Lecture 50 : Inorganic Fibres : Asbestos, Textile Glass and Optical Fibres

[ sounds] Hello everybody.[ vocalized-noise] So, welcome back to theclass once again, so where we are talking about the asbestos fibers. And what we have seen[ vocalized-noise] thatone particular potpourrus, that implies, one particular group can be helpful[ vocalized-noise] formaking these particular type of fibers[ vocalized-noise ]. So, the purpose of this acquiring is that wecan have a diaphragm, we know that a particular type of filtration process can be achievedthrough[ vocalized-noise] a diaphragm. Diaphragm can be a piece of cloth likewise[ vocalized-noise ]. So, chlor alkali diaphragm sheaths wherewe can use it can have a normal employment as the layer too[ vocalized-noise ]. So, the chlor alkali process we already seenearlier in our one of our previous class, various classifies mostly[ vocalized-noise] we have discussed the chlor alkali process. So, the chlor alkali diaphragm tissue[ vocalized-noise] used for making the chlorine.So, there we can use that special diaphragmand these diaphragm can be[ vocalized-noise] make use of your this particular asbestos material.[ vocalized-noise] Then we can use this asbestos information as vinyl storey tiles, because these are the correspondingsupport material because the original information can be of vinyl polymer, but the vinyl polymercan is in favour on the asbestos textile[ vocalized-noise ]. So, vinyl floor tiles we know that the differenttypes of floor tiles or the storey sheets we basically use[ vocalized-noise] which is foldablealso .[ vocalized-noise] Then the storey sheet alsotiles are very hard and saw their most thickness is also very high.[ vocalized-noise] Then sometimes the vinylbased cements are also there, where some amount of asbestos is there.[ vocalized-noise] Then as a very useful fire proofing textile, if we are to be able have the fireproof for your wallsof the dwelling,[ vocalized-noise] then any other places where we can have some chances of catchingfire even in the laboratories[ vocalized-noise] or service industries,[ vocalized-noise] becausethis particular material the asbestos will not very quickly take fire or catch fire.[ vocalized-noise] So, one such example isyour gloves that which can withstand a very high temperature, because it can have alsothe insulation material[ vocalized-noise ]. So, gloves, a gauntlet made of your asbestosmaterial which can withstand a very high temperature likewise you are eligible to put that gauntlet and we can holdsome hot rod too[ vocalized-noise ]. So, it can have a good heat fighting aswell as it can have a shoot proofing information too because this with this glove[ vocalized-noise] you are eligible to hold any open fire likewise[ vocalized-noise ]. Then different types of industrial and marinegaskets we can use. So, the different kinds of industrial andmarine gaskets because that[ vocalized-noise] whether it was possible have some division, that means, industrial gaskets which is filling some phase[ vocalized-noise] or which in some you canhave some valves.[ vocalized-noise] So, valves we are able to have somegaskets we know that most of the time it is the rubbery material,[ vocalized-noise] butthe asbestos can also be a very good material for as the gaskets. Because that asbestos weaves we know[ vocalized-noise] that we can put in the plumbing also in for the water lines too[ vocalized-noise] wecan use this as the correspond thread.[ vocalized-noise] Then different types of thermal hose separation, because the thermal piping is there and we dontwant to go for loss in that special temperature of the thermal piping .[ vocalized-noise] So, we articulated this particularcovering with that of your asbestos cloth.[ vocalized-noise] Then filters of removingfine particles, just now what we have seen in case of your preparation of your chlorineas the membrane drawing process, or the diaphragm impelling process. So,[ vocalized-noise] if we can uniformlyput those molecules or those fibers that is asbestos fibers then we can have some threadingof those asbestos fibers,[ vocalized-noise] so punishment mesh length can be produced such thatonly big particles of a particular mesh such as your 10 or 20 mesh lengths can passthrough that special membrane others will be retained. So, it can be used as a filtering materialthat means, the spray; that necessitates, the cellulose located filter paper cannot be useful sometime[ vocalized-noise ]. So, asbestos based