【作者】 刘冠鹏；

【导师】 李凤生；

【作者基本信息】 南京理工大学 ， 材料科学与工程， 2008， 博士

【摘要】 高速鱼雷是一种新概念武器,其依靠金属与水之间的反应提供能源（动力）,具有高能、高速、巡航能力强等优点,是近年来重点发展的水下武器系统。为保证金属/水反应推进剂的能量性能,其配方中固体金属粉含量往往较高,相继带来点火困难、燃烧不充分、贮存性能差等棘手的问题,无法满足推进剂的基本性能要求,因此对该推进剂中金属燃料进行相应的改性处理是解决上述困难的根本途径。本文选取高热值的Al、Mg金属粉作为金属/水反应推进剂的主要燃料,以表面包覆及机械合金化为主要改性手段,在一定程度上解决了金属/水推进剂点火和燃烧困难等问题;此外对金属/水反应推进剂的能量性能进行了全面评估,同时详细讨论了改性后金属/水推进剂的反应机制,为该类推进剂的研究提供了详细的试验数据和坚实的理论基础。首先,为了提高Mg粉的水反应活性及其贮存性能,对Mg粉分别进行了两次包覆改性处理,得到了具有核—壳—膜结构的复合金属燃料粉。在一次处理中将常温稳定、水环境中易水解出强酸性物质的材料致密地包覆于微米Mg粒子的表面作为复合粉体的壳,显著提高了Mg粉的水反应活性;为进一步提高该壳—核材料的稳定性和贮存性能,采用不同高聚物对复合粒子进行了二次包覆改性处理。与原料Mg粉比较,所制备的复合金属粉与水反应生成H₂的速率在低温阶段降低,甚至不反应,但高温阶段显著提高,整个反应过程中产生H₂的总量较原料Mg粉提高2.7倍。其次,为了提高金属/水反应推进剂的能量性能,并同时改善其点火和燃烧性能,采用机械法进行改性处理,制备出具有较多晶体缺陷的高反应活性片状Al粉及Al/Mg合金粉。热分析结果表明,片状Al粉和Al/Mg合金粉的氧化增重分别达到44.5%和60%,较球形Al粉的23.3%有显著提高,说明机械改性处理可在很大程度上提高金属粉的氧化反应效率。第三,将金属粉及其它组分制成金属/水反应推进剂样品,研究了包覆处理以及添加新型氧化剂和纳米催化剂对推进剂热分解的影响。结果表明,当推进剂中Mg粉经HTPB、双基药二次包覆处理后,推进剂样品的放热峰峰温分别约提前了16℃和10℃。而片状Al和Al/Mg（含Mg20%）合金粉代替球形Al粉后,推进剂分解峰峰温分别提前了约26℃和36℃;采用新型氧化剂（ADN）部分取代高氯酸铵（AP）以及添加纳米催化剂也可以使金属/水反应推进剂分解峰峰温提前,这有助于改善金属/水反应推进剂的一次燃烧。第四,分析研究了金属/水反应推进剂的能量性能以及燃烧产物。结果表明推进剂的一次燃烧温度随配方中氧化剂——AP含量的增加而增加,7MPa下含Mg推进剂的一次燃烧温度在1600K～2600K之间,高温可使Mg气化;含Al推进剂一次燃烧温度在2000K～2500K之间,一次燃烧产物中Al主要以凝聚态形式存在。增加推进剂配方中的金属粉含量、增大水与推进剂的质量比（水燃比W/F）均可有效增加推进剂的比冲。W/F过小会造成金属燃烧不充分,而过大的W/F会生成金属的氢氧化物,并造成燃烧温度降低。经实验和理论分析得到金属/水反应推进剂的优化配方为:Mg/AP/HTPB≈55/30/15,W/F≈3,此时推进剂的比冲约为3994N·s·kg^-1,二次燃烧温度为683K;Al/AP/HTPB≈55/30/15,W/F≈3.5,此时推进剂的比冲高达4547N·s·kg^-1,二次燃烧温度为684K,在这些条件下系统的燃烧温度均大于600K,可以保证推进剂在水下工作时喷出的H₂O为气态。第五,对Mg（Al）金属粉与水的反应机理进行了研究。分析认为,新型包覆剂（Tec）主要通过改变反应体系中的pH值来加速低温下金属粉与水的反应速率。高温下Mg（Al）与水反应的燃烧时间主要受水蒸汽的浓度和金属粉的粒径控制。选择合适的W/F、选用适当粒径的金属粉作为燃料,并对金属粉进行改性处理,可以改善金属粉在水蒸气中的燃烧。更多还原

