pp. 12-18
Anupriya Rana*, Gaurav Sharma
School of Applied Sciences
Suresh Gyan Vihar University, Jaipur Rajasthan
*E-mail- gaurav.sharma@mygyanvihar.com
ABSTRACT
Nanofluids are represents as a mile stone in scientific era or research due to their potential efficiency. They are very useful in drug delivery and at major cases of oil recovery not only in Drug cases but also they are very advanced thermophysical heat transferable fluids. Nanofluids are greatly effective but there are some aspect which have to be considered before the application of nanofluids induced. Major concept and problem with nanofluids is their stability and their operational performance. If we have to maintain their true thermophysical ability then stability point must be acquired otherwise no functioning can take place as the true application of nanofluids. In this article our main focus is on upon the major application field of Nanofluids , their preparation method and mostly on their future aspect how can they will going to be ready for future requirement. Their preparation method is basically two type of which is used to produce the correct amount and specific character of nanofluids.
Key words– Nanofluids , Drug delivery , Thermophysical ability , Stability mechanism, preparation methods.
Introduction
Fluids are the general combination of of liquid with some sort of solute particles either organic or inorganic, but if we are using fluids in scientific era they probably have some ability to establish them specifically and effectively . There are many kinds of fluids present in our surrounding either natural or artificially synthesized.
As in today’s world Nanotechnology touches the sky of success due to their very specific and effective application .Nanotechnology performing their function in different form of raw material like Nanoparticles Nanowires ,Nanotubes and Nanofluids etc.
Nanofluids are a very special class of fluids basically made up of nano- sized material like Nanofibers , Nanotubes , Nanorods or sheets. Size of these material is lower than the 100nm but they have specific chemical and physical properties. Year 1995 A scientist name Choi develop the nanofluids from the nanoparticle. These nanofluids are in the form of colloidal suspension with dense nanomaterial composition. These nanofluid having two phase in which one is liquid and other one is solid. They are used in enhancing the capacity of thermal conductivity , viscosity and diffusivity . There are many other possible importance of nanofluids has been seen. Phase one is ok with dealing in application but phase two show some difficulties cause of stability factor of nanofluids. This is very crucial to attain desired stability in the case of nanofluids.[1-7] Many scientist have been working on the stability matter of nanofluids some of them acquired accessible successful in that .
These nanofluids are only much more effective because of their size and large surface area and large size of particle can not pass the several membrane of different passes but due to below than 100nm size nanofluid solute particles can cross the membrane just through very small negligible passes that’s why they are extremely helpful and progressive in scientific work done.
There are two specific method of preparing the nanofluids . First method is One step and second method is Two step method . Majorly Two step method is very well known and understood in appropriate way. We will discuss about them briefly in this paper.
Methodology
Two step method
This method is very commonly used in scientific zone because it is very economic and easy to perform . Error points can be reduced during the phages of preparation. This method basically occurs in two parts. Nanofluids prepare from the nanomaterial like the nanotubes ,nanorods ,nanoparticle, nanowires. They are the basic raw material for preparation. Firstly these raw material have to be convert in the form of powder through many physical and chemical method . There are many methods are available in today’s market to prepare the nano powder because of the high demand of nanotechnology in scientific research. When we get the powder of nanoparticles then we have to mix that powder in a fluid with intensive force of magnetism ,homogenizing or with the help of ultrasonic agitation . It is very useful and easy to maintain because of we have many ways to make nano powder and mixing is not a much big task ,but there is a problem can be faced or most of the time if happens because of the fast aggregation ability of nano particles , they aggregate very quickly. So a big question of having stability arises. Stability of nanofluids is a typical task specially in condition of increasing temperature. Surfactants are majorly used to attain stability of nanofluids.[1]
One step method
One step method is using generally to reduce agglomeration of these nanoparticles, (Eastman et al) . The scientist use this method on the core basis of physical mode vapor condensation methodology to form the Cu/ethylenegycol.[10] This method donot contain any two different method either of that this directly synthesized the nanoparticle and mix them with the fluids at the same time. This process of one step is avoid several step of two step methodology like they do not contain the Transportation ,Drying, Dispersion and storage of the raw material or nanoparticles.[9] Through avoiding this mediatory steps there are less chance of nanoparticle to get aggregate or agglomeration do not take place so the stability of nanoparticle can be maintain[6] . This process gave us uniformly distributed particles in the fluids. Morphology of particles lead to different functionality of the fluids . There are some disadvantages of this method , like they are not very economic means they are costly .preparation of this method quite difficult so we can’t make a large amount of fluids from this methodology.
