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Zirconia Toughening Extends Refractory Service Life

Improving ceramic thermal shock resistance through unstabilized monoclinic zirconia additions that enhance crack deflection mechanisms.

refractoriesthermal-shockzirconiaaluminatoughening 1 min read

The Challenge

Al2O3–CaAl12O19 composites are ideal high-temperature structural ceramics, but their poor thermal shock resistance limits application under thermal shock conditions. These materials are used in metal processing, glass manufacturing, and other industries where rapid temperature changes cause crack formation and material failure. Improving thermal shock resistance without sacrificing other properties is essential for expanding their use.

The Solution

This research prepared composites from ferrotitanium slag, adding 12.5 wt.% unstabilized monoclinic zirconia for reinforcement. The GrindoSonic MK7 enabled measurement of elastic modulus before and after thermal cycling, quantifying damage accumulation through property degradation and assessing how crack formation affects material stiffness. Systematic analysis of phase compositions and microstructural evolution revealed the crack propagation resistance mechanisms.

Results

Enhanced thermal shock resistance results from multiple crack propagation resistance mechanisms, including stress-induced tetragonal to monoclinic phase transformation in t-ZrO2 and microcracking associated with m-ZrO2. Coarsened ZrO2 particles doped with TiO2 from the ferrotitanium slag are beneficial to both mechanisms. This understanding enables development of more durable refractories for high-temperature industrial applications.

Key takeaway: Adding 12.5 wt.% unstabilized monoclinic zirconia to Al2O3-CaAl12O19 composites enhanced thermal shock resistance through dual mechanisms: stress-induced phase transformation and microcracking from TiO2-coarsened ZrO2 particles.

Frequently Asked Questions

How does adding unstabilized monoclinic zirconia improve thermal shock resistance?
Adding 12.5 wt.% unstabilized monoclinic zirconia enhances crack propagation resistance through two mechanisms: stress-induced tetragonal-to-monoclinic (t to m) phase transformation in t-ZrO2, and microcracking associated with m-ZrO2. Coarsened ZrO2 particles doped with TiO2 from ferrotitanium slag promote both mechanisms, significantly improving the thermal shock resistance of Al2O3-CaAl12O19 composites.
How does IET measure thermal shock damage in ceramic composites?
The GrindoSonic MK7 measures elastic modulus before and after thermal cycling, quantifying damage accumulation through the reduction in stiffness. Since cracks and microstructural degradation directly reduce a material's elastic modulus, tracking this property through successive thermal shock cycles provides a precise, non-destructive assessment of how well the composite resists thermal damage.
Why were ferrotitanium slag composites chosen for this refractory research?
Ferrotitanium slag serves as the main raw material, providing both the Al2O3-CaAl12O19 matrix and TiO2-doped ZrO2 particles. The TiO2 from the slag coarsens the ZrO2 particles, which is beneficial because larger particles are more effective at triggering both stress-induced phase transformation and microcracking, the two key mechanisms responsible for the enhanced crack propagation resistance.

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