【作者】 王昆；

【导师】 张建国；

【作者基本信息】 北京理工大学 ， 兵器科学与技术， 2015， 博士

【摘要】 世界各国当前都在面临极其严峻的环境问题,尤其是我国近几年突显的城市雾霾问题,更是需要新型的清洁能源来替换传统的化石燃料以实现节能减排。氢能作为一种清洁能源一直引起广泛的关注,然而其安全储存一直是人类面临的难题。近年来,基于金属硼氨储氢化合物的固态储氢材料具有广阔的潜在应用价值,已日益成为新能源领域的研究热点之一。本论文以金属氨硼烷为主要目标化合物,以理论计算为主要研究手段,结合已有的实验数据,系统研究了一元金属氨硼烷、二元金属氨硼烷、以及金属氨硼烷衍生物——金属硼氨络合物的电子结构、热分解机理、热力学和动力学性质,为寻求新型储氢材料提供基础数据和理论依据。同时,积极探索该类化合物在含能材料领域的应用。主要在以下方面开展了相关研究:1)金属氨硼烷的电子结构和释氢机理由于单金属氨硼烷(MNH2BH3,MAB)具有良好的储氢性质,因此有望成为未来理想储氢材料的重要候选物。首先,通过Monte-Carlo方法预测了未获得单晶结构的MAB化合物的周期性结构。其次,通过第一性原理详细探究了轻金属Li、Na、K、Mg、Al和Ca为取代金属的金属氨硼烷固态体系的电子结构,设计并计算了其分解过程中相关释氢和释氨过程以及反应热力学函数变化。最后,通过气相分子动力学和传统过渡态理论研究了其释氢键的形成机理(N-Hδ+···-δH-B)、反应势能面和释氢速率常数。由于二元金属氨硼烷化合物(MM’AB)中多金属离子间的相互作用,使得其比相应的一元金属化合物有更好的储氢性能和释氢表现。首先在试验合成SMAB的基础上,结合Monte-Carlo方法预测了SMAB的周期性结构并对其进行了优化。计算了4种MM’AB的相关结构与电子能态、声子谱及热力学性质。其次,详细的讨论了分子中两种H原子的解离过程,设计并研究了分解反应中涉及的释氢和释氨过程及其反应焓、反应Gibbs自由能。第三,通过使用NVT系综,结合BOMD动力学方法计算了300 K下4种化合物中两种不同氢原子的扩散均方根速率。最后,对Na2Mg(NH2BH3)4和Na[Li(NH2BH3)2]的单分子结构,设计了不同的释氢反应路径,研究得到了反应最小势能面以及温度-速率方程。2)金属硼氨络合物的电子结构和释氢机理金属硼氨络合物(缩写为AMB)相对于MAB具备更高的储氢含量,且通过NH3上的Hδ+与[BH4]δ+中的Hδ-之间形成释氢键释氢时,反应能垒更低。通过研究Li2Al(BH4)5(NH3)6(AALB)、LiMg(BH4)3(NH3)2(AMLB)和LiCa(BH4)3(NH3)2(ACLB)共3种含LiBH4结构的金属硼氨络合物的结构、初始释氢机理和反应热力学性质,并与[Li(BH4)(NH3)]2(ALLB)相关性质进行了对比。AMB由于中心金属离子的不同,会表现出完全相反的分解机理和释氢性能。通过采用Car-Parrinello分子动力学方法对两种结构类似、分解过程截然不同的两种金属硼氨络合物Mg(BH4)2(NH3)2和Li BH4NH3的分解机理的研究,发现了不同类型的金属硼氨络合物的分解过程以及其所分解所涉及的过渡态与中间体。3)硼氨化合物对含能材料的催化性能探索研究了典型的硼氨类储氢化合物对硝基高能化合物的热分解过程的影响。选取了AB和LAB两种储氢材料分别与CL20、RDX和PETN共3种不同类型的硝基高能化合物,通过不同比例混合,得到一系列LAB/AB和CL20/RDX/PETN来探讨硼氨类储氢化合物对传统硝胺或硝酸酯类猛炸药热分解过程中的催化性能。并通过对不同混合体系建立模型,使用传统分子动力学方法计算了不同组分之间的相互作用能以及相容性,通过静态力学方法分析其相应的力学性能,从理论上探讨了复杂体系的组分、结构和性能的关系。更多还原

