Carbon nanotubes are unique nanostructures that have remarkable electrical, thermal and mechanical properties.
They were discovered in the early 1970 by Morinobu Endo, as part of his PhD studies at the University of Orleans in France. He grew carbon fibers about 7 nm in diameter using a vapor-growth technique, but these filaments were not recognized and were not studied systematically.
In 1997, NEC Laboratory researcher Sumio Iijima, observed carbon nanotubes using high-resolution transmission electron microscopy.
An ideal carbon nanotube is a hexagonal network of carbon atoms, rolled to make a seamless cylindrical structure. This cylinder can approximately be ten microns long with each end ‘capped’ with a half fullerene molecule.
Nanotubes are cylindrical structures based on the hexagonal lattice of carbon atoms that forms crystalline graphite. They are classified as single-walled and multi-walled carbon nanotubes. Single-walled carbon nanotubes are the primary structures for multi-walled carbon nanotubes, which are a series of single-walled tubes arranged in a concentric fashion.
The unique properties of carbon nanotubes are a result of the quantum confinement of electrons, perpedicular to the length-wise nanotube axis.
Due to this quantum confinement, the electrons can move along the nanotube axis and because of their extraordinary properties they can be used in almost any field ranging from electronic displays to materials and life sciences.
Carbon nanotubes are polymers of pure carbon and can be reacted and manipulated using the tremendously rich carbon chemistry.
They are also molecularly perfect, which makes them free of property degrading flaws. Since they are probably the best electron-field emitters, they can be used in flat panel field emission displays. Plastics have often been developed as an alternative to metals, but they lack the electrical properties that metals possess. In fact, plastics are well known as good insulators.
To improve upon this, plastics are loaded with fillers such as graphite and carbon black, which makes it heavy and which degrades their structural properties.
Carbon nanotubes can reduce the ratio of loading and thereby make the plastic conductive as well as lightweight. Carbon nanotube-enhanced plastics are used for EMI/RFI (Electromagnetic interference/radio frequency interference) shielding and as antistatic materials.
They are also being used as thermal conductive materials, in which fast dissipation of heat is required.
Nanobase resin
A nanobase resin is a very global term that refers to any thermosetting resin filled with any nanoparticles such as carbon nanotubes, nanoclays, nanosilica or block copolymer. It is worth noting that this term is dedicated to resins filled with well disperserd nanoparticles, a key factor to performance enhancement. The curing (or crosslinking) of these nanobase resins will lead to a nanocomposite.
Nanobase system
As for conventional product (i.e. without nanoparticles), a system (or formula) is most often made of two parts: part A and part B.
Part A is the resin. Part B is the hardener (or crosslinker). Part A and Part B are mixed together to enable the crosslinking reaction (or curing) to yield the final material.
To sum up, when nanoparticles are integrated in an epoxy building block, this results in a nanobase resin. This nanobase resin is then formulated with additives to give the Part A of the nanobase formula.
Nanoclays
The most widespread nanoclays are found in the shape of about 1 nm thick platelets. The other dimension ranges from 50 nm up to several microns. Chemically speaking, these layered platelets are made of a well-structured arrangement of silicon atoms and magnesium or aluminium hydroxide. Nanoclays family encompasses several phyllosilicates such as montmorillonite, hectorite and saponite to name a few. In the pristine state, nanoclays are hydrophilic and thereby fully incompatible with most of the polymers. This drawback is overcome by a judicious chemical modification that makes the nanoclays and the organic polymer more similar.
Due to their nanometer scale size, nanoclays are excellent candidates for polymer mechanical reinforcement. Moreover, their aspect ratio makes them fully interesting for other properties such as flame retardancy. As for other nanoparticles, these benefits arose from a successful integration.
Nanosilica
Nanosilica are spherical particles having a diameter less than 100 nm. Chemically speaking, they are made of silicon and oxygen atoms.
Although silica was up to now widely used in polymer formulation as additives to master the system rheology and enhance mechanical properties of some particular polymers, nanosilica throws the door wide open new applications.
Silica synthesis evolved during last decades from thermal hydrolysis of silane resulting in not easily dispersible aggregated nanoparticles to sol-gel process resulting in well-defined nanoparticles highly compatible with the targeted matrix.
Processes enabling chemically tuned and well integrated particles together with the nanoscale effect are a highway to high performance nanocomposite materials having enhanced mechanical properties and excellent surface properties.
Nanometer
Nanometer is a unit of length. 1 nanometer = 10-9 meter. For example, a carbon nanotubes has a diameter which is 1/100 000 the one a hair.
Nanoparticle
A nanoparticle is defined by its dimensions. One can consider a particle as nano as far as one of its three dimensions is below 100 nm. For example, nanoclays have a thickness of about 1 nm and carbon nanotubes have a diameter of several nanometers.
Crack propagation resistance
This measure gives access to the toughness of the material. As crack propagation is involved in several failure mechanisms such as fatigue, this data is of prime importance. It is worth noting that nanocomposites have impressive crack propagation resistance properties.
