 Hello, welcome to the NPTEL video course on advanced characterization techniques. Myself Dr. Kisharno Viswas, this course will be designed by myself and one of my colleagues in the department of materials and engineering at IIT Kanpur. So at least 20 lectures of this course will be delivered by me and the remaining 20 will be delivered. So you can see that in the next slide the outline of the course which is given, this course contains different advanced characterization techniques. First one, advanced diffraction techniques includes small angle exit diffractions, small angle Newton scattering, low energy, electron diffraction, read and as well as x-apps. Second one which is again advanced surface characterization techniques exclusively for XA photoelectron spectroscopy, Auger photoelectron spectroscopy and secondary ion mass spectroscopy. So therefore these two sessions will consist of 20 lectures. Second course mostly microscopic techniques and the spectroscopic techniques. So when the microscopic techniques we are going to discuss in detail about transmissive electron microscopes including high resolution, high angle and dark field imaging, same in situ microscopic techniques like in situ ACM and in situ TEM, electron backscatter diffraction, AFM that is atomic force microscopy, STM that is scanning tunneling microscopy as well as laser confocal microscopy. This will be delivered by me and I am going to start the first lecture of this in the next one. The last part of the course is basically on advanced spectroscopic techniques which are very important nowadays for research on nanomaterials and many other things. This includes visible ultraviolet, Fourier transform, infrared, Raman spectroscopy as well as in the microscopic techniques STEM, electron energy loss spectroscopy. So therefore this course basically talks about the advanced characterization techniques. So to understand this course one needs to know the basics of the normal characterization techniques that is why the characteristic course requirement for this kind of course must be the basic knowledge on the basic material characterization techniques and this kind of course is already been developed by Dr. S. Sankaran from IIT Madras and Dr. Vijay Agarwal of IIT Rukhi as a web course as a part of the NPTEL lecture series. So whatever discussions I am going to do for the different character techniques has lot of inputs from this material characterization course by two of our colleagues. So now we shall discuss the detail lecture wise break up of this course. This is basically required to tell you that how the different lecture modules will be developed. So first lecture which is today I am going to talk about relevance of advanced characterization techniques for materials development. Basically these are required for scientific understanding of the different phenomena in the material science engineering. Then the next two parts that is advanced diffraction techniques and advanced surface characterization techniques the detail lecture wise break up is shown in the slides and this will be discussed by Dr. Gautama in different lectures. I will straight away go to the last two topics in the advanced microscopic techniques first lecture of that will be devoted on electron material interaction. This will be followed by four lectures on transmission electron microscopy mostly on higher resolution and other allied techniques remaining two lectures will be delivered on SEM related things like in situ SEM and the electron backscatter diffraction whereas atomic force microscopy and scanning transmission canning canning microscopy will be dealt in two lectures and lastly the laser confocal microscopy will be discussed in the advanced spectroscopic techniques seven lectures will be delivered on electromagnetic spectroscopies mostly eb visible and photo luminescent spectroscopy infrared spectroscopy and also the Raman spectroscopy last lectures of this course last three lectures of this course will be delivered on scanning transmission electron microscopy related spectroscopy techniques that is yields and EDS that will sum up 20 lectures in these two techniques well as any other course we need to have some reference and the books so in this slides I am showing you some of the important books these are not exhaustive there are many other books available in the libraries or even the market but I am listing down the most important ones and the ones which I am going to use and Dr. Gautama also going to use is going to use for his lectures the first one is the material characters in techniques by Jank Lee and Kumar it is published in 2008 which will talk about all the characters in techniques in brief second one is basically on transmission electron microscopy by Williams and Carter third one is on modern ESCA the principles and the practice of excess photoelectron spectroscopy by Per from again CRC pace fourth one is on scanning electron microscopy and extra microanalysis by Goldstein and others fifth one is an advanced techniques for material characterization it is basically a monograph by the material science foundation edited by Tiagi Roy Pulcesta and Banerjee the all the techniques can be easily obtained or rather can be easily accessed in encyclopedia called encyclopedia of material characterization edited by Brindle Evans Wilson published by Butterworth Hinman Boston and this is a very exhaustive book so therefore I will not prefer you at the beginning to go into the encyclopedia rather than concentrate on the different books on different subject matters obviously first lecture is on relevance of the characterization techniques so giving you an idea of the core structure and the modules I have to now discuss why one needs to study such a kind of course those of you who have some idea about the characterization must have seen different characterization labs in the different parts of our country coming up as a part of schemes by department of science and technology and many cases even by other allied organizations these centers are actually called characterization centers there are centers in many IITs even in IIT Kanpur IIT Madras Indian Institute of