x Abu Dhabi, UAEMonday 24 July 2017

How the humble pencil could write the future of energy

Researchers have dreamt for decades of finding a superconductor that works at room temperature and a team in Germany has come up with a startlingly simple solution.

Electric power transmission lines are seen in Neuhof, near Hamburg July 13, 2012. REUTERS/Morris Mac Matzen (GERMANY - Tags: BUSINESS)
Electric power transmission lines are seen in Neuhof, near Hamburg July 13, 2012. REUTERS/Morris Mac Matzen (GERMANY - Tags: BUSINESS)

Asked to name the raw ingredients for the next technological revolution, chances are you wouldn't pick pencil-lead and water.

Yet according to new research, simply mixing graphite with water and baking the result may be enough to create an effect with legendary status in science: room-temperature superconductivity.

If confirmed, the claim could transform the energy sector, making power generation and distribution far more efficient, and slashing demand for fossil fuels, including oil.

That's because superconductivity is exactly what it says: the bizarre property of certain compounds, under certain conditions, to become perfect conductors of electricity.

First discovered a century ago, superconductivity has largely failed to live up to its huge promise of transforming electricity use and boosting energy efficiency, because it usually appears only in materials chilled to within a few degrees of absolute zero, the ultimate low temperature of minus 273C.

Attaining and maintaining such temperatures is neither cheap nor easy, and has so far kept superconductivity out of mainstream use.

There was huge excitement in the mid-1980s when scientists at the IBM laboratories in Zurich found the first evidence for so-called High Temperature Superconductivity (HTS) in a ceramic material.

The name is somewhat misleading, though: it still needed to be cooled to around minus 250C, with expensive and dangerous liquid helium.

Since then, researchers have created materials that become superconducting at temperatures above minus 135C - still pretty extreme, but at least attainable with less expensive liquid nitrogen.

But the dream has always been to find a material that displays this amazing ability at room temperature.

Now a team led by Pablo Esquinazi at the University of Leipzig in Germany claims to have seen evidence of just this in a startlingly ho-hum combination of materials: graphite and water.

In the current issue of the journal Advanced Materials, they describe how they mixed 0.1g of ultra-pure graphite powder with a few teaspoonsful of distilled water, and persuaded the two to mix by stirring it for hours on end. The combination was then filtered, and the resulting powder baked overnight at 100C.

Tests on samples made using this recipe repeatedly revealed the existence of superconductivity at room temperature.

Prof Esquinazi and his colleagues stress that the effect is confined to just the surfaces of the tiny graphite grains, and disappeared if they tried to make pellets of the stuff.

Even so, the fact that it appears at all looks set to spark an international effort to replicate and understand the finding.

Other scientists certainly won't dismiss it as ludicrous, as the quotidian nature of the ingredients is deceptive.

Graphite is now among the hottest research topics in material science. It's made up of sheets of a honeycomb-like arrangement of carbon atoms known as graphene, which possess many unusual properties, while water is renowned for being one of the most peculiar liquids known.

Indeed, Prof Esquinazi and his colleagues were led to perform their experiments by previous studies suggesting the combination might throw up something unusual.

Even so, the appearance of an effect as spectacular as superconductivity is far from obvious. And explaining it is likely to be a major challenge, given that even 25 years after their discovery, there's no accepted theory to explain HTS materials, and even the basic theory of superconductivity is less than perfect.

The key challenge is explaining how electrons that struggle to get through a material suddenly flow like a torrent when the same material is chilled below a certain temperature.

The answer is thought to lie in the pairing up of electrons in such materials, allowing them to slip through the crystal lattice more easily.

What brings about this pairing is a mystery - not least because the temperatures at which it takes place should keep the electrons apart.

Recent experiments on HTS materials suggest that wavelike distortions in the arrangement of atoms within them play some role in keeping the electrons together - as they do in conventional superconductors.

Some kind of magnetic effect also seems to be involved, providing extra "glue" between the electrons.

What researchers have been crying out for are radically new types of HTS materials on which to test their ideas. Now it seems their wish may have been granted.

Intriguingly, this isn't the first hint that room temperature superconductivity might be possible. Over the years, tantalising glimpses of the phenomenon have been reported, only to vanish again.

In 1974, in the journal Nature, a researcher at Nicolas Copernicus University in Torun, Poland, claimed to have detected room-temperature superconductivity in a sandwich-like layer of aluminium plus carbon - the element at the centre of the latest claim.

Prof Esquinazi and his team think their findings may be a replication of this 40-year-old sighting. Only replications of their own claims will reveal the truth.

Even if it is confirmed, a lot of work will be needed to put it to practical use. The researchers estimate that the superconductivity appears only in about 0.1 per cent of the total mass of the powder.

Some way of bulking out the material will be needed if it is to be exploited in sizeable products such as cables and magnets.

It will also have to be made robust enough for mass production - a problem that long bedevilled other HTS. And there's always the possibility that the superconductivity will vanish when exposed to typical working conditions.

Prof Esquinazi and his team have been scrupulous about not overselling their claim. Despite its implications, they declined to go public with it until it was published in a respected academic journal.

Even the title of their paper - "Can doping graphite trigger room temperature superconductivity?" - contains a judicious question-mark.

In this the team are following a distinguished tradition.

In 1905 a paper appeared entitled "Does the inertia of a body depend on its energy content?" Its author was Albert Einstein, and its subject was the derivation of the most important scientific formula of all time, E = Mc2.

If room temperature superconductivity can be made a practical reality, the consequences will hardly be less important.

 

Robert Matthews is visiting reader in science at Aston University, Birmingham, England