Carbon Nanotube Reinforced Composites: Metal and Ceramic ...

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Figure 1.14 Carbon nanotubes in highly strained configuration. The white scale bars at the bottom of each figure represent 500 nm. (a) The original shape of MWNT, 10.5 nm in diameter and 850 nm long. The tube is bent in steps, first upwards (b), until it bends all the way back onto itself (c). 1.5 Mechanical Properties of Carbon Nanotubesj27 The tube is then bent all the way back the other way onto itself (d), to a final curvature similar to that in (c). Reproduced with permission from [141]. Copyright Ó (1997) Nature Publishing Company. and mathematical equations based on continuum mechanics, they determined the stiffness to be 1.28 TPa. The bending strength was found to be 14 GPa. Salvetat et al. also used AFM to determine the stiffness of the arc- and CVD- grown MWNTs. The nanotube was clamped at both ends during the measurements [145]. A Si3N4 microscope tip was employed to apply the force and for measuring the deflection of the CNT. They obtained an average modulus value of 810 GPa for arc-grown MWNT, and 27 GPa for CVD-MWNT. They attributed the lower stiffness of CVD-MWNT to the formation of defect or structural disorder in the tube. On the basis of TEM observation the graphitic planes are tilted with an angle of 30 with respect to the tube axis. Yu et al. performed in situ tensile measurements in a scanning electron microscope, yielding stiffness values range from 270 to 950 GPa for arcgrown MWNT [146]. They also demonstrated that the MWNT break in the outermost layer, resulting in the morphology commonly described as sword-in-sheath feature. The tensile strength of this layer ranges from 11 to 63 GPa. In general, SWNTs always agglomerate to form ropes with diameters of several tens of nanometers. Using the same equipment, Yu et al. obtained an average Young s modulus of 1 TPa and tensile strength of 30 GPa for SWNT ropes [147]. The tensile strength of SWNT ropes is over 40 times the tensile strength (745 MPa) of typical annealed low alloy steels such as SAE 4340. Low alloys steels are extensively used in
28j 1 Introduction Table 1.6 Experimental Young s modulus and tensile strength of carbon nanotubes synthesized from different techniques. Investigator Young s modulus (TPa) Tensile strength (GPa) Nanotube type Synthesis process Test method Treacy et al. [142] 1.8 — MWNT Electric arc TEM (thermal vibration) Krishnam et al. [143] 1.25 — SWNT Laser ablation TEM (thermal vibration) Wong et al. [144] 1.28 — MWNT Electric arc AFM Salvetat et al. [145] 0.81 — MWNT Electric arc AFM Salvetat et al. [145] 0.027 — MWNT CVD AFM Yu et al. [146] 0.27–0.95 11–63 MWNT Electric Arc SEM (tension) Yu et al. [147] 1 30 SWNT rope Laser ablation SEM (tension) Xie et al. [148] 0.45 3.6 MWNT bundle CVD SEM (tension) Demczyk et al. [149] 0.9 150 MWNT Electric Arc TEM (tension) the manufacture of automotive parts that require high strength and toughness. Xie et al. also determined the stiffness of aligned CVD-MWNT bundle employing a technique similar to Yu et al. [148]. Recently, Demczyk et al. performed in situ tension measurement in a TEM for arc-grown MWNT, producing a stiffness of 0.9 TPa and a tensile strength of 0.15 TPa [149]. The results of these investigators are summarized in Table 1.6. From the above discussion, both theoretical and experimental studies confirm that nanotubes have exceptional stiffness and strength. However, a large variation in experimentally measured stiffness and strength is observed, particularly a noticeable reduction in stiffness for CVD-MWNTs when compared with arc-grown MWNTs. This can be expected as these reported values are obtained from a variety of CNTs synthesized from various techniques having different lengths, diameters, disorder structures, level of metal impurities and carbonaceous species. As mentioned above, the fracture tensile strain of CNTs predicted by the MD simulations could reach up to 30% [136], or even higher depending on simulated temperature and interatomic potential model adopted [150]. Recently, Huang et al. reported that the SWNT fractured at room temperature with a strain 15% [151]. However, the fracture tensile strain of SWNTcould reach up to 280% at temperatures 2000 C. (Figure 1.15). In other words, CNT deformed in a superplastic mode at elevated temperatures. In the measurement, a piezo manipulator was used to pull the SWNT to increase the strain under a constant bias of 2.3 V inside a TEM. The temperatures are estimated to be 2000 C under a bias of 2.3 V. As a result, kinks and pointdefectsarefullyactivatedin thenanotube, resultingin superplasticdeformation. For VGCFs, the modulus has a strong dependence on the graphite plane misorientation [13]. This is because VGCFs are formed by stacking graphite layers into cone and cup structures. The graphite layers are not parallel to the fiber axis. Accordingly, a wide range of stiffness values have been reported in the literature.
