Silicon Seduced From Silica

Roland Piquepaille writes "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. Their technique is based on the immersion of silica in a bath of molten calcium chloride salt at 850 C, which should reduce the costs of making silicon -- and other elements, like zirconium. Check this column for a summary or read this article from Nature for additional details."

Comments

zirconium!

[lingqi]

Zirconium plays a vital part in metallocene catalysis, which is the method of manufacturing high molecular density polyethylene, in another word, spectra. (stronger than steel (10x pound for pound), floats, i.e. stronger than KEVLAR and ~40-45% lighter, better chemical, UV resistance than kevlar, etc).

not related to silicon, but i like to point that out. in case people are looking for uses for zirconium =).

for those that thought about it - no spectra is not good enough for space elevator. only 3GPa tensile strength (steel about .25 for cheap ones and 5 for REALLY good ones). space elevator needs ~62GPa. nanotubes ~150GPa theoretical.

okay. end rant.

Re:zirconium!

[simong_oz]

okay. start my own rant.

As an engineer I get fed up with people claiming product X is stronger than steel, etc, etc. You almost always (as in the case of spectra) find that what they are talking about is specific strength, which measures mechanical strength per unit weight. It doesn't mean it's stronger than steel. The modulus of steel (el cheapo low carbon) is roughly 200GPa, spectra is 60-124 or less than half as strong.

the tensile strength of 3GPa is the UTS - ultimate tensile strength. UTS is where the material catastrophically, and unrecoverably, fails. The material will have yielded (and possibly weakened) well before this stress level is reached.

Steel will almost always be the basic material of choice, except when weight is important, for the simple reasons that it is strong, easy to work with, easy to manufacture into almost anything and, most importantly, cheap.

okay. end my own rant :)

Impact and Solar Cells

[Anonymous Coward]

Obviously it will reduce the cost of silicon chips ... a little. In fact a 3 inch Si wafer costs about 3 USD. So you Intel Hexium Pro 10 GHz chip cost will not be much affected by this. However the solar power industry has often used Si cutoffs from teh chips industry, a kind of recycling and there the cost scale is very different.

As wafers have grown in size (and changed from inches to metrics), up to 300 mm production size today, it means there is effectively less cutoffs available to make cheap polycrystalline solar cells. Sure, mono crystalline solar cells are more efficient but also far more costly.

This new process then can mean a lot more cheap solar cells. Imagine like all available roof areas being covered, down to the top of all cars.

Great for Solar Energy

[markus_baertschi]

The cost of the silicon wafers has an enormous impact on the cost of silicon solar cells. If this cost can be brought down with this new technology suddenly solar energy becomes competitive !

Markus

Delicate silicon

[asciimonster]

If you just eject oxygen from a structure, it would be likely that you are left with a very brittle structure, if not a powder. Remember the oxigen in the SiO2 (the sand) bridges the silicon atoms therfore the structure must be completely ruined.

Therefore the collected silicon mus be remelted, drawn, cleaned, sliced into tiny placks, etched, washed and polished. However this is also has to be done with silicon obtained in other ways. Nowadays there are machines who can perform most of these procedures in one run.

A short explanation of this can be found here

Cost of silicon wafers

[Randatola]

The companies that make silicon wafers for semiconductor production start with what is considered "chemically pure" silicon, and purify it some more until it is "electronics grade" silicon. A billet (I forget their technical term for it) of silicon is grown off of a seed crystal in a furnace, in a process that takes about a month. This is then sliced along a crystal axis into wafers which are polished to a rather extraordinary degree.

I don't know how much the raw silicon costs, but I suspect that most of the cost of the wafers comes from this month-long crystal growth and planarization. Good (ie, very flat) 200mm silicon wafers for semiconductor production can cost up to $1000 each, although they are probably much cheaper now due to lack of demand. Many processes also don't require the flattest wafers and so one can get by with wafers that cost a small fraction of that.

Not the semiconductor industry...

[FuzzyDaddy]

Most of the silicon in the world is actually used in processing metal, including steel, of various kinds.

Only a small fraction is actually turned into wafers, and the expense in that process has less to do with turning silica into silicon, but turning impure silicon into really, really pure, single crystal silicon. [It's actually a really cool process, I wish I could remember the details. It involves bonding the silicon to something, and distilling it.] And this cost is very small compared to the cost of turning a wafer into chips.

This discovery, if it actually saves money, will have some impact on the steel industry, but practically none on the semiconductor industry.

Re:3rd post!

[pyr0]

Actually, most volcanic sands don't have much quartz at all, and here is why. If it has been derived from a basaltic volcano (ie Hawaii), the composition of the sand will be extremely high in mafic (very silica poor) minerals since the source magma was low in silica. Then, if you are talking about a volcano whose melt composition is closer to the felsic (silica rich...so much so that you get quartz precipitating) side, these are typically very explosive volcanos that produce lots and lots of fine grained ash but no lava flows to weather from. What you *really* want is a sand eroding from an exposed granite. You get great big fat quartz crystals, and feldspars that turn to clay very quickly. And that's just if you want to find a loose sand that will be quartz rich. What I would do is actually get a hold of some mining rights out in the Southwest US somewhere and start a quarry operation on all the excellent quartz sandstone they've got.