There are also some other method to prepare the nonofluids like SANSS , this method is also quite lean to make fluids at different dielectric points and their functionality of thermal conductivity is depend on their morphology. They can be many shape and size like polygonal, circular, needle shaped or square .[15]
Stability of Nanofluids
The stabiltiy of nanofluids is a very big concern because of the aggregation ability of nanoparticle. If stability not attained it also effect the quality of work of fluids and decrease its thermophysical property which is the key point of nanofluids. There are many ways to maintain the stability of nanoparticle. For stability evaluation – Centrifugation and sedimentation method, Zeta potential method, Spectral absorbency.For Enhancement of stability – Surfactant , Surface modification Stability mechanism for Nanofluids .In this paper we focused on the Stability enhancement on the basis of Surfactant.[1]
Surfactant based stability
Dispersant is an another name of surfactant used in nanofluid for the stability enhancement. Surfactant used majorly in two phase method cause of it is easy to use in that way and very economic for attaining stability. These Surfactants are very efficient for nanoparticle surface characteristics. Surfactant having a bipolar nature cause of they have one hydrophilic tail and hydrocarbon chain in middle and with another end they have a hydrophilic end. They are used to increase the wettability of two element, a surfactant used to be present in between of two phases ,one is of nanoparticle and other phase is fluids. Theses surfactant having four kind of heads on the basis of these heads these surfactants are divided in different categories.
Nonionic Surfactant – They do not have any charge in their head.
Anionic Surfactant – They contain negative charge in their head.
Cationic Surfactant – They have positive charge in their head.[1,23]
Amphoteric Surfactant – These surfactant contain the zwitterionic head and they are know because of Betaines and some certain lecithins.
Now the selection of surfactant for specific fluids is a very careful step we have to be very careful for their selection. There are some guidelines to select a specific surfactant like if we are choose the fluid which is polar in nature then we have to take the surfactant which is water soluble. These surfactant reduce the thermal conductivity between the nanofluids and fluids cause of it stability can be attained.
Application of Nano fluids
Heat energy transfer intensification–Therml conductivity this property of nanofluid is well known that they are very useful in transforming the heat from one place to another. There are many other reasons of being that much efficient for conductive nature of nanofluids. MgO-EG has to be found the best nanofluid for thermal conductivity and creating low viscosity and many other features.[1,4-7,24]
Electronic applicataion – Chips having higher density and designing of electronic items cause the heat dissipation in troubleome and heat transfer do not take place but now days many new approach has been introduced to make this task easier. One methos is making an optimum geometry for cooling. Other way is Nanofluids which have high rate of thermal conductivity. So these fluids can increase the thermal activity of a coolant.[25]
Transportation – Some nanofluids like ethylene glycerol are the very beneficial for activating and effecting the cooling system. They improve potential of automotive and also the rate of cooling of heavy engine , they basically increase their efficiency to work . This efficient cooling rate can helpful in reducing the rate of heat produce by the horsepower engine. Reducing heat can be very helpful in long sustaining of that automotive. These nanofluids also very helpful in reducing their friction.[26-28]
Space and defense – These fluids are very light weighted and easy to carry out cause of their tiny particle size. Space ship need to be this type of cooling devices for their space ship to maintain the heat equilibrium. [32]Other devices are larger and not suitable to carry out in space easily they create several problems, in place of them nanofluids are more efficient way to cool down the system and also their work efficiency is better than the other balky elements. Same for defense these fluids is easily carry out in every kind of environment and with a very little weight . Machine are getting heat up at cause of the continue friction and this continue friction can lead to non functionality of machines at that time these nano fluids can work as a lubricant for them and increase the working ability of machines.[33]
Heating building and reducing pollution- There are many cold region in world . these places have a high level of child environment which is not easily to be sustainable so people there use some technique of heating building to keep them warm to live their life gently. They make a combination of propylene glycol and ethylene with water as in different kind of proportion for heat transferring fluid. Water is a general base fluid. We see that if we use nano fluid in this transferring system of heat then it shows some effect like deduction in mass flow and volumetric rates. These nano fluids produce the equal amount of energy as big heating system but these fluids thermal energy are less expensive as compare to big one. Big settler gave more energy even though which is not much needed to heating up but the nano fluids give the exact amount of thermal energy which is needed for heating building so the lesser amount of chemical releases which are beneficial in controlling the environmental pollution which is a necessity of today’s world.
