Carbon Nanotube Reinforced Composites: Metal and Ceramic ...

More documents

Recommendations

Info

Figure 5.26 TEM images of titania coated MWNT composite prepared by sol-gel method using (a) Ti(OEt) 4 and (b) Ti(OPr) 4 precursor. Inset in (a) is higher magnification view of coating layer. (c) MWNTs coated with TiO2 prepared by hydrothermal method. Reproduced with permission from [102]. Copyright Ó (2004) Elsevier. electrostatic attraction between positively charged ZrOCl2.8H2O precursor and negatively charged MWNTs. 5.5 Carbide-Based Nanocomposites 5.5.1 Silicon Carbide Matrix 5.5 Carbide-Based Nanocompositesj157 Non-oxide ceramics such as silicon carbide, boron carbide and silicon nitride are attractive structural materials for high temperature applications because of their low density, very high hardness, excellent thermal and chemical stability [109–111]. Despite these advantages they are susceptible to fast fracture during mechanical loading due to their inherently brittle nature. The incorporation of metal nanoparticles into such ceramics can mitigate the problems associated with brittleness. Carbon nanotubes with high aspect ratios are excellent reinforcing and toughening materials for improving the toughness of non-oxide ceramics.
158j 5 Carbon Nanotube–Ceramic Nanocomposites Silicon carbide exhibits different crystalline structures from hexagonal (a-SiC), cubic (b-SiC) to rhombohedral. Of these, cubic b-SiC is particularly important because of its higher bending strength, hardness, stiffness and fracture toughness when compared with a-SiC. Because of the high melting point of silicon carbide, PM method becomes the primary processing technique for making ceramic products. Further, silicon carbide exhibits poor sinterability due to its strong covalent bonding and high melting point. Thus, sintering aids must be added to obtain dense ceramic specimens. SiC-CNT nanocomposites have been fabricated by spray pyrolysis [112], conventional powder mixing followed by hot pressing [41] or by SPS [113, 114], microwave synthesis [115] and preceramic polymer precursor methods [116]. Spray pyrolysis of xylene suspension containing ferrocene and SiC powders into a reactor at 1000 C produces SiC composite flakes with uneven distribution of nanotubes [112]. Ma et al. [41] fabricated the (SiC þ 1% B4C)/10%CNT nanocomposite by blending SiC nanopowder (80 nm), CNTand sintering aid (B4C) in butylalcohol ultrasonically, followed by hot-pressing at 2000 C for 1 h. High temperature is required for good consolidation of these powders into bulk nanocomposite. However, high temperature sintering can result in severe grain growth and destruction of the integrity of nanotubes. Spark plasma sintering with very short processing time is an alternative consolidation route for SiC-CNT nanocomposites. However, SPS of SiC-based materials must be carried out at temperatures 1800 C due to the strong covalent bonding of ceramics. Hirota et al. studied the effect of SPS temperature on the microstructure of monolithic SiC and its composites reinforced with carbon nanofibers [114]. Monolithic SiC and its composites were prepared by direct mixing of powder constituents in methyl alcohol followed by ball milling and SPS. Figure 5.27 shows the density and average grain size of monolithic b-SiC as a function of plasma sintering temperature. The relative density of b-SiC sintered at 1700 C is only 80.9% but increases to 96.4% at 1800 C. The density saturates with further increasing temperature. Further, the grain size of b-SiC increases with increasing temperature as expected. The incorporation of carbon nanofibers into monolithic SiC has little effect on the relative density with the value kept at about 96%. However, the grain size decreases sharply from 4.2 mm to 1.3 mm by adding 5 vol% VGCF, and reduces slightly to 1.2 mmat 15 vol% VGCF (Figure 5.28). To preserve the properties of CNTs, it is advantageous to fabricate the SiC/CNT nanocomposites at lower temperatures, about 1300 C. In this regard, polymer derived ceramics (PDCs) show promise to make such composites at relatively lower temperatures. This process involves the initial cross-linking of polymer precursors followed by a thermal induced polymer to ceramic transformation. The networks of organoelement compounds are directly converted into covalent bonded ceramics during pyrolysis. Typical polymer precursors commonly used include polycarbosilane (PCS), polysiloxane (PSO), and polysilazane (PSZ), producing amorphous Si C, Si O Si and Si C N ceramics respectively upon pyrolysis. PDCs offer several advantages over conventional powder mixing and sintering in terms of the ease of controlling the structure of ceramics by designing the chemistry of polymer precursors, homogeneous chemical distribution at molecular level, near net shape
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 22 and 23:
MWNTs can be as high as 70% of the
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
Page 60 and 61:
isostatic pressing. In certain case
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
Page 72 and 73:
Figure 2.11 Bright field TEM microg
Page 74 and 75:
Figure 2.13 TEM image of bulk Al/5
Page 76 and 77:
2.5 Magnesium-Based Nanocomposites
Page 78 and 79:
limited improvement in ultimate ten
Page 80 and 81:
Figure 2.18 SEM micrographs of the
Page 82 and 83:
Figure 2.19 (a) Low and (b) high ma
Page 84 and 85:
Figure 2.22 SEM micrographs of (a)
Page 86 and 87:
Figure 2.25 (a) TEM micrograph show
Page 88 and 89:
2.8 Transition Metal-Based Nanocomp
Page 90 and 91:
Figure 2.27 TEM image of electrodep
Page 92 and 93:
Figure 2.29 SEM micrographs of (a)
Page 94 and 95:
Figure 2.31 Schematic representatio
Page 96 and 97:
einforcement content SiCp/Al compos
Page 98 and 99:
Materials Science Forum, 534-536 (P
Page 100 and 101:
composite. Materials Science and En
Page 102:
111 Cha, S.I., Kim, K.T., Arshad, S
Page 105 and 106:
90j 3 Physical Properties of Carbon
Page 107 and 108:
Page 109 and 110:
Page 111 and 112:
Page 113 and 114:
Page 115 and 116:
100j 3 Physical Properties of Carbo
Page 117 and 118:
102j 3 Physical Properties of Carbo
Page 119 and 120:
104j 4 Mechanical Characteristics o
Page 121 and 122: 106j 4 Mechanical Characteristics o
Page 147 and 148: 132j 5 Carbon Nanotube-Ceramic Nano
Page 171: 156j 5 Carbon Nanotube-Ceramic Nano
Page 185 and 186: 170j 6 Physical Properties of Carbo
Page 201 and 202: 186j 7 Mechanical Properties of Car
Page 223 and 224:
208j 7 Mechanical Properties of Car
Page 225 and 226:
Page 227 and 228:
Page 229 and 230:
Page 231 and 232:
Table 8.1 Patent processes for maki
Page 233 and 234:
218j 8 Conclusions development of c
Page 235 and 236:
220j 8 Conclusions Figure 8.2 TEM m
Page 237 and 238:
222j 8 Conclusions increase in Vick
Page 239 and 240:
224j 8 Conclusions References 1 Cha
Page 241 and 242:
226j 8 Conclusions nano-matrix. Scr
Page 243:
228j Index l laser ablation 7 load
show all

Carbon Nanotube Reinforced Composites: Metal and Ceramic ...

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?