Nanomaterials in aerospace

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A look at nanotech in the aerospace and aviation industries where coatings, composites and propulsion nanotechnologies are already in use.

Due to the risks involved in flying, aircraft manufacturers are striving to make the aerospace components stronger, tougher, and longer lasting. The industry is also seeking to reduce weight in an on-going bid to reduce fuel consumption and, by extension, operating costs. Further, pressure for air travel to be ‘greener’ has also come to bear.

Nanomaterials are utilised in the aerospace industry for improved (or tailored) properties that improve their functional performance (e.g. mechanical or electrical properties) or that deliver multi-functional properties (e.g. lightweight conductive nanocomposites). The bulk of R&D into aerospace applications of nanomaterials at present focuses on structural reinforcement of composite materials. Nanomaterials will potentially allow for the development of lighter, high-performance, robust and cost-efficient, multi-functional aircraft. Nanostructured coatings are already being applied for improving the life span, reliability and durability of components; erosion, sliding and wear resistance; improving surface quality; de-icing; and corrosion resistance against pitting, peeling, oxidation and heat. Coatings are currently being commercialised to detect corrosion and mechanical damage to aircraft skin; react to chemical and physical damage, improve adhesion, and increase the life span of metal parts. Lightweight, high-strength, heat stable nanomaterials are also under development for aircraft engines.

A number of aerospace companies and agencies are beginning to use, or investigate the use of, nanomaterials to add special characteristics to aircraft frames and interior and engine parts and component surfaces, which can include properties such as: self-cleaning; improved hardness; wear and corrosion resistance; improvement in fuel efficiency; and improved thermal performance and flame retardancy.

COATINGS

Nanostructured coatings are being developed for aerospace application for increased life span for engine applications/aerospace alloys. Nanocoatings exhibit improved tribological properties in combination with other desirable properties such as improved adhesion and hardness over a wide range of environmental conditions. For example, they are allowing for prevention of rotor blade abrasion from rainfall as nanostructured coatings exhibit over six times more protection than conventional coatings.

 

Figure 1: EasyJet are using nanocoatings to increase the fuel efficiency of their aircraft

Nanocoatings will allow for new aerodynamic concepts that will reduce the air resistance and thus the fuel consumption of aircraft. Easyjet has applied a nanocoating from tripleO (http://www.tripleops.com) for  fuel savings and carbon footprint reduction. The coating reduces drag by up to 39%.

In spaceflight, nanocoatings allow for the protection of substrate structural materials in extreme temperature conditions against the unacceptable risks of thermal oxidation to enable the fuselage of spacecraft to endure exposure to 4,200°F for a period during orbital re-entry. Nanomaterials have increased the duration of protection by 78 time’s previous testing-from ten seconds to thirteen plus minutes. Because of the size of the nanoparticles, they do not scatter light and can be added to a coating formulation without affecting its optical properties such as gloss and transparency. Incorporation of nanoparticles also provides a mechanism for efficient dissipation of stress throughout the polymer matrix, preventing catastrophic failure.

Companies developing nanocoatings for application in the aerospace industry include:

CG2 NanoCoatings, Inc.: The company has developed a process to utilize nanoscale properties by first functionalizing nanoparticles and then incorporating them into a base material (polymers, metals, ceramics or composites) for anti-icing coatings. www.cg2nanocoatings.com

EnvAerospace: The company uses NPS-PVD

(Physical Vapour Deposition) to produce a wide range of wear-resistant, anti-corrosive, thin ultra-hard films applicable to aerospace applications. www.envaerospace.com

Inframat Corporation: Nanocoatings are used to insulate hot section metallic components (turbine blades, turbine vanes, combustors) from the hot gas stream in all modern aircraft gas turbine engines. www.inframat.com

Integran: Nanovate NVTM (Nanovar), a nanometal surface coating for carbon fiber reinforced plastic (CFRP) aerospace tools, designed to protect them from damage. www.integran.com

