There are two general approaches to the synthesis of nanomaterials, they are (a) The top-down approach (b) The bottom-up approach (a) The top-down approach It is a approach in which smaller objects are made by carving or fabricating larger or bulk materials. It is like stone made into pieces from mountains (b) The bottom-up approach
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Nanomaterials have the structural features in between of those of atoms or molecules and the bulk materials. The properties of nanomaterials change as their size approaches the nanoscale. Thermal properties : Nanomaterials have lower melting temperatures, when the particle size decreases below 100 nm. It is due to the fact that the surface energy level increases as
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The term nano originated from the Greek nanos which means “dwarf”. It is one billionth of a meter. Therefore, whenever we think about nonoscience or nanomaterials very small objects come to the mind. A nanometre or nm is one thousand millionth of a metre, (ie), 1 nm=10−9 m=10−3 m=10 A. All materials are composed of grains, which in
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Ni-Ti alloy was developed in 1962 by Naval Ordnance Laboratory, White Oak, Maryland, USA and is commercialized under the name nitinol (nickel-titanium Naval Ordance Laboratory). Ni-Ti alloy shows shape memory effect when temperature or stress is applied. The Ni-Ti has proven to be the most flexible and beneficial in engineering applications. The Ni-Ti alloy have
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Shape memory effect It is the phenomenon in which the shape memory alloy apparently deforms at lower temperature and returns to its original shape (former shape) when heated at higher temperature. Let us consider a shape memory alloy for which the temperature is decreased. Due to decrease in temperature, phase transformation takes place from austenite
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Definition : Shape memory alloys are special type of alloys that have the ability to return to a original defined shape when heated. Shape memory alloys are also called as smart materials (or) intelligent materials (or) active materials. The shape memory transformation was first observed by Chang and Read in 1932. Examples of SMA’s a)
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Since the atoms in the metallic glasses are disordered, they have some peculiar properties as follows. a) Structural properties Metallic glass have tetrahedral closely packed (TCP) structure rather than hexagonal closely packed (HCP) structure. They do not have any crystal defects such as grain boundaries, dislocations, etc. b) Mechanical (or) General properties The metallic glasses
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1. Calculate the intrinsic carrier concentration in germanium at 300 K. Given that me *=1.09 m0, mh *=0.31 m0 and Eg = 0.68 eV. Given T = 300 K, k=1.38×10-23 Jk-1, h=6.626×10-34 Js, m0 = 9.11×10-31 Kg, Eg = 0.68 eV = 0.68×1.6×10-19 J, me *=1.09 m0 = 9.929×10-31 Kg, mp* = 0.31 m0 =
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1. A uniform silver wire has a resistivity of 1.54 × 10-8 Ωm at room temperature, for an electrical field along the wire of 1 V/cm. Compute the drift velocity of electron assuming the there are 5.8 × 1028 Conducting electrons/m³. Also calculate the mobility. Given ρ = 1.54 × 10-8 Ωm, E = 1
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1. If an ionic crystal is subjected to an electric field of 1000 V/m and the resulting polarization is 4.3 × 10-8 cm², Calculate the relative permittivity of the crystal. Given E = 1000 V/m, ε0 =8.85×10-12 F/m, P = 4.3 × 10-8 C/m², εr = ? Solution :- [latex] \begin{aligned} P & =\varepsilon_{\mathrm{o}}\left(\varepsilon_{\mathrm{r}}-1\right) \mathrm{E} \\
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