19-05-2012, 10:42 AM
NANOTECHNOLOGY- Study of nanoparticles
NANOTECHNOLOGY.ppt (Size: 1.34 MB / Downloads: 80)
BASICS OF NANOTECHNOLOGY
nanotechnology deals with developing materials, devices, or other structures possessing at least one dimension sized from 1 to 100 nanometres
INTRODUCTION
Nanoparticles (these are materials which are of size 10-9 m) consist of several tens or hundreds of atoms or molecules and may have a variety of sizes and morphologiesthese can be:amorphous, crystalline, spherical, needles, etc…
A brief intro
Nanoparticles are small clusters of atoms about 1 to 100 nanometers long.
'Nano' derives from the Greek word "nanos", which means dwarf or extremely small. It can be used as a prefix for any unit like a second or a liter to mean a billionth of that unit. A nanosecond is a billionth of a second. A nanoliter is a billionth of a liter. And therefore a nanometer is a billionth of a meter or 10-9 m.
Particles and comparisons
In nanotechnology, a particle is defined as a small object that behaves as a whole unit in terms of its transport and properties. Particles are further classified according to size: in terms of diameter, fine particles cover a range between 100 and 2500 nanometers. On the other hand, ultrafine particles are sized between 1 and 100 nanometers.
Similar to ultrafine particles, nanoparticles are sized between 1 and 100 nanometers. The reason for this double name of the same object is that, during the 1970-80's, when the first large-scale projects were running with "nanoparticles" in the USA and Japan, they were called "ultrafine particles" (UFP).
Surface characteristics
High surface area is critical factor in performance of catalysis and structures such as electrodes allowing imporvement in such technologies as fuel cells or batteries.
The large surface area of nano particles also results in a lot of interactions between the intermixed materials in nano composites leading to special properties such as increased strength and increased chemical or heat resistance.
Nanoparticles specifications
Nanoparticles are often defined as particles of less than 100nm in diameter
There is an increase in ratio of surface area to volume.
The increase in surface are to volume ratio which is the gradual progression as the particle get smaller leads to an increase dominance of the behaviour of atoms on the surface of particles over that those in the interior of the particles
Nanoparticles are the smallest identifiable pieces of a material or substance. These particles can be taken from any material, however the size of any one particle cannot exceed one nanometer in size. Their size is indicated in the "nano" prefix, meaning one billionth so one nanometer is approximately one billionth of a meter. Something this small is not visible to the human eye, so high-powered microscopes are required to work with these materials. Their unusually small size opens up a whole new world of science and discovery.
Production techniques
There are variety of techniques for producing nanoparticles.
They fall in to three categories
Condensation from a vapor
Chemical synthesis
Solid sate processes such as milling
Particels then can be coated with hydrophilic substances or hydrophobic substnaces depending on desired use.
CONDENSATION TECHNIQUE
Used to make metallic and metal oxide ceramic nano particles.
It involves evaporatio of solid metal followed by condensation of to form naano sized clusters that settles in the form of a powder
Various approaches to vaporize the metal can be used. And variation of jte medium in which in to which the vapor is to released affects the nature and size of the particles.
The main advantage of this technique is low contamination. Final particle size can be controlled by varitation in tmeeprature, gas enviroenmnt and evaporation rate
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AFM- ATOMIC FORCE MICROSCOPE
The atomic force microscope (AFM) is ideally suited for characterizing nanoparticles. It offers the capability of 3D
visualization and both qualitative and quantitative information on many physical properties including size, morphology, surface texture and roughness. Statistical information, including size, surface area, and volume distributions,
can be determined as well. A wide range of particle sizes can be characterized in the same scan, from 1 nanometer
AFM can be performed in liquid or gas mediums. This capability can be very advantageous for nanoparticle characterization. For example, with combustion-generated nanoparticles, a major component of the particles are volatile components that are only present in ambient conditions.