Direct observation of toughening mechanisms in carbon nanotube ceramic matrix composites
Direct observation of toughening mechanisms in carbon nanotube ceramic matrix composites
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DOI：
10.1016/j.actamat.2003.10.050
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发表时间：
2004-02-23
期刊：
影响因子：
9.4
通讯作者：
Xu, JM
中科院分区：
文献类型：
--
作者：
Xia, Z;Riester, L;Xu, JM
碳纳米管 (CNTS) 优异的机械性能正在推动创建新型坚固、坚韧的纳米复合材料系统的研究。在这里，提出了碳纳米管增强陶瓷复合材料中增韧机制的第一个证据。在氧化铝基质中制造了高度有序的平行多壁碳纳米管阵列。纳米压痕引入了受控裂纹，并通过扫描电子显微镜检查了损坏情况。这些纳米复合材料表现出微米级纤维复合材料增韧的三个特征：CNT/基体界面处的裂纹偏转；碳纳米管的裂纹桥接；以及断裂面上的 CNT 拉拔。因此，在微观结构接近原子尺度的材料中可能会发生界面脱粘和滑动。此外，对于某些几何形状，会出现“剪切带”中纳米管塌陷的新机制，而不是形成裂纹，这表明这些材料可以具有多轴损伤容限。定量压痕数据和计算模型用于确定多壁 CNT 轴向杨氏模量为 200-570 GPa，具体取决于纳米管的几何形状和质量。三维 FEM 分析表明，这些材料中的基体残余应力维持在 300 MPa 的量级，而不会自发开裂，这表明残余应力可用于设计增强的性能。因此，这些纳米级陶瓷复合材料具有亚微米级增韧和损伤容限的潜力，因此是耐磨涂层的绝佳候选者。由 Elsevier Ltd 代表 Acta Materialia Inc. 出版。
The excellent mechanical properties of carbon nanotubes (CNTS) are driving research into the creation of new strong, tough nanocomposite systems. Here, the first evidence of toughening mechanisms operating in carbon-nanotube-reinforced ceramic composites is presented. A highly ordered array of parallel multiwall CNTs in an alumina matrix was fabricated. Nanoindentation introduced controlled cracks and the damage was examined by scanning electron microscopy. These nanocomposites exhibit the three hallmarks of toughening found in micron-scale fiber composites: crack deflection at the CNT/matrix interface; crack bridging by CNTs; and CNT pullout on the fracture surfaces. Interface debonding and sliding can thus occur in materials with microstructures approaching the atomic scale. Furthermore, for certain geometries a new mechanism of nanotube collapse in "shear bands" occurs, rather than crack formation, suggesting that these materials can have multiaxial damage tolerance. The quantitative indentation data and computational models are used to determine the multiwall CNT axial Young's modulus as 200-570 GPa, depending on the nanotube geometry and quality. Three-dimensional FEM analysis indicates that matrix residual stresses on the order of 300 MPa are sustained in these materials without spontaneous cracking, suggesting that residual stress can be used to engineer enhanced performance. These nanoscale ceramic composites thus have potential for toughening and damage tolerance at submicron scales, and so are excellent candidates for wear-resistant coatings. Published by Elsevier Ltd on behalf of Acta Materialia Inc.