Good morning. I'm Mary Ellen from the channel Mary Ellen after 60 and I'm here today to film my last video of the year and just to share some more of my slacker ways and announce five secret giveaway winners and just kind of hang out with you. I'm glad you all enjoyed our 2020 favorite collaboration that we all did together. It was Natalie the Beauty Diva and Carol from The Old Carol Show and I always really enjoy making that video and collaborating with Natalie and Carol.  Well when I reply to comments I don't go underneath the video that there's a comment part of it and it just is comments that come in from other videos from recent videos and at the very top there's a section and it reads held for review. Well they used to have numbers by there. To make a long story short I clicked on it just to see and there were like 25 comments that were held for review and the only thing I can figure out is that YouTube thought people were sending links because if like if somebody typed a word and then put a period and then started another word I noticed that was on several of them but I did reply to all of you and I want to apologize because there was one woman and her name is Kay that there were three comments in there so I'm sure she thought I was ignoring her but you know I'm not Kay. 2020 has been a very hard year for a lot of people. People I know personally some people weren't affected that much from it and some people were devastated and it has been hard and I will tell you what has gotten me through it is my faith and counting my blessings. Every single time I look at a clock I look at my watch I will take time to count all the blessings that I have and sometimes I'm you know sometimes they're just real easy and sometimes I really dig hard but I used to do very well through the day only doing that first thing in the morning when I was still in bed and also at the end of the day but I've just been counting my blessings every time I look at a clock or my watch.  Well I didn't do a giveaway on my 20 of 2020 favorites and I wanted to give one before the end of the year so what I did I went to the last giveaway that I did and that was for some tart eyeshadow palettes and I had asked people just to tell me their favorite flavor. Well I loaded all those comments it's easy to do you just highlighted and put it in random comment picker and I picked out five winners to get a $50 e-gift card or a deposit to your PayPal and I've already have the winners listed here. I did have one person probably in the summer that I sent an Amazon gift card to an e-gift card and it shows that it was received but she lost it so if you get an e-gift card make sure you save that if you if that's what you choose to do and I can wherever I can get an e-gift card whether it be to Ulta to Walmart to Amazon Target there's so many places that you can buy e-gift cards that's what I will send you and I'm gonna go ahead and list the names of the winner and I'm gonna go in the order that they were picked and I have five winners the first winner is Teresa Kehoe congratulations Teresa the next winner is Kim Moke congratulations Kim Wendy Gessner is the next winner congratulations Wendy the next winner is Elizabeth Walker congratulations Elizabeth and the last winner is Kay Johnson so all of you make sure you leave a comment below and I'll let you know how to get in touch with me well you know the definition of a slacker I think is people who avoid work people who try to get out of work don't want to put in much effort well I kind of think that myself as a slacker because I do things to prevent having to do a lot of work it's kind of what how I do it and the things I do usually either save me money or save me time and even when I had one dollar left in my bank account the day before payday and I was raising two small children I knew that I had more money than time I mean I didn't have very much money but time was short I worked full-time you know I had two active children so I've always wanted to save money and I've always wanted to save time so I've kind of lived by a couple of sayings and ounce of prevention is worth a pound of cure and I think the other one is a stitch in time saved nine and that is so true and at the end of this video and in the show more section below I will leave a link to my first slacker my first slacker ways video if you go there be sure and read the comments because in that video I asked people to share their slacker ways and I had found some good ideas but the ones I'm gonna talk about are the ones that I've done throughout my life and that I didn't hear about from YouTube or anybody else because if I ever hear a tip from somebody else I always want to give him credit so I'm gonna go ahead and get started and you all may do this a lot and this saves me time and money when I wash my sheets I usually put the same ones back on I buy my sheets in separates I buy separate fitted sheets because those are the ones that tend to wear out first and I put a safety pin on a corner and I rotate it so I always know how to put my sheet on I don't think I've ever had very many pillowcases or top sheets that wore out but that saves me time because I don't have to fold the sheets because I can put them right back on the bed and it saves me money because I only have to replace what needs to be replaced and normally my top sheets are a print of some type and my bottom sheets are always like gray so anyway I want to share that I sell them if ever I mean I don't know the last time I bought a drink at a fast food restaurant I don't know when I've been to fast food restaurant but Jim always likes to get a Coke and