Science Bangalore NCL Pune and many other places where in one roof all the different characterization techniques are housed so therefore you have those of you have visited these places I have got some idea about the different sophisticated characterization tools are used for characterization materials so I am not going to discuss the way the characterization techniques can be used rather I will give you some examples from our own study where characterization is to be used by our own students to understand the material science phenomena in different processes and also to process different kinds of material these are all done by our students so therefore this are taken from my own research group and most of these works are done on very small size particles like nanoparticles or nanomaterials so I will one by one I will illustrate you that how important it is to use characterization techniques before that I would like to tell you then the last 10 years there is a huge improvement in the characterization techniques as far as the limits of the use of this instrument as concerned one of the example is the high resolution transmission electron microscope in late 90s even at the beginning of the 21st century the resolution limits for transmission electron microscope we used to be in a Armstrong level that is above one Armstrong but because of the advent of new technologies especially the aberration corrected microscopic technologies we could have very high resolution we can reach resolution of 0.6 Armstrong so this barrier of breaking the resolution level below one Armstrong was possible only because of the technological advance and I will show you in some of my lectures how this microscopes can be used to decipher different structures and also the understand the problems of material science so let me give you the examples the first example is on deposition of nano crystalline copper coatings by pulsed electro deposition technique we know that nano crystalline copper is very important because nowadays in the electronic industry the connectors are normally made by copper previously those connections and the visors used to be made from gold or aluminum or tungsten but technology has seen a rapid change because copper can be easily deposited in those positions of the semiconductor devices where the connections are required the basic requirement for those kind of connections are very strong and very good electrical conductivity of copper not only that the brightness of the deposits by the electro deposition should be also very good these requirements can only be satisfied if one develops a nano crystalline copper deposits by using a special technique called pulse electro deposition this is here shown in the slides what you can see is a first one is basically showing you the pulse electro deposition technique where current is plotted as a function of time in this case we use pulsed current for about 8 millisecond followed by no current supply for about 30 milliseconds that means the T on the current is on for all the 8 millisecond followed by T of 32 milliseconds then again the current is on for about 80 milliseconds so therefore by using this pulsed current cycles one can deposit this kind of nano crystalline copper I will not be able to go into detail of this deposition technique except to show you that this can be done in a normal electrochemical cell double wall cell where anode is a copper and cathode is basically stainless steel 304 grade so therefore if we apply a current when this whole the both the electrodes are dipped into a copper sulphate sulphuric acid solution at about 303 degree Kelvin one can see the deposition of copper from anode to the cathode taking place and by that one can deposit different copper of different thickness on the stainless steel substrate the reason for using stainless steel is that it is easy to peel off the copper flame from the stainless steel substrate to give an example how this deposition is done is shown in this case or normally if you deposit copper using pulse electrochemical technique we do not get nano crystalline grain sizes so therefore many cases we add different additives and these additives can be anything like PEG polyethylene glycol or any other sulfur compounds like thiorea thiorea is most notably used because it is nothing but a sulphur containing compounds and this sulphur containing compounds can change the deposition kinetics so and so that it is possible to develop a nano crystalline copper grains in the deposit the reason for this was not known people have seen this happen but why and how the thiorea is affecting the deposition process so that nano crystalline copper again can be obtained was not known so one of our students in my research group started looking at this problem and found several interesting observations to understand the effect of thiorea on the deposition of nano crystalline copper on 304 stainless steel first I will show you two SEM pictures scanning electron microscopy's images of the thin flame deposited on stainless steel substrate first one is deposited when there is no thiorea so you can see very discontinuous deposits and obviously using laser scanning per kilometer one can measure the roughness to characterize quantitatively how rough the deposit which is shown on the right side of the picture you can clearly see that the roughness is very high some cases mean roughness can be over of several tens of micron so therefore if you know that thiorea deposits are very discontinuous and also rough on the other hand if you add very small amount of thiorea about 36 milligram per liter deposits become very smooth one can see in the picture here deposit is very smooth and also if you measure the surface roughness roughness is very very high sorry very very low so that means roughness can be easily controlled by the thiore addition and this were required when copper is deposited on any kind of PCB board or visors on the electronic circuitry so this was observed very nicely by using a scanning electron microscopic technique followed by laser surface per kilometer these two are the advanced characterization techniques used in many cases the common