Wednesday, December 28, 2005

Weird Cooling Compound

Someone on eBay is selling a product called "Liquid Metal" for use as a thermal-paste between heatsink and processor. This substance is 100% metal which makes it more conductive of heat than other thermal compounds which contain non-metalic substances as well. This substance is also a liquid at room temperature. This seems like a very good material to use as their tests show a significant temperature decrease, even greater than that of Arctic Silver 5 (my choice thermal compount at the moment).
A little problem was pointed out to me today regarding this product; it will eat through heatsinks and kill cooling performance. I looked into this and indeed there is a simple cause for this: the liquid is primarily made of a mercury-based alloy. It may also be a gallium alloy which has similar properties. There is a little problem when mercury or gallium comes in contact with aluminum, you can watch it corrode before you eyes. Aluminum is a very reactive material that will react almost instantly with anything. It reacts with O2 in the air and creates a clear, crystaline coating that is very strong (I believe aluminum-oxide is also what rubys are made of). When mercury is added to the equation it prevents this coating from forming, causing the aluminum to completely corrode away at a very rapid pace. If you have a heatsink made of aluminum it won't like this compound and will begin to corrode and disintegrate right on your processor. This is actually pretty cool to see, but really uncool for cooling purposes. This shouldn't be much of a problem if you use copper heatsinks.
I'm not sure I'd really want to use mercury or gallium as a thermal paste for my system. However I have never seen anyone try to use mercury as the fluid in a liquid-cooled system. I'd like to see how effective that is, but I'm not sure where I can cheaply get mercury by the litre.

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