Nanotechnology deals with the understanding, control and manufacture of matter in the nanoscale regime, usually between 1 nm to 100 nm, and exploiting them for a useful application. At this length scale unique properties and phenomena arise as a result of increased surface-to-volume ratio and dominance of quantum mechanical effects. Nanotechnology applications are affecting almost all aspects of human life – food, clothing, medicine, communication and so on. Some of them, like anti-bacterial textiles, self-cleaning coatings, bio-sensors etc, are available commercially.
This technology will have many potential applications in the maritime environment including materials (including energetic materials, information science, biology and multidisciplinary efforts.
It is envisioned the Navy will benefit in many applications areas that take advantage of the potentially superior properties of nanomaterials. Innovations in nanomaterials can improve robustness of vessel equipment, delivering more fuel efficiency and bringing down operating costs. Nano-enabled marine technologies promise effectual functionality in all kinds of vessels ranging from yatchs, cruise ships, and container vessels to aircraft carriers operated by the Navy.
Desirable functionality, such as environmental sensing, self-cleaning, self-healing, enhanced electrical conductance and shape modification, is anticipated through the development of nano-materials, and, in turn, will deliver performance benefits in the commercial shipping, naval and ocean space industries.
Examples include fracture resistance in nanostructured coatings for greater lifetimes; scattering of multiple phonon frequencies providing enhanced thermal management materials and thermoelectric devices; reduced diffusion distances in electrodes and cell architectures enabling simultaneous increases in battery power and energy densities; high surface area particles for sensing and novel catalyst applications; and, enhanced electron transport in nanowire composites providing potential for controlled dielectric constants.
Any marine vessel which is intended for any function ranging from weapon carrying platform, cargo carrier to research vessel has to have sea worthy structure. Currently heavy fibreglass or aluminium based hulls are designed which l require larger, heavier engines and in turn a spiral of additional weight in support structures. The use of Naonomaterials can lead to lightweight hull can also allow the selection of smaller engines while still delivering the desired range/speed characteristics required.
Researchers in United States have found that Nano Aluminium Composite a superior material for tough and lightweight structural applications. This nano-treated aluminium can be an extremely efficient substitute for making aluminium hulls, aluminium superstructures and various other ship structures where light weight and high strength are highly desirable.
It is made through the process known as cryomilling nano aluminium is combined with the standard aluminium. This process leads to the formation of nanoscale aluminium oxide and nitride particles, which makes the material stronger and stabilizes the microscopic orientation and structure. The tests conducted on the yield and tensile strength have shown improvements of 150 percent in strength over untreated aluminium.
Carbon nanotubes (CNTs) are hollow cylindrical tubes formed by rolling a sheet of carbon atoms arranged in a hexagonal ring, they are also extremely light weight. They exhibit extraordinary strength and unique electrical properties, at the individual tube level: 200X the strength and 5X the elasticity of steel; 5X the electrical conductivity, 15X the thermal conductivity and 1,000X the current capacity of copper; at almost half the density of aluminum.
Unmanned vessels made with CNTs can operate remotely and for thousands of miles before needing to refuel due to their light weight nature. CNTs can be impregnated into polymers for explosion proof structures, safety harnesses and electromagnetic shielding. These can be used for various riggings and load bearing applications.
A significant amount of the fuel consumed by marine vehicles is expended to overcome skin-friction drag resulting from turbulent boundary layer flows. Hence, a substantial reduction in this frictional drag would notably reduce cost and environmental impact. Superhydrophobic surfaces (SHSs), which entrap a layer of air underwater, have shown promise in reducing drag in small-scale applications and/or in laminar flow conditions.
New research out of UBC Okanagan have created hydrophobic surface using mixture of nanoparticles and plastic, that could help boats travel through water faster and not get wet. “This technology has been around for at least five years, and people had shown that these type of surfaces can reduce drag on boats, but only in steady, calm water. “These coatings also introduce roughness, so no one really knew if you had roughness, could you actually achieve lower drag? What we figured out is you can still reduce drag if you minimize the size of these particles while still keeping as much air trapped at the surface as possible.”
