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Module 1: Synthesis of Nanomaterials

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Now moving on to this line what we are having next is, so we talked about the inert gascondensation, now from here we move onto physical vapour deposition.Physical vapour deposition is again is a collective set of processes commonly used for so.Physical vapour deposition, so physical vapour deposition is a collective set of processescommonly used for producing nano material and to deposit thin layer of material typicallyin the range of few nanometer to several micron meter.So you see here that whole deposition on the substrate is what is happening, so basicallywhat you are doing if I had to understand this whole technique.So, you are creating a vapour phase and, so you are the material.You are creating a vapour phase and you are depositing the vapour on top of a substrate.So, again in order to take something into the vapour phase requires a significant amountof energy and then you place it on the substrate.So, you are forming layer or thin films on the substrate and these are some of the techniqueswhich are pretty extensively used in the electronic industry and all other manufacturing industries.So, coming to the physical vapour deposition, so what you are doing is which is also calledPVD is an environmentally friendly vacuum deposition technique consisting of 3 fundamentalsteps.So, you realize that you need conditions of vacuum in such situation.And this is the first thing is vapourization of the material from a solid source this isstep1, step 2 is transportation of vaporize material.This is step 2 and the third step is nucleation and growth to generate thin films.So, the whole area of thin films, thin film generation by nucleation and growth.So, the whole area of thin film generation is dependent on this kind of physical vapourdeposition.The most commonly use PVD methods are sputtering followed by it could be electron beam evaporationand you might wonder why I am highlighting this technique.Because if you do appreciate the biological roots of synthesis that realize how much complexthese processes are, how much energy intensive and instrument intensive these processors.Pulse laser deposition and then will be needing vacuum or so this is what I was talking toyou, pulse vapour depositions.So, these are some of the ways by which physical vapour deposition works sputtering is a vacuumbased PVD process which is often used to deposit films of nano material.And a sputtering works on the principle of momentum transfer in which the atoms fromthe target which is made up of the material to be deposited at ejected by the ion bombardment.The deposition of material by sputtering can be achieved using DC pulse or direct currentpulse, pulse DC or radio frequency as I told you that you can use all these kinds of energies.And the plasma of the natural glass commonly argon is generated between 2 electrodes bythe collision of electron to the gaseous molecules.Ions present in the plasma are the accelerated towards the target by applying potential betweenthe 2 electrodes.And these ions with appropriate energy thus hit the target leading to the ejection ofthe material from the target.So, it is something like if you follow this picture.And ejected material is the transported and deposited onto the substrate, say basicallymaking them travel through this nano slit are the aperture and getting them deposited.And there are 2 advantages they led to higher deposition rate and prevent target over hittingand damage, so this is what essentially the sputtering is all about similarly you haveelectron beam evaporation EBE technique EBE are electron beam evaporation is a vacuumbased again all these are vacuum based PVD process pulse vapour deposition process orphysical vapour deposition process which is used to fabricate the thin films of nano materials.And EBE system consist of vacuum unit electron beam source and target material again yousee you have a vacuum unit out here as I showed you aggregation zone which is vacuum unitthan you have electrons source.And then you have a deposition ground, so the weight works is very simple electron beamhits the target and hit the target material.The target material atoms evaporate when temperature which is above its boiling point.And evaporated material then transported condensed on the substrate and the advantage is againhigh deposition rate and can be used to deposit material ranging from conducting to insulatingand unlike thermal evaporation electron beam evaporation can be used to deposit materialof high boiling point.So, you realizing that all these techniques if I talk about all the physical forces Itold you in the very beginning.It could be mechanical, it could be high energy radiation, it could be thermal, it could beelectrical, it could be magnetic.So, using all these forces, so in other word, if you logically brake down the whole thingwhat is happening is you have this bulk material and you are using all these different physicalforces on this bulk material.Here is your bulk material these are the physical forces and you are applying the physicalforces and most of the situation in vacuum situation and you making thin films by depositingthem.And all sorts of different kind of things what you are achieving by using these techniques,so then we talk about the laser ablation or pulse laser deposition.Laser ablation methods utilizes high power laser beam.So, again here the physical forces are now laserand laser ablation method utilizing the high-power laser beam that evaporates the particle froma solid particle.So, from the solid material, so from here the evaporation is happening because of thelaser beam it is a high energy laser.So, in normal laser