idea of deposition model is this this will help us understanding how thiorea actually affect the deposition process so when there is no thiorea obviously substrate will have lot of surface steps on this like any other surface and the copper ions will move to the different places of the substrate most notably the copper and we will be able to move on the high or on the crest of the surface instead of tops here so thereby depositing on the crest and making them thicker and thicker and creating deposits the one which I have shown you which is kind of discontinuous on the surface if I add thiorea molecules into the deposit or into the electrolyte rather the thiorea molecules will basically gets deposited on the surfaces of on the crest and that is that is how they will not allow the copper ions to go on the surf on this crest instead of they will be forced to go on the tops here and because of that the stops will get filled up and we will form a very continuous deposit so that roughness can be reduced very easily this is the common idea which is been reported in the literature but knowing this does it happen in the actual sense to do that we have done a very careful spectroscopic analysis using a scanning electron microscope picture here shows the scanning electron microscopy image of the copper deposit in which there are two large and also very you know something which is protruding out of the surface of the deposit if we do edex analysis that is the energy disperses spectroscopic analysis attached to the ACM which is nothing but a spectroscopic technique using electron beam one can see the presence of sulfur pick very easily coming from the surface not only that one can even further analyze this using the edex mapping if you do edex mapping on the whole surface you see sulfur is basically segregated on the surface remember the sulfur is a part of the thiorea molecule and this thiorea molecule is formula is given by NH2 O2 CS so therefore sulfur is obviously is part of the molecules wherever we see sulfur we can assume that's how it is present there because copper doesn't contain any sulfur so that's why we can say that the model which has been developed by different scientist can be proved by different kinds of spectroscopic technique if you see on the copper Mac if we uniformly distributed on the whole surface except the position where there is a protrusion which has been can be mapped very easily using the scanning electron microscope image not only that one can go on use a different other techniques this one is called transmission electron microscopic technique which can be used to know the fine scale structure inside these deposits the left one showing you the transmission electron microscopic image in the bright field mode of the sample deposited without addition of any thiorea where you can see that very large grain this bar is a microns bar 1 micron so grains are very large of the order of 2 to 3 micron and they contain lot of dislocation inside it which are marked by this white arrows on the other hand if we add thiorea per liter we can see the grain size is extensively reduced from micron size to nanometer size if this much length is 15 nanometer so most of the grains are less than 100 nanometer size so this really tells us thiorea affects the grain size reduction process in fact one can also see the defect structure inside this grains are not dislocations only but also twins notably twins and this is shown in the inside picture here which shows large number of twins on the inside the grains. So therefore thiorea not only affecting the deposition process per se but also affecting the microstructure which can be only understood using transmission electron microscope which is having you know which is one of the best techniques available to understand the fine scale microstructure features one can also add up to this story much by using highly synlectro microscopy which will be part of the syllabus of this course here I am showing a one small grain approximately 40 to 50 nanometer diameter and if you look at in high resolution mode one can see the twins which are there in the grain and this twins can also be seen here on this on this bright fill microgap on the left side of my slide on the right side basically it shows high resolution microscope microscopic image telling you the twins are not in coherent rather coherent twins and these are also been reported in the literature these twins increases the 10th strength of the material extensively. So therefore whole process as you have seen different techniques were used to decipher the different aspects of the deposition process in fact the role of thiorea can be easily brought about by this technique this all published literature so one can access very easily from the literature so I am not going to tell you our details of that but very easily by searching our names you can find out the literature. In fact to probe that thiorea really affects the grain size reduction by pinning the grain boundaries of the copper grains we need to use a special technique known as energy filter imaging which is normally used attached to the electron energy law spectroscopy I am not I am not going to discuss in this technique in detail in subsequent lectures while not talk about the technique per se but I will show you the effect or use of this technique in understanding the whole process of deposition the left side of the image is basically normal bite-fill image taken by times electron micrograph microscope writes of the image shows you the sulfur energy map in fact in the electron energy law spectroscopy you can select the energies of a element which are given as a edge energy edge here we are using sulfur energy edge to image and we can see this white continues which are present along the grain boundaries signifying the sulfur. So therefore sulfur or rather thiorea is getting deposited at the gain boundaries of copper and thereby pinning the gain boundaries not along the sulfur with copper against to grow this is equivalent to saying that copper grains are actually capped by the sulfur or thiorea molecules and thereby they cannot go further remain in the nanometric