PPT NANOMATERIALS

• Nanomaterials

  The first – and broadest – definition of nanomaterials states that, these are materials where the sizes of the individual building blocks are less than 100 nm, in at least one dimension (nm; equivalent to the diameter of approximately 500 atoms, 10-9m).
• • Nanomaterials has attractive properties and amazing technological possibilities, and can be any one of the four basic types - metals, ceramics, polymers or composites.
• • Nanomaterials appear in many branches of science, such as materials science, physics and chemistry, and are also applied in biology and medicine.
  • Their use relies on their high surface area to volume ratio, size, and antibacterial properties.
• • Usually nanomaterials are developed to show innovative characteristics compared to the same material without the nanoscale features, which includes, increased strength, chemical reactivity or conductivity.
  • Ex. Mesoporous silica is biodegradable, unlike other silica types. 
• Conventional Technology

  It favors the “top-down” approach, meaning it uses large pieces of material first and produces the expected structure through mechanical or chemical methods.
• Nanotechnology

  • Favors the “bottom-up” approach, where atoms are used as the building blocks to create nanoparticles, nanotubes, or nanorods, or thin films or layered structures.
• 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. 
• • 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 3.0, where the layers are independent. At the circumference of each layer, the bonds are not saturated.
  • The dangling bonds (short lines) need additional energy; thus, there is a strong tendency to saturate these dangling bonds.
• • The use of compounds that crystallize in only one dimension is the third possibility of obtaining nanotubes. In concept, this is the most promising way to obtain long fibers, but unfortunately the importance of this route is negligible as the numbers of compounds coming into question is small.
• • Imogolite is the most important compound in the context of nanorods, with an ideal composition of Al2SiO3(OH)4. The ratio of silicon and aluminum can be used to adjust the tube’s diameter. The tubes have internal diameters of 1 nm and external diameters of 2 nm. 
• • Formation of Nanocarbons

  Graphite is known for crystallizing in a layered hexagonal structure in which each carbon atom is bound to it’s three neighbors. 
• • The fourth electron isn’t bound and is delocalized within the layers, but perpendicular to the layers, graphite is an insulator. The interior of the layers are bound with strong covalent bonds, but between the layers, they’re only bound by van der Waals forces.
• • Because of the weak van der Waals forces, it’s possible to cleave off layers of graphite. The single layers of graphite are called graphene and because of its structure and bonding graphene is often denominated as an infinitely extended, two-dimensional aromatic compound.
• Nanocarbons

  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. 
• Fullerenes

   

  • Fullerenes are an allotrope of carbon, consisting of carbons connected by single & double bonds, forming a closed or partially closed mesh.
  • containing fused rings of 5-6 atoms, these molecules being known for their hollow sphere of ellipsoid-like forms
• Allotropy

     (from Ancient greek ἄλλος (allos) 'other' and τρόπος (tropos) 'manner, form'),

  Allotropy is the property of some chemical elements existing in two or more different forms
• Allotropy

  • different structural forms of the same element and can exhibit quite different physical properties and chemical behaviours.
  • The change between allotropic forms is triggered by the same forces that affect other structures, i.e., pressure, light, and temperature.
• Fullerenes (closed mesh)

  • The closed fullerenes, especially C60, are also informally called buckyballs for their resemblance to the standard ball of association football ("soccer"). 
  • Nested closed fullerenes have been named bucky onions.
•  Fullerenes (closed mesh)

  • Fullerenes with a closed mesh topology are denoted by the emprical formula Cn, where n is the number of carbon atoms, though for some values of n there may be more than 1 isomer
  • The family is named after buckminsterfullerene (C60), the most famous member, which in turn is named after Buckminster Fuller.
• Carbon nanotubes

  • A carbon nanotube is a tube made of carbon with a diameter in the nanometre range (nanoscale). They are one of the allotropes of carbon. Of which two broad classes of carbon nanotubes are recognized.
• Single-walled carbon nanotubes

  • Single-walled carbon nanotubes (SWCNTs) have diameters around 0.5–2.0 nanometres, about 100,000 times smaller than the width of a human hair. 
  • They can be idealised as cutouts from a two-dimensional graphene sheet rolled up to form a hollow cylinder.
• Multi-walled carbon nanotubes 

  Multi-walled carbon nanotubes (MWCNTs) consist of nested single - walled carbon nanotubes in a nested, tube-in-tube structure. Double and triple-walled carbon nanotubes are special cases of MWCNT.
• • The interlayer distance in multi-walled nanotubes is close to the distance between graphene layers in graphite, approximately 3.4 Å (3.4 nanometres).
• Mechanicalㅤpropertiesㅤof Carbonㅤnanotubes

  • Carbon nanotubes are the strongest and stiffest materials yet discovered 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 gigapascals (9,100,000 psi).
• • Since carbon nanotubes have a low density for a solid of 1.3 to 1.4 g/cm3, its specific strength of up to 48,000 kN·m·kg−1 is the best of known materials, compared to high-carbon steel's 154 kN·m·kg−1.
  • Because CNTs are themselves 1D materials, the well-known generation and multiplication mechanisms (such as a Frank-Read source) for 1D dislocations do not apply. is the external strain. This activation energy barrier partially explains the low ductility of CNTs (~6–15%) at room temperature.
• Carbon nanotubes possess unique electrical properties that depend on the orientation of their structural units. They can act as either metals or semiconductors, which allows for diverse applications.
• Carbon nanotubes

   As a metal,they can be used for wiring in small-scale circuits, while in their semiconductor state, they can function as transistors and diodes. 
• Carbon nanotubes

  Furthermore, nanotubes are excellent electric field emitters. As such, they can be used for flat-screen displays (e.g., television screens and computer monitors). 
• Potential applications carbon nanotubes

  • More efficient solar cells 
  • Better capacitors to replace batteries  
  • Heat removal applications 
  • Cancer treatments (target and destroy cancer cells) 
• Potential applications carbon nanotubes

  • Biomaterial applications (e.g., artificial skin, monitor and evaluate engineered tissues)  
  • Body armor  
  • Municipal water-treatment plants (more efficient removal of pollutants and contaminants) 
• Graphene

  • The newest member of the nanocarbons.
  • A single-atomic-layer of graphite, composed of hexagonally sp2 bonded carbon atoms.
• Graphene

  These bonds are extremely strong, yet flexible, which allows the sheets to bend.
• Graphene

  The first graphene material was produced using the micromechanical exfoliation, or the adhesive-tape method.
• Graphene

  This method involves peeling apart a piece of graphite, layer by layer using plastic adhesive tape until only a single layer of carbon remained.
• Two characteristics of graphene

  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.
• Two characteristics of graphene

  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. 
• Properties of graphene

                      Ultimate material 

  • Transparent
  • Chemically inert and;
  • Has a modulus of elasticity comparable to the other nanocarbons (~1 TPa).
• Potential applications for Graphene

  Given this set of properties, the technological potential for graphene is enormous, and it is expected to modernize many industries to include:

  Electronics

  (touchscreens, conductive ink for electronic printing, transparent conductors, transistors, heat sinks)
• Potential applications for Graphene

  Energy

  (polymer solar cells, catalysts in fuel cells, battery electrodes, supercapacitors )

      Medicine/Biotechnology

  (artificial muscle, enzyme and DNA biosensors, photoimaging)