From Silica to Silicon

For those too lazy or drunk to click a single URL, here's a brief summary:

Chemically, the process is to remove the oxidized magnesium from the silica structure, resulting in pure silicon.

It may be done by heating to 650 ^oC to generate magnesium gas, which reduces the silica to elemental silicon, or by dipping the silica in a bath of hydrochloric acid to remove the oxidized magnesium. Happy Easter

Hi to all,

this looks great.

Maybe by this way the shortage for solar cell grade silicon can be overcome.

Is there an estimate about purity and cost?

Have nice holidays

RHABE

RHABE,

Who are the current suppliers of silicon for photovoltaics and why is there such a shortage? Is this temporary or a longer term problem/opportunity?

Thanks,

Hi,

low purity silicon (99%) is made in huge electric furnaces with consumable electrodes of carbon at 1650°C. Quartz pepples are used as input. In the electric arc the carbon is reacting with the oxygen from the SiO2 and burning to CO and CO2.

This is used in alloying Fe to transformer steel and some types of spring steel and is low cost (1$/kg).

This Si raw material is highly purified by reacting with chlorine to produce SiCl4 and distillation of this flammable liquid and decomposing the purified stuff to Si in heat.

This Si is vacuum melted and crystallised in bars of 100 to 400mm diameter to produce the semiconductor grade Si. (Cost is ranging according to quality inbetween 500 to 5000$/kg). The bars to be cut to wafers of 0.7mm thickness, grinding, polishing and etching to result in 0.3 to 0.5mm thickness will make the wafers for transistors ICs and processors-computer chips including memories.

If something went wrong and the purity is not sufficient for semiconductors also the no longer usable end pieces of the bars are remelted and cast to produce the solar cells.

So the solar cell production relies on the scrap from semiconductor production.

This was good for many years but now with rising demand for solar cells there is a shortage and active trials to get sufficient quality chep silicon for solar cells.

One attempt is a better hot decomposition of SiCl4 to Si.

I don't know the details about may be new processes. Nor the momentary price of the materials.

Wacker Siltronic is one of the major producers (both semiconductor and solar cell grade.)

Have nice Holidays

RHABE

Rhabe and all who share in the interests of this subject, please note some common themes delineated in an article I wrote recently for insidegreentech.com. insidegreentech.com/node/478 is the url. We are looking to the manufacturers of MG-Si or SoG-Si, to support our teams with development funding to scale up the reactor vessels for our new process suited to a unique silica starter material.

Thanks, Peter Duchon, info @ asappower.com

If large scale bulk processes are inefficient, perhaps it would be better to use small amounts of silica in very small scale refining devices that can automatically test their outputs for purity and reprocess it when necessary. Large volumes of high quality silicon could then be produced by running lots of small refining devices in parallel.

Small is beautiful. Thumbs Up!

This theme is evident in the article linked in a reply to Rhabe.

Peter Duchon