Nanomaterials exhibit different chemical and physical properties, such as nano range size, size distribution, surface area to volume ratio, various surface properties, shape, chemical composition and agglomeration state. These are not always apparent in bulk materials. Hence, it is not shocking that implementation of nanotechnology techniques in several industrial areas, such as cosmetics, medicine, food, transportation, construction materials, etc., have significantly grown in the last decade.
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This article is on the applications of nanotechnology in transportation. When the size of a material is reduced to nanometer range, the chemical, physical and biological properties of the material change. They become entirely different from the properties of their atoms and molecules as bulk materials. These changes are due to a large surface area to volume ratio, spatial confinement, considerable surface energy, and reduced imperfection.
Higher hardness, super elasticity at high temperatures, improved breaking strength and increased fracture toughness are the important mechanical properties that are considerably improved, which results in the extended durability of machines, effective lubrication systems, lightweight materials, etc.
Applications of Nanotechnology in Automobiles
Nanotechnology is applied to car body parts like emissions, chassis, tires, automobile interiors, electrics, etc. Body part applications include paint coatings, lightweight parts, self-cleaning and scratch resistant nanopolymers.
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Every body part is painted with a color, using different methods. Paintings are mostly done for attractive and protective purposes. Usually painting in automobiles has three coats - a primer, a basecoat, and a clear coat. However, in most cases, it varies from four to six layers to impart various properties into it.
Rust shielding, cost, appearance, and strength are the vital performance factors driving the automotive coating technologies. Modern automotive varnish processes mainly consist of five steps - pretreatment electrode positions, a sealer, a primer and finally the topcoats. Pretreatment cleans and removes excess metals and forms a surface for bonding of corrosion protective layers.
The corrosion protection layer is then deposited by the electrode position method. Sealer prevents water leaks and minimizes vibrational noise and chipping. The most common sealer is Poly Vinyl Chloride (PVC).
The main purpose of a primer is the adhesion between the basecoat and the surface, and imparts anti-chipping properties. The primer acts as a protector from ultra-violet (UV) rays, corrosion, bumps, and stone chips.
The basecoat gives visual properties and color effects. The clear coat is the translucent and lustrous coating that has an interface with the environment. It can be either waterborne or a solvent and is chemically stable.
Gangotri D. L. et al., 2004 showed some developments in flame-retardant coating like titanium esters with aluminum flakes dispersed into binders. These can resist temperatures of up to 4000C. “Burn off” occurs above this temperature, which leads to the formation of a complex coating of titanium aluminum that deposits on the surface and it enhances the thermal resistance up to 8000C.
However, it is not enough to hold the devastating temperature of fire, and it results in great damage to vehicles and lives. Therefore, the need for better fire-resistant coatings is constantly growing. Chemical properties of flame retardant coatings can be enhanced by incorporating concentrates of nanosized magnesium aluminum layered double hydroxides (LDH). When a specific amount of LDH nanoparticles is dispersed with the paint solution, it improves the char formation and fire-resistant properties of the coating. The nano LDH will absorb the heat and sent out carbon dioxide and water when burns and thereby reduces the temperature of the surface in addition to enhancement in char formation.
It is a challenge for scientists and researchers to develop scratch and abrasion resistant coatings without affecting their other properties. Glasel et al. reported use of siloxane encapsulated SiO2 nanoparticles to produce a scratch and abrasion resistant films. Due to the homogeneous distribution of nanoparticles in the polymer, scratch resistance property can be improved without sacrificing any other properties.
Khanna A.S., 2008 showed the performance of the alumina NPS dispersed coating was compared with the neat coating and is expressed as X times improvement with the neat coating. The alumina NPS significantly improve the performance of the coating (up to nine times) even at a very low concentration of alumina dispersed in the composite coating. These types of nanopaints are already being used in different models of Mercedes Benz.
Lightweight Body Parts
Weight reduction of vehicles is one of the most discussed topics in the automobile research field. On the one hand, by reducing the weight, we can increase the fuel efficiency, reduce CO2 emissions and production cost. It is estimated that by reducing the weight of an automobile by 10%, there will be fuel economy of 7%. On the other hand, while reducing the weight there will be a problem related to stability, crash resistance and smooth working, which is a great concern for the safety of the vehicle.
