CHAPTER – 1
1. INTRODUCTION
Carbon nanotubes are allotropes of carbon with cylindrical nanostructure. Constructed with length-to - diameter ratio of up to 132,000,000 :1. These cylindrical carbon molecules have unusual properties, which are valuable for nanotechnology, electronics, optics and other fields of materials science and technology. Nanotubes are members of fullerene structural family. Nanotube’s walls are formed by one-atom thick sheet of carbon called Graphene. The combination of rolling angle and radius decides the nanotube’s properties. They have extraordinary thermal conductivity, mechanical, and electrical properties. There are two types of CNTs: Multi-walled carbon nanotubes (MWNTs) and Single-walled carbon nanotubes (SWNTs). …show more content…
CNTs grow on the catalyst in the reactor, which are collected upon cooling the system to room temperature. In the case of a liquid hydrocarbon (benzene, alcohol, etc.), the liquid is heated in a flask and an inert gas is purged through it, which in turn carries the hydrocarbon vapor into the reaction zone. If a solid hydrocarbon is to be used as the CNT precursor, it can be directly kept in the low-temperature zone of the reaction tube. Volatile materials (camphor, naphthalene, ferrocence etc.) directly turn from solid to vapor, and perform CVD while passing over the catalyst kept in the high-temperature zone. Like the CNT precursors, also the catalyst precursors in CVD may be used in any form: solid, liquid or gas, which may be suitably placed inside the reactor or fed from outside. Pyrolysis of the catalyst vapor at a suitable temperature liberates metal nanoparticles in-situ (such a process is known as floating catalyst method). Alternatively, catalyst-coated substrates can be placed in the hot zone of the furnace to catalyze the CNT …show more content…
Surface modification of CNTs with desired organic, inorganic compounds through covalent or non-covalent bonds represents an emerging area in the research on nanotube-based materials. Such modification can result in a significant enhancement of properties and open up a broad range of novel application perspectives. Non-covalent or covalent functionalization of CNTs can enhance their compatibility and solubility. The non-covalent functionalization of CNTs includes non-covalent coating with surfactants, surface wrapping with long polymer chains, non-covalent adsorption of non-charged polymer chains, etc. the advantage of non-covalent functionalization is that the structure and original properties of CNTs are not changed after modification14. Non-covalent approaches utilize π-stacking or van der Waals interactions between functional species and
1. INTRODUCTION
Carbon nanotubes are allotropes of carbon with cylindrical nanostructure. Constructed with length-to - diameter ratio of up to 132,000,000 :1. These cylindrical carbon molecules have unusual properties, which are valuable for nanotechnology, electronics, optics and other fields of materials science and technology. Nanotubes are members of fullerene structural family. Nanotube’s walls are formed by one-atom thick sheet of carbon called Graphene. The combination of rolling angle and radius decides the nanotube’s properties. They have extraordinary thermal conductivity, mechanical, and electrical properties. There are two types of CNTs: Multi-walled carbon nanotubes (MWNTs) and Single-walled carbon nanotubes (SWNTs). …show more content…
CNTs grow on the catalyst in the reactor, which are collected upon cooling the system to room temperature. In the case of a liquid hydrocarbon (benzene, alcohol, etc.), the liquid is heated in a flask and an inert gas is purged through it, which in turn carries the hydrocarbon vapor into the reaction zone. If a solid hydrocarbon is to be used as the CNT precursor, it can be directly kept in the low-temperature zone of the reaction tube. Volatile materials (camphor, naphthalene, ferrocence etc.) directly turn from solid to vapor, and perform CVD while passing over the catalyst kept in the high-temperature zone. Like the CNT precursors, also the catalyst precursors in CVD may be used in any form: solid, liquid or gas, which may be suitably placed inside the reactor or fed from outside. Pyrolysis of the catalyst vapor at a suitable temperature liberates metal nanoparticles in-situ (such a process is known as floating catalyst method). Alternatively, catalyst-coated substrates can be placed in the hot zone of the furnace to catalyze the CNT …show more content…
Surface modification of CNTs with desired organic, inorganic compounds through covalent or non-covalent bonds represents an emerging area in the research on nanotube-based materials. Such modification can result in a significant enhancement of properties and open up a broad range of novel application perspectives. Non-covalent or covalent functionalization of CNTs can enhance their compatibility and solubility. The non-covalent functionalization of CNTs includes non-covalent coating with surfactants, surface wrapping with long polymer chains, non-covalent adsorption of non-charged polymer chains, etc. the advantage of non-covalent functionalization is that the structure and original properties of CNTs are not changed after modification14. Non-covalent approaches utilize π-stacking or van der Waals interactions between functional species and