Presented BY:KOUSHIK AGARWALA

CHEMICAL ENGINEERING05/CHE/30

HALDIA INSTITUTE OF TECHNOLOGY

INTRODUCTION

The basis of nanotechnology is the ability to form nano-sized particles, for example nano powders, which are solid particles that measure on the nano scale, usually comprised of three to five molecules together. Nano powders have been of extreme interest in the pharmaceutical field. Moreover,they are also used in the ceramics, electronics, and in the production of metals with no dislocations.

Methods of productionThere are several methods for the production of Nano

powders the conventional methods like particle size reduction include milling, grinding, jet milling, crushing, and air micronization, but there are several drawbacks with these methods.

Three Different methods of production of Nano Powders are 1) Rapid Expansion of Supercritical Fluids 2) Particle from Gas Saturated Solution 3) Depressurization of an Expanded Liquid Organic Solution

Rapid Expansion of Super critical Fluids (RESS)It is a crystallization technique and uses the properties

of supercritical fluid. The super critical fluid is mainly CO2 it mainly acts as solvent in the production of Nano powder. The driving force is rapid de pressurization of super critical fluid (CO2) dissolved in solute of interest through a nozzle to cause fast nucleation and fine particle generation.

Flow diagram of ress process

Advantages and disadvantagesThe Advantage of this process is that since it is operated

at high pressure the temperature required is fairly low. This lowers the energy cost and since CO2 is non hazardous gas, so no environmental considerations have to be taken into account.

The Disadvantages are that due to high pressure the cost of pumping and production cost are high and the equipments used are also fairly large in number.

Particle from Gas Saturated SolutionThe Particle from Gas Saturated Solution (PGSS) process

uses a SCF, usually CO2, as a solute to crystallize a solution. The PGSS process can be used to create micro sized particles with the ability to control particle size distribution. The driving force of the PGSS is a sudden temperature drop of the solution below the melting point of the solvent. This occurs as the solution is expanded from a working pressure to atmospheric conditions due to the Joule-Thompson effect. The rapid cooling produces amorphous powder which is mainly used in pharmaceutical industries

Flow diagram of pgss process

Advantages and DisadvantagesIn this method there is no need for the solvent to form

Nano powder. All that is needed is solute and super critical fluid. Lack of solvent means product formed is much more pure. We can produce nano powders for wide range of materials.

The disadvantages are that although at higher working pressures dissolution becomes more effective, there are compounds for which a Super Critical Fluid can have low solubility.

Nano powder produced by (pgss) Process

Depressurization of an Expanded Liquid Organic Solution

In the (DELOS) model the super critical fluid acts as a co solvent for the formation of micro sized particles. The (DELOS) process is mainly used to Organic compounds with Organic solvents.The driving force for the DELOS process is a fast and large temperature drop. This occurs when the pressurized solution is expanded from a working pressure to Atmospheric pressure.

Flow diagram of delos process

Advantage and DisadvantagesThe main advantage of (DELOS) is the encapsulation and

it’s a very cost effective and nano powders formed are much more pure and highest quality.

The disadvantage is that solubility is limited and reaches saturation very fast and the products formed are not in spherical shape and needs to treat by other techniques to produce spherical shapes which are costly. The Shape of the crystals formed are dendrite and cylindrical in form.

Nano powder produced by (DELOS) Process

Applications of Nano Powders

Ceramics used in nano sized powders are more ductile at elevated temperatures compared to coarse grained ceramics and can be sintered at low temperatures.

Nano sized powders of iron and copper have hardness about 4-6 times higher than the bulk materials.

Nano sized copper and silver are used in conducting ink and polymers.

Nano powder has various applications in the pharmaceutical and medical field.

From nanotechnology we can be able to understand the living cells. Magnetic nano particles can act as sensors to detect the cancer cellsGold coated Nano particles are used to detect HIV viruses.

Comparison of the processesTOPIC RESS PGSS DELOS

Application Small Mol High purity Large Mol

Role of SCF Solvent Solute Co Solvent

Driving force Pressure Temperature Temperature

Working pressure Dependence

SCF Morphology SCF

Working temperature dependence

SCF Highest SCF

Length of procedure 2 Steps 2 Steps 3 Steps

Particle size Micro & Nano Micro & Nano Micro & Nano

Encapsulation Yes Yes Yes

Conclusion

In the recent years the demand for nano powders are increased drastically because of its wide range of applications by producing Nano powder with metals like aluminum, iron and copper. This Novel technology is used in the production of aluminum powder which has applications in aviation industry.

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