Candy GlassCandy GlassFiber Drawing Using the Fiber Drawing Using the Double Crucible MethodDouble Crucible Method

By Tara SchneiderBy Tara SchneiderSummer 2005Summer 2005

Advisors: Bill Heffner and Himanshu JainAdvisors: Bill Heffner and Himanshu JainIMI-NFG at Lehigh UniversityIMI-NFG at Lehigh University

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

IntroductionIntroduction This slide show includes background This slide show includes background

information on optical fibers, Snell’s information on optical fibers, Snell’s Law, and glass science.Law, and glass science.

At the end of the slide show is a lab At the end of the slide show is a lab that can be performed using that can be performed using ingredients and supplies you can find ingredients and supplies you can find in your kitchen.in your kitchen.

Fiber OpticsFiber OpticsBackground InformationBackground Information

The following topics relate to fiber The following topics relate to fiber optics: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 CladdingA fiber optics cable is a A fiber optics cable is a long string of glass that long string of glass that consists of a core and a consists of a core and a cladding (Picture). The cladding (Picture). The cladding surrounds the cladding surrounds the core and has a lower core and has a lower

index of refraction, n. index of refraction, n. The core can transmit The core can transmit one or more colors of one or more colors of light. Total internal light. Total internal reflection in the core reflection in the core

keeps light from keeps light from escaping.escaping.

Core

Cladding

A slice of a fiber optics cable.

Note: In our experiment, we create a fiber optics cable with a

core and a cladding to demonstrate the double crucible method. The core and cladding do not have different indices of

refraction, n values.

Snell’s LawSnell’s Law What is total internal What is total internal

reflection (TIR)? To reflection (TIR)? To understand why TIR understand why TIR occurs, one must know occurs, one must know Snell’s Law.Snell’s Law.

Snell’s law states: Snell’s law states: • nn11sinsinθθ11=n=n22sinsinθθ2 2 (see (see

diagram).diagram).• The reflected angle The reflected angle

equals the incident angle. equals the incident angle. θ1==θr Note: The dotted line is Note: The dotted line is

the normal. All angles are the normal. All angles are measured from the normal.measured from the normal.

θ1

n1

n2 θ2

θr

Reflection and Refraction. n1>n2

Total Internal Reflection Keeps Light in.

Incident ra

yReflected ray

Refracted ray

Total Internal ReflectionTotal Internal Reflection

If If θθ22 is greater than 90 is greater than 90° then no ° then no light is refracted. The incident light 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 becomes becomes nn11sinsinθθcc=n=n22sin sin 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.

Incident ra

yReflected ray

UsesUses Fiber optics cables Fiber optics cables

can be used for the can be used for the following applications:following applications:– CommunicationCommunication

TelephoneTelephone TelevisionTelevision InternetInternet

– SurgerySurgery– ToysToys– Uses yet to be Uses 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%20notes/fiber_optic_cable.jpg>.

Comparison to Wires and Comparison to Wires and CurrentCurrent

A wire can transmit current, either in a A wire can transmit current, either in a positive direction or a negative direction.positive direction or a negative direction.

A fiber optics cable can transmit light in A fiber optics cable can transmit light in two directions at the same time. It can two directions at the same time. It can also transmit light in different phases, also transmit light in different phases, amplitudes, and sometimes different amplitudes, and sometimes different colors.colors.

Optical fibers can carry more information, Optical fibers can carry more information, and they can carry it a farther distance and they can carry it a farther distance than wires.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 is Most solids are crystalline, but glass is

amorphous. Glass does not have a amorphous. Glass does not have a repeated molecular structure.repeated molecular structure.

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

Crystallization and Glass Crystallization and Glass FormingForming

If you heat a crystal up to above the melting If you heat a crystal up to above the melting temperature, 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 a If given enough time, the melt will become a crystal. The molecules rearrange into their crystal. The molecules rearrange into their lowest energy states which are very ordered.lowest energy states which are very ordered.

If you cool the melt quickly, it will not have If you cool the melt quickly, it will not have time to rearrange to become a crystal. time to rearrange to become a crystal. Instead, it will become a supercooled liquid, Instead, it will become a supercooled liquid, on its way to glass formation.on its way to glass formation.

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

highly viscous material flows slowly highly viscous material flows slowly like honey, and a material with low like honey, and a material with low viscosity flows easily like water.viscosity flows easily like water.

As this supercooled liquid becomes As this supercooled liquid becomes cooler and cooler, the viscosity cooler and cooler, the viscosity becomes greater and greater.becomes greater and greater.

TTgg (tē-jē)(tē-jē)

When the viscosity becomes so high that When the viscosity becomes so high that the material behaves more like a solid the material behaves more like a solid than a liquid, it has become a glass. It has than a liquid, it has become a glass. It has hit Thit Tgg..

TTgg is the glass transition temperature. T is the glass transition temperature. Tgg is lower than the melting temperature, Tis lower than the melting temperature, Tmm..

Fiber DrawingFiber DrawingIn 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.Video will run after download – please be patient.