regime. This is another special techniques at one catch the techniques which allowed us to understand the whole deposition process next relaxation which I am going to talk about this again from our own work one of my students is such work is on in situ technique you know in situ techniques are very important nowadays especially in situ inside any microscope either a transmission electron microscope or scanning electron microscope or even atomic force microscopes are very popular nowadays in fact there are conferences on in situ microscopic techniques. So in situ is a big part of the whole advanced characterization techniques we are going to show you some sort of few that how this can be used to understand the phase transformation in the nanomaterials almost notably alloy nanoparticles. So I am going to talk about melting as behavior of this nanoparticles inside a microscope okay so that you can get a feeling that an advanced characterization technique can be done the way this technique is done if you look at any transmission electron microscope those who have seen you can understand basically those who have not seen why I am going to discuss with you in the next subsequent lectures in a transmission electron microscope one can use a holder known as a heating holder. So the sample can be heated up at a different rates are very specified by the user and can be viewed on a continuous mode like a video and from those videos one can basically obtain the transformation phase transformation taking place in the material. So therefore it is a very very easy to monitor easy to do a technique and in this technique one can heat up to temperature approximately 1000 to 1500 max. So nowadays even the holders available which you allow you to heat at the rate of maximum 500 degrees per second. So therefore immediately you can heat up the material look at what is happening by passing all kinds of solid state transformations. So this is a very advanced and very useful technique used in many material scientists to understand the basic behavior or basic phenomena taking place for any material especially used on nanomaterials like how the nanomaterial grows how the nanomaterial transformation do takes place in a system like alloy which I am going to discuss. So for this purpose I am going to say you also how different techniques can be used. So here I am going to give an example on lead tin which is a very low melting eutectic alloy particles size below 100 nanometers embedded in an aluminum matrix this is basically prepared by root called melt spinning in which aluminum along with lead tin alloy was melted and because lead and tin are immiscible with aluminum. So therefore they there will be liquid phase separation and if you rapidly certify this can lead to the small size nanoparticles the left side of the image shows you image for using hard if that is high angle annular duct fill image this is also attached to the transmission electron microscope. This gives you images based on Z contrast that is the atomic number contrast just like in ACM we can get atomic number contrast using backscatter electron imaging mode here we can get atomic number contrast using hard if image in fact this can be used in high-resolution mode also to see different type of atoms in the high-resolution images but we are showing you normal white film image using this detector which is attached with the electron electron microscope what you can see here in this image is the black background which is basically aluminum low atomic number elements therefore the it will be seen as a gray or black on which there are nanoparticles like this one this one or this one or maybe this one or different sizes each nanoparticle shows a double contrast or two phase contrast one at the top one at the bottom or vice versa depends on how the particles are oriented you can clearly see the different contrast in all the particles existing that clearly still said they are two different kinds of phases they are two different types of atomic numbers are average atomic numbers so therefore by using this technique want to easily map the whole microstructure using Z or G or atomic number contrast if it a normal electron or white film microscopic imaging one can see these particles which are very small about less than 100 nanometers and it contains lead and tin within the aluminum matrix where tin is the bulk part of these particle lead is forming the cap so by knowing this one can understand the morphology orientations of this particle with respect to the aluminum and many other stuffs which I am not going to discuss in detail but this all available in the published literature if you just do a normal difference in scanning calamity analysis which is not part of the servers but probably have heard of it this techniques will tell you if you heat or cool a sample if there is a phase transformation taking place or not here left hand side is basically the y axis basically power and xx is a temperature temperature varying from 100 to 210 degree Celsius that saw the late in normally melts you technically in particles so if I hit it which is shown by red curve you can see the melting pick which is very very convincing to us that is a strong melting events but once you cool it down the solidification does not take place at a fixed temperature or range of temperature it takes place a wide range of temperature even the solidification peak is also very diffused so they it tells you lot of different stuffs or different aspects of the whole melting solidification behavior which is can be can take longer time to discuss but what you understand is a melting is very sharp and there is a melting events before the melting event there is something happens here that is why the peak it asymmetric so to understand it we put the sample to the sample inside a microscope or a heating stage microscope rather and heat it up I am showing you a set of dark fill images which will tell you how this can be used to understand the phase transformation if you start from room temperature to 90 degrees or even 145 degrees nothing much happens to the particle a dark fill image basically taken in such way the lead