【作者】 余宗学；

【导师】 陆路德；

【作者基本信息】 南京理工大学 ， 化学工程与技术， 2009， 博士

【摘要】 固体推进剂的燃烧性能是装药技术的核心,通过催化剂对推进剂主要组分的热分解性能的影响可以预估其对推进剂燃烧性能的影响。本论文主要有两方面工作,一是纳米过渡金属氧化物的制备、表征及催化AP热分解的应用,为进一步开发催化性能优异的催化剂提供实验和理论基础;二是利用催化剂原位生成技术的机理,研究微米级的过渡金属草酸盐和乙酸盐对AP热分解的催化,为制备AP体系催化剂提供一个新思路。主要研究内容如下:通过微乳液法制备了正交晶系的NdCrO₃和立方晶系的NdCoO₃纳米晶。用XRD,TEM,HRTEM,SEM,EDS,BET等手段对产物进行表征,产物与原料的投入比例一致。利用DSC/TG-MS热分析方法研究了NdCrO₃和NdCoO₃两种催化剂对AP热分解的催化作用。研究表明,在NdCrO₃催化剂的作用下,AP的热分解反应峰值温度下降了87℃,表观分解反应热从655 J·g^-1增加到到1073 J·g^-1;在NdCoO₃催化剂的作用下,AP的热分解反应峰值温度下降了100℃,表观分解反应热从655 J·g^-1增加到到1363 J·g^-1。通过TG-MS研究发现,产生的气态逸出物一步产生,主要分解物质为H₂O（m/z=18）,NH₃（m/z=17）,O₂（m/z=16,32）,HCl（m/z=35,36,37,38）,Cl₂（m/z=70,72,74）,NO（m/z=30）,N₂O（m/z=44）和NO₂（m/z=46）。在NdCrO₃催化剂的作用下,逸出气态产物在336℃左右大量产生,产生的最大离子流强度大幅度升高,峰型尖锐,分解反应在很短的时间内完成;NdCoO₃催化AP的热分解,逸出气态产物在318℃左右大量产生,与NdCrO₃催化AP比较峰型较宽。由于纳米催化剂具有较大的比表面,提供了大量的表面反应活性中心,通过反应活性中心的吸附作用,加速AP的分解和氨的氧化,使反应放热量得到大幅度的增加。在金属氧化物表面吸附氧生成过氧化离子（O₂^-）和氧离子(O^-,O^2-),这是加速AP分解反应的主要原因。由于在活性中心大量吸附氧而生成大量的过氧化离子（O₂^-）和氧离子(O^-,O^2-),它们作为质子接受体可以加速AP的热分解,同时可以简化分解反应的步骤,使热分解反应瞬间完成。通过自蔓延燃烧法制备了ReCrO₃（Re=Y,Sm,Er）等系列钙钛矿型结构的纳米晶。用XRD,TEM,HRTEM,SEM,EDS等手段对产物进行表征,产物与原料的投入比例一致,没有偏析现象。通过热分析法考察了ReCrO₃（Re=Y,Sm,Er）纳米晶对AP热分解的催化作用,结果表明这些纳米氧化物均能不同程度的催化AP。YCrO₃使AP高温分解峰降低68℃,表观放热量增加595J.g^-1;SmCrO₃使AP高温分解峰降低82℃,表观放热量增加551J.g^-1;ErCrO₃使AP高温分解峰降低79℃,表观放热量增加758J.g^-1。通过TG-MS研究发现这类催化剂在达到分解温度时,分解产生的离子流强度峰型尖锐,说明ReCrO₃（Re=Y,Sm,Er）纳米晶均能快速催化分解AP,使反应瞬间完成。通过盐助溶液燃烧法,以硝酸铜、硝酸铬和硝酸钴为原料,尿素为燃烧剂,KCl为反应惰性盐制备尖晶石型纳米钴酸铜和铬酸铜。使用XRD,FT-IR、Raman,TEM等检测手段对于纳米钴酸铜和铬酸铜的结构和形貌进行表征。结果表明,制得的纳米粒子具有较完美的立方晶体结构,分散性较好,粒径较小。利用DTA和DSC研究了纳米钴酸铜和铬酸铜对高氯酸铵热分解的催化性能。结果表明:特有的尖晶石结构使纳米钴酸铜和铬酸铜具有较高的催化活性,催化效果明显优于单一组分的纳米金属氧化物。采用沉淀法制备了Cu、Co、Er、La的草酸盐,通过XRD、Raman、FT-IR、SEM等检测手段对草酸盐粒子的结构和形貌进行表征。采用DSC/TG-MS联用技术研究了草酸钴对高氯酸铵的原位催化。结果表明,草酸钴原位分解生成的钴氧化物对高氯酸铵有较强的催化作用,添加2%的草酸钴使高氯酸铵的分解温度降低104℃,分解放热量从655 J/g增大到1469 J/g。分解的气相产物主要有H₂O,NH₃,O₂,HCl,Cl₂,NO,N₂O和NO₂。由于氧在新生态的纳米钴氧化物表面形成过氧化活性离子（O₂^-）和氧离子(O^-,O^2-),使氨氧化在钴氧化物的过氧化表面活性中心进行,加速了高氯酸铵的热分解,使其表观放热量大幅度增加。草酸铜也能强烈催化AP的热分解,使分解温度降低119℃,分解放热量从655 J/g增大到1560 J/g。研究了过渡金属乙酸盐对AP热分解的影响。研究表明乙酸钴使高氯酸铵的分解温度大幅度降低,分解温度提前119℃,放热量增大985 J/g;乙酸铜对AP的低温分解温度没有影响,使AP的高温分解温度提前69℃,放热量增大919 J/g。乙酸钴和乙酸铜原位催化AP,纳米级的钴氧化物和CuO在催化介质中直接生成,生成的新生态金属氧化物催化活性高,比表面积大,即时参与催化反应,最大程度发挥了纳米催化剂的催化效能。更多还原

【Abstract】 The solid propellant of combustion properties composes the core part in the technology of powders and explosives.According to the thermal decomposition of the predominant components in composite propellants,the behavior of the catalysts can be derived.This dissertation contains two aspects of works.Firstly,a series of nano-sized compound transition metal oxides are prepared and characterized,and their catalytic effects on the thermal decomposition of ammonium perchlorate（AP） are studied.This work affords the experimental and theoretical basis for developing catalysts which have good catalytic performance.Secondly,the catalytic effects of micron-sized transition metal oxalates and acetates on the thermal decomposition of AP via the in situ catalytic mechanism are studied,to afford a new way of preparing the catalysts for the thermal decomposition of AP.Main research contents are shown as follows.Orthorhombic structural