filtering textile, filteringmembrane or diaphragm can also be useful sometime[ vocalized-noise ]. Then one more important thing is that thedrilling fluid supplements, because when we drill that skin-deep of our earth to get irrigate, to get oil, to get gas, we use some drilling fluid.So, teaching liquor can be mingled with theseasbestos textile. So, it has some good advantage for additionof this particular asbestos substance, asbestos fiber or powder sometime[ vocalized-noise] to get a good type of these drilling supplements for this your teaching flowing. Then HVAC flexible canal connector. Because nowadays for[ vocalized-noise] thiscommon the heating, that vacuum-clean, then ac thing in the office or the lab or the industryplaces,[ vocalized-noise] we can have the in house uttering of the heating process, vacuumof that particular that conveys, we want to evacuate some time and that the natural acprocess[ vocalized-noise] that conveys, cooling of the air or the heating of the breeze is required, and we can supply fresh air from the outside[ vocalized-noise] we can supply through someduct to the different laboratories, different offices and different cavities basically .[ vocalized-noise] So, we are able to have the flexibleduct and the majority of them ducts are made of with these asbestos cloths. So,[ vocalized-noise] very useful use andthe consumption of these making this flexible passage connector is with that for performing thedifferent HVAC contingents.[ vocalized-noise] Then what we see that we can have four important asbestos forms. What we can find now[ vocalized-noise] thatwe can have four important asbestos categories and these asbestos types what we have seenthat[ vocalized-noise] by figure we can have,[ vocalized-noise] so chrysotile, crocidolite, anthophyllite and actinolite.So, these are the mentions basically and sometimesit can be very difficult also to remember.[ vocalized-noise] But if we think in termsof their correspond chemical form[ vocalized-noise] will always be interestedas an inorganic chemist that what should be your corresponding substance constitution ofthese four different potpourruss.[ vocalized-noise] So, first one basically the chrysotile, chrysotile mostly the chrysotile is your conventional materialwhich is basically magnesium silicate. As we all know what we use day-to-day as difficultdifferent types of talcum powder. What is talc?[ vocalized-noise] Talc or the talcum powderis nothing but your hydrated magnesium .[ vocalized-noise] So, this is also that sortof hydrated magnesium silicate of different structure.[ vocalized-noise] So, chemical compositionof this material of this asbestos type is typically that of your talc or talcum powder[ vocalized-noise] is basically made up of your only magnesium silicate which is hydratedof different level.[ vocalized-noise] Then crocidolite, crocidolite is basically is correlating one where you have iron youdont have any magnesium you have sodium and iron along with a huge silicate structure.[ vocalized-noise] So, all these materialsare a very complex silicate structure. So, mostly these are silicate substances.[ vocalized-noise] So, we are studying we arestill continuing with those silicate materials of very useful in the different purposes.[ vocalized-noise] Then anthophyllite anthophyllite is again we bring the first category of magnesium theniron,[ vocalized-noise] and of all categories of the silicate fabric and the large numberof hydroxy radicals are there[ vocalized-noise ]. So, those hydroxy radicals can be the terminalone attached to your silicon or can be attached to your the correspond metal ions hub .[ vocalized-noise] Then actinolite, actinoliteis basically based on your calcium magnesium thing.[ vocalized-noise] So, when you find this chemical arrangement, the authorities concerned will always conclude or talk about the differentstructures,[ vocalized-noise] and those different designs of these materials are of differenttypes[ vocalized-noise ]. So, chrysotile and amphibole asbestos havea considerable[ vocalized-noise] influence on their physical belongings.[ vocalized-noise] So, the constitution andthe structure will tell us that no it can have a different physical belonging as wellsuch that you can have a different organization. So, it is feasible[ vocalized-noise] mostly modifyits characteristics or the physical qualities or the physical behavior[ vocalized-noise ]. So, chrysotile asbestos fibers consists ofbundle of hollow micro fibers. What are those?