Carbon Nanotube Reinforced Composites: Metal and Ceramic ...

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prevention of agglomeration of CNTs is of particular importance for nanocomposites because most of their unique properties are only associated with individual nanotubes. As mentioned before, fabrication technologies play a dominant role in the uniform dispersion of nanotubes within the metal matrix. For CNT-Al nanocomposites prepared by conventional powder mixing, hot pressing and hot extrusion, the tensile strength of nanocomposites is inferior to that of pure Al due to the clustering of nanotubes [Chap. 2, Ref. 16]. This demonstrates the absence of the load transfer effect across the nanotube–matrix interface during tensile deformation. George et al. [13] prepared the Al/MWNT and Al/SWNT nanocomposites by ball milling composite mixtures followed by sintering at 580 C and hot extrusion at 560 C. Pure aluminum was also fabricated under the same processing conditions. All these specimens were then subjected to tensile testing. The pure Al specimen exhibits low yield strength of 80 MPa and Young s modulus of 70 GPa. The experimental Young s modulus, yield strength and tensile strength of such nanocomposites are summarized in Table 4.1. Apparently, the elastic modulus of Al increases by 12 and 23% by adding 0.5 and 2 vol% MWNT, respectively. The elastic modulus values of the Al/0.5 vol% MWNT and Al/2 vol% MWNT nanocomposites correlate reasonably with those predicted from the shear-lag model assuming an aspect ratio of 100. Similarly, SWNT additions also enhance the stiffness and strength of aluminum as expected. The enhanced yield strength of nanotube-reinforced composites demonstrates that the applied load is effectively transferred across the nanotube–matrix interface. Deng et al. prepared the 2024 Al/MWNT nanocomposites by PM followed by cold isostatic pressing and hot extrusion [Chap. 2, Ref. 35]. In the process, CNTs and 2024 Al powder (4.20 wt% Cu, 1.47 wt% Mg, 0.56 wt% Mn, 0.02 wt% Zr, 0.40 wt% Fe, 0.27 wt% Si) were dispersed in ethanol under sonication. The powder mixtures were dried, mechanically milled, followed by cold isostatic pressing and hot extrusion at 450 C. Figure 4.2 shows the variations of relative density and Vickers hardness of 2024 Al/MWNT nanocomposites with nanotube content. The relative density and hardness increase with increasing nanotube content up to 1 wt%. At 2 wt% MWNT, the relative density and hardness decrease sharply due to the agglomeration of nanotubes. The Young s modulus and tensile strength of 2024 Al/MWNT nanocomposites also reach an apparent maximum at 1 wt% (Figure 4.3). The tensile Table 4.1 Comparison of theoretical and experimental tensile data for Al/MWNT and Al/SWNT nanocomposites. Materials Shear lag Young s modulus (GPa) Experimental Young s modulus (GPa) Experimental yield strength (MPa) Al/0.5 vol%MWNT 74.31 78.1 86 134 Al/2 vol% MWNT 87.38 85.85 99 138 Al/1 vol% SWNT 79.17 70 79.8 141 Al/2 vol% SWNT 88.36 79.3 90.8 134 Reproduced with permission from [13]. Copyright Ó (2005) Elsevier. 4.2 Tensile Deformation Behaviorj107 Experimental ultimate tensile strength (MPa)
108j 4 Mechanical Characteristics of Carbon Nanotube–Metal Nanocomposites Figure 4.2 Relative density and Vickers microhardness as a function of carbon nanotube content for 2024 Al/MWNT nanocomposites. Reproduced with permission from [Chap. 2, Ref. 35]. Copyright Ó (2007) Elsevier. Figure 4.3 Tensile strength, Young s modulus and elongation vs carbon nanotube content for 2024 Al/MWNT nanocomposites. Reproduced with permission from [Chap. 2, Ref. 35]. Copyright Ó (2007) Elsevier.
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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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Page 74 and 75: Figure 2.13 TEM image of bulk Al/5
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Page 80 and 81: Figure 2.18 SEM micrographs of the
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Page 84 and 85: Figure 2.22 SEM micrographs of (a)
Page 86 and 87: Figure 2.25 (a) TEM micrograph show
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Page 90 and 91: Figure 2.27 TEM image of electrodep
Page 92 and 93: Figure 2.29 SEM micrographs of (a)
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Page 98 and 99: Materials Science Forum, 534-536 (P
Page 100 and 101: composite. Materials Science and En
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158j 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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