What the heck are nanotubes?
Nanotubes are a form of carbon, an allotrope of that element that forms cylindrical nano-sized structures. They have unusual properties and are the darlings of material science. A typical nanotube has a diameter of around one nanometer and a length of millions of times that. They are amazingly stiff and have unbelievable tensile strength and elastic modulus. They have been proposed as the means of creating the conductor wire for an elevator to space. A one square millimeter (0.0016 square inches) carbon nanotube cable can endure a 6422 kilograms-force (62,980 Newtons). They have a tensile strength of 9,100,000 pounds per square inch. This is much higher than steel.
Carbon nanontubes were thought to be the answer to the creation of amazing electronics because they have semiconductor properties. They have been used to create carbon nanotube field-effect transistors that operate at room temperature. They were used to make memory circuits. However the construction of carbon nanotube circuits comparable to CMOS has not yet been accomplished.
Another application is a so-called paper battery. This is made from a paper-thin sheet of cellulose infused with aligned carbon nanotubes, which makes it more efficient because it only has one component and is able to deliver steady power as well as a burst of energy. I don't know why we haven't seen these things in cell phones.
Nanotubes were hyped to be able to make TV displays, much stronger carbon fiber, and sporting equipment. The hype cycle extends from 1991 when Sumio lijima first produced them to the present where we now have a method to make homogeneous nanotubes.
Nanoengineering was once believed to be the greatest new technology ever. It was going to be a revolution and it would change the world forever. What happened to this amazing prediction? The answer is that it got caught up in the inexorable flow of public interest in science and technology. At one time nanotubes were touted as being the salvation of mankind. Now, they have been swamped by the introduction of many new technologies. The truth is that they didn't replace silicon as the main semiconductor material. No one wants to spend the money to make a space elevator. Nano-science has moved on to new ideas involving graphene and other wonder materials. They are more interested in creating nano-sized robotic devices that will be able to repair our bodies from the inside out without surgery and will be able to analyze our health without our bodies being subjected to radiation like wiht MRI or Cat Scans.
Graphene is an allotrope of carbon in a sheet form. Nanotubes are essentially graphene rolled up. They can either single walled or multi-walled. The ultimate use of these amazing forms of carbon will probably be in composite materials and batteries to improve strength and efficiency. The manufacturing has been worked out for nanotubes. One needs three things to make them: a carbon source, metal catalyst particles and heat. Carbon is atomized using an oven, a laser or lab generated lighting. The Catalyst particles collect vaporized carbon atoms and build the hollow tube structure one atom at a time.
Another problem with nanotubes is that they have potential health risk mostly because of their tiny dimensions. The research on this has only just begun. Stay tuned.
Thanks for reading.