【Abstract】 The ultrahigh speed torpedo is a new concept in underwater weaponry and it is currently an active area of research. These types of weapons utilize high energy density reaction between metal and water to provide them with superior speed and increased range. However, the high metal content adversely affects the ignition and combustion characteristics of the propellant which are the most important properties of the propellant. This work focuses on the modification of aluminium and magnesium powders and their application in metal/water propellants.As a first step in this research, magnesium pellets were modified using vapour and liquid deposition and the technics to improve the reactivity of magnesium with water, as well as the shelf life. The structure of the modified magnesium powder was characterized utilizing scanning electron microscope. It was found that the modified magnesium power had three distinct layers. The modification led to improvement in the control of the magnesium and water reactions under certain conditions. The modified magnesium pellets had little effect on the energy density of the reaction but increased the hydrogen generating ability by 2.7 times.The second objective of this project is to improve the ignition and combustion properties of the propellant by incorporating aluminium powder. Aluminium flakes, as well as aluminium/magnesium alloy with variable proportions of magnesium were obtained from spherical aluminium powder using a new type of mill. The modification of these metal powders decreased the ignition temperature of the propellant and improved the oxidation performance. The analysis of the various powders using DSC-TG showed that the weight of the spherical aluminium powder was increased by 23.3% due to the oxidation. Under same oxidation conditions the weight of superfine aluminium flakes and Al/Mg alloy was increased by 44.5% and 60%, respectively.The third outcome of this project was that the modification of the metal powder can affect the thermal decomposition temperature of the propellants. Based on the DSC-TG analysis results, the modification of magnesium by the addition of HTPB and double-base propellant decreased the thermal decomposition temperature by 16℃and 10℃, respectively. Similarly, by modifying spherical aluminium to superfine aluminium flakes and aluminium/magnesium alloy （contains 20% magnesium by weight）, the thermal decomposition temperature decreased by 26℃and 37℃, respectively. This resulted in more favourable ignition and improved the decomposition characteristics of the propellants. Other experimental results indicated that the addition of the oxidizer ADN and a catalyst deceased the thermal decomposition temperature.The combustion energy and products of the Al/H₂O and Mg/H₂O propellants were systematically calculated and analysed. Results showed that the temperature of the first stage of combustion enhanced with increasing AP content. Under 7MPa the combustion temperature of Mg/H₂O propellant was between 1600K and 2600K, which resulted in the vaporization of the magnesium; while for Al/H₂O propellant, the combustion temperature was between 2000K and 2500K, the aluminium existed in the combustion products mainly as the condensed phase. The specific impulse （Isp） can be improved by increasing the proportions of the metal powder in the propellants, or the ratio between water and propellant （W/F）. However, if the W/F value is too low, it will result in the incomplete combustion of the metal. Very high W/F ratios result in the formation of metal hydroxide and lower combustion temperatures. The optimized formulas for two propellants were determined to be: Mg/AP/HTPB≈55/30/15, W/F≈3, Isp≈3994N·s·kg^-1 with the second stage combustion temperature of 683K; Al/AP/HTPB≈55/30/15, W/F≈3.5, Isp≈4547N·s·kg^-1 with the second stage combustion temperature of 684K. The second stage combustion temperatures above 600K ensured that the water produced by the propellant was completely vaporized.The mechanism of Al/Mg and water reaction was explored as part of this project. The results suggested that additive Tec accelerated the reaction under lower temperature mainly by changing the pH of the reaction systems. The water vapour concentration and the metallic powder size are the dominant factors that affect the high temperature combustion reaction time. Under certain conditions, the combustion reaction can be controlled and the propellants combustion characteristics can be improved by the modification of the metal powders.更多还原