[ vocalized-noise] Those are bundles of hollowmicro fiber, so those that is why these are interesting to know what are known as thedifferent types of micro fibers, we known as fibrils.So, these are the usual expression what we usein the biological oath likewise[ vocalized-noise] in the bio organic chemistry or the biochemistrywe know the the protein fibrils.[ vocalized-noise] So, the fibrils are hollowmicrofibers nothing but this. So, “youve had” the very small channel. So, these are the hollow microfibers[ vocalized-noise] of 15 to 40 nanometer in diameter. So, diameter is also not very much it is onlywithin 50 nanometer[ vocalized-noise ]. So, when we go for these asbestos fibers, so we can have a particular process. So, industrial distillation or industrial isolation[ vocalized-noise] can be used through a baked process. How it starts? It starts with crushing and tightening or batchesof[ vocalized-noise] the raw asbestos fabrics which are coming out of the cliff.[ vocalized-noise] So, the rock-and-roll substance isa starting cloth. So, the volume cliff material we can go for theloosening[ vocalized-noise] of those rocks with the mouth crushers. So, jaw is there. So, the jaws we are familiar[ vocalized-noise] thatthe mouths can take out and then remove those fibers or the[ vocalized-noise] correspondingmicro fibers also .[ vocalized-noise] So, one of the following options that symbolizes two things we use basically the jaw crushers, these arethe common instruments industrially people use all the time one is the jaw crusher[ vocalized-noise] another is the double roll mills[ vocalized-noise ]. So, the mouth crusher will separate and doubleroll mills can wheel. And bundle of those special type of asbestosmaterial like that of our jute fabric what we get which is also a embed substance. So, plant textile which we can put as isa very good fiber. So, asbestos is like of that of your jute, and we use it in the double roll mill[ vocalized-noise] to for their wheel we can consider thisas the rolling mills too .[ vocalized-noise] So, one particular process is known as the humid process. When we follow this particular wet processfor performing these it are able to for narrower fiber portion distribution to be obtained foramphibole asbestos. So, where reference is acquire these amphibole asbestos, so we basically leave narrower fiber section rationing. So, the delivery so everything is notuniform,[ vocalized-noise] but most of the time we will find that one particular varietyof fiber segment and its distribution was essential[ vocalized-noise] to give a characteristicpattern and the characteristic structure.[ vocalized-noise] So, we separate it fromthe boulder textile how by squeeze or the crushed combination by using a hydro cyclone and the longerand shorter fibers are separated with a rotary sieve.So, we have a rotating sieving[ vocalized-noise] mechanism such that the longer one will be separated from the shorter one. So, shorter will be[ vocalized-noise] separatedat one point and the longer are separated out from that particular break-up process.[ vocalized-noise] Now, once we have the differenttypes of these fibers, their microfiber formations, their length, and all these things are usefulbecause a particular type of behavior or special type of use or special dimension of thoseasbestos substances are dependent upon the type, what asbestos type “youve had”, what asbestostype we are getting from the natural sort[ vocalized-noise] or from the natural textile .[ vocalized-noise] Then where from we get that particular type of deposit like that of your geographicalorigin or geographical origin of that special stone diversity.[ vocalized-noise] Then clearly, the chemicalcomposition when you go up to that end,[ vocalized-noise] either you have magnesium, whether you haveiron and how much of silicon is there, and the silicon structure.[ vocalized-noise] Then the fiber segment as we have seen just now the shorter span and the longer lengthwe can separate it out, so we can use for one particular purpose the shorter fiber segment ,[ vocalized-noise] and the longer one for the other purpose,[ vocalized-noise] then degreeof disintegration if we want to degrade this.If we want to get the powder material outof those fabrics, so it can also be dependent on the strength of that particular material, and how quickly we can cheapen this particular[ vocalized-noise] material for our use. So, the largest quantity of these asbestosare the different types of asbestos composites we can compile. So, what we see now that we can use that wecan frame those asbestos information in some other material like that we know that in metal scienceor the polymer science[ vocalized-noise] that we draw some composite substance, where thebasic material is your polymeric substance. And we placed something else such that we canincrease the strong, the durability, the structure, the its corresponding affinityfor sacrificing different contours will be changed.