Candy GlassCandy Glass Similarities between Candy and GlassSimilarities between Candy and Glass

– Amorphous solidsAmorphous 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, H for sodium silicate glass, H22O for candy, reduces O for candy, reduces

melting temperature and decreases chemical durabilitymelting temperature and decreases chemical durability– Other stuff: Corn syrup reduces crystallization in candy. Dr. Jain’s Other stuff: Corn syrup reduces crystallization in candy. Dr. Jain’s

paper says that adding stuff to glass can increase glass forming ability. paper says that adding stuff to glass can increase glass forming ability. (Source: Jain, Himanshu and Isha Jain, “Learning the Principles of Glass Science and Technology from Candy Making.” (Source: Jain, Himanshu and Isha Jain, “Learning the Principles of Glass Science and Technology from Candy Making.” Lehigh UniversityLehigh University. . No Date. Lehigh University. 5 Aug. 2005 <http://www.lehigh.edu/~inmatsci/faculty/candy_making.pdf>.)No Date. Lehigh University. 5 Aug. 2005 <http://www.lehigh.edu/~inmatsci/faculty/candy_making.pdf>.) Note: Corn Note: Corn syrup is made of simpler sugars than sucrose. Sucrose is fructose syrup is made of simpler sugars than sucrose. Sucrose is fructose CC1212HH2424OO1212 and glucose C and glucose C1212HH2424OO1212 bonded together. Corn syrup is bonded together. Corn syrup is fructose, glucose, water and other stuff which the Karo company does fructose, glucose, water and other stuff which the Karo company does not disclose.not disclose.

Differences between Candy and GlassDifferences between Candy and Glass– Candy will decompose (CCandy will decompose (C1212HH2424OO1212 bonds will break) at a temperature bonds will break) at a temperature

that is very high or when not much water is present that is very high or when not much water is present (Source: Jain, Himanshu. Personal (Source: Jain, Himanshu. Personal Interview. June 2005.)Interview. June 2005.)

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

And Now for the ExperimentAnd Now for the Experiment

Set-UpSet-Up SuppliesSupplies

– A stove or hot plateA stove or hot plate– Oven mittsOven 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 diameter Outside funnel: Stem diameter ≈ 1.4cm≈ 1.4cm Inside funnel: Stem diameter ≈ .7cm, preferably longer than stem of outside Inside funnel: Stem diameter ≈ .7cm, preferably longer than stem of outside

funnel.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 ingredientsA scale to measure ingredients– A metal tray to catch hot candy and store fibersA metal tray to catch hot candy and store fibers– A glass rod to draw fibers withA glass rod to draw fibers with– A reflection microscopeA reflection microscope– A razorA razor

Supercool Set-UpSupercool Set-Up Set up funnels as shown:Set up funnels as shown:

– Place paper towel between Place paper towel between the clamp and the funnel.the clamp and the funnel.

– Make sure the funnels are Make sure the funnels are concentric at the top and concentric at the top and bottom of the stem.bottom of the stem.

– Set it up so that the inside Set it up so that the inside funnel sticks out a little bit funnel sticks out a little bit at the bottom (this will at the bottom (this will help you see if the help you see if the cladding is surrounding the cladding is surrounding the core on all sides).core on all sides).

– Is anything going to get in Is anything going to get in the way of you pouring the way of you pouring your supercooled liquid?your supercooled liquid?

– You will have a little time You will have a little time during cooking and the during cooking and the beginning of the pour to beginning of the pour to make final adjustments.make final adjustments.

“Double Crucible” Set Up.June 2005.

Concentric Funnel Stems.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 Measure 205g sugar, 120g water and 50g corn syrup into

each beaker. Stir before cooking but not during cooking.each beaker. Stir before cooking but not during cooking. Cook on a high setting on the stove until both syrups reach Cook 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.Pour immediately. Pour colored liquid into inside beaker Pour colored liquid into inside beaker

and clear (or yellow) into outside beaker.and 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 If cladding is not surrounding core on all sides, readjust

funnels.funnels. Use spoon to test viscosity. If you can pull long fibers, then Use spoon to test viscosity. If you can pull long fibers, then

the viscosity is right for fiber drawing.the 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 Experience Fiber Drawing Success!Success!Video plays after download – brief wait

Procedure: Examination of Procedure: Examination of FiberFiber

To view fibers under microscope, tape To view fibers under microscope, tape three microscope slides together.three microscope slides together.

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

damp paper towel.damp paper towel. Tape fiber vertically to the three slides.Tape fiber vertically to the three slides. Position the three slides in the Position the three slides in the

microscope the way you would microscope the way you would normally position a single slide.normally position a single slide.

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

Professor Himanshu Jain, Lehigh Professor Himanshu Jain, Lehigh UniversityUniversity

My Lab Partner: Raina JainMy Lab Partner: Raina Jain Funding Provided by: The National Funding Provided by: The National

Science Foundation through the Science Foundation through the International Materials Institute, International Materials Institute, Lehigh UniversityLehigh University