Weekend Nanotech – The Inconvenient Ash

By Elf Eldridge 25/06/2011 3


Estimated Ash distribution map from: http://passingparade-2009.blogspot.com/
Estimated Ash distribution map from: http://passingparade-2009.blogspot.com/

Most people will be aware by now there is a rather large ash cloud spreading across the Southern Hemisphere from the eruption in Chile. Here in NZ it has been playing havoc with flights across the board- but many people aren’t sure why we’re so worried about ash! So I though I’d take the opportunity to explain a bit, and push a nanotech solution!

First we need to understand what conditions are like inside a jet engine. In a word? Hot. 1200 degrees Celsius hot. Spinning at several thousand revolutions per minute (RPM). Now imagine throwing something into that. Something small (a few microns in diameter), hard and rocky (most volcanic ashes are some form of silicate) [2]. Another word that comes to mind. Chaos.

Jet Engine in action
Jet Engine in action

Ash Particle
Ash Particle

(BAD)
(BAD)

The only reason the metal parts of the engines remain intact under these conditions is that they are coated with ceramics that drastically reduce the amount of heat that reaches the metal parts of the engines. And here’s where the problem with ash is – it’s not necessarily it’s small sharp nature that’s the problem, it’s that the temperature of the engine turns it glassy and causes it to fuse with the protective ceramic coating of the engine causing it to flake off [1]. This of course allows the heat from the engine to penetrate into the engine parts that simply can’t withstand the conditions leading to what the paper below refers to as “catastrophic engine failure”.

Fortunately, due to the estimated 2 Billion dollars lost by the eruption of Eyjafjallajokull last year, scientists have been researching ways to stop this from happening and have come up with several nanotech coatings for the protective ceramic that prevents the ash from fusing with it. In fact the ash fuses with the nanotech layer due to its high porosity, creating a second protective glass-like layer ontop of the ceramic layer. What’s more this is ONLY possible due to the unique nanotechnology designed into the coating – it wouldn’t work without it![1] Just goes to show that whilst people may not be aware of it – nanotech is slowly but surely revolutionizing our world! That said, the coating has only been shown to work under testing conditions and it will take serious time and investment before it reaches commercial application, but it’s difficult not to get excited about this elegant solution!

References:

1) Drexler Et al. “Jet Engine Coatings for Resisting Volcanic Ash Damage” Advanced Materials (2011) doi: 10.1002/adma.201004783

2) http://volcanoes.usgs.gov/ash/properties.html


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