Engineered Nanomaterials PDF

Chemistry of Engineering Materials: Engineered Nanomaterials Introduction of Nanotechnology and Nanomaterials Formation of Nanomaterials Properties and Applications of Nanomaterials  Introduction Nanomaterials has attractive properties and amazing technologi...

Chemistry of Engineering Materials: Engineered Nanomaterials Introduction of Nanotechnology and Nanomaterials Formation of Nanomaterials Properties and Applications of Nanomaterials  Introduction Nanomaterials has attractive properties and amazing technological possibilities, which can be any one of the four basic types - metals, ceramics, polymers or composites. But difficulties with nanomaterials arise from the fact that, in contrast to conventional materials, a profound knowledge of materials science is not sufficient. Nanomaterials lie at the intersection of materials science, physics, chemistry, and for many of the most interesting applications – also of biology and medicine https://youtu.be/xW8Oocswn9s https://youtu.be/1QwyMWM0Jjg  Introduction nanometer – one billionth or 10-9 of a meter Nanotechnology – design, fabrication and utilization of materials, structures and devices which is less than 100nm Nanotechnology VS Conventional Technology The main difference between nanotechnology and conventional technologies is that the “bottom-up” approach is favored in nanotechnology, whereas conventional technologies generally use the “top-down” approach. “Top-down” means starting from large pieces of material and producing the expected structure by mechanical or chemical methods. As long as the structures are within a range of sizes that are accessible by either mechanical tools or photolithographic processes, then top-down processes have an unmatched flexibility in their application. Nanotechnology VS Conventional Technology The condition is different in “bottom-up” processes where atoms or molecules are used as the building blocks to produce nanoparticles, nanotubes, or nanorods, or thin films or layered structures. Given their dimensionality, these features are also referred to as zero-, one-, or two-dimensional nanostructures. Although such processes provide exceptional freedom among the resultant products, the number of possible structures to be obtained is comparatively small. In order to obtain ordered structures, bottom-up processes must be supplemented by the self- organization of individual particles.  Chemistry of Engineering Materials: Engineered Nanomaterials Introduction of Nanotechnology and Nanomaterials Formation of Nanomaterials Properties and Applications of Nanomaterials  Formation of Nanomaterials FORMATION OF RODS AND PLATES In the formation of nanorods and nanoplates, the influence of surface energy is to be considered. For nonspherical nanostructures, this is especially important in the case of anisotropic (noncubic) structures. But for surface-active molecules it is possible to grow rods or plates even from isotropic materials. In this context, it should be noted that even from gold, the existence of cubic material, nanorods, and nanoplates is well known  Formation of Nanomaterials FORMATION OF RODS AND PLATES The second possibility of obtaining nanorods and nanotubes is related to layered structures, where the crystal structure is built from layers held together with van der Waals forces rather than by electrostatic attraction. The general arrangement of a particle crystallized in such a layered structure is shown schematically in Figure 5a, where the layers are independent. At the circumference of each layer, the bonds are not saturated (these “dangling bonds” are indicated in Figure 5b). Based on this explanation, it is clear that all compounds that crystallize in layered structures show a tendency to form nanotubes. Typical examples are boron nitride (BN), WS2, MoS2, WSe2, MoSe2, and, most importantly, carbon.  Formation of Nanomaterials FORMATION OF CARBON NANOTUBES Discussions about graphite and fullerenes as special modification of carbon is essential in order to understand carbon nanotubes. The modifications of a substance differ in the ways in which the atoms are arranged and bond with each other, and so different modifications will have different physical and chemical properties. For example, graphite crystallizes in a layered hexagonal structure in which each carbon atom is bound covalently to its three neighbors.  Formation of Nanomaterials FORMATION OF CARBON NANOTUBES Consequently, only three of the four valences of the carbon atom are saturated. The fourth electron of the atoms remains unbound and becomes delocalized across the hexagonal atomic sheets of carbon. Electrons in graphite are mobile which shows electrical conductivity within the layers; perpendicularly to the layers, graphite is an insulator. Within the layers are strong covalent bonds, whereas in between the layers are weak van der Waals bonds and, accordingly, it is possible to cleave pieces of monocrystalline graphite. These single layers of graphite are known as graphene, and because of its structure and bonding graphene is often denominated as an infinitely extended, two-dimensional aromatic compound.  