Carbon Nanotube Reinforced Composites: Metal and Ceramic ...

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Table 7.5 Mechanical properties of monolithic Si3N4 and Si3N4/1 wt% MWNT nanocomposite spark plasma sintered at different temperatures. Materials 7.6 Wear Behavior Sintering temperature ( C) Density (g cm 3 ) Vickers hardness (GPa) Fracture toughness (MPa m 1/2 ) Si3N4 1500 3.23 20.1 0.9 5.2 Si 3N 4 1650 3.24 18.3 0.5 6.5 Si3N4/1 wt% MWNT 1500 3.17 16.6 0.4 5.3 Si 3N 4/1 wt% MWNT 1650 3.19 19.1 0.6 4.4 Reproduced with permission from [Chap. 5, Ref. 120]. Copyright Ó (2005) Elsevier. 7.6 Wear Behaviorj207 Hard and superhard ceramic nanocomposite coatings have attracted increasing attention due to their potential applications in diverse areas such as cutting tools, bearings, micro-electro-mechanical systems (MEMS), magnetic disk drives, and so on. Hard coatings improve the durability of substrate materials in hostile environments against severe wear, thus prolonging the materials life. Typical ceramic nanocomposite coatings are composed of nanocrystalline transition metal carbides embedded in amorphous covalent nitride (e.g., Si3N4, or BN) matrix [26]. Hard nanocomposite coatings are often very brittle, which strongly limits their practical use. Tough nanocomposite coatings can be realized by embedding solid lubricant soft phase such as transition metal dichalgonenides (MoS2, WS2, NbSe2, etc.) in an amorphous ceramic matrix [27] as shown in Figure 7.19(a) and (b). As mentioned before, CNTs also exhibit self-lubrication behavior. In combination with their other attractive mechanical and physical properties, CNTs have consistently outperformed their transition metal dichalgonenide rivals. Ceramic-CNT nanocomposites have been shown to exhibit low friction coefficient and wear rate, making them useful as wear-resistant materials for structural components in industrial sectors. In general, the distribution of CNTs in ceramic matrix affects the wear behavior of ceramic-CNTnanocomposites considerably. Recently, Lim et al. investigated the effect of CNT dispersion on tribological behavior of the of Al2O3/ MWNT nanocomposites [28]. Two processing routes were adopted to prepare nanocomposites. The first processing route consisted of ball milling of CNTs and alumina powders in ethanol followed by hot pressing at 1850 C. The second route was ball milling of slurry consisting of a mixture of MWNT, alumina, methyl-isobutyl ketone, poly(vinyl)butyral and dibutyl phthalate. These organic agents acted as solvent, dispersant, binder and plasticizer, respectively. The slurry was poured into a tape-casting equipment, followed by lamination and hot pressing at 1850 C. Tape casting gives better distribution of CNTs in alumina matrix, resulting in the formation of dense nanocomposites (Figure 7.20). However, the r.d. of hot-pressed nanocomposites decreases continuously with increasing nanotube content.
208j 7 Mechanical Properties of Carbon Nanotube–Ceramic Nanocomposites Figure 7.19 (a) Schematic representation of a tough nanocomposite coating design, combining a nanocrystalline/ amorphous structure with a functionally gradient interface and (b) TEM image of an Al2O3/MoS2 nanocomposite coating consisted of an amorphous Al2O3 ceramic matrix encapsulating 5–10 nm inclusions of nanocrystalline MoS 2 grains. Reproduced with permission from [27]. Copyright Ó (2005) Elsevier. Enhanced densification in tape-cast nanocomposites contributes to higher wear resistance and low friction coefficient, as expected. Figures 7.21 and 7.22 show the variations of wear weight loss and friction coefficient with CNT content for Al2O3/ MWNT nanocomposites prepared by hot pressing and tape casting, respectively. Apparently, the weight loss of the hot-pressed nanocomposites decreases initially by adding 4 wt% MWNT. It then increases with further increasing filler content. This is due to poor dispersion of MWNTs in alumina matrix at higher filler content. In contrast, the weight loss of tape-cast nanocomposites decreases linearly with increasing nanotube content as a result of better dispersion of nanotubes in
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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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