【作者】 孔纪兰；

【导师】 周上祺；

【作者基本信息】 重庆大学 ， 材料科学与工程， 2006， 博士

【摘要】 纳米科技是20世纪80年代末刚刚产生并正在崛起的新技术，纳米材料是纳米科技发展的物质基础。纳米材料中纳米碳管因具有独特的结构和优异的性能，而成为世界性的纳米材料领域研究的前沿和热点之一。论文一方面进行纳米碳管的制备和镍磷-纳米碳管复合镀，研究纳米碳管对镀层组织、结构和力学性能的影响；另一方面从理论上用量子化学方法研究纳米碳管与镍磷基体间的界面结构，用有限元方法分析复合镀层在单向拉伸时的细观力学行为，以探讨该复合镀层的有关理论和应用前景，所得结果具有重要的理论意义和应用参考价值。研究表明：用氨气作还原气体，以硝酸镍为原料，制备镍催化剂的最佳温度范围为700℃-800℃；而用氢气作为还原气体制备催化剂的最佳温度为600℃-700℃。氨气兼有载气和还原气体的双重作用。以氨气、乙炔为气源可以采用一步法制备纳米碳管，简化工艺和设备。和非晶态的Ni-P镀层相比，纳米碳管的加入使镀层发生了由非晶向纳米晶的转化。这是因为镀液中有纳米碳管时，对磷有捕获作用，使镀层中的磷向纳米碳管偏聚。纳米碳管的加入，使镀层表面呈颗粒状，纳米碳管的含量越高，粒状物越小，密度越大。对Ni-P-CNTs复合镀试样的拉伸实验研究表明，Ni-P合金镀层断口为平整光滑的与拉伸方向垂直的脆性断口。随着镀层中纳米碳管含量的增加，镀层的韧性增加，断口上出现韧窝。实验中发现了Ni-P-CNTs复合镀层靠近断口的侧面有波纹状的裂纹群，并用有限元法从理论上作出了合理的解释。随CNTs含量的增加，Ni-P-CNTs复合镀试样的硬度、最大延伸率和断面收缩率增加，因此，可以用加入纳米碳管的方法改善复合材料的韧性；而抗拉强度、断裂强度和弹性模量等参数随着纳米碳管含量的增加而降低。实验数据表明，复合镀层的弹性模量E_c，Ni-P镀层的弹性模量Em与纳米碳管的质量分数m_n满足以下关系E_c=E_m（1-Km_n）式中K为与界面结合强度有关的常数，本实验中其值等于3.3781；针对目前复合材料的强度表达式只考虑基体和增强体的现状，在实验的基础上，本文认为应考虑界面对强度的影响，提出了界面强度因子的概念，此时，对于纤维三维随机分布的复合材料的强度公式为σ_c=1／4Kσ_f（1-L_C／（2L））V_f+σ_m^*V_mL_C≤Lσ_c=K₁τL/4dV_f+σ_mV_m L_c＞L式中K和K₁为界面强度因子，它可取正值也可为负值。取正值时，增强纤维起到了增强作用；取负值时，表明增强纤维削弱了基体的强度。用有限元法分析了在单向拉伸条件下，界面为机械结合或物理、化学结合时复合镀层中的应力、应变分布规律。结果表明，最大应力出现在纳米碳管的端部，而最大应变出现在纳米碳管端部相接触的基体中。纳米碳管位向，长度，直径以及纳米碳管和基体的结合强度，都影响应力、应变分布。纳米碳管排成阵列时，在单向拉伸状态下，在靠外侧纳米碳管端部以及和其接触的基体中所对应的应力最大，在靠外侧纳米碳管端部的界面／基体中应变最大；外力作用对靠外侧纳米碳管的影响较大，对内侧纳米碳管的影响较小。对Ni-P-CNTs复合镀层的界面进行的量子化学研究表明，在化学镀过程中，镍、磷和纳米碳管都可以成键，磷原子更容易在纳米碳管周围富集，使磷在纳米碳管周围偏聚。磷、碳键为共价键，镍、碳键部分为共价键，部分为范德华键。镍、磷在纳米碳管缺陷处结合时，键能最大，是Ni-P合金基体与纳米碳管的强结合点，而纳米碳管结构完整的部位，与镍、磷的结合较弱。Ni-P合金基体与纳米碳管之间的界面，为结合比较弱的双原子界面，一侧为碳原子，另一侧为磷或镍原子。更多还原