An important concept can be the usage of clay nanoparticles comprising of aluminosilicates popularly known as ‘nanoflakes’. Added to composites, the nanoflakes can enhance flame retardance, anti-ultraviolet and anti-corrosive nature of a material.
A research indicates, an addition of 5 per cent of the mass fraction of these nanoparticles in composite fibres shows an increase by 40 per cent in tensile strength and 60 per cent higher flexural strength. In the shipping industry, the modified materials can be used for making robust sails, boat hulls and additives for paints.
The trend with all metallic, ceramic, polymeric and composite materials is to achieve improved capabilities such as strength, toughness, durability and other useful functionalities by designing it at the nano-scale and harnessing those properties in large structures.
It has been witnessed that when metal oxide nanoparticles of titanium, aluminium, zinc and magnesium are added to fibres and paint coatings, the antimicrobial ultraviolet blocking and self-decontaminating functions surge. Oxides of these metals can be used for making better ship structures
Application of nano-size particulate on flame-retardant coatings can improve fire retardance of the paint films. This is because the flame spread rate reduces with an increase in weight percentage of nanocomposites. This leads to fire redundancy for the coatings with an increased reaction time for fire fighting. This can improvise fire safety for the coatings applied inside the ship compartments.
Similarly, nanocellular foam structure, in materials, results in the reduction of weight, good thermal insulation and high cracking resistance without affecting the mechanical strength of the structure. While constructing ships, this can be an advantage in providing better insulation to materials which are extensively used in the outfitting.
Enhanced functionality using Nanocoatings
The marine environment is one of the harshest environments any structure could be subjected to in its lifecycle. Corrosion poses a daunting challenge for all marine structures. High strength, corrosion resistant coatings are another military use for nanotechnology in order to improve durability, corrosion resistance and reliability. These materials can sense damage or corrosion and automatically initiate repair of some damage. The potential is also there for coatings to change colour when required.
Ultra Violet Resistant Coatings: The photochemical degradation caused by ultra violet (UV) rays is a common mode of failure of most of the coating systems. This causes the oxidation and decomposition of polymer films along with inorganic or organic pigments which leads to discoloration and cracking of paint films. Using nano particles like titania or zinc oxide (ZnO) have shown improved UV resistance in the coatings.
This apart, addition of nano particles to coating systems increases the surface area and pore volume, which increases the surface roughness. This has been observed to make the surface water and oil repellent. Water and oil repellent surfaces can be utilised as self-cleaning mirrors, constructing exteriors and domes of the ship.
Under Water Warfare
Research is vigorously on to improve future anti submarine warfare/ mine warfare capabilities through the use of nanotechnology.
Researchers at the University of Southern California are working on developing technology to build nanobots which will be able to monitor oil/water for contaminants. The sensors in nanobots will be able to communicate with one another and will be active so that they can move around and make decisions.
The ability to develop nano based micro-sensors that could be scattered on the ocean floor to detect enemy submarines could lead to a paradigm shift in the Navy’s undersea warfare systems and capabilities. The same concept can be tailored for detecting enemy mines in the littorals. These furturistic nano based sensors will be networked and can be laid/controlled from distant locations.
On the artificial intelligence perspective, nanotechnology can prove to be a revolution. It is expected that the application of nanobots could help enhance the 100 trillion very slow interneuron connections with high speed virtual connections. With the advent of nanotechnology, the processing capability of artificial intelligence can exceed biological intelligence significantly. This will open up vast applications like nanobots manning unmanned vehicles, a paradigm shift in decision making of automated controls and may be the use of virtual crew to man automated ships.
Naval researchers have long been interested in the ability of micro-particle nano-coatings to help minimise bio-fouling and its associated drag and turbulence, but recent work has begun to demonstrate a major potential acoustic benefit too. The idea, in the words of Nicholas Fang, professor of mechanical science and engineering at the University of Illinois, “is not about dampening noise, but to guide sound waves around structures. If we have a coating on a submarine that bends acoustic waves before they hit the surface, guiding them around the submarine smoothly, then you won’t be able to detect a submarine using sonar.”
His team have already successfully managed to demonstrate a functional acoustic cloak capable of hiding a submerged steel cylinder from a sonar sensor array in the laboratory.