[ vocalized-noise] So, when we use asbestos as a composite textile or composite entry to get the composites isknown as asbestos composites .[ vocalized-noise] So, these asbestos compositesare utilized, the most important application is our cement application, because we willbe seeing maybe in our today’s class or in the next class how we form plaster are more[ vocalized-noise] helpful substance what we compile the inorganic pharmacists keep the correspondingindustrial sector because we use it large amount of cement we use it, but the basicidea or representing up all these things is your usual knowledge of inorganic chemistry[ vocalized-noise ]. So, how we get that cement cloth? So, right now when we are talking about thisasbestos information make us know how we can improve the strength of that special cement substance. So, if we articulated that signifies, you can have a composite, why we conclude these composites again in particular word, these are the general terminology.[ vocalized-noise] The buttres that intends, we are increasing the strength of that special substance such that we are able to have some impregnatedthing[ vocalized-noise] that like that of our backbone type of thing, when we threw therod in the concrete, it varies the correspond strength of this tower of the building.So, in some other form, the reinforcementfor the concrete information is not simply by the addition of the gravels or the beach,[ vocalized-noise] but the additive of the asbestos fabric will giving you the corresponding cement[ vocalized-noise] as the asbestos cement.[ vocalized-noise] Then some organic materialwe can put inside it. So, the organic matter when catching thisasbestos cloth as the[ vocalized-noise] ring-binder cloth as the organic ring-binder thatmeans the polyvinyl chloride[ vocalized-noise] then other synthetic rubber or the naturalrubber such as that of your neoprene rubber.[ vocalized-noise] And some of the duromersthat intends, the polymeric items having higher stability is known as duromers[ vocalized-noise ]. So, duromers can have your ring-binders which cantrap those asbestos to use these composites.[ vocalized-noise] So, where we use basicallythats why the reinforcement can be achieved for cement,[ vocalized-noise] can be achievedfor PVC, can be achieved for rubber, and can be achieved for the duromers. Then how we define a particular type of compositeany kind of composite is a general call .[ vocalized-noise] So, the composite when wethink in terms of the asbestos, we can consider it as asbestos composite[ vocalized-noise ]. So, we supply the fiber the asbestos fiber. When we supply these asbestos fiber to thecement material, cement is the powdery formation what we will see[ vocalized-noise] in ournext class possibly that the pulverize textile when i got mingled with spray and we allow it forsome placing season, we get something but we can get the plaster of some building[ vocalized-noise] or we get some the corresponding concrete[ vocalized-noise ]. So, when asbestos as the corresponding fiberis given, so we take one very useful or well known cement type[ vocalized-noise] is knownas the portland cement.[ vocalized-noise] So, this portland cementcan be reinforced with up to a 10 to 20 percent[ vocalized-noise] opening of the asbestosmaterial and chrysotile asbestos is added such that you can improve the correspondingcement substance when we go for its correspond met as the correspond concrete manufacturing orany other type of use.So, we see now that how we make this asbestoscement. So, if we get that, because this is a drymaterial that asbestos itself is a cool cloth,[ vocalized-noise] after dehydration like thatof your zeolite load we determine[ vocalized-noise] that we can get this asbestos for this particularpurpose[ vocalized-noise] that you can have this asbestos cement. So, you get that the slurry of the plaster. So, asbestos will be put inside[ vocalized-noise] with asbestos fibers is filtered. So, slurry of plaster with asbestos fibersis filtered placed under moldings at a very high pressure and left to set for 24 to 48 hours. So, you hear within 1 or two days it will beset. So, asbestos cement substance or asbestos concretematerial can be established[ vocalized-noise] if we have the add-on of asbestos fabric tothe slurry of cement.