【作者】 王昆鹏；

【导师】 师春生；

【作者基本信息】 天津大学 ， 材料学， 2008， 硕士

【摘要】 随着碳纳米管(CNTs)增强金属基复合材料(MMCs)研究的深入,利用掺杂、涂敷、电镀等方法对CNTs进行改性以改善复合材料界面的研究备受瞩目。在本论文中,采用基于密度泛函理论的第一性原理方法研究了掺杂硼(B)、氮(N)和硼氮(B,N)共掺杂对单壁开口的扶手椅型和锯齿型两种碳纳米管(CNTs)对金属镁(Mg)、铝(Al)的单原子和原子链的吸附的影响,分析了吸附位置、结合能、电子结构。此外把石墨烯片近似的看为大直径CNTs的外壁,模拟了其金属原子吸附和掺杂B(N)的效应。计算结果表明金属Mg原子在CNTs外壁表现为极弱吸附,结合能几乎为零;金属Al与CNTs之间有一定的结合能,但仍属于弱的化学吸附,这对CNTs增强轻金属Mg、Al复合材料不利。掺B、N后,与未掺杂单壁CNTs的金属原子吸附相比,CNTs的电子结构发生改变,其中掺B形成电子缺乏区,掺N形成电子聚集区。吸附体系中在Fermi能级附近的一部分电子由金属Mg,Al的外层电子所提供,金属与有缺陷的CNTs发生了突出的化学结合,掺杂提高了CNTs与金属的分波态密度在价带和导带上轨道杂化重合,尤其是掺B显著提高金属Mg、Al原子及其原子链的结合,掺N对提高金属原子的吸附结合也有一定作用,但在某些情况致使金属的吸附能下降。金属在未掺杂和掺杂石墨烯上的吸附比在相应的小直径CNTs上的吸附更弱。此外,硼氮共掺未能显著提高金属原子在CNTs外壁的吸附。理论计算表明掺杂有望改善CNTs和金属Mg、Al基体的界面结合,对CNTs增强金属基材料的设计有指导作用,但以上模型只是初步研究和解释了金属原子及其原子链与CNTs结合的情况,需要对更真实的界面结合模型进行进一步研究。更多还原

【Abstract】 Researches on carbon nanotubes (CNTs) reinforced metal matrix composites (MMCs) are booming in recent years. The use of doping, coating and electroplating etc. to improve the binding of interfaces has attracted much attention. In this paper, first principles calculations based on density functional theory (DFT) were carried out to evaluate the effect of B (N)-doping on adsorption of a metal (Mg, Al) atom (chain) on armchair and zigzag SWCNTs with opened-cap. The stable positions, the geometric structures and binding energies of metal atoms adsorbed on CNTs were investigated. The adsorption and the doping influences on graphene were also studied to simulate the SWCNT with a large diameter.The adsorption of Mg atom on both two kinds of CNTs is weak, with binding energies nearly zero. Although there is stronger interaction between Al atom and CNTs, it remains a weak physical adsorption, which could not construct an effective interfacial binding in Mg, Al based composites. Compared with undoped CNTs, the B (N)-dopant changes the electronic structures of the CNTs. The B-doping forms electron-rich states, while N-doping induces electron-deficient states. The interaction of Mg (Al) atom adsorbed on pristine SWCNTs which is normally very weak, can be enhanced upon functionalization by A-doped (A=boron, nitrogen) substituting. Especially B-doped increase the binding energy dramatically both in armchair and zigzag SWCNTs. The binding energies of metal atoms in the graphene models are lower than in the CNTs models with small diameter. In addition, codoping of B and N failed to signigicantly improve the adsorption of the Mg (Al) atom on CNTs.The theoretical calculations show that the doping is help to improve the interfacial binding between the CNTs and Al (Mg), which provide a potential guide for the designing of the CNTs reinforced MMCs. However, the modeling is just first step of design to explain and improve the reaction of interfaces between Metal atoms and CNTs, further study on the interfacial models should be carried out.更多还原