Carbon Nanotube Reinforced Composites: Metal and Ceramic ...

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Figure 7.10 Low-and high magnification SEM micrographs of (a) dense and (b) porous alumina showing top views of Vickers indentation sites with radial cracks formation. Low-and high magnification SEM micrographs of (c) Al2O3/10 vol% SWNT composite showing no radial cracks formation at indentation sites. Reproduced with permission from [21]. Copyright Ó (2004) Nature Publishing Group. 7.3 Oxide-Based Nanocompositesj197
198j 7 Mechanical Properties of Carbon Nanotube–Ceramic Nanocomposites Table 7.3 Comparison of processing conditions for making Al2O3/10 vol% SWNT nanocomposite. Comparison parameters Mukherjee s group Ref. [Chap. 5, Ref. 44] Padture s group Ref. [21] Sintering materials SWNT and Al2O3 SWNT and Al2O3 Dispersing and mixing methods Wet-milling and sieving No sieving SPS processing conditions 1150 C, 3 min, 63 MPa 1450–1550 C, 3–10 min, 40 MPa Relative density (%) 100 95.1 Grain size 200 nm 1000–2000 nm Fracture toughness 194% increase (VIF) No toughening (VIF and SEVNB) Reproduced with permission from [23]. Copyright Ó (2008) Elsevier. improvement in the facture toughness of alumina by adding 10 vol% SWNT. In other words, the Al 2O 3/10 vol% SWNT and Al 2O 3/10 vol% graphite composites are as brittle as the dense alumina. One possible explanation for low fracture toughness of the Al2O3/10 vol% SWNT nanocomposite obtained from the SEVNB standard method is the employment of high SPS temperatures (i.e., 1450–1550 C) for the consolidation of powder mixture. Table 7.3 summarizes the processing conditions from Mukherjee and Padture s research groups for fabrication of the Al2O3/10 vol% SWNT nanocomposite. Apparently, the SPS temperature of the Al2O3/10 vol% SWNT nanocomposite prepared by Padture s group is significantly higher, thereby leading to large matrix grain size of the resulting composite. The effect of hybrid reinforcements (1 vol% SiC and 5–10 vol% MWNT) on the mechanical properties of alumina nanocomposites is now considered. The hybrid reinforcements offer distinct advantages by combining different properties of nanofillers to produce nanocomposites with higher toughness. The hybrids were fabricated by blending MWNTs, SiC and alumina in ethanol ultrasonically followed by ball-milling and drying. Dried composite powders were spark plasma sintered at 1550 C. For comparison, pure alumina and Al2O3/1 vol% SiC nanocomposite were also prepared under the same processing conditions. Figure 7.11 shows the r.d., fracture strength, bending strength and hardness for dense Al2O3, Al2O3/1 vol% SiC composite and Al2O3/(MWNT þ SiC) hybrids [Chap. 5, Ref. 75]. It is obvious that SiC nanoparticles inhibit densification of alumina but its addition improves both the bending strength and fracture toughness of alumina. Additions of 5 and 7 vol% MWNT to the Al2O3/1 vol% SiC nanocomposite further improve the fracture toughness but the bending strength decrease slightly. The r.d. and all mechanical properties of the hybrid deteriorate by adding 10 vol% MWNT due to the nanotube agglomeration. SEM fractographs reveal that crack bridging and crack deflection by MWNTs are responsible for improving the toughness of hybrid nanocomposites. In the case of plasma-sprayed nanocomposite coatings, Agarwal s group indicated that the MWNT additions are beneficial to enhance the toughness of alumina
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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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Figure 2.18 SEM micrographs of the
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Figure 2.19 (a) Low and (b) high ma
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Figure 2.22 SEM micrographs of (a)
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Figure 2.25 (a) TEM micrograph show
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2.8 Transition Metal-Based Nanocomp
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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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102j 3 Physical Properties of Carbo
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104j 4 Mechanical Characteristics o
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132j 5 Carbon Nanotube-Ceramic Nano
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