when I get home I bring in the cup and this one happens to be from Burger King and I don't know how old it is but I wash it out dry it and I stick it underneath my sink and so anytime I have food that needs to go outside instead of down my garbage and I don't want to put it in my trash I just use these fill them up it may be grease let it cool put it in here and I throw it away so at least there's two uses sometimes I have more than two uses because if it's if it's something that's not greasy I'll go dump it outside and then come back and rinse it out again ever since you could take photos with your phone and stretch them out I have taken photos of directions that were small a lot of times on the prescription bottle it's too small to read the prescription number so I just take pictures of it and I just stretch it out and I've shown Jim how to do that and that's kind of like a release emigration L from the channel L is for living says there is a good app you can put on your phone and I'll try to find her video and let you know what that is but she uses it for magnification so I haven't done it that way yet but I do do that a lot I have a lock box at the bank and it's it's you know fairly good size I've always put all of my negatives we don't have negatives anymore I don't anyway for photos but I have my family movies that I took when my children were babies I have all the negatives of the pictures I took I have my thumb drives I have copies of credit card driver's license passport and and they're all safe at the bank so that's something that makes my life a little easier because I know exactly where to find it none of these are profound these are just things that have made my life just a little bit easier you know I put my foundation on with my fingers today I have on the powder foundation the celebration foundation but and I do use a brush for that but if it's a regular liquid foundation I don't use brushes and I don't use sponges number one you have to wash them a lot and I don't even know I think sponges are very hard to get clean but I've just never used a brush or a sponge to apply my foundation because I'm a slacker and my fingers have worked wonderfully well well throughout the years before I put on makeup I wash my hands and I'm not worried about my own germs and I've had some questions about this I use the grande brow and I don't have to do anything with my brows sometimes I put a little hairspray on them to keep them if I like put my hand up there at night when I've been sleeping but I still derma roll my eyebrows but I've only derma rolled the tails so the grande brow has definitely thickened up my eyebrows and I'm going to continue derma rolling my tails because I think I'm getting a little bit of a benefit from doing that with my eye so yes I do that and that way I don't have to think about eyebrow products I've talked about this in other videos I don't not in my slacker video but I have a flat iron that the only thing I use it for is kind of pressing hymns or plackets down a shirt or the collar and I don't know it know when the last time I got an iron out it's been a long time this I'm just really careful when I wash things kind of hang them up damp and then I can just use this and it works really well this is a two-inch and I think any brand would work that it works for me and I started doing that when my daughter she's 42 when she was just a little girl I would run her ribbons across my curling iron to get any of the little wrinkles out of it so when I saw flat irons I thought immediately oh my gosh I'm gonna get that to iron with now this just kind of helps with aggravation dropping things looking for things the only the eye drops I use are the renew for contacts and I can always keep it in a little organza bag and the reason if you drop it it will not roll and I can't tell you how many times I drop something and it rolls under something and I have to stop what I'm doing I have to go hunt for it so this is a tip for anything that is round that will roll away and I know that I am a true slacker the other one other thing I use my organza bags for are all different kinds of lids of caps I have caps to retinae I keep a cap before I throw away or you know do my empties I take the caps off and I have my small ones in here and I and then I have a bag in my dressing room for the larger caps a larger organza bag but it's just so easy if you need a cap chances are you have one and I have to share something that really did save me time and made my house look nice I don't do it anymore but I used to put linens on top of my like my desk my shiffer robe end tables coffee tables and I had beautiful linens and I didn't mind ironing those that's one thing I didn't mind ironing but you would not believe how much less dusty something looks so I could get by not dusting as often and this this was back when I was busy running around with my kids but it sure did make my things look nice on top and that's where something gets dustier and I'm admitting what a slacker I am and if you're still here this is going to be another giveaway in the months of October November and this month my videos my older videos especially have gotten so many more views I don't know why but they have and so when the more views you get the more money you make from AdSense and that's a person I guess that's probably Google but that's how you get paid for making videos and you don't make very much maybe I don't know I heard somebody say a penny of you but those views add up especially if people watch them for the whole video so I have been putting back money every month to do a giveaway at the end of the year so