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

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ABSTRACT THE EFFECTS OF OXIDIZERS ON THE DIAMETERS OF THE CARBON NANOTUBES GROWN BY CHEMICAL VAPOR DEPOSITION METHOD This <strong>the</strong>sis was focused on growing high quality and small-diameter carbon (C) nanotube (NT) on Fe/Al2O3/SiO2/Si thin film catalyst by ethylene decomposition <strong>the</strong>rmal chemical vapor deposition (CVD) method in <strong>the</strong> presence <strong>of</strong> a weak oxidizer (CO2). Moreover, <strong>the</strong> importance and functional properties <strong>of</strong> <strong>the</strong> oxidizer in pretreatment and CNT growth were determined. At first, it was worked in different growth conditions to examine <strong>the</strong> <strong>effects</strong> <strong>of</strong> CO2 in CNT growth. The main parameters were pretreatment time, CO2 gas flow rates during pretreatment and growth, growth temperature. Pretreatment and growth times were kept at 15 min. each and CO2 introduced 5 and 10 min. during pretreatment stage prior to <strong>the</strong> CNT growth with <strong>the</strong> flow rates 8:2, 10:2, 10:8 and 10:10 sccm, respectively. Additionally, three different growth temperatures; 750 o C, 760 o C and 770 o C were studied. Secondly, pretreatment time was kept at 15 min. The <strong>effects</strong> <strong>of</strong> CO2, which was sent in <strong>the</strong> system at 8:2, 10:2, 10:8 and 10:10 sccm ratios, on density and height <strong>of</strong> <strong>the</strong> catalyst particles were investigated. At last, all catalyst particles and CNTs obtained from <strong>the</strong> experiments were analyzed by several characterization techniques such as AFM, EDX, SEM, STEM and Raman Spectroscopy, respectively. The optimal values <strong>of</strong> amount and introduction time <strong>of</strong> CO2, <strong>the</strong> ratio <strong>of</strong> CO2 in growth to that in pretreatment were identified. Moreover, <strong>the</strong> relation between currently obtained catalyst particles and previously being grown CNTs on <strong>the</strong>m were determined. It was observed that using <strong>the</strong> appropriate amount <strong>of</strong> CO2 in pretreatment and growth process positively affected <strong>the</strong> catalyst sizes and CNT diameter distributions. iv
ÖZET KİMYASAL BUHAR BİRİKTİRME YÖNTEMİ İLE BÜYÜTÜLEN KARBON NANOTÜPLERİN ÇAPLARINA OKSİTLEYİCİLERİN ETKİLERİ Bu tez, Fe/Al2O3/SiO/Si ince film kataliz üzerine, zayıf oksitleyici (CO2) varlığında etilen dekompozisyonu termal kimyasal buhar biriktirme (CVD) tekniği ile kaliteli ve düşük çaplı karbon (C) nanotüp (NT) sentezlenmesine odaklandı. Ayrıca, oksitleyicinin önişlem ve CNT büyütmesi üzerindeki önemi ve işlevsel özellikleri belirlendi. İlk olarak, CNT büyümesinde CO2 gazının etkisinin araştırılması için farklı büyütme koşullarında çalışıldı. Önişlem süresi, önişlem ve büyütme süresi boyunca gönderilen CO2 gaz akış oranları ve büyütme sıcaklığı çalışılan ana parametrelerdir. Deneyler boyunca önişlem ve büyütme süresi 15 dakika olarak seçilmekle birlikte, CO2 gazı bu süre içinde gaz akış oranları sırasıyla 8:2, 10:2, 10:8 ve 10:10 sccm olarak önişlem süresi boyunca 5 ve 10 dakikalık sürelerle sisteme gönderildi. Diğer bir parametre olan sıcaklık ise 750 o C, 760 o C ve 770 o C değerlerinde çalışıldı. İkinci olarak, 15 dakika seçilen önişlem süresince 8: 2, 10: 2, 10: 8 ve 10: 10 sccm oranlarında gönderilen CO2 gazının kataliz parçacıklarının yoğunlukları ve yükseklikleri üzerindeki etkileri araştırıldı. Son olarak, bahsedilen parametreler kullanılarak yapılan deneyler sonucunda elde edilen kataliz ve CNT‟ler sırasıyla AFM, EDX, SEM, STEM ve Raman Spektroskopi gibi çeşitli karakterizasyon teknikleriyle analiz edildi. CO2 gazının optimal miktarı ve gönderme süresi ile önişlem ve büyütme evrelerindeki oranı belirlendi. Elde edilen kataliz parçacıkları ve daha önce bunlar üzerlerine büyütülen CNT‟ler arasındaki ilişki değerlendirildi. Önişlem ve büyütme işlemlerinde uygun miktarda kullanılan CO2 gazının kataliz büyüklüğü ve CNT çap dağılımlarını olumlu etkilediği gözlendi. v
Page 1 and 2: THE EFFECTS OF OXIDIZERS ON THE DIA
Page 3: ACKNOWLEDGEMENTS During my master <
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 and 26: Table 2.1. Advantages and disadvant
Page 27 and 28: 2.3.2. The Laser-Ablation Method Th
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
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a b c e Figure 5.4. The growths wit
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Figure 5.5. (cont.) Count 35 30 25
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Due to the lack <s
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a c e Figure 5.8. The growths with
Page 67 and 68:
Page 69 and 70:
Table 5.6 shows that the</s
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a c e Figure 5.12. The growths with
Page 73 and 74:
Page 75 and 76:
In this part, for the</stro
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For FeAlO15 substrate, two differen
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For FeAlO16 substrate, two differen
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e f Figure 5.20. (cont.) Due to <st
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5.2.1.3. CNT Formation at Different
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Count 30 25 20 15 10 5 0 a 5 10 15
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Count 35 30 25 20 15 10 5 0 a CNT 8
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Count 40 35 30 25 20 15 10 5 0 a CN
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Count 45 40 35 30 25 20 15 10 5 0 a
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Count 30 25 20 15 10 5 0 a 5 10 15
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for SWNTs, there i
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Table 5.17. (cont.) FeAlO15 CNT773
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Intensity (a.u.) 2700 1800 900 CNT8
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Intensity (a.u.) 2100 1400 700 CNT9
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whole face. The formed catalyst par
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Diameter Diameter 10 8 6 4 2 0 5 5
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5.4. Statistical Analysis Results A
Page 109 and 110:
Kurtosis value is a descriptor <str
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Very thin Fe films were grown on Si
Page 113 and 114:
REFERENCES Amama, P.B., C.L. Pint,
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Hasegawa, K. and S. Noda. 2011a. Mi
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Makita, Y., S. Suzuki, H. Kataura,
Page 119 and 120:
Vesselényi, I., K. Niesz, A. Siska
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