Nanotechnology will soon become a household word. Expected to fundamentally alter many sectors of manufacturing over the long-term, the technology, over the mid-term, will change the materials consumers and businesses use everyday. Until now, the high costs of nanomaterials have been one of the barriers to market entry.
A new breed of nanomaterials eliminates this problem and offers potential for greater performance in a wide range of applications and markets including renewable energy, aerospace, automotive, marine, electronics, construction, medical and telecommunications. Called nano-graphene platelets (NGPs), the newcomer is a cost effective yet high quality alternative to carbon nanotubes (CNT) and carbon nanofibers (CNF).
Carbon nanotubes (CNT), discovered in 1991, promised enhanced thermal, mechanical and electrical performance properties. But the material stuck together in clumps and was extremely difficult to form into composites. CNTs and CNFs are effective materials for many enabling nanocomposite, molecular electronic, and medical applications. However, even the moderately priced CNF remains too expensive to be used as a substitute material for carbon black and milled carbon fiber in high volume polymer composite and battery applications. Processing of nanocomposites with high CNT or CNF filler concentrations can also be problematic due to the high melt viscosity.
An NGP is a nanoscale platelet composed of one or more layers of graphene plane (with a thickness of 0.34 nm to 100 nm). In a graphene plane, carbon atoms occupy a two-dimensional hexagonal lattice. These carbon atoms are bonded together through strong covalent bonds lying on this plane. In the c-axis direction, several graphene planes may be weakly bonded together through van der Waals forces. Single-sheet NGPs have demonstrated a much higher thermal conductivity and twice the specific surface areas when compared with single-walled CNTs.
Because NGPs can be mixed with different materials and comes in different forms, the material offers manufacturers interested in using it a flexible option for a wide range of applications. The nano-graphene material is able to reinforce polymer materials including thermoset, thermoplastics and elastomers. Melt and solution processing techniques typically used for plastics such as injection molding and extrusion can be used to process NGP-polymer composites. These processes don't require special equipment. Something as conventional as a twin-screw extruder can be used to blend an NGP-polymer recipe.
NGPs are available in several forms from NGP powders and nano-intermediates (NGP dispersions and master batches), to NGP-enhanced nanocomposites. NGPs can also be mixed with other nano materials such as carbon nano-fibers (CNFs), carbon nanotubes (CNTs), and nano clay platelets, to produce hybrid nanocomposites. .
Testing of NGPs and NGP nanocomposites have demonstrated the following features and benefits:
* The highest thermal conductivity known today (up to ~ 5,300 W/(mK), five times that of copper, a capability that provides faster thermal dissipation
* Electrical conductivity similar to copper yet the material's density is four times lower, resulting in lighter weight components
* Fifty times stronger than steel with a surface area twice that of CNTs
* Chemical bonding to a range of resins for tailored composite properties
* Readily forms reactive oxygen, sulfur, and nitrogen sites on graphene plate edges or surfaces
* Capable of removing heavy metals and radionucleides from wastewater and ground water
* Highly adsorptive for organic materials
* Ultra-high Young's modulus (approximately 1,000 GPa) and highest intrinsic strength (~ 130 GPa estimated)
* Exceptional in-plane electrical conductivity (up to ~ 20,000 S/cm)
* High specific surface area (up to ~ 2,675 m2/g)
* Low density (2.25 g/cm3)
* Outstanding resistance to gas permeation.
* Readily surface-functionalizable
* Dispersible in many polymers and common solvents
* Available in a wide range of platelet lengths (typically 1-20 m) and thicknesses (approximately 0.34 nm to 100 nm).
* High loading in nanocomposites
Single-layer and multi-layer graphene structures have been isolated from partially graphitized polymeric carbons obtained from a polymer to successfully produce nano graphene sheets. The availability of processable graphene sheets in large quantities is also an essential ingredient in the exploitation of composite and other applications. Several processes for mass-producing nano graphene material have been developed with the capability to produce up to three tons per year.
NGPs are especially suited to Lithium Ion (Li-ion) battery, fuel cell and conductive composite applications ' initiatives that continue to gain national interest. Further development of Li-ion battery technology is crucial to advancing the transition from gasoline-powered to electric vehicles. The technical challenge has been the inability to maintain electron path continuity in the electrode during repeated charge-discharge cycles. The approach of mixing Silicon (Si) nano particles with carbon to solve this problem has been pursued by researchers worldwide for over a decade, but with limited success. By mixing NGPs with silicon, an innovative NGP-SI composite has been created that maintains its structural integrity throughout multiple charge-discharge cycles.
Because NGP nanocomposites can deliver lower cost, high conductivity, low weight, small volume (thin plate), high resistance to gas permeability, high corrosion resistance, and good mass production capability, the result is a much higher output per fuel cell at a significantly lower fuel cell cost while improving system reliability. The NGP nanocomposite-based bipolar plate technologies also support current industry-wide efforts to reduce the cost, weight, and size of fuel cell systems in order to achieve successful commercialization of Proton Exchange Membrane (PEM) fuel cells.
Airlines have posted a $2 billion annual loss due to lightning-related delays. Insurance industry losses total $5 billion annually. More than 50 percent of military aircraft weather-related in-flight mishaps are caused by lightning. Copper mesh is considered an alternative that has proven effective but the metal is heavy and hard to work with.
Improved EMI shielding offers a solution to avionic manufacturers being pressured to allow personal electronic devices (PED) in the airplane cabin and for new airplanes filled with highly sensitive antennae ' open sources to internal avionic equipment. EMI shielding also allows for defense against emerging weapons technologies such as electromagnetic pulse. Both the aerospace market and applications with ground-based and non-ground-based objects also require next generation lightning strike protection. Current materials used for this protection are made of metals and add significantly to the weight of aircrafts. With an electrical conductivity similar to copper yet with a density four times lower, NGPs offer a cost effective, lighter weight option to overcome these market challenges. The nano graphene material can also meet aerospace needs for thermal management, radio frequency interference (RFI) and electrostatic discharge.
The author of this piece, Dr. Bor Jang, is CEO and co-founder of Angstron Materials LLC, a nanotechnology manufacturing company based in Dayton, Ohio. Angstron developed nano-graphene platelets (NGPs) and claims to be the first company to isolate single-layer and multi-layer graphene structures and successfully produce nano-graphene sheets in large quantities.
For more information about the company call 937-672-7100 or visit http://angstronmaterials.com/
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