I'm going to do another giveaway and this time I'm going to have four fifty dollar winners and it's going to be e-gift cards or PayPal and the only thing I want you to do in the comments below just tell me something you learned this year I don't care what it is it may be something very small it may be something pretty big that we all can learn from but just in your comments below mention something that you've learned this year and because this is a giveaway I cannot reply to these comments but if you go to any video even though it says I can't reply in the beginning of the video I can because all those giveaways are over and you can leave me a question a comment and I will get back to you on the older videos but to be in this giveaway the comments need to be below this video and all you have to be is 18 years older older and leave a comment below to enter in this giveaway it has been a very interesting year I'm hoping 2021 is it's going to be a lot easier but it is all good I appreciate you being here I appreciate your time your comments and just your friendship and I will see you in my next video take care I used to put very and I will announce the winners and it says and I think it helps a deposit to your bank account and I and I usually placid placid because I know exactly where


previous class we have seen the pressure composition temperature isotherms as it says isotherm that means these are drawn at a particular temperature. We have also seen the want of plots. Now we have seen how to draw the want of plot like when the pressure composition isotherms they are drawn at different a series of temperatures and from these when the equilibrium pressure is extracted and that is plotted with respect to 1 upon T we get a want of plot. Now this want of plot that gives very important information about the metal hydride reaction, about the metal hydride materials itself. That slope of the curve we have seen in the previous class that tells the delta H value or the enthalpy of reaction or enthalpy of formation. It not only tells about the stability of the material, but it also tells like how much amount of heat will be released in the charging process during the hydrogen uptake and how much amount of hydrogen need to be supplied during the discharging process or during the release of hydrogen and that helps in designing such systems. In metal hydrides which operate under optimum conditions it is even possible to get the required heat of desorption from waste heat of either fuel cell or IC engine. So it is usually required that the operational temperature or the working temperature and pressure should be such that the temperature could be say at max 100 degree centigrade or lower than 100 degree centigrade and pressure required should be close to ambient, but depending upon the what sort of applications we write which we are looking at that may be say in the range of 1 to 100 bar maximum. Now if we look at the want-off plot for various binary hydrides, then we can see from this particular curve that most of the binary hydrides they are actually not having desired thermodynamic properties. That means the binary hydrides if we see the want-off plot pressure versus 1 upon T curve then these binary hydrides they are having higher thermodynamic stability. Like if we consider an equilibrium pressure of 1 bar then they may have a temperature of desorption which is higher than 300 degree centigrade. For example for magnesium hydride like it desorbs above 300 degree centigrade at the same time the heat of reaction that even could be higher like for magnesium hydride it is 75 kilojoule per mole. Now the typical examples of such hydrides are alkali hydrides, alkaline hydrides or transition metal hydrides like the scandium, titanium or vanadium groups. Now the more electropositive hydrides they elements they react with hydrogen to form ionic hydrides while this magnesium hydride is a sort of intermediate. Intermediate in the sense between the ionic hydrides and the covalent hydrides of the other elements in the first two periods. If we look at the high temperature hydrides like the hydrides which at an equilibrium pressure of say 1 bar they desorb at temperature higher than 700 degree centigrade then the typical examples could be like the zirconium hydride or the lanthanum hydride. Now this zirconium hydride this has a very high desorption temperature although the volumetric capacity of hydrogen storage in zirconium hydride this is high like about 119 grams per liter of hydrogen being stored. But as compared to say liquid state storage where the volumetric density 70.8 grams per liter that is in the liquid hydrogen storage or in case of compressed hydrogen storage that is 21 grams per liter for 350 bar compressed hydrogen storage or 38 grams per liter for 700 bar compressed hydrogen storage. This zirconium hydride like many other hydrides it forms different hydride phases like it could be ZR H2-X and this composition can be something between say 1.332 it can be ZR H2. The another binary hydride is like vanadium hydride now this vanadium hydride again has a very high volumetric capacity vanadium hydride has a high volumetric capacity of 190 grams per liter. But the major problem that lies is if we see this box this is the alone hydride which lies in the range of optimal conditions of temperature and pressure rest either they have high desorption temperature. So most of the hydrides if we see they have higher desorption temperature or higher stability. Now it was in the year 1958 that Libowitz at all they came up with a completely new class of materials so that was a major breakthrough in the