Transparent aluminium is used in ‘the Star Trek Universe’ to make exterior windows of star ships. This material features strongly in the plot of the movie Star Trek IV: The Voyage Home. The crew of the enterprise has gone back in time to bring back a pair of whales to communicate with an alien probe. Once they have travelled to the past set about building a giant aquarium, but not having any earth money with which to buy the materials needed. In the end the aquarium isn’t made from transparent aluminium but from a giant sheet of perspex they get by trading the recipe for the transparent aluminium.
Fairly realistic claims have been made about the mechanical properties of transparent aluminium, it claimed to be as clear as glass, and have the strength and density of high-grade aluminium. Star Trek science consultant André Bormanis has reasoned that the transparent aluminium is unlikely to be a conductor of electricity, presumably because it lacks free electrons that would usually give a metal it’s metallic appearance. If that is the case then this material is mis-named.
Transparent aluminium seems to be a popular meme. Aluminium Oxynitride is a polycrystalline ceramic with spinel structure which is said to have similar mechanical properties to transparent aluminium (made from aluminium, oxygen and nitrogen and processed by powder technique), which is used for high temperature viewing windows and for armour. In 2009 scientists from Oxford lead an experiment at the DESY facility in Hamburg Nagler et al. (“Turning solid aluminium transparent by intense soft X-ray photoionization”, Nature Physics 5, 693–696, 2009), in which aluminium was rendered transparent for short periods of time by bombardment with a very strong light source, which allowed exotic states of matter to be investigated. More recently Röhlsberger et al. (“Electromagnetically induced transparency with resonant nuclei in a cavity”, Nature, 482, 199–203, 2012), have reported a similar phenomena for small clusters of atoms where the optical properties of or interest.