Lighter, Cheaper, Safer, Stronger: Nanotechnology-Enabled Materials


 

There are a number of ways National Nanotechnology Initiative-supported materials research will change the products and infrastructure we use. Not only can nanotechnology-enabled materials improve fuel efficiency for vehicles (from spacecraft to your car) by being lightweight, other such “nanomaterials” can protect conventional materials from corrosion and cracking. Nanoscale materials are helping make products more lightweight, flexible, smart, and damage-tolerant.

Enhancing Performance for Next-Generation Air Vehicles

The Air Force Commercialization Readiness Program (CRP) accelerates the transition of technologies developed under the Small Business Innovation Research/Small Business Technology Transfer programs into real-world military and commercial applications. CRP supports General Nano, LLC, a nanotechnology company formed by University of Cincinnati scientists. General Nano is working to transition its carbon nanotube sheet product to commercial scale. This material is both lightweight and conductive, making it ideal for conductive composites, electromagnetic shielding, thermal management, thermal detectors, and optical devices. These attributes can lead to enhanced performance of next-generation air vehicles.

 Photo courtesy of General Nano LLC | Veelo

Reducing Stress and Corrosion in Concrete

The Federal Highway Administration’s Exploratory Advanced Research Program is funding research on the use of carbon nanotubes and nanofibers in cement. The High-Performance Stress-Relaxing Cementitious Composites for Crack-Free Pavements and Transportation Structures project, conducted at Texas A&M University's Texas Transportation Institute, incorporates nanofibers and nanotubes into construction materials to intentionally introduce cracking on a controlled nano- to micro-scale. This process enables researchers to reduce tensile stresses and mitigate cracking in concrete due to shrinkage, thermal changes, and corrosion.

Carbon nanofibers spanning nano/micro crack in a cementitious composite. Publication No. FHWA-HRT-09-065

Proactively Detecting, Monitoring, and Repairing Bridges

While nanoscale materials help protect and prevent cracking in structures, nanotechnology is also being developed to help engineers proactively detect, monitor, and repair bridge cracks. This is the purpose of the Low-Cost Self-Powered Wireless Nanosensors for Real-Time Structural Integrity Monitoring of Steel Bridges project at the Georgia Institute of Technology, funded by the Federal Highway Administration’s Exploratory Advanced Research Program. Researchers have harnessed state-of-the-art wireless and nano-based technologies to develop a real-time, rugged, low-cost, wireless sensing system that remotely monitors the presence of cracks. The sensing network at the core of this project detects and quantifies multiple small cracks using individual sensors printed on a flexible thin film with inkjet printers and nanoscale conductive inks. The sensors form a low-cost antenna that will be applied to fatigue-prone areas of a bridge and interrogated by a portable reader. When a small crack develops, antennas in the immediate area can measure the crack length based on the frequency shift caused by the deformation.

Substantially Reducing Maintenance Costs for Steel Bridges

The Nation spends an estimated $500 million annually on the maintenance and rehabilitation of steel bridges from damage caused by corrosion. The Federal Highway Administration’s Exploratory Advanced Research Program is funding work at The City College of New York (CCNY), Green Advanced Coatings for Application on Steel Structures and Bridges, to produce coatings that protect steel from corrosion. Nanomaterials, including a polyaniline epoxy and a nanomaterial-enhanced calcium sulfonate alkyd, have been incorporated into novel coating systems to improve corrosion and scratch resistance and to reduce the environmental risk of using zinc as corrosion protection. CCNY researchers continue to explore additives and to conduct further corrosion and weathering studies to determine the realistic expected life of the new coating system. Ultimately, this project will lead to substantially reduced annual maintenance and painting costs for steel bridges.

Providing the Same Level of Protection with Less Material

The National Aeronautics and Space Administration (NASA) funds the development of protective nanotechnology-enabled materials. Aerogels have potential applications as thermal insulation, purification media, catalyst supports, and sensor platforms but traditionally suffer from poor mechanical and environmental durability; conventional silica aerogels are easily crushed and extremely sensitive to moisture. Researchers at NASA Glenn Research Center have developed polyimide aerogels that are 500 times stronger than silica aerogels and can be produced as either rigid solids or flexible thin films. These new aerogels’ thermal insulating ability is five times better than conventional fiberglass. This makes these novel aerogels ideal as thermal insulation in spacecraft because less material is needed to provide the same level of insulation. In addition to their advantageous thermal properties, these nanoporous  Photo courtesy of NASA

aerogels have extremely low dielectric constants, which make them attractive for other applications, including substrates for broadband RF antennas for aircraft. Commercial and military aircraft can have as many as 15–100 antenna systems for communication and navigation, adding significant weight to the aircraft. An aerogel antenna prototype has exhibited 67% higher bandwidth at 3dB and higher maximum gain than a comparable antenna fabricated on a conventional substrate, with 1/10th the mass.

Protecting against Chemical and Biological Threats using New Materials

The Defense Threat Reduction Agency’s Joint Science and Technology Office for Chemical and Biological Defense is funding research on metal organic frameworks (MOFs) that protect against chemical and biological (CB) threats. Computational methods used to predict appropriate MOFs, new synthetic strategies for building and scaling them, and rapid screening methods for predictive selection all contribute to development of novel MOFs targeted as enhanced CB protective materials. Scientists from Northwestern University, Georgia Institute of Technology, UC Berkeley, and Edgewood Chemical Biological Center have significantly contributed to the development of computational tools leading to the design of MOFs that are uniquely tailored to increase protection against CB threats and toxic industrial chemicals beyond that of current carbon-

 Photo courtesy of O. Farha, Northwestern  University

based materials. Researchers have demonstrated the ability to impart reactive sites with catalytic properties, improve chemical and thermal stability, and increase the selective target molecule adsorption into MOFs. This research has also motivated the establishment of a new company, NuMAT Technologies, Inc. NuMAT’s MOFs are tailored to offer high performance in the storage, transport, and separation of gases, particularly methane. MOFs have emerged as a promising CB defense technology through research directed at nanoscale design, demonstrating properties that can be flexibly tuned through modification of their chemical structure. 

Overcoming Challenges for a Breakthrough in Optical Coatings

Rugate filters, a breakthrough in optical coatings, have been developed by Air Force Research Laboratory (AFRL) scientists. The primary significance of rugate filter technology is the ability to tailor a coating to reflect single or multiple bands of light while allowing all other wavelengths to pass through. This technology can be found in a wide variety of applications such as spectroscopy, astronomy, head-up display technology, and optical sensing. The AFRL team overcame two seemingly insurmountable technical challenges: one in materials properties and the other in processing. The first was to successfully predict, via computer modeling, changes in the dispersion of the index of refraction of a composite, taking into account the total range in chemical composition that results from the mixing of two materials into nanoscale structures. The second challenge was to develop a real-time monitoring and control process to successfully fabricate rugate coatings that are deposited at a rate of a few nanometers per minute, while both the physical thickness and index of refraction change simultaneously.