hydrogen storage materials. So prior to that as we have seen in binary hydrides they are not suitable for hydrogen storage. But then when they came up with this class of materials which is known as inter metallic compounds they observed that these compounds they reversibly react with hydrogen storing hydrogen at the same time they have a thermodynamic stability which is intermediate between the two compounds and this opened up a completely new field of research. So in 1958 they came up with the inter metallic compound that was zirconium nickel and they mentioned that this zirconium nickel they observed that that forms a ternary hydride and that ternary hydride the interesting thing that they found was that was having a thermodynamic stability between the highly stable zirconium hydride that has an enthalpy delta H of formation of 169 kilo joule per mole and an unstable hydride of nickel hydride that had an enthalpy of formation of 8.8 kilo joule per mole. So the interesting finding from this particular work was that the zirconium nickel bond which is being formed in this ternary hydride that had a strong destabilizing effect on the metal hydride that is the stable hydride zirconium hydride and it was observed that if we consider the equilibrium pressure of one bar the desorption temperature highly reduces it reduces from 900 degree to 300 degree centigrade. And that opened up a completely new research field of hydrogen storage materials and hundreds of more inter metallic compounds were developed and were studied. But most of them they were found to follow the well known miderma rule and that was in fact a relationship that connected the delta H value of these inter metallic compounds with their individual hydrides and the inter metallic compounds itself. So as per the miderma rule if A and B these are the two elements in such that the delta H of A and Bm Hx plus y is equal to delta H of A and Hx hydride of A plus delta H Bm Hy minus delta H An Bm. Now this rule we are able to explain or we are able to find out the delta H enthalpy of reaction for most of the hydrides. Another breakthrough was when in 1974 the low enthalpy of formation metal hydrides were found. So the two well known metal hydrides we know today are LA Ni5 and FETI. So these were developed, these were discovered in the year 1974 and it was observed that lanthanum nickel 5 which forms LA Ni5 H6 it has at say 2 bar of equilibrium pressure when it desorbs at 1300 degree centigrade. However it was observed that lanthanum hydride LA H2 at a equilibrium pressure of say 2 bar it desorbs hydrogen at 1300 degree centigrade. However the compound which was found inter metallic compound LA Ni5 H6 that desorbed hydrogen at 2 bar equilibrium pressure and at a temperature of 20 degree centigrade. Another interesting compound was iron titanium and also magnesium nickel Mg2 Ni. So in late in 1984 Griesen and Griesen they came up with a more accurate formula compared to the Medema rule the correlating the enthalpy of reaction with the characteristic energy of the electronic structure of the host metal. So they came up with a semi empirical band structure model which showed that there is a linear relationship between the delta H and delta E. So delta H is equal to alpha times delta E plus beta where alpha and beta these are constant having these values while the delta E is the difference of Fermi energy E f and E s where E s is the center of the lowest band of host metal. Now after this there were wide number of inter metallic compounds that were reported. It was found that the host of these inter metallic compounds they generally are ordered stoichiometric compounds and these are being formed from two species two metallic components A and B. So these origin is there are two compounds inter metallic compounds in various compositions forming nearly or stoichiometric compounds and also we have seen in the previous class that interstitial hydrides when hydrogen enters into the interstitial sites there occurs an expansion of the lattice. So it was also found that the lattice parameter or the unit cell volume it is related to even the plattue pressure in the different materials. Now coming up to these inter metallic compounds as we mentioned that the inter metallic compound it refers to a combined phase or an integrated phase between two metallic species A and B. Now alloying of these two species together it increases the degrees of freedom of the final product in the product material like that may change several properties of the material its hydrogen storage properties will change. So when we alloy these together it increases the degrees of freedom in terms of the change in the structure it there may be a change in the there would be defects or anti-phase boundaries which are created and that may help in improving on to the hydrogen storage properties of these materials. Now among the inter metallic compounds between this A and B so these are A and B making an inter metallic compound the metal element A is such that it is a transition metal or a rare earth and that element A has a stronger affinity towards hydrogen. Once it has a stronger affinity with hydrogen that may that means it makes a stronger bond with hydrogen and that makes that hydride highly thermally stable. So the examples of elements that appear at A side could be yttrium, lanthanum, titanium, zirconium or there could be more. Similarly the other element B in these compounds it could be a transition metal but that transition metal which forms an unstable hydride example chromium, magnesium, iron, cobalt and nickel. So these are they form unstable hydride and they absorb