perovskite NdCrO₃ nanocrystals and cubic structural perovskite NdCoO₃ were prepared by microemulsion method,and characterized by XRD, TEM,HRTEM,SEM,EDS and BET.The catalytic effects of NdCrO₃ and NdCoO₃ for thermal decomposition of AP were investigated by differential scanning calorimetry（DSC） and thermogravimetry-mass spectrometry（TG-MS）.The results revealed that the NdCrO₃ nanoparticles had effective catalysis on the thermal decomposition of AP.Adding 2%of NdCrO₃ nanoparticles to AP decreased the temperature of thermal decomposition by 87℃and increased the heat of decomposition from 655 J g^-1 to 1073 J g^-1;adding 2%of NdCoO₃ nanoparticles to AP decreased the temperature of thermal decomposition by 100℃and increased the heat of decomposition from 655 J g^-1 to 1363 J g^-1.Gaseous products during thermal decomposition of AP were NH₃（m/z=17）, H₂O（m/z=18）,O₂（m/z=16,32）,HCl（m/z=35,36,37,38）,N₂O（m/z=30）,NO（m/z=44）,NO₂ （m/z=46）and Cl₂（m/z=70,72,74）.With the catalysis of NdCrO₃,the gaseous products were produced at around 336℃.The ion current intensities increased greatly and the curves exhibited shaper shape.The decomposition process was finished in shorter times;with the catalysis of NdCoO₃.the gaseous products were produced at around 318℃and the curves had broader shape comparing to the curves under the catalysis of NdCrO₃ on the thermal decomposition of AP.The oxidation reaction is occurred colliding with ammonia and oxygen adsorbed by NdCrO₃.Besides,the catalytic activity is dependent on the specific surface area of NdCrO₃. Due to the large area and more reaction active centers of NdCrO₃ nanoparticles,it is beneficial for the adsorption of NH₃ and O₂ on the surface of NdCrO₃.The nanocrystalline can produce large numbers of the reaction active center.Nanosized NdCrO₃ should be considered to be the catalyst accelerating both the decomposition of perchloric acid and oxidation of ammonia.The mechanism of catalytic action is based on the presence of superoxide ion（O₂） and oxygenic ion(O^-,O^2-) on the surface of NdCrO₃.The O₂^-,O^- and O^2-.ions formed during decomposition of perchlorates and the surface of the oxides itself are proton traps.Thus they simplify thermal decomposition of AP.When the partial pressure of oxygen is increased,the formation of O₂^- covered sites on NdCrO₃ is increased, and then the presence of oxygen accelerates the thermal decomposition process of AP as well as the oxidation of NH₃.The self-propagating combustion synthesis method was used to synthesis YCrO₃, SmCrO₃ and ErCrO₃ nanocrystals.The products were characterized by XRD,TEM, HERTEM,SEM,EDS and BET.The catalytic effect of YCrO₃,SmCrO₃ and ErCrO₃ for thermal decomposition of AP was investigated by DSC and TG-MS.The results revealed that the ReCrO₃（Re=Y,Sm,Er） nanoparticles had effective catalysis on the thermal decomposition of AP.Adding 2%of YCrO₃ nanoparticles to AP decreased the temperature of thermal decomposition by 68℃and increased the heat of decomposition by 595 J g^-1; adding SmCrO₃ nanoparticles to AP decreased the temperature of thermal decomposition by 82℃and increased