Fabrication of Alumina/Alkali Zinc Phosphate (AZP) Glass Laminates
Yeon J. Kim
George Washington University
Advising Professor: Rodney Trice

Introduction:

When a crack is present at an interface in a material, it can do one of two things - the crack can get deflected down the interface or propagate straight through. The crack behavior of a material with an elastic/elastic interface has been carefully studied and well characterized. However, these findings are not applicable when the material has an elastic/viscous interface.

The goal of the summer is to make a model material that has both elastic and viscous properties. The material would be a laminate of alternating layers of alumina and alkali zinc phosphate glass

Project Objectives:

  • Make an alumina/AZP glass laminate with negligible porosity and investigate the laminate's properties.
  • Remove the air bubbles from the AZP glass layer.

Experimental Approach:

  • Prepare samples by cutting pre-made sheets of alumina.
  • Use a hobby gun to put down a layer of glass (AZP glass is dispersed in isopropanol).
  • Place the prepared sample in a vacuum furnace to melt the glass powder.
  • Determine the conditions that are necessary to produce a sample of alumina/glass with no air bubbles in the glass layer:
    • Variables investigated were -
      • Temperature
      • Holding Time
      • Vacuum Time
      • Rate of Temperature Increase
      • Thickness of Glass Layer
      • Ratio of Glass Powder to the Dispersant (isopropanol)
    • Find the conditions needed for lamination.

Research Findings:

(Melting the AZP glass)

  • AZP glass is very temperature sensitive.
  • As processing temperature increases, fewer pores are observed.
  • Long heating times or high temperatures crystallize the glass.
  • Using a 20:1 ratio (20 mL isopropanol for every 1g AZP glass powder), and pre-melting the glass at a temperature below its Tg in a vacuum furnace before raising the temperature to completely melt the glass, removed most of the air bubbles in the glass layer.

(Making the Laminate)

  • Gaps were found in the glass layer.
  • Further investigation into the properties of the glass layer and alumina needs to be conducted. (i.e. choose a substrate that has a coefficient of thermal expansion close to that of AZP, or sandblast the alumina to provide more surface area for the glass).


Cross section of an alumina/glass laminate.

Furnace used to process alumina/glass laminates.
Final Research Presentation