This module contains several VR based simulations developed in Virtual Reality Modeling Language (VRML) 2.0 for learning purposes. Snapshots of some of the VR based simulations - Single Walled Nano-tubes (SWNT), Multi Walled Nano-tubes (MWNT), Nano gears, and Laser ablation technique are shown below. Information sources for the creation of this module include books (Timp, G. (1999), Nanaotechnology, Lucent Technologies, ISBN 0-387-98334-1. Springer Verlag New York Inc.), research papers (Daenen, M., de Fouw, R. D., Hammers, B., Janssen, P. G. A., Schouteden, K., Veld, M. A. J. (February, 2003). “The Wondrous World of Carbon Nanotubes: a review of current nanotube technologies”, Eindhoven University of Technology), articles and other Internet sites (http://grin.hq.nasa.gov/ABSTRACTS/GPN-2000-001535.html ).
Nano-tubes are generally hollow cylindrical structures made up of carbon atoms having high strength and low weight so that they can be used for manufacturing of satellites and spacecrafts. They exist in various shapes - cylinders, spheres, cones, tubes and also complicated shapes.
Single Walled Nano-tubes (SWNT) can be considered as long graphene sheets. Nano-tubes generally have a length to diameter ratio of 1000 so they can be approximated as one-dimensional structures.
VRML model of Single Walled Nano-tubes created at VEEL
Multi Walled Nano-tubes (MWNT) can be considered as a collection of concentric SWNTs with different diameters, lengths, and properties.
VRML model of Multi Walled Nano-tube created at VEEL
Carbon nano-tube synthesis
Carbon nano-tubes are generally produced by three main techniques:
1. Arc discharge
In this synthesis technique, vapor is created by an arc discharge between two carbon electrodes with or without catalyst. Nano-tubes self-assemble from the resulting carbon vapor. This method generally produces large quantities of impure material.
2. Laser ablation
The model below shows the Laser ablation technique, in which a pulsed or continuous Nd YAG laser impinges on a graphite target placed in an oven at 1200º C and 500 Torr. The graphite target gets vaporized to form small carbon molecules and atoms which condense to form single walled nano-tubes held together by van der Waals forces. SWNT are produced if the target consists of graphite mixed with cobalt, nickel or iron. A pure graphite target yields MWNT.
VRML animation of Laser ablation (before self assembly) created at VEEL
VRML animation of Laser ablation (after self assembly) created at VEEL
3. Chemical vapor deposition
Chemical vapor deposition (CVD) results in MWNTs or poor quality SWNTs. The SWNTs produced with CVD have a large diameter range, which can be poorly controlled.
Nano-gears
Nano-gears below are modeled using VRML 2.0 to demonstrate that gears constructed from nano-tubes may replace the current manufacturing processes.
VRML model of Nano Gears created at VEEL
The source for some of the descriptions in this page is given below