What is nanotechnology?(1):> 1. The Significance of the Nanoscale(2):>2. New Materials: Nanomaterials(3):>2.1 Nanomaterials(4):>3. Nanomaterial Science(5):>3.1 Nanoscale in Two Dimensions(6):>3.2 Nanoscale in Two Dimensions(cont.)(7):>3.3 Nanoscale in Three Dimensions(cont.)(8):>3.4 Nanoscale in Three Dimensions(cont.)
3.2 Nanoscale in Two Dimensions
Two dimensional nanomaterials such as tubes and wires have generated considerable interest among the scientific community in recent years. In particular, their novel electrical and mechanical properties are the subject of intense research.
a) Carbon NanotubesCarbon nanotubes (CNTs) were first observed by Sumio Iijima in 1991. CNTs are extended tubes of rolled graphene sheets. There are two types of CNT: single-walled (one tube) or multi-walled (several concentric tubes). Both of these are typically a few nanometres in diameter and several micrometres to centimetres long. CNTs have assumed an important role in the context of nanomaterials, because of their novel chemical and physical properties. They are mechanically very strong (their Young’s modulus is over 1 terapascal, making CNTs as stiff as diamond), flexible (about their axis), and can conduct electricity extremely well (the helicity of the graphene sheet determines whether the CNT is a semiconductor or metallic). All of these remarkable properties give CNTs a range of potential applications: for example, in reinforced composites, sensors, nanoelectronics and display devices.Watch an animation of various nanotubes and a fullerene (buckyball):
CNTs are now available commercially in limited quantities. They can be grown by several techniques. However, the selective and uniform production of CNTs with specific dimensions and physical properties is yet to be achieved. The potential similarity in size and shape between CNTs and asbestos fibres has led to concerns about their safety.
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