Crystalline vs Amorph

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Candy GlassCandy Glass

Fiber Drawing Using the DoubleFiber Drawing Using the DoubleCrucible MethodCrucible Method

By Tara Schneider

Summer 2005

Advisors: Bill Heffner and Himanshu Jain

IMI-NFG at Lehigh University

Work Supported By NSF’s International Materials Institute for New Functionality in Glass



IntroductionIntroduction

This slide show includes backgroundThis slide show includes background

information on optical fibers, Snell’s Law,information on optical fibers, Snell’s Law,

and glass science.and glass science.

At the end of the slide show is a lab that At the end of the slide show is a lab that

can be performed using ingredients andcan be performed using ingredients and

supplies you can find in your kitchen.supplies you can find in your kitchen.



Fiber OpticsFiber Optics

Background InformationBackground Information

The following topics relate to fiber optics:The following topics relate to fiber optics:

– Core and CladdingCore and Cladding – Total Internal ReflectionTotal Internal Reflection

– UsesUses

– Comparison to Wires and CurrentComparison to Wires and Current



Core and CladdingCore and Cladding

A fiber optics cable is a A fiber optics cable is a

long string of glass thatlong string of glass that

consists of a core and aconsists of a core and a

cladding (Picture). Thecladding (Picture). Thecladding surrounds thecladding surrounds the

core and has a lower indexcore and has a lower index

of refraction, n. The coreof refraction, n. The core

can transmit one or morecan transmit one or more

colors of light. Totalcolors of light. Total

internal reflection in theinternal reflection in the

core keeps light fromcore keeps light from

escaping.escaping.

Core

Cladding

A slice of a fiber optics cable.

Note: In our experiment, we create afiber optics cable with a core and acladding to demonstrate the double

crucible method. The core andcladding do not have different indices

of refraction, n values.



Snell’s LawSnell’s Law

What is total internalWhat is total internalreflection (TIR)? Toreflection (TIR)? Tounderstand why TIR understand why TIR occurs, one must knowoccurs, one must know

Snell’s Law.Snell’s Law. Snell’s law states:Snell’s law states:

• nn11sinsinθθ11=n=n22sinsinθθ22 (see(seediagram).diagram).

• The reflected angle equalsThe reflected angle equalsthe incident angle.the incident angle. θ1==θr

Note: The dotted line is theNote: The dotted line is thenormal. All angles arenormal. All angles aremeasured from the normal.measured from the normal.

θ1

n1

n2θ2

θr

Reflection and Refraction. n1>n2

Total Internal Reflection

Keeps Light in.

I n c i d

e n t r

a yR e f l e c t e d r a y

R e f r a c t e

d r a y



Total Internal ReflectionTotal Internal Reflection

If If θθ22 is greater than 90is greater than 90° then no° then no

light is refracted. The incidentlight is refracted. The incident

angle that would cause this 90°angle that would cause this 90°

angle of refraction,angle of refraction, θθ22, is called, is called

the critical angle,the critical angle, θθcc..

nn11sinsinθθ11=n=n22sinsinθθ22 becomesbecomes

nn11sinsinθθcc=n=n22sinsin 9090°.°.

So the critical angle isSo the critical angle is

sinsinθθcc=n=n22 /n /n11

θc

n1

n2

θr

Critical Angle and

Reflected Angle. n1>n2.

Total Internal Reflection

Keeps Light in.

I n c i d

e n t r

a yR e f l e c t e d r a y



UsesUses

Fiber optics cables canFiber optics cables can

be used for thebe used for the

following applications:following applications:

– CommunicationCommunication TelephoneTelephone

TelevisionTelevision

InternetInternet

– SurgerySurgery – ToysToys

– Uses yet to beUses yet to be

imagined!imagined!

Fiber Optic Fish.Photo courtesy of Robert Backman.

“Fiber Optic Cable.” 18 April, 2002. Online Image. www.accs.net- /users/kriel/ch12 notes/. 4 August, 2005.<http://www.accs.net/users/kriel/ch12%20note

s/fiber_optic_cable.jpg>.



Comparison to Wires and CurrentComparison to Wires and Current

A wire can transmit current, either in a positive A wire can transmit current, either in a positive

direction or a negative direction.direction or a negative direction.

A fiber optics cable can transmit light in two A fiber optics cable can transmit light in two

directions at the same time. It can also transmitdirections at the same time. It can also transmitlight in different phases, amplitudes, andlight in different phases, amplitudes, and

sometimes different colors.sometimes different colors.

Optical fibers can carry more information, andOptical fibers can carry more information, and

they can carry it a farther distance than wires.they can carry it a farther distance than wires.



GlassGlass

Topics covered include:Topics covered include:

– Crystalline and Amorphous SolidsCrystalline and Amorphous Solids

– Supercooled Liquid and ViscositySupercooled Liquid and Viscosity

– Glass Transition TemperatureGlass Transition Temperature

– Fiber DrawingFiber Drawing

– Similarities Between Candy and GlassSimilarities Between Candy and Glass



Crystalline vs. AmorphousCrystalline vs. Amorphous

Most solids are crystalline, but glass isMost solids are crystalline, but glass isamorphous. Glass does not have a repeatedamorphous. Glass does not have a repeatedmolecular structure.molecular structure.

