Properties of Nanomaterials and Applications of Nanomaterials | BE 825, Study notes of Engineering

Download Properties of Nanomaterials and Applications of Nanomaterials | BE 825 and more Study notes Engineering in PDF only on Docsity! Lecture 19. Properties of nanomaterials — Applications of Nanomaterials 1. Insulation materials For example of Aerogels • Extremely light weight and often translucent appearance • aerogels are often called solid smoke. • An ounce of aerogel has the surface area of 10 football fields, more accurately it has a surface area as high as 1,000 m2 per gram. A demonstration of an aerogel's exceptional insulating properties, from: http://eetd.lbl.gov/ECS/Aerogels/images/flower.html 1 Corpo Nove incorporated the Spaceloft™ version of the NASA-developed aerogel material into this jacket, which was tested during an Antarctic expedition Aerogels can also be made in varying grades of clarity for windows, from: http://www.sculptors.com/~salsbury/House/panels.html History of silica aerogels: http://eetd.lbl.gov/ECS/Aerogels/aerogels.htm 2. Machine tools The uses of materials are determined by their mechanical and chemical properties, such as elasticity, hardness, conductivity, wear-resistance, and erosion-resistance etc. For example of hardness of some nanomaterials: Nanocrystals of titanium nitride: 60 Gigapascals of hardness (the hardness is measured by the pressure required to indent the material) 2 If hydrogen fuel is to be stored on-board a vehicle, a high-volume, low weight, safe storage system must be devised. Some possibilities for storage tanks include: steel tanks and composite tanks. The pressure for steel tanks and composite tanks are 5,000 psi and 10, 000 psi, respectively. Compared to steel tanks, composite tanks, comprised of polyethylene, have a higher storage capacity (about 7% by weight) and less weight. The principle of hydrogen nano-pore storage is that molecules of hydrogen, under high temperatures and pressures, can enter the microscopic holes in media such as carbon nanotubes, graphite nanofibers and zeolites. Hydrogen remains trapped in the cavities of the material, but can be released again when the temperature is re-elevated. Buckminsterfullerenes, also known as buckyballs, have a theoretical hydrogen storage ability of 7 percent by weight. Using this theory, hydrogen could be stored in solid materials at room temperature, taking up much less space than when stored in pure solid or liquid form. In the car, the materials could be heated and hydrogen fuel could be extracted. 4. Auto and aerospace manufacturing Boeing nearly supersonic sonic cruiser and Airbus A380 super jumbo are using carbon fiber materials extensively to keep aircraft light enough and strong enough to fly. However, carbon fiber, as one of micro-materials, can not match engineering properties of nano-composites. Carbon fiber or carbon fibre can refer to carbon filament thread. Each carbon filament thread is a bundle of many thousand carbon filaments. A single such filament is a thin tube with a diameter of 5–8 micrometers and consists almost exclusively of carbon. The carbon fiber can become further enhanced by heat treatment processes. Carbon heated in the range of 1500-2000 °C (carbonization) exhibits the highest tensile strength (820,000 psi or 5,650 MPa or 5,650 N/mm²), while carbon fiber heated from 2500 to 3000 °C (graphitizing) exhibits a higher modulus of elasticity (77,000,000 psi or 531 GPa or 531 kN/mm²). Carbon fiber is most notably used to reinforce composite materials, particularly the class of materials known as carbon fiber reinforced plastics. This class of materials is used in aircraft parts, high-performance vehicles, sports equipment such as racing bikes, radio controlled vehicles, wind generator blades and gears and other demanding mechanical applications; Carbon fiber is one of the leading materials used in Formula One car production since the introduction of the fiber into common commercial use in the early 1980s. Carbon nanotubes are one of the strongest and stiffest materials known, in terms of tensile strength and elastic modulus respectively. This strength results from the covalent sp² bonds formed between the individual carbon atoms. In 2000, a multi-walled carbon nanotube was tested to have a tensile strength of 63 GPa. In comparison, high- carbon steel has a tensile strength of approximately 1.2 GPa. CNTs have very high elastic moduli, on the order of 1 TPa. Since carbon nanotubes have a low density for a 5 solid of 1.3-1.4 g/cm³, its specific strength of up to 48,462 kN·m/kg is the best of known materials, compared to high-carbon steel's 154 kN·m/kg. 5. Medical applications Nanotechnology and medical use, from: http://technology.newscientist.com/data/images/archive/2311/23114201.jpg 6 6. Biodiesel production (Nano-catalysts) Biodiesel has several advantages over diesel fuel made from petroleum. Biodiesel: 1. Is biodegradable in water. Up to 98% biodegrades in three weeks. 2. Contains negligible sulfur and increases lubricity. 3. Production can enhance rural revitalization. 4. Is neutral with regard to carbon dioxide emissions. 5. Use leads to significant reductions in most harmful exhaust emissions. 6. Has a high flash combustion temperature. In addition to the above advantages of being a "green fuel", biodiesel, such as soy diesel (methyl soyate), is becoming increasingly useful in industrial solvent formulations for removing grease and resins, as carrier solvents, and as agents for shoreline oil spill clean-up. The most common method for bio-diesel manufacture is synthesis by reacting a glyceride-containing plant oil with a short chain alcohol such as methanol or ethanol in a step known as transesterification. Disadvantages of traditional biodiesel production: a. Relatively high reaction temperature of 50-70C b. Long reaction time of 5-8 hours c. Alcohol recycling is needed d. Overdosed alkaline needs to be neutralized In terms of overcoming these disadvantages traditional biodiesel production has, nano-catalyst as one of alternatives can be used to produce biodiesel in such a way with short reaction time, mild reaction temperature, and pollutant-free process. (a) 7