Many developments had done in this field like reducing the number of engine components and using lower weighted parts, but they failed to coordinate both the efficiency and safety. The materials near to the engine parts should possess high thermal resistance, whereas the exterior and structural parts should be made of materials that have high mechanical strengths.
However, commonly used materials like thermoplastics have limited mechanical properties and thermal resistance; therefore, it can be used only after modified by reinforcements. Carbon nanotubes (CNT) have very less weight and around 150 times stronger than that of steel. Therefore, CNTs are a good substitute for steel in automobile parts which give us more strength and weight reduction.
Addition of nanoscale clay in a polymer matrix can develop a nanocomposite which is used to manufacture automobile parts near to the engine as they have good thermal properties. Clay nanocomposites with PP (Polypropylene), PA (Polyamide), PB (Poly butylene terephthalate), and PC (Polycarbonates) are the commonly used polymer nanocomposites . When these nanoscale clays are mixed with polymers, their flame retardance and thermal resistance will increase.
- Engines: By coating the cylinder wall with nanocrystalline materials we can reduce abrasion and friction and in turn the fuel consumption. There are research projects going on, which aim to directly coat tracks of the aluminum crankcase with nanomaterials. Iron carbide and boride nanocrystals with size 50 nm to 120 nm are used to coat the engine parts which result in an extremely hard surface with very low friction.
- Tires: Sanjiv T., 2012 reported the first nanomaterial that added to the tire was carbon black as a reinforcing element and pigment. Silica and soot are the most important ingredients used in the tires as reinforcing element. By adding soot in nanoscale higher fuel efficiency and prolonged durability is achieved as they have coarser surface than those we use in ordinary tires. As nanoparticles have high surface energy, the interaction of the soot nanoparticles with natural rubber in the tires is high which leads to better rolling resistance and reduced inner friction.
- Reflecting mirrors: Ultra reflecting a thin layer of aluminum oxide having a thickness less than 100 nm is applied to the surface of mirrors and headlights. This makes the mirrors to equip surfaces with fat, dirty water and repellant features. Hydrophobic and oleophobic nanometer layers are applied over the surface of the mirrors by chemical vapor deposition (CVD) method. Mainly fluoro-organic material layers of thickness 5–10 nm are used as they have high resistance to friction and are applicable for longer times. To prevent the problems created by the light of other vehicles falling on our eyes at night, nanotechnology and electrochromic properties are applied together.
- Interiors: We interact mostly with the interior parts of the automobile such as seats, door paddings, dashboard, airbags, seat belts, boot carpets, etc. These are the place where microbial and bacterial infections are most common. Since the interior is the place of an automobile where we interact mostly, it should be free from all bacterial and microbial infections. The most important nanostructured antibacterial and antimicrobial agents are silver, gold, titanium oxide, zinc oxide, titania nanotubes, gallium, liposomes loaded nanoparticles and copper nanoparticles. They are commonly used as incorporated nanoparticles in a matrix such as silica network. The action of these nanoparticles is initiated either by a photocatalytic reaction or by the biocidal process.
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Application of Nanotechnology in Marine Transportation
The function of marine transportation ranges from passenger traveling, weapon carrying platform, cargo carrier, and numerous others. The main problem in marine transportation is corrosion of the ship by sea water and atmosphere. Stainless steel which is a good corrosion resistant in normal atmosphere even will undergo partial corrosion in sea atmosphere.
Another problem in water transportation is the marine microbial fouling and erosion in the bottom of the ship and waterline area due to a long soak in water. All these will adversely affect the reliability of the ship survivability at sea. US-based researchers have found that usage of advanced nanoscience technology of ‘cyromilling’ in the processing of aluminum gives superior material for light and tough applications.
The cyromilling process introduces nanosized aluminum in the conventional one and forms nanoscale aluminum oxide and nitride particles which makes them stronger and stabilizes its microscopic structure and orientation which makes them an efficient alternative for making aluminum hull where high strength and light weight are highly desirable. Metal oxide nanoparticles of TiO2, ZnO, MgO, and Al2O3 added to paint coatings and fibers increase the ultraviolet blocking and antimicrobial properties which can be used for better coatings and fibers.
By the application of nanotechnology, it is made possible to make transportations more efficient, smart looking, stronger and durable.