The eruption of the Eyjafjallajökull volcano, Iceland, in April 2010 caused major disruptions to air travel: Modern jet engines are vulnerable to damage when molten ash penetrates their insulating barrier coatings. Damaged coatings can sheer off and expose the bare metal to dangerously hot gases.

Nitin Padture and co-workers, Ohio State University, USA, have developed two new thermal barrier coatings. The first consists of Gd₂Zr₂O₇ while the second is made of a ZrO₂ ceramic containing Y₂O₃, Al₂O₃, and TiO₂. Molten ash could penetrate both coatings to a certain depth (approx. 5 % of Gd coating thickness and 17 % of Al). Once the top surface pores and cracks were filled with ash, it reacted to form an impervious crystalline layer that prevented further penetration. The authors note that this partial penetration is likely to cause some loss of strain tolerance but significantly less than the complete penetration seen with current barrier coatings.

• Jet Engine Coatings for Resisting Volcanic Ash Damage
  J. M. Drexler, A. D. Gledhill, K. Shinoda, A. L. Vasiliev, K. M. Reddy, S. Sampath, N. P. Padture,
  Adv. Mater. 2011.
  DOI: 10.1002/adma.201004783