hydrogen only at a higher pressure. So a combination of one element which has a strong hydride forming tendency form the stable hydride and another element which has a which forms an unstable hydride gives rise to a inter metallic compound which will have intermediate between the two properties. So they will have different chemical and physical properties compared to both A and B. A typical example could be like at A side if it is lanthanum at B side if it is nickel. So an example being lan i5 such that the delta H value of lan i5 is 32 kilo joule per mol. However lanthanum hydride we have already seen that this is a stable hydride having a delta H value of 208 kilo joule per mol, nickel forms an unstable hydride with a delta H value of 8.8 kilo joule per mol. But when an inter metallic compound is formed with lan n i it forms lan i5 and having an enthalpy of formation of 32 kilo joule per mol which lies in between the two. Now depending upon the way these are combined, so what are the different elements being used? What are the different combinations? These inter metallic compounds can be divided into different classes. So there could be either an AB5 type of compound, it could be A2B, it could be AB2 type of compound, AB, A3, B7, AB3 type of compounds. So these are the different classes of inter metallic compounds. So as we have seen in this A and B, A is a strong hydriding element, B is a weak hydriding element and that forms the inter metallic compound. Their different compositions can lead to different thermodynamic properties. Now when we are selecting these inter metallic compounds for different hydrogen storage applications what we need to look at is what are the operating conditions? What are the temperature and pressure? What is the capacity of that alloy? Is it affected by the presence of impurities in the material itself as well as in the gaseous gas hydrogen?  Usually the desirable is it should have a faster kinetics. What is the platinum pressure or the equilibrium pressure for that particular inter metallic compound? How easily it can be activated? So activation we have seen in the previous class and ease of activation also plays an important role. What is the cost of that material and how easily is that available? So rare earth could be avoided. Now these are the typical examples of the most widely studied class of these compounds like for AB iron titanium has been widely studied, for AB2 zirconium magnitude, for A2B MG2NI, for AB5 LANI5, for AB3 CENI3, for A2B7 ND2 NI7 and other compounds. So their reversible storage capacity may vary, their delta H value may be different, their equilibrium pressure, temperature and crystal structures may vary and these are quite important when we design a particular metal hydride based hydrogen storage system. All these needs to be considered while selecting a appropriate material. Now starting with AB5 class of compounds, these AB5 class of compounds these have been widely studied. This is because of their special applications like that was in the case of electrochemical applications. So they have good electrochemical properties as such these have been studied and a vast range of such compounds they have been studied, they have been developed. The reason being is of substitution at the A and B sides. The typical structures are of CuC5 type and the first material in this class which was studied was SMCO5 and that was studied for their magnetic properties and there after the development of the AB5 type of hydrogen storage materials started. Now in this AB5 type of compounds, the first element A here, this is either, it could be either lanthanide, it could be calcium, it could be yttrium, it could be zirconium or mish metal. Now this mish metal is in fact a combination of different rare earths and that is in their naturally occurring composition. So it can have different composition depending upon the different source. Usually a general composition could be like 45% of lanthanum, 50% of cerium, others could be neodymium or pressed dimium. On the B side, it could be nickel, tin, titanium, aluminium, cobalt, iron, copper, silicon. Now when this alloy class is being considered, because of this alloy they have a different, they have a hydrogen storage characteristics and their stability of these compounds, all that depends upon what is the plattue pressure. So the factors that govern stability will be what is the plattue pressure and their hydrogen storage properties as well. What is the slope of the plattue? What is hysteresis? All these terms we have seen in the last class. Does these compounds have hysteresis? Are they tolerant to the impurities present in the material itself as well as in the gas? How good is the cyclic life of these materials? And all these can be controlled by appropriate selection of elements onto the A and B sides and that makes these class of compounds very interesting in the sense that we can tailor the properties, the required hydrogen storage properties by appropriate selection of A and B at the same time substitution of these elements. But sometimes what happens is, if we try to improve one property, let us say for hydrogen storage property, resorption temperature may be higher. So if we try to improve one property, that may deteriorate the other. So that makes it little complex in that case. Among this class of compound, the most widely studied one is the LENI-5. Now this is having several advantages because it has a favorable pressure composition temperature isotherm. This is very low hysteresis. At the same time if we see the plattue pressure at room temperature is 20 bar and both like the