【Abstract】 Since their first observation by Iijima in 1991, carbon nanotubes （CNTs） have been the focus of considerable research. Numerous investigators have reported remarkable physical, mechanical and electrochemical properties for them, such as unique electronic properties, high aspect ratio, outstanding thermal conductivity and strength et al. In the nature of things, CNTs are the perfect reinforce to composite materials, which offering tremendous opportunities for the development of mechanical and electronic industry. For the sake of making full use of their favorable properties, much work has been done and study on carbon nanotubes’ preparation and application has being become the front-line of carbon nanotubes’ research fields. This paper, basing on studying CNTs’ preparation technology, researched the composition, morphology, structure and performance of Ni-P-CNTs composite electroless plating. The results show that,The optimum temperature range is from 700℃to 800℃, during the process of the preparations for nickel catalyst, by the reducing gas of ammonia and the raw material of nickel nitrate. While the optimum temperature range is from 600℃to 700℃, during the process of the preparations for nickel catalyst, by the reducing gas of hydrogen and the raw material of nickel nitrate, which is about 100℃lower than that of using the reducing gas of ammonia. The ammonia has double functions of carrier gas and reducing gas. CNTs can be synthesized with one-step method by using of ammonia and acetylene as source gas, which can simplify technology and equipment.The surface of Ni-P-carbon nanotubes （Ni-P-CNTs） electroless composite plating based on copper sheet consists of compact particles. With the increment of carbon nanotubes content in electroless plating solution, the grain size on the sample surface decreases, while the density of grains and the hardness for composite deposit increases. The presence of carbon nanotubes make phosphorous segregation in platings and improves the degree of crystallization for composite deposit helping the plating transform from amorphous state to nanocrystal state.The tensile test of Ni-P-CNTs composite electroless plating on the basis of copper sheet shows that, the maximum extensibility, the reduction of area and the crack density of the fracture side of Ni-P-CNTs composite electroless plating samples increase with the increment of CNTs content, while the tensile strength, the fracture strength and Young’s modulus decrease. Adding carbon nanotubes to Ni-P alloys benefits the toughness of Ni-P-CNTs composite electroless to improve, while decreases the combining power between composite plating and copper sheet. The data show that the Young’s modulus of Ni-P-CNTs composite electroless platings （E_c）, the Young’s modulus of Ni-P alloys （Em） and the content of CNTs （m_n） fit the formula ofE_c=E_m（1-Km_n） K is a constant correlated with interface conditions in it. It’s 3.3781 in this paper.It’s thinked that interface conditions should be considered in the strength formula of composite materials. What’s more, interface strength factor is put forward at the first time and the strength formula for composite materials consisting of three dimensional random distribution fibre and matrix is modified, asσ_c=1/4Kσ_f（1-L_c/2L）V_f+σ_m^*V_m L_c≤Lσ_c=K₁τL/4dV_f+σ_mV_m L_c＞L K and K₁ are interface strength factors. If K or K₁ is greater than zero, fibre can act as reinforcing materials. If K or K₁ is less than zero, fibre cannot act as reinforcing materials and weaken the matrix strength.The stress and strain distribution under the condition of simple tension were analysed by finite element method. The results show that whenever the interface is under the condition of mechanical bonding or physical or chemical bonding, the biggest stress is at the end of CNTs and the biggest strain is in the martrix who connect with the end of CNTs among the cells. The placement azimuth, the length and the diameter of CNTs combining with the interface strength influence the stress and strain distribution. If the array CNTs is under the condition of simple tension, the ends of the outer CNTs and the matrix who connects with the CNTs ends have the biggest stress among the cells, while the biggest strain is in the interface or matrix, which connects with the CNTs ends. The external force influences the outer CNTs of array CNTs much more than the inner ones.The study of quantum chemistry method to the interface of Ni-P-CNTs electroless composite plating shows that, during the process of electroless plating, nickel and phosphorus can combine with carbon nanotubes, which makes the energy of whole system decrease, or to say there’s some bonding power between nickel and carbon as well as phosphorus and carbon, and the energy decrease of nickel and carbon combining is bigger than that of phosphorus and carbon. It’s easier for Phosphorus to enrich around carbon nanotubes than for nickel, resulting in Phosphorus segregation about carbon nanotubes. The bond energy of phosphorus and carbon is greater than that of nickel and carbon.In all models of particles and carbon nanotube what have been studied, the system energy decreases most while nickel and phosphorus combines with carbon nanotubes at the collapse indication, which is the strong bonding point at the interface of Ni-P alloy, and the corresponding bond energy is largest. The combination between the perfect parts of carbon nanotubes and nickel is weak, while that between the perfect ones and phosphorus is strong. It’s obviously that the interface formed by Ni-P and carbon nanotubes is biatomic, one side of it are carbon atoms and the other side are nickel atoms or phosphorus atoms. The property of phosphorus carbon bonds is covalent bond, while some of the nickel carbon bonds represent van der waals bond property partly.更多还原