Me1d02 Products and Materials in Modern Society with English Writing Requirements

ME1D02 Products and Materials in Modern Society

with English Writing Requirements

([Dr. Haihui RUAN])

[Final] Submission:

[Carbon Nanotube]

Abstract

        In 1991, Mr Iijima found a hollow carbon roll though Electron Microscopy, which called carbon nanotube. Carbon nanotube has a good Mechanical Properties, chemical properties. The engineers are using those properties, to invent difference product. Carbon nanotube accelerates the technology development; in this article has separate in four parts:

1. Background information of Carbon nanotube
2. Synthesis and characterization of carbon nanotube
3. Properties of Carbon nanotube
4. Application and Development of Carbon nanotube

Introduction

1. Nanotechnology

        The concept of Nanotechnology was started in 1959 by physicist Richard Feynman in his talk “There’s Plenty of Room at the Bottom”, that described the atom structure. Until now nanotechnology not just a concept, but also apply in our daily life, such as umbrella, tennis ball. The dimension size of nanotechnology is between 1 and 100 nanometers. In this report, I will discuss one of material come from nanotechnology; it called “Carbon nanotube”. It can apply in biomedicine, energy storage technology and so on.  

1. Discovery of Carbon nanotube

Carbon is the one of the common element in nature. In the past, human only discovered three kind and structure of carbon; they are diamond, amorphous carbon, and graphite. The Discovery of Fullerene (C60) pushed the research of carbon in a new stage in 1985. In 1991, Mr. Iijima found the carbon nanotube in soot of graphite electrodes during an arc discharge and HRTEM. The carbon nanotube has further changed the physics, chemistry and material science.

1. Carbon nanotube [pic 1]

        Carbon nanotubes are long cylinders of 3-coordinated carbon, slightly pyramidalized by curvature from the pure sp2 hybridization of graphene, toward the diamond-like sp3. sp3 meant each carbon particle connect with four carbon particle. However, carbon nanotube is connected with three carbon particle and then from a hexagon carbon structure. Infinitely long in principle, a perfect tube is capped at both ends by hemi-fullerenes, leaving no dangling bonds. (Figure 1)

        For each carbon nanotube they have three kind of forming structure, they are Armchair, Chiral and Zigzag (Figure 2). [pic 2]

According to the number of layer of carbon [1], the carbon nanotube can be separated into two kinds of wall tubes structure. The first one is called “single-wall tubes (SWNT)”, it just a simple sharp of nanotube. The another one is called “Multiwall tube (MWNT)”, it has more constrain and completed structure than SWNT, because the length of the wall between each other should be about 0.347 nm, and do not have same form in each layer. For a common MWNT is formed a hollow cylinder by several nanotube. However, the research team of X.F.Zhang found the structure of MWNT not just in hollow cylinder; it can become a hexagon and scroll structure which was found by S.Amelinckx.  

Synthesis and characterization of carbon nanotube materials [2]

        The Synthesis of carbon nanotube have three method, and they are arc-discharge methods, laser ablation methods, chemical vapor deposition methods.

1. Arc-discharge methods [pic 3]

        The principle of Arc-discharge methods is the graphite anode part may product a high current and heat, so that the graphite may vaporize, and form the carbon nanotube at the cathode side.

Disadvantage

The process do not so many nanotube, also numerous of carbon nano particle and waste may be produced. The arc-discharge may have lots of factor many affect the quality of carbon nanotube. For example, the process may generate too much heat, that may damage the structure of nanotube.

1. Laser ablation methods

A graphite with some metal catalyst are shot by a continous and high pulse of UV light or visible laser, and them the graphite may produce the carbon nanotube.  Laser ablation methods should be working in a noble gas container, because the noble gas can maintain a low temperature during the process, also the noble gas is the main element for combining the metal particle and graphite that produce some liquid. After the isolation of the liquid, the carbon nanotube may be come out. [pic 4]

Disadvantage

        The process should perform in the noble gas environment.

1. Chemical vapor deposition methods

        Chemical vapor deposition methods are the comman methods that produce the carbon nanotube. Six or less than six Carbon compound may mainly use in this process such as CO2. Generating heat energy, the carbon compound may break down to form some carbon particle. And then, carbon particle may stick on the nano-catalyst particle. After the catalysis with Transition metal the carbon nanotube may appear.

Disadvantage[pic 5]

        In this process, difference heat producing location may affect the result collected, so that the scientists invent four methods to prevent the error. They are fluidized-bed reactor catalyzed pyrolysis, hot filament chemical vapor deposition, plasma-enhanced hot filament chemical vapor deposition and

Properties

        At the end of twentieth century, different counties are promoting the numerous opportunities about carbon nanotube. It is because nanotube is the key of nanotechnology also it contains great potential properties. The new materials seem likely that the first large-scale application for nanotubes will arise from multi-functionality.

1. Mechanical Properties

        “Since the carbon nanotube is formed by each carbon particle that contain with three carbon particles thought the covalent bond. Also the carbon nanotube is connect by the carbon- carbon bonds, which is stiffer and stronger than any known substance and demonstrate a remarkable “bend, don't break”, there though carbon nanotube can give a good mechanical properties” [3]. The tensile strength of is about 50- 200 GPa and the Young’s modulus of a cantilevered individual MWNT was measured as 1.0 to 1.8 TPa from the amplitude of thermally driven vibrations observed in the TEM. Although it acts an external force on the nanotube, it can be reform after the force release in a few second.