the effects of oxidizers on the diameters of the carbon nanotubes ...

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Figure 2.9. Schematic illustration <strong>of</strong> an arc-discharge apparatus (Source: Harris 2007) The principle <strong>of</strong> this method depends on an electric discharge produced by applying direct current (DC) <strong>of</strong> ~200 A at a low voltage (20-40 V) (Iijima 1991) between anode and cathode under an inert atmosphere <strong>of</strong> helium or argon (Journet and Bernier 1998, Popov 2004) and also in methane (Ando, et al. 2004). Arc-discharge method can be utilized with or without catalyst (such as Fe, Co, Ni); catalyst is necessary for <strong>the</strong> production <strong>of</strong> SWNT while for <strong>the</strong> production <strong>of</strong> MWNT is not, (Journet and Bernier 1998). The temperature <strong>of</strong> <strong>the</strong> anode surface (~4000 o C) is higher than <strong>the</strong> cathode surface (~3500 o C) during <strong>the</strong> process, so that carbon atoms evaporate from <strong>the</strong> anode and accumulate on <strong>the</strong> cathode, and <strong>the</strong> length <strong>of</strong> <strong>the</strong> anode decreases with <strong>the</strong> nano particles forming. The voltage and current are <strong>the</strong> parameters <strong>of</strong> <strong>the</strong> arc-discharge method (Zhu, et al. 2002). Fur<strong>the</strong>rmore, <strong>the</strong> conditions and choice <strong>of</strong> catalyst are important (Baddour and Briens 2005) and <strong>the</strong> pressure <strong>of</strong> inert gas has a strong influence on <strong>the</strong> CNTs grown. Even though this technique is simple, inexpensive and <strong>the</strong> most widely used syn<strong>the</strong>sis method, CNT yields can be limited. Moreover, <strong>the</strong> purification <strong>of</strong> CNTs is a problem due to <strong>the</strong>ir location among vaporized debris (Hornyak, et al. 2008, Merkoçi 2006), so it needs to be separated from <strong>the</strong> crude product containing various side products and catalytic metals (Baddour and Briens 2005). The o<strong>the</strong>r drawback <strong>of</strong> this method is that CNTs may be damaged during <strong>the</strong> process. 11
2.3.2. The Laser-Ablation Method The first CNT syn<strong>the</strong>sis by laser-ablation method was reported by Guo (Guo, et al. 1995). This method, which is useful, more simple and powerful for producing CNT, has a similar principle with <strong>the</strong> arc-discharge method. It can be considered as a <strong>the</strong>rmal and a high-energy method (Hornyak, et al. 2008). A typical illustration <strong>of</strong> a laser-ablation apparatus is depicted in Figure 2.10. Figure 2.10. Schematic illustration <strong>of</strong> a laser-ablation apparatus (Source: Ando, et al. 2004) Although MWNT growth is not possible by using <strong>the</strong> laser-ablation method (Baddour and Briens 2005), it can syn<strong>the</strong>size SWNT with <strong>the</strong> highest purity (up to about 90% purity) in comparison with o<strong>the</strong>r techniques (Makita, et al. 2005). The laser-ablation method is performed nearly at 1200 o C in an argon or helium gas environment kept at 500 Torr pressure (Baddour and Briens 2005) in a temperature controlled furnace in which a graphite target is placed in <strong>the</strong> middle <strong>of</strong> a quartz tube (Harris 2007). In comparison with <strong>the</strong> o<strong>the</strong>r vaporization devices, <strong>the</strong> energy density <strong>of</strong> <strong>the</strong> lasers used in this technique is much higher than those, so <strong>the</strong> laser has an appropriate usage for materials with a high melting temperature, such as graphite (Ando, et al. 2004). 12
Page 1 and 2: THE EFFECTS OF OXIDIZERS ON THE DIA
Page 3 and 4: ACKNOWLEDGEMENTS During my master <
Page 5 and 6: ÖZET KİMYASAL BUHAR BİRİKTİRME
Page 7 and 8: TABLE OF CONTENTS LIST OF FIGURES .
Page 9 and 10: LIST OF FIGURES Figure Page Figure
Page 11 and 12: Figure 5.12. The growths with CO2 (
Page 13 and 14: Figure 5.36. Raman spectra
Page 15 and 16: Table 5.12. The amounts of<
Page 17 and 18: first two methods, arc discharge an
Page 19 and 20: Graphite is the mo
Page 21 and 22: preferred nanotube type because <st
Page 23 and 24: Figure 2.7. An illustration <strong
Page 25: Table 2.1. Advantages and disadvant
Page 29 and 30: hydrocarbons (Cui, et al. 2003) wit
Page 31 and 32: 2.3.3.1.2. Thin Film Support Layer
Page 33 and 34: 2.4. Growth Mechanism of</s
Page 35 and 36: (Amama, et al. 2009, Hata, et al. 2
Page 37 and 38: that the small amo
Page 39 and 40: Figure 4.1. The Magnetron Sputterin
Page 41 and 42: the tube as <stron
Page 43 and 44: Table 4.1 (cont.) FeAlO15CNT840 750
Page 45 and 46: their diameter rou
Page 47 and 48: The principle of R
Page 49 and 50: Figure 4.6. Schematic picture showi
Page 51 and 52: 5.1.1. AFM Results There exists a p
Page 53 and 54: a ) Figure 5.2. AFM micrographs <st
Page 55 and 56: c Figure 5.3. (cont.) Element Wt %
Page 57 and 58: Table 5.2. (cont.) FeAlO12CNT771 76
Page 59 and 60: a b c e Figure 5.4. The growths wit
Page 61 and 62: Figure 5.5. (cont.) Count 35 30 25
Page 63 and 64: Due to the lack <s
Page 65 and 66: a c e Figure 5.8. The growths with
Page 69 and 70: Table 5.6 shows that the</s
Page 71 and 72: a c e Figure 5.12. The growths with
Page 75 and 76: In this part, for the</stro
Page 77 and 78:
For FeAlO15 substrate, two differen
Page 79 and 80:
For FeAlO16 substrate, two differen
Page 81 and 82:
e f Figure 5.20. (cont.) Due to <st
Page 83 and 84:
5.2.1.3. CNT Formation at Different
Page 85 and 86:
Count 30 25 20 15 10 5 0 a 5 10 15
Page 87 and 88:
Count 35 30 25 20 15 10 5 0 a CNT 8
Page 89 and 90:
Count 40 35 30 25 20 15 10 5 0 a CN
Page 91 and 92:
Count 45 40 35 30 25 20 15 10 5 0 a
Page 93 and 94:
Count 30 25 20 15 10 5 0 a 5 10 15
Page 95 and 96:
for SWNTs, there i
Page 97 and 98:
Table 5.17. (cont.) FeAlO15 CNT773
Page 99 and 100:
Intensity (a.u.) 2700 1800 900 CNT8
Page 101 and 102:
Intensity (a.u.) 2100 1400 700 CNT9
Page 103 and 104:
whole face. The formed catalyst par
Page 105 and 106:
Diameter Diameter 10 8 6 4 2 0 5 5
Page 107 and 108:
5.4. Statistical Analysis Results A
Page 109 and 110:
Kurtosis value is a descriptor <str
Page 111 and 112:
Very thin Fe films were grown on Si
Page 113 and 114:
REFERENCES Amama, P.B., C.L. Pint,
Page 115 and 116:
Hasegawa, K. and S. Noda. 2011a. Mi
Page 117 and 118:
Makita, Y., S. Suzuki, H. Kataura,
Page 119 and 120:
Vesselényi, I., K. Niesz, A. Siska
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