Superconducting cuttlefish bonesUpdate: 4/13/2015
UK chemists have used cuttlefish bones to template the growth of new superconductors.
Simon Hall at the University of Bristol and colleagues soaked the cuttlefish bone - cuttlebone - in a solution of the precursors of the yttrium barium copper oxide superconductor Y123 and then heated the sample to over 900 °C to form the superconductor. Cuttlebone has an open structure, consisting of calcium carbonate layers connected by pillars. This allows the sample to be oxidised efficiently when heated, so unlike other synthesis methods flowing oxygen is not needed to produce high quality Y123.
The researchers found that the complex porous structure of the cuttlebone was retained, giving a lightweight superconducting material. They also discovered that the critical current density of their material was almost two orders of magnitude higher than that of the commercially available Y123 powder.
The critical current density is the amount of electrical current the superconductor can carry before it reverts to a non-superconducting state. 'The higher the critical current density,' said Hall, 'the more current the superconductor can carry and the better it is.'
'Cuttlebone is a cheap, readily available and, most importantly, morphologically complex material,' explained Hall. 'It is particularly good for templating inorganic growth as the entire cuttlebone structure is covered with an organic layer of chitin, a polysaccharide which has tremendous affinity for metal ions.'
Because the superconducting material is lightweight, it could have future applications in areas where weight is important, according to the researchers. Hall is interested in examining a range of biopolymers to see how they affect the crystal growth of superconducting materials. 'A big challenge is to control the way crystals grow in order that their use in device applications may be improved and extended,' he explained.