Fabrication of Alumina/ Alkali Zinc Phosphate (AZP) Glass Laminates

MSE REUSummer 2002

Presented by: Yeon KimAdvisor: Prof. Trice

My Goals for SummerDevelop a model material Ceramic Has both elastic and viscous properties

Elastic substance – Alumina Viscous substance – AZP glass

Why these particular materials? Alumina is relatively inexpensive and easy to buy in sheet

form. AZP glass is also relatively easy to process and has a low Tg

Al2O3

Al2O3

Al2O3 AZP

AZP

(Laminate to be Made)

Possible ApplicationsMay be possible to design an all ceramic system capable of absorbing a lot of energy – I.e. ballistic applications. Why not just use metals? Ceramics are much less dense.

Most high temperature ceramic materials have a glassy phase – developing this model material would make it easier to observe and study behavior between elastic/ viscous materials.

Experimental ApproachGlass Properties: Highly sensitive to temperature No melting point but a glass transition temperature AZP Glass has a much lower Tg than the melting point of the

alumina

Specific

Volume

Temperature

Tg

Viscous region

Elastic Region

Supercooled

liquid

Liquid

Solid

Initial ApproachFind a good working temperature of the glass: Cut pre-made sheets of Alumina (elastic material). AZP glass powder is dispersed in isopropanol (using 1 gram of

glass powder for every 10 mL isopropanol). Spray AZP/isopropanol mixture onto Alumina using a hobby gun. Heat in a vacuum furnace at varying temperatures and dwell

times.

Vacuum

Goal: Melt glass powder and remove air bubbles.

Heat

Initial Findings

•Many bubbles in the glass layer.

•Increasing processing T decreases the amount of pores.

•Too much heat or long durations in the furnace crystallize the glass.

Revised ApproachHeat (590oC)Vacuum

Heat (450oC)

•Melting the glass to just below its Tg makes the glass viscous enough to allow air to flow better than it would in the glass’s powder form.

Time (hr)

Temp.

450oC

590oC

15 Sprays 30 Sprays

Thinner layer produced less air bubbles.

Successful Method

Negligible pores:Use a 1:20 ratio of AZP glass powder to

isopropanolPre-melt at 450oC Hold in vacuum furnace for 17 hoursMelt glass (590oC @ 1 hour)

Making a Two Layer LaminateAl2O3 Al2O3

AZP AZP

Al2O3

AZP

Al2O3AZP

Al2O3

AZP

Al2O3AZP

Weight

Setter

Setter

Al2O3

AZP

Al2O3AZP

Weight

Setter

Vacuum

Heat (450oC)

Vacuum

I IIHeat (590oC)

ProblemGaps found in the glass layer

Air Gap Glass Layer

Processing VariablesMelt glass on one piece of alumina and layer, or melt glass on both pieces of alumina

Vary thickness of glass layer Vary rate of temperature increase

Al2O3

AZP

Al2O3

AZP

Al2O3

Al2O3

AZP

Results

Laminate made with only one side melted with glass tends to fall apart more readily than laminates made with both sides Thicker layer of glass produce less gaps than thinner layerIncreasing T at a slower rate produced laminates that fell apart more readily

Conclusions/Future WorkLaminates don’t seem to have enough glassReadily falls apart Glass layer has large gaps in between

Coefficient of Thermal ExpansionAlumina: ~ 9e-6 1/oCAZP Glass: ~ 20e-6 1/oC

Sandblast the AluminaChoose a different substrate