Composites date back to 1500 B.C., when early Egyptians and Mesopotamians mixed straw with mud and formed adobe to build their homes. The straw gave the mixture structure and strength, while the mud bound it together and held the straw in place.
With the discovery of plastic in the early 1900s, modern composites were able to be produced. Fiber Reinforced Polymers (FRP), for example, were created by combining fiberglass with plastic. Military aircraft were the first to use FRP during World War II, and other products, such as boat hulls and surfboards, used the composite after the war.
As we enter the age of nanotechnology, composites will draw on nanomaterials for even stronger and tougher fibers and resins for lighter, stronger, and more durable products.
A nanocomposite is a matrix to which nanoparticles—particles between 1 and 100 nanometers in size (a nanometer being equal to one billionth of a meter)—have been added to improve a particular property of the material. The properties of nanocomposites differ from conventional composite materials due to the exceptionally high surface to volume ratio of the reinforcing phase and/or its exceptionally high aspect ratio.
The reinforcing material can be made up of particles (e.g., minerals), sheets (such as exfoliated clay stacks), or fibers (like carbon nanotubes or electrospun fibers). The area of the interface between the matrix and reinforcement phase(s) is typically an order of magnitude greater than for conventional composite materials.
Nanocomposites are also found in nature. The structure of the abalone shell and bone, for example, is made of microscopic calcium carbonate tiles stacked like bricks and cemented together by a clingy protein substance. The shell is exceptionally strong, and when hit the tiles slide instead of shattering and the protein stretches to absorb the energy of the blow.
Advantages of composites and nanocomposites
The primary advantage currently driving the adoption of composites across various industries is the lightweight properties, which can help industries, such as transportation, create more fuel savings and improve acceleration for airplanes and cars.
Besides weight savings, composites are also non-corrosive, non-conductive, flexible, and deliver low maintenance, long life, and design flexibility. By incorporating nanoparticles into composites, they can be made even stronger, lighter, more durable, more reactive, or become better electrical conductors.
Where are nanocomposites used today?
- Tougher body armor: Researchers at the University of Wollongong (UOW) have used graphene to develop a new composite material which can produce the toughest fibers to date—even tougher than spider silk and Kevlar. The new graphene composite can be wet-spun into fibers and potentially be used in bullet-proof vests. Graphene works just like carbon nanotubes (CNTs), a more common toughening agent, in polymer composites, but is a cheaper material that can be easily produced in large quantities.
- Disease fighting MRIs: By utilizing nanocomposites, Magnetic Resonance Imaging (MRI) technology could become a more powerful tool to detect and fight disease. Scientists at Rice University and The Methodist Hospital Research Institute led a team to create composite particles that can be injected into patients and guided by magnetic fields. These silicon mesoporous particles (SiMPS) may be heated to kill malignant tissues or trigger the release of drugs at the site. By packaging thousands of iron oxide particles—with magnetic cores as small as five nanometers across—inside larger particles, the particles can be manipulated by magnets, provide excellent contrast under MRI, create heat when triggered, and degrade quickly.
- Faster WaveRunners: Yamaha, along with Interplastic, discovered that a nanotechnology-based material, exfoliated clay, could successfully be incorporated into Sheet Moulding Compound and save weight, improve overall performance, and reducing the fuel consumption of its watercraft. Using exfoliated clay, the two companies were able to successfully develop a new nanocomposite called NanoXcel in 2008. NanoXcel provides higher mechanical properties and durability on the hulls and decks of products like the WaveRunner, and allows Yamaha to add improvements to each new model. The new 2014 WaveRunner, for example, is 65 pounds lighter than 2013 models.
- More efficient wind turbines: Advancements are being made in wind turbines as the demand for wind energy industry increases. Bayer MaterialScience LLC has developed a new class of polyurethane turbine blades that are lighter weight with increased strength and stiffness.“Incorporation of a small amount of multi-walled carbon nanotubes improves the fracture of both polyurethane and epoxy composites by as much as 48 percent,” says Dr. Usama Younes, principal scientist with Bayer MaterialScience LLC. “The addition of carbon nanotubes is a viable option to improve the strength of wind turbine blades.”Additional opportunities for nanocomposites in wind turbines include de-icing coatings, self-cleaning coatings, lubricants, new sealants, and power pack improvements.
- Cleaner water: Nanoclay particles are being used to filter water in areas where access to clean drinking water is life threatening. At India’s Institute of Technology Madras, researchers have created a new portable water purification system based on nanoparticle filtration. The system uses nanoparticles to remove not just biological hazards, but toxic heavy metals as well. The two-stage filtration process provides 10 liters of clean water in an hour. The biggest challenge was determining how to deliver a minimal amount of silver ions into the water to be processed, without using electricity. They used a new material that employs silver nanoparticles that are trapped in tiny cage-like structures made of other clay materials. The team hopes this system will provide a low cost, portable water purification device that would provide daily drinking water to a family of four.
With nanocomposites charting new territory, we can expect to see advances in current materials as well as exciting new applications in every type of industry.