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
Al2O3AZP
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 Approach
Glass 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 Laminate
Al2O3 Al2O3
AZP AZP
Al2O3
AZP
Al2O3
AZP
Al2O3
AZP
Al2O3
AZP
Weight
Setter
Setter
Al2O3
AZP
Al2O3
AZP
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