An amorphous solid resembles a liquid frozen in An amorphous solid resembles a liquid frozen intime.time.

“Molecular arrangement in a crystal.” No

date. Online image. http://math.ucr.edu/. 3 August, 2005.

<http://math.ucr.edu/home/baez/physics/General/Glass/glass.html>.

“Molecular arrangement in a glass.” No date. Online image. http://math.ucr.edu /. 3 August, 2005.

<http://math.ucr.edu/home/baez/physics/General/Glass/glass.html>.

http://math.ucr.edu/











Crystallization and Glass FormingCrystallization and Glass Forming

If you heat a crystal up to above the meltingIf you heat a crystal up to above the meltingtemperature, Ttemperature, Tmm, and then cool it, it might, and then cool it, it might

become a crystal or it might become a glass.become a crystal or it might become a glass.

If given enough time, the melt will become aIf given enough time, the melt will become acrystal. The molecules rearrange into theircrystal. The molecules rearrange into theirlowest energy states which are very ordered.lowest energy states which are very ordered.

If you cool the melt quickly, it will not have timeIf you cool the melt quickly, it will not have time

to rearrange to become a crystal. Instead, it willto rearrange to become a crystal. Instead, it willbecome a supercooled liquid, on its way to glassbecome a supercooled liquid, on its way to glassformation.formation.



Viscosity Viscosity

Viscosity is the resistance to flow. A Viscosity is the resistance to flow. A

highly viscous material flows slowly likehighly viscous material flows slowly like

honey, and a material with low viscosityhoney, and a material with low viscosity

flows easily like water.flows easily like water.

As this supercooled liquid becomes cooler As this supercooled liquid becomes cooler

and cooler, the viscosity becomes greaterand cooler, the viscosity becomes greater

and greater.and greater.

T



Tgg

(tē-jē)(tē-jē)

When the viscosity becomes so high thatWhen the viscosity becomes so high thatthe material behaves more like a solidthe material behaves more like a solid

than a liquid, it has become a glass. Itthan a liquid, it has become a glass. It

has hit Thas hit Tgg..

TTgg is the glass transition temperature. Tis the glass transition temperature. Tgg

is lower than the melting temperature, Tis lower than the melting temperature, Tmm..



Fiber DrawingFiber Drawing

In the experiment, we will draw fibers from a supercooled liquid.In the experiment, we will draw fibers from a supercooled liquid.

Video will run after download – please be patient.



Candy GlassCandy Glass

Similarities between Candy and GlassSimilarities between Candy and Glass – Amorphous solids Amorphous solids – Tendency to crystallize under certain conditionsTendency to crystallize under certain conditions

– Glass former: SiOGlass former: SiO22 (Silicate) for glass, C(Silicate) for glass, C1212HH2424OO1212 (Sucrose) for candy(Sucrose) for candy

– Glass modifier: NaGlass modifier: Na22COCO33 for sodium silicate glass, Hfor sodium silicate glass, H22O for candy, reduces meltingO for candy, reduces meltingtemperature and decreases chemical durabilitytemperature and decreases chemical durability

– Other stuff: Corn syrup reduces crystallization in candy. Dr. Jain’s paper saysOther stuff: Corn syrup reduces crystallization in candy. Dr. Jain’s paper saysthat adding stuff to glass can increase glass forming ability.that adding stuff to glass can increase glass forming ability. (Source: Jain, Himanshu and Isha Jain,(Source: Jain, Himanshu and Isha Jain,

“Learning the Principles of Glass Science and Technology from Candy Making.” “Learning the Principles of Glass Science and Technology from Candy Making.” Lehigh UniversityLehigh University. No Date. Lehigh University. 5 Aug. 2005. No Date. Lehigh University. 5 Aug. 2005

<http://www.lehigh.edu/~inmatsci/faculty/candy_making.pdf>.)<http://www.lehigh.edu/~inmatsci/faculty/candy_making.pdf>.) Note: Corn syrup is made of simpler sugarsNote: Corn syrup is made of simpler sugarsthan sucrose. Sucrose is fructose Cthan sucrose. Sucrose is fructose C1212HH2424OO1212 and glucose Cand glucose C1212HH2424OO1212 bondedbondedtogether. Corn syrup is fructose, glucose, water and other stuff which the Karotogether. Corn syrup is fructose, glucose, water and other stuff which the Karocompany does not disclose.company does not disclose.

Differences between Candy and GlassDifferences between Candy and Glass

– Candy will decompose (CCandy will decompose (C1212HH2424OO1212 bonds will break) at a temperature that is verybonds will break) at a temperature that is veryhigh or when not much water is presenthigh or when not much water is present (Source: Jain, Himanshu. Personal Interview. June 2005.)(Source: Jain, Himanshu. Personal Interview. June 2005.)

