An Attractive Prospect for the New Ideas of the Metal Material

Aluminium was once more costly than gold. Napoleon III, emperor of France, reserved cutlery made from it for his most favoured guests, and the Washington monument, in America’s capital, was capped with it not because the builders were cheapskates but because they wanted to show off. How times change. And in aluminium’s case they changed because, in the late 1880s, Charles Hall and Paul Héroult worked out how to separate the stuff from its oxide using electricity rather than chemical reducing agents. Now, a small British firm, hope to do much the same with tantalum, titanium and a host of other recherché and expensive metallic elements including neodymium, tungsten and vanadium.

The effect could be profound. Tantalum is an ingredient of the best electronic capacitors. At the moment it is so expensive ($500-2,000 a kilogram) that it is worth using only in things where size and weight matter a lot, such as mobile phones. Drop that price and it could be deployed more widely. Neodymium is used in the magnets of motors in electric cars. Vanadium and tungsten give strength to steel, but at great expense. And the strength, lightness, high melting point and ability to resist corrosion of titanium make it an ideal material for building aircraft parts, supercars and medical implants—but it can cost 50 times as much as steel. Guppy Dhariwal, Metalysis’s boss, thinks however that the company can make titanium powder (the product of its new process) for less than a tenth of such powder’s current price.

The difference between its process and that of Hall and Héroult (and why electrolysis has not previously been used to make metals such as tantalum and titanium) is that the Hall-Héroult method requires both input oxide and output metal to be in liquid form. That demands heat. But aluminium has a fairly low melting point and its oxide can be dissolved in a substance called cryolite that also has a low melting point, so the amount of heat needed is manageable. Titanium and tantalum are not so obliging. The company trick is to do the electrolysis on powdered oxides directly, without melting them.

This was shown to be possible in 1997 when researchers at Cambridge University found that immersing small samples of certain oxides in baths of molten salt and passing a current through them transformed the material directly into metal. Metalysis was set up in 2001 to commercialise the idea and in 2005 the firm moved to Wath-upon-Dearne, a village near Sheffield, in South Yorkshire, in order to tap the local engineering skills that once made the county (home of silver plate, stainless steel and the Bessemer converter) the California of metallurgy. These skills turned a technique that could produce a few grams of metal in a laboratory into a process that operates on an industrial scale.

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