Nanotechnology
The word Nanotechnology may be relatively new to some but the existence of nano structures and Nano devices is not new at all. Richard Feynman is the one who gave the basic idea of Nanotechnology for the very first time in 1959. However in 1974 Norio Taniguchi gave the term “Nano-technology”.
We often get confused between Nanoscience and Nanotechnology. Let us first clear the difference between both.
Nanoscience
Nanoscience is dealing with the study of properties of materials at nano scales; however the properties differ significantly for the same material when look at in bulk.
Nanotechnology
Nanotechnology is dealing with the characterization, design, production and various applications of nanostructures and nanodevices and nanosystems.
It is important to note that when the size of material is reduced to nanoscale, it shows different properties than the same material in bulk form. Let us take a look at the physical and chemical properties of Nanomaterial.
Physical properties
Inter atomic distance: As the size of material is reduced to Nano scale, surface area to volume ratio increases. With increase in surface area, a large number of atoms will appear at the surface as compared to those inside. So Interatomic spacing decreases with size.
Thermal properties: As we know Nanomaterials show different properties than that of bulk materials. For nanomaterials Debye Temperature and ferroelectric phase transition temperature is low comparatively. As the particle size of gold decreases from 300 Å to 200 Å its melting point of decreases from 1200 K to 800K.
Optical properties: When light incident on nanaoparticles, Nanoparticles with different size scatters in different directions and show different colours. For example nano gold does not show the same colour as bulk gold. Depending on the grain size of gold nanoparticles they show orange, purple, red or greenish colour. Also nanoparticle copper is transparent whereas bulk copper is opaque.
Magnetic properties:, we use single domains to explain the magnetic behaviour of nanomaterials. For bulk materials we use a large number of domains . The Single domain has a very high coercivity value.
For example: Fe, Co, and Ni show superparamagnetism but are ferromagnetic in bulk. Na, K, and Rh show ferromagnetic behaviour but are paramagnetic in bulk. Cr is superparamagnetic but is anti-ferromagnetic in bulk.
Mechanical properties: The mechanical properties such as hardness, elastic modulus, young’s modulus etc., of nano materials are also different from that of bulk materials.
In case of metals and alloys, the hardness and toughness increases with decreases the size of the nanoparticles. In ceramics, ductility and super plasticity are increases with decrease the grain size.
Chemical properties
Nanocrystalline materials are chemically active as they are strong, hard, erosion and corrosion resistant. They have following chemical properties.
In electrochemical reactions, As the particle size reduced, the rate of increase in mass transport increases.
The solubilites of nanoparticles, equilibrium vapour pressure and chemical potentials are greater than that for the same bulk material.
As we know that most of the metals do not absorb hydrogen. But with the decrease of cluster size in Ni, Pt and Pd metals the absorption of hydrogen increases.
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