– Melting temperature TMelting temperature Tmm and glass transition temperature Tand glass transition temperature Tgg are much lower forare much lower forcandy than for glass.candy than for glass.



And Now for the Experiment And Now for the Experiment



Set-UpSet-Up

SuppliesSupplies – A stove or hot plate A stove or hot plate – Oven mittsven mitts – Two 600 mL beakersTwo 600 mL beakers – Two thermometers that can read 144.5Two thermometers that can read 144.5°C°C – 410g sugar410g sugar

– 240g corn syrup240g corn syrup – 100g water100g water – Food coloringFood coloring – Two glass funnels-the shorter the stem the betterTwo glass funnels-the shorter the stem the better

Outside funnel: Stem diameterOutside funnel: Stem diameter ≈ 1.4cm≈ 1.4cm Inside funnel: Stem diameter ≈ .7cm, preferably longer than stem of outside funnel.Inside funnel: Stem diameter ≈ .7cm, preferably longer than stem of outside funnel.

– A clamp to hold the funnels, paper towel to protect funnels from scratching. A clamp to hold the funnels, paper towel to protect funnels from scratching.

– A scale to measure ingredients A scale to measure ingredients – A metal tray to catch hot candy and store fibers A metal tray to catch hot candy and store fibers – A glass rod to draw fibers with A glass rod to draw fibers with – A reflection microscope A reflection microscope – A razor A razor



Supercool Set-UpSupercool Set-Up

Set up funnels as shown:Set up funnels as shown: – Place paper towel betweenPlace paper towel between

the clamp and the funnel.the clamp and the funnel. – Make sure the funnels areMake sure the funnels are

concentric at the top andconcentric at the top and

bottom of the stem.bottom of the stem. – Set it up so that the insideSet it up so that the insidefunnel sticks out a little bitfunnel sticks out a little bitat the bottom (this will helpat the bottom (this will helpyou see if the cladding isyou see if the cladding issurrounding the core on allsurrounding the core on allsides).sides).

– Is anything going to get inIs anything going to get inthe way of you pouringthe way of you pouringyour supercooled liquid?your supercooled liquid?

– You will have a little time You will have a little timeduring cooking and theduring cooking and thebeginning of the pour tobeginning of the pour tomake final adjustments.make final adjustments.

“Double Crucible” Set Up.June 2005.

ConcentricFunnelStems.June 2005.



Procedure: Fiber DrawingProcedure: Fiber Drawing

You have the cooking mitts for a reason! Don’t get burned. You have the cooking mitts for a reason! Don’t get burned. Measure 205g sugar, 120g water and 50g corn syrup into eachMeasure 205g sugar, 120g water and 50g corn syrup into each

beaker. Stir before cooking but not during cooking.beaker. Stir before cooking but not during cooking. Cook on a high setting on the stove until both syrups reachCook on a high setting on the stove until both syrups reach

144.5144.5°C.°C.

Add 20 drops food coloring to one beaker. Add 20 drops food coloring to one beaker. Pour immediately.our immediately. Pour colored liquid into inside beaker andPour colored liquid into inside beaker and

clear (or yellow) into outside beaker.clear (or yellow) into outside beaker. Candy will drip out on its own at first.Candy will drip out on its own at first. If cladding is not surrounding core on all sides, readjust funnels.If cladding is not surrounding core on all sides, readjust funnels. Use spoon to test viscosity. If you can pull long fibers, then theUse spoon to test viscosity. If you can pull long fibers, then the

viscosity is right for fiber drawing.viscosity is right for fiber drawing. Pull the fibers, and save them on the metal tray.Pull the fibers, and save them on the metal tray. Notice how rate of pulling affects thickness of fibers.Notice how rate of pulling affects thickness of fibers. Notice how viscosity affects thickness of fibers.Notice how viscosity affects thickness of fibers.



Experience Fiber Drawing Success!Experience Fiber Drawing Success! Video plays after download – brief wait



Procedure: Examination of FiberProcedure: Examination of Fiber

To view fibers under microscope, tapeTo view fibers under microscope, tapethree microscope slides together.three microscope slides together.

Cut fiber with razor.Cut fiber with razor. Polish fiber by twisting one end on a dampPolish fiber by twisting one end on a damp

paper towel.paper towel. Tape fiber vertically to the three slides.Tape fiber vertically to the three slides.

Position the three slides in the microscopePosition the three slides in the microscopethe way you would normally position athe way you would normally position asingle slide.single slide.



Acknowledgements Acknowledgements

My Advisors: Dr. Bill Heffner andMy Advisors: Dr. Bill Heffner and

Professor Himanshu Jain, LehighProfessor Himanshu Jain, Lehigh

UniversityUniversity

My Lab Partner: Raina JainMy Lab Partner: Raina Jain

Funding Provided by: The NationalFunding Provided by: The National

Science Foundation through theScience Foundation through the

International Materials Institute, LehighInternational Materials Institute, Lehigh

UniversityUniversity

Crystalline vs Amorph

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