Carbon Nanotube Reinforced Composites: Metal and Ceramic ...

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MWNTs can be as high as 70% of the reaction product. Auger electron spectroscopic analysis reveals that nitrogen is not incorporated in the MWNTs. This technique is considered an economical route for large scale synthesis of high crystalline MWNTs as liquid nitrogen replaces expensive inert gas and cooling system for the cathode. It is worth noting that SWNTs can only be synthesized through the arc discharge process in the presence of metal catalysts. Typical catalysts include transition metals, for example, Fe, Co and Ni, rare earths such as Yand Gd, and platinum group metals such as Rh, Ru and Pt [25–32]. In this respect, the graphite anode is doped with such metal catalysts. The synthesized nanotubes generally possess an average diameter of 1–2 nm and tangle together to form bundles in the soot, web and string-like structures. The as-grown SWNTs exhibit a high degree of crystallinity as a result of the high temperature of the arc plasma [30]. However, SWNTs contain a lot of metal catalyst and amorphous carbon, and must be purified to remove them. The yield of SWNTs produced from electric arc discharge is relatively low. The diameter and yield of SWNTs can be controlled by using a mixed gaseous atmosphere such as inert–inert or inert–hydrogen mixture [29, 30], and a mixture of metal catalyst particles [28, 32]. 1.3.2 Laser Ablation 1.3 Synthesis of Carbon Nanotubesj7 Laser ablation involves the generation of carbon vapor species from graphite target using high energy laser beams followed by the condensation of such species. The distinct advantages of laser ablation include ease of operation and production of high quality product, because it allows better control over processing parameters. The disadvantages are high cost of the laser Source and low yield of nanotubes produced. Laser beams are coherent and intense with the capability of attaining very fast rates of vaporization of target materials. In the process, graphite target is placed inside a quartz tube surrounded by a furnace operated at 1200 C under an inert atmosphere. The target is irradiated with a laser beam, forming hot carbon vapor species (e.g. C3, C2 and C). These species are swept by the flowing gas from the high-temperature zone to a conical copper collector located at the exit end of the furnace [33, 34]. Pulsed laser beam with wavelengths in infrared and visible (CO2, Nd:YAG) or ultravioletUV (excimer) range can be used to vaporize a graphite target. This is commonly referred to as pulsed laser vaporization (PLV) technique [35–40]. Moreover, CO2 and Nd:YAG lasers operated in continuous wave mode have been also reported to produce nanotubes [41–43]. SWNTs can also be produced by laser ablation but require metal catalysts as in the case of electric arc discharge. Figure 1.6 shows a TEM image of deposits formed by the laser (XeCl excimer) ablation of a graphite target containing 1.2% Ni and 1.2% Co [42]. Bimetal catalysts are believed to synthesize SWNTs more effectively than monometal catalysts [33, 36]. From Figure 1.6, SWNTs having a narrow diameter distribution (average diameter of about 1.5 nm) tend to tangle with each other to form bundles or ropes with a thickness of about 20 nm. Their surfaces are coated with amorphous carbon. Metal nanoparticles catalysts with the size of few to 10 nm can be
8j 1 Introduction Figure 1.6 Transmission electron micrograph of a weblike deposit formed by laser ablation of a graphite target containing 1.2% Ni and 1.2%Co. The metal catalysts appeared as dark spots in the micrograph. Reproduced with permission from [40]. Copyright Ó (2007) Elsevier. readily seen in the micrograph. The diameter and yield of SWNTs are strongly dependent on processing parameters such as furnace temperature, chamber pressure, laser properties (energy, wavelength, pulse duration and repetition rate) and composition of target material. The diameter of SWNTs produced by pulsed Nd:YAG laser can be tuned to smaller sizes by reducing the furnace temperature from 1200 C down to a threshold temperature of 850 C [35]. Using UV laser irradiation, SWNTs can be synthesized at a lower furnace temperature of 550 C, which is much lower than the threshold temperature of 850 C by using Nd:YAG laser [37]. Recently, Elkund et al. employed ultrafast (subpicosecond) laser pulses for large-scale synthesis of SWNTs at a rate of 1.5 g h 1 [44]. To achieve controlled growth of the SWNTs, a fundamental understanding of their growth mechanism is of particular importance. The basic growth mechanism of SWNTs synthesized by physical vapor depositionPVD techniques is still poorly understood. The vapor–liquid–solid (VLS) mechanism is widely used to describe the catalytic formation of nanotubes via PVD [44, 45] and chemical vapor deposition (CVD) techniques [46, 47]. This model was originally proposed by Wagner and Willis to explain the formation of Si whiskers in 1964 [48]. The whiskers were grown by heating a Si substrate containing Au metal particles in a mixture of SiCl 4 and H 2 atmosphere. An Au–Si liquid droplet was formed on the surface of the Si substrate, acting as a preferred sink for arriving Si atoms. With continued incorporation of silicon atoms into the liquid droplets, the liquid droplet became saturated. Once the liquid droplet was saturated, growth occurred at the solid–liquid interface by precipitation of Si from the droplet. Wu and Yang [49] then observed direct formation
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 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 42 and 43: Figure 1.14 Carbon nanotubes in hig
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
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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
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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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104j 4 Mechanical Characteristics o
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132j 5 Carbon Nanotube-Ceramic Nano
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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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