Luna Innovations: Developing ultrahydrophobic coatings to offer improved corrosion resistance on aluminum and the ability to scale to large substrates (such as spray coating for aircraft). Luna’s coatings could reduce maintenance, decrease life cycle costs, and increase readiness by limiting equipment down-time. www.lunainnovations.com

Magnetic Shield: Nanovate electromagnetic shield coatings. www.magnetic-shield.com

Nanovere: Nanocoatings to significantly reduce ice adhesion, de-icing maintenance costs, and reduce the coefficient of wind and water drag resistance, thereby decreasing the cost of jet fuel. www.nanovere.com

NCoat, Inc.: The company manufacturers high performance nano-formulated and micronized coatings with improved bond strength, heat management, corrosion resistance, abrasion protection, friction reduction, and appearance enhancement for the automotive, aerospace, defense, diesel engine, recreational vehicles, and energy services industries.. www.ncoat.com

NTC Nano Tech Coatings: The company produces scratch resistant, corrosion resistant and easy to clean coatings. NTC mainly focuses on coatings for light metals (Aluminium and Magnesium) and various kinds of steel, such as technical parts for cars and aircrafts as well as engine parts and production areas for food technology. www.ntcgmbh.com

Powdermet, Inc.: PComP(TM) nanocomposite coating technology for use in repair and refurbishment of aircraft components. This nanocomposite coating technology replaces heavy and costly WC-Co, and toxic electrolytic hard chrome with a higher performance, lower cost nanocomposite alternative. www.powdermetinc.com

Pureti: The company produces a water based solution that air dries to form an invisible, well adhered, ultra thin, long lasting coating that actively protects all surfaces to which it is applied from the buildup of any organic matter – including bio-film, bacteria, molds or fungi. PURETi products can be applied to virtually any surface, including buildings, signs, solar panels, sidewalks, outdoor furniture, holding tanks, boats, and planes. www.pureti.com

Ross Technology Corporation: The company is producing super hydrophobic nanocoatings. www.rosstechnology.com/divisions_nanotech.htm

Tesla NanoCoatings: Corrosion control coatings with fullerene carbon nanotube cathodic protection of metal to the aerospace/military, petrochemical, transportation, marine, and industrial markets. www.teslanano.com

COMPOSITES

Metal oxide nanopowders find application as additives to airframe composites materials. Polymer nanocomposites may provide significantly increased modulus, gas barrier, thermal performance, atomic oxygen resistance, resistance to small molecule permeation and improved ablative performance when compared to typical traditional carbon-fiber-reinforced polymeric composites. Carbon nanotubes could help create extremely strong, very lightweight structural composites used to produce highly fuel-efficient performance aircraft.  Stronger, tougher and long lasting aerospace components are needed to make flying risk-free. The major problem faced by aircraft manufacturers is the fatigue strength of aircraft components which decreases with the component’s age.  Fatigue strength can be increased by reducing the grain size of the material which in turn makes the material stronger, thereby, increasing the life of the aircraft.

Nanotubes provide such a significant reduction in the grain size over conventional materials so that the fatigue life is increased by an average of 200-300%.  Composite materials display improved fatigue life, damping properties and higher damage tolerance properties due to nanomaterials inclusions.

Nanoclays have been used in carbon fibre/epoxy reinforced composites for cryogenic storage systems with improved mechanical and thermal expansion (CTE) characteristics thereby avoiding micro cracking and thermal cycling.

Polymer nanocomposites are also under investigation for areas such as longer-range missiles and a greater payload for aircraft as fire retardant coatings, rocket propulsion insulation, rocket nozzle ablative materials, damage tolerant performance, etc. Ablatives are required to protect aerospace launching systems against solid rocket exhaust plumes (36000˚C) at very high velocity. Companies developing nanocomposites for application in the aerospace industry include:

Buckeye Composites: Conductive elastomers for aerospace applications, non-metallic EMI shielding for electronic enclosures, lightning strike protection of composites, ionic liquids for lubricants, greases, and single phase thermofluids for extreme environments. www.buckeyecomposites.com

