Research Team: Prof. Charles Sorrell, A/Prof. Pramod Koshy, Dr. Sajjad Mofarah, Dr. Uttam Kumar, Dr. Mohannad Mayyas, Dr. Esmaeil Adabifiroozjaei
Industry Partner: Topfibre Pty Ltd
Timeframe: 2017 (direct industry funding), 2017 – 2019 (ARC Linkage project)
Objectives
Outcomes
Objectives
- Develop the means of fabricating single-crystal mullite fibres from topaz that are suitable for reinforcement of metal and ceramic matrix composites and to use all of the fluorine by-product to generate a low-value product
- The work will focus on different process parameters including varying topaz particle size, topaz powder volume, decomposition temperature, decomposition time, and fluorosilicic acid and orthosilicic acid flow rates.
Outcomes
- Use of loose unmilled topaz and enclosure within nested crucibles seems to be able to enhance retention of the vapour phase and form distinct and separable whiskers
- Longer heating times resulted in longer and thicker whiskers but these resulted in increased interfibre bonding strength, which made separation more difficult
- The locations of the whiskers within the bed affected the extent of calcination and whisker size
- Re-orientation of the fibres is possible with high pulling rates to enhance the extent of re-orientation, although there is a upper limit
- The type and amount of glass flux is an important factor since the glass phase needs to have sufficient fluidity to optimise fibre re-orientation and growth
- Metal infiltration trials showed promising data for MMC fabrication with specific alloys but further work was limited by the temperatures that could be achieved in the vacuum furnace