as well as low sensitivity and less pollution. Motivated by these issues, I have chosen two new type fuel systems, and studied their thermal decomposition and combustion mechanisms in this dissertation.The dissertation can be logically divided into two parts. Part I focuses on the experimental and theoretical studies of thermal decomposition and combustion of high-energy solid GAP/B based propellant. Both the advantages and disadvantages of B used as a propellant component are discussed, and some coating processing methods are proposed for improving ignition and combustion performances of B. Thermal decomposition investigation of GAP was carried out in detail. The nitrogen elimination reaction has been attracting great research interests due to its high energy release in short time. Thus, the nitrogen elimination for one monomer have been explored with B3LYP/6-31G（d）//G2 method, and the reaction channels were identified, and the relative energies of reactant, product and intermediates were presented simultaneously. As to the combustion study of GAP, the free-energy minimization method was introduced to calculate the combustion temperature and mole fractions of final products under normal pressure adiabatic condition. Several exploratory boron-contained propellants were prepared, and some important parameters were tested and analyzed. PartⅡpays much attention to experimental investigations of Al/H₂O based fuel. Al powders with three particle sizes were put to use in ignition tests under different pressures to determine the suitable fuel component Al. The flash pyrolysis of the key addition agent polyacrylamide in argon were carried out at 300℃, 450℃, 600℃, respectively, and the formation mechanism for liquid and gas products, as well as the effects on improving the characteristics of Al/H₂O propellant were discussed. Moreover, the influences of some other addition agents, including amorphous state nano-B/Co alloy, HMX, RDX, AP, CL-20, etc., were studied, and some basic parameters were preliminarily obtained. Otherwise, the new concept of micro-propulsion system was described in some extent, and a kind of ideal fuel material, Methylmethacrylate （MMA）, for this application was presented. Also, it was supposed to work as the combustion stabilizer and improver for Al/H₂O based propellant. Then, the laminar premixed lean combustion of MMA was carried out by tunable synchrotron radiation VUV photoionization molecular beam mass spectrometry. The species in the flame were identified by their PIE spectra, and displayed the relevant mole fraction profiles together. What is noteworthy is that the more vivid understanding of thermal decomposition of GAP was newly formed, and the combustion mechanism of MMA was comprehensively studied for the first time, which would definitely provide some valuable information for mathematical and physical modeling. The optimal composition of Al/H₂O propellant in Ar environment was proposed. This demonstrates that the dissertation has certain originalities.The findings obtained from the above researches are summarized as following.（I） Recent research progresses on GAP/B and Al/H₂O based fuels, including some basic properties, the combustion behaviors, the improvement methods for fuels’ characteristics, and so forth, were reviewed.（Ⅱ） An analytical method was employed to accurately measure the B wt% and B₂O₃ wt%, and other impurities were quantitatively measured by AAS and ICP. Two chemical coating methods, i.e., recrystallization and neutralization deposit, were proposed to treat B powders, aiming at improving its ignition and combustion characteristics. AP and LiF were used as the coating materials. The coating effects were analyzed by DSC and ignition testing, and more comparisons about the practicability underwent when coated B acted as the propellant component. The results showed that the double-layer coating methods exhibited the outstanding ignition and combustion performances. （Ⅲ） Laser light scattering method was introduced to proceed the in-situ characterization of the polymer properties of GAP. The results show the number average molecular weight and the mass average molecular weight are 3981 and 5497, respectively, thus the diversity is 1.38.（Ⅳ） Thermal decomposition of uncured GAP and GAP coated Boron (B^GAP) under normal pressure in air or N₂ was investigated by TG/DTG and in-situ FTIR combined with pyrolyzer, and some kinetic parameters for the first weight loss process were calculated by Kissinger method. The results showed that B^GAP exhibited different decomposition behaviors from pure GAP, including much lower initial temperature and different reaction pathways demonstrated by the formation of some special groups. The activation energies for the first decomposition step of both pure GAP and B^GAP in air were respectively smaller than that in N₂. Moreover, the activation energy of B^GAPwas smaller than that of pure GAP. These indicated that the existence of Boron did induce the reaction mechanism variate to some easy-proceeding path. The reaction pathway for the nitrogen elimination step was studied by the Gaussian 03 