part is illuminated of the particle team part is not please do not get confused from the earlier picture this is just to orientate so that we can understand the process and the these vector G is used to image the lead part of the particle if you heat from room temperature 90 degrees the small adjustment of the phase mixer takes place because of the eutectic phase diagram 145 again little bit adjustment the most notable thing happens at about 170 degree 1 degree Celsius temperature these temperatures are obtained from the heating holder heating holder will have a thermocouple attached to it and this thermocouple will sense the temperature therefore heating holder cannot really sense the temperature of the sample but it can sense the temperature of the furnace so there will be some temperature difference between the furnace and the sample so but we do not bother much because we cannot measure the exact less temperature of this nanoparticle by putting a sensor which is not possible till today at 170 1 degree Celsius temperature the whole particles become laid rich so therefore a eutectic particle which is consisting of two phases transform to a single phase particle before even it melts down and then melting begin at 178 degree Celsius temperature part of the particle is already molten and about 82 degree 182 degree Celsius temperature whole particle is molten so therefore the melting temperature particle almost even same I know we know that late in eutectic melts at 182 degree Celsius temperature but the whole particle does not melt like eutectic which has been reported in the literature you do not need to bother about the basic things inside it what you need to understand or I want to need to know is that the by using this in situ technique we can probe even how a small size particle which is approximately 100 nanometers can be understood so therefore we need to have this the advanced characters in techniques will be used in the day to live time to know this and this is again to show you that this is the only the case the particle transform to a single phase laid rich solution so this is wrong this will be laid rich solution before even melting the third one of the last example which I am going to give you to you is on we are performance of nano crystalline copper lead we know that copper lead alloys are very important because they used in the bearing material they are actually bearing material for many of the objects or the machines we use because of the under friction and the lubricating properties of the lead which is normally obtained by preparing a copper lead composites because late is normally very low temperature yeah so essential liquid for bearing application is that it must have a duplex microstructure with a homogeneous distribution of this soft lead phase and hard matrix in which the lead is embedded is basically provides a wear and the resistance and also the helps the laid particles to perform as a lubricating ones so normally this can be done using casting techniques the samples can be prepared but casting techniques leads to enormous microstructures many cases this also leads to some kind of laid big particles of laid inside the samples so that is why sintering is adopted and if you want use a normal sintering technique it can takes you very high temperature about 500 to 900 Celsius temperature for long time to obtain good center products so we have not used that in our study where we use a technique called sparks plasma sintering technique in which the sintering can be done at 3 to 400 Celsius temperature and also at a time to meet up 20 minutes so therefore one can actually form the nano crystalline copper grains structure then sintering process because of the use of low temperatures and so the time used in this technique is low so these are all published in the different literatures what I am going to show you some use of characters and techniques the first one is use of scanning electron microscope which is shown here this is the backscattered electron images of the copper 10% lead copper 22.5% lead and copper 15% lead and all the cases you see the white color things are laid because this is a high atomic number the gray contest is from the copper and you can clearly observe the uniform distribution of lead in the copper this doesn't tells us whether copper grains are nano crystalline or not to do it to understand it we go for the time select of microscopy where we can see that these grains are indeed approximately 100 to 100 less than 100 or even something is 120 nanometers and lead can be seen between the two gain of the copper or the gain junction point triple junction points one can observe even lead particles which has fallen off during TM celebration so these two techniques using scanning telling list of microscopy and also time select of microscopy we can see both the late distribution as well as the copper grain size now if you understand it will obviously it has a very good distribution of lead in copper with the nano grain copper will have very good friction properties that is what it been done in this case you can see the coefficient of friction can be as low as 0.4 in all the cases and by showing it we can say that the frictional property of the material has improved but how to understand that we have looked at the wear surface in on a CM or scanning electron microscope one can see different kind of things one can see delamination one can see even the breakage of the particles by using this character of microscope even if you use the HEDAX that is the electron spectroscopy energy dispersion spectroscopy by using electrons and character of microscope we can see the peaks coming from iron oxygen copper lead even iron is very predominant because we used the iron ball or the steel balls for abrading the surface so iron comes into picture and forms a tidal layer not only that to even understand that how the oxygen is affecting the microstructure wear process we can use Raman spectroscopy very small size laser beam can be focused on the sample and the Raman peaks can be obtained this shows us presence of Cu2O Fe2O3 lead oxide on the surface therefore oxidative wire takes place