Page 2 and 3: Sie Chin Tjong Carbon Nanotube Rein
Page 4 and 5: Sie Chin Tjong Carbon Nanotube Rein
Page 6 and 7: Contents Preface IX List of Abbrevi
Page 8 and 9: 5 Carbon Nanotube-Ceramic Nanocompo
Page 10: Preface Carbon nanotubes are nanost
Page 13 and 14: XII List of Abbreviations HIP hot i
Page 16 and 17: 1 Introduction 1.1 Background Compo
Page 18 and 19: Figure 1.2 Transmission electron mi
Page 20 and 21: 1.3 Synthesis of Carbon Nanotubes 1
Page 22 and 23: MWNTs can be as high as 70% of the
Page 24 and 25: Figure 1.7 In situ TEM images recor
Page 26 and 27: 1.3 Synthesis of Carbon Nanotubesj1
Page 28 and 29: show TEM images of MWNTs synthesize
Page 30 and 31: Since then, large efforts have been
Page 32 and 33: 1.3.4 Patent Processes Carbon nanot
Page 34 and 35: 1.4 Purification of Carbon Nanotube
Page 36 and 37: Table 1.3 Patent processes for the
Page 38 and 39: Figure 1.13 Schematic illustration
Page 40 and 41: 1.5 Mechanical Properties of Carbon
Page 44 and 45: Figure 1.15 In situ tensile deforma
Page 46 and 47: Table 1.7 Theoretical and experimen
Page 48 and 49: Nomenclature ~a 1 , ~a 2 Unit vecto
Page 50 and 51: carbon nanotubes. Physical Review L
Page 52 and 53: 70 Jang, I., Uh, H.S., Cho, H.J., L
Page 54 and 55: 108 Shelimov, K.B., Esenaliev, R.O.
Page 56 and 57: Bonnamy, S., Beguin, F., Burnham, N
Page 58 and 59: 2 Carbon Nanotube-Metal Nanocomposi
Page 60 and 61: isostatic pressing. In certain case
Page 62 and 63: This implies the absence of effecti
Page 64 and 65: coating material, the plasma gun an
Page 66 and 67: Table 2.4 Changes in the size and v
Page 68 and 69: Figure 2.6 (a) Low and (b) high mag
Page 70 and 71: Figure 2.8 SEM micrographs showing
Page 72 and 73: Figure 2.11 Bright field TEM microg
Page 74 and 75: Figure 2.13 TEM image of bulk Al/5
Page 76 and 77: 2.5 Magnesium-Based Nanocomposites
Page 78 and 79: limited improvement in ultimate ten
Page 80 and 81: Figure 2.18 SEM micrographs of the
Page 82 and 83: Figure 2.19 (a) Low and (b) high ma
Page 84 and 85: Figure 2.22 SEM micrographs of (a)
Page 86 and 87: Figure 2.25 (a) TEM micrograph show
Page 88 and 89: 2.8 Transition Metal-Based Nanocomp
Page 90 and 91: Figure 2.27 TEM image of electrodep
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Figure 2.29 SEM micrographs of (a)
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Figure 2.31 Schematic representatio
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einforcement content SiCp/Al compos
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Materials Science Forum, 534-536 (P
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composite. Materials Science and En
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111 Cha, S.I., Kim, K.T., Arshad, S
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90j 3 Physical Properties of Carbon
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100j 3 Physical Properties of Carbo
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Table 8.1 Patent processes for maki
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218j 8 Conclusions development of c
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220j 8 Conclusions Figure 8.2 TEM m
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226j 8 Conclusions nano-matrix. Scr
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228j Index l laser ablation 7 load
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