Alumina in glass could stop smartphones cracking up

Trekkies will remember how Scotty bestowed transparent aluminium on the world in Star Trek IV, The Voyage Home. Now Japanese researchers have added alumina to glass to try and make it tough enough for the hard life of the smartphone.

In Nature Scientific Reports, the boffins from the University of Tokyo and Japan's Synchrotron Radiation Research Institute describe their oxide glass, which they reckon will also be useful in buildings and cars.

Scientists have wanted to add alumina to oxide glasses for some time, to strengthen the bonds between silicon dioxide, but the mixture crystallises in contact with the container it's being mixed in.

Alumina – Al₂O₃ to its friends – has a very high “disassociation energy”, but as the paper states, “the glass forming ability of a composition typically decreases as the quantity of Al₂O₃ increases”.

To form a useful glass, the Japanese scientists levitated pellets of their source materials “in an oxygen gas flow and melted using two CO2 lasers at approximately 2000 °C. The melt was rapidly solidified by shutting off the lasers … to obtain fully vitrified samples.”

The samples were only small – 2mm diameter spheres – but the researchers say the glass is extremely hard, colourless, and transparent.

Atsunobu Masuno told the BBC the glass shows Young's modulus (a measure of stiffness) values greater than some metals and “on the way” to steel.

The next trick will be to turn the containerless processing technique into mass production, which will probably be easier for smartphone-sized outputs than for (small-w) windows. ®