on that to clarify it even one can do vacuum wear test and then map the elements using electron micropermalizer if you see that the oxygen presence on this sample which is tested in back room is very small on the other hand tested in air oxygen signal is very high other signals are copper and lead so which will be present predominantly on the sample this is another important techniques like electron micropermalizer which is using a special gun like focus at the field emission gun can give us a very high resolution then one can actually look at soft surface imaging using focused and beam in this technique sample is dig a trench is made in the sample and the surface inside this trench is seen either on an ion beam to show the cracks or the different particle present or on a time select on a scanning electron micrograph like that but you can see this copper cranes or coagulated copper grains lead particles even some of the lead particles can be seen to a factured steps to be formed and some cases they are sinter you can see some cases they are sinter actually here so therefore all kinds of phenomenon a phenomena can be easily observed if you look at the subsurface imaging using focused and beam this is again shown here how different particles has been factured steps as form of sinter so in summary what I can say you is this that we need to use different advanced characterization techniques to understand the phenomena taking place processing third illustration or the last one in this class in this lecture is on wear performance of nano crystalline copper laid alloys we know that copper laid alloys are used extensively in bearing applications and this is done for long time because of the antifixion properties of lead also self lubricating properties of the lead within the copper copper and lead are immiscible in actual sense in solid and liquid state so therefore they form very nice distribution of the lead in the copper normally for any bearing applications we know the material must have the following requirements as far as the microstructure is concerned this must have a duplex microstructure we know that for bearing application the material must have following microstructures or requirements first of all it must have a duplex microstructure consisting of homogeneous distribution of the second particles like lead here in a matrix of copper the matrix actually resist the wear becoming harder and the soft phase which is the lead here with can act as a lubricating agent thereby reduces the wear and tear so it has been seen that copper laid alloys can be prepared by casting roots and this roots leads to you know in a distribution of the lead in the copper that is because the lead is immiscible with copper and that is why the distribution of the lead in copper will be very bad because of the different problems in the casting techniques that is why no one uses normally the casting route to prepare copper laid alloys rather use sintering techniques or the powder metallurgy techniques in the condition sintering roots where copper and lead powders are mixed and then sintered by pressure less technique it has been observed that it takes about 500 to 99 recesses temperature by hitting the sample or the powder mixture for about 6 to 10 hours to get dense sintered product and this temperature and the time obviously will lead to extensive grain growth of the matrix of copper and also it can lead to oxidation of the both copper and lead so that is why nowadays one can use special techniques to stop the grain growth for keeping the nano crystalline copper grains in the microstructure at the same time to stop the oxidation both are required for better performance of the material this can be done by using a special technique known as spark plasma sintering technique which is a very recent one which has been developed in 90s and hardly about 20 years old so this can allow us to use lower temperatures of 3 to 400 recesses temperature for sintering copper laid alloys and the whole sintering cycle can be finished within 10 minutes so therefore it will stop the grown grain growth because of low temperatures and time and also because of less time at high temperature oxidation can be reduced in our case we have used this techniques to prepare the samples then we have analyzed the sample using different characters techniques so that we can understand the way we are of this material first I will show you the initial microstructure here I am showing you the microstructure of the copper laid alloys with different date concentration 10 12.5 and 15% lead what you can see is this white phases some cases they are discontinuous and some cases they are particles they actually lead these images are obtained in scanning electron microscopic image using basket electron mode which we will discuss as a part of this course which can show up the Z contrast or the atomic number contrast a lead having the higher atomic number will be seen as a white so a lead is uniformly distributed in all the samples as you can clearly see and copper can be seen as a gray contrast but grains of the copper cannot be seen in the same they are very small to observe the grains of the copper we need to see the samples in transmission electron microscope and these are the two images taken from the sector microscope of the copper laid sample you can see the grains are very small this is the 100 nanometer bar so approximately 100 to 120 nanometer some cases even lower than 100 nanometers grains can be seen and lead particles are seen to be situated between the copper grains many cases between in the triple junction points of the grains or some cases lead particles has fallen off during TMS operation so therefore by using both the scanning that is electron microscopy and the time is electron microscopic techniques we can understand the microstructure very well and by seeing the microstructure you could probably understand that this is a very good material for where resistance study this has been done using the fitting wire technique and here I am showing you some coefficient of friction values obtained by our study you can see that for different concentration of the late 