the heat of decomposition by 551 J g^-1;adding ErCrO₃ nanoparticles to AP decreased the temperature of thermal decomposition by 79℃and increased the heat of decomposition by 758 J g^-1.With the catalysis of ReCrO₃（Re=Y,Sm, Er）,the ion current intensities increased greatly,the curves exhibited shaper shape at around the decomposition temperatures and the decomposition process was finished in shorter times.Nano-CuCo₂O₄ and nano-CuCr₂O₄ were prepared by salt-assisted solution combustion synthesis.The prepared nano-CuCo₂O₄ and nano-CuCr₂O₄ were characterized by XRD,TEM,FT-IR,Laser Raman Spectroscopy（LRS） and SEM.The results showed that the nanocrystalline of CuCo₂O₄ and CuCr₂O₄ were almost cubic-like,and the sizes were about 50nm and 150nm,respectively,with good dispersion.The catalysis performance of the thermal decomposition of AP by nano-CuCo₂O₄ and nano-CuCr₂O₄ was studied by differential thermal analysis（DTA）.It was found that their catalytic performance on thermal decomposition of AP were superior to a single-component nano-metal oxides,such as CuO,Co₃O₄ and Cr₂O₃,etc.This was probably related to the specific spinel structure of metal oxides.Transition metal and rare earth oxalates were prepared by co-precipitation.The prepared oxalates were characterized by XRD,FT-IR,Raman and SEM.In situ catalytic thermal decomposition of AP was investigated over COC₂O₄.The catalytic activity measurements were carried out by DSC and TG-MS.The results show that the new ecological nano-cobalt oxides exhibit better catalytic performance in thermal decomposition of AP.Adding 2%of COC₂O₄ to AP decreases the decomposition temperature by 104℃and increases the heat of decomposition from 655 J/g to1469 J/g. Products of thermal decomposition of AP are H₂O,NH₃,O₂,HCl,Cl₂,NO,N₂O,and NO₂.The oxidation of adsorbed ammonia by cobalt oxides via the superoxide active centers takes place on the surface of cobalt oxide.The presence of oxygen can accelerate the oxidation of thermal decomposition process of AP,with a clear increase in DSC heat release.Adding 2%of CUC₂O₄ to AP decreases the decomposition temperature by 119℃and increases the heat of decomposition from 655 J/g to 1560 J/g.The influence of metal acetates on the thermal decomposition of AP was studied. Results showed that cobalt acetate decrease the thermal decomposition temperature greatly. The decomposition temperature was decreased by 119℃and the heat was increased by 985J/g;copper acetate has little influence at lower decomposition temperatures during the thermal decomposition of AP.After adding copper acetate,the decomposition temperature was decreased by 69℃and the heat was increased by 919J/g.Cobalt acetate and copper acetate have in-situ catalytic performance on the thermal decomposition of AP.During the decomposition process,the nano-sized cobalt oxides and copper oxides were formed directly among the catalytic mediums media.The new-ecology catalysts had better catalytic effects as well as greater surface area,and took part in the catalytic reaction directly,which full play the catalytic effects of nano-sized catalysts.更多还原