ablation process the laser can either be continuous laser or pulse laser.You could have a continuous source of laser or you can pulse it depending on what kindof evaporation pattern you want.So, laser ablation offers flexible approach in the production of micro and nanostructureof polymeric materials.So, if you have to work with the polymers what will the talking about while talkingabout the applications.So, there will be lot of such applications of laser and laser assisted or laser ablationtechnique or pulse laser deposition techniques.Then we talk about the vacuum arc or vacuum based PVD process in which the arc is usedto vaporize the materials.So, you are using as a physical force you are using a vacuum arc which is again a veryhigh energy process and using the vacuum arc.You are ablating the material in which the arc is used to vaporize the material fromfor the synthesis of metallic ceramic and composite nano materials and films.So vacuum arc uses for metallic, ceramics, composites, whereas laser is used for polymericand many other of course one of the areas is polymeric materials.Then you have laser pyrolysis, the laser pyrolysis technique is again vapour base synthesis process.This method can be used to synthesis wide vacuum nano material like titanium oxide,silicon oxide, aluminium oxide, iron oxide like you know tio2, sio2.So, you have following up where I told you, so this is what we have talking about laserpyrolysis and laser pyrolysis could be used for synthesis of Tio2, sio2, Al2 O3, F2o3.And there are series of other oxides and non-oxides like, so these are all the metal oxides andamong the non-oxides you are having silicon, silicon carbide, silicon nitride, molybdenumsulphide.There is series of things which you could produce using laser pyrolysis in this processthe resultant condensable product or generate from the laser induce chemical reaction atthe interface of the laser beam.And the molecular flow up gaseous vapour phase reactants.So, again the logic is the same you are using different kind of high energy processes togenerate these kinds of nano materials similarly you are having flame spray pyrolysis whichis flame or flashes by pyrolysis which is the latest of all the flame arrows old technologies.It is one step combustion process where the precursor is in the liquid form.So, realized for this kind of things you have to have theprecursor in the liquid phase that is very essential your precursor is in the liquidphase.It is a one step combustion process where the precursor is in the liquid form with significantlyhigher combustion enthalpy that is more than 50% of the total energy of combustion usuallyit is an organic solvent.The important technological element of this process includes self-sustaining flame usageof liquid feeds and less volatile precursor.And it has very high scalability high temperature flame and large temperature gradient.So, these are some of the techniques some of the prerequisites for flame spray pyrolysisoaky.The same line your next things come is the electro spraying techniques which is thistechnique.Electro spraying is the techniques similar to electro spinning.But it differs in the type of material to be produce, so electro spraying is basicallydone is for synthesis of nano material where as electro spinning is being done for developingdifferent kind of fibers.So, lot of fibers nano fiber rest materials especially the polymer fibers are being usedor which are being used are produced by electro spinning technique.But electro spraying on the country is that which is logically pretty much similar ituses it is used for nano material mostly nano particle synthesis.So, coming back to the electro spraying techniques what we are talking about, so your electrospraying is basically the electro spraying method is based on electro mechanical devicein which mixture of solution.So, its semi-liquid phase containing the selected polymer and the solvent is taken up by a syringeand high voltages applied to the capillarity that results in the production of charge droplets.The solvent is evaporated on it is a way to the counter electrode.And particle or fiber are then collected at the n product, the electro spraying techniqueprovides goes flexibility and control of the surface parameters.And electro spraying is one pretty neat process to produce nano particles, so then last ofthis lot is melt mixing.So, melt mixing is essentially a method involve mechanical mixing of a polymer with modifiednano colors by extrusion or needing and less commonly by injection molding techniques.This is one of the oldest methods to design polymer composites with nano particles, so,this is used for mostly the polymer composite development.And one of the oldest techniques available, this is one of the oldest methods to designpolymer composites with nano particle as a pellet which he designs material characteristics.This is most commonly used mechanical process because it is friendly and it is also wellsuited for current industrial practices.So, over all this is what we needed to understand about the physical methods of synthesis ofnano material which find applications for high energy synthesis using physical forcesas I have already mentioned.So, here you have the bulk material which here is the bulk material which is exposedto this kind of different kind of forces which are enlisted here.And the process what happen is this mechanical material abrasion melting evaporation condensationand this leads to the nano structure formation.So, keep this key in mind, so most of these techniques if you realize these are top downapproach big material you are bringing down smaller sizes.So, next what we will do I will close in here next we will talk about the chemical and thebiological mode of synthesis, thank you.