[ vocalized-noise] So, all kinds of consumer products we can make out of this asbestos cement, wherethis asbestos impregnated plaster rather to clear the different kinds of committees, differenttypes of roof singles; that symbolizes, asbestos roofs we all know that we can use as the asbestossheets for roofing,[ vocalized-noise] then the different kinds of hoses and the moldedproducts.So, one such is your the corrugated type ofasbestos sheet, what we can use as the ceiling information for seeing mansions. So, we gets the idea that asbestos materialis a frequently fiber substance. So, we get a general call for this cementis the fiber cement.[ vocalized-noise] So, what is that fiber cementfiber cement is therefore a composite building[ vocalized-noise] or structure information[ vocalized-noise] used in roofing and facade produces that signifies, you can have the plasterof the[ vocalized-noise] walls likewise because of his strong and durability.So, we can improve. So, is a basically a evaluate addition we canimprove the corresponding caliber of the plaster because we know will see too that large typesof a large[ vocalized-noise] number of different types of plasters are there, where your silicacontent is different, where iron oxide content is different, our alumina content is different[ vocalized-noise] or also the corresponding add-on of slags giving you the slag cement[ vocalized-noise ]. So, if we have a pure variety of that cementpowder and plaster pulverize we putting water we get the slurry and that is fixed[ vocalized-noise ]. Now, after the additive of this asbestos fiber, we get the fiber cement which have[ vocalized-noise] higher fortitude compared against your originalstructure what can be obtained from the pulverize plaster.[ vocalized-noise] Then we will see something as your glass fiber, which is also a very useful fiber inorganicfiber what we can must be considered[ vocalized-noise] and we can use this or we can manufacture those fiberslike that of your textiles also.So, we can put in the textile cloth alsoor the textile like of these fibers we are able to have,[ vocalized-noise] like that of yourplastic material. So, the polymeric fabric the nylon fabric[ vocalized-noise ]. So, the plastics could be reinforced by glassfiber. So, some plastic material if we are able to situated orif we can put inside the correspond reinforcement material as your glass fiber,[ vocalized-noise] you can have a different type of cloth we can obtain[ vocalized-noise ]. So, large number of this type that means, the optical fibre in pregnant plastics or the textile fibers in can have[ vocalized-noise ]. And now to simplify that classification of allthese things instead of returning a complicated epithet of geological origin,[ vocalized-noise] we are able to have the ordinary A, B, C, D type of nomenclature[ vocalized-noise ]. So, the first assortment is known as E-glass. What is E-glass, E-glass is nothing but yourtextile fiber glass[ vocalized-noise ]. So, E-glass will be made of a particular typeof glass, which is calcium aluminum boron silicate glass, because the glass we knowa particular variety of[ vocalized-noise] your sand silicon dioxide exclusively. So, where reference is framed boron in it, we get the borosilicateglass[ vocalized-noise ]. Then sometimes a better quality of that particularglass can be improved by the addition of aluminium as well as calcium.And it can be used for your polymer reinforcementand application is in the commonly in the electrical area,[ vocalized-noise] becauseif we have this glass fabric we are able to have the insulation that implies, the[ vocalized-noise] corresponding reporting of the simple wire. The electrical cable mostly, because wewant to have the ordinary isolation of the electrical wire for high voltage transmissionalso. So, the electrical engineering industry canbe very much dependent on this particular type of E-glass variety for its reinforcementin the polymer[ vocalized-noise] for varnish of the cables[ vocalized-noise ]. Then the next one is the -Aglass, -Aglassis the very basic glass what we know that which is obtained from your sodium silicates ,[ vocalized-noise] which your