operational conditions if we see are very favorable room temperature and 20 bar, both are quite favorable operational condition. So the reversible capacity of these type of materials, LENI-5 materials, this is 1.25 weight percent. Now if we consider some of the examples like on the A side, if this A side it is MISH metal or lengthenum or calcium, these are substituted with MISH metal, lengthenum or calcium. B side is NI. So MMNI-5 or LANI-5 or calcium nickel-5, we see that they will have different storage characteristics like MMNI-5 has a weight percent gravimetric capacity of 1.46 weight percent, LANI-5 has 1.49 weight percent, calcium nickel-5 has 1.05 weight percent. Delta H value we can see that it also with this substitution in this order it increases 21, 30, 31.9. The desorption pressure at a temperature of 25 degrees centigrade, it is also decreasing. So for MISH metal it was 23 atmosphere for LANI-5 it is 1.8 atmosphere for calcium nickel-5 it is 0.5 atmosphere. At the same time on this substitution on the A side that reduces the hysteresis. So for 1.65 it has reduced to 0.13 and then it has slightly increased to 0.16. At the same time the slope of the plateau has also reduced and then increased in the calcium nickel-5. Now this shows the effect of substitution on the A side. However it has been found that these two LANI-5 and calcium nickel-5 on repeated cycling we have seen that when hydrogen gets into the lattice there is an expansion and when it is released then there is a contraction. So because of that repeated cycling it is possible that significant disproportionation can result in these type of compounds like LANI-5 and CNI-5 and that disproportionation can cause the property changes can lead to loss in the reversible capacity during cycling and that could be taken care of by partial substitution onto the nickel side. So a typical example of this partial substitution reducing this disproportionation is substitution by means of tin. So on nickel side if we substitute LANI 4.8 tin 0.2 it was found that this has a better cyclic stability. It has weight percent 1.4 percent, delta is 32.8, plateau pressure reduces 0.5, hysteresis 0.19 and slope being 0.22. Similarly if we consider other substitution on the nickel side for mesh metal like that of iron that again changes the characteristic like the weight percent however is found to reduced compared to MMNI-5 from 1.46 to 1.14, delta H value has increased 25.3. Similarly the desorption pressure has reduced to 11, hysteresis also was found to reduce 0.17 on iron substitution, slope was also found to reduce to 0.36. Similarly if we substitute on the mesh metal side on the nickel side in the mesh metal alloy of MMNI-5 if we substitute to the nickel 3.5, cobalt 0.7, AL 0.8. So this we can see that the weight percent has however reduced the delta H value has increased the desorption pressure it reduces to 0.11 hysteresis as well as slope. We can see that these are also changed when it is substituted on the nickel side. Now the advantages of AB-5 type of alloys is they have good kinetics, they show good cyclability, they have a low hysteresis that is very important they are tolerant towards impurities but the disadvantages of these class of compounds is they have a low hydrogen storage capacity of 1.28 percent. At the same time the cost of the raw material is also high but mesh metal is could be used for large scale production because the cost of mesh metal is lower. Now the another class of compounds is AB-2 type of compounds and these are usually the levis phase type of compounds where in the crystal structure they have 3 different type of crystal structures they show different phases like the C14 phase which has a typical structure of hexagonal of structure of mg Zn2, a C15 phase which is cubic which is structure of mg Cu2 and a C36 phase hexagonal with mg Ni2 type of structure. Among the different class of metal intermetallic compounds this is the compound which are most widely being studied and being developed. So this is the largest group of intermetallic compounds and it is observed that the stability of these type of compounds it depends upon their geometry, what is the packing density, what is the valence electron concentration and the electronegativity difference between the A and B sites. These are being studied a lot the reason being they are very attractive because of their high capacity, they show good kinetics, they have a longer cycle life but the major disadvantages associated are that they form stable hydrides at room temperature. So they are too stable at room temperature at the same time they can get poisoned to the impurity. So they are sensitive to impurities present in the gas or in the solid as well. So the first such structure Levis phase was reported in 1960 and the typical most studied structures are titanium chromium II and zirconium chromium II. Now among this AB II type of compounds usually this A site could be either titanium, zirconium, hafnium or lanthanides and the B could be either a transition metal or it can be a non-transition metal including vanadium, chromium, manganese or iron. Now these materials can be instead of have being ordered stoichiometric these could be slightly sub or super stoichiometric example that of zirconium Mn II-x. Now when this II-x if we consider that x is positive. So when we are considering it to be II-x what happens is the equilibrium platiopressure that reduces compared to ZrMn II. Equilibrium platiopressure reduces at the same time capacity also reduces when x is positive or the structure is or the composition is ZrMn II-x. However and it is II-x then the equilibrium