【作者】 张明；

【导师】 柳东明；

【作者基本信息】 安徽工业大学 ， 材料科学与工程， 2018， 硕士

【摘要】 铝粉具有相对较高的体积燃烧焓和能量密度,其作为金属燃烧剂被广泛应用于推进剂等领域,通过制备铝基二元合金可以大幅改善铝粉的燃烧性能。而氢是一种高能量密度的绿色新能源,将氢以氢化物形式引入铝基合金燃烧剂后,燃烧过程中氢气的释放可以促进氧化剂的燃烧从而放出大量热量,对改善燃烧剂的点火和燃烧性能十分有利。为此,本文将氢引入Al₂Mg合金,采用热分析（TG-DSC）、X射线衍射分析（XRD）、扫描电子显微分析（SEM）和能谱分析（EDS）手段,研究了Al₂Mg合金氢化物及其球磨产物的燃烧性能和燃烧机理,并将制得的氢化物与氧化剂混合制得铝热剂,以改善其燃烧性能并研究燃烧机理。将Al₂Mg合金氢化后,颗粒细化且疏松多孔。Al₂Mg合金氢化物在第一阶段燃烧过程中存在高温放氢过程,生成新鲜Mg相和大量晶体缺陷,且Mg蒸汽的存在促进了氧分子分解,使其着火点比Al₂Mg合金（未氢化）降低了150℃左右。由于Al₂Mg合金氢化物在第一阶段燃烧后晶粒粒径较合金更小且晶体缺陷更多,使得氢化物在第二阶段燃烧过程中的每一小步氧化较Al₂Mg合金都更易发生。由于两者第一阶段燃烧后相分布和缺陷程度不同,第二阶段燃烧中合金氢化物比合金燃烧放热更集中并剧烈,且更不易生成AlN,从而更贴近实际应用。对Al₂Mg合金氢化物进行球磨处理,颗粒细化和平滑程度与球磨时间基本成正比。Al₂Mg合金氢化物球磨2、5、10 h产物（分别表示为Al₂Mg-H（bm2）、Al₂Mg-H（bm5）和Al₂Mg-H（bm10））的着火点均比合金氢化物（未球磨）降低了50℃左右,其中Al₂Mg-H（bm5）反应活性最好。随着球磨时间延长,颗粒比表面积增大,引入的晶体缺陷增多,Al₂Mg-H（bm10）的第二阶段氧化反应起始点和最终氧化完全温度最低,但表面低的MgO覆盖度使其更易发生团聚,对实际应用产生不利影响。将制得的Al₂Mg合金氢化物与超细化KMnO₄进行混合。从燃烧现象来看,Al₂Mg/KMnO₄和Al₂Mg-H（bm10）/KMnO₄铝热剂的燃烧性能比Al₂Mg-H/KMn O₄和Al₂Mg-H（bm2）/KMnO₄好;从反应活性来看,Al₂Mg-H（bm10）/KMnO₄>Al₂Mg-H/KMnO₄>Al₂Mg/KMnO₄铝热剂;从固-固相反应完全度和放热量来看,Al₂Mg-H（bm10）/KMnO₄>Al₂Mg/KMnO₄>Al₂Mg-H/KMnO₄铝热剂。由于粒径和颗粒表面形貌对金属与氧化剂混合均匀程度和接触面积有很大影响,从而对着火点、反应完成度、放热量、反应速率带来影响,综合发现,Al₂Mg-H（bm10）/KMnO₄铝热剂燃烧性能最佳。该含氢铝热剂的燃烧过程与未含氢铝热剂不同,首先MgH₂、Al与K₂Mn₄O₈（KMnO₄的分解产物）反应生成Al（OH）₃和MgO,然后K₂Mn₄O₈、MgO与Al（OH）₃反应生成MgAl₂O₄、K_xMnO₂,最后K_xMnO₂与Al反应还原出Mn原子。更多还原