soda-lime glass. So, sodium silicate as well as some calciumbased lime is added,[ vocalized-noise] calcium oxide is added or calcium carbonate is added. So, is it can have the little necessitating application, but you are eligible to have the very basic material you can make for making this soda lime glass forit[ vocalized-noise ]. So, the third one is basically apart fromyour lime and alkali that necessitates, soda and lime you employed boron, boron already we know[ vocalized-noise] that boron can improve the quality of the corresponding glassy fabric[ vocalized-noise ]. So, it will have a high chemical resistancethat is why the borosilicate glasses we use that that of your correspond, where theglass wires for our laboratory consume or manufacture use for industrial chemicals[ vocalized-noise ]. Then you can have the D-glass, another varietyafter C is the D for high dielectric requirements[ vocalized-noise ]. So, you change simply by the correspondingglass type[ vocalized-noise] then we can have R-glass, S-glass and all different sorts ofglasses we can have,[ vocalized-noise] where you can have a high mechanical demand at hightemperature. So, it can have high-pitched backbone mechanical strengthwill be more and it can withstand a high temperature too[ vocalized-noise ]. Then the other potpourrus what we can think ofthat one is known as alkali-resistant glass, which is known as air glass[ vocalized-noise ]. So, you are eligible to put already “were having” seen thatit can have a very high temperature bear if we use zirconium dioxide or zircon[ vocalized-noise ]. So, zircon containing glass with improvedresistance to alkali. So, we can have all diversities, one can beof acid opposition,[ vocalized-noise] one can be of alkali resistant, one can be oftemperature resistance[ vocalized-noise ]. So, these things can be very useful and somewill be simply chemical resistant that entails, any other type of chemical[ vocalized-noise] can be handled with the use of that special material for constituting of all sorts of hose orany type of[ vocalized-noise] other resilient substance for use[ vocalized-noise ]. So, the other one other most interesting oneis our use of your optical fibre, so that glass fiber what we know that optical fibercable[ vocalized-noise] in the communication sector, through electronics engineering peopleand electronics industry as well as the telecommunication industry is very much dependent on this particularfiber,[ vocalized-noise] but it has a conventional root of inorganic descent[ vocalized-noise ]. So, the industrial in organic chemistry canalso be obtained from the knowledge of procreating of glass fiber,[ vocalized-noise] how industrycan start for making this particular type of optical fiber[ vocalized-noise ]. So, what is that optical fiber, why it isspecially mentioned and specially designed[ vocalized-noise ]. So, it can have a core glass structure. So, so the core of this material the fiber, it can have a good core[ vocalized-noise] and this core is basically made up of glass[ vocalized-noise] with a high refractive index that means, germanium dioxide or phosphoruspentoxide narcotic quartz glass, is a special variety of glass,[ vocalized-noise] we maynot get it ah naturally from world markets[ vocalized-noise ]. So, it is a special variety of glass and theprice of this glass would be therefore, clearly higher,[ vocalized-noise] because you improvethat in terms of its now high refractive index[ vocalized-noise] such that you can have thetotal internal reflection[ vocalized-noise ]. You can have a material prism like materialand you go for total internal thoughtfulnes[ vocalized-noise ]. So, total internal thinking will carry theinformation, carry the light-headed, carry the theme with that of your glass fiber[ vocalized-noise ]. And one is your cladding glass that claddingglass is reporting your core glass. So, the cladding glass will have a lower refractiveindex. So, any other type of[ vocalized-noise] normallyused glass, what we use in the laboratory also can be used[ vocalized-noise] such thatyour borosilicate glass or the fluorosilicate glass[ vocalized-noise ]. Sometime we can use the plastic material evenalso,[ vocalized-noise] like silicon resins too and the different kinds of fluoropolymersalso, it is not that[ vocalized-noise] you can you have use other glass likewise,[ vocalized-noise] but your core is of different types.So, core glass is the important factor formaking this particular type of optical