Carbon Nanotube Reinforced Composites: Metal and Ceramic ...

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Figure 4.10 (a) Compressive true stress–strain curves of pure Cu, and Cu/MWNT nanocomposites prepared by molecular level mixing and spark plasma sintering. (b) Young s modulus and compressive yield strength vs carbon content for Cu/MWNT nanocomposites. Reproduced with permission from [Chap. 2, Ref. 86]. Copyright Ó (2005) Wiley-VCH Verlag GmbH. 4.2 Tensile Deformation Behaviorj115 point due to homogenous dispersion of nanotubes in the copper matrix. The yield strength of copper improves dramatically with the incorporation of nanotubes. The yield strength of Cu/5 vol% MWNT nanocomposite is 360 MPa, which is 2.4 times that of Cu (150 MPa). The compressive yield strength increases to 455 MPa when the nanotube content reaches 10 vol%, being 3 times that of Cu. This is attributed to the high load-transfer efficiency of nanotubes in the matrix as a result of strong interfacial bonding between the copper matrix and nanotubes through molecular level mixing. From Equation 4.4, the strengthening efficiency of the reinforcement (R) can be expressed as S/2, thereby yielding: sc ¼ smð1 þ Vf RÞ ð4:15Þ R ¼ ðsc smÞ : ð4:16Þ Vf sm
116j 4 Mechanical Characteristics of Carbon Nanotube–Metal Nanocomposites Figure 4.11 Experimental and theoretical yield strength of Cu/ MWNT nanocomposites as a function of carbon nanotube content. Reproduced with permission from [Chap. 2, Ref. 89]. Copyright Ó (2008) Wiley-VCH Verlag GmbH. The R values for the Cu/5 vol% MWNTand Cu/10 vol% MWNTnanocomposites are determined to be 14 and 20.3, respectively. These values are much higher than those of SiC particle and SiC whisker reinforcements. Figure 4.11 shows a comparison between theoretical and experimental compressive yield strength vs nanotube content for Cu/MWNTnanocomposites. Theoretical predictions are made assuming the aspect ratios of nanotubes to be 40, 50 and 60. Apparently, the measured yield strength agrees reasonably well with the estimated values from Equation 4.4 for the composites with aspect ratios of 40 and 50. In addition to the load transfer mechanism, metallurgical factors, such as refinement of matrix grains and higher dislocation density resulting from the coefficient of thermal expansion between the matrix and nanotubes, also contribute to the strength of nanocomposites [20]. 4.2.4 Nickel-Based Nanocomposites Electrodeposition is widely known as an effective technique for depositing dense nanocrystalline nickel coatings for mechanical characterization. Nanocrystalline nickel coatings generally exhibit much higher tensile strength and stiffness but poorer tensile ductility compared with microcrystalline Ni. It is considered that CNTs with superior tensile strength, stiffness and fracture strain can further improve the mechanical properties of Ni coatings. Table 4.5 lists the tensile properties of nanocrystalline Ni and nanocrystalline Ni/MWNT composite prepared by electrodeposition [Chap. 2, Ref. 100]. The hardness and tensile strength of Ni/MWNT composite are considerably higher than those of nanocrystalline Ni. The tensile elongation of nanocrystalline Ni decreases very slightly by incorporating MWNTs. It can be said that the tensile elongation is quite similar and not affected by the nanotube additions. Sun et al. [Chap. 2, Ref. 105] demonstrated that
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Sie Chin Tjong Carbon Nanotube Rein
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Sie Chin Tjong Carbon Nanotube Rein
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Contents Preface IX List of Abbrevi
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5 Carbon Nanotube-Ceramic Nanocompo
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Preface Carbon nanotubes are nanost
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XII List of Abbreviations HIP hot i
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1 Introduction 1.1 Background Compo
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Figure 1.2 Transmission electron mi
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1.3 Synthesis of Carbon Nanotubes 1
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MWNTs can be as high as 70% of the
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Figure 1.7 In situ TEM images recor
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1.3 Synthesis of Carbon Nanotubesj1
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show TEM images of MWNTs synthesize
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Since then, large efforts have been
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1.3.4 Patent Processes Carbon nanot
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1.4 Purification of Carbon Nanotube
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Table 1.3 Patent processes for the
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Figure 1.13 Schematic illustration
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1.5 Mechanical Properties of Carbon
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Figure 1.14 Carbon nanotubes in hig
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Figure 1.15 In situ tensile deforma
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Table 1.7 Theoretical and experimen
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Nomenclature ~a 1 , ~a 2 Unit vecto
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carbon nanotubes. Physical Review L
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70 Jang, I., Uh, H.S., Cho, H.J., L
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108 Shelimov, K.B., Esenaliev, R.O.
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Bonnamy, S., Beguin, F., Burnham, N
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2 Carbon Nanotube-Metal Nanocomposi
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isostatic pressing. In certain case
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This implies the absence of effecti
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coating material, the plasma gun an
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Table 2.4 Changes in the size and v
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Figure 2.6 (a) Low and (b) high mag
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Figure 2.8 SEM micrographs showing
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Figure 2.11 Bright field TEM microg
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Figure 2.13 TEM image of bulk Al/5
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2.5 Magnesium-Based Nanocomposites
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limited improvement in ultimate ten
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Page 86 and 87: Figure 2.25 (a) TEM micrograph show
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Page 98 and 99: Materials Science Forum, 534-536 (P
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166j 5 Carbon Nanotube-Ceramic Nano
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168j 5 Carbon Nanotube-Ceramic Nano
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170j 6 Physical Properties of Carbo
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186j 7 Mechanical Properties of Car
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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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222j 8 Conclusions increase in Vick
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224j 8 Conclusions References 1 Cha
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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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