16
D. K. Subbiah et al.
the source material is heated from its solid to liquid state before attaining the vapour
phase. Hence, the source material is supported from beneath (bottom) and the targeted
substrate where the material going to deposit will be placed horizontally at the top.
A quartz crystal sensor enables control of the source material vaporization rate. The
rate is coupled with a movable shield, to allow specific film thickness deposition on
the sample fabric. Evacuation of the chamber gases is required before the source
material can be deposited onto the textile. The first step is to achieve the required
vacuum environment. Like all other PVD techniques, thermal evaporation makes
use of different types of vacuum pumps to reach the desired operating pressure. The
rotary pump generally helps to achieve 10
−2 Pa. The turbo molecular pump is used
to reach even lower pressures.
Resistive heating vaporizes the source material. Once the desired rate of vaporization is reached, the shield is moved to expose the textile surface. Vaporized source
material impinges on the substrate surface where it settles and condenses eventually.
Once a film of desired thickness is obtained, the shield is returned back to its original
position to cover the sample and resistive heating slowly is ceased [88]. This method
is directional due to a larger mean free path of the vaporized source material. One
of the major draws of this method, however, is that the film adhesion can be poor in
the case of fabric substrates.
3.3 Chemical Techniques
Surface modified textile is a growing field of research in nanotechnology in recent
times. These modified textile materials are used predominantly in applications like
UV-blocking, super-hydrophobicity and odour control materials. The textile materials are coated with the nanoparticles that exhibit extraordinary properties thereby
changing the behaviour of the conventional materials. Various techniques are followed to coat the textile material with nanoparticles among which chemical solution
deposition is one of the easiest and high yield techniques to produce the modified
textiles. Some of the methods used in modifying the textiles are discussed below:
3.3.1 Electrospinning
Nanomaterial comprises zero-dimensional (Quantum dots), one-dimensional (nanotubes, rods, wires and nanofibers) and two-dimensional (nanosheets) structures.
Among all other structures, nanofibers stand out for great potential due to high surface to volume ratio, higher aspect ratio, high porosity, etc., which are favourable
for wide range of applications such as energy storage devices, batteries, solar cells,
generators, fuel cells and supercapacitors [89]. Electrospinning is highly established
and widely used techniques to prepare nanofibrous structures due to its merits of
low cost, high efficiency, simple and reproducibility, which is working based on the
principle of electrostatic interaction [90]. It consists of a syringe pump, electric filed
D. K. Subbiah et al.
the source material is heated from its solid to liquid state before attaining the vapour
phase. Hence, the source material is supported from beneath (bottom) and the targeted
substrate where the material going to deposit will be placed horizontally at the top.
A quartz crystal sensor enables control of the source material vaporization rate. The
rate is coupled with a movable shield, to allow specific film thickness deposition on
the sample fabric. Evacuation of the chamber gases is required before the source
material can be deposited onto the textile. The first step is to achieve the required
vacuum environment. Like all other PVD techniques, thermal evaporation makes
use of different types of vacuum pumps to reach the desired operating pressure. The
rotary pump generally helps to achieve 10
−2 Pa. The turbo molecular pump is used
to reach even lower pressures.
Resistive heating vaporizes the source material. Once the desired rate of vaporization is reached, the shield is moved to expose the textile surface. Vaporized source
material impinges on the substrate surface where it settles and condenses eventually.
Once a film of desired thickness is obtained, the shield is returned back to its original
position to cover the sample and resistive heating slowly is ceased [88]. This method
is directional due to a larger mean free path of the vaporized source material. One
of the major draws of this method, however, is that the film adhesion can be poor in
the case of fabric substrates.
3.3 Chemical Techniques
Surface modified textile is a growing field of research in nanotechnology in recent
times. These modified textile materials are used predominantly in applications like
UV-blocking, super-hydrophobicity and odour control materials. The textile materials are coated with the nanoparticles that exhibit extraordinary properties thereby
changing the behaviour of the conventional materials. Various techniques are followed to coat the textile material with nanoparticles among which chemical solution
deposition is one of the easiest and high yield techniques to produce the modified
textiles. Some of the methods used in modifying the textiles are discussed below:
3.3.1 Electrospinning
Nanomaterial comprises zero-dimensional (Quantum dots), one-dimensional (nanotubes, rods, wires and nanofibers) and two-dimensional (nanosheets) structures.
Among all other structures, nanofibers stand out for great potential due to high surface to volume ratio, higher aspect ratio, high porosity, etc., which are favourable
for wide range of applications such as energy storage devices, batteries, solar cells,
generators, fuel cells and supercapacitors [89]. Electrospinning is highly established
and widely used techniques to prepare nanofibrous structures due to its merits of
low cost, high efficiency, simple and reproducibility, which is working based on the
principle of electrostatic interaction [90]. It consists of a syringe pump, electric filed