Chemistry of Engineering Materials: Engineered Nanomaterials Introduction of Nanotechnology and Nanomaterials Formation of Nanomaterials Properties and Applications of Nanomaterials Properties & Application of Nanomaterials NANOCARBONS Nanocarbons which are a class of recently discovered materials have innovative and exceptional properties and are currently being used in some cutting-edge technologies and will certainly play an important role in future high-tech applications. Three nanocarbons that belong to this class are fullerenes, carbon nanotubes, and graphene. Properties & Application of Nanomaterials FULLERENES The material composed of C60 molecules is known as buckminsterfullerene, (or buckyball for short), named in honor of R. Buckminster Fuller, who invented the geodesic dome; each C60 is simply a molecular replica of such a dome. The term fullerene is used to denote the class of materials that are composed of this type of molecule. In the solid state, the C60 units form a crystalline structure and pack together in a face- centered cubic array. This material is called fullerite. A few fullerene compounds have been developed which have uncommon chemical, physical and biological characteristics and does have the potential to be used in a of new applications. Some of these compounds involve atoms or groups of atoms that are enclosed within the cage of carbon atoms (and are termed endohedral fullerenes). For other compounds, atoms, ions, or clusters of atoms are attached to the outside of the fullerene shell (exohedral fullerenes). Uses and potential applications of fullerenes include antioxidants in personal care products, biopharmaceuticals, catalysts, organic solar cells, long-life batteries, high- temperature superconductors, and molecular magnets. Properties & Application of Nanomaterials CARBON NANOTUBES Carbon nanotubes are another molecular form of carbon which has recently been discovered that has some unique and technologically promising properties. Its structure consists of a single sheet of graphite (i.e., graphene) that is rolled into a tube; the term single-walled carbon nanotube (abbreviated SWCNT) is used to denote this structure. Each nanotube is a single molecule composed of millions of atoms; the length of this molecule is much greater (on the order of thousands of times greater) than its diameter. Multiple-walled carbon nanotubes (MWCNTs) consisting of concentric cylinders also exist. Carbon nanotubes also have unique and structure-sensitive electrical characteristics. Depending on the orientation of the hexagonal units in the graphene plane (i.e., tube wall) with the tube axis, the nanotube may behave electrically as either a metal or a semiconductor. As a metal, they have the potential for use as wiring for small-scale circuits. In the semiconducting state they may be used for transistors and diodes. Furthermore, nanotubes are excellent electric field emitters. As such, they can be used for flat-screen displays (e.g., television screens and computer monitors). Properties & Application of Nanomaterials CARBON NANOTUBES Other potential applications are varied and numerous, and include the following: More efficient solar cells Better capacitors to replace batteries Heat removal applications Cancer treatments (target and destroy cancer cells) Biomaterial applications (e.g., artificial skin, monitor and evaluate engineered tissues) Body armor Municipal water-treatment plants (more efficient removal of pollutants and contaminants) Properties & Application of Nanomaterials GRAPHENE Graphene as the newest member of the nanocarbons, is a single-atomic-layer of graphite, composed of hexagonally sp2 bonded carbon atoms. These bonds are extremely strong, yet flexible, which allows the sheets to bend. Two characteristics of graphene make it an exceptional material. First is the perfect order found in its sheets where no atomic defects such as vacancies exist; also these sheets are extremely pure and only carbon atoms are present. The second characteristic relates to the nature of the unbonded electrons: at room temperature, they move much faster than conducting electrons in ordinary metals and semiconducting materials. In terms of its properties, graphene could be labeled the ultimate material. Furthermore, it is transparent, chemically inert, and has a modulus of elasticity comparable to the other nanocarbons Properties & Application of Nanomaterials GRAPHENE Given this set of properties, the technological potential for graphene is enormous, and it is expected to modernize many industries to include electronics, energy, transportation, medicine/biotechnology, and aeronautics. However, before this revolution can begin to be realized, economical and reliable methods for the mass production of graphene must be developed. The following is a short list of some of the potential applications for graphene: touch-screens, conductive ink for electronic printing, transparent conductors, transistors, heat sinks (electronics); polymer solar cells, catalysts in fuel cells, battery electrodes, supercapacitors (energy); artificial muscle, enzyme and DNA biosensors, photoimaging (medicine/biotechnology); chemical sensors (for explosives); and nanocomposites for aircraft structural components (aeronautics).  Supplementary videos HOW NANOTECHNOLOGY CHANGES LIFE ► https://youtu.be/IGjCOJqINPA ► https://youtu.be/xgPbKWVJFEM