【Abstract】 Aluminum powder has a high volumetric combustion enthalpy and energy density,thus can be widely used as a metal combustion agent for propeller.The combustion performance of aluminum powder can be improved by preparation of binary alloy.Hydrogen is a new green energy carrier.The introduce of hydrogen into Al-based alloy combustion agent via hydride can promote the combustion of oxidant and the release of heat,which is helpful to enhance the ignition and combustion performance.In this dissertation,hydrogen was introduced into Al₂Mg alloy,and the combustion performance and mechanism of Al₂Mg alloy hydride and its ball-milled products were studied by means of thermal analysis（TG-DSC）,X-ray diffraction（XRD）,scanning electron microscopy（SEM）and energy dispersive spectrum analysis（EDS）.Moreover,the Al₂Mg alloy hydride was applied to prepare the thermite by mixing with oxidant to improve the combustion performance.After hydrogenation of Al₂Mg alloy,the particles was refined and porous.In the first combustion stage of the Al₂Mg alloy hydride,there was a high-temperature dehydrogenation process,which generated fresh Mg phase and a large amount of crystal defects.The existence of Mg steam also promoted the decomposition of oxygen molecules.As a result,the ignition point was lowered as much as about 150°C in comparison with the Al₂Mg alloy（not hydrogenated）.Because the Al₂Mg alloy hydride had a smaller grain size and more crystal defect after the first-stage combustion,its every sub-step of combustion was easier to occur in the second combustion stage as compared to the Al₂Mg alloy.Moreover,due to the difference in the phase distribution and defect degree after the first-stage combustion,combustion and heat release of the alloy hydride was more concentrate and violent in the second combustion stage,and it was more difficult to generate AlN phase,which was beneficial to the practical application.When the Al₂Mg Alloy hydride was subjected to ball milling,the particle size became small and smooth and the degree of them was proportional to the milling time.The ignition points of 2 h,5 h and 10 h ball-milled products（denoted as Al₂Mg-H（bm2）,Al₂Mg-H（bm5）and Al₂Mg-H（bm10）,respectively）were all decreased about 50°C with respect to the sample without ball milling,and the Al₂Mg-H（bm5）sample had the best reaction activity.With the increase of ball milling time,the specific surface werea of particles and the crystal defects introduced were increased.The Al₂Mg-H（bm10）sample had the lowest onset and final oxidation temperature for the second-stage oxidation reaction.However the lower MgO coverage degree on the surface made it easier to be agglomerated,which was harmful to the practical application.The Al₂Mg alloy hydride was mixed with ultrafine KMnO₄.It was found that the Al₂Mg/KMnO₄ and Al₂Mg-H（bm10）/KMnO₄ thermites had a better combustion performance than that of the Al₂Mg-H/KMnO₄ and Al₂Mg-H（bm2）/KMnO₄ thermites from the point of view of combustion phenomenon.The combustion performance was Al₂Mg-H（bm10）/KMnO₄>Al₂Mg-H/KMnO₄>Al₂Mg/KMnO₄ from the reaction activity.And the combustion performance was Al₂Mg-H（bm10）/KMnO₄>Al₂Mg/KMnO₄>Al₂Mg-H/KMnO₄ from the degree of solid-solid reaction and heat release.The particle size and surface morphology had a great influence on the mixing uniformity of metal and oxidant as well as the contact area,thus having affects on the ignition point,reaction degree,heat release and reaction rate.Based on the above analysis,Al₂Mg-H（bm10）/KMnO₄ thermite exhibits the best comprehensive combustion performance.The combustion process of the hydrogen-containing thermite was different from that without hydrogen.Firstly,MgH₂ and Al reacted with K₂Mn₄O₈（decomposition products of KMnO₄）to generate Al（OH）₃ and MgO.Then,K₂Mn₄O₈,MgO and Al（OH）₃ reacted to form MgAl₂O₄ and K_xMnO₂.Finally,K_xMnO₂ and Al reacted to form Mn.更多还原