UT Dallas researchers have found that carbon nanotube sheets perform well as underwater sound generators and noise-canceling speakers, two highly desirable traits for submarine sonar and stealth capabilities. The study, which was published in the American Chemical Society’s journal Nano Letters, reveals that nanoscience speakers perform as well underwater as they do on land, and that one day they could replace traditional submarine sonar arrays.
Unlike alcohol or other liquids, water has an interesting effect on carbon nanotubes. The tiny tubes repel water slightly and form a layer of air along their perimeter. Once energized, the thin, light sheets of nanotubes heat and cool incredibly quickly, producing a pressure wave in the air around the nanotube that our ears and other devices perceive as sound.
Researchers at the University of Texas are harnessing energised carbon nano-tubes to generate ultra-low frequency sound, offering the long term promise of a thin coating for subs that could provide noise-cancelling against incoming enemy pings, while additionally helping enhance the submarine’s own sonar system.
Sailor Combat Outfits.
A significant amount of research is directed at use of nanotechnology for ‘lightening the load’ of soldier/sailor in combat. In 2002, the Institute for Soldier Nanotechnology (ISN) was created at the Massachusetts Institute of Technology (MIT), with a five-year grant of $50 million from the US Army. A battlesuit such us that being developed by ISN would be required to remain lightweight and comfortable while stopping bullets, protecting against toxins, monitoring vital signs and administering first aid where possible.
US researchers have developed cobalt-rich, nanocrystalline alloy that had significantly enhanced fracture toughness over conventional iron based magnetic alloys was developed. Yield rates for the fabrication of complex magnetic components can be as low as 20%. Damage resistant magnetic materials offer expanded motor design options with significantly reduced manufacturing costs
Nanoelectronics is another revolution in information technology hardware rivaling the microelectronics revolution that that promises sensor suites with x1000 smaller size/power; processors with x100 faster speed, x100 higher density and x1000 less power per function; non-volatile, radiation resistant static memory with x100 higher density and x50 faster access speed; flat, foldable displays with x10 greater brightness (nanophosphors) without concomitant increase in power requirements; communications with x100 greater bandwidth; and the merger of biological and non-biological entities into integrated systems.
The impact of such improvements will be high density, low power, high functionality circuits that will be the basis for intelligent sensors implemented in future Naval applications and on all Naval platforms, including aircraft, submarine, ship, satellite, man-portable, and autonomous vehicles.
Nanostructured materials can play a significant role in developing a new class of energetic materials with controlled and tailored energy release. One approach to increasing performance is to place the metal fuel and nitramine material in much closer proximity to each other than can be realized by traditional formulation, which should enhance the metal oxidation reaction.
A second approach of improving performance is to look at the possibility of functionalization of Aluminium particles using self assembled monolayers(SAMs) The hope is that this formulation of SAM on metal particles will increase solids loading and allow incorporation of chemical functionalities into the materials.
Energy and power
Nano Battery System: The availability of uninterruptible power supply (UPS) on naval ships is a vital requirement. In order to ensure UPS, two generators are kept online to ensure uninterrupted power supply. Research is being undertaken in the United States to design a large-scale nano lithium titanate military battery system. In case the primary generator fails, this nano battery system is estimated to provide UPS till a secondary generator comes online.
Graphene is a single layer of carbon atoms packed together like a honeycomb. It is extremely thin, light and strong. It’s also the best known conductor of heat and electricity. Most ships rely on copper or other metals to move electricity. Unfortunately, this process is relatively inefficient due to process called Joule heating. You lose a great deal of energy that way,” Cemal Basaran, PhD, a professor in UB’s Department of Civil, Structural and Environmental Engineering says. “With graphene, you avoid those collisions because it conducts electricity in a different process, known as semi-ballistic conduction. Another limitation of metal-based power distribution is the bulky infrastructure – transistors, copper wires, transformers, etc. – needed to move electricity.
Graphene nanoribbons offer a potential solution because they can act as both a conductor (instead of copper) and semiconductor (instead of silicon). Moreover, their ability to withstand failure under extreme energy loads is roughly 1,000 times greater than copper
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