發(fā)布時間：2018-03-10 08:45

  本文選題：Mg基儲氫材料　切入點：釋氫性能　出處：《湘潭大學》2015年碩士論文　論文類型：學位論文

【摘要】：Mg元素因其具有儲氫量大(7.6wt%)、資源豐富、成本低等優(yōu)點而被譽為是最具發(fā)展前景的金屬儲氫材料之一。而Mg基儲氫材料要實現(xiàn)廣泛應用,則必須很好地解決由氫在Mg表面難解離、難脫附所導致的吸、釋氫速率緩慢的動力學問題和由其本身結(jié)構(gòu)穩(wěn)定性偏高所導致釋氫溫度偏高的熱力學問題。目前,人們通過納米結(jié)構(gòu)調(diào)制、添加催化劑等方式已基本解決Mg基儲氫材料吸、釋氫速率緩慢的動力學問題,而釋氫溫度偏高的熱力學問題仍是Mg基儲氫材料走向?qū)嶋H應用所面臨的難題。本論文以Mg基氫化物(MgH2)為研究對象,通過實驗與理論計算相結(jié)合的方式,逐層深入研究了過渡金屬與碳材料單獨、復合摻雜對MgH2釋氫性能的影響規(guī)律,著重分析了其摻雜改性機理。具體研究所得結(jié)論如下:(1)采用機械球磨的方法將過渡金屬(Ti或Ni)單獨摻雜以及復合摻雜于MgH2粉末中,結(jié)合理論計算研究表明:當Ni、Ti單獨摻雜時,不僅能夠改善MgH2體系的吸、釋氫動力學性能,而且通過固溶的方式致使MgH2的晶格變形、結(jié)構(gòu)穩(wěn)定性降低,進而使體系初始釋氫溫度大幅度降低,其中,Ni的摻雜效果尤為明顯,相對于純MgH2降低了近136℃;而當Ni、Ti復合摻雜時,由于NiTi新相的生成使得體系合金表面張力增加,從而使體系顆粒細化效果較單獨摻雜時并未提高,但復合摻雜體系的初始釋氫溫度較單獨摻雜時卻進一步降低,體系的初始釋氫溫度較純MgH2降低了近161℃。(2)為緩解過渡金屬摻雜致使MgH2體系儲氫容量下降的問題,首先選擇了本身具有物理儲氫特性的碳材料(如Graphite、Graphene)作為摻雜物,研究了碳材料摻雜對MgH2釋氫性能的影響及機理,研究表明:Graphite與Graphene摻雜,均對MgH2顆粒起到結(jié)構(gòu)限域作用,使其顆粒細化且尺寸均勻,進而使MgH2體系初始釋氫溫度降低,其中Graphene的摻雜效果優(yōu)于Graphite,相對于純MgH2降低了近33℃;其摻雜機理在于碳材料的結(jié)構(gòu)限域作用,削弱了MgH2中的Mg-H鍵,從而使其釋氫溫度降低。(3)基于(1)、(2)研究結(jié)果,選取摻雜效果優(yōu)異的Ni與Graphene作為摻雜物,進一步研究了過渡金屬與碳材料復合摻雜對MgH2釋氫性能的影響及機理,研究表明:由于Graphene對MgH2顆粒的包覆緩沖作用,其摻雜順序?qū)gH2體系釋氫性能具有顯著影響,即當Graphene與Ni同時摻雜時,體系初始釋氫溫度并未降低;而先摻雜Ni球磨4h、后摻雜Graphene球磨2h時,則使得MgH2體系的初始釋氫溫度較單獨摻雜體系進一步降低,相對于純MgH2體系而言,其初始釋氫溫度降低了近175℃,很好地實現(xiàn)了過渡金屬與碳材料的協(xié)同摻雜效應。
[Abstract]:Mg element is regarded as one of the most promising metal hydrogen storage materials for its advantages of large hydrogen storage capacity, high hydrogen storage capacity, rich resources and low cost. However, if mg based hydrogen storage materials are to be widely used, it must be well resolved that hydrogen is difficult to dissociate from mg surface. The kinetics of the slow rate of hydrogen release and the thermodynamics of the high temperature of hydrogen release caused by the high stability of its own structure. At present, it is modulated by nanostructures. The kinetics of Mg-based hydrogen storage materials has been basically solved by adding catalysts, such as the slow rate of hydrogen release. However, the high temperature of hydrogen release is still a difficult problem in the practical application of Mg-based hydrogen storage materials. In this paper, the Mg-based hydride (MgH2) is taken as the research object, and the experimental results are combined with the theoretical calculation. The effects of transition metals and carbon materials on the hydrogen release properties of MgH2 were studied layer by layer. The mechanism of doping modification was emphatically analyzed. The conclusions are as follows: (1) the transition metal Ti or Ni) is doped by mechanical ball milling alone or by composite doping into MgH2 powder. The theoretical calculation results show that: when Niti is doped alone, It can not only improve the adsorption and hydrogen release kinetics of MgH2 system, but also deform the lattice of MgH2 by solid solution, decrease the stability of the structure, and decrease the initial hydrogen release temperature of the system, especially the doping effect of Ni. Compared with pure MgH2, the surface tension of the alloy is increased due to the formation of the new phase of NiTi, and the grain refinement effect of the system is not improved compared with that of the single doping, and the surface tension of the alloy is increased due to the formation of the new phase in the Niti Ti composite doping. However, the initial hydrogen release temperature of the composite doping system is further lower than that of the single doping system, and the initial hydrogen release temperature of the complex doping system is nearly 161 鈩，

本文編號：1592598