Solar absorption – solar energy is a marvelous form of energy with very low impact on environment. This energy is directly collected by the universal source of light sun and after absorption of this energy it been utilized in various field. Their application is world wide. This energy is collected by collector in absorption pattern , so the absorption of sun energy directly dependent on the absorbent media and there efficiency. Now this absorption technique combines with the nano fluid to make it more advance and important. When we collect energy with modified collector in addition with nano fluids then an extensive growth of 5 to 9 % has been noticed , in simple means nano particle fluid can increase the rate of absorption at different level. So this phenomena can be very economic and helpful in conservation of more energy at cheap levels. When sani et al, investigate he found that the thermal and optical ability of carbon nanohorn can increase the solar absorption rate much faster , they increase overall efficiency rate.[42]
Mechanical application – These nanofluids have wide range friction reduction property cause of nanoparticles which are present in nano fluids have a surface of protective film with a very low amount of hardness and elasticity , having these qualities some of many nano particles consist of best lubricant smoothing properties which are responsible for reduction of friction at larger level. A very special example of magnetic fluids which are very generous kind of nanofluids with no such maintenance and helpful in many application.[1]
Biomedical application –Many of the nanoparticles have the special property of being carrier they show specific kind of antibiotic activity and also show drug delivery. That’s why nanofluids containing these kind of nanoparticle can show some of there relevant properties.[1]
Antibacterial Activity – organic material are not much stable at higher temperature neither on high pressure. Metal and their oxide show some significant role in antibacterial activity. There are some metallic oxide which show higher negative influence on the bacterial cell and easily destroyed them. ZnO show much better result of antibacterial activity specially on Ecoli. If we increase the ZnO ration in presence of Ecoli then it will be going to step in death. ZnO cause of Ecoli death because it change the configuration of its cell membrane and lead them to death basically protein and lipid of membrane has to be replaced.[36] CuO nanoparticles also show some great antibacterial property . This metaloxide posses the shape less than the pore size of cell membrane of bacteria . Cause of having this much small size they easily pass through the membrane of any microorganism. They are also very efficient in forming bond with vitality of cell plasma like proteins and enzymes and cause of their death.[37] Fabrics gain many bacteria cause of having many time hand washing and laundering by machines , there is Colloidal form of silver help here in a very efficient way . They are practically a very special tiny particle having a great antibacterial property . If we add colloidal solution of silver oxide performing by one step method on the fabrics they surly perform antibacterial activity.[38]
Nano drug delivery- Nano particles are a significant advisor for drug delivery mechanism . As they are having small tiny size , they take much advantage of their this property .[39] bulky particles are less corporative in drug delivery because having a slight bigger size cause them many problem including mass conduction they properly cant cross the wall and membrane of many microorganism and cell so , the lesser amount of drugs can be achieved by respective demanding place .[40] In the place of bulky particles nano particles take advantage of having small size they easily cross the any barrier and membrane because their size are much smaller even of their pore size .They also having larger surface area and transforming capability with complexity of cellular organism. Gold nanoparticles perform a very important side in drug delivery. Their surface conducting different charges and the property of hydrophobicity .[41] They also attain stability in cellular organism , thus the nanofluid are very efficient in drug delivery system .[43]
Conclusion
Nanoparticles as well as nanofluids contain many fascinating property which lead them to the pillar of success in scientific world. As we discussed nanofluids in this review paper we have seen many impressive properties of nanofluids like they are having very small size and this property are their fundamental mile stone , they also posses many more qualities having large surface area , charge holding capacity , heat transforming capability and they can attain stability within cellular organism. They can prepare by two method in generally first method is Two step and second one is one step method. They are basically the fluids which are containg different kind of nanoparticles having specific property. Their major application in Biomedical field , Heat transfer, Drug delivery , many mechanical applications, very helpful in solar absorption, Defense and also space research and in their labs.
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