Nanomaterials, Nanoparticles and Carbon Nanotubes
Protection from the Environment
There are many fascinating examples of nanotechnology applications in new materials. For example, polymer coatings are notoriously easily damaged, and affected by heat. Adding only 2% of nanoparticulate clay minerals to a polymer coating makes a dramatic difference, resulting in coatings that are tough, durable and scratch resistant. This has implications for situations where a material fits a particular application in terms of its weight and strength, but needs protection from an external, potentially corrosive environment - which a reinforced polymer nanocoating can provide.
Other nanocoatings can prevent the adherence of grafitti, enabling them to be easily removed by hosing with water once the coating has been applied. This has the important knock-on effect of improving urban environments, making them more attractive to bona fide citizens and less encouraging to criminals. These kinds of coatings, invented in Mexico, have been shown to work well in parts of Mexico City. They are currently helping to transform seedy crime-ridden neighbourhoods into increasingly respectable suburbs.
What is Graphene?
Particles at the nanoscale are below the wavelength of visible light, and therefore cannot be seen. Consequently, they can impart new properties while being invisible themselves! Fluorescent nanoparticles, or quantum dots (mentioned earlier) have a whole range of possible applications. They are invisible until 'lit up' by ultraviolet light, and can even be made to exhibit a range of colours, depending on their composition and size.
Such nanoparticles are ideal for crime prevention, where goods can be invisibly 'tagged', preventing counterfeiting; stolen goods can be traced by their invisible 'bar code' and illicit drugs by the fact they have no legal identification. In some countries, cheap agricultural fuel is 'laced' with harmless nanoparticles, making it easy for police to identify a stolen consignment, merely by using ultraviolet light.
Nanoparticles can seem to be quite strange as they have new and unusual properties that are not obvious in the corresponding bulk material. This is because a nanoparticle has a large surface area in relation to its size, and is consequently highly reactive. This is exemplified by the fine grained materials that we use in our daily lives, such as flour, which can become explosive in some circumstances. Applications of nanoparticles include nanoparticulate titanium dioxide for sunscreens, and it also acts as a photocatalytic agent in coatings that can be applied to stay-clean windows, causing the dirt to be oxidized and easily washed away by rain.
Carbon Nanotubes - The Miracle Material of the 21st Century?
Properties of Carbon Nanotubes
Carbon nanotubes are a recently discovered unique material possessing amazing electronic, thermal, and structural properties. They are highly conductive both to electricity and heat, with an electrical conductivity as high as copper, and a thermal conductivity as great as diamond. They offer amazing possibilities for creating future nanoelectronic devices, circuits and computers. Carbon nanotubes also have extraordinary mechanical properties - they are 100 times stronger than steel, while only one sixth of the weight.
These mechanical properties offer huge possibilities, for example, in the production of new stronger and lighter materials for military, aerospace and medical applications. Other applications include lubricants, coatings, catalysts and electro-optical devices.
Application Hurdles and Potential Uses
The cost, purification, separation of nanotube types (Single Walled NanoTubes from Multi Walled NanoTubes), constraints in processing and scaling up and assembly methods are still hurdles for some applications. However, there are already products containing nanotubes on the market, for example, in some tennis racquets nanotubes are used to reinforce the frame and improve the racquet's ability to absorb shocks.
Carbon nanotubes can also be mixed with many different materials such as plastics and textiles, for example to produce lightweight bullet-proof vests. According to engineers at the Fraunhofer Technology Development Group in Stuttgart the greatest potential for creating new products lies in harnessing the electrical properties of lightweight and robust nanotubes to generate heat. Applications range from electric blankets to heatable aircraft wings that no longer ice up, to 'wallpaper' heating for cold walls.