12.5 15 or this is also 12.5 but at different hardness so what you can see that the coefficient of friction is pretty low as compared to copper coefficient of friction of copper is about 0.8 against steel and this wire test is done using a steel ball on a fitting wire machine so the because of that the coefficient of friction is because it is low that means laid as a prominent low reducing the coefficient of friction not only that the hardness of these materials are pretty high as you can clearly see because of the nanochristian copper grains. So now how the characterization techniques can help us understand the wire process here I am showing you the wax car during the fitting wire at a low magnification picture which is approximately about several millimeters because this is 0.1 millimeter so therefore it will be approximately several tens of millimeters and within that if you just look at in zoom view you can see delamination you can see even cracks some cases you can even see the lead particles spade across the sample so if you take a edacs of this surface the edacs means in energy dispatch spectroscopic technique attach the ACM you can see presence of oxygen iron copper obviously and lead iron is predominantly present there this is because iron is getting transferred from the steel ball oxygen is also present therefore what is the exact role of oxygen one needs to understand very clearly that to do that we have done Raman spectroscopy on this wire sample or the own surface if you do that using a laser beam of 540.5 nanometer the very small laser power one can see presence of lead oxide copper oxide iron oxides on the surface therefore oxidation do takes place on the surface because of wire but one can easily prove it even using a better technique known as electron micropropan analyzer here we have done test where test in vacuum by testing air to see the oxidation if you use electron micropan analyzer in a fake epima that is the field emission can epima had the beam size is very small resolution will be better so you can see the oxygen is very small even on the surface for the sample tested in a vacuum on an oxygen is quite large in a sample tested in the air copper and lead are obviously present on the sample and this is the same image of the sample on which this epima analysis is done. So therefore by using these two techniques Raman's and the epima we can clearly see how the oxidation do takes place oxygen dust takes place in the wear process and changes the wear kinetics to you want to look at this subsurface deformation characteristics one needs to use another kind of character in technique which is known as focus the end beam to prepare the sample so what do you do take this wear track and cut in middle and make a trench we can do on a different actually wear surfaces this is so in the next figure here we have made a trench cut using focus time beam or the gallium beams in the focus time beam machine and if you just tilt the sample and view even in the focus time beam by using the end beam contrast one can see even different black color things which are basically particles you can see even they have cracks which is going like this better image can be obtained if you see this trench in scanning electron microscope you can see the lead particles pick white color and also the copper agglomerated grains leads are seen to be factored in many cases some cases steps to form on the surface of the lead and some cases leads a small size particle some cases they agglomerated because the sintering so therefore during whole wear process temperature do rise in the subsurface domain of the sample and leads to the sintering and during deformation some of these lead particles do gets deformed and steps forms on the surface and factoring also do happen so this is again shown here in a very high magnification picture with insets so this you can see very clearly so what I am trying to convince you is that by using this set of characterization techniques which are known as advanced character techniques we can see the surface subsurface of the sample during wear process and understand the wear mechanism very easily see in summary and also for the subsequent lecture I am going to say you something here that in summary I can say that we need to use advanced characterization techniques for not only to understand the material science phenomenon in a particular process but also to understand the processing techniques which are used required for the whole you know material science domain many cases we need to engineer the material and engineering the material means which is in changing the processing parameters change the sample characteristics sample compositions how does these parameters affect how do this parameter actually affect the processing and the material properties later on can only be deciphered if you look at the samples using different characterization techniques and this characterization techniques can be either microscopic techniques as we have seen or you can be spectroscopic techniques many cases we need to use even diffraction techniques to understand the processes which I am not showing in the first lecture or many cases even one can need to use the surface characterization techniques like the audio electro spectroscopy or any other spectroscopic techniques which can give us surface properties this is more important for the particles which are very small size like nano size or even some cases micron size so therefore in a nutshell what I can say is that that we need to know in detail the detail characterization techniques which are used or which will be used by many of these labs for understanding the material science phenomena so in the next class I am going to start with microscopic techniques will be used to understand microstructure so therefore the connecting the microstructure with the material processing can be only done by using different microscopic techniques this will involve SEM, TEM, AFM, STM as well as confocal microscopy we will discuss one by one this techniques I will first start with TEM in the next lecture then move into SEM and finally other techniques will be dealt with thank you.