The Direct Growth of Carbon Nanotubes and Its Substrate Dependence

<p>The unique combination of light weight, small dimensions, structural diversity, excellent mechanical strength and remarkable electronic properties make carbon nanotubes an attractive field of discovery for a wide range of applications, from reinforcing materials to molecular sensing. The immediate problem is in reliably and reproducibly fabricating carbon nanotubes and nanotube arrays with a certain exclusive structure. The reason for this is the large number of parameters integral to nanotube growth. This thesis describes the effect of several synthesis parameters - including temperature, catalyst, and water addition - on the growth of carbon nanotubes by a thermal chemical vapour deposition method. In all instances, multi-walled nanotubes were the only carbon nanotube products observed. The chemical vapour deposition method employed here involves hexane as a volatile carbon precursor and ferrocene as a floating catalyst. The hexane is introduced into the system by passing a stream of nitrogen carrier gas through a bubbler containing the carbon precursor, while the ferrocene catalyst is positioned inside the working tube where it can evaporate gradually. The products of this method are large, vertically aligned arrays of clean multi-walled nanotubes. The second part of this thesis describes the role of the supporting layer in affecting the growth of these extended nanotube arrays. A number of substrates have been examined - both conducting and non-conducting - and the products from these were analysed. It was found that all non-conductive, metal oxide substrates used - these included quartz, alumina, glazed porcelain, Pythagoras, and also fluorite - produced extended fields of carbon nanotubes. Conversely, many conductive substrates - including nickel, molybdenum, glassy carbon, highly ordered pyrolitic graphite and nickel-iron-silicon metal alloys - produce only small amounts of carbon nanotubes. This difference is likely caused by the deactivation of the iron catalyst at high temperature due to diffusion into the substrate surface.</p>

The Direct Growth of Carbon Nanotubes and Its Substrate Dependence

<p>The unique combination of light weight, small dimensions, structural diversity, excellent mechanical strength and remarkable electronic properties make carbon nanotubes an attractive field of discovery for a wide range of applications, from reinforcing materials to molecular sensing. The immediate problem is in reliably and reproducibly fabricating carbon nanotubes and nanotube arrays with a certain exclusive structure. The reason for this is the large number of parameters integral to nanotube growth. This thesis describes the effect of several synthesis parameters - including temperature, catalyst, and water addition - on the growth of carbon nanotubes by a thermal chemical vapour deposition method. In all instances, multi-walled nanotubes were the only carbon nanotube products observed. The chemical vapour deposition method employed here involves hexane as a volatile carbon precursor and ferrocene as a floating catalyst. The hexane is introduced into the system by passing a stream of nitrogen carrier gas through a bubbler containing the carbon precursor, while the ferrocene catalyst is positioned inside the working tube where it can evaporate gradually. The products of this method are large, vertically aligned arrays of clean multi-walled nanotubes. The second part of this thesis describes the role of the supporting layer in affecting the growth of these extended nanotube arrays. A number of substrates have been examined - both conducting and non-conducting - and the products from these were analysed. It was found that all non-conductive, metal oxide substrates used - these included quartz, alumina, glazed porcelain, Pythagoras, and also fluorite - produced extended fields of carbon nanotubes. Conversely, many conductive substrates - including nickel, molybdenum, glassy carbon, highly ordered pyrolitic graphite and nickel-iron-silicon metal alloys - produce only small amounts of carbon nanotubes. This difference is likely caused by the deactivation of the iron catalyst at high temperature due to diffusion into the substrate surface.</p>

Influence of Pyrolysis Parameters Using Microwave toward Structural Properties of ZnO/CNS Intermediate and Application of ZnCr2O4/CNS Final Product for Dark Degradation of Pesticide in Wet Paddy Soil

Pesticide is a pollution problem in agriculture. The usage of ZnCr2O4/CNS and H2O2 as additive in liquid fertilizer has potency for catalytic pesticide degradation. Colloid condition is needed for easy spraying. Rice husk and sawdust were used as carbon precursor and ZnCl2 as activator. The biomass–ZnCl2 mixtures were pyrolyzed using microwave (400–800 W, 50 min). The products were dispersed in water by blending then evaporated to obtain ZnO/CNS. The composites were reacted with KOH, CrCl3·6H2O, more ZnCl2, and little water by microwave (600 W, 5 min). The ZnCr2O4/CNS and H2O2 were used for degradation of buthylphenylmethyl carbamate (BPMC) in wet deactivated paddy soil. TOC was measured using TOC meter. The FTIR spectra of the ZnO/CNS composites indicated the completed carbonization except at 800 W without ZnCl2. The X-ray diffractograms of the composites confirmed ZnO/CNS structure. SEM images showed irregular particle shapes for using both biomass. ZnCr2O4/CNS structure was confirmed by XRD as the final product with crystallite size of 74.99 nm. The sawdust produced more stable colloids of CNS and ZnO/CNS composite than the rice husk. The pyrolysis without ZnCl2 formed more stable colloid than with ZnCl2. The ZnCr2O4/CNS from sawdust gave better dark catalytic degradation of BPMC than from rice husk, i.e., 2.5 and 1.6 times larger for 400 and 800 W pyrolysis, respectively.