Mach I, Inc.: The company is a producer of iron oxide nanopowders and also a distributor of aerospace sealants for Dupont and 3M. www.machichemicals.com

M.E.R. Corporation: The company’s fullerenes  are utilized in composite materials showing exceptionally high-strength and lightweight structure materials for aerospace and military applications, and conductive flexible films for electrical and thermal management applications. www.mercorp.com

Nanocomp Technologies, Inc.: The company’s proprietary product is the CTex™ CNT yarn and CNT mats. Main application markets are in aerospace and aviation markets for nanotube materials to save weight in a variety of complex systems, as well as to provide electrostatic discharge (ESD) and electromagnetic interference (EMI) shielding components. www.nanocomptech.com

Nanoledge: The NANO IN™ base resins product line demonstrates third-party-validated improvements in strength, flexibility, toughness, conductivity and material fatigue. The NANO IN integrated nanoparticles create/improve conductivity, strength, flexibility, toughness, chemical resistance, compression & fatigue of materials. Main applications are in Sporting Goods, Wind Energy and Aerospace industries. www.nanoledge.com

Natural Nano, Inc.: The company has over twenty issued or pending patents and proprietary know-how for extraction and separation processes, of halloysite and other nanotubes, in combination with other materials. The company’s main product is a turnkey halloysite nanotube polymer concentrate, in pellet form, that can be added directly into a polymer extruder. The company is currently focused on leveraging this new drop-in, turnkey advantage to a select number of industrial compounders who supply major industries such as automotive, performance sporting goods and aerospace. http://naturalnano.com

PROPULSION

Energetic nano-sized particles have been shown to have a great potential for use in the aerospace propulsion applications. The unique combustion properties of nano-particles such as very rapid ignition and short combustion times make them particularly valuable for propulsion systems; they can be included in solid fuels, solid propellants, or even as energetic gellant in liquid systems. GE are active in developing technology in this area (http://ge.geglobalresearch.com/technologies/advanced-technologies/). Other companies with activities include:

Mach I, Inc.: NANOCAT® Superfine Iron Oxide is an amorphous ferric oxide with a much finer particle size and greater specific surface area than any other commercially available form. It excels as a catalyst for chemical processes including synthesis, cracking, and oxidation. In solid rocket propellants it provides high burning rate, low pressure exponent, and safety. Properly dispersed, it is a remarkably effective screening agent for ultraviolet light. Synthesized by a unique vapor-phase process, NANOCAT® SFIO is free of impurities that poison conventional catalysts and is suitable for use in foods, drugs, and cosmetics. www.machichemicals.com

SRI International: SRI are developing fullerenes as efficient hydrogen-transfer catalysts, methane activation, as catalysts for upgrading resins, ion propulsion, and permselective membranes, energy conversion and storage, optical materials and pharmaceuticals. www.sri.com

Canano Technologies LLC: Aluminium nanopowder is treated to produce a thin protective layer of aluminium oxide, which prevents the powder from being pyrophoric.  Nano aluminium may be used in paints, polymers, coatings, textiles, fuel cells, solar energy, airbag propellants and energetic materials.  Tensile strength is increased by factors 2-4. www.cananopowders.com

Nanomaterials Discovery Corporation: The company is developing fuel cells that utilize energetic materials, such as explosives and propellants, as fuels. This new class of fuel cells has a broad spectrum of applications in both the military and commercial sectors. Applications include point-of-use and portable power, fusing, improving the safety of land mines and cluster munitions, and remediation of old and obsolete ordinance. New capabilities for “self-sterilizing” smart land mines and cluster munitions that render themselves harmless after a certain period of time are made possible by NDC’s advanced materials and energetics technologies. www.nanomaterialsdiscovery.com

Nanotechnology will increasingly have an impact on numerous commercial, military and space aero-applications and as outlined is already finding it’s way into products and materials. Beyond these applications other products that are already on the market or will appear in the mid-term include nano-enabled cabin filtration technologies, self-repair materials and sensors.

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