pressure rises and capacity is a very small reduction, negligibly small reduction as against ZrMn II. So we can see that we can tune the desired properties like platiopressure can be either increased or it can be decreased by changing the composition here. We can also get the required properties with such compounds by having multi-component system. A typical example of such multi-component system is like Zr1-x TxMn Cr it is either Mn or Cr2-yMy where this T could be either titanium, yttrium, hafnium, scandium, neobium or M could be this M could be vanadium, olivadanium, manganese, chromium, iron, cubald, nickel, copper or anything else as well. So we can have multi-component such systems so as to get the required hydrogen storage properties. Now if we see certain examples of this type of material we can say that titanium chromium 1.8 and if chromium this is B site if it is Mn or on A site if it is zirconium. So we can see that if it is titanium chromium 1.8 the weight percent which could be achieved is 2.43 weight percent this is reasonably good. We see that with such change the plattue pressure the desorption pressure at 25 degree centigrade that changes significantly. So from A site if it is Zr, Mn2 it is 0.001 atmosphere however when it is B site it is Mn, titanium Mn 1.5 it is 8.4 atmosphere for titanium chromium 1.8 it is 182 atmosphere. Similarly there is a change in the hysteresis and the plattue slope. Now multi-component systems also can be seen like the ternary compound where this is Zr Fe 1.5, Cr 0.5 this gives the weight percent of 1.5 weight percent, delta H value of 25.6, desorption pressure of 4 atmosphere hysteresis 0.34 and a slope of 1.26. Titanium manganese vanadium compound the titanium Mn 1.4 vanadium 0.62 it has a capacity of 2.15 weight percent delta H value of 28.6 kilojoule per mole, desorption pressure of 3.6 atmosphere and a slope of 1.4 atmosphere. So among these compounds we see that there is a low hysteresis for the compound titanium chromium 1.8. The maximum hydrogen storage capacity is 1.86 for titanium manganese 1.5 and reversible hydrogen storage capacity that could be achieved could be even 1.15 percent or even higher. Now the advantages of these compounds is we can get a higher capacity compared to the AB5 type of compounds. Correspondingly they have a lower cost, they can operate at temperatures closer to room temperature but the biggest challenge with these class of compounds is there is a problem in activation. So the first hydrogenation requires higher temperature and pressures. Another class of compound is AB type of compound. Now compared to AB5 and AB2 type of compound the different compositions studied in AB class are very less. So the first study was in 1958 on zirconium nickel and that we have seen that shows the desorption temperature of 300 degree centigrade. They have structure ordered BCC and the most widely studied structure in AB type of compounds is iron titanium compound and this was for the first time studied by Relay and Westwall and that was in 1970. The biggest advantage of this class of material FETI is that they absorb and desorb at room temperature and that is highly desirable when we select a material for hydrogen storage. It can give maximum hydrogen storage capacity of 1.98 percent at H by M ratio of 0.975 with a reversible capacity of 1.58 percent. But the major challenge that lies is the problem in activation and it requires a high temperature for activation greater than 400 degree centigrade. At the same time it shows two plateaus that we have seen in the previous class there is two step absorption and there are two plateaus. There are two different hydrides which are formed beta gamma phases and there is large hysteresis in these type of systems. However, we can address these problems by partial substitution and that if we do a partial substitution then that will change the hydrogen absorption characteristics. Examples like if we consider the parent iron titanium now as I mentioned that there are two plateaus if we only consider the lower plateau then that corresponds to a weight percent like if we consider the only the lower plateau then the desorption pressure corresponding to 25 degree centigrade is 4.1 atmosphere for FETI. But if we substitute on the iron side by manganese 0.85 is iron and 0.15 is manganese then the desorption pressure reduces to 2.6 atmosphere. But the capacity increases to 1.98 percent. If we substitute it by nickel so titanium iron 0.8 nickel 0.2 so the lower plateau for the lower plateau we see that the desorption pressure further decreases to 0.1. In this process like we can see that the maximum weight percent is obtained for manganese substitution the maximum delta H value is for nickel substitution and the lowest desorption pressure is for nickel substitution. So the desorption pressure decreases as we move from iron titanium to its substitution to manganese and nickel. And this particular alloy titanium iron 0.85 manganese 0.15 is known to have good cyclic stability. So this particular class of compounds they have advantage that they have very good hydrogen storage capacity they have low cost they operate at room temperature but the major challenge remains is there is a requirement for activation step before the hydrogenation and that activation is step involves high temperature and pressure conditions. At the same time these compounds are sensitive to the presence of impurities in the gas and there lies the upper plateau instabilities. Now another class of compounds are solid solutions. Solid solutions these are formed by dissolving one or more minor element in smaller quantities