fibre[ vocalized-noise ]. So, we are able to have two steps mostly for it, one is your step index fiber, so two types they are; so step index fiber and anotheris the graded index fiber. So, step index fiber you alter the indexof your refractive index in a stepwise manner. So, constant refractive index in the fibercore[ vocalized-noise ]. So, you cannot change that particular refractiveindex and another is the graded indicator fiber[ vocalized-noise] endlessly decreasingthe refractive index from the fiber core to the outside of the fiber[ vocalized-noise ]. So, whatever refractive index you have atthe core which is decaying down, when you reach to the outer surface of the fiber,[ vocalized-noise] so that is the particular type of idea and particular type of approach can be usedfor making this particular type of glass fiber[ vocalized-noise ]. So, step index fibers what we apply or whatwe make are manufactured by which way[ vocalized-noise ]. So, step index fibers are manufactured byusing the rod and tube or the double crucible process. So, the process of making this particularstep index fiber is by pole tubing or the double crucible process[ vocalized-noise ]. In which special process the core and thecladding glass, because we have seen that we can have two types of glasses; one is thecore glass, another is the cladding glass; one is that the core and another is coveringit[ vocalized-noise] or in the molten mood. And they find themselves in the molten country separatelyfrom ultra pure pulverization, because[ vocalized-noise] pollutant will be a detrimental thing for allmaking of all these things.So, the piety is most important that is why[ vocalized-noise] the cost of these glass were high, apart from its involvement of Ge O 2 or P 2 O 5[ vocalized-noise ]. The purity difficulties also, because we are dealingwith something of high accuracy material. So, this high precision material you can haveonly if you have 99.999 percent purity with respect to a particular variety[ vocalized-noise] or a particular material[ vocalized-noise ]. So, the core of this particular one is formedfrom the ultrapure gunpowder we its utilization and that ultrapure pulverizes are moving into twocrucibles. So, you should have a very good idea or verygood knowledge about what is known as crucibles we are familiar[ vocalized-noise ]. The very small crucibles, the nickel crucible, the porcelain crucible, the[ vocalized-noise] sintered locate glass crucible, use in the day-to-daylaboratory castes in all chemistry laboratory grades we use[ vocalized-noise ]. So, if we use it in a bigger size, it willbe of semi industrial magnitude;[ vocalized-noise] but if we go for a much bigger size, it willbe of industrial magnitude[ vocalized-noise ]. So, your receptacle for doing all these reactionswill definitely be the crucible[ vocalized-noise ]. So, this particular case we can have two differenttwo types of crucibles we can have with a concentric orifice. So, you can have a crucible type of structurethat will see in our next class that what sort of these particular crucibles we canhave[ vocalized-noise ]. But the thing is that in the molten malady, because you can employed the temperature high-flown[ vocalized-noise] for those working crucibles. So, the material within this crucible willbe in the molten precondition,[ vocalized-noise] and formerly you allow it to pass through someorifice. So, you are eligible to have the concentric orifice throughone will go that special core glass information, and on the outside will allow to pass thecorresponding cladding glass cloth[ vocalized-noise ]. At the bottom of that particular crucible, so crucibles are not having no outside excerpt at the bottom, but it will have the passagefrom the bottom[ vocalized-noise ]. And when it is guided, it is then coolingand the coldnes thing of this fiber is giving you the matching preparation of thisoptical fiber[ vocalized-noise ]. So, it is coming out as a thread out of this. So, one thread is coming out at the core threadcovered with the cladding glass and which will be coming out at the bottom of that particularcrucible[ vocalized-noise ]. So, next day in our next class will considerthe corresponding design of that special crucible and how we utilize these things aretwo molten predicaments within two concentric crucibles is gonna be exercised[ vocalized-noise] for obliging of this particular type of optical fiber ok. Thank you very much ..

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