Making silicon is an expensive process, which conventionally involves carbothermal reduction, in which the oxygen is removed from silica by a heterogeneous-homogeneous reaction sequence at approximately 1,700 °C.
Now, Japanese researchers have developed a new technique which uses electricity to remove the oxygen from silica. In this article, Nature tells us more.
A new technique for producing silicon might make this technologically vital element cheaper. It could also give engineers new ways to design silicon chips.
The process, developed by Toshiyuki Nohira and colleagues at Kyoto University in Japan, uses electricity to strip oxygen from silica, the natural oxide of silicon. The method could make large amounts of silicon from mineral silica, such as the quartz that makes up the bulk of sand.
Here is how it works.
They immerse a piece of silica -- a quartz plate, say -- in a bath of molten calcium chloride salt at 850 ºC, and pass an electric current through a metal wire touching the quartz.
Where metal touches silica, the oxygen atoms in the silica become oxide ions, which dissolve in the molten salt -- and the silica turns slowly into silicon.
The researchers also experimented with different kinds of salts, allowing them to reduce the temperature of the bath to 500 ºC.
They think their methodology can be applied to other elements -- Nature mentions zirconium. However, the article doesn't say when this process will be commercially available.
You can read their research paper, "Pinpoint and bulk electrochemical reduction of insulating silicon dioxide to silicon," in PDF format -- providing you're a subscriber to Nature.
Source: Philip Ball, Nature, May 19, 2003
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