which is solute here into another major compound which is solvent that is the hydrogen absorbing element. So if one or more elements of solute they are dissolved into a solvent that is the hydrogen absorbing element that are known as solid solution alloys. Now in case of inter metallic compounds it was those used to be either stoichiometric or nearly stoichiometric. Now these it is not essential that these may follow the same. So solid solutions can be either non stoichiometric as well. Usually the solvent that is used here could be either palladium or titanium or zirconium or vanadium. If palladium is used then the problem is we get a low capacity and the cost is high with zirconium and titanium. These are two stable they form two stable hydrides and for vanadium it has several advantage for hydrogen storage like they have ideal PCT the required PCT the capacities are also higher. So we can form such solid solutions high capacity solid solutions like we can even get 4 weight percent with titanium iron and vanadium titanium vanadium chromium manganese. So for them like we can get a 4 weight percent capacity but then they have two plateaus and then if we consider higher plateau because the higher plateau could be considered for hydrogen storage then it reduces the reversible storage capacity that we will get is 2.5 weight percent. Similarly for titanium chromium vanadium the reversible capacity is 2.3 weight percent and the important is that they have a very good cycle life like this is capacity is 2 weight percent even after 1000 cycles. We can have several composition variations in the solid solution alloys and one possible variation could be we can have Leves phase related BCC solid solution like the example of such compounds is titanium vanadium manganese or titanium vanadium chromium or titanium vanadium chromium and manganese. Now in these type of compounds which are Leves phase related BCC solid solutions the advantages they show better hydrogen storage performance. These were first identified in 1980 and usually the most studied ones are the vanadium based BCC solid solutions. They can even give a maximum hydrogen storage capacity of 3.6 weight percent which is appreciably higher. So they the thing is that they have both Leves phase at the same time they have BCC phase as well and both of these phases contribute towards hydrogenation and they have almost similar equilibrium pressure. Now example ZR 0.5 titanium 0.5 vanadium and manganese that shows 3 phases it is C14 BCC and a ZRO2 oxide phase. Another example titanium vanadium chromium they can give 2 weight percent of reversible capacity has smaller hysteresis and only one activation cycle is required. But the major disadvantage with these type of solid solution alloys is that they form two different hydride phase. There is a mono hydride phase which is much more stable and then there is a hydride dihydride phase which is the one which is responsible for giving the required hydrogen storage capacity. So the major challenge which remains is to destabilize this mono hydride phase and to improve the capacity or the reversible capacity of this dihydride phase. So the advantages of BCC solid solutions is they operate at room temperature, they have very good hydrogen storage capacity but the problems are they are difficult to activate. The vanadium is involved that has a higher cost and then the presence of slope in the platinum. If we want to improve the crevimetric capacity of these materials we have to consider lighter elements because that only can improve on to the crevimetric capacity. One of the example is magnesium based hydride. So the lighter elements could be considered, could be calcium or magnesium. Magnesium hydride it has a very high storage capacity of 7.68% but the problem is that of slow kinetics and the desorption temperature is very high that is 300 degrees centigrade it forms an ionic hydride. Another advantage of this class of material is that they have a lower cost other than the high crevimetric capacity. So what we need to address is the sluggish kinetics at the same time the high desorption temperature and that can several measures can be taken so as to reduce the desorption temperature and improve on to the kinetics charging and discharging. What has been reported in literature is to by reducing the particle size, by reducing the size, by alloying them with other elements like forming MG2NI, MG17LA2, MGAL or by forming composites we can address these challenges to a certain extent like ball milling with graphitic carbon forming composites or mixed with different other hydrides like titanium hydride has shown to work well with magnesium hydride to reduce the desorption temperature. However, still the desorption temperature achieved in this class of compounds are way higher. To summarize what we have seen today is we have learned the different inter metallic compounds we have seen that they offer a wide variation in the hydrogen absorption properties variation in terms of the kinetics variation in the terms of desorption temperature pressure conditions variation in terms of storage capacities. What is required is an intermediate enthalpy of formation which can be achieved by alloying two different metallic species in an inter metallic compound. But the problem still lies is that they have a poor gravimetric capacity. What could be a solution is use of lightweight elements to improve on to the gravimetric capacity. So, this can be achieved by certain noble metals. However, those noble metals also have their own disadvantages. What are those noble metals we will see in the next class. Thank you.