method, B3LYP/6-31G（d）//G2; the structures and the energies of reactants, transition state, intermediates and products were calculated. Thermal decomposition of GAP under low pressure in Ar was studied by tunable synchrotron radiation VUV photoionization reflectron time-of-flight mass spectrometry combined with molecular beam sampling technology. The thermal decomposition of GAP was found to begin at about 70℃,and the products are basically with low molecular weight. The production amount of ammonia is small at low temperature thermal decomposition stage, but increases a lot at the high temperature. Many intermediates and free radicals have been identified with the measurements of photoionization mass spectrum and the PIE spectra by scanning photon energies. Azide radical has been detected. The possible ionization energies of some thermal decomposition species, such as vinyloxy radical, acetyl cyanide, 3-azide propylene et al., were given.（V） Combustion of GAP under normal pressure adiabatic condition was theoretically investigated by free-energy minimization method, and the combustion temperature was calculated to be 1475 K, and the mole fractions of the products are: 0.2238 N₂+ 0.2842 C + 0.1402 CO + 0.1200 CO₂ + 0.0219 CH₄ + 0.3220 H₂+ 0.0067 H₂O.（Ⅵ） A series of high Boron content propellants contained various Boron powders （coated & uncoated） and binders （GAP & HTPB） were prepared, and the basic characteristics were measured in a laboratory-scale combustion chamber installation with two parallel glass windows by several experimental approaches. The results show that B^GAP （1:0.3） has the obvious advantages for being used as the incendiary agent of propellants.（Ⅶ） A variety of experimental methods were employed to detailed study Al/H₂O based fuels. Firstly, the average particle size of Al powders used was confirmed to within nanometer scale, which would be ignited under relative temperate conditions. Then, flash pyrolysis investigation of polyacrylamide （PAM） solution was carried out in an off-line furnace-type pyrolyzer at 300℃, 450℃and 600℃with Ar as the carrier gas, and many flammable compounds were identified by GC/MS in liquid products, especially some cyclic nitrogenous substances, i.e., 1,2,4-Triazine-3,5（2H,4H）-dione, 5-Nitro furfural semicarbazone, Hexadecanamide etc., were considered to release much energy under combustion condition. There were just a few gas products formed at 600℃, which were all flammable small molecules and believed to favor the combustion of the propellants. The FTIR results showed that the contents of tar and char compounds in residues increase as the temperature increasing. The addition of PAM evidently improved the burning rate and energy release of propellants, as well as decreased the pressure exponent -60%.（Ⅷ） Amorphous state nano-B/Co alloy was prepared. Both XRD and SEM tests were carried out to determine the average particle size to be -21 nm. It was then used as an addition agent for basic Al/H₂O based propellant, and some regular parameters were measured. The results showed it had an obvious promotion effects compared to the blank recipe, for example, the burning rate and the detonation heat in 1 MPa Ar were increased by 4.52 mm·s^-1 and 718.53 J·g^-1, respectively. However, adding the oxidizers widely used in solid propellants, such as AP, HMX, RDX, CL-20 etc., into Al/H₂O propellants increased the ignition threshold, and unexpectedly leaded to the degradation of combustion performances. A competition reaction mechanism was preliminarily proposed to explain the phenomena. It could be conjectured that under-water propulsion engine should be equipped an additional oxygen-containing accessory in order to make the most of the advantages of these oxidizers.（Ⅸ） A fuel-lean laminar premixed methylmethacrylate/oxygen/argon flame at 2.67 kPa with an equivalence ratio （（?）） of 0.75 has been investigated with the tunable synchrotron vacuum ultraviolet （VUV） photoionization and molecular beam sampling mass spectrometry techniques. Isomers of most observed species in the flame have been identified by measurements of photoionization mass spectra and the near-threshold photoionization efficiency spectra. Mole fraction profiles for about 42 flame species are displayed. Combined with the mole fraction profiles, the formation mechanisms of the free radicals, oxygenated compounds and other molecular intermediates are proposed. C₃H₂O was found to be the key radical in the whole combustion process for the first time.（Ⅹ） Finally, based on the variety of experimental results, the optimal recipes of Al/H₂O based propellants under Ar were proposed for adaptting to different demands, which were （a） nano-Al+1 wt% PAM solution+5 wt% B/Co+ MMA （<5 wt%）; （b） nano-Al+3 wt% PAM solution+5 wt% B/Co+ MMA （>5 wt%）, and m_Al:m_H2O=1:1. （a） would be with high energy release, low pressure exponent, relative high burning rate, outstanding combustion stability and excellent combustion efficiency for Al. （b） would possess the characteristics of high energy release, high pressure exponent, more higher burning rate, and good combustion efficiency for Al.更多还原