【Abstract】 It’s a quite serious statement that all the world has to face the environment suffering even further. Especially the city haze in many Chinese cities which is calling for a new clean energetic resource to substitute the traditional fossil fuel. Hydrogen energy as obviously a typical environment-friendly power attracts more and more attention. But it is always very difficult to find a safe way to store or transmit hydrogen. Recently, scientists synthesis a new solidate hydrogen-storage material based on the backbone of boron-nitrogen-hydrogen, which is a quite potential material in the future application. Here we present a series hydrogen-storage compounds on the basis of metallic amidoborane including mono/bi metallic amidoborane, amine metallic borohydride. All the corresponding results are analyzed in this thesis including geometric structures, electronic structures, decomposition mechanisms, thermodynamic and kinetic properties. All the contents could be a database for the further study of novel hydrogen-storage material. In addition, we also explore the potential application of hydrogen-storage material in energetic field.1) The electronic structure and dehydrogenation mechanism of metallic amidoboraneMonometallic amidoborane is a kind of important optional compound since its high hydrogen content and stable chemical properties especially the light metallic amidoborane. On the basis of the previous study, here we predict the periodic structures without any Single crystal reports by Monte-Carlo method. First principle method has been used to explore the geometric and the electronic structures of MAB(M = Li,Na,K,Mg,Al and Ca). It have been designed and explained their dehydrogenation/deammoniation mechanisms and thermodynamic properties by designing the decomposition process of them. As well, the mechanisms of the formation of the dihydrogen bond(N-Hδ+···-δH-B) with the corresponding potential surfaces and the rate constants have been calculated on the basis of kinetic theory and traditional transition state theory.The interaction among multi-metallic cation lead to a better performance of bimetallic amidoborane than the corresponding monometallic amidoborane. First, we predict the structure of SMAB using Monte-Carlo method and optimize it with castep code. Then the electronic structures, phononic calculation and the analysis of the thermodynamic properties of all the four MM’AB have been summarized. Secondly, by designing different decomposition reactions, the different hydrogen removal energies with the reaction enthalpies and Gibbs energies of dehydrogenation and deammoniation can be obtained. Finally, BOMD method has been used to calculate the mean square desperation to trace the two kinds of hydrogen at the temperature of 300 K. Futhermore, the molecular dehydrogenation mechanisms of Na2Mg(NH2BH3)4 and Na[Li(NH2BH3)2] have been proposed and confirmed.2) The electronic structures and the dehydrogenation mechanism of amine metallic borohydrideAmmine metal borohydrides(AMBs) have recently emerged as an attractive candidates for hydrogen storage materials because their high percentage of available hydrogen. In this thesis, we employed first principle calculations based on density functional theory(DFT) to investigate the periodic structures and their electronic structures, hydrogen desorption, deammoniation and deborane, and their thermodynamics in solid AMM’B with the component of Li(BH4). And also we compare all the properties with [Li(BH4)(NH3)]2(ALLB).AMB will appear reversed properties in the dehydrogenation as the different center metallic cation. As for MM’AB, two different metal play different roles. Here we first give the overall intermediates in the decomposition process of ALB and AMg B by using Car-Parrinello molecular dynamics, which is quite helpful to us to further understand the transition states and the intermediates in the decomposition process of the series compounds.3) The catalysis application of the boron-amine materials in the energetic fieldIt has been discussed that the high hydrogen content and pure product of boro-amine hydrogen-storage material which make it as an important energy resource. We discuss the potential application of boro-amine compounds in the decomposition of Nitamine high-energeticcompounds. We have chose two typical amidoborane(AB and LAB) to represent the boro-amine compounds and CL20, RDX and PETN to represent oxidized explosive. In the experiment, we discussed the catalyst effect by mixing two different components with different ratios. Theoretically, Molecular mechanic method has been used to build different 2-phrase systems for the research of the compatibility and interaction between the two phrases. Correspondingly, the properties of the mechanical properties of the compliable systems have been calculated and obtained as well as the relationshipIV between the structure and the properties.更多还原