Inasmuch as I have been expecting this result in association withgraphene I am not surprised at all and look forward to intense effortto winkle this effect into existence on a graphene substrate. Thisachievement is critical to the easy manufacture of Magnetic FieldExclusion Vessels (MFEVs).
This result is the first hint that it is even possible and nowlikely.
From the work done to date it is clear that small bits did it andthat further work needs to be conducted on graphene in order tocontrol the variables. What happens when a current carrying carbonnanotube penetrates a graphene plain? That is a pretty interestinggeometry with plenty of promise. Does the induced magnetic fielddecay?
A lot needs to be done but I suggest that we take the hint.
Raised eyebrowsgreet graphite superconductivity claim
24 September 2012Simon Hadlington
Can graphite treatedmerely with water become a superconductor at room temperature? Thisis theextraordinary claim made by scientists in Germany.Unsurprisingly, this has been met with scepticism – from measuredto outright – by other experts in superconductivity.
Pablo Esquinazi andhis team at the University of Leipzig say that they observed a‘tantalising hint’ of superconductivity at room temperature insamples of graphite powder that had been mixed with water and driedovernight at 100oC. The researchers placed the material in a magneticfield and observed changes in the graphite’s magnetism – tracinga hysteresis loop – that are characteristic of asuperconductor. Analysis showed that only a tiny fraction of thesample, around one part in 10,000, was producing the response.
But when the teamcompressed the powder into pellets – necessary to measure theelectrical resistance of the material – the signal disappeared.Esquinazi speculates that a proportion of the graphite could includemisaligned interfaces that are superconducting, with the possibilityof dissociated hydrogen from the water playing a role. ‘Our resultsare tantalising,’ says Esquinazi. ‘But not 100% proof. Thesuperconductor yield is too low and we do not know where thesuperconducting phase is or what the critical temperature is.’Esquinazi is satisfied that his team has eliminated all possiblesources of potential artefacts in the data. ‘Either this issuperconductivity or it is something completely new,’ he says. Thenext step is to attempt to pinpoint the superconducting phase at thegrain interfaces and to increase yields, Esquinazi says.
Questions remain
But other experts arenot convinced. ‘There is no physical evidence of superconductivity,by which I mean primarily there are no resistance measurements thatshow the material has become superconducting,’ saysMark Ellerby ofUniversity College London in the UK, who works on graphite-basedsuperconductors. ‘Graphite is a very interesting material that hasa lot of magnetic properties of its own and these are only alludedto. My feeling is that this is a highly suppositional paper that usesinterpretation in a strongly philosophic nature, without providingphysical evidence.’
Archie Campbell,emeritus professor at the University of Cambridge, UK, is equallysceptical. ‘They do the right thing in measuring the magnetisationas a function of field. This appears to show hysteresis but the loopsat increasing amplitude of field do not correspond to those of asuperconductor,’ he says. ‘Also, the critical current does notseem to change significantly between 5K and 300K which is highlyimprobable. The model they have is that there are a fewsuperconducting grains, but the signal is only one in 104 ofwhat you would expect from a solid superconductor so only 1 grain in104 is superconducting. There is no reason for this in a simplehomogeneous system such as this. I think it is an experimentalartefact.’
On the disappearanceof the signal when the sample is compressed, Ted Forgan ofthe University of Birmingham in the UK, says: ‘The authors givereasons why the signal should be smaller, but I am not convinced thatit would go away completely on their model. Graphite is flaky, with avery large and anisotropic diamagnetism [the creation of a magneticfield in opposition to the externally applied field]. One couldimagine changing diamagnetic signals from realignment of micron-sizedgraphite particles which would go away if the sample were compressedso the particles could not rotate